G2Cdb::Gene report

Gene id
Gene symbol
Homo sapiens
optic atrophy 1 (autosomal dominant)
G00000782 (Mus musculus)

Databases (7)

ENSG00000198836 (Ensembl human gene)
4976 (Entrez Gene)
1199 (G2Cdb plasticity & disease)
OPA1 (GeneCards)
605290 (OMIM)
Marker Symbol
HGNC:8140 (HGNC)
Protein Sequence
O60313 (UniProt)

Synonyms (5)

  • FLJ12460
  • KIAA0567
  • MGM1
  • NPG
  • NTG

Literature (92)

Pubmed - other

  • Alu-element insertion in an OPA1 intron sequence associated with autosomal dominant optic atrophy.

    Gallus GN, Cardaioli E, Rufa A, Da Pozzo P, Bianchi S, D'Eramo C, Collura M, Tumino M, Pavone L and Federico A

    Department of Neurological, Neurosurgical and Behavioural Sciences, University of Siena, 53100 Siena, Italy.

    Purpose: Autosomal dominant optic atrophy (ADOA) is the most common form of hereditary optic neuropathy caused by mutations in the optic atrophy 1 (OPA1) gene. It is characterized by insidious onset with a selective degeneration of retinal ganglion cells, variable loss of visual acuity, temporal optic nerve pallor, tritanopia, and development of central, paracentral, or cecocentral scotomas. Here we describe the clinical and molecular findings in a large Italian family with ADOA.

    Methods: Routine ophthalmologic examination and direct sequencing of all coding regions of the OPA1 gene were performed. Further characterization of a new OPA1 gene insertion was performed by reverse transcription-PCR (RT-PCR) of RNA from patients and control subjects.

    Results: We identified an Alu-element insertion located in intron 7 of OPA1 causing an in-frame deletion of exon 8 in 18 family members.

    Conclusions: The predicted consequence of this mutation is the loss of the guanosine triphosphatase (GTPase) activity of OPA1. Alu insertions have been reported in the literature as causing human genetic disease. However, this is the first report of a pathogenic OPA1 gene mutation resulting from an Alu insertion.

    Molecular vision 2010;16;178-83

  • Novel mutations of the OPA1 gene in Chinese dominant optic atrophy.

    Yen MY, Wang AG, Lin YC, Fann MJ and Hsiao KJ

    Department of Ophthalmology, Taipei Veterans General Hospital, Taipei, Taiwan. myyen@vghtpe.gov.tw

    Purpose: To investigate OPA1 gene mutations in Chinese patients with autosomal dominant optic atrophy and sporadic optic atrophy.

    Design: Molecular genetic studies and observational case series.

    Participants: Twenty-four patients from 10 unrelated Chinese pedigrees of autosomal-dominant optic atrophy, 35 isolated cases with bilateral optic atrophy of unknown cause, and 50 unrelated normal controls.

    Methods: Genomic DNA was extracted from peripheral blood leukocytes. All 28 coding exons of the OPA1 gene and flanking intron splice sites were sequenced. Putative mutations were reexamined for segregation in the respective families by direct sequencing. Further characterization of selected splicing site mutations was performed by reverse transcription-polymerase chain reaction (PCR) of each patient's leukocyte mRNA.

    Direct sequencing of the OPA1 gene.

    Results: Four OPA1 gene mutations were detected, including 2 splicing site mutations (c.1065+2T>C on intron 10 and c.1212+2insT on intron 12), 1 deletion (c.1776_1778delACT on exon 19), and 1 missense mutation (c.2846 T>C on exon 28). The c.1212+2insT, c.1776_1778delACT, and c.2846T>C mutations were newly identified OPA1 mutations. Reverse transcription (RT)-PCR and direct sequencing revealed that the splicing site mutations on c.1065+2T>C and c.1212+2insT caused skipping of exons 10 and 12, respectively. The c.1776_1778delACT mutation led to a deletion of the Leu amino acid on residue 593. OPA1 mutations were found in 4 of 10 familial cases (40 %) and in 1 of 35 sporadic cases of optic atrophy.

    Conclusions: OPA1 gene mutations are causative in Chinese autosomal-dominant optic atrophy and sporadic optic atrophy. Screening for OPA1 gene mutations in patients with childhood onset optic atrophy who have no affected relatives is useful in making the diagnosis.

    Ophthalmology 2010;117;2;392-6.e1

  • Mutation of OPA1 gene causes deafness by affecting function of auditory nerve terminals.

    Huang T, Santarelli R and Starr A

    Department of Pediatrics, University of California, Irvine, CA, USA.

    Autosomal dominant optic atrophy (DOA) is a retinal neuronal degenerative disease characterized by a progressive bilateral visual loss. We report on two affected members of a family with dominantly inherited neuropathy of both optic and auditory nerves expressed by impaired visual acuity, moderate pure tone hearing loss, and marked loss of speech perception. We investigated cochlear abnormalities accompanying the hearing loss and the effects of cochlear implantation. We sequenced OPA1 gene and recorded cochlear receptor and neural potentials before cochlear implantation. Genetic analysis identified R445H mutation in OPA1 gene. Audiological studies showed preserved cochlear receptor outer hair cell activities (otoacoustic emissions) and absent or abnormally delayed auditory brainstem responses (ABRs). Trans-tympanic electrocochleography (ECochG) showed prolonged low amplitude negative potentials without auditory nerve compound action potentials. The latency of onset of the cochlear potentials was within the normal range found for inner hair cell summating receptor potentials. The duration of the negative potential was reduced to normal during rapid stimulation consistent with adaptation of neural sources generating prolonged cochlear potentials. Both subjects had cochlear implants placed with restoration of hearing thresholds, speech perception, and synchronous activity in auditory brainstem pathways. The results suggest that deafness accompanying this OPA1 mutation is due to altered function of terminal unmyelinated portions of auditory nerve. Electrical stimulation of the cochlea activated proximal myelinated portions of auditory nerve to restore hearing.

    Funded by: NEI NIH HHS: NEI 1R01EY018876; NIDCD NIH HHS: DC-02168

    Brain research 2009;1300;97-104

  • Mitochondrial OPA1, apoptosis, and heart failure.

    Chen L, Gong Q, Stice JP and Knowlton AA

    Molecular and Cellular Cardiology, Department of Medicine, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.

    Aims: Mitochondrial fusion and fission are essential processes for preservation of normal mitochondrial function. We hypothesized that fusion proteins would be decreased in heart failure (HF), as the mitochondria in HF have been reported to be small and dysfunctional.

    Expression of optic atrophy 1 (OPA1), a mitochondrial fusion protein, was decreased in both human and rat HF, as observed by western blotting. OPA1 is important for maintaining normal cristae structure and function, for preserving the inner membrane structure and for protecting cells from apoptosis. Confocal and electron microscopy studies demonstrated that the mitochondria in the failing hearts were small and fragmented, consistent with decreased fusion. OPA1 mRNA levels did not differ between failing and normal hearts, suggesting post-transcriptional control. Simulated ischaemia in the cardiac myogenic cell line H9c2 cells reduced OPA protein levels. Reduction of OPA1 expression with shRNA resulted in increased apoptosis and fragmentation of the mitochondria. Overexpression of OPA1 increased mitochondrial tubularity, but did not protect against simulated ischaemia-induced apoptosis. Cytochrome c release from the mitochondria was increased both with reduction in OPA1 and with overexpression of OPA1.

    Conclusion: This is the first report, to our knowledge, of changes in mitochondrial fusion/fission proteins in cardiovascular disease. These changes have implications for mitochondrial function and apoptosis, contributing to the cell loss which is part of the downward progression of the failing heart.

    Funded by: NHLBI NIH HHS: HL077281, HL079071, R01 HL077281, R01 HL079071

    Cardiovascular research 2009;84;1;91-9

  • Evaluation of nine candidate genes in patients with normal tension glaucoma: a case control study.

    Wolf C, Gramer E, Müller-Myhsok B, Pasutto F, Reinthal E, Wissinger B and Weisschuh N

    Centre for Ophthalmology, Institute for Ophthalmic Research, Molecular Genetics Laboratory, Tuebingen, Germany. cwolf@mpipsykl.mpg.de

    Background: Normal tension glaucoma is a major subtype of glaucoma, associated with intraocular pressures that are within the statistically normal range of the population. Monogenic forms following classical inheritance patterns are rare in this glaucoma subtype. Instead, multigenic inheritance is proposed for the majority of cases. The present study tested common sequence variants in candidate genes for association with normal tension glaucoma in the German population.

    Methods: Ninety-eight SNPs were selected to tag the common genetic variation in nine genes, namely OPTN (optineurin), RDX (radixin), SNX16 (sorting nexin 16), OPA1 (optic atrophy 1), MFN1 (mitofusin 1), MFN2 (mitofusin 2), PARL (presenilin associated, rhomboid-like), SOD2 (superoxide dismutase 2, mitochondrial) and CYP1B1 (cytochrome P450, family 1, subfamily B, polypeptide 1). These SNPs were genotyped in 285 cases and 282 fully evaluated matched controls. Statistical analyses comprised single polymorphism association as well as haplogroup based association testing.

    Results: Results suggested that genetic variation in five of the candidate genes (RDX, SNX16, OPA1, SOD2 and CYP1B1) is unlikely to confer major risk to develop normal tension glaucoma in the German population. In contrast, we observed a trend towards association of single SNPs in OPTN, MFN1, MFN2 and PARL. The SNPs of OPTN, MFN2 and PARL were further analysed by multimarker haplotype-based association testing. We identified a risk haplotype being more frequent in patients and a vice versa situation for the complementary protective haplotype in each of the three genes.

    Conclusion: Common variants of OPTN, PARL, MFN1 and MFN2 should be analysed in other cohorts to confirm their involvement in normal tension glaucoma.

    BMC medical genetics 2009;10;91

  • Loss of Drp1 function alters OPA1 processing and changes mitochondrial membrane organization.

    Möpert K, Hajek P, Frank S, Chen C, Kaufmann J and Santel A

    Silence Therapeutics AG, 13125 Berlin, Germany.

    RNAi mediated loss of Drp1 function changes mitochondrial morphology in cultured HeLa and HUVEC cells by shifting the balance of mitochondrial fission and fusion towards unopposed fusion. Over time, inhibition of Drp1 expression results in the formation of a highly branched mitochondrial network along with "bulge"-like structures. These changes in mitochondrial morphology are accompanied by a reduction in levels of Mitofusin 1 (Mfn1) and 2 (Mfn2) and a modified proteolytic processing of OPA1 isoforms, resulting in the inhibition of cell proliferation. In addition, our data imply that bulge formation is driven by Mfn1 action along with particular proteolytic short-OPA1 (s-OPA1) variants: Loss of Mfn2 in the absence of Drp1 results in an increase of Mfn1 levels along with processed s-OPA1-isoforms, thereby enhancing continuous "fusion" and bulge formation. Moreover, bulge formation might reflect s-OPA1 mitochondrial membrane remodeling activity, resulting in the compartmentalization of cytochrome c deposits. The proteins Yme1L and PHB2 appeared not associated with the observed enhanced OPA1 proteolysis upon RNAi of Drp1, suggesting the existence of other OPA1 processing controlling proteins. Taken together, Drp1 appears to affect the activity of the mitochondrial fusion machinery by unbalancing the protein levels of mitofusins and OPA1.

    Experimental cell research 2009;315;13;2165-80

  • OPA1-related dominant optic atrophy is not strongly influenced by mitochondrial DNA background.

    Pierron D, Ferré M, Rocher C, Chevrollier A, Murail P, Thoraval D, Amati-Bonneau P, Reynier P and Letellier T

    Université Bordeaux 1, Laboratoire d'Anthropologie des Populations du Passé, UMR 5199 PACEA, 33400 Talence, France. d.pierron@anthropologie.u-bordeaux1.fr

    Background: Leber's hereditary optic neuropathy (LHON) and autosomal dominant optic atrophy (ADOA) are the most frequent forms of hereditary optic neuropathies. LHON is associated with mitochondrial DNA (mtDNA) mutations whereas ADOA is mainly due to mutations in the OPA1 gene that encodes a mitochondrial protein involved in the mitochondrial inner membrane remodeling. A striking influence of mtDNA haplogroup J on LHON expression has been demonstrated and it has been recently suggested that this haplogroup could also influence ADOA expression. In this study, we have tested the influence of mtDNA backgrounds on OPA1 mutations.

    Methods: To define the relationships between OPA1 mutations and mtDNA backgrounds, we determined the haplogroup affiliation of 41 French patients affected by OPA1-related ADOA by control-region sequencing and RFLP survey of their mtDNAs.

    Results: The comparison between patient and reference populations did not revealed any significant difference.

    Conclusion: Our results argue against a strong influence of mtDNA background on ADOA expression. These data allow to conclude that OPA1 could be considered as a "severe mutation", directly responsible of the optic atrophy, whereas OPA1-negative ADOA and LHON mutations need an external factor(s) to express the pathology (i.e. synergistic interaction with mitochondrial background).

    BMC medical genetics 2009;10;70

  • Molecular screening of 980 cases of suspected hereditary optic neuropathy with a report on 77 novel OPA1 mutations.

    Ferré M, Bonneau D, Milea D, Chevrollier A, Verny C, Dollfus H, Ayuso C, Defoort S, Vignal C, Zanlonghi X, Charlin JF, Kaplan J, Odent S, Hamel CP, Procaccio V, Reynier P and Amati-Bonneau P

    INSERM, U694, Angers, F-49000, France. MaFerre@chu-angers.fr

    We report the results of molecular screening in 980 patients carried out as part of their work-up for suspected hereditary optic neuropathies. All the patients were investigated for Leber's hereditary optic neuropathy (LHON) and autosomal dominant optic atrophy (ADOA), by searching for the ten primary LHON-causing mtDNA mutations and examining the entire coding sequences of the OPA1 and OPA3 genes, the two genes currently identified in ADOA. Molecular defects were identified in 440 patients (45% of screened patients). Among these, 295 patients (67%) had an OPA1 mutation, 131 patients (30%) had an mtDNA mutation, and 14 patients (3%), belonging to three unrelated families, had an OPA3 mutation. Interestingly, OPA1 mutations were found in 157 (40%) of the 392 apparently sporadic cases of optic atrophy. The eOPA1 locus-specific database now contains a total of 204 OPA1 mutations, including 77 novel OPA1 mutations reported here. The statistical analysis of this large set of mutations has led us to propose a diagnostic strategy that should help with the molecular work-up of optic neuropathies. Our results highlight the importance of investigating LHON-causing mtDNA mutations as well as OPA1 and OPA3 mutations in cases of suspected hereditary optic neuropathy, even in absence of a family history of the disease.

    Human mutation 2009;30;7;E692-705

  • Prefrontal cortex shotgun proteome analysis reveals altered calcium homeostasis and immune system imbalance in schizophrenia.

    Martins-de-Souza D, Gattaz WF, Schmitt A, Rewerts C, Maccarrone G, Dias-Neto E and Turck CW

    Laboratório de Neurociências, Instituto de Psiquiatria, Universidade de São Paulo, Rua. Dr. Ovidio Pires de Campos, no 785, Consolação, São Paulo, SP 05403-010, Brazil.

    Schizophrenia is a complex disease, likely to be caused by a combination of serial alterations in a number of genes and environmental factors. The dorsolateral prefrontal cortex (Brodmann's Area 46) is involved in schizophrenia and executes high-level functions such as working memory, differentiation of conflicting thoughts, determination of right and wrong concepts and attitudes, correct social behavior and personality expression. Global proteomic analysis of post-mortem dorsolateral prefrontal cortex samples from schizophrenia patients and non-schizophrenic individuals was performed using stable isotope labeling and shotgun proteomics. The analysis resulted in the identification of 1,261 proteins, 84 of which showed statistically significant differential expression, reinforcing previous data supporting the involvement of the immune system, calcium homeostasis, cytoskeleton assembly, and energy metabolism in schizophrenia. In addition a number of new potential markers were found that may contribute to the understanding of the pathogenesis of this complex disease.

    European archives of psychiatry and clinical neuroscience 2009;259;3;151-63

  • Genomic rearrangements in OPA1 are frequent in patients with autosomal dominant optic atrophy.

    Fuhrmann N, Alavi MV, Bitoun P, Woernle S, Auburger G, Leo-Kottler B, Yu-Wai-Man P, Chinnery P and Wissinger B

    Molecular Genetics Laboratory, Centre for Ophthalmology, Röntgenweg 11, Tübingen, Germany.

    Introduction: Autosomal dominant optic atrophy (ADOA) is considered as the most common form of hereditary optic neuropathy. Although genetic linkage studies point to the OPA1 locus on chromosome 3q28-q29 as by far the most common gene locus, previous screening studies-based on sequencing of the coding exons-detected OPA1 mutations in only 32-70% of ADOA patients. We therefore hypothesised that larger deletions or duplications that remained undetected in previous screening approaches may substantially contribute to the prevalence of OPA1 mutations in ADOA.

    Methods: 42 independent ADOA patients were analysed for the presence of genomic rearrangements in OPA1 by means of multiplex ligation probe amplification (MLPA). Deletions or duplications were confirmed either by long distance polymerase chain reaction (PCR) and breakpoint sequencing or loss of heterozygosity analyses with flanking microsatellite markers. Patients underwent ophthalmological examination including visual acuity, colour vision testings, perimetry and funduscopy.

    Results: We identified genomic rearrangements in 8 of 42 patients, including single exon deletions of exon 9 and exon 24, respectively, a deletion of exons 1-5, two different deletions of the complete OPA1 gene as well as a duplication of the exons 7-9, with the latter being present in three unrelated families. Patients' phenotypes were highly variable, similar to patients with point mutation in OPA1.

    Discussion: Our findings show that gross genomic aberrations at the OPA1 gene locus are frequent in ADOA and substantially contribute to the spectrum and prevalence of OPA1 mutations in ADOA patients. They further strengthen the hypothesis that haploinsufficiency is a major pathomechanism in OPA1 associated ADOA.

    Funded by: Wellcome Trust: 084980

    Journal of medical genetics 2009;46;2;136-44

  • Caspases indirectly regulate cleavage of the mitochondrial fusion GTPase OPA1 in neurons undergoing apoptosis.

    Loucks FA, Schroeder EK, Zommer AE, Hilger S, Kelsey NA, Bouchard RJ, Blackstone C, Brewster JL and Linseman DA

    Research Service, Veterans Affairs Medical Center, Denver, Colorado, USA.

    The critical processes of mitochondrial fission and fusion are regulated by members of the dynamin family of GTPases. Imbalances in mitochondrial fission and fusion contribute to neuronal cell death. For example, increased fission mediated by the dynamin-related GTPase, Drp1, or decreased fusion resulting from inactivating mutations in the OPA1 GTPase, causes neuronal apoptosis and/or neurodegeneration. Recent studies indicate that post-translational processing regulates OPA1 function in non-neuronal cells and moreover, aberrant processing of OPA1 is induced during apoptosis. To date, the post-translational processing of OPA1 during neuronal apoptosis has not been examined. Here, we show that cerebellar granule neurons (CGNs) or neuroblastoma cells exposed to pro-apoptotic stressors display a novel N-terminal cleavage of OPA1 which is blocked by either pan-caspase or caspase-8 selective inhibitors. OPA1 cleavage occurs concurrently with mitochondrial fragmentation and cytochrome c release in CGNs deprived of depolarizing potassium (5K condition). Although a caspase-8 selective inhibitor prevents both 5K-induced OPA1 cleavage and mitochondrial fragmentation, recombinant caspase-8 fails to cleave OPA1 in vitro. In marked contrast, either caspase-8 or caspase-3 stimulates OPA1 cleavage in digitonin-permeabilized rat brain mitochondria, suggesting that OPA1 is cleaved by an intermembrane space protease which is regulated by active caspases. Finally, the N-terminal truncation of OPA1 induced during neuronal apoptosis removes an essential residue (K301) within the GTPase domain. These data are the first to demonstrate OPA1 cleavage during neuronal apoptosis and they implicate caspases as indirect regulators of OPA1 processing in degenerating neurons.

    Funded by: NIGMS NIH HHS: R15 GM065139-02A1

    Brain research 2009;1250;63-74

  • Acute and late-onset optic atrophy due to a novel OPA1 mutation leading to a mitochondrial coupling defect.

    Nochez Y, Arsene S, Gueguen N, Chevrollier A, Ferré M, Guillet V, Desquiret V, Toutain A, Bonneau D, Procaccio V, Amati-Bonneau P, Pisella PJ and Reynier P

    Centre Hospitalier Universitaire de Tours, Service d'Ophtalmologie, Tours, France. yannick.nochez@free.fr

    Purpose: Autosomal dominant optic atrophy (ADOA, OMIM 165500), an inherited optic neuropathy that leads to retinal ganglion cell degeneration and reduced visual acuity during the early decades of life, is mainly associated with mutations in the OPA1 gene. Here we report a novel ADOA phenotype associated with a new pathogenic OPA1 gene mutation.

    Methods: The patient, a 62-year-old woman, was referred for acute, painless, and severe visual loss in her right eye. Acute visual loss in her left eye occurred a year after initial presentation. MRI confirmed the diagnosis of isolated atrophic bilateral optic neuropathy. We performed DNA sequencing of the entire coding sequence and the exon/intron junctions of the OPA1 gene, and we searched for the mitochondrial DNA mutations responsible for Leber hereditary optic atrophy by sequencing entirely mitochondrial DNA. Mitochondrial respiratory chain complex activity and mitochondrial morphology were investigated in skin fibroblasts from the patient and controls.

    Results: We identified a novel heterozygous missense mutation (c.2794C>T) in exon 27 of the OPA1 gene, resulting in an amino acid change (p.R932C) in the protein. This mutation, which affects a highly conserved amino acids, has not been previously reported, and was absent in 400 control chromosomes. Mitochondrial DNA sequence analysis did not reveal any mutation associated with Leber hereditary optic neuropathy or any pathogenic mutations. The investigation of skin fibroblasts from the patient revealed a coupling defect of oxidative phosphorylation and a larger proportion of short mitochondria than in controls.

    Conclusions: The presence of an OPA1 mutation indicates that this sporadic, late-onset acute case of optic neuropathy is related to ADOA and to a mitochondrial energetic defect. This suggests that the mutational screening of the OPA1 gene would be justified in atypical cases of optic nerve atrophy with no evident cause.

    Molecular vision 2009;15;598-608

  • OPA1 in multiple mitochondrial DNA deletion disorders.

    Stewart JD, Hudson G, Yu-Wai-Man P, Blakeley EL, He L, Horvath R, Maddison P, Wright A, Griffiths PG, Turnbull DM, Taylor RW and Chinnery PF

    Mitochondrial Research Group, School of Neurology, Neurobiology and Psychiatry, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.

    Funded by: Department of Health; Medical Research Council: G0701386, MC_U127584475; Wellcome Trust: 074454

    Neurology 2008;71;22;1829-31

  • A novel deletion in the GTPase domain of OPA1 causes defects in mitochondrial morphology and distribution, but not in function.

    Spinazzi M, Cazzola S, Bortolozzi M, Baracca A, Loro E, Casarin A, Solaini G, Sgarbi G, Casalena G, Cenacchi G, Malena A, Frezza C, Carrara F, Angelini C, Scorrano L, Salviati L and Vergani L

    Neurosciences Department, University of Padova, Italy. marco.spinazzi@unipd.it

    Autosomal dominant optic atrophy (ADOA), the commonest cause of inherited optic atrophy, is caused by mutations in the ubiquitously expressed gene optic atrophy 1 (OPA1), involved in fusion and biogenesis of the inner membrane of mitochondria. Bioenergetic failure, mitochondrial network abnormalities and increased apoptosis have all been proposed as possible causal factors. However, their relative contribution to pathogenesis as well as the prominent susceptibility of the retinal ganglion cell (RGC) in this disease remains uncertain. Here we identify a novel deletion of OPA1 gene in the GTPase domain in three patients affected by ADOA. Muscle biopsy of the patients showed neurogenic atrophy and abnormal morphology and distribution of mitochondria. Confocal microscopy revealed increased mitochondrial fragmentation in fibroblasts as well as in myotubes, where mitochondria were also unevenly distributed, with clustered organelles alternating with areas where mitochondria were sparse. These abnormalities were not associated with altered bioenergetics or increased susceptibility to pro-apoptotic stimuli. Therefore, changes in mitochondrial shape and distribution can be independent of other reported effects of OPA1 mutations, and therefore may be the primary cause of the disease. The arrangement of mitochondria in RGCs, which degenerate in ADOA, may be exquisitely sensitive to disturbance, and this may lead to bioenergetic crisis and/or induction of apoptosis. Our results highlight the importance of mitochondrial dynamics in the disease per se, and point to the loss of the fine positioning of mitochondria in the axons of RGCs as a possible explanation for their predominant degeneration in ADOA.

    Funded by: Telethon: GTB07001, TCR07002

    Human molecular genetics 2008;17;21;3291-302

  • The natural history of OPA1-related autosomal dominant optic atrophy.

    Cohn AC, Toomes C, Hewitt AW, Kearns LS, Inglehearn CF, Craig JE and Mackey DA

    Centre for Eye Research Australia, University of Melbourne, Department of Ophthalmology, Royal Victorian Eye and Ear Hospital, Melbourne, Australia.

    Autosomal dominant optic atrophy (ADOA) is a genetically heterogenous disease. However, a large proportion of this disease is accounted for by mutations in OPA1. The aim of this longitudinal study was to investigate disease progression in Australian ADOA patients with confirmed OPA1 mutations.

    Methods: Probands with characteristic clinical findings of ADOA were screened for OPA1 mutations, and relatives of identified mutation carriers were invited to participate. Disease progression was determined by sequential examination or using historical records over a mean of 9.6 (range 1-42) years.

    Results: OPA1 mutation carriers (n = 158) were identified in 11 ADOA pedigrees. Sixty-nine mutation carriers were available for longitudinal follow-up. Using the right eye as the default, best-corrected visual acuity (BCVAR) remained unchanged (defined as visual acuity at or within one line of original measurement) in 43 patients (62%). BCVAR worsened by 2 lines in 13 patients (19%). BCVAR deteriorated by more than 2 lines in six patients (9%). Ten per cent of patients had an improvement in visual acuity. Mean time to follow-up was 9.6 years with the mean visual acuity being 6/18 for both the initial and subsequent measurements. There was no statistical significance in the rate of BCVAR loss across different OPA1 mutations (p = 0.55).

    Conclusion: OPA1-related ADOA generally progresses slowly and functional visual acuity is usually maintained. Longitudinal disease studies are important to enable appropriate counselling of patients. This study enables a better understanding of the natural history of ADOA.

    Funded by: Wellcome Trust

    The British journal of ophthalmology 2008;92;10;1333-6

  • Mitochondrial oxidative phosphorylation in autosomal dominant optic atrophy.

    Mayorov VI, Lowrey AJ, Biousse V, Newman NJ, Cline SD and Brown MD

    Division of Basic Medical Sciences, Mercer University School of Medicine, Macon, GA 31207, USA. mayorov_vi@mercer.edu

    Background: Autosomal dominant optic atrophy (ADOA), a form of progressive bilateral blindness due to loss of retinal ganglion cells and optic nerve deterioration, arises predominantly from mutations in the nuclear gene for the mitochondrial GTPase, OPA1. OPA1 localizes to mitochondrial cristae in the inner membrane where electron transport chain complexes are enriched. While OPA1 has been characterized for its role in mitochondrial cristae structure and organelle fusion, possible effects of OPA1 on mitochondrial function have not been determined.

    Results: Mitochondria from six ADOA patients bearing OPA1 mutations and ten ADOA patients with unidentified gene mutations were studied for respiratory capacity and electron transport complex function. Results suggest that the nuclear DNA mutations that give rise to ADOA in our patient population do not alter mitochondrial electron transport.

    Conclusion: We conclude that the pathophysiology of ADOA likely stems from the role of OPA1 in mitochondrial structure or fusion and not from OPA1 support of oxidative phosphorylation.

    Funded by: NEI NIH HHS: EY014393, R01 EY014393, R01 EY014393-03

    BMC biochemistry 2008;9;22

  • Metalloprotease-mediated OPA1 processing is modulated by the mitochondrial membrane potential.

    Guillery O, Malka F, Landes T, Guillou E, Blackstone C, Lombès A, Belenguer P, Arnoult D and Rojo M

    Inserm U582, 75651 Paris cedex 13, France.

    Human OPA1 (optic atrophy type 1) is a dynamin-related protein of the mitochondrial IMS (intermembrane space) involved in membrane fusion and remodelling. Similarly to its yeast orthologue Mgm1p that exists in two isoforms generated by the serine protease Pcp1p/Rbd1p, OPA1 exists in various isoforms generated by alternative splicing and processing. In the present paper, we focus on protease processing of OPA1.

    Results: We find that various mammalian cell types display a similar pattern of OPA1 isoforms [two L-OPA1 (long isoforms of OPA1) and three S-OPA1 (short isoforms of OPA1)] and that loss of the inner membrane potential, but not inhibition of oxidative phosphorylation or glycolysis, induces rapid and complete processing of L-OPA1 to S-OPA1. In isolated mitochondria, OPA1 processing was inhibited by heavy-metal chelators, pointing to processing by a mitochondrial metalloprotease. The pattern of OPA1 isoforms and its processing kinetics were normal in mitochondria devoid of the serine protease PARL (presenilins-associated rhomboid-like protein) - the human orthologue of Pcp1/Rbd1 - and in cells from patients carrying homozygous mutations in SPG7 (spastic paraplegia type 7), a gene encoding the matrix-oriented metalloprotease paraplegin. In contrast, OPA1 processing kinetics were delayed upon knock-down of YME1L (human yme1-like protein), an IMS-oriented metalloprotease. OPA1 processing was also stimulated during apoptosis, but inhibition of this processing did not affect apoptotic release of OPA1 and cytochrome c. Finally, we show that all OPA1 isoforms interact with Mfn1 (mitofusin 1) and Mfn2 and that these interactions are not affected by dissipation of DeltaPsim (inner mitochondrial membrane potential) or OPA1 processing.

    Conclusions: Metalloprotease-mediated processing of OPA1 is modulated by the inner membrane potential and is likely to be mediated by the YME1L protease.

    Funded by: Intramural NIH HHS

    Biology of the cell 2008;100;5;315-25

  • Reversible optic neuropathy with OPA1 exon 5b mutation.

    Cornille K, Milea D, Amati-Bonneau P, Procaccio V, Zazoun L, Guillet V, El Achouri G, Delettre C, Gueguen N, Loiseau D, Muller A, Ferré M, Chevrollier A, Wallace DC, Bonneau D, Hamel C, Reynier P and Lenaers G

    Institut National de la Santé et de la Recherche Médicale U583, Institut des Neurosciences de Montpellier, Université de Montpellier I et II, Montpellier, France.

    A new c.740G>A (R247H) mutation in OPA1 alternate spliced exon 5b was found in a patient presenting with bilateral optic neuropathy followed by partial, spontaneous visual recovery. R247H fibroblasts from the patient and his unaffected father presented unusual highly tubular mitochondrial network, significant increased susceptibility to apoptosis, oxidative phosphorylation uncoupling, and altered OPA1 protein profile, supporting the pathogenicity of this mutation. These results suggest that the clinical spectrum of the OPA1-associated optic neuropathies may be larger than previously described, and that spontaneous recovery may occur in cases harboring an exon 5b mutation.

    Annals of neurology 2008;63;5;667-71

  • Multiple sclerosis-like disorder in OPA1-related autosomal dominant optic atrophy.

    Verny C, Loiseau D, Scherer C, Lejeune P, Chevrollier A, Gueguen N, Guillet V, Dubas F, Reynier P, Amati-Bonneau P and Bonneau D

    Département de Neurologie, Centre Hospitalier Universitaire, INSERM U694, Angers, France.

    Neurology 2008;70;13 Pt 2;1152-3

  • Mutation of OPA1 causes dominant optic atrophy with external ophthalmoplegia, ataxia, deafness and multiple mitochondrial DNA deletions: a novel disorder of mtDNA maintenance.

    Hudson G, Amati-Bonneau P, Blakely EL, Stewart JD, He L, Schaefer AM, Griffiths PG, Ahlqvist K, Suomalainen A, Reynier P, McFarland R, Turnbull DM, Chinnery PF and Taylor RW

    Mitochondrial Research Group, School of Neurology, Neurobiology and Psychiatry, The Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.

    Mutations in nuclear genes involved in mitochondrial DNA (mtDNA) maintenance cause a wide range of clinical phenotypes associated with the secondary accumulation of multiple mtDNA deletions in affected tissues. The majority of families with autosomal dominant progressive external ophthalmoplegia (PEO) harbour mutations in genes encoding one of three well-characterized proteins--pol gamma, Twinkle or Ant 1. Here we show that a heterozygous mis-sense mutation in OPA1 leads to multiple mtDNA deletions in skeletal muscle and a mosaic defect of cytochrome c oxidase (COX). The disorder presented with visual failure and optic atrophy in childhood, followed by PEO, ataxia, deafness and a sensory-motor neuropathy in adult life. COX-deficient skeletal muscle fibres contained supra-threshold levels of multiple mtDNA deletions, and genetic linkage, sequencing and expression analysis excluded POLG1, PEO1 and SLC25A4, the gene encoding Ant 1, as the cause. This demonstrates the importance of OPA1 in mtDNA maintenance, and implicates OPA1 in diseases associated with secondary defects of mtDNA.

    Funded by: Medical Research Council: G0601943, G108/539; Wellcome Trust: 074454

    Brain : a journal of neurology 2008;131;Pt 2;329-37

  • OPA1 mutations associated with dominant optic atrophy impair oxidative phosphorylation and mitochondrial fusion.

    Zanna C, Ghelli A, Porcelli AM, Karbowski M, Youle RJ, Schimpf S, Wissinger B, Pinti M, Cossarizza A, Vidoni S, Valentino ML, Rugolo M and Carelli V

    Dipartimento di Biologia Evoluzionistica Sperimentale, Università di Bologna, Via Irnerio 42, 40126 Bologna, Italy. zanna@alma.unibo.it

    Dominant optic atrophy (DOA) is characterized by retinal ganglion cell degeneration leading to optic neuropathy. A subset of DOA is caused by mutations in the OPA1 gene, encoding for a dynamin-related GTPase required for mitochondrial fusion. The functional consequences of OPA1 mutations in DOA patients are still poorly understood. This study investigated the effect of five different OPA1 pathogenic mutations on the energetic efficiency and mitochondrial network dynamics of skin fibroblasts from patients. Although DOA fibroblasts maintained their ATP levels and grew in galactose medium, i.e. under forced oxidative metabolism, a significant impairment in mitochondrial ATP synthesis driven by complex I substrates was found. Furthermore, balloon-like structures in the mitochondrial reticulum were observed in galactose medium and mitochondrial fusion was completely inhibited in about 50% of DOA fibroblasts, but not in control cells. Respiratory complex assembly and the expression level of complex I subunits were similar in control and DOA fibroblasts. Co-immunoprecipitation experiments revealed that OPA1 directly interacts with subunits of complexes I, II and III, but not IV and with apoptosis inducing factor. The results disclose a novel link between OPA1, apoptosis inducing factor and the respiratory complexes that may shed some light on the pathogenic mechanism of DOA.

    Funded by: Telethon: GGP06233

    Brain : a journal of neurology 2008;131;Pt 2;352-67

  • OPA1 mutations induce mitochondrial DNA instability and optic atrophy 'plus' phenotypes.

    Amati-Bonneau P, Valentino ML, Reynier P, Gallardo ME, Bornstein B, Boissière A, Campos Y, Rivera H, de la Aleja JG, Carroccia R, Iommarini L, Labauge P, Figarella-Branger D, Marcorelles P, Furby A, Beauvais K, Letournel F, Liguori R, La Morgia C, Montagna P, Liguori M, Zanna C, Rugolo M, Cossarizza A, Wissinger B, Verny C, Schwarzenbacher R, Martín MA, Arenas J, Ayuso C, Garesse R, Lenaers G, Bonneau D and Carelli V

    Département de Biochimie et Génétique, Centre Hospitalier Universitaire d'Angers, Angers, France.

    Mutations in OPA1, a dynamin-related GTPase involved in mitochondrial fusion, cristae organization and control of apoptosis, have been linked to non-syndromic optic neuropathy transmitted as an autosomal-dominant trait (DOA). We here report on eight patients from six independent families showing that mutations in the OPA1 gene can also be responsible for a syndromic form of DOA associated with sensorineural deafness, ataxia, axonal sensory-motor polyneuropathy, chronic progressive external ophthalmoplegia and mitochondrial myopathy with cytochrome c oxidase negative and Ragged Red Fibres. Most remarkably, we demonstrate that these patients all harboured multiple deletions of mitochondrial DNA (mtDNA) in their skeletal muscle, thus revealing an unrecognized role of the OPA1 protein in mtDNA stability. The five OPA1 mutations associated with these DOA 'plus' phenotypes were all mis-sense point mutations affecting highly conserved amino acid positions and the nuclear genes previously known to induce mtDNA multiple deletions such as POLG1, PEO1 (Twinkle) and SLC25A4 (ANT1) were ruled out. Our results show that certain OPA1 mutations exert a dominant negative effect responsible for multi-systemic disease, closely related to classical mitochondrial cytopathies, by a mechanism involving mtDNA instability.

    Funded by: Telethon: GGP06233

    Brain : a journal of neurology 2008;131;Pt 2;338-51

  • A phenotypic variation of dominant optic atrophy and deafness (ADOAD) due to a novel OPA1 mutation.

    Liguori M, La Russa A, Manna I, Andreoli V, Caracciolo M, Spadafora P, Cittadella R and Quattrone A

    Journal of neurology 2008;255;1;127-9

  • Comprehensive cDNA study and quantitative transcript analysis of mutant OPA1 transcripts containing premature termination codons.

    Schimpf S, Fuhrmann N, Schaich S and Wissinger B

    Molecular Genetics Laboratory, University Eye Hospital, Tuebingen, Germany. Simone.Schimpf@uni-tuebingen.de

    Autosomal dominant optic atrophy (adOA) is most commonly caused by mutations in the OPA1 gene. There is a considerable allelic heterogeneity among adOA-associated OPA1 mutations, however these mutations have mostly been identified and studied only at the genomic DNA level. Here we report the identification of 22 novel OPA1 mutations and their analysis at the cDNA level along with 15 already known OPA1 mutations. We found that 18 of these mutations cause splice defects that involve either skipping of the adjacent exon or the activation of a cryptic splice site. We also observed a reduced level of the mutant transcript in several adOA subjects. Allele-specific quantification of the transcript steady-state level was performed for 13 different OPA1 mutations applying pyrosequencing to a RT-PCR amplified cSNP (c.2109C>T) in OPA1. Using this new assay we could demonstrate that the majority of OPA1 mutations that lead to a premature termination codon (PTC) undergo nonsense-mediated mRNA decay (NMD). Mutant transcript levels were reduced between 1.25- and 2.5-fold and varied between PTC containing mutations, and between subjects. Our results emphasize the value of cDNA analysis in the characterization of OPA1 mutations and further strengthen the model of haploinsufficiency as a major pathomechanism in OPA1-associated adOA.

    Human mutation 2008;29;1;106-12

  • Identification of two novel OPA1 mutations in Chinese families with autosomal dominant optic atrophy.

    Li Y, Deng T, Tong Y, Peng S, Dong B and He D

    Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, China.

    Purpose: To report the clinical features and identification of two novel mutations in two Chinese pedigrees with autosomal dominant optic atrophy (ADOA).

    Methods: Two families (F1 and F2) including ten affected members and nine unaffected family individuals were examined clinically. After informed consent was obtained, peripheral blood samples of all the participants were obtained, and genomic DNA was extracted. Linkage analysis was performed with two microsatellite markers around the OPA1 gene (D3S2305 and D3S3562) in family F1. The coding region (exon 1-28), including intron-exon boundary of the OPA1 gene, were screened in the 2 families by polymerase chain reaction (PCR) and direct DNA sequencing. Whenever substitutions were identified in a patient, single strand conformation polymorphism (SSCP) analysis was performed on all available family members and 100 normal controls. To characterize a splicing site mutation, RT-PCR of total RNA of leukocytes obtained from three patients and seven unaffected individuals of family F1 was performed with the specific primers.

    Results: The affected individuals all presented with bilateral visual failure and temporal or total pallor of the optic discs. Genotyping of family F1 revealed the linkage to the OPA1 gene on 3q28-29. After sequencing of OPA1 gene, a novel heterozygous splicing site mutation c.985 -2A>G in intron 9 was found in family F1. RT-PCR result showed the skipping of the exon 10 in the mutant transcript, which results in loss of 27 amino acids in the OPA1 protein. A novel heterozygous nonsense mutation c.2197C>T(p.R733X)was detected in family F2.

    Conclusions: Our findings expand the spectrum of OPA1 mutations and further established the role of OPA1 gene in Chinese patients with ADOA.

    Molecular vision 2008;14;2451-7

  • No association between OPA1 polymorphisms and primary open-angle glaucoma in three different populations.

    Liu Y, Schmidt S, Qin X, Gibson J, Munro D, Wiggs JL, Hauser MA and Allingham RR

    Center for Human Genetics, Duke University Medical Center, Durham, NC, USA.

    Purpose: To investigate whether recently described polymorphisms in the optic atrophy 1 gene (OPA1) are associated with primary open-angle glaucoma (POAG) with elevated intraocular pressure in the Caucasian, African-American, and Ghanaian (West African) populations.

    Methods: POAG was defined as the presence of glaucomatous optic nerve damage, associated visual field loss, and elevated intraocular pressure (>21 mm of mercury in both eyes). We used TaqMan allelic discrimination assays to genotype two single nucleotide polymorphisms (SNPs, rs10451941 and rs166850) in OPA1 in the Caucasian (279 cases, 227 controls), African American (193 cases, 97 controls), and Ghanaian (170 cases, 138 controls) populations. Allele, genotype, and haplotype frequencies were compared between the cases and controls from each population.

    Results: There was no significant difference in OPA1 allele or genotype frequencies between POAG patients and controls at the rs10451941 and rs166850 SNPs in any population (p>0.05). Haplotype analysis also failed to demonstrate a significant association with POAG. The age-of-onset distribution in the Caucasian POAG patients was independent from genotypes at rs10451941.

    Conclusions: There was no association between two previously implicated OPA1 polymorphisms and a POAG phenotype that includes elevated intraocular pressure. This represents the first association analysis of OPA1 in high tension glaucoma in the African American and Ghanaian populations and is the largest study to date on the investigation of the potential association between OPA1 and POAG with elevated intraocular pressure. OPA1 association with POAG may be limited to patients with normal tension glaucoma in these populations.

    Funded by: NEI NIH HHS: R01EY013315, R01EY015543, R01EY015872, R03EY014939

    Molecular vision 2007;13;2137-41

  • OPA1 cleavage depends on decreased mitochondrial ATP level and bivalent metals.

    Baricault L, Ségui B, Guégand L, Olichon A, Valette A, Larminat F and Lenaers G

    LBCMCP, CNRS, Université de Toulouse, France. baricaul@cict.fr

    OPA1, an intra-mitochondrial dynamin GTPase, is a key actor of outer and inner mitochondrial membrane dynamic. OPA1 amino-terminal cleavage by PARL and m-AAA proteases was recently proposed to participate to the mitochondrial network dynamic in a DeltaPsi(m)-dependent way, and to apoptosis. Here, by an in vitro approach combining the use of purified mitochondrial fractions and mitochondrial targeting drugs, we intended to identify the central stimulus responsible for OPA1 cleavage. We confirm that apoptosis induction and PTPore opening, as well as DeltaPsi(m) dissipation induce OPA1 cleavage. Nevertheless, our experiments evidenced that decreased mitochondrial ATP levels, either generated by apoptosis induction, DeltaPsi(m) dissipation or inhibition of ATP synthase, is the common and crucial stimulus that controls OPA1 processing. In addition, we report that ectopic iron addition activates OPA1 cleavage, whereas zinc inhibits this process. These results suggest that the ATP-dependent OPA1 processing plays a central role in correlating the energetic metabolism to mitochondrial dynamic and might be involved in the pathophysiology of diseases associated to excess of iron or depletion of zinc and ATP.

    Experimental cell research 2007;313;17;3800-8

  • A novel mutation of the OPA1 gene in a Japanese patient with autosomal dominant optic atrophy.

    Ban Y, Yoshida Y, Kawasaki S and Mochida C

    Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie 2007;245;10;1581-3

  • OPA1 processing reconstituted in yeast depends on the subunit composition of the m-AAA protease in mitochondria.

    Duvezin-Caubet S, Koppen M, Wagener J, Zick M, Israel L, Bernacchia A, Jagasia R, Rugarli EI, Imhof A, Neupert W, Langer T and Reichert AS

    Institute for Physiological Chemistry, Ludwig Maximilians University, 81377 Munich, Germany.

    The morphology of mitochondria in mammalian cells is regulated by proteolytic cleavage of OPA1, a dynamin-like GTPase of the mitochondrial inner membrane. The mitochondrial rhomboid protease PARL, and paraplegin, a subunit of the ATP-dependent m-AAA protease, were proposed to be involved in this process. Here, we characterized individual OPA1 isoforms by mass spectrometry, and we reconstituted their processing in yeast to identify proteases involved in OPA1 cleavage. The yeast homologue of OPA1, Mgm1, was processed both by PARL and its yeast homologue Pcp1. Neither of these rhomboid proteases cleaved OPA1. The formation of small OPA1 isoforms was impaired in yeast cells lacking the m-AAA protease subunits Yta10 and Yta12 and was restored upon expression of murine or human m-AAA proteases. OPA1 processing depended on the subunit composition of mammalian m-AAA proteases. Homo-oligomeric m-AAA protease complexes composed of murine Afg3l1, Afg3l2, or human AFG3L2 subunits cleaved OPA1 with higher efficiency than paraplegin-containing m-AAA proteases. OPA1 processing proceeded normally in murine cell lines lacking paraplegin or PARL. Our results provide evidence for different substrate specificities of m-AAA proteases composed of different subunits and reveal a striking evolutionary switch of proteases involved in the proteolytic processing of dynamin-like GTPases in mitochondria.

    Molecular biology of the cell 2007;18;9;3582-90

  • Reduction of inner retinal thickness in patients with autosomal dominant optic atrophy associated with OPA1 mutations.

    Ito Y, Nakamura M, Yamakoshi T, Lin J, Yatsuya H and Terasaki H

    Departments of Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Japan.

    Purpose: To determine the morphologic changes in the retina in the macula and around the optic disc in patients with autosomal dominant optic atrophy (ADOA) associated with a mutation in the OPA1 gene.

    Methods: Cross-sectional images of the macular area of the retina were obtained by optical coherence tomography (OCT) in patients with ADOA who had a heterozygous mutation in the OPA1 gene. There were 15 eyes of eight patients from five families: four men and four women. The average age of the patients was 48.1 years. In the OCT images, the cross sections of the sensory retina were divided manually into four areas. The thickness of the overall sensory retina and the divided areas were measured at 1 and 2 mm on the temporal, nasal, superior, and inferior sides of the fovea as well as at the fovea. The thickness of the retinal nerve fiber layer (RNFL) around the optic discs was measured by taking circular scans (3.4 mm in diameter) centered on the optic disc. The results in the patients with ADOA were compared with those from 11 normal control subjects.

    Results: The overall thickness of the sensory retina in the macular area was significantly thinner in the patients with ADOA than in the control subjects at all points except the fovea (P < 0.0001). The RNFL in the macular area in the patients with ADOA was significantly thinner than that in control subjects at all points (P < 0.0001), especially at 1 mm from the fovea. The circumpapillary RNFL was significantly thinner at the temporal, superior, and inferior areas in patients with ADOA but not in the nasal area. The total cross-sectional area of the circumpapillary RNFL was significantly correlated with visual acuity. The thickness of the combined ganglion cell layer, inner plexiform layer, inner nuclear layer, and outer plexiform layer in the macular area was significantly thinner in the patients (P < 0.0056). The thickness of the outer nuclear layer and the photoreceptor inner segments and the thickness of the photoreceptor outer segments were not significantly different between the patients with ADOA and normal control subjects.

    Conclusions: The RNFL and the layer including the ganglion cell layer are significantly thinner in patients with ADOA associated with an OPA1 gene mutation, whereas the photoreceptor layers are not affected morphologically. The inner retina is the main area of the retina altered in ADOA.

    Investigative ophthalmology & visual science 2007;48;9;4079-86

  • OPA1 processing controls mitochondrial fusion and is regulated by mRNA splicing, membrane potential, and Yme1L.

    Song Z, Chen H, Fiket M, Alexander C and Chan DC

    Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.

    OPA1, a dynamin-related guanosine triphosphatase mutated in dominant optic atrophy, is required for the fusion of mitochondria. Proteolytic cleavage by the mitochondrial processing peptidase generates long isoforms from eight messenger RNA (mRNA) splice forms, whereas further cleavages at protease sites S1 and S2 generate short forms. Using OPA1-null cells, we developed a cellular system to study how individual OPA1 splice forms function in mitochondrial fusion. Only mRNA splice forms that generate a long isoform in addition to one or more short isoforms support substantial mitochondrial fusion activity. On their own, long and short OPA1 isoforms have little activity, but, when coexpressed, they functionally complement each other. Loss of mitochondrial membrane potential destabilizes the long isoforms and enhances the cleavage of OPA1 at S1 but not S2. Cleavage at S2 is regulated by the i-AAA protease Yme1L. Our results suggest that mammalian cells have multiple pathways to control mitochondrial fusion through regulation of the spectrum of OPA1 isoforms.

    Funded by: NIGMS NIH HHS: GM062967, R01 GM062967

    The Journal of cell biology 2007;178;5;749-55

  • Regulation of the mitochondrial dynamin-like protein Opa1 by proteolytic cleavage.

    Griparic L, Kanazawa T and van der Bliek AM

    Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.

    The dynamin-related protein Opa1 is localized to the mitochondrial intermembrane space, where it facilitates fusion between mitochondria. Apoptosis causes Opa1 release into the cytosol and causes mitochondria to fragment. Loss of mitochondrial membrane potential also causes mitochondrial fragmentation but not Opa1 release into the cytosol. Both conditions induce the proteolytic cleavage of Opa1, suggesting that mitochondrial fragmentation is triggered by Opa1 inactivation. The opposite effect was observed with knockdown of the mitochondrial intermembrane space protease Yme1. Knockdown of Yme1 prevents the constitutive cleavage of a subset of Opa1 splice variants but does not affect carbonyl cyanide m-chlorophenyl hydrazone or apoptosis-induced cleavage. Knockdown of Yme1 also increases mitochondrial connectivity, but this effect is independent of Opa1 because it also occurs in Opa1 knockdown cells. We conclude that Yme1 constitutively regulates a subset of Opa1 isoforms and an unknown mitochondrial morphology protein, whereas the loss of membrane potential induces the further proteolysis of Opa1.

    Funded by: NIGMS NIH HHS: GM051866, R01 GM051866

    The Journal of cell biology 2007;178;5;757-64

  • Mitochondrial fission and fusion mediators, hFis1 and OPA1, modulate cellular senescence.

    Lee S, Jeong SY, Lim WC, Kim S, Park YY, Sun X, Youle RJ and Cho H

    Department of Biochemistry, Ajou University School of Medicine, Ajou University, 5 Wonchon-dong, Yeongtong-gu, Suwon 443-721, Korea.

    The number and morphology of mitochondria within a cell are precisely regulated by the mitochondrial fission and fusion machinery. The human protein, hFis1, participates in mitochondrial fission by recruiting the Drp1 into the mitochondria. Using short hairpin RNA, we reduced the expression levels of hFis1 in mammalian cells. Cells lacking hFis1 showed sustained elongation of mitochondria and underwent significant cellular morphological changes, including enlargement, flattening, and increased cellular granularity. In these cells, staining for acidic senescence-associated beta-galactosidase activity was elevated, and the rate of cell proliferation was greatly reduced, indicating that cells lacking hFis1 undergo senescence-associated phenotypic changes. Reintroduction of the hFis1 gene into hFis1-depleted cells restored mitochondrial fragmentation and suppressed senescence-associated beta-galactosidase activity. Moreover, depletion of both hFis1 and OPA1, a critical component of mitochondrial fusion, resulted in extensive mitochondrial fragmentation and markedly rescued cells from senescence-associated phenotypic changes. Intriguingly, sustained elongation of mitochondria was associated with decreased mitochondrial membrane potential, increased reactive oxygen species production, and DNA damage. The data indicate that sustained mitochondrial elongation induces senescence-associated phenotypic changes that can be neutralized by mitochondrial fragmentation. Thus, one of the key functions of mitochondrial fission might be prevention of the sustained extensive mitochondrial elongation that triggers cellular senescence.

    The Journal of biological chemistry 2007;282;31;22977-83

  • Autosomal dominant optic atrophy: penetrance and expressivity in patients with OPA1 mutations.

    Cohn AC, Toomes C, Potter C, Towns KV, Hewitt AW, Inglehearn CF, Craig JE and Mackey DA

    Ocular Diagnostic Clinic, Royal Victorian Eye and Ear Hospital, Melbourne, Australia.

    Purpose: We identified families with autosomal dominant optic atrophy (ADOA), determined the number and type of OPA1 mutations, and investigated the phenotypic variation and penetrance in ADOA Australian pedigrees.

    Design: Cross-sectional genetics study.

    Methods: Probands were identified on the basis of characteristic clinical features of ADOA. We screened the OPA1 gene using single-strand conformational polymorphism, heteroduplex analysis (SSCP/HA), or by direct sequencing. Penetrance for pedigrees in which a mutation of OPA1 had been identified was calculated initially using all recruited individuals, and subanalysis was performed using only those families for which there was total recruitment of siblings.

    Results: A total of 406 patients from 17 pedigrees were recruited, and OPA1 mutations were identified in 11/17 (65%) of these. The mean age at clinical examination was 38.2 +/- 19.9 years (median age, 35 years; range, four to 83 years). The median best-corrected visual acuity in OPA1-mutation carriers was 20/70 (range, 20/16 to hand movements [HM]). The penetrance in Australian ADOA pedigrees in the families with complete sibling recruitment was 82.5%. On the other hand, overall penetrance for all individuals harboring an OPA1 mutation was 88%.

    Conclusions: OPA1 mutations were identified in 11/17 (65%) of the ADOA pedigrees in this study. The penetrance in our cohort was lower than originally described (82.5% vs 98%) but higher than some recent studies since the availability of genotyping. It is anticipated that this figure would be even lower as more asymptomatic individuals are identified. There are likely to be other genetic and environmental modifiers influencing disease penetrance.

    American journal of ophthalmology 2007;143;4;656-62

  • OPA1 alternate splicing uncouples an evolutionary conserved function in mitochondrial fusion from a vertebrate restricted function in apoptosis.

    Olichon A, Elachouri G, Baricault L, Delettre C, Belenguer P and Lenaers G

    Laboratoire de Biologie Cellulaire et Moléculaire du Contrôle de la Prolifération, CNRS UMR 5088, Université Paul Sabatier, 118 route de Narbonne, Toulouse Cedex, France.

    In most eucaryote cells, release of apoptotic proteins from mitochondria involves fission of the mitochondrial network and drastic remodelling of the cristae structures. The intramitochondrial dynamin OPA1, as a potential central actor of these processes, exists as eight isoforms resulting from the alternate splicing combinations of exons (Ex) 4, 4b and 5b, which functions remain undetermined. Here, we show that Ex4 that is conserved throughout evolution confers functions to OPA1 involved in the maintenance of the DeltaPsi(m) and in the fusion of the mitochondrial network. Conversely, Ex4b and Ex5b, which are vertebrate specific, define a function involved in cytochrome c release, an apoptotic process also restricted to vertebrates. The drastic changes of OPA1 variant abundance in different organs suggest that nuclear splicing can control mitochondrial dynamic fate and susceptibility to apoptosis and pathologies.

    Cell death and differentiation 2007;14;4;682-92

  • Dominant optic atrophy in a Japanese family with OPA1 frameshift mutation (V942fsX966).

    Hayashi T, Takeuchi T, Gekka T and Kitahara K

    Department of Ophthalmology, Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan. taka@jikei.ac.jp

    Purpose: The authors report the ophthalmic characteristics of a male proband in a Japanese family with autosomal dominant optic atrophy (DOA) harboring a frameshift mutation in the OPA1 gene.

    Methods: Conventional ophthalmologic examinations including static automated perimetry were performed, as well as assessment of the three-generation family history. The peripapillary retinal nerve fiber layer (RNFL) was evaluated using scanning laser polarimetry. Mutation screening of the OPA1 gene was performed with polymerase chain reaction amplification and direct sequencing.

    Results: A frameshift mutation (p.V942fsX966) was identified in the proband and his mother. In comparison with the adolescent onset of visual loss in the proband and his maternal grandfather, the mother presented with only subtle temporal disc pallor and has never been aware of any visual disturbances. Symmetric thinned peripapillary RNFL was detected in the proband, whose visual field abnormalities were limited to central scotomas and were without mean deviation worsening between 11 to 17 years of age in both eyes. The proband's logMAR visual acuity (0.52 to 0.7) has remained almost unchanged for more than 10 years since initial evaluation at age 10.

    Conclusions: The OPA1 mutation may be correlated with slow progression of DOA, and with phenotypic variations within the family. Further study is necessary to determine whether symmetric thinned peripapillary RNFL represents a feature of DOA.

    European journal of ophthalmology 2007;17;2;253-8

  • [A novel mutation of the OPA1 gene responsible for isolated autosomal dominant optic atrophy in two brothers].

    Macarez R, Amati-Bonneau P, Burelle X, Vanimschoot M, Dot C, Ocamica P, Kovalski JL and May F

    Service d'Ophtalmologie, HIA Clermont-Tonnerre, Brest.

    Autosomal dominant optic atrophy, or Kjer disease, is the most frequent form of autosomal dominant optic neuropathy. We report a novel mutation of the OPA1 gene in two brothers with autosomal dominant optic atrophy and describe their clinical features. The two patients, aged 41 and 37, presented with a bilateral visual impairment that had been detected at the age of 4 in both of them. Their ophthalmoscopic examinations disclosed a bilateral optic atrophy and their Goldmann visual fields showed cecocentral scotomas. The patients thought their disease might be a Leber's hereditary optic neuropathy; however, mutations had ever been sought. When first seen by us, they wished to know whether their disorder might be transmitted to their children. They had a family history of visual impairment. We carried out mtDNA sequencing but we did not identify any primary or rare Leber's hereditary optic neuropathy mutations. On the other hand, the 30 coding exons of the OPA1 gene and the intron-exon junctions were amplified by polymerase chain reaction and sequenced. A novel mutation of the OPA1 gene was found in both brothers: a deletion of four nucleotides in intron 19, associated with anomalous splicing, demonstrating the pathogenicity of the mutation. These molecular analyses contributed to identifying a novel mutation of the OPA1 gene with a clinical phenotype of isolated optic atrophy.

    Journal francais d'ophtalmologie 2007;30;2;161-4

  • A novel OPA1 mutation responsible for autosomal dominant optic atrophy with high frequency hearing loss in a Chinese family.

    Chen S, Zhang Y, Wang Y, Li W, Huang S, Chu X, Wang L, Zhang M and Liu Z

    Department of Medical Genetics, Zhongshan Medical College, Sun Yat-sen University, Guangzhou, P.R. China.

    Purpose: To investigate the genetic findings and phenotypic characters of autosomal dominant optic atrophy (ADOA).

    Design: Case report and experimental study.

    Methods: Molecular genetic analysis and clinical examinations were performed in a Chinese family with ADOA. Mutations in OPA1 were detected by direct sequencing. Haplotypes were constructed and compared with the phenotypes in the family.

    Results: Nine family members were diagnosed with ADOA and some of them were accompanied with hearing loss and/or high myopia. A novel heterozygous mutation, c.2848_2849delGA(p.Asp950CysfsX4), was detected in all ADOA patients. The mutation and the mutation bearing haplotype cosegregated with the nine affected members. One family member had high myopia without vision or hearing loss. This patient along with unaffected ones did not harbor the mutation.

    Conclusions: A novel mutation, c.2848_2849delGA in OPA1, was identified in a Chinese family with ADOA. This mutation is associated with hearing loss, but likely not high myopia.

    American journal of ophthalmology 2007;143;1;186-188

  • The OPA1 gene polymorphism is associated with normal tension and high tension glaucoma.

    Mabuchi F, Tang S, Kashiwagi K, Yamagata Z, Iijima H and Tsukahara S

    Department of Ophthalmology, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo-shi, Yamanashi 409-3898, Japan. fmabushi@yamanashi.ac.jp

    Purpose: To assess whether genetic polymorphisms of optic atrophy 1 (OPA1) are associated with primary open-angle glaucoma (POAG).

    Design: Prospective case control association study.

    Methods: Japanese patients with normal tension glaucoma (NTG, n = 194), and high tension glaucoma (HTG, n = 191), and 185 control subjects were analyzed for the OPA1 intervening sequence (IVS) 8+4 cystosine thymine (C/T) and IVS 8+32 thymine cystosine (T/C) polymorphisms using pyrosequencing technique.

    Results: There was a significant difference in the OPA1 IVS 8 +32 T/C genotype frequencies between the NTG patients and control subjects (P = .0074), and the frequency of the cystosine (C) allele was significantly higher in the NTG patients compared with the control subjects (19.3% vs 11.6%, P = .0036). Adjusted for age, gender, refractive error, and intraocular pressure, an almost two-fold increased risk of NTG (P = .004, odds ratio 2.27, 95% confidence interval 1.30 to 3.97) was found with the OPA1 IVS 8 +32 C allele. Although there was no significant difference in the OPA1 IVS 8 +32 T/C genotype frequencies between the HTG patients and control subjects (P = .24), the age at the time of diagnosis (53 +/- 11.0 years, median value +/- median absolute deviation) in the HTG patients with the OPA1 IVS 8 +32 C allele was significantly younger than that (57 +/- 12.0 years) in the HTG patients without C allele (P = .048).

    Conclusions: The OPA1 IVS 8 +32 T/C polymorphism is associated with NTG, and may be used as a marker for this disease association. This polymorphism also influences the phenotypic feature in patients with HTG and should be considered to be a genetic risk factor not only for NTG, but also for HTG.

    American journal of ophthalmology 2007;143;1;125-130

  • [Genetic basis of hereditary optic atrophies].

    Wawrocka A and Krawczyński MR

    Katedry i Zakładu Genetyki Medycznej Akademii Medycznej w Poznaniu.

    The most common forms of optic atrophy are: autosomatic dominant optic atrophy (ADOA, Kjer type) and maternally-inherited Leber's hereditary optic neuropathy. Rare forms of hereditary optic neuropathies are: optic atrophy X-linked and autosomatic recessive form of optic atrophy. Autosomatic dominant optic atrophy (ADOA) is the most frequent hereditary optic neuropathy. Three loci have been reported for ADOA, a major locus maps to 3q28-q29 (OPA1). The majority of mutations responsible for autosomatic dominant optic atrophy are localized in OPA1 gene. Second locus is linked to 18q12.2-q12.3 (OPA4) and a third locus on 22q12.1-q13.1 (OPA5). This study presents the actual state of knowledge about molecular changes in different forms of optic atrophy and shows hypothesis indicating the significant participation of mitochondrial dysfunction in it's pathogenesis.

    Klinika oczna 2007;109;10-12;470-4

  • [Role of transmembrane GTPases in mitochondrial morphology and activity].

    Pawlikowska P and Orzechowski A

    Katedra Nauk Fizjologicznych, Wydział Medycyny Weterynaryjnej, Szkoła Główna Gospodarstwa Wiejskiego, Warszawa.

    Mitochondria play crucial role in the energetic metabolism, thermogenesis, maintenance of calcium homeostasis and apoptosis. Cyclic changes in fusion and fission of mitochondria are required for properly functioning organelles, especially in tissues with high dependence on energy supply such as skeletal muscles, heart, or neurons. The key role of mitochondrial fusion is observed in embryonic development and maintaining unchanged mtDNA pool under conditions of oxidative stress. There is a large number of data indicating that mitochondrial networks often accompany the resistance to apoptotic stimuli. In contrast to fusion--the mitochondrial fission precedes apoptosis. According to the newest knowledge precise interactions between a few proteins are required for mitochondrial fusion and division. Among them Drp1, Mfn1, Mfn2 and Opal are considered the most important. Recent reports shed some light on the physiological importance of proteins participating in mitochondrial membrane dynamics in energy production, apoptosis and cellular signaling. In this review the authors report on the recent knowledge concerning structural changes of mitochondria with a particular interest to transmembrane GTPases and their role in cellular physiology.

    Postepy biochemii 2007;53;1;53-9

  • Proteolytic processing of OPA1 links mitochondrial dysfunction to alterations in mitochondrial morphology.

    Duvezin-Caubet S, Jagasia R, Wagener J, Hofmann S, Trifunovic A, Hansson A, Chomyn A, Bauer MF, Attardi G, Larsson NG, Neupert W and Reichert AS

    Adolf-Butenandt-Institut für Physiologische Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5, 81377 München, Germany.

    Many muscular and neurological disorders are associated with mitochondrial dysfunction and are often accompanied by changes in mitochondrial morphology. Mutations in the gene encoding OPA1, a protein required for fusion of mitochondria, are associated with hereditary autosomal dominant optic atrophy type I. Here we show that mitochondrial fragmentation correlates with processing of large isoforms of OPA1 in cybrid cells from a patient with myoclonus epilepsy and ragged-red fibers syndrome and in mouse embryonic fibroblasts harboring an error-prone mitochondrial mtDNA polymerase gamma. Furthermore, processed OPA1 was observed in heart tissue derived from heart-specific TFAM knock-out mice suffering from mitochondrial cardiomyopathy and in skeletal muscles from patients suffering from mitochondrial myopathies such as myopathy encephalopathy lactic acidosis and stroke-like episodes. Dissipation of the mitochondrial membrane potential leads to fast induction of proteolytic processing of OPA1 and concomitant fragmentation of mitochondria. Recovery of mitochondrial fusion depended on protein synthesis and was accompanied by resynthesis of large isoforms of OPA1. Fragmentation of mitochondria was prevented by overexpressing OPA1. Taken together, our data indicate that proteolytic processing of OPA1 has a key role in inducing fragmentation of energetically compromised mitochondria. We present the hypothesis that this pathway regulates mitochondrial morphology and serves as an early response to prevent fusion of dysfunctional mitochondria with the functional mitochondrial network.

    The Journal of biological chemistry 2006;281;49;37972-9

  • Prognostic DNA testing and counselling for dominant optic atrophy due to a novel OPA1 mutation.

    Yoshida S, Yamaji Y, Yoshida A, Kuwahara R, Fujisawa K and Ishibashi T

    Department of Ophthalmology, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan. yosida@med.kyushu-u.ac.jp

    To report the case of a 26-year-old woman with a family history of dominant optic atrophy who requested DNA testing and counselling. Ophthalmologic examination showed her affected father had bilateral temporal papillary pallor. Direct genomic sequencing of the OPA1 gene revealed a novel heterozygous nonsense mutation (Arg879stop). Because no mutation in OPA1 was detected in the daughter, we could counsel her that the possibility was very low that she was a carrier or would pass the disease-causing gene to her children.

    Comments: Our study provides evidence of the apparent value of molecular genetic analysis of OPA1 gene as predictive DNA testing, although the exact risk and benefit of this type of analysis awaits further study.

    Canadian journal of ophthalmology. Journal canadien d'ophtalmologie 2006;41;5;614-6

  • Regulation of mitochondrial morphology through proteolytic cleavage of OPA1.

    Ishihara N, Fujita Y, Oka T and Mihara K

    Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan.

    The dynamin-like GTPase OPA1, a causal gene product of human dominant optic atrophy, functions in mitochondrial fusion and inner membrane remodeling. It has several splice variants and even a single variant is found as several processed forms, although their functional significance is unknown. In yeast, mitochondrial rhomboid protease regulates mitochondrial function and morphology through proteolytic cleavage of Mgm1, the yeast homolog of OPA1. We demonstrate that OPA1 variants are synthesized with a bipartite-type mitochondrial targeting sequence. During import, the matrix-targeting signal is removed and processed forms (L-isoforms) are anchored to the inner membrane in type I topology. L-isoforms undergo further processing in the matrix to produce S-isoforms. Knockdown of OPA1 induced mitochondrial fragmentation, whose network morphology was recovered by expression of L-isoform but not S-isoform, indicating that only L-isoform is fusion-competent. Dissipation of membrane potential, expression of m-AAA protease paraplegin, or induction of apoptosis stimulated this processing along with the mitochondrial fragmentation. Thus, mammalian mitochondrial function and morphology is regulated through processing of OPA1 in a DeltaPsi-dependent manner.

    The EMBO journal 2006;25;13;2966-77

  • Evaluation of the association between OPA1 polymorphisms and primary open-angle glaucoma in Barbados families.

    Yao W, Jiao X, Hejtmancik JF, Leske MC, Hennis A, Nemesure B and Barbados Family Study Group

    Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda 20892-1860, MD.

    Purpose: To investigate whether single nucleotide polymorphisms (SNPs) in the OPA1 gene are associated with two primary open-angle glaucoma (POAG) subgroups: those with elevated intraocular pressure (POAG/IOP) and those with normal tension glaucoma (NTG) in the African-Caribbean population of Barbados, West Indies.

    Methods: SNPs at intervening sequence (IVS) 8, +4, and +32 of the OPA1 gene were directly sequenced from 48 individuals with POAG/IOP, 48 nonglaucomatous controls, and 61 people with NTG. The remaining exons of OPA1 were screened for sequence variations in the same 48 POAG/IOP participants and 48 controls by denaturing high performance liquid chromatography (dHPLC), and identified variations were confirmed by bidirectional sequencing. Genotype and allele frequencies of all SNPs were compared for statistically significant differences using the chi2 and Fisher's exact test. Haplotypes and compound genotypes were also analyzed to evaluate the combined effect of the two IVS8 SNPs.

    Results: The analyses of the genotype and haplotype frequencies of IVS8 +4 and +32 do not show statistically significant differences between those with POAG/IOP or NTG and controls. At IVS8 +32, although there are suggestions of possible associations of the CC genotype with NTG (chi2 = 3.81, p = 0.05), and the TC genotype with POAG/IOP (chi2 = 4.23, p = 0.04), these differences do not reach statistical significance at the level of 0.017 after a Bonferroni correction. In addition, the combined genotype comparisons at IVS8 +32 do not support the association (for controls compared to NTG chi2 = 4.19, p = 0.12, df = 2; and for controls compared to POAG chi2 = 4.83, p = 0.09, df = 2). Sixteen variants are observed in the OPA1 gene, of which 10 are novel. Neither genotype nor allele frequencies of any SNP are found to be associated with POAG/IOP.

    Conclusions: Although some results are suggestive, there is not sufficient evidence to support an association of the SNPs evaluated in OPA1 with POAG/IOP or NTG in the African-Caribbean population of Barbados, West Indies.

    Funded by: PHS HHS: EYO11000

    Molecular vision 2006;12;649-54

  • A novel mutation producing premature termination codon at the OPA1 gene causes autosomal dominant optic atrophy.

    Cardaioli E, Gallus GN, Da Pozzo P, Rufa A, Franceschini R, Motolese E, Caporossi A, Dotti MT and Federico A

    Journal of neurology 2006;253;5;672-3

  • Mitochondrial dynamics and disease, OPA1.

    Olichon A, Guillou E, Delettre C, Landes T, Arnauné-Pelloquin L, Emorine LJ, Mils V, Daloyau M, Hamel C, Amati-Bonneau P, Bonneau D, Reynier P, Lenaers G and Belenguer P

    Laboratoire de Biologie Cellulaire et Moléculaire du Contrôle de la Prolifération, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse, France.

    The mitochondria are dynamic organelles that constantly fuse and divide. An equilibrium between fusion and fission controls the morphology of the mitochondria, which appear as dots or elongated tubules depending the prevailing force. Characterization of the components of the fission and fusion machineries has progressed considerably, and the emerging question now is what role mitochondrial dynamics play in mitochondrial and cellular functions. Its importance has been highlighted by the discovery that two human diseases are caused by mutations in the two mitochondrial pro-fusion genes, MFN2 and OPA1. This review will focus on data concerning the function of OPA1, mutations in which cause optic atrophy, with respect to the underlying pathophysiological processes.

    Biochimica et biophysica acta 2006;1763;5-6;500-9

  • OPA1 mutations and mitochondrial DNA haplotypes in autosomal dominant optic atrophy.

    Han J, Thompson-Lowrey AJ, Reiss A, Mayorov V, Jia H, Biousse V, Newman NJ and Brown MD

    Department of Basic Medical Sciences, Mercer University School of Medicine, Macon, GA, USA.

    Purpose: Autosomal dominant optic atrophy is a form of blindness, due in part to mutations affecting the mitochondrial-targeted OPA1 gene product. Both OPA1-positive and OPA1-negative families exhibit variable expressivity and incomplete penetrance. The purpose of this study was therefore to determine if the background mtDNA genotype acts as a genetic modifier for the expression of this disease.

    Methods: To find novel pathogenic OPA1 mutations, we performed complete OPA1 gene exon sequencing in 30 patients. To assess the possibility that mitochondrial DNA haplotype acts as a genetic modifier, we determined the mitochondrial DNA haplotype in 29 Caucasian OPA1-positive and OPA1-negative patients. Deviations in haplotype distribution between patient and control groups were determined by statistical means.

    Results: Seven new pathogenic OPA1 mutations were found. Most were detected in the mitochondrial targeting N-terminus or in the coiled-coil domain at the C-terminus. Mitochondrial DNA haplotype analysis indicated that the European haplogroup distribution was different between Caucasian patients and controls. Further, haplogroup J was three-fold over-represented in OPA1-negative patients.

    Conclusions: Overall, our results support haploinsufficiency as a genetic mechanism in OPA1-positive cases and also suggest that mtDNA genetic background may influence disease expression in a subset of cases.

    Funded by: NEI NIH HHS: P30 EY06360, R01 EY014393

    Genetics in medicine : official journal of the American College of Medical Genetics 2006;8;4;217-25

  • Novel mutations in the OPA1 gene and associated clinical features in Japanese patients with optic atrophy.

    Nakamura M, Lin J, Ueno S, Asaoka R, Hirai T, Hotta Y, Miyake Y and Terasaki H

    Department of Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Japan. makonaka@med.nagoya-u.ac.jp

    Purpose: Autosomal dominant optic atrophy (ADOA) is characterized by symmetrical bilateral optic atrophy associated with reduced corrected visual acuity (VA), central or centrocecal scotoma, and color vision disturbances. The disease is genetically heterogeneous, and the OPA1 gene has been identified as the only causative gene. The aims of this study were to identify and report mutations in the OPA1 gene in Japanese patients with ADOA and to describe the clinical features associated with the mutations.

    Design: Molecular genetic study and observational case reports.

    Participants: Nine unrelated Japanese families with optic atrophy and 8 isolated cases of optic atrophy.

    Methods: Genomic DNA was extracted from peripheral leukocytes, and all exons containing the open reading frame of the OPA1 gene and the flanking intron splice sites were sequenced directly. Complete ophthalmologic examinations were performed.

    Direct sequencing of the OPA1 gene and clinical evaluations including VA, visual field, color vision, and disc appearance.

    Results: Ten different heterozygous mutations, including 6 novel mutations, were detected in the OPA1 gene. The identified mutations included 5 deletions/insertions (c.2061delA, c.2098_2103delCTTAAA, c.2538insT, c.2591insC, and c.2708_2711delTTAG), 4 nonsense mutations (c.112C>T [p.R38X], c.181C>T [p.Q61X], c.946A>T [p.R316X], and c.2713C>T [p.R905X]), and 1 missense mutation (c.1635C>A [p.S545R]). The most common mutation in Caucasians (c.2708_2711delTTAG) was found in 3 unrelated families, suggesting that it is a mutational hot spot. We detected an OPA1 mutation in 8 of 9 familial cases of optic atrophy and in 4 of 8 cases that were initially considered to be sporadic from the patients' family histories. Examinations of family members of 2 sporadic probands revealed the existence of other family members with the OPA1 mutations whose phenotype was very mild or within normal limits. This indicates that patients with ADOA sometimes seem to be sporadic because of the extensive variation in the phenotype or, alternatively, a low penetrance of ADOA.

    Conclusions: OPA1 gene mutations are causative in most familial cases of ADOA in Japanese. Sporadic cases of optic atrophy frequently may be caused by OPA1 mutations in the Japanese population. Molecular genetic examinations are useful in determining the hereditary patterns in some cases of optic atrophy.

    Ophthalmology 2006;113;3;483-488.e1

  • Activation of cryptic splice sites is a frequent splicing defect mechanism caused by mutations in exon and intron sequences of the OPA1 gene.

    Schimpf S, Schaich S and Wissinger B

    Molecular Genetics Laboratory, University Eye Hospital, Tuebingen, Germany. simone.schimpf@uni-tuebingen.de

    Mutations in OPA1 are the most frequent cause underlying autosomal dominant optic atrophy (adOA). Until now only few putative splicing mutations in the OPA1 gene have been investigated at the mRNA level and all these result in exon skipping. Here, we report the identification and cDNA analysis of four intronic and three exonic OPA1 gene mutations that cause a variety of splicing defects including activation of cryptic splice sites in either flanking exon or intron sequences, and a leaky splicing mutation. Our results show that cDNA analysis is of prime importance for the full evaluation of the effect of putative splicing mutations in the OPA1 gene.

    Human genetics 2006;118;6;767-71

  • Optic atrophy and negative electroretinogram in a patient associated with a novel OPA1 mutation.

    Nakamura M and Miyake Y

    Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv für klinische und experimentelle Ophthalmologie 2006;244;2;274-5

  • Diversification of transcriptional modulation: large-scale identification and characterization of putative alternative promoters of human genes.

    Kimura K, Wakamatsu A, Suzuki Y, Ota T, Nishikawa T, Yamashita R, Yamamoto J, Sekine M, Tsuritani K, Wakaguri H, Ishii S, Sugiyama T, Saito K, Isono Y, Irie R, Kushida N, Yoneyama T, Otsuka R, Kanda K, Yokoi T, Kondo H, Wagatsuma M, Murakawa K, Ishida S, Ishibashi T, Takahashi-Fujii A, Tanase T, Nagai K, Kikuchi H, Nakai K, Isogai T and Sugano S

    Life Science Research Laboratory, Central Research Laboratory, Hitachi, Ltd., Kokubunji, Tokyo, 185-8601, Japan.

    By analyzing 1,780,295 5'-end sequences of human full-length cDNAs derived from 164 kinds of oligo-cap cDNA libraries, we identified 269,774 independent positions of transcriptional start sites (TSSs) for 14,628 human RefSeq genes. These TSSs were clustered into 30,964 clusters that were separated from each other by more than 500 bp and thus are very likely to constitute mutually distinct alternative promoters. To our surprise, at least 7674 (52%) human RefSeq genes were subject to regulation by putative alternative promoters (PAPs). On average, there were 3.1 PAPs per gene, with the composition of one CpG-island-containing promoter per 2.6 CpG-less promoters. In 17% of the PAP-containing loci, tissue-specific use of the PAPs was observed. The richest tissue sources of the tissue-specific PAPs were testis and brain. It was also intriguing that the PAP-containing promoters were enriched in the genes encoding signal transduction-related proteins and were rarer in the genes encoding extracellular proteins, possibly reflecting the varied functional requirement for and the restricted expression of those categories of genes, respectively. The patterns of the first exons were highly diverse as well. On average, there were 7.7 different splicing types of first exons per locus partly produced by the PAPs, suggesting that a wide variety of transcripts can be achieved by this mechanism. Our findings suggest that use of alternate promoters and consequent alternative use of first exons should play a pivotal role in generating the complexity required for the highly elaborated molecular systems in humans.

    Genome research 2006;16;1;55-65

  • OPA1 R445H mutation in optic atrophy associated with sensorineural deafness.

    Amati-Bonneau P, Guichet A, Olichon A, Chevrollier A, Viala F, Miot S, Ayuso C, Odent S, Arrouet C, Verny C, Calmels MN, Simard G, Belenguer P, Wang J, Puel JL, Hamel C, Malthièry Y, Bonneau D, Lenaers G and Reynier P

    INSERM U694, Laboratoire de Biochimie et Biologie Moléculaire, Centre Hospitalier Universitaire, F-49033 Angers, France.

    The heterozygous R445H mutation in OPA1 was found in five patients with optic atrophy and deafness. Audiometry suggested that the sensorineural deafness resulted from auditory neuropathy. Skin fibroblasts showed hyperfragmentation of the mitochondrial network, decreased mitochondrial membrane potential, and adenosine triphosphate synthesis defect. In addition, OPA1 was found to be widely expressed in the sensory and neural cochlear cells of the guinea pig. Thus, optic atrophy and deafness may be related to energy defects due to a fragmented mitochondrial network.

    Annals of neurology 2005;58;6;958-63

  • Release of OPA1 during apoptosis participates in the rapid and complete release of cytochrome c and subsequent mitochondrial fragmentation.

    Arnoult D, Grodet A, Lee YJ, Estaquier J and Blackstone C

    Cellular Neurology Unit, Surgical Neurology Branch, NINDS, National Institutes of Health, Bethesda, Maryland 20892, USA.

    Mitochondria are important participants in apoptosis, releasing cytochrome c into the cytoplasm and undergoing extensive fragmentation. However, mechanisms underlying these processes remain unclear. Here, we demonstrate that cytochrome c release during apoptosis precedes mitochondrial fragmentation. Unexpectedly, OPA1, a dynamin-like GTPase of the mitochondrial intermembrane space important for maintaining cristae structure, is co-released with cytochrome c. To mimic the loss of OPA1 occurring after its release, we knocked down OPA1 expression using RNA interference. This triggered structural changes in the mitochondrial cristae and caused increased fragmentation by blocking mitochondrial fusion. Because cytochrome c is mostly sequestered within cristae folds but released rapidly and completely during apoptosis, we examined the effect of OPA1 loss on cytochrome c release, demonstrating that it is accelerated. Thus, our results suggest that an initial mitochondrial leak of OPA1 leads to cristae structural alterations and exposure of previously sequestered protein pools, permitting continued release in a feed-forward manner to completion. Moreover, our findings indicate that the resulting OPA1 depletion causes a block in mitochondrial fusion, providing a compelling mechanism for the prominent increase in mitochondrial fragmentation seen during apoptosis.

    Funded by: Intramural NIH HHS; Wellcome Trust

    The Journal of biological chemistry 2005;280;42;35742-50

  • Optic atrophy and sensorineural hearing loss in a family caused by an R445H OPA1 mutation.

    Li C, Kosmorsky G, Zhang K, Katz BJ, Ge J and Traboulsi EI

    Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences Center, Salt Lake City, UT 84132, USA.

    Autosomal dominant optic atrophy (ADOA) is the most common form of inherited optic atrophy. Four genetic loci have been associated with ADOA: OPA1, OPA2, OPA3, and OPA4. Out of these four loci, only one gene has been identified, OPA1. We previously described a unique syndrome of optic atrophy, sensorineural hearing loss, ptosis, and ophthalmoplegia in two unrelated families associated with an R445H mutation in OPA1. The R445H mutation is the only OPA1 mutation that has been associated with this syndrome. In this manuscript, we clinically characterize an unrelated family with four members affected by optic atrophy and hearing loss without extraocular motility abnormalities or ptosis. This family also harbors the R445H mutation. These cases help illustrate the intra- and inter-family variability in phenotype associated with this mutation. As we continue to learn more about OPA1 and the function of its protein product, we will begin to understand the pathophysiology of optic atrophy. This understanding will ultimately lead to novel treatments directed toward preventing the visual loss and disability associated with this inherited disease.

    Funded by: NCRR NIH HHS: K23 RR16427; NEI NIH HHS: R01 EY14438, R01 EY14448

    American journal of medical genetics. Part A 2005;138A;3;208-11

  • Dominant optic atrophy caused by a novel OPA1 splice site mutation (IVS20+1G-->A) associated with intron retention.

    Hayashi T, Gekka T, Omoto S, Takeuchi T and Kitahara K

    Department of Ophthalmology, Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo, Japan. taka@jikei.ac.jp

    Dominant optic atrophy (DOA) is the most common form of inherited primary optic neuropathy. The purpose of the current study was to report a novel OPA1 splice site mutation and investigate the impact of the mutation on pre-mRNA splicing in a female proband and her father diagnosed with DOA. We evaluated visual acuity, retinal fundi and kinetic visual fields. Color vision phenotypes were determined using the Farnsworth Panel D-15 and the Farnsworth-Munsell 100-hue tests. All 28 coding exons of the OPA1 gene were analyzed with polymerase chain reaction (PCR) amplification and direct sequencing. Total RNA extraction from white blood cells followed by reverse transcription-PCR (RT-PCR) was performed. We identified a novel heterozygous G to A mutation at position +1 of intron 20 (g.IVS20+1G-->A) in both patients. RT-PCR analysis revealed that the first 25 bp from intron 20 plus exon 20 were spliced onto exon 21. No difference in expression of mutant and wild-type transcripts was found within the linear range of amplification. Clinically, both patients exhibited reduced visual acuities, pallor of optic discs, decreased sensitivities of central visual fields and blue-yellow color vision defects. Previously, only one mechanism (skipping of exon) of pre-mRNA splicing defects has been reported among OPA1 splice site mutations. Our study demonstrates that the mechanism of intron retention is a novel type of pre-mRNA splicing defects. The mutant transcript with a premature termination codon is likely to encode a truncated protein, due to a translational frameshift (V672fsX675), that lacks 289 amino acids of the C-terminal end. Therefore, it is suggested that haploinsufficiency underlies DOA in the patients. However, we could not exclude the possibility that the truncated protein has a dominant negative activity because the mutant transcript is insusceptible to nonsense-mediated mRNA decay.

    Ophthalmic research 2005;37;4;214-24

  • eOPA1: an online database for OPA1 mutations.

    Ferré M, Amati-Bonneau P, Tourmen Y, Malthièry Y and Reynier P

    INSERM-E0018, Laboratoire de Biochimie et Biologie Moléculaire, CHU Angers, France. marc.ferre@med.univ-angers.fr

    Autosomal dominant optic atrophy (ADOA), also known as Kjer disease, is characterized by moderate to severe loss of visual acuity with an insidious onset in early childhood, blue-yellow dyschromatopsia, and central scotoma. An optic atrophy gene, called OPA1, has been identified in most cases of the disease. A total of 83 OPA1 mutations, often family-specific, have been reported so far, and the observations support the hypothesis that haploinsufficiency and the functional loss of a single allele may lead to ADOA. We have developed a new locus-specific database (LSDB), eOPA1 (http://lbbma.univ-angers.fr/eOPA1/) aimed at collecting published and unpublished sequence variations in OPA1. The database has been designed to incorporate new submissions rapidly and will provide a secured online catalog of OPA1 mutations and nonpathogenic sequence variants (NPSVs). The LSDB should prove useful for molecular diagnosis, large-scale mutation statistics, and the determination of original genotype-phenotype correlations in studies on ADOA.

    Human mutation 2005;25;5;423-8

  • OPA1, associated with autosomal dominant optic atrophy, is widely expressed in the human brain.

    Bette S, Schlaszus H, Wissinger B, Meyermann R and Mittelbronn M

    Molecular Genetics Laboratory, University Eye hospital, Tübingen, Germany.

    Autosomal dominant optic atrophy (adOA) is the most prevalent hereditary optic neuropathy with moderate to severe visual field loss and loss of retinal ganglion cells. The majority of cases of adOA is associated with mutations in the OPA1 gene. Northern blot analyses showed that OPA1 is expressed in all tissues examined, with the highest transcript level in the retina and in the brain. Here we addressed the cell type-specific expression of the OPA1 protein in human brain sections using immunohistochemical techniques and Western blotting. We studied OPA1 expression in normal cerebellum and various cerebral CNS tissue specimen of different areas obtained at autopsy from patients with no reported neurological symptoms or diseases and no neuropathological alterations using a polyclonal antibody raised against a C-terminal peptide of OPA1. We found OPA1 expression in somata and dendrites of neurons of the layers II-VI of the motor cortex and frontal brain. In the cerebellar cortex, OPA1 expression was detected in the Purkinje cell layer, in the granule cell layer and in the molecular layer. Double-labeling experiments showed also OPA1 expression in GFAP-positive astrocytes. Since mutations in the OPA1 gene specifically causes optic atrophy and occurrence of cerebral anomalies in adOA patients is not characteristic, this finding may suggest different cellular susceptibility of OPA1 in brain and retinal tissues.

    Acta neuropathologica 2005;109;4;393-9

  • A third locus for dominant optic atrophy on chromosome 22q.

    Barbet F, Hakiki S, Orssaud C, Gerber S, Perrault I, Hanein S, Ducroq D, Dufier JL, Munnich A, Kaplan J and Rozet JM

    Journal of medical genetics 2005;42;1;e1

  • Investigation of the association between OPA1 polymorphisms and normal-tension glaucoma in Korea.

    Woo SJ, Kim DM, Kim JY, Park SS, Ko HS and Yoo T

    Department of Ophthalmology, Seoul National University Hospital, Seoul, Korea.

    Purpose: OPA1, the gene responsible for autosomal dominant optic atrophy, represents a good candidate gene for normal-tension glaucoma (NTG). Single nucleotide polymorphisms on intervening sequence (IVS) 8 of the OPA1 gene (IVS8+4C>T; +32T>C) were recently found to be strongly associated with NTG in a Caucasian population. We investigated whether these polymorphisms in the OPA1 gene were associated with NTG in Korea.

    Sixty-five Korean NTG patients and 101 healthy Korean subjects were enrolled. DNA from peripheral blood leukocytes was extracted and the genotypes of two polymorphisms (IVS8+4C>T; +32T>C) in the OPA1 gene were determined using the restriction fragment length polymorphism method. The genotype and allele frequencies of two polymorphism in patients with NTG and normal controls were compared using the Fisher exact test and the chi test. Frequencies of haplotypes and haplotypes groups were also analyzed to assess the combined effect of two polymorphisms.

    Results: The frequencies of the CT genotype of IVS8+4C>T, CC genotype of IVS8+32T>C, and TT genotype of IVS8+32T>C were not significantly different between NTG patients and controls (4.6% versus 0.0%, P = 0.058 by the Fisher exact test; 10.8% versus 4.0%, P = 0.11 by the Fisher exact test; 61.5% versus 67.3%, P = 0.45 by the chi test, respectively). Any haplotype or haplotype group of IVS8+4C>T and IVS8+32T>C was not associated with NTG, and the C allele of IVS8+32T>C was not a significant modifier of IVS8+4C>T.

    Conclusions: There were no significant associations between IVS8+4C>T; +32T>C polymorphisms and NTG in the Korean population. These results do not support the results in Caucasians and indicate that ethnic differences may exist in the association between polymorphisms in the OPA1 gene and NTG.

    Journal of glaucoma 2004;13;6;492-5

  • Deficit of in vivo mitochondrial ATP production in OPA1-related dominant optic atrophy.

    Lodi R, Tonon C, Valentino ML, Iotti S, Clementi V, Malucelli E, Barboni P, Longanesi L, Schimpf S, Wissinger B, Baruzzi A, Barbiroli B and Carelli V

    Dipartimento di Medicina Clinica e Biotecnologia Applicata, Universita di Bologna, Bologna, Italy. raffaele.lodi@unibo.it

    Dominant optic atrophy has been associated with mutations in the OPA1 gene, which encodes for a dynamin-related GTPase, a mitochondrial protein implicated in the formation and maintenance of mitochondrial network and morphology. We used phosphorus magnetic resonance spectroscopy to assess calf muscle oxidative metabolism in six patients from two unrelated families carrying the c.2708-2711delTTAG deletion in exon 27 of the OPA1 gene. The rate of postexercise phosphocreatine resynthesis, a measure of mitochondrial adenosine triphosphate production rate, was significantly delayed in the patients. Our in vivo results show for the first time to our knowledge a deficit of oxidative phosphorylation in OPA1-related DOA.

    Annals of neurology 2004;56;5;719-23

  • Dominant optic atrophy, sensorineural hearing loss, ptosis, and ophthalmoplegia: a syndrome caused by a missense mutation in OPA1.

    Payne M, Yang Z, Katz BJ, Warner JE, Weight CJ, Zhao Y, Pearson ED, Treft RL, Hillman T, Kennedy RJ, Meire FM and Zhang K

    Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences Center, Salt Lake City, Utah, USA.

    Purpose: To describe the clinical features of and identify the disease-causing mutation in a large Utah family segregating a dominantly inherited syndrome of optic atrophy, sensorineural hearing loss, ptosis, and ophthalmoplegia.

    Design: Observational case series.

    Methods: Thirty individuals at risk for a syndrome of optic atrophy, sensorineural hearing loss, ptosis, and ophthalmoplegia in a single family underwent clinical examinations and venipuncture. Linkage analysis and mutation screening of the optic atrophy 1 gene (OPA1) were performed.

    Results: Eighteen individuals demonstrated characteristics of the syndrome. Genetic analysis identified a G-->A substitution at nucleotide position 1334 in exon 14 of OPA1 causing an arginine-to-histidine change (R445H) in all affected members of the family. This change segregated with the disease phenotype in the study family with a LOD score of 7.02 at theta; = 0 and was not found in 200 normal control subjects. Analysis of an unrelated Belgian family with a similar phenotype revealed the same R445H mutation segregating with the disease phenotype.

    Conclusions: This study describes a mutation in OPA1 causing a unique syndrome of optic atrophy, sensorineural hearing loss, ptosis, and ophthalmoplegia. These results expand the spectrum of human disease associated with mutations of OPA1 and indicate that ophthalmologists caring for patients with optic atrophy should inquire about possible associated hearing loss. Although OPA1 is a nuclear gene, the gene product localizes to mitochondria, suggesting that mitochondrial dysfunction may be the final common pathway for many forms of syndromic and nonsyndromic optic atrophy, hearing loss, and external ophthalmoplegia.

    Funded by: NCRR NIH HHS: K23 RR16427; NEI NIH HHS: R01 EY14428, R01 EY14448; PHS HHS: T35 H107744

    American journal of ophthalmology 2004;138;5;749-55

  • Roles of the mammalian mitochondrial fission and fusion mediators Fis1, Drp1, and Opa1 in apoptosis.

    Lee YJ, Jeong SY, Karbowski M, Smith CL and Youle RJ

    Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.

    During apoptosis, the mitochondrial network fragments. Using short hairpin RNAs for RNA interference, we manipulated the expression levels of the proteins hFis1, Drp1, and Opa1 that are involved in mitochondrial fission and fusion in mammalian cells, and we characterized their functions in mitochondrial morphology and apoptosis. Down-regulation of hFis1 powerfully inhibits cell death to an extent significantly greater than down-regulation of Drp1 and at a stage of apoptosis distinct from that induced by Drp1 inhibition. Cells depleted of Opa1 are extremely sensitive to exogenous apoptosis induction, and some die spontaneously by a process that requires hFis1 expression. Wild-type Opa1 may function normally as an antiapoptotic protein, keeping spontaneous apoptosis in check. However, if hFis1 is down-regulated, cells do not require Opa1 to prevent apoptosis, suggesting that Opa1 may be normally counteracting the proapoptotic action of hFis1. We also demonstrate in this study that mitochondrial fragmentation per se does not result in apoptosis. However, we provide further evidence that multiple components of the mitochondrial morphogenesis machinery can positively and negatively regulate apoptosis.

    Molecular biology of the cell 2004;15;11;5001-11

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

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

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

    Funded by: PHS HHS: N01-C0-12400

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

  • Transcriptome characterization elucidates signaling networks that control human ES cell growth and differentiation.

    Brandenberger R, Wei H, Zhang S, Lei S, Murage J, Fisk GJ, Li Y, Xu C, Fang R, Guegler K, Rao MS, Mandalam R, Lebkowski J and Stanton LW

    Geron Corporation, Menlo Park, California 94025, USA. rbrandenberger@geron.com

    Human embryonic stem (hES) cells hold promise for generating an unlimited supply of cells for replacement therapies. To characterize hES cells at the molecular level, we obtained 148,453 expressed sequence tags (ESTs) from undifferentiated hES cells and three differentiated derivative subpopulations. Over 32,000 different transcripts expressed in hES cells were identified, of which more than 16,000 do not match closely any gene in the UniGene public database. Queries to this EST database revealed 532 significantly upregulated and 140 significantly downregulated genes in undifferentiated hES cells. These data highlight changes in the transcriptional network that occur when hES cells differentiate. Among the differentially regulated genes are several components of signaling pathways and transcriptional regulators that likely play key roles in hES cell growth and differentiation. The genomic data presented here may facilitate the derivation of clinically useful cell types from hES cells.

    Nature biotechnology 2004;22;6;707-16

  • Robust phosphoproteomic profiling of tyrosine phosphorylation sites from human T cells using immobilized metal affinity chromatography and tandem mass spectrometry.

    Brill LM, Salomon AR, Ficarro SB, Mukherji M, Stettler-Gill M and Peters EC

    Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, USA. lbrill@gnf.org

    Protein tyrosine phosphorylation cascades are difficult to analyze and are critical for cell signaling in higher eukaryotes. Methodology for profiling tyrosine phosphorylation, considered herein as the assignment of multiple protein tyrosine phosphorylation sites in single analyses, was reported recently (Salomon, A. R.; Ficarro, S. B.; Brill, L. M.; Brinker, A.; Phung, Q. T.; Ericson, C.; Sauer, K.; Brock, A.; Horn, D. M.; Schultz, P. G.; Peters, E. C. Proc. Natl. Acad. Sci. U.S.A. 2003, 100, 443-448). The technology platform included the use of immunoprecipitation, immobilized metal affinity chromatography (IMAC), liquid chromatography, and tandem mass spectrometry. In the present report, we show that when using complex mixtures of peptides from human cells, methylation improved the selectivity of IMAC for phosphopeptides and eliminated the acidic bias that occurred with unmethylated peptides. The IMAC procedure was significantly improved by desalting methylated peptides, followed by gradient elution of the peptides to a larger IMAC column. These improvements resulted in assignment of approximately 3-fold more tyrosine phosphorylation sites, from human cell lysates, than the previous methodology. Nearly 70 tyrosine-phosphorylated peptides from proteins in human T cells were assigned in single analyses. These proteins had unknown functions or were associated with a plethora of fundamental cellular processes. This robust technology platform should be broadly applicable to profiling the dynamics of tyrosine phosphorylation.

    Analytical chemistry 2004;76;10;2763-72

  • Loss of the intermembrane space protein Mgm1/OPA1 induces swelling and localized constrictions along the lengths of mitochondria.

    Griparic L, van der Wel NN, Orozco IJ, Peters PJ and van der Bliek AM

    Department of Biological Chemistry, David Geffen School of Medicine, UCLA, Los Angeles, California 90095, USA.

    Mgm1 is a member of the dynamin family of GTP-binding proteins. Mgm1 was first identified in yeast, where it affects mitochondrial morphology. The human homologue of Mgm1 is called OPA1. Mutations in the OPA1 gene are the prevailing cause of dominant optic atrophy, a hereditary disease in which progressive degeneration of the optic nerve can lead to blindness. Here we investigate the properties of the Mgm1/OPA1 protein in mammalian cells. We find that Mgm1/OPA1 is localized to the mitochondrial intermembrane space, where it is tightly bound to the outer surface of the inner membrane. Overexpression of wild type or mutant forms of the Mgm1/OPA1 protein cause mitochondria to fragment and, in some cases, cluster near the nucleus, whereas the loss of protein caused by small interfering RNA (siRNA) leads to dispersal of mitochondrial fragments throughout the cytosol. The cristae of these fragmented mitochondria are disorganized. At early time points after transfection with Mgm1/OPA1 siRNA, the mitochondria are not yet fragmented. Instead, the mitochondria swell and stretch, after which they form localized constrictions similar to the mitochondrial abnormalities observed during the early stages of apoptosis. These abnormalities might be the earliest effects of losing Mgm1/OPA1 protein.

    Funded by: NIGMS NIH HHS: GM051866

    The Journal of biological chemistry 2004;279;18;18792-8

  • Complete sequencing and characterization of 21,243 full-length human cDNAs.

    Ota T, Suzuki Y, Nishikawa T, Otsuki T, Sugiyama T, Irie R, Wakamatsu A, Hayashi K, Sato H, Nagai K, Kimura K, Makita H, Sekine M, Obayashi M, Nishi T, Shibahara T, Tanaka T, Ishii S, Yamamoto J, Saito K, Kawai Y, Isono Y, Nakamura Y, Nagahari K, Murakami K, Yasuda T, Iwayanagi T, Wagatsuma M, Shiratori A, Sudo H, Hosoiri T, Kaku Y, Kodaira H, Kondo H, Sugawara M, Takahashi M, Kanda K, Yokoi T, Furuya T, Kikkawa E, Omura Y, Abe K, Kamihara K, Katsuta N, Sato K, Tanikawa M, Yamazaki M, Ninomiya K, Ishibashi T, Yamashita H, Murakawa K, Fujimori K, Tanai H, Kimata M, Watanabe M, Hiraoka S, Chiba Y, Ishida S, Ono Y, Takiguchi S, Watanabe S, Yosida M, Hotuta T, Kusano J, Kanehori K, Takahashi-Fujii A, Hara H, Tanase TO, Nomura Y, Togiya S, Komai F, Hara R, Takeuchi K, Arita M, Imose N, Musashino K, Yuuki H, Oshima A, Sasaki N, Aotsuka S, Yoshikawa Y, Matsunawa H, Ichihara T, Shiohata N, Sano S, Moriya S, Momiyama H, Satoh N, Takami S, Terashima Y, Suzuki O, Nakagawa S, Senoh A, Mizoguchi H, Goto Y, Shimizu F, Wakebe H, Hishigaki H, Watanabe T, Sugiyama A, Takemoto M, Kawakami B, Yamazaki M, Watanabe K, Kumagai A, Itakura S, Fukuzumi Y, Fujimori Y, Komiyama M, Tashiro H, Tanigami A, Fujiwara T, Ono T, Yamada K, Fujii Y, Ozaki K, Hirao M, Ohmori Y, Kawabata A, Hikiji T, Kobatake N, Inagaki H, Ikema Y, Okamoto S, Okitani R, Kawakami T, Noguchi S, Itoh T, Shigeta K, Senba T, Matsumura K, Nakajima Y, Mizuno T, Morinaga M, Sasaki M, Togashi T, Oyama M, Hata H, Watanabe M, Komatsu T, Mizushima-Sugano J, Satoh T, Shirai Y, Takahashi Y, Nakagawa K, Okumura K, Nagase T, Nomura N, Kikuchi H, Masuho Y, Yamashita R, Nakai K, Yada T, Nakamura Y, Ohara O, Isogai T and Sugano S

    Helix Research Institute, 1532-3 Yana, Kisarazu, Chiba 292-0812, Japan.

    As a base for human transcriptome and functional genomics, we created the "full-length long Japan" (FLJ) collection of sequenced human cDNAs. We determined the entire sequence of 21,243 selected clones and found that 14,490 cDNAs (10,897 clusters) were unique to the FLJ collection. About half of them (5,416) seemed to be protein-coding. Of those, 1,999 clusters had not been predicted by computational methods. The distribution of GC content of nonpredicted cDNAs had a peak at approximately 58% compared with a peak at approximately 42%for predicted cDNAs. Thus, there seems to be a slight bias against GC-rich transcripts in current gene prediction procedures. The rest of the cDNAs unique to the FLJ collection (5,481) contained no obvious open reading frames (ORFs) and thus are candidate noncoding RNAs. About one-fourth of them (1,378) showed a clear pattern of splicing. The distribution of GC content of noncoding cDNAs was narrow and had a peak at approximately 42%, relatively low compared with that of protein-coding cDNAs.

    Nature genetics 2004;36;1;40-5

  • The association of autosomal dominant optic atrophy and moderate deafness may be due to the R445H mutation in the OPA1 gene.

    Amati-Bonneau P, Odent S, Derrien C, Pasquier L, Malthiéry Y, Reynier P and Bonneau D

    INSERM E0018 et Laboratoire de Biochimie et Biologie moléculaire, CHU Angers, Angers, France. pabonneau@chu-angers.fr

    Purpose: To examine the involvement of the optic atrophy 1 (OPA1) gene in optic atrophy associated with moderate deafness.

    Design: Observational case report. The entire coding sequence of the OPA1 gene was directly sequenced in the case of a patient suffering from optic atrophy associated with moderate deafness.

    Results: A de novo heterozygous mutation R445H in the OPA1 gene was found. No similar mutation was detected in either of the patient's parents or in the 100 chromosome controls.

    Conclusion: The R445H mutation in OPA1 might be the cause of the association between dominant optic atrophy and moderate deafness, a phenotype that may be currently underdiagnosed.

    American journal of ophthalmology 2003;136;6;1170-1

  • Electrophysiology and ocular blood flow in a family with dominant optic nerve atrophy and a mutation in the OPA1 gene.

    Gränse L, Bergstrand I, Thiselton D, Ponjavic V, Heijl A, Votruba M and Andréasson S

    Department of Ophthalmology, University Hospital of Lund, Lund, Sweden. lotta.granse@telia.com

    Objective: To characterize the clinical phenotype, with emphasis on electrophysiology and blood flow measurements, of a family with dominant optic nerve atrophy and an identified mutation in the OPA1 gene.

    Methods: Seven family members were examined. Ophthalmological evaluation included testing of visual acuity, ophthalmolscopy, kinetic perimetry, color vision testing, full-field electroretinography (ERG), multifocal electroretinography (MERG), and multifocal visual evoked potential (MVEP). Retrobulbar arterial blood flow and retinal capillary perfusion was measured in three patients using scanning laser Doppler flowmetry (SLDF) and color Doppler imaging techniques. PCR-SSCP and DNA sequencing determined the presence of a mutation in exon 18 of the OPA1 gene.

    Results: The clinical characteristics varied considerably in the family. The ERG and the MERG demonstrated normal retinal function, while the MVEP was abnormal in all examined patients. Retinal and optic nerve head capillary perfusion was significantly decreased in the three patients examined with SLDF. Retrobulbar blood flow velocities were significantly decreased in the central retinal and ophthalmic arteries. In all seven examined subjects, a microdeletion (1756-1767del(12 bp)) in the OPA1 gene was identified.

    Conclusion: Patients with a mutation in the OPA1 gene have a very variable phenotype. MVEP and blood flow measurements are two new objective methods for an easier detection of this specific genetic optic nerve atrophy.

    Ophthalmic genetics 2003;24;4;233-45

  • Hereditary motor and sensory neuropathy type VI with optic atrophy.

    Voo I, Allf BE, Udar N, Silva-Garcia R, Vance J and Small KW

    Department of Ophthalmology, UCLA School of Medicine, Jules Stein Eye Institute, Los Angeles, California 90095, USA.

    Purpose: To present the detailed clinical findings of a large family with hereditary motor and sensory neuropathy type VI (HMSN VI), a syndrome featuring optic atrophy.

    Design: Observational case series.

    Methods: A detailed history was obtained and physical examination was made of the extended family of the proband for evidence of neurologic dysfunction. The OPA1 gene was screened for mutations by direct DNA sequencing.

    Results: Twelve of 97 family members examined are affected with signs of HMSN VI. Three other members have either optic atrophy or peripheral neuropathy, thus allowing an appreciation of the full clinical spectrum of disease. No mutations were found in the OPA1 gene.

    Conclusions: This family demonstrates the variable expressivity of this disorder as well as incomplete penetrance. This is the largest known family with HMSN VI. No association was found with changes in the OPA1 gene.

    American journal of ophthalmology 2003;136;4;670-7

  • Polymorphisms in OPA1 are associated with normal tension glaucoma.

    Powell BL, Toomes C, Scott S, Yeung A, Marchbank NJ, Spry PG, Lumb R, Inglehearn CF and Churchill AJ

    Division of Ophthalmology, University of Bristol, Bristol, United Kingdom.

    Purpose: [corrected] To confirm whether specific polymorphisms in intron 8 (IVS8) of the OPA1 gene are found more commonly in patients with normal tension glaucoma (NTG) compared to normal controls.

    Methods: This is a cohort study of 61 patients with NTG, 49 known healthy controls and 119 individuals from the general population. The DNA sequence was determined at the +4 and +32 positions of IVS8 of the OPA1 gene. Hardy-Weinberg equilibrium was confirmed in our population by comparing the allele frequencies in two additional genes, TP53 and TYRP1. Genotypes for the NTG and control groups were compared for statistically significant differences.

    Results: There were no differences in the OPA1 genotypes of the NTG and control groups at the +4 location, as had been suggested in a previous study, but a significant difference was observed at the +32 location of IVS8. The CC genotype was found in 28% of NTG patients compared to 13% of controls (p=0.006). The TC genotype was more prevalent in the control population (p=0.02) but this difference did not reach statistical significance when the Bonferroni adjustment was made for multiple analyses.

    Conclusions: We have refined the previously reported association between OPA1 sequence changes and NTG by identifying a specific CC genotype at position +32 in IVS8 of the OPA1 gene that acts as a marker for NTG. At the current time, NTG is frequently diagnosed late when loss of neurons has already caused significant and irreversible peripheral field loss. If a test could be designed to identify those people at risk of developing NTG, then careful screening might detect earlier signs of disease allowing commencement of treatment before significant field loss has occurred.

    Molecular vision 2003;9;460-4

  • OPA1 gene mutations in Japanese patients with bilateral optic atrophy unassociated with mitochondrial DNA mutations at nt 11778, 3460, and 14484.

    Yamada T, Hayasaka S, Matsumoto M, Budu, Esa T, Hayasaka Y, Endo M, Nagaki Y, Fujiki K, Murakami A and Kanai A

    Department of Ophthalmology, Toyama Medical and Pharmaceutical University, Toyama, Japan.

    Purpose: To report mutations in the OPA1 gene in Japanese patients with bilateral optic atrophy unassociated with mitochondrial DNA mutations at nt 11778, 3460, and 14484.

    Methods: Twelve unrelated patients with bilateral optic atrophy and 100 healthy controls were examined. Each exon of the OPA1 gene was amplified by polymerase chain reaction (PCR). All PCR products were sequenced.

    Results: Of the 12 patients, 2 had nonsense mutations of the OPA1 gene (nt 1039G --> T and nt 1096C --> T, leading to Glu347Stop and Arg366Stop, respectively). These nonsense mutations were not found in the 100 healthy controls. Two of the patients had silent mutations of OPA1 gene (nt 1177T --> G and nt 1923G --> A causing no amino acid change).

    Conclusions: The mutations (Glu347Stop and Arg366Stop) of the OPA1 gene are involved in the pathogenesis of bilateral optic atrophy in Japanese patients.

    Japanese journal of ophthalmology 2003;47;4;409-11

  • Loss of OPA1 perturbates the mitochondrial inner membrane structure and integrity, leading to cytochrome c release and apoptosis.

    Olichon A, Baricault L, Gas N, Guillou E, Valette A, Belenguer P and Lenaers G

    Laboratoire de Biologie Cellulaire et Moléculaire du Contrôle de la Prolifération, UMR 5088, Université Paul Sabatier, Bât. 4R3-B1, 118 route de Narbonne, F-31062 Toulouse cedex 04, France.

    OPA1 encodes a large GTPase related to dynamins, anchored to the mitochondrial cristae inner membrane, facing the intermembrane space. OPA1 haplo-insufficiency is responsible for the most common form of autosomal dominant optic atrophy (ADOA, MIM165500), a neuropathy resulting from degeneration of the retinal ganglion cells and optic nerve atrophy. Here we show that down-regulation of OPA1 in HeLa cells using specific small interfering RNA (siRNA) leads to fragmentation of the mitochondrial network concomitantly to the dissipation of the mitochondrial membrane potential and to a drastic disorganization of the cristae. These events are followed by cytochrome c release and caspase-dependent apoptotic nuclear events. Similarly, in NIH-OVCAR-3 cells, the OPA1 siRNA induces mitochondrial fragmentation and apoptosis, the latter being inhibited by Bcl2 overexpression. These results suggest that OPA1 is a major organizer of the mitochondrial inner membrane from which the maintenance of the cristae integrity depends. As loss of OPA1 commits cells to apoptosis without any other stimulus, we propose that OPA1 is involved in the cytochrome c sequestration and might be a target for mitochondrial apoptotic effectors. Our results also suggest that abnormal apoptosis is a possible pathophysiological process leading to the retinal ganglion cells degeneration in ADOA patients.

    The Journal of biological chemistry 2003;278;10;7743-6

  • A novel mutation in the OPA1 gene in a Japanese patient with optic atrophy.

    Shimizu S, Mori N, Kishi M, Sugata H, Tsuda A and Kubota N

    Department of Ophthalmology, Teikyo University School of Medicine, Tokyo, Japan. Stkshimi@aol.com

    Purpose: To report a novel mutation of the OPA1 gene in a Japanese patient with optic atrophy and to describe the clinical features of the patient.

    Design: Observational case report.

    Methods: Genomic DNA was extracted from leukocytes of four unrelated Japanese patients with optic atrophy. All the exons and splice sites of the OPA1 gene were amplified by polymerase chain reaction and directly sequenced.

    Results: One patient with optic atrophy had a heterozygous Arg445His mutation in the OPA1 gene. The Arg445His mutation was detected neither in 110 control subjects nor in the patient's healthy family members.

    Conclusions: A novel mutation of the OPA1 gene, similar to those reported in Western countries, was detected in a Japanese patient with optic atrophy. Mutations of the OPA1 gene may contribute to the development of optic nerve atrophy in Japanese cases of optic atrophy.

    American journal of ophthalmology 2003;135;2;256-7

  • The phenotype of normal tension glaucoma patients with and without OPA1 polymorphisms.

    Aung T, Okada K, Poinoosawmy D, Membrey L, Brice G, Child AH, Bhattacharya SS, Lehmann OJ, Garway-Heath DF and Hitchings RA

    Moorfields Eye Hospital, London, UK. aung_tin@yahoo.co.uk

    Aim: Polymorphisms in OPA1, the gene responsible for autosomal dominant optic atrophy, were recently found to be strongly associated with normal tension glaucoma (NTG). The aim of this study was to determine whether OPA1 polymorphisms affect the phenotype of NTG patients.

    Methods: A retrospective analysis was performed of 108 well characterised NTG patients who had been genotyped for OPA1 variations, and who had previously undergone automated perimetry and Heidelberg retina tomography (HRT). 25 NTG patients had the at-risk OPA1 genotype (IVS 8 +4 C/T; +32 T/C) and 83 NTG patients did not. Differences between groups were sought in a wide range of structural, psychophysical, and demographic factors. These included sex, age at diagnosis, family history of glaucoma, history of ischaemic risk factors and vasospasm, laterality of glaucoma, presenting and highest diurnal intraocular pressure (IOP), initial cup-disc (CD) ratio, baseline visual field global indices, and optic disc parameters as measured by HRT. For a subgroup of patients with at least 5 years of follow up and 10 visual field tests, pointwise linear regression analysis (PROGRESSOR for Windows software) was applied to the visual field series.

    Results: There was no significant difference in the two groups with respect to sex, age at diagnosis, family history of glaucoma, history of ischaemic risk factors and vasospasm, or laterality of glaucoma. The comparison of IOP, CD ratio and visual field global indices, MD and CPSD in the two groups showed no significant difference. There were no differences in the mean values for any of the HRT parameters analysed. For the subgroup of patients with at least 5 years of follow up, there was also no significant difference in the number of patients with progressing locations, the mean number of progressing locations per subject, the mean slope of the progressing locations or the mean slope for whole visual field.

    Conclusions: The absence of phenotypic differences in normal tension glaucoma patients with and without the OPA1 polymorphisms IVS 8 +4 C/T; +32 T/C suggest that these OPA1 polymorphisms do not underlie any major phenotypic diversity in these patients.

    The British journal of ophthalmology 2003;87;2;149-52

  • Differential sublocalization of the dynamin-related protein OPA1 isoforms in mitochondria.

    Satoh M, Hamamoto T, Seo N, Kagawa Y and Endo H

    Department of Biochemistry, Jichi Medical School, 3311-1 Yakushiji, Minamikawachi-mach, Tochigi 329-0498, Japan.

    OPA1 is a cause gene for autosomal dominant optic atrophy and possesses eight alternative splicing variants. Here, we identified two isoforms of OPA1 proteins in HeLa cells and examined their submitochondrial localization and complex formations. RT-PCR shows that HeLa cells mainly express isoforms 7 and 1 of OPA1. Since the third cleavage site is mainly utilized in HeLa cells, the predicted molecular masses of their processed proteins are consistent with the 93- and 88-kDa proteins. Biochemical examinations indicate that both of the OPA1 isoforms are present in the intermembrane space. Submitochondrial fractionation by sucrose density-gradient centrifugation shows that the 88-kDa protein predominantly associates with the mitochondrial outer membrane, on the contrary, the 93-kDa protein associates with the inner membrane. Gel filtration analysis indicates that they compose the different molecular mass complexes in mitochondria. These differences between two isoforms of OPA1 would suggest their crucial role involved in the mitochondrial membrane formation.

    Biochemical and biophysical research communications 2003;300;2;482-93

  • Deletion of the OPA1 gene in a dominant optic atrophy family: evidence that haploinsufficiency is the cause of disease.

    Marchbank NJ, Craig JE, Leek JP, Toohey M, Churchill AJ, Markham AF, Mackey DA, Toomes C and Inglehearn CF

    Molecular Medicine Unit, University of Leeds, Clinical Sciences Building, St James's University Hospital, Leeds LS9 7TF, UK.

    Journal of medical genetics 2002;39;8;e47

  • The human dynamin-related protein OPA1 is anchored to the mitochondrial inner membrane facing the inter-membrane space.

    Olichon A, Emorine LJ, Descoins E, Pelloquin L, Brichese L, Gas N, Guillou E, Delettre C, Valette A, Hamel CP, Ducommun B, Lenaers G and Belenguer P

    Laboratoire de Biologie Cellulaire et Moléculaire du Contrôle de la Prolifération and Laboratoire de Biologie Moléculaire des Eucaryotes, IFR109, Université Paul Sabatier, 118 route de Narbonne, 31062 cedex 04, Toulouse, France.

    Mutations in the OPA1 gene are associated with autosomal dominant optic atrophy. OPA1 encodes a dynamin-related protein orthologous to Msp1 of Schizosaccharomyces pombe and Mgm1p of Saccharomyces cerevisiae, both involved in mitochondrial morphology and genome maintenance. We present immuno-fluorescence and biochemical evidences showing that OPA1 resides in the mitochondria where it is imported through its highly basic amino-terminal extension. Proteolysis experiments indicate that OPA1 is present in the inter-membrane space and electron microscopy further localizes it close to the cristae. The strong association of OPA1 with membranes suggests its anchoring to the inner membrane.

    FEBS letters 2002;523;1-3;171-6

  • A comprehensive survey of mutations in the OPA1 gene in patients with autosomal dominant optic atrophy.

    Thiselton DL, Alexander C, Taanman JW, Brooks S, Rosenberg T, Eiberg H, Andreasson S, Van Regemorter N, Munier FL, Moore AT, Bhattacharya SS and Votruba M

    Department of Molecular Genetics, Institute of Ophthalmology, London, United Kingdom.

    Purpose: To characterize the spectrum of mutations in the OPA1 gene in a large international panel of patients with autosomal dominant optic atrophy (adOA), to improve understanding of the range of functional deficits attributable to sequence variants in this gene, and to assess any genotype-phenotype correlations.

    Methods: All 28 coding exons of OPA1, intron-exon splice sites, 273 bp 5' to exon 1, and two intronic regions with putative function were screened in 94 apparently unrelated white patients of European origin with adOA by single-strand conformational polymorphism (SSCP)-heteroduplex analysis and direct sequencing. Clinical data were collated, and putative mutations were tested for segregation in the respective families by SSCP analysis or direct sequencing and in 100 control chromosomes. Further characterization of selected splice site mutations was performed by RT-PCR of patient leukocyte RNA. Staining of mitochondria in leukocytes of patients and control subjects was undertaken to assess gross differences in morphology and cellular distribution.

    Results: Twenty different mutations were detected, of which 14 were novel disease mutations (missense, nonsense, deletion-frameshift, and splice site alterations) and six were known mutations. Mutations were found in 44 (47%) of the 94 families included in the study. Ten new polymorphisms in the OPA1 gene were also identified. Mutations occur throughout the gene, with three clusters emerging: in the mitochondrial leader, in the highly conserved guanosine triphosphate (GTP)-binding domain, and in the -COOH terminus. Examination of leukocyte mitochondria from two unrelated patients with splice site mutations in OPA1 revealed no abnormalities of morphology or cellular distribution when compared with control individuals.

    Conclusions: This study describes 14 novel mutations in the OPA1 gene in patients with adOA, bringing the total number so far reported to 54. It is likely that many cases of adOA are due to mutations outside the coding region of OPA1 or to large-scale rearrangements. Evaluation of the mutation spectrum indicates more than one pathophysiological mechanism for adOA. Preliminary data suggests that phenotype-genotype correlation is complex, implying a role for other genetic modifying or environmental factors. No evidence was found of pathologic changes in leukocyte mitochondria of patients with adOA.

    Investigative ophthalmology & visual science 2002;43;6;1715-24

  • Primary structure of a dynamin-related mouse mitochondrial GTPase and its distribution in brain, subcellular localization, and effect on mitochondrial morphology.

    Misaka T, Miyashita T and Kubo Y

    Department of Physiology, Tokyo Medical and Dental University, Graduate School and Faculty of Medicine, Bunkyo, Tokyo 113-8519, Japan.

    A new member of the dynamin GTPase family (OPA1) was recently identified in humans and shown to be mutated in patients with dominant optic atrophy. To understand better the function of mammalian OPA1, we isolated a mouse ortholog (mOPA1) from brain and raised a specific antibody against its C terminus. The subcellular distribution of mOPA1 overexpressed in COS-7 cells largely overlapped that of endogenous cytochrome c, a well known mitochondrial marker, and dramatically affected mitochondrial morphology, altering it from tubular to vesicular. Mitochondrial targeting was mediated by the N-terminal region of mOPA1 as follows: deletion of the 124 N-terminal amino acids eliminated mitochondrial targeting, although fusion of the N-terminal 60 or 90 amino acids of mOPA1 with green fluorescent protein resulted in its mitochondrial targeting. mOPA1 was expressed widely in the mouse brain, especially in neurons of olfactory bulb, cerebral cortex, piriform cortex, hypothalamus, hippocampus, red nucleus, cochlear nucleus, motor trigeminal nucleus, facial nucleus, cerebellar nucleus, and Purkinje cells. Within dissociated cerebellar cells, mOPA1 protein was clearly observed in the dendrites and somas of neuronal cells, as well as in astrocytes and meningeal cells. In each case, it was distributed in the vesicular pattern seen in other cell types.

    The Journal of biological chemistry 2002;277;18;15834-42

  • Investigating the association between OPA1 polymorphisms and glaucoma: comparison between normal tension and high tension primary open angle glaucoma.

    Aung T, Ocaka L, Ebenezer ND, Morris AG, Brice G, Child AH, Hitchings RA, Lehmann OJ and Bhattacharya SS

    Department of Molecular Genetics, Institute of Ophthalmology, University College London, Bath Street, London EC1V 9EL, UK. aung_tin@yahoo.co.uk

    OPA1, the gene responsible for autosomal dominant optic atrophy, represents a good candidate gene for glaucoma, as there are similarities in the clinical phenotype and OPA1 is expressed in the optic nerve. Single nucleotide polymorphisms on intervening sequence (IVS) 8 of the OPA1gene (genotype IVS8+4 C/T;+32T/C) were recently found to be strongly associated with normal tension glaucoma (NTG). In order to investigate whether this association exists in patients with high-tension glaucoma (HTG), 90 well-characterized HTG patients were examined for the presence of these OPA1polymorphisms by PCR amplification followed by bi-directional sequencing. Five out of 90 HTG subjects (5.6%; 95% CI 1.8-12.5) were found to carry the OPA1 genotype IVS 8+4 C/T; +32 T/C, compared with 32/163 (19.6%; 95% CI 13.8-26.6) NTG subjects [chi(2)=9.2, P=0.002, OR 4.1 (95% CI 1.6-11.1)], and 7/186 (3.8%; 95% CI 1.5-7.6) control subjects [chi(2)=0.47, P=0.49, OR 1.5 (95% CI 0.5-4.9)]. These results indicate that unlike NTG, the OPA1 genotype IVS8+4 C/T,+32T/C is not significantly associated with high-tension primary open angle glaucoma, and suggest genetic heterogeneity between the conditions.

    Human genetics 2002;110;5;513-4

  • A major marker for normal tension glaucoma: association with polymorphisms in the OPA1 gene.

    Aung T, Ocaka L, Ebenezer ND, Morris AG, Krawczak M, Thiselton DL, Alexander C, Votruba M, Brice G, Child AH, Francis PJ, Hitchings RA, Lehmann OJ and Bhattacharya SS

    Singapore National Eye Centre, Singapore. tin11@pacific.net.sg

    Normal tension glaucoma (NTG) is a major form of glaucoma, associated with intraocular pressures that are within the statistically normal range of the population. OPA1, the gene responsible for autosomal dominant optic atrophy represents an excellent candidate gene for NTG, as the clinical phenotypes are similar and OPA1 is expressed in the retina and optic nerve. Eighty-three well-characterized NTG patients were screened for mutations in OPA1 by heteroduplex analysis and bi-directional sequencing. Sequences found to be altered in NTG subjects were examined for variations in 100 population controls. A second cohort of 80 NTG patients and 86 population controls was subsequently screened to determine whether the initial findings could be replicated. A single nucleotide polymorphism (SNP) on intervening sequence (IVS) 8 (IVS8 + 4 C/T) was found to be strongly associated with the occurrence of NTG in both cohorts (chi(2)=7.97, P=0.005 in the first cohort, chi(2)=9.93, P=0.002 in the second cohort; odds ratio 3.1 (95% CI: 1.8-5.6). A second SNP (IVS8 + 32 T/C) appeared to be associated with disease in the first cohort (chi(2)=4.71, P=0.030), but this finding could not be replicated in the second cohort. In the combined cohort, the compound at-risk genotype IVS8 + 4 C/T, + 32 T/C was strongly associated with the occurrence of NTG (chi(2)=22.04, P=0.00001 after correcting for testing four genotypes). These results indicate that polymorphisms in the OPA1 gene are associated with NTG and may be a marker for the disease.

    Human genetics 2002;110;1;52-6

  • Mutation spectrum and splicing variants in the OPA1 gene.

    Delettre C, Griffoin JM, Kaplan J, Dollfus H, Lorenz B, Faivre L, Lenaers G, Belenguer P and Hamel CP

    Inserm U. 254, 71, rue de Navacelles, 34090 Montpellier, France.

    Optic atrophy type 1 (OPA1, MIM 165500) is a dominantly inherited optic neuropathy that features low visual acuity leading in many cases to legal blindness. We have recently shown, with others, that mutations in the OPA1 gene encoding a dynamin-related mitochondrial protein, underlie the dominant form of optic atrophy. Here we report that OPA1 has eight mRNA isoforms as a result of the alternative splicing of exon 4 and two novel exons named 4b and 5b. In addition, we screened a cohort of 19 unrelated patients with dominant optic atrophy by direct sequencing of the 30 OPA1 exons (including exons 4b and 5b) and found mutations in 17 (89%) of them of which 8 were novel. A majority of these mutations were truncative (65%) and located in exons 8 to 28, but a number of them were amino acid changes predominantly found in the GTPase domain (exons 8 to 15). We hypothesize that at least two modifications of OPA1 may lead to dominant optic atrophy, that is alteration in GTPase activity and loss of the last seven C-terminal amino acids that putatively interact with other proteins.

    Human genetics 2001;109;6;584-91

  • A frameshift mutation in exon 28 of the OPA1 gene explains the high prevalence of dominant optic atrophy in the Danish population: evidence for a founder effect.

    Thiselton DL, Alexander C, Morris A, Brooks S, Rosenberg T, Eiberg H, Kjer B, Kjer P, Bhattacharya SS and Votruba M

    Department of Molecular Genetics, Institute of Ophthalmology, University College London, EC1 V 9EL, UK. dthiselt@hgmp.mrc.ac.uk

    Dominant optic atrophy (DOA) is a hereditary optic neuropathy characterised by decreased visual acuity, colour vision deficits, centro-coecal scotoma and optic nerve pallor. The gene OPA1, encoding a dynamin-related GTPase, has recently been identified within the genetic linkage interval for the major locus for DOA on chromosome 3q28 and shown to harbour genetic aberrations segregating with disease in DOA families. The prevalence of the disorder in Denmark is reported to be the highest of any geographical location, suggestive of a founder effect. In order to establish the genetic basis of disease in a sample of 33 apparently unrelated Danish families, we screened DNA from affected members for OPA1 gene mutations by heteroduplex analysis and direct sequencing. A novel identical mutation in exon 28 (2826delT) was associated with DOA in 14 pedigrees and led to a frameshift and abnormal OPA1 protein -COOH terminus. Haplotype analysis of a region of approximately 1 Mb flanking the OPA1 gene using eight polymorphic markers revealed a common haplotype shared by all 14 patients; this haplotype was markedly over-represented compared with ethnically matched controls. Statistical analysis confirmed significant linkage disequilibrium with DOA over approximately 600 kb encompassing the disease mutation. We have therefore demonstrated that the relatively high frequency of DOA in Denmark is attributable to a founder mutation responsible for approximately 42% of the examined families and suggest that presymptomatic screening for the (2826delT) mutation may facilitate diagnosis and genetic counselling in a significant proportion of DOA patients of Danish ancestry.

    Human genetics 2001;109;5;498-502

  • Spectrum, frequency and penetrance of OPA1 mutations in dominant optic atrophy.

    Toomes C, Marchbank NJ, Mackey DA, Craig JE, Newbury-Ecob RA, Bennett CP, Vize CJ, Desai SP, Black GC, Patel N, Teimory M, Markham AF, Inglehearn CF and Churchill AJ

    Molecular Medicine Unit, Clinical Sciences Building, University of Leeds, St James's University Hospital, Leeds, LS9 7TF, UK.

    Dominant optic atrophy (DOA) is the commonest form of inherited optic neuropathy. Although heterogeneous, a major locus has been mapped to chromosome 3q28 and the gene responsible, OPA1, was recently identified. We therefore screened a panel of 35 DOA patients for mutations in OPA1. This revealed 14 novel mutations and a further three known mutations, which together accounted for 20 of the 35 families (57%) included in this study. This more than doubles the number of OPA1 mutations reported in the literature, bringing the total to 25. These are predominantly null mutations generating truncated proteins, strongly suggesting that the mechanism underlying DOA is haploinsufficiency. The mutations are largely family-specific, although a common 4 bp deletion in exon 27 (eight different families) and missense mutations in exons 8 (two families) and 9 (two families) have been identified. Haplotype analysis of individuals with the exon 27 2708del(TTAG) mutation suggests that this is a mutation hotspot and not an ancient mutation, thus excluding a major founder effect at the OPA1 locus. The mutation screening in this study also identified a number of asymptomatic individuals with OPA1 mutations. A re-calculation of the penetrance of this disorder within two of our families indicates figures as low as 43 and 62% associated with the 2708del(TTAG) mutation. If haploinsufficiency is the mechanism underlying DOA it is unlikely that this figure will be mutation-specific, indicating that the penetrance in DOA is much lower than the 98% reported previously. To investigate whether Leber's hereditary optic neuropathy (LHON) could be caused by mutations in OPA1 we also screened a panel of 28 LHON patients who tested negatively for the three major LHON mutations. No mutations were identified in any LHON patients, indicating that DOA and LHON are genetically distinct.

    Human molecular genetics 2001;10;13;1369-78

  • Nuclear gene OPA1, encoding a mitochondrial dynamin-related protein, is mutated in dominant optic atrophy.

    Delettre C, Lenaers G, Griffoin JM, Gigarel N, Lorenzo C, Belenguer P, Pelloquin L, Grosgeorge J, Turc-Carel C, Perret E, Astarie-Dequeker C, Lasquellec L, Arnaud B, Ducommun B, Kaplan J and Hamel CP

    Inserm U. 254, Laboratoire de Neurobiologie de l'audition, Montpellier, France.

    Optic atrophy type 1 (OPA1, MIM 165500) is a dominantly inherited optic neuropathy occurring in 1 in 50,000 individuals that features progressive loss in visual acuity leading, in many cases, to legal blindness. Phenotypic variations and loss of retinal ganglion cells, as found in Leber hereditary optic neuropathy (LHON), have suggested possible mitochondrial impairment. The OPA1 gene has been localized to 3q28-q29 (refs 13-19). We describe here a nuclear gene, OPA1, that maps within the candidate region and encodes a dynamin-related protein localized to mitochondria. We found four different OPA1 mutations, including frameshift and missense mutations, to segregate with the disease, demonstrating a role for mitochondria in retinal ganglion cell pathophysiology.

    Nature genetics 2000;26;2;207-10

  • OPA1, encoding a dynamin-related GTPase, is mutated in autosomal dominant optic atrophy linked to chromosome 3q28.

    Alexander C, Votruba M, Pesch UE, Thiselton DL, Mayer S, Moore A, Rodriguez M, Kellner U, Leo-Kottler B, Auburger G, Bhattacharya SS and Wissinger B

    Department of Molecular Genetics, Insititute of Ophthalmology, University College London, London, UK.

    Autosomal dominant optic atrophy (ADOA) is the most prevalent hereditary optic neuropathy resulting in progressive loss of visual acuity, centrocoecal scotoma and bilateral temporal atrophy of the optic nerve with an onset within the first two decades of life. The predominant locus for this disorder (OPA1; MIM 165500) has been mapped to a 1.4-cM interval on chromosome 3q28-q29 flanked by markers D3S3669 and D3S3562 (ref. 3). We established a PAC contig covering the entire OPA1 candidate region of approximately 1 Mb and a sequence skimming approach allowed us to identify a gene encoding a polypeptide of 960 amino acids with homology to dynamin-related GTPases. The gene comprises 28 coding exons and spans more than 40 kb of genomic sequence. Upon sequence analysis, we identified mutations in seven independent families with ADOA. The mutations include missense and nonsense alterations, deletions and insertions, which all segregate with the disease in these families. Because most mutations probably represent null alleles, dominant inheritance of the disease may result from haploinsufficiency of OPA1. OPA1 is widely expressed and is most abundant in the retina. The presence of consensus signal peptide sequences suggests that the product of the gene OPA1 is targeted to mitochondria and may exert its function in mitochondrial biogenesis and stabilization of mitochondrial membrane integrity.

    Nature genetics 2000;26;2;211-5

  • Dominant optic atrophy. Refining the clinical diagnostic criteria in light of genetic linkage studies.

    Johnston RL, Seller MJ, Behnam JT, Burdon MA and Spalton DJ

    Department of Ophthalmology, St Thomas' Hospital, London, England, UK.

    Objective: To describe the clinical findings and refine the clinical diagnostic criteria for dominant optic atrophy based on eight British families in which the diagnosis was confirmed by linkage analysis.

    Case series; 92 subjects in 8 pedigrees had both eyes examined.

    Intervention: Family members received a domiciliary examination based on best-corrected visual acuity, color vision using Ishihara and Hardy Richter Rand (HRR) plates, confrontation field testing using a red target, and optic disc evaluation using a direct ophthalmoscope. Genomic DNA was extracted from leukocytes or buccal mucosal cells and genotyped using 12 fluorescently labeled microsatellite markers from the region 3q27-q29.

    Subjects were classified clinically as definitely or possibly affected on the basis of the domiciliary examination before genetic analysis, and these results were compared with the haplotype analysis.

    Results: Clinically, 43 subjects were identified as definitely affected, 4 as possibly affected, and 45 as unaffected. Visual acuity in affected subjects ranged from 6/6 to count fingers and declined with age. On genetic analysis, a haplotype was identified in each family, which was found in all definitely affected members but not in those regarded as unaffected. The four possibly affected individuals also bore the haplotype that segregated with the disease.

    Conclusions: Simple clinical tests are highly efficacious in diagnosing dominant optic atrophy. Contrary to accepted criteria, symptoms begin before the age of 10 years in only 58% of affected individuals. Visual acuity in affected subjects is highly variable. A mild degree of temporal or diffuse pallor of the optic disc and minimal color vision defects, in the context of a family with dominant optic atrophy, are highly suggestive of an individual being affected, even if the visual acuity is normal. This widens the generally accepted diagnostic criteria for this disease.

    Ophthalmology 1999;106;1;123-8

  • Prediction of the coding sequences of unidentified human genes. IX. The complete sequences of 100 new cDNA clones from brain which can code for large proteins in vitro.

    Nagase T, Ishikawa K, Miyajima N, Tanaka A, Kotani H, Nomura N and Ohara O

    Kazusa DNA Research Institute, Kisarazu, Chiba, Japan.

    As an extension of a series of projects for sequencing human cDNA clones derived from relatively long transcripts, we herein report the entire sequences of 100 newly determined cDNA clones with the potential of coding for large proteins in vitro. The cDNA clones were isolated from size-fractionated human brain cDNA libraries with insert sizes between 4.5 and 8.3 kb. The sequencing of these clones revealed that the average size of the cDNA inserts and of their open reading frames was 5.3 kb and 2.8 kb (930 amino acid residues), respectively. Homology search against public databases indicated that the predicted coding sequences of 86 clones exhibited significant similarities to known genes; 51 of them (59%) were related to those for cell signaling/communication, nucleic acid management, and cell structure/motility. All the clones characterized in this study are accompanied by their expression profiles in 14 human tissues examined by reverse transcription-coupled polymerase chain reaction and the chromosomal mapping data.

    DNA research : an international journal for rapid publication of reports on genes and genomes 1998;5;1;31-9

  • Demonstration of a founder effect and fine mapping of dominant optic atrophy locus on 3q28-qter by linkage disequilibrium method: a study of 38 British Isles pedigrees.

    Votruba M, Moore AT and Bhattacharya SS

    Department of Molecular Genetics, Institute of Ophthalmology, London, UK. mvotruba@hgmp.mrc.ac.uk

    Dominant optic atrophy, a hereditary optic neuropathy causing decreased visual acuity, colour vision deficits, a centro-caecal scotoma and optic nerve pallor, has been mapped to a genetic interval of 1.4 cM between loci D3S3669 and D3S3562 on chromosome 3q28-qter. In order to further refine the critical disease interval, and to test the power of haplotype analysis and linkage disequilibrium mapping, we identified a total of 38 families with dominant optic atrophy, unrelated on the basis of genealogy, from a data base of genetic eye disease families originating from the British Isles. They were studied with 12 highly polymorphic microsatellite markers spanning a region of 12 cM around the dominant optic atrophy locus (OPA1). Allelic frequency analysis [chi-squared test, likelihood ratio test (LRT) and P values] and haplotype parsimony analysis showed evidence of a founder effect in 36 of the 38 pedigrees. Six markers (D3S3669, D3S1523, D3S3642, D3S2305, D3S3590 and D3S3562), spanning 1.4 cM across the disease-associated region, demonstrated significant linkage disequilibrium by LRT (P < 0.05). A peak LRT value of 10.86 (P < 0.0005, lambda = 0.4) occurred at D3S3669. On linkage disequilibrium multipoint analysis the maximum lod score of 8.01 is achieved at D3S1523, and 95% confidence intervals suggest that OPA1 lies within ca. 400 kb of D3S1523.

    Funded by: Wellcome Trust

    Human genetics 1998;102;1;79-86

Gene lists (7)

Gene List Source Species Name Description Gene count
L00000009 G2C Homo sapiens Human PSD Human orthologues of mouse PSD adapted from Collins et al (2006) 1080
L00000010 G2C Homo sapiens Human mitochondria Human orthologues of mouse mitochondria adapted from Collins et al (2006) 91
L00000016 G2C Homo sapiens Human PSP Human orthologues of mouse PSP adapted from Collins et al (2006) 1121
L00000059 G2C Homo sapiens BAYES-COLLINS-HUMAN-PSD-CONSENSUS Human cortex PSD consensus 748
L00000061 G2C Homo sapiens BAYES-COLLINS-MOUSE-PSD-CONSENSUS Mouse cortex PSD consensus (ortho) 984
L00000069 G2C Homo sapiens BAYES-COLLINS-HUMAN-PSD-FULL Human cortex biopsy PSD full list 1461
L00000071 G2C Homo sapiens BAYES-COLLINS-MOUSE-PSD-FULL Mouse cortex PSD full list (ortho) 1556
© G2C 2014. The Genes to Cognition Programme received funding from The Wellcome Trust and the EU FP7 Framework Programmes:
EUROSPIN (FP7-HEALTH-241498), SynSys (FP7-HEALTH-242167) and GENCODYS (FP7-HEALTH-241995).

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