Mice were generated by inserting a 2A sequence, mCherry, 2A sequence, and the C terminal 36 amino acids of the DnaE split intein sequence from Nostoc punctiforme (Npu) fused to the C-terminal fragment of improved cre (iCre) recombinase (aa 105-343), FLAG tag, and Frt-flanked neomycin resistance cassette immediately in front of the stop codon of Scgb1a1 coding sequence by homologous recombination. The Frt-flanked neomycin resistance cassette was removed by crossing with hACTB-Flpe deleter mice.