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Nikjoo H, Rahmanian S, Taleei R. Modelling DNA damage-repair and beyond. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2024; 190:1-18. [PMID: 38754703 DOI: 10.1016/j.pbiomolbio.2024.05.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 03/27/2024] [Accepted: 05/10/2024] [Indexed: 05/18/2024]
Abstract
The paper presents a review of mechanistic modelling studies of DNA damage and DNA repair, and consequences to follow in mammalian cell nucleus. We hypothesize DNA deletions are consequences of repair of double strand breaks leading to the modifications of genome that play crucial role in long term development of genetic inheritance and diseases. The aim of the paper is to review formation mechanisms underlying naturally occurring DNA deletions in the human genome and their potential relevance for bridging the gap between induced DNA double strand breaks and deletions in damaged human genome from endogenous and exogenous events. The model of the cell nucleus presented enables simulation of DNA damage at molecular level identifying the spectrum of damage induced in all chromosomal territories and loops. Our mechanistic modelling of DNA repair for double stand breaks (DSB), single strand breaks (SSB) and base damage (BD), shows the complexity of DNA damage is responsible for the longer repair times and the reason for the biphasic feature of mammalian cells repair curves. In the absence of experimentally determined data, the mechanistic model of repair predicts the in vivo rate constants for the proteins involved in the repair of DSB, SSB, and of BD.
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Affiliation(s)
- Hooshang Nikjoo
- Department of Physiology, Anatomy and Genetics (DPAG), Oxford University, Oxford, OX1 3PT, UK.
| | | | - Reza Taleei
- Medical Physics Division, Department of Radiation Oncology Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA, 19107, USA.
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Asakawa JI, Kodaira M, Miura A, Tsuji T, Nakamoto Y, Imanaka M, Kitamura J, Cullings H, Nishimura M, Shimada Y, Nakamura N. Genome-Wide Deletion Screening with the Array CGH Method in Mouse Offspring Derived from Irradiated Spermatogonia Indicates that Mutagenic Responses are Highly Variable among Genes. Radiat Res 2016; 186:568-576. [PMID: 27869554 DOI: 10.1667/rr14402.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Until the end of the 20th century, mouse germ cell data on induced mutation rates, which were collected using classical genetic methods at preselected specific loci, provided the principal basis for estimates of genetic risks from radiation in humans. The work reported on here is an extension of earlier efforts in this area using molecular methods. It focuses on validating the use of array comparative genomic hybridization (array CGH) methods for identifying radiation-induced copy number variants (CNVs) and specifically for DNA deletions. The emphasis on deletions stems from the view that it constitutes the predominant type of radiation-induced genetic damage, which is relevant for estimating genetic risks in humans. In the current study, deletion mutations were screened in the genomes of F1 mice born to unirradiated or 4 Gy irradiated sires at the spermatogonia stage (100 offspring each). The array CGH analysis was performed using a "2M array" with over 2 million probes with a mean interprobe distance of approximately 1 kb. The results provide evidence of five molecularly-confirmed paternally-derived deletions in the irradiated group (5/100) and one in the controls (1/100). These data support a calculation, which estimates that the mutation rate is 1 × 10-2/Gy per genome for induced deletions; this is much lower than would be expected if one assumes that the specific locus rate of 1 × 10-5/locus per Gy (at 34 loci) is applicable to other genes in the genome. The low observed rate of induced deletions suggests that the effective number of genes/genomic regions at which recoverable deletions could be induced would be only approximately 1,000. This estimate is far lower than expected from the size of the mouse genome (>20,000 genes). Such a discrepancy between observation and expectation can occur if the genome contains numerous genes that are far less sensitive to radiation-induced deletions, if many deletion-bearing offspring are not viable or if the current method is substandard for detecting small deletions.
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Affiliation(s)
- Jun-Ichi Asakawa
- Department of aGenetics, Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan
| | - Mieko Kodaira
- Department of aGenetics, Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan
| | - Akiko Miura
- Department of aGenetics, Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan
| | - Takahiro Tsuji
- Department of aGenetics, Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan
| | - Yoshiko Nakamoto
- Department of aGenetics, Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan
| | - Masaaki Imanaka
- Department of aGenetics, Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan
| | - Jun Kitamura
- Department of aGenetics, Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan
| | - Harry Cullings
- b Department of Statistics, Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan
| | - Mayumi Nishimura
- c Radiobiology for Children's Health Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Yoshiya Shimada
- c Radiobiology for Children's Health Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Nori Nakamura
- Department of aGenetics, Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan
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Howard M, Charalambous M. Molecular basis of imprinting disorders affecting chromosome 14: lessons from murine models. Reproduction 2015; 149:R237-49. [DOI: 10.1530/rep-14-0660] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Uniparental inheritance of chromosome 14q32 causes developmental failure during gestation and early postnatal development due to mis-expression of a cluster of imprinted genes under common epigenetic control. Two syndromes associated with chromosome 14q32 abnormalities have been described, Kagami–Ogata and Temple syndromes. Both of these syndromes are characterised by specific impairments of intrauterine development, placentation and early postnatal survival. Such abnormalities arise because the processes of intrauterine growth and postnatal adaptation are critically modulated by the dosage of imprinted genes in the chromosome 14q32 cluster. Much of our understanding of how the imprinted genes in this cluster are regulated, as well as their individual functions in the molecular pathways controlling growth and postnatal adaptation, has come from murine models. Mouse chromosome 12qF1 contains an imprinted region syntenic to human chromosome 14q32, collectively referred to as the Dlk1–Dio3 cluster. In this review, we will summarise the wealth of information derived from animal models of chromosome 12 imprinted gene mis-regulation, and explore the relationship between the functions of individual genes and the phenotypic result of their mis-expression. As there is often a considerable overlap between the functions of genes in the Dlk1–Dio3 cluster, we propose that the expression dosage of these genes is controlled by common regulatory mechanisms to co-ordinate the timing of growth and postnatal adaptation. While the diseases associated with mis-regulated chromosome 14 imprinting are rare, studies carried out in mice on the functions of the affected genes as well as their normal regulatory mechanisms have revealed new mechanistic pathways for the control of growth and survival in early life.
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Mao M, Alavi MV, Labelle-Dumais C, Gould DB. Type IV Collagens and Basement Membrane Diseases. CURRENT TOPICS IN MEMBRANES 2015; 76:61-116. [DOI: 10.1016/bs.ctm.2015.09.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Sankaranarayanan K, Taleei R, Rahmanian S, Nikjoo H. Ionizing radiation and genetic risks. XVII. Formation mechanisms underlying naturally occurring DNA deletions in the human genome and their potential relevance for bridging the gap between induced DNA double-strand breaks and deletions in irradiated germ cells. Mutat Res 2013; 753:114-130. [PMID: 23948232 DOI: 10.1016/j.mrrev.2013.07.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Revised: 06/27/2013] [Accepted: 07/22/2013] [Indexed: 12/21/2022]
Abstract
While much is known about radiation-induced DNA double-strand breaks (DSBs) and their repair, the question of how deletions of different sizes arise as a result of the processing of DSBs by the cell's repair systems has not been fully answered. In order to bridge this gap between DSBs and deletions, we critically reviewed published data on mechanisms pertaining to: (a) repair of DNA DSBs (from basic studies in this area); (b) formation of naturally occurring structural variation (SV) - especially of deletions - in the human genome (from genomic studies) and (c) radiation-induced mutations and structural chromosomal aberrations in mammalian somatic cells (from radiation mutagenesis and radiation cytogenetic studies). The specific aim was to assess the relative importance of the postulated mechanisms in generating deletions in the human genome and examine whether empirical data on radiation-induced deletions in mouse germ cells are consistent with predictions of these mechanisms. The mechanisms include (a) NHEJ, a DSB repair process that does not require any homology and which functions in all stages of the cell cycle (and is of particular relevance in G0/G1); (b) MMEJ, also a DSB repair process but which requires microhomology and which presumably functions in all cell cycle stages; (c) NAHR, a recombination-based DSB repair mechanism which operates in prophase I of meiosis in germ cells; (d) MMBIR, a microhomology-mediated, replication-based mechanism which operates in the S phase of the cell cycle, and (e) strand slippage during replication (involved in the origin of small insertions and deletions (INDELs). Our analysis permits the inference that, between them, these five mechanisms can explain nearly all naturally occurring deletions of different sizes identified in the human genome, NAHR and MMBIR being potentially more versatile in this regard. With respect to radiation-induced deletions, the basic studies suggest that those arising as a result of the operation of NHEJ/MMEJ processes, as currently formulated, are expected to be relatively small. However, data on induced mutations in mouse spermatogonial stem cells (irradiation in G0/G1 phase of the cell cycle and DSB repair presumed to be via NHEJ predominantly) show that most are associated with deletions of different sizes, some in the megabase range. There is thus a 'discrepancy' between what the basic studies suggest and the empirical observations in mutagenesis studies. This discrepancy, however, is only an apparent but not a real one. It can be resolved by considering the issue of deletions in the broader context of and in conjunction with the organization of chromatin in chromosomes and nuclear architecture, the conceptual framework for which already exists in studies carried out during the past fifteen years or so. In this paper, we specifically hypothesize that repair of DSBs induced in chromatin loops may offer a basis to explain the induction of deletions of different sizes and suggest an approach to test the hypothesis. We emphasize that the bridging of the gap between induced DSB and resulting deletions of different sizes is critical for current efforts in computational modeling of genetic risks.
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Affiliation(s)
- Krishnaswami Sankaranarayanan
- Radiation Biophysics Group, Department of Oncology-Pathology, Karolinska Instituet, Box 260, Stockholm SE 17176, Sweden
| | - Reza Taleei
- Radiation Biophysics Group, Department of Oncology-Pathology, Karolinska Instituet, Box 260, Stockholm SE 17176, Sweden
| | - Shirin Rahmanian
- Radiation Biophysics Group, Department of Oncology-Pathology, Karolinska Instituet, Box 260, Stockholm SE 17176, Sweden
| | - Hooshang Nikjoo
- Radiation Biophysics Group, Department of Oncology-Pathology, Karolinska Instituet, Box 260, Stockholm SE 17176, Sweden.
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Nitta Y, Shigeyoshi Y, Nakagata N, Kaneko T, Nitta K, Harada T, Ishizaki F, Townsend J. Kinetics of blood glucose in mice carrying hemizygous Pax6. Exp Anim 2009; 58:105-12. [PMID: 19448333 DOI: 10.1538/expanim.58.105] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The genotype-phenotype relationship was examined experimentally for the Pax6(Sey-4H) mutant, which carries deletion of its chromosome 2 middle region hemizygously. The genotyping has indicated that this deleted segment is between 102.6 and 109.2 Mb from the centromere. The glucose-6-phosphatase gene followed by the glucagon and carboxyl ester lipase genes were mapped adjacent to the deleted region. Phenotyping indicates that the Pax6(Sey-4H) mutant is more susceptible to diabetes. The glucose tolerance test showed that the mutants were less capable of reducing their level of blood glucose to the standard level than the normal sibs. The insulin-loading test revealed their inability to elevate their blood glucose levels up to normal levels. The time it took for the onset of diabetes induced by streptozotocin was shorter in the mutants than in normal sibs. Both the haploinsufficiency of the genes in the hemizygous segment of chromosome 2 and the quantitative imbalance of the whole genome could contribute the development of this phenotype in the mutant.
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Affiliation(s)
- Yumiko Nitta
- Department of Anatomy and Neuroscience, Faculty of Medicine, Kinki University, Osaka-Sayama, Japan
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Analysis of Pax6 contiguous gene deletions in the mouse, Mus musculus, identifies regions distinct from Pax6 responsible for extreme small-eye and belly-spotting phenotypes. Genetics 2009; 182:1077-88. [PMID: 19474196 DOI: 10.1534/genetics.109.104562] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In the mouse Pax6 function is critical in a dose-dependent manner for proper eye development. Pax6 contiguous gene deletions were shown to be homozygous lethal at an early embryonic stage. Heterozygotes express belly spotting and extreme microphthalmia. The eye phenotype is more severe than in heterozygous Pax6 intragenic null mutants, raising the possibility that deletions are functionally different from intragenic null mutations or that a region distinct from Pax6 included in the deletions affects eye phenotype. We recovered and identified the exact regions deleted in three new Pax6 deletions. All are homozygous lethal at an early embryonic stage. None express belly spotting. One expresses extreme microphthalmia and two express the milder eye phenotype similar to Pax6 intragenic null mutants. Analysis of Pax6 expression levels and the major isoforms excluded the hypothesis that the deletions expressing extreme microphthalmia are directly due to the action of Pax6 and functionally different from intragenic null mutations. A region distinct from Pax6 containing eight genes was identified for belly spotting. A second region containing one gene (Rcn1) was identified for the extreme microphthalmia phenotype. Rcn1 is a Ca(+2)-binding protein, resident in the endoplasmic reticulum, participates in the secretory pathway and expressed in the eye. Our results suggest that deletion of Rcn1 directly or indirectly contributes to the eye phenotype in Pax6 contiguous gene deletions.
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Sankaranarayanan K, Wassom J. Reflections on the impact of advances in the assessment of genetic risks of exposure to ionizing radiation on international radiation protection recommendations between the mid-1950s and the present. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2008; 658:1-27. [DOI: 10.1016/j.mrrev.2007.10.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 10/31/2007] [Indexed: 10/22/2022]
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Blei F. Literature watch. Dellinger, MT, RJ Hunter, et al. (2007). Chy-3 mice are Vegfc haploinsufficient and exhibit defective dermal superficial to deep lymphatic transition and dermal lymphatic hypoplasia. Dev Dyn 236:2346-2355. Lymphat Res Biol 2007; 5:203-4. [PMID: 18035938 DOI: 10.1089/lrb.2007.5308] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Dellinger MT, Hunter RJ, Bernas MJ, Witte MH, Erickson RP. Chy-3mice areVegfchaploinsufficient and exhibit defective dermal superficial to deep lymphatic transition and dermal lymphatic hypoplasia. Dev Dyn 2007; 236:2346-55. [PMID: 17584866 DOI: 10.1002/dvdy.21208] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Recent advances in molecular lymphology and lymphatic phenotyping techniques in small animals offer new opportunities to delineate mutant mouse models. Chy-3 mutant mice were originally named for their chylous ascites, but the underlying lymphatic disorder was not defined. We now re-examined these mice and applied advanced genotyping and lymphatic phenotyping techniques to pinpoint the specific lymphatic defect in this mouse model. We demonstrated that Chy-3 mice carry a large chromosomal deletion that includes Vegfc and narrowed this region by monitoring the heterozygosity of genetic markers. We found that Chy-3 mice not only exhibited chylous ascites but also lymphedema of the hind paws and, in approximately half of the males, lymphedema of the penis. Visual lymphangiography and immunofluorescence staining showed a hypoplastic dermal lymphatic network, whereas the blood vasculature appeared unaffected. This hypoplastic lymphatic network was functional, and all adult Chy-3 mice exhibited a lateral lymphatic pathway directly connecting the inguinal to the axillary lymph node. The dermal superficial to deep lymphatic connections in upper limbs and in all cervical regions were intact and functionally drained the upper body. Lymphatic tracer was not transported from the dermal to the deep truncal lymphatic system in the lower limbs, even though the deep lymphatic vessels and nodes were present and patent. These findings further delineate the lymphatic phenotype of Chy-3 mice, identify a collateral lymph drainage pathway previously undescribed in other genetic models of lymphedema, and demonstrate a predilection for lymphatic abnormalities of the lower limbs.
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Affiliation(s)
- Michael T Dellinger
- Department of Molecular and Cellular Biology, The University of Arizona, Tucson, Arizona, USA
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Wu J, Morimyo M, Hongo E, Higashi T, Okamoto M, Kawano A, Ohmachi Y. Radiation-induced germline mutations detected by a direct comparison of parents and first-generation offspring DNA sequences containing SNPs. Mutat Res 2006; 596:1-11. [PMID: 16483616 DOI: 10.1016/j.mrfmmm.2005.09.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2005] [Revised: 09/20/2005] [Accepted: 09/30/2005] [Indexed: 11/18/2022]
Abstract
Germline mutation induction has been detected in mice but not in humans. To estimate the genetic risk of germline mutation induction in humans, new techniques for extrapolating from animal data to humans or directly detecting radiation-induced mutations in man are expected to be developed. We have developed a new method to detect germline mutations by directly comparing the DNA sequences of parents and first-generation offspring. C3H male mice were irradiated with gamma-rays of 3, 2 and 1 Gy and 3 weeks later were mated with C57BL female mice of the same age. The nucleotide sequences of 160 UniSTS markers containing 300-900 bp and SNPs of the DNA of parent and offspring mice were determined by direct sequencing. At each dose of radiation, a total of 5 Mb DNA sequences were examined for radiation-induced mutations. We found 7 deletions in 3 Gy-irradiated mice, 1 deletion in 2 Gy-irradiated mice, 1 deletion in 1 Gy-irradiated mice and no mutations in control mice. The maximum mutation frequency was 2.0 x 10(-4)/locus/Gy at 3 Gy, and these results suggested that a non-linear increase of mutations with dose.
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Affiliation(s)
- Jianyu Wu
- Project Group of Low-Dose Radiation Effects, Research Center for Radiation Safety, National Institute of Radiological Sciences, 9-1, Anagawa-4-Chome, Chiba 263-8555, Japan
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Nomura T, Nakajima H, Ryo H, Li LY, Fukudome Y, Adachi S, Gotoh H, Tanaka H. Transgenerational transmission of radiation- and chemically induced tumors and congenital anomalies in mice: studies of their possible relationship to induced chromosomal and molecular changes. Cytogenet Genome Res 2004; 104:252-60. [PMID: 15162048 DOI: 10.1159/000077499] [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: 09/13/2003] [Accepted: 12/16/2003] [Indexed: 11/19/2022] Open
Abstract
This article provides a broad overview of our earlier studies on the induction of tumors and congenital anomalies in the progeny of X-irradiated or chemically treated mice and our subsequent (published, hitherto unpublished and on-going) investigations aimed at identifying potential relationships between genetic changes induced in germ cells and the adverse effects manifest as tumors and congenital anomalies using cytogenetic and molecular approaches. The earlier studies document the fact that tumors and congenital anomalies can be induced by irradiation or treatment with certain chemicals such as urethane and that these phenotypes are heritable i.e., transmitted to generations beyond the first generation. These findings support the view that transmissible induced genetic changes are involved. The induced rates of congenital abnormalities and tumors are about two orders of magnitude higher than those recorded in the literature from classical mutation studies with specific locus mutations. The cytogenetic studies addressed the question of whether there were any relationships between induced translocations and induced tumors. The available data permit the inference that gross chromosomal changes may not be involved but do not exclude smaller induced genetic changes that are beyond the resolution of the techniques used in these studies. Other work on possible relationship between visible chromosomal anomalies (in bone marrow preparations) and tumors were likewise negative. However, there were indications that some induced cytogenetic changes might underlie induced congenital anomalies, i.e., trisomies, deletions and inversions were observed in induced and transmissible congenital anomalies (such as dwarfs, tail anomalies). Studies that explored possible relationships between induction of minisatellite mutations at the Pc-3 locus and tumors were negative. However, gene expression analysis of tumor (hepatoma)-susceptible offspring of progeny descended from irradiated male mice showed abnormal expression of many genes. Of these, only very few were oncogenes. This lends some support to our hypothesis that cumulative changes in gene expression of many genes, which perform normal cellular functions, may contribute to the occurrence of tumors in the offspring of irradiated or chemically treated mice.
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MESH Headings
- 4-Nitroquinoline-1-oxide/toxicity
- Abnormalities, Drug-Induced/genetics
- Abnormalities, Radiation-Induced/genetics
- Animals
- Carcinogens/toxicity
- Chromosome Aberrations
- Chromosomes/drug effects
- Chromosomes/genetics
- Chromosomes/radiation effects
- Chromosomes/ultrastructure
- Female
- Gene Expression Profiling
- Genes, Lethal
- Germ Cells/drug effects
- Germ Cells/radiation effects
- Infectious Disease Transmission, Vertical
- Male
- Mice
- Mice, Inbred ICR
- Minisatellite Repeats/drug effects
- Neoplasms, Experimental/chemically induced
- Neoplasms, Experimental/etiology
- Neoplasms, Experimental/genetics
- Neoplasms, Radiation-Induced/etiology
- Neoplasms, Radiation-Induced/genetics
- Neoplastic Syndromes, Hereditary/chemically induced
- Neoplastic Syndromes, Hereditary/etiology
- Neoplastic Syndromes, Hereditary/genetics
- Oncogenes
- Polychlorinated Dibenzodioxins/toxicity
- Radiation Injuries, Experimental/genetics
- Translocation, Genetic
- Urethane/toxicity
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Affiliation(s)
- T Nomura
- Department of Radiation Biology and Medical Genetics, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
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Abstract
The doubling dose (DD) is a very valuable concept in attempts to assess the genetic risks of radiation in man. It was long thought that the value of the doubling dose obtained from specific locus experiments in mice could be applied to man. James Neel, as a result of his studies on the offspring of atomic bomb survivors, showed that this was not so, but that different doubling doses could be inferred from different endpoints.
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Affiliation(s)
- Mary F Lyon
- MRC Mammalian Genetics Unit, Harwell, Didcot OX11 0RD, UK.
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Peters J, Ball ST. Biochemical and recessive visible specific locus responses of C3H/HeH to fractionated, acute radiation. Mutat Res 2003; 543:137-43. [PMID: 12644183 DOI: 10.1016/s1383-5742(03)00011-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The recessive visible specific locus test has been widely used for many years to investigate the genetic effects of radiation in mice. We devised an electrophoretic-specific locus test so that biochemical mutations leading to alterations in the activity or amount of four enzymes and proteins, as well as charge changes could be detected. We measured the yield of recessive visible and electrophoretic mutations in the same experiment so that a direct comparison of mutation incidence could be made. Dominant visible mutations were also scored. The recessive visible specific locus response of male C3H/HeH to a fractionated dose of 3 + 3 Gy X-irradiation separated by 24 h was similar to that previously reported for the F1 hybrid widely used in mutagenesis studies, and other strains. The response of C3H/HeH was significantly greater for the recessive visible mutations than for the biochemical mutations, supporting the contention that the recessive visible loci are more mutable than others. Mutational analysis of some of the mutants showed that the lesions ranged from a very deletion (30% of chromosome 14 deleted) to a point mutation. The number of loci scored in the electrophoretic test has been reassessed, and it is now considered that six, not four were scored, and this has implications for the calculation of the doubling dose.
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Affiliation(s)
- Jo Peters
- MRC Mammalian Genetics Unit, Harwell, Didcot OX11 0RD, UK.
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Chao HHJ, Mentzer SE, Schimenti JC, You Y. Overlapping deletions define novel embryonic lethal loci in the mouse t complex. Genesis 2003; 35:133-42. [PMID: 12533796 DOI: 10.1002/gene.10174] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
SUMMARY The t complex region of mouse chromosome 17 contains genetic information critical for embryonic development. To identify and map loci required for normal embryogenesis, a set of overlapping deletions (D17Aus9(df10J), D17Aus9(df12J), and D17Aus9(df13J)) surrounding the D17Aus9 locus and one encompassing the T locus, Del(17)T(7J), were bred in various combinations and the consequences of nullizygosity in overlapping regions were examined. The results indicated that there are at least two functional units within 1 cM of D17Aus9. l17J1 is a peri-implantation lethal mutation within the region deleted in D17Aus9(df13J), whereas l17J2 is a later-acting lethal defined by the region of overlap between Del(17)T(7J) and D17Aus9(df12J). Del(17)T(7J)/D17Aus9(df12J) embryos die around 10.5 dpc. The development of the mutant embryos is characterized by lack of axial rotation, an abnormal notochord structure, and a ballooning pericardium. These studies demonstrate the value of overlapping deletion complexes, as opposed to individual deletion complexes, for the identification, mapping, and analysis of genes required for embryonic development.
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Affiliation(s)
- Hanna H J Chao
- Life Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6445, USA
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Abstract
In the postgenomic era the mouse will be central to the challenge of ascribing a function to the 40,000 or so genes that constitute our genome. In this review, we summarize some of the classic and modern approaches that have fueled the recent dramatic explosion in mouse genetics. Together with the sequencing of the mouse genome, these tools will have a profound effect on our ability to generate new and more accurate mouse models and thus provide a powerful insight into the function of human genes during the processes of both normal development and disease.
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Rajaraman S, Davis WS, Mahakali-Zama A, Evans HK, Russell LB, Bedell MA. An Allelic Series of Mutations in the Kit ligand Gene of Mice. I. Identification of Point Mutations in Seven Ethylnitrosourea-Induced KitlSteel Alleles. Genetics 2002; 162:331-40. [PMID: 12242244 PMCID: PMC1462231 DOI: 10.1093/genetics/162.1.331] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
An allelic series of mutations is an extremely valuable genetic resource for understanding gene function. Here we describe eight mutant alleles at the Steel (Sl) locus of mice that were induced with N-ethyl-N-nitrosourea (ENU). The product of the Sl locus is Kit ligand (or Kitl; also known as mast cell growth factor, stem cell factor, and Steel factor), which is a member of the helical cytokine superfamily and is the ligand for the Kit receptor tyrosine kinase. Seven of the eight ENU-induced KitlSl alleles, of which five cause missense mutations, one causes a nonsense mutation and exon skipping, and one affects a splice site, were found to contain point mutations in Kitl. Interestingly, each of the five missense mutations affects residues that are within, or very near, conserved α-helical domains of Kitl. These ENU-induced mutants should provide important information on structural requirements for function of Kitl and other helical cytokines.
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Affiliation(s)
- S Rajaraman
- Department of Genetics, University of Georgia, Athens, Georgia 30602-7223, USA
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18
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Davies K, Bowden L, Smith P, Dean W, Hill D, Furuumi H, Sasaki H, Cattanach B, Reik W. Disruption of mesodermal enhancers forIgf2in the minute mutant. Development 2002; 129:1657-68. [PMID: 11923202 DOI: 10.1242/dev.129.7.1657] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The radiation-induced mutation minute (Mnt) in the mouse leads to intrauterine growth retardation with paternal transmission and has been linked to the distal chromosome 7 cluster of imprinted genes. We show that the mutation is an inversion, whose breakpoint distal to H19 disrupts and thus identifies an enhancer for Igf2 expression in skeletal muscle and tongue, and separates the gene from other mesodermal and extra-embryonic enhancers. Paternal transmission of Mnt leads to drastic downregulation of Igf2 transcripts in all mesodermal tissues and the placenta. Maternal transmission leads to methylation of the H19 differentially methylated region (DMR) and silencing of H19, showing that elements 3′ of H19 can modify the maternal imprint. Methylation of the maternal DMR leads to biallelic expression of Igf2 in endodermal tissues and foetal overgrowth, demonstrating that methylation in vivo can open the chromatin boundary upstream of H19. Our work shows that most known enhancers for Igf2 are located 3′ of H19 and establishes an important genetic paradigm for the inheritance of complex regulatory mutations in imprinted gene clusters.
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Affiliation(s)
- Karen Davies
- Laboratory of Developmental Genetics and Imprinting, Developmental Genetics Programme, Babraham Institute, Cambridge CB2 4AT, UK
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19
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Browning VL, Bergstrom RA, Daigle S, Schimenti JC. A haplolethal locus uncovered by deletions in the mouse T complex. Genetics 2002; 160:675-82. [PMID: 11861570 PMCID: PMC1461990 DOI: 10.1093/genetics/160.2.675] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Proper levels of gene expression are important for normal mammalian development. Typically, altered gene dosage caused by karyotypic abnormalities results in embryonic lethality or birth defects. Segmental aneuploidy can be compatible with life but often results in contiguous gene syndromes. The ability to manipulate the mouse genome allows the systematic exploration of regions that are affected by alterations in gene dosage. To explore the effects of segmental haploidy in the mouse t complex on chromosome 17, radiation-induced deletion complexes centered at the Sod2 and D17Leh94 loci were generated in embryonic stem (ES) cells. A small interval was identified that, when hemizygous, caused specific embryonic lethal phenotypes (exencephaly and edema) in most fetuses. The penetrance of these phenotypes was background dependent. Additionally, evidence for parent-of-origin effects was observed. This genetic approach should be useful for identifying genes that are imprinted or whose dosage is critical for normal embryonic development.
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Kurihara LJ, Semenova E, Miller W, Ingram RS, Guan XJ, Tilghman SM. Candidate genes required for embryonic development: a comparative analysis of distal mouse chromosome 14 and human chromosome 13q22. Genomics 2002; 79:154-61. [PMID: 11829485 DOI: 10.1006/geno.2002.6692] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mice homozygous for the Ednrb(s-1Acrg) deletion arrest at embryonic day 8.5 from defects associated with mesoderm development. To determine the molecular basis of this phenotype, we initiated a positional cloning of the Acrg minimal region. This region was predicted to be gene-poor by several criteria. From comparative analysis with the syntenic human locus at 13q22 and gene prediction program analysis, we found a single cluster of four genes within the 1.4-to 2-Mb contig over the Acrg minimal region that is flanked by a gene desert. We also found 130 highly conserved nonexonic sequences that were distributed over the gene cluster and desert. The four genes encode the TBC (Tre-2, BUB2, CDC16) domain-containing protein KIAA0603, the ubiquitin carboxy-terminal hydrolase L3 (UCHL3), the F-box/PDZ/LIM domain protein LMO7,and a novel gene. On the basis of their expression profile during development, all four genes are candidates for the Ednrb(s-1Acrg) embryonic lethality. Because we determined that a mutant of Uchl3 was viable, three candidate genes remain within the region.
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Affiliation(s)
- Laurie Jo Kurihara
- Howard Hughes Medical Institute and Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
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21
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Abstract
With the completion of the human genome, sequence analysis of gene function will move into the center of future genome research. One of the key strategies for studying gene function involves the genetic dissection of biological processes in animal models. Mouse mutants are of particular importance for the analysis of disease pathogenesis and transgenic techniques, and gene targeting have become routine tools. Recently, phenotype-driven strategies using chemical mutagenesis have been the target of increasing interest. In this review, the current state of ENU mutagenesis and its application as a systematic tool of genome analysis are examined.
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Affiliation(s)
- R Balling
- German Research Centre for Biotechnology, D-38124 Braunschweig, Germany.
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22
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Fukamachi S, Shimada A, Naruse K, Shima A. Genomic analysis of gamma-ray-induced germ-cell mutations at the b locus recovered from the medaka specific-locus test. Mutat Res 2001; 458:19-29. [PMID: 11406418 DOI: 10.1016/s1383-5726(01)00009-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To study how gamma-ray-induced germ-cell mutations are fixed at the early embryonic stage of the next generation, genomic alterations in the b locus mutants (colorless melanophores) detected during development in the medaka specific-locus test (SLT) were analyzed. First, nine anonymous DNA markers linked to the b locus were cloned and mapped into the region extending about 47cM surrounding the b locus. Next, losses of paternal alleles of these DNA markers were examined in each of the 51 gamma-ray-induced b locus mutants obtained after irradiation of sperm or spermatids. In these mutants, 47 were dominant lethals, three were semi-viable and one was viable. All the mutants examined had large deletions surrounding the b locus. One viable mutant had an interstitial deletion, while all the semi-viable and dominant lethal ones appeared to have terminal deletions. Deletions extending about 20-35cM were the most frequently observed in 18 of the 51 mutants examined. The largest one extended more than 40cM. These results suggest that most of the gamma-ray induced germ cell mutations recovered as total specific-locus mutants were accompanied by large genomic deletions, which eventually led the mutant embryos to dominant lethality.
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Affiliation(s)
- S Fukamachi
- Laboratory of Radiation Biology, Department of Biological Sciences, School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, 113-0033, Tokyo, Japan.
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23
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Watson GE, Pocock DA, Papworth D, Lorimore SA, Wright EG. In vivo chromosomal instability and transmissible aberrations in the progeny of haemopoietic stem cells induced by high- and low-LET radiations. Int J Radiat Biol 2001; 77:409-17. [PMID: 11304435 DOI: 10.1080/09553000010028476] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
PURPOSE To study stable and unstable chromosomal aberrations in the haemopoietic cells of CBA/H mice after exposure to both high- and low-LET radiations. MATERIALS AND METHODS Chromosomal aberrations were scored in the clonal progeny of X-, alpha- or non-irradiated short-term repopulating stem cells using the spleen colony-forming unit (CFU-S) assay, 12 days post-transplantation and in the bone marrow reconstituted by X-, neutron- or non-irradiated exogenous (transplanted) or endogenous (X- or neutron whole-body-irradiated) long-term repopulating stem cells for up to 24 months. RESULTS Chromosomal instability was demonstrated in 3-6% of cells in all cases. After transplantation of X- or neutron-irradiated bone marrow approximately 8% of cells with stable aberrations were recorded at all times. After 3Gy X- or 0.5 Gy neutron- whole-body irradiation stable aberrations were detected in approximately 17 and 5% of cells respectively. CONCLUSIONS Chromosomal instability induced in vitro can be transmitted in vivo by transplantation of haemopoietic stem cells exposed to high- or low-LET radiations. Comparable instability can be induced and shown to persist for the remaining lifetime after whole-body irradiation. There was no direct relationship between the expression of stable and unstable aberrations and significant interanimal variation in the expression of both stable and unstable aberrations.
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Affiliation(s)
- G E Watson
- Radiation and Genome Stability Unit, Medical Research Council, Harwell, UK
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Sankaranarayanan K. Estimation of the hereditary risks of exposure to ionizing radiation: history, current status, and emerging perspectives. HEALTH PHYSICS 2001; 80:363-369. [PMID: 11281204 DOI: 10.1097/00004032-200104000-00013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
This paper provides a brief overview of the advances in the field of the estimation of the genetic risks of exposure of human populations to ionizing radiation from the early 1950's to the present and of the developments that are anticipated in the coming years. The latter are based on the view that the insights gained from human genetics, especially human molecular genetics, will be increasingly applied to address problems in risk estimation. Owing to the paucity of human data on radiation-induced mutations, mouse data on radiation-induced mutations are used to predict the risk of genetic diseases in humans using the doubling dose method. With this method, the risk per unit dose is expressed as a product of three quantities, i.e., P x 1/DD x MC where P is the baseline frequency of genetic diseases, 1/DD (the relative mutation risk per unit dose; DD refers to the doubling dose, i.e., the radiation dose required to produce as many mutations as those that occur spontaneously in a generation) and MC is the disease class-specific mutation component (a measure of the relative increase in disease frequency per unit relative increase in mutation rate). The five important changes that are now introduced in genetic risk estimation include (1) an upward revision of the baseline frequency of Mendelian diseases to 2.4% (from 1.25% used until the early 1990's); (2) a reversion to the conceptual basis for DD calculations used in the 1972 BEIR report of the U.S. National Academy of Sciences, namely, the use of human data on spontaneous mutation rates and mouse data on induced mutation rates (instead of the use of mouse data for both these rates as has been the case from mid-1970's until the early 1990's); (3) the fuller development and use of the MC concept for predicting the responsiveness of Mendelian and multifactorial diseases to increases in mutation rate; (4) the introduction of a new disease-class-specific quantity called the "potential recoverability correction factor" or PRCF in the risk equation to bridge the gap between the rates of induced mutations in mice and the risk of inducible genetic diseases in humans; and (5) the introduction of the concept that multisystem developmental abnormalities are likely to be among the principal phenotypes of radiation induced genetic damage in humans. All these advances now permit, for the first time in 40 y, the estimation of risks for all classes of genetic diseases. For a population exposed to low-LET, chronic or low-dose irradiation, the risks predicted for the first generation progeny are the following (all estimates are per million live born progeny per gray of parental irradiation): autosomal dominant and x-linked diseases, approximately 750 to 1,500 cases; autosomal recessive, nearly zero; chronic multifactorial diseases, approximately 250 to 1,200 cases; and congenital abnormalities, approximately 2000 cases. The total risk per gray is of the order of approximately 3,000 to 4,700 cases, which represent approximately 0.4 to 0.6% of the baseline frequency of these diseases (738,000 per million) in the population. The advances anticipated in the coming years are likely to permit the estimation of genetic risks of radiation with greater precision than is now possible.
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Affiliation(s)
- K Sankaranarayanan
- Department of Radiation Genetics and Chemical Mutagenesis, Leiden University Medical Centre, The Netherlands.
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25
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Roix JJ, Hagge-Greenberg A, Bissonnette DM, Rodick S, Russell LB, O'Brien TP. Molecular and functional mapping of the piebald deletion complex on mouse chromosome 14. Genetics 2001; 157:803-15. [PMID: 11156998 PMCID: PMC1461538 DOI: 10.1093/genetics/157.2.803] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The piebald deletion complex is a set of overlapping chromosomal deficiencies surrounding the endothelin receptor B locus collected during the Oak Ridge specific-locus-test mutagenesis screen. These chromosomal deletions represent an important resource for genetic studies to dissect the functional content of a genomic region, and several developmental defects have been associated with mice homozygous for distinct piebald deletion alleles. We have used molecular markers to order the breakpoints for 20 deletion alleles that span a 15.7-18-cM region of distal mouse chromosome 14. Large deletions covering as much as 11 cM have been identified that will be useful for regionally directed mutagenesis screens to reveal recessive mutations that disrupt development. Deletions identified as having breakpoints positioned within previously described critical regions have been used in complementation studies to further define the functional intervals associated with the developmental defects. This has focused our efforts to isolate genes required for newborn respiration and survival, skeletal patterning and morphogenesis, and central nervous system development.
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Affiliation(s)
- J J Roix
- The Jackson Laboratory, 600 Main St., Bar Harbor, ME 04609, USA
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26
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Sankaranarayanan K, Chakraborty R. Ionizing radiation and genetic risks. XIII. Summary and synthesis of papers VI to XII and estimates of genetic risks in the year 2000. Mutat Res 2000; 453:183-97. [PMID: 11024485 DOI: 10.1016/s0027-5107(00)00106-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
This paper recapitulates the advances in the field of genetic risk estimation that have occurred during the past decade and using them as a basis, presents revised estimates of genetic risks of exposure to radiation. The advances include: (i) an upward revision of the estimates of incidence for Mendelian diseases (2.4% now versus 1.25% in 1993); (ii) the introduction of a conceptual change for calculating doubling doses; (iii) the elaboration of methods to estimate the mutation component (i.e. the relative increase in disease frequency per unit relative increase in mutation rate) and the use of the estimates obtained through these methods for assessing the impact of induced mutations on the incidence of Mendelian and chronic multifactorial diseases; (iv) the introduction of an additional factor called the "potential recoverability correction factor" in the risk equation to bridge the gap between radiation-induced mutations that have been recovered in mice and the risk of radiation-inducible genetic disease in human live births and (v) the introduction of the concept that the adverse effects of radiation-induced genetic damage are likely to be manifest predominantly as multi-system developmental abnormalities in the progeny. For all classes of genetic disease (except congenital abnormalities), the estimates of risk have been obtained using a doubling dose of 1 Gy. For a population exposed to low LET, chronic/ low dose irradiation, the current estimates for the first generation progeny are the following (all estimates per million live born progeny per Gy of parental irradiation): autosomal dominant and X-linked diseases, approximately 750-1500 cases; autosomal recessive, nearly zero and chronic multifactorial diseases, approximately 250-1200 cases. For congenital abnormalities, the estimate is approximately 2000 cases and is based on mouse data on developmental abnormalities. The total risk per Gy is of the order of approximately 3000-4700 cases which represent approximately 0.4-0.6% of the baseline frequency of these diseases (738,000 per million) in the population.
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Affiliation(s)
- K Sankaranarayanan
- Sylvius Laboratories, Department of Radiation Genetics and Chemical Mutagenesis, Leiden University Medical Center, Wassenaarseweg 72, 2333, AL Leiden, The Netherlands.
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Sankaranarayanan K, Chakraborty R. Ionizing radiation and genetic risks. XII. The concept of "potential recoverability correction factor" (PRCF) and its use for predicting the risk of radiation-inducible genetic disease in human live births. Mutat Res 2000; 453:129-81. [PMID: 11024484 DOI: 10.1016/s0027-5107(00)00107-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Genetic risks of radiation exposure of humans are generally expressed as expected increases in the frequencies of genetic diseases over those that occur naturally in the population as a result of spontaneous mutations. Since human data on radiation-induced germ cell mutations and genetic diseases remain scanty, the rates derived from the induced frequencies of mutations in mouse genes are used for this purpose. Such an extrapolation from mouse data to the risk of genetic diseases will be valid only if the average rates of inducible mutations in human genes of interest and the average rates of induced mutations in mice are similar. Advances in knowledge of human genetic diseases and in molecular studies of radiation-induced mutations in experimental systems now question the validity of the above extrapolation. In fact, they (i) support the view that only in a limited number of genes in the human genome, induced mutations may be compatible with viability and hence recoverable in live births and (ii) suggest that the average rate of induced mutations in human genes of interest from the disease point of view will be lower than that assumed from mouse results. Since, at present, there is no alternative to the use of mouse data on induced mutation rates, there is a need to bridge the gap between these and the risk of potentially inducible genetic diseases in human live births. In this paper, we advance the concept of what we refer to here as "the potential recoverability correction factor" (PRCF) to bridge the above gap in risk estimation and present a method to estimate PRCF. In developing the concept of PRCF, we first used the available information on radiation-induced mutations recovered in experimental studies to define some criteria for assessing potential recoverability of induced mutations and then applied these to human genes on a gene-by-gene basis. The analysis permitted us to estimate unweighted PRCFs (i.e. the fraction of genes among the total studied that might contribute to recoverable induced mutations) and weighted PRCFs (i.e. PRCFs weighted by the incidences of the respective diseases). The estimates are: 0.15 (weighted) to 0.30 (unweighted) for autosomal dominant and X-linked diseases and 0.02 (weighted) to 0.09 (unweighted) for chronic multifactorial diseases. The PRCF calculations are unnecessary for autosomal recessive diseases since the risks projected for the first few generations even without using PRCFs are already very small. For congenital abnormalities, PRCFs cannot be reliably estimated. With the incorporation of PRCF into the equation used for predicting risk, the risk per unit dose becomes the product of four quantities (risk per unit dose=Px(1/DD)xMCxPRCF) where P is the baseline frequency of the genetic disease, 1/DD is the relative mutation risk per unit dose, MC is the mutation component and PRCF is the disease-class-specific potential recoverability correction factor instead of the first three (as has been the case thus far). Since PRCF is a fraction, it is obvious that the estimate of risk obtained with the revised risk equation will be smaller than previously calculated values.
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Affiliation(s)
- K Sankaranarayanan
- Department of Radiation Genetics and Chemical Mutagenesis, Leiden University Medical Centre, Sylvius Laboratories, Wassenaarseweg 72, 2333, AL Leiden, The Netherlands.
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28
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Abstract
Genetic modifications of imprinted genes have been generated in the mouse to investigate the regulation of their expression. They show classical imprinted gene inheritances. Here we describe two imprinted gene mutations deriving from mutagenesis experiments. One is expressed only when transmitted through males. It causes a prenatal growth retardation which resembles that of the Igf2 knockout and maps close to the locus on chromosome 7. Differences from the knockout, which include an abnormal head phenotype, homozygous lethality, and an inability to rescue a TME: (Igf2r-deficient) lethality, suggest that Igf2 itself may not be directly affected. The second mutation maps close to the GNAS: cluster of imprinted genes on distal chromosome 2. It gives two distinct phenotypes according to parental origin, a gross neonatal oedema with microcardia and a postnatal growth retardation. The oedema phenotype is effectively lethal and resembles that of mice with paternal partial disomy for distal chromosome 2, as well as that of mice having a maternally derived GNAS: exon 2 knockout. However, the second growth retardation phenotype differs from that of the maternal partial disomy and the paternal knockout. A hypothesis to explain the phenotypes associated with the three genotypes based on the NESP:/NESPAS: sense/antisense and GNASXL: transcripts in the GNAS: cluster is offered.
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Affiliation(s)
- B M Cattanach
- Medical Research Council, Mammalian Genetics Unit, Harwell, Didcot, Oxfordshire OX11 0RD, UK.
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29
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LePage DF, Church DM, Millie E, Hassold TJ, Conlon RA. Rapid generation of nested chromosomal deletions on mouse chromosome 2. Proc Natl Acad Sci U S A 2000; 97:10471-6. [PMID: 10984539 PMCID: PMC27048 DOI: 10.1073/pnas.97.19.10471] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nested chromosomal deletions are powerful genetic tools. They are particularly suited for identifying essential genes in development either directly or by screening induced mutations against a deletion. To apply this approach to the functional analysis of mouse chromosome 2, a strategy for the rapid generation of nested deletions with Cre recombinase was developed and tested. A loxP site was targeted to the Notch1 gene on chromosome 2. A targeted line was cotransfected with a second loxP site and a plasmid for transient expression of Cre. Independent random integrations of the second loxP site onto the targeted chromosome in direct repeat orientation created multiple nested deletions. By virtue of targeting in an F(1) hybrid embryonic stem cell line, F(1)(129S1xCast/Ei), the deletions could be verified and rapidly mapped. Ten deletions fell into seven size classes, with the largest extending six or seven centiMorgans. The cytology of the deletion chromosomes were determined by fluorescent in situ hybridization. Eight deletions were cytologically normal, but the two largest deletions had additional rearrangements. Three deletions, including the largest unrearranged deletion, have been transmitted through the germ line. Several endpoints also have been cloned by plasmid rescue. These experiments illustrate the means to rapidly create and map deletions anywhere in the mouse genome. They also demonstrate an improved method for generating nested deletions in embryonic stem cells.
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Affiliation(s)
- D F LePage
- Department of Genetics, Case Western Reserve University School of Medicine and University Hospitals of Cleveland, 10900 Euclid Avenue, Cleveland, OH 44106-4955, USA
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30
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Abstract
Cells of higher eukaryotes possess several very efficient systems for the repair of radiation-induced lesions in DNA. Different strategies have been adopted at the cellular level to remove or even tolerate various types of lesions in order to assure survival and limit the mutagenic consequences. In mammalian cells, the main DNA repair systems comprise direct reversion of damage, excision of damage and exchange mechanisms with intact DNA. Among these, the direct ligation of single strand breaks (SSB) by a DNA ligase and the multi-enzymatic repair systems of mismatch repair, base and nucleotide excision repair as well as the repair of double strand breaks (DSB) by homologous recombination or non homologous end-joining are the most important systems. Most of these processes are error-free except the non homologous end-joining pathway used mainly for the repair of DSB. Moreover, certain lesions can be tolerated by more or less accurately acting polymerases capable of performing translesional DNA syntheses. The DNA repair systems are intimately integrated in the network of cellular regulation. Some of their components are DNA damage inducible. Radiation-induced mutagenesis is largely due to unrepaired DNA damage but also involves error-prone repair processes like the repair of DSB by non-homologous end-joining. Generally, mammalian cells are well prepared to repair radiation-induced lesions. However, some questions remain to be asked about mechanistic details and efficiencies of the systems for removing certain types of radiation-damage and about their order and timing of action. The answers to these questions would be important for radioprotection as well as radiotherapy.
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Affiliation(s)
- D Averbeck
- Institut Curie, laboratoires Raymond-Latarjet, UMR2027 CNRS, centre universitaire d'Orsay, France
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31
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Su H, Wang X, Bradley A. Nested chromosomal deletions induced with retroviral vectors in mice. Nat Genet 2000; 24:92-5. [PMID: 10615136 DOI: 10.1038/71756] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Chromosomal deletions, especially nested deletions, are major genetic tools in diploid organisms that facilitate the functional analysis of large chromosomal regions and allow the rapid localization of mutations to specific genetic intervals. In mice, well-characterized overlapping deletions are only available at a few chromosomal loci, partly due to drawbacks of existing methods. Here we exploit the random integration of a retrovirus to generate high-resolution sets of nested deletions around defined loci in embryonic stem (ES) cells, with sizes extending from a few kilobases to several megabases. This approach expands the application of Cre-loxP-based chromosome engineering because it not only allows the construction of hundreds of overlapping deletions, but also provides molecular entry points to regions based on the retroviral tags. Our approach can be extended to any region of the mouse genome.
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Affiliation(s)
- H Su
- Program in Developmental Biology, Department of Molecular Genetics, Baylor College of Medicine, Houston, Texas, USA
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32
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Hart PE, Glantz JN, Orth JD, Poynter GM, Salisbury JL. Testis-specific murine centrin, Cetn1: genomic characterization and evidence for retroposition of a gene encoding a centrosome protein. Genomics 1999; 60:111-20. [PMID: 10486202 DOI: 10.1006/geno.1999.5880] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Centrin is a centrosome component in species from yeast to humans. Here, the mouse centrin 1 gene (Cetn1) is analyzed with respect to its genomic structure, chromosome localization, tissue-specific expression, and phylogenetic relationship to the other mouse centrin genes and their human orthologs. Cetn1 is an intronless gene located on chromosome 18A2 that encodes a 172-amino-acid protein with a predicted molecular mass of 19,696 Da (pI 4.61) and all of the structural features common to centrin. Cetn1 possesses the sequence features of an expressed retroposon: the gene lacks introns, the open reading frame is not interrupted by stop codons, and the coding region is flanked by a pair of direct repeats. Reverse transcriptase-polymerase chain reaction and Northern blot analysis demonstrate that Cetn1 expression is limited exclusively to the testis in adult male mice. Cetn1 expression is first seen in the neonatal testis at 14 days postpartum, reaching adult levels by day 17. These observations provide new insight into the regulation, function, and evolutionary history of centrin in higher eukaryotes.
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Affiliation(s)
- P E Hart
- Tumor Biology Program, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA
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33
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Sankaranarayanan K. Ionizing radiation and genetic risks. X. The potential "disease phenotypes" of radiation-induced genetic damage in humans: perspectives from human molecular biology and radiation genetics. Mutat Res 1999; 429:45-83. [PMID: 10434024 DOI: 10.1016/s0027-5107(99)00100-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Estimates of genetic risks of radiation exposure of humans are traditionally expressed as expected increases in the frequencies of genetic diseases (single-gene, chromosomal and multifactorial) over and above those of naturally-occurring ones in the population. An important assumption in expressing risks in this manner is that gonadal radiation exposures can cause an increase in the frequency of mutations and that this would result in an increase in the frequency of genetic diseases under study. However, despite compelling evidence for radiation-induced mutations in experimental systems, no increases in the frequencies of genetic diseases of concern or other adverse effects (i.e., those which are not formally classified as genetic diseases), have been found in human studies involving parents who have sustained radiation exposures. The known differences between spontaneous mutations that underlie naturally-occurring single-gene diseases and radiation-induced mutations studied in experimental systems now permit us to address and resolve these issues to some extent. The fact that spontaneous mutations (among which are point mutations and DNA deletions generally restricted to the gene) originate through a number of different mechanisms and that the latter are intimately related to the DNA organization of the genes, are now well-documented. Further, spontaneous mutations include those that cause diseases through loss of function as well as gain of function of genes. In contrast, most radiation-induced mutations studied in experimental systems (although identified through the phenotypes of the marker genes) are predominantly multigene deletions which cause loss of function; the recoverability of an induced deletion in a livebirth seems dependent on whether the gene and the genomic region in which it is located can tolerate heterozygosity for the deletion and yet be compatible with viability. In retrospect, the successful mutation test systems (such as the mouse specific locus test) used in radiation studies have involved genes which are non-essential for survival and are also located in genomic regions, likewise non-essential for survival. In contrast, most of the human genes at which induced mutations have been looked for, do not seem to have these attributes. The inference therefore is that the failure to find induced germline mutations in humans is not due to the resistance of human genes to induced mutations but due to the structural and functional constraints associated with their recoverability in livebirths. Since the risk of inducible genetic diseases in humans is estimated using rates of "recovered" mutations in mice, there is a need to introduce appropriate correction factors to bridge the gap between these rates and the rates at which mutations causing diseases are potentially recoverable in humans. Since the whole genome is the "target" for radiation-induced genetic damage, the failure to find increases in the frequencies of specific single-gene diseases of societal concern does not imply that there are no genetic risks of radiation exposures: the problem lies in delineating the phenotypes of recoverable genetic damage that are recognizable in livebirths. Data from studies of naturally-occurring microdeletion syndromes in humans and those from mouse radiation studies are instructive in this regard. They (i) support the view that growth retardation, mental retardation and multisystem developmental abnormalities are likely to be among the quantitatively more important adverse effects of radiation-induced genetic damage than mutations in a few selected genes and (ii) underscore the need to expand the focus in risk estimation from known genetic diseases (as has been the case thus far) to include these induced adverse developmental effects although most of these are not formally classified as "genetic diseases". (ABSTRACT TRUNCATED)
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Affiliation(s)
- K Sankaranarayanan
- MGC, Department of Radiation Genetics and Chemical Mutagenesis, Leiden University Medical Centre, Sylvius Laboratories, Wassenaarseweg 72, 2333 AL, Leiden, Netherlands.
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34
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Abstract
Autosomal trisomy causes a large proportion of all human pregnancy loss and so is a significant source of lethality in the human population. The autosomal trisomy syndromes each have a different phenotype and are probably caused by the effects of specific genes that are present in three copies, rather than the normal two. Identifying these genes will require the application of classical genetic and new genome-manipulation approaches. Recent advances in chromosome engineering are now allowing us to create precisely defined autosomal trisomies in the mouse, and so provide new routes to identifying the critical, dosage-sensitive genes that are responsible for these highly deleterious, yet very common, syndromes.
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Affiliation(s)
- D Hernandez
- Department of Neurogenetics, Imperial College School of Medicine (St Mary's), Norfolk Place, London, UK W2 1PG.
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35
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Liu P, Zhang H, McLellan A, Vogel H, Bradley A. Embryonic lethality and tumorigenesis caused by segmental aneuploidy on mouse chromosome 11. Genetics 1998; 150:1155-68. [PMID: 9799267 PMCID: PMC1460401 DOI: 10.1093/genetics/150.3.1155] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Chromosome engineering in mice enables the construction of models of human chromosomal diseases and provides key reagents for genetic studies. To begin to define functional information for a small portion of chromosome 11, deficiencies, duplications, and inversions were constructed in embryonic stem cells with sizes ranging from 1 Mb to 22 cM. Two deficiencies and three duplications were established in the mouse germline. Mice with a 1-Mb duplication developed corneal hyperplasia and thymic tumors, while two different 3- to 4-cM deficiencies were embryonically lethal in heterozygous mice. A duplication corresponding to one of these two deficiencies was able to rescue its haplolethality.
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Affiliation(s)
- P Liu
- Department of Human and Molecular Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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36
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Abstract
The mouse mutant resource is a valuable tool for gene function studies in the post-genomics era. However, despite a seemingly large catalogue of mouse mutants, it is recognized that we have access to mutations at only a small fraction of the total number of mouse genes. There is a phenotype gap that needs to be narrowed by the implementation of large-scale, systematic mutagenesis programmes in the mouse. Both genotype-driven and phenotype-driven approaches can be employed to recover new mouse mutations. Genotype-driven approaches include large-scale genome-wide mutagenesis by gene trapping in embryonic stem cells. For genotype-driven approaches, the initial focus is on the characterization of the mutational change to the genome. Identification of the mutated gene is relatively trivial, but the genotype-driven route provides little indication of the likely phenotypic outcome of the mutation. In contrast, phenotype-driven approaches employ mutagenesis procedures that emphasize the recovery of novel phenotypes without prior assumptions about the underlying gene or pathway that has been disrupted--although identifying the underlying gene may not be trivial. One phenotype-driven approach includes chemical mutagenesis using N-ethyl-N-nitrosourea (ENU). ENU mutagenesis programmes are increasingly being brought to bear on increasing the breadth and depth of the mouse mutant resource, and in so doing narrowing the phenotype gap.
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Affiliation(s)
- S D Brown
- MRC Mammalian Genetics Unit, Harwell, UK
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37
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Abstract
Significant progress has been made in sequencing the genomes of several model organisms, and efforts are now underway to complete the sequencing of the human genome. In parallel with this effort, new approaches are being developed for the elucidation of the functional content of the human genome. The mouse will have an important role in this phase of the genome project as a model system. In this review we discuss and compare classical genetic approaches to gene function-phenotype-based mutagenesis screens aimed at the establishment of a large collection of single gene mutations affecting a wide range of phenotypic traits in the mouse. Whereas large scale genome-wide screens that are directed at the identification of all loci contributing to a specific phenotype may be impractical, region-specific saturation screens that provide mutations within a delimited chromosomal region are a feasible alternative. Region-specific screens in the mouse can be performed in only two generations by combining high-efficiency chemical mutagenesis with deletion complexes generated using embryonic stem (ES) cells. The ability to create and analyze deletion complexes rapidly, as well as to map novel chemically-induced mutations within these complexes, will facilitate systematic functional analysis of the mouse genome and corresponding gene sequences in humans. Furthermore, as the extent of the mouse genome sequencing effort is still uncertain, we underscore a necessity to direct sequencing efforts to those chromosomal regions that are targets for extensive mutagenesis screens.
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Affiliation(s)
- J Schimenti
- The Jackson Laboratory, Bar Harbor, Maine 04609 USA
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38
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You Y, Bersgtram R, Klemm M, Nelson H, Jaenisch R, Schimenti J. Utility of C57BL/6J x 129/SvJae embryonic stem cells for generating chromosomal deletions: tolerance to gamma radiation and microsatellite polymorphism. Mamm Genome 1998; 9:232-4. [PMID: 9501308 DOI: 10.1007/s003359900731] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We have previously reported a method for making nested deletion complexes in mice by irradiation of ES cells. The key to this technology is that F1 hybrid ES cells (called v17.2) of the genotype (BALB/cTa x 129/SvJae) retain germline colonizing ability after exposure to levels of ionizing radiation that induce chromosomal deletions. In an effort to identify other genotypes of ES cells that are suitable for this technology, the radiation sensitivity of the cell line v6.4, which is of the genotype (C57BL/6J x 129/SvJae), was investigated. After treatment with a range of radiation exposures, the developmental potential of these cells was assayed by injecting them into blastocysts to generate chimeric mice. These experiments showed that while cell lethality increased as the level of radiation increased, the surviving ES cells retained full totipotency at all exposure levels, up to 400 Rads. Because polymorphism between parental microsatellite alleles in the F1 hybrid ES cells is important for ascertaining the sizes of induced deletions, the 129/SvJ and 129/SvJae allele sizes of 48 microsatellite loci on chromosome (Chr) 17 were determined. This revealed a higher level of polymorphism between 129 and C57BL/6J on Chr 17. The radiation tolerance, high polymorphism between parental strains, and presence of the widely used C57BL/6J strain component make v6.4 ES cells an attractive cell line for generating radiation-induced chromosomal deletions.
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Affiliation(s)
- Y You
- Jackson Laboratory, Bar Harbor, Maine 04609, USA
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39
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Thomas JW, LaMantia C, Magnuson T. X-ray-induced mutations in mouse embryonic stem cells. Proc Natl Acad Sci U S A 1998; 95:1114-9. [PMID: 9448294 PMCID: PMC18691 DOI: 10.1073/pnas.95.3.1114] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Deletion complexes consisting of multiple chromosomal deletions induced at single loci can provide a means for functional analysis of regions spanning several centimorgans in model genetic systems. A strategy to identify and map deletions at any cloned locus in the mouse is described here. First, a highly polymorphic, germ-line competent F1(129/Sv-+Tyr+p x CAST/Ei) mouse embryonic stem cell line was established. Then, x-ray and UV-induced mutagenesis was performed to determine the feasibility of generating deletion complexes throughout the mouse genome. Reported here are the selection protocols, induced mutation frequencies, cytogenetic and extensive molecular analysis of mutations at the X-chromosome-linked hypoxanthine phosphoribosyltransferase (Hprt) locus and at the neural cell adhesion molecule (Ncam) locus located on chromosome 9. Mutation analysis with PCR-based polymorphic microsatellite markers revealed deletions of <3 cM at the Hprt locus, whereas results consistent with deletions covering >28 cM were observed at the Ncam locus. Fluorescence in situ hybridization with a chromosome 9 paint revealed that some of the Ncam deletions were accompanied by complex chromosome rearrangements. In addition, deletion mapping in combination with loss of heterozygosity of microsatellite markers revealed a putative haploinsufficient region distal to Ncam. These data indicate that it is feasible to generate x-ray-induced deletion complexes in mouse embryonic stem cells.
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Affiliation(s)
- J W Thomas
- Department of Genetics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4955, USA
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40
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Smiraglia DJ, Ratty AK, Gross KW. Physical characterization of the chromosomal rearrangements that accompany the transgene insertion in the chakragati mouse mutant. Genomics 1997; 45:562-71. [PMID: 9367681 DOI: 10.1006/geno.1997.4975] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The circling phenotype of the chakragati mouse is a result of a transgenic insertional mutation. The absence of the phenotype in mice heterozygous for the transgene insertion suggests that this is due to a loss of function of an endogenous gene. Efforts to identify this gene have led to a previous report that sequences flanking the transgene, D16Ros1 and D16Ros2, map 10 cM apart in wildtype mice. We present here physical mapping data indicating that the proximity of D16Ros1 and D16Ros2 in the ckr mouse is explained by a duplication of D16Ros2 and its insertion along with the transgene at D16Ros1. We further demonstrate that D16Ros1 sequences are also duplicated and that this duplication is also part of the insertion at the endogenous D16Ros1 locus.
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Affiliation(s)
- D J Smiraglia
- Cell and Molecular Biology Department, Roswell Park Cancer Institute, Buffalo, New York, 14263, USA
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41
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Smiraglia DJ, Wu C, Ellsworth MK, Ratty AK, Chapman VM, Gross KW. Genetic characterization of the chromosomal rearrangements that accompany the transgene insertion in the chakragati mouse mutant. Genomics 1997; 45:572-9. [PMID: 9367682 DOI: 10.1006/geno.1997.4976] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We have previously reported that the circling phenotype of the chakragati mouse segregates with the transgene integration event as an autosomal recessive trait. It was unclear, however, whether the phenotype was linked to the transgene integration point near D16Ros1 or to a potential disruption at D16Ros2, 10 cM away. We report here that animals recombinant between D16Ros1 and D16Ros2, homozygous for the transgene insertion at D16Ros1, but wildtype for D16Ros2, do indeed show the phenotype. We conclude that any potential disruption at the D16Ros2 locus is not responsible for the circling phenotype. We further show that recombination between D16Ros1 and D16Ros2 occurs at a greatly reduced level in the chakragati mouse compared to wildtype strains. Detailed genetic analysis of recombinants indicates that the proximal-most 4.5 cM shows no recombination in over 1400 meioses. We propose that this is due to an inversion in this region, and we genetically define the proposed distal inversion break point to a 1.3-cM region between D16Mit63 and D16Mit169.
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Affiliation(s)
- D J Smiraglia
- Cell and Molecular Biology Department, Roswell Park Cancer Institute, Buffalo, New York, 14263, USA
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42
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Cecchi C, Biasotto M, Tosi M, Avner P. The mottled mouse as a model for human Menkes disease: identification of mutations in the Atp7a gene. Hum Mol Genet 1997; 6:425-33. [PMID: 9147646 DOI: 10.1093/hmg/6.3.425] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Mutations in the Atp7a gene, the mouse homologue of the MNK (ATP7A) gene, have been suggested to be responsible for the mottled phenotype. To date, despite considerable effort, changes associated with the mottled mutations have been detected in only two such mutants. In this study, we identify changes in the level of Atp7a transcript and mutations which could explain the mottled phenotype in nine out of the 10 mutants analysed. The fluorescence-assisted mismatch analysis method used here has proved particularly well suited for mRNA scanning of heterozygous carrier animals, because of its ability to detect mutations even in the presence of an excess of wild-type mRNA. The three new underlying mutations identified at the Atp7a locus include a splice mutation and two missense mutations. While the spectrum of mutations detected in the Atp7a murine gene provides an explanation for at least part of the wide phenotypic variation observed in mottled mutant mice, there is a singular absence of deletions which are associated with a sizeable fraction of human Menkes syndrome cases.
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Affiliation(s)
- C Cecchi
- Unité de Génétique Moléculaire Murine, Institut Pasteur, Paris, France
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43
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Affiliation(s)
- L H Looijenga
- Dr. Daniel den Hoed Cancer Center, University Hospital Rotterdam, the Netherlands
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44
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Affiliation(s)
- S D Brown
- MRC Mammalian Genetics Unit, Harwell, Oxfordshire, UK.
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45
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Hoyes KP, Morris ID. Environmental radiation and male reproduction. INTERNATIONAL JOURNAL OF ANDROLOGY 1996; 19:199-204. [PMID: 8940657 DOI: 10.1111/j.1365-2605.1996.tb00463.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- K P Hoyes
- School of Biological Sciences, University of Manchester, UK
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46
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Tease C, Fisher G. Cytogenetic and genetic studies of radiation-induced chromosome damage in mouse oocytes. I. Numerical and structural chromosome anomalies in metaphase II oocytes, pre- and post-implantation embryos. Mutat Res 1996; 349:145-53. [PMID: 8569787 DOI: 10.1016/0027-5107(95)00182-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The incidences of X-ray induced numerical and structural chromosome anomalies were screened in a range of developmental stages from metaphase II oocytes through to post-implantation embryos. Following 1 Gy of acute X-rays to immediately preovulatory stage oocytes, the rate of hyperploidy (chromosome gain) was found to be elevated over levels in unirradiated controls, at metaphase II, in 1-cell and 3.5 day pre-implantation embryos but not in 8.5 day post-implantation foetuses. In the latter, however, the frequency of mosiacism was significantly increased. A similar response of an increase in mosaicism but not in hyperploidy in 8.5 day post-implantation embryos was also found after irradiation of dictyate stage oocytes with 4 Gy of acute X-rays. Significantly elevated frequencies of structural chromosome anomalies were present in metaphase II oocytes and pre-implantation embryonic stages, but could not be detected in block-stained chromosome preparations from 8.5 day post-implantation foetuses. However, analysis of chromosome preparations after G-banding showed that almost 14% of 14.5 day foetuses carried a chromosome rearrangement after 1 Gy of X-rays to immediately preovulatory stage oocytes. Overall, our data indicate that the presence of radiation-induced chromosome gains are incompatible with embryonic survival but that a proportion of embryos with structural chromosome damage develop past mid-gestation. These latter embryos are therefore potentially capable of contributing to the genetic burden of the next generation.
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Affiliation(s)
- C Tease
- MRC Radiobiology Unit, Chilton, Didcot UK
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47
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Tease C, Fisher G. Cytogenetic and genetic studies of radiation-induced chromosome damage in mouse oocytes. II. Induced chromosome loss and dominant visible mutations. Mutat Res 1996; 349:155-62. [PMID: 8569788 DOI: 10.1016/0027-5107(95)00183-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The rates of X-ray induced loss of chromosome 19 in mouse oocytes were investigated in 2 experiments using a genetic complementation test. After 1 Gy of acute X-rays to immediately preovulatory stage oocytes, chromosome 19 loss was estimated to have occurred in 1.68% of cells. In comparison, after 4 Gy of acute X-rays to dictyate stage oocytes, the rate was estimated at 1.18%. The slightly higher rate of chromosome loss in the former cell stage after a smaller dose of radiation reflects the known increased radiosensitivity of mouse oocytes in the period shortly before ovulation. Comparison of the observations here for chromosome 19 with published data for chromosome 1 suggests that chromosome length is one of the principal factors in determining the initial rate of induced loss in mouse oocytes. Ten dominant visible mutations were recovered among 1674 offspring following irradiation of preovulatory oocytes, and 8 in 2025 offspring after treatment of dictyate cells. Nine dominant mutations were karyotyped, 5 of these were found to be associated with a visible chromosome rearrangement. The data obtained in the present study show that radiation-induced chromosome anomalies in female germ cells are not all filtered out by prenatal embryonic death but that a proportion has the potential to contribute to the genetic burden of the next generation.
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Affiliation(s)
- C Tease
- MRC Radiobiology Unit, Chilton, Didcot, UK
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48
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Sankaranarayanan K. Environmental chemical mutagens and genetic risks: lessons from radiation genetics. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 1996; 28:65-70. [PMID: 8844986 DOI: 10.1002/(sici)1098-2280(1996)28:2<65::aid-em1>3.0.co;2-d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Affiliation(s)
- K Sankaranarayanan
- Department of Radiation Genetics and Chemical Mutagenesis, Sylvius Laboratories, Leiden University, The Netherlands
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49
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Favor J. Mutagenesis and human genetic disease: dominant mutation frequencies and a characterization of mutational events in mice and humans. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 1995; 25 Suppl 26:81-87. [PMID: 7789366 DOI: 10.1002/em.2850250612] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Dominant deleterious traits are generally regarded to be the most relevant genetic endpoints when the expected increased mutational load of genetic diseases associated with exposure to mutagenic agents is considered in humans. At present, human risk estimation procedures rely on results from laboratory mammal germ-cell mutagenicity experiments as well as on data from human epidemiology and medical genetics. A comparison of the mouse and human data indicates that a small subset of loci, which when mutated result in a dominant phenotype, is contributing disproportionately to the observed mutation frequency. This is likely due to the fact that those loci with an observed high mutation frequency are inherently unstable, the function of such loci is critical, and/or the wild-type phenotype requires two copies of the normal gene (haploinsufficiency). The locus specificity of the observed spontaneous and induced mutation frequencies implies that efforts must be made to closely match those genetic endpoints screened in the mouse with the human genetic endpoints considered relevant in estimating the genetic risk after exposure to mutagenic agents. The contributions to our understanding of the organization, function, and stability of the mouse and human genomes provided by molecular biological techniques should make compliance with this restriction feasible.
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Affiliation(s)
- J Favor
- Institut für Säugetiergenetik, GSF-Forschungszentrum für Umwelt und Gesundheit, Oberschleissheim, Germany
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50
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Johannisson R, Mörmel R, Brandenburg B. Synaptonemal complex damage in fetal mouse oocytes induced by ionizing irradiation. Mutat Res 1994; 311:319-28. [PMID: 7526197 DOI: 10.1016/0027-5107(94)90190-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Fetal female mice were exposed to ionizing irradiation of 2 Gy in a single dose at days 14, 16, and 17 of gestation. Synaptonemal complexes of primary oocytes were analyzed on day 17. It has been demonstrated that electron beam irradiation of early oocytes on day 14 with 2 Gy is accompanied by a duplication of atretic cells. A significant increase in fragmentations of the synaptonemal complexes over the base level became evident when mice were exposed to irradiation on days 16 and 17 of gestation. Frequencies of multivalent formation and univalents were not increased over the levels in the control group. Reduction of fertility and malsegregation of chromosomes may be a reflection of the consequences of the observed nuclear lesions.
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Affiliation(s)
- R Johannisson
- Institut für Pathologie, Medizinische Universität zu Lübeck, Germany
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