Motor-driven advection competes with crowding to drive spatiotemporally heterogeneous transport in cytoskeleton composites

TL;DR

This study investigates how motor-driven advection and crowding influence complex transport behaviors in cytoskeleton composites, revealing multi-mode dynamics and the impact of actomyosin content on particle movement.

Contribution

It combines advanced microscopy techniques to characterize multi-scale transport phenomena in active cytoskeletal networks, highlighting the interplay between advection, crowding, and heterogeneity.

Findings

Particles show transition from subdiffusion to superdiffusion at tunable timescales.

Higher actomyosin content increases superdiffusivity but also enhances short-time subdiffusion.

Transport behaviors include non-Gaussian, asymmetric displacement distributions with directed advection.

Abstract

The cytoskeleton -- a composite network of biopolymers, molecular motors, and associated binding proteins -- is a paradigmatic example of active matter. Particle transport through the cytoskeleton can range from anomalous and heterogeneous subdiffusion to superdiffusion and advection. Yet, recapitulating and understanding these properties -- ubiquitous to the cytoskeleton and other out-of-equilibrium soft matter systems -- remains challenging. Here, we combine light sheet microscopy with differential dynamic microscopy and single-particle tracking to elucidate anomalous and advective transport in actomyosin-microtubule composites. We show that particles exhibit multi-mode transport that transitions from pronounced subdiffusion to superdiffusion at tunable crossover timescales. Surprisingly, while higher actomyosin content enhances superdiffusivity, it also markedly increases the degree of subdiffusion at short timescales and generally slows transport. Corresponding displacement distributions display unique combinations of non-Gaussianity, asymmetry, and non-zero modes, indicative of directed advection coupled with caged diffusion and hopping. At larger spatiotemporal scales, particles undergo superdiffusion which generally increases with actomyosin content, in contrast to normal, yet faster, diffusion without actomyosin. Our specific results shed important new light on the interplay between non-equilibrium processes, crowding and heterogeneity in active cytoskeletal systems. More generally, our approach is broadly applicable to active matter systems to elucidate transport and dynamics across scales.