Maternal vgll4a is required for proper organization of the actomyosin ring. (A-D′) Confocal images of wt and MZvgll4a embryos at 75% epiboly stage (lateral views) stained with phalloidin and Hoechst to visualize F-actin and nuclei, respectively. Note that the actomyosin ring in MZvgll4a embryos is thinner (white brackets in A′, B′) and rather separated from the DEL margin (yellow arrows in A, B) as compared to wt embryos. Note also that F-actin distribution of EVL cells in MZvgll4a embryos is ruffled and disorganized (yellow arrowheads in D′) in contrast to the well aligned distribution in wt embryos. Asterisk in D, D′ indicates loss of cell-cell contacts. (E,F) Quantification of the actomyosin ring width and DEL-EVL distance in wt (n = 24) and MZvgll4a (n = 34) embryos. Mann-Whitney test, p < 0.0001). (G) The graphs show the expression level of arhgap18 transcripts in MZvgll4a and wt embryos at 75% epiboly stage. t-test, p = 0.041, as determined by qRT-PCR analysis. *, p < 0.05. ****, p < 0.0001. Scale Bars, a-b´ 50µm, c-d´, 20 µm.
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