The Eph-ephrin system in neuropsychiatric and neurodevelopmental disorders

Erythropoietin-producing hepatocellular (Eph) receptors are tyrosine kinase receptors that are canonically activated by their membrane tethered ligands, the ephrins. The Eph-ephrin system is critical in neurodevelopment, involved in processes such as neuronal growth and proliferation, axonal growth cone guidance, and cell survival. However, there is a significant knowledge gap in our understanding of the functional role of the Eph-ephrin system in later development, in both the adolescent and the adult brain. As various Eph receptor subtypes, and their associated ephrin ligands, are involved in the regulation of processes implicated in brain disorder pathogenesis, the Eph-ephrin system may represent an unexplored avenue for therapeutic target identification. Here, we will consolidate what is known about the Eph-ephrin system in synaptic plasticity, inflammation, and vascular permeability, linking the effects of specific ephrins and Eph receptors to depression and anxiety, autism, and schizophrenia. Novel insights into those Eph receptors with the most therapeutic promise will be provided and potential challenges of targeting these widely expressed receptor kinases discussed.