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Selvanathan A, Teo J, Parayil Sankaran B. Hematologic Manifestations in Primary Mitochondrial Diseases. J Pediatr Hematol Oncol 2024; 46:e338-e347. [PMID: 38857202 DOI: 10.1097/mph.0000000000002890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Accepted: 04/23/2024] [Indexed: 06/12/2024]
Abstract
Primary mitochondrial disorders (PMDs) are known for their pleiotropic manifestations in humans, affecting almost any organ or system at any time. Hematologic manifestations, such as cytopenias and sideroblastic anemia, occur in 10% to 30% of patients with confirmed PMDs. These can be the initial presenting features or complications that develop over time. Surveillance for these manifestations allows for prompt identification and treatment. This article provides an overview of the pathophysiology underpinning the hematologic effects of mitochondrial dysfunction, discussing the 3 key roles of the mitochondria in hematopoiesis: providing energy for cell differentiation and function, synthesizing heme, and generating iron-sulfur clusters. Subsequently, the diagnosis and management of mitochondrial disorders are discussed, focusing on hematologic manifestations and the specific conditions commonly associated with them. Through this, we aimed to provide a concise point of reference for those considering a mitochondrial cause for a patient's hematologic abnormality, or for those considering a hematologic manifestation in a patient with known or suspected mitochondrial disease.
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Affiliation(s)
- Arthavan Selvanathan
- Genetic Metabolic Disorders Service, The Children's Hospital at Westmead, Westmead, NSW, Australia
| | - Juliana Teo
- Haematology Department, The Children's Hospital at Westmead, Westmead, NSW, Australia
| | - Bindu Parayil Sankaran
- Discipline of Child and Adolescent Health, Faculty of Medicine and Health, University of Sydney, NSW, Australia
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2
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Liu H, Gao M, Sun Q, Chen S, Luo Y, Yang H, Li Q, Li J, Yang G. A case of mitochondrial myopathy and chronic progressive external ophthalmoplegia. ZHONG NAN DA XUE XUE BAO. YI XUE BAN = JOURNAL OF CENTRAL SOUTH UNIVERSITY. MEDICAL SCIENCES 2023; 48:1760-1768. [PMID: 38432868 PMCID: PMC10929950 DOI: 10.11817/j.issn.1672-7347.2023.220605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Indexed: 03/05/2024]
Abstract
Mitochondrial myopathy is a group of multi-system diseases in which mitochondrial DNA (mtDNA) or nuclear DNA (nDNA) defects lead to structural and functional dysfunction of mitochondria. The clinical manifestations of mitochondrial myopathy are complex and varied, and the testing for mtDNA and nDNA is not widely available, so misdiagnosis or missed diagnosis is common. Chronic progressive external ophthalmoplegia (CPEO) is a common type of mitochondrial myopathy, which is characterized by blepharoptosis. Here we report a 38-year-old female with mitochondrial myopathy presented with chronic numbness and weakness of the limbs, accompanied by blepharoptosis that was recently noticed. Laboratory and head magnetic resonance imaging (MRI) examinations showed no obvious abnormalities. Muscle and nerve biopsies showed characteristic ragged red fibers (RRFs) and large aggregates of denatured mitochondria. Testing for mtDNA and nDNA showed a known mutation c.2857C>T (p.R953C) and a novel variant c.2391G>C (p.M797I) in the polymerase gamma (POLG)gene, so the patient was diagnosed as mitochondrial myopathy. Clinicians should pay more attention to long-term unexplained skeletal muscle diseases with recent onset blepharoptosis. Histopathologic examination and genetic testing are of great value in the early diagnosis and therapeutic intervention.
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Affiliation(s)
- Haokun Liu
- Department of Neurology, Xiangya Hospital, Central South University, Changsha 410008.
| | - Ming Gao
- Department of Geriatrics, Xiangya Hospital, Central South University, Changsha 410008
| | - Qiying Sun
- Department of Geriatrics, Xiangya Hospital, Central South University, Changsha 410008
| | - Si Chen
- Department of Neurology, Xiangya Hospital, Central South University, Changsha 410008
| | - Yuebei Luo
- Department of Neurology, Xiangya Hospital, Central South University, Changsha 410008
| | - Huan Yang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha 410008
| | - Qiuxiang Li
- Department of Neurology, Xiangya Hospital, Central South University, Changsha 410008
| | - Jing Li
- Department of Neurology, Xiangya Hospital, Central South University, Changsha 410008
| | - Guang Yang
- Department of General Medicine, Xiangya Hospital, Central South University, Changsha 410008, China.
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3
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Verma M, Francis L, Lizama BN, Callio J, Fricklas G, Wang KZQ, Kaufman BA, D'Aiuto L, Stolz DB, Watkins SC, Nimgaonkar VL, Soto-Gutierrez A, Goldstein A, Chu CT. iPSC-Derived Neurons from Patients with POLG Mutations Exhibit Decreased Mitochondrial Content and Dendrite Simplification. THE AMERICAN JOURNAL OF PATHOLOGY 2023; 193:201-212. [PMID: 36414085 PMCID: PMC9976192 DOI: 10.1016/j.ajpath.2022.11.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 10/18/2022] [Accepted: 11/03/2022] [Indexed: 11/21/2022]
Abstract
Mutations in POLG, the gene encoding the catalytic subunit of DNA polymerase gamma, result in clinical syndromes characterized by mitochondrial DNA (mtDNA) depletion in affected tissues with variable organ involvement. The brain is one of the most affected organs, and symptoms include intractable seizures, developmental delay, dementia, and ataxia. Patient-derived induced pluripotent stem cells (iPSCs) provide opportunities to explore mechanisms in affected cell types and potential therapeutic strategies. Fibroblasts from two patients were reprogrammed to create new iPSC models of POLG-related mitochondrial diseases. Compared with iPSC-derived control neurons, mtDNA depletion was observed upon differentiation of the POLG-mutated lines to cortical neurons. POLG-mutated neurons exhibited neurite simplification with decreased mitochondrial content, abnormal mitochondrial structure and function, and increased cell death. Expression of the mitochondrial kinase PTEN-induced kinase 1 (PINK1) mRNA was decreased in patient neurons. Overexpression of PINK1 increased mitochondrial content and ATP:ADP ratios in neurites, decreasing cell death and rescuing neuritic complexity. These data indicate an intersection of polymerase gamma and PINK1 pathways that may offer a novel therapeutic option for patients affected by this spectrum of disorders.
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Affiliation(s)
- Manish Verma
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Lily Francis
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Britney N Lizama
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Jason Callio
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Gabriella Fricklas
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Kent Z Q Wang
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Brett A Kaufman
- Department of Medicine, Vascular Medicine Institute, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Leonardo D'Aiuto
- Department of Psychiatry, Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Donna B Stolz
- Center for Biologic Imaging (CBI), University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Simon C Watkins
- Center for Biologic Imaging (CBI), University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Vishwajit L Nimgaonkar
- Department of Psychiatry, Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; Department of Human Genetics, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pennsylvania
| | | | - Amy Goldstein
- Mitochondrial Medicine Frontier Program, Division of Human Genetics, Department of Pediatrics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania; Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Charleen T Chu
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
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4
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Pokrovsky MV, Korokin MV, Krayushkina AM, Zhunusov NS, Lapin KN, Soldatova MO, Kuzmin EA, Gudyrev OS, Kochkarova IS, Deikin AV. CONVENTIONAL APPROACHES TO THE THERAPY OF HEREDITARY MYOPATHIES. PHARMACY & PHARMACOLOGY 2022. [DOI: 10.19163/2307-9266-2022-10-5-416-431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The aim of the work was to analyze the available therapeutic options for the conventional therapy of hereditary myopathies.Materials and methods. When searching for the material for writing a review article, such abstract databases as PubMed and Google Scholar were used. The search was carried out on the publications during the period from 1980 to September 2022. The following words and their combinations were selected as parameters for the literature selection: “myopathy”, “Duchenne”, “myodystrophy”, “metabolic”, “mitochondrial”, “congenital”, “symptoms”, “replacement”, “recombinant”, “corticosteroids”, “vitamins”, “tirasemtiv”, “therapy”, “treatment”, “evidence”, “clinical trials”, “patients”, “dichloracetate”.Results. Congenital myopathies are a heterogeneous group of pathologies that are caused by atrophy and degeneration of muscle fibers due to mutations in genes. Based on a number of clinical and pathogenetic features, hereditary myopathies are divided into: 1) congenital myopathies; 2) muscular dystrophy; 3) mitochondrial and 4) metabolic myopathies. At the same time, treatment approaches vary significantly depending on the type of myopathy and can be based on 1) substitution of the mutant protein; 2) an increase in its expression; 3) stimulation of the internal compensatory pathways expression; 4) restoration of the compounds balance associated with the mutant protein function (for enzymes); 5) impact on the mitochondrial function (with metabolic and mitochondrial myopathies); 6) reduction of inflammation and fibrosis (with muscular dystrophies); as well as 7) an increase in muscle mass and strength. The current review presents current data on each of the listed approaches, as well as specific pharmacological agents with a description of their action mechanisms.Conclusion. Currently, the following pharmacological groups are used or undergoing clinical trials for the treatment of various myopathies types: inotropic, anti-inflammatory and antifibrotic drugs, antimyostatin therapy and the drugs that promote translation through stop codons (applicable for nonsense mutations). In addition, metabolic drugs, metabolic enzyme cofactors, mitochondrial biogenesis stimulators, and antioxidants can be used to treat myopathies. Finally, the recombinant drugs alglucosidase and avalglucosidase have been clinically approved for the replacement therapy of metabolic myopathies (Pompe’s disease).
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Affiliation(s)
| | | | | | | | - K. N. Lapin
- V.A. Negovsky Research Institute of General Reanimatology, Federal Scientific and Clinical Center for Resuscitation and Rehabilitology
| | | | - E. A. Kuzmin
- Sechenov First Moscow State Medical University (Sechenov University)
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Wang L, Yang Z, He X, Pu S, Yang C, Wu Q, Zhou Z, Cen X, Zhao H. Mitochondrial protein dysfunction in pathogenesis of neurological diseases. Front Mol Neurosci 2022; 15:974480. [PMID: 36157077 PMCID: PMC9489860 DOI: 10.3389/fnmol.2022.974480] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Accepted: 08/08/2022] [Indexed: 11/21/2022] Open
Abstract
Mitochondria are essential organelles for neuronal function and cell survival. Besides the well-known bioenergetics, additional mitochondrial roles in calcium signaling, lipid biogenesis, regulation of reactive oxygen species, and apoptosis are pivotal in diverse cellular processes. The mitochondrial proteome encompasses about 1,500 proteins encoded by both the nuclear DNA and the maternally inherited mitochondrial DNA. Mutations in the nuclear or mitochondrial genome, or combinations of both, can result in mitochondrial protein deficiencies and mitochondrial malfunction. Therefore, mitochondrial quality control by proteins involved in various surveillance mechanisms is critical for neuronal integrity and viability. Abnormal proteins involved in mitochondrial bioenergetics, dynamics, mitophagy, import machinery, ion channels, and mitochondrial DNA maintenance have been linked to the pathogenesis of a number of neurological diseases. The goal of this review is to give an overview of these pathways and to summarize the interconnections between mitochondrial protein dysfunction and neurological diseases.
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Affiliation(s)
- Liang Wang
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital of Sichuan University, Chengdu, China
| | - Ziyun Yang
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital of Sichuan University, Chengdu, China
- School of Life Sciences, Guangxi Normal University, Guilin, China
- Guangxi Universities, Key Laboratory of Stem Cell and Biopharmaceutical Technology, Guangxi Normal University, Guilin, China
- Research Center for Biomedical Sciences, Guangxi Normal University, Guilin, China
| | - Xiumei He
- School of Life Sciences, Guangxi Normal University, Guilin, China
- Guangxi Universities, Key Laboratory of Stem Cell and Biopharmaceutical Technology, Guangxi Normal University, Guilin, China
- Research Center for Biomedical Sciences, Guangxi Normal University, Guilin, China
| | - Shiming Pu
- School of Life Sciences, Guangxi Normal University, Guilin, China
- Guangxi Universities, Key Laboratory of Stem Cell and Biopharmaceutical Technology, Guangxi Normal University, Guilin, China
- Research Center for Biomedical Sciences, Guangxi Normal University, Guilin, China
| | - Cheng Yang
- School of Life Sciences, Guangxi Normal University, Guilin, China
- Guangxi Universities, Key Laboratory of Stem Cell and Biopharmaceutical Technology, Guangxi Normal University, Guilin, China
- Research Center for Biomedical Sciences, Guangxi Normal University, Guilin, China
| | - Qiong Wu
- School of Life Sciences, Guangxi Normal University, Guilin, China
- Guangxi Universities, Key Laboratory of Stem Cell and Biopharmaceutical Technology, Guangxi Normal University, Guilin, China
- Research Center for Biomedical Sciences, Guangxi Normal University, Guilin, China
| | - Zuping Zhou
- Guangxi Universities, Key Laboratory of Stem Cell and Biopharmaceutical Technology, Guangxi Normal University, Guilin, China
- Research Center for Biomedical Sciences, Guangxi Normal University, Guilin, China
| | - Xiaobo Cen
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital of Sichuan University, Chengdu, China
| | - Hongxia Zhao
- School of Life Sciences, Guangxi Normal University, Guilin, China
- Guangxi Universities, Key Laboratory of Stem Cell and Biopharmaceutical Technology, Guangxi Normal University, Guilin, China
- Research Center for Biomedical Sciences, Guangxi Normal University, Guilin, China
- Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
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Whole-Exome Sequencing Identifies a Novel POLG Frameshift Variant in an Adult Patient Presenting with Progressive External Ophthalmoplegia and Mitochondrial DNA Depletion. Case Rep Genet 2021; 2021:9969071. [PMID: 34777884 PMCID: PMC8589515 DOI: 10.1155/2021/9969071] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Accepted: 10/16/2021] [Indexed: 11/30/2022] Open
Abstract
Mitochondrial DNA (mtDNA) depletion syndromes are a group of autosomal recessive disorders associated with a spectrum of clinical diseases, which include progressive external ophthalmoplegia (PEO). They are caused by variants in nuclear DNA (nDNA) encoded genes, and the gene that encodes for mtDNA polymerase gamma (POLG) is commonly involved. A splice-site mutation in POLG, c.3104+3A > T, was previously identified in three families with findings of PEO, and studies demonstrated this variant to result in skipping of exon 19. Here, we report a 57-year-old female who presented with ophthalmoplegia, ptosis, muscle weakness, and exercise intolerance with a subsequent muscle biopsy demonstrating mitochondrial myopathy on histopathologic evaluation and multiple mtDNA deletions by southern blot analysis. Whole-exome sequencing identified the previously characterized c. 3104+3A > T splice-site mutation in compound heterozygosity with a novel frameshift variant, p.Gly23Serfs∗236 (c.67_88del). mtDNA copy number analysis performed on the patient's muscle showed mtDNA depletion, as expected in a patient with biallelic pathogenic mutations in POLG. This is the first reported case with POLG p.Gly23Serfs∗236, discovered in a patient presenting with features of PEO.
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7
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Pizzamiglio C, Bugiardini E, Macken WL, Woodward CE, Hanna MG, Pitceathly RDS. Mitochondrial Strokes: Diagnostic Challenges and Chameleons. Genes (Basel) 2021; 12:1643. [PMID: 34681037 PMCID: PMC8535945 DOI: 10.3390/genes12101643] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Revised: 10/06/2021] [Accepted: 10/12/2021] [Indexed: 01/18/2023] Open
Abstract
Mitochondrial stroke-like episodes (SLEs) are a hallmark of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS). They should be suspected in anyone with an acute/subacute onset of focal neurological symptoms at any age and are usually driven by seizures. Suggestive features of an underlying mitochondrial pathology include evolving MRI lesions, often originating within the posterior brain regions, the presence of multisystemic involvement, including diabetes, deafness, or cardiomyopathy, and a positive family history. The diagnosis of MELAS has important implications for those affected and their relatives, given it enables early initiation of appropriate treatment and genetic counselling. However, the diagnosis is frequently challenging, particularly during the acute phase of an event. We describe four cases of mitochondrial strokes to highlight the considerable overlap that exists with other neurological disorders, including viral and autoimmune encephalitis, ischemic stroke, and central nervous system (CNS) vasculitis, and discuss the clinical, laboratory, and imaging features that can help distinguish MELAS from these differential diagnoses.
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Affiliation(s)
- Chiara Pizzamiglio
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London WC1N 3BG, UK; (C.P.); (E.B.); (W.L.M.); (M.G.H.)
| | - Enrico Bugiardini
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London WC1N 3BG, UK; (C.P.); (E.B.); (W.L.M.); (M.G.H.)
| | - William L. Macken
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London WC1N 3BG, UK; (C.P.); (E.B.); (W.L.M.); (M.G.H.)
| | - Cathy E. Woodward
- Neurogenetics Unit, The National Hospital for Neurology and Neurosurgery, London WC1N 3BH, UK;
| | - Michael G. Hanna
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London WC1N 3BG, UK; (C.P.); (E.B.); (W.L.M.); (M.G.H.)
| | - Robert D. S. Pitceathly
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London WC1N 3BG, UK; (C.P.); (E.B.); (W.L.M.); (M.G.H.)
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8
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Cakmak C, Zempel H. A perspective on human cell models for POLG-spectrum disorders: advantages and disadvantages of CRISPR-Cas-based vs. patient-derived iPSC models. MED GENET-BERLIN 2021; 33:245-249. [PMID: 38835703 PMCID: PMC11006303 DOI: 10.1515/medgen-2021-2090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Accepted: 10/21/2021] [Indexed: 06/06/2024]
Abstract
Neurogenetic diseases represent a broad group of diseases with variable genetic causes and clinical manifestations. Among these, polymerase-gamma (POLG)-spectrum disorders are relatively frequent with an estimated disease frequency of ∼1:10.000. Also, mutations in the POLG gene are by far the most important cause for mitochondriopathy. POLG-spectrum disorders usually result in progressive loss of brain function and may involve severe and deadly encephalopathy, seizures, and neuromuscular disease, as well as cardiac and hepatic failure in some cases. Onset of disease may range from birth to late adulthood, and disease duration ranges from weeks in severe cases to decades. There is no curative treatment; current animal models do not faithfully recapitulate human disease, complicating preclinical therapeutic studies. Human-based preclinical model systems must be developed to understand the human disease mechanisms and develop therapeutic approaches. In this review, we provide an overview of the current approaches to model neurogenetic disorders in a human cellular and neuronal environment with a focus on POLG-spectrum disorders. We discuss the necessity of using neuronal cells and the advantages and pitfalls of currently available cell model approaches, namely (i) CRISPR-based (i. e., genetically engineered) and induced pluripotent stem cell (iPSC) (i. e., stem cell like)-derived neuronal models and (ii) the reprogramming of patient-derived cells into iPSCs and derived neurons. Despite the fact that cell models are by definition in vitro systems incapable of recapitulating all aspects of human disease, they are still the reasonable point of start to discover disease mechanisms and develop therapeutic approaches to treat neurogenetic diseases.
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Affiliation(s)
- Cagla Cakmak
- Institute of Human Genetics, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Hans Zempel
- Institute of Human Genetics, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
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9
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Silva-Pinheiro P, Pardo-Hernández C, Reyes A, Tilokani L, Mishra A, Cerutti R, Li S, Rozsivalova DH, Valenzuela S, Dogan SA, Peter B, Fernández-Silva P, Trifunovic A, Prudent J, Minczuk M, Bindoff L, Macao B, Zeviani M, Falkenberg M, Viscomi C. DNA polymerase gamma mutations that impair holoenzyme stability cause catalytic subunit depletion. Nucleic Acids Res 2021; 49:5230-5248. [PMID: 33956154 PMCID: PMC8136776 DOI: 10.1093/nar/gkab282] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 03/29/2021] [Accepted: 04/08/2021] [Indexed: 01/31/2023] Open
Abstract
Mutations in POLG, encoding POLγA, the catalytic subunit of the mitochondrial DNA polymerase, cause a spectrum of disorders characterized by mtDNA instability. However, the molecular pathogenesis of POLG-related diseases is poorly understood and efficient treatments are missing. Here, we generate the PolgA449T/A449T mouse model, which reproduces the A467T change, the most common human recessive mutation of POLG. We show that the mouse A449T mutation impairs DNA binding and mtDNA synthesis activities of POLγ, leading to a stalling phenotype. Most importantly, the A449T mutation also strongly impairs interactions with POLγB, the accessory subunit of the POLγ holoenzyme. This allows the free POLγA to become a substrate for LONP1 protease degradation, leading to dramatically reduced levels of POLγA in A449T mouse tissues. Therefore, in addition to its role as a processivity factor, POLγB acts to stabilize POLγA and to prevent LONP1-dependent degradation. Notably, we validated this mechanism for other disease-associated mutations affecting the interaction between the two POLγ subunits. We suggest that targeting POLγA turnover can be exploited as a target for the development of future therapies.
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Affiliation(s)
- Pedro Silva-Pinheiro
- MRC/University of Cambridge Mitochondrial Biology Unit, Hills Road, CB2 0XY Cambridge, UK
| | - Carlos Pardo-Hernández
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Medicinaregatan 9A P.O. Box 440, SE405 30 Gothenburg, Sweden
| | - Aurelio Reyes
- MRC/University of Cambridge Mitochondrial Biology Unit, Hills Road, CB2 0XY Cambridge, UK
| | - Lisa Tilokani
- MRC/University of Cambridge Mitochondrial Biology Unit, Hills Road, CB2 0XY Cambridge, UK
| | - Anup Mishra
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Medicinaregatan 9A P.O. Box 440, SE405 30 Gothenburg, Sweden
| | - Raffaele Cerutti
- Department of Neurosciences, University of Padova, via Giustiniani, 2-35128 Padova, Italy
| | - Shuaifeng Li
- Center for Cancer Biology, Life Science of Institution, Zhejiang University, Hangzhou 310058, China
| | - Dieu-Hien Rozsivalova
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD) and Center for Molecular Medicine (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Sebastian Valenzuela
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Medicinaregatan 9A P.O. Box 440, SE405 30 Gothenburg, Sweden
| | - Sukru A Dogan
- Department of Molecular Biology and Genetics, Center for Life Sciences and Technologies, Bogazici University, 34342 Istanbul, Turkey
| | - Bradley Peter
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Medicinaregatan 9A P.O. Box 440, SE405 30 Gothenburg, Sweden
| | - Patricio Fernández-Silva
- Biochemistry and Molecular and Cell Biology Department, University of Zaragoza, C/ Pedro Cerbuna s/n 50.009-Zaragoza, and Biocomputation and Complex Systems Physics Institute (BIFI), C/ Mariano Esquillor, 50.018-Zaragoza, Spain
| | - Aleksandra Trifunovic
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD) and Center for Molecular Medicine (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany
| | - Julien Prudent
- MRC/University of Cambridge Mitochondrial Biology Unit, Hills Road, CB2 0XY Cambridge, UK
| | - Michal Minczuk
- MRC/University of Cambridge Mitochondrial Biology Unit, Hills Road, CB2 0XY Cambridge, UK
| | - Laurence Bindoff
- Department of Clinical Medicine, University of Bergen, 5007 Bergen, Norway
- Neuro-SysMed, Department of Neurology, Haukeland University Hospital, Jonas Lies vei 65, 5021 Bergen, Norway
| | - Bertil Macao
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Medicinaregatan 9A P.O. Box 440, SE405 30 Gothenburg, Sweden
| | - Massimo Zeviani
- Department of Neurosciences, University of Padova, via Giustiniani, 2-35128 Padova, Italy
- Venetian Institute of Molecular Medicine, via Orus 2-35128 Padova, Italy
| | - Maria Falkenberg
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Medicinaregatan 9A P.O. Box 440, SE405 30 Gothenburg, Sweden
| | - Carlo Viscomi
- Department of Biomedical Sciences, University of Padova, via Ugo Bassi 58/B-35131 Padova, Italy
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Li LX, Jiang LT, Pan YG, Zhang XL, Pan LZ, Nie ZY, Chen YH, Jin LJ. Clinical and Molecular Features of POLG-Related Sensory Ataxic Neuropathy with Dysarthria and Ophthalmoparesis. J Mol Neurosci 2021; 71:2462-2467. [PMID: 33791913 DOI: 10.1007/s12031-021-01831-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Accepted: 03/15/2021] [Indexed: 10/21/2022]
Abstract
Sensory ataxic neuropathy, dysarthria, and ophthalmoparesis (SANDO) is a rare mitochondrial disorder associated with mutations in the POLG gene, which encodes the DNA polymerase gamma catalytic subunit. A few POLG-related SANDO cases have been reported, but the genotype-phenotype correlation remains unclear. Here, we report a patient with SANDO carrying two novel missense variants (c.2543G>C, p.G848A and c.452 T>C, p.L151P) in POLG. We also reviewed previously reported cases to systematically evaluate the clinical and genetic features of POLG-related SANDO. A total of 35 distinct variants in the coding region of POLG were identified in 63 patients with SANDO. The most frequent variant was the p.A467T variant, followed by the p.W748S variant. The clinical spectrum of SANDO is heterogeneous. No clear correlation has been observed between the mutation types and clinical phenotypes. Our findings expand the mutational spectrum of POLG and contribute to clinical management and genetic counseling for POLG-related SANDO.
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Affiliation(s)
- Li-Xi Li
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - Li-Ting Jiang
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - You-Gui Pan
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - Xiao-Long Zhang
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - Li-Zhen Pan
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - Zhi-Yu Nie
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yu-Hui Chen
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - Ling-Jing Jin
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China.
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11
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Pitceathly RD, Keshavan N, Rahman J, Rahman S. Moving towards clinical trials for mitochondrial diseases. J Inherit Metab Dis 2021; 44:22-41. [PMID: 32618366 PMCID: PMC8432143 DOI: 10.1002/jimd.12281] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 06/22/2020] [Accepted: 06/30/2020] [Indexed: 12/11/2022]
Abstract
Primary mitochondrial diseases represent some of the most common and severe inherited metabolic disorders, affecting ~1 in 4,300 live births. The clinical and molecular diversity typified by mitochondrial diseases has contributed to the lack of licensed disease-modifying therapies available. Management for the majority of patients is primarily supportive. The failure of clinical trials in mitochondrial diseases partly relates to the inefficacy of the compounds studied. However, it is also likely to be a consequence of the significant challenges faced by clinicians and researchers when designing trials for these disorders, which have historically been hampered by a lack of natural history data, biomarkers and outcome measures to detect a treatment effect. Encouragingly, over the past decade there have been significant advances in therapy development for mitochondrial diseases, with many small molecules now transitioning from preclinical to early phase human interventional studies. In this review, we present the treatments and management strategies currently available to people with mitochondrial disease. We evaluate the challenges and potential solutions to trial design and highlight the emerging pharmacological and genetic strategies that are moving from the laboratory to clinical trials for this group of disorders.
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Affiliation(s)
- Robert D.S. Pitceathly
- Department of Neuromuscular DiseasesUCL Queen Square Institute of Neurology and The National Hospital for Neurology and NeurosurgeryLondonUK
| | - Nandaki Keshavan
- Mitochondrial Research GroupUCL Great Ormond Street Institute of Child HealthLondonUK
- Metabolic UnitGreat Ormond Street Hospital for Children NHS Foundation TrustLondonUK
| | - Joyeeta Rahman
- Mitochondrial Research GroupUCL Great Ormond Street Institute of Child HealthLondonUK
| | - Shamima Rahman
- Mitochondrial Research GroupUCL Great Ormond Street Institute of Child HealthLondonUK
- Metabolic UnitGreat Ormond Street Hospital for Children NHS Foundation TrustLondonUK
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12
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Rossi M, van der Veen S, Merello M, Tijssen MAJ, van de Warrenburg B. Myoclonus-Ataxia Syndromes: A Diagnostic Approach. Mov Disord Clin Pract 2020; 8:9-24. [PMID: 33426154 DOI: 10.1002/mdc3.13106] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 09/30/2020] [Accepted: 10/14/2020] [Indexed: 12/30/2022] Open
Abstract
Background A myriad of disorders combine myoclonus and ataxia. Most causes are genetic and an increasing number of genes are being associated with myoclonus-ataxia syndromes (MAS), due to recent advances in genetic techniques. A proper etiologic diagnosis of MAS is clinically relevant, given the consequences for genetic counseling, treatment, and prognosis. Objectives To review the causes of MAS and to propose a diagnostic algorithm. Methods A comprehensive and structured literature search following PRISMA criteria was conducted to identify those disorders that may combine myoclonus with ataxia. Results A total of 135 causes of combined myoclonus and ataxia were identified, of which 30 were charted as the main causes of MAS. These include four acquired entities: opsoclonus-myoclonus-ataxia syndrome, celiac disease, multiple system atrophy, and sporadic prion diseases. The distinction between progressive myoclonus epilepsy and progressive myoclonus ataxia poses one of the main diagnostic dilemmas. Conclusions Diagnostic algorithms for pediatric and adult patients, based on clinical manifestations including epilepsy, are proposed to guide the differential diagnosis and corresponding work-up of the most important and frequent causes of MAS. A list of genes associated with MAS to guide genetic testing strategies is provided. Priority should be given to diagnose or exclude acquired or treatable disorders.
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Affiliation(s)
- Malco Rossi
- Movement Disorders Section Neuroscience Department Buenos Aires Argentina.,Argentine National Scientific and Technological Research Council (CONICET) Buenos Aires Argentina
| | - Sterre van der Veen
- Pontificia Universidad Católica Argentina (UCA) Buenos Aires Argentina.,Department of Neurology University of Groningen, University Medical Center Groningen Groningen The Netherlands
| | - Marcelo Merello
- Movement Disorders Section Neuroscience Department Buenos Aires Argentina.,Argentine National Scientific and Technological Research Council (CONICET) Buenos Aires Argentina.,Pontificia Universidad Católica Argentina (UCA) Buenos Aires Argentina
| | - Marina A J Tijssen
- Department of Neurology University of Groningen, University Medical Center Groningen Groningen The Netherlands.,Expertise Center Movement Disorders Groningen University Medical Center Groningen (UMCG) Groningen The Netherlands
| | - Bart van de Warrenburg
- Department of Neurology, Donders Institute for Brain, Cognition & Behaviour Radboud University Medical Center Nijmegen The Netherlands
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13
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POLG1-Related Epilepsy: Review of Diagnostic and Therapeutic Findings. Brain Sci 2020; 10:brainsci10110768. [PMID: 33113942 PMCID: PMC7690674 DOI: 10.3390/brainsci10110768] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 10/14/2020] [Accepted: 10/20/2020] [Indexed: 11/30/2022] Open
Abstract
Background: The clinical spectrum associated with POLG1 gene mutations ranges from non-syndromic epilepsy or mild isolated neurological signs to neurodegenerative disorders. Our aim was to review diagnostic findings, therapeutic approaches and outcomes of reported cases of epilepsy related to POLG1 mutation. Methods: The articles for review were identified through a systematic research on PubMed and EMBASE databases from January 2003 to April 2020, searching for the terms “Epilepsy AND POLG OR polymerase gamma,” OR “POLG1”. Results: Forty-eight articles were selected for review, which included 195 patients. Two main peaks of age at epilepsy onset were found: at ages 1 and 13 years. The most frequent seizure type was myoclonic. The occurrence of Status Epilepticus was reported in 46.4% of cases. Epileptiform and slow abnormalities were most frequently seen over occipital regions. Brain Magnetic Resonance Imaging (MRI) revealed increased T2 signal intensities in thalamic regions. Genetic analysis revealed a prevalence of A467T, W748S and G848S (74.2% of patients) mutations. Survival at 5 years was estimated at very low levels (30.2% of patients). Conclusion: In this review, we included cases with both pediatric and adult epilepsy onset. The analysis of data regarding prognosis showed that survival is related to age at onset of epilepsy.
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14
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Oliveira MT, Pontes CDB, Ciesielski GL. Roles of the mitochondrial replisome in mitochondrial DNA deletion formation. Genet Mol Biol 2020; 43:e20190069. [PMID: 32141473 PMCID: PMC7197994 DOI: 10.1590/1678-4685-gmb-2019-0069] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Accepted: 08/12/2019] [Indexed: 01/07/2023] Open
Abstract
Mitochondrial DNA (mtDNA) deletions are a common cause of human mitochondrial
diseases. Mutations in the genes encoding components of the mitochondrial
replisome, such as DNA polymerase gamma (Pol γ) and the mtDNA helicase Twinkle,
have been associated with the accumulation of such deletions and the development
of pathological conditions in humans. Recently, we demonstrated that changes in
the level of wild-type Twinkle promote mtDNA deletions, which implies that not
only mutations in, but also dysregulation of the stoichiometry between the
replisome components is potentially pathogenic. The mechanism(s) by which
alterations to the replisome function generate mtDNA deletions is(are) currently
under debate. It is commonly accepted that stalling of the replication fork at
sites likely to form secondary structures precedes the deletion formation. The
secondary structural elements can be bypassed by the replication-slippage
mechanism. Otherwise, stalling of the replication fork can generate single- and
double-strand breaks, which can be repaired through recombination leading to the
elimination of segments between the recombination sites. Here, we discuss
aberrances of the replisome in the context of the two debated outcomes, and
suggest new mechanistic explanations based on replication restart and template
switching that could account for all the deletion types reported for
patients.
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Affiliation(s)
- Marcos T Oliveira
- Universidade Estadual Paulista Júlio de Mesquita Filho, Faculdade de Ciências Agrárias e Veterinárias, Departamento de Tecnologia, Jaboticabal, SP, Brazil
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15
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Abstract
The POLG gene encodes the mitochondrial DNA polymerase that is responsible for replication of the mitochondrial genome. Mutations in POLG can cause early childhood mitochondrial DNA (mtDNA) depletion syndromes or later-onset syndromes arising from mtDNA deletions. POLG mutations are the most common cause of inherited mitochondrial disorders, with as many as 2% of the population carrying these mutations. POLG-related disorders comprise a continuum of overlapping phenotypes with onset from infancy to late adulthood. The six leading disorders caused by POLG mutations are Alpers-Huttenlocher syndrome, which is one of the most severe phenotypes; childhood myocerebrohepatopathy spectrum, which presents within the first 3 years of life; myoclonic epilepsy myopathy sensory ataxia; ataxia neuropathy spectrum; autosomal recessive progressive external ophthalmoplegia; and autosomal dominant progressive external ophthalmoplegia. This Review describes the clinical features, pathophysiology, natural history and treatment of POLG-related disorders, focusing particularly on the neurological manifestations of these conditions.
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16
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Abstract
Apart from reliable management of the "powerhouse" of the cell, mitochondria faithfully orchestrate a diverse array of important and critical functions in governing cellular signaling, apoptosis, autophagy, mitophagy and innate and adaptive immune system. Introduction of instability and imbalance in the mitochondrial own genome or the nuclear encoded mitochondrial proteome would result in the manifestation of various diseases through alterations in the oxidative phosphorylation system (OXPHOS) and nuclear-mitochondria retrograde signaling. Understanding mitochondrial biology and dynamism are thus of paramount importance to develop strategies to prevent or treat various diseases caused due to mitochondrial alterations.
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Affiliation(s)
- Santanu Dasgupta
- Department of Medicine, The University of Texas Health Science Center at Tyler, Tyler, Texas, USA
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17
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Comment on "Proximal Myopathy due to m.5835G>A Mutation in Mitochondrial MT-TY Gene". Case Rep Neurol Med 2019; 2019:3514894. [PMID: 31355027 PMCID: PMC6632500 DOI: 10.1155/2019/3514894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 04/22/2019] [Indexed: 11/18/2022] Open
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18
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Finsterer J. Cerebral imaging in adult mitochondrial disorders. J Neurol Sci 2019; 404:29-35. [PMID: 31323519 DOI: 10.1016/j.jns.2019.07.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2019] [Revised: 06/06/2019] [Accepted: 07/09/2019] [Indexed: 01/15/2023]
Abstract
OBJECTIVES Among the organs/tissues affected in mitochondrial disorders (MIDs), the brain is the second most frequently affected. Cerebral imaging may correlate with clinical findings but not necessarily. This review summarises and discusses current knowledge and recent advances concerning cerebral abnormalities on imaging in adult MIDs (≥18y). METHODS Systematic literature review. RESULTS The most common cerebral abnormalities in imaging in adult MIDs are, as in pediatric MIDs, white matter lesions, grey matter lesions, atrophy, optic atrophy, stroke-like lesions, calcifications, and ischemic stroke. Cerebral lesions may remain stable over years but some may undergo dynamic changes within shorter or longer period of times. Typical dynamic lesions are stroke-like lesions and grey matter lesions in the sense of progression or regression. Since cerebral lesions on imaging may or may not go along with clinical manifestations, it is crucial to screen all MID patients for cerebral involvement, which can be effectively accomplished by application of the MRI. CONCLUSIONS Cerebral imaging is of paramount importance for diagnosing and monitoring cerebral involvement in MIDs. Cerebral imaging in MIDs contributes to the understanding of the pathogenesis of cerebral involvement in MIDs.
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Affiliation(s)
- Josef Finsterer
- Krankenanstalt Rudolfstiftung, Messerli Institute, Postfach 20, 1180 Vienna, Austria.
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19
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Papandreou A, Rahman S, Fratter C, Ng J, Meyer E, Carr LJ, Champion M, Clarke A, Gissen P, Hemingway C, Hussain N, Jayawant S, King MD, Lynch BJ, Mewasingh L, Patel J, Prabhakar P, Neergheen V, Pope S, Heales SJR, Poulton J, Kurian MA. Spectrum of movement disorders and neurotransmitter abnormalities in paediatric POLG disease. J Inherit Metab Dis 2018; 41:1275-1283. [PMID: 30167885 PMCID: PMC6326959 DOI: 10.1007/s10545-018-0227-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 06/15/2018] [Accepted: 06/26/2018] [Indexed: 11/26/2022]
Abstract
OBJECTIVES To describe the spectrum of movement disorders and cerebrospinal fluid (CSF) neurotransmitter profiles in paediatric patients with POLG disease. METHODS We identified children with genetically confirmed POLG disease, in whom CSF neurotransmitter analysis had been undertaken. Clinical data were collected retrospectively. CSF neurotransmitter levels were compared to both standardised age-related reference ranges and to non-POLG patients presenting with status epilepticus. RESULTS Forty-one patients with POLG disease were identified. Almost 50% of the patients had documented evidence of a movement disorder, including non-epileptic myoclonus, choreoathetosis and ataxia. CSF neurotransmitter analysis was undertaken in 15 cases and abnormalities were seen in the majority (87%) of cases tested. In many patients, distinctive patterns were evident, including raised neopterin, homovanillic acid and 5-hydroxyindoleacetic acid levels. CONCLUSIONS Children with POLG mutations can manifest with a wide spectrum of abnormal movements, which are often prominent features of the clinical syndrome. Underlying pathophysiology is probably multifactorial, and aberrant monoamine metabolism is likely to play a role.
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Affiliation(s)
- A Papandreou
- Molecular Neurosciences, Developmental Neurosciences Programme, UCL Great Ormond Street Institute of Child Health, 30 Guildford Street, London, WC1N 1EH, UK
- Department of Neurology, Great Ormond Street Hospital for Children, London, UK
- Genetics and Genomics Medicine Programme, UCL Great Ormond Street Institute of Child Health, London, UK
| | - S Rahman
- Mitochondrial Research Group, Genetics and Genomic Medicine Programme, UCL Great Ormond Street Institute of Child Health, London, UK
- Metabolic Department, Great Ormond Street Hospital for Children, London, UK
| | - C Fratter
- Oxford Medical Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - J Ng
- Molecular Neurosciences, Developmental Neurosciences Programme, UCL Great Ormond Street Institute of Child Health, 30 Guildford Street, London, WC1N 1EH, UK
| | - E Meyer
- Molecular Neurosciences, Developmental Neurosciences Programme, UCL Great Ormond Street Institute of Child Health, 30 Guildford Street, London, WC1N 1EH, UK
| | - L J Carr
- Department of Neurology, Great Ormond Street Hospital for Children, London, UK
| | - M Champion
- Department of Inherited Metabolic Disease, Evelina London Children's Hospital, London, UK
| | - A Clarke
- Paediatric Neurology Department, St George's University Hospital, London, UK
| | - P Gissen
- Genetics and Genomics Medicine Programme, UCL Great Ormond Street Institute of Child Health, London, UK
- Metabolic Department, Great Ormond Street Hospital for Children, London, UK
- UCL-MRC Laboratory of Molecular Cell Biology, London, UK
| | - C Hemingway
- Department of Neurology, Great Ormond Street Hospital for Children, London, UK
| | - N Hussain
- Department of Paediatric Neurology, University Hospital of Leicester, Leicester, UK
| | - S Jayawant
- Department of Paediatric Neurology, John Radcliffe Hospital, Oxford, UK
| | - M D King
- Department of Paediatric Neurology and Clinical Neurophysiology, Children's University Hospital, Temple Street, Dublin, Ireland
| | - B J Lynch
- Department of Neurology and Clinical Neurophysiology, Children's University Hospital, Temple Street, Dublin, Ireland
| | - L Mewasingh
- Department of Paediatric Neurology, Imperial College Healthcare NHS Trust, London, UK
| | - J Patel
- Department of Paediatric Neurology, Bristol Royal Hospital for Children, Bristol, UK
| | - P Prabhakar
- Department of Neurology, Great Ormond Street Hospital for Children, London, UK
| | - V Neergheen
- Neurometabolic Unit, National Hospital for Neurology and Neurosurgery, London, UK
| | - S Pope
- Neurometabolic Unit, National Hospital for Neurology and Neurosurgery, London, UK
| | - S J R Heales
- Neurometabolic Unit, National Hospital for Neurology and Neurosurgery, London, UK
- Department of Paediatric Laboratory Medicine, Great Ormond Street Hospital for Children, London, UK
| | - J Poulton
- Nuffield Department of Women's and Reproductive Health, University of Oxford, The Women's Centre, Oxford, UK
| | - Manju A Kurian
- Molecular Neurosciences, Developmental Neurosciences Programme, UCL Great Ormond Street Institute of Child Health, 30 Guildford Street, London, WC1N 1EH, UK.
- Department of Neurology, Great Ormond Street Hospital for Children, London, UK.
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20
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Hayhurst H, Anagnostou ME, Bogle HJ, Grady JP, Taylor RW, Bindoff LA, McFarland R, Turnbull DM, Lax NZ. Dissecting the neuronal vulnerability underpinning Alpers' syndrome: a clinical and neuropathological study. Brain Pathol 2018; 29:97-113. [PMID: 30021052 PMCID: PMC7379503 DOI: 10.1111/bpa.12640] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 06/29/2018] [Indexed: 11/28/2022] Open
Abstract
Alpers’ syndrome is an early‐onset neurodegenerative disorder often caused by biallelic pathogenic variants in the gene encoding the catalytic subunit of polymerase‐gamma (POLG) which is essential for mitochondrial DNA (mtDNA) replication. Alpers’ syndrome is characterized by intractable epilepsy, developmental regression and liver failure which typically affects children aged 6 months–3 years. Although later onset variants are now recognized, they differ in that they are primarily an epileptic encephalopathy with ataxia. The disorder is progressive, without cure and inevitably leads to death from drug‐resistant status epilepticus, often with concomitant liver failure. Since our understanding of the mechanisms contributing the neurological features in Alpers’ syndrome is rudimentary, we performed a detailed and quantitative neuropathological study on 13 patients with clinically and histologically‐defined Alpers’ syndrome with ages ranging from 2 months to 18 years. Quantitative immunofluorescence showed severe respiratory chain deficiencies involving mitochondrial respiratory chain subunits of complex I and, to a lesser extent, complex IV in inhibitory interneurons and pyramidal neurons in the occipital cortex and in Purkinje cells of the cerebellum. Diminished densities of these neuronal populations were also observed. This study represents the largest cohort of post‐mortem brains from patients with clinically defined Alpers’ syndrome where we provide quantitative evidence of extensive complex I defects affecting interneurons and Purkinje cells for the first time. We believe interneuron and Purkinje cell pathology underpins the clinical development of seizures and ataxia seen in Alpers’ syndrome. This study also further highlights the extensive involvement of GABAergic neurons in mitochondrial disease.
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Affiliation(s)
- Hannah Hayhurst
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Maria-Eleni Anagnostou
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Helen J Bogle
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - John P Grady
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Robert W Taylor
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Laurence A Bindoff
- Department of Clinical Medicine, University of Bergen, Bergen, Norway.,Department of Neurology, Haukeland University, Bergen, Norway
| | - Robert McFarland
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Doug M Turnbull
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Nichola Z Lax
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
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21
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Kirschenbaum D, Hedberg-Oldfors C, Oldfors A, Scherer E, Budka H. Distinctive cerebral neuropathology in an adult case of sensory ataxic neuropathy with dysarthria and ophthalmoplegia (SANDO) syndrome. Neuropathol Appl Neurobiol 2018; 44:639-642. [DOI: 10.1111/nan.12429] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Revised: 07/12/2017] [Accepted: 08/09/2017] [Indexed: 11/27/2022]
Affiliation(s)
- D. Kirschenbaum
- Institute of Neuropathology; University Hospital Zurich; Zurich University; Zurich Switzerland
| | - C. Hedberg-Oldfors
- Department of Pathology; Sahlgrenska University Hospital; University of Gothenburg; Gothenburg Sweden
| | - A. Oldfors
- Department of Pathology; Sahlgrenska University Hospital; University of Gothenburg; Gothenburg Sweden
| | - E. Scherer
- NeuroZentrum Hirslanden; Zurich Switzerland
| | - H. Budka
- Institute of Neuropathology; University Hospital Zurich; Zurich University; Zurich Switzerland
- Institute of Neurology; Medical University Vienna; Vienna Austria
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22
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Abstract
This narrative review focuses on the pathophysiology, diagnosis, and management of status epilepticus in the context of primary mitochondrial disease. Epilepsy is common in mitochondrial disease, reported in >20% of adult cases and 40%-60% of pediatric cohorts. Status epilepticus is less frequently reported and appears to be associated with particular subgroups of mitochondrial disorders, namely defects of the mitochondrial DNA and its maintenance, and disorders of mitochondrial translation and dynamics. Mechanisms underlying mitochondrial status epilepticus are incompletely understood, and may include bioenergetic failure, oxidative stress, immune dysfunction, and impaired mitochondrial dynamics. Treatments tried in mitochondrial status epilepticus include antiepileptic drugs, anesthetic agents, magnesium, high-dose steroids, immune globulins, vagus nerve stimulation, and surgical procedures, all with variable success. The outcome of mitochondrial status epilepticus is extremely poor, and effective therapeutic options have not been reported. Improved understanding of the mechanisms underpinning mitochondrial status epilepticus is needed in order to develop more effective treatments.
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Affiliation(s)
- Shamima Rahman
- Mitochondrial Research Group, UCL Great Ormond Street Institute of Child Health, London, UK.,Metabolic Unit, Great Ormond Street Hospital for Children, NHS Foundation Trust, London, UK
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23
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Alves CAPF, Gonçalves FG, Grieb D, Lucato LT, Goldstein AC, Zuccoli G. Neuroimaging of Mitochondrial Cytopathies. Top Magn Reson Imaging 2018; 27:219-240. [PMID: 30086109 DOI: 10.1097/rmr.0000000000000173] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Mitochondrial diseases are a complex and heterogeneous group of genetic disorders that occur as a result of either nuclear DNA or mitochondrial DNA pathogenic variants, leading to a decrease in oxidative phosphorylation and cellular energy (ATP) production. Increasing knowledge about molecular, biochemical, and genetic abnormalities related to mitochondrial dysfunction has expanded the neuroimaging phenotypes of mitochondrial disorders. As a consequence of this growing field, the imaging recognition patterns of mitochondrial cytopathies are continually evolving. In this review, we describe the main neuroimaging characteristics of pediatric mitochondrial diseases, ranging from classical to more recent and challenging features. Due to the increased knowledge about the imaging findings of mitochondrial cytopathies, the pediatric neuroradiologist plays a crucial role in the diagnosis and evaluation of these patients.
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Affiliation(s)
| | | | - Dominik Grieb
- Department of Radiology and Neuroradiology, Sana Kliniken Duisburg, Germany
| | - Leandro Tavares Lucato
- Neuroradiology Section, Hospital das Clínicas- HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo, SP, Brazil
| | - Amy C Goldstein
- Division of Human Genetics, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA
| | - Giulio Zuccoli
- Department of Radiology, University of Pittsburgh School of Medicine, Director of Pediatric Neuroradiology, Children Hospital of Pittsburgh, Pittsburgh, PA
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24
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Rahman J, Rahman S. Mitochondrial medicine in the omics era. Lancet 2018; 391:2560-2574. [PMID: 29903433 DOI: 10.1016/s0140-6736(18)30727-x] [Citation(s) in RCA: 151] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Revised: 02/28/2018] [Accepted: 03/14/2018] [Indexed: 12/16/2022]
Abstract
Mitochondria are dynamic bioenergetic organelles whose maintenance requires around 1500 proteins from two genomes. Mutations in either the mitochondrial or nuclear genome can disrupt a plethora of cellular metabolic and homoeostatic functions. Mitochondrial diseases represent one of the most common and severe groups of inherited genetic disorders, characterised by clinical, biochemical, and genetic heterogeneity, diagnostic odysseys, and absence of disease-modifying curative therapies. This Review aims to discuss recent advances in mitochondrial biology and medicine arising from widespread use of high-throughput omics technologies, and also includes a broad discussion of emerging therapies for mitochondrial disease. New insights into both bioenergetic and biosynthetic mitochondrial functionalities have expedited the genetic diagnosis of primary mitochondrial disorders, and identified novel mitochondrial pathomechanisms and new targets for therapeutic intervention. As we enter this new era of mitochondrial medicine, underpinned by global unbiased approaches and multifaceted investigation of mitochondrial function, omics technologies will continue to shed light on unresolved mitochondrial questions, paving the way for improved outcomes for patients with mitochondrial diseases.
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Affiliation(s)
- Joyeeta Rahman
- Mitochondrial Research Group, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Shamima Rahman
- Mitochondrial Research Group, UCL Great Ormond Street Institute of Child Health, London, UK; Metabolic Unit, Great Ormond Street Hospital NHS Foundation Trust, London, UK.
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25
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Jerath NU, Shy ME. Asymmetric Ataxia, Depression, Memory Loss, Epilepsy, and Axonal Neuropathy Associated with A Heterozygous DNA Polymerase Gamma Variant of Uncertain Significance, c1370G>a (R457Q). J Neuromuscul Dis 2018; 5:99-104. [PMID: 29278894 DOI: 10.3233/jnd-170229] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
INTRODUCTION Mutations in the gene encoding DNA polymerase gamma (POLG) impair its ability to proofread mitochondrial DNA (mtDNA) during replication [1]. This results in a high frequency of randomly distributed mtDNA mutations and thus a wide range of phenotypes, including seizures, neuropathy, and cerebellar ataxia [1, 2]. We document a phenotype associated with the rare POLG variant c.1370G>A (p.R457Q). METHODS Over 10 years, we performed electrodiagnostic and neuropsychologic on a patient who presented with a variety of neurologic symptoms. RESULTS Testing revealed an axonal sensorimotor polyneuropathy, depression and executive function difficulties, and asymmetric ataxia. Genetic testing revealed a POLG variant of uncertain significance (c.1370G>A, p.R457Q) in a heterozygous state. CONCLUSIONS We have identified a mutation in POLG that could result in a diverse array of symptoms and signs of our patient. However, interpreting pathogenicity of rare variants such as R457Q is challenging and will likely require identification of patients with similar phenotypes caused by the variant of uncertain significance.
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Affiliation(s)
- Nivedita U Jerath
- Department of Neurology, University of Florida College of Medicine, Gainesville, FL, USA.,Department of Neurology, University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - Michael E Shy
- Department of Neurology, University of Iowa Carver College of Medicine, Iowa City, IA, USA
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Richter JE, Robles HG, Mauricio E, Mohammad A, Atwal PS, Caulfield TR. Protein molecular modeling shows residue T599 is critical to wild-type function of POLG and description of a novel variant associated with the SANDO phenotype. Hum Genome Var 2018; 5:18016. [PMID: 29644085 PMCID: PMC5885040 DOI: 10.1038/hgv.2018.16] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 11/22/2017] [Accepted: 12/12/2017] [Indexed: 01/21/2023] Open
Abstract
Sensory ataxic neuropathy with dysarthria and ophthalmoparesis (SANDO) is a rare phenotype resulting from pathogenic variants of mitochondrial DNA polymerase gamma (POLG). We modeled a novel POLG variant, T599P, that causes the SANDO phenotype and another variant at the same residue, p.T599E, to observe their effect on protein function and confirm the pathogenicity of T599P. Through neoteric molecular modeling techniques, we show that changes at the T599 residue position introduce extra rigidity into the surrounding helix–loop–helix, which places steric pressure on nearby nucleotides. We also provide a clinical description of the T599P variant, which was found in a 42-year-old female proband. The proband presented a 1-year history of progressive gait instability, dysarthria and foot numbness. Her neurologic examination revealed ataxic dysarthria, restricted eye movements, head and palatal tremors, reduced lower limb reflexes, distal multimodal sensory loss and a wide, unsteady ataxic gait. Electromyography studies indicated a sensory neuropathy. Whole-exome sequencing was pursued after tests for infectious, inflammatory and paraneoplastic causes were negative.
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Affiliation(s)
- John E Richter
- Department of Clinical Genomics, Mayo Clinic, Jacksonville, FL, USA
| | | | | | - Ahmed Mohammad
- Department of Clinical Genomics, Mayo Clinic, Jacksonville, FL, USA
| | - Paldeep S Atwal
- Department of Clinical Genomics, Mayo Clinic, Jacksonville, FL, USA
| | - Thomas R Caulfield
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA.,Mayo Graduate School, Neurobiology of Disease, Mayo Clinic, Jacksonville, FL, USA.,Department of Health Sciences Research, Mayo Clinic, Jacksonville, FL, USA
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Pickett SJ, Grady JP, Ng YS, Gorman GS, Schaefer AM, Wilson IJ, Cordell HJ, Turnbull DM, Taylor RW, McFarland R. Phenotypic heterogeneity in m.3243A>G mitochondrial disease: The role of nuclear factors. Ann Clin Transl Neurol 2018; 5:333-345. [PMID: 29560378 PMCID: PMC5846390 DOI: 10.1002/acn3.532] [Citation(s) in RCA: 87] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 12/21/2017] [Indexed: 01/23/2023] Open
Abstract
Objective The pathogenic mitochondrial DNA m.3243A>G mutation is associated with a wide range of clinical features, making disease prognosis extremely difficult to predict. We aimed to understand the cause of this heterogeneity. Methods We examined the phenotypic profile of 238 adult m.3243A>G carriers (patients and asymptomatic carriers) from the UK MRC Mitochondrial Disease Patient Cohort using the Newcastle Mitochondrial Disease Adult Scale. We modeled the role of risk factors for the development of specific phenotypes using proportional odds logistic regression. As mitochondria are under the dual control of their own and the nuclear genome, we examined the role of additive nuclear genetic factors in the development of these phenotypes within 46 pedigrees from the cohort. Results Seizures and stroke‐like episodes affect 25% and 17% of patients, respectively; more common features include hearing impairment, gastrointestinal disturbance, psychiatric involvement, and ataxia. Age, age‐adjusted blood heteroplasmy levels, and sex are poor predictors of phenotypic severity. Hearing impairment, diabetes, and encephalopathy show the strongest associations, but pseudo‐R2 values are low (0.14–0.17). We found a high heritability estimate for psychiatric involvement (h2=0.76, P = 0.0003) and moderate estimates for cognition (h2=0.46, P = 0.0021), ataxia (h2 = 0.45, P = 0.0011), migraine (h2 = 0.41, P = 0.0138), and hearing impairment (h2 = 0.40, P = 0.0050). Interpretation Our results provide good evidence for the presence of nuclear genetic factors influencing clinical outcomes in m.3234A>G‐related disease, paving the way for future work identifying these through large‐scale genetic linkage and association studies, increasing our understanding of the pathogenicity of m.3243A>G and providing improved estimates of prognosis.
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Affiliation(s)
- Sarah J Pickett
- Wellcome Centre for Mitochondrial Research Institute of Neuroscience Newcastle University Newcastle upon Tyne UK
| | - John P Grady
- Wellcome Centre for Mitochondrial Research Institute of Neuroscience Newcastle University Newcastle upon Tyne UK.,Present address: Kinghorn Centre for Clinical Genomics Garvan Institute Sydney NSW Australia
| | - Yi Shiau Ng
- Wellcome Centre for Mitochondrial Research Institute of Neuroscience Newcastle University Newcastle upon Tyne UK
| | - Gráinne S Gorman
- Wellcome Centre for Mitochondrial Research Institute of Neuroscience Newcastle University Newcastle upon Tyne UK
| | - Andrew M Schaefer
- Wellcome Centre for Mitochondrial Research Institute of Neuroscience Newcastle University Newcastle upon Tyne UK
| | - Ian J Wilson
- Institute of Genetic Medicine Newcastle University Newcastle upon Tyne UK
| | - Heather J Cordell
- Institute of Genetic Medicine Newcastle University Newcastle upon Tyne UK
| | - Doug M Turnbull
- Wellcome Centre for Mitochondrial Research Institute of Neuroscience Newcastle University Newcastle upon Tyne UK
| | - Robert W Taylor
- Wellcome Centre for Mitochondrial Research Institute of Neuroscience Newcastle University Newcastle upon Tyne UK
| | - Robert McFarland
- Wellcome Centre for Mitochondrial Research Institute of Neuroscience Newcastle University Newcastle upon Tyne UK
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Vidaurre J, Gedela S, Yarosz S. Antiepileptic Drugs and Liver Disease. Pediatr Neurol 2017; 77:23-36. [PMID: 29097018 DOI: 10.1016/j.pediatrneurol.2017.09.013] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 09/05/2017] [Accepted: 09/19/2017] [Indexed: 12/22/2022]
Abstract
Acute, symptomatic seizures or epilepsy may complicate the course of hepatic disease. Choosing the most appropriate antiepileptic drug in this setting represents a difficult challenge, as most medications are metabolized by the liver. This article focuses on the acute and chronic treatment of seizures in patients with advanced liver disease and reviews the hepatotoxic potential of specific antiepileptic drugs. Newer antiepileptic drugs without, or with minimal, hepatic metabolism, such as levetiracetam, lacosamide, topiramate, gabapentin, and pregabalin should be used as first-line therapy. Medications undergoing extensive hepatic metabolism, such as valproic acid, phenytoin, and felbamate should be used as drugs of last resort. In special circumstances, as in patients affected by acute intermittent porphyria, exposure to most antiepileptic drugs could precipitate attacks. In this clinical scenario, bromides, levetiracetam, gabapentin, and vigabatrin constitute safe choices. For the treatment of status epilepticus, levetiracetam and lacosamide, available in intravenous preparations, are good second-line therapies after benzodiazepines fail to control seizures. Hepatotoxicity is also a rare and unexpected side effect of some antiepileptic drugs. Drugs such as valproic acid, phenytoin, and felbamate, have a well-recognized association with liver toxicity. Other antiepileptic drugs, including phenobarbital, benzodiazepines, ethosuximide, and the newer generations of antiepileptic drugs, have only rarely been linked to hepatotoxicity. Thus physicians should be mindful of the pharmacokinetic profile and the hepatotoxic potential of the different antiepileptic drugs available to treat patients affected by liver disease.
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Affiliation(s)
- Jorge Vidaurre
- Division of Pediatric Neurology, Department of Pediatrics, Nationwide Children's Hospital, Columbus, Ohio.
| | - Satyanarayana Gedela
- Division of Pediatric Neurology, Department of Pediatrics, Nationwide Children's Hospital, Columbus, Ohio
| | - Shannon Yarosz
- Division of Pediatric Neurology, Department of Pediatrics, Nationwide Children's Hospital, Columbus, Ohio
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29
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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.
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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.
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30
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Morrow EH, Camus MF. Mitonuclear epistasis and mitochondrial disease. Mitochondrion 2017; 35:119-122. [PMID: 28603048 DOI: 10.1016/j.mito.2017.06.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 06/06/2017] [Accepted: 06/06/2017] [Indexed: 12/01/2022]
Affiliation(s)
- Edward H Morrow
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom.
| | - M Florencia Camus
- Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, United Kingdom
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Kammenga JE. The background puzzle: how identical mutations in the same gene lead to different disease symptoms. FEBS J 2017; 284:3362-3373. [PMID: 28390082 DOI: 10.1111/febs.14080] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2017] [Revised: 03/31/2017] [Accepted: 04/05/2017] [Indexed: 01/05/2023]
Abstract
Identical disease-causing mutations can lead to different symptoms in different people. The reason for this has been a puzzling problem for geneticists. Differential penetrance and expressivity of mutations has been observed within individuals with different and similar genetic backgrounds. Attempts have been made to uncover the underlying mechanisms that determine differential phenotypic effects of identical mutations through studies of model organisms. From these studies evidence is accumulating that to understand disease mechanism or predict disease prevalence, an understanding of the influence of genetic background is as important as the putative disease-causing mutations of relatively large effect. This review highlights current insights into phenotypic variation due to gene interactions, epigenetics and stochasticity in model organisms, and discusses their importance for understanding the mutational effect on disease symptoms.
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Affiliation(s)
- Jan E Kammenga
- Laboratory of Nematology, Wageningen University, The Netherlands
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Nurminen A, Farnum GA, Kaguni LS. Pathogenicity in POLG syndromes: DNA polymerase gamma pathogenicity prediction server and database. BBA CLINICAL 2017; 7:147-156. [PMID: 28480171 PMCID: PMC5413197 DOI: 10.1016/j.bbacli.2017.04.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 04/11/2017] [Accepted: 04/12/2017] [Indexed: 12/19/2022]
Abstract
DNA polymerase gamma (POLG) is the replicative polymerase responsible for maintaining mitochondrial DNA (mtDNA). Disorders related to its functionality are a major cause of mitochondrial disease. The clinical spectrum of POLG syndromes includes Alpers-Huttenlocher syndrome (AHS), childhood myocerebrohepatopathy spectrum (MCHS), myoclonic epilepsy myopathy sensory ataxia (MEMSA), the ataxia neuropathy spectrum (ANS) and progressive external ophthalmoplegia (PEO). We have collected all publicly available POLG-related patient data and analyzed it using our pathogenic clustering model to provide a new research and clinical tool in the form of an online server. The server evaluates the pathogenicity of both previously reported and novel mutations. There are currently 176 unique point mutations reported and found in mitochondrial patients in the gene encoding the catalytic subunit of POLG, POLG. The mutations are distributed nearly uniformly along the length of the primary amino acid sequence of the gene. Our analysis shows that most of the mutations are recessive, and that the reported dominant mutations cluster within the polymerase active site in the tertiary structure of the POLG enzyme. The POLG Pathogenicity Prediction Server (http://polg.bmb.msu.edu) is targeted at clinicians and scientists studying POLG disorders, and aims to provide the most current available information regarding the pathogenicity of POLG mutations. Multi-level access to crucial data supporting diagnosis/prognosis of POLG syndromes Clustering protocol enables identification of novel neutral polymorphisms Identical alleles displaying variable symptoms evidence unidentified components POLG enzymes with premature stop codons, insertions/deletions group biochemically Dominant POLG mutations all lie within a critical location in the structure
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Key Words
- AHS, Alpers-Huttenlocher syndrome
- ANS, Ataxia neuropathy spectrum
- DNA polymerase gamma
- IP, Intrinsic processivity subdomain of POLGA spacer-domain
- MCHS, Childhood myocerebrohepatopathy spectrum
- MEMSA, Myoclonic epilepsy myopathy sensory ataxia
- Mitochondrial disorder
- Mutation database
- PDB ID, Four-character identification code for a protein structure in the RSCB PDB database
- PEO, Progressive external ophthalmoplegia
- PNF, Putatively non-functional enzyme
- POLG syndrome
- POLG, DNA polymerase gamma
- POLGA, Catalytic subunit of DNA polymerase gamma
- POLGB, Accessory subunit of DNA polymerase gamma
- Pathogenicity prediction
- Patient database
- SNP, Single nucleotide polymorphism/non-pathogenic mutation
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Affiliation(s)
- Anssi Nurminen
- Institute of Biosciences and Medical Technology, University of Tampere, Tampere, Finland
| | - Gregory A Farnum
- Department of Biochemistry and Molecular Biology and Center for Mitochondrial Science and Medicine, Michigan State University, East Lansing, MI, USA
| | - Laurie S Kaguni
- Institute of Biosciences and Medical Technology, University of Tampere, Tampere, Finland.,Department of Biochemistry and Molecular Biology and Center for Mitochondrial Science and Medicine, Michigan State University, East Lansing, MI, USA
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When the word doesn't come out: A synthetic overview of dysarthria. J Neurol Sci 2016; 369:354-360. [DOI: 10.1016/j.jns.2016.08.048] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 07/30/2016] [Accepted: 08/22/2016] [Indexed: 12/14/2022]
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Rossi M, Medina Escobar A, Radrizzani M, Tenembaum S, Perandones C, Merello M. Dystonia in a Patient with Autosomal-Dominant Progressive External Ophthalmoplegia Type 1 Caused by Mutation in the POLG Gene. Mov Disord Clin Pract 2016; 4:266-269. [PMID: 30838265 DOI: 10.1002/mdc3.12397] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 05/14/2016] [Accepted: 05/16/2016] [Indexed: 11/11/2022] Open
Affiliation(s)
- Malco Rossi
- Movement Disorders Section Neuroscience Department Raul Carrea Institute for Neurological Research (FLENI) Buenos Aires Argentina
| | - Alex Medina Escobar
- Movement Disorders Section Neuroscience Department Raul Carrea Institute for Neurological Research (FLENI) Buenos Aires Argentina
| | - Martin Radrizzani
- Laboratory of Neuro and Molecular Cytogenetic (CONICET) School of Sciences and Technology CESyMA National University of San Martin Buenos Aires Argentina
| | - Silvia Tenembaum
- Department of Pediatric Neurology National Pediatric Hospital Dr. Juan P. Garrahan Buenos Aires Argentina
| | - Claudia Perandones
- Scientific and Technological Coordination Unit of the ANLIS Directorate National Administration of Laboratories and Institutes of Health, Dr. Carlos G. Malbran Buenos Aires Argentina.,Argentine National Scientific and Technological Research Council (CONICET) Buenos Aires Argentina
| | - Marcelo Merello
- Movement Disorders Section Neuroscience Department Raul Carrea Institute for Neurological Research (FLENI) Buenos Aires Argentina.,Argentine National Scientific and Technological Research Council (CONICET) Buenos Aires Argentina
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McKenzie M, Duchen MR. Impaired Cellular Bioenergetics Causes Mitochondrial Calcium Handling Defects in MT-ND5 Mutant Cybrids. PLoS One 2016; 11:e0154371. [PMID: 27110715 PMCID: PMC4844100 DOI: 10.1371/journal.pone.0154371] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 04/12/2016] [Indexed: 11/18/2022] Open
Abstract
Mutations in mitochondrial DNA (mtDNA) can cause mitochondrial disease, a group of metabolic disorders that affect both children and adults. Interestingly, individual mtDNA mutations can cause very different clinical symptoms, however the factors that determine these phenotypes remain obscure. Defects in mitochondrial oxidative phosphorylation can disrupt cell signaling pathways, which may shape these disease phenotypes. In particular, mitochondria participate closely in cellular calcium signaling, with profound impact on cell function. Here, we examined the effects of a homoplasmic m.13565C>T mutation in MT-ND5 on cellular calcium handling using transmitochondrial cybrids (ND5 mutant cybrids). We found that the oxidation of NADH and mitochondrial membrane potential (Δψm) were significantly reduced in ND5 mutant cybrids. These metabolic defects were associated with a significant decrease in calcium uptake by ND5 mutant mitochondria in response to a calcium transient. Inhibition of glycolysis with 2-deoxy-D-glucose did not affect cytosolic calcium levels in control cybrids, but caused an increase in cytosolic calcium in ND5 mutant cybrids. This suggests that glycolytically-generated ATP is required not only to maintain Δψm in ND5 mutant mitochondria but is also critical for regulating cellular calcium homeostasis. We conclude that the m.13565C>T mutation in MT-ND5 causes defects in both mitochondrial oxidative metabolism and mitochondrial calcium sequestration. This disruption of mitochondrial calcium handling, which leads to defects in cellular calcium homeostasis, may be an important contributor to mitochondrial disease pathogenesis.
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Affiliation(s)
- Matthew McKenzie
- Centre for Genetic Diseases, Hudson Institute of Medical Research, Clayton, Melbourne, Victoria 3168, Australia
- The Department of Molecular and Translational Science, Monash University, Clayton, Melbourne, Victoria 3168, Australia
- * E-mail:
| | - Michael R. Duchen
- Department of Physiology, University College London, Gower St, London, UK WC1E6BT
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