Symmetry breaking in reconstituted actin cortices.

Enas Abu Shah,Kinneret Keren

doi:10.7554/elife.01433

Abstract

The actin cortex plays a pivotal role in cell division, in generating and maintaining cell polarity and in motility. In all these contexts, the cortical network has to break symmetry to generate polar cytoskeletal dynamics. Despite extensive research, the mechanisms responsible for regulating cortical dynamics in vivo and inducing symmetry breaking are still unclear. Here we introduce a reconstituted system that self-organizes into dynamic actin cortices at the inner interface of water-in-oil emulsions. This artificial system undergoes spontaneous symmetry breaking, driven by myosin-induced cortical actin flows, which appears remarkably similar to the initial polarization of the embryo in many species. Our in vitro model system recapitulates the rich dynamics of actin cortices in vivo, revealing the basic biophysical and biochemical requirements for cortex formation and symmetry breaking. Moreover, this synthetic system paves the way for further exploration of artificial cells towards the realization of minimal model systems that can move and divide.DOI: http://dx.doi.org/10.7554/eLife.01433.001.

Highlights

The actin cytoskeleton plays a central role in many cellular processes including polarization, cell shape determination, intracellular transport, cell division and movement (Pollard and Cooper, 2009)
The formation of artificial actin cortices was induced by localizing the ActA protein from the pathogenic bacteria L. monocytogenes to the inner interface of water-in-oil emulsions (Figure 1)
A soluble ActA construct was purified from L. monocytogenes and conjugated to a fluorescent hydrophobic linker made with Bodipy-FL, to generate an amphiphilic complex (‘Materials and methods’)

Summary

Introduction

The actin cytoskeleton plays a central role in many cellular processes including polarization, cell shape determination, intracellular transport, cell division and movement (Pollard and Cooper, 2009). The structure and function of the cytoskeleton arise from the self-organized dynamics of numerous molecular building blocks. This self-organization spans several orders of magnitude in space and time and involves a complex interplay between biochemical and biophysical processes; A myriad of proteins interact with the actin cytoskeleton and influence its behavior, in a manner that is dependent on the global mechanical properties of the network but at the same time determines it (Lecuit and Lenne, 2007; Pollard and Cooper, 2009; Mullins and Hansen, 2013). We are still far from understanding the complexity of cytoskeletal dynamics in vivo, and recapitulating even basic cellular phenomena such as polarization, division and directed movement in synthetic systems remains an outstanding challenge

Methods

Results

Conclusion