Wall thinning and less differentiated myocardial vasculature in E15.5 left ventricles of CHF1/Hey2 knockout mice. PECAM immunostaining (a-d) and isolectin B4 labeling(e, f) were performed to detect endothelial cells of the myocardial vasculature. The control hearts (a, c; n = 5) generally form fine vessels (c, inset, e, arrows) and some larger vessels with stable lumens (c, inset, e, arrowheads) that give rise to the coronary vasculature. In contrast, mutant hearts (b, d; n = 7) are improperly remodeled and only form collapsed fine vessels (d, inset, f, arrows) and dysmorphic larger vessels (d, inset, f, arrowheads, inset) when compared to those in wild-type. Cos; primordium of costal cartilage, IVS; interventricular septum, MV; mitral valve, Peri; parietal pericardial wall. Scale bars = 1 mm in a, b; 200 μm in c-f.