Centralspindlin is partially required for C. elegans anchor cell specification, vulval induction and morphogenesis

Caenorhabditis elegans vulval development is a relatively simple model of organ development whereby a signal from the overlying gonad induces three epithelial cells to undergo three rounds of cell division to generate 22 cells that make up the vulva. Specification of the vulval cell fates requires coordination between cell division and cell signaling via LIN-12/Notch and LET-23/EGFR pathways in the somatic gonad and the underlying epithelium. Here we characterize the role of the centralspindlin complex in vulval development. Centralspindlin, a heterotetramer of ZEN-4/KIF23 and CYK-4/RacGAP1, is essential for completion of cytokinesis during early embryonic cell divisions. We found that centralspindlin is required for completion of cytokinesis in the developing somatic gonad and hence specification of the LIN-3/EGF-secreting anchor cell (AC) critical for LET-23/EGFR-mediated vulval induction. However, the requirements for centralspindlin for cytokinesis during postembryonic development are incomplete as the AC is frequently specified, though often binucleate. The presence of the binucleate AC correlates with vulval induction demonstrating that LET-23/EGFR signaling is largely functional. Centralspindlin is also partially required for cytokinesis of the vulval cells where it is required for vulval morphogenesis rather than induction. We also found that the GAP domain of CYK-4/RacGAP1 required for contractile ring assembly during embryonic division is not essential for development of the somatic gonad and the vulva. Thus, there appears to be different requirements for centralspindlin during postembryonic development of the somatic gonad and vulva as compared to early embryogenesis.