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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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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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Chaudhary SK, Chavan A, Tandon R. Anti-NMDA receptor encephalitis with "Hockey stick sign" mimicking CJD. Neurol Sci 2023; 44:741-743. [PMID: 36251206 DOI: 10.1007/s10072-022-06455-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 10/10/2022] [Indexed: 11/07/2022]
Affiliation(s)
- Sarvesh Kumar Chaudhary
- Department of Neurology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, 226014, India
| | - Ajay Chavan
- Department of Neurology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, 226014, India
| | - Ruchika Tandon
- Department of Neurology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, 226014, India.
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4
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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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Gaudino S, Gangemi E, Colantonio R, Botto A, Ruberto E, Calandrelli R, Martucci M, Vita MG, Masullo C, Cerase A, Colosimo C. Neuroradiology of human prion diseases, diagnosis and differential diagnosis. Radiol Med 2017; 122:369-385. [PMID: 28110369 DOI: 10.1007/s11547-017-0725-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 01/03/2017] [Indexed: 01/14/2023]
Abstract
Human transmissible spongiform encephalopathies (TSEs), or prion diseases, are invariably fatal conditions associated with a range of clinical presentations. TSEs are classified as sporadic [e.g. sporadic Creutzfeldt-Jakob disease (sCJD), which is the most frequent form], genetic (e.g. Gerstmann-Straussler-Scheinker disease, fatal familial insomnia, and inherited CJD), and acquired or infectious (e.g. Kuru, iatrogenic CJD, and variant CJD). In the past, brain imaging played a supporting role in the diagnosis of TSEs, whereas nowadays magnetic resonance imaging (MRI) plays such a prominent role that MRI findings have been included in the diagnostic criteria for sCJD. Currently, MRI is required for all patients with a clinical suspicion of TSEs. Thus, MRI semeiotics of TSEs should become part of the cultural baggage of any radiologist. The purposes of this update on the neuroradiology of CJD are to (i) review the pathophysiology and clinical presentation of TSEs, (ii) describe both typical and atypical MRI findings of CJD, and (iii) illustrate diseases mimicking CJD, underlining the MRI key findings useful in the differential diagnosis.
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Affiliation(s)
- Simona Gaudino
- Department of Radiological Sciences, Institute of Radiology, Fondazione Policlinico Universitario A. Gemelli, School of Medicine, Catholic University, Largo A. Gemelli, 8, 00168, Rome, Italy.
| | - Emma Gangemi
- Department of Radiological Sciences, Institute of Radiology, Fondazione Policlinico Universitario A. Gemelli, School of Medicine, Catholic University, Largo A. Gemelli, 8, 00168, Rome, Italy
| | - Raffaella Colantonio
- Department of Radiological Sciences, Institute of Radiology, Fondazione Policlinico Universitario A. Gemelli, School of Medicine, Catholic University, Largo A. Gemelli, 8, 00168, Rome, Italy
| | - Annibale Botto
- Department of Radiological Sciences, Institute of Radiology, Fondazione Policlinico Universitario A. Gemelli, School of Medicine, Catholic University, Largo A. Gemelli, 8, 00168, Rome, Italy
| | - Emanuela Ruberto
- Department of Radiological Sciences, Institute of Radiology, Fondazione Policlinico Universitario A. Gemelli, School of Medicine, Catholic University, Largo A. Gemelli, 8, 00168, Rome, Italy
| | - Rosalinda Calandrelli
- Department of Radiological Sciences, Institute of Radiology, Fondazione Policlinico Universitario A. Gemelli, School of Medicine, Catholic University, Largo A. Gemelli, 8, 00168, Rome, Italy
| | - Matia Martucci
- Department of Radiological Sciences, Institute of Radiology, Fondazione Policlinico Universitario A. Gemelli, School of Medicine, Catholic University, Largo A. Gemelli, 8, 00168, Rome, Italy
| | - Maria Gabriella Vita
- Institute of Neurology, Fondazione Policlinico Universitario A. Gemelli, School of Medicine, Catholic University, Largo A. Gemelli, 8, 00168, Rome, Italy
| | - Carlo Masullo
- Institute of Neurology, Fondazione Policlinico Universitario A. Gemelli, School of Medicine, Catholic University, Largo A. Gemelli, 8, 00168, Rome, Italy
| | - Alfonso Cerase
- Unit of Neuroimaging and Neurointervention, Department of Neurological and Sensorineural Sciences, Azienda Ospedaliera Università Senese, "Santa Maria alle Scotte" University and NHS Hospital, Viale Mario Bracci, 16, 53100, Siena, Italy
| | - Cesare Colosimo
- Department of Radiological Sciences, Institute of Radiology, Fondazione Policlinico Universitario A. Gemelli, School of Medicine, Catholic University, Largo A. Gemelli, 8, 00168, Rome, Italy
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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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7
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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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8
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Zheng J, Sha-sha G, Xiao-wen T, Yi Z, Min-xin G. Human Mitochondrial tRNA Mutations in Maternally Inherited Deafness. J Otol 2013. [DOI: 10.1016/s1672-2930(13)50006-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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9
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Guitart T, Picchioni D, Piñeyro D, Ribas de Pouplana L. Human mitochondrial disease-like symptoms caused by a reduced tRNA aminoacylation activity in flies. Nucleic Acids Res 2013; 41:6595-608. [PMID: 23677612 PMCID: PMC3711456 DOI: 10.1093/nar/gkt402] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The translation of genes encoded in the mitochondrial genome requires specific machinery that functions in the organelle. Among the many mutations linked to human disease that affect mitochondrial translation, several are localized to nuclear genes coding for mitochondrial aminoacyl-transfer RNA synthetases. The molecular significance of these mutations is poorly understood, but it is expected to be similar to that of the mutations affecting mitochondrial transfer RNAs. To better understand the molecular features of diseases caused by these mutations, and to improve their diagnosis and therapeutics, we have constructed a Drosophila melanogaster model disrupting the mitochondrial seryl-tRNA synthetase by RNA interference. At the molecular level, the knockdown generates a reduction in transfer RNA serylation, which correlates with the severity of the phenotype observed. The silencing compromises viability, longevity, motility and tissue development. At the cellular level, the knockdown alters mitochondrial morphology, biogenesis and function, and induces lactic acidosis and reactive oxygen species accumulation. We report that administration of antioxidant compounds has a palliative effect of some of these phenotypes. In conclusion, the fly model generated in this work reproduces typical characteristics of pathologies caused by mutations in the mitochondrial aminoacylation system, and can be useful to assess therapeutic approaches.
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Affiliation(s)
- Tanit Guitart
- Institute for Research in Biomedicine (IRB Barcelona), Gene Translation Laboratory, c/Baldiri Reixac 10, Barcelona, 08028, Catalonia, Spain
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10
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Jing Z, Yan–chun J, Min–Xin G. Mitochondrial tRNA mutations associated with deafness. J Otol 2012. [DOI: 10.1016/s1672-2930(12)50009-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Zheng J, Ji Y, Guan MX. Mitochondrial tRNA mutations associated with deafness. Mitochondrion 2012; 12:406-13. [PMID: 22538251 DOI: 10.1016/j.mito.2012.04.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 03/15/2012] [Accepted: 04/09/2012] [Indexed: 10/28/2022]
Abstract
Mitochondrial tRNA mutations are one of the important causes of both syndromic and non-syndromic deafness. Of those, syndromic deafness-associated tRNA mutations such as tRNA(Leu(UUR)) 3243A>G are often present in heteroplasmy, while non-syndromic deafness-associated tRNA mutations including tRNA(Ser(UCN)) 7445A>G often occur in homplasmy or in high levels of heteroplasmy. These tRNA mutations are the primary mutations leading to hearing loss. However, other tRNA mutations such as tRNA(Thr) 15927G>A and tRNA(Ser(UCN)) 7444G>A may act in synergy with the primary mitochondrial DNA mutations, modulating the phenotypic manifestation of the primary mitochondrial DNA mutations. Theses tRNA mutations cause structural and functional alteration. A failure in tRNA metabolism caused by these tRNA mutations impaired mitochondrial translation and respiration, thereby causing mitochondrial dysfunctions responsible for deafness. These data offer valuable information for the early diagnosis, management and treatment of maternally inherited deafness.
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Affiliation(s)
- Jing Zheng
- Attardi Institute of Mitochondrial Biomedicine, Wenzhou Medical College, Wenzhou, Zhejiang, China
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13
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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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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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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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16
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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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Lévêque M, Marlin S, Jonard L, Procaccio V, Reynier P, Amati-Bonneau P, Baulande S, Pierron D, Lacombe D, Duriez F, Francannet C, Mom T, Journel H, Catros H, Drouin-Garraud V, Obstoy MF, Dollfus H, Eliot MM, Faivre L, Duvillard C, Couderc R, Garabedian EN, Petit C, Feldmann D, Denoyelle F. Whole mitochondrial genome screening in maternally inherited non-syndromic hearing impairment using a microarray resequencing mitochondrial DNA chip. Eur J Hum Genet 2007; 15:1145-55. [PMID: 17637808 DOI: 10.1038/sj.ejhg.5201891] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Mitochondrial DNA (mtDNA) mutations have been implicated in non-syndromic hearing loss either as primary or as predisposing factors. As only a part of the mitochondrial genome is usually explored in deafness, its prevalence is probably under-estimated. Among 1350 families with non-syndromic sensorineural hearing loss collected through a French collaborative network, we selected 29 large families with a clear maternal lineage and screened them for known mtDNA mutations in 12S rRNA, tRNASer(UCN) and tRNALeu(UUR) genes. When no mutation could be identified, a whole mitochondrial genome screening was performed, using a microarray resequencing chip: the MitoChip version 2.0 developed by Affymetrix Inc. Known mtDNA mutations was found in nine of the 29 families, which are described in the article: five with A1555G, two with the T7511C, one with 7472insC and one with A3243G mutation. In the remaining 20 families, the resequencing Mitochip detected 258 mitochondrial homoplasmic variants and 107 potentially heteroplasmic variants. Controls were made by direct sequencing on selected fragments and showed a high sensibility of the MitoChip but a low specificity, especially for heteroplasmic variations. An original analysis on the basis of species conservation, frequency and phylogenetic investigation was performed to select the more probably pathogenic variants. The entire genome analysis allowed us to identify five additional families with a putatively pathogenic mitochondrial variant: T669C, C1537T, G8078A, G12236A and G15077A. These results indicate that the new MitoChip platform is a rapid and valuable tool for identification of new mtDNA mutations in deafness.
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