pac-1and cdc-42 regulate junctional actin morphology and dynamics. (A–C, top) Near-TIRF high-resolution imaging of LifeAct-GFP in control, pac-1 (see Video 8) and cdc-42(MZ) embryos at 1.3-fold elongation. Insets (middle) show the junctions between the seam cells (S) and ventral cells (V). Insets (bottom) are pseudo-colored images depicting actin dynamics (STDEV/AVERAGE values at each pixel) over the course of the movie (16 s: 512 time points imaging at 32 frames/s). (D and E) Junctional actin dynamics (STDEV/AVERAGE of pixel intensity over 512 time points, imaging at 32 fps) taken from a subset of junctions between seam and ventral cells, as depicted to the right from the graph (D). Embryos in (D) were 1.3-fold: control (n = 23), pac-1 (n = 20); embryos in (E) were 1.2-fold: control (n = 13), cdc-42(MZ) (n = 17). Each data point shows the average value for one embryo. Individual data points from two independent experiments were pooled for each data set. Red bars and error bars are mean ± SD. P-values were calculated using a Mann-Whitney U test. ***, P < 0.001. (F–H, top) CFBs in control, hmp-1(fe4), and hmp-1(fe4); pac-1 embryos. Insets (bottom) show the CFBs in dorsal cells (labeled D) and disconnection of CFBs (arrowheads) from the junction with seam cells (S). Blue dashed line depicts the junction between dorsal (D) and seam (S) cells. Bars, 5 µm.