Gt(ROSA)26Sor^{tm1(cre/ERT)Brn}

The endogenous locus was modified by insertion of a construct containing the rabbit beta-globin 3' splice site followed by the cre/ERT fusion gene, which encodes Cre recombinase joined to the G321R mutant hormone-binding domain of the human estrogen receptor that is activated by 4-hydroxytamoxifen (4-OHT), but not by the natural ER ligand 17-beta-estradiol. The fusion gene is followed by the rabbit beta-globin polyadenylation signal and a PGK-puro (puromycin resistance) cassette. Efficient Cre-mediated recombination in transgenic mice carrying floxed reporter genes was reported to reflect constitutive expression of the Gt(ROSA)26Sor from preimplantation stages onward. (J:80160)