Figure 1. (A) Proper expression and activity of CASZ1 in endothelial cells results in transcriptional activation of Egfl7 and subsequent RhoA activity, thereby promoting the assembly of a well-branched, lumenized vascular system. (B) Disruption of CASZ1 function results in cords of endothelial cells lacking a central lumen and angiogenic sprouts. Branches that are apparent consist of thin, elongated cells that are unable to maintain adhesion to the underlying matrix or existing vasculature.