Fig. 6.

Stalling cell movements in the epidermis removes the requirement for Crb to maintain cell polarity. (A-C) As the stomodeum invaginates Baz localisation is progressively lost in the neighbouring epidermal cells (arrows). (D-K) Stage 11 wild-type (D), Kr (E), crb (F,H,J) and Kr;crb (G,I,K) mutant embryos stained for Baz (green) and Neurotactin (Nrt, red; D-G), Sas (green) and Dlg (red; H,I), and E-cad (J,K). Boxed areas in D-G are enlarged in D′-G′ and D″-G″. (D) Baz localises to the apical surfaces of epidermal cells and Nrt to the lateral membranes. (E) The germ band does not extend fully in Kr mutant embryos and cell polarity is unaffected. (F,H,J) In crb mutant embryos, epidermal polarity is lost by stage 11; apical proteins such as Baz (F, green) and Sas (H, green) are delocalised throughout the cell, basolateral proteins such as Nrt (F, red) and Dlg (H, red) spread around the cell membrane, and junctional proteins such as Ecad are fragmented (J). (G,I,K) In Kr;crb double mutants there is a marked rescue of epidermal cell polarity. Baz and Sas localise to the apical membrane (G,I), and Nrt and Dlg are restricted basolaterally (G,I). ZAs are largely rescued, as seen by circumferential labelling of Ecad (compare K with crb mutant J). (L) In crb mutants, most of the cuticle is absent with only fragments of cuticle remaining. (M) Embryos mutant for Kr and crb show a marked rescue of the crb phenotype, as a continuous cuticle is formed. (H, I) Images taken of the epidermis, just posterior to the tip of the germband. (J,K) Enface views of the dorsal epidermis.