Fig. 9. Inhibition of laminin-induced complex AChR clustering by RhoN19. (A) To determine whether laminin-induced complex AChR cluster formation is dependent on activation of the Rho GTPases, as are soluble laminin-induced AChR clusters, C2 myotubes transfected with GFP-tagged RhoN19 were replated on laminin-coated coverslips. Cultures were surface-labeled with TMR-Bgt and examined at day 4 post-replating by confocal microscopy. Myotubes expressing RhoN19 (a) did not display AChR clusters (b) compared with nontransfected adjacent cells that formed complex clusters. (B) Quantitative comparison of the number of AChR clusters on the surface of transfected myotubes expressing the Rho mutant (hatched bars) versus control myotubes (black bars) clearly documents the inhibiting effect of the dominant interfering RhoN19 on complex AChR cluster formation in response to substrate laminin at all stages of development (error bars represent ±s.e.m.; n=40 cells from five separate platings).