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Hikmat O, Naess K, Engvall M, Klingenberg C, Rasmussen M, Brodtkorb E, Ostergaard E, de Coo I, Pias-Peleteiro L, Isohanni P, Uusimaa J, Majamaa K, Kärppä M, Ortigoza-Escobar JD, Tangeraas T, Berland S, Harrison E, Biggs H, Horvath R, Darin N, Rahman S, Bindoff LA. Status epilepticus in POLG disease: a large multinational study. J Neurol 2024:10.1007/s00415-024-12463-5. [PMID: 38822839 DOI: 10.1007/s00415-024-12463-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Revised: 05/16/2024] [Accepted: 05/20/2024] [Indexed: 06/03/2024]
Abstract
We aimed to provide a detailed phenotypic description of status epilepticus (SE) in a large cohort of patients with POLG disease and identify prognostic biomarkers to improve the management of this life-threatening condition. In a multinational, retrospective study with data on patients with POLG disease from seven European countries, we identified those who had SE. The age of SE onset, accompanying clinical, laboratory, imaging and genetic findings were analysed. One hundred and ninety-five patients with genetically confirmed POLG disease were recruited, of whom 67% (130/194) had epilepsy. SE was identified in 77% (97/126), with a median age of SE onset of 7 years. SE was the presenting symptom of the disease in 43% (40/93) of those with SE, while 57% (53/93) developed SE during the disease course. Convulsive SE was reported in 97% (91/94) followed by epilepsia partialis continua in 67% (56/84). Liver impairment 78% (74/95), ataxia 69% (60/87), stroke-like episodes 57% (50/88), were the major comorbidities. In the majority (66%; 57/86) with SE this became refractory or super-refractory. The presence of seizures was associated with significantly higher mortality compared to those without (P ≤ 0.001). The median time from SE debut to death was 5 months. SE is a major clinical feature of POLG disease in early and juvenile to adult-onset disease and can be the presenting feature or arise as part of a multisystem disease. It is associated with high morbidity and mortality, with the majority of patients with SE going on to develop refractory or super-refractory SE.
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Affiliation(s)
- Omar Hikmat
- Department of Paediatrics and Adolescent Medicine, Haukeland University Hospital, Bergen, Norway.
- Department of Clinical Medicine (K1), University of Bergen, Bergen, Norway.
- European Reference Network for Hereditary Metabolic Disorders, Oslo, Norway.
| | - Karin Naess
- Centre for Inherited Metabolic Diseases, Karolinska University Hospital, Stockholm, Sweden
- Department of Neuropediatrics, Astrid Lindgren Childrens Hospital, Karolinska University Hospital, Stockholm, Sweden
| | - Martin Engvall
- Centre for Inherited Metabolic Diseases, Karolinska University Hospital, Stockholm, Sweden
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Claus Klingenberg
- Department of Paediatric and Adolescent Medicine, University Hospital of North Norway, Tromso, Norway
- Paediatric Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, Tromso, Norway
| | - Magnhild Rasmussen
- Division of Paediatric and Adolescent Medicine, Department of Clinical Neurosciences for Children, Oslo University Hospital, Oslo, Norway
- Department of Neurology, Unit for Congenital and Hereditary Neuromuscular Disorders, Oslo University Hospital, Oslo, Norway
| | - Eylert Brodtkorb
- Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway
- Department of Neurology and Clinical Neurophysiology, St. Olav University Hospital, Trondheim, Norway
| | - Elsebet Ostergaard
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
- Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Irenaeus de Coo
- Faculty of Health, Medicine and Life Sciences, Department of Toxicology, University of Maastricht, Maastricht, The Netherlands
| | - Leticia Pias-Peleteiro
- Neurometabolic Disorders Unit, Department of Child Neurology/ Department of Genetics and Molecular Medicine, Sant Joan de Déu Children´S Hospital, Barcelona, Spain
| | - Pirjo Isohanni
- Department of Pediatric Neurology, Children's Hospital and Pediatric Research Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- European Reference Network for Hereditary Metabolic Disorders, Helsinki, Finland
| | - Johanna Uusimaa
- Research Unit of Clinical Medicine, University of Oulu, Oulu, Finland
- Department of Pediatric Neurology, Clinic for Children and Adolescents and Medical Research Center, Oulu University Hospital, Oulu, Finland
| | - Kari Majamaa
- Research Unit of Clinical Medicine, Neurology, and Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland
- Neurocenter, Oulu University Hospital, Oulu, Finland
| | - Mikko Kärppä
- Research Unit of Clinical Medicine, Neurology, and Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland
- Neurocenter, Oulu University Hospital, Oulu, Finland
| | - Juan Dario Ortigoza-Escobar
- Movement Disorders Unit, Institut de Recerca Sant Joan de Déu, CIBERER-ISCIII, Barcelona, Spain
- European Reference Network for Rare Neurological Diseases (ERN-RND), Barcelona, Spain
| | - Trine Tangeraas
- European Reference Network for Hereditary Metabolic Disorders, Oslo, Norway
- Norwegian National Unit for Newborn Screening, Division of Pediatric and Adolescent Medicine, Oslo University Hospital, Oslo, Norway
| | - Siren Berland
- Department of Medical Genetics, Haukeland University Hospital, Bergen, Norway
| | - Emma Harrison
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Heather Biggs
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Rita Horvath
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Niklas Darin
- Department of Pediatrics, Institute of Clinical Sciences, University of Gothenburg, Queen Silvia Children's Hospital, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - 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
- European Reference Network for Hereditary Metabolic Disorders, London, UK
| | - Laurence A Bindoff
- Department of Clinical Medicine (K1), University of Bergen, Bergen, Norway
- European Reference Network for Hereditary Metabolic Disorders, Oslo, Norway
- Department of Neurology, Haukeland University Hospital, 5021, Bergen, Norway
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Wang C, Li M, Liu Z, Guo Y, Liu H, Zhao P. Genetic evaluation in indeterminate acute liver failure: A post hoc analysis. Arab J Gastroenterol 2024; 25:125-128. [PMID: 38705812 DOI: 10.1016/j.ajg.2024.03.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2023] [Revised: 01/28/2024] [Accepted: 03/20/2024] [Indexed: 05/07/2024]
Abstract
BACKGROUND AND STUDY AIMS There are limited data regarding indeterminate acute liver failure (ALF). The study aims to perform a post hoc analysis using genetic methods for the ALF cases with indeterminate etiology. PATIENTS AND METHODS Stored blood samples from these patients with indeterminate ALF were collected. Whole-exome sequencing (WES) was used to evaluate the pathogenesis of indeterminate ALF. RESULTS A total of 16 samples from 11 adult patients and 5 pediatric patients with indeterminate ALF were available. Among the adult patients, one female patient was identified with two heterozygous variants (c.2333G > T (p.Arg778Leu) and c.2310C > G (p.Leu770 = )) in the adenosine triphosphatase copper-transporting beta (ATP7B) gene, and two male patients were found to harbor heterozygous and homozygous variants (c.686C > A (p.Pro229Gln) plus homozygousvariantA(TA)6TAAinsTA (-), andc.1456 T > G (p.Tyr486Asp) plus c.211G > A (p.Gly71Arg)) in the uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) gene. For the pediatric patients, single heterozygous variant (c.2890C > T (p.Arg964Cys)) in the polymerase gamma (POLG) gene was found in 1 male child, and two heterozygous variants (c.1909A > G (p.Lys637Glu) and c.3646G > A (p.Val1216Ile)) in the tetratricopeptide repeat domain 37 (TTC37) gene were found in 1 female child. No variants clinically associated with known liver diseases were revealed in the remaining patients. CONCLUSION These results expand the knowledge of ALF with indeterminate etiology. WES is helpful to reveal possible candidate genes for indeterminate ALF, but incomplete consistency between the genotype and phenotype in some cases still challenge the accurate diagnosis.
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Affiliation(s)
- Chunya Wang
- Beijing Anzhen Hospital, Capital Medical University, Beijing 100029, China
| | - Meina Li
- Faculty of Military Health Services, Second Military Medical University, Shanghai 200433,China
| | - Zhenhua Liu
- Department of Pathology, Seventh Medical Center, Chinese PLA General Hospital, Beijing 100010, China
| | - Yupeng Guo
- College of Public Health, Mudanjiang Medical University, Mudanjiang 157011, Heilongjiang, China
| | - Huijuan Liu
- Fifth Medical Center (formerly Beijing 302 Hospital), Chinese PLA General Hospital, Beijing 100039, China
| | - Pan Zhao
- Fifth Medical Center (formerly Beijing 302 Hospital), Chinese PLA General Hospital, Beijing 100039, China.
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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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Malyshev SM, Popov KD, Simakov KV, Marichev AO, Topuzova MP, Smirnova AY, Ryzhkov AV, Basek IV, Yanishevskij SN, Alekseeva TM, Schlyakhto EV. [Status epilepticus in a pregnant patient with a previously unrecognized POLG-associated disease]. Zh Nevrol Psikhiatr Im S S Korsakova 2023; 123:129-135. [PMID: 37966452 DOI: 10.17116/jnevro2023123101129] [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] [Indexed: 11/16/2023]
Abstract
POLG-associated diseases are rare causes of pharmacoresistant epilepsy and status epilepticus, especially in adult patients. Phenotypic and genotypic variability in these conditions causes the complexity of their diagnosis. In the study, we report a case of a 33-year-old female patient who developed recurrent convulsive status epilepticus with focal clonic onset at the week 22/23 of pregnancy. Intensive anti-seizure therapy was administered, including the use of valproic acid, as well as the treatment of somatic complications. Given the acute onset, the semiology of seizures, the presence of psychopathological symptoms, autoimmune etiology of the disease was initially suspected. A month after the withdrawal of valproic acid, the patient began to show signs of toxic hepatitis, which eventually led to death. According to the results of whole-exome sequencing obtained later, the patient was a carrier of a pathogenic homozygous variant c.2243G>C (p.W748S) in the POLG gene. The presented case highlights the importance of molecular genetic testing and the risk associated with valproic acid hepatotoxicity in patients with cryptogenic epileptic status.
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Affiliation(s)
- S M Malyshev
- Almazov National Medical Research Centre, St Petersburg, Russia
| | - K D Popov
- Almazov National Medical Research Centre, St Petersburg, Russia
| | - K V Simakov
- Almazov National Medical Research Centre, St Petersburg, Russia
| | - A O Marichev
- Almazov National Medical Research Centre, St Petersburg, Russia
| | - M P Topuzova
- Almazov National Medical Research Centre, St Petersburg, Russia
| | - A Yu Smirnova
- Almazov National Medical Research Centre, St Petersburg, Russia
| | - A V Ryzhkov
- Almazov National Medical Research Centre, St Petersburg, Russia
| | - I V Basek
- Almazov National Medical Research Centre, St Petersburg, Russia
| | | | - T M Alekseeva
- Almazov National Medical Research Centre, St Petersburg, Russia
| | - E V Schlyakhto
- Almazov National Medical Research Centre, St Petersburg, Russia
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Falabella M, Minczuk M, Hanna MG, Viscomi C, Pitceathly RDS. Gene therapy for primary mitochondrial diseases: experimental advances and clinical challenges. Nat Rev Neurol 2022; 18:689-698. [PMID: 36257993 DOI: 10.1038/s41582-022-00715-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/25/2022] [Indexed: 11/09/2022]
Abstract
The variable clinical and biochemical manifestations of primary mitochondrial diseases (PMDs), and the complexity of mitochondrial genetics, have proven to be a substantial barrier to the development of effective disease-modifying therapies. Encouraging data from gene therapy trials in patients with Leber hereditary optic neuropathy and advances in DNA editing techniques have raised expectations that successful clinical transition of genetic therapies for PMDs is feasible. However, obstacles to the clinical application of genetic therapies in PMDs remain; the development of innovative, safe and effective genome editing technologies and vectors will be crucial to their future success and clinical approval. In this Perspective, we review progress towards the genetic treatment of nuclear and mitochondrial DNA-related PMDs. We discuss advances in mitochondrial DNA editing technologies alongside the unique challenges to targeting mitochondrial genomes. Last, we consider ongoing trials and regulatory requirements.
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Affiliation(s)
- Micol Falabella
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Michal Minczuk
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK
| | - Michael G Hanna
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
- NHS Highly Specialised Service for Rare Mitochondrial Disorders, Queen Square Centre for Neuromuscular Diseases, The National Hospital for Neurology and Neurosurgery, London, UK
| | - Carlo Viscomi
- Department of Biomedical Sciences, University of Padova, Padova, Italy
- CESNE - Center for the Study of Neurodegeneration, University of Padova, Padova, Italy
| | - Robert D S Pitceathly
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK.
- NHS Highly Specialised Service for Rare Mitochondrial Disorders, Queen Square Centre for Neuromuscular Diseases, The National Hospital for Neurology and Neurosurgery, London, UK.
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6
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Pedersen ZO, Holm-Yildiz S, Dysgaard T. Nutritional Interventions for Patients with Mitochondrial POLG-Related Diseases: A Systematic Review on Efficacy and Safety. Int J Mol Sci 2022; 23:ijms231810658. [PMID: 36142570 PMCID: PMC9502393 DOI: 10.3390/ijms231810658] [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: 08/21/2022] [Revised: 09/08/2022] [Accepted: 09/09/2022] [Indexed: 12/03/2022] Open
Abstract
Ketogenic diet is recommended as a treatment to reduce seizure frequency in patients with intractable epilepsy. The evidence and safety results are sparse for diet interventions in patients with pathogenic polymerase gamma (POLG) variants and intractable epilepsy. The aim of this systematic review is to summarize the efficacy of diet treatment on seizure frequency, clinical symptoms, and potential deleterious effect of liver involvement in patients with mitochondrial diseases caused by pathogenic POLG variants. Literature was searched in PubMed, Embase; and Cochrane in April 2022; no filter restrictions were imposed. The reference lists of retrieved studies were checked for additional literature. Eligibility criteria included verified pathogenic POLG variant and diet treatment. Overall, 880 studies were identified, providing eight case-reports representing nine patients eligible for inclusion. In eight of nine cases, clinical symptoms were improved; six out of nine cases reported improvements in seizure frequency. However, increasing levels of liver enzymes after initiating ketogenic diet were found in four of the nine cases, with one case revealing decreased levels of liver enzymes after initiating long-chain triglyceride restriction. Viewed together, the studies imply that ketogenic diet can have a positive impact on seizure frequency, but may induce progression of liver impairment in patients with pathogenic POLG variants.
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Rahman MM, Young CKJ, Goffart S, Pohjoismäki JLO, Young MJ. Heterozygous p.Y955C mutation in DNA polymerase γ leads to alterations in bioenergetics, complex I subunit expression, and mtDNA replication. J Biol Chem 2022; 298:102196. [PMID: 35760101 PMCID: PMC9307957 DOI: 10.1016/j.jbc.2022.102196] [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: 01/23/2022] [Revised: 06/16/2022] [Accepted: 06/17/2022] [Indexed: 12/03/2022] Open
Abstract
In human cells, ATP is generated using oxidative phosphorylation machinery, which is inoperable without proteins encoded by mitochondrial DNA (mtDNA). The DNA polymerase gamma (Polγ) repairs and replicates the multicopy mtDNA genome in concert with additional factors. The Polγ catalytic subunit is encoded by the POLG gene, and mutations in this gene cause mtDNA genome instability and disease. Barriers to studying the molecular effects of disease mutations include scarcity of patient samples and a lack of available mutant models; therefore, we developed a human SJCRH30 myoblast cell line model with the most common autosomal dominant POLG mutation, c.2864A>G/p.Y955C, as individuals with this mutation can present with progressive skeletal muscle weakness. Using on-target sequencing, we detected a 50% conversion frequency of the mutation, confirming heterozygous Y955C substitution. We found mutated cells grew slowly in a glucose-containing medium and had reduced mitochondrial bioenergetics compared with the parental cell line. Furthermore, growing Y955C cells in a galactose-containing medium to obligate mitochondrial function enhanced these bioenergetic deficits. Also, we show complex I NDUFB8 and ND3 protein levels were decreased in the mutant cell line, and the maintenance of mtDNA was severely impaired (i.e., lower copy number, fewer nucleoids, and an accumulation of Y955C-specific replication intermediates). Finally, we show the mutant cells have increased sensitivity to the mitochondrial toxicant 2′-3′-dideoxycytidine. We expect this POLG Y955C cell line to be a robust system to identify new mitochondrial toxicants and therapeutics to treat mitochondrial dysfunction.
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Affiliation(s)
- Md Mostafijur Rahman
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901
| | - Carolyn K J Young
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901
| | - Steffi Goffart
- Department of Environmental and Biological Sciences, University of Eastern Finland, 80101 Joensuu, Finland
| | - Jaakko L O Pohjoismäki
- Department of Environmental and Biological Sciences, University of Eastern Finland, 80101 Joensuu, Finland
| | - Matthew J Young
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901.
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Roy A, Kandettu A, Ray S, Chakrabarty S. Mitochondrial DNA replication and repair defects: Clinical phenotypes and therapeutic interventions. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2022; 1863:148554. [PMID: 35341749 DOI: 10.1016/j.bbabio.2022.148554] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 03/06/2022] [Accepted: 03/16/2022] [Indexed: 12/15/2022]
Abstract
Mitochondria is a unique cellular organelle involved in multiple cellular processes and is critical for maintaining cellular homeostasis. This semi-autonomous organelle contains its circular genome - mtDNA (mitochondrial DNA), that undergoes continuous cycles of replication and repair to maintain the mitochondrial genome integrity. The majority of the mitochondrial genes, including mitochondrial replisome and repair genes, are nuclear-encoded. Although the repair machinery of mitochondria is quite efficient, the mitochondrial genome is highly susceptible to oxidative damage and other types of exogenous and endogenous agent-induced DNA damage, due to the absence of protective histones and their proximity to the main ROS production sites. Mutations in replication and repair genes of mitochondria can result in mtDNA depletion and deletions subsequently leading to mitochondrial genome instability. The combined action of mutations and deletions can result in compromised mitochondrial genome maintenance and lead to various mitochondrial disorders. Here, we review the mechanism of mitochondrial DNA replication and repair process, key proteins involved, and their altered function in mitochondrial disorders. The focus of this review will be on the key genes of mitochondrial DNA replication and repair machinery and the clinical phenotypes associated with mutations in these genes.
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Affiliation(s)
- Abhipsa Roy
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
| | - Amoolya Kandettu
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
| | - Swagat Ray
- Department of Life Sciences, School of Life and Environmental Sciences, University of Lincoln, Lincoln LN6 7TS, United Kingdom
| | - Sanjiban Chakrabarty
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India.
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Jha R, Patel H, Dubey R, Goswami JN, Bhagwat C, Saini L, K Manokaran R, John BM, Kovilapu UB, Mohimen A, Saxena A, Sondhi V. Clinical and molecular spectrum associated with Polymerase-γ related disorders. J Child Neurol 2022; 37:246-255. [PMID: 34986040 DOI: 10.1177/08830738211067065] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND POLG pathogenic variants are the commonest single-gene cause of inherited mitochondrial disease. However, the data on clinicogenetic associations in POLG-related disorders are sparse. This study maps the clinicogenetic spectrum of POLG-related disorders in the pediatric population. METHODS Individuals were recruited across 6 centers in India. Children diagnosed between January 2015 and August 2020 with pathogenic or likely pathogenic POLG variants and age of onset <15 years were eligible. Phenotypically, patients were categorized into Alpers-Huttenlocher syndrome; myocerebrohepatopathy syndrome; myoclonic epilepsy, myopathy, and sensory ataxia; ataxia-neuropathy spectrum; Leigh disease; and autosomal dominant / recessive progressive external ophthalmoplegia. RESULTS A total of 3729 genetic reports and 4256 hospital records were screened. Twenty-two patients with pathogenic variants were included. Phenotypically, patients were classifiable into Alpers-Huttenlocher syndrome (8/22; 36.4%), progressive external ophthalmoplegia (8/22; 36.4%), Leigh disease (2/22; 9.1%), ataxia-neuropathy spectrum (2/22; 9.1%), and unclassified (2/22; 9.1%). The prominent clinical manifestations included developmental delay (n = 14; 63.7%), neuroregression (n = 14; 63.7%), encephalopathy (n = 11; 50%), epilepsy (n = 11; 50%), ophthalmoplegia (n = 8; 36.4%), and liver dysfunction (n = 8; 36.4%). Forty-four pathogenic variants were identified at 13 loci, and these were clustered at exonuclease (18/44; 40.9%), linker (13/44; 29.5%), polymerase (10/44; 22.7%), and N-terminal domains (3/44; 6.8%). Genotype-phenotype analysis suggested that serious outcomes including neuroregression (odds ratio [OR] 11, 95% CI 2.5, 41), epilepsy (OR 9, 95% CI 2.4, 39), encephalopathy (OR 5.7, 95% CI 1.4, 19), and hepatic dysfunction (OR 4.6, 95% CI 21.3, 15) were associated with at least 1 variant involving linker or polymerase domain. CONCLUSIONS We describe the clinical subgroups and their associations with different POLG domains. These can aid in the development of follow-up and management strategies of presymptomatic individuals.
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Affiliation(s)
- Ruchika Jha
- Department of Pediatrics, 29590Armed Forces Medical College, Pune, India
| | - Harshkumar Patel
- Department of Pediatric Neurology, 246889Zydus Hospital, Ahmedabad, India
| | - Rachana Dubey
- Department of Pediatric Neurology, Medanta Hospital, Indore, India
| | - Jyotindra N Goswami
- Department of Pediatrics, Army Hospital (Research & Referral), New Delhi, India
| | - Chandana Bhagwat
- Department of Pediatrics, Pediatric Neurology Unit, 29751Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Lokesh Saini
- Department of Pediatrics, Pediatric Neurology Unit, 29751Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Ranjith K Manokaran
- Division of Pediatric Neurology, Department of Neurology, 204733Sri Ramachandra Institute of Higher Education, Chennai, India
| | - Biju M John
- Department of Pediatrics, 29590Armed Forces Medical College, Pune, India
| | - Uday B Kovilapu
- Department of Radiodiagnosis, 29590Armed Forces Medical College, Pune, India
| | - Aneesh Mohimen
- Department of Radiodiagnosis, 462017Command Hospital (Central Command), Lucknow, India
| | - Apoorv Saxena
- Department of Pediatrics, 29590Armed Forces Medical College, Pune, India
| | - Vishal Sondhi
- Department of Pediatrics, 29590Armed Forces Medical College, Pune, India
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Yapa NMB, Lisnyak V, Reljic B, Ryan MT. Mitochondrial dynamics in health and disease. FEBS Lett 2021; 595:1184-1204. [PMID: 33742459 DOI: 10.1002/1873-3468.14077] [Citation(s) in RCA: 126] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 03/08/2021] [Accepted: 03/09/2021] [Indexed: 12/11/2022]
Abstract
In animals, mitochondria are mainly organised into an interconnected tubular network extending across the cell along a cytoskeletal scaffold. Mitochondrial fission and fusion, as well as distribution along cytoskeletal tracks, are counterbalancing mechanisms acting in concert to maintain a mitochondrial network tuned to cellular function. Balanced mitochondrial dynamics permits quality control of the network including biogenesis and turnover, and distribution of mitochondrial DNA, and is linked to metabolic status. Cellular and organismal health relies on a delicate balance between fission and fusion, and large rearrangements in the mitochondrial network can be seen in response to cellular insults and disease. Indeed, dysfunction in the major components of the fission and fusion machineries including dynamin-related protein 1 (DRP1), mitofusins 1 and 2 (MFN1, MFN2) and optic atrophy protein 1 (OPA1) and ensuing imbalance of mitochondrial dynamics can lead to neurodegenerative disease. Altered mitochondrial dynamics is also seen in more common diseases. In this review, the machinery involved in mitochondrial dynamics and their dysfunction in disease will be discussed.
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Affiliation(s)
- Nethmi M B Yapa
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Vic, Australia
| | - Valerie Lisnyak
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Vic, Australia
| | - Boris Reljic
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Vic, Australia
| | - Michael T Ryan
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Vic, Australia
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11
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Mitochondrial DNA maintenance disorders in 102 patients from different parts of Russia: Mutational spectrum and phenotypes. Mitochondrion 2021; 57:205-212. [PMID: 33486010 DOI: 10.1016/j.mito.2021.01.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 01/02/2021] [Accepted: 01/16/2021] [Indexed: 11/20/2022]
Abstract
Currently, pathogenic variants in more than 25 nuclear genes, involved in mtDNA maintenance, are associated with human disorders. mtDNA maintenance disorders manifest with a wide range of phenotypes, from severe infantile-onset forms of myocerebrohepatopathy to late-onset forms of myopathies, chronic progressive external ophthalmoplegia, and parkinsonism. This study represents the results of molecular genetic analysis and phenotypes of 102 probands with mtDNA maintenance disorders. So far, this is the largest Russian cohort for this group of diseases. Mutations were identified in 10 mtDNA maintenance genes: POLG (n = 59), DGUOK (n = 14), TWNK (n = 14), TK2 (n = 8), MPV17 (n = 2), OPA3 (n = 1), FBXL4 (n = 1), RRM2B (n = 1), SUCLG1 (n = 1) and TYMP (n = 1). We review a mutation spectrum for the DGUOK and TWNK genes, that can be specific for the Russian population. In 34 patients we measured the blood mtDNA copy number and showed its significant reduction. Novel variants were found in 41 cases, which significantly expands the mutational landscape of mtDNA maintenance disorders.
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12
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Gowda V, Srinivasan V, Shivappa S. Childhood myocerebrohepatopathy spectrum disorder due to polymerase gamma pathogenic variant. Ann Indian Acad Neurol 2021; 24:942-943. [PMID: 35359545 PMCID: PMC8965953 DOI: 10.4103/aian.aian_607_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 07/16/2020] [Accepted: 08/03/2020] [Indexed: 11/30/2022] Open
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13
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Young CKJ, Wheeler JH, Rahman MM, Young MJ. The antiretroviral 2',3'-dideoxycytidine causes mitochondrial dysfunction in proliferating and differentiated HepaRG human cell cultures. J Biol Chem 2021; 296:100206. [PMID: 33334881 PMCID: PMC7948951 DOI: 10.1074/jbc.ra120.014885] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 12/15/2020] [Accepted: 12/17/2020] [Indexed: 02/06/2023] Open
Abstract
Nucleoside reverse transcriptase inhibitors (NRTIs) were the first drugs used to treat human immunodeficiency virus infection, and their use can cause mitochondrial toxicity, including mitochondrial DNA (mtDNA) depletion in several cases. The first-generation NRTIs, including 2',3'-dideoxycytidine (ddC), were originally and are still pursued as anticancer agents. NRTI-sensitive DNA polymerases localizing to mitochondria allow for the opportunity to poison proliferating cancer cell mtDNA replication as certain cancers rely heavily on mitochondrial functions. However, mtDNA replication is independent of the cell cycle creating a significant concern that toxicants such as ddC impair mtDNA maintenance in both proliferating and nonproliferating cells. To examine this possibility, we tested the utility of the HepaRG cell line to study ddC-induced toxicity in isogenic proliferating (undifferentiated) and nonproliferating (differentiated) cells. Following ddC exposures, we measured cell viability, mtDNA copy number, and mitochondrial bioenergetics utilizing trypan blue, Southern blotting, and extracellular flux analysis, respectively. After 13 days of 1 μM ddC exposure, proliferating and differentiated HepaRG harbored mtDNA levels of 0.9% and 17.9% compared with control cells, respectively. Cells exposed to 12 μM ddC contained even less mtDNA. By day 13, differentiated cell viability was maintained but declined for proliferating cells. Proliferating HepaRG bioenergetic parameters were severely impaired by day 8, with 1 and 12 μM ddC, whereas differentiated cells displayed defects of spare and maximal respiratory capacities (day 8) and proton-leak linked respiration (day 14) with 12 μM ddC. These results indicate HepaRG is a useful model to study proliferating and differentiated cell mitochondrial toxicant exposures.
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Affiliation(s)
- Carolyn K J Young
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois, USA
| | - Joel H Wheeler
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois, USA
| | - Md Mostafijur Rahman
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois, USA
| | - Matthew J Young
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois, USA.
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Saneto RP. Mitochondrial diseases: expanding the diagnosis in the era of genetic testing. JOURNAL OF TRANSLATIONAL GENETICS AND GENOMICS 2020; 4:384-428. [PMID: 33426505 PMCID: PMC7791531 DOI: 10.20517/jtgg.2020.40] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mitochondrial diseases are clinically and genetically heterogeneous. These diseases were initially described a little over three decades ago. Limited diagnostic tools created disease descriptions based on clinical, biochemical analytes, neuroimaging, and muscle biopsy findings. This diagnostic mechanism continued to evolve detection of inherited oxidative phosphorylation disorders and expanded discovery of mitochondrial physiology over the next two decades. Limited genetic testing hampered the definitive diagnostic identification and breadth of diseases. Over the last decade, the development and incorporation of massive parallel sequencing has identified approximately 300 genes involved in mitochondrial disease. Gene testing has enlarged our understanding of how genetic defects lead to cellular dysfunction and disease. These findings have expanded the understanding of how mechanisms of mitochondrial physiology can induce dysfunction and disease, but the complete collection of disease-causing gene variants remains incomplete. This article reviews the developments in disease gene discovery and the incorporation of gene findings with mitochondrial physiology. This understanding is critical to the development of targeted therapies.
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Affiliation(s)
- Russell P. Saneto
- Center for Integrative Brain Research, Neuroscience Institute, Seattle, WA 98101, USA
- Department of Neurology/Division of Pediatric Neurology, Seattle Children’s Hospital/University of Washington, Seattle, WA 98105, USA
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15
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Mental health and health related quality of life in mitochondrial POLG disease. Mitochondrion 2020; 55:95-99. [PMID: 32976988 DOI: 10.1016/j.mito.2020.09.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 09/01/2020] [Accepted: 09/18/2020] [Indexed: 11/20/2022]
Abstract
We aimed to assess the impact of POLG disease on mental health and quality of life in 15 patients using the Symptom Checklist-90-R (SCL-90-R) and Short-Form 36 Health Survey (RAND-36). We found increased scores in all nine subscales of SCL-90-R, particularly phobic anxiety, depression and somatization. Further, patients reported considerably lower scores in all RAND-36 domains. This study revealed a global decline in mental health and poor quality of life in patients with POLG disease and highlights the need for increased awareness and systematic assessment in order to improve their quality of life and mental health.
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Hikmat O, Naess K, Engvall M, Klingenberg C, Rasmussen M, Tallaksen CME, Samsonsen C, Brodtkorb E, Ostergaard E, de Coo R, Pias-Peleteiro L, Isohanni P, Uusimaa J, Darin N, Rahman S, Bindoff LA. The impact of gender, puberty, and pregnancy in patients with POLG disease. Ann Clin Transl Neurol 2020; 7:2019-2025. [PMID: 32949115 PMCID: PMC7545595 DOI: 10.1002/acn3.51199] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 08/28/2020] [Accepted: 08/28/2020] [Indexed: 12/31/2022] Open
Abstract
Objective To study the impact of gender, puberty, and pregnancy on the expression of POLG disease, one of the most common mitochondrial diseases known. Methods Clinical, laboratory, and genetic data were collected retrospectively from 155 patients with genetically confirmed POLG disease recruited from seven European countries. We used the available data to study the impact of gender, puberty, and pregnancy on disease onset and deterioration. Results We found that disease onset early in life was common in both sexes but there was also a second peak in females around the time of puberty. Further, pregnancy had a negative impact with 10 of 14 women (71%) experiencing disease onset or deterioration during pregnancy. Interpretation Gender clearly influences the expression of POLG disease. While onset very early in life was common in both males and females, puberty in females appeared associated both with disease onset and increased disease activity. Further, both disease onset and deterioration, including seizure aggravation and status epilepticus, appeared to be associated with pregnancy. Thus, whereas disease activity appears maximal early in life with no subsequent peaks in males, both menarche and pregnancy appear associated with disease onset or worsening in females. This suggests that hormonal changes may be a modulating factor.
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Affiliation(s)
- Omar Hikmat
- Department of Paediatrics and Adolescent Medicine, Haukeland University Hospital, Bergen, 5021, Norway.,Department of Clinical Medicine (K1), University of Bergen, Bergen, Norway
| | - Karin Naess
- Centre for Inherited Metabolic Diseases, Karolinska University Hospital, Stockholm, Sweden.,Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden
| | - Martin Engvall
- Centre for Inherited Metabolic Diseases, Karolinska University Hospital, Stockholm, Sweden.,Department of Molecular Medicine and Surgery, Karolinska Institute, Stockholm, Sweden
| | - Claus Klingenberg
- Department of Paediatric and Adolescent Medicine, University Hospital of North Norway, Tromso, Norway.,Paediatric Research Group, Department of Clinical Medicine, UiT- The Arctic University of Norway, Tromso, Norway
| | - Magnhild Rasmussen
- Women and Children's Division, Department of Clinical Neurosciences for Children, Oslo University Hospital, Oslo, Norway.,Unit for Congenital and Hereditary Neuromuscular Disorders, Department of Neurology, Oslo University Hospital, Oslo, Norway
| | - Chantal M E Tallaksen
- Department of Neurology, Oslo University Hospital, Oslo, Norway.,Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Christian Samsonsen
- Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway.,Department of Neurology and Clinical Neurophysiology, St. Olav's University Hospital, Trondheim, Norway
| | - Eylert Brodtkorb
- Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway.,Department of Neurology and Clinical Neurophysiology, St. Olav's University Hospital, Trondheim, Norway
| | - Elsebet Ostergaard
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Rene de Coo
- Department of Neurology, Medical Spectrum Twente, Enschede, The Netherlands.,Department of Genetics and Cell Biology, University of Maastricht, Maastricht, The Netherlands
| | | | - Pirjo Isohanni
- Department of Pediatric Neurology, Children's Hospital, Helsinki University Hospital, Helsinki, Finland.,Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Johanna Uusimaa
- PEDEGO Research Unit, University of Oulu, Oulu, Finland.,Department of Pediatric Neurology, Clinic for Children and Adolescents, Medical Research Center, Oulu University Hospital, Oulu, Finland
| | - Niklas Darin
- Department of Pediatrics, The Queen Silvia Children's Hospital, University of Gothenburg, Gothenburg, Sweden
| | - Shamima Rahman
- Mitochondrial Research Group, UCL Great Ormond Street Institute of Child Health, London, United Kingdom.,Metabolic Unit, Great Ormond Street Hospital for Children, NHS Foundation Trust, London, United Kingdom
| | - Laurence A Bindoff
- Department of Clinical Medicine (K1), University of Bergen, Bergen, Norway.,Department of Neurology, Haukeland University Hospital, Bergen, 5021, Norway
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17
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Hikmat O, Naess K, Engvall M, Klingenberg C, Rasmussen M, Tallaksen CM, Brodtkorb E, Ostergaard E, de Coo IFM, Pias-Peleteiro L, Isohanni P, Uusimaa J, Darin N, Rahman S, Bindoff LA. Simplifying the clinical classification of polymerase gamma (POLG) disease based on age of onset; studies using a cohort of 155 cases. J Inherit Metab Dis 2020; 43:726-736. [PMID: 32391929 DOI: 10.1002/jimd.12211] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 01/02/2020] [Accepted: 01/03/2020] [Indexed: 01/14/2023]
Abstract
BACKGROUND Variants in POLG are one of the most common causes of inherited mitochondrial disease. Phenotypic classification of POLG disease has evolved haphazardly making it complicated and difficult to implement in everyday clinical practise. The aim of our study was to simplify the classification and facilitate better clinical recognition. METHODS A multinational, retrospective study using data from 155 patients with POLG variants recruited from seven European countries. RESULTS We describe the spectrum of clinical features associated with POLG variants in the largest known cohort of patients. While clinical features clearly form a continuum, stratifying patients simply according to age of onset-onset prior to age 12 years; onset between 12 and 40 years and onset after the age of 40 years, permitted us to identify clear phenotypic and prognostic differences. Prior to 12 years of age, liver involvement (87%), seizures (84%), and feeding difficulties (84%) were the major features. For those with onset between 12 and 40 years, ataxia (90%), peripheral neuropathy (84%), and seizures (71%) predominated, while for those with onset over 40 years, ptosis (95%), progressive external ophthalmoplegia (89%), and ataxia (58%) were the major clinical features. The earlier the onset the worse the prognosis. Patients with epilepsy and those with compound heterozygous variants carried significantly worse prognosis. CONCLUSION Based on our data, we propose a simplified POLG disease classification, which can be used to guide diagnostic investigations and predict disease course.
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Affiliation(s)
- Omar Hikmat
- Department of Pediatrics, Haukeland University Hospital, Bergen, Norway
- Department of Clinical Medicine (K1), University of Bergen, Bergen, Norway
| | - Karin Naess
- Centre for Inherited Metabolic Diseases, Karolinska University Hospital, Stockholm, Sweden
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Martin Engvall
- Centre for Inherited Metabolic Diseases, Karolinska University Hospital, Stockholm, Sweden
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Claus Klingenberg
- Department of Paediatric and Adolescent Medicine, University Hospital of North Norway, Tromso, Norway
- Paediatric Research Group, Department of Clinical Medicine, UiT - The Arctic University of Norway, Tromso, Norway
| | - Magnhild Rasmussen
- Women and Children's Division, Department of Clinical Neurosciences for Children, Oslo University Hospital, Oslo, Norway
- Unit for Congenital and Hereditary Neuromuscular Disorders, Department of Neurology, Oslo University Hospital, Oslo, Norway
| | - Chantal Me Tallaksen
- Department of Neurology, Oslo University Hospital, Oslo, Norway
- Faculty of Medicine, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Eylert Brodtkorb
- Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway
- Department of Neurology and Clinical Neurophysiology, St. Olav's University Hospital, Trondheim, Norway
| | - Elsebet Ostergaard
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - I F M de Coo
- Department of Neurology, Medical Spectrum Twente, Enschede, The Netherlands
- Department of Genetics and Cell Biology, University of Maastricht, Maastricht, The Netherlands
| | | | - Pirjo Isohanni
- Department of Pediatric Neurology, Children's Hospital and Pediatric Research Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Johanna Uusimaa
- PEDEGO Research Unit, University of Oulu, Oulu, Finland
- Biocenter Oulu, University of Oulu, Oulu, Finland
- Department of Pediatric Neurology, Clinic for Children and Adolescents, Medical Research Center, Oulu University Hospital, Oulu, Finland
| | - Niklas Darin
- Department of Pediatrics, The Queen Silvia Children's Hospital, University of Gothenburg, Gothenburg, Sweden
| | - 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
| | - Laurence A Bindoff
- Department of Clinical Medicine (K1), University of Bergen, Bergen, Norway
- Department of Neurology, Haukeland University Hospital, Bergen, Norway
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18
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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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19
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Infectious stress triggers a POLG-related mitochondrial disease. Neurogenetics 2019; 21:19-27. [PMID: 31655921 DOI: 10.1007/s10048-019-00593-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 09/22/2019] [Indexed: 01/22/2023]
Abstract
A 3-year-old girl presented with severe epilepsy in the context of Borrelia infection. After ceftriaxone/lidocaine administration, she showed secondarily generalized focal crises that led to neurological and motor sequelae. Genetic studies identified in the patient two heterozygous POLG mutations (c.2591A>G; p.Asn864Ser and c.3649G>C; p.Ala1217Pro). Through analysis of POLG activity in cultured fibroblasts, we confirmed that the mutations altered the mtDNA turnover. Moreover, patient fibroblasts were more sensitive than controls in the presence of a mitochondrial replication-affecting drug, the antiretroviral azidothymidine. To test if ceftriaxone treatment could worsen the deleterious effect of the patient mutations, toxicity assays were performed. Cell toxicity, without direct effect on mitochondrial respiratory function, was detected at different antibiotic concentrations. The clinical outcome, together with the different in vitro sensitivity to ceftriaxone among patient and control cells, suggested that the mitochondrial disease symptoms were hastened by the infection and were possibly worsened by the pharmacological treatment. This study underscores the benefit of early genetic diagnosis of the patients with mitochondrial diseases, since they may be a target group of patients especially vulnerable to environmental factors.
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20
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Shukla A, Saneto RP, Hebbar M, Mirzaa G, Girisha KM. A neurodegenerative mitochondrial disease phenotype due to biallelic loss-of-function variants in PNPLA8 encoding calcium-independent phospholipase A2γ. Am J Med Genet A 2019; 176:1232-1237. [PMID: 29681094 DOI: 10.1002/ajmg.a.38687] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 03/05/2018] [Accepted: 03/05/2018] [Indexed: 12/19/2022]
Abstract
Animal studies have demonstrated the critical roles of the patatin-like protein family plays in cellular growth, lipid homeostasis, and second messenger signaling the nervous system. Of the nine known calcium-independent phospholipase A2γ, only PNPLA2, PNLPA6, PNPLA9 and most recently a single patient with PNPLA8 are associated with mitochondrial-related neurodegeneration. Using whole exome sequencing, we report two unrelated individuals with variable but similar clinical features of microcephaly, severe global developmental delay, spasticity, lactic acidosis, and progressive cerebellar atrophy with biallelic loss-of-function variants in PNPLA8.
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Affiliation(s)
- Anju Shukla
- Department of Medical Genetics, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, India
| | - Russell P Saneto
- Center for Integrative Brain Research, Neuroscience Institute, Seattle Children's Research Institute, Seattle, Washington, USA.,Division of Pediatric Neurology, Department of Neurology, Neuroscience Institute, Seattle Children's Hospital, Seattle, Washington, USA
| | - Malavika Hebbar
- Department of Medical Genetics, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, India
| | - Ghayda Mirzaa
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, USA.,Department of Pediatrics, University of Washington, Seattle, Washington, USA
| | - Katta M Girisha
- Department of Medical Genetics, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, India
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21
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Mitochondrial disease genetics update: recent insights into the molecular diagnosis and expanding phenotype of primary mitochondrial disease. Curr Opin Pediatr 2018; 30:714-724. [PMID: 30199403 PMCID: PMC6467265 DOI: 10.1097/mop.0000000000000686] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
PURPOSE OF REVIEW Primary mitochondrial disease (PMD) is a genetically and phenotypically diverse group of inherited energy deficiency disorders caused by impaired mitochondrial oxidative phosphorylation (OXPHOS) capacity. Mutations in more than 350 genes in both mitochondrial and nuclear genomes are now recognized to cause primary mitochondrial disease following every inheritance pattern. Next-generation sequencing technologies have dramatically accelerated mitochondrial disease gene discovery and diagnostic yield. Here, we provide an up-to-date review of recently identified, novel mitochondrial disease genes and/or pathogenic variants that directly impair mitochondrial structure, dynamics, and/or function. RECENT FINDINGS A review of PubMed publications was performed from the past 12 months that identified 16 new PMD genes and/or pathogenic variants, and recognition of expanded phenotypes for a wide variety of mitochondrial disease genes. SUMMARY Broad-based exome sequencing has become the standard first-line diagnostic approach for PMD. This has facilitated more rapid and accurate disease identification, and greatly expanded understanding of the wide spectrum of potential clinical phenotypes. A comprehensive dual-genome sequencing approach to PMD diagnosis continues to improve diagnostic yield, advance understanding of mitochondrial physiology, and provide strong potential to develop precision therapeutics targeted to diverse aspects of mitochondrial disease pathophysiology.
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22
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Saneto RP. An update on Alpers-Huttenlocher syndrome: pathophysiology of disease and rational treatment designs. Expert Opin Orphan Drugs 2018. [DOI: 10.1080/21678707.2018.1540979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Russell P. Saneto
- Department of Neurology, Division of Pediatric Neurology, University of Washington and Seattle Children’s Hospital, Seattle, WA, USA
- Neuroscience Institute, Center for Integrative Brain Research, Seattle Children’s Hospital, Seattle, WA, USA
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23
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Specific EEG markers in POLG1 Alpers’ syndrome. Clin Neurophysiol 2018; 129:2127-2131. [DOI: 10.1016/j.clinph.2018.07.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 06/29/2018] [Accepted: 07/18/2018] [Indexed: 11/21/2022]
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Inbar-Feigenberg M, Blaser S, Hawkins C, Shannon P, Hewson S, Chitayat D. Mitochondrial POLG related disorder presenting prenatally with fetal cerebellar growth arrest. Metab Brain Dis 2018; 33:1369-1373. [PMID: 29574624 DOI: 10.1007/s11011-018-0218-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 03/12/2018] [Indexed: 11/27/2022]
Abstract
We report the prenatal findings of severe cerebellar growth arrest in two siblings with POLG1 mutations. The first presented with seizures and lactic acidosis immediately after premature birth and was diagnosed with mitochondrial disease on muscle biopsy. Molecular DNA analysis confirmed homozygous missense mutation in the POLG1 gene. The pregnancy of the second sibling was monitored closely by repeat fetal ultrasounds since the parents declined invasive testing. A detailed fetal ultrasound at 19 weeks gestation showed a small cerebellum with transcerebellar diameter (TCD) on axial cranial imaging, measuring below the 5th centile for gestational age. Molecular analysis confirmed the same homozygous familial mutation in the POLG1gene. This report further delineates the phenotypic features of the POLG related disorders and expands it to the prenatal era. Subsequent pregnancies were monitored by molecular analysis, using chorionic villus sampling (CVS).
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Affiliation(s)
- Michal Inbar-Feigenberg
- Division of Clinical and Metabolic Genetics, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada.
| | - Susan Blaser
- Department of Diagnostic Imaging, Division of Neuroradiology, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada
| | - Cynthia Hawkins
- Department of Paediatric Laboratory Medicine, Division of Neuropathology, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada
| | - Patrick Shannon
- Department of Pathology & Lab Medicine, Division of Neuropathology, Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada
| | - Stacy Hewson
- Division of Clinical and Metabolic Genetics, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada
| | - David Chitayat
- Division of Clinical and Metabolic Genetics, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada
- The Prenatal Diagnosis and Medical Genetics Program, Department of Obstetrics and Gynecology, Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada
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25
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Hikmat O, Naess K, Engvall M, Klingenberg C, Rasmussen M, Tallaksen CME, Brodtkorb E, Fiskerstrand T, Isohanni P, Uusimaa J, Darin N, Rahman S, Bindoff LA. Elevated cerebrospinal fluid protein inPOLG-related epilepsy: Diagnostic and prognostic implications. Epilepsia 2018; 59:1595-1602. [DOI: 10.1111/epi.14459] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/24/2018] [Indexed: 12/01/2022]
Affiliation(s)
- Omar Hikmat
- Department of Pediatrics; Haukeland University Hospital; Bergen Norway
- Department of Clinical Medicine (K1); University of Bergen; Bergen Norway
| | - Karin Naess
- Center for Inherited Metabolic Diseases; Karolinska University Hospital; Stockholm Sweden
- Department of Medical Biochemistry and Biophysics; Karolinska Institute; Stockholm Sweden
| | - Martin Engvall
- Center for Inherited Metabolic Diseases; Karolinska University Hospital; Stockholm Sweden
- Department of Molecular Medicine and Surgery; Karolinska Institute; Stockholm Sweden
| | - Claus Klingenberg
- Department of Pediatric and Adolescent Medicine; University Hospital of North Norway; Tromso Norway
- Pediatric Research Group; Department of Clinical Medicine; UiT-Arctic University of Norway; Tromso Norway
| | - Magnhild Rasmussen
- Women and Children's Division; Department of Clinical Neurosciences for Children; Oslo University Hospital; Oslo Norway
- Unit for Congenital and Hereditary Neuromuscular Disorders; Department of Neurology; Oslo University Hospital; Oslo Norway
| | - Chantal M. E. Tallaksen
- Department of Neurology; Oslo University Hospital; Oslo Norway
- Institute of Clinical Medicine; Faculty of Medicine; University of Oslo; Oslo Norway
| | - Eylert Brodtkorb
- Department of Neuroscience; Norwegian University of Science and Technology; Trondheim Norway
- Department of Neurology and Clinical Neurophysiology; St. Olav's University Hospital; Trondheim Norway
| | - Torunn Fiskerstrand
- Department of Medical Genetics and Molecular Medicine; Haukeland University Hospital; Bergen Norway
- Department of Clinical Science (K2); University of Bergen; Bergen Norway
| | - Pirjo Isohanni
- Department of Pediatric Neurology; Children's Hospital; University of Helsinki and Helsinki University Hospital; Helsinki Finland
- Research Programs Unit; Molecular Neurology; Biomedicum Helsinki; University of Helsinki; Helsinki Finland
| | - Johanna Uusimaa
- PEDEGO Research Unit and Biocenter Oulu; University of Oulu; Oulu Finland
- Department of Children and Adolescents; Medical Research Center; Oulu University Hospital; Oulu Finland
| | - Niklas Darin
- Department of Pediatrics; Queen Silvia Children's Hospital; University of Gothenburg; Gothenburg Sweden
| | - Shamima Rahman
- Mitochondrial Research Group; University College London Great Ormond Street Institute of Child Health; London UK
- Metabolic Unit; Great Ormond Street Hospital for Children; National Health Service Foundation Trust; London UK
| | - Laurence A. Bindoff
- Department of Clinical Medicine (K1); University of Bergen; Bergen Norway
- Department of Neurology; Haukeland University Hospital; Bergen Norway
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Abstract
Purpose of review The groundwork for mitochondrial medicine was laid 30 years ago with identification of the first disease-causing mitochondrial DNA (mtDNA) mutations in 1988. Three decades later, mutations in nearly 300 genes involving every possible mode of inheritance within both nuclear and mitochondrial genomes are now recognized to collectively comprise the largest class of inherited metabolic disease affecting at least 1 in 4,300 individuals across all ages. Significant progress has been made in recent years to improve understanding of mitochondrial biology and disease pathophysiology. Recent findings Markedly improved understanding of the highly diverse molecular etiologies of multi-systemic phenotypes in primary mitochondrial disease has resulted from massively parallel genomic sequencing technologies and improved bioinformatic resources that enable identification in individual patients of their disease's precise genetic etiology. Key informatics resources of particular utility to the mitochondrial disease genomics community have been developed, including: (1) Mitocarta 2.0 repository of 1200+ verified mitochondria-localized proteins, (2) MITOMAP Web resource of curated mtDNA genome variants, and (3) Mitochondrial Disease Sequence Data Resource (MSeqDR) that centralizes Web curation and annotation of mitochondrial disease genes and variants in both genomes, ontology-defined phenotypes, and access to many analytic tools to support genomic data mining and interpretation. Gene and mutation-based disease categorization has proven particularly useful to identify the full clinical spectrum of disease that may affect a given individual. Summary Extensive genomic advances, both in technologic platforms and bioinformatics resources, have facilitated dramatic improvement in the accurate recognition and understanding of primary mitochondrial disease.
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Family A and B DNA Polymerases in Cancer: Opportunities for Therapeutic Interventions. BIOLOGY 2018; 7:biology7010005. [PMID: 29301327 PMCID: PMC5872031 DOI: 10.3390/biology7010005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 12/14/2017] [Accepted: 12/29/2017] [Indexed: 02/07/2023]
Abstract
DNA polymerases are essential for genome replication, DNA repair and translesion DNA synthesis (TLS). Broadly, these enzymes belong to two groups: replicative and non-replicative DNA polymerases. A considerable body of data suggests that both groups of DNA polymerases are associated with cancer. Many mutations in cancer cells are either the result of error-prone DNA synthesis by non-replicative polymerases, or the inability of replicative DNA polymerases to proofread mismatched nucleotides due to mutations in 3'-5' exonuclease activity. Moreover, non-replicative, TLS-capable DNA polymerases can negatively impact cancer treatment by synthesizing DNA past lesions generated from treatments such as cisplatin, oxaliplatin, etoposide, bleomycin, and radiotherapy. Hence, the inhibition of DNA polymerases in tumor cells has the potential to enhance treatment outcomes. Here, we review the association of DNA polymerases in cancer from the A and B families, which participate in lesion bypass, and conduct gene replication. We also discuss possible therapeutic interventions that could be used to maneuver the role of these enzymes in tumorigenesis.
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Young MJ. Off-Target Effects of Drugs that Disrupt Human Mitochondrial DNA Maintenance. Front Mol Biosci 2017; 4:74. [PMID: 29214156 PMCID: PMC5702650 DOI: 10.3389/fmolb.2017.00074] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 10/31/2017] [Indexed: 12/17/2022] Open
Abstract
Nucleoside reverse transcriptase inhibitors (NRTIs) were the first drugs used to treat human immunodeficiency virus (HIV) the cause of acquired immunodeficiency syndrome. Development of severe mitochondrial toxicity has been well documented in patients infected with HIV and administered NRTIs. In vitro biochemical experiments have demonstrated that the replicative mitochondrial DNA (mtDNA) polymerase gamma, Polg, is a sensitive target for inhibition by metabolically active forms of NRTIs, nucleotide reverse transcriptase inhibitors (NtRTIs). Once incorporated into newly synthesized daughter strands NtRTIs block further DNA polymerization reactions. Human cell culture and animal studies have demonstrated that cell lines and mice exposed to NRTIs display mtDNA depletion. Further complicating NRTI off-target effects on mtDNA maintenance, two additional DNA polymerases, Pol beta and PrimPol, were recently reported to localize to mitochondria as well as the nucleus. Similar to Polg, in vitro work has demonstrated both Pol beta and PrimPol incorporate NtRTIs into nascent DNA. Cell culture and biochemical experiments have also demonstrated that antiviral ribonucleoside drugs developed to treat hepatitis C infection act as off-target substrates for POLRMT, the mitochondrial RNA polymerase and primase. Accompanying the above-mentioned topics, this review examines: (1) mtDNA maintenance in human health and disease, (2) reports of DNA polymerases theta and zeta (Rev3) localizing to mitochondria, and (3) additional drugs with off-target effects on mitochondrial function. Lastly, mtDNA damage may induce cell death; therefore, the possibility of utilizing compounds that disrupt mtDNA maintenance to kill cancer cells is discussed.
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Affiliation(s)
- Matthew J Young
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, IL, United States
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29
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Hikmat O, Tzoulis C, Klingenberg C, Rasmussen M, Tallaksen CME, Brodtkorb E, Fiskerstrand T, McFarland R, Rahman S, Bindoff LA. The presence of anaemia negatively influences survival in patients with POLG disease. J Inherit Metab Dis 2017; 40:861-866. [PMID: 28865037 DOI: 10.1007/s10545-017-0084-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 08/15/2017] [Accepted: 08/18/2017] [Indexed: 10/18/2022]
Abstract
BACKGROUND Mitochondria play an important role in iron metabolism and haematopoietic cell homeostasis. Recent studies in mice showed that a mutation in the catalytic subunit of polymerase gamma (POLG) was associated with haematopoietic dysfunction including anaemia. The aim of this study was to analyse the frequency of anaemia in a large cohort of patients with POLG related disease. METHODS We conducted a multi-national, retrospective study of 61 patients with confirmed, pathogenic biallelic POLG mutations from six centres, four in Norway and two in the United Kingdom. Clinical, laboratory and genetic data were collected using a structured questionnaire. Anaemia was defined as an abnormally low haemoglobin value adjusted for age and sex. Univariate survival analysis was performed using log-rank test to compare differences in survival time between categories. RESULTS Anaemia occurred in 67% (41/61) of patients and in 23% (14/61) it was already present at clinical presentation. The frequency of anaemia in patients with early onset disease including Alpers syndrome and myocerebrohepatopathy spectrum (MCHS) was high (72%) and 35% (8/23) of these had anaemia at presentation. Survival analysis showed that the presence of anaemia was associated with a significantly worse survival (P = 0.004). CONCLUSION Our study reveals that anaemia can be a feature of POLG-related disease. Further, we show that its presence is associated with significantly worse prognosis either because anaemia itself is impacting survival or because it reflects the presence of more serious disease. In either case, our data suggests anaemia is a marker for negative prognosis.
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Affiliation(s)
- Omar Hikmat
- Department of Pediatrics, Haukeland University Hospital, 5021, Bergen, Norway
- Department of Clinical Medicine (K1), University of Bergen, Bergen, Norway
| | - Charalampos Tzoulis
- Department of Clinical Medicine (K1), University of Bergen, Bergen, Norway
- Department of Neurology, Haukeland University Hospital, 5021, Bergen, Norway
| | - Claus Klingenberg
- Department of Paediatric and Adolescent Medicine, University Hospital of North Norway, Tromsø, Norway
- Paediatric Research Group, Department of Clinical Medicine, UiT- The Arctic University of Norway, Tromsø, Norway
| | - Magnhild Rasmussen
- Women and Children's Division, Department of Clinical Neurosciences for Children, Oslo University Hospital, Oslo, Norway
- Unit for Congenital and Hereditary Neuromuscular Disorders, Department of Neurology, Oslo University Hospital, Oslo, Norway
| | - Chantal M E Tallaksen
- Department of Neurology, Oslo University Hospital, Oslo, Norway
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Eylert Brodtkorb
- Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway
- Department of Neurology and Clinical Neurophysiology, St. Olav's University Hospital, Trondheim, Norway
| | - Torunn Fiskerstrand
- Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway
- Department of Clinical Science (K2), University of Bergen, Bergen, Norway
| | - Robert McFarland
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School Framlington Place, Newcastle University, Newcastle upon Tyne, 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
| | - Laurence A Bindoff
- Department of Clinical Medicine (K1), University of Bergen, Bergen, Norway.
- Department of Neurology, Haukeland University Hospital, 5021, Bergen, Norway.
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30
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Saneto RP. Epilepsy and Mitochondrial Dysfunction. JOURNAL OF INBORN ERRORS OF METABOLISM AND SCREENING 2017. [DOI: 10.1177/2326409817733012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Affiliation(s)
- Russell P. Saneto
- Division of Pediatric Neurology, Department of Neurology, University of Washington, Seattle, WA, USA
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31
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Paucar M, Engvall M, Gordon L, Tham E, Synofzik M, Svenningsson P. POLG-Associated Ataxia Presenting as a Fragile X Tremor/Ataxia Phenocopy Syndrome. THE CEREBELLUM 2017; 15:632-5. [PMID: 27071669 DOI: 10.1007/s12311-016-0777-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Hyperintensities in the middle cerebellar peduncles (MCP), known as the MCP sign, and progressive late-onset ataxia constitute major characteristics of the fragile X tremor/ataxia syndrome (FXTAS). Here, we describe a 60-year-old male affected by ataxia due to biallelic mutations in the mitochondrial polymerase gamma (POLG) gene in which hyperintensities of the middle cerebellar peduncles (MCP) were found. The initial suspicion of FXTAS was however ruled out by a normal CGG expansion size in the FMR1 gene. We discuss the features of late-onset POLG-A as a phenocopy of FXTAS.
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Affiliation(s)
- Martin Paucar
- Department of Neurology, Karolinska University Hospital, Stockholm, Sweden. .,Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
| | - Martin Engvall
- Department of Neurology, Karolinska University Hospital, Stockholm, Sweden.,Center for Inherited Metabolic Disorders, Karolinska University Hospital, Stockholm, Sweden
| | - Lisa Gordon
- Department of Neurology, Karolinska University Hospital, Stockholm, Sweden
| | - Emma Tham
- Department of Clinical Genetics, Karolinska University Hospital, Stockholm, Sweden.,Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Matthis Synofzik
- Department of Neurodegenerative Diseases, Hertie Institute for Clinical Brain Research, Tübingen, Germany.,German Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany
| | - Per Svenningsson
- Department of Neurology, Karolinska University Hospital, Stockholm, Sweden.,Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
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32
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Abstract
Mitochondria are intracellular organelles responsible for adenosine triphosphate production. The strict control of intracellular energy needs require proper mitochondrial functioning. The mitochondria are under dual controls of mitochondrial DNA (mtDNA) and nuclear DNA (nDNA). Mitochondrial dysfunction can arise from changes in either mtDNA or nDNA genes regulating function. There are an estimated ∼1500 proteins in the mitoproteome, whereas the mtDNA genome has 37 proteins. There are, to date, ∼275 genes shown to give rise to disease. The unique physiology of mitochondrial functioning contributes to diverse gene expression. The onset and range of phenotypic expression of disease is diverse, with onset from neonatal to seventh decade of life. The range of dysfunction is heterogeneous, ranging from single organ to multisystem involvement. The complexity of disease expression has severely limited gene discovery. Combining phenotypes with improvements in gene sequencing strategies are improving the diagnosis process. This chapter focuses on the interplay of the unique physiology and gene discovery in the current knowledge of genetically derived mitochondrial disease.
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Affiliation(s)
- Russell P Saneto
- Seattle Children's Hospital/University of Washington, Seattle, WA, United States.
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33
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Hikmat O, Eichele T, Tzoulis C, Bindoff LA. Understanding the Epilepsy in POLG Related Disease. Int J Mol Sci 2017; 18:ijms18091845. [PMID: 28837072 PMCID: PMC5618494 DOI: 10.3390/ijms18091845] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 08/18/2017] [Accepted: 08/21/2017] [Indexed: 12/31/2022] Open
Abstract
Epilepsy is common in polymerase gamma (POLG) related disease and is associated with high morbidity and mortality. Epileptiform discharges typically affect the occipital regions initially and focal seizures, commonly evolving to bilateral convulsive seizures which are the most common seizure types in both adults and children. Our work has shown that mtDNA depletion—i.e., the quantitative loss of mtDNA—in neurones is the earliest and most important factor of the subsequent development of cellular dysfunction. Loss of mtDNA leads to loss of mitochondrial respiratory chain (MRC) components that, in turn, progressively disables energy metabolism. This critically balanced neuronal energy metabolism leads to both a chronic and continuous attrition (i.e., neurodegeneration) and it leaves the neurone unable to cope with increased demand that can trigger a potentially catastrophic cycle that results in acute focal necrosis. We believe that it is the onset of epilepsy that triggers the cascade of damage. These events can be identified in the stepwise evolution that characterizes the clinical, Electroencephalography (EEG), neuro-imaging, and neuropathology findings. Early recognition with prompt and aggressive seizure management is vital and may play a role in modifying the epileptogenic process and improving survival.
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Affiliation(s)
- Omar Hikmat
- Department of Pediatrics, Haukeland University Hospital, 5021 Bergen, Norway.
- Department of Clinical Medicine (K1), University of Bergen, 5020 Bergen, Norway.
| | - Tom Eichele
- K.G. Jebsen Center for Research on Neuropsychiatric Disorders, University of Bergen, 5009 Bergen, Norway.
- Department of Biological and Medical Psychology, University of Bergen, 5009 Bergen, Norway.
- Department of Neurology, Haukeland University Hospital, 5021 Bergen, Norway.
| | - Charalampos Tzoulis
- Department of Clinical Medicine (K1), University of Bergen, 5020 Bergen, Norway.
- Department of Neurology, Haukeland University Hospital, 5021 Bergen, Norway.
| | - Laurence A Bindoff
- Department of Clinical Medicine (K1), University of Bergen, 5020 Bergen, Norway.
- Department of Neurology, Haukeland University Hospital, 5021 Bergen, Norway.
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34
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The clinical spectrum and natural history of early-onset diseases due to DNA polymerase gamma mutations. Genet Med 2017; 19:1217-1225. [DOI: 10.1038/gim.2017.35] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Revised: 02/16/2017] [Accepted: 02/17/2017] [Indexed: 12/26/2022] Open
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35
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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.
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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
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36
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Saneto RP. Alpers-Huttenlocher syndrome: the role of a multidisciplinary health care team. J Multidiscip Healthc 2016; 9:323-33. [PMID: 27555780 PMCID: PMC4968991 DOI: 10.2147/jmdh.s84900] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Alpers–Huttenlocher syndrome (AHS) is a mitochondrial DNA-depletion syndrome. Age of onset is bimodal: early onset at 2–4 years and later adolescent onset at 17–24 years of age. Early development is usually normal, with epilepsy heralding the disorder in ~50% of patients. The onset of seizures is coupled with progressive cognitive decline. Hepatopathy is variable, and when present is a progressive dysfunction leading to liver failure in many cases. These features of seizures, cognitive degeneration, and hepatopathy represent the “classic triad” of AHS. However, most patients develop other system involvement. Therefore, although AHS is ultimately a lethal disorder, medical care is required for sustained quality of life. Frequently, additional organ systems – gastrointestinal, respiratory, nutritional, and psychiatric – abnormalities appear and need treatment. Rarely, cardiovascular dysfunction and even pregnancy complicate medical treatment. Optimal care requires a team of physicians and caretakers to make sure quality of life is optimized. The care team, together with the family and palliative care specialists, need to be in communication as the disease progresses and medical changes occur. Although the unpredictable losses of function challenge medical care, the team approach can foster the individual quality-of-life care needed for the patient and family.
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Affiliation(s)
- Russell P Saneto
- Department of Neurology, University of Washington; Division of Pediatric Neurology, Seattle Children's Hospital, Seattle, WA, USA
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37
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Young MJ, Copeland WC. Human mitochondrial DNA replication machinery and disease. Curr Opin Genet Dev 2016; 38:52-62. [PMID: 27065468 DOI: 10.1016/j.gde.2016.03.005] [Citation(s) in RCA: 129] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 03/03/2016] [Accepted: 03/08/2016] [Indexed: 12/21/2022]
Abstract
The human mitochondrial genome is replicated by DNA polymerase γ in concert with key components of the mitochondrial DNA (mtDNA) replication machinery. Defects in mtDNA replication or nucleotide metabolism cause deletions, point mutations, or depletion of mtDNA. The resulting loss of cellular respiration ultimately induces mitochondrial genetic diseases, including mtDNA depletion syndromes (MDS) such as Alpers or early infantile hepatocerebral syndromes, and mtDNA deletion disorders such as progressive external ophthalmoplegia, ataxia-neuropathy, or mitochondrial neurogastrointestinal encephalomyopathy. Here we review the current literature regarding human mtDNA replication and heritable disorders caused by genetic changes of the POLG, POLG2, Twinkle, RNASEH1, DNA2, and MGME1 genes.
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Affiliation(s)
- Matthew J Young
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, P.O. Box 12233, Research Triangle Park, NC 27709, United States
| | - William C Copeland
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, P.O. Box 12233, Research Triangle Park, NC 27709, United States.
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38
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Akhmedov AT, Marín-García J. Mitochondrial DNA maintenance: an appraisal. Mol Cell Biochem 2015; 409:283-305. [DOI: 10.1007/s11010-015-2532-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 08/06/2015] [Indexed: 12/13/2022]
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39
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The in cis T251I and P587L POLG1 base changes: Description of a new family and literature review. Neuromuscul Disord 2015; 25:333-9. [DOI: 10.1016/j.nmd.2015.01.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 01/07/2015] [Accepted: 01/14/2015] [Indexed: 11/19/2022]
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41
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Abstract
Mitochondrial DNA is replicated by DNA polymerase γ in concert with accessory proteins such as the mitochondrial DNA helicase, single-stranded DNA binding protein, topoisomerase, and initiating factors. Defects in mitochondrial DNA replication or nucleotide metabolism can cause mitochondrial genetic diseases due to mitochondrial DNA deletions, point mutations, or depletion, which ultimately cause loss of oxidative phosphorylation. These genetic diseases include mitochondrial DNA depletion syndromes such as Alpers or early infantile hepatocerebral syndromes, and mitochondrial DNA deletion disorders, such as progressive external ophthalmoplegia, ataxia-neuropathy, or mitochondrial neurogastrointestinal encephalomyopathy. This review focuses on our current knowledge of genetic defects of mitochondrial DNA replication (POLG, POLG2, C10orf2, and MGME1) that cause instability of mitochondrial DNA and mitochondrial disease.
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Affiliation(s)
- William C. Copeland
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina
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42
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Al-Zubeidi D, Thangarajh M, Pathak S, Cai C, Schlaggar BL, Storch GA, Grange DK, Watson ME. Fatal human herpesvirus 6-associated encephalitis in two boys with underlying POLG mitochondrial disorders. Pediatr Neurol 2014; 51:448-52. [PMID: 25160553 DOI: 10.1016/j.pediatrneurol.2014.04.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 04/01/2014] [Accepted: 04/05/2014] [Indexed: 12/17/2022]
Abstract
BACKGROUND Human herpesvirus 6 is a significant cause of the febrile illness roseola infantum in young children. Infection with human herpesvirus 6 typically causes a self-limited febrile illness but occasionally is associated with central nervous system manifestations, including febrile seizures and encephalitis. Host factors associated with severe manifestations of human herpesvirus 6-associated neurological disease remain poorly characterized. CASE REPORTS We report two previously healthy young boys with human herpesvirus 6-associated encephalitis who developed a progressive, and ultimately fatal, encephalopathy with refractory movement disorder concurrent with acquisition of acute human herpesvirus 6 infection. Both children were treated with the antiviral ganciclovir without improvement of their neurological symptoms, although quantitative human herpesvirus 6 polymerase chain reaction of cerebrospinal fluid and/or blood confirmed a decline in viral load with treatment. The clinical course in both cases was most consistent with Alpers-Huttenlocher syndrome, given the intractable seizures, developmental regression, and, ultimately, death due to liver and renal failure. In support of this, postmortem analysis identified both children to be compound heterozygous for mutations in the mitochondrial polymerase γ gene, POLG. CONCLUSIONS POLG mutations are associated with Alpers-Huttenlocher syndrome; however, no prior studies have examined the role of acute human herpesvirus 6 infection in these patients presenting with severe neurological disease. It is possible the POLG mutation phenotype was unmasked and/or exacerbated by human herpesvirus 6 infection in these two patients, potentially contributing to a more rapid clinical deterioration. This report provides new insight into a previously unrecognized association between POLG mutations and poor neurological outcome after human herpesvirus 6 infection.
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Affiliation(s)
- Duha Al-Zubeidi
- Division of Pediatric Infectious Diseases, Department of Pediatrics, Children's Mercy Hospital, Kansas City, Missouri
| | - Mathula Thangarajh
- Division of Epilepsy, Neurophysiology, and Critical Care Neurology, Department of Neurology, Children's National Medical Center, Washington, DC
| | - Sheel Pathak
- Department of Neurology, Washington University, St. Louis, Missouri
| | - Chunyu Cai
- Department of Pathology and Immunology, Washington University, St. Louis, Missouri
| | | | - Gregory A Storch
- Division of Pediatric Infectious Diseases, Department of Pediatrics, Washington University, St. Louis, Missouri
| | - Dorothy K Grange
- Division of Genetics and Genomic Medicine, Department of Pediatrics, Washington University, St. Louis, Missouri
| | - Michael E Watson
- Division of Pediatric Infectious Diseases, Department of Pediatrics, University of Michigan, Ann Arbor, Michigan.
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Abstract
Human mitochondria harbor an essential, high copy number, 16,569 base pair, circular DNA genome that encodes 13 gene products required for electron transport and oxidative phosphorylation. Mutation of this genome can compromise cellular respiration, ultimately resulting in a variety of progressive metabolic diseases collectively known as 'mitochondrial diseases'. Mutagenesis of mtDNA and the persistence of mtDNA mutations in cells and tissues is a complex topic, involving the interplay of DNA replication, DNA damage and repair, purifying selection, organelle dynamics, mitophagy, and aging. We briefly review these general elements that affect maintenance of mtDNA, and we focus on nuclear genes encoding the mtDNA replication machinery that can perturb the genetic integrity of the mitochondrial genome.
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Affiliation(s)
- William C Copeland
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, Durham, NC 27709, USA.
| | - Matthew J Longley
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, Durham, NC 27709, USA
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Farnum GA, Nurminen A, Kaguni LS. Mapping 136 pathogenic mutations into functional modules in human DNA polymerase γ establishes predictive genotype-phenotype correlations for the complete spectrum of POLG syndromes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1113-21. [PMID: 24508722 DOI: 10.1016/j.bbabio.2014.01.021] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Revised: 01/28/2014] [Accepted: 01/29/2014] [Indexed: 01/21/2023]
Abstract
We establish the genotype-phenotype correlations for the complete spectrum of POLG syndromes by refining our previously described protocol for mapping pathogenic mutations in the human POLG gene to functional clusters in the catalytic core of the mitochondrial replicase, Pol γ (1). We assigned 136 mutations to five clusters and identify segments of primary sequence that can be used to delimit the boundaries of each cluster. We report that compound heterozygotes with two mutations from different clusters manifested more severe, earlier-onset POLG syndromes, whereas two mutations from the same cluster are less common and generally are associated with less severe, later onset POLG syndromes. We also show that specific cluster combinations are more severe than others and have a higher likelihood to manifest at an earlier age. Our clustering method provides a powerful tool to predict the pathogenic potential and predicted disease phenotype of novel variants and mutations in POLG, the most common nuclear gene underlying mitochondrial disorders. We propose that such a prediction tool would be useful for routine diagnostics for mitochondrial disorders. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference.
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Affiliation(s)
- Gregory A Farnum
- Department of Biochemistry and Molecular Biology and Center for Mitochondrial Science and Medicine, Michigan State University, East Lansing, MI 48824-1319, USA
| | - Anssi Nurminen
- Institute of Biosciences and Medical Technology, University of Tampere, 33014 Tampere, Finland
| | - Laurie S Kaguni
- Department of Biochemistry and Molecular Biology and Center for Mitochondrial Science and Medicine, Michigan State University, East Lansing, MI 48824-1319, USA; Institute of Biosciences and Medical Technology, University of Tampere, 33014 Tampere, Finland
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Abstract
To highlight differences between early-onset and adult mitochondrial depletion syndromes (MDS) concerning etiology and genetic background, pathogenesis, phenotype, clinical presentation and their outcome. MDSs most frequently occur in neonates, infants, or juveniles and more rarely in adolescents or adults. Mutated genes phenotypically presenting with adult-onset MDS include POLG1, TK2, TyMP, RRM2B, or PEO1/twinkle. Adult MDS manifest similarly to early-onset MDS, as myopathy, encephalo-myopathy, hepato-cerebral syndrome, or with chronic progressive external ophthalmoplegia (CPEO), fatigue, or only minimal muscular manifestations. Diagnostic work-up or treatment is not at variance from early-onset cases. Histological examination of muscle may be normal but biochemical investigations may reveal multiple respiratory chain defects. The outcome appears to be more favorable in adult than in early-onset forms. Mitochondrial depletion syndromes is not only a condition of neonates, infants, or juveniles but rarely also occurs in adults, presenting with minimal manifestations or manifestations like in the early-onset forms. Outcome of adult-onset MDS appears more favorable than early-onset MDS.
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Bandettini di Poggio M, Nesti C, Bruno C, Meschini MC, Schenone A, Santorelli FM. Dopamine-agonist responsive Parkinsonism in a patient with the SANDO syndrome caused by POLG mutation. BMC MEDICAL GENETICS 2013; 14:105. [PMID: 24099403 PMCID: PMC3851930 DOI: 10.1186/1471-2350-14-105] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Accepted: 09/25/2013] [Indexed: 11/10/2022]
Abstract
BACKGROUND Disorders of oxidative phosphorylation affects 1/5000 individuals and present heterogeneous involvement of tissues highly dependent upon ATP production. CASE PRESENTATION Here we present the case of a 48-year-old woman carrying a homozygous mutation (p.A899T) in mitochondrial polymerase gamma (POLG) and manifesting with a complex neurological phenotype including Dopamine-agonist responsive Parkinsonism. CONCLUSION This case report is further evidence that mitochondrial dysfunction might play a role in Parkinson's Disease pathogenesis and helps in identification of apparent mutation-specific clinical characteristics. Mutations in POLG should be looked for in cases of Parkinsonism, especially when multisystem neurological involvement is found.
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Affiliation(s)
- Monica Bandettini di Poggio
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova and IRCSS Azienda Opedaliera Universitaria San Martino-IST, Largo Daneo 3-16132, Genova, Italy.
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Stumpf JD, Saneto RP, Copeland WC. Clinical and molecular features of POLG-related mitochondrial disease. Cold Spring Harb Perspect Biol 2013; 5:a011395. [PMID: 23545419 DOI: 10.1101/cshperspect.a011395] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The inability to replicate mitochondrial genomes (mtDNA) by the mitochondrial DNA polymerase (pol γ) leads to a subset of mitochondrial diseases. Many mutations in POLG, the gene that encodes pol γ, have been associated with mitochondrial diseases such as myocerebrohepatopathy spectrum (MCHS) disorders, Alpers-Huttenlocher syndrome, myoclonic epilepsy myopathy sensory ataxia (MEMSA), ataxia neuropathy spectrum (ANS), and progressive external ophthalmoplegia (PEO). This chapter explores five important topics in POLG-related disease: (1) clinical symptoms that identify and distinguish POLG-related diseases, (2) molecular characterization of defects in polymerase activity by POLG disease variants, (3) the importance of holoenzyme formation in disease presentation, (4) the role of pol γ exonuclease activity and mutagenesis in disease and aging, and (5) novel approaches to therapy and avoidance of toxicity based on primary research in pol γ replication.
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Affiliation(s)
- Jeffrey D Stumpf
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
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Abstract
Since the first description of a mitochondrial DNA (mtDNA)-associated disease in the late 1980s, there have been more than 275 mutations within the mtDNA genome described causing human disease. The phenotypic expression of these disorders is vast, as disturbances of the unique physiology of mitochondria can create a wide range of clinical heterogeneity. Features of heteroplasmy, threshold effect, genetic bottleneck, mtDNA depletion, mitotic segregation, and maternal inheritance have been identified and described as a result of novel biochemical and genetic controls of mitochondrial function. We hope that as we unfold this fascinating part of clinical medicine, the reader will see how alterations in the tapestry of mitochondrial biochemistry and genetics can give rise to human illness.
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Affiliation(s)
- Russell P Saneto
- Division of Pediatric Neurology, Seattle Children's Hospital/University of Washington, Seattle, WA 98105, USA.
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McCormick E, Place E, Falk MJ. Molecular genetic testing for mitochondrial disease: from one generation to the next. Neurotherapeutics 2013; 10:251-61. [PMID: 23269497 PMCID: PMC3625386 DOI: 10.1007/s13311-012-0174-1] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Molecular genetic diagnostic testing for mitochondrial disease has evolved continually since the first genetic basis for a clinical mitochondrial disease syndrome was identified in the late 1980s. Owing to global limitations in both knowledge and technology, few individuals, even among those with strong clinical or biochemical evidence of mitochondrial respiratory chain dysfunction, ever received a definitive molecular diagnosis prior to 2005. Clinically available genetic diagnostic testing options improved by 2006 to include sequencing and deletion analysis of an increasing number of individual nuclear genes linked to mitochondrial disease, genome-wide microarray analysis for chromosomal copy number abnormalities, and mitochondrial DNA whole genome sequence analysis. To assess the collective effect of these tests on the genetic diagnosis of suspected mitochondrial disease, we report here results from a retrospective review of the diagnostic yield in patients evaluated from 2008 to 2011 in the Mitochondrial-Genetics Diagnostic Clinic at The Children's Hospital of Philadelphia. Among 152 patients aged 6 weeks to 81 years referred for clinical evaluation of multisystem presentations concerning for suspected mitochondrial disease, a genetic etiology was established that confirmed definite mitochondrial disease in 16.4% and excluded primary mitochondrial disease in 9.2%. Substantial diagnostic challenges remain owing to the clinical difficulty and frank low yield of a priori selecting individual nuclear genes to sequence based on particular symptomatic or biochemical manifestations of suspected mitochondrial disease. These findings highlight the particular utility of massively parallel nuclear exome sequencing technologies, whose benefits and limitations are explored relative to the clinical genetic diagnostic evaluation of mitochondrial disease.
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Affiliation(s)
- Elizabeth McCormick
- />Divisions of Human Genetics and Child Development and Metabolic Disease, Department of Pediatrics, The Children’s Hospital of Philadelphia and University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104 USA
| | - Emily Place
- />Divisions of Human Genetics and Child Development and Metabolic Disease, Department of Pediatrics, The Children’s Hospital of Philadelphia and University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104 USA
- />Department of Ophthalmology, Ocular Genomics Institute, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA USA
| | - Marni J. Falk
- />Divisions of Human Genetics and Child Development and Metabolic Disease, Department of Pediatrics, The Children’s Hospital of Philadelphia and University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104 USA
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