Getting in shape and swimming: the role of cortical forces and membrane heterogeneity in eukaryotic cells

TL;DR

This paper investigates how cortical forces and membrane heterogeneity influence cell shape and motility, focusing on tension gradients that enable swimming without cyclic shape changes, and analyzes their effects on cell movement and efficiency.

Contribution

It introduces a model of cell swimming driven by membrane tension gradients without cyclic shape changes, exploring the influence of membrane heterogeneity and fluid interactions.

Findings

Membrane tension gradients can induce diverse cell shapes.

Tension and bending modulus distributions determine movement direction.

Cell motility efficiency depends on fluid properties and membrane heterogeneity.

Abstract

Recent research has shown that motile cells can adapt their mode of propulsion to the mechanical properties of the environment in which they find themselves--crawling in some environments while swimming in others. The latter can involve movement by blebbing or other cyclic shape changes, and both highlysimplified and more realistic models of these modes have been studied previously. Herein we study swimming that is driven by membrane tension gradients that arise from flows in the actin cortex underlying the membrane, and does not involve imposed cyclic shape changes. Such gradients can lead to a number of different characteristic cell shapes, and our first objective is to understand how different distributions of membrane tension influence the shape of cells in an inviscid quiescent fluid. We then analyze the effects of spatial variation in other membrane properties, and how they interact with tension gradients to determine the shape. We also study the effect of fluid--cell interactions and show how tension leads to cell movement, how the balance between tension gradients and a variable bending modulus determine the shape and direction of movement, and how the efficiency of movement depends on the properties of the fluid and the distribution of tension and bending modulus in the membrane.