Figure 5. Photoactivation of dominant negative PA-Rac reduces protrusion dynamics.

(a) Quantification of mean lamellipodial area (grey area) and mean filopodial length (black line) over time, prior to photoactivation (t0) and after each consecutive round of photoactivation (t1–t9) in cells expressing the dominant negative form of PA-Rac. The size of both does not significantly change upon photoactivation (t0, before photoactivation, is compared to each of the nine rounds of photoactivation t1–t9, using Student's t-test, n=10 lamellipodia, n=32 filopodia). (b) Mean extension and retraction rates of filopodia from cells expressing a dominant negative form of PA-Rac (n=31 filopodia) before, during and after photoactivation. (c) Mean extension and retraction rates of filopodia from cells expressing a photo-insensitive (PI, n=66 filopodia), a dominant negative (DN, n=34 filopodia) and a constitutively active (CA, n=88 filopodia) form of PA-Rac during photoactivation. Error bars represent s.e.m. Student's t-test was performed to determine statistical significance and P values are shown on graph. P>0.5 was considered not significant, *P<0.05, **P<0.01, ***P<0.001, ****P<0.0001.