Ephrin-B3 is a protein that in humans is encoded by the EFNB3 gene. EFNB3, a member of the ephrin gene family, is important in brain development as well as in its maintenance. The EPH and EPH-related receptors comprise the largest subfamily of receptor protein-tyrosine kinases. EPH receptors typically have a single kinase domain and an extracellular region containing a Cysteine-rich domain and 2 fibronectin type III repeats. The ephrin ligands and receptors have been named by the Eph Nomenclature Committee (1997) based on their structures and sequence relationships. Ephrins are divided into the ephrin-A (EFNA) class, which are anchored to the membrane by a glycosylphosphatidylinositol linkage, and the ephrin-B (EFNB) class, which are transmembrane proteins. Ephrin-B ligands also contain an