The tetO-EDN1 transgene was designed with a bidirectional tetracycline operator (tetO; also called tetracycline-responsive element (TRE, TetRE) or tet-operator), pBi-1, between two cytomegalovirus (CMV) minimal promoters in the opposite orientation. One CMV promoter drives expression of the human endothelin (EDN1 or ET-1) gene, followed by a simian virus 40 (SV40) polyadenylation (polyA) signal, while the other drives expression of a beta-galactosidase (lacZ) reporter followed by a beta-globin polyA signal. Three lines were generated (9, 101, and 403). Line 9 exhibits high levels of expression in the myocardium.