Demilune cell and parotid protein 1, encoded by the Dcpp1 gene, is a secretory protein found in oviduct epithelium and salivary glands. These knock-in mice express the GCE cassette (an EGFP/creERT2 fusion gene) from the endogenous Dcpp1 locus. When Dcpp1GCE mice are bred with mice containing loxP-flanked sequence, tamoxifen-inducible, cre-mediated recombination will result in deletion of the floxed sequences. Tamoxifen administration in double mutant mice, carrying this GCE cassette and a reporter, induces Cre recombination in serous demilune cells of the sublingual gland and intercalated duct cells of the parotid gland. The inducible cre recombinase activity pattern mimics the endogenous Dcpp1 expression pattern. EGFP expression is not detected by direct fluorescence or anti-GFP antibody (immunofluorescence). Although homozygotes are predicted to be viable and fertile, the Donating Investigator has not made the strain homozygous. During backcrossing, the Y chromosome may not have been fixed to the C57BL/6J genetic background.
The Cre-ERT2 fusion protein consists of Cre recombinase fused to a triple mutant form of the human estrogen receptor, which does not bind its natural ligand (17β-estradiol) at physiological concentrations, but will bind the synthetic estrogen receptor ligands 4-hydroxytamoxifen (OHT or tamoxifen) and, with lesser sensitivity, ICI 182780. Restricted to the cytoplasm, Cre-ERT2 can only gain access to the nuclear compartment after exposure to tamoxifen. To counteract the mixed estrogen agonist effects of tamoxifen injections, which can result in late fetal abortions in pregnant mice, progesterone may be coadministered.
