EphA3 is a member of the Ephrin (Eph) family. The Ephrins and Eph-related receptors comprise the largest subfamily of receptor protein-tyrosine kinases and have been implicated in mediating developmental events, especially in the nervous system and in erythropoiesis. Based on their structures and sequence relationships, ephrins are divided into the Ephrin A (EphA) class, which are anchored to the membrane by a glycosylphosphatidylinositol linkage, and the Ephrin B (EphB) class, which are transmembrane proteins. Receptors in the EPH subfamily typically have a single kinase domain and an extracellular region containing a Cys-rich domain and 2 fibronectin type III repeats.