Eph-related receptors and their ligands: Mediators of contact dependent cell interactions

Recent studies of the large families of Eph-related receptor tyrosine kinases and their ligands suggest that they have key roles in embryonic development. These receptors mediate cell contact dependent signalling by binding to membrane-bound ligands, and certain ligands may themselves transduce signals. Functional studies indicate that in a number of tissues the receptors and ligands are expressed in complementary domains and mediate repulsive interactions that restrict cell and axon migration. In addition, they can also stimulate cell mig:ration. Eph-related receptors and their ligands are therefore mediators of cell interactions required for tissue patterning and neuronal pathfinding during development. The potential clinical implications of these findings are discussed.