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Long read mitochondrial genome sequencing using Cas9-guided adaptor ligation. Mitochondrion 2022; 65:176-183. [PMID: 35787470 DOI: 10.1016/j.mito.2022.06.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 05/11/2022] [Accepted: 06/19/2022] [Indexed: 11/21/2022]
Abstract
The mitochondrial genome (mtDNA) is an important source of disease-causing genetic variability, but existing sequencing methods limit understanding, precluding phased measurement of mutations and clear detection of large sporadic deletions. We adapted a method for amplification-free sequence enrichment using Cas9 cleavage to obtain full length nanopore reads of mtDNA. We then utilized the long reads to phase mutations in a patient with an mtDNA-linked syndrome and demonstrated that this method can map age-induced mtDNA deletions. We believe this method will offer deeper insight into our understanding of mtDNA variation.
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2
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Shayota BJ, Soler-Alfonso C, Bekheirnia MR, Mizerik E, Boyer SW, Xiao R, Yang Y, Elsea SH, Scaglia F. Case report and novel treatment of an autosomal recessive Leigh syndrome caused by short-chain enoyl-CoA hydratase deficiency. Am J Med Genet A 2019; 179:803-807. [PMID: 30848071 PMCID: PMC9873404 DOI: 10.1002/ajmg.a.61074] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 12/18/2018] [Accepted: 12/21/2018] [Indexed: 01/26/2023]
Abstract
Short chain enoyl-CoA hydratase (SCEH) deficiency leads to a severe form of autosomal recessive Leigh syndrome with inevitable neurological decline and early mortality. SCEH is most notably involved in valine catabolism, a deficiency of which results in various metabolic alterations, including increased levels of the highly reactive metabolite 2-methacrylyl-CoA. With no proven treatments available to date, it has been speculated that patients may respond to a valine restricted diet and/or N-acetylcysteine supplementation, as suggested by early studies of a very similar inborn error of metabolism, 3-hydroxyisobutyryl-CoA hydrolase deficiency. We describe a patient with typical Leigh syndrome clinical findings and identified compound heterozygous variants in ECSH1. Valine-restricted diet was initiated at 6 months of age and N-acetylcysteine supplementation at 9 months with subsequent improvement in growth and slow progress in developmental milestones. However, at 15 months, the patient aspirated during a breakthrough seizure from which he did not recover and died soon after from related complications. This report highlights some of the challenges that remain in the management and treatment of SCEH deficiency, while demonstrating that a valine restricted diet and N-acetylcysteine can be safely administered with the potential for clinical improvement.
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Affiliation(s)
- Brian J. Shayota
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas,Texas Children’s Hospital, Houston, Texas
| | - Claudia Soler-Alfonso
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas,Texas Children’s Hospital, Houston, Texas
| | - Mir Reza Bekheirnia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas,Texas Children’s Hospital, Houston, Texas,Department of Pediatrics, Renal Section, Baylor College of Medicine, Houston, Texas
| | - Elizabeth Mizerik
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas,Texas Children’s Hospital, Houston, Texas
| | - Suzy W. Boyer
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas,Texas Children’s Hospital, Houston, Texas
| | - Rui Xiao
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas,Baylor Genetics, Houston, Texas
| | - Yaping Yang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas,Baylor Genetics, Houston, Texas
| | - Sarah H. Elsea
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas,Baylor Genetics, Houston, Texas
| | - Fernando Scaglia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas,Texas Children’s Hospital, Houston, Texas,BCM-CUHK Center of Medical Genetics, Prince of Wales Hospital, Sha Tin, Hong Kong SAR
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3
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Uittenbogaard M, Wang H, Zhang VW, Wong LJ, Brantner CA, Gropman A, Chiaramello A. The nuclear background influences the penetrance of the near-homoplasmic m.1630 A > G MELAS variant in a symptomatic proband and asymptomatic mother. Mol Genet Metab 2019; 126:429-438. [PMID: 30709774 PMCID: PMC6773428 DOI: 10.1016/j.ymgme.2019.01.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 01/23/2019] [Accepted: 01/24/2019] [Indexed: 01/17/2023]
Abstract
In this study, we report the metabolic consequences of the m.1630 A > G variant in fibroblasts from the symptomatic proband affected with the mitochondrial encephalomyopathy lactic acidosis and stroke-like episode Syndrome and her asymptomatic mother. By long-range PCR followed by massively parallel sequencing of the mitochondrial genome, we accurately measured heteroplasmy in fibroblasts from the proband (89.6%) and her mother (94.8%). Using complementary experimental approaches, we show a functional correlation between manifestation of clinical symptoms and bioenergetic potential. Our mitochondrial morphometric analysis reveals a link between defects of mitochondrial cristae ultrastructure and symptomatic status. Despite near-homoplasmic level of the m.1630A > G variant, the mother's fibroblasts have a normal OXPHOS metabolism, which stands in contrast to the severely impaired OXPHOS response of the proband's fibroblasts. The proband's fibroblasts also exhibit glycolysis at near constitutive levels resulting in a stunted compensatory glycolytic response to offset the severe OXPHOS defect. Whole exome sequencing reveals the presence of a heterozygous nonsense VARS2 variant (p.R334X) exclusively in the proband, which removes two thirds of the VARS2 protein containing key domains interacting with the mt-tRNAval and may play a role in modulating the penetrance of the m.1630A > G variant despite similar near homoplasmic levels. Our transmission electron microscopy study also shows unexpected ultrastructural changes of chromatin suggestive of differential epigenomic regulation between the proband and her mother that may explain the differential OXPHOS response between the proband and her mother. Future study will decipher by which molecular mechanisms the nuclear background influences the penetrance of the m.1630 A > G variant causing MELAS.
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Affiliation(s)
- Martine Uittenbogaard
- Department of Anatomy and Cell Biology, George Washington University School of Medicine and Health Sciences, Washington, DC 20037, USA
| | - Hao Wang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Victor Wei Zhang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; AmCare Genomics Laboratory, GuangZhou 510300, China
| | - Lee-Jun Wong
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Christine A Brantner
- GW Nanofabrication and Imaging Center, Office of the Vice President for Research, George Washington University, Washington, DC 20052, USA
| | - Andrea Gropman
- Children's National Medical Center, Division of Neurogenetics and Developmental Pediatrics, Washington, DC 20010, USA
| | - Anne Chiaramello
- Department of Anatomy and Cell Biology, George Washington University School of Medicine and Health Sciences, Washington, DC 20037, USA.
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4
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De Silva D, Tu YT, Amunts A, Fontanesi F, Barrientos A. Mitochondrial ribosome assembly in health and disease. Cell Cycle 2015; 14:2226-50. [PMID: 26030272 DOI: 10.1080/15384101.2015.1053672] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The ribosome is a structurally and functionally conserved macromolecular machine universally responsible for catalyzing protein synthesis. Within eukaryotic cells, mitochondria contain their own ribosomes (mitoribosomes), which synthesize a handful of proteins, all essential for the biogenesis of the oxidative phosphorylation system. High-resolution cryo-EM structures of the yeast, porcine and human mitoribosomal subunits and of the entire human mitoribosome have uncovered a wealth of new information to illustrate their evolutionary divergence from their bacterial ancestors and their adaptation to synthesis of highly hydrophobic membrane proteins. With such structural data becoming available, one of the most important remaining questions is that of the mitoribosome assembly pathway and factors involved. The regulation of mitoribosome biogenesis is paramount to mitochondrial respiration, and thus to cell viability, growth and differentiation. Moreover, mutations affecting the rRNA and protein components produce severe human mitochondrial disorders. Despite its biological and biomedical significance, knowledge on mitoribosome biogenesis and its deviations from the much-studied bacterial ribosome assembly processes is scarce, especially the order of rRNA processing and assembly events and the regulatory factors required to achieve fully functional particles. This article focuses on summarizing the current available information on mitoribosome assembly pathway, factors that form the mitoribosome assembly machinery, and the effect of defective mitoribosome assembly on human health.
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Affiliation(s)
- Dasmanthie De Silva
- a Department of Biochemistry and Molecular Biology ; University of Miami Miller School of Medicine ; Miami , FL USA
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5
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Brown A, Amunts A, Bai XC, Sugimoto Y, Edwards PC, Murshudov G, Scheres SHW, Ramakrishnan V. Structure of the large ribosomal subunit from human mitochondria. Science 2014; 346:718-722. [PMID: 25278503 DOI: 10.1126/science.1258026] [Citation(s) in RCA: 229] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Human mitochondrial ribosomes are highly divergent from all other known ribosomes and are specialized to exclusively translate membrane proteins. They are linked with hereditary mitochondrial diseases and are often the unintended targets of various clinically useful antibiotics. Using single-particle cryogenic electron microscopy, we have determined the structure of its large subunit to 3.4 angstrom resolution, revealing 48 proteins, 21 of which are specific to mitochondria. The structure unveils an adaptation of the exit tunnel for hydrophobic nascent peptides, extensive remodeling of the central protuberance, including recruitment of mitochondrial valine transfer RNA (tRNA(Val)) to play an integral structural role, and changes in the tRNA binding sites related to the unusual characteristics of mitochondrial tRNAs.
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Affiliation(s)
- Alan Brown
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Alexey Amunts
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Xiao-Chen Bai
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Yoichiro Sugimoto
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Patricia C Edwards
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Garib Murshudov
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Sjors H W Scheres
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - V Ramakrishnan
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
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6
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Villar P, Bretón B, García-Pavía P, González-Páramos C, Blázquez A, Gómez-Bueno M, García-Silva T, García-Consuegra I, Martín MA, Garesse R, Bornstein B, Gallardo ME. Cardiac Dysfunction in Mitochondrial Disease. Circ J 2013; 77:2799-806. [DOI: 10.1253/circj.cj-13-0557] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Pedro Villar
- Biochemistry Unit, “Hospital Universitario Puerta de Hierro”
- Research Institute “Puerta de Hierro” Majadahonda (IDIPHIM)
| | - Begoña Bretón
- Biochemistry Unit, “Hospital Universitario Puerta de Hierro”
- Research Institute “Puerta de Hierro” Majadahonda (IDIPHIM)
| | - Pablo García-Pavía
- Cardiology Unit, “Hospital Universitario Puerta de Hierro”
- Net of Clinical and Basic Research in Heart Failure (REDINSCOR)
- Research Institute “Puerta de Hierro” Majadahonda (IDIPHIM)
| | | | - Alberto Blázquez
- Rare Diseases Biomedical Research Centre (CIBERER)
- Health Research Institute “Hospital 12 de Octubre (i+12)”
- Laboratory of Mitochondrial Diseases, Research Centre
| | - Manuel Gómez-Bueno
- Cardiology Unit, “Hospital Universitario Puerta de Hierro”
- Net of Clinical and Basic Research in Heart Failure (REDINSCOR)
- Research Institute “Puerta de Hierro” Majadahonda (IDIPHIM)
| | - Teresa García-Silva
- Health Research Institute “Hospital 12 de Octubre (i+12)”
- Pediatrics Unit, “Hospital Universitario 12 de Octubre”
| | - Ines García-Consuegra
- Health Research Institute “Hospital 12 de Octubre (i+12)”
- Laboratory of Mitochondrial Diseases, Research Centre
| | - Miguel Angel Martín
- Rare Diseases Biomedical Research Centre (CIBERER)
- Health Research Institute “Hospital 12 de Octubre (i+12)”
- Laboratory of Mitochondrial Diseases, Research Centre
| | - Rafael Garesse
- Biochemistry Departament, Biomedical Research Institute “Alberto Sols”, Medicine College, UAM-CSIC
- Rare Diseases Biomedical Research Centre (CIBERER)
- Health Research Institute “Hospital 12 de Octubre (i+12)”
| | - Belen Bornstein
- Biochemistry Departament, Biomedical Research Institute “Alberto Sols”, Medicine College, UAM-CSIC
- Rare Diseases Biomedical Research Centre (CIBERER)
- Health Research Institute “Hospital 12 de Octubre (i+12)”
- Biochemistry Unit, “Hospital Universitario Puerta de Hierro”
- Research Institute “Puerta de Hierro” Majadahonda (IDIPHIM)
| | - M. Esther Gallardo
- Biochemistry Departament, Biomedical Research Institute “Alberto Sols”, Medicine College, UAM-CSIC
- Rare Diseases Biomedical Research Centre (CIBERER)
- Health Research Institute “Hospital 12 de Octubre (i+12)”
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7
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Tzoulis C, Bindoff LA. Acute mitochondrial encephalopathy reflects neuronal energy failure irrespective of which genome the genetic defect affects. Brain 2012; 135:3627-34. [PMID: 23065482 DOI: 10.1093/brain/aws223] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mitochondrial dysfunction and disease may arise as a result of mutations in either the mitochondrial genome itself or nuclear encoded genes involved in mitochondrial homeostasis and function. Irrespective of which genome is affected, mitochondrial encephalopathies share clinical and biochemical features suggesting common pathophysiological pathways. Two common paradigms of mitochondrial encephalopathy are mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes caused by maternally transmitted mutations of mitochondrial DNA and mitochondrial spinocerebellar ataxia and epilepsy caused by recessively inherited mutations of the nuclear-encoded DNA polymerase gamma, which replicates and repairs the mitochondrial genome. We studied and compared the disease mechanisms involved in these two syndromes. Despite having different genetic origins, their pathophysiological pathways converge on one critical event, damage to the respiratory chain leading to insufficient energy to maintain cellular homeostasis. In the central nervous system, this appears to cause selective neuronal damage leading to the development of lesions that mimic ischaemic damage, but which lack evidence of decreased tissue perfusion. Although these stroke-like lesions may expand or regress dynamically, the critical factor that dictates prognosis is the presence of epilepsy. Epileptic seizures increase the energy requirements of the metabolically already compromised neurons establishing a vicious cycle resulting in worsening energy failure and neuronal death. We believe that it is this cycle of events that determines outcome and which provides us with a mechanistic structure to understand the pathophysiology of acute mitochondrial encephalopathies and plan future treatments.
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Affiliation(s)
- Charalampos Tzoulis
- Department of Neurology, Haukeland University Hospital, 5021 Bergen, Norway.
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8
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Arredondo JJ, Gallardo ME, García-Pavía P, Domingo V, Bretón B, García-Silva MT, Sedano MJ, Martín MA, Arenas J, Cervera M, Garesse R, Bornstein B. Mitochondrial tRNA valine as a recurrent target for mutations involved in mitochondrial cardiomyopathies. Mitochondrion 2011; 12:357-62. [PMID: 21986556 DOI: 10.1016/j.mito.2011.09.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Revised: 09/15/2011] [Accepted: 09/20/2011] [Indexed: 11/28/2022]
Abstract
The aim of this study was to identify the genetic defect in two patients having cardiac dysfunction accompanied by neurological symptoms, and in one case MRI evidence of cortical and cerebellar atrophy with hyperintensities in the basal ganglia. Muscle biopsies from each patient revealed single and combined mitochondrial respiratory chain deficiency. The complete mtDNA sequencing of both patients revealed two transitions in the mitochondrial tRNA(Val) gene (MT-TV) (m.1628C>T in Patient 1, and m.1644G>A in Patient 2). The functional and molecular analyses reported here suggest that the MT-TV gene should be routinely considered in the diagnosis of mitochondrial cardiomyopathies.
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Affiliation(s)
- Juan J Arredondo
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Facultad de Medicina, Universidad Autónoma de Madrid, Spain
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9
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Say RE, Whittaker RG, Turnbull HE, McFarland R, Taylor RW, Turnbull DM. Mitochondrial disease in pregnancy: a systematic review. Obstet Med 2011; 4:90-4. [PMID: 27579099 PMCID: PMC4989604 DOI: 10.1258/om.2011.110008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/22/2011] [Indexed: 01/08/2023] Open
Abstract
Mitochondrial diseases are heterogeneous in clinical presentation and genotype. The incidence of known pathogenic mitochondrial DNA mutations in the general population is 1 in 500. Little is known about the implications of pregnancy for women with mitochondrial disease. We undertook a systematic review of the literature on mitochondrial disease in pregnancy. Ten case reports were identified. The most common complications were threatened preterm labour (5 women) and preeclampsia (4 women). Two women experienced magnesium sulphate toxicity. Pregnancy had a varied effect on mitochondrial disease with some women being asymptomatic; others developing mild symptoms such as exercise intolerance or muscle weakness which resolved postnatally; and others developed more serious, persistent symptoms such as symptomatic Wolff-Parkinson-White syndrome, persistent paraesthesia and focal segmental glomerulosclerosis. Women with mitochondrial disease appear to be at increased risk of complications during pregnancy and labour but further prospective cohort studies are needed.
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Affiliation(s)
- R E Say
- Institute of Cellular Medicine
| | - R G Whittaker
- Mitochondrial Research Group, Newcastle University, Newcastle upon Tyne, UK
| | - H E Turnbull
- Mitochondrial Research Group, Newcastle University, Newcastle upon Tyne, UK
| | - R McFarland
- Mitochondrial Research Group, Newcastle University, Newcastle upon Tyne, UK
| | - R W Taylor
- Mitochondrial Research Group, Newcastle University, Newcastle upon Tyne, UK
| | - D M Turnbull
- Mitochondrial Research Group, Newcastle University, Newcastle upon Tyne, UK
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10
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Mezghani N, Mnif M, Kacem M, Mkaouar-Rebai E, Hadj Salem I, Kallel N, charfi N, Abid M, fakhfakh F. A whole mitochondrial genome screening in a MELAS patient: A novel mitochondrial tRNAVal mutation. Biochem Biophys Res Commun 2011; 407:747-52. [DOI: 10.1016/j.bbrc.2011.03.094] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Accepted: 03/18/2011] [Indexed: 10/18/2022]
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11
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Horváth R, Bender A, Abicht A, Holinski-Feder E, Czermin B, Trips T, Schneiderat P, Lochmüller H, Klopstock T. Heteroplasmic mutation in the anticodon-stem of mitochondrial tRNA(Val) causing MNGIE-like gastrointestinal dysmotility and cachexia. J Neurol 2009; 256:810-5. [PMID: 19252805 DOI: 10.1007/s00415-009-5023-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Revised: 12/28/2008] [Accepted: 01/07/2009] [Indexed: 12/20/2022]
Abstract
While mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is typically associated with mutations in the nuclear gene encoding for thymidine phosphorylase (ECGF1, TYMP), a similar clinical phenotype was described in patients carrying mutations in the nuclear-encoded polymerase gamma (POLG1) as well as a few mitochondrial tRNA genes. Here we report a novel mutation in the mitochondrial tRNA(Val) (MTTV) gene in a girl presenting with clinical symptoms of MNGIE-like gastrointestinal dysmotility and cachexia. Clinical, histological, biochemical and single cell investigations were performed. The heteroplasmic m.1630A>G mutation was detected in the mitochondrial tRNA(Val) (MTTV) gene in the patient's muscle, blood leukocytes and myoblasts, as well as in blood DNA of the unaffected mother. We provide clinical, biochemical, histological, and molecular genetic evidence on the single cell level for the pathogenicity of this mutation. Our finding adds to the genetic heterogeneity of MNGIE-like gastrointestinal symptoms and highlights the importance of a thorough genetic workup in case of suspected mitochondrial disease.
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Affiliation(s)
- Rita Horváth
- Friedrich-Baur-Institute, Department of Neurology, Ludwig-Maximilians-University, Ziemssenstr. 1a, Munich 80336, Germany.
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12
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Abstract
In 1998, Wallace et al. (Science 1988; 242: 1427-30) published evidence that the mutation m.11778G>A was responsible for causing Leber's hereditary optic neuropathy. This was the first account of a mitochondrial DNA mutation being irrefutably linked with a human disease and was swiftly followed by a report from Holt et al. (Nature 1988; 331: 717-9) identifying deletions in mitochondrial DNA as a cause for myopathy. During the subsequent 20 years there has been an exponential growth in 'mitochondrial medicine', with clinical, biochemical and genetic characterizations of a wide range of mitochondrial diseases and evidence implicating mitochondria in a host of many other clinical conditions including ageing, neurodegenerative illness and cancer. In this review we shall focus on the diagnosis and management of mitochondrial diseases that lead directly or indirectly to disruption of the process of oxidative phosphorylation.
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Affiliation(s)
- R McFarland
- Mitochondrial Research Group, School of Neurology, Neurobiology and Psychiatry, Newcastle University, Newcastle-upon-Tyne, UK.
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13
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The role of complex I genes in MELAS: a novel heteroplasmic mutation 3380G>A in ND1 of mtDNA. Neuromuscul Disord 2008; 18:553-6. [PMID: 18590963 DOI: 10.1016/j.nmd.2008.05.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2007] [Revised: 03/17/2008] [Accepted: 05/06/2008] [Indexed: 11/20/2022]
Abstract
While Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes (MELAS) is typically associated with mutations in the mitochondrial tRNA(Leu) gene, mutations in complex I subunit genes of the mtDNA have emerged as a second significant cause. Here we report a novel mutation in the mitochondrial complex I subunit gene ND1 in a patient with late-onset MELAS. The 3380G>A mutation shows very good evidence of pathogenicity as it is heteroplasmic, undetectable in controls, alters a highly conserved amino acid, and is more abundant in ragged-red than in normal muscle fibers. These findings support the significant role of complex I mutations in MELAS.
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14
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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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15
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Tanji K, Kaufmann P, Naini AB, Lu J, Parsons TC, Wang D, Willey JZ, Shanske S, Hirano M, Bonilla E, Khandji A, Dimauro S, Rowland LP. A novel tRNA(Val) mitochondrial DNA mutation causing MELAS. J Neurol Sci 2008; 270:23-7. [PMID: 18314141 DOI: 10.1016/j.jns.2008.01.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Revised: 01/15/2008] [Accepted: 01/18/2008] [Indexed: 11/29/2022]
Abstract
Mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS) is the most common mitochondrial disease due to mitochondrial DNA (mtDNA) mutations. At least 15 distinct mtDNA mutations have been associated with MELAS, and about 80% of the cases are caused by the A3243G tRNA(Leu(UUR)) gene mutation. We report here a novel tRNA(Val) mutation in a 37-year-old woman with manifestations of MELAS, and compare her clinicopathological phenotype with other rare cases associated tRNA(Val) mutations.
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Affiliation(s)
- Kurenai Tanji
- Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
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16
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Abstract
Mitochondria are ubiquitous organelles that are intimately involved in many cellular processes, but whose principal task is to provide the energy necessary for normal cell functioning and maintenance. Disruption of this energy supply can have devastating consequences for the cell, organ, and individual. Over the last two decades, mutations in both mitochondrial DNA (mtDNA) and nuclear DNA have been identified as causative in a number of well-characterized clinical syndromes, although for mtDNA mutations in particular, this relationship between genotype and phenotype is often not straightforward. Despite this, a number of epidemiological studies have been undertaken to assess the prevalence of mtDNA mutations and these have highlighted the impact that mtDNA disease has on both the community and individual families. Although there has been considerable improvement in the diagnosis of mitochondrial disorders, disappointingly this has not been matched by developments toward effective treatment. Nevertheless, our understanding of mitochondrial biology is gathering pace and progress in this area will be crucial to devising future treatment strategies. In addition to mitochondrial disease, evidence for a central role of mitochondria in other processes, such as aging and neurodegeneration, is slowly accumulating, although their role in cancer remains controversial. In this chapter, we discuss these issues and offer our own views based on our cumulative experience of investigating and managing these diseases over the last 20 years.
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Affiliation(s)
- R McFarland
- Mitochondrial Research Group, School of Neurology, Neurobiology, and Psychiatry, The Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4HH, United Kingdom
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17
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Blakely EL, Poulton J, Pike M, Wojnarowska F, Turnbull DM, McFarland R, Taylor RW. Childhood neurological presentation of a novel mitochondrial tRNA(Val) gene mutation. J Neurol Sci 2005; 225:99-103. [PMID: 15465092 DOI: 10.1016/j.jns.2004.07.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2004] [Revised: 06/29/2004] [Accepted: 07/02/2004] [Indexed: 11/26/2022]
Abstract
We describe a young girl with a novel 1659T>C mutation in the tRNA(Val) gene of mitochondrial DNA (mtDNA) who presented with learning difficulties, hemiplegia, and a movement disorder, together with a raised cerebrospinal fluid (CSF) lactate. The mutation, which was present at high levels of heteroplasmy in patient tissues, interrupts a conserved Watson-Crick basepair in the TPsiC stem and has not previously been described in controls. This report further confirms the frequent association of mitochondrial tRNA mutation with neurological presentations, even in paediatric cases.
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Affiliation(s)
- Emma L Blakely
- Mitochondrial Research Group, School of Neurology, Neurobiology, and Psychiatry, The Medical School, University of Newcastle upon Tyne, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
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Thambisetty M, Newman NJ, Glass JD, Frankel MR. A practical approach to the diagnosis and management of MELAS: case report and review. Neurologist 2002; 8:302-12. [PMID: 12803677 DOI: 10.1097/00127893-200209000-00003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Mitochondrial encephalomyopathy, lactic acidosis with stroke-like episodes (MELAS) is a mitochondrial disorder and an important diagnostic consideration in the young patient with nonhemorrhagic stroke. Its presentation is varied and diagnosis is based on early recognition of the clinical features and correct interpretation of laboratory and radiologic studies. SUMMARY In this article, we report a patient with MELAS and review the clinical, laboratory, and neuroradiologic features of the condition. In the young patient with multiple stroke-like episodes in different vascular territories and neuroradiologic features of transient abnormalities in varying regions, laboratory testing for MELAS must be performed. The presence of ragged red fibers in skeletal muscle and biochemical demonstration of defects in mitochondrial respiratory enzymes strongly support the diagnosis. Molecular genetic testing for abnormalities in mitochondrial DNA will confirm the diagnosis. The importance of a thorough assessment of family history is also emphasized. The basic principles of mitochondrial genetics and the common point mutations and rearrangements of mitochondrial DNA associated with MELAS are reviewed. Although treatment options are limited, several therapeutic agents have been studied. CONCLUSIONS The diagnosis of MELAS should be considered in the young patient with stroke, especially when accompanied by other clinical features such as seizures, encephalopathy, and muscle weakness. Laboratory evaluation can provide an accurate diagnosis, especially when the appropriate mitochondrial DNA studies are performed. Genetic counseling should be provided to patients with MELAS associated with mitochondrial DNA point mutations. Better understanding of the molecular basis of the condition may result in the development of effective treatment strategies.
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Affiliation(s)
- Madhav Thambisetty
- Department of Neurology, Emory University School of Medicine, Atlanta, Georgia, USA
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19
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Weinstock A, Giglio P, Cohen ME, Bakshi R, Januario J, Balos L. Diffuse magnetic resonance imaging white-matter changes in a 15-year-old boy with mitochondrial encephalomyopathy. J Child Neurol 2002; 17:47-9. [PMID: 11913571 DOI: 10.1177/088307380201700112] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We report a 15-year-old boy who presented with recurrent headaches associated with numbness, confusion, and speech difficulty. Brain magnetic resonance imaging (MRI) revealed diffuse bilateral white-matter hyperintensity on fluid-attenuated inversion-recovery and T2-weighted images in the internal capsule, periventricular and subcortical white matter, base of the pons, and middle cerebellar peduncles. Lesions were isointense on T1-weighted images and nonenhancing. Muscle biopsy showed changes consistent with a mitochondrial myopathy. Mitochondrial respiratory chain enzyme activity analysis revealed a significant reduction in complex II activity. Genetic testing was negative. We conclude that mitochondrial encephalomyopathy may present with unusual diffuse supratentorial and infratentorial white-matter changes on MRI.
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Affiliation(s)
- Arie Weinstock
- Department of Neurology, Children's Hospital of Buffalo, State University of New York at Buffalo, 14222, USA
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20
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Abstract
The mitochondrial encephalomyopathies are a genetically heterogeneous group of disorders associated with impaired oxidative phosphorylation. Patients may exhibit a wide range of clinical symptoms and experience significant morbidity and mortality. There is currently no curative treatment. At present the majority of genetically defined mitochondrial encephalomyopathies are caused by mutations in mitochondrial DNA. The underlying molecular mechanisms and the complex relationship between genotype and phenotype in these mitochondrial DNA diseases remain only partially understood. We describe the key features of mitochondrial DNA genetics and outline some of the common disease phenotypes associated with mtDNA defects. A classification of pathogenic mitochondrial DNA point mutations which may have therapeutic implications is outlined.
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Affiliation(s)
- T Pulkes
- Muscle and Neurogenetics Sections, University Department of Clinical Neurology, Institute of Neurology, University College London, Queen Square, WC1N 3BG, London, UK
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21
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De Coo IFM, Renier WO, Ruitenbeek W, Ter Laak HJ, Bakker M, Sch�gger H, Van Oost BA, Smeets HJM. A 4-base pair deletion in the mitochondrial cytochromeb gene associated with parkinsonism/MELAS overlap syndrome. Ann Neurol 2001. [DOI: 10.1002/1531-8249(199901)45:1<130::aid-art21>3.0.co;2-z] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Morgan-Hughes JA, Hanna MG. Mitochondrial encephalomyopathies: the enigma of genotype versus phenotype. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1410:125-45. [PMID: 10076022 DOI: 10.1016/s0005-2728(98)00162-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Over the past decade a large body of evidence has accumulated implicating defects of human mitochondrial DNA in the pathogenesis of a group of disorders known collectively as the mitochondrial encephalomyopathies. Although impaired oxidative phosphorylation is likely to represent the final common pathway leading to cellular dysfunction in these diseases, fundamental issues still remain elusive. Perhaps the most challenging of these is to understand the mechanisms which underlie the complex relationship between genotype and phenotype. Here we examine this relationship and discuss some of the factors which are likely to be involved.
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Affiliation(s)
- J A Morgan-Hughes
- University Department of Clinical Neurology, Institute of Neurology, Queen Square, London WC1H 3BG, UK
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