Critical component of the guidance pathway underlying endothelial cell migration and blood vessel patterning. Involved in mediating membrane localization of ephrin proteins, which have been shown to provide guidance cues for endothelial cell migration. Specifically expressed in subsets of neuronal tissues, epithelial cells, and developing somites through which vascular endothelial cells migrate from large ventral axial vessels to form stereotypic intersegmental blood vessels (ISV).