EFNA5 A gene on chromosome 5q21 that encodes ephrin-A5, a cell surface GPI-bound ligand for the Eph family of tyrosine kinase receptors, which are crucial for migration, repulsion and adhesion during neuronal, vascular and epithelial development. EFNA5 activates the EPHA3 receptor to regulate cell–cell adhesion and cytoskeletal organisation. With the receptor EPHA2, EFNA5 may regulate lens fibre shape and interactions, and may be key for maintaining lens transparency. The interaction of EFNA5 with EPHA5 also mediates communication between pancreatic islet cells to regulate glucose-stimulated insulin secretion. EFNA5 is the cognate/functional ligand for EPHA7; together they regulate brain development, modulating cell–cell adhesion and repulsion. It interacts with and activates EPHA8.