KCNE1 and atrial fibrillation: Thus, it is no surprise that mutations in KCNE1, KCNE2, KCNE3, KCNE4 and KCNE5, encoding regulatory β-subunits of Kv7.1, have been identified in AF and been demonstrated to exert gain-of-function effects on IKs and to have potential effect on Ito and IKr [55,57,58,59,60,61,62,63].