Rok-RNAi LEC labelled with Sqh::GFP showing impaired contractile behaviour during constriction. Confocal micrographs. Cell merely shows diffuse Sqh::GFP activity compared to controls (Movie 4). Apicomedial cytoskeletal activity resembles that of early boundary LECs (Movie 5). Scale bar, 10 μm; a, anterior; p, posterior; m, medial (corresponds to dorsal); l, lateral (corresponds to ventral).