Figure 2.

Endothelial Sox17 (SRY [sex-determining region Y]-box 17) is required for correct brain vascular morphogenesis and barrier function. A, Scheme of tamoxifen administration at E11.5, E13.5 (black arrows), and embryo analysis at E15.5 (red arrow). See Methods section for details. B, Summary assessment of Sox17^iECKO embryos presenting brain hemorrhages (brown columns) after tamoxifen treatment (as indicated in A). Data are presented as percentage of total number of embryos analyzed (n). E15.5 harvesting time was selected for subsequent experiments. At E17.5 (yellow column) none of the Sox17^iECKO embryos was alive. C, Sox17^iECKO embryos display brain hemorrhages. D and E, Sectioning of different regions of the embryonic brain showed enlarged vessels (arrows) stained with collagen IV (light blue) and extensive hemorrhages. Ter119 (orange) indicates red blood cell (arrowheads). Scale bar: 200 μm in C, 100 μm in D. F, Average count of hemorrhagic spots per section (n=3 wild-type [wt] and 5 Sox17^iECKO, mean±SEM, *P<0.05, Mann-Whitney test). G, Confocal microscopy analysis of embryonic brain cryosections. Collagen IV (magenta) and IgG (green) of wt and Sox17^iECKO revealed the presence of IgG leakage in Sox17^iECKO embryos. Scale bar: 500 μm. H, Quantification of IgG leakage (left; n=3 wt and 5 Sox17^iECKO, mean±SD, P=0.08, 2-tailed t test).