Figure 2.

Junction remodeling during anastomosis and pruning. (A) Vessel fusion. Opposing tip cells project dynamic filopodia. On contact formation, filopodia are retracted and adhesion proteins are deposited at the contact site. The site is further elaborated into a ring-shaped junction and apical membrane is specified. Further junction remodeling results in the formation of a multicellular tube. (B) Vessel pruning. Irregular flow initiates vessel regression. Cells in the regressing branch rearrange their junctions to form a unicellular tube. Cells migrate away from the low-flow-branch resolving the junction between them. Cells from the regressing branch are incorporated into the neighboring vessels.