Alternative splicing of the nuclear progestin receptor in a perciform teleost generates novel mechanisms of dominant-negative transcriptional regulation

► Higher orders of Teleostei retain a single copy of the nuclear pgr gene. ► Four nuclear Pgr splice variants are coexpressed in the seabream ovary. ► Two Pgr isoforms show distinct mechanisms of dominant-negative inhibition. ► Pgr isoform expression is differentially regulated during ovarian development in vivo. ► FSH and E2 differentially regulate the expression of ovarian pgr isoforms in vitro.