Fig. 6

careg is expressed in embryonic CMs and the outer wall of developing ventricle.

(a–l) Longitudinal sections of careg:EGFP;cmlc2:DsRed2-Nuc double transgenic hearts at different time points during development. Cardiac nuclei are marked by DsRed expression. The endogenous fluorescence was quenched with HCl treatment before immunostaining. GFP and DsRed were detected by antibody staining. (a–f) At 1 and 3 d.p.f. (days post-fertilization), careg:EGFP and endogenous embCMHC are co-expressed in embryonic CMs. (g–i) At 12 d.p.f., a few careg:EGFP⁺ CMs delaminate from the outer heart surface and invade into the ventricle (V) chamber, as seen by the residual EGFP. (j–l) At 30 d.p.f., careg:EGFP is restricted to the outer layer of the ventricular wall, and is downregulated in the trabecular myocardium. careg:EGFP is also expressed in non-myocytes of the bulbus arteriosus (BA) and a few cells of the atrium (A). (m–o) Longitudinal sections of careg:dmKO2;cmlc2:EGFP transgenic heart at 30 d.p.f. immunostained for GFP (green) and dmKO2 (red). The careg:dmKO2 transgenic line has a cardiac developmental expression pattern similar to that of careg:EGFP (Supplementary Fig. 10). N≥5.