Figure 1.

Effect of Tc-regulated Prox1 expression on the morphology and sheet formation of ESC-derived ECs and HUVECs. (A) Flk1+ endothelial progenitor cells were sorted from the differentiated ESCs carrying a Tc-regulated transgene encoding FLAG-epitope-tagged mouse Prox1 (Tc-Prox1) or control transgene (Tc-Empty) and redifferentiated in the presence (+) or absence (−) of Tc to obtain PECAM-1–positive ECs (bottom, red) and smooth muscle α-actin (SMA)-positive mural cells (bottom, green). Expression of FLAG-Prox1 (top, blue) and the morpholoby and sheet formation of ECs (bottom, red) were examined. Scale bars, 100 μm. (B) Quantitation of colony formation, EC and mural cell production, and endothelial sheet formation. Flk1+ cells derived from Tc-Prox1 ESCs were cultured sparsely with 10% fetal calf serum in the absence or presence of Tc for 4 d and stained for PECAM1 (red) and SMA (green). Numbers of different types of colonies per well were counted to determine the effects of Prox1 on colony formation of Flk1+ cells. Four colony types were observed: pure ECs forming sheet structures (EC-sheet, red); pure scattered ECs (EC-scattered, pink); pure mural cells (MC, green); and mixed colonies consisting of endothelial and mural cells (Mix, yellow). Experiments were repeated at least three times with essentially the same results. Bars, 50 μm. (C) Morphology of HUVECs infected with adenoviruses encoding LacZ, DNA-binding mutant (Mut), or wild-type (WT) Prox1. Bars, 100 μm.