1
|
Riccio A, Brannon A, Krahn J, Bouvette J, Williams J, Borgnia M, Copeland W. Coordinated DNA polymerization by Polγ and the region of LonP1 regulated proteolysis. Nucleic Acids Res 2024; 52:7863-7875. [PMID: 38932681 PMCID: PMC11260448 DOI: 10.1093/nar/gkae539] [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: 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.
Collapse
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
| |
Collapse
|
2
|
Bernardino Gomes TM, Vincent AE, Menger KE, Stewart JB, Nicholls TJ. Mechanisms and pathologies of human mitochondrial DNA replication and deletion formation. Biochem J 2024; 481:683-715. [PMID: 38804971 DOI: 10.1042/bcj20230262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Revised: 05/13/2024] [Accepted: 05/14/2024] [Indexed: 05/29/2024]
Abstract
Human mitochondria possess a multi-copy circular genome, mitochondrial DNA (mtDNA), that is essential for cellular energy metabolism. The number of copies of mtDNA per cell, and their integrity, are maintained by nuclear-encoded mtDNA replication and repair machineries. Aberrant mtDNA replication and mtDNA breakage are believed to cause deletions within mtDNA. The genomic location and breakpoint sequences of these deletions show similar patterns across various inherited and acquired diseases, and are also observed during normal ageing, suggesting a common mechanism of deletion formation. However, an ongoing debate over the mechanism by which mtDNA replicates has made it difficult to develop clear and testable models for how mtDNA rearrangements arise and propagate at a molecular and cellular level. These deletions may impair energy metabolism if present in a high proportion of the mtDNA copies within the cell, and can be seen in primary mitochondrial diseases, either in sporadic cases or caused by autosomal variants in nuclear-encoded mtDNA maintenance genes. These mitochondrial diseases have diverse genetic causes and multiple modes of inheritance, and show notoriously broad clinical heterogeneity with complex tissue specificities, which further makes establishing genotype-phenotype relationships challenging. In this review, we aim to cover our current understanding of how the human mitochondrial genome is replicated, the mechanisms by which mtDNA replication and repair can lead to mtDNA instability in the form of large-scale rearrangements, how rearranged mtDNAs subsequently accumulate within cells, and the pathological consequences when this occurs.
Collapse
Affiliation(s)
- Tiago M Bernardino Gomes
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- NHS England Highly Specialised Service for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE2 4HH, U.K
| | - Amy E Vincent
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
| | - Katja E Menger
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
| | - James B Stewart
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
| | - Thomas J Nicholls
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
| |
Collapse
|
3
|
Wu C, Zhu H, Zhang Y, Ding L, Wang J. Interference with mitochondrial metabolism could serve as a potential therapeutic strategy for advanced prostate cancer. PLoS One 2024; 19:e0290753. [PMID: 38598542 PMCID: PMC11006138 DOI: 10.1371/journal.pone.0290753] [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: 03/06/2023] [Accepted: 08/15/2023] [Indexed: 04/12/2024] Open
Abstract
Metabolic reprogramming has been defined as a hallmark of malignancies. Prior studies have focused on the single nucleotide polymorphism (SNP) of POLG2 gene, which is reportedly responsible for encoding mitochondrial DNA genes and is implicated in the material and energy metabolism of tumor cells, whereas its function in prostate cancer has been elusive. Gene expression profile matrix and clinical information were downloaded from TCGA (The Cancer Genome Atlas) data portal, and GSE3325 and GSE8511 were retrieved from GEO (Gene Expression Omnibus) database. We conducted analysis of the relative expression of POLG2, clinical characterization, survival analysis, GO / KEGG and GSEA (Gene Set Enrichment Analysis) enrichment analysis in R and employed STRING portal to acquaint ourselves with the protein-protein interaction (PPI). IHC (Immunohistochemical) profiles of POLG2 protein between normal and cancerous tissues were consulted via HPA (Human protein atlas) database and the immunohistochemical POLG2 were verified between para-cancerous and cancerous tissues in tissue array. At the cellular level, Mitochondrial dysfunction assay, DNA synthesis test, wound healing assay, and invasion assay were implemented to further validate the phenotype of POLG2 knockdown in PCa cell lines. RT-qPCR and western blotting were routinely adopted to verify variations of molecular expression within epithelial mesenchymal transition (EMT). Results showed that POLG2 was over-expressed in most cancer types, and the over-expression of POLG2 was correlated with PCa progression and suggested poor OS (Overall Survival) and PFI (Progress Free Interval). Multivariate analysis showed that POLG2 might be an independent prognostic factor of prostate cancer. We also performed GO/KEGG, GSEA analysis, co-expression genes, and PPI, and observed the metabolism-related gene alterations in PCa. Furthermore, we verified that POLG2 knockdown had an inhibitory effect on mitochondrial function, proliferation, cell motility, and invasion, we affirmed POLG2 could affect the prognosis of advanced prostate cancer via EMT. In summary, our findings indicate that over-expressed POLG2 renders poor prognosis in advanced prostate cancer. This disadvantageous factor can serve as a potential indicator, making it possible to target mitochondrial metabolism to treat advanced prostate cancer.
Collapse
Affiliation(s)
- Chuang Wu
- Department of Urology, Jiangsu Province Geriatric Hospital, Nanjing, Jiangsu, China
| | - Huihuang Zhu
- Department of Urology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Yang Zhang
- Department of Urology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Li Ding
- Department of Urology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Junqi Wang
- Department of Urology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
| |
Collapse
|
4
|
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.
Collapse
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
| |
Collapse
|
5
|
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.
Collapse
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
| |
Collapse
|
6
|
Erdinc D, Rodríguez‐Luis A, Fassad MR, Mackenzie S, Watson CM, Valenzuela S, Xie X, Menger KE, Sergeant K, Craig K, Hopton S, Falkous G, Poulton J, Garcia‐Moreno H, Giunti P, de Moura Aschoff CA, Morales Saute JA, Kirby AJ, Toro C, Wolfe L, Novacic D, Greenbaum L, Eliyahu A, Barel O, Anikster Y, McFarland R, Gorman GS, Schaefer AM, Gustafsson CM, Taylor RW, Falkenberg M, Nicholls TJ. Pathological variants in TOP3A cause distinct disorders of mitochondrial and nuclear genome stability. EMBO Mol Med 2023; 15:e16775. [PMID: 37013609 PMCID: PMC10165364 DOI: 10.15252/emmm.202216775] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 03/10/2023] [Accepted: 03/14/2023] [Indexed: 04/05/2023] Open
Abstract
Topoisomerase 3α (TOP3A) is an enzyme that removes torsional strain and interlinks between DNA molecules. TOP3A localises to both the nucleus and mitochondria, with the two isoforms playing specialised roles in DNA recombination and replication respectively. Pathogenic variants in TOP3A can cause a disorder similar to Bloom syndrome, which results from bi-allelic pathogenic variants in BLM, encoding a nuclear-binding partner of TOP3A. In this work, we describe 11 individuals from 9 families with an adult-onset mitochondrial disease resulting from bi-allelic TOP3A gene variants. The majority of patients have a consistent clinical phenotype characterised by bilateral ptosis, ophthalmoplegia, myopathy and axonal sensory-motor neuropathy. We present a comprehensive characterisation of the effect of TOP3A variants, from individuals with mitochondrial disease and Bloom-like syndrome, upon mtDNA maintenance and different aspects of enzyme function. Based on these results, we suggest a model whereby the overall severity of the TOP3A catalytic defect determines the clinical outcome, with milder variants causing adult-onset mitochondrial disease and more severe variants causing a Bloom-like syndrome with mitochondrial dysfunction in childhood.
Collapse
Affiliation(s)
- Direnis Erdinc
- Department of Medical Biochemistry and Cell BiologyUniversity of GothenburgGothenburgSweden
| | - Alejandro Rodríguez‐Luis
- Wellcome Centre for Mitochondrial Research, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
- Biosciences Institute, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
| | - Mahmoud R Fassad
- Wellcome Centre for Mitochondrial Research, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
- Translational and Clinical Research Institute, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
| | - Sarah Mackenzie
- The Newcastle Upon Tyne Hospitals NHS Foundation TrustNewcastle upon TyneUK
| | - Christopher M Watson
- North East and Yorkshire Genomic Laboratory Hub, Central LabSt. James's University HospitalLeedsUK
- Leeds Institute of Medical ResearchUniversity of Leeds, St. James's University HospitalLeedsUK
| | - Sebastian Valenzuela
- Department of Medical Biochemistry and Cell BiologyUniversity of GothenburgGothenburgSweden
| | - Xie Xie
- Department of Medical Biochemistry and Cell BiologyUniversity of GothenburgGothenburgSweden
| | - Katja E Menger
- Wellcome Centre for Mitochondrial Research, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
- Biosciences Institute, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
| | - Kate Sergeant
- Oxford Genetics LaboratoriesOxford University Hospitals NHS Foundation TrustOxfordUK
| | - Kate Craig
- Wellcome Centre for Mitochondrial Research, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
- NHS Highly Specialised Service for Rare Mitochondrial DisordersNewcastle upon Tyne Hospitals NHS Foundation TrustNewcastle upon TyneUK
| | - Sila Hopton
- Wellcome Centre for Mitochondrial Research, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
- NHS Highly Specialised Service for Rare Mitochondrial DisordersNewcastle upon Tyne Hospitals NHS Foundation TrustNewcastle upon TyneUK
| | - Gavin Falkous
- Wellcome Centre for Mitochondrial Research, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
- NHS Highly Specialised Service for Rare Mitochondrial DisordersNewcastle upon Tyne Hospitals NHS Foundation TrustNewcastle upon TyneUK
| | | | - Joanna Poulton
- Nuffield Department of Women's & Reproductive Health, The Women's CentreUniversity of OxfordOxfordUK
| | - Hector Garcia‐Moreno
- Department of Clinical and Movement Neurosciences, Ataxia CentreUCL Queen Square Institute of NeurologyLondonUK
| | - Paola Giunti
- Department of Clinical and Movement Neurosciences, Ataxia CentreUCL Queen Square Institute of NeurologyLondonUK
| | | | - Jonas A Morales Saute
- Medical Genetics ServiceHospital de Clínicas de Porto Alegre (HCPA)Porto AlegreBrazil
- Department of Internal MedicineUniversidade Federal do Rio Grande do SulPorto AlegreBrazil
- Graduate Program in Medicine: Medical SciencesUniversidade Federal do Rio Grande do SulPorto AlegreBrazil
| | - Amelia J Kirby
- Department of PediatricsWake Forest School of MedicineWinston‐SalemNCUSA
| | - Camilo Toro
- Undiagnosed Diseases ProgramNational Human Genome Research Institute, National Institutes of HealthBethesdaMDUSA
| | - Lynne Wolfe
- Undiagnosed Diseases ProgramNational Human Genome Research Institute, National Institutes of HealthBethesdaMDUSA
| | - Danica Novacic
- Undiagnosed Diseases ProgramNational Human Genome Research Institute, National Institutes of HealthBethesdaMDUSA
| | - Lior Greenbaum
- The Danek Gertner Institute of Human GeneticsSheba Medical CenterTel HashomerIsrael
- The Joseph Sagol Neuroscience Center, Sheba Medical CenterTel HashomerIsrael
- Sackler Faculty of MedicineTel Aviv UniversityTel AvivIsrael
| | - Aviva Eliyahu
- The Danek Gertner Institute of Human GeneticsSheba Medical CenterTel HashomerIsrael
- Sackler Faculty of MedicineTel Aviv UniversityTel AvivIsrael
| | - Ortal Barel
- Genomics UnitThe Center for Cancer Research, Sheba Medical CenterTel HashomerIsrael
| | - Yair Anikster
- Sackler Faculty of MedicineTel Aviv UniversityTel AvivIsrael
- Metabolic Disease UnitEdmond and Lily Safra Children's Hospital, Sheba Medical CenterTel HashomerIsrael
| | - Robert McFarland
- Wellcome Centre for Mitochondrial Research, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
- Translational and Clinical Research Institute, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
| | - Gráinne S Gorman
- Wellcome Centre for Mitochondrial Research, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
- Translational and Clinical Research Institute, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
| | - Andrew M Schaefer
- Wellcome Centre for Mitochondrial Research, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
- NHS Highly Specialised Service for Rare Mitochondrial DisordersNewcastle upon Tyne Hospitals NHS Foundation TrustNewcastle upon TyneUK
| | - Claes M Gustafsson
- Department of Medical Biochemistry and Cell BiologyUniversity of GothenburgGothenburgSweden
- Department of Clinical ChemistrySahlgrenska University HospitalGothenburgSweden
| | - Robert W Taylor
- Wellcome Centre for Mitochondrial Research, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
- Translational and Clinical Research Institute, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
- NHS Highly Specialised Service for Rare Mitochondrial DisordersNewcastle upon Tyne Hospitals NHS Foundation TrustNewcastle upon TyneUK
| | - Maria Falkenberg
- Department of Medical Biochemistry and Cell BiologyUniversity of GothenburgGothenburgSweden
| | - Thomas J Nicholls
- Wellcome Centre for Mitochondrial Research, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
- Biosciences Institute, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
| |
Collapse
|
7
|
Gupta R, Kanai M, Durham TJ, Tsuo K, McCoy JG, Chinnery PF, Karczewski KJ, Calvo SE, Neale BM, Mootha VK. Nuclear genetic control of mtDNA copy number and heteroplasmy in humans. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2023:2023.01.19.23284696. [PMID: 36711677 PMCID: PMC9882621 DOI: 10.1101/2023.01.19.23284696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Human mitochondria contain a high copy number, maternally transmitted genome (mtDNA) that encodes 13 proteins required for oxidative phosphorylation. Heteroplasmy arises when multiple mtDNA variants co-exist in an individual and can exhibit complex dynamics in disease and in aging. As all proteins involved in mtDNA replication and maintenance are nuclear-encoded, heteroplasmy levels can, in principle, be under nuclear genetic control, however this has never been shown in humans. Here, we develop algorithms to quantify mtDNA copy number (mtCN) and heteroplasmy levels using blood-derived whole genome sequences from 274,832 individuals of diverse ancestry and perform GWAS to identify nuclear loci controlling these traits. After careful correction for blood cell composition, we observe that mtCN declines linearly with age and is associated with 92 independent nuclear genetic loci. We find that nearly every individual carries heteroplasmic variants that obey two key patterns: (1) heteroplasmic single nucleotide variants are somatic mutations that accumulate sharply after age 70, while (2) heteroplasmic indels are maternally transmitted as mtDNA mixtures with resulting levels influenced by 42 independent nuclear loci involved in mtDNA replication, maintenance, and novel pathways. These nuclear loci do not appear to act by mtDNA mutagenesis, but rather, likely act by conferring a replicative advantage to specific mtDNA molecules. As an illustrative example, the most common heteroplasmy we identify is a length variant carried by >50% of humans at position m.302 within a G-quadruplex known to serve as a replication switch. We find that this heteroplasmic variant exerts cis -acting genetic control over mtDNA abundance and is itself under trans -acting genetic control of nuclear loci encoding protein components of this regulatory switch. Our study showcases how nuclear haplotype can privilege the replication of specific mtDNA molecules to shape mtCN and heteroplasmy dynamics in the human population.
Collapse
Affiliation(s)
- Rahul Gupta
- Howard Hughes Medical Institute and Department of Molecular Biology, Massachusetts General Hospital, United States
- Broad Institute of MIT and Harvard, United States
- Analytic and Translational Genetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, United States
| | - Masahiro Kanai
- Broad Institute of MIT and Harvard, United States
- Analytic and Translational Genetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, United States
| | - Timothy J Durham
- Howard Hughes Medical Institute and Department of Molecular Biology, Massachusetts General Hospital, United States
- Broad Institute of MIT and Harvard, United States
| | - Kristin Tsuo
- Broad Institute of MIT and Harvard, United States
- Analytic and Translational Genetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, United States
| | - Jason G McCoy
- Howard Hughes Medical Institute and Department of Molecular Biology, Massachusetts General Hospital, United States
- Broad Institute of MIT and Harvard, United States
| | - Patrick F Chinnery
- Department of Clinical Neurosciences & MRC Mitochondrial Biology Unit, University of Cambridge, United Kingdom
| | - Konrad J Karczewski
- Broad Institute of MIT and Harvard, United States
- Analytic and Translational Genetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, United States
| | - Sarah E Calvo
- Howard Hughes Medical Institute and Department of Molecular Biology, Massachusetts General Hospital, United States
- Broad Institute of MIT and Harvard, United States
| | - Benjamin M Neale
- Broad Institute of MIT and Harvard, United States
- Analytic and Translational Genetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, United States
| | - Vamsi K Mootha
- Howard Hughes Medical Institute and Department of Molecular Biology, Massachusetts General Hospital, United States
- Broad Institute of MIT and Harvard, United States
- Department of Systems Biology, Harvard Medical School, United States
| |
Collapse
|
8
|
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.
Collapse
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
| |
Collapse
|
9
|
Burgoyne T, Toms M, Way C, Tracey-White D, Futter CE, Moosajee M. Changes in Mitochondrial Size and Morphology in the RPE and Photoreceptors of the Developing and Ageing Zebrafish. Cells 2022; 11:cells11223542. [PMID: 36428971 PMCID: PMC9688747 DOI: 10.3390/cells11223542] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 10/05/2022] [Accepted: 11/04/2022] [Indexed: 11/12/2022] Open
Abstract
Mitochondria are essential adenosine triphosphate (ATP)-generating cellular organelles. In the retina, they are highly numerous in the photoreceptors and retinal pigment epithelium (RPE) due to their high energetic requirements. Fission and fusion of the mitochondria within these cells allow them to adapt to changing demands over the lifespan of the organism. Using transmission electron microscopy, we examined the mitochondrial ultrastructure of zebrafish photoreceptors and RPE from 5 days post fertilisation (dpf) through to late adulthood (3 years). Notably, mitochondria in the youngest animals were large and irregular shaped with a loose cristae architecture, but by 8 dpf they had reduced in size and expanded in number with more defined cristae. Investigation of temporal gene expression of several mitochondrial-related markers indicated fission as the dominant mechanism contributing to the changes observed over time. This is likely to be due to continued mitochondrial stress resulting from the oxidative environment of the retina and prolonged light exposure. We have characterised retinal mitochondrial ageing in a key vertebrate model organism, that provides a basis for future studies of retinal diseases that are linked to mitochondrial dysfunction.
Collapse
Affiliation(s)
- Thomas Burgoyne
- UCL Institute of Ophthalmology, University College London, London EC1V 9EL, UK
- Royal Brompton Hospital, Guy’s and St Thomas’ NHS Foundation Trust, London SW3 6NP, UK
| | - Maria Toms
- UCL Institute of Ophthalmology, University College London, London EC1V 9EL, UK
- The Francis Crick Institute, London NW1 1AT, UK
| | - Chris Way
- UCL Institute of Ophthalmology, University College London, London EC1V 9EL, UK
| | - Dhani Tracey-White
- UCL Institute of Ophthalmology, University College London, London EC1V 9EL, UK
| | - Clare E. Futter
- UCL Institute of Ophthalmology, University College London, London EC1V 9EL, UK
| | - Mariya Moosajee
- UCL Institute of Ophthalmology, University College London, London EC1V 9EL, UK
- The Francis Crick Institute, London NW1 1AT, UK
- Department of Ophthalmology, Great Ormond Street Hospital for Children NHS Foundation Trust, London WC1N 3JH, UK
- Department of Genetics, Moorfields Eye Hospital NHS Foundation Trust, London EC1V 2PD, UK
- Correspondence:
| |
Collapse
|
10
|
Detection of repeat expansions in large next generation DNA and RNA sequencing data without alignment. Sci Rep 2022; 12:13124. [PMID: 35907931 PMCID: PMC9338934 DOI: 10.1038/s41598-022-17267-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 07/22/2022] [Indexed: 11/10/2022] Open
Abstract
Bioinformatic methods for detecting short tandem repeat expansions in short-read sequencing have identified new repeat expansions in humans, but require alignment information to identify repetitive motif enrichment at genomic locations. We present superSTR, an ultrafast method that does not require alignment. superSTR is used to process whole-genome and whole-exome sequencing data, and perform the first STR analysis of the UK Biobank, efficiently screening and identifying known and potential disease-associated STRs in the exomes of 49,953 biobank participants. We demonstrate the first bioinformatic screening of RNA sequencing data to detect repeat expansions in humans and mouse models of ataxia and dystrophy.
Collapse
|
11
|
232nd ENMC International Workshop: Recommendations for treatment of mitochondrial DNA maintenance disorders. 16 – 18 June 2017, Heemskerk, The Netherlands. Neuromuscul Disord 2022; 32:609-620. [DOI: 10.1016/j.nmd.2022.05.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 05/12/2022] [Indexed: 11/24/2022]
|
12
|
Milenkovic D, Sanz-Moreno A, Calzada-Wack J, Rathkolb B, Veronica Amarie O, Gerlini R, Aguilar-Pimentel A, Misic J, Simard ML, Wolf E, Fuchs H, Gailus-Durner V, de Angelis MH, Larsson NG. Mice lacking the mitochondrial exonuclease MGME1 develop inflammatory kidney disease with glomerular dysfunction. PLoS Genet 2022; 18:e1010190. [PMID: 35533204 PMCID: PMC9119528 DOI: 10.1371/journal.pgen.1010190] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 05/19/2022] [Accepted: 04/05/2022] [Indexed: 12/27/2022] Open
Abstract
Mitochondrial DNA (mtDNA) maintenance disorders are caused by mutations in ubiquitously expressed nuclear genes and lead to syndromes with variable disease severity and tissue-specific phenotypes. Loss of function mutations in the gene encoding the mitochondrial genome and maintenance exonuclease 1 (MGME1) result in deletions and depletion of mtDNA leading to adult-onset multisystem mitochondrial disease in humans. To better understand the in vivo function of MGME1 and the associated disease pathophysiology, we characterized a Mgme1 mouse knockout model by extensive phenotyping of ageing knockout animals. We show that loss of MGME1 leads to de novo formation of linear deleted mtDNA fragments that are constantly made and degraded. These findings contradict previous proposal that MGME1 is essential for degradation of linear mtDNA fragments and instead support a model where MGME1 has a critical role in completion of mtDNA replication. We report that Mgme1 knockout mice develop a dramatic phenotype as they age and display progressive weight loss, cataract and retinopathy. Surprisingly, aged animals also develop kidney inflammation, glomerular changes and severe chronic progressive nephropathy, consistent with nephrotic syndrome. These findings link the faulty mtDNA synthesis to severe inflammatory disease and thus show that defective mtDNA replication can trigger an immune response that causes age-associated progressive pathology in the kidney. We have addressed the controversy of the role of the mitochondrial genome and maintenance exonuclease 1 (MGME1) in mtDNA metabolism by characterization of knockout mice. Our findings show that loss of MGME1 leads to increased de novo formation of linear deleted mtDNA, thus contradicting previous report that MGME1 degrades long linear mtDNA molecules. In addition, we report that loss of MGME1 leads to age-associated pathology manifested as progressive weight loss, cataract and retinopathy. Aged knockout mice also develop kidney inflammation leading to glomerular changes, fibrosis and nephrotic syndrome. Defective mtDNA replication causing the formation of linear deleted mtDNA can thus trigger an immune response that leads to the development of progressive kidney disease in ageing animals.
Collapse
Affiliation(s)
| | - Adrián Sanz-Moreno
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
| | - Julia Calzada-Wack
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
| | - Birgit Rathkolb
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
- Institute of Molecular Animal Breeding and Biotechnology, Gene Center, Ludwig-Maximilians-University Munich, Munich, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Oana Veronica Amarie
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
| | - Raffaele Gerlini
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Antonio Aguilar-Pimentel
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
| | - Jelena Misic
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | | | - Eckhard Wolf
- Institute of Molecular Animal Breeding and Biotechnology, Gene Center, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Helmut Fuchs
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
| | - Valerie Gailus-Durner
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
| | - Martin Hrabě de Angelis
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
- Chair of Experimental Genetics, TUM School of Life Sciences, Technische Universität München, Freising, Germany
- * E-mail: (NGL); (MH)
| | - Nils-Göran Larsson
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
- * E-mail: (NGL); (MH)
| |
Collapse
|
13
|
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.
Collapse
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
| |
Collapse
|
14
|
Wang L, Sun L, Wan QH, Fang SG. Comparative Genomics Provides Insights into Adaptive Evolution in Tactile-Foraging Birds. Genes (Basel) 2022; 13:genes13040678. [PMID: 35456484 PMCID: PMC9028243 DOI: 10.3390/genes13040678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 04/07/2022] [Accepted: 04/11/2022] [Indexed: 11/28/2022] Open
Abstract
Tactile-foraging birds have evolved an enlarged principal sensory nucleus (PrV) but smaller brain regions related to the visual system, which reflects the difference in sensory dependence. The “trade-off” may exist between different senses in tactile foragers, as well as between corresponding sensory-processing areas in the brain. We explored the mechanism underlying the adaptive evolution of sensory systems in three tactile foragers (kiwi, mallard, and crested ibis). The results showed that olfaction-related genes in kiwi and mallard and hearing-related genes in crested ibis were expanded, indicating they may also have sensitive olfaction or hearing, respectively. However, some genes required for visual development were positively selected or had convergent amino acid substitutions in all three tactile branches, and it seems to show the possibility of visual degradation. In addition, we may provide a new visual-degradation candidate gene PDLIM1 who suffered dense convergent amino acid substitutions within the ZM domain. At last, two genes responsible for regulating the proliferation and differentiation of neuronal progenitor cells may play roles in determining the relative sizes of sensory areas in brain. This exploration offers insight into the relationship between specialized tactile-forging behavior and the evolution of sensory abilities and brain structures.
Collapse
|
15
|
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.
Collapse
|
16
|
Manini A, Meneri M, Rodolico C, Corti S, Toscano A, Comi GP, Musumeci O, Ronchi D. Case Report: Thymidine Kinase 2 (TK2) Deficiency: A Novel Mutation Associated With Childhood-Onset Mitochondrial Myopathy and Atypical Progression. Front Neurol 2022; 13:857279. [PMID: 35280287 PMCID: PMC8914305 DOI: 10.3389/fneur.2022.857279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 01/31/2022] [Indexed: 11/30/2022] Open
Abstract
The nuclear gene TK2 encodes the mitochondrial thymidine kinase, an enzyme involved in the phosphorylation of deoxycytidine and deoxythymidine nucleosides. Biallelic TK2 mutations are associated with a spectrum of clinical presentations mainly affecting skeletal muscle and featuring muscle mitochondrial DNA (mtDNA) instability. Current classification includes infantile- ( ≤ 1 year), childhood- (1–12 years), and late-onset (≥12 years) forms. In addition to age at onset, these forms differ for progression, life expectancy, and signs of mtDNA instability (mtDNA depletion vs. accumulation of multiple mtDNA deletions). Childhood-onset TK2 deficiency typically causes a rapidly progressive proximal myopathy, which leads to wheelchair-bound status within 10 years of disease onset, and severe respiratory impairment. Muscle biopsy usually reveals a combination of mitochondrial myopathy and dystrophic features with reduced mtDNA content. Here we report the case of an Italian patient presenting childhood-onset, slowly progressive mitochondrial myopathy, ptosis, hypoacusis, dysphonia, and dysphagia, harboring the TK2 variants c.278A>G and c.543del, the latter unreported so far. Compared to other childhood-onset TK2-patients, our case displays atypical features, including slowly progressive muscle weakness and absence of respiratory failure, which are usually observed in late-onset forms. This report extends the genetic background of TK2-related myopathy, highlighting the clinical overlap among different forms.
Collapse
Affiliation(s)
- Arianna Manini
- Dino Ferrari Center, Neuroscience Section, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
| | - Megi Meneri
- Dino Ferrari Center, Neuroscience Section, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Carmelo Rodolico
- Unit of Neurology and Neuromuscular Disorders, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Stefania Corti
- Dino Ferrari Center, Neuroscience Section, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Antonio Toscano
- Unit of Neurology and Neuromuscular Disorders, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Giacomo Pietro Comi
- Dino Ferrari Center, Neuroscience Section, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
- Neuromuscular and Rare Diseases Unit, Department of Neuroscience, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Olimpia Musumeci
- Unit of Neurology and Neuromuscular Disorders, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
- Olimpia Musumeci
| | - Dario Ronchi
- Dino Ferrari Center, Neuroscience Section, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
- *Correspondence: Dario Ronchi
| |
Collapse
|
17
|
Mitochondrial Neurodegeneration. Cells 2022; 11:cells11040637. [PMID: 35203288 PMCID: PMC8870525 DOI: 10.3390/cells11040637] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 01/28/2022] [Accepted: 02/06/2022] [Indexed: 01/27/2023] Open
Abstract
Mitochondria are cytoplasmic organelles, which generate energy as heat and ATP, the universal energy currency of the cell. This process is carried out by coupling electron stripping through oxidation of nutrient substrates with the formation of a proton-based electrochemical gradient across the inner mitochondrial membrane. Controlled dissipation of the gradient can lead to production of heat as well as ATP, via ADP phosphorylation. This process is known as oxidative phosphorylation, and is carried out by four multiheteromeric complexes (from I to IV) of the mitochondrial respiratory chain, carrying out the electron flow whose energy is stored as a proton-based electrochemical gradient. This gradient sustains a second reaction, operated by the mitochondrial ATP synthase, or complex V, which condensates ADP and Pi into ATP. Four complexes (CI, CIII, CIV, and CV) are composed of proteins encoded by genes present in two separate compartments: the nuclear genome and a small circular DNA found in mitochondria themselves, and are termed mitochondrial DNA (mtDNA). Mutations striking either genome can lead to mitochondrial impairment, determining infantile, childhood or adult neurodegeneration. Mitochondrial disorders are complex neurological syndromes, and are often part of a multisystem disorder. In this paper, we divide the diseases into those caused by mtDNA defects and those that are due to mutations involving nuclear genes; from a clinical point of view, we discuss pediatric disorders in comparison to juvenile or adult-onset conditions. The complementary genetic contributions controlling organellar function and the complexity of the biochemical pathways present in the mitochondria justify the extreme genetic and phenotypic heterogeneity of this new area of inborn errors of metabolism known as ‘mitochondrial medicine’.
Collapse
|
18
|
Berardo A, Engelstad K, Hirano M. Advances in Thymidine Kinase 2 Deficiency: Clinical Aspects, Translational Progress, and Emerging Therapies. J Neuromuscul Dis 2022; 9:225-235. [PMID: 35094997 PMCID: PMC9028656 DOI: 10.3233/jnd-210786] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Defects in the replication, maintenance, and repair of mitochondrial DNA (mtDNA) constitute a growing and genetically heterogeneous group of mitochondrial disorders. Multiple genes participate in these processes, including thymidine kinase 2 (TK2) encoding the mitochondrial matrix protein TK2, a critical component of the mitochondrial nucleotide salvage pathway. TK2 deficiency (TK2d) causes mtDNA depletion, multiple deletions, or both, which manifest predominantly as mitochondrial myopathy. A wide clinical spectrum phenotype includes a severe, rapidly progressive, early onset form (median survival: < 2 years); a less severe childhood-onset form; and a late-onset form with a variably slower rate of progression. Clinical presentation typically includes progressive weakness of limb, neck, facial, oropharyngeal, and respiratory muscle, whereas limb myopathy with ptosis, ophthalmoparesis, and respiratory involvement is more common in the late-onset form. Deoxynucleoside monophosphates and deoxynucleosides that can bypass the TK2 enzyme defect have been assessed in a mouse model, as well as under open-label compassionate use (expanded access) in TK2d patients, indicating clinical efficacy with a favorable side-effect profile. This treatment is currently undergoing testing in clinical trials intended to support approval in the US and European Union (EU). In the early expanded access program, growth differentiation factor 15 (GDF-15) appears to be a useful biomarker that correlates with therapeutic response. With the advent of a specific treatment and given the high morbidity and mortality associated with TK2d, clinicians need to know how to recognize and diagnose this disorder. Here, we summarize translational research about this rare condition emphasizing clinical aspects.
Collapse
Affiliation(s)
- Andres Berardo
- Department of Neurology, Columbia University Irving Medical Center, New York, NY, USA
| | - Kristin Engelstad
- Department of Neurology, Columbia University Irving Medical Center, New York, NY, USA
| | - Michio Hirano
- Department of Neurology, Columbia University Irving Medical Center, New York, NY, USA
| |
Collapse
|
19
|
Jiang M, Xie X, Zhu X, Jiang S, Milenkovic D, Misic J, Shi Y, Tandukar N, Li X, Atanassov I, Jenninger L, Hoberg E, Albarran-Gutierrez S, Szilagyi Z, Macao B, Siira SJ, Carelli V, Griffith JD, Gustafsson CM, Nicholls TJ, Filipovska A, Larsson NG, Falkenberg M. The mitochondrial single-stranded DNA binding protein is essential for initiation of mtDNA replication. SCIENCE ADVANCES 2021; 7:eabf8631. [PMID: 34215584 PMCID: PMC11057760 DOI: 10.1126/sciadv.abf8631] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 05/20/2021] [Indexed: 06/13/2023]
Abstract
We report a role for the mitochondrial single-stranded DNA binding protein (mtSSB) in regulating mitochondrial DNA (mtDNA) replication initiation in mammalian mitochondria. Transcription from the light-strand promoter (LSP) is required both for gene expression and for generating the RNA primers needed for initiation of mtDNA synthesis. In the absence of mtSSB, transcription from LSP is strongly up-regulated, but no replication primers are formed. Using deep sequencing in a mouse knockout model and biochemical reconstitution experiments with pure proteins, we find that mtSSB is necessary to restrict transcription initiation to optimize RNA primer formation at both origins of mtDNA replication. Last, we show that human pathological versions of mtSSB causing severe mitochondrial disease cannot efficiently support primer formation and initiation of mtDNA replication.
Collapse
Affiliation(s)
- Min Jiang
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China
- Department of Mitochondrial Biology, Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Xie Xie
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden
| | - Xuefeng Zhu
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden
| | - Shan Jiang
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 17177, Sweden
| | - Dusanka Milenkovic
- Department of Mitochondrial Biology, Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Jelena Misic
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 17177, Sweden
| | - Yonghong Shi
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden
| | - Nirwan Tandukar
- Lineberger Comprehensive Cancer Center, Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27514, USA
| | - Xinping Li
- Proteomics Core Facility, Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Ilian Atanassov
- Proteomics Core Facility, Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Louise Jenninger
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden
| | - Emily Hoberg
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden
| | - Sara Albarran-Gutierrez
- Department of Mitochondrial Biology, Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Zsolt Szilagyi
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden
| | - Bertil Macao
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden
| | - Stefan J Siira
- Harry Perkins Institute of Medical Research and ARC Centre of Excellence in Synthetic Biology, Nedlands, WA 6009, Australia
- Telethon Kids Institute, Northern Entrance, Perth Children's Hospital, 15 Hospital Avenue, Nedlands, WA, Australia
| | - Valerio Carelli
- Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, Bologna, Italy
| | - Jack D Griffith
- Lineberger Comprehensive Cancer Center, Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27514, USA
| | - Claes M Gustafsson
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden
| | - Thomas J Nicholls
- Wellcome Centre for Mitochondrial Research, Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Aleksandra Filipovska
- Harry Perkins Institute of Medical Research and ARC Centre of Excellence in Synthetic Biology, Nedlands, WA 6009, Australia
- Telethon Kids Institute, Northern Entrance, Perth Children's Hospital, 15 Hospital Avenue, Nedlands, WA, Australia
| | - Nils-Göran Larsson
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 17177, Sweden.
| | - Maria Falkenberg
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden.
| |
Collapse
|
20
|
Ramón J, Vila-Julià F, Molina-Granada D, Molina-Berenguer M, Melià MJ, García-Arumí E, Torres-Torronteras J, Cámara Y, Martí R. Therapy Prospects for Mitochondrial DNA Maintenance Disorders. Int J Mol Sci 2021; 22:6447. [PMID: 34208592 PMCID: PMC8234938 DOI: 10.3390/ijms22126447] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 06/10/2021] [Accepted: 06/11/2021] [Indexed: 02/07/2023] Open
Abstract
Mitochondrial DNA depletion and multiple deletions syndromes (MDDS) constitute a group of mitochondrial diseases defined by dysfunctional mitochondrial DNA (mtDNA) replication and maintenance. As is the case for many other mitochondrial diseases, the options for the treatment of these disorders are rather limited today. Some aggressive treatments such as liver transplantation or allogeneic stem cell transplantation are among the few available options for patients with some forms of MDDS. However, in recent years, significant advances in our knowledge of the biochemical pathomechanisms accounting for dysfunctional mtDNA replication have been achieved, which has opened new prospects for the treatment of these often fatal diseases. Current strategies under investigation to treat MDDS range from small molecule substrate enhancement approaches to more complex treatments, such as lentiviral or adenoassociated vector-mediated gene therapy. Some of these experimental therapies have already reached the clinical phase with very promising results, however, they are hampered by the fact that these are all rare disorders and so the patient recruitment potential for clinical trials is very limited.
Collapse
Affiliation(s)
- Javier Ramón
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Ferran Vila-Julià
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - David Molina-Granada
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Miguel Molina-Berenguer
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Maria Jesús Melià
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Elena García-Arumí
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Javier Torres-Torronteras
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Yolanda Cámara
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Ramon Martí
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| |
Collapse
|
21
|
Jang YH, Ahn SR, Shim JY, Lim KI. Engineering Genetic Systems for Treating Mitochondrial Diseases. Pharmaceutics 2021; 13:810. [PMID: 34071708 PMCID: PMC8227772 DOI: 10.3390/pharmaceutics13060810] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 05/23/2021] [Accepted: 05/24/2021] [Indexed: 12/13/2022] Open
Abstract
Mitochondria are intracellular energy generators involved in various cellular processes. Therefore, mitochondrial dysfunction often leads to multiple serious diseases, including neurodegenerative and cardiovascular diseases. A better understanding of the underlying mitochondrial dysfunctions of the molecular mechanism will provide important hints on how to mitigate the symptoms of mitochondrial diseases and eventually cure them. In this review, we first summarize the key parts of the genetic processes that control the physiology and functions of mitochondria and discuss how alterations of the processes cause mitochondrial diseases. We then list up the relevant core genetic components involved in these processes and explore the mutations of the components that link to the diseases. Lastly, we discuss recent attempts to apply multiple genetic methods to alleviate and further reverse the adverse effects of the core component mutations on the physiology and functions of mitochondria.
Collapse
Affiliation(s)
- Yoon-ha Jang
- Department of Chemical and Biological Engineering, Sookmyung Women’s University, Yongsan-gu, Seoul 04310, Korea; (Y.-h.J.); (J.-y.S.)
| | - Sae Ryun Ahn
- Industry Collaboration Center, Industry-Academic Cooperation Foundation, Sookmyung Women’s University, Yongsan-gu, Seoul 04310, Korea;
| | - Ji-yeon Shim
- Department of Chemical and Biological Engineering, Sookmyung Women’s University, Yongsan-gu, Seoul 04310, Korea; (Y.-h.J.); (J.-y.S.)
| | - Kwang-il Lim
- Department of Chemical and Biological Engineering, Sookmyung Women’s University, Yongsan-gu, Seoul 04310, Korea; (Y.-h.J.); (J.-y.S.)
- Industry Collaboration Center, Industry-Academic Cooperation Foundation, Sookmyung Women’s University, Yongsan-gu, Seoul 04310, Korea;
| |
Collapse
|
22
|
Lee Y, Kim T, Lee M, So S, Karagozlu MZ, Seo GH, Choi IH, Lee PCW, Kim CJ, Kang E, Lee BH. De Novo Development of mtDNA Deletion Due to Decreased POLG and SSBP1 Expression in Humans. Genes (Basel) 2021; 12:genes12020284. [PMID: 33671400 PMCID: PMC7922481 DOI: 10.3390/genes12020284] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 02/10/2021] [Accepted: 02/14/2021] [Indexed: 02/07/2023] Open
Abstract
Defects in the mitochondrial genome (mitochondrial DNA (mtDNA)) are associated with both congenital and acquired disorders in humans. Nuclear-encoded DNA polymerase subunit gamma (POLG) plays an important role in mtDNA replication, and proofreading and mutations in POLG have been linked with increased mtDNA deletions. SSBP1 is also a crucial gene for mtDNA replication. Here, we describe a patient diagnosed with Pearson syndrome with large mtDNA deletions that were not detected in the somatic cells of the mother. Exome sequencing was used to evaluate the nuclear factors associated with the patient and his family, which revealed a paternal POLG mutation (c.868C > T) and a maternal SSBP1 mutation (c.320G > A). The patient showed lower POLG and SSBP1 expression than his healthy brothers and the general population of a similar age. Notably, c.868C in the wild-type allele was highly methylated in the patient compared to the same site in both his healthy brothers. These results suggest that the co- deficient expression of POLG and SSBP1 genes could contribute to the development of mtDNA deletion.
Collapse
Affiliation(s)
- Yeonmi Lee
- Department of Convergence Medicine and Stem Cell Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.L.); (M.L.); (S.S.); (M.Z.K.)
| | - Taeho Kim
- Medical Genetics Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea; (T.K.); (G.H.S.); (I.H.C.)
| | - Miju Lee
- Department of Convergence Medicine and Stem Cell Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.L.); (M.L.); (S.S.); (M.Z.K.)
| | - Seongjun So
- Department of Convergence Medicine and Stem Cell Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.L.); (M.L.); (S.S.); (M.Z.K.)
| | - Mustafa Zafer Karagozlu
- Department of Convergence Medicine and Stem Cell Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.L.); (M.L.); (S.S.); (M.Z.K.)
| | - Go Hun Seo
- Medical Genetics Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea; (T.K.); (G.H.S.); (I.H.C.)
| | - In Hee Choi
- Medical Genetics Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea; (T.K.); (G.H.S.); (I.H.C.)
| | - Peter C. W. Lee
- Department of Biomedical Sciences, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea;
| | - Chong-Jai Kim
- Department of Pathology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea;
| | - Eunju Kang
- Department of Convergence Medicine and Stem Cell Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.L.); (M.L.); (S.S.); (M.Z.K.)
- Correspondence: (E.K.); (B.H.L.); Tel.: +82-2-3010-8547 (E.K.); +82-2-3010-5950 (B.H.L.)
| | - Beom Hee Lee
- Medical Genetics Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea; (T.K.); (G.H.S.); (I.H.C.)
- Correspondence: (E.K.); (B.H.L.); Tel.: +82-2-3010-8547 (E.K.); +82-2-3010-5950 (B.H.L.)
| |
Collapse
|
23
|
Crooks DR, Maio N, Lang M, Ricketts CJ, Vocke CD, Gurram S, Turan S, Kim YY, Cawthon GM, Sohelian F, De Val N, Pfeiffer RM, Jailwala P, Tandon M, Tran B, Fan TWM, Lane AN, Ried T, Wangsa D, Malayeri AA, Merino MJ, Yang Y, Meier JL, Ball MW, Rouault TA, Srinivasan R, Linehan WM. Mitochondrial DNA alterations underlie an irreversible shift to aerobic glycolysis in fumarate hydratase-deficient renal cancer. Sci Signal 2021; 14:14/664/eabc4436. [PMID: 33402335 DOI: 10.1126/scisignal.abc4436] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Understanding the mechanisms of the Warburg shift to aerobic glycolysis is critical to defining the metabolic basis of cancer. Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is an aggressive cancer characterized by biallelic inactivation of the gene encoding the Krebs cycle enzyme fumarate hydratase, an early shift to aerobic glycolysis, and rapid metastasis. We observed impairment of the mitochondrial respiratory chain in tumors from patients with HLRCC. Biochemical and transcriptomic analyses revealed that respiratory chain dysfunction in the tumors was due to loss of expression of mitochondrial DNA (mtDNA)-encoded subunits of respiratory chain complexes, caused by a marked decrease in mtDNA content and increased mtDNA mutations. We demonstrated that accumulation of fumarate in HLRCC tumors inactivated the core factors responsible for replication and proofreading of mtDNA, leading to loss of respiratory chain components, thereby promoting the shift to aerobic glycolysis and disease progression in this prototypic model of glucose-dependent human cancer.
Collapse
Affiliation(s)
- Daniel R Crooks
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Nunziata Maio
- Molecular Medicine Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Martin Lang
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Christopher J Ricketts
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Cathy D Vocke
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Sandeep Gurram
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Sevilay Turan
- Sequencing Facility, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research Inc., Frederick, MD 21701, USA
| | - Yun-Young Kim
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - G Mariah Cawthon
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Ferri Sohelian
- Electron Microscopy Laboratory, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research Inc., Frederick, MD 21702, USA
| | - Natalia De Val
- Electron Microscopy Laboratory, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research Inc., Frederick, MD 21702, USA
| | - Ruth M Pfeiffer
- Biostatistics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, MD 20850, USA
| | - Parthav Jailwala
- CCR Collaborative Bioinformatics Resource (CCBR), Frederick National Laboratory for Cancer Research, Leidos Biomedical Research Inc., Frederick, MD 21702, USA.,Advanced Biomedical Computational Science, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research Inc., Frederick, MD 21702, USA
| | - Mayank Tandon
- CCR Collaborative Bioinformatics Resource (CCBR), Frederick National Laboratory for Cancer Research, Leidos Biomedical Research Inc., Frederick, MD 21702, USA.,Advanced Biomedical Computational Science, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research Inc., Frederick, MD 21702, USA
| | - Bao Tran
- Sequencing Facility, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research Inc., Frederick, MD 21701, USA
| | - Teresa W-M Fan
- Center for Environmental and Systems Biochemistry, Department of Toxicology and Cancer Biology and Markey Cancer Center, University of Kentucky, Lexington, KY 40536, USA
| | - Andrew N Lane
- Center for Environmental and Systems Biochemistry, Department of Toxicology and Cancer Biology and Markey Cancer Center, University of Kentucky, Lexington, KY 40536, USA
| | - Thomas Ried
- Genetics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Darawalee Wangsa
- Genetics Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Ashkan A Malayeri
- Radiology and Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA
| | - Maria J Merino
- Genitourinary Pathology Section, Laboratory of Pathology, National Cancer Institute, Bethesda, MD 20892, USA
| | - Youfeng Yang
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Jordan L Meier
- Epigenetics and Metabolism Section, Chemical Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
| | - Mark W Ball
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Tracey A Rouault
- Molecular Medicine Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Ramaprasad Srinivasan
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - W Marston Linehan
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA.
| |
Collapse
|
24
|
Fontana GA, Gahlon HL. Mechanisms of replication and repair in mitochondrial DNA deletion formation. Nucleic Acids Res 2020; 48:11244-11258. [PMID: 33021629 PMCID: PMC7672454 DOI: 10.1093/nar/gkaa804] [Citation(s) in RCA: 102] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 09/07/2020] [Accepted: 09/25/2020] [Indexed: 02/06/2023] Open
Abstract
Deletions in mitochondrial DNA (mtDNA) are associated with diverse human pathologies including cancer, aging and mitochondrial disorders. Large-scale deletions span kilobases in length and the loss of these associated genes contributes to crippled oxidative phosphorylation and overall decline in mitochondrial fitness. There is not a united view for how mtDNA deletions are generated and the molecular mechanisms underlying this process are poorly understood. This review discusses the role of replication and repair in mtDNA deletion formation as well as nucleic acid motifs such as repeats, secondary structures, and DNA damage associated with deletion formation in the mitochondrial genome. We propose that while erroneous replication and repair can separately contribute to deletion formation, crosstalk between these pathways is also involved in generating deletions.
Collapse
Affiliation(s)
- Gabriele A Fontana
- Department of Health Sciences and Technology, ETH Zürich, Schmelzbergstrasse 9, 8092 Zürich, Switzerland
| | - Hailey L Gahlon
- To whom correspondence should be addressed. Tel: +41 44 632 3731;
| |
Collapse
|
25
|
A PRIMPOL mutation and variants in multiple genes may contribute to phenotypes in a familial case with chronic progressive external ophthalmoplegia symptoms. Neurosci Res 2020; 157:58-63. [DOI: 10.1016/j.neures.2019.07.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 07/04/2019] [Accepted: 07/22/2019] [Indexed: 11/22/2022]
|
26
|
Piro-Mégy C, Sarzi E, Tarrés-Solé A, Péquignot M, Hensen F, Quilès M, Manes G, Chakraborty A, Sénéchal A, Bocquet B, Cazevieille C, Roubertie A, Müller A, Charif M, Goudenège D, Lenaers G, Wilhelm H, Kellner U, Weisschuh N, Wissinger B, Zanlonghi X, Hamel C, Spelbrink JN, Sola M, Delettre C. Dominant mutations in mtDNA maintenance gene SSBP1 cause optic atrophy and foveopathy. J Clin Invest 2020; 130:143-156. [PMID: 31550237 PMCID: PMC6934222 DOI: 10.1172/jci128513] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 09/19/2019] [Indexed: 01/20/2023] Open
Abstract
Mutations in genes encoding components of the mitochondrial DNA (mtDNA) replication machinery cause mtDNA depletion syndromes (MDSs), which associate ocular features with severe neurological syndromes. Here, we identified heterozygous missense mutations in single-strand binding protein 1 (SSBP1) in 5 unrelated families, leading to the R38Q and R107Q amino acid changes in the mitochondrial single-stranded DNA-binding protein, a crucial protein involved in mtDNA replication. All affected individuals presented optic atrophy, associated with foveopathy in half of the cases. To uncover the structural features underlying SSBP1 mutations, we determined a revised SSBP1 crystal structure. Structural analysis suggested that both mutations affect dimer interactions and presumably distort the DNA-binding region. Using patient fibroblasts, we validated that the R38Q variant destabilizes SSBP1 dimer/tetramer formation, affects mtDNA replication, and induces mtDNA depletion. Our study showing that mutations in SSBP1 cause a form of dominant optic atrophy frequently accompanied with foveopathy brings insights into mtDNA maintenance disorders.
Collapse
Affiliation(s)
- Camille Piro-Mégy
- Institute of Neurosciences of Montpellier, INSERM, University of Montpellier, Montpellier, France
| | - Emmanuelle Sarzi
- Institute of Neurosciences of Montpellier, INSERM, University of Montpellier, Montpellier, France
| | - Aleix Tarrés-Solé
- Structural MitoLab, Department of Structural Biology, "Maria de Maeztu" Unit of Excellence, Molecular Biology Institute Barcelona (IBMB-CSIC), Barcelona, Spain
| | - Marie Péquignot
- Institute of Neurosciences of Montpellier, INSERM, University of Montpellier, Montpellier, France
| | - Fenna Hensen
- Radboud Center for Mitochondrial Medicine, Department of Paediatrics, Radboudumc, Nijmegen, Netherlands
| | - Mélanie Quilès
- Institute of Neurosciences of Montpellier, INSERM, University of Montpellier, Montpellier, France
| | - Gaël Manes
- Institute of Neurosciences of Montpellier, INSERM, University of Montpellier, Montpellier, France
| | - Arka Chakraborty
- Structural MitoLab, Department of Structural Biology, "Maria de Maeztu" Unit of Excellence, Molecular Biology Institute Barcelona (IBMB-CSIC), Barcelona, Spain
| | - Audrey Sénéchal
- Institute of Neurosciences of Montpellier, INSERM, University of Montpellier, Montpellier, France
| | - Béatrice Bocquet
- Institute of Neurosciences of Montpellier, INSERM, University of Montpellier, Montpellier, France.,CHU Montpellier, Centre of Reference for Genetic Sensory Diseases, Gui de Chauliac Hospital, Montpellier, France
| | - Chantal Cazevieille
- Institute of Neurosciences of Montpellier, INSERM, University of Montpellier, Montpellier, France
| | - Agathe Roubertie
- Institute of Neurosciences of Montpellier, INSERM, University of Montpellier, Montpellier, France.,CHU Montpellier, Centre of Reference for Genetic Sensory Diseases, Gui de Chauliac Hospital, Montpellier, France
| | - Agnès Müller
- Institute of Neurosciences of Montpellier, INSERM, University of Montpellier, Montpellier, France.,Faculté de Pharmacie, Université de Montpellier, Montpellier, France
| | - Majida Charif
- UMR CNRS 6015-INSERM U1083, MitoVasc Institute, Angers University, Angers, France
| | - David Goudenège
- UMR CNRS 6015-INSERM U1083, MitoVasc Institute, Angers University, Angers, France
| | - Guy Lenaers
- UMR CNRS 6015-INSERM U1083, MitoVasc Institute, Angers University, Angers, France
| | - Helmut Wilhelm
- University Eye Hospital, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Ulrich Kellner
- Rare Retinal Disease Center, AugenZentrum Siegburg, MVZ Augenärztliches Diagnostik- und Therapiecentrum Siegburg GmbH, Siegburg, Germany
| | - Nicole Weisschuh
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Bernd Wissinger
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Xavier Zanlonghi
- Centre de Compétence Maladie Rares, Clinique Pluridisciplinaire Jules Verne, Nantes, France
| | - Christian Hamel
- Institute of Neurosciences of Montpellier, INSERM, University of Montpellier, Montpellier, France.,CHU Montpellier, Centre of Reference for Genetic Sensory Diseases, Gui de Chauliac Hospital, Montpellier, France
| | - Johannes N Spelbrink
- Radboud Center for Mitochondrial Medicine, Department of Paediatrics, Radboudumc, Nijmegen, Netherlands
| | - Maria Sola
- Structural MitoLab, Department of Structural Biology, "Maria de Maeztu" Unit of Excellence, Molecular Biology Institute Barcelona (IBMB-CSIC), Barcelona, Spain
| | - Cécile Delettre
- Institute of Neurosciences of Montpellier, INSERM, University of Montpellier, Montpellier, France
| |
Collapse
|
27
|
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.
Collapse
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.
| |
Collapse
|
28
|
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.
Collapse
|
29
|
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.
Collapse
|
30
|
A Brief History of Mitochondrial Pathologies. Int J Mol Sci 2019; 20:ijms20225643. [PMID: 31718067 PMCID: PMC6888695 DOI: 10.3390/ijms20225643] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 10/22/2019] [Accepted: 10/23/2019] [Indexed: 01/19/2023] Open
Abstract
The history of "mitochondrial pathologies", namely genetic pathologies affecting mitochondrial metabolism because of mutations in nuclear DNA-encoded genes for proteins active inside mitochondria or mutations in mitochondrial DNA-encoded genes, began in 1988. In that year, two different groups of researchers discovered, respectively, large-scale single deletions of mitochondrial DNA (mtDNA) in muscle biopsies from patients with "mitochondrial myopathies" and a point mutation in the mtDNA gene for subunit 4 of NADH dehydrogenase (MTND4), associated with maternally inherited Leber's hereditary optic neuropathy (LHON). Henceforth, a novel conceptual "mitochondrial genetics", separate from mendelian genetics, arose, based on three features of mtDNA: (1) polyplasmy; (2) maternal inheritance; and (3) mitotic segregation. Diagnosis of mtDNA-related diseases became possible through genetic analysis and experimental approaches involving histochemical staining of muscle or brain sections, single-fiber polymerase chain reaction (PCR) of mtDNA, and the creation of patient-derived "cybrid" (cytoplasmic hybrid) immortal fibroblast cell lines. The availability of the above-mentioned techniques along with the novel sensitivity of clinicians to such disorders led to the characterization of a constantly growing number of pathologies. Here is traced a brief historical perspective on the discovery of autonomous pathogenic mtDNA mutations and on the related mendelian pathology altering mtDNA integrity.
Collapse
|
31
|
Tiosano D, Mears JA, Buchner DA. Mitochondrial Dysfunction in Primary Ovarian Insufficiency. Endocrinology 2019; 160:2353-2366. [PMID: 31393557 PMCID: PMC6760336 DOI: 10.1210/en.2019-00441] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 08/01/2019] [Indexed: 12/14/2022]
Abstract
Primary ovarian insufficiency (POI) is defined by the loss or dysfunction of ovarian follicles associated with amenorrhea before the age of 40. Symptoms include hot flashes, sleep disturbances, and depression, as well as reduced fertility and increased long-term risk of cardiovascular disease. POI occurs in ∼1% to 2% of women, although the etiology of most cases remains unexplained. Approximately 10% to 20% of POI cases are due to mutations in a single gene or a chromosomal abnormality, which has provided considerable molecular insight into the biological underpinnings of POI. Many of the genes for which mutations have been associated with POI, either isolated or syndromic cases, function within mitochondria, including MRPS22, POLG, TWNK, LARS2, HARS2, AARS2, CLPP, and LRPPRC. Collectively, these genes play roles in mitochondrial DNA replication, gene expression, and protein synthesis and degradation. Although mutations in these genes clearly implicate mitochondrial dysfunction in rare cases of POI, data are scant as to whether these genes in particular, and mitochondrial dysfunction in general, contribute to most POI cases that lack a known etiology. Further studies are needed to better elucidate the contribution of mitochondria to POI and determine whether there is a common molecular defect in mitochondrial function that distinguishes mitochondria-related genes that when mutated cause POI vs those that do not. Nonetheless, the clear implication of mitochondrial dysfunction in POI suggests that manipulation of mitochondrial function represents an important therapeutic target for the treatment or prevention of POI.
Collapse
Affiliation(s)
- Dov Tiosano
- Division of Pediatric Endocrinology, Ruth Rappaport Children’s Hospital, Rambam Medical Center, Haifa, Israel
- Rappaport Family Faculty of Medicine, Technion—Israel Institute of Technology, Haifa, Israel
| | - Jason A Mears
- Center for Mitochondrial Diseases, Case Western Reserve University, Cleveland, Ohio
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio
| | - David A Buchner
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, Ohio
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio
- Research Institute for Children’s Health, Case Western Reserve University, Cleveland, Ohio
| |
Collapse
|
32
|
Al Khatib I, Shutt TE. Advances Towards Therapeutic Approaches for mtDNA Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1158:217-246. [PMID: 31452143 DOI: 10.1007/978-981-13-8367-0_12] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mitochondria maintain and express their own genome, referred to as mtDNA, which is required for proper mitochondrial function. While mutations in mtDNA can cause a heterogeneous array of disease phenotypes, there is currently no cure for this collection of diseases. Here, we will cover characteristics of the mitochondrial genome important for understanding the pathology associated with mtDNA mutations, and review recent approaches that are being developed to treat and prevent mtDNA disease. First, we will discuss mitochondrial replacement therapy (MRT), where mitochondria from a healthy donor replace maternal mitochondria harbouring mutant mtDNA. In addition to ethical concerns surrounding this procedure, MRT is only applicable in cases where the mother is known or suspected to carry mtDNA mutations. Thus, there remains a need for other strategies to treat patients with mtDNA disease. To this end, we will also discuss several alternative means to reduce the amount of mutant mtDNA present in cells. Such methods, referred to as heteroplasmy shifting, have proven successful in animal models. In particular, we will focus on the approach of targeting engineered endonucleases to specifically cleave mutant mtDNA. Together, these approaches offer hope to prevent the transmission of mtDNA disease and potentially reduce the impact of mtDNA mutations.
Collapse
Affiliation(s)
- Iman Al Khatib
- Deparments of Medical Genetics and Biochemistry & Molecular Biology, Cumming School of Medicine, Alberta Children's Hospital Research Institute, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Timothy E Shutt
- Deparments of Medical Genetics and Biochemistry & Molecular Biology, Cumming School of Medicine, Alberta Children's Hospital Research Institute, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
| |
Collapse
|
33
|
Homozygous R627W mutations in POLG cause mitochondrial DNA depletion leading to encephalopathy, seizures and stroke-like episodes. Mitochondrion 2019; 48:78-83. [DOI: 10.1016/j.mito.2019.08.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 08/05/2019] [Accepted: 08/14/2019] [Indexed: 01/21/2023]
|
34
|
Lee SJ, Kanwal S, Yoo DH, Park HR, Choi BO, Chung KW. A POLG2 Homozygous Mutation in an Autosomal Recessive Epilepsy Family Without Ophthalmoplegia. J Clin Neurol 2019; 15:418-420. [PMID: 31286721 PMCID: PMC6620465 DOI: 10.3988/jcn.2019.15.3.418] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 04/09/2019] [Accepted: 04/09/2019] [Indexed: 11/17/2022] Open
Affiliation(s)
- Su Jeong Lee
- Department of Biological Sciences, Kongju National University, Gongju, Korea
| | - Sumaira Kanwal
- Department of Biosciences, COMSATS University Islamabad, Sahiwal, Pakistan
| | - Da Hye Yoo
- Department of Biological Sciences, Kongju National University, Gongju, Korea
| | - Hye Ri Park
- Department of Biological Sciences, Kongju National University, Gongju, Korea
| | - Byung Ok Choi
- Department of Neurology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
| | - Ki Wha Chung
- Department of Biological Sciences, Kongju National University, Gongju, Korea.
| |
Collapse
|
35
|
Peter B, Farge G, Pardo-Hernandez C, Tångefjord S, Falkenberg M. Structural basis for adPEO-causing mutations in the mitochondrial TWINKLE helicase. Hum Mol Genet 2019; 28:1090-1099. [PMID: 30496414 PMCID: PMC6423418 DOI: 10.1093/hmg/ddy415] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 11/27/2018] [Accepted: 11/28/2018] [Indexed: 11/13/2022] Open
Abstract
TWINKLE is the helicase involved in replication and maintenance of mitochondrial DNA (mtDNA) in mammalian cells. Structurally, TWINKLE is closely related to the bacteriophage T7 gp4 protein and comprises a helicase and primase domain joined by a flexible linker region. Mutations in and around this linker region are responsible for autosomal dominant progressive external ophthalmoplegia (adPEO), a neuromuscular disorder associated with deletions in mtDNA. The underlying molecular basis of adPEO-causing mutations remains unclear, but defects in TWINKLE oligomerization are thought to play a major role. In this study, we have characterized these disease variants by single-particle electron microscopy and can link the diminished activities of the TWINKLE variants to altered oligomeric properties. Our results suggest that the mutations can be divided into those that (i) destroy the flexibility of the linker region, (ii) inhibit ring closure and (iii) change the number of subunits within a helicase ring. Furthermore, we demonstrate that wild-type TWINKLE undergoes large-scale conformational changes upon nucleoside triphosphate binding and that this ability is lost in the disease-causing variants. This represents a substantial advancement in the understanding of the molecular basis of adPEO and related pathologies and may aid in the development of future therapeutic strategies.
Collapse
Affiliation(s)
- Bradley Peter
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Sweden
| | - Geraldine Farge
- Centre Nacionale de la Recherche Scientifique/Institut National de Physique Nucléaire et des Particules, Laboratoire de Physique de Clermont, Université Clermont Auvergne, BP 10448, Clermont-Ferrand, France
| | | | - Stefan Tångefjord
- Discovery Sciences, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Maria Falkenberg
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Sweden
| |
Collapse
|
36
|
Chen Z, Zhang F, Xu H. Human mitochondrial DNA diseases and Drosophila models. J Genet Genomics 2019; 46:201-212. [DOI: 10.1016/j.jgg.2019.03.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 03/05/2019] [Accepted: 03/25/2019] [Indexed: 01/06/2023]
|
37
|
Gorvin CM, Ahmad BN, Stechman MJ, Loh NY, Hough TA, Leo P, Marshall M, Sethi S, Bentley L, Piret SE, Reed A, Jeyabalan J, Christie PT, Wells S, Simon MM, Mallon AM, Schulz H, Huebner N, Brown MA, Cox RD, Brown SD, Thakker RV. An N-Ethyl-N-Nitrosourea (ENU)-Induced Tyr265Stop Mutation of the DNA Polymerase Accessory Subunit Gamma 2 (Polg2) Is Associated With Renal Calcification in Mice. J Bone Miner Res 2019; 34:497-507. [PMID: 30395686 PMCID: PMC6446808 DOI: 10.1002/jbmr.3624] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2018] [Revised: 10/12/2018] [Accepted: 10/28/2018] [Indexed: 12/24/2022]
Abstract
Renal calcification (RCALC) resulting in nephrolithiasis and nephrocalcinosis, which affects ∼10% of adults by 70 years of age, involves environmental and genetic etiologies. Thus, nephrolithiasis and nephrocalcinosis occurs as an inherited disorder in ∼65% of patients, and may be associated with endocrine and metabolic disorders including: primary hyperparathyroidism, hypercalciuria, renal tubular acidosis, cystinuria, and hyperoxaluria. Investigations of families with nephrolithiasis and nephrocalcinosis have identified some causative genes, but further progress is limited as large families are unavailable for genetic studies. We therefore embarked on establishing mouse models for hereditary nephrolithiasis and nephrocalcinosis by performing abdominal X-rays to identify renal opacities in N-ethyl-N-nitrosourea (ENU)-mutagenized mice. This identified a mouse with RCALC inherited as an autosomal dominant trait, designated RCALC type 2 (RCALC2). Genomewide mapping located the Rcalc2 locus to a ∼16-Mbp region on chromosome 11D-E2 and whole-exome sequence analysis identified a heterozygous mutation in the DNA polymerase gamma-2, accessory subunit (Polg2) resulting in a nonsense mutation, Tyr265Stop (Y265X), which co-segregated with RCALC2. Kidneys of mutant mice (Polg2+/Y265X ) had lower POLG2 mRNA and protein expression, compared to wild-type littermates (Polg2+/+ ). The Polg2+/Y265X and Polg2+/+ mice had similar plasma concentrations of sodium, potassium, calcium, phosphate, chloride, urea, creatinine, glucose, and alkaline phosphatase activity; and similar urinary fractional excretion of calcium, phosphate, oxalate, and protein. Polg2 encodes the minor subunit of the mitochondrial DNA (mtDNA) polymerase and the mtDNA content in Polg2+/Y265X kidneys was reduced compared to Polg2+/+ mice, and cDNA expression profiling revealed differential expression of 26 genes involved in several biological processes including mitochondrial DNA function, apoptosis, and ubiquitination, the complement pathway, and inflammatory pathways. In addition, plasma of Polg2+/Y265X mice, compared to Polg2+/+ littermates had higher levels of reactive oxygen species. Thus, our studies have identified a mutant mouse model for inherited renal calcification associated with a Polg2 nonsense mutation. © 2018 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Caroline M Gorvin
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Bushra N Ahmad
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Michael J Stechman
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Nellie Y Loh
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Tertius A Hough
- Mary Lyon Centre and Mammalian Genetics Unit, Medical Research Council, Harwell, UK
| | - Paul Leo
- Translational Genomics Group, Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology at Translational Research Institute, Brisbane, Australia
| | - Mhairi Marshall
- Translational Genomics Group, Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology at Translational Research Institute, Brisbane, Australia
| | - Siddharth Sethi
- Mary Lyon Centre and Mammalian Genetics Unit, Medical Research Council, Harwell, UK
| | - Liz Bentley
- Mary Lyon Centre and Mammalian Genetics Unit, Medical Research Council, Harwell, UK
| | - Sian E Piret
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Anita Reed
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Jeshmi Jeyabalan
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Paul T Christie
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Sara Wells
- Mary Lyon Centre and Mammalian Genetics Unit, Medical Research Council, Harwell, UK
| | - Michelle M Simon
- Mary Lyon Centre and Mammalian Genetics Unit, Medical Research Council, Harwell, UK
| | - Ann-Marie Mallon
- Mary Lyon Centre and Mammalian Genetics Unit, Medical Research Council, Harwell, UK
| | - Herbert Schulz
- Max-Delbrück-Center for Molecular Medicine, Berlin, Germany
| | | | - Matthew A Brown
- Translational Genomics Group, Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology at Translational Research Institute, Brisbane, Australia
| | - Roger D Cox
- Mary Lyon Centre and Mammalian Genetics Unit, Medical Research Council, Harwell, UK
| | - Steve D Brown
- Mary Lyon Centre and Mammalian Genetics Unit, Medical Research Council, Harwell, UK
| | - Rajesh V Thakker
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| |
Collapse
|
38
|
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.
Collapse
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:
| |
Collapse
|
39
|
Molecular signature pathway of gene protein interaction in human mitochondrial DNA (mtDNA) metabolism linked disease. INDIAN JOURNAL OF MEDICAL SPECIALITIES 2018. [DOI: 10.1016/j.injms.2018.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
40
|
Mice lacking the mitochondrial exonuclease MGME1 accumulate mtDNA deletions without developing progeria. Nat Commun 2018; 9:1202. [PMID: 29572490 PMCID: PMC5865154 DOI: 10.1038/s41467-018-03552-x] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 02/21/2018] [Indexed: 12/17/2022] Open
Abstract
Replication of mammalian mitochondrial DNA (mtDNA) is an essential process that requires high fidelity and control at multiple levels to ensure proper mitochondrial function. Mutations in the mitochondrial genome maintenance exonuclease 1 (MGME1) gene were recently reported in mitochondrial disease patients. Here, to study disease pathophysiology, we generated Mgme1 knockout mice and report that homozygous knockouts develop depletion and multiple deletions of mtDNA. The mtDNA replication stalling phenotypes vary dramatically in different tissues of Mgme1 knockout mice. Mice with MGME1 deficiency accumulate a long linear subgenomic mtDNA species, similar to the one found in mtDNA mutator mice, but do not develop progeria. This finding resolves a long-standing debate by showing that point mutations of mtDNA are the main cause of progeria in mtDNA mutator mice. We also propose a role for MGME1 in the regulation of replication and transcription termination at the end of the control region of mtDNA. It has been debated whether premature ageing in mitochondrial DNA mutator mice is driven by point mutations or deletions of mtDNA. Matic et al generate Mgme1 knockout mice and show here that these mice have tissue-specific replication stalling and accumulate deleted mtDNA, without developing progeria.
Collapse
|
41
|
Kuszak AJ, Espey MG, Falk MJ, Holmbeck MA, Manfredi G, Shadel GS, Vernon HJ, Zolkipli-Cunningham Z. Nutritional Interventions for Mitochondrial OXPHOS Deficiencies: Mechanisms and Model Systems. ANNUAL REVIEW OF PATHOLOGY 2018; 13:163-191. [PMID: 29099651 PMCID: PMC5911915 DOI: 10.1146/annurev-pathol-020117-043644] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Multisystem metabolic disorders caused by defects in oxidative phosphorylation (OXPHOS) are severe, often lethal, conditions. Inborn errors of OXPHOS function are termed primary mitochondrial disorders (PMDs), and the use of nutritional interventions is routine in their supportive management. However, detailed mechanistic understanding and evidence for efficacy and safety of these interventions are limited. Preclinical cellular and animal model systems are important tools to investigate PMD metabolic mechanisms and therapeutic strategies. This review assesses the mechanistic rationale and experimental evidence for nutritional interventions commonly used in PMDs, including micronutrients, metabolic agents, signaling modifiers, and dietary regulation, while highlighting important knowledge gaps and impediments for randomized controlled trials. Cellular and animal model systems that recapitulate mutations and clinical manifestations of specific PMDs are evaluated for their potential in determining pathological mechanisms, elucidating therapeutic health outcomes, and investigating the value of nutritional interventions for mitochondrial disease conditions.
Collapse
Affiliation(s)
- Adam J Kuszak
- Office of Dietary Supplements, National Institutes of Health, Bethesda, Maryland 20852, USA;
| | - Michael Graham Espey
- Division of Cancer Biology, National Cancer Institute, Rockville, Maryland 20850, USA;
| | - Marni J Falk
- Department of Pediatrics, Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA;
- Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Marissa A Holmbeck
- Department of Pathology, Yale School of Medicine, New Haven, Connecticut 06510-8023, USA;
| | - Giovanni Manfredi
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY 10065, USA;
| | - Gerald S Shadel
- Department of Pathology, Yale School of Medicine, New Haven, Connecticut 06510-8023, USA;
- Department of Genetics, Yale School of Medicine, New Haven, Connecticut 06520-8023, USA;
| | - Hilary J Vernon
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA;
| | - Zarazuela Zolkipli-Cunningham
- Department of Pediatrics, Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA;
| |
Collapse
|
42
|
Chan SSL. Inherited mitochondrial genomic instability and chemical exposures. Toxicology 2017; 391:75-83. [PMID: 28756246 DOI: 10.1016/j.tox.2017.07.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 06/12/2017] [Accepted: 07/24/2017] [Indexed: 12/21/2022]
Abstract
There are approximately 1500 proteins that are needed for mitochondrial structure and function, most of which are encoded in the nuclear genome (Calvo et al., 2006). Each mitochondrion has its own genome (mtDNA), which in humans encodes 13 polypeptides, 22 tRNAs and 2 rRNAs required for oxidative phosphorylation. The mitochondrial genome of humans and most vertebrates is approximately 16.5kbp, double-stranded, circular, with few non-coding bases. Thus, maintaining mtDNA stability, that is, the ability of the cell to maintain adequate levels of mtDNA template for oxidative phosphorylation is essential and can be impacted by the level of mtDNA mutation currently within the cell or mitochondrion, but also from errors made during normal mtDNA replication, defects in mitochondrial quality control mechanisms, and exacerbated by exposures to exogenous and/or endogenous genotoxic agents. In this review, we expand on the origins and consequences of mtDNA instability, the current state of research regarding the mechanisms by which mtDNA instability can be overcome by cellular and chemical interventions, and the future of research and treatments for mtDNA instability.
Collapse
Affiliation(s)
- Sherine S L Chan
- Drug Discovery and Biomedical Sciences, College of Pharmacy, Medical University of South Carolina, Charleston, SC 29425, United States; Neuroene Therapeutics, Mt. Pleasant, SC 29464, United States.
| |
Collapse
|
43
|
Pyal A, Paramasivam A, Meena AK, Bhavana VB, Thangaraj K. MPV17 hepatocerebral mitochondrial DNA depletion syndrome presenting as acute flaccid paralysis - A case report. Mitochondrion 2017; 37:41-45. [PMID: 28673863 DOI: 10.1016/j.mito.2017.06.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 04/29/2017] [Accepted: 06/19/2017] [Indexed: 12/01/2022]
Abstract
Mutations in human MPV17 have been reported in patients with severe mitochondrial DNA (mtDNA) depletion manifesting as early childhood onset failure to thrive, hypoglycemia, encephalopathy and progressive liver failure. We describe an 11 year old girl, born to consanguineous parents, who presented with rapidly progressive weakness of all 4 limbs with symmetrical proximal and distal weakness, gastrointestinal disease and leukoencephalopathy. Genetic analysis of the patient revealed a homozygous pathogenic mutation c.121C>T (p.R41W) in the MPV17 gene. Further, screening for this mutation in the parents revealed the presence of heterozygous mutation in both the parents, suggesting the recessive nature of the disease.
Collapse
Affiliation(s)
- Anjan Pyal
- Department of Neurology, Nizam's Institute of Medical Sciences, Hyderabad, India
| | | | | | | | | |
Collapse
|
44
|
Viscomi C, Zeviani M. MtDNA-maintenance defects: syndromes and genes. J Inherit Metab Dis 2017; 40:587-599. [PMID: 28324239 PMCID: PMC5500664 DOI: 10.1007/s10545-017-0027-5] [Citation(s) in RCA: 123] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 02/10/2017] [Accepted: 02/13/2017] [Indexed: 02/02/2023]
Abstract
A large group of mitochondrial disorders, ranging from early-onset pediatric encephalopathic syndromes to late-onset myopathy with chronic progressive external ophthalmoplegia (CPEOs), are inherited as Mendelian disorders characterized by disturbed mitochondrial DNA (mtDNA) maintenance. These errors of nuclear-mitochondrial intergenomic signaling may lead to mtDNA depletion, accumulation of mtDNA multiple deletions, or both, in critical tissues. The genes involved encode proteins belonging to at least three pathways: mtDNA replication and maintenance, nucleotide supply and balance, and mitochondrial dynamics and quality control. In most cases, allelic mutations in these genes may lead to profoundly different phenotypes associated with either mtDNA depletion or multiple deletions.
Collapse
Affiliation(s)
- Carlo Viscomi
- MRC-Mitochondrial Biology Unit, MRC MBU, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK
| | - Massimo Zeviani
- MRC-Mitochondrial Biology Unit, MRC MBU, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK.
| |
Collapse
|
45
|
El-Hattab AW, Craigen WJ, Scaglia F. Mitochondrial DNA maintenance defects. Biochim Biophys Acta Mol Basis Dis 2017; 1863:1539-1555. [PMID: 28215579 DOI: 10.1016/j.bbadis.2017.02.017] [Citation(s) in RCA: 180] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 01/31/2017] [Accepted: 02/14/2017] [Indexed: 01/12/2023]
Abstract
The maintenance of mitochondrial DNA (mtDNA) depends on a number of nuclear gene-encoded proteins including a battery of enzymes forming the replisome needed to synthesize mtDNA. These enzymes need to be in balanced quantities to function properly that is in part achieved by exchanging intramitochondrial contents through mitochondrial fusion. In addition, mtDNA synthesis requires a balanced supply of nucleotides that is achieved by nucleotide recycling inside the mitochondria and import from the cytosol. Mitochondrial DNA maintenance defects (MDMDs) are a group of diseases caused by pathogenic variants in the nuclear genes involved in mtDNA maintenance resulting in impaired mtDNA synthesis leading to quantitative (mtDNA depletion) and qualitative (multiple mtDNA deletions) defects in mtDNA. Defective mtDNA leads to organ dysfunction due to insufficient mtDNA-encoded protein synthesis, resulting in an inadequate energy production to meet the needs of affected organs. MDMDs are inherited as autosomal recessive or dominant traits, and are associated with a broad phenotypic spectrum ranging from mild adult-onset ophthalmoplegia to severe infantile fatal hepatic failure. To date, pathogenic variants in 20 nuclear genes known to be crucial for mtDNA maintenance have been linked to MDMDs, including genes encoding enzymes of mtDNA replication machinery (POLG, POLG2, TWNK, TFAM, RNASEH1, MGME1, and DNA2), genes encoding proteins that function in maintaining a balanced mitochondrial nucleotide pool (TK2, DGUOK, SUCLG1, SUCLA2, ABAT, RRM2B, TYMP, SLC25A4, AGK, and MPV17), and genes encoding proteins involved in mitochondrial fusion (OPA1, MFN2, and FBXL4).
Collapse
Affiliation(s)
- Ayman W El-Hattab
- Division of Clinical Genetics and Metabolic Disorders, Pediatrics Department, Tawam Hospital, Al-Ain, United Arab Emirates
| | - William J Craigen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
| | - Fernando Scaglia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| |
Collapse
|
46
|
DeBalsi KL, Longley MJ, Hoff KE, Copeland WC. Synergistic Effects of the in cis T251I and P587L Mitochondrial DNA Polymerase γ Disease Mutations. J Biol Chem 2017; 292:4198-4209. [PMID: 28154168 DOI: 10.1074/jbc.m116.773341] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 01/26/2017] [Indexed: 01/28/2023] Open
Abstract
Human mitochondrial DNA (mtDNA) polymerase γ (Pol γ) is the only polymerase known to replicate the mitochondrial genome. The Pol γ holoenzyme consists of the p140 catalytic subunit (POLG) and the p55 homodimeric accessory subunit (POLG2), which enhances binding of Pol γ to DNA and promotes processivity of the holoenzyme. Mutations within POLG impede maintenance of mtDNA and cause mitochondrial diseases. Two common POLG mutations usually found in cis in patients primarily with progressive external ophthalmoplegia generate T251I and P587L amino acid substitutions. To determine whether T251I or P587L is the primary pathogenic allele or whether both substitutions are required to cause disease, we overproduced and purified WT, T251I, P587L, and T251I + P587L double variant forms of recombinant Pol γ. Biochemical characterization of these variants revealed impaired DNA binding affinity, reduced thermostability, diminished exonuclease activity, defective catalytic activity, and compromised DNA processivity, even in the presence of the p55 accessory subunit. However, physical association with p55 was unperturbed, suggesting intersubunit affinities similar to WT. Notably, although the single mutants were similarly impaired, a dramatic synergistic effect was found for the double mutant across all parameters. In conclusion, our analyses suggest that individually both T251I and P587L substitutions functionally impair Pol γ, with greater pathogenicity predicted for the single P587L variant. Combining T251I and P587L induces extreme thermal lability and leads to synergistic nucleotide and DNA binding defects, which severely impair catalytic activity and correlate with presentation of disease in patients.
Collapse
Affiliation(s)
- Karen L DeBalsi
- From the Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Matthew J Longley
- From the Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Kirsten E Hoff
- From the Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - William C Copeland
- From the Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709
| |
Collapse
|
47
|
DeBalsi KL, Hoff KE, Copeland WC. Role of the mitochondrial DNA replication machinery in mitochondrial DNA mutagenesis, aging and age-related diseases. Ageing Res Rev 2017; 33:89-104. [PMID: 27143693 DOI: 10.1016/j.arr.2016.04.006] [Citation(s) in RCA: 117] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 04/19/2016] [Accepted: 04/19/2016] [Indexed: 12/19/2022]
Abstract
As regulators of bioenergetics in the cell and the primary source of endogenous reactive oxygen species (ROS), dysfunctional mitochondria have been implicated for decades in the process of aging and age-related diseases. Mitochondrial DNA (mtDNA) is replicated and repaired by nuclear-encoded mtDNA polymerase γ (Pol γ) and several other associated proteins, which compose the mtDNA replication machinery. Here, we review evidence that errors caused by this replication machinery and failure to repair these mtDNA errors results in mtDNA mutations. Clonal expansion of mtDNA mutations results in mitochondrial dysfunction, such as decreased electron transport chain (ETC) enzyme activity and impaired cellular respiration. We address the literature that mitochondrial dysfunction, in conjunction with altered mitochondrial dynamics, is a major driving force behind aging and age-related diseases. Additionally, interventions to improve mitochondrial function and attenuate the symptoms of aging are examined.
Collapse
Affiliation(s)
- Karen L DeBalsi
- 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
| | - 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.
| |
Collapse
|
48
|
Van Maldergem L, Besse A, De Paepe B, Blakely EL, Appadurai V, Humble MM, Piard J, Craig K, He L, Hella P, Debray FG, Martin JJ, Gaussen M, Laloux P, Stevanin G, Van Coster R, Taylor RW, Copeland WC, Mormont E, Bonnen PE. POLG2 deficiency causes adult-onset syndromic sensory neuropathy, ataxia and parkinsonism. Ann Clin Transl Neurol 2016; 4:4-14. [PMID: 28078310 PMCID: PMC5221457 DOI: 10.1002/acn3.361] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 08/09/2016] [Accepted: 08/12/2016] [Indexed: 01/06/2023] Open
Abstract
Objective Mitochondrial dysfunction plays a key role in the pathophysiology of neurodegenerative disorders such as ataxia and Parkinson's disease. We describe an extended Belgian pedigree where seven individuals presented with adult‐onset cerebellar ataxia, axonal peripheral ataxic neuropathy, and tremor, in variable combination with parkinsonism, seizures, cognitive decline, and ophthalmoplegia. We sought to identify the underlying molecular etiology and characterize the mitochondrial pathophysiology of this neurological syndrome. Methods Clinical, neurophysiological, and neuroradiological evaluations were conducted. Patient muscle and cultured fibroblasts underwent extensive analyses to assess mitochondrial function. Genetic studies including genome‐wide sequencing were conducted. Results Hallmarks of mitochondrial dysfunction were present in patients’ tissues including ultrastructural anomalies of mitochondria, mosaic cytochrome c oxidase deficiency, and multiple mtDNA deletions. We identified a splice acceptor variant in POLG2, c.970‐1G>C, segregating with disease in this family and associated with a concomitant decrease in levels of POLG2 protein in patient cells. Interpretation This work extends the clinical spectrum of POLG2 deficiency to include an overwhelming, adult‐onset neurological syndrome that includes cerebellar syndrome, peripheral neuropathy, tremor, and parkinsonism. We therefore suggest to include POLG2 sequencing in the evaluation of ataxia and sensory neuropathy in adults, especially when it is accompanied by tremor or parkinsonism with white matter disease. The demonstration that deletions of mtDNA resulting from autosomal‐dominant POLG2 variant lead to a monogenic neurodegenerative multicomponent syndrome provides further evidence for a major role of mitochondrial dysfunction in the pathomechanism of nonsyndromic forms of the component neurodegenerative disorders.
Collapse
Affiliation(s)
- Lionel Van Maldergem
- Centre de génétique humaine Université de Franche-Comté Besançon France; Metabolic Unit Centre of Human Genetics University Hospital Liège Belgium
| | - Arnaud Besse
- Department of Molecular and Human Genetics Baylor College of Medicine Houston Texas
| | - Boel De Paepe
- Department of Pediatrics Division of Child Neurology & Metabolism Ghent University Hospital Belgium
| | - Emma L Blakely
- Wellcome Trust Centre for Mitochondrial Research Institute of Neuroscience Newcastle University Newcastle upon Tyne United Kingdom
| | - Vivek Appadurai
- Department of Molecular and Human Genetics Baylor College of Medicine Houston Texas
| | - Margaret M Humble
- Mitochondrial DNA Replication Group National Institute of Environmental Health Sciences Durham North Carolina
| | - Juliette Piard
- Centre de génétique humaine Université de Franche-Comté Besançon France
| | - Kate Craig
- Wellcome Trust Centre for Mitochondrial Research Institute of Neuroscience Newcastle University Newcastle upon Tyne United Kingdom
| | - Langping He
- Wellcome Trust Centre for Mitochondrial Research Institute of Neuroscience Newcastle University Newcastle upon Tyne United Kingdom
| | - Pierre Hella
- Department of Neurology Sambre and Meuse Regional Hospital Namur Belgium
| | | | | | - Marion Gaussen
- Inserm U1127 CNRS UMR 7225 Sorbonne Universités UPMC Paris France; Institut du Cerveau et de la Moelle épinière Hopital Pitié-Salpêtrière Paris France; Ecole Pratique des Hautes Etudes PSL Université Laboratoire de neurogénétique F-75013 Paris France
| | - Patrice Laloux
- Université catholique de Louvain CHU UCL Namur Department of Neurology B5530 Yvoir Belgium; UCL Institute of Neuroscience (IoNS) B1200 Brussels Belgium
| | - Giovanni Stevanin
- Inserm U1127 CNRS UMR 7225 Sorbonne Universités UPMC Paris France; Institut du Cerveau et de la Moelle épinière Hopital Pitié-Salpêtrière Paris France; Ecole Pratique des Hautes Etudes PSL Université Laboratoire de neurogénétique F-75013 Paris France
| | - Rudy Van Coster
- Department of Pediatrics Division of Child Neurology & Metabolism Ghent University Hospital Belgium
| | - Robert W Taylor
- Wellcome Trust Centre for Mitochondrial Research Institute of Neuroscience Newcastle University Newcastle upon Tyne United Kingdom
| | - William C Copeland
- Mitochondrial DNA Replication Group National Institute of Environmental Health Sciences Durham North Carolina
| | - Eric Mormont
- Université catholique de Louvain CHU UCL Namur Department of Neurology B5530 Yvoir Belgium; UCL Institute of Neuroscience (IoNS) B1200 Brussels Belgium
| | - Penelope E Bonnen
- Department of Molecular and Human Genetics Baylor College of Medicine Houston Texas
| |
Collapse
|
49
|
Nascimento A, Ortez C, Jou C, O'Callaghan M, Ramos F, Garcia-Cazorla À. Neuromuscular Manifestations in Mitochondrial Diseases in Children. Semin Pediatr Neurol 2016; 23:290-305. [PMID: 28284391 DOI: 10.1016/j.spen.2016.11.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Mitochondrial diseases exhibit significant clinical and genetic heterogeneity. Mitochondria are highly dynamic organelles that are the major contributor of adenosine triphosphate, through oxidative phosphorylation. These disorders may be developed at any age, with isolated or multiple system involvement, and in any pattern of inheritance. Defects in the mitochondrial respiratory chain impair energy production and almost invariably involve skeletal muscle and peripheral nerves, causing exercise intolerance, cramps, recurrent myoglobinuria, or fixed weakness, which often affects extraocular muscles and results in droopy eyelids (ptosis), progressive external ophthalmoplegia, peripheral ataxia, and peripheral polyneuropathy. This review describes the main neuromuscular symptomatology through different syndromes reported in the literature and from our experience. We want to highlight the importance of searching for the "clue clinical signs" associated with inheritance pattern as key elements to guide the complex diagnosis process and genetic studies in mitochondrial diseases.
Collapse
Affiliation(s)
- Andrés Nascimento
- Department of Neurology, Neuromuscular Units, Hospital Sant Joan de Déu, Instituto de Salud Carlos III, Barcelona, Spain; Center for Biomedical Research on Rare Diseases (CIBERER), Institute of Pediatric Research Sant Joan de Déu, Madrid, Spain.
| | - Carlos Ortez
- Department of Neurology, Neuromuscular Units, Hospital Sant Joan de Déu, Instituto de Salud Carlos III, Barcelona, Spain
| | - Cristina Jou
- Department of Neurology, Neuromuscular Units, Hospital Sant Joan de Déu, Instituto de Salud Carlos III, Barcelona, Spain; Center for Biomedical Research on Rare Diseases (CIBERER), Institute of Pediatric Research Sant Joan de Déu, Madrid, Spain
| | - Mar O'Callaghan
- Center for Biomedical Research on Rare Diseases (CIBERER), Institute of Pediatric Research Sant Joan de Déu, Madrid, Spain; Department of Neurology, Neurometabolic Units, Hospital Sant Joan de Déu, Instituto de Salud Carlos III, Barcelona, Spain
| | - Federico Ramos
- Center for Biomedical Research on Rare Diseases (CIBERER), Institute of Pediatric Research Sant Joan de Déu, Madrid, Spain; Department of Neurology, Neurometabolic Units, Hospital Sant Joan de Déu, Instituto de Salud Carlos III, Barcelona, Spain
| | - Àngels Garcia-Cazorla
- Center for Biomedical Research on Rare Diseases (CIBERER), Institute of Pediatric Research Sant Joan de Déu, Madrid, Spain; Department of Neurology, Neurometabolic Units, Hospital Sant Joan de Déu, Instituto de Salud Carlos III, Barcelona, Spain
| |
Collapse
|
50
|
Abstract
Mitochondrial diseases are a group of genetic disorders that are characterized by defects in oxidative phosphorylation and caused by mutations in genes in the nuclear DNA (nDNA) and mitochondrial DNA (mtDNA) that encode structural mitochondrial proteins or proteins involved in mitochondrial function. Mitochondrial diseases are the most common group of inherited metabolic disorders and are among the most common forms of inherited neurological disorders. One of the challenges of mitochondrial diseases is the marked clinical variation seen in patients, which can delay diagnosis. However, advances in next-generation sequencing techniques have substantially improved diagnosis, particularly in children. Establishing a genetic diagnosis allows patients with mitochondrial diseases to have reproductive options, but this is more challenging for women with pathogenetic mtDNA mutations that are strictly maternally inherited. Recent advances in in vitro fertilization techniques, including mitochondrial donation, will offer a better reproductive choice for these women in the future. The treatment of patients with mitochondrial diseases remains a challenge, but guidelines are available to manage the complications of disease. Moreover, an increasing number of therapeutic options are being considered, and with the development of large cohorts of patients and biomarkers, several clinical trials are in progress.
Collapse
|