Molecular cloning of estrogen receptor and its function on vitellogenesis in pompano (Trachinotus ovatus)

Abstract

Estrogen receptors (ERs) play a critical role in vitellogenesis (Vtgs). However, the contribution of each ER for the regulation of vtgs expression was not analyzed clearly in teleosts. In the present study, three ers isoforms (erα, erβ1, and erβ2) were cloned in pompano (Trachinotus ovatus). Real-time PCR and enzyme-linked immunosorbent assay (ELISA) was used to detect the effects of 17β-estradiol (E₂) on ERs and Vtgs in the liver of pompano. In vivo injection experiments showed that E₂ significantly increased the expressions of ers and vtgs. ER broad spectrum antagonist Fulvestrant significantly attenuated the E₂- induced up-regulation of ers and vtgs in a dose-dependent manner. ERα antagonist Methyl-piperidino pyrazole (MPP) significantly attenuated the up-regulation of erα, erβ2, vtg-B and vtg-C, and promoted the expressions of erβ1 and vtg-A. ERβ antagonist Cyclofenil significantly inhibited the expressions of erβ1, erβ2, vtg-A and vtg-C, and promoted the expressions of erα and vtg-B. In addition, E₂ significantly increased the protein level of Vtg, while Fulvestrant, MPP and Cyclofenil significantly inhibited the protein level of Vtg in a dose-dependent manner. Our results indicate that E₂ may regulate the expression of each vtg with different subtypes of ERs, and shows a distinct compensatory expression effect on the regulation for ers and vtgs, which provides a theoretical basis for reproductive endocrinology study in pompano.

Keywords: Estrogen; Estrogen receptor; Estrogen receptor antagonist; Trachinotus ovatus; Vitellogenesis.