Fig. 10

Concomitant partial loss of Ecad in the EVL of MZepcam mutants leads to severely compromised epiboly movements of deep cells.

(A–D, E,G) wild-type (A,C,E) or MZepam mutant (B,D,G) embryos injected with low amounts of ecad MO; (F) wild-type embryo injected with high amounts of ecad MO. (A,B) Phalloidin stainings of the actin cytoskeleton at 80% epiboly stage (for explanation of labeling, see Figure 5). The ecad hypo-morphant appears normal (A; compare with Figure 5C as un-injected control), whereas partial loss of Ecad activity in the epcam mutants leads to an arrest of deep cell epiboly (B; note the reduced A-dc distance compared to panel A and to Figure 5D). In contrast, EVL epiboly is not more affected than in the un-injected mutant (B; note the normal A-evl distance compared to Figure 5D). (C,D) Genetic mosaics at 80% epiboly stage, after co-transplantation of deep cells from wild-type embryos (anti-RFP immunostaining; in red) and from MZepcam mutants injected with low amounts of ecad MO (anti-GFP immunostaining; in red), shortly before the onset of epiboly (4 hpf). Epiboly behavior of the transplanted deep cells does not depend on their own genotype, but on that of the host embryo/the overlying EVL. (E–G) Stills of time-lapse video recordings of the external layer of deep cells, starting at early gastrula stages (5.5 hpf). For evaluation, only cells were considered that moved up from internal into the external layer of the deep cells during the first half (0–10 min) of the recordings. Individual cells are pseudo-colored in light red when in the external layer, but un-colored when in lower layers. Note that the cell in (E) remains in the external layer throughout the second half of the video (10–20 min), whereas cells in (F,G) move up and down. White spots label representative neighboring cells of the external deep cell layer, demonstrating their increasing distance in (E), but constant distances in (F,G).