Heterogeneity in collective endothelial cell behavior is a driver of arterio-venous remodeling

During vascular development, arteries and veins form in a stepwise process that combines vasculogenesis and sprouting angiogenesis. Despite extensive data on the mechanisms governing blood vessel assembly at the single cell level, little is known about how cell populations migrate in a finely tuned and coordinated manner, and distribute precisely between arteries and veins. Here, we use an endothelial-specific zebrafish reporter, arteriobow, to label small cohorts of arterial cells and trace their progeny from the initial events of vasculogenesis through the process of arterio-venous remodeling. We reveal that the genesis of both arteries and veins relies on the coordination of ten types of collective cell behaviors originating from discrete endothelial cell clusters. Within these behavioral categories, we identify a heterogeneity of collective cell dynamics specific to either arterial or venous remodeling. Using pharmacological blockade, we further show that factors known to control vascular patterning such as cell-intrinsic Notch signaling and cell-extrinsic blood flow, potentially act as regulators by coordinating endothelial cohorts behavior, which in turn instructs the future territory of arterio-venous remodeling.