1. Non-autonomous protective effect of dying cells
Earlier this year, we reported a phenomenon wherein induction of apoptosis by a variety of means in wing imaginal discs of Drosophila larvae resulted in the activation of an anti-apoptotic microRNA, bantam. Cells in the vicinity of apoptotic cells also become harder to kill by ionizing radiation (IR)-induced apoptosis. The protective effect spanned as much as 100 microns away from dying cells. Both ban activation and increased protection from IR required receptor tyrosine kinase Tie, which we identified in a genetic screen for modifiers of ban. Apoptotic cells showed increased expression of transcriptional reporters for Pvf1 and Pvf2, putative ligands for Tie. We proposed that apoptotic cells activate ban in surviving cells through Tie to make the latter cells harder to kill, thereby preserving tissues and ensuring organism survival.