Figure 2. Developmental defects in hearts of Crim1^{Δflox/Δflox} embryos.

(A,B,D,E) Representative whole-mount views of 14.5 dpc embryonic hearts (A,B, Crim1^+/+; D,E Crim1^{Δflox/Δflox}). (B,E) Magnified, left lateral views of (A,D) respectively. (C,F) Representative whole-mount views of 17 dpc embryonic hearts (C, Crim1^+/+; (F) Crim1^{Δflox/Δflox}). Note the reduced size of the ventricles in the Crim1^{Δflox/Δflox} heart (D–F). Epicardial defects in Crim1^{Δflox/Δflox} hearts. (G–I) Hematoxylin and eosin-stained sections of the ventricular region of 13.5 dpc (G) Crim1^+/+ and (H,I) two different Crim1^{Δflox/Δflox} hearts. Note the irregular appearance of the epicardium in Crim1^{Δflox/Δflox} embryos, with one example showing blebbing (H). (J–M) Scanning electron micrographs of the ventricular surface of 13.5 dpc Crim1^+/+ (J,L) and Crim1^{Δflox/Δflox} (K,M) hearts. (K) Note the loss of the even spacing of cells of the mesothelial epicardium, and (M) diffusely arranged microvilli. (N) Quantification of penetrance of epicardial defects, specifically either epicardial blebbing or a loss of squamous morphology, between Crim1^+/+ and Crim1^{Δflox/Δflox} hearts at 13.5 dpc. Z-score -3.8801. *P < 0.0001. cm, compact myocardium; ep, epicardium. Scale bars; A–F, 500 μm; G-I, 50 μm; J-K, 20 μm; L-M, 2 μm.