The porcine TGFbeta1 (TGFB1) cDNA containing a double mutation where cysteines at positions 223 and 225 converted to serines is driven by a heptameric tetO sequence and a CMV minimal promoter. The construct also contains a beta-globin intron. Founders were identified by Southern blotting. Mice express the porcine TGFB1 constitutively as a result of the two mutations. TGFB1 expression can be suppressed by crossing this line with a line expressing the tTA transactivator and maintaining pregnant females on a doxycycline-containing water supply.