Fig. 4. Loss of Has2 function leads to blockage of dorsal convergence, but not of extension, and can be compensated by constitutively active Rac1. (A-I) Distribution of labeled cell clusters at onset of gastrulation, mid-gastrulation and end of gastrulation; lateral views, dorsal to the right. (A-C) Wild type; (D-F) has2 morphant; (G-I) embryo co-injected with has2 MO and caRac1 RNA. (A,D,G) Shield (6 hpf), directly after labeling of cell clusters by fluorochrome uncaging; (B,E,H) 80% epiboly (8 hpf); (C,F,I) tailbud (10.5 hpf). (J) Graph showing angle between labeled cells and dorsal axis at different time points, measuring dorsal convergence (indicated in B by blue bar). All clones start at 90° from the shield. (K) Graph showing the anteroposterior extension of labeled lateral cell populations (indicated in B by red bar) at different time points. In J and K, 10 embryos per treatment were evaluated, and standard deviations are indicated.