An IRESCreERT-lox-PGKneo-lox cassette was knocked into the 3' UTR of a 9.3 kb fragment of the Scgb1a1 locus. The targeting construct was electroporated into 129/SvEv ES cells for homologous recombination. Chimeras were generated by blastocyst injection of recombined ES cells. The PGK-neo cassette was deleted by crosses with Gt(ROSA)26Sortm1(FLP1)Dym (FLPeR) mice. Cre expression from the Scgb1a1 locus is induced by tamoxifen administration.