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Wojtaszek JL, Hoff KE, Longley MJ, Kaur P, Andres S, Wang H, Williams R, Copeland W. Structure-specific roles for PolG2-DNA complexes in maintenance and replication of mitochondrial DNA. Nucleic Acids Res 2023; 51:9716-9732. [PMID: 37592734 PMCID: PMC10570022 DOI: 10.1093/nar/gkad679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 07/13/2023] [Accepted: 08/09/2023] [Indexed: 08/19/2023] Open
Abstract
The homodimeric PolG2 accessory subunit of the mitochondrial DNA polymerase gamma (Pol γ) enhances DNA binding and processive DNA synthesis by the PolG catalytic subunit. PolG2 also directly binds DNA, although the underlying molecular basis and functional significance are unknown. Here, data from Atomic Force Microscopy (AFM) and X-ray structures of PolG2-DNA complexes define dimeric and hexameric PolG2 DNA binding modes. Targeted disruption of PolG2 DNA-binding interfaces impairs processive DNA synthesis without diminishing Pol γ subunit affinities. In addition, a structure-specific DNA-binding role for PolG2 oligomers is supported by X-ray structures and AFM showing that oligomeric PolG2 localizes to DNA crossings and targets forked DNA structures resembling the mitochondrial D-loop. Overall, data indicate that PolG2 DNA binding has both PolG-dependent and -independent functions in mitochondrial DNA replication and maintenance, which provide new insight into molecular defects associated with PolG2 disruption in mitochondrial disease.
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Affiliation(s)
- Jessica L Wojtaszek
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Kirsten E Hoff
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Matthew J Longley
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Parminder Kaur
- Physics Department, North Carolina State University, Raleigh, NC 27695, USA
- Center for Human Health and the Environment, North Carolina State University, Raleigh, NC 27695, USA
| | - Sara N Andres
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Hong Wang
- Physics Department, North Carolina State University, Raleigh, NC 27695, USA
- Center for Human Health and the Environment, North Carolina State University, Raleigh, NC 27695, USA
- Toxicology Program, North Carolina State University, Raleigh, NC 27695, USA
| | - R Scott Williams
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - William C Copeland
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
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2
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Corkery-Hayward M, Metherell LA. Adrenal Dysfunction in Mitochondrial Diseases. Int J Mol Sci 2023; 24:ijms24021126. [PMID: 36674647 PMCID: PMC9862368 DOI: 10.3390/ijms24021126] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 01/02/2023] [Accepted: 01/04/2023] [Indexed: 01/10/2023] Open
Abstract
Cortisol is central to several homeostatic mechanisms including the stress and immune response. Adrenal insufficiency and impaired cortisol production leads to severe, potentially fatal disorders. Several fundamental stages of steroidogenesis occur within the mitochondria. These dynamic organelles not only contribute ATP for steroidogenesis, but also detoxify harmful by-products generated during cortisol synthesis (reactive oxygen species). Mutations in nuclear or mitochondrial DNA that impair mitochondrial function lead to debilitating multi-system diseases. Recently, genetic variants that impair mitochondrial function have been identified in people with isolated cortisol insufficiency. This review aimed to clarify the association between mitochondrial diseases and adrenal insufficiency to produce cortisol. Mitochondrial diseases are rare and mitochondrial diseases that feature adrenal insufficiency are even rarer. We identified only 14 cases of adrenal insufficiency in people with confirmed mitochondrial diseases globally. In line with previous reviews, adrenal dysfunction was most prevalent in mitochondrial deletion syndromes (particularly Pearson syndrome and Kearns-Sayre syndrome) and with point mutations that compromised oxidative phosphorylation. Although adrenal insufficiency has been reported with mitochondrial diseases, the incidence reflects that expected in the general population. Thus, it is unlikely that mitochondrial mutations alone are responsible for an insufficiency to produce cortisol. More research is needed into the pathogenesis of adrenal disease in these individuals.
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Affiliation(s)
| | - Louise A. Metherell
- Centre for Endocrinology, William Harvey Research Institute, Queen Mary University of London, London EC1M 6BQ, UK
- Correspondence:
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3
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Franklin AD, Chaudhari BP, Koboldt DC, Machut KZ. Polymerase Gamma Mitochondrial DNA Depletion Syndrome Initially Presenting as Disproportionate Respiratory Distress in a Moderately Premature Neonate: A Case Report. Front Genet 2021; 12:664278. [PMID: 34194468 PMCID: PMC8238196 DOI: 10.3389/fgene.2021.664278] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 05/04/2021] [Indexed: 11/13/2022] Open
Abstract
A 32-week premature infant presented with respiratory failure, later progressing to pulmonary hypertension (PH), liver failure, lactic acidosis, and encephalopathy. Using exome sequencing, this patient was diagnosed with a rare Polymerase Gamma (POLG)-related mitochondrial DNA (mtDNA) depletion syndrome. This case demonstrates that expanding the differential to uncommon diagnoses is important for complex infants, even in premature neonates whose condition may be explained partially by their gestational age (GA). It also shows that patients with complex neonatal diseases with significant family history may benefit from exome sequencing for diagnosis.
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Affiliation(s)
- Andrew D Franklin
- Division of Neonatology, NorthShore University HealthSystem, Evanston, IL, United States
| | - Bimal P Chaudhari
- Division of Genetic and Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, United States.,Division of Neonatology, Nationwide Children's Hospital, Columbus, OH, United States.,The Steve and Cindy Rasmussen Institute for Genomic Medicine at Nationwide Children's Hospital, Columbus, OH, United States.,Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, United States
| | - Daniel C Koboldt
- The Steve and Cindy Rasmussen Institute for Genomic Medicine at Nationwide Children's Hospital, Columbus, OH, United States
| | - Kerri Z Machut
- Division of Neonatology, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, United States.,Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
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4
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Silva-Pinheiro P, Pardo-Hernández C, Reyes A, Tilokani L, Mishra A, Cerutti R, Li S, Rozsivalova DH, Valenzuela S, Dogan SA, Peter B, Fernández-Silva P, Trifunovic A, Prudent J, Minczuk M, Bindoff L, Macao B, Zeviani M, Falkenberg M, Viscomi C. DNA polymerase gamma mutations that impair holoenzyme stability cause catalytic subunit depletion. Nucleic Acids Res 2021; 49:5230-5248. [PMID: 33956154 PMCID: PMC8136776 DOI: 10.1093/nar/gkab282] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 03/29/2021] [Accepted: 04/08/2021] [Indexed: 01/31/2023] Open
Abstract
Mutations in POLG, encoding POLγA, the catalytic subunit of the mitochondrial DNA polymerase, cause a spectrum of disorders characterized by mtDNA instability. However, the molecular pathogenesis of POLG-related diseases is poorly understood and efficient treatments are missing. Here, we generate the PolgA449T/A449T mouse model, which reproduces the A467T change, the most common human recessive mutation of POLG. We show that the mouse A449T mutation impairs DNA binding and mtDNA synthesis activities of POLγ, leading to a stalling phenotype. Most importantly, the A449T mutation also strongly impairs interactions with POLγB, the accessory subunit of the POLγ holoenzyme. This allows the free POLγA to become a substrate for LONP1 protease degradation, leading to dramatically reduced levels of POLγA in A449T mouse tissues. Therefore, in addition to its role as a processivity factor, POLγB acts to stabilize POLγA and to prevent LONP1-dependent degradation. Notably, we validated this mechanism for other disease-associated mutations affecting the interaction between the two POLγ subunits. We suggest that targeting POLγA turnover can be exploited as a target for the development of future therapies.
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Affiliation(s)
- Pedro Silva-Pinheiro
- MRC/University of Cambridge Mitochondrial Biology Unit, Hills Road, CB2 0XY Cambridge, UK
| | - Carlos Pardo-Hernández
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Medicinaregatan 9A P.O. Box 440, SE405 30 Gothenburg, Sweden
| | - Aurelio Reyes
- MRC/University of Cambridge Mitochondrial Biology Unit, Hills Road, CB2 0XY Cambridge, UK
| | - Lisa Tilokani
- MRC/University of Cambridge Mitochondrial Biology Unit, Hills Road, CB2 0XY Cambridge, UK
| | - Anup Mishra
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Medicinaregatan 9A P.O. Box 440, SE405 30 Gothenburg, Sweden
| | - Raffaele Cerutti
- Department of Neurosciences, University of Padova, via Giustiniani, 2-35128 Padova, Italy
| | - Shuaifeng Li
- Center for Cancer Biology, Life Science of Institution, Zhejiang University, Hangzhou 310058, China
| | - Dieu-Hien Rozsivalova
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD) and Center for Molecular Medicine (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Sebastian Valenzuela
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Medicinaregatan 9A P.O. Box 440, SE405 30 Gothenburg, Sweden
| | - Sukru A Dogan
- Department of Molecular Biology and Genetics, Center for Life Sciences and Technologies, Bogazici University, 34342 Istanbul, Turkey
| | - Bradley Peter
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Medicinaregatan 9A P.O. Box 440, SE405 30 Gothenburg, Sweden
| | - Patricio Fernández-Silva
- Biochemistry and Molecular and Cell Biology Department, University of Zaragoza, C/ Pedro Cerbuna s/n 50.009-Zaragoza, and Biocomputation and Complex Systems Physics Institute (BIFI), C/ Mariano Esquillor, 50.018-Zaragoza, Spain
| | - Aleksandra Trifunovic
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD) and Center for Molecular Medicine (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Julien Prudent
- MRC/University of Cambridge Mitochondrial Biology Unit, Hills Road, CB2 0XY Cambridge, UK
| | - Michal Minczuk
- MRC/University of Cambridge Mitochondrial Biology Unit, Hills Road, CB2 0XY Cambridge, UK
| | - Laurence Bindoff
- Department of Clinical Medicine, University of Bergen, 5007 Bergen, Norway
- Neuro-SysMed, Department of Neurology, Haukeland University Hospital, Jonas Lies vei 65, 5021 Bergen, Norway
| | - Bertil Macao
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Medicinaregatan 9A P.O. Box 440, SE405 30 Gothenburg, Sweden
| | - Massimo Zeviani
- Department of Neurosciences, University of Padova, via Giustiniani, 2-35128 Padova, Italy
- Venetian Institute of Molecular Medicine, via Orus 2-35128 Padova, Italy
| | - Maria Falkenberg
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Medicinaregatan 9A P.O. Box 440, SE405 30 Gothenburg, Sweden
| | - Carlo Viscomi
- Department of Biomedical Sciences, University of Padova, via Ugo Bassi 58/B-35131 Padova, Italy
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Patel J, Baptiste BA, Kim E, Hussain M, Croteau DL, Bohr VA. DNA damage and mitochondria in cancer and aging. Carcinogenesis 2021; 41:1625-1634. [PMID: 33146705 DOI: 10.1093/carcin/bgaa114] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 10/23/2020] [Accepted: 10/28/2020] [Indexed: 12/21/2022] Open
Abstract
Age and DNA repair deficiencies are strong risk factors for developing cancer. This is reflected in the comorbidity of cancer with premature aging diseases associated with DNA damage repair deficiencies. Recent research has suggested that DNA damage accumulation, telomere dysfunction and the accompanying mitochondrial dysfunction exacerbate the aging process and may increase the risk of cancer development. Thus, an area of interest in both cancer and aging research is the elucidation of the dynamic crosstalk between the nucleus and the mitochondria. In this review, we discuss current research on aging and cancer with specific focus on the role of mitochondrial dysfunction in cancer and aging as well as how nuclear to mitochondrial DNA damage signaling may be a driving factor in the increased cancer incidence with aging. We suggest that therapeutic interventions aimed at the induction of autophagy and mediation of nuclear to mitochondrial signaling may provide a mechanism for healthier aging and reduced tumorigenesis.
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Affiliation(s)
- Jaimin Patel
- Laboratory of Molecular Gerontology, National Institute on Aging, Baltimore, MD, USA
| | - Beverly A Baptiste
- Laboratory of Molecular Gerontology, National Institute on Aging, Baltimore, MD, USA
| | - Edward Kim
- Laboratory of Molecular Gerontology, National Institute on Aging, Baltimore, MD, USA
| | - Mansoor Hussain
- Laboratory of Molecular Gerontology, National Institute on Aging, Baltimore, MD, USA
| | - Deborah L Croteau
- Laboratory of Molecular Gerontology, National Institute on Aging, Baltimore, MD, USA
| | - Vilhelm A Bohr
- Laboratory of Molecular Gerontology, National Institute on Aging, Baltimore, MD, USA
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Sullivan ED, Longley MJ, Copeland WC. Polymerase γ efficiently replicates through many natural template barriers but stalls at the HSP1 quadruplex. J Biol Chem 2021; 295:17802-17815. [PMID: 33454015 DOI: 10.1074/jbc.ra120.015390] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 10/05/2020] [Indexed: 12/27/2022] Open
Abstract
Faithful replication of the mitochondrial genome is carried out by a set of key nuclear-encoded proteins. DNA polymerase γ is a core component of the mtDNA replisome and the only replicative DNA polymerase localized to mitochondria. The asynchronous mechanism of mtDNA replication predicts that the replication machinery encounters dsDNA and unique physical barriers such as structured genes, G-quadruplexes, and other obstacles. In vitro experiments here provide evidence that the polymerase γ heterotrimer is well-adapted to efficiently synthesize DNA, despite the presence of many naturally occurring roadblocks. However, we identified a specific G-quadruplex-forming sequence at the heavy-strand promoter (HSP1) that has the potential to cause significant stalling of mtDNA replication. Furthermore, this structured region of DNA corresponds to the break site for a large (3,895 bp) deletion observed in mitochondrial disease patients. The presence of this deletion in humans correlates with UV exposure, and we have found that efficiency of polymerase γ DNA synthesis is reduced after this quadruplex is exposed to UV in vitro.
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Affiliation(s)
- Eric D Sullivan
- Mitochondrial DNA Replication Group, Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina, USA
| | - Matthew J Longley
- Mitochondrial DNA Replication Group, Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina, USA
| | - William C Copeland
- Mitochondrial DNA Replication Group, Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina, USA.
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7
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Darin N, Siibak T, Peter B, Hedberg-Oldfors C, Kollberg G, Kalbin V, Moslemi AR, Macao B, Oldfors A, Falkenberg M. Functional analysis of a novel POLγA mutation associated with a severe perinatal mitochondrial encephalomyopathy. Neuromuscul Disord 2021; 31:348-358. [PMID: 33579567 DOI: 10.1016/j.nmd.2021.01.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 01/05/2021] [Accepted: 01/06/2021] [Indexed: 12/18/2022]
Abstract
Mutations in the mitochondrial DNA polymerase gamma catalytic subunit (POLγA) compromise the stability of mitochondrial DNA (mtDNA) by leading to mutations, deletions and depletions in mtDNA. Patients with mutations in POLγA often differ remarkably in disease severity and age of onset. In this work we have studied the functional consequence of POLγA mutations in a patient with an uncommon and a very severe disease phenotype characterized by prenatal onset with intrauterine growth restriction, lactic acidosis from birth, encephalopathy, hepatopathy, myopathy, and early death. Muscle biopsy identified scattered COX-deficient muscle fibers, respiratory chain dysfunction and mtDNA depletion. We identified a novel POLγA mutation (p.His1134Tyr) in trans with the previously identified p.Thr251Ile/Pro587Leu double mutant. Biochemical characterization of the purified recombinant POLγA variants showed that the p.His1134Tyr mutation caused severe polymerase dysfunction. The p.Thr251Ile/Pro587Leu mutation caused reduced polymerase function in conditions of low dNTP concentration that mimic postmitotic tissues. Critically, when p.His1134Tyr and p.Thr251Ile/Pro587Leu were combined under these conditions, mtDNA replication was severely diminished and featured prominent stalling. Our data provide a molecular explanation for the patient´s mtDNA depletion and clinical features, particularly in tissues such as brain and muscle that have low dNTP concentration.
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Affiliation(s)
- Niklas Darin
- Department of Pediatrics, Institute of Clinical Sciences, University of Gothenburg, Gothenburg, Sweden.
| | - Triinu Siibak
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, University of Gothenburg, Box 440, 40530 Gothenburg, Sweden
| | - Bradley Peter
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, University of Gothenburg, Box 440, 40530 Gothenburg, Sweden
| | - Carola Hedberg-Oldfors
- Department of Laboratory Medicine, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Gittan Kollberg
- Department of Laboratory Medicine, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Vassili Kalbin
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, University of Gothenburg, Box 440, 40530 Gothenburg, Sweden
| | - Ali-Reza Moslemi
- Department of Laboratory Medicine, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Bertil Macao
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, University of Gothenburg, Box 440, 40530 Gothenburg, Sweden
| | - Anders Oldfors
- Department of Laboratory Medicine, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Maria Falkenberg
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, University of Gothenburg, Box 440, 40530 Gothenburg, Sweden.
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8
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Abstract
The POLG gene encodes the mitochondrial DNA polymerase that is responsible for replication of the mitochondrial genome. Mutations in POLG can cause early childhood mitochondrial DNA (mtDNA) depletion syndromes or later-onset syndromes arising from mtDNA deletions. POLG mutations are the most common cause of inherited mitochondrial disorders, with as many as 2% of the population carrying these mutations. POLG-related disorders comprise a continuum of overlapping phenotypes with onset from infancy to late adulthood. The six leading disorders caused by POLG mutations are Alpers-Huttenlocher syndrome, which is one of the most severe phenotypes; childhood myocerebrohepatopathy spectrum, which presents within the first 3 years of life; myoclonic epilepsy myopathy sensory ataxia; ataxia neuropathy spectrum; autosomal recessive progressive external ophthalmoplegia; and autosomal dominant progressive external ophthalmoplegia. This Review describes the clinical features, pathophysiology, natural history and treatment of POLG-related disorders, focusing particularly on the neurological manifestations of these conditions.
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9
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Hedberg-Oldfors C, Macao B, Basu S, Lindberg C, Peter B, Erdinc D, Uhler JP, Larsson E, Falkenberg M, Oldfors A. Deep sequencing of mitochondrial DNA and characterization of a novel POLG mutation in a patient with arPEO. NEUROLOGY-GENETICS 2020; 6:e391. [PMID: 32042919 PMCID: PMC6975171 DOI: 10.1212/nxg.0000000000000391] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 11/13/2019] [Indexed: 12/31/2022]
Abstract
Objective To determine the pathogenicity of a novel POLG mutation in a man with late-onset autosomal recessive progressive external ophthalmoplegia using clinical, molecular, and biochemical analyses. Methods A multipronged approach with detailed neurologic examinations, muscle biopsy analyses, molecular genetic studies, and in vitro biochemical characterization. Results The patient had slowly progressive bilateral ptosis and severely reduced horizontal and vertical gaze. Muscle biopsy showed slight variability in muscle fiber size, scattered ragged red fibers, and partial cytochrome c oxidase deficiency. Biallelic mutations were identified in the POLG gene encoding the catalytic A subunit of POLγ. One allele carried a novel mutation in the exonuclease domain (c.590T>C; p.F197S), and the other had a previously characterized null mutation in the polymerase domain (c.2740A>C; p.T914P). Biochemical characterization revealed that the novel F197S mutant protein had reduced exonuclease and DNA polymerase activities and confirmed that T914P was inactive. By deep sequencing of mitochondrial DNA (mtDNA) extracted from muscle, multiple large-scale rearrangements were mapped and quantified. Conclusions The patient's phenotype was caused by biallelic POLG mutations, resulting in one inactive POLγA protein (T914P) and one with decreased polymerase and exonuclease activity (F197S). The reduction in polymerase activity explains the presence of multiple pathogenic large-scale deletions in the patient's mtDNA.
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Affiliation(s)
- Carola Hedberg-Oldfors
- Department of Pathology and Genetics (C.H.-O., A.O.) and Medical Biochemistry and Cell Biology (B.M., S.B., B.P., D.E., J.P.U., E.L., M.F.), University of Gothenburg; and Neuromuscular Centre (C.L.), Department of Neurology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Bertil Macao
- Department of Pathology and Genetics (C.H.-O., A.O.) and Medical Biochemistry and Cell Biology (B.M., S.B., B.P., D.E., J.P.U., E.L., M.F.), University of Gothenburg; and Neuromuscular Centre (C.L.), Department of Neurology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Swaraj Basu
- Department of Pathology and Genetics (C.H.-O., A.O.) and Medical Biochemistry and Cell Biology (B.M., S.B., B.P., D.E., J.P.U., E.L., M.F.), University of Gothenburg; and Neuromuscular Centre (C.L.), Department of Neurology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Christopher Lindberg
- Department of Pathology and Genetics (C.H.-O., A.O.) and Medical Biochemistry and Cell Biology (B.M., S.B., B.P., D.E., J.P.U., E.L., M.F.), University of Gothenburg; and Neuromuscular Centre (C.L.), Department of Neurology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Bradley Peter
- Department of Pathology and Genetics (C.H.-O., A.O.) and Medical Biochemistry and Cell Biology (B.M., S.B., B.P., D.E., J.P.U., E.L., M.F.), University of Gothenburg; and Neuromuscular Centre (C.L.), Department of Neurology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Direnis Erdinc
- Department of Pathology and Genetics (C.H.-O., A.O.) and Medical Biochemistry and Cell Biology (B.M., S.B., B.P., D.E., J.P.U., E.L., M.F.), University of Gothenburg; and Neuromuscular Centre (C.L.), Department of Neurology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Jay P Uhler
- Department of Pathology and Genetics (C.H.-O., A.O.) and Medical Biochemistry and Cell Biology (B.M., S.B., B.P., D.E., J.P.U., E.L., M.F.), University of Gothenburg; and Neuromuscular Centre (C.L.), Department of Neurology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Erik Larsson
- Department of Pathology and Genetics (C.H.-O., A.O.) and Medical Biochemistry and Cell Biology (B.M., S.B., B.P., D.E., J.P.U., E.L., M.F.), University of Gothenburg; and Neuromuscular Centre (C.L.), Department of Neurology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Maria Falkenberg
- Department of Pathology and Genetics (C.H.-O., A.O.) and Medical Biochemistry and Cell Biology (B.M., S.B., B.P., D.E., J.P.U., E.L., M.F.), University of Gothenburg; and Neuromuscular Centre (C.L.), Department of Neurology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Anders Oldfors
- Department of Pathology and Genetics (C.H.-O., A.O.) and Medical Biochemistry and Cell Biology (B.M., S.B., B.P., D.E., J.P.U., E.L., M.F.), University of Gothenburg; and Neuromuscular Centre (C.L.), Department of Neurology, Sahlgrenska University Hospital, Gothenburg, Sweden
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10
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Mitochondrial Dysfunction in Aging and Cancer. J Clin Med 2019; 8:jcm8111983. [PMID: 31731601 PMCID: PMC6912717 DOI: 10.3390/jcm8111983] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 11/01/2019] [Accepted: 11/13/2019] [Indexed: 12/14/2022] Open
Abstract
Aging is a major risk factor for developing cancer, suggesting that these two events may represent two sides of the same coin. It is becoming clear that some mechanisms involved in the aging process are shared with tumorigenesis, through convergent or divergent pathways. Increasing evidence supports a role for mitochondrial dysfunction in promoting aging and in supporting tumorigenesis and cancer progression to a metastatic phenotype. Here, a summary of the current knowledge of three aspects of mitochondrial biology that link mitochondria to aging and cancer is presented. In particular, the focus is on mutations and changes in content of the mitochondrial genome, activation of mitochondria-to-nucleus signaling and the newly discovered mitochondria-telomere communication.
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11
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Mutations in MTHFR and POLG impaired activity of the mitochondrial respiratory chain in 46-year-old twins with spastic paraparesis. J Hum Genet 2019; 65:91-98. [PMID: 31645654 DOI: 10.1038/s10038-019-0689-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Revised: 09/03/2019] [Accepted: 10/04/2019] [Indexed: 12/21/2022]
Abstract
Hereditary spastic paraplegias (HSPs) are characterized by lower extremity spasticity and weakness. HSP is often caused by mutations in SPG genes, but it may also be produced by inborn errors of metabolism. We performed next-generation sequencing of 4813 genes in one adult twin pair with HSP and severe muscular weakness occurring at the same age. We found two pathogenic compound heterozygous variants in MTHFR, including a variant not referenced in international databases, c.197C>T (p.Pro66Leu) and a known variant, c.470G>A (p.Arg157Gln), and two heterozygous pathogenic variants in POLG, c.1760C>T (p.Pro587Leu) and c.752C>T (p.Thr251Ile). MTHFR and POLG mutations were consistent with the severe muscle weakness and the metabolic changes, including hyperhomocysteinemia and decreased activity of both N(5,10)methylenetetrahydrofolate reductase (MTHFR) and complexes I and II of the mitochondrial respiratory chain. These data suggest the potential role of MTHFR and POLG mutations through consequences on mitochondrial dysfunction in the occurrence of spastic paraparesis phenotype with combined metabolic, muscular, and neurological components.
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12
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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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13
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Castiglioni C, Fattori F, Udd B, de Los Angeles Avaria M, Suarez B, D'Amico A, Malandrini A, Carrozzo R, Verrigni D, Bertini E, Tasca G. Neuromyopathy with congenital cataracts and glaucoma: a distinct syndrome caused by POLG variants. Eur J Hum Genet 2018; 26:367-373. [PMID: 29358615 DOI: 10.1038/s41431-017-0003-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2017] [Accepted: 08/23/2017] [Indexed: 11/09/2022] Open
Abstract
We identified three non-related patients manifesting a childhood-onset progressive neuromyopathy with congenital cataracts, delayed walking, distal weakness and wasting, glaucoma and swallowing difficulties. Electrophysiology and nerve biopsies showed a mixed axonal and demyelinating neuropathy, while muscle biopsy disclosed both neurogenic and myopathic changes with ragged red fibers, and muscle MRI showed consistent features across patients, with a peculiar concentric disto-proximal gradient of fatty replacement. We used targeted next generation sequencing and candidate gene approach to study these families. Compound biallelic heterozygous variants, p.[(Pro648Arg)]; [(His932Tyr)] and p.[(Thr251Ile),(Pro587Leu)]; [(Arg943Cys)], were found in the three patients causing this homogeneous phenotype. Our report on a subset of unrelated patients, that showed a distinct autosomal recessive childhood-onset neuromyopathy with congenital cataracts and glaucoma, expands the clinical spectrum of POLG-related disorders. It also confirms the association between cataracts and neuropathy with variants in POLG. Early onset cataract is otherwise rare in POLG-related disorders and so far reported only in a few patients with the clinical pattern of distal myopathy or neuromyopathy.
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Affiliation(s)
| | - Fabiana Fattori
- Unit of Neuromuscular and Neurodegenerative Disorders, Bambino Gesù Children's Research Hospital, Rome, Italy
| | - Bjarne Udd
- University of Helsinki, Folkhälsan Institute of Genetics, Helsinki, Finland.,Neuromuscular Research Center, Tampere University and University Hospital, Tampere, Finland.,Department of Neurology, Vasa Central Hospital, Vaasa, Finland
| | | | - Bernardita Suarez
- Department of Pediatric Neurology, Clinica Las Condes, Santiago, Chile
| | - Adele D'Amico
- Unit of Neuromuscular and Neurodegenerative Disorders, Bambino Gesù Children's Research Hospital, Rome, Italy
| | | | - Rosalba Carrozzo
- Unit of Neuromuscular and Neurodegenerative Disorders, Bambino Gesù Children's Research Hospital, Rome, Italy
| | - Daniela Verrigni
- Unit of Neuromuscular and Neurodegenerative Disorders, Bambino Gesù Children's Research Hospital, Rome, Italy
| | - Enrico Bertini
- Unit of Neuromuscular and Neurodegenerative Disorders, Bambino Gesù Children's Research Hospital, Rome, Italy.
| | - Giorgio Tasca
- Istituto di Neurologia, Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario "A. Gemelli", Rome, Italy
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