Absence of venous valves in mice lacking Connexin37

► In valved veins, Cx37, Cx43, and Cx47 are expressed exclusively at valves. ► Cx expression is highly polarized between the two sides of the venous valve. ► Cx47 is highly restricted to a small subset of cells in the venous valve. ► Cx37 is required for venous valves: Cx37 deficient mice lack valves. ► Wounding of the overlying skin induces Cx43 in the non-valve venous endothelium.