Fig. 3. Vessel remodeling and maturation defect in Alk3 CKO embryos. Yolk sacs (A,B) and embryo proper (C,D) were subjected to whole-mount staining with anti-PECAM1 (CD31) antibodies and were visualized by alkaline phosphatase. The Alk3 CKO embryos display the primary vascular plexus in yolk sacs (B) and abnormal vascular patterning in the brain (D), but the controls showed normal vasculature pattern (A,C). Scale bars: 1 mm. (E) RNAs from E8.5-E10.5 yolk sacs were subjected to qRT-PCR for Id genes (Id1-Id4). The relative expression level of Id1, Id2, Id3 and Id4 in wild-type yolk sacs is shown. (F) Expression of all Id genes, Plau1 and Serpine1 was examined and compared in the Alk3 CKO and the controls. RNAs from two wild-type (wt) and two Alk3 CKO embryos were used for qRT-PCR, respectively. ^*P<0.05.