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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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Tábara LC, Burr SP, Frison M, Chowdhury SR, Paupe V, Nie Y, Johnson M, Villar-Azpillaga J, Viegas F, Segawa M, Anand H, Petkevicius K, Chinnery PF, Prudent J. MTFP1 controls mitochondrial fusion to regulate inner membrane quality control and maintain mtDNA levels. Cell 2024:S0092-8674(24)00526-9. [PMID: 38851188 DOI: 10.1016/j.cell.2024.05.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Revised: 03/19/2024] [Accepted: 05/09/2024] [Indexed: 06/10/2024]
Abstract
Mitochondrial dynamics play a critical role in cell fate decisions and in controlling mtDNA levels and distribution. However, the molecular mechanisms linking mitochondrial membrane remodeling and quality control to mtDNA copy number (CN) regulation remain elusive. Here, we demonstrate that the inner mitochondrial membrane (IMM) protein mitochondrial fission process 1 (MTFP1) negatively regulates IMM fusion. Moreover, manipulation of mitochondrial fusion through the regulation of MTFP1 levels results in mtDNA CN modulation. Mechanistically, we found that MTFP1 inhibits mitochondrial fusion to isolate and exclude damaged IMM subdomains from the rest of the network. Subsequently, peripheral fission ensures their segregation into small MTFP1-enriched mitochondria (SMEM) that are targeted for degradation in an autophagic-dependent manner. Remarkably, MTFP1-dependent IMM quality control is essential for basal nucleoid recycling and therefore to maintain adequate mtDNA levels within the cell.
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Affiliation(s)
- Luis Carlos Tábara
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK.
| | - Stephen P Burr
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK; Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Michele Frison
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK; Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Suvagata R Chowdhury
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Vincent Paupe
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Yu Nie
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK; Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Mark Johnson
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Jara Villar-Azpillaga
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Filipa Viegas
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Mayuko Segawa
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Hanish Anand
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Kasparas Petkevicius
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Patrick F Chinnery
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK; Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Julien Prudent
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK.
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3
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Yu C, Asadian S, Tigano M. Molecular and cellular consequences of mitochondrial DNA double-stranded breaks. Hum Mol Genet 2024; 33:R12-R18. [PMID: 38779775 PMCID: PMC11112379 DOI: 10.1093/hmg/ddae048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 03/06/2024] [Accepted: 03/08/2024] [Indexed: 05/25/2024] Open
Abstract
Mitochondria are subcellular organelles essential for life. Beyond their role in producing energy, mitochondria govern various physiological mechanisms, encompassing energy generation, metabolic processes, apoptotic events, and immune responses. Mitochondria also contain genetic material that is susceptible to various forms of damage. Mitochondrial double-stranded breaks (DSB) are toxic lesions that the nucleus repairs promptly. Nevertheless, the significance of DSB repair in mammalian mitochondria is controversial. This review presents an updated view of the available research on the consequences of mitochondrial DNA DSB from the molecular to the cellular level. We discuss the crucial function of mitochondrial DNA damage in regulating processes such as senescence, integrated stress response, and innate immunity. Lastly, we discuss the potential role of mitochondrial DNA DSB in mediating the cellular consequences of ionizing radiations, the standard of care in treating solid tumors.
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Affiliation(s)
- Chenxiao Yu
- Department of Pathology and Genomic Medicine, Thomas Jefferson University, 1020 Locust Street, Philadelphia 19107, United States
- Department of Radiotherapy and Oncology, The Second Affiliated Hospital of Soochow University, 199 Renai Road, Suzhou 215123, China
| | - Samieh Asadian
- Tehran University of Medical Sciences, Pour Sina St, Tehran 1416634793, Iran
| | - Marco Tigano
- Department of Pathology and Genomic Medicine, Thomas Jefferson University, 1020 Locust Street, Philadelphia 19107, United States
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4
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Spinazzola A, Perez-Rodriguez D, Ježek J, Holt IJ. Mitochondrial DNA competition: starving out the mutant genome. Trends Pharmacol Sci 2024; 45:225-242. [PMID: 38402076 DOI: 10.1016/j.tips.2024.01.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2023] [Revised: 01/11/2024] [Accepted: 01/22/2024] [Indexed: 02/26/2024]
Abstract
High levels of pathogenic mitochondrial DNA (mtDNA) variants lead to severe genetic diseases, and the accumulation of such mutants may also contribute to common disorders. Thus, selecting against these mutants is a major goal in mitochondrial medicine. Although mutant mtDNA can drift randomly, mounting evidence indicates that active forces play a role in the selection for and against mtDNA variants. The underlying mechanisms are beginning to be clarified, and recent studies suggest that metabolic cues, including fuel availability, contribute to shaping mtDNA heteroplasmy. In the context of pathological mtDNAs, remodeling of nutrient metabolism supports mitochondria with deleterious mtDNAs and enables them to outcompete functional variants owing to a replicative advantage. The elevated nutrient requirement represents a mutant Achilles' heel because small molecules that restrict nutrient consumption or interfere with nutrient sensing can purge cells of deleterious mtDNAs and restore mitochondrial respiration. These advances herald the dawn of a new era of small-molecule therapies to counteract pathological mtDNAs.
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Affiliation(s)
- Antonella Spinazzola
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, Royal Free Campus, London NW3 2PF, UK.
| | - Diego Perez-Rodriguez
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, Royal Free Campus, London NW3 2PF, UK
| | - Jan Ježek
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, Royal Free Campus, London NW3 2PF, UK
| | - Ian J Holt
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, Royal Free Campus, London NW3 2PF, UK; Biodonostia Health Research Institute, 20014 San Sebastián, Spain; IKERBASQUE (Basque Foundation for Science), 48013 Bilbao, Spain; CIBERNED (Center for Networked Biomedical Research on Neurodegenerative Diseases, Ministry of Economy and Competitiveness, Institute Carlos III), 28031 Madrid, Spain; Universidad de País Vasco, Barrio Sarriena s/n, 48940 Leioa, Bilbao, Spain.
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5
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Volobaev VP, Kunizheva SS, Uralsky LI, Kupriyanova DA, Rogaev EI. Quantifying human genome parameters in aging. Vavilovskii Zhurnal Genet Selektsii 2023; 27:495-501. [PMID: 37808212 PMCID: PMC10551942 DOI: 10.18699/vjgb-23-60] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 02/07/2023] [Accepted: 02/07/2023] [Indexed: 10/10/2023] Open
Abstract
Healthy human longevity is a global goal of the world health system. Determining the causes and processes influencing human longevity is the primary fundamental goal facing the scientific community. Currently, the main efforts of the scientific community are aimed at identifying the qualitative characteristics of the genome that determine the trait. At the same time, when evaluating qualitative characteristics, there are many challenges that make it difficult to establish associations. Quantitative traits are burdened with such problems to a lesser extent, but they are largely overlooked in current genomic studies of aging and longevity. Although there is a wide repertoire of quantitative trait analyses based on genomic data, most opportunities are ignored by authors, which, along with the inaccessibility of published data, leads to the loss of this important information. This review focuses on describing quantitative traits important for understanding aging and necessary for analysis in further genomic studies, and recommends the inclusion of the described traits in the analysis. The review considers the relationship between quantitative characteristics of the mitochondrial genome and aging, longevity, and age-related neurodegenerative diseases, such as the frequency of extensive mitochondrial DNA (mtDNA) deletions, mtDNA half-life, the frequency of A>G replacements in the mtDNA heavy chain, the number of mtDNA copies; special attention is paid to the mtDNA methylation sign. A separate section of this review is devoted to the correlation of telomere length parameters with age, as well as the association of telomere length with the amount of mitochondrial DNA. In addition, we consider such a quantitative feature as the rate of accumulation of somatic mutations with aging in relation to the lifespan of living organisms. In general, it may be noted that there are quite serious reasons to suppose that various quantitative characteristics of the genome may be directly or indirectly associated with certain aspects of aging and longevity. At the same time, the available data are clearly insufficient for definitive conclusions and the determination of causal relationships.
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Affiliation(s)
- V P Volobaev
- Sirius University of Science and Technology, Scientific Center for Genetics and Life Sciences, Sochi, Russia
| | - S S Kunizheva
- Sirius University of Science and Technology, Scientific Center for Genetics and Life Sciences, Sochi, Russia Vavilov Institute of General Genetics, Russian Academy of Sciences, Department of Genomics and Human Genetics, Moscow, Russia Lomonosov Moscow State University, Center for Genetics and Genetic Technologies, Faculty of Biology, Moscow, Russia
| | - L I Uralsky
- Sirius University of Science and Technology, Scientific Center for Genetics and Life Sciences, Sochi, Russia Vavilov Institute of General Genetics, Russian Academy of Sciences, Department of Genomics and Human Genetics, Moscow, Russia
| | - D A Kupriyanova
- Sirius University of Science and Technology, Scientific Center for Genetics and Life Sciences, Sochi, Russia
| | - E I Rogaev
- Sirius University of Science and Technology, Scientific Center for Genetics and Life Sciences, Sochi, Russia Vavilov Institute of General Genetics, Russian Academy of Sciences, Department of Genomics and Human Genetics, Moscow, Russia Lomonosov Moscow State University, Center for Genetics and Genetic Technologies, Faculty of Biology, Moscow, Russia University of Massachusetts Chan Medical School, Department of Psychiatry, Shrewsbury, USA
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6
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Headley CA, Tsao PS. Building the case for mitochondrial transplantation as an anti-aging cardiovascular therapy. Front Cardiovasc Med 2023; 10:1141124. [PMID: 37229220 PMCID: PMC10203246 DOI: 10.3389/fcvm.2023.1141124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 04/11/2023] [Indexed: 05/27/2023] Open
Abstract
Mitochondrial dysfunction is a common denominator in both biological aging and cardiovascular disease (CVD) pathology. Understanding the protagonist role of mitochondria in the respective and independent progressions of CVD and biological aging will unravel the synergistic relationship between biological aging and CVD. Moreover, the successful development and implementation of therapies that can simultaneously benefit mitochondria of multiple cell types, will be transformational in curtailing pathologies and mortality in the elderly, including CVD. Several works have compared the status of mitochondria in vascular endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) in CVD dependent context. However, fewer studies have cataloged the aging-associated changes in vascular mitochondria, independent of CVD. This mini review will focus on the present evidence related to mitochondrial dysfunction in vascular aging independent of CVD. Additionally, we discuss the feasibility of restoring mitochondrial function in the aged cardiovascular system through mitochondrial transfer.
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7
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Burgstaller JP, Chiaratti MR. Mitochondrial Inheritance Following Nuclear Transfer: From Cloned Animals to Patients with Mitochondrial Disease. Methods Mol Biol 2023; 2647:83-104. [PMID: 37041330 DOI: 10.1007/978-1-0716-3064-8_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/13/2023]
Abstract
Mitochondria are indispensable power plants of eukaryotic cells that also act as a major biochemical hub. As such, mitochondrial dysfunction, which can originate from mutations in the mitochondrial genome (mtDNA), may impair organism fitness and lead to severe diseases in humans. MtDNA is a multi-copy, highly polymorphic genome that is uniparentally transmitted through the maternal line. Several mechanisms act in the germline to counteract heteroplasmy (i.e., coexistence of two or more mtDNA variants) and prevent expansion of mtDNA mutations. However, reproductive biotechnologies such as cloning by nuclear transfer can disrupt mtDNA inheritance, resulting in new genetic combinations that may be unstable and have physiological consequences. Here, we review the current understanding of mitochondrial inheritance, with emphasis on its pattern in animals and human embryos generated by nuclear transfer.
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Affiliation(s)
- Jörg P Burgstaller
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine, Vienna, Austria
| | - Marcos R Chiaratti
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil.
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8
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Stochastic survival of the densest and mitochondrial DNA clonal expansion in aging. Proc Natl Acad Sci U S A 2022; 119:e2122073119. [PMID: 36442091 PMCID: PMC9894218 DOI: 10.1073/pnas.2122073119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The expansion of mitochondrial DNA molecules with deletions has been associated with aging, particularly in skeletal muscle fibers; its mechanism has remained unclear for three decades. Previous accounts have assigned a replicative advantage (RA) to mitochondrial DNA containing deletion mutations, but there is also evidence that cells can selectively remove defective mitochondrial DNA. Here we present a spatial model that, without an RA, but instead through a combination of enhanced density for mutants and noise, produces a wave of expanding mutations with speeds consistent with experimental data. A standard model based on RA yields waves that are too fast. We provide a formula that predicts that wave speed drops with copy number, consonant with experimental data. Crucially, our model yields traveling waves of mutants even if mutants are preferentially eliminated. Additionally, we predict that mutant loads observed in single-cell experiments can be produced by de novo mutation rates that are drastically lower than previously thought for neutral models. Given this exemplar of how spatial structure (multiple linked mtDNA populations), noise, and density affect muscle cell aging, we introduce the mechanism of stochastic survival of the densest (SSD), an alternative to RA, that may underpin other evolutionary phenomena.
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9
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Hollar DW. The competition of ecological resonances in the quantum metabolic model of cancer: Potential energetic interventions. Biosystems 2022; 222:104798. [DOI: 10.1016/j.biosystems.2022.104798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 10/19/2022] [Accepted: 10/21/2022] [Indexed: 11/02/2022]
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10
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Chiaratti MR, Chinnery PF. Modulating mitochondrial DNA mutations: factors shaping heteroplasmy in the germ line and somatic cells. Pharmacol Res 2022; 185:106466. [PMID: 36174964 DOI: 10.1016/j.phrs.2022.106466] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 09/21/2022] [Accepted: 09/23/2022] [Indexed: 11/30/2022]
Abstract
Until recently it was thought that most humans only harbor one type of mitochondrial DNA (mtDNA), however, deep sequencing and single-cell analysis has shown the converse - that mixed populations of mtDNA (heteroplasmy) are the norm. This is important because heteroplasmy levels can change dramatically during transmission in the female germ line, leading to high levels causing severe mitochondrial diseases. There is also emerging evidence that low level mtDNA mutations contribute to common late onset diseases such as neurodegenerative disorders and cardiometabolic diseases because the inherited mutation levels can change within developing organs and non-dividing cells over time. Initial predictions suggested that the segregation of mtDNA heteroplasmy was largely stochastic, with an equal tendency for levels to increase or decrease. However, transgenic animal work and single-cell analysis have shown this not to be the case during germ-line transmission and in somatic tissues during life. Mutation levels in specific mtDNA regions can increase or decrease in different contexts and the underlying molecular mechanisms are starting to be unraveled. In this review we provide a synthesis of recent literature on the mechanisms of selection for and against mtDNA variants. We identify the most pertinent gaps in our understanding and suggest ways these could be addressed using state of the art techniques.
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Affiliation(s)
- Marcos R Chiaratti
- Departamento de Genética e Evolução, Centro de Ciências Biológicas e da Saúde, Universidade Federal de São Carlos, São Carlos, Brazil.
| | - Patrick F Chinnery
- Department of Clinical Neurosciences, School of Clinical Medicine, University of Cambridge, Cambridge Biomedical Campus, Cambridge, UK; Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, Cambridge, UK.
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11
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Hussein Ali T, Mousa Mandal A, Alhasan A, Dehaen W. Surface fabrication of magnetic core-shell silica nanoparticles with perylene diimide as a fluorescent dye for nucleic acid visualization. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.119345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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12
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Smith ALM, Whitehall JC, Greaves LC. Mitochondrial
DNA
mutations in aging and cancer. Mol Oncol 2022; 16:3276-3294. [PMID: 35842901 PMCID: PMC9490137 DOI: 10.1002/1878-0261.13291] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 06/18/2022] [Accepted: 07/15/2022] [Indexed: 11/09/2022] Open
Abstract
Advancing age is a major risk factor for malignant transformation and the development of cancer. As such, over 50% of neoplasms occur in individuals over the age of 70. The pathologies of both ageing and cancer have been characterized by respective groups of molecular hallmarks, and while some features are divergent between the two pathologies, several are shared. Perturbed mitochondrial function is one such common hallmark, and this observation therefore suggests that mitochondrial alterations may be of significance in age‐related cancer development. There is now considerable evidence documenting the accumulation of somatic mitochondrial DNA (mtDNA) mutations in ageing human postmitotic and replicative tissues. Similarly, mutations of the mitochondrial genome have been reported in human cancers for decades. The plethora of functions in which mitochondria partake, such as oxidative phosphorylation, redox balance, apoptosis and numerous biosynthetic pathways, manifests a variety of ways in which alterations in mtDNA may contribute to tumour growth. However, the specific mechanisms by which mtDNA mutations contribute to tumour progression remain elusive and often contradictory. This review aims to consolidate current knowledge and describe future direction within the field.
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Affiliation(s)
- Anna LM Smith
- Wellcome Centre for Mitochondrial Research, Biosciences Institute Newcastle University Newcastle Upon Tyne NE2 4HH UK
| | - Julia C Whitehall
- Wellcome Centre for Mitochondrial Research, Biosciences Institute Newcastle University Newcastle Upon Tyne NE2 4HH UK
| | - Laura C Greaves
- Wellcome Centre for Mitochondrial Research, Biosciences Institute Newcastle University Newcastle Upon Tyne NE2 4HH UK
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13
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Small Vessel Disease: Ancient Description, Novel Biomarkers. Int J Mol Sci 2022; 23:ijms23073508. [PMID: 35408867 PMCID: PMC8998274 DOI: 10.3390/ijms23073508] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 03/20/2022] [Accepted: 03/21/2022] [Indexed: 12/22/2022] Open
Abstract
Small vessel disease (SVD) is one of the most frequent pathological conditions which lead to dementia. Biochemical and neuroimaging might help correctly identify the clinical diagnosis of this relevant brain disease. The microvascular alterations which underlie SVD have common origins, similar cognitive outcomes, and common vascular risk factors. Nevertheless, the arteriolosclerosis process, which underlines SVD development, is based on different mechanisms, not all completely understood, which start from a chronic hypoperfusion state and pass through a chronic brain inflammatory condition, inducing a significant endothelium activation and a consequent tissue remodeling action. In a recent review, we focused on the pathophysiology of SVD, which is complex, involving genetic conditions and different co-morbidities (i.e., diabetes, chronic hypoxia condition, and obesity). Currently, many points still remain unclear and discordant. In this paper, we wanted to focus on new biomarkers, which can be the expression of the endothelial dysfunction, or of the oxidative damage, which could be employed as markers of disease progression or for future targets of therapies. Therefore, we described the altered response to the endothelium-derived nitric oxide-vasodilators (ENOV), prostacyclin, C-reactive proteins, and endothelium-derived hyperpolarizing factors (EDHF). At the same time, due to the concomitant endothelial activation and chronic neuroinflammatory status, we described hypoxia-endothelial-related markers, such as HIF 1 alpha, VEGFR2, and neuroglobin, and MMPs. We also described blood–brain barrier disruption biomarkers and imaging techniques, which can also describe perivascular spaces enlargement and dysfunction. More studies should be necessary, in order to implement these results and give them a clinical benefit.
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14
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DNA dyes: toxicity, remediation strategies and alternatives. Folia Microbiol (Praha) 2022; 67:555-571. [PMID: 35292916 DOI: 10.1007/s12223-022-00963-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 03/08/2022] [Indexed: 11/04/2022]
Abstract
Release of untreated effluent from processing or manufacturing industries and other commercial premises into water bodies is a major threat to environment and human health. In this regard, the effluent generated from laboratories and other research facilities is of great concern. Among other harmful chemicals, the effluent is rich in toxic organic dyes, which get exposed to the environment and pose serious health risk. The dyes used in nucleic acid analysis specially the DNA dyes are known for their teratogenicity and mutagenic potential, which mainly depends upon the organism and circumstances under which it is exposed. Among animals and humans, exposure to theses dyes may lead to irritation in mouth, eyes and respiratory tract and many other possible effects which are yet to be explored. To overcome these problems, dyes present in the effluents from laboratories must be degraded to non-toxic forms. Various strategies have been proposed and investigated for degradation and remediation of contaminated laboratory effluent. As a modern and cost-effective technique, biodegradation using microbes and plants is potentially eco-friendly and sustainable technique for detoxifying these dyes. In this article, we have discussed and reviewed the structure, properties and toxicity profile of prominent nucleic acid dyes, along with the strategies of remediation of laboratory effluents contaminated with these dyes. In addition, we have also discussed the feasibility and limitations of these remediation strategies and identified research gaps that can help researchers to explore more effective solutions to manage this area of great concern. We have also reviewed various less toxic alternatives of these common as safer options of these dyes.
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15
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Hernández-Ainsa C, López-Gallardo E, García-Jiménez MC, Climent-Alcalá FJ, Rodríguez-Vigil C, García Fernández de Villalta M, Artuch R, Montoya J, Ruiz-Pesini E, Emperador S. Development and characterization of cell models harbouring mtDNA deletions for in vitro study of Pearson syndrome. Dis Model Mech 2022; 15:dmm049083. [PMID: 35191981 PMCID: PMC8906170 DOI: 10.1242/dmm.049083] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 12/06/2021] [Indexed: 01/19/2023] Open
Abstract
Pearson syndrome is a rare multisystem disease caused by single large-scale mitochondrial DNA deletions (SLSMDs). The syndrome presents early in infancy and is mainly characterised by refractory sideroblastic anaemia. Prognosis is poor and treatment is supportive, thus the development of new models for the study of Pearson syndrome and new therapy strategies is essential. In this work, we report three different cell models carrying an SLMSD: fibroblasts, transmitochondrial cybrids and induced pluripotent stem cells (iPSCs). All studied models exhibited an aberrant mitochondrial ultrastructure and defective oxidative phosphorylation system function, showing a decrease in different parameters, such as mitochondrial ATP, respiratory complex IV activity and quantity or oxygen consumption. Despite this, iPSCs harbouring 'common deletion' were able to differentiate into three germ layers. Additionally, cybrid clones only showed mitochondrial dysfunction when heteroplasmy level reached 70%. Some differences observed among models may depend on their metabolic profile; therefore, we consider that these three models are useful for the in vitro study of Pearson syndrome, as well as for testing new specific therapies. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Carmen Hernández-Ainsa
- Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, 50013 Zaragoza, Spain
- Instituto de Investigación Sanitaria de Aragón (IIS-Aragón), 50009 Zaragoza, Spain
- Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), 28029 Madrid, Spain
| | - Ester López-Gallardo
- Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, 50013 Zaragoza, Spain
- Instituto de Investigación Sanitaria de Aragón (IIS-Aragón), 50009 Zaragoza, Spain
- Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), 28029 Madrid, Spain
| | | | | | | | | | - Rafael Artuch
- Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), 28029 Madrid, Spain
- Clinical Biochemistry, Genetics, Pediatric Neurology and Neonatalogy Departments, Institut de Recerca Sant Joan de Déu, 08950 Barcelona, Spain
| | - Julio Montoya
- Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, 50013 Zaragoza, Spain
- Instituto de Investigación Sanitaria de Aragón (IIS-Aragón), 50009 Zaragoza, Spain
- Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), 28029 Madrid, Spain
| | - Eduardo Ruiz-Pesini
- Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, 50013 Zaragoza, Spain
- Instituto de Investigación Sanitaria de Aragón (IIS-Aragón), 50009 Zaragoza, Spain
- Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), 28029 Madrid, Spain
| | - Sonia Emperador
- Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, 50013 Zaragoza, Spain
- Instituto de Investigación Sanitaria de Aragón (IIS-Aragón), 50009 Zaragoza, Spain
- Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), 28029 Madrid, Spain
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16
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Valiente-Pallejà A, Tortajada J, Bulduk BK, Vilella E, Garrabou G, Muntané G, Martorell L. Comprehensive summary of mitochondrial DNA alterations in the postmortem human brain: A systematic review. EBioMedicine 2022; 76:103815. [PMID: 35085849 PMCID: PMC8790490 DOI: 10.1016/j.ebiom.2022.103815] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 12/24/2021] [Accepted: 01/05/2022] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Mitochondrial DNA (mtDNA) encodes 37 genes necessary for synthesizing 13 essential subunits of the oxidative phosphorylation system. mtDNA alterations are known to cause mitochondrial disease (MitD), a clinically heterogeneous group of disorders that often present with neuropsychiatric symptoms. Understanding the nature and frequency of mtDNA alterations in health and disease could be a cornerstone in disentangling the relationship between biochemical findings and clinical symptoms of brain disorders. This systematic review aimed to summarize the mtDNA alterations in human brain tissue reported to date that have implications for further research on the pathophysiological significance of mtDNA alterations in brain functioning. METHODS We searched the PubMed and Embase databases using distinct terms related to postmortem human brain and mtDNA up to June 10, 2021. Reports were eligible if they were empirical studies analysing mtDNA in postmortem human brains. FINDINGS A total of 158 of 637 studies fulfilled the inclusion criteria and were clustered into the following groups: MitD (48 entries), neurological diseases (NeuD, 55 entries), psychiatric diseases (PsyD, 15 entries), a miscellaneous group with controls and other clinical diseases (5 entries), ageing (20 entries), and technical issues (5 entries). Ten entries were ascribed to more than one group. Pathogenic single nucleotide variants (pSNVs), both homo- or heteroplasmic variants, have been widely reported in MitD, with heteroplasmy levels varying among brain regions; however, pSNVs are rarer in NeuD, PsyD and ageing. A lower mtDNA copy number (CN) in disease was described in most, but not all, of the identified studies. mtDNA deletions were identified in individuals in the four clinical categories and ageing. Notably, brain samples showed significantly more mtDNA deletions and at higher heteroplasmy percentages than blood samples, and several of the deletions present in the brain were not detected in the blood. Finally, mtDNA heteroplasmy, mtDNA CN and the deletion levels varied depending on the brain region studied. INTERPRETATION mtDNA alterations are well known to affect human tissues, including the brain. In general, we found that studies of MitD, NeuD, PsyD, and ageing were highly variable in terms of the type of disease or ageing process investigated, number of screened individuals, studied brain regions and technology used. In NeuD and PsyD, no particular type of mtDNA alteration could be unequivocally assigned to any specific disease or diagnostic group. However, the presence of mtDNA deletions and mtDNA CN variation imply a role for mtDNA in NeuD and PsyD. Heteroplasmy levels and threshold effects, affected brain regions, and mitotic segregation patterns of mtDNA alterations may be involved in the complex inheritance of NeuD and PsyD and in the ageing process. Therefore, more information is needed regarding the type of mtDNA alteration, the affected brain regions, the heteroplasmy levels, and their relationship with clinical phenotypes and the ageing process. FUNDING Hospital Universitari Institut Pere Mata; Institut d'Investigació Sanitària Pere Virgili; Instituto de Salud Carlos III, Ministerio de Ciencia e Innovación (PI18/00514).
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Affiliation(s)
- Alba Valiente-Pallejà
- Research Department, Hospital Universitari Institut Pere Mata (HUIPM); Institut d'Investigació Sanitària Pere Virgili (IISPV); Faculty of Medicine and Health Sciences, Universitat Rovira i Virgili (URV), 43201 Reus, Catalonia, Spain; Biomedical Network Research Centre on Mental Health (CIBERSAM), 28029 Madrid, Spain
| | - Juan Tortajada
- Research Department, Hospital Universitari Institut Pere Mata (HUIPM); Institut d'Investigació Sanitària Pere Virgili (IISPV); Faculty of Medicine and Health Sciences, Universitat Rovira i Virgili (URV), 43201 Reus, Catalonia, Spain; Biomedical Network Research Centre on Mental Health (CIBERSAM), 28029 Madrid, Spain
| | - Bengisu K Bulduk
- Research Department, Hospital Universitari Institut Pere Mata (HUIPM); Institut d'Investigació Sanitària Pere Virgili (IISPV); Faculty of Medicine and Health Sciences, Universitat Rovira i Virgili (URV), 43201 Reus, Catalonia, Spain; Biomedical Network Research Centre on Mental Health (CIBERSAM), 28029 Madrid, Spain
| | - Elisabet Vilella
- Research Department, Hospital Universitari Institut Pere Mata (HUIPM); Institut d'Investigació Sanitària Pere Virgili (IISPV); Faculty of Medicine and Health Sciences, Universitat Rovira i Virgili (URV), 43201 Reus, Catalonia, Spain; Biomedical Network Research Centre on Mental Health (CIBERSAM), 28029 Madrid, Spain
| | - Glòria Garrabou
- Laboratory of Muscle Research and Mitochondrial Function, Department of Internal Medicine-Hospital Clínic of Barcelona (HCB); Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS); Faculty of Medicine and Health Sciences, Universitat de Barcelona (UB), 08036 Barcelona, Catalonia, Spain; Biomedical Network Research Centre on Rare Diseases (CIBERER), 28029 Madrid, Spain
| | - Gerard Muntané
- Research Department, Hospital Universitari Institut Pere Mata (HUIPM); Institut d'Investigació Sanitària Pere Virgili (IISPV); Faculty of Medicine and Health Sciences, Universitat Rovira i Virgili (URV), 43201 Reus, Catalonia, Spain; Biomedical Network Research Centre on Mental Health (CIBERSAM), 28029 Madrid, Spain; Institute of Evolutionary Biology (IBE), Universitat Pompeu Fabra (UPF), 08003 Barcelona, Catalonia, Spain
| | - Lourdes Martorell
- Research Department, Hospital Universitari Institut Pere Mata (HUIPM); Institut d'Investigació Sanitària Pere Virgili (IISPV); Faculty of Medicine and Health Sciences, Universitat Rovira i Virgili (URV), 43201 Reus, Catalonia, Spain; Biomedical Network Research Centre on Mental Health (CIBERSAM), 28029 Madrid, Spain.
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17
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Jeedigunta SP, Minenkova AV, Palozzi JM, Hurd TR. Avoiding Extinction: Recent Advances in Understanding Mechanisms of Mitochondrial DNA Purifying Selection in the Germline. Annu Rev Genomics Hum Genet 2021; 22:55-80. [PMID: 34038145 DOI: 10.1146/annurev-genom-121420-081805] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Mitochondria are unusual organelles in that they contain their own genomes, which are kept apart from the rest of the DNA in the cell. While mitochondrial DNA (mtDNA) is essential for respiration and most multicellular life, maintaining a genome outside the nucleus brings with it a number of challenges. Chief among these is preserving mtDNA genomic integrity from one generation to the next. In this review, we discuss what is known about negative (purifying) selection mechanisms that prevent deleterious mutations from accumulating in mtDNA in the germline. Throughout, we focus on the female germline, as it is the tissue through which mtDNA is inherited in most organisms and, therefore, the tissue that most profoundly shapes the genome. We discuss recent progress in uncovering the mechanisms of germline mtDNA selection, from humans to invertebrates.
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Affiliation(s)
- Swathi P Jeedigunta
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5G 1M1, Canada;
| | - Anastasia V Minenkova
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5G 1M1, Canada;
| | - Jonathan M Palozzi
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5G 1M1, Canada;
| | - Thomas R Hurd
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5G 1M1, Canada;
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18
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Porter TM, Hajibabaei M. Profile hidden Markov model sequence analysis can help remove putative pseudogenes from DNA barcoding and metabarcoding datasets. BMC Bioinformatics 2021; 22:256. [PMID: 34011275 PMCID: PMC8136176 DOI: 10.1186/s12859-021-04180-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 05/10/2021] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND Pseudogenes are non-functional copies of protein coding genes that typically follow a different molecular evolutionary path as compared to functional genes. The inclusion of pseudogene sequences in DNA barcoding and metabarcoding analysis can lead to misleading results. None of the most widely used bioinformatic pipelines used to process marker gene (metabarcode) high throughput sequencing data specifically accounts for the presence of pseudogenes in protein-coding marker genes. The purpose of this study is to develop a method to screen for nuclear mitochondrial DNA segments (nuMTs) in large COI datasets. We do this by: (1) describing gene and nuMT characteristics from an artificial COI barcode dataset, (2) show the impact of two different pseudogene removal methods on perturbed community datasets with simulated nuMTs, and (3) incorporate a pseudogene filtering step in a bioinformatic pipeline that can be used to process Illumina paired-end COI metabarcode sequences. Open reading frame length and sequence bit scores from hidden Markov model (HMM) profile analysis were used to detect pseudogenes. RESULTS Our simulations showed that it was more difficult to identify nuMTs from shorter amplicon sequences such as those typically used in metabarcoding compared with full length DNA barcodes that are used in the construction of barcode libraries. It was also more difficult to identify nuMTs in datasets where there is a high percentage of nuMTs. Existing bioinformatic pipelines used to process metabarcode sequences already remove some nuMTs, especially in the rare sequence removal step, but the addition of a pseudogene filtering step can remove up to 5% of sequences even when other filtering steps are in place. CONCLUSIONS Open reading frame length filtering alone or combined with hidden Markov model profile analysis can be used to effectively screen out apparent pseudogenes from large datasets. There is more to learn from COI nuMTs such as their frequency in DNA barcoding and metabarcoding studies, their taxonomic distribution, and evolution. Thus, we encourage the submission of verified COI nuMTs to public databases to facilitate future studies.
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Affiliation(s)
- T M Porter
- Department of Integrative Biology and Centre for Biodiversity Genomics, University of Guelph, 50 Stone Road East, Guelph, ON, Canada.
| | - M Hajibabaei
- Department of Integrative Biology and Centre for Biodiversity Genomics, University of Guelph, 50 Stone Road East, Guelph, ON, Canada
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19
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Ghiselli F, Iannello M, Piccinini G, Milani L. Bivalve molluscs as model systems for studying mitochondrial biology. Integr Comp Biol 2021; 61:1699-1714. [PMID: 33944910 DOI: 10.1093/icb/icab057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The class Bivalvia is a highly successful and ancient taxon including ∼25,000 living species. During their long evolutionary history bivalves adapted to a wide range of physicochemical conditions, habitats, biological interactions, and feeding habits. Bivalves can have strikingly different size, and despite their apparently simple body plan, they evolved very different shell shapes, and complex anatomic structures. One of the most striking features of this class of animals is their peculiar mitochondrial biology: some bivalves have facultatively anaerobic mitochondria that allow them to survive prolonged periods of anoxia/hypoxia. Moreover, more than 100 species have now been reported showing the only known evolutionarily stable exception to the strictly maternal inheritance of mitochondria in animals, named doubly uniparental inheritance. Mitochondrial activity is fundamental to eukaryotic life, and thanks to their diversity and uncommon features, bivalves represent a great model system to expand our knowledge about mitochondrial biology, so far limited to a few species. We highlight recent works studying mitochondrial biology in bivalves at either genomic or physiological level. A link between these two approaches is still missing, and we believe that an integrated approach and collaborative relationships are the only possible ways to be successful in such endeavour.
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Affiliation(s)
- Fabrizio Ghiselli
- Department of Biological, Geological, and Environmental Sciences, University of Bologna, Italy
| | - Mariangela Iannello
- Department of Biological, Geological, and Environmental Sciences, University of Bologna, Italy
| | - Giovanni Piccinini
- Department of Biological, Geological, and Environmental Sciences, University of Bologna, Italy
| | - Liliana Milani
- Department of Biological, Geological, and Environmental Sciences, University of Bologna, Italy
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20
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Nanopore Sequencing Resolves Elusive Long Tandem-Repeat Regions in Mitochondrial Genomes. Int J Mol Sci 2021; 22:ijms22041811. [PMID: 33670420 PMCID: PMC7918261 DOI: 10.3390/ijms22041811] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Accepted: 02/08/2021] [Indexed: 01/06/2023] Open
Abstract
Long non-coding, tandem-repetitive regions in mitochondrial (mt) genomes of many metazoans have been notoriously difficult to characterise accurately using conventional sequencing methods. Here, we show how the use of a third-generation (long-read) sequencing and informatic approach can overcome this problem. We employed Oxford Nanopore technology to sequence genomic DNAs from a pool of adult worms of the carcinogenic parasite, Schistosoma haematobium, and used an informatic workflow to define the complete mt non-coding region(s). Using long-read data of high coverage, we defined six dominant mt genomes of 33.4 kb to 22.6 kb. Although no variation was detected in the order or lengths of the protein-coding genes, there was marked length (18.5 kb to 7.6 kb) and structural variation in the non-coding region, raising questions about the evolution and function of what might be a control region that regulates mt transcription and/or replication. The discovery here of the largest tandem-repetitive, non-coding region (18.5 kb) in a metazoan organism also raises a question about the completeness of some of the mt genomes of animals reported to date, and stimulates further explorations using a Nanopore-informatic workflow.
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21
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Zakirova EG, Muzyka VV, Mazunin IO, Orishchenko KE. Natural and Artificial Mechanisms of Mitochondrial Genome Elimination. Life (Basel) 2021; 11:life11020076. [PMID: 33498399 PMCID: PMC7909434 DOI: 10.3390/life11020076] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 01/18/2021] [Accepted: 01/19/2021] [Indexed: 01/11/2023] Open
Abstract
The generally accepted theory of the genetic drift of mitochondrial alleles during mammalian ontogenesis is based on the presence of a selective bottleneck in the female germline. However, there is a variety of different theories on the pathways of genetic regulation of mitochondrial DNA (mtDNA) dynamics in oogenesis and adult somatic cells. The current review summarizes present knowledge on the natural mechanisms of mitochondrial genome elimination during mammalian development. We also discuss the variety of existing and developing methodologies for artificial manipulation of the mtDNA heteroplasmy level. Understanding of the basics of mtDNA dynamics will shed the light on the pathogenesis and potential therapies of human diseases associated with mitochondrial dysfunction.
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Affiliation(s)
- Elvira G. Zakirova
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.G.Z.); (V.V.M.)
| | - Vladimir V. Muzyka
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.G.Z.); (V.V.M.)
- Department of Genetic Technologies, Novosibirsk State University, 630090 Novosibirsk, Russia
| | - Ilya O. Mazunin
- Skolkovo Institute of Science and Technology, 143026 Skolkovo, Russia;
| | - Konstantin E. Orishchenko
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.G.Z.); (V.V.M.)
- Department of Genetic Technologies, Novosibirsk State University, 630090 Novosibirsk, Russia
- Correspondence:
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22
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Stewart JB, Chinnery PF. Extreme heterogeneity of human mitochondrial DNA from organelles to populations. Nat Rev Genet 2020; 22:106-118. [PMID: 32989265 DOI: 10.1038/s41576-020-00284-x] [Citation(s) in RCA: 97] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/25/2020] [Indexed: 02/06/2023]
Abstract
Contrary to the long-held view that most humans harbour only identical mitochondrial genomes, deep resequencing has uncovered unanticipated extreme genetic variation within mitochondrial DNA (mtDNA). Most, if not all, humans contain multiple mtDNA genotypes (heteroplasmy); specific patterns of variants accumulate in different tissues, including cancers, over time; and some variants are preferentially passed down or suppressed in the maternal germ line. These findings cast light on the origin and spread of mtDNA mutations at multiple scales, from the organelle to the human population, and challenge the conventional view that high percentages of a mutation are required before a new variant has functional consequences.
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Affiliation(s)
- James B Stewart
- Max Planck Institute for Biology of Ageing, Cologne, Germany.,Wellcome Centre for Mitochondrial Research, Newcastle University Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Patrick F Chinnery
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK. .,Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK.
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23
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Lawless C, Greaves L, Reeve AK, Turnbull DM, Vincent AE. The rise and rise of mitochondrial DNA mutations. Open Biol 2020; 10:200061. [PMID: 32428418 PMCID: PMC7276526 DOI: 10.1098/rsob.200061] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Accepted: 04/23/2020] [Indexed: 12/24/2022] Open
Abstract
How mitochondrial DNA mutations clonally expand in an individual cell is a question that has perplexed mitochondrial biologists for decades. A growing body of literature indicates that mitochondrial DNA mutations play a major role in ageing, metabolic diseases, neurodegenerative diseases, neuromuscular disorders and cancers. Importantly, this process of clonal expansion occurs for both inherited and somatic mitochondrial DNA mutations. To complicate matters further there are fundamental differences between mitochondrial DNA point mutations and deletions, and between mitotic and post-mitotic cells, that impact this pathogenic process. These differences, along with the challenges of investigating a longitudinal process occurring over decades in humans, have so far hindered progress towards understanding clonal expansion. Here we summarize our current understanding of the clonal expansion of mitochondrial DNA mutations in different tissues and highlight key unanswered questions. We then discuss the various existing biological models, along with their advantages and disadvantages. Finally, we explore what has been achieved with mathematical modelling so far and suggest future work to advance this important area of research.
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Affiliation(s)
| | | | | | - Doug M. Turnbull
- Wellcome Centre for Mitochondrial Research, Clinical and Translational Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle NE2 4HH, UK
| | - Amy E. Vincent
- Wellcome Centre for Mitochondrial Research, Clinical and Translational Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle NE2 4HH, UK
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24
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Klucnika A, Ma H. A battle for transmission: the cooperative and selfish animal mitochondrial genomes. Open Biol 2020; 9:180267. [PMID: 30890027 PMCID: PMC6451365 DOI: 10.1098/rsob.180267] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The mitochondrial genome is an evolutionarily persistent and cooperative component of metazoan cells that contributes to energy production and many other cellular processes. Despite sharing the same host as the nuclear genome, the multi-copy mitochondrial DNA (mtDNA) follows very different rules of replication and transmission, which translate into differences in the patterns of selection. On one hand, mtDNA is dependent on the host for its transmission, so selections would favour genomes that boost organismal fitness. On the other hand, genetic heterogeneity within an individual allows different mitochondrial genomes to compete for transmission. This intra-organismal competition could select for the best replicator, which does not necessarily give the fittest organisms, resulting in mito-nuclear conflict. In this review, we discuss the recent advances in our understanding of the mechanisms and opposing forces governing mtDNA transmission and selection in bilaterians, and what the implications of these are for mtDNA evolution and mitochondrial replacement therapy.
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Affiliation(s)
- Anna Klucnika
- 1 Wellcome Trust/Cancer Research UK Gurdon Institute , Tennis Court Road, Cambridge CB2 1QN , UK.,2 Department of Genetics, University of Cambridge , Downing Street, Cambridge CB2 3EH , UK
| | - Hansong Ma
- 1 Wellcome Trust/Cancer Research UK Gurdon Institute , Tennis Court Road, Cambridge CB2 1QN , UK.,2 Department of Genetics, University of Cambridge , Downing Street, Cambridge CB2 3EH , UK
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25
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van den Ameele J, Li AY, Ma H, Chinnery PF. Mitochondrial heteroplasmy beyond the oocyte bottleneck. Semin Cell Dev Biol 2020; 97:156-166. [DOI: 10.1016/j.semcdb.2019.10.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 09/17/2019] [Accepted: 10/01/2019] [Indexed: 12/31/2022]
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26
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Dubie JJ, Caraway AR, Stout MM, Katju V, Bergthorsson U. The conflict within: origin, proliferation and persistence of a spontaneously arising selfish mitochondrial genome. Philos Trans R Soc Lond B Biol Sci 2019; 375:20190174. [PMID: 31787044 DOI: 10.1098/rstb.2019.0174] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Mitochondrial genomes can sustain mutations that are simultaneously detrimental to individual fitness and yet, can proliferate within individuals owing to a replicative advantage. We analysed the fitness effects and population dynamics of a mitochondrial genome containing a novel 499 bp deletion in the cytochrome b(1) (ctb-1) gene (Δctb-1) encoding the cytochrome b of complex III in Caenorhabditis elegans. Δctb-1 reached a high heteroplasmic frequency of 96% in one experimental line during a mutation accumulation experiment and was linked to additional spontaneous mutations in nd5 and tRNA-Asn. The Δctb-1 mutant mitotype imposed a significant fitness cost including a 65% and 52% reduction in productivity and competitive fitness, respectively, relative to individuals bearing wild-type (WT) mitochondria. Deletion-bearing worms were rapidly purged within a few generations when competed against WT mitochondrial DNA (mtDNA) bearing worms in experimental populations. By contrast, the Δctb-1 mitotype was able to persist in large populations comprising heteroplasmic individuals only, although the average intracellular frequency of Δctb-1 exhibited a slow decline owing to competition among individuals bearing different frequencies of the heteroplasmy. Within experimental lines subjected to severe population bottlenecks (n = 1), the relative intracellular frequency of Δctb-1 increased, which is a hallmark of selfish drive. A positive correlation between Δctb-1 and WT mtDNA copy-number suggests a mechanism that increases total mtDNA per se, and does not discern the Δctb-1 mitotype from the WT mtDNA. This study demonstrates the selfish nature of the Δctb-1 mitotype, given its transmission advantage and substantial fitness load for the host, and highlights the importance of population size for the population dynamics of selfish mtDNA. This article is part of the theme issue 'Linking the mitochondrial genotype to phenotype: a complex endeavour'.
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Affiliation(s)
- Joseph James Dubie
- Department of Veterinary Integrative Biosciences, Texas A&M University, 402 Raymond Stotzer Parkway, College Station, TX 77845, USA
| | - Avery Robert Caraway
- Department of Veterinary Integrative Biosciences, Texas A&M University, 402 Raymond Stotzer Parkway, College Station, TX 77845, USA
| | - McKenna Margaret Stout
- Department of Veterinary Integrative Biosciences, Texas A&M University, 402 Raymond Stotzer Parkway, College Station, TX 77845, USA
| | - Vaishali Katju
- Department of Veterinary Integrative Biosciences, Texas A&M University, 402 Raymond Stotzer Parkway, College Station, TX 77845, USA
| | - Ulfar Bergthorsson
- Department of Veterinary Integrative Biosciences, Texas A&M University, 402 Raymond Stotzer Parkway, College Station, TX 77845, USA
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27
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Abstract
Mitochondria, a nearly ubiquitous feature of eukaryotes, are derived from an ancient symbiosis. Despite billions of years of cooperative coevolution - in what is arguably the most important mutualism in the history of life - the persistence of mitochondrial genomes also creates conditions for genetic conflict with the nucleus. Because mitochondrial genomes are present in numerous copies per cell, they are subject to both within- and among-organism levels of selection. Accordingly, 'selfish' genotypes that increase their own proliferation can rise to high frequencies even if they decrease organismal fitness. It has been argued that uniparental (often maternal) inheritance of cytoplasmic genomes evolved to curtail such selfish replication by minimizing within-individual variation and, hence, within-individual selection. However, uniparental inheritance creates conditions for cytonuclear conflict over sex determination and sex ratio, as well as conditions for sexual antagonism when mitochondrial variants increase transmission by enhancing maternal fitness but have the side-effect of being harmful to males (i.e., 'mother's curse'). Here, we review recent advances in understanding selfish replication and sexual antagonism in the evolution of mitochondrial genomes and the mechanisms that suppress selfish interactions, drawing parallels and contrasts with other organelles (plastids) and bacterial endosymbionts that arose more recently. Although cytonuclear conflict is widespread across eukaryotes, it can be cryptic due to nuclear suppression, highly variable, and lineage-specific, reflecting the diverse biology of eukaryotes and the varying architectures of their cytoplasmic genomes.
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Affiliation(s)
- Justin C Havird
- Department of Integrative Biology, The University of Texas, Austin, TX 78712, USA.
| | - Evan S Forsythe
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - Alissa M Williams
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - John H Werren
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
| | - Damian K Dowling
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia
| | - Daniel B Sloan
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
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28
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Hoitzing H, Gammage PA, Haute LV, Minczuk M, Johnston IG, Jones NS. Energetic costs of cellular and therapeutic control of stochastic mitochondrial DNA populations. PLoS Comput Biol 2019; 15:e1007023. [PMID: 31242175 PMCID: PMC6615642 DOI: 10.1371/journal.pcbi.1007023] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2018] [Revised: 07/09/2019] [Accepted: 04/11/2019] [Indexed: 12/28/2022] Open
Abstract
The dynamics of the cellular proportion of mutant mtDNA molecules is crucial for mitochondrial diseases. Cellular populations of mitochondria are under homeostatic control, but the details of the control mechanisms involved remain elusive. Here, we use stochastic modelling to derive general results for the impact of cellular control on mtDNA populations, the cost to the cell of different mtDNA states, and the optimisation of therapeutic control of mtDNA populations. This formalism yields a wealth of biological results, including that an increasing mtDNA variance can increase the energetic cost of maintaining a tissue, that intermediate levels of heteroplasmy can be more detrimental than homoplasmy even for a dysfunctional mutant, that heteroplasmy distribution (not mean alone) is crucial for the success of gene therapies, and that long-term rather than short intense gene therapies are more likely to beneficially impact mtDNA populations.
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Affiliation(s)
- Hanne Hoitzing
- Department of Mathematics, Imperial College London, London, SW7 2AZ, United Kingdom
| | - Payam A. Gammage
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY, United Kingdom
- CRUK Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | - Lindsey Van Haute
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY, United Kingdom
| | - Michal Minczuk
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY, United Kingdom
| | - Iain G. Johnston
- Faculty of Mathematics and Natural Sciences, University of Bergen, Bergen, Norway
- Alan Turing Institute, London, United Kingdom
| | - Nick S. Jones
- Department of Mathematics, Imperial College London, London, SW7 2AZ, United Kingdom
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29
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Mitochondrial Theory of Skeletal Muscle Ageing - New Facts, New Doubts. J Vet Res 2019; 63:149-160. [PMID: 30989147 PMCID: PMC6458556 DOI: 10.2478/jvetres-2019-0015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 02/27/2019] [Indexed: 11/21/2022] Open
Abstract
For many years, scientists have been pursuing research on skeletal muscle ageing both in humans and animals. Studies on animal models have extended our knowledge of this mechanism in humans. Most researchers agree that the major processes of muscle ageing occur in the mitochondria as the major energy production centres in muscle cells. It is believed that decisive changes occur at the enzymatic activity level as well as in protein synthesis and turnover ability. Deregulation of ion channels and oxidative stress also play significant roles. In particular, in recent years the free radical theory of ageing has undergone considerable modification; researchers are increasingly highlighting the partly positive effects of free radicals on processes occurring in cells. In addition, the influence of diet and physical activity on the rate of muscle cell ageing is widely debated as well as the possibility of delaying it through appropriate physical exercise and diet programmes. Numerous studies, especially those related to genetic processes, are still being conducted, and in the near future the findings could provide valuable information on muscle ageing. The results of ongoing research could answer the perennial question of whether and how we can influence the rate of ageing both in animals and humans.
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Vincent AE, Rosa HS, Pabis K, Lawless C, Chen C, Grünewald A, Rygiel KA, Rocha MC, Reeve AK, Falkous G, Perissi V, White K, Davey T, Petrof BJ, Sayer AA, Cooper C, Deehan D, Taylor RW, Turnbull DM, Picard M. Subcellular origin of mitochondrial DNA deletions in human skeletal muscle. Ann Neurol 2018; 84:289-301. [PMID: 30014514 PMCID: PMC6141001 DOI: 10.1002/ana.25288] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 07/02/2018] [Accepted: 07/02/2018] [Indexed: 01/07/2023]
Abstract
OBJECTIVE In patients with mitochondrial DNA (mtDNA) maintenance disorders and with aging, mtDNA deletions sporadically form and clonally expand within individual muscle fibers, causing respiratory chain deficiency. This study aimed to identify the sub-cellular origin and potential mechanisms underlying this process. METHODS Serial skeletal muscle cryosections from patients with multiple mtDNA deletions were subjected to subcellular immunofluorescent, histochemical, and genetic analysis. RESULTS We report respiratory chain-deficient perinuclear foci containing mtDNA deletions, which show local elevations of both mitochondrial mass and mtDNA copy number. These subcellular foci of respiratory chain deficiency are associated with a local increase in mitochondrial biogenesis and unfolded protein response signaling pathways. We also find that the commonly reported segmental pattern of mitochondrial deficiency is consistent with the three-dimensional organization of the human skeletal muscle mitochondrial network. INTERPRETATION We propose that mtDNA deletions first exceed the biochemical threshold causing biochemical deficiency in focal regions adjacent to the myonuclei, and induce mitochondrial biogenesis before spreading across the muscle fiber. These subcellular resolution data provide new insights into the possible origin of mitochondrial respiratory chain deficiency in mitochondrial myopathy. Ann Neurol 2018;84:289-301.
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Affiliation(s)
- Amy E Vincent
- Wellcome Centre for Mitochondrial Research and Newcastle Centre for Ageing and Vitality, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Hannah S Rosa
- Wellcome Centre for Mitochondrial Research and Newcastle Centre for Ageing and Vitality, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Kamil Pabis
- Wellcome Centre for Mitochondrial Research and Newcastle Centre for Ageing and Vitality, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Conor Lawless
- Wellcome Centre for Mitochondrial Research and Newcastle Centre for Ageing and Vitality, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Chun Chen
- Wellcome Centre for Mitochondrial Research and Newcastle Centre for Ageing and Vitality, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Anne Grünewald
- Wellcome Centre for Mitochondrial Research and Newcastle Centre for Ageing and Vitality, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom.,Institute of Neurogenetics, University of Lübeck, Lübeck, Germany.,Molecular and Functional Neurobiology Group, Luxembourg Center for Systems Biomedicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Karolina A Rygiel
- Wellcome Centre for Mitochondrial Research and Newcastle Centre for Ageing and Vitality, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Mariana C Rocha
- Wellcome Centre for Mitochondrial Research and Newcastle Centre for Ageing and Vitality, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Amy K Reeve
- Wellcome Centre for Mitochondrial Research and Newcastle Centre for Ageing and Vitality, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Gavin Falkous
- Wellcome Centre for Mitochondrial Research and Newcastle Centre for Ageing and Vitality, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Valentina Perissi
- Department of Biochemistry, Boston University School of Medicine, Boston, MA
| | - Kathryn White
- Electron Microscopy Research Services, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Tracey Davey
- Electron Microscopy Research Services, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Basil J Petrof
- Meakins-Christie Laboratories, Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada
| | - Avan A Sayer
- National Institute for Health Research Newcastle Biomedical Research Centre, Newcastle upon Tyne Hospitals National Health Service Foundation Trust and Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Cyrus Cooper
- Medical Research Council Lifecourse Epidemiology Unit, University of Southampton, Southampton, United Kingdom
| | - David Deehan
- Institute of Cellular Medicine, Newcastle University, Newcastle Upon Tyne, United Kingdom
| | - Robert W Taylor
- Wellcome Centre for Mitochondrial Research and Newcastle Centre for Ageing and Vitality, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Doug M Turnbull
- Wellcome Centre for Mitochondrial Research and Newcastle Centre for Ageing and Vitality, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Martin Picard
- Department of Psychiatry, Division of Behavioral Medicine, Columbia University Medical Center, New York, NY.,Department of Neurology and Columbia Translational Neuroscience Initiative, H. Houston Merritt Center, Columbia University Medical Center, New York, NY.,Columbia University Aging Center, Columbia University, New York, NY
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31
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Clonal expansion of mtDNA deletions: different disease models assessed by digital droplet PCR in single muscle cells. Sci Rep 2018; 8:11682. [PMID: 30076399 PMCID: PMC6076247 DOI: 10.1038/s41598-018-30143-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 07/18/2018] [Indexed: 01/07/2023] Open
Abstract
Deletions in mitochondrial DNA (mtDNA) are an important cause of human disease and their accumulation has been implicated in the ageing process. As mtDNA is a high copy number genome, the coexistence of deleted and wild-type mtDNA molecules within a single cell defines heteroplasmy. When deleted mtDNA molecules, driven by intracellular clonal expansion, reach a sufficiently high level, a biochemical defect emerges, contributing to the appearance and progression of clinical pathology. Consequently, it is relevant to determine the heteroplasmy levels within individual cells to understand the mechanism of clonal expansion. Heteroplasmy is reflected in a mosaic distribution of cytochrome c oxidase (COX)-deficient muscle fibers. We applied droplet digital PCR (ddPCR) to single muscle fibers collected by laser-capture microdissection (LCM) from muscle biopsies of patients with different paradigms of mitochondrial disease, characterized by the accumulation of single or multiple mtDNA deletions. By combining these two sensitive approaches, ddPCR and LCM, we document different models of clonal expansion in patients with single and multiple mtDNA deletions, implicating different mechanisms and time points for the development of COX deficiency in these molecularly distinct mitochondrial cytopathies.
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32
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The mitochondrial DNA genetic bottleneck: inheritance and beyond. Essays Biochem 2018; 62:225-234. [PMID: 29880721 DOI: 10.1042/ebc20170096] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 05/21/2018] [Accepted: 05/23/2018] [Indexed: 12/11/2022]
Abstract
mtDNA is a multicopy genome. When mutations exist, they can affect a varying proportion of the mtDNA present within every cell (heteroplasmy). Heteroplasmic mtDNA mutations can be maternally inherited, but the proportion of mutated alleles differs markedly between offspring within one generation. This led to the genetic bottleneck hypothesis, explaining the rapid changes in allele frequency seen during transmission from one generation to the next. Although a physical reduction in mtDNA has been demonstrated in several species, a comprehensive understanding of the molecular mechanisms is yet to be revealed. Several questions remain, including the role of selection for and against specific alleles, whether all bottlenecks are the same, and precisely how the bottleneck is controlled during development. Although originally thought to be limited to the germline, there is evidence that bottlenecks exist in other cell types during development, perhaps explaining why different tissues in the same organism contain different levels of mutated mtDNA. Moreover, tissue-specific bottlenecks may occur throughout life in response to environmental influences, adding further complexity to the situation. Here we review key recent findings, and suggest ways forward that will hopefully advance our understanding of the role of mtDNA in human disease.
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33
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Clinical syndromes associated with mtDNA mutations: where we stand after 30 years. Essays Biochem 2018; 62:235-254. [DOI: 10.1042/ebc20170097] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 05/29/2018] [Accepted: 05/30/2018] [Indexed: 01/16/2023]
Abstract
The landmark year 1988 can be considered as the birthdate of mitochondrial medicine, when the first pathogenic mutations affecting mtDNA were associated with human diseases. Three decades later, the field still expands and we are not ‘scraping the bottom of the barrel’ yet. Despite the tremendous progress in terms of molecular characterization and genotype/phenotype correlations, for the vast majority of cases we still lack a deep understanding of the pathogenesis, good models to study, and effective therapeutic options. However, recent technological advances including somatic cell reprogramming to induced pluripotent stem cells (iPSCs), organoid technology, and tailored endonucleases provide unprecedented opportunities to fill these gaps, casting hope to soon cure the major primary mitochondrial phenotypes reviewed here. This group of rare diseases represents a key model for tackling the pathogenic mechanisms involving mitochondrial biology relevant to much more common disorders that affect our currently ageing population, such as diabetes and metabolic syndrome, neurodegenerative and inflammatory disorders, and cancer.
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34
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Kozlov S, Afonin A, Evsyukov I, Bondarenko A. Alzheimer's disease: as it was in the beginning. Rev Neurosci 2018; 28:825-843. [PMID: 28704198 DOI: 10.1515/revneuro-2017-0006] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 05/19/2017] [Indexed: 01/09/2023]
Abstract
Since Alzheimer's disease was first described in 1907, many attempts have been made to reveal its main cause. Nowadays, two forms of the disease are known, and while the hereditary form of the disease is clearly caused by mutations in one of several genes, the etiology of the sporadic form remains a mystery. Both forms share similar sets of neuropathological and molecular manifestations, including extracellular deposition of amyloid-beta, intracellular accumulation of hyperphosphorylated tau protein, disturbances in both the structure and functions of mitochondria, oxidative stress, metal ion metabolism disorders, impairment of N-methyl-D-aspartate receptor-related signaling pathways, abnormalities of lipid metabolism, and aberrant cell cycle reentry in some neurons. Such a diversity of symptoms led to proposition of various hypotheses for explaining the development of Alzheimer's disease, the amyloid hypothesis, which postulates the key role of amyloid-beta in Alzheimer's disease development, being the most prominent. However, this hypothesis does not fully explain all of the molecular abnormalities and is therefore heavily criticized. In this review, we propose a hypothetical model of Alzheimer's disease progression, assuming a key role of age-related mitochondrial dysfunction, as was postulated in the mitochondrial cascade hypothesis. Our model explains the connections between all the symptoms of Alzheimer's disease, with particular attention to autophagy, metal metabolism disorders, and aberrant cell cycle re-entry in neurons. Progression of the Alzheimer's disease appears to be a complex process involving aging and too many protective mechanisms affecting one another, thereby leading to even greater deleterious effects.
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35
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Resolving the Enigma of the Clonal Expansion of mtDNA Deletions. Genes (Basel) 2018; 9:genes9030126. [PMID: 29495484 PMCID: PMC5867847 DOI: 10.3390/genes9030126] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 02/14/2018] [Accepted: 02/16/2018] [Indexed: 12/31/2022] Open
Abstract
Mitochondria are cell organelles that are special since they contain their own genetic material in the form of mitochondrial DNA (mtDNA). Damage and mutations of mtDNA are not only involved in several inherited human diseases but are also widely thought to play an important role during aging. In both cases, point mutations or large deletions accumulate inside cells, leading to functional impairment once a certain threshold has been surpassed. In most cases, it is a single type of mutant that clonally expands and out-competes the wild type mtDNA, with different mutant molecules being amplified in different cells. The challenge is to explain where the selection advantage for the accumulation comes from, why such a large range of different deletions seem to possess this advantage, and how this process can scale to species with different lifespans such as those of rats and man. From this perspective, we provide an overview of current ideas, present an update of our own proposal, and discuss the wider relevance of the phenomenon for aging.
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36
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Preferential amplification of a human mitochondrial DNA deletion in vitro and in vivo. Sci Rep 2018; 8:1799. [PMID: 29379065 PMCID: PMC5789095 DOI: 10.1038/s41598-018-20064-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 12/27/2017] [Indexed: 01/19/2023] Open
Abstract
We generated induced pluripotent stem cells (iPSCs) from patient fibroblasts to yield cell lines containing varying degrees of heteroplasmy for a m.13514 A > G mtDNA point mutation (2 lines) and for a ~6 kb single, large scale mtDNA deletion (3 lines). Long term culture of the iPSCs containing a single, large-scale mtDNA deletion showed consistent increase in mtDNA deletion levels with time. Higher levels of mtDNA heteroplasmy correlated with increased respiratory deficiency. To determine what changes occurred in deletion level during differentiation, teratomas comprising all three embryonic germ layers were generated from low (20%) and intermediate heteroplasmy (55%) mtDNA deletion clones. Regardless of whether iPSCs harbouring low or intermediate mtDNA heteroplasmy were used, the final levels of heteroplasmy in all teratoma germ layers increased to a similar high level (>60%). Thus, during human stem cell division, cells not only tolerate high mtDNA deletion loads but seem to preferentially replicate deleted mtDNA genomes. This has implications for the involvement of mtDNA deletions in both disease and ageing.
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37
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Affinity purification of cell-specific mitochondria from whole animals resolves patterns of genetic mosaicism. Nat Cell Biol 2018; 20:352-360. [DOI: 10.1038/s41556-017-0023-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 12/05/2017] [Indexed: 12/21/2022]
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38
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Antipova VN, Lomaeva MG, Zyrina NV. Mitochondrial DNA deletions in tissues of mice after ionizing radiation exposure. Int J Radiat Biol 2018; 94:282-288. [DOI: 10.1080/09553002.2018.1419299] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Valeriya N. Antipova
- Laboratory of Biophysics of Active Media, Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
| | - Milena G. Lomaeva
- Laboratory of Radiation Molecular Biology, Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
| | - Nadezhda V. Zyrina
- Laboratory of Crystallophysics and X-ray Research, Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
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39
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Lack of Parkin Anticipates the Phenotype and Affects Mitochondrial Morphology and mtDNA Levels in a Mouse Model of Parkinson's Disease. J Neurosci 2017; 38:1042-1053. [PMID: 29222404 DOI: 10.1523/jneurosci.1384-17.2017] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 08/24/2017] [Accepted: 10/03/2017] [Indexed: 02/08/2023] Open
Abstract
PARK2 is the most common gene mutated in monogenic recessive familial cases of Parkinson's disease (PD). Pathogenic mutations cause a loss of function of the encoded protein Parkin. ParkinKO mice, however, poorly represent human PD symptoms as they only exhibit mild motor phenotypes, minor dopamine metabolism abnormalities, and no signs of dopaminergic neurodegeneration. Parkin has been shown to participate in mitochondrial turnover, by targeting damaged mitochondria with low membrane potential to mitophagy. We studied the role of Parkin on mitochondrial quality control in vivo by knocking out Parkin in the PD-mito-PstI mouse (males), where the mitochondrial DNA (mtDNA) undergoes double-strand breaks only in dopaminergic neurons. The lack of Parkin promoted earlier onset of dopaminergic neurodegeneration and motor defects in the PD-mito-PstI mice, but it did not worsen the pathology. The lack of Parkin affected mitochondrial morphology in dopaminergic axons and was associated with an increase in mtDNA levels (mutant and wild type). Unexpectedly, it did not cause a parallel increase in mitochondrial mass or mitophagy. Our results suggest that Parkin affects mtDNA levels in a mitophagy-independent manner.SIGNIFICANCE STATEMENT Parkinson's disease is characterized by progressive motor symptoms due to the selective loss of dopaminergic neurons in the substantia nigra. Loss-of-function mutations of Parkin cause some monogenic forms of Parkinson's disease, possibly through its role in mitochondrial turnover and quality control. To study whether Parkin has a role in vivo in the context of mitochondrial damage, we knocked out Parkin in a mouse model in which the mitochondrial DNA is damaged in dopaminergic neurons. We found that the loss of Parkin did not exacerbate the parkinsonian pathology already present in the mice, but it was associated with an increase in mtDNA levels (mutant and wild-type) without altering mitochondrial mass. These results shed new light on the function of Parkin in vivo.
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40
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Regulation of Small Mitochondrial DNA Replicative Advantage by Ribonucleotide Reductase in Saccharomyces cerevisiae. G3-GENES GENOMES GENETICS 2017; 7:3083-3090. [PMID: 28717049 PMCID: PMC5592933 DOI: 10.1534/g3.117.043851] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Small mitochondrial genomes can behave as selfish elements by displacing wild-type genomes regardless of their detriment to the host organism. In the budding yeast Saccharomyces cerevisiae, small hypersuppressive mtDNA transiently coexist with wild-type in a state of heteroplasmy, wherein the replicative advantage of the small mtDNA outcompetes wild-type and produces offspring without respiratory capacity in >95% of colonies. The cytosolic enzyme ribonucleotide reductase (RNR) catalyzes the rate-limiting step in dNTP synthesis and its inhibition has been correlated with increased petite colony formation, reflecting loss of respiratory function. Here, we used heteroplasmic diploids containing wild-type (rho+) and suppressive (rho−) or hypersuppressive (HS rho−) mitochondrial genomes to explore the effects of RNR activity on mtDNA heteroplasmy in offspring. We found that the proportion of rho+ offspring was significantly increased by RNR overexpression or deletion of its inhibitor, SML1, while reducing RNR activity via SML1 overexpression produced the opposite effects. In addition, using Ex Taq and KOD Dash polymerases, we observed a replicative advantage for small over large template DNA in vitro, but only at low dNTP concentrations. These results suggest that dNTP insufficiency contributes to the replicative advantage of small mtDNA over wild-type and cytosolic dNTP synthesis by RNR is an important regulator of heteroplasmy involving small mtDNA molecules in yeast.
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41
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DeBalsi KL, Hoff KE, Copeland WC. Role of the mitochondrial DNA replication machinery in mitochondrial DNA mutagenesis, aging and age-related diseases. Ageing Res Rev 2017; 33:89-104. [PMID: 27143693 DOI: 10.1016/j.arr.2016.04.006] [Citation(s) in RCA: 117] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 04/19/2016] [Accepted: 04/19/2016] [Indexed: 12/19/2022]
Abstract
As regulators of bioenergetics in the cell and the primary source of endogenous reactive oxygen species (ROS), dysfunctional mitochondria have been implicated for decades in the process of aging and age-related diseases. Mitochondrial DNA (mtDNA) is replicated and repaired by nuclear-encoded mtDNA polymerase γ (Pol γ) and several other associated proteins, which compose the mtDNA replication machinery. Here, we review evidence that errors caused by this replication machinery and failure to repair these mtDNA errors results in mtDNA mutations. Clonal expansion of mtDNA mutations results in mitochondrial dysfunction, such as decreased electron transport chain (ETC) enzyme activity and impaired cellular respiration. We address the literature that mitochondrial dysfunction, in conjunction with altered mitochondrial dynamics, is a major driving force behind aging and age-related diseases. Additionally, interventions to improve mitochondrial function and attenuate the symptoms of aging are examined.
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Affiliation(s)
- Karen L DeBalsi
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Kirsten E Hoff
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - William C Copeland
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
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42
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Biomarkers of chondriome topology and function: implications for the extension of healthy aging. Biogerontology 2016; 18:201-215. [PMID: 28028686 DOI: 10.1007/s10522-016-9673-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2016] [Accepted: 12/19/2016] [Indexed: 12/27/2022]
Abstract
Multiple theories of aging (e.g., free radical, error catastrophe, mitochondrial) are complementary but fail to provide adequate models that comprehensively predict lifelong aging processes and that are valid across species. Hayflick (PLoS Genet 3(12):2351-2354, 2007) described six universal characteristics of aging that focus upon post-reproductive molecular entropy. Here we present a thermodynamic potential model of aging in which the energetic and topological properties of the mitochondrion drive functional and structural stabilities within living systems. Using multivariate regressions of physiological assessments from the National Health and Nutrition Examination Survey, VO2 max consistently declined with age regardless of gender or race, although it had a significantly greater decline for African American females. Percent fat (negative), hematocrit (negative), and urine creatinine (negative) were strongly and significantly associated with VO2 max and male aging, although cholesterol (positive) was an additional factor for African American males. Bioenergetic measures such as VO2 max can be useful for physical assessments to promote healthy aging.
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43
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Volmering E, Niehusmann P, Peeva V, Grote A, Zsurka G, Altmüller J, Nürnberg P, Becker AJ, Schoch S, Elger CE, Kunz WS. Neuropathological signs of inflammation correlate with mitochondrial DNA deletions in mesial temporal lobe epilepsy. Acta Neuropathol 2016; 132:277-288. [PMID: 26993140 DOI: 10.1007/s00401-016-1561-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 02/26/2016] [Accepted: 03/11/2016] [Indexed: 11/27/2022]
Abstract
Accumulation of mitochondrial DNA (mtDNA) deletions has been proposed to be responsible for the presence of respiratory-deficient neurons in several CNS diseases. Deletions are thought to originate from double-strand breaks due to attack of reactive oxygen species (ROS) of putative inflammatory origin. In epileptogenesis, emerging evidence points to chronic inflammation as an important feature. Here we aimed to analyze the potential association of inflammation and mtDNA deletions in the hippocampal tissue of patients with mesial temporal lobe epilepsy (mTLE) and hippocampal sclerosis (HS). Hippocampal and parahippocampal tissue samples from 74 patients with drug-refractory mTLE served for mtDNA analysis by multiplex PCR as well as long-range PCR, single-molecule PCR and ultra-deep sequencing of mtDNA in selected samples. Patients were sub-classified according to neuropathological findings. Semi-quantitative assessment of neuronal cell loss was performed in the hippocampal regions CA1-CA4. Inflammatory infiltrates were quantified by cell counts in the CA1, CA3 and CA4 regions from well preserved hippocampal samples (n = 33). Samples with HS showed a significantly increased frequency of a 7436-bp mtDNA deletion (p < 0.0001) and a higher proportion of somatic G>T transversions compared to mTLE patients with different histopathology. Interestingly, the number of T-lymphocytes in the hippocampal CA1, CA3 and CA4 regions was, similar to the 7436-bp mtDNA deletion, significantly increased in samples with HS compared to other subgroups. Our findings show a coincidence of HS, increased somatic G>T transversions, the presence of a specific mtDNA deletion, and increased inflammatory infiltrates. These results support the hypothesis that chronic inflammation leads to mitochondrial dysfunction by ROS-mediated mtDNA mutagenesis which promotes epileptogenesis and neuronal cell loss in patients with mTLE and HS.
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Affiliation(s)
- Elisa Volmering
- Department of Neuropathology, University of Bonn Medical Center, Bonn, Germany
| | - Pitt Niehusmann
- Department of Neuropathology, University of Bonn Medical Center, Bonn, Germany
- Department of Neuro-/Pathology, Oslo University Hospital, Oslo, Norway
| | - Viktoriya Peeva
- Division of Neurochemistry, Department of Epileptology, University Bonn Medical Center, Sigmund-Freud-Str. 25, 53105, Bonn, Germany
| | - Alexander Grote
- Department of Neurosurgery, University of Bonn Medical Center, Bonn, Germany
| | - Gábor Zsurka
- Division of Neurochemistry, Department of Epileptology, University Bonn Medical Center, Sigmund-Freud-Str. 25, 53105, Bonn, Germany
| | - Janine Altmüller
- Cologne Center for Genomics, University of Cologne, Cologne, Germany
- Institute of Human Genetics, University of Cologne, Cologne, Germany
| | - Peter Nürnberg
- Cologne Center for Genomics, University of Cologne, Cologne, Germany
| | - Albert J Becker
- Department of Neuropathology, University of Bonn Medical Center, Bonn, Germany
- Translational Epilepsy Research Section, University of Bonn Medical Center, Bonn, Germany
| | - Susanne Schoch
- Department of Neuropathology, University of Bonn Medical Center, Bonn, Germany
- Translational Epilepsy Research Section, University of Bonn Medical Center, Bonn, Germany
| | - Christian E Elger
- Division of Neurochemistry, Department of Epileptology, University Bonn Medical Center, Sigmund-Freud-Str. 25, 53105, Bonn, Germany
| | - Wolfram S Kunz
- Division of Neurochemistry, Department of Epileptology, University Bonn Medical Center, Sigmund-Freud-Str. 25, 53105, Bonn, Germany.
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Gitschlag BL, Kirby CS, Samuels DC, Gangula RD, Mallal SA, Patel MR. Homeostatic Responses Regulate Selfish Mitochondrial Genome Dynamics in C. elegans. Cell Metab 2016; 24:91-103. [PMID: 27411011 PMCID: PMC5287496 DOI: 10.1016/j.cmet.2016.06.008] [Citation(s) in RCA: 119] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 05/27/2016] [Accepted: 06/13/2016] [Indexed: 02/08/2023]
Abstract
Mutant mitochondrial genomes (mtDNA) can be viewed as selfish genetic elements that persist in a state of heteroplasmy despite having potentially deleterious metabolic consequences. We sought to study regulation of selfish mtDNA dynamics. We establish that the large 3.1-kb deletion-bearing mtDNA variant uaDf5 is a selfish genome in Caenorhabditis elegans. Next, we show that uaDf5 mutant mtDNA replicates in addition to, not at the expense of, wild-type mtDNA. These data suggest the existence of a homeostatic copy-number control that is exploited by uaDf5 to "hitchhike" to high frequency. We also observe activation of the mitochondrial unfolded protein response (UPR(mt)) in uaDf5 animals. Loss of UPR(mt) causes a decrease in uaDf5 frequency, whereas its constitutive activation increases uaDf5 levels. UPR(mt) activation protects uaDf5 from mitophagy. Taken together, we propose that mtDNA copy-number control and UPR(mt) represent two homeostatic response mechanisms that play important roles in regulating selfish mitochondrial genome dynamics.
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Affiliation(s)
- Bryan L Gitschlag
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA; Interdisciplinary Graduate Program, Vanderbilt University, Nashville, TN 37232, USA
| | - Cait S Kirby
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA; Biological Sciences Graduate Program, Vanderbilt University, Nashville, TN 37232, USA
| | - David C Samuels
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA; Vanderbilt Genetics Institute, Vanderbilt University, Nashville, TN 37232, USA
| | - Rama D Gangula
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Simon A Mallal
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Institute for Immunology and Infectious Diseases, Murdoch University, Murdoch, WA 6150, Australia
| | - Maulik R Patel
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA; Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA.
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Tsai T, St John JC. The role of mitochondrial DNA copy number, variants, and haplotypes in farm animal developmental outcome. Domest Anim Endocrinol 2016; 56 Suppl:S133-46. [PMID: 27345311 DOI: 10.1016/j.domaniend.2016.03.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 03/11/2016] [Accepted: 03/15/2016] [Indexed: 01/20/2023]
Abstract
The vast majority of cellular energy is generated through the process of oxidative phosphorylation, which takes place in the electron transport chain in the mitochondria. The electron transport chain is encoded by 2 genomes, the chromosomal and the mitochondrial genomes. Mitochondrial DNA is associated with a number of traits, which include tolerance to heat, growth and physical performance, meat and milk quality, and fertility. Mitochondrial genomes can be clustered into groups known as mtDNA haplotypes. Mitochondrial DNA haplotypes are a potential genetic source for manipulating phenotypes in farm animals. The use of assisted reproductive technologies, such as nuclear transfer, allows favorable chromosomal genetic traits to be mixed and matched with sought after mtDNA haplotype traits. As a result super breeds can be generated.
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Affiliation(s)
- Tesha Tsai
- Centre for Genetic Diseases, Hudson Institute of Medical Research, Clayton, Vic, 3168, Australia; Department of Molecular and Translational Science, Monash University, Clayton, Vic, 3168, Australia
| | - Justin C St John
- Centre for Genetic Diseases, Hudson Institute of Medical Research, Clayton, Vic, 3168, Australia; Department of Molecular and Translational Science, Monash University, Clayton, Vic, 3168, Australia.
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Wachsmuth M, Hübner A, Li M, Madea B, Stoneking M. Age-Related and Heteroplasmy-Related Variation in Human mtDNA Copy Number. PLoS Genet 2016; 12:e1005939. [PMID: 26978189 PMCID: PMC4792396 DOI: 10.1371/journal.pgen.1005939] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 02/24/2016] [Indexed: 12/17/2022] Open
Abstract
The mitochondrial (mt) genome is present in many copies in human cells, and intra-individual variation in mtDNA sequences is known as heteroplasmy. Recent studies found that heteroplasmies are highly tissue-specific, site-specific, and allele-specific, however the functional implications have not been explored. This study investigates variation in mtDNA copy numbers (mtCN) in 12 different tissues obtained at autopsy from 152 individuals (ranging in age from 3 days to 96 years). Three different methods to estimate mtCN were compared: shotgun sequencing (in 4 tissues), capture-enriched sequencing (in 12 tissues) and droplet digital PCR (ddPCR, in 2 tissues). The highest precision in mtCN estimation was achieved using shotgun sequencing data. However, capture-enrichment data provide reliable estimates of relative (albeit not absolute) mtCNs. Comparisons of mtCN from different tissues of the same individual revealed that mtCNs in different tissues are, with few exceptions, uncorrelated. Hence, each tissue of an individual seems to regulate mtCN in a tissue-related rather than an individual-dependent manner. Skeletal muscle (SM) samples showed an age-related decrease in mtCN that was especially pronounced in males, while there was an age-related increase in mtCN for liver (LIV) samples. MtCN in SM samples was significantly negatively correlated with both the total number of heteroplasmic sites and with minor allele frequency (MAF) at two heteroplasmic sites, 408 and 16327. Heteroplasmies at both sites are highly specific for SM, accumulate with aging and are part of functional elements that regulate mtDNA replication. These data support the hypothesis that selection acting on these heteroplasmic sites is reducing mtCN in SM of older individuals.
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Affiliation(s)
- Manja Wachsmuth
- Department of Evolutionary Genetics, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Alexander Hübner
- Department of Evolutionary Genetics, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | | | - Burkhard Madea
- Institut für Rechtsmedizin, Universitätsklinikum Bonn, Bonn, Germany
| | - Mark Stoneking
- Department of Evolutionary Genetics, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
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Stewart JB, Chinnery PF. The dynamics of mitochondrial DNA heteroplasmy: implications for human health and disease. Nat Rev Genet 2015; 16:530-42. [PMID: 26281784 DOI: 10.1038/nrg3966] [Citation(s) in RCA: 551] [Impact Index Per Article: 61.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Common genetic variants of mitochondrial DNA (mtDNA) increase the risk of developing several of the major health issues facing the western world, including neurodegenerative diseases. In this Review, we consider how these mtDNA variants arose and how they spread from their origin on one single molecule in a single cell to be present at high levels throughout a specific organ and, ultimately, to contribute to the population risk of common age-related disorders. mtDNA persists in all aerobic eukaryotes, despite a high substitution rate, clonal propagation and little evidence of recombination. Recent studies have found that de novo mtDNA mutations are suppressed in the female germ line; despite this, mtDNA heteroplasmy is remarkably common. The demonstration of a mammalian mtDNA genetic bottleneck explains how new germline variants can increase to high levels within a generation, and the ultimate fixation of less-severe mutations that escape germline selection explains how they can contribute to the risk of late-onset disorders.
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Affiliation(s)
- James B Stewart
- Max Planck Institute for Biology of Ageing, Cologne 50931, Germany
| | - Patrick F Chinnery
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 1BZ, UK
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Abstract
In the past century, considerable efforts were made to understand the role of mitochondrial DNA (mtDNA) mutations and of oxidative stress in aging. The classic mitochondrial free radical theory of aging, in which mtDNA mutations cause genotoxic oxidative stress, which in turn creates more mutations, has been a central hypothesis in the field for decades. In the past few years, however, new elements have discredited this original theory. The major sources of mitochondrial DNA mutations seem to be replication errors and failure of the repair mechanisms, and the accumulation of these mutations as observed in aged organisms seems to occur by clonal expansion and not to be caused by a reactive oxygen species-dependent vicious cycle. New hypotheses of how age-associated mitochondrial dysfunction may lead to aging are based on the role of reactive oxygen species as signaling molecules and on their role in mediating stress responses to age-dependent damage. Here, we review the changes that mtDNA undergoes during aging and the past and most recent hypotheses linking these changes to the tissue failure observed in aging.
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Affiliation(s)
- Milena Pinto
- Department of Neurology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Carlos T Moraes
- Department of Neurology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA; Department of Cell Biology and Anatomy, Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
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Gruber J, Chen CB, Fong S, Ng LF, Teo E, Halliwell B. Caenorhabditis elegans: What We Can and Cannot Learn from Aging Worms. Antioxid Redox Signal 2015; 23:256-79. [PMID: 25544992 DOI: 10.1089/ars.2014.6210] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
SIGNIFICANCE The nematode Caenorhabditis elegans is a widely used model organism for research into aging. However, nematodes diverged from other animals between 600 and 1300 million years ago. Beyond the intuitive impression that some aspects of aging appear to be universal, is there evidence that insights into the aging process of nematodes may be applicable to humans? RECENT ADVANCES There have been a number of results in nematodes that appear to contradict long-held beliefs about mechanisms and causes of aging. For example, ablation of several key antioxidant systems has often failed to result in lifespan shortening in C. elegans. CRITICAL ISSUES While it is clear that some central signaling pathways controlling lifespan are broadly conserved across large evolutionary distances, it is less clear to what extent downstream molecular mechanisms of aging are conserved. In this review we discuss the biology of C. elegans and mammals in the context of aging and age-dependent diseases. We consider evidence from studies that attempt to investigate basic, possibly conserved mechanisms of aging especially in the context of the free radical theory of aging. Practical points, such as the need for blinding of lifespan studies and for appropriate biomarkers, are also considered. FUTURE DIRECTIONS As data on the aging process(es) in different organisms increase, it is becoming increasingly clear that there are both conserved (public) and private aspects to aging. It is important to explore the dividing lines between these two aspects and to be aware of the large gray areas in-between.
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Affiliation(s)
- Jan Gruber
- 1 Department of Biochemistry, National University of Singapore , Singapore, Singapore .,2 Yale-NUS College , Singapore, Singapore
| | - Ce-Belle Chen
- 3 Department of Physics, National University of Singapore , Singapore, Singapore
| | - Sheng Fong
- 4 Duke-NUS Graduate Medical School , Singapore, Singapore
| | - Li Fang Ng
- 1 Department of Biochemistry, National University of Singapore , Singapore, Singapore
| | - Emelyne Teo
- 1 Department of Biochemistry, National University of Singapore , Singapore, Singapore
| | - Barry Halliwell
- 1 Department of Biochemistry, National University of Singapore , Singapore, Singapore
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MitoTALEN: A General Approach to Reduce Mutant mtDNA Loads and Restore Oxidative Phosphorylation Function in Mitochondrial Diseases. Mol Ther 2015; 23:1592-9. [PMID: 26159306 DOI: 10.1038/mt.2015.126] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 06/21/2015] [Indexed: 12/23/2022] Open
Abstract
We have designed mitochondrially targeted transcription activator-like effector nucleases or mitoTALENs to cleave specific sequences in the mitochondrial DNA (mtDNA) with the goal of eliminating mtDNA carrying pathogenic point mutations. To test the generality of the approach, we designed mitoTALENs to target two relatively common pathogenic mtDNA point mutations associated with mitochondrial diseases: the m.8344A>G tRNA(Lys) gene mutation associated with myoclonic epilepsy with ragged red fibers (MERRF) and the m.13513G>A ND5 mutation associated with MELAS/Leigh syndrome. Transmitochondrial cybrid cells harbouring the respective heteroplasmic mtDNA mutations were transfected with the respective mitoTALEN and analyzed after different time periods. MitoTALENs efficiently reduced the levels of the targeted pathogenic mtDNAs in the respective cell lines. Functional assays showed that cells with heteroplasmic mutant mtDNA were able to recover respiratory capacity and oxidative phosphorylation enzymes activity after transfection with the mitoTALEN. To improve the design in the context of the low complexity of mtDNA, we designed shorter versions of the mitoTALEN specific for the MERRF m.8344A>G mutation. These shorter mitoTALENs also eliminated the mutant mtDNA. These reductions in size will improve our ability to package these large sequences into viral vectors, bringing the use of these genetic tools closer to clinical trials.
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