Figure 6

Notch regulates the expression of key genes and the remodeling of the yolk sac vasculature. (A) Proposed model depicts the Notch pathway as a key component in the regulation of the remodeling of the vasculature. In wild type yolk sac Notch acts in concert with VEGF and other signaling families to direct the integration of the endothelial cells into both large and small caliber vessels. When Notch is activated this integration is increased leading to very large caliber vessels with limited intra-vascular space. When Notch activity is abrogated the integration is limited and the vascular retains the simple unremodeled appearance of the early vascular plexus. (B) Proposed model of signaling in the endodermal and endothelial cells of the early yolk sac. Signaling from the endoderm and regulation from blood flow activates Notch signaling in select endothelial cells. Notch activates the expression of select secreted genes that act in both a paracrine and juxtacrine manner to direct endothelial cell migration and integration within the developing vasculature.