Vinculin controls endothelial cell junction dynamics during vascular lumen formation

Abstract

Blood vessel morphogenesis is driven by coordinated endothelial cell behaviors, which depend on dynamic cell-cell interactions. Remodeling of endothelial cell-cell junctions promote morphogenetic cellular events while preserving vascular integrity. Here, we have analyzed the dynamics of endothelial cell-cell junctions during lumen formation in angiogenic sprouts. By live-imaging of the formation of intersegmental blood vessels in zebrafish, we demonstrate that lumen expansion is accompanied by the formation of transient finger-shaped junctions. Formation and maintenance of these junctional fingers are positively regulated by blood pressure whereas inhibition of blood flow prevents their formation. Using fluorescent reporters, we show that the tension-sensor Vinculin localizes to junctional fingers. Furthermore, loss of vinculin function, in vinculin a and -b double knockouts, prevents junctional finger formation in angiogenic sprouts, whereas endothelial expression of a vinculin transgene is sufficient to restore junctional fingers. Taken together, our findings suggest a mechanism in which lumen expansion during angiogenesis leads to an increase in junctional tension, which triggers recruitment of vinculin and formation of junctional fingers. We propose that endothelial cells may employ force-dependent junctional remodeling to react to changes in external forces to protect cell-cell contacts and to maintain vascular integrity during sprouting angiogenesis.