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Brodsky MC, Olson RJ, Asumda FZ, Lopour MQ, Schimmenti LA, Klee EW. Identification of AFG3L2 dominant optic atrophy following reanalysis of clinical exome sequencing. Am J Ophthalmol Case Rep 2023; 30:101825. [PMID: 36974169 PMCID: PMC10038781 DOI: 10.1016/j.ajoc.2023.101825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Revised: 02/09/2023] [Accepted: 02/24/2023] [Indexed: 03/11/2023] Open
Abstract
Purpose To highlight the importance of the utility of clinical exome sequencing, and show how it led to the diagnosis of nonsyndromic autosomal dominant optic atrophy arising from an autosomal dominant variant in AFG3L2. Observations A healthy father and daughter of East African heritage experienced the onset of vision loss in the first decade of life due to optic atrophy. No additional neurologic or neuroimaging abnormalities were detected. Clinical exome sequencing was initially performed and provided a negative result. Reanalysis of the sequencing data revealed an autosomal dominant pathogenic variant in AFG3L2, c.1064C>T (p.Thr355Met), a gene that was recently identified to be associated with non-syndromic optic atrophy. This variant has previously been reported in a patient with optic atrophy, motor disturbances, and an abnormal brain MRI. Conclusions As the causes of dominant optic atrophy continue to expand, accurate genetic diagnosis is aided by an iterative reanalysis process for individuals and families when initial exome and genome testing does not provide an answer.
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Affiliation(s)
- Michael C. Brodsky
- Department of Ophthalmology, Mayo Clinic, Rochester, MN, United States
- Department of Neurology, Mayo Clinic, Rochester, MN, United States
- Corresponding author. Mayo Clinic, Department of Ophthalmology, 200 First St SW, Rochester, MN, 55905, United States.
| | - Rory J. Olson
- Center for Individualized Medicine, Mayo Clinic, Rochester, MN, United States
| | - Faizal Z. Asumda
- Department of Clinical Genomics, Mayo Clinic, Rochester, MN, United States
- Department of Pediatrics, Medical College of Georgia, Augusta University, Augusta, GA, United States
| | | | - Lisa A. Schimmenti
- Department of Clinical Genomics, Mayo Clinic, Rochester, MN, United States
- Department of Otorhinolaryngology, Mayo Clinic, Rochester, MN, United States
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, United States
| | - Eric W. Klee
- Center for Individualized Medicine, Mayo Clinic, Rochester, MN, United States
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Abstract
Mitochondrial optic neuropathies have a leading role in the field of mitochondrial medicine ever since 1988, when the first mutation in mitochondrial DNA was associated with Leber's hereditary optic neuropathy (LHON). Autosomal dominant optic atrophy (DOA) was subsequently associated in 2000 with mutations in the nuclear DNA affecting the OPA1 gene. LHON and DOA are both characterized by selective neurodegeneration of retinal ganglion cells (RGCs) triggered by mitochondrial dysfunction. This is centered on respiratory complex I impairment in LHON and defective mitochondrial dynamics in OPA1-related DOA, leading to distinct clinical phenotypes. LHON is a subacute, rapid, severe loss of central vision involving both eyes within weeks or months, with age of onset between 15 and 35 years old. DOA is a more slowly progressive optic neuropathy, usually apparent in early childhood. LHON is characterized by marked incomplete penetrance and a clear male predilection. The introduction of next-generation sequencing has greatly expanded the genetic causes for other rare forms of mitochondrial optic neuropathies, including recessive and X-linked, further emphasizing the exquisite sensitivity of RGCs to compromised mitochondrial function. All forms of mitochondrial optic neuropathies, including LHON and DOA, can manifest either as pure optic atrophy or as a more severe multisystemic syndrome. Mitochondrial optic neuropathies are currently at the forefront of a number of therapeutic programs, including gene therapy, with idebenone being the only approved drug for a mitochondrial disorder.
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Affiliation(s)
- Valerio Carelli
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy; IRCCS Istituto di Scienze Neurologiche di Bologna, Programma di Neurogenetica, Bologna, Italy.
| | - Chiara La Morgia
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy; IRCCS Istituto di Scienze Neurologiche di Bologna, Programma di Neurogenetica, Bologna, Italy
| | - Patrick Yu-Wai-Man
- John van Geest Centre for Brain Repair and MRC Mitochondrial Biology Unit, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom; Cambridge Eye Unit, Addenbrooke's Hospital, Cambridge University Hospitals, Cambridge, United Kingdom; Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom; Institute of Ophthalmology, University College London, London, United Kingdom
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3
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Dong T, Zhang X, Liu Y, Xu S, Chang H, Chen F, Pan L, Hu S, Wang M, Lu M. Opa1 Prevents Apoptosis and Cisplatin-Induced Ototoxicity in Murine Cochleae. Front Cell Dev Biol 2021; 9:744838. [PMID: 34621753 PMCID: PMC8490775 DOI: 10.3389/fcell.2021.744838] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 08/30/2021] [Indexed: 01/25/2023] Open
Abstract
Optic atrophy1 (OPA1) is crucial for inner mitochondrial membrane (IMM) fusion and essential for maintaining crista structure and mitochondrial morphology. Optic atrophy and hearing impairment are the most prevalent clinical features associated with mutations in the OPA1 gene, but the function of OPA1 in hearing is still unknown. In this study, we examined the ability of Opa1 to protect against cisplatin-induced cochlear cell death in vitro and in vivo. Our results revealed that knockdown of Opa1 affects mitochondrial function in HEI-OC1 and Neuro 2a cells, as evidenced by an elevated reactive oxygen species (ROS) level and reduced mitochondrial membrane potential. The dysfunctional mitochondria release cytochrome c, which triggers apoptosis. Opa1 expression was found to be significantly reduced after cell exposed to cisplatin in HEI-OC1 and Neuro 2a cells. Loss of Opa1 aggravated the apoptosis and mitochondrial dysfunction induced by cisplatin treatment, whereas overexpression of Opa1 alleviated cisplatin-induced cochlear cell death in vitro and in explant. Our results demonstrate that overexpression of Opa1 prevented cisplatin-induced ototoxicity, suggesting that Opa1 may play a vital role in ototoxicity and/or mitochondria-associated cochlear damage.
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Affiliation(s)
- Tingting Dong
- Biobank of Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xuejie Zhang
- Biobank of Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yiqing Liu
- Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Shan Xu
- Shanghai Ninth People's Hospital, Shanghai Institute of Precision Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Haishuang Chang
- Shanghai Ninth People's Hospital, Shanghai Institute of Precision Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Fengqiu Chen
- Biobank of Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Lulu Pan
- Biobank of Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Shaoru Hu
- Biobank of Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Min Wang
- Biobank of Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Min Lu
- Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases, Department of Orthopaedics, Ruijin Hospital, Shanghai Institute of Traumatology and Orthopaedics, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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Montano V, Gruosso F, Simoncini C, Siciliano G, Mancuso M. Clinical features of mtDNA-related syndromes in adulthood. Arch Biochem Biophys 2020; 697:108689. [PMID: 33227288 DOI: 10.1016/j.abb.2020.108689] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 11/06/2020] [Accepted: 11/15/2020] [Indexed: 01/26/2023]
Abstract
Mitochondrial diseases are the most common inheritable metabolic diseases, due to defects in oxidative phosphorylation. They are caused by mutations of nuclear or mitochondrial DNA in genes involved in mitochondrial function. The peculiarity of "mitochondrial DNA genetics rules" in part explains the marked phenotypic variability, the complexity of genotype-phenotype correlations and the challenge of genetic counseling. The new massive genetic sequencing technologies have changed the diagnostic approach, enhancing mitochondrial DNA-related syndromes diagnosis and often avoiding the need of a tissue biopsy. Here we present the most common phenotypes associated with a mitochondrial DNA mutation with the recent advances in diagnosis and in therapeutic perspectives.
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Affiliation(s)
- V Montano
- Department of Clinical and Experimental Medicine, Neurological Clinic, University of Pisa, Italy
| | - F Gruosso
- Department of Clinical and Experimental Medicine, Neurological Clinic, University of Pisa, Italy
| | - C Simoncini
- Department of Clinical and Experimental Medicine, Neurological Clinic, University of Pisa, Italy
| | - G Siciliano
- Department of Clinical and Experimental Medicine, Neurological Clinic, University of Pisa, Italy
| | - M Mancuso
- Department of Clinical and Experimental Medicine, Neurological Clinic, University of Pisa, Italy.
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5
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Le Roux B, Lenaers G, Zanlonghi X, Amati-Bonneau P, Chabrun F, Foulonneau T, Caignard A, Leruez S, Gohier P, Procaccio V, Milea D, den Dunnen JT, Reynier P, Ferré M. OPA1: 516 unique variants and 831 patients registered in an updated centralized Variome database. Orphanet J Rare Dis 2019; 14:214. [PMID: 31500643 PMCID: PMC6734442 DOI: 10.1186/s13023-019-1187-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 08/30/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The dysfunction of OPA1, a dynamin GTPase involved in mitochondrial fusion, is responsible for a large spectrum of neurological disorders, each of which includes optic neuropathy. The database dedicated to OPA1 ( https://www.lovd.nl/OPA1 ), created in 2005, has now evolved towards a centralized and more reliable database using the Global Variome shared Leiden Open-source Variation Database (LOVD) installation. RESULTS The updated OPA1 database, which registers all the patients from our center as well as those reported in the literature, now covers a total of 831 patients: 697 with isolated dominant optic atrophy (DOA), 47 with DOA "plus", and 83 with asymptomatic or unclassified DOA. It comprises 516 unique OPA1 variants, of which more than 80% (414) are considered pathogenic. Full clinical data for 118 patients are documented using the Human Phenotype Ontology, a standard vocabulary for referencing phenotypic abnormalities. Contributors may now make online submissions of phenotypes related to OPA1 mutations, giving clinical and molecular descriptions together with detailed ophthalmological and neurological data, according to an international thesaurus. CONCLUSIONS The evolution of the OPA1 database towards the LOVD, using unified nomenclature, should ensure its interoperability with other databases and prove useful for molecular diagnoses based on gene-panel sequencing, large-scale mutation statistics, and genotype-phenotype correlations.
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Affiliation(s)
- Bastien Le Roux
- Département d'Ophtalmologie, Centre Hospitalier Universitaire d'Angers, Angers, France
| | - Guy Lenaers
- Unité Mixte de Recherche MITOVASC, CNRS 6015/INSERM 1083, Université d'Angers, Angers, France
| | - Xavier Zanlonghi
- Centre de Compétence Maladie Rare, Clinique Jules Verne, Nantes, France
| | - Patrizia Amati-Bonneau
- Unité Mixte de Recherche MITOVASC, CNRS 6015/INSERM 1083, Université d'Angers, Angers, France.,Département de Biochimie et Génétique, Centre Hospitalier Universitaire d'Angers, Angers, France
| | - Floris Chabrun
- Unité Mixte de Recherche MITOVASC, CNRS 6015/INSERM 1083, Université d'Angers, Angers, France.,Département de Biochimie et Génétique, Centre Hospitalier Universitaire d'Angers, Angers, France
| | - Thomas Foulonneau
- Unité Mixte de Recherche MITOVASC, CNRS 6015/INSERM 1083, Université d'Angers, Angers, France
| | - Angélique Caignard
- Département d'Ophtalmologie, Centre Hospitalier Universitaire d'Angers, Angers, France
| | - Stéphanie Leruez
- Département d'Ophtalmologie, Centre Hospitalier Universitaire d'Angers, Angers, France
| | - Philippe Gohier
- Département d'Ophtalmologie, Centre Hospitalier Universitaire d'Angers, Angers, France
| | - Vincent Procaccio
- Unité Mixte de Recherche MITOVASC, CNRS 6015/INSERM 1083, Université d'Angers, Angers, France.,Département de Biochimie et Génétique, Centre Hospitalier Universitaire d'Angers, Angers, France
| | - Dan Milea
- Singapore National Eye Center, Singapore Eye Research Institute, Duke-NUS, Singapore, Singapore
| | - Johan T den Dunnen
- Human Genetics and Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Pascal Reynier
- Unité Mixte de Recherche MITOVASC, CNRS 6015/INSERM 1083, Université d'Angers, Angers, France.,Département de Biochimie et Génétique, Centre Hospitalier Universitaire d'Angers, Angers, France
| | - Marc Ferré
- Unité Mixte de Recherche MITOVASC, CNRS 6015/INSERM 1083, Université d'Angers, Angers, France.
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6
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OPA1: How much do we know to approach therapy? Pharmacol Res 2018; 131:199-210. [PMID: 29454676 DOI: 10.1016/j.phrs.2018.02.018] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Revised: 02/12/2018] [Accepted: 02/12/2018] [Indexed: 01/01/2023]
Abstract
OPA1 is a GTPase that controls several functions, such as mitochondrial dynamics and energetics, mtDNA maintenance and cristae integrity. In the last years, there have been described other cellular pathways and mechanisms involving OPA1 directly or through its interaction. All this new information, by implementing our knowledge on OPA1 is instrumental to elucidating the pathogenic mechanisms of OPA1 mutations. Indeed, these are associated with dominant optic atrophy (DOA), one of the most common inherited optic neuropathies, and with an increasing number of heterogeneous neurodegenerative disorders. In this review, we overview all recent findings on OPA1 protein functions, on its dysfunction and related clinical phenotypes, focusing on the current therapeutic options and future perspectives to treat DOA and the other associated neurological disorders due to OPA1 mutations.
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8
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Santarelli R, Rossi R, Scimemi P, Cama E, Valentino ML, La Morgia C, Caporali L, Liguori R, Magnavita V, Monteleone A, Biscaro A, Arslan E, Carelli V. OPA1-related auditory neuropathy: site of lesion and outcome of cochlear implantation. ACTA ACUST UNITED AC 2015; 138:563-76. [PMID: 25564500 PMCID: PMC4339771 DOI: 10.1093/brain/awu378] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Santarelli et al. reveal that hearing impairments in patients carrying OPA1 missense mutations are the result of disordered synchrony in auditory nerve fibre activity owing to degeneration of terminal dendrites. Cochlear implantation improves speech perception and synchronous activation of auditory pathways in these patients by bypassing the lesion site. Hearing impairment is the second most prevalent clinical feature after optic atrophy in dominant optic atrophy associated with mutations in the OPA1 gene. In this study we characterized the hearing dysfunction in OPA1-linked disorders and provided effective rehabilitative options to improve speech perception. We studied two groups of OPA1 subjects, one comprising 11 patients (seven males; age range 13–79 years) carrying OPA1 mutations inducing haploinsufficiency, the other, 10 subjects (three males; age range 5–58 years) carrying OPA1 missense mutations. Both groups underwent audiometric assessment with pure tone and speech perception evaluation, and otoacoustic emissions and auditory brainstem response recording. Cochlear potentials were recorded through transtympanic electrocochleography from the group of patients harbouring OPA1 missense mutations and were compared to recordings obtained from 20 control subjects with normal hearing and from 19 subjects with cochlear hearing loss. Eight patients carrying OPA1 missense mutations underwent cochlear implantation. Speech perception measures and electrically-evoked auditory nerve and brainstem responses were obtained after 1 year of cochlear implant use. Nine of 11 patients carrying OPA1 mutations inducing haploinsufficiency had normal hearing function. In contrast, all but one subject harbouring OPA1 missense mutations displayed impaired speech perception, abnormal brainstem responses and presence of otoacoustic emissions consistent with auditory neuropathy. In electrocochleography recordings, cochlear microphonic had enhanced amplitudes while summating potential showed normal latency and peak amplitude consistent with preservation of both outer and inner hair cell activities. After cancelling the cochlear microphonic, the synchronized neural response seen in both normally-hearing controls and subjects with cochlear hearing loss was replaced by a prolonged, low-amplitude negative potential that decreased in both amplitude and duration during rapid stimulation consistent with neural generation. The use of cochlear implant improved speech perception in all but one patient. Brainstem potentials were recorded in response to electrical stimulation in five of six subjects, whereas no compound action potential was evoked from the auditory nerve through the cochlear implant. These findings indicate that underlying the hearing impairment in patients carrying OPA1 missense mutations is a disordered synchrony in auditory nerve fibre activity resulting from neural degeneration affecting the terminal dendrites. Cochlear implantation improves speech perception and synchronous activation of auditory pathways by bypassing the site of lesion.
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Affiliation(s)
- Rosamaria Santarelli
- 1 Department of Neurosciences, University of Padova, Via Giustiniani 2, 35128 Padova, Italy 2 Audiology and Phoniatrics Service, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy
| | - Roberta Rossi
- 1 Department of Neurosciences, University of Padova, Via Giustiniani 2, 35128 Padova, Italy 2 Audiology and Phoniatrics Service, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy
| | - Pietro Scimemi
- 1 Department of Neurosciences, University of Padova, Via Giustiniani 2, 35128 Padova, Italy 2 Audiology and Phoniatrics Service, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy
| | - Elona Cama
- 1 Department of Neurosciences, University of Padova, Via Giustiniani 2, 35128 Padova, Italy 2 Audiology and Phoniatrics Service, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy
| | - Maria Lucia Valentino
- 3 Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Via Ugo Foscolo 7, 40123 Bologna, Italy 4 IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Via Altura 3, 40139 Bologna, Italy
| | - Chiara La Morgia
- 3 Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Via Ugo Foscolo 7, 40123 Bologna, Italy 4 IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Via Altura 3, 40139 Bologna, Italy
| | - Leonardo Caporali
- 3 Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Via Ugo Foscolo 7, 40123 Bologna, Italy 4 IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Via Altura 3, 40139 Bologna, Italy
| | - Rocco Liguori
- 3 Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Via Ugo Foscolo 7, 40123 Bologna, Italy 4 IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Via Altura 3, 40139 Bologna, Italy
| | - Vincenzo Magnavita
- 1 Department of Neurosciences, University of Padova, Via Giustiniani 2, 35128 Padova, Italy 2 Audiology and Phoniatrics Service, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy
| | - Anna Monteleone
- 2 Audiology and Phoniatrics Service, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy
| | - Ariella Biscaro
- 2 Audiology and Phoniatrics Service, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy
| | - Edoardo Arslan
- 1 Department of Neurosciences, University of Padova, Via Giustiniani 2, 35128 Padova, Italy 2 Audiology and Phoniatrics Service, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy
| | - Valerio Carelli
- 3 Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Via Ugo Foscolo 7, 40123 Bologna, Italy 4 IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Via Altura 3, 40139 Bologna, Italy
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Ferré M, Caignard A, Milea D, Leruez S, Cassereau J, Chevrollier A, Amati-Bonneau P, Verny C, Bonneau D, Procaccio V, Reynier P. Improved Locus-Specific Database forOPA1Mutations Allows Inclusion of Advanced Clinical Data. Hum Mutat 2014; 36:20-5. [DOI: 10.1002/humu.22703] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 09/12/2014] [Indexed: 11/09/2022]
Affiliation(s)
- Marc Ferré
- CNRS 6214/INSERM 1083; Angers University; Angers France
- Department of Biochemistry and Genetics; University Hospital; Angers France
| | - Angélique Caignard
- CNRS 6214/INSERM 1083; Angers University; Angers France
- Department of Ophthalmology; University Hospital; Angers France
| | - Dan Milea
- CNRS 6214/INSERM 1083; Angers University; Angers France
- Department of Ophthalmology; University Hospital; Angers France
- Singapore National Eye Centre, Singapore Eye Research Institute; Duke-NUS Singapore
| | - Stéphanie Leruez
- CNRS 6214/INSERM 1083; Angers University; Angers France
- Department of Ophthalmology; University Hospital; Angers France
| | - Julien Cassereau
- CNRS 6214/INSERM 1083; Angers University; Angers France
- Department of Neurology; University Hospital; Angers France
| | | | - Patrizia Amati-Bonneau
- CNRS 6214/INSERM 1083; Angers University; Angers France
- Department of Biochemistry and Genetics; University Hospital; Angers France
| | - Christophe Verny
- CNRS 6214/INSERM 1083; Angers University; Angers France
- Department of Neurology; University Hospital; Angers France
| | - Dominique Bonneau
- CNRS 6214/INSERM 1083; Angers University; Angers France
- Department of Biochemistry and Genetics; University Hospital; Angers France
| | - Vincent Procaccio
- CNRS 6214/INSERM 1083; Angers University; Angers France
- Department of Biochemistry and Genetics; University Hospital; Angers France
| | - Pascal Reynier
- CNRS 6214/INSERM 1083; Angers University; Angers France
- Department of Biochemistry and Genetics; University Hospital; Angers France
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Yu-Wai-Man P, Griffiths PG, Chinnery PF. Mitochondrial optic neuropathies - disease mechanisms and therapeutic strategies. Prog Retin Eye Res 2011; 30:81-114. [PMID: 21112411 PMCID: PMC3081075 DOI: 10.1016/j.preteyeres.2010.11.002] [Citation(s) in RCA: 426] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Leber hereditary optic neuropathy (LHON) and autosomal-dominant optic atrophy (DOA) are the two most common inherited optic neuropathies in the general population. Both disorders share striking pathological similarities, marked by the selective loss of retinal ganglion cells (RGCs) and the early involvement of the papillomacular bundle. Three mitochondrial DNA (mtDNA) point mutations; m.3460G>A, m.11778G>A, and m.14484T>C account for over 90% of LHON cases, and in DOA, the majority of affected families harbour mutations in the OPA1 gene, which codes for a mitochondrial inner membrane protein. Optic nerve degeneration in LHON and DOA is therefore due to disturbed mitochondrial function and a predominantly complex I respiratory chain defect has been identified using both in vitro and in vivo biochemical assays. However, the trigger for RGC loss is much more complex than a simple bioenergetic crisis and other important disease mechanisms have emerged relating to mitochondrial network dynamics, mtDNA maintenance, axonal transport, and the involvement of the cytoskeleton in maintaining a differential mitochondrial gradient at sites such as the lamina cribosa. The downstream consequences of these mitochondrial disturbances are likely to be influenced by the local cellular milieu. The vulnerability of RGCs in LHON and DOA could derive not only from tissue-specific, genetically-determined biological factors, but also from an increased susceptibility to exogenous influences such as light exposure, smoking, and pharmacological agents with putative mitochondrial toxic effects. Our concept of inherited mitochondrial optic neuropathies has evolved over the past decade, with the observation that patients with LHON and DOA can manifest a much broader phenotypic spectrum than pure optic nerve involvement. Interestingly, these phenotypes are sometimes clinically indistinguishable from other neurodegenerative disorders such as Charcot-Marie-Tooth disease, hereditary spastic paraplegia, and multiple sclerosis, where mitochondrial dysfunction is also thought to be an important pathophysiological player. A number of vertebrate and invertebrate disease models has recently been established to circumvent the lack of human tissues, and these have already provided considerable insight by allowing direct RGC experimentation. The ultimate goal is to translate these research advances into clinical practice and new treatment strategies are currently being investigated to improve the visual prognosis for patients with mitochondrial optic neuropathies.
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MESH Headings
- Animals
- DNA, Mitochondrial/genetics
- Disease Models, Animal
- Humans
- Optic Atrophy, Autosomal Dominant/pathology
- Optic Atrophy, Autosomal Dominant/physiopathology
- Optic Atrophy, Autosomal Dominant/therapy
- Optic Atrophy, Hereditary, Leber/pathology
- Optic Atrophy, Hereditary, Leber/physiopathology
- Optic Atrophy, Hereditary, Leber/therapy
- Optic Nerve/pathology
- Phenotype
- Point Mutation
- Retinal Ganglion Cells/pathology
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Affiliation(s)
- Patrick Yu-Wai-Man
- Mitochondrial Research Group, Institute for Ageing and Health, The Medical School, Newcastle University, UK.
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11
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Carelli V, Schimpf S, Fuhrmann N, Valentino ML, Zanna C, Iommarini L, Papke M, Schaich S, Tippmann S, Baumann B, Barboni P, Longanesi L, Rugolo M, Ghelli A, Alavi MV, Youle RJ, Bucchi L, Carroccia R, Giannoccaro MP, Tonon C, Lodi R, Cenacchi G, Montagna P, Liguori R, Wissinger B. A clinically complex form of dominant optic atrophy (OPA8) maps on chromosome 16. Hum Mol Genet 2011; 20:1893-905. [PMID: 21349918 DOI: 10.1093/hmg/ddr071] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Dominant optic atrophy (DOA) is genetically heterogeneous and pathogenic mutations have been identified in the OPA1 and OPA3 genes, both encoding for mitochondrial proteins. We characterized clinical and laboratory features in a large OPA1-negative family with complicated DOA. Search for mitochondrial dysfunction was performed by studying muscle biopsies, fibroblasts, platelets and magnetic resonance (MR) spectroscopy. Genetic investigations included mitochondrial DNA (mtDNA) analysis, linkage analysis, copy number variation (CNV) analysis and candidate gene screening. Optic neuropathy was undistinguishable from that in OPA1-DOA and frequently associated with late-onset sensorineural hearing loss, increases of central conduction times at somato-sensory evoked potentials and various cardiac abnormalities. Serum lactic acid after exercise, platelet respiratory complex activities, adenosine triphosphate (ATP) content in fibroblasts and muscle phosphorus MR spectroscopy all failed to reveal a mitochondrial dysfunction. However, muscle biopsies and their mtDNA analysis showed increased mitochondrial biogenesis. Furthermore, patient's fibroblasts grown in the galactose medium were unable to increase ATP content compared with controls, and exhibited abnormally high rate of fusion activity. Genome-wide linkage revealed a locus on chromosome 16q21-q22 with a maximum two-point LOD score of 8.84 for the marker D16S752 and a non-recombinant interval of ∼ 6.96 cM. Genomic screening of 45 genes in this interval including several likely candidate genes (CALB2, CYB5B, TK2, DHODH, PLEKHG4) revealed no mutation. Moreover, we excluded the presence of CNVs using array-based comparative genome hybridization. The identification of a new OPA locus (OPA8) in this pedigree demonstrates further genetic heterogeneity in DOA, and our results indicate that the pathogenesis may still involve mitochondria.
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Affiliation(s)
- Valerio Carelli
- Department of Neurological Sciences, University of Bologna, Via Ugo Foscolo 7, 40123 Bologna, Italy.
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Scherer C, Procaccio V, Ferre M, Guillet V, Reynier P, Amati-Bonneau P, Dubas F, Bonneau D, Verny C. [Hereditary optic atrophies]. Rev Neurol (Paris) 2010; 166:959-65. [PMID: 21056443 DOI: 10.1016/j.neurol.2010.07.033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Revised: 04/20/2010] [Accepted: 07/20/2010] [Indexed: 10/18/2022]
Abstract
INTRODUCTION Hereditary optic neuropathies, resulting from retinal ganglion cell degeneration, are a heterogeneous group of diseases ranging from asymptomatic forms to legal blindness. STATE OF KNOWLEDGE Two most frequent phenotypes are Kjer's disease, an autosomal dominant optic atrophy caused by OPA1 gene mutations, and Leber's disease due to maternally inherited mitochondrial DNA mutations. PROSPECTS AND CONCLUSION Both optic neuropathies usually isolated are sometimes associated with extraocular symptoms, especially neurological symptoms, thus justifying a systematic neurological evaluation and brain imaging.
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Affiliation(s)
- C Scherer
- Département de neurologie, CHU d'Angers, Angers, France
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Yu-Wai-Man P, Griffiths PG, Gorman GS, Lourenco CM, Wright AF, Auer-Grumbach M, Toscano A, Musumeci O, Valentino ML, Caporali L, Lamperti C, Tallaksen CM, Duffey P, Miller J, Whittaker RG, Baker MR, Jackson MJ, Clarke MP, Dhillon B, Czermin B, Stewart JD, Hudson G, Reynier P, Bonneau D, Marques W, Lenaers G, McFarland R, Taylor RW, Turnbull DM, Votruba M, Zeviani M, Carelli V, Bindoff LA, Horvath R, Amati-Bonneau P, Chinnery PF. Multi-system neurological disease is common in patients with OPA1 mutations. ACTA ACUST UNITED AC 2010; 133:771-86. [PMID: 20157015 PMCID: PMC2842512 DOI: 10.1093/brain/awq007] [Citation(s) in RCA: 315] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Additional neurological features have recently been described in seven families transmitting pathogenic mutations in OPA1, the most common cause of autosomal dominant optic atrophy. However, the frequency of these syndromal 'dominant optic atrophy plus' variants and the extent of neurological involvement have not been established. In this large multi-centre study of 104 patients from 45 independent families, including 60 new cases, we show that extra-ocular neurological complications are common in OPA1 disease, and affect up to 20% of all mutational carriers. Bilateral sensorineural deafness beginning in late childhood and early adulthood was a prominent manifestation, followed by a combination of ataxia, myopathy, peripheral neuropathy and progressive external ophthalmoplegia from the third decade of life onwards. We also identified novel clinical presentations with spastic paraparesis mimicking hereditary spastic paraplegia, and a multiple sclerosis-like illness. In contrast to initial reports, multi-system neurological disease was associated with all mutational subtypes, although there was an increased risk with missense mutations [odds ratio = 3.06, 95% confidence interval = 1.44-6.49; P = 0.0027], and mutations located within the guanosine triphosphate-ase region (odds ratio = 2.29, 95% confidence interval = 1.08-4.82; P = 0.0271). Histochemical and molecular characterization of skeletal muscle biopsies revealed the presence of cytochrome c oxidase-deficient fibres and multiple mitochondrial DNA deletions in the majority of patients harbouring OPA1 mutations, even in those with isolated optic nerve involvement. However, the cytochrome c oxidase-deficient load was over four times higher in the dominant optic atrophy + group compared to the pure optic neuropathy group, implicating a causal role for these secondary mitochondrial DNA defects in disease pathophysiology. Individuals with dominant optic atrophy plus phenotypes also had significantly worse visual outcomes, and careful surveillance is therefore mandatory to optimize the detection and management of neurological disability in a group of patients who already have significant visual impairment.
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Affiliation(s)
- P Yu-Wai-Man
- Mitochondrial Research Group, The Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
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Amati-Bonneau P, Milea D, Bonneau D, Chevrollier A, Ferré M, Guillet V, Gueguen N, Loiseau D, Crescenzo MAPD, Verny C, Procaccio V, Lenaers G, Reynier P. OPA1-associated disorders: Phenotypes and pathophysiology. Int J Biochem Cell Biol 2009; 41:1855-65. [DOI: 10.1016/j.biocel.2009.04.012] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Revised: 04/09/2009] [Accepted: 04/14/2009] [Indexed: 10/20/2022]
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Carelli V, La Morgia C, Valentino ML, Barboni P, Ross-Cisneros FN, Sadun AA. Retinal ganglion cell neurodegeneration in mitochondrial inherited disorders. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:518-28. [DOI: 10.1016/j.bbabio.2009.02.024] [Citation(s) in RCA: 166] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2008] [Revised: 02/24/2009] [Accepted: 02/26/2009] [Indexed: 01/30/2023]
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Li C, Kosmorsky G, Zhang K, Katz BJ, Ge J, Traboulsi EI. Optic atrophy and sensorineural hearing loss in a family caused by an R445H OPA1 mutation. Am J Med Genet A 2008; 138A:208-11. [PMID: 16158427 DOI: 10.1002/ajmg.a.30794] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
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.
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Affiliation(s)
- Chunmei Li
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences Center, Salt Lake City, UT 84132, USA
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Eiberg H, Hansen L, Kjer B, Hansen T, Pedersen O, Bille M, Rosenberg T, Tranebjaerg L. Autosomal dominant optic atrophy associated with hearing impairment and impaired glucose regulation caused by a missense mutation in the WFS1 gene. J Med Genet 2006; 43:435-40. [PMID: 16648378 PMCID: PMC2649014 DOI: 10.1136/jmg.2005.034892] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Autosomal dominant optic atrophy (ADOA) is genetically heterogeneous, with OPA1 on 3q28 being the most prevalently mutated gene. Additional loci are OPA3, OPA4, and OPA5, located at 19q13.2, 18q12.2, and 22q12.1-q13.1, respectively. Mutations in the WFS1 gene, at 4p16.3, are associated with either optic atrophy (OA) as part of the autosomal recessive Wolfram syndrome or with autosomal dominant progressive low frequency sensorineural hearing loss (LFSNHL) without any ophthalmological abnormalities. Linkage and sequence mutation analyses of the ADOA candidate genes OPA1, OPA3, OPA4, and OPA5, including the genes WFS1, GJB2, and GJB6 associated with recessive inherited OA or dominant LFSNHL, were performed. We identified one novel WFS1 missense mutation E864K, c.2590G-->A in exon 8 that co-segregates with ADOA combined with hearing impairment and impaired glucose regulation. This is the first example of autosomal dominant optic atrophy and hearing loss associated with a WFS1 mutation, supporting the notion that mutations in WFS1 as well as in OPA1 may lead to ADOA combined with impaired hearing.
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Affiliation(s)
- H Eiberg
- Department of Medical Biochemistry and Genetics, Panum Institute, University of Copenhagen, DK-2200 Copenhagen N, Denmark.
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Puomila A, Huoponen K, Mäntyjärvi M, Hämäläinen P, Paananen R, Sankila EM, Savontaus ML, Somer M, Nikoskelainen E. Dominant optic atrophy: correlation between clinical and molecular genetic studies. ACTA ACUST UNITED AC 2005; 83:337-46. [PMID: 15948788 DOI: 10.1111/j.1600-0420.2005.00448.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE To assess the clinical picture and molecular genetics of 14 Finnish families with dominant optic atrophy (DOA). METHODS The clinical status of family members was based on the assessment of visual acuity, colour vision, visual fields and optic nerve appearance; 31 individuals were affected, two suspect and 21 unaffected. A total of 30 coding exons and exon- intron boundaries of the OPA1 gene were sequenced in order to detect mutations. RESULTS Half the patients were diagnosed at the age of < or = 20 years. Ten out of 20 affected individuals followed up for > or = 6 years had a progressive disease and 10 had a stable disease. According to WHO criteria, 36% of the affected patients were visually handicapped. Eight OPA1 pathogenic mutations, all but one novel, and 18 neutral polymorphisms were detected. CONCLUSION The most sensitive indicators of DOA were optic disc pallor and dyschromatopsia. With molecular genetic analysis, asymptomatic mutation carriers and DOA cases with a mild clinical outcome were ascertained. No mutational hotspot or Finnish major mutation in the OPA1 gene could be demonstrated as most families carried a unique mutation. No obvious genotype- phenotype correlation could be detected. Detailed clinical assessment and exclusion of non-DOA families prior to mutation screening are necessary for obtaining a high mutation detection rate.
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Affiliation(s)
- Anu Puomila
- Department of Medical Genetics, University of Turku, Turku, Finland.
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Payne M, Yang Z, Katz BJ, Warner JEA, Weight CJ, Zhao Y, Pearson ED, Treft RL, Hillman T, Kennedy RJ, Meire FM, Zhang K. Dominant optic atrophy, sensorineural hearing loss, ptosis, and ophthalmoplegia: a syndrome caused by a missense mutation in OPA1. Am J Ophthalmol 2004; 138:749-55. [PMID: 15531309 DOI: 10.1016/j.ajo.2004.06.011] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/03/2004] [Indexed: 11/21/2022]
Abstract
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.
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Affiliation(s)
- Marielle Payne
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences Center, Salt Lake City, Utah, USA
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Delettre C, Lenaers G, Pelloquin L, Belenguer P, Hamel CP. OPA1 (Kjer type) dominant optic atrophy: a novel mitochondrial disease. Mol Genet Metab 2002; 75:97-107. [PMID: 11855928 DOI: 10.1006/mgme.2001.3278] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Dominant optic atrophy (DOA) is the most common form of inherited optic neuropathy. Although heterogeneous, a major locus has been mapped to chromosome 3q28 and the responsible gene, OPA1, was recently identified. OPA1 is a mitochondrial dynamin-related GTPase implicated in the formation and maintenance of the mitochondrial network. To date, 62 mutations have been identified in a total of 201 DOA patients. Most of them (90%) are distributed from exons 8 to 28 with a majority in the GTPase domain (54%). None were found in the alternatively spliced exons 4, 4b, and 5b. Half of them are truncative mutations (50%) with a frequent recurrent allele, c.2708delTTAG. Most missense mutations (81%) cluster within the putative GTPase domain. Various pathogenic mechanisms may play a role in OPA1 DOA. Truncative mutations in the N-terminal region and perhaps missense mutations in the GTPase domain lead to a loss of function of the encoded protein and haplotype insufficiency. However, there is a cluster of truncation mutations in the in C-terminus, a putative dimerization domain, that could act through a dominant negative effect. The findings that OPA1-type DOA, as Leber optic neuropathy, is caused by the impairment of a mitochondrial protein address the question of the vulnerability of the retinal ganglion cell in response to mitochondrial defects.
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Affiliation(s)
- Cécile Delettre
- Inserm U.254, Laboratoire de Neurobiologie de l'audition, 71, rue de Navacelles, 34090Montpellier, France.
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Votruba M, Moore AT, Bhattacharya SS. Clinical features, molecular genetics, and pathophysiology of dominant optic atrophy. J Med Genet 1998; 35:793-800. [PMID: 9783700 PMCID: PMC1051452 DOI: 10.1136/jmg.35.10.793] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Inherited optic neuropathies are a significant cause of childhood and adult blindness and dominant optic atrophy (DOA) is the most common form of autosomally inherited (non-glaucomatous) optic neuropathy. Patients with DOA present with an insidious onset of bilateral visual loss and they characteristically have temporal optic nerve pallor, centrocaecal visual field scotoma, and a colour vision deficit, which is frequently blue-yellow. Evidence from histological and electrophysiological studies suggests that the pathology is confined to the retinal ganglion cell. A gene for dominant optic atrophy (OPA1) has been mapped to chromosome 3q28-qter, and studies are under way to refine the genetic interval in which the gene lies, to map the region physically, and hence to clone the gene. A second locus for dominant optic atrophy has recently been shown to map to chromosome 18q12.2-12.3 near the Kidd blood group locus. The cloning of genes for dominant optic atrophy will provide important insights into the pathophysiology of the retinal ganglion cell in health and disease. These insights may prove to be of great value in the understanding of other primary ganglion cell diseases, such as the mitochondrially inherited Leber's hereditary optic neuropathy and other diseases associated with ganglion cell loss, such as glaucoma.
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Affiliation(s)
- M Votruba
- Department of Molecular Genetics, Institute of Ophthalmology, University College London, UK
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Assink JJ, Tijmes NT, ten Brink JB, Oostra RJ, Riemslag FC, de Jong PT, Bergen AA. A gene for X-linked optic atrophy is closely linked to the Xp11.4-Xp11.2 region of the X chromosome. Am J Hum Genet 1997; 61:934-9. [PMID: 9382106 PMCID: PMC1715990 DOI: 10.1086/514884] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The aim of this study was to identify the chromosomal location of the disease-causing gene in a family apparently segregating X-linked optic atrophy. A large family of 45 individuals with a four-generation history of X-linked optic atrophy was reexamined in a full ophthalmic as well as electrophysiological examination. A DNA linkage analysis of the family was undertaken in order to identify the chromosomal location of the disease-causing gene. Linkage analysis was performed with 26 markers that spanned the entire X chromosome. The affected males showed very early onset and slow progression of the disease. Ophthalmic study of the female carriers did not reveal any abnormalities. Close linkage without recombination was found at the MAOB locus (maximum LOD score [Zmax] 4.19). The Zmax - 1 support interval was found at a recombination fraction of .076 distal and .018 proximal to MAOB. Multipoint linkage analysis placed the optic atrophy-causing gene in the Xp11.4-p11.21 interval between markers DXS993 and DXS991, whereas any other localization along the X chromosome could be excluded.
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Affiliation(s)
- J J Assink
- Department of Ophthalmogenetics, The Netherlands Ophthalmic Research Institute, Amsterdam
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