Fig. S2

No appreciable change in arterial flt4 expression in dll4 morphants between 25 and 31 hpf. (A-H) Expression of flt4 in trunk arteries and veins in stage-matched wild-type uninjected control and dll4 MO-injected (6 ng/embryo) embryos. No difference was observed at 25 hpf (A,B) between control (n=15) and morphant (n=28) embryos. At 27 hpf (C,D), no difference was seen between carefully stage-matched control (n=18) and morphant (n=29) embryos. Some morphants that were clearly developmentally delayed (n=11) showed higher levels of flt4 expression than controls, consistent with the dynamic downregulation of ISA flt4 expression between 25 and 29 hpf, and demonstrating the need to stage match rather than age match embryos during this analysis. At 29 hpf (E,F; n=16 control and n=34 morphant embryos) and at 31 hpf (G,H; n=16 control and n=33 morphant embryos), no difference was observed in the ISA expression of flt4 between control and morphant embryos. Embryos from the same MO-injection sessions were grown to 3 dpf and the robust dll4 MO-induced hyperbranching phenotype observed, demonstrating that the embryos analysed were morphants.