Expression of estrogen receptor β is developmentally regulated in reproductive tissues of male and female mice

By the use of ribonuclease protection assay (RPA) combined with immunohistochemical techniques, the expression of estrogen receptor (ER) or and ERP was mapped in the developing gonads and reproductive tracts of male and female mice from fetal day 14 to postnatal day 26 (PND 26), This study was designed to determine the pattern of expression of both ER subtypes in specific tissue compartments during development. In ovaries, ER alpha mRNA was detected at all ages examined; ER beta mRNA was seen as early as PND 1, and its expression increased with age. Immunolocalization showed ER beta in differentiating granulosa cells of the ovary, whereas ER alpha was predominantly seen in interstitial cells. The remainder of the female reproductive tract showed ER alpha mRNA at all ages examined with little or no significant levels of ER beta, except on END 1 when a low level of message appeared. In males, ER alpha and ERP mRNA were detected in the fetal testis; however, ER beta gradually increased until PND 5 and subsequently diminished to undetectable levels by PND 26. Immunolocalization showed ER alpha in the interstitial compartment of the testis, whereas ER beta was seen predominantly in developing spermatogonia, The remainder of the male reproductive tract showed varying amounts of both receptors by RPA and immunostaining throughout development. These studies provide information useful in studying the role of both ER subtypes in normal differentiation, and they provide indications of differential tissue expression during development.