Fig. 4. Fine localization of the Gata2 endothelium-specific enhancer. (A) Schematic illustrations of transgenic constructs (TKSXß, TKSRß, TKAAß, TKSXAAß and TKANß) used to functionally localize the Gata2 endothelium-specific enhancer element. Sub-fragments of Gata2 intron 4 were individually cis-linked to a TK promoter-lacZ reporter gene. The positions of relevant restriction enzyme sites (AlwNI, A; ApaI, Ap; NcoI, N; RsrII, R, SfiI, S; XbaI, X) and the restriction fragment lengths (in bp) are indicated. The numbers on the right indicate the number of embryos with cardiovascular ß-gal staining/total number of transgene-positive embryos. The arrows represent the positions of the primer pairs used to amplify the 167 bp VE enhancer (see Fig. 5). (B-E) E10.5 embryos bearing TKSRß (B) or TKAAß (C) transgenes showed widespread endothelial ß-gal staining, whereas the TKSXAAß (D) and TKANß (E) transgenic embryos were devoid of endothelial X-gal accumulation. In the latter embryos, only ectopic ß-gal activity was observed.