G2Cdb::Gene report

Gene id
Gene symbol
Mag (MGI)
Mus musculus
myelin-associated glycoprotein
G00001901 (Homo sapiens)

Databases (10)

ENSMUSG00000036634 (Ensembl mouse gene)
17136 (Entrez Gene)
1067 (G2Cdb plasticity & disease)
Gene Expression
MGI:96912 (Allen Brain Atlas)
g00537 (BGEM)
17136 (Genepaint)
mag (gensat)
159460 (OMIM)
Marker Symbol
MGI:96912 (MGI)
Protein Sequence
P20917 (UniProt)

Synonyms (2)

  • Gma
  • siglec-4a

Literature (130)

Pubmed - other

  • Myelin suppresses axon regeneration by PIR-B/SHP-mediated inhibition of Trk activity.

    Fujita Y, Endo S, Takai T and Yamashita T

    Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, Osaka, Japan.

    Paired immunoglobulin-like receptor B (PIR-B) partially mediates the regeneration-inhibiting effects of the myelin-derived protein Nogo, myelin-associated glycoprotein (MAG), and oligodendrocyte-myelin glycoprotein (OMgp). In this study, we report that inhibition of the PIR-B signaling cascades in neurons enhances axon regeneration in the central nervous system (CNS). Binding of MAG to PIR-B led to the association of PIR-B with tropomyosin receptor kinase (Trk) neurotrophin receptors. Src homology 2-containing protein tyrosine phosphatase (SHP)-1 and SHP-2, which were recruited to PIR-B upon MAG binding, functioned as Trk tyrosine phosphatases. Further, SHP-1 and SHP-2 inhibition reduced MAG-induced dephosphorylation of Trk receptors and abolished the inhibitory effect of MAG on neurite growth. Thus, PIR-B associated with Trk to downregulate basal and neurotrophin-regulated Trk activity through SHP-1/2 in neurons. Moreover, in vivo transfection of small interfering RNA (siRNA) for SHP-1 or SHP-2 induced axonal regeneration after optic nerve injury in mice. Our results thus identify a new molecular target to enhance regeneration of the injured CNS.

    The EMBO journal 2011;30;7;1389-401

  • Myelin-associated glycoprotein protects neurons from excitotoxicity.

    Lopez PH, Ahmad AS, Mehta NR, Toner M, Rowland EA, Zhang J, Doré S and Schnaar RL

    Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.

    In addition to supporting rapid nerve conduction, myelination nurtures and stabilizes axons and protects them from acute toxic insults. One myelin molecule that protects and sustains axons is myelin-associated glycoprotein (MAG). MAG is expressed on the innermost wrap of myelin, apposed to the axon surface, where it interacts with axonal receptors that reside in lateral membrane domains including gangliosides, the glycosylphosphatidylinositol-anchored Nogo receptors, and β1-integrin. We report here that MAG protection extends beyond the axon to the neurons from which those axons emanate, protecting them from excitotoxicity. Compared to wild type mice, Mag-null mice displayed markedly increased seizure activity in response to intraperitoneal injection of kainic acid, an excitotoxic glutamate receptor agonist. Mag-null mice also had larger lesion volumes in response to intrastriatal injection of the excitotoxin NMDA. Prior injection of a soluble form of MAG partially protected Mag-null mice from NMDA-induced lesions. Hippocampal neurons plated on proteins extracted from wild-type rat or mouse myelin were resistant to kainic acid-induced excitotoxicity, whereas neurons plated on proteins from Mag-null myelin were not. Protection was reversed by anti-MAG antibody and replicated by addition of soluble MAG. MAG-mediated protection from excitotoxicity was dependent on Nogo receptors and β1-integrin. We conclude that MAG engages membrane-domain resident neuronal receptors to protect neurons from excitotoxicity, and that soluble MAG mitigates excitotoxic damage in vivo.

    Funded by: NIA NIH HHS: AG022971, R01 AG022971; NINDS NIH HHS: NS037096, NS046400, NS059529, R01 NS037096, R01 NS046400, R21 NS059529, R37 NS037096, R37 NS037096-27, R37 NS037096-28, R37 NS037096-29

    Journal of neurochemistry 2011;116;5;900-8

  • 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

  • Rheb1 is required for mTORC1 and myelination in postnatal brain development.

    Zou J, Zhou L, Du XX, Ji Y, Xu J, Tian J, Jiang W, Zou Y, Yu S, Gan L, Luo M, Yang Q, Cui Y, Yang W, Xia X, Chen M, Zhao X, Shen Y, Chen PY, Worley PF and Xiao B

    The State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, People's Republic of China.

    mTor kinase is involved in cell growth, proliferation, and differentiation. The roles of mTor activators, Rheb1 and Rheb2, have not been established in vivo. Here, we report that Rheb1, but not Rheb2, is critical for embryonic survival and mTORC1 signaling. Embryonic deletion of Rheb1 in neural progenitor cells abolishes mTORC1 signaling in developing brain and increases mTORC2 signaling. Remarkably, embryonic and early postnatal brain development appears grossly normal in these Rheb1f/f,Nes-cre mice with the notable exception of deficits of myelination. Conditional expression of Rheb1 transgene in neural progenitors increases mTORC1 activity and promotes myelination in the brain. In addition the Rheb1 transgene rescues mTORC1 signaling and hypomyelination in the Rheb1f/f,Nes-cre mice. Our study demonstrates that Rheb1 is essential for mTORC1 signaling and myelination in the brain, and suggests that mTORC1 signaling plays a role in selective cellular adaptations, rather than general cellular viability.

    Funded by: NIDA NIH HHS: DA00266-36, P50 DA000266, R37 DA010309, R37 DA010309-16; NIMH NIH HHS: MH068830-05, P50 MH068830, R01 MH053608, R01 MH053608-17

    Developmental cell 2011;20;1;97-108

  • Quaking I controls a unique cytoplasmic pathway that regulates alternative splicing of myelin-associated glycoprotein.

    Zhao L, Mandler MD, Yi H and Feng Y

    Department of Pharmacology, School of Medicine, Emory University, Atlanta, GA 30322, USA.

    Precise control of alternative splicing governs oligodendrocyte (OL) differentiation and myelination in the central nervous system (CNS). A well-known example is the developmentally regulated expression of splice variants encoding myelin-associated glycoprotein (MAG), which generates two protein isoforms that associate with distinct cellular components crucial for axon-glial recognition during myelinogenesis and axon-myelin stability. In the quakingviable (qk(v)) hypomyelination mutant mouse, diminished expression of isoforms of the selective RNA-binding protein quaking I (QKI) leads to severe dysregulation of MAG splicing. The nuclear isoform QKI-5 was previously shown to bind an intronic element of MAG and modulate alternative exon inclusion from a MAG minigene reporter. Thus, QKI-5 deficiency was thought to underlie the defects of MAG splicing in the qk(v) mutant. Surprisingly, we found that transgenic expression of the cytoplasmic isoform QKI-6 in the qk(v) OLs completely rescues the dysregulation of MAG splicing without increasing expression or nuclear abundance of QKI-5. In addition, cytoplasmic QKI-6 selectively associates with the mRNA that encodes heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1), a well-characterized splicing factor. Furthermore, QKI deficiency in the qk(v) mutant results in abnormally enhanced hnRNPA1 translation and overproduction of the hnRNPA1 protein but not hnRNPA1 mRNA, which can be successfully rescued by the QKI-6 transgene. Finally, we show that hnRNPA1 binds MAG pre-mRNA and modulates alternative inclusion of MAG exons. Together, these results reveal a unique cytoplasmic pathway in which QKI-6 controls translation of the splicing factor hnRNPA1 to govern alternative splicing in CNS myelination.

    Funded by: NIGMS NIH HHS: T32 GM008367; NINDS NIH HHS: R01 NS056097, R01 NS056097A

    Proceedings of the National Academy of Sciences of the United States of America 2010;107;44;19061-6

  • Bex1 is involved in the regeneration of axons after injury.

    Khazaei MR, Halfter H, Karimzadeh F, Koo JH, Margolis FL and Young P

    Department of Neurology, University Hospital of Münster, Münster, Germany.

    Successful axonal regeneration is a complex process determined by both axonal environment and endogenous neural capability of the regenerating axons in the central and the peripheral nervous systems. Numerous external inhibitory factors inhibit axonal regeneration after injury. In response, neurons express various regeneration-associated genes to overcome this inhibition and increase the intrinsic growth capacity. In the present study, we show that the brain-expressed X-linked (Bex1) protein was over-expressed as a result of peripheral axonal damage. Bex1 antagonized the axon outgrowth inhibitory effect of myelin-associated glycoprotein. The involvement of Bex1 in axon regeneration was further confirmed in vivo. We have demonstrated that Bex1 knock-out mice showed lower capability for regeneration after peripheral nerve injury than wild-type animals. Wild-type mice could recover from sciatic nerve injury much faster than Bex1 knock-out mice. Our findings suggest that Bex1 could be considered as regeneration-associated gene.

    Funded by: NIDCD NIH HHS: DC03112, R01 DC003112, R01 DC003112-12

    Journal of neurochemistry 2010;115;4;910-20

  • Assessing spinal axon regeneration and sprouting in Nogo-, MAG-, and OMgp-deficient mice.

    Lee JK, Geoffroy CG, Chan AF, Tolentino KE, Crawford MJ, Leal MA, Kang B and Zheng B

    Department of Neurosciences, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA.

    A central hypothesis for the limited capacity for adult central nervous system (CNS) axons to regenerate is the presence of myelin-derived axon growth inhibitors, the role of which, however, remains poorly understood. We have conducted a comprehensive genetic analysis of the three major myelin inhibitors, Nogo, MAG, and OMgp, in injury-induced axonal growth, including compensatory sprouting of uninjured axons and regeneration of injured axons. While deleting any one inhibitor in mice enhanced sprouting of corticospinal or raphespinal serotonergic axons, there was neither associated behavioral improvement nor a synergistic effect of deleting all three inhibitors. Furthermore, triple-mutant mice failed to exhibit enhanced regeneration of either axonal tract after spinal cord injury. Our data indicate that while Nogo, MAG, and OMgp may modulate axon sprouting, they do not play a central role in CNS axon regeneration failure.

    Funded by: NINDS NIH HHS: F32 NS056697, F32 NS056697-02, F32NS056697, P30 NS047101, P30 NS047101-01, P30NS047101, R01 NS054734, R01 NS054734-01A2, R01 NS054734-02, R01 NS054734-03, R01 NS054734-04, R01NS054734

    Neuron 2010;66;5;663-70

  • MAG and OMgp synergize with Nogo-A to restrict axonal growth and neurological recovery after spinal cord trauma.

    Cafferty WB, Duffy P, Huebner E and Strittmatter SM

    Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, Connecticut 06536, USA.

    Functional recovery after adult CNS damage is limited in part by myelin inhibitors of axonal regrowth. Three molecules, Nogo-A, MAG, and OMgp, are produced by oligodendrocytes and share neuronal receptor mechanisms through NgR1 and PirB. While each has an axon-inhibitory role in vitro, their in vivo interactions and relative potencies have not been defined. Here, we compared mice singly, doubly, or triply mutant for these three myelin inhibitor proteins. The myelin extracted from Nogo-A mutant mice is less inhibitory for axons than is that from wild-type mice, but myelin lacking MAG and OMgp is indistinguishable from control. However, myelin lacking all three inhibitors is less inhibitory than Nogo-A-deficient myelin, uncovering a redundant and synergistic role for all three proteins in axonal growth inhibition. Spinal cord injury studies revealed an identical in vivo hierarchy of these three myelin proteins. Loss of Nogo-A allows corticospinal and raphespinal axon growth above and below the injury, as well as greater behavioral recovery than in wild-type or heterozygous mutant mice. In contrast, deletion of MAG and OMgp stimulates neither axonal growth nor enhanced locomotion. The triple-mutant mice exhibit greater axonal growth and improved locomotion, consistent with a principal role for Nogo-A and synergistic actions for MAG and OMgp, presumably through shared receptors. These data support the hypothesis that targeting all three myelin ligands, as with NgR1 decoy receptor, provides the optimal chance for overcoming myelin inhibition and improving neurological function.

    Funded by: NINDS NIH HHS: R01 NS039962, R01 NS039962-11, R01 NS042304, R01 NS042304-09, R01 NS056485, R01 NS056485-05, R37 NS033020, R37 NS033020-19

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2010;30;20;6825-37

  • 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

  • Calpain-mediated down-regulation of myelin-associated glycoprotein in lysophosphatidic acid-induced neuropathic pain.

    Xie W, Uchida H, Nagai J, Ueda M, Chun J and Ueda H

    Division of Molecular Pharmacology and Neuroscience, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.

    Lysophosphatidic acid receptor (LPA(1)) signaling initiates neuropathic pain through demyelination of the dorsal root (DR). Although LPA is found to cause down-regulation of myelin proteins underlying demyelination, the detailed mechanism remains to be determined. In the present study, we found that a single intrathecal injection of LPA evoked a dose- and time-dependent down-regulation of myelin-associated glycoprotein (MAG) in the DR through LPA(1) receptor. A similar event was also observed in ex vivo DR cultures. Interestingly, LPA-induced down-regulation of MAG was significantly inhibited by calpain inhibitors (calpain inhibitor X, E-64 and E-64d) and LPA markedly induced calpain activation in the DR. The pre-treatment with calpain inhibitors attenuated LPA-induced neuropathic pain behaviors such as hyperalgesia and allodynia. Moreover, we found that sciatic nerve injury activates calpain activity in the DR in a LPA(1) receptor-dependent manner. The E-64d treatments significantly blocked nerve injury-induced MAG down-regulation and neuropathic pain. However, there was no significant calpain activation in the DR by complete Freund's adjuvant treatment, and E-64d failed to show anti-hyperalgesic effects in this inflammation model. The present study provides strong evidence that LPA-induced calpain activation plays a crucial role in the manifestation of neuropathic pain through MAG down-regulation in the DR.

    Funded by: NIMH NIH HHS: MH51699, R01 MH051699; NINDS NIH HHS: NS048478, R01 NS048478, R01 NS048478-01A1

    Journal of neurochemistry 2010;113;4;1002-11

  • Conduction block in PMP22 deficiency.

    Bai Y, Zhang X, Katona I, Saporta MA, Shy ME, O'Malley HA, Isom LL, Suter U and Li J

    Department of Neurology, Wayne State University, Detroit, Michigan, USA.

    Patients with PMP22 deficiency present with focal sensory and motor deficits when peripheral nerves are stressed by mechanical force. It has been hypothesized that these focal deficits are due to mechanically induced conduction block (CB). To test this hypothesis, we induced 60-70% CB (defined by electrophysiological criteria) by nerve compression in an authentic mouse model of hereditary neuropathy with liability to pressure palsies (HNPP) with an inactivation of one of the two pmp22 alleles (pmp22(+/-)). Induction time for the CB was significantly shorter in pmp22(+/-) mice than that in pmp22(+/+) mice. This shortened induction was also found in myelin-associated glycoprotein knock-out mice, but not in the mice with deficiency of myelin protein zero, a major structural protein of compact myelin. Pmp22(+/-) nerves showed intact tomacula with no segmental demyelination in both noncompressed and compressed conditions, normal molecular architecture, and normal concentration of voltage-gated sodium channels by [(3)H]-saxitoxin binding assay. However, focal constrictions were observed in the axonal segments enclosed by tomacula, a pathological hallmark of HNPP. The constricted axons increase axial resistance to action potential propagation, which may hasten the induction of CB in Pmp22 deficiency. Together, these results demonstrate that a function of Pmp22 is to protect the nerve from mechanical injury.

    Funded by: NIGMS NIH HHS: GM007315-31, T32 GM007315; NINDS NIH HHS: K08 NS048204, R01 NS064245

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2010;30;2;600-8

  • 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

  • Notch1 signaling plays a role in regulating precursor differentiation during CNS remyelination.

    Zhang Y, Argaw AT, Gurfein BT, Zameer A, Snyder BJ, Ge C, Lu QR, Rowitch DH, Raine CS, Brosnan CF and John GR

    Corinne Goldsmith Dickinson Center for Multiple Sclerosis, Department of Neurology, Mount Sinai School of Medicine, New York, NY 10029, USA.

    In the developing CNS, Notch1 and its ligand, Jagged1, regulate oligodendrocyte differentiation and myelin formation, but their role in repair of demyelinating lesions in diseases such as multiple sclerosis remains unresolved. To address this question, we generated a mouse model in which we targeted Notch1 inactivation to oligodendrocyte progenitor cells (OPCs) using Olig1Cre and a floxed Notch1 allele, Notch1(12f). During CNS development, OPC differentiation was potentiated in Olig1Cre:Notch1(12f/12f) mice. Importantly, in adults, remyelination of demyelinating lesions was also accelerated, at the expense of proliferation within the progenitor population. Experiments in vitro confirmed that Notch1 signaling was permissive for OPC expansion but inhibited differentiation and myelin formation. These studies also revealed that astrocytes exposed to TGF-beta1 restricted OPC maturation via Jagged1-Notch1 signaling. These data suggest that Notch1 signaling is one of the mechanisms regulating OPC differentiation during CNS remyelination. Thus, Notch1 may represent a potential therapeutical avenue for lesion repair in demyelinating disease.

    Funded by: NCI NIH HHS: CA095823, CA1022, R24 CA095823; NINDS NIH HHS: NS011920, NS040511, NS046620, NS050389, NS056074, NS08952, P50 NS011920, R01 NS008952, R01 NS040511, R01 NS046620, R01 NS050389, R01 NS056074, R01 NS062703; PHS HHS: 95022

    Proceedings of the National Academy of Sciences of the United States of America 2009;106;45;19162-7

  • 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

  • Integrin-linked kinase is required for radial sorting of axons and Schwann cell remyelination in the peripheral nervous system.

    Pereira JA, Benninger Y, Baumann R, Gonçalves AF, Ozçelik M, Thurnherr T, Tricaud N, Meijer D, Fässler R, Suter U and Relvas JB

    Institute of Cell Biology, Department of Biology, Eidgenössische Technische Hochschule Zurich, Zurich, Switzerland.

    During development, Schwann cells (SCs) interpret different extracellular cues to regulate their migration, proliferation, and the remarkable morphological changes associated with the sorting, ensheathment, and myelination of axons. Although interactions between extracellular matrix proteins and integrins are critical to some of these processes, the downstream signaling pathways they control are still poorly understood. Integrin-linked kinase (ILK) is a focal adhesion protein that associates with multiple binding partners to link integrins to the actin cytoskeleton and is thought to participate in integrin and growth factor-mediated signaling. Using SC-specific gene ablation, we report essential functions for ILK in radial sorting of axon bundles and in remyelination in the peripheral nervous system. Our in vivo and in vitro experiments show that ILK negatively regulates Rho/Rho kinase signaling to promote SC process extension and to initiate radial sorting. ILK also facilitates axon remyelination, likely by promoting the activation of downstream molecules such as AKT/protein kinase B.

    The Journal of cell biology 2009;185;1;147-61

  • Calcineurin/NFAT signaling is required for neuregulin-regulated Schwann cell differentiation.

    Kao SC, Wu H, Xie J, Chang CP, Ranish JA, Graef IA and Crabtree GR

    Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA.

    Schwann cells develop from multipotent neural crest cells and form myelin sheaths around axons that allow rapid transmission of action potentials. Neuregulin signaling through the ErbB receptor regulates Schwann cell development; however, the downstream pathways are not fully defined. We find that mice lacking calcineurin B1 in the neural crest have defects in Schwann cell differentiation and myelination. Neuregulin addition to Schwann cell precursors initiates an increase in cytoplasmic Ca2+, which activates calcineurin and the downstream transcription factors NFATc3 and c4. Purification of NFAT protein complexes shows that Sox10 is an NFAT nuclear partner and synergizes with NFATc4 to activate Krox20, which regulates genes necessary for myelination. Our studies demonstrate that calcineurin and NFAT are essential for neuregulin and ErbB signaling, neural crest diversification, and differentiation of Schwann cells.

    Funded by: Howard Hughes Medical Institute; NIAID NIH HHS: AI60037, R01 AI060037, R01 AI060037-01, R01 AI060037-02, R01 AI060037-03, R01 AI060037-04, R01 AI060037-05; NICHD NIH HHS: HD55391, R01 HD055391; NINDS NIH HHS: NS046789, R01 NS046789, R01 NS046789-01, R01 NS046789-02, R01 NS046789-03, R01 NS046789-04, R01 NS046789-05, R21 NS061702, R21 NS061702-01, R37 NS046789

    Science (New York, N.Y.) 2009;323;5914;651-4

  • Axonal protective effects of the myelin-associated glycoprotein.

    Nguyen T, Mehta NR, Conant K, Kim KJ, Jones M, Calabresi PA, Melli G, Hoke A, Schnaar RL, Ming GL, Song H, Keswani SC and Griffin JW

    Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA. tnguyena@jhmi.edu

    Progressive axonal degeneration follows demyelination in many neurological diseases, including multiple sclerosis and inherited demyelinating neuropathies, such as Charcot-Marie-Tooth disease. One glial molecule, the myelin-associated glycoprotein (MAG), located in the adaxonal plasmalemma of myelin-producing cells, is known to signal to the axon and to modulate axonal caliber through phosphorylation of axonal neurofilament proteins. This report establishes for the first time that MAG also promotes resistance to axonal injury and prevents axonal degeneration both in cell culture and in vivo. This effect on axonal stability depends on the RGD domain around arginine 118 in the extracellular portion of MAG, but it is independent of Nogo signaling in the axon. Exploiting this pathway may lead to therapeutic strategies for neurological diseases characterized by axonal loss.

    Funded by: NINDS NIH HHS: K08 NS055135, K08 NS055135-01, K08 NS055135-02, K08 NS055135-03, R37 NS037096

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2009;29;3;630-7

  • Genetic variants of Nogo-66 receptor with possible association to schizophrenia block myelin inhibition of axon growth.

    Budel S, Padukkavidana T, Liu BP, Feng Z, Hu F, Johnson S, Lauren J, Park JH, McGee AW, Liao J, Stillman A, Kim JE, Yang BZ, Sodi S, Gelernter J, Zhao H, Hisama F, Arnsten AF and Strittmatter SM

    Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut 06536, USA.

    In schizophrenia, genetic predisposition has been linked to chromosome 22q11 and myelin-specific genes are misexpressed in schizophrenia. Nogo-66 receptor 1 (NGR or RTN4R) has been considered to be a 22q11 candidate gene for schizophrenia susceptibility because it encodes an axonal protein that mediates myelin inhibition of axonal sprouting. Confirming previous studies, we found that variation at the NGR locus is associated with schizophrenia in a Caucasian case-control analysis, and this association is not attributed to population stratification. Within a limited set of schizophrenia-derived DNA samples, we identified several rare NGR nonconservative coding sequence variants. Neuronal cultures demonstrate that four different schizophrenia-derived NgR1 variants fail to transduce myelin signals into axon inhibition, and function as dominant negatives to disrupt endogenous NgR1. This provides the first evidence that certain disease-derived human NgR1 variants are dysfunctional proteins in vitro. Mice lacking NgR1 protein exhibit reduced working memory function, consistent with a potential endophenotype of schizophrenia. For a restricted subset of individuals diagnosed with schizophrenia, the expression of dysfunctional NGR variants may contribute to increased disease risk.

    Funded by: NIMH NIH HHS: U01 MH046276, U01 MH046289, U01 MH046318; NINDS NIH HHS: R01 NS039962, R01 NS039962-09, R01 NS042304, R01 NS042304-07, R01 NS056485, R01 NS056485-03, R37 NS033020, R37 NS033020-16

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2008;28;49;13161-72

  • Opalin, a transmembrane sialylglycoprotein located in the central nervous system myelin paranodal loop membrane.

    Yoshikawa F, Sato Y, Tohyama K, Akagi T, Hashikawa T, Nagakura-Takagi Y, Sekine Y, Morita N, Baba H, Suzuki Y, Sugano S, Sato A and Furuichi T

    Laboratory for Molecular Neurogenesis and Laboratory for Neural Architecture, RIKEN Brain Science Institute, Wako, Japan.

    In contrast to compact myelin, the series of paranodal loops located in the outermost lateral region of myelin is non-compact; the intracellular space is filled by a continuous channel of cytoplasm, the extracellular surfaces between neighboring loops keep a definite distance, but the loop membranes have junctional specializations. Although the proteins that form compact myelin have been well studied, the protein components of paranodal loop membranes are not fully understood. This report describes the biochemical characterization and expression of Opalin as a novel membrane protein in paranodal loops. Mouse Opalin is composed of a short N-terminal extracellular domain (amino acid residues 1-30), a transmembrane domain (residues 31-53), and a long C-terminal intracellular domain (residues 54-143). Opalin is enriched in myelin of the central nervous system, but not that of the peripheral nervous system of mice. Enzymatic deglycosylation showed that myelin Opalin contained N- and O-glycans, and that the O-glycans, at least, had negatively charged sialic acids. We identified two N-glycan sites at Asn-6 and Asn-12 and an O-glycan site at Thr-14 in the extracellular domain. Site-directed mutations at the glycan sites impaired the cell surface localization of Opalin. In addition to the somata and processes of oligodendrocytes, Opalin immunoreactivity was observed in myelinated axons in a spiral fashion, and was concentrated in the paranodal loop region. Immunogold electron microscopy demonstrated that Opalin was localized at particular sites in the paranodal loop membrane. These results suggest a role for highly sialylglycosylated Opalin in an intermembranous function of the myelin paranodal loops in the central nervous system.

    The Journal of biological chemistry 2008;283;30;20830-40

  • Nogo-A and myelin-associated glycoprotein differently regulate oligodendrocyte maturation and myelin formation.

    Pernet V, Joly S, Christ F, Dimou L and Schwab ME

    Department of Biology, Brain Research Institute, University of Zurich, Swiss Federal Institute of Technology, CH-8057 Zurich, Switzerland. pernet@hifo.uzh.ch

    Nogo-A is one of the most potent oligodendrocyte-derived inhibitors for axonal regrowth in the injured adult CNS. However, the physiological function of Nogo-A in development and in healthy oligodendrocytes is still unknown. In the present study, we investigated the role of Nogo-A for myelin formation in the developing optic nerve. By quantitative real-time PCR, we found that the expression of Nogo-A increased faster in differentiating oligodendrocytes than that of the major myelin proteins MBP (myelin basic protein), PLP (proteolipid protein)/DM20, and CNP (2',3'-cyclic nucleotide 3'-phosphodiesterase). The analysis of optic nerves and cerebella of mice deficient for Nogo-A (Nogo-A(-/-)) revealed a marked delay of oligodendrocyte differentiation, myelin sheath formation, and axonal caliber growth within the first postnatal month. The combined deletion of Nogo-A and MAG caused a more severe transient hypomyelination. In contrast to MAG(-/-) mice, Nogo-A(-/-) mutants did not present abnormalities in the structure of myelin sheaths and Ranvier nodes. The common binding protein for Nogo-A and MAG, NgR1, was exclusively upregulated in MAG(-/-) animals, whereas the level of Lingo-1, a coreceptor, remained unchanged. Together, our results demonstrate that Nogo-A and MAG are differently involved in oligodendrocyte maturation in vivo, and suggest that Nogo-A may influence also remyelination in pathological conditions such as multiple sclerosis.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2008;28;29;7435-44

  • P0 protein is required for and can induce formation of schmidt-lantermann incisures in myelin internodes.

    Yin X, Kidd GJ, Nave KA and Trapp BD

    Department of Neurosciences, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195, USA.

    Axons in the PNS and CNS are ensheathed by multiple layers of tightly compacted myelin membranes. A series of cytoplasmic channels connect outer and inner margins of PNS, but not CNS, myelin internodes. Membranes of these Schmidt-Lantermann (S-L) incisures contain the myelin-associated glycoprotein (MAG) but not P(0) or proteolipid protein (PLP), the structural proteins of compact PNS (P(0)) and CNS (PLP) myelin. We show here that incisures are present in MAG-null and absent from P(0)-null PNS internodes. To test the possibility that P(0) regulates incisure formation, we replaced PLP with P(0) in CNS myelin. S-L incisures formed in P(0)-CNS myelin internodes. Furthermore, axoplasm ensheathed by 65% of the CNS incisures examined by electron microscopy had focal accumulations of organelles, indicating that these CNS incisures disrupt axonal transport. These data support the hypotheses that P(0) protein is required for and can induce S-L incisures and that P(0)-induced CNS incisures can be detrimental to axonal function.

    Funded by: NINDS NIH HHS: NS 38186, R01 NS038186, R37 NS038186, R37 NS038186-08, R37 NS038186-09, R37 NS038186-10

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2008;28;28;7068-73

  • BMP signaling through BMPRIA in astrocytes is essential for proper cerebral angiogenesis and formation of the blood-brain-barrier.

    Araya R, Kudo M, Kawano M, Ishii K, Hashikawa T, Iwasato T, Itohara S, Terasaki T, Oohira A, Mishina Y and Yamada M

    Yamada Research Unit, RIKEN Brain Science Institute, Saitama 351-0198, Japan.

    Bone morphogenetic protein (BMP) signaling is involved in differentiation of neural precursor cells into astrocytes, but its contribution to angiogenesis is not well characterized. This study examines the role of BMP signaling through BMP type IA receptor (BMPRIA) in early neural development using a conditional knockout mouse model, in which Bmpr1a is selectively disrupted in telencephalic neural stem cells. The conditional mutant mice show a significant increase in the number of cerebral blood vessels and the level of vascular endothelial growth factor (VEGF) is significantly upregulated in the mutant astrocytes. The mutant mice also show leakage of immunoglobulin around cerebral microvessels in neonatal mice, suggesting a defect in formation of the blood-brain-barrier. In addition, astrocytic endfeet fail to encircle cortical blood vessels in the mutant mice. These results suggest that BMPRIA signaling in astrocytes regulates the expression of VEGF for proper cerebrovascular angiogenesis and has a role on in the formation of the blood-brain-barrier.

    Funded by: Intramural NIH HHS: Z01 ES071003-10; NIEHS NIH HHS: ES071003-10, Z01 ES071003

    Molecular and cellular neurosciences 2008;38;3;417-30

  • Ganglioside inhibition of neurite outgrowth requires Nogo receptor function: identification of interaction sites and development of novel antagonists.

    Williams G, Wood A, Williams EJ, Gao Y, Mercado ML, Katz A, Joseph-McCarthy D, Bates B, Ling HP, Aulabaugh A, Zaccardi J, Xie Y, Pangalos MN, Walsh FS and Doherty P

    Wolfson Centre for Age-Related Diseases, King's College London, London SE1 1UL, United Kingdom.

    Gangliosides are key players in neuronal inhibition, with antibody-mediated clustering of gangliosides blocking neurite outgrowth in cultures and axonal regeneration post injury. In this study we show that the ganglioside GT1b can form a complex with the Nogo-66 receptor NgR1. The interaction is shown by analytical ultracentrifugation sedimentation and is mediated by the sialic acid moiety on GT1b, with mutations in FRG motifs on NgR1 attenuating the interaction. One FRG motif was developed into a cyclic peptide (N-AcCLQKFRGSSC-NH(2)) antagonist of GT1b, reversing the GT1b antibody inhibition of cerebellar granule cell neurite outgrowth. Interestingly, the peptide also antagonizes neurite outgrowth inhibition mediated by soluble forms of the myelin-associated glycoprotein (MAG). Structure function analysis of the peptide point to the conserved FRG triplet being the minimal functional motif, and mutations within this motif inhibit NgR1 binding to both GT1b and MAG. Finally, using gene ablation, we show that the cerebellar neuron response to GT1b antibodies and soluble MAG is indeed dependent on NgR1 function. The results suggest that gangliosides inhibit neurite outgrowth by interacting with FRG motifs in the NgR1 and that this interaction can also facilitate the binding of MAG to the NgR1. Furthermore, the results point to a rational strategy for developing novel ganglioside antagonists.

    The Journal of biological chemistry 2008;283;24;16641-52

  • Disruption of Krox20-Nab interaction in the mouse leads to peripheral neuropathy with biphasic evolution.

    Desmazières A, Decker L, Vallat JM, Charnay P and Gilardi-Hebenstreit P

    Inserm U784, 75230 Paris Cedex 05, France.

    Krox20/Egr2 is a zinc finger transcription factor that plays essential roles in several developmental processes, including peripheral nervous system myelination by Schwann cells, where it acts as a master gene regulator. Krox20 is known to interact with cofactors of the Nab family and a mutation affecting isoleucine 268, which prevents this interaction, has been shown to result in congenital hypomyelinating neuropathy in humans. To further investigate the role of this interaction, we have introduced such a mutation, Krox20(I268F), in the mouse germ line. Clinical, immunohistochemical, and ultrastructural analyses of the homozygous mutants reveal that they develop a severe hypomyelination phenotype that mimics the human syndrome. Furthermore, a time-course analysis of the disease indicates that it follows a biphasic evolution, the hypomyelination phase being followed by a dramatic demyelination. Although for the regulation of most analyzed Krox20 target genes the mutation behaves as a loss of function, this is not the case for a few of them. This differential effect indicates that the molecular function of the Krox20-Nab interaction is target dependent and might explain the degradation of the residual myelin, because of imbalances in its composition. In conclusion, this work provides a novel and useful model for severe human peripheral neuropathies.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2008;28;23;5891-900

  • Ascl1 is required for oligodendrocyte development in the spinal cord.

    Sugimori M, Nagao M, Parras CM, Nakatani H, Lebel M, Guillemot F and Nakafuku M

    Division of Developmental Biology, Cincinnati Children's Hospital Research Foundation, 3333 Burnet Avenue, and Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA.

    Development of oligodendrocytes, myelin-forming glia in the central nervous system (CNS), proceeds on a protracted schedule. Specification of oligodendrocyte progenitors (OLPs) begins early in development, whereas their terminal differentiation occurs at late embryonic and postnatal periods. How these distinct steps are controlled remains unclear. Our previous study demonstrated an important role of the helix-loop-helix (HLH) transcription factor Ascl1 in early generation of OLPs in the developing spinal cord. Here, we show that Ascl1 is also involved in terminal differentiation of oligodendrocytes late in development. Ascl1-/- mutant mice showed a deficiency in differentiation of myelin-expressing oligodendrocytes at birth. In vitro culture studies demonstrate that the induction and maintenance of co-expression of Olig2 and Nkx2-2 in OLPs, and thyroid hormone-responsive induction of myelin proteins are impaired in Ascl1-/- mutants. Gain-of-function studies further showed that Ascl1 collaborates with Olig2 and Nkx2-2 in promoting differentiation of OLPs into oligodendrocytes in vitro. Overexpression of Ascl1, Olig2 and Nkx2-2 alone stimulated the specification of OLPs, but the combinatorial action of Ascl1 and Olig2 or Nkx2-2 was required for further promoting their differentiation into oligodendrocytes. Thus, Ascl1 regulates multiple aspects of oligodendrocyte development in the spinal cord.

    Funded by: Medical Research Council: MC_U117570528

    Development (Cambridge, England) 2008;135;7;1271-81

  • Distinct endocytic recycling of myelin proteins promotes oligodendroglial membrane remodeling.

    Winterstein C, Trotter J and Krämer-Albers EM

    Department of Biology, Unit of Molecular Cell Biology, University of Mainz, Bentzelweg 3, 55128 Mainz, Germany.

    The central nervous system myelin sheath is a multilayered specialized membrane with compacted and non-compacted domains of defined protein composition. How oligodendrocytes regulate myelin membrane trafficking and establish membrane domains during myelination is largely unknown. Oligodendroglial cells respond to neuronal signals by adjusting the relative levels of endocytosis and exocytosis of the major myelin protein, proteolipid protein (PLP). We investigated whether endocytic trafficking is common to myelin proteins and analyzed the endocytic fates of proteins with distinct myelin subdomain localization. Interestingly, we found that PLP, myelin-associated glycoprotein (MAG) and myelin-oligodendrocyte glycoprotein (MOG), which localize to compact myelin, periaxonal loops and abaxonal loops, respectively, exhibit distinct endocytic fates. PLP was internalized via clathrin-independent endocytosis, whereas MAG was endocytosed by a clathrin-dependent pathway, although both proteins were targeted to the late-endosomal/lysosomal compartment. MOG was also endocytosed by a clathrin-dependent pathway, but in contrast to MAG, trafficked to the recycling endosome. Endocytic recycling resulted in the association of PLP, MAG and MOG with oligodendroglial membrane domains mimicking the biochemical characteristics of myelin domains. Our results suggest that endocytic sorting and recycling of myelin proteins may assist plasma membrane remodeling, which is necessary for the morphogenesis of myelin subdomains.

    Journal of cell science 2008;121;Pt 6;834-42

  • Myelin-associated glycoprotein reduces axonal branching and enhances functional recovery after sciatic nerve transection in rats.

    Tomita K, Kubo T, Matsuda K, Yano K, Tohyama M and Hosokawa K

    Department of Plastic Surgery, Graduate School of Medicine, Osaka University, Osaka, Japan. tomita@psurg.med.osaka-u.ac.jp

    The mature peripheral nervous system (PNS) generally shows better regeneration of injured axons as opposed to the central nervous system (CNS). However, complete functional recovery is rarely achieved even in the PNS although morphologically good axonal regeneration often occurs. This mainly results from aberrant reinnervation due to extensive branching of cut axons with consequent failure of synchronized movements of the muscles. Myelin-associated glycoprotein (MAG), a well-characterized molecule existing both in the CNS and PNS myelin, is considered to be a potent inhibitor of axonal regeneration especially in the CNS. In the present study, we investigated whether MAG has any effects not only on axonal elongation, but also on axonal branching. We show herein that MAG minimized branching of the peripheral axons both in vitro and in vivo via activation of RhoA. Furthermore, after sciatic nerve transection in rats, focal and temporary application of MAG to the lesion dramatically enhanced the functional recovery. Using double retrograde labeling and preoperative/postoperative labeling of spinal neurons, reduced hyperinnervation and improved accuracy of target reinnervation was confirmed, respectively. In conclusion, as MAG significantly improves the quality of axonal regeneration, it can be used as a new therapeutic approach for peripheral nerve repair with possible focal and temporary application.

    Glia 2007;55;14;1498-507

  • Neural MMP-28 expression precedes myelination during development and peripheral nerve repair.

    Werner SR, Mescher AL, Neff AW, King MW, Chaturvedi S, Duffin KL, Harty MW and Smith RC

    Biotherapeutic Discovery Research, Lilly Research Laboratories, Eli Lilly and Co., Indianapolis, Indiana 46225, USA. wernerse@lilly.com

    Mammalian matrix metalloproteinase 28 (MMP-28) is expressed in several normal adult tissues, and during cutaneous wound healing. We show that, in frog and mouse embryos, MMP-28 is expressed predominantly throughout the nervous system. Xenopus expression increases during neurulation and remains elevated through early limb development where it is expressed in nerves. In the mouse, neural expression peaks at embryonic day (E) 14 but remains detectable through E17. During frog hindlimb regeneration XMMP-28 is not initially expressed in the regenerating nerves but is detectable before myelination. Following hindlimb denervation, XMMP-28 expression is detectable along regenerating nerves before myelination. In embryonic rat neuron-glial co-cultures, MMP-28 decreases after the initiation of myelination. Incubation of embryonic brain tissue with purified MMP-28 leads to the degradation of multiple myelin proteins. These results suggest that MMP-28 plays an evolutionarily conserved role in neural development and is likely to modulate the axonal-glial extracellular microenvironment.

    Developmental dynamics : an official publication of the American Association of Anatomists 2007;236;10;2852-64

  • Gangliosides and Nogo receptors independently mediate myelin-associated glycoprotein inhibition of neurite outgrowth in different nerve cells.

    Mehta NR, Lopez PH, Vyas AA and Schnaar RL

    Department of Pharmacology, The Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA.

    In the injured nervous system, myelin-associated glycoprotein (MAG) on residual myelin binds to receptors on axons, inhibits axon outgrowth, and limits functional recovery. Conflicting reports identify gangliosides (GD1a and GT1b) and glycosylphosphatidylinositol-anchored Nogo receptors (NgRs) as exclusive axonal receptors for MAG. We used enzymes and pharmacological agents to distinguish the relative roles of gangliosides and NgRs in MAG-mediated inhibition of neurite outgrowth from three nerve cell types, dorsal root ganglion neurons (DRGNs), cerebellar granule neurons (CGNs), and hippocampal neurons. Primary rat neurons were cultured on control substrata and substrata adsorbed with full-length native MAG extracted from purified myelin. The receptors responsible for MAG inhibition of neurite outgrowth varied with nerve cell type. In DRGNs, most of the MAG inhibition was via NgRs, evidenced by reversal of inhibition by phosphatidylinositol-specific phospholipase C (PI-PLC), which cleaves glycosylphosphatidylinositol anchors, or by NEP1-40, a peptide inhibitor of NgR. A smaller percentage of MAG inhibition of DRGN outgrowth was via gangliosides, evidenced by partial reversal by addition of sialidase to cleave GD1a and GT1b or by P4, an inhibitor of ganglioside biosynthesis. Combining either PI-PLC and sialidase or NEP1-40 and P4 was additive. In contrast to DRGNs, in CGNs MAG inhibition was exclusively via gangliosides, whereas inhibition of hippocampal neuron outgrowth was mostly reversed by sialidase or P4 and only modestly reversed by PI-PLC or NEP1-40 in a non-additive fashion. A soluble proteolytic fragment of native MAG, dMAG, also inhibited neurite outgrowth. In DRGNs, dMAG inhibition was exclusively NgR-dependent, whereas in CGNs it was exclusively ganglioside-dependent. An inhibitor of Rho kinase reversed MAG-mediated inhibition in all nerve cells, whereas a peptide inhibitor of the transducer p75(NTR) had cell-specific effects quantitatively similar to NgR blockers. Our data indicate that MAG inhibits axon outgrowth via two independent receptors, gangliosides and NgRs.

    Funded by: NIGMS NIH HHS: T32GM008763; NINDS NIH HHS: R37 NS037096, R37 NS037096-26, R37NS037096

    The Journal of biological chemistry 2007;282;38;27875-86

  • A role for Nogo receptor in macrophage clearance from injured peripheral nerve.

    Fry EJ, Ho C and David S

    Center for Research in Neuroscience, The McGill University Health Center, 1650 Cedar Avenue, Montreal, Quebec, Canada.

    We report a role for Nogo receptors (NgRs) in macrophage efflux from sites of inflammation in peripheral nerve. Increasing numbers of macrophages in crushed rat sciatic nerves express NgR1 and NgR2 on the cell surface in the first week after injury. These macrophages show reduced binding to myelin and MAG in vitro, which is reversed by NgR siRNA knockdown and by inhibiting Rho-associated kinase. Fourteen days after sciatic nerve crush, regenerating nerves with newly synthesized myelin have fewer macrophages than cut/ligated nerves that lack axons and myelin. Almost all macrophages in the cut/ligated nerves lie within the Schwann cell basal lamina, while in the crushed regenerating nerves the majority migrate out. Furthermore, crush-injured nerves of NgR1- and MAG-deficient mice and Y-27632-treated rats show impaired macrophage efflux from Schwann cell basal lamina containing myelinated axons. These data have implications for the resolution of inflammation in peripheral nerve and CNS pathologies.

    Funded by: NINDS NIH HHS: NS 048058

    Neuron 2007;53;5;649-62

  • PlexinA1 signaling directs the segregation of proprioceptive sensory axons in the developing spinal cord.

    Yoshida Y, Han B, Mendelsohn M and Jessell TM

    Howard Hughes Medical Institute, Department of Biochemistry and Molecular Biophysics, Center for Neurobiology and Behavior, Columbia University, New York, New York 10032, USA. yy2032@columbia.edu

    As different classes of sensory neurons project into the CNS, their axons segregate and establish distinct trajectories and target zones. One striking instance of axonal segregation is the projection of sensory neurons into the spinal cord, where proprioceptive axons avoid the superficial dorsal horn-the target zone of many cutaneous afferent fibers. PlexinA1 is a proprioceptive sensory axon-specific receptor for sema6C and sema6D, which are expressed in a dynamic pattern in the dorsal horn. The loss of plexinA1 signaling causes the shafts of proprioceptive axons to invade the superficial dorsal horn, disrupting the organization of cutaneous afferents. This disruptive influence appears to involve the intermediary action of oligodendrocytes, which accompany displaced proprioceptive axon shafts into the dorsal horn. Our findings reveal a dedicated program of axonal shaft positioning in the mammalian CNS and establish a role for plexinA1-mediated axonal exclusion in organizing the projection pattern of spinal sensory afferents.

    Funded by: NIMH NIH HHS: P50 MH050733; Wellcome Trust

    Neuron 2006;52;5;775-88

  • 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

  • Unraveling the differential expression of the two isoforms of myelin-associated glycoprotein in a mouse expressing GFP-tagged S-MAG specifically regulated and targeted into the different myelin compartments.

    Erb M, Flueck B, Kern F, Erne B, Steck AJ and Schaeren-Wiemers N

    Neurobiology, Department of Research, University Hospital Basel, Pharmacenter 7007, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland.

    The two myelin-associated glycoprotein (MAG) isoforms are cell adhesion molecules that differ only in their cytoplasmic domains, but their specific roles are not well understood. In this study, we present a transgenic mouse line that specifically expresses GFP-tagged S-MAG correctly regulated and targeted into the myelin sheath allowing the specific discrimination of L- and S-MAG on the subcellular level. Here, we describe the differential expression pattern and spatial distribution of L- and S-MAG during development as well as in the adult central and peripheral nervous system. In peripheral nerves, where S-MAG is the sole isoform, we observed S-MAG concentrated in different ring-like structures such as periaxonal and abaxonal rings, and discs spanning through the compact myelin sheath perpendicular to the axon. In summary, our data provide new insight in the subcellular distribution of the two isoforms fundamental for the understanding of their specific functions in myelin formation and maintenance.

    Molecular and cellular neurosciences 2006;31;4;613-27

  • 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

  • Myelin-associated glycoprotein and complementary axonal ligands, gangliosides, mediate axon stability in the CNS and PNS: neuropathology and behavioral deficits in single- and double-null mice.

    Pan B, Fromholt SE, Hess EJ, Crawford TO, Griffin JW, Sheikh KA and Schnaar RL

    Department of Pharmacology and Molecular Sciences, The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA.

    Complementary interacting molecules on myelin and axons are required for long-term axon-myelin stability. Their disruption results in axon degeneration, contributing to the pathogenesis of demyelinating diseases. Myelin-associated glycoprotein (MAG), a minor constituent of central and peripheral nervous system myelin, is a member of the Siglec family of sialic acid-binding lectins and binds to gangliosides GD1a and GT1b, prominent molecules on the axon surface. Mice lacking the ganglioside biosynthetic gene Galgt1 fail to express complex gangliosides, including GD1a and GT1b. In the current studies, CNS and PNS histopathology and behavior of Mag-null, Galgt1-null, and double-null mice were compared on the same mouse strain background. When back-crossed to >99% C57BL/6 strain purity, Mag-null mice demonstrated marked CNS, as well as PNS, axon degeneration, in contrast to prior findings using mice of mixed strain background. On the same background, Mag- and Galgt1-null mice exhibited quantitatively and qualitatively similar CNS and PNS axon degeneration and nearly identical decreases in axon diameter and neurofilament spacing. Double-null mice had qualitatively similar changes. Consistent with these findings, Mag- and Galgt1-null mice had similar motor behavioral deficits, with double-null mice only modestly more impaired. Despite their motor deficits, Mag- and Galgt1-null mice demonstrated hyperactivity, with spontaneous locomotor activity significantly above that of wild type mice. These data demonstrate that MAG and complex gangliosides contribute to axon stability in both the CNS and PNS. Similar neuropathological and behavioral deficits in Galgt1-, Mag-, and double-null mice support the hypothesis that MAG binding to gangliosides contributes to long-term axon-myelin stability.

    Funded by: NINDS NIH HHS: NS37096, NS42888, R01 NS037096, R01 NS042888, R37 NS037096

    Experimental neurology 2005;195;1;208-17

  • Overexpression of myelin-associated glycoprotein after axotomy of the perforant pathway.

    Mingorance A, Fontana X, Soriano E and Del Río JA

    Development and Regeneration of the CNS, Cellular Biology Department, Barcelona Science Park-IRB, University of Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain.

    Myelin-associated glycoprotein (MAG) contributes to the prevention of axonal regeneration in the adult central nervous system (CNS). However, changes in MAG expression following lesions and the involvement of MAG in the failure of cortical connections to regenerate are still poorly understood. Here, we show that MAG expression is differently regulated in the entorhinal cortex (EC) and the hippocampus in response to axotomy of the perforant pathway. In the EC, MAG mRNA is transiently overexpressed by mature oligodendrocytes after lesion. In the hippocampus, MAG overexpression is accompanied by an increase in the number of MAG-expressing cells. Lastly, the participation of MAG in preventing axonal regeneration was tested in vitro, where neuraminidase treatment of axotomized entorhino-hippocampal cultures potentiates axonal regeneration. These results demonstrate that MAG expression is regulated in response to cortical axotomy, and indicate that it may limit axonal regeneration after CNS injury.

    Molecular and cellular neurosciences 2005;29;3;471-83

  • Re-establishing the regenerative potential of central nervous system axons in postnatal mice.

    Cho KS, Yang L, Lu B, Feng Ma H, Huang X, Pekny M and Chen DF

    Schepens Eye Research Institute, Program in Neuroscience and Department of Ophthalmology, Harvard Medical School, 20 Staniford Street, Boston, MA 02114, USA.

    At a certain point in development, axons in the mammalian central nervous system lose their ability to regenerate after injury. Using the optic nerve model, we show that this growth failure coincides with two developmental events: the loss of Bcl-2 expression by neurons and the maturation of astrocytes. Before postnatal day 4, when astrocytes are immature, overexpression of Bcl-2 alone supported robust and rapid optic nerve regeneration over long distances, leading to innervation of brain targets by day 4 in mice. As astrocytes matured after postnatal day 4, axonal regeneration was inhibited in mice overexpressing Bcl-2. Concurrent induction of Bcl-2 and attenuation of reactive gliosis reversed the failure of CNS axonal re-elongation in postnatal mice and led to rapid axonal regeneration over long distances and reinnervation of the brain targets by a majority of severed optic nerve fibers up to 2 weeks of age. These results suggest that an early postnatal downregulation of Bcl-2 and post-traumatic reactive gliosis are two important elements of axon regenerative failure in the CNS.

    Funded by: NEI NIH HHS: R01 EY012983

    Journal of cell science 2005;118;Pt 5;863-72

  • CNS myelin paranodes require Nkx6-2 homeoprotein transcriptional activity for normal structure.

    Southwood C, He C, Garbern J, Kamholz J, Arroyo E and Gow A

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

    Homeodomain proteins play critical roles during development in cell fate determination and proliferation, but few studies have defined gene regulatory networks for this class of transcription factors in differentiated cells. Using a lacZ-knock-in strategy to ablate Nkx6-2, we find that the Nkx6-2 promoter is active embryonically in neuroblasts and postnatally in oligodendrocytes. In addition to neurological deficits, we find widespread ultrastructural abnormalities in CNS white matter and aberrant expression of three genes encoding a paranodal microtubule destabilizing protein, stathmin 1, and the paranodal cell adhesion molecules neurofascin and contactin. The involvement of these downstream proteins in cytoskeletal function and cell adhesion reveals mechanisms whereby Nkx6-2 directly or indirectly regulates axon- glial interactions at myelin paranodes. Nkx6-2 does not appear to be the central regulator of axoglial junction assembly; nonetheless, our data constitute the first evidence of such a regulatory network and provide novel insights into the mechanism and effector molecules that are involved.

    Funded by: NIDCD NIH HHS: DC006262, R01 DC006262

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2004;24;50;11215-25

  • Myelination triggers local loss of axonal CNR/protocadherin alpha family protein expression.

    Morishita H, Kawaguchi M, Murata Y, Seiwa C, Hamada S, Asou H and Yagi T

    KOKORO Biology Group, Laboratories for Integrated Biology, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita 565-0871, Japan.

    The cadherin-related neuronal receptor (CNR)/protocadherin (Pcdh) alpha family is one of the diverse protocadherin families expressed in developing axons. We observed a strong axonal expression of these proteins at late embryonic and early postnatal stages corresponding to regions where fibers had not yet been myelinated. We therefore followed the postnatal localization of CNR/Pcdh alpha protein in major axonal tracts, such as the internal capsule, lateral olfactory tract, and optic nerve, and found that its axonal localization was dramatically lost in parallel with the increased expression of myelin markers. Moreover, the hypomyelinated optic nerve tracts of the myelin-deficient Shiverer mouse exhibited elevated levels of CNR/Pcdh alpha expression. These axonal expression patterns of CNR/Pcdh alpha in wild-type and Shiverer mice were similar to those of growth associated protein 43 (GAP-43) and L1, both of which are associated with axonal maturation. Thus, myelination may be a trigger for the local loss of axonal CNR/Pcdh alpha protein, and this process may be important in the maturation of neural circuits.

    The European journal of neuroscience 2004;20;11;2843-7

  • Comparison of myelin, axon, lipid, and immunopathology in the central nervous system of differentially myelin-compromised mutant mice: a morphological and biochemical study.

    Loers G, Aboul-Enein F, Bartsch U, Lassmann H and Schachner M

    Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, D-20251 Hamburg, Germany.

    The present study was carried out to compare different myelin-compromised mouse mutants with regard to myelin morphology in relation to axon-, lipid-, and immunopathology as a function of age. Mouse mutants deficient in the myelin-associated glycoprotein (MAG) and myelin basic protein (MBP) display subtle and severe myelin pathologies in the central nervous system (CNS), respectively. Animals doubly deficient in MAG and the neural cell adhesion molecule (NCAM) show defects similar to those present in MAG single mutants while mice deficient in MAG and the nonreceptor type tyrosine kinase Fyn are severely hypomyelinated, in addition to the MAG-specific myelin abnormalities. These mutant mice showed distinct myelin pathologies in different regions of the central nervous system and generally displayed a decrease in axonal integrity with age. Myelin pathology did not correlate locally with axon transection and with an involvement of the immune system as seen by numbers of CD3-positive lymphocytes and MAC-3-positive macrophages. Interestingly, the degree of these cellular abnormalities also did not correlate with abnormalities in levels of phospholipids, arachidonic acid, cholesterol, and apolipoprotein E (apoE). Moreover, these changes in lipid metabolism, including immune system-related arachidonic acid, preceded cellular pathology. The combined observations point to differences, but also similarities in the relation of myelin, axon, and immunopathology with genotype, and to a common aggravation of the phenotype with age.

    Molecular and cellular neurosciences 2004;27;2;175-89

  • Regulation of Nogo and Nogo receptor during the development of the entorhino-hippocampal pathway and after adult hippocampal lesions.

    Mingorance A, Fontana X, Solé M, Burgaya F, Ureña JM, Teng FY, Tang BL, Hunt D, Anderson PN, Bethea JR, Schwab ME, Soriano E and del Río JA

    Development and Regeneration of the CNS, Barcelona Science Park-IRBB, University of Barcelona, E-08028 Barcelona, Spain.

    Axonal regeneration in the adult CNS is limited by the presence of several inhibitory proteins associated with myelin. Nogo-A, a myelin-associated inhibitor, is responsible for axonal outgrowth inhibition in vivo and in vitro. Here we study the onset and maturation of Nogo-A and Nogo receptor in the entorhino-hippocampal formation of developing and adult mice. We also provide evidence that Nogo-A does not inhibit embryonic hippocampal neurons, in contrast to other cell types such as cerebellar granule cells. Our results also show that Nogo and Nogo receptor mRNA are expressed in the adult by both principal and local-circuit hippocampal neurons, and that after lesion, Nogo-A is also transiently expressed by a subset of reactive astrocytes. Furthermore, we analyzed their regulation after kainic acid (KA) treatment and in response to the transection of the entorhino-hippocampal connection. We found that Nogo-A and Nogo receptor are differentially regulated after kainic acid or perforant pathway lesions. Lastly, we show that the regenerative potential of lesioned entorhino-hippocampal organotypic slice co-cultures is increased after blockage of Nogo-A with two IN-1 blocking antibodies. In conclusion, our results show that Nogo and its receptor might play key roles during development of hippocampal connections and that they are implicated in neuronal plasticity in the adult.

    Molecular and cellular neurosciences 2004;26;1;34-49

  • Loss of K-Cl co-transporter KCC3 causes deafness, neurodegeneration and reduced seizure threshold.

    Boettger T, Rust MB, Maier H, Seidenbecher T, Schweizer M, Keating DJ, Faulhaber J, Ehmke H, Pfeffer C, Scheel O, Lemcke B, Horst J, Leuwer R, Pape HC, Völkl H, Hübner CA and Jentsch TJ

    Zentrum für Molekulare Neurobiologie, ZMNH, Universität Hamburg, Falkenried 94, D-20251 Hamburg, Germany.

    K-Cl co-transporters are encoded by four homologous genes and may have roles in transepithelial transport and in the regulation of cell volume and cytoplasmic chloride. KCC3, an isoform mutated in the human Anderman syndrome, is expressed in brain, epithelia and other tissues. To investigate the physiological functions of KCC3, we disrupted its gene in mice. This severely impaired cell volume regulation as assessed in renal tubules and neurons, and moderately raised intraneuronal Cl(-) concentration. Kcc3(-/-) mice showed severe motor abnormalities correlating with a progressive neurodegeneration in the peripheral and CNS. Although no spontaneous seizures were observed, Kcc3(-/-) mice displayed reduced seizure threshold and spike-wave complexes on electrocorticograms. These resembled EEG abnormalities in patients with Anderman syndrome. Kcc3(-/-) mice also displayed arterial hypertension and a slowly progressive deafness. KCC3 was expressed in many, but not all cells of the inner ear K(+) recycling pathway. These cells slowly degenerated, as did sensory hair cells. The present mouse model has revealed important cellular and systemic functions of KCC3 and is highly relevant for Anderman syndrome.

    The EMBO journal 2003;22;20;5422-34

  • The transmembrane semaphorin Sema4D/CD100, an inhibitor of axonal growth, is expressed on oligodendrocytes and upregulated after CNS lesion.

    Moreau-Fauvarque C, Kumanogoh A, Camand E, Jaillard C, Barbin G, Boquet I, Love C, Jones EY, Kikutani H, Lubetzki C, Dusart I and Chédotal A

    Institut National de la Santé et de la Recherche Médicale U106, Hôpital de la Salpêtrière, 75013 Paris, France.

    Semaphorins are a family of secreted and membrane-bound proteins, known to regulate axonal pathfinding. Sema4D, also called CD100, was first isolated in the immune system where it is involved in B and T cell activation. We found that in the mouse, Sema4D is expressed in cells throughout the CNS white matter, with a peak during the myelination period. Double-labeling experiments with different markers of oligodendrocyte lineage such as olig1, olig2, platelet-derived growth factor receptor alpha, and proteolipid protein showed that Sema4D was expressed selectively by oligodendrocytes and myelin. The presence of Sema4D in myelin was confirmed using Western blot. Sema4D expression in myelinating oligodendrocytes was further observed using neuron-oligodendrocyte cocultures. Moreover, using stripe assay, we found that Sema4D is strongly inhibitory for postnatal sensory and cerebellar granule cell axons. This prompted us to examine whether Sema4D expression is modified after CNS injury. At 8 d after spinal cord lesions, Sema4D expression was strongly upregulated in oligodendrocytes at the periphery of the lesion. Sema4D-positive cells were not colabeled with the astrocyte marker GFAP, with the microglial and macrophagic marker isolectin B4, or with NG2, a marker of oligodendrocyte precursors. This upregulation was transient because from 1 month after the lesion, Sema4D expression was back to its normal level. These results indicate that Sema4D is a novel inhibitory factor for axonal regeneration expressed in myelin.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2003;23;27;9229-39

  • Association of TAG-1 with Caspr2 is essential for the molecular organization of juxtaparanodal regions of myelinated fibers.

    Traka M, Goutebroze L, Denisenko N, Bessa M, Nifli A, Havaki S, Iwakura Y, Fukamauchi F, Watanabe K, Soliven B, Girault JA and Karagogeos D

    Department of Basic Science, University of Crete Medical School, Heraklion 71110, Crete, Greece.

    Myelination results in a highly segregated distribution of axonal membrane proteins at nodes of Ranvier. Here, we show the role in this process of TAG-1, a glycosyl-phosphatidyl-inositol-anchored cell adhesion molecule. In the absence of TAG-1, axonal Caspr2 did not accumulate at juxtaparanodes, and the normal enrichment of shaker-type K+ channels in these regions was severely disrupted, in the central and peripheral nervous systems. In contrast, the localization of protein 4.1B, an axoplasmic partner of Caspr2, was only moderately altered. TAG-1, which is expressed in both neurons and glia, was able to associate in cis with Caspr2 and in trans with itself. Thus, a tripartite intercellular protein complex, comprised of these two proteins, appears critical for axo-glial contacts at juxtaparanodes. This complex is analogous to that described previously at paranodes, suggesting that similar molecules are crucial for different types of axo-glial interactions.

    Funded by: NINDS NIH HHS: R01 NS039346, R01 NS39346-01

    The Journal of cell biology 2003;162;6;1161-72

  • BMP receptor 1b is required for axon guidance and cell survival in the developing retina.

    Liu J, Wilson S and Reh T

    Department of Biological Structure, University of Washington, School of Medicine, Seattle, WA 98195, USA. tomreh@u.washington.edu

    Previous work has documented the importance of BMPs in eye development. Loss-of-function studies in mice, with targeted deletions in either the Bmp7 or Bmp4 genes, have shown that these molecules are critical for early eye development. On the basis of the asymmetry in the dorsal-ventral expression patterns of several members of this family, it has been proposed that these molecules are critical for some aspect of dorsal-ventral patterning in the eye; however, it has been difficult to test this hypothesis because of the early requirement for BMPs in eye development. We have therefore examined the effects of loss of one of the BMP receptors, the BmprIb, on the development of the eye by using targeted deletion. We have found that BmprIb is expressed exclusively in the ventral retina during embryonic development and is required for normal ventral ganglion cell axon targeting to the optic nerve head. In mice with a targeted deletion of the BmprIb gene, many axons arising from the ventrally located ganglion cells fail to enter the optic nerve head, and instead, make abrupt turns in this region. A second phenotype in these mice is a significantly elevated inner retinal apoptosis during a distinct phase of postnatal development, at the end of neurogenesis. Our results therefore show two distinct requirements for BmprIb in mammalian retinal development.

    Funded by: NINDS NIH HHS: R01 NS28308

    Developmental biology 2003;256;1;34-48

  • Tomacula in MAG-deficient mice.

    Cai Z, Sutton-Smith P, Swift J, Cash K, Finnie J, Turnley A, Thompson PD and Blumbergs PC

    Department of Neurology, Royal Adelaide Hospital, South Australia.

    The pathogenesis of tomacula in mice with a null mutation of the myelin-associated glycoprotein (MAG) gene is not well understood. This study, using a novel teased nerve fiber technique, demonstrates that tomacula in MAG-deficient mice are formed by redundant myelin infoldings and outfoldings in the paranodal regions as early as 4 weeks after birth and increase in size and frequency with age. Although tomacula show degenerative changes with increasing age, there was no significant evidence of demyelination/remyelination. Longitudinal sections of normal teased nerve fibers show early redundant myelin foldings in externally normal paranodal regions. These data and the absence of internodal tomacula support a role for MAG in the maintenance of myelin at the paranodal regions.

    Journal of the peripheral nervous system : JPNS 2002;7;3;181-9

  • Notch1 control of oligodendrocyte differentiation in the spinal cord.

    Genoud S, Lappe-Siefke C, Goebbels S, Radtke F, Aguet M, Scherer SS, Suter U, Nave KA and Mantei N

    Department of Biology, Institute of Cell Biology, Swiss Federal Institute of Technology, ETH-Hönggerberg, CH-8093 Zürich, Switzerland.

    We have selectively inhibited Notch1 signaling in oligodendrocyte precursors (OPCs) using the Cre/loxP system in transgenic mice to investigate the role of Notch1 in oligodendrocyte (OL) development and differentiation. Early development of OPCs appeared normal in the spinal cord. However, at embryonic day 17.5, premature OL differentiation was observed and ectopic immature OLs were present in the gray matter. At birth, OL apoptosis was strongly increased in Notch1 mutant animals. Premature OL differentiation was also observed in the cerebrum, indicating that Notch1 is required for the correct spatial and temporal regulation of OL differentiation in various regions of the central nervous system. These findings establish a widespread function of Notch1 in the late steps of mammalian OPC development in vivo.

    The Journal of cell biology 2002;158;4;709-18

  • Myelin-associated glycoprotein as a functional ligand for the Nogo-66 receptor.

    Liu BP, Fournier A, GrandPré T and Strittmatter SM

    Department of Neurology and Section of Neurobiology, Yale University School of Medicine, New Haven, CT 06510, USA.

    Axonal regeneration in the adult central nervous system (CNS) is limited by two proteins in myelin, Nogo and myelin-associated glycoprotein (MAG). The receptor for Nogo (NgR) has been identified as an axonal glycosyl-phosphatidyl-inositol (GPI)-anchored protein, whereas the MAG receptor has remained elusive. Here, we show that MAG binds directly, with high affinity, to NgR. Cleavage of GPI-linked proteins from axons protects growth cones from MAG-induced collapse, and dominant-negative NgR eliminates MAG inhibition of neurite outgrowth. MAG-resistant embryonic neurons are rendered MAG-sensitive by expression of NgR. MAG and Nogo-66 activate NgR independently and serve as redundant NgR ligands that may limit axonal regeneration after CNS injury.

    Science (New York, N.Y.) 2002;297;5584;1190-3

  • CNS myelinogenesis in vitro: myelin basic protein deficient shiverer oligodendrocytes.

    Seiwa C, Kojima-Aikawa K, Matsumoto I and Asou H

    Department of Neurobiology, Tokyo Metropolitan Institute of Gerontology, Japan.

    The shiverer mutant mouse is an autosomal recessive mutant characterized by incomplete myelin sheath formation in the central nervous system (CNS). Such mice contain a deletion in the MBP gene, do not produce MBP proteins, and have little or no compact myelin in the CNS. To investigate the myelin sheath formation in shiverer mutant mice resulting from the absence of compact myelin, firstly we developed new methods for generating oligodendrocyte precursor cells (OPCs) from an E17 mouse brain, and examined homozygous shiverer (shi/shi) OPCs with respect to myelinogenesis in vitro. After treatment of shi/shi OPCs in vitro with PDGF or bFGF, proliferation of shi/shi OPCs was enhanced similar to that observed in wild-type OPCs. The majority of cells from the shiverer mutant mouse, however, remained as A2B5-immunoreactive early OPCs. To determine which molecular events affect the differentiation of shi/shi OPCs, we determined the signaling pathway that could be responsible for activating myelin sheath-specific proteins. We found that the developmental schedule of shi/shi OPCs in vitro was accelerated by the addition of cyclic AMP analogs, dibutyryl cAMP (dbcAMP). Treatment of shi/shi OPCs with dbcAMP had significant effect on the differentiation of OPCs that became MAG-expressing oligodendrocytes. To further determine the possible mechanism involved in the activation of MAG by dbcAMP, we examined the cAMP-dependent signaling cascades. The activation of JNK was markedly stimulated by treatment with dbcAMP, and the phosphorylation of transcription factor ATF-2 was also stimulated by dbcAMP. We demonstrated that the MAG-positive shi/shi oligodendrocytes extend processes around axons and finally covered the axon, this was clearly observed by immunocytochemistry of shi/shi oligodendrocyte-DRG cocultures. These results suggest that ATF-2 coupled to specific signal transduction cascades plays an important regulatory role in MAG expression at a specific stage of shi/shi oligodendrocyte differentiation, and OPCs grow to become myelin-forming cells with numerous cell processes that wraps around an axon to form a thin myelin sheath.

    Journal of neuroscience research 2002;69;3;305-17

  • Role of long-range repulsive forces in organizing axonal neurofilament distributions: evidence from mice deficient in myelin-associated glycoprotein.

    Kumar S, Yin X, Trapp BD, Paulaitis ME and Hoh JH

    Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.

    When the axon of a motor neuron is sectioned and visualized by electron microscopy, a two-dimensional distribution of neurofilaments (NFs) with nonrandom spacing is revealed; this ordered arrangement implies the presence of physical interactions between the NFs. To gain insight into the molecular basis of this organization, we characterized NF distributions from mouse sciatic nerve cross sections using two statistical mechanical measures: radial distribution functions and occupancy probability distributions. Our analysis shows that NF organization may be described in terms of effective pairwise interactions. In addition, we show that these statistical mechanical measures can detect differences in NF architecture between wild-type and myelin-associated glycoprotein null mutant mice. These differences are age dependent, with marked contrast between the NF distributions by 9 months of age. Finally, using Monte Carlo simulations, we compare the experimental results with predictions for models in which adjacent NFs interact through rigid cross bridges, deformable cross bridges, and long-range repulsive forces. Among the models tested, a model in which the filaments interact through a long-range repulsive force is most consistent with the results of our analysis.

    Funded by: NINDS NIH HHS: NS38186

    Journal of neuroscience research 2002;68;6;681-90

  • Myelin-associated glycoprotein and myelin galactolipids stabilize developing axo-glial interactions.

    Marcus J, Dupree JL and Popko B

    UNC Neuroscience Center, University of North Carolina at Chapel Hill, 27599, USA.

    We have analyzed mice that lack both the myelin-associated glycoprotein (MAG) and the myelin galactolipids, two glial components implicated in mediating axo-glial interactions during the myelination process. The single-mutant mice produce abnormal myelin containing similar ultrastructural abnormalities, suggesting that these molecules may play an overlapping role in myelin formation. Furthermore, the absence of the galactolipids results in a disruption in paranodal axo-glial interactions, and we show here that similar, albeit less severe, abnormalities exist in the developing MAG mutant. In the double-mutant mice, maintenance of axo-glial adhesion is significantly more affected than in the single mutants, supporting the overlapping function hypothesis. We also show that independently of MAG, galactolipids, and paranodal junctional components, immature nodes of Ranvier form normally, but rapidly destabilize in their absence. These data indicate that distinct molecular mechanisms are responsible for the formation and maintenance of axo-glial interactions.

    Funded by: NINDS NIH HHS: NS27736

    The Journal of cell biology 2002;156;3;567-77

  • Terminal differentiation of myelin-forming oligodendrocytes depends on the transcription factor Sox10.

    Stolt CC, Rehberg S, Ader M, Lommes P, Riethmacher D, Schachner M, Bartsch U and Wegner M

    Institut für Biochemie, Universität Erlangen-Nürnberg, 91054 Erlangen, Germany.

    Sox10 is a high-mobility-group transcriptional regulator in early neural crest. Without Sox10, no glia develop throughout the peripheral nervous system. Here we show that Sox10 is restricted in the central nervous system to myelin-forming oligodendroglia. In Sox10-deficient mice progenitors develop, but terminal differentiation is disrupted. No myelin was generated upon transplantation of Sox10-deficient neural stem cells into wild-type hosts showing the permanent, cell-autonomous nature of the defect. Sox10 directly regulates myelin gene expression in oligodendrocytes, but does not control erbB3 expression as in peripheral glia. Sox10 thus functions in peripheral and central glia at different stages and through different mechanisms.

    Genes & development 2002;16;2;165-70

  • Oligodendrocytes expressing exclusively the DM20 isoform of the proteolipid protein gene: myelination and development.

    Spörkel O, Uschkureit T, Büssow H and Stoffel W

    Laboratory of Molecular Neuroscience, University of Cologne, Cologne, Germany.

    Oligodendroglia and Schwann cells synthesize myelin-specific proteins and lipids for the assembly of the highly organized myelin membrane of the motor-sensory axons in the central (CNS) and peripheral nervous system (PNS), respectively, allowing rapid saltatory conduction. The isoforms of the main myelin proteins, the peripheral myelin basic isoproteins (MBP) and the integral proteolipid proteins, PLP and DM20, arise from alternative splicing. Activation of a cryptic splice site in exon III of plp leads to the deletion of 105 bp encoding the PLP-specific 35 amino acid residues within the cytosolic loop 3 of the four-transmembrane domain (TMD) integral membrane protein. To study the different proposed functions of DM20 during the development of oligodendrocytes and in myelination, we targeted the plp locus in embryonic stem cells by homologous recombination by a construct, which allows solely the expression of the DM20 specific exon III sequence. The resulting dm20(only) mouse line expresses exclusively DM20 isoprotein, which is functionally assembled into the membrane, forming a highly ordered and tightly compacted myelin sheath. The truncated cytosolic loop devoid of the PLP-specific 35 amino acid residues, including two thioester groups, had no impact on the periodicity of CNS myelin. In contrast to the PLP/DM20-deficient mouse, mutant CNS of dm20(only) mice showed no axonal swellings and neurodegeneration but a slow punctuated disintegration of the compact layers of the myelin sheath and a rare oligodendrocyte death developing with aging.

    Glia 2002;37;1;19-30

  • Nerve conduction abnormalities in aging mice deficient for myelin-associated glycoprotein.

    Weiss MD, Luciano CA and Quarles RH

    Myelin and Brain Development Section, NINDS, National Institutes of Health, Building 49, Room 2A28, Bethesda, Maryland 20892, USA.

    Ultrastructural, biochemical, and electrophysiological analyses were done on 12-14-month-old mice deficient for myelin-associated glycoprotein (MAG) to further characterize the neuropathy that develops as they age. Electron microscopy demonstrated normal myelin compaction and axonal degeneration in a large number of myelinated nerve fibers. Western blots showed that the proteins of compact myelin, P0 glycoprotein, and myelin basic protein were not significantly altered in the mutants; however, the Schwann cell protein, 2',3'-cyclic nucleotide 3'-phosphodiesterase, was reduced to less than half the control level. Also, both total and phosphorylated high-molecular-weight neurofilament proteins (TNFH and PNFH, respectively) were significantly decreased, as was the PNFH:TNFH ratio. Electrophysiological evaluation revealed a mild, but statistically significant, reduction of conduction velocity and a nonsignificant mild decrease in compound muscle action potential amplitudes. This constellation of findings in aging MAG-null mice is consistent with an axonopathy that resembles axonal Charcot-Marie-Tooth (CMT2) disease in many respects. Thus, mutation of a myelin-associated gene expressed by Schwann cells can induce axonal degeneration and cause a neuropathy with minimal signs of demyelination.

    Muscle & nerve 2001;24;10;1380-7

  • The neural recognition molecule L1 is a sialic acid-binding lectin for CD24, which induces promotion and inhibition of neurite outgrowth.

    Kleene R, Yang H, Kutsche M and Schachner M

    Zentrum für Molekulare Neurobiologie, Universität Hamburg, Martinistr. 52, D-20246 Hamburg, Germany.

    Among the recognition molecules that determine a neuron's interaction with other cells, L1 and CD24 have been suggested to cooperate with each other in neurite outgrowth and signal transduction. Here we report that binding of CD24 to L1 depends on alpha2,3-sialic acid on CD24, which determines the CD24 induced and cell type-specific promotion or inhibition of neurite outgrowth. Using knockout mutants, we could show that the CD24-induced effects on neurite outgrowth are mediated via L1, and not GPI-linked CD24, by trans-interaction of L1 with sialylated CD24. This glycoform is excluded together with L1 from raft microdomains, suggesting that molecular compartmentation in the surface membrane could play a role in signal transduction.

    The Journal of biological chemistry 2001;276;24;21656-63

  • Differential expression of the actin-binding proteins, alpha-actinin-2 and -3, in different species: implications for the evolution of functional redundancy.

    Mills M, Yang N, Weinberger R, Vander Woude DL, Beggs AH, Easteal S and North K

    Neurogenetics Research Unit, Children's Hospital at Westmead, Westmead, Sydney, NSW 2145, Australia.

    The alpha-actinins are a multigene family of four actin-binding proteins related to dystrophin. The two skeletal muscle isoforms of alpha-actinin (ACTN2 and ACTN3) are major structural components of the Z-line involved in anchoring the actin-containing thin filaments. In humans, ACTN2 is expressed in all muscle fibres, while ACTN3 expression is restricted to a subset of type 2 fibres. We have recently demonstrated that alpha-actinin-3 is absent in approximately 18% of individuals in a range of human populations, and that homozygosity for a premature stop codon (577X) accounts for most cases of true alpha-actinin-3 deficiency. Absence of alpha-actinin-3 is not associated with an obvious disease phenotype, raising the possibility that ACTN3 is functionally redundant in humans, and that alpha-actinin-2 is able to compensate for alpha-actinin-3 deficiency. We now present data concerning the expression of ACTN3 in other species. Genotyping of non-human primates indicates that the 577X null mutation has likely arisen in humans. The mouse genome contains four orthologues which all map to evolutionarily conserved syntenic regions for the four human genes. Murine Actn2 and Actn3 are differentially expressed, spatially and temporally, during embryonic development and, in contrast to humans, alpha-actinin-2 expression does not completely overlap alpha-actinin-3 in postnatal skeletal muscle, suggesting independent function. Furthermore, sequence comparison of human, mouse and chicken alpha-actinin genes demonstrates that ACTN3 has been conserved over a long period of evolutionary time, implying a constraint on evolutionary rate imposed by continued function of the gene. These observations provide a real framework in which to test theoretical models of genetic redundancy as they apply to human populations. In addition we highlight the need for caution in making conclusions about gene function from the phenotypic consequences of loss-of-function mutations in animal knockout models.

    Funded by: NIAMS NIH HHS: K02 AR02026, R01 AR44345

    Human molecular genetics 2001;10;13;1335-46

  • Severe hypomyelination of the murine CNS in the absence of myelin-associated glycoprotein and fyn tyrosine kinase.

    Biffiger K, Bartsch S, Montag D, Aguzzi A, Schachner M and Bartsch U

    Institute for Neurobiology, Federal Institute of Technology, Hönggerberg, CH-8093 Zürich, Switzerland.

    The analysis of mice deficient in the myelin-associated glycoprotein (MAG) or Fyn, a nonreceptor-type tyrosine kinase proposed to act as a signaling molecule downstream of MAG, has revealed that both molecules are involved in the initiation of myelination. To obtain more insights into the role of the MAG-Fyn signaling pathway during initiation of myelination and formation of morphologically intact myelin sheaths, we have analyzed optic nerves of MAG-, Fyn- and MAG/Fyn-deficient mice. We observed a slight hypomyelination in optic nerves of MAG mutants that was significantly increased in Fyn mutants and massive in MAG/Fyn double mutants. The severe morphological phenotype of MAG/Fyn mutants, accompanied by behavioral deficits, substantiates the importance of both molecules for the initiation of myelination. The different severity of the phenotype of different genotypes indicates that the MAG-Fyn signaling pathway is complex and suggests the presence of compensatory mechanisms in the single mutants. However, data are also compatible with the possibility that MAG and Fyn act independently to initiate myelination. Hypomyelination of optic nerves was not related to a loss of oligodendrocytes, indicating that the phenotype results from impaired interactions between oligodendrocyte processes and axons and/or impaired morphological maturation of oligodendrocytes. Finally, we demonstrate that Fyn, unlike MAG, is not involved in the formation of ultrastructurally intact myelin sheaths.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2000;20;19;7430-7

  • Early onset of axonal degeneration in double (plp-/-mag-/-) and hypomyelinosis in triple (plp-/-mbp-/-mag-/-) mutant mice.

    Uschkureit T, Sporkel O, Stracke J, Bussow H and Stoffel W

    Laboratory for Molecular Neuroscience, University of Cologne, D-50931 Cologne, Germany, and Institute of Anatomy, University of Bonn, D-53115 Bonn, Germany.

    Double (plp-/-mag-/-) and triple (plp-/-mbp-/-mag-/-) null-allelic mouse lines deficient in proteolipid protein (PLP), myelin-associated glycoprotein (MAG), and myelin basic protein (MBP) were generated and characterized genetically, biochemically, and morphologically including their behavioral capacities. The plp-/-mag-/- mutant develops a rapidly progressing axon degeneration in CNS with severe cognitive and motor coordinative deficits but has a normal longevity. CNS axons of the plp-/-mbp-/-mag-/- mouse are hypomyelinated and ensheathed by "pseudomyelin" with disturbed protein and complex lipid composition. The shiverer trait in the plp-/-mbp-/-mag-/- similar to the plp-/-mbp-/- mutant is significantly ameliorated, and its lifespan is considerably prolonged. The longevity of these dysmyelinosis mouse mutants recommends them as suitable models for the long-term evaluation of stem cell therapeutic strategies.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2000;20;14;5225-33

  • Multiple functions of the myelin-associated glycoprotein MAG (siglec-4a) in formation and maintenance of myelin.

    Schachner M and Bartsch U

    Zentrum für Molekulare Neurobiologie, Universität Hamburg, Hamburg, Germany. melitta.schachner@zmnh.uni-hamburg.de

    The myelin-associated glycoprotein, a minor component of myelin in the central and peripheral nervous system, has been implicated in the formation and maintenance of myelin. Although the analysis of MAG null mutants confirms this view, the phenotype of this mutant is surprisingly subtle. In the CNS of MAG-deficient mice, initiation of myelination, formation of morphologically intact myelin sheaths and to a minor extent, integrity of myelin is affected. In the PNS, in comparison, only maintenance of myelin is impaired. Recently, the large isoform of MAG has been identified as the functionally important isoform in the CNS, whereas the small MAG isoform is sufficient to maintain the integrity of myelinated fibers in the PNS. Remarkably, none of the different defects in the MAG mutant is consistently associated with each myelinated fiber. These observations suggest that other molecules performing similar functions as MAG might compensate, at least partially, for the absence of MAG in the null mutant.

    Glia 2000;29;2;154-65

  • Myelin galactolipids: mediators of axon-glial interactions?

    Popko B

    Department of Biochemistry and Molecular Biology, Neuroscience Center, Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, North Carolina 27599-7250, USA. bpopko@css.unc.edu

    The precise alignment of myelin segments along the length of the axon is essential for the saltatory propagation of an electrical impulse. Furthermore, node of Ranvier formation and function are dependent on the proper interactions between myelinating glial cells and the axon. Nevertheless, the molecules that regulate the placement and association of myelinating cells with axons remain largely unidentified. Recently, however, the analysis of mutant mice incapable of synthesizing the galactolipids of myelin has revealed defects in these processes. The galactolipid-deficient mice display alterations in the spacing of internodal segments along the axon: large unmyelinated gaps are common and overlapping myelin segments are observed. Moreover, the normal tight association between the lateral loops of the myelinating cell and the axonal membrane at the paranode region is also disrupted in these animals. Strikingly, there is a complete absence of transverse bands at the axon-glial junction, with the lateral loops frequently turning away from the axon. These data indicate that the galactolipids play an essential role in axon-glial interactions and node of Ranvier formation.

    Funded by: NINDS NIH HHS: NS27336

    Glia 2000;29;2;149-53

  • Heterophilic binding of L1 on unmyelinated sensory axons mediates Schwann cell adhesion and is required for axonal survival.

    Haney CA, Sahenk Z, Li C, Lemmon VP, Roder J and Trapp BD

    Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA.

    This study investigated the function of the adhesion molecule L1 in unmyelinated fibers of the peripheral nervous system (PNS) by analysis of L1- deficient mice. We demonstrate that L1 is present on axons and Schwann cells of sensory unmyelinated fibers, but only on Schwann cells of sympathetic unmyelinated fibers. In L1-deficient sensory nerves, Schwann cells formed but failed to retain normal axonal ensheathment. L1-deficient mice had reduced sensory function and loss of unmyelinated axons, while sympathetic unmyelinated axons appeared normal. In nerve transplant studies, loss of axonal-L1, but not Schwann cell-L1, reproduced the L1-deficient phenotype. These data establish that heterophilic axonal-L1 interactions mediate adhesion between unmyelinated sensory axons and Schwann cells, stabilize the polarization of Schwann cell surface membranes, and mediate a trophic effect that assures axonal survival.

    Funded by: NEI NIH HHS: R01 EY005285; NINDS NIH HHS: R01 NS038186, R01-NS32770, R01-NS38186

    The Journal of cell biology 1999;146;5;1173-84

  • Subtle roles of neural cell adhesion molecule and myelin-associated glycoprotein during Schwann cell spiralling in P0-deficient mice.

    Carenini S, Montag D, Schachner M and Martini R

    Department of Neurobiology, Swiss Federal Institute of Technology, Hönggerberg, Zürich, Switzerland.

    Peripheral nerves of P0-deficient mice display a severe dysmyelinating phenotype, confirming the view that P0 mediates myelin formation and compaction. In addition to the compromised myelin organization, an elevated expression of several cell recognition molecules was described in the axon-Schwann cell units of P0-deficient mice. The present study was performed to focus on the subcellular localization and functional roles of two of these up-regulated molecules, the neural cell adhesion molecule (N-CAM) and the myelin-associated glycoprotein (MAG). We show by postembedding immunoelectron microscopy that in peripheral nerves of P0-deficient mice both molecules are expressed in noncompacted myelin-like regions. In addition, N-CAM, but not MAG, is detected in partially compacted myelin. By the generation of P0/N-CAM- and P0/MAG-deficient double mutants, we investigated the roles of the dysregulated molecules in P0-deficient mice. In 4-week-old double mutants, the dysmyelinating phenotype of the axon-Schwann cell units was very similar to that seen in the P0-deficient single mutants, suggesting that neither N-CAM nor MAG are responsible for the poor myelin compaction in P0-deficient mice. However, the noncompacted turns surrounding the abnormally compacted regions were significantly reduced in number in P0/MAG mutants as compared to P0 or N-CAM/P0 mice. During formation of myelin sheaths, absence of N-CAM resulted in a transient retardation of Schwann cell spiralling in P0-deficient mice, whereas absence of MAG impaired Schwann cell spiralling for a more extended time period. Our findings demonstrate for the first time that MAG and also N-CAM can play significant roles during myelin formation in the peripheral nervous system. Because these functional roles are detectable only in the absence of P0, our results confirm the view that myelin-related molecules can play distinct, but also partially overlapping roles.

    Glia 1999;27;3;203-12

  • Cell-surface glycoprotein of oligodendrocyte progenitors involved in migration.

    Niehaus A, Stegmüller J, Diers-Fenger M and Trotter J

    Department of Neurobiology, University of Heidelberg, 69120 Heidelberg, Germany.

    Myelination by oligodendrocytes in the CNS involves the migration to and recognition and ensheathment of axons. These distinct developmental phases of myelination are assumed to involve the interplay of a precisely regulated set of cell adhesion molecules expressed by both neurons and glial cells. These molecules remain largely unelucidated. In this paper we have identified a large (330 kDa) glycoprotein expressed by murine oligodendrocyte progenitor cells in vitro and in vivo that is downregulated as oligodendrocytes mature. Antigen-positive oligodendrocyte progenitor cells purified by panning develop into myelin-associated glycoprotein-positive oligodendrocytes and also adhere to cultured neurons. Polyclonal antibodies directed against the protein reduce the migration of oligodendrocyte progenitor cells. The observations suggest that the AN2 antigen may play a role in early stages of myelination.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 1999;19;12;4948-61

  • The close homologue of the neural adhesion molecule L1 (CHL1): patterns of expression and promotion of neurite outgrowth by heterophilic interactions.

    Hillenbrand R, Molthagen M, Montag D and Schachner M

    Department of Neurobiology, Swiss Federal Institute of Technology, Hönggerberg, CH-8093 Zürich, Switzerland.

    The close homologue of L1 (CHL1), a member of the L1 family of neural adhesion molecules, is first expressed at times of neurite outgrowth during brain development, and is detectable in subpopulations of neurons, astrocytes, oligodendrocyte precursors and Schwann cells of the mouse and rat. Aggregation assays with CHL1-transfected cells show that CHL1 does not promote homophilic adhesion or does it mediate heterophilic adhesion with L1. CHL1 promotes neurite outgrowth by hippocampal and small cerebellar neurons in substrate-bound and soluble form. The observation that CHL1 and L1 show overlapping, but also distinct patterns of synthesis in neurons and glia, suggests differential effects of L1-like molecules on neurite outgrowth.

    The European journal of neuroscience 1999;11;3;813-26

  • The novel skin-specific cytochrome P450 Cyp2b19 maps to proximal chromosome 7 in the mouse, near a cluster of Cyp2 family genes.

    Keeney DS

    Department of Biochemistry and Department of Medicine (Dermatology), Vanderbilt University, Nashville, Tennessee, 37232, USA. diane.keeney@vanderbilt.edu

    Funded by: NIAMS NIH HHS: P30 AR41943; NIDDK NIH HHS: P30 DK26657; NIEHS NIH HHS: P30 ES00267; ...

    Genomics 1998;53;3;417-9

  • Evidence against altered forms of MAG in the dysmyelinated mouse mutant claw paw.

    Niemann S, Sidman RL and Nave KA

    Zentrum für Molekulare Biologie (ZMBH), University of Heidelberg, Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany.

    Mammalian genome : official journal of the International Mammalian Genome Society 1998;9;11;903-4

  • The effect of the mouse mutation claw paw on myelination and nodal frequency in sciatic nerves.

    Koszowski AG, Owens GC and Levinson SR

    Department of Physiology and Biophysics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.

    Despite the biophysical and clinical importance of differentiating nodal and internodal axolemma, very little is known about the process. We chose to study myelination and node of Ranvier formation in the hypomyelinating mouse mutant claw paw (clp). The phenotype of clp is delayed myelination in the peripheral nervous system. The specific defect is unknown but is thought to arise from a breakdown in the complex signaling mechanism between axon and Schwann cell. Myelination was assessed in sciatic nerve cross sections from adult and postnatal day 14 (P14) heterozygous and homozygous clp mice. Antibodies to P0, myelin-associated glycoprotein (MAG), and neural cell adhesion molecule were used to assess the stage of myelination. P14 homozygous clp mice showed an atypical staining pattern of immature myelin, which resolved into a relatively normal pattern by adulthood. Sodium channel clustering and node of Ranvier frequency were studied in whole-mount sciatic nerves with sodium channel and MAG antibodies. P14 homozygous clp nerves again showed an atypical, immature pattern with diffuse sodium channel clusters suggesting nodal formation was delayed. In the adult, homozygous clp sciatic nerves displayed dramatically shortened internodal distances. The data from this study support the hypotheses that node of Ranvier formation begins with the onset of myelination and that the number and location of nodes of Ranvier in the sciatic nerve are determined by myelinating Schwann cells.

    Funded by: NINDS NIH HHS: NS34375

    The Journal of neuroscience : the official journal of the Society for Neuroscience 1998;18;15;5859-68

  • Tissue-specific expression and mapping of the Cox7ah gene in mouse.

    Jaradat SA, Ko MS and Grossman LI

    Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.

    We have isolated and examined the gene for the heart isoform of cytochrome c oxidase subunit VIIa (COX VIIa-H) in mouse, an isoform gene previously thought to be lacking in rodents. Interspecies amino acid comparisons indicate that mouse COX VIIa-H protein displays 82.5 and 70.9% identity with the bovine and human heart isoforms of COX VIIa, but only 53.7% identity with the paralogous mouse liver isoform (COX VIIa-L). Expression in adult mouse tissues is limited to heart and skeletal muscle, as found in other species. In the early mouse embryo, Cox7al was the exclusive isoform expressed and Cox7ah mRNA was not detectable until day 17 postcoitum. That the mouse Cox7ah gene characterized in this study is orthologous to the human COX7AH gene was also suggested by its mapping to mouse chromosome 7, to a conserved region syntenic with the human chromosome location of COX7AH, 19q13.1. As a result, all three COX heart isoform genes in mouse group to chromosome 7. Interestingly, mapping of the mouse Cox7al to chromosome 9 suggests a new syntenic region between the mouse and the human genomes.

    Funded by: NICHD NIH HHS: HD32243; NIGMS NIH HHS: GM48517

    Genomics 1998;49;3;363-70

  • The cytoplasmic domain of the large myelin-associated glycoprotein isoform is needed for proper CNS but not peripheral nervous system myelination.

    Fujita N, Kemper A, Dupree J, Nakayasu H, Bartsch U, Schachner M, Maeda N, Suzuki K and Popko B

    Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.

    The myelin-associated glycoprotein (MAG) is a member of the immunoglobulin gene superfamily and is thought to play a critical role in the interaction of myelinating glial cells with the axon. Myelin from mutant mice incapable of expressing MAG displays various subtle abnormalities in the CNS and degenerates with age in the peripheral nervous system (PNS). Two distinct isoforms, large MAG (L-MAG) and small MAG (S-MAG), are produced through the alternative splicing of the primary MAG transcript. The cytoplasmic domain of L-MAG contains a unique phosphorylation site and has been shown to associate with the fyn tyrosine kinase. Moreover, L-MAG is expressed abundantly early in the myelination process, possibly indicating an important role in the initial stages of myelination. We have adapted the gene-targeting approach in embryonic stem cells to generate mutant mice that express a truncated form of the L-MAG isoform, eliminating the unique portion of its cytoplasmic domain, but that continue to express S-MAG. Similar to the total MAG knockouts, these animals do not express an overt clinical phenotype. CNS myelin of the L-MAG mutant mice displays most of the pathological abnormalities reported for the total MAG knockouts. In contrast to the null MAG mutants, however, PNS axons and myelin of older L-MAG mutant animals do not degenerate, indicating that S-MAG is sufficient to maintain PNS integrity. These observations demonstrate a differential role of the L-MAG isoform in CNS and PNS myelin.

    Funded by: NINDS NIH HHS: NS24289, NS24453, NS27336; ...

    The Journal of neuroscience : the official journal of the Society for Neuroscience 1998;18;6;1970-8

  • Myelin-associated glycoprotein is a myelin signal that modulates the caliber of myelinated axons.

    Yin X, Crawford TO, Griffin JW, Tu Ph, Lee VM, Li C, Roder J and Trapp BD

    Department of Neurosciences, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.

    Myelination increases neuronal conduction velocity through its insulating properties and an unidentified extrinsic effect that increases axonal caliber. Although it is well established that demyelination can cause axonal atrophy, the myelin molecule that regulates axonal caliber is not known. Loss of the structural proteins of compact peripheral nervous system (PNS) myelin, P0 protein, and myelin basic protein does not lead to axonal atrophy. This study demonstrates that mice with a null mutation of the myelin-associated glycoprotein (MAG) gene have a chronic atrophy of myelinated PNS axons that results in paranodal myelin tomaculi and axonal degeneration. Absence of MAG was correlated with reduced axonal calibers, decreased neurofilament spacing, and reduced neurofilament phosphorylation. Because axonal atrophy and degeneration in MAG-deficient mice occur in the absence of inflammation, hypomyelination, significant demyelination-remyelination, or gain of function mutations, these data support a functional role for MAG in modulating the maturation and viability of myelinated axons.

    Funded by: NINDS NIH HHS: NS29818

    The Journal of neuroscience : the official journal of the Society for Neuroscience 1998;18;6;1953-62

  • Myelin associated glycoprotein modulates glia-axon contact in vivo.

    Li C, Trapp B, Ludwin S, Peterson A and Roder J

    Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada. chumei.li@utoronto.ca

    Myelin-associated glycoprotein (MAG) was postulated to play an important role in myelination. However, we showed previously that MAG null mutants exhibited no gross abnormality in myelination. Ultrastructural studies revealed subtle alterations in periaxonal organisation, indicating a restricted structural role for MAG in the formation and maintenance of periaxonal structures (Li et al., 1994). Here we show that myelination in MAG deficient mice is not as finely controlled as it is in wild type mice. The abnormalities manifest themselves as a decrease in the proportion of myelinated axons and a reciprocal increase in the proportion of unmyelinated axons in mutants' optic nerves. In addition, dysregulated myelination is occasionally observed in the form of multiply myelinated fibres, grouping of myelinated axons and myelin debris by a large myelin sheath, redundant myelin loops and, very rarely, massive myelin surrounding relatively small axons. Thus, in the absence of MAG, some glial cells seem unable to determine when, where and how much myelin should be laid down. These data support the notion of MAG being a glial recognition/adhesion molecule. A model is proposed regarding the roles MAG could play in the formation and maintenance of myelin structure.

    Journal of neuroscience research 1998;51;2;210-7

  • Mapping of eight testis-specific genes to mouse chromosomes.

    Taketo MM, Araki Y, Matsunaga A, Yokoi A, Tsuchida J, Nishina Y, Nozaki M, Tanaka H, Koga M, Uchida K, Matsumiya K, Okuyama A, Rochelle JM, Nishimune Y, Matsui M and Seldin MF

    Laboratory of Biomedical Genetics, Graduate School of Pharmaceutical Sciences, University of Tokyo, Japan. taketo@mol.f.u-tokyo.ac.jp

    We previously identified eight testis-specific genes using antibodies raised against testicular germ cells. They are expressed during spermatogenesis and are presumed to be involved in testicular germ cell differentiation and sperm formation. We have mapped the genomic loci for these testis-specific genes using restriction fragment length variants in interspecific backcross mice. The calmegin gene (Clgn) was mapped to Chr 8. The synaptonemal complex protein gene 1 (Sycp1) probe hybridized with two sequences on different chromosomes; Sycp1-rs2 was mapped to Chr 3, whereas Sycp1-rs3 was mapped to Chr 7. The relaxin-like factor gene (Rlnl) was mapped to Chr 8, and collapsin response mediator protein 1 (Crmp1) was mapped to Chr 5. Three novel genes encoding testis-specific proteins A2 (Tsga2), A8 (Tsga8), and A12 (Tsga12) were mapped to chromosomes 3, X, and 10, respectively.

    Funded by: NHGRI NIH HHS: HG00734

    Genomics 1997;46;1;138-42

  • Genetic mapping of 262 loci derived from expressed sequences in a murine interspecific cross using single-strand conformational polymorphism analysis.

    Brady KP, Rowe LB, Her H, Stevens TJ, Eppig J, Sussman DJ, Sikela J and Beier DR

    Division of Genetics, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.

    We have demonstrated previously that noncoding sequences of genes are a robust source of polymorphisms between mouse species when tested using single-strand conformation polymorphism (SSCP) analysis, and that these polymorphisms are useful for genetic mapping. In this report we demonstrate that presumptive 3'-untranslated region sequence obtained from expressed sequence tags (ESTs) can be analyzed in a similar fashion, and we have used this approach to map 262 loci using an interspecific backcross. These results demonstrate SSCP analysis of genes or ESTs is a simple and efficient means for the genetic localization of transcribed sequences, and is furthermore an approach that is applicable to any system for which there is sufficient sequence polymorphism.

    Funded by: NHGRI NIH HHS: HG00941, HG00951

    Genome research 1997;7;11;1085-93

  • Sodium channel distribution in axons of hypomyelinated and MAG null mutant mice.

    Vabnick I, Messing A, Chiu SY, Levinson SR, Schachner M, Roder J, Li C, Novakovic S and Shrager P

    Department of Biophysics, University of Rochester, New York 14642, USA.

    Na+ channel organization was studied with immunofluorescence in the peripheral nervous system of mice genetically altered to produce abnormal myelin. In two of these strains, transcription of inserted transgenes was targeted to myelinating Schwann cells through linkage to a promoter for the myelin protein P0. Adults of both of these strains had hindlimb paralysis and a tremor on lifting by the tail. In one case, Schwann cells were eliminated via expression of the diphtheria toxin A chain (DT-A). During postnatal days 3-7, Na+ channel clustering at forming nodes was dramatically reduced compared with that of normal animals. At 1-3 months of age, Na+ channel immunofluorescence was often found spread over long stretches of the axolemma, instead of being confined to nodal gaps. In the second P0-linked transgenic model, Schwann cell expression of the large T antigen tsA-1609 resulted in cell cycle dysfunction. Adult axons had regions of diffuse Na+ channel labeling. Focal clusters were rare within these zones, which were characterized by a series of cells of myelinating phenotype tightly apposed to the axon. Previous studies suggested that Schwann cells had to reach the stage of ensheathment characterized by periaxonal myelin associated glycoprotein (MAG) expression in order to induce Na+ channel clustering. However, in MAG-deficient mice, Na+ channel labeling patterns within sciatic nerves were normal.

    Funded by: NINDS NIH HHS: NS15879, NS17965, NS23375

    Journal of neuroscience research 1997;50;2;321-36

  • Molecular cloning, chromosomal assignment and tissue-specific expression of a murine alpha(1,2)fucosyltransferase expressed in thymic and epididymal epithelial cells.

    Domino SE, Hiraiwa N and Lowe JB

    Department of Obstetrics and Gynecology, The University of Michigan Medical School, Ann Arbor, Michigan 48109-0650, USA.

    Terminal Fucalpha(1-2)Galbeta epitopes have been proposed to play significant roles in cell-cell interactions in development, cell adhesion, and malignant transformation. To begin to investigate the regulation and function of alpha(1-2)fucosylated epitopes in an animal model, we have isolated and characterized a mouse genomic DNA segment encoding a protein orthologous to the human H blood group locus alpha(1,2)fucosyltransferase (FUT1). This segment maintains an open reading frame encoding 376 amino acids sharing 75% sequence identity with the enzyme encoded by human FUT1, and 55% sequence identity with the enzyme encoded by the human Secretor blood group locus (FUT2). Expression of the open reading frame in COS-7 cells yields an alpha(1,2)fucosyltransferase activity with a Km of 7.6 mM for phenyl-beta-d-galactoside. Southern blotting and interspecific backcross analyses indicate that this murine locus represents a single copy sequence mapping to a novel locus 2.1 centimorgans from the Klk1 locus, in a region of homology between mouse chromosome 7 and the human FUT1 locus on the long arm of chromosome 19. Mouse FUT1 yields a 2.8 kb mRNA transcript identifiable in many organs, including thymus, lung, stomach, pancreas, small intestine, colon, uterus and epidiymis. Hybridization analyses in situ localize expression of FUT1 transcripts to thymic medullary and epididymal epithelial cells, implying that this gene determines the expression of cell surface Fucalpha(1-2)Galbeta epitopes in these tissues.

    Funded by: NCRR NIH HHS: M01RR00042; NICHD NIH HHS: K12HD00849-08

    The Biochemical journal 1997;327 ( Pt 1);105-15

  • Calumenin, a Ca2+-binding protein retained in the endoplasmic reticulum with a novel carboxyl-terminal sequence, HDEF.

    Yabe D, Nakamura T, Kanazawa N, Tashiro K and Honjo T

    Department of Medical Chemistry, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto 606, Japan.

    We have identified and characterized a cDNA encoding a novel Ca2+-binding protein named calumenin from mouse heart by the signal sequence trap method. The deduced amino acid sequence (315 residues) of calumenin contains an amino-terminal signal sequence and six Ca2+-binding (EF-hand) motifs and shows homology with reticulocalbin, Erc-55, and Cab45. These proteins seem to form a new subset of the EF-hand protein family expressed in the lumen of the endoplasmic reticulum (ER) and Golgi apparatus. Purified calumenin had Ca2+-binding ability. The carboxyl-terminal tetrapeptide His-Asp-Glu-Phe was shown to be responsible for retention of calumenin in ER by the retention assay, immunostaining with a confocal laser microscope, and the deglycosylation assay. This is the first report indicating that the Phe residue is included in the ER retention signal. Calumenin is expressed most strongly in heart of adult and 18.5-day embryos. The calumenin gene (Calu) was mapped at the proximal portion of mouse chromosome 7.

    The Journal of biological chemistry 1997;272;29;18232-9

  • Increased number of unmyelinated axons in optic nerves of adult mice deficient in the myelin-associated glycoprotein (MAG).

    Bartsch S, Montag D, Schachner M and Bartsch U

    Department of Neurobiology, Swiss Federal Institute of Technology, Zürich.

    We have recently demonstrated that the formation of myelin sheaths in the optic nerve of young postnatal mice deficient in the myelin-associated glycoprotein (MAG) is retarded when compared to age-matched wild-type mice. In the present study, we analyzed whether impaired myelination of retinal ganglion cell axons is detectable in adult MAG mutants. In optic nerves of 2- and 9-month-old MAG-deficient mice, we observed a significantly increased number of unmyelinated axons compared to age-matched wild-type mice. At both ages, unmyelinated axons in optic nerves of MAG mutants were of small caliber. The number of unmyelinated axons decreased significantly in 9-month-old MAG mutants when compared to 2-month-old MAG mutants, indicative of a slow and long-lasting myelination of axons in the mutant. Our observations support the view that MAG is involved in the initiation of myelination in the CNS.

    Brain research 1997;762;1-2;231-4

  • The gene encoding the transcription factor Spi-B maps to mouse chromosome 7.

    Peters LL, Ciciotte SL, Su GH and Simon MC

    The Jackson Laboratory, 600 Main Street, Bar Harbor, ME 04609, USA.

    Funded by: NHLBI NIH HHS: HL52094, HL55321, R01 HL055321

    Mammalian genome : official journal of the International Mammalian Genome Society 1997;8;6;452-3

  • Fig1, an interleukin 4-induced mouse B cell gene isolated by cDNA representational difference analysis.

    Chu CC and Paul WE

    North Shore University Hospital, Department of Medicine, Manhasset, NY 11030, USA.

    Interleukin 4 (IL-4) is a cytokine that regulates growth and differentiation of lymphoid and nonlymphoid cells. To study the molecular basis of IL-4 function, we used a cDNA subtraction approach based on the representational difference analysis method. This subtractive amplification technique allowed us to use small amounts of RNA from lipopolysaccharide +/- IL-4-stimulated normal B cells to obtain IL-4-induced genes from these cells. We report here on one such gene, Fig1 (interleukin-four induced gene 1), the first characterized immediate-early IL-4 inducible gene from B cells. Fig1 expression is strikingly limited to the lymphoid compartment. B cells, but not T cells or mast cells, express Fig1 in response to IL-4 within 2 hr in a cycloheximide resistant manner. IL-2, IL-5, and I1-6 do not induce Fig1 in culture. Fig1 maps between Klk1 and Ldh3 on mouse chromosome 7, near two loci involved with murine lupus, Sle3 and Lbw5. The Fig1 cDNA sequence encodes a predicted 70-kDa flavoprotein with best homology to the monoamine oxidases, particularly in domains responsible for FAD binding.

    Proceedings of the National Academy of Sciences of the United States of America 1997;94;6;2507-12

  • Dying-back oligodendrogliopathy: a late sequel of myelin-associated glycoprotein deficiency.

    Lassmann H, Bartsch U, Montag D and Schachner M

    Institute of Neurology, University of Vienna, Austria.

    Ultrastructural analysis of myelin from 8-month-old mice deficient in the myelin-associated glycoprotein revealed pronounced and characteristic alterations of the periaxonal oligodendrocyte processes, consisting of intracytoplasmic deposition of vesicular material, multivesicular bodies, mitochondria, and lipofuscin granules, as well as granular or paracrystalline inclusions. These alterations are similar to those described before as "dying-back oligodendrogliopathy" in diseases of toxic or immune-mediated demyelination including multiple sclerosis.

    Glia 1997;19;2;104-10

  • Absence of the myelin-associated glycoprotein (MAG) and the neural cell adhesion molecule (N-CAM) interferes with the maintenance, but not with the formation of peripheral myelin.

    Carenini S, Montag D, Cremer H, Schachner M and Martini R

    Department of Neurobiology, Swiss Federal Institute of Technology, Hönggerberg, CH-8093 Zürich, Switzerland.

    We have previously shown that mice deficient in the gene for the myelin-associated glycoprotein (MAG) develop normal myelin in the peripheral nerves, but show axon and myelin degeneration at eight months of age, suggesting that MAG is involved in the maintenance of axon-Schwann cell integrity. The search for molecules that might replace MAG during myelination revealed an overexpression of the neural cell adhesion molecule (N-CAM) at those aspects where MAG is detectable in wild type mice. To test whether N-CAM might compensate for MAG during myelination in MAG-deficient mice, double mutants deficient in both MAG and N-CAM (MAG-/N-CAM- mice) were generated by cross-breeding the single mutants. Whereas alterations of myelin development were not detectable in either of the single or double mutants, degeneration of myelin and axons occurred approximately 4 weeks earlier in MAG-/N-CAM- than in MAG- mutants. Furthermore, at 8 weeks of age, single fiber preparation and electron microscopy revealed that the number of profiles indicative of degeneration was substantially increased in MAG-/N-CAM- mutants when compared to MAG- mice. These data suggest that in MAG-deficient mice N-CAM does not compensate for MAG in myelin formation but partially substitutes for it in the maintenance of axon-myelin integrity.

    Cell and tissue research 1997;287;1;3-9

  • Identification of candidate proteins binding to prion protein.

    Yehiely F, Bamborough P, Da Costa M, Perry BJ, Thinakaran G, Cohen FE, Carlson GA and Prusiner SB

    Department of Neurology, University of California, San Francisco, California, 94143, USA.

    Prion diseases are disorders of protein conformation that produce neurodegeneration in humans and animals. Studies of transgenic (Tg) mice indicate that a factor designated protein X is involved in the conversion of the normal cellular prion protein (PrPC) into the scrapie isoform (PrPSc); protein X appears to interact with PrPC but not with PrPSc. To search for PrPC binding proteins, we fused PrP with alkaline phosphatase (AP) to produce a soluble, secreted probe. PrP-AP was used to screen a lambdagt11 mouse brain cDNA library, and six clones were isolated. Four cDNAs are novel while two clones are fragments of Nrf2 (NF-E2 related factor 2) transcription factor and Aplp1 (amyloid precursor-like protein 1). The observation that PrP binds to a member of the APP (amyloid precursor protein) gene family is intriguing, in light of possible relevance to Alzheimer's disease. Four of the isolated clones are expressed preferentially in the mouse brain and encode a similar motif.

    Funded by: NIA NIH HHS: AG02132, AG08967; NINDS NIH HHS: NS14069; ...

    Neurobiology of disease 1997;3;4;339-55

  • The mouse gene (Mobp) encoding myelin-associated oligodendrocytic basic protein maps to distal chromosome 9.

    McCallion AS, Guénet JL, Montague P, Griffiths IR, Savioz A and Davies RW

    University of Glasgow, Institute of Biomedical and Life Sciences, Glasgow, Scotland, UK.

    Mammalian genome : official journal of the International Mammalian Genome Society 1996;7;11;847-9

  • Detailed comparative map of human chromosome 19q and related regions of the mouse genome.

    Stubbs L, Carver EA, Shannon ME, Kim J, Geisler J, Generoso EE, Stanford BG, Dunn WC, Mohrenweiser H, Zimmermann W, Watt SM and Ashworth LK

    Biology Division, Oak Ridge National Laboratory, Tennessee 37831-8077, USA. stubbsl@bioaxl.bio.ornl.gov

    One of the larger contiguous blocks of mouse-human genomic homology includes the proximal portion of mouse chromosome 7 and the long arm of human chromosome 19. Previous studies have demonstrated the close relationship between the two regions, but have also indicated significant rearrangements in the relative orders of homologous mouse and human genes. Here we present the genetic locations of the homologs of 42 human chromosome 19q markers in the mouse, with an emphasis on genes also included in the human chromosome 19 physical map. Our results demonstrate that despite an overall inversion of sequences relative to the centromere, apparent "transpositions" of three gene-rich segments, and a local inversion of markers mapping near the 19q telomere, gene content, order, and spacing are remarkably well conserved throughout the lengths of these related mouse and human regions. Although most human 19q markers have remained genetically linked in mouse, one small human segment forms a separate region of homology between human chromosome 19q and mouse chromosome 17. Three of the four rearrangements of mouse versus human 19q sequences involve segments that are located directly adjacent to each other in 19q13.3-q13.4, suggesting either the coincident occurrence of these events or their common association with unstable DNA sequences. These data permit an unusually in-depth examination of this large region of mouse-human genomic homology and provide an important new tool to aid in the mapping of genes and associated phenotypes in both species.

    Genomics 1996;35;3;499-508

  • The POU factor Oct-6 and Schwann cell differentiation.

    Jaegle M, Mandemakers W, Broos L, Zwart R, Karis A, Visser P, Grosveld F and Meijer D

    Medical Genetics Center, Department of Cell Biology and Genetics, Erasmus University, Post Office Box 1738, 3000 DR Rotterdam, Netherlands.

    The POU transcription factor Oct-6, also known as SCIP or Tst-1, has been implicated as a major transcriptional regulator in Schwann cell differentiation. Microscopic and immunochemical analysis of sciatic nerves of Oct-6(-/-) mice at different stages of postnatal development reveals a delay in Schwann cell differentiation, with a transient arrest at the promyelination stage. Thus, Oct-6 appears to be required for the transition of promyelin cells to myelinating cells. Once these cells progress past this point, Oct-6 is no longer required, and myelination occurs normally.

    Science (New York, N.Y.) 1996;273;5274;507-10

  • Chromosomal location of fifteen unique mouse KRAB-containing zinc finger loci.

    Marine JC, Gilbert DJ, Bellefroid EJ, Martial JA, Ihle JN, Copeland NG and Jenkins NA

    Laboratoire de Biologie Moléculaire et de Génie Génétique, Université de Liège, Belgium.

    The mammalian genome contains hundreds if not thousands of zinc finger protein (Zfp) genes. While the function of most of these genes remains to be determined, it is clear that a few of them play important roles in gene regulation and development. In studies described here, we have used an interspecific mouse backcross mapping panel to determine the chromosomal location of 15 KRAB-containing zinc finger loci. These loci map to nine different mouse autosomes and the X Chromosome (Chr). Two Chrs, 7 and 9, contain cosegregating pairs of KRAB-containing Zfp genes, indicating that the KRAB-containing Zfp genes have evolved through processes involving regional as well as genome-wide duplication events.

    Funded by: NCI NIH HHS: CA1020; PHS HHS: P30C21765

    Mammalian genome : official journal of the International Mammalian Genome Society 1996;7;6;413-6

  • Disruption of the gene for the myelin-associated glycoprotein improves axonal regrowth along myelin in C57BL/Wlds mice.

    Schäfer M, Fruttiger M, Montag D, Schachner M and Martini R

    Department of Neurobiology, Swiss Federal Institute of Technology, Zürich, Switzerland.

    The myelin-associated glycoprotein (MAG) has been shown to be inhibitory for certain neurons in vitro (Mukhopadhyay et al., 1994; McKerracher et al., 1994). To investigate whether MAG is an inhibitory component in peripheral myelin in vivo, MAG-deficient mutant mice were cross-bred with C57BL/Wlds mice that have delayed lesion-induced myelin degeneration and axon regrowth. While in crushed nerves of C57BL/Wlds mice expressing MAG, only 16% of myelin sheaths were associated with regrowing axons, this number was doubled in MAG-deficient C57BL/Wlds mice. These observations suggest that the absence of MAG may contribute to the improved axonal regrowth in the double mutants. Therefore, degeneration of MAG-containing myelin might be an important prerequisite to optimize axonal regrowth after peripheral nerve injury.

    Neuron 1996;16;6;1107-13

  • Myelination and axonal regeneration in the central nervous system of mice deficient in the myelin-associated glycoprotein.

    Bartsch U

    Department of Neurobiology, Swiss Federal Institute of Technology, Zürich, Switzerland.

    The myelin-associated glycoprotein, a member of the immunoglobulin superfamily, has been implicated in the formation and maintenance of myelin sheaths. In addition, recent studies have demonstrated that myelin-associated glycoprotein is inhibitory for neurite elongation in vitro and it has therefore been suggested that myelin-associated glycoprotein prevents axonal regeneration in lesioned nervous tissue. The generation of mice deficient in the expression of myelin-associated glycoprotein by targeted disruption of the mag gene via homologous recombination in embryonic stem cells has allowed the study of the functional role of this molecule in vivo. This review summarizes experiments aimed at answering the following questions: (i) is myelin-associated glycoprotein involved in the formation and maintenance of myelin in the CNS? and (ii) does myelin-associated glycoprotein restrict axonal regeneration in the adult mammalian CNS? Analysis of optic nerves from mutant mice revealed a delay in myelination when compared to optic nerves of wild-type animals, a lack of a periaxonal cytoplasmic collar from most myelin sheaths, and the presence of some doubly and multiply myelinated axons. Axonal regeneration in the CNS of adult myelin-associated glycoprotein deficient mice was not improved when compared to wild-type animals. These observations indicate that myelin-associated glycoprotein is functionally involved in the recognition of axons by oligodendrocytes and in the morphological maturation of myelin sheaths. However, results do not support a role of myelin-associated glycoprotein as a potent inhibitor of axonal regeneration in the adult mammalian CNS.

    Journal of neurocytology 1996;25;5;303-13

  • The myelin-associated glycoprotein of the peripheral nervous system in trembler mutants contains increased alpha 2-3 sialic acid and galactose.

    Bartoszewicz ZP, Lauter CJ and Quarles RH

    Myelin and Brain Development Section, Laboratory of Molecular and Cellular Neurobiology, NINDS, NIH, Bethesda, Maryland, USA.

    The myelin-associated glycoprotein (MAG) exhibits an abnormally high apparent molecular weight in sciatic nerve, but not in brain, of dysmyelinating trembler mutants (Inuzuka et al.: J Neurochem 44:793-797, 1985). Antibodies to the large and small isoforms of MAG (L- and S-MAG) and probes for oligosaccharide structure were used to determine if this was due to overexpression of L-MAG or increased glycosylation. Nerves from both control and trembler 36-day-old mice contained primarily S-MAG with only traces of L-MAG. The distribution of the two isoforms appeared normal in trembler mice, and both isoforms exhibited the higher apparent molecular weight. Lectin binding showed that, in contrast to brain in which most glycoproteins contain primarily alpha 2-3 linked sialic acid, most glycoproteins of both control and trembler nerve contained primarily alpha 2-6 linked sialic acid. Lectin binding and glycosidase treatments demonstrated that the higher molecular weight of MAG in trembler nerves was due to an increased content of alpha 2-3 linked sialic acid and galactose. The abnormal glycosylation of MAG in trembler mutants may contribute to the myelin pathology.

    Journal of neuroscience research 1996;43;5;587-93

  • Molecular and developmental characterization of novel cDNAs of the myelin-associated/oligodendrocytic basic protein.

    Holz A, Schaeren-Wiemers N, Schaefer C, Pott U, Colello RJ and Schwab ME

    Brain Research Institute, University of Zurich, Switzerland.

    Several novel myelin-associated/oligodendrocytic basic protein (MOBP) isoforms were identified in this study by cDNA cloning. They are small, highly basic polypeptides comprising 69, 81, and 99 amino acids (8.2, 9.7, and 11.7 kDa, respectively) and show no significant homology with described proteins or domain structures. All (as yet) identified MOBP isoforms are identical in amino acids 1-68 but differ in the length and polarity of the C-terminal region. One isoform, designated MOBP81, was shown to be expressed abundantly during development. Interestingly, MOBP81 has a significant clustering of positively charged residues at positions 69-81, a feature that also has been observed for myelin basic protein (MBP) and Po. As demonstrated by in situ hybridization, MOBP gene expression occurs during development of the rat optic nerve later than that of MBP and proteolipid protein and coincides exactly with the beginning of myelin compaction. The 2.6 kb MOBP81-A transcript is localized in the processes of oligodendrocytes, whereas the 3.8 kb MOBP81-B transcript is restricted to the perinuclear region. Therefore, MOBP81-A and related mRNAs seem to be transported to the periphery of the oligodendrocytes, as is known for the transcripts of the MBP gene. The late developmental expression of the MOBP gene suggests that the MOBP proteins act at the late steps of myelin formation, possibly in myelin compaction and in the maintenance of the myelin sheath.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 1996;16;2;467-77

  • Location of the DBP transcription factor gene in human and mouse.

    Stubbs L, Carver E, Ashworth L and Lopez-Molina L

    Biology Division, Oak Ridge National Laboratory, Tennessee 37831-8077, USA.

    Mammalian genome : official journal of the International Mammalian Genome Society 1996;7;1;65-7

  • Endocytic depletion of L-MAG from CNS myelin in quaking mice.

    Bö L, Quarles RH, Fujita N, Bartoszewicz Z, Sato S and Trapp BD

    Department of Neurosciences, Cleveland Clinic Foundation, Ohio 44195, USA.

    Quaking is an autosomal recessive hypo/dysmyelinating mutant mouse which has a 1-Mbp deletion on chromosome 17. The mutation exhibits pleiotrophy and does not include genes encoding characterized myelin proteins. The levels of the 67-kD isoform of the myelin-associated glycoprotein (S-MAG) relative to those of the 72-kD isoform (L-MAG) are increased in the quaking CNS, but not in other dysmyelinating mutants. Abnormal expression of MAG isoforms in quaking may result from altered transcription of the MAG gene or from abnormal sorting, transport, or targeting of L-MAG or S-MAG. To test these hypotheses, we have determined the distribution of L-MAG and S-MAG in cervical spinal cord of 7-, 14-, 21-, 28-, and 35-d-old quaking mice. In 7-d-old quaking and control spinal cord, L- and S-MAG was detectable in periaxonal regions of myelinated fibers and in the perinuclear cytoplasm of oligodendrocytes. Between 7 and 35 d, L-MAG was removed from the periaxonal membrane of quaking but not control mice. Compared to control mice, a significant increase in MAG labeling of endosomes occurred within oligodendrocyte cytoplasm of 35-d-old quaking mice. S-MAG remained in periaxonal membranes of both quaking and control mice. Analysis of the cytoplasmic domain of L-MAG identifies amino acid motifs at tyrosine 35 and tyrosine 65 which meet the criteria for "tyrosine internalization signals" that direct transmembrane glycoproteins into the endocytic pathway. These results establish that L-MAG is selectively removed from the periaxonal membrane of CNS-myelinated fibers by receptor-mediated endocytosis. The loss of L-MAG from quaking periaxonal membranes results from increased endocytosis of L-MAG and possibly a decrease in L-MAG production.

    Funded by: NINDS NIH HHS: NS29818

    The Journal of cell biology 1995;131;6 Pt 2;1811-20

  • Lack of evidence that myelin-associated glycoprotein is a major inhibitor of axonal regeneration in the CNS.

    Bartsch U, Bandtlow CE, Schnell L, Bartsch S, Spillmann AA, Rubin BP, Hillenbrand R, Montag D, Schwab ME and Schachner M

    Department of Neurobiology, Swiss Federal Institute of Technology, Hönggerberg, CH-8093 Zürich, Switzerland.

    The MAG-deficient mouse was used to test whether MAG acts as a significant inhibitor of axonal regeneration in the adult mammalian CNS, as suggested by cell culture experiments. Cell spreading, neurite elongation, or growth cone collapse of different cell types in vitro was not significantly different when myelin preparations or optic nerve cryosections from either MAG-deficient or wild-type mice were used as a substrate. More importantly, the extent of axonal regrowth in lesioned optic nerve and corticospinal tract in vivo was similarly poor in MAG-deficient and wild-type mice. However, axonal regrowth increased significantly and to a similar extent in both genotypes after application of the IN-1 antibody directed against the neurite growth inhibitors NI-35 and NI-250. These observations do not support the view that MAG is a significant inhibitor of axonal regeneration in the adult CNS.

    Neuron 1995;15;6;1375-81

  • Multiply myelinated axons in the optic nerve of mice deficient for the myelin-associated glycoprotein.

    Bartsch U, Montag D, Bartsch S and Schachner M

    Department of Neurobiology, Swiss Federal Institute of Technology, Hönggerberg, Zurich.

    We recently reported that some retinal ganglion cell axons in mice deficient for the myelin-associated glycoprotein are concentrically surrounded by more than one myelin sheath. In the present study, we demonstrate that myelin sheaths displaced from the axon reveal a normal ultrastructure of compact myelin, with the only exception that multiple myelination of axons frequently correlates with the presence of unfused regions of major dense lines. Supernumerary sheaths terminated on other sheaths or on astrocyte cell surfaces in a pattern closely resembling the morphology of a true paranode. The thickness of compact myelin of multiply myelinated axons was significantly increased when compared with axons of similar caliber surrounded by a single myelin sheath. Our observations demonstrate that maintenance of compact myelin and paranodal regions is not dependent on direct axonal contact and that the presence of more than one concentric myelin sheath around an axon results in dysregulation of the axon-to-fiber ratio.

    Glia 1995;14;2;115-22

  • Abnormal expression and glycosylation of the large and small isoforms of myelin-associated glycoprotein in dysmyelinating quaking mutants.

    Bartoszewicz ZP, Noronha AB, Fujita N, Sato S, Bö L, Trapp BD and Quarles RH

    Myelin and Brain Development Section, NINDS, National Institutes of Health, Bethesda, Maryland, USA.

    The relative expression of large (L) and small (S) isoforms of the myelin-associated glycoprotein (MAG) and their glycosylation were compared in developing spinal cord of quaking and control mice. Using antisera specific for L- and S-MAG, respectively, it was shown that S-MAG is the principal isoform in quaking mice at all ages between 13 and 72 days, although L-MAG was just detectable by western blotting at the early ages. Both L- and S-MAG have higher apparent molecular weights in quaking mice than in controls. Experiments involving lectin binding and glycosidase treatment demonstrated that the higher molecular weight of MAG in the quaking mutant was due to a higher content of N-acetylneuraminic acid residues linked alpha 2-3 to galactose as well as to more branching of oligosaccharide moieties indicated by a higher content of subterminal galactose residues. The total sialic acid measured by HPAE-chromatography in purified quaking MAG was 40% higher than in control MAG. By contrast, quaking MAG contained less of the adhesion-related, HNK-1 carbohydrate epitope. Another difference was that a lower molecular weight form of MAG with predominantly high mannose oligosaccharides was prominent in young quaking mice, but not in controls. The abnormalities of MAG expression related to splicing of its mRNA and glycosylation may contribute to the myelin pathology in quaking mutants.

    Journal of neuroscience research 1995;41;1;27-38

  • Crucial role for the myelin-associated glycoprotein in the maintenance of axon-myelin integrity.

    Fruttiger M, Montag D, Schachner M and Martini R

    Department of Neurobiology, Swiss Federal Institute of Technology, Hönggerberg, Zurich.

    It has recently been shown that mice deficient in the gene for myelin-associated glycoprotein develop normal myelin sheaths in the peripheral nervous system. Here we report that in mutant mice older than 8 months the maintenance of axon-myelin units is disturbed, resulting in both axon and myelin degeneration. Morphological features include those typically seen in human peripheral neuropathies, where demyelination-induced Schwann cell proliferation and remyelination lead to the formation of so-called onion bulbs. Expression of tenascin-C, a molecule indicative of peripheral nerve degeneration, was up-regulated by axon-deprived Schwann cells and regenerating axons were occasionally seen. Myelin-associated glycoprotein thus appears to play a crucial role in the long-term maintenance of the integrity of both myelin and axons.

    The European journal of neuroscience 1995;7;3;511-5

  • The molecular basis of the neuropathies of mouse and human.

    Snipes GJ, Suter U, Welcher AA and Shooter EM

    Department of Neurobiology, Stanford University School of Medicine, CA 94305-5401, USA.

    Funded by: NINDS NIH HHS: NS01559, NS04270

    Progress in brain research 1995;105;319-25

  • Molecular genetic analyses of myelin deficiency and cerebellar ataxia.

    Mikoshiba K, Okano H, Miyawaki A, Furuichi T and Ikenaka K

    Department of Molecular Neurobiology, University of Tokyo, Japan.

    Progress in brain research 1995;105;23-41

  • Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily.

    Kelm S, Pelz A, Schauer R, Filbin MT, Tang S, de Bellard ME, Schnaar RL, Mahoney JA, Hartnell A, Bradfield P et al.

    Biochemisches Institut II, University of Kiel, Germany.

    Background: Protein-carbohydrate interactions are believed to be important in many biological processes that involve cell-cell communication. Apart from the selectins, the only well-characterized vertebrate sialic acid-dependent adhesion molecules are CD22 and sialoadhesin; CD22 is a member of the immunoglobulin superfamily that is expressed by B lymphocytes and sialoadhesin is a macrophage receptor. The recent cloning of the gene encoding sialoadhesin has shown that it is also immunoglobulin-like. Both proteins share sequence similarity with the myelin-associated glycoprotein, an adhesion molecule of oligodendrocytes and Schwann cells that has been implicated in the process of myelination, raising the important question of whether myelin-associated glycoprotein is also a sialic acid-binding protein.

    Results: We have investigated the binding properties of these three receptors when expressed either in monkey COS cells or as chimaeric proteins containing the Fc portion of human immunoglobulin G. We demonstrate that, like sialoadhesin and CD22, myelin-associated glycoprotein mediates cell adhesion by binding to cell-surface glycans that contain sialic acid. We have dissected the specificities of these three adhesins further: whereas sialoadhesin binds equally to the sugar moieties NeuAc alpha 2-->3Gal beta 1-->3(4)GlcNAc or NeuAc alpha 2-->3Gal beta 1-->3GalNAc, myelin-associated glycoprotein recognizes only NeuAc alpha 2-->3Gal beta 1-->3GalNAc and CD22 binds specifically to NeuAc alpha 2-->6Gal beta 1-->4GlcNAc. Furthermore, we show that the recognition of sialylated glycans on the surfaces of particular cell types leads to the selective binding of sialoadhesin to neutrophils, myelin-associated glycoprotein to neurons and CD22 to lymphocytes.

    Conclusions: Our findings demonstrate that a subgroup of the immunoglobulin superfamily can mediate diverse biological processes through recognition of specific sialylated glycans on cell surfaces. We propose that this subgroup of proteins be called the sialoadhesin family.

    Current biology : CB 1994;4;11;965-72

  • Krox-20 controls myelination in the peripheral nervous system.

    Topilko P, Schneider-Maunoury S, Levi G, Baron-Van Evercooren A, Chennoufi AB, Seitanidou T, Babinet C and Charnay P

    Unité 368 de l'Institut National de la Santé et de la Recherche Médicale, Ecole Normale Supérieure, Paris, France.

    The molecular mechanisms controlling the process of myelination by Schwann cells remain elusive, despite recent progress in the identification and characterization of genes encoding myelin components (reviewed in ref. 1). We have created a null allele in the mouse Krox-20 gene, which encodes a zinc-finger transcription factor, by in-frame insertion of the Escherichia coli lacZ gene, and have shown that hindbrain segmentation is affected in Krox-20-/- embryos. We demonstrate here that Krox-20 is also activated in Schwann cells before the onset of myelination and that its disruption blocks Schwann cells at an early stage in their differentiation, thus preventing myelination in the peripheral nervous system. In Krox-20-/- mice, Schwann cells wrap their cytoplasmic processes only one and a half turns around the axon, and although they express the early myelin marker, myelin-associated glycoprotein, late myelin gene products are absent, including those for protein zero and myelin basic protein. Therefore Krox-20 is likely to control a set of genes required for completion of myelination in the peripheral nervous system.

    Funded by: Telethon: 94

    Nature 1994;371;6500;796-9

  • Mice deficient for the myelin-associated glycoprotein show subtle abnormalities in myelin.

    Montag D, Giese KP, Bartsch U, Martini R, Lang Y, Blüthmann H, Karthigasan J, Kirschner DA, Wintergerst ES, Nave KA et al.

    Department of Neurobiology, Swiss Federal Institute of Technology Hönggerberg, Zürich, Switzerland.

    Using homologous recombination in embryonic stem cells, we have generated mice with a null mutation in the gene encoding the myelin-associated glycoprotein (MAG), a recognition molecule implicated in myelin formation. MAG-deficient mice appeared normal in motor coordination and spatial learning tasks. Normal myelin structure and nerve conduction in the PNS, with N-CAM overexpression at sites normally expressing MAG, suggested compensatory mechanisms. In the CNS, the onset of myelination was delayed, and subtle morphological abnormalities were detected in that the content of oligodendrocyte cytoplasm at the inner aspect of most myelin sheaths was reduced and that some axons were surrounded by two or more myelin sheaths. These observations suggest that MAG participates in the formation of the periaxonal cytoplasmic collar of oligodendrocytes and in the recognition between oligodendrocyte processes and axons.

    Funded by: NICHD NIH HHS: HD-18655; NINDS NIH HHS: NINCDS NS-20824

    Neuron 1994;13;1;229-46

  • Myelination in the absence of myelin-associated glycoprotein.

    Li C, Tropak MB, Gerlai R, Clapoff S, Abramow-Newerly W, Trapp B, Peterson A and Roder J

    Samuel Lunenfeld Research Institute, University of Toronto, Ontario, Canada.

    The hypothesis that myelin-associated glycoprotein (MAG) initiates myelin formation is based in part on observations that MAG has an adhesive role in interactions between oligodendrocytes and neurons. Furthermore, the over- or underexpression of MAG in transfected Schwann cells in vitro leads to accelerated myelination or hypomyelination, respectively. Here we test this idea by creating a null mutation in the mag locus and deriving mice that are totally deficient in MAG expression at the RNA and protein level. In adult mutant animals the degree of myelination and its compaction are normal, whereas the organization of the periaxonal region is partially impaired. Mutant animals show a subtle intention tremor. Our findings do not support the widely held view that MAG is critical for myelin formation but rather indicate that MAG is necessary for maintenance of the cytoplasmic collar and periaxonal space of myelinated fibres.

    Nature 1994;369;6483;747-50

  • Voltage-gated potassium channel genes are clustered in paralogous regions of the mouse genome.

    Lock LF, Gilbert DJ, Street VA, Migeon MB, Jenkins NA, Copeland NG and Tempel BL

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

    Cloning of the Drosophila Shaker gene established that a neurological phenotype including locomotor dysfunction can be caused by a mutation in a voltage-gated potassium (K) channel gene. Shaker sequences have been used to isolate a large family of related K channel genes from both flies and mammals. Toward elucidating the evolutionary relationship between loci and the potential causal connection that K channels may have to mammalian genetic disorders, we report here the genetic mapping of 12-16 different murine, voltage-gated K channel genes. We find that multiple genes, in some cases from distantly related K channel subfamilies, occur in clusters in the mouse genome. These mapping results suggest that the K channel gene subfamilies arose through ancient localized gene duplication events, followed by chromosomal duplications and rearrangements as well as further gene duplication. We also note that several neurologic disorders of both mouse and human are associated with the chromosomal regions containing K channel genes.

    Funded by: NINDS NIH HHS: NS-27206; PHS HHS: N01-C0-74101

    Genomics 1994;20;3;354-62

  • Refining the genetic map for the region flanking the X-linked hypophosphataemic rickets locus (Xp22.1-22.2).

    Rowe PS, Goulding J, Read A, Lehrach H, Francis F, Hanauer A, Oudet C, Biancalana V, Kooh SW, Davies KE et al.

    Middlesex Hospital, London, UK.

    We have screened fourteen kindreds with X-linked hypophosphataemic rickets with four microsatellite markers, viz AFM163yh2, DXS999 (AFM234yf12), DXS443 and DXS365, in order to refine the genetic map flanking the gene, and to define a close flanking interval for the construction of a yeast artificial chromosome (YAC) and cosmid contig. The genetic data were enhanced after the isolation of a large 1.2-megabase YAC derived from AFM163yh2, in which marker DXS274 was present but not DXS365 or DXS443. Against HYP, DXS365, AFM163yh2 and DXS443 showed no recombinants (Zmax = 18.1, Zmax = 9.9, and Zmax = 16.0 respectively). DXS999 gave Zmax = 9.6 at 4% recombination and lies distal to HYP but proximal to DXS197 and DXS43. The disease gene and markers AFM163yh2 and DXS365 are flanked by DXS443 and DXS274. Combining the genetic and physical data, we are able to propose the following gene marker order: Xptel-DXS43-DXS197-DXS999-DXS443-[(DXS3 65-AFM163yh2), HYP]-DXS274-DXS41-Xcen.

    Human genetics 1994;93;3;291-4

  • Lessons from genetic knockout mice deficient in neural recognition molecules.

    Schachner M

    Department of Neurobiology, Swiss Federal Institute of Technology, Zurich.

    Progress in brain research 1994;100;25-30

  • Chromosomal localization of uroplakin genes of cattle and mice.

    Ryan AM, Womack JE, Yu J, Lin JH, Wu XR, Sun TT, Clarke V and D'Eustachio P

    Department of Veterinary Pathobiology, Texas A&M University, College Station 77843.

    The asymmetric unit membrane (AUM) of the apical surface of mammalian urinary bladder epithelium contains several major integral membrane proteins, including uroplakins IA and IB (both 27 kDa), II (15 kDa), and III (47 kDa). These proteins are synthesized only in terminally differentiated bladder epithelial cells. They are encoded by separate genes and, except for uroplakins IA and IB, appear to be unrelated in their amino acid sequences. The genes encoding these uroplakins were mapped to chromosomes of cattle through their segregation in a panel of bovine x rodent somatic cell hybrids. Genes for uroplakins IA, IB, and II were mapped to bovine (BTA) Chromosomes (Chrs) 18 (UPK1A), 1 (UPK1B), and 15 (UPK2), respectively. Two bovine genomic DNA sequences reactive with a uroplakin III cDNA probe were identified and mapped to BTA 6 (UPK3A) and 5 (UPK3B). We have also mapped genes for uroplakins IA and II in mice, to the proximal regions of mouse Chr 7 (Upk1a) and 9 (Upk2), respectively, by analyzing the inheritance of restriction fragment length variants in recombinant inbred mouse strains. These assignments are consistent with linkage relationships known to be conserved between cattle and mice. The mouse genes for uroplakins IB and III were not mapped because the mouse genomic DNA fragments reactive with each probe were invariant among the inbred strains tested. Although the stoichiometry of AUM proteins is nearly constant, the fact that the uroplakin genes are unlinked indicates that their expression must be independently regulated. Our results also suggest likely positions for two human uroplakin genes and should facilitate further analysis of their possible involvement in disease.

    Funded by: NHGRI NIH HHS: HG00300; NIADDK NIH HHS: AM39749; NIDDK NIH HHS: DK39753

    Mammalian genome : official journal of the International Mammalian Genome Society 1993;4;11;656-61

  • A single B1 subunit mapped to mouse chromosome 7 may be a common component of Na channel isoforms from brain, skeletal muscle and heart.

    Tong J, Potts JF, Rochelle JM, Seldin MF and Agnew WS

    Dept. of Physiology, Johns Hopkins University School of Medicine.

    A beta 1 subunit associated with one or more isoforms of brain voltage-sensitive Na channels has previously been cloned, sequenced and expressed. Northern and Western blot analyses have suggested that homologues to this protein are expressed in skeletal muscle and heart. Here, reverse transcriptase-polymerase chain reaction (RT-PCR)/cloning reveals that transcripts encoding identical beta 1 subunit ORFs are expressed in adult rat brain, skeletal muscle and heart. Heterologous co-expression of beta 1 with brain (RIIA) and skeletal muscle (mu 1) alpha subunits caused a stabilization of normal, rapidly inactivating (mode 1) gating relative to anomalous, non-inactivating (mode 2) states and a negative shift in steady state inactivation. Chromosome mapping of the beta 1 subunit showed a single locus (Scn1b) in mouse chromosome 7 1.8 cM (+/- 1.2 cM) distal to D19F11S1h and 0.9 cM (+/- 0.9 cM) proximal to Pkca. This locus is in the region of the mouse mutant "quivering," characterized by a variety of neurological disorders and muscle paralysis. A mutation in a single beta 1 subunit forming functional complexes with multiple Na channel isoforms could underlie these deficits.

    Funded by: NINDS NIH HHS: NS 17928-12

    Biochemical and biophysical research communications 1993;195;2;679-85

  • Organization of the murine Cd22 locus. Mapping to chromosome 7 and characterization of two alleles.

    Law CL, Torres RM, Sundberg HA, Parkhouse RM, Brannan CI, Copeland NG, Jenkins NA and Clark EA

    Department of Microbiology SC-42, University of Washington, Seattle 98195.

    Murine CD22 (mCD22) is a B cell-associated adhesion protein with seven extracellular Ig-like domains that has 62% amino acid identity to its human homologue. Southern analysis on genomic DNA isolated from tissues and cell lines from several mouse strains using mCD22 cDNA demonstrated that the Cd22 locus encoding mCD22 is a single copy gene of < or = 30 kb. Digestion of genomic DNA preparations with four restriction endonucleases revealed the presence of restriction fragment length polymorphisms (RFLP) in BALB/c, C57BL/6, and C3H strains vs DBA/2J, NZB, and NZC strains, suggesting the presence of two or more Cd22 alleles. Using a mCD22 cDNA clone derived from the BALB/c strain, we isolated genomic clones from a DBA/2J genomic library that contained all the exons necessary to encode the full length mCD22 cDNA. Fifteen exons, including exon 3 that encodes the translation start codon, were identified. Each extracellular Ig-like domain of mCD22 is encoded by a single exon. A comparison between the nucleotide sequences of the BALB/c CD22 cDNA and the exons of the DBA/2J CD22 genomic clones revealed an 18-nucleotide deletion in exon 4 (encoding the most distal Ig-like domain 1 of mCD22) of the DBA/2J genomic sequence in addition to a number of substitutions, insertions, and deletions in other exons. These nucleotide differences were also present in a cDNA clone isolated from total RNA of LPS-activated DBA/2J splenocytes by reverse transcription-polymerase chain reaction. The Cd22 locus was mapped to the proximal region of chromosome 7, a region sytenic to human chromosome 19q, close to the previously reported loci, Lyb-8 and Mag (a homologue of Cd22). An antibody (CY34) against the Lyb-8.2 B cell marker reacted with a BHK transfectant expressing the full length mCD22 cDNA, thus demonstrating that Lyb-8 and Cd22 loci are identical. Furthermore, a rat anti-mCD22 mAb, NIM-R6, bound to sIgM+ DBA/2J B cells, confirming the expression of a CD22 protein by the Cd22a/Lyb-8a allele.

    Funded by: NCI NIH HHS: N01-CO-74101; NIGMS NIH HHS: GM42508

    Journal of immunology (Baltimore, Md. : 1950) 1993;151;1;175-87

  • The ras superfamily of GTP-binding proteins: guidelines on nomenclature.

    Kahn RA, Der CJ and Bokoch GM

    FASEB journal : official publication of the Federation of American Societies for Experimental Biology 1992;6;8;2512-3

  • Characterization of murine carcinoembryonic antigen gene family members.

    Rudert F, Saunders AM, Rebstock S, Thompson JA and Zimmermann W

    Institut für Immunbiologie, Universität Freiburg, FRG.

    The carcinoembryonic antigen (CEA) is a human tumor marker whose gene belongs to a family with more than 20 members. This gene family codes for a group of proteins with in vitro cell adhesion properties and for a group of abundantly expressed pregnancy-specific glycoproteins (PSG) with unknown functions. As a basis for in vivo functional studies, we have started to analyze the murine CEA gene family and have identified five new members (Cea-2 to Cea-6). cDNA clones were isolated for Cea-2, Cea-3, and Cea-6. The deduced amino acid sequences of Cea-2 and Cea-6 indicate three IgV-like (N), followed by one IgC-like (A) domain (N1-N2-N3-A). We have also partially characterized the Cea-2 gene and two additional ones, Cea-4 and Cea-5. Cea-2 and Cea-4 are separated by only 16 kb, suggesting a close linkage of murine CEA-related genes, as found for the human CEA gene family. Cea-5 was located to the proximal region of mouse Chromosome (Chr) 7, which is syntenic to part of human Chr 19, containing the human CEA gene family cluster. Cea-2, Cea-3, and a Cea-4-like gene are differentially transcribed in the placenta during pregnancy, but not in other organs tested. This expression pattern strongly suggests that they represent counterparts of the human PSG subgroup members, despite the presence of multiple IgV-like domains, a feature not found for human PSGs. The more distantly related Cea-5 seems to be ubiquitously expressed. The putative promoter region of Cea-2 lacks typical TATA- or CAAT-boxes, but contains other conserved motifs that could play a role in the initiation of transcription.

    Mammalian genome : official journal of the International Mammalian Genome Society 1992;3;5;262-73

  • Schwann cells infected with a recombinant retrovirus expressing myelin-associated glycoprotein antisense RNA do not form myelin.

    Owens GC and Bunge RP

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

    To elucidate the role of myelin-associated glycoprotein (MAG) in the axon-Schwann cell interaction leading to myelination, neonatal rodent Schwann cells were infected in vitro with a recombinant retrovirus expressing MAG antisense RNA or MAG sense RNA. Stably infected Schwann cells and uninfected cells were then cocultured with purified sensory neurons under conditions permitting extensive myelination in vitro. A proportion of the Schwann cells infected with the MAG antisense virus did not myelinate axons and expressed lower levels of MAG than control myelinating Schwann cells, as measured by immunofluorescence. Electron microscopy revealed that the affected cells failed to segregate large axons and initiate a myelin spiral despite having formed a basal lamina, which normally triggers Schwann cell differentiation. Cells infected with the MAG sense virus formed normal compact myelin. These observations strongly suggest that MAG is the critical Schwann cell component induced by neuronal interaction that initiates peripheral myelination.

    Funded by: NINDS NIH HHS: NS 09923

    Neuron 1991;7;4;565-75

  • Structure of mouse myelin-associated glycoprotein gene.

    Nakano R, Fujita N, Sato S, Inuzuka T, Sakimura K, Ishiguro H, Mishina M and Miyatake T

    Department of Neurology, Niigata University, Japan.

    The mouse myelin-associated glycoprotein gene was isolated from a mouse gene library. This gene was split into 13 exons distributed about 15 kb in length. Each extracellular immunoglobulin-related domain was encoded by a single exon, and RNA splicing between those exons occurred between the first and second nucleotides of the junctional codon, the features of which are conserved in most of the genes of the immunoglobulin superfamily. The sequence of the 5'-flanking region appeared to have some regions homologous to other myelin proteins, which suggested that they were possible cis-elements for specific expression of oligodendrocytes.

    Biochemical and biophysical research communications 1991;178;1;282-90

  • Chromosomal location of the octamer transcription factors, Otf-1, Otf-2, and Otf-3, defines multiple Otf-3-related sequences dispersed in the mouse genome.

    Siracusa LD, Rosner MH, Vigano MA, Gilbert DJ, Staudt LM, Copeland NG and Jenkins NA

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

    Chromosomal locations have been assigned for the octamer transcription factor, Otf, gene family (previously named the octamer-binding protein, Oct, gene family) using an interspecific backcross of [(C57BL/6J x Mus spretus)F1 x C57BL/6J] mice and the BXH recombinant inbred strains. Molecular probes for Otf-1 and Otf-2 recognized single loci on mouse chromosomes 1 and 7, respectively, whereas probes for Otf-3 recognized a minimum of eight independently segregating loci (designated Otf-3a through Otf-3h). Members of the Otf-3 family mapped to mouse chromosomes 1, 2, 3, 6, 14, 17, and the X chromosome, indicating that the Otf family has become widely dispersed during evolution. Several Otf loci mapped near developmental mutations, raising the possibility that these mutations result from defects in Otf family members.

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

    Genomics 1991;10;2;313-26

  • Differential expression of MAG isoforms during development.

    Pedraza L, Frey AB, Hempstead BL, Colman DR and Salzer JL

    Department of Cell Biology, New York University Medical School 10016.

    The myelin-associated glycoproteins (MAG) mediate the cell interactions of oligodendrocytes and Schwann cells with axons that are myelinated. MAG exists in two developmentally regulated isoforms: large MAG (L-MAG) and small MAG (S-MAG). In this paper, we have studied the tissue-specific and developmentally regulated alternative splicing of these isoforms using monospecific antibodies that recognize epitopes common to both isoforms or that are present only on L-MAG. In the central nervous system (CNS), L-MAG is the major form synthesized early in development, and it persists as a significant proportion of the MAG present in the adult. In the peripheral nervous system (PNS), L-MAG is expressed at modest levels during development; it is virtually absent in the adult. Thus, the expression of L-MAG is not limited to the CNS, as was formerly believed, suggesting that it plays a common role during the early stages of myelin formation by both oligodendrocytes and Schwann cells. In both the CNS and PNS, S-MAG is the predominant isoform in the adult. A higher-molecular-weight form of MAG is present in the PNS at low abundance, that is developmentally regulated, and appears to be a glycosylation variant. An analysis of the carbohydrate residues on MAG demonstrates that it contains both N-linked and O-linked sugars that could be modulated during development. These results suggest a possible mechanism for the regulation of MAG function during myelinogenesis via the expression of alternative isoforms and carbohydrate modifications.

    Funded by: NINDS NIH HHS: NS26001, NS27680

    Journal of neuroscience research 1991;29;2;141-8

  • A molecular genetic linkage map of mouse chromosome 7.

    Saunders AM and Seldin MF

    Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710.

    The homology between mouse chromosome 7 and human chromosomes 11, 15, and 19 was examined using interspecific backcross animals derived from mating C3H/HeJ-gld/gld and Mus spretus mice. In an earlier study, we reported on the linkage relationships of 16 loci on mouse chromosome 7 and the homologous relationship between this chromosome and the myotonic dystrophy gene region on human chromosome 19. Segregation analyses were used to extend the gene linkage relationships on mouse chromosome 7 by an additional 21 loci. Seven of these genes (Cyp2a, D19F11S1h, Myod-1, Otf-2, Rnu1p70, Rnu2pa, and Xrcc-1) were previously unmapped in the mouse. Several potential mouse chromosome 7 genes (Mel, Hkr-1, Icam-1, Pvs) did not segregate with chromosome 7 markers, and provisional chromosomal assignments were made. This study establishes a detailed molecular genetic linkage map of mouse chromosome 7 that will be useful as a framework for determining linkage relationships of additional molecular markers and for identifying homologous disease genes in mice and humans.

    Funded by: NHGRI NIH HHS: HG00101; NINDS NIH HHS: NS19999

    Genomics 1990;8;3;525-35

  • Expression of recombinant myelin-associated glycoprotein in primary Schwann cells promotes the initial investment of axons by myelinating Schwann cells.

    Owens GC, Boyd CJ, Bunge RP and Salzer JL

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

    Myelin-associated glycoprotein (MAG) is an integral membrane protein expressed by myelinating glial cells that occurs in two developmentally regulated forms with different carboxyterminal cytoplasmic domains (L-MAG and S-MAG). To investigate the role of MAG in myelination a recombinant retrovirus was used to introduce a MAG cDNA (L-MAG form) into primary Schwann cells in vitro. Stably infected populations of cells were obtained that constitutively expressed MAG at the cell surface without the normal requirement for neuronal contact to induce expression. Constitutive expression of L-MAG did not affect myelination. In long term co-culture with purified sensory neurons, the higher level of MAG expression on infected Schwann cells was reduced to control levels on cells that formed myelin. On the other hand, unlike normal Schwann cells, infected Schwann cells associated with nonmyelinated axons or undergoing Wallerian degeneration expressed high levels of MAG. This suggests that a posttranscriptional mechanism modulates MAG expression during myelination. Immunostaining myelinating cultures with an antibody specific to L-MAG showed that L-MAG was normally transiently expressed at the earliest stages of myelination. In short term co-culture with sensory neurons, infected Schwann cells expressing only L-MAG segregated and ensheathed larger axons after 4 d in culture provided that an exogenous basal lamina was supplied. Similar activity was rarely displayed by control Schwann cells correlating with the low level of MAG induction after 4 d. These data strongly suggest that L-MAG promotes the initial investment by Schwann cells of axons destined to be myelinated.

    Funded by: NINDS NIH HHS: NS 19923, NS 26001

    The Journal of cell biology 1990;111;3;1171-82

  • Chromosomal localization of seven members of the murine TGF-beta superfamily suggests close linkage to several morphogenetic mutant loci.

    Dickinson ME, Kobrin MS, Silan CM, Kingsley DM, Justice MJ, Miller DA, Ceci JD, Lock LF, Lee A, Buchberg AM et al.

    Department of Cell Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.

    Chromosomal locations have been assigned to seven members of the TGF-beta superfamily using an interspecific mouse backcross. Probes for the Tgfb-1, -2, and -3, Bmp-2a and -3, and Vgr-1 genes recognized only single loci, whereas the Bmp-2b probe recognized two independently segregating loci (designated Bmp-2b1 and Bmp-2b2). The results show that the seven members of the TGF-beta superfamily map to eight different chromosomes, indicating that the TGF-beta family has become widely dispersed during evolution. Five of the eight loci (Tgfb-1, Bmp-2a, Bmp-2b1, Bmp-2b2, Vgr-1) mapped near mutant loci associated with connective tissue and skeletal disorders, raising the possibility that at least some of these mutations result from defects in TGF-beta-related genes.

    Funded by: NCI NIH HHS: N01-CO-74101; NEI NIH HHS: R01 EY08000-01; NIGMS NIH HHS: GM12721-01; ...

    Genomics 1990;6;3;505-20

  • The syntenic relationship of proximal mouse chromosome 7 and the myotonic dystrophy gene region on human chromosome 19q.

    Saunders AM and Seldin MF

    Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710.

    The syntenic relationship of the myotonic dystrophy (DM) gene region on human chromosome 19q and proximal mouse chromosome 7 was examined using an interspecific backcross between C3H/HeJ-gld/gld mice and Mus spretus. Segregation analyses were used to order homologs of nine human loci linked with the DM gene. Their order from the centromere was Prkcg, [Apoe, Atpa-2, Ckmm, D19S19h, Ercc-2], Cyp2b, Mag, Lhb. Two other murine loci, D7Rp2 and Ngfg, were also positioned within this interval. Homologs for five human chromosome 11 and 15 loci (Calc, Fes, Hras-1, Igflr, Tyr) were localized within an 18-cM span telomeric to Lhb. Comparison of the gene orders indicates an inversion extending from Prkcg through the interval between Mag and Lhb. This study establishes a detailed map of proximal mouse chromosome 7 that will be useful in identifying and determining whether new human chromosome 19 probes are linked to the DM region.

    Funded by: NINDS NIH HHS: NS19999

    Genomics 1990;6;2;324-32

  • cDNA cloning of mouse myelin-associated glycoprotein: a novel alternative splicing pattern.

    Fujita N, Sato S, Kurihara T, Kuwano R, Sakimura K, Inuzuka T, Takahashi Y and Miyatake T

    Department of Neurology, Niigata University, Japan.

    The structures of three forms of mouse myelin-associated glycoprotein mRNAs were determined from full-length cDNA clones. Two forms of mRNAs have been reported to be different by alternate inclusion of exon 2 and 12 in rat brain. One of the three forms of clones obtained here appeared to be a novel mRNA which lacked both the exon 2 and 12 portions, although others were identical splicing patterns to those of rat. Northern blot analysis using specific probes to mRNAs with or without the exon 2 portion in normal and quaking mouse confirmed that the splicing of exon 2 and 12 occurred independently.

    Biochemical and biophysical research communications 1989;165;3;1162-9

  • Developmentally regulated alternative splicing of brain myelin-associated glycoprotein mRNA is lacking in the quaking mouse.

    Fujita N, Sato S, Kurihara T, Inuzuka T, Takahashi Y and Miyatake T

    Department of Neurology, Niigata University, Japan.

    Evidence is presented that expression of the two myelin-associated glycoprotein mRNAs is developmentally regulated in mouse brain. In quaking mouse, the mRNA without a 45-nucleotide exon portion was scarcely expressed throughout development. We conclude that the mechanism of splicing out the 45-nucleotide exon portion is lacking in quaking mouse.

    FEBS letters 1988;232;2;323-7

  • Expression of myelin protein genes in quaking mouse brain.

    Konat G, Trojanowska M, Gantt G and Hogan EL

    Department of Neurology, Medical University of South Carolina, Charleston 29425.

    The expression of myelin proteins in actively myelinating quaking and control brains was studied. RNA was extracted from the brains of 18- and 27-day-old mice and analyzed by northern blot using cDNA probes for proteolipid protein (PLP), basic protein (BP), and myelin-associated glycoprotein (MAG). Two PLP transcripts of 3.2 and 2.4 kb (kilobase) were found, whereas PB and MAG probes hybridized to single regions of 2.2 and 2.5 kb, respectively. No abnormality in the transcript pattern was detectable in the quaking brain at either 18 or 27 days of age. Over this 9-day period the level of PLP and BP message in the control brain decreased by approximately 10%, whereas the level of MAG message decreased by approximately 50%. In the 18-day-old quaking brain the expression of PLP and BP was severely reduced amounting to one-third and one-half of the control values, respectively. The reduction at the age of 27 days was less. On the other hand, the quaking brain produced more MAG mRNA amounting to 1.6- and 3.2-fold control on the 18th and 27th day. The results indicate a reduced expression of the PLP and BP genes and a developmental delay in the mutant, whereas the genetic expression of MAG is enhanced and appears to be progressively dysregulated.

    Funded by: NINDS NIH HHS: NS 12044-12

    Journal of neuroscience research 1988;20;1;19-22

  • Chromosomal localization of human Na+, K+-ATPase alpha- and beta-subunit genes.

    Yang-Feng TL, Schneider JW, Lindgren V, Shull MM, Benz EJ, Lingrel JB and Francke U

    Department of Human Genetics, Yale University School of Medicine, New Haven, Connecticut 06510.

    Na+, K+-ATPase is a heterodimeric enzyme responsible for the active maintenance of sodium and potassium gradients across the plasma membrane. Recently, cDNAs for several tissue-specific isoforms of the larger catalytic alpha-subunit and the smaller beta-subunit have been cloned. We have hybridized rat brain and human kidney cDNA probes, as well as human genomic isoform-specific DNA fragments, to Southern filters containing panels of rodent X human somatic cell hybrid lines. The results obtained have allowed us to assign the loci for the ubiquitously expressed alpha-chain (ATP1A1) to human chromosome 1, region 1p21----cen, and for the alpha 2 isoform that predominates in neural and muscle tissues (ATP1A2) to chromosome 1, region cen----q32. A common PstI RFLP was detected with the ATP1A2 probe. The alpha 3 gene, which is expressed primarily in neural tissues (ATP1A3), was assigned to human chromosome 19. A fourth alpha gene of unknown function (alpha D) that was isolated by molecular cloning (ATP1AL1) was mapped to chromosome 13. Although evidence to date had suggested a single gene for the beta-subunit, we found hybridizing restriction fragments derived from two different human chromosomes. On the basis of knowledge of conserved linkage groups on human and murine chromosomes, we propose that the coding gene ATP 1B is located on the long arm of human chromosome 1 and that the sequence on human chromosome 4 (ATP 1BL1) is either a related gene or a pseudogene.

    Funded by: NHLBI NIH HHS: HL28573; NIGMS NIH HHS: GM26105, T32GM07439

    Genomics 1988;2;2;128-38

  • Chromosomal location of the mouse gene that encodes the myelin-associated glycoproteins.

    D'Eustachio P, Colman DR and Salzer JL

    Department of Biochemistry, New York University School of Medicine, NY 10016.

    The two myelin-associated glycoprotein (MAG) species, designated large MAG (L-MAG) and small MAG (S-MAG), are believed to be generated by differential splicing from a single RNA transcript. We have now defined the genetic locus encoding the two MAG proteins in the mouse. Analysis of a panel of interspecies somatic cell hybrids indicated that all MAG coding sequences reside on chromosome 7. Following the inheritance of a restriction fragment length polymorphism associated with MAG coding sequences allowed the locus to be positioned 0.5 centimorgans from the locus Abpa (androgen binding protein alpha) on proximal chromosome 7. These data strongly support the hypothesis that a single gene encodes the two MAG proteins, and we propose the name Mag for this locus. This localization places Mag in close proximity to the neurological mutant locus qv (quivering) and raises the possibility of a functional relationship or identity between Mag and qv. However, an analysis of the MAG gene, its RNA transcripts, and its protein products revealed no abnormalities in homozygous qv mutant mice, suggesting that this chromosomal linkage is not etiologically significant.

    Funded by: NINDS NIH HHS: NS 000905, NS 20147

    Journal of neurochemistry 1988;50;2;589-93

  • The myelin-associated glycoprotein gene: mapping to human chromosome 19 and mouse chromosome 7 and expression in quivering mice.

    Barton DE, Arquint M, Roder J, Dunn R and Francke U

    Department of Human Genetics, Yale University School of Medicine, New Haven, Connecticut 06510.

    Myelin-associated glycoprotein (MAG), a membrane glycoprotein of 100 kDa, is thought to be involved in the process of myelination. A cDNA encoding the amino-terminal half of rat MAG has recently been isolated and sequenced. We have used this cDNA in Southern blot analysis of DNA from 32 somatic cell hybrids to assign the human locus for MAG to chromosome 19 and the mouse locus to chromosome 7. Since the region of mouse chromosome 7-known to contain several other genes that are homologous to genes on human chromosome 19-also carries the quivering (qv) locus, we considered the possibility that a mutation in the MAG gene could be responsible for this neurological disorder. While MAG-specific DNA restriction fragments, mRNA, and protein from qv/qv mice were apparently normal in size and abundance, we have not ruled out the possibility that qv could be caused by a point mutation in the MAG gene.

    Funded by: NIGMS NIH HHS: GM26105

    Genomics 1987;1;2;107-12

  • Comparison of the distribution of Na+,K+-ATPase and myelin-associated glycoprotein (MAG) in the optic nerve, spinal cord and trigeminal ganglion of shiverer (shi/shi) and control (+/+) mice.

    Sheedlo HJ and Siegel GJ

    Na+,K+ ATPase and myelin-associated glycoprotein (MAG) were studied by immunocytochemistry on paraffin sections of the spinal cord, optic nerve and trigeminal ganglion of adult control (+/+) and CNS myelin-deficient shiverer (shi/shi) mice. Immunostaining for Na+, K+-ATPase outlined the periphery of nerve fibers in the spinal cord white matter, optic nerve and trigeminal ganglion of +/+ and shi/shi mice. Immunostaining for Na+,K+-ATPase appeared somewhat denser in the optic nerve and spinal cord lateral funiculi of shi/shi than in +/+ mice. In addition, immunostaining for Na+,K+-ATPase was demonstrated at the plasmalemma of presumed satellite cells situated at the periphery of ganglion cell bodies in the trigeminal ganglion of both species of mice. Immunostaining for MAG was localized along the periphery of nerve fibers in the spinal cord funiculi (with little immunostaining within gray horns), optic nerve and trigeminal ganglion of both +/+ and shi/shi mice. The major differences between shi/shi and +/+ mice were that the number of MAG-immunostained nerve fibers was greatly reduced in the spinal cord funiculi and the density of immunostaining was slightly increased in the optic nerve of shi/shi mice. The numbers of MAG-immunostained nerve fibers in trigeminal ganglion were similar in both species. Also, the cytoplasm of some oligodendrocyte-like cells was found densely immunostained for MAG in the spinal cord and optic nerve of shi/shi mice, but not of +/+ mice. This light microscopic study provides evidence that the defective shiverer gene leads to a decrease in MAG deposition and to aggregations of MAG-like material within perikarya of oligodendrocyte-like cells in regions of the CNS.

    Funded by: NINDS NIH HHS: NS 07222, NS 15935

    Brain research 1987;415;1;105-14

  • Molecular cloning and primary structure of myelin-associated glycoprotein.

    Arquint M, Roder J, Chia LS, Down J, Wilkinson D, Bayley H, Braun P and Dunn R

    Myelin-associated glycoprotein (MAG) may play a role in the cellular interactions leading to myelination. Using monoclonal antibodies and conventional antisera against MAG, we have isolated a cDNA clone from an expression library prepared from rat brain mRNA. The identity of the clone was confirmed by the exact match between its nucleotide sequence and two peptide sequences of 13 and 9 amino acids that we obtained by Edman degradation of two CNBr fragments of MAG. The cDNA clone hybridized to two size species of mRNA in rat approximately 3.5 kilobases in length. These mRNAs were present in brain but not liver and were expressed most abundantly at the time of active myelination (day 14). The mRNA for MAG was present at barely detectable levels in hypomyelinating jimpy mice compared to normal littermate controls. Therefore the MAG cDNA clone is both brain and myelin specific. DNA sequence analysis revealed that our MAG cDNA was derived from the same mRNA as clone p1B236, a randomly selected, brain-specific, partial cDNA isolated by Sutcliffe et al. [Sutcliffe, J. G., Milner, R. J., Shinnick, T. M. & Bloom, F. E. (1983) Cell 33, 671-682]. Analysis of the predicted protein sequence suggests that MAG has a long extracellular domain (499 amino acids), followed by a short transmembrane segment (20 amino acids) and an intracellular carboxyl-terminal domain (90 amino acids). The molecule has several glycosylation sites, three internal repeats homologous to a repeat in the neural cell adhesion molecule (N-CAM), and sites for phosphorylation near the carboxyl terminus. The primary structure reported here provides a molecular framework for further investigations into the function of the MAG molecule.

    Proceedings of the National Academy of Sciences of the United States of America 1987;84;2;600-4

  • G proteins: transducers of receptor-generated signals.

    Gilman AG

    Funded by: NIGMS NIH HHS: GM34497

    Annual review of biochemistry 1987;56;615-49

  • Sequence of the alpha subunit of photoreceptor G protein: homologies between transducin, ras, and elongation factors.

    Lochrie MA, Hurley JB and Simon MI

    A bovine retinal complementary DNA clone encoding the alpha subunit of transducin (T alpha) was isolated with the use of synthetic oligodeoxynucleotides as probes, and the complete nucleotide sequence of the insert was determined. THe predicted protein sequence of 354 amino acids includes the known sequences of four tryptic peptides and sequences adjacent to the residues that undergo adenosine diphosphate ribosylation by cholera toxin and pertussis toxin. On the basis of homologies to other proteins, such as the elongation factors of protein synthesis and the ras oncogene proteins, regions are identified that are predicted to be acylated and involved in guanine nucleotide binding and hydrolysis. Amino acid sequence similarity between T alpha and ras is confined to these regions of the molecules.

    Science (New York, N.Y.) 1985;228;4695;96-9

  • Myelin-associated glycoprotein and other proteins in Trembler mice.

    Inuzuka T, Quarles RH, Heath J and Trapp BD

    The myelin-associated glycoprotein (MAG) and other myelin proteins were quantitated in homogenates of whole sciatic nerve from adult and 20-day-old Trember mice. In the nerves of adult mice, the concentration of MAG was increased from 1.1 ng/micrograms of total protein in the controls to 1.4 ng/micrograms protein in the Tremblers. By contrast, the concentrations of P0 glycoprotein and myelin basic proteins were reduced to 27% and 20% of control levels, respectively. Immunoblots demonstrated that P2 was also greatly reduced in the Trembler nerves. The specific activity of 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) was 65% of the control level. Immunoblot analysis showed that MAG had a higher than normal apparent Mr in the sciatic nerves of the Trembler mice, but its apparent Mr was normal in the brains of these mutants. In 20-day-old Tremblers, the P0 and myelin basic protein were reduced slightly less to about 40% of the level in the nerves of age-matched controls. CNP and MAG levels were not significantly different from those in controls, and MAG exhibited a shift toward higher apparent Mr similar to that in the adults. The maintenance of high MAG levels despite the severe deficit of myelin, as reflected by the decrease of the major myelin proteins, is consistent with the immunocytochemical localization of MAG in periaxonal Schwann cell membranes, Schmidt-Lantermann incisures, lateral loops, and the outer mesaxon and its absence from compact myelin. The abnormal form of MAG in the peripheral nervous system (PNS) of the Trembler mice may contribute to the pathology in this mutant.

    Journal of neurochemistry 1985;44;3;793-7

  • G proteins and dual control of adenylate cyclase.

    Gilman AG

    Funded by: NINDS NIH HHS: NS18153

    Cell 1984;36;3;577-9

Gene lists (4)

Gene List Source Species Name Description Gene count
L00000001 G2C Mus musculus Mouse PSD Mouse PSD adapted from Collins et al (2006) 1080
L00000008 G2C Mus musculus Mouse PSP Mouse PSP adapted from Collins et al (2006) 1121
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
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EUROSPIN (FP7-HEALTH-241498), SynSys (FP7-HEALTH-242167) and GENCODYS (FP7-HEALTH-241995).

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