Characterization of estrogen receptor β2 and expression of the estrogen receptor subtypes α, β1, and β2 in the protandrous black porgy (Acanthopagrus schlegeli) during the sex change process

Estrogens play an important role in many physiological processes in both female and male vertebrates, mediated by specific nuclear receptor, estrogen receptors (ERs). We have isolated a third ER (ERβ2), which was found to contain 2004 nucleotides including an open reading frame that encodes 667 amino acids. We have also cloned ERα and ERβ1 from the published information (GenBank accession nos. AY074780 and AY074779) and investigated the expression pattern of these ER subtypes in the gonads during gonad sex change of black porgy by quantitative polymerase chain reaction. Maturity stages can be divided into five stages during the sex change process from immature male to female (immature male, mature male, male of mostly testis, male of mostly ovary and mature female). The expression of ERα mRNA was highest in the ovary of mature female, followed by the testis of mature male and testicular portion of mostly testis. ERβ1 expression was higher in the mature testis and ovary than in the gonads of other maturity stages. In contrast to that, ERβ2 was highest in the ovary of mature female, and significantly lower levels of ERβ2 expression were observed in the gonads of the other maturity stages. The present study describes the molecular characterization of ERβ2, and documents the expression changes of three ER subtypes during sex change process of the protandrous black porgy.