The CC10-rtTA-hGH construct contains the CC10 promoter, the reverse tetracycline transactivator (rtTA), and human growth hormone (hGH) intronic and polyadenylation sequences. The tet-O-CMV-IFNgamma-hGH construct contains a polymeric tetracycline operator (tet-O), minimal CMV promoter, murine IFNgamma cDNA, and hGH intronic and polyadenylation signals. Both constructs were coinjected into fertilized oocytes, and dual positive founder animals were obtained. In the presence of doxycycline (dox), rtTA is able to bind in trans to the tet-O, and the VP-16 transactivator activates LIF gene transcription. In the absence of dox, rtTA binding occurs at very low levels, and only low level gene transcription is noted. Transgenic lines 15 and 21 were also created.