Fig. 8. Myocardial differentiation is disrupted in Foxp1^–/– hearts. In-situ hybridization was performed using probes specific for Irx3 (A,B), Anf (C,D) and N-myc (E-H) on wild-type (A,C,E,G) and Foxp1^–/– (B,D,F,H) hearts at E11.5 (E,F) and E14.5 (A-D,G,H). Irx3 expression is expanded to encompass almost all compact and trabecular myocardium (B). N-myc expression was significantly reduced in the ventricular wall of Foxp1^–/– embryos (compare E,F,G,H). H+E staining of wild-type and Foxp1^–/– hearts at E11.5 shows a thin compact zone in the myocardial wall of the ventricle wall of Foxp1^–/– hearts (I,J, brackets). Transmission electron microscopy was performed on E11.5 wild-type (K) and Foxp1^–/– (L) hearts. Wild-type compact zone myocardium shows a laminated appearance, while Foxp1^–/– heart compact zone myocardium has a disorganized appearance (compare bracketed regions). Scale bars: 250 µm in A,B; 400 µm in C-F; 800 µm in G,H; 100 µm in I,J.