Nov expression and histology of embryonic and adult hearts. A, B: RNA in situ hybridization showing Nov expression in the endothelial and smooth muscle cells of the aortic outflow tract, pulmonary trunk and in a subset of cells near the origins of the great vessels at E16.5. C-F: Haematoxylin and Eosin stained sections of wild type (C,D) and Novdel3-/- (E,F) E13.5 embryonic hearts showing abnormal expansion of the endocardial cushions (EC) and delay in fusion of the septum (S) in the mutant mouse (arrow). G-M: Haematoxylin and Eosin stained sections of wild type (G, J) and Novdel3-/- (H, I, K) adult hearts, showing accumulation of blood in the sub-endothelial space between the right ventricle and septum (H) and hypertrophy of the septum near the origins of the great vessels, (H, I, K). Areas of calcification on the septal wall of the right ventricle (K, L), stain with Von Kossa (M). There is no associated fibrosis. Scale bars in A,D,F = 20 μm; B,L = 10 μm; C,E = 50 μm; G,H,I = 1 mm; J,K = 50 μm; M = 5 μm.