1
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Rahmadanthi FR, Maksum IP. Transfer RNA Mutation Associated with Type 2 Diabetes Mellitus. BIOLOGY 2023; 12:871. [PMID: 37372155 DOI: 10.3390/biology12060871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 06/09/2023] [Accepted: 06/12/2023] [Indexed: 06/29/2023]
Abstract
Transfer RNA (tRNA) genes in the mitochondrial DNA genome play an important role in protein synthesis. The 22 tRNA genes carry the amino acid that corresponds to that codon but changes in the genetic code often occur such as gene mutations that impact the formation of adenosine triphosphate (ATP). Insulin secretion does not occur because the mitochondria cannot work optimally. tRNA mutation may also be caused by insulin resistance. In addition, the loss of tRNA modification can cause pancreatic β cell dysfunction. Therefore, both can be indirectly associated with diabetes mellitus because diabetes mellitus, especially type 2, is caused by insulin resistance and the body cannot produce insulin. In this review, we will discuss tRNA in detail, several diseases related to tRNA mutations, how tRNA mutations can lead to type 2 diabetes mellitus, and one example of a point mutation that occurs in tRNA.
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Affiliation(s)
- Fanny Rizki Rahmadanthi
- Departement of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Padjadjaran, Sumedang 45363, Indonesia
| | - Iman Permana Maksum
- Departement of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Padjadjaran, Sumedang 45363, Indonesia
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2
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Wada KI, Hosokawa K, Ito Y, Mizuo M, Harada Y, Yonemitsu Y. Generation of transmitochondrial cybrids using a microfluidic device. Exp Cell Res 2022; 418:113233. [PMID: 35659971 DOI: 10.1016/j.yexcr.2022.113233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Revised: 05/26/2022] [Accepted: 05/28/2022] [Indexed: 11/04/2022]
Abstract
Mitochondrial cloning is a promising approach to achieve homoplasmic mitochondrial DNA (mtDNA) mutations. We previously developed a microfluidic device that performs single mitochondrion transfer from a mtDNA-intact cell to a mtDNA-less (ρ0) cell by promoting cytoplasmic connection through a microtunnel between them. In the present study, we described a method for generating transmitochondrial cybrids using the microfluidic device. After achieving mitochondrial transfer between HeLa cells and thymidine kinase-deficient ρ0143B cells using the microfluidic device, selective culture was carried out using a pyruvate and uridine (PU)-absent and 5-bromo-2'-deoxyuridine-supplemented culture medium. The resulting cells contained HeLa mtDNA and 143B nuclei, but both 143B mtDNA and HeLa nuclei were absent in these cells. Additionally, these cells showed lower lactate production than parent ρ0143B cells and disappearance of PU auxotrophy for cell growth. These results suggest successful generation of transmitochondrial cybrids using the microfluidic device. Furthermore, we succeeded in selective harvest of generated transmitochondrial cybrids under a PU-supplemented condition by removing unfused ρ0 cells with puromycin-based selection in the microfluidic device.
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Affiliation(s)
- Ken-Ichi Wada
- R&D Laboratory for Innovative Biotherapeutics, Graduate School of Pharmaceutical Sciences, Kyushu Univ., 3-1-1 Maidasi, Higashi, Fukuoka, 8112-8582, Japan; Bioengineering Laboratory, Cluster for Pioneering Research, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan; Nano Medical Engineering Laboratory, Cluster for Pioneering Research, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.
| | - Kazuo Hosokawa
- Bioengineering Laboratory, Cluster for Pioneering Research, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Yoshihiro Ito
- Nano Medical Engineering Laboratory, Cluster for Pioneering Research, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Maeda Mizuo
- Bioengineering Laboratory, Cluster for Pioneering Research, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Yui Harada
- R&D Laboratory for Innovative Biotherapeutics, Graduate School of Pharmaceutical Sciences, Kyushu Univ., 3-1-1 Maidasi, Higashi, Fukuoka, 8112-8582, Japan
| | - Yoshikazu Yonemitsu
- R&D Laboratory for Innovative Biotherapeutics, Graduate School of Pharmaceutical Sciences, Kyushu Univ., 3-1-1 Maidasi, Higashi, Fukuoka, 8112-8582, Japan
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3
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Abstract
The study of the mitochondrial DNA (mtDNA) has been hampered by the lack of methods to genetically manipulate the mitochondrial genome in living animal cells. This limitation has been partially alleviated by the ability to transfer mitochondria (and their mtDNAs) from one cell into another, as long as they are from the same species. This is done by isolating mtDNA-containing cytoplasts and fusing these to cells lacking mtDNA. This transmitochondrial cytoplasmic hybrid (cybrid) technology has helped the field understand the mechanism of several pathogenic mutations. In this chapter, we describe procedures to obtain transmitochondrial cybrids.
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Affiliation(s)
- Sandra R Bacman
- Department of Neurology, University of Miami School of Medicine, Miami, FL, United States
| | - Nadee Nissanka
- Department of Neurology, University of Miami School of Medicine, Miami, FL, United States
| | - Carlos T Moraes
- Department of Neurology, University of Miami School of Medicine, Miami, FL, United States.
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4
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Zereg E, Chaussenot A, Morel G, Bannwarth S, Sacconi S, Soriani MH, Attarian S, Cano A, Pouget J, Bellance R, Tranchant C, Lannes B, de Paula AM, Saadi Ait-El-Mkadem S, Chafino B, Berthet M, Fragaki K, Paquis-Flucklinger V, Rouzier C. Single-fiber studies for assigning pathogenicity of eight mitochondrial DNA variants associated with mitochondrial diseases. Hum Mutat 2020; 41:1394-1406. [PMID: 32419253 DOI: 10.1002/humu.24037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 03/29/2020] [Accepted: 04/19/2020] [Indexed: 12/21/2022]
Abstract
Whole mitochondrial DNA (mtDNA) sequencing is now systematically used in clinical laboratories to screen patients with a phenotype suggestive of mitochondrial disease. Next Generation Sequencing (NGS) has significantly increased the number of identified pathogenic mtDNA variants. Simultaneously, the number of variants of unknown significance (VUS) has increased even more, thus challenging their interpretation. Correct classification of the variants' pathogenicity is essential for optimal patient management, including treatment and genetic counseling. Here, we used single muscle fiber studies to characterize eight heteroplasmic mtDNA variants, among which were three novel variants. By applying the pathogenicity scoring system, we classified four variants as "definitely pathogenic" (m.590A>G, m.9166T>C, m.12293G>A, and m.15958A>T). Two variants remain "possibly pathogenic" (m.4327T>C and m.5672T>C) but should these be reported in a different family, they would be reclassified as "definitely pathogenic." We also illustrate the contribution of single-fiber studies to the diagnostic approach in patients harboring pathogenic variants with low level heteroplasmy.
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Affiliation(s)
- Elamine Zereg
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France
| | - Annabelle Chaussenot
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
| | - Godelieve Morel
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France
| | - Sylvie Bannwarth
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
| | - Sabrina Sacconi
- Department of Clinical Neurosciences, Neuromuscular Diseases Centre, Nice Teaching Hospital, Nice, France
| | - Marie-Hélène Soriani
- Department of Clinical Neurosciences, Neuromuscular Diseases Centre, Nice Teaching Hospital, Nice, France
| | - Shahram Attarian
- Neurology Department, Referral Center for ALS and Neuromuscular Diseases, Timone University Hospital, Aix-Marseille University, Marseille, France
| | - Aline Cano
- Pediatric Neurology Department, Reference Center for Inherited Metabolic Diseases, Timone Hospital, Marseille, France
| | - Jean Pouget
- Neurology Department, Referral Center for ALS and Neuromuscular Diseases, Timone University Hospital, Aix-Marseille University, Marseille, France
| | - Rémi Bellance
- Neuromyology Department, Neuromuscular Reference Center, Fort-de-France Teaching Hospital, Fort-de-France, France
| | - Christine Tranchant
- Department of Movement Pathology, Strasbourg Teaching Hospital, Strasbourg, France
| | - Béatrice Lannes
- Pathology Department, Hôpitaux Universitaires de Strasbourg, Hôpital de Hautepierre, Strasbourg, France
| | - André Maues de Paula
- Pathology Department, Timone University Hospital, Aix-Marseille University, Marseille, France
| | - Samira Saadi Ait-El-Mkadem
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
| | - Bernadette Chafino
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France
| | - Mathieu Berthet
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France
| | - Konstantina Fragaki
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
| | - Véronique Paquis-Flucklinger
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
| | - Cécile Rouzier
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
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5
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Buford TW, Manini TM, Kairalla JA, McDermott MM, Vaz Fragoso CA, Chen H, Fielding RA, King AC, Newman AB, Tranah GJ. Mitochondrial DNA Sequence Variants Associated With Blood Pressure Among 2 Cohorts of Older Adults. J Am Heart Assoc 2019; 7:e010009. [PMID: 30371200 PMCID: PMC6222953 DOI: 10.1161/jaha.118.010009] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Background Age‐related changes in blood pressure are associated with a variety of poor health outcomes. Genetic factors are proposed contributors to age‐related increases in blood pressure, but few genetic loci have been identified. We examined the role of mitochondrial genomic variation in blood pressure by sequencing the mitochondrial genome. Methods and Results Mitochondrial DNA (mtDNA) data from 1755 participants from the LIFE (Lifestyle Interventions and Independence for Elders) studies and 788 participants from the Health ABC (Health, Aging, and Body Composition) study were evaluated using replication analysis followed by meta‐analysis. Participants were aged ≥69 years, of diverse racial backgrounds, and assessed for systolic blood pressure (SBP), diastolic blood pressure, and mean arterial pressure. After meta‐analysis across the LIFE and Health ABC studies, statistically significant associations of mtDNA variants with higher SBP (m.3197T>C, 16S rRNA; P=0.0005) and mean arterial pressure (m.15924A>G, t‐RNA‐thr; P=0.004) were identified in white participants. Among black participants, statistically significant associations with higher SBP (m.93A>G, HVII; m.16183A>C, HVI; both P=0.0001) and mean arterial pressure (m.16172T>C, HVI; m.16183A>C, HVI; m.16189T>C, HVI; m.12705C>T; all P's<0.0004) were observed. Significant pooled effects on SBP were observed across all transfer RNA regions (P=0.0056) in white participants. The individual and aggregate variant results are statistically significant after multiple comparisons adjustment for the number of mtDNA variants and mitochondrial regions examined. Conclusions These results suggest that mtDNA‐encoded variants are associated with variation in SBP and mean arterial pressure among older adults. These results may help identify mitochondrial activities to explain differences in blood pressure in older adults and generate new hypotheses surrounding mtDNA variation and the regulation of blood pressure. Clinical Trial Registration URL: http://www.ClinicalTrials.gov. Unique identifiers: NCT01072500 and NCT00116194.
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Affiliation(s)
- Thomas W Buford
- 1 Department of Medicine University of Alabama at Birmingham AL
| | - Todd M Manini
- 2 Department of Aging and Geriatric Research University of Florida Gainesville FL
| | - John A Kairalla
- 3 Department of Biostatistics University of Florida Gainesville FL
| | - Mary M McDermott
- 4 Department of Medicine and Preventive Medicine Northwestern University Feinberg School of Medicine Chicago IL
| | | | - Haiying Chen
- 7 Department of Biostatistical Sciences Wake Forest School of Medicine Winston-Salem NC
| | - Roger A Fielding
- 8 Jean Mayer USDA Human Nutrition Research Center on Aging Tufts University Boston MA
| | - Abby C King
- 9 Department of Health Research and Policy and Stanford Prevention Research Center Stanford University Stanford CA
| | - Anne B Newman
- 10 Department of Epidemiology University of Pittsburgh PA
| | - Gregory J Tranah
- 11 California Pacific Medical Center Research Institute, San Francisco San Francisco CA
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6
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Schlapakow E, Peeva V, Zsurka G, Jeub M, Wabbels B, Kornblum C, Kunz WS. Distinct segregation of the pathogenic m.5667G>A mitochondrial tRNA Asn mutation in extraocular and skeletal muscle in chronic progressive external ophthalmoplegia. Neuromuscul Disord 2019; 29:358-367. [PMID: 30962064 DOI: 10.1016/j.nmd.2019.02.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 01/08/2019] [Accepted: 02/19/2019] [Indexed: 12/13/2022]
Abstract
Chronic progressive external ophthalmoplegia (CPEO) is a frequent clinical manifestation of disorders caused by pathogenic mitochondrial DNA mutations. However, for diagnostic purposes skeletal muscle tissue is used, since extraocular muscle tissue is usually not available for work-up. In the present study we aimed to identify causative factors that are responsible for extraocular muscle to be primarily affected in CPEO. We performed comparative histochemical and molecular genetic analyses of extraocular muscle and skeletal muscle single fibers in a case of isolated CPEO caused by the heteroplasmic m.5667G>A mutation in the mitochondrial tRNAAsn gene (MT-TN). Histochemical analyses revealed higher proportion of cytochrome c oxidase deficient fibers in extraocular muscle (41%) compared to skeletal muscle (10%). However, genetic analyses of single fibers revealed no significant difference either in the mutation loads between extraocular muscle and skeletal muscle cytochrome c oxidase deficient single fibers (extraocular muscle 86% ± 4.6%; skeletal muscle 87.8 %± 5.7%, p = 0.246) nor in the mutation threshold (extraocular muscle 74% ± 3%; skeletal muscle 74% ± 4%). We hypothesize that higher proportion of cytochrome c oxidase deficient fibers in extraocular muscle compared to skeletal muscle might be due to facilitated segregation of the m.5667G>A mutation into extraocular muscle, which may explain the preferential ocular manifestation and clinically isolated CPEO.
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Affiliation(s)
- Elena Schlapakow
- Department of Neurology, University Hospital of Bonn, Germany; Center for Rare Diseases, University Hospital of Bonn, Germany
| | - Viktoriya Peeva
- Division of Neurochemistry, Institute of Experimental Epileptology and Cognition Research, University of Bonn, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany
| | - Gábor Zsurka
- Division of Neurochemistry, Institute of Experimental Epileptology and Cognition Research, University of Bonn, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany; Department of Epileptology, University of Bonn, Germany
| | - Monika Jeub
- Department of Neurology, University Hospital of Bonn, Germany
| | | | - Cornelia Kornblum
- Department of Neurology, University Hospital of Bonn, Germany; Center for Rare Diseases, University Hospital of Bonn, Germany
| | - Wolfram S Kunz
- Division of Neurochemistry, Institute of Experimental Epileptology and Cognition Research, University of Bonn, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany; Department of Epileptology, University of Bonn, Germany.
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7
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Hatakeyama H, Goto YI. Concise Review: Heteroplasmic Mitochondrial DNA Mutations and Mitochondrial Diseases: Toward iPSC-Based Disease Modeling, Drug Discovery, and Regenerative Therapeutics. Stem Cells 2016; 34:801-8. [DOI: 10.1002/stem.2292] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 11/20/2015] [Accepted: 12/09/2015] [Indexed: 01/19/2023]
Affiliation(s)
- Hideyuki Hatakeyama
- Department of Mental Retardation and Birth Defect Research; National Institute of Neuroscience, National Center of Neurology and Psychiatry; Tokyo Japan
- AMED-CREST, Japan Agency for Medical Research and Development; Tokyo Japan
| | - Yu-ichi Goto
- Department of Mental Retardation and Birth Defect Research; National Institute of Neuroscience, National Center of Neurology and Psychiatry; Tokyo Japan
- Medical Genome Center, National Center of Neurology and Psychiatry; Tokyo Japan
- AMED-CREST, Japan Agency for Medical Research and Development; Tokyo Japan
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8
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Tranah GJ, Yaffe K, Katzman SM, Lam ET, Pawlikowska L, Kwok PY, Schork NJ, Manini TM, Kritchevsky S, Thomas F, Newman AB, Harris TB, Coleman AL, Gorin MB, Helzner EP, Rowbotham MC, Browner WS, Cummings SR. Mitochondrial DNA Heteroplasmy Associations With Neurosensory and Mobility Function in Elderly Adults. J Gerontol A Biol Sci Med Sci 2015; 70:1418-24. [PMID: 26328603 DOI: 10.1093/gerona/glv097] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 06/05/2015] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Mitochondrial DNA (mtDNA) heteroplasmy is a mixture of normal and mutated mtDNA molecules in a cell. High levels of heteroplasmy at specific mtDNA sites lead to inherited mitochondrial diseases with neurological, sensory, and movement impairments. Here we test the hypothesis that heteroplasmy levels in elderly adults are associated with impaired function resembling mild forms of mitochondrial disease. METHODS We examined platelet mtDNA heteroplasmy at 20 disease-causing sites for associations with neurosensory and mobility function among 137 participants from the community-based Health, Aging, and Body Composition Study. RESULTS Elevated mtDNA heteroplasmy at four mtDNA sites in complex I and tRNA genes was nominally associated with reduced cognition, vision, hearing, and mobility: m.10158T>C with Modified Mini-Mental State Examination score (p = .009); m.11778G>A with contrast sensitivity (p = .02); m.7445A>G with high-frequency hearing (p = .047); and m.5703G>A with 400 m walking speed (p = .007). CONCLUSIONS These results indicate that increased mtDNA heteroplasmy at disease-causing sites is associated with neurosensory and mobility function in older persons. We propose the novel use of mtDNA heteroplasmy as a simple, noninvasive predictor of age-related neurologic, sensory, and movement impairments.
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Affiliation(s)
- Gregory J Tranah
- California Pacific Medical Center Research Institute, San Francisco.
| | - Kristine Yaffe
- Department of Psychiatry, Department of Neurology and Department of Epidemiology, University of California San Francisco and the San Francisco VA Medical Center
| | | | | | - Ludmila Pawlikowska
- Department of Anesthesia and Perioperative Care, University of California San Francisco. Institute for Human Genetics, University of California San Francisco
| | - Pui-Yan Kwok
- Institute for Human Genetics, University of California San Francisco
| | - Nicholas J Schork
- J. Craig Venter Institute and the University of California, San Diego
| | - Todd M Manini
- Department of Aging and Geriatric Research, University of Florida, Gainesville
| | - Stephen Kritchevsky
- Sticht Center on Aging, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Fridtjof Thomas
- Department of Preventive Medicine, The University of Tennessee Health Science Center, Memphis
| | - Anne B Newman
- Department of Epidemiology, University of Pittsburgh, Pennsylvania
| | - Tamara B Harris
- Intramural Research Program, Laboratory of Epidemiology and Population Sciences, National Institute on Aging, Bethesda, Maryland
| | - Anne L Coleman
- Jules Stein Eye Institute and UCLA Department of Ophthalmology, Los Angeles, California
| | - Michael B Gorin
- Jules Stein Eye Institute and UCLA Department of Ophthalmology, Los Angeles, California
| | - Elizabeth P Helzner
- Department of Epidemiology and Biostatistics, SUNY Downstate Medical Center, Brooklyn, New York
| | | | - Warren S Browner
- California Pacific Medical Center Research Institute, San Francisco
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9
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Hatakeyama H, Katayama A, Komaki H, Nishino I, Goto YI. Molecular pathomechanisms and cell-type-specific disease phenotypes of MELAS caused by mutant mitochondrial tRNA(Trp). Acta Neuropathol Commun 2015; 3:52. [PMID: 26297375 PMCID: PMC4546323 DOI: 10.1186/s40478-015-0227-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 07/22/2015] [Indexed: 01/19/2023] Open
Abstract
Introduction Numerous pathogenic mutations responsible for mitochondrial diseases have been identified in mitochondrial DNA (mtDNA)-encoded tRNA genes. In most cases, however, the detailed molecular pathomechanisms and cellular pathophysiology of these mtDNA mutations —how such genetic defects determine the variation and the severity of clinical symptoms in affected individuals— remain unclear. To investigate the molecular pathomechanisms and to realize in vitro recapitulation of mitochondrial diseases, intracellular mutant mtDNA proportions must always be considered. Results We found a disease-causative mutation, m.5541C>T heteroplasmy in MT-TW gene, in a patient exhibiting mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) with multiple organ involvement. We identified the intrinsic molecular pathomechanisms of m.5541C>T. This mutation firstly disturbed the translation machinery of mitochondrial tRNATrp and induced mitochondrial respiratory dysfunction, followed by severely injured mitochondrial homeostasis. We also demonstrated cell-type-specific disease phenotypes using patient-derived induced pluripotent stem cells (iPSCs) carrying ~100 % mutant m.5541C>T. Significant loss of terminally differentiated iPSC-derived neurons, but not their stem/progenitor cells, was detected most likely due to serious mitochondrial dysfunction triggered by m.5541C>T; in contrast, m.5541C>T did not apparently affect skeletal muscle development. Conclusions Our iPSC-based disease models would be widely available for understanding the "definite" genotype-phenotype relationship of affected tissues and organs in various mitochondrial diseases caused by heteroplasmic mtDNA mutations, as well as for further drug discovery applications. Electronic supplementary material The online version of this article (doi:10.1186/s40478-015-0227-x) contains supplementary material, which is available to authorized users.
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10
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Van Haute L, Pearce SF, Powell CA, D’Souza AR, Nicholls TJ, Minczuk M. Mitochondrial transcript maturation and its disorders. J Inherit Metab Dis 2015; 38:655-80. [PMID: 26016801 PMCID: PMC4493943 DOI: 10.1007/s10545-015-9859-z] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Revised: 04/27/2015] [Accepted: 04/29/2015] [Indexed: 11/03/2022]
Abstract
Mitochondrial respiratory chain deficiencies exhibit a wide spectrum of clinical presentations owing to defective mitochondrial energy production through oxidative phosphorylation. These defects can be caused by either mutations in the mitochondrial DNA (mtDNA) or mutations in nuclear genes coding for mitochondrially-targeted proteins. The underlying pathomechanisms can affect numerous pathways involved in mitochondrial biology including expression of mtDNA-encoded genes. Expression of the mitochondrial genes is extensively regulated at the post-transcriptional stage and entails nucleolytic cleavage of precursor RNAs, RNA nucleotide modifications, RNA polyadenylation, RNA quality and stability control. These processes ensure proper mitochondrial RNA (mtRNA) function, and are regulated by dedicated, nuclear-encoded enzymes. Recent growing evidence suggests that mutations in these nuclear genes, leading to incorrect maturation of RNAs, are a cause of human mitochondrial disease. Additionally, mutations in mtDNA-encoded genes may also affect RNA maturation and are frequently associated with human disease. We review the current knowledge on a subset of nuclear-encoded genes coding for proteins involved in mitochondrial RNA maturation, for which genetic variants impacting upon mitochondrial pathophysiology have been reported. Also, primary pathological mtDNA mutations with recognised effects upon RNA processing are described.
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Affiliation(s)
| | - Sarah F. Pearce
- MRC Mitochondrial Biology Unit, Hills Road, Cambridge, CB2 0XY UK
| | | | - Aaron R. D’Souza
- MRC Mitochondrial Biology Unit, Hills Road, Cambridge, CB2 0XY UK
| | - Thomas J. Nicholls
- MRC Mitochondrial Biology Unit, Hills Road, Cambridge, CB2 0XY UK
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Gothenburg, Sweden
| | - Michal Minczuk
- MRC Mitochondrial Biology Unit, Hills Road, Cambridge, CB2 0XY UK
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11
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Bacman SR, Williams SL, Pinto M, Moraes CT. The use of mitochondria-targeted endonucleases to manipulate mtDNA. Methods Enzymol 2014; 547:373-97. [PMID: 25416366 DOI: 10.1016/b978-0-12-801415-8.00018-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
For more than a decade, mitochondria-targeted nucleases have been used to promote double-strand breaks in the mitochondrial genome. This was done in mitochondrial DNA (mtDNA) homoplasmic systems, where all mtDNA molecules can be affected, to create models of mitochondrial deficiencies. Alternatively, they were also used in a heteroplasmic model, where only a subset of the mtDNA molecules were substrates for cleavage. The latter approach showed that mitochondrial-targeted nucleases can reduce mtDNA haplotype loads in affected tissues, with clear implications for the treatment of patients with mitochondrial diseases. In the last few years, designer nucleases, such as ZFN and TALEN, have been adapted to cleave mtDNA, greatly expanding the potential therapeutic use. This chapter describes the techniques and approaches used to test these designer enzymes.
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Affiliation(s)
- Sandra R Bacman
- Department of Neurology, University of Miami School of Medicine, Miami, Florida, USA
| | - Sion L Williams
- Department of Neurology, University of Miami School of Medicine, Miami, Florida, USA
| | - Milena Pinto
- Department of Neurology, University of Miami School of Medicine, Miami, Florida, USA
| | - Carlos T Moraes
- Department of Neurology, University of Miami School of Medicine, Miami, Florida, USA.
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12
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Mkaouar-Rebai E, Ben Mahmoud A, Chamkha I, Chabchoub I, Kammoun T, Hachicha M, Fakhfakh F. A novel MT-CO2 m.8249G > A pathogenic variation and the MT-TW m.5521G > A mutation in patients with mitochondrial myopathy. ACTA ACUST UNITED AC 2013; 25:394-9. [DOI: 10.3109/19401736.2013.803086] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Emna Mkaouar-Rebai
- Laboratory of Human Molecular Genetics, Faculty of Medicine, University of SfaxTunisia
| | - Afif Ben Mahmoud
- Laboratory of Human Molecular Genetics, Faculty of Medicine, University of SfaxTunisia
| | - Imen Chamkha
- Laboratory of Human Molecular Genetics, Faculty of Medicine, University of SfaxTunisia
| | - Imen Chabchoub
- Service de Pédiatrie, C.H.U. Habib Bourguiba de SfaxTunisia
| | | | | | - Faiza Fakhfakh
- Laboratory of Human Molecular Genetics, Faculty of Medicine, University of SfaxTunisia
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Pinós T, Melià MJ, Ortiz N, Martinez-Vea A, Raventós-Estellé A, Gallardo E, Hernández-Losa J, Cámara Y, Andreu AL, García-Arumí E. Identification of the novel mutation m.5658T>C in the mitochondrial tRNA(Asn) gene in a patient with myopathy, bilateral ptosis and ophthalmoparesis. Neuromuscul Disord 2013; 23:330-6. [PMID: 23375258 DOI: 10.1016/j.nmd.2013.01.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 09/25/2012] [Accepted: 01/02/2013] [Indexed: 12/13/2022]
Abstract
We report a heteroplasmic novel mutation m.5658T>C in the mt-tRNA(Asn) gene in a patient who initially presented myopathy, bilateral ptosis and ophthalmoparesis and several years later developed a non-nephrotic proteinuria. The muscle biopsy showed cytochrome c oxidase (COX) negative and ragged red fibers and in the kidney biopsy that was taken in order to identify the causes of non-nephrotic proteinuria, a focal segmental glomerulosclerosis was observed. Using laser capture microdissection we isolated COX negative fibers and COX positive fibers from the muscle of the patient and determined that there was a clear increase in the mutation load in the COX negative muscle fibers. However, the low degree of mutation load found in the renal biopsy of the patient does not allow us to conclude that the m.5658T>C mutation is responsible for focal glomerulosclerosis. Additionally, we hypothesize that the mutated m.5658T nucleotide might be structurally relevant, as it is one of the fifteen nucleotides conserved in all the species analyzed and is situated contiguously to the discriminator base in the 3'end of the mt-tRNA, where the tRNase Z cleaves the 3' trailer sequence during mt-tRNA maturation.
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Affiliation(s)
- Tomàs Pinós
- Departament de Patología Mitocondrial i Neuromuscular, Hospital Universitari Vall d'Hebron Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona, Spain
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14
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Wenz T, Wang X, Marini M, Moraes CT. A metabolic shift induced by a PPAR panagonist markedly reduces the effects of pathogenic mitochondrial tRNA mutations. J Cell Mol Med 2012; 15:2317-25. [PMID: 21129152 PMCID: PMC3361135 DOI: 10.1111/j.1582-4934.2010.01223.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Mutations in mitochondrial DNA-encoded tRNA genes are associated with many human diseases. Activation of peroxisome proliferator-activated receptors (PPARs) by synthetic agonists stimulates oxidative metabolism, induces an increase in mitochondrial mass and partially compensates for oxidative phosphorylation system (OXPHOS) defects caused by single OXPHOS enzyme deficiencies in vitro and in vivo. Here, we analysed whether treatment with the PPAR panagonist bezafibrate in cybrids homoplasmic for different mitochondrial tRNA mutations could ameliorate the OXPHOS defect. We found that bezafibrate treatment increased mitochondrial mass, mitochondrial tRNA steady state levels and enhanced mitochondrial protein synthesis. This improvement resulted in increased OXPHOS activity and finally in enhanced mitochondrial ATP generating capacity. PPAR panagonists are known to increase the expression of PPAR gamma coactivator-1α (PGC-1α), a master regulator of mitochondrial biogenesis. Accordingly, we found that clones of a line harbouring a mutated mitochondrial tRNA gene mutation selected for the ability to grow in a medium selective for OXPHOS function had a 3-fold increase in PGC-1α expression, an increase that was similar to the one observed after bezafibrate treatment. These findings show that increasing mitochondrial mass and thereby boosting residual OXPHOS capacity can be beneficial to an important class of mitochondrial defects reinforcing the potential therapeutic use of approaches stimulating mitochondrial proliferation for mitochondrial disorders.
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Affiliation(s)
- Tina Wenz
- Department of Neurology, University of Miami School of Medicine, Miami, FL 33136, USA
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15
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Belostotsky R, Frishberg Y, Entelis N. Human mitochondrial tRNA quality control in health and disease: a channelling mechanism? RNA Biol 2012; 9:33-9. [PMID: 22258151 DOI: 10.4161/rna.9.1.18009] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Mutations in human mitochondrial tRNA genes are associated with a number of multisystemic disorders. These single nucleotide substitutions in various domains of tRNA molecules may affect different steps of tRNA biogenesis. Often, the prominent decrease of aminoacylation and/or steady-state levels of affected mitochondrial tRNA have been demonstrated in patients' tissues and in cultured cells. Similar effect has been observed for pathogenic mutations in nuclear genes encoding mitochondrial aminoacyl-tRNA-synthetases, while over-expression of mitochondrial aminoacyl-tRNA synthetases or elongation factor EF-Tu rescued mutated tRNAs from degradation. In this review we summarize experimental data concerning the possible regulatory mechanisms governing mitochondrial tRNA steady-state levels, and propose a hypothesis based on the tRNA channelling principle. According to this hypothesis, interaction of mitochondrial tRNA with proteins ensures not only tRNA synthesis, maturation and function, but also protection from degradation. Mutations perturbing this interaction lead to decreased tRNA stability.
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Affiliation(s)
- Ruth Belostotsky
- Division of Pediatric Nephrology, Shaare Zedek Medical Center; Jerusalem, Israel
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16
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Christian BE, Spremulli LL. Mechanism of protein biosynthesis in mammalian mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2011; 1819:1035-54. [PMID: 22172991 DOI: 10.1016/j.bbagrm.2011.11.009] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 11/03/2011] [Accepted: 11/08/2011] [Indexed: 01/25/2023]
Abstract
Protein synthesis in mammalian mitochondria produces 13 proteins that are essential subunits of the oxidative phosphorylation complexes. This review provides a detailed outline of each phase of mitochondrial translation including initiation, elongation, termination, and ribosome recycling. The roles of essential proteins involved in each phase are described. All of the products of mitochondrial protein synthesis in mammals are inserted into the inner membrane. Several proteins that may help bind ribosomes to the membrane during translation are described, although much remains to be learned about this process. Mutations in mitochondrial or nuclear genes encoding components of the translation system often lead to severe deficiencies in oxidative phosphorylation, and a summary of these mutations is provided. This article is part of a Special Issue entitled: Mitochondrial Gene Expression.
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Affiliation(s)
- Brooke E Christian
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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17
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Yan N, Cai S, Guo B, Mou Y, Zhu J, Chen J, Zhang T, Li R, Liu X. A novel mitochondrial tRNA(Val) T1658C mutation identified in a CPEO family. Mol Vis 2010; 16:1736-42. [PMID: 20806033 PMCID: PMC2927373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Accepted: 08/20/2010] [Indexed: 11/15/2022] Open
Abstract
PURPOSE To analyze mitochondrial DNA (mt DNA) gene mutations in a 19-year-old female patient, who presented with chronic progressive external ophthalmoplegia (CPEO), together with her mother and younger sister. METHODS The diagnosis of mitochondrial myopathy was made based on clinical and biologic analysis. Histochemical methods were used to detect ragged-red fibers (RRFs) and ragged-blue fibers (RBFs) on a muscle biopsy of the patient. All mitochondrial gene DNA fragments of the patient, her mother, and younger sister were amplified by polymerase chain reaction. The products were sequenced and compared with reference databases. RESULTS A novel T1658C mutation and a known A10006G mutation were identified in the mitochondrial tRNA(Val) gene and the tRNA(Gly) gene, respectively, in the patient, her mother, and younger sister. The T1658C mutation changes the T loop structure of mitochondrial tRNA(Val) and the A10006G mutation disturbs the D loop of mitochondrial tRNA(Gly). CONCLUSIONS The T1658C and A10006G mutations of mtDNA may be responsible for the pathogenesis of the patient with CPEO.
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Affiliation(s)
- Naihong Yan
- Ophthalmic Laboratories and Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, Sichuan, P.R. China
| | - Shuping Cai
- Ophthalmic Laboratories and Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, Sichuan, P.R. China
| | - Bo Guo
- Ophthalmic Laboratories and Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, Sichuan, P.R. China
| | - Yi Mou
- Ophthalmic Laboratories and Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, Sichuan, P.R. China
| | - Jing Zhu
- Ophthalmic Laboratories and Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, Sichuan, P.R. China
| | - Jun Chen
- Ophthalmic Laboratories and Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, Sichuan, P.R. China
| | - Ting Zhang
- Ophthalmic Laboratories and Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, Sichuan, P.R. China
| | - Ronghua Li
- Department of Medical Genetics, West China Hospital, Sichuan University, Chengdu, Sichuan, P.R. China
| | - Xuyang Liu
- Ophthalmic Laboratories and Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, Sichuan, P.R. China
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18
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Jones CN, Jones CI, Graham WD, Agris PF, Spremulli LL. A disease-causing point mutation in human mitochondrial tRNAMet rsults in tRNA misfolding leading to defects in translational initiation and elongation. J Biol Chem 2008; 283:34445-56. [PMID: 18835817 DOI: 10.1074/jbc.m806992200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mitochondrial tRNA genes are hot spots for mutations that lead to human disease. A single point mutation (T4409C) in the gene for human mitochondrial tRNA(Met) (hmtRNA(Met)) has been found to cause mitochondrial myopathy. This mutation results in the replacement of U8 in hmtRNA(Met) with a C8. The hmtRNA(Met) serves both in translational initiation and elongation in human mitochondria making this tRNA of particular interest in mitochondrial protein synthesis. Here we show that the single 8U-->C mutation leads to a failure of the tRNA to respond conformationally to Mg(2+). This mutation results in a drastic disruption of the structure of the hmtRNA(Met), which significantly reduces its aminoacylation. The small fraction of hmtRNA(Met) that can be aminoacylated is not formylated by the mitochondrial Met-tRNA transformylase preventing its function in initiation, and it is unable to form a stable ternary complex with elongation factor EF-Tu preventing any participation in chain elongation. We have used structural probing and molecular reconstitution experiments to examine the structures formed by the normal and mutated tRNAs. In the presence of Mg(2+), the normal tRNA displays the structural features expected of a tRNA. However, even in the presence of Mg(2+), the mutated tRNA does not form the cloverleaf structure typical of tRNAs. Thus, we believe that this mutation has disrupted a critical Mg(2+)-binding site on the tRNA required for formation of the biologically active structure. This work establishes a foundation for understanding the physiological consequences of the numerous mitochondrial tRNA mutations that result in disease in humans.
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Affiliation(s)
- Christie N Jones
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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19
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Scaglia F, Wong LJC. Human mitochondrial transfer RNAs: role of pathogenic mutation in disease. Muscle Nerve 2008; 37:150-71. [PMID: 17999409 DOI: 10.1002/mus.20917] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The human mitochondrial genome encodes 13 proteins. All are subunits of the respiratory chain complexes involved in energy metabolism. These proteins are translated by a set of 22 mitochondrial transfer RNAs (tRNAs) that are required for codon reading. Human mitochondrial tRNA genes are hotspots for pathogenic mutations and have attracted interest over the last two decades with the rapid discovery of point mutations associated with a vast array of neuromuscular disorders and diverse clinical phenotypes. In this review, we use a scoring system to determine the pathogenicity of the mutations and summarize the current knowledge of structure-function relationships of these mutant tRNAs. We also provide readers with an overview of a large variety of mechanisms by which mutations may affect the mitochondrial translation machinery and cause disease.
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Affiliation(s)
- Fernando Scaglia
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
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20
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Sacconi S, Salviati L, Nishigaki Y, Walker WF, Hernandez-Rosa E, Trevisson E, Delplace S, Desnuelle C, Shanske S, Hirano M, Schon EA, Bonilla E, De Vivo DC, DiMauro S, Davidson MM. A functionally dominant mitochondrial DNA mutation. Hum Mol Genet 2008; 17:1814-20. [PMID: 18337306 PMCID: PMC2900892 DOI: 10.1093/hmg/ddn073] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Mutations in mitochondrial DNA (mtDNA) tRNA genes can be considered functionally recessive because they result in a clinical or biochemical phenotype only when the percentage of mutant molecules exceeds a critical threshold value, in the range of 70-90%. We report a novel mtDNA mutation that contradicts this rule, since it caused a severe multisystem disorder and respiratory chain (RC) deficiency even at low levels of heteroplasmy. We studied a 13-year-old boy with clinical, radiological and biochemical evidence of a mitochondrial disorder. We detected a novel heteroplasmic C>T mutation at nucleotide 5545 of mtDNA, which was present at unusually low levels (<25%) in affected tissues. The pathogenic threshold for the mutation in cybrids was between 4 and 8%, implying a dominant mechanism of action. The mutation affects the central base of the anticodon triplet of tRNA(Trp) and it may alter the codon specificity of the affected tRNA. These findings introduce the concept of dominance in mitochondrial genetics and pose new diagnostic challenges, because such mutations may easily escape detection. Moreover, similar mutations arising stochastically and accumulating in a minority of mtDNA molecules during the aging process may severely impair RC function in cells.
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Affiliation(s)
- Sabrina Sacconi
- Féderation des maladies neuromusculaires, CHU de Nice and INSERM U638, Nice, France
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21
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Srivastava S, Barrett JN, Moraes CT. PGC-1alpha/beta upregulation is associated with improved oxidative phosphorylation in cells harboring nonsense mtDNA mutations. Hum Mol Genet 2007; 16:993-1005. [PMID: 17341490 PMCID: PMC2652746 DOI: 10.1093/hmg/ddm045] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
We have studied the functional effects of nonsense mitochondrial DNA (mtDNA) mutations in the COXI and ND5 genes in a colorectal tumor cell line. Surprisingly, these cells had an efficient oxidative phosphorylation (OXPHOS); however, when mitochondria from these cells were transferred to an osteosarcoma nuclear background (osteosarcoma cybrids), the rate of respiration markedly declined suggesting that the phenotypic expression of the mtDNA mutations was prevented by the colorectal tumor nuclear background. We found that there was a significant increase in the steady-state levels of PGC-1alpha and PGC-1beta transcriptional coactivators in these cells and a parallel increase in the steady-state levels of several mitochondrial proteins. Accordingly, adenoviral-mediated overexpression of PGC-1alpha and PGC-1beta in the osteosarcoma cybrids stimulated mitochondrial respiration suggesting that an upregulation of PGC-1alpha/beta coactivators can partially rescue an OXPHOS defect. In conclusion, upregulation of PGC-1alpha and PGC-1beta in the colorectal tumor cells can be part of an adaptation mechanism to help overcome the severe consequences of mtDNA mutations on OXPHOS.
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Affiliation(s)
- Sarika Srivastava
- Department of Neurology, University of Miami, Miller School of Medicine, 1095 NW 14th Terrace, Miami, FL 33136, USA
| | - John N. Barrett
- Department of Physiology & Biophysics, University of Miami, Miller School of Medicine, 1095 NW 14th Terrace, Miami, FL 33136, USA
| | - Carlos T. Moraes
- Department of Neurology, University of Miami, Miller School of Medicine, 1095 NW 14th Terrace, Miami, FL 33136, USA
- Department of Cell Biology & Anatomy, University of Miami, Miller School of Medicine, 1095 NW 14th Terrace, Miami, FL 33136, USA
- To whom correspondence should be addressed at: Tel: +1 3052435858; Fax: +1 3052433914;
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22
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Affiliation(s)
- Sandra R Bacman
- Department of Neurology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
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23
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Bornstein B, Mas J, Patrono C, Fernández-Moreno M, González-Vioque E, Campos Y, Carrozzo R, Martín M, Hoyo P, Santorelli F, Arenas J, Garesse R. Comparative analysis of the pathogenic mechanisms associated with the G8363A and A8296G mutations in the mitochondrial tRNA(Lys) gene. Biochem J 2006; 387:773-8. [PMID: 15554876 PMCID: PMC1135008 DOI: 10.1042/bj20040949] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Two mutations (G8363A and A8296G) in the mtDNA (mitochondrial DNA) tRNA(Lys) gene have been associated with severe mitochondrial diseases in a number of reports. Their functional significance, however, remains unknown. We have already shown that homoplasmic cybrids harbouring the A8296G mutation display normal oxidative phosphorylation, although the possibility of a subtle change in mitochondrial respiratory capacity remains an open issue. We have now investigated the pathogenic mechanism of another mutation in the tRNA(Lys) gene (G8363A) by repopulating an mtDNA-less human osteosarcoma cell line with mitochondria harbouring either this genetic variant alone or an unusual combination of the two mutations (A8296G+G8363A). Cybrids homoplasmic for the single G8363A or the A8296G+G8363A mutations have defective respiratory-chain enzyme activities and low oxygen consumption, indicating a severe impairment of the oxidative phosphorylation system. Generation of G8363A cybrids within a wild-type or the A8296G mtDNA genetic backgrounds resulted in an important alteration in the conformation of the tRNA(Lys), not affecting tRNA steady-state levels. Moreover, mutant cybrids have an important decrease in the proportion of amino-acylated tRNA(Lys) and, consequently, mitochondrial protein synthesis is greatly decreased. Our results demonstrate that the pathogenicity of the G8363A mutation is due to a change in the conformation of the tRNA that severely impairs aminoacylation in the absence of changes in tRNA stability. The only effect detected in the A8296G mutation is a moderate decrease in the aminoacylation capacity, which does not affect mitochondrial protein biosynthesis.
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Affiliation(s)
- Belén Bornstein
- *Departamento de Bioquímica, Instituto de Investigaciones Biomédicas ‘Alberto Sols’, CSIC-UAM, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain
- †Servicio de Bioquímica, Hospital Severo Ochoa, Leganés, Madrid, Spain
| | - José Antonio Mas
- *Departamento de Bioquímica, Instituto de Investigaciones Biomédicas ‘Alberto Sols’, CSIC-UAM, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain
| | - Clarice Patrono
- *Departamento de Bioquímica, Instituto de Investigaciones Biomédicas ‘Alberto Sols’, CSIC-UAM, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain
- ‡Unit of Molecular Medicine, Children's Hospital ‘Bambino Gesù’, Rome, Italy
| | - Miguel Angel Fernández-Moreno
- *Departamento de Bioquímica, Instituto de Investigaciones Biomédicas ‘Alberto Sols’, CSIC-UAM, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain
| | - Emiliano González-Vioque
- *Departamento de Bioquímica, Instituto de Investigaciones Biomédicas ‘Alberto Sols’, CSIC-UAM, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain
| | - Yolanda Campos
- §Centro de Investigación, Hospital 12 de Octubre, Madrid, Spain
| | - Rosalba Carrozzo
- ‡Unit of Molecular Medicine, Children's Hospital ‘Bambino Gesù’, Rome, Italy
| | | | - Pilar del Hoyo
- §Centro de Investigación, Hospital 12 de Octubre, Madrid, Spain
| | | | - Joaquín Arenas
- §Centro de Investigación, Hospital 12 de Octubre, Madrid, Spain
| | - Rafael Garesse
- *Departamento de Bioquímica, Instituto de Investigaciones Biomédicas ‘Alberto Sols’, CSIC-UAM, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain
- To whom correspondence should be addressed (email )
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24
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Kolesnikova O, Entelis N, Kazakova H, Brandina I, Martin RP, Tarassov I. Targeting of tRNA into yeast and human mitochondria: the role of anticodon nucleotides. Mitochondrion 2005; 2:95-107. [PMID: 16120312 DOI: 10.1016/s1567-7249(02)00013-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2002] [Revised: 03/29/2002] [Accepted: 03/29/2002] [Indexed: 12/27/2022]
Abstract
In vivo, yeast mitochondria import a single cytoplasmic tRNA, tRNA(CUU)Lys, while human mitochondria do not import any cytoplasmic tRNA. We have previously demonstrated that both yeast and human isolated mitochondria can specifically internalize tRNA(CUU)Lys, several of its mutant versions and some mutant versions of yeast cytosolic tRNA(UUU)Lys (not imported in vivo). Aminoacylation of tRNA(CUU)Lys by the cytoplasmic lysyl-tRNA synthetase was a prerequisite for its import. Here we are studying the influence of one-base replacements in the anticodon of tRNAs(Lys) on their aminoacylation, on binding to the precursor of the mitochondrial lysyl-tRNA synthetase (carrier protein directing the import), and on the efficiency of import into isolated yeast and human mitochondria. We show that the base U35 is the main identity element for the yeast cytoplasmic lysyl-tRNA synthetase. The single replacement that abolished import was C34G, while all the others only modulated the import efficiency. The need of aminoacylation for import and for interaction with the carrier protein was shown only for a subset of mutant versions, while the others could be recognized and internalized without aminoacylation or in misacylated forms.
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Affiliation(s)
- O Kolesnikova
- FRE 2375 CNRS Modèles Levures de Pathologies Humaines, Institut de Physiologie et Chimie Biologique, 21 rue René Descartes 67084, Strasbourg, France
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25
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Levinger L, Mörl M, Florentz C. Mitochondrial tRNA 3' end metabolism and human disease. Nucleic Acids Res 2004; 32:5430-41. [PMID: 15477393 PMCID: PMC524294 DOI: 10.1093/nar/gkh884] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Over 150 mutations in the mitochondrial genome have been shown to be associated with human disease. Remarkably, two-thirds of them are found in tRNA genes, which constitute only one-tenth of the mitochondrial genome. A total of 22 tRNAs punctuate the genome and are produced together with 11 mRNAs and 2 rRNAs from long polycistronic primary transcripts with almost no spacers. Pre-tRNAs thus require precise endonucleolytic excision. Furthermore, the CCA triplet which forms the 3' end of all tRNAs is not encoded, but must be synthesized by the CCA-adding enzyme after 3' end cleavage. Amino acid attachment to the CCA of mature tRNA is performed by aminoacyl-tRNA synthetases, which, like the preceding processing enzymes, are nuclear-encoded and imported into mitochondria. Here, we critically review the effectiveness and reliability of evidence obtained from reactions with in vitro transcripts that pathogenesis-associated mutant mitochondrial tRNAs can lead to deficiencies in tRNA 3' end metabolism (3' end cleavage, CCA addition and aminoacylation) toward an understanding of molecular mechanisms underlying human tRNA disorders. These defects probably contribute, individually and cumulatively, to the progression of human mitochondrial diseases.
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Affiliation(s)
- Louis Levinger
- York College/CUNY, 94-20 Guy R. Brewer Boulevard, Jamaica, NY 11451, USA.
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26
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Bacman SR, Atencio DP, Moraes CT. Decreased mitochondrial tRNALys steady-state levels and aminoacylation are associated with the pathogenic G8313A mitochondrial DNA mutation. Biochem J 2003; 374:131-6. [PMID: 12737626 PMCID: PMC1223569 DOI: 10.1042/bj20030222] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2003] [Revised: 04/10/2003] [Accepted: 05/09/2003] [Indexed: 11/17/2022]
Abstract
Mutations in human mitochondrial tRNA genes cause a number of multisystemic disorders. A G-to-A transition at position 8313 (G8313A) transition in the mitochondrial tRNALys gene has been associated with a childhood syndrome characterized by gastrointestinal-system involvement and encephaloneuropathy. We have used transmitochondrial cybrid clones harbouring patient-derived mitochondrial DNA with the G8313A mutation for the study of the molecular pathogenesis. Our results showed that mutant mitochondrial cybrids respired poorly, and had severely defective mitochondrial protein synthesis and respiratory-chain-enzyme activity. Mutant cybrids also showed a marked decrease in tRNALys steady-state levels and aminoacylation, suggesting that these molecular abnormalities may underlie the pathogenesis of the mitochondrial G8313A mutation.
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Affiliation(s)
- Sandra R Bacman
- Department of Neurology, University of Miami School of Medicine, 1095 NW 14th Terrace, Miami, FL 33136, USA
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27
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Affiliation(s)
- Yau-Huei Wei
- Department of Biochemistry, Center for Cellular and Molecular Biology, National Yang-Ming University, Taipei, Taiwan, Republic of China
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28
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Gajewski CD, Lin MT, Cudkowicz ME, Beal MF, Manfredi G. Mitochondrial DNA from platelets of sporadic ALS patients restores normal respiratory functions in rho(0) cells. Exp Neurol 2003; 179:229-35. [PMID: 12618129 DOI: 10.1016/s0014-4886(02)00022-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease, which affects the anterior horn cells of the spinal cord and cortical motor neurons. A pathophysiological role for mtDNA mutations was postulated based on the finding that cybrids obtained from mitochondria of sporadic ALS patients exhibited impaired respiratory chain activities, increased free radical scavenging enzymes, and altered calcium homeostasis. To date, however, no distinct mtDNA alterations associated with ALS have been reported. Therefore, we reexamined the hypotheses that mtDNA mutations accumulate in ALS and that cybrids generated from ALS patients' blood have impaired mitochondrial respiration. Cybrid cell lines were generated from 143B osteosarcoma rho(0) cells and platelet mitochondria of sporadic ALS patients or age-matched controls. We found no statistically significant differences in mitochondrial respiration between ALS and control cybrids, even when the electron transport chain was stressed with low concentrations of respiratory chain inhibitors. Mitochondrial respiratory chain enzyme activities were also normal in ALS cybrids, and there was no increase in free radical production. Therefore, we showed that mtDNA from platelets of ALS patients was able to restore normal respiratory function in rho(0) cells, suggesting that the presence of mtDNA mutations capable of affecting mitochondrial respiration was unlikely.
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Affiliation(s)
- Carl D Gajewski
- Department of Neurology and Neuroscience, Weill Medical College of Cornell University, New York, NY 10021, USA
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29
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Vives-Bauza C, Del Toro M, Solano A, Montoya J, Andreu AL, Roig M. Genotype-phenotype correlation in the 5703G>A mutation in the tRNA(ASN) gene of mitochondrial DNA. J Inherit Metab Dis 2003; 26:507-8. [PMID: 14518831 DOI: 10.1023/a:1025133629685] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The 5703G>A mutation in the tRNA gene of mitochondrial DNA seems to show a tissue-specific phenotype: early age of clinical presentation, progressive external ophthalmoplegia, fatigability and 'extremely thin appearance'. We report a second patient with the same mutation and phenotype.
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Affiliation(s)
- C Vives-Bauza
- Centre d'Investigacions en Bioquimica i Biologia Molecular, Hospital Universitari Vall d'Hebron, Barcelona, Spain
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Bayona-Bafaluy MP, Fernández-Silva P, Enríquez JA. The thankless task of playing genetics with mammalian mitochondrial DNA: a 30-year review. Mitochondrion 2002; 2:3-25. [PMID: 16120305 DOI: 10.1016/s1567-7249(02)00044-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2002] [Revised: 05/22/2002] [Accepted: 06/05/2002] [Indexed: 10/27/2022]
Abstract
The advances obtained through the genetic tools available in yeast for studying the oxidative phosphorylation (OXPHOS) biogenesis and in particular the role of the mtDNA encoded genes, strongly contrast with the very limited benefits that similar approaches have generated for the study of mammalian mtDNA. Here we review the use of the genetic manipulation in mammalian mtDNA, its difficulty and the main types of mutants accumulated in the past 30 years and the information derived from them. We also point out the need for a substantial improvement in this field in order to obtain new tools for functional genetic studies and for the generation of animal models of mtDNA-linked diseases.
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Affiliation(s)
- M Pilar Bayona-Bafaluy
- Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, Miguel Servet 177, Zaragoza 50013, Spain
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Diaz F, Bayona-Bafaluy MP, Rana M, Mora M, Hao H, Moraes CT. Human mitochondrial DNA with large deletions repopulates organelles faster than full-length genomes under relaxed copy number control. Nucleic Acids Res 2002; 30:4626-33. [PMID: 12409452 PMCID: PMC135822 DOI: 10.1093/nar/gkf602] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Partially-deleted mitochondrial DNA (DeltamtDNA) accumulates during aging of postmitotic tissues. This accumulation has been linked to decreased metabolic activity, increased reactive oxygen species formation and the aging process. Taking advantage of cell lines with heteroplasmic mtDNA mutations, we showed that, after severe mtDNA depletion, organelles are quickly and predominantly repopulated with DeltamtDNA, whereas repopulation with the wild-type counterpart is slower. This behavior was not observed for full-length genomes with pathogenic point mutations. The faster repopulation of smaller molecules was supported by metabolic labeling of mtDNA with [3H]thymidine during relaxed copy number control conditions. We also showed that hybrid cells containing two defective mtDNA haplotypes tend to retain the smaller one as they adjust their normal mtDNA copy number. Taken together, our results indicate that, under relaxed copy number control, DeltamtDNAs repopulate mitochondria more efficiently than full-length genomes.
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Affiliation(s)
- Francisca Diaz
- Department of Neurology, University of Miami, School of Medicine, Miami, FL 33136, USA
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32
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Affiliation(s)
- C T Moraes
- Department of Neurology, University of Miami School of Medicine, Miami, Florida 33136, USA
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33
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Entelis N, Kolesnikova O, Kazakova H, Brandina I, Kamenski P, Martin RP, Tarassov I. Import of nuclear encoded RNAs into yeast and human mitochondria: experimental approaches and possible biomedical applications. GENETIC ENGINEERING 2002; 24:191-213. [PMID: 12416306 DOI: 10.1007/978-1-4615-0721-5_9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/19/2023]
Abstract
Mitochondria import from the cytoplasm the vast majority of proteins and some RNAs. Although there exists extended knowledge concerning the mechanisms of protein import, the import of RNA is poorly understood. It was almost exclusively studied on the model of tRNA import, in several protozoans, plants and yeast. Mammalian mitochondria, which do not import tRNAs naturally, are hypothesized to import other small RNA molecules from the cytoplasm. We studied tRNA import in the yeast system, both in vitro and in vivo, and applied similar approaches to study 5S rRNA import into human mitochondria. Despite the obvious divergence of RNA import systems suggested for different species, we find that in yeast and human cells this pathway involves similar mechanisms exploiting cytosolic proteins to target the RNA to the organelle and requiring the integrity of pre-protein import apparatus. The import pathway might be of interest from a biomedical point of view, to target into mitochondria RNAs that could suppress pathological mutations in mitochondrial DNA. Yeast represents a good model to elaborate such a gene therapy approach. We have described here the various approaches and protocols to study RNA import into mitochondria of yeast and human cells in vitro and in vivo.
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Affiliation(s)
- N Entelis
- FRE 2375 of the CNRS (MEPH), Institut de Physiologie et Chimie Biologique 21, rue René Descartes, 67084 Strasbourg, France
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34
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Abstract
Mitochondria, though containing their own genome, import the vast majority of their macromolecular components from the cytoplasm. If the mechanisms of pre-protein import are well understood, the import of nuclear-coded RNAs into mitochondria was investigated to a much lesser extent. This targeting, if not universal, is widely spread among species. The origin and the mechanisms of RNA import seem to differ from one system to another and striking differences are observed even in closely related species. We describe data concerning the various experimental systems of studying RNA import with emphasis on the model of the yeast Saccharomyces cerevisiae, which was studied in our laboratory. We compare various requirements of RNA import into mitochondria in different species and demonstrate that this pathway can be transferred from yeast to human cells, in which tRNAs normally are not imported. We speculate on the possibility to use RNA import for biomedical purposes.
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Affiliation(s)
- N S Entelis
- FRE 2168 CNRS, 21, rue René Descartes, 67084 Strasbourg, France
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35
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Campos Y, Gámez J, García A, Andreu AL, Rubio JC, Martín MA, del Hoyo P, Navarro C, Cervera C, Garesse R, Arenas J. A new mtDNA mutation in the tRNA(Leu(UUR)) gene associated with ocular myopathy. Neuromuscul Disord 2001; 11:477-80. [PMID: 11404120 DOI: 10.1016/s0960-8966(00)00223-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We studied a patient with ptosis, ophthalmoparesis, and exercise intolerance who showed in her muscle biopsy ragged-red fibers and combined defects of the complexes I and IV of the mitochondrial respiratory chain. Molecular analysis revealed a T3273C transition in the mitochondrial DNA tRNA(Leu(UUR)) gene. The mutation was heteroplasmic and very abundant in muscle from the proposita, less abundant in her other tissues studied, and still less abundant in blood from her maternal relatives. Single muscle fiber analysis showed significantly higher levels of mutant genomes in ragged-red fibers than in normal fibers. The T3273C mutation affects a strictly conserved base pair in the anticodon stem and was not found in controls, thus satisfying the accepted criteria for pathogenicity.
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Affiliation(s)
- Y Campos
- Centro de Investigación, Hospital 12 de Octubre, Avda de Córdoba km 5.4, 28041, Madrid, Spain
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36
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Florentz C, Sissler M. Disease-related versus polymorphic mutations in human mitochondrial tRNAs. Where is the difference? EMBO Rep 2001; 2:481-6. [PMID: 11415979 PMCID: PMC1083905 DOI: 10.1093/embo-reports/kve111] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
A number of point mutations in human mitochondrial (mt) tRNA genes are correlated with a variety of neuromuscular and other severe disorders including encephalopathies, myopathies, cardiopathies and diabetes. The complexity of the genotype/phenotype relationships, the diversity of possible molecular impacts of the different mutations at the tRNA structure/function levels, and the exponential discovery of new mutations call for the search for unifying features. Here, the basic features (at the levels of primary and secondary structure) of 68 'pathogenic' mutations are compared with those of 64 'polymorphic' neutral mutations, revealing that these standard parameters for mutant analysis are not sufficient to predict the pathogenicity of mt tRNA mutations. Thus, case by case molecular investigation remains the only means of assessing the growing family of pathogenic mutations in mt tRNAs. New lines of research are suggested.
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Affiliation(s)
- C Florentz
- UPR 9002 du CNRS, Département Mécanismes et Macromolécules de la Synthèse Protéique et Cristallogenèse, Institut de Biologie Moléculaire et Cellulaire, 15 rue René Descartes, F-67084 Strasbourg Cedex, France.
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37
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Rana M, De Coo I, Diaz F, Smeets H, Moraes CT. An out-of-frame cytochromeb gene deletion from a patient with parkinsonism is associated with impaired complex III assembly and an increase in free radical production. Ann Neurol 2001. [DOI: 10.1002/1531-8249(200011)48:5<774::aid-ana11>3.0.co;2-i] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Fernández-Moreno MA, Bornstein B, Petit N, Garesse R. The pathophysiology of mitochondrial biogenesis: towards four decades of mitochondrial DNA research. Mol Genet Metab 2000; 71:481-95. [PMID: 11073716 DOI: 10.1006/mgme.2000.3083] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mitochondria are with very few exceptions ubiquitous organelles in eukaryotic cells where they are essential for cell life and death. Mitochondria play a central role not only in a variety of metabolic pathways including the supply of the bulk of cellular ATP through oxidative phosphorylation (OXPHOS), but also in complex processes such as development, apoptosis, and aging. Mitochondria contain their own genome that is replicated and expressed within the organelle. It encodes 13 polypeptides all of them components of the OXPHOS system, and thus, the integrity of the mitochondrial DNA (mtDNA) is critical for cellular energy supply. In the past 12 years more than 50 point mutations and around 100 rearrangements in the mtDNA have been associated with human diseases. Also in recent years, several mutations in nuclear genes that encode structural or regulatory factors of the OXPHOS system or the mtDNA metabolism have been described. The development of increasingly powerful techniques and the use of cellular and animal models are opening new avenues in the study of mitochondrial medicine. The detailed molecular characterization of the effects produced by different mutations that cause mitochondrial cytopathies will be critical for designing rational therapeutic strategies for this group of devastating diseases.
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Affiliation(s)
- M A Fernández-Moreno
- Departamento de Bioquímica, Facultad de Medicina, Instituto de Investigaciones Biomédicas "Alberto Sols" CSIC-UAM, Universidad Autónoma de Madrid, c/ Arzobispo Morcillo 4, Madrid, 28029, Spain
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39
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Barrientos A, Müller S, Dey R, Wienberg J, Moraes CT. Cytochrome c oxidase assembly in primates is sensitive to small evolutionary variations in amino acid sequence. Mol Biol Evol 2000; 17:1508-19. [PMID: 11018157 DOI: 10.1093/oxfordjournals.molbev.a026250] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Respiring mitochondria require many interactions between nuclear and mitochondrial genomes. Although mitochondrial DNA (mtDNA) from the gorilla and the chimpanzee are able to restore oxidative phosphorylation in a human cell, mtDNAs from more distant primate species are functionally incompatible with human nuclear genes. Using microcell-mediated chromosome and mitochondria transfer, we introduced and maintained a functional orangutan mtDNA in a human nuclear background. However, partial oxidative phosphorylation function was restored only in the presence of most orangutan chromosomes, suggesting that human oxidative phosphorylation-related nuclear-coded genes are not able to replace many orangutan ones. The respiratory capacity of these hybrids was decreased by 65%-80%, and cytochrome c oxidase (COX) activity was decreased by 85%-95%. The function of other respiratory complexes was not significantly altered. The translation of mtDNA-coded COX subunits was normal, but their steady-state levels were approximately 10% of normal ones. Nuclear-coded COX subunits were loosely associated with mitochondrial membranes, a characteristic of COX assembly-defective mutants. Our results suggest that many human nuclear-coded genes not only cannot replace the orangutan counterparts, but also exert a specific interference at the level of COX assembly. This cellular model underscores the precision of COX assembly in mammals and sheds light on the nature of nuclear-mtDNA coevolutionary constraints.
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Affiliation(s)
- A Barrientos
- Department of Neurology, University of Miami, School of Medicine, Miami, FL 33136, USA
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40
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Moraes CT, Kenyon L, Hao H. Mechanisms of human mitochondrial DNA maintenance: the determining role of primary sequence and length over function. Mol Biol Cell 1999; 10:3345-56. [PMID: 10512871 PMCID: PMC25601 DOI: 10.1091/mbc.10.10.3345] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Although the regulation of mitochondrial DNA (mtDNA) copy number is performed by nuclear-coded factors, very little is known about the mechanisms controlling this process. We attempted to introduce nonhuman ape mtDNA into human cells harboring either no mtDNA or mutated mtDNAs (partial deletion and tRNA gene point mutation). Unexpectedly, only cells containing no mtDNA could be repopulated with nonhuman ape mtDNA. Cells containing a defective human mtDNA did not incorporate or maintain ape mtDNA and therefore died under selection for oxidative phosphorylation function. On the other hand, foreign human mtDNA was readily incorporated and maintained in these cells. The suicidal preference for self-mtDNA showed that functional parameters associated with oxidative phosphorylation are less relevant to mtDNA maintenance and copy number control than recognition of mtDNA self-determinants. Non-self-mtDNA could not be maintained into cells with mtDNA even if no selection for oxidative phosphorylation was applied. The repopulation kinetics of several mtDNA forms after severe depletion by ethidium bromide treatment showed that replication and maintenance of mtDNA in human cells are highly dependent on molecular features, because partially deleted mtDNA molecules repopulated cells significantly faster than full-length mtDNA. Taken together, our results suggest that mtDNA copy number may be controlled by competition for limiting levels of trans-acting factors that recognize primarily mtDNA molecular features. In agreement with this hypothesis, marked variations in mtDNA levels did not affect the transcription of nuclear-coded factors involved in mtDNA replication.
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Affiliation(s)
- C T Moraes
- Department of Neurology, University of Miami, School of Medicine, Miami, Florida 33136, USA.
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41
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Taanman JW. The mitochondrial genome: structure, transcription, translation and replication. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1410:103-23. [PMID: 10076021 DOI: 10.1016/s0005-2728(98)00161-3] [Citation(s) in RCA: 994] [Impact Index Per Article: 39.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Mitochondria play a central role in cellular energy provision. The organelles contain their own genome with a modified genetic code. The mammalian mitochondrial genome is transmitted exclusively through the female germ line. The human mitochondrial DNA (mtDNA) is a double-stranded, circular molecule of 16569 bp and contains 37 genes coding for two rRNAs, 22 tRNAs and 13 polypeptides. The mtDNA-encoded polypeptides are all subunits of enzyme complexes of the oxidative phosphorylation system. Mitochondria are not self-supporting entities but rely heavily for their functions on imported nuclear gene products. The basic mechanisms of mitochondrial gene expression have been solved. Cis-acting mtDNA sequences have been characterised by sequence comparisons, mapping studies and mutation analysis both in vitro and in patients harbouring mtDNA mutations. Characterisation of trans-acting factors has proven more difficult but several key enzymes involved in mtDNA replication, transcription and protein synthesis have now been biochemically identified and some have been cloned. These studies revealed that, although some factors may have an additional function elsewhere in the cell, most are unique to mitochondria. It is expected that cell cultures of patients with mitochondrial diseases will increasingly be used to address fundamental questions about mtDNA expression.
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Affiliation(s)
- J W Taanman
- Department of Clinical Neurosciences, Royal Free Hospital School of Medicine, University of London, Rowland Hill Street, London NW3 2PF,
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42
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Howell N. Human mitochondrial diseases: answering questions and questioning answers. INTERNATIONAL REVIEW OF CYTOLOGY 1998; 186:49-116. [PMID: 9770297 DOI: 10.1016/s0074-7696(08)61051-7] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Since the first identification in 1988 of pathogenic mitochondrial DNA (mtDNA) mutations, the mitochondrial diseases have emerged as a major clinical entity. The most striking feature of these disorders is their marked heterogeneity, which extends to their clinical, biochemical, and genetic characteristics. The major mitochondrial encephalomyopathies include MELAS (mitochondrial encephalopathy with lactic acidosis and stroke-like episodes), MERRF (myoclonic epilepsy with ragged red fibers), KSS/CPEO (Kearns-Sayre syndrome/chronic progressive external ophthalmoplegia), and NARP/MILS (neuropathy, ataxia, and retinitis pigmentosum/maternally inherited Leigh syndrome) and they typically present highly variable multisystem defects that usually involve abnormalities of skeletal muscle and/or the CNS. The primary emphasis here is to review recent investigations of these mitochondrial diseases from the standpoint of how the complexities of mitochondrial genetics and biogenesis might determine their varied features. In addition, the mitochondrial encephalomyopathies are compared and contrasted to Leber hereditary optic neuropathy, a mitochondrial disease in which the pathogenic mtDNA mutations produce a more uniform and focal neuropathology. All of these disorders involve, at some level, a mitochondrial respiratory chain dysfunction. Because mitochondrial genetics differs so strikingly from the Mendelian inheritance of chromosomes, recent research on the origin and subsequent segregation and transmission of mtDNA mutations is reviewed.
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Affiliation(s)
- N Howell
- Department of Radiation Oncology, University of Texas Medical Branch, Galveston 77555, USA.
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43
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Kleinle S, Schneider V, Moosmann P, Brandner S, Krähenbühl S, Liechti-Gallati S. A novel mitochondrial tRNA(Phe) mutation inhibiting anticodon stem formation associated with a muscle disease. Biochem Biophys Res Commun 1998; 247:112-5. [PMID: 9636664 DOI: 10.1006/bbrc.1998.8729] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have identified a novel mitochondrial (mt) DNA mutation in the tRNA(Phe)-gene in a patient with an isolated mitochondrial myopathy. This T to C transition at position 618 disrupts a strictly conserved base pair within the anticodon stem of tRNA(Phe). Computer analysis showed that the affected base pair is essential for anticodon stem formation of tRNA(Phe). The mutant mtDNA was heteroplasmic in skeletal muscle (95% mutant) and peripheral blood cells (20% mutant) from the patient but was undetectable in blood cells from his healthy sister. The patient presented with ragged red fibers and reduced activities of complex I and complex III in skeletal muscle. The T618C mutation described here is the second found in this region. Both mutations affect the same base pair of the tRNA(Phe) anticodon stem substantiating the pathogenic nature of both mutations.
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Affiliation(s)
- S Kleinle
- Department of Pediatrics, University of Berne, Switzerland
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44
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Barrientos A, Kenyon L, Moraes CT. Human xenomitochondrial cybrids. Cellular models of mitochondrial complex I deficiency. J Biol Chem 1998; 273:14210-7. [PMID: 9603924 DOI: 10.1074/jbc.273.23.14210] [Citation(s) in RCA: 148] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The subunits forming the mitochondrial oxidative phosphorylation system are coded by both nuclear and mitochondrial genes. Recently, we attempted to introduce mtDNA from non-human apes into a human cell line lacking mtDNA (rho degrees), and succeeded in producing human-common chimpanzee, human-pigmy chimpanzee, and human-gorilla xenomitochondrial cybrids (HXC). Here, we present a comprehensive characterization of oxidative phosphorylation function in these cells. Mitochondrial complexes II, III, IV, and V had activities indistinguishable from parental human or non-human primate cells. In contrast, a complex I deficiency was observed in all HXC. Kinetic studies of complex I using decylubiquinone or NADH as limiting substrates showed that the Vmax was decreased in HXC by approximately 40%, and the Km for the NADH was significantly increased (3-fold, p < 0.001). Rotenone inhibition studies of intact cell respiration and pyruvate-malate oxidation in permeabilized cells showed that 3 nM rotenone produced a mild effect in control cells (0-10% inhibition) but produced a marked inhibition of HXC respiration (50-75%). Immunoblotting analyses of three subunits of complex I (ND1, 75 and 49 kDa) showed that their relative amounts were not significantly altered in HXC cells. These results establish HXC as cellular models of complex I deficiency in humans and underscore the importance of nuclear and mitochondrial genomes co-evolution in optimizing oxidative phosphorylation function.
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Affiliation(s)
- A Barrientos
- Department of Neurology, University of Miami, School of Medicine, Miami, Florida 33136, USA
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