Actin network self-assembly




Micropatterning techniques can be used to graft locally actin nucleators such as pWA.








The addition of the minimum set of purified components that are necessary for actin polymerization can be used to induce filament growth out of the micropattern.
See the associated paper for more details (Reymann et al, Nature Materials, 2010)




Various network architectures are formed in response to specific geometries of actin nucleation sites:








See the associated paper for more detailed description of networks assembly and architecture (Reymann et al, Nature Materials, 2010).





The analysis of these networks MANY informations about the rules governing actin network architectures. One of them is the rule regulating the parallel versus anti-parallel association of filaments into bundles. Parallel associations are found in filopodia and centripetal fibers. Anti-parallel associations are found in transverse arc (or circumferential bundles) and stress fibers.











Filament growth and interaction on star-shaped provides very interesting information about this parallel versus anti-parallel assembly. Filament form anti-parallel bundles in the proximal part of the structure and parallel bundles in the distal part. This could be fully described by a simple physical model based on a first probabilistic event followed by a cooperative assembly of filament. See (Reymann et al, Nature Materials, 2010).








 





This video, taken in TRIF microscopy, shows the lateral vibrations of filaments as they grow toward each others and the fact that once two of them change their orientation and form parallel association all the others followed the same orientation. Thus there is a brutal transition between parallel and anti-parallel filament association.











The distance between the nucleation regions will also affect the shape of the central bundle:















This can be nicely confirmed by overlaying and averaging several of these structures:















See the associated paper for more details (Reymann et al, Nature Materials, 2010)


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