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Nogueira C, Pereira C, Silva L, Laranjeira M, Lopes A, Neiva R, Rodrigues E, Campos T, Martins E, Bandeira A, Coelho M, Magalhães M, Damásio J, Gaspar A, Janeiro P, Gomes AL, Ferreira AC, Jacinto S, Vieira JP, Diogo L, Santos H, Mendonça C, Vilarinho L. The genetic landscape of mitochondrial diseases in the next-generation sequencing era: a Portuguese cohort study. Front Cell Dev Biol 2024; 12:1331351. [PMID: 38465286 PMCID: PMC10920333 DOI: 10.3389/fcell.2024.1331351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 01/30/2024] [Indexed: 03/12/2024] Open
Abstract
Introduction: Rare disorders that are genetically and clinically heterogeneous, such as mitochondrial diseases (MDs), have a challenging diagnosis. Nuclear genes codify most proteins involved in mitochondrial biogenesis, despite all mitochondria having their own DNA. The development of next-generation sequencing (NGS) technologies has revolutionized the understanding of many genes involved in the pathogenesis of MDs. In this new genetic era, using the NGS approach, we aimed to identify the genetic etiology for a suspected MD in a cohort of 450 Portuguese patients. Methods: We examined 450 patients using a combined NGS strategy, starting with the analysis of a targeted mitochondrial panel of 213 nuclear genes, and then proceeding to analyze the whole mitochondrial DNA. Results and Discussion: In this study, we identified disease-related variants in 134 (30%) analyzed patients, 88 with nuclear DNA (nDNA) and 46 with mitochondrial DNA (mtDNA) variants, most of them being pediatric patients (66%), of which 77% were identified in nDNA and 23% in mtDNA. The molecular analysis of this cohort revealed 72 already described pathogenic and 20 novel, probably pathogenic, variants, as well as 62 variants of unknown significance. For this cohort of patients with suspected MDs, the use of a customized gene panel provided a molecular diagnosis in a timely and cost-effective manner. Patients who cannot be diagnosed after this initial approach will be further selected for whole-exome sequencing. Conclusion: As a national laboratory for the study and research of MDs, we demonstrated the power of NGS to achieve a molecular etiology, expanding the mutational spectrum and proposing accurate genetic counseling in this group of heterogeneous diseases without therapeutic options.
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Affiliation(s)
- C. Nogueira
- Research & Development Unit, Human Genetics Department, National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal
- Newborn Screening, Metabolism & Genetics Unit, Human Genetics Department, National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal
| | - C. Pereira
- Newborn Screening, Metabolism & Genetics Unit, Human Genetics Department, National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal
| | - L. Silva
- Research & Development Unit, Human Genetics Department, National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal
- Newborn Screening, Metabolism & Genetics Unit, Human Genetics Department, National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal
| | - Mateus Laranjeira
- Research & Development Unit, Human Genetics Department, National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal
| | - A. Lopes
- Newborn Screening, Metabolism & Genetics Unit, Human Genetics Department, National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal
| | - R. Neiva
- Newborn Screening, Metabolism & Genetics Unit, Human Genetics Department, National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal
| | - E. Rodrigues
- Inherited Metabolic Diseases Reference Centre, São João Hospital University Centre, Porto, Portugal
| | - T. Campos
- Inherited Metabolic Diseases Reference Centre, São João Hospital University Centre, Porto, Portugal
| | - E. Martins
- Inherited Metabolic Diseases Reference Centre, Santo António Hospital University Centre, Porto, Portugal
| | - A. Bandeira
- Inherited Metabolic Diseases Reference Centre, Santo António Hospital University Centre, Porto, Portugal
| | - M. Coelho
- Inherited Metabolic Diseases Reference Centre, Santo António Hospital University Centre, Porto, Portugal
| | - M. Magalhães
- Neurology Department, Santo António Hospital University Centre, Porto, Portugal
| | - J. Damásio
- Neurology Department, Santo António Hospital University Centre, Porto, Portugal
| | - A. Gaspar
- Inherited Metabolic Diseases Reference Centre, Lisboa Norte Hospital University Centre, Lisboa, Portugal
| | - P Janeiro
- Inherited Metabolic Diseases Reference Centre, Lisboa Norte Hospital University Centre, Lisboa, Portugal
| | - A. Levy Gomes
- Neurology Department, Lisboa Norte Hospital University Centre, Lisboa, Portugal
| | - A. C. Ferreira
- Inherited Metabolic Diseases Reference Centre, Lisboa Central Hospital Centre, Lisboa, Portugal
| | - S. Jacinto
- Inherited Metabolic Diseases Reference Centre, Lisboa Central Hospital Centre, Lisboa, Portugal
| | - J. P. Vieira
- Inherited Metabolic Diseases Reference Centre, Lisboa Central Hospital Centre, Lisboa, Portugal
| | - L. Diogo
- Inherited Metabolic Diseases Reference Centre, Coimbra Hospital and University Centre, Coimbra, Portugal
| | - H. Santos
- Inherited Metabolic Diseases Reference Centre, Vila Nova de Gaia Hospital Centre, Vila Nova de Gaia, Portugal
| | - C. Mendonça
- Pediatric Department, Faro Hospital and University Centre, Faro, Portugal
| | - L. Vilarinho
- Research & Development Unit, Human Genetics Department, National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal
- Newborn Screening, Metabolism & Genetics Unit, Human Genetics Department, National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal
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2
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The Mitochondrial tRNA Ser(UCN) Gene: A Novel m.7484A>G Mutation Associated with Mitochondrial Encephalomyopathy and Literature Review. Life (Basel) 2023; 13:life13020554. [PMID: 36836911 PMCID: PMC9963529 DOI: 10.3390/life13020554] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 01/26/2023] [Accepted: 02/14/2023] [Indexed: 02/18/2023] Open
Abstract
Mitochondrial tRNASer(UCN) is considered a hot-spot for non-syndromic and aminoglycoside-induced hearing loss. However, many patients have been described with more extensive neurological diseases, mainly including epilepsy, myoclonus, ataxia, and myopathy. We describe a novel homoplasmic m.7484A>G mutation in the tRNASer(UCN) gene affecting the third base of the anticodon triplet in a girl with profound intellectual disability, spastic tetraplegia, sensorineural hearing loss, a clinical history of epilepsia partialis continua and vomiting, typical of MELAS syndrome, leading to a myoclonic epilepticus status, and myopathy with severe COX deficiency at muscle biopsy. The mutation was also found in the homoplasmic condition in the mother who presented with mild cognitive deficit, cerebellar ataxia, myoclonic epilepsy, sensorineural hearing loss and myopathy with COX deficient ragged-red fibers consistent with MERRF syndrome. This is the first anticodon mutation in the tRNASer(UCN) and the second homoplasmic mutation in the anticodon triplet reported to date.
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Pedersen M, Abbott DF, Jackson GD. Wearable OPM-MEG: A changing landscape for epilepsy. Epilepsia 2022; 63:2745-2753. [PMID: 35841260 PMCID: PMC9805039 DOI: 10.1111/epi.17368] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2022] [Revised: 07/13/2022] [Accepted: 07/14/2022] [Indexed: 01/09/2023]
Abstract
Magnetoencephalography with optically pumped magnometers (OPM-MEG) is an emerging and novel, cost-effective wearable system that can simultaneously record neuronal activity with high temporal resolution ("when" neuronal activity occurs) and spatial resolution ("where" neuronal activity occurs). This paper will first outline recent methodological advances in OPM-MEG compared to conventional superconducting quantum interference device (SQUID)-MEG before discussing how OPM-MEG can become a valuable and noninvasive clinical support tool in epilepsy surgery evaluation. Although OPM-MEG and SQUID-MEG share similar data features, OPM-MEG is a wearable design that fits children and adults, and it is also robust to head motion within a magnetically shielded room. This means that OPM-MEG can potentially extend the application of MEG into the neurobiology of severe childhood epilepsies with intellectual disabilities (e.g., epileptic encephalopathies) without sedation. It is worth noting that most OPM-MEG sensors are heated, which may become an issue with large OPM sensor arrays (OPM-MEG currently has fewer sensors than SQUID-MEG). Future implementation of triaxial sensors may alleviate the need for large OPM sensor arrays. OPM-MEG designs allowing both awake and sleep recording are essential for potential long-term epilepsy monitoring.
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Affiliation(s)
- Mangor Pedersen
- Department of Psychology and NeuroscienceAuckland University of TechnologyAucklandNew Zealand
| | - David F. Abbott
- Florey Institute of Neuroscience and Mental HealthMelbourneVictoriaAustralia,Department of Medicine, Austin Health and Florey Department of Neuroscience and Mental HealthUniversity of MelbourneMelbourneVictoriaAustralia
| | - Graeme D. Jackson
- Florey Institute of Neuroscience and Mental HealthMelbourneVictoriaAustralia,Department of Medicine, Austin Health and Florey Department of Neuroscience and Mental HealthUniversity of MelbourneMelbourneVictoriaAustralia
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4
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Capristo M, Del Dotto V, Tropeano CV, Fiorini C, Caporali L, La Morgia C, Valentino ML, Montopoli M, Carelli V, Maresca A. Rapamycin rescues mitochondrial dysfunction in cells carrying the m.8344A > G mutation in the mitochondrial tRNA Lys. Mol Med 2022; 28:90. [PMID: 35922766 PMCID: PMC9347137 DOI: 10.1186/s10020-022-00519-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 07/25/2022] [Indexed: 11/25/2022] Open
Abstract
Background Myoclonus, Epilepsy and Ragged-Red-Fibers (MERRF) is a mitochondrial encephalomyopathy due to heteroplasmic mutations in mitochondrial DNA (mtDNA) most frequently affecting the tRNALys gene at position m.8344A > G. Defective tRNALys severely impairs mitochondrial protein synthesis and respiratory chain when a high percentage of mutant heteroplasmy crosses the threshold for full-blown clinical phenotype. Therapy is currently limited to symptomatic management of myoclonic epilepsy, and supportive measures to counteract muscle weakness with co-factors/supplements. Methods We tested two therapeutic strategies to rescue mitochondrial function in cybrids and fibroblasts carrying different loads of the m.8344A > G mutation. The first strategy was aimed at inducing mitochondrial biogenesis directly, over-expressing the master regulator PGC-1α, or indirectly, through the treatment with nicotinic acid, a NAD+ precursor. The second was aimed at stimulating the removal of damaged mitochondria through prolonged rapamycin treatment. Results The first approach slightly increased mitochondrial protein expression and respiration in the wild type and intermediate-mutation load cells, but was ineffective in high-mutation load cell lines. This suggests that induction of mitochondrial biogenesis may not be sufficient to rescue mitochondrial dysfunction in MERRF cells with high-mutation load. The second approach, when administered chronically (4 weeks), induced a slight increase of mitochondrial respiration in fibroblasts with high-mutation load, and a significant improvement in fibroblasts with intermediate-mutation load, rescuing completely the bioenergetics defect. This effect was mediated by increased mitochondrial biogenesis, possibly related to the rapamycin-induced inhibition of the Mechanistic Target of Rapamycin Complex 1 (mTORC1) and the consequent activation of the Transcription Factor EB (TFEB). Conclusions Overall, our results point to rapamycin-based therapy as a promising therapeutic option for MERRF. Supplementary Information The online version contains supplementary material available at 10.1186/s10020-022-00519-z.
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Affiliation(s)
- Mariantonietta Capristo
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, via Altura 3, 40139, Bologna, Italy
| | - Valentina Del Dotto
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, via Altura 3, 40139, Bologna, Italy
| | - Concetta Valentina Tropeano
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, via Altura 3, 40139, Bologna, Italy
| | - Claudio Fiorini
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, via Altura 3, 40139, Bologna, Italy
| | - Leonardo Caporali
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, via Altura 3, 40139, Bologna, Italy
| | - Chiara La Morgia
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, via Altura 3, 40139, Bologna, Italy
| | - Maria Lucia Valentino
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, via Altura 3, 40139, Bologna, Italy.,Department of Biomedical and NeuroMotor Sciences, University of Bologna, via Altura 3, 40139, Bologna, Italy
| | - Monica Montopoli
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, via Largo Meneghetti 2, 3513, Padova, Italy
| | - Valerio Carelli
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, via Altura 3, 40139, Bologna, Italy. .,Department of Biomedical and NeuroMotor Sciences, University of Bologna, via Altura 3, 40139, Bologna, Italy.
| | - Alessandra Maresca
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, via Altura 3, 40139, Bologna, Italy.
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A mitochondrial myopathy-associated tRNA Ser(UCN) 7453G>A mutation alters tRNA metabolism and mitochondrial function. Mitochondrion 2020; 57:1-8. [PMID: 33279600 DOI: 10.1016/j.mito.2020.11.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 10/09/2020] [Accepted: 11/23/2020] [Indexed: 12/25/2022]
Abstract
BACKGROUND Mitochondrial disorders are a group of heterogeneous diseases characterized by biochemical disturbances in oxidative phosphorylation (OXPHOS). Mutations in mitochondrial transfer RNA (mt-tRNA) genes are the most frequently in mitochondrial disease. However, few studies have detailed the molecular mechanisms behind these mutations. METHODS We performed clinical evaluation, genetic analysis, muscle histochemistry, and molecular and biochemical investigations in muscle tissue and proband-derived cybrid cell lines. RESULTS We found a mitochondrial tRNASer(UCN) mutation (m.7453G>A) in a 15-year-old patient with severe mitochondrial myopathy. We demonstrated that this mutation caused impairment of mitochondrial translation, respiratory deficiency, overproduction of reactive oxygen species (ROS), and decreased mitochondrial membrane potential (MMP), which ultimately led to severe mitochondrial myopathy. CONCLUSION Our findings offer valuable new insights into the tRNASer(UCN) m.7453G>A mutation for both the pathogenic mechanism and functional consequences.
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6
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Moore HL, Blain AP, Turnbull DM, Gorman GS. Systematic review of cognitive deficits in adult mitochondrial disease. Eur J Neurol 2019; 27:3-17. [PMID: 31448495 PMCID: PMC6916601 DOI: 10.1111/ene.14068] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 08/21/2019] [Indexed: 11/27/2022]
Abstract
The profile and trajectory of cognitive impairment in mitochondrial disease are poorly defined. This systematic review sought to evaluate the current literature on cognition in mitochondrial disease, and to determine future research directions. A systematic review was conducted, employing PubMed, Medline, Psycinfo, Embase and Web of Science, and 360‐degree citation methods. English language papers on adult patients were included. The literature search yielded 2421 articles, of which 167 met inclusion criteria. Case reports and reviews of medical reports of patients yielded broad diagnoses of dementia, cognitive impairment and cognitive decline. In contrast, systematic investigations of cognitive functioning using detailed cognitive batteries identified focal cognitive rather than global deficits. Results were variable, but included visuospatial functioning, memory, attention, processing speed and executive functions. Conclusions from studies have been hampered by small sample sizes, variation in genotype and the breadth and depth of assessments undertaken. Comprehensive cognitive research with concurrent functional neuroimaging and physical correlates of mitochondrial disease in larger samples of well‐characterized patients may discern the aetiology and progression of cognitive deficits. These data provide insights into the pattern and trajectory of cognitive impairments, which are invaluable for clinical monitoring, health planning and clinical trial readiness.
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Affiliation(s)
- H L Moore
- Newcastle University, Newcastle upon Tyne, UK
| | - A P Blain
- Newcastle University, Newcastle upon Tyne, UK
| | - D M Turnbull
- Newcastle University, Newcastle upon Tyne, UK.,NIHR Newcastle BRC, NuTH-NHS Foundation Trust, Newcastle upon Tyne, UK
| | - G S Gorman
- Newcastle University, Newcastle upon Tyne, UK.,NIHR Newcastle BRC, NuTH-NHS Foundation Trust, Newcastle upon Tyne, UK
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7
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You C, Tao R, Su Q, Lu Y, Wang L, Liu S, Wang L, Wang L, Xue F, Che F. Mitochondrial DNA analyses found five novel mutations in idiopathic epilepsy patients. Mitochondrial DNA B Resour 2019; 4:2387-2391. [PMID: 33365557 PMCID: PMC7707843 DOI: 10.1080/23802359.2019.1633963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2018] [Accepted: 06/15/2019] [Indexed: 11/11/2022] Open
Abstract
Epilepsy is a common and chronic neurological disease with a high degree of genetic heterogeneity. The etiology and pathogenesis of the disease have not been fully understood. Many studies suggested that there was a reciprocal relationship between mitochondrial dysfunction and epilepsy, but few studies focused on the mitochondrial genome (mtDNA) of the epilepsy patient which was extremely important for the mitochondrial function. In our study, we obtained complete mtDNA sequences of 27 idiopathic epilepsy patients and healthy people, and compared the sequence data with 30,000 GenBank sequences including 277 Han Chinese mtDNA sequences. We analyzed each variant that might be related to disease and examined the statistically significant variant in more than 300 patients and healthy people. Ultimately, we identified 27 variants which were reported to be associated with diseases, 4 rare variants (321T > G, 15973 T > C, 3897C > A, 12580 C > T), and a nonsynonymous variant (3571 C > T) which was predicted to be damaging. Although no variant was found to be significantly associated with epilepsy, our study provided a new insight into epilepsy study on an aspect of the mitochondrial genome.
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Affiliation(s)
- Cuiping You
- Department of Central Laboratory, Linyi People’s Hospital, Shandong University, Linyi, Shandong Province, China
| | - Rui Tao
- Department of Neurology, Linyi People’s Hospital, Shandong University, Linyi, Shandong Province, China
| | - Quanping Su
- Department of Central Laboratory, Linyi People’s Hospital, Shandong University, Linyi, Shandong Province, China
| | - Yucheng Lu
- Department of Central Laboratory, Linyi People’s Hospital, Shandong University, Linyi, Shandong Province, China
| | - Long Wang
- Department of Central Laboratory, Linyi People’s Hospital, Shandong University, Linyi, Shandong Province, China
| | - Shu Liu
- Department of Central Laboratory, Linyi People’s Hospital, Shandong University, Linyi, Shandong Province, China
| | - Lifen Wang
- Department of Central Laboratory, Linyi People’s Hospital, Shandong University, Linyi, Shandong Province, China
| | - Lijuan Wang
- Department of Central Laboratory, Linyi People’s Hospital, Shandong University, Linyi, Shandong Province, China
| | - Fuzhong Xue
- Department of Epidemiology and Biostatistics, School of Public Health, Shandong University, Jinan, China
| | - Fengyuan Che
- Department of Central Laboratory, Linyi People’s Hospital, Shandong University, Linyi, Shandong Province, China
- Department of Neurology, Linyi People’s Hospital, Shandong University, Linyi, Shandong Province, China
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8
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Clinical syndromes associated with mtDNA mutations: where we stand after 30 years. Essays Biochem 2018; 62:235-254. [DOI: 10.1042/ebc20170097] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 05/29/2018] [Accepted: 05/30/2018] [Indexed: 01/16/2023]
Abstract
The landmark year 1988 can be considered as the birthdate of mitochondrial medicine, when the first pathogenic mutations affecting mtDNA were associated with human diseases. Three decades later, the field still expands and we are not ‘scraping the bottom of the barrel’ yet. Despite the tremendous progress in terms of molecular characterization and genotype/phenotype correlations, for the vast majority of cases we still lack a deep understanding of the pathogenesis, good models to study, and effective therapeutic options. However, recent technological advances including somatic cell reprogramming to induced pluripotent stem cells (iPSCs), organoid technology, and tailored endonucleases provide unprecedented opportunities to fill these gaps, casting hope to soon cure the major primary mitochondrial phenotypes reviewed here. This group of rare diseases represents a key model for tackling the pathogenic mechanisms involving mitochondrial biology relevant to much more common disorders that affect our currently ageing population, such as diabetes and metabolic syndrome, neurodegenerative and inflammatory disorders, and cancer.
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9
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Kytövuori L, Gardberg M, Majamaa K, Martikainen MH. The m.7510T>C mutation: Hearing impairment and a complex neurologic phenotype. Brain Behav 2017; 7:e00859. [PMID: 29299381 PMCID: PMC5745241 DOI: 10.1002/brb3.859] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Revised: 09/05/2017] [Accepted: 09/22/2017] [Indexed: 12/12/2022] Open
Abstract
OBJECTIVES Mutations in mitochondrial DNA cause a variety of clinical phenotypes ranging from a mild hearing impairment (HI) to severe encephalomyopathy. The MT-TS1 gene is a hotspot for mutations causing HI. The m.7510T>C mutation in MT-TS1 has been previously associated with non-syndromic HI in four families from different ethnic backgrounds. MATERIALS AND METHODS We describe the clinical, genetic, and histopathological findings in a Finnish family with the heteroplasmic m.7510T>C mutation in mitochondrial DNA. RESULTS The family proband presented with a progressive mitochondrial disease phenotype including migraine, epilepsy, mild ataxia, and cognitive impairment in addition to HI. One young adult presented with HI only. Other family members had a mild phenotype comprising ataxia and tremor in addition to HI. Mutation heteroplasmy was 90% in the blood of maternal grandmother and ≥99% in the muscle and blood of the three other family members. Muscle histology was consistent with mitochondrial myopathy in three family members. The mitochondrial haplogroup of the family was a different branch of the haplogroup H than in the previous reports of this mutation. CONCLUSION Our results suggest that, in addition to sensorineural HI, the m.7510T>C mutation is associated with a spectrum of mitochondrial disease clinical features including migraine, epilepsy, cognitive impairment, ataxia, and tremor, and with evidence of mitochondrial myopathy.
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Affiliation(s)
- Laura Kytövuori
- Research Unit of Clinical Neuroscience University of Oulu Oulu Finland.,Medical Research Center Oulu Oulu University Hospital and University of Oulu Oulu Finland.,Department of Neurology Oulu University Hospital Oulu Finland
| | - Maria Gardberg
- Department of Pathology University of Turku and Turku University Hospital Turku Finland
| | - Kari Majamaa
- Research Unit of Clinical Neuroscience University of Oulu Oulu Finland.,Medical Research Center Oulu Oulu University Hospital and University of Oulu Oulu Finland.,Department of Neurology Oulu University Hospital Oulu Finland
| | - Mika H Martikainen
- Division of Clinical Neurosciences University of Turku and Turku University Hospital Turku Finland
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10
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Subathra M, Ramesh A, Selvakumari M, Karthikeyen NP, Srisailapathy CRS. Genetic Epidemiology of Mitochondrial Pathogenic Variants Causing Nonsyndromic Hearing Loss in a Large Cohort of South Indian Hearing Impaired Individuals. Ann Hum Genet 2017; 80:257-73. [PMID: 27530448 DOI: 10.1111/ahg.12161] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 05/16/2016] [Indexed: 01/28/2023]
Abstract
Mitochondria play a critical role in the generation of metabolic energy in the form of ATP. Tissues and organs that are highly dependent on aerobic metabolism are involved in mitochondrial disorders including nonsyndromic hearing loss (NSHL). Seven pathogenic variants leading to NSHL have so far been reported on two mitochondrial genes: MT-RNR1 encoding 12SrRNA and MT-TS1 encoding tRNA for Ser((UCN)) . We screened 729 prelingual NSHL subjects to determine the prevalence of MT-RNR1 variants at position m.961, m.1555A>G and m.1494C>T, and MT-TS1 m.7445A>G, m.7472insC m.7510T>C and m.7511T>C variants. Mitochondrial pathogenic variants were found in eight probands (1.1%). Five of them were found to have the m.1555A>G variant, two others had m.7472insC and one proband had m.7444G>A. The extended relatives of these probands showed variable degrees of hearing loss and age at onset. This study shows that mitochondrial pathogenic alleles contribute to about 1% prelingual hearing loss. This study will henceforth provide the reference for the prevalence of mitochondrial pathogenic alleles in the South Indian population, which to date has not been estimated. The m.1555A>G variant is a primary predisposing genetic factor for the development of hearing loss. Our study strongly suggests that mitochondrial genotyping should be considered for all hearing impaired individuals and particularly in families where transmission is compatible with maternal inheritance, after ruling out the most common variants.
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Affiliation(s)
- Mahalingam Subathra
- Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai, India
| | - Arabandi Ramesh
- Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai, India
| | - Mathiyalagan Selvakumari
- Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai, India
| | - N P Karthikeyen
- DOAST (Doctrine Oriented Art of Symbiotic Treatment) Hearing Care Center and Integrated Therapy Center for Autism, Anna Nagar West, Chennai, India
| | - C R Srikumari Srisailapathy
- Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai, India
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11
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Hsu CC, Tseng LM, Lee HC. Role of mitochondrial dysfunction in cancer progression. Exp Biol Med (Maywood) 2016; 241:1281-95. [PMID: 27022139 DOI: 10.1177/1535370216641787] [Citation(s) in RCA: 187] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Deregulated cellular energetics was one of the cancer hallmarks. Several underlying mechanisms of deregulated cellular energetics are associated with mitochondrial dysfunction caused by mitochondrial DNA mutations, mitochondrial enzyme defects, or altered oncogenes/tumor suppressors. In this review, we summarize the current understanding about the role of mitochondrial dysfunction in cancer progression. Point mutations and copy number changes are the two most common mitochondrial DNA alterations in cancers, and mitochondrial dysfunction induced by chemical depletion of mitochondrial DNA or impairment of mitochondrial respiratory chain in cancer cells promotes cancer progression to a chemoresistance or invasive phenotype. Moreover, defects in mitochondrial enzymes, such as succinate dehydrogenase, fumarate hydratase, and isocitrate dehydrogenase, are associated with both familial and sporadic forms of cancer. Deregulated mitochondrial deacetylase sirtuin 3 might modulate cancer progression by regulating cellular metabolism and oxidative stress. These mitochondrial defects during oncogenesis and tumor progression activate cytosolic signaling pathways that ultimately alter nuclear gene expression, a process called retrograde signaling. Changes in the intracellular level of reactive oxygen species, Ca(2+), or oncometabolites are important in the mitochondrial retrograde signaling for neoplastic transformation and cancer progression. In addition, altered oncogenes/tumor suppressors including hypoxia-inducible factor 1 and tumor suppressor p53 regulate mitochondrial respiration and cellular metabolism by modulating the expression of their target genes. We thus suggest that mitochondrial dysfunction plays a critical role in cancer progression and that targeting mitochondrial alterations and mitochondrial retrograde signaling might be a promising strategy for the development of selective anticancer therapy.
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Affiliation(s)
- Chia-Chi Hsu
- Department and Institute of Pharmacology, School of Medicine, National Yang-Ming University, Taipei 112, Taiwan
| | - Ling-Ming Tseng
- Department of Surgery, Taipei Veterans General Hospital, Taipei 112, Taiwan Department of Surgery, School of Medicine, National Yang-Ming University, Taipei 112, Taiwan Taipei-Veterans General Hospital Comprehensive Breast Health Center, Taipei 112, Taiwan
| | - Hsin-Chen Lee
- Department and Institute of Pharmacology, School of Medicine, National Yang-Ming University, Taipei 112, Taiwan
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Mohammed FMA, Rezaee Khorasany AR, Mosaieby E, Houshmand M. Mitochondrial A12308G alteration in tRNA(Leu(CUN)) in colorectal cancer samples. Diagn Pathol 2015; 10:115. [PMID: 26189042 PMCID: PMC4506765 DOI: 10.1186/s13000-015-0337-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Accepted: 06/26/2015] [Indexed: 12/14/2022] Open
Abstract
Background Colorectal cancer is the third most common type of cancer in men and women and the second leading cause of cancer-related deaths in the United States and UK. Colorectal cancer is strongly related to age, with almost three-quarters of cases occurring in people aged 65 or over. Pre-symptomatic screening is one of the most powerful tools for preventing colorectal cancer. Recently, the use of mitochondrial tRNA genes mutation or polymorphism patterns as a biomarker is rapidly expanding in different cancers because tRNA genes perform several functions including processing and translation which are essential components of mitochondrial protein synthesis. The aim of the present study was to find out the association of mitochondrial A12308G alteration in tRNALeu(CUN) in colorectal cancer and its usage as a new biomarker screening test. Methods A tumor tissues from 30 patients who had colorectal cancer were selected randomly. The A12308G alteration in tRNALeu (CUN) was screened in the 30 colorectal tumor tissues. For comparison, 100 blood samples of healthy controls using PCR-sequencing methods were selected and the following results were found. Result The A12308G, a polymorphic mutation in V-loop tRNALeu(CUN), was found in 6 Colorectal tumor tissues and 3 healthy controls. A statistical significant difference was found between cases and control regarding the association of the A12308G mutation with the colorectal tumor (P < 0.05). Conclusions The A12308G, a polymorphic mutation in V-loop tRNALeu(CUN), could be considered as pathogenic mutation in combination with mitochondrial external conditions and other mitochondrial genes in developing different diseases especially cancers and could be used as one of the diagnostic tool. Also it seems that maybe there is relevance between A12308G mutation and other mutations that it can cause various phenotypes. Electronic supplementary material The online version of this article (doi:10.1186/s13000-015-0337-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Fawziah M A Mohammed
- Medical Laboratory Sciences, Faculty of Allied Health Sciences, Kuwait University, Kuwait.
| | - Ali Reza Rezaee Khorasany
- Department of Pharmacodynamy and Toxicology, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran.
| | - Elaheh Mosaieby
- Department of cellular and molecular biology, Mazandaran university, Babolsar, Iran.
| | - Massoud Houshmand
- Department of Medical Genetics, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran.
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Abstract
Hearing loss is the most common form of sensory impairment in humans and affects more than 40 million people in the United States alone. No drug-based therapy has been approved by the Food and Drug Administration, and treatment mostly relies on devices such as hearing aids and cochlear implants. Over recent years, more than 100 genetic loci have been linked to hearing loss and many of the affected genes have been identified. This understanding of the genetic pathways that regulate auditory function has revealed new targets for pharmacological treatment of the disease. Moreover, approaches that are based on stem cells and gene therapy, which may have the potential to restore or maintain auditory function, are beginning to emerge.
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Affiliation(s)
- Ulrich Müller
- Department of Molecular and Cellular Neuroscience, Dorris Neuroscience Center, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, San Diego, California 92037, USA
| | - Peter G Barr-Gillespie
- Oregon Hearing Research Center, Vollum Institute, Oregon Health &Science University, 3181 South West Sam Jackson Park Road, Portland, Oregon 97239, USA
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Mustoe AM, Liu X, Lin PJ, Al-Hashimi HM, Fierke CA, Brooks CL. Noncanonical secondary structure stabilizes mitochondrial tRNA(Ser(UCN)) by reducing the entropic cost of tertiary folding. J Am Chem Soc 2015; 137:3592-9. [PMID: 25705930 PMCID: PMC4399864 DOI: 10.1021/ja5130308] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Mammalian mitochondrial tRNA(Ser(UCN)) (mt-tRNA(Ser)) and pyrrolysine tRNA (tRNA(Pyl)) fold to near-canonical three-dimensional structures despite having noncanonical secondary structures with shortened interhelical loops that disrupt the conserved tRNA tertiary interaction network. How these noncanonical tRNAs compensate for their loss of tertiary interactions remains unclear. Furthermore, in human mt-tRNA(Ser), lengthening the variable loop by the 7472insC mutation reduces mt-tRNA(Ser) concentration in vivo through poorly understood mechanisms and is strongly associated with diseases such as deafness and epilepsy. Using simulations of the TOPRNA coarse-grained model, we show that increased topological constraints encoded by the unique secondary structure of wild-type mt-tRNA(Ser) decrease the entropic cost of folding by ∼2.5 kcal/mol compared to canonical tRNA, offsetting its loss of tertiary interactions. Further simulations show that the pathogenic 7472insC mutation disrupts topological constraints and hence destabilizes the mutant mt-tRNA(Ser) by ∼0.6 kcal/mol relative to wild-type. UV melting experiments confirm that insertion mutations lower mt-tRNA(Ser) melting temperature by 6-9 °C and increase the folding free energy by 0.8-1.7 kcal/mol in a largely sequence- and salt-independent manner, in quantitative agreement with our simulation predictions. Our results show that topological constraints provide a quantitative framework for describing key aspects of RNA folding behavior and also provide the first evidence of a pathogenic mutation that is due to disruption of topological constraints.
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Affiliation(s)
- Anthony M. Mustoe
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Xin Liu
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Paul J. Lin
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Hashim M. Al-Hashimi
- Departments of Biochemistry and Chemistry, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Carol A. Fierke
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48109-1055, USA
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Charles L. Brooks
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48109-1055, USA
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
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Park JH, Yoon BR, Kim HJ, Lee PH, Choi BO, Chung KW. Compound mitochondrial DNA mutations in a neurological patient with ataxia, myoclonus and deafness. J Genet 2014; 93:173-7. [PMID: 24840835 DOI: 10.1007/s12041-014-0317-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ji Hoon Park
- Department of Biological Science, Kongju National University, 182 sinkwan-dong, Gongju, Chungnam 314-701, Republic of Korea.
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Mitochondrial disorders and epilepsy. Rev Neurol (Paris) 2014; 170:375-80. [DOI: 10.1016/j.neurol.2014.03.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Revised: 03/27/2014] [Accepted: 03/28/2014] [Indexed: 11/21/2022]
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Finsterer J, Zarrouk Mahjoub S. Mitochondrial epilepsy in pediatric and adult patients. Acta Neurol Scand 2013; 128:141-52. [PMID: 23480231 DOI: 10.1111/ane.12122] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/11/2013] [Indexed: 01/04/2023]
Abstract
Few data are available about the difference between epilepsy in pediatric mitochondrial disorders (MIDs) and adult MIDs. This review focuses on the differences between pediatric and adult mitochondrial epilepsy with regard to seizure type, seizure frequency, and underlying MID. A literature search via Pubmed using the keywords 'mitochondrial', 'epilepsy', 'seizures', 'adult', 'pediatric', and all MID acronyms, was carried out. Frequency of mitochondrial epilepsy strongly depends on the type of MID included and is higher in pediatric compared to adult patients. In pediatric patients, mitochondrial epilepsy is more frequent due to mutations in nDNA-located than mtDNA-located genes and vice versa in adults. In pediatric patients, mitochondrial epilepsy is associated with a syndromic phenotype in half of the patients and in adults more frequently with a non-syndromic phenotype. In pediatric patients, focal seizures are more frequent than generalized seizures and vice versa in adults. Electro-clinical syndromes are more frequent in pediatric MIDs compared to adult MIDs. Differences between pediatric and adult mitochondrial epilepsy concern the onset of epilepsy, frequency of epilepsy, seizure type, type of electro-clinical syndrome, frequency of syndromic versus non-syndromic MIDs, and the outcome. To optimize management of mitochondrial epilepsy, it is essential to differentiate between early and late-onset forms.
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Affiliation(s)
| | - S. Zarrouk Mahjoub
- Laboratory of Biochemistry; UR ‘Human Nutrition and Metabolic Disorders’ Faculty of Medicine Monastir; Tunisia
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Kato T, Nishigaki Y, Noguchi Y, Fuku N, Ito T, Mikami E, Kitamura K, Tanaka M. Extended screening for major mitochondrial DNA point mutations in patients with hereditary hearing loss. J Hum Genet 2012; 57:772-5. [DOI: 10.1038/jhg.2012.109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Gourfinkel-An I, Baulac S, Brice A, Leguern E, Baulac M. Genetics of inherited human epilepsies. DIALOGUES IN CLINICAL NEUROSCIENCE 2012. [PMID: 22034131 PMCID: PMC3181638 DOI: 10.31887/dcns.2001.3.1/igourfinkelan] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Major advances have recently been made in our understanding of the genetic basis of monogenic inherited epilepsies. Progress has been particularly spectacular with respect to idiopathic epilepsies, with the discovery that mutations in ion channel subunits are implicated. However, important advances have also been made in many inherited symptomatic epilepsies, for which direct molecular diagnosis is now possible, simplifying previously complex investigations, it is expected that identification of the genes implicated in familial forms of epilepsies will lead to a better understanding of the underlying pathophysiological mechanisms of these disorders and to the development of experimental models and new therapeutic strategies, in this article, we review the clinical and genetic data concerning most of the inherited human epilepsies.
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Affiliation(s)
- I Gourfinkel-An
- Unité d'Epileptologie, Hôpital Pitié-Salpêtrière, Paris, France; Service d'Electrophysiologie, Hôpital Pitié-Salpêtrière, Paris, France
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Yarham JW, McFarland R, Taylor RW, Elson JL. A proposed consensus panel of organisms for determining evolutionary conservation of mt-tRNA point mutations. Mitochondrion 2012; 12:533-8. [PMID: 22781547 PMCID: PMC3510436 DOI: 10.1016/j.mito.2012.06.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Revised: 04/19/2012] [Accepted: 06/28/2012] [Indexed: 11/23/2022]
Abstract
Assigning pathogenicity to mt-tRNA variants requires multiple strands of evidence. Evolutionary conservation is often considered mandatory, but lack of a standard panel of organisms to assess conservation complicates comparison between reports and undermines the value of conservation-based evidence. We demonstrate that intra-species MTT sequence variation is sufficiently low for sequence data from a single organism to adequately represent a species. On this basis, we propose a standardised panel of organisms for conservation assessment and describe integration of this conservation panel into a pathogenicity scoring system designed to assess mt-tRNA variation associated with mitochondrial disease.
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Affiliation(s)
- John W Yarham
- Mitochondrial Research Group, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
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23
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Finsterer J, Zarrouk Mahjoub S. Epilepsy in mitochondrial disorders. Seizure 2012; 21:316-21. [DOI: 10.1016/j.seizure.2012.03.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 03/04/2012] [Accepted: 03/05/2012] [Indexed: 10/28/2022] Open
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Abstract
Mitochondrial respiratory chain disorders are relatively common inborn errors of energy metabolism, with a combined prevalence of one in 5000. These disorders typically affect tissues with high energy requirements, and cerebral involvement occurs frequently in childhood, often manifesting in seizures. Mitochondrial diseases are genetically heterogeneous; to date, mutations have been reported in all 37 mitochondrially encoded genes and more than 80 nuclear genes. The major genetic causes of mitochondrial epilepsy are mitochondrial DNA mutations (including those typically associated with the mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes [MELAS] and myoclonic epilepsy with ragged red fibres [MERRF] syndromes); mutations in POLG (classically associated with Alpers syndrome but also presenting as the mitochondrial recessive ataxia syndrome [MIRAS], spinocerebellar ataxia with epilepsy [SCAE], and myoclonus, epilepsy, myopathy, sensory ataxia [MEMSA] syndromes in older individuals) and other disorders of mitochondrial DNA maintenance; complex I deficiency; disorders of coenzyme Q(10) biosynthesis; and disorders of mitochondrial translation such as RARS2 mutations. It is not clear why some genetic defects, but not others, are particularly associated with seizures. Epilepsy may be the presenting feature of mitochondrial disease but is often part of a multisystem clinical presentation. Mitochondrial epilepsy may be very difficult to manage, and is often a poor prognostic feature. At present there are no curative treatments for mitochondrial disease. Individuals with mitochondrial epilepsy are frequently prescribed multiple anticonvulsants, and the role of vitamins and other nutritional supplements and the ketogenic diet remain unproven.
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Affiliation(s)
- Shamima Rahman
- Mitochondrial Research Group, Clinical and Molecular Genetics Unit, UCL Institute of Child Health, University College London, 30 Guilford Street, London, UK.
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Moustris A, Edwards MJ, Bhatia KP. Movement disorders and mitochondrial disease. HANDBOOK OF CLINICAL NEUROLOGY 2011; 100:173-92. [PMID: 21496577 DOI: 10.1016/b978-0-444-52014-2.00010-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Andreas Moustris
- Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, London, UK
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Abstract
Myoclonus can be classified as physiologic, essential, epileptic, and symptomatic. Animal models of myoclonus include DDT and posthypoxic myoclonus in the rat. 5-Hydrotryptophan, clonazepam, and valproic acid suppress myoclonus induced by posthypoxia. The diagnostic evaluation of myoclonus is complex and involves an extensive work-up including basic electrolytes, glucose, renal and hepatic function tests, paraneoplastic antibodies, drug and toxicology screens, thyroid antibody and function studies, neurophysiology testing, imaging, and tests for malabsorption disorders, assays for enzyme deficiencies, tissue biopsy, copper studies, alpha-fetoprotein, cytogenetic analysis, radiosensitivity DNA synthesis, genetic testing for inherited disorders, and mitochondrial function studies. Treatment of myoclonus is targeted to the underlying disorder. If myoclonus physiology cannot be demonstrated, treatment should be aimed at the common pattern of symptoms. If the diagnosis is not known, treatment could be directed empirically at cortical myoclonus as the most common physiology. In cortical myoclonus, the most effective drugs are sodium valproic acid, clonazepam, levetiracetam, and piracetam. For cortical-subcortical myoclonus, valproic acid is the drug of choice. Here, lamotrigine can be used either alone or in combination with valproic acid. Ethosuximide, levetiracetam, or zonisamide can also be used as adjunct therapy with valproic acid. A ketogenic diet can be considered if everything else fails. Subcortical-nonsegmental myoclonus may respond to clonazepam and deep-brain stimulation. Rituximab, adrenocorticotropic hormone, high-dose dexamethasone pulse, or plasmapheresis have been reported to improve opsoclonus myoclonus syndrome. Reticular reflex myoclonus can be treated with clonazepam, diazepam and 5-hydrotryptophan. For palatal myoclonus, a variety of drugs have been used.
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Zsurka G, Kunz WS. Mitochondrial dysfunction in neurological disorders with epileptic phenotypes. J Bioenerg Biomembr 2010; 42:443-8. [DOI: 10.1007/s10863-010-9314-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Tang X, Li R, Zheng J, Cai Q, Zhang T, Gong S, Zheng W, He X, Zhu Y, Xue L, Yang A, Yang L, Lu J, Guan MX. Maternally inherited hearing loss is associated with the novel mitochondrial tRNA Ser(UCN) 7505T>C mutation in a Han Chinese family. Mol Genet Metab 2010; 100:57-64. [PMID: 20153673 DOI: 10.1016/j.ymgme.2010.01.008] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Revised: 01/18/2010] [Accepted: 01/18/2010] [Indexed: 11/18/2022]
Abstract
Mutations in mitochondrial DNA (mtDNA) have been found to be one of the most important causes of sensorineural hearing loss. We report here a clinical, genetic, molecular and biochemical characterization of a Han Chinese pedigree with maternally transmitted nonsyndromic hearing impairment. Seven of nine matrilineal relatives exhibited a variable severity and age-at-onset (8 years old) of hearing loss. Mutational analysis of mtDNA identified the novel homoplasmic tRNA(Ser(UCN)) 7505T>C mutation and other 37 variants belonging to haplogroup F1. The 7505T>C mutation, which is absent in 449 Chinese controls, is located at a highly conserved base-pairing (10A-20U) of tRNA(Ser(UCN)). The abolishment of 10A-20U base-pairing likely alters the tRNA(Ser(UCN)) metabolism. Functional significant of this mutation was supported by approximately 65% reductions in the level of tRNA(Ser(UCN)) observed in the lymphoblastoid cell lines carrying the 7505T>C mutation, compared with the wild-type cell lines. This reduced tRNA level is below the proposed threshold to support a normal respiration in lymphoblastoid cells. Furthermore, the highly conserved tRNA(Ala) 5587T>C and Cytb C93Y variants may have a modifying role of deafness expression associated with the 7505T>C mutation. However, genotyping analysis of nuclear modifier gene TRMU and the prominent deafness-cause gene GJB2 failed to detect any mutations in the member of this family. These data strongly indicate that the novel tRNA(Ser(UCN)) 7505T>C mutation is involved in maternally transmitted hearing loss. However, other genetic, epigenetic or environmental factors may contribute to the phenotypic variability of this family. Our findings will be helpful for counseling families of maternally inherited hearing loss.
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Affiliation(s)
- Xiaowen Tang
- Attardi Institute of Mitochondrial Biomedicine and Zhejiang Provincial Key Laboratory of Medical Genetics, School of Life Sciences, Wenzhou Medical College, Wenzhou, Zhejiang, China
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El Sabbagh S, Lebre AS, Bahi-Buisson N, Delonlay P, Soufflet C, Boddaert N, Rio M, Rötig A, Dulac O, Munnich A, Desguerre I. Epileptic phenotypes in children with respiratory chain disorders. Epilepsia 2010; 51:1225-35. [PMID: 20196775 DOI: 10.1111/j.1528-1167.2009.02504.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE Epilepsy is a commonly reported but rarely described clinical hallmark of mitochondrial respiratory chain defects (RCDs) with encephalopathy. METHODS From 1990-2006 we collected data about 56 children with RCD (single, n = 24 or multiple, n = 20 mitochondrial complex deficiencies; mtDNA mutation, n = 11; mtDNA depletion n = 10 of 21; and nuclear gene mutation n = 11). Epileptic features were reviewed retrospectively. RESULTS First seizures were frequently (47 patients, 82.5%) preceded by failure to thrive, psychomotor delay, ataxia, or multisystemic dysfunction. Sixty percent of the patients had several seizure types. Six age-related epilepsy phenotypes could be identified: status epilepticus complicating neonatal multivisceral deficiency (2 patients), neonatal myoclonic encephalopathy (3 patients), infantile spasms (8 patients), refractory or recurrent status epilepticus (21 patients), epilepsia partialis continua (4 patients), and myoclonic epilepsy (18 patients). Except for infantile spasms, epilepsy was difficult to control in most patients (95%). Valproate was administered to 25 patients, one of whom developed acute liver failure 6 days later. Twenty-two patients (45%) died, half of them within 9 months from the onset of epilepsy. DISCUSSION In RCD, epilepsy is not only difficult to control but its occurrence often indicates a severe turn in the course of the disease. For one-third of the patients, classical biochemical measures failed to reveal any abnormality and RCD could be detected in the liver only.
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Hung WY, Wu CW, Yin PH, Chang CJ, Li AFY, Chi CW, Wei YH, Lee HC. Somatic mutations in mitochondrial genome and their potential roles in the progression of human gastric cancer. Biochim Biophys Acta Gen Subj 2009; 1800:264-70. [PMID: 19527772 DOI: 10.1016/j.bbagen.2009.06.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2009] [Accepted: 06/06/2009] [Indexed: 01/02/2023]
Abstract
BACKGROUND Somatic mutation in mitochondrial DNA (mtDNA) has been proposed to contribute to initiation and progression of human cancer. In our previous study, high frequency of somatic mutations was found in the D-loop region of mtDNA of gastric cancers. However, it is unclear whether somatic mutations occur in the coding region of mtDNA of gastric cancers. METHODS Using DNA sequencing, we studied 31 gastric cancer specimens and corresponding non-cancerous stomach tissues. Moreover, a human gastric cancer SC-M1 cell line was treated with oligomycin to induce mitochondrial dysfunction. Cisplatin sensitivity and cell migration were analyzed. RESULTS We identified eight somatic mutations in the coding region of mtDNAs of seven gastric cancer samples (7/31, 22.6%). Patients with somatic mutations in the entire mtDNA of gastric cancers did not show significant association with their clinicopathologic features. Among the eight somatic mutations, five point mutations (G3697A, G4996A, G9986A, C12405T and T13015C) are homoplasmic and three mutations (5895delC, 7472insC and 12418insA) are heteroplasmic. Four (4/8, 50%) of these somatic mutations result in amino acid substitutions in the highly conserved regions of mtDNA, which potentially lead to mitochondrial dysfunction. In addition, in vitro experiments in SC-M1 cells revealed that oligomycin-induced mitochondrial dysfunction promoted resistance to cisplatin and enhanced cell migration. N-acetyl cysteine was effective in the prevention of the oligomycin-enhanced migration, which suggests that reactive oxygen species generated by defective mitochondria may be involved in the enhanced migration of SC-M1 cells. GENERAL SIGNIFICANCE Our results suggest that somatic mtDNA mutations and mitochondrial dysfunction may play an important role in the malignant progression of gastric cancer.
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Affiliation(s)
- Wen-Yi Hung
- Department and Institute of Pharmacology, School of Medicine, National Yang-Ming University, Taipei, Taiwan 112, ROC
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Kudin AP, Zsurka G, Elger CE, Kunz WS. Mitochondrial involvement in temporal lobe epilepsy. Exp Neurol 2009; 218:326-32. [PMID: 19268667 DOI: 10.1016/j.expneurol.2009.02.014] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2008] [Revised: 02/13/2009] [Accepted: 02/19/2009] [Indexed: 10/21/2022]
Abstract
Mitochondrial dysfunction has been identified as a potential cause of epileptic seizures and therapy-resistant forms of severe epilepsy. Thus, a broad variety of mutation in mitochondrial DNA or nuclear genes leading to the impairment of mitochondrial respiratory chain or of mitochondrial ATP synthesis has been associated with epileptic phenotypes. Additionally, with a variety of different methods impaired mitochondrial function has been reported for the seizure focus of patients with temporal lobe epilepsy and Ammon's horn sclerosis and of animal models of temporal lobe epilepsy. Since mitochondrial oxidative phosphorylation provides the major source of ATP in neurons and mitochondria participate in cellular Ca(2+) homeostasis, their dysfunction strongly affects neuronal excitability and synaptic transmission, which is proposed to be highly relevant for seizure generation. Additionally, mitochondrial dysfunction is known to trigger neuronal cell death, which is a prominent feature of therapy-resistant temporal lobe epilepsy. Therefore, mitochondria have to be considered as promising targets for neuroprotective strategies in epilepsy.
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Affiliation(s)
- Alexei P Kudin
- Department of Epileptology, University Bonn Medical Center, Germany
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Cortical hyperexcitability and epileptogenesis: Understanding the mechanisms of epilepsy – Part 1. J Clin Neurosci 2009; 16:355-65. [DOI: 10.1016/j.jocn.2008.08.026] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Accepted: 08/12/2008] [Indexed: 11/22/2022]
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Ouyang XM, Yan D, Yuan HJ, Pu D, Du LL, Han DY, Liu XZ. The genetic bases for non-syndromic hearing loss among Chinese. J Hum Genet 2009; 54:131-40. [PMID: 19197336 DOI: 10.1038/jhg.2009.4] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Deafness is an etiologically heterogeneous trait with many known genetic, environmental causes or a combination thereof. The identification of more than 120 independent genes for deafness has provided profound new insights into the pathophysiology of hearing. However, recent findings indicate that a large proportion of both syndromic and non-syndromic forms of deafness in the Chinese population are caused by defects in a small number of genes. Studies of the genetic epidemiology and molecular genetic features revealed that there is a clear relevance of genes causing deafness in Chinese deaf patients as well as a unique spectrum of common and rare deafness gene mutations in the Chinese population. This review is focused on the genetic aspects of non-syndromic and mitochondrial deafness, in which unique molecular genetic features of hearing impairment have been identified in the Chinese population. The current China population is approximately 1.3 billion. It is estimated that 30,000 infants are born with congenital sensorineural hearing loss each year. Better understanding of the genetic causes of deafness in the Chinese population is important for accurate genetics counseling and early diagnosis for timely intervention and treatment options.
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Affiliation(s)
- Xiao Mei Ouyang
- Department of Otolaryngology, University of Miami, Miami, FL 33136, USA
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35
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Kunz WS, Bimpong-Buta NYB, Kudin AP, Elger CE. The Role of Mitochondria in Epilepsy: Implications for Neurodegenerative Diseases. Toxicol Mech Methods 2008; 14:19-23. [DOI: 10.1080/15376520490257374] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Liu >X, Angeli S, Ouyang X, Liu W, Ke X, Liu Y, Liu S, Du L, Deng X, Yuan H, Yan D. Audiological and genetic features of the mtDNA mutations. Acta Otolaryngol 2008; 128:732-8. [PMID: 18568513 DOI: 10.1080/00016480701719011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
CONCLUSIONS Significant difference in the incidence of mitochondrial DNA (mtDNA) mutations was found between the Chinese and USA populations. The identification of the mtDNA A1555G mutation in a large proportion of Chinese probands with nonsyndromic sensorineural hearing loss (NSHL) provides a molecular explanation for the high prevalence of aminoglycoside-induced deafness in China. OBJECTIVE The aim was to characterize the audiological and genetic features of NSHL due to mutations in mtDNA. SUBJECTS AND METHODS The mtDNA and audiogram analyses were performed in 498 NSHL patients (290 from China and 208 from the USA) with and without history of aminoglycoside exposure. A PCR and restriction enzyme digestion protocol was used for mutational screening and the European Workshop on Genetic Hearing Loss criteria were applied for audiological classification. RESULTS All Chinese probands (15.5%) with mtDNA mutation were found to carry the homoplasmic mtDNA A1555G mutation, whereas four probands (1.9%) from the USA were found to carry the mtDNA A1555G and two (1%) had mtDNA G7444A. Approximately 63% of the probands with mtDNA mutations had post-lingual hearing loss and 56.8% of them had a medical history of exposure to aminoglycosides. Hearing losses are bilateral, sensorineural, and symmetric. The main audiogram shapes found were sloping.
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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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A homoplasmic mtDNA variant can influence the phenotype of the pathogenic m.7472Cins MTTS1 mutation: are two mutations better than one? Eur J Hum Genet 2008; 16:1265-74. [PMID: 18398437 DOI: 10.1038/ejhg.2008.65] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Mutations in mitochondrial tRNA (mt-tRNA) genes are well recognized as a common cause of human disease, exhibiting a significant degree of clinical heterogeneity. While these differences are explicable, in part, by differences in the innate pathogenicity of the mutation, its distribution and abundance, other factors, including nuclear genetic background, mitochondrial DNA (mtDNA) haplotype and additional mtDNA mutations may influence the expression of mt-tRNA mutations. We describe the clinical, biochemical and molecular findings in a family with progressive myopathy, deafness and diabetes and striking respiratory chain abnormalities due to a well-characterized heteroplasmic mt-tRNA mutation in the mt-tRNA(Ser(UCN)) (MTTS1) gene. In addition to the m.7472Cins mutation, all individuals were homoplasmic for another variant, m.7472A > C, affecting the adjacent nucleotide in the mt-tRNA(Ser(UCN)) structure. In addition to available patient tissues, we have analysed transmitochondrial cybrid clones harbouring homoplasmic levels of m.7472A > C and varying levels of the m.7472Cins mutation in an attempt to clarify the precise role of the m.7472A > C transversion in the underlying respiratory chain abnormality. Evidence from both in vivo and in vitro studies demonstrate that the m.7472A > C is able to modify the expression of the m.7472Cins mutation and would suggest that it is not a neutral variant but appears to cause a biochemical defect by itself, confirming that homoplasmic mtDNA variants can modulate the phenotypic expression of pathogenic, heteroplasmic mtDNA mutations.
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Lee YM, Kang HC, Lee JS, Kim SH, Kim EY, Lee SK, Slama A, Kim HD. Mitochondrial respiratory chain defects: underlying etiology in various epileptic conditions. Epilepsia 2008; 49:685-90. [PMID: 18266755 DOI: 10.1111/j.1528-1167.2007.01522.x] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE To determine if defects in mitochondrial respiratory chain enzyme complexes (MRCs) contribute to the etiology of childhood epilepsy. METHODS We reviewed the clinical and laboratory features of 48 epileptic patients (23 male, 25 female) with MRC defects that were confirmed by biochemical assays using muscle biopsies. RESULTS (1) Thirty-five cases (72.9%) were MRC I deficient, one case (2.1%) was MRC II deficient, 11 cases (22.9%) were MRC IV deficient, and one case (2.1%) had combined MRC I and IV deficiencies. (2) In our clinical diagnosis, there were 10 cases (20.8%) with Leigh disease and one case each with myopathy, encephalopathy, lactic acidosis, stroke-like episodes (MELAS) or Alpers' disease (2.1%). Most of the remaining cases (75.0%) had uncategorized mitochondrial cytopathy with nonspecific encephalopathy. (3) For epileptic classification, there were two cases (4.2%) of Ohtahara syndrome, 10 cases (20.8%) of West syndrome, 12 cases (25.0%) of Lennox-Gastaut syndrome, two cases (4.2%) of Landau-Kleffner syndrome, 14 cases (29.2%) of generalized epilepsy, and eight cases (16.7%) of partial epilepsy. (4) The mean age of seizure onset was 2.68 +/- 2.21 (range: 1 month - 5.5 years). (5) Magnetic resonance imaging (MRI) showed diffuse cortical atrophy in 34 cases (70.8%), basal ganglia signal changes in 18 cases (37.5%) and thalamus signal changes in 12 cases (25.0%). (6) A ketogenic diet produced clinical improvements, including seizure reduction and global functional improvement in 75% of 24 patients. CONCLUSIONS MRC defects are one of the important causes of probably symptomatic childhood epilepsy. A ketogenic diet should be carefully considered for treatment of intractable epilepsy related to MRC defects.
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Affiliation(s)
- Young Mock Lee
- Department of Pediatrics, Severance Children's Hospital, The Institute for Handicapped Children, Yonsei University College of Medicine, Seoul, Korea
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Abstract
UNLABELLED BACKGROUND, OBJECTIVE AND METHODS: We describe a female patient with a mitochondrial encephalopathy, lactic acidosis and stroke-like episodes syndrome. As a child, she developed epilepsy and stroke-like episodes giving cognitive impairment and ataxia but no hearing impairment. At the age of 44 years, she suffered a cerebral sinus thrombosis which was warfarin treated. One month later, she developed an episode of severe acidosis associated with encephalopathy and myelopathy. RESULTS She was found to harbour a 7512T>C mutation in the mitochondrial encoded tRNA(Ser(UCN)) gene (MTTS1). The mutation load was 91% in muscle and 24% in blood. Enzyme histochemical analysis of the muscle tissue showed numerous cytochrome c oxidase (COX)-negative fibres. Restriction fragment length polymorphism (RFLP) analysis of single muscle fibres showed significantly higher level (median 97%, range: 94-99%) of the mutation in the COX-negative fibres compared with COX-positive fibres (median 36%, range: 12-91%), demonstrating the pathogenic effect of the mutation. Different levels of heteroplasmy (range 34-61%) were detected in hair shafts analysed by RFLP. CONCLUSION This case adds to the spectrum of clinical presentations, i.e. sinus thrombosis, in patients having MTTS1 mutations.
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Affiliation(s)
- C Lindberg
- Department of Neurology, Neuromuscular Center, Sahlgrenska University Hospital, Göteborg, Sweden.
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Bannwarth S, Procaccio V, Rouzier C, Fragaki K, Poole J, Chabrol B, Desnuelle C, Pouget J, Azulay JP, Attarian S, Pellissier JF, Gargus JJ, Abdenur JE, Mozaffar T, Calvas P, Labauge P, Pages M, Wallace DC, Lambert JC, Paquis-Flucklinger V. Rapid identification of mitochondrial DNA (mtDNA) mutations in neuromuscular disorders by using surveyor strategy. Mitochondrion 2007; 8:136-45. [PMID: 18078792 DOI: 10.1016/j.mito.2007.10.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2007] [Revised: 10/22/2007] [Accepted: 10/26/2007] [Indexed: 11/18/2022]
Abstract
Mutations of mitochondrial genome are responsible for respiratory chain defects in numerous patients. We have used a strategy, based on the use of a mismatch-specific DNA endonuclease named " Surveyor Nuclease", for screening the entire mtDNA in a group of 50 patients with neuromuscular features, suggesting a respiratory chain dysfunction. We identified mtDNA mutations in 20% of patients (10/50). Among the identified mutations, four are not found in any mitochondrial database and have not been reported previously. We also confirm that mtDNA polymorphisms are frequently found in a heteroplasmic state (15 different polymorphisms were identified among which five were novel).
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Affiliation(s)
- S Bannwarth
- Department of Medical Genetics, Archet 2 Hospital, CHU Nice, France
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Abstract
Non-syndromic deafness can be caused by mutations in both nuclear and mitochondrial genes. More than 50 nuclear genes have been shown to be involved in non-syndromic hearing loss, but mutations in mitochondrial DNA (mtDNA) might also cause hearing impairment. As mitochondria are responsible for oxidative phosphorylation, the primary energy-producing system in all eukaryotic cells, mitochondrial dysfunction has pleiotropic effects. Many mutations in mtDNA can lead to multisystem disorders, such as Kearns-Sayre syndrome, NARP, MELAS, or MERRF syndromes, the presentation of which may include hearing loss. A more specific association of mitochondrially inherited deafness and diabetes known as MIDD syndrome can be caused by a limited number of specific mitochondrial mutations. In addition, several rare mutations in the mitochondrial MTTS1 and MTRNR1 genes have been found to be responsible for non-syndromic hearing loss. The most frequent form of non-syndromic deafness is presbyacusis, affecting more than 50% of the elderly. This age-related hearing loss is a paradigm for multifactorial inheritance, involving a multitude of inherited and acquired mutations in the nuclear and mitochondrial genomes, each with a low penetrance, in complex interplay with environmental factors, such as ototoxic medication, that accumulate with age. This study reviews the different mitochondrial mutations, leading to syndromic and especially non-syndromic deafness.
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Affiliation(s)
- H Kokotas
- Department of Genetics, Institute of Child Health, Athens, Greece
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Abstract
The human ear is a delicate sensory apparatus of hearing for normal communication, and its proper functioning is highly dependent on mitochondrial oxidative phosphorylation. The first mitochondrial point mutation for nonsyndromic and aminoglycoside-induced hearing loss was identified in 1993. Since then a number of inherited mitochondrial mutations have been implicated in hearing loss. Most of the molecular defects responsible for mitochondrial disorder-associated hearing loss are mutations in the 12S rRNA gene and tRNA genes. In this review, after a short description of normal hearing mechanisms and mitochondrial genetics, we outline the recent advances that have been made in the identification of deafness-associated mitochondrial mutations, and discuss how mitochondrial dysfunction contributes to hearing loss.
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Affiliation(s)
- Guangqian Xing
- Department of Otolaryngology, the First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China.
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Ramelli GP, Gallati S, Weis J, Krähenbühl S, Burgunder JM. Point mutation tRNA(Ser(UCN)) in a child with hearing loss and myoclonus epilepsy. J Child Neurol 2006; 21:253-5. [PMID: 16901431 DOI: 10.2310/7010.2006.00047] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We report on a family with a 12-year-old boy who suffered from a maternally inherited syndrome characterized by a combination of sensorineural hearing loss, myoclonus epilepsy, ataxia, severe psychomotor retardation, short stature, and diabetes mellitus. First, he showed a muscular hypotonia with hearing loss; later, he developed a myoclonus epilepsy, growth failure, and severe psychomotor retardation. At the age of 10 years, he developed diabetes mellitus. After initiation of combined ubiquinone and vitamin C treatment, we observed a progression in psychomotor development. Lactate and pyruvate levels in blood and cerebrospinal fluid were normal. No ragged red fibers or ultrastructural abnormalities were seen in a skeletal muscle biopsy. Biochemical assays of respiratory chain complex activities revealed decreased activity of complexes I and IV. By sequence analysis of mitochondrial DNA encoding transfer ribonucleic acids (RNAs), a homoplasmic T to C substitution at nucleotide position 7512 was found affecting a highly conserved base pair in the tRNA(ser(UCN)) acceptor stem. Asymptomatic family members of the maternal line were heteroplasmic for the mutation in blood samples. Analysis of mitochondrial DNA in patients with hearing loss and myoclonus epilepsy is recommended, even in the absence of laboratory findings. Therapeutically, ubiquinone and antioxidants can be beneficial.
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Affiliation(s)
- Gian Paolo Ramelli
- Department of Pediatrics, Ospedale San Giovanni, Bellinzona, Switzerland.
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Cardaioli E, Da Pozzo P, Cerase A, Sicurelli F, Malandrini A, De Stefano N, Stromillo ML, Battisti C, Dotti MT, Federico A. Rapidly progressive neurodegeneration in a case with the 7472insC mutation and the A7472C polymorphism in the mtDNA tRNA ser(UCN) gene. Neuromuscul Disord 2005; 16:26-31. [PMID: 16368237 DOI: 10.1016/j.nmd.2005.11.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2005] [Revised: 09/28/2005] [Accepted: 11/02/2005] [Indexed: 10/25/2022]
Abstract
The authors report the clinical, neuroimaging, muscle biopsy and mtDNA findings in a patient affected by bilateral hearing loss and mental retardation since infancy, presenting at age 31 years with a rapid deterioration of mental status and ataxia leading to vegetative condition and death at the age of 32 years. Clinical and genetic studies have been also performed in the mother, affected by neurosensorial hearing loss. Muscle biopsy showed severe mitochondrial alterations in the propositus and evidence of mitochondrial alterations in his mother. Direct mtDNA sequencing in all family members revealed the known 7472insC mutation and the recently described A7472C sequence variation in the tRNA(Ser(UCN))gene. RFLP-PCR confirmed the heteroplasmic nature of the two mutations and failed to find the second transversion in 200 controls. The percentage of mutant genomes harbouring 7472insC ranged from 3 to 7% in asymptomatic family members to 70% in the proband and his mother, whereas the percentage of A7472C mutant genomes was about 90% in all maternal relatives except the proband (56%) and his sister (5%). In conclusion, this is the first report of a rapidly progressive encephalopathy in association with the 7472insC mutation in mtDNA, combined with an A>C variation at the same nucleotide with a possible suppression effect on the pathogenic mutation.
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Affiliation(s)
- Elena Cardaioli
- Department of Neurological and Behavioural Sciences, Medical School, University of Siena, Viale Bracci 2, 53100 Siena, Italy
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Carrozzo R, Wittig I, Santorelli FM, Bertini E, Hofmann S, Brandt U, Schägger H. Subcomplexes of human ATP synthase mark mitochondrial biosynthesis disorders. Ann Neurol 2005; 59:265-75. [PMID: 16365880 DOI: 10.1002/ana.20729] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE METHODS We describe biochemically and clinically relevant aspects of mitochondrial ATP synthase, the enzyme that supplies most ATP for the cells energy demand. RESULTS Analyzing human Rho zero cells we could identify three subcomplexes of ATP synthase: F1 catalytic domain, F1 domain with bound natural IF1 inhibitor protein, and F1-c subcomplex, an assembly of F1 domain and a ring of F(O)-subunits c. Large amounts of F1 subcomplexes accumulated also in mitochondria of patients with specific mitochondrial disorders. By quantifying the F1 subcomplexes and other oxidative phosphorylation complexes in parallel, we were able to discriminate three classes of defects in mitochondrial biosynthesis, namely, mitochondrial DNA depletion, mitochondrial transfer RNA (tRNA) mutations, and mutations in the mitochondrial ATP6 gene. INTERPRETATION The relatively simple electrophoretic assay used here is a straightforward approach to differentiate between various types of genetic alterations affecting the biosynthesis of oxidative phosphorylation complexes and will be useful to guide molecular genetic diagnostics in the field of mitochondrial neuromuscular disorders.
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Affiliation(s)
- Rosalba Carrozzo
- Unit of Molecular Medicine, Bambino Gesù Hospital and Research Institute, Rome, Italy
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Crimi M, Galbiati S, Sciacco M, Bordoni A, Natali MG, Raimondi M, Bresolin N, Comi GP. Mitochondrial-DNA nucleotides G4298A and T10010C as pathogenic mutations: the confirmation in two new cases. Mitochondrion 2005; 3:279-83. [PMID: 16120360 DOI: 10.1016/j.mito.2004.02.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2003] [Revised: 11/28/2003] [Accepted: 02/05/2004] [Indexed: 10/26/2022]
Abstract
Mitochondrial encephalomyopathies are highly variable clinically and at the genetic level. In practice, when the mitochondrial DNA (mtDNA) of any mitochondrial-patient is sequenced, a very high number of variations are noted. The vast majority of these differences are simply polymorphisms, that is, non-pathologic, homoplasmic sequence variations; however, when a heteroplasmic variant is detected (co-existence of two different populations in the same tissue) this is clinically significant. We identified two different heteroplasmic mutations in the mtDNA of two subjects: G4298A in the tRNA(Ala) (Alanine) gene and T10010C in the tRNA(Gly) (Glycine), both of which have been reported previously. This work confirms the pathogenicity of these mutations and helps define the correlation between genotype and phenotype.
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Affiliation(s)
- Marco Crimi
- Dipartimento di Scienze Neurologiche, Università degli Studi di Milano, IRCCS Ospedale Maggiore Policlinico, Centro Dino Ferrari, 20122 Milan, Italy.
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Müller T, Deschauer M, Neudecker S, Zierz S. Late-onset mitochondrial myopathy with dystrophic changes due to a G7497A mutation in the mitochondrial tRNA(Ser(UCN)) gene. Acta Neuropathol 2005; 110:426-30. [PMID: 16133542 DOI: 10.1007/s00401-005-1063-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2005] [Revised: 06/30/2005] [Accepted: 06/30/2005] [Indexed: 11/28/2022]
Abstract
Mutations of mitochondrial tRNA genes are usually associated with multi-systemic disorders with onset of symptoms in childhood or early adulthood. Dystrophic myopathic changes are not typical features of these disorders. We report two siblings with a severe progressive myopathy of late onset without external ophthalmoplegia and without involvement of the central and peripheral nervous system. Muscle biopsy specimens showed severe myopathic changes similar to those found in muscular dystrophies. Molecular analysis revealed a G7497A mutation in the mitochondrial tRNA(Ser(UCN)) gene. In both patients, the proportion of mutated mitochondrial DNA in muscle was more than 97%. Mitochondrial disorder associated with the G7497A mutation has to be included into the differential diagnosis of severe progressive late-onset myopathy with histopathological dystrophic myopathic changes. Mitochondrial myopathy and high level of mutated mtDNA might be a characteristic of the G7497A tRNA(Ser(UCN)) mutation.
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Affiliation(s)
- Tobias Müller
- Universitätsklinik und Poliklinik für Neurologie, Martin-Luther-Universität Halle-Wittenberg, Ernst-Grube-Str. 40, 06097, Halle (Saale), Germany.
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Möllers M, Maniura-Weber K, Kiseljakovic E, Bust M, Hayrapetyan A, Jaksch M, Helm M, Wiesner RJ, von Kleist-Retzow JC. A new mechanism for mtDNA pathogenesis: impairment of post-transcriptional maturation leads to severe depletion of mitochondrial tRNASer(UCN) caused by T7512C and G7497A point mutations. Nucleic Acids Res 2005; 33:5647-58. [PMID: 16199753 PMCID: PMC1240115 DOI: 10.1093/nar/gki876] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have studied the consequences of two homoplasmic, pathogenic point mutations (T7512C and G7497A) in the tRNA(Ser(UCN)) gene of mitochondrial (mt) DNA using osteosarcoma cybrids. We identified a severe reduction of tRNA(Ser(UCN)) to levels below 10% of controls for both mutations, resulting in a 40% reduction in mitochondrial protein synthesis rate and in a respiratory chain deficiency resembling that in the patients muscle. Aminoacylation was apparently unaffected. On non-denaturating northern blots we detected an altered electrophoretic mobility for G7497A containing tRNA molecules suggesting a structural impact of this mutation, which was confirmed by structural probing. By comparing in vitro transcribed molecules with native RNA in such gels, we also identified tRNA(Ser(UCN)) being present in two isoforms in vivo, probably corresponding to the nascent, unmodified transcripts co-migrating with the in vitro transcripts and a second, faster moving isoform corresponding to the mature tRNA. In cybrids containing either mutations the unmodified isoforms were severely reduced. We hypothesize that both mutations lead to an impairment of post-transcriptional modification processes, ultimately leading to a preponderance of degradation by nucleases over maturation by modifying enzymes, resulting in severely reduced tRNA(Ser(UCN)) steady state levels. We infer that an increased degradation rate, caused by disturbance of tRNA maturation and, in the case of the G7497A mutant, alteration of tRNA structure, is a new pathogenic mechanism of mt tRNA point mutations.
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MESH Headings
- Aminoacylation
- Base Sequence
- Cell Line
- Child
- Child, Preschool
- DNA, Mitochondrial/genetics
- Electron Transport Complex I/metabolism
- Electron Transport Complex IV/metabolism
- Humans
- Male
- Mitochondrial Diseases/genetics
- Mitochondrial Diseases/metabolism
- Mitochondrial Proteins/biosynthesis
- Molecular Sequence Data
- Point Mutation
- RNA/chemistry
- RNA/genetics
- RNA/metabolism
- RNA Precursors/metabolism
- RNA Processing, Post-Transcriptional
- RNA Stability
- RNA, Mitochondrial
- RNA, Transfer, Ser/chemistry
- RNA, Transfer, Ser/genetics
- RNA, Transfer, Ser/metabolism
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Affiliation(s)
- Myriam Möllers
- Institute of Vegetative Physiology, University of KölnRobert-Koch-Strasse 39, 50931 Köln, Germany
| | - Katharina Maniura-Weber
- Institute of Vegetative Physiology, University of KölnRobert-Koch-Strasse 39, 50931 Köln, Germany
| | - Emina Kiseljakovic
- Institute of Vegetative Physiology, University of KölnRobert-Koch-Strasse 39, 50931 Köln, Germany
- Department of Biochemistry, Medical FacultySarajevo, Cekalusa 90, Bosnia and Herzegovina
| | - Maria Bust
- Institute of Vegetative Physiology, University of KölnRobert-Koch-Strasse 39, 50931 Köln, Germany
| | - Armine Hayrapetyan
- Institute of Pharmacy and Molecular Biotechnology, University of HeidelbergIm Neuenheimer Feld 364, 69120 Heidelberg, Germany
| | - Michaela Jaksch
- Institute of Clinical Chemistry and Mitochondrial GeneticsKölner Platz 1, 80804 München, Germany
| | - Mark Helm
- Institute of Pharmacy and Molecular Biotechnology, University of HeidelbergIm Neuenheimer Feld 364, 69120 Heidelberg, Germany
| | - Rudolf J. Wiesner
- Institute of Vegetative Physiology, University of KölnRobert-Koch-Strasse 39, 50931 Köln, Germany
- Center for Molecular Medicine Cologne (CMMC), University of KölnJoseph-Stelzmann-Strasse 52, 50931 Köln, Germany
- To whom correspondence should be addressed. Tel: +49 221 478 3610; Fax: +49 221 478 3538;
| | - Jürgen-Christoph von Kleist-Retzow
- Center for Molecular Medicine Cologne (CMMC), University of KölnJoseph-Stelzmann-Strasse 52, 50931 Köln, Germany
- Department of Pediatrics, University of KölnKerpener Strasse 62, 50924 Köln, Germany
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