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Borsche M, Dulovic-Mahlow M, Baumann H, Tunc S, Lüth T, Schaake S, Özcakir S, Westenberger A, Münchau A, Knappe E, Trinh J, Brüggemann N, Lohmann K. POLG2-Linked Mitochondrial Disease: Functional Insights from New Mutation Carriers and Review of the Literature. CEREBELLUM (LONDON, ENGLAND) 2024; 23:479-488. [PMID: 37085601 PMCID: PMC10951043 DOI: 10.1007/s12311-023-01557-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/05/2023] [Indexed: 04/23/2023]
Abstract
Different pathogenic variants in the DNA polymerase-gamma2 (POLG2) gene cause a rare, clinically heterogeneous mitochondrial disease. We detected a novel POLG2 variant (c.1270 T > C, p.Ser424Pro) in a family with adult-onset cerebellar ataxia and progressive ophthalmoplegia. We demonstrated altered mitochondrial integrity in patients' fibroblast cultures but no changes of the mitochondrial DNA were found when compared to controls. We consider this novel, segregating POLG2 variant as disease-causing in this family. Moreover, we systematically screened the literature for POLG2-linked phenotypes and re-evaluated all mutations published to date for pathogenicity according to current knowledge. Thereby, we identified twelve published, likely disease-causing variants in 19 patients only. The core features included progressive ophthalmoplegia and cerebellar ataxia; parkinsonism, neuropathy, cognitive decline, and seizures were also repeatedly found in adult-onset heterozygous POLG2-related disease. A severe phenotype relates to biallelic pathogenic variants in POLG2, i.e., newborn-onset liver failure, referred to as mitochondrial depletion syndrome. Our work underlines the broad clinical spectrum of POLG2-related disease and highlights the importance of functional characterization of variants of uncertain significance to enable meaningful genetic counseling.
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Affiliation(s)
- Max Borsche
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
- Department of Neurology, University of Lübeck and University Hospital Schleswig-Holstein, Campus Lübeck, Lübeck, Germany
| | | | - Hauke Baumann
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
| | - Sinem Tunc
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
- Department of Neurology, University of Lübeck and University Hospital Schleswig-Holstein, Campus Lübeck, Lübeck, Germany
- Institute of Systems Motor Science, University of Lübeck, Lübeck, Germany
| | - Theresa Lüth
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
| | - Susen Schaake
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
| | - Selin Özcakir
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
| | - Ana Westenberger
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
| | - Alexander Münchau
- Institute of Systems Motor Science, University of Lübeck, Lübeck, Germany
| | - Evelyn Knappe
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
| | - Joanne Trinh
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
| | - Norbert Brüggemann
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany.
- Department of Neurology, University of Lübeck and University Hospital Schleswig-Holstein, Campus Lübeck, Lübeck, Germany.
| | - Katja Lohmann
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
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Abstract
Progressive external ophthalmoplegia (PEO), characterized by ptosis and impaired eye movements, is a clinical syndrome with an expanding number of etiologically distinct subtypes. Advances in molecular genetics have revealed numerous pathogenic causes of PEO, originally heralded in 1988 by the detection of single large-scale deletions of mitochondrial DNA (mtDNA) in skeletal muscle of people with PEO and Kearns-Sayre syndrome. Since then, multiple point variants of mtDNA and nuclear genes have been identified to cause mitochondrial PEO and PEO-plus syndromes, including mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) and sensory ataxic neuropathy dysarthria ophthalmoplegia (SANDO). Intriguingly, many of those nuclear DNA pathogenic variants impair maintenance of the mitochondrial genome causing downstream mtDNA multiple deletions and depletion. In addition, numerous genetic causes of nonmitochondrial PEO have been identified.
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Affiliation(s)
- Michio Hirano
- H. Houston Merritt Neuromuscular Research Center, Neuromuscular Medicine Division, Department of Neurology, Columbia University Irving Medical Center, New York, NY, United States.
| | - Robert D S Pitceathly
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, United Kingdom; NHS Highly Specialised Service for Rare Mitochondrial Disorders, Queen Square Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, London, United Kingdom
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3
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Finsterer J. Multisystem presentation of a homozygous POLG2 variant. Eur J Med Genet 2020; 63:103899. [DOI: 10.1016/j.ejmg.2020.103899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 02/29/2020] [Indexed: 10/24/2022]
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Dosekova P, Dubiel A, Karlowicz A, Zietkiewicz S, Rydzanicz M, Habalova V, Pienkowski VM, Skirkova M, Han V, Mosejova A, Gdovinova Z, Kaliszewska M, Tońska K, Szymanski MR, Skorvanek M, Ploski R. Answer to Finsterer about “Multisystem presentation of a homozygous POLG2 variant”. Eur J Med Genet 2020; 63:103900. [DOI: 10.1016/j.ejmg.2020.103900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 02/29/2020] [Indexed: 11/15/2022]
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Maeda-Katahira A, Nakamura N, Hayashi T, Katagiri S, Shimizu S, Ohde H, Matsunaga T, Kaga K, Nakano T, Kameya S, Matsuura T, Fujinami K, Iwata T, Tsunoda K. Autosomal dominant optic atrophy with OPA1 gene mutations accompanied by auditory neuropathy and other systemic complications in a Japanese cohort. Mol Vis 2019; 25:559-573. [PMID: 31673222 PMCID: PMC6798706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 10/03/2019] [Indexed: 12/05/2022] Open
Abstract
PURPOSE This study aimed to describe the genetic and clinical characteristics of four Japanese patients with autosomal dominant optic atrophy (DOA) accompanied by auditory neuropathy and other systemic complications (i.e., DOA-plus disease). METHODS Four patients from four independent families underwent comprehensive ophthalmic and auditory examinations and were diagnosed with DOA-plus disease. The disease-causing gene variants in the OPA1 gene were identified by direct sequencing. The genetic and clinical data of 48 DOA patients without systemic complications-that is, with simple DOA-were compared to those of DOA-plus patients. RESULTS DOA-plus patients noticed a decrease in vision before the age of 14 and hearing impairment 3 to 13 years after the development of visual symptoms. Two patients had progressive external ophthalmoplegia, and one patient had vestibular dysfunction and ataxia. The DOA-plus phenotypes accounted for 13.3% (4/30) of the families with the OPA1 gene mutations. Each DOA-plus patient harbored one of the monoallelic mutations in the OPA1 gene: c.1334G>A, p.R445H, c.1618A>C, p.T540P, and c.892A>C, p.S298R. Missense mutations accounted for 100% (4/4) of the DOA-plus families and only 11.5% (3/26) of the families with simple DOA. CONCLUSIONS All the patients with the DOA-plus phenotype carried one of the missense mutations in the OPA1 gene. They all had typical ocular symptoms and signs of DOA in their first or second decade, and other systemic complications-such as auditory neuropathy, vestibular dysfunction, and ataxia-followed the ocular symptoms. We should consider the occurrence of extraocular complications in cases with DOA, especially when they carry the missense mutations in the OPA1 gene.
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Affiliation(s)
- Akiko Maeda-Katahira
- Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan,Department of Ophthalmology, Tokyo Metropolitan Ohtsuka Hospital, Tokyo, Japan
| | - Natsuko Nakamura
- Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan,Department of Ophthalmology, The University of Tokyo, Tokyo, Japan
| | - Takaaki Hayashi
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Satoshi Katagiri
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Satoko Shimizu
- Department of Ophthalmology, Teikyo University, Tokyo, Japan
| | - Hisao Ohde
- Department of Ophthalmology, Keio University, Tokyo, Japan
| | - Tatsuo Matsunaga
- Division of Hearing and Balance Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan,Department of Otolaryngology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
| | - Kimitaka Kaga
- National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
| | - Tadashi Nakano
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Shuhei Kameya
- Department of Ophthalmology, Nippon Medical School Chiba Hokusoh Hospital, Chiba, Japan
| | - Tomokazu Matsuura
- Department of Laboratory Medicine, The Jikei University School of Medicine, Tokyo, Japan
| | - Kaoru Fujinami
- Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan,UCL Institute of Ophthalmology, London, UK
| | - Takeshi Iwata
- Division of Molecular and Cellular Biology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
| | - Kazushige Tsunoda
- Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
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Bagli E, Zikou AK, Agnantis N, Kitsos G. Mitochondrial Membrane Dynamics and Inherited Optic Neuropathies. ACTA ACUST UNITED AC 2018; 31:511-525. [PMID: 28652416 DOI: 10.21873/invivo.11090] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 04/14/2017] [Accepted: 04/19/2017] [Indexed: 12/12/2022]
Abstract
Inherited optic neuropathies are a genetically diverse group of disorders mainly characterized by visual loss and optic atrophy. Since the first recognition of Leber's hereditary optic neuropathy, several genetic defects altering primary mitochondrial respiration have been proposed to contribute to the development of syndromic and non-syndromic optic neuropathies. Moreover, the genomics and imaging revolution in the past decade has increased diagnostic efficiency and accuracy, allowing recognition of a link between mitochondrial dynamics machinery and a broad range of inherited neurodegenerative diseases involving the optic nerve. Mutations of novel genes modifying mainly the balance between mitochondrial fusion and fission have been shown to lead to overlapping clinical phenotypes ranging from isolated optic atrophy to severe, sometimes lethal multisystem disorders, and are reviewed herein. Given the particular vulnerability of retinal ganglion cells to mitochondrial dysfunction, the accessibility of the eye as a part of the central nervous system and improvements in technical imaging concerning assessment of the retinal nerve fiber layer, optic nerve evaluation becomes critical - even in asymptomatic patients - for correct diagnosis, understanding and early treatment of these complex and enigmatic clinical entities.
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Affiliation(s)
- Eleni Bagli
- Institute of Molecular Biology and Biotechnology-FORTH, Division of Biomedical Research, Ioannina, Greece.,Department of Ophthalmology, University of Ioannina, Ioannina, Greece
| | - Anastasia K Zikou
- Department of Clinical Radiology, University of Ioannina, Ioannina, Greece
| | - Niki Agnantis
- Department of Pathology, University of Ioannina, Ioannina, Greece
| | - Georgios Kitsos
- Department of Ophthalmology, University of Ioannina, Ioannina, Greece
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Finsterer J, Zarrouk-Mahjoub S. Leigh-like syndrome due to OPA1 mutations. Eur J Paediatr Neurol 2017; 21:921-922. [PMID: 28711503 DOI: 10.1016/j.ejpn.2017.06.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 06/29/2017] [Indexed: 10/19/2022]
Affiliation(s)
| | - Sinda Zarrouk-Mahjoub
- University of Tunis El Manar and Genomics Platform, Pasteur Institute of Tunis, Tunisia
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Liskova P, Tesarova M, Dudakova L, Svecova S, Kolarova H, Honzik T, Seto S, Votruba M. OPA1 analysis in an international series of probands with bilateral optic atrophy. Acta Ophthalmol 2017; 95:363-369. [PMID: 27860320 DOI: 10.1111/aos.13285] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 09/02/2016] [Indexed: 01/16/2023]
Abstract
PURPOSE To determine the molecular genetic cause in previously unreported probands with optic atrophy from the United Kingdom, Czech Republic and Canada. METHODS OPA1 coding regions and flanking intronic sequences were screened by direct sequencing in 82 probands referred with a diagnosis of bilateral optic atrophy. Detected rare variants were assessed for pathogenicity by in silico analysis. Segregation of the identified variants was performed in available first degree relatives. RESULTS A total of 29 heterozygous mutations evaluated as pathogenic were identified in 42 probands, of these seven were novel. In two probands, only variants of unknown significance were found. 76% of pathogenic mutations observed in 30 (71%) of 42 probands were evaluated to lead to unstable transcripts resulting in haploinsufficiency. Three probands with the following disease-causing mutations c.1230+1G>A, c.1367G>A and c.2965dup were documented to suffer from hearing loss and/or neurological impairment. CONCLUSIONS OPA1 gene screening in patients with bilateral optic atrophy is an important part of clinical evaluation as it may establish correct clinical diagnosis. Our study expands the spectrum of OPA1 mutations causing dominant optic atrophy and supports the fact that haploinsufficiency is the most common disease mechanism.
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Affiliation(s)
- Petra Liskova
- Institute of Inherited Metabolic Disorders; First Faculty of Medicine; Charles University and General University Hospital in Prague; Prague Czech Republic
- Department of Ophthalmology; First Faculty of Medicine; Charles University and General University Hospital in Prague; Prague Czech Republic
| | - Marketa Tesarova
- Department of Paediatrics and Adolescent Medicine; First Faculty of Medicine; Charles University and General University Hospital in Prague; Prague Czech Republic
| | - Lubica Dudakova
- Institute of Inherited Metabolic Disorders; First Faculty of Medicine; Charles University and General University Hospital in Prague; Prague Czech Republic
| | - Stepanka Svecova
- Department of Paediatrics and Adolescent Medicine; First Faculty of Medicine; Charles University and General University Hospital in Prague; Prague Czech Republic
| | - Hana Kolarova
- Department of Paediatrics and Adolescent Medicine; First Faculty of Medicine; Charles University and General University Hospital in Prague; Prague Czech Republic
| | - Tomas Honzik
- Department of Paediatrics and Adolescent Medicine; First Faculty of Medicine; Charles University and General University Hospital in Prague; Prague Czech Republic
| | - Sharon Seto
- Cardiff Eye Unit; University Hospital of Wales; Cardiff UK
- School of Optometry & Vision Sciences; Cardiff University; Cardiff UK
| | - Marcela Votruba
- Cardiff Eye Unit; University Hospital of Wales; Cardiff UK
- School of Optometry & Vision Sciences; Cardiff University; Cardiff UK
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9
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Wedding IM, Koht J, Tran GT, Misceo D, Selmer KK, Holmgren A, Frengen E, Bindoff L, Tallaksen CME, Tzoulis C. Spastic paraplegia type 7 is associated with multiple mitochondrial DNA deletions. PLoS One 2014; 9:e86340. [PMID: 24466038 PMCID: PMC3899233 DOI: 10.1371/journal.pone.0086340] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2013] [Accepted: 12/11/2013] [Indexed: 11/19/2022] Open
Abstract
Spastic paraplegia 7 is an autosomal recessive disorder caused by mutations in the gene encoding paraplegin, a protein located at the inner mitochondrial membrane and involved in the processing of other mitochondrial proteins. The mechanism whereby paraplegin mutations cause disease is unknown. We studied two female and two male adult patients from two Norwegian families with a combination of progressive external ophthalmoplegia and spastic paraplegia. Sequencing of SPG7 revealed a novel missense mutation, c.2102A>C, p.H 701P, which was homozygous in one family and compound heterozygous in trans with a known pathogenic mutation c.1454_1462del in the other. Muscle was examined from an additional, unrelated adult female patient with a similar phenotype caused by a homozygous c.1047insC mutation in SPG7. Immunohistochemical studies in skeletal muscle showed mosaic deficiency predominantly affecting respiratory complex I, but also complexes III and IV. Molecular studies in single, microdissected fibres showed multiple mitochondrial DNA deletions segregating at high levels (38-97%) in respiratory deficient fibres. Our findings demonstrate for the first time that paraplegin mutations cause accumulation of mitochondrial DNA damage and multiple respiratory chain deficiencies. While paraplegin is not known to be directly associated with the mitochondrial nucleoid, it is known to process other mitochondrial proteins and it is possible therefore that paraplegin mutations lead to mitochondrial DNA deletions by impairing proteins involved in the homeostasis of the mitochondrial genome. These studies increase our understanding of the molecular pathogenesis of SPG7 mutations and suggest that SPG7 testing should be included in the diagnostic workup of autosomal recessive, progressive external ophthalmoplegia, especially if spasticity is present.
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Affiliation(s)
- Iselin Marie Wedding
- Department of Neurology, Oslo University Hospital, Ullevål, Oslo, Norway
- University of Oslo, Faculty of Medicine, Oslo, Norway
| | - Jeanette Koht
- University of Oslo, Faculty of Medicine, Oslo, Norway
- Department of Neurology, Drammen Hospital, Vestre Viken Health Trust, Norway
| | - Gia Tuong Tran
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
- Department of Neurology, Haukeland University Hospital, Bergen, Norway
| | - Doriana Misceo
- University of Oslo, Faculty of Medicine, Oslo, Norway
- Department of Medical Genetics, Oslo University Hospital, Ullevål, Oslo, Norway
| | - Kaja Kristine Selmer
- University of Oslo, Faculty of Medicine, Oslo, Norway
- Department of Medical Genetics, Oslo University Hospital, Ullevål, Oslo, Norway
| | - Asbjørn Holmgren
- University of Oslo, Faculty of Medicine, Oslo, Norway
- Department of Medical Genetics, Oslo University Hospital, Ullevål, Oslo, Norway
| | - Eirik Frengen
- University of Oslo, Faculty of Medicine, Oslo, Norway
- Department of Medical Genetics, Oslo University Hospital, Ullevål, Oslo, Norway
| | - Laurence Bindoff
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
- Department of Neurology, Haukeland University Hospital, Bergen, Norway
| | - Chantal M. E. Tallaksen
- Department of Neurology, Oslo University Hospital, Ullevål, Oslo, Norway
- University of Oslo, Faculty of Medicine, Oslo, Norway
| | - Charalampos Tzoulis
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
- Department of Neurology, Haukeland University Hospital, Bergen, Norway
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Qian Y, Kachroo AH, Yellman CM, Marcotte EM, Johnson KA. Yeast cells expressing the human mitochondrial DNA polymerase reveal correlations between polymerase fidelity and human disease progression. J Biol Chem 2014; 289:5970-85. [PMID: 24398692 DOI: 10.1074/jbc.m113.526418] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutations in the human mitochondrial polymerase (polymerase-γ (Pol-γ)) are associated with various mitochondrial disorders, including mitochondrial DNA (mtDNA) depletion syndrome, Alpers syndrome, and progressive external opthamalplegia. To correlate biochemically quantifiable defects resulting from point mutations in Pol-γ with their physiological consequences, we created "humanized" yeast, replacing the yeast mtDNA polymerase (MIP1) with human Pol-γ. Despite differences in the replication and repair mechanism, we show that the human polymerase efficiently complements the yeast mip1 knockouts, suggesting common fundamental mechanisms of replication and conserved interactions between the human polymerase and other components of the replisome. We also examined the effects of four disease-related point mutations (S305R, H932Y, Y951N, and Y955C) and an exonuclease-deficient mutant (D198A/E200A). In haploid cells, each mutant results in rapid mtDNA depletion, increased mutation frequency, and mitochondrial dysfunction. Mutation frequencies measured in vivo equal those measured with purified enzyme in vitro. In heterozygous diploid cells, wild-type Pol-γ suppresses mutation-associated growth defects, but continuous growth eventually leads to aerobic respiration defects, reduced mtDNA content, and depolarized mitochondrial membranes. The severity of the Pol-γ mutant phenotype in heterozygous diploid humanized yeast correlates with the approximate age of disease onset and the severity of symptoms observed in humans.
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Affiliation(s)
- Yufeng Qian
- From the Institute for Cellular and Molecular Biology
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Abstract
Mitochondrial diseases involve the respiratory chain, which is under the dual control of nuclear and mitochondrial DNA (mtDNA). The complexity of mitochondrial genetics provides one explanation for the clinical heterogeneity of mitochondrial diseases, but our understanding of disease pathogenesis remains limited. Classification of Mendelian mitochondrial encephalomyopathies has been laborious, but whole-exome sequencing studies have revealed unexpected molecular aetiologies for both typical and atypical mitochondrial disease phenotypes. Mendelian mitochondrial defects can affect five components of mitochondrial biology: subunits of respiratory chain complexes (direct hits); mitochondrial assembly proteins; mtDNA translation; phospholipid composition of the inner mitochondrial membrane; or mitochondrial dynamics. A sixth category-defects of mtDNA maintenance-combines features of Mendelian and mitochondrial genetics. Genetic defects in mitochondrial dynamics are especially important in neurology as they cause optic atrophy, hereditary spastic paraplegia, and Charcot-Marie-Tooth disease. Therapy is inadequate and mostly palliative, but promising new avenues are being identified. Here, we review current knowledge on the genetics and pathogenesis of the six categories of mitochondrial disorders outlined above, focusing on their salient clinical manifestations and highlighting novel clinical entities. An outline of diagnostic clues for the various forms of mitochondrial disease, as well as potential therapeutic strategies, is also discussed.
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Leruez S, Milea D, Defoort-Dhellemmes S, Colin E, Crochet M, Procaccio V, Ferré M, Lamblin J, Drouin V, Vincent-Delorme C, Lenaers G, Hamel C, Blanchet C, Juul G, Larsen M, Verny C, Reynier P, Amati-Bonneau P, Bonneau D. Sensorineural hearing loss in OPA1-linked disorders. Brain 2013; 136:e236. [DOI: 10.1093/brain/aws340] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kostrominova TY, Reiner DS, Haas RH, Ingermanson R, McDonough PM. Automated methods for the analysis of skeletal muscle fiber size and metabolic type. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 306:275-332. [PMID: 24016528 DOI: 10.1016/b978-0-12-407694-5.00007-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
It is of interest to quantify the size, shape, and metabolic subtype of skeletal muscle fibers in many areas of biomedical research. To do so, skeletal muscle samples are sectioned transversely to the length of the muscle and labeled for extracellular or membrane proteins to delineate the fiber boundaries and additionally for biomarkers related to function or metabolism. The samples are digitally photographed and the fibers "outlined" for quantification of fiber cross-sectional area (CSA) using pointing devices interfaced to a computer, which is tedious, prone to error, and can be nonobjective. Here, we review methods for characterizing skeletal muscle fibers and describe new automated techniques, which rapidly quantify CSA and biomarkers. We discuss the applications of these methods to the characterization of mitochondrial dysfunctions, which underlie a variety of human afflictions, and we present a novel approach, utilizing images from the online Human Protein Atlas to predict relationships between fiber-specific protein expression, function, and metabolism.
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14
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Martikainen MH, Hinttala R, Röyttä M, Jääskeläinen S, Wendelin-Saarenhovi M, Parkkola R, Majamaa K. Progressive external ophthalmoplegia in southwestern Finland: a clinical and genetic study. Neuroepidemiology 2012; 38:114-9. [PMID: 22377773 DOI: 10.1159/000336112] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Accepted: 12/12/2011] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Progressive external ophthalmoplegia (PEO) is a common phenotype of mitochondrial disease. Molecular etiologies include sporadic, large-scale deletions in mitochondrial DNA (mtDNA), multiple mtDNA deletions secondary to autosomal dominant or recessive mutations and mtDNA point mutations. METHODS We studied the prevalence and clinical and genetic characteristics of PEO in a defined population in southwestern Finland. A total of 620 patients were first identified from the patient registry at the Turku University Hospital over an 18-year period. The medical records of these patients were scrutinized, and those with clinical features compatible with PEO were ascertained. RESULTS We identified 10 patients with possible PEO. The patients were examined clinically, and DNA was analyzed for mtDNA deletions and for the m.3243A>G and m.8344A>G mtDNA point mutations. The ANT1, PEO1, POLG1 and POLG2 genes were sequenced. We confirmed the clinical diagnosis of PEO in 6 patients. Large-scale mtDNA deletions were detected in 3 out of 6 PEO patients and mutations in the POLG1 gene in 1 out of 6. We did not find any mutations in the ANT1, PEO1 or POLG2 genes. CONCLUSIONS Our results suggest that molecular investigation of patients with PEO, either sporadic or familial, should start with an analysis for mtDNA deletions, followed by an analysis of the POLG1 gene.
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Vantyghem MC, Dobbelaere D, Mention K, Wemeau JL, Saudubray JM, Douillard C. Endocrine manifestations related to inherited metabolic diseases in adults. Orphanet J Rare Dis 2012; 7:11. [PMID: 22284844 PMCID: PMC3349544 DOI: 10.1186/1750-1172-7-11] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2011] [Accepted: 01/28/2012] [Indexed: 02/07/2023] Open
Abstract
Most inborn errors of metabolism (IEM) are recessive, genetically transmitted diseases and are classified into 3 main groups according to their mechanisms: cellular intoxication, energy deficiency, and defects of complex molecules. They can be associated with endocrine manifestations, which may be complications from a previously diagnosed IEM of childhood onset. More rarely, endocrinopathies can signal an IEM in adulthood, which should be suspected when an endocrine disorder is associated with multisystemic involvement (neurological, muscular, hepatic features, etc.). IEM can affect all glands, but diabetes mellitus, thyroid dysfunction and hypogonadism are the most frequent disorders. A single IEM can present with multiple endocrine dysfunctions, especially those involving energy deficiency (respiratory chain defects), and metal (hemochromatosis) and storage disorders (cystinosis). Non-autoimmune diabetes mellitus, thyroid dysfunction and/or goiter and sometimes hypoparathyroidism should steer the diagnosis towards a respiratory chain defect. Hypogonadotropic hypogonadism is frequent in haemochromatosis (often associated with diabetes), whereas primary hypogonadism is reported in Alström disease and cystinosis (both associated with diabetes, the latter also with thyroid dysfunction) and galactosemia. Hypogonadism is also frequent in X-linked adrenoleukodystrophy (with adrenal failure), congenital disorders of glycosylation, and Fabry and glycogen storage diseases (along with thyroid dysfunction in the first 3 and diabetes in the last). This is a new and growing field and is not yet very well recognized in adulthood despite its consequences on growth, bone metabolism and fertility. For this reason, physicians managing adult patients should be aware of these diagnoses.
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Affiliation(s)
- Marie-Christine Vantyghem
- Service d'Endocrinologie et Maladies Métaboliques, 1, Rue Polonovski, Hôpital C Huriez, Centre Hospitalier Régional et Universitaire de Lille, 59037 Lille cedex, France.
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Finsterer J. Inherited Mitochondrial Disorders. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 942:187-213. [DOI: 10.1007/978-94-007-2869-1_8] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Zhang L, Chan SSL, Wolff DJ. Mitochondrial disorders of DNA polymerase γ dysfunction: from anatomic to molecular pathology diagnosis. Arch Pathol Lab Med 2011. [PMID: 21732785 DOI: 10.1043/2010-0356-rar.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
CONTEXT Primary mitochondrial dysfunction is one of the most common causes of inherited disorders predominantly involving the neuromuscular system. Advances in the molecular study of mitochondrial DNA have changed our vision and our approach to primary mitochondrial disorders. Many of the mitochondrial disorders are caused by mutations in nuclear genes and are inherited in an autosomal recessive pattern. Among the autosomal inherited mitochondrial disorders, those related to DNA polymerase γ dysfunction are the most common and the best studied. Understanding the molecular mechanisms and being familiar with the recent advances in laboratory diagnosis of this group of mitochondrial disorders are essential for pathologists to interpret abnormal histopathology and laboratory results and to suggest further studies for a definitive diagnosis. OBJECTIVES To help pathologists better understand the common clinical syndromes originating from mutations in DNA polymerase γ and its associated proteins and use the stepwise approach of clinical, laboratory, and pathologic diagnosis of these syndromes. DATA SOURCES Review of pertinent published literature and relevant Internet databases. CONCLUSIONS Mitochondrial disorders are now better recognized with the development of molecular tests for clinical diagnosis. A cooperative effort among primary physicians, diagnostic pathologists, geneticists, and molecular biologists with expertise in mitochondrial disorders is required to reach a definitive diagnosis.
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Affiliation(s)
- Linsheng Zhang
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29425, USA.
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18
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Zhang L, Chan SSL, Wolff DJ. Mitochondrial disorders of DNA polymerase γ dysfunction: from anatomic to molecular pathology diagnosis. Arch Pathol Lab Med 2011; 135:925-34. [PMID: 21732785 PMCID: PMC3158670 DOI: 10.5858/2010-0356-rar.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
CONTEXT Primary mitochondrial dysfunction is one of the most common causes of inherited disorders predominantly involving the neuromuscular system. Advances in the molecular study of mitochondrial DNA have changed our vision and our approach to primary mitochondrial disorders. Many of the mitochondrial disorders are caused by mutations in nuclear genes and are inherited in an autosomal recessive pattern. Among the autosomal inherited mitochondrial disorders, those related to DNA polymerase γ dysfunction are the most common and the best studied. Understanding the molecular mechanisms and being familiar with the recent advances in laboratory diagnosis of this group of mitochondrial disorders are essential for pathologists to interpret abnormal histopathology and laboratory results and to suggest further studies for a definitive diagnosis. OBJECTIVES To help pathologists better understand the common clinical syndromes originating from mutations in DNA polymerase γ and its associated proteins and use the stepwise approach of clinical, laboratory, and pathologic diagnosis of these syndromes. DATA SOURCES Review of pertinent published literature and relevant Internet databases. CONCLUSIONS Mitochondrial disorders are now better recognized with the development of molecular tests for clinical diagnosis. A cooperative effort among primary physicians, diagnostic pathologists, geneticists, and molecular biologists with expertise in mitochondrial disorders is required to reach a definitive diagnosis.
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Affiliation(s)
- Linsheng Zhang
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29425, USA.
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19
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Young MJ, Longley MJ, Li FY, Kasiviswanathan R, Wong LJ, Copeland WC. Biochemical analysis of human POLG2 variants associated with mitochondrial disease. Hum Mol Genet 2011; 20:3052-66. [PMID: 21555342 DOI: 10.1093/hmg/ddr209] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Defects in mitochondrial DNA (mtDNA) maintenance comprise an expanding repertoire of polymorphic diseases caused, in part, by mutations in the genes encoding the p140 mtDNA polymerase (POLG), its p55 accessory subunit (POLG2) or the mtDNA helicase (C10orf2). In an exploration of nuclear genes for mtDNA maintenance linked to mitochondrial disease, eight heterozygous mutations (six novel) in POLG2 were identified in one control and eight patients with POLG-related mitochondrial disease that lacked POLG mutations. Of these eight mutations, we biochemically characterized seven variants [c.307G>A (G103S); c.457C>G (L153V); c.614C>G (P205R); c.1105A>G (R369G); c.1158T>G (D386E); c.1268C>A (S423Y); c.1423_1424delTT (L475DfsX2)] that were previously uncharacterized along with the wild-type protein and the G451E pathogenic variant. These seven mutations encode amino acid substitutions that map throughout the protein, including the p55 dimer interface and the C-terminal domain that interacts with the catalytic subunit. Recombinant proteins harboring these alterations were assessed for stimulation of processive DNA synthesis, binding to the p140 catalytic subunit, binding to dsDNA and self-dimerization. Whereas the G103S, L153V, D386E and S423Y proteins displayed wild-type behavior, the P205R and R369G p55 variants had reduced stimulation of processivity and decreased affinity for the catalytic subunit. Additionally, the L475DfsX2 variant, which possesses a C-terminal truncation, was unable to bind the p140 catalytic subunit, unable to bind dsDNA and formed aberrant oligomeric complexes. Our biochemical analysis helps explain the pathogenesis of POLG2 mutations in mitochondrial disease and emphasizes the need to quantitatively characterize the biochemical consequences of newly discovered mutations before classifying them as pathogenic.
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Affiliation(s)
- Matthew J Young
- Laboratory of Molecular Genetics, NIEHS, National Institutes of Health, DHHS, Research Triangle Park, NC 27709, USA
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20
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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: 440] [Impact Index Per Article: 33.8] [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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21
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Wang W, Shen P, Thiyagarajan S, Lin S, Palm C, Horvath R, Klopstock T, Cutler D, Pique L, Schrijver I, Davis RW, Mindrinos M, Speed TP, Scharfe C. Identification of rare DNA variants in mitochondrial disorders with improved array-based sequencing. Nucleic Acids Res 2010; 39:44-58. [PMID: 20843780 PMCID: PMC3017602 DOI: 10.1093/nar/gkq750] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
A common goal in the discovery of rare functional DNA variants via medical resequencing is to incur a relatively lower proportion of false positive base-calls. We developed a novel statistical method for resequencing arrays (SRMA, sequence robust multi-array analysis) to increase the accuracy of detecting rare variants and reduce the costs in subsequent sequence verifications required in medical applications. SRMA includes single and multi-array analysis and accounts for technical variables as well as the possibility of both low- and high-frequency genomic variation. The confidence of each base-call was ranked using two quality measures. In comparison to Sanger capillary sequencing, we achieved a false discovery rate of 2% (false positive rate 1.2 × 10−5, false negative rate 5%), which is similar to automated second-generation sequencing technologies. Applied to the analysis of 39 nuclear candidate genes in disorders of mitochondrial DNA (mtDNA) maintenance, we confirmed mutations in the DNA polymerase gamma POLG in positive control cases, and identified novel rare variants in previously undiagnosed cases in the mitochondrial topoisomerase TOP1MT, the mismatch repair enzyme MUTYH, and the apurinic-apyrimidinic endonuclease APEX2. Some patients carried rare heterozygous variants in several functionally interacting genes, which could indicate synergistic genetic effects in these clinically similar disorders.
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Affiliation(s)
- Wenyi Wang
- Stanford Genome Technology Center, Stanford University, Palo Alto, CA 94304, USA.
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22
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The clinical diagnosis of POLG disease and other mitochondrial DNA depletion disorders. Methods 2010; 51:364-73. [DOI: 10.1016/j.ymeth.2010.05.008] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Accepted: 05/25/2010] [Indexed: 01/06/2023] Open
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23
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Mitochondrial retention of Opa1 is required for mouse embryogenesis. Mamm Genome 2010; 21:350-60. [DOI: 10.1007/s00335-010-9272-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Accepted: 06/21/2010] [Indexed: 10/19/2022]
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24
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Yu-Wai-Man P, Sitarz KS, Samuels DC, Griffiths PG, Reeve AK, Bindoff LA, Horvath R, Chinnery PF. OPA1 mutations cause cytochrome c oxidase deficiency due to loss of wild-type mtDNA molecules. Hum Mol Genet 2010; 19:3043-52. [PMID: 20484224 PMCID: PMC2901142 DOI: 10.1093/hmg/ddq209] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Pathogenic OPA1 mutations cause autosomal dominant optic atrophy (DOA), a condition characterized by the preferential loss of retinal ganglion cells and progressive optic nerve degeneration. Approximately 20% of affected patients will also develop more severe neuromuscular complications, an important disease subgroup known as DOA+. Cytochrome c oxidase (COX)-negative fibres and multiple mitochondrial DNA (mtDNA) deletions have been identified in skeletal muscle biopsies from patients manifesting both the pure and syndromal variants, raising the possibility that the accumulation of somatic mtDNA defects contribute to the disease process. In this study, we investigated the mtDNA changes induced by OPA1 mutations in skeletal muscle biopsies from 15 patients with both pure DOA and DOA+ phenotypes. We observed a 2- to 4-fold increase in mtDNA copy number at the single-fibre level, and patients with DOA+ features had significantly greater mtDNA proliferation in their COX-negative skeletal muscle fibres compared with patients with isolated optic neuropathy. Low levels of wild-type mtDNA molecules were present in COX-deficient muscle fibres from both pure DOA and DOA+ patients, implicating haplo-insufficiency as the mechanism responsible for the biochemical defect. Our findings are consistent with the ‘maintenance of wild-type’ hypothesis, the secondary mtDNA deletions induced by OPA1 mutations triggering a compensatory mitochondrial proliferative response in order to maintain an optimal level of wild-type mtDNA genomes. However, when deletion levels reach a critical level, further mitochondrial proliferation leads to replication of the mutant species at the expense of wild-type mtDNA, resulting in the loss of respiratory chain COX activity.
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Affiliation(s)
- Patrick Yu-Wai-Man
- Mitochondrial Research Group, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
- Department of Ophthalmology, Royal Victoria Infirmary, Newcastle upon Tyne, UK
| | - Kamil S. Sitarz
- Mitochondrial Research Group, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - David C. Samuels
- Department of Molecular Physiology and Biophysics, Center for Human Genetics Research, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Philip G. Griffiths
- Mitochondrial Research Group, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
- Department of Ophthalmology, Royal Victoria Infirmary, Newcastle upon Tyne, UK
| | - Amy K. Reeve
- Mitochondrial Research Group, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Laurence A. Bindoff
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
- Department of Neurology, Haukeland University Hospital, Bergen, Norway and
| | - Rita Horvath
- Mitochondrial Research Group, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Patrick F. Chinnery
- Mitochondrial Research Group, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
- Institute of Human Genetics, Newcastle University, Newcastle upon Tyne, UK
- To whom correspondence should be addressed. Tel: +44 1912824375; Fax: +44 1912824373;
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25
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Walter MC, Czermin B, Muller-Ziermann S, Bulst S, Stewart JD, Hudson G, Schneiderat P, Abicht A, Holinski-Feder E, Lochmüller H, Chinnery PF, Klopstock T, Horvath R. Late-onset ptosis and myopathy in a patient with a heterozygous insertion in POLG2. J Neurol 2010; 257:1517-23. [DOI: 10.1007/s00415-010-5565-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2010] [Revised: 03/12/2010] [Accepted: 03/30/2010] [Indexed: 10/19/2022]
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26
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Spelbrink JN. Functional organization of mammalian mitochondrial DNA in nucleoids: history, recent developments, and future challenges. IUBMB Life 2010; 62:19-32. [PMID: 20014006 DOI: 10.1002/iub.282] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Various proteins involved in replication, repair, and the structural organization of mitochondrial DNA (mtDNA) have been characterized in detail over the past 25 or so years. In addition, in recent years, many proteins were identified with a role in the dynamics of the mitochondrial network. Using advanced imaging and an increasing number of cytological techniques, we have begun to realize that an important aspect to mtDNA maintenance, in both health and disease, is its organization within the dynamic mitochondrial network in discrete protein-DNA complexes usually termed nucleoids. Here, I review recent developments in the study of nucleoid dynamics and proteins. I will discuss the implications of the organization of mtDNA in nucleoids in light of DNA replication, repair, gene expression, segregation, and inheritance.
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Affiliation(s)
- Johannes N Spelbrink
- FinMIT Centre of Excellence, Institute of Medical Technology and Tampere University Hospital, University of Tampere, Tampere 33014 TAY, Finland.
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27
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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: 325] [Impact Index Per Article: 23.2] [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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28
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Hogewind BF, Pennings RJ, Hol FA, Kunst HP, Hoefsloot EH, Cruysberg JR, Cremers CW. Autosomal dominant optic neuropathy and sensorineual hearing loss associated with a novel mutation of WFS1. Mol Vis 2010; 16:26-35. [PMID: 20069065 PMCID: PMC2805421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2009] [Accepted: 01/06/2010] [Indexed: 11/06/2022] Open
Abstract
PURPOSE To describe the phenotype of a novel Wolframin (WFS1) mutation in a family with autosomal dominant optic neuropathy and deafness. The study is designed as a retrospective observational case series. METHODS Seven members of a Dutch family underwent ophthalmological, otological, and genetical examinations in one institution. Fasting serum glucose was assessed in the affected family members. RESULTS All affected individuals showed loss of neuroretinal rim of the optic nerve at fundoscopy with enlarged blind spots at perimetry. They showed a red-green color vision defect at color vision tests and deviations at visually evoked response tests. The audiograms of the affected individuals showed hearing loss and were relatively flat. The unaffected individuals showed no visual deviations or hearing impairment. The affected family members had no glucose intolerance. Leber hereditary optic neuropathy (LHON) mitochondrial mutations and mutations in the Optic atrophy-1 gene (OPA1) were excluded. In the affected individuals, a novel missense mutation c.2508G>C (p.Lys836Asn) in exon 8 of WFS1 was identified. CONCLUSIONS This study describes the phenotype of a family with autosomal dominant optic neuropathy and hearing impairment associated with a novel missense mutation in WFS1.
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Affiliation(s)
- Barend F.T. Hogewind
- Department of Ophthalmology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Ronald J.E. Pennings
- Department of Otorhinolaryngology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Frans A. Hol
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Henricus P.M. Kunst
- Department of Otorhinolaryngology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Elisabeth H. Hoefsloot
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Johannes R.M. Cruysberg
- Department of Ophthalmology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Cor W.R.J. Cremers
- Department of Otorhinolaryngology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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29
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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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30
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Yu-Wai-Man P, Davies VJ, Piechota MJ, Cree LM, Votruba M, Chinnery PF. Secondary mtDNA defects do not cause optic nerve dysfunction in a mouse model of dominant optic atrophy. Invest Ophthalmol Vis Sci 2009; 50:4561-6. [PMID: 19443720 PMCID: PMC4034167 DOI: 10.1167/iovs.09-3634] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE The majority of patients with autosomal dominant optic atrophy (DOA) harbor pathogenic OPA1 mutations and certain missense mutations, mostly within the GTPase domain, have recently been shown to cause multiple mitochondrial DNA (mtDNA) deletions in skeletal muscle. This raises the possibility that the optic neuropathy could be the result of secondary mtDNA defects accumulating within retinal ganglion cells (RGCs). To explore this hypothesis, the authors looked for evidence of mitochondrial dysfunction in a mouse model of DOA and documented the visual and neurologic progression in aging mutant mice. METHODS Visual function was assessed with a rotating optokinetic (OKN) drum at ages 13 and 18 months and neurologic phenotyping was performed using the primary SHIRPA screen at age 13 months, comparing mutant Opa1(+/)(-) mice with wild-type C57Bl/6 mice. The presence of cytochrome c oxidase (COX) deficiency and multiple mtDNA deletions was investigated in gastrocnemius muscle and eye specimens harvested from 2- and 11-month-old Opa1(+/+) and Opa1(+/)(-) mice. RESULTS At age 13 months, Opa1(+/)(-) mice had a statistically significant reduction in OKN responses compared to C57Bl/6 controls with both 2 degrees and 8 degrees gratings (P < 0.001). At age 18 months, the difference between the two groups was significant for the 8 degrees grating (P = 0.003) but not for the 2 degrees grating (P = 0.082). Opa1(+/)(-) mice did not exhibit any significant neuromuscular deficits and no COX deficient areas or secondary mtDNA deletions were identified in skeletal muscle or the RGC layer. There was also no evidence of significant mtDNA depletion or proliferation in skeletal muscle from Opa1(+/)(-) mice. CONCLUSIONS COX deficiency and mtDNA abnormalities do not contribute to optic nerve dysfunction in pure DOA.
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MESH Headings
- Adenosine Triphosphatases/metabolism
- Animals
- Cytochrome-c Oxidase Deficiency/genetics
- DNA, Mitochondrial/genetics
- Disease Models, Animal
- Electron Transport Complex IV/metabolism
- GTP Phosphohydrolases/genetics
- Gene Deletion
- Mice
- Mice, Inbred C57BL
- Mitochondria, Muscle/metabolism
- Mitochondrial Diseases/genetics
- Mitochondrial Diseases/metabolism
- Mitochondrial Diseases/pathology
- Muscle, Skeletal/enzymology
- Mutation, Missense
- Nystagmus, Optokinetic
- Optic Atrophy, Autosomal Dominant/genetics
- Optic Atrophy, Autosomal Dominant/metabolism
- Optic Atrophy, Autosomal Dominant/pathology
- Retinal Ganglion Cells/enzymology
- Retinal Ganglion Cells/pathology
- Succinate Dehydrogenase/metabolism
- Vision Disorders/genetics
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Affiliation(s)
- Patrick Yu-Wai-Man
- Mitochondrial Research Group, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom.
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31
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Aggarwal D, Carelli V, Sadun AA. Genotype–phenotype correlations in mitochondrial optic neuropathies. EXPERT REVIEW OF OPHTHALMOLOGY 2009. [DOI: 10.1586/eop.09.32] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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32
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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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Torraco A, Diaz F, Vempati UD, Moraes CT. Mouse models of oxidative phosphorylation defects: powerful tools to study the pathobiology of mitochondrial diseases. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1793:171-80. [PMID: 18601959 PMCID: PMC2652735 DOI: 10.1016/j.bbamcr.2008.06.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Revised: 05/28/2008] [Accepted: 06/04/2008] [Indexed: 01/14/2023]
Abstract
Defects in the oxidative phosphorylation system (OXPHOS) are responsible for a group of extremely heterogeneous and pleiotropic pathologies commonly known as mitochondrial diseases. Although many mutations have been found to be responsible for OXPHOS defects, their pathogenetic mechanisms are still poorly understood. An important contribution to investigate the in vivo function of several mitochondrial proteins and their role in mitochondrial dysfunction, has been provided by mouse models. Thanks to their genetic and physiologic similarity to humans, mouse models represent a powerful tool to investigate the impact of pathological mutations on metabolic pathways. In this review we discuss the main mouse models of mitochondrial disease developed, focusing on the ones that directly affect the OXPHOS system.
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Affiliation(s)
- Alessandra Torraco
- Department of Neurology, University of Miami Miller School of Medicine, 1095 NW 14th Terrace, Miami, FL 33136, USA
| | - Francisca Diaz
- Department of Neurology, University of Miami Miller School of Medicine, 1095 NW 14th Terrace, Miami, FL 33136, USA
| | - Uma D. Vempati
- Department of Neurology, University of Miami Miller School of Medicine, 1095 NW 14th Terrace, Miami, FL 33136, USA
| | - Carlos T. Moraes
- Department of Neurology, University of Miami Miller School of Medicine, 1095 NW 14th Terrace, Miami, FL 33136, USA
- Department of Cell Biology and Anatomy, University of Miami Miller School of Medicine, 1095 NW 14th Terrace, Miami, FL 33136, USA
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DiMauro S, Hirano M. Pathogenesis and treatment of mitochondrial disorders. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 652:139-70. [PMID: 20225024 PMCID: PMC10440730 DOI: 10.1007/978-90-481-2813-6_10] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In the past 50 years, our understanding of the biochemical and molecular causes of mitochondrial diseases, defined restrictively as disorders due to defects of the mitochondrial respiratory chain (RC), has made great strides. Mitochondrial diseases can be due to mutations in mitochondrial DNA (mtDNA) or in nuclear DNA (nDNA) and each group can be subdivided into more specific classes. Thus, mtDNA-related disorders can result from mutations in genes affecting protein synthesis in toto or mutations in protein-coding genes. Mendelian mitochondrial disorders can be attributed to mutations in genes that (i) encode subunits of the RC ("direct hits"); (ii) encode assembly proteins or RC complexes ("indirect hits"); (iii) encode factors needed for mtDNA maintenance, replication, or translation (intergenomic signaling); (iv) encode components of the mitochondrial protein import machinery; (v) control the synthesis and composition of mitochondrial membrane phospholipids; and (vi) encode proteins involved in mitochondrial dynamics.In contrast to this wealth of knowledge about etiology, our understanding of pathogenic mechanism is very limited. We discuss pathogenic factors that can influence clinical expression, especially ATP shortage and reactive oxygen radicals (ROS) excess. Therapeutic options are limited and fall into three modalities: (i) symptomatic interventions, which are palliative but crucial for day-to-day management; (ii) radical approaches aimed at correcting the biochemical or molecular error, which are interesting but still largely experimental; and (iii) pharmacological means of interfering with the pathogenic cascade of events (e.g. boosting ATP production or scavenging ROS), which are inconsistently and incompletely effective, but can be safe and helpful.
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Affiliation(s)
- Salvatore DiMauro
- Department of Neurology, Columbia University Medical Center, 3-313 Russ Berrie Medical Science Pavilion, New York, NY 10032, USA.
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Chan SSL, Copeland WC. DNA polymerase gamma and mitochondrial disease: understanding the consequence of POLG mutations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1787:312-9. [PMID: 19010300 DOI: 10.1016/j.bbabio.2008.10.007] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Revised: 10/09/2008] [Accepted: 10/15/2008] [Indexed: 11/18/2022]
Abstract
DNA polymerase gamma is the only known DNA polymerase in human mitochondria and is essential for mitochondrial DNA replication and repair. It is well established that defects in mtDNA replication lead to mitochondrial dysfunction and disease. Over 160 coding variations in the gene encoding the catalytic subunit of DNA polymerase gamma (POLG) have been identified. Our group and others have characterized a number of the more common and interesting mutations, as well as those disease mutations in the DNA polymerase gamma accessory subunit. We review the results of these studies, which provide clues to the mechanisms leading to the disease state.
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Affiliation(s)
- Sherine S L Chan
- National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
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36
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Current World Literature. Curr Opin Otolaryngol Head Neck Surg 2008; 16:490-5. [DOI: 10.1097/moo.0b013e3283130f63] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Wang X, Salinas K, Zuo X, Kucejova B, Chen XJ. Dominant membrane uncoupling by mutant adenine nucleotide translocase in mitochondrial diseases. Hum Mol Genet 2008; 17:4036-44. [PMID: 18809618 DOI: 10.1093/hmg/ddn306] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Adenine nucleotide translocase (Ant) is the most abundant protein on the mitochondrial inner membrane (MIM) primarily involved in ADP/ATP exchange. Ant also possesses a discrete membrane uncoupling activity. Specific mis-sense mutations in the human Ant1 cause autosomal dominant Progressive External Ophthalmoplegia (adPEO), mitochondrial myopathy and cardiomyopathy, which are commonly manifested by fractional mitochondrial DNA (mtDNA) deletions. It is currently thought that the pathogenic mutations alter substrate preference (e.g. ATP versus ADP) thereby dominantly disturbing adenine nucleotide homeostasis in mitochondria. This may interfere with mtDNA replication, consequently affecting mtDNA stability and oxidative phosphorylation. Here, we showed that the adPEO-type A128P, A106D and M114P mutations in the yeast Aac2p share the following common dominant phenotypes: electron transport chain damage, intolerance to moderate over-expression, synthetic lethality with low Deltapsi(m) conditions, hypersensitivity to the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) and mtDNA instability. More interestingly, the aac2(A137D) allele mimicking ant1(A123D) in mitochondrial myopathy and cardiomyopathy exhibits similar dominant phenotypes. Because Aac2(A137D) is known to completely lack transport activity, it is strongly argued that the dominant mitochondrial damages are not caused by aberrant nucleotide transport. The four pathogenic mutations occur in a structurally dynamic gating region on the cytosolic side. We provided direct evidence that the mutant alleles uncouple mitochondrial respiration. The pathogenic mutations likely enhance the intrinsic proton-conducting activity of Ant, which excessively uncouples the MIM thereby affecting energy transduction and mitochondrial biogenesis. mtDNA disintegration is a phenotype co-lateral to mitochondrial damages. These findings provide mechanistic insights into the pathogenesis of the Ant1-induced diseases.
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Affiliation(s)
- Xiaowen Wang
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, NY 13210, USA
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