Fig. 5. Dominant interfering Rho inhibits the ability of laminin to cluster AChR. (A) In order to assess the contribution of Rho activation to laminin-induced AChR clustering, differentiated muscle cells were microinjected with RhoN19 or vector. After microinjection, the cells were treated with laminin (10 nM) overnight. One day after injection, the effects of AChR surface distribution in RhoN19-expressing (c,d) versus vector-expressing cells (a,b) treated with laminin were examined by confocal microscopy of cultures surface-labeled with TMR-Bgt. Those myotubes injected with RhoN19 were identified with co-injected FITC-goat anti-mouse antibody (a,c). Myotubes expressing RhoN19 did not display full-sized AChR clusters after treatment with laminin (d), compared with those myotubes injected with vector only (b). Scale bar, 10 µm. (B) Quantitative comparison of the number of AChR clusters on the surface of myotubes expressing the Rho mutant versus control myotubes clearly documents the inhibiting effect of the dominant interfering RhoN19 on AChR cluster (black bars) and microcluster (grey bars) formation in response to laminin (10 nM) treatment (error bars represent ±s.e.m.; n=40 cells from five or more separate platings).