300–500 cells were counted and percent BrdU incorporation was calculated as the total BrdU positive cells divided by the total NESTIN positive cells in a field. Statistical significance was calculated using ANOVA. CHIR-99021 effects on proliferation were measured in parallel cell cultures and were treated with DMSO (vehicle) and CHIR-99021 (custom synthesized as for Pan et al.41) at a final concentration of 5 µM for 16 hours before BrdU labeling.
