Molecular cloning and characterization of an estrogen receptor gene in the marine polychaete Perinereis aibuhitensis

Estrogen receptors (ERs) are the primary mediators of estrogen signaling, and play crucial roles in the reproduction and development of vertebrates. The full-length cDNA of Perinereis aibuhitensis estrogen receptor (paER) was cloned and characterized for the first time. The positions of the cysteine residues and the residues around them, which constitute two zinc finger motifs and a P-box, are conserved in both vertebrates and invertebrates. A phylogenetic analysis revealed that paER is an orthologue of ER in the polychaete Platynereis dumerilii. A tissue distribution analysis of paER mRNA showed that it is expressed in various tissues, including the body wall, head, esophageal gland, esophagus, stomach, and most strongly in the intestines. Its expression was also measured in P. aibuhitensis after exposure to 17β-estradiol (E2) for 48 h. The paER mRNA levels in the body wall were measured after 6, 12, 24, and 48 h in E2-exposed and control animals. However, no significant differences in paER expression were observed between them at any time point. This report describes the first molecular characterization of full-length paER and its tissue-specific expression in P. aibuhitensis.