Fig. 4. Regulatory pathways that influence germline cell death. (A) The pathways that influence C. elegans germline cell apoptosis. Proteins discussed in the text are included. A physiological germ cell death is mediated through the ras pathway, with MPK-1 (MAP kinase) representing the most downstream component. Genotoxic treatments such as radiation induce checkpoint genes and p53-mediated apoptosis. Both pathways act to regulate a core pathway required for all normal cell deaths in C. elegans. EGL-38 and PAX-2 are drawn to act in parallel to the other two pathways, but could alternatively act downstream of MPK-1 (or CEP-1). (B) Genetic epistasis experiments between C. elegans Pax2/5/8 genes and other genes that affect germline apoptosis, carried out in an otherwise wild-type genetic background. (C) Genetic epistasis experiments between C. elegans Pax2/5/8 genes and other genes that affect germline apoptosis, carried out in animals RNAi-depleted for ced-10, a gene required for corpse engulfment. Germ-cell corpses were quantified as described in Materials and methods. Data are mean number of cell corpses per gonad arm±s.e.m. Wild type is N2.