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Abstract
Progressive external ophthalmoplegia (PEO), characterized by ptosis and impaired eye movements, is a clinical syndrome with an expanding number of etiologically distinct subtypes. Advances in molecular genetics have revealed numerous pathogenic causes of PEO, originally heralded in 1988 by the detection of single large-scale deletions of mitochondrial DNA (mtDNA) in skeletal muscle of people with PEO and Kearns-Sayre syndrome. Since then, multiple point variants of mtDNA and nuclear genes have been identified to cause mitochondrial PEO and PEO-plus syndromes, including mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) and sensory ataxic neuropathy dysarthria ophthalmoplegia (SANDO). Intriguingly, many of those nuclear DNA pathogenic variants impair maintenance of the mitochondrial genome causing downstream mtDNA multiple deletions and depletion. In addition, numerous genetic causes of nonmitochondrial PEO have been identified.
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Affiliation(s)
- Michio Hirano
- H. Houston Merritt Neuromuscular Research Center, Neuromuscular Medicine Division, Department of Neurology, Columbia University Irving Medical Center, New York, NY, United States.
| | - Robert D S Pitceathly
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, United Kingdom; NHS Highly Specialised Service for Rare Mitochondrial Disorders, Queen Square Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, London, United Kingdom
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2
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Kimura Y, Saito H, Osaki T, Ikegami Y, Wakigawa T, Ikeuchi Y, Iwasaki S. Mito-FUNCAT-FACS reveals cellular heterogeneity in mitochondrial translation. RNA (NEW YORK, N.Y.) 2022; 28:895-904. [PMID: 35256452 PMCID: PMC9074903 DOI: 10.1261/rna.079097.122] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/02/2022] [Accepted: 02/12/2022] [Indexed: 06/03/2023]
Abstract
Mitochondria possess their own genome that encodes components of oxidative phosphorylation (OXPHOS) complexes, and mitochondrial ribosomes within the organelle translate the mRNAs expressed from the mitochondrial genome. Given the differential OXPHOS activity observed in diverse cell types, cell growth conditions, and other circumstances, cellular heterogeneity in mitochondrial translation can be expected. Although individual protein products translated in mitochondria have been monitored, the lack of techniques that address the variation in overall mitochondrial protein synthesis in cell populations poses analytic challenges. Here, we adapted mitochondrial-specific fluorescent noncanonical amino acid tagging (FUNCAT) for use with fluorescence-activated cell sorting (FACS) and developed mito-FUNCAT-FACS. The click chemistry-compatible methionine analog L-homopropargylglycine (HPG) enabled the metabolic labeling of newly synthesized proteins. In the presence of cytosolic translation inhibitors, HPG was selectively incorporated into mitochondrial nascent proteins and conjugated to fluorophores via the click reaction (mito-FUNCAT). The application of in situ mito-FUNCAT to flow cytometry allowed us to separate changes in net mitochondrial translation activity from those of the organelle mass and detect variations in mitochondrial translation in cancer cells. Our approach provides a useful methodology for examining mitochondrial protein synthesis in individual cells.
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Affiliation(s)
- Yusuke Kimura
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan
- RNA Systems Biochemistry Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama 351-0198, Japan
| | - Hironori Saito
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan
- RNA Systems Biochemistry Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama 351-0198, Japan
| | - Tatsuya Osaki
- Institute of Industrial Science, The University of Tokyo, Meguro-ku, Tokyo 153-8505, Japan
| | - Yasuhiro Ikegami
- Institute of Industrial Science, The University of Tokyo, Meguro-ku, Tokyo 153-8505, Japan
| | - Taisei Wakigawa
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan
- RNA Systems Biochemistry Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama 351-0198, Japan
| | - Yoshiho Ikeuchi
- Institute of Industrial Science, The University of Tokyo, Meguro-ku, Tokyo 153-8505, Japan
- Institute for AI and Beyond, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Shintaro Iwasaki
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan
- RNA Systems Biochemistry Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama 351-0198, Japan
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3
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Apostolopoulos A, Iwasaki S. Into the matrix: current methods for mitochondrial translation studies. J Biochem 2022; 171:379-387. [PMID: 35080613 DOI: 10.1093/jb/mvac005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Accepted: 01/18/2022] [Indexed: 11/12/2022] Open
Abstract
In addition to the cytoplasmic translation system, eukaryotic cells house additional protein synthesis machinery in mitochondria. The importance of this in organello translation is exemplified by clinical pathologies associated with mutations in mitochondrial translation factors. Although a detailed understanding of mitochondrial translation has long been awaited, quantitative, comprehensive, and spatiotemporal measurements have posed analytic challenges. The recent development of novel approaches for studying mitochondrial protein synthesis has overcome these issues and expands our understanding of the unique translation system. Here, we review the current technologies for the investigation of mitochondrial translation and the insights provided by their application.
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Affiliation(s)
- Antonios Apostolopoulos
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan.,RNA Systems Biochemistry Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama 351-0198, Japan
| | - Shintaro Iwasaki
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan.,RNA Systems Biochemistry Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama 351-0198, Japan
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4
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Dawod PGA, Jancic J, Marjanovic A, Brankovic M, Jankovic M, Samardzic J, Gamil Anwar Dawod A, Novakovic I, Abdel Motaleb FI, Radlovic V, Kostic VS, Nikolic D. Mutational Analysis and mtDNA Haplogroup Characterization in Three Serbian Cases of Mitochondrial Encephalomyopathies and Literature Review. Diagnostics (Basel) 2021; 11:1969. [PMID: 34829316 PMCID: PMC8620769 DOI: 10.3390/diagnostics11111969] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2021] [Revised: 10/19/2021] [Accepted: 10/21/2021] [Indexed: 12/15/2022] Open
Abstract
Mitochondrial encephalomyopathies (MEMP) are heterogeneous multisystem disorders frequently associated with mitochondrial DNA (mtDNA) mutations. Clinical presentation varies considerably in age of onset, course, and severity up to death in early childhood. In this study, we performed molecular genetic analysis for mtDNA pathogenic mutation detection in Serbian children, preliminary diagnosed clinically, biochemically and by brain imaging for mitochondrial encephalomyopathies disorders. Sanger sequencing analysis in three Serbian probands revealed two known pathogenic mutations. Two probands had a heteroplasmic point mutation m.3243A>G in the MT-TL1 gene, which confirmed mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episode syndrome (MELAS), while a single case clinically manifested for Leigh syndrome had an almost homoplasmic (close to 100%) m.8993T>G mutation in the MT-ATP6 gene. After full mtDNA MITOMASTER analysis and PhyloTree build 17, we report MELAS' association with haplogroups U and H (U2e and H15 subclades); likewise, the mtDNA-associated Leigh syndrome proband shows a preference for haplogroup H (H34 subclade). Based on clinical-genetic correlation, we suggest that haplogroup H may contribute to the mitochondrial encephalomyopathies' phenotypic variability of the patients in our study. We conclude that genetic studies for the distinctive mitochondrial encephalomyopathies should be well-considered for realizing clinical severity and possible outcomes.
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Affiliation(s)
- Phepy G. A. Dawod
- Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia; (P.G.A.D.); (J.J.); (A.M.); (M.B.); (I.N.); (V.R.); (V.S.K.)
- Department of Medical Biochemistry and Molecular Biology, Faculty of Medicine, Ain Shams University, Cairo 11591, Egypt;
| | - Jasna Jancic
- Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia; (P.G.A.D.); (J.J.); (A.M.); (M.B.); (I.N.); (V.R.); (V.S.K.)
- Clinic of Neurology and Psychiatry of Children and Youth, 11000 Belgrade, Serbia
| | - Ana Marjanovic
- Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia; (P.G.A.D.); (J.J.); (A.M.); (M.B.); (I.N.); (V.R.); (V.S.K.)
| | - Marija Brankovic
- Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia; (P.G.A.D.); (J.J.); (A.M.); (M.B.); (I.N.); (V.R.); (V.S.K.)
| | - Milena Jankovic
- Neurology Clinic, Clinical Center of Serbia, 11000 Belgrade, Serbia;
| | - Janko Samardzic
- Institute of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia;
| | - Ayman Gamil Anwar Dawod
- Internal Medicine, Hepatogastroenterology and Endoscopy Department, Faculty of Medicine, Ain Shams University, Cairo 11591, Egypt;
| | - Ivana Novakovic
- Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia; (P.G.A.D.); (J.J.); (A.M.); (M.B.); (I.N.); (V.R.); (V.S.K.)
| | - Fayda I. Abdel Motaleb
- Department of Medical Biochemistry and Molecular Biology, Faculty of Medicine, Ain Shams University, Cairo 11591, Egypt;
| | - Vladimir Radlovic
- Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia; (P.G.A.D.); (J.J.); (A.M.); (M.B.); (I.N.); (V.R.); (V.S.K.)
- Pediatric Surgery Department, University Children’s Hospital, 11000 Belgrade, Serbia
| | - Vladimir S. Kostic
- Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia; (P.G.A.D.); (J.J.); (A.M.); (M.B.); (I.N.); (V.R.); (V.S.K.)
- Neurology Clinic, Clinical Center of Serbia, 11000 Belgrade, Serbia;
| | - Dejan Nikolic
- Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia; (P.G.A.D.); (J.J.); (A.M.); (M.B.); (I.N.); (V.R.); (V.S.K.)
- Physical Medicine and Rehabilitation Department, University Children’s Hospital, Tirsova 10, 11000 Belgrade, Serbia
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5
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de Boer E, Ockeloen CW, Matalonga L, Horvath R, Rodenburg RJ, Coenen MJH, Janssen M, Henssen D, Gilissen C, Steyaert W, Paramonov I, Trimouille A, Kleefstra T, Verloes A, Vissers LELM. A MT-TL1 variant identified by whole exome sequencing in an individual with intellectual disability, epilepsy, and spastic tetraparesis. Eur J Hum Genet 2021; 29:1359-1368. [PMID: 34075211 PMCID: PMC8440635 DOI: 10.1038/s41431-021-00900-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 03/25/2021] [Accepted: 04/15/2021] [Indexed: 11/09/2022] Open
Abstract
The genetic etiology of intellectual disability remains elusive in almost half of all affected individuals. Within the Solve-RD consortium, systematic re-analysis of whole exome sequencing (WES) data from unresolved cases with (syndromic) intellectual disability (n = 1,472 probands) was performed. This re-analysis included variant calling of mitochondrial DNA (mtDNA) variants, although mtDNA is not specifically targeted in WES. We identified a functionally relevant mtDNA variant in MT-TL1 (NC_012920.1:m.3291T > C; NC_012920.1:n.62T > C), at a heteroplasmy level of 22% in whole blood, in a 23-year-old male with severe intellectual disability, epilepsy, episodic headaches with emesis, spastic tetraparesis, brain abnormalities, and feeding difficulties. Targeted validation in blood and urine supported pathogenicity, with heteroplasmy levels of 23% and 58% in index, and 4% and 17% in mother, respectively. Interestingly, not all phenotypic features observed in the index have been previously linked to this MT-TL1 variant, suggesting either broadening of the m.3291T > C-associated phenotype, or presence of a co-occurring disorder. Hence, our case highlights the importance of underappreciated mtDNA variants identifiable from WES data, especially for cases with atypical mitochondrial phenotypes and their relatives in the maternal line.
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Affiliation(s)
- Elke de Boer
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Charlotte W Ockeloen
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.
| | - Leslie Matalonga
- CNAG-CRG, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Rita Horvath
- Department of Clinical Neurosciences, University of Cambridge, John Van Geest Cambridge Centre for Brain Repair, Cambridge, UK
| | - Richard J Rodenburg
- Department of Laboratory Medicine, Translational Metabolic Laboratory, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Marieke J H Coenen
- Department of Human Genetics, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Mirian Janssen
- Department of Internal Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Dylan Henssen
- Department of Medical Imaging, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Christian Gilissen
- Department of Human Genetics, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Wouter Steyaert
- Department of Human Genetics, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Ida Paramonov
- CNAG-CRG, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Aurélien Trimouille
- Service de Génétique Médicale, Centre Hospitalier Universitaire de Bordeaux, Bordeaux, France
- MRGM, Maladies Rares: Génétique et Métabolisme, lNSERM U1211, Université de Bordeaux, Bordeaux, France
| | - Tjitske Kleefstra
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Alain Verloes
- Département de Génétique, APHP Robert DEBRE University Hospital and INSERM U1141, Paris, France
| | - Lisenka E L M Vissers
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
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6
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Li SHJ, Nofal M, Parsons LR, Rabinowitz JD, Gitai Z. Monitoring mammalian mitochondrial translation with MitoRiboSeq. Nat Protoc 2021; 16:2802-2825. [PMID: 33953394 PMCID: PMC8610098 DOI: 10.1038/s41596-021-00517-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 02/05/2021] [Indexed: 02/03/2023]
Abstract
Several essential components of the electron transport chain, the major producer of ATP in mammalian cells, are encoded in the mitochondrial genome. These 13 proteins are translated within mitochondria by 'mitoribosomes'. Defective mitochondrial translation underlies multiple inborn errors of metabolism and has been implicated in pathologies such as aging, metabolic syndrome and cancer. Here, we provide a detailed ribosome profiling protocol optimized to interrogate mitochondrial translation in mammalian cells (MitoRiboSeq), wherein mitoribosome footprints are generated with micrococcal nuclease and mitoribosomes are separated from cytosolic ribosomes and other RNAs by ultracentrifugation in a single straightforward step. We highlight critical steps during library preparation and provide a step-by-step guide to data analysis accompanied by open-source bioinformatic code. Our method outputs mitoribosome footprints at single-codon resolution. Codons with high footprint densities are sites of mitoribosome stalling. We recently applied this approach to demonstrate that defects in mitochondrial serine catabolism or in mitochondrial tRNA methylation cause stalling of mitoribosomes at specific codons. Our method can be applied to study basic mitochondrial biology or to characterize abnormalities in mitochondrial translation in patients with mitochondrial disorders.
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Affiliation(s)
| | - Michel Nofal
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Chemistry, Princeton University, Princeton, NJ, USA
| | - Lance R Parsons
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
| | - Joshua D Rabinowitz
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA.
- Department of Chemistry, Princeton University, Princeton, NJ, USA.
| | - Zemer Gitai
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA.
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7
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Tarnopolsky MA, Kerkhof J, Stuart A, Bujak A, Nilsson MI, Hettinga B, May L, Rupar CA, Sadikovic B. Bone marrow-derived mitochondrial DNA has limited capacity for inter-tissue transfer in vivo. FASEB J 2020; 34:9297-9306. [PMID: 32441840 DOI: 10.1096/fj.202000463r] [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: 03/04/2020] [Revised: 04/17/2020] [Accepted: 04/26/2020] [Indexed: 12/25/2022]
Abstract
Studies have shown that mitochondrial DNA (mtDNA) can be exchanged between tissues; however, the mechanism(s) behind this phenomenon remain unclear. Exosomes and other extracellular vesicles (EVs) including microvesicles (MV) have been shown to contain mtDNA. EVs can be derived from a number of tissues; however, the source and relative proportion of EVs containing mtDNA remains unknown. We sampled whole blood and the EV fractions (exosome-enriched, MV-enriched, and apoptotic body-enriched) as well as several tissues (epithelial-cheek and urine sediment), connective (fibroblasts), and skeletal muscle in two subjects who received allogenic bone marrow transplants. Next generation sequencing of the mtDNA confirmed that all EV fractions contained mtDNA and most was derived from the donor, confirming that most of the EV fractions in the serum are bone marrow/blood cell-derived. Even after exposure to the donor mtDNA in EV fractions (and potentially free in the plasma) for years, there was little to no transfer of the donor mtDNA to the host mtDNA fraction in epithelial, connective, or skeletal muscle tissues. These data call into question the potential therapeutic use of bone marrow transplant or EV-based delivery systems for mtDNA-based disorders and establish bone marrow as the primary source of most of the mtDNA enriched EVs in serum.
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Affiliation(s)
| | - Jennifer Kerkhof
- Molecular Genetics Laboratory, Molecular Diagnostics Division, London Health Sciences Centre, Children's Health Research Institute, London, ON, Canada
| | - Alan Stuart
- Molecular Genetics Laboratory, Molecular Diagnostics Division, London Health Sciences Centre, Children's Health Research Institute, London, ON, Canada
| | - Adam Bujak
- Exerkine Corporation, McMaster University, Hamilton, ON, Canada
| | - Mats I Nilsson
- Department of Pediatrics, McMaster University, Hamilton, ON, Canada
| | - Bart Hettinga
- Exerkine Corporation, McMaster University, Hamilton, ON, Canada
| | - Linda May
- Department of Pediatrics, McMaster University, Hamilton, ON, Canada
| | - C Anthony Rupar
- Departments of Pathology and Laboratory Medicine, Pediatrics, Biochemistry and Children's Health Research Institute, Western University, London, ON, Canada
| | - Bekim Sadikovic
- Molecular Genetics Laboratory, Molecular Diagnostics Division, London Health Sciences Centre, Children's Health Research Institute, London, ON, Canada
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Bulduk BK, Kiliç HB, Bekircan-Kurt CE, Haliloğlu G, Erdem Özdamar S, Topaloğlu H, Kocaefe YÇ. A Novel Amplification-Refractory Mutation System-PCR Strategy to Screen MT-TL1 Pathogenic Variants in Patient Repositories. Genet Test Mol Biomarkers 2020; 24:165-170. [PMID: 32167396 DOI: 10.1089/gtmb.2019.0079] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Aim: Pathogenic variants within mitochondrial tRNA and rRNA genes negatively affect protein synthesis function and cause oxidative phosphorylation defects. The majority of mitochondrial cytopathies are caused by pathogenic point variants within the mitochondrial tRNA gene for leucine (MT-TL1). This study was designed to evaluate a novel amplification-refractory mutation system (ARMS)-PCR based assay to screen patient samples with a clinical diagnosis of mitochondrial cytopathies. Methods: Tissue DNA samples from 219 affected individuals were screened for the pathogenic variants m.3271T>C, m.3291Ty >C, m.3303C>T, m.3256C>T, and m.3260A>G along with the most frequent m.3243A>G mutation in the MT-TL1 gene. The assay included a "High Resolution Melt curve analysis" to enhance detection limits. The precision of the assay was verified using synthetic controls with variant heteroplasmy ratios. Results: The screening identified the second reported m.3303C>T case as well as two patients with m.3243A>G variants and a rare variant exhibiting m.3290T>C. Conclusion: ARMS-PCR is superior to Sanger sequencing for the detection of variations exhibiting low heteroplasmy. These results provide "proof of concepts" for the implementation of this application for future screening of rare mtDNA variations in sample repositories.
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Affiliation(s)
- Bengisu Kevser Bulduk
- Department of Medical Biology, Hacettepe University School of Medicine, Ankara, Turkey
| | - Hasan Basri Kiliç
- Department of Medical Biology, Hacettepe University School of Medicine, Ankara, Turkey
| | | | - Göknur Haliloğlu
- Department of Pediatric Neurology, Hacettepe University School of Medicine, Ankara, Turkey
| | - Sevim Erdem Özdamar
- Department of Neurology, Hacettepe University School of Medicine, Ankara, Turkey
| | - Haluk Topaloğlu
- Department of Pediatric Neurology, Hacettepe University School of Medicine, Ankara, Turkey
| | - Y Çetin Kocaefe
- Department of Medical Biology, Hacettepe University School of Medicine, Ankara, Turkey
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Patient-specific neural progenitor cells derived from induced pluripotent stem cells offer a promise of good models for mitochondrial disease. Cell Tissue Res 2020; 380:15-30. [PMID: 31925525 DOI: 10.1007/s00441-019-03164-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 12/19/2019] [Indexed: 02/06/2023]
Abstract
Mitochondria are the primary generators of ATP in eukaryotic cells through the process of oxidative phosphorylation. Mitochondria are also involved in several other important cellular functions including regulation of intracellular Ca2+, cell signaling and apoptosis. Mitochondrial dysfunction causes disease and since it is not possible to perform repeated studies in humans, models are essential to enable us to investigate the mechanisms involved. Recently, the discovery of induced pluripotent stem cells (iPSCs), made by reprogramming adult somatic cells (Takahashi and Yamanaka 2006; Yamanaka and Blau 2010), has provided a unique opportunity for studying aspects of disease mechanisms in patient-specific cells and tissues. Reprogramming cells to neuronal lineage such as neural progenitor cells (NPCs) generated from the neural induction of reprogrammed iPSCs can thus provide a useful model for investigating neurological disease mechanisms including those caused by mitochondrial dysfunction. In addition, NPCs display a huge clinical potential in drug screening and therapeutics.
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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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Kelland E, Rupar C, Prasad AN, Tay K, Downie A, Prasad C. Response to: Letter to the Editor Regarding: The Expanding Phenotype of MELAS Caused by the m.3291 T > C tRNA Mutation E Kelland, C. A. Rupar, Asuri N. Prasad, K. Y. Tay, A. Downie and C. Prasad (1) by Josef Finsterer, MD, PhD [1], Sinda Zarrouk-Mahjoub, PhD [2] [1] Krankenanstalt Rudolfstiftung, Vienna [2] Genomics Platform, Pasteur Institute of Tunis, Tunisia. Mol Genet Metab Rep 2016; 8:41-2. [PMID: 27493879 PMCID: PMC4963257 DOI: 10.1016/j.ymgmr.2016.07.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 07/07/2016] [Indexed: 11/18/2022] Open
Affiliation(s)
- E. Kelland
- Department of Pediatrics, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
| | - C.A. Rupar
- Department of Pediatrics, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
- Department of Biochemistry, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
- Department of Pathology and Laboratory Medicine, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
- Children's Health Research Institute, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
- Western University, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
| | - Asuri N. Prasad
- Department of Pediatrics, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
- Department of Neurology, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
- Children's Health Research Institute, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
- Western University, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
| | - K.Y. Tay
- Medical Imaging, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
- Western University, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
| | - A. Downie
- Western University, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
- Paediatric Psychology, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
| | - C. Prasad
- Department of Pediatrics, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
- Children's Health Research Institute, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
- Western University, Children's Hospital London Health Sciences Centre, London, Ontario, Canada
- Corresponding author at: Department of Pediatrics, Children's Hospital London Health Sciences Centre, London, Ontario, Canada.Department of PediatricsChildren's Hospital London Health Sciences CentreLondonOntarioCanada
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12
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Response to: Letter to the Editor regarding: The expanding phenotype of MELAS caused by the m.3291T>C tRNA mutation E. Kelland, C.A. Rupar, Asuri N. Prasad, A. Downie and C. Prasad (1) by Josef Finsterer, MD, PhD [1], Sinda Zarrouk-Mahjoub, PhD [2]. Mol Genet Metab Rep 2016; 7:96-7. [PMID: 27331010 PMCID: PMC4901176 DOI: 10.1016/j.ymgmr.2016.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 05/09/2016] [Indexed: 11/23/2022] Open
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Finsterer J, Zarrouk-Mahjoub S. MELAS syndrome due to the m.3291T > C mutation. Mol Genet Metab Rep 2016; 7:50. [PMID: 27134825 PMCID: PMC4834681 DOI: 10.1016/j.ymgmr.2016.03.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 03/30/2016] [Indexed: 11/19/2022] Open
Affiliation(s)
- Josef Finsterer
- Krankenanstalt Rudolfstiftung, Vienna, Austria
- Corresponding author at: Postfach 20, 1180 Vienna, Austria.Postfach 20Vienna1180Austria
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