Early myelin abnormalities but mild microgliosis in cerebellum. (A-F) Immunohistochemistry was performed to visualize microglia (F4/80, green), damaged axons (SMI32, red) and myelin (MBP, blue). Compared to the control mice (A) several fibers in the cerebellar folia of the Nestin-Pex5
−/− already lack myelin at two weeks (B), which was even more pronounced at three weeks (C-D) and six weeks (E-F). SMI32 positive axons, indicative of degeneration, were observed at six weeks (F). (G-I) Axonal loss was analyzed by the use of an antibody recognizing healthy phosphorylated axons (SMI31). Decreased SMI31 immunoreactivity was observed at six (H) and 12 weeks (I), in comparison with the control littermates (G). In addition, several axonal swellings were present (H-I, arrows). (J-L) Astrocytes were visualized by anti-GFAP, which revealed higher immunoreactivity at three weeks in white matter of the folia, but also in the molecular layer (K). At 12 weeks astrocyte proliferation and activation was even more pronounced (L). (M) Double labeling of myelin (MBP, blue) and activated/phagocytotic microglia with MAC-3 (green) in the cerebellum of a nine-week-old Nestin-Pex5
−/− mouse. (N-O) An antibody specific for potassium channels (K+) was used for the investigation of paranodal structures. Cerebellar axons displayed an abnormal distribution of potassium channels (O, arrows), as compared to the strict juxtaparanodal localization in the control (N). All panels of each row were stained with the same antibodies. Scale bars: A-M: 100 μm; N-O: 10 μm. GFAP: glial fibrillary acidic protein, K
: potassium, MAC: macrophage, MBP: myelin basic protein, SMI: Sternberger Monoclonals Inc.