Swirling Instability of the Microtubule Cytoskeleton

TL;DR

This paper investigates how fluid-structure interactions in the microtubule cytoskeleton lead to a swirling instability, causing large-scale vortical flows during cellular processes like cytoplasmic streaming.

Contribution

It introduces a discrete-filament model and a continuum theory demonstrating a swirling instability driven by motor-induced deformations of microtubules.

Findings

Identification of a swirling instability mechanism

Models reproduce observed cell-spanning vortical flows

Transition from disordered to ordered cytoskeletal states

Abstract

In the cellular phenomena of cytoplasmic streaming, molecular motors carrying cargo along a network of microtubules entrain the surrounding fluid. The piconewton forces produced by individual motors are sufficient to deform long microtubules, as are the collective fluid flows generated by many moving motors. Studies of streaming during oocyte development in the fruit fly $D.~melanogaster$ have shown a transition from a spatially-disordered cytoskeleton, supporting flows with only short-ranged correlations, to an ordered state with a cell-spanning vortical flow. To test the hypothesis that this transition is driven by fluid-structure interactions we study a discrete-filament model and a coarse-grained continuum theory for motors moving on a deformable cytoskeleton, both of which are shown to exhibit a $swirling~instability$ to spontaneous large-scale rotational motion, as observed.