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. 2020 May 18;143(5):1383–1399. doi: 10.1093/brain/awaa080

Figure 3.

Figure 3

Evidence for dysmyelination, demyelination and axon degeneration in PMD. (A and B) Cervical and lumbar cord (Patient 1) stained for MBP. While the majority of white matter is stained strongly, symmetrical areas of pallor are present in the central posterior columns (short arrows) and the periphery of the lateral columns (arrows) in A and in the posterior columns (short arrows) in B. Scale bars = 2 mm. (C and D) Sections from control for comparison. Scale bars = 2 mm. (E and F) Regions of the fasciculus gracilis (F. gracilis) and peripheral fasciculus cuneatus (F. cuneatus) double immunostained for MBP (green) and phosphorylated heavy chain neurofilament (NF, red). (G and H) Sections from control for comparison. Scale bars = 50 µm. There are a reduced number of fibres in the F. gracilis and many axons have no myelin sheath. In the F. cuneatus the majority of axons have a myelin sheath. (I) Resin section from periphery of lateral columns. There is a marked reduction in myelinated nerve fibres and replacement by astrocytic processes. A swollen axon (large arrow) and axons with thin myelin sheaths (small arrow) are present. Scale bar = 10 μm. (J) Electron micrograph from one of the areas of MBP pallor. Myelinated fibres are reduced and astrocyte processes are increased. One axon (A1) has a myelin sheath of normal thickness; another (A2) has a thin sheath; a third (A3) has no myelin sheath. Scale bar = 1 μm. Inset: Regular structure of major dense and intraperiod lines. Scale bar = 0.05 μm. (K and L) PMD and control optic nerves, immunostained for MBP. Strong, generalized staining is present in both. Scale bars = 1 mm. (M) Area from PMD cerebellum immunostained for MBP. The white matter is relatively well stained in the central part of the folium, tending to decrease in the branches. Two regions of more reduced MBP staining are present (arrows). Scale bar = 1 mm. (N) Area from cerebellum from control for comparison. Scale bar = 1 mm. (O and P) Cerebellar white matter from folia stained by double immunofluorescence for MBP (green) and NF (red). In O, only a minority of axons are lacking myelin whereas in P, an area of naked axons is present on the left with an island of myelin in the centre. Scale bars = 50 μm. (Q) Higher magnification image. Few axons have an intact myelin sheath and the myelin is present as globules, suggesting demyelination. Scale bar = 20 μm. (R) Cerebellar white matter from control for comparison with O and P. Scale bar = 50 μm. (S and T) Resin sections of the PMD corpus callosum. There is a considerable loss of myelinated axons (asterisks) with replacement by astrocytic processes. Scale bars = 10 μm.