Notch signalling and the regulation of angiogenesis.

Angiogenesis, or the formation of new blood vessels from preexisting ones, is essential to establish the vascular circuit during embryonic development. During angiogenic sprouting, endothelial cells exhibit a diverse array of cellular behaviors. Endothelial tip cells must migrate extensively and proliferate in response to proangiogenic cues while trailing cells need to maintain their position and connection to the patent vasculature, despite exposure to the same proangiogenic molecules. Several new studies have now shed light on the underlying mechanisms that are responsible for coordinating this process. In particular, this work has identified a conserved role for the Notch signalling pathway in limiting the cellular angiogenic response, in part by reducing the level of vascular endothelial growth factor receptors in endothelial cells. In this overview, we discuss the emerging concepts elucidated by these studies and propose a model in which Notch acts reiteratively throughout the angiogenic process, likely by acting as a switch to determine a cell's response to Vegf.