Cell migration is influenced by chemodirectants including a large family of receptor tyrosine kinases collectively referred to as Ephs. Ephs are divided into two classes based on their extracellular structure and ligand specificity. Eph receptors that bind preferentially to ephrin-A ligands are referred to as EphA and Eph receptors that bind preferentially to ephrin-B ligands are referred to as EphB. All Eph receptors contain an N-terminal Ig-like domain, a cysteine-rich region with 19 conserved cysteines and two fibronectin type III domains. The cytoplasmic region contains a typical tyrosine kinase organization.