Spatiotemporal Analysis of Actin Ruffling Dynamics in Living Cells

Mechanisms controlling actin polymerization at cell edges remain unclear. To measure the spatiotemporal distribution of edge ruffling, time-lapse optical images of cells expressing fluorescent actin were acquired during a step increase in fluid shear stress and were segmented using an active contour algorithm. Intensity profiles directed normal to the cell boundary were computed, and the spatial distribution of actin features within 1 mum of the cell edge were identified by peak detection. Features associated with filopodia and peripheral stress fibers were removed. These results suggest that cells regulate actin dynamics spatially in response to mechanical stimuli to guide the establishment of directional cell polarity.