Study of biological responses to ionizing radiation in the germline cells of C. elegans

Abstract

Ionizing radiation causes DNA double-strand breaks. Organisms have a DNA repair system to maintain the integrity of genome. When DNA is severely damaged in Metazoa, apoptosis is induced to eliminate the damaged cells. A proto-oncogene c-Abl1 is involved in the positive regulation of DNA repair system in mammals. Furthermore the frequency of radiation-induced germline apoptosis increases in a C. elegans abl-1 deletion mutant. It indicates that another function is involved in the negative regulation of DNA damage-induced apoptosis. In this study, we carried out comprehensive analyses of gene expression after γ-ray irradiation in the wild-type and abl-1 adult hermaphrodites using the nematode DNA microarray. In the wild type, 1313 genes were up-regulated above twice 3 hr after irradiation. Especially 117 genes were up-regulated more than 1.4 times in the abl-1 deletion mutant irradiated as compared with the wild type. BH3-only protein gene egl-1 and ced-13 that are apoptosis-inducing signals were found in the 117 genes. In addition, certain genes of cytochrome P450 subfamily induced after irradiation in the wild type were remarkably repressed and not up-regulated in the abl-1 mutant. In this presentation, we also show the results of cell-cycle arrest, apoptosis, and little bystander effect in the germline cells following heavy-ion microbeam irradiation.