Jarid2 is deleted in the endocardium of Jarid2en mice. A and B, E12.5 Jarid2F/F mouse heart displays Jarid2 expression in the myocardium and endocardium (arrows) as indicated by red fluorescent staining. C, Hoechst staining to indicate nuclei. B and C, the arrows indicate the nuclei of endocardial cells positive for Jarid2 staining. D and E, Jarid2en mice display a lack of red fluorescent staining in the endocardium, indicating a lack of Jarid2 expression. F, Hoechst staining to indicate nuclei. E and F, the arrows indicate the nuclei of endocardial cells negative for Jarid2 staining. The scale bar in A represents 100 μm.