Fig. 2. Notch4 gain-of-function mutation causes enlargement of DA prior to SMC recruitment and leads to vascular shunting. (A,B) Whole-mount lacZ staining for the arterial marker ephrin B2-tauLacZ in E9.5 embryos reveals an enlarged DA (bracket) in the mutant (B). (C,D) Whole-mount lacZ staining for the venous marker EphB4-tauLacZ in E9.5 embryos shows reduced staining in the CV (black arrowheads) in the mutant (D). Common CV (CCV), blue arrowheads. In A-D, anterior is upwards, dorsal is rightwards. (E,F) Vasculature of E9.5 (24 ss) embryos as revealed by ink injection. In the control (E), ink filled the DA (black arrows) evenly from the heart to the tip of the tail. In the mutant (F), ink leaked into head vessels (blue arrow) and the venous compartment (arrowheads), and failed to reach the tip of the tail (red arrow). (G,H) CD31 (green) and SMA (red) staining of E9.0 (18 ss) embryos. DA enlargement in the mutant (H) occurs before recruitment of SMCs to the vessel walls. Scale bars: 200 µm in B,D,H; 800 µm in F. ^**, heart in A,B,E-H.