Cytosolic flow induced symmetry breaking in a conceptual polarity model

TL;DR

This study investigates how cytosolic flow influences cell polarity patterns, revealing that flow can induce symmetry breaking, pattern propagation, and qualitative changes in protein distribution, with implications for understanding cellular processes.

Contribution

The paper introduces a minimal mass-conserving model demonstrating how cytosolic flow affects protein pattern formation and symmetry breaking in cell polarity.

Findings

Membrane-bound patterns propagate against cytoplasmic flow.

Flow speed influences pattern propagation speed.

Flow can qualitatively change membrane patterns.

Abstract

Important cellular processes, such as cell motility and cell division, are coordinated by cell polarity, which is determined by the non-uniform distribution of certain proteins. Such protein patterns form via an interplay of protein reactions and protein transport. Since Turing's seminal work, the formation of protein patterns resulting from the interplay between reactions and diffusive transport has been widely studied. Over the last few years, increasing evidence shows that also advective transport, resulting from cytosolic and cortical flows, is present in many cells. However, it remains unclear how and whether these flows contribute to protein-pattern formation. To address this question, we use a minimal model that conserves the total protein mass to characterize the effects of cytosolic flow on pattern formation. Combining a linear stability analysis with numerical simulations, we find that membrane-bound protein patterns propagate against the direction of cytoplasmic flow with a speed that is maximal for intermediate flow speed. We show that the mechanism underlying this pattern propagation relies on a higher protein influx on the upstream side of the pattern compared to the downstream side. Furthermore, we find that cytosolic flow can change the membrane pattern qualitatively from a peak pattern to a mesa pattern. Finally, our study shows that a non-uniform flow profile can induce pattern formation by triggering a regional lateral instability.