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Sahara T, Kashio A, Kamogashira T, Ogata E, Akamatsu Y, Yamasoba T. Cochlear implantation for progressive hearing loss caused by an A8296G mutation in mitochondrial DNA. Auris Nasus Larynx 2024; 51:82-85. [PMID: 37573175 DOI: 10.1016/j.anl.2023.07.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Revised: 07/21/2023] [Accepted: 07/26/2023] [Indexed: 08/14/2023]
Abstract
Mitochondrial DNA mutations such as A3243G or A1555G are widely reported to cause hearing loss, but few reports exist on the A8296G mutation, which can also cause hearing loss. This report presents the case of a patient with the A8296G mutation and severe bilateral sensorineural hearing loss (SNHL) that progressed over two decades. The patient had no history of diabetes, but did have a family history of SNHL in her father and maternal grandmother. She was first diagnosed with SNHL at 45 years of age, and an A8296G mutation was found. The hearing threshold in the low-frequency range of the right ear was preserved at diagnosis, but eventually declined resulting in severe bilateral hearing loss by the age of 66 years, and cochlear implantation (CI) was performed in the left ear. The hearing threshold three months after CI was 25-45 dB HL, and the phoneme speech discrimination score in the left ear improved from 20% without CI to 74% with CI. SNHL patients with the A8295G mutation are good candidates for treatment with CI.
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Affiliation(s)
- Toshihito Sahara
- Department of Otolaryngology and Head and Neck Surgery, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan
| | - Akinori Kashio
- Department of Otolaryngology and Head and Neck Surgery, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan
| | - Teru Kamogashira
- Department of Otolaryngology and Head and Neck Surgery, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan
| | - Erika Ogata
- Department of Otolaryngology and Head and Neck Surgery, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan
| | - Yusuke Akamatsu
- Department of Otolaryngology and Head and Neck Surgery, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan
| | - Tatsuya Yamasoba
- Department of Otolaryngology and Head and Neck Surgery, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
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Aldosary M, Al-Bakheet A, Al-Dhalaan H, Almass R, Alsagob M, Al-Younes B, AlQuait L, Mustafa OM, Bulbul M, Rahbeeni Z, Alfadhel M, Chedrawi A, Al-Hassnan Z, AlDosari M, Al-Zaidan H, Al-Muhaizea MA, AlSayed MD, Salih MA, AlShammari M, Faiyaz-Ul-Haque M, Chishti MA, Al-Harazi O, Al-Odaib A, Kaya N, Colak D. Rett Syndrome, a Neurodevelopmental Disorder, Whole-Transcriptome, and Mitochondrial Genome Multiomics Analyses Identify Novel Variations and Disease Pathways. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2020; 24:160-171. [PMID: 32105570 DOI: 10.1089/omi.2019.0192] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Rett syndrome (RTT) is a severe neurodevelopmental disorder reported worldwide in diverse populations. RTT is diagnosed primarily in females, with clinical findings manifesting early in life. Despite the variable rates across populations, RTT has an estimated prevalence of ∼1 in 10,000 live female births. Among 215 Saudi Arabian patients with neurodevelopmental and autism spectrum disorders, we identified 33 patients with RTT who were subsequently examined by genome-wide transcriptome and mitochondrial genome variations. To the best of our knowledge, this is the first in-depth molecular and multiomics analyses of a large cohort of Saudi RTT cases with a view to informing the underlying mechanisms of this disease that impact many patients and families worldwide. The patients were unrelated, except for 2 affected sisters, and comprised of 25 classic and eight atypical RTT cases. The cases were screened for methyl-CpG binding protein 2 (MECP2), CDKL5, FOXG1, NTNG1, and mitochondrial DNA (mtDNA) variants, as well as copy number variations (CNVs) using a genome-wide experimental strategy. We found that 15 patients (13 classic and two atypical RTT) have MECP2 mutations, 2 of which were novel variants. Two patients had novel FOXG1 and CDKL5 variants (both atypical RTT). Whole mtDNA sequencing of the patients who were MECP2 negative revealed two novel mtDNA variants in two classic RTT patients. Importantly, the whole-transcriptome analysis of our RTT patients' blood and further comparison with previous expression profiling of brain tissue from patients with RTT revealed 77 significantly dysregulated genes. The gene ontology and interaction network analysis indicated potentially critical roles of MAPK9, NDUFA5, ATR, SMARCA5, RPL23, SRSF3, and mitochondrial dysfunction, oxidative stress response and MAPK signaling pathways in the pathogenesis of RTT genes. This study expands our knowledge on RTT disease networks and pathways as well as presents novel mutations and mtDNA alterations in RTT in a population sample that was not previously studied.
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Affiliation(s)
- Mazhor Aldosary
- Department of Genetics, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - AlBandary Al-Bakheet
- Department of Genetics, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Hesham Al-Dhalaan
- Department of Neuroscience, and King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Rawan Almass
- Department of Genetics, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Maysoon Alsagob
- Department of Genetics, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Banan Al-Younes
- Department of Genetics, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Laila AlQuait
- Department of Genetics, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Osama Mufid Mustafa
- Department of Genetics, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Mustafa Bulbul
- Department of Genetics, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Zuhair Rahbeeni
- Department of Medical Genetics, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Majid Alfadhel
- King Abdullah International Medical Research Centre, King Saud bin Abdulaziz University for Health Sciences, Genetics Division, Department of Pediatrics, King Abdullah Specialized Children Hospital, Riyadh, Saudi Arabia
| | - Aziza Chedrawi
- Department of Neuroscience, and King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Zuhair Al-Hassnan
- Department of Medical Genetics, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Mohammed AlDosari
- Center for Pediatric Neurosciences, Cleveland Clinic, Cleveland, Ohio
| | - Hamad Al-Zaidan
- Department of Medical Genetics, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Mohammad A Al-Muhaizea
- Department of Neuroscience, and King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Moeenaldeen D AlSayed
- Department of Medical Genetics, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Mustafa A Salih
- Division of Pediatric Neurology, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Mai AlShammari
- Department of Genetics, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | | | - Mohammad Azhar Chishti
- Department of Biochemistry, King Khalid Hospital, King Saud University, Riyadh, Saudi Arabia
| | - Olfat Al-Harazi
- Department of Biostatistics, Epidemiology, and Scientific Computing, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Ali Al-Odaib
- Department of Genetics, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Namik Kaya
- Department of Genetics, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Dilek Colak
- Department of Biostatistics, Epidemiology, and Scientific Computing, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
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Abstract
BACKGROUND Given the etiologic heterogeneity of disease classification using clinical phenomenology, we employed contemporary criteria to classify variants associated with myoclonic epilepsy with ragged-red fibers (MERRF) syndrome and to assess the strength of evidence of gene-disease associations. Standardized approaches are used to clarify the definition of MERRF, which is essential for patient diagnosis, patient classification, and clinical trial design. METHODS Systematic literature and database search with application of standardized assessment of gene-disease relationships using modified Smith criteria and of variants reported to be associated with MERRF using modified Yarham criteria. RESULTS Review of available evidence supports a gene-disease association for two MT-tRNAs and for POLG. Using modified Smith criteria, definitive evidence of a MERRF gene-disease association is identified for MT-TK. Strong gene-disease evidence is present for MT-TL1 and POLG. Functional assays that directly associate variants with oxidative phosphorylation impairment were critical to mtDNA variant classification. In silico analysis was of limited utility to the assessment of individual MT-tRNA variants. With the use of contemporary classification criteria, several mtDNA variants previously reported as pathogenic or possibly pathogenic are reclassified as neutral variants. CONCLUSIONS MERRF is primarily an MT-TK disease, with pathogenic variants in this gene accounting for ~90% of MERRF patients. Although MERRF is phenotypically and genotypically heterogeneous, myoclonic epilepsy is the clinical feature that distinguishes MERRF from other categories of mitochondrial disorders. Given its low frequency in mitochondrial disorders, myoclonic epilepsy is not explained simply by an impairment of cellular energetics. Although MERRF phenocopies can occur in other genes, additional data are needed to establish a MERRF disease-gene association. This approach to MERRF emphasizes standardized classification rather than clinical phenomenology, thus improving patient diagnosis and clinical trial design.
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Abstract
Imaging of central-nervous-system (CNS) abnormalities is important in patients with mitochondrial disorders (MCDs) since the CNS is the organ second most frequently affected in MCDs and some of them are potentially treatable. Clinically relevant imaging techniques for visualization of CNS abnormalities in MCDs are computed tomography, magnetic resonance imaging, and MR-spectroscopy. The CNS abnormalities in MCDs visualized by imaging techniques include stroke-like lesions with cytotoxic or vasogenic edema, laminar cortical necrosis, basal ganglia necrosis, focal or diffuse white matter lesions, focal or diffuse atrophy, intra-cerebral calcifications, cysts, lacunas, hypometabolisation, lactacidosis, hemorrhages, cerebral hypo- or hyperperfusion, intra-cerebral artery stenoses, or moyamoya syndrome. The CNS lesions may proceed with or without clinical manifestations, why neuroimaging should be routinely carried out in all MCDs to assess the degree of CNS involvement. Some of these lesions may remain unchanged for years, some may show contiguous spread and progression, but some may even disappear, spontaneously or in response to medication. Dynamics of Stroke-like lesions may be positively influenced by L-arginine, dichloracetate, steroids, edavarone, or antiepileptics. Symptomatic treatment of CNS abnormalities in MCD patients may positively influence their outcome.
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González-Vioque E, Bornstein B, Gallardo ME, Fernández-Moreno MÁ, Garesse R. The pathogenicity scoring system for mitochondrial tRNA mutations revisited. Mol Genet Genomic Med 2013; 2:107-14. [PMID: 24689073 PMCID: PMC3960052 DOI: 10.1002/mgg3.47] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2013] [Revised: 09/27/2013] [Accepted: 10/09/2013] [Indexed: 11/14/2022] Open
Abstract
Confirming the pathogenicity of mitochondrial tRNA point mutations is one of the classical challenges in the field of mitochondrial medicine. In addition to genetic and functional studies, the evaluation of a genetic change using a pathogenicity scoring system is extremely useful to discriminate between disease-causing mutations from neutral polymorphisms. The pathogenicity scoring system is very robust for confirming pathogenicity, especially of mutations that show impaired activity in functional studies. However, mutations giving normal results using the same functional approaches are disregarded, and this compromises the power of the system to rule out pathogenicity. We propose to include a new criterion in the pathogenicity scoring systems regarding mutations which fail to show any mitochondrial defect in functional studies. To evaluate this proposal we characterized two mutations, m.8296A>G and m.8347A>G, in the mitochondrial tRNALys gene (MT-TK) using trans-mitochondrial cybrid analysis. m.8347A>G mutation severely impairs oxidative phosphorylation, suggesting that it is highly pathogenic. By contrast, the behavior of cybrids homoplasmic for the m.8296A>G mutation is similar to cybrids containing wild-type mitochondrial DNA (mtDNA). The results indicate that including not only positive but also negative outcomes of functional studies in the scoring system is critical for facilitating the diagnosis of this complex group of diseases.
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Affiliation(s)
- Emiliano González-Vioque
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas "Alberto Sols" UAM-CSIC and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Universidad Autónoma de Madrid 28029, Madrid, Spain ; Laboratorio de Enfermedades Mitocondriales, Instituto de Investigación Sanitaria Hospital 12 de Octubre (i+12) Madrid, Spain
| | - Belén Bornstein
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas "Alberto Sols" UAM-CSIC and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Universidad Autónoma de Madrid 28029, Madrid, Spain ; Servicio de Bioquímica, Instituto de Investigación Sanitaria Puerta de Hierro Majadahonda Madrid, Spain
| | - María Esther Gallardo
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas "Alberto Sols" UAM-CSIC and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Universidad Autónoma de Madrid 28029, Madrid, Spain ; Laboratorio de Enfermedades Mitocondriales, Instituto de Investigación Sanitaria Hospital 12 de Octubre (i+12) Madrid, Spain
| | - Miguel Ángel Fernández-Moreno
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas "Alberto Sols" UAM-CSIC and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Universidad Autónoma de Madrid 28029, Madrid, Spain ; Laboratorio de Enfermedades Mitocondriales, Instituto de Investigación Sanitaria Hospital 12 de Octubre (i+12) Madrid, Spain
| | - Rafael Garesse
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas "Alberto Sols" UAM-CSIC and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Universidad Autónoma de Madrid 28029, Madrid, Spain ; Laboratorio de Enfermedades Mitocondriales, Instituto de Investigación Sanitaria Hospital 12 de Octubre (i+12) Madrid, Spain
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Wolf J, Obermaier-Kusser B, Jacobs M, Milles C, Mörl M, von Pein HD, Grau AJ, Bauer MF. A new mitochondrial point mutation in the transfer RNA(Lys) gene associated with progressive external ophthalmoplegia with impaired respiratory regulation. J Neurol Sci 2012; 316:108-11. [PMID: 22326363 DOI: 10.1016/j.jns.2012.01.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Revised: 01/13/2012] [Accepted: 01/20/2012] [Indexed: 11/18/2022]
Abstract
We report a novel heteroplasmic point mutation G8299A in the gene for mitochondrial tRNA(Lys) in a patient with progressive external ophthalmoplegia complicated by recurrent respiratory insufficiency. Biochemical analysis of respiratory chain complexes in muscle homogenate showed a combined complex I and IV deficiency. The transition does not represent a known neutral polymorphism and affects a position in the tRNA acceptor stem which is conserved in primates, leading to a destabilization of this functionally important domain. In vitro analysis of an essential maturation step of the tRNA transcript indicates the probable pathogenicity of this mutation. We hypothesize that there is a causal relationship between the novel G8299A transition and progressive external ophthalmoplegia with recurrent respiratory failure due to a depressed respiratory drive.
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Affiliation(s)
- Joachim Wolf
- Department of Neurology, Klinikum Ludwigshafen, Germany.
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Duraisamy P, Elango S, Vishwanandha VP, Balamurugan R. Prevalence of mitochondrial tRNA gene mutations and their association with specific clinical phenotypes in patients with type 2 diabetes mellitus of Coimbatore. Genet Test Mol Biomarkers 2010; 14:49-55. [PMID: 20143911 DOI: 10.1089/gtmb.2009.0024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The association of mitochondrial DNA mutation with type 2 diabetes mellitus (T2DM) is well established. In this study we aimed to assess the frequency of A3243G, A8296G, and other mitochondrial mutations with reference to clinical features in the diabetic population of Coimbatore, India. The study group included 150 patients (89 women and 61 men) with T2DM, whereas the control group included 100 nondiabetic people (59 women and 41 men). Genotyping was done by polymerase chain reaction followed by single-strand confirmation polymorphism method. A3243G and A8296G mutations were found to be prevalent in patients with T2DM when compared with the control group. The A3243G mutation was found in two patients, and both these patients showed similar clinical characteristics, thus representing a putative clinical subtype. A8296G mutation was detected in one patient. The same mutation was shared with his mother who was diagnosed to have diabetes mellitus (DM) with neuromuscular disorder. The siblings of the patient did not show any symptoms of DM. Lipid profile and urea and creatinine levels were found to be significantly high (10% and 0.064%) in patients with T2DM compared with control subjects. We concluded that the identification of these mitochondrial point mutations indicates a new genetic predisposition of DM in Coimbatore population.
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Affiliation(s)
- Pradeepa Duraisamy
- School of Biotechnology and Genetic Engineering, Bharathiar University, Coimbatore, India
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Iizuka T, Sakai F. Pathophysiology of stroke-like episodes in MELAS: neuron–astrocyte uncoupling in neuronal hyperexcitability. FUTURE NEUROLOGY 2010. [DOI: 10.2217/fnl.09.71] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) is a distinct clinical syndrome characterized by fluctuated encephalopathy, migraineous headache, seizure and stroke-like episodes. The molecular mechanism of MELAS mutations has been elucidated; however, the pathogenesis of stroke-like episodes remains largely unknown. Three main hypotheses include ischemic, metabolic and neuronal hyperexcitability hypotheses. Recently, emerging hypotheses include alterations in nitric oxide homeostasis and over-reduction/oxidative stress mechanisms. Although neuron–astrocyte communication is crucial in various physiological functions, it has not been seriously considered in the pathophysiology of stroke-like episodes. This review summarizes what is known about the molecular mechanisms of gene mutation, clinico-radiological, clinico-physiological and pathological features of stroke-like episodes, as well as its pathogenesis. We finally discuss potential mechanisms involved in the pathogenesis of stroke-like episodes based on currently available clinical data and the current understanding of the mechanisms of neuron–astrocyte communications. We propose that neuron–astrocyte uncoupling is a new target of research in mitochondrial disorders.
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Affiliation(s)
- Takahiro Iizuka
- Department of Neurology, School of Medicine, Kitasato University, Kanagawa, Japan
| | - Fumihiko Sakai
- International Headache Center, Shinyurigaoka, Kanagawa, Japan
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9
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Kim IS, Ki CS, Park KJ. Pediatric-onset dystonia associated with bilateral striatal necrosis and G14459A mutation in a Korean family: a case report. J Korean Med Sci 2010; 25:180-4. [PMID: 20052369 PMCID: PMC2800009 DOI: 10.3346/jkms.2010.25.1.180] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Accepted: 07/14/2008] [Indexed: 11/30/2022] Open
Abstract
We describe a Korean family presenting with pediatric-onset, progressive, generalized dystonia with bilateral striatal necrosis and the homoplasmic G14459A mutation in the mitochondrial ND6 gene. The G14459A mutation has been reported in families presenting with Leber hereditary optic neuropathy (LHON) alone, LHON plus dystonia, or pediatric-onset dystonia. The proband had shown dysarthria, progressive generalized dystonia, and spasticity at 5 yr. Brain MRI demonstrated bilateral striatal necrosis. Additional investigation of family members revealed the presence of homoplasmic G14459A mutation in asymptomatic individuals. The clinical manifestation of the homoplasmic G14459A mtDNA mutation within the same family showed asymptomatic or pediatric-onset dystonia, without optic neuropathy. This study reemphasizes that the G14459A mutation is a candidate mutation for maternally inherited dystonia, regardless of optic neuropathy, and supports the hypothesis that nuclear genes may play a role in modifying the clinical expression of mitochondrial disease.
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Affiliation(s)
- In-Suk Kim
- Department of Laboratory Medicine, Gyeongsang National University Hospital, Jinju, Korea
| | - Chang-Seok Ki
- Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Ki-Jong Park
- Department of Neurology, Gyeongsang Institute of Health Science, Gyeongsang National University School of Medicine, Jinju, Korea
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10
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Du W, Li W, Chen G, Cao H, Tang H, Tang X, Jin Q, Sun Z, Zhao H, Zhou W, He S, Lv Y, Zhao J, Zhang X. Detection of known base substitution mutations in human mitochondrial DNA of MERRF and MELAS by biochip technology. Biosens Bioelectron 2008; 24:2371-6. [PMID: 19155171 DOI: 10.1016/j.bios.2008.12.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2008] [Revised: 11/07/2008] [Accepted: 12/03/2008] [Indexed: 11/25/2022]
Abstract
We developed a DNA biochip specialized for detection of known base substitution mutations in mitochondrial DNA causing mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) and myoclonic epilepsy associated with ragged-red fibers (MERRF). A set of probes sharing a given allele-specific sequence with a single base substitution near the middle of the sequence was covalently immobilized. Cy5-labeled DNA targets were amplified from sample DNAs containing 31 potential MELAS and/or MERRF mutations by a multiplex PCR method. Detection parameters for the DNA biochip-based assay were accordingly optimized. Seven clinically confirmed patients with MELAS, 5 patients with MERRF, 1 suspected MERRF case and 25 healthy controls were tested using the DNA biochip. For discriminating of homoplasmic and heteroplasmic point mutations in mtDNA, a diagnostic factor based on the ratio between the hybridization signals from the reference and test targets with each probe was used. The results showed that all the cases with MELAS had a causal heteroplasmic A3243G tRNA(Leu(UUR)) mutation. In the MERRF patients, four cases were found to be a homoplasmic A8344G tRNA(Lys) mutation and one case was a heteroplasmic T8356C tRNA(Lys) mutation. None of the healthy controls carried the potential mutations. The results of the DNA biochip were completely consistent with those by DNA sequencing. Thus, the DNA biochip would potentially become a valuable tool in clinical specific screening of the mtDNA point mutations associated with MELAS and/or MERRF syndrome.
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Affiliation(s)
- Weidong Du
- Key Lab of Gene Resource Utilization for Severe Hereditary Diseases of Ministry of Education of China, Anhui Medical University, Hefei 230032, China.
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11
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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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12
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Finsterer J. Genetic, pathogenetic, and phenotypic implications of the mitochondrial A3243G tRNALeu(UUR) mutation. Acta Neurol Scand 2007; 116:1-14. [PMID: 17587249 DOI: 10.1111/j.1600-0404.2007.00836.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Mitochondrial disorders are frequently caused by mutations in mitochondrial genes and usually present as multisystem disease. One of the most frequent mitochondrial mutations is the A3,243G transition in the tRNALeu(UUR) gene. The phenotypic expression of the mutation is variable and comprises syndromic or non-syndromic mitochondrial disorders. Among the syndromic manifestations the mitochondrial encephalopathy, lactacidosis, and stroke-like episode (MELAS) syndrome is the most frequent. In single cases the A3,243G mutation may be associated with maternally inherited diabetes and deafness syndrome, myoclonic epilepsy and ragged-red fibers (MERRF) syndrome, MELAS/MERRF overlap syndrome, maternally inherited Leigh syndrome, chronic external ophthalmoplegia, or Kearns-Sayre syndrome. The wide phenotypic variability of the mutation is explained by the peculiarities of the mitochondrial DNA, such as heteroplasmy and mitotic segregation, resulting in different mutation loads in different tissues and family members. Moreover, there is some evidence that additional mtDNA sequence variations (polymorphisms, haplotypes) influence the phenotype of the A3,243G mutation. This review aims to give an overview on the actual knowledge about the genetic, pathogenetic, and phenotypic implications of the A3,243G mtDNA mutation.
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Affiliation(s)
- J Finsterer
- Krankenanstalt Rudolfstiftung, Vienna, Austria.
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13
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Abstract
The central nervous system (CNS) is, after the peripheral nervous system, the second most frequently affected organ in mitochondrial disorders (MCDs). CNS involvement in MCDs is clinically heterogeneous, manifesting as epilepsy, stroke-like episodes, migraine, ataxia, spasticity, extrapyramidal abnormalities, bulbar dysfunction, psychiatric abnormalities, neuropsychological deficits, or hypophysial abnormalities. CNS involvement is found in syndromic and non-syndromic MCDs. Syndromic MCDs with CNS involvement include mitochondrial encephalomyopathy, lactacidosis, stroke-like episodes syndrome, myoclonic epilepsy and ragged red fibers syndrome, mitochondrial neuro-gastrointestinal encephalomyopathy syndrome, neurogenic muscle weakness, ataxia, and retinitis pigmentosa syndrome, mitochondrial depletion syndrome, Kearns-Sayre syndrome, and Leigh syndrome, Leber's hereditary optic neuropathy, Friedreich's ataxia, and multiple systemic lipomatosis. As CNS involvement is often subclinical, the CNS including the spinal cord should be investigated even in the absence of overt clinical CNS manifestations. CNS investigations comprise the history, clinical neurological examination, neuropsychological tests, electroencephalogram, cerebral computed tomography scan, and magnetic resonance imaging. A spinal tap is indicated if there is episodic or permanent impaired consciousness or in case of cognitive decline. More sophisticated methods are required if the CNS is solely affected. Treatment of CNS manifestations in MCDs is symptomatic and focused on epilepsy, headache, lactacidosis, impaired consciousness, confusion, spasticity, extrapyramidal abnormalities, or depression. Valproate, carbamazepine, corticosteroids, acetyl salicylic acid, local and volatile anesthetics should be applied with caution. Avoiding certain drugs is often more beneficial than application of established, apparently indicated drugs.
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Affiliation(s)
- J Finsterer
- Krankenanstalt Rudolfstiftung, Vienna, Austria.
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14
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Kong QP, Bandelt HJ, Sun C, Yao YG, Salas A, Achilli A, Wang CY, Zhong L, Zhu CL, Wu SF, Torroni A, Zhang YP. Updating the East Asian mtDNA phylogeny: a prerequisite for the identification of pathogenic mutations. Hum Mol Genet 2006; 15:2076-86. [PMID: 16714301 DOI: 10.1093/hmg/ddl130] [Citation(s) in RCA: 305] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Knowledge about the world phylogeny of human mitochondrial DNA (mtDNA) is essential not only for evaluating the pathogenic role of specific mtDNA mutations but also for performing reliable association studies between mtDNA haplogroups and complex disorders. In the past few years, the main features of the East Asian portion of the mtDNA phylogeny have been determined on the basis of complete sequencing efforts, but representatives of several basal lineages were still lacking. Moreover, some recently published complete mtDNA sequences did apparently not fit into the known phylogenetic tree and conflicted with the established nomenclature. To refine the East Asian mtDNA tree and resolve data conflicts, we first completely sequenced 20 carefully selected mtDNAs--likely representatives of novel sub-haplogroups--and then, in order to distinguish diagnostic mutations of novel haplogroups from private variants, we applied a 'motif-search' procedure to a large sample collection. The novel information was incorporated into an updated East Asian mtDNA tree encompassing more than 1000 (near-) complete mtDNA sequences. A reassessment of the mtDNA data from a series of disease studies testified to the usefulness of such a refined mtDNA tree in evaluating the pathogenicity of mtDNA mutations. In particular, the claimed pathogenic role of mutations G3316A, T3394C, A4833G and G15497A appears to be most questionable as those initial claims were derived from anecdotal findings rather than e.g. appropriate association studies. Following a guideline based on the phylogenetic knowledge as proposed here could help avoiding similar problems in the future.
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Affiliation(s)
- Qing-Peng Kong
- Laboratory of Cellular and Molecular Evolution, and Molecular Biology of Domestic Animals, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China.
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15
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Bornstein B, Mas J, Patrono C, Fernández-Moreno M, González-Vioque E, Campos Y, Carrozzo R, Martín M, Hoyo P, Santorelli F, Arenas J, Garesse R. Comparative analysis of the pathogenic mechanisms associated with the G8363A and A8296G mutations in the mitochondrial tRNA(Lys) gene. Biochem J 2006; 387:773-8. [PMID: 15554876 PMCID: PMC1135008 DOI: 10.1042/bj20040949] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Two mutations (G8363A and A8296G) in the mtDNA (mitochondrial DNA) tRNA(Lys) gene have been associated with severe mitochondrial diseases in a number of reports. Their functional significance, however, remains unknown. We have already shown that homoplasmic cybrids harbouring the A8296G mutation display normal oxidative phosphorylation, although the possibility of a subtle change in mitochondrial respiratory capacity remains an open issue. We have now investigated the pathogenic mechanism of another mutation in the tRNA(Lys) gene (G8363A) by repopulating an mtDNA-less human osteosarcoma cell line with mitochondria harbouring either this genetic variant alone or an unusual combination of the two mutations (A8296G+G8363A). Cybrids homoplasmic for the single G8363A or the A8296G+G8363A mutations have defective respiratory-chain enzyme activities and low oxygen consumption, indicating a severe impairment of the oxidative phosphorylation system. Generation of G8363A cybrids within a wild-type or the A8296G mtDNA genetic backgrounds resulted in an important alteration in the conformation of the tRNA(Lys), not affecting tRNA steady-state levels. Moreover, mutant cybrids have an important decrease in the proportion of amino-acylated tRNA(Lys) and, consequently, mitochondrial protein synthesis is greatly decreased. Our results demonstrate that the pathogenicity of the G8363A mutation is due to a change in the conformation of the tRNA that severely impairs aminoacylation in the absence of changes in tRNA stability. The only effect detected in the A8296G mutation is a moderate decrease in the aminoacylation capacity, which does not affect mitochondrial protein biosynthesis.
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Affiliation(s)
- Belén Bornstein
- *Departamento de Bioquímica, Instituto de Investigaciones Biomédicas ‘Alberto Sols’, CSIC-UAM, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain
- †Servicio de Bioquímica, Hospital Severo Ochoa, Leganés, Madrid, Spain
| | - José Antonio Mas
- *Departamento de Bioquímica, Instituto de Investigaciones Biomédicas ‘Alberto Sols’, CSIC-UAM, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain
| | - Clarice Patrono
- *Departamento de Bioquímica, Instituto de Investigaciones Biomédicas ‘Alberto Sols’, CSIC-UAM, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain
- ‡Unit of Molecular Medicine, Children's Hospital ‘Bambino Gesù’, Rome, Italy
| | - Miguel Angel Fernández-Moreno
- *Departamento de Bioquímica, Instituto de Investigaciones Biomédicas ‘Alberto Sols’, CSIC-UAM, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain
| | - Emiliano González-Vioque
- *Departamento de Bioquímica, Instituto de Investigaciones Biomédicas ‘Alberto Sols’, CSIC-UAM, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain
| | - Yolanda Campos
- §Centro de Investigación, Hospital 12 de Octubre, Madrid, Spain
| | - Rosalba Carrozzo
- ‡Unit of Molecular Medicine, Children's Hospital ‘Bambino Gesù’, Rome, Italy
| | | | - Pilar del Hoyo
- §Centro de Investigación, Hospital 12 de Octubre, Madrid, Spain
| | | | - Joaquín Arenas
- §Centro de Investigación, Hospital 12 de Octubre, Madrid, Spain
| | - Rafael Garesse
- *Departamento de Bioquímica, Instituto de Investigaciones Biomédicas ‘Alberto Sols’, CSIC-UAM, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain
- To whom correspondence should be addressed (email )
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Ueki I, Koga Y, Povalko N, Akita Y, Nishioka J, Yatsuga S, Fukiyama R, Matsuishi T. Mitochondrial tRNA gene mutations in patients having mitochondrial disease with lactic acidosis. Mitochondrion 2006; 6:29-36. [PMID: 16337222 DOI: 10.1016/j.mito.2005.10.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2005] [Revised: 10/17/2005] [Accepted: 10/19/2005] [Indexed: 11/25/2022]
Abstract
Lactic acidosis has been associated with a variety of clinical conditions and can be due to mutation in nuclear or mitochondrial genes. We performed mutations screening of all mitochondrial tRNA genes in 44 patients who referred as hyperlactic acidosis. Patients showed heterogeneous phenotypes including Leigh disease in four, MELAS in six, unclassified mitochondrial myopathy in 10, cardiomyopathy in five, MERRF in one, pure lactic acidosis in six, and others in 12 including facio-scaplo-femoral muscular dystrophy (FSFD), familial cerebellar ataxia, recurrent Reye syndrome, cerebral palsy with mental retardation. We measured enzymatic activities of pyruvate dehydrogenase complex, and respiratory chain enzymes. All mitochondrial tRNA genes and known mutation of ATPase 6 were studied by single strand conformation polymorphism (SSCP), automated DNA sequence and PCR-RFLP methods. We have found one patient with PDHC deficiency and six patients with Complex I+IV deficiency, though the most of the patients showed subnormal to deficient state of respiratory chain enzyme activities. We have identified one of the nucleotide changes in 29 patients. Single nucleotide changes in mitochondrial tRNA genes are found in 27 patients and one in ATPase 6 gene in two patients. One of four pathogenic point mutations (A3243G, C3303T, A8348G, and T8993G) was identified in 12 patients who showed the phenotype of Leigh syndrome, MELAS, cardimyopathy and cerebral palsy with epilepsy. Seventeen patients have one of the normal polymorphisms in the mitochondrial tRNA gene reported before. SSCP and PCR-RFLP could detect the heteroplasmic condition when the percentage of mutant up to 5, however, it cannot be observed by direct sequencing method. It is important to screen the mtDNA mutation not only by direct sequence but also by PCR-RFLP and the other sensitive methods to detect the heroplasmy when lactic acidosis has been documented in the patients who are not fulfilled the criteria of mitochondrial disorders.
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Affiliation(s)
- Isao Ueki
- Department of Pediatrics and Child Health, Kurume University School of Medicine, 67 Asahi-Machi, Kurume 830-0011, Japan
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17
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Guo LJ, Oshida Y, Fuku N, Takeyasu T, Fujita Y, Kurata M, Sato Y, Ito M, Tanaka M. Mitochondrial genome polymorphisms associated with type-2 diabetes or obesity. Mitochondrion 2005; 5:15-33. [PMID: 16060290 DOI: 10.1016/j.mito.2004.09.001] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Although a strong correlation between type-2 diabetes and obesity has been found, no comparative analysis between diabetes and obesity has been performed with respect to mitochondrial DNA (mtDNA) polymorphisms. To test the hypothesis that certain mitochondrial single nucleotide polymorphisms (mtSNPs) might be associated with obesity or type-2 diabetes, we determined the entire sequences of the mitochondrial genomes from 96 patients with type-2 diabetes and those from 96 young obese adults by direct sequencing and compared the frequencies of mtSNPs between these two groups. A mtSNP, 8684C > T (T53I) in the mitochondrial ATP synthase subunit 6 gene (ATP6), was detected in 5 of the 96 patients with type-2 diabetes, whereas this substitution was not detected in any of the 96 young obese adults. Two mtSNPs, 3497C > T (A64V) in NADH dehydrogenase subunit 1 gene (ND1) and 1119T > C (472U > C) in the 12S rRNA gene, were detected in 5 of the 96 young obese adults, whereas these substitutions were not detected in any of the 96 diabetic patients. The 8684C > T transition associated with type-2 diabetes represents haplogroup M8a, and the 3497C > T and 1119T > C transitions predisposing to obesity represent haplogroup B4c. These results suggest that distinct mtSNPs contribute to susceptibility to type-2 diabetes or obesity, pointing out the necessity of large-scale case control studies.
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MESH Headings
- Adult
- Amino Acid Substitution
- Animals
- Base Sequence
- DNA, Mitochondrial/genetics
- Diabetes Mellitus, Type 2/genetics
- Genome, Human
- Humans
- Japan
- Mammals/genetics
- Middle Aged
- Mitochondrial Proteins/chemistry
- Mitochondrial Proteins/genetics
- Mitochondrial Proton-Translocating ATPases/chemistry
- Mitochondrial Proton-Translocating ATPases/genetics
- Models, Molecular
- Molecular Sequence Data
- NADH Dehydrogenase/genetics
- Nucleic Acid Conformation
- Obesity/genetics
- Phylogeny
- Polymorphism, Single Nucleotide
- Protein Structure, Secondary
- RNA, Ribosomal/chemistry
- RNA, Ribosomal/genetics
- RNA, Transfer/chemistry
- RNA, Transfer/genetics
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Affiliation(s)
- Li-Jun Guo
- Department of Sports Medicine, Graduate School of Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
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18
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Abstract
Muscle biopsy provides the best tissue to confirm a mitochondrial cytopathy. Histochemical features often correlate with specific syndromes and facilitate the selection of biochemical and genetic studies. Ragged-red fibres nearly always indicate a combination defect of respiratory complexes I and IV. Increased punctate lipid within myofibers is a regular feature of Kearns-Sayre and PEO, but not of MELAS and MERRF. Total deficiency of succinate dehydrogenase indicates a severe defect in Complex II; total absence of cytochrome-c-oxidase activity in all myofibres correlates with a severe deficiency of Complex IV or of coenzyme-Q10. The selective loss of cytochrome-c-oxidase activity in scattered myofibers, particularly if accompanied by strong succinate dehydrogenase staining in these same fibres, is good evidence of mitochondrial cytopathy and often of a significant mtDNA mutation, though not specific for Complex IV disorders. Glycogen may be excessive in ragged-red zones. Ultrastructure provides morphological evidence of mitochondrial cytopathy, in axons and endothelial cells as well as myocytes. Abnormal axonal mitochondria may contribute to neurogenic atrophy of muscle, a secondary chronic feature. Quantitative determinations of respiratory chain enzyme complexes, with citrate synthase as an internal control, confirm the histochemical impressions or may be the only evidence of mitochondrial disease. Biological and technical artifacts may yield falsely low enzymatic activities. Genetic studies screen common point mutations in mtDNA. The brain exhibits characteristic histopathological alterations in mitochondrial diseases. Skin biopsy is useful for mitochondrial ultrastructure in smooth erector pili muscles and axons; skin fibroblasts may be grown in culture. Mitochondrial alterations occur in many nonmitochondrial diseases and also may be induced by drugs and toxins.
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