Dock1 and Elmo2 regulate actin dynamics at cell–cell contacts. (A) Cells treated with the indicated siRNAs were fixed 1 h after plating on collagen and imaged by epifluorescence for Dock1 and actin distributions. Yellow arrowheads indicate the boundary of the cell–cell contact. (B) Quantification of Dock1 and actin fluorescence intensities in a 1-pixel-wide line along four cell contacts. A.U., arbitrary unit. (C) Montage of images from a video of live cells expressing E-cadherin–GFP and LifeAct-RFP and treated with scramble or Elmo2 siRNAs. Yellow arrows indicate the boundary of the cell–cell contact. (D) Representative kymographs of membrane protrusions in cells treated scramble or Elmo2 siRNAs. 2-pixel-wide kymographs were compiled over 10 min. (E) Number of protrusions over a 10-min interval (left) and mean protrusion velocity (right) were measured in cells expressing scramble or Elmo2 siRNA. 10 cells with 33 protrusions (siRNA scramble) and 10 cells with 37 protrusions (siRNA Elmo2) were quantified. Results are presented in a box and whisker format, in which the ends of the box mark the upper and lower quartiles, the horizontal line in the box indicates the median, and the whiskers outside the box extend to the highest and lowest value within 1.5× the interquartile range. Outliers are indicated by dots. Bars, 5 µm.