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Davies MJ, Phillips BJ, Rumsby PC. Molecular analysis of chemically-induced mutations in mammalian cell assays. Toxicol In Vitro 2012; 9:513-8. [PMID: 20650122 DOI: 10.1016/0887-2333(95)00048-d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Two mammalian cell mutation assays, the HPRT/V79 assay and the TK/mouse lymphoma assay, were compared for their ability to respond to the genotoxic chemicals ethyl methanesulfonate (EMS) and mitomycin C (MMC). Whereas EMS induced a high mutant frequency at both loci, MMC produced few mutants at the hprt locus, but induced a large number of mutants at the tk locus. Southern blotting analysis showed that this difference was due to the type of genetic damage induced by the two chemicals. Intragenic changes ranging from point mutations to loss of the entire gene were recovered as viable mutants at both the hprt and tk loci. Thus, EMS which causes mainly intragenic mutations induced similar mutant frequencies at both loci. The large multilocus deletions induced by MMC, in which the damage was assumed in many cases to extend into a gene essential for growth since most TK mutants were slow-growing, could not be recovered at the hprt locus. Whereas both loci will detect intergenic mutations, mutants carrying large-scale damage are recoverable only at the heterozygous tk locus. At the hemizygous hprt locus no homologous chromosome exists to provide the function of essential genes if these are lost along with hprt in multilocus deletions. Most human cancers develop as a highly complex process involving both gene and multilocus mutations in oncogenes and tumour suppressor genes. Thus the TK/mouse lymphoma assay is a more appropriate in vitro test for the detection of chemicals capable of causing the types of DNA lesions important in human cancer.
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Affiliation(s)
- M J Davies
- BIBRA International, Woodmansterne Road, Carshalton, Surrey SM5 4DS, UK
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2
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Russo D, Fronza G, Ottaggio L, Monti P, Inga A, Iyer P, Gold B, Menichini P. High frequency of genomic deletions induced by Me-lex, a sequence selective N3-adenine methylating agent, at the Hprt locus in Chinese hamster ovary cells. Mutat Res 2009; 671:58-66. [PMID: 19729030 DOI: 10.1016/j.mrfmmm.2009.08.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Revised: 07/17/2009] [Accepted: 08/26/2009] [Indexed: 01/21/2023]
Abstract
We have investigated the mutagenicity induced at the Hprt locus in Chinese hamster ovary (CHO) cells treated with increasing concentrations of Me-lex, a minor groove selective methylating agent that efficiently generates more than 90-95% of 3-MeA DNA adducts. Me-lex treatment was cytotoxic but weakly mutagenic, resulting in up to 7-fold induction above background in the Hprt mutation frequency. The molecular nature of 43 Hprt mutations induced by Me-lex was determined by sequence analysis of the Hprt cDNA and genomic analysis of the gene locus. Base pair substitutions represented about 25% of Me-lex induced mutations. The mutation spectrum revealed a high percentage of genomic deletions (51%) comprising single/multiple exon(s) and even the loss of the complete locus. When the distribution of mutations among different classes was considered, the difference between the spontaneous and Me-lex induced CHO spectra was statistically significant (p<0.012), indicating that the sites where mutations occurred were Me-lex specific. Based upon these results we hypothesize that a large proportion of mutations may result from the processing of 3-MeA, the main adduct induced by Me-lex, within A/T rich sequences in non-coding regions of the Hprt gene. The processing of these lesions by DNA polymerases could result in recombination and genomic deletions, thus representing a severe threat for genome integrity.
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Affiliation(s)
- Debora Russo
- Molecular Mutagenesis and DNA Repair Unit, Department of Epidemiology and Prevention, National Cancer Research Institute (IST), L.go R. Benzi, 10, 16132 Genova, Italy
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Kinashi Y, Masunaga S, Nagata K, Suzuki M, Takahashi S, Ono K. A Bystander Effect Observed in Boron Neutron Capture Therapy: A Study of the Induction of Mutations in the HPRT Locus. Int J Radiat Oncol Biol Phys 2007; 68:508-14. [PMID: 17418970 DOI: 10.1016/j.ijrobp.2007.02.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2006] [Revised: 01/26/2007] [Accepted: 02/01/2007] [Indexed: 11/19/2022]
Abstract
PURPOSE To investigate bystander mutagenic effects induced by alpha-particles during boron neutron capture therapy, we mixed cells that were electroporated with borocaptate sodium (BSH), which led to the accumulation of (10)B inside the cells, and cells that did not contain the boron compound. The BSH-containing cells were irradiated with alpha-particles produced by the 10B(n,alpha)7Li reaction, whereas cells without boron were affected only by the 1H(n,gamma)2H and 14N(n,rho)14C reactions. METHODS AND MATERIALS The lethality and mutagenicity measured by the frequency of mutations induced in the hypoxanthine-guanine phosphoribosyltransferase locus were examined in Chinese hamster ovary cells irradiated with neutrons (Kyoto University Research Reactor: 5 MW). Neutron irradiation of 1:1 mixtures of cells with and without BSH resulted in a survival fraction of 0.1, and the cells that did not contain BSH made up 99.4% of the resulting cell population. The molecular structures of the mutations were determined using multiplex polymerase chain reactions. RESULTS Because of the bystander effect, the frequency of mutations increased in the cells located nearby the BSH-containing cells compared with control cells. Molecular structural analysis indicated that most of the mutations induced by the bystander effect were point mutations and that the frequencies of total and partial deletions induced by the bystander effect were less than those induced by the original neutron irradiation. CONCLUSION These results suggested that in boron neutron capture therapy, the mutations caused by the bystander effect and those caused by the original neutron irradiation are induced by different mechanisms.
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Affiliation(s)
- Yuko Kinashi
- Research Reactor Institute, Kyoto University, Osaka, Japan.
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Dahle J, Noordhuis P, Stokke T, Svendsrud DH, Kvam E. Multiplex Polymerase Chain Reaction Analysis of UV-A- and UV-B-induced Delayed and Early Mutations in V79 Chinese Hamster Cells¶. Photochem Photobiol 2007. [DOI: 10.1111/j.1751-1097.2005.tb01529.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Silva MJ, Costa P, Dias A, Valente M, Louro H, Boavida MG. Comparative analysis of the mutagenic activity of oxaliplatin and cisplatin in the Hprt gene of CHO cells. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2005; 46:104-15. [PMID: 15887215 DOI: 10.1002/em.20138] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Oxaliplatin is a platinum-derived antitumor drug that is active against cisplatin-resistant tumors and has lower overall toxicity than does cisplatin. DNA adduct formation is believed to mediate the cytotoxic activity of both compounds; however, the adducts may also be responsible for mutagenic and secondary tumorigenic activities. In this study, we have compared the mutagenicity of oxaliplatin and cisplatin in the Hprt gene of CHO-K1 cells. Both drugs produced dose-related increases in mutant frequency. For 1-hr treatments, oxaliplatin was less mutagenic than cisplatin at equimolar doses, while similar mutant frequencies were induced at equitoxic doses. Sequencing of mutant Hprt genes indicated that the mutation spectra of both oxaliplatin and cisplatin were significantly different from the spontaneous mutation spectrum (P = 0.014 and P = 0.008, respectively). A significant difference was also observed between the spectra of oxaliplatin- and cisplatin-induced mutations (P = 0.033). Although G:C-->T:A transversion was the most common mutation produced by both compounds, oxaliplatin produced higher frequencies of A:T-->T:A transversion than did cisplatin, most commonly at nucleotide 307, and higher frequencies of small deletions/insertions. Also, cisplatin induced tandem base-pair substitutions, mainly at positions 135/136, and a higher frequency of G:C-->A:T transition than did oxaliplatin. These results provide the first evidence that oxaliplatin is mutagenic and that the profiles of cisplatin- and oxaliplatin-induced mutations display not only similarities but also distinctive features relating to the type and sequence-context preference for mutation. Environ.
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Affiliation(s)
- Maria J Silva
- Centro de Genética Humana, Instituto Nacional de Saúde Dr. Ricardo Jorge, Lisboa, Portugal.
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6
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Dahle J, Noordhuis P, Stokke T, Svendsrud DH, Kvam E. Multiplex Polymerase Chain Reaction Analysis of UV-A– and UV-B–induced Delayed and Early Mutations in V79 Chinese Hamster Cells¶. Photochem Photobiol 2005. [DOI: 10.1562/2004-05-19-ra-174.1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Coryell VH, Stearns DM. Molecular analysis ofhprt mutations generated in Chinese hamster ovary EM9 cells by uranyl acetate, by hydrogen peroxide, and spontaneously. Mol Carcinog 2005; 45:60-72. [PMID: 16299811 DOI: 10.1002/mc.20155] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Naturally occurring uranium and depleted uranium (DU) are believed to be health hazards by virtue of both their chemical and radiological properties. The mechanism(s) behind uranium's chemotoxic effects has yet to be elucidated. Previous work has shown that DU, as uranyl acetate (UA), was mutagenic at the hypoxanthine (guanine) phosphoribosyltransferase (hprt) locus in XRCC1-deficient CHO EM9 cells. The purpose of the current study was to characterize the mutations induced by UA at the hprt locus of CHO EM9 cells and compare the mutation spectrum of UA with those of hydrogen peroxide and spontaneous mutations in the same line. The hypothesis being tested was that if DU as UA is chemically genotoxic then the mutation spectrum induced by the heavy metal should be distinct from that produced spontaneously or by H2O2. A total of 59 UA-induced, 38 spontaneous, and 45 H2O2-induced mutations were identified. Base substitutions comprised 29%, 42%, and 16% of UA, spontaneous, and H2O2 mutants, respectively. The frequency of G --> T or C --> A substitutions was not significantly different in spontaneous or H2O2-induced mutants than in UA-induced mutants, suggesting a possible role for 8-oxodG damage in UA mutagenesis. However, the observation that UA produced significantly more major genomic rearrangements (multiexon insertions and deletions) than occurred spontaneously suggests the possibility that DNA strand breaks or crosslinks could also be UA-induced mutagenic lesions. The unique mutation spectrum elicited by exposure to UA suggests that UA generates mutations in ways that are different from spontaneous and free radical as well as radiological mechanisms.
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Affiliation(s)
- Virginia H Coryell
- Department of Chemistry and Biochemistry, Northern Arizona University, Flagstaff, Arizona 86011-5698, USA
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Themis M, May D, Coutelle C, Newbold RF. Mutational effects of retrovirus insertion on the genome of V79 cells by an attenuated retrovirus vector: implications for gene therapy. Gene Ther 2003; 10:1703-11. [PMID: 12923569 DOI: 10.1038/sj.gt.3302059] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Attenuated retroviruses are currently the most widely used vectors in clinical gene therapy because of their potential to effect stable and permanent gene transfer. Since gene delivery is accompanied by random insertion of foreign genetic material into the recipient chromosomal DNA, the potential for insertional mutagenesis exists. In this study, we used a defective retrovirus vector containing a selectable marker, the hygromycin phosphotransferase gene, to investigate the mutagenic effects of vector integration on the mammalian genome. V79 Chinese hamster cells were infected with virus supernatants or by coculture with virus producer cells, and provirus insertion events occurred at low and high frequencies, respectively. The frequency of hprt mutagenesis was increased by a factor of 2.3 over the spontaneous hprt mutation frequency only following multiple provirus insertions/cell genome. Multiple provirus insertions (>3/genome) resulted in instability at the hprt locus in 63% of the virally induced hprt mutants, as indicated by rearrangements at the molecular level, whereas no rearrangements were found when the provirus copy number was 1-2/genome. To demonstrate direct proviral involvement in mutagenesis, the defective MLV vector was retrieved along with flanking genomic hprt sequences from one mutant, and localized within intron 5 of the hprt gene. These data suggest that provirus copy number is a key factor when considering the potential hazards of using retrovirus vectors for gene therapy.
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Affiliation(s)
- M Themis
- Division of Cell and Molecular Biology, Imperial College, London, UK
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Kenner O, Kneisel A, Klingler J, Bartelt B, Speit G, Vogel W, Kaufmann D. Targeted gene correction of hprt mutations by 45 base single-stranded oligonucleotides. Biochem Biophys Res Commun 2002; 299:787-92. [PMID: 12470647 DOI: 10.1016/s0006-291x(02)02749-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Targeted correction of a single base in a gene of an eucaryotic cell by specific oligonucleotides is a yet controversial technique. Here, we introduce the correction of point mutations in the hypoxanthine-guanine-phosphoribosyl-transferase (HPRT) gene as an additional model system to test targeted gene correction. In human, Hprt mutations cause Lesch-Nyhan syndrome. Using hamster V79 cells, we generated three cell lines with one hprt point mutation each. These cell lines were treated with specific single-stranded 45 base phosphothioate modified oligonucleotides and selected by HAT medium. The surviving clones were investigated for the correction of the respective hprt mutation. Treatment with the oligonucleotides was successful in repairing all three hprt mutations (hprt cDNA position 74, C --> T; position 151, C --> T; and position 400, G --> A). The correction efficiency was very low but reproducible. We suggest that this system allows one to investigate targeted gene correction in dependence on the target sequence and the oligonucleotides used.
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Affiliation(s)
- Oliver Kenner
- Department of Human Genetics, University of Ulm, Albert-Einstein-Allee 11, D 89070 Ulm, Germany
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Nakajima M, Takeuchi T, Ogino K, Morimoto K. Lack of direct involvement of 8-hydroxy-2'-deoxyguanosine in hypoxanthine-guanine phosphoribosyltransferase mutagenesis in V79 cells treated with N,N'-bis(2-hydroxyperoxy-2-methoxyethyl)-1,4,5,8-naphthalenetetracarboxylic-diimide (NP-III) or riboflavin. Jpn J Cancer Res 2002; 93:247-52. [PMID: 11927005 PMCID: PMC5926961 DOI: 10.1111/j.1349-7006.2002.tb02165.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The object of this study is to investigate the relationship between a typical product of oxidative DNA damage, 8-hydroxy-2'-deoxyguanosine (8OHdG), and mutagenesis in V79 cells through a molecular analysis of hypoxanthine-guanine phosphoribosyltransferase (hprt) gene mutants. We performed a direct sequencing analysis of the cDNA of mutants obtained after treatment with N,N'-bis(2-hydroxyperoxy-2-methoxyethyl)-1,4,5,8-naphthalenetetracarboxylic-diimide (NP-III) or riboflavin, each of which induces the formation of 8OHdG in cellular DNA upon UVA irradiation. The frequency of mutation after both treatments was no more than 2 to 5 times the control value. A considerable number of the mutants could not be amplified by RT-PCR, and this was also the case for the control mutants. Among the mutants analyzed, deletions and a TA-->AT transversion occurred predominantly. The reasons for the weak association of induction of 8OHdG with frequency of mutation and the possible mechanism of oxidative-stress-derived mutagenesis are discussed.
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Affiliation(s)
- Madoka Nakajima
- Department of Environmental and Preventive Medicine, Kanazawa University Graduate School of Medical Science, Kanazawa, Ishikawa 920-8640, Japan
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Huo L, Nagasawa H, Little JB. HPRT mutants induced in bystander cells by very low fluences of alpha particles result primarily from point mutations. Radiat Res 2001; 156:521-5. [PMID: 11604065 DOI: 10.1667/0033-7587(2001)156[0521:hmiibc]2.0.co;2] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We have shown previously that damage signals may be transmitted from irradiated cells to nonirradiated cells in monolayer cultures, leading to changes in gene expression and an enhanced frequency of mutations in these "bystander" cells. The present study was designed to test the hypothesis that mutations occurring in bystander cells result from a different mechanism than those occurring in irradiated cells, and thus show differences in molecular structure. Structural changes in the HPRT gene of Chinese hamster ovary (CHO) cells were determined by multiplex PCR analysis. A total of 790 mutant clones derived from monolayer cultures exposed to mean doses of 0, 0.5 or 10 cGy of alpha-particle radiation (0, 3% or 44%, respectively, of nuclei traversed by one or more alpha particles) were examined. Whereas mutations induced by 10 cGy included a high frequency of deletions, nearly all mutations occurring in bystander cells in cultures irradiated with 0.5 cGy involved point mutations, confirming our hypothesis that they are induced by a different mechanism.
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Affiliation(s)
- L Huo
- Department of Cancer Cell Biology, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
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12
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Romney CA, Paulauskis JD, Nagasawa H, Little JB. Multiple manifestations of X-ray-induced genomic instability in Chinese hamster ovary (CHO) cells. Mol Carcinog 2001; 32:118-27. [PMID: 11746824 DOI: 10.1002/mc.1071] [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: 11/11/2022]
Abstract
Carcinogenesis is postulated to follow a multistep cascade in which the first genetic event may destabilize cells and thereby facilitate the induction of subsequent mutations within the same cell. It has recently been shown that exposure to ionizing radiation can in itself induce a persistent, heritable genetic instability in cells. To further investigate this phenomenon, we utilized a mutationally unstable population derived from a single Chinese hamster ovary (CHO) cell that survived X irradiation. We exposed these cells to a second dose of radiation, selected hypoxanthine phosphoribosyl transferase (HPRT) mutant subclones, and identified the type of mutations involved. We found complete deletions, continuous tract partial deletions, single-exon deletions, discontinuous-exon deletions ("skip mutations"), and point mutations (changes of less than 100 bp) among the isolated HPRT mutants. We hypothesized that the skip mutation clones might be more likely to demonstrate genomic instability. To test this hypothesis, mutant subclones were screened for three markers of genetic instability: alteration of minisatellite sequences, change in telomere length, and induction of chromosomal aberrations. Clones with skip mutations and single-exon deletions possessed elevated frequencies of minisatellite alterations and chromosomal aberrations, particularly rings and dicentrics. All mutant clones showed longer telomere terminal restriction fragment lengths than did wild-type cells. These results are consistent with the hypothesis that irradiation may induce a global instability phenotype, since the multiple alterations observed are mechanistically distinct, heritable cellular modifications that arose in the clonogenic progeny of the irradiated cells. Skip mutations may be one manifestation of this instability, but their presence was not specifically associated with the other genetic alterations.
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Affiliation(s)
- C A Romney
- Department of Cancer Cell Biology, Harvard School of Public Health, Boston, Massachusetts 02115, USA
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13
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Balestrieri E, Zanier R, Degrassi F. Molecular characterisation of camptothecin-induced mutations at the hprt locus in Chinese hamster cells. Mutat Res 2001; 476:63-9. [PMID: 11336984 DOI: 10.1016/s0027-5107(01)00083-5] [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: 01/29/2023]
Abstract
The capacity of the topoisomerase I inhibitor camptothecin (CPT) to induce single locus mutations at the hypoxanthine-guanine phosphoribosyltransferase (hprt) gene and the DNA changes underlying induced mutations were analysed in Chinese hamster ovary cells. Camptothecin treatments increased hprt mutations up to 50-fold over the spontaneous levels at highly cytotoxic doses. Genomic DNA was isolated from 6-thioguanine resistant clones and subjected to multiplex PCR to screen for gross alterations in the gene structure. The molecular analysis revealed that deletion mutants represented 80% of the analysed clones, including total hprt deletion, multiple and single exon deletions. Furthermore, a fraction of the analysed clones showed deletions of more than one exon that were characterised by the absence of non-contiguous exons. These data show that single locus mutations induced by camptothecin are characterised by large deletions or complex rearrangements rather than single base substitutions and suggest that the recombinational repair of camptothecin-induced strand breaks at replication fork may be involved in the generations of these alterations at the chromatin structure level.
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Affiliation(s)
- E Balestrieri
- Centre of Evolutionary Genetics, National Research Council, c/o Department of Genetics and Molecular Biology, La Sapienza University, Via degli Apuli 4, 00185 Rome, Italy
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Kinashi Y, Sakurai Y, Masunaga S, Suzuki M, Takagaki M, Akaboshi M, Ono K. Molecular structural analysis of HPRT mutations induced by thermal and epithermal neutrons in Chinese hamster ovary cells. Radiat Res 2000; 154:313-8. [PMID: 10956438 DOI: 10.1667/0033-7587(2000)154[0313:msaohm]2.0.co;2] [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: 11/03/2022]
Abstract
Chinese hamster ovary (CHO) cells were exposed to thermal and epithermal neutrons, and the occurrence of mutations at the HPRT locus was investigated. The Kyoto University Research Reactor (KUR), which has been improved for use in neutron capture therapy, was the neutron source. Neutron energy spectra ranging from nearly pure thermal to epithermal can be chosen using the spectrum shifters and thermal neutron filters. To determine mutant frequency and cell survival, cells were irradiated with thermal and epithermal neutrons under three conditions: thermal neutron mode, mixed mode with thermal and epithermal neutrons, and epithermal neutron mode. The mutagenicity was different among the three irradiation modes, with the epithermal neutrons showing a mutation frequency about 5-fold that of the thermal neutrons and about 1.5-fold that of the mixed mode. In the thermal neutron and mixed mode, boron did not significantly increase the frequency of the mutants at the same dose. Therefore, the effect of boron as used in boron neutron capture therapy (BNCT) is quantitatively minimal in terms of mutation induction. Over 300 independent neutron-induced mutant clones were isolated from 12 experiments. The molecular structure of HPRT mutations was determined by analysis of all nine exons by multiplex polymerase chain reaction. In the thermal neutron and mixed modes, total and partial deletions were dominant and the fraction of total deletions was increased in the presence of boron. In the epithermal neutron mode, more than half of the mutations observed were total deletions. Our results suggest that there are clear differences between thermal and epithermal neutron beams in their mutagenicity and in the structural pattern of the mutants that they induce. Mapping of deletion breakpoints of 173 partial-deletion mutants showed that regions of introns 3-4, 7/8-9 and 9-0 are sensitive to the induction of mutants by neutron irradiation.
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Affiliation(s)
- Y Kinashi
- Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan
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Caron RM, Nagasawa H, Yu Y, Pfenning T, Vetrovs H, Little JB. Evidence for a role for genomic instability in radiation-induced mutagenesis. RADIATION ONCOLOGY INVESTIGATIONS 2000; 5:119-23. [PMID: 9303068 DOI: 10.1002/(sici)1520-6823(1997)5:3<119::aid-roi7>3.0.co;2-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- R M Caron
- Department of Cancer Biology, Harvard School of Public Health, Boston, Massachusetts 02115, USA
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Kinashi Y, Sakurai Y, Masunaga S, Suzuki M, Akaboshi M, Ono K. Dimethyl sulfoxide protects against thermal and epithermal neutron-induced cell death and mutagenesis of Chinese hamster ovary (CHO) cells. Int J Radiat Oncol Biol Phys 2000; 47:1371-8. [PMID: 10889392 DOI: 10.1016/s0360-3016(00)00588-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
PURPOSE To investigate the protective effects of dimethyl sulfoxide (DMSO) on cell killing and mutagenicity at the HPRT locus in Chinese hamster ovary (CHO) cells against thermal and epithermal neutrons produced at the Kyoto University Research (KUR) reactor. METHODS AND MATERIALS DMSO was added to cells 15 min before irradiation and removed 15 min after irradiation. Cells were irradiated by thermal and epithermal neutrons with or without boron at 10 ppm. The biological endpoint of cell survival was measured by colony formation assay. The mutagenicity was measured by the mutant frequency in the HPRT locus. A total of 378 independent neutron-induced mutant clones were isolated in separate experiments. The molecular structure of HPRT mutations was determined by analysis by multiplex polymerase chain reaction of all nine exons. RESULTS The D(0) values of epithermal and thermal neutrons in three different modes, i.e., thermal, epithermal, and mixtures of thermal and epithermal, were 0.8-1.2 Gy. When cells were treated with DMSO, the D(0) values increased to 1.0-2.3, especially in the absence of boron. DMSO showed a protective effect against mutagenesis of the HPRT locus induced by epithermal and thermal neutron irradiation. After DMSO treatment, the mutagenicity was decreased, especially when the cells were irradiated in epithermal neutron mode. Molecular structure analysis indicated that total and partial deletions were dominant and the incidence of total deletions was increased in the presence of boron in the thermal neutron and mixed modes. In the epithermal neutron mode, more than half of the mutations were total deletions. When cells were treated with DMSO, the incidence of total deletions by thermal neutron irradiation with boron and epithermal irradiation decreased. CONCLUSIONS Our results suggest that DMSO has various protective effects against cytotoxic and mutagenic effects of thermal and epithermal neutrons, and that the extent of protection is reflected by the percentage of absorbed dose distribution for each neutron irradiation mode.
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Affiliation(s)
- Y Kinashi
- Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-gun, Osaka, Japan.
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Visser JE, Bär PR, Jinnah HA. Lesch-Nyhan disease and the basal ganglia. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 2000; 32:449-75. [PMID: 10760551 DOI: 10.1016/s0165-0173(99)00094-6] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The purpose of this review is to summarize emerging evidence that the neurobehavioral features of Lesch-Nyhan disease (LND), a developmental disorder caused by congenital deficiency of the purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT), may be attributable to dysfunction of the basal ganglia. Affected individuals have severe motor disability described by prominent extrapyramidal features that are characteristic of dysfunction of the motor circuits of the basal ganglia. They also display disturbances of ocular motility, cognition, and behavioral control that may reflect disruption of other circuits of the basal ganglia. Though neuropathologic studies of autopsy specimens have revealed no obvious neuroanatomical abnormalities in LND, neurochemical studies have demonstrated 60-90% reductions in the dopamine content of the basal ganglia. In addition, recent PET studies have documented significant reductions in dopamine transporters and [18F]fluorodopa uptake in the basal ganglia. These findings support the proposal that many of the neurobehavioral features of LND might be related to dysfunction of the basal ganglia.
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Affiliation(s)
- J E Visser
- Laboratory of Experimental Neurology, Rudolf Magnus Institute for Neurosciences, Utrecht University, Utrecht, Netherlands
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Helleday T, Nilsson R, Jenssen D. Arsenic[III] and heavy metal ions induce intrachromosomal homologous recombination in the hprt gene of V79 Chinese hamster cells. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2000; 35:114-122. [PMID: 10712745 DOI: 10.1002/(sici)1098-2280(2000)35:2<114::aid-em6>3.0.co;2-q] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In the present study the carcinogenic metal ions Cd[II], Co[II], Cr[VI], Ni[II], and Pb[II], as well as As[III], were examined for their ability to induce intrachromosomal homologous and nonhomologous recombination in the hprt gene of two V79 Chinese hamster cell lines, SPD8 and Sp5, respectively. With the exception of Pb[II], all of these ions enhanced homologous recombination, the order of potency being Cr>Cd>As>Co>Ni. In contrast, Cr[VI] was the only ion to enhance recombination of the nonhomologous type. In order to obtain additional information on the mechanism of recombination in the SPD8 cell line, individual clones exhibiting metal-induced recombination were isolated, and the sequence of their hprt gene determined. These findings confirmed that all recombinogenic events in this cell line were of the homologous type, involving predominantly a chromatid exchange mechanism. The mechanisms underlying the recombination induced by these ions are discussed in relationship to their genotoxicity, as well as to DNA repair and replication. Induced recombination may constitute a novel mechanism for induction of neoplastic disease.
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Affiliation(s)
- T Helleday
- Department of Genetic and Cellular Toxicology, Wallenberg Laboratory, Stockholm University, Stockholm, Sweden.
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19
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Kiefer J, Schreiber A, Gutermuth F, Koch S, Schmidt P. Mutation induction by different types of radiation at the Hprt locus. Mutat Res 1999; 431:429-48. [PMID: 10636006 DOI: 10.1016/s0027-5107(99)00184-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Mutation induction at the Hprt locus in Chinese hamster cells was studied after exposure to ultraviolet light, X-rays and alpha particles. While mutant frequency as a function of dose or fluence followed a linear-quadratic relationship with UV and X-rays, it showed a linear dependence for alpha particles. If mutant frequency is plotted vs. the logarithm of surviving fraction, a linear relationship is found in all cases although with different slopes. These are about equal with the two types of ionising radiations but about 10 times larger for UV. They can be used as a measure of mutagenic potential and are termed mutagenicity. It is shown that this parameter is correlated with the maximum of mutant yield, i.e., the number of mutants per cell at risk. It is concluded from this analysis that the maximum mutant yield is always found at doses or fluences which lead to 37% survival irrespective of the kind of radiation. If mutation induction is measured in X-irradiated cells after pre-exposure to UV, mutant frequency is higher than expected on the basis of independent action of the two radiations. Deletion spectra were determined by using multiplex polymerase chain reaction. It was found that the background of spontaneous mutants varied considerably and showed frequently repetitive patterns, presumably because of clonal expansion of pre-formed mutants. UV-induced mutants did not contain any deletions, while those with both X-rays and alpha particles the majority displayed partial and total deletions. Based on a total number of 134 X-ray- and 192 alpha-induced mutants, it is concluded that the total fraction of mutant clones without deletions (partial or total) is about 40% for X-rays and only about 20% for alpha-particles.
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Affiliation(s)
- J Kiefer
- Strahlenzentrum der Justus-Liebig-Universität, Giessen, Germany.
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20
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Schweikl H, Schmalz G. Triethylene glycol dimethacrylate induces large deletions in the hprt gene of V79 cells. Mutat Res 1999; 438:71-8. [PMID: 9858690 DOI: 10.1016/s1383-5718(98)00164-8] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Acrylate esters are applied in industrial and consumer products often associated with polymers and resins. The difunctional methacrylate, triethylene glycol dimethacrylate (TEGDMA), is also frequently included in dental composite materials. Recently, mutagenicity testing of the compound revealed the induction of gene mutations at the hprt locus in V79 cell [H. Schweikl, G. Schmalz, K. Rackebrandt, The mutagenic activity of unpolymerized resin monomers in Salmonella typhimurium and V79 cells, Mutat. Res. 415 (1998) 119-130]. In the present study, TEGDMA caused a dose dependent increase of the number of micronuclei in V79 cells. Furthermore, the mutation spectra induced in exon sequences of the hprt gene in HPRT-deficient V79 cell clones were analyzed by the polymerase chain reaction (PCR). No DNA sequence deletions were observed in spontaneously occurring HPRT-deficient cell clones at the molecular level after PCR analysis, indicating that all spontaneous mutations were caused by point mutations. However, TEGDMA treated V79 cell cultures exhibited different mutation spectra. Only one cell clone among a total of 25 contained all exon sequences of the hprt gene. Large DNA sequences were deleted in 24 cell clones. Partial gene deletions occurred in four clones from exon 5 through 9, and exon 1 was not amplified in one cell clone. Exon sequences of the hprt gene were totally deleted in 19 HPRT-deficient clones. The induction of mostly large deletions in the genome of mammalian cells, like the mutation spectra induced by TEGDMA in V79 cells here, is probably typical for crosslinking agents, including anticancer drugs. Identical types of mutations including chromosomal aberrations and the formation of micronuclei in vitro were observed for acrylates and methacrylates tested so far in various mutation assays. Therefore, we conclude by analogy that the induction of large DNA sequence deletions as shown here with the reactive dimethacrylate, triethylene glycol dimethacrylate, is probably common for acrylates and methacrylates.
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Affiliation(s)
- H Schweikl
- Department of Operative Dentistry and Periodontology, University of Regensburg, D-93042, Regensburg, Germany.
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21
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Schmidt P, Kiefer J. Deletion-pattern analysis of alpha-particle and X-ray induced mutations at the HPRT locus of V79 Chinese hamster cells. Mutat Res 1998; 421:149-61. [PMID: 9852989 DOI: 10.1016/s0027-5107(98)00159-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
To investigate the mutagenic mechanisms of low-energy alpha particles V79 Chinese hamster cells were irradiated with 241Am-alpha particles (mean LET of 112 keV/micron). Parallel experiments were performed using 300 kV X-rays. Cell inactivation and mutation induction cross sections were measured. At approximately 20%--survival level, DNA deletions were analysed at the HPRT locus by multiplex-PCR-analysis of all nine exons of 47 alpha-irradiated and 36 background mutants. 92 HPRT- mutants isolated after 300 kV-X-irradiation were analysed similarly for comparison, along with 15 corresponding background mutants. The resulting mutant deletion-pattern distributions were corrected for background mutations. alpha Particles induced a larger fraction of deletions than X-rays. Furthermore, non-contiguous partial deletions were present among the alpha-induced mutants, a type not found after X-irradiation.
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Affiliation(s)
- P Schmidt
- Strahlenzentrum der Justus-Liebig-Universität, Giessen, Germany
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22
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Majumdar A, Khorlin A, Dyatkina N, Lin FL, Powell J, Liu J, Fei Z, Khripine Y, Watanabe KA, George J, Glazer PM, Seidman MM. Targeted gene knockout mediated by triple helix forming oligonucleotides. Nat Genet 1998; 20:212-4. [PMID: 9771719 DOI: 10.1038/2530] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Triple helix forming oligonucleotides (TFOs) recognize and bind sequences in duplex DNA and have received considerable attention because of their potential for targeting specific genomic sites. TFOs can deliver DNA reactive reagents to specific sequences in purified chromosomal DNA (ref. 4) and nuclei. However, chromosome targeting in viable cells has not been demonstrated, and in vitro experiments indicate that chromatin structure is incompatible with triplex formation. We have prepared modified TFOs, linked to the DNA-crosslinking reagent psoralen, directed at a site in the Hprt gene. We show that stable Hprt-deficient clones can be recovered following introduction of the TFOs into viable cells and photoactivation of the psoralen. Analysis of 282 clones indicated that 85% contained mutations in the triplex target region. We observed mainly deletions and some insertions. These data indicate that appropriately constructed TFOs can find chromosomal targets, and suggest that the chromatin structure in the target region is more dynamic than predicted by the in vitro experiments.
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Affiliation(s)
- A Majumdar
- National Institute on Aging, NIH, Baltimore, Maryland 21224-6825, USA
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23
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Colussi N, van Leeuwen X, Lohman PH. Similar mutational spectra in the HPRT gene of human and hamster cell lines after exposure to either low dose rate or high dose rate X-rays. Mutat Res 1998; 401:89-97. [PMID: 9639682 DOI: 10.1016/s0027-5107(97)00318-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The dose rate at which cells are exposed to X-rays may influence the nature of induced mutations. To investigate this, the molecular spectra were determined at the HPRT gene in a hamster (V79) and a human (WI-L2-NS) cell line after the same total dose of X-rays has been administered at either a low dose rate (LDR; 3.33 mGy/min) or a high dose rate (HDR; 1.24-1.4 Gy/min) X-irradiation. Mutational spectra appeared similar, the fraction of mutants carrying deletions ranging between 59%-66% for the V79 strain and between 64%-75% for the WI-L2-NS strain, and independent of the irradiation conditions. The data indicate no effect of ongoing repair processes under LDR conditions on the kind of induced mutations in mammalian cells.
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Affiliation(s)
- N Colussi
- Department of Radiation Genetics and Chemical Mutagenesis (MGC), Leiden University, Wassenaarseweg 72, 2333 AL Leiden, The Netherlands
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24
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Chen T, Mittelstaedt RA, Heflich RH. DNA sequence flanking the protein coding regions of the rat Hprt gene. Mutat Res 1998; 382:79-80. [PMID: 9691986 DOI: 10.1016/s1383-5726(97)00014-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- T Chen
- Division of Genetic and Reproductive Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA.
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25
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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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26
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Miyata Y, Ohdan H, Noriyuki T, Shintaku S, Shibata S, Yamamoto H, Yoshioka S, Asahara T, Fukuda Y, Kimura A, Dohi K. Analysis of xenogeneic microchimerism in hamster-to-rat lung xenotransplantation. Transplant Proc 1997; 29:3505-7. [PMID: 9414812 DOI: 10.1016/s0041-1345(97)00997-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Y Miyata
- Second Department of Surgery, Hiroshima University, School of Medicine, Japan
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27
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Albrecht T, Fons MP, Deng CZ, Boldogh I. Increased frequency of specific locus mutation following human cytomegalovirus infection. Virology 1997; 230:48-61. [PMID: 9126261 DOI: 10.1006/viro.1997.8467] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The effect of human cytomegalovirus (HCMV) infection on the frequency of mutations at the hypoxanthine-guanine phosphoribosyl transferase (hprt) locus was studied in Chinese hamster lung V79 cells. When V79 cells were infected with HCMV (strain AD169) at multiplicities of 0.1 to 50 plaque forming units (PFU) per cell the presumptive mutation frequency, as determined by the number of 6-thioguanine-resistant (TGr) colonies, was increased up to 16.8-fold (P < 0.005), depending on the multiplicity of infection. Increases in the mutation frequency at the hprt locus were also observed for other laboratory-adapted HCMV strains (C-87, Davis) and for low passage clinical isolates (82-1, 84-2). The expression time required for the maximum increase in TGr colonies was 3 days and was consistent among the HCMV strains evaluated in this study. UV-irradiation of HCMV stock up to a dose of 9.6 x 10(4) ergs/mm2 increased the mutation frequency, but further exposure to UV light or to heat (56 degrees for 30 min) significantly decreased the frequency of TGr-resistant colonies, suggesting that expression of HCMV genes was involved in the mutation process. HCMV-induced TGr cells demonstrated substantially reduced (> 96%) incorporation of [3H]hypoxanthine. PCR analysis of the hprt locus demonstrated deletions in 9 of 19 HCMV-induced TGr colonies randomly selected for further study, while 2 of 17 spontaneously developed TGr colonies demonstrated deletions. Although insertions were not detected in spontaneously developed clones, 3 of 19 HCMV-induced TGr clones had insertions in the hprt gene. Neither HCMV-specific DNA sequences nor HCMV-specific proteins were detected in the TGr clones obtained after HCMV infection. Infection of V79 cells with HCMV also increased their sensitivity to mutation with N-methyl-N'-nitro-N-nitrosoguanidine, giving a synergistic enhancement of the mutation frequency. These results indicate that HCMV infection has the capacity to induce mutations in the cellular genome and increase the sensitivity of infected cells to mutation by genotoxic chemicals. Although inactivated HCMV particles are responsible for a modest increase in the mutation frequency, expression of HCMV genes is associated with a substantial enhancement of the mutation frequency.
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Affiliation(s)
- T Albrecht
- Department of Microbiology and Immunology, University of Texas Medical Branch at Galveston 77555-1019, USA.
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28
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Bui T, Kuo C, Rotwein P, Straus DS. Prostaglandin A2 specifically represses insulin-like growth factor-I gene expression in C6 rat glioma cells. Endocrinology 1997; 138:985-93. [PMID: 9048599 DOI: 10.1210/endo.138.3.4980] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The cyclopentenone PGs (PGA and PGJ series) inhibit tumor cell proliferation in vitro and tumorigenesis in vivo via mechanisms that are at present poorly understood. The C6 rat glioma cell line synthesizes and secretes insulin-like growth factor-I (IGF-I), which is believed to act as an autocrine factor for these cells. PGA2 inhibits the proliferation of the C6 cells and causes an increase in the fraction of cells in the G1 phase of the cell cycle. The inhibition of cell proliferation by PGA2 is accompanied by a decrease in the abundance of IGF-I messenger RNA (mRNA). This regulation of IGF-I gene expression is specific, as the abundance of hypoxanthine-guanine phosphoribosyl transferase (HPRT) and ubiquitin mRNA is not significantly affected by PGA2. The repression of IGF-I gene expression is observed at PGA2 concentrations as low as 10 microM and is evident within 4 h after treatment of the C6 cells with PGA2. In addition to specifically regulating the expression of the IGF-I gene, PGA2 also decreases the abundance of cyclin D1 mRNA and increases the abundance of Waf1 mRNA. The inhibition of cell proliferation by PGA2 is partially reversed by coaddition of IGF-I, indicating partial dominance of IGF-I action over PGA2 action. To investigate the molecular basis for the regulation of IGF-I gene expression by PGA2, we developed a sensitive RT-PCR assay for IGF-I nuclear transcripts. A similar assay was developed for quantifying HPRT transcripts, which were used as a control. Treatment of the C6 cells with 20 microM PGA2 resulted in approximately a 6-fold decrease in IGF-I mRNA and IGF-I nuclear transcripts. In contrast, HPRT mRNA and nuclear transcript levels were not significantly affected by PGA2. These results indicate that the decrease in IGF-I mRNA abundance that occurs in response to PGA2 is caused largely by a decrease in IGF-I nuclear transcript levels. To identify the cis-acting element that mediates the effect of PGA2 on IGF-I transcription, C6 cells were transiently transfected with IGF-I/luciferase expression constructs in which luciferase transcription is driven by IGF-I P1 promoter fragments extending from -1711 to -328 or from -1114 to +328 relative to the beginning of exon 1. Treatment of cells with PGA2 in these transient transfection assays did not decrease luciferase activity. These results suggest that the cis-acting regulatory element required for the response to PGA2 is located outside the -1711 to +328 promoter interval.
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Affiliation(s)
- T Bui
- Biomedical Sciences Division, University of California, Riverside 92521-0121, USA
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29
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Ohdan H, Fukuda Y, Shintaku S, Miyata Y, Tashiro H, Hoshino S, Sumimoto R, Asahara T, Kimura A, Dohi K. Prolongation of hamster-to-rat liver xenograft survival by donor bone marrow augmentation. Transplant Proc 1997; 29:925-7. [PMID: 9123589 DOI: 10.1016/s0041-1345(96)00239-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- H Ohdan
- Second Department of Surgery, Hiroshima University, School of Medicine, Japan
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30
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Yang JL, Yeh SC, Chang CY. Lead acetate mutagenicity and mutational spectrum in the hypoxanthine guanine phosphoribosyltransferase gene of Chinese hamster ovary K1 cells. Mol Carcinog 1996; 17:181-91. [PMID: 8989911 DOI: 10.1002/1098-2744(199612)17:4<181::aid-mc2940170402>3.0.co;2-f] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The molecular nature of lead-induced mutations was examined in this study to more thoroughly understand lead mutagenesis. Chinese hamster ovary K1 cells were exposed to 0.5-3 mM lead acetate for 24 h. The median lethal dose (LD50) value was 1.5 mM, and the hypoxanthine guanine phosphoribosyltransferase (HPRT) mutant frequency increased linearly as lead concentrations were raised from 0.5 to 1.5 mM. We also amplified the HPRT cDNAs of 56 independent lead-induced mutants by reverse transcriptase-polymerase chain reaction (PCR). Forty-two mutant cDNAs were successfully amplified: 36 mutants had transcripts of normal or slightly smaller than normal size, and six mutants had large deletions. The other 14 mutants whose HPRT cDNA could not be amplified were subjected to genomic-DNA PCR analysis. All of those mutants had one or more exons missing from their genomic HPRT DNA. DNA sequencing of mutant cDNAs showed that 22 had single-base substitutions, four had small alterations, 10 had single-exon deletions, and six were missing two or three exons. Furthermore, DNA sequencing of the HPRT intron-exon boundaries in eight splice mutants revealed that all of them had single-base substitutions in their genomic DNA. G.C base substitutions occurred 3.3-fold more frequently than A.T base substitutions. Similar frequencies were observed for G.C-->A.T, G.C-->T.A, and G.C-->C.G mutations. These results suggest that G.C base pairs may be the primary target sites for lead mutagenesis.
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Affiliation(s)
- J L Yang
- Department of Life Sciences, National Tsing Hua University, Hsinchu, Taiwan, Republic of China
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31
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Darè E, Zhang LH, Jenssen D. Characterization of mutants involving partial exon duplications in the hprt gene of Chinese hamster V79 cells. SOMATIC CELL AND MOLECULAR GENETICS 1996; 22:201-10. [PMID: 8914605 DOI: 10.1007/bf02369910] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Sequencing of hprt cDNA revealed that three spontaneous mutants in V79 Chinese hamster cells exhibit tandem duplications of exon(s), i.e., either exons 2 and 3 or exon 7. Sequences of different sizes (4.5-8 Kb) were found to be duplicated and inserted in tandem into the hprt gene. These mutants demonstrated spontaneous reversion frequencies which were about 40-fold higher than those observed with other types of spontaneous mutants, but on the same order of magnitude as spontaneous reversions in Sp5, a mutant with a duplication insertion involving exon 2 in this gene. These data suggest that all of the duplications found have the same genetic instability, regardless of the type, size or position of the duplicated fragment. The coding sequence of the hprt cDNA and the restriction pattern of the revertants were virtually identical to the wild-type, indicating restoration of a functional hprt gene by precise deletion of the duplicated fragment.
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Affiliation(s)
- E Darè
- Department of Molecular Medicine, Karolinska Hospital, Stockholm, Sweden.
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32
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Cussac C, Laval F. Reduction of the toxicity and mutagenicity of aziridine in mammalian cells harboring the Escherichia coli fpg gene. Nucleic Acids Res 1996; 24:1742-6. [PMID: 8649994 PMCID: PMC145839 DOI: 10.1093/nar/24.9.1742] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Aziridine (ethyleneimine) reacts with DNA in vitro, mainly at the N7 position of guanine and N3 of adenine, then imidazole ring opening of the modified guanine results in formation of formamidopyrimidine (FaPy) residues. The Escherichia coli fpg gene encodes a DNA glycosylase that removes FaPy residues from DNA. To determine whether aziridine produces FaPy lesions in mammalian cells we have expressed the E.coli fpg gene in CHO cells. The transfected cells, expressing high levels of the bacterial protein, are more resistant to the toxic and mutagenic effects of aziridine than the control population. Less DNA damage was measured by quantitative PCR analysis in transfected than in control cells treated with equimolar concentrations of aziridine. The results suggest that aziridine produces in vivo FaPy residues that could account for the deleterious effects of this compound.
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Affiliation(s)
- C Cussac
- Unité 347 INSERM, Le Kremlin-Bicêtre, France
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33
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Schwartz JL, Porter RC, Hsie AW. The molecular nature of spontaneous mutations at the hprt locus in the radiosensitive CHO mutant xrs-5. Mutat Res 1996; 351:53-60. [PMID: 8602174 DOI: 10.1016/0027-5107(95)00194-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The radiosensitive mutant xrs-5, a derivative of the Chinese hamster ovary (CHO) K1 cell, is defective in DNA double-strand break rejoining ability and in V(D)J recombination. The radiosensitivity and defective repair phenotype are complemented by the 80-kDa subunit of the Ku protein. We determined the nature of the mutations that develop spontaneously at the hprt locus in this cell line using both multiplex PCR deletion screening and DNA sequencing. Ninety-two independent spontaneous mutants were analyzed and the results were compared to the mutation spectrum of 64 previously analyzed hprt spontaneous mutants isolated from the parental CHO-K1 cell line. More than 50% of the spontaneous xrs-5 mutants had lost one or more exons while less than 25% of spontaneous CHO-K1 mutants had lost one or more exons. Most of the deletions in xrs-5 cells involved the loss of multiple exons while single exon deletions predominated in CHO-K1. There was also a nonrandom distribution of breakpoints in both CHO-K1 and xrs-5. Most of the deletion breakpoints were 3' to exon 9, around exons 4-6, or near exon 1. Although the frequency of base substitutions was lower in xrs-5, the spectrum of base substitutions was qualitatively similar to that of CHO-K1. There was no significant difference in the spontaneous mutant frequency in xrs-5 and CHO-K1. The results suggest that in certain regions of the hprt gene, base alterations can be converted to large deletions, and that alterations in the Ku protein complex can influence this process.
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Affiliation(s)
- J L Schwartz
- Center for Mechanistic Biology and Biotechnology, Argonne National Laboratory, IL 60439, USA
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34
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Suzuki K, Hei TK. Mutation induction in gamma-irradiated primary human bronchial epithelial cells and molecular analysis of the HPRT- mutants. Mutat Res 1996; 349:33-41. [PMID: 8569790 DOI: 10.1016/0027-5107(95)00123-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We have examined various radiobiological parameters using commercially-available primary normal human bronchial epithelial (NHBE) cells, which can be subcultured more than 20 population doublings, and have established the mutation system in order to characterize the molecular changes in gamma-irradiated primary cells. The survival curve, obtained after irradiation of cells with 137Cs gamma-rays, indicates that the D0, Dq, and n values are 1.34 Gy, 1.12 Gy, and 2.3, respectively. The induction of HPRT- mutation was dose-dependent and the mutant fraction increased in a non-linear fashion. Since the doubling number of NHBE cells is limited, DNA was extracted directly from the single mutant colonies and alteration in the HPRT gene locus was analyzed using multiplex PCR technique. Among spontaneous mutants, the proportion with total and partial deletions of the gene was 10.0% (2/20) and 60.0% (12/20), respectively, while 30.0% (6/20) did not have any detectable changes in the nine exons examined. On the other hand, the fraction of total deletion increased by more than 2-fold among mutants induced by gamma-rays in that 26.3% (10/38) of them showed the total gene deletions. Twenty-five out of 38 gamma-induced mutants (65.8%) had partial deletions and 3 mutants (7.9%) had no detectable alteration. The present results showed that gamma-irradiation efficiently induced HPRT gene mutation in primary human epithelial cells and that most of the induced mutants suffered larger deletions compared to that observed in spontaneous mutants. This system provides an useful tool for determination of mutagenicity and understanding the molecular mechanisms of environmental carcinogens in primary human bronchial cells.
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Affiliation(s)
- K Suzuki
- Center for Radiological Research VC11-218, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
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35
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Rincón-Limas DE, Amaya-Manzanares F, Niño-Rosales ML, Yu Y, Yang TP, Patel PI. Ubiquitous and neuronal DNA-binding proteins interact with a negative regulatory element of the human hypoxanthine phosphoribosyltransferase gene. Mol Cell Biol 1995; 15:6561-71. [PMID: 8524221 PMCID: PMC230909 DOI: 10.1128/mcb.15.12.6561] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The hypoxanthine phosphoribosyltransferase (HPRT) gene is constitutively expressed at low levels in all tissues but at higher levels in the brain; the significance and mechanism of this differential expression are unknown. We previously identified a 182-bp element (hHPRT-NE) within the 5'-flanking region of the human HPRT (hHPRT) gene, which is involved not only in conferring neuronal specificity but also in repressing gene expression in nonneuronal tissues. Here we report that this element interacts with different nuclear proteins, some of which are present specifically in neuronal cells (complex I) and others of which are present in cells showing constitutive expression of the gene (complex II). In addition, we found that complex I factors are expressed in human NT2/D1 cells following induction of neuronal differentiation by retinoic acid. This finding correlates with an increase of HPRT gene transcription following neuronal differentiation. We also mapped the binding sites for both complexes to a 60-bp region (Ff; positions -510 to -451) which, when analyzed in transfection assays, functioned as a repressor element analogous to the full-length hHPRT-NE sequence. Methylation interference footprintings revealed a minimal unique DNA motif, 5'-GGAAGCC-3', as the binding site for nuclear proteins from both neuronal and nonneuronal sources. However, site-directed mutagenesis of the footprinted region indicated that different nucleotides are essential for the associations of these two complexes. Moreover, UV cross-linking experiments showed that both complexes are formed by the association of several different proteins. Taken together, these data suggest that differential interaction of DNA-binding factors with this regulatory element plays a crucial role in the brain-preferential expression of the gene, and they should lead to the isolation of transcriptional regulators important in neuronal expression of the HPRT gene.
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Affiliation(s)
- D E Rincón-Limas
- Department of Neurology, Baylor College of Medicine, Houston, Texas 77030, USA
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36
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Vos P, Hogers R, Bleeker M, Reijans M, van de Lee T, Hornes M, Frijters A, Pot J, Peleman J, Kuiper M. AFLP: a new technique for DNA fingerprinting. Nucleic Acids Res 1995; 23:4407-14. [PMID: 7501463 PMCID: PMC307397 DOI: 10.1093/nar/23.21.4407] [Citation(s) in RCA: 4933] [Impact Index Per Article: 170.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
A novel DNA fingerprinting technique called AFLP is described. The AFLP technique is based on the selective PCR amplification of restriction fragments from a total digest of genomic DNA. The technique involves three steps: (i) restriction of the DNA and ligation of oligonucleotide adapters, (ii) selective amplification of sets of restriction fragments, and (iii) gel analysis of the amplified fragments. PCR amplification of restriction fragments is achieved by using the adapter and restriction site sequence as target sites for primer annealing. The selective amplification is achieved by the use of primers that extend into the restriction fragments, amplifying only those fragments in which the primer extensions match the nucleotides flanking the restriction sites. Using this method, sets of restriction fragments may be visualized by PCR without knowledge of nucleotide sequence. The method allows the specific co-amplification of high numbers of restriction fragments. The number of fragments that can be analyzed simultaneously, however, is dependent on the resolution of the detection system. Typically 50-100 restriction fragments are amplified and detected on denaturing polyacrylamide gels. The AFLP technique provides a novel and very powerful DNA fingerprinting technique for DNAs of any origin or complexity.
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Affiliation(s)
- P Vos
- Keygene N.V., Wageningen, The Netherlands
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37
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Stoll U, Schneider E, Kranert T, Kiefer J. Induction of HPRT- mutants in Chinese hamster V79 cells after heavy ion exposure. RADIATION AND ENVIRONMENTAL BIOPHYSICS 1995; 34:91-94. [PMID: 7652157 DOI: 10.1007/bf01275212] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The induction of resistance to 6-thioguanine by heavy ion exposure was investigated with various accelerated ions (oxygen-uranium) up to linear energy transfer (LET) values of about 15,000 keV/microns. Survival curves are exponential with fluence; mutation induction shows a linear dependence. Cross-sections (sigma i: inactivation, sigma m: mutation) were derived from the respective slopes. Generally, sigma i rises over the whole LET range, but separates into different declining curves for single ions with LET values above 200 keV/microns. Similar behaviour is seen for sigma m. The new SIS facility at GSI, Darmstadt, makes it possible to study the effects of ions with the same LET but very different energies and track structures. Experiments using nickel and oxygen ions (up to 400 MeV/u) showed that inactivation cross-sections do not depend very much on track structure, i.e. similar values are found with different ions at the same LET. This is not the case for mutation induction, where very energetic ions display considerably smaller induction cross-sections, compared with low-energy ions of identical LET. Preliminary analyses using the polymerase chain reaction (PCR) demonstrate that even heavy ions cause "small alterations" (small deletions or base changes). The proportion of the total deletions seems to increase with LET.
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Affiliation(s)
- U Stoll
- Strahlenzentrum der Justus-Liebig-Universität, Giessen, Germany
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38
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Helbig R, Gerland E, Zdzienicka MZ, Speit G. The pattern of mutations induced by neocarzinostatin and methyl methanesulfonate in the ataxia telangiectasia-like Chinese hamster cell line V-E5. Mutat Res 1995; 336:307-16. [PMID: 7739617 DOI: 10.1016/0921-8777(95)00005-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The Chinese hamster cell line V-E5 is a mutant cell line isolated from V79 cells. The phenotypic characteristics of V-E5 strongly resemble those of cells from patients suffering from the genomic instability syndrome ataxia telangiectasia. In order to further characterize the mutant cell line and to get insight into the underlying genetic defect we compared the clastogenic and mutagenic effects of neocarzinostatin (NCS) and methyl methanesulfonate (MMS) in V-E5 and V79 wild-type cells (V79-LE). V-E5 cells were 2-3 times more sensitive to the cytotoxic effect of NCS or MMS. The clastogenic action of NCS was characterized by the predominant induction of chromosome breaks and dicentrics in both cell lines, whereas MMS mainly induced chromatid-type aberrations. The frequency of mutations induced by NCS as well as MMS was slightly enhanced in V-E5 cells compared to V79 cells treated with the same dose. However, the mutant cell line was found to be hypomutable when considering the same survival level as in the parental cell line. Molecular analysis of mutants induced by NCS revealed a high frequency of total deletions of the hprt gene in both cell lines. In contrast, among MMS-induced mutations only 11% deletion mutations were found in V79-LE, whereas in V-E5 MMS-induced deletions were seen in 52% of the hprt-deficient mutants. These results are discussed with respect to a possible relation between genomic instability, cell cycle control and mutational spectra.
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Affiliation(s)
- R Helbig
- Universität Ulm, Abteilung Klinische Genetik, Germany
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39
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Kinashi Y, Nagasawa H, Little JB. Molecular structural analysis of 417 HPRT mutations induced by restriction endonucleases in Chinese hamster ovary (CHO) cells. Mutat Res 1995; 326:83-92. [PMID: 7528888 DOI: 10.1016/0027-5107(94)00151-t] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
CHO cells were exposed to 11 different restriction endonucleases by electroporation and their mutagenicity was measured. Nine of them have one or more recognition sites within exons of the HPRT gene, whereas the remaining two cut in introns only. The mutagenic efficiency of the various enzymes varied markedly; mutagenicity of Sau3AI was considerably higher than that of the other enzymes. Neither cytotoxicity nor mutagenicity could be related to the number or location of recognition sites within the cDNA. A total of 417 independent restriction enzyme induced mutant clones were isolated from 20 separate experiments for molecular analysis; all nine exons of the HPRT gene were analyzed by a modified multiplex deletion screening method with polymerase chain reaction (PCR) amplification. Among spontaneously arising mutants, 70.8% showed no change in PCR pattern, indicating a small scale change (point mutation), whereas partial deletions were observed in 24.7%, and total deletions in 4.5% of mutant clones. In contrast, approximately 70% of restriction enzyme induced mutants showed partial or total deletions. There was no obvious relationship between type of break (blunt versus staggered ends), and the DNA structure of the mutations induced. For partial deletions, the distribution of breakpoints within introns appeared to occur at random, and did not correlate with the mutagenicity of a given enzyme. Thus, though DNA double-strand breaks appear to be important mutagenic lesions that can induce a high frequency of deletion mutants, no specific relationship of mutagenic potential to the type of breaks, their sites within the HPRT gene or the molecular structure of the mutations induced could be identified.
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Affiliation(s)
- Y Kinashi
- Department of Cancer Biology, Harvard School of Public Health, Boston, MA 02115
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40
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Valentine CR, Heflich RH. Genomic DNA sequencing of mRNA splicing mutants in the hprt gene of Chinese hamster ovary cells. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 1995; 25:85-96. [PMID: 7698111 DOI: 10.1002/em.2850250202] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
We have analyzed 41 mRNA-splicing mutants from the hypoxanthine-guanine phosphoribosyl-transferase (hprt) gene of Chinese hamster ovary (CHO) cells. Twenty-two of these mutants produced single cDNA PCR products with a partial or complete exon deletion; 19 mutants produced multiple cDNA PCR products, and most of these products contained one or more deleted exons. The affected exons and surrounding introns were amplified from genomic DNA and sequenced in order to identify mutations causing aberrant splicing. We found acceptor site mutations in 10 mutants, exonic mutations in 8 mutants, and no mutations in 5 mutants. Four mutants from solvent controls did not amplify the appropriate exons and were considered genomic deletion mutants. Our previous work [Manjanatha MG et al. (1994): Mutat Res 308;65-75] showed that nonsense mutants in the hprt gene of CHO cells are associated with multiple cDNA PCR products containing deleted exons and a low abundance of hprt mRNA if the mutation is found in an internal exon. The present results are consistent with these associations being facilitated by instability of mRNA after ribosome termination at nonsense codons.
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Affiliation(s)
- C R Valentine
- Division of Genetic Toxicology, National Center for Toxicological Research, Jefferson, Arkansas 72079-9502, USA
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41
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Xu Z, Yu Y, Schwartz JL, Meltz ML, Hsie AW. Molecular nature of spontaneous mutations at the hypoxanthine-guanine phosphoribosyltransferase (hprt) locus in Chinese hamster ovary cells. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 1995; 26:127-138. [PMID: 7556109 DOI: 10.1002/em.2850260206] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The hypoxanthine-guanine phosphoribosyltransferase (hprt) locus has been widely used as a selectable genetic marker for studies of mammalian cell mutagenesis. We report here the spontaneous mutation spectrum at the hprt locus in 64 independently isolated mutants of Chinese hamster ovary (CHO) cells. All nine hprt exons were simultaneously analyzed via multiplex polymerase chain reaction (PCR) for rapid detection of gene deletions or insertions. Structural point mutations were identified by direct sequence analysis of the PCR amplified cDNA. The molecular nature of RNA splicing errors and insertions was analyzed by solid-phase direct exon sequencing. Single base substitutions were found in 24 mutants (38%), of which 21 were missense and 3 were nonsense mutations. Transversions were about twice as frequent as transitions. Fifteen mutants (23%) had deletions involving either intragenic small fragments (2), single exons (9), or multiple exons (4). The majority of deletion breakpoints (71%) were located in regions surrounding exons 4, 5, and 6. RNA splicing mutations were observed in 15 mutants (23%) and affected exons 3-8; most (6/15) resulted in the loss of exon 7. Two insertion mutants, one with a 209 bp insert in exon 4 and the other with a 88 bp insert accompanied by a 24 bp deletion in exon 6, represent novel mutations reported for the first time in spontaneous mutants of the mammalian hprt gene.
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Affiliation(s)
- Z Xu
- Department of Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston, USA
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42
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Noyce L, Piper AA. Isolation of a potentially functional HPRT processed pseudogene from the hill kangaroo Macropus robustus. Gene 1994; 150:361-5. [PMID: 7821807 DOI: 10.1016/0378-1119(94)90453-7] [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: 01/27/2023]
Abstract
A highly conserved hypoxanthine phosphoribosyltransferase processed pseudogene (KPH) has been isolated from a female kangaroo (Macropus robustus) lambda EMBL3 genomic library. The pseudogene contains only transcribed material with all of the introns precisely removed and has possible direct repeats at either end of the message. It has a 654-nucleotide open reading frame (ORF) from the Met start codon to the stop codon that contains no additions, deletions or premature stops relative to expressed HPRT genes and, therefore, the possibility exists that it is expressed in vivo. Possible CAAT and GC boxes are present in the region 5' to the ORF and a polyadenylation signal is present in the region 3' to the ORF. If not expressed, the age of the pseudogene is estimated to be 10.7 million years. We propose that integration into the genome occurred specifically in a homocopolymeric region within a highly repeated region unique to the kangaroo genome.
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Affiliation(s)
- L Noyce
- Department of Biochemistry and Physiology, University of Technology, Sydney, NSW, Australia
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43
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Abstract
We have analyzed mutations in exon 8 of the hypoxanthine-guanine phosphoribosyltransferase (hprt) gene in T-lymphocytes from the spleens of ethylnitrosourea-treated female rats. Presumptive hprt- mutants were isolated by clonal growth in the presence of 6-thioguanine. DNA from 6-thioguanine-resistant colonies was amplified by the polymerase chain reaction using intronic primers flanking hprt exon 8. The identification of mutant sequences and the separation of mutant DNA from contaminating wild-type DNA was accomplished by denaturing gradient gel electrophoresis. Of 118 clones analyzed, 19 contained mutations and DNA sequence analysis identified eight unique sequence alterations. We also used single-strand conformation polymorphism analysis to screen for mutations in the same fragment of the hprt gene. This analysis was less successful than denaturing gradient gel electrophoresis in detecting the eight unique mutations. The procedures described here may represent a useful approach for studying the mechanisms of in vivo mutation.
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Affiliation(s)
- R A Mittelstaedt
- Division of Genetic Toxicology, National Center for Toxicological Research, Jefferson, AR 72079
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44
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Abstract
Adriamycin (ADR), a commonly used cancer chemotherapy antibiotic, exhibits a variety of genotoxicities. In this study, we have examined the mutagenicity of ADR at the hypoxanthine-guanine phosphoribosyltransferase gene (hprt) in Chinese hamster ovary (CHO) cells and the xanthine-guanine phosphoribosyltransferase locus (gpt) in a pSV2gpt-transformed CHO cell line, AS52. Although ADR induced a dose-dependent increase of mutant frequency at both loci, it was more mutagenic to the gpt gene than to the hprt locus. Multiplex PCR analysis revealed that 35% of the 103 independent ADR-induced HPRT-deficient mutants carried large deletions. Among these deletion mutants, 33% were total gene deletions, 22% affected multiple exons, and 42% involved a single exon, of which most (9/15) were exon 1. The majority (63%) of ADR-induced AS52 mutants had a total deletion of the gpt gene. These observations indicate that ADR induces large deletions as a major type of gene mutation in mammalian cells, suggesting the involvement of reactive oxygen species as one mutagenic pathway in the mutagenesis of ADR.
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Affiliation(s)
- Y Yu
- Department of Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston 77555
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45
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Rincón-Limas DE, Geske RS, Xue JJ, Hsu CY, Overbeek PA, Patel PI. 5'-flanking sequences of the human HPRT gene direct neuronal expression in the brain of transgenic mice. J Neurosci Res 1994; 38:259-67. [PMID: 7523686 DOI: 10.1002/jnr.490380304] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Total deficiency of hypoxanthine phosphoribosyltransferase (HPRT) in humans causes the neurological disorder Lesch-Nyhan syndrome. The HPRT gene is expressed at basal levels in all tissues but at higher levels in the brain, the relevance and mechanism of which is unknown. To determine if cis-acting DNA elements play a role in the tissue-differential pattern of expression, we generated transgenic mice carrying different sequences of the human HPRT (hHPRT) promoter fused to the bacterial lacZ gene. We show that a 1.6 kb fragment of the hHPRT promoter contains essential information to direct beta-galactosidase expression preferentially to the basal ganglia, cerebral cortex, hippocampus, and several other areas of the forebrain. At least two elements within the 1.6 kb fragment appear to be required for neuronal expression. A 182 bp element (hHPRT-NE) represents one of these sequences and is involved not only in conferring neuronal specificity but also in repressing transgene expression in non-neuronal tissues. These studies provide molecular insight into the mechanism of increased HPRT expression in the brain.
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Affiliation(s)
- D E Rincón-Limas
- Department of Neurology, Baylor College of Medicine, Houston, TX 77030
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46
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Fuscoe JC, Nelsen AJ, Pilia G. Detection of deletion mutations extending beyond the HPRT gene by multiplex PCR analysis. SOMATIC CELL AND MOLECULAR GENETICS 1994; 20:39-46. [PMID: 8197475 DOI: 10.1007/bf02257484] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A multiplex PCR assay was developed for the rapid analysis of deletion size at the hypoxanthine phosphoribosyltransferase (hprt) locus. The DNA sequence of mapped DNA segments flanking the hprt gene was determined. These cloned DNAs were derived from the ends of a set of overlapping yeast artificial chromosomes (YAC) defining a contig of 8 Mb at Xq26 and including hprt. We used "bubble" PCR to isolate an additional YAC end-clone. Seven primer pairs were derived from DNA sequence analysis of the clones and incorporated into a multiplex PCR assay. These primer pairs define loci located approximately 750 kb and 350 kb upstream of hprt and 300 kb, 540 kb, 900 kb, 1260 kb, and 1400 kb downstream of hprt. A primer pair for an unlinked and unselected gene sequence (K-ras) was also included in the multiplex reaction to serve as an internal positive control. Using this new assay, hprt mutant DNAs can be screened to determine the extent of deletion. Deletions larger than 2 Mb have been identified and show that large deletions can be tolerated at this hemizygous locus.
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Affiliation(s)
- J C Fuscoe
- Environmental Health Research and Testing, Inc., Research Triangle Park, North Carolina
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47
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Zu Z, Yu Y, Gibbs RA, Caskey CT, Hsie AW. Multiplex DNA amplification and solid-phase direct sequencing for mutation analysis at the hprt locus in Chinese hamster cells. Mutat Res 1993; 288:237-48. [PMID: 7688083 DOI: 10.1016/0027-5107(93)90090-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We report here the development of multiplex in vitro DNA amplification and solid-phase direct exon sequencing for the analysis of mutations at the hypoxanthine-guanine phosphoribosyltransferase (hprt) locus in Chinese hamster cells. 18 representative HPRT-deficient mutants, derived either spontaneously, or after exposure to UV light or ionizing radiation, were analyzed. All 9 hprt exons were simultaneously amplified via the polymerase chain reaction (PCR) for rapid deletion detection. 5 mutants involve single- or multiple-exon deletions. Altered multiplex PCR patterns were detected in mutants Bsp-040, Bsp-065 and BGR-606. Subsequent direct sequence analysis reveals that Bsp-040 and Bsp-065 carry a 52-bp and a 13-bp intragenic DNA deletion in exon 3, respectively. BGR-606 contains a 223-bp insertion accompanied by a 10-bp deletion of intron sequence within exon 4 fragment. Other subtle DNA alterations identified by direct exon sequence analysis include single-base substitutions, small deletions and insertions, and RNA splicing mutations.
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Affiliation(s)
- Z Zu
- Department of Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston 77555
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48
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Vatteroni L, Piras A, Simi S, Mariani L, Moretti A, Citti L, Mariani T, Rainaldi G. Analysis of electroporation-induced genetic damages in V79/AP4 Chinese hamster cells. Mutat Res 1993; 291:163-9. [PMID: 7685057 DOI: 10.1016/0165-1161(93)90156-t] [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: 01/26/2023]
Abstract
Electroporation is a recent technique used to introduce exogenous DNA into eukaryotic cells. It is important to establish that the gene of interest is transferred into a functional, non-mutated recipient cell. V79/AP4 Chinese hamster cells were exposed to high-voltage pulsed electric fields and some biological and genetic effects were measured. The results showed that cytotoxicity was related in a dose-dependent manner to the number of applied pulses. Thioguanine-resistant colony-forming cells as well as chromosomal aberrations were also induced whereas ouabain resistants and sister-chromatid exchanges were not or slightly induced. Spontaneous and electroporation-induced clones that were phenotypically TGR/HATS were used to investigate the hprt locus. Molecular screening of the locus showed that the number of deleted exons was significantly higher in induced than in spontaneous TG-resistant clones, suggesting that the genetic damages induced by electroporation concern the loss of regions well over the size of the hprt locus.
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Affiliation(s)
- L Vatteroni
- Istituto di Mutagenesi e Differenziamento, CNR, Pisa, Italy
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49
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Abstract
DNA deletions of more than one or two base pairs are induced frequently enough so that these form a reasonable fraction of mutations for only a few mutagens. Of these agents, some such as ionizing radiations form DNA double-strand breaks, and very large deletions are thought to result from a DNA end from one break ligating with a second break on the same DNA molecule. However, deletions of kilobase pairs and more are sometimes induced by ionizing radiation at a higher rate than can be accounted for by the numbers of double-strand breaks. Published data on induced deletions in particular Escherichia coli strains suggest a process involving a single lesion that could explain several features of large deletions: frequent occurrence in mammalian cells and scarcity in prokaryotes, nonrandom location which is perhaps associated with locations of origins of replication, and differences in the fraction of deletions among mutations in various genes. Some agents inducing deletions make single-strand nicks, not double-strand breaks, and the proposed mechanism hypothesizes that the inducing lesion is a persistent nick in one DNA strand--for example, a radiation-induced single-strand break with associated damage on the complementary strand that interferes with repair.
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Affiliation(s)
- F Hutchinson
- Radiobiology Laboratory, Yale University School of Medicine, New Haven, CT 06510
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50
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Davies MJ, Phillips BJ, Anderson D, Rumbsy PC. Molecular analysis of mutation at the hprt locus of Chinese hamster V79 cells induced by ethyl methanesulphonate and mitomycin C. Mutat Res 1993; 291:117-24. [PMID: 7680415 DOI: 10.1016/0165-1161(93)90150-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Mutations at the hprt locus of Chinese hamster V79 cells were induced by treatment with ethyl methanesulphonate (EMS), considered primarily a point mutagen and mitomycin C (MMC), a potent clastogen. EMS gave a dose-dependent induction of mutants while MMC induced a poor mutagenic response. Mutations were analysed using Southern and Northern blotting. Analysis of 9 EMS-induced and 4 spontaneous mutants yielded no detectable alterations in the hprt locus after digestion of DNA with 6 restriction enzymes. Mutants without detectable changes carried presumptive point mutations. In contrast, 4 out of 12 MMC-induced mutants had detectable alterations. 2 of these appeared to have lost the entire hprt gene while the other 2 had probable partial deletions. For these 4 deletion mutants no hprt mRNA was detected. 3 MMC-induced and 1 EMS-induced mutants had reduced levels of hprt mRNA. All the other mutants showed normal levels of hprt mRNA and the message detected was always of the correct size. It is suggested that the poor mutagenic response induced by MMC may be due to the lethal nature of large deletions involving both the hemizygous hprt locus and adjacent essential genes. This may lead to an underestimate of the mutagenicity of clastogenic agents such as MMC in the V79 HPRT mutation assay.
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Affiliation(s)
- M J Davies
- BIBRA Toxicology International, Carshalton, Surrey UK
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