The GLP-1/Notch transmembrane receptor is required for mitotic proliferation of germline stem cells (GSCs) and for early embryonic development in C. elegans. We identified
daf-21(
om40), formerly called
ego-3(
om40), in a screen for genetic enhancers of a
glp-1 temperature sensitive allele,
glp-1(
bn18ts).
daf-21 encodes the molecular chaperone HSP90, thus the discovery of this
daf-21/glp-1 interaction reveals an important role for HSP90 in GLP-1/Notch signaling and germline development in C. elegans. Proper HSP90 function requires the activity of numerous co-chaperones; at least two dozen co-chaperones are known from various organisms and most have orthologs in C. elegans. An obvious question, then, is which, if any, of these co-chaperones play a role in GLP-1/Notch signaling in C. elegans. Therefore, we are using the
glp-1(
bn18ts) sensitized background as a tool to identify additional components of the HSP90 molecular chaperone system required for proper GLP-1/Notch function in germline and embryonic development. We are using RNAi by feeding to systematically knock down the expression of all known C. elegans co-chaperone orthologs in wildtype N2 and
glp-1(
bn18ts) worms. In the initial stage of this project, we are examining the effects on brood size and embryonic/early larval viability. To date, we have done RNAi knockdown of four co-chaperone genes for which there is evidence of germline expression:
pph-5 (encodes PP5),
hip-1 (encodes Hip), C01G10.8 (encodes Aha1), and C56C10.10 (encodes Aip). Preliminary analysis of these data shows that
pph-5 and
hip-1 knockdowns significantly reduced embryonic and early larval viability in
glp-1(
bn18ts) compared to the same knockdowns in N2. We did not detect a significant reduction in brood size for knock down of any the tested genes. We hypothesize that the HSP90 co-chaperones PPH-5 and HIP-1 promote GLP-1/Notch signaling during embryonic and early larval development.