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Zereg E, Chaussenot A, Morel G, Bannwarth S, Sacconi S, Soriani MH, Attarian S, Cano A, Pouget J, Bellance R, Tranchant C, Lannes B, de Paula AM, Saadi Ait-El-Mkadem S, Chafino B, Berthet M, Fragaki K, Paquis-Flucklinger V, Rouzier C. Single-fiber studies for assigning pathogenicity of eight mitochondrial DNA variants associated with mitochondrial diseases. Hum Mutat 2020; 41:1394-1406. [PMID: 32419253 DOI: 10.1002/humu.24037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 03/29/2020] [Accepted: 04/19/2020] [Indexed: 12/21/2022]
Abstract
Whole mitochondrial DNA (mtDNA) sequencing is now systematically used in clinical laboratories to screen patients with a phenotype suggestive of mitochondrial disease. Next Generation Sequencing (NGS) has significantly increased the number of identified pathogenic mtDNA variants. Simultaneously, the number of variants of unknown significance (VUS) has increased even more, thus challenging their interpretation. Correct classification of the variants' pathogenicity is essential for optimal patient management, including treatment and genetic counseling. Here, we used single muscle fiber studies to characterize eight heteroplasmic mtDNA variants, among which were three novel variants. By applying the pathogenicity scoring system, we classified four variants as "definitely pathogenic" (m.590A>G, m.9166T>C, m.12293G>A, and m.15958A>T). Two variants remain "possibly pathogenic" (m.4327T>C and m.5672T>C) but should these be reported in a different family, they would be reclassified as "definitely pathogenic." We also illustrate the contribution of single-fiber studies to the diagnostic approach in patients harboring pathogenic variants with low level heteroplasmy.
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Affiliation(s)
- Elamine Zereg
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France
| | - Annabelle Chaussenot
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
| | - Godelieve Morel
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France
| | - Sylvie Bannwarth
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
| | - Sabrina Sacconi
- Department of Clinical Neurosciences, Neuromuscular Diseases Centre, Nice Teaching Hospital, Nice, France
| | - Marie-Hélène Soriani
- Department of Clinical Neurosciences, Neuromuscular Diseases Centre, Nice Teaching Hospital, Nice, France
| | - Shahram Attarian
- Neurology Department, Referral Center for ALS and Neuromuscular Diseases, Timone University Hospital, Aix-Marseille University, Marseille, France
| | - Aline Cano
- Pediatric Neurology Department, Reference Center for Inherited Metabolic Diseases, Timone Hospital, Marseille, France
| | - Jean Pouget
- Neurology Department, Referral Center for ALS and Neuromuscular Diseases, Timone University Hospital, Aix-Marseille University, Marseille, France
| | - Rémi Bellance
- Neuromyology Department, Neuromuscular Reference Center, Fort-de-France Teaching Hospital, Fort-de-France, France
| | - Christine Tranchant
- Department of Movement Pathology, Strasbourg Teaching Hospital, Strasbourg, France
| | - Béatrice Lannes
- Pathology Department, Hôpitaux Universitaires de Strasbourg, Hôpital de Hautepierre, Strasbourg, France
| | - André Maues de Paula
- Pathology Department, Timone University Hospital, Aix-Marseille University, Marseille, France
| | - Samira Saadi Ait-El-Mkadem
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
| | - Bernadette Chafino
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France
| | - Mathieu Berthet
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France
| | - Konstantina Fragaki
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
| | - Véronique Paquis-Flucklinger
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
| | - Cécile Rouzier
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
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Barcia G, Assouline Z, Pennisi A, Steffann J, Boddaert N, Gitiaux C, Rötig A, Bonnefont JP, Munnich A. Expanding the clinical spectrum of MTTF mutations. Mol Genet Metab Rep 2019; 21:100501. [PMID: 31463198 PMCID: PMC6706677 DOI: 10.1016/j.ymgmr.2019.100501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 08/07/2019] [Indexed: 11/30/2022] Open
Abstract
We report on a de novo m.586G > A MTTF mutation in a 14 yrs old boy with non-progressive muscle weakness, myalgia, normal brain MRI, normal schooling and absent central nervous system involvement. The same m.586G > A MTTF mutation has been previously reported in a 57 yrs-old woman with a progressive neurodegenerative disorder, akinesia-rigidity, abnormal movements, dementia, and psychiatric disorder. Those two strikingly different clinical presentations emphasize the impact of either mitochondrial factors (heteroplasmy, mitotic segregation) or hitherto unknown nuclear factors on the clinical expression of genetically homogeneous mtDNA mutations.
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Itkis Y, Krylova T, Pechatnikova NL, De Grassi A, Tabakov VY, Pierri CL, Aleshin V, Boyko A, Bunik VI, Zakharova EY. A novel variant m.641A>T in the mitochondrial MT-TF gene is associated with epileptic encephalopathy in adolescent. Mitochondrion 2019; 47:10-17. [PMID: 31009750 DOI: 10.1016/j.mito.2019.04.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 03/21/2019] [Accepted: 04/17/2019] [Indexed: 01/15/2023]
Abstract
We present a 14-year-old girl with loss of motor functions, tetraplegia, epilepsy and nystagmus, caused by a novel heteroplasmic m.641A>T transition in an evolutionary conserved region of mitochondrial genome, affecting the aminoacyl stem of mitochondrial tRNA-Phe. In silico prediction, respirometry, Western blot and enzymatic analyses in skin fibroblasts support the pathogenicity of the m.641A>T substitution. This is the 18th MT-TF point mutation associated with a mitochondrial disorder. The onset and the severity of the disease, however, is unique in this case and broadens the clinical picture related to mutations of mitochondrial tRNA-Phe.
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Affiliation(s)
- Yulia Itkis
- Department of Inborn Errors of Metabolism, FSBI 'Research Centre for Medical Genetics', Moscow, Russia.
| | - Tatiana Krylova
- Department of Inborn Errors of Metabolism, FSBI 'Research Centre for Medical Genetics', Moscow, Russia
| | | | - Anna De Grassi
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, Bari, Italy
| | - Vyacheslav Yu Tabakov
- Common Use Center "Biobank", FSBI 'Research Centre for Medical Genetics", Moscow, Russia
| | - Ciro Leonardo Pierri
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, Bari, Italy
| | - Vasily Aleshin
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russia; Belozersky Institute of Physicochemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Alexandra Boyko
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russia
| | - Victoria I Bunik
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russia; Belozersky Institute of Physicochemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Ekaterina Yu Zakharova
- Department of Inborn Errors of Metabolism, FSBI 'Research Centre for Medical Genetics', Moscow, Russia
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Peverelli L, Gold CA, Naini AB, Tanji K, Akman HO, Hirano M, Dimauro S. Mitochondrial myopathy with dystrophic features due to a novel mutation in the MTTM gene. Muscle Nerve 2014; 50:292-5. [PMID: 24711008 DOI: 10.1002/mus.24262] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/04/2014] [Indexed: 11/11/2022]
Abstract
INTRODUCTION A 61-year-old woman with a 5-year history of progressive muscle weakness and atrophy had a muscle biopsy characterized by a combination of dystrophic features (necrotic fibers and endomysial fibrosis) and mitochondrial alterations [ragged-red, cytochrome c oxidase (COX)-negative fibers]. METHODS Sequencing of the whole mtDNA, assessment of the mutation load in muscle and accessible nonmuscle tissues, and single fiber polymerase chain reaction. RESULTS Muscle mitochondrial DNA (mtDNA) sequencing revealed a novel heteroplasmic mutation (m.4403G>A) in the gene (MTTM) that encodes tRNA(Met). The mutation was not present in accessible nonmuscle tissues from the patient or 2 asymptomatic sisters. CONCLUSIONS The clinical features and muscle morphology in this patient are very similar to those described in a previous patient with a different mutation, also in MTTM, which suggests that mutations in this gene confer a distinctive "dystrophic" quality. This may be a diagnostic clue in patients with isolated mitochondrial myopathy.
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Affiliation(s)
- Lorenzo Peverelli
- Department of Neurology, Columbia University Medical Center, College of Physicians & Surgeons, 630 West 168th Street, New York, New York, USA
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Byun HM, Panni T, Motta V, Hou L, Nordio F, Apostoli P, Bertazzi PA, Baccarelli AA. Effects of airborne pollutants on mitochondrial DNA methylation. Part Fibre Toxicol 2013; 10:18. [PMID: 23656717 PMCID: PMC3660297 DOI: 10.1186/1743-8977-10-18] [Citation(s) in RCA: 144] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 05/01/2013] [Indexed: 11/23/2022] Open
Abstract
Background Mitochondria have small mitochondrial DNA (mtDNA) molecules independent from the nuclear DNA, a separate epigenetic machinery that generates mtDNA methylation, and are primary sources of oxidative-stress generation in response to exogenous environments. However, no study has yet investigated whether mitochondrial DNA methylation is sensitive to pro-oxidant environmental exposures. Methods We sampled 40 male participants (20 high-, 20 low-exposure) from each of three studies on airborne pollutants, including investigations of steel workers exposed to metal-rich particulate matter (measured as PM1) in Brescia, Italy (Study 1); gas-station attendants exposed to air benzene in Milan, Italy (Study 2); and truck drivers exposed to traffic-derived Elemental Carbon (EC) in Beijing, China (Study 3). We have measured DNA methylation from buffy coats of the participants. We measured methylation by bisulfite-Pyrosequencing in three mtDNA regions, i.e., the transfer RNA phenylalanine (MT-TF), 12S ribosomal RNA (MT-RNR1) gene and “D-loop” control region. All analyses were adjusted for age and smoking. Results In Study 1, participants with high metal-rich PM1 exposure showed higher MT-TF and MT-RNR1 methylation than low-exposed controls (difference = 1.41, P = 0.002); MT-TF and MT-RNR1 methylation was significantly associated with PM1 exposure (beta = 1.35, P = 0.025); and MT-RNR1 methylation was positively correlated with mtDNA copy number (r = 0.36; P = 0.02). D-loop methylation was not associated with PM1 exposure. We found no effects on mtDNA methylation from air benzene (Study 2) and traffic-derived EC exposure (Study 3). Conclusions Mitochondrial MT-TF and MT-RNR1 DNA methylation was associated with metal-rich PM1 exposure and mtDNA copy number. Our results suggest that locus-specific mtDNA methylation is correlated to selected exposures and mtDNA damage. Larger studies are needed to validate our observations.
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Affiliation(s)
- Hyang-Min Byun
- Laboratory of Environmental Epigenetics, Exposure Epidemiology and Risk Program, Harvard School of Public Health, Boston, MA 02115, USA.
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Dowlati MA, Derakhshandeh-peykar P, Houshmand M, Farhadi M, Shojaei A, Bazzaz JT. Novel human mitochondrial tRNAphemutation in a patient with hearing impairment: A case study. ACTA ACUST UNITED AC 2012; 24:132-6. [DOI: 10.3109/19401736.2012.717935] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Sakiyama Y, Okamoto Y, Higuchi I, Inamori Y, Sangatsuda Y, Michizono K, Watanabe O, Hatakeyama H, Goto YI, Arimura K, Takashima H. A new phenotype of mitochondrial disease characterized by familial late-onset predominant axial myopathy and encephalopathy. Acta Neuropathol 2011; 121:775-83. [PMID: 21424749 PMCID: PMC3098999 DOI: 10.1007/s00401-011-0818-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Revised: 03/11/2011] [Accepted: 03/11/2011] [Indexed: 01/08/2023]
Abstract
Axial myopathy is a rare neuromuscular disease that is characterized by paraspinal muscle atrophy and abnormal posture, most notably camptocormia (also known as bent spine). The genetic cause of familial axial myopathy is unknown. Described here are the clinical features and cause of late-onset predominant axial myopathy and encephalopathy. A 73-year-old woman presented with a 10-year history of severe paraspinal muscle atrophy and cerebellar ataxia. Her 84-year-old sister also developed late-onset paraspinal muscle atrophy and generalized seizures with encephalopathy. Computed tomography showed severe atrophy and fatty degeneration of their paraspinal muscles. Their mother and maternal aunt also developed bent spines. The existence of many ragged-red fibers and cytochrome c oxidase-negative fibers in the biceps brachii muscle of the proband indicated a mitochondrial abnormality. No significant abnormalities were observed in the respiratory chain enzyme activities; however, the activities of complexes I and IV were relatively low compared with the activities of other complexes. Sequence analysis of the mitochondrial DNA from the muscle revealed a novel heteroplasmic mutation (m.602C>T) in the mitochondrial tRNAPhe gene. This familial case of late-onset predominant axial myopathy and encephalopathy may represent a new clinical phenotype of a mitochondrial disease.
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Affiliation(s)
- Yusuke Sakiyama
- Department of Neurology and Geriatrics, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima City, Kagoshima 890-8520 Japan
| | - Yuji Okamoto
- Department of Neurology and Geriatrics, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima City, Kagoshima 890-8520 Japan
| | - Itsuro Higuchi
- Department of Neurology and Geriatrics, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima City, Kagoshima 890-8520 Japan
| | - Yukie Inamori
- Department of Neurology and Geriatrics, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima City, Kagoshima 890-8520 Japan
| | - Yoko Sangatsuda
- Department of Psychiatry, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - Kumiko Michizono
- Department of Neurology and Geriatrics, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima City, Kagoshima 890-8520 Japan
| | - Osamu Watanabe
- Department of Neurology and Geriatrics, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima City, Kagoshima 890-8520 Japan
| | - Hideyuki Hatakeyama
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Yu-ichi Goto
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | | | - Hiroshi Takashima
- Department of Neurology and Geriatrics, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima City, Kagoshima 890-8520 Japan
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Iizuka T, Goto YI, Miyakawa S, Sato M, Wang Z, Suzuki K, Hamada J, Kurata A, Sakai F. Progressive carotid artery stenosis with a novel tRNA phenylalanine mitochondrial DNA mutation. J Neurol Sci 2008; 278:35-40. [PMID: 19091329 DOI: 10.1016/j.jns.2008.11.016] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Revised: 11/07/2008] [Accepted: 11/12/2008] [Indexed: 02/09/2023]
Abstract
Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) is a distinct clinical syndrome caused by mutations in the mitochondrial DNA. The pathogenesis of stroke-like episodes remains unknown but major vessels stenosis is not a cause of stroke-like episodes. We describe a novel heteroplasmic G617A transition in the mitochondrial transfer RNA phenylalanine gene in a patient with encephalomyopathy who presented with recurrent embolic ischemic strokes accompanied by transient occlusion of middle cerebral, anterior cerebral and internal carotid arteries. These ischemic strokes were presumed to be artery-to artery embolisms associated with carotid artery stenosis. Single muscle fiber analysis revealed the pathogenicity of the mutation although its causative role on carotid artery stenosis remains to be elucidated. This case expands phenotypic spectrum of mitochondrial disorders in terms of macroangiopathy, but macroangiopathy-related ischemic strokes should be distinguished from classic stroke-like episodes of MELAS that are speculated to be microangioapthy-related or non-ischemic neurovascular events.
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Affiliation(s)
- Takahiro Iizuka
- Department of Neurology, School of Medicine, Kitasato University, Kanagawa, Japan.
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Valente L, Piga D, Lamantea E, Carrara F, Uziel G, Cudia P, Zani A, Farina L, Morandi L, Mora M, Spinazzola A, Zeviani M, Tiranti V. Identification of novel mutations in five patients with mitochondrial encephalomyopathy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1787:491-501. [PMID: 18977334 DOI: 10.1016/j.bbabio.2008.10.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2008] [Revised: 09/26/2008] [Accepted: 10/01/2008] [Indexed: 10/21/2022]
Abstract
MELAS, MERRF, LHON and NARP, are well-established mitochondrial syndromes associated with specific point mutations of mitochondrial DNA (mtDNA). However, these recurrent mtDNA mutations account for only a minority of mitochondrial disease cases. To evaluate the impact of novel mtDNA mutations, we performed mtDNA sequence analysis in muscle and other tissues of 240 patients with different mitochondrial neuromuscular syndromes. We identified a total of 33 subjects with novel, private or uncommon mutations. Among these, five novel mutations were found in both paediatric and adult cases. We here report on the clinical description of these patients, as well as the biochemical and molecular genetic characterization of the corresponding mutations. Patients 1 and 2 showed changes in ND genes, patient 3 carried a heteroplasmic deletion in the COI gene, patients 4 and 5 carried heteroplasmic mutations in tRNA(Trp) and tRNA(Phe), respectively. Altogether, these data indicate that mtDNA analysis must become part of the routine screening for mitochondrial disorders.
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Affiliation(s)
- Lucia Valente
- IRCCS Foundation Neurological Institute C. Besta, Milan, Italy
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Scaglia F, Wong LJC. Human mitochondrial transfer RNAs: role of pathogenic mutation in disease. Muscle Nerve 2008; 37:150-71. [PMID: 17999409 DOI: 10.1002/mus.20917] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The human mitochondrial genome encodes 13 proteins. All are subunits of the respiratory chain complexes involved in energy metabolism. These proteins are translated by a set of 22 mitochondrial transfer RNAs (tRNAs) that are required for codon reading. Human mitochondrial tRNA genes are hotspots for pathogenic mutations and have attracted interest over the last two decades with the rapid discovery of point mutations associated with a vast array of neuromuscular disorders and diverse clinical phenotypes. In this review, we use a scoring system to determine the pathogenicity of the mutations and summarize the current knowledge of structure-function relationships of these mutant tRNAs. We also provide readers with an overview of a large variety of mechanisms by which mutations may affect the mitochondrial translation machinery and cause disease.
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Affiliation(s)
- Fernando Scaglia
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
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11
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Ling J, Roy H, Qin D, Rubio MAT, Alfonzo JD, Fredrick K, Ibba M. Pathogenic mechanism of a human mitochondrial tRNAPhe mutation associated with myoclonic epilepsy with ragged red fibers syndrome. Proc Natl Acad Sci U S A 2007; 104:15299-304. [PMID: 17878308 PMCID: PMC2000536 DOI: 10.1073/pnas.0704441104] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Indexed: 11/18/2022] Open
Abstract
Human mitochondrial tRNA (hmt-tRNA) mutations are associated with a variety of diseases including mitochondrial myopathies, diabetes, encephalopathies, and deafness. Because the current understanding of the precise molecular mechanisms of these mutations is limited, there is no efficient method to treat their associated mitochondrial diseases. Here, we use a variety of known mutations in hmt-tRNA(Phe) to investigate the mechanisms that lead to malfunctions. We tested the impact of hmt-tRNA(Phe) mutations on aminoacylation, structure, and translation elongation-factor binding. The majority of the mutants were pleiotropic, exhibiting defects in aminoacylation, global structure, and elongation-factor binding. One notable exception was the G34A anticodon mutation of hmt-tRNA(Phe) (mitochondrial DNA mutation G611A), which is associated with MERRF (myoclonic epilepsy with ragged red fibers). In vitro, the G34A mutation decreases aminoacylation activity by 100-fold, but does not affect global folding or recognition by elongation factor. Furthermore, G34A hmt-tRNA(Phe) does not undergo adenosine-to-inosine (A-to-I) editing, ruling out miscoding as a possible mechanism for mitochondrial malfunction. To improve the aminoacylation state of the mutant tRNA, we modified the tRNA binding domain of the nucleus-encoded human mitochondrial phenylalanyl-tRNA synthetase, which aminoacylates hmt-tRNA(Phe) with cognate phenylalanine. This variant enzyme displayed significantly improved aminoacylation efficiency for the G34A mutant, suggesting a general strategy to treat certain classes of mitochondrial diseases by modification of the corresponding nuclear gene.
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Affiliation(s)
| | - Hervé Roy
- Department of Microbiology, and
- Ohio State RNA Group, Ohio State University, Columbus, OH 43210
| | | | - Mary Anne T. Rubio
- Department of Microbiology, and
- Ohio State RNA Group, Ohio State University, Columbus, OH 43210
| | - Juan D. Alfonzo
- *Ohio State Biochemistry Program
- Department of Microbiology, and
- Ohio State RNA Group, Ohio State University, Columbus, OH 43210
| | - Kurt Fredrick
- *Ohio State Biochemistry Program
- Department of Microbiology, and
- Ohio State RNA Group, Ohio State University, Columbus, OH 43210
| | - Michael Ibba
- *Ohio State Biochemistry Program
- Department of Microbiology, and
- Ohio State RNA Group, Ohio State University, Columbus, OH 43210
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Darin N, Kollberg G, Moslemi AR, Tulinius M, Holme E, Grönlund MA, Andersson S, Oldfors A. Mitochondrial myopathy with exercise intolerance and retinal dystrophy in a sporadic patient with a G583A mutation in the mt tRNA(phe) gene. Neuromuscul Disord 2006; 16:504-6. [PMID: 16806928 DOI: 10.1016/j.nmd.2006.05.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2006] [Revised: 04/05/2006] [Accepted: 05/19/2006] [Indexed: 11/25/2022]
Abstract
We describe a second patient with the 583G>A mutation in the tRNA(phe) gene of mitochondrial DNA (mtDNA). This 17-year-old girl had a mitochondrial myopathy with exercise intolerance and an asymptomatic retinopathy. Muscle investigations showed occasional ragged red fibers, 30% cytochrome c oxidase (COX)-negative fibers, and reduced activities of complex I+IV in the respiratory chain. The mutation was heteroplasmic (79%) in muscle but undetectable in other tissues. Analysis of single muscle fibers revealed a significantly higher level of mutated mtDNA in COX-negative fibers. Our study indicates that the 583G>A mutation is pathogenic and expands the clinical spectrum of this mutation.
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Affiliation(s)
- N Darin
- Department of Pediatrics, Sahlgrenska University Hospital, Göteborg, Sweden.
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13
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Meierhofer D, Mayr JA, Ebner S, Sperl W, Kofler B. Rapid screening of the entire mitochondrial DNA for low-level heteroplasmic mutations. Mitochondrion 2005; 5:282-96. [PMID: 16050991 DOI: 10.1016/j.mito.2005.06.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2005] [Revised: 05/30/2005] [Accepted: 06/02/2005] [Indexed: 01/28/2023]
Abstract
Alterations of the mitochondrial DNA (mtDNA) are implicated in various pathological conditions. In this study, we used denaturing high performance liquid chromatography (DHPLC) as a method to rapidly screen the entire mtDNA for mutations. Overlapping DNA fragments, amplified by one single cycling protocol from frozen pre-formulated PCR mixes, were subjected to DHPLC analysis. Single DHPLC injections of fragments yielded straightforward interpretation of results with a detection limit down to 1% mtDNA heteroplasmy. Furthermore, collection and re-amplification of low degree heteroduplex peak-fractions allowed sequence analysis of mtDNA mutations down to the detection limit of the DHPLC method. In order to demonstrate that the method has diagnostic value, we analyzed and confirmed known mtDNA mutations in patient samples.
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Affiliation(s)
- David Meierhofer
- Department of Paediatrics, Paracelsus Private Medical University Salzburg, Muellner Hauptstr. 48, A-5020 Salzburg, Austria
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