Expression of the estrogen receptor gene across the life cycle in the polychaete, Capitella teleta

Vertebrate estrogen receptors (ERs; NR3A subfamily genes) are essential for regulating multiple biological processes in vertebrates. However, little is known about ERs (NR3D subfamily genes) in invertebrates. Capitella teleta is a marine polychaete with a single ER gene that is ligand-activated with low concentrations of estradiol in vitro; yet the physiological role of this receptor is unclear. We used whole-mount in situ hybridization to investigate spatial and temporal expression patterns of the ER in larval stages and RT-qPCR to detect temporal ER gene expression patterns across age and sex in juvenile and adults. The ER gene was expressed in the brain and foregut across multiple larval stages, suggesting a role in brain and gastrointestinal development. Whole-body juvenile ER gene expression was similar between two and six weeks of age. ER expression was similar across sex between head fragments, gastrointestinal systems, or whole bodies of sexually mature worms. These data show that the ER does not exhibit a sexually dimorphic expression as is stereotypical in vertebrates, and suggests that the ER may may not play a big role in sexual maturation in C. teleta. Collectively, ER is expressed across multiple life stages and suggests a role in brain and foregut development, and possibly a gastrointestinal function in adults. This study aids in uncovering the physiological functions of ER in lophotrochozoans.