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Learning from Yeast about Mitochondrial Carriers. Microorganisms 2021; 9:microorganisms9102044. [PMID: 34683364 PMCID: PMC8539049 DOI: 10.3390/microorganisms9102044] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 09/14/2021] [Accepted: 09/23/2021] [Indexed: 12/23/2022] Open
Abstract
Mitochondria are organelles that play an important role in both energetic and synthetic metabolism of eukaryotic cells. The flow of metabolites between the cytosol and mitochondrial matrix is controlled by a set of highly selective carrier proteins localised in the inner mitochondrial membrane. As defects in the transport of these molecules may affect cell metabolism, mutations in genes encoding for mitochondrial carriers are involved in numerous human diseases. Yeast Saccharomyces cerevisiae is a traditional model organism with unprecedented impact on our understanding of many fundamental processes in eukaryotic cells. As such, the yeast is also exceptionally well suited for investigation of mitochondrial carriers. This article reviews the advantages of using yeast to study mitochondrial carriers with the focus on addressing the involvement of these carriers in human diseases.
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Carreño-Gago L, Blázquez-Bermejo C, Díaz-Manera J, Cámara Y, Gallardo E, Martí R, Torres-Torronteras J, García-Arumí E. Identification and Characterization of New RNASEH1 Mutations Associated With PEO Syndrome and Multiple Mitochondrial DNA Deletions. Front Genet 2019; 10:576. [PMID: 31258551 PMCID: PMC6588129 DOI: 10.3389/fgene.2019.00576] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 05/31/2019] [Indexed: 12/13/2022] Open
Abstract
Mitochondrial DNA (mtDNA) depletion and deletion syndrome encompasses a group of disorders caused by mutations in genes involved in mtDNA replication and maintenance. The clinical phenotype ranges from fatal infantile hepatocerebral forms to mild adult onset progressive external ophthalmoplegia (PEO). We report the case of a patient with PEO and multiple mtDNA deletions, with two new homozygous mutations in RNASEH1. The first mutation (c.487T>C) is located in the same catalytic domain as the four previously reported mutations, and the second (c.258_260del) is located in the connection domain, where no mutations have been reported. In silico study of the mutations predicted only the first mutation as pathogenic, but functional studies showed that both mutations cause loss of ribonuclease H1 activity. mtDNA replication dysfunction was demonstrated in patient fibroblasts, which were unable to recover normal mtDNA copy number after ethidium bromide-induced mtDNA depletion. Our results demonstrate the pathogenicity of two new RNASEH1 variants found in a patient with PEO syndrome, multiple deletions, and mild mitochondrial myopathy.
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Affiliation(s)
- Lidia Carreño-Gago
- Departament de Patologia Mitocondrial i Neuromuscular, Hospital Universitari Vall d'Hebron Institut de Recerca (VHIR), Universitat Autònoma de Barcelona, Barcelona, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain
| | - Cora Blázquez-Bermejo
- Departament de Patologia Mitocondrial i Neuromuscular, Hospital Universitari Vall d'Hebron Institut de Recerca (VHIR), Universitat Autònoma de Barcelona, Barcelona, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain
| | - Jordi Díaz-Manera
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain.,Servei de Neurologia, Malalties Neuromusculars, Hospital de la Santa Creu i Sant Pau i Institut de Recerca de HSCSP, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Yolanda Cámara
- Departament de Patologia Mitocondrial i Neuromuscular, Hospital Universitari Vall d'Hebron Institut de Recerca (VHIR), Universitat Autònoma de Barcelona, Barcelona, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain
| | - Eduard Gallardo
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain.,Servei de Neurologia, Malalties Neuromusculars, Hospital de la Santa Creu i Sant Pau i Institut de Recerca de HSCSP, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Ramon Martí
- Departament de Patologia Mitocondrial i Neuromuscular, Hospital Universitari Vall d'Hebron Institut de Recerca (VHIR), Universitat Autònoma de Barcelona, Barcelona, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain
| | - Javier Torres-Torronteras
- Departament de Patologia Mitocondrial i Neuromuscular, Hospital Universitari Vall d'Hebron Institut de Recerca (VHIR), Universitat Autònoma de Barcelona, Barcelona, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain
| | - Elena García-Arumí
- Departament de Patologia Mitocondrial i Neuromuscular, Hospital Universitari Vall d'Hebron Institut de Recerca (VHIR), Universitat Autònoma de Barcelona, Barcelona, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain.,Àrea de Genètica Clínica i Molecular, Hospital Universitari Vall d'Hebron, Barcelona, Spain
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3
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Varga NÁ, Pentelényi K, Balicza P, Gézsi A, Reményi V, Hársfalvi V, Bencsik R, Illés A, Prekop C, Molnár MJ. Mitochondrial dysfunction and autism: comprehensive genetic analyses of children with autism and mtDNA deletion. Behav Brain Funct 2018; 14:4. [PMID: 29458409 PMCID: PMC5819172 DOI: 10.1186/s12993-018-0135-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 01/16/2018] [Indexed: 12/27/2022] Open
Abstract
Background The etiology of autism spectrum disorders (ASD) is very heterogeneous. Mitochondrial dysfunction has been described in ASD; however, primary mitochondrial disease has been genetically proven in a small subset of patients. The main goal of the present study was to investigate correlations between mitochondrial DNA (mtDNA) changes and alterations of genes associated with mtDNA maintenance or ASD. Methods Sixty patients with ASD and sixty healthy individuals were screened for common mtDNA mutations. Next generation sequencing was performed on patients with major mtDNA deletions (mtdel-ASD) using two gene panels to investigate nuclear genes that are associated with ASD or are responsible for mtDNA maintenance. Cohorts of healthy controls, ASD patients without mtDNA alterations, and patients with mitochondrial disorders (non-ASD) harbouring mtDNA deletions served as comparison groups. Results MtDNA deletions were confirmed in 16.6% (10/60) of patients with ASD (mtdel-ASD). In 90% of this mtdel-ASD children we found rare SNVs in ASD-associated genes (one of those was pathogenic). In the intergenomic panel of this cohort one likely pathogenic variant was present. In patients with mitochondrial disease in genes responsible for mtDNA maintenance pathogenic mutations and variants of uncertain significance (VUS) were detected more frequently than those found in patients from the mtdel-ASD or other comparison groups. In healthy controls and in patients without a mtDNA deletion, only VUS were detected in both panel. Conclusions MtDNA alterations are more common in patients with ASD than in control individuals. MtDNA deletions are not isolated genetic alterations found in ASD; they coexist either with other ASD-associated genetic risk factors or with alterations in genes responsible for intergenomic communication. These findings indicate that mitochondrial dysfunction is not rare in ASD. The occurring mtDNA deletions in ASD may be mostly a consequence of the alterations of the causative culprit genes for autism or genes responsible for mtDNA maintenance, or because of the harmful effect of environmental factors. Electronic supplementary material The online version of this article (10.1186/s12993-018-0135-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Noémi Ágnes Varga
- Institute of Genomic Medicine and Rare Disorders, Semmelweis University, Tömő Str. 25-29, Budapest, 1083, Hungary
| | - Klára Pentelényi
- Institute of Genomic Medicine and Rare Disorders, Semmelweis University, Tömő Str. 25-29, Budapest, 1083, Hungary
| | - Péter Balicza
- Institute of Genomic Medicine and Rare Disorders, Semmelweis University, Tömő Str. 25-29, Budapest, 1083, Hungary
| | - András Gézsi
- Institute of Genomic Medicine and Rare Disorders, Semmelweis University, Tömő Str. 25-29, Budapest, 1083, Hungary.,Department of Genetics, Cell- and Immunobiology, Semmelweis University, Nagyvárad tér 4, Budapest, 1089, Hungary
| | - Viktória Reményi
- Institute of Genomic Medicine and Rare Disorders, Semmelweis University, Tömő Str. 25-29, Budapest, 1083, Hungary
| | - Vivien Hársfalvi
- Institute of Genomic Medicine and Rare Disorders, Semmelweis University, Tömő Str. 25-29, Budapest, 1083, Hungary
| | - Renáta Bencsik
- Institute of Genomic Medicine and Rare Disorders, Semmelweis University, Tömő Str. 25-29, Budapest, 1083, Hungary
| | - Anett Illés
- Institute of Genomic Medicine and Rare Disorders, Semmelweis University, Tömő Str. 25-29, Budapest, 1083, Hungary
| | - Csilla Prekop
- Vadaskert Foundation for Children's Mental Health, Lipótmezei Str. 1-5, Budapest, 1021, Hungary
| | - Mária Judit Molnár
- Institute of Genomic Medicine and Rare Disorders, Semmelweis University, Tömő Str. 25-29, Budapest, 1083, Hungary.
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Lee SR, Han J. Mitochondrial Mutations in Cardiac Disorders. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 982:81-111. [PMID: 28551783 DOI: 10.1007/978-3-319-55330-6_5] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Mitochondria individually encapsulate their own genome, unlike other cellular organelles. Mitochondrial DNA (mtDNA) is a circular, double-stranded, 16,569-base paired DNA containing 37 genes: 13 proteins of the mitochondrial respiratory chain, two ribosomal RNAs (rRNAs; 12S and 16S), and 22 transfer RNAs (tRNAs). The mtDNA is more vulnerable to oxidative modifications compared to nuclear DNA because of its proximity to ROS-producing sites, limited presence of DNA damage repair systems, and continuous replication in the cell. mtDNA mutations can be inherited or sporadic. Simple mtDNA mutations are point mutations, which are frequently found in mitochondrial tRNA loci, causing mischarging of mitochondrial tRNAs or deletion, duplication, or reduction in mtDNA content. Because mtDNA has multiple copies and a specific replication mechanism in cells or tissues, it can be heterogenous, resulting in characteristic phenotypic presentations such as heteroplasmy, genetic drift, and threshold effects. Recent studies have increased the understanding of basic mitochondrial genetics, providing an insight into the correlations between mitochondrial mutations and cardiac manifestations including hypertrophic or dilated cardiomyopathy, arrhythmia, autonomic nervous system dysfunction, heart failure, or sudden cardiac death with a syndromic or non-syndromic phenotype. Clinical manifestations of mitochondrial mutations, which result from structural defects, functional impairment, or both, are increasingly detected but are not clear because of the complex interplay between the mitochondrial and nuclear genomes, even in homoplasmic mitochondrial populations. Additionally, various factors such as individual susceptibility, nutritional state, and exposure to chemicals can influence phenotypic presentation, even for the same mtDNA mutation.In this chapter, we summarize our current understanding of mtDNA mutations and their role in cardiac involvement. In addition, epigenetic modifications of mtDNA are briefly discussed for future elucidation of their critical role in cardiac involvement. Finally, current strategies for dealing with mitochondrial mutations in cardiac disorders are briefly stated.
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Affiliation(s)
- Sung Ryul Lee
- Department of Integrated Biomedical Science, Cardiovascular and Metabolic Disease Center, College of Medicine, Inje University, Busan, 47392, South Korea
| | - Jin Han
- National Research Laboratory for Mitochondrial Signaling, Cardiovascular and Metabolic Disease Center, Department of Physiology, College of Medicine, Inje University, Busan, 47392, South Korea.
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Vernau K, Napoli E, Wong S, Ross-Inta C, Cameron J, Bannasch D, Bollen A, Dickinson P, Giulivi C. Thiamine Deficiency-Mediated Brain Mitochondrial Pathology in Alaskan Huskies with Mutation in SLC19A3.1. Brain Pathol 2014; 25:441-53. [PMID: 25117056 DOI: 10.1111/bpa.12188] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Accepted: 08/05/2014] [Indexed: 02/05/2023] Open
Abstract
Alaskan Husky encephalopathy (AHE(1) ) is a fatal brain disease associated with a mutation in SLC19A3.1 (c.624insTTGC, c.625C>A). This gene encodes for a thiamine transporter 2 with a predominately (CNS) central nervous system distribution. Considering that brain is particularly vulnerable to thiamine deficiency because of its reliance on thiamine pyrophosphate (TPP)-dependent metabolic pathways involved in energy metabolism and neurotransmitter synthesis, we characterized the impact of this mutation on thiamine status, brain bioenergetics and the contribution of oxidative stress to this phenotype. In silico modeling of the mutated transporter indicated a significant loss of alpha-helices resulting in a more open protein structure suggesting an impaired thiamine transport ability. The cerebral cortex and thalamus of affected dogs were severely deficient in TPP-dependent enzymes accompanied by decreases in mitochondrial mass and oxidative phosphorylation (OXPHOS) capacity, and increases in oxidative stress. These results along with the behavioral and pathological findings indicate that the phenotype associated with AHE is consistent with a brain-specific thiamine deficiency, leading to brain mitochondrial dysfunction and increased oxidative stress. While some of the biochemical deficits, neurobehavior and affected brain areas in AHE were shared by Wernicke's and Korsakoff's syndromes, several differences were noted likely arising from a tissue-specific vs. that from a whole-body thiamine deficiency.
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Affiliation(s)
- Karen Vernau
- Department of Surgical and Radiological Sciences, University of California Davis, Toronto, Ontario, Canada
| | - Eleonora Napoli
- Molecular Biosciences, University of California Davis, Toronto, Ontario, Canada
| | - Sarah Wong
- Molecular Biosciences, University of California Davis, Toronto, Ontario, Canada
| | - Catherine Ross-Inta
- Molecular Biosciences, University of California Davis, Toronto, Ontario, Canada
| | - Jessie Cameron
- Department of Genetics and Genome Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Danika Bannasch
- Pathology, Microbiology and Immunology, University of California Davis, Sacramento, CA
| | - Andrew Bollen
- Department of Pathology and Laboratory Medicine, University of California San Francisco
| | - Peter Dickinson
- Department of Surgical and Radiological Sciences, University of California Davis, Toronto, Ontario, Canada
| | - Cecilia Giulivi
- Molecular Biosciences, University of California Davis, Toronto, Ontario, Canada.,Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, Sacramento, CA
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Fuke S, Kametani M, Yamada K, Kasahara T, Kubota-Sakashita M, Kujoth GC, Prolla TA, Hitoshi S, Kato T. Heterozygous Polg mutation causes motor dysfunction due to mtDNA deletions. Ann Clin Transl Neurol 2014; 1:909-20. [PMID: 25540805 PMCID: PMC4265062 DOI: 10.1002/acn3.133] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 09/25/2014] [Accepted: 09/25/2014] [Indexed: 12/27/2022] Open
Abstract
Objective Mutations in nuclear-encoded mitochondrial DNA (mtDNA) polymerase (POLG) are known to cause autosomal dominant chronic progressive external ophthalmoplegia (adCPEO) with accumulation of multiple mtDNA deletions in muscles. However, no animal model with a heterozygous Polg mutation representing mtDNA impairment and symptoms of CPEO has been established. To understand the pathogenic mechanism of CPEO, it is important to determine the age dependency and tissue specificity of mtDNA impairment resulting from a heterozygous mutation in the Polg gene in an animal model. Methods We assessed behavioral phenotypes, tissue-specific accumulation of mtDNA deletions, and its age dependency in heterozygous PolgD257A knock-in mice carrying a proofreading-deficient mutation in the Polg. Results Heterozygous PolgD257A knock-in mice exhibited motor dysfunction in a rotarod test. Polg+/D257A mice had significant accumulation of multiple mtDNA deletions, but did not show significant accumulation of point mutations or mtDNA depletion in the brain. While mtDNA deletions increased in an age-dependent manner regardless of the tissue even in Polg+/+ mice, the age-dependent accumulation of mtDNA deletions was enhanced in muscles and in the brain of Polg+/D257A mice. Interpretation Heterozygous PolgD257A knock-in mice showed tissue-specific, age-dependent accumulation of multiple mtDNA deletions in muscles and the brain which was likely to result in neuromuscular symptoms. Polg+/D257A mice may be used as an animal model of adCPEO associated with impaired mtDNA maintenance.
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Affiliation(s)
- Satoshi Fuke
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute Wako, Saitama, Japan, 351-0198 ; Department of Integrative Physiology, Shiga University of Medical Science Otsu, Shiga, Japan, 520-2192
| | - Mizue Kametani
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute Wako, Saitama, Japan, 351-0198
| | - Kazuyuki Yamada
- Research Resources Center, RIKEN Brain Science Institute Wako, Saitama, Japan, 351-0198
| | - Takaoki Kasahara
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute Wako, Saitama, Japan, 351-0198
| | - Mie Kubota-Sakashita
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute Wako, Saitama, Japan, 351-0198
| | - Gregory C Kujoth
- Department of Neurological Surgery, University of Wisconsin Madison, Wisconsin, 53792
| | - Tomas A Prolla
- Departments of Genetics and Medical Genetics, University of Wisconsin Madison, Wisconsin, 53706
| | - Seiji Hitoshi
- Department of Integrative Physiology, Shiga University of Medical Science Otsu, Shiga, Japan, 520-2192
| | - Tadafumi Kato
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute Wako, Saitama, Japan, 351-0198
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Vartiainen S, Chen S, George J, Tuomela T, Luoto KR, O'Dell KMC, Jacobs HT. Phenotypic rescue of a Drosophila model of mitochondrial ANT1 disease. Dis Model Mech 2014; 7:635-48. [PMID: 24812436 PMCID: PMC4036471 DOI: 10.1242/dmm.016527] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
A point mutation in the Drosophila gene that codes for the major adult isoform of adenine nuclear translocase (ANT) represents a model for human diseases that are associated with ANT insufficiency [stress-sensitive B1 (sesB1)]. We characterized the organismal, bioenergetic and molecular phenotype of sesB1 flies then tested strategies to compensate the mutant phenotype. In addition to developmental delay and mechanical-stress-induced seizures, sesB1 flies have an impaired response to sound, defective male courtship, female sterility and curtailed lifespan. These phenotypes, excluding the latter two, are shared with the mitoribosomal protein S12 mutant, tko25t. Mitochondria from sesB1 adults showed a decreased respiratory control ratio and downregulation of cytochrome oxidase. sesB1 adults exhibited ATP depletion, lactate accumulation and changes in gene expression that were consistent with a metabolic shift towards glycolysis, characterized by activation of lactate dehydrogenase and anaplerotic pathways. Females also showed downregulation of many genes that are required for oogenesis, and their eggs, although fertilized, failed to develop to the larval stages. The sesB1 phenotypes of developmental delay and mechanical-stress-induced seizures were alleviated by an altered mitochondrial DNA background. Female sterility was substantially rescued by somatic expression of alternative oxidase (AOX) from the sea squirt Ciona intestinalis, whereas AOX did not alleviate developmental delay. Our findings illustrate the potential of different therapeutic strategies for ANT-linked diseases, based on alleviating metabolic stress.
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Affiliation(s)
- Suvi Vartiainen
- BioMediTech and Tampere University Hospital, FI-33014 University of Tampere, Finland
| | - Shanjun Chen
- BioMediTech and Tampere University Hospital, FI-33014 University of Tampere, Finland
| | - Jack George
- BioMediTech and Tampere University Hospital, FI-33014 University of Tampere, Finland
| | - Tea Tuomela
- BioMediTech and Tampere University Hospital, FI-33014 University of Tampere, Finland
| | - Kaisa R Luoto
- BioMediTech and Tampere University Hospital, FI-33014 University of Tampere, Finland
| | - Kevin M C O'Dell
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
| | - Howard T Jacobs
- BioMediTech and Tampere University Hospital, FI-33014 University of Tampere, Finland. Research Program of Molecular Neurology, FI-00014 University of Helsinki, Finland.
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Bird MJ, Thorburn DR, Frazier AE. Modelling biochemical features of mitochondrial neuropathology. Biochim Biophys Acta Gen Subj 2013; 1840:1380-92. [PMID: 24161927 DOI: 10.1016/j.bbagen.2013.10.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 08/29/2013] [Accepted: 10/11/2013] [Indexed: 12/20/2022]
Abstract
BACKGROUND The neuropathology of mitochondrial disease is well characterised. However, pathophysiological mechanisms at the level of biochemistry and cell biology are less clear. Progress in this area has been hampered by the limited accessibility of neurologically relevant material for analysis. SCOPE OF REVIEW Here we discuss the recent development of a variety of model systems that have greatly extended our capacity to understand the biochemical features associated with mitochondrial neuropathology. These include animal and cell based models, with mutations in both nuclear and mitochondrial DNA encoded genes, which aim to recapitulate the neuropathology and cellular biochemistry of mitochondrial diseases. MAJOR CONCLUSIONS Analysis of neurological tissue and cells from these models suggests that although there is no unifying mode of pathogenesis, dysfunction of the oxidative phosphorylation (OXPHOS) system is often central. This can be associated with altered reactive oxygen species (ROS) generation, disruption of the mitochondrial membrane potential (ΔΨm) and inadequate ATP synthesis. Thus, other cellular processes such as calcium (Ca(2+)) homeostasis, cellular signaling and mitochondrial morphology could be altered, ultimately compromising viability of neuronal cells. GENERAL SIGNIFICANCE Mechanisms of neuronal dysfunction in mitochondrial disease are only just beginning to be characterised, are system dependent and complex, and not merely driven by energy deficiency. The diversity of pathogenic mechanisms emphasises the need for characterisation in a wide range of models, as different therapeutic strategies are likely to be needed for different diseases. This article is part of a Special Issue entitled Frontiers of Mitochondrial Research.
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Affiliation(s)
- Matthew J Bird
- The Murdoch Childrens Research Institute, The Royal Children's Hospital, Melbourne, Australia; Department of Paediatrics, The University of Melbourne, Melbourne, Australia
| | - David R Thorburn
- The Murdoch Childrens Research Institute, The Royal Children's Hospital, Melbourne, Australia; Department of Paediatrics, The University of Melbourne, Melbourne, Australia; Victorian Clinical Genetics Services, Royal Children's Hospital, Melbourne, Australia
| | - Ann E Frazier
- The Murdoch Childrens Research Institute, The Royal Children's Hospital, Melbourne, Australia; Department of Paediatrics, The University of Melbourne, Melbourne, Australia.
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The human MSH5 (MutS Homolog 5) protein localizes to mitochondria and protects the mitochondrial genome from oxidative damage. Mitochondrion 2012; 12:654-65. [DOI: 10.1016/j.mito.2012.07.111] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 07/14/2012] [Accepted: 07/20/2012] [Indexed: 01/07/2023]
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10
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Pitceathly R, Rahman S, Hanna M. Single deletions in mitochondrial DNA – Molecular mechanisms and disease phenotypes in clinical practice. Neuromuscul Disord 2012; 22:577-86. [DOI: 10.1016/j.nmd.2012.03.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Revised: 02/26/2012] [Accepted: 03/21/2012] [Indexed: 12/20/2022]
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Kawamata H, Tiranti V, Magrané J, Chinopoulos C, Manfredi G. adPEO mutations in ANT1 impair ADP-ATP translocation in muscle mitochondria. Hum Mol Genet 2011; 20:2964-74. [PMID: 21586654 DOI: 10.1093/hmg/ddr200] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Mutations in the heart and muscle isoform of adenine nucleotide translocator 1 (ANT1) are associated with autosomal-dominant progressive external opthalmoplegia (adPEO) clinically characterized by exercise intolerance, ptosis and muscle weakness. The pathogenic mechanisms underlying the mitochondrial myopathy caused by ANT1 mutations remain largely unknown. In yeast, expression of ANT1 carrying mutations corresponding to the human adPEO ones causes a wide range of mitochondrial abnormalities. However, functional studies of ANT1 mutations in mammalian cells are lacking, because they have been hindered by the fact that ANT1 expression leads to apoptotic cell death in commonly utilized replicating cell lines. Here, we successfully express functional ANT1 in differentiated mouse myotubes, which naturally contain high levels of ANT1, without causing cell death. We demonstrate, for the first time in these disease-relevant mammalian cells, that mutant human ANT1 causes dominant mitochondrial defects characterized by decreased ADP-ATP exchange function and abnormal translocator reversal potential. These abnormalities are not due to ANT1 loss of function, because knocking down Ant1 in myotubes causes functional changes different from ANT1 mutants. Under certain physiological conditions, mitochondria consume ATP to maintain membrane potential by reversing the ADP-ATP transport. The modified properties of mutant ANT1 can be responsible for disease pathogenesis in adPEO, because exchange reversal occurring at higher than normal membrane potential can cause excessive energy depletion and nucleotide imbalance in ANT1 mutant muscle cells.
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Affiliation(s)
- Hibiki Kawamata
- Department of Neurology and Neuroscience, Weill Medical College of Cornell University, New York, NY 10065, USA
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12
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Fuke S, Kubota-Sakashita M, Kasahara T, Shigeyoshi Y, Kato T. Regional variation in mitochondrial DNA copy number in mouse brain. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1807:270-4. [PMID: 21145305 DOI: 10.1016/j.bbabio.2010.11.016] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Revised: 11/10/2010] [Accepted: 11/30/2010] [Indexed: 11/17/2022]
Abstract
Mitochondria have their own DNA (mitochondrial DNA [mtDNA]). Although mtDNA copy number is dependent on tissues and its decrease is associated with various neuromuscular diseases, detailed distribution of mtDNA copies in the brain remains uncertain. Using real-time quantitative PCR assay, we examined regional variation in mtDNA copy number in 39 brain regions of male mice. A significant regional difference in mtDNA copy number was observed (P<4.8×10(-35)). High levels of mtDNA copies were found in the ventral tegmental area and substantia nigra, two major nuclei containing dopaminergic neurons. In contrast, cerebellar vermis and lobes had significantly lower copy numbers than other regions. Hippocampal dentate gyrus also had a relatively low mtDNA copy number. This study is the first quantitative analysis of regional variation in mtDNA copy number in mouse brain. Our findings are important for the physiological and pathophysiological studies of mtDNA in the brain.
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Affiliation(s)
- Satoshi Fuke
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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13
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Wang W, Shen P, Thiyagarajan S, Lin S, Palm C, Horvath R, Klopstock T, Cutler D, Pique L, Schrijver I, Davis RW, Mindrinos M, Speed TP, Scharfe C. Identification of rare DNA variants in mitochondrial disorders with improved array-based sequencing. Nucleic Acids Res 2010; 39:44-58. [PMID: 20843780 PMCID: PMC3017602 DOI: 10.1093/nar/gkq750] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
A common goal in the discovery of rare functional DNA variants via medical resequencing is to incur a relatively lower proportion of false positive base-calls. We developed a novel statistical method for resequencing arrays (SRMA, sequence robust multi-array analysis) to increase the accuracy of detecting rare variants and reduce the costs in subsequent sequence verifications required in medical applications. SRMA includes single and multi-array analysis and accounts for technical variables as well as the possibility of both low- and high-frequency genomic variation. The confidence of each base-call was ranked using two quality measures. In comparison to Sanger capillary sequencing, we achieved a false discovery rate of 2% (false positive rate 1.2 × 10−5, false negative rate 5%), which is similar to automated second-generation sequencing technologies. Applied to the analysis of 39 nuclear candidate genes in disorders of mitochondrial DNA (mtDNA) maintenance, we confirmed mutations in the DNA polymerase gamma POLG in positive control cases, and identified novel rare variants in previously undiagnosed cases in the mitochondrial topoisomerase TOP1MT, the mismatch repair enzyme MUTYH, and the apurinic-apyrimidinic endonuclease APEX2. Some patients carried rare heterozygous variants in several functionally interacting genes, which could indicate synergistic genetic effects in these clinically similar disorders.
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Affiliation(s)
- Wenyi Wang
- Stanford Genome Technology Center, Stanford University, Palo Alto, CA 94304, USA.
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Berardo A, DiMauro S, Hirano M. A diagnostic algorithm for metabolic myopathies. Curr Neurol Neurosci Rep 2010; 10:118-26. [PMID: 20425236 DOI: 10.1007/s11910-010-0096-4] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Metabolic myopathies comprise a clinically and etiologically diverse group of disorders caused by defects in cellular energy metabolism, including the breakdown of carbohydrates and fatty acids to generate adenosine triphosphate, predominantly through mitochondrial oxidative phosphorylation. Accordingly, the three main categories of metabolic myopathies are glycogen storage diseases, fatty acid oxidation defects, and mitochondrial disorders due to respiratory chain impairment. The wide clinical spectrum of metabolic myopathies ranges from severe infantile-onset multisystemic diseases to adult-onset isolated myopathies with exertional cramps. Diagnosing these diverse disorders often is challenging because clinical features such as recurrent myoglobinuria and exercise intolerance are common to all three types of metabolic myopathy. Nevertheless, distinct clinical manifestations are important to recognize as they can guide diagnostic testing and lead to the correct diagnosis. This article briefly reviews general clinical aspects of metabolic myopathies and highlights approaches to diagnosing the relatively more frequent subtypes (Fig. 1). Fig. 1 Clinical algorithm for patients with exercise intolerance in whom a metabolic myopathy is suspected. CK-creatine kinase; COX-cytochrome c oxidase; CPT-carnitine palmitoyl transferase; cyt b-cytochrome b; mtDNA-mitochondrial DNA; nDNA-nuclear DNA; PFK-phosphofructokinase; PGAM-phosphoglycerate mutase; PGK-phosphoglycerate kinase; PPL-myophosphorylase; RRF-ragged red fibers; TFP-trifunctional protein deficiency; VLCAD-very long-chain acyl-coenzyme A dehydrogenase.
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Affiliation(s)
- Andres Berardo
- Department of Neurology, Columbia University Medical Center, 630 West 168th Street, P&S 4-423, New York, NY 10032, USA
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15
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Bailey CM, Anderson KS. A mechanistic view of human mitochondrial DNA polymerase gamma: providing insight into drug toxicity and mitochondrial disease. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2010; 1804:1213-22. [PMID: 20083238 DOI: 10.1016/j.bbapap.2010.01.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Revised: 12/30/2009] [Accepted: 01/04/2010] [Indexed: 02/08/2023]
Abstract
Mitochondrial DNA polymerase gamma (Pol gamma) is the sole polymerase responsible for replication of the mitochondrial genome. The study of human Pol gamma is of key importance to clinically relevant issues such as nucleoside analog toxicity and mitochondrial disorders such as progressive external ophthalmoplegia. The development of a recombinant form of the human Pol gamma holoenzyme provided an essential tool in understanding the mechanism of these clinically relevant phenomena using kinetic methodologies. This review will provide a brief history on the discovery and characterization of human mitochondrial DNA polymerase gamma, focusing on kinetic analyses of the polymerase and mechanistic data illustrating structure-function relationships to explain drug toxicity and mitochondrial disease.
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Affiliation(s)
- Christopher M Bailey
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
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Villarroya J, Giralt M, Villarroya F. Mitochondrial DNA: an up-and-coming actor in white adipose tissue pathophysiology. Obesity (Silver Spring) 2009; 17:1814-20. [PMID: 19461585 DOI: 10.1038/oby.2009.152] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Joan Villarroya
- Departament de Bioquimica i Biologia Molecular, i Institut de Biomedicina de la Universitat de Barcelona (IBUB), Barcelona, Spain
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Todorov IN, Todorov GI. Multifactorial nature of high frequency of mitochondrial DNA mutations in somatic mammalian cells. BIOCHEMISTRY (MOSCOW) 2009; 74:962-70. [DOI: 10.1134/s000629790909003x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Bailey LJ, Cluett TJ, Reyes A, Prolla TA, Poulton J, Leeuwenburgh C, Holt IJ. Mice expressing an error-prone DNA polymerase in mitochondria display elevated replication pausing and chromosomal breakage at fragile sites of mitochondrial DNA. Nucleic Acids Res 2009; 37:2327-35. [PMID: 19244310 PMCID: PMC2673436 DOI: 10.1093/nar/gkp091] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Expression of a proof-reading deficient form of mitochondrial DNA (mtDNA) polymerase γ, POLG, causes early death accompanied by features of premature ageing in mouse. However, the mechanism of cellular senescence remains unresolved. In addition to high levels of point mutations of mtDNA, the POLG mutator mouse harbours linear mtDNAs. Using one- and two-dimensional agarose gel electrophoresis, we show that the linear mtDNAs derive from replication intermediates and are indicative of replication pausing and chromosomal breakage at the accompanying fragile sites. Replication fork arrest is not random but occurs at specific sites close to two cis-elements known as OH and OL. Pausing at these sites may be enhanced in the case of exonuclease-deficient POLG owing to delayed resumption of DNA replication, or replisome instability. In either case, the mtDNA replication cycle is perturbed and this might explain the progeroid features of the POLG mutator mouse.
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Affiliation(s)
- Laura J Bailey
- MRC-Dunn Human Nutrition Unit, Wellcome Trust-MRC Building, Cambridge, UK
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Abstract
Mitochondrial function degenerates with ageing and in ageing-related neuromuscular degenerative diseases, causing physiological decline of the cell. Factors that can delay the degenerative process are actively sought after. Here, we show that reduced cytosolic protein synthesis is a robust cellular strategy that suppresses ageing-related mitochondrial degeneration. We modelled autosomal dominant progressive external ophthalmoplegia (adPEO), an adult- or later-onset degenerative disease, by introducing the A128P mutation into the adenine nucleotide translocase Aac2p of Saccharomyces cerevisiae. The aac2(A128P) allele dominantly induces ageing-dependent mitochondrial degeneration and phenotypically tractable degenerative cell death, independently of its ADP/ATP exchange activity. Mitochondrial degeneration was suppressed by lifespan-extending nutritional interventions and by eight longevity mutations, which are all known to reduce cytosolic protein synthesis. These longevity interventions also independently suppressed ageing-related mitochondrial degeneration in the pro-ageing prohibitin mutants. The aac2(A128P) mutant has reduced mitochondrial membrane potential (delta psi(m)) and is synthetically lethal to low delta psi(m) conditions, including the loss of prohibitin. Mitochondrial degeneration was accelerated by defects in protein turnover on the inner membrane and was suppressed by cycloheximide, a specific inhibitor of cytosolic ribosomes. Reduced cytosolic protein synthesis suppressed membrane depolarization and defects in mitochondrial gene expression in aac(A128P) cells. Our finding thus establishes a link between protein homeostasis (proteostasis), cellular bioenergetics and mitochondrial maintenance during ageing.
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Scarpulla RC. Transcriptional paradigms in mammalian mitochondrial biogenesis and function. Physiol Rev 2008; 88:611-38. [PMID: 18391175 DOI: 10.1152/physrev.00025.2007] [Citation(s) in RCA: 1156] [Impact Index Per Article: 72.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Mitochondria contain their own genetic system and undergo a unique mode of cytoplasmic inheritance. Each organelle has multiple copies of a covalently closed circular DNA genome (mtDNA). The entire protein coding capacity of mtDNA is devoted to the synthesis of 13 essential subunits of the inner membrane complexes of the respiratory apparatus. Thus the majority of respiratory proteins and all of the other gene products necessary for the myriad mitochondrial functions are derived from nuclear genes. Transcription of mtDNA requires a small number of nucleus-encoded proteins including a single RNA polymerase (POLRMT), auxiliary factors necessary for promoter recognition (TFB1M, TFB2M) and activation (Tfam), and a termination factor (mTERF). This relatively simple system can account for the bidirectional transcription of mtDNA from divergent promoters and key termination events controlling the rRNA/mRNA ratio. Nucleomitochondrial interactions depend on the interplay between transcription factors (NRF-1, NRF-2, PPARalpha, ERRalpha, Sp1, and others) and members of the PGC-1 family of regulated coactivators (PGC-1alpha, PGC-1beta, and PRC). The transcription factors target genes that specify the respiratory chain, the mitochondrial transcription, translation and replication machinery, and protein import and assembly apparatus among others. These factors are in turn activated directly or indirectly by PGC-1 family coactivators whose differential expression is controlled by an array of environmental signals including temperature, energy deprivation, and availability of nutrients and growth factors. These transcriptional paradigms provide a basic framework for understanding the integration of mitochondrial biogenesis and function with signaling events that dictate cell- and tissue-specific energetic properties.
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Affiliation(s)
- Richard C Scarpulla
- Department of Cell and Molecular Biology, Northwestern Medical School, Chicago, Illinois 60611, USA
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Ashley N, O'Rourke A, Smith C, Adams S, Gowda V, Zeviani M, Brown GK, Fratter C, Poulton J. Depletion of mitochondrial DNA in fibroblast cultures from patients with POLG1 mutations is a consequence of catalytic mutations. Hum Mol Genet 2008; 17:2496-506. [PMID: 18487244 PMCID: PMC2486441 DOI: 10.1093/hmg/ddn150] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigated clinical and cellular phenotypes of 24 children with mutations in the catalytic (alpha) subunit of the mitochondrial DNA (mtDNA) gamma polymerase (POLG1). Twenty-one had Alpers syndrome, the commonest severe POLG1 autosomal recessive phenotype, comprising hepatoencephalopathy and often mtDNA depletion. The cellular mtDNA content reflected the genotype more closely than did clinical features. Patients with tissue depletion of mtDNA all had at least one allele with either a missense mutation in a catalytic domain or a nonsense mutation. Four out of 12 patients exhibited a progressive, mosaic pattern of mtDNA depletion in cultured fibroblasts. All these patients had mutations in a catalytic domain in both POLG1 alleles, in either the polymerase or exonuclease domain or both. The tissue mtDNA content of patients who had two linker mutations was normal, and their phenotypes the mildest. Epilepsy and/or movement disorder were major features in all 21. Previous studies have implicated replication stalling as a mechanism for mtDNA depletion. The mosaic cellular depletion that we have demonstrated in cell cultures may be a manifestation of severe replication stalling. One patient with a severe cellular and clinical phenotype was a compound heterozygote with POLG1 mutations in the polymerase and exonuclease domain intrans. This suggests that POLG1 requires both polymerase and 3'-5' exonuclease activity in the same molecule. This is consistent with current functional models for eukaryotic DNA polymerases, which alternate between polymerizing and editing modes, as determined by competition between these two active sites for the 3' end of the DNA.
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Affiliation(s)
- Neil Ashley
- Nuffield Department of Obstetrics and Gynaecology, University of Oxford, The Women's Centre, John Radcliffe Hospital, Oxford OX3 9DU, UK
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Korhonen JA, Pande V, Holmlund T, Farge G, Pham XH, Nilsson L, Falkenberg M. Structure–Function Defects of the TWINKLE Linker Region in Progressive External Ophthalmoplegia. J Mol Biol 2008; 377:691-705. [DOI: 10.1016/j.jmb.2008.01.035] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2007] [Revised: 12/28/2007] [Accepted: 01/15/2008] [Indexed: 02/06/2023]
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Development of hepatocellular carcinoma in Iqgap2-deficient mice is IQGAP1 dependent. Mol Cell Biol 2008; 28:1489-502. [PMID: 18180285 DOI: 10.1128/mcb.01090-07] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
IQGAPs are multidomain scaffolding proteins that integrate Rho GTPase and Ca2+/calmodulin signals with cell adhesive and cytoskeletal reorganizational events. Targeted disruption of the murine Iqgap2 gene resulted in the age-dependent development of apoptosis and hepatocellular carcinoma (HCC), characterized by the overexpression of IQGAP1, the loss of membrane E-cadherin expression, the cytoplasmic translocation (and activation) of beta-catenin, and the overexpression of a nuclear target of beta-catenin, cyclin D1. In normal hepatocytes, IQGAP2 was found to exist as one component of a multifunctional scaffolding complex comprising IQGAP1, beta-catenin, and E-cadherin, with no evidence for direct IQGAP1-IQGAP2 interactions. Interbreeding of Iqgap2(-/-) mice into the Iqgap1(-/-) background resulted in the phenotypic correction of the preexisting hepatopathy, decreases in the incidence and sizes of HCC tumors, and the normalization of overall survival rates compared to those of Iqgap2(-/-) mice, suggesting that maximal penetrance of the Iqgap2(-/-) HCC phenotype requires the coordinate expression of IQGAP1. These results identify Iqgap2 as a novel tumor suppressor gene specifically linked to the development of HCC and the activation of the Wnt/beta-catenin signaling pathway, while also suggesting that IQGAP1 and IQGAP2 retain functionally divergent roles in hepatocellular carcinogenesis.
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Acton BM, Lai I, Shang X, Jurisicova A, Casper RF. Neutral Mitochondrial Heteroplasmy Alters Physiological Function in Mice1. Biol Reprod 2007; 77:569-76. [PMID: 17554081 DOI: 10.1095/biolreprod.107.060806] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Cytoplasmic transfer is an assisted reproductive technique that involves the infusion of ooplasm from a donor oocyte into a recipient oocyte of inferior developmental competence. Although this technique has shown some success for couples with recurrent in vitro fertilization failure, it results in mitochondrial heteroplasmy in the offspring, defined as the presence of two different mitochondrial genomes in the same individual. Because the long-term health consequences of mitochondrial heteroplasmy are unknown, there is a need for appropriate animal models to evaluate any physiological changes of dual mtDNA genotypes. This longitudinal study was designed as a preliminary screen of basic physiological functions for heteroplasmic mice (NZB mtDNA on a BALB/cByJ background). The mice were tested for cardiovascular and metabolic function, hematological parameters, body mass analysis, ovarian reserve, and tissue histologic abnormalities over a period of 15 mo. Heteroplasmic mice developed systemic hypertension that corrected over time and was accompanied by cardiac changes consistent with pulmonary hypertension. In addition, heteroplasmic animals had increased body mass and fat mass compared with controls at all ages. Finally, these animals had abnormalities in electrolytes and hematological parameters. Our findings suggest that there are significant physiological differences between heteroplasmic and control mice. Because ooplasm transfer appears to be consistently associated with mitochondrial heteroplasmy, children conceived through ooplasm transfer should be closely followed to determine if they are at risk for any health problems.
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Affiliation(s)
- B M Acton
- Division of Reproductive Endocrinology and Infertility, Department of Obstetrics and Gynecology, University of Toronto, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada M5G 1X5
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Kohler JJ, Lewis W. A brief overview of mechanisms of mitochondrial toxicity from NRTIs. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2007; 48:166-72. [PMID: 16758472 DOI: 10.1002/em.20223] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Nucleoside reverse transcriptase inhibitors (NRTIs) in combinations with other antiretrovirals (highly active antiretroviral therapy, HAART) are the cornerstones of AIDS therapy, turning HIV infection into a manageable clinical entity. Despite the initial positive impact of NRTIs, therapeutic experience revealed serious side effects that appeared to originate in the mitochondria and which ultimately manifested as dysfunction of that organelle. It may be reasonable to consider that as the AIDS epidemic continues and as survival with HIV infection is prolonged by treatment with HAART, long-term side effects of NRTIs may become increasingly common. This consideration may be underscored in children who are born to HIV-infected mothers who received NRTI therapy in utero during gestation. The long-term effect of that NRTI exposure in utero is not clear yet. This review examines some proposed mechanisms of NRTI mitochondrial toxicity, including genetic predisposition, defects in mitochondria DNA replication, the encompassing "DNA pol-gamma hypothesis," the relationship between mitochondrial nucleotide and NRTI pools, mitochondrial DNA mutation and dysfunction, and oxidative stresses related to HIV infection and NRTIs. Mechanisms of mitochondrial toxicity are reviewed with respect to key cell biological, pathological, and pharmacological events.
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Affiliation(s)
- James J Kohler
- Department of Pathology, Emory University, Atlanta, Georgia
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Harvey AJ, Gibson TC, Quebedeaux TM, Brenner CA. Impact of Assisted Reproductive Technologies: A Mitochondrial Perspective of Cytoplasmic Transplantation. Curr Top Dev Biol 2007; 77:229-49. [PMID: 17222706 DOI: 10.1016/s0070-2153(06)77009-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Many of the assisted reproductive techniques associated with maternal aging, disease states, or implantation failure aim to correct poor developmental capacity. These techniques are highly invasive and require the exchange of nuclear or cytoplasmic material from a donor oocyte to compensate for deficiencies inherent in the affected individual. These techniques are based on the assumption that the cytoplasm of the donor oocyte can effectively substitute the necessary component(s) to enable development to proceed. Several studies have attempted to inject cytoplasm from "normal" (young) donors, into aged eggs, again assuming that beneficial components of the cytoplasm are transferred to restore developmental capacity. These invasive assisted reproduction technology (ART) procedures aim to eliminate chromosomal abnormalities, improve the quality of oocytes deficient in some important cytoplasmic factors necessary for maturation and/or subsequent development, and eliminate maternally inherited diseases (particularly mitochondrial myopathies). However, in order to develop such ART, understanding the processes involving mitochondrial DNA replication and transcription is imperative, as asynchrony between mitochondrial and nuclear genomes may cause problems in mitochondrial function, localization, and biogenesis.
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Affiliation(s)
- A J Harvey
- Department of Biology, University of New Orleans New Orleans, Louisiana 70148, USA
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Taylor RW, Chinnery PF, Turnbull DM. Investigation of metabolic myopathies. HANDBOOK OF CLINICAL NEUROLOGY 2007; 86:193-204. [PMID: 18809001 DOI: 10.1016/s0072-9752(07)86009-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
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28
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Oldfors A, Tulinius M. Mitochondrial encephalomyopathies. HANDBOOK OF CLINICAL NEUROLOGY 2007; 86:125-165. [PMID: 18808998 DOI: 10.1016/s0072-9752(07)86006-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
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Rostedt Punga A, Ahlqvist K, Bartoccioni E, Scuderi F, Marino M, Suomalainen A, Kalimo H, Stålberg EV. Neurophysiological and mitochondrial abnormalities in MuSK antibody seropositive myasthenia gravis compared to other immunological subtypes. Clin Neurophysiol 2006; 117:1434-43. [PMID: 16737845 DOI: 10.1016/j.clinph.2006.03.028] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2005] [Revised: 03/21/2006] [Accepted: 03/30/2006] [Indexed: 11/19/2022]
Abstract
OBJECTIVE To compare the electrophysiological and histopathological features of immunological myasthenia gravis (MG) subtypes. METHODS Fifty MG patients underwent clinical examination, MuSK-Ab and AChR-Ab analysis. The majority underwent quantitative and single-fiber electromyography (QEMG, SFEMG), repetitive nerve stimulation and deltoid muscle biopsy. From muscle specimens with histological mitochondrial dysfunction, we amplified mitochondrial DNA (mtDNA). In specimens with mtDNA deletions, the nuclear gene POLG1 was sequenced. RESULTS Five AChR-Ab seropositive [AChR(+)] and 5 seronegative [AChR(-)] patients were MuSK-Ab seropositive [MuSK(+)]. Five of 7 neurophysiologically examined MuSK(+) patients (71%) had proximal myopathic pattern, compared to 7 of 31 MuSK(-)/AChR(+) patients (23%) (P=0.012). SFEMG was abnormal in all examined MuSK(+) patients. All 7 biopsied MuSK(+) and 32 MuSK(-) patients (89%) had cytochrome c oxidase (COX) negative fibers. Three of five MuSK(+) and 13 of 20 MuSK(-) patients analyzed had multiple mtDNA deletions but no POLG1 mutations. CONCLUSIONS Similar degree of SFEMG abnormalities was present in proximal muscles among MuSK(+) and AChR(+) patients. Proximal myopathy was over-represented in MuSK(+) patients; however, both MuSK(+) and MuSK(-) patients had mild myopathy with frequent mitochondrial abnormalities. SIGNIFICANCE The weakness in MuSK(+) patients is most likely due to disturbed neuromuscular transmission. The frequently encountered mitochondrial dysfunction in MG warrants further study.
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Affiliation(s)
- A Rostedt Punga
- Department of Clinical Neurophysiology, University Hospital, S-75185 Uppsala, Sweden.
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Liu CS, Cheng WL, Lee CF, Ma YS, Lin CY, Huang CC, Wei YH. Alteration in the copy number of mitochondrial DNA in leukocytes of patients with mitochondrial encephalomyopathies. Acta Neurol Scand 2006; 113:334-41. [PMID: 16629770 DOI: 10.1111/j.1600-0404.2006.00586.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVES We investigated whether mutation of mitochondrial DNA (mtDNA) affects the copy number of the mitochondrial genome in patients with mitochondrial myopathy encephalopathy with lactic acidosis and stroke-like episodes (MELAS) and those with myoclonic epilepsy with ragged-red fiber (MERRF) syndromes. MATERIALS AND METHODS Forty-eight Taiwanese patients with MELAS syndrome and 20 patients with MERRF syndrome were recruited in this study. RESULTS In relation to controls, the copy numbers of mtDNA in leukocytes of patients with MELAS or MERRF syndrome were significantly higher at a young age but lower at an advanced age. In addition, MELAS patients harboring higher proportions of mtDNA with A3243G transition had lower mtDNA copy numbers. The MELAS or MERRF patients with multi-system disorders had lower mtDNA copy numbers in leukocytes. Furthermore, higher proportions of mtDNA with 4977 bp deletion were found in leukocytes of MERRF patients with multi-system involvement. CONCLUSION In leukocytes, alteration in the copy number of mtDNA is related to the proportion of mtDNA with a point mutation or large-scale deletion, which may serve as a biomarker in the pathogenesis and disease progression of MELAS and MERRF syndromes.
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Affiliation(s)
- C-S Liu
- Vascular and Genomic Research Center, Changhua Christian Hospital, Changhua, Taiwan
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Spikings EC, Alderson J, St John JC. Transmission of mitochondrial DNA following assisted reproduction and nuclear transfer. Hum Reprod Update 2006; 12:401-15. [PMID: 16581809 DOI: 10.1093/humupd/dml011] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Mitochondria are the organelles responsible for producing the majority of a cell's ATP and also play an essential role in gamete maturation and embryo development. ATP production within the mitochondria is dependent on proteins encoded by both the nuclear and the mitochondrial genomes, therefore co-ordination between the two genomes is vital for cell survival. To assist with this co-ordination, cells normally contain only one type of mitochondrial DNA (mtDNA) termed homoplasmy. Occasionally, however, two or more types of mtDNA are present termed heteroplasmy. This can result from a combination of mutant and wild-type mtDNA molecules or from a combination of wild-type mtDNA variants. As heteroplasmy can result in mitochondrial disease, various mechanisms exist in the natural fertilization process to ensure the maternal-only transmission of mtDNA and the maintenance of homoplasmy in future generations. However, there is now an increasing use of invasive oocyte reconstruction protocols, which tend to bypass mechanisms for the maintenance of homoplasmy, potentially resulting in the transmission of either form of mtDNA heteroplasmy. Indeed, heteroplasmy caused by combinations of wild-type variants has been reported following cytoplasmic transfer (CT) in the human and following nuclear transfer (NT) in various animal species. Other techniques, such as germinal vesicle transfer and pronuclei transfer, have been proposed as methods of preventing transmission of mitochondrial diseases to future generations. However, resulting embryos and offspring may contain mtDNA heteroplasmy, which itself could result in mitochondrial disease. It is therefore essential that uniparental transmission of mtDNA is ensured before these techniques are used therapeutically.
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Affiliation(s)
- E C Spikings
- The Mitochondrial and Reproductive Genetics Group, The Medical School, University of Birmingham, Birmingham B15 2TT, UK
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Mömke S, Distl O. Bilateral convergent strabismus with exophthalmus (BCSE) in cattle: an overview of clinical signs and genetic traits. Vet J 2006; 173:272-7. [PMID: 16434218 DOI: 10.1016/j.tvjl.2005.11.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/29/2005] [Indexed: 11/26/2022]
Abstract
Bilateral convergent strabismus with exophthalmus (BCSE) is a heritable eye defect prevalent in many cattle breeds and known worldwide. BCSE shows a progressive course often terminating in complete blindness. The onset of the defect can sometimes be slowly progressing (late in life) and, as the first signs of the defect are frequently not noticed prior to first breeding, prevention cannot be achieved only by exclusion of affected animals from the breeding program. This paper provides an overview of the clinical signs, histopathology and genetics of BCSE, its distribution in different cattle breeds and analyses the association between milk production traits and US Brown Swiss. There were different modes of inheritance proposed for BCSE, but although an autosomal dominant major gene is considered most likely in German Brown cattle, an association with milk production traits could not be found. Comparative molecular genetic approaches could help to characterize the responsible genes for this ocular disease in cattle.
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Affiliation(s)
- Stefanie Mömke
- Institute for Animal Breeding and Genetics, University of Veterinary Medicine Hannover, Foundation, Bünteweg 17p, 30559 Hannover, Germany
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Hisama FM, Mancuso M, Filosto M, DiMauro S. Progressive external ophthalmoplegia: a new family with tremor and peripheral neuropathy. Am J Med Genet A 2005; 135:217-9. [PMID: 15800909 DOI: 10.1002/ajmg.a.30672] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Hance N, Ekstrand MI, Trifunovic A. Mitochondrial DNA polymerase gamma is essential for mammalian embryogenesis. Hum Mol Genet 2005; 14:1775-83. [PMID: 15888483 DOI: 10.1093/hmg/ddi184] [Citation(s) in RCA: 178] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Mitochondrial DNA (mtDNA) polymerase gamma (Polg) is a heterodimeric enzyme containing a Pol I-like catalytic core (PolgA) and an accessory subunit. Mutations in POLGA, affecting the stability of mtDNA, have been identified in several human pathologies such as progressive external ophthalmoplegia and Alpers' syndrome. Extensive literature shows mitochondrial toxicity effects nucleoside analogue reverse transcriptase inhibitors used in the treatment of HIV and chronic hepatitis B as a consequence of an inhibitory effect on Polg. We have previously shown that mice with an error-prone version of PolgA accumulate higher levels of somatic mtDNA mutations resulting in a premature aging phenotype. In the present paper, we demonstrate PolgA deficiency in mouse embryos causes an early developmental arrest between embryonic days 7.5 and 8.5 associated with severe mtDNA depletion. Heterozygous knockout mice have half the wild-type levels of PolgA transcripts and a slight reduction in mtDNA levels but develop normally. Surprisingly, amounts of PolgA transcripts in heterozygous knockout mice are increased in response to artificially elevated mtDNA copy number, revealing a possible regulatory link between mtDNA maintenance and PolgA expression. Our results show that Polg indeed is the only DNA polymerase capable of maintaining mtDNA in mammalian mitochondria. In addition, presence of Polg is absolutely essential for the organogenesis during mammalian embryonic development.
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Affiliation(s)
- Nicole Hance
- Department of Medical Nutrition at Novum, Karolinska Institute, Stockholm, Sweden
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35
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Chen XJ. Sal1p, a calcium-dependent carrier protein that suppresses an essential cellular function associated With the Aac2 isoform of ADP/ATP translocase in Saccharomyces cerevisiae. Genetics 2005; 167:607-17. [PMID: 15238515 PMCID: PMC1470917 DOI: 10.1534/genetics.103.023655] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Adenine nucleotide translocase (Ant) catalyzes ADP/ATP exchange between the cytosol and the mitochondrial matrix. It is also proposed to form or regulate the mitochondrial permeability transition pore, a megachannel of high conductancy on the mitochondrial membranes. Eukaryotic genomes generally contain multiple isoforms of Ant. In this study, it is shown that the Ant isoforms are functionally differentiated in Saccharomyces cerevisiae. Although the three yeast Ant proteins can equally support respiration (the R function), Aac2p and Aac3p, but not Aac1p, have an additional physiological function essential for cell viability (the V function). The loss of V function in aac2 mutants leads to a lethal phenotype under both aerobic and anaerobic conditions. The lethality is suppressed by a strain-polymorphic locus, named SAL1 (for Suppressor of aac2 lethality). SAL1 was identified to encode an evolutionarily conserved protein of the mitochondrial carrier family. Notably, the Sal1 protein was shown to bind calcium through two EF-hand motifs located on its amino terminus. Calcium binding is essential for the suppressor activity. Finally, Sal1p is not required for oxidative phosphorylation and its overexpression does not complement the R(-) phenotype of aac2 mutants. On the basis of these observations, it is proposed that Aac2p and Sal1p may define two parallel pathways that transport a nucleotide substrate in an operational mode distinct from ADP/ATP exchange.
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Affiliation(s)
- Xin Jie Chen
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9148, USA.
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36
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Abstract
Despite recent epidemiological studies confirming that mitochondrial respiratory chain disorders due to mutations in either the mitochondrial or nuclear genome are amongst the most common inherited human diseases, realistic therapeutic strategies for these patients remain limited. The disappointing response to various vitamins, cofactors and electron acceptors that have been administered to patients in an attempt to bypass the underlying respiratory chain defect, coupled with the complexities of human mitochondrial genetics, means that novel and innovative means are required to offer realistic treatments. Several 'gene therapy' strategies have therefore been proposed to treat patients with pathogenic mitochondrial DNA mutations, and although these are not without their own inherent problems, several exciting approaches promise much in the near future. This review will provide a basic background to mitochondrial genetics and mitochondrial DNA disorders before introducing the various strategies being tested in vitro at present, in cell culture and animal models, and, in the example of therapeutic exercise, in patients themselves.
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Affiliation(s)
- Robert W Taylor
- University of Newcastle upon Tyne, Mitochondrial Research Group, School of Neurology, Neurobiology and Psychiatry, Newcastle upon Tyne, NE2 4HH, UK.
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37
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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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Schaefer AM, Blakely EL, Griffiths PG, Turnbull DM, Taylor RW. Ophthalmoplegia due to mitochondrial DNA disease: The need for genetic diagnosis. Muscle Nerve 2005; 32:104-7. [PMID: 15795893 DOI: 10.1002/mus.20319] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We describe a patient with chronic progressive external ophthalmoplegia (CPEO) who underwent muscle biopsy for suspected mitochondrial disease. In spite of normal histocytochemical cytochrome c oxidase (COX) activity and respiratory chain enzyme measurements in muscle, subsequent molecular genetic analysis revealed the presence of a single, large-scale deletion of mitochondrial DNA (mtDNA). The case serves to illustrate the importance of pursuing the proposed mitochondrial genetic abnormality, even in patients with normal biopsy findings.
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Affiliation(s)
- Andrew M Schaefer
- School of Neurology, Neurobiology and Psychiatry, The Medical School, Framlington Place, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4HH, United Kingdom
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39
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DiMauro S. Mitochondrial diseases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2004; 1658:80-8. [PMID: 15282178 DOI: 10.1016/j.bbabio.2004.03.014] [Citation(s) in RCA: 173] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2004] [Revised: 03/23/2004] [Accepted: 03/25/2004] [Indexed: 12/12/2022]
Abstract
By convention, the term "mitochondrial diseases" refers to disorders of the mitochondrial respiratory chain, which is the only metabolic pathway in the cell that is under the dual control of the mitochondrial genome (mtDNA) and the nuclear genome (nDNA). Therefore, a genetic classification of the mitochondrial diseases distinguishes disorders due to mutations in mtDNA, which are governed by the relatively lax rules of mitochondrial genetics, and disorders due to mutations in nDNA, which are governed by the stricter rules of mendelian genetics. Mutations in mtDNA can be divided into those that impair mitochondrial protein synthesis in toto and those that affect any one of the 13 respiratory chain subunits encoded by mtDNA. Essential clinical features for each group of diseases are reviewed. Disorders due to mutations in nDNA are more abundant not only because most respiratory chain subunits are nucleus-encoded but also because correct assembly and functioning of the respiratory chain require numerous steps, all of which are under the control of nDNA. These steps (and related diseases) include: (i) synthesis of assembly proteins; (ii) intergenomic signaling; (iii) mitochondrial importation of nDNA-encoded proteins; (iv) synthesis of inner mitochondrial membrane phospholipids; (v) mitochondrial motility and fission.
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Affiliation(s)
- Salvatore DiMauro
- Department of Neurology, 4-420 College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, NY 10032, USA.
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40
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Rutledge JC, Finn LS. Pediatric mitochondrial disease: do we have the energy to make the diagnosis? Pediatr Dev Pathol 2004; 7:641-5. [PMID: 15630536 DOI: 10.1007/s10024-004-5049-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2004] [Accepted: 07/26/2004] [Indexed: 11/25/2022]
Affiliation(s)
- Joe C Rutledge
- Department of Laboratory Medicine, University of Washington School of Medicine and Children's Hospital and Regional Medical Center, 4800 Sand Point Way NE, Seattle, WA 98105, USA.
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41
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Dimmick J. Conjugated hyperbilirubinemia in infancy (mitochondrial DNA depletion syndrome, liver). Pediatr Dev Pathol 2004; 7:625-8. [PMID: 15630532 DOI: 10.1007/s10024-004-5052-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2004] [Accepted: 07/26/2004] [Indexed: 10/26/2022]
Affiliation(s)
- James Dimmick
- Department of Pathology and Laboratory Medicine, University of British Columbia and British Columbia Childrens and Womens Hospital, 2211 Wesbrook Mall, UBC, Vancouver, BC, V6T 2B5, Canada.
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Tyynismaa H, Sembongi H, Bokori-Brown M, Granycome C, Ashley N, Poulton J, Jalanko A, Spelbrink JN, Holt IJ, Suomalainen A. Twinkle helicase is essential for mtDNA maintenance and regulates mtDNA copy number. Hum Mol Genet 2004; 13:3219-27. [PMID: 15509589 DOI: 10.1093/hmg/ddh342] [Citation(s) in RCA: 180] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Mechanisms of mitochondrial DNA (mtDNA) maintenance have recently gained wide interest owing to their role in inherited diseases as well as in aging. Twinkle is a new mitochondrial 5'-3' DNA helicase, defects of which we have previously shown to underlie a mitochondrial disease, progressive external ophthalmoplegia with multiple mtDNA deletions. Mouse Twinkle is highly similar to the human counterpart, suggesting conserved function. Here, we have characterized the mouse Twinkle gene and expression profile and report that the expression patterns are not conserved between human and mouse, but are synchronized with the adjacent gene MrpL43, suggesting a shared promoter. To elucidate the in vivo role of Twinkle in mtDNA maintenance, we generated two transgenic mouse lines overexpressing wild-type Twinkle. We could demonstrate for the first time that increased expression of Twinkle in muscle and heart increases mtDNA copy number up to 3-fold higher than controls, more than any other factor reported to date. Additionally, we utilized cultured human cells and observed that reduced expression of Twinkle by RNA interference mediated a rapid drop in mtDNA copy number, further supporting the in vivo results. These data demonstrate that Twinkle helicase is essential for mtDNA maintenance, and that it may be a key regulator of mtDNA copy number in mammals.
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Affiliation(s)
- Henna Tyynismaa
- Department of Neurology and Programme of Neurosciences, University of Helsinki, 00290 Helsinki, Finland
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43
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Korpelainen H. The evolutionary processes of mitochondrial and chloroplast genomes differ from those of nuclear genomes. Naturwissenschaften 2004; 91:505-18. [PMID: 15452701 DOI: 10.1007/s00114-004-0571-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
This paper first introduces our present knowledge of the origin of mitochondria and chloroplasts, and the organization and inheritance patterns of their genomes, and then carries on to review the evolutionary processes influencing mitochondrial and chloroplast genomes. The differences in evolutionary phenomena between the nuclear and cytoplasmic genomes are highlighted. It is emphasized that varying inheritance patterns and copy numbers among different types of genomes, and the potential advantage achieved through the transfer of many cytoplasmic genes to the nucleus, have important implications for the evolution of nuclear, mitochondrial and chloroplast genomes. Cytoplasmic genes transferred to the nucleus have joined the more strictly controlled genetic system of the nuclear genome, including also sexual recombination, while genes retained within the cytoplasmic organelles can be involved in selection and drift processes both within and among individuals. Within-individual processes can be either intra- or intercellular. In the case of heteroplasmy, which is attributed to mutations or biparental inheritance, within-individual selection on cytoplasmic DNA may provide a mechanism by which the organism can adapt rapidly. The inheritance of cytoplasmic genomes is not universally maternal. The presence of a range of inheritance patterns indicates that different strategies have been adopted by different organisms. On the other hand, the variability occasionally observed in the inheritance mechanisms of cytoplasmic genomes reduces heritability and increases environmental components in phenotypic features and, consequently, decreases the potential for adaptive evolution.
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Affiliation(s)
- Helena Korpelainen
- Department of Applied Biology, University of Helsinki, PO Box 27, 00014, Helsinki, Finland.
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Luoma P, Melberg A, Rinne JO, Kaukonen JA, Nupponen NN, Chalmers RM, Oldfors A, Rautakorpi I, Peltonen L, Majamaa K, Somer H, Suomalainen A. Parkinsonism, premature menopause, and mitochondrial DNA polymerase gamma mutations: clinical and molecular genetic study. Lancet 2004; 364:875-82. [PMID: 15351195 DOI: 10.1016/s0140-6736(04)16983-3] [Citation(s) in RCA: 393] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Mutations in the gene encoding mitochondrial DNA polymerase gamma (POLG), the enzyme that synthesises mitochondrial DNA (mtDNA), have been associated with a mitochondrial disease-autosomal dominant or recessive progressive external ophthalmoplegia-and multiple deletions of mtDNA. Mitochondrial dysfunction is also suspected to participate in the pathogenesis of Parkinson's disease. However, no primary gene defects affecting mitochondrial proteins causing mendelian transmission of parkinsonism have been characterised. We aimed to analyse the gene sequence of POLG in patients with progressive external ophthalmoplegia and their healthy relatives. METHODS In seven families of various ethnic origins we assessed patients with progressive external ophthalmoplegia and unaffected individuals by clinical, biochemical, morphological, and molecular genetic characterisation and positron emission tomography (PET). FINDINGS We recorded mutations in POLG in members of all seven families. Clinical assessment showed significant cosegregation of parkinsonism with POLG mutations (p<0.0001), and PET findings were consistent with dopaminergic neuron loss. Post-mortem examination in two individuals showed loss of pigmented neurons and pigment phagocytosis in substantia nigra without Lewy bodies. Furthermore, most women with progressive external ophthalmoplegia had early menopause-before age 35 years. The POLG gene defect resulted in secondary accumulation of mtDNA deletions in patients' tissues. INTERPRETATION Dysfunction of mitochondrial POLG causes a severe progressive multisystem disorder including parkinsonism and premature menopause, which are not typical of mitochondrial disease. Cosegregation of parkinsonism and POLG mutations in our families suggests that when defective, this gene can underlie mendelian transmission of parkinsonism. RELEVANCE TO PRACTICE Awareness that mitochondrial POLG mutations can underlie parkinsonism is important for clinicians working in diagnosis of movement disorders, as well as for studies of the genetics of Parkinson's disease. Further, progressive external ophthalmoplegia with muscle weakness and neuropathy can mask symptoms of parkinsonism, and clinicians should pay special attention to detect and treat parkinsonism in those individuals.
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Affiliation(s)
- Petri Luoma
- Department of Neurology and Programme of Neurosciences, Biomedicum-Helsinki, Helsinki University, and Helsinki University Central Hospital, Helsinki, Finland
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45
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Kiechl S, Horváth R, Luoma P, Kiechl-Kohlendorfer U, Wallacher-Scholz B, Stucka R, Thaler C, Wanschitz J, Suomalainen A, Jaksch M, Willeit J. Two families with autosomal dominant progressive external ophthalmoplegia. J Neurol Neurosurg Psychiatry 2004; 75:1125-8. [PMID: 15258213 PMCID: PMC1739155 DOI: 10.1136/jnnp.2003.025890] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
OBJECTIVES We report here the clinical and genetic features of two new families with autosomal dominant progressive external ophthalmoplegia (adPEO). PATIENTS AND METHODS The examination of index patients included a detailed clinical characterisation, histological analysis of muscle biopsy specimens, and genetic testing of mitochondrial and nuclear DNA extracted from muscle and leucocytes. RESULTS Index patients in both families presented with PEO and developed other clinical disease manifestations, such as myopathy and cardiomyopathy (patient 1) and axonal neuropathy, diabetes mellitus, hearing loss, and myopathy (patient 2), later in the course of illness. Both patients had ragged red fibres on muscle histology. Southern blot of mtDNA from muscle of patient 2 showed multiple deletions. In this case, a novel heterozygous missense mutation F485L was identified in the nuclear encoded putative mitochondrial helicase Twinkle. The mutation co-segregated with the clinical phenotype in the family and was not detected in 150 control chromosomes. In the other index patient, sequencing of ANT1, C10orf2 (encoding for Twinkle), and POLG1 did not reveal pathogenic mutations. CONCLUSIONS Our cases illustrate the clinical variability of adPEO, add a novel pathogenic mutation in Twinkle (F485L) to the growing list of genetic abnormalities in adPEO, and reinforce the relevance of other yet unidentified genes in mtDNA maintenance and pathogenesis of adPEO.
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Affiliation(s)
- S Kiechl
- Department of Neurology, University Hospital Innsbruck, Austria.
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46
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Moraes CT, Atencio DP, Oca-Cossio J, Diaz F. Techniques and pitfalls in the detection of pathogenic mitochondrial DNA mutations. J Mol Diagn 2004; 5:197-208. [PMID: 14573777 PMCID: PMC1907336 DOI: 10.1016/s1525-1578(10)60474-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Mutations in the mitochondrial DNA (mtDNA) are now recognized as major contributors to human pathologies and possibly to normal aging. A large number of rearrangements and point mutations in protein coding and tRNA genes have been identified in patients with mitochondrial disorders. In this review, we discuss genotype-phenotype correlations in mitochondrial diseases and common techniques used to identify pathogenic mtDNA mutations in human tissues. Although most of these approaches employ standard molecular biology tools, the co-existence of wild-type and mutated mtDNA (mtDNA heteroplasmy) in diseased tissues complicates both the detection and accurate determination of the size of the mutated fractions. To address these problems, novel approaches were developed and are discussed in this review.
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Affiliation(s)
- Carlos T Moraes
- Department of Neurology, University of Miami School of Medicine, Miami, Florida 33136, USA.
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47
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Taylor RW, Schaefer AM, Barron MJ, McFarland R, Turnbull DM. The diagnosis of mitochondrial muscle disease. Neuromuscul Disord 2004; 14:237-45. [PMID: 15019701 DOI: 10.1016/j.nmd.2003.12.004] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2003] [Revised: 11/24/2003] [Accepted: 12/23/2003] [Indexed: 10/26/2022]
Abstract
Mitochondrial respiratory chain abnormalities are an important cause of neuromuscular disease and may be due to defects of either the mitochondrial or nuclear genome. On account of the clinical and genetic heterogeneity exhibited by the mitochondrial myopathies, their investigation and diagnosis remains a challenge, requiring a combination of techniques including muscle histochemistry, biochemical assessment of respiratory chain function and molecular genetic studies. Here, we describe a step-by-step approach to the clinical and laboratory diagnosis of mitochondrial muscle disease, highlighting the many potential problems that can hinder reaching the correct diagnosis.
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Affiliation(s)
- Robert W Taylor
- 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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48
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Liu CS, Tsai CS, Kuo CL, Chen HW, Lii CK, Ma YS, Wei YH. Oxidative stress-related alteration of the copy number of mitochondrial DNA in human leukocytes. Free Radic Res 2004; 37:1307-17. [PMID: 14753755 DOI: 10.1080/10715760310001621342] [Citation(s) in RCA: 221] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The role of oxidative stress in the regulation of the copy number of mitochondrial DNA (mtDNA) in human leukocytes is unclear. In this study, we investigated the redox factors in plasma that may contribute to the alteration of mtDNA copy number in human leukocytes. A total of 156 healthy subjects of 25-80 years of age who exhibited no significant difference in the distribution of subpopulations of leukocytes in blood were recruited. Small-molecular-weight antioxidants and thiobarbituric acid reactive substances (TBARS) in plasma and 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 4,977bp deletion of mtDNA in leukocytes were determined. The mtDNA copy number in leukocytes was determined by real-time PCR. The results showed that the copy number of mtDNA in leukocytes was changed with age in a biphasic manner that fits in a positively quadratic regression model (P = 0.001). Retinol (P = 0.005), non-protein thiols (P = 0.001) and ferritin (P = 0.004) in plasma and total glutathione in erythrocytes (P = 0.046) were the significant redox factors that correlated with the mtDNA copy number in leukocytes in a positive manner. By contrast, alpha-tocopherol levels in plasma (P = 0.001) and erythrocytes (P = 0.033) were negatively correlated with the mtDNA copy number in leukocytes. Three oxidative indices including the incidence of 4,977 bp deletion of mtDNA (P = 0.016) and 8-OHdG content in leukocytes (P = 0.003) and TBARS in plasma (P = 0.001) were all positively correlated with the copy number of mtDNA in leukocytes. Taken these findings together, we suggest that the copy number of mtDNA in leukocytes is affected by oxidative stress in blood circulation elicited by the alteration of plasma antioxidants/prooxidants and oxidative damage to DNA.
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Affiliation(s)
- Chin-San Liu
- Department of Neurology and Vascular and Genomic Research Center, Changhua Christian Hospital, Changhua 500, Taiwan
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49
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Korhonen JA, Gaspari M, Falkenberg M. TWINKLE Has 5' -> 3' DNA helicase activity and is specifically stimulated by mitochondrial single-stranded DNA-binding protein. J Biol Chem 2003; 278:48627-32. [PMID: 12975372 DOI: 10.1074/jbc.m306981200] [Citation(s) in RCA: 225] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutations in TWINKLE cause autosomal dominant progressive external ophthalmoplegia, a human disorder associated with multiple deletions in the mitochondrial DNA. TWINKLE displays primary sequence similarity to the phage T7 gene 4 primase-helicase, but no specific enzyme activity has been assigned to the protein. We have purified recombinant TWINKLE to near homogeneity and demonstrate here that TWINKLE is a DNA helicase with 5' to 3' directionality and distinct substrate requirements. The protein needs a stretch of 10 nucleotides of single-stranded DNA on the 5'-side of the duplex to unwind duplex DNA. In addition, helicase activity is not observed unless a short single-stranded 3'-tail is present. The helicase activity has an absolute requirement for hydrolysis of a nucleoside 5'-triphosphate, with UTP being the optimal substrate. DNA unwinding by TWINKLE is specifically stimulated by the mitochondrial single-stranded DNA-binding protein. Our enzymatic characterization strongly supports the notion that TWINKLE is the helicase at the mitochondrial DNA replication fork and provides evidence for a close relationship of the DNA replication machinery in bacteriophages and mammalian mitochondria.
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Affiliation(s)
- Jenny A Korhonen
- Department of Medical Nutrition, Karolinska Institutet, Novum, SE-141 86 Huddinge, Sweden
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50
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Deschauer M, Kiefer R, Blakely EL, He L, Zierz S, Turnbull DM, Taylor RW. A novel Twinkle gene mutation in autosomal dominant progressive external ophthalmoplegia. Neuromuscul Disord 2003; 13:568-72. [PMID: 12921794 DOI: 10.1016/s0960-8966(03)00071-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Autosomal dominant progressive external ophthalmoplegia is a common neurological presentation of mitochondrial disease and is characterised by multiple deletions of mitochondrial DNA in muscle. We describe a family with autosomal dominant progressive external ophthalmoplegia caused by a novel heterozygous A to C transversion at nucleotide 956 of the Twinkle gene. The deltoid muscle biopsy of the index case revealed sparse respiratory deficient cells. Multiple mitochondrial DNA deletions were clearly evident in the index case by both long-range and real-time polymerase chain reaction assays but not by Southern blotting, highlighting the diagnostic difficulties associated with characterising patients with multiple mitochondrial DNA deletions.
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Affiliation(s)
- Marcus Deschauer
- Department of Neurology, The Medical School, Framlington Place, University of Newcastle upon Tyne, NE2 4HH, Newcastle upon Tyne, UK
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