The promoter region of endoglin and conserved Ets binding sites are required for the in vivo endothelial activity of the –8 enhancer. E11.5 F₀ embryos were generated using either (A) E1/E3/LacZ (wild-type –8 enhancer with the endoglin promoter), (B) E1/SV/LacZ (wild-type –8 enhancer with the SV minimal promoter), or (C) N1/E3/LacZ (mutant –8 enhancer with the endoglin promoter). Representative F₀ embryos are shown for each construct.