Fig. 3.

Endocardial loss of Smad4 causes acellular endocardial cushions. Parasagital heart sections showing the atrioventricular canal (A–D) and outflow tract (E–H) endocardial cushions from wild-type (A, C, E, and G) and Tie2:Cre⁺; Smad4^fl/− (B, D, F, and H) embryos at E10.5. Tie2:Cre⁺; Smad4^fl/− atrioventricular and outflow endocardial cushions are acellular (black arrowheads in D and H) compared with wild type (black arrowheads in C and G). In situ hybridization of sections from wild-type (A, C, E, G, I, and K) and Tie2:Cre⁺; Smad4^fl/− (B, D, F, H, J, and L) embryos at E10.5. The patterns of expression for Gata4 (I and J), Notch1 (K and L), and Tbx2 (M and N) were comparable in wild-type and Tie2:Cre⁺; Smad4^fl/− mutant embryos. (Magnification in A, B, E, F, I, J, K, L, M, and N: 40×; C, D, G, and H: 100×.)