title: Local cortical tension by myosin II guides 3D endothelial cell branching.
abstract: A key feature of angiogenesis is directional control of endothelial cell (EC) morphogenesis and movement [1]. During angiogenic sprouting, endothelial "tip cells" directionally branch from existing vessels in response to biochemical cues such as VEGF or hypoxia and migrate and invade the surrounding extracellular matrix (ECM) in a process that requires ECM remodeling by matrix metalloproteases (MMPs) [2-4]. Tip EC branching is mediated by directional protrusion of subcellular pseudopodial branches [5, 6]. Here, we seek to understand how EC pseudopodial branching is locally regulated to directionally guide angiogenesis. We develop an in vitro 3D EC model system in which migrating ECs display branched pseudopodia morphodynamics similar to those in living zebrafish. Using this system, we find that ECM stiffness and ROCK-mediated myosin II activity inhibit EC pseudopodial branch initiation. Myosin II is dynamically localized to the EC cortex and is partially released under conditions that promote branching. Local depletion of cortical myosin II precedes branch initiation, and initiation can be induced by local inhibition of myosin II activity. Thus, local downregulation of myosin II cortical contraction allows pseudopodium initiation to mediate EC branching and hence guide directional migration and angiogenesis.
authors.affiliation: Laboratory of Cell and Tissue Morphodynamics, Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA. fischerr2@mail.nih.gov
authors.forename: Robert S
authors.initials: RS
authors.lastname: Fischer
authors.forename: Margaret
authors.initials: M
authors.lastname: Gardel
authors.forename: Xuefei
authors.initials: X
authors.lastname: Ma
authors.forename: Robert S
authors.initials: RS
authors.lastname: Adelstein
authors.forename: Clare M
authors.initials: CM
authors.lastname: Waterman
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002465:Cell Movement / Q000502:physiology*; D042783:Endothelial Cells / Q000166:cytology* / Q000378:metabolism; D005109:Extracellular Matrix / Q000502:physiology; D008953:Models, Anatomic; D009024:Morphogenesis / Q000502:physiology*; D024462:Myosin Type II / Q000378:metabolism / Q000502:physiology*; D018919:Neovascularization, Physiologic / Q000502:physiology*; D011554:Pseudopodia / Q000502:physiology; D015027:Zebrafish
chemical_list: D024462:Myosin Type II