KCNJ8 and Cowden syndrome 1: Gain-of-function (GOF) missense mutations in genes encoding the pore-forming (Kir6.1, KCNJ8) and regulatory (SUR2, ABCC9) subunits of the predominantly cardiovascular isoforms of an ATP-sensitive potassium channel (KATP) have been identified in CS patients (Harakalova et al., 2012; van Bon et al., 2012; Brownstein et al., 2013; Cooper et al., 2014).