Activity induces traveling waves, vortices and spatiotemporal chaos in a model actomyosin layer

Abstract

Inspired by the actomyosin cortex in biological cells, we investigate the spatiotemporal dynamics of a model describing a contractile active polar fluid sandwiched between two external media. The external media impose frictional forces at the interface with the active fluid. The fluid is driven by a spatially-homogeneous activity measuring the strength of the active stress that is generated by processes consuming a chemical fuel. We observe that as the activity is increased over two orders of magnitude the active polar fluid first shows spontaneous flow transition followed by transition to oscillatory dynamics with traveling waves and traveling vortices in the flow field. In the flow-tumbling regime, the active polar fluid also shows transition to spatiotemporal chaos at sufficiently large activities. These results demonstrate that level of activity alone can be used to tune the operating point of actomyosin layers with qualitatively different spatiotemporal dynamics.

Coherent motion of dense active matter

“…3d). Similar behaviour has been observed for contractile polar fluids modeling actomyosin cortex flow within free-slip boundaries representing cytosol and membrane [37] and also in kinetic mean-field simulations [26]. However, rather more surprisingly, here the vortices are accompanied by a dynamically ordered array of topological defects.…”

Computational modeling of active deformable membranes embedded in three-dimensional flows

“…This movement induces active stresses in the cell cortex [2][3][4][5][6][7] which are transmitted via anchor proteins to the plasma membrane separating the interior of the cell from its surroundings. Active stresses have an inherent non-equilibrium character and are the basis of physically unique processes in active fluid layers such as instabilities [8,9], the emergence of spontaneous flows [10] or the creation of geometrical structures [11,12]. They are furthermore responsible for large shape deformations during cell morphogenesis [13][14][15], cell division [16][17][18][19][20][21], cell locomotion [22][23][24][25][26], cell rheology [27,28] or spike formation on artificial vesicles [29].…”

Emergence of epithelial cell density waves

“…We checked that these additional terms, while making the model more complex, do not change our qualitative conclusions: activity-driven traveling waves occur in large regions of the parameter space that govern active polar media (see also [31,34]). As an example motivated by [23], we add to our minimal model the β a p 2 term in (19), and show in Fig.…”