Pattern formation and polarity sorting of driven actin filaments on lipid membranes

Proc Natl Acad Sci U S A. 2021 Feb 9;118(6):e2017047118. doi: 10.1073/pnas.2017047118.

Abstract

Collective motion of active matter is ubiquitously observed, ranging from propelled colloids to flocks of bird, and often features the formation of complex structures composed of agents moving coherently. However, it remains extremely challenging to predict emergent patterns from the binary interaction between agents, especially as only a limited number of interaction regimes have been experimentally observed so far. Here, we introduce an actin gliding assay coupled to a supported lipid bilayer, whose fluidity forces the interaction between self-propelled filaments to be dominated by steric repulsion. This results in filaments stopping upon binary collisions and eventually aligning nematically. Such a binary interaction rule results at high densities in the emergence of dynamic collectively moving structures including clusters, vortices, and streams of filaments. Despite the microscopic interaction having a nematic symmetry, the emergent structures are found to be polar, with filaments collectively moving in the same direction. This is due to polar biases introduced by the stopping upon collision, both on the individual filaments scale as well as on the scale of collective structures. In this context, positive half-charged topological defects turn out to be a most efficient trapping and polarity sorting conformation.

Keywords: actin motility assay; active matter; high-density gliding assay; ordering phenomena; self-propelled rods.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Actin Cytoskeleton / genetics*
  • Actin Cytoskeleton / metabolism
  • Cell Membrane / genetics
  • Cell Movement / genetics
  • Cell Polarity / genetics
  • Colloids / metabolism
  • Cytoskeleton / genetics*
  • Cytoskeleton / metabolism
  • Lipid Bilayers / metabolism*
  • Lipid Metabolism / genetics
  • Membrane Lipids / genetics*
  • Membrane Lipids / metabolism
  • Microtubules / genetics
  • Microtubules / metabolism
  • Protein Transport / genetics

Substances

  • Colloids
  • Lipid Bilayers
  • Membrane Lipids