Fig. 2. Phenotype of embryos with endothelial-restricted inactivation of Gata4 (Gata4^T2del). (A) Gata4^T2del embryos die by E12.5-E13.5. The incidence of Gata4^T2del embryos is plotted against gestational age; expected incidence was 25%. Numbers indicate total number of embryos genotyped. (B) Gross appearance of E12.5 control and Gata4^T2del littermates. Mutants showed liver hypoplasia (L) and variable growth retardation, peripheral hemorrhage and pericardial effusion (arrowhead). (C) E12.5 Gata4^T2del embryo with severe pericardial effusion (arrowhead). Scale bars: 50 µm. (D-G) Formation of AV cushion mesenchyme requires Gata4 activity in endothelial-derived cells. By E10.5, the AV cushions of control embryos were populated by numerous mesenchymal cells (asterisk, D), whereas in Gata4^T2del embryos the AV cushions were severely hypocellular (asterisk, F). The endocardium overlying the AV cushions became several cell layers thick in mutant embryos (arrow, G), whereas it was one cell layer thick in control embryos (E).