Ephrin-B2 expression in the embryonic vascular system.

(A-B) Ephrin-B2 expression was detected by whole-mount X-gal staining of ephrin-B2^LacZ/+ mouse embryos32 at E11.5. (C-D) The vascular network of E11.5 mouse embryos is visualized by Tie-2 expression. To detect Tie-2 expression, whole-mount X-gal staining of Tie-2 promoter(p)-LacZ mouse embryos generated from crossing CAG-CAT-Z indicator TG mice42 and Tie-2p Cre mice was performed.33 Panels B and D show higher magnification views of the black square in the head region of panels A and C, respectively. Arrows in panels B and D indicate internal carotid artery (ICA), and open arrowheads in panel D indicate anterior cardinal vein (ACV). Panels E and F show X-gal staining of cross sections of embryos representing the blue square in panel A. Stars show ephrin-B2 expression in the caudal region of somites. A higher magnification of the intersomitic region is shown in panel F. Arrows indicate that there is no ephrin-B2 staining in vessels between ephrin-B2⁺arteries (arrowheads) and ephrin-B2⁺ somites (stars). (G-I) Serial cross sections of the E11.5 mouse vascular system in trunk region of ephrin-B2^LacZ/+ mouse. X-gal staining shows that ephrin-B2⁺ vessel (arrowheads) is sprouted from dorsal artery (DA), while ephrin-B2⁻ vessel (arrows) is sprouted from cardinal vein (CV). Sections were counterstained with nuclear fast red. Bars indicate 100 μm in panels E and G-I; 50 μm in panel F.