Monomer and homodimer. Expressed in most developing organs which contain mucus-secreting cells, including the epidermis, olfactory bulbs, otic vesicles, pharynx, esophagus, pneumatic duct, swim bladder, and intestine. Expressed in the gill, pharynx/esophagus, swim bladder/pneumatic duct, and intestine in the adult. Expressed after the segmentation stage. Belongs to the AGR family.