Generation and characterization of a complete null estrogen receptor α mouse using Cre/LoxP technology.

Abstract  Conventional estrogen receptor α knockout (neo-ERαKO, neo-ERα−/−) mice contain a truncated and chimeric ERα fusion protein that retains 35% estrogen-dependent transactivation activity, and therefore the in vivo ERα function is difficult to study thoroughly. Furthermore, these neo-ERα−/− mice cannot be used for tissue and temporal specific ERα deletion. Therefore, there is a clear need to establish a floxed ERα mouse line that can knockout ERα specifically and completely in each selected cell type. Here we generated floxed ERα mice using a self-excising ACN (tACE-Cre/Neo) cassette. Mating the floxed ERα mice with ACTB-Cre mice produces a deletion of the floxed allele disrupting the reading frame of the ERα transcript so that no ERα protein is detected in the ACTB-Cre/ERα−/− mice. Expression of ERα target genes, such as G-6-PD and lactoferrin, is diminished by over 90% in the ACTB-Cre/ERα−/− uterus, but not in the neo-ERα−/− uterus. Furthermore, we also validated that ACTB-Cre/ERα−/− females have a hypoplastic internal genital tract, polycystic ovaries with hemorrhagic follicles, infertility, and higher body weight. Together, our data clearly demonstrate that the newly established floxed ERα mouse is a reliable mouse model for future studies of ERα roles in vivo in the selective estrogen target tissues. The complete knockout of ERα in the ACTB-Cre/ERα−/− mice will also provide an improved mouse model to study the role of ERα in vivo. [ABSTRACT FROM AUTHOR]