Fig. 5.

Schematic representation of the epistatic relationship between Shox2 and Isl1. Schematic illustration of the mammalian conduction system highlighting a novel transcriptional regulation in the sinoatrial node. Previously we could show that Tbx5 regulates Shox2 in the SAN of the developing heart (12). In the present study, we demonstrate a novel epistatic relationship and a direct functional link between Shox2 and Isl1 in this compartment of the heart with important function in the pacemaking system. AVN atrioventricular node, HB bundle of His, ICV inferior caval vein, LA left atrium, LBB left bundle branch, LV left ventricle, PF Purkinje fibers, RA right atrium, RBB right bundle branch, RV right ventricle, SAN sinoatrial node, SCV superior caval vein