'Blue heart': characterization of a mifepristone-dependent system for conditional gene expression in genetically modified animals

摘要

A detailed characterization of a cardiac muscle-specific, ligand-regulated gene expression system was performed in transgenic mice using the inducing ligand mifepristone (MFP). Several lines of double transgenic mice were created that expressed a bacterial lacZ reporter gene in the heart, under the control of a MFP-activated transcription factor constitutively expressed in cardiac muscle. The transgenic mice, which were administered MFP at a dose of 1μmol/l in the drinking water, responded to the ligand within 24 h. Induction of β-galactosidase enzyme activity in the heart continued for up to 21 days and resulted in an average 17-fold increase in enzyme activity. The highest individual animal response measured was a 94-fold increase in enzyme activity. The EC_(50) for MFP induction of β-galactosidase activity in the heart was 0.7μmol/l when MFP was administered in the drinking water. Pharmacokinetic analysis of MFP dosing in wild-type FVB/N mice showed that absorption was very rapid (T_(max) 1-10 min), bioavailability was modest (～10%) and the t_(1/2) of MFP in mouse plasma was determined to be approximately 5 h. Thus, the system functions effectively in transgenic mouse heart where induction of gene expression is sensitive and can be accomplished by a simple and broadly applicable drinking water protocol.