Fig. 3

Increasing Oligodendrocyte Number Recapitulates Wrapping of Neuronal Cell Bodies

(A) Double myelin and oligodendrocyte reporter (4 dpf), treated with vehicle DMSO, Skp2C25, or GANT61.

(B and C) Oligodendrocyte (e.g., asterisk) number and myelinated cell bodies (e.g., arrowheads) number is increased in the dorsal spinal cord of Skp2C25-treated animals and reduced in GANT61-treated animals, quantified in (B) (p_{[Skp2C25-DMSO]} = 0.0004, n = 20 DMSO and n = 10 Skp2C25; p_[C646-DMSO] < 0.0001, n = 22 DMSO and n = 19 C646; p_{[GANT61-DMSO]} < 0.0001, n = 9 DMSO and n = 13 GANT61; t tests; data normalized to control average) and in (C) (p_{[Skp2C25-DMSO]} < 0.0001, n = 20 DMSO and n = 10 Skp2C25; p_[C646-DMSO] < 0.0001, n = 22 DMSO and n = 19 C646; p_{[GANT61-DMSO]} = 0.011, n = 9 DMSO and n = 13 GANT61; t tests; data normalized to control average; GANT61 data and its control plotted on right y axis), respectively.

(D) Plotting all normalized data shows that myelinated cell body number positively correlates to oligodendrocyte number (Pearson’s r correlation and p value displayed for each treatment).

(E) TEM of 4 dpf medial-dorsal spinal cord shows increased number of myelinated axons (red asterisks) in Skp2C25-treated animals whereas controls still have many unmyelinated large-caliber axons (green circles).

(F) Total number of large-caliber (>0.5 μm diameter) axons in the medial-dorsal spinal cord is normal in Skp2C25-treated animals (p = 0.852; n = 4 DMSO and n = 5 Skp2C25; t test).

(G) Myelinated axon number is increased with Skp2C25 (p = 0.006; n = 8 DMSO and n = 9 Skp2C25; t test).

(H) Smallest myelinated axons in Skp2C25-treated animals remain above 0.4 μm diameter (p = 0.961 for all bin comparisons; n = 7 DMSO and n = 9 Skp2C25; corrected t tests).

(I) 4 dpf double myelin and Rohon-Beard (RB) neuron reporter (Tg(isl1(ss):Gal4; UAS:DsRed)), focusing in the dorsal spinal cord.

(J and K) Skp2C25-treated animals have more “very dorsal” myelin sheaths (arrows), quantified in (J) (p = 0.011; n = 19 DMSO and n = 19 Skp2C25; t test), which add up to a higher total myelin sheath length, quantified in (K) (p = 0.013; n = 19 DMSO and n = 19 Skp2C25; t test), as well as readily identifiable myelinated cell bodies (arrowheads). Examples of very rare myelin sheaths on dsRed+ large-caliber RB axons (arrows in merged panels), which are not increased with Skp2C25 (see main text for details), are shown.

All graphs display mean and SD. The scale bars represent 20 μm (A) and 10 μm (I). See also Figure S1.