Network Development

Abstract

Development The circulatory system is made up of complex vascular networks that originate from the association of numerous angiogenic sprouts with motile tip cells and trailing stalk cells. Tip cells contact each other, fuse, and subsequently form an interconnected lumen. Herwig et al. now visualize the behavior of single zebrafish endothelial cells during blood vessel fusion (anastomosis) and lumen formation. They used transgenic zebrafish whose endothelial cell junctions of dorsal longitudinal anastomotic vessels were fluorescently labeled to monitor cell movements and cell shape. Anastomosis is seen to result from different morphogenetic mechanisms—one involving cell rearrangement for a process of cord hollowing to generate a multicellular tube or through cell shape changes involving membrane invagination for a unicellular tube. These processes are associated with lumen formation at the position of vessel fusion. In addition, the luminal membrane compartments are polarized apically. With the elegant complexity of the vascular network, perhaps it is not surprising that multiple mechanisms are used to establish blood vessel morphology. Curr. Biol. 21 , 1942 (2011).