Figure 3.

mTOR is required for the excess myelination of fbxw7 mutant larvae. A, Graph showing number of Sox10⁺ oligodendrocyte lineage cells in 4 dpf control, mutant, and rapamycin-treated larvae. n = 10 larvae for each group. *p < 0.05, ****p < 0.0001, unpaired two-tailed Student's t test. Error bars indicate SEM. B, Graph showing percent change in dorsal olig2:EGFP⁺ OPCs in fbxw7^−/− control and rapamycin-treated larvae between 3 and 4 dpf and 4 and 5 dpf. n = 9 larvae each for 3–4 dpf and 8 larvae each for 4–5 dpf. **p < 0.01; ns, no significant difference, unpaired two-tailed Student's t test. Error bars indicate SEM. C–N, Transverse sections of 4 dpf larvae at the level of the trunk spinal cord, with dorsal up, processed for in situ RNA hybridization to detect myelin gene expression. Transcript levels appear reduced in fbxw7^−/−;mtor^−/− larvae (F, J, N) relative to fbxw7^−/− larvae (D, H, L). O–R, Transverse sections through trunk spinal cord processed for immunohistochemistry to detect Mbp. Mbp level in fbxw7^−/−;mtor^−/− larva (R) is lower than in wild-type (O) and fbxw7^−/− (P) and similar to mtor^−/− (Q). Scale bar, 10 μm. S, T, Graphs showing relative levels of myelin gene (S) and cholesterol pathway gene (T) transcripts in 4 dpf wild-type and fbxw7 mutant larvae without (−) or with (+) rapamycin treatment. n = 3 biological replicates consisting of 20 larvae for each measurement. *p < 0.05, **p < 0.01, ***p < 0.005, ****p < 0.0001, two-tailed Mann–Whitney test. Error bars indicate SEM.