The human KCNQ1 isoform 2 is under the control of the mouse alpha-myosin heavy chain promoter (including introns, and three noncoding exons). The stop codon was removed and an 11-amino acid T7 epitope tag was added in frame at the carboxyl terminus of KCNQ1. Isoform 2 does not form functional channels but exerts dominant-negative effects on isoform 1 channels. Western blot analysis confirmed expression. This is the high expressing line.