Fig. 4

erg acts synergistically with etsrp to regulate vascular development. (A) Panels show GFP-marked vasculature in wild-type and ergMO, etsrpMO and double morphants on the Tg(fli1:EGFP) line at 48 hpf. erg knock-down with an antisense morpholino oligonucleotide had no effect on vascular development unless introduced on a sensitised etsrp morphant background. Note the slight disruption of intersegmental vessel sprouting from the dorsal aorta to form the dorsal longitudinal anastomotic vessels in etsrpMO morphants, and the much more severe disruption in ergMO and etsrpMO double morphants (full arrowheads). (B) Vascular development was quantified by counting intersegmental vessels that fully connected the dorsal aorta to dorsal longitudinal anastomotic vessels in embryos at 48 hpf. Collated data show significant reduction of intersegmental sprouting in ergMO + etsrpMO versus ergMO morphants. Collectively the morphological and quantitative data indicate a synergistic but redundant role for erg in vascular development. Error bars are standard errors (uninjected, morphant groups; n = 3 experiments) and standard deviation (control MO, n = 23 embryos from one experiment). Numbers within bars indicate collated number of embryos scored for each group.