Design principles for selective self-assembly of active networks

TL;DR

This study uses simulations to explore how varying concentrations and kinetics of crosslinkers and motors lead to different actin cytoskeleton structures with distinct functions, informing design principles for active materials.

Contribution

It introduces a minimal cytoskeletal model and new metrics to classify structural phases, linking assembly conditions to functional outcomes.

Findings

Identified three structural phases: bundled, polarity-sorted, and contracted.

Demonstrated that motor and crosslinker kinetics can optimize force generation and transport.

Provided quantitative relationships between assembly conditions, structures, and functions.

Abstract

Living cells dynamically modulate the local morphologies of their actin cytoskeletons to perform biological functions, including force transduction, intracellular transport, and cell division. A major challenge is to understand how diverse structures of the actin cytoskeleton are assembled from a limited set of molecular building blocks. Here we study the spontaneous self-assembly of a minimal model of cytoskeletal materials, consisting of semiflexible actin filaments, crosslinkers, and molecular motors. Using coarse-grained simulations, we demonstrate that by changing concentrations and kinetics of crosslinkers and motors we can generate three distinct structural phases of actomyosin assemblies: bundled, polarity-sorted, and contracted. We introduce new metrics to distinguish these structural phases and demonstrate their functional roles. We find that the binding kinetics of motors and crosslinkers can be tuned to optimize contractile force generation, motor transport, and mechanical response. By quantitatively characterizing the relationships between modes of cytoskeletal self-assembly, the resulting structures, and their functional consequences, our work suggests new principles for the design of active materials.