Reconstitution of cortical actin networks within water-in-oil emulsions.

We describe the reconstitution of dynamic cortical actin networks within cell-like compartments. The approach is based on encapsulation of Xenopus egg extract within water-in-oil emulsions. The growth of cortical actin networks is catalyzed by an amphiphilic actin nucleation-promoting factor that localizes to the water/oil interface. We first describe the preparation of cell-free Xenopus egg extract that provides all the soluble components of the actin machinery. We then describe the preparation of the amphiphilic, fluorescent actin nucleation-promoting factor that directs actin polymerization to the interface. Finally, we describe the steps required for assembly of dynamic actin cortices within water-in-oil emulsions, including the emulsification process and the sample preparation procedures. We provide recommendations for handling sensitive system components and discuss potential uses of this reconstitution approach for cytoskeletal research.