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Kalogerou M, Ioannou S, Kolovos P, Prokopiou E, Potamiti L, Kyriacou K, Panagiotidis M, Ioannou M, Fella E, Worth EP, Georgiou T. Omega-3 fatty acids promote neuroprotection, decreased apoptosis and reduced glial cell activation in the retina of a mouse model of OPA1-related autosomal dominant optic atrophy. Exp Eye Res 2022; 215:108901. [DOI: 10.1016/j.exer.2021.108901] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 12/13/2021] [Accepted: 12/15/2021] [Indexed: 01/10/2023]
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Weisschuh N, Schimpf-Linzenbold S, Mazzola P, Kieninger S, Xiao T, Kellner U, Neuhann T, Kelbsch C, Tonagel F, Wilhelm H, Kohl S, Wissinger B. Mutation spectrum of the OPA1 gene in a large cohort of patients with suspected dominant optic atrophy: Identification and classification of 48 novel variants. PLoS One 2021; 16:e0253987. [PMID: 34242285 PMCID: PMC8270428 DOI: 10.1371/journal.pone.0253987] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 06/17/2021] [Indexed: 12/18/2022] Open
Abstract
Autosomal dominant optic atrophy is one of the most common inherited optic neuropathies. This disease is genetically heterogeneous, but most cases are due to pathogenic variants in the OPA1 gene: depending on the population studied, 32–90% of cases harbor pathogenic variants in this gene. The aim of this study was to provide a comprehensive overview of the entire spectrum of likely pathogenic variants in the OPA1 gene in a large cohort of patients. Over a period of 20 years, 755 unrelated probands with a diagnosis of bilateral optic atrophy were referred to our laboratory for molecular genetic investigation. Genetic testing of the OPA1 gene was initially performed by a combined analysis using either single-strand conformation polymorphism or denaturing high performance liquid chromatography followed by Sanger sequencing to validate aberrant bands or melting profiles. The presence of copy number variations was assessed using multiplex ligation-dependent probe amplification. Since 2012, genetic testing was based on next-generation sequencing platforms. Genetic screening of the OPA1 gene revealed putatively pathogenic variants in 278 unrelated probands which represent 36.8% of the entire cohort. A total of 156 unique variants were identified, 78% of which can be considered null alleles. Variant c.2708_2711del/p.(V903Gfs*3) was found to constitute 14% of all disease-causing alleles. Special emphasis was placed on the validation of splice variants either by analyzing cDNA derived from patients´ blood samples or by heterologous splice assays using minigenes. Splicing analysis revealed different aberrant splicing events, including exon skipping, activation of exonic or intronic cryptic splice sites, and the inclusion of pseudoexons. Forty-eight variants that we identified were novel. Nine of them were classified as pathogenic, 34 as likely pathogenic and five as variant of uncertain significance. Our study adds a significant number of novel variants to the mutation spectrum of the OPA1 gene and will thereby facilitate genetic diagnostics of patients with suspected dominant optic atrophy.
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Affiliation(s)
- Nicole Weisschuh
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Simone Schimpf-Linzenbold
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany.,CeGaT GmbH and Praxis für Humangenetik Tübingen, Tübingen, Germany
| | - Pascale Mazzola
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, Tübingen, Germany
| | - Sinja Kieninger
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Ting Xiao
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Ulrich Kellner
- Zentrum für seltene Netzhauterkrankungen, AugenZentrum Siegburg, MVZ Augenärztliches Diagnostik- und Therapiecentrum Siegburg GmbH, Siegburg, Germany.,RetinaScience, Bonn, Germany
| | | | - Carina Kelbsch
- Centre for Ophthalmology, University Eye Hospital, University of Tübingen, Tübingen, Germany
| | - Felix Tonagel
- Centre for Ophthalmology, University Eye Hospital, University of Tübingen, Tübingen, Germany
| | - Helmut Wilhelm
- Centre for Ophthalmology, University Eye Hospital, University of Tübingen, Tübingen, Germany
| | - Susanne Kohl
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Bernd Wissinger
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
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Bevan RJ, Williams PA, Waters CT, Thirgood R, Mui A, Seto S, Good M, Morgan JE, Votruba M, Erchova I. OPA1 deficiency accelerates hippocampal synaptic remodelling and age-related deficits in learning and memory. Brain Commun 2020; 2:fcaa101. [PMID: 33094281 PMCID: PMC7566495 DOI: 10.1093/braincomms/fcaa101] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 04/09/2020] [Accepted: 05/27/2020] [Indexed: 12/13/2022] Open
Abstract
A healthy mitochondrial network is essential for the maintenance of neuronal synaptic integrity. Mitochondrial and metabolic dysfunction contributes to the pathogenesis of many neurodegenerative diseases including dementia. OPA1 is the master regulator of mitochondrial fusion and fission and is likely to play an important role during neurodegenerative events. To explore this, we quantified hippocampal dendritic and synaptic integrity and the learning and memory performance of aged Opa1 haploinsufficient mice carrying the Opa1Q285X mutation (B6; C3-Opa1Q285STOP ; Opa1+/- ). We demonstrate that heterozygous loss of Opa1 results in premature age-related loss of spines in hippocampal pyramidal CA1 neurons and a reduction in synaptic density in the hippocampus. This loss is associated with subtle memory deficits in both spatial novelty and object recognition. We hypothesize that metabolic failure to maintain normal neuronal activity at the level of a single spine leads to premature age-related memory deficits. These results highlight the importance of mitochondrial homeostasis for maintenance of neuronal function during ageing.
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Affiliation(s)
- Ryan J Bevan
- School of Optometry and Vision Sciences, Cardiff University, Maindy Rd, Cardiff, CF24 4HQ, UK
| | - Pete A Williams
- Department of Clinical Neuroscience, Division of Eye and Vision, St. Erik Eye Hospital, Karolinska Institutet, Polhemsgatan 50, 112 82 Stockholm, Sweden
| | - Caroline T Waters
- School of Optometry and Vision Sciences, Cardiff University, Maindy Rd, Cardiff, CF24 4HQ, UK
| | - Rebecca Thirgood
- School of Optometry and Vision Sciences, Cardiff University, Maindy Rd, Cardiff, CF24 4HQ, UK
| | - Amanda Mui
- School of Optometry and Vision Sciences, Cardiff University, Maindy Rd, Cardiff, CF24 4HQ, UK
| | - Sharon Seto
- School of Optometry and Vision Sciences, Cardiff University, Maindy Rd, Cardiff, CF24 4HQ, UK
| | - Mark Good
- School of Psychology, Cardiff University, Tower Building, 70 Park Place, Cardiff, CF10 3AT, UK
| | - James E Morgan
- School of Optometry and Vision Sciences, Cardiff University, Maindy Rd, Cardiff, CF24 4HQ, UK
| | - Marcela Votruba
- School of Optometry and Vision Sciences, Cardiff University, Maindy Rd, Cardiff, CF24 4HQ, UK
| | - Irina Erchova
- School of Optometry and Vision Sciences, Cardiff University, Maindy Rd, Cardiff, CF24 4HQ, UK
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Dietz JV, Bohovych I, Viana MP, Khalimonchuk O. Proteolytic regulation of mitochondrial dynamics. Mitochondrion 2019; 49:289-304. [PMID: 31029640 DOI: 10.1016/j.mito.2019.04.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Accepted: 04/19/2019] [Indexed: 12/23/2022]
Abstract
Spatiotemporal changes in the abundance, shape, and cellular localization of the mitochondrial network, also known as mitochondrial dynamics, are now widely recognized to play a key role in mitochondrial and cellular physiology as well as disease states. This process involves coordinated remodeling of the outer and inner mitochondrial membranes by conserved dynamin-like guanosine triphosphatases and their partner molecules in response to various physiological and stress stimuli. Although the core machineries that mediate fusion and partitioning of the mitochondrial network have been extensively characterized, many aspects of their function and regulation are incompletely understood and only beginning to emerge. In the present review we briefly summarize current knowledge about how the key mitochondrial dynamics-mediating factors are regulated via selective proteolysis by mitochondrial and cellular proteolytic machineries.
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Affiliation(s)
- Jonathan V Dietz
- Department of Biochemistry, University of Nebraska, Lincoln, NE 68588, United States of America
| | - Iryna Bohovych
- Department of Biochemistry, University of Nebraska, Lincoln, NE 68588, United States of America
| | - Martonio Ponte Viana
- Department of Biochemistry, University of Nebraska, Lincoln, NE 68588, United States of America
| | - Oleh Khalimonchuk
- Department of Biochemistry, University of Nebraska, Lincoln, NE 68588, United States of America; Nebraska Redox Biology Center, University of Nebraska, Lincoln, NE 68588, United States of America; Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, United States of America.
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5
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Mitochondrial pathophysiology beyond the retinal ganglion cell: occipital GABA is decreased in autosomal dominant optic neuropathy. Graefes Arch Clin Exp Ophthalmol 2018; 256:2341-2348. [PMID: 30324419 PMCID: PMC6224020 DOI: 10.1007/s00417-018-4153-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 07/05/2018] [Accepted: 09/24/2018] [Indexed: 01/05/2023] Open
Abstract
PURPOSE It has remained a mystery why some genetic mitochondrial disorders affect predominantly specific cell types such as the retinal ganglion cell. This is particularly intriguing concerning retinal and cortical function since they are tightly linked in health and disease. Autosomal dominant optic neuropathy (ADOA) is a mitochondrial disease that affects the ganglion cell. However, it is unknown whether alterations are also present in the visual cortex, namely in excitation/inhibition balance. METHODS In this study, we performed in vivo structural and biochemical proton magnetic resonance imaging in 14 ADOA and 11 age-matched control participants focusing on the visual cortex, with the aim of establishing whether in this genetically determined disease an independent cortical neurochemical phenotype could be established irrespective of a putative structural phenotype. Cortical thickness of anatomically defined visual areas was estimated, and a voxel-based morphometry approach was used to assess occipital volumetric changes in ADOA. Neurochemical measurements were focused on γ-aminobutyric acid (GABA) and glutamate, as indicators of the local excitatory/inhibitory balance. RESULTS We found evidence for reduced visual cortical GABA and preserved glutamate concentrations in the absence of cortical or subcortical atrophy. These changes in GABA levels were explained by neither structural nor functional measures of visual loss, suggesting a developmental origin. CONCLUSIONS These results suggest that mitochondrial disorders that were previously believed to only affect retinal function may also affect cortical physiology, especially the GABAergic system, suggesting reduced brain inhibition vs. excitation. This GABA phenotype, independent of sensory loss or cortical atrophy and in the presence of preserved glutamate levels, suggests a neurochemical developmental change at the cortical level, leading to a pathophysiological excitation/inhibition imbalance.
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Distributed abnormalities of brain white matter architecture in patients with dominant optic atrophy and OPA1 mutations. J Neurol 2015; 262:1216-27. [DOI: 10.1007/s00415-015-7696-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 02/27/2015] [Accepted: 02/27/2015] [Indexed: 01/08/2023]
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Manners DN, Rizzo G, La Morgia C, Tonon C, Testa C, Barboni P, Malucelli E, Valentino ML, Caporali L, Strobbe D, Carelli V, Lodi R. Diffusion Tensor Imaging Mapping of Brain White Matter Pathology in Mitochondrial Optic Neuropathies. AJNR Am J Neuroradiol 2015; 36:1259-65. [PMID: 25792533 DOI: 10.3174/ajnr.a4272] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 12/05/2014] [Indexed: 01/04/2023]
Abstract
BACKGROUND AND PURPOSE Brain white matter is frequently affected in mitochondrial diseases; optic atrophy gene 1-autosomal dominant optic atrophy and Leber hereditary optic neuropathy are the most frequent mitochondrial monosymptomatic optic neuropathies. In this observational study, brain white matter microstructure was characterized by DTI in patients with optic atrophy gene 1-autosomal dominant optic atrophy and Leber hereditary optic neuropathy, in relation to clinical and genetic features. MATERIALS AND METHODS Nineteen patients with optic atrophy gene 1-autosomal dominant optic atrophy and 17 with Leber hereditary optic neuropathy older than 18 years of age, all genetically diagnosed, and 19 healthy volunteers underwent DTI by using a 1.5T MR imaging scanner and neurologic and ophthalmologic assessments. Brain white matter DTI metrics were calculated for all participants, and, in patients, their correlations with genetics and clinical findings were calculated. RESULTS Compared with controls, patients with optic atrophy gene 1-autosomal dominant optic atrophy had an increased mean diffusivity in 29.2% of voxels analyzed within major white matter tracts distributed throughout the brain, while fractional anisotropy was reduced in 30.3% of voxels. For patients with Leber hereditary optic neuropathy, the proportion of altered voxels was only 0.5% and 5.5%, respectively, of which half was found within the optic radiation and 3.5%, in the smaller acoustic radiation. In almost all regions, fractional anisotropy diminished with age in patients with optic atrophy gene 1-autosomal dominant optic atrophy and correlated with average retinal nerve fiber layer thickness in several areas. Mean diffusivity increased in those with a missense mutation. Patients with Leber hereditary optic neuropathy taking idebenone had slightly milder changes. CONCLUSIONS Patients with Leber hereditary optic neuropathy had preferential involvement of the optic and acoustic radiations, consistent with trans-synaptic degeneration, whereas patients with optic atrophy gene 1-autosomal dominant optic atrophy presented with widespread involvement suggestive of a multisystemic, possibly a congenital/developmental, disorder. White matter changes in Leber hereditary optic neuropathy and optic atrophy gene 1-autosomal dominant optic atrophy may be exploitable as biomarkers.
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Affiliation(s)
- D N Manners
- From the Functional MR Unit (D.N.M., G.R., C.Tonon, C.Testa, R.L.)
| | - G Rizzo
- From the Functional MR Unit (D.N.M., G.R., C.Tonon, C.Testa, R.L.) Neurology Unit (G.R., C.L.M., M.L.V., L.C., D.S., V.C.), Department of Biomedical and NeuroMotor Sciences
| | - C La Morgia
- Neurology Unit (G.R., C.L.M., M.L.V., L.C., D.S., V.C.), Department of Biomedical and NeuroMotor Sciences "Istituto di Ricovero e Cura a Carattere Scientifico Istituto delle Scienze Neurologiche di Bologna" (C.L.M., M.L.V., L.C., D.S., V.C.), Bologna, Italy
| | - C Tonon
- From the Functional MR Unit (D.N.M., G.R., C.Tonon, C.Testa, R.L.)
| | - C Testa
- From the Functional MR Unit (D.N.M., G.R., C.Tonon, C.Testa, R.L.)
| | - P Barboni
- Studio Oculistico d'Azeglio (P.B.), Bologna, Italy
| | - E Malucelli
- Department of Pharmacy and Biotechnology (E.M.), University of Bologna, Bologna, Italy
| | - M L Valentino
- Neurology Unit (G.R., C.L.M., M.L.V., L.C., D.S., V.C.), Department of Biomedical and NeuroMotor Sciences "Istituto di Ricovero e Cura a Carattere Scientifico Istituto delle Scienze Neurologiche di Bologna" (C.L.M., M.L.V., L.C., D.S., V.C.), Bologna, Italy
| | - L Caporali
- Neurology Unit (G.R., C.L.M., M.L.V., L.C., D.S., V.C.), Department of Biomedical and NeuroMotor Sciences "Istituto di Ricovero e Cura a Carattere Scientifico Istituto delle Scienze Neurologiche di Bologna" (C.L.M., M.L.V., L.C., D.S., V.C.), Bologna, Italy
| | - D Strobbe
- Neurology Unit (G.R., C.L.M., M.L.V., L.C., D.S., V.C.), Department of Biomedical and NeuroMotor Sciences "Istituto di Ricovero e Cura a Carattere Scientifico Istituto delle Scienze Neurologiche di Bologna" (C.L.M., M.L.V., L.C., D.S., V.C.), Bologna, Italy
| | - V Carelli
- Neurology Unit (G.R., C.L.M., M.L.V., L.C., D.S., V.C.), Department of Biomedical and NeuroMotor Sciences "Istituto di Ricovero e Cura a Carattere Scientifico Istituto delle Scienze Neurologiche di Bologna" (C.L.M., M.L.V., L.C., D.S., V.C.), Bologna, Italy
| | - R Lodi
- From the Functional MR Unit (D.N.M., G.R., C.Tonon, C.Testa, R.L.)
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9
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Alaimo A, Gorojod RM, Beauquis J, Muñoz MJ, Saravia F, Kotler ML. Deregulation of mitochondria-shaping proteins Opa-1 and Drp-1 in manganese-induced apoptosis. PLoS One 2014; 9:e91848. [PMID: 24632637 PMCID: PMC3954806 DOI: 10.1371/journal.pone.0091848] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 02/17/2014] [Indexed: 01/15/2023] Open
Abstract
Mitochondria are dynamic organelles that undergo fusion and fission processes. These events are regulated by mitochondria-shaping proteins. Changes in the expression and/or localization of these proteins lead to a mitochondrial dynamics impairment and may promote apoptosis. Increasing evidence correlates the mitochondrial dynamics disruption with the occurrence of neurodegenerative diseases. Therefore, we focused on this topic in Manganese (Mn)-induced Parkinsonism, a disorder associated with Mn accumulation preferentially in the basal ganglia where mitochondria from astrocytes represent an early target. Using MitoTracker Red staining we observed increased mitochondrial network fission in Mn-exposed rat astrocytoma C6 cells. Moreover, Mn induced a marked decrease in fusion protein Opa-1 levels as well as a dramatic increase in the expression of fission protein Drp-1. Additionally, Mn provoked a significant release of high MW Opa-1 isoforms from the mitochondria to the cytosol as well as an increased Drp-1 translocation to the mitochondria. Both Mdivi-1, a pharmacological Drp-1 inhibitor, and rat Drp-1 siRNA reduced the number of apoptotic nuclei, preserved the mitochondrial network integrity and prevented cell death. CsA, an MPTP opening inhibitor, prevented mitochondrial Δψm disruption, Opa-1 processing and Drp-1 translocation to the mitochondria therefore protecting Mn-exposed cells from mitochondrial disruption and apoptosis. The histological analysis and Hoechst 33258 staining of brain sections of Mn-injected rats in the striatum showed a decrease in cellular mass paralleled with an increase in the occurrence of apoptotic nuclei. Opa-1 and Drp-1 expression levels were also changed by Mn-treatment. Our results demonstrate for the first time that abnormal mitochondrial dynamics is implicated in both in vitro and in vivo Mn toxicity. In addition we show that the imbalance in fusion/fission equilibrium might be involved in Mn-induced apoptosis. This knowledge may provide new therapeutic tools for the treatment of Manganism and other neurodegenerative diseases.
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Affiliation(s)
- Agustina Alaimo
- Laboratorio de Apoptosis en el Sistema Nervioso y Nano-Oncología, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Química Biológica, Ciencias Exactas y Naturales (IQUIBICEN-CONICET), Buenos Aires, Argentina
| | - Roxana M. Gorojod
- Laboratorio de Apoptosis en el Sistema Nervioso y Nano-Oncología, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Química Biológica, Ciencias Exactas y Naturales (IQUIBICEN-CONICET), Buenos Aires, Argentina
| | - Juan Beauquis
- Laboratorio de Neurobiología, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Biología y Medicina Experimental (IBYME-CONICET), Buenos Aires, Argentina
| | - Manuel J. Muñoz
- Departamento de Fisiología, Biología Molecular y Celular and Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE-CONICET), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Flavia Saravia
- Laboratorio de Neurobiología, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Biología y Medicina Experimental (IBYME-CONICET), Buenos Aires, Argentina
| | - Mónica L. Kotler
- Laboratorio de Apoptosis en el Sistema Nervioso y Nano-Oncología, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Química Biológica, Ciencias Exactas y Naturales (IQUIBICEN-CONICET), Buenos Aires, Argentina
- * E-mail:
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Riazifar H, Jia Y, Chen J, Lynch G, Huang T. Chemically induced specification of retinal ganglion cells from human embryonic and induced pluripotent stem cells. Stem Cells Transl Med 2014; 3:424-32. [PMID: 24493857 DOI: 10.5966/sctm.2013-0147] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The loss of retinal ganglion cells (RGCs) is the primary pathological change for many retinal degenerative diseases. Although there is currently no effective treatment for this group of diseases, cell transplantation to replace lost RGCs holds great potential. However, for the development of cell replacement therapy, better understanding of the molecular details involved in differentiating stem cells into RGCs is essential. In this study, a novel, stepwise chemical protocol is described for the differentiation of human embryonic stem cells and induced pluripotent stem cells into functional RGCs. Briefly, stem cells were differentiated into neural rosettes, which were then cultured with the Notch inhibitor N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (DAPT). The expression of neural and RGC markers (BRN3A, BRN3B, ATOH7/Math5, γ-synuclein, Islet-1, and THY-1) was examined. Approximately 30% of the cell population obtained expressed the neuronal marker TUJ1 as well the RGC markers. Moreover, the differentiated RGCs generated action potentials and exhibited both spontaneous and evoked excitatory postsynaptic currents, indicating that functional and mature RGCs were generated. In combination, these data demonstrate that a single chemical (DAPT) can induce PAX6/RX-positive stem cells to undergo differentiation into functional RGCs.
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Affiliation(s)
- Hamidreza Riazifar
- Department of Pediatrics, Division of Human Genetics, Department of Anatomy and Neurobiology, Department of Psychiatry and Human Behavior, MitoMed Molecular Diagnostic Laboratory, Department of Pathology, Department of Developmental and Cell Biology, and Department of Ophthalmology, University of California, Irvine, Irvine, California, USA; Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
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Barnard AR, Charbel Issa P, Perganta G, Williams PA, Davies VJ, Sekaran S, Votruba M, MacLaren RE. Specific deficits in visual electrophysiology in a mouse model of dominant optic atrophy. Exp Eye Res 2011; 93:771-7. [PMID: 21803037 DOI: 10.1016/j.exer.2011.07.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 07/11/2011] [Accepted: 07/16/2011] [Indexed: 11/24/2022]
Abstract
Autosomal dominant optic atrophy (ADOA) is a slowly progressive optic neuropathy caused by mutations in the OPA1 gene. OPA1 is ubiquitously expressed and plays a key role in mitochondrial fusion. Heterozygous Opa1 mutant mice (B6; C3-Opa1(Q285STOP)), have previously been reported to develop visual defects and optic nerve changes. In this study, in vivo visual electrophysiological testing (ERGs and VEPs) was performed on 11-13 month old B6; C3-Opa1(Q285STOP) mice (n = 5) and age/sex matched wildtype littermate controls. Full intensity series were recorded in response to brief (4 ms) single flash stimuli delivered in a Ganzfeld dome under dark- and light-adapted conditions. The major ERG components (a-wave and b-wave) showed no detectable difference from wildtype in the amplitude or implicit time of dark-adapted ERGs across the full intensity range tested. This was also true for the components of the dark-adapted VEP. However, the light-adapted ERG responses revealed a significant reduction in the photopic negative response (PhNR) amplitude in Opa1(+/-) animals relative to wildtypes at the brighter intensities tested. Elements of the light-adapted VEP were also abnormal in mutant mice. Overall Opa1(+/-) mice display functional deficits in electrophysiology that are consistent with ganglion cell dysfunction. These deficits may correlate with a reduction in the dendritic arborisation of retinal ganglion cells, which has been previously reported to occur at a similar age in the same mutant mouse line (Williams et al., 2010). The functional phenotype we have described in this mouse model may be useful in the robust and accurate assessment of potential treatments for ADOA.
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12
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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: 431] [Impact Index Per Article: 33.2] [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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Fraser JA, Biousse V, Newman NJ. The neuro-ophthalmology of mitochondrial disease. Surv Ophthalmol 2010; 55:299-334. [PMID: 20471050 PMCID: PMC2989385 DOI: 10.1016/j.survophthal.2009.10.002] [Citation(s) in RCA: 177] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Revised: 09/21/2009] [Accepted: 10/01/2009] [Indexed: 01/16/2023]
Abstract
Mitochondrial diseases frequently manifest neuro-ophthalmologic symptoms and signs. Because of the predilection of mitochondrial disorders to involve the optic nerves, extraocular muscles, retina, and even the retrochiasmal visual pathways, the ophthalmologist is often the first physician to be consulted. Disorders caused by mitochondrial dysfunction can result from abnormalities in either the mitochondrial DNA or in nuclear genes which encode mitochondrial proteins. Inheritance of these mutations will follow patterns specific to their somatic or mitochondrial genetics. Genotype-phenotype correlations are inconstant, and considerable overlap may occur among these syndromes. The diagnostic approach to the patient with suspected mitochondrial disease entails a detailed personal and family history, careful ophthalmic, neurologic, and systemic examination, directed investigations, and attention to potentially life-threatening sequelae. Although curative treatments for mitochondrial disorders are currently lacking, exciting research advances are being made, particularly in the area of gene therapy. Leber hereditary optic neuropathy, with its window of opportunity for timely intervention and its accessibility to directed therapy, offers a unique model to study future therapeutic interventions. Most patients and their relatives benefit from informed genetic counseling.
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Affiliation(s)
- J. Alexander Fraser
- Departments of Ophthalmology (J.A.F., V.B., N.J.N.), Neurology (V.B., N.J.N.), and Neurological Surgery (N.J.N.), Emory University School of Medicine, Atlanta, GA
| | - Valérie Biousse
- Departments of Ophthalmology (J.A.F., V.B., N.J.N.), Neurology (V.B., N.J.N.), and Neurological Surgery (N.J.N.), Emory University School of Medicine, Atlanta, GA
| | - Nancy J. Newman
- Departments of Ophthalmology (J.A.F., V.B., N.J.N.), Neurology (V.B., N.J.N.), and Neurological Surgery (N.J.N.), Emory University School of Medicine, Atlanta, GA
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Fuhrmann N, Schimpf S, Kamenisch Y, Leo-Kottler B, Alexander C, Auburger G, Zrenner E, Wissinger B, Alavi MV. Solving a 50 year mystery of a missing OPA1 mutation: more insights from the first family diagnosed with autosomal dominant optic atrophy. Mol Neurodegener 2010; 5:25. [PMID: 20546606 PMCID: PMC2893178 DOI: 10.1186/1750-1326-5-25] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2009] [Accepted: 06/14/2010] [Indexed: 12/16/2022] Open
Abstract
Background Up to the 1950s, there was an ongoing debate about the diversity of hereditary optic neuropathies, in particular as to whether all inherited optic atrophies can be ascribed to Leber's hereditary optic neuropathy (LHON) or represent different disease entities. In 1954 W. Jaeger published a detailed clinical and genealogical investigation of a large family with explicit autosomal dominant segregation of optic atrophy thus proving the existence of a discrete disease different from LHON, which is nowadays known as autosomal dominant optic atrophy (ADOA). Since the year 2000 ADOA is associated with genomic mutations in the OPA1 gene, which codes for a protein that is imported into mitochondria where it is required for mitochondrial fusion. Interestingly enough, the underlying mutation in this family has not been identified since then. Results We have reinvestigated this family with the aim to identify the mutation and to further clarify the underlying pathomechanism. Patients showed a classical non-syndromic ADOA. The long term deterioration in vision in the two teenagers examined 50 years later is of particular note 5/20 to 6/120. Multiplex ligation probe amplification revealed a duplication of the OPA1 exons 7-9 which was confirmed by long distance PCR and cDNA analysis, resulting in an in-frame duplication of 102 amino acids. Segregation was verified in 53 available members of the updated pedigree and a penetrance of 88% was calculated. Fibroblast cultures from skin biopsies were established to assess the mitochondrial network integrity and to qualitatively and quantitatively study the consequences of the mutation on transcript and protein level. Fibroblast cultures demonstrated a fragmented mitochondrial network. Processing of the OPA1 protein was altered. There was no correlation of the OPA1 transcript levels and the OPA1 protein levels in the fibroblasts. Intriguingly an overall decrease of mitochondrial proteins was observed in patients' fibroblasts, while the OPA1 transcript levels were elevated. Conclusions The thorough study of this family provides a detailed clinical picture accompanied by a molecular investigation of patients' fibroblasts. Our data show a classic OPA1-associated non-syndromic ADOA segregating in this family. Cell biological findings suggest that OPA1 is regulated by post-translational mechanisms and we would like to hypothesize that loss of OPA1 function might lead to impaired mitochondrial quality control. With the clinical, genetic and cell biological characterisation of a family described already more than 50 years ago, we span more than half a century of research in optic neuropathies.
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Affiliation(s)
- Nico Fuhrmann
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Germany.
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15
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Edwards JL, Quattrini A, Lentz SI, Figueroa-Romero C, Cerri F, Backus C, Hong Y, Feldman EL. Diabetes regulates mitochondrial biogenesis and fission in mouse neurons. Diabetologia 2010; 53:160-9. [PMID: 19847394 PMCID: PMC4011390 DOI: 10.1007/s00125-009-1553-y] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Accepted: 09/02/2009] [Indexed: 10/20/2022]
Abstract
AIMS/HYPOTHESIS Normal mitochondrial activity is a critical component of neuronal metabolism and function. Disruption of mitochondrial activity by altered mitochondrial fission and fusion is the root cause of both neurodegenerative disorders and Charcot-Marie-Tooth type 2A inherited neuropathy. This study addressed the role of mitochondrial fission in the pathogenesis of diabetic neuropathy. METHODS Mitochondrial biogenesis and fission were assayed in both in vivo and in vitro models of diabetic neuropathy. Gene, protein, mitochondrial DNA and ultrastructural analyses were used to assess mitochondrial biogenesis and fission. RESULTS There was greater mitochondrial biogenesis in dorsal root ganglion neurons from diabetic compared with non-diabetic mice. An essential step in mitochondrial biogenesis is mitochondrial fission, regulated by the mitochondrial fission protein dynamin-related protein 1 (DRP1). Evaluation of diabetic neurons in vivo indicated small, fragmented mitochondria, suggesting increased fission. In vitro studies revealed that short-term hyperglycaemic exposure increased levels of DRP1 protein. The influence of hyperglycaemia-mediated mitochondrial fission on cell viability was evaluated by knockdown of Drp1 (also known as Dnm1l). Knockdown of Drp1 resulted in decreased susceptibility to hyperglycaemic damage. CONCLUSIONS/INTERPRETATION We propose that: (1) mitochondria undergo biogenesis in response to hyperglycaemia, but the increased biogenesis is insufficient to accommodate the metabolic load; (2) hyperglycaemia causes an excess of mitochondrial fission, creating small, damaged mitochondria; and (3) reduction of aberrant mitochondrial fission increases neuronal survival and indicates an important role for the fission-fusion equilibrium in the pathogenesis of diabetic neuropathy.
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Affiliation(s)
- J L Edwards
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
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16
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Alavi MV, Fuhrmann N, Nguyen HP, Yu-Wai-Man P, Heiduschka P, Chinnery PF, Wissinger B. Subtle neurological and metabolic abnormalities in an Opa1 mouse model of autosomal dominant optic atrophy. Exp Neurol 2009; 220:404-9. [DOI: 10.1016/j.expneurol.2009.09.026] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2009] [Revised: 09/09/2009] [Accepted: 09/28/2009] [Indexed: 12/20/2022]
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17
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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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18
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Shahrestani P, Leung HT, Le PK, Pak WL, Tse S, Ocorr K, Huang T. Heterozygous mutation of Drosophila Opa1 causes the development of multiple organ abnormalities in an age-dependent and organ-specific manner. PLoS One 2009; 4:e6867. [PMID: 19718456 PMCID: PMC2730818 DOI: 10.1371/journal.pone.0006867] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Accepted: 06/22/2009] [Indexed: 11/19/2022] Open
Abstract
Optic Atrophy 1 (OPA1) is a ubiquitously expressed dynamin-like GTPase in the inner mitochondrial membrane. It plays important roles in mitochondrial fusion, apoptosis, reactive oxygen species (ROS) and ATP production. Mutations of OPA1 result in autosomal dominant optic atrophy (DOA). The molecular mechanisms by which link OPA1 mutations and DOA are not fully understood. Recently, we created a Drosophila model to study the pathogenesis of optic atrophy. Heterozygous mutation of Drosophila OPA1 (dOpa1) by P-element insertion results in no obvious morphological abnormalities, whereas homozygous mutation is embryonic lethal. In eye-specific somatic clones, homozygous mutation of dOpa1 causes rough (mispatterning) and glossy (decreased lens deposition) eye phenotypes in adult Drosophila. In humans, heterozygous mutations in OPA1 have been associated with mitochondrial dysfunction, which is predicted to affect multiple organs. In this study, we demonstrated that heterozygous dOpa1 mutation perturbs the visual function and an ERG profile of the Drosophila compound eye. We independently showed that antioxidants delayed the onset of mutant phenotypes in ERG and improved larval vision function in phototaxis assay. Furthermore, heterozygous dOpa1 mutation also caused decreased heart rate, increased heart arrhythmia, and poor tolerance to stress induced by electrical pacing. However, antioxidants had no effects on the dysfunctional heart of heterozygous dOpa1 mutants. Under stress, heterozygous dOpa1 mutations caused reduced escape response, suggesting abnormal function of the skeletal muscles. Our results suggest that heterozygous mutation of dOpa1 shows organ-specific pathogenesis and is associated with multiple organ abnormalities in an age-dependent and organ-specific manner.
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Affiliation(s)
- Parvin Shahrestani
- Ecology and Evolution, University of California Irvine, Irvine, California, United States of America
| | - Hung-Tat Leung
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Phung Khanh Le
- Division of Human Genetics, Department of Pediatrics, University of California Irvine, Irvine, California, United States of America
| | - William L. Pak
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Stephanie Tse
- Division of Human Genetics, Department of Pediatrics, University of California Irvine, Irvine, California, United States of America
| | - Karen Ocorr
- Burnham Institute for Medical Research, Program for Systems and Developmental Biology, Center for Neuroscienes and Aging, La Jolla, California, United States of America
| | - Taosheng Huang
- Division of Human Genetics, Department of Pediatrics, University of California Irvine, Irvine, California, United States of America
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, California, United States of America
- Department of Pathology, University of California Irvine, Irvine, California, United States of America
- * E-mail:
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19
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Yu-Wai-Man P, Griffiths PG, Hudson G, Chinnery PF. Inherited mitochondrial optic neuropathies. J Med Genet 2009; 46:145-58. [PMID: 19001017 PMCID: PMC2643051 DOI: 10.1136/jmg.2007.054270] [Citation(s) in RCA: 287] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2008] [Revised: 09/08/2008] [Accepted: 10/07/2008] [Indexed: 02/02/2023]
Abstract
Leber hereditary optic neuropathy (LHON) and autosomal dominant optic atrophy (DOA) are the two most common inherited optic neuropathies and they result in significant visual morbidity among young adults. Both disorders are the result of mitochondrial dysfunction: LHON from primary mitochondrial DNA (mtDNA) mutations affecting the respiratory chain complexes; and the majority of DOA families have mutations in the OPA1 gene, which codes for an inner mitochondrial membrane protein critical for mtDNA maintenance and oxidative phosphorylation. Additional genetic and environmental factors modulate the penetrance of LHON, and the same is likely to be the case for DOA which has a markedly variable clinical phenotype. The selective vulnerability of retinal ganglion cells (RGCs) is a key pathological feature and understanding the fundamental mechanisms that underlie RGC loss in these disorders is a prerequisite for the development of effective therapeutic strategies which are currently limited.
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MESH Headings
- DNA, Mitochondrial
- Female
- GTP Phosphohydrolases/genetics
- Humans
- Male
- Optic Atrophy, Autosomal Dominant/diagnosis
- Optic Atrophy, Autosomal Dominant/epidemiology
- Optic Atrophy, Autosomal Dominant/genetics
- Optic Atrophy, Autosomal Dominant/pathology
- Optic Atrophy, Hereditary, Leber/diagnosis
- Optic Atrophy, Hereditary, Leber/epidemiology
- Optic Atrophy, Hereditary, Leber/genetics
- Optic Atrophy, Hereditary, Leber/pathology
- Point Mutation
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Affiliation(s)
- P Yu-Wai-Man
- Mitochondrial Research Group, The Medical School, Newcastle University, Newcastle upon Tyne, UK
- Department of Ophthalmology, Royal Victoria Infirmary, Newcastle upon Tyne, UK
| | - P G Griffiths
- Department of Ophthalmology, Royal Victoria Infirmary, Newcastle upon Tyne, UK
| | - G Hudson
- Mitochondrial Research Group, The Medical School, Newcastle University, Newcastle upon Tyne, UK
| | - P F Chinnery
- Mitochondrial Research Group, The Medical School, Newcastle University, Newcastle upon Tyne, UK
- Institute of Human Genetics, Newcastle University, Newcastle upon Tyne, NE1 3BZ, UK
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20
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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, Vergani L. A novel deletion in the GTPase domain of OPA1 causes defects in mitochondrial morphology and distribution, but not in function. Hum Mol Genet 2008; 17:3291-302. [PMID: 18678599 DOI: 10.1093/hmg/ddn225] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
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.
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21
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Yarosh W, Monserrate J, Tong JJ, Tse S, Le PK, Nguyen K, Brachmann CB, Wallace DC, Huang T. The molecular mechanisms of OPA1-mediated optic atrophy in Drosophila model and prospects for antioxidant treatment. PLoS Genet 2008; 4:e6. [PMID: 18193945 PMCID: PMC2174975 DOI: 10.1371/journal.pgen.0040006] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2007] [Accepted: 11/27/2007] [Indexed: 11/18/2022] Open
Abstract
Mutations in optic atrophy 1 (OPA1), a nuclear gene encoding a mitochondrial protein, is the most common cause for autosomal dominant optic atrophy (DOA). The condition is characterized by gradual loss of vision, color vision defects, and temporal optic pallor. To understand the molecular mechanism by which OPA1 mutations cause optic atrophy and to facilitate the development of an effective therapeutic agent for optic atrophies, we analyzed phenotypes in the developing and adult Drosophila eyes produced by mutant dOpa1 (CG8479), a Drosophila ortholog of human OPA1. Heterozygous mutation of dOpa1 by a P-element or transposon insertions causes no discernable eye phenotype, whereas the homozygous mutation results in embryonic lethality. Using powerful Drosophila genetic techniques, we created eye-specific somatic clones. The somatic homozygous mutation of dOpa1 in the eyes caused rough (mispatterning) and glossy (decreased lens and pigment deposition) eye phenotypes in adult flies; this phenotype was reversible by precise excision of the inserted P-element. Furthermore, we show the rough eye phenotype is caused by the loss of hexagonal lattice cells in developing eyes, suggesting an increase in lattice cell apoptosis. In adult flies, the dOpa1 mutation caused an increase in reactive oxygen species (ROS) production as well as mitochondrial fragmentation associated with loss and damage of the cone and pigment cells. We show that superoxide dismutase 1 (SOD1), Vitamin E, and genetically overexpressed human SOD1 (hSOD1) is able to reverse the glossy eye phenotype of dOPA1 mutant large clones, further suggesting that ROS play an important role in cone and pigment cell death. Our results show dOpa1 mutations cause cell loss by two distinct pathogenic pathways. This study provides novel insights into the pathogenesis of optic atrophy and demonstrates the promise of antioxidants as therapeutic agents for this condition. Optic atrophies are a group of neurodegenerative disorders characterized by a gradual loss of vision, color vision defects, and temporal optic pallor. Autosomal dominant optic atrophy (DOA), a type of optic atrophy, contributes to a large portion of optic atrophy cases. Mutations of the optic atrophy 1 (OPA1) gene are responsible for this condition. Here we describe mutant Drosophila that contain insertions in the Drosophila OPA1 ortholog, dOpa1. Heterozygous mutation causes no discernable eye phenotype, and homozygous mutation results in embryonic lethality. Using the powerful Drosophila genetic techniques, we created eye-specific mutants, giving rise to cells with two mutant copies of dOpa1 only in the Drosophila eye, and found that these eyes were rough (mispatterned) and glossy (decreased lens and pigment deposition). We found that these phenotypes were associated with fragmented mitochondria and were caused by elevated reactive oxygen species. The administration of antioxidants could ameliorate the phenotypes caused by mutation of dOpa1, offering new insight into treatment of this disease.
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MESH Headings
- Amino Acid Sequence
- Animals
- Antioxidants/therapeutic use
- DNA Transposable Elements/genetics
- Disease Models, Animal
- Drosophila
- Drosophila Proteins/chemistry
- Drosophila Proteins/genetics
- Drosophila Proteins/metabolism
- Eye/ultrastructure
- GTP Phosphohydrolases/chemistry
- GTP Phosphohydrolases/genetics
- GTP Phosphohydrolases/metabolism
- Gene Dosage
- Genes, Dominant
- Genes, Insect
- Genetic Techniques
- Homozygote
- Humans
- Membrane Proteins/chemistry
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Molecular Sequence Data
- Mutagenesis, Insertional
- Mutation
- Optic Atrophy, Autosomal Dominant/etiology
- Optic Atrophy, Autosomal Dominant/genetics
- Optic Atrophy, Autosomal Dominant/pathology
- Optic Atrophy, Autosomal Dominant/therapy
- Penetrance
- Protein Structure, Tertiary
- Sequence Homology, Amino Acid
- Superoxide Dismutase/therapeutic use
- Vitamin E/therapeutic use
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Affiliation(s)
- Will Yarosh
- Department of Pediatrics, Division of Human Genetics, University of California Irvine, Irvine, California, United States of America
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, California, United States of America
| | - Jessica Monserrate
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, California, United States of America
| | - James Jiayuan Tong
- Department of Biological Chemistry, University of California Irvine, Irvine, California, United States of America
- Center for Molecular and Mitochondrial Medicine and Genetics, University of California Irvine, Irvine, California, United States of America
| | - Stephanie Tse
- Department of Pediatrics, Division of Human Genetics, University of California Irvine, Irvine, California, United States of America
| | - Phung Khanh Le
- Department of Pediatrics, Division of Human Genetics, University of California Irvine, Irvine, California, United States of America
| | - Kimberly Nguyen
- Department of Pediatrics, Division of Human Genetics, University of California Irvine, Irvine, California, United States of America
| | - Carrie B Brachmann
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, California, United States of America
| | - Douglas C Wallace
- Department of Biological Chemistry, University of California Irvine, Irvine, California, United States of America
- Center for Molecular and Mitochondrial Medicine and Genetics, University of California Irvine, Irvine, California, United States of America
| | - Taosheng Huang
- Department of Pediatrics, Division of Human Genetics, University of California Irvine, Irvine, California, United States of America
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, California, United States of America
- Department of Pathology, University of California Irvine, Irvine, California, United States of America
- * To whom correspondence should be addressed. E-mail:
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22
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Bette S, Zimmermann U, Wissinger B, Knipper M. OPA1, the disease gene for optic atrophy type Kjer, is expressed in the inner ear. Histochem Cell Biol 2007; 128:421-30. [PMID: 17828551 DOI: 10.1007/s00418-007-0321-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/19/2007] [Indexed: 11/26/2022]
Abstract
Autosomal dominant optic atrophy (adOA) is the most common form of hereditary optic neuropathy. The majority of cases are associated with mutations in the OPA1 gene. A few cases of adOA are known to be associated with moderate progressive hearing loss. To gain insight into the pathogenesis of this hearing loss, we performed expression analyses of OPA1 in the rat auditory and vestibular organ. In cochlear tissue, several splice variants of OPA1 were detected, which are also expressed in retinal tissue. OPA1 mRNA and protein was found in the hair cells and ganglion cells of the cochlea and vestibular organ. In ganglion cells, OPA1 mRNA and protein was already detectable at birth, whereas in the organ of Corti OPA1 mRNA and protein was up-regulated after birth and reached mature-like expression level during the onset of hearing. Comparison of an antibody directed to the mitochondrial marker protein HSP60 with antibodies directed to different amino acid stretches of OPA1 revealed a sub-cellular distribution of OPA1 in areas of significant density of mitochondria. The data suggest that defects in OPA1 cause hearing disorders due to a progressing metabolic disturbance of hair and ganglion cells in the inner ear.
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Affiliation(s)
- Stefanie Bette
- Molecular Genetics Laboratory, University Eye Hospital, Röntgenweg 11, 72076, Tübingen, Germany
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23
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Mabuchi F, Tang S, Kashiwagi K, Yamagata Z, Iijima H, Tsukahara S. The OPA1 gene polymorphism is associated with normal tension and high tension glaucoma. Am J Ophthalmol 2007; 143:125-130. [PMID: 17188046 DOI: 10.1016/j.ajo.2006.09.028] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2006] [Revised: 08/26/2006] [Accepted: 09/12/2006] [Indexed: 10/24/2022]
Abstract
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.
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Affiliation(s)
- Fumihiko Mabuchi
- Department of Ophthalmology, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo-shi, Yamanashi 409-3898, Japan.
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