The alpha-myosin heavy chain promoter drives cardiac-specific expression of a dominant negative rat Kcnj8 mutant, in which the subunit pore region was mutated from glycine-phenylalanine-glycine to three alanines, with a COOH-terminal enhanced green fluorescent protein. RT-PCR and Western blotting confirmed expression of the transgene specifically in the heart. Several lines were made but only one was further analyzed.