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Epilepsy: HELP
Articles by Robert W. Taylor
Based on 12 articles published since 2010
(Why 12 articles?)

Between 2010 and 2020, R. W. Taylor wrote the following 12 articles about Epilepsy.
+ Citations + Abstracts
1 Review Epilepsy due to mutations in the mitochondrial polymerase gamma (POLG) gene: A clinical and molecular genetic review. 2016

Anagnostou, Maria-Eleni / Ng, Yi Shiau / Taylor, Robert W / McFarland, Robert. ·Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom. · Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom. robert.mcfarland@newcastle.ac.uk. ·Epilepsia · Pubmed #27554452.

ABSTRACT: We performed a systematic review of the clinical, molecular, and biochemical features of polymerase gamma (POLG)-related epilepsy and current evidence on seizure management. Patients were identified from a combined electronic search of articles using Ovid Medline and Scopus databases, published from January 2000 to January 2015. Only patients with a confirmed genetic diagnosis of POLG mutations were considered. Seventy-two articles were included for analysis. We identified 128 pathogenic variants in 372 patients who had POLG-related epilepsy. Among these, 84% of the cases harbored at least one of these pathogenic variants: p.Ala467Thr, p.Trp748Ser, and p.Gly848Ser. A bimodal distribution of disease onset was present in early childhood (<5 years) and adolescence; female patients had a later presentation than male patients (median age 4.00 vs. 1.83 years, p-value = 0.041). Focal-onset seizure including convulsive, myoclonus, and occipital seizures was common at the outset and was refractory to pharmacotherapy. We confirmed that homozygous pathogenic variants located in the linker region of POLG were associated with later age of onset and longer survival compared to compound heterozygous variants. In addition, biochemical and molecular heterogeneities in different tissues were frequently observed. POLG-related epilepsy is clinically heterogeneous, and the prognosis is, in part, influenced by the location of the variants in the gene and the presence of hepatic involvement. Normal muscle and fibroblast studies do no exclude the diagnosis of POLG-related mitochondrial disease and direct sequencing of the POLG gene should be the gold standard when investigating suspected cases.

2 Article Three families with 'de novo' m.3243A > G mutation. 2016

de Laat, Paul / Janssen, Mirian C H / Alston, Charlotte L / Taylor, Robert W / Rodenburg, Richard J T / Smeitink, Jan A M. ·Radboud University Medical Center Amalia Children's Hospital, Department of Pediatrics, Radboud Center for Mitochondrial Medicine, Nijmegen, The Netherlands. · Radboud University Medical Center Amalia Children's Hospital, Department of Pediatrics, Radboud Center for Mitochondrial Medicine, Nijmegen, The Netherlands; Radboud University Medical Center, Department of Internal Medicine, Radboud Center for Mitochondrial Medicine, Nijmegen, The Netherlands. · Wellcome Trust Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK. ·BBA Clin · Pubmed #27331024.

ABSTRACT: The m.3243A > G mutation is the most prevalent, disease-causing mitochondrial DNA (mtDNA) mutation. In a national cohort study of 48 families harbouring the m.3243A > G mutation, we identified three families in which the mutation appeared to occur sporadically within these families. In this report we describe these three families. Based on detailed mtDNA analysis of three different tissues using two different quantitative pyrosequencing assays with sensitivity to a level of 1% mutated mtDNA, we conclude that the m.3243A > G mutation has arisen de novo in each of these families. The symptomatic carriers presented with a variety of symptoms frequently observed in patients harbouring the m.3243A > G mutation. A more severe phenotype is seen in the de novo families compared to recent cohort studies, which might be due to reporting bias. The observation that de novo m.3243A > G mutations exist is of relevance for both diagnostic investigations and genetic counselling. Firstly, even where there is no significant (maternal) family history in patients with stroke-like episodes, diabetes and deafness or other unexplained organ dysfunction, the m.3243A > G mutation should be screened as a possible cause of the disease. Second, analysis of maternally-related family members is highly recommended to provide reliable counselling for these families, given that the m.3243A > G mutation may have arisen de novo.

3 Article Short peptides from leucyl-tRNA synthetase rescue disease-causing mitochondrial tRNA point mutations. 2016

Perli, Elena / Fiorillo, Annarita / Giordano, Carla / Pisano, Annalinda / Montanari, Arianna / Grazioli, Paola / Campese, Antonio F / Di Micco, Patrizio / Tuppen, Helen A / Genovese, Ilaria / Poser, Elena / Preziuso, Carmela / Taylor, Robert W / Morea, Veronica / Colotti, Gianni / d'Amati, Giulia. ·Department of Radiology, Oncology and Pathology. · Department of Biochemical Sciences "A. Rossi Fanelli". · Department of Biology and Biotechnologies 'Charles Darwin' and Pasteur Institute-Cenci Bolognetti Foundation, Rome 00161, Italy. · Department of Molecular Medicine, Sapienza University of Rome, Rome 00161, Italy. · Wellcome Trust Center for Mitochondrial Research, Institute for Ageing and Health, Newcastle University, Newcastle upon Tyne NE1 7RU, UK and. · National Research Council of Italy, Institute of Molecular Biology and Pathology, Rome 00185, Italy. · National Research Council of Italy, Institute of Molecular Biology and Pathology, Rome 00185, Italy giulia.damati@uniroma1.it gianni.colotti@uniroma1.it. · Department of Radiology, Oncology and Pathology, Pasteur Institute-Cenci Bolognetti Foundation, Rome 00161, Italy, giulia.damati@uniroma1.it gianni.colotti@uniroma1.it. ·Hum Mol Genet · Pubmed #26721932.

ABSTRACT: Mutations in mitochondrial (mt) genes coding for mt-tRNAs are responsible for a range of syndromes, for which no effective treatment is available. We recently showed that the carboxy-terminal domain (Cterm) of human mt-leucyl tRNA synthetase rescues the pathologic phenotype associated either with the m.3243A>G mutation in mt-tRNA(Leu(UUR)) or with mutations in the mt-tRNA(Ile), both of which are aminoacylated by Class I mt-aminoacyl-tRNA synthetases (mt-aaRSs). Here we show, by using the human transmitochondrial cybrid model, that the Cterm is also able to improve the phenotype caused by the m.8344A>G mutation in mt-tRNA(Lys), aminoacylated by a Class II aaRS. Importantly, we demonstrate that the same rescuing ability is retained by two Cterm-derived short peptides, β30_31 and β32_33, which are effective towards both the m.8344A>G and the m.3243A>G mutations. Furthermore, we provide in vitro evidence that these peptides bind with high affinity wild-type and mutant human mt-tRNA(Leu(UUR)) and mt-tRNA(Lys), and stabilize mutant mt-tRNA(Leu(UUR)). In conclusion, we demonstrate that small Cterm-derived peptides can be effective tools to rescue cellular defects caused by mutations in a wide range of mt-tRNAs.

4 Article Epilepsy in adults with mitochondrial disease: A cohort study. 2015

Whittaker, Roger G / Devine, Helen E / Gorman, Grainne S / Schaefer, Andrew M / Horvath, Rita / Ng, Yi / Nesbitt, Victoria / Lax, Nichola Z / McFarland, Robert / Cunningham, Mark O / Taylor, Robert W / Turnbull, Douglass M. ·Institute of Neuroscience, Henry Wellcome Building for Neuroecology, Newcastle University, Newcastle upon Tyne, United Kingdom. · Wellcome Trust Center for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom. · Institute of Genetic Medicine, International Center for Life, Newcastle University, Newcastle upon Tyne, United Kingdom. ·Ann Neurol · Pubmed #26381753.

ABSTRACT: OBJECTIVE: The aim of this work was to determine the prevalence and progression of epilepsy in adult patients with mitochondrial disease. METHODS: We prospectively recruited a cohort of 182 consecutive adult patients attending a specialized mitochondrial disease clinic in Newcastle upon Tyne between January 1, 2005 and January 1, 2008. We then followed this cohort over a 7-year period, recording primary outcome measures of occurrence of first seizure, status epilepticus, stroke-like episode, and death. RESULTS: Overall prevalence of epilepsy in the cohort was 23.1%. Mean age of epilepsy onset was 29.4 years. Prevalence varied widely between genotypes, with several genotypes having no cases of epilepsy, a prevalence of 34.9% in the most common genotype (m.3243A>G mutation), and 92.3% in the m.8344A>G mutation. Among the cohort as a whole, focal seizures, with or without progression to bilateral convulsive seizures, was the most common seizure type. Conversely, all of the patients with the m.8344A>G mutation and epilepsy experienced myoclonic seizures. Patients with the m.3243A>G mutation remain at high risk of developing stroke-like episodes (1.16% per year). However, although the standardized mortality ratio for the entire cohort was high (2.86), this ratio did not differ significantly between patients with epilepsy (2.96) and those without (2.83). INTERPRETATION: Epilepsy is a common manifestation of mitochondrial disease. It develops early in the disease and, in the case of the m.3243A>G mutation, often presents in the context of a stroke-like episode or status epilepticus. However, epilepsy does not itself appear to contribute to the increased mortality in mitochondrial disease.

5 Article A novel de novo STXBP1 mutation is associated with mitochondrial complex I deficiency and late-onset juvenile-onset parkinsonism. 2015

Keogh, Michael J / Daud, D / Pyle, A / Duff, J / Griffin, H / He, L / Alston, C L / Steele, H / Taggart, S / Basu, A P / Taylor, R W / Horvath, R / Ramesh, V / Chinnery, Patrick F. ·Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, NE1 3BZ, UK. ·Neurogenetics · Pubmed #25418441.

ABSTRACT: Mutations in STXBP1 have recently been identified as a cause of infantile epileptic encephalopathy. The underlying mechanism of the disorder remains unclear and, recently, several case reports have described broad and progressive neurological phenotypes in addition to early-onset epilepsy. Herein, we describe a patient with early-onset epilepsy who subsequently developed a progressive neurological phenotype including parkinsonism in her early teens. A de novo mutation in STXBP1 (c.416C>T, p.(Pro139Leu)) was detected with exome sequencing together with profound impairment of complex I of the mitochondrial respiratory chain on muscle biopsy. These findings implicate a secondary impairment of mitochondrial function in the progressive nature of the disease phenotype.

6 Article The urinary proteome and metabonome differ from normal in adults with mitochondrial disease. 2015

Hall, Andrew M / Vilasi, Annalisa / Garcia-Perez, Isabel / Lapsley, Marta / Alston, Charlotte L / Pitceathly, Robert D S / McFarland, Robert / Schaefer, Andrew M / Turnbull, Doug M / Beaumont, Nick J / Hsuan, Justin J / Cutillas, Pedro R / Lindon, John C / Holmes, Elaine / Unwin, Robert J / Taylor, Robert W / Gorman, Grainne S / Rahman, Shamima / Hanna, Michael G. ·Institute of Anatomy, University of Zurich, Zurich, Switzerland. · Laboratory of Mass Spectrometry and Proteomics, Institute of Protein Biochemistry-CNR, Naples, Italy. · Computational and Systems Medicine, Department of Surgery and Cancer, Imperial College London, London, UK. · South West Thames Institute for Renal Research, St Helier University Hospitals, Surrey, UK. · Wellcome Trust Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK. · Medical Research Council Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, University College London Institute of Neurology, London, UK. · Division of Medicine, Institute for Liver & Digestive Health, University College London, London, UK. · Centre for Haemato-Oncology, Barts Cancer Institute, Queen Mary, University of London, London, UK. · UCL Centre for Nephrology, Royal Free Hospital, London, UK. · UCL Institute of Child Health, London, UK. ·Kidney Int · Pubmed #25207879.

ABSTRACT: We studied the extent and nature of renal involvement in a cohort of 117 adult patients with mitochondrial disease, by measuring urinary retinol-binding protein (RBP) and albumin; established markers of tubular and glomerular dysfunction, respectively. Seventy-five patients had the m.3243A>G mutation and the most frequent phenotypes within the entire cohort were 14 with MELAS, 33 with MIDD, and 17 with MERRF. Urinary RBP was increased in 29 of 75 of m.3243A>G patients, whereas albumin was increased in 23 of the 75. The corresponding numbers were 16 and 14, respectively, in the 42 non-m.3243A>G patients. RBP and albumin were higher in diabetic m.3243A>G patients than in nondiabetics, but there were no significant differences across the three major clinical phenotypes. The urine proteome (mass spectrometry) and metabonome (nuclear magnetic resonance) in a subset of the m.3243A>G patients were markedly different from controls, with the most significant alterations occurring in lysosomal proteins, calcium-binding proteins, and antioxidant defenses. Differences were also found between asymptomatic m.3243A>G carriers and controls. No patients had an elevated serum creatinine level, but 14% had hyponatremia, 10% had hypophosphatemia, and 14% had hypomagnesemia. Thus, abnormalities in kidney function are common in adults with mitochondrial disease, exist in the absence of elevated serum creatinine, and are not solely explained by diabetes.

7 Article Distal weakness with respiratory insufficiency caused by the m.8344A > G "MERRF" mutation. 2014

Blakely, Emma L / Alston, Charlotte L / Lecky, Bryan / Chakrabarti, Biswajit / Falkous, Gavin / Turnbull, Douglass M / Taylor, Robert W / Gorman, Grainne S. ·Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne NE2 2HH, UK. · The Walton Centre NHS Foundation Trust, Liverpool L9 7LJ, UK. · Aintree Chest Centre, University Hospital Aintree, Liverpool L9 7AL, UK. · Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne NE2 2HH, UK. Electronic address: grainne.gorman@ncl.ac.uk. ·Neuromuscul Disord · Pubmed #24792523.

ABSTRACT: The m.8344A>G mutation in the mt-tRNA(Lys) gene, first described in myoclonic epilepsy and ragged red fibers (MERRF), accounts for approximately 80% of mutations in individuals with MERRF syndrome. Although originally described in families with a classical syndrome of myoclonus, ataxia, epilepsy and ragged red fibers in muscle biopsy, the m.8344A>G mutation is increasingly recognised to exhibit marked phenotypic heterogeneity. This paper describes the clinical, morphological and laboratory features of an unusual phenotype in a patient harboring the m.8344A>G 'MERRF' mutation. We present the case of a middle-aged woman with distal weakness since childhood who also had ptosis and facial weakness and who developed mid-life respiratory insufficiency necessitating non-invasive nocturnal ventilator support. Neurophysiological and acetylcholine receptor antibody analyses excluded myasthenia gravis whilst molecular genetic testing excluded myotonic dystrophy, prompting a diagnostic needle muscle biopsy. Mitochondrial histochemical abnormalities including subsarcolemmal mitochondrial accumulation (ragged-red fibers) and in excess of 90% COX-deficient fibers, was seen leading to sequencing of the mitochondrial genome in muscle. This identified the m.8344A>G mutation commonly associated with the MERRF phenotype. This case extends the evolving phenotypic spectrum of the m.8344A>G mutation and emphasizes that it may cause indolent distal weakness with respiratory insufficiency, with marked histochemical defects in muscle. Our findings support consideration of screening of this gene in cases of indolent myopathy resembling distal limb-girdle muscular dystrophy in which screening of the common genes prove negative.

8 Article Mutation of the human mitochondrial phenylalanine-tRNA synthetase causes infantile-onset epilepsy and cytochrome c oxidase deficiency. 2014

Almalki, Abdulraheem / Alston, Charlotte L / Parker, Alasdair / Simonic, Ingrid / Mehta, Sarju G / He, Langping / Reza, Mojgan / Oliveira, Jorge M A / Lightowlers, Robert N / McFarland, Robert / Taylor, Robert W / Chrzanowska-Lightowlers, Zofia M A. ·Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, Newcastle University, Newcastle upon Tyne NE2 4HH, UK. Electronic address: abdulraheem.almalki@newcastle.ac.uk. ·Biochim Biophys Acta · Pubmed #24161539.

ABSTRACT: Mitochondrial aminoacyl-tRNA synthetases (aaRSs) are essential enzymes in protein synthesis since they charge tRNAs with their cognate amino acids. Mutations in the genes encoding mitochondrial aaRSs have been associated with a wide spectrum of human mitochondrial diseases. Here we report the identification of pathogenic mutations (a partial genomic deletion and a highly conserved p. Asp325Tyr missense variant) in FARS2, the gene encoding mitochondrial phenylalanyl-tRNA synthetase, in a patient with early-onset epilepsy and isolated complex IV deficiency in muscle. The biochemical defect was expressed in myoblasts but not in fibroblasts and associated with decreased steady state levels of COXI and COXII protein and reduced steady state levels of the mt-tRNA(Phe) transcript. Functional analysis of the recombinant mutant p. Asp325Tyr FARS2 protein showed an inability to bind ATP and consequently undetectable aminoacylation activity using either bacterial tRNA or human mt-tRNA(Phe) as substrates. Lentiviral transduction of cells with wildtype FARS2 restored complex IV protein levels, confirming that the p.Asp325Tyr mutation is pathogenic, causing respiratory chain deficiency and neurological deficits on account of defective aminoacylation of mt-tRNA(Phe).

9 Article Near-identical segregation of mtDNA heteroplasmy in blood, muscle, urinary epithelium, and hair follicles in twins with optic atrophy, ptosis, and intractable epilepsy. 2013

Spyropoulos, Achilles / Manford, Mark / Horvath, Rita / Alston, Charlotte L / Yu-Wai-Man, Patrick / He, Langping / Taylor, Robert W / Chinnery, Patrick F. ·Wellcome Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle Upon Tyne, England. · Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, England. · Wellcome Centre for Mitochondrial Research, Institute of Ageing and Health, Newcastle University, Newcastle Upon Tyne, England. ·JAMA Neurol · Pubmed #24126373.

ABSTRACT: IMPORTANCE: Mitochondrial DNA (mtDNA) disorders have emerged as major causes of inherited neurologic disease. Despite being well recognized for more than 2 decades, the clinical presentation continues to broaden. The phenotypic heterogeneity is partly owing to different percentage levels of mutant mtDNA heteroplasmy in different tissues, but the factors influencing this are poorly understood. OBSERVATIONS: This case report describes monozygotic male twins with ptosis, optic atrophy, and recent-onset intractable myoclonic epilepsy. The assessment of respiratory chain enzyme activities in the muscle from 1 twin revealed a severe and isolated defect involving mitochondrial complex I. Mitochondrial DNA sequencing revealed a pathogenic m.14487T>C MTND6 mutation, which was present at very high levels of heteroplasmy in muscle (84%) and lower levels in blood (15%), urinary epithelium (75%), and buccal mucosa (58%). Of particular interest, his identical twin was found to harbor very similar levels of the m.14487T>C mutation in his blood, urine, buccal mucosa, and hair follicle DNA samples, while the presence of low levels in the mother's tissues confirmed maternal transmission. CONCLUSIONS AND RELEVANCE: It was shown that m14487T>C can also cause the unusual combination of optic atrophy, ptosis, and encephalomyopathy leading to intractable seizures. Near-identical heteroplasmy levels in different tissues in both siblings support a nuclear genetic mechanism controlling the tissue segregation of mtDNA mutations.

10 Article The UK MRC Mitochondrial Disease Patient Cohort Study: clinical phenotypes associated with the m.3243A>G mutation--implications for diagnosis and management. 2013

Nesbitt, Victoria / Pitceathly, Robert D S / Turnbull, Doug M / Taylor, Robert W / Sweeney, Mary G / Mudanohwo, Ese E / Rahman, Shamima / Hanna, Michael G / McFarland, Robert. ·Wellcome Trust Centre for Mitochondrial Research Group, Institute for Ageing and Health, Newcastle University, Newcastle upon Tyne, UK. ·J Neurol Neurosurg Psychiatry · Pubmed #23355809.

ABSTRACT: BACKGROUND: Population-based studies suggest the m.3243A>G mutation in MTTL1 is the most common disease-causing mtDNA mutation, with a carrier rate of 1 in 400 people. The m.3243A>G mutation is associated with several clinical syndromes including mitochondrial encephalopathy lactic acidosis and stroke-like episodes (MELAS), maternally inherited deafness and diabetes (MIDD) and progressive external ophthalmoplegia (PEO). Many patients affected by this mutation exhibit a clinical phenotype that does not fall within accepted criteria for the currently recognised classical mitochondrial syndromes. METHODS: We have defined the phenotypic spectrum associated with the m.3243A>G mtDNA mutation in 129 patients, from 83 unrelated families, recruited to the Mitochondrial Disease Patient Cohort Study UK. RESULTS: 10% of patients exhibited a classical MELAS phenotype, 30% had MIDD, 6% MELAS/MIDD, 2% MELAS/chronic PEO (CPEO) and 5% MIDD/CPEO overlap syndromes. 6% had PEO and other features of mitochondrial disease not consistent with another recognised syndrome. Isolated sensorineural hearing loss occurred in 3%. 28% of patients demonstrated a panoply of clinical features, which were not consistent with any of the classical syndromes associated with the m.3243A>G mutation. 9% of individuals harbouring the mutation were clinically asymptomatic. CONCLUSION: Following this study we propose guidelines for screening and for the management of confirmed cases.

11 Article Mutations in the mitochondrial tRNA Ser(AGY) gene are associated with deafness, retinal degeneration, myopathy and epilepsy. 2012

Tuppen, Helen A L / Naess, Karin / Kennaway, Nancy G / Al-Dosary, Mazhor / Lesko, Nicole / Yarham, John W / Bruhn, Helene / Wibom, Rolf / Nennesmo, Inger / Weleber, Richard G / Blakely, Emma L / Taylor, Robert W / McFarland, Robert. ·Mitochondrial Research Group, Institute for Ageing and Health, Newcastle University, Newcastle upon Tyne, UK. ·Eur J Hum Genet · Pubmed #22378285.

ABSTRACT: Although over 200 pathogenic mitochondrial DNA (mtDNA) mutations have been reported to date, determining the genetic aetiology of many cases of mitochondrial disease is still not straightforward. Here, we describe the investigations undertaken to uncover the underlying molecular defect(s) in two unrelated Caucasian patients with suspected mtDNA disease, who presented with similar symptoms of myopathy, deafness, neurodevelopmental delay, epilepsy, marked fatigue and, in one case, retinal degeneration. Histochemical and biochemical evidence of mitochondrial respiratory chain deficiency was observed in the patient muscle biopsies and both patients were discovered to harbour a novel heteroplasmic mitochondrial tRNA (mt-tRNA)(Ser(AGY)) (MTTS2) mutation (m.12264C>T and m.12261T>C, respectively). Clear segregation of the m.12261T>C mutation with the biochemical defect, as demonstrated by single-fibre radioactive RFLP, confirmed the pathogenicity of this novel variant in patient 2. However, unusually high levels of m.12264C>T mutation within both COX-positive (98.4 ± 1.5%) and COX-deficient (98.2 ± 2.1%) fibres in patient 1 necessitated further functional investigations to prove its pathogenicity. Northern blot analysis demonstrated the detrimental effect of the m.12264C>T mutation on mt-tRNA(Ser(AGY)) stability, ultimately resulting in decreased steady-state levels of fully assembled complexes I and IV, as shown by blue-native polyacrylamide gel electrophoresis. Our findings expand the spectrum of pathogenic mutations associated with the MTTS2 gene and highlight MTTS2 mutations as an important cause of retinal and syndromic auditory impairment.

12 Article POLG mutations cause decreased mitochondrial DNA repopulation rates following induced depletion in human fibroblasts. 2011

Stewart, Joanna D / Schoeler, Susanne / Sitarz, Kamil S / Horvath, Rita / Hallmann, Kerstin / Pyle, Angela / Yu-Wai-Man, Patrick / Taylor, Robert W / Samuels, David C / Kunz, Wolfram S / Chinnery, Patrick F. ·Mitochondrial Research Group, Institute of Human Genetics, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ, UK. ·Biochim Biophys Acta · Pubmed #21138766.

ABSTRACT: Disorders of mitochondrial DNA (mtDNA) maintenance have emerged as an important cause of human genetic disease, but demonstrating the functional consequences of de novo mutations remains a major challenge. We studied the rate of depletion and repopulation of mtDNA in human fibroblasts exposed to ethidium bromide in patients with heterozygous POLG mutations, POLG2 and TK2 mutations. Ethidium bromide induced mtDNA depletion occurred at the same rate in human fibroblasts from patients and healthy controls. By contrast, the restoration of mtDNA levels was markedly delayed in fibroblasts from patients with compound heterozygous POLG mutations. Specific POLG2 and TK2 mutations did not delay mtDNA repopulation rates. These observations are consistent with the hypothesis that mutations in POLG impair mtDNA repopulation within intact cells, and provide a potential method of demonstrating the functional consequences of putative pathogenic alleles causing a defect of mtDNA synthesis.