Tg(Ins1-itTA)#Fto

MIce bearing this transgene express the improved-codon tetracycline transactivator (itTA) coding sequence under control of the promoter sequences of the mouse insulin 1 (Ins1) gene. The transgene was generated from the C57BL/6J-derived mouse bacterial artificial chromosome (BAC) clone RP23-401C13, containing the insulin 1 (Ins1) coding region and 110 kb and 87 kb of genomic DNA sequence upstream of its start codon and downstream of its polyadenylation signal, respectively. A cassette containing the itTA coding sequence followed by a single FRT site has replaced a 317-bp DNA segment beginning 3 bp upstream of the translation-initiating ATG of Ins1, disrupting the Ins1 open reading frame. X-gal staining of organ sections of mice carrying this and a second transgene expressing the E. coli lacZ gene under control of the tetracycline operator (tetO), in the absence of doxycycline, reveals beta-galactosidase expression that is restricted at embryonic day (E) 13.5 to the pancreatic buds, at E15 to the entire pancreas, and in the adult to insulin-expressing beta cells of the pancreatic islets. (J:223993)