Coordinated tractions increase the size of a collectively moving pack in a cell monolayer

Aashrith Saraswathibhatla, Silke Henkes, Emmett E. Galles, Rastko Sknepnek, Jacob Notbohm (Lead / Corresponding author)

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)
54 Downloads (Pure)


Cells in an epithelial monolayer coordinate motion with their neighbors giving rise to collectively moving packs of sizes spanning multiple cell diameters. The physical mechanism controlling the pack size, however, remains unclear. A potential mechanism comes from assuming that cell–substrate traction forces persist over some time scale: with large enough persistence time, collective cell packs emerge. To test this hypothesis, we measured the velocity and net traction of each cell. The data showed that in addition to having some temporal persistence, tractions were spatially correlated, suggesting that cells coordinate with their neighbors to apply tractions in the same direction. Chemical inhibitors and activators of actomyosin contraction were used to determine effects of altering the traction persistence and alignment. Numerical simulations based on the self-propelled Voronoi model, augmented to include both traction persistence and alignment and calibrated against the experimental data, matched the experimentally measured pack size. The model identified that if there were no alignment of traction between neighboring cells, the size of the collective pack would be substantially smaller than observed in the experiments. Hence, combining experiments and a simple mechanical model, this study confirms the long-standing assumption of traction persistence and adds the notion of traction alignment between neighbors. Together, persistence and alignment are two factors controlling the size of a collectively moving cell pack.

Original languageEnglish
Article number101438
Number of pages6
JournalExtreme Mechanics Letters
Early online date15 Jul 2021
Publication statusPublished - Oct 2021


  • Collective cell migration
  • Self-propelled Voronoi model
  • Traction alignment
  • Traction persistence

ASJC Scopus subject areas

  • Bioengineering
  • Chemical Engineering (miscellaneous)
  • Engineering (miscellaneous)
  • Mechanics of Materials
  • Mechanical Engineering


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