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Riccio AA, Brannon AJ, Krahn JM, Bouvette J, Williams JG, Borgnia MJ, Copeland WC. Coordinated DNA polymerization by Polγ and the region of LonP1 regulated proteolysis. Nucleic Acids Res 2024:gkae539. [PMID: 38932681 DOI: 10.1093/nar/gkae539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 05/09/2024] [Accepted: 06/10/2024] [Indexed: 06/28/2024] Open
Abstract
The replicative mitochondrial DNA polymerase, Polγ, and its protein regulation are essential for the integrity of the mitochondrial genome. The intricacies of Polγ regulation and its interactions with regulatory proteins, which are essential for fine-tuning polymerase function, remain poorly understood. Misregulation of the Polγ heterotrimer, consisting of (i) PolG, the polymerase catalytic subunit and (ii) PolG2, the accessory subunit, ultimately results in mitochondrial diseases. Here, we used single particle cryo-electron microscopy to resolve the structure of PolG in its apoprotein state and we captured Polγ at three intermediates within the catalytic cycle: DNA bound, engaged, and an active polymerization state. Chemical crosslinking mass spectrometry, and site-directed mutagenesis uncovered the region of LonP1 engagement of PolG, which promoted proteolysis and regulation of PolG protein levels. PolG2 clinical variants, which disrupted a stable Polγ complex, led to enhanced LonP1-mediated PolG degradation. Overall, this insight into Polγ aids in an understanding of mitochondrial DNA replication and characterizes how machinery of the replication fork may be targeted for proteolytic degradation when improperly functioning.
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Affiliation(s)
- Amanda A Riccio
- Mitochondrial DNA Replication group, Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
| | - Asia J Brannon
- Mitochondrial DNA Replication group, Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
| | - Juno M Krahn
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
| | - Jonathan Bouvette
- Molecular Microscopy Consortium, Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
| | - Jason G Williams
- Mass Spectrometry Research and Support Group, Epigenetics and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
| | - Mario J Borgnia
- Molecular Microscopy Consortium, Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
| | - William C Copeland
- Mitochondrial DNA Replication group, Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA
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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: 0] [Impact Index Per Article: 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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Parkinson's Disease, Parkinsonisms, and Mitochondria: the Role of Nuclear and Mitochondrial DNA. Curr Neurol Neurosci Rep 2023; 23:131-147. [PMID: 36881253 DOI: 10.1007/s11910-023-01260-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/16/2023] [Indexed: 03/08/2023]
Abstract
PURPOSE OF REVIEW Overwhelming evidence indicates that mitochondrial dysfunction is a central factor in Parkinson's disease (PD) pathophysiology. This paper aims to review the latest literature published, focusing on genetic defects and expression alterations affecting mitochondria-associated genes, in support of their key role in PD pathogenesis. RECENT FINDINGS Thanks to the use of new omics approaches, a growing number of studies are discovering alterations affecting genes with mitochondrial functions in patients with PD and parkinsonisms. These genetic alterations include pathogenic single-nucleotide variants, polymorphisms acting as risk factors, and transcriptome modifications, affecting both nuclear and mitochondrial genes. We will focus on alterations of mitochondria-associated genes described by studies conducted on patients or on animal/cellular models of PD or parkinsonisms. We will comment how these findings can be taken into consideration for improving the diagnostic procedures or for deepening our knowledge on the role of mitochondrial dysfunctions in PD.
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4
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Hou Y, Zhao X, Xie Z, Yu M, Lv H, Zhang W, Yuan Y, Wang Z. Novel and recurrent nuclear gene variations in a cohort of Chinese progressive external ophthalmoplegia patients with multiple mtDNA deletions. Mol Genet Genomic Med 2022; 10:e1921. [PMID: 35289132 PMCID: PMC9034679 DOI: 10.1002/mgg3.1921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 12/30/2021] [Accepted: 02/25/2022] [Indexed: 11/07/2022] Open
Abstract
Objectives This study aimed to investigate the clinical and genetic spectrum in Chinese patients with multiple mtDNA deletions presenting with autosomal‐inherited mitochondrial progressive external ophthalmoplegia (PEO). Methods Long‐range polymerase chain reaction and massively parallel sequencing of the mitochondrial genome were performed to detect deletions in muscle mtDNA of 274 unrelated families. Then, targeted next generation sequencing was used to detect nuclear gene variations in patients with multiple mtDNA deletions. Results A total of 40 Chinese PEO patients (10 males and 30 females) from 20 families were found to have multiple mtDNA deletions in this study, and the median age at onset was 35 (1–70) years. PEO and positive family history were the two prominent features of these patients, and ataxia, neuropathy, and hypogonadism were also present as onset symptoms in some patients. Fifteen of 20 probands with multiple mtDNA deletions were identified to carry nuclear gene variants; eight (40.0%) probands had variants within POLG, two (10.0%) within TWNK, two (10.0%) within RRM2B, two (10.0%) within TK2, and one (5.0%) within POLG2. A total of 24 variants were found in these five nuclear genes, of which 19 were novel. The causal nuclear genetic factors in five pedigrees remain undetermined. Conclusions The POLG gene is the most common disease‐causing gene in this group of PEO patients with multiple mtDNA deletions. While inherited PEO is the most prominent symptoms in these patients, genotypic and phenotypic heterogeneity still exist, for example in onset age, initial symptoms, and accompanying manifestations.
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Affiliation(s)
- Yue Hou
- Department of Neurology, Peking University First Hospital, Beijing, China.,Department of Geriatrics, Peking University First Hospital, Beijing, China
| | - Xutong Zhao
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Zhiying Xie
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Meng Yu
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - He Lv
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Wei Zhang
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Yun Yuan
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Zhaoxia Wang
- Department of Neurology, Peking University First Hospital, Beijing, China.,Beijing Key Laboratory of Neurovascular Disease Discovery, Beijing, China
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Manini A, Abati E, Comi GP, Corti S, Ronchi D. Mitochondrial DNA homeostasis impairment and dopaminergic dysfunction: A trembling balance. Ageing Res Rev 2022; 76:101578. [PMID: 35114397 DOI: 10.1016/j.arr.2022.101578] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 12/26/2021] [Accepted: 01/28/2022] [Indexed: 02/07/2023]
Abstract
Maintenance of mitochondrial DNA (mtDNA) homeostasis includes a variety of processes, such as mtDNA replication, repair, and nucleotides synthesis, aimed at preserving the structural and functional integrity of mtDNA molecules. Mutations in several nuclear genes (i.e., POLG, POLG2, TWNK, OPA1, DGUOK, MPV17, TYMP) impair mtDNA maintenance, leading to clinical syndromes characterized by mtDNA depletion and/or deletions in affected tissues. In the past decades, studies have demonstrated a progressive accumulation of multiple mtDNA deletions in dopaminergic neurons of the substantia nigra in elderly population and, to a greater extent, in Parkinson's disease patients. Moreover, parkinsonism has been frequently described as a prominent clinical feature in mtDNA instability syndromes. Among Parkinson's disease-related genes with a significant role in mitochondrial biology, PARK2 and LRRK2 specifically take part in mtDNA maintenance. Moreover, a variety of murine models (i.e., "Mutator", "MitoPark", "PD-mitoPstI", "Deletor", "Twinkle-dup" and "TwinkPark") provided in vivo evidence that mtDNA stability is required to preserve nigrostriatal integrity. Here, we review and discuss the clinical, genetic, and pathological background underlining the link between impaired mtDNA homeostasis and dopaminergic degeneration.
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6
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Molecular Genetics Overview of Primary Mitochondrial Myopathies. J Clin Med 2022; 11:jcm11030632. [PMID: 35160083 PMCID: PMC8836969 DOI: 10.3390/jcm11030632] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 01/13/2022] [Accepted: 01/20/2022] [Indexed: 12/29/2022] Open
Abstract
Mitochondrial disorders are the most common inherited conditions, characterized by defects in oxidative phosphorylation and caused by mutations in nuclear or mitochondrial genes. Due to its high energy request, skeletal muscle is typically involved. According to the International Workshop of Experts in Mitochondrial Diseases held in Rome in 2016, the term Primary Mitochondrial Myopathy (PMM) should refer to those mitochondrial disorders affecting principally, but not exclusively, the skeletal muscle. The clinical presentation may include general isolated myopathy with muscle weakness, exercise intolerance, chronic ophthalmoplegia/ophthalmoparesis (cPEO) and eyelids ptosis, or multisystem conditions where there is a coexistence with extramuscular signs and symptoms. In recent years, new therapeutic targets have been identified leading to the launch of some promising clinical trials that have mainly focused on treating muscle symptoms and that require populations with defined genotype. Advantages in next-generation sequencing techniques have substantially improved diagnosis. So far, an increasing number of mutations have been identified as responsible for mitochondrial disorders. In this review, we focused on the principal molecular genetic alterations in PMM. Accordingly, we carried out a comprehensive review of the literature and briefly discussed the possible approaches which could guide the clinician to a genetic diagnosis.
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7
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Müller‐Nedebock AC, Westhuizen FH, Kõks S, Bardien S. Nuclear Genes Associated with Mitochondrial
DNA
Processes as Contributors to Parkinson's Disease Risk. Mov Disord 2021; 36:815-831. [DOI: 10.1002/mds.28475] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 12/07/2020] [Accepted: 12/16/2020] [Indexed: 12/11/2022] Open
Affiliation(s)
- Amica C. Müller‐Nedebock
- Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences Stellenbosch University Cape Town South Africa
| | | | - Sulev Kõks
- Perron Institute for Neurological and Translational Science Nedlands Western Australia Australia
- Centre for Molecular Medicine and Innovative Therapeutics Murdoch University Murdoch Western Australia Australia
| | - Soraya Bardien
- Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences Stellenbosch University Cape Town South Africa
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8
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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. Whole exome sequencing identifies a homozygous POLG2 missense variant in an adult patient presenting with optic atrophy, movement disorders, premature ovarian failure and mitochondrial DNA depletion. Eur J Med Genet 2020; 63:103821. [PMID: 31778857 DOI: 10.1016/j.ejmg.2019.103821] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 11/09/2019] [Accepted: 11/24/2019] [Indexed: 12/31/2022]
Abstract
POLG2 associated disorders belong to the group of mitochondrial DNA (mtDNA) diseases and present with a heterogeneous clinical spectrum, various age of onset, and disease severity. We report a 39-year old female presenting with childhood-onset and progressive neuroophthalmic manifestation with optic atrophy, mixed polyneuropathy, spinal and cerebellar ataxia and generalized chorea associated with mtDNA depletion. Whole-exome sequencing identified an ultra-rare homozygous missense mutation located at Chr17: 062474101-C > A (p.Asp433Tyr) in nuclear POLG2 gene encoding PolγB, an accessory subunits of mitochondrial polymerase γ responsible for mtDNA replication. The healthy parents and 2 sisters of the patient were heterozygous for the variant. To our best knowledge, this is the first case of homozygous variant in the POLG2 gene resulting in mitochondrial depletion syndrome in an adult patient and its clinical manifestations extend the clinical spectrum of POLG2 associated diseases.
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Affiliation(s)
- Petra Dosekova
- Dept. of Neurology, P.J. Safarik University, Kosice, Slovakia; Dept. of Neurology, University Hospital L. Pasteur, Kosice, Slovakia.
| | - Andrzej Dubiel
- Intercollegiate Faculty of Biotechnology of the University of Gdansk and Medical University of Gdansk, Gdansk, Poland
| | - Anna Karlowicz
- Intercollegiate Faculty of Biotechnology of the University of Gdansk and Medical University of Gdansk, Gdansk, Poland
| | - Szymon Zietkiewicz
- Intercollegiate Faculty of Biotechnology of the University of Gdansk and Medical University of Gdansk, Gdansk, Poland
| | | | - Viera Habalova
- Dept. of Medical Biology, P. J. Safarik University, Kosice, Slovakia
| | - Victor Murcia Pienkowski
- Dept. of Medical Genetics, Medical University of Warsaw, Warsaw, Poland; Postgraduate School of Molecular Medicine, Medical University of Warsaw, Warsaw, Poland
| | - Miriam Skirkova
- Dept. of Ophtalmology, P. J. Safarik University and University Hospital L. Pasteur, Kosice, Slovakia
| | - Vladimir Han
- Dept. of Neurology, P.J. Safarik University, Kosice, Slovakia; Dept. of Neurology, University Hospital L. Pasteur, Kosice, Slovakia
| | - Alexandra Mosejova
- Dept. of Neurology, P.J. Safarik University, Kosice, Slovakia; Dept. of Neurology, University Hospital L. Pasteur, Kosice, Slovakia
| | - Zuzana Gdovinova
- Dept. of Neurology, P.J. Safarik University, Kosice, Slovakia; Dept. of Neurology, University Hospital L. Pasteur, Kosice, Slovakia
| | - Magdalena Kaliszewska
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Katarzyna Tońska
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Michal R Szymanski
- Intercollegiate Faculty of Biotechnology of the University of Gdansk and Medical University of Gdansk, Gdansk, Poland
| | - Matej Skorvanek
- Dept. of Neurology, P.J. Safarik University, Kosice, Slovakia; Dept. of Neurology, University Hospital L. Pasteur, Kosice, Slovakia
| | - Rafal Ploski
- Dept. of Medical Genetics, Medical University of Warsaw, Warsaw, Poland.
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Camptocormia as a Novel Phenotype in a Heterozygous POLG2 Mutation. Diagnostics (Basel) 2020; 10:diagnostics10020068. [PMID: 31991853 PMCID: PMC7168901 DOI: 10.3390/diagnostics10020068] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 01/19/2020] [Accepted: 01/23/2020] [Indexed: 12/04/2022] Open
Abstract
Mitochondrial dysfunction is known to play a key role in the pathophysiological pathway of neurodegenerative disorders. Nuclear-encoded proteins are involved in mtDNA replication, including DNA polymerase gamma, which is the only known replicative mtDNA polymerase, encoded by nuclear genes Polymerase gamma 1 (POLG) and Polymerase gamma 2 (POLG2). POLG mutations are well-known as a frequent cause of mitochondrial myopathies of nuclear origin. However, only rare descriptions of POLG2 mutations leading to mitochondriopathies exist. Here we describe a 68-year-old woman presenting with a 20-year history of camptocormia, mild proximal weakness, and moderate CK increase. Muscle histology showed COX-negative fibres. Genetic analysis by next generation sequencing revealed an already reported heterozygous c.1192-8_1207dup24 mutation in the POLG2 gene. This is the first report on a POLG2 mutation leading to camptocormia as the main clinical phenotype, extending the phenotypic spectrum of POLG2 associated diseases. This underlines the broad phenotypic spectrum found in mitochondrial diseases, especially in mitochondrial disorders of nuclear origin.
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10
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Hoff KE, DeBalsi KL, Sanchez-Quintero MJ, Longley MJ, Hirano M, Naini AB, Copeland WC. Characterization of the human homozygous R182W POLG2 mutation in mitochondrial DNA depletion syndrome. PLoS One 2018; 13:e0203198. [PMID: 30157269 PMCID: PMC6114919 DOI: 10.1371/journal.pone.0203198] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Accepted: 08/14/2018] [Indexed: 12/18/2022] Open
Abstract
Mutations in mitochondrial DNA (mtDNA) have been linked to a variety of metabolic, neurological and muscular diseases which can present at any time throughout life. MtDNA is replicated by DNA polymerase gamma (Pol γ), twinkle helicase and mitochondrial single-stranded binding protein (mtSSB). The Pol γ holoenzyme is a heterotrimer consisting of the p140 catalytic subunit and a p55 homodimeric accessory subunit encoded by the nuclear genes POLG and POLG2, respectively. The accessory subunits enhance DNA binding and promote processive DNA synthesis of the holoenzyme. Mutations in either POLG or POLG2 are linked to disease and adversely affect maintenance of the mitochondrial genome, resulting in depletion, deletions and/or point mutations in mtDNA. A homozygous mutation located at Chr17: 62492543G>A in POLG2, resulting in R182W substitution in p55, was previously identified to cause mtDNA depletion and fatal hepatic liver failure. Here we characterize this homozygous R182W p55 mutation using in vivo cultured cell models and in vitro biochemical assessments. Compared to control fibroblasts, homozygous R182W p55 primary dermal fibroblasts exhibit a two-fold slower doubling time, reduced mtDNA copy number and reduced levels of POLG and POLG2 transcripts correlating with the reported disease state. Expression of R182W p55 in HEK293 cells impairs oxidative-phosphorylation. Biochemically, R182W p55 displays DNA binding and association with p140 similar to WT p55. R182W p55 mimics the ability of WT p55 to stimulate primer extension, support steady-state nucleotide incorporation, and suppress the exonuclease function of Pol γin vitro. However, R182W p55 has severe defects in protein stability as determined by differential scanning fluorimetry and in stimulating function as determined by thermal inactivation. These data demonstrate that the Chr17: 62492543G>A mutation in POLG2, R182W p55, severely impairs stability of the accessory subunit and is the likely cause of the disease phenotype.
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Affiliation(s)
- Kirsten E. Hoff
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC, United States of America
| | - Karen L. DeBalsi
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC, United States of America
| | - Maria J. Sanchez-Quintero
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY, United States of America
| | - Matthew J. Longley
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC, United States of America
| | - Michio Hirano
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY, United States of America
| | - Ali B. Naini
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY, United States of America
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States of America
- Division of Personalized Genomic Medicine, Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY, United States of America
| | - William C. Copeland
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC, United States of America
- * E-mail:
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11
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Movement disorders in mitochondrial disease: a clinicopathological correlation. Curr Opin Neurol 2018; 31:472-483. [DOI: 10.1097/wco.0000000000000583] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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12
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Mitochondrial DNA replication: clinical syndromes. Essays Biochem 2018; 62:297-308. [PMID: 29950321 DOI: 10.1042/ebc20170101] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 03/17/2018] [Accepted: 05/23/2018] [Indexed: 02/08/2023]
Abstract
Each nucleated cell contains several hundreds of mitochondria, which are unique organelles in being under dual genome control. The mitochondria contain their own DNA, the mtDNA, but most of mitochondrial proteins are encoded by nuclear genes, including all the proteins required for replication, transcription, and repair of mtDNA. MtDNA replication is a continuous process that requires coordinated action of several enzymes that are part of the mtDNA replisome. It also requires constant supply of deoxyribonucleotide triphosphates(dNTPs) and interaction with other mitochondria for mixing and unifying the mitochondrial compartment. MtDNA maintenance defects are a growing list of disorders caused by defects in nuclear genes involved in different aspects of mtDNA replication. As a result of defects in these genes, mtDNA depletion and/or multiple mtDNA deletions develop in affected tissues resulting in variable manifestations that range from adult-onset mild disease to lethal presentation early in life.
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13
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Plutino M, Chaussenot A, Rouzier C, Ait-El-Mkadem S, Fragaki K, Paquis-Flucklinger V, Bannwarth S. Targeted next generation sequencing with an extended gene panel does not impact variant detection in mitochondrial diseases. BMC MEDICAL GENETICS 2018; 19:57. [PMID: 29625556 PMCID: PMC5889585 DOI: 10.1186/s12881-018-0568-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 03/21/2018] [Indexed: 12/29/2022]
Abstract
Background Since the advent of next generation sequencing (NGS), several studies have tried to evaluate the relevance of targeted gene panel sequencing and whole exome sequencing for molecular diagnosis of mitochondrial diseases. The comparison between these different strategies is extremely difficult. A recent study analysed a cohort of patients affected by a mitochondrial disease using a NGS approach based on a targeted gene panel including 132 genes. This strategy led to identify the causative mutations in 15.2% of cases. The number of novel genes responsible for respiratory chain deficiency increases very rapidly. Methods In order to determine the impact of larger panels used as a first screening strategy on molecular diagnosis success, we analysed a cohort of 80 patients affected by a mitochondrial disease with a first mitochondrial DNA (mtDNA) NGS screening and secondarily a targeted mitochondrial panel of 281 nuclear genes. Results Pathogenic mtDNA abnormalities were identified in 4.1% (1/24) of children and 25% (14/56) of adult patients. The remaining 65 patients were analysed with our targeted mitochondrial panel and this approach enabled us to achieve an identification rate of 21.7% (5/23) in children versus 7.1% (3/42) in adults. Conclusions Our results confirm that larger gene panels do not improve diagnostic yield of mitochondrial diseases due to (i) their very high genetic heterogeneity, (ii) the ongoing discovery of novel genes and (iii) mutations in genes apparently not related to mitochondrial function that lead to secondary respiratory chain deficiency. Electronic supplementary material The online version of this article (10.1186/s12881-018-0568-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Morgane Plutino
- Université Côte d'Azur, CHU de Nice, Inserm, CNRS, IRCAN, Nice, France
| | | | - Cécile Rouzier
- Université Côte d'Azur, CHU de Nice, Inserm, CNRS, IRCAN, Nice, France
| | | | | | | | - Sylvie Bannwarth
- Université Côte d'Azur, CHU de Nice, Inserm, CNRS, IRCAN, Nice, France. .,IRCAN UMR CNRS 7284/INSERM U1081, Medicine School, 28 av de Valombrose, 06107, Nice cedex 2, France.
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