ABCC9 and Cowden syndrome 1: Although SUR2[A478V] has only been identified in one isolated CS individual, SUR2[R1154Q] is the most common CS-associated KATP mutation, occurring in ∼30% of CS patients.6 As recently discussed,34 the SUR2[R1154Q] mutation leads to an unexpected alternate splicing in the expressed mouse transcripts that results in marked loss of expressed protein in cardiovascular tissues, counteracting the otherwise marked molecular GoF of R1154Q mutant channels.