Fig 5

(A-B) sox10 mRNA in situ hybridization (ISH) in WT (A) and mz ypel3 mutant (B) showing maintained sox10 expression (red arrows) in the mz ypel3 mutant at 26 hpf. (C-D) Schwann cell precursors migrate correctly in the region of the developing motor nerves in the mz ypel3 mutant. WT (C) and mz ypel3 mutant (D) embryos at 26 hpf. Arrowheads indicate Schwann cell precursors. (E-F) Initial ensheathing of motor axons by Schwann cells occurs properly in the mz ypel3 mutant. WT (E) and mz ypel3 mutant (F) larvae at 56 hpf. Arrowheads indicate motor nerves. Arrow indicates ventral Schwann cells ensheathing motor nerve. (G-H) Schwann cells fail to form normal structures in the mz ypel3 mutant. At 5 days postfertilization (dpf), in WT (G), Schwann cells form slender rod-like structures (arrows). At this stage, the mRFP signal has cleared from the ventral myotome. In the mz ypel3 mutant (F), Schwann cells fail to wrap the motor axon tightly and sox10 expression as indicated by mRFP is maintained within the ventral region of the myotome. Yellow dashed lines outline melanocytes. Green arrowheads indicate blood vessels. All images are lateral views. Scale bars: 25 μm. (I) Quantification of the average number of motor nerves per somite labeled with sox10:mRFP at 56 hpf. (J) Quantification of the average number of motor nerves per somite labeled with sox10:mRFP at the level of ventral myotome. Bars represent +/-SEM.