(A) Lateral views with animal pole to the top of z-confocal projections of phalloidin stained WT, MZrab25a and MZrab25b embryos stage-matched at 80% epiboly; red arrows show reduced cortical actin in normal sized cells; yellow arrows show reduced actin in large cells; Scale bar 20 μm. (A’) Quantification of normalized tricellular and bicellular F-actin intensity at 80% epiboly. WT (n = 90,N = 9), MZrab25a (n = 90,N = 9) and MZrab25b (n = 90,N = 9). Means: SEM; Mann-Whitney, **,p<0.001. (B) Confocal z-confocal projections of WT and MZrab25b embryos at 80% epiboly antibody stained for pMyosin. Red arrows denote uneven distribution of pMyosin along individual MZrab25b cellular junctions. Scale bar 20 μm. (C–D’) Confocal z-confocal projections of WT or MZrab25a Tg(Myl1.1-Gfp) at 60% epiboly; lateral positioned embryo focused on EVL margin; red line marks the ablated junction. Scale bar 5 μm. (E–G’) Initial recoil velocity, relaxation time and distance retracted in WT and MZrab25a embryos following junction laser cutting (see Materials and methods). WT and MZrab25a perpendicular and parallel cuts (n = 26,23);(n = 21,25).
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