Figure 6.

Effects of reduced NG2 expression on neurite growth. A, Purified proliferating NG2 cells were cotransfected with plasmids containing NG2_7217hp and pCA-gapgfpm4 and immunolabeled for NG2 (red) 4 d later. GFP+ cells (green) have little (arrowhead) or no detectable NG2 (arrows), whereas GFP-negative untransfected cells expressed NG2. B, Purified proliferating NG2 cells transfected with NG2_7217hp plasmid and double labeled for NG2 (red) and PDGFRα (green) 4 d later. Cells that have little or no NG2 express PDGFRα (arrows). Scale bar: (in B) A, B, 24 μm. C, D, Quantification of neurites from P1 hippocampal neurons grown for 16 h on PLL, untransfected NG2 cells and on NG2 cells transfected with NG2_7217hp (si_7217) or NG2_7292hp (si_7292) and double labeled for NG2 and βIII-tubulin. C, Percentage of βIII-tubulin+ hippocampal neurite tips contacting untransfected NG2 cells (control) or NG2 cells transfected with either NG2_7217hp siRNA (si_7217) or NG2_7292hp siRNA (si_7292). There was no statistically significant difference between the percentage of neurite tips contacting control NG2 cells and those contacting siRNA-transfected NG2 cells (P = 0.29, Student's t test). D, Lengths of βIII-tubulin+ hippocampal neurites per neuron grown on uninfected NG2 cells (control) or on siRNA-transfected NG2 cells or directly on PLL. There was no statistical difference between the lengths of neurites from neurons grown on control NG2 cells and those on siRNA-transfected NG2 cells. Neurites on transfected and untransfected NG2 cells were both longer than neurites grown on PLL (P < 0.01, one-way ANOVA with Tukey's post test). For neurons seeded on siRNA-transfected NG2 cells, only neurons grown on NG2 cells expressing reduced levels of NG2 were included for analysis. Error bars indicate SE.