Orphan nuclear receptor. Binds to the hormone response element in the upstream promoter region of the CYIIIB gene in vitro. Both isoform 1 and isoform 2 bind DNA. Binds DNA as a monomer. The subcellular location of isoform 1 alters throughout development. In the unfertilized egg, isoform 1 expression is cytoplasmic and concentrated around the pronucleus. Following fertilization, the cytoplasmic protein rapidly enters the embryonic nuclei where it appears as speckles. From the fourth cleavage stage onwards it resides as speckles in the cytoplasm and the nucleus. The cytoplasmic localization also differs between cells, maintaining an apical position in polarized ectodermal and endodermal cells, whereas in non-polarized cells the cytoplasmic distribution is uniform. In contrast, isoform 2 resides in the nucleus in both 4-cell and 16-cell embryos. Expressed uniformly in the early embryo. In contrast, larval expression is localized to the epaulettes and mouth epithelium. Expressed in multiple adult organs including lantern muscle, tubefeet, intestine, coelomocytes and gonads. In the adult ovaries and testes, expression is specifically localized to the smooth muscle epithelial layer of cells which surround the ovarioles and acini, respectively (at protein level). Expressed both maternally and zygotically. Present in the unfertilized egg and in all embryonic stages up to the pluteus stage, followed by depletion of expression in the late embryo. Expression starts again just prior to metamorphosis in larva at 35 days post-fertilization (dpf). Also expressed in adults (at protein level). May be due to exon skipping. Belongs to the nuclear hormone receptor family. NR2 subfamily.