Fig. 6. Wnt7b^lacZ–/– embryos and neonates exhibit pulmonary hemorrhage due to defects in the vasculature. Analysis of Wnt7b^lacZ–/– embryos at E18.5 shows dilatation of large blood vessels compared with wild-type littermates (A,B, arrowheads; C,D). The blood vessel wall is also thicker in Wnt7b^lacZ–/– embryos (D, double-headed arrow). Injection of latex resin to form a cast of the embryonic vasculature reveals that the branched vessels in Wnt7b^lacZ–/– embryos are larger in diameter and the degree of reiterated branching is reduced (E,F, arrows). However, the main trunk vessel diameter is unchanged in Wnt7b^lacZ–/– embryos (E,F, arrowheads). At birth, Wnt7b^lacZ–/– neonates exhibit extensive hemorrhage in the lungs, primarily surrounding the larger blood vessels (G,H). Scale bars: 500 µm in A,B; 75 µm in C,D; 250 µm in G,H.