KCNQ1 and familial long QT syndrome: In contrast, KCNQ1 D242N, R243C and R243H variants, located in the C-terminal half of S4, strongly shifted the VDA to depolarizing potentials or produced low IKs and are thus associated with LQTS (Franqueza et al., 1999; Chouabe et al., 2000; Park et al., 2005; Moreno et al., 2017).