Figure 5.

Locally pulsatile Cdc42 activity in the absence of actin polymerization argue for the existence of an excitable network. (a) Examples of locally pulsatile Cdc42 activity revealed by treating cells with LatA (1μM). Cdc42 activity is indicated by the color scale. White dots mark the location of maximum Cdc42 activity. The images were taken every 2 seconds for 120 seconds. Scale bar is 10μm. (b) Kymographs of Cdc42 activity for a cell 1 in Figure 5a treated with LatA (1μM), showing different time scales. The Cdc42 activity was averaged over the vertical (y-axis) direction to get a one dimensional profile for each timepoint. For this analysis, images were taken at 2 second intervals. Cdc42 activity is indicated by the color scale. (c) Kymograph of a line scan Cdc42 activity in a LatA (1μM)-treated cell. For this analysis, images were taken every 5 seconds for 420 seconds. Cdc42 activity is indicated by the color scale. (d) Quantitative measurements of local Cdc42 activity in LatA (1μM)-treated cells. Shown is a temporal trace for a selected 5 μm square region within an individual cells. For this analysis, images were taken every 5 seconds for 420 seconds. (e) Temporal profile of peaks of Cdc42 activity in LatA (1μM)-treated cells. Peaks of Cdc42 activity were automatically detected from timecourses of activity in 6 μm square regions within cells. The peaks were aligned at their maxima and then averaged. For this analysis, images were taken at 2 second intervals. Error bars indicate ± s.e.m. of n=66 cells. (f) Spatial autocorrelation of Cdc42 activity in LatA (1μM)-treated cells. For this analysis, images were taken at 2 second intervals. Error bars indicate ± s.e.m. of n=85 cells. (g) Histogram of instantaneous speeds of Cdc42 waves. n=107 cells. For this analysis, images were taken at 2 second intervals.