A targeting vector used to insert a synthetic modified tetracycline-regulated transactivator (tTA2S) gene and 3' UTR region of the somatostatin exon 2 into the ATG transcriptional start site of the somatostatin gene (Sst). Specifically, the targeting vector was designed with (from 5' to 3') an frt3 site, a Cre recombinase gene, a bovine growth hormone polyA sequence, a second frt3 site, a tTA2S gene, the 3' UTR region from somatostatin exon 2, an AttB site, PGK-Neo-polyA cassette, an frt5 site, an RNA splice acceptor, the 3' portion of the hygromycin gene with SV40 polyA signal, and an AttP site. (J:176570)