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Lim AZ, Blakely EL, Baty K, He L, Hopton S, Falkous G, McWilliam K, Cozens A, McFarland R, Taylor RW. A novel pathogenic m.4412G>A MT-TM mitochondrial DNA variant associated with childhood-onset seizures, myopathy and bilateral basal ganglia changes. Mitochondrion 2019; 47:18-23. [PMID: 31022467 PMCID: PMC6617384 DOI: 10.1016/j.mito.2019.04.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 04/18/2019] [Accepted: 04/19/2019] [Indexed: 12/03/2022]
Abstract
Mitochondrial DNA variants in the MT-TM (mt-tRNAMet) gene are rare, typically associated with myopathic phenotypes. We identified a novel MT-TM variant resulting in prolonged seizures with childhood-onset myopathy, retinopathy, short stature and elevated CSF lactate associated with bilateral basal ganglia changes on neuroimaging. Muscle biopsy confirmed multiple respiratory chain deficiencies and focal cytochrome c oxidase (COX) histochemical abnormalities. Next-generation sequencing of the mitochondrial genome revealed a novel m.4412G>A variant at high heteroplasmy levels in muscle that fulfils all accepted criteria for pathogenicity including segregation within single muscle fibres, thus broadening the genotypic and phenotypic landscape of mitochondrial tRNA-related disease.
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Affiliation(s)
- Albert Z Lim
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Emma L Blakely
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK; NHS Highly Specialised Service for Rare Mitochondrial Disorders of Adults and Children, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE2 4HH, UK
| | - Karen Baty
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK; NHS Highly Specialised Service for Rare Mitochondrial Disorders of Adults and Children, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE2 4HH, UK
| | - Langping He
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK; NHS Highly Specialised Service for Rare Mitochondrial Disorders of Adults and Children, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE2 4HH, UK
| | - Sila Hopton
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK; NHS Highly Specialised Service for Rare Mitochondrial Disorders of Adults and Children, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE2 4HH, UK
| | - Gavin Falkous
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK; NHS Highly Specialised Service for Rare Mitochondrial Disorders of Adults and Children, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE2 4HH, UK
| | - Kenneth McWilliam
- Department of Paediatric Neurology, Royal Hospital for Sick Children, Edinburgh EH9 1LF, UK
| | - Alison Cozens
- Inherited Metabolic Disorders Scotland, NHS National Services Scotland, Glasgow G2 6QE, UK
| | - Robert McFarland
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Robert W Taylor
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK; NHS Highly Specialised Service for Rare Mitochondrial Disorders of Adults and Children, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE2 4HH, UK.
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Kuwajima M, Goto M, Kurane K, Shimbo H, Omika N, Jimbo EF, Muramatsu K, Tajika M, Shimura M, Murayama K, Kurosawa K, Yamagata T, Osaka H. MELAS syndrome with m.4450 G > A mutation in mitochondrial tRNA Met gene. Brain Dev 2019; 41:465-469. [PMID: 30739820 DOI: 10.1016/j.braindev.2019.01.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 01/02/2019] [Accepted: 01/22/2019] [Indexed: 10/27/2022]
Abstract
Mutations in the mitochondrial tRNAMet gene have been reported in only five patients to date, all of whom presented with muscle weakness and exercise intolerance as signs of myopathy. We herein report the case of a 12-year-old girl with focal epilepsy since the age of eight years. At age 11, the patient developed sudden visual disturbances and headaches accompanied by recurrent, stroke-like episodes with lactic acidosis (pH 7.279, lactic acid 11.6 mmol/L). The patient frequently developed a delirious state, exhibited regression of intellectual ability. Brain magnetic resonance imaging revealed high-intensity signals on T2-weighted images of the left occipital lobe. Mitochondrial gene analysis revealed a heteroplasmic m.4450G > A mutation in the mitochondrial tRNAMet. The heteroplasmic rate of the m.4450G > A mutation in blood, skin, urinary sediment, hair, saliva, and nail samples were 20, 38, 59, 41, 27, and 35%, respectively. The patient's fibroblast showed an approximately 53% reduction in the oxygen consumption rate, compared to a control, and decreased complex I and IV activities. Stroke-like episodes, lactic acidosis, encephalopathy with brain magnetic resonance imaging findings, and declined mitochondrial function were consistent with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome. To our knowledge, the findings associated with this first patient with MELAS syndrome harboring the m.4450G > A mutation in mitochondrial tRNAMet expand the phenotypic spectrum of tRNAMet gene.
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Affiliation(s)
- Mari Kuwajima
- Department of Pediatrics, Jichi Medical University, Japan
| | - Masahide Goto
- Department of Pediatrics, Jichi Medical University, Japan
| | - Koyuru Kurane
- Department of Pediatrics, Jichi Medical University, Japan
| | - Hiroko Shimbo
- Department of Genetics, Kanagawa Children's Medical Center, Yokohama, Kanagawa, Japan
| | - Narumi Omika
- Department of Pediatrics, Jichi Medical University, Japan
| | - Eriko F Jimbo
- Department of Pediatrics, Jichi Medical University, Japan
| | | | - Makiko Tajika
- Department of Metabolism, Chiba Children's Hospital, Japan
| | - Masaru Shimura
- Department of Metabolism, Chiba Children's Hospital, Japan
| | - Kei Murayama
- Department of Metabolism, Chiba Children's Hospital, Japan
| | - Kenji Kurosawa
- Department of Genetics, Kanagawa Children's Medical Center, Yokohama, Kanagawa, Japan
| | | | - Hitoshi Osaka
- Department of Pediatrics, Jichi Medical University, Japan.
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Triska P, Kaneva K, Merkurjev D, Sohail N, Falk MJ, Triche TJ, Biegel JA, Gai X. Landscape of Germline and Somatic Mitochondrial DNA Mutations in Pediatric Malignancies. Cancer Res 2019; 79:1318-1330. [PMID: 30709931 PMCID: PMC6445760 DOI: 10.1158/0008-5472.can-18-2220] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 11/15/2018] [Accepted: 01/22/2019] [Indexed: 01/21/2023]
Abstract
Little is known about the spectrum of mitochondrial DNA (mtDNA) mutations across pediatric malignancies. In this study, we analyzed matched tumor and normal whole genome sequencing data from 616 pediatric patients with hematopoietic malignancies, solid tumors, and brain tumors. We identified 391 mtDNA mutations in 284 tumors including 45 loss-of-function mutations, which clustered at four statistically significant hotspots in MT-COX3, MT-ND4, and MT-ND5, and at a mutation hotspot in MT-tRNA-MET. A skewed ratio (4.83) of nonsynonymous versus synonymous (dN/dS) mtDNA mutations with high statistical significance was identified on the basis of Monte Carlo simulations in the tumors. In comparison, opposite ratios of 0.44 and 0.93 were observed in 616 matched normal tissues and in 249 blood samples from children without cancer, respectively. mtDNA mutations varied by cancer type and mtDNA haplogroup. Collectively, these results suggest that deleterious mtDNA mutations play a role in the development and progression of pediatric cancers. SIGNIFICANCE: This pan-cancer mtDNA study establishes the landscape of germline and tumor mtDNA mutations and identifies hotspots of tumor mtDNA mutations to pinpoint key mitochondrial functions in pediatric malignancies.
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Affiliation(s)
- Petr Triska
- Center for Personalized Medicine, Department of Pathology and Laboratory Medicine, Children's Hospital Los Angeles, Los Angeles, California
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Kristiyana Kaneva
- Center for Personalized Medicine, Department of Pathology and Laboratory Medicine, Children's Hospital Los Angeles, Los Angeles, California
- Division of Hematology, Oncology, and Blood and Marrow Transplant Program, Children's Center for Cancer and Blood Diseases, Department of Pediatrics, Children's Hospital Los Angeles, Los Angeles, California
| | - Daria Merkurjev
- Center for Personalized Medicine, Department of Pathology and Laboratory Medicine, Children's Hospital Los Angeles, Los Angeles, California
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Noor Sohail
- Center for Epigenetics, Van Andel Research Institute, Grand Rapids, Michigan
| | - Marni J Falk
- University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
- Division of Human Genetics, Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Timothy J Triche
- Center for Epigenetics, Van Andel Research Institute, Grand Rapids, Michigan
| | - Jaclyn A Biegel
- Center for Personalized Medicine, Department of Pathology and Laboratory Medicine, Children's Hospital Los Angeles, Los Angeles, California.
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Xiaowu Gai
- Center for Personalized Medicine, Department of Pathology and Laboratory Medicine, Children's Hospital Los Angeles, Los Angeles, California.
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, California
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Agris PF, Narendran A, Sarachan K, Väre VYP, Eruysal E. The Importance of Being Modified: The Role of RNA Modifications in Translational Fidelity. Enzymes 2017; 41:1-50. [PMID: 28601219 DOI: 10.1016/bs.enz.2017.03.005] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The posttranscriptional modifications of tRNA's anticodon stem and loop (ASL) domain represent a third level, a third code, to the accuracy and efficiency of translating mRNA codons into the correct amino acid sequence of proteins. Modifications of tRNA's ASL domain are enzymatically synthesized and site specifically located at the anticodon wobble position-34 and 3'-adjacent to the anticodon at position-37. Degeneracy of the 64 Universal Genetic Codes and the limitation in the number of tRNA species require some tRNAs to decode more than one codon. The specific modification chemistries and their impact on the tRNA's ASL structure and dynamics enable one tRNA to decode cognate and "wobble codons" or to expand recognition to synonymous codons, all the while maintaining the translational reading frame. Some modified nucleosides' chemistries prestructure tRNA to read the two codons of a specific amino acid that shares a twofold degenerate codon box, and other chemistries allow a different tRNA to respond to all four codons of a fourfold degenerate codon box. Thus, tRNA ASL modifications are critical and mutations in genes for the modification enzymes and tRNA, the consequences of which is a lack of modification, lead to mistranslation and human disease. By optimizing tRNA anticodon chemistries, structure, and dynamics in all organisms, modifications ensure translational fidelity of mRNA transcripts.
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Affiliation(s)
- Paul F Agris
- The RNA Institute, State University of New York, Albany, NY, United States.
| | - Amithi Narendran
- The RNA Institute, State University of New York, Albany, NY, United States
| | - Kathryn Sarachan
- The RNA Institute, State University of New York, Albany, NY, United States
| | - Ville Y P Väre
- The RNA Institute, State University of New York, Albany, NY, United States
| | - Emily Eruysal
- The RNA Institute, State University of New York, Albany, NY, United States
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Born AP, Duno M, Rafiq J, Risom L, Wibrand F, Østergaard E, Vissing J. A mitochondrial tRNA(Met) mutation causing developmental delay, exercise intolerance and limb girdle phenotype with onset in early childhood. Eur J Paediatr Neurol 2015; 19:69-71. [PMID: 25468263 DOI: 10.1016/j.ejpn.2014.10.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 10/24/2014] [Indexed: 11/16/2022]
Abstract
A 10-year-old girl presented with exercise intolerance, learning difficulty, and muscle weakness in a limb girdle distribution. She had delayed achievement of motor milestones and difficulties with social interaction at pre-school age. Muscle biopsy showed no myopathic or dystrophic features, but 90% COX negative fibres and ragged blue fibres. Respiratory chain enzyme analysis in muscle showed a combined deficiency and mitochondrial DNA sequencing revealed the presence of an m.4450G>A mutation in the MT-TM gene encoding the tRNA for methionine. The mutation was only detected in mtDNA extracted from muscle and skin fibroblast, and could not be found in other tissues or in the mother. This is the second patient reported in the literature with a mitochondrial myopathy due to a mt-tRNA(Met) mutation. The first patient, a 30-year-old woman, presented with exercise intolerance, limb girdle muscle weakness, lactic acidosis, learning difficulty, and growth retardation in early childhood. Thus, the two patients exhibit strikingly overlapping phenotypes.
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Affiliation(s)
- Alfred Peter Born
- Paediatric Clinic, University of Copenhagen, Rigshospitalet, Denmark.
| | - Morten Duno
- Department of Clinical Genetics, University of Copenhagen, Rigshospitalet, Denmark
| | - Jabin Rafiq
- Neuromuscular Research Unit, University of Copenhagen, Rigshospitalet, Denmark
| | - Lotte Risom
- Department of Clinical Genetics, University of Copenhagen, Rigshospitalet, Denmark
| | - Flemming Wibrand
- Department of Clinical Genetics, University of Copenhagen, Rigshospitalet, Denmark
| | - Elsebet Østergaard
- Department of Clinical Genetics, University of Copenhagen, Rigshospitalet, Denmark
| | - John Vissing
- Neuromuscular Research Unit, University of Copenhagen, Rigshospitalet, Denmark
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Peverelli L, Gold CA, Naini AB, Tanji K, Akman HO, Hirano M, Dimauro S. Mitochondrial myopathy with dystrophic features due to a novel mutation in the MTTM gene. Muscle Nerve 2014; 50:292-5. [PMID: 24711008 DOI: 10.1002/mus.24262] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/04/2014] [Indexed: 11/11/2022]
Abstract
INTRODUCTION A 61-year-old woman with a 5-year history of progressive muscle weakness and atrophy had a muscle biopsy characterized by a combination of dystrophic features (necrotic fibers and endomysial fibrosis) and mitochondrial alterations [ragged-red, cytochrome c oxidase (COX)-negative fibers]. METHODS Sequencing of the whole mtDNA, assessment of the mutation load in muscle and accessible nonmuscle tissues, and single fiber polymerase chain reaction. RESULTS Muscle mitochondrial DNA (mtDNA) sequencing revealed a novel heteroplasmic mutation (m.4403G>A) in the gene (MTTM) that encodes tRNA(Met). The mutation was not present in accessible nonmuscle tissues from the patient or 2 asymptomatic sisters. CONCLUSIONS The clinical features and muscle morphology in this patient are very similar to those described in a previous patient with a different mutation, also in MTTM, which suggests that mutations in this gene confer a distinctive "dystrophic" quality. This may be a diagnostic clue in patients with isolated mitochondrial myopathy.
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Affiliation(s)
- Lorenzo Peverelli
- Department of Neurology, Columbia University Medical Center, College of Physicians & Surgeons, 630 West 168th Street, New York, New York, USA
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Implications of mitochondrial DNA mutations and mitochondrial dysfunction in tumorigenesis. Cell Res 2009; 19:802-15. [PMID: 19532122 DOI: 10.1038/cr.2009.69] [Citation(s) in RCA: 194] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Alterations in oxidative phosphorylation resulting from mitochondrial dysfunction have long been hypothesized to be involved in tumorigenesis. Mitochondria have recently been shown to play an important role in regulating both programmed cell death and cell proliferation. Furthermore, mitochondrial DNA (mtDNA) mutations have been found in various cancer cells. However, the role of these mtDNA mutations in tumorigenesis remains largely unknown. This review focuses on basic mitochondrial genetics, mtDNA mutations and consequential mitochondrial dysfunction associated with cancer. The potential molecular mechanisms, mediating the pathogenesis from mtDNA mutations and mitochondrial dysfunction to tumorigenesis are also discussed.
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Bortot B, Barbi E, Biffi S, Angelini C, Faleschini E, Severini G, Carrozzi M. Two novel cosegregating mutations in tRNAMet and COX III, in a patient with exercise intolerance and autoimmune polyendocrinopathy. Mitochondrion 2009; 9:123-9. [DOI: 10.1016/j.mito.2009.01.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2008] [Revised: 11/27/2008] [Accepted: 01/12/2009] [Indexed: 01/25/2023]
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Lusic H, Gustilo EM, Vendeix FAP, Kaiser R, Delaney MO, Graham WD, Moye VA, Cantara WA, Agris PF, Deiters A. Synthesis and investigation of the 5-formylcytidine modified, anticodon stem and loop of the human mitochondrial tRNAMet. Nucleic Acids Res 2008; 36:6548-57. [PMID: 18927116 PMCID: PMC2582600 DOI: 10.1093/nar/gkn703] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Human mitochondrial methionine transfer RNA (hmtRNA(Met)(CAU)) has a unique post-transcriptional modification, 5-formylcytidine, at the wobble position-34 (f(5)C(34)). The role of this modification in (hmtRNA(Met)(CAU)) for the decoding of AUA, as well as AUG, in both the peptidyl- and aminoacyl-sites of the ribosome in either chain initiation or chain elongation is still unknown. We report the first synthesis and analyses of the tRNA's anticodon stem and loop domain containing the 5-formylcytidine modification. The modification contributes to the tRNA's anticodon domain structure, thermodynamic properties and its ability to bind codons AUA and AUG in translational initiation and elongation.
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Affiliation(s)
- Hrvoje Lusic
- Department of Chemistry, Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695 and Dharmacon, 2650 Crescent Drive #100, Lafayette, CO 80026, USA
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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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Sachadyn P, Zhang XM, Clark LD, Naviaux RK, Heber-Katz E. Naturally occurring mitochondrial DNA heteroplasmy in the MRL mouse. Mitochondrion 2008; 8:358-66. [PMID: 18761428 DOI: 10.1016/j.mito.2008.07.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Revised: 07/21/2008] [Accepted: 07/23/2008] [Indexed: 11/30/2022]
Abstract
The MRL/MpJ mouse is an inbred laboratory strain of Mus musculus, known to exhibit enhanced autoimmunity, increased wound healing, and increased regeneration properties. We report the full-length mitochondrial DNA (mtDNA) sequence of the MRL mouse (Accession # EU450583), and characterize the discovery of two naturally occurring heteroplasmic sites. The first is a T3900C substitution in the TPsiC loop of the tRNA methionine gene (tRNA-Met; mt-Tm). The second is a heteroplasmic insertion of 1-6 adenine nucleotides in the A-tract of the tRNA arginine gene (tRNA-Arg; mt-Tr) at positions 9821-9826. The level of heteroplasmy varied independently at these two sites in MRL individuals. The length of the tRNA-Arg A-tract increased with age, but heteroplasmy at the tRNA-Met site did not change with age. The finding of naturally occurring mtDNA heteroplasmy in an inbred strain of mouse makes the MRL mouse a powerful new experimental model for studies designed to explore therapeutic measures to alter the cellular burden of heteroplasmy.
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Affiliation(s)
- Paweł Sachadyn
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
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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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Abstract
Splenic marginal zone lymphoma (SMZL) is a specific low-grade small B-cell lymphoma that is incorporated in the World Health Organization classification. Characteristic features are splenomegaly, moderate lymphocytosis with villous morphology, intrasinusoidal pattern of involvement of various organs, especially bone marrow, and relative indolent course. Tumor progression with increase of blastic forms and aggressive behavior are observed in a minority of patients. Molecular and cytogenetic studies have shown heterogeneous results probably because of the lack of standardized diagnostic criteria. To date, no definitive therapy has been established. Therapeutic options include treatment abstention, splenectomy, splenic irradiation, and chemotherapy.
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Affiliation(s)
- Vito Franco
- Istituto di Anatomia e Istologia Patologica and Divisione di Ematologia con TMO, University of Palermo, Palermo, Italy.
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Chapter 3 Molecular Genetic Basis of the Mitochondrial Encephalomyopathies. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s1877-3419(09)70062-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Abstract
It is nearly a decade since the discovery of the first mutations in mitochondrial DNA associated with mitochondrial encephalomyopathy, and the pace of discovery of new mitochondrial DNA mutations continues unabated. Nuclear gene defects in these disorders have been more difficult to identify; only one is known, but others have been mapped by linkage analysis. The rules governing transmission and segregation of mitochondrial DNA sequence variants are beginning to be unravelled and progress has been made in understanding genotype-phenotype relationships and elucidating mechanisms of pathogenesis.
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