Particle-tracking reveals heterogeneous subdiffusion in in vitro cytoskeleton composites
Date:
Excerpt of abstract: The diffusion of microscopic particles through the cell, important to processes such as transcription, viral infection, transfection and gene delivery, is largely controlled by the complex cytoskeletal network that pervades the cytoplasm. The cytoskeleton is predominantly made up of thin semiflexible actin filaments and thicker, more rigid microtubules, as well as binding proteins that can crosslink each filament. By varying the relative concentrations of actin and microtubules, as well as the degree to which each filament is crosslinked, the cytoskeleton can display a host of different structural and dynamic properties that in turn impact the diffusion of particles through the network. Here we use single particle tracking methods to quantify the mean-squared displacements of microspheres diffusing in custom-designed in vitro composites of actin and microtubules. We show that particles exhibit subdiffusion, with scaling exponents and transport coefficients that decrease as the relative fraction of actin in composites increases. By evaluating the distributions of bead displacements, we also find that composites induce unique non-gaussian diffusion characteristics and substantial heterogeneities in particle trajectories.