Actin filament polymerization: Modeling of elongation kinetics based on analysis of TIRFM images

Actin proteins spontaneously assemble into long polymers to build networks and bundles of filaments that are used by cells to move and change shape.  An experimental method to study the kinetics of single actin filament growth in vitro is total internal reflection microscopy (TIRFM).  In TIRFM experiments, fluorescently-labeled actin filaments grow parallel to a glass slide by addition of monomers from a bulk solution. The kinetics of actin filament growth is captured in hundreds of microscopic images that record the nucleation and elongation of tens of individual actin filaments simultaneously.

 

Our team develops automated image analysis methods for measuring actin filament length versus time in TIRFM images of actin polymerization.  In this way, we can systematically calculate the two basic parameters of actin polymerization kinetics: rate of filament elongation, and fluctuations in the average rate.  The information is used to develop computational and mathematical models that describe the dependence of actin filament elongation rate and fluctuations on the concentration of actin and cofactors.  In this way, we can study and understand the mechanisms that cells use to regulate the dynamics of the actin cytoskeleton.