We measure genotoxic damage in the C. elegans intestine by irradiating L1 larvae and quantifying anaphase bridges in DAPI-stained young adults. The method is reliable for all types of radiation tested, shows a robust dose-response and distinguishes between different radiation types. Analysis of dose-responses for cells in different intestinal rings shows that they have unique radiosensitivities not correlated with their lineages. We present evidence that germline cells may modulate individual E cell radiosensitivity leading to the observed patterns. Thus, mutations in
dig-1,
mes-1, and
glp-4 which alter P4 fates or shift gonad position change the E cell radiosensitivity patterns. A statistical analysis of responses for pairs of E cells shows that neighboring cells also influence each other such that damage to one E cell enhances the probability of damage in its neighbor. Such "bystander" effects have been observed in cultured cell systems and are thought to be propagated by reactive oxygen species and cytokines. An RNAi and mutant screen was initiated to identify genes required for the signaling. The screen includes genes for DNA repair systems, cell junctions, extracellular matrix components and signal transduction. So far, we have shown that mutations or knock-down in components of the non-homologous end joining DNA repair pathway (
cku-70, Y47D3A.4;
cku-80, R07E5.8; and
lig-4, C07H6.1) and the MAP kinase
sek-1 (R03G5.2) result in strong (up to 7-fold) overall sensitization of the cells but do not influence their relative sensitivity patterns. An up-to-date summary will be presented. Precision irradiations of body segments with alpha particles confirms that middle and anterior E cells react to damage in posterior E cells but irradiation of the head from the posterior margin of the pharynx does elicit a response from the intestine. Work is in progress to conduct single cell irradiations with a particle microbeam at Texas A&M University to test individual cells and the topology of the putative bystander signaling.