KCNH2 and Familial short QT syndrome: Replacing hERG S631 with alanine (in hERG S631A) to match the equivalent EAG sequence was shown many years ago to result in loss of inactivation (Schonherr and Heinemann, 1996); this mutation has recently been found as a rare natural hERG variant with a clinical manifestation of SQTS (Akdis et al., 2018).