Fig. 7. CYK-4 and RGA-3/4 fulfil different functions in the early C. elegans embryo. To compare the functions of the three RhoGAPs - RGA-3/4 and CYK-4 - present in the early embryo, RNAi epistasis experiments were performed by injecting dsRNA into the embryos. Whereas CYK-4 was essential for the first division and to recruit GFP::PAR-2 to the posterior cortex (upper panels), RGA-3/4 played a role in downregulating contraction (middle panels). Simultaneous knockdown of all three RhoGAPs resulted in a combination of both phenotypes; embryos did not undergo cytokinesis, the cortex remained contractile and NMY-2 spread over the entire cortex (lower panels). Scale bar: 20 µm.