Detection and Characterization of Estrogen Receptor Beta Expression in the Brain with Newly Developed Transgenic Mice

Two types of nuclear estrogen receptors, ERα and ERβ, have been shown to be differentially involved in the regulation of various types of behaviors. Due to a lack of tools for identifying ERβ expression, detailed anatomical distribution and neurochemical characteristics of ERβ expressing cells and cellular co-expression with ERα remain unclear. We have generated transgenic mice ERβ-RFP^tg, in which RFP was inserted downstream of ERβ BAC promotor. We verified RFP signals as ERβ by confirming: (1) high ERβ mRNA levels in RFP-expressing cells collected by fluorescence-activated cell sorting; and (2) co-localization of ERβ mRNA and RFP proteins in the paraventricular nucleus (PVN). Strong ERβ-RFP signals were found in the PVN, medial preoptic area (MPOA), bed nucleus of the stria terminalis, medial amygdala (MeA), and dorsal raphe nucleus (DRN). In the MPOA and MeA, three types of cell populations were identified; those expressing both ERα and ERβ, and those expressing exclusively either ERα or ERβ. The majority of PVN and DRN cells expressed only ERβ-RFP. Further, ERβ-RFP positive cells co-expressed oxytocin in the PVN, and tryptophan hydroxylase 2 and progesterone receptors in the DRN. In the MeA, some ERβ-RFP positive cells co-expressed oxytocin receptors. These findings collectively suggest that ERβ-RFP^tg mice can be a powerful tool for future studies on ERβ function in the estrogenic regulation of social behaviors.