GPR56, also known as TM7XN1, is an orphan G-protein-coupled receptor (GPCR) containing seven transmembrane domains and a mucin-like domain in the N-terminal region. The total length of the human GPR56 gene is approximately 15 kb, and it consists of 13 exons and encodes 693 amino acids. GPR56 is expressed in a wide range of tissues, such as brain, thyroid gland, and heart. Mutations in human GPR56 gene were found to cause a specific brain malformation called bilateral frontoparietal polymicrogyria. Recently, GPR56 was found specifically expressed on cytotoxic NK and T lymphocytes, including CD8+, CD4+, and gammadelta T cells, which might affect the migratory properties of these cells. GPR56 was also found significantly downregulated in some cancer cells, suggesting that it may play a role in growth suppression and cancer metastasis.