Ephrin-A1 (EFNA1) is also known as EPLG1, LERK1, TNFAIP4, Immediate early response protein B61, which belongs to the ephrin family. EFNA1 contains one ephrin RBD (ephrin receptor-binding) domain. EFNA1 is cell surface GPI-bound ligand for Eph receptors, and is a family of receptor tyrosine kinases which are crucial for migration, repulsion and adhesion during neuronal, vascular and epithelial development. EFNA1 binds promiscuously Eph receptors residing on adjacent cells, leading to contact-dependent bidirectional signaling into neighboring cells. EFNA1 plays an important role in angiogenesis and tumor neovascularization.