Fig. 10. Cell polarities are properly orientated in wsp-1(RNAi)-treated embryos. (A-C) Time-lapse recording of the three-cell to four-cell stage by DIC microscopy. The P blastomere on the right side is dividing. (A) Wild-type, (B) wsp-1(RNAi)- and (C) cdc42(RNAi)-treated embryos. In cdc42(RNAi) embryos, the spindle of the P blastomere is oriented longitudinally resulting in the same direction of cell division as in the AB blastomere, as reported previously (Kay and Hunter, 2001; Gotta et al., 2001). In wsp-1(RNAi)-treated embryos showing ventral enclosure abnormalities, normal positioning of the spindle followed by proper directional P cell division was still observed. The direction of the spindle is indicated with double-headed arrows. In A-C, the anterior is positioned to the left and the posterior to the right.