Figure 7: Lck^−/− mice exhibit abnormal myelin folding.

(a) Time course analysis of sciatic nerves. Sciatic nerve cross-sections of WT (left panels top to bottom) and Lck^−/− (right panels top to bottom) mice. The morphology of myelin was compared at the age of 14 days (upper two panels), 2 months (second row of panels), 4 months (third row) and 7 months (last row). Two animals were analysed per age and phenotype, and representative pictures are shown. Examples of affected axons with aberrant myelin loops in Lck^−/− mice are marked with arrowheads. Scale bar for all panels: 25 μm. (b) Quantification of aberrant myelin loops during the time course (14 days–7 months). For each time interval the sciatic nerves from two mice were isolated and semithin sections were quantified. The number of affected myelin fibres increases with age in Lck^−/− mice. The results are presented as average±s.d. and statistical significance is denoted as *P<0.05. (c) Electron microscopic analysis of sciatic nerves from Lck^−/− mice shows abnormal myelin outfoldings (upper left panel) and infoldings (upper right) in large-diameter axons (marked by arrowheads). Longitudinal electron microscope sections show aberrant myelin loops at the paranodal region of Lck^−/− mice (bottom panels). Myelin loops are marked with an arrow. A, axon; N, node. Scale bars, 2 μm. Statistical significance was determined by two-tailed Student’s t-test.