Order and flows via polymerization, motor activity and elastic stress in model cytoskeletal systems

Cytoskeletal assemblies exhibit striking emergent organization and flows driven by polymerization dynamics, cross-linkers, and elastic stresses. I will present filament-resolved computational studies, based on the aLENS platform and custom code, that demonstrate these physical mechanisms in three fundamental cytoskeletal phenomena: (1) self-assembly of actin rings in confinement, (2) actin comet-based motility, and (3) active nematic and active gel states in microtubule–kinesin mixtures. First, we show that ring formation in confined actin networks with passive cross-linkers occurs via self-similar coarsening through filament merging, zippering, and cross-linker condensation, producing stable rings prior to kinetic arrest. Second, our model of branched actin assembly simulates Arp2/3-activated shell growth and comet-tail formation around micron scale objects. By accounting for force elongation relations, capping, and severing, the model addresses long-standing questions regarding the relative contributions of gel squeezing forces and direct polymerization forces in symmetry breaking, propulsion, and saltatory motion. Finally, simulations of microtubule–kinesin mixtures reproduce hallmarks of active gels and active nematics, including defect creation and motility, and turbulent flows, directly from discrete filament–motor interactions while preserving detailed balance of binding/unbinding kinetics. We provide predictions for microtubule polarity and force distributions in these systems.