Fig. 4. Linking PAR polarity to contractile polarity: CDC-42. Illustrations of C. elegans embryos: (A) wild type; (B) depleted of CDC-42; (C) expressing a PAR-6-CRIB mutant; (D,E) depleted of Rho early (D) and late (E) in the first cell cycle. The acto-myosin network (pink) is indicated from a surface view of the embryo cortex; CDC-42 (purple dashed line) and PAR-6 (red) are shown in the embryo mid-plane. Embryo anterior, or the meiotic pole in C, is to the left. Embryos lacking CDC-42 or the CDC-42-binding CRIB domain of PAR-6 have reduced cortical localization of PAR-6, indicated by the dotted red line in B and C. Both PAR-6 and CDC-42 remain uniformly distributed around the cortex despite asymmetry of the acto-myosin network in rho-1(RNAi) embryos late in the cell cycle (E), suggesting that CDC-42 cannot respond to the acto-myosin network when Rho signaling is disrupted.