Genetics and Molecular Biology
Print version ISSN 1415-4757
AYRES, Flávio Monteiro; CRUZ, Aparecido Divino da; STEELE, Patricia and GLICKMAN, Barry W.. Low doses of gamma ionizing radiation increase hprt mutant frequencies of TK6 cells without triggering the mutator phenotype pathway. Genet. Mol. Biol. [online]. 2006, vol.29, n.3, pp. 558-561. ISSN 1415-4757. http://dx.doi.org/10.1590/S1415-47572006000300027.
The TK6 lymphoblastoid cell line is known to be mismatch repair (MMR) and p53 proficient. Deficiency in MMR results in a mutator phenotype characterized by microsatellite instability (MSI) and increased hprt mutant frequency (MF). Increased hprt MF is also a biomarker of effect for exposure to ionizing radiation. In order to test if a mutator phenotype could be induced by low doses of gamma ionizing radiation, an hprt cloning assay and a MSI investigation were performed after radiation exposure. The spontaneous MF was 1.6 x 10-6. The groups exposed to 0.2, 0.5 and 1.0 Gy had hprt MFs of 2.3, 3.3 and 2.2 x 10-6, respectively. The spontaneous MSI frequency per allele in non-selected cells was 5.4 x 10-3, as evidenced at the loci D11S35, nm23-H1, D8S135 and p53. MSI frequencies in the groups exposed to 0.2, 0.5 and 1.0 Gy were found to be < 4.7, < 7.7 and < 12 x 10-3, respectively. The frequencies of hprt mutants and MSI found in this study suggest that low doses of ionizing radiation increase hprt mutant frequency without triggering the mutator phenotype pathway.
Keywords : mutator phenotype; hprt; microsatellite instability; TK6 cells; ionizing radiation.