Fig. 7.

WtipC interferes with Shroom3 localization at the junctions. Embryos were injected with indicated RNAs as described in the legend of Fig. 6D-F. (A-C) Stage 10 gastrula ectoderm was stained with anti-Myc antibody. Note the lack of junctional staining in cells expressing GFP-WtipC (C). Scale bar: 10 µm. The images are representative of three different experiments. (D) Protein expression was analyzed by western blot. Shroom3 expression level is not affected by WtipN or WtipC. (E) A positive feedback model for apical constriction. Wtip associates with the apical junctional complex (AJC) via its N-terminus, whereas its C-terminal domain binds to and recruits Shroom3 to the apical junctions. The increased tension during apical constriction promotes further recruitment of Wtip to the AJC. Wtip function may also be regulated by an intramolecular interaction between its N- and C-terminus (dashed arrow).