WASp^I294T 300.19 cells form dysmorphic microvilli. (A) SEM micrographs of WASp^WT and WASp^I294T 300.19 cells. Enlarged sections of the same cells are shown in the bottom panels, with dysmorphic microvilli visible in WASp^I294T cells (arrowheads). Scale bars represent 1 μm. Images were acquired viewing in a JEOL 6700F FESEM, captured using JEOL software and analyzed with Adobe Photoshop (crop, image size, and brightness/contrast functions only). (B) Cells were blindly scored by 2 independent reseachers for presence of normal fingerlike or dysmorphic broad microvilli. The quantification for at least 50 cells from each condition is shown. WASp^I294T cells showed a significantly increased percentage of cells predominantly forming dysmorphic structures and a significantly reduced percentage of cells with a predominance of fingerlike microvilli (P < .05 for both; Fisher exact 1-tailed test). (C) Anti–p-ERM Western blotting of extracts derived from 300.19 cells expressing EGFP (SEW), WASp^WT, or WASp reveals that overall ERM activity remains unaltered between the cell types. Top panel represents Western blot of p-ERM; bottom panel, total ERM staining to monitor equal loading between samples. Immunoblots are representative of 3 independent experiments.