Quantitative RT-PCR analysis of endothelial markers and novel genes in WT, Flk1 KO embryos, and ECs. Quantitative RT-PCR analysis showed that Arhegf15, RhoJ, Lrrc33, Gpr116, Gcom1, CSgalnact1, She, Exoc3l, Arap3, Gpr182, Mirp2, Cd109, Fam70a, Plvap, Tmem204, and Rapgef3 were down-regulated in Flk1 KO embryos proper and were highly expressed in developing ECs (Flk1 GFP high cells), but not in hematopoietic cells. VE-cadherin and Pecam1 are endothelial markers. BC indicates blood cells.