Fig. 4. cta mutants resemble abl mutants. Embryos, antigens and genotypes are indicated. (A-F) VFs from cta mutants. (A,B,E,F) Grazing-sections, (C,D,G-J') Cross-sections. (A,C) Constricted (arrows) and unconstricted (arrowheads) cells at early gastrulation. (B,D) Late gastrulation. (B, arrow) Mesoderm internalized at varying angles. (D, arrow) Asymmetric cell shape. (E,F) During furrow ingression, apical myosin and RhoGEF2 are concentrated in constricting VF cells (arrows) and are diffusely localized elsewhere (arrowheads). (G-J') Myosin and RhoGEF2 levels are comparable at sites of apical constriction (arrows) in wild type (G,I) and cta mutants (H,J), but, in the mutants, they are not concentrated in unconstricted cells (arrowheads). Scale bar: 20 µm.