Giant fluctuations and structural effects in a flocking epithelium

TL;DR

This study investigates how reactivating motility in epithelial cell monolayers via RAB5A overexpression induces flocking behavior, large-scale fluctuations, and structural fluidization, revealing the role of active self-propulsion and alignment mechanisms.

Contribution

It demonstrates that RAB5A-induced flocking causes large-scale fluctuations and structural changes, linking cellular activity to collective behavior in epithelial layers.

Findings

Reactivation of motility leads to flocking and large-scale fluctuations.

The monolayer becomes fluidized at the single-cell level.

Numerical simulations attribute fluctuations to active self-propulsion and alignment.

Abstract

Epithelial cells cultured in a monolayer are very motile in isolation but reach a near-jammed state when mitotic division increases their number above a critical threshold. We have recently shown that a monolayer can be reawakened by over-expression of a single protein, RAB5A, a master regulator of endocytosis. This reawakening of motility was explained in term of a flocking transition that promotes the emergence of a large-scale collective migratory pattern. Here we focus on the impact of this reawakening on the structural properties of the monolayer. We find that the unjammed monolayer is characterised by a fluidisation at the single cell level and by enhanced non-equilibrium large-scale number fluctuations at a larger length scale. Also with the help of numerical simulations, we trace back the origin of these fluctuations to the self-propelled active nature of the constituents and to the existence of a local alignment mechanism, leading to the spontaneous breaking of the orientational symmetry.