Analysis of developmental angiogenesis at E9.5. (A-D) Micrographs of CD31-stained whole-mounted A10ΔEC (A,C) and control (B,D) embryos at E9.5 (superficial cranial vessels are marked by arrows, and intersomitic vessels by arrowheads). (E,F) Representative micrographs of CD31-stained sections of the vasculature of the fourth ventricular floor in A10ΔEC (E) and control (F) embryos at E9.5 showed a similar distribution of small caliber vessels (arrowheads). (G) Whole-mounted LacZ staining of a Tie2-Cre/R26R control E8.5 embryo showed patchy β-galactosidase staining within cranial vessels (arrow). Scale bars in panels A-B,G: 600 μm; C-D: 400 μm; E-F: 30 μm.