Cloning of bovine estrogen receptor beta (ER beta): expression of novel deleted isoforms in reproductive tissues

cDNAs coding for bovine estrogen receptor beta (ER beta) isoforms were clon ed from bovine granulosa cells using a combination of several RT-PCR strate gies. The cloned full-length receptor contains an open reading frame of 474 amino acids encoding a protein with high homology to the ER beta sequences from other species. A second isoform nearly totally lacking the ligand bin ding domain was cloned that is expressed to relatively high levels in repro ductive tissues. Expression of both ER beta isoforms is down-regulated in c orpus luteum and endometrium during the luteal phase of the female cycle. I n addition, in granulosa cells several ER beta isoforms carrying major inte rnal deletions were detected by RT-PCR and cloned. Transient transfection s tudies expressing the two major bovine ER beta isoforms together with an ER E reporter construct show estrogen-dependent transactivation by the full-le ngth isoform, whereas the isoform lacking the ligand binding domain did not show any transactivation. (C) 1999 Elsevier Science Ireland Ltd. All right s reserved.