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HPRT Mutations (hprt + mutation)
Selected AbstractsHPRT mutations, TCR gene rearrangements, and HTLV-1 integration sites define in vivo T-cell clonal lineages,ENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 2-3 2005Mark Allegretta Abstract HPRT mutations in vivo in human T-lymphocytes are useful probes for mechanistic investigations. Molecular analyses of isolated mutants reveal their underlying mutational changes as well as the T-cell receptor (TCR) gene rearrangements present in the cells in question. The latter provide temporal reference points for other perturbations in the in vivo clones as well as evidence of clonal relationships among mutant isolates. Immunological studies and investigations of genomic instability have benefited from such analyses. A method is presented describing a T-cell lineage analysis in a patient with HTLV-1 infection. Lineage reconstruction of an in vivo proliferating HPRT mutant clone allows timing of the integration event to a postthymic differentiated cell prior to the occurrence of HPRT mutations. Environ. Mol. Mutagen., 2005. © 2005 Wiley-Liss, Inc. [source] Childhood hyperuricemia and acute renal failure resulting from a missense mutation in the HPRT geneAMERICAN JOURNAL OF MEDICAL GENETICS, Issue 3 2002Tarak Srivastava Abstract A 6-year-old boy was determined to have partial hypoxanthine phosphoribosyl transferase (HPRT) enzyme deficiency without the phenotypic features of Lesch-Nyhan syndrome. He presented with recurrent acute renal failure (ARF) from hyperuricemia. Treatment with allopurinol prevented further attacks of renal failure. T lymphocyte cultures were used to sequence the HPRT cDNA and a novel single nucleotide substitution at codon 65 in exon 3 was found (193C,>,T, 65leu,>,phe). This mutation was confirmed by genomic DNA sequencing and was also detected in his heterozygous, asymptomatic mother and sister. Unlike the cells from patients with classic Lesch-Nyhan syndrome, the in vitro cultures of our patient's T-lymphocytes did not proliferate in the presence of purine analogue 6-thioguanine (TG). This report highlights the unusual occurrence of recurrent ARF in a child with partial HPRT enzyme deficiency. The absence of TG resistance in vitro with this mutation shows that even small alterations in enzyme activity in vivo can result in disease symptoms, in this instance, hyperuricemia sufficient to cause ARF. Atypical HPRT mutations should also be considered in cases of unusual renal failure, because correct diagnosis can allow appropriate treatment, as well as informed genetic counseling. © 2002 Wiley-Liss, Inc. [source] Genotoxic potential of xenobiotic growth promoters and their metabolites,APMIS, Issue 2 2001Review article This paper reviews data reported in the literature as well as recent and unpublished studies from our laboratory on the metabolism and genotoxicity of the xenobiotic growth promoters 17,-trenbolone, melengestrol acetate and zeranol. In our metabolic study, the oxidative in vitro metabolites generated by hepatic microsomes from rats, bovine and humans were analyzed by HPLC and GC/MS. 17,-Trenbolone gave rise to at least 13 monohydroxylated products, whereas 12 mono- and dihydroxylated metabolites were obtained with melengestrol acetate and at least 5 with zeranol. The genotoxic potential of the parent compounds was studied using the following endpoints: induction of HPRT mutations in cultured V79 cells and of lacI mutations in E. coli; induction of micronuclei in V79 cells; and formation of DNA adducts in cultured primary rat hepatocytes. Negative results were obtained in most of these assay systems. Only the micronucleus induction was marginally positive with 17,-trenbolone and zeranol at near-cytotoxic concentrations. Commercial melengestrol acetate was found to contain an impurity causing apoptosis in V79 cells. The genotoxic potential of the numerous oxidative metabolites of the xenobiotic growth promoters remains to be studied. [source] Bacterial and mammalian-cell genotoxicity of mixtures of chlorohydroxyfuranones, by-products of water chlorinationENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 4 2004Jorma Mäki-Paakkanen Abstract The genotoxic responses of mixtures of four chlorohydroxyfuranones (CHFs), 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), 3,4-dichloro-5-hydroxy-2(5H)-furanone (MCA), 3-chloro- 4-(chloromethyl)-5-hydroxy-2(5H)-furanone (CMCF) and 3-chloro-4-methyl-5-hydroxy-2(5H)-furanone (MCF), were compared with the genotoxicity of the individual compounds. Genotoxicity was evaluated in the Salmonella reversion assay (Ames test), the in vitro Chinese hamster ovary (CHO) cell Hprt mutation assay, and in the CHO chromosome aberration test. When tested individually, the concentrations of the chemicals that were chosen for the mixtures induced no or only a modest increase in the genotoxic effects, and caused little or no cytotoxicity. In the Ames test, the genotoxic responses caused by the mixtures of CHFs did not follow simple additivity. Synergism was observed with strains TA97 and TA98, and antagonism with strain TA100. In the CHO/Hprt mutation assay, the mutagenic response of the mixtures was inconsistent, with near additivity seen with a mixture of CHFs that resulted in 12% cell survival. In contrast, the four CHFs together consistently caused more structural chromosome damage (mainly chromatid-type breaks and exchanges) compared to the sum of net effects of the four CHFs tested alone. Also, a potentiating effect was consistently seen for the cytotoxicity of the CHF mixtures both in the CHO/Hprt mutation assay and the chromosome aberration test. The present results indicate that the genotoxic effects of CHF mixtures can be greater than additive. Such effects may be worth considering in the cancer risk assessment of chlorinated drinking water. Environ. Mol. Mutagen. 43:217,225, 2004. © 2004 Wiley-Liss, Inc. [source] Expression of the E. coli fpg protein in CHO cells lowers endogenous oxypurine clustered damage levels and decreases accumulation of endogenous Hprt mutations,ENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 5 2006Sunirmal Paul Abstract Endogenous DNA damage clusters,two or more oxidized bases, abasic sites, or strand breaks within about 20 base pairs on opposing strands,can accumulate in unirradiated mammalian cells, and may be significant origins of spontaneous detrimental biological effects. Factors determining the levels of such endogenous clusters are largely unknown. To determine if cellular repair genotype can affect endogenous cluster levels in mammalian cells, the authors examined cluster levels, growth rates, and mutant frequencies in Chinese hamster ovary cells expressing the Escherichia coli glycosylase fpg protein, whose principal substrates are oxidized purines. In cells expressing high levels of fpg protein, the levels of oxypurine clustered damages were decreased while those of oxypyrimidine clusters and abasic clusters were unchanged. Furthermore, in these cells, the growth rates were increased and the level of spontaneous background mutants in the hypoxanthine guanine phosphoribosyl transferase gene was decreased. These results suggest that endogenous clusters are potentially detrimental DNA damages, and that their levels,as well as the detrimental consequences of their presence,can be effectively reduced by increased cellular activity of specific DNA repair proteins. Environ. Mol. Mutagen., 2006. Published 2006 Wiley-Liss, Inc. [source] Characterization of Hprt mutations in cDNA and genomic DNA of T-cell mutants from control and 1,3-butadiene-exposed male B6C3F1 mice and F344 ratsENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 2 2004Quanxin Meng Abstract A multiplex PCR procedure for analysis of genomic DNA mutations in the mouse hypoxanthine-guanine phosphoribosyltransferase (Hprt) gene was developed and then used with other established methods for the coincident identification of large- and small-scale genetic alterations in the Hprt gene of mutant T-cell isolates propagated from sham- and 1,3-butadiene (BD)-exposed mice and rats. The spectra data for RT-PCR/cDNA analysis and multiplex PCR of genomic DNA from Hprt mutants were combined, and statistical analyses of the mutant fractions for the classes of mutations identified in control versus exposed animals were conducted. Under the assumption that the mutant fractions are distributed as Poisson variates, BD exposure of mice significantly increased the frequencies of (1) nearly all types of base substitutions; (2) single-base deletions and insertions; and (3) all subcategories of deletions. Significantly elevated fractions of G:C,C:G and A:T,T:A transversions in the Hprt gene of BD-exposed mice were consistent with the occurrence of these substitutions as the predominant ras gene mutations in multiple tumor types increased in incidence in carcinogenicity studies of BD in mice. BD exposure of rats produced significant increases in (1) base substitutions only at A:T base pairs; (2) single-base insertions; (3) complex mutations; and (4) deletions (mainly 5, partial and complete gene deletions). Future coincident analyses of large- and small-scale mutations in rodents exposed to specific BD metabolites should help identify species differences in the sources of deletion mutations and other types of mutations induced by BD exposures in mice versus rats. Environ. Mol. Mutagen. 43:75,92, 2004. © 2004 Wiley-Liss, Inc. [source] | ||||||||||