The F-actin foci persist until late stages of embryogenesis and reside exclusively in FCMs in dpak3^zyg mutant embryos. (A) DPak3 genetically interacts with the Arp2/3 NPFs WASP and Scar. Stage 15 wasp (a), dpak3,wasp (b), scar (c), and scar;dpak3 (d) mutant embryos labeled with α-MHC. Note the more severe fusion defects in the double mutants compared with the respective single mutants (see Table S1 for quantification). (B) Increased F-actin foci number in dpak3^zyg mutant embryos. Late stage 14 embryos triple labeled with phalloidin (green), α-Duf (red), and α-Lame duck (Lmd, blue; FCMs; Duan et al., 2001). Three hemisegments are shown in each panel. Note that the number of F-actin foci significantly increased in dpak3^zyg mutant (b) compared with wild-type (a, wt) embryos. (C) F-actin foci are generated in FCMs of dpak3^zyg mutant embryos. Stage 14 embryos triple labeled with α-GFP (green), phalloidin (red), and α-Duf (blue). Note that GFP-actin expressed in FCMs with sns-GAL4 colocalized with the dense F-actin foci (a, arrows), whereas GFP-actin expressed in founder cells with rP298-GAL4 did not colocalize with the dense F-actin foci (b, arrowheads). Bars: (A and B) 25 µm; (C) 5 µm.