Fig. 2.

Expression of the key SAN transcription factors during inflow tract development and the regulatory network controlling SAN morphogenesis. a Dynamic expression of key transcription factors (Tbx5, Nkx2-5, Isl1, Pitx2, Tbx18, Tbx3, Shox2) during development in the posterior second heart field (SHF), sinus venosus (SV), sinus horn (SH) and sinoatrial node (SAN), and surrounding atrial working myocardium. b A cross-repressive regulatory network that controls pacemaker cell (PC) and atrial working cardiomyocyte (WCM) development