Fig. 5.

Conditional deletion of CCM2 from endothelial cells results in major vascular defects in ECKO embryos. (A-H) Whole-mount PECAM staining of control (left panels) and ECKO embryos (right panels) at E9.5 (A,B) and E10.5 (C-H). (I-L) E10.5 PECAM-stained embryo sections after counterstaining with eosin. The presence of PECAM-positive DA, somitic vessels and branchial arch arteries (numbered in red) at E9.5 demonstrates the occurrence of vasculogenesis (A,B). However, at E10.5 (C-H), the arterial and venous blood vessels are abnormal in ECKO embryos and the internal carotid artery is difficult to distinguish [red arrow (D)]. Further, DA are highly irregular in appearance and common cardinal veins are enlarged (F,J). In some animals, the caudal part of the DA fails to fuse (red arrows (H,L)]. (M-P) Double staining for PECAM [red (M,N)] and SMA [green (O,P)] on E10.5 DA sections from the trunk. Note the impaired recruitment of vascular smooth muscle cells/pericytes in the DA of ECKO embryos (P). CCV, common cardinal vein; DA, dorsal aorta; ICA, internal carotid artery; LB, limb bud; NT, neural tube; S, somite; Bars, 500 μm (A,B); 50 μm (M-P).