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Matlosz S, Franzdóttir SR, Pálsson A, Jónsson ZO. DNA methylation reprogramming in teleosts. Evol Dev 2024:e12486. [PMID: 38783650 DOI: 10.1111/ede.12486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2023] [Revised: 04/29/2024] [Accepted: 05/14/2024] [Indexed: 05/25/2024]
Abstract
Early embryonic development is crucially important but also remarkably diverse among animal taxa. Axis formation and cell lineage specification occur due to both spatial and temporal control of gene expression. This complex system involves various signaling pathways and developmental genes such as transcription factors as well as other molecular interactants that maintain cellular states, including several types of epigenetic marks. 5mC DNA methylation, the chemical modification of cytosines in eukaryotes, represents one such mark. By influencing the compaction of chromatin (a high-order DNA structure), DNA methylation can either repress or induce transcriptional activity. Mammals exhibit a reprogramming of DNA methylation from the parental genomes in the zygote following fertilization, and later in primordial germ cells (PGCs). Whether these periods of methylation reprogramming are evolutionarily conserved, or an innovation in mammals, is an emerging question. Looking into these processes in other vertebrate lineages is thus important, and teleost fish, with their extensive species richness, phenotypic diversity, and multiple rounds of whole genome duplication, provide the perfect research playground for answering such a question. This review aims to present a concise state of the art of DNA methylation reprogramming in early development in fish by summarizing findings from different research groups investigating methylation reprogramming patterns in teleosts, while keeping in mind the ramifications of the methodology used, then comparing those patterns to reprogramming patterns in mammals.
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Affiliation(s)
- Sébastien Matlosz
- Institute of Life and Environmental Sciences, University of Iceland, Reykjavík, Iceland
| | | | - Arnar Pálsson
- Institute of Life and Environmental Sciences, University of Iceland, Reykjavík, Iceland
| | - Zophonías O Jónsson
- Institute of Life and Environmental Sciences, University of Iceland, Reykjavík, Iceland
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2
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Burr SP, Chinnery PF. Origins of tissue and cell-type specificity in mitochondrial DNA (mtDNA) disease. Hum Mol Genet 2024; 33:R3-R11. [PMID: 38779777 PMCID: PMC11112380 DOI: 10.1093/hmg/ddae059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 12/21/2023] [Accepted: 02/05/2024] [Indexed: 05/25/2024] Open
Abstract
Mutations of mitochondrial (mt)DNA are a major cause of morbidity and mortality in humans, accounting for approximately two thirds of diagnosed mitochondrial disease. However, despite significant advances in technology since the discovery of the first disease-causing mtDNA mutations in 1988, the comprehensive diagnosis and treatment of mtDNA disease remains challenging. This is partly due to the highly variable clinical presentation linked to tissue-specific vulnerability that determines which organs are affected. Organ involvement can vary between different mtDNA mutations, and also between patients carrying the same disease-causing variant. The clinical features frequently overlap with other non-mitochondrial diseases, both rare and common, adding to the diagnostic challenge. Building on previous findings, recent technological advances have cast further light on the mechanisms which underpin the organ vulnerability in mtDNA diseases, but our understanding is far from complete. In this review we explore the origins, current knowledge, and future directions of research in this area.
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Affiliation(s)
- Stephen P Burr
- Department of Clinical Neurosciences, School of Clinical Medicine, University of Cambridge, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0QQ, United Kingdom
| | - Patrick F Chinnery
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY, United Kingdom
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3
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Tarbashevich K, Ermlich L, Wegner J, Pfeiffer J, Raz E. The mitochondrial protein Sod2 is important for the migration, maintenance, and fitness of germ cells. Front Cell Dev Biol 2023; 11:1250643. [PMID: 37954204 PMCID: PMC10639133 DOI: 10.3389/fcell.2023.1250643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 10/16/2023] [Indexed: 11/14/2023] Open
Abstract
To maintain a range of cellular functions and to ensure cell survival, cells must control their levels of reactive oxygen species (ROS). The main source of these molecules is the mitochondrial respiration machinery, and the first line of defense against these toxic substances is the mitochondrial enzyme superoxide dismutase 2 (Sod2). Thus, investigating early expression patterns and functions of this protein is critical for understanding how an organism develops ways to protect itself against ROS and enhance tissue fitness. Here, we report on expression pattern and function of zebrafish Sod2, focusing on the role of the protein in migration and maintenance of primordial germ cells during early embryonic development. We provide evidence that Sod2 is involved in purifying selection of vertebrate germ cells, which can contribute to the fitness of the organism in the following generations.
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Affiliation(s)
- Katsiaryna Tarbashevich
- Institute of Cell Biology, Center for Molecular Biology of Inflammation (ZMBE), Muenster, Germany
| | - Laura Ermlich
- Institute of Cell Biology, Center for Molecular Biology of Inflammation (ZMBE), Muenster, Germany
| | - Julian Wegner
- Institute of Cell Biology, Center for Molecular Biology of Inflammation (ZMBE), Muenster, Germany
| | - Jana Pfeiffer
- Institute of Cell Biology, Center for Molecular Biology of Inflammation (ZMBE), Muenster, Germany
| | - Erez Raz
- Institute of Cell Biology, Center for Molecular Biology of Inflammation (ZMBE), Muenster, Germany
- Max Planck Institute for Molecular Biomedicine, Münster, Germany
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Ross SE, Vázquez-Marín J, Gert KRB, González-Rajal Á, Dinger ME, Pauli A, Martínez-Morales JR, Bogdanovic O. Evolutionary conservation of embryonic DNA methylome remodelling in distantly related teleost species. Nucleic Acids Res 2023; 51:9658-9671. [PMID: 37615576 PMCID: PMC10570028 DOI: 10.1093/nar/gkad695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 07/28/2023] [Accepted: 08/09/2023] [Indexed: 08/25/2023] Open
Abstract
Methylation of cytosines in the CG context (mCG) is the most abundant DNA modification in vertebrates that plays crucial roles in cellular differentiation and identity. After fertilization, DNA methylation patterns inherited from parental gametes are remodelled into a state compatible with embryogenesis. In mammals, this is achieved through the global erasure and re-establishment of DNA methylation patterns. However, in non-mammalian vertebrates like zebrafish, no global erasure has been observed. To investigate the evolutionary conservation and divergence of DNA methylation remodelling in teleosts, we generated base resolution DNA methylome datasets of developing medaka and medaka-zebrafish hybrid embryos. In contrast to previous reports, we show that medaka display comparable DNA methylome dynamics to zebrafish with high gametic mCG levels (sperm: ∼90%; egg: ∼75%), and adoption of a paternal-like methylome during early embryogenesis, with no signs of prior DNA methylation erasure. We also demonstrate that non-canonical DNA methylation (mCH) reprogramming at TGCT tandem repeats is a conserved feature of teleost embryogenesis. Lastly, we find remarkable evolutionary conservation of DNA methylation remodelling patterns in medaka-zebrafish hybrids, indicative of compatible DNA methylation maintenance machinery in far-related teleost species. Overall, these results suggest strong evolutionary conservation of DNA methylation remodelling pathways in teleosts, which is distinct from the global DNA methylome erasure and reestablishment observed in mammals.
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Affiliation(s)
- Samuel E Ross
- Garvan Institute of Medical Research, Sydney, Australia
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
- School of Life and Environmental Sciences, University of Sydney, Sydney, Australia
| | - Javier Vázquez-Marín
- Centro Andaluz de Biología del Desarrollo, CSIC-Universidad Pablo de Olavide-Junta de Andalucía, Seville, Spain
| | - Krista R B Gert
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, Vienna, Austria
- Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, A-1030, Vienna, Austria
| | - Álvaro González-Rajal
- Garvan Institute of Medical Research, Sydney, Australia
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
| | - Marcel E Dinger
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
- School of Life and Environmental Sciences, University of Sydney, Sydney, Australia
| | - Andrea Pauli
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-Biocenter 1, Vienna, Austria
| | - Juan Ramon Martínez-Morales
- Centro Andaluz de Biología del Desarrollo, CSIC-Universidad Pablo de Olavide-Junta de Andalucía, Seville, Spain
| | - Ozren Bogdanovic
- Garvan Institute of Medical Research, Sydney, Australia
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
- Centro Andaluz de Biología del Desarrollo, CSIC-Universidad Pablo de Olavide-Junta de Andalucía, Seville, Spain
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5
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Kozal JS, Jayasundara N, Massarsky A, Lindberg CD, Oliveri AN, Cooper EM, Levin ED, Meyer JN, Giulio RTD. Mitochondrial dysfunction and oxidative stress contribute to cross-generational toxicity of benzo(a)pyrene in Danio rerio. Aquat Toxicol 2023; 263:106658. [PMID: 37722151 PMCID: PMC10591944 DOI: 10.1016/j.aquatox.2023.106658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 08/06/2023] [Accepted: 08/10/2023] [Indexed: 09/20/2023]
Abstract
The potential for polycyclic aromatic hydrocarbons (PAHs) to have adverse effects that persist across generations is an emerging concern for human and wildlife health. This study evaluated the role of mitochondria, which are maternally inherited, in the cross-generational toxicity of benzo(a)pyrene (BaP), a model PAH and known mitochondrial toxicant. Mature female zebrafish (F0) were fed diets containing 0, 12.5, 125, or 1250 μg BaP/g at a feed rate of 1% body weight twice/day for 21 days. These females were bred with unexposed males, and the embryos (F1) were collected for subsequent analyses. Maternally-exposed embryos exhibited altered mitochondrial function and metabolic partitioning (i.e. the portion of respiration attributable to different cellular processes), as evidenced by in vivo oxygen consumption rates (OCRs). F1 embryos had lower basal and mitochondrial respiration and ATP turnover-mediated OCR, and increased proton leak and reserve capacity. Reductions in mitochondrial DNA (mtDNA) copy number, increases in mtDNA damage, and alterations in biomarkers of oxidative stress were also found in maternally-exposed embryos. Notably, the mitochondrial effects in offspring occurred largely in the absence of effects in maternal ovaries, suggesting that PAH-induced mitochondrial dysfunction may manifest in subsequent generations. Maternally-exposed larvae also displayed swimming hypoactivity. The lowest observed effect level (LOEL) for maternal BaP exposure causing mitochondrial effects in offspring was 12.5 µg BaP/g diet (nominally equivalent to 250 ng BaP/g fish). It was concluded that maternal BaP exposure can cause significant mitochondrial impairments in offspring.
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Affiliation(s)
- Jordan S Kozal
- Nicholas School of the Environment, Duke University, Durham, NC, USA.
| | | | - Andrey Massarsky
- Nicholas School of the Environment, Duke University, Durham, NC, USA
| | - Casey D Lindberg
- Nicholas School of the Environment, Duke University, Durham, NC, USA
| | - Anthony N Oliveri
- Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, NC, USA
| | - Ellen M Cooper
- Nicholas School of the Environment, Duke University, Durham, NC, USA
| | - Edward D Levin
- Nicholas School of the Environment, Duke University, Durham, NC, USA; Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, NC, USA; Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC, USA
| | - Joel N Meyer
- Nicholas School of the Environment, Duke University, Durham, NC, USA
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Kim SY, Chiara V, Álvarez-Quintero N, da Silva A, Velando A. Maternal effect senescence via reduced DNA repair ability in the three-spined stickleback. Mol Ecol 2023; 32:4648-4659. [PMID: 37291748 DOI: 10.1111/mec.17046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 05/24/2023] [Accepted: 05/30/2023] [Indexed: 06/10/2023]
Abstract
Maternal effect senescence, a decline in offspring viability with maternal age, has been documented across diverse animals, but its mechanisms remain largely unknown. Here, we test maternal effect senescence and explore its possible molecular mechanisms in a fish. We compared the levels of maternal mRNA transcripts of DNA repair genes and mtDNA copies in eggs and the levels of DNA damage in somatic and germline tissues between young and old female sticklebacks. We also tested, in an in vitro fertilization experiment, whether maternal age and sperm DNA damage level interactively influence the expression of DNA repair genes in early embryos. Old females transferred less mRNA transcripts of DNA repair genes into their eggs than did young females, but maternal age did not influence egg mtDNA density. Despite a higher level of oxidative DNA damage in the skeletal muscle, old females had a similar level of damage in the gonad to young females, suggesting the prioritization for germline maintenance during ageing. The embryos of both old and young mothers increased the expression of DNA repair genes in response to an increased level of oxidative DNA damage in sperm used for their fertilization. The offspring of old mothers showed higher rates of hatching, morphological deformity and post-hatching mortality and had smaller body size at maturity. These results suggest that maternal effect senescence may be mediated by reduced capacity of eggs to detect and repair DNA damages, especially prior to the embryonic genomic activation.
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Affiliation(s)
- Sin-Yeon Kim
- Grupo Ecoloxía Animal, Torre CACTI, Centro de Investigación Mariña, Universidade de Vigo, Vigo, Spain
| | - Violette Chiara
- Grupo Ecoloxía Animal, Torre CACTI, Centro de Investigación Mariña, Universidade de Vigo, Vigo, Spain
| | - Náyade Álvarez-Quintero
- Grupo Ecoloxía Animal, Torre CACTI, Centro de Investigación Mariña, Universidade de Vigo, Vigo, Spain
- Department of Biology, University of Padova, Padova, Italy
| | - Alberto da Silva
- Grupo Ecoloxía Animal, Torre CACTI, Centro de Investigación Mariña, Universidade de Vigo, Vigo, Spain
| | - Alberto Velando
- Grupo Ecoloxía Animal, Torre CACTI, Centro de Investigación Mariña, Universidade de Vigo, Vigo, Spain
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7
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Abstract
Mitochondrial diseases require customized approaches for reproductive counseling, addressing differences in recurrence risks and reproductive options. The majority of mitochondrial diseases is caused by mutations in nuclear genes and segregate in a Mendelian way. Prenatal diagnosis (PND) or preimplantation genetic testing (PGT) are available to prevent the birth of another severely affected child. In at least 15%-25% of cases, mitochondrial diseases are caused by mitochondrial DNA (mtDNA) mutations, which can occur de novo (25%) or be maternally inherited. For de novo mtDNA mutations, the recurrence risk is low and PND can be offered for reassurance. For maternally inherited, heteroplasmic mtDNA mutations, the recurrence risk is often unpredictable, due to the mitochondrial bottleneck. PND for mtDNA mutations is technically possible, but often not applicable given limitations in predicting the phenotype. Another option for preventing the transmission of mtDNA diseases is PGT. Embryos with mutant load below the expression threshold are being transferred. Oocyte donation is another safe option to prevent the transmission of mtDNA disease to a future child for couples who reject PGT. Recently, mitochondrial replacement therapy (MRT) became available for clinical application as an alternative to prevent the transmission of heteroplasmic and homoplasmic mtDNA mutations.
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8
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Radzvilavicius AL, Johnston IG. Organelle bottlenecks facilitate evolvability by traversing heteroplasmic fitness valleys. Front Genet 2022; 13:974472. [DOI: 10.3389/fgene.2022.974472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Accepted: 10/11/2022] [Indexed: 11/13/2022] Open
Abstract
Bioenergetic organelles—mitochondria and plastids—retain their own genomes (mtDNA and ptDNA), and these organelle DNA (oDNA) molecules are vital for eukaryotic life. Like all genomes, oDNA must be able to evolve to suit new environmental challenges. However, mixed oDNA populations in cells can challenge cellular bioenergetics, providing a penalty to the appearance and adaptation of new mutations. Here we show that organelle “bottlenecks,” mechanisms increasing cell-to-cell oDNA variability during development, can overcome this mixture penalty and facilitate the adaptation of beneficial mutations. We show that oDNA heteroplasmy and bottlenecks naturally emerge in evolutionary simulations subjected to fluctuating environments, demonstrating that this evolvability is itself evolvable. Usually thought of as a mechanism to clear damaging mutations, organelle bottlenecks therefore also resolve the tension between intracellular selection for pure cellular oDNA populations and the “bet-hedging” need for evolvability and adaptation to new environments. This general theory suggests a reason for the maintenance of organelle heteroplasmy in cells, and may explain some of the observed diversity in organelle maintenance and inheritance across taxa.
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Schwartz AZA, Tsyba N, Abdu Y, Patel MR, Nance J. Independent regulation of mitochondrial DNA quantity and quality in Caenorhabditis elegans primordial germ cells. eLife 2022; 11:e80396. [PMID: 36200990 PMCID: PMC9536838 DOI: 10.7554/elife.80396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 09/15/2022] [Indexed: 11/13/2022] Open
Abstract
Mitochondria harbor an independent genome, called mitochondrial DNA (mtDNA), which contains essential metabolic genes. Although mtDNA mutations occur at high frequency, they are inherited infrequently, indicating that germline mechanisms limit their accumulation. To determine how germline mtDNA is regulated, we examined the control of mtDNA quantity and quality in C. elegans primordial germ cells (PGCs). We show that PGCs combine strategies to generate a low point in mtDNA number by segregating mitochondria into lobe-like protrusions that are cannibalized by adjacent cells, and by concurrently eliminating mitochondria through autophagy, reducing overall mtDNA content twofold. As PGCs exit quiescence and divide, mtDNAs replicate to maintain a set point of ~200 mtDNAs per germline stem cell. Whereas cannibalism and autophagy eliminate mtDNAs stochastically, we show that the kinase PTEN-induced kinase 1 (PINK1), operating independently of Parkin and autophagy, preferentially reduces the fraction of mutant mtDNAs. Thus, PGCs employ parallel mechanisms to control both the quantity and quality of the founding population of germline mtDNAs.
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Affiliation(s)
- Aaron ZA Schwartz
- Department of Cell Biology, NYU Grossman School of MedicineNew YorkUnited States
- Skirball Institute of Biomolecular Medicine, NYU Grossman School of MedicineNew YorkUnited States
| | - Nikita Tsyba
- Department of Biological Sciences, Vanderbilt UniversityNashvilleUnited States
| | - Yusuff Abdu
- Department of Cell Biology, NYU Grossman School of MedicineNew YorkUnited States
- Skirball Institute of Biomolecular Medicine, NYU Grossman School of MedicineNew YorkUnited States
| | - Maulik R Patel
- Department of Biological Sciences, Vanderbilt UniversityNashvilleUnited States
- Department of Cell and Developmental Biology, Vanderbilt University School of MedicineNashvilleUnited States
- Diabetes Research and Training Center, Vanderbilt University School of MedicineNashvilleUnited States
| | - Jeremy Nance
- Department of Cell Biology, NYU Grossman School of MedicineNew YorkUnited States
- Skirball Institute of Biomolecular Medicine, NYU Grossman School of MedicineNew YorkUnited States
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Schaffner SH, Patel MR. Plant organellar genomes utilize gene conversion to drive heteroplasmic sorting. Proc Natl Acad Sci U S A 2022; 119:e2213014119. [PMID: 36044538 PMCID: PMC9477390 DOI: 10.1073/pnas.2213014119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Samantha H. Schaffner
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232
- Evolutionary Studies, Vanderbilt University, Nashville, TN 37235
| | - Maulik R. Patel
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232
- Evolutionary Studies, Vanderbilt University, Nashville, TN 37235
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232
- Diabetes Research and Training Center, Vanderbilt University Medical Center, Nashville, TN 37232
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Broz AK, Keene A, Fernandes Gyorfy M, Hodous M, Johnston IG, Sloan DB. Sorting of mitochondrial and plastid heteroplasmy in Arabidopsis is extremely rapid and depends on MSH1 activity. Proc Natl Acad Sci U S A 2022; 119:e2206973119. [PMID: 35969753 PMCID: PMC9407294 DOI: 10.1073/pnas.2206973119] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 07/11/2022] [Indexed: 12/16/2022] Open
Abstract
The fate of new mitochondrial and plastid mutations depends on their ability to persist and spread among the numerous organellar genome copies within a cell (heteroplasmy). The extent to which heteroplasmies are transmitted across generations or eliminated through genetic bottlenecks is not well understood in plants, in part because their low mutation rates make these variants so infrequent. Disruption of MutS Homolog 1 (MSH1), a gene involved in plant organellar DNA repair, results in numerous de novo point mutations, which we used to quantitatively track the inheritance of single nucleotide variants in mitochondrial and plastid genomes in Arabidopsis. We found that heteroplasmic sorting (the fixation or loss of a variant) was rapid for both organelles, greatly exceeding rates observed in animals. In msh1 mutants, plastid variants sorted faster than those in mitochondria and were typically fixed or lost within a single generation. Effective transmission bottleneck sizes (N) for plastids and mitochondria were N ∼ 1 and 4, respectively. Restoring MSH1 function further increased the rate of heteroplasmic sorting in mitochondria (N ∼ 1.3), potentially because of its hypothesized role in promoting gene conversion as a mechanism of DNA repair, which is expected to homogenize genome copies within a cell. Heteroplasmic sorting also favored GC base pairs. Therefore, recombinational repair and gene conversion in plant organellar genomes can potentially accelerate the elimination of heteroplasmies and bias the outcome of this sorting process.
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Affiliation(s)
- Amanda K. Broz
- Department of Biology, Colorado State University, Fort Collins, CO 80523
| | - Alexandra Keene
- Department of Biology, Colorado State University, Fort Collins, CO 80523
| | | | - Mychaela Hodous
- Department of Biology, Colorado State University, Fort Collins, CO 80523
| | - Iain G. Johnston
- Department of Mathematics, University of Bergen, Bergen, 5007, Norway
- Computational Biology Unit, University of Bergen, Bergen, 5007, Norway
| | - Daniel B. Sloan
- Department of Biology, Colorado State University, Fort Collins, CO 80523
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12
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Kim SY, Chiara V, Álvarez-Quintero N, Velando A. Mitochondrial DNA content in eggs as a maternal effect. Proc Biol Sci 2022; 289:20212100. [PMID: 35042411 PMCID: PMC8767187 DOI: 10.1098/rspb.2021.2100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 12/13/2021] [Indexed: 01/28/2023] Open
Abstract
The transmission of detrimental mutations in animal mitochondrial DNA (mtDNA) to the next generation is avoided by a high level of mtDNA content in mature oocytes. Thus, this maternal genetic material has the potential to mediate adaptive maternal effects if mothers change mtDNA level in oocytes in response to their environment or body condition. Here, we show that increased mtDNA abundance in mature oocytes was associated with fast somatic growth during early development but at the cost of increased mortality in three-spined sticklebacks. We also examined whether oocyte mtDNA and sperm DNA damage levels have interacting effects because they can determine the integrity of mitochondrial and nuclear genes in offspring. The level of oxidative DNA damage in sperm negatively affected fertility, but there was no interacting effect of oocyte mtDNA abundance and sperm DNA damage. Oocyte mtDNA level increased towards the end of the breeding season, and the females exposed to warmer temperatures during winter produced eggs with increased mtDNA copies. Our results suggest that oocyte mtDNA level can vary according to the expected energy demands for offspring during embryogenesis and early growth. Thus, mothers can affect offspring development and viability through the context-dependent effects of oocyte mtDNA abundance.
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Affiliation(s)
- Sin-Yeon Kim
- Grupo Ecoloxía Animal, Torre CACTI, Centro de Investigación Mariña, Universidade de Vigo, 36310 Vigo, Spain
| | - Violette Chiara
- Grupo Ecoloxía Animal, Torre CACTI, Centro de Investigación Mariña, Universidade de Vigo, 36310 Vigo, Spain
| | - Náyade Álvarez-Quintero
- Grupo Ecoloxía Animal, Torre CACTI, Centro de Investigación Mariña, Universidade de Vigo, 36310 Vigo, Spain
| | - Alberto Velando
- Grupo Ecoloxía Animal, Torre CACTI, Centro de Investigación Mariña, Universidade de Vigo, 36310 Vigo, Spain
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13
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Li B, Kalinowski P, Kim B, Pauls AD, Poburko D. Emerging methods for and novel insights gained by absolute quantification of mitochondrial DNA copy number and its clinical applications. Pharmacol Ther 2021;:107995. [PMID: 34592204 DOI: 10.1016/j.pharmthera.2021.107995] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 08/26/2021] [Accepted: 09/01/2021] [Indexed: 02/07/2023]
Abstract
The past thirty years have seen a surge in interest in pathophysiological roles of mitochondria, and the accurate quantification of mitochondrial DNA copy number (mCN) in cells and tissue samples is a fundamental aspect of assessing changes in mitochondrial health and biogenesis. Quantification of mCN between studies is surprisingly variable due to a combination of physiological variability and diverse protocols being used to measure this endpoint. The advent of novel methods to quantify nucleic acids like digital polymerase chain reaction (dPCR) and high throughput sequencing offer the ability to measure absolute values of mCN. We conducted an in-depth survey of articles published between 1969 -- 2020 to create an overview of mCN values, to assess consensus values of tissue-specific mCN, and to evaluate consistency between methods of assessing mCN. We identify best practices for methods used to assess mCN, and we address the impact of using specific loci on the mitochondrial genome to determine mCN. Current data suggest that clinical measurement of mCN can provide diagnostic and prognostic value in a range of diseases and health conditions, with emphasis on cancer and cardiovascular disease, and the advent of means to measure absolute mCN should improve future clinical applications of mCN measurements.
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14
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Pezet MG, Gomez-Duran A, Klimm F, Aryaman J, Burr S, Wei W, Saitou M, Prudent J, Chinnery PF. Oxygen tension modulates the mitochondrial genetic bottleneck and influences the segregation of a heteroplasmic mtDNA variant in vitro. Commun Biol 2021; 4:584. [PMID: 33990696 DOI: 10.1038/s42003-021-02069-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 03/31/2021] [Indexed: 12/30/2022] Open
Abstract
Most humans carry a mixed population of mitochondrial DNA (mtDNA heteroplasmy) affecting ~1–2% of molecules, but rapid percentage shifts occur over one generation leading to severe mitochondrial diseases. A decrease in the amount of mtDNA within the developing female germ line appears to play a role, but other sub-cellular mechanisms have been implicated. Establishing an in vitro model of early mammalian germ cell development from embryonic stem cells, here we show that the reduction of mtDNA content is modulated by oxygen and reaches a nadir immediately before germ cell specification. The observed genetic bottleneck was accompanied by a decrease in mtDNA replicating foci and the segregation of heteroplasmy, which were both abolished at higher oxygen levels. Thus, differences in oxygen tension occurring during early development likely modulate the amount of mtDNA, facilitating mtDNA segregation and contributing to tissue-specific mutation loads. Using an in vitro culture system, Pezet et al. studied the influence of oxygen on the mitochondrial DNA (mtDNA) in primordial germ cell-like cells (PGCLCs) in vitro. Low oxygen levels resembling in vivo reduced the cell mtDNA content causing a genetic bottleneck and the segregation of different mtDNA genotypes.
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15
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Abstract
Mitochondrial disorders make up a large class of heritable diseases that cause a broad array of different human pathologies. They can affect many different organ systems, or display very specific tissue presentation, and can lead to illness either in childhood or later in life. While the over 1200 genes encoded in the nuclear DNA play an important role in human mitochondrial disease, it has been known for over 30 years that mutations of the mitochondria's own small, multicopy DNA chromosome (mtDNA) can lead to heritable human diseases. Unfortunately, animal mtDNA has resisted transgenic and directed genome editing technologies until quite recently. As such, animal models to aid in our understanding of these diseases, and to explore preclinical therapeutic research have been quite rare. This review will discuss the unusual properties of animal mitochondria that have hindered the generation of animal models. It will also discuss the existing mammalian models of human mtDNA disease, describe the methods employed in their generation, and will discuss recent advances in the targeting of DNA-manipulating enzymes to the mitochondria and how these may be employed to generate new models.
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Affiliation(s)
- James Bruce Stewart
- Max Planck Institute for Biology of Ageing, Cologne, Germany
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
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16
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Kang J, Zhou H, Sun F, Chen Y, Zhao J, Yang WJ, Xu S, Chen C. Caenorhabditis elegans homologue of Fam210 is required for oogenesis and reproduction. J Genet Genomics 2020; 47:694-704. [PMID: 33547005 DOI: 10.1016/j.jgg.2020.10.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 09/11/2020] [Accepted: 10/16/2020] [Indexed: 11/30/2022]
Abstract
Mitochondria are the central hub for many metabolic processes, including the citric acid cycle, oxidative phosphorylation, and fatty acid oxidation. Recent studies have identified a new mitochondrial protein family, Fam210, that regulates bone metabolism and red cell development in vertebrates. The model organism Caenorhabditis elegans has a Fam210 gene, y56a3a.22, but it lacks both bones and red blood cells. In this study, we report that Y56A3A.22 plays a crucial role in regulating mitochondrial protein homeostasis and reproduction. The nematode y56a3a.22 is expressed in various tissues, including the intestine, muscle, hypodermis, and germline, and its encoded protein is predominantly localized in mitochondria. y56a3a.22 deletion mutants are sterile owing to impaired oogenesis. Loss of Y56A3A.22 induced mitochondrial unfolded protein response (UPRmt), which is mediated through the ATFS-1-dependent pathway, in tissues such as the intestine, germline, hypodermis, and vulval muscle. We further show that infertility and UPRmt induces by Y56A3A.22 deficiency are not attributed to systemic iron deficiency. Together, our study reveals an important role of Y56A3A.22 in regulating mitochondrial protein homeostasis and oogenesis and provides a new genetic tool for exploring the mechanisms regulating mitochondrial metabolism and reproduction as well as the fundamental role of the Fam210 family.
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Affiliation(s)
- Jing Kang
- MOE Key Laboratory of Biosystems Homeostasis and Protection, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Hengda Zhou
- Center for Stem Cell and Regenerative Medicine and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Fengxiu Sun
- MOE Key Laboratory of Biosystems Homeostasis and Protection, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Yongtian Chen
- MOE Key Laboratory of Biosystems Homeostasis and Protection, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Jianzhi Zhao
- Center for Stem Cell and Regenerative Medicine and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Wei-Jun Yang
- MOE Key Laboratory of Biosystems Homeostasis and Protection, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Suhong Xu
- Center for Stem Cell and Regenerative Medicine and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Caiyong Chen
- MOE Key Laboratory of Biosystems Homeostasis and Protection, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
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17
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Babich R, Ulrich JC, Ekanayake EMDV, Massarsky A, De Silva PMCS, Manage PM, Jackson BP, Ferguson PL, Di Giulio RT, Drummond IA, Jayasundara N. Kidney developmental effects of metal-herbicide mixtures: Implications for chronic kidney disease of unknown etiology. Environ Int 2020; 144:106019. [PMID: 32818823 DOI: 10.1016/j.envint.2020.106019] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 07/24/2020] [Accepted: 07/28/2020] [Indexed: 06/11/2023]
Abstract
Chronic kidney disease of unknown etiology (CKDu) is an emerging global concern affecting several agricultural communities in the Americas and South Asia. Environmental contaminants such as heavy metals (e.g., Cd, As, Pb, and V) and organic pesticides (e.g., glyphosate) in the drinking water have been hypothesized to play a role in childhood onset and progression of this disease. However, a comprehensive analysis of chemical contaminants in the drinking water and effects of these compounds and their mixtures on kidney development and function remains unknown. Here, we conducted targeted and non-targeted chemical analyses of sediment and drinking water in CKDu affected regions in Sri Lanka, one of the most affected countries. Using zebrafish Danio rerio, a toxicology and kidney disease model, we then examined kidney developmental effects of exposure to (i) environmentally derived samples from CKDu endemic and non-endemic regions and (ii) Cd, As, V, Pb, and glyphosate as individual compounds and in mixtures. We found that drinking water is contaminated with various organic chemicals including nephrotoxic compounds as well as heavy metals, but at levels considered safe for drinking. Histological studies and gene expression analyses examining markers of kidney development (pax2a) and kidney injury (kim1) showed novel metal and glyphosate-metal mixture specific effects on kidney development. Mitochondrial dysfunction is directly linked to kidney failure, and examination of mixture specific mitochondrial toxicity showed altered mitochondrial function following treatment with environmental samples from endemic regions. Collectively, we show that metals in drinking water, even at safe levels, can impede kidney development at an early age, potentiating increased susceptibility to other agrochemicals such as glyphosate. Drinking water contaminant effects on mitochondria can further contribute to progression of kidney dysfunction and our mitochondrial assay may help identify regions at risk of CKDu.
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Affiliation(s)
- Remy Babich
- Department of Molecular and Biomedical Sciences, University of Maine, Orono, ME 04469, USA.
| | - Jake C Ulrich
- Civil and Environmental Engineering, Duke University, Durham, NC 27708, USA
| | | | - Andrey Massarsky
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA; Cardno ChemRisk, Aliso Viejo, CA 92656, USA
| | | | - Pathmalal M Manage
- Centre for Water Quality and Algae Research, Department of Zoology, University of Sri Jayewardenepura, Gangodawila, Nugegoda, Sri Lanka
| | - Brian P Jackson
- Department of Earth Sciences, Dartmouth College, Hanover, NH 03755, USA
| | - P Lee Ferguson
- Civil and Environmental Engineering, Duke University, Durham, NC 27708, USA
| | | | - Iain A Drummond
- Mount Desert Island Biological Laboratory, Bar Harbor, ME 04609, USA
| | - Nishad Jayasundara
- Department of Molecular and Biomedical Sciences, University of Maine, Orono, ME 04469, USA; Nicholas School of the Environment, Duke University, Durham, NC 27708, USA; School of Marine Sciences, University of Maine, Orono, ME 04469, USA
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18
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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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19
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Lubośny M, Przyłucka A, Śmietanka B, Burzyński A. Semimytilus algosus: first known hermaphroditic mussel with doubly uniparental inheritance of mitochondrial DNA. Sci Rep 2020; 10:11256. [PMID: 32647112 PMCID: PMC7347871 DOI: 10.1038/s41598-020-67976-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 06/11/2020] [Indexed: 11/08/2022] Open
Abstract
Doubly uniparental inheritance (DUI) of mitochondrial DNA is a rare phenomenon occurring in some freshwater and marine bivalves and is usually characterized by the mitochondrial heteroplasmy of male individuals. Previous research on freshwater Unionida mussels showed that hermaphroditic species do not have DUI even if their closest gonochoristic counterparts do. No records showing DUI in a hermaphrodite have ever been reported. Here we show for the first time that the hermaphroditic mussel Semimytilus algosus (Mytilida), very likely has DUI, based on the complete sequences of both mitochondrial DNAs and the distribution of mtDNA types between male and female gonads. The two mitogenomes show considerable divergence (34.7%). The presumably paternal M type mitogenome dominated the male gonads of most studied mussels, while remaining at very low or undetectable levels in the female gonads of the same individuals. If indeed DUI can function in the context of simultaneous hermaphroditism, a change of paradigm regarding its involvement in sex determination is needed. It is apparently associated with gonadal differentiation rather than with sex determination in bivalves.
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Affiliation(s)
- Marek Lubośny
- Department of Genetics and Marine Biotechnology, Institute of Oceanology Polish Academy of Sciences, Sopot, Poland.
| | - Aleksandra Przyłucka
- Department of Genetics and Marine Biotechnology, Institute of Oceanology Polish Academy of Sciences, Sopot, Poland
| | - Beata Śmietanka
- Department of Genetics and Marine Biotechnology, Institute of Oceanology Polish Academy of Sciences, Sopot, Poland
| | - Artur Burzyński
- Department of Genetics and Marine Biotechnology, Institute of Oceanology Polish Academy of Sciences, Sopot, Poland
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20
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Babich R, Hamlin H, Thayer L, Dorr M, Wei Z, Neilson A, Jayasundara N. Mitochondrial response and resilience to anthropogenic chemicals during embryonic development. Comp Biochem Physiol C Toxicol Pharmacol 2020; 233:108759. [PMID: 32259593 DOI: 10.1016/j.cbpc.2020.108759] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 03/27/2020] [Accepted: 03/31/2020] [Indexed: 12/28/2022]
Abstract
Mitochondria are integral to maintaining cellular homeostasis. Optimum mitochondrial function is critical during embryonic development, as they play a key role in early signaling cascades and epigenetic programming, in addition to sustaining an adequate energy production. Mitochondria are sensitive targets of environmental toxins, potentially even at levels considered safe under current regulatory limits. Most mitochondrial analyses have focused only on chemical exposure effects in vitro or in isolated mitochondria. However, comparatively little is known about mitochondrial effects of chemical exposure during vertebrate embryogenesis, especially during the recovery phase following a chemical insult. Here, we used the zebrafish (Danio rerio), in a 96-well plate system, to examine mitochondrial effects of 24 chemicals including pharmaceuticals, industrial chemicals, and agrochemicals. We used oxygen consumption rate (OCR) during embryogenesis as a proxy for mitochondrial function. Embryonic OCR (eOCR) was measured in clean egg water immediately following 24 h of chemical exposure and subsequently for an additional 8 h. Each chemical, dependent upon the concentration, resulted in a unique eOCR response profile. While some eOCR effects were persistent or recoverable over time, some effects were only detected several hours after being removed from the exposure. Non-monotonic dose response effects as well as mitochondrial hormesis were also detected following exposure to some chemicals. Collectively, our study shows that mitochondrial response to chemicals are highly dynamic and warrant careful consideration when determining mitochondrial toxicity of a given chemical.
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Affiliation(s)
- Remy Babich
- The School of Marine Sciences, University of Maine, Orono, ME 04469, USA.
| | - Heather Hamlin
- The School of Marine Sciences, University of Maine, Orono, ME 04469, USA
| | - LeeAnne Thayer
- The School of Marine Sciences, University of Maine, Orono, ME 04469, USA
| | - Madeline Dorr
- The Department of Mathematics and Statistics, University of Maine, Orono, ME, 04469, USA
| | - Zheng Wei
- The Department of Mathematics and Statistics, University of Maine, Orono, ME, 04469, USA
| | | | - Nishad Jayasundara
- The School of Marine Sciences, University of Maine, Orono, ME 04469, USA
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21
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Otten ABC, Kamps R, Lindsey P, Gerards M, Pendeville-Samain H, Muller M, van Tienen FHJ, Smeets HJM. Tfam Knockdown Results in Reduction of mtDNA Copy Number, OXPHOS Deficiency and Abnormalities in Zebrafish Embryos. Front Cell Dev Biol 2020; 8:381. [PMID: 32596237 PMCID: PMC7303330 DOI: 10.3389/fcell.2020.00381] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 04/27/2020] [Indexed: 11/13/2022] Open
Abstract
High mitochondrial DNA (mtDNA) copy numbers are essential for oogenesis and embryogenesis and correlate with fertility of oocytes and viability of embryos. To understand the pathology and mechanisms associated with low mtDNA copy numbers, we knocked down mitochondrial transcription factor A (tfam), a regulator of mtDNA replication, during early zebrafish development. Reduction of tfam using a splice-modifying morpholino (MO) resulted in a 42 ± 17% decrease in mtDNA copy number in embryos at 4 days post fertilization. Morphant embryos displayed abnormal development of the eye, brain, heart, and muscle, as well as a 50 ± 22% decrease in ATP production. Transcriptome analysis revealed a decrease in protein-encoding transcripts from the heavy strand of the mtDNA, and down-regulation of genes involved in haem production and the metabolism of metabolites, which appear to trigger increased rRNA and tRNA synthesis in the nucleoli. However, this stress or compensatory response appears to fall short as pathology emerges and expression of genes related to eye development are severely down-regulated. Taken together, this study highlights the importance of sufficient mtDNA copies for early zebrafish development. Zebrafish is an excellent model to manipulate the mtDNA bottleneck and study its effect on embryogenesis rapidly and in large numbers of offspring.
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Affiliation(s)
- Auke B. C. Otten
- Department of Genetics and Cell Biology, Maastricht University, Maastricht, Netherlands
- Department of Dermatology, University of California, San Diego, La Jolla, CA, United States
- School for Oncology and Developmental Biology (GROW), Maastricht University Medical Centre, Maastricht, Netherlands
| | - Rick Kamps
- Department of Genetics and Cell Biology, Maastricht University, Maastricht, Netherlands
- School for Mental Health and Neurosciences (MHeNS), Maastricht University Medical Centre, Maastricht, Netherlands
| | - Patrick Lindsey
- Department of Genetics and Cell Biology, Maastricht University, Maastricht, Netherlands
- School for Oncology and Developmental Biology (GROW), Maastricht University Medical Centre, Maastricht, Netherlands
| | - Mike Gerards
- Maastricht Centre for Systems Biology (MaCSBio), Maastricht University Medical Centre, Maastricht, Netherlands
| | | | - Marc Muller
- Laboratory of Organogenesis and Regeneration, Univérsité Liège, Liège, Belgium
| | - Florence H. J. van Tienen
- Department of Genetics and Cell Biology, Maastricht University, Maastricht, Netherlands
- School for Mental Health and Neurosciences (MHeNS), Maastricht University Medical Centre, Maastricht, Netherlands
| | - Hubert J. M. Smeets
- Department of Genetics and Cell Biology, Maastricht University, Maastricht, Netherlands
- School for Oncology and Developmental Biology (GROW), Maastricht University Medical Centre, Maastricht, Netherlands
- School for Mental Health and Neurosciences (MHeNS), Maastricht University Medical Centre, Maastricht, Netherlands
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22
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Ortega-Recalde O, Hore TA. DNA methylation in the vertebrate germline: balancing memory and erasure. Essays Biochem 2019; 63:649-61. [PMID: 31755927 DOI: 10.1042/EBC20190038] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 10/02/2019] [Accepted: 10/03/2019] [Indexed: 02/07/2023]
Abstract
Cytosine methylation is a DNA modification that is critical for vertebrate development and provides a plastic yet stable information module in addition to the DNA code. DNA methylation memory establishment, maintenance and erasure is carefully balanced by molecular machinery highly conserved among vertebrates. In mammals, extensive erasure of epigenetic marks, including 5-methylcytosine (5mC), is a hallmark of early embryo and germline development. Conversely, global cytosine methylation patterns are preserved in at least some non-mammalian vertebrates over comparable developmental windows. The evolutionary mechanisms which drove this divergence are unknown, nevertheless a direct consequence of retaining epigenetic memory in the form of 5mC is the enhanced potential for transgenerational epigenetic inheritance (TEI). Given that DNA methylation dynamics remains underexplored in most vertebrate lineages, the extent of information transferred to offspring by epigenetic modification might be underestimated.
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23
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Wei W, Chinnery PF. Inheritance of mitochondrial DNA in humans: implications for rare and common diseases. J Intern Med 2020; 287:634-644. [PMID: 32187761 PMCID: PMC8641369 DOI: 10.1111/joim.13047] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2019] [Revised: 11/01/2019] [Accepted: 12/10/2019] [Indexed: 12/27/2022]
Abstract
The first draft human mitochondrial DNA (mtDNA) sequence was published in 1981, paving the way for two decades of discovery linking mtDNA variation with human disease. Severe pathogenic mutations cause sporadic and inherited rare disorders that often involve the nervous system. However, some mutations cause mild organ-specific phenotypes that have a reduced clinical penetrance, and polymorphic variation of mtDNA is associated with an altered risk of developing several late-onset common human diseases including Parkinson's disease. mtDNA mutations also accumulate during human life and are enriched in affected organs in a number of age-related diseases. Thus, mtDNA contributes to a wide range of human pathologies. For many decades, it has generally been accepted that mtDNA is inherited exclusively down the maternal line in humans. Although recent evidence has challenged this dogma, whole-genome sequencing has identified nuclear-encoded mitochondrial sequences (NUMTs) that can give the false impression of paternally inherited mtDNA. This provides a more likely explanation for recent reports of 'bi-parental inheritance', where the paternal alleles are actually transmitted through the nuclear genome. The presence of both mutated and wild-type variant alleles within the same individual (heteroplasmy) and rapid shifts in allele frequency can lead to offspring with variable severity of disease. In addition, there is emerging evidence that selection can act for and against specific mtDNA variants within the developing germ line, and possibly within developing tissues. Thus, understanding how mtDNA is inherited has far-reaching implications across medicine. There is emerging evidence that this highly dynamic system is amenable to therapeutic manipulation, raising the possibility that we can harness new understanding to prevent and treat rare and common human diseases where mtDNA mutations play a key role.
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Affiliation(s)
- W Wei
- From the, Department of Clinical Neurosciences, School of Clinical Medicine, University of Cambridge, Cambridge, UK.,Medical Research Council Mitochondrial Biology Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
| | - P F Chinnery
- From the, Department of Clinical Neurosciences, School of Clinical Medicine, University of Cambridge, Cambridge, UK.,Medical Research Council Mitochondrial Biology Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK
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24
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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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Johnston IG, Burgstaller JP. Evolving mtDNA populations within cells. Biochem Soc Trans 2019; 47:1367-82. [PMID: 31484687 DOI: 10.1042/BST20190238] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 08/06/2019] [Accepted: 08/08/2019] [Indexed: 12/14/2022]
Abstract
Mitochondrial DNA (mtDNA) encodes vital respiratory machinery. Populations of mtDNA molecules exist in most eukaryotic cells, subject to replication, degradation, mutation, and other population processes. These processes affect the genetic makeup of cellular mtDNA populations, changing cell-to-cell distributions, means, and variances of mutant mtDNA load over time. As mtDNA mutant load has nonlinear effects on cell functionality, and cell functionality has nonlinear effects on tissue performance, these statistics of cellular mtDNA populations play vital roles in health, disease, and inheritance. This mini review will describe some of the better-known ways in which these populations change over time in different organisms, highlighting the importance of quantitatively understanding both mutant load mean and variance. Due to length constraints, we cannot attempt to be comprehensive but hope to provide useful links to some of the many excellent studies on these topics.
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26
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Abstract
Mitochondrial DNA (mtDNA) molecules exist in populations within cells, and may carry mutations. Different cells within an organism, and organisms within a family, may have different proportions of mutant mtDNA in these cellular populations. This diversity is often thought of as arising from a “genetic bottleneck.” This article surveys approaches to characterize and model the generation of this genetic diversity, aiming to provide an introduction to the range of concepts involved, and to highlight some recent advances in understanding. In particular, differences between the statistical “genetic bottleneck” (mutant proportion spread) and the physical mtDNA bottleneck and other cellular processes are highlighted. Particular attention is paid to the quantitative analysis of the “genetic bottleneck,” estimation of its magnitude from observed data, and inference of its underlying mechanisms. Evidence that the “genetic bottleneck” (mutant proportion spread) varies with age, between individuals and species, and across mtDNA sequences, is described. The interpretation issues that arise from sampling errors, selection, and different quantitative definitions are also discussed.
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Affiliation(s)
- Iain G Johnston
- Department of Mathematics, Faculty of Mathematics and Natural Sciences, University of Bergen, Bergen, Norway
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27
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Poulton J, Steffann J, Burgstaller J, McFarland R. 243rd ENMC international workshop: Developing guidelines for management of reproductive options for families with maternally inherited mtDNA disease, Amsterdam, the Netherlands, 22–24 March 2019. Neuromuscul Disord 2019; 29:725-733. [DOI: 10.1016/j.nmd.2019.08.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 08/13/2019] [Indexed: 01/13/2023]
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28
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Zhang X, Li X, Li R, Zhang Y, Li Y, Li S. Transcriptomic profile of early zebrafish PGCs by single cell sequencing. PLoS One 2019; 14:e0220364. [PMID: 31412047 PMCID: PMC6693734 DOI: 10.1371/journal.pone.0220364] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 07/15/2019] [Indexed: 12/30/2022] Open
Abstract
Single cell RNA-seq is a powerful and sensitive way to capture the genome-wide gene expression. Here, single cell RNA-seq was utilized to study the transcriptomic profile of early zebrafish PGCs (primordial germ cells) at three different developmental stages. The three stages were 6, 11 and 24 hpf (hours post fertilization). For each developmental stage, three zebrafish PGCs from one embryo were collected, and 9 samples in total were used in this experiment. Single cell RNA-seq results showed that 5099–7376 genes were detected among the 9 samples, and the number of expressed genes decreased as development progressed. Based on the gene expression pattern, samples from 6 and 11 hpf clustered closely, while samples from 24 hpf were more dispersed. By WGCNA (weighted gene co-expression network analysis), the two biggest modules that had inverse gene expression patterns were found to be related to PGC formation or migration. Functional enrichment analysis for these two modules showed that PGCs mainly conducted migration and cell division in early development (6/11 hpf) and translation activity became active in late development (24 hpf). Differentially expressed gene analyses showed that more genes were downregulated than upregulated between two adjacent stages, and genes related to PGC formation or migration reported by previous studies decreased significantly from 11 to 24 hpf. Our results provide base knowledge about zebrafish PGC development at the single cell level and can be further studied by other researchers interested in biological development.
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Affiliation(s)
- Xiaoyuan Zhang
- State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.,Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.,CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Xintian Li
- State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.,Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.,CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Ronghong Li
- State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.,Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.,CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Yunbin Zhang
- State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.,Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.,CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Yiping Li
- State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.,Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.,CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Shifeng Li
- State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.,Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China.,CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Zhang H, Burr SP, Chinnery PF. The mitochondrial DNA genetic bottleneck: inheritance and beyond. Essays Biochem 2018; 62:225-34. [PMID: 29880721 DOI: 10.1042/EBC20170096] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [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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Aryaman J, Johnston IG, Jones NS. Mitochondrial DNA density homeostasis accounts for a threshold effect in a cybrid model of a human mitochondrial disease. Biochem J 2017; 474:4019-34. [PMID: 29079678 DOI: 10.1042/BCJ20170651] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 10/24/2017] [Accepted: 10/27/2017] [Indexed: 12/16/2022]
Abstract
Mitochondrial dysfunction is involved in a wide array of devastating diseases, but the heterogeneity and complexity of the symptoms of these diseases challenges theoretical understanding of their causation. With the explosion of omics data, we have the unprecedented opportunity to gain deep understanding of the biochemical mechanisms of mitochondrial dysfunction. This goal raises the outstanding need to make these complex datasets interpretable. Quantitative modelling allows us to translate such datasets into intuition and suggest rational biomedical treatments. Taking an interdisciplinary approach, we use a recently published large-scale dataset and develop a descriptive and predictive mathematical model of progressive increase in mutant load of the MELAS 3243A>G mtDNA mutation. The experimentally observed behaviour is surprisingly rich, but we find that our simple, biophysically motivated model intuitively accounts for this heterogeneity and yields a wealth of biological predictions. Our findings suggest that cells attempt to maintain wild-type mtDNA density through cell volume reduction, and thus power demand reduction, until a minimum cell volume is reached. Thereafter, cells toggle from demand reduction to supply increase, up-regulating energy production pathways. Our analysis provides further evidence for the physiological significance of mtDNA density and emphasizes the need for performing single-cell volume measurements jointly with mtDNA quantification. We propose novel experiments to verify the hypotheses made here to further develop our understanding of the threshold effect and connect with rational choices for mtDNA disease therapies.
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32
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Jaja-Chimedza A, Sanchez K, Gantar M, Gibbs P, Schmale M, Berry JP. Carotenoid glycosides from cyanobacteria are teratogenic in the zebrafish (Danio rerio) embryo model. Chemosphere 2017; 174:478-489. [PMID: 28189893 PMCID: PMC5835316 DOI: 10.1016/j.chemosphere.2017.01.145] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 01/25/2017] [Accepted: 01/30/2017] [Indexed: 05/24/2023]
Abstract
Toxigenicity of cyanobacteria is widely associated with production of several well-described toxins that pose recognized threats to human and ecosystem health as part of both freshwater eutrophication, and episodic blooms in freshwater and coastal habitats. However, a preponderance of evidence indicates contribution of additional bioactive, and potentially toxic, metabolites. In the present study, the zebrafish (Danio rerio) embryo was used as a model of vertebrate development to identify, and subsequently isolate and characterize, teratogenic metabolites from two representative strains of C. raciborskii. Using this approach, three chemically related carotenoids - and specifically the xanthophyll glycosides, myxol 2'-glycoside (1), 4-ketomyxol 2'-glycoside (2) and 4-hydroxymyxol 2'-glycoside (3) - which are, otherwise, well known pigment molecules from cyanobacteria were isolated as potently teratogenic compounds. Carotenoids are recognized "pro-retinoids" with retinoic acid, as a metabolic product of the oxidative cleavage of carotenoids, established as both key mediator of embryo development and, consequently, a potent teratogen. Accordingly, a comparative toxicological study of chemically diverse carotenoids, as well as apocarotenoids and retinoids, was undertaken. Based on this, a working model of the developmental toxicity of carotenoids as pro-retinoids is proposed, and the teratogenicity of these widespread metabolites is discussed in relation to possible impacts on aquatic vertebrate populations.
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Affiliation(s)
- Asha Jaja-Chimedza
- Department of Chemistry and Biochemistry, Marine Science Program, Florida International University, 3000 NE 151st Street, North Miami, FL 33181, USA.
| | - Kristel Sanchez
- Department of Biological Sciences, Florida International University, 11200 SW 8th Street, Miami, FL 33199, USA.
| | - Miroslav Gantar
- Department of Biological Sciences, Florida International University, 11200 SW 8th Street, Miami, FL 33199, USA.
| | - Patrick Gibbs
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33146, USA.
| | - Michael Schmale
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33146, USA.
| | - John P Berry
- Department of Chemistry and Biochemistry, Marine Science Program, Florida International University, 3000 NE 151st Street, North Miami, FL 33181, USA.
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Marlow FL. Mitochondrial matters: Mitochondrial bottlenecks, self-assembling structures, and entrapment in the female germline. Stem Cell Res 2017; 21:178-86. [PMID: 28336253 DOI: 10.1016/j.scr.2017.03.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 11/22/2016] [Accepted: 03/10/2017] [Indexed: 12/17/2022] Open
Abstract
Mitochondrial replacement therapy, a procedure to generate embryos with the nuclear genome of a donor mother and the healthy mitochondria of a recipient egg, has recently emerged as a promising strategy to prevent transmission of devastating mitochondrial DNA diseases and infertility. The procedure may produce an embryo that is free of diseased mitochondria. A recent study addresses important fundamental questions about the mechanisms underlying maternal inheritance and translational questions regarding the transgenerational effectiveness of this promising therapeutic strategy. This review considers recent advances in our understanding of maternal inheritance of mitochondria, implications for fertility and mitochondrial disease, and potential roles for the Balbiani body, an ancient oocyte structure, in mitochondrial selection in oocytes, with emphasis on therapies to remedy mitochondrial disorders.
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Otten AB, Stassen AP, Adriaens M, Gerards M, Dohmen RG, Timmer AJ, Vanherle SJ, Kamps R, Boesten IB, Vanoevelen JM, Muller M, Smeets HJ. Replication Errors Made During Oogenesis Lead to Detectable De Novo mtDNA Mutations in Zebrafish Oocytes with a Low mtDNA Copy Number. Genetics 2016; 204:1423-31. [PMID: 27770035 DOI: 10.1534/genetics.116.194035] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 10/13/2016] [Indexed: 01/30/2023] Open
Abstract
Of all pathogenic mitochondrial DNA (mtDNA) mutations in humans, ∼25% is de novo, although the occurrence in oocytes has never been directly assessed. We used next-generation sequencing to detect point mutations directly in the mtDNA of 3-15 individual mature oocytes and three somatic tissues from eight zebrafish females. Various statistical and biological filters allowed reliable detection of de novo variants with heteroplasmy ≥1.5%. In total, we detected 38 de novo base substitutions, but no insertions or deletions. These 38 de novo mutations were present in 19 of 103 mature oocytes, indicating that ∼20% of the mature oocytes carry at least one de novo mutation with heteroplasmy ≥1.5%. This frequency of de novo mutations is close to that deducted from the reported error rate of polymerase gamma, the mitochondrial replication enzyme, implying that mtDNA replication errors made during oogenesis are a likely explanation. Substantial variation in the mutation prevalence among mature oocytes can be explained by the highly variable mtDNA copy number, since we previously reported that ∼20% of the primordial germ cells have a mtDNA copy number of ≤73 and would lead to detectable mutation loads. In conclusion, replication errors made during oogenesis are an important source of de novo mtDNA base substitutions and their location and heteroplasmy level determine their significance.
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