This transgene contains constitutively active Gsk3b (an S9A mutation was introduced to make it constitutively active) under transcriptional control of a minimally active mouse alpha myosin heavy chain (Myh6) promoter fused to seven copies of the tetracycline-responsive promoter element (tetO). To make the Myh6 promoter minimally active, three GATA sites and two thyroid-like response elements are ablated. When bred with transgenic mice expressing a tetracycline transactivator or reverse transactivator protein, cardiac-specific expression of the constitutively active Gsk3b can be controlled by withdrawal or administration of a tetracycline analog. (J:125131)