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Bernardino Gomes TM, Vincent AE, Menger KE, Stewart JB, Nicholls TJ. Mechanisms and pathologies of human mitochondrial DNA replication and deletion formation. Biochem J 2024; 481:683-715. [PMID: 38804971 DOI: 10.1042/bcj20230262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Revised: 05/13/2024] [Accepted: 05/14/2024] [Indexed: 05/29/2024]
Abstract
Human mitochondria possess a multi-copy circular genome, mitochondrial DNA (mtDNA), that is essential for cellular energy metabolism. The number of copies of mtDNA per cell, and their integrity, are maintained by nuclear-encoded mtDNA replication and repair machineries. Aberrant mtDNA replication and mtDNA breakage are believed to cause deletions within mtDNA. The genomic location and breakpoint sequences of these deletions show similar patterns across various inherited and acquired diseases, and are also observed during normal ageing, suggesting a common mechanism of deletion formation. However, an ongoing debate over the mechanism by which mtDNA replicates has made it difficult to develop clear and testable models for how mtDNA rearrangements arise and propagate at a molecular and cellular level. These deletions may impair energy metabolism if present in a high proportion of the mtDNA copies within the cell, and can be seen in primary mitochondrial diseases, either in sporadic cases or caused by autosomal variants in nuclear-encoded mtDNA maintenance genes. These mitochondrial diseases have diverse genetic causes and multiple modes of inheritance, and show notoriously broad clinical heterogeneity with complex tissue specificities, which further makes establishing genotype-phenotype relationships challenging. In this review, we aim to cover our current understanding of how the human mitochondrial genome is replicated, the mechanisms by which mtDNA replication and repair can lead to mtDNA instability in the form of large-scale rearrangements, how rearranged mtDNAs subsequently accumulate within cells, and the pathological consequences when this occurs.
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Affiliation(s)
- Tiago M Bernardino Gomes
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- NHS England Highly Specialised Service for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE2 4HH, U.K
| | - Amy E Vincent
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
| | - Katja E Menger
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
| | - James B Stewart
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
| | - Thomas J Nicholls
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
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2
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Dahal S, Siddiqua H, Katapadi VK, Iyer D, Raghavan SC. Characterization of G4 DNA formation in mitochondrial DNA and their potential role in mitochondrial genome instability. FEBS J 2021; 289:163-182. [PMID: 34228888 DOI: 10.1111/febs.16113] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 05/29/2021] [Accepted: 07/06/2021] [Indexed: 12/16/2022]
Abstract
Mitochondria possess their own genome which can be replicated independently of nuclear DNA. Mitochondria being the powerhouse of the cell produce reactive oxygen species, due to which the mitochondrial genome is frequently exposed to oxidative damage. Previous studies have demonstrated an association of mitochondrial deletions to aging and human disorders. Many of these deletions were present adjacent to non-B DNA structures. Thus, we investigate noncanonical structures associated with instability in mitochondrial genome. In silico studies revealed the presence of > 100 G-quadruplex motifs (of which 5 have the potential to form 3-plate G4 DNA), 23 inverted repeats, and 3 mirror repeats in the mitochondrial DNA (mtDNA). Further analysis revealed that among the deletion breakpoints from patients with mitochondrial disorders, majority are located at G4 DNA motifs. Interestingly, ~ 50% of the deletions were at base-pair positions 8271-8281, ~ 35% were due to deletion at 12362-12384, and ~ 12% due to deletion at 15516-15545. Formation of 3-plate G-quadruplex DNA structures at mitochondrial fragile regions was characterized using electromobility shift assay, circular dichroism (CD), and Taq polymerase stop assay. All 5 regions could fold into both intramolecular and intermolecular G-quadruplex structures in a KCl-dependent manner. G4 DNA formation was in parallel orientation, which was abolished in the presence of LiCl. The formation of G4 DNA affected both replication and transcription. Finally, immunolocalization of BG4 with MitoTracker confirmed the formation of G-quadruplex in mitochondrial genome. Thus, we characterize the formation of 5 different G-quadruplex structures in human mitochondrial region, which may contribute toward formation of mitochondrial deletions.
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Affiliation(s)
- Sumedha Dahal
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - Humaira Siddiqua
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - Vijeth K Katapadi
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - Divyaanka Iyer
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - Sathees C Raghavan
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
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3
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Mitochondrial genome stability in human: understanding the role of DNA repair pathways. Biochem J 2021; 478:1179-1197. [DOI: 10.1042/bcj20200920] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 02/15/2021] [Accepted: 02/17/2021] [Indexed: 11/17/2022]
Abstract
Mitochondria are semiautonomous organelles in eukaryotic cells and possess their own genome that replicates independently. Mitochondria play a major role in oxidative phosphorylation due to which its genome is frequently exposed to oxidative stress. Factors including ionizing radiation, radiomimetic drugs and replication fork stalling can also result in different types of mutations in mitochondrial DNA (mtDNA) leading to genome fragility. Mitochondria from myopathies, dystonia, cancer patient samples show frequent mtDNA mutations such as point mutations, insertions and large-scale deletions that could account for mitochondria-associated disease pathogenesis. The mechanism by which such mutations arise following exposure to various DNA-damaging agents is not well understood. One of the well-studied repair pathways in mitochondria is base excision repair. Other repair pathways such as mismatch repair, homologous recombination and microhomology-mediated end joining have also been reported. Interestingly, nucleotide excision repair and classical nonhomologous DNA end joining are not detected in mitochondria. In this review, we summarize the potential causes of mitochondrial genome fragility, their implications as well as various DNA repair pathways that operate in mitochondria.
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Fontana GA, Gahlon HL. Mechanisms of replication and repair in mitochondrial DNA deletion formation. Nucleic Acids Res 2020; 48:11244-11258. [PMID: 33021629 PMCID: PMC7672454 DOI: 10.1093/nar/gkaa804] [Citation(s) in RCA: 102] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 09/07/2020] [Accepted: 09/25/2020] [Indexed: 02/06/2023] Open
Abstract
Deletions in mitochondrial DNA (mtDNA) are associated with diverse human pathologies including cancer, aging and mitochondrial disorders. Large-scale deletions span kilobases in length and the loss of these associated genes contributes to crippled oxidative phosphorylation and overall decline in mitochondrial fitness. There is not a united view for how mtDNA deletions are generated and the molecular mechanisms underlying this process are poorly understood. This review discusses the role of replication and repair in mtDNA deletion formation as well as nucleic acid motifs such as repeats, secondary structures, and DNA damage associated with deletion formation in the mitochondrial genome. We propose that while erroneous replication and repair can separately contribute to deletion formation, crosstalk between these pathways is also involved in generating deletions.
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Affiliation(s)
- Gabriele A Fontana
- Department of Health Sciences and Technology, ETH Zürich, Schmelzbergstrasse 9, 8092 Zürich, Switzerland
| | - Hailey L Gahlon
- To whom correspondence should be addressed. Tel: +41 44 632 3731;
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Oliveira MT, Pontes CDB, Ciesielski GL. Roles of the mitochondrial replisome in mitochondrial DNA deletion formation. Genet Mol Biol 2020; 43:e20190069. [PMID: 32141473 PMCID: PMC7197994 DOI: 10.1590/1678-4685-gmb-2019-0069] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Accepted: 08/12/2019] [Indexed: 01/07/2023] Open
Abstract
Mitochondrial DNA (mtDNA) deletions are a common cause of human mitochondrial
diseases. Mutations in the genes encoding components of the mitochondrial
replisome, such as DNA polymerase gamma (Pol γ) and the mtDNA helicase Twinkle,
have been associated with the accumulation of such deletions and the development
of pathological conditions in humans. Recently, we demonstrated that changes in
the level of wild-type Twinkle promote mtDNA deletions, which implies that not
only mutations in, but also dysregulation of the stoichiometry between the
replisome components is potentially pathogenic. The mechanism(s) by which
alterations to the replisome function generate mtDNA deletions is(are) currently
under debate. It is commonly accepted that stalling of the replication fork at
sites likely to form secondary structures precedes the deletion formation. The
secondary structural elements can be bypassed by the replication-slippage
mechanism. Otherwise, stalling of the replication fork can generate single- and
double-strand breaks, which can be repaired through recombination leading to the
elimination of segments between the recombination sites. Here, we discuss
aberrances of the replisome in the context of the two debated outcomes, and
suggest new mechanistic explanations based on replication restart and template
switching that could account for all the deletion types reported for
patients.
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Affiliation(s)
- Marcos T Oliveira
- Universidade Estadual Paulista Júlio de Mesquita Filho, Faculdade de Ciências Agrárias e Veterinárias, Departamento de Tecnologia, Jaboticabal, SP, Brazil
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Yusoff AAM, Abdullah WSW, Khair SZNM, Radzak SMA. A comprehensive overview of mitochondrial DNA 4977-bp deletion in cancer studies. Oncol Rev 2019; 13:409. [PMID: 31044027 PMCID: PMC6478002 DOI: 10.4081/oncol.2019.409] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Accepted: 02/19/2019] [Indexed: 01/04/2023] Open
Abstract
Mitochondria are cellular machines essential for energy production. The biogenesis of mitochondria is a highly complex and it depends on the coordination of the nuclear and mitochondrial genome. Mitochondrial DNA (mtDNA) mutations and deletions are suspected to be associated with carcinogenesis. The most described mtDNA deletion in various human cancers is called the 4977-bp common deletion (mDNA4977) and it has been explored since two decades. In spite of that, its implication in carcinogenesis still unknown and its predictive and prognostic impact remains controversial. This review article provides an overview of some of the cellular and molecular mechanisms underlying mDNA4977 formation and a detailed summary about mDNA4977 reported in various types of cancers. The current knowledges of mDNA4977 as a prognostic and predictive marker are also discussed.
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Affiliation(s)
- Abdul Aziz Mohamed Yusoff
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia
| | - Wan Salihah Wan Abdullah
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia
| | | | - Siti Muslihah Abd Radzak
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia
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7
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Nissanka N, Minczuk M, Moraes CT. Mechanisms of Mitochondrial DNA Deletion Formation. Trends Genet 2019; 35:235-244. [PMID: 30691869 DOI: 10.1016/j.tig.2019.01.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 01/07/2019] [Accepted: 01/08/2019] [Indexed: 02/02/2023]
Abstract
Mitochondrial DNA (mtDNA) encodes a subset of genes which are essential for oxidative phosphorylation. Deletions in the mtDNA can ablate a number of these genes and result in mitochondrial dysfunction, which is associated with bona fide mitochondrial disorders. Although mtDNA deletions are thought to occur as a result of replication errors or following double-strand breaks, the exact mechanism(s) behind deletion formation have yet to be determined. In this review we discuss the current knowledge about the fate of mtDNA following double-strand breaks, including the molecular players which mediate the degradation of linear mtDNA fragments and possible mechanisms of recircularization. We propose that mtDNA deletions formed from replication errors versus following double-strand breaks can be mediated by separate pathways.
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Affiliation(s)
- Nadee Nissanka
- Department of Neurology, University of Miami, Miller School of Medicine, FL 33136, USA
| | - Michal Minczuk
- Medical Research Council (MRC) Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK
| | - Carlos T Moraes
- Department of Neurology, University of Miami, Miller School of Medicine, FL 33136, USA.
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Zinovkina LA. Mechanisms of Mitochondrial DNA Repair in Mammals. BIOCHEMISTRY (MOSCOW) 2018; 83:233-249. [PMID: 29625543 DOI: 10.1134/s0006297918030045] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Accumulation of mutations in mitochondrial DNA leads to the development of severe, currently untreatable diseases. The contribution of these mutations to aging and progress of neurodegenerative diseases is actively studied. Elucidation of DNA repair mechanisms in mitochondria is necessary for both developing approaches to the therapy of diseases caused by mitochondrial mutations and understanding specific features of mitochondrial genome functioning. Mitochondrial DNA repair systems have become a subject of extensive studies only in the last decade due to development of molecular biology methods. DNA repair systems of mammalian mitochondria appear to be more diverse and effective than it had been thought earlier. Even now, one may speak about the existence of mitochondrial mechanisms for the repair of single- and double-stranded DNA lesions. Homologous recombination also takes place in mammalian mitochondria, although its functional significance and molecular mechanisms remain obscure. In this review, I describe DNA repair systems in mammalian mitochondria, such as base excision repair (BER) and microhomology-mediated end joining (MMEJ) and discuss a possibility of existence of mitochondrial DNA repair mechanisms otherwise typical for the nuclear DNA, e.g., nucleotide excision repair (NER), mismatch repair (MMR), homologous recombination, and classical non-homologous end joining (NHEJ). I also present data on the mechanisms for coordination of the nuclear and mitochondrial DNA repair systems that have been actively studied recently.
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Affiliation(s)
- L A Zinovkina
- Lomonosov Moscow State University, Faculty of Bioengineering and Bioinformatics, Moscow, 119234, Russia.
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9
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Tadi SK, Sebastian R, Dahal S, Babu RK, Choudhary B, Raghavan SC. Microhomology-mediated end joining is the principal mediator of double-strand break repair during mitochondrial DNA lesions. Mol Biol Cell 2015; 27:223-35. [PMID: 26609070 PMCID: PMC4713127 DOI: 10.1091/mbc.e15-05-0260] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 11/18/2015] [Indexed: 12/13/2022] Open
Abstract
Repair of double-strand breaks in mammalian mitochondria depends on microhomology-mediated end joining (MMEJ). Classical NHEJ is not detectable in mitochondria. DNA ligase III, but not ligase IV or ligase I, is involved in mitochondrial MMEJ. The protein machinery involved in miitochondrial MMEJ includes CtIP, FEN1, ligase III, MRE11, and PARP1. Mitochondrial DNA (mtDNA) deletions are associated with various mitochondrial disorders. The deletions identified in humans are flanked by short, directly repeated mitochondrial DNA sequences; however, the mechanism of such DNA rearrangements has yet to be elucidated. In contrast to nuclear DNA (nDNA), mtDNA is more exposed to oxidative damage, which may result in double-strand breaks (DSBs). Although DSB repair in nDNA is well studied, repair mechanisms in mitochondria are not characterized. In the present study, we investigate the mechanisms of DSB repair in mitochondria using in vitro and ex vivo assays. Whereas classical NHEJ (C-NHEJ) is undetectable, microhomology-mediated alternative NHEJ efficiently repairs DSBs in mitochondria. Of interest, robust microhomology-mediated end joining (MMEJ) was observed with DNA substrates bearing 5-, 8-, 10-, 13-, 16-, 19-, and 22-nt microhomology. Furthermore, MMEJ efficiency was enhanced with an increase in the length of homology. Western blotting, immunoprecipitation, and protein inhibition assays suggest the involvement of CtIP, FEN1, MRE11, and PARP1 in mitochondrial MMEJ. Knockdown studies, in conjunction with other experiments, demonstrated that DNA ligase III, but not ligase IV or ligase I, is primarily responsible for the final sealing of DSBs during mitochondrial MMEJ. These observations highlight the central role of MMEJ in maintenance of mammalian mitochondrial genome integrity and is likely relevant for deletions observed in many human mitochondrial disorders.
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Affiliation(s)
- Satish Kumar Tadi
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
| | - Robin Sebastian
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
| | - Sumedha Dahal
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
| | - Ravi K Babu
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
| | - Bibha Choudhary
- Institute of Bioinformatics and Applied Biotechnology, Bangalore 560 100, India
| | - Sathees C Raghavan
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
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10
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Montiel-Sosa JF, Herrero MD, Munoz MDL, Aguirre-Campa LE, Pérez-Ramírez G, García-Ramírez R, Ruiz-Pesini E, Montoya J. Phylogenetic analysis of mitochondrial DNA in a patient with Kearns-Sayre syndrome containing a novel 7629-bp deletion. ACTA ACUST UNITED AC 2013; 24:420-31. [PMID: 23391298 DOI: 10.3109/19401736.2012.760550] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mitochondrial DNA mutations have been associated with different illnesses in humans, such as Kearns-Sayre syndrome (KSS), which is related to deletions of different sizes and positions among patients. Here, we report a Mexican patient with typical features of KSS containing a novel deletion of 7629 bp in size with 85% heteroplasmy, which has not been previously reported. Sequence analysis revealed 3-bp perfect short direct repeats flanking the deletion region, in addition to 7-bp imperfect direct repeats within 9-10 bp. Furthermore, sequencing, alignment and phylogenetic analysis of the hypervariable region revealed that the patient may belong to a founder Native American haplogroup C4c.
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Affiliation(s)
- Jose Francisco Montiel-Sosa
- Department of Biochemistry and Molecular and Cellular Biology, Universidad de Zaragoza, CIBER de Enfermedades Raras, Zaragoza, Spain
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Abstract
Mutations that arise in mitochondrial DNA (mtDNA) may be sporadic, maternally inherited, or Mendelian in character and include mtDNA rearrangements such as deletions, inversions or duplications, point mutations, or copy number depletion. Primary mtDNA mutations occur sporadically or exhibit maternal inheritance and arise due in large part to the high mutation rate of mtDNA. mtDNA mutations may also occur because of defects in the biogenesis or maintenance of mtDNA, reflecting the contribution of nuclear-encoded genes to these processes, and in this case exhibit Mendelian inheritance. Whether maternally inherited, sporadic, or Mendelian, mtDNA mutations can exhibit a complex and broad spectrum of disease manifestations due to the central role mitochondria play in a variety of cellular functions. In addition, because there exist hundreds to thousands of copies of mtDNA in each cell, the proportion of mutant mtDNA molecules can have a profound effect on the cellular and clinical phenotype. This chapter reviews the classification of mtDNA mutations and the clinical features that determine the diagnosis of a primary mtDNA disorder.
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Affiliation(s)
- William J Craigen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
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12
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Lestienne PP. Priming DNA replication from triple helix oligonucleotides: possible threestranded DNA in DNA polymerases. Mol Biol Int 2011; 2011:562849. [PMID: 22229092 PMCID: PMC3200174 DOI: 10.4061/2011/562849] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 07/02/2011] [Indexed: 11/20/2022] Open
Abstract
Triplex associate with a duplex DNA presenting the same polypurine or polypyrimidine-rich sequence in an antiparallel orientation. So far, triplex forming oligonucleotides (TFOs) are known to inhibit transcription, replication, and to induce mutations. A new property of TFO is reviewed here upon analysis of DNA breakpoint yielding DNA rearrangements; the synthesized sequence of the first direct repeat displays a skewed polypurine- rich sequence. This synthesized sequence can bind the second homologous duplex sequence through the formation of a triple helix, which is able to prime further DNA replication. In these case, the d(G)-rich Triple Helix Primers (THP) bind the homologous strand in a parallel manner, possibly via a RecA-like mechanism. This novel property is shared by all tested DNA polymerases: phage, retrovirus, bacteria, and human. These features may account for illegitimate initiation of replication upon single-strand breakage and annealing to a homologous sequence where priming may occur. Our experiments suggest that DNA polymerases can bind three instead of two polynucleotide strands in their catalytic centre.
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Affiliation(s)
- Patrick P Lestienne
- U 1053 INSERM, Université Victor Segalen Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux, France
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Chen T, He J, Huang Y, Zhao W. The generation of mitochondrial DNA large-scale deletions in human cells. J Hum Genet 2011; 56:689-94. [DOI: 10.1038/jhg.2011.97] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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A Tunisian patient with Pearson syndrome harboring the 4.977 kb common deletion associated to two novel large-scale mitochondrial deletions. Biochem Biophys Res Commun 2011; 411:381-6. [DOI: 10.1016/j.bbrc.2011.06.154] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Accepted: 06/24/2011] [Indexed: 11/23/2022]
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Sadikovic B, Wang J, El-Hattab AW, Landsverk M, Douglas G, Brundage EK, Craigen WJ, Schmitt ES, Wong LJC. Sequence homology at the breakpoint and clinical phenotype of mitochondrial DNA deletion syndromes. PLoS One 2010; 5:e15687. [PMID: 21187929 PMCID: PMC3004954 DOI: 10.1371/journal.pone.0015687] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Accepted: 11/22/2010] [Indexed: 01/07/2023] Open
Abstract
Mitochondrial DNA (mtDNA) deletions are a common cause of mitochondrial disorders. Large mtDNA deletions can lead to a broad spectrum of clinical features with different age of onset, ranging from mild mitochondrial myopathies (MM), progressive external ophthalmoplegia (PEO), and Kearns-Sayre syndrome (KSS), to severe Pearson syndrome. The aim of this study is to investigate the molecular signatures surrounding the deletion breakpoints and their association with the clinical phenotype and age at onset. MtDNA deletions in 67 patients were characterized using array comparative genomic hybridization (aCGH) followed by PCR-sequencing of the deletion junctions. Sequence homology including both perfect and imperfect short repeats flanking the deletion regions were analyzed and correlated with clinical features and patients' age group. In all age groups, there was a significant increase in sequence homology flanking the deletion compared to mtDNA background. The youngest patient group (<6 years old) showed a diffused pattern of deletion distribution in size and locations, with a significantly lower sequence homology flanking the deletion, and the highest percentage of deletion mutant heteroplasmy. The older age groups showed rather discrete pattern of deletions with 44% of all patients over 6 years old carrying the most common 5 kb mtDNA deletion, which was found mostly in muscle specimens (22/41). Only 15% (3/20) of the young patients (<6 years old) carry the 5 kb common deletion, which is usually present in blood rather than muscle. This group of patients predominantly (16 out of 17) exhibit multisystem disorder and/or Pearson syndrome, while older patients had predominantly neuromuscular manifestations including KSS, PEO, and MM. In conclusion, sequence homology at the deletion flanking regions is a consistent feature of mtDNA deletions. Decreased levels of sequence homology and increased levels of deletion mutant heteroplasmy appear to correlate with earlier onset and more severe disease with multisystem involvement.
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Affiliation(s)
- Bekim Sadikovic
- Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
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Mkaouar-Rebai E, Chamkha I, Kammoun T, Chabchoub I, Aloulou H, Fendri N, Hachicha M, Fakhfakh F. A case of Kearns-Sayre syndrome with two novel deletions (9.768 and 7.253 kb) of the mtDNA associated with the common deletion in blood leukocytes, buccal mucosa and hair follicles. Mitochondrion 2010; 10:449-55. [PMID: 20388556 DOI: 10.1016/j.mito.2010.04.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Revised: 02/06/2010] [Accepted: 04/02/2010] [Indexed: 11/26/2022]
Abstract
Kearns-Sayre syndrome is a mitochondrial disorder characterized by the emergence before the age of 20 years of progressive external ophthalmoplegia, pigmentary retinopathy, with other heterogeneous clinical manifestations. Generally, mitochondrial DNA deletions were associated with KSS but the size and position of these deletions differ among patients. This study reported a Tunisian patient with typical features of KSS. Long-range PCR amplification of the mtDNA in different tissues from this patient showed multiple mitochondrial deletions: two novel 9.768 and 7.253 kb deletions spanning respectively nucleotides 6124-15,893 and 8572-15,826 associated with the common 4.977 kb deletion.
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Affiliation(s)
- Emna Mkaouar-Rebai
- Human Molecular Genetic Laboratory, Faculty of Medicine of Sfax, Tunisia.
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17
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Lestienne PP. Are there three polynucleotide strands in the catalytic centre of DNA polymerases? Biochimie 2009; 91:1523-30. [PMID: 19628017 DOI: 10.1016/j.biochi.2009.07.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Accepted: 07/15/2009] [Indexed: 10/20/2022]
Abstract
Mitochondrial DNA may undergo large-scale rearrangements, thus leading to diseases. The mechanisms of these rearrangements are still the matter of debates. Several lines of evidence indicate that breakpoints are characterized by direct repeats (DR), one of them being eliminated from the normal genome. Analysis of DR showed their skewed nucleotide content compatible with the formation of known triple helices. Here, I propose a novel mechanism involving the formation of triplex structures that result from the dissociation of the [synthesized repeat-DNA polymerase] complex. Upon binding to the homologous sequence, replication is initiated from the primer bound in a triple helix manner. This feature implies the initiation of replication on the double-stranded DNA from the triple helix primer. Hereby, I review evidences supporting this model. Indeed, all short d(G)-rich primers 10 nucleotides long can be elongated on double-stranded DNA by phage, bacterial, reverse transcriptases and eukaryotic DNA polymerases. Mismatches may be tolerated between the primer and its double-stranded binding site. In contrast to previous studies, evidences for the parallel binding of the triple helix to its homologous strand are provided. This suggest the displacement of the non-template strand by the triple helix primer upon binding within the DNA polymerase catalytic centre. Computer modelling indicates that the triple helix primer lies within the major groove of the double helix, with its 3' hydroxyl end nearby the catalytic amino acids. Taken together, I bring new concepts on DNA rearrangements, and novel features of triple helices and DNA polymerases that can bind three polynucleotide strands similar to RNA polymerases.
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Affiliation(s)
- Patrick P Lestienne
- U 889 INSERM, Université Victor Segalen Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux, France
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Dezfulian M, Shokrgozar MA, Sardari S, Parivar K, Javadi G. Can phages cause Alzheimer's disease? Med Hypotheses 2008; 71:651-6. [PMID: 18701222 DOI: 10.1016/j.mehy.2008.07.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 06/04/2008] [Accepted: 06/25/2008] [Indexed: 11/16/2022]
Abstract
UNLABELLED Alzheimer's disease (AD) is a progressive neurodegenerative disorder with progressive dementia. Multiple processes have been implicated in AD, notably including abnormal beta-amyloid production, tau hyperphosphorylation and neurofibrillary tangles (NFTs), synaptic pathology, oxidative stress, inflammation, protein processing or misfolding, calcium dyshomeostasis, aberrant reentry of neurons into the cell cycle, cholesterol synthesis, and effects of hormones or growth factors. The complexity of the disease, which affects numerous molecules, cells, and systems and impedes attempts to determine which alterations are specifically associated with early pathology. Chlamydia pneumoniae is an obligate intracellular bacterium. Infection with this organism has been suggested to be a risk factor for AD. C. pneumoniae has two phages phiCPAR39 and phage related to phiCPG1. HYPOTHESIS we propose that these two phages by entering into mitochondria of chlamydia's host cell can work as slow viruses and can initiate AD.
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Affiliation(s)
- Mehrouz Dezfulian
- Department of Biology, Islamic Azad University, Science and Research Branch, Hesarak, Pounak, Tehran, Iran.
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19
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Yamashita S, Nishino I, Nonaka I, Goto YI. Genotype and phenotype analyses in 136 patients with single large-scale mitochondrial DNA deletions. J Hum Genet 2008; 53:598. [PMID: 18414780 DOI: 10.1007/s10038-008-0289-8] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Accepted: 03/17/2008] [Indexed: 10/22/2022]
Abstract
We examined 136 patients with mitochondrial DNA (mtDNA) deletion. Clinical diagnoses included chronic progressive external ophthalmoplegia (94 patients); Kearns-Sayre syndrome (KSS; 33 patients); Pearson's marrow-pancreas syndrome (six patients); and Leigh syndrome, Reye-like syndrome, and mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (one patient). The length and location of deletion were highly variable. Only one patient had deletion within the so-called shorter arc between the two origins of mtDNA replication. The length of deletion and the number of deleted transfer ribonucleic acid (tRNAs) showed a significant relationship with age at onset. Furthermore, KSS patients had longer and larger numbers of deleted tRNAs, which could be risk factors for the systemic involvement of single mtDNA deletion diseases. We found 81 patterns of deletion. Direct repeats of 4 bp or longer flanking the breakpoints were found in 96 patients (70.5%) and those of 10 bp or longer in 49 patients (36.0%). We found two other common deletions besides the most common deletion (34 patients: 25.0%): the 2,310-bp deletion from nt 12113 to nt 14421 (11 patients: 8.0%) and the 7,664-bp deletion from nt 6330 to nt 13993 (ten patients: 7.3%). These deletions had incomplete direct repeats longer than 13 bp with one base mismatch.
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Affiliation(s)
- Shintaro Yamashita
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), 4-1-1 Ogawahigashi, Kodaira, Tokyo, 187-8502, Japan.,Department of Pediatrics and Adolescent Medicine, Juntendo University School of Medicine, Bunkyo-ku, Tokyo, Japan
| | - Ichizo Nishino
- Department of Neuromuscular Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), Kodaira, Tokyo, Japan
| | - Ikuya Nonaka
- Department of Neuromuscular Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), Kodaira, Tokyo, Japan
| | - Yu-Ichi Goto
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), 4-1-1 Ogawahigashi, Kodaira, Tokyo, 187-8502, Japan.
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20
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Mallabaeva DS, Ignatov AN, Sheiko IA, Isikov VP, Gelyuta VP, Boiko NG, Seryapin AA, Dorokhov DB. Use of RAPD and ITE molecular markers in studying the genetic structure of the Crimean population of T. boeoticum Boiss. CYTOL GENET+ 2007. [DOI: 10.3103/s0095452707030085] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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21
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Ji F, Pierre Z, Liu S, Hwang BJ, Hill HZ, Hubbard K, Steinberg M. Novel mitochondrial deletions in human epithelial cells irradiated with an FS20 ultraviolet light source in vitro. J Photochem Photobiol A Chem 2006. [DOI: 10.1016/j.jphotochem.2006.04.037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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22
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Harbottle A, Birch-Machin MA. Real-time PCR analysis of a 3895 bp mitochondrial DNA deletion in nonmelanoma skin cancer and its use as a quantitative marker for sunlight exposure in human skin. Br J Cancer 2006; 94:1887-93. [PMID: 16721366 PMCID: PMC2361359 DOI: 10.1038/sj.bjc.6603178] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Previous findings from our own laboratory have shown that the frequency of occurrence (i.e. the simple presence or absence) of the 3895 bp mitochondrial DNA deletion is increased with increasing sun exposure. The present study has significantly extended this work by developing, validating and then using a quantitative real-time PCR assay to investigate for the first time the actual level (as opposed to the frequency of occurrence) of the 3895 bp deletion in human skin from different sun-exposed body sites and tumours from nonmelanoma skin cancer patients. We investigated the 3895 bp deletion in 104 age-matched split human skin samples taken from various sun-exposed sites defined as usually exposed (n=60) and occasionally exposed (n=44) when outdoors. The results clearly show an increased level of the 3895 bp deletion with increasing sun exposure. Specifically, there was a significantly higher level of the deletion in the usually sun-exposed compared to the occasionally sun-exposed skin (P=0.0009 for dermis, P=0.008 for epidermis; two-tailed t-test). Our study has also extended previous findings by showing that the level of the 3895 bp deletion is significantly higher in the dermis compared with the epidermis both in the occasionally sun-exposed samples (P=0.0143) and in the usually sun-exposed skin. (P=0.0007).
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Affiliation(s)
- A Harbottle
- Dermatological Sciences, School of Clinical and Laboratory Sciences, University of Newcastle, Newcastle upon Tyne NE2 4HH, UK
| | - M A Birch-Machin
- Dermatological Sciences, School of Clinical and Laboratory Sciences, University of Newcastle, Newcastle upon Tyne NE2 4HH, UK
- E-mail:
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23
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Krishnan KJ, Birch-Machin MA. The incidence of both tandem duplications and the common deletion in mtDNA from three distinct categories of sun-exposed human skin and in prolonged culture of fibroblasts. J Invest Dermatol 2006; 126:408-15. [PMID: 16374450 DOI: 10.1038/sj.jid.5700099] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The use of mtDNA damage as a biomarker of cumulative sunlight exposure in human skin is a relatively new field of research. Previous investigations have simply compared the frequency of occurrence of the mtDNA common deletion (CD), and to a much lesser extent that of tandem duplications (TDs), to distinguish between sun-protected and sun-exposed skin. This approach is limited because non-melanoma skin cancer is predominantly formed on body sites that are "usually" sun-exposed as opposed to sites that are "occasionally" sun-exposed and as such they differ in their cumulative UV exposure. This study addresses this limitation by investigating the frequency of occurrence of the CD and TDs in 116 age-matched human skin samples taken from three different sun-exposed body sites. There was a greater frequency of the mtDNA damage in "usually" sun-exposed compared to "occasionally" sun-exposed body sites for both the CD and the TDs (P < 0.0001 and P = 0.058, respectively). In addition, we identified a 260 bp triplication of the mtDNA D-loop for the first time in skin. No evidence of the CD or TDs was observed in sun-protected (ie rarely exposed) skin (n = 20). Comparatively little is known about mtDNA damage in prolonged skin cell culture. We have furthered this work by studying the level of the CD and the frequency of the TDs during continued culture of human fibroblasts derived from skin samples taken from usually sun-exposed sites (n = 7 patients). The level of the CD decreases with culture, whereas the frequency of TDs can be maintained.
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Affiliation(s)
- Kim J Krishnan
- Dermatological Sciences, School of Clinical and Laboratory Sciences, Medical School, University of Newcastle, Newcastle upon Tyne, UK
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24
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Krishnan KJ, Harbottle A, Birch-Machin MA. The Use of a 3895 bp Mitochondrial DNA Deletion as a Marker for Sunlight Exposure in Human Skin. J Invest Dermatol 2004; 123:1020-4. [PMID: 15610508 DOI: 10.1111/j.0022-202x.2004.23457.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Previous work has examined the use of mitochondrial DNA (mtDNA) damage as a biomarker of cumulative sun exposure in human skin. These studies have simply compared mtDNA damage between sun-protected and sun exposed skin. This approach is limited because non-melanoma skin cancer (NMSC) is predominantly formed on body sites which are 'usually' sun exposed as opposed to sites which are 'occasionally' sun exposed and as such they differ in their cumulative ultraviolet (UV) exposure. This study addresses this limitation by investigating the frequency of occurrence of a rarely reported 3895 bp mtDNA deletion in 104 age-matched human skin samples taken from different sun-exposed body sites. There was a significant increase in the deletion frequency with increasing UV exposure (p<0.0001). Furthermore there was a significantly greater deletion frequency in 'usually' sun exposed compared with 'occasionally' sun-exposed body sites in both the dermis (p=0.0018) and epidermis (p<0.0001). Investigation of the 3895 bp deletion in the same NMSC samples used in a previous study of the 4977 bp common deletion, showed a greater frequency of the 3895 bp deletion (8/10 vs 4/10, respectively). Additionally, we have linked the 3895 bp deletion with the UVR component of sunlight by inducing the deletion in vitro with repetitive sub-lethal doses of a UVA+UVB light source.
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Affiliation(s)
- Kim J Krishnan
- Dermatological Sciences, University of Newcastle, Newcastle upon Tyne, UK
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25
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Nickander KK, Schmelzer JD, Low PA. Assessment of the "common" 4.8-kb mitochondrial DNA deletion and identification of several closely related deletions in the dorsal root ganglion of aging and streptozotocin rats. J Peripher Nerv Syst 2002; 7:96-103. [PMID: 12090301 DOI: 10.1046/j.1529-8027.2002.02012.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The identification of several mitochondrial DNA (mtDNA) deletions and the accumulation of the "common" 4.8-kb mitochondrial DNA deletion (mtDNA(4834)) with aging and experimental streptozotocin-induced diabetes (STZ) were studied in the rat dorsal root ganglion (DRG). Twenty-one mtDNA deletions, including mtDNA(4834), were identified in rat L4-L6 DRG mtDNA of 15-month-old Spraque-Dawley rats with 13 months of STZ and age-matched controls. These deletions were flanked by breakpoints that ranged from 16-bp direct repeats to no direct repeats. The sciatic nerve contained undetectable levels of mtDNA deletions. Levels of mtDNA(4834) in rat DRG mtDNA significantly accumulated with age at a rate much higher than those reported in the brain, yet were not statistically different in STZ. Southern blot analysis demonstrated no significant accumulation of the total amount of mtDNA deletions in STZ over age-matched controls. The accumulation of mtDNA(4834) has not been studied in rat peripheral nerve tissue. Our identification of several mtDNA deletions with and without direct repeats at their breakpoint support the hypothesis that deletions can occur by both the slip-replication model and random recombination. Although there is a significant increase in accumulation of mtDNA(4834) associated with aging, the lack of significant accumulations of mtDNA deletions in STZ over age-matched controls indicates that this type of mtDNA damage is likely not a major alteration in STZ, although the changes could be confined to a small population of neurons that undergo apoptosis between 8 and 15 months.
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Affiliation(s)
- Kim K Nickander
- Department of Neurology, Mayo Clinic and Foundation, Rochester, Minnesota, USA
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26
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Rocher C, Letellier T, Copeland WC, Lestienne P. Base composition at mtDNA boundaries suggests a DNA triple helix model for human mitochondrial DNA large-scale rearrangements. Mol Genet Metab 2002; 76:123-32. [PMID: 12083809 DOI: 10.1016/s1096-7192(02)00024-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Different mechanisms have been proposed to account for mitochondrial DNA (mtDNA) instability based on the presence of short homologous sequences (direct repeats, DR) at the potential boundaries of mtDNA rearrangements. Among them, slippage-mispairing of the replication complex during the asymmetric replication cycle of the mammalian mitochondrial DNA has been proposed to account for the preferential localization of deletions. This mechanism involves a transfer of the replication complex from the first neo-synthesized heavy (H) strand of the DR1, to the DR2, thus bypassing the intervening sequence and producing a deleted molecule. Nevertheless, the nature of the bonds between the DNA strands remains unknown as the forward sequence of DR2, beyond the replication complex, stays double-stranded. Here, we have analyzed the base composition of the DR at the boundaries of mtDNA deletions and duplications and found a skewed pyrimidine content of about 75% in the light-strand DNA template. This suggests the possible building of a DNA triple helix between the G-rich neo-synthesized DR1 and the base-paired homologous G.C-rich DR2. In vitro experiments with the purified human DNA polymerase gamma subunits enabled us to show that the third DNA strand may be used as a primer for DNA replication, using a template with the direct repeat forming a hairpin, with which the primer could initiate DNA replication. These data suggest a novel molecular basis for mitochondrial DNA rearrangements through the distributive nature of the DNA polymerase gamma, at the level of the direct repeats. A general model accounting for large-scale mitochondrial DNA deletion and duplication is proposed. These experiments extend to a DNA polymerase from an eucaryote source the use of a DNA triple helix strand as a primer, like other DNA polymerases from phage and bacterial origins.
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Affiliation(s)
- Christophe Rocher
- EMI 99.29 INSERM, Génétique Mitochondriale, Université Victor Segalen Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France
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27
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Abstract
The mitochondrial DNA encodes only a few gene products compared to the nuclear DNA. These products, however, play a decisive role in determining cell function. Should this DNA mutate spontaneously or be damaged by free radicals the functionality of the gene products will be compromised. A number of mitochondrial genetic diseases have been identified. Some of these are quite serious and involve the central nervous system as well as muscle, heart, liver and kidney. Aging has been characterized by a gradual increase in base deletions in this DNA. This increase in deletion mutation has been suggested to be the cumulative result of exposure to free radicals.
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Affiliation(s)
- C D Berdanier
- Department of Foods and Nutrition, University of Georgia, 30602, Athens, GA, USA.
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28
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Michel U, Stringaris AK, Nau R, Rieckmann P. Differential expression of sense and antisense transcripts of the mitochondrial DNA region coding for ATPase 6 in fetal and adult porcine brain: identification of novel unusually assembled mitochondrial RNAs. Biochem Biophys Res Commun 2000; 271:170-80. [PMID: 10777698 DOI: 10.1006/bbrc.2000.2595] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The mammalian mitochondrial genome is a double-stranded circular DNA molecule, which is transcribed from both strands as polycistronic RNAs, which are further processed to yield the mature polyadenylated mRNAs, rRNAs and tRNAs. We compared the gene expression patterns of foetal and adult porcine brains and identified a sequence tag from the ATPase 6 region of the mitochondrial genome which, in adult brain, was more abundant in the sense (H-strand) form, but, in foetal brain, more abundant in the antisense form (L-strand). By means of solution hybridisation/S1 nuclease protection assay, Northern blotting, and PCR based techniques, we demonstrated that the ATPase 6 region of the porcine mitochondrial genome is transcribed as co-existing, stable sense and antisense RNAs. Furthermore, we identified sense and antisense transcripts from this region consisting of inversely assembled fragments joined together at a direct repeat of 7 nucleotides. Our results suggest that transcription and post-transcriptional processing of mitochondrial RNAs are much more complex than presently thought.
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Affiliation(s)
- U Michel
- Laboratory of Neurobiology, Department of Neurology, University of Göttingen, Robert-Koch-Strasse 40, Göttingen, 37075, Germany
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29
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Kotake K, Nonami T, Kurokawa T, Nakao A, Murakami T, Shimomura Y. Human livers with cirrhosis and hepatocellular carcinoma have less mitochondrial DNA deletion than normal human livers. Life Sci 1999; 64:1785-91. [PMID: 10353633 DOI: 10.1016/s0024-3205(99)00117-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
We measured the populations of mutated mitochondrial DNAs with the 7,436 bp or the 4,977 bp deletion from apparently normal human liver and human livers with chronic hepatitis, cirrhosis, and hepatocellular carcinoma. The amount of the mutated mitochondrial DNA was at the same level between normal and chronically hepatitic livers but was significantly lower in human livers with cirrhosis and hepatocellular carcinoma, especially the latter, suggesting that the mutated mitochondrial DNAs may be decreased with the progress of liver disease from chronic hepatitis to cirrhosis and hepatocellular carcinoma. This phenomenon is opposite to that occuring in the ageing process.
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Affiliation(s)
- K Kotake
- Department of Surgery II, Nagoya University, School of Medicine, Japan
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30
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Abstract
Hearing impairment is a common disorder, largely genetic in origin, and showing classical features of a heterogeneous genetic disease. Up to 100 independently acting nuclear genes are involved in the disorder, of which around 30 have been mapped, but only a handful identified. Mutations in mitochondrial DNA also play a significant role in both syndromic and nonsyndromic sensorineural hearing impairment. Environmental agents such as aminoglycoside antibiotics and as yet unidentified nuclear genes interact with mitochondrial mutations in the expression of auditory phenotypes. The spectrum of different mitochondrial mutations associated with hearing impairment, taken together with mechanistic studies at the molecular level, suggests that the pathogenic process involves the accumulation of abnormal translation products inside mitochondria, in sensitive cells of the auditory system. This leads to a prediction of the involvement of a novel class of nuclear genes in hearing impairment, namely those with roles in 'mitochondrial protein quality control'.
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Affiliation(s)
- H T Jacobs
- Institute of Medical Technology, University of Tampere, Finland.
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31
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32
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Marzuki S, Berkovic SF, Saifuddin Noer A, Kapsa RM, Kalnins RM, Byrne E, Sasmono T, Sudoyo H. Developmental genetics of deleted mtDNA in mitochondrial oculomyopathy. J Neurol Sci 1997; 145:155-62. [PMID: 9094043 DOI: 10.1016/s0022-510x(96)00241-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Heteroplasmic populations of mtDNA, consisting of normal mtDNA and mtDNA with large deletions, are found in the skeletal muscle and other tissues of certain patients with mitochondrial respiratory chain deficiencies, particularly in those with the CPEO (chronic progressive external ophthalmoplegia) phenotype. To study the developmental genetics of this mitochondrial disorder, the distribution of the deleted mtDNA in a wide range of tissues of different embryonic origins (total 34 samples from 27 tissues obtained at autopsy) was investigated in a patient with the CPEO syndrome. Three species of partially deleted mtDNA were observed, with deletions of 2.3 kb, 5.0 kb and 6.4 kb. Their tissue distribution suggests that the mtDNA deletions have occurred very early during embryonic development, prior to the differentiation events that lead to the formation of the three primary embryonic germ layers, and that the partially deleted mtDNA species were segregated during development mainly to the skeletal muscle and to tissues of the central nervous system.
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Affiliation(s)
- S Marzuki
- Eijkman Institute for Molecular Biology, Jakarta, Indonesia
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33
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Abstract
Age-associated alterations of the mitochondrial genome occur in several different species; however, their physiological relevance remains unclear. The age-associated changes of mitochondrial DNA (mtDNA) include nucleotide point mutations and modifications, as well as deletions. In this review, we summarize the current literature on age-associated mtDNA mutations and deletions and comment on their abundance. A clear need exists for a more thorough evaluation of the total damage to the mitochondrial genome that accumulates in aged tissues.
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Affiliation(s)
- C M Lee
- Department of Animal Health and Biomedical Sciences, University of Wisconsin, Madison 53706, USA
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34
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Moslemi AR, Melberg A, Holme E, Oldfors A. Clonal expansion of mitochondrial DNA with multiple deletions in autosomal dominant progressive external ophthalmoplegia. Ann Neurol 1996; 40:707-13. [PMID: 8957011 DOI: 10.1002/ana.410400506] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Sporadic progressive external ophthalmoplegia and Kearns-Sayre syndrome are usually associated with single large-scale mitochondrial DNA deletions in muscle. In progressive external ophthalmoplegia with autosomal dominant inheritance, multiple mitochondrial DNA deletions have been reported. We studied several members of a Swedish family with autosomal dominant progressive external ophthalmoplegia and multiple mitochondrial DNA deletions by polymerase chain reaction analysis of single muscle fibers and by in situ hybridization, combined with enzyme histochemical analysis. Muscle fiber segments with deficiency of cytochrome c oxidase, which is partially encoded by mitochondrial DNA, had accumulated mitochondrial DNA with deletions and showed reduced levels of wild-type mitochondrial DNA. The deletions varied between individual muscle fibers. There was one predominant deletion in each cytochrome c oxidase-deficient muscle fiber segment. Sequencing of the deletion breakpoints showed that most but not all of the deletions were flanked by direct repeats. Young, clinically affected individuals of this family without limb muscle symptoms did not show mitochondrial DNA deletions or cytochrome c oxidase-deficient muscle fibers. Our results indicate that a nuclear factor predisposes to the development of somatic multiple mitochondrial DNA deletions. Mitochondrial DNA with multiple different deletions shows clonal expansion, which leads to mitochondrial myopathy with ragged-red fibers and muscle weakness.
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MESH Headings
- Adolescent
- Adult
- Base Sequence
- Blotting, Southern
- Cloning, Molecular
- Cytochrome-c Oxidase Deficiency
- DNA Probes
- DNA, Complementary
- DNA, Mitochondrial/biosynthesis
- DNA, Mitochondrial/genetics
- DNA, Mitochondrial/isolation & purification
- Female
- Genes, Dominant
- Humans
- Male
- Middle Aged
- Molecular Sequence Data
- Muscle Fibers, Skeletal/enzymology
- Muscle Fibers, Skeletal/pathology
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Ophthalmoplegia, Chronic Progressive External/genetics
- Ophthalmoplegia, Chronic Progressive External/pathology
- Pedigree
- Polymerase Chain Reaction
- Sequence Deletion
- Sweden
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Affiliation(s)
- A R Moslemi
- Department of Pathology, Sahlgrenska University Hospital, Göteborg, Sweden
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35
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Hou JH, Wei YH. The unusual structures of the hot-regions flanking large-scale deletions in human mitochondrial DNA. Biochem J 1996; 318 ( Pt 3):1065-70. [PMID: 8836157 PMCID: PMC1217724 DOI: 10.1042/bj3181065] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Large-scale deletions of mitochondrial DNA (mtDNA) are common events that have been found to occur in human ageing and in patients with mitochondrial myopathies. The mechanisms by which these deletions occur remain unclear, but several mechanisms have been proposed, such as slipped-mispairing, illegitimate recombination, and oxidative reactions elicited by free radicals. In addition, the DNA topological stress and local DNA structures have been suggested as the important factors in eliciting the recombinational events. Upon examination of 128 breakpoints of human mtDNA deletions that have been published in the past 8 years, we found that these large-scale deletions often occur at some 'hot-regions'. We thus hypothesized that there exist unusual structures in these regions of human mtDNA that are important for eliciting the deletions. To test this hypothesis, we used PCR techniques to amplify the sequences of the so-called hot-regions and analysed the PCR products by two-dimensional gel electrophoresis. We found that the sequences of nucleotide position (np) 5221-5988, np 6928-7493, np 7901-8732 and np 15327-16228 exhibited retarded mobilities like bent DNA structures; np 5989-6750, np 13282-13653 and np 13282-14850 showed increased mobilities like anti-bent DNA structures. Moreover, except for the sequences of np 1175-1766 found in 12 S and 16 S rRNA genes exhibiting abnormal mobility like bent DNA structures, we did not observe significant mobility abnormalities in the np 499-5545 region where deletions rarely occurred. We thus conclude that these hot-regions assume some kinds of unusual DNA structures, which may render these regions more sensitive to the attack of free radicals or serve as recognition motifs for certain recombination machinery that is involved in the large-scale deletions of human mtDNA.
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Affiliation(s)
- J H Hou
- Department of Biochemistry, National Yang-Ming University, Taipei, Taiwan, Republic of China
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36
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Van Tuyle GC, Gudikote JP, Hurt VR, Miller BB, Moore CA. Multiple, large deletions in rat mitochondrial DNA: evidence for a major hot spot. Mutat Res 1996; 349:95-107. [PMID: 8569796 DOI: 10.1016/0027-5107(95)00165-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
This study identified 33 different deletions in mitochondrial DNA from four aging Fischer-344 rat brains and from a cultured rat lymphoma cell line (Nb2 cells). The deletions were located in the longer arc between the heavy and light strand origins of replication. PCR products that spanned across the deleted regions were sequenced, and deletions ranging between 6548 bp and 9977 bp in length were identified. Short direct repeats of < or = 8 bp were present at the end points of all but one of the deletions. The remaining deletion contained, instead, a near-perfect direct repeat (9/10 bp) within two base pairs of its end points. In 24 of the deletions, a sequence equivalent to one member of the paired direct repeats was lost with the deleted segment. In the remaining nine, either more or less of the base pairs of a single repeat were lost. Twelve of the 33 different deletions terminated on one side at a common locus (major hot spot) of 5 bp in length, located at the 5' end of the tRNAThr gene. The opposite ends of these 12 deletions were at different sites. The hot spot was located in a region of the mtDNA with strong potential for secondary structure and was flanked by a pair of AT-rich sequences. The utilization of the hot spot as an end point for deletions appeared to be widespread in that it was represented in 1/3-1/2 of the deletions characterized in each of the five mtDNA sources examined. In addition, several minor hot spots, where one end of two or three different deletions coincided, were also identified.
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Affiliation(s)
- G C Van Tuyle
- Department of Biochemistry and Molecular Biophysics, Virginia Commonwealth University, Richmond 23298, USA.
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37
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Eimon PM, Chung SS, Lee CM, Weindruch R, Aiken JM. Age-associated mitochondrial DNA deletions in mouse skeletal muscle: comparison of different regions of the mitochondrial genome. DEVELOPMENTAL GENETICS 1996; 18:107-13. [PMID: 8934872 DOI: 10.1002/(sici)1520-6408(1996)18:2<107::aid-dvg3>3.0.co;2-d] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The abundance of mitochondrial DNA (mtDNA) deletions has been shown to increase with age in a number of species and may contribute to the aging process. Estimating the total mtDNA deletion load of an individual is essential in evaluating the potential physiological impact. In this study, we compared three 5-kb regions of the mitochondrial genome: one in the major arc, one in the minor arc, and a third containing the light strand origin of replication. Through PCR analysis of mouse skeletal muscle, we have determined that not all regions produce equal numbers of age-associated deletions. There are, on average, twofold more detectable deletions in the major arc region than in the minor arc region. Deletions that result in the loss of the light strand origin of replication are rarely detected. Furthermore, the mechanism of deletion formation seems to be similar in both the major and minor arcs, with direct repeats playing an important, although not essential, role.
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Affiliation(s)
- P M Eimon
- Department of Animal Health and Biomedical Sciences, University of Wisconsin, Madison 53706, USA
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38
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Tanhauser SM, Laipis PJ. Multiple deletions are detectable in mitochondrial DNA of aging mice. J Biol Chem 1995; 270:24769-75. [PMID: 7559594 DOI: 10.1074/jbc.270.42.24769] [Citation(s) in RCA: 119] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Mutational damage to human mitochondrial DNA (mtDNA) can cause disorders in oxidative phosphorylation; speculation that such damage is involved in degenerative diseases and aging is common. We have detected deletions in mouse mtDNA which resemble those found in elderly humans or patients with certain mtDNA disorders. Five different mtDNA deletions, predicted from the positions of short, direct DNA repeats, were present in aged, but not young, mice. Deleted regions were surrounded by either exact or inexact repeats and occurred in both the major and minor regions of the mtDNA genome. The abundance of a particular deletion was generally related to the thermodynamic stability of the bounding repeat sequence. Deletions in aged mice were present at low levels (less than 0.01% of total mtDNA). However, in contrast to results from aged humans, deletions were more abundant in liver than in brain, heart, or skeletal muscle. These results make it possible to predict the location and relative abundance of deletions in any sequenced mtDNA, including inbred mouse strains differing in inherent natural lifespan. The inbred mouse model will allow a critical examination of the relationship between the presence and abundance of mtDNA deletions and the aging process.
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Affiliation(s)
- S M Tanhauser
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville 32610, USA
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39
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Vázquez-Acevedo M, Coria R, González-Astiazarán A, Medina-Crespo V, Ridaura-Sanz C, González-Halphen D. Characterization of a 5025 base pair mitochondrial DNA deletion in Kearns-Sayre syndrome. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1271:363-8. [PMID: 7605803 DOI: 10.1016/0925-4439(95)00062-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We characterized a mitochondrial DNA deletion in a patient with Kearns-Sayre syndrome. Southern blot hybridization showed that 86 to 93% of the mitochondrial genome harbored a 5.0 kb deletion. The percentage of affected genomes is higher than in previously described cases. Direct sequencing of the breakpoint region revealed that the deletion extended 5025 bp from nt 10,050 in the tRNA Gly gene to nt 15,076 in the cytochrome b gene, thus 30% of the total mitochondrial genome was lost by this deletion. A pair of extremely short mirror sequences flanking the mitochondrial DNA breakpoints were identified. These flanking sequences differ from previously published consensus 'hot-spots', known to give rise to deletions in human mitochondrial DNA.
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Affiliation(s)
- M Vázquez-Acevedo
- Departamento de Bioenergética, Universidad Nacional Autónoma de México, Mexico City
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40
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Lestienne P, Bataillé N, Lucas-Héron B. Role of the mitochondrial DNA and calmitine in myopathies. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1271:159-63. [PMID: 7599203 DOI: 10.1016/0925-4439(95)00023-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We present data on mitochondrial DNA deletions and mitochondrial diseases. The mechanism of their occurrence is discussed on the basis of deletion breakpoints and particularly with the slippage mispairing hypothesis. As the correlation between the genotypes and the phenotypes is not always straightforward, a classification of mitochondrial diseases is suggested according to the genotype (deletions, depletions and duplications, mutations affecting structural genes or tRNA genes) rather than the phenotype. The effect of mitochondrial DNA alterations on the expression of nuclear encoded proteins is presented, and the nucleus can be found to respond differently but in a coordinate way according to the kind of mitochondrial DNA alteration. The search for a nuclear gene affecting the expression of Leber's disease could not show any correlation between the alleles of TAP2 (transporter antigen peptide) and the expression of the disease. Finally, we present new data on another class of myopathies, namely Duchenne muscular dystrophy (DMD), where mitochondria could play an unexpected role in the metabolism of calcium. In some patients with DMD a mitochondrial calcium binding protein that is mainly located in the mitochondrial matrix and which is named 'calmitine' was found to disappear. We have thus cloned its cDNA and found that it was identical with to calsequestrine which is a high-capacity but low-affinity Ca2+ binding protein from the sarcoplasmic reticulum.
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Affiliation(s)
- P Lestienne
- U 298 INSERM, Institut National de la Santé et de la Recherche Médicale, Centre Hospitalier Regional, Angers, France
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41
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Degoul F, Diry M, Rodriguez D, Robain O, Francois D, Ponsot G, Marsac C, Desguerre I. Clinical, biochemical, and molecular analysis of a maternally inherited case of Leigh syndrome (MILS) associated with the mtDNA T8993G point mutation. J Inherit Metab Dis 1995; 18:682-8. [PMID: 8750605 DOI: 10.1007/bf02436757] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We report a new case of Leigh disease (subacute necrotizing encephalomyelopathy) in a girl with mitochondrial DNA (mtDNA) mutation in the ATPase6 gene at nucleotide position 8993. Sequence analysis of mtDNA revealed a T-to-G transversion at nucleotide position 8993 in the ATPase6 gene. Southern blot restriction analysis of patient muscle mtDNA showed only a mutant pattern for the mutation 8993. Molecular analysis of seven subjects from the family showed that except for the father they all carried the 8993 mtDNA mutation in all studied tissues, with high percentages in the two symptomatic children and even in one asymptomatic boy.
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Affiliation(s)
- F Degoul
- INSERM U75, Faculte de medecine Necker-Enfants Malades, Universite Paris V, France
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42
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Lee CM, Eimon P, Weindruch R, Aiken JM. Direct repeat sequences are not required at the breakpoints of age-associated mitochondrial DNA deletions in rhesus monkeys. Mech Ageing Dev 1994; 75:69-79. [PMID: 9128755 DOI: 10.1016/0047-6374(94)90029-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The large majority of mitochondrial DNA (mtDNA) deletions analyzed from mitochondrial myopathies and aging humans have been found to be flanked by direct repeats, a finding which has led to the slip-replication hypothesis of deletion formation. In this study, we have characterized 13 mtDNA deletion breakpoints from skeletal muscle harvested from 9- to 27-year-old rhesus monkeys. Seven of the deletions, five of which were unique to a particular animal, did not have direct repeats at the deletion breakpoints. In contrast, two of the three deletions common to several animals had direct repeats flanking the breakpoints. It appears, therefore, that at least two different mechanisms exist by which mtDNA deletions are formed during aging, one requiring and one independent of flanking direct repeats. Furthermore, the species in which mtDNA deletions are detected may determine which mechanism predominates.
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Affiliation(s)
- C M Lee
- Department of Animal Health and Biomedical Sciences, University of Wisconsin-Madison 53706, USA
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43
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Chung SS, Weindruch R, Schwarze SR, McKenzie DI, Aiken JM. Multiple age-associated mitochondrial DNA deletions in skeletal muscle of mice. AGING (MILAN, ITALY) 1994; 6:193-200. [PMID: 7993927 DOI: 10.1007/bf03324239] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Multiple mitochondrial DNA (mtDNA) deletions have been associated with aging in humans and monkeys. Since the inbred mouse strain, C57BL/6, has been extensively studied gerontologically, we sought to investigate its utility as a model for examining the importance of mtDNA deletions in aging. Using the polymerase chain reaction (PCR), we analyzed hind limb skeletal muscle from mice of three age groups (5, 16 and 25 months) for the presence of age-associated mtDNA deletions. We observed multiple mtDNA deletions in all three age groups. Further, the number of deletions detected per mouse increased greatly with advancing age.
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Affiliation(s)
- S S Chung
- Department of Animal Health and Biomedical Sciences, University of Wisconsin-Madison 53706
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44
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Stanton DJ, Daehler LL, Moritz CC, Brown WM. Sequences with the potential to form stem-and-loop structures are associated with coding-region duplications in animal mitochondrial DNA. Genetics 1994; 137:233-41. [PMID: 8056313 PMCID: PMC1205940 DOI: 10.1093/genetics/137.1.233] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Tandem duplications of gene-encoding regions occur in the mitochondrial DNA (mt DNA) of some individuals belonging to several species of whiptail lizards (genus Cnemidophorus). All or part of the duplicated regions of the mtDNAs from five different species were sequenced. In all, the duplication endpoints were within or immediately adjacent to sequences in tRNA, rRNA or protein genes that are capable of forming energetically stable stem-and-loop structures. In two of these mtDNAs, the duplication endpoints were also associated with a direct sequence repeat of 13 bp. The consistent association of stem-and-loop structures with duplication endpoints suggests that these structures may play a role in the duplication process. These data, combined with the absence of direct or palindromic repeats at three of the pairs of duplication endpoints, also suggest the existence of a mechanism for generating de novo duplications that is qualitatively different from those previously modeled.
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Affiliation(s)
- D J Stanton
- Department of Biology and Museum of Zoology, University of Michigan, Ann Arbor 48109-1048
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Baumer A, Zhang C, Linnane AW, Nagley P. Age-related human mtDNA deletions: a heterogeneous set of deletions arising at a single pair of directly repeated sequences. Am J Hum Genet 1994; 54:618-30. [PMID: 8128959 PMCID: PMC1918099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Deletions in mtDNA accumulate during the human aging process, arising from either intramolecular illegitimate recombination or strand slippage during replication, which results in subgenomic mtDNA molecules. We identify here two classes of mtDNA deletions--class A deletions, which are homogeneous at the breakpoints, with all subgenomic molecules therefore being identical in size, and class B deletions, which arise from a less stringent process that gives rise to heterogeneity at the breakpoints, with the subgenomic molecules being of slightly different sizes. A novel approach is described that offers a global overview of the populations of different deletions in individual tissues. It is based on PCR cycle-sequencing reactions that are carried out directly on mtDNA segments, amplified by PCR from total cellular DNA. The results show a clear size homogeneity of the subgenomic mtDNA molecules representative of class A, which carry a commonly detected 4,977-bp deletion occurring at a pair of 13-bp directly repeated sequences. In this case, precisely one copy of the repeat is retained in the subgenomic molecules. We then describe a class B situation comprising a family of at least nine closely related 8.04-kb deletions involving the same pair of 5-bp direct repeats. In this situation, the breakpoints differ at the base-pair level (8,037-8,048-bp deletions); the subgenomic molecules retain > 1 copy, 1 copy, or < 1 copy of the 5-bp repeat. In different tissues from either the same individual or among different individuals, there is a widely variable occurrence of particular deletions in the subgenomic mtDNA population within this class B set. Class B deletions offer a new approach for studying the accumulation of mtDNA deletions, thereby providing insight into the independent somatic origin of mutated mtDNA molecules, both in aging and in mitochondrial diseases. We also report a convenient method for ascertaining whether a given PCR product results from the amplification of a subgenomic mtDNA template, on the basis of the selective degradation of full-length mtDNA molecules prior to PCR.
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Affiliation(s)
- A Baumer
- Department of Biochemistry, Monash University, Clayton, Victoria, Australia
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46
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Abstract
We review the main features of human mitochondrial function and structure, and in particular mitochondrial transcription, translation, and replication cycles. Furthermore, some pecularities such as mitochondria's high polymorphism, the existence of mitochondrial pseudogenes, and the various considerations to take into account when studying mitochondrial diseases will also be mentioned. Mitochondrial syndromes mostly affecting the nervous system have, during the past few years, been associated with mitochondrial DNA (mt DNA) alterations such as deletions, duplications, mutations and depletions. We suggest a possible classification of mitochondrial diseases according to the kind of mt DNA mutations: structural mitochondrial gene mutation as in LHON (Leber's Hereditary Optic Neuropathy) and NARP (Neurogenic muscle weakness, Ataxia and Retinitis Pigmentosa) as well as some cases of Leigh's syndrome; transfer RNA and ribosomal RNA mitochondrial gene mutation as in MELAS (Mitochondrial Encephalomyopathy, Lactic Acidosis and Strokelike Episodes) or MERRF (Myoclonic Epilepsy with Ragged Red Fibers) or deafness with aminoglycoside; structural with transfer RNA mitochondrial gene mutations as observed in large-scale deletions or duplications in Kearns-Sayre syndrome, Pearson's syndrome, diabetes mellitus with deafness, and CPEO (Chronic Progressive External Ophtalmoplegia). Depletions of the mt DNA may also be classified in this category. Even though mutations are generally maternally inherited, most of the deletions are sporadic. However, multiple deletions or depletions may be transmitted in a mendelan trait which suggests that nuclear gene products play a primary role in these processes. The relationship between a mutation and a particular phenotype is far from being fully understood. Gene dosage and energic threshold, which are tissue-specific, appear to be the best indicators. However, the recessive or dominant behavior of both the wild type or the mutated genome appears to play a significant role, which can be verified with in vitro studies.
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47
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Lawen A, Martinus RD, McMullen GL, Nagley P, Vaillant F, Wolvetang EJ, Linnane AW. The universality of bioenergetic disease: the role of mitochondrial mutation and the putative inter-relationship between mitochondria and plasma membrane NADH oxidoreductase. Mol Aspects Med 1994; 15 Suppl:s13-27. [PMID: 7752823 DOI: 10.1016/0098-2997(94)90009-4] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- A Lawen
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
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48
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Nørby S, Lestienne P, Nelson I, Nielsen IM, Schmalbruch H, Sjö O, Warburg M. Juvenile Kearns-Sayre syndrome initially misdiagnosed as a psychosomatic disorder. J Med Genet 1994; 31:45-50. [PMID: 8151637 PMCID: PMC1049598 DOI: 10.1136/jmg.31.1.45] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We have investigated a 15 year old girl with progressive external ophthalmoplegia, including bilateral ptosis and retinal rod and cone cell dysfunction with atypical retinal pigmentation, complicated by cerebellar ataxia, partial cardiac conduction block, and diabetes mellitus. In infancy she had a severe crisis of bone marrow depression, and as a child she suffered from hypersensitivity to light, increasing fatigue, and vertigo, signs that were initially though to be psychosomatic. Histological examination showed mitochondrial myopathy, and subsequent mitochondrial DNA (mtDNA) analysis showed a deletion of approximately 5500 base pairs in 35 to 40% of her muscle mtDNA. We therefore conclude that this patient has developed the Kearns-Sayre syndrome after a Pearson syndrome-like crisis in her first year of life.
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Affiliation(s)
- S Nørby
- Institute of Forensic Genetics, University of Copenhagen, Denmark
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49
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Nelson I, Gerasimov S, Marsac C, Lestienne P, Boursot P. Sequence analysis of a deleted mitochondrial DNA molecule in heteroplasmic mice. Mamm Genome 1993; 4:680-3. [PMID: 8281018 DOI: 10.1007/bf00360907] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- I Nelson
- INSERM U75, CHU, Necker-Enfants Malades, Paris, France
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50
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Madsen CS, Ghivizzani SC, Hauswirth WW. In vivo and in vitro evidence for slipped mispairing in mammalian mitochondria. Proc Natl Acad Sci U S A 1993; 90:7671-5. [PMID: 8356068 PMCID: PMC47204 DOI: 10.1073/pnas.90.16.7671] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Slipped mispairing between repeated sequences during DNA replication is an important mutagenic event. It is one of several suggested mechanisms thought to be responsible for generating polymorphic regions and large-scale deletions found in mammalian mitochondrial DNA. In the porcine mitochondrial genome, a domain carrying a 10-bp tandemly repeated sequence displays a unique in vivo pattern of repeat copy number polymorphs. Upon passage in Escherichia coli, a recombinant plasmid containing this domain also displays a unique polymorphic pattern that is different from that seen in the animal. To test the hypothesis that these polymorphisms were slippage induced and that the different polymorphic patterns reflected differences in modes of replication, we performed a series of in vitro primer extension reactions. By utilizing either single- or double-stranded templates containing the repeat domain we were able to correlate in vitro generated repeat polymorphism patterns with those seen in the mitochondria or the bacteria, respectively, thus providing experimental evidence that slippage replication is responsible for a major class of mammalian mutations.
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Affiliation(s)
- C S Madsen
- Department of Immunology and Medical Microbiology, University of Florida, Gainesville 32610
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