Tyro3 (also known as Sky and Rse), with 890-amino acid protein (about 98kDa), belongs to the Axl/Tyro3 family of receptor tyrosine kinases, which also includes Axl and Mer.Gas6 (growth arrest-specific gene-6) is a ligand for all members of the Axl family and they play essential roles in spermatogenesis, immunoregulation, and phagocytosis.Tyro3 was expressed at high levels during postnatal development and in the adult in the cortex.Tyro3 and Gas6 have neurotrophic roles in the nervous system.In addition, the signalling interactions of Axl and Tyro3 may play roles in tumourigenesis, inflammation as well as other cell proliferative diseases.