Fig. 4. Actin reorganization and altered morphology of NIH 3T3 cells overexpressing the RBD. (A-C) Cells transfected with EGFP-63-448mDia1. (A,B) Double fluorescence analysis showing EGFP fluorescence (A) and F-actin (B). (C) Nomarski optics. The mDia1-fragment-expressing cells are flatter, lack stress fibers and display prominent ruffles (arrowheads). Bar: 10 µm. Insets are enlargements of the area marked by the arrowhead. (D) Catalogue of the fragments (expressed as fusion proteins with EGFP) tested with respect to loss of stress fibers and ruffling activity. Note that the exogenous, isolated RBD induces loss of stress fibers, while ruffling also requires the presence of either the N-terminal extension or the complete FH3 domain.