These mice express a lacZ reporter from the proximal -497 bp Tnnt2 promoter segment derived from rat. LacZ is specifically expressed in the paired cardiogenic mesoderm of day 7.5 postcoitum (p.c.) embryos and in the looping heart tube of day 8 p.c. embryo myocardial cells. As development proceeds, lacZ expression is distributed uniformly throughout both atria and ventricles. By day 10.5 p.c., a low level of lacZ expression starts to be detected in developing somites. At fetal stages, lacZ expression is also detected in developing skeletal muscles, such as intercostal muscles; brachial muscles; muscles associated with metacarpal bones, metatarsal bones, and lower legs; and muscles surrounding the developing vertebrae. The level of transgene expression in the developing skeletal muscle is much lower than that seen in the developing heart. In the adult, lacZ is expressed only in the heart, and not in other tissues tested, including skeletal muscles, liver, spleen, lung, kidney, brain, stomach, and intestine. Recent findings indicate that expression is also seen in cardiomyocytes of pulmonary veins, implicated in the genesis of human cardiac disease and atrial fibrillation.
The construct confers cardiac-specific expression in vivo and faithfully recapitulates endogenous expression during development.
