Protogenin (Prtg) has been identified as a gene which is highly expressed in the mouse mandible at embryonic day 10.5 (E10.5) by a cDNA subtraction method between mandibles at E10.5 and E12.0. Prtg is a new member of the deleted in colorectal carcinoma (DCC) family, which is composed of DCC, Neogenin, Punc and Nope. These members play an important role in the development of the embryonic central nervous system. Prtg protein is restrictedly expressed between E7 and E10 in mouse embryo and acts as a receptor by binding its ligand ERdj3. Protogenin (PRTG) is a transmembrane protein of immunoglobulin superfamily, which has multiple roles in embryogenesis as a receptor or an adhesion molecule.