Germ cell apoptosis is an evolutionary conserved process important to maintain oocytes quality. In C. elegans, fifty percent of germ cells are eliminated during oogenesis by an unknown mechanism. Higher levels of apoptosis can be triggered by DNA damage and pathogen infections. The BH3-only domain protein EGL-1 participates in both types of apoptosis, but DNA damaged-induced apoptosis is also dependent of the transcriptional factor
p53 (CEP-1). Heat shock, oxidative, and osmotic stresses, also induce germ cell apoptosis through the MAPKK pathway in a mechanism independent of EGL-1 and
p53. Another stress condition that induces germ cell apoptosis is starvation however, its regulation is independent of EGL-1, CEP-1, or MAPKKs. In an RNAi screening to search for genes important for starvation-induced apoptosis we found C18A3.5; one of the three TIA-1/TIAR homologs in C. elegans. TIA-1 and TIAR are RNA binding proteins that promote the assembly of stress granules, and induce apoptosis in mammals. Stress granules are discrete cytoplasmic inclusions into which stalled translation initiation complexes are dynamically recruited in cells subjected to environmental stress. C18A3.5 mRNA is enriched in the hermaphrodite gonad and decreased during starvation. C18A3.5
(tm361) animals are temperature sensitive sterile, and have defects during oogenesis and embryogenesis. C18A3.5 is required to induce germ cell apoptosis in response to different stress conditions. To test if C18A3.5 is important for processing bodies and stress granules formation, we exposed wild type and C18A3.5
(tm361) animals to starvation and heat shock. When nematodes are exposed to starvation or heat shock, large CGH-1 positive granules become visible in the core distal part of the gonad. In the absence of C18A3.5, CGH-1 is found in small granules and P granules, however no large CGH-1 granules were observed in the core of the gonad under stress conditions suggesting that, as in mammals, this protein is important for granules assembly. The other TIA-1/TIAR related C. elegans genes are not required to induce germ cell apoptosis or to participate during assembly of granules under stress conditions.