Growth factor signaling pathways in vascular development

Recent research on the formation and maintenance of the vasculature in the embryo and in the adult has provided a greater understanding of the cellula r signals involved in these processes, With this understanding comes the po tential means of controlling vascularization in pathological situations suc h as tumorigenesis and wounding. For the purpose of this review, we will di scuss the key receptor tyrosine kinases involved in vascular function and t he molecules which relay signals downstream of receptor activation. The rec eptor tyrosine kinases discussed include the vascular endothelial cell grow th factor receptors, Eph receptors, Tie1, and Tie2, all of which: are expre ssed on vascular endothelial cells. We also discuss the roles of the platel et derived growth factor receptors which are expressed on vascular smooth m uscle cells.: While all of these receptor tyrosine kinases activate many si milar effector molecules, some of the signals initiated appear to be distin ct. This may explain, at least in part, how different receptor tyrosine kin ases expressed in overlapping patterns on the developing vasculature, direc t unique biological functions.