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Zattera ML, Bruschi DP. Transposable Elements as a Source of Novel Repetitive DNA in the Eukaryote Genome. Cells 2022; 11:cells11213373. [PMID: 36359770 PMCID: PMC9659126 DOI: 10.3390/cells11213373] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 09/23/2022] [Accepted: 09/26/2022] [Indexed: 12/02/2022] Open
Abstract
The impact of transposable elements (TEs) on the evolution of the eukaryote genome has been observed in a number of biological processes, such as the recruitment of the host’s gene expression network or the rearrangement of genome structure. However, TEs may also provide a substrate for the emergence of novel repetitive elements, which contribute to the generation of new genomic components during the course of the evolutionary process. In this review, we examine published descriptions of TEs that give rise to tandem sequences in an attempt to comprehend the relationship between TEs and the emergence of de novo satellite DNA families in eukaryotic organisms. We evaluated the intragenomic behavior of the TEs, the role of their molecular structure, and the chromosomal distribution of the paralogous copies that generate arrays of repeats as a substrate for the emergence of new repetitive elements in the genome. We highlight the involvement and importance of TEs in the eukaryote genome and its remodeling processes.
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Affiliation(s)
- Michelle Louise Zattera
- Departamento de Genética, Programa de Pós-Graduação em Genética, Setor de Ciências Biológicas, Universidade Federal do Paraná, Curitiba 81530-000, PR, Brazil
| | - Daniel Pacheco Bruschi
- Departamento de Genética, Laboratorio de Citogenética Evolutiva e Conservação Animal, Setor de Ciências Biológicas, Universidade Federal do Paraná, Curitiba 81530-000, PR, Brazil
- Correspondence:
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2
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Abstract
According to the results of recent studies, parental exposure to ionizing radiation not only leads to mutation induction in the germline of irradiated animals but also affects their non-exposed offspring. These radiation-induced transgenerational effects belong to an epigenetic phenomenon that could not be defined as a transmission of altered phenotypes from the irradiated parents to their non-exposed offspring. In this review, we present the results of laboratory studies aimed to evaluate the transgenerational effects of parental irradiation on a number of traits in the offspring of exposed parents. The results of animal studies showing compromised viability, fertility and genome stability among the non-exposed offspring of irradiated parents are presented and discussed. So far, the epigenetic phenomenon of radiation-induced transgenerational effects has been established in laboratory studies. Future work should address the important issue of manifestation of radiation-induced transgenerational effects in populations inhabiting radioactive-contaminated areas, as well as the mechanisms of transgenerational effects.
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Affiliation(s)
- Yuri E Dubrova
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
| | - Elena I Sarapultseva
- Department of Biotechnology, National Research Nuclear University MEPhI, Moscow, Russian Federation.,A. Tsyb Medical Radiological Research Centre, National Medical Research Radiological Center of the Ministry of Health of the Russian Federation, Obninsk, Russian Federation
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Paço A, Freitas R, Vieira-da-Silva A. Conversion of DNA Sequences: From a Transposable Element to a Tandem Repeat or to a Gene. Genes (Basel) 2019; 10:E1014. [PMID: 31817529 PMCID: PMC6947457 DOI: 10.3390/genes10121014] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Revised: 11/18/2019] [Accepted: 11/29/2019] [Indexed: 01/24/2023] Open
Abstract
Eukaryotic genomes are rich in repetitive DNA sequences grouped in two classes regarding their genomic organization: tandem repeats and dispersed repeats. In tandem repeats, copies of a short DNA sequence are positioned one after another within the genome, while in dispersed repeats, these copies are randomly distributed. In this review we provide evidence that both tandem and dispersed repeats can have a similar organization, which leads us to suggest an update to their classification based on the sequence features, concretely regarding the presence or absence of retrotransposons/transposon specific domains. In addition, we analyze several studies that show that a repetitive element can be remodeled into repetitive non-coding or coding sequences, suggesting (1) an evolutionary relationship among DNA sequences, and (2) that the evolution of the genomes involved frequent repetitive sequence reshuffling, a process that we have designated as a "DNA remodeling mechanism". The alternative classification of the repetitive DNA sequences here proposed will provide a novel theoretical framework that recognizes the importance of DNA remodeling for the evolution and plasticity of eukaryotic genomes.
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Affiliation(s)
- Ana Paço
- MED-Mediterranean Institute for Agriculture, Environment and Development, University of Évora, 7002–554 Évora, Portugal;
| | - Renata Freitas
- IBMC-Institute for Molecular and Cell Biology, University of Porto, R. Campo Alegre 823, 4150–180 Porto, Portugal;
- I3S-Institute for Innovation and Health Research, University of Porto, Rua Alfredo Allen, 208, 4200–135 Porto, Portugal
- ICBAS-Institute of Biomedical Sciences Abel Salazar, University of Porto, 4050-313 Porto, Portugal
| | - Ana Vieira-da-Silva
- MED-Mediterranean Institute for Agriculture, Environment and Development, University of Évora, 7002–554 Évora, Portugal;
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4
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Dubrova Y. Mutation Induction in Humans and Mice: Where Are We Now? Cancers (Basel) 2019; 11:cancers11111708. [PMID: 31683966 PMCID: PMC6895811 DOI: 10.3390/cancers11111708] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 10/21/2019] [Accepted: 10/30/2019] [Indexed: 01/09/2023] Open
Abstract
The analysis of mutation induction in human families exposed to mutagens provides the only source of reliable estimates of factors contributing to the genetic risk of human exposure to mutagens. In this paper, I briefly summarize the results of recent studies on the pattern of mutation induction in the human and mouse germline. The results of recent studies on the genome-wide effects of exposure to mutagens on mutation induction in the mammalian germline are presented and discussed. Lastly, this review also addresses the issue of transgenerational effects of parental exposure to mutagens on mutation rates in their non-exposed offspring, which are known as transgenerational instability. The possible contribution of transgenerational instability to the genetic risk of human exposure to mutagens is discussed.
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Affiliation(s)
- Yuri Dubrova
- Department of Genetics and Genome Biology, University of Leicester, Leicester LE1 7RH, UK.
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5
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Rowan-Carroll A, Beal MA, Williams A, Marchetti F, Yauk CL. Dose-response mutation and spectrum analyses reveal similar responses at two microsatellite loci in benzo(a)pyrene-exposed mouse spermatogonia. Mutagenesis 2018; 32:463-470. [PMID: 28575466 DOI: 10.1093/mutage/gex008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 03/23/2017] [Indexed: 11/14/2022] Open
Abstract
Identifying chemical exposures that can cause germline mutations is important as these mutations can be inherited, impacting both individual and population health. However, germline mutations are extremely rare and difficult to detect. Chemically induced germline mutations can be detected through analysis of highly unstable tandem repeat DNA. We recently developed a single-molecule PCR (SM-PCR) approach to quantify mutations at a mouse microsatellite locus (Mm2.2.1) in sperm for such purposes. In this study, we refine this approach through the combined analysis of mouse microsatellites Mm2.2.1 and Mm19.2.3. Mice were exposed to 0, 25, 50 or 100 mg/kg/day benzo(a)pyrene (BaP) by oral gavage for 28 days and sperm sampled 42 days after the end of exposure to measure effects on dividing spermatogonia. DNA was diluted to a single genome per PCR well for amplification of microsatellites in singleplex and multiplex reactions, and alleles were sized to identify mutations using capillary electrophoresis. Analysis of ~300-500 molecules per animal at both microsatellite loci, when tested individually, showed a ~2-fold increase in mutations relative to the controls at both the 50 and 100 mg/kg/day BaP doses. Multiplex SM-PCR revealed similar increases in mutation frequencies in both microsatellites. Comparison with results from a previous lacZ mutation assay conducted on the same mice revealed that although microsatellite mutations are a sensitive endpoint for detecting changes in mutation frequencies at lower doses, they appear to be saturable and thus have a reduced dynamic range. These results confirm that BaP is a male germ cell mutagen that broadly impacts tandem repeat DNA. Likewise, addition of a second hypervariable microsatellite increases the sensitivity of this assay.
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Affiliation(s)
- Andrea Rowan-Carroll
- Mechanistic Studies Division, Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario K1A 0K9, Canada
| | - Marc A Beal
- Mechanistic Studies Division, Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario K1A 0K9, Canada
| | - Andrew Williams
- Biostatistics and Epidemiology Division, Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada
| | - Francesco Marchetti
- Mechanistic Studies Division, Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario K1A 0K9, Canada
| | - Carole L Yauk
- Mechanistic Studies Division, Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario K1A 0K9, Canada
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7
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Beal MA, Rowan-Carroll A, Campbell C, Williams A, Somers CM, Marchetti F, Yauk CL. Single-molecule PCR analysis of an unstable microsatellite for detecting mutations in sperm of mice exposed to chemical mutagens. Mutat Res 2015; 775:26-32. [PMID: 25863182 DOI: 10.1016/j.mrfmmm.2015.03.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 03/16/2015] [Accepted: 03/22/2015] [Indexed: 12/15/2022]
Abstract
Single-molecule PCR (SM-PCR) analysis of long and repetitive DNA sequences, known as expanded simple tandem repeats (ESTRs), has been the most efficient method for studying germline mutation induction in endogenous sequences to date. However, the long length of these sequences makes mutation detection imprecise and laborious, and they have been characterized only in mice. Here, we explore the use of unstable microsatellite sequences that can be typed with high precision by capillary electrophoresis as alternative loci for detecting germline mutations. We screened 24 microsatellite loci across inbred mouse strains and identified Mm2.2.1 as the most polymorphic microsatellite locus. We then optimized SM-PCR of Mm2.2.1 to detect mutations in sperm. SM-PCR analysis of sperm from untreated B6C3F1 and Muta(™)Mouse samples revealed mutation frequencies that are consistent with rates derived from family pedigree analysis (∼ 5 × 10(-3)). To determine whether this locus can be used to detect chemically induced germline mutations, Muta(™)Mouse males were exposed by oral gavage to a single dose of 100mg/kg of N-ethyl-N-nitrosourea (ENU) or to 100mg/kg of benzo(a)pyrene (BaP) for 28 days alongside vehicle treated controls. Sperm were collected 10 weeks post-ENU exposure to sample sperm exposed as spermatogonial stem cells and 6 weeks post-BaP exposure to sample sperm that were dividing spermatogonia when the exposure was terminated. Both treatments resulted in a significant (approximately 2-fold) increase in mutation frequency in sperm compared to the control animals. The work establishes the utility of this microsatellite for studying mutation induction in the germ cells of mice. Because microsatellites are found in virtually every species, this approach holds promise for other organisms, including humans.
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Affiliation(s)
- Marc A Beal
- Carleton University, Ottawa, Ontario K1S 5B6, Canada; Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario K1A 0K9, Canada.
| | - Andrea Rowan-Carroll
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario K1A 0K9, Canada.
| | - Caleigh Campbell
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario K1A 0K9, Canada.
| | - Andrew Williams
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario K1A 0K9, Canada.
| | | | - Francesco Marchetti
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario K1A 0K9, Canada.
| | - Carole L Yauk
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario K1A 0K9, Canada.
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8
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Wilson JW, Haines J, Sienkiewicz Z, Dubrova YE. The effects of extremely low frequency magnetic fields on mutation induction in mice. Mutat Res 2015; 773:22-26. [PMID: 25769183 DOI: 10.1016/j.mrfmmm.2015.01.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 12/05/2014] [Accepted: 01/21/2015] [Indexed: 06/04/2023]
Abstract
The growing human exposure to extremely low frequency (ELF) magnetic fields has raised a considerable concern regarding their genotoxic effects. The aim of this study was to evaluate the in vivo effects of ELF magnetic fields irradiation on mutation induction in the germline and somatic tissues of male mice. Seven week old BALB/c×CBA/Ca F1 hybrid males were exposed to 10, 100 or 300μT of 50Hz magnetic fields for 2 or 15h. Using single-molecule PCR, the frequency of mutation at the mouse Expanded Simple Tandem Repeat (ESTR) locus Ms6-hm was established in sperm and blood samples of exposed and matched sham-treated males. ESTR mutation frequency was also established in sperm and blood samples taken from male mice exposed to 1Gy of acute X-rays. The frequency of ESTR mutation in DNA samples extracted from blood of mice exposed to magnetic fields did not significantly differ from that in sham-treated controls. However, there was a marginally significant increase in mutation frequency in sperm but this was not dose-dependent. In contrast, acute exposure X-rays led to significant increases in mutation frequency in sperm and blood of exposed males. The results of our study suggest that, within the range of doses analyzed here, the in vivo mutagenic effects of ELF magnetic fields are likely to be minor if not negligible.
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Affiliation(s)
- James W Wilson
- Department of Genetics, University of Leicester, Leicester LE1 7RH, UK
| | - Jackie Haines
- Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Chilton, Didcot, Oxfordshire OX11 0RQ, UK
| | - Zenon Sienkiewicz
- Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Chilton, Didcot, Oxfordshire OX11 0RQ, UK
| | - Yuri E Dubrova
- Department of Genetics, University of Leicester, Leicester LE1 7RH, UK.
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9
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Yauk CL, Aardema MJ, Benthem JV, Bishop JB, Dearfield KL, DeMarini DM, Dubrova YE, Honma M, Lupski JR, Marchetti F, Meistrich ML, Pacchierotti F, Stewart J, Waters MD, Douglas GR. Approaches for identifying germ cell mutagens: Report of the 2013 IWGT workshop on germ cell assays(☆). MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2015; 783:36-54. [PMID: 25953399 DOI: 10.1016/j.mrgentox.2015.01.008] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 01/23/2015] [Indexed: 01/06/2023]
Abstract
This workshop reviewed the current science to inform and recommend the best evidence-based approaches on the use of germ cell genotoxicity tests. The workshop questions and key outcomes were as follows. (1) Do genotoxicity and mutagenicity assays in somatic cells predict germ cell effects? Limited data suggest that somatic cell tests detect most germ cell mutagens, but there are strong concerns that dictate caution in drawing conclusions. (2) Should germ cell tests be done, and when? If there is evidence that a chemical or its metabolite(s) will not reach target germ cells or gonadal tissue, it is not necessary to conduct germ cell tests, notwithstanding somatic outcomes. However, it was recommended that negative somatic cell mutagens with clear evidence for gonadal exposure and evidence of toxicity in germ cells could be considered for germ cell mutagenicity testing. For somatic mutagens that are known to reach the gonadal compartments and expose germ cells, the chemical could be assumed to be a germ cell mutagen without further testing. Nevertheless, germ cell mutagenicity testing would be needed for quantitative risk assessment. (3) What new assays should be implemented and how? There is an immediate need for research on the application of whole genome sequencing in heritable mutation analysis in humans and animals, and integration of germ cell assays with somatic cell genotoxicity tests. Focus should be on environmental exposures that can cause de novo mutations, particularly newly recognized types of genomic changes. Mutational events, which may occur by exposure of germ cells during embryonic development, should also be investigated. Finally, where there are indications of germ cell toxicity in repeat dose or reproductive toxicology tests, consideration should be given to leveraging those studies to inform of possible germ cell genotoxicity.
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Affiliation(s)
- Carole L Yauk
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada.
| | | | - Jan van Benthem
- National Institute for Public Health and the Environment, Bilthoven, The Netherlands
| | - Jack B Bishop
- National Institute of Environmental Health Sciences, NC, USA
| | | | | | | | | | - James R Lupski
- Department of Molecular and Human Genetics, and Department of Pediatrics, Baylor College of Medicine, USA
| | - Francesco Marchetti
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada
| | | | - Francesca Pacchierotti
- ENEA, Italian National Agency for New Technologies, Energy and Sustainable Economic Development, Italy
| | | | | | - George R Douglas
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, Canada.
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Merrifield M, Kovalchuk O. Epigenetics in radiation biology: a new research frontier. Front Genet 2013; 4:40. [PMID: 23577019 PMCID: PMC3616258 DOI: 10.3389/fgene.2013.00040] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Accepted: 03/06/2013] [Indexed: 11/13/2022] Open
Abstract
The number of people that receive exposure to ionizing radiation (IR) via occupational, diagnostic, or treatment-related modalities is progressively rising. It is now accepted that the negative consequences of radiation exposure are not isolated to exposed cells or individuals. Exposure to IR can induce genome instability in the germline, and is further associated with transgenerational genomic instability in the offspring of exposed males. The exact molecular mechanisms of transgenerational genome instability have yet to be elucidated, although there is support for it being an epigenetically induced phenomenon. This review is centered on the long-term biological effects associated with IR exposure, mainly focusing on the epigenetic mechanisms (DNA methylation and small RNAs) involved in the molecular etiology of IR-induced genome instability, bystander and transgenerational effects. Here, we present evidence that IR-mediated effects are maintained by epigenetic mechanisms, and demonstrate how a novel, male germline-specific, small RNA pathway is posited to play a major role in the epigenetic inheritance of genome instability.
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Affiliation(s)
- Matt Merrifield
- Department of Biological Sciences, University of Lethbridge Lethbridge, AB, Canada
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11
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Beal MA, Glenn TC, Lance SL, Somers CM. Characterization of unstable microsatellites in mice: no evidence for germline mutation induction following gamma-radiation exposure. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2012; 53:599-607. [PMID: 22930577 DOI: 10.1002/em.21726] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Accepted: 07/19/2012] [Indexed: 06/01/2023]
Abstract
Large tandem repeat DNA loci such as expanded simple tandem repeats and minisatellites are efficient markers for detecting germline mutations; however, mutation detection using these loci can be imprecise and difficult to standardize across labs. Short-tandem repeats, such as microsatellites, offer more precise and high-throughput mutation detection, but germline mutation induction at these loci has not yet been studied in model organisms such as mice. In this study, we used microsatellite enrichment and large-scale DNA sequencing of several closely related inbred mouse lines to identify a panel of 19 polymorphic microsatellites with potentially high spontaneous mutation frequencies. We used this panel and four additional loci from other sources to quantify spontaneous mutation frequency in pedigrees of outbred Swiss-Webster mice. In addition, we also examined mutation induction in families in which sires were treated with acute doses of either 0.5 Gy or 1.0 Gy gamma-irradiation to spermatogonial stem cells. Per locus mutation frequencies ranged from 0 to 5.03 × 10(-3). Considering only the 11 loci with mutations, the mutation frequencies were: control 2.78 × 10(-3), 0.5 Gy 4.09 × 10(-3), and 1.0 Gy 1.82 × 10(-3). There were no statistically significant changes in mutation frequencies among treatment groups. Our study provides the first direct quantification of microsatellite mutation frequency in the mouse germline, but shows no evidence for mutation induction at pre-meiotic male germ cells following acute gamma-irradiation. Further work using the panel is needed to examine mutation induction at different doses of radiation, exposure durations, and stages during spermatogenesis.
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Affiliation(s)
- Marc A Beal
- Department of Biology, University of Regina, Regina, Saskatchewan, Canada S4S 0A2
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Beal MA, Glenn TC, Somers CM. Whole genome sequencing for quantifying germline mutation frequency in humans and model species: cautious optimism. Mutat Res 2012; 750:96-106. [PMID: 22178956 DOI: 10.1016/j.mrrev.2011.11.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 11/29/2011] [Accepted: 11/30/2011] [Indexed: 05/31/2023]
Abstract
Factors affecting the type and frequency of germline mutations in animals are of significant interest from health and toxicology perspectives. However, studies in this field have been limited by the use of markers with low detection power or uncertain relevance to phenotype. Whole genome sequencing (WGS) is now a potential option to directly determine germline mutation type and frequency in family groups at all loci simultaneously. Medical studies have already capitalized on WGS to identify novel mutations in human families for clinical purposes, such as identifying candidate genes contributing to inherited conditions. However, WGS has not yet been used in any studies of vertebrates that aim to quantify changes in germline mutation frequency as a result of environmental factors. WGS is a promising tool for detecting mutation induction, but it is currently limited by several technical challenges. Perhaps the most pressing issue is sequencing error rates that are currently high in comparison to the intergenerational mutation frequency. Different platforms and depths of coverage currently result in a range of 10-10(3) false positives for every true mutation. In addition, the cost of WGS is still relatively high, particularly when comparing mutation frequencies among treatment groups with even moderate sample sizes. Despite these challenges, WGS offers the potential for unprecedented insight into germline mutation processes. Refinement of available tools and emergence of new technologies may be able to provide the improved accuracy and reduced costs necessary to make WGS viable in germline mutation studies in the very near future. To streamline studies, researchers may use multiple family triads per treatment group and sequence a targeted (reduced) portion of each genome with high (20-40 ×) depth of coverage. We are optimistic about the application of WGS for quantifying germline mutations, but caution researchers regarding the resource-intensive nature of the work using existing technology.
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Affiliation(s)
- Marc A Beal
- University of Regina, Department of Biology, 3737 Wascana Parkway, Regina, Saskatchewan, Canada S4S 0A2
| | - Travis C Glenn
- University of Georgia, Environmental Health Science, College of Public Health, Athens, GA 30602, USA
| | - Christopher M Somers
- University of Regina, Department of Biology, 3737 Wascana Parkway, Regina, Saskatchewan, Canada S4S 0A2.
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Kodaira M, Ryo H, Kamada N, Furukawa K, Takahashi N, Nakajima H, Nomura T, Nakamura N. No Evidence of Increased Mutation Rates at Microsatellite Loci in Offspring of A-Bomb Survivors. Radiat Res 2010; 173:205-13. [DOI: 10.1667/rr1991.1] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- M. Kodaira
- Departments of Genetics and, Radiation Effects Research Foundation, Hiroshima, Japan
| | - H. Ryo
- Department of Radiation Biology and Medical Genetics, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - N. Kamada
- Departments of Statistics and, Radiation Effects Research Foundation, Hiroshima, Japan
| | - K. Furukawa
- Departments of Statistics and, Radiation Effects Research Foundation, Hiroshima, Japan
| | - N. Takahashi
- Departments of Genetics and, Radiation Effects Research Foundation, Hiroshima, Japan
| | - H. Nakajima
- Department of Radiation Biology and Medical Genetics, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - T. Nomura
- Department of Radiation Biology and Medical Genetics, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - N. Nakamura
- Departments of Chief Scientist, Radiation Effects Research Foundation, Hiroshima, Japan
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Hardwick RJ, Tretyakov MV, Dubrova YE. Age-related accumulation of mutations supports a replication-dependent mechanism of spontaneous mutation at tandem repeat DNA Loci in mice. Mol Biol Evol 2009; 26:2647-54. [PMID: 19679753 DOI: 10.1093/molbev/msp182] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Expanded simple tandem repeat (ESTR) loci belong to the class of highly unstable loci in the mouse genome. The mechanisms underlying the very high spontaneous instability at these loci still remain poorly understood. Using single-molecule polymerase chain reaction, here we have compared the pattern of mutation accumulation in tissues with different proliferation capacities in male mice of age 12, 26, 48, and 96 weeks. In the nonproliferating brain, we did not observe any measurable age-related accumulation of ESTR mutations. In contrast, a highly elevated frequency of ESTR mutation was detected in the sperm samples taken from old mice; similar changes were also observed in the bone marrow tissue. The spectra of ESTR mutations accumulated in all tissues of young and old mice did not significantly differ. Taken together, these data clearly imply that spontaneous ESTR mutations occur almost exclusively in replication-proficient cells. To gain further insights into the mechanisms of ESTR mutation, we developed a stochastic model of age-related mutation accumulation. The observed spectra of ESTR mutants accumulated in the brain and sperm were fairly accurately approximated assuming the values of ESTR mutation rate, ranging from 0.01 to 0.04 per cell division. As these estimates dramatically exceed those for protein-coding genes and microsatellite loci, our data therefore suggest that ESTRs represent one of the most unstable loci in the mammalian genome. The results of our study also imply that ESTR loci can be regarded as a class of expanded microsatellites, with the mechanism of spontaneous mutation most probably attributed to replication slippage.
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Affiliation(s)
- Robert J Hardwick
- Department of Genetics University of Leicester, Leicester, United Kingdom
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Liu YR, Zhou Y, Qiu W, Zeng JY, Shen LL, Li AP, Zhou JW. Exposure to formaldehyde induces heritable DNA mutations in mice. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2009; 72:767-773. [PMID: 19492241 DOI: 10.1080/15287390902841615] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Our recent studies showed that exposure to mixed indoor air pollutants in a newly decorated residential apartment induced expanded simple tandem repeats (ESTR) mutations in mice, and the mutations were mainly inherited from the paternal germ line. Formaldehyde (FA) is a type of major volatile organic chemical (VOC) present in indoor air, and a constituent known to be associated with sick building syndrome. In the present study, mice were exposed to different concentrations of FA (0, 2, 20, or 200 mg/m(3)). The germline mutations were detected in their offspring using three ESTR probes, Ms6-hm, Hm-2, and MMS10. Data indicated that mice exposed to 200 mg/m(3) FA demonstrated a significant elevation in ESTR mutations, which is due primarily to an increase in mutations inherited through the paternal germ line. These results suggest that FA induced ESTR mutations in mice. It is postulated that single FA exposure might be a useful model to identify indoor air mixture exposure-induced heritable DNA damage.
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Affiliation(s)
- Yun-Ru Liu
- Department of Molecular Cell Biology and Toxicology, Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, People's Republic of China
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16
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Zhou Y, Liu Y, Qiu W, Zeng J, Chen X, Zhou H, Li A, Zhou J. Exposure to residential indoor air induces heritable DNA mutations in mice. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2009; 72:1561-1566. [PMID: 20077230 DOI: 10.1080/15287390903232442] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Exposure to the mixed indoor air pollutants released from synthetic materials and chemical products poses a serious public health problem, but little evidence has been provided to clarify whether such pollutants at environmentally relevant concentrations produce inheritable germline mutations. In the present study, mice were exposed to samples of indoor air from a newly decorated apartment bedroom. Results showed expanded simple tandem repeat (ESTR) mutations occurring in the germline of control and exposed parents, which were also detected in their offspring using three probes, Ms6-hm, Hm-2, and MMS10. Data indicated that mice being exposed to indoor air triggered a significant increase in frequency of ESTR mutations, which may be due primarily to a rise in mutations inherited through the paternal germline. These results suggest that exposure to a mixture of pollutants in indoor air obtained from an apartment in China induced ESTR mutations. Thus, humans exposed to polluted indoor apartment air in China may be at risk for developing germline mutations.
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Affiliation(s)
- Yin Zhou
- Department of Molecular Cell Biology and Toxicology, School of Public Health, Nanjing Medical University, Nanjing
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17
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Somers CM, Cooper DN. Air pollution and mutations in the germline: are humans at risk? Hum Genet 2008; 125:119-30. [PMID: 19112582 DOI: 10.1007/s00439-008-0613-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2008] [Accepted: 12/16/2008] [Indexed: 01/27/2023]
Abstract
Genotoxic air pollution is ubiquitous in urban and industrial areas. A variety of studies has linked human exposure to air pollution with a number of different somatic cell endpoints including cancer. However, the potential for inducing mutations in the human germline remains unclear. Sentinel animal studies of germline mutations at tandem-repeat loci (specifically minisatellites and expanded simple tandem repeats) have recently provided proof of principle that germline mutations can be induced in vertebrates (birds and mice) by air pollution under ambient conditions. Although humans may also be susceptible to induced germline mutations in polluted areas, uncertainties regarding causative agents, doses, and mutational mechanisms at repetitive DNA loci currently preclude extrapolation from animal data to the evaluation of human risk. Nevertheless, several recent studies have linked air pollution exposure to DNA damage in human sperm, indicating that our germ cells are not impervious to the genotoxic effects of air pollution. Thus, both sentinel animal and human studies have raised the possibility that ambient air pollution may increase human germline mutation rates, especially at repetitive DNA loci. Given that some human genetic conditions appear to be modulated by length mutations at tandem-repeat loci (e.g. HRAS1 cancers, type 1 diabetes, etc.), there is an urgent need for extensive study in this area. Research should be primarily focused upon: (1) the direct measurement of mutation frequencies at repetitive DNA loci in human male germ cells as a function of air pollution exposure, (2) large-scale epidemiology studies of inherited disorders and tandem-repeat associated genetic conditions and air pollution, and (3) the characterization of mutational mechanisms at hypervariable tandem-repeat loci.
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18
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Glen CD, Smith AG, Dubrova YE. Single-molecule PCR analysis of germ line mutation induction by anticancer drugs in mice. Cancer Res 2008; 68:3630-6. [PMID: 18483245 DOI: 10.1158/0008-5472.can-08-0484] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Understanding and estimating the genetic hazards of exposure to chemical mutagens and anticancer drugs in humans requires the development of efficient systems for monitoring germ line mutation. The suitability of a single-molecule PCR-based approach for monitoring mutation induction at the mouse expanded simple tandem repeat (ESTR) locus Ms6-hm by chemical mutagens and anticancer drugs has been validated. The frequency of ESTR mutation was evaluated in the germ line of male mice exposed to the well-characterized alkylating agent and mutagen, ethylnitrosourea, and four widely used anticancer drugs, bleomycin, cyclophosphamide, mitomycin C, and procarbazine. The dose-response of ethylnitrosourea-induced mutation was found to be very close to that previously established using a pedigree-based approach for ESTR mutation detection. Paternal exposure to the clinically relevant doses of bleomycin (15-30 mg/kg), cyclophosphamide (40-80 mg/kg), and mitomycin C (2.5-5 mg/kg) led to statistically significant, dose-dependent increases in ESTR mutation frequencies in the germ line of treated male mice. Exposure to procarbazine led to a maximal increase in mutation frequency at 50 mg/kg, with a plateau at the higher concentrations. The results of this study show that the single-molecule PCR technique provides a new and efficient experimental system for monitoring the genetic effects of anticancer drugs, capable of detecting increases in mutation rates at clinically relevant doses of exposure. In addition, this approach dramatically reduces the number of mice needed for the measurement of germ line mutation induction.
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Affiliation(s)
- Colin D Glen
- Department of Genetics and Medical Research Council Toxicology Unit, University of Leicester, Leicester, United Kingdom
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19
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Shanks M, Riou L, Fouchet P, Dubrova YE. Stage-specificity of spontaneous mutation at a tandem repeat DNA locus in the mouse germline. Mutat Res 2008; 641:58-60. [PMID: 18423770 DOI: 10.1016/j.mrfmmm.2008.03.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Revised: 03/10/2008] [Accepted: 03/14/2008] [Indexed: 05/26/2023]
Abstract
Mouse expanded simple tandem repeat (ESTR) loci are the most unstable loci in the mouse genome. Despite the fact that over the last decade these loci have been extensively used for studying germline mutation induction in mice, to date little is known about the mechanisms underlying spontaneous and induced ESTR mutation. Here we used flow cytometry and single-molecule PCR to compare the frequency of ESTR mutation in four flow-sorted fractions of the mouse male germ cells - spermatogonia, spermatocytes I, round and elongated spermatids. The frequency and the spectrum of ESTR mutation did not significantly differ between different stages of mouse spermatogenesis. Considering these data and the results of other publications, we propose that spontaneous ESTR mutation is mostly attributed to replication slippage in spermatogonia and these loci may be regarded as a class of expanded microsatellites.
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Affiliation(s)
- Morag Shanks
- Department of Genetics, University of Leicester, Leicester, University Road, Leicester LE1 7RH, United Kingdom
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20
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Somers CM, Valdes EV, Kjoss VA, Vaillancourt AL, Quinn JS. Influence of a contaminated fish diet on germline expanded-simple-tandem-repeat mutation frequency in mice. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2008; 49:238-248. [PMID: 18288721 DOI: 10.1002/em.20380] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Herring gulls (Larus argentatus) in polluted areas on the North American Great Lakes were previously shown to have elevated germline mutation frequencies at minisatellite DNA loci. Airborne or dietary contaminants likely caused induced mutations, but the importance of each exposure type was unknown. Follow-up experiments with lab mice determined that air pollution significantly induced germline mutations; however, an evaluation of mutations induced by the diet of herring gulls has not yet been conducted. To address this issue, we fed mice a high-fish diet (58% wet mass) of the most common prey species for herring gulls nesting in Hamilton Harbour, a polluted industrial area on Lake Ontario. We bred the mice and screened pedigrees for germline mutations at expanded-simple-tandem-repeat (ESTR) DNA loci. Mutation frequencies were compared to those in a reference group that was fed fish from Atlantic Canada, and a control group that was fed commercial chow. Germline mutation frequencies were highest in mice fed contaminated fish, but were only marginally or not significantly affected by diet treatment. Statistical power to detect differences among treatment groups was low, and the effect of diet may have more clearly emerged if larger sample sizes were available. Levels of organic pollutants in the fish from Hamilton Harbour were higher than those from Atlantic Canada, but their ability to induce ESTR mutations is unknown. Our findings suggest that a contaminated fish diet may contribute to the elevated germline mutation frequencies observed previously in gulls at this site, but air pollution is likely a more important route of exposure.
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21
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Malysheva DN, Tokarskaya ON, Petrosyan VG, Danielyan FD, Darevsky IS, Ryskov AP. Genomic variation in parthenogenetic lizard Darevskia armeniaca: evidence from DNA fingerprinting data. ACTA ACUST UNITED AC 2007; 98:173-8. [PMID: 17374876 DOI: 10.1093/jhered/esm003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Microsatellites, or short tandem repeats, are abundant across genomes of most organisms. It is evident that the most straightforward and conclusive way of studying mutations in microsatellite-containing loci is to use clonally transmitted genomes or DNA sequences inherited in multigeneration pedigrees. At present, little is known about the origin of genetic variation in species that lack effective genetic recombination. DNA fingerprinting in 43 families of the parthenogenetic lizard species Darevskia armeniaca (131 siblings), using (GACA)(4), (GGCA)(4), (GATA)(4), and (CAC)(5) probes, revealed mutant fingerprints in siblings that differed from their mothers in several restriction DNA fragments. In some cases, the mutant fingerprints detected in siblings were also found in population samples. The mutation rate for new restriction fragment length estimated by using multilocus probes varied from 0.8 x 10(-2) to 4.9 x 10(-2) per band/per sibling. Probably, the most variations detected as restriction fragment length polymorphism have germ-line origin, but somatic changes of (CAC)(n) fingerprints in adult lizards were also observed. These results provide new evidence of existing unstable regions in genomes of parthenogenetic vertebrate animals, which provide genetic variation in unisexual populations.
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Affiliation(s)
- D N Malysheva
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia.
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22
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Desmarais E, Belkhir K, Garza JC, Bonhomme F. Local mutagenic impact of insertions of LTR retrotransposons on the mouse genome. J Mol Evol 2006; 63:662-75. [PMID: 17075698 DOI: 10.1007/s00239-005-0301-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2005] [Accepted: 07/26/2006] [Indexed: 11/24/2022]
Abstract
Solitary LTR loci are the predominant form of LTR retrotransposons in most eukaryotic genomes. They originate from recombination between the two LTRs of an ancestral retrovirus and are therefore incapable of transposition. Despite this inactivity, they appear to have a substantial impact on the host genome. Here we use the murine RMER10 LTR family as an example to describe how such elements can reshape regions of the genome through multiple mutations on an evolutionary time scale. Specifically, we use phylogenetic analysis of multiple copies of RMER10 in rodent species, as well as comparisons of orthologous pairs in mouse and rat, to argue that insertions of members of this family have locally induced the emergence of tandem repeat loci as well as many indels. Analysis of structural aspects of these sequences (secondary structures and transcription factors signals) may explain why RMER10 can become endogenous "mutagenic" factors through induction of replication fork blockages and/or error-prone repair of aberrant DNA structures. This hypothesis is also consistent with features of other interspersed repeated elements.
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Affiliation(s)
- Erick Desmarais
- Laboratoire Génome, Populations, Interactions, Adaptation, UMR5171 CNRS-IFREMER, Université Montpellier II, CC-G3 Montpellier Place E. Bataillon 34095, France.
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23
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Dubrova YE. Genomic instability in the offspring of irradiated parents: Facts and interpretations. RUSS J GENET+ 2006. [DOI: 10.1134/s1022795406100048] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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24
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Boreham DR, Dolling JA, Somers C, Quinn J, Mitchel REJ. The adaptive response and protection against heritable mutations and fetal malformation. Dose Response 2006; 4:317-26. [PMID: 18648586 DOI: 10.2203/dose-response.06-104.boreham] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
There are a number of studies that show radiation can cause heritable mutations in the offspring of irradiated organisms. These "germ-line mutations" have been shown to occur in unique sequences of DNA called "minisatellite loci". The high frequencies of spontaneous and induced mutations at minisatellite loci allow mutation induction to be measured at low doses of exposure in a small population, making minisatellite mutation a powerful tool to investigate radiation-induced heritable mutations. However, the biological significance of these mutations is uncertain, and their relationship to health risk or population fitness is unknown. We have adopted this mutation assay to study the role of adaptive response in protecting mice against radiation-induced heritable defects. We have shown that male mice, adapted to radiation with a low dose priming exposure, do not pass on mutations to their offspring caused by a subsequent large radiation exposure to the adapted males. This presentation and paper provide a general overview of radiation-induced mutations in offspring and explain the effect of low dose exposures and the adaptive response on these mutations.It is also known that exposure of pregnant females to high doses of radiation can cause death or malformation (teratogenesis) in developing fetuses. Malformation can only occur during a specialized stage of organ formation known as organogenesis. Studies in rodents show that radiation-induced fetal death and malformation can be significantly reduced when a pregnant female is exposed to a prior low dose of ionizing radiation. The mechanism of this protective effect, through an adaptive response, depends on the stage of organogenesis when the low dose exposures are delivered. To better understand this process, we have investigated the role of an important gene known as p53. Therefore, this report will also discuss fetal effects of ionizing radiation and explain the critical stages of development when fetuses are at risk. Research will be explained that investigates the biological and genetic systems (p53) that protect the developing fetus and discuss the role of low dose radiation adaptive response in these processes.
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Affiliation(s)
- D R Boreham
- Medical Physics and Applied Radiation Sciences Unit, McMaster University, Hamilton, Ontario, Canada.
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25
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Bouffler SD, Bridges BA, Cooper DN, Dubrova Y, McMillan TJ, Thacker J, Wright EG, Waters R. Assessing radiation-associated mutational risk to the germline: repetitive DNA sequences as mutational targets and biomarkers. Radiat Res 2006; 165:249-68. [PMID: 16494513 DOI: 10.1667/rr3506.1] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
This review assesses recent data on mutational risk to the germline after radiation exposure obtained by molecular analysis of tandemly repeated DNA loci (TRDLs): minisatellites in humans and expanded simple tandem repeats in mice. Some studies, particularly those including exposure to internal emitters, indicate that TRDL mutation can be used as a marker of human radiation exposure; most human studies, however, are negative. Although mouse studies have suggested that TRDL mutation analysis may be more widely applicable in biomonitoring, there are important differences between the structure of mouse and human TRDLs. Mutational mechanisms probably differ between the two species, and so care should be taken in predicting effects in humans from mouse data. In mice and humans, TRDL mutations are largely untargeted with only limited evidence of dose dependence. Transgenerational mutation has been observed in mice but not in humans, but the mechanisms driving such mutation transmission are unknown. Some minisatellite variants are associated with human diseases and may affect gene transcription, but causal relationships have not yet been established. It is concluded that at present the TRDL mutation data do not warrant a dramatic revision of germline or cancer risk estimates for radiation.
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Affiliation(s)
- S D Bouffler
- Health Protection Agency Radiation Protection Division, Chilton, Didcot, Oxon OX11 0RQ, United Kingdom.
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26
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Somers CM. Expanded simple tandem repeat (ESTR) mutation induction in the male germline: lessons learned from lab mice. Mutat Res 2006; 598:35-49. [PMID: 16500683 DOI: 10.1016/j.mrfmmm.2006.01.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Expanded simple tandem repeat (ESTR) DNA loci that are unstable in the germline have provided the most sensitive tool ever developed for investigating low-dose heritable mutation induction in laboratory mice. Ionizing radiation exposures have shown that ESTR mutations occur mainly in pre-meiotic spermatogonia and stem cells. The average spermatogonial doubling dose is 0.62-0.69 Gy for low LET, and 0.18-0.34 Gy for high LET radiation. Chemical alkylating agents also cause significant ESTR mutation induction in pre-meiotic spermatogonia and stem cells, but are much less effective per unit dose than radiation. ESTR mutation induction efficiency is maximal at low doses of radiation or chemical mutagens, and may decrease at higher dose ranges. DNA repair deficient mice (SCID and PARP-1) with elevated levels of single and double-strand DNA breaks have spontaneously elevated ESTR mutation frequencies, and surprisingly do not show additional ESTR mutation induction following irradiation. In contrast, ESTR mutation induction in p53 knock-outs is indistinguishable from that of wild-type mice. Studies of sentinel mice exposed in situ to ambient air pollution showed elevated ESTR mutation frequencies in males exposed to high levels of particulate matter. These studies highlight the application of the ESTR assay for assessing environmental hazards under real-world conditions. All ESTR studies to date have shown untargeted mutations that occur at much higher frequencies than predicted. The mechanism of this untargeted mutation induction is unknown, and must be elucidated before we can fully understand the biological significance of ESTR mutations, or use these markers for formal risk assessment. Future studies should focus on the mechanism of ESTR mutation induction, refining dose responses, and developing ESTR markers for other animal species.
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Affiliation(s)
- Christopher M Somers
- Department of Biology, The University of Regina, 3737 Wascana Parkway, Regina, SK, Canada S4S 0A2.
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27
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Dubrova YE. Radiation-Induced Mutation at Tandem Repeat DNA Loci in the Mouse Germline: Spectra and Doubling Doses. Radiat Res 2005; 163:200-7. [PMID: 15658896 DOI: 10.1667/rr3296] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The spectra and dose response for mutations at expanded simple tandem repeat (ESTR) loci in the germline of male mice acutely exposed to low-LET X or gamma rays at pre-meiotic stages of spermatogenesis were compared in five strains of laboratory mice. Most mutation events involved the gain or loss of a relatively small number of repeat units, and the distributions of length changes were indistinguishable between the exposed and control males. Overall, a significant bias toward gains of repeats was detected, with approximately 60% of mutants showing gains. The values for ESTR mutation induction did not differ substantially between strains. The highest values of doubling dose were obtained for two genetically related strains, BALB/c and C.B17 (mean value 0.98 Gy). The estimates of doubling dose for three other strains (CBA/H, C57BL/6 x CBA/H F1 and 129SVJ x C57BL/6) were lower, with a mean value of 0.44 Gy. The dose response for ESTR mutation across all five strains was very close to that for the specific loci (Russell 7-locus test). The mechanisms of ESTR mutation induction and applications of this system for monitoring radiation-induced mutation in the mouse germline are discussed.
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Affiliation(s)
- Yuri E Dubrova
- Department of Genetics, University of Leicester, Leicester LE1 7RH, United Kingdom.
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28
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Malysheva DN, Tokarskaya ON, Danielyan FD, Darevsky IS, Ryskov AP. Identification of microsatellite mutations in parthenogenetic lizards Darevskia armeniaca. DOKL BIOCHEM BIOPHYS 2005; 400:28-31. [PMID: 15846978 DOI: 10.1007/s10628-005-0025-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- D N Malysheva
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, 117334 Russia
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29
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Somers CM, Sharma R, Quinn JS, Boreham DR. Gamma radiation-induced heritable mutations at repetitive DNA loci in out-bred mice. Mutat Res 2004; 568:69-78. [PMID: 15530540 DOI: 10.1016/j.mrfmmm.2004.06.047] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2004] [Revised: 05/14/2004] [Accepted: 06/04/2004] [Indexed: 05/01/2023]
Abstract
Recent studies have shown that expanded-simple-tandem-repeat (ESTR) DNA loci are efficient genetic markers for detecting radiation-induced germline mutations in mice. Dose responses following irradiation, however, have only been characterized in a small number of inbred mouse strains, and no studies have applied ESTRs to examine potential modifiers of radiation risk, such as adaptive response. We gamma-irradiated groups of male out-bred Swiss-Webster mice with single acute doses of 0.5 and 1.0 Gy, and compared germline mutation rates at ESTR loci to a sham-irradiated control. To test for evidence of adaptive response we treated a third group with a total dose of 1.1 Gy that was fractionated into a 0.1 Gy adapting dose, followed by a challenge dose of 1.0 Gy 24h later. Paternal mutation rates were significantly elevated above the control in the 0.5 Gy (2.8-fold) and 1.0 Gy (3.0-fold) groups, but were similar to each other despite the difference in radiation dose. The doubling dose for paternal mutation induction was 0.26 Gy (95% CI = 0.14-0.51 Gy). Males adapted with a 0.1 Gy dose prior to a 1.0 Gy challenge dose had mutation rates that were not significantly elevated above the control, and were 43% reduced compared to those receiving single doses. We conclude that pre-meiotic male germ cells in out-bred Swiss-Webster mice are sensitive to ESTR mutations induced by acute doses of ionizing radiation, but mutation induction may become saturated at a lower dose than in some strains of inbred mice. Reduced mutation rates in the adapted group provide intriguing evidence for suppression of ESTR mutations in the male germline through adaptive response. Repetitive DNA markers may be useful tools for exploration of biological factors affecting the probability of heritable mutations caused by low-dose ionizing radiation exposure. The biological significance of ESTR mutations in terms of radiation risk assessment, however, is still undetermined.
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Affiliation(s)
- C M Somers
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, Ont., Canada L8S 4K1.
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30
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Barber RC, Miccoli L, van Buul PPW, Burr KLA, van Duyn-Goedhart A, Angulo JF, Dubrova YE. Germline mutation rates at tandem repeat loci in DNA-repair deficient mice. Mutat Res 2004; 554:287-95. [PMID: 15450426 DOI: 10.1016/j.mrfmmm.2004.05.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2003] [Revised: 05/06/2004] [Accepted: 05/12/2004] [Indexed: 04/30/2023]
Abstract
Mutation rates at two expanded simple tandem repeat (ESTR) loci were studied in the germline of non-exposed and irradiated severe combined immunodeficient (scid) and poly(ADP-ribose) polymerase (PARP-1-/-) deficient male mice. Non-exposed scid and PARP-/- male mice showed considerably elevated ESTR mutation rates, far higher than those in wild-type isogenic mice and other inbred strains. The irradiated scid and PARP-1-/- male mice did not show any detectable increases in their mutation rate, whereas significant ESTR mutation induction was observed in the irradiated wild-type isogenic males. ESTR mutation spectra in the scid and PARP-1-/- strains did not differ from those in the isogenic wild-type strains. Considering these data and the results of previous studies, we propose that a delay in repair of DNA damage in scid and PARP-1-/- mice could result in replication fork pausing which, in turn, may affect ESTR mutation rate in the non-irradiated males. The lack of mutation induction in irradiated scid and PARP-1-/- can be explained by the high cell killing effects of irradiation on the germline of deficient mice.
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Affiliation(s)
- Ruth C Barber
- Department of Genetics, University of Leicester, LE1 7RH, UK
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31
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Somers CM, McCarry BE, Malek F, Quinn JS. Reduction of particulate air pollution lowers the risk of heritable mutations in mice. Science 2004; 304:1008-10. [PMID: 15143280 DOI: 10.1126/science.1095815] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Urban and industrial air pollution can cause elevated heritable mutation rates in birds and rodents. The relative importance of airborne particulate matter versus gas-phase substances in causing these genetic effects under ambient conditions has been unclear. Here we show that high-efficiency particulate-air (HEPA) filtration of ambient air significantly reduced heritable mutation rates at repetitive DNA loci in laboratory mice housed outdoors near a major highway and two integrated steel mills. These findings implicate exposure to airborne particulate matter as a principal factor contributing to elevated mutation rates in sentinel mice and add to accumulating evidence that air pollution may pose genetic risks to humans and wildlife.
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Affiliation(s)
- Christopher M Somers
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada
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32
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Korchagin VI, Churikov NA, Tokarskaya ON, Sevast'yanova GA, Filippovich YB, Ryskov AP. Molecular cloning and characteristics of allele variants (GATA)n, the microsatellite locus Du281 of parthenogenetic caucasian rock lizard (Darevskia unisexualis) genome. DOKL BIOCHEM BIOPHYS 2004; 394:46-8. [PMID: 15116568 DOI: 10.1023/b:dobi.0000017153.56861.ec] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- V I Korchagin
- Moscow State Pedagogical University, ul. Malaya Pirogovskaya 1, Moscow, 119992 Russia
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33
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Dubrova YE. Germline mutation induction at mouse and human tandem repeat DNA loci. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2004; 518:115-29. [PMID: 12817681 DOI: 10.1007/978-1-4419-9190-4_10] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Yuri E Dubrova
- Department of Genetics, University of Leicester, Leicester, LE1 7RH, United Kingdom.
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34
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Martienssen R, Lippman Z, May B, Ronemus M, Vaughn M. Transposons, tandem repeats, and the silencing of imprinted genes. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2004; 69:371-9. [PMID: 16117670 DOI: 10.1101/sqb.2004.69.371] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Affiliation(s)
- R Martienssen
- Watson School of Biological Sciences, Cold Spring Harbor, New York 11724, USA
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35
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Abstract
To date, the analysis of mutation induction has provided an irrefutable evidence for an elevated germline mutation rate in the parents directly exposed to ionizing radiation and a number of chemical mutagens. However, the results of numerous publications suggest that radiation may also have an indirect effect on genome stability, which is transmitted through the germ line of irradiated parents to their offspring. This review describes the phenomenon of transgenerational instability and focuses on the data showing increased cancer incidence and elevated mutation rates in the germ line and somatic tissues of the offspring of irradiated parents. The possible mechanisms of transgenerational instability are also discussed.
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Affiliation(s)
- Yuri E Dubrova
- Department of Genetics, University of Leicester, Leicester LE1 7RH, UK.
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36
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Tokarskaya ON, Martirosyan IA, Badaeva TN, Malysheva DN, Korchagin VI, Darevsky IS, Danielyan FD, Ryskov AP. Instability of (GATA)n microsatellite loci in the parthenogenetic Caucasian rock lizard Darevskia unisexualis (Lacertidae). Mol Genet Genomics 2003; 270:509-13. [PMID: 14618391 DOI: 10.1007/s00438-003-0936-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2003] [Accepted: 09/22/2003] [Indexed: 10/26/2022]
Abstract
Mini- and microsatellites, comprising tandemly repeated short nucleotide sequences, are abundant dispersed repetitive elements that are ubiquitous in eukaryotic genomes. In humans and other bisexual species hypervariable mini- and microsatellite loci provide highly informative systems for monitoring of germline and somatic instability. However, little is known about the mechanisms by which these loci mutate in species that lack effective genetic recombination. Here, multilocus DNA fingerprinting was used to study M13 minisatellite and (GATA)n microsatellite instability in the parthenogenetic Caucasian rock lizard Darevskia unisexualis (Lacertidae). DNA fingerprinting of 25 parthenogenetic families, from six isolated populations in Armenia (comprising a total of 84 siblings), using the oligonucleotide (GATA)4 as a hybridization probe, revealed mutant fingerprinting phenotypes in 13 siblings that differed from their mothers in several restriction DNA fragments. In three families (8 siblings), the mutations were present in the germline. Moreover, the mutant fingerprint phenotypes detected in siblings were also present in population DNA samples. No intrafamily variations in DNA fingerprint patterns were observed with the M13 minisatellite probe. Estimates of the mutation rate for (GATA)n microsatellite loci in D. unisexualis showed that it was as high as that seen in some bisexual species, reaching 15% per sibling or 0.95% per microsatellite band. Furthermore, in one case, a somatic (GATA)n microsatellite mutation was observed in an adult lizard. These findings directly demonstrate that mutations in (GATA)n microsatellite loci comprise an important source of genetic variation in parthenogenetic populations of D. unisexualis.
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Affiliation(s)
- O N Tokarskaya
- Institute of Gene Biology, Russian Academy of Sciences, Vavilov St. 34/5, 119334 Moscow, Russia.
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37
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Abstract
Minisatellites are a class of highly polymorphic GC-rich tandem repeats. They include some of the most variable loci in the human genome, with mutation rates ranging from 0.5% to >20% per generation. Structurally, they consist of 10- to 100-bp intermingled variant repeats, making them ideal tools for dissecting mechanisms of instability at tandem repeats. Distinct mutation processes generate rare intra-allelic somatic events and frequent complex conversion-like germline mutations in these repeats. Furthermore, turnover of repeats at human minisatellites is controlled by intense recombinational activity in DNA flanking the repeat array. Surprisingly, whereas other mammalian genomes possess minisatellite-like sequences, hypermutable loci have not been identified that suggest human-specific turnover processes at minisatellite arrays. Attempts to transfer minisatellite germline instability to the mouse have failed. However, yeast models are now revealing valuable information regarding the mechanisms regulating instability at these tandem repeats. Finally, minisatellites and tandem repeats provide exquisitely sensitive molecular tools to detect genomic insults such as ionizing radiation exposure. Surprisingly, by a mechanism that remains elusive, there are transgenerational increases in minisatellite instability.
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Affiliation(s)
- Philippe R J Bois
- St. Jude Children's Research Hospital, Department of Genetics and Tumor Cell Biology, 332 North Lauderdale, Memphis, TN 38105, USA.
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38
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Tokarskaya ON, Darevsky IS, Martirosyan IA, Badaeva TN, Korochkin LI, Danielyan FD, Petrosyan VG, Ryskov AP. Genetic instability of (GATA)n microsatellite DNA repeats and somatic mosaicism in the unisexual lizards Darevskia unisexualis. DOKL BIOCHEM BIOPHYS 2003; 388:64-6. [PMID: 12741137 DOI: 10.1023/a:1022572932747] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- O N Tokarskaya
- Institute of Gene Biology, Russian Academy of Sciences, ul. Vavilova 34/5, Moscow, 117334 Russia
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39
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Somers CM, Yauk CL, White PA, Parfett CLJ, Quinn JS. Air pollution induces heritable DNA mutations. Proc Natl Acad Sci U S A 2002; 99:15904-7. [PMID: 12473746 PMCID: PMC138537 DOI: 10.1073/pnas.252499499] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Hundreds of thousands of people worldwide live or work in close proximity to steel mills. Integrated steel production generates chemical pollution containing compounds that can induce genetic damage (1, 2). Previous investigations of herring gulls in the Great Lakes demonstrated elevated DNA mutation rates near steel mills (3, 4) but could not determine the importance of airborne or aquatic routes of contaminant exposure, or eliminate possible confounding factors such as nutritional status and disease burden. To address these issues experimentally, we exposed laboratory mice in situ to ambient air in a polluted industrial area near steel mills. Heritable mutation frequency at tandem-repeat DNA loci in mice exposed 1 km downwind from two integrated steel mills was 1.5- to 2.0-fold elevated compared with those at a reference site 30 km away. This statistically significant elevation was due primarily to an increase in mutations inherited through the paternal germline. Our results indicate that human and wildlife populations in proximity to integrated steel mills may be at risk of developing germline mutations more frequently because of the inhalation of airborne chemical mutagens.
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Affiliation(s)
- Christopher M Somers
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada L8S 4K1
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40
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Barber R, Plumb MA, Boulton E, Roux I, Dubrova YE. Elevated mutation rates in the germ line of first- and second-generation offspring of irradiated male mice. Proc Natl Acad Sci U S A 2002; 99:6877-82. [PMID: 11997464 PMCID: PMC124497 DOI: 10.1073/pnas.102015399] [Citation(s) in RCA: 158] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mutation rates at two expanded simple tandem repeat loci were studied in the germ line of first- and second-generation offspring of inbred male CBA/H, C57BL/6, and BALB/c mice exposed to either high linear energy transfer fission neutrons or low linear energy transfer x-rays. Paternal CBA/H exposure to either x-rays or fission neutrons resulted in increased mutation rates in the germ line of two subsequent generations. Comparable transgenerational effects were observed also in neutron-irradiated C57BL/6 and x-irradiated BALB/c mice. The levels of spontaneous mutation rates and radiation-induced transgenerational instability varied between strains (BALB/c>CBA/H>C57BL/6). Pre- and postmeiotic paternal exposure resulted in similar increases in mutation rate in the germ line of both generations of CBA/H mice, which together with our previous results suggests that radiation-induced expanded simple tandem repeat instability is manifested in diploid cells after fertilization. The remarkable finding that radiation-induced germ-line instability persists for at least two generations raises important issues of risk evaluation in humans.
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Affiliation(s)
- Ruth Barber
- Department of Genetics, University of Leicester, Leicester LE1 7RH, United Kingdom
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41
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Yauk CL, Dubrova YE, Grant GR, Jeffreys AJ. A novel single molecule analysis of spontaneous and radiation-induced mutation at a mouse tandem repeat locus. Mutat Res 2002; 500:147-56. [PMID: 11890944 DOI: 10.1016/s0027-5107(02)00005-2] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Expanded simple tandem repeat (ESTR) loci include some of the most unstable DNA in the mouse genome and have been extensively used in pedigree studies of germline mutation. We now show that repeat DNA instability at the mouse ESTR locus Ms6-hm can also be monitored by single molecule PCR analysis of genomic DNA. Unlike unstable human minisatellites which mutate almost exclusively in the germline by a meiotic recombination-based process, mouse Ms6-hm shows repeat instability both in germinal (sperm) DNA and in somatic (spleen, brain) DNA. There is no significant variation in mutation frequency between mice of the same inbred strain. However, significant variation occurs between tissues, with mice showing the highest mutation frequency in sperm. The size spectra of somatic and sperm mutants are indistinguishable and heavily biased towards gains and losses of only a few repeat units, suggesting repeat turnover by a mitotic replication slippage process operating both in the soma and in the germline. Analysis of male mice following acute pre-meiotic exposure to X-rays showed a significant increase in sperm but not somatic mutation frequency, though no change in the size spectrum of mutants. The level of radiation-induced mutation at Ms6-hm was indistinguishable from that established by conventional pedigree analysis following paternal irradiation. This confirms that mouse ESTR loci are very sensitive to ionizing radiation and establishes that induced germline mutation results from radiation-induced mutant alleles being present in sperm, rather than from unrepaired sperm DNA lesions that subsequently lead to the appearance of mutants in the early embryo. This single molecule monitoring system has the potential to substantially reduce the number of mice needed for germline mutation monitoring, and can be used to study not only germline mutation but also somatic mutation in vivo and in cell culture.
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Affiliation(s)
- Carole L Yauk
- Department of Genetics, University of Leicester, Leicester LE1 7RH, UK.
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Dubrova YE, Plumb MA. Ionising radiation and mutation induction at mouse minisatellite loci. The story of the two generations. Mutat Res 2002; 499:143-50. [PMID: 11827707 DOI: 10.1016/s0027-5107(01)00284-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The analysis of the effects of ionising radiation on germline mutations is limited by the number of offspring that need to be analysed following exposure to a dose, which is relevant to risk assessment in humans. We have developed a new experimental approach using hypervariable mouse expanded simple tandem repeat (ESTR) loci (minisatellites) which are both highly sensitive to ionising radiation and which permit changes in mutation rates to be detected in relatively small samples. Here, we review the progress made in validating the model, and the unexpected features it has revealed, including a novel form of radiation-induced genetic instability that can be transmitted from one generation to the next.
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Affiliation(s)
- Yuri E Dubrova
- Department of Genetics, University of Leicester, Adrian Building, University Road, LE1 7RH, Leicester, UK.
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Barber R, Plumb M, Smith AG, Cesar CE, Boulton E, Jeffreys AJ, Dubrova YE. No correlation between germline mutation at repeat DNA and meiotic crossover in male mice exposed to X-rays or cisplatin. Mutat Res 2000; 457:79-91. [PMID: 11106800 DOI: 10.1016/s0027-5107(00)00130-5] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
To test the hypothesis that mouse germline expanded simple tandem repeat (ESTR) mutations are associated with recombination events during spermatogenesis, crossover frequencies were compared with germline mutation rates at ESTR loci in male mice acutely exposed to 1Gy of X-rays or to 10mg/kg of the anticancer drug cisplatin. Ionising radiation resulted in a highly significant 2.7-3.6-fold increase in ESTR mutation rate in males mated 4, 5 and 6 weeks after exposure, but not 3 weeks after exposure. In contrast, irradiation had no effect on meiotic crossover frequencies assayed on six chromosomes using 25 polymorphic microsatellite loci spaced at approximately 20cM intervals and covering 421cM of the mouse genome. Paternal exposure to cisplatin did not affect either ESTR mutation rates or crossover frequencies, despite a report that cisplatin can increase crossover frequency in mice. Correlation analysis did not reveal any associations between the paternal ESTR mutation rate and crossover frequency in unexposed males and in those exposed to X-rays or cisplatin. This study does not, therefore, support the hypothesis that mutation induction at mouse ESTR loci results from a general genome-wide increase in meiotic recombination rate.
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Affiliation(s)
- R Barber
- Department of Genetics, University of Leicester, LE1 7RH, Leicester, UK
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44
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Dubrova YE, Plumb M, Brown J, Boulton E, Goodhead D, Jeffreys AJ. Induction of minisatellite mutations in the mouse germline by low-dose chronic exposure to gamma-radiation and fission neutrons. Mutat Res 2000; 453:17-24. [PMID: 11006408 DOI: 10.1016/s0027-5107(00)00068-3] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Germline mutation induction at mouse minisatellite loci by paternal low-dose (0.125-1 Gy) exposure to chronic (1.66 x 10(-4) Gy min(-1)) low-linear energy transfer (low-LET) gamma-irradiation and high-LET fission neutrons (0.003 Gy min(-1)) was studied at pre-meiotic stages of spermatogenesis. Both types of radiation produced linear dose-response curves for mutation of the paternal allele. In contrast to previous results using higher doses, the pattern of induction of minisatellite mutation after chronic gamma-irradiation was similar to acute (0.5 Gy min(-1)) exposure to X-rays, indicating that the elevated mutation rate was independent of the ability of the cell to repair damage induced immediately or over a period of up to 100 h. Chronic exposure to fission neutrons was more effective than acute or chronic low-LET exposure (relative biological effectiveness, RBE=3.36). The data also provide strong support for the previous conclusion that increases in minisatellite mutation rate are not caused by radiation-induced DNA damage at minisatellite loci themselves, but rather from damage induced by ionising radiation elsewhere in the genome/cell.
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Affiliation(s)
- Y E Dubrova
- Department of Genetics, University of Leicester, Leicester LE1 7RH, UK.
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45
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Buard J, Collick A, Brown J, Jeffreys AJ. Somatic versus germline mutation processes at minisatellite CEB1 (D2S90) in humans and transgenic mice. Genomics 2000; 65:95-103. [PMID: 10783256 DOI: 10.1006/geno.2000.6161] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The most variable human minisatellites show extreme germline instability dominated by complex intra-allelic rearrangements plus a lower frequency of inter-allelic transfers of repeat units. In contrast, little is known about somatic instability at such loci. We have therefore used single-molecule PCR to analyze mutation at minisatellite CEB1 (D2S90) in human blood DNA. Somatic mutants were rare and involved only relatively simple intra-allelic events, with no bias toward expansions, in sharp contrast to the complex gain-biased rearrangements seen in sperm. Somatic and germline mutation processes were further analyzed in mice transgenic for a cosmid insert containing CEB1. Mutant molecules in transgenic sperm and blood were detected but only at the low frequencies seen in human blood and arose mainly by simple duplications and deletions as seen for somatic mutations in human. These data suggest distinct pathways for germline and somatic CEB1 mutations with germline instability involving recombination-based repair of meiotic double-strand breaks and somatic mutation arising by replication slippage or mitotic recombination. The problem of transferring germline-specific features of minisatellite instability from human to mouse suggests, with other recent observations, that long-range chromatin conformation may be required for the recombination-based mode of germline instability at human minisatellites.
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Affiliation(s)
- J Buard
- Department of Genetics, University of Leicester, Leicester, LE1 7RH, United Kingdom.
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46
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Pâques F, Haber JE. Multiple pathways of recombination induced by double-strand breaks in Saccharomyces cerevisiae. Microbiol Mol Biol Rev 1999; 63:349-404. [PMID: 10357855 PMCID: PMC98970 DOI: 10.1128/mmbr.63.2.349-404.1999] [Citation(s) in RCA: 1640] [Impact Index Per Article: 65.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The budding yeast Saccharomyces cerevisiae has been the principal organism used in experiments to examine genetic recombination in eukaryotes. Studies over the past decade have shown that meiotic recombination and probably most mitotic recombination arise from the repair of double-strand breaks (DSBs). There are multiple pathways by which such DSBs can be repaired, including several homologous recombination pathways and still other nonhomologous mechanisms. Our understanding has also been greatly enriched by the characterization of many proteins involved in recombination and by insights that link aspects of DNA repair to chromosome replication. New molecular models of DSB-induced gene conversion are presented. This review encompasses these different aspects of DSB-induced recombination in Saccharomyces and attempts to relate genetic, molecular biological, and biochemical studies of the processes of DNA repair and recombination.
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Affiliation(s)
- F Pâques
- Rosenstiel Center and Department of Biology, Brandeis University, Waltham, Massachusetts 02454-9110, USA
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47
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Bois P, Stead JD, Bakshi S, Williamson J, Neumann R, Moghadaszadeh B, Jeffreys AJ. Isolation and characterization of mouse minisatellites. Genomics 1998; 50:317-30. [PMID: 9676426 DOI: 10.1006/geno.1998.5329] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Minisatellites provide the most informative system for analyzing processes of tandem repeat turnover in humans. However, little is known about minisatellites and the mechanisms by which they mutate in other species. To this end, we have isolated and characterized 76 endogenous mouse VNTRs. Fifty-one loci have been localized on mouse chromosomes and, unlike in humans, show no clustering in proterminal regions. Sequence analysis of 25 loci revealed the majority to be authentic minisatellites with GC-rich repeat units ranging from 14 to 47 bp in length. We have further characterized 3 of the most polymorphic loci both in Mus musculus subspecies and in inbred strains by using minisatellite variant repeat mapping (MVR) by PCR to gain insight into allelic diversity and turnover processes. MVR data suggest that mouse minisatellites mutate mainly by intra-allelic nonpolar events at a rate well below 10(-3) per gamete, in contrast to the high-frequency complex meiotic gene conversion-like events seen in humans. These results may indicate a fundamental difference in mechanisms of minisatellite mutation and genome turnover between mice and humans.
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Affiliation(s)
- P Bois
- Department of Genetics, University of Leicester, United Kingdom.
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