Fig. 5

EpCAM is required for EVL and deep cell layer epiboly.

(A,B) Live animals at the 90% epiboly stage, dorsal to the right; (C–F,I,J) phalloidin stainings of the actin cytoskeleton at 80% epiboly. (A,B) One of the morphogenetic processes during epiboly is the constriction of marginal EVL cells [10]. In mutants, this constriction does occur, however, at aberrant, slightly more animal positions, leading to a protrusion of the yolk plaque (B). (C,D) Overview over entire embryos; red bars indicate the animal (A) - vegetal (V) axis, and the margins of the deep cell layers (dc) and the enveloping layer (evl). The mutant (D) displays slightly retarded epiboly of the EVL and the deep cells (see larger distances between the evl margin and the vegetal pole (evl-V) and between the dc margin and the vegetal pole (d-V) compared to wild-type control in C). (G) Graphic demonstration of average progression of evl and dc epiboly in MZ-/- mutants and wild-type controls (WT). Percentage values were calculated from images like in (C,D) as (distance A-evl)/(distance A-V) or (distance A-dc)/distance (A-V). Standard deviations are indicated. For exact numbers see Text S1. (E,F) Magnified views on the evl and dc margins; dc margins are indicated by dashed red lines. (H) Graphic demonstration of average evl-dc distances in MZ-/- mutants and WT controls, as shown in (E,F). n = 5; standard errors are indicated. (I,J) Magnified views on EVL in regions slightly animal of the deep cell border (merged Z-stacks of confocal images), revealing ruffle-like protrusions in the wild type (I) that are missing in the mutant (J). The presence of intracellular, vesicular-like phalloidin staining varied from embryo to embryo, and even from cell to cell, but seemed unrelated to the epcam genotype. (K) Graphic demonstration of average horizontal sizes of EVL cells of WT and MZ-/- embryos at 80% epiboly, as shown in (E,F). n = 30; standard errors are indicated.