MIIB activation by MLC-DD generates a cellular trailing edge. (A) Representative images of B16 cells expressing GFP-MIIB, MLC-DD-GFP, MLC-WT-mChe + GFP-MIIB, or MLC-DD-mChe + GFP-MIIB. Bar, 10 μm. Note the formation of a robust tail in the cell expressing MLC-DD-mChe + GFP-MIIB. Video 2 accompanies this figure and represents a cell expressing MLC-DD-mChe. Note the anterior distribution of MLC-DD. (B) Quantification of the phenotypes described in A. Percentage of cells displaying the indicated morphology. Morphologies were defined as follows: “not polarized” are cells with a P.I <1.5; “crescent” are cells morphologically similar to those shown in Fig. 4 A (MIIB or MLC-DD top panels), showing a PI <1.5 and a flat or nonextended rear; “tailed” are cells with a P.I >1.5 and that show an extended rear or tail similar to the one shown in Fig. 4 A (bottom panels). Data are the mean ± SD of >300 cells per condition in two independent experiments. *, Student's t test of MLC-DD+MIIB vs. untransfected/MIIB alone.