Programmed cell death (apoptosis) is an important component of animal development and homeostasis. Genetic analysis of apoptosis in C. elegans has shown that the death machinery is largely conserved between worms and humans. We propose that the upstream regulatory pathways that control activation of this conserved death program are themselves also conserved and we are currently using the C. elegans germ line as a genetic model system to understand how the apoptotic machinery is activated in response to various signals. Unlike somatic cells, germ cells in C. elegans do not have a fixed lineage, yet they are one of the best characterised and most extensively studied cell types in C. elegans. In normal adult hermaphrodites, over half of all potential oocytes undergo apoptosis during meiotic maturation, a process we termed physiological germ cell death. Germ cell death is mediated by the same execution machinery as somatic cell deaths (CED-3 and CED-4). However, this pathway is activated by a distinct mechanism, as loss of EGL-1 function, as well as a gain of function mutation of CED-9, both of which completely prevent somatic cell death, have little effect on physiological germ cell death. In order to identify new genes involved in physiological germ cell death, a forward genetic screen was performed to identify mutants with increased germline apoptosis. Three alleles of
gla-3 (germ line apoptosis), which encodes a protein with a single CCCH zinc finger domain, were identified. Of these
op212 and
op216 are strong mutants with about 10 corpses per gonad arm, while the third allele,
op203 is weaker. Furthermore,
op212 has high embryonic lethality, is sterile at 25oC and has a weak Him phenotype. Interestingly, these defects are not suppressed by mutations in
ced-3, suggesting that they are not simply the result of excessive apoptosis. Thus, GLA-3 likely has a function other than (or in addition to) the direct regulation of germ cell death. One possibility is that
gla-3 has a role in germ cell development (and possibly embryogenesis) and that the absence of
gla-3 results in some defect that activates the apoptotic machinery via a hypothetical "quality control" program. To identify genes required for germ cell death following loss of
gla-3 function, we performed a forward genetic screen to isolate mutations that suppress apoptosis in a
gla-3 background. Furthermore, polyclonal antibodies are used to study the expression pattern of GLA-3 in various developmental stages of the worm and to assess possible subcellular localisation of the protein as well as interacting partners.