Silencing of SRF affects PM blebbing. (A) Cartoon illustrating the induction of PM blebbing and entotic invasion by plating cells on poly-HEMA–coated surfaces to prevent cellular attachment. (B) Western blot confirming efficient siRNA-mediated knockdown of SRF in MCF10A cells stably expressing GFP. Tubulin served as a loading control. (C) Live MCF10A cells stably expressing GFP were plated on poly-HEMA and imaged over time to visualize the dynamics of PM blebbing. Cells were treated with either control or siRNA directed against SRF as indicated. Boxes indicate areas that are shown magnified over time to highlight outgrowth and retraction of individual blebs (asterisks). Time is indicated in seconds. Bars: (overview) 5 µm; (magnifications) 2 µm. (D) Quantification of maximum bleb expansion in cells stably expressing GFP. Cells were treated with the indicated siRNAs, and the maximum length reached by individual blebs was compared. (E) MCF10A cells stably expressing GFP were treated with siRNA as indicated to measure the time for expansion and retraction of individual blebs. Note a significant and specific difference in the bleb retraction times resulting in an overall prolonged bleb cycle in SRF-silenced cells. (D and E) ≥60 blebs and 15 cells per condition. Error bars indicate SD. Asterisks indicate statistical significance (****, P ≤ 0.0001). ns indicates no significance (P > 0.05).