251
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Abstract
Mitochondrial DNA (mtDNA) accumulates both base-substitution mutations and deletions with aging in several tissues in mammals. Here, we examine the evidence supporting a causative role for mtDNA mutations in mammalian aging. We describe and compare human diseases and mouse models associated with mitochondrial genome instability. We also discuss potential mechanisms for the generation of these mutations and the means by which they may mediate their pathological consequences. Strategies for slowing the accumulation and attenuating the effects of mtDNA mutations are discussed.
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252
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Abstract
Among the human diseases that result from abnormalities in mitochondrial genome stability or maintenance are several that result from mutations affecting enzymes of deoxyribonucleoside triphosphate (dNTP) metabolism. In addition, it is evident that the toxicity of antiviral nucleoside analogs is determined in part by the extent to which their intracellular conversion to dNTP analogs occurs within the mitochondrion. Finally, recent work from this laboratory has shown considerable variation among different mammalian tissues with respect to mitochondrial dNTP pool sizes and has suggested that natural asymmetries in mitochondrial dNTP concentrations may contribute to the high rates at which the mitochondrial genome undergoes mutation. These factors suggest that much more information is needed about maintenance and regulation of dNTP pools within mammalian mitochondria. This review summarizes our current understanding and suggests directions for future research.
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Affiliation(s)
- Christopher K Mathews
- Department of Biochemistry and Biophysics, Oregon State University, 2011 Agricultural and Life Sciences Bldg., Corvallis, OR 97331-7305, USA.
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253
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Lewis W, Day BJ, Kohler JJ, Hosseini SH, Chan SSL, Green EC, Haase CP, Keebaugh ES, Long R, Ludaway T, Russ R, Steltzer J, Tioleco N, Santoianni R, Copeland WC. Decreased mtDNA, oxidative stress, cardiomyopathy, and death from transgenic cardiac targeted human mutant polymerase gamma. J Transl Med 2007; 87:326-35. [PMID: 17310215 PMCID: PMC1831462 DOI: 10.1038/labinvest.3700523] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
POLG is the human gene that encodes the catalytic subunit of DNA polymerase gamma (Pol gamma), the replicase for human mitochondrial DNA (mtDNA). A POLG Y955C point mutation causes human chronic progressive external ophthalmoplegia (CPEO), a mitochondrial disease with eye muscle weakness and mtDNA defects. Y955C POLG was targeted transgenically (TG) to the murine heart. Survival was determined in four TG (+/-) lines and wild-type (WT) littermates (-/-). Left ventricle (LV) performance (echocardiography and MRI), heart rate (electrocardiography), mtDNA abundance (real time PCR), oxidation of mtDNA (8-OHdG), histopathology and electron microscopy defined the phenotype. Cardiac targeted Y955C POLG yielded a molecular signature of CPEO in the heart with cardiomyopathy (CM), mitochondrial oxidative stress, and premature death. Increased LV cavity size and LV mass, bradycardia, decreased mtDNA, increased 8-OHdG, and cardiac histopathological and mitochondrial EM defects supported and defined the phenotype. This study underscores the pathogenetic role of human mutant POLG and its gene product in mtDNA depletion, mitochondrial oxidative stress, and CM as it relates to the genetic defect in CPEO. The transgenic model pathophysiologically links human mutant Pol gamma, mtDNA depletion, and mitochondrial oxidative stress to the mtDNA replication apparatus and to CM.
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Affiliation(s)
- William Lewis
- Department of Pathology, Emory University School of Medicine, Atlanta, GA 30322, USA.
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254
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Abstract
Mitochondrial diseases are disorders caused by impairment of the mitochondrial respiratory chain, characterized by clinical-genetic heterogeneity and frequent multisystemic involvement. It is difficult to establish a precise genotype/phenotype correlation and obtain a definitive nosology. Today's genetic classification distinguishes disorders caused by defects in the mitochondrial genome (sporadic or maternally-inherited) from disorders caused by defects in the nuclear genome (autosomally-inherited). We report an updated classification, briefly review the main clinical syndromes and describe the most recent genetic knowledge.
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Affiliation(s)
- M Filosto
- Neurological Clinic, Section for Neuromuscular Diseases and Neuropathies, University Hospital Spedali Civili of Brescia, Brescia, Italy.
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255
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Mayr JA, Merkel O, Kohlwein SD, Gebhardt BR, Böhles H, Fötschl U, Koch J, Jaksch M, Lochmüller H, Horváth R, Freisinger P, Sperl W. Mitochondrial phosphate-carrier deficiency: a novel disorder of oxidative phosphorylation. Am J Hum Genet 2007; 80:478-84. [PMID: 17273968 PMCID: PMC1821108 DOI: 10.1086/511788] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2006] [Accepted: 12/11/2006] [Indexed: 12/16/2022] Open
Abstract
The mitochondrial phosphate carrier SLC25A3 transports inorganic phosphate into the mitochondrial matrix, which is essential for the aerobic synthesis of adenosine triphosphate (ATP). We identified a homozygous mutation--c.215G-->A (p.Gly72Glu)--in the alternatively spliced exon 3A of this enzyme in two siblings with lactic acidosis, hypertrophic cardiomyopathy, and muscular hypotonia who died within the 1st year of life. Functional investigation of intact mitochondria showed a deficiency of ATP synthesis in muscle but not in fibroblasts, which correlated with the tissue-specific expression of exon 3A in muscle versus exon 3B in fibroblasts. The enzyme defect was confirmed by complementation analysis in yeast. This is the first report of patients with mitochondrial phosphate-carrier deficiency.
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Affiliation(s)
- Johannes A Mayr
- Department of Pediatrics, Paracelsus Private Medical University, Salzburg, Austria.
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256
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Ostergaard E, Hansen FJ, Sorensen N, Duno M, Vissing J, Larsen PL, Faeroe O, Thorgrimsson S, Wibrand F, Christensen E, Schwartz M. Mitochondrial encephalomyopathy with elevated methylmalonic acid is caused by SUCLA2 mutations. Brain 2007; 130:853-61. [PMID: 17287286 DOI: 10.1093/brain/awl383] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We have identified 12 patients with autosomal recessive mitochondrial encephalomyopathy with elevated methylmalonic acid. The disorder has a high incidence of 1 in 1700 in the Faroe Islands due to a founder effect, and a carrier frequency of 1 in 33. The symptoms comprise hypotonia, muscle atrophy, hyperkinesia, severe hearing impairment and postnatal growth retardation. Neuroimaging showed demyelination and central and cortical atrophy, including atrophy of the basal ganglia, and some of the patients fulfilled the criteria for Leigh syndrome. Urine and plasma methylmalonic acid were elevated. Homozygosity mapping with the Affymetrix 10 K array revealed a homozygous region on chromosome 13q14 harbouring the SUCLA2 gene. Mutations in SUCLA2 were recently shown to cause a similar disorder in a small Israeli family. Mutation analysis identified a novel splice site mutation in SUCLA2, IVS4 + 1G --> A, leading to skipping of exon 4. The SUCLA2 gene encodes the ATP-forming beta subunit of the Krebs cycle enzyme succinyl-CoA ligase. The hallmark of the condition, elevated methylmalonic acid, can be explained by an accumulation of the substrate of the enzyme, succinyl-CoA, which in turn leads to elevated methylmalonic acid, because the conversion of methylmalonyl-CoA to succinyl-CoA is inhibited.
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Affiliation(s)
- Elsebet Ostergaard
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark.
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257
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Nury H, Dahout-Gonzalez C, Trézéguet V, Lauquin GJM, Brandolin G, Pebay-Peyroula E. Relations between structure and function of the mitochondrial ADP/ATP carrier. Annu Rev Biochem 2007; 75:713-41. [PMID: 16451122 DOI: 10.1146/annurev.biochem.75.103004.142747] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Import and export of metabolites through mitochondrial membranes are vital processes that are highly controlled and regulated at the level of the inner membrane. Proteins of the mitochondrial carrier family ( MCF ) are embedded in this membrane, and each member of the family achieves the selective transport of a specific metabolite. Among these, the ADP/ATP carrier transports ADP into the mitochondrial matrix and exports ATP toward the cytosol after its synthesis. Because of its natural abundance, the ADP/ATP carrier is the best characterized within MCF, and a high-resolution structure of one conformation is known. The overall structure is basket shaped and formed by six transmembrane helices that are not only tilted with respect to the membrane, but three of them are also kinked at the level of prolines. The functional mechanisms, nucleotide recognition, and conformational changes for the transport, suggested from the structure, are discussed along with the large body of biochemical and functional results.
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Affiliation(s)
- H Nury
- Institut de Biologie Structurale Jean-Pierre Ebel, UMR 5075 CEA-CNRS-Université Joseph Fourier, F-38027 Grenoble cedex 1, France.
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258
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Higuchi M. Regulation of mitochondrial DNA content and cancer. Mitochondrion 2007; 7:53-7. [PMID: 17320491 PMCID: PMC1868520 DOI: 10.1016/j.mito.2006.12.001] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2006] [Accepted: 09/21/2006] [Indexed: 12/14/2022]
Abstract
Enzymatic activities of the proteins encoded in nuclear genome are regulated by transcriptional, translational and post-transcriptional level. Enzymatic activities of proteins encoded in mitochondrial DNA (mtDNA) have been considered to be regulated by the same steps although detailed mechanisms might differ. However, dynamic change of the number of mtDNA, from some hundred to more than ten thousand, should be considered as another novel mechanism to regulate mtDNA-encoded proteins. Recently, we showed the connection of mtDNA depletion and deletion to cancer progression [Higuchi, M., Kudo, T., Suzuki, S., Evans, T.T., Sasaki, R., Wada, Y., Shirakawa, T., Sawyer, J.R., Gotoh, A., 2006. Mitochondrial DNA determines androgen dependence in prostate cancer cell lines. Oncogene 25, 1437-1445]. This review focuses and describes the possible connections of the mitochondrial DNA depletion and deletion to cancer.
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Affiliation(s)
- Masahiro Higuchi
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, 4301 West Markham, Slot 516 Little Rock, AR 72205-7199, USA.
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259
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Matsushima Y, Kaguni LS. Differential phenotypes of active site and human autosomal dominant progressive external ophthalmoplegia mutations in Drosophila mitochondrial DNA helicase expressed in Schneider cells. J Biol Chem 2007; 282:9436-9444. [PMID: 17272269 PMCID: PMC4853901 DOI: 10.1074/jbc.m610550200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We report the cloning and molecular analysis of Drosophila mitochondrial DNA helicase (d-mtDNA helicase) homologous to human TWINKLE, which encodes one of the genes responsible for autosomal dominant progressive external ophthalmoplegia. An RNA interference construct was designed that reduces expression of d-mtDNA helicase to an undetectable level in Schneider cells. RNA interference knockdown of d-mtDNA helicase decreases the copy number of mitochondrial DNA (mtDNA) approximately 5-fold. In a corollary manner, overexpression of d-mtDNA helicase increases mtDNA levels 1.4-fold. Overexpression of helicase active site mutants K388A and D483A results in a severe depletion of mtDNA and a dominant negative lethal phenotype. Overexpression of mutants analogous to human autosomal dominant progressive external ophthalmoplegia mutations shows differential effects. Overexpression of I334T and A442P mutants yields a dominant negative effect as for the active site mutants. In contrast, overexpression of A326T, R341Q, and W441C mutants results in increased mtDNA copy number, as observed with wild-type overexpression. Our dominant negative analysis of d-mtDNA helicase in cultured cells provides a tractable model for understanding human autosomal dominant progressive external ophthalmoplegia mutations.
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Affiliation(s)
- Yuichi Matsushima
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824
| | - Laurie S Kaguni
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824.
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260
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Alemi M, Prigione A, Wong A, Schoenfeld R, DiMauro S, Hirano M, Taroni F, Cortopassi G. Mitochondrial DNA deletions inhibit proteasomal activity and stimulate an autophagic transcript. Free Radic Biol Med 2007; 42:32-43. [PMID: 17157191 PMCID: PMC1927835 DOI: 10.1016/j.freeradbiomed.2006.09.014] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Revised: 07/29/2006] [Accepted: 09/14/2006] [Indexed: 01/01/2023]
Abstract
Deletions within the mitochondrial DNA (mtDNA) cause Kearns Sayre syndrome (KSS) and chronic progressive external opthalmoplegia (CPEO). The clinical signs of KSS include muscle weakness, heart block, pigmentary retinopathy, ataxia, deafness, short stature, and dementia. The identical deletions occur and rise exponentially as humans age, particularly in substantia nigra. Deletions at >30% concentration cause deficits in basic bioenergetic parameters, including membrane potential and ATP synthesis, but it is poorly understood how these alterations cause the pathologies observed in patients. To better understand the consequences of mtDNA deletions, we microarrayed six cell types containing mtDNA deletions from KSS and CPEO patients. There was a prominent inhibition of transcripts encoding ubiquitin-mediated proteasome activity, and a prominent induction of transcripts involved in the AMP kinase pathway, macroautophagy, and amino acid degradation. In mutant cells, we confirmed a decrease in proteasome biochemical activity, significantly lower concentration of several amino acids, and induction of an autophagic transcript. An interpretation consistent with the data is that mtDNA deletions increase protein damage, inhibit the ubiquitin-proteasome system, decrease amino acid salvage, and activate autophagy. This provides a novel pathophysiological mechanism for these diseases, and suggests potential therapeutic strategies.
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Affiliation(s)
- Mansour Alemi
- Department of Molecular Biosciences, 1311 Haring Hall, University of California, Davis, CA 95616, USA
| | - Alessandro Prigione
- Department of Molecular Biosciences, 1311 Haring Hall, University of California, Davis, CA 95616, USA
| | - Alice Wong
- Department of Molecular Biosciences, 1311 Haring Hall, University of California, Davis, CA 95616, USA
| | - Robert Schoenfeld
- Department of Molecular Biosciences, 1311 Haring Hall, University of California, Davis, CA 95616, USA
| | - Salvatore DiMauro
- Department of Neurology, Columbia University Medical Center, 630 West 168 Street, New York, NY 10032
| | - Michio Hirano
- Department of Neurology, Columbia University Medical Center, 630 West 168 Street, New York, NY 10032
| | - Franco Taroni
- Division of Biochemistry and Genetics, Istituto Nazionale Neurologico Carlo Besta, Milan, Italy
| | - Gino Cortopassi
- Department of Molecular Biosciences, 1311 Haring Hall, University of California, Davis, CA 95616, USA
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261
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Abstract
Mitochondria are ubiquitous organelles that are intimately involved in many cellular processes, but whose principal task is to provide the energy necessary for normal cell functioning and maintenance. Disruption of this energy supply can have devastating consequences for the cell, organ, and individual. Over the last two decades, mutations in both mitochondrial DNA (mtDNA) and nuclear DNA have been identified as causative in a number of well-characterized clinical syndromes, although for mtDNA mutations in particular, this relationship between genotype and phenotype is often not straightforward. Despite this, a number of epidemiological studies have been undertaken to assess the prevalence of mtDNA mutations and these have highlighted the impact that mtDNA disease has on both the community and individual families. Although there has been considerable improvement in the diagnosis of mitochondrial disorders, disappointingly this has not been matched by developments toward effective treatment. Nevertheless, our understanding of mitochondrial biology is gathering pace and progress in this area will be crucial to devising future treatment strategies. In addition to mitochondrial disease, evidence for a central role of mitochondria in other processes, such as aging and neurodegeneration, is slowly accumulating, although their role in cancer remains controversial. In this chapter, we discuss these issues and offer our own views based on our cumulative experience of investigating and managing these diseases over the last 20 years.
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Affiliation(s)
- R McFarland
- Mitochondrial Research Group, School of Neurology, Neurobiology, and Psychiatry, The Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4HH, United Kingdom
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262
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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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263
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Kang D, Hamasaki N. Mitochondrial disease: maintenance of mitochondrial genome and molecular diagnostics. Adv Clin Chem 2006; 42:217-54. [PMID: 17131628 DOI: 10.1016/s0065-2423(06)42006-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Mitochondrial DNA (mtDNA) is essential for the aerobic ATP synthesis system that is responsible for about 80% of normal cellular energy demands. In addition to rare genetic disorders causing neuromyopathy, alterations of mtDNA have been found also in so-called common diseases such as heart failure, diabetes, and cancer. Although some of these alterations are inherited, some are considered to be generated and/or accumulated in somatic cells with age. One reason for the somatic mutations is that mtDNA is more vulnerable than is nuclear DNA. For example, mitochondrial respiratory chain produces a large amount of reactive oxygen species as inevitable byproducts of oxidative phosphorylation. However, the molecular mechanisms for maintenance of mitochondrial genome are much less elucidated than those for nuclear genome. In spite of its increasing importance, the molecular diagnosis of mitochondrial DNA-related diseases is well done only in very limited expert laboratories. In this chapter, we focus on maintenance of mtDNA in somatic cells, its clinical importance, and recent developments of molecular tests.
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Affiliation(s)
- Dongchon Kang
- Department of Clinical Chemistry and Laboratory Medicine, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan
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264
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Kubota M, Kasahara T, Nakamura T, Ishiwata M, Miyauchi T, Kato T. Abnormal Ca2+ dynamics in transgenic mice with neuron-specific mitochondrial DNA defects. J Neurosci 2006; 26:12314-24. [PMID: 17122057 PMCID: PMC6675445 DOI: 10.1523/jneurosci.3933-06.2006] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2006] [Revised: 10/12/2006] [Accepted: 10/15/2006] [Indexed: 11/21/2022] Open
Abstract
Maintenance of mitochondrial DNA (mtDNA) depends on nuclear-encoded proteins such as mtDNA polymerase (POLG), whose mutations are involved in the diseases caused by mtDNA defects including mutation and deletion. The defects in mtDNA and in intracellular Ca2+ ([Ca2+]i) homeostasis have been reported in bipolar disorder (BD). To understand the relevance of the mtDNA defects to BD, we studied transgenic (Tg) mice in which mutant POLG (mutPOLG) was expressed specifically in neurons. mtDNA defects were accumulated in the brains of mutPOLG Tg mice in an age-dependent manner and the mutant mice showed BD-like behavior. However, the molecular and cellular basis for the abnormalities has not been clarified. In this study, we investigated Ca2+ regulation by isolated mitochondria and [Ca2+]i dynamics in the neurons of mutPOLG Tg mice. Mitochondria from the mutant mice sequestered Ca2+ more rapidly, whereas Ca2+ retention capacity and membrane potential, a driving force of Ca2+ uptake, of mitochondria were unaffected. To elucidate the molecular mechanism of the altered Ca2+ uptake, we performed DNA microarray analysis and found that the expression of cyclophilin D (CyP-D), a component of the permeability transition pore, was downregulated in the brains of mutPOLG Tg mice. Cyclosporin A, an inhibitor of CyP-D, mimicked the enhanced Ca2+ uptake in mutant mice. Furthermore, G-protein-coupled receptor-mediated [Ca2+]i increase was attenuated in hippocampal neurons of the mutant mice. These findings suggest that mtDNA defects lead to enhancement of Ca2+ uptake rate via CyP-D downregulation and alter [Ca2+]i dynamics, which may be involved in the pathogenesis of BD.
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Affiliation(s)
- Mie Kubota
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute, Wako-shi, Saitama 351-0198, Japan, and
| | - Takaoki Kasahara
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute, Wako-shi, Saitama 351-0198, Japan, and
| | - Takeshi Nakamura
- Department of Physiology, Juntendo University School of Medicine, Bunkyo-ku, Tokyo 113-8421, Japan
| | - Mizuho Ishiwata
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute, Wako-shi, Saitama 351-0198, Japan, and
| | - Taeko Miyauchi
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute, Wako-shi, Saitama 351-0198, Japan, and
| | - Tadafumi Kato
- Laboratory for Molecular Dynamics of Mental Disorders, RIKEN Brain Science Institute, Wako-shi, Saitama 351-0198, Japan, and
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265
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Hudson G, Chinnery PF. Mitochondrial DNA polymerase-gamma and human disease. Hum Mol Genet 2006; 15 Spec No 2:R244-52. [PMID: 16987890 DOI: 10.1093/hmg/ddl233] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The maintenance of mitochondrial DNA (mtDNA) is critically dependent upon polymerase-gamma (pol-gamma), encoded by the nuclear gene POLG. Over the last 5 years, it has become clear that mutations of POLG are a major cause of human disease. Secondary mtDNA defects characterize these disorders, with mtDNA depletion, multiple mtDNA deletions or multiple point mutations of mtDNA in clinically affected tissues. The secondary mtDNA defects cause cell and tissue-specific deficiencies of mitochondrial oxidative phosphorylation, leading to organ dysfunction and human disease. Functional genetic variants of POLG are present in up to approximately 0.5% of the general population, and pathogenic mutations have been described in most exons of the gene. Clinically, POLG mutations can present from early neonatal life to late middle age, with a spectrum of phenotypes that includes common neurological disorders such as migraine, epilepsy and Parkinsonism. Transgenic mice and biochemical studies of recombinant mutated proteins are helping to unravel mechanisms of pathogenesis, and patterns are beginning to emerge relating genotype to phenotype.
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Affiliation(s)
- Gavin Hudson
- Mitochondrial Research Group and Institute of Human Genetics, M41014, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
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266
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Dahout-Gonzalez C, Nury H, Trézéguet V, Lauquin GJM, Pebay-Peyroula E, Brandolin G. Molecular, functional, and pathological aspects of the mitochondrial ADP/ATP carrier. Physiology (Bethesda) 2006; 21:242-9. [PMID: 16868313 DOI: 10.1152/physiol.00005.2006] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In providing the cell with ATP generated by oxidative phosphorylation, the mitochondrial ADP/ATP carrier plays a central role in aerobic eukaryotic cells. Combining biochemical, genetic, and structural approaches contributes to understanding the molecular mechanism of this essential transport system, the dysfunction of which is implicated in neuromuscular diseases.
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Affiliation(s)
- C Dahout-Gonzalez
- Département de Réponse et Dynamique Cellulaires, CEA-Grenoble, Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, UMR 5092 CEA-CNRS-Université Joseph Fourier, Grenoble, France
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267
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Sánchez-Martínez Á, Luo N, Clemente P, Adán C, Hernández-Sierra R, Ochoa P, Fernández-Moreno MÁ, Kaguni LS, Garesse R. Modeling human mitochondrial diseases in flies. BIOCHIMICA ET BIOPHYSICA ACTA 2006; 1757:1190-8. [PMID: 16806050 PMCID: PMC4853902 DOI: 10.1016/j.bbabio.2006.05.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2006] [Revised: 04/24/2006] [Accepted: 05/05/2006] [Indexed: 01/16/2023]
Abstract
Human mitochondrial diseases are associated with a wide range of clinical symptoms, and those that result from mutations in mitochondrial DNA affect at least 1 in 8500 individuals. The development of animal models that reproduce the variety of symptoms associated with this group of complex human disorders is a major focus of current research. Drosophila represents an attractive model, in large part because of its short life cycle, the availability of a number of powerful techniques to alter gene structure and regulation, and the presence of orthologs of many human disease genes. We describe here Drosophila models of mitochondrial DNA depletion, deafness, encephalopathy, Freidreich's ataxia, and diseases due to mitochondrial DNA mutations. We also describe several genetic approaches for gene manipulation in flies, including the recently developed method of targeted mutagenesis by recombinational knock-in.
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Affiliation(s)
- Álvaro Sánchez-Martínez
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas “Alberto Sols” CSIC-UAM. Facultad de Medicina, Universidad Autónoma de Madrid, Arzobispo Morcillo 4, E-28029 Madrid, Spain
| | - Ningguang Luo
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824-1319, USA
| | - Paula Clemente
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas “Alberto Sols” CSIC-UAM. Facultad de Medicina, Universidad Autónoma de Madrid, Arzobispo Morcillo 4, E-28029 Madrid, Spain
| | - Cristina Adán
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas “Alberto Sols” CSIC-UAM. Facultad de Medicina, Universidad Autónoma de Madrid, Arzobispo Morcillo 4, E-28029 Madrid, Spain
| | - Rosana Hernández-Sierra
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas “Alberto Sols” CSIC-UAM. Facultad de Medicina, Universidad Autónoma de Madrid, Arzobispo Morcillo 4, E-28029 Madrid, Spain
| | - Pilar Ochoa
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas “Alberto Sols” CSIC-UAM. Facultad de Medicina, Universidad Autónoma de Madrid, Arzobispo Morcillo 4, E-28029 Madrid, Spain
| | - Miguel Ángel Fernández-Moreno
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas “Alberto Sols” CSIC-UAM. Facultad de Medicina, Universidad Autónoma de Madrid, Arzobispo Morcillo 4, E-28029 Madrid, Spain
| | - Laurie S. Kaguni
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824-1319, USA
| | - Rafael Garesse
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas “Alberto Sols” CSIC-UAM. Facultad de Medicina, Universidad Autónoma de Madrid, Arzobispo Morcillo 4, E-28029 Madrid, Spain
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268
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Wang Y, Bogenhagen DF. Human Mitochondrial DNA Nucleoids Are Linked to Protein Folding Machinery and Metabolic Enzymes at the Mitochondrial Inner Membrane. J Biol Chem 2006; 281:25791-802. [PMID: 16825194 DOI: 10.1074/jbc.m604501200] [Citation(s) in RCA: 222] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondrial DNA (mtDNA) is packaged into bacterial nucleoid-like structures, each containing several mtDNA molecules. The distribution of nucleoids during mitochondrial fission and fusion events and during cytokinesis is important to the segregation of mitochondrial genomes in heteroplasmic cells bearing a mixture of wild-type and mutant mtDNA molecules. We report fractionation of HeLa cell mtDNA nucleoids into two subsets of complexes that differ in their sedimentation velocity and their association with cytoskeletal proteins. Pulse labeling studies indicated that newly replicated mtDNA molecules are evenly represented in the rapidly and slowly sedimenting fractions. Slowly sedimenting nucleoids were immunoaffinity purified using antibodies to either of two abundant mtDNA-binding proteins, TFAM or mtSSB. These two different immunoaffinity procedures yielded very similar sets of proteins, with 21 proteins in common, including most of the proteins previously shown to play roles in mtDNA replication and transcription. In addition to previously identified mitochondrial proteins, multiple peptides were observed for one novel DNA metabolic protein, the DEAH-box helicase DHX30. Antibodies raised against a recombinant fragment of this protein confirmed the mitochondrial localization of a specific isoform of DHX30.
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Affiliation(s)
- Yousong Wang
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York 11794-8651, USA
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269
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Baruffini E, Lodi T, Dallabona C, Puglisi A, Zeviani M, Ferrero I. Genetic and chemical rescue of the Saccharomyces cerevisiae phenotype induced by mitochondrial DNA polymerase mutations associated with progressive external ophthalmoplegia in humans. Hum Mol Genet 2006; 15:2846-55. [PMID: 16940310 DOI: 10.1093/hmg/ddl219] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The human POLG gene encodes the catalytic subunit of mitochondrial DNA polymerase gamma (pol gamma). Mutations in pol gamma are associated with a spectrum of disease phenotypes including autosomal dominant and recessive forms of progressive external ophthalmoplegia, spino-cerebellar ataxia and epilepsy, and Alpers-Huttenlocher hepatocerebral poliodystrophy. Multiple deletions, or depletion of mtDNA in affected tissues, are the molecular hallmarks of pol gamma mutations. To shed light on the pathogenic mechanisms leading to these phenotypes, we have introduced in MIP1, the yeast homologue of POLG, two mutations equivalent to the human Y955C and G268A mutations, which are associated with dominant and recessive PEO, respectively. Both mutations induced the generation of petite colonies, carrying either rearranged (rho-) or no (rho0) mtDNA. Mutations in genes that control the mitochondrial supply of deoxynucleotides (dNTP) affect the mtDNA integrity in both humans and yeast. To test whether the manipulation of the dNTP pool can modify the effects of pol gamma mutations in yeast, we have overexpressed a dNTP checkpoint enzyme, ribonucleotide reductase, RNR1, or deleted its inhibitor, SML1. In both mutant strains, the petite mutability was dramatically reduced. The same result was obtained by exposing the mutant strains to dihydrolipoic acid, an anti-oxidant agent. Therefore, an increase of the mitochondrial dNTP pool and/or a decrease of reactive oxygen species can prevent the mtDNA damage induced by pol gamma mutations in yeast and, possibly, in humans.
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Affiliation(s)
- Enrico Baruffini
- Department of Genetics, Biology of Microorganisms, Anthropology, Evolution, University of Parma, Italy
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270
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Abstract
Intracellular concentrations of the four deoxyribonucleoside triphosphates (dNTPs) are closely regulated, and imbalances in the four dNTP pools have genotoxic consequences. Replication errors leading to mutations can occur, for example, if one dNTP in excess drives formation of a non-Watson-Crick base pair or if it forces replicative DNA chain elongation past a mismatch before DNA polymerase can correct the error by 3' exonuclease proofreading. This review focuses on developments since 1994, when the field was last reviewed comprehensively. Emphasis is placed on the following topics: 1) novel aspects of dNTP pool regulation, 2) dNTP pool asymmetries as mutagenic determinants, 3) dNTP metabolism and hypermutagenesis of retroviral genomes, 4) dNTP metabolism and mutagenesis in the mitochondrial genome, 5) chemical modification of nucleotides as a premutagenic event, 6) relationships between dNTP metabolism, genome stability, aging, and cancer.
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Affiliation(s)
- Christopher K Mathews
- Department of Biochemistry and Biophysics, Oregon State University, 2011 Agricultural & Life Sciences Bldg., Corvallis, Oregon 97331-7305, USA.
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271
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Abstract
Defects of mitochondrial metabolism cause a wide range of human diseases that include examples from all medical subspecialties. This review updates the topic of mitochondrial diseases by reviewing the most important recent advances in this area. The factors influencing inheritance, maintenance and replication of mtDNA are reviewed and the genotype-phenotype of mtDNA disorders has been expanded, with new insights into epidemiology, pathogenesis and its role in ageing. Recently identified nuclear gene mutations of mitochondrial proteins include mutations of frataxin causing Friedreich's ataxia, PINK1, DJ1 causing Parkinson's disease and POLG causing infantile mtDNA depletion syndrome, ophthalmoplegia, parkinsonism, male subfertility and, in a transgenic mouse model, premature senescence. Mitochondrial defects in neurodegenerative diseases include Parkinson's, Alzheimer's and Huntington's disease. Improved understanding of mtDNA inheritance and mutation penetrance patterns, and novel techniques for mtDNA modification offer significant prospects for more accurate genetic counselling and effective future therapies.
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Affiliation(s)
- Anthony H V Schapira
- University Department of Clinical Neurosciences, Royal Free and University College Medical School, and Institute of Neurology, University College London, London NW3 2PF, UK.
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272
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Naïmi M, Bannwarth S, Procaccio V, Pouget J, Desnuelle C, Pellissier JF, Rötig A, Munnich A, Calvas P, Richelme C, Jonveaux P, Castelnovo G, Simon M, Simon M, Clanet M, Wallace D, Paquis-Flucklinger V. Molecular analysis of ANT1, TWINKLE and POLG in patients with multiple deletions or depletion of mitochondrial DNA by a dHPLC-based assay. Eur J Hum Genet 2006; 14:917-22. [PMID: 16639411 DOI: 10.1038/sj.ejhg.5201627] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
ANT1, TWINKLE and POLG genes affect mtDNA stability and are involved in autosomal dominant PEO, while mutations in POLG are responsible for numerous clinical presentations, including autosomal recessive PEO, sensory ataxic neuropathy, dysarthria and ophthalmoparesis (SANDO), spino-cerebellar ataxia and epilepsy (SCAE) or Alpers syndrome. In this study, we report on the mutational analysis of ANT1, TWINKLE and POLG genes in 15 unrelated patients, using a dHPLC-based protocol. This series of patients illustrates the large array of clinical presentations associated with mtDNA stability defects, ranging from isolated benign PEO to fatal Alpers syndrome. A total of seven different mutations were identified in six of 15 patients (40%). Six different recessive mutations were found in POLG, one in TWINKLE while no mutation was identified in ANT1. Among the POLG mutations, three are novel and include two missense and one frameshift changes. Seventeen neutral changes and polymorphisms were also identified, including four novel neutral polymorphisms. Overall, this study illustrates the variability of phenotypes associated with mtDNA stability defects, increases the mutational spectrum of POLG variants and provides an efficient and reliable detection protocol for ANT1, TWINKLE and POLG mutational screening.
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Affiliation(s)
- Mourad Naïmi
- Department of Medical Genetics, Archet 2 Hospital, CHU Nice, France
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273
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Graziewicz MA, Longley MJ, Copeland WC. DNA polymerase gamma in mitochondrial DNA replication and repair. Chem Rev 2006; 106:383-405. [PMID: 16464011 DOI: 10.1021/cr040463d] [Citation(s) in RCA: 211] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Maria A Graziewicz
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA
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274
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Malka F, Lombès A, Rojo M. Organization, dynamics and transmission of mitochondrial DNA: focus on vertebrate nucleoids. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:463-72. [PMID: 16730385 DOI: 10.1016/j.bbamcr.2006.04.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Revised: 04/04/2006] [Accepted: 04/04/2006] [Indexed: 11/21/2022]
Abstract
Eukaryotic cells contain numerous copies of the mitochondrial genome (from 50 to 100 copies in the budding yeast to some thousands in humans) that localize to numerous intramitochondrial nucleoprotein complexes called nucleoids. The transmission of mitochondrial DNA differs significantly from that of nuclear genomes and depends on the number, molecular composition and dynamic properties of nucleoids and on the organization and dynamics of the mitochondrial compartment. While the localization, dynamics and protein composition of mitochondrial DNA nucleoids begin to be described, we are far from knowing all mechanisms and molecules mediating and/or regulating these processes. Here, we review our current knowledge on vertebrate nucleoids and discuss similarities and differences to nucleoids of other eukaryots.
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Affiliation(s)
- Florence Malka
- INSERM U582, Institut de Myologie, Groupe Hospitalier Pitié-Salpêtrière, Université Pierre et Marie Curie, IFR14, 47, boulevard de l'Hôpital, 75651 Paris cedex 13, France
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275
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Higuchi M, Kudo T, Suzuki S, Evans TT, Sasaki R, Wada Y, Shirakawa T, Sawyer JR, Gotoh A. Mitochondrial DNA determines androgen dependence in prostate cancer cell lines. Oncogene 2006; 25:1437-45. [PMID: 16278679 PMCID: PMC2215312 DOI: 10.1038/sj.onc.1209190] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Prostate cancer progresses from an androgen-dependent to androgen-independent stage after androgen ablation therapy. Mitochondrial DNA plays a role in cell death and metastatic competence. Further, heteroplasmic large-deletion mitochondrial DNA is very common in prostate cancer. To investigate the role of mitochondrial DNA in androgen dependence of prostate cancers, we tested the changes of normal and deleted mitochondrial DNA in accordance with the progression of prostate cancer. We demonstrated that the androgen-independent cell line C4-2, established by inoculation of the androgen-dependent LNCaP cell line into castrated mice, has a greatly reduced amount of normal mitochondrial DNA and an accumulation of large-deletion DNA. Strikingly, the depletion of mitochondrial DNA from androgen-dependent LNCaP resulted in a loss of androgen dependence. Reconstitution of normal mitochondrial DNA to the mitochondrial DNA-depleted clone restored androgen dependence. These results indicate that mitochondrial DNA determines androgen dependence of prostate cancer cell lines. Further, mitochondrial DNA-deficient cells formed tumors in castrated athymic mice, whereas LNCaP did not. The accumulation of large deletion and depletion of mitochondrial DNA may thus play a role in the development of androgen independence, leading to progression of prostate cancers.
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Affiliation(s)
- M Higuchi
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA.
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276
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Celotto AM, Frank AC, McGrath SW, Fergestad T, Van Voorhies WA, Buttle KF, Mannella CA, Palladino MJ. Mitochondrial encephalomyopathy in Drosophila. J Neurosci 2006; 26:810-20. [PMID: 16421301 PMCID: PMC6675365 DOI: 10.1523/jneurosci.4162-05.2006] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Mitochondrial encephalomyopathies are common and devastating multisystem genetic disorders characterized by neuromuscular dysfunction and tissue degeneration. Point mutations in the human mitochondrial ATP6 gene are known to cause several related mitochondrial disorders: NARP (neuropathy, ataxia, and retinitis pigmentosa), MILS (maternally inherited Leigh's syndrome), and FBSN (familial bilateral striatal necrosis). We identified a pathogenic mutation in the Drosophila mitochondrial ATP6 gene that causes progressive, adult-onset neuromuscular dysfunction and myodegeneration. Our results demonstrate ultrastructural defects in the mitochondrial innermembrane, neural dysfunction, and a marked reduction in mitochondrial ATP synthase activity associated with this mutation. This Drosophila mutant recapitulates key features of the human neuromuscular disorders enabling detailed in vivo studies of these enigmatic diseases.
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Affiliation(s)
- Alicia M Celotto
- Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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277
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Abstract
BACKGROUND Mitochondrial respiratory chain disorders are the most prevalent group of inherited neurometabolic diseases. They present with central and peripheral neurological features usually in association with other organ involvement including the eye, the heart, the liver, and kidneys, diabetes mellitus and sensorineural deafness. Current treatment is largely supportive and the disorders progress relentlessly causing significant morbidity and premature death. Vitamin supplements, pharmacological agents and exercise therapy have been used in isolated cases and small clinical trials, but the efficacy of these interventions is unclear. OBJECTIVES To determine whether there is objective evidence to support the use of current treatments for mitochondrial disease. SEARCH STRATEGY We searched the Cochrane Neuromuscular Disease Group trials register (searched September 2003), the Cochrane Central Register of Controlled Trials, MEDLINE (January 1966 to October 3 2003), EMBASE (January 1980 to October 3 2003) and the European Neuromuscular Centre (ENMC) clinical trials register, and contacted experts in the field. SELECTION CRITERIA We included randomised controlled trials (including crossover studies) and quasi-randomised trials comparing pharmacological treatments, and non-pharmacological treatments (vitamins and food supplements), and physical training in individuals with mitochondrial disorders. The primary outcome measures included an improvement in muscle strength and/or endurance, or neurological clinical features. Secondary outcome measures included quality of life assessments, biochemical markers of disease and negative outcomes. DATA COLLECTION AND ANALYSIS Details of the number of randomised patients, treatment, study design, study category, allocation concealment and patient characteristics were extracted. Analysis was based on intention to treat data. We planned to use meta-analysis, but this did not prove necessary. MAIN RESULTS Six hundred and seventy-eight abstracts were reviewed, and six fulfilled the entry criteria. Two trials studied the effects of co-enzyme Q10 (ubiquinone), one reporting a subjective improvement and a significant increase in a global scale of muscle strength, but the other trial did not show any benefit. Two trials used creatine, with one reporting improved measures of muscle strength and post-exercise lactate, but the other reported no benefit. One trial of dichloroacetate showed an improvement in secondary outcome measures of mitochondrial metabolism, and one trial using dimethylglycine showed no significant effect. AUTHORS' CONCLUSIONS There is currently no clear evidence supporting the use of any intervention in mitochondrial disorders. Further research is needed to establish the role of a wide range of therapeutic approaches.
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Affiliation(s)
- P Chinnery
- University of Newcastle upon Tyne, Department of Neurology, Medical School, Framlington Place, Newcastle Upon Tyne, UK, NE24 4HH.
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278
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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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279
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Lodi T, Bove C, Fontanesi F, Viola AM, Ferrero I. Mutation D104G in ANT1 gene: complementation study in Saccharomyces cerevisiae as a model system. Biochem Biophys Res Commun 2006; 341:810-5. [PMID: 16438935 DOI: 10.1016/j.bbrc.2006.01.034] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Accepted: 01/11/2006] [Indexed: 11/24/2022]
Abstract
Mutations in the human ANT1 gene, coding for the ADP/ATP carrier, are responsible for the autosomal dominant and recessive forms of progressive external ophthalmoplegia, mitochondrial disorders characterized by the presence of multiple deletions of mitochondrial DNA in affected tissues. By introducing these mutations at equivalent position in AAC2, the yeast orthologue of ANT1, we created a suitable model for validation of the pathogenicity of the human mutations. Here, we describe the use of this approach in the case of mutations mapping in domains not conserved between human and yeast, taking advantage of a yAAC2/hANT1 chimeric construction as a template to introduce pathogenic hANT1 mutations. Application to the case of the D104G mutation indicated that the chimeric construction could be a tool for validation of pathogenic ANT1 mutations in yeast.
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Affiliation(s)
- Tiziana Lodi
- Department of Genetics Anthropology Evolution, University of Parma, 43100 Parma, Italy.
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280
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Abstract
Mitochondrial DNA (mtDNA) encodes essential components of the cellular energy-producing apparatus, and lesions in mtDNA and mitochondrial dysfunction contribute to numerous human diseases. Understanding mtDNA organization and inheritance is therefore an important goal. Recent studies have revealed that mitochondria use diverse metabolic enzymes to organize and protect mtDNA, drive the segregation of the organellar genome, and couple the inheritance of mtDNA with cellular metabolism. In addition, components of a membrane-associated mtDNA segregation apparatus that might link mtDNA transmission to mitochondrial movements are beginning to be identified. These findings provide new insights into the mechanisms of mtDNA maintenance and inheritance.
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Affiliation(s)
- Xin Jie Chen
- Department of Molecular Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, Texas 75390-9148, USA
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281
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Abstract
Mitochondrial disorders of oxidative phosphorylation (OXPHOS) comprise a growing list of potentially lethal diseases caused by mutations in either mitochondrial (mtDNA) or nuclear DNA (nDNA). Two such conditions, autosomal dominant progressive external ophthalmoplegia (adPEO) and Senger's Syndrome, are associated with dysfunction of the heart and muscle-specific isoform of the adenine nucleotide translocase (ANT1), a nDNA gene product that facilitates transport of ATP and ADP across the inner mitochondrial membrane. AdPEO is a mtDNA deletion disorder broadly characterized by pathology involving the eyes, skeletal muscle, and central nervous system. In addition to ANT1, mutations in at least two other nuclear genes, twinkle and POLG, have been shown to cause mtDNA destabilization associated with adPEO. Senger's syndrome is an autosomal recessive condition characterized by congenital heart defects, abnormalities of skeletal muscle mitochondria, cataracts, and elevated circulatory levels of lactic acid. This syndrome is associated with severe depletion of ANT1, which may be the result of an as yet unidentified ANT1-specific transcriptional or translational processing error. ANT1 has also been associated with a third condition, autosomal dominant facioscapulohumeral muscular dystrophy (FSHD), an adult onset disorder characterized by variable muscle weakness in the face, feet, shoulders, and hips. FSHD patients possess specific DNA deletions on chromosome 4, which appear to cause derepression of several nearby genes, including ANT1. Early development of FSHD may involve mitochondrial dysfunction and increased oxidative stress, possibly associated with overexpression of ANT1.
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Affiliation(s)
- J Daniel Sharer
- Department of Genetics, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
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282
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Hayashi M, Imanaka-Yoshida K, Yoshida T, Wood M, Fearns C, Tatake RJ, Lee JD. A crucial role of mitochondrial Hsp40 in preventing dilated cardiomyopathy. Nat Med 2005; 12:128-32. [PMID: 16327803 DOI: 10.1038/nm1327] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2005] [Accepted: 10/14/2005] [Indexed: 11/08/2022]
Abstract
Many heat-shock proteins (Hsp) are members of evolutionarily conserved families of chaperone proteins that inhibit the aggregation of unfolded polypeptides and refold denatured proteins, thereby remedying phenotypic effects that may result from protein aggregation or protein instability. Here we report that the mitochondrial chaperone Hsp40, also known as Dnaja3 or Tid1, is differentially expressed during cardiac development and pathological hypertrophy. Mice deficient in Dnaja3 developed dilated cardiomyopathy (DCM) and died before 10 weeks of age. Progressive respiratory chain deficiency and decreased copy number of mitochondrial DNA were evident in cardiomyocytes lacking Dnaja3. Profiling of Dnaja3-interacting proteins identified the alpha-subunit of DNA polymerase gamma (Polga) as a client protein. These findings suggest that Dnaja3 is crucial for mitochondrial biogenesis, at least in part, through its chaperone activity on Polga and provide genetic evidence of the necessity for mitochondrial Hsp40 in preventing DCM.
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MESH Headings
- Animals
- Aorta/pathology
- Cardiomyopathy, Dilated/pathology
- Cardiomyopathy, Dilated/prevention & control
- Cell Line
- DNA/metabolism
- DNA Polymerase gamma
- DNA, Mitochondrial/metabolism
- DNA-Directed DNA Polymerase/metabolism
- Electron Transport
- Electron Transport Complex IV/metabolism
- Evolution, Molecular
- Green Fluorescent Proteins/metabolism
- HSP40 Heat-Shock Proteins/chemistry
- HSP40 Heat-Shock Proteins/genetics
- HSP40 Heat-Shock Proteins/metabolism
- HSP40 Heat-Shock Proteins/physiology
- Humans
- Immunoblotting
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Microscopy, Fluorescence
- Mitochondria/metabolism
- Myocytes, Cardiac/metabolism
- Protein Binding
- Protein Denaturation
- Protein Folding
- Protein Renaturation
- Protein Structure, Tertiary
- Reverse Transcriptase Polymerase Chain Reaction
- Time Factors
- Transfection
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Affiliation(s)
- Masaaki Hayashi
- Department of Immunology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037-1000, USA
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283
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Wallace DC. The mitochondrial genome in human adaptive radiation and disease: on the road to therapeutics and performance enhancement. Gene 2005; 354:169-80. [PMID: 16024186 DOI: 10.1016/j.gene.2005.05.001] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2005] [Accepted: 05/05/2005] [Indexed: 10/25/2022]
Abstract
The human mitochondrial genome consists of approximately 1500 genes, 37 encoded by the maternally inherited mitochondrial DNA (mtDNA) and the remainder encoded in the nuclear DNA (nDNA). The mtDNA is present in thousands of copies per cell and encodes proteins that are essential components of the mitochondrial energy generation pathway, oxidative phosphorylation (OXPHOS). OXPHOS generates heat to maintain our body temperature and ATP to do work. The mitochondria also produce much of the cellular reactive oxygen species (ROS) and can initiate apoptosis through activation of the mitochondrial permeability transition pore (mtPTP) in response to energy deficiency and oxidative damage. Mitochondrial ROS mutates the mtDNA and mtDNA mutations have been associated with a wide range of age-related diseases including neurodegenerative diseases, cardiomyopathy, diabetes and various cancers. The cellular accumulation of mtDNA mutations may also be the aging clock. Ancient mtDNA variants have also been adaptive and may influence individual health today. Mutations in nDNA-encoded mitochondrial genes can also disrupt OXPHOS, alter mtDNA replication, and affect mitochondrial division. In an effort to treat mitochondrial disease, both metabolic and genetic interventions have been attempted. Metabolic interventions have been directed at increasing energy output, reducing ROS production and stabilizing the mtPTP. Genetic therapies have attempted introduction of nucleic acids into the mitochondrion, nDNA-mitochondrial genes into the nucleus, and mtDNA-encoded genes into the nucleus. These therapeutic approaches might also be used to enhance performance, but we must be careful that catering to short term individual interests might undermine our capacity to adapt and survive.
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Affiliation(s)
- Douglas C Wallace
- Center for Molecular and Mitochondrial Medicine and Genetics, Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, CA 92697-3940, USA.
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284
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Spinazzola A, Zeviani M. Disorders of nuclear-mitochondrial intergenomic signaling. Gene 2005; 354:162-8. [PMID: 15921863 DOI: 10.1016/j.gene.2005.03.025] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2005] [Accepted: 03/25/2005] [Indexed: 11/20/2022]
Abstract
Depletion and multiple deletions of mitochondrial DNA (mtDNA) have been associated with a number of autosomal disorders classified as defects of nuclear-mitochondrial intergenomic signaling. The mendelian forms of progressive external ophthalmoplegia (PEO) are clinically and genetically heterogeneous disorders characterized by the accumulation of multiple deletions of mtDNA in postmitotic patient's tissues. Most of the autosomal dominant PEO (adPEO) families carry heterozygous mutations in either one of three genes: ANT1, Twinkle, and POLG1. Mutations in POLG1 can also cause autosomal recessive PEO (arPEO) and apparently sporadic cases. In addition, recessive POLG1 mutations are responsible for sensory-atactic neuropathy, dysarthria and ophthalmoplegia (SANDO), juvenile spino-cerebellar ataxia-epilepsy syndrome (SCAE) and Alpers-Huttenlocher hepatopathic poliodystrophy. Mutations in thymidine phosphorylase gene (TP) are linked to mitochondrial neurogastrointestinal encephalomyopathy (MNGIE), an autosomal recessive disorder in which PEO is associated with gastrointestinal dysmotility and leukodystrophy. Finally, mitochondrial DNA depletion syndromes (MDS), defined by tissue-reduction in mtDNA copy number, have been linked to mutations in two genes involved in deoxyribonucleotide (dNTP) metabolism: thymidine kinase 2 (TK2) and deoxyguanosine kinase (DGUOK).
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Affiliation(s)
- Antonella Spinazzola
- Unit of Molecular Neurogenetics, Pierfranco and Luisa Mariani Center for the Study of Children's Mitochondrial Disorders, National Neurological Institute, Milan, Italy
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285
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Limongelli A, Tiranti V. Inherited Mendelian defects of nuclear-mitochondrial communication affecting the stability of mitochondrial DNA. Mitochondrion 2005; 2:39-46. [PMID: 16120307 DOI: 10.1016/s1567-7249(02)00043-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2001] [Revised: 05/20/2002] [Accepted: 05/24/2002] [Indexed: 12/24/2022]
Abstract
The presence of mtDNA abnormalities inherited as Mendelian traits indicates the existence of mutations in nuclear genes affecting the integrity of the mitochondrial genome. Two groups of nucleus-driven abnormalities have been described: qualitative alterations of mtDNA, i.e. multiple large-scale deletions of mtDNA, and quantitative decrease of the mtDNA copy number, i.e. tissue-specific depletion of mtDNA. Autosomal dominant or recessive (adPEO), progressive ophthalmoplegia and autosomal-recessive mitochondrial neurogastrointestinal encephalomyopathy (MNGIE), are three neurodegenerative disorders associated with the coexistence of wild-type mtDNA with several deletion-containing mtDNA species. Heterozygous mutations of the genes encoding the muscle-heart isoform of the adenosine diphosphate/adenosine triphosphate mitochondrial translocator (ANT1), the main subunit of polymerase gamma (POLG1), and of the putative mtDNA helicase (Twinkle) have been found in adPEO families linked to three different loci, on chromosomes 4q34-35, 10q24, and 15q25, respectively. Mutations in the gene encoding thymidine phosphorylase have been identified in several MNGIE patients. Severe, tissue-specific depletion of mtDNA is the molecular hallmark of rapidly progressive hepatopathies or myopathies of infancy and childhood. Two genes, deoxyguanosine kinase and thymidine kinase type 2, both involved in the mitochondrion-specific salvage pathways of deoxynucleotide pools, have been associated with depletion syndromes in selected families.
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Affiliation(s)
- Anna Limongelli
- Unit of Molecular Neurogenetics--Pierfranco and Luisa Mariani Center for the Study of Mitochondrial Disorders in Children, National Neurological Institute Carlo Besta, via Temolo 4, 20133, Milan, Italy
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286
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Chang KT, Min KT. Drosophila melanogaster homolog of Down syndrome critical region 1 is critical for mitochondrial function. Nat Neurosci 2005; 8:1577-85. [PMID: 16222229 DOI: 10.1038/nn1564] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2005] [Accepted: 09/14/2005] [Indexed: 11/09/2022]
Abstract
Mitochondrial dysfunction has emerged as a common theme that underlies numerous neurological disorders, including Down syndrome. Down syndrome cultures and tissues show mitochondrial damage such as impaired mitochondrial enzyme activities, defective mitochondrial DNA repairs and accumulation of toxic free radicals, but the cause of mitochondrial dysfunction remains elusive. Here we demonstrate that the Drosophila melanogaster homolog of human Down syndrome critical region gene 1 (DSCR1), nebula (also known as sarah, sra), has a crucial role in the maintenance of mitochondrial function and integrity. We report that nebula protein is located in the mitochondria. An alteration in the abundance of nebula affects mitochondrial enzyme activities, mitochondrial DNA content, and the number and size of mitochondria. Furthermore, nebula interacts with the ADP/ATP translocator and influences its activity. These results identify nebula/DSCR1 as a regulator of mitochondrial function and integrity and further suggest that an increased level of DSCR1 may contribute to the mitochondrial dysfunction seen in Down syndrome.
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Affiliation(s)
- Karen T Chang
- Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
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287
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Jacobs LJAM, de Wert G, Geraedts JPM, de Coo IFM, Smeets HJM. The transmission of OXPHOS disease and methods to prevent this. Hum Reprod Update 2005; 12:119-36. [PMID: 16199488 DOI: 10.1093/humupd/dmi042] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Diseases owing to defects of oxidative phosphorylation (OXPHOS) affect approximately 1 in 8,000 individuals. Clinical manifestations can be extremely variable and range from single-affected tissues to multisystemic syndromes. In general, tissues with a high energy demand, like brain, heart and muscle, are affected. The OXPHOS system is under dual genetic control, and mutations in both nuclear and mitochondrial genes can cause OXPHOS diseases. The expression and segregation of mitochondrial DNA (mtDNA) mutations is different from nuclear gene defects. The mtDNA mutations can be either homoplasmic or heteroplasmic and in the latter case disease becomes manifest when the mutation exceeds a tissue-specific threshold. This mutation load can vary between tissues and often an exact correlation between mutation load and phenotypic expression is lacking. The transmission of mtDNA mutations is exclusively maternal, but the mutation load between embryos can vary tremendously because of a segregational bottleneck. Diseases by nuclear gene mutations show a normal Mendelian inheritance pattern and often have a more constant clinical manifestation. Given the prevalence and severity of OXPHOS disorders and the lack of adequate therapy, existing and new methods for the prevention of transmission of OXPHOS disorders, like prenatal diagnosis (PND), preimplantation genetic diagnosis (PGD), cytoplasmic transfer (CT) and nuclear transfer (NT), are technically and ethically evaluated.
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Affiliation(s)
- L J A M Jacobs
- Department of Genetics and Cell Biology, University of Maastricht, 6200 MD Maastricht, The Netherlands
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288
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Palmieri L, Alberio S, Pisano I, Lodi T, Meznaric-Petrusa M, Zidar J, Santoro A, Scarcia P, Fontanesi F, Lamantea E, Ferrero I, Zeviani M. Complete loss-of-function of the heart/muscle-specific adenine nucleotide translocator is associated with mitochondrial myopathy and cardiomyopathy. Hum Mol Genet 2005; 14:3079-88. [PMID: 16155110 DOI: 10.1093/hmg/ddi341] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Multiple mitochondrial DNA deletions are associated with clinically heterogeneous disorders transmitted as mendelian traits. Dominant missense mutations were found in the gene encoding the heart and skeletal muscle-specific isoform of the adenine nucleotide translocator (ANT1) in families with autosomal dominant progressive external opthalmoplegia and in a sporadic patient. We herein report on a sporadic patient who presented with hypertrophic cardiomyopathy, mild myopathy with exercise intolerance and lactic acidosis but no ophthalmoplegia. A muscle biopsy showed the presence of numerous ragged-red fibers, and Southern blot analysis disclosed multiple deletions of muscle mitochondrial DNA. Molecular analysis revealed a C to A homozygous mutation at nucleotide 368 of the ANT1 gene. The mutation converted a highly conserved alanine into an aspartic acid at codon 123 and was absent in 500 control individuals. This is the first report of a recessive mutation in the ANT1 gene. The clinical and biochemical features are different from those found in dominant ANT1 mutations, resembling those described in ANT1 knockout mice. No ATP uptake was measured in proteoliposomes reconstituted with protein extracts from the patient's muscle. The equivalent mutation in AAC2, the yeast ortholog of human ANT1, resulted in a complete loss of transport activity and in the inability to rescue the severe Oxidative Phosphorylation phenotype displayed by WB-12, an AAC1/AAC2 defective strain. Interestingly, exposure to reactive oxygen species (ROS) scavengers dramatically increased the viability of the WB-12 transformant, suggesting that increased redox stress is involved in the pathogenesis of the disease and that anti-ROS therapy may be beneficial to patients.
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Affiliation(s)
- Luigi Palmieri
- Department of Pharmaco-Biology, Laboratory of Biochemistry and Molecular Biology, University of Bari, Italy
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289
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Nikali K, Suomalainen A, Saharinen J, Kuokkanen M, Spelbrink JN, Lönnqvist T, Peltonen L. Infantile onset spinocerebellar ataxia is caused by recessive mutations in mitochondrial proteins Twinkle and Twinky. Hum Mol Genet 2005; 14:2981-90. [PMID: 16135556 DOI: 10.1093/hmg/ddi328] [Citation(s) in RCA: 147] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Infantile onset spinocerebellar ataxia (IOSCA) (MIM 271245) is a severe autosomal recessively inherited neurodegenerative disorder characterized by progressive atrophy of the cerebellum, brain stem and spinal cord and sensory axonal neuropathy. We report here the molecular background of this disease based on the positional cloning/candidate approach of the defective gene. Having established the linkage to chromosome 10q24, we restricted the critical DNA region using single nucleotide polymorphism-based haplotypes. After analyzing all positional candidate transcripts, we identified two point mutations in the gene C10orf2 encoding Twinkle, a mitochondrial deoxyribonucleic acid (mtDNA)-specific helicase, and a rarer splice variant Twinky, underlying IOSCA. The founder IOSCA mutation, homozygous in all but one of the patients, leads to a Y508C amino acid change in the polypeptides. One patient, heterozygous for Y508C, carries a silent coding region cytosine to thymine transition mutation in his paternal disease chromosome. This allele is expressed at a reduced level, causing the preponderance of messenger RNAs encoding Y508C polypeptides and thus leads to the IOSCA disease phenotype. Previously, we have shown that different mutations in this same gene cause autosomal dominant progressive external ophthalmoplegia (adPEO) with multiple mtDNA deletions (MIM 606075), a neuromuscular disorder sharing a spectrum of symptoms with IOSCA. IOSCA phenotype is the first recessive one due to Twinkle and Twinky mutations, the dominant PEO mutations affecting mtDNA maintenance, but in IOSCA, mtDNA stays intact. The severe neurological phenotype observed in IOSCA, a result of only a single amino acid substitution in Twinkle and Twinky, suggests that these proteins play a crucial role in the maintenance and/or function of specific affected neuronal subpopulations.
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Affiliation(s)
- Kaisu Nikali
- Department of Molecular Medicine, National Public Health Institute, University of Helsinki, Finland.
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290
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Dörner A, Giessen S, Gaub R, Grosse Siestrup H, Schwimmbeck PL, Hetzer R, Poller W, Schultheiss HP. An isoform shift in the cardiac adenine nucleotide translocase expression alters the kinetic properties of the carrier in dilated cardiomyopathy. Eur J Heart Fail 2005; 8:81-9. [PMID: 16107323 DOI: 10.1016/j.ejheart.2005.05.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2004] [Revised: 12/08/2004] [Accepted: 05/05/2005] [Indexed: 10/25/2022] Open
Abstract
BACKGROUND Impaired mitochondrial ADP/ATP transport and altered adenine nucleotide translocase (ANT) isoform expression characterized by enhanced ANT1 and decreased ANT2 expression have been implicated in the pathophysiology of dilated cardiomyopathy (DCM). It is still unknown whether restricted ANT function results from exogenous factors, or mutations in the ANT genes, or whether the imbalance in the isoform composition causes the reduced ADP/ATP transport. We performed DNA mutation screening of ANT genes and analyzed the kinetic properties of ANT protein isolated from DCM hearts and controls in a reconstituted system excluding natural environmental influences. RESULTS A G1409T polymorphism in ANT2 leads to an exchange from Arg111 to Leu111 in healthy blood donors (n = 60) with allele frequencies of 76% and 24%. This polymorphism was neither associated with DCM (74%, 26%; n = 93) nor with altered myocardial ANT isoform expression or restricted ANT function (89%, 11%; n = 8). However, there was a remarkable reduction in the maximum transport activity (v(max)) of reconstituted ANT from DCM hearts with altered ANT isoform expression (498 +/- 113 micromol min(-1) g(-1) incorporated protein vs. 1112 +/- 178 micromol min(-1) g(-1) incorporated protein, p < 0.01). Moreover, the substrate affinity of DCM myocardial ANT to ATP was slightly reduced with an increased K(m) value of 104.3 +/- 2.4 microM vs. 90.4 +/- 2.9 microM in controls (p < 0.03). CONCLUSION The altered isoform expression in DCM hearts entails changes in the kinetic properties of total ANT protein restricting ANT function and contributing to disturbed energy metabolism in DCM.
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Affiliation(s)
- Andrea Dörner
- Charité University Medicine, Campus Benjamin Franklin, Department of Cardiology, Berlin, Germany.
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291
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Kang D, Hamasaki N. Mitochondrial DNA in somatic cells: A promising target of routine clinical tests. Clin Biochem 2005; 38:685-95. [PMID: 15946663 DOI: 10.1016/j.clinbiochem.2005.04.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2005] [Revised: 04/07/2005] [Accepted: 04/21/2005] [Indexed: 10/25/2022]
Abstract
Alterations of mitochondrial DNA have long been considered only from a point of view of rare genetic disorders causing neuromyopathy. Recently, alterations of mitochondrial DNA have been found in so-called common diseases such as heart failure, diabetes, and cancer; some of these alterations are inherited, and some are generated and/or accumulated in somatic cells with age. Mitochondrial DNA is more vulnerable to alteration than is nuclear DNA. For example, mitochondria produce a large amount of reactive oxygen species as an inevitable byproduct of oxidative phosphorylation. Therefore, mitochondrial DNA is under much stronger oxidative stress than is nuclear DNA. In spite of the importance, it is much less elucidated in the mitochondrial genome than in the nuclear genome how the genome is maintained. In this review, we focus on maintenance of mitochondrial DNA in somatic cells and its clinical importance.
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Affiliation(s)
- Dongchon Kang
- Department of Clinical Chemistry and Laboratory Medicine, Kyushu University Graduate School of Medical Sciences, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
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292
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Li FY, Cuddon PA, Song J, Wood SL, Patterson JS, Shelton GD, Duncan ID. Canine spongiform leukoencephalomyelopathy is associated with a missense mutation in cytochrome b. Neurobiol Dis 2005; 21:35-42. [PMID: 16026996 DOI: 10.1016/j.nbd.2005.06.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2005] [Revised: 05/26/2005] [Accepted: 06/06/2005] [Indexed: 11/29/2022] Open
Abstract
Two families of dogs (Australian cattle dogs and Shetland sheepdogs) with an inherited "spongiform leukoencephalomyelopathy" were identified, with widespread vacuolation of white matter of the brain and spinal cord. Affected dogs of both breeds developed tremors at 2-9 weeks of age followed by progressive neurological worsening with ataxia, paresis, paralysis, spasticity, and cranial nerve dysfunction. The modes of inheritance of both families were most likely maternal. The cerebrospinal fluid (CSF) analysis showed elevated ratio of 3-OH butyrate to acetoacetic acid. Mitochondrial DNA sequencing showed a G to A transition at 14,474 nt (G14474A, GenBank accession no. NC002008 ) that results in an amino acid change of valine-98 to methionine (V98M) of mitochondrial encoded cytochrome b. Western blot analysis showed increased levels of core I and core II but decreased level of cytochrome c1 of the complex III and cytochrome c oxidase of the complex IV of the respiratory chain.
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Affiliation(s)
- Fang-Yuan Li
- Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, USA.
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293
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Flierl A, Chen Y, Coskun PE, Samulski RJ, Wallace DC. Adeno-associated virus-mediated gene transfer of the heart/muscle adenine nucleotide translocator (ANT) in mouse. Gene Ther 2005; 12:570-8. [PMID: 15647764 PMCID: PMC1456758 DOI: 10.1038/sj.gt.3302443] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Mitochondrial myopathy, associated with muscle weakness and progressive external ophthalmoplegia, is caused by mutations in mitochondria oxidative phosphorylation genes including the heart-muscle isoform of the mitochondrial adenine nucleotide translocator (ANT1). To develop therapies for mitochondrial disease, we have prepared a recombinant adeno-associated viral vector (rAAV) carrying the mouse Ant1 cDNA. This vector has been used to transduce muscle cells and muscle from Ant1 mutant mice, which manifest mitochondrial myopathy. AAV-ANT1 transduction resulted in long-term, stable expression of the Ant1 transgene in muscle precursor cells as well as differentiated muscle fibers. The transgene ANT1 protein was targeted to the mitochondrion, was inserted into the mitochondrial inner membrane, formed a functional ADP/ATP carrier, increased the mitochondrial export of ATP and reversed the histopathological changes associated with the mitochondrial myopathy. Thus, AAV transduction has the potential of providing symptomatic relief for the ophthalmoplegia and ptosis resulting from paralysis of the extraocular eye muscles cause by mutations in the Ant1 gene.
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Affiliation(s)
- A Flierl
- MAMMAG, University of California, Irvine, CA 92697-3940, USA
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294
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Longley MJ, Graziewicz MA, Bienstock RJ, Copeland WC. Consequences of mutations in human DNA polymerase γ. Gene 2005; 354:125-31. [PMID: 15913923 DOI: 10.1016/j.gene.2005.03.029] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2004] [Revised: 01/20/2005] [Accepted: 03/25/2005] [Indexed: 10/25/2022]
Abstract
DNA polymerase gamma is responsible for replication and repair of the mitochondrial genome. Human DNA polymerase gamma is composed of a 140-kDa catalytic subunit and a 55-kDa accessory subunit. Mutations in the gene for the catalytic subunit (POLG) have been shown to be a frequent cause of mitochondrial disorders. To date over 40 disease mutations and 9 nonsynonymous polymorphisms in POLG have been found to be associated with autosomal recessive and dominant progressive external ophthalmoplegia (PEO), Alpers syndrome, sensory ataxia, neuropathy, dysarthria and ophthalmoparesis (SANDO), Parkinsonism, and male infertility. In this paper we review the literature of POLG mutations and discuss their impact on mitochondrial diseases. We also describe a public access web database to annotate POLG mutations for the research community.
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Affiliation(s)
- Matthew J Longley
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, P.O. Box 12233, Research Triangle Park, NC 27709, USA
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295
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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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296
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Disorders of the mitochondrial respiratory chain. NEURODEGENER DIS 2005. [DOI: 10.1017/cbo9780511544873.063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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297
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Luoma PT, Luo N, Löscher WN, Farr CL, Horvath R, Wanschitz J, Kiechl S, Kaguni LS, Suomalainen A. Functional defects due to spacer-region mutations of human mitochondrial DNA polymerase in a family with an ataxia-myopathy syndrome. Hum Mol Genet 2005; 14:1907-20. [PMID: 15917273 DOI: 10.1093/hmg/ddi196] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Defects of mitochondrial polymerase gamma (POLG) underlie neurological diseases ranging from myopathies to parkinsonism and infantile Alpers syndrome. The most severe manifestations have been associated with mutations of the 'spacer' region of POLG, the function of which has remained unstudied in humans. We identified a family, segregating three POLG amino acid variants, A467T, R627Q and Q1236H. The first two affect the spacer region and the third is a polymorphism, allelic with R627Q. Three grades of disease severity appeared to correlate with the genotypes. The patient with the most severe outcome, cerebellar ataxia syndrome, had all three variants, those with R627Q and Q1236H had juvenile-onset ptosis and gait disturbance and those with a single A467T allele had late-onset ptosis. To evaluate the molecular pathogenesis of these spacer defects, we expressed and purified the mutant proteins and studied their catalytic properties in vitro. The A467T substitution resulted in clearly decreased activity, DNA binding and processivity of the polymerase. Our biochemical data, the dominant manifestation of A467T and its previously reported high frequency in the Belgian population (0.6%), emphasize the role of this mutation as a common cause of neurological disease. Further, biochemical evidence that a polymorphic variant may modify the function of a mutant POLG, if occurring in the same polypeptide, is shown here. Finally, and surprisingly, other pathogenic spacer mutants showed DNA-binding affinities and processivities similar to or higher than the controls, suggesting that the disease-causing mechanisms of spacer mutations extend beyond the basic catalytic functions of POLG.
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Affiliation(s)
- Petri T Luoma
- Programme of Neurosciences, Biomedicum-Helsinki, Helsinki University, Finland
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298
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Abstract
Strabismus (misalignment of the eyes; also known as "squint") comprises a common heterogeneous group of disorders characterised by a constant or intermittent ocular deviation often associated with amblyopia (uniocular failure of normal visual development) and reduced or absent binocular vision. The associated poor cosmetic appearance may also interfere with social and psychological development. Extensive twin and family studies suggest a significant genetic component to the aetiology of strabismus. The complexity of the molecular basis of strabismus is now beginning to be elucidated with the identification of genetic loci and disease causing genes. Currently greater insights have been gained into the incomitant subtype (differing magnitude of ocular misalignment according to direction of gaze), whereas less is known about the pathogenesis of the more common childhood concomitant strabismus. It is hoped that a greater understanding of the molecular genetics of these disorders will lead to improved knowledge of disease mechanisms and ultimately to more effective treatment. The aim of this paper is to review current knowledge of the molecular genetics of both incomitant and concomitant strabismus.
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Affiliation(s)
- M Michaelides
- Institute of Ophthalmology, University College London, 11-43 Bath Street, London, EC1V 9EL, UK
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299
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Kato T. Mitochondrial dysfunction in bipolar disorder: from 31P-magnetic resonance spectroscopic findings to their molecular mechanisms. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2005; 63:21-40. [PMID: 15797464 DOI: 10.1016/s0074-7742(05)63002-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Affiliation(s)
- Tadafumi Kato
- Laboratory for Molecular Dynamics of Mental Disorders Brain Science Institute, RIKEN Saitama 351-0198, Japan
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300
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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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