Effects of Dll4 knockdown on endothelial cell behaviour. (A) Schematic depiction of ISV and DLAV formation and the concomitant changes in endothelial cell morphology. (B,C) Leading cell of an ISV sprout at 30 hpf in a living uninjected embryo (B) or in a living embryo injected with 10 ng MO[Dll4] (C). (D,E) DLAV and dorsal ISVs at 2.5 dpf in a living uninjected embryo (D) or in a living embryo injected with 10 ng MO[Dll4] (E). (F-I) Similar region at 2.5 dpf of living embryos treated with 100 μm DAPT (G,I) or control embryos treated with DMSO (F,H). Treatment with DMSO or DAPT began at either 33 hpf (F,G) or at 48 hpf (H,I) and continued through the course of the experiment. Higher magnifications of D-I are shown in D'-I'. (J) DLAV and ISVs of a 3-dpf embryo injected with 7 ng of a morpholino targeted against Notch1b. (K,L) ISV sprouts at 30 hpf of a normal sibling (K) and a hsp70:Gal4;UAS:NICD embryo (L). Embryos in K and L were given a heat shock at 24 hpf. S, somite. Scale bar: 50 μm in B-I; 17 μm in D'-I'; 40 μm in J; 70 μm in K,L.