Fig. 2. BMP4 prompts, whereas LIF reduces, exit of GFAP⁺ cells from the cell cycle. Neurosphere cells were plated and allowed to differentiate with or without cytokines for 6 days, followed by 16 hours of labeling with BrdU. (A,F) Only a small percentage of GFAP⁺ cells (green) incorporate BrdU (red). (B,F) Treatment with noggin to inhibit endogenous BMP signaling enhances BrdU incorporation. (C,D,F) Treatment with LIF alone does not significantly alter BrdU incorporation. However, LIF treatment in the presence of noggin greatly increases BrdU incorporation compared with treatment with noggin alone. (E,F) BMP4 treatment virtually abolishes BrdU incorporation. (F) Quantitation of the percentage of GFAP⁺ cells that incorporate BrdU. ^*P<0.01, ^**P<0.001 ANOVA. Scale bars: 20 µm in A-E.