Fig. 1.
Outlines of experimental procedure.
(A) Partial structure of the murine Flk-1 locus and a reporter gene construct. The GFP gene is flanked by aFlk-1 promoter fragment (prom) spanning bp −640 to bp +299 and an enhancer sequence between bp +1677 and bp +3947 in the first intron. (B) For induction of differentiation in vitro, undifferentiated ES cells were transferred to a type IV collagen–coated plate and incubated for 4 days in the absence of LIF. Cultured cells were harvested and analyzed for expression of GFP and Flk-1 by flow cytometry. The Flk-1+ cells were sorted for secondary culture on OP9 stromal cells. These cells were recovered after 1 to 5 days and analyzed for expression of GFP, VE-cadherin, CD45, and TER119 or for hemangiogenic ability.