“…The FHF, positive for Tbx5 and Hcn4 , gives rise to the left ventricle and parts of the atria (Bruneau et al., ; Liang et al., ; Später et al., ). While the SHF, positive for Islet1 , Tbx1 , Tbx20 , Sall1, Mef2c‐AHF enhancer and secreted molecules encoded by Fgf8 and Fgf10 , gives rise to the right ventricle, the OFT and parts of the atria (Cai et al., ; Kelly, Brown, & Buckingham, ; Morita et al., ; Takeuchi et al., ; Verzi, McCulley, De Val, Dodou, & Black, ; Yamagishi et al., ). The facts mentioned above show that the ventricular septum is formed at the boundary of the FHF and SHF in mammals.…”