Tg(Krt1-15-cre/PGR*)22Cot

The transgene comprises the entire 5.0-kb mouse Krt1-15 promoter region driving expression of a fusion protein composed of an amino-terminal nuclear localization signal followed by Cre recombinase joined to the carboxyl-terminal hormone-binding domain (HBD) of a mutant human progesterone receptor. This mutant HBD, whose carboxyl-terminal is truncated by 42 amino acids, fails to bind endogenous progestins but binds and, paradoxically, is activated by progesterone receptor antagonists such as RU486. Constitutive expression of the fusion protein is directed by the Krt1-15 promoter to epithelial stem cells in the bulge region of the hair follicle. It remains inactive in the cytoplasm until bound to RU486, whereupon it translocates to the nucleus and can catalyze loxP-mediated recombination. (J:84610, J:94076, J:94082)