Figure 2.

mTOR positively regulates myelination. A, B, Transverse sections of 4 dpf larvae at the level of the trunk spinal cord, with dorsal up, processed for immunohistochemistry to detect Sox10 expression marking oligodendrocyte lineage cells (asterisks). Scale bar, 10 μm. C, Graph showing number of Sox10⁺ cells in wild-type (wt) and mtor mutant larvae. (n = 10 larvae for each genotype; p = 0.0138, unpaired two-tailed Student's t test). Error bars indicate SEM. D–I, Transverse sections of 4 dpf larvae at the level of the trunk spinal cord. Compared with wild-type (D–F), myelin gene expression appears weak in mtor mutant larvae (G–I). Scale bar, 10 μm. J, K, Graphs showing relative levels of myelin gene (J) and cholesterol pathway gene (K) transcripts in 4 dpf wild-type (wt) and mtor mutant (m) larvae measured by qPCR. n = 3 biological replicates consisting of 20 larvae for each measurement; *p < 0.05, **p < 0.01, ***p < 0.005 two-tailed Mann–Whitney test. Error bars indicate SEM. L–O, Transverse sections of 7 dpf wild-type and mtor mutant larvae processed to reveal Mbp by immunohistochemistry (L, N) and myelin using Fluoromyelin staining (M, O). Dashed circles outline the spinal cord (sc). Processing was performed in parallel and images acquired using identical exposure settings. Scale bar, 10 μm. P, Q, Electron micrographs of transverse ventral spinal cord sections from 8 dpf wild-type and mutant larvae. Arrows indicate myelinated axons. Scale bar, 1 μm. R, Graph showing the size distribution of wild-type and mutant myelinated axons in ventral spinal cord of 8 dpf larvae.