A mouse model engineered to spatiotemporally control Cre expression in progesterone receptor positive cells†

The Cre/loxP system is widely used for site-specific genetic manipulation in mice. The PgrCre mouse model, where Cre recombinase is driven by the progesterone receptor promoter, is commonly used for gene ablation in Pgr-positive uterine cells. However, the PgrCre is active in the neonatal uterus and does not allow temporal control. To enhance the functionality of the PgrCre mouse, we generated and characterized an inducible PgriCreERT2 mouse, in which iCreERT2 is inserted downstream of the endogenous Pgr promoter. PgriCreERT2 mice crossed with Rosa26-CAG-LSL-Sun1-sfGFP-myc reporter mice demonstrated tamoxifen-dependent recombination in uterine stromal fibroblasts and a subset of epithelial cells. Tamoxifen-induced ablation of PGR expression was accomplished by crossing PgriCreERT2 mice with the Pgrflox/flox mice. Resulting PgriCreERT2/Pgr:flox and Pgrflox/flox mice were treated with tamoxifen or oil vehicle daily for 3 days and assayed for fertility 1 month after treatment. Tamoxifen-treated PgriCreERT2/Pgr:flox mice exhibited implantation failure, dysregulation of uterine epithelial and stromal cell proliferation, and loss of decidualization response with no impact on ovulation or embryo transport. A 6-month breading trial demonstrated that 4/6 tamoxifen-treated PgriCreERT2/Pgr:flox mice were completely infertile, and the remaining 2/6 delivered only three total pups each near the end of the trial. In contrast, tamoxifen-treated Cre-negative females were fertile with normal uterine receptivity compared to vehicle controls, indicating that tamoxifen administration with a month-long recovery period did not impair pregnancy. Together, these data demonstrate the utility of this inducible PgriCreERT2 mouse model for spatiotemporally controlled gene ablation in Pgr-positive cells of the uterus.