Fig. 6.

Redeployment of Myosin II to anterior and posterior cell edges during denticle field patterning. Snapshots from live imaging of ventral epidermis in embryos expressing Sqh-GFP. (A) Stage 8 embryo, during convergence extension movements. Note the polarized accumulation of Sqh-GFP to A–P cell edges (arrow) as there is reduced accumulation on D–V cell edges (such that these are less visible in the micrograph, arrowhead) (Bertet et al., 2004; Zallen and Wieschaus, 2004). Asterisks in panels A and B highlight signal that is an aggregation artifact of the Sqh-GFP fusion protein, we do not see these aggregates when using an antibody to Zipper. (B) Stage 11 embryo, prior to denticle field patterning. Note that Sqh-GFP distributes roughly homogenously around most apical cell contours. (C–E) Embryos during denticle field patterning. (C) Stage 13, note the general enrichment along A/P cell edges (arrows) at the expense of D–Vedges. Some D–Vedges (arrowheads) do show Sqh-GFP to levels equivalent to that at A–P edges. There is also some accumulation on the cell face, likely matching the accumulation of actin in a meshwork at the apical cortex (see Fig. 3B). (D) Early stage 14. Accumulation of Sqh-GFP along A–P edges is still quite apparent (arrows), as well as on nascent actin protrusion (arrowhead). (E) Late stage 14 embryo. Sqh-GFP continues to appear enriched along A–P cell edges and definitively along protrusions. There is also an encirclement of the protrusion at its base. A = anterior, P = posterior, D = dorsal, V = ventral; scale bar = 25 μm.