Figure 6.

A subpopulation of postmitotic oligodendrocytes undergoes apoptosis. A, Reduction in oligodendrocyte differentiation in the p75–ErbB1 ^KD mice. Sagittal brain sections were stained for O1 at different developmental stages. O1 staining was reduced in the white-matter tracts of the cerebellum in the transgenic mice compared with NTG at every developmental stage analyzed. A similar pattern was also observed with CNPase staining (data not shown). Scale bar, 20 μm. B, Reduction in the number of mature oligodendrocytes in the p75–ErbB1 ^KD mice. Quantification of CC1 ⁺ cells was done from the white-matter tract of the cerebellum using P25 mice (n = 3). Error bars indicate SEM. C, An increase in BrdU incorporation in the p75–ErbB1 ^KD. Sagittal brain sections were stained with anti-BrdU. BrdU staining was increased in the white-matter tracts of the cerebellum in the p75–ErbB1 ^KD mice compared with NTG at every developmental stage analyzed. Scale bar, 20 μm. D, Quantification of BrdU ⁺ cells in the cerebellar white-matter tract during development. Error bars indicate SEM. E, Increased proliferation of NG2 ⁺ cells in the transgenic mice. The P5 brain sections were stained for NG2 and PCNA. Note the increase in the number of NG2 ⁺/PCNA ⁺ cells in the white-matter tracts in the cerebellum (arrows). Scale bar, 12.5 μm.