Fig. 3. PC12 cells transfected with dominant negative RhoA extend neurites on MAG substrates. a,b, Mock-transfected cells (a) do not extend neurites on MAG, whereas N19TRhoA cells (b) were able to spread and extend neurites on MAG substrates. Scale bar, 80 μm. c, ADP-ribosylation of Rho proteins in PC12 cell membranes reveal that PC12 cells express RhoA, RhoB, and RhoC. d, Quantitative comparison of the percentage of mock-transfected (open bars) or N19TRhoA (filled bars) cells that grow neurites on different test substrates. The number of cells that grow neurites (top) was significantly different from N19TRhoA cells plated on MAG. c, ADP-ribosylation of Rho proteins in PC12 cell membranes. Isolation of crude plasma membrane, ADP-ribosylation, and two-dimensional gel electrophoresis was performed as described previously (Santos et al., 1997). RhoA, RhoB, RhoC, and an unidentified protein are ADP-ribosylated.