The VE-cadherin-tTA (TET-Off) driver mice where generously provided by Dr. Laura Benjamin (Sun et al. 2005 (link)). The TetO-Ang2 responder has been previously described in detail (Holopainen et al. 2012b (link)) and was backcrossed to C57Bl/6J for at least seven generations in this study. The driver and responder transgenic mouse lines were crossed to obtain DTG VE-cadherin;TetO-Ang2 offspring. Ang2 expression in DTG embryos was repressed by 2 mg/mL tetracycline (Sigma-Aldrich) in 5% sucrose in the drinking water for the pregnant females, starting within 2 d post-coitum, until Ang2 expression was induced by discontinuing tetracycline administration. The tetracycline-containing water was changed every 2–3 d. Single transgenic or wild-type littermates were used as controls for DTG mice or embryos. Ang2−/− mice were bred as previously reported (Gale et al. 2002 (link); Fiedler et al. 2006 (link)). Eight-week-old male mice or P5 pups were analyzed for their LEC junctions. The Pdgfb-Cre-EGFP mice have been previously described (Claxton et al. 2008 (link)). PDGFB was visualized by staining for EGFP. The embryonic time points were determined according to vaginal plugs. The Committee for Animal Experiments of the District of Southern Finland approved all animal experiments.