Host: The Japan Radiation Research Society
Co-host: Asian Association for Radiation Research
It is extremely important to investigate the genetic effects of the chromosome aberrations caused by radiation exposure at low-dose or low-dose rate from the view points of influences on human health. Here, we used LOH (Loss of Heterozygosity) analysis system in human lymphoblastoid cell TK6, which has been established as a sensitive detection methodology. After TK6 cells were exposed to a low dose-rate gamma rays (1.2 mGy/hr, total 30 mGy), the frequency of mutations induced in thymidine kinase (TK) gene locus, selected as early mutants (EMs), was about 2.8 times as high as that of unirradiated cells. The rate of LOH mutants among EMs was shown to be increased by radiation exposure (0/3→5/7), and most of the LOH mutants were hemi-type observed near the TK locus. On the other hand, the frequency of lately induced TK mutants (LMs) decreased to about 60% of non-irradiation level. Most of obtained LMs showed LOH regardless of the irradiation. In addition, the hemi-type events were detected only after the radiation exposure. It can be suggested that the repair of DNA double double strand breaks by non-homologous end-joining is responsible for the induction of hemi-type LOHs. Moreover, there were almost no differences in the total mutation frequency (EM + LM) between irradiated and unirradiated samples, reflecting a difficulty in the detection of mutation in the low-dose range. These preliminary results are now under the confirmation.
