Abstract
In this study, we analyzed the morphological changes in the cells that were irradiated with UV or ionizing radiation (IR) to clarify the molecular mechanism of cell death which is induced by DNA damages. The RIC (Radiation Induced Curly tailed malformation) mutants are isolated by ENU mutagenesis screening in the Medaka. We have reported that RIC1 mutant has the defect in the mechanism that repair the double-strand breaks of DNA stands induced by IR in embryos. We established cultured cell lines derived from wild-type (CAB strain) and ric (RIC1 and RIC2) and the time-laps observation of morphological change after irradiation of IR, UVA, and UVC was performed. When we irradiated the cells with 20Gy of IR, the giant cells and cells with many vacuoles were observed and such cells were observed more frequently in RIC1 cells than in wild type cells. When CAB and RIC1-derived cells were irradiated with UVC (20J/m2), the fibroblast-like cells became rounded and detached from the bottom of the culture dish, then fragmented into small pieces and finally died. RIC1 cells were more sensitive to UVC irradiation than CAB cells. When CAB cells were irradiated with UVA (50kJ/m2), there was little effect. UVA-irradiated RIC1 cells became rounded and detached from the bottom. After UVA irradiation, RIC2 cells still attached to the bottom of the culture dish and maintained their pseudopodia and their fibroblast-like figure, but their nuclei were clarified, just same as in fixed cells.
