Cloning, sequencing, and localization of bovine estrogen receptor-β within the ovarian follicle

The potential role of estrogen receptor-beta (ER beta) in normal ovarian folliculogenesis and in reproductive disorders such as ovarian follicular cysts has not been well defined. Therefore, we were interested in cloning, sequencing, and localizing ER beta mRNA and protein within the bovine ovary, Bovine ERP (bER beta) was amplified by reverse transcription-polymerase chain reaction (RT-PCR), then cloned and sequenced. Results showed that the open reading frame of bER beta cDNA spanned 1584 nucleotides encoding a protein of 527 amino acids, The N-terminal region of bER beta was found to be 80% homologous to human and mouse ERP and 79% homologous to rat ERP. Bovine ERP DNA-binding domain was 100% homologous to human, mouse, and rat ERP sequences. The C-terminal/ligand-binding domain of bER beta was 89% homologous to human, 86% homologous to moose, and 88% homologous to rat ER beta, Human and bovine ER beta amino acid sequences are similar in that their coding region extended farther 5' than initially reported for the published rat ER beta sequence. Using in situ hybridization and immunohistochemistry, ERP mRNA and protein, respectively, were demonstrated to be present in granulosa cells of antral follicles in various stages of follicular growth. These findings suggest a role for bER beta in ovarian follicular growth and maturation.