Early progenitors were grown in the absence (Cont) or presence of rapamycin from 0 to 5 days and analyzed by double immunolabeling for O1, and CNP (A,B) or O1 and MBP (C,D). Quantification of the percentage of O1+ cells that co-express CNP (B) or MBP (D) shows that while there was no effect of mTOR inhibition on the transition of O1+ immature OLs to CNP+ immature OLs, their progression to MBP+ mature OLs was significantly inhibited. Error bars, SEM, N=4 independent cultures in duplicates. Scale bars, 50 um.