G2Cdb::Gene report

Gene id
G00000568
Gene symbol
Nefl (MGI)
Species
Mus musculus
Description
neurofilament, light polypeptide
Orthologue
G00001817 (Homo sapiens)

Databases (12)

Curated Gene
OTTMUSG00000016377 (Vega mouse gene)
Gene
ENSMUSG00000022055 (Ensembl mouse gene)
18039 (Entrez Gene)
118 (G2Cdb plasticity & disease)
Gene Expression
NM_010910 (Allen Brain Atlas)
g01738 (BGEM)
EMAGE:3371 (EMAGE)
18039 (Genepaint)
nefl (gensat)
Literature
162280 (OMIM)
Marker Symbol
MGI:97313 (MGI)
Protein Sequence
P08551 (UniProt)

Synonyms (4)

  • CMT2E
  • NF-L
  • NF68
  • Nfl

Literature (193)

Pubmed - other

  • A high-resolution anatomical atlas of the transcriptome in the mouse embryo.

    Diez-Roux G, Banfi S, Sultan M, Geffers L, Anand S, Rozado D, Magen A, Canidio E, Pagani M, Peluso I, Lin-Marq N, Koch M, Bilio M, Cantiello I, Verde R, De Masi C, Bianchi SA, Cicchini J, Perroud E, Mehmeti S, Dagand E, Schrinner S, Nürnberger A, Schmidt K, Metz K, Zwingmann C, Brieske N, Springer C, Hernandez AM, Herzog S, Grabbe F, Sieverding C, Fischer B, Schrader K, Brockmeyer M, Dettmer S, Helbig C, Alunni V, Battaini MA, Mura C, Henrichsen CN, Garcia-Lopez R, Echevarria D, Puelles E, Garcia-Calero E, Kruse S, Uhr M, Kauck C, Feng G, Milyaev N, Ong CK, Kumar L, Lam M, Semple CA, Gyenesei A, Mundlos S, Radelof U, Lehrach H, Sarmientos P, Reymond A, Davidson DR, Dollé P, Antonarakis SE, Yaspo ML, Martinez S, Baldock RA, Eichele G and Ballabio A

    Telethon Institute of Genetics and Medicine, Naples, Italy.

    Ascertaining when and where genes are expressed is of crucial importance to understanding or predicting the physiological role of genes and proteins and how they interact to form the complex networks that underlie organ development and function. It is, therefore, crucial to determine on a genome-wide level, the spatio-temporal gene expression profiles at cellular resolution. This information is provided by colorimetric RNA in situ hybridization that can elucidate expression of genes in their native context and does so at cellular resolution. We generated what is to our knowledge the first genome-wide transcriptome atlas by RNA in situ hybridization of an entire mammalian organism, the developing mouse at embryonic day 14.5. This digital transcriptome atlas, the Eurexpress atlas (http://www.eurexpress.org), consists of a searchable database of annotated images that can be interactively viewed. We generated anatomy-based expression profiles for over 18,000 coding genes and over 400 microRNAs. We identified 1,002 tissue-specific genes that are a source of novel tissue-specific markers for 37 different anatomical structures. The quality and the resolution of the data revealed novel molecular domains for several developing structures, such as the telencephalon, a novel organization for the hypothalamus, and insight on the Wnt network involved in renal epithelial differentiation during kidney development. The digital transcriptome atlas is a powerful resource to determine co-expression of genes, to identify cell populations and lineages, and to identify functional associations between genes relevant to development and disease.

    Funded by: Medical Research Council: MC_U127527203; Telethon: TGM11S03

    PLoS biology 2011;9;1;e1000582

  • Nestin is required for the proper self-renewal of neural stem cells.

    Park D, Xiang AP, Mao FF, Zhang L, Di CG, Liu XM, Shao Y, Ma BF, Lee JH, Ha KS, Walton N and Lahn BT

    Department of Human Genetics, University of Chicago, Howard Hughes Medical Institute, Chicago, Illinois, USA. donghyun@uchicago.edu

    The intermediate filament protein, nestin, is a widely employed marker of multipotent neural stem cells (NSCs). Recent in vitro studies have implicated nestin in a number of cellular processes, but there is no data yet on its in vivo function. Here, we report the construction and functional characterization of Nestin knockout mice. We found that these mice show embryonic lethality, with neuroepithelium of the developing neural tube exhibiting significantly fewer NSCs and much higher levels of apoptosis. Consistent with this in vivo observation, NSC cultures derived from knockout embryos show dramatically reduced self-renewal ability that is associated with elevated apoptosis but no overt defects in cell proliferation or differentiation. Unexpectedly, nestin deficiency has no detectable effect on the integrity of the cytoskeleton. Furthermore, the knockout of Vimentin, which abolishes nestin's ability to polymerize into intermediate filaments in NSCs, does not lead to any apoptotic phenotype. These data demonstrate that nestin is important for the proper survival and self-renewal of NSCs, and that this function is surprisingly uncoupled from nestin's structural involvement in the cytoskeleton.

    Funded by: Howard Hughes Medical Institute

    Stem cells (Dayton, Ohio) 2010;28;12;2162-71

  • Reversal of neuropathy phenotypes in conditional mouse model of Charcot-Marie-Tooth disease type 2E.

    Dequen F, Filali M, Larivière RC, Perrot R, Hisanaga S and Julien JP

    Research Centre of CHUQ, Department of Psychiatry and Neurosciences, Laval University, Québec, Canada.

    Mutations in the gene encoding for the neurofilament light subunit (NF-L) are responsible for Charcot-Marie-Tooth (CMT) neuropathy type 2E. To address whether CMT2E disease is potentially reversible, we generated a mouse model with conditional doxycycline-responsive gene system that allows repression of mutant hNF-LP22S transgene expression in adult neurons. The hNF-LP22S;tTa transgenic (tg) mice recapitulated key features of CMT2E disease, including aberrant hindlimb posture, motor deficits, hypertrophy of muscle fibres and loss of muscle innervation without neuronal loss. Remarkably, a 3-month treatment of hNF-LP22S;tTa mice with doxycycline after onset of disease efficiently down-regulated expression of hNF-LP22S and it caused reversal of CMT neurological phenotypes with restoration of muscle innervation and of neurofilament protein distribution along the sciatic nerve. These data suggest that therapeutic approaches aimed at abolishing expression or neutralizing hNF-L mutants might not only halt the progress of CMT2E disease, but also revert the disabilities.

    Funded by: Canadian Institutes of Health Research

    Human molecular genetics 2010;19;13;2616-29

  • Basal enrichment within neuroepithelia suggests novel function(s) for Celsr1 protein.

    Formstone CJ, Moxon C, Murdoch J, Little P and Mason I

    MRC Centre for Developmental Biology, New Hunts House, Kings College, London SE1 1UL, UK. caroline.formstone@kcl.ac.uk <caroline.formstone@kcl.ac.uk&gt;

    A characteristic of the 7TM-cadherins, Flamingo and Celsr1, is their asymmetric protein distribution and polarized activity at neighboring epithelial cell interfaces along defined axes of planar cell polarity. Here, we describe a novel distribution of Celsr1 protein to the basal surface of neuroepithelial cells within both the early neural tube and a less well-defined group of ventricular zone cells at the midline of the developing spinal cord. Importantly, this basal enrichment is lost in embryos homozygous for a mutant Celsr1 allele. We also demonstrate an intimate association between basal enrichment of Celsr1 protein and dorsal sensory tract morphogenesis, an intriguing spatio-temporal organization of Celsr1 protein along the apico-basal neuroepithelial axis suggestive of multiple Celsr1 protein isoforms and the existence of distinct cell surface Celsr1 protein species with direct signaling potential. Together, these data raise compelling new questions concerning the role of Celsr1 during neural development.

    Funded by: Biotechnology and Biological Sciences Research Council; Medical Research Council; Wellcome Trust

    Molecular and cellular neurosciences 2010;44;3;210-22

  • A genomic atlas of mouse hypothalamic development.

    Shimogori T, Lee DA, Miranda-Angulo A, Yang Y, Wang H, Jiang L, Yoshida AC, Kataoka A, Mashiko H, Avetisyan M, Qi L, Qian J and Blackshaw S

    RIKEN-BSI, 2-1 Hirosawa, Wako-shi, Saitama, Japan. tshimogori@brain.riken.jp

    The hypothalamus is a central regulator of many behaviors that are essential for survival, such as temperature regulation, food intake and circadian rhythms. However, the molecular pathways that mediate hypothalamic development are largely unknown. To identify genes expressed in developing mouse hypothalamus, we performed microarray analysis at 12 different developmental time points. We then conducted developmental in situ hybridization for 1,045 genes that were dynamically expressed over the course of hypothalamic neurogenesis. We identified markers that stably labeled each major hypothalamic nucleus over the entire course of neurogenesis and constructed a detailed molecular atlas of the developing hypothalamus. As a proof of concept of the utility of these data, we used these markers to analyze the phenotype of mice in which Sonic Hedgehog (Shh) was selectively deleted from hypothalamic neuroepithelium and found that Shh is essential for anterior hypothalamic patterning. Our results serve as a resource for functional investigations of hypothalamic development, connectivity, physiology and dysfunction.

    Funded by: NINDS NIH HHS: R21 NS067393

    Nature neuroscience 2010;13;6;767-75

  • BDNF+/- mice exhibit deficits in oligodendrocyte lineage cells of the basal forebrain.

    Vondran MW, Clinton-Luke P, Honeywell JZ and Dreyfus CF

    Department of Neuroscience and Cell Biology, UMDNJ/Robert Wood Johnson Medical School, Piscataway, New Jersey, USA.

    Previous work indicated that brain-derived neurotrophic factor (BDNF), through the trkB receptor, increases DNA synthesis in oligodendrocyte (OLG) progenitor cells (OPCs) and differentiation of postmitotic OLGs of the basal forebrain (BF). In the present studies, BDNF knockout animals were used to investigate BDNF's effects on OLG lineage cells (OLCs) in vivo. OLCs of the BF were found to express the trkB receptor, suggesting they are responsive to BDNF. Immunohistochemistry using NG2 and CC1 antibodies was utilized to examine the numbers of NG2+ OPCs and CC1+ postmitotic BF OLGs. At embryonic day 17 (E17), BDNF-/- animals display reduced NG2+ cells. This reduction was also observed in BDNF+/- mice at E17 and at postnatal day 1 (P1), P14, and adult stage, suggesting that BDNF plays a role in OPC development. BDNF+/- mice do not exhibit deficits in numbers of CC1+ OLGs. However, myelin basic protein, myelin associated glycoprotein, and proteolipid protein are reduced in BDNF+/- mice, suggesting that BDNF plays a role in differentiation. These data indicate that progenitor cells and myelin proteins may be affected in vivo by a decrease in BDNF.

    Funded by: NINDS NIH HHS: NS036647, R01 NS036647, R56 NS036647, R56 NS036647-08

    Glia 2010;58;7;848-56

  • Emx2 and early hair cell development in the mouse inner ear.

    Holley M, Rhodes C, Kneebone A, Herde MK, Fleming M and Steel KP

    Department of Biomedical Science, Addison Building, Western Bank, Sheffield S10 2TN, UK. m.c.holley@sheffield.ac.uk

    Emx2 is a homeodomain protein that plays a critical role in inner ear development. Homozygous null mice die at birth with a range of defects in the CNS, renal system and skeleton. The cochlea is shorter than normal with about 60% fewer auditory hair cells. It appears to lack outer hair cells and some supporting cells are either absent or fail to differentiate. Many of the hair cells differentiate in pairs and although their hair bundles develop normally their planar cell polarity is compromised. Measurements of cell polarity suggest that classic planar cell polarity molecules are not directly influenced by Emx2 and that polarity is compromised by developmental defects in the sensory precursor population or by defects in epithelial cues for cell alignment. Planar cell polarity is normal in the vestibular epithelia although polarity reversal across the striola is absent in both the utricular and saccular maculae. In contrast, cochlear hair cell polarity is disorganized. The expression domain for Bmp4 is expanded and Fgfr1 and Prox1 are expressed in fewer cells in the cochlear sensory epithelium of Emx2 null mice. We conclude that Emx2 regulates early developmental events that balance cell proliferation and differentiation in the sensory precursor population.

    Funded by: Medical Research Council: G0300212; Wellcome Trust

    Developmental biology 2010;340;2;547-56

  • Alternative splicing produces high levels of noncoding isoforms of bHLH transcription factors during development.

    Kanadia RN and Cepko CL

    Department of Genetics, Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02115, USA; and Department of Ophthalmology, Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.

    During development, multiple cell types within a tissue often arise from a common pool of progenitor cells (PCs). PCs typically expand in number, while simultaneously producing post-mitotic cells (PMCs). This balance is partly regulated by transcription factors that are expressed within PCs, such as the basic helix-loop-helix (bHLH) gene mouse atonal homolog 7 (Math5), which is expressed in retinal PCs. Here we report that alternative splicing (AS) of Math5 serves as another layer of regulation of Math5 activity. Specifically, Math5, a single exon gene, is alternatively spliced such that the major isoform lacks the entire coding sequence. Similarly, neurogenin 3 (Ngn3), a Math5 paralog expressed in pancreatic PCs, is also alternatively spliced such that the major isoform fails to code for Ngn3 protein. The consequence of reducing the abundance of protein-coding isoforms is likely crucial, as we found that introduction of coding isoforms leads to a reduction in cycling PCs. Thus, AS can limit the number of PCs expressing key regulatory proteins that control PC expansion versus PMC production.

    Funded by: Howard Hughes Medical Institute

    Genes & development 2010;24;3;229-34

  • Conditional deletion of beta1-integrin in astroglia causes partial reactive gliosis.

    Robel S, Mori T, Zoubaa S, Schlegel J, Sirko S, Faissner A, Goebbels S, Dimou L and Götz M

    Department of Physiological Genomics, Institute of Physiology, Ludwig-Maximilians University Munich, Munich, Germany.

    Astrocytes play many pivotal roles in the adult brain, including their reaction to injury. A hallmark of astrocytes is the contact of their endfeet with the basement membrane surrounding blood vessels, but still relatively little is known about the signaling mediated at the contact site. Here, we examine the role of beta1-integrin at this interface by its conditional deletion using different Cre lines. Thereby, the protein was reduced only at postnatal stages either in both glia and neurons or specifically only in neurons. Strikingly, only the former resulted in reactive gliosis, with the hallmarks of reactive astrocytes comprising astrocyte hypertrophy and up-regulation of the intermediate filaments GFAP and vimentin as well as pericellular components, such as Tenascin-C and the DSD-1 proteoglycan. In addition, we also observed to a certain degree a non-cell autonomous activation of microglial cells after conditional beta1-integrin deletion. However, these reactive astrocytes did not divide, suggesting that the loss of beta1-integrin-mediated signaling is not sufficient to elicit proliferation of these cells as observed after brain injury. Interestingly, this partial reactive gliosis appeared in the absence of cell death and blood brain barrier disturbances. As these effects did not appear after neuron-specific deletion of beta1-integrin, we conclude that beta1-integrin-mediated signaling in astrocytes is required to promote their acquisition of a mature, nonreactive state. Alterations in beta1-integrin-mediated signaling may hence be implicated in eliciting specific aspects of reactive gliosis after injury.

    Glia 2009;57;15;1630-47

  • Cytosolic TDP-43 expression following axotomy is associated with caspase 3 activation in NFL-/- mice: support for a role for TDP-43 in the physiological response to neuronal injury.

    Moisse K, Mepham J, Volkening K, Welch I, Hill T and Strong MJ

    Molecular Brain Research Group, Robarts Research Institute, PO Box 5015, 100 Perth Drive, London ON, Canada.

    TAR DNA binding protein (TDP-43) mislocalization has been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). We have recently reported that TDP-43 and PGRN expression is altered in response to axotomy in C57BL6 mice and that normal expression is restored following recovery. We have performed axotomies in two different presymptomatic models of motor neuron degeneration, low molecular weight neurofilament knockout (NFL(-/-)) mice and mutant SOD1(G93A) transgenic (mtSOD1(G93A)) mice aged 6 weeks, and observed TDP-43 and PGRN expression patterns in axotomized spinal motor neurons over 28 days. In contrast to both C57BL6 mice and mtSOD1(G93A) mice, behavioural deficits in NFL(-/-) mice were sustained. We did not observe differences in TDP-43 or PGRN expression between C57BL6 mice and mtSOD1(G93A) mice throughout the observation period. However, compared to C57BL6 mice and mtSOD1(G93A) mice, NFL(-/-) mice exhibited late upregulation of cytosolic TDP-43 expression and persistent downregulation of neuronal PGRN expression accompanied by caspase 3 activation on post-injury day 28. By post-injury day 42, no cytosolic TDP-43-positive neurons remained in NFL(-/-) mice, suggesting that they had undergone apoptotic cell death. These findings suggest that whereas TDP-43 expression is normally upregulated transiently following axotomy, in the absence of NFL this response is delayed and associated with caspase 3 activation and neuronal death. These results further support that TDP-43 is involved in neurofilament mRNA metabolism and transport, and provide insight into the pathogenesis of motor neuron death in ALS in which NFL mRNA levels are selectively suppressed.

    Brain research 2009;1296;176-86

  • The oligodendrocyte-specific G protein-coupled receptor GPR17 is a cell-intrinsic timer of myelination.

    Chen Y, Wu H, Wang S, Koito H, Li J, Ye F, Hoang J, Escobar SS, Gow A, Arnett HA, Trapp BD, Karandikar NJ, Hsieh J and Lu QR

    Department of Developmental Biology and Kent Waldrep Foundation Center for Basic Neuroscience Research on Nerve Growth and Regeneration, University of Texas Southwestern Medical Center, Dallas, Texas, USA.

    The basic helix-loop-helix transcription factor Olig1 promotes oligodendrocyte maturation and is required for myelin repair. We characterized an Olig1-regulated G protein-coupled receptor, GPR17, whose function is to oppose the action of Olig1. Gpr17 was restricted to oligodendrocyte lineage cells, but was downregulated during the peak period of myelination and in adulthood. Transgenic mice with sustained Gpr17 expression in oligodendrocytes exhibited stereotypic features of myelinating disorders in the CNS. Gpr17 overexpression inhibited oligodendrocyte differentiation and maturation both in vivo and in vitro. Conversely, Gpr17 knockout mice showed early onset of oligodendrocyte myelination. The opposing action of Gpr17 on oligodendrocyte maturation reflects, at least partially, upregulation and nuclear translocation of the potent oligodendrocyte differentiation inhibitors ID2/4. Collectively, these findings suggest that GPR17 orchestrates the transition between immature and myelinating oligodendrocytes via an ID protein-mediated negative regulation and may serve as a potential therapeutic target for CNS myelin repair.

    Funded by: NIAID NIH HHS: K24 AI079272, K24 AI079272-01A1, K24 AI079272-02; NINDS NIH HHS: R01 NS050389, R01 NS050389-05, R01 NS060017, R01 NS060017-01A1, R01 NS060017-02, R01 NS060017-03, R01 NS060017-04

    Nature neuroscience 2009;12;11;1398-406

  • Comparative analysis of uncoupling protein 4 distribution in various tissues under physiological conditions and during development.

    Smorodchenko A, Rupprecht A, Sarilova I, Ninnemann O, Bräuer AU, Franke K, Schumacher S, Techritz S, Nitsch R, Schuelke M and Pohl EE

    Institute of Cell Biology and Neurobiology, Charité - Universitätsmedizin, Berlin, Germany.

    UCP4 is a member of the mitochondrial uncoupling protein subfamily and one of the three UCPs (UCP2, UCP4, UCP5), associated with the nervous system. Its putative functions include thermogenesis, attenuation of reactive oxidative species (ROS), regulation of mitochondrial calcium concentration and involvement in cell differentiation and apoptosis. Here we investigate UCP4's subcellular, cellular and tissue distribution, using an antibody designed specially for this study, and discuss the findings in terms of the protein's possible functions. Western blot and immunohistochemistry data confirmed that UCP4 is expressed predominantly in the central nervous system (CNS), as previously shown at mRNA level. No protein was found in heart, spleen, stomach, intestine, lung, thymus, muscles, adrenal gland, testis and liver. The reports revealing UCP4 mRNA in kidney and white adipose tissue were not confirmed at protein level. The amount of UCP4 varies in the mitochondria of different brain regions, with the highest protein content found in cortex. We show that UCP4 is present in fetal murine brain tissue as early as embryonic days 12-14 (E12-E14), which coincides with the beginning of neuronal differentiation. The UCP4 content in mitochondria decreases as the age of mice increases. UCP4 preferential expression in neurons and its developmental expression pattern under physiological conditions may indicate a specific protein function, e.g. in neuronal cell differentiation.

    Biochimica et biophysica acta 2009;1788;10;2309-19

  • In vivo role for CREB signaling in the noradrenergic differentiation of sympathetic neurons.

    Rüdiger R, Binder E, Tsarovina K, Schmidt M, Reiff T, Stubbusch J and Rohrer H

    RG Developmental Neurobiology, Department Neurochemistry, Max-Planck-Institute for Brain Research, Deutschordenstr. 46, D-60528 Frankfurt/M, Germany.

    Signaling pathways involving cAMP and CREB have been implicated in several aspects of sympathetic neuron differentiation. Here, we used in vivo loss-of-function approaches in both mouse and chick embryos to characterize the physiological role of cAMP/CREB. Whereas sympathetic neuron development proceeds normally in CREB-deficient mouse embryos, a decrease in noradrenergic differentiation (TH, DBH) was observed in chick sympathetic ganglia in response to ACREB, a dominant-negative CREB variant which interferes with the function of all CREB family members. In contrast, expression of the generic neuronal marker SCG10 was not affected by ACREB. As the decrease in noradrenergic gene expression is compensated at later stages of development and TH expression in differentiated neurons is not CREB-dependent, a transient role for CREB is proposed, accelerating noradrenergic but not generic neuronal differentiation of sympathetic neurons.

    Molecular and cellular neurosciences 2009;42;2;142-51

  • Novel features of boundary cap cells revealed by the analysis of newly identified molecular markers.

    Coulpier F, Le Crom S, Maro GS, Manent J, Giovannini M, Maciorowski Z, Fischer A, Gessler M, Charnay P and Topilko P

    INSERM, CNRS, IFR36, Plate-forme Transcriptome, 46 rue d'Ulm, 75230 Paris Cedex 05, France.

    Neural crest (NC) cells are a multipotent, highly migratory cell population that generates most of the components of the peripheral nervous system (PNS), including the glial Schwann cells (SC) and boundary cap (BC) cells. These latter cells are located at the interface between the central nervous system and PNS, at the exit/entry points of ventral motor/dorsal sensory axons and give rise to all SC in the nerve roots and to a subset of nociceptive neurons and satellite cells in the dorsal root ganglia. In the present study we have compared BC cells with two closely related cell types, NC and Schwann cell precursors (SCpr), by RNA profiling. This led to the definition of a set of 10 genes that show specific expression in BC cells and/or in their derivatives along the nerve roots. Analysis of the expression of these genes during mouse development revealed novel features, of those most important are: (i) dorsal and ventral nerve root BC cell derivatives express different sets of genes, suggesting that they have distinct properties; (ii) these cells undergo major modifications in their gene expression pattern between embryonic days 14.5 and 17.5, possibly linked to the SCpr-immature Schwann cell transition; (iii) nerve roots SC differ from more distal SC not only in their origins and locations, but also in their gene expression patterns. In conclusion, the identification of these novel makers opens the way for a detailed characterization of BC cells in both mouse and man.

    Glia 2009;57;13;1450-7

  • MSC p43 required for axonal development in motor neurons.

    Zhu X, Liu Y, Yin Y, Shao A, Zhang B, Kim S and Zhou J

    Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai 200031, China.

    Neuron connectivity and correct neural function largely depend on axonal integrity. Neurofilaments (NFs) constitute the main cytoskeletal network maintaining the structural integrity of neurons and exhibit dynamic changes during axonal and dendritic growth. However, the mechanisms underlying axonal development and maintenance remain poorly understood. Here, we identify that multisynthetase complex p43 (MSC p43) is essential for NF assembly and axon maintenance. The MSC p43 protein was predominantly expressed in central neurons and interacted with NF light subunit in vivo. Mice lacking MSC p43 exhibited axon degeneration in motor neurons, defective neuromuscular junctions, muscular atrophy, and motor dysfunction. Furthermore, MSC p43 depletion in mice caused disorganization of the axonal NF network. Mechanistically, MSC p43 is required for maintaining normal phosphorylation levels of NFs. Thus, MSC p43 is indispensable in maintaining axonal integrity. Its dysfunction may underlie the NF disorganization and axon degeneration associated with motor neuron degenerative diseases.

    Proceedings of the National Academy of Sciences of the United States of America 2009;106;37;15944-9

  • Neurofilaments bind tubulin and modulate its polymerization.

    Bocquet A, Berges R, Frank R, Robert P, Peterson AC and Eyer J

    Laboratoire Neurobiologie and Transgenese, Unité Propre de Recherche de l'Enseignement Supérieur EA3143, Inserm, Centre Hospitalier Universitaire, 49033 Angers, France.

    Neurofilaments assemble from three intermediate-filament proteins, contribute to the radial growth of axons, and are exceptionally stable. Microtubules are dynamic structures that assemble from tubulin dimers to support intracellular transport of molecules and organelles. We show here that neurofilaments, and other intermediate-filament proteins, contain motifs in their N-terminal domains that bind unassembled tubulin. Peptides containing such motifs inhibit the in vitro polymerization of microtubules and can be taken up by cultured cells in which they disrupt microtubules leading to altered cell shapes and an arrest of division. In transgenic mice in which neurofilaments are withheld from the axonal compartment, axonal tubulin accumulation is normal but microtubules assemble in excessive numbers. These observations suggest a model in which axonal neurofilaments modulate local microtubule assembly. This capacity also suggests novel mechanisms through which inherited or acquired disruptions in intermediate filaments might contribute to pathogenesis in multiple conditions.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2009;29;35;11043-54

  • Neuronal differentiation is regulated by leucine-rich acidic nuclear protein (LANP), a member of the inhibitor of histone acetyltransferase complex.

    Kular RK, Cvetanovic M, Siferd S, Kini AR and Opal P

    Davee Department of Neurology and Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA.

    Neuronal differentiation is a tightly regulated process characterized by temporal and spatial alterations in gene expression. A number of studies indicate a significant role for histone acetylation in the regulation of genes involved in development. Histone acetylation is regulated by histone deacetylases and histone acetyltransferases. Recent findings suggest that these catalytic activities, in turn, are modulated by yet another set of regulators. Of considerable interest in this context is the possible role of the INHAT (inhibitor of histone acetyltransferase) complex, comprised of a group of acidic proteins that suppress histone acetylation by a novel "histone-masking" mechanism. In this study, we specifically examined the role of the leucine-rich acidic nuclear protein (LANP), a defining member of the INHAT complex whose expression is tightly regulated in neuronal development. We report that depleting LANP in neuronal cell lines promotes neurite outgrowth by inducing changes in gene expression. In addition, we show that LANP directly regulates expression of the neurofilament light chain, an important neuron-specific cytoskeletal gene, by binding to the promoter of this gene and modulating histone acetylation levels. Finally, we corroborated our findings in vivo by demonstrating increased neurite outgrowth in primary neurons obtained from LANP null mice, which is also accompanied by increased histone acetylation at the NF-L promoter. Taken together, these results implicate INHATs as a distinct class of developmental regulators involved in the epigenetic modulation of neuronal differentiation.

    Funded by: NINDS NIH HHS: 5T32 NS41234-01, K02 NS051340, K08 NS02246, R21 NS060080

    The Journal of biological chemistry 2009;284;12;7783-92

  • Essential and overlapping functions for mammalian Argonautes in microRNA silencing.

    Su H, Trombly MI, Chen J and Wang X

    Department of Biochemistry, Northwestern University, Evanston, Illinois 60208, USA.

    MicroRNA (miRNA) silencing fine-tunes protein output and regulates diverse biological processes. Argonaute (Ago) proteins are the core effectors of the miRNA pathway. In lower organisms, multiple Agos have evolved specialized functions for distinct RNA silencing pathways. However, the roles of mammalian Agos have not been well characterized. Here we show that mouse embryonic stem (ES) cells deficient for Ago1-4 are completely defective in miRNA silencing and undergo apoptosis. In miRNA silencing-defective ES cells, the proapoptotic protein Bim, a miRNA target, is increased, and up-regulation of Bim is sufficient to induce ES cell apoptosis. Expression of activated Akt inhibits Bim expression and partially rescues the growth defect in Ago-deficient ES cells. Furthermore, reintroduction of any single Ago into Ago-deficient cells is able to rescue the endogenous miRNA silencing defect and apoptosis. Consistent with this, each Ago is functionally equivalent with bulged miRNA duplexes for translational repression, whereas Ago1 and Ago2 appear to be more effective at utilizing perfectly matched siRNAs. Thus, our results demonstrate that mammalian Agos all contribute to miRNA silencing, and individual Agos have largely overlapping functions in this process.

    Funded by: NIGMS NIH HHS: 5R21GM079528

    Genes & development 2009;23;3;304-17

  • The bHLH transcription factor Olig3 marks the dorsal neuroepithelium of the hindbrain and is essential for the development of brainstem nuclei.

    Storm R, Cholewa-Waclaw J, Reuter K, Bröhl D, Sieber M, Treier M, Müller T and Birchmeier C

    Max-Delbrück-Centrum for Molecular Medicine, Robert-Rössle-Strasse 10, 13125 Berlin, Germany.

    The Olig3 gene encodes a bHLH factor that is expressed in the ventricular zone of the dorsal alar plate of the hindbrain. We found that the Olig3(+) progenitor domain encompassed subdomains that co-expressed Math1, Ngn1, Mash1 and Ptf1a. Olig3(+) cells give rise to neuronal types in the dorsal alar plate that we denote as class A neurons. We used genetic lineage tracing to demonstrate that class A neurons contribute to the nucleus of the solitary tract and to precerebellar nuclei. The fate of class A neurons was not correctly determined in Olig3 mutant mice. As a consequence, the nucleus of the solitary tract did not form, and precerebellar nuclei, such as the inferior olivary nucleus, were absent or small. At the expense of class A neurons, ectopic Lbx1(+) neurons appeared in the alar plate in Olig3 mutant mice. By contrast, electroporation of an Olig3 expression vector in the chick hindbrain suppressed the emergence of Lbx1(+) neurons. Climbing fiber neurons of the inferior olivary nucleus express Foxd3 and require Olig3 as well as Ptf1a for the determination of their fate. We observed that electroporation of Olig3 and Ptf1a expression vectors, but not either alone, induced Foxd3. We therefore propose that Olig3 can cooperate with Ptf1a to determine the fate of climbing fiber neurons of the inferior olivary nucleus.

    Development (Cambridge, England) 2009;136;2;295-305

  • Temporal requirement of the alternative-splicing factor Sfrs1 for the survival of retinal neurons.

    Kanadia RN, Clark VE, Punzo C, Trimarchi JM and Cepko CL

    Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.

    Alternative splicing is the primary mechanism by which a limited number of protein-coding genes can generate proteome diversity. We have investigated the role of the alternative-splicing factor Sfrs1, an arginine/serine-rich (SR) protein family member, during mouse retinal development. Loss of Sfrs1 function during embryonic retinal development had a profound effect, leading to a small retina at birth. In addition, the retina underwent further degeneration in the postnatal period. Loss of Sfrs1 function resulted in the death of retinal neurons that were born during early to mid-embryonic development. Ganglion cells, cone photoreceptors, horizontal cells and amacrine cells were produced and initiated differentiation. However, these neurons subsequently underwent cell death through apoptosis. By contrast, Sfrs1 was not required for the survival of the neurons generated later, including later-born amacrine cells, rod photoreceptors, bipolar cells and Müller glia. Our results highlight the requirement of Sfrs1-mediated alternative splicing for the survival of retinal neurons, with sensitivity defined by the window of time in which the neuron was generated.

    Funded by: Howard Hughes Medical Institute

    Development (Cambridge, England) 2008;135;23;3923-33

  • Proteomics analysis identifies phosphorylation-dependent alpha-synuclein protein interactions.

    McFarland MA, Ellis CE, Markey SP and Nussbaum RL

    National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20891, USA.

    Mutations and copy number variation in the SNCA gene encoding the neuronal protein alpha-synuclein have been linked to familial Parkinson disease (Thomas, B., and Beal, M. F. (2007) Parkinson's disease. Hum. Mol. Genet. 16, R183-R194). The carboxyl terminus of alpha-synuclein can be phosphorylated at tyrosine 125 and serine 129, although only a small fraction of the protein is phosphorylated under normal conditions (Okochi, M., Walter, J., Koyama, A., Nakajo, S., Baba, M., Iwatsubo, T., Meijer, L., Kahle, P. J., and Haass, C. (2000) Constitutive phosphorylation of the Parkinson's disease associated alpha-synuclein. J. Biol. Chem. 275, 390-397). Under pathological conditions, such as in Parkinson disease, alpha-synuclein is a major component of Lewy bodies, a pathological hallmark of Parkinson disease, and is mostly phosphorylated at Ser-129 (Anderson, J. P., Walker, D. E., Goldstein, J. M., de Laat, R., Banducci, K., Caccavello, R. J., Barbour, R., Huang, J. P., Kling, K., Lee, M., Diep, L., Keim, P. S., Shen, X. F., Chataway, T., Schlossmacher, M. G., Seubert, P., Schenk, D., Sinha, S., Gai, W. P., and Chilcote, T. J. (2006) Phosphorylation of Ser-129 is the dominant pathological modification of alpha-synuclein in familial and sporadic Lewy body disease. J. Biol. Chem. 281, 29739-29752). Controversy exists over the extent to which phosphorylation of alpha-synuclein and/or the visible protein aggregation in Lewy bodies are steps in disease pathogenesis, are protective, or are neutral markers for the disease process. Here we used the combination of peptide pulldown assays and mass spectrometry to identify and compare protein-protein interactions of phosphorylated and non-phosphorylated alpha-synuclein. We showed that non-phosphorylated alpha-synuclein carboxyl terminus pulled down protein complexes that were highly enriched for mitochondrial electron transport proteins, whereas alpha-synuclein carboxyl terminus phosphorylated on either Ser-129 or Tyr-125 did not. Instead the set of proteins pulled down by phosphorylated alpha-synuclein was highly enriched in certain cytoskeletal proteins, in vesicular trafficking proteins, and in a small number of enzymes involved in protein serine phosphorylation. This targeted comparative proteomics approach for unbiased identification of protein-protein interactions suggests that there are functional consequences when alpha-synuclein is phosphorylated.

    Funded by: Intramural NIH HHS; NIMH NIH HHS: Z01 MH000279

    Molecular & cellular proteomics : MCP 2008;7;11;2123-37

  • Rewiring the retinal ganglion cell gene regulatory network: Neurod1 promotes retinal ganglion cell fate in the absence of Math5.

    Mao CA, Wang SW, Pan P and Klein WH

    Department of Biochemistry and Molecular Biology, The University of Texas M. D. Anderson Cancer Center, Medical School, Houston, TX 77030, USA.

    Retinal progenitor cells (RPCs) express basic helix-loop-helix (bHLH) factors in a strikingly mosaic spatiotemporal pattern, which is thought to contribute to the establishment of individual retinal cell identity. Here, we ask whether this tightly regulated pattern is essential for the orderly differentiation of the early retinal cell types and whether different bHLH genes have distinct functions that are adapted for each RPC. To address these issues, we replaced one bHLH gene with another. Math5 is a bHLH gene that is essential for establishing retinal ganglion cell (RGC) fate. We analyzed the retinas of mice in which Math5 was replaced with Neurod1 or Math3, bHLH genes that are expressed in another RPC and are required to establish amacrine cell fate. In the absence of Math5, Math5Neurod1-KI was able to specify RGCs, activate RGC genes and restore the optic nerve, although not as effectively as Math5. By contrast, Math5Math3-KI was much less effective than Math5Neurod1-KI in replacing Math5. In addition, expression of Neurod1 and Math3 from the Math5Neurod1-KI/Math3-KI allele did not result in enhanced amacrine cell production. These results were unexpected because they indicated that bHLH genes, which are currently thought to have evolved highly specialized functions, are nonetheless able to adjust their functions by interpreting the local positional information that is programmed into the RPC lineages. We conclude that, although Neurod1 and Math3 have evolved specialized functions for establishing amacrine cell fate, they are nevertheless capable of alternative functions when expressed in foreign environments.

    Funded by: NCI NIH HHS: CA016672; NEI NIH HHS: EY010608-139005, EY011930

    Development (Cambridge, England) 2008;135;20;3379-88

  • Acrolein, the toxic endogenous aldehyde, induces neurofilament-L aggregation.

    Jeong MS and Kang JH

    Department of Genetic Engineering, Cheongju University, Cheongju, South Korea.

    Acrolein is a highly reactive by product of lipid peroxidation and individuals with neurodegenerative disorders have been shown to contain elevated concentrations of this molecule in the brain. In the present study, we examined the pattern of neurofilament-L (NF-L) modification elicited by acrolein. When NF-L was incubated with acrolein, protein aggregation occurred in a acrolein concentration-dependent manner. Exposure of NF-L to acrolein also led to the generation of protein carbonyl compounds. Through the addition of free radical scavengers we observed a significant decrease in acrolein-mediated NF-L aggregation. These results indicate that free radicals may be involved in the modification of NF-L by acrolein. In addition, dityrosine crosslink formation was observed in acrolein-mediated NF-L aggregates and these aggregates displayed thioflavin T reactivity, reminiscent of amyloid. This study suggests that acrolein-mediated NF-L aggregation might be closely related to oxidative reactions, thus these reactions may play a critical role in neurodegenerative diseases.

    BMB reports 2008;41;9;635-9

  • Als2 mRNA splicing variants detected in KO mice rescue severe motor dysfunction phenotype in Als2 knock-down zebrafish.

    Gros-Louis F, Kriz J, Kabashi E, McDearmid J, Millecamps S, Urushitani M, Lin L, Dion P, Zhu Q, Drapeau P, Julien JP and Rouleau GA

    Department of Medicine, Center for Excellence in Neuromics, CHUM Research Center, University of Montreal, Montreal, QC, Canada.

    Recessive ALS2 mutations are linked to three related but slightly different neurodegenerative disorders: amyotrophic lateral sclerosis, hereditary spastic paraplegia and primary lateral sclerosis. To investigate the function of the ALS2 encoded protein, we generated Als2 knock-out (KO) mice and zAls2 knock-down zebrafish. The Als2(-/-) mice lacking exon 2 and part of exon 3 developed mild signs of neurodegeneration compatible with axonal transport deficiency. In contrast, zAls2 knock-down zebrafish had severe developmental abnormalities, swimming deficits and motor neuron perturbation. We identified, by RT-PCR, northern and western blotting novel Als2 transcripts in mouse central nervous system. These Als2 transcripts were present in Als2 null mice as well as in wild-type littermates and some rescued the zebrafish phenotype. Thus, we speculate that the newly identified Als2 mRNA species prevent the Als2 KO mice from developing severe neurodegenerative disease and might also regulate the severity of the motor neurons phenotype observed in ALS2 patients.

    Human molecular genetics 2008;17;17;2691-702

  • Deficiency in ubiquitin ligase TRIM2 causes accumulation of neurofilament light chain and neurodegeneration.

    Balastik M, Ferraguti F, Pires-da Silva A, Lee TH, Alvarez-Bolado G, Lu KP and Gruss P

    Max Planck Institute of Biophysical Chemistry, 37077 Goettingen, Germany. mbalasti@bidmc.harvard.edu

    TRIM RING finger proteins have been shown to play an important role in cancerogenesis, in the pathogenesis of some human hereditary disorders, and in the defense against viral infection, but the function of the majority of TRIM proteins remains unknown. Here, we show that TRIM RING finger protein TRIM2, highly expressed in the nervous system, is an UbcH5a-dependent ubiquitin ligase. We further demonstrate that TRIM2 binds to neurofilament light subunit (NF-L) and regulates NF-L ubiquitination. Additionally, we show that mice deficient in TRIM2 have increased NF-L level in axons and NF-L-filled axonal swellings in cerebellum, retina, spinal cord, and cerebral cortex. The axonopathy is followed by progressive neurodegeneration accompanied by juvenile-onset tremor and ataxia. Our results demonstrate that TRIM2 is an ubiquitin ligase and point to a mechanism regulating NF-L metabolism through an ubiquitination pathway that, if deregulated, triggers neurodegeneration.

    Funded by: NIA NIH HHS: AG022082, R01 AG022082

    Proceedings of the National Academy of Sciences of the United States of America 2008;105;33;12016-21

  • Structural requirement of TAG-1 for retinal ganglion cell axons and myelin in the mouse optic nerve.

    Chatzopoulou E, Miguez A, Savvaki M, Levasseur G, Muzerelle A, Muriel MP, Goureau O, Watanabe K, Goutebroze L, Gaspar P, Zalc B, Karagogeos D and Thomas JL

    Institut National de la Santé et de la Recherche Médicale, Unité 711, Université Pierre et Marie Curie, Faculté de Médecine, Hôpital de la Salpêtrière, Institut Fédératif de Recherche 70, F-75013 Paris, France.

    White matter axons organize into fascicles that grow over long distances and traverse very diverse environments. The molecular mechanisms preserving this structure of white matter axonal tracts are not well known. Here, we used the optic nerve as a model and investigated the role of TAG-1, a cell adhesion molecule expressed by retinal axons. TAG-1 was first expressed in the embryonic retinal ganglion cells (RGCs) and later in the postnatal myelin-forming cells in the optic nerve. We describe the consequences of genetic loss of Tag-1 on the developing and adult retinogeniculate tract. Tag-1-null embryos display anomalies in the caliber of RGC axons, associated with an abnormal organization of the astroglial network in the optic nerve. The contralateral projections in the lateral geniculate nucleus are expanded postnatally. In the adult, Tag-1-null mice show a loss of RGC axons, with persistent abnormalities of axonal caliber and additional cytoskeleton and myelination defects. Therefore, TAG-1 is an essential regulator of the structure of RGC axons and their surrounding glial cells in the optic nerve.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2008;28;30;7624-36

  • Identification of Phox2b-regulated genes by expression profiling of cranial motoneuron precursors.

    Pla P, Hirsch MR, Le Crom S, Reiprich S, Harley VR and Goridis C

    Ecole normale supérieure, Département de Biologie, 75005 Paris, France. Patrick.Pla@curie.u-psud.fr

    Background: Branchiomotor neurons comprise an important class of cranial motor neurons that innervate the branchial-arch-derived muscles of the face, jaw and neck. They arise in the ventralmost progenitor domain of the rhombencephalon characterized by expression of the homeodomain transcription factors Nkx2.2 and Phox2b. Phox2b in particular plays a key role in the specification of branchiomotor neurons. In its absence, generic neuronal differentiation is defective in the progenitor domain and no branchiomotor neurons are produced. Conversely, ectopic expression of Phox2b in spinal regions of the neural tube promotes cell cycle exit and neuronal differentiation and, at the same time, induces genes and an axonal phenotype characteristic for branchiomotor neurons. How Phox2b exerts its pleiotropic functions, both as a proneural gene and a neuronal subtype determinant, has remained unknown.

    Results: To gain further insights into the genetic program downstream of Phox2b, we searched for novel Phox2b-regulated genes by cDNA microarray analysis of facial branchiomotor neuron precursors from heterozygous and homozygous Phox2b mutant embryos. We selected for functional studies the genes encoding the axonal growth promoter Gap43, the Wnt antagonist Sfrp1 and the transcriptional regulator Sox13, which were not previously suspected to play roles downstream of Phox2b and whose expression was affected by Phox2b misexpression in the spinal cord. While Gap43 did not produce an obvious phenotype when overexpressed in the neural tube, Sfrp1 induced the interneuron marker Lhx1,5 and Sox13 inhibited neuronal differentiation. We then tested whether Sfrp1 and Sox13, which are down-regulated by Phox2b in the facial neuron precursors, would antagonize some aspects of Phox2b activity. Co-expression of Sfrp1 prevented Phox2b from repressing Lhx1,5 and alleviated the commissural axonal phenotype. When expressed together with Sox13, Phox2b was still able to promote cell cycle exit and neuronal differentiation, but the cells failed to relocate to the mantle layer and to extinguish the neural stem cell marker Sox2.

    Conclusion: Our results suggest novel roles for Sfrp1 and Sox13 in neuronal subtype specification and generic neuronal differentiation, respectively, and indicate that down-regulation of Sfrp1 and Sox13 are essential aspects of the genetic program controlled by Phox2b in cranial motoneurons.

    Neural development 2008;3;14

  • Robos are required for the correct targeting of retinal ganglion cell axons in the visual pathway of the brain.

    Plachez C, Andrews W, Liapi A, Knoell B, Drescher U, Mankoo B, Zhe L, Mambetisaeva E, Annan A, Bannister L, Parnavelas JG, Richards LJ and Sundaresan V

    The University of Maryland, Baltimore, School of Medicine, Baltimore, Maryland, USA.

    Axonal projections from the retina to the brain are regulated by molecules including the Slit family of ligands [Thompson, H., Barker, D., Camand, O., Erskine, L., 2006a. Slits contribute to the guidance of retinal ganglion cell axons in the mammalian optic tract. Dev. Biol. 296, 476-484, Thompson, H., Camand, O., Barker, D., Erskine, L., 2006b. Slit proteins regulate distinct aspects of retinal ganglion cell axon guidance within dorsal and ventral retina. J. Neurosci. 26, 8082-8091]. However, the roles of Slit receptors in mammals, (termed Robos), have not been investigated in visual system development. Here we examined Robo1 and 2 mutant mice and found that Robos regulate the correct targeting of retinal ganglion cell (RGC) axons along the entire visual projection. We noted aberrant projections of RGC axons into the cerebral cortex, an area not normally targeted by RGC axons. The optic chiasm was expanded along the rostro-caudal axis (similar to Slit mutant mice, Plump, A.S., Erskine, L., Sabatier, C., Brose, K., Epstein, C.J., Goodman, C.S., Mason, C.A., Tessier-Lavigne, M., 2002. Slit1 and Slit2 cooperate to prevent premature midline crossing of retinal axons in the mouse visual system. Neuron 33, 219-232), with ectopic crossing points, and some axons projecting caudally toward the corticospinal tract. Further, we found that axons exuberantly projected into the diencephalon. These defects were more pronounced in Robo2 than Robo1 knockout animals, implicating Robo2 as the predominant Robo receptor in visual system development.

    Funded by: Wellcome Trust: 074549

    Molecular and cellular neurosciences 2008;37;4;719-30

  • Eomesodermin, a target gene of Pou4f2, is required for retinal ganglion cell and optic nerve development in the mouse.

    Mao CA, Kiyama T, Pan P, Furuta Y, Hadjantonakis AK and Klein WH

    Department of Biochemistry and Molecular Biology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.

    The mechanisms regulating retinal ganglion cell (RGC) development are crucial for retinogenesis and for the establishment of normal vision. However, these mechanisms are only vaguely understood. RGCs are the first neuronal lineage to segregate from pluripotent progenitors in the developing retina. As output neurons, RGCs display developmental features very distinct from those of the other retinal cell types. To better understand RGC development, we have previously constructed a gene regulatory network featuring a hierarchical cascade of transcription factors that ultimately controls the expression of downstream effector genes. This has revealed the existence of a Pou domain transcription factor, Pou4f2, that occupies a key node in the RGC gene regulatory network and that is essential for RGC differentiation. However, little is known about the genes that connect upstream regulatory genes, such as Pou4f2 with downstream effector genes responsible for RGC differentiation. The purpose of this study was to characterize the retinal function of eomesodermin (Eomes), a T-box transcription factor with previously unsuspected roles in retinogenesis. We show that Eomes is expressed in developing RGCs and is a mediator of Pou4f2 function. Pou4f2 directly regulates Eomes expression through a cis-regulatory element within a conserved retinal enhancer. Deleting Eomes in the developing retina causes defects reminiscent of those in Pou4f2(-/-) retinas. Moreover, myelin ensheathment in the optic nerves of Eomes(-/-) embryos is severely impaired, suggesting that Eomes regulates this process. We conclude that Eomes is a crucial regulator positioned immediately downstream of Pou4f2 and is required for RGC differentiation and optic nerve development.

    Funded by: NCI NIH HHS: CA16672, P30 CA008748, P30 CA016672; NEI NIH HHS: EY010608-139005, EY013128, EY11930, R01 EY011930, R01 EY013128; NICHD NIH HHS: HD052115, R01 HD052115, R01 HD052115-03

    Development (Cambridge, England) 2008;135;2;271-80

  • Genetically-directed, cell type-specific sparse labeling for the analysis of neuronal morphology.

    Rotolo T, Smallwood PM, Williams J and Nathans J

    Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA.

    Background: In mammals, genetically-directed cell labeling technologies have not yet been applied to the morphologic analysis of neurons with very large and complex arbors, an application that requires extremely sparse labeling and that is only rendered practical by limiting the labeled population to one or a few predetermined neuronal subtypes.

    In the present study we have addressed this application by using CreER technology to non-invasively label very small numbers of neurons so that their morphologies can be fully visualized. Four lines of IRES-CreER knock-in mice were constructed to permit labeling selectively in cholinergic or catecholaminergic neurons [choline acetyltransferase (ChAT)-IRES-CreER or tyrosine hydroxylase (TH)-IRES-CreER], predominantly in projection neurons [neurofilament light chain (NFL)-IRES-CreER], or broadly in neurons and some glia [vesicle-associated membrane protein2 (VAMP2)-IRES-CreER]. When crossed to the Z/AP reporter and exposed to 4-hydroxytamoxifen in the early postnatal period, the number of neurons expressing the human placental alkaline phosphatase reporter can be reproducibly lowered to fewer than 50 per brain. Sparse Cre-mediated recombination in ChAT-IRES-CreER;Z/AP mice shows the full axonal and dendritic arbors of individual forebrain cholinergic neurons, the first time that the complete morphologies of these very large neurons have been revealed in any species.

    Conclusions: Sparse genetically-directed, cell type-specific neuronal labeling with IRES-creER lines should prove useful for studying a wide variety of questions in neuronal development and disease.

    Funded by: Howard Hughes Medical Institute

    PloS one 2008;3;12;e4099

  • Disruption of neurofilament network with aggregation of light neurofilament protein: a common pathway leading to motor neuron degeneration due to Charcot-Marie-Tooth disease-linked mutations in NFL and HSPB1.

    Zhai J, Lin H, Julien JP and Schlaepfer WW

    Division of Neuropathology, Department of Pathology and Laboratory Medicine, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104,-6100, USA. jinbin@mail.med.upenn.edu

    Mutations in neurofilament light (NFL) subunit and small heat-shock protein B1 (HSPB1) cause autosomal-dominant axonal Charcot-Marie-Tooth disease type 2E (CMT2E) and type 2F (CMT2F). Previous studies have shown that CMT mutations in NFL and HSPB1 disrupt NF assembly and cause aggregation of NFL protein. In this study, we investigate the role of aggregation of NFL protein in the neurotoxicity of CMT mutant NFL and CMT mutant HSPB1 in motor neurons. We find that expression of CMT mutant NFL leads to progressive degeneration and loss of neuronal viability of cultured motor neurons. Degenerating motor neurons show fragmentation and loss of neuritic processes associated with disruption of NF network and aggregation of NFL protein. Co-expression of wild-type HSPB1 diminishes aggregation of CMT mutant NFL, induces reversal of CMT mutant NFL aggregates and reduces CMT mutant NFL-induced loss of motor neuron viability. Like CMT mutant NFL, expression of S135F CMT mutant HSPB1 also leads to progressive degeneration of motor neurons with disruption of NF network and aggregation of NFL protein. Further studies show that wild-type and S135F mutant HSPB1 associate with wild-type and CMT mutant NFL and that S135F mutant HSPB1 has dominant effect on disruption of NF assembly and aggregation of NFL protein. Finally, we show that deletion of NFL markedly reduces degeneration and loss of motor neuron viability induced by S135F mutant HSPB1. Together, our data support the view that disruption of NF network with aggregation of NFL is a common triggering event of motor neuron degeneration in CMT2E and CMT2F disease.

    Human molecular genetics 2007;16;24;3103-16

  • Immunoreactivity to neurofilaments in the rodent anterior pituitary is associated with the expression of alpha 1A protein subunits of voltage-gated Ca2+ channels.

    Fiordelisio T, Jiménez N, Baba S, Shiba K and Hernández-Cruz A

    Instituto de Fisiología Celular, Departamento de Biofísica, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, México City, Mexico. tfiorde@ifc.unam.mx

    We recently reported that rodent anterior pituitary (AP) cells (with the exception of corticotrophs and melanotrophs) express neuronal markers, including 68-kDa neurofilaments (NF68) in an oestrogen-dependent manner. The functional significance of neurofilament (NF) expression in the AP is unknown, but recent data in myelinated nerve fibres from NF-null mice suggest that NFs can regulate ion channel function. Because Ca(2+) influx through voltage-gated Ca(2+) channels is required for hormone secretion in AP cells, and oestrogen regulates the expression of Ca(2+) channels in AP cells, the present study examined the expression of alpha1 subunits of voltage gated Ca(2+) channels in relation to that of NF68. Using quantitative immunofluorescence, we demonstrate that alpha 1C and alpha 1D subunits are abundantly expressed in female AP cells, alpha 1A subunits are moderately expressed, and alpha 1G and alpha 1B subunits are expressed at the lowest levels. Double-immunostaining showed that NF68 expression is not correlated with that of alpha 1C, alpha 1D or alpha 1B. Expression of alpha 1G and NF68 appear to be mutually exclusive from each other. Moreover, alpha 1A subunit and NF68 expression are significantly correlated and alpha 1A immunoreactivity is sexually dimorphic (i.e. low in males and high in females) and its levels of expression vary during the oestrous cycle, similar to NF68. Finally, omega-agatoxin IVA, a specific blocker of P/Q type Ca(2+) currents that are a result of the activity of alpha 1A subunits, inhibited to a greater extent spontaneous [Ca(2+)](i) fluctuations in AP cells from females in oestrous and dioestrous, whereas cells from females in pro-oestrous and males were less affected by this toxin. These results suggest a preferential participation of P/Q-type Ca(2+) channels and hence alpha 1A subunits, in regulating spontaneous Ca(2+) transients in AP cells under conditions where the proportion of NF68-expressing cells is high. It remains to be determined whether the expression of NF68 affects that of alpha 1A Ca(2+) channel subunits or vice versa.

    Journal of neuroendocrinology 2007;19;11;870-81

  • Fibroblast growth factor receptors cooperate to regulate neural progenitor properties in the developing midbrain and hindbrain.

    Saarimäki-Vire J, Peltopuro P, Lahti L, Naserke T, Blak AA, Vogt Weisenhorn DM, Yu K, Ornitz DM, Wurst W and Partanen J

    Institute of Biotechnology, Viikki Biocenter, University of Helsinki, 00014 Helsinki, Finland.

    Fibroblast growth factors (FGFs) secreted from the midbrain-rhombomere 1 (r1) boundary instruct cell behavior in the surrounding neuroectoderm. For example, a combination of FGF and sonic hedgehog (SHH) can induce the development of the midbrain dopaminergic neurons, but the mechanisms behind the action and integration of these signals are unclear. We studied how FGF receptors (FGFRs) regulate cellular responses by analyzing midbrain-r1 development in mouse embryos, which carry different combinations of mutant Fgfr1, Fgfr2, and Fgfr3 alleles. Our results show that the FGFRs act redundantly to support cell survival in the dorsal neuroectoderm, promote r1 tissue identity, and regulate the production of ventral neuronal populations, including midbrain dopaminergic neurons. The compound Fgfr mutants have apparently normal WNT/SHH signaling and neurogenic gene expression in the ventral midbrain, but the number of proliferative neural progenitors is reduced as a result of precocious neuronal differentiation. Our results suggest a SoxB1 family member, Sox3, as a potential FGF-induced transcription factor promoting progenitor renewal. We propose a model for regulation of progenitor cell self-renewal and neuronal differentiation by combinatorial intercellular signals in the ventral midbrain.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2007;27;32;8581-92

  • Molecular heterogeneity of developing retinal ganglion and amacrine cells revealed through single cell gene expression profiling.

    Trimarchi JM, Stadler MB, Roska B, Billings N, Sun B, Bartch B and Cepko CL

    Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.

    During development of the central nervous system (CNS), cycling uncommitted progenitor cells give rise to a variety of distinct neuronal and glial cell types. As these different cell types are born they progress from newly specified cells to fully differentiated neurons and glia. In order to define the developmental processes of individual cell types, single cell expression profiling was carried out on developing ganglion and amacrine cells of the murine retina. Individual cells from multiple developmental stages were isolated and profiled on Affymetrix oligonucleotide arrays. Two-color fluorescent in situ hybridization on dissociated retinas was used to verify and extend the microarray results by allowing quantitative measurements of a large number of cells coexpressing two genes. Together, these experiments have yielded an expanded view of the processes underway in developing retinal ganglion and amacrine cells, as well as several hundred new marker genes for these cell types. In addition, this study has allowed for the definition of some of the molecular heterogeneity both between developing ganglion and amacrine cells and among subclasses of each cell type.

    Funded by: NEI NIH HHS: EY08064, F32 EY014495, T32 EY007145

    The Journal of comparative neurology 2007;502;6;1047-65

  • Protein aggregate-containing neuron-like cells are differentiated from bone marrow mesenchymal stem cells from mice with neurofilament light subunit gene deficiency.

    Chao YX, He BP, Cao Q and Tay SS

    Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, MD10, 4 Medical Drive, Singapore 117597, Singapore.

    Autologous bone marrow mesenchymal stem cell (MSC) transplantation has great potential in cell therapy used for the treatment of neurodegenerative disorders. Since many genetic deficiencies have been reported in pathogenesis of the diseases, genetic backgrounds of donor stem cells should be concerned. In this study, effects of neurofilament light subunit (NFL) gene deficiency on proliferation and neuronal differentiation of MSCs were studied in vitro. Lower proliferation rate was observed in NFL-/- MSCs. When exposed to retinoic acid (RA), both NFL-/- and normal MSCs could express several markers of neuronal lineage, such as Nestin, MAP-2, NeuN, O4 and GFAP. However, the NFL expression at mRNA and protein levels was observed only in normal MSCs but absent in NFL-/- MSCs. Significant reductions in amount of neurofilament heavy subunit (NFH) protein and number of neuron-like cells were detected in differentiated NFL-/- MSCs. Interestingly, NFH positive protein accumulations were observed in the neuron-like cells derived from NFL-/- MSCs. These accumulations were perinuclear and morphologically similar to protein aggregations in motoneurons of the spinal cord in NFL-/- mice. The results suggest that NFL gene deficiency could retard MSCs proliferation and neuronal generation, even though the capability of neuronal lineage differentiation of MSCs may not be deterred. Moreover, the NFL-/- MSCs differentiated neuron-like cells carried on the genetic and pathologic deficiency, suggesting that the genetic quality of donor cells must not only be tested, but also modified before transplantation. This also points towards the possibility of creating a stem cell-derived cell model for pathogenesis study.

    Neuroscience letters 2007;417;3;240-5

  • Conditional NF-L transgene expression in mice for in vivo analysis of turnover and transport rate of neurofilaments.

    Millecamps S, Gowing G, Corti O, Mallet J and Julien JP

    Centre de Recherche du Centre Hospitalier de l'Université Laval, Department of Anatomy and Physiology of Laval University, Quebec, Canada.

    We generated mice with doxycycline control of a human neurofilament light (NF-L) transgene in the context of the absence (tTA;hNF-L;NF-L(-/-)) or presence (tTA;hNF-L;NF-L(+/-)) of endogenous mouse NF-L proteins. Doxycycline treatment caused the rapid disappearance of human NF-L (hNF-L) mRNA in tTA;hNF-L mice, but the hNF-L proteins remained with a half-life of 3 weeks in the brain. In the sciatic nerve, the disappearance of hNF-L proteins after doxycycline treatment occurred in synchrony along the sciatic nerve, suggesting a proteolysis of NF proteins along the entire axon. The presence of permanent NF network in tTA;hNF-L;NF-L(+/-) mice further stabilized and extended longevity of hNF-L proteins by several months. Surprisingly, after cessation of doxycycline treatment, there was no evidence of leading front of newly synthesized hNF-L proteins migrating into sciatic nerve axons devoid of NF structures. The hNF-L proteins detected at weekly intervals reappeared and accumulated in synchrony at similar rate along nerve segments, a phenomenon consistent with a fast hNF-L transport into axons. We estimated the hNF-L transport rate to be of approximately 10 mm/d in axons devoid of NF structures based on the use of an adenovirus encoding tet-responsive transcriptional activator to transactivate the hNF-L transgene in hypoglossal motor neurons. These results provide in vivo evidence that the stationary NF network in axons is a key determinant of half-life and transport rate of NF proteins.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2007;27;18;4947-56

  • Lbx1 acts as a selector gene in the fate determination of somatosensory and viscerosensory relay neurons in the hindbrain.

    Sieber MA, Storm R, Martinez-de-la-Torre M, Müller T, Wende H, Reuter K, Vasyutina E and Birchmeier C

    Department of Neuroscience, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany.

    Distinct types of relay neurons in the hindbrain process somatosensory or viscerosensory information. How neurons choose between these two fates is unclear. We show here that the homeobox gene Lbx1 is essential for imposing a somatosensory fate on relay neurons in the hindbrain. In Lbx1 mutant mice, viscerosensory relay neurons are specified at the expense of somatosensory relay neurons. Thus Lbx1 expression distinguishes between the somatosensory or viscerosensory fate of relay neurons.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2007;27;18;4902-9

  • Retrolinkin, a membrane protein, plays an important role in retrograde axonal transport.

    Liu JJ, Ding J, Wu C, Bhagavatula P, Cui B, Chu S, Mobley WC and Yang Y

    Department of Neurology, Stanford University School of Medicine, Stanford, CA 94305, USA.

    Retrograde axonal transport plays an important role in the maintenance of neuronal functions, but the mechanism is poorly defined partly because the constituents of the retrograde transport system and their interactions have yet to be elucidated. Of special interest is how dynein/dynactin motor proteins interact with membrane cargoes. Here, we report that an endosomal vesicle protein, termed retrolinkin, functions as a receptor tethering vesicles to dynein/dynactin through BPAG1n4. Retrolinkin, a membrane protein highly enriched in neuronal endosomes, binds directly to BPAG1n4. Deletion of retrolinkin membrane-association domains disrupts retrograde vesicular transport, recapitulating the BPAG1 null phenotype. We propose that retrolinkin acts with BPAG1n4 to specifically regulate retrograde axonal transport. Our work lays the foundation for understanding fundamental issues of axonal transport and provides insights into the molecular mechanisms underlying human neurodegenerative disorders.

    Funded by: NINDS NIH HHS: K02 NS043281, NS24054, NS42791, NS43281, R01 NS024054, R01 NS042791

    Proceedings of the National Academy of Sciences of the United States of America 2007;104;7;2223-8

  • Neurofilaments switch between distinct mobile and stationary states during their transport along axons.

    Trivedi N, Jung P and Brown A

    Center for Molecular Neurobiology and Department of Neuroscience, Ohio State University, Columbus, Ohio 43210, USA.

    We have developed a novel pulse-escape fluorescence photoactivation technique to investigate the long-term pausing behavior of axonal neurofilaments. Cultured sympathetic neurons expressing a photoactivatable green fluorescent neurofilament fusion protein were illuminated with violet light in a short segment of axon to create a pulse of fluorescent neurofilaments. Neurofilaments departed from the photoactivated regions at rapid velocities, but the overall loss of fluorescence was slow because many of the neurofilaments paused for long periods of time before moving. The frequency of neurofilament departure was more rapid initially and slower at later times, resulting in biphasic decay kinetics. By computational simulation of the kinetics, we show that the neurofilaments switched between two distinct states: a mobile state characterized by intermittent movements and short pauses (average = 30 s) and a stationary state characterized by remarkably long pauses (average = 60 min). On average, the neurofilaments spent 92% of their time in the stationary state. Combining short and long pauses, they paused for 97% of the time, resulting in an average transport rate of 0.5 mm/d. We speculate that the relative proportion of the time that neurofilaments spend in the stationary state may be a principal determinant of their transport rate and distribution along axons, and a potential target of mechanisms that lead to abnormal neurofilament accumulations in disease.

    Funded by: NINDS NIH HHS: NS-38526, R01 NS038526-06, R01 NS038526-07, R01 NS038526-08, R01 NS038526-09, R01 NS038526-10

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2007;27;3;507-16

  • Genomic organization of the region spanning D14Mit262 and D14Mit86 on mouse chromosome 14 and exclusion of Adam28 and Adamdec1 as the cataract-causing gene, lr2.

    Kim E, Rhee SD, Bae Y, Okumoto M, Yoon JB, Song CW and Yoon SK

    Research Institute of Molecular Genetics, the Catholic University of Korea, Seoul, Korea.

    Mice with recessive cataract, CXSD, show the first clinical symptoms of cataract at five weeks, with complete penetrance. We previously localized the cataract-causing lens rupture 2 gene (lr2) to mouse chromosome 14. In the process of positional cloning of the lr2 gene, we determined the genomic organization of the critical region, defined by D14Mit262 and D14Mit86, and compared it to recently published map information. In addition, mutational analysis using reverse transcription polymerase chain reaction (RT-PCR) followed by direct sequencing as well as quantitative realtime PCR (RQ-PCR) was performed to investigate Adam28 and Adamdec1 as lr2 candidate genes in this study. There was no mutation cosegregating with the phenotype of CXSD mice, which excluded these genes as the lr2 gene. Identification of more transcripts from this region and their mutation analyses are required to isolate the lr2 gene.

    Cytogenetic and genome research 2007;116;1-2;12-7

  • Sensory defects in Necdin deficient mice result from a loss of sensory neurons correlated within an increase of developmental programmed cell death.

    Andrieu D, Meziane H, Marly F, Angelats C, Fernandez PA and Muscatelli F

    Institut de Biologie du Développement de Marseille Luminy, Campus de Luminy Case 907 13288 Marseille Cedex 09, France. andrieu@ibdml.univ-mrs.fr <andrieu@ibdml.univ-mrs.fr&gt;

    Background: The human NECDIN gene is involved in a neurodevelopmental disorder, Prader-Willi syndrome (PWS). Previously we reported a mouse Necdin knock-out model with similar defects to PWS patients. Despite the putative roles attributed to Necdin, mainly from in vitro studies, its in vivo function remains unclear. In this study, we investigate sensory-motor behaviour in Necdin deficient mice. We reveal cellular defects and analyse their cause.

    Results: We report sensory differences in Necdin deficient mice compared to wild type animals. These differences led us to investigate sensory neuron development in Necdin deficient mouse embryos. First, we describe the expression pattern of Necdin in developing DRGs and report a reduction of one-third in specified sensory neurons in dorsal roots ganglia and show that this neuronal loss is achieved by E13.5, when DRGs sensory neurons are specified. In parallel, we observed an increase of 41% in neuronal apoptosis during the wave of naturally occurring cell death at E12.5. Since it is assumed that Necdin is a P75NTR interactor, we looked at the P75NTR-expressing cell population in Necdin knock-out embryos. Unexpectedly, Necdin loss of function has no effect on p75NTR expressing neurons suggesting no direct genetic interaction between Necdin and P75NTR in this context. Although we exclude a role of Necdin in axonal outgrowth from spinal sensory neurons in early developmental stages; such a role could occur later in neuronal differentiation. Finally we also exclude an anti-proliferative role of Necdin in developing sensory neurons.

    Conclusion: Overall, our data show clearly that, in early development of the nervous system, Necdin is an anti-apoptotic or survival factor.

    BMC developmental biology 2006;6;56

  • Mice with targeted disruption of neurofilament light subunit display formation of protein aggregation in motoneurons and downregulation of complement receptor type 3 alpha subunit in microglia in the spinal cord at their earlier age: a possible feature in pre-clinical development of neurodegenerative diseases.

    Li ZH, Lu J, Tay SS, Wu YJ, Strong MJ and He BP

    Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, MD10, 4 Medical Drive, Singapore 117597, Singapore.

    The pathogenesis of neurodegenerative diseases prior to the onset of symptoms is generally not clear. The present study has employed a mouse model with a lack of the low-molecular-weight neurofilament subunit (NFL-/-), in which formation of protein aggregates occurs in neurons, to investigate glial cellular reactions in the lumbar cord segments of NFL-/- mice at ages from 1 to 6 months. Age-matched C57BL/6 mice serve as the control. Apparent neurofilament positive aggregates in the cytoplasm of motoneurons have been observed in NFL-/- mice. However, there were no noticeable changes in microglial numbers and GFAP staining of astrocytes. Unexpectedly, a downregulation in expression of complement receptor type 3 alpha subunit (CD11b) was detected in the spinal cord of NFL-/- mice, while there was no obvious difference between NFL-/- and C57BL/6 mice in the CD11b staining intensity of macrophages from livers and spleens. In addition, retardation in morphological transformation from activated to amoeboid microglia in response to sciatic nerve injury, differential expressions of some cytokines in the lumbar cord segments and induction of Iba-1 (ionized calcium-binding adaptor molecule-1) expression in microglia were observed in NFL-/- mice. Our results suggest not only the existence of an inhibitory niche for CD11b expression in microglia in the lumbar cord segments of NFL-/- mice but also differential microglial reactions between earlier and later stages of neuropathogenesis. Although the real cause for such inhibition is still unknown, this effect might play a particular role in the survival of the abnormal protein aggregate-bearing motoneurons in the early development stage of neurodegeneration in the NFL-/- mice.

    Brain research 2006;1113;1;200-9

  • Alpha-internexin is structurally and functionally associated with the neurofilament triplet proteins in the mature CNS.

    Yuan A, Rao MV, Sasaki T, Chen Y, Kumar A, Veeranna, Liem RK, Eyer J, Peterson AC, Julien JP and Nixon RA

    Center for Dementia Research, Nathan Kline Institute, Orangeburg, New York 10962, USA. yuan@nki.rfmh.org

    Alpha-internexin, a neuronal intermediate filament protein implicated in neurodegenerative disease, coexists with the neurofilament (NF) triplet proteins (NF-L, NF-M, and NF-H) but has an unknown function. The earlier peak expression of alpha-internexin than the triplet during brain development and its ability to form homopolymers, unlike the triplet, which are obligate heteropolymers, have supported a widely held view that alpha-internexin and neurofilament triplet form separate filament systems. Here, we demonstrate, however, that despite a postnatal decline in expression, alpha-internexin is as abundant as the triplet in the adult CNS and exists in a relatively fixed stoichiometry with these subunits. Alpha-internexin exhibits transport and turnover rates identical to those of triplet proteins in optic axons and colocalizes with NF-M on single neurofilaments by immunogold electron microscopy. Alpha-internexin also coassembles with all three neurofilament proteins into a single network of filaments in quadruple-transfected SW13vim(-) cells. Genetically deleting NF-M alone or together with NF-H in mice dramatically reduces alpha-internexin transport and content in axons throughout the CNS. Moreover, deleting alpha-internexin potentiates the effects of NF-M deletion on NF-H and NF-L transport. Finally, overexpressing a NF-H-LacZ fusion protein in mice induces alpha-internexin and neurofilament triplet to aggregate in neuronal perikarya and greatly reduces their transport and content selectively in axons. Our data show that alpha-internexin and the neurofilament proteins are functionally interdependent. The results strongly support the view that alpha-internexin is a fourth subunit of neurofilaments in the adult CNS, providing a basis for its close relationship with neurofilaments in CNS diseases associated with neurofilament accumulation.

    Funded by: NIA NIH HHS: AG05604

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2006;26;39;10006-19

  • Different expression of synemin isoforms in glia and neurons during nervous system development.

    Izmiryan A, Cheraud Y, Khanamiryan L, Leterrier JF, Federici T, Peltekian E, Moura-Neto V, Paulin D, Li Z and Xue ZG

    Université Pierre et Marie Curie-Paris 6, UMR 7079, Paris, France.

    The synemin gene encodes proteins belonging to the intermediate filament family. These proteins confer resistance to mechanical stress and modulate cell shape. Three synemin isoforms, of 180 (H), 150 (M) and 41 (L) kDa, are produced by alternative splicing of the pre-mRNA and are regulated differently during development. The three isoforms differ in their C-terminal tail domains, while their IF rod domains are identical. Synemins H/M occurred together with nestin and vimentin in glial progenitors during the early differentiation of the developing mouse central nervous system. They are later found in GFAP-labeled cells. In contrast, the L isoform appeared only in neurons, together with neurofilaments and betaIII-tubulin in the brain after birth. However, synemin L appeared from E13 in the peripheral nervous system, where it was confined to the neurons of spinal ganglia. In the meantime, the synemin H/M isoforms were found in both the neurons and Schwann cells of the sensorial ganglia from E11. Tissue fractionation and purification of IFs from adult mouse spinal cord revealed that the synemin L isoform binds to neurofilaments associated with the membrane compartment. This report describes the synthesis of the three synemin isoforms by selective cell types, and their temporal and spatial distributions. Mechanisms specific to neurons and glia probably control the splicing of the common synemin mRNA and the synthesis of each synemin isoform.

    Glia 2006;54;3;204-13

  • Proper patterning of the optic fissure requires the sequential activity of BMP7 and SHH.

    Morcillo J, Martínez-Morales JR, Trousse F, Fermin Y, Sowden JC and Bovolenta P

    Departamento de Neurobiología del Desarrollo, Instituto Cajal, CSIC, Dr Arce 37, Madrid 28002, Spain.

    The optic disc develops at the interface between optic stalk and retina, and enables both the exit of visual fibres and the entrance of mesenchymal cells that will form the hyaloid artery. In spite of the importance of the optic disc for eye function, little is known about the mechanisms that control its development. Here, we show that in mouse embryos, retinal fissure precursors can be recognised by the expression of netrin 1 and the overlapping distribution of both optic stalk (Pax2, Vax1) and ventral neural retina markers (Vax2, Raldh3). We also show that in the absence of Bmp7, fissure formation is not initiated. This absence is associated with a reduced cell proliferation and apoptosis in the proximoventral quadrant of the optic cup, lack of the hyaloid artery, optic nerve aplasia, and intra-retinal misrouting of RGC axons. BMP7 addition to organotypic cultures of optic vesicles from Bmp7-/- embryos rescues Pax2 expression in the ventral region, while follistatin, a BMP7 antagonist, prevents it in early, but not in late, optic vesicle cultures from wild-type embryos. The presence of Pax2-positive cells in late optic cup is instead abolished by interfering with Shh signalling. Furthermore, SHH addition re-establishes Pax2 expression in late optic cups derived from ocular retardation (or) embryos, where optic disc development is impaired owing to the near absence of SHH-producing RGC. Collectively, these data indicate that BMP7 is required for retinal fissure formation and that its activity is needed, before SHH signalling, for the generation of PAX2-positive cells at the optic disc.

    Development (Cambridge, England) 2006;133;16;3179-90

  • The muscle protein Dok-7 is essential for neuromuscular synaptogenesis.

    Okada K, Inoue A, Okada M, Murata Y, Kakuta S, Jigami T, Kubo S, Shiraishi H, Eguchi K, Motomura M, Akiyama T, Iwakura Y, Higuchi O and Yamanashi Y

    Department of Cell Regulation, Medical Research Institute, Tokyo Medical and Dental University, Tokyo 113-8510, Japan.

    The formation of the neuromuscular synapse requires muscle-specific receptor kinase (MuSK) to orchestrate postsynaptic differentiation, including the clustering of receptors for the neurotransmitter acetylcholine. Upon innervation, neural agrin activates MuSK to establish the postsynaptic apparatus, although agrin-independent formation of neuromuscular synapses can also occur experimentally in the absence of neurotransmission. Dok-7, a MuSK-interacting cytoplasmic protein, is essential for MuSK activation in cultured myotubes; in particular, the Dok-7 phosphotyrosine-binding domain and its target in MuSK are indispensable. Mice lacking Dok-7 formed neither acetylcholine receptor clusters nor neuromuscular synapses. Thus, Dok-7 is essential for neuromuscular synaptogenesis through its interaction with MuSK.

    Science (New York, N.Y.) 2006;312;5781;1802-5

  • Comprehensive identification of phosphorylation sites in postsynaptic density preparations.

    Trinidad JC, Specht CG, Thalhammer A, Schoepfer R and Burlingame AL

    Mass Spectrometry Facility, Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143, USA.

    In the mammalian central nervous system, the structure known as the postsynaptic density (PSD) is a dense complex of proteins whose function is to detect and respond to neurotransmitter released from presynaptic axon terminals. Regulation of protein phosphorylation in this molecular machinery is critical to the activity of its components, which include neurotransmitter receptors, kinases/phosphatases, scaffolding molecules, and proteins regulating cytoskeletal structure. To characterize the phosphorylation state of proteins in PSD samples, we combined strong cation exchange (SCX) chromatography with IMAC. Initially, tryptic peptides were separated by cation exchange and analyzed by reverse phase chromatography coupled to tandem mass spectrometry, which led to the identification of phosphopeptides in most SCX fractions. Because each of these individual fractions was too complex to characterize completely in single LC-MS/MS runs, we enriched for phosphopeptides by performing IMAC on each SCX fraction, yielding at least a 3-fold increase in identified phosphopeptides relative to either approach alone (SCX or IMAC). This enabled us to identify at least one site of phosphorylation on 23% (287 of 1,264) of all proteins found to be present in the postsynaptic density preparation. In total, we identified 998 unique phosphorylated peptides, mapping to 723 unique sites of phosphorylation. At least one exact site of phosphorylation was determined on 62% (621 of 998) of all phosphopeptides, and approximately 80% of identified phosphorylation sites are novel.

    Funded by: NCRR NIH HHS: RR14606; Wellcome Trust

    Molecular & cellular proteomics : MCP 2006;5;5;914-22

  • O-linked N-acetylglucosamine proteomics of postsynaptic density preparations using lectin weak affinity chromatography and mass spectrometry.

    Vosseller K, Trinidad JC, Chalkley RJ, Specht CG, Thalhammer A, Lynn AJ, Snedecor JO, Guan S, Medzihradszky KF, Maltby DA, Schoepfer R and Burlingame AL

    Mass Spectrometry Facility, Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143, USA. kav27@drexel.edu

    O-GlcNAc is a widespread dynamic carbohydrate modification of cytosolic and nuclear proteins with features analogous to phosphorylation. O-GlcNAc acts critically in many cellular processes, including signal transduction, protein degradation, and regulation of gene expression. However, the study of its specific regulatory functions has been limited by difficulties in mapping sites of O-GlcNAc modification. We report methods for direct enrichment and identification of in vivo O-GlcNAc-modified peptides through lectin weak affinity chromatography (LWAC) and mass spectrometry. The effectiveness of this strategy on complex peptide mixtures was demonstrated through enrichment of 145 unique O-GlcNAc-modified peptides from a postsynaptic density preparation. 65 of these O-GlcNAc-modified peptides were sequenced and belonged to proteins with diverse functions in synaptic transmission. Beta-elimination/Michael addition, MS(3) on O-GlcNAc neutral loss ions, and electron capture dissociation were shown to facilitate analysis of O-GlcNAc-modified peptides/sites from lectin weak affinity chromatography enriched postsynaptic density samples. Bassoon and Piccolo, proteins critical to synapse assembly and vesicle docking, were extensively modified by O-GlcNAc. In some cases, O-GlcNAc was mapped to peptides previously identified as phosphorylated, indicating potential interplay between these modifications. Shared substrate amino acid context was apparent in subsets of O-GlcNAc-modified peptides, including "PVST" and a novel "TTA" motif (two hydroxyl-containing amino acids adjacent to an alanine). The results suggest specific roles for O-GlcNAc modification in synaptic transmission, establish a basis for site-specific regulatory studies, and provide methods that will facilitate O-GlcNAc proteome analysis across a wide variety of cells and tissues.

    Funded by: NCRR NIH HHS: RR14606; Wellcome Trust

    Molecular & cellular proteomics : MCP 2006;5;5;923-34

  • BGEM: an in situ hybridization database of gene expression in the embryonic and adult mouse nervous system.

    Magdaleno S, Jensen P, Brumwell CL, Seal A, Lehman K, Asbury A, Cheung T, Cornelius T, Batten DM, Eden C, Norland SM, Rice DS, Dosooye N, Shakya S, Mehta P and Curran T

    Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee, United States.

    Funded by: NINDS NIH HHS: 5R37NS036558, N01-NS-0-2331, R37 NS036558

    PLoS biology 2006;4;4;e86

  • Notch 1 inhibits photoreceptor production in the developing mammalian retina.

    Jadhav AP, Mason HA and Cepko CL

    Department of Genetics and Howard Hughes Medical Institute, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA.

    The transmembrane receptor Notch1 plays a role in development and homeostasis in vertebrates and invertebrates. The mammalian retina is an excellent tissue in which to dissect the precise role of Notch signaling in regulating cell fate and proliferation. However, a systematic analysis has been limited by the early embryonic lethality of Notch1-null mice. Here, Notch1 was conditionally removed from the murine retina either early or late in development. Removal of Notch1 early led to a reduction in the size of the retina as well as aberrant morphology. A decrease in the number of progenitor cells and premature neurogenesis accounted for the reduction in size. Unexpectedly, ablation of Notch1 in early progenitor cells led to enhanced cone photoreceptor production, and ablation of Notch1 at later points led to an almost exclusive production of rod photoreceptor cells. These data suggest that Notch1 not only maintains the progenitor state, but is required to inhibit the photoreceptor fate. These cone enriched mutant mice should prove to be a valuable resource for the study of this relatively rare mammalian photoreceptor cell type.

    Funded by: NEI NIH HHS: T32EY007110; PHS HHS: EYO 86767

    Development (Cambridge, England) 2006;133;5;913-23

  • Connexin29 is highly expressed in cochlear Schwann cells, and it is required for the normal development and function of the auditory nerve of mice.

    Tang W, Zhang Y, Chang Q, Ahmad S, Dahlke I, Yi H, Chen P, Paul DL and Lin X

    Department of Otolaryngology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.

    Connexins (Cxs) are a family of protein subunits constituting gap junctions, which facilitate exchanges of molecules important for cellular signaling and metabolic activities intercellularly or between different regions of the cytoplasm in the same cells. Mutations in Cxs are the major cause of nonsyndromic childhood deafness, which are mostly found in Cx26 and Cx30 expressed in cochlear supporting cells and fibrocytes. So far, little is known about the functional contribution of Cxs in other types of cochlear cells. Here, we show that Cx29 was highly expressed in the cochlea. The developmental expression time course of Cx29 was similar to that of a myelin marker [myelin associate glycoprotein (MAG)]. Immunolabeling identified Cx29 exclusively in the Schwann cells myelinating the soma and fiber of spiral ganglion (SG) neurons. The absence of the Cx29 gene in mice (Cx29(-/-) mice), with a penetrance of approximately 50%, caused a delay in the maturation of hearing thresholds, an early loss of high-frequency sensitivities, a prolongation in latency and distortion in the wave I of the auditory brainstem responses, and elevated sensitivity to noise damages. The morphology of sensory hair cells and otoacoustic emissions that depend on the integrity of hair cells were normal in Cx29(-/-) mice. In contrast, decreases in MAG expression and severe demyelination at the soma of SG neurons were found in Cx29(-/-) mice. Our findings demonstrated the requirement of Cx29 for normal cochlear functions and suggest that Cx29 is a new candidate gene for studying the auditory neuropathy.

    Funded by: NICHD NIH HHS: P30-HD18655; NIDCD NIH HHS: R01 DC006483, R01-DC006483, R01-DC04709; NIGMS NIH HHS: GM37751

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2006;26;7;1991-9

  • Molecular mechanisms underlying inner ear patterning defects in kreisler mutants.

    Choo D, Ward J, Reece A, Dou H, Lin Z and Greinwald J

    Department of Otolaryngology Head and Neck Surgery, Center for Hearing and Deafness Research, University of Cincinnati College of Medicine, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, OH 45229-3039, USA. daniel.choo@cchmc.org

    Prior studies have shown that kreisler mutants display early inner ear defects that are related to abnormal hindbrain development and signaling. These defects in kreisler mice have been linked to mutation of the kr/mafB gene. To investigate potential relevance of kr/mafB and abnormal hindbrain development in inner ear patterning, we analyzed the ear morphogenesis in kreisler mice using a paint-fill technique. We also examined the expression patterns of a battery of genes important for normal inner ear patterning and development. Our results indicate that the loss of dorsal otic structures such as the endolymphatic duct and sac is attributable to the downregulation of Gbx2, Dlx5 and Wnt2b in the dorsal region of the otocyst. In contrast, the expanded expression domain of Otx2 in the ventral otic region likely contributes to the cochlear phenotype seen in kreisler mutants. Sensory organ development is also markedly disrupted in kreisler mutants. This pattern of defects and gene expression changes is remarkably similar to that observed in Gbx2 mutants. Taken together, the data show an important role for hindbrain cues, and indirectly, kr/mafB, in guiding inner ear morphogenesis. The data also identify Gbx2, Dlx5, Wnt2b and Otx2 as key otic genes ultimately affected by perturbation of the kr/mafB-hindbrain pathway.

    Developmental biology 2006;289;2;308-17

  • Cells of proopiomelanocortin lineage from the rodent anterior pituitary lack sexually dimorphic expression of neurofilaments.

    Fiordelisio T, Millán-Aldaco D and Hernández-Cruz A

    Departamento de Biofísica, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México City, México.

    Lactotrophs, gonadotrophs, thyrotrophs and somatotrophs of the rat anterior pituitary (AP) express 68-kDa neurofilaments (NF68) and other neuronal markers. NF68 expression in the AP appears to be estrogen-dependent, but its significance is unknown. The aims of this work were: (1) to establish the expression pattern of NF68 immunoreactivity in the mouse AP, and (2) discover if corticotrophs and melanotrophs from both rodent species also express NF68. Primary cultures and frozen sections of AP from sexually mature mice were immunolabeled with anti-NF68 antibodies. In separate experiments, samples were immunostained for NF68 and AP hormones. Here we report that mouse lactotrophs, gonadotrophs, thyrotrophs and somatotrophs also express NF68 in a sexually dimorphic manner. The percentages of non-expressing, weakly expressing and strongly expressing cells were similar between both rodent species, although NF68+ cells were about 50% less abundant in the mouse compared to the rat pituitary. Remarkably, our study shows for the first time that rodent pituitary cells from the proopiomelanocortin lineage nearly completely lack NF68 immunoreactivity. In this regard, they differ from the rest of the AP population. Our findings establish a foundation for experiments aimed at investigating the functional significance of estrogen-dependent regulation of NF68 expression in rodent AP cells.

    Neuroendocrinology 2006;83;5-6;360-70

  • RNA-binding protein is involved in aggregation of light neurofilament protein and is implicated in the pathogenesis of motor neuron degeneration.

    Lin H, Zhai J and Schlaepfer WW

    Division of Neuropathology, University of Pennsylvania Medical School, Philadelphia, PA 19104, USA.

    Abnormal protein aggregation is emerging as a common theme in the pathogenesis of neurodegenerative disease. Our previous studies have shown that overexpression of untranslated light neurofilament (NF-L) RNA causes motor neuron degeneration in transgenic mice, leads to accumulation of ubiquitinated aggregates in degenerating cultured motor neurons and triggers aggregation of NF-L protein and co-aggregation of mutant SOD1 protein in neuronal cells. Here, we report that p190RhoGEF, an RNA-binding protein that binds to a destabilizing element in NF-L mRNA, is involved in aggregation of NF-L protein and is implicated in the pathogenesis of motor neuron degeneration. We show that p190RhoGEF co-aggregates with unassembled NF-L protein and that co-aggregation is associated with down-regulation of parent NF-L mRNA in neuronal cells. Co-expression of NF-M increases NF assembly and reduces RNA-triggered aggregation as well as loss of solubility of NF-L protein. siRNA-induced down-regulation of p190RhoGEF not only reduces aggregation and promotes assembly of NF-L and NF-M, but also causes reversal of aggregation and recovery of NF assembly in transfected cells. Examination of transgenic models of motor neuron disease shows that prominent aggregates of p190RhoGEF and NF-L and down-regulation of NF-L expression occur in degenerating motor neurons of mice expressing untranslated NF-L RNA or a G93A mutant SOD1 transgene. Moreover, aggregates of p190RhoGEF and NF-L appear as early pathological changes in presymptomatic G93A mutant SOD1 transgenic mice. Together, the findings indicate that p190RhoGEF is involved in aggregation of NF-L protein and support a working hypothesis that aggregation of p190RhoGEF and NF-L is an upstream event triggering neurotoxicity in motor neuron disease.

    Human molecular genetics 2005;14;23;3643-59

  • Lack of an adrenal cortex in Sf1 mutant mice is compatible with the generation and differentiation of chromaffin cells.

    Gut P, Huber K, Lohr J, Brühl B, Oberle S, Treier M, Ernsberger U, Kalcheim C and Unsicker K

    Neuroanatomy and Interdisciplinary Center for Neurosciences (IZN) of Heidelberg, INF 307, D-69120 Heidelberg, Germany.

    The diversification of neural-crest-derived sympathoadrenal (SA) progenitor cells into sympathetic neurons and neuroendocrine adrenal chromaffin cells was thought to be largely understood. In-vitro studies with isolated SA progenitor cells had suggested that chromaffin cell differentiation depends crucially on glucocorticoids provided by adrenal cortical cells. However, analysis of mice lacking the glucocorticoid receptor gene had revealed that adrenal chromaffin cells develop mostly normally in these mice. Alternative cues from the adrenal cortex that may promote chromaffin cell determination and differentiation have not been identified. We therefore investigated whether the chromaffin cell phenotype can develop in the absence of an adrenal cortex, using mice deficient for the nuclear orphan receptor steroidogenic factor-1 (SF1), which lack adrenal cortical cells and gonads. We show that in Sf1-/- mice typical chromaffin cells assemble correctly in the suprarenal region adjacent to the suprarenal sympathetic ganglion. The cells display most features of chromaffin cells, including the typical large chromaffin granules. Sf1-/- chromaffin cells are numerically reduced by about 50% compared with the wild type at embryonic day (E) 13.5 and E17.5. This phenotype is not accounted for by reduced survival or cell proliferation beyond E12.5. However, already at E12.5 the 'adrenal' region in Sf1-/- mice is occupied by fewer PHOX2B+ and TH+ SA cells as well as SOX10+ neural crest cells. Our results suggest that cortical cues are not essential for determining chromaffin cell fate, but may be required for proper migration of SA progenitors to and/or colonization of the adrenal anlage.

    Development (Cambridge, England) 2005;132;20;4611-9

  • Temporal profiles of neuronal degeneration, glial proliferation, and cell death in hNFL(+/+) and NFL(-/-) mice.

    McLean JR, Sanelli TR, Leystra-Lantz C, He BP and Strong MJ

    Department of Pathology, Schulich School of Medicine, University of Western Ontario, London, Ontario, Canada.

    Neurofilament (NF) aggregate formation within motor neurons is a pathological hallmark of both the sporadic and familial forms of amyotrophic lateral sclerosis (ALS). The relationship between aggregate formation and both microglial and astrocytic proliferation, as well as additional neuropathological features of ALS, is unknown. To examine this, we have used transgenic mice that develop NF aggregates, through either a lack of the low-molecular-weight NF subunit [NFL (-/-)] or the overexpression of human NFL [hNFL (+/+)]. Transgenic and wild-type C57bl/6 mice were examined from 1 month to 18 months of age, and the temporal pattern of motor neuron degeneration, microglial and astrocytic proliferation, and heat shock protein-70 (HSP-70) expression characterized. We observed three overlapping phases in both transgenic mice, including transient aggregate formation, reactive microgliosis, and progressive motor neuron loss. However, only NFL (-/-) mice demonstrated significant astrogliosis and HSP-70 upregulation in both motor neurons and astrocytes. These in vivo models suggest that the development of NF aggregates in motor neurons leads to motor neuron death, but that the interaction between the degenerating motor neurons and the adjacent non-neuronal cells may differ significantly depending on the etiology of the NF aggregate itself.

    Glia 2005;52;1;59-69

  • GDF11 controls the timing of progenitor cell competence in developing retina.

    Kim J, Wu HH, Lander AD, Lyons KM, Matzuk MM and Calof AL

    Department of Anatomy and Neurobiology, University of California, Irvine, CA 92697, USA.

    The orderly generation of cell types in the developing retina is thought to be regulated by changes in the competence of multipotent progenitors. Here, we show that a secreted factor, growth and differentiation factor 11 (GDF11), controls the numbers of retinal ganglion cells (RGCs), as well as amacrine and photoreceptor cells, that form during development. GDF11 does not affect proliferation of progenitors-a major mode of GDF11 action in other tissues-but instead controls duration of expression of Math5, a gene that confers competence for RGC genesis, in progenitor cells. Thus, GDF11 governs the temporal windows during which multipotent progenitors retain competence to produce distinct neural progeny.

    Funded by: NIAMS NIH HHS: AR44528; NICHD NIH HHS: HD32067, HD38761; NIDCD NIH HHS: DC03583

    Science (New York, N.Y.) 2005;308;5730;1927-30

  • Mice with the deleted neurofilament of low-molecular-weight (Nefl) gene: 1. Effects on regional brain metabolism.

    Dubois M, Lalonde R, Julien JP and Strazielle C

    Faculté des Sciences, UPRES PSY.CO EA 1780, Université de Rouen, Mont-Saint-Aignan, France.

    Neuronal intermediate filaments consist of the NFL subunit linked with NFM and NFH, and their alterations have been proposed as a pathogenesic cause in motor neuron diseases. Depletion of the Nefl gene in mice mimicks the reduced NFL mRNA levels seen in amyotrophic lateral sclerosis and causes perikaryal accumulation of neurofilament proteins and axonal hypotrophy in motoneurons. NFL -/- mice were evaluated for regional brain metabolism by means of quantitative histochemical estimation of cytochrome oxidase (COx) activity. The NFL null mice displayed enzymatic activity alterations in numerous hindbrain regions, mainly the cerebellum, connected regions of the brainstem (red nucleus, vestibular nuclei, and reticular formation), and cranial nerve nuclei. All of the affected regions presented elevated COx activity, except for the Purkinje cells of the cerebellum and the magnocellular red nucleus, where enzymatic activity was lower. NFL-disrupted mice displayed functional alterations in brainstem sensorimotor regions affected in amyotrophic lateral sclerosis.

    Journal of neuroscience research 2005;80;6;741-50

  • Mice with the deleted neurofilament of low molecular weight (Nefl) gene: 2. Effects on motor functions and spatial orientation.

    Dubois M, Strazielle C, Julien JP and Lalonde R

    Faculté des Sciences, Université de Rouen, UPRES PSY.CO EA 1780, Mont-Saint-Aignan, France.

    Mice with a null mutation of the Nefl gene were compared with normal controls in tests of motor activity, equilibrium, and spatial orientation. Despite a normal capacity to ambulate, NFL -/- mice had fewer rears in an open field, crossed fewer segments on stationary beams, and fell more frequently when suspended on a horizontal bar. In addition, the distance swum before reaching the escape platform was greater in NFL -/- mice than in controls during acquisition of place learning in the Morris water maze at the start of training. The motor impairments were linearly correlated with increased cytochrome oxidase activity seen in cerebellum and brainstem. These results indicate that, as early as 6 months, depletion of the NFL protein is sufficient to cause mild sensorimotor dysfunctions and spatial deficits, but without overt signs of paresis.

    Journal of neuroscience research 2005;80;6;751-8

  • Gbx2 is required for the morphogenesis of the mouse inner ear: a downstream candidate of hindbrain signaling.

    Lin Z, Cantos R, Patente M and Wu DK

    Laboratory of Molecular Biology, National Institutes on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20850, USA.

    Gbx2 is a homeobox-containing transcription factor that is related to unplugged in Drosophila. In mice, Gbx2 and Otx2 negatively regulate each other to establish the mid-hindbrain boundary in the neural tube. Here, we show that Gbx2 is required for the development of the mouse inner ear. Absence of the endolymphatic duct and swelling of the membranous labyrinth are common features in Gbx2-/- inner ears. More severe mutant phenotypes include absence of the anterior and posterior semicircular canals, and a malformed saccule and cochlear duct. However, formation of the lateral semicircular canal and its ampulla is usually unaffected. These inner ear phenotypes are remarkably similar to those reported in kreisler mice, which have inner ear defects attributed to defects in the hindbrain. Based on gene expression analyses, we propose that activation of Gbx2 expression within the inner ear is an important pathway whereby signals from the hindbrain regulate inner ear development. In addition, our results suggest that Gbx2 normally promotes dorsal fates such as the endolymphatic duct and semicircular canals by positively regulating genes such as Wnt2b and Dlx5. However, Gbx2 promotes ventral fates such as the saccule and cochlear duct, possibly by restricting Otx2 expression.

    Development (Cambridge, England) 2005;132;10;2309-18

  • The role of Phox2B in chromaffin cell development.

    Huber K, Karch N, Ernsberger U, Goridis C and Unsicker K

    Neuroanatomy, Interdisciplinary Center for Neurosciences, University of Heidelberg, INF 307, D-69120 Heidelberg, Germany. katrin.huber@ana.uni-heidelberg.de

    Phox2B, a homeodomain transcription factor closely related to Phox2A, is expressed in peripheral and central noradrenergic neurons. In neural crest (NC) derivatives Phox2B is restricted to sympathetic and parasympathetic ganglia, enteric neurons, and adrenal and extraadrenal chromaffin cells. Similar to MASH-1, Phox2B has been implicated in synchronizing pan-neuronal and catecholaminergic phenotype-specific aspects of neurogenesis. The role of Phox2B for the differentiation of the neuroendocrine NC derivatives, the adrenal medullary chromaffin cells, has not been explored. We have previously reported that in MASH-1-deficient mice most chromaffin cells are arrested at the early neuroblast stage and lack catecholaminergic differentiation. We show now that in Phox2B knockout/lacZ knockin mice the maturation of presumptive chromaffin cells is arrested at an even earlier stage of development. The cells lack the catecholaminergic marker enzyme TH and fail to form a centrally located medulla. In contrast to MASH-1 (-/-) mice they do not express dHand, Phox2A, c-ret, neurofilament, neuron-specific tubulin, and NCAM and appear ultrastructurally more immature. Many of these cells die by apoptosis. Despite the complete lack of differentiation, few lacZ-positive adrenal cells can still be found at E16.5. We conclude that Phox2B regulates very early events in the differentiation of adrenal chromaffin cells distinct to steps, which essentially require MASH-1.

    Developmental biology 2005;279;2;501-8

  • Reelin signaling is necessary for a specific step in the migration of hindbrain efferent neurons.

    Rossel M, Loulier K, Feuillet C, Alonso S and Carroll P

    EPHE Quantitative Cell Biology, INSERM EMI 343, IFR 122, University Montpellier 2, 34090 Montpellier, France. mrossel@univ-montp2.fr

    The cytoarchitecture of the hindbrain results from precise and co-ordinated sequences of neuronal migrations. Here, we show that reelin, an extracellular matrix protein involved in neuronal migration during CNS development, is necessary for an early, specific step in the migration of several hindbrain nuclei. We identified two cell populations not previously known to be affected in reeler mutants that show a common migratory defect: the olivocochlear efferent neurons and the facial visceral motor nucleus. In control embryos, these cells migrate first toward a lateral position within the neural tube, and then parallel to the glial cell processes, to a ventral position where they settle close to the pial surface. In reeler mutants, the first migration is not affected, but the neurons are unable to reach the pial surface and remain in an ectopic position. Indeed, this is the first evidence that the migration of specific hindbrain nuclei can be divided into two parts: a reelin-independent and a reelin-dependent migration. We also show that reelin is expressed at high levels at the final destination of the migratory process, while the reelin intracellular effector Dab1 was expressed by cell groups that included the two populations affected. Mice mutant at the Dab1 locus, called scrambler, exhibit the same phenotype, a failure of final migration. However, examination of mice lacking both reelin receptors, ApoER2 and VLDLR, did not reveal the same phenotype, suggesting involvement of an additional reelin-binding receptor. In the hindbrain, reelin signaling might alter the adhesive properties of efferent neurons and their ability to respond to directional cues, as has been suggested for the migration of olfactory bulb precursors.

    Development (Cambridge, England) 2005;132;6;1175-85

  • Axonopathy and transport deficits early in the pathogenesis of Alzheimer's disease.

    Stokin GB, Lillo C, Falzone TL, Brusch RG, Rockenstein E, Mount SL, Raman R, Davies P, Masliah E, Williams DS and Goldstein LS

    Howard Hughes Medical Institute and Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego (UCSD), 9500 Gilman Drive, La Jolla, CA 92093, USA.

    We identified axonal defects in mouse models of Alzheimer's disease that preceded known disease-related pathology by more than a year; we observed similar axonal defects in the early stages of Alzheimer's disease in humans. Axonal defects consisted of swellings that accumulated abnormal amounts of microtubule-associated and molecular motor proteins, organelles, and vesicles. Impairing axonal transport by reducing the dosage of a kinesin molecular motor protein enhanced the frequency of axonal defects and increased amyloid-beta peptide levels and amyloid deposition. Reductions in microtubule-dependent transport may stimulate proteolytic processing of beta-amyloid precursor protein, resulting in the development of senile plaques and Alzheimer's disease.

    Funded by: NEI NIH HHS: EY12598, EY13408, R01 EY007042, R01 EY007042-19, R01 EY013408, R01 EY013408-02; NIA NIH HHS: P50 AG05131

    Science (New York, N.Y.) 2005;307;5713;1282-8

  • Fibroblast growth factor signalling and regional specification of the pharyngeal ectoderm.

    Trokovic N, Trokovic R and Partanen J

    Institute of Biotechnology, Viikki Biocenter, University of Helsinki, Finland.

    Branchial arch development involves dynamic interactions between neural crest cells as well as ectodermal, endodermal and mesodermal cell populations. Despite their importance and evolutionary conservation, the intercellular interactions guiding the early development of the branchial arches are still poorly understood. We have here studied fibroblast growth factor (FGF) signalling in early pharyngeal development. In mice homozygous for a hypomorphic allele of Fgfr1, neural crest cells migrating from the hindbrain mostly fail to enter the second branchial arch. This defect is non-cell-autonomous suggesting that Fgfr1 provides a permissive environment for neural crest cell migration. Here we demonstrate localized down-regulation of the expression of the FGF responsive gene, Sprouty1 in the epithelium covering the presumptive second branchial arch of hypomorphic Fgfr1 mutants. This appears to result in a failure to establish an ectodermal signalling center expressing Fgf3 and Fgf15. We also studied differentiation of the ectoderm in the second branchial arch region. Development of the geniculate placode as well as the VIIth cranial ganglion is affected in Fgfr1 hypomorphs. Our results suggest that Fgfr1 is important for localized signalling in the pharyngeal ectoderm and consequently for normal tissue interactions in the developing second branchial arch.

    The International journal of developmental biology 2005;49;7;797-805

  • Novel retinal genes discovered by mining the mouse embryonic RetinalExpress database.

    Liang S, Zhao S, Mu X, Thomas T and Klein WH

    Department of Biochemistry and Molecular Biology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.

    Purpose: Bioinformatics has emerged as a powerful tool for identifying novel genes and pathways associated with retinal biology and disease. The developing mouse retina expresses an exceedingly large and complex variety of genes. Many of these genes have not been characterized but nevertheless are likely to have important developmental or physiological functions. The purpose of this study was to use an in silico approach with a mouse embryonic retinal database of cDNAs/expressed sequence tags (ESTs) named RetinalExpress to identify previously uncharacterized genes that are represented in the developing retina.

    Methods: cDNA clones unique to the RetinalExpress database were identified by comparing clones in the RetinalExpress database with those in other cDNA/EST databases. We used a hierarchical filtering procedure with high stringency criteria that included sequence quality, colinearity with hypothetical gene sequences, and absence of any substantial existing annotation to select clones that were likely to represent novel genes. Selected clones were located on mouse chromosomes using National Center for Biotechnology Informatics Map Viewer software and the database from the University of California at Santa Cruz Genome Bioinformatics Web browser. The expression of selected retinal transcripts was determined using reverse transcriptase (RT)-PCR. In situ hybridization of sectioned embryonic and postnatal retinas was performed to determine spatial expression patterns of selected transcripts.

    Results: Of the 27,765 cDNA clones from RetinalExpress that we filtered through several public cDNA/EST databases, 26 cDNA/EST sequences were identified that, at the time of the analysis, were unique to RetinalExpress. Seventeen clones were selected for RT-PCR analysis, and retinal transcripts corresponding to previously uncharacterized genes were unambiguously detected for six clones. Three genes encoded open reading frames containing putative functional domains; one sequence contained an HMG DNA binding domain, another, an RFX DNA binding domain, and another, a phospholipase C catalytic domain X. Transcripts from the genes encoding DNA binding domains were expressed in embryonic and postnatal retinas with distinct spatial patterns.

    Conclusions: The characterization of 26 mouse genes whose partial nucleotide sequences were uniquely represented in the RetinalExpress cDNA/EST database demonstrated the feasibility of retinal gene discovery using in silico analysis. Two of these genes had distinctive spatial expression patterns in the retina and one was likely to function as a DNA binding protein in embryonic and postnatal retinas. The gene identification approach described here demonstrates the usefulness of establishing large cDNA/EST databases from highly specialized neuronal tissues such as the retina to find novel genes.

    Funded by: NCI NIH HHS: CA16672; NEI NIH HHS: EY11930, EY13523

    Molecular vision 2004;10;773-86

  • The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).

    Gerhard DS, Wagner L, Feingold EA, Shenmen CM, Grouse LH, Schuler G, Klein SL, Old S, Rasooly R, Good P, Guyer M, Peck AM, Derge JG, Lipman D, Collins FS, Jang W, Sherry S, Feolo M, Misquitta L, Lee E, Rotmistrovsky K, Greenhut SF, Schaefer CF, Buetow K, Bonner TI, Haussler D, Kent J, Kiekhaus M, Furey T, Brent M, Prange C, Schreiber K, Shapiro N, Bhat NK, Hopkins RF, Hsie F, Driscoll T, Soares MB, Casavant TL, Scheetz TE, Brown-stein MJ, Usdin TB, Toshiyuki S, Carninci P, Piao Y, Dudekula DB, Ko MS, Kawakami K, Suzuki Y, Sugano S, Gruber CE, Smith MR, Simmons B, Moore T, Waterman R, Johnson SL, Ruan Y, Wei CL, Mathavan S, Gunaratne PH, Wu J, Garcia AM, Hulyk SW, Fuh E, Yuan Y, Sneed A, Kowis C, Hodgson A, Muzny DM, McPherson J, Gibbs RA, Fahey J, Helton E, Ketteman M, Madan A, Rodrigues S, Sanchez A, Whiting M, Madari A, Young AC, Wetherby KD, Granite SJ, Kwong PN, Brinkley CP, Pearson RL, Bouffard GG, Blakesly RW, Green ED, Dickson MC, Rodriguez AC, Grimwood J, Schmutz J, Myers RM, Butterfield YS, Griffith M, Griffith OL, Krzywinski MI, Liao N, Morin R, Morrin R, Palmquist D, Petrescu AS, Skalska U, Smailus DE, Stott JM, Schnerch A, Schein JE, Jones SJ, Holt RA, Baross A, Marra MA, Clifton S, Makowski KA, Bosak S, Malek J and MGC Project Team

    The National Institutes of Health's Mammalian Gene Collection (MGC) project was designed to generate and sequence a publicly accessible cDNA resource containing a complete open reading frame (ORF) for every human and mouse gene. The project initially used a random strategy to select clones from a large number of cDNA libraries from diverse tissues. Candidate clones were chosen based on 5'-EST sequences, and then fully sequenced to high accuracy and analyzed by algorithms developed for this project. Currently, more than 11,000 human and 10,000 mouse genes are represented in MGC by at least one clone with a full ORF. The random selection approach is now reaching a saturation point, and a transition to protocols targeted at the missing transcripts is now required to complete the mouse and human collections. Comparison of the sequence of the MGC clones to reference genome sequences reveals that most cDNA clones are of very high sequence quality, although it is likely that some cDNAs may carry missense variants as a consequence of experimental artifact, such as PCR, cloning, or reverse transcriptase errors. Recently, a rat cDNA component was added to the project, and ongoing frog (Xenopus) and zebrafish (Danio) cDNA projects were expanded to take advantage of the high-throughput MGC pipeline.

    Funded by: PHS HHS: N01-C0-12400

    Genome research 2004;14;10B;2121-7

  • The role of Pax2 in mouse inner ear development.

    Burton Q, Cole LK, Mulheisen M, Chang W and Wu DK

    National Institute on Deafness and Other Communication Disorders, Bethesda, MD 20892, USA.

    The paired box transcription factor, Pax2, is important for cochlear development in the mouse inner ear. Two mutant alleles of Pax2, a knockout and a frameshift mutation (Pax21Neu), show either agenesis or severe malformation of the cochlea, respectively. In humans, mutations in the PAX2 gene cause renal coloboma syndrome that is characterized by kidney abnormalities, optic nerve colobomas and mild sensorineural deafness. To better understand the role of Pax2 in inner ear development, we examined the inner ear phenotype in the Pax2 knockout mice using paint-fill and gene expression analyses. We show that Pax2-/- ears often lack a distinct saccule, and the endolymphatic duct and common crus are invariably fused. However, a rudimentary cochlea is always present in all Pax2 knockout inner ears. Cochlear outgrowth in the mutants is arrested at an early stage due to apoptosis of cells that normally express Pax2 in the cochlear anlage. Lack of Pax2 affects tissue specification within the cochlear duct, particularly regions between the sensory tissue and the stria vascularis. Because the cochlear phenotypes observed in Pax2 mutants are more severe than those observed in mice lacking Otx1 and Otx2, we postulate that Pax2 plays a key role in regulating the differential growth within the cochlear duct and thus, its proper outgrowth and coiling.

    Developmental biology 2004;272;1;161-75

  • In vitro assembly properties of mutant and chimeric intermediate filament proteins: insight into the function of sequences in the rod and end domains of IF.

    Gu L, Troncoso JC, Wade JB and Monteiro MJ

    Molecular and Cell Biology Graduate Program, University of Maryland Biotechnology Institute, Baltimore 21201, USA.

    The factors and mechanisms regulating assembly of intermediate filament (IF) proteins to produce filaments with their characteristic 10 nm diameter are not fully understood. All IF proteins contain a central rod domain flanked by variable head and tail domains. To elucidate the role that different domains of IF proteins play in filament assembly, we used negative staining and electron microscopy (EM) to study the in vitro assembly properties of purified bacterially expressed IF proteins, in which specific domains of the proteins were either mutated or swapped between a cytoplasmic (mouse neurofilament-light (NF-L) subunit) and nuclear intermediate filament protein (human lamin A). Our results indicate that filament formation is profoundly influenced by the composition of the assembly buffer. Wild type (wt) mouse NF-L formed 10 nm filaments in assembly buffer containing 175 mM NaCl, whereas a mutant deleted of 18 NH2-terminal amino acids failed to assemble under similar conditions. Instead, the mutant assembled efficiently in buffers containing CaCl2 > or = 6 mM forming filaments that were 10 times longer than those formed by wt NF-L, although their diameter was significantly smaller (6-7 nm). These results suggest that the 18 NH2-terminal sequence of NF-L might serve two functions, to inhibit filament elongation and to promote lateral association of NF-L subunits. We also demonstrate that lengthening of the NF-L rod domain, by inserting a 42 aa sequence unique to nuclear IF proteins, does not compromise filament assembly in any noticeable way. Our results suggests that the known inability of nuclear lamin proteins to assemble into 10 nm filaments in vitro cannot derive solely from their longer rod domain. Finally, we demonstrate that the head domain of lamin A can substitute for that of NF-L in filament assembly, whereas substitution of both the head and tail domains of lamins for those of NF-L compromises assembly. Therefore, the effect of lamin A "tail" domain alone, or the synergistic effect of lamin "head" and the "tail" domains together, interferes with assembly into 10-nm filaments.

    Experimental cell research 2004;298;1;249-61

  • Oxidative modification of neurofilament-L by the Cu,Zn-superoxide dismutase and hydrogen peroxide system.

    Kim NH, Jeong MS, Choi SY and Hoon Kang J

    Department of Genetic Engineering, Cheongju University, Cheongju 360-764, Korea.

    Neurofilament-L (NF-L) is a major element of neuronal cytoskeletons and known to be important for their survival in vivo. Since oxidative stress might play a critical role in the pathogenesis of neurodegenerative diseases, we investigated the role of Cu,Zn-superoxide dismutase (SOD) in the modification of NF-L. When disassembled NF-L was incubated with Cu,Zn-SOD and H2O2, the aggregation of protein was proportional to the concentration of hydrogen peroxide. Cu,Zn-SOD/H2O2-mediated modification of NF-L was significantly inhibited by radical scavenger, spin trap agents and copper chelators. Dityrosine crosslink formation was obtained in Cu,Zn-SOD/H2O2-mediated NF-L aggregates. Antioxidant molecules, carnosine and anserine significantly inhibited the aggregation of NF-L and the formation of dityrosine. This study suggests that copper-mediated NF-L modification may be closely related to oxidative reactions which play a critical role in neurodegenerative diseases.

    Biochimie 2004;86;8;553-9

  • A NUDEL-dependent mechanism of neurofilament assembly regulates the integrity of CNS neurons.

    Nguyen MD, Shu T, Sanada K, Larivière RC, Tseng HC, Park SK, Julien JP and Tsai LH

    Department of Pathology, Harvard Medical School and Howard Hughes Medical Institute, 77 Avenue Louis Pasteur, New Research Building, Room 856-8, MA 02115, USA. minh-dang_nguyen@hms.harvard.edu

    The cytoskeleton controls the architecture and survival of central nervous system (CNS) neurons by maintaining the stability of axons and dendrites. Although neurofilaments (NFs) constitute the main cytoskeletal network in these structures, the mechanism that underlies subunit incorporation into filaments remains a mystery. Here we report that NUDEL, a mammalian homologue of the Aspergillus nidulans nuclear distribution molecule NudE, is important for NF assembly, transport and neuronal integrity. NUDEL facilitates the polymerization of NFs through a direct interaction with the NF light subunit (NF-L). Knockdown of NUDEL by RNA interference (RNAi) in a neuroblastoma cell line, primary cortical neurons or post-natal mouse brain destabilizes NF-L and alters the homeostasis of NFs. This results in NF abnormalities and morphological changes reminiscent of neurodegeneration. Furthermore, variations in levels of NUDEL correlate with disease progression and NF defects in a mouse model of neurodegeneration. Thus, NUDEL contributes to the integrity of CNS neurons by regulating NF assembly.

    Nature cell biology 2004;6;7;595-608

  • Fine localization of Nefl and Nef3 and its exclusion as candidate gene for lens rupture 2(lr2).

    Rhee SD, Kim E, Yoon SK, Yang SD, Okumoto M, Han SS and Song CW

    Korea Research Institute of Chemical Technology, Yusong-gu, Taejon.

    Cataract causing lr2 gene is found in the CXSD mouse, which is a recombinant inbred strain of BALB/c and STS mice. For the process of positional cloning of lr2, several candidate genes were selected in the middle region of chromosome 14, but most of them were excluded by combination of recombination and homozygosity mapping. Components of neurofilament proteins, neurofilament light polypeptide (Nefl) and neurofilament3 medium (Nef3), were linked to D14Mit87 which was not separated from the lr2 locus in the homozygosity mapping. When the expression levels of Nefl and Nef3 in eyes were compared in CXSD and BALB/c mice, there were no differences in expression levels. The cDNA sequences of the two genes from CXSD, BALB/c and STS mice were subsequently compared. Several nucleotide differences in cDNA sequences were detected between the mice strains but the majority of the changes were silent mutations that did not alter the amino acids. The sole amino acid difference, E567K in the glutamate rich region of Nfm, between BALB/c and CXSD was found to be a simple genetic polymorphism because the same substitution existed in STS, a non-cataract mouse strain. Therefore we excluded Nefl and Nef3 from the candidate genes for lr2 based on expression and mutation analyses.

    Experimental animals 2004;53;4;295-301

  • Immuno-characterization of the switch of peptide elongation factors eEF1A-1/EF-1alpha and eEF1A-2/S1 in the central nervous system during mouse development.

    Pan J, Ruest LB, Xu S and Wang E

    Bloomfield Center for Research in Aging, Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital and Department of Medicine, McGill University, Montréal, Canada.

    During early postnatal development, a switch occurs between eEF1A-1/EF-1alpha and eEF1A-2/S1, homologous peptide elongation factors, in brain, heart, and skeletal muscle; eEF1A-2/S1 becomes the major form expressed in maturity. By immunofluorescent labeling, we detected both homologues in the developing brains of wild-type and wasted mutant mice, carrying a deletion in the eEF1A-2/S1 gene; we found that brain expression of eEF1A-2/S1 protein is restricted to mature, terminally differentiated neurons, and coincides with the disappearance of eEF1A-1/EF-1alpha 20 days after birth. Furthermore, no elongation factor 1A is present in wasted mutant mice neurons following the developmental switch, indicating that the genetic regulation silencing eEF1A-1/EF-1alpha is still functional.

    Funded by: NIA NIH HHS: AG10821, P01 AG010821-060005

    Brain research. Developmental brain research 2004;149;1;1-8

  • 3' untranslated region in a light neurofilament (NF-L) mRNA triggers aggregation of NF-L and mutant superoxide dismutase 1 proteins in neuronal cells.

    Lin H, Zhai J, Cañete-Soler R and Schlaepfer WW

    Division of Neuropathology, University of Pennsylvania Medical School, Philadelphia, Pennsylvania 19104, USA.

    The pathogenesis of neurodegenerative diseases is believed to involve abnormal aggregation of proteins, but the mechanisms initiating protein aggregation are unclear. Here we report a novel phenomenon that could be instrumental in triggering protein aggregation in neurodegenerative diseases. We show that the 3' untranslated region (3'UTR) of a light neurofilament (NF-L) transcript enhances the reactivity of its own translated product and leads to loss of solubility and aggregation of NF-L protein and to coaggregation of mutant superoxide dismutase 1 (SOD1) protein. Full-length mouse NF-L cDNAs, with and without NF-L 3'UTR, were fused to the C terminus of a green fluorescent protein (GFP) reporter gene, and the GFP-tagged NF-L proteins were examined in transfected Neuro2a cells. The GFP-tagged NF-L protein expressed from the transgene containing NF-L 3'UTR, but not from the transgene lacking NF-L 3'UTR, colocalizes with endogenous heavy neurofilament protein and, at high-level expression, leads to loss of solubility and aggregation of GFP-tagged NF-L protein. Aggregation of GFP-tagged NF-L protein triggers coaggregation and loss of solubility of coexpressed DsRed-tagged mutant (G93A) SOD1 protein but not wild-type SOD1 protein. Deletional mutagenesis maps the RNA sequence causing aggregation of GFP-tagged NF-L protein to the proximal 45 nucleotides of NF-L 3'UTR. This is the site of a major destabilizing element in NF-L RNA and binding site for RNA-binding proteins. Our findings support a working model whereby NF-L RNA, or cognate RNA-binding factors, enhances the reactivity of NF-L protein and provides a triggering mechanism leading to aggregation of NF-L and other proteins in neurodegenerative diseases.

    Funded by: NINDS NIH HHS: NS37552, R01 NS15722

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2004;24;11;2716-26

  • Discrete gene sets depend on POU domain transcription factor Brn3b/Brn-3.2/POU4f2 for their expression in the mouse embryonic retina.

    Mu X, Beremand PD, Zhao S, Pershad R, Sun H, Scarpa A, Liang S, Thomas TL and Klein WH

    Department of Biochemistry and Molecular Biology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.

    Brn3b/Brn-3.2/POU4f2 is a POU domain transcription factor that is essential for retinal ganglion cell (RGC) differentiation, axonal outgrowth and survival. Our goal was to establish a link between Brn3b and the downstream events leading to RGC differentiation. We sought to determine both the number and types of genes that depend on Brn3b for their expression. RNA probes from wild-type and Brn3b(-/-) E14.5, E16.5 and E18.5 mouse retinas were hybridized to a microarray containing 18,816 retina-expressed cDNAs. At E14.5, we identified 87 genes whose expression was significantly altered in the absence of Brn3b and verified the results by real-time PCR and in situ hybridization. These genes fell into discrete sets that encoded transcription factors, proteins associated with neuron integrity and function, and secreted signaling molecules. We found that Brn3b influenced gene expression in non RGCs of the retina by controlling the expression of secreted signaling molecules such as sonic hedgehog and myostatin/Gdf8. At later developmental stages, additional alterations in gene expression were secondary consequences of aberrant RGC differentiation caused by the absence of Brn3b. Our results demonstrate that a small but crucial fraction of the RGC transcriptome is dependent on Brn3b. The Brn3b-dependent gene sets therefore provide a unique molecular signature for the developing retina.

    Funded by: NCI NIH HHS: CA16672; NEI NIH HHS: EY11930, EY13523

    Development (Cambridge, England) 2004;131;6;1197-210

  • Neurofilament transport in vivo minimally requires hetero-oligomer formation.

    Yuan A, Rao MV, Kumar A, Julien JP and Nixon RA

    Center for Dementia Research, Nathan Kline Institute, New York University School of Medicine, Orangeburg, New York 10962, USA. yuan@nki.rfmh.org

    Neurofilament assembly requires at minimum the polymerization of neurofilament light chain (NF-L) with either neurofilament medium chain (NF-M) or neurofilament heavy chain (NF-H) subunits, but requirements for their axonal transport have long been controversial. Using a gene deletion approach, we generated mice containing only NF-L or NF-M. In vivo pulse radiolabeling analyses in retinal ganglion cell neurons revealed that NF-L alone is incapable of efficient transport, whereas nearly one-half of the normal level of NF-M is transported along optic axons in the absence of the other triplet subunits. Under these conditions, however, NF-M transport is completely abolished by deleting alpha-internexin. Our results strongly suggest that efficient neurofilament protein transport in vivo minimally requires hetero-oligomer formation. They also show that NF-M can partner with intermediate filament proteins other than the NF-H and NF-L subunits in neurons to support slow transport and possibly other functions of neuronal intermediate filaments.

    Funded by: NIA NIH HHS: AG05604; NIDDK NIH HHS: P30-DK19525

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2003;23;28;9452-8

  • Myotubularin-related 2 protein phosphatase and neurofilament light chain protein, both mutated in CMT neuropathies, interact in peripheral nerve.

    Previtali SC, Zerega B, Sherman DL, Brophy PJ, Dina G, King RH, Salih MM, Feltri L, Quattrini A, Ravazzolo R, Wrabetz L, Monaco AP and Bolino A

    Neuropathology Unit, Department of Neurology, San Raffaele Scientific Institute, 20132 Milan, Italy.

    Charcot-Marie-Tooth disease type 4B1, CMT4B1, is a severe, autosomal-recessive, demyelinating peripheral neuropathy, due to mutations in the Myotubularin-related 2 gene, MTMR2. MTMR2 is widely expressed and encodes a phosphatase whose substrates include phosphoinositides. However, this does not explain how MTMR2 mutants specifically produce demyelination in the peripheral nerve. Therefore, we analysed the cellular and subcellular distribution of Mtmr2 in nerve. Mtmr2 was detected in all cytoplasmic compartments of myelin-forming Schwann cells, as well as in the cytoplasm of non-myelin-forming Schwann cells and both sensory and motorneurons. In contrast, Mtmr2 was detected in the nucleus of Schwann cells and motorneurons, but not in the nucleus of sensory neurons. As Mtmr2 is diffusely present also within the nerve, a specific function could derive instead from nerve-specific interacting proteins. Therefore, we performed two yeast two-hybrid screenings, using either fetal brain or peripheral nerve cDNA libraries. The neurofilament light chain protein, NF-L, was identified repeatedly in both screenings, and found to interact with MTMR2 in both Schwann cells and neurons. Interestingly, NF-L, encoding NF-L, is mutated in CMT2E. These data may provide a basis for the nerve-specific pathogenesis of CMT4B1, and further support for the notion that hereditary demyelinating and axonal neuropathies may represent different clinical manifestations of a common pathological mechanism.

    Funded by: NINDS NIH HHS: NS 41319, NS 45630; Telethon: TCP00062

    Human molecular genetics 2003;12;14;1713-23

  • Peripherin is not a contributing factor to motor neuron disease in a mouse model of amyotrophic lateral sclerosis caused by mutant superoxide dismutase.

    Larivière RC, Beaulieu JM, Nguyen MD and Julien JP

    Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, McGill University, Montréal, Québec H3G 1A4, Canada.

    Peripherin is a type III intermediate filament protein detected in axonal spheroids associated with amyotrophic lateral sclerosis (ALS). The overexpression of peripherin induces degeneration of spinal motor neurons during aging in transgenic mice and in cultured neuronal cells derived from peripherin transgenic embryos. Here, we investigated whether peripherin is a contributor of pathogenesis in mice overexpressing a mutant superoxide dismutase 1 (SOD1(G37R)) gene linked to familial ALS. This was done by the generation and analysis of SOD1(G37R) mice that either overexpress a peripherin transgene (G37R;TgPer mice) or lack the endogenous peripherin gene (G37R;Per-/- mice). Surprisingly, upregulation or suppression of peripherin expression had no effects on disease onset, mortality, and loss of motor neurons in SOD1(G37R) mice. These results provide compelling evidence that peripherin is not a key contributor of motor neuron degeneration associated with toxicity of mutant SOD1.

    Funded by: NINDS NIH HHS: 5R01 NS 41583-02

    Neurobiology of disease 2003;13;2;158-66

  • Neuromuscular synapses mediate motor axon branching and motoneuron survival during the embryonic period of programmed cell death.

    Banks GB, Choy PT, Lavidis NA and Noakes PG

    School of Biomedical Sciences, Department of Physiology and Pharmacology and SRC for Bio-informatics and Applied Genomics, University of Queensland, 4072, St. Lucia, Queensland, Australia.

    The embryonic period of motoneuron programmed cell death (PCD) is marked by transient motor axon branching, but the role of neuromuscular synapses in regulating motoneuron number and axonal branching is not known. Here, we test whether neuromuscular synapses are required for the quantitative association between reduced skeletal muscle contraction, increased motor neurite branching, and increased motoneuron survival. We achieved this by comparing agrin and rapsyn mutant mice that lack acetylcholine receptor (AChR) clusters. There were significant reductions in nerve-evoked skeletal muscle contraction, increases in intramuscular axonal branching, and increases in spinal motoneuron survival in agrin and rapsyn mutant mice compared with their wild-type littermates at embryonic day 18.5 (E18.5). The maximum nerve-evoked skeletal muscle contraction was reduced a further 17% in agrin mutants than in rapsyn mutants. This correlated to an increase in motor axon branch extension and number that was 38% more in agrin mutants than in rapsyn mutants. This suggests that specializations of the neuromuscular synapse that ensure efficient synaptic transmission and muscle contraction are also vital mediators of motor axon branching. However, these increases in motor axon branching did not correlate with increases in motoneuron survival when comparing agrin and rapsyn mutants. Thus, agrin-induced synaptic specializations are required for skeletal muscle to effectively control motoneuron numbers during embryonic development.

    Developmental biology 2003;257;1;71-84

  • The nNOS inhibitor, AR-R17477AR, prevents the loss of NF68 immunoreactivity induced by methamphetamine in the mouse striatum.

    Sanchez V, Zeini M, Camarero J, O'Shea E, Bosca L, Green AR and Colado MI

    Departamento de Farmacologia and Facultad de Medicina Instituto de Bioquimica CSIC-UCM, Facultad de Farmacia, Universidad Complutense, Madrid, Spain. colado@med.ucm.es

    The present study examined the time-course and regionally-selective changes in the levels of the neurofilament protein NF68 in the mouse brain induced by methamphetamine (METH). The ability of low ambient temperature, or of the specific neuronal nitric oxide synthase (nNOS) inhibitor AR-R17477AR, to protect against both long-term striatal NF68 and dopamine loss induced by METH (3 mg/kg, i.p.) was also studied. Seven days after METH administration (3, 6 and 9 mg/kg, i.p., three times at 3 h intervals), mice showed a reduction of about 40% in immunoreactivity for NF68 in the striatum. This effect was not produced in cortex after METH administration at the dose of 3 mg/kg. No difference from controls was observed when measurements were carried out 1 h and 24 h after the last METH injection at the dose of 3 mg/kg. The loss of NF68 immunoreactivity seems to be associated with the long-term dopamine depletion induced by METH, since no change in serotonin concentration is observed in either the striatum or cortex 7 days after dosing. Animals kept at a room temperature of 4 degrees C showed a loss of NF68 similar to those treated at 22 degrees C but an attenuation of dopamine depletion in the striatum. Pre-treatment with AR-R17477AR (5 mg/kg, s.c.) 30 min before each of the three METH (3 mg/kg, i.p.) injections provided complete protection against METH-induced loss of NF68 immunoreactivity and attenuated the decrease in striatal dopamine and HVA concentrations by about 50%. These data indicate that both the reduction of NF68 immunoreactivity and the loss of dopamine concentration are due to an oxidative stress process mediated by reactive nitrogen species, and are not due to changes in body temperature.

    Journal of neurochemistry 2003;85;2;515-24

  • Defective somite patterning in mouse embryos with reduced levels of Tbx6.

    White PH, Farkas DR, McFadden EE and Chapman DL

    Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.

    During vertebrate embryogenesis, paraxial mesoderm gives rise to somites, which subsequently develop into the dermis, skeletal muscle, ribs and vertebrae of the adult. Mutations that disrupt the patterning of individual somites have dramatic effects on these tissues, including fusions of the ribs and vertebrae. The T-box transcription factor, Tbx6, is expressed in the paraxial mesoderm but is downregulated as somites develop. It is essential for the formation of posterior somites, which are replaced with ectopic neural tubes in Tbx6-null mutant embryos. We show that partial restoration of Tbx6 expression in null mutants rescues somite development, but that rostrocaudal patterning within them is defective, ultimately resulting in rib and vertebral fusions, demonstrating that Tbx6 activity in the paraxial mesoderm is required not simply for somite specification but also for their normal patterning. Somite patterning is dependent upon Notch signaling and we show that Tbx6 genetically interacts with the Notch ligand, delta-like 1 (Dll1). Dll1 expression, which is absent in the Tbx6-null mutant, is restored at reduced levels in the partially rescued mutants, suggesting that Dll1 is a target of Tbx6. We also identify the spontaneous mutation rib-vertebrae as a hypomorphic mutation in Tbx6. The similarity in the phenotypes we describe here and that of some human birth defects, such as spondylocostal dysostosis, raises the possibility that mutations in Tbx6 or components of this pathway may be responsible for these defects.

    Funded by: NICHD NIH HHS: HD38786

    Development (Cambridge, England) 2003;130;8;1681-90

  • Peripherin-mediated death of motor neurons rescued by overexpression of neurofilament NF-H proteins.

    Beaulieu JM and Julien JP

    Centre for Research in Neurosciences, McGill University, The Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada.

    In previous studies, we showed that overexpression of peripherin, a neuronal intermediate filament (IF) protein, in mice deficient for neurofilament light (NF-L) subunits induced a progressive adult-onset degeneration of spinal motor neurons characterized by the presence of IF inclusion bodies reminiscent of axonal spheroids found in amyotrophic lateral sclerosis (ALS). In contrast, the overexpression of human neurofilament heavy (NF-H) proteins provoked the formation of massive perikaryal IF protein accumulations with no loss of motor neurons. To further investigate the toxic properties of IF protein inclusions, we generated NF-L null mice that co-express both peripherin and NF-H transgenes. The axonal count in L5 ventral roots from 6 and 8-month-old transgenic mice showed that NF-H overexpression rescued the peripherin-mediated degeneration of motor neurons. Our analysis suggests that the protective effect of extra NF-H proteins is related to the sequestration of peripherin into the perikaryon of motor neurons, thereby abolishing the development of axonal IF inclusions that might block transport. These findings illustrate the importance of IF protein stoichiometry in formation, localization and toxicity of neuronal inclusion bodies.

    Journal of neurochemistry 2003;85;1;248-56

  • A neurotoxic peripherin splice variant in a mouse model of ALS.

    Robertson J, Doroudchi MM, Nguyen MD, Durham HD, Strong MJ, Shaw G, Julien JP and Mushynski WE

    Centre for Research in Neurosciences, Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec, H3G 1A4, Canada. janice.robertson@mcgill.ca

    Peripherin, a neuronal intermediate filament (nIF) protein found associated with pathological aggregates in motor neurons of patients with amyotrophic lateral sclerosis (ALS) and of transgenic mice overexpressing mutant superoxide dismutase-1 (SOD1G37R), induces the selective degeneration of motor neurons when overexpressed in transgenic mice. Mouse peripherin is unique compared with other nIF proteins in that three peripherin isoforms are generated by alternative splicing. Here, the properties of the peripherin splice variants Per 58, Per 56, and Per 61 have been investigated in transfected cell lines, in primary motor neurons, and in transgenic mice overexpressing peripherin or overexpressing SOD1G37R. Of the three isoforms, Per 61 proved to be distinctly neurotoxic, being assembly incompetent and inducing degeneration of motor neurons in culture. Using isoform-specific antibodies, Per 61 expression was detected in motor neurons of SOD1G37R transgenic mice but not of control or peripherin transgenic mice. The Per 61 antibody also selectively labeled motor neurons and axonal spheroids in two cases of familial ALS and immunoprecipitated a higher molecular mass peripherin species from disease tissue. This evidence suggests that expression of neurotoxic splice variants of peripherin may contribute to the neurodegenerative mechanism in ALS.

    Funded by: Wellcome Trust

    The Journal of cell biology 2003;160;6;939-49

  • Myosin Va binding to neurofilaments is essential for correct myosin Va distribution and transport and neurofilament density.

    Rao MV, Engle LJ, Mohan PS, Yuan A, Qiu D, Cataldo A, Hassinger L, Jacobsen S, Lee VM, Andreadis A, Julien JP, Bridgman PC and Nixon RA

    Center for Dementia Research, Nathan Kline Institute, NYU School of Medicine, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA.

    The identification of molecular motors that modulate the neuronal cytoskeleton has been elusive. Here, we show that a molecular motor protein, myosin Va, is present in high proportions in the cytoskeleton of mouse CNS and peripheral nerves. Immunoelectron microscopy, coimmunoprecipitation, and blot overlay analyses demonstrate that myosin Va in axons associates with neurofilaments, and that the NF-L subunit is its major ligand. A physiological association is indicated by observations that the level of myosin Va is reduced in axons of NF-L-null mice lacking neurofilaments and increased in mice overexpressing NF-L, but unchanged in NF-H-null mice. In vivo pulse-labeled myosin Va advances along axons at slow transport rates overlapping with those of neurofilament proteins and actin, both of which coimmunoprecipitate with myosin Va. Eliminating neurofilaments from mice selectively accelerates myosin Va translocation and redistributes myosin Va to the actin-rich subaxolemma and membranous organelles. Finally, peripheral axons of dilute-lethal mice, lacking functional myosin Va, display selectively increased neurofilament number and levels of neurofilament proteins without altering axon caliber. These results identify myosin Va as a neurofilament-associated protein, and show that this association is essential to establish the normal distribution, axonal transport, and content of myosin Va, and the proper numbers of neurofilaments in axons.

    Funded by: NIA NIH HHS: 2T32 AG 00222, AG 05604, R01 AG005604, R37 AG005604, T32 AG000222; NIDDK NIH HHS: P30 DK 19525, P30 DK019525

    The Journal of cell biology 2002;159;2;279-90

  • Development of chromaffin cells depends on MASH1 function.

    Huber K, Brühl B, Guillemot F, Olson EN, Ernsberger U and Unsicker K

    Neuroanatomy, Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg, INF 307, D-69120 Heidelberg, Germany.

    The sympathoadrenal (SA) cell lineage is a derivative of the neural crest (NC), which gives rise to sympathetic neurons and neuroendocrine chromaffin cells. Signals that are important for specification of these two types of cells are largely unknown. MASH1 plays an important role for neuronal as well as catecholaminergic differentiation. Mash1 knockout mice display severe deficits in sympathetic ganglia, yet their adrenal medulla has been reported to be largely normal suggesting that MASH1 is essential for neuronal but not for neuroendocrine differentiation. We show now that MASH1 function is necessary for the development of the vast majority of chromaffin cells. Most adrenal medullary cells in Mash1(-/-) mice identified by Phox2b immunoreactivity, lack the catecholaminergic marker tyrosine hydroxylase. Mash1 mutant and wild-type mice have almost identical numbers of Phox2b-positive cells in their adrenal glands at embryonic day (E) 13.5; however, only one-third of the Phox2b-positive adrenal cell population seen in Mash1(+/+) mice is maintained in Mash1(-/-) mice at birth. Similar to Phox2b, cells expressing Phox2a and Hand2 (dHand) clearly outnumber TH-positive cells. Most cells in the adrenal medulla of Mash1(-/-) mice do not contain chromaffin granules, display a very immature, neuroblast-like phenotype, and, unlike wild-type adrenal chromaffin cells, show prolonged expression of neurofilament and Ret comparable with that observed in wild-type sympathetic ganglia. However, few chromaffin cells in Mash1(-/-) mice become PNMT positive and downregulate neurofilament and Ret expression. Together, these findings suggest that the development of chromaffin cells does depend on MASH1 function not only for catecholaminergic differentiation but also for general chromaffin cell differentiation.

    Development (Cambridge, England) 2002;129;20;4729-38

  • Neurofilament L gene is not a genetic factor of sporadic and familial Parkinson's disease.

    Rahner N, Holzmann C, Krüger R, Schöls L, Berger K and Riess O

    Department of Medical Genetics, Children's Hospital, University Rostock, Rembrandt Strasse 16/17, 18055, Rostock, Germany.

    Mutations in two genes, alpha-synuclein and parkin, have been identified as some rare causes for familial Parkinson's disease (PD). alpha-Synuclein and parkin protein have subsequently been identified in Lewy bodies (LB). To gain further insight into the pathogenesis of PD we investigated the role of neurofilament light (NF-L), another component of LB aggregation. A detailed mutation search of the NF-L gene in 328 sporadic and familial PD patients of German ancestry revealed three silent DNA changes (G163A, C224T, C487T) in three unrelated patients. Analysis of the promoter region of the NF-L gene identified a total of three base pair substitutions defining five haplotypes. Association studies based on these haplotypes revealed no significant differences between PD patients and 344 control individuals. Therefore, NF-L is unlikely to play a major role in the pathogenesis of PD.

    Brain research 2002;951;1;82-6

  • Untranslated element in neurofilament mRNA has neuropathic effect on motor neurons of transgenic mice.

    Nie Z, Wu J, Zhai J, Lin H, Ge W, Schlaepfer WW and Cañete-Soler R

    Division of Neuropathology, University of Pennsylvania Medical School, Philadelphia, Pennsylvania 19104-6100, USA.

    Studies of experimental motor neuron degeneration attributable to expression of neurofilament light chain (NF-L) transgenes have raised the possibility that the neuropathic effects result from overexpression of NF-L mRNA, independent of NF-L protein effects (Cañete-Soler et al., 1999). The present study was undertaken to test for an RNA-mediated pathogenesis. Transgenic mice were derived using either an enhanced green fluorescent protein reporter construct or modified chimeric constructs that differ only in their 3' untranslated regions (UTRs). Motor function and spinal cord histology were normal in mice expressing the unmodified reporter transgene. In mice expressing a chimeric transgene in which sequence of NF-L 3' UTR was inserted into the 3' UTR of the reporter transgene, we observed growth retardation and reduced kinetic activity during postnatal development. Older mice developed impairment of motor function and atrophy of nerve fibers in the ventral roots. A similar but more severe phenotype was observed when the chimeric transgene contained a 36 bp c-myc insert in an mRNA destabilizing element of the NF-L sequence. Our results suggest that neuropathic effects of overexpressing NF-L can occur at the level of transgene RNA and are mediated by sequences in the NF-L 3' UTR.

    Funded by: NINDS NIH HHS: NS35572

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2002;22;17;7662-70

  • Normal dendritic arborization in spinal motoneurons requires neurofilament subunit L.

    Zhang Z, Casey DM, Julien JP and Xu Z

    Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester 01655, USA.

    Neurofilaments, composed of three polypeptide subunits, NF-L, NF-M, and NF-H, are major cytoskeletal elements in large neurons with long axons. Neurofilaments play a critical role in the development of axonal diameter; however, their role in the development of dendrites is largely unknown. By overexpressing different neurofilament subunits, we previously demonstrated that alteration of neurofilament subunit composition resulted in dramatic changes in dendritic arborization. To further determine the role of neurofilaments in dendritic growth, we examined and compared the dendritic architecture of spinal cord neurons in young NF-L knockout (-/-), heterozygous (+/-), and wild-type (+/+) mice. We show that an absence or reduction in the expression of NF-L inhibited dendritic growth most dramatically in large motoneurons, mildly in medium neurons, but had no effect on small neurons. We also reveal that a decrease in NF-L leads to an increase in NF-M and NF-H subunits in cell bodies and their reduction in dendrites. These results demonstrate that NF-L is a critical intrinsic factor for dendritic growth in large motoneurons.

    Funded by: NINDS NIH HHS: NS35750

    The Journal of comparative neurology 2002;450;2;144-52

  • Characterization of mouse homolog of brain acyl-CoA hydrolase: molecular cloning and neuronal localization.

    Kuramochi Y, Takagi-Sakuma M, Kitahara M, Emori R, Asaba Y, Sakaguchi R, Watanabe T, Kuroda J, Hiratsuka K, Nagae Y, Suga T and Yamada J

    Department of Clinical Biochemistry, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, 192-0392, Tokyo, Japan.

    Acyl-CoA hydrolase could provide a mechanism via its potency to modulate cellular concentrations of acyl-CoAs for the regulation of various cellular events including fatty acid metabolism and gene expression. However, only limited evidence of this is available. To better understand the physiological role of this enzyme, we characterized a mouse brain acyl-CoA hydrolase, mBACH. The cloned cDNA for mBACH encoded a 338-amino-acid polypeptide with >95% identity to the human and rat homologs, indicating that the BACH gene is highly conserved among species. This was supported by the similarity in genomic organization of the BACH gene between humans and mice. Bacterially expressed mBACH was highly active against long-chain acyl-CoAs with a relatively broad specificity for chain length. While palmitoyl-CoA hydrolase activity was widely distributed in mouse tissues, it was marked in the brain, consistent with mBACH being almost exclusively distributed in this tissue, where >80% of the enzyme activity was explained by mBACH present in the cytosol. Immunohistochemistry demonstrated a neuronal localization of mBACH in both the central and peripheral nervous systems. In neurons, mBACH was distributed throughout the cell body and neurites. Although four isoforms except mBACH itself, that may be generated by the alternative use of exons of a single mBACH gene, were cloned, their mRNA levels in the brain were estimated to be negligible. However, a 50-kDa polypeptide besides the major one of 43-kDa seemed to be translated from the mBACH mRNA with differential in-frame ATG triplets used as the initiation codon. These findings will contribute to the functional analysis of the BACH gene using mice including genetic studies.

    Brain research. Molecular brain research 2002;98;1-2;81-92

  • Slit1 and Slit2 cooperate to prevent premature midline crossing of retinal axons in the mouse visual system.

    Plump AS, Erskine L, Sabatier C, Brose K, Epstein CJ, Goodman CS, Mason CA and Tessier-Lavigne M

    Department of Anatomy, Howard Hughes Medical Institute, CA, USA.

    During development, retinal ganglion cell (RGC) axons either cross or avoid the midline at the optic chiasm. In Drosophila, the Slit protein regulates midline axon crossing through repulsion. To determine the role of Slit proteins in RGC axon guidance, we disrupted Slit1 and Slit2, two of three known mouse Slit genes. Mice defective in either gene alone exhibited few RGC axon guidance defects, but in double mutant mice a large additional chiasm developed anterior to the true chiasm, many retinal axons projected into the contralateral optic nerve, and some extended ectopically-dorsal and lateral to the chiasm. Our results indicate that Slit proteins repel retinal axons in vivo and cooperate to establish a corridor through which the axons are channeled, thereby helping define the site in the ventral diencephalon where the optic chiasm forms.

    Funded by: NEI NIH HHS: EY 12736; NINDS NIH HHS: P0 NS 30532

    Neuron 2002;33;2;219-32

  • Brn3b/Brn3c double knockout mice reveal an unsuspected role for Brn3c in retinal ganglion cell axon outgrowth.

    Wang SW, Mu X, Bowers WJ, Kim DS, Plas DJ, Crair MC, Federoff HJ, Gan L and Klein WH

    Department of Biochemistry and Molecular Biology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.

    In mice, Brn3 POU domain transcription factors play essential roles in the differentiation and survival of projection neurons within the retina, inner ear, dorsal root and trigeminal ganglia. During retinal ganglion cell differentiation, Brn3b is expressed first, followed by Brn3a and Brn3c. Targeted deletion of Brn3b, but not Brn3a or Brn3c, leads to a loss of most retinal ganglion cells before birth. However, as a few retinal ganglion cells are still present in Brn3b(-/-) mice, Brn3a and Brn3c may partially compensate for the loss of Brn3b. To examine the role of Brn3c in retinal ganglion cell development, we generated Brn3b/Brn3c double knockout mice and analyzed their retinas and optic chiasms. Retinal ganglion cell axons from double knockout mice were more severely affected than were those from Brn3b-deficient mice, indicating that Brn3c was required for retinal ganglion cell differentiation and could partially compensate for the loss of Brn3b. Moreover, Brn3c had functions in retinal ganglion cell differentiation separate from those of Brn3b. Ipsilateral and misrouted projections at the optic chiasm were overproduced in Brn3b(-/-) mice but missing were entirely in optic chiasms of Brn3b/Brn3c double knockout mice, suggesting that Brn3c controlled ipsilateral axon production. Forced expression of Brn3c in Brn3b(-/-) retinal explants restored neurite outgrowth, demonstrating that Brn3c could promote axon outgrowth in the absence of Brn3b. Our results reveal a complex genetic relationship between Brn3b and Brn3c in regulating the retinal ganglion cell axon outgrowth.

    Funded by: NEI NIH HHS: EY11930; NIA NIH HHS: AG 18254

    Development (Cambridge, England) 2002;129;2;467-77

  • Attenuated neurodegenerative disease phenotype in tau transgenic mouse lacking neurofilaments.

    Ishihara T, Higuchi M, Zhang B, Yoshiyama Y, Hong M, Trojanowski JQ and Lee VM

    Center for Neurodegenerative Disease Research, Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.

    Previous studies have shown that transgenic (Tg) mice overexpressing human tau protein develop filamentous tau aggregates in the CNS. The most abundant tau aggregates are found in spinal cord and brainstem in which they colocalize with neurofilaments (NFs) as spheroids in axons. To elucidate the role of NF subunit proteins in tau aggregate formation and to test the hypothesis that NFs are pathological chaperones in the formation of intraneuronal tau inclusions, we crossbred previously described tau (T44) Tg mice overexpressing the smallest human tau isoform with knock-out mice devoid of NFL (NFL-/-) or NFH (NFH-/-). Depletion of NF subunit proteins from the T44 mice (i.e., T44;NFL-/- and T44;NFH-/-), in particular NFL, resulted in a dramatic decrease in the total number of tau-positive spheroids in spinal cord and brainstem. Concomitant with the reduction in spheroid number, the bigenic mice showed delayed accumulation of insoluble tau protein in the CNS, increased viability, reduced weight loss, and improved behavioral phenotype when compared with the single T44 Tg mice. These results imply that NFs are pathological chaperones in the development of tau spheroids and suggest a role for NFs in the pathogenesis of neurofibrillary tau lesions in neurodegenerative disorders that contain both NFs and tau proteins.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2001;21;16;6026-35

  • Regionalized neurofilament accumulation and motoneuron degeneration are linked phenotypes in wobbler neuromuscular disease.

    Pernas-Alonso R, Perrone-Capano C, Volpicelli F and di Porzio U

    International Institute of Genetics and Biophysics, CNR, Naples, Italy.

    Abnormal neurofilament aggregates are pathological hall-mark of most neurodegenerative diseases, although their pathogenic role remains unclear. Increased expression of medium neurofilament (NFM) is an early molecular marker of wobbler mouse, an animal model of motoneuron disease. In the wr/wr, a vacuolar neuronal degeneration (VND) starts at 15 days postnatally, selectively in cervical spinal cord and brain stem motoneurons. Here we show that nfm gene hyperexpression is restricted to the aforementioned motoneurons and is specific for wr mutation. NF proteins accumulate in wr/wr before VND. wr/+ mice, which are asymptomatic, show intermediate NF accumulation between wr/wr and +/+ littermates, suggesting a gene dosage dependence of the wobbler pathology. Altogether our data indicate that NF hyperexpression and regionalized motoneuron degeneration are linked to the wr mutation, although with a still unknown relationship to the mutant gene activity.

    Neurobiology of disease 2001;8;4;581-9

  • Characterization of elongation factor-1A (eEF1A-1) and eEF1A-2/S1 protein expression in normal and wasted mice.

    Khalyfa A, Bourbeau D, Chen E, Petroulakis E, Pan J, Xu S and Wang E

    Bloomfield Center for Research in Aging, Lady Davis Institute for Medical Research, The Sir Mortimer B. Davis-Jewish General Hospital, McGill University, Montréal, Québec H3T 1E2, Canada.

    The eEF1Alpha-2 gene (S1) encodes a tissue-specific isoform of peptide elongation factor-1A (eEF1A-1); its mRNA is expressed only in brain, heart, and skeletal muscle, tissues dominated by terminally differentiated, long-lived cells. Homozygous mutant mice exhibit muscle wasting and neurodegeneration, resulting in death around postnatal day 28. eEF1Alpha-2/S1 protein shares 92% identity with eEF1A-1; because specific antibodies for each were not available previously, it was difficult to study the developmental expression patterns of these two peptide elongation factors 1A in wasted and wild-type mice. We generated a peptide-derived antiserum that recognizes the eEF1Alpha-2/S1 isoform and does not cross-react with eEF1A-1. We characterized the expression profiles of eEF1A-1 and eEF1A-2/S1 during development in wild-type (+/+), heterozygous (+/wst), and homozygous (wst/wst) mice. In wild-type and heterozygous animals, eEF1A-2/S1 protein is present only in brain, heart, and muscle; the onset of its expression coincides with a concomitant decrease in the eEF1A-1 protein level. In wasted mutant tissues, even though eEF1A-2/S1 protein is absent, the scheduled decline of eEF1A-1 occurs nonetheless during postnatal development, as it does in wild-type counterparts. In the brain of adult wild-type mice, the eEF1A-2/S1 isoform is localized in neurons, whereas eEF1A-1 is found in non-neuronal cells. In neurons prior to postnatal day 7, eEF1A-1 is the major isoform, but it is later replaced by eEF1A-2/S1, which by postnatal day 14 is the only isoform present. The postdevelopmental appearance of eEF1A-2/S1 protein and the decline in eEF1A-1 expression in brain, heart, and muscle suggest that eEF1A-2/S1 is the adult form of peptide elongation factor, whereas its sister is the embryonic isoform, in these tissues. The absence of eEF1A-2/S1, as well as the on-schedule development-dependent disappearance of its sister gene, eEF1A, in wst/wst mice may result in loss of protein synthesis ability, which may account for the numerous defects and ultimate fatality seen in these mice.

    The Journal of biological chemistry 2001;276;25;22915-22

  • Deregulation of Cdk5 in a mouse model of ALS: toxicity alleviated by perikaryal neurofilament inclusions.

    Nguyen MD, Larivière RC and Julien JP

    Centre for Research in Neurosciences, McGill University, Research Institute of the McGill University, Health Centre, H3G 1A4, Montreal, Quebec, Canada.

    Recent studies suggest that increased activity of cyclin-dependent kinase 5 (Cdk5) may contribute to neuronal death and cytoskeletal abnormalities in Alzheimer's disease. We report here such deregulation of Cdk5 activity associated with the hyperphosphorylation of tau and neurofilament (NF) proteins in mice expressing a mutant superoxide dismutase (SOD1(G37R)) linked to amyotrophic lateral sclerosis (ALS). A Cdk5 involvement in motor neuron degeneration is supported by our analysis of three SOD1(G37R) mouse lines exhibiting perikaryal inclusions of NF proteins. Our results suggest that perikaryal accumulations of NF proteins in motor neurons may alleviate ALS pathogenesis by acting as a phosphorylation sink for Cdk5 activity, thereby reducing the detrimental hyperphosphorylation of tau and other neuronal substrates.

    Neuron 2001;30;1;135-47

  • A role for the EphA family in the topographic targeting of vomeronasal axons.

    Knöll B, Zarbalis K, Wurst W and Drescher U

    Department of Physical Biology, Max-Planck-Institute for Developmental Biology, Spemannstrasse 35 / I, 72076 Tübingen, Germany.

    We have investigated the role of the Eph family of receptor tyrosine kinases and their ligands in the establishment of the vomeronasal projection in the mouse. Our data show intriguing differential expression patterns of ephrin-A5 on vomeronasal axons and of EphA6 in the accessory olfactory bulb (AOB), such that axons with high ligand concentration project onto regions of the AOB with high receptor concentration and vice versa. These data suggest a mechanism for development of this projection that is the opposite of the repellent interaction between Eph receptors and ligands observed in other systems. In support of this idea, when given the choice of whether to grow on lanes containing EphA-F(c)/laminin or F(c)/laminin protein (in the stripe assay), vomeronasal axons prefer to grow on EphA-F(c)/laminin. Analysis of ephrin-A5 mutant mice revealed a disturbance of the topographic targeting of vomeronasal axons to the AOB. In summary, these data, which are derived from in vitro and in vivo experiments, indicate an important role of the EphA family in setting up the vomeronasal projection.

    Development (Cambridge, England) 2001;128;6;895-906

  • Neurofilament homeostasis and motoneurone degeneration.

    Perrone Capano C, Pernas-Alonso R and di Porzio U

    International Institute of Genetics and Biophysics, CNR, via Marconi 12, 80125 Naples, Italy. perrone@iigb.na.cnr.it

    Neurofilament disorganisation is a hallmark of various neurodegenerative diseases. We review here current knowledge of neurofilament structure, gene expression and function. Neurofilament involvement in motoneurone neurological diseases is discussed in view of recent data from transgenic and spontaneous mouse mutants. In the mammalian neurone, the three neurofilament subunits are assembled into intermediate filaments as obligate heteropolymers. The subunits are expressed differentially during development and adult life according to the cell type and its physiological state. In addition to the well-established role of neurofilaments in the control of axonal calibre, there is increasing evidence that neurofilaments can interact with other cytoskeletal components and can modulate the axoplasmic flow. Although the extent to which neurofilament abnormalities contribute to the pathogenesis in human diseases remains unknown, emerging evidence suggests that disorganised neurofilaments can provoke degeneration and death of neurones. BioEssays 23:24-33, 2001.

    BioEssays : news and reviews in molecular, cellular and developmental biology 2001;23;1;24-33

  • Cytoskeletal abnormalities in amyotrophic lateral sclerosis: beneficial or detrimental effects?

    Julien JP and Beaulieu JM

    Centre for Research in Neurosciences, McGill University, The Montreal General Hospital Research Institute, 1650 Cedar Avenue, Montreal, Quebec H3G 1A4, Canada. mdju@musica.mcgill.ca

    Cytoskeletal abnormalities have been reported in cases of amyotrophic lateral sclerosis (ALS) including abnormal inclusions containing neurofilaments (NFs) and/or peripherin, reduced mRNA levels for the NF light (NF-L) protein and mutations in the NF heavy (NF-H) gene. Recently, transgenic mouse approaches have been used to address whether cytoskeletal changes may contribute to motor neuron disease. Mice lacking one of the three NF subunits are viable and do not develop motor neuron disease. Nonetheless, mice with null mutations for NF-L or for both NF-M and NF-H genes developed severe atrophy of ventral and dorsal root axons. The atrophic process is associated with hind limb paralysis during aging in mice deficient for both NF-M and NF-H proteins. The overexpression in mice of transgenes coding for wild-type or mutant NF proteins can provoke abnormal NF accumulations, axonal atrophy and sometimes motor dysfunction. However, the perikaryal NF accumulations are generally well tolerated by motor neurons and, except for expression of a mutant NF-L transgene, they did not provoke massive motor neuron death. Increasing the levels of perikaryal NF proteins may even confer protection in motor neuron disease caused by ALS-linked mutations in the superoxide dismutase (SOD1). In contrast, the overexpression of wild-type peripherin, a type of IF gene upregulated by inflammatory cytokines, provoked the formation of toxic IF inclusions with the high-molecular-weight NF proteins resulting in the death of motor neurons during aging. These results together with the detection of peripherin inclusions at early stage of disease in mice expressing mutant SOD1 suggest that IF inclusions containing peripherin may play a contributory role in ALS pathogenesis.

    Journal of the neurological sciences 2000;180;1-2;7-14

  • Reduction of axonal caliber does not alleviate motor neuron disease caused by mutant superoxide dismutase 1.

    Nguyen MD, Larivière RC and Julien JP

    Centre for Research in Neurosciences, McGill University, The Montreal General Hospital Research Institute, Montréal, PQ H3G 1A4, Canada.

    It is well established that motor neurons with large axon caliber are selectively affected in amyotrophic lateral sclerosis (ALS). To investigate whether high neurofilament (NF) content and large axonal caliber are factors that predispose motor neurons to selective degeneration in ALS, we generated mice expressing a mutant form of superoxide dismutase 1 (SOD1(G37R)) linked to familial ALS in a context of one allele for each NF gene being disrupted. A approximately 40% decrease of NF protein content detected in triple heterozygous knockout mice shifted the calibers of large axons in L5 ventral root from 5-9 microm to 1-5 microm, altering neither the normal subunit stoichiometry and morphological distribution of NFs nor levels of other cytoskeletal proteins. This considerable reduction in NF burden and caliber of axons did not extend the life span of SOD1(G37R) mice nor did it alleviate the loss of motor axons. Moreover, increasing the density of NFs in axons by overexpressing a NF-L transgene did not accelerate disease in SOD1(G37R) mice. These results do not support the current view that high NF content and large caliber of axons may account for the selective vulnerability of motor neurons in ALS caused by mutant SOD1.

    Proceedings of the National Academy of Sciences of the United States of America 2000;97;22;12306-11

  • Nkx3.1, a murine homolog of Ddrosophila bagpipe, regulates epithelial ductal branching and proliferation of the prostate and palatine glands.

    Tanaka M, Komuro I, Inagaki H, Jenkins NA, Copeland NG and Izumo S

    Cardiovascular Division, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.

    Nkx3.1 is a homeobox gene related to Drosophila bagpipe. Nkx3.1 is an early marker of the sclerotome and a subset of vascular smooth muscle cells, and at later stages, this gene is expressed in the prostate, palatine glands, kidney, and restricted regions of the central nervous system. In the present study, we determined the chromosomal localization of Nkx3.1 and examined the function of Nkx3. 1 in vivo by using gene targeting technique. Interestingly, Nkx3.1 mapped to the central region of the mouse chromosome 14 and was linked to Nkx2.6, a murine homolog of Drosophila tinman. Homozygous mutant mice for Nkx3.1 were viable and fertile, and the phenotype was, unexpectedly, confined to the prostate and palatine glands. The homozygous mutant mice exhibited defective branching morphogenesis of the prostate and palatine glands. Moreover, epithelial cells of the mutant prostate and palatine glands showed significant hyperplasia. No abnormalities were detected in the sclerotome, blood vessels, kidney, or brain. These results indicate that Nkx3.1 plays a critical role in epithelial branching and proliferation in the prostate and palatine glands. However, we did not observe prostate cancer in homozygous mutant mice up to 2 years of age. Therefore, involvement of NKX3.1 in carcinogenesis in men needs to be carefully determined by further investigation.

    Funded by: NHLBI NIH HHS: R01HL51253

    Developmental dynamics : an official publication of the American Association of Anatomists 2000;219;2;248-60

  • FGF/FGFR-2(IIIb) signaling is essential for inner ear morphogenesis.

    Pirvola U, Spencer-Dene B, Xing-Qun L, Kettunen P, Thesleff I, Fritzsch B, Dickson C and Ylikoski J

    Institute of Biotechnology and Department of Otorhinolaryngology, University of Helsinki, 00014 Helsinki, Finland. ulla.pirvola@helsinki.fi

    Interactions between FGF10 and the IIIb isoform of FGFR-2 appear to be crucial for the induction and growth of several organs, particularly those that involve budding morphogenesis. We determined their expression patterns in the inner ear and analyzed the inner ear phenotype of mice specifically deleted for the IIIb isoform of FGFR-2. FGF10 and FGFR-2(IIIb) mRNAs showed distinct, largely nonoverlapping expression patterns in the undifferentiated otic epithelium. Subsequently, FGF10 mRNA became confined to the presumptive cochlear and vestibular sensory epithelia and to the neuronal precursors and neurons. FGFR-2(IIIb) mRNA was expressed in the nonsensory epithelium of the otocyst that gives rise to structures such as the endolymphatic and semicircular ducts. These data suggest that in contrast to mesenchymal-epithelial-based FGF10 signaling demonstrated for other organs, the inner ear seems to depend on paracrine signals that operate within the epithelium. Expression of FGF10 mRNA partly overlapped with FGF3 mRNA in the sensory regions, suggesting that they may form parallel signaling pathways within the otic epithelium. In addition, hindbrain-derived FGF3 might regulate otocyst morphogenesis through FGFR-2(IIIb). Targeted deletion of FGFR-2(IIIb) resulted in severe dysgenesis of the cochleovestibular membraneous labyrinth, caused by a failure in morphogenesis at the otocyst stage. In addition to the nonsensory epithelium, sensory patches and the cochleovestibular ganglion remained at a rudimentary stage. Our findings provide genetic evidence that signaling by FGFR-2(IIIb) is critical for the morphological development of the inner ear.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2000;20;16;6125-34

  • Formation of intermediate filament protein aggregates with disparate effects in two transgenic mouse models lacking the neurofilament light subunit.

    Beaulieu JM, Jacomy H and Julien JP

    Centre for Research in Neurosciences, McGill University, The Montreal General Hospital Research Institute, Montreal, Quebec, Canada H3G 1A4.

    Protein aggregates containing intermediate filaments (IFs) are a hallmark of degenerating spinal motor neurons in amyotrophic lateral sclerosis (ALS). Recently, we reported that a deficiency in neurofilament light subunit (NF-L), a phenomenon associated with ALS, promoted the formation of IF inclusions with ensuing motor neuron death in transgenic mice overproducing peripherin, a type III IF protein detected in axonal inclusions of ALS patients. To further assess the role of NF-L in the formation of abnormal IF inclusions, we generated transgenic mice overexpressing human neurofilament heavy subunits (hNF-H) in a context of targeted disruption of the NF-L gene (hH;L-/- mice). The hH;L-/- mice exhibited motor dysfunction, and they developed nonfilamentous protein aggregates containing NF-H and peripherin proteins in the perikarya of spinal motor neurons. However, the perikaryal protein aggregates in the hH;L-/- mice did not provoke motor neuron death, unlike toxic IF inclusions induced by peripherin overexpression in NF-L null mice (Per;L-/- mice). Our results indicate that different types of IF protein aggregates with distinct properties may occur in a context of NF-L deficiency and that an axonal localization of such aggregates may be an important factor of toxicity.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2000;20;14;5321-8

  • The subcellular localization of Otx2 is cell-type specific and developmentally regulated in the mouse retina.

    Baas D, Bumsted KM, Martinez JA, Vaccarino FM, Wikler KC and Barnstable CJ

    Department of Ophthalmology and Visual Science, Yale School of Medicine, 330 Cedar Street, New Haven, CT 06520, USA. Dominique.Bass@ens-lyon.fr

    Recent evidence implicates homeodomain-containing proteins in the specification of cell fates in the central nervous system. Here we report that in the embryonic mouse eye Otx2, a paired homeodomain transcription factor, was found in retinal pigment epithelial cells and a restricted subset of retinal neurons, including ganglion cells. In the postnatal and adult eye, however, both the cellular and subcellular distribution of the Otx2 protein were cell type-specific. Otx2 was detected only in the nuclei of retinal pigment epithelial and bipolar cells, but was present in the cytoplasm of rod photoreceptors. Immunohistochemical studies of retinal explants and transfected cell lines both suggested that the retention of Otx2 in the cytoplasm of immature rods is a developmentally regulated process. The differential distribution of Otx2 in the cytoplasm of rods and the nucleus of other cell types, suggests that subcellular localization of this transcription factor may participate cell fate determination during specific phases of retinal development.

    Funded by: NEI NIH HHS: EY 09917, EY06890; NINDS NIH HHS: NS 20483; ...

    Brain research. Molecular brain research 2000;78;1-2;26-37

  • Structure, expression, and chromosome mapping of LATS2, a mammalian homologue of the Drosophila tumor suppressor gene lats/warts.

    Yabuta N, Fujii T, Copeland NG, Gilbert DJ, Jenkins NA, Nishiguchi H, Endo Y, Toji S, Tanaka H, Nishimune Y and Nojima H

    Department of Molecular Genetics, Department of Science for Laboratory Animal Experimentation, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.

    We have cloned and characterized LATS2, a novel mammalian homologue of the Drosophila tumor suppressor gene lats/warts. Northern blot analysis showed ubiquitous expression of mouse LATS2 (MmLATS2) mRNA, whereas expression of human LATS2 (HsLATS2) mRNA was enhanced in skeletal muscle and heart. Immunoblotting analysis of fractionated cell lysates showed HsLats2 to be a nuclear protein. We mapped the MmLATS2 gene to mouse chromosome 14 by interspecific backcross analysis. We also mapped the HsLATS2 gene (by fluorescence in situ hybridization) to the 13q11-q12 region, in which a loss of heterozygosity has been frequently observed in many primary cancers and to which the tumor suppressor genes RB and BRCA2 have also been mapped.

    Genomics 2000;63;2;263-70

  • Cysteine-rich domain isoforms of the neuregulin-1 gene are required for maintenance of peripheral synapses.

    Wolpowitz D, Mason TB, Dietrich P, Mendelsohn M, Talmage DA and Role LW

    Columbia University, College of Physicians and Surgeons, Program in Neurobiology and Behavior, New York, New York 10032, USA.

    Neuregulin-1 (NRG-1) signaling has been implicated in inductive interactions between pre- and postsynaptic partners during synaptogenesis. We used gene targeting to selectively disrupt cysteine-rich domain-(CRD-) containing NRG-1 isoforms. In CRD-NRG-1-/-mice, peripheral projections defasciculated and displayed aberrant branching patterns within their targets. Motor nerve terminals were transiently associated with broad bands of postsynaptic ACh receptor (AChR) clusters. Initially, Schwann cell precursors accompanied peripheral projections, but later, Schwann cells were absent from axons in the periphery. Following initial stages of synapse formation, sensory and motor nerves withdrew and degenerated. Our data demonstrate the essential role of CRD-NRG-1-mediated signaling for coordinating nerve, target, and Schwann cell interactions in the normal maintenance of peripheral synapses, and ultimately in the survival of CRD-NRG-1-expressing neurons.

    Funded by: NCRR NIH HHS: 1S10RR10506; NIDA NIH HHS: DA09366; NINDS NIH HHS: NS29071, R01 NS029071, R01 NS029071-11, R01 NS029071-12, R01 NS029071-13, R01 NS029071-13S1, R01 NS029071-14, R01 NS029071-15, R01 NS029071-16, R01 NS029071-17

    Neuron 2000;25;1;79-91

  • Late onset of motor neurons in mice overexpressing wild-type peripherin.

    Beaulieu JM, Nguyen MD and Julien JP

    Centre for Research in Neurosciences, McGill University, The Montréal General Hsopital Research Institute, Montréal, Québec, H3G 1A4, Canada.

    Peripherin, a type III intermediate filament (IF) protein, upregulated by injury and inflammatory cytokines, is a component of IF inclusion bodies associated with degenerating motor neurons in sporadic amyotrophic lateral sclerosis (ALS). We report here that sustained overexpression of wild-type peripherin in mice provokes massive and selective degeneration of motor axons during aging. Remarkably, the onset of peripherin-mediated disease was precipitated by a deficiency of neurofilament light (NF-L) protein, a phenomenon associated with sporadic ALS. In NF-L null mice, the overexpression of peripherin led to early- onset formation of IF inclusions and to the selective death of spinal motor neurons at 6 mo of age. We also report the formation of similar peripherin inclusions in presymptomatic transgenic mice expressing a mutant form of superoxide dismutase linked to ALS. Taken together, these results suggest that IF inclusions containing peripherin may play a contributory role in motor neuron disease.

    The Journal of cell biology 1999;147;3;531-44

  • Neurofilament functions in health and disease.

    Julien JP

    Centre for Research in Neuroscience McGill University The Montreal General Hospital Research Institute 1650 Cedar Avenue, Montreal, Québec, Canada H3G 1A4,. mdju@musica.mcgill.ca

    Transgenic approaches have recently been used to investigate the functions of neuronal intermediate filaments. Gene knockout studies have demonstrated that neurofilaments are not required for axogenesis and that individual neurofilament proteins play distinct roles in filament assembly and in the radial growth of axons. The involvement of neurofilaments in disease is supported by the discovery of novel mutations in the neurofilament heavy gene from cases of amyotrophic lateral sclerosis and by reports of neuronal death in mouse models expressing neurofilament and alpha-internexin transgenes. However, mouse studies have shown that axonal neurofilaments are not required for pathogenesis caused by mutations in superoxide dismutase and that increasing perikaryal levels of neurofilament proteins may even confer protection in this disease.

    Current opinion in neurobiology 1999;9;5;554-60

  • Disruption of type IV intermediate filament network in mice lacking the neurofilament medium and heavy subunits.

    Jacomy H, Zhu Q, Couillard-Després S, Beaulieu JM and Julien JP

    Montreal General Hospital Research Institute, Québec, Canada.

    To clarify the role of the neurofilament (NF) medium (NF-M) and heavy (NF-H) subunits, we generated mice with targeted disruption of both NF-M and NF-H genes. The absence of the NF-M subunit resulted in a two- to threefold reduction in the caliber of large myelinated axons, whereas the lack of NF-H subunits had little effect on the radial growth of motor axons. In NF-M-/- mice, the velocity of axonal transport of NF light (NF-L) and NF-H proteins was increased by about two-fold, whereas the steady-state levels of assembled NF-L were reduced. Although the NF-M or NF-H subunits are each dispensable for the formation of intermediate filaments, the absence of both subunits in double NF-M; NF-H knockout mice led to a scarcity of intermediate filament structures in axons and to a marked approximately twofold increase in the number of microtubules. Protein analysis indicated that the levels of NF-L and alpha-internexin proteins were reduced dramatically throughout the nervous system. Immunohistochemistry of spinal cord from the NF-M-/-;NF-H-/- mice revealed enhanced NF-L staining in the perikaryon of motor neurons but a weak NF-L staining in axons. In addition, axonal transport studies carried out by the injection of [35S]methionine into spinal cord revealed after 30 days very low levels of newly synthesized NF-L proteins in the sciatic nerve of NF-M-/-;NF-H-/- mice. The combined results demonstrate a requirement of the high-molecular-weight subunits for the assembly of type IV intermediate filament proteins and for the efficient translocation of NF-L proteins into the axonal compartment.

    Journal of neurochemistry 1999;73;3;972-84

  • Bcl-2 overexpression does not protect neurons from mutant neurofilament-mediated motor neuron degeneration.

    Houseweart MK and Cleveland DW

    Ludwig Institute for Cancer Research, University of California at San Diego, La Jolla, California 92093, USA.

    Transgenic mice with a point mutation in the light neurofilament gene develop amyotrophic lateral sclerosis-like motor neuron disease characterized by selective spinal motor neuron loss, neurofilamentous accumulations, and severe muscle atrophy. To test whether the large motor neurons at risk in this disease could be protected from mutant neurofilament-mediated killing, these mice were bred to mice overexpressing the human Bcl-2 proto-oncogene. Elevated levels of Bcl-2 increased the numbers of motor and sensory axons surviving after the developmental period of naturally occurring cell death but did not greatly reduce the number of degenerating axons or protect the large motor neurons from mutant neurofilament-mediated death.

    Funded by: NINDS NIH HHS: NS 27093

    The Journal of neuroscience : the official journal of the Society for Neuroscience 1999;19;15;6446-56

  • Integrators of the cytoskeleton that stabilize microtubules.

    Yang Y, Bauer C, Strasser G, Wollman R, Julien JP and Fuchs E

    Howard Hughes Medical Institute, Department of Molecular Genetics and Cell Biology, Chicago, Illinois 60637, USA.

    Sensory neurodegeneration occurs in mice defective in BPAG1, a gene encoding cytoskeletal linker proteins capable of anchoring neuronal intermediate filaments to actin cytoskeleton. While BPAG1 null mice fail to anchor neurofilaments (NFs), BPAG1/NF null mice still degenerate in the absence of NFs. We report a novel neural splice form that lacks the actin-binding domain and instead binds and stabilizes microtubules. This interaction is functionally important; in mice and in vitro, neurons lacking BPAG1 display short, disorganized, and unstable microtubules defective in axonal transport. Ironically, BPAG1 neural isoforms represent microtubule-associated proteins that when absent lead to devastating consequences. Moreover, BPAG1 can functionally account for the extraordinary stability of axonal microtubules necessary for transport over long distances. Its isoforms interconnect all three cytoskeletal networks, a feature apparently central to neuronal survival.

    Funded by: NIAMS NIH HHS: R01-AR27883

    Cell 1999;98;2;229-38

  • Otx1 and Otx2 activities are required for the normal development of the mouse inner ear.

    Morsli H, Tuorto F, Choo D, Postiglione MP, Simeone A and Wu DK

    National Institute on Deafness and Other Communication Disorders, Rockville, MD 20850, USA.

    The Otx1 and Otx2 genes are two murine orthologues of the Orthodenticle (Otd) gene in Drosophila. In the developing mouse embryo, both Otx genes are expressed in the rostral head region and in certain sense organs such as the inner ear. Previous studies have shown that mice lacking Otx1 display abnormal patterning of the brain, whereas embryos lacking Otx2 develop without heads. In this study, we examined, at different developmental stages, the inner ears of mice lacking both Otx1 and Otx2 genes. In wild-type inner ears, Otx1, but not Otx2, was expressed in the lateral canal and ampulla, as well as part of the utricle. Ventral to the mid-level of the presumptive utricle, Otx1 and Otx2 were co-expressed, in regions such as the saccule and cochlea. Paint-filled membranous labyrinths of Otx1-/- mutants showed an absence of the lateral semicircular canal, lateral ampulla, utriculosaccular duct and cochleosaccular duct, and a poorly defined hook (the proximal part) of the cochlea. Defects in the shape of the saccule and cochlea were variable in Otx1-/- mice and were much more severe in an Otx1-/-;Otx2(+/)- background. Histological and in situ hybridization experiments of both Otx1-/- and Otx1-/-;Otx2(+/)- mutants revealed that the lateral crista was absent. In addition, the maculae of the utricle and saccule were partially fused. In mutant mice in which both copies of the Otx1 gene were replaced with a human Otx2 cDNA (hOtx2(1)/ hOtx2(1)), most of the defects associated with Otx1-/- mutants were rescued. However, within the inner ear, hOtx2 expression failed to rescue the lateral canal and ampulla phenotypes, and only variable rescues were observed in regions where both Otx1 and Otx2 are normally expressed. These results suggest that both Otx genes play important and differing roles in the morphogenesis of the mouse inner ear and the development of its sensory organs.

    Funded by: Telethon: D.037

    Development (Cambridge, England) 1999;126;11;2335-43

  • No requirement of alpha-internexin for nervous system development and for radial growth of axons.

    Levavasseur F, Zhu Q and Julien JP

    Centre for Research in Neuroscience, McGill University, The Montreal General Hospital Research Institute, L12-218, 1650 Cedar Avenue, Montreal, Quebec, Canada.

    Alpha-Internexin is a type IV intermediate filament protein that is expressed abundantly in neurons during development of the peripheral and central nervous systems as well as in few neurons of the adult central nervous system. It has been suggested that alpha-internexin may act as a scaffold for the formation of neuronal intermediate filaments during early development. In addition, recent reports suggest that alpha-internexin could play a major role in two degenerative neurological disorders. We report here an analysis of mice with a targeted disruption of alpha-internexin gene. Unexpectedly, alpha-internexin -/- mice developed normally and did not exhibit overt phenotypes. Moreover, the absence of alpha-internexin did not interfere with neurite extension of cultured DRG neurons. The number and caliber of L4 ventral root axons remained unchanged in alpha-internexin -/- mice. In the retina, alpha-internexin begins to be expressed in retinal ganglion cells when their first axons reach the optic chiasma. Using HRP tracer, we show that the projection pattern of the RGC axons is not modified by the absence of alpha-internexin. Electron microscopy did not reveal significant differences in axonal calibers, in myelination of axons and in neurofilament structures between alpha-internexin -/- and control mice during development and at adult stage. These data indicate that alpha-internexin is not required for the polymerization of neurofilament in vivo. Mice deficient for both alpha-internexin and neurofilament light chain (NF-L) exhibited no over phenotypes as well. No intermediate filament structures were detectable in optic nerve of alpha-internexin -/-; NF-L -/- mice. Ours results do not support the hypothesis of a role for type IV intermediate filaments in axonal outgrowth during development of nervous system.

    Brain research. Molecular brain research 1999;69;1;104-12

  • The cytoskeleton of the myenteric neurons during murine embryonic life.

    Faussone-Pellegrini MS, Matini P and DeFelici M

    Department of Human Anatomy and Histology, University of Florence, Italy. s_faussone@cesit1.unifi.it

    The organization of the cytoskeleton has been studied during mouse differentiation in cells of the myenteric neuronal lineage. The entire gut was examined starting from day 12.5 of embryonic life (E12.5) until birth (P0). Immunocytochemistry was performed to evaluate the expression of five of the most represented neurofilaments proteins (the low, NF-L, medium, NF-M, and heavy, NF-H, molecular weight subunits, alpha-internexin and peripherin) and of two of the microtubule-associated proteins (MAPI and MAP2a+2b). In parallel, the appearance in the differentiating myenteric neurons of filamentous and microtubular structures and their intracytoplasmatic distribution were observed under the electron microscope. A differential immunohistochemical expression of the structural proteins was found. Immature cells expressed alpha-internexin, peripherin, NF-M and MAP1 by day E12.5; alpha-internexin expression was strong in these cells, but gradually decreased with age and was practically absent in adulthood. Conversely, the expression of the other three proteins increased with cell differentiation and was still present in adulthood. NF-L and NF-H expression appeared later, by day E16.5, and was weak for the entire pre- and postnatal life. MAP2a+2b was never expressed. Under the electron microscope, at day E12.5 the cytoskeleton was already organized in filamentous and microtubular structures. At this age neurofilaments were few and mainly located in the cell processes, and microtubules were numerous and mainly assembled in the neuritic growth cones, together with synaptic vesicles. With ageing, neurofilaments and microtubules were ubiquitous in the neuron. Data obtained demonstrate that cytoskeletal proteins gradually accumulate in the cells of the neuronal lineage in parallel with the organization of the cytoskeletal structures, which in turn mediate important neural events by the earliest stages of murine embryonic life, including growth of nerve processes and initiation of axonal transport.

    Anatomy and embryology 1999;199;5;459-69

  • Genomic structure, mapping, activity and expression of fibroblast growth factor 17.

    Xu J, Lawshe A, MacArthur CA and Ornitz DM

    Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, MO 63110, USA.

    Fibroblast growth factors are essential molecules for development. Here we characterize Fgfl7, a new member of the fibroblast growth factor (FGF) family. The Fgfl7 gene maps to mouse chromosome 14 and is highly conserved between mouse and human (93% identity). It exhibits 60% amino acid identity with Fgf8 and 50% identity with Fgf8. Both Fgf8 and Fgf17 have a similar structure and a similar pattern of alternative splicing in the 5' coding region. When expressed in 3T3 fibroblasts, mouse FGF17 is transforming, indicating that it can activate the 'c' splice form of either FGF receptor (FGFR) one or two. During midgestation embryogenesis, in situ hybridization analysis localized Fgf17 expression to specific sites in the midline structures of the forebrain, the midbrain-hindbrain junction, the developing skeleton and in developing arteries. Comparison to Fgf8 revealed a striking similarity in expression patterns, especially in the central nervous system (CNS), suggesting that both genes may be important for CNS development, although Fgf17 is expressed somewhat later than Fgf8. In the developing skeleton, both genes are expressed in costal cartilage while Fgf8 is preferentially expressed in long bones. In the developing great vessels Fgfl7 is preferentially expressed, suggesting that it may have a more prominent role in vascular growth.

    Mechanisms of development 1999;83;1-2;165-78

  • Severe neuronal losses with age in the parietal cortex and ventrobasal thalamus of mice transgenic for the human NF-L neurofilament protein.

    Ma D, Descarries L, Micheva KD, Lepage Y, Julien JP and Doucet G

    Département de pathologie et biologie cellulaire and Centre de recherche en sciences neurologiques, Université de Montréal, Québec, Canada.

    Transgenic mice expressing human light neurofilament protein (NF-L) display early perikaryal accumulations of disarrayed neurofilaments in layers II/III of the parietal cortex and in the ventrobasal complex of thalamus. This cytoskeletal abnormality, reflected by strong NF-L immunoreactivity, is transient in the developing cortex but persists until old age in the thalamus. To investigate whether it leads to neuronal death, the unbiased cell counting method of the dissector was applied to the parietal cortex and the thalamus of normal and transgenic mice at various postnatal (P10, P20, P90) and advanced ages (14-18 months). Similar data were also obtained from the primary visual cortex free of NF-L accumulation. Compared with normal, the total number of neurons in the parietal (but not occipital) cortex of transgenic mice showed little change during the postnatal period, but decreased markedly with old age, particularly in layers II/III. Severe neuronal loss was also documented in the thalamic ventrobasal complex of aged transgenic mice. The delayed neuronal death in the parietal cortex, occurring long after recovery from the NF-L accumulations, was suggestive of a combination of deleterious factors, including the early overproduction of neurofilament protein and subsequent loss of afferent input from the affected somatosensory thalamic nuclei. Furthermore, strong accumulation of lipofuscin in the neurons of aged transgenic mice suggested that oxidative stress partakes in the mechanisms through which NF-L overproduction compromises neuronal viability.

    The Journal of comparative neurology 1999;406;4;433-48

  • Technology development at the interface of proteome research and genomics: mapping nonpolymorphic proteins on the physical map of mouse chromosomes.

    Nock C, Gauss C, Schalkwyk LC, Klose J, Lehrach H and Himmelbauer H

    Max-Planck-Institute for Molecular Genetics, Berlin-Dahlem, Germany.

    Data obtained from protein spots by peptide mass fingerprinting are used to identify the corresponding genes in sequence databases. The relevant cDNAs are obtained as clones from the Integrated Molecular Analysis of Genome Expression (I.M.A.G.E.) consortium. Mapping of I.M.A.G.E. clones is performed in two steps: first, cDNA clones are hybridized against a 10-hit genomic mouse bacterial artificial chromosome (BAC) library. Second, interspersed repetitive sequence polymerase chain reaction (IRS-PCR) using a single primer directed against the mouse B1 repeat element is performed on BACs. As each cDNA detects several BACs, and each individual BAC has a 50% chance to recover an IRS-PCR fragment, the majority of cDNAs produce at least a single IRS-PCR fragment. Individual IRS fragments are hybridized against high-density spotted filter grids containing the three-dimensional permutated pools of yeast artificial chromosome (YAC) library resources that are currently being used to construct a physical map of the mouse genome. IRS fragments that hybridize to YAC clones already placed into contigs immediately provide highly precise map positions. This technology therefore is able to draw links between proteins detected by 2-D gel electrophoresis and the corresponding gene loci in the mouse genome.

    Electrophoresis 1999;20;4-5;1027-32

  • Mutation in neurofilament transgene implicates RNA processing in the pathogenesis of neurodegenerative disease.

    Cañete-Soler R, Silberg DG, Gershon MD and Schlaepfer WW

    Division of Neuropathology, University of Pennsylvania Medical School, Philadelphia, Pennsylvania 19104-6079, USA.

    A mouse neurofilament light subunit (NF-L) transgene with a 36 bp c-myc insert at the end of the coding region was found to have neuropathic effects on enteric and motor neurons of transgenic mice. The severity of phenotype was related directly to the levels of transgenic mRNA expression. High levels of transgene expression were lethal to newborn pups, causing profound alterations in the development of the enteric nervous system and extensive vacuolar changes in motor neurons. Lower levels of transgene expression led to a transient stunting of growth and focal alterations of enteric and motor neurons. Because the positioning of the c-myc insert coincided with the location of the major stability determinant of the NF-L mRNA (Cañete-Soler et al., 1998a,b), additional studies were undertaken. These studies showed that the c-myc insert alters the ribonucleoprotein (RNP) complexes that bind to the stability determinant and disrupts their ability to regulate the stability of the transcripts. The findings indicate that expression of an NF-L transgene with a mutant mRNA stability determinant is highly disruptive to enteric and motor neurons and implicate alterations in RNA processing in the pathogenesis of a neurodegenerative condition.

    Funded by: NINDS NIH HHS: NS15722

    The Journal of neuroscience : the official journal of the Society for Neuroscience 1999;19;4;1273-83

  • The intermediate filament protein peripherin is the specific interaction partner of mouse BPAG1-n (dystonin) in neurons.

    Leung CL, Sun D and Liem RK

    Departments of Biochemistry and Molecular Biophysics, Columbia University College of Physicians and Surgeons, New York 10032, USA.

    The dystonia musculorum (dt) mouse suffers from severe degeneration of primary sensory neurons. The mutated gene product is named dystonin and is identical to the neuronal isoform of bullous pemphigoid antigen 1 (BPAG1-n). BPAG1-n contains an actin-binding domain at its NH2 terminus and a putative intermediate filament-binding domain at its COOH terminus. Because the degenerating sensory neurons of dt mice display abnormal accumulations of intermediate filaments in the axons, BPAG1-n has been postulated to organize the neuronal cytoskeleton by interacting with both the neurofilament triplet proteins (NFTPs) and microfilaments. In this paper we show by a variety of methods that the COOH-terminal tail domain of mouse BPAG1 interacts specifically with peripherin, but in contrast to a previous study (Yang, Y., J. Dowling, Q.C. Yu, P. Kouklis, D.W. Cleveland, and E. Fuchs. 1996. Cell. 86:655-665), mouse BPAG1 fails to associate with full-length NFTPs. The tail domains interfered with the association of the NFTPs with BPAG1. In dt mice, peripherin is present in axonal swellings of degenerating sensory neurons in the dorsal root ganglia and is downregulated even in other neural regions, which have no obvious signs of pathology. Since peripherin and BPAG1-n also display similar expression patterns in the nervous system, we suggest that peripherin is the specific interaction partner of BPAG1-n in vivo.

    Funded by: NIA NIH HHS: AG00189, T32 AG000189; NINDS NIH HHS: NS15182, R01 NS015182

    The Journal of cell biology 1999;144;3;435-46

  • Spatial and temporal changes in chondroitin sulfate distribution in the sclerotome play an essential role in the formation of migration patterns of mouse neural crest cells.

    Kubota Y, Morita T, Kusakabe M, Sakakura T and Ito K

    Department of Biology, Graduate School of Science, Osaka University, Japan.

    We have examined the roles of pertinent extracellular matrix molecules in the formation of the neural crest cell migration patterns in the sclerotome of the mouse embryo. The present data indicate that permissiveness for migration is inversely correlated with chondroitin sulfate content. Experimental removal of chondroitin sulfate proteoglycans in the embryo causes neural crest cells to migrate even within the posterior half of the somite, which they do not invade ordinarily. Moreover, three different sclerotomal regions defined by the presence or absence of the ventromedial and/or ventrolateral pathways are present along the anteroposterior axis and undergo systematic temporal changes that affect migration patterns. The most anterior portion of the sclerotome is conducive to both ventromedial and ventrolateral migration (Anterior Region). The intermediate portion is conducive to ventromedial migration only (Intermediate Region). No neural crest cells are seen within the posterior portion of the sclerotome (Posterior Region). At this level, they are observed exclusively in the dorsolateral space adjacent to the roof of the neural tube. With advancing embryonic development, the rostrocaudal length of the Anterior Region decreases and is accompanied by a corresponding enlargement of the Intermediate Region. These results suggest that temporal and regional differences in the sclerotome contribute to the neural crest cell migration patterns in the mouse. To refine our understanding of the underlying mechanisms, regional differences and temporal changes in the distribution of extracellular matrix molecules have been examined during migration. In the sclerotome, chondroitin sulfate displays distinct distribution patterns that are closely correlated with the migration patterns of mouse neural crest cells. Furthermore, their migration patterns are altered in embryos treated with the inhibitors of chondroitin sulfate proteoglycan biosynthesis, sodium chlorate, and beta-D-xyloside. In inhibitor-treated embryos, neural crest cell migration occurs even in the posterior portion of the sclerotome. The metameric organization of dorsal root ganglia is disturbed in these embryos. Our observations provide novel evidence for the importance of sclerotomal chondroitin sulfate distribution patterns in mouse crest cell migration patterns. We conclude that systematic spatiotemporal changes in the distribution of chondroitin sulfate proteoglycans are a key requisite for the formation of migration patterns of mouse neural crest cells in the sclerotome.

    Funded by: NICHD NIH HHS: N01-HD-7-3263

    Developmental dynamics : an official publication of the American Association of Anatomists 1999;214;1;55-65

  • LIM homeodomain factors Lhx3 and Lhx4 assign subtype identities for motor neurons.

    Sharma K, Sheng HZ, Lettieri K, Li H, Karavanov A, Potter S, Westphal H and Pfaff SL

    Gene Expression Laboratory, The Salk Institute, La Jolla, California 92037, USA.

    The circuits that control movement are comprised of discrete subtypes of motor neurons. How motor neuron subclasses develop and extend axons to their correct targets is still poorly understood. We show that LIM homeodomain factors Lhx3 and Lhx4 are expressed transiently in motor neurons whose axons emerge ventrally from the neural tube (v-MN). Motor neurons develop in embryos deficient in both Lhx3 and Lhx4, but v-MN cells switch their subclass identity to become motor neurons that extend axons dorsally from the neural tube (d-MN). Conversely, the misexpression of Lhx3 in dorsal-exiting motor neurons is sufficient to reorient their axonal projections ventrally. Thus, Lhx3 and Lhx4 act in a binary fashion during a brief period in development to specify the trajectory of motor axons from the neural tube.

    Funded by: NINDS NIH HHS: NS37116

    Cell 1998;95;6;817-28

  • Distribution of neuronal intermediate filament proteins in the developing mouse olfactory system.

    Chien CL, Lee TH and Lu KS

    Department of Anatomy, College of Medicine, National Taiwan University, Taipei, Republic of China.

    The distribution of neuronal intermediate filament proteins in the developing mouse olfactory bulb and olfactory epithelium was characterized by immunocytochemical approach. Antibodies against alpha-internexin, neurofilament triplet proteins (NFTPs; NF-L, NF-M, and NF-H) and peripherin were used to determine their expression at different developmental stages. Alpha-internexin and peripherin were first found to be co-localized in the olfactory neuroepithelium during early development. At the perinatal stage, expression patterns of alpha-internexin and peripherin are distinguishable by spatial and temporal manner: peripherin is predominantly expressed in the olfactory nerves; whereas alpha-internexin is expressed in both olfactory nerves and olfactory bulb. Our observation suggests that peripherin as well as alpha-internexin may play some roles in the process formation of olfactory nerves during development. In the developing olfactory periglomerulus, alpha-internexin was found around postnatal Day 3, whereas NFTPs were not observed until postnatal Day 7. Our data showed that the expression of alpha-internexin preceded those of the NFTPs in most neurons of the developing olfactory bulb. Some small neurons in the adult olfactory bulb were uniquely labeled with antibody to alpha-internexin. Our results suggest that alpha-internexin may play a functional role in the neuronal cytoarchitecture of developing olfactory system, and can be a neuronal marker for detecting postmitotic migrating neurons in the adult olfactory bulb.

    Journal of neuroscience research 1998;54;3;353-63

  • Transgenic mice in the study of ALS: the role of neurofilaments.

    Julien JP, Couillard-Després S and Meier J

    Centre for Research in Neuroscience, McGill University, The Montreal General Hospital Research Institute, Québec, Canada. mdju@musica.mcgill.ca

    Amyotrophic lateral sclerosis (ALS) is an adult-onset neurological disorder of multiple etiologies that affects primarily motor neurons in the brain and spinal cord. Abnormal accumulations of neurofilaments (NFs) in motor neurons and a down-regulation of mRNA for the NF light subunit (NF-L) are associated with ALS, but it remains unclear to what extent these NF perturbations contribute to human disease. Transgenic mouse studies demonstrated that overexpression of normal and mutant NF proteins can sometimes provoke a motor neuronopathy characterized by the presence of abnormal NF accumulations resembling those found in ALS. Remarkably, the motor neuronopathy in transgenic mice overexpressing human NF heavy (NF-H) subunits was rescued by the co-expression of a human NF-L transgene at levels that restored a correct stoichiometry of NF-L to NF-H subunits. Transgenic approaches have also been used to investigate the role of NFs in disease caused by Cu/Zn superoxide dismutase (SOD1) mutations, which is responsible for approximately 2% cases of ALS. Studies with transgenic mice expressing low levels of a fusion NF-H/lacZ protein, in which NFs are withheld from the axonal compartment, suggested that axonal NFs are not toxic intermediates required for SOD1-mediated disease. On the contrary, overexpression of human NF-H proteins was found to confer an effective protection against mutant SOD1 toxicity in transgenic mice, a phenomenon that may be due to the ability of NF proteins to chelate calcium. In conclusion, transgenic studies showed that disorganized NFs can sometimes have noxious effects resulting in neuronopathy. However, in the context of motor neuron disease caused by mutant SOD1, there is emerging evidence that NF proteins rather play a protective role.

    Brain pathology (Zurich, Switzerland) 1998;8;4;759-69

  • Absence of neurofilaments reduces the selective vulnerability of motor neurons and slows disease caused by a familial amyotrophic lateral sclerosis-linked superoxide dismutase 1 mutant.

    Williamson TL, Bruijn LI, Zhu Q, Anderson KL, Anderson SD, Julien JP and Cleveland DW

    Ludwig Institute for Cancer Research, University of California at San Diego, La Jolla, CA 92093, USA.

    Mutations in superoxide dismutase 1 (SOD1), the only proven cause of amyotrophic lateral sclerosis (ALS), provoke disease through an unidentified toxic property. Neurofilament aggregates are pathologic hallmarks of both sporadic and SOD1-mediated familial ALS. By deleting NF-L, the major neurofilament subunit required for filament assembly, onset and progression of disease caused by familial ALS-linked SOD1 mutant G85R are significantly slowed, while selectivity of mutant-mediated toxicity for motor neurons is reduced. In NF-L-deleted animals, levels of the two remaining neurofilament subunits, NF-M and NF-H, are markedly reduced in axons but are elevated in motor neuron cell bodies. Thus, while neither perikaryal nor axonal neurofilaments are essential for SOD1-mediated disease, the absence of assembled neurofilaments both diminishes selective vulnerability and slows SOD1(G85R) mutant-mediated toxicity to motor neurons.

    Funded by: NINDS NIH HHS: NS 27036, R01 NS027036, R37 NS027036

    Proceedings of the National Academy of Sciences of the United States of America 1998;95;16;9631-6

  • Gli2 is required for induction of floor plate and adjacent cells, but not most ventral neurons in the mouse central nervous system.

    Matise MP, Epstein DJ, Park HL, Platt KA and Joyner AL

    Developmental Genetics Program and Howard Hughes Medical Institute, and Department of Cell Biology and Physiology and Neuroscience, NYU Medical Center, New York, NY 10016, USA.

    Induction of the floor plate at the ventral midline of the neural tube is one of the earliest events in the establishment of dorsoventral (d/v) polarity in the vertebrate central nervous system (CNS). The secreted molecule, Sonic hedgehog, has been shown to be both necessary and sufficient for this induction. In vertebrates, several downstream components of this signalling pathway have been identified, including members of the Gli transcription factor family. In this study, we have examined d/v patterning of the CNS in Gli2 mouse mutants. We have found that the floor plate throughout the midbrain, hindbrain and spinal cord does not form in Gli2 homozygotes. Despite this, motoneurons and ventral interneurons form in their normal d/v positions at 9.5 to 12.5 days postcoitum (dpc). However, cells that are generated in the region flanking the floor plate, including dopaminergic and serotonergic neurons, were greatly reduced in number or absent in Gli2 homozygous embryos. These results suggest that early signals derived from the notochord can be sufficient for establishing the basic d/v domains of cell differentiation in the ventral spinal cord and hindbrain. Interestingly, the notochord in Gli2 mutants does not regress ventrally after 10.5 dpc, as in normal embryos. Finally, the spinal cord of Gli1/Gli2 zinc-finger-deletion double homozygous mutants appeared similar to Gli2 homozygotes, indicating that neither gene is required downstream of Shh for the early development of ventral cell fates outside the ventral midline.

    Funded by: NICHD NIH HHS: R01HD35768

    Development (Cambridge, England) 1998;125;15;2759-70

  • FRIP, a hematopoietic cell-specific rasGAP-interacting protein phosphorylated in response to cytokine stimulation.

    Nelms K, Snow AL, Hu-Li J and Paul WE

    Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.

    The human IL-4 receptor contains a sequence (the 14R motif) centered on Y497 that, when phosphorylated, interacts with phosphotyrosine-binding (PTB) domain proteins. Here, we describe a PTB domain protein, FRIP, that is phosphorylated in response to cytokine stimulation. FRIP is related to the rasGAP-associated protein p62dok and is bound by the N-terminal SH2 domain of rasGAP. The frip gene maps to the hairless (hr) locus on mouse chromosome 14. hr/hr mice exhibit lymphadenopathy, and their lymph node T cells proliferate more vigorously to anti-CD3 with IL-4 or IL-2 stimulation than +/hr T cells. FRIP expression is significantly reduced in T cells from hr/hr mice. FRIP may negatively regulate proliferation by acting as an adapter molecule between rasGAP and receptor complexes.

    Immunity 1998;9;1;13-24

  • Development of LBP110 expression by neural crest-derived enteric precursors: migration and differentiation potential in ls/ls mutant mice.

    Howard MJ and Gershon MD

    Department of Anatomy and Neurobiology, Medical College of Ohio, Toledo 43699, USA.

    Neural crest-derived cells acquire a 110-kD laminin-binding protein (LBP110) when they colonize the murine bowel. Laminin stimulates LBP110-expressing cells to develop as neurons. We have followed the development of LBP110 by neural crest-derived cells as they enter the gut of control and ls/ls mutant mice. The expression of neurofilament and choline acetyltransferase was used as markers of a neuronal phenotype. Tyrosine hydroxylase was used as a marker for the mash-1-dependent lineage of enteric precursors, while calcitonin gene-related peptide was used as a marker for the mash-1-independent lineage of crest-derived cells. A subset of cells expressing LBP110 was located along the vagi at E10 at cervical and thoracic levels. At E12, cells expressing LBP110 extended from the foregut to the midgut. The expression of neurofilament protein lagged behind that of LBP110 by about 0.5 day and then became coincident with LBP110 immunoreactivity. By E15, cells doubly labeled with antibodies to LBP110 and neurofilament protein were located along the entire extent of the bowel up to but not including the terminal colon. By E16, both the proximal and terminal colon contained cells expressing LBP110 and neurofilaments. The pattern of immunoreactivity could not be distinguished between ls/ls and control animals prior to E16. By E16, when the terminal colon of control animals contained many cells expressing LBP110 and neurofilaments, the terminal colon of ls/ls animals lacked cells expressing these proteins; nevertheless, structures outside of the terminal colon were heavily endowed with cells expressing LBP110 and neurofilaments. These ectopically located cells derived from both mash-1-dependent and -independent lineages of crest-derived precursors.

    Funded by: NICHD NIH HHS: HD 28184; NINDS NIH HHS: NS15547

    Journal of neurobiology 1998;35;4;341-54

  • Absence of the mid-sized neurofilament subunit decreases axonal calibers, levels of light neurofilament (NF-L), and neurofilament content.

    Elder GA, Friedrich VL, Bosco P, Kang C, Gourov A, Tu PH, Lee VM and Lazzarini RA

    Department of Psychiatry, Mount Sinai School of Medicine, New York 10029, USA.

    Neurofilaments (NFs) are prominent components of large myelinated axons and probably the most abundant of neuronal intermediate filament proteins. Here we show that mice with a null mutation in the mid-sized NF (NF-M) subunit have dramatically decreased levels of light NF (NF-L) and increased levels of heavy NF (NF-H). The calibers of both large and small diameter axons in the central and peripheral nervous systems are diminished. Axons of mutant animals contain fewer neurofilaments and increased numbers of microtubules. Yet the mice lack any overt behavioral phenotype or gross structural defects in the nervous system. These studies suggest that the NF-M subunit is a major regulator of the level of NF-L and that its presence is required to achieve maximal axonal diameter in all size classes of myelinated axons.

    Funded by: NIA NIH HHS: P50 AG005138, P50 AGO 513811

    The Journal of cell biology 1998;141;3;727-39

  • Isolation and characterization of a bovine neural specific protein (CRMP-2) cDNA homologous to unc-33, a C. elegans gene implicated in axonal outgrowth and guidance.

    Kamata T, Subleski M, Hara Y, Yuhki N, Kung H, Copeland NG, Jenkins NA, Yoshimura T, Modi W and Copeland TD

    SAIC/Frederick, IRSP, National Cancer Institute (NCI)-FCRDC, Frederick, MD 21702, USA.

    We have cloned the cDNA encoding bovine CRMP-2 from bovine brains. A full length cDNA encoding bovine CRMP-2 was isolated and sequenced. The deduced amino acid sequence reveals that the gene encodes a protein of 572 amino acids and is highly homologous to Caenorhabditis elegans unc-33, which controls the guidance and outgrowth of neuronal axons. The CRMP-2 transcript was present in bovine brains but not non-neural tissues, and its protein product existed in both soluble and membrane-bound forms. The expression of CRMP-2 protein and mRNA was upregulated during neuronal differentiation of rat PC12 cells. Immunoprecipitation of PC12 cell extracts shows that CRMP-2 was co-immunoprecipitated with a 190 kDa protein (p190). Both CRMP-2 and p190 were phosphorylated on serine residues in vivo and in vitro in a kinase assay of CRMP-2 immune complexes. Immunocytochemistry shows that CRMP-2 was exclusively localized in both the central and peripheral nervous systems in mouse embryos and detectable in the adult brain although the level of CRMP-2 decreased. The protein was expressed in the axon, dendrite, and cytoplasm of postmitotic neurons and in the cytoplasm of oligodendrocytes and astrocytes. The CRMP-2 gene maps to the region of mouse chromosome 14 syntenic with human chromosome 8p21. Taken together, these data suggest multi-functional roles for CRMP-2 in developing and adult nervous systems, and the biological activity of CRMP-2 could be regulated by phosphorylation reaction.

    Brain research. Molecular brain research 1998;54;2;219-36

  • Neurofilament (NF) assembly; divergent characteristics of human and rodent NF-L subunits.

    Carter J, Gragerov A, Konvicka K, Elder G, Weinstein H and Lazzarini RA

    Brookdale Center for Developmental and Molecular Biology, Mount Sinai School of Medicine, New York, New York 10029, USA.

    Previous studies have shown that rodent neurofilaments (NF) are obligate heteropolymers requiring NF-L plus either NF-M or NF-H for filament formation. We have assessed the competence of human NF-L and NF-M to assemble and find that unlike rat NF-L, human NF-L is capable of self-assembly. However, human NF-M cannot form homopolymers and requires the presence of NF-L for incorporation into filaments. To investigate the stage at which filament formation is blocked, the rod domains or the full-length subunits of human NF-L, human NF-M, and rodent NF-L were analyzed in the yeast "interaction trap" system. These studies demonstrated that the fundamental block to filament formation in those neurofilaments that do not form homopolymers is at the level of dimer formation. Based on theoretical biophysical considerations of the requirements for the formation of coiled-coil structures, we predicted which amino acid differences were likely to be responsible for the differing dimerization potentials of the rat and human NF-L rod domains. We tested these predictions using site-specific mutagenesis. Interestingly, single amino acid changes in the rod domains designed to restore or eliminate the coiled-coil propensity were found respectively to convert rat NF-L into a subunit capable of homopolymerization and human NF-L into a protein that is no longer able to self-assemble. Our results additionally suggest that the functional properties of the L12 linker region of human NF-L, generally thought to assume an extended beta-sheet conformation, are consonant with an alpha-helix that positions the heptad repeats before and after it in an orientation that allows coiled-coil dimerization. These studies reveal an important difference between the assembly properties of the human and rodent NF-L subunits possibly suggesting that the initiating events in neurofilament assembly may differ in the two species.

    Funded by: NIA NIH HHS: P50 AGO 5138-11; NIDA NIH HHS: DA 00060; NIDDK NIH HHS: DK4 6943

    The Journal of biological chemistry 1998;273;9;5101-8

  • Three neural tubes in mouse embryos with mutations in the T-box gene Tbx6.

    Chapman DL and Papaioannou VE

    Department of Genetics and Development, College of Physicians and Surgeons of Columbia University, New York, New York 10032, USA.

    Somites, segmented mesodermal units of the vertebrate embryo, are the precursors of adult skeletal muscle, bone and cartilage. During embryogenesis, somite progenitor cells ingress through the primitive streak, move laterally to a paraxial position (alongside the body axis) and segment into epithelial somites. Little is known about how this paraxial mesoderm tissue is specified. We have previously described a mouse T-box gene, Tbx6, which codes for a putative DNA-binding protein. The embryonic pattern of expression of Tbx6 in somite precursor cells suggests that this gene may be involved in the specification of paraxial mesoderm. We now report the creation of a mutation in Tbx6 that profoundly affects the differentiation of paraxial mesoderm. Irregular somites form in the neck region of mutant embryos, whereas more posterior paraxial tissue does not form somites but instead differentiates along a neural pathway, forming neural-tube-like structures that flank the axial neural tube. These paraxial tubes show dorsal/ventral patterning that is characteristic of the neural tube, and have differentiated motor neurons. These results indicate that Tbx6 is needed for cells to choose between a mesodermal and a neuronal differentiation pathway during gastrulation; Tbx6 is essential for the specification of posterior paraxial mesoderm, and in its absence cells destined to form posterior somites differentiate along a neuronal pathway.

    Nature 1998;391;6668;695-7

  • Delayed maturation of regenerating myelinated axons in mice lacking neurofilaments.

    Zhu Q, Couillard-Després S and Julien JP

    Centre for Research in Neuroscience, McGill University, Montreal General Hospital Research Institute, Quebec, Canada.

    Using the technique of homologous recombination in embryonic stem cells, we generated mice bearing a targeted disruption of the gene encoding the neurofilament light (NF-L) protein. The absence of NF-L protein in mice resulted in dramatic declines of approximately 20-fold in the levels of neurofilament medium and heavy proteins in the brain and sciatic nerve while increases were detected for other cytoskeletal proteins such as tubulin and GAP-43. Despite a lack of neurofilaments and hypotrophy of axons, the NF-L knockout mice develop normally and do not exhibit overt phenotypes. However, in both NF-L -/- and NF-L +/- mice, the regeneration of myelinated axons following crush injury of peripheral nerves was found to be abnormal. In the second week after axotomy, the number of newly regenerated myelinated axons in the sciatic nerve and facial nerve of NF-L -/- mice corresponded to only approximately 25 and approximately 5% of the number of myelinated axons found in normal mice, respectively. At this early postaxotomy stage, electron microscopy of nerve segments distal to the crush site in NF-L -/- mice revealed abundant clusters of axonal sprouts that were indicative of retarded maturation of regenerating fibers. The analysis of the distal sciatic nerve at 2 months after crush indicated that neurofilament-deficient axons have the capacity to regrow for a long distance and to remyelinate, albeit at a slower rate. These results provide the first direct evidence for a role of neurofilaments in the maturation of regenerating myelinated axons.

    Experimental neurology 1997;148;1;299-316

  • Transgenic analyses reveal developmentally regulated neuron- and muscle-specific elements in the murine neurofilament light chain gene promoter.

    Yaworsky PJ, Gardner DP and Kappen C

    Samuel C. Johnson Medical Research Center, Mayo Clinic Arizona, Scottsdale, Arizona 85259, USA.

    We report here the developmental activity of regulatory elements that reside within 1.7 kilobases of the murine neurofilament light chain (NF-L) gene promoter. NF-L promoter activity is first detected at embryonic day 8.5 in neuroepithelial cells. Neuron-specific gene expression is maintained in the spinal cord until embryonic day 12.5 and at later developmental stages in the brain and sensory neuroepithelia. After day 14.5, the promoter becomes active in myogenic cells. Transgene expression in both neurons and muscle is consistent with the detection of endogenous NF-L transcript in both neuronal and myogenic tissues of neonates by reverse transcriptase-polymerase chain reaction. Neuron- and muscle-specific activities of the NF-L promoter decrease and are nearly undetectable after birth. Thus, the 1.7-kilobase NF-L promoter contains regulatory elements for initiation but not maintenance of transcription from the NF-L locus. Deletion analyses reveal that independent regulatory elements control the observed tissue-specific activities and implicate a potential MyoD binding site as the muscle-specific enhancer. Our results demonstrate that the NF-L promoter contains distinct regulatory elements for both neuron- and muscle-specific gene expression and that these activities are temporally separated during embryogenesis.

    The Journal of biological chemistry 1997;272;40;25112-20

  • ADAM7, a member of the ADAM (a disintegrin and metalloprotease) gene family is specifically expressed in the mouse anterior pituitary and epididymis.

    Cornwall GA and Hsia N

    Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock 79430, USA.

    The maturation of spermatozoa in the epididymis is a complex process that requires the active involvement of the epididymal epithelium. The primary focus toward elucidating the role of the epididymis in the maturation process has been the study of epididymal secretory proteins and their interaction with spermatozoa. To date there is a paucity of information regarding epididymal epithelial cell surface proteins, which may also play important roles in epididymal function. Through a subtractive hybridization approach to identify genes specifically expressed in the caput epididymidis, the mouse homologue of a member of the ADAM (a disintegrin and metalloprotease) family of proteins was identified. This rapidly growing gene family encodes cell surface proteins that possess putative adhesion and protease domains. Northern blot analyses demonstrated that the mouse ADAM gene, termed ADAM7, is expressed in the caput region of the epididymis and in the anterior pituitary gonadotropes with no detectable expression in the twenty-six other tissues examined. Furthermore, in situ hybridization experiments revealed that the ADAM7 messenger RNA (mRNA) exhibited an apical localization within the proximal caput epididymal epithelium that may correlate with an unusual sparsely granulated endoplasmic reticulum uniquely present in the proximal region of the epididymidis and to which no known function has been ascribed. Hormonal, surgical, and genetic strategies demonstrated that ADAM7 gene expression requires, in a region-dependent manner, androgens as well as testicular factors for expression. Interestingly, the apical localization of ADAM7 mRNA is dependent upon an intact testis, because in situ hybridization analyses of the proximal caput epididymidis from a testosterone maintained castrate mouse did not show the apical localization of ADAM7 mRNA. Finally, chromosomal mapping demonstrated that the ADAM7 gene maps to the central region of mouse Chromosome 14, approximately 4-5 cM distal from the fertilin beta locus, which encodes another reproductive-specific ADAM protein.

    Funded by: NICHD NIH HHS: HD-33903

    Endocrinology 1997;138;10;4262-72

  • Mmot1, a new helix-loop-helix transcription factor gene displaying a sharp expression boundary in the embryonic mouse brain.

    Malgaretti N, Pozzoli O, Bosetti A, Corradi A, Ciarmatori S, Panigada M, Bianchi ME, Martinez S and Consalez GG

    Department of Biological and Technological Research (DIBIT), San Raffaele Scientific Institute (HSR), I-20132 Milan, Italy.

    Several genetic factors have been proven to contribute to the specification of the metencephalic-mesencephalic territory, a process that sets the developmental foundation for prospective morphogenesis of the cerebellum and mesencephalon. However, evidence stemming from genetic and developmental studies performed in man and various model organisms suggests the contribution of many additional factors in determining the fine subdivision and differentiation of these central nervous system regions. In man, the cerebellar ataxias/aplasias represent a large and heterogeneous family of genetic disorders. Here, we describe the identification by differential screening and the characterization of Mmot1, a new gene encoding a DNA-binding protein strikingly similar to the helix-loop-helix factor Ebf/Olf1. Throughout midgestation embryogenesis, Mmot1 is expressed at high levels in the metencephalon, mesencephalon, and sensory neurons of the nasal cavity. In vitro DNA binding data suggest some functional equivalence of Mmot1 and Ebf/Olf1, possibly accounting for the reported lack of olfactory or neural defects in Ebf-/- knockout mutants. The isolation of Mmot1 and of an additional homolog in the mouse genome defines a novel, phylogenetically conserved mammalian family of transcription factor genes of potential relevance in studies of neural development and its aberrations.

    Funded by: Telethon: E.0501

    The Journal of biological chemistry 1997;272;28;17632-9

  • A novel cdc2-related protein kinase expressed in the nervous system.

    Lazzaro MA, Albert PR and Julien JP

    Centre for Research in Neuroscience, McGill University and Montreal General Hospital Research Institute, Quebec, Canada.

    We report the cloning and characterization of a cDNA encoding a cdc2-related protein kinase, named PFTAIRE, that is expressed primarily in the postnatal and adult nervous system. We have demonstrated by in situ hybridization and indirect immunofluorescence that several populations of terminally differentiated neurons and some neuroglia expressed PFTAIRE mRNA and protein. In neurons, PFTAIRE protein was localized in the nucleus and cytoplasm of cell bodies. The anatomical, cellular, and ontogenic patterns of PFTAIRE expression in the nervous system differed from those of p34cdc2 and cdk5, which are expressed in brain and several other mitotic tissues. Proteins of approximately 58-60 kDa coprecipitated specifically with PFTAIRE from cytosolic protein preparations of adult mouse brain and transfected cells. These proteins appeared to be the major endogenous substrates associated with this kinase activity. The temporal and spatial expression patterns of PFTAIRE in the postnatal and adult nervous system suggest that PFTAIRE kinase activity may be associated with the postmitotic and differentiated state of cells in the nervous system and that its function may be distinct from those of p34cdc2 and cdk5.

    Journal of neurochemistry 1997;69;1;348-64

  • The genes of the lysosomal cysteine proteinases cathepsin B, H, L, and S map to different mouse chromosomes.

    Deussing J, Roth W, Rommerskirch W, Wiederanders B, von Figura K and Peters C

    Zentrum Biochemie und Molekulare Zellbiologie, Abt. Biochemie II, Universität Göttingen, Gosslerstrasse 12D, 37073 Göttingen, Germany.

    The mouse genes for the lysosomal cysteine proteinases cathepsin B, H, L, and S were mapped to Chromosomes (Chrs) 14, 9, 13, and 3, respectively. Two of the DNA probes used in this study detected an additional, independently segregating locus. The cathepsin B-specific probe hybridized to a locus on Chr 2, and the cathepsin H probe to a locus on the X Chr. These loci either correspond to pseudogenes or to cathepsin B- and cathepsin H-related genes. The four cysteine proteinases mapped in this study lie within known regions of conserved synteny between mouse and human chromosomes, when compared with the corresponding positions of their human homologs. Assuming that the genes of the cysteine proteinase gene family arose from a common ancestral gene, our results suggest that these four cysteine proteinases had been dispersed over different chromosomes before separation of mouse and human in evolution.

    Mammalian genome : official journal of the International Mammalian Genome Society 1997;8;4;241-5

  • Developmental expression of morphoregulatory genes in the mouse embryo: an analytical approach using a novel technology.

    Craig JC, Eberwine JH, Calvin JA, Wlodarczyk B, Bennett GD and Finnell RH

    Department of Veterinary Anatomy and Public Health, Texas A&M University, College Station 77843, USA.

    The molecular techniques of in situ transcription and antisense RNA amplification (IST/aRNA) have allowed for the monitoring of coordinate changes in the expression of multiple genes simultaneously. However, the analysis of their concurrent behavior during murine embryogenesis has been problematic. Studies involving the investigation of temporal and spatial gene expression during embryogenesis have focused solely on the analysis of isolated, single gene events. Such an approach has failed to provide an integrative picture of genetic control over the varied and complicated cellular processes governing embryogenesis. In order to interpret the enormous amount of gene expression data generated by these procedures, we have attempted to develop an analytical framework by employing the statistical concepts of principal components analysis (PCA). For the current study, we performed IST/aRNA on neural tubes dissected from the highly inbred LM/Bc murine strain collected during four gestational time periods. A subset of these genes, representing a partial signaling pathway in the developing neuroepithelium, was then subjected to PCA. Here, we report that PCA highlighted the transcriptional interplay among the genes p53, wee-1, Tgf beta-2, and bcl-2 such that the combined reciprocal regulation of their gene products is suggestive of a predominant proliferative state for the developing neuroepithelium. The application of PCA to the gene expression data has elucidated previously unknown interrelationships among cell cycle genes, growth, and transcription factors on a transcriptional level during critical stages of neurulation. The information gleaned from this analysis, while not definitive, suggests distinct hypotheses to guide future research.

    Funded by: NIDCR NIH HHS: DE 11303; NIEHS NIH HHS: ES 07165

    Biochemical and molecular medicine 1997;60;2;81-91

  • Cx43 gap junction gene expression and gap junctional communication in mouse neural crest cells.

    Lo CW, Cohen MF, Huang GY, Lazatin BO, Patel N, Sullivan R, Pauken C and Park SM

    Biology Department, University of Pennsylvania, Philadelphia, USA.

    Although gap junctions are not known to be important in mediating cell-cell interactions amongst migratory cells, our studies showed that the connexin 43 (Cx43) gap junction gene is widely expressed in mouse neural crest cell lineages. Using in situ hybridization analysis, Cx43 expression was detected in presumptive neural crest cells emerging from the neural folds of the early postimplantation embryo. Neural crest expression of the Cx43 gap junction gene was also indicated by the analysis of transgenic mice containing a lacZ reporter construct driven by the Cx43 promoter. In neural tube explant cultures of these transgenic mice, lacZ expression was observed in the emerging neural crest outgrowths. Whole mount X-gal staining of these transgenic embryos at various stages of development showed lacZ expression in neural crest cells distributed along the entire craniocaudal axis, with expression found in both cranial and trunk neural crest cells contributing to a wide range of embryonic tissues. This included presumptive cardiac neural crest cells localized in the heart. In light of the widespread expression of Cx43 in neural crest cell lineages, dye injection studies, were carried out to determine if neural crest cells are functionally coupled via gap junctions. Such studies revealed extensive dye coupling among presumptive neural crest cells, thus demonstrating that these migratory cells are indeed gap junctional communication competent. In total, these observations suggest that gap junctions may play a role in mouse neural crest development. This possibility is particularly intriguing given the recent finding that the Cx43 knockout mice die of defects associated with the outflow tract [Reaume et al., 1995], a region of the heart in which neural crest cells are required for normal development.

    Funded by: NICHD NIH HHS: HD29573

    Developmental genetics 1997;20;2;119-32

  • Okadaic acid suppresses neural differentiation-dependent expression of the neurofilament-L gene in P19 embryonal carcinoma cells by post-transcriptional modification.

    Sasahara Y, Kobayashi T, Onodera H, Onoda M, Ohnishi M, Kato S, Kusuda K, Shima H, Nagao M, Abe H, Yanagawa Y, Hiraga A and Tamura S

    Department of Biochemistry, Institute of Development, Aging and Cancer, Tohoku University, Sendai 980, Japan.

    Mouse P19 embryonal carcinoma cells in aggregation culture in the presence of 10(-6) M retinoic acid followed by monolayer culture differentiate into nerve and glial cells. In this study, we demonstrated that the neurofilament-L (NF-L) mRNA and protein levels of these cells were enhanced in accordance with their retinoic acid-induced neural differentiation. Okadaic acid (OA) treatment of the cells markedly suppressed this differentiation-dependent NF-L gene expression increase and neurite outgrowth of the cells. Similar results were obtained when tautomycin was used instead of OA, suggesting that inhibition of protein phosphatase(s) is involved in the suppression of neural differentiation. OA treatment did not affect the NF-L gene transcription level, determined by the nuclear run-on transcription assay, but it did reduce the stability of both the 3.5- and 2.3-kilobase NF-L mRNAs. The expression and activity levels of protein phosphatase 2A (PP2A) and 2B (PP2B) but not protein phosphatase 1 (PP1) in P19 cells increased in accordance with the enhanced NF-L gene expression. The presence of OA in the culture medium during the course of the neural differentiation caused a reduced PP2A activity but not PP1 and PP2B activities of the cell extracts. On the other hand, both PP1 and PP2B activities but not PP2A activity of cell extracts were suppressed by the addition of cyclosporin A or FK506 in the culture medium. However, both cyclosporin A and FK506 treatments affected neither NF-L gene expression nor neurite outgrowth. These results demonstrate that the OA treatment inhibits the differentiation-dependent increase in NF-L gene expression by destabilizing its mRNAs and suggest that PP2A plays key roles in the differentiation-dependent enhanced expression of the NF-L gene and is the point of the action of OA.

    The Journal of biological chemistry 1996;271;42;25950-7

  • M-cadherin distribution in the mouse adult neuromuscular system suggests a role in muscle innervation.

    Cifuentes-Diaz C, Goudou D, Padilla F, Facchinetti P, Nicolet M, Mège RM and Rieger F

    INSERM U153, Développement, Pathologie, Régénération du Système Neuromusculaire, Paris, France.

    M-cadherin belongs to the Ca(2+)-dependent cadherin family of cell adhesion molecules and was first isolated from a mouse muscle cell line cDNA library. It is specifically expressed in muscle tissue during development and is supposed to play an important role in secondary myogenesis. In the present study the expression of M-cadherin mRNA and protein and its localization were investigated in adult mouse skeletal muscle and peripheral nerve. The mRNA was abundant in embryonic legs from embryonic day (E)14 to E18. It remained expressed in new-born and adult muscles. In the adult muscle M-cadherin immunoreactivity was only detected at the neuromuscular junction, associated with perijunctional mononucleated cells and on intramuscular nerves. Peripheral nerves were also M-cadherin-positive. The molecule was found at the surface of myelinated nerve fibres where it was concentrated at the node of Ranvier. When a nerve was crushed and allowed to regenerate, M-cadherin was over-expressed at the site of nerve injury and in the distal stump. M-cadherin was also upregulated on the sarcolemma of denervated muscle fibres. Taken together, these observations point toward a much wider tissue distribution of M-cadherin than previously thought. M-cadherin might be involved not only in specific steps of myogenesis but also in some aspects of synaptogenesis, axon/Schwann cell interactions and node of Ranvier structural maintenance.

    The European journal of neuroscience 1996;8;8;1666-76

  • Characterization of DNase I hypersensitive sites in the mouse 68-kDa neurofilament gene.

    Kure R, Ivanov TR and Brown IR

    Department of Zoology, University of Toronto, West Hill, Ontario, Canada.

    Four brain-specific DNase I hypersensitive sites (HSS) have previously been identified flanking the mouse 68-kDa neurofilament gene within a 1.7 kb upstream sequence which confers neuronal specificity of expression of this gene in transgenic mice. Previously several DNA-binding factors were detected at the HSS closest to the transcription start site (HSS1). However, no major brain-specific factors were identified, suggesting a possible role for the three remaining HSS in conferring tissue-specificity to the NF-L gene. Sequence analysis of the NF-L promoter region demonstrated the presence of an extensive CT repeat and several potential binding sites which are also found in other neurofilament promoters. Gel mobility shift assays revealed a similar but not identical banding pattern with brain and liver nuclear extracts at HSS2, and HSS3, however the banding pattern for HSS4 was predominantly brain-specific. DNase I footprinting revealed several factors binding to the upstream HSS regions in brain and liver nuclear extracts. These include a CCAAT box at HSS2, a novel brain-specific footprint near an adenovirus promoter element E2aE-C beta and a single liver-specific footprint associated with an POU/octamer binding site at HSS4. The presence of brain-specific gel shift bands and tissue-specific footprints associated with HSS4, suggest that this region may play an important role in the regulation of the NF-L gene.

    Neurochemical research 1996;21;6;713-22

  • Early upregulation of medium neurofilament gene expression in developing spinal cord of the wobbler mouse mutant.

    Pernas-Alonso R, Schaffner AE, Perrone-Capano C, Orlando A, Morelli F, Hansen CT, Barker JL, Esposito B, Cacucci F and di Porzio U

    International Institute of Genetics and Biophysics, C.N.R., Naples, Italy.

    Homozygous wobbler mouse mutants develop a progressive paralysis due to spinal motoneuron degeneration. To understand the molecular aspect underlying the genetic defect we have studied the embryonic (from E13) and postnatal expression of the three neurofilament and choline acetyltransferase genes in each member from several wild-type (wt) and wobbler (wr) progenies. There are no variations among wt littermates at all ages studied. In contrast, analyses of neurofilament mRNA reveals a 3-4-fold increase of medium neurofilament (NFM) mRNA in wobbler mice (wr/wr). The pattern of increased NFM mRNA during development, prior to the appearance of the wobbler phenotype, among littermates (from heterozygous carriers) conforms to a mendelian inheritance of a single gene defect 1:2:1 (wr/wr:wr/+:+/+). Light and heavy neurofilament mRNA levels are also increased later in development exclusively in those individuals with high NFM mRNA values indicating that increase of the latter is associated with increase of the light and heavy subunit expression. Also NF proteins are increased. Expression of choline acetyltransferase gene is instead always comparable to normal control. Our study provides novel insights into the nature of the wobbler defect, strengthening the hypothesis that neurofilament accumulation plays a pivotal role in the etiopathogenesis of motoneuron degeneration.

    Brain research. Molecular brain research 1996;38;2;267-75

  • Transcription factor AP-2 essential for cranial closure and craniofacial development.

    Schorle H, Meier P, Buchert M, Jaenisch R and Mitchell PJ

    Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, USA.

    During closure of the neural tube in the mouse, transcription factor AP-2 is expressed in ectoderm and in neural-crest cells migrating from the cranial neural folds. Cranial neural crest cells provide patterning information for craniofacial morphogenesis, generate most of the skull bones, and together with placodal ectoderm, form the cranial ganglia. To study the role of AP-2 during embryogenesis, we undertook a targeted mutagenesis of the AP-2 gene in the mouse. Here we report that AP-2(-/-) mice died perinatally with cranio-abdominoschisis and severe dismorphogenesis of the face, skull, sensory organs and cranial ganglia. Failure of cranial closure between 9 and 9.5 days postcoitum coincided with increased apoptosis in the midbrain, anterior hindbrain and proximal mesenchyme of the first branchial arch, but did not involve loss of expression of twist or Pax-3, two other regulatory genes known to be required for cranial closure.

    Nature 1996;381;6579;235-8

  • Chromosomal localization of the mammalian peptide-methionine sulfoxide reductase gene and its differential expression in various tissues.

    Moskovitz J, Jenkins NA, Gilbert DJ, Copeland NG, Jursky F, Weissbach H and Brot N

    Roche Institute of Molecular Biology, Roche Research Center, Nutley, NJ 07110-1199, USA.

    Peptide methionine sulfoxide reductase (MsrA; EC 1.8.4.6) is a ubiquitous protein that can reduce methionine sulfoxide residues in proteins as well as in a large number of methyl sulfoxide compounds. The expression of MsrA in various rat tissues was determined by using immunocytochemical staining. Although the protein was found in all tissues examined, it was specifically localized to renal medulla and retinal pigmented epithelial cells, and it was prominent in neurons and throughout the nervous system. In addition, blood and alveolar macrophages showed high expression of the enzyme. The msrA gene was mapped to the central region of mouse chromosome 14, in a region of homology with human chromosomes 13 and 8p21.

    Proceedings of the National Academy of Sciences of the United States of America 1996;93;8;3205-8

  • Expression and activity of L-Myc in normal mouse development.

    Hatton KS, Mahon K, Chin L, Chiu FC, Lee HW, Peng D, Morgenbesser SD, Horner J and DePinho RA

    Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.

    To determine the role of L-Myc in normal mammalian development and its functional relationship to other members of the Myc family, we determined the normal patterns of L-myc gene expression in the developing mouse by RNA in situ hybridization and assessed the phenotypic impact of L-Myc deficiency produced through standard gene targeting methodology. L-myc transcripts were detected in the developing kidney and lung as well as in both the proliferative and the differentiative zones of the brain and neural tube. Despite significant expression of L-myc in developing mouse tissue, homozygous null L-myc mice were found to be viable, reproductively competent, and represented in expected frequencies from heterozygous matings. A detailed histological survey of embryonic and adult tissues, characterization of an embryonic neuronal marker, and measurement of cellular proliferation in situ did not reveal any congenital abnormalities. The lack of an apparent phenotype associated with L-Myc deficiency indicates that L-Myc is dispensable for gross morphological development and argues against a unique role for L-Myc in early central nervous system development as had been previously suggested. Although overlapping expression patterns among myc family members raise the possibility of complementation of L-Myc deficiency by other Myc oncoproteins, compensatory changes in the levels of c- and/or N-myc transcripts were not detected in homozygous null L-myc mice.

    Funded by: NCI NIH HHS: 2P30CA13330, CA09173; NINDS NIH HHS: NS23840; ...

    Molecular and cellular biology 1996;16;4;1794-804

  • NGF, BDNF and NT-3 play unique roles in the in vitro development and patterning of innervation of the mammalian inner ear.

    Staecker H, Van De Water TR, Lefebvre PP, Liu W, Moghadassi M, Galinovic-Schwartz V, Malgrange B and Moonen G

    Department of Otolaryngology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.

    Developing cochleovestibular ganglion (CVG) neurons depend upon interaction with the otocyst, their peripheral target tissue, for both trophic support and tropic guidance. RT-PCR of E11 through E14 otocyst-CVG RNA extracts have shown that NGF as well as BDNF and NT-3 are expressed in the developing inner ear (in situ RT-PCR on tissue sections of E12 otocysts localized all three neurotrophins to the otocyst). To evaluate the functional significance of NGF, BDNF and NT-3 expression, E10.5 otocyst-CVG explants were treated with antisense oligonucleotides and compared to sense treated and control cultures. Confocal microscopic analysis revealed that treatment with BDNF antisense resulted in extensive neuronal cell death, downregulation of NGF caused an inhibition of neuritogenesis and a decrease in the neuronal population of the CVG, whereas treatment with NT-3 antisense resulted in a loss of target directed CVG neuritic ingrowth in this in vitro model. The effect of NGF or BDNF antisense treatment could be prevented by the simultaneous addition of the respective growth factor. These findings demonstrate that each of the three neurotrophins have important roles during the onset of neuritic ingrowth of the CVG neurons to the otocyst.

    Funded by: NIDCD NIH HHS: DC0088

    Brain research. Developmental brain research 1996;92;1;49-60

  • A large family of putative transmembrane receptors homologous to the product of the Drosophila tissue polarity gene frizzled.

    Wang Y, Macke JP, Abella BS, Andreasson K, Worley P, Gilbert DJ, Copeland NG, Jenkins NA and Nathans J

    Department of Molecular Biology, Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.

    In Drosophila melanogaster, the frizzled gene plays an essential role in the development of tissue polarity as assessed by the orientation of cuticular structures. Through a combination of random cDNA sequencing, degenerate polymerase chain reaction amplification, and low stringency hybridization we have identified six novel frizzled homologues from mammals, at least 11 from zebrafish, several from chicken and sea urchin, and one from Caenorhabditis elegans. The complete deduced amino acid sequences of the mammalian and nematode homologues share with the Drosophila frizzled protein a conserved amino-terminal cysteine-rich domain and seven putative transmembrane segments. Each of the mammalian homologues is expressed in a distinctive set of tissues in the adult, and at least three are expressed during embryogenesis. As hypothesized for the Drosophila frizzled protein, the frizzled homologues are likely to act as transmembrane receptors for as yet unidentified ligands. These observations predict the existence of a family of signal transduction pathways that are homologous to the pathway that determines tissue polarity in Drosophila.

    The Journal of biological chemistry 1996;271;8;4468-76

  • Structure and expression of the mouse necdin gene. Identification of a postmitotic neuron-restrictive core promoter.

    Uetsuki T, Takagi K, Sugiura H and Yoshikawa K

    Department of Molecular Neurobiology, Tokyo Metropolitan Institute for Neuroscience, Japan.

    Necdin is a 325 amino acid residue protein encoded by a cDNA clone isolated from neurally differentiated embryonal carcinoma cells. In situ hybridization histochemistry revealed that necdin mRNA-containing cells in vivo coincided with postmitotic neurons in the mouse brain from early periods of neurogenesis until adulthood. To study the regulation of necdin gene expression, we have isolated and characterized the necdin gene from a mouse genomic DNA library. The necdin gene contains no intron, and its upstream region lacks canonical TATA and CAAT boxes. To assess promoter activity, the 5'-flanking sequence (844 base pairs) of the necdin gene was fused to the LacZ reporter gene and transiently transfected into retinoic acid-treated P19 embryonal carcinoma cells. Most of the transfectants expressing high levels of LacZ immunoreactivity were postmitotic neurons differentiated from P19 cells. Deletion analysis using luciferase reporter genes demonstrated that a neuron-restrictive core promoter is localized to positions -80 to -35, in which a G+C-rich domain and a putative binding site for transcription factors with PAS (per, arnt, and single-minded) dimerization domain are comprised. These results suggest that postmitotic neuron-restrictive expression of the necdin gene is mediated by the specific cis-acting elements and that this promoter is applicable to postmitotic neuron-targeted expression of various transgenic systems.

    The Journal of biological chemistry 1996;271;2;918-24

  • The cellular function of MASH1 in autonomic neurogenesis.

    Sommer L, Shah N, Rao M and Anderson DJ

    Division of Biology 216-76, California Institute of Technology, Pasadena 91125, USA.

    Using primary cultures and immortalized multipotential stem cell lines derived from wild-type and Mash1 mutant neural crest cells, we have analyzed the cellular function of MASH1 in autonomic neurogenesis. We present evidence for the existence of a precursor expressing MASH1 and neuronal markers such as neurofilament, neuron-specific tubulin, and tetanus toxin receptor. This cell has a nonneuronal morphology. Differentiation of this precursor to neurons that express markers such as SCG10, peripherin, and neuron-specific enolase is dependent upon MASH1 function. These data imply that the differentiation of autonomic neurons from uncommitted neural crest cells occurs in several sequential steps. Moreover, they suggest that MASH1 does not commit multipotent cells to a neural fate, like its Drosophila achaete-scute counterparts, but rather promotes the differentiation of a committed neuronal precursor.

    Neuron 1995;15;6;1245-58

  • New seizure frequency QTL and the complex genetics of epilepsy in EL mice.

    Frankel WN, Valenzuela A, Lutz CM, Johnson EW, Dietrich WF and Coffin JM

    Jackson Laboratory, Bar Harbor, Maine 04609, USA.

    EL/Suz (EL) mice experience recurrent seizures that are similar to common partial complex epilepsy in humans. In the mice, seizures occur naturally at 90-100 days of age, but can be induced in younger mice and analyzed as a semi-quantitative trait after gentle rhythmic stimulation. A previous genetic mapping study of EL backcrosses to the strains ABP/LeJ or DBA/2J showed two quantitative trait loci (QTL) with large effects on seizure frequency (El1, Chr 9; El2, Chr 2) and implied the existence of other QTL with lesser effects. To further the understanding of EL-derived seizure alleles, we examined intercross progeny of EL and the strains ABP/LeJ and DDY/Jcl, and also a backcross of (EL x DDY)F1 hybrids to DDY. A new large-effect seizure frequency QTL was found (El5, Chr 14), a more minor QTL confirmed (El3, Chr 10), and two additional QTL proposed (El4, Chr 9; El6, Chr 11). The serotonin receptor gene, Htr2a, maps near and is a candidate for El5, and linkages of other serotonin receptor genes to seizure frequency QTL are noted. In addition, a strong gender effect was revealed, and epistasis was found between Chr 9 and Chr 14 markers. Despite this progress, however, our results revealed a more complex determinism of epilepsy in EL mice than previously described. In particular, no single El locus or pair was essential for frequent seizures, as QTL with large effects, such as El5, El2, and El1, were highly dependent on genetic context. Our studies highlight the importance of gene interaction in some complex mammalian traits defined by natural variation.

    Funded by: NINDS NIH HHS: NS31348

    Mammalian genome : official journal of the International Mammalian Genome Society 1995;6;12;830-8

  • Identification and characterization of a novel related adhesion focal tyrosine kinase (RAFTK) from megakaryocytes and brain.

    Avraham S, London R, Fu Y, Ota S, Hiregowdara D, Li J, Jiang S, Pasztor LM, White RA, Groopman JE et al.

    Deaconess Hospital, Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215, USA.

    We have isolated a cDNA encoding a novel human intracytoplasmic tyrosine kinase, termed RAFTK (for a related adhesion focal tyrosine kinase). In addition, we have cloned and characterized the murine homolog of the human RAFTK cDNA. Comparison of the deduced amino acid sequences of human RAFTK and murine Raftk cDNAs revealed 95% homology, indicating that RAFTK is highly conserved between these species. The RAFTK cDNA clone, encoding a polypeptide of 1009 amino acids, has closest homology (48% identity, 65% similarity) to the focal adhesion kinase (pp125FAK). Comparison of the deduced amino acid sequences also indicates that RAFTK, like pp125FAK, lacks a transmembrane region, myristylation sites, and SH2 and SH3 domains. In addition, like pp125FAK, RAFTK contains a kinase domain flanked by large N-terminal (426 residues) and C-terminal (331 residues) domains, and the C-terminal region contains a predicted proline-rich stretch of residues. In fetal tissues, RAFTK expression was abundant in brain, and low levels were observed in lung and liver. In adult tissues, it was less restricted, indicating that RAFTK expression is developmentally up-regulated. Expression of RAFTK was also observed in human CD34+ marrow cells, primary bone marrow megakaryocytes, platelets, and various areas of brain. The human RAFTK gene was assigned to human chromosome 8 using genomic DNAs from human/rodent somatic cell hybrid lines. The mouse Raftk gene was mapped to chromosome 14, closely linked to gonadotropin-releasing hormone. Using specific antibodies for RAFTK, a approximately 123-kDa protein from the human megakaryocytic CMK cell line was immunoprecipitated. Treatment of the megakaryocytic CMK cells with thrombin caused a rapid induction of tyrosine phosphorylation of RAFTK protein. The structural features of RAFTK suggest that it is a member of the focal adhesion kinase gene family and may participate in signal transduction in human megakaryocytes and brain as well as in other cell types.

    Funded by: NHLBI NIH HHS: HL46668, HL51456

    The Journal of biological chemistry 1995;270;46;27742-51

  • Deletion of 3'-untranslated region alters the level of mRNA expression of a neurofilament light subunit transgene.

    Schwartz ML, Bruce J, Shneidman PS and Schlaepfer WW

    Division of Neuropathology, University of Pennsylvania Medical School, Philadelphia 19104-6079, USA.

    High levels of neurofilament (NF) mRNA expression are attained during early postnatal development and are a major determinant of axonal size. High level NF expression is also dependent upon axonal continuity since NF mRNA levels are down-regulated after nerve transection. This study shows that both postnatal up-regulation and axotomy-induced down-regulation are altered by deletion of 3'-UTR from the mouse light NF subunit (NF-L). Transgenes with (NF-L+) or without (NF-L-) 3'-UTR display similar patterns of neuron-specific expression but differ in their respective levels of expression. Whereas changes in the level of NF-L+ mRNA parallel those of the endogenous mouse NF-L mRNA, changes in the level of NF-L- mRNA differ from the pattern of endogenous NF-L expression during postnatal up-regulation and axotomy-induced down-regulation. Specifically, the NF-L- transgene undergoes a 3-fold aberrant up-regulation between embryonic days 15 (E15) and 18 (E18) and has lost its susceptibility to axotomy-induced down-regulation. Studies of transfected P19 cells show that 3'-UTR deletion leads to a severalfold stabilization of NF-L mRNA and an increase in steady-state mRNA level. The findings support the working hypothesis that the 3'-UTR contains determinants that alter stability and that stabilization of NF-L mRNA regulates the levels of NF-L mRNA in neuronal tissues and cells.

    Funded by: NINDS NIH HHS: R01 NS15722, T32 NS07064

    The Journal of biological chemistry 1995;270;44;26364-9

  • Expression of catenins during mouse embryonic development and in adult tissues.

    Butz S and Larue L

    Max-Planck-Institut für Immunbiologie, Freiburg, Germany.

    Classical cadherins are cell-surface glycoproteins that mediate calcium-dependent cell adhesion. The cytoplasmic domain of these glycoproteins is linked to the cytoskeleton through the catenins (alpha, beta and gamma). The catenins are intracellular polypeptides that are part of a complex sub-membranous network modulating the adhesive ability of the cells. One approach to elucidate the role of these molecules in the cell is to investigate their distribution during mouse development and in adult tissues. This study reports that catenins are widely expressed but in varying amounts in embryos and adult tissues. The expression of all three catenins is most prominent in the adult heart muscle and in epithelia of all developmental stages. In other embryonic and adult tissues, lower expression of catenins was detected, e.g., in smooth muscle or connective tissue. Catenins are coexpressed with various cadherins in different tissues. Gastrulation is the first time during embryogenesis when a discrepancy occurs between the expression of catenins and E-cadherin. E-cadherin expression is suppressed in mesodermal cells but not the expression of catenins. This discrepancy suggests that another cadherin may interact with catenins. Similarly, E-cadherin is generally expressed in adult liver but not in the regions surrounding the central veins. In contrast, catenins are uniformly expressed in the liver, suggesting that they are associated with other cadherins in E-cadherin negative cells. Finally, the three catenins are not always concurrently expressed. For example, in peripheral nerves, only beta-catenin is observable, and in smooth muscle plakoglobin is not detectable.

    Cell adhesion and communication 1995;3;4;337-52

  • The first intron of the mouse neurofilament light gene (NF-L) increases gene expression.

    Hsu C, Janicki S and Monteiro MJ

    Medical Biotechnology Center, University of Maryland Biotechnology Institute, Baltimore, USA.

    Neurofilament expression is developmentally and post-transcriptionally controlled. Using transient transfection assays in mouse L cells, we demonstrate that the expression of the mouse neurofilament light subunit (NF-L) is influenced by intron sequences. NF-L expression was decreased twenty fold upon deletion of the three intron sequences. Elements contained principally within a 350 bp region of intron 1 were responsible for enhanced NF-L expression. Enhancement of expression did not occur when intron I was placed 3' to a heterologous chloramphenicol acetyl transferase (CAT) gene whose expression was driven by NF-L 5' sequences. The intron enhancement of NF-L expression was not promoter-specific and also occurred with the mouse sarcoma virus (MSV) LTR promoter. These data suggest intron sequences may be important in regulating NF gene expression.

    Funded by: NIA NIH HHS: AG11386

    Brain research. Molecular brain research 1995;32;2;241-51

  • Involvement of Wnt-1 in the formation of the mes/metencephalic boundary.

    Bally-Cuif L, Cholley B and Wassef M

    INSERM U106, Hopital de la Salpêtrière, Paris, France.

    Wnt-1, a putative signaling molecule, is required before the 7 somite stage (E8.5) for the development of midbrain structures in the mouse. We show here that Wnt-1 is also needed for the formation of a boundary between the mesencephalic and metencephalic domains of the neural tube. In embryos homozygous for the Wnt-1sw allele, mesencephalic and metencephalic markers fail to segregate and the establishment of a straight limit of Otx-2 and Wnt-1 expression at the mid-hindbrain junction is impaired. In addition, as observed previously in heterotopic mes/metencephalic transplantation experiments in avian embryos, Wnt-1 expression is induced at the border of ectopic mes- and metencephalic islands observed in Wnt-1sw/sw mutants, suggesting that, in situ, interactions between mes- and metencephalic cells reinforce Wnt-1 expression at the boundary.

    Mechanisms of development 1995;53;1;23-34

  • Mouse chromosomal location of the CCAAT/enhancer binding proteins C/EBP beta (Cebpb), C/EBP delta (Cebpd), and CRP1 (Cebpe).

    Jenkins NA, Gilbert DJ, Cho BC, Strobel MC, Williams SC, Copeland NG and Johnson PF

    ABL-Basic Research Program, NCI-Frederick Cancer Research and Development Center, Maryland 21702-1201, USA.

    There are four known members of the C/EBP family of basic region-leucine zipper transcription factors: Cebpa, Cebpb, Cebpd, and Cebpe. Cebpa has previously been mapped to mouse chromosome 7. Here, we show that Cebpb maps to mouse chromosome 2, Cebpd to chromosome 16, and Cebpe to chromosome 14. The assignment of Cebpd to chromosome 16 identifies a new region of homology between mouse chromosome 16 and human chromosome 8.

    Funded by: NCI NIH HHS: N01-CO-46000

    Genomics 1995;28;2;333-6

  • Expression of low-molecular-weight neurofilament (NF-L) mRNA during postnatal development of the mouse brain.

    Kure R and Brown IR

    Department of Zoology, University of Toronto, Ontario, Canada.

    A regional Northern blot analysis demonstrated that the highest levels of NF-L mRNA in the adult mouse brain are present in brain stem followed by mid-brain, with lower levels found in neocortex, cerebellum, and hippocampus. The study was extended to the cellular level over course of postnatal development using in situ hybridization. This developmental analysis revealed that the expression of NF-L mRNA closely follows the differentiation pattern of many large neurons during postnatal neurogenesis. Neurons which differentiate early such as Purkinje, mitral, pyramidal, and large neurons of brain stem and thalamic nuclei, expressed high levels of NF-L mRNA at postnatal day 1. Early expression of NF-L mRNA may be required for the maintenance of the extensive neurofilament protein networks that are detected within the axons of larger neurons. Smaller neurons which differentiate later, such as dentate gyrus granule cells, small pyramidal and granule cells of the neocortex, and granule cells of the cerebellum, exhibit a delayed expression of NF-L mRNA.

    Neurochemical research 1995;20;7;833-46

  • Axonal atrophy in aging is associated with a decline in neurofilament gene expression.

    Parhad IM, Scott JN, Cellars LA, Bains JS, Krekoski CA and Clark AW

    Department of Pathology, University of Calgary, Alberta, Canada.

    Neurofilaments (Nfs) are major determinants of axonal caliber. Nf transcript levels increase during development and maturation, and are associated with an increase in Nf protein, Nf numbers, and caliber of axons. With aging there is axonal atrophy. In this study we asked whether the axonal atrophy of aging was associated with a decline in Nf transcript expression, Nf protein levels, and Nf numbers. Expression of transcripts for the three Nf subunits was evaluated in dorsal root ganglia (DRG) of Fischer-344 rats aged 3-32 months by Northern and in situ hybridization. There was an approximately 50% decrease in Nf subunit mRNA levels in DRG of aged (> 23 months) as compared to young and mature (3 and 12 months) rats, whereas expression of another neuronal mRNA, GAP-43, showed no decline. Western analysis showed a corresponding decrease in Nf subunit proteins and no decline in GAP-43. Morphometric analysis showed a 50% decrease in Nf numbers within axons. The decrease in Nf gene expression and Nf numbers was accompanied by a decrease in cross-sectional area and circularity of all myelinated fibers, with the largest fibers showing the most marked changes, and a shrinkage in the perikaryal area of large neurons. Furthermore, we found a concomitant decrease in the expression of transcripts for the nerve growth factor receptors trkA and p75 with aging. Although the mechanisms leading to the decrease in Nf gene expression with aging are not known, a decrease in the availability of growth factors, or the neuron's ability to respond to them, may play a role in this process.

    Journal of neuroscience research 1995;41;3;355-66

  • Overexpression of the human NFM subunit in transgenic mice modifies the level of endogenous NFL and the phosphorylation state of NFH subunits.

    Tu PH, Elder G, Lazzarini RA, Nelson D, Trojanowski JQ and Lee VM

    Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104-4283, USA.

    Neurofilaments (NFs), the major intermediate filaments of central nervous system (CNS) and peripheral nervous system (PNS) neurons, are heteropolymers formed from the high (NFH), middle (NFM), and low (NFL) molecular weight NF subunits. To gain insights into how the expression of NF subunit proteins is regulated in vivo, two transgenes harboring coding sequences for human NFM (hNFM) with or without the hNFM multiphosphorylation repeat domain were introduced into mice. Expression of both hNFM constructs was driven by the hNFM promoter and resulted in increased levels of hNFM subunits concomitant with an elevation in the levels of mouse NFL (mNFL) proteins in the CNS of both lines of transgenic mice. The increased levels of mNFL appear specific to NFM because previous studies of transgenic mice overexpressing either NFL or NFH did not result in increased expression of either of the other two NF subunits. Further, levels of the most heavily phosphorylated isoforms of mouse NFH (mNFH) were reduced in the brains of these transgenic mice, and electron microscopic studies showed a higher packing density of NFs in large-diameter CNS axons of transgenic versus wild-type mice. Thus, reduced phosphorylation of the mNFH carboxy terminal domain may be a compensatory response of CNS neurons to the increase in NFs, and reduced negative charges on mNFH sidearms may allow axons to accommodate more NFs by increasing their packing density. Taken together, these studies imply that NFM may play a dominant role in the in vivo regulation of the levels of NFL protein, the stoichiometry of NF subunits, and the phosphorylation state of NFH. NFM and NFH proteins may assume similar functions in regulation of NF packing density in vivo.

    The Journal of cell biology 1995;129;6;1629-40

  • The gene encoding the erythrocyte membrane skeleton protein dematin (Epb4.9) maps to mouse chromosome 14.

    Peters LL, Eicher EM, Azim AC and Chishti AH

    Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.

    Funded by: NCRR NIH HHS: RR01183; NHLBI NIH HHS: HL37462

    Genomics 1995;26;3;634-5

  • CNS distribution and overexpression of neurofilament light proteins (NF-L) in mice transgenic for the human NF-L: aberrant accumulation in thalamic perikarya.

    Mathieu JF, Ma D, Descarries L, Vallée A, Parent A, Julien JP and Doucet G

    Département de pathologie, Faculté de médecine, Université de Montréal, Québec, Canada.

    Light microscopic immunocytochemistry with monoclonal antibodies recognizing both murine and human light neurofilament proteins (mNF-L and hNF-L) or hNF-L only was used to examine the distribution of NF-L in the CNS of adult mice, normal or transgenic for the human gene. In normal mice, major fiber bundles were immunoreactive to the first antibody, with few exceptions such as the internal capsule, anterior commissure, and corpus callosum. Strong immunoreactivity was also present in the perikarya of motoneurons in the spinal cord and brainstem, as well as in other brainstem nuclei. Faint cell body staining was visible in layers II, III, and V of the parietal cortex and layers V and VI of the retrosplenial cingulate cortex. In transgenic mice, all forebrain as well as brainstem fiber tracts were intensely immunoreactive to both antibodies. Cell body staining was more intense than in normal mouse and involved additional forebrain and brainstem regions, including extended areas of cerebral cortex. Abnormal cell body labeling was particularly striking in several thalamic nuclei, where numerous darkly stained perikarya were considerably enlarged by accumulated immunoreactive material and exhibited eccentric and fragmented nuclei. At the electron microscopic level, these perikarya were filled with disarrayed filaments displacing all other organelles against the cytoplasmic membrane. Such aberrant accumulation of NF-L was presumably the result of an overexpression in selective subpopulations of CNS neurons. It was compatible with prolonged survival of the animal and could provide a new experimental model of neurodegenerative disease.

    Experimental neurology 1995;132;1;134-46

  • Nestin mRNA expression correlates with the central nervous system progenitor cell state in many, but not all, regions of developing central nervous system.

    Dahlstrand J, Lardelli M and Lendahl U

    Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institute, Stockholm, Sweden.

    Nestin is a recently discovered intermediate filament (IF) gene. Nestin expression has been extensively used as a marker for central nervous system (CNS) progenitor cells in different contexts, based on observations indicating a correlation between nestin expression and this cell type in vivo. To evaluate this correlation in more detail nestin mRNA expression in developing and adult mouse CNS was analysed by in situ hybridization. We find that nestin is expressed from embryonic day (E) 7.75 and that expression is detected in many proliferating CNS regions: at E10.5 nestin is expressed in cells of both the rostral and caudal neural tube, including the radial glial cells; at E15.5 and postnatal day (P) 0 expression is observed largely in the developing cerebellum and in the ventricular and subventricular areas of the developing telencephalon. Furthermore, the transition from a proliferating to a post-mitotic cell state is accompanied by a rapid decrease in nestin mRNA for motor neurons in the ventral spinal cord and for neurons in the marginal layer of developing telencephalon. In contrast to these data we observe two proliferating areas, the olfactory epithelium and the precursor cells of the hippocampal granule neurons, which do not express nestin at detectable levels. Thus, nestin mRNA expression correlates with many, but not all, regions of proliferating CNS progenitor cells. In addition to its temporal and spatial regulation nestin expression also appears to be regulated at the level of subcellular mRNA localization: in columnar neuroepithelial and radial glial cells nestin mRNA is predominantly localized to the pial endfeet.

    Brain research. Developmental brain research 1995;84;1;109-29

  • Altered gene expression in murine branchial arches following in utero exposure to retinoic acid.

    Taylor LE, Bennett GD and Finnell RH

    Department of Veterinary Anatomy and Public Health, Texas A&M University, College Station 77843-4458, USA.

    Retinoic acid (RA) in the form of isotretinoin (Accutane) and tretinoin (Retin-A) is a clinically important compound in the treatment of dermatologic disorders. However, it is also a potent teratogen associated with a number of serious congenital malformations. Generally, these malformations involve the craniofacial structures derived from the first and second branchial arches. To determine how altered gene expression may contribute to the observed RA-induced defects, pregnant LM/Bc mice were administered (5 mg/kg) all-trans RA on gestational day (GD) 8:12. First and second branchial arches were removed from control and teratogen-treated embryos on GD 10:00 10:12, or 12:00, processed by in situ transcription/aRNA techniques, and analyzed for alterations in gene expression. In these studies, a panel of 40 candidate genes that are known to be important in mammalian craniofacial development were examined. This analysis revealed significant differences in the expression level of the nicotinic acetylcholine receptor subunit alpha (NAChR), transforming growth factor beta 2 (TGF beta 2), type 1 cellular retinoid binding protein (CRBP-1), retinoic acid receptor gamma (RAR gamma), and cAMP response element binding protein (CREB). The alterations observed in the expression of these genes following RA exposure may prohibit normal morphogenetic processes within the second branchial arch and lead to the observed malformations.

    Funded by: NIDCR NIH HHS: DE 11303; NINDS NIH HHS: NS 30108

    Journal of craniofacial genetics and developmental biology 1995;15;1;13-25

  • Stage-specific expression of alkaline phosphatase during neural development in the mouse.

    Narisawa S, Hasegawa H, Watanabe K and Millán JL

    La Jolla Cancer Research Foundation, Cancer Research Center, California 92037.

    The expression pattern of tissue nonspecific alkaline phosphatase (TNAP) in the developing neural tube of mouse is reported. Homogeneous AP activity in the neuroepithelium becomes prominent at E8.5. At E9.5, distinctly AP-positive cells appear in the brain and spinal cord area. At stages E10.5 to E12.5, AP positivity is observed between the mesencephalon and the rhombencephalon, along the entire spinal cord and cranial nerves emerging from the myelencephalon. At E13.5, strongly AP positive fibers become prominent in the pons. At E14.5, AP expression in brain tissue is considerably reduced and there is a complete absence of AP activity in the nerve cells and glial cells of adult brain. The choroid plexus remains distinctly positive for AP expression until the adult stage. Northern blot analysis and reverse-transcriptase polymerase chain reaction amplification of RNA indicate that this AP activity results from the expression of the Akp-2 locus. This AP expression pattern is distinct from those reported for the expression of GD3, nestin, Hox 2.3, and Wnt-1 during brain development. We conclude that AP is a useful marker of a subpopulation of neuroectodermal cells present in the neural tube as early as E8.5, at which stages there are no other AP positive intraembryonic cells except PGCs.

    Funded by: NICHD NIH HHS: HD25938

    Developmental dynamics : an official publication of the American Association of Anatomists 1994;201;3;227-35

  • A mutant neurofilament subunit causes massive, selective motor neuron death: implications for the pathogenesis of human motor neuron disease.

    Lee MK, Marszalek JR and Cleveland DW

    Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.

    A direct role of aberrant neurofilament accumulation in the etiology of human motor neuron diseases, including amyotrophic lateral sclerosis, is suggested by the presence of abnormal accumulations of neurofilaments as an early hallmark of the pathogenic process. Furthermore, forcing increased expression of neurofilament subunits in transgenic mouse models leads to motor neuron dysfunction, albeit without the widespread motor neuron death typical of human disease. We now show that accumulation of a modest level of a point mutant in the smallest neurofilament subunit (NF-L) causes massive, selective degeneration of spinal motor neurons accompanied by abnormal accumulations of neurofilaments and severe neurogenic atrophy of skeletal muscles. As in human disease, sensory neurons show only a modest level of degenerative changes. Thus, neurofilament mutations can cause selective motor neuron death, and neurofilamentous abnormalities may be a common toxic intermediate that significantly contributes to the motor neuron death in human disease.

    Funded by: NINDS NIH HHS: NS27036

    Neuron 1994;13;4;975-88

  • Novel cDNA clones obtained by antibody screening of a mouse cerebellar cDNA expression library.

    Kambouris M, Triarhou LC, Dlouhy SR, Sangameswaran L, Luo F, Ghetti B and Hodes ME

    Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis 46202.

    In order to obtain cDNAs of genes that are expressed in cerebellar granule cells (GC), an antiserum was raised against GC isolated from mouse cerebella. Western blot analysis demonstrated that antibodies against multiple proteins were present and immunohistochemical analysis showed that at least some of these proteins were localized to cerebellar GC. The antiserum was used to screen an expression library derived from mouse cerebellar cDNA. Twenty-two granule cell antibody-positive (GCAP) clones were obtained. Of these, eight represented genes previously described and 14 were novel clones (not found in the GenBank database). In situ hybridization histochemistry showed that eight of the novel clones had moderate to strong expression in cerebellar GC and some of these clones were expressed also in the hippocampal formation. One such clone, GCAP-7, appears to represent a single-copy gene and the entire cDNA insert (2,688 bp) has been sequenced. The clone appears to consist primarily of the 3' untranslated portion, including a poly(A) tail and polyadenylation signals, of a 5 kb transcript. The GCAP clones should be useful for future studies of molecular biology of GC in normal individuals and in inherited neurologic disease with GC degeneration.

    Funded by: NINDS NIH HHS: P01-NS27613, R01-NS14426

    Brain research. Molecular brain research 1994;25;3-4;183-91

  • The murine homeobox genes Nkx2.3 and Nkx2.6 are located on chromosomes 19 and 14, respectively.

    Copeland NG, Jenkins NA and Harvey RP

    Mammalian Genetics Laboratory, ABL-Basic Research Program, National Cancer Institute, Frederick Cancer Research and Development Center, Maryland 21702.

    Funded by: NCI NIH HHS: N01-CO-74101

    Genomics 1994;22;3;655-6

  • Targeted disruption of the neurofibromatosis type-1 gene leads to developmental abnormalities in heart and various neural crest-derived tissues.

    Brannan CI, Perkins AS, Vogel KS, Ratner N, Nordlund ML, Reid SW, Buchberg AM, Jenkins NA, Parada LF and Copeland NG

    Mammalian Genetics Laboratory, Frederick Cancer Research and Development Center, Maryland 21702-1201.

    The neurofibromatosis (NF1) gene shows significant homology to mammalian GAP and is an important regulator of the ras signal transduction pathway. To study the function of NF1 in normal development and to try and develop a mouse model of NF1 disease, we have used gene targeting in ES cells to generate mice carrying a null mutation at the mouse Nf1 locus. Although heterozygous mutant mice, aged up to 10 months, likely attributable to a severe malformation of the heart. Interestingly, mutant embryos also display hyperplasia of neural crest-derived sympathetic ganglia. These results identify new roles for NF1 in development and indicate that some of the abnormal growth phenomena observed in NF1 patients can be recapitulated in neurofibromin-deficient mice.

    Funded by: NCI NIH HHS: N01-CO-74101; NINDS NIH HHS: NS28840

    Genes & development 1994;8;9;1019-29

  • Expanding roles for alpha 4 integrin and its ligands in development.

    Sheppard AM, Onken MD, Rosen GD, Noakes PG and Dean DC

    Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110.

    Interaction of alpha 4 integrins with vascular cell adhesion molecule-1 (VCAM-1) is classically important for immune function. However, we found recently that these receptors have a second role, in embryogenesis, where they mediate cell-cell interactions that are important for skeletal muscle differentiation. Here, we present evidence of an expanding role for these receptors in murine development. alpha 4 and VCAM-1 were found at embryonic sites of hematopoiesis, suggesting a role for these receptors during embryogenesis that parallels their hematopoietic function in adult bone marrow. During angiogenesis in the lung, alpha 4 and VCAM-1 were found on mesenchyme that gives rise to vascular endothelium and smooth muscle. alpha 4 persisted on the smooth muscle and the endothelium of newly forming vessels where it colocalized with its extracellular matrix ligand, fibronectin (FN). These patterns suggest several roles for alpha 4 integrins and their ligands in angiogenesis. alpha 4 was also found on neural crest derivatives where it colocalized with FN. alpha 4 was expressed selectively on cells in the dorsal root ganglia: it was apparent along ventral projections, but absent from dorsal projections, suggesting that alpha 4 integrins could be involved in defining neuronal fates. Although VCAM-1 was not expressed on most neural crest derivatives, it was found in the neural crest-derived outflow tract of the embryonic heart, where it colocalized with alpha 4. These results imply that alpha 4 integrins and their ligands could be important for migration or differentiation of neural crest. alpha 4 was also expressed on embryonic retina and FN was found on inductive mesenchyme surrounding the eye, suggesting a role for these proteins in eye development. Finally, based on their patterns of expression, we conclude that VCAM-1 only participates in a subset of interactions involving alpha 4 integrins, whereas FN appears to be the more general ligand.

    Funded by: NHLBI NIH HHS: HL43418; NIAMS NIH HHS: AR41908

    Cell adhesion and communication 1994;2;1;27-43

  • Changes of the expression and distribution of retinoic acid receptors during neurogenesis in mouse embryos.

    Yamagata T, Momoi MY, Yanagisawa M, Kumagai H, Yamakado M and Momoi T

    Department of Pediatrics, Jichi Medical School, Tochigi, Japan.

    The expression and distribution of three retinoic acid receptors, alpha, beta, and gamma, were investigated in the CNS of mouse embryos during development. mRNAs and protein of RAR-beta that were expressed in the spinal cord of the 12.5-day mouse embryo decreased during development but they were not decreased in the brain. The RAR-beta-positive cells were already present in the ventral region of the spinal cord of 10.5-day mouse embryos, gradually appeared in the dorsal region during development and then disappeared from the spinal cord after birth. In the brain, RAR-beta-positive cells were detected in the mesencephalon and rhombencephalon but not in the telencephalon of the 12.5-day mouse embryos. RAR-beta-positive cells were present in the hippocampus and cingulum but not in the neocortex of 14.5-day mouse embryos. Most neurons in the hippocampus of 16.5-day mouse embryos and the cortex of newborn mice were RAR-beta-positive. In the spinal cord, RAR-alpha mRNAs and proteins also decreased during development but more gradually than RAR-beta mRNAs and proteins. During development, the distributions of RAR-alpha and -beta in the spinal cord and brain did not differ substantially. The main difference was the appearance of a subtypes of RAR-alpha, a 52-kDa protein, in the brain of newborn mice. On the other hand, RAR-gamma proteins were only faintly detected in the spinal cord and the brain of the mice during the embryonal stages but these increased after birth. The distribution of RAR-alpha- or -beta-positive cells were consistent with the neurogenesis during development in the spinal cord and brain.

    Brain research. Developmental brain research 1994;77;2;163-76

  • Aberrant expression of Pax-2 in Danforth's short tail (Sd) mice.

    Phelps DE and Dressler GR

    Laboratory of Mammalian Genes and Development, National Institute of Child Health and Human Development, Bethesda, Maryland 20892.

    The pattern of Pax-2 expression was studied in Danforth's short tail homozygous mice using Pax-2-specific antibodies. Because these mice lack a notochord in caudal regions, the floor plate of the spinal cord is not induced and posterior mesoderm-derived structures are also affected. The expression of Pax-2 during neural differentiation in the spinal cord was normal in anterior sections, but ectopic expression in the ventral half of the basal plate was observed in regions lacking the floor plate. The data support the hypothesis that Pax-2 expression domains are influenced by signals emanating from the floor plate and that Pax-2 functions during the dorsal-ventral patterning of the spinal cord. In the developing excretory system, Pax-2 expression was normal in the anterior structures, such as the mesonephros, and in the mesonephric duct. However, Pax-2 was not expressed in the uninduced metanephric mesenchyme. Thus, activation of Pax-2 in the mesenchyme is an early response to inductive signals emanating from the ureter. The Danforth's short tail mutation is a useful model for the study of developmentally regulated genes that are under the influence of the notochord or floor plate.

    Developmental biology 1993;157;1;251-8

  • Increased expression of neurofilament subunit NF-L produces morphological alterations that resemble the pathology of human motor neuron disease.

    Xu Z, Cork LC, Griffin JW and Cleveland DW

    Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.

    Excessive accumulation of neurofilaments in the cell bodies and proximal axons of motor neurons is a major pathological hallmark during the early stages of many human motor neuron diseases. To test directly the consequence of overexpression of the major neurofilament subunit NF-L, we produced transgenic mice that accumulate NF-L to approximately 4-fold the normal level in the sciatic nerve. In young animals, the motor neurons of the ventral horn of the spinal cord have massive accumulations of neurofilaments, swollen perikarya, and eccentrically localized nuclei. NF-L accumulation is accompanied by an increased frequency of axonal degeneration, proximal axon swelling, and severe skeletal muscle atrophy. These data indicate that extensive accumulation of neurofilaments in motor neurons can trigger the neurodegenerative process.

    Cell 1993;73;1;23-33

  • Formation of primary and secondary myotubes in aneural muscles in the mouse mutant peroneal muscular atrophy.

    Ashby PR, Wilson SJ and Harris AJ

    Centre for Neuroscience, University of Otago Medical School, Dunedin, New Zealand.

    The role of motor innervation in supporting and regulating muscle development was studied using aneural muscles in the hindlimb of the mouse mutant peroneal muscular atrophy (pma). This is a single-locus autosomal mutation where homozygous animals lack the common peroneal nerve, so that muscles in the anterolateral compartment of the lower leg develop entirely without innervation. In adults, these muscles are extremely atrophied, and the mice display a clubfoot deformity. The mutant animals provide a preparation in which aspects of muscle formation can be studied in muscles that have never been exposed to direct contact with somatic motor or sensory axons, without pharmacological or surgical intervention. Using quantitative electron microscopy, we found that normal numbers of primary myotubes formed in aneural pma EDL muscles, but a greater than normal proportion degenerated during the first 2 days after their formation. Secondary myotubes appeared at their normal time and position within the muscle, initially in normal numbers, so that the ratio of secondary to primary myotubes initially was greater in pma than in CF1 control strain mice. No abnormalities in ultrastructure were seen until the time of birth, when retardation in development was obvious, together with invading macrophages and degenerating myofibres. The results show that secondary myotube formation in the mouse, as in the chick (B. J. Fredette and L. T. Landmesser, Dev. Biol. 143, 19-35, 1991) is not directly dependent on innervation. In control muscles, secondary myotubes first form in the vicinity of endplates on primary myotubes. No aggregations of ACh receptors or acetylcholinesterase were present in the aneural muscles, showing that these are neurally induced in the mouse, but secondary myotubes formed in their normal position indicating that positional information related to endplate formation is present in aneural muscles.

    Developmental biology 1993;156;2;519-28

  • Methylation and expression of neurofilament genes in tissues and in cell lines of the mouse.

    Bruce J, Schwartz ML, Shneidman PS and Schlaepfer WW

    Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical School, Philadelphia 19104-6079.

    The light (NF-L), mid-sized (NF-M) and heavy (NF-H) neurofilament (NF) genes were probed with methylation-sensitive restriction enzymes and patterns of methylation and expression of the NF genes were compared in tissues and cell lines of the mouse. The 5' regions of all three NF genes are identified as CpG islands that remain unmethylated in expressing and non-expressing tissues, although partial methylation occurs at -795 in NF-H and at -525 in NF-M. Methylation of the NF CpG islands is associated with the inactivation of NF genes in L cells and with the selective inactivation of NF-L and NF-M in Neuro 2a cells. We also show that methylation diminishes the ability of the NF promoters to drive transcription of a CAT reporter gene. Hence, the presence of CpG islands may be important in determining patterns of NF transcription in vitro. Moreover, the preservation of CpG islands may be an evolutionary link that bears upon the nature of the NF genes and the mechanisms that have evolved to limit NF expression.

    Funded by: NINDS NIH HHS: R01-NS15722, T32-NS07064

    Brain research. Molecular brain research 1993;17;3-4;269-78

  • 43K protein and acetylcholine receptors colocalize during the initial stages of neuromuscular synapse formation in vivo.

    Noakes PG, Phillips WD, Hanley TA, Sanes JR and Merlie JP

    Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110.

    The 43K protein is a cytoplasmic peripheral membrane protein concentrated subsynaptically in skeletal muscle. Recombinant 43K has been shown to cause clustering of acetylcholine receptors (AChRs) in cultured cells. However, the role of 43K in vivo is disputed, because in some cases it appears only after AChRs have clustered. We therefore examined the expression and distribution of 43K and AChRs during synapse formation in embryonic mouse muscles. Messenger RNA for 43K was detected on Embryonic Day (E) 12, a day prior to the first AChR clusters. Immunofluorescence showed that both AChRs and 43K were colocalized in patches by E13, the stage at which intramuscular nerves were first detected. The AChR/43K patches were nerve associated, and more than 98% of AChR patches were accompanied by 43K. The precise colocalization of 43K and AChRs persisted through development. These results are consistent with 43K being involved in the nerve-induced clustering of AChRs during synapse formation.

    Developmental biology 1993;155;1;275-80

  • Mapping of the neural retina leucine zipper gene, Nrl, to mouse chromosome 14.

    Bespalova IN, Farjo Q, Mortlock DP, Jackson AU, Meisler MH, Swaroop A and Burmeister M

    Mental Health Research Institute, University of Michigan, Ann Arbor 48109.

    Funded by: NIGMS NIH HHS: GM24872, T32GM07544

    Mammalian genome : official journal of the International Mammalian Genome Society 1993;4;10;618-20

  • Comparative analysis of Pax-2 protein distributions during neurulation in mice and zebrafish.

    Püschel AW, Westerfield M and Dressler GR

    Institute of Neuroscience, University of Oregon, Eugene 97403.

    Members of different vertebrate species share a number of developmental mechanisms and control genes, suggesting that they have similar genetic programs of development. We compared the expression patterns of the Pax-2 protein in Mus musculus and Brachydanio rerio to gain a better understanding of the evolution of developmental control genes. We found that the tissue specificity and the time course of Pax-2 expression relative to specific developmental processes are remarkably similar during the early development of the two organisms. The brain, the optic stalk, the auditory vesicle, the pronephros, and single cells in the spinal cord and the hindbrain express Pax-2 in both species. The Pax-2 expression domain in the prospective brain of E8 mouse embryos has not been described previously. Expression appears first during early neurulation at the junction between the midbrain and hindbrain. However, there are some differences in Pax-2 expression between the two species. Most notable, expression at the midbrain/hindbrain boundary is no longer detectable after E11 in the mouse. Using monoclonal antibodies, we could exclude that primary neurons express Pax-2 in the zebrafish spinal cord. Our results confirm that Pax genes are highly conserved both in sequences and in expression patterns, indicating that they may have a function during early development that has been conserved during vertebrate evolution.

    Funded by: NICHD NIH HHS: HD22486

    Mechanisms of development 1992;38;3;197-208

  • Intragenic regulatory elements contribute to transcriptional control of the neurofilament light gene.

    Beaudet L, Charron G, Houle D, Tretjakoff I, Peterson A and Julien JP

    Montreal General Hospital Research Institute, Quebec, Canada.

    To date, no DNA regions involved in the neuron-specific expression of the neurofilament light gene (NF-L) have been defined using transfection assays in cultured cells. To identify those regulatory regions in the human NF-L gene, we generated transgenic mice with a construct containing the basal NF-L promoter (-292 to +15) fused to the cat gene and with three DNA fragments of 21.5, 7.6 and 4.9 kb each, including NF-L with different lengths of either 5'- or 3'-flanking sequences. We show that the proximal NF-L 5' region (0.3 kb) constitutes a weak promoter and that it lacks information to confer neural specificity. However, appropriate expression in the nervous system occurred when this minimal promoter was combined with either 7.3 or 4.6 kb of NF-L sequences downstream from the transcription start point. We conclude that the intragenic NF-L region contains cis-acting elements conferring cell-type-specific regulation on the basal activity of the NF-L promoter. Interestingly, AP-2 motifs were found within homologously placed introns of all three NF genes, as well as in the promoter regulatory regions of many neuronal genes. We propose that the acquisition of introns by an ancestral intronless IF gene may have contributed to the emergence of a lineage of IF genes expressed in the nervous system.

    Gene 1992;116;2;205-14

  • Interaction of multiple nuclear proteins with the promoter region of the mouse 68-kDa neurofilament gene.

    Ivanov TR and Brown IR

    Department of Zoology, University of Toronto, West Hill, Ontario, Canada.

    Four brain-specific, DNase I hypersensitive sites (HSS) have been mapped to the 5' flanking region of the mouse 68-kDa neurofilament gene. These sites are contained within a 1.7-kb sequence that confers neuronal specificity of expression of this gene in transgenic mice. To identify DNA sequences that might be involved in gene regulation, the HSS situated near the promoter region has been analyzed by gel mobility shift assays and DNase I footprinting to investigate protein binding sequences. Of particular interest are two footprints localized to a 9-nucleotide sequence that flanks both the light and medium neurofilament gene in mouse and to a sequence that demonstrates partial homology to several promoter regions, including element-1, a motif required for neuron specificity in Drosophila. A prominent footprint was also detected at a sequence that contains a near-perfect palindrome centered at a PstI restriction site.

    Journal of neuroscience research 1992;32;2;149-58

  • Negative regulatory regions are present upstream in the three mouse neurofilament genes.

    Shneidman PS, Bruce J, Schwartz ML and Schlaepfer WW

    Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical School, Philadelphia 19104-6079.

    We have cloned and examined the 5' flanking regions of the heavy (NF-H), light (NF-L) and mid-sized (NF-M) mouse neurofilament (NF) genes in order to begin to characterize the regions of each gene that regulate NF transcription. Chimeric plasmids bearing the CAT reporter gene and deletion mutants of the upstream NF genes were transiently transfected into neuronal (PC12 and Neuro 2A) and non-neuronal (HeLa) cell lines. Constructs bearing upstream regions to -4000 in NF-H, to -5600 in NF-L and to -4500 in NF-M were expressed at low levels in neuronal and in non-neuronal cells. Progressive deletion of 5' flanking sequence to -385 in NF-H, to -325 in NF-L and to -505 in NF-M caused a several-fold increase of transcription from the transfected plasmids. Increases of transcription by deletion mutants followed a similar pattern in neuronal and in non-neuronal cell lines. Negative upstream regions are located between -1314 and -385 in NF-H, between -936 and -325 in NF-L and between -874 and -505 in NF-M. Additional negative regions are present further upstream in NF-L and in NF-H. The negative regions of NF-H and of NF-L suppress transcription when placed in either orientation in front of the SV40 or a heterologous NF promoter. These studies demonstrate that the three mouse NF genes possess similar functional features, namely, that of a relatively strong and promiscuous promoter with negative upstream elements. The role of the negative elements in regulating NF expression remains unclear.

    Funded by: NINDS NIH HHS: R01 NS 15722, T32 NS07064

    Brain research. Molecular brain research 1992;13;1-2;127-38

  • Identification of Ser-55 as a major protein kinase A phosphorylation site on the 70-kDa subunit of neurofilaments. Early turnover during axonal transport.

    Sihag RK and Nixon RA

    Laboratory for Molecular Neuroscience, McLean Hospital, Belmont, Massachusetts 02178.

    The 70-kDa neurofilament protein subunit (NF-L) is phosphorylated in vivo on at least three sites (L1 to L3) (Sihag, R. K. and Nixon, R. A. (1989) J. Biol. Chem. 264, 457-464). The turnover of phosphate groups on NF-L during axonal transport was determined after the neurofilaments in retinal ganglion cells were phosphorylated in vivo by injecting mice intravitreally with [32P]orthophosphate. Two-dimensional phosphopeptide maps of NF-L from optic axons of mice 10 to 90 h after injection showed that radiolabel decreased faster from peptides L2 and L3 than from L1 as neurofilaments were transported. To identify phosphorylation sites on peptide L2, axonal cytoskeletons were phosphorylated by protein kinase A in the presence of heparin. After the isolated NF-L subunits were digested with alpha-chymotrypsin, 32P-peptides were separated by high performance liquid chromatography on a reverse-phase C8 column. Two-dimensional peptide mapping showed that the alpha-chymotrypsin 32P-peptide accepting most of the phosphates from protein kinase A migrated identically with the in vivo-labeled phosphopeptide L2. The sequence of this peptide (S-V-R-R-S-Y) analyzed by automated Edman degradation corresponded to amino acid residues 51-56 of the NF-L sequence. A synthetic 13-mer (S-L-S-V-R-R-S-Y-S-S-S-S-G) corresponding to amino acid residues 49-61 of NF-L was also phosphorylated by protein kinase A. alpha-Chymotryptic digestion of the 13-mer generated a peptide which contained most of the phosphates and co-migrated with the phosphopeptide L2 on two-dimensional phosphopeptide maps. Edman degradation of the phosphorylated 13-mer identified serine residue 55 which is located within a consensus phosphorylation sequence for protein kinase A as the major site of phosphorylation. Since protein kinase A-mediated phosphorylation influences intermediate filament assembly/disassembly in vitro, we propose that the phosphopeptide L2 region is a neurofilament-assembly domain and that the cycle of phosphorylation and dephosphorylation of Ser-55 on NF-L, which occurs relatively early after subunit synthesis in vivo, regulaaes a step in neurofilament assembly or initial interactions during axonal transport.

    Funded by: NIA NIH HHS: AG02126, AG05604

    The Journal of biological chemistry 1991;266;28;18861-7

  • Additional microsatellite markers for mouse genome mapping.

    Hearne CM, McAleer MA, Love JM, Aitman TJ, Cornall RJ, Ghosh S, Knight AM, Prins JB and Todd JA

    Nuffield Department of Surgery, John Radcliffe Hospital, Headington, Oxford, UK.

    Mouse sequence information from the EMBL and GenBank databases, published sequences and genomic clones have been analyzed for simple repetitive elements or microsatellites. Each microsatellite has been amplified by the polymerase chain reaction (PCR) as a single locus marker. PCR primers were designed from unique sequence flanking each repeat. Size variation of PCR products less than 750 base pairs (bp) between mouse strains has been determined using ethidium bromide-stained acrylamide or agarose gels. A further 74 newly characterized microsatellites are presented in this paper, bringing to 185 the total we have analyzed. Of these, 157/185 (85%) have more than one allele, 143/178 (80%) vary in length between C57BL/6J and Mus spretus, and 82/168 (49%) vary between DBA/2J and C57BL/6J. Microsatellites provide informative single locus probes for linkage analysis in the construction of a genetic map of the mouse genome.

    Mammalian genome : official journal of the International Mammalian Genome Society 1991;1;4;273-82

  • NCAM in the organ of Corti of the developing mouse.

    Whitlon DS and Rutishauser US

    Department of Neurology, University of Wisconsin, Madison.

    During development in the cochlea, NCAM is present on all neuronal systems--radial fibres, inner spiral bundle, inner pillar bundle (described by Sobkowicz & Emmerling, 1989), and outer spiral fibres. In cochleae from E17 mice, NCAM-positive puncta, possibly associated with growth cones, dot the area of the inner spiral bundle. The region overlying the basilar membrane is also NCAM positive. Until about P7, NCAM immunoreactivity surrounds the inner and outer hair cells. During the second postnatal week, NCAM no longer covers the hair cell surfaces. At this time, NCAM is present on the inner spiral and inner pillar bundles. In the outer hair cell region, immunoreactivity concentrates in neuronal endings with 'Y'-like or 'dot'-like appearances typical of cholinergic efferents. At a time when neuronal fibres are regenerating in the cochlea of the Bronx waltzer mutant mouse, many NCAM-positive puncta dot the regions of the inner spiral bundle and inner spiral sulcus, suggesting that these puncta correspond to growth cones. In organotypic culture, hair cells and nerve fibres retain their immunoreactivity up to 7 days. In conclusion, NCAM is present on the surfaces of neurons and on their cochlear targets at the time when nerve-target recognition is proceeding. NCAM disappears from targets during the time of maturation of efferent synapses. NCAM is also present along the growth path of the nerve fibres. These studies suggest that NCAM is properly positioned in the cochlea for possible roles in axon guidance and nerve-target interactions.

    Funded by: NIDCD NIH HHS: 8-R01-DC-26513

    Journal of neurocytology 1990;19;6;970-7

  • Structure of the 68-kDa neurofilament gene and regulation of its expression.

    Nakahira K, Ikenaka K, Wada K, Tamura T, Furuichi T and Mikoshiba K

    Division of Regulation of Macromolecular Functions, Osaka University, Japan.

    The complete structure of the mouse 68-kDa neurofilament (NF-L) gene was elucidated. We cloned cDNAs corresponding to 3.5- and 2.3-kb NF-L mRNA, including their polyadenylation sites. Sequence analysis revealed that these NF-L mRNAs arose from the alternative use of two polyadenylation sites in exon 4. Promoter analysis using NF-L promoter-beta-galactosidase fusion plasmids determined regions responsible for its basic promoter activity, which were located between -328 and -36 base pairs from the transcription initiation site. These promoter fusion plasmids induced a significant level of beta-galactosidase in NF-nonproducing C6 cells as well as in NF-producing PC12h cells. The in vitro transcription assay using HeLa cell extract also showed that this promoter exhibited strong transcriptional activity. Little difference in NF-L mRNA stability was observed between the two cells. However, nuclear run-off assay revealed that the NF-L gene was not transcribed in NF-nonproducing C6 cells. These data suggest that the strong promoter activity of the NF-L gene is repressed in vivo at the transcription initiation level in a tissue-specific manner.

    The Journal of biological chemistry 1990;265;32;19786-91

  • Assembly properties of dominant and recessive mutations in the small mouse neurofilament (NF-L) subunit.

    Gill SR, Wong PC, Monteiro MJ and Cleveland DW

    Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.

    We have generated a set of amino- and carboxy-terminal deletions of the NF-L neurofilament gene and determined the assembly properties of the encoded subunits after coexpression with vimentin or wild-type NF-L. NF-L molecules missing greater than 30% (31 amino acids of the head) or 90% (128 amino acids of the tail) failed to incorporate into intermediate filament networks. Carboxy-terminal deletions into the rod domain yield dominant mutants that disrupt arrays assembled from wild-type subunits, even when present at levels of approximately 2% of the wild-type subunits. Even mutants retaining 55% of the tail (61 amino acids) disrupt normal arrays when accumulated above approximately 10% of wild-type subunits. Since deletion of greater than 90% of the head domain produces "recessive" assembly incompetent subunits that do not affect wild-type filament arrays, whereas smaller deletions yield efficient network disruption, we conclude that some sequence(s) in the head domain (within residues 31-87) are required for the earliest steps in filament assembly. Insertional mutagenesis in the nonhelical spacer region within the rod domain reveals that as many as eight additional amino acids can be tolerated without disrupting assembly competence.

    Funded by: NINDS NIH HHS: NS 27036

    The Journal of cell biology 1990;111;5 Pt 1;2005-19

  • Expression of NF-L and NF-M in fibroblasts reveals coassembly of neurofilament and vimentin subunits.

    Monteiro MJ and Cleveland DW

    Johns Hopkins University, School of Medicine, Department of Biological Chemistry, Baltimore, Maryland 21205.

    We have used transient and stable DNA transfection to force synthesis of the mouse NF-L and NF-M genes in nonneuronal cultured animal cells. When the authentic NF-L gene (containing 1.7 kb of sequences 5' to the transcription initiation site) was transfected into L cells, correctly initiated NF-L mRNA was produced from the transfected gene but not the endogenous NF-L genes. Therefore, the normal restriction of NF-L expression to neurons cannot derive exclusively from absence in nonneuronal cells of neuron-specific transcription factors. When the NF-L coding region was linked to the strong promoter from Moloney Murine Sarcoma virus, we obtained high levels of synthesis of NF-L subunits (accumulating to as much as 9% of cell protein in stable cell lines). Although NF-L and NF-M polypeptides are normally expressed exclusively in postmitotic neurons, NF-L or NF-M polypeptides expressed in fibroblasts were efficiently assembled into intermediate filament arrays, thus demonstrating the competence of both NF-L and NF-M to assemble in vivo in the absence of additional neuron-specific factors. As judged by immunofluorescence localization and by the alteration in the solubility of the endogenous vimentin filaments, filaments containing NF-L appeared to be copolymers with vimentin. Neither the alteration in the properties of the vimentin array nor the accumulation of NF-L to a level that made it the second most abundant cellular protein (after actin) had any observable effect on cell viability or growth rate.

    The Journal of cell biology 1989;108;2;579-93

  • Chromosomal localization of the mouse gene coding for the 68 kDa neurofilament subunit.

    Mattei MG, Duprey P, Li ZL, Mattei JF and Paulin D

    INSERM U 242, Centre de Génétique Médicale, Hôpital d'Enfants de la Timone, Marseille, France.

    The chromosomal localization of the mouse gene coding for the 68 kDa intermediate filament subunit of neurones (NF-L) was determined by in situ hybridization using specific 3H-labelled DNA probes. There is only one copy of the NF-L gene. The gene encoding NF-L is located on chromosome 14 region (D1-E1).

    Biology of the cell 1989;67;2;235-7

  • Sequence and structure of the mouse gene coding for the largest neurofilament subunit.

    Julien JP, Côté F, Beaudet L, Sidky M, Flavell D, Grosveld F and Mushynski W

    Institut du Cancer de Montréal, Centre Hospitalier Notre-Dame, Canada.

    We have determined the complete nucleotide sequence of the mouse gene encoding the neurofilament NF-H protein. The C-terminal domain of NF-H is very rich in charged amino acids (aa) and contains a 3-aa sequence, Lys-Ser-Pro, that is repeated 51 times within a stretch of 368 aa. The location of this serine-rich repeat in the phosphorylated domain of NF-H indicates that it represents the major protein kinase recognition site. The nfh gene shares two common intron positions with the nfl and nfm genes, but has an additional intron that occurs at a location equivalent to one of the introns in non-neuronal intermediate filament-coding genes. This additional nfh intron may have been acquired via duplication of a primordial intermediate filament gene.

    Gene 1988;68;2;307-14

  • Localization of the 68,000-Da human neurofilament gene (NF68) using a murine cDNA probe.

    Somerville MJ, McLachlan DR and Percy ME

    Department of Physiology, University of Toronto, Ont., Canada.

    A recent investigation, using a human genomic probe, has indicated that the 68,000 dalton neurofilament gene (NF68) is on the short arm of chromosome 8. We have used a murine cDNA probe on 65 metaphase spreads in situ to localize the human NF68 gene to 8p21 (20/370 grains; p less than 0.0001). In addition, we have found secondary hybridization sites at the centromeric region of chromosome 2 and the long arm of chromosome 7, which are putative loci for other intermediate filaments.

    Genome 1988;30;4;499-500

  • Expression and assembly of a human neurofilament protein in transgenic mice provide a novel neuronal marking system.

    Julien JP, Tretjakoff I, Beaudet L and Peterson A

    Institut du Cancer de Montréal, Centre Hospitalier Notre-Dame, Canada.

    To investigate the regulation of neurofilament gene expression, we have generated several lines of transgenic mice carrying multiple copies of a cloned human neurofilament (NF-L) gene. We show that a 21.5-kb DNA fragment including the human NF-L gene contains essential information for correct expression in nervous tissue of transgenic mice. The integrated genes are arranged in multiple tandem arrays, but the extent of transgene expression does not correlate with copy number nor does it influence the expression of the endogenous neurofilament genes. However, the levels of human NF-L protein recovered in neurofilament preparations from brains of transgenic mice correlate directly with the relative abundance of human NF-L mRNA detected in each line. There is an apparent delay in the accumulation of human NF-L protein during development, as determined by immunoblotting with a human-specific monoclonal antibody. Finally, immunohistochemical localization of the human NF-L protein results in the specific staining of neurons and their processes in transgenic mice.

    Genes & development 1987;1;10;1085-95

  • Structure and evolutionary origin of the gene encoding mouse NF-M, the middle-molecular-mass neurofilament protein.

    Levy E, Liem RK, D'Eustachio P and Cowan NJ

    We describe the complete sequence of the gene encoding mouse NF-M, the middle-molecular-mass neurofilament protein. The coding sequence is interrupted by two intervening sequences which align perfectly with the first two intervening sequences in the gene encoding NF-L (the low-molecular-mass neurofilament protein); there is no intron in the gene encoding NF-M corresponding to the third intron in NF-L. Therefore, both the number of introns and their arrangement in the genes coding NF-L and NF-M contrast sharply with the number and arrangement of introns in the genes of known sequence, encoding other members of the intermediate filament multigene family (desmin, vimentin, glial fibrillary acidic protein and the acidic and basic keratins); with the exception of a single truncated keratin gene that lacks an encoded tailpiece, these genes all contain eight introns, of which at least six are placed at homologous locations. Assuming the existence of a primordial intermediate filament gene containing most (if not all) the introns found in contemporary non-neurofilament intermediate filament genes, it seems likely that an RNA-mediated transposition event was involved in the generation of an ancestral gene encoding the NF polypeptides. A combination of insertional transposition and gene-duplication events could then explain the anomalous number and placement of introns within these genes. Consistent with this notion, we show that the genes encoding NF-M and NF-L are linked.

    European journal of biochemistry 1987;166;1;71-7

  • Cloning and developmental expression of the murine neurofilament gene family.

    Julien JP, Meyer D, Flavell D, Hurst J and Grosveld F

    DNA clones encoding the 3 mouse neurofilament (NF) genes have been isolated by cross-hybridization with a previously described NF-L cDNA probe from the rat. Screening of a lambda gt10 cDNA library prepared from mouse brain RNA led to the cloning of an NF-L cDNA of 2.0 kb that spans the entire coding region of 541 amino acids and of an NF-M cDNA that covers 219 amino acids from the internal alpha-helical region and the carboxy-terminal domains of the protein. These cDNA clones were used as probes to screen mouse genomic libraries, and cosmid clones containing both NF-L and NF-M sequences were isolated as well as overlapping cosmids containing the NF-H gene. This strongly suggests that the 3 neurofilament genes are organised in a cluster and derived by gene duplication of a common ancestral gene. RNA blot analyses using specific DNA probes for each of the genes indicate that NF mRNAs are differentially expressed during brain development. The NF-L and NF-M mRNAs are detected early in the embryonal brain, with a progressive increase in their levels during development, while the NF-H mRNA is barely detectable at embryonal stages and accumulates later in the postnatal brain.

    Brain research 1986;387;3;243-50

  • Anomalous placement of introns in a member of the intermediate filament multigene family: an evolutionary conundrum.

    Lewis SA and Cowan NJ

    The origin of introns and their role (if any) in gene expression, in the evolution of the genome, and in the generation of new expressed sequences are issues that are understood poorly, if at all. Multigene families provide a favorable opportunity for examining the evolutionary history of introns because it is possible to identify changes in intron placement and content since the divergence of family members from a common ancestral sequence. Here we report the complete sequence of the gene encoding the 68-kilodalton (kDa) neurofilament protein; the gene is a member of the intermediate filament multigene family that diverged over 600 million years ago. Five other members of this family (desmin, vimentin, glial fibrillary acidic protein, and type I and type II keratins) are encoded by genes with six or more introns at homologous positions. To our surprise, the number and placement of introns in the 68-kDa neurofilament protein gene were completely anomalous, with only three introns, none of which corresponded in position to introns in any characterized intermediate filament gene. This finding was all the more unexpected because comparative amino acid sequence data suggest a closer relationship of the 68-kDa neurofilament protein to desmin, vimentin, and glial fibrillary acidic protein than between any of these three proteins and the keratins. It appears likely that an mRNA-mediated transposition event was involved in the evolution of the 68-kDa neurofilament protein gene and that subsequent events led to the acquisition of at least two of the three introns present in the contemporary sequence.

    Molecular and cellular biology 1986;6;5;1529-34

  • Genetics, evolution, and expression of the 68,000-mol-wt neurofilament protein: isolation of a cloned cDNA probe.

    Lewis SA and Cowan NJ

    A 1.2-kilobase (kb) cDNA clone (NF68) encoding the mouse 68,000-mol-wt neurofilament protein is described. The clone was isolated from a mouse brain cDNA library by low-stringency cross-hybridization with a cDNA probe encoding mouse glial fibrillary acidic protein (Lewis et al., 1984, Proc. Natl. Acad. Sci. USA., 81:2743-2746). The identity of NF68 was established by hybrid selection using mouse brain polyA+ mRNA, and cell-free translation of the selected mRNA species. The cell-free translation product co-migrated with authentic 68,000-mol-wt neurofilament protein on an SDS/polyacrylamide gel, and was immunoprecipitable with a monospecific rabbit anti-bovine neurofilament antiserum. In addition, DNA sequence analysis of NF68 showed 90% homology at the amino acid level compared with the sequence of the porcine 68,000-mol-wt neurofilament protein. At high stringency, NF68 detects a single genomic sequence encoding the mouse 68,000-mol-wt neurofilament protein. Two mRNA species of 2.5 kb and 4.0 kb are transcribed from the single gene in mouse brain. The level of expression of these mRNAs remains almost constant in postnatal mouse brains of all ages and, indeed, in the adult. At reduced stringency, NF68 detects a number of mRNAs that are expressed in mouse brain, one of which encodes the 150,000-mol-wt neurofilament protein. The NF68 probe cross-hybridizes at high stringency with genomic sequences in species as diverse as human, chicken, and (weakly) frog, but not with DNA from Drosophila or sea urchin.

    The Journal of cell biology 1985;100;3;843-50

Gene lists (9)

Gene List Source Species Name Description Gene count
L00000001 G2C Mus musculus Mouse PSD Mouse PSD adapted from Collins et al (2006) 1080
L00000007 G2C Mus musculus Mouse NRC Mouse NRC adapted from Collins et al (2006) 186
L00000008 G2C Mus musculus Mouse PSP Mouse PSP adapted from Collins et al (2006) 1121
L00000024 G2C Mus musculus Pocklington M6 Cluster 6 (mouse) from Pocklington et al (2006) 5
L00000050 G2C Mus musculus TAP-PSD-95-CORE TAP-PSD-95 pull-down core list 120
L00000060 G2C Mus musculus BAYES-COLLINS-HUMAN-PSD-CONSENSUS Human cortex PSD consensus (ortho) 748
L00000062 G2C Mus musculus BAYES-COLLINS-MOUSE-PSD-CONSENSUS Mouse cortex PSD consensus 984
L00000070 G2C Mus musculus BAYES-COLLINS-HUMAN-PSD-FULL Human cortex biopsy PSD full list (ortho) 1461
L00000072 G2C Mus musculus BAYES-COLLINS-MOUSE-PSD-FULL Mouse cortex PSD full list 1556
© G2C 2014. The Genes to Cognition Programme received funding from The Wellcome Trust and the EU FP7 Framework Programmes:
EUROSPIN (FP7-HEALTH-241498), SynSys (FP7-HEALTH-242167) and GENCODYS (FP7-HEALTH-241995).

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