title: Quantification of cell edge velocities and traction forces reveals distinct motility modules during cell spreading.
abstract: Actin-based cell motility and force generation are central to immune response, tissue development, and cancer metastasis, and understanding actin cytoskeleton regulation is a major goal of cell biologists. Cell spreading is a commonly used model system for motility experiments -- spreading fibroblasts exhibit stereotypic, spatially-isotropic edge dynamics during a reproducible sequence of functional phases: 1) During early spreading, cells form initial contacts with the surface. 2) The middle spreading phase exhibits rapidly increasing attachment area. 3) Late spreading is characterized by periodic contractions and stable adhesions formation. While differences in cytoskeletal regulation between phases are known, a global analysis of the spatial and temporal coordination of motility and force generation is missing. Implementing improved algorithms for analyzing edge dynamics over the entire cell periphery, we observed that a single domain of homogeneous cytoskeletal dynamics dominated each of the three phases of spreading. These domains exhibited a unique combination of biophysical and biochemical parameters -- a motility module. Biophysical characterization of the motility modules revealed that the early phase was dominated by periodic, rapid membrane blebbing; the middle phase exhibited continuous protrusion with very low traction force generation; and the late phase was characterized by global periodic contractions and high force generation. Biochemically, each motility module exhibited a different distribution of the actin-related protein VASP, while inhibition of actin polymerization revealed different dependencies on barbed-end polymerization. In addition, our whole-cell analysis revealed that many cells exhibited heterogeneous combinations of motility modules in neighboring regions of the cell edge. Together, these observations support a model of motility in which regions of the cell edge exhibit one of a limited number of motility modules that, together, determine the overall motility function. Our data and algorithms are publicly available to encourage further exploration.
authors.affiliation: Department of Biological Sciences, Columbia University, New York, NY, USA. ben@cellmotion.org
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Dubin-Thaler
authors.forename: Jake M
authors.initials: JM
authors.lastname: Hofman
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Cai
authors.forename: Harry
authors.initials: H
authors.lastname: Xenias
authors.forename: Ingrid
authors.initials: I
authors.lastname: Spielman
authors.forename: Anna V
authors.initials: AV
authors.lastname: Shneidman
authors.forename: Lawrence A
authors.initials: LA
authors.lastname: David
authors.forename: Hans-Günther
authors.initials: HG
authors.lastname: Döbereiner
authors.forename: Chris H
authors.initials: CH
authors.lastname: Wiggins
authors.forename: Michael P
authors.initials: MP
authors.lastname: Sheetz
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001696:Biomechanical Phenomena; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002465:Cell Movement / Q000187:drug effects; D015638:Cytochalasin D / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D011554:Pseudopodia / Q000187:drug effects / Q000378:metabolism; D000098662:Vasodilator-Stimulated Phosphoprotein
chemical_list: D015815:Cell Adhesion Molecules; D008840:Microfilament Proteins; D010750:Phosphoproteins; D000098662:Vasodilator-Stimulated Phosphoprotein; D015638:Cytochalasin D