Radiation-induced bystander signaling from somatic cells to germ cells in Caenorhabditis elegans

Recently, radiation-induced bystander effects (RIBE) have been studied in mouse models in vivo, which clearly demonstrated bystander effects among somatic cells. However, there is currently no evidence for RIBE between somatic cells and germ cells in animal models in vivo. In the current study, the model animal Caenorhabditis elegans was used to investigate the bystander signaling from somatic cells to germ cells, as well as underlying mechanisms. C. elegans body size allows for precise microbeam irradiation and the abundant mutant strains for genetic dissection relative to currently adopted mouse models make it ideal for such analysis. Our results showed that irradiation of posterior pharynx bulbs and tails of C. elegans enhanced the level of germ cell apoptosis in bystander gonads. The irradiation of posterior pharynx bulbs also increased the level of DNA damage in bystander germ cells and genomic instability in the F1 progeny of irradiated worms, suggesting a potential carcinogenic risk in progeny even only somatic cells of parents are exposed to ionizing radiation (IR). It was also shown that DNA damage-induced germ cell death machinery and MAPK signaling pathways were both involved in the induction of germ cell apoptosis by microbeam induced bystander signaling, indicating a complex cooperation among multiple signaling pathways for bystander effects from somatic cells to germ cells.