Abstract
We have previously shown that a radiation sensitive medaka mutant ric1 strain has the defects in phosphorylated H2AX (gamma-H2AX) foci formation, induction of apoptosis, regulation of cell cycle and Homologous recombination (HR) repair after gamma-rays irradiation [Aizawa et al., 2004; Hidaka et al., 2010; 51th Annual Meeting of JRRS]. These results suggested that the gene responsible for the phenotype in ric1 strain is involved in phosphorylation of H2AX, and instability of gamma-H2AX foci formation causes aberrant DNA damage responses. To confirm the hypothesis, we examined whether DNA damage response genes which interact with H2AX are recruited to and released from DNA damage site after irradiation with a laser microbeam in ric1 cultured cells. Previous studies indicate that Non-homologous end joining (NHEJ) complements the low repair activities of HR in ric1 cells [52th Annual Meeting of JRRS]. Since NHEJ is error-prone pathway, we considered that the radiation-induced mutation frequency increases in ric1 cells. To estimate the mutation frequency, we used a mutation assay system. This assay can detect mutations at the exogenous gene by GFP expression. Consequently, it is possible to measure mutations by flow cytometry and visualize mutated cells on Fluorescent microscopy. We will discuss ric1 gene function.
