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Genotypic and phenotypic analysis of the polymorphic thiopurine S-methyltransferase gene (TPMT) in a European population.

ABSTRACT: 1. Characterization of allelic variants of the TPMT gene (TPMT) responsible for changes in TPMT activity, and elucidation of the mechanism by which these alleles act, are required because of the clinical importance of this polymorphism for patients receiving thiopurine drugs. 2. We defined the mutational and allelic spectrum of TPMT in a group of 191 Europeans. Using PCR-SSCP, we screened for mutation the entire coding sequence, the exon-intron boundaries, the promoter region and the 3'-flanking region of the gene. Six mutations were detected throughout the ten exons and seven TPMT alleles were characterized. Four of them, TPMT*2, *3A, *3C and *7, harbouring the known mutations, G238C, G460A, A719G or T681G, were nonfunctional and accounted for 0.5, 5.7, 0.8 and 0.3% of the allele totality, respectively. 3. Within the promoter region, six alleles corresponding to a variable number of tandem repeats (VNTR), were identified. VNTR*V4 and *V5a which harbour four or five repeats of a 17-18 bp unit, were the most frequent (55% and 34%, respectively). The other VNTR alleles, having from five to eight repeats, were rarer. 4. The TPMT phenotype was correctly predicted by genotyping for 87% of individuals. A clear negative correlation between the total number of repeats from both alleles and the TPMT activity level was observed, indicating that VNTRs contribute to interindividual variations of TPMT activity. Therefore, additional analysis of the promoter region of TPMT can improve the phenotype prediction rate by genotyping.

SUBMITTER: Spire-Vayron de la Moureyre C

PROVIDER: S-EPMC1571045 | biostudies-other | 1998 Oct

REPOSITORIES: biostudies-other

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Genotypic and phenotypic analysis of the polymorphic thiopurine S-methyltransferase gene (TPMT) in a European population.

Spire-Vayron de la Moureyre C C Debuysere H H Mastain B B Vinner E E Marez D D Lo Guidice J M JM Chevalier D D Brique S S Motte K K Colombel J F JF Turck D D Noel C C Flipo R M RM Pol A A Lhermitte M M Lafitte J J JJ Libersa C C Broly F F

British journal of pharmacology 19981001 4

1. Characterization of allelic variants of the TPMT gene (TPMT) responsible for changes in TPMT activity, and elucidation of the mechanism by which these alleles act, are required because of the clinical importance of this polymorphism for patients receiving thiopurine drugs. 2. We defined the mutational and allelic spectrum of TPMT in a group of 191 Europeans. Using PCR-SSCP, we screened for mutation the entire coding sequence, the exon-intron boundaries, the promoter region and the 3'-flanking ...[more]

PMID: 9831928

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Project description:To sum up our results, we managed to isolate a reproducible SP cell fraction of human gastric carcinoma cell lines for the first time. Those cells differed from the rest of the population regarding morphology and biological behaviour. They had the ability to build a population resembling the basic tumor population and therefore performed differenziation and asymmetric cell division. SP cells expressed potential stem cell markers like musashi 1 and Cd133 and also showed a high expression of genes that encode for stem cell properties. The so identified phenotypic and genetic factors showed a variable expression in tumor samples of patient series and might be applicable as prognostic factors in the diagnosis of gastric carcinoma. Aims: The side population (SP) of tumor cell lines shares characteristics with tumor stem cells. In this study we phenotypically and genotypically characterized the SP of gastric cancer cell lines. Methods: The SP was obtained from MKN45- and AGS-gastric cancer cells using Hoechst 33342 staining and fluorescence-activated cell sorting (FACS). SP cells were subsequently studied morphologically (cytology, immunocytochemistry), on the transcriptional level (gene array) and in cell culture (recultivation assays). Genes differentially expressed in the SP cells were finally searched by immunohistochemistry in neoplastic and non-neoplastic gastric tissue from gastric cancer patients. Results: The SP was reproducibly obtained from gastric cancer cell lines. The SP cells were smaller and rounder then non-SP cells. SP cells self-renewed in re-cultivation experiments and differentiated into SP- and non-SP cells. Re-cultivated SP- and non-SP cells showed distinct phenotypes in culture regarding cell shape and colony-formation. SP cells had increased levels of the stem cell markers CD133 and Musashi 1. Transcriptional analyses demonstrated that SP cells express genes that encode for stem cell properties like FZD7, HEY1, SMO and ADAM17. Finally we detected the transcripts of these genes in tissue samples from patients with gastric cancer. Conclusions: Human gastric cancer cell lines enclose a phenotypically and genotypically distinct cell population with tumor stem cell features. Phenotypical characteristics of this distinct cell population are also present in gastric cancer tissue.

Project description:BackgroundGenomic analysis has revealed extensive contamination among laboratory-maintained microbes including malaria parasites, Mycobacterium tuberculosis and Salmonella spp. Here, we provide direct evidence for recent contamination of a laboratory schistosome parasite population, and we investigate its genomic consequences. The Brazilian Schistosoma mansoni population SmBRE has several distinctive phenotypes, showing poor infectivity, reduced sporocysts number, low levels of cercarial shedding and low virulence in the intermediate snail host, and low worm burden and low fecundity in the vertebrate rodent host. In 2021 we observed a rapid change in SmBRE parasite phenotypes, with a ~10x increase in cercarial production and ~4x increase in worm burden.MethodsTo determine the underlying genomic cause of these changes, we sequenced pools of SmBRE adults collected during parasite maintenance between 2015 and 2023. We also sequenced another parasite population (SmLE) maintained alongside SmBRE without phenotypic changes.ResultsWhile SmLE allele frequencies remained stable over the eight-year period, we observed sudden changes in allele frequency across the genome in SmBRE between July 2021 and February 2023, consistent with expectations of laboratory contamination. (i) SmLE-specific alleles rose in the SmBRE population from 0 to 41-46% across the genome between September and October 2021, documenting the timing and magnitude of the contamination event. (ii) After contamination, strong selection (s = ~0.23) drove replacement of low fitness SmBRE with high fitness SmLE alleles. (iii) Allele frequency changed rapidly across the whole genome, except for a region on chromosome 4 where SmBRE alleles remained at high frequency.ConclusionsWe were able to detect contamination in this case because SmBRE shows distinctive phenotypes. However, this would likely have been missed with phenotypically similar parasites. These results provide a cautionary tale about the importance of tracking the identity of parasite populations, but also showcase a simple approach to monitor changes within populations using molecular profiling of pooled population samples to characterize fixed single nucleotide polymorphisms. We also show that genetic drift results in continuous change even in the absence of contamination, causing parasites maintained in different labs (or sampled from the same lab at different times) to diverge.

Dataset Information

Genotypic and phenotypic analysis of the polymorphic thiopurine S-methyltransferase gene (TPMT) in a European population.

Publications

Genotypic and phenotypic analysis of the polymorphic thiopurine S-methyltransferase gene (TPMT) in a European population.

Similar Datasets

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