The C. elegans genome encodes an 11-member family of non-chitinase, chitin binding domain-containing proteins (CBDs) with distinct expression profiles. Our lab is investigating the roles of chitin and CBDs in development. We have shown that chitin and two CBD family members, CEJ-1 and CPG-2, are required in the single-cell embryo for high fidelity segregation of meiotic chromosomes, for polar body extrusion and for polarization (Johnston et al., 2006). Interestingly, while CEJ-1 and CPG-2 are functionally redundant for embryonic development, localization of CEJ-1::mCherry and CPG-2::Venus is largely distinct. CEJ-1::mCherry has a punctate cortical localization in oocytes, and is non-punctate and gradually enriched in the eggshell. Conversely, CPG-2::Venus is detected in the zone between the eggshell and the embryo. These findings imply that meiotic chromosome segregation, polar body extrusion and polarization require a very small amount of CEJ-1 or CPG-2. We are also investigating the developmental role of another CBD family member, H02I12.1, which is embryonic lethal by RNAi. H02I12.1::GFP is expressed at boundaries between developing germline nuclei. Chitin is not detected in the germline, suggesting that H02I12.1 may bind to non-chitin glycoconjugates. H02I12.1(RNAi) embryos have chitin, but are fragile, and often pinch in two as they enter the uterus, suggesting somatic gonad contraction/dilation may be defective. Furthermore, the germline is also defective, with an extended zone of oocyte phosphohistone H3, and a Pro phenotype in which there is a zone of germline proliferation proximal to the region of gametogenesis. The Pro phenotype has previously been reported for
glp-1 alleles with mutations in the extracellular domain, and for mutant alleles of genes involved in ribosome biogenesis in the somatic gonad. Taken together, these results suggest that H02I12.1 interacting with non-chitin glycoconjugates may modulate signaling between germ cells and the somatic gonad.