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Pekeles H, Berrahmoune S, Dassi C, Cheung AC, Gagnon T, Waters PJ, Eberhard R, Buhas D, Myers KA. Safety and efficacy of deoxycytidine/deoxythymidine combination therapy in POLG-related disorders: 6-month interim results of an open-label, single arm, phase 2 trial. EClinicalMedicine 2024; 74:102740. [PMID: 39091670 PMCID: PMC11293517 DOI: 10.1016/j.eclinm.2024.102740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2024] [Revised: 06/16/2024] [Accepted: 07/02/2024] [Indexed: 08/04/2024] Open
Abstract
Background DNA polymerase gamma (POLG)-related disorders are a group of rare neurodegenerative mitochondrial diseases caused by pathogenic variants in POLG, the gene encoding POLG. Patients may experience a range of signs and symptoms, including seizures, vision loss, myopathy, neuropathy, developmental impairment or regression, and liver failure. The diseases follow a progressive, degenerative course, with most affected individuals dying within 3 months-12 years of diagnosis. At present, there are no effective treatments for POLG-related disorders. Methods In this study we report the interim 6-month data from a long term open-label, single arm phase 2 trial, in which we assessed the safety and efficacy of combination therapy with deoxycytidine and deoxythymidine (dC/dT) in children with POLG-related disorders. dC/dT was given enterally in powder form, dissolved in water. The primary outcome measures included Newcastle Mitochondrial Disease Scale (NMDS) score, serum growth differentiation factor 15 (GDF-15; a biomarker of mitochondrial dysfunction), electroencephalography (EEG), seizure diary, and blood and urine tests to assess end organ and mitochondrial function. Secondary outcome measures included recording of all adverse events to evaluate the safety of the intervention. The trial is registered with ClinicalTrials.gov, NCT04802707 (https://clinicaltrials.gov/ct2/show/NCT04802707). Data were collected from 14 October, 2021 to 13 December, 2023. Findings We present 6-month interim data from the first ten people with POLG-related disorders enrolled in the trial, six with Alpers-Huttenlocher syndrome, two with ataxia-neuropathy spectrum, and two who do not fit into a classical POLG-related phenotype. During the 6 months of treatment, NMDS score improved from a mean of 27.3 at baseline to 20.7 at 6 months (estimated difference 6.0; 95% CI 2.5-∞). GDF-15 values remained stable or decreased in all patients; the mean decreased from 1031 pg/ml to 729 pg/ml (estimated difference 200; 95% CI 12-∞). 8/10 patients had abnormal baseline EEG; improvement in EEG was seen in 5 of these 8. There were no significant changes in other blood and urine testing. Regarding adverse events, two patients experienced diarrhea that spontaneously resolved. Interpretation dC/dT is a promising treatment option for people with POLG-related disorders. Further research is needed to assess the long-term safety and efficacy in POLG-related disorders, as well as safety and efficacy in other mitochondrial DNA depletion disorders. Funding This study was primarily funded by the Liam Foundation, with additional funding from the Savoy Foundation, Grand Défi Pierre Lavoie Foundation, and Fonds de Recherche du Québec - Santé.
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Affiliation(s)
- Heather Pekeles
- Division of Neurology, Department of Pediatrics, Montreal Children’s Hospital, McGill University Health Centre, 1001 Décarie Boulevard, Montreal, Quebec, H4A 3J1, Canada
| | - Saoussen Berrahmoune
- Research Institute of the McGill University Health Centre, 2155 Guy Street, Suite 500, Montreal, Quebec, H3H 2R9, Canada
| | - Christelle Dassi
- Research Institute of the McGill University Health Centre, 2155 Guy Street, Suite 500, Montreal, Quebec, H3H 2R9, Canada
| | - Anthony C.T. Cheung
- Division of Medical Genetics, Department of Specialized Medicine, McGill University Health Centre, 1001 Décarie Boulevard, Montreal, Quebec, H4A 3J1, Canada
| | - Tommy Gagnon
- Medical Genetics Service, Department of Laboratory Medicine, CHUS and Department of Pediatrics, Université de Sherbrooke, Sherbrooke, Quebec, J1K 2R1, Canada
| | - Paula J. Waters
- Medical Genetics Service, Department of Laboratory Medicine, CHUS and Department of Pediatrics, Université de Sherbrooke, Sherbrooke, Quebec, J1K 2R1, Canada
- Centre de Recherche du Centre Hospitalier Universitaire de Sherbrooke (CRCHUS), 12e Avenue N Porte 6, Sherbrooke, Quebec, J1H 5N4, Canada
| | - Ralf Eberhard
- Division of Neurology, Department of Pediatrics, Montreal Children’s Hospital, McGill University Health Centre, 1001 Décarie Boulevard, Montreal, Quebec, H4A 3J1, Canada
| | - Daniela Buhas
- Division of Medical Genetics, Department of Specialized Medicine, McGill University Health Centre, 1001 Décarie Boulevard, Montreal, Quebec, H4A 3J1, Canada
- Department of Human Genetics, McGill University, Montreal, Quebec, Canada
| | - Kenneth A. Myers
- Division of Neurology, Department of Pediatrics, Montreal Children’s Hospital, McGill University Health Centre, 1001 Décarie Boulevard, Montreal, Quebec, H4A 3J1, Canada
- Research Institute of the McGill University Health Centre, 2155 Guy Street, Suite 500, Montreal, Quebec, H3H 2R9, Canada
- Department of Neurology and Neurosurgery, Montreal Children’s Hospital, McGill University Health Centre, 1001 Décarie Boulevard, Montreal, Quebec, H4A 3J1, Canada
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Dombi E, Marinaki T, Spingardi P, Millar V, Hadjichristou N, Carver J, Johnston IG, Fratter C, Poulton J. Nucleoside supplements as treatments for mitochondrial DNA depletion syndrome. Front Cell Dev Biol 2024; 12:1260496. [PMID: 38665433 PMCID: PMC11043827 DOI: 10.3389/fcell.2024.1260496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 03/11/2024] [Indexed: 04/28/2024] Open
Abstract
Introduction: In mitochondrial DNA (mtDNA) depletion syndrome (MDS), patients cannot maintain sufficient mtDNA for their energy needs. MDS presentations range from infantile encephalopathy with hepatopathy (Alpers syndrome) to adult chronic progressive external ophthalmoplegia. Most are caused by nucleotide imbalance or by defects in the mtDNA replisome. There is currently no curative treatment available. Nucleoside therapy is a promising experimental treatment for TK2 deficiency, where patients are supplemented with exogenous deoxypyrimidines. We aimed to explore the benefits of nucleoside supplementation in POLG and TWNK deficient fibroblasts. Methods: We used high-content fluorescence microscopy with software-based image analysis to assay mtDNA content and membrane potential quantitatively, using vital dyes PicoGreen and MitoTracker Red CMXRos respectively. We tested the effect of 15 combinations (A, T, G, C, AT, AC, AG, CT, CG, GT, ATC, ATG, AGC, TGC, ATGC) of deoxynucleoside supplements on mtDNA content of fibroblasts derived from four patients with MDS (POLG1, POLG2, DGUOK, TWNK) in both a replicating (10% dialysed FCS) and quiescent (0.1% dialysed FCS) state. We used qPCR to measure mtDNA content of supplemented and non-supplemented fibroblasts following mtDNA depletion using 20 µM ddC and after 14- and 21-day recovery in a quiescent state. Results: Nucleoside treatments at 200 µM that significantly increased mtDNA content also significantly reduced the number of cells remaining in culture after 7 days of treatment, as well as mitochondrial membrane potential. These toxic effects were abolished by reducing the concentration of nucleosides to 50 µM. In POLG1 and TWNK cells the combination of ATGC treatment increased mtDNA content the most after 7 days in non-replicating cells. ATGC nucleoside combination significantly increased the rate of mtDNA recovery in quiescent POLG1 cells following mtDNA depletion by ddC. Conclusion: High-content imaging enabled us to link mtDNA copy number with key read-outs linked to patient wellbeing. Elevated G increased mtDNA copy number but severely impaired fibroblast growth, potentially by inhibiting purine synthesis and/or causing replication stress. Combinations of nucleosides ATGC, T, or TC, benefited growth of cells harbouring POLG mutations. These combinations, one of which reflects a commercially available preparation, could be explored further for treatment of POLG patients.
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Affiliation(s)
- Eszter Dombi
- Nuffield Department of Women’s and Reproductive Health, University of Oxford, Oxford, United Kingdom
| | - Tony Marinaki
- Purine Research Laboratory, Department of Biochemical Sciences, Guy’s and St Thomas’ Hospitals, London, United Kingdom
| | - Paolo Spingardi
- Ludwig Institute for Cancer Research, Nuffield Department of Medicine, Medical Sciences Division, University of Oxford, Oxford, United Kingdom
| | - Val Millar
- Target Discovery Institute, Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | | | - Janet Carver
- Nuffield Department of Women’s and Reproductive Health, University of Oxford, Oxford, United Kingdom
| | - Iain G. Johnston
- Department of Mathematics, University of Bergen, Bergen, Norway
- Computational Biology Unit, University of Bergen, Bergen, Norway
| | - Carl Fratter
- Oxford Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom
| | - Joanna Poulton
- Nuffield Department of Women’s and Reproductive Health, University of Oxford, Oxford, United Kingdom
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Kristiansen CK, Furriol J, Chen A, Sullivan GJ, Bindoff LA, Liang KX. Deoxyribonucleoside treatment rescues EtBr-induced mtDNA depletion in iPSC-derived neural stem cells with POLG mutations. FASEB J 2023; 37:e23139. [PMID: 37584631 DOI: 10.1096/fj.202300650rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 07/26/2023] [Accepted: 07/31/2023] [Indexed: 08/17/2023]
Abstract
Mutations in POLG, the gene encoding the catalytic subunit of the mitochondrial DNA (mtDNA) polymerase gamma (Pol-γ), lead to diseases driven by defective mtDNA maintenance. Despite being the most prevalent cause of mitochondrial disease, treatments for POLG-related disorders remain elusive. In this study, we used POLG patient-induced pluripotent stem cell (iPSC)-derived neural stem cells (iNSCs), one homozygous for the POLG mutation c.2243G>C and one compound heterozygous with c.2243G>C and c.1399G>A, and treated these iNSCs with ethidium bromide (EtBr) to study the rate of depletion and repopulation of mtDNA. In addition, we investigated the effect of deoxyribonucleoside (dNs) supplementation on mtDNA maintenance during EtBr treatment and post-treatment repopulation in the same cells. EtBr-induced mtDNA depletion occurred at a similar rate in both patient and control iNSCs, however, restoration of mtDNA levels was significantly delayed in iNSCs carrying the compound heterozygous POLG mutations. In contrast, iNSC with the homozygous POLG mutation recovered their mtDNA at a rate similar to controls. When we treated cells with dNs, we found that this reduced EtBr-induced mtDNA depletion and significantly increased repopulation rates in both patient iNSCs. These observations are consistent with the hypothesis that mutations in POLG impair mtDNA repopulation also within intact neural lineage cells and suggest that those with compound heterozygous mutation have a more severe defect of mtDNA synthesis. Our findings further highlight the potential for dNs to improve mtDNA replication in the presence of POLG mutations, suggesting that this may offer a new therapeutic modality for mitochondrial diseases caused by disturbed mtDNA homeostasis.
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Affiliation(s)
- Cecilie Katrin Kristiansen
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
- Neuro-SysMed, Center of Excellence for Clinical Research in Neurological Diseases, Haukeland University Hospital, Bergen, Norway
| | - Jessica Furriol
- Department of Medicine, Haukeland University Hospital, Bergen, Norway
| | - Anbin Chen
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
- Department of Neurosurgery, Xinhua Hospital Affiliated with Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Gareth John Sullivan
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
- Institute of Immunology, Oslo University Hospital, Oslo, Norway
- Department of Pediatric Research, Oslo University Hospital, Oslo, Norway
| | - Laurence A Bindoff
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
- Department of Neurology, Haukeland University Hospital, Bergen, Norway
- National Advisory Unit for Congenital Metabolic Diseases, Oslo University Hospital, Oslo, Norway
| | - Kristina Xiao Liang
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
- Neuro-SysMed, Center of Excellence for Clinical Research in Neurological Diseases, Haukeland University Hospital, Bergen, Norway
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Restrepo-Vera JL, Rovira-Moreno E, Ramón J, Codina-Sola M, Llauradó A, Salvadó M, Sánchez-Tejerina D, Sotoca J, Martínez-Sáez E, Martí R, García-Arumí E, Juntas-Morales R. Identification of two novel RRM2B variants associated with autosomal recessive progressive external ophthalmoplegia in a family with pseudodominant inheritance pattern. J Hum Genet 2023:10.1038/s10038-023-01144-2. [PMID: 36959467 DOI: 10.1038/s10038-023-01144-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 02/07/2023] [Accepted: 02/28/2023] [Indexed: 03/25/2023]
Abstract
RRM2B encodes the p53-inducible small subunit (p53R2) of ribonucleotide reductase, a key protein for mitochondrial DNA (mtDNA) synthesis. Pathogenic variants in this gene result in familial mitochondrial disease in adults and children, secondary to a maintenance disorder of mtDNA. This study describes two patients, mother and son, with early-onset chronic progressive external ophthalmoplegia (PEO). Skeletal muscle biopsy from the latter was examined: cytochrome c oxidase (COX)-negative fibres were shown, and molecular studies revealed multiple mtDNA deletions. A next-generation sequencing gene panel for nuclear-encoded mitochondrial maintenance genes identified two unreported heterozygous missense variants (c.514 G > A and c.682 G > A) in the clinically affected son. The clinically affected mother harboured the first variant in homozygous state, and the clinically unaffected father harboured the remaining variant in heterozygous state. In silico analyses predicted both variants as deleterious. Cell culture studies revealed that patients' skin fibroblasts, but not fibroblasts from healthy controls, responded to nucleoside supplementation with enhanced mtDNA repopulation, thus suggesting an in vitro functional difference in patients' cells. Our results support the pathogenicity of two novel RRM2B variants found in two patients with autosomal recessive PEO with multiple mtDNA deletions inherited with a pseudodominant pattern.
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Affiliation(s)
- Juan Luis Restrepo-Vera
- Neuromuscular Diseases Unit, European Reference Network on Rare Neuromuscular Diseases, Department of Neurology, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Eulàlia Rovira-Moreno
- Department of Clinical and Molecular Genetics, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
- Medicine Genetics Group, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Javier Ramón
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Marta Codina-Sola
- Department of Clinical and Molecular Genetics, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
- Medicine Genetics Group, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Arnau Llauradó
- Neuromuscular Diseases Unit, European Reference Network on Rare Neuromuscular Diseases, Department of Neurology, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Maria Salvadó
- Neuromuscular Diseases Unit, European Reference Network on Rare Neuromuscular Diseases, Department of Neurology, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Daniel Sánchez-Tejerina
- Neuromuscular Diseases Unit, European Reference Network on Rare Neuromuscular Diseases, Department of Neurology, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Javier Sotoca
- Neuromuscular Diseases Unit, European Reference Network on Rare Neuromuscular Diseases, Department of Neurology, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Elena Martínez-Sáez
- Department of Pathology, Hospital Vall d'Hebron, Universitat Autònoma Barcelona, 08035, Barcelona, Spain
| | - Ramon Martí
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Elena García-Arumí
- Department of Clinical and Molecular Genetics, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain.
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain.
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain.
| | - Raul Juntas-Morales
- Neuromuscular Diseases Unit, European Reference Network on Rare Neuromuscular Diseases, Department of Neurology, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain.
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5
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Feng J, Chen Z, Liang W, Wei Z, Ding G. Roles of Mitochondrial DNA Damage in Kidney Diseases: A New Biomarker. Int J Mol Sci 2022; 23:ijms232315166. [PMID: 36499488 PMCID: PMC9735745 DOI: 10.3390/ijms232315166] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 11/27/2022] [Accepted: 11/28/2022] [Indexed: 12/05/2022] Open
Abstract
The kidney is a mitochondria-rich organ, and kidney diseases are recognized as mitochondria-related pathologies. Intact mitochondrial DNA (mtDNA) maintains normal mitochondrial function. Mitochondrial dysfunction caused by mtDNA damage, including impaired mtDNA replication, mtDNA mutation, mtDNA leakage, and mtDNA methylation, is involved in the progression of kidney diseases. Herein, we review the roles of mtDNA damage in different setting of kidney diseases, including acute kidney injury (AKI) and chronic kidney disease (CKD). In a variety of kidney diseases, mtDNA damage is closely associated with loss of kidney function. The level of mtDNA in peripheral serum and urine also reflects the status of kidney injury. Alleviating mtDNA damage can promote the recovery of mitochondrial function by exogenous drug treatment and thus reduce kidney injury. In short, we conclude that mtDNA damage may serve as a novel biomarker for assessing kidney injury in different causes of renal dysfunction, which provides a new theoretical basis for mtDNA-targeted intervention as a therapeutic option for kidney diseases.
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Affiliation(s)
- Jun Feng
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan 430060, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan 430060, China
| | - Zhaowei Chen
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan 430060, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan 430060, China
| | - Wei Liang
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan 430060, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan 430060, China
| | - Zhongping Wei
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan 430060, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan 430060, China
| | - Guohua Ding
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan 430060, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan 430060, China
- Correspondence:
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Stimulating Mitochondrial Biogenesis with Deoxyribonucleosides Increases Functional Capacity in ECHS1-Deficient Cells. Int J Mol Sci 2022; 23:ijms232012610. [PMID: 36293464 PMCID: PMC9604038 DOI: 10.3390/ijms232012610] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 10/13/2022] [Accepted: 10/17/2022] [Indexed: 11/17/2022] Open
Abstract
The lack of effective treatments for mitochondrial disease has seen the development of new approaches, including those that stimulate mitochondrial biogenesis to boost ATP production. Here, we examined the effects of deoxyribonucleosides (dNs) on mitochondrial biogenesis and function in Short chain enoyl-CoA hydratase 1 (ECHS1) ‘knockout’ (KO) cells, which exhibit combined defects in both oxidative phosphorylation (OXPHOS) and mitochondrial fatty acid β-oxidation (FAO). DNs treatment increased mitochondrial DNA (mtDNA) copy number and the expression of mtDNA-encoded transcripts in both CONTROL (CON) and ECHS1 KO cells. DNs treatment also altered global nuclear gene expression, with key gene sets including ‘respiratory electron transport’ and ‘formation of ATP by chemiosmotic coupling’ increased in both CON and ECHS1 KO cells. Genes involved in OXPHOS complex I biogenesis were also upregulated in both CON and ECHS1 KO cells following dNs treatment, with a corresponding increase in the steady-state levels of holocomplex I in ECHS1 KO cells. Steady-state levels of OXPHOS complex V, and the CIII2/CIV and CI/CIII2/CIV supercomplexes, were also increased by dNs treatment in ECHS1 KO cells. Importantly, treatment with dNs increased both basal and maximal mitochondrial oxygen consumption in ECHS1 KO cells when metabolizing either glucose or the fatty acid palmitoyl-L-carnitine. These findings highlight the ability of dNs to improve overall mitochondrial respiratory function, via the stimulation mitochondrial biogenesis, in the face of combined defects in OXPHOS and FAO due to ECHS1 deficiency.
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232nd ENMC International Workshop: Recommendations for treatment of mitochondrial DNA maintenance disorders. 16 – 18 June 2017, Heemskerk, The Netherlands. Neuromuscul Disord 2022; 32:609-620. [DOI: 10.1016/j.nmd.2022.05.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 05/12/2022] [Indexed: 11/24/2022]
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Ramón J, Vila-Julià F, Molina-Granada D, Molina-Berenguer M, Melià MJ, García-Arumí E, Torres-Torronteras J, Cámara Y, Martí R. Therapy Prospects for Mitochondrial DNA Maintenance Disorders. Int J Mol Sci 2021; 22:6447. [PMID: 34208592 PMCID: PMC8234938 DOI: 10.3390/ijms22126447] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 06/10/2021] [Accepted: 06/11/2021] [Indexed: 02/07/2023] Open
Abstract
Mitochondrial DNA depletion and multiple deletions syndromes (MDDS) constitute a group of mitochondrial diseases defined by dysfunctional mitochondrial DNA (mtDNA) replication and maintenance. As is the case for many other mitochondrial diseases, the options for the treatment of these disorders are rather limited today. Some aggressive treatments such as liver transplantation or allogeneic stem cell transplantation are among the few available options for patients with some forms of MDDS. However, in recent years, significant advances in our knowledge of the biochemical pathomechanisms accounting for dysfunctional mtDNA replication have been achieved, which has opened new prospects for the treatment of these often fatal diseases. Current strategies under investigation to treat MDDS range from small molecule substrate enhancement approaches to more complex treatments, such as lentiviral or adenoassociated vector-mediated gene therapy. Some of these experimental therapies have already reached the clinical phase with very promising results, however, they are hampered by the fact that these are all rare disorders and so the patient recruitment potential for clinical trials is very limited.
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Affiliation(s)
- Javier Ramón
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Ferran Vila-Julià
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - David Molina-Granada
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Miguel Molina-Berenguer
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Maria Jesús Melià
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Elena García-Arumí
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Javier Torres-Torronteras
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Yolanda Cámara
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Ramon Martí
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
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Clinico-pathological and Molecular Spectrum of Mitochondrial Polymerase γ Mutations in a Cohort from India. J Mol Neurosci 2021; 71:2219-2228. [PMID: 33469851 DOI: 10.1007/s12031-020-01765-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 11/23/2020] [Indexed: 01/03/2023]
Abstract
Polymerase γ catalytic subunit (POLG), a nuclear gene, encodes the enzyme responsible for mitochondrial DNA (mtDNA) replication. POLG mutations are a major cause of inherited mitochondrial diseases. They present with varied phenotypes, age of onset, and severity. Reports on POLG mutations from India are limited. Hence, this study aimed to describe the clinico-pathological and molecular observations of POLG mutations. A total of 446 patients with clinical diagnosis of mitochondrial disorders were sequenced for all exons and intron-exon boundaries of POLG. Of these, 19 (4.26%) patients (M:F: 10:9) had POLG mutations. The age of onset ranged from 5 to 55 years with an overlapping phenotypic spectrum. Ptosis, peripheral neuropathy, seizures, and ataxia were the common neurological features observed. The most common clinical phenotype was chronic progressive external ophthalmoplegia (CPEO) and CPEO plus (n = 14). Muscle biopsy showed characteristic features of mitochondrial myopathy in fourteen patients (14/19) and respiratory chain enzyme deficiency in eleven patients (11/19). Multiple mtDNA deletions were seen in 47.36% (9/19) patients. Eight pathogenic POLG variations including two novel variations (p.G132R and p.V1106A) were identified. The common pathogenic mutation identified was p.L304R, being present in eight patients (42.1%) predominantly in the younger age group followed by p.W748S in four patients (21%). To the best of our knowledge, this is the first extensive study from India, highlights the clinico-pathological and molecular spectrum of POLG mutations.
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Hämäläinen RH, Landoni JC, Ahlqvist KJ, Goffart S, Ryytty S, Rahman MO, Brilhante V, Icay K, Hautaniemi S, Wang L, Laiho M, Suomalainen A. Reply to: Proofreading deficiency in mitochondrial DNA polymerase does not affect total dNTP pools in mouse embryos. Nat Metab 2020; 2:676-677. [PMID: 32778835 DOI: 10.1038/s42255-020-0265-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 07/14/2020] [Indexed: 11/09/2022]
Affiliation(s)
- Riikka H Hämäläinen
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland.
- Research Programs Unit, Stem Cells and Metabolism, University of Helsinki, Helsinki, Finland.
| | - Juan C Landoni
- Research Programs Unit, Stem Cells and Metabolism, University of Helsinki, Helsinki, Finland
| | - Kati J Ahlqvist
- Research Programs Unit, Stem Cells and Metabolism, University of Helsinki, Helsinki, Finland
| | - Steffi Goffart
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
| | - Sanna Ryytty
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - M Obaidur Rahman
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Virginia Brilhante
- Research Programs Unit, Stem Cells and Metabolism, University of Helsinki, Helsinki, Finland
| | - Katherine Icay
- Research Programs Unit, Genome-Scale Biology, University of Helsinki, Helsinki, Finland
| | - Sampsa Hautaniemi
- Research Programs Unit, Genome-Scale Biology, University of Helsinki, Helsinki, Finland
| | - Liya Wang
- Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Marikki Laiho
- Department of Radiation Oncology and Molecular Radiation Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Anu Suomalainen
- Research Programs Unit, Stem Cells and Metabolism, University of Helsinki, Helsinki, Finland.
- University Hospital, Department of Neurology, Helsinki, Finland.
- Neuroscience Center, University of Helsinki, Helsinki, Finland.
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Rodríguez-López C, García-Cárdaba LM, Blázquez A, Serrano-Lorenzo P, Gutiérrez-Gutiérrez G, San Millán-Tejado B, Muelas N, Hernández-Laín A, Vílchez JJ, Gutiérrez-Rivas E, Arenas J, Martín MA, Domínguez-González C. Clinical, pathological and genetic spectrum in 89 cases of mitochondrial progressive external ophthalmoplegia. J Med Genet 2020; 57:643-646. [PMID: 32161153 DOI: 10.1136/jmedgenet-2019-106649] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 02/06/2020] [Accepted: 02/22/2020] [Indexed: 11/03/2022]
Abstract
BACKGROUND Mitochondrial progressive external ophthalmoplegia (PEO) encompasses a broad spectrum of clinical and genetic disorders. We describe the phenotypic subtypes of PEO and its correlation with molecular defects and propose a diagnostic algorithm. METHODS Retrospective analysis of the clinical, pathological and genetic features of 89 cases. RESULTS Three main phenotypes were found: 'pure PEO' (42%), consisting of isolated palpebral ptosis with ophthalmoparesis; Kearns-Sayre syndrome (10%); and 'PEO plus', which associates extraocular symptoms, distinguishing the following subtypes: : myopathic (33%), bulbar (12%) and others (3%). Muscle biopsy was the most accurate test, showing mitochondrial changes in 95%. Genetic diagnosis was achieved in 96% of the patients. Single large-scale mitochondrial DNA (mtDNA) deletion was the most frequent finding (63%), followed by multiple mtDNA deletions (26%) due to mutations in TWNK (n=8), POLG (n=7), TK2 (n=6) or RRM2B (n=2) genes, and point mtDNA mutations (7%). Three new likely pathogenic mutations were identified in the TWNK and MT-TN genes. CONCLUSIONS Phenotype-genotype correlations cannot be brought in mitochondrial PEO. Muscle biopsy should be the first step in the diagnostic flow of PEO when mitochondrial aetiology is suspected since it also enables the study of mtDNA rearrangements. If no mtDNA deletions are identified, whole mtDNA sequencing should be performed.
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Affiliation(s)
| | | | - Alberto Blázquez
- Mitochondrial Disorders Laboratory, Clinical Biochemistry Department, Hospital Universitario 12 de Octubre. Instituto de Investigación Sanitaria Hospital 12 de Octubre (imas12), Madrid, Spain.,Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Pablo Serrano-Lorenzo
- Mitochondrial Disorders Research Group, Instituto de Investigación Sanitaria Hospital 12 de Octubre (imas12), Madrid, Comunidad de Madrid, Spain
| | | | | | - Nuria Muelas
- Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain.,Neurology, Hospital Universitari i Politecnic La Fe, Valencia, Valenciana, Spain
| | - Aurelio Hernández-Laín
- Pathology, Neuropathology Section, Hospital Universitario 12 de Octubre, Madrid, Comunidad de Madrid, Spain
| | - Juan J Vílchez
- Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain.,Neuromuscular Diseases Unit, Neurology Department, Hospital Universitari i Politecnic La Fe, Valencia, Valenciana, Spain.,Neuromuscular and Ataxias Research Group, Instituto de Investigacion Sanitaria La Fe, Valencia, Spain
| | | | - Joaquín Arenas
- Mitochondrial Disorders Laboratory, Clinical Biochemistry Department, Hospital Universitario 12 de Octubre. Instituto de Investigación Sanitaria Hospital 12 de Octubre (imas12), Madrid, Spain.,Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Miguel A Martín
- Mitochondrial Disorders Laboratory, Clinical Biochemistry Department, Hospital Universitario 12 de Octubre. Instituto de Investigación Sanitaria Hospital 12 de Octubre (imas12), Madrid, Spain .,Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Cristina Domínguez-González
- Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain.,Mitochondrial Disorders Research Group, Instituto de Investigación Sanitaria Hospital 12 de Octubre (imas12), Madrid, Comunidad de Madrid, Spain.,Neuromuscular Unit, Hospital Universitario 12 de Octubre, Madrid, Comunidad de Madrid, Spain
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12
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Hämäläinen RH, Landoni JC, Ahlqvist KJ, Goffart S, Ryytty S, Rahman MO, Brilhante V, Icay K, Hautaniemi S, Wang L, Laiho M, Suomalainen A. Defects in mtDNA replication challenge nuclear genome stability through nucleotide depletion and provide a unifying mechanism for mouse progerias. Nat Metab 2019; 1:958-965. [PMID: 32694840 DOI: 10.1038/s42255-019-0120-1] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 09/04/2019] [Indexed: 01/07/2023]
Abstract
Mitochondrial DNA (mtDNA) mutagenesis and nuclear DNA repair defects are considered cellular mechanisms of ageing. mtDNA mutator mice with increased mtDNA mutagenesis show signs of premature ageing. However, why patients with mitochondrial diseases, or mice with other forms of mitochondrial dysfunction, do not age prematurely remains unknown. Here, we show that cells from mutator mice display challenged nuclear genome maintenance similar to that observed in progeric cells with defects in nuclear DNA repair. Cells from mutator mice show slow nuclear DNA replication fork progression, cell cycle stalling and chronic DNA replication stress, leading to double-strand DNA breaks in proliferating progenitor or stem cells. The underlying mechanism involves increased mtDNA replication frequency, sequestering of nucleotides to mitochondria, depletion of total cellular nucleotide pools, decreased deoxynucleoside 5'-triphosphate (dNTP) availability for nuclear genome replication and compromised nuclear genome maintenance. Our data indicate that defects in mtDNA replication can challenge nuclear genome stability. We suggest that defects in nuclear genome maintenance, particularly in the stem cell compartment, represent a unified mechanism for mouse progerias. Therefore, through their destabilizing effects on the nuclear genome, mtDNA mutations are indirect contributors to organismal ageing, suggesting that the direct role of mtDNA mutations in driving ageing-like symptoms might need to be revisited.
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Affiliation(s)
- Riikka H Hämäläinen
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland.
- Research Program in Stem Cells and Metabolism, University of Helsinki, Helsinki, Finland.
| | - Juan C Landoni
- Research Program in Stem Cells and Metabolism, University of Helsinki, Helsinki, Finland
| | - Kati J Ahlqvist
- Research Program in Stem Cells and Metabolism, University of Helsinki, Helsinki, Finland
| | - Steffi Goffart
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
| | - Sanna Ryytty
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - M Obaidur Rahman
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Virginia Brilhante
- Research Program in Stem Cells and Metabolism, University of Helsinki, Helsinki, Finland
| | - Katherine Icay
- Research Program in Systems Oncology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Sampsa Hautaniemi
- Research Program in Systems Oncology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Liya Wang
- Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Marikki Laiho
- Department of Radiation Oncology and Molecular Radiation Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Anu Suomalainen
- Research Program in Stem Cells and Metabolism, University of Helsinki, Helsinki, Finland.
- Helsinki University Hospital, Department of Neurosciences, Helsinki, Finland.
- Neuroscience Center, University of Helsinki, Helsinki, Finland.
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13
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Wanrooij PH, Chabes A. Ribonucleotides in mitochondrial DNA. FEBS Lett 2019; 593:1554-1565. [PMID: 31093968 DOI: 10.1002/1873-3468.13440] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 05/09/2019] [Accepted: 05/09/2019] [Indexed: 01/05/2023]
Abstract
The incorporation of ribonucleotides (rNMPs) into DNA during genome replication has gained substantial attention in recent years and has been shown to be a significant source of genomic instability. Studies in yeast and mammals have shown that the two genomes, the nuclear DNA (nDNA) and the mitochondrial DNA (mtDNA), differ with regard to their rNMP content. This is largely due to differences in rNMP repair - whereas rNMPs are efficiently removed from the nuclear genome, mitochondria lack robust mechanisms for removal of single rNMPs incorporated during DNA replication. In this minireview, we describe the processes that determine the frequency of rNMPs in the mitochondrial genome and summarise recent findings regarding the effect of incorporated rNMPs on mtDNA stability and function.
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Affiliation(s)
- Paulina H Wanrooij
- Department of Medical Biochemistry and Biophysics, Umeå University, Sweden
| | - Andrei Chabes
- Department of Medical Biochemistry and Biophysics, Umeå University, Sweden.,Laboratory for Molecular Infection Medicine Sweden, Umeå University, Sweden
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