Because little is known how microtubules contribute to cell migration in a physiological three-dimensional environment, we analyzed microtubule function and dynamics during in vitro angiogenesis in which endothelial cells form networks on a reconstituted basement membrane. Endothelial network formation resulted from distinct cell behaviors: matrix reorganization by myosin-mediated contractile forces, and active cell migration along reorganized, bundled matrix fibers. Inhibition of microtubule dynamics inhibited persistent cell migration, but not matrix reorganization. In addition, microtubule polymerization dynamics and CLASP2-binding to microtubules were spatially regulated to promote microtubule growth into endothelial cell protrusions along matrix tension tracks. We propose that microtubules counter-act contractile forces of the cortical actin cytoskeleton and are required to stabilize endothelial cell protrusions in a soft three-dimensional environment.
Keywords: CLASP2; blebbistatin; cell migration; cytoskeleton; endothelial cells; in vitro angiogenesis; microtubule dynamics; nocodazole.