Grading the thalamus: how can an 'Eph' be excellent?

The Eph family of receptor tyrosine kinases and their partner ligands, the ephrins, mediate cell-cell interactions in the developing nervous system. Signaling events between Eph receptors and ephrin ligands on interacting cells affect the growth, maturation, migration and connectivity of individual neurons and neural networks. Here we review the known roles of Eph-ephrin signaling in the development of the thalamus and its connections, and pose new questions for experimental study.