Scribble regulates myelin thickness and ERK activation in oligodendrocytes.

<p>A,B,D,E; At P40, decreased myelination of small-diameter axons in both optic nerve (B) and spinal cord (E) of Scribble cKO mice persists relative to wild-type littermates (A,D). This is quantified for optic nerve in C (0.3–0.4μm: WT = 68.4% ± 6.4%, cKO = 36.2% ± 10.1% myelinated, <i>p</i> = 0.0002; 0.4–0.5μm: WT = 87.8% ± 6.0%, cKO = 68.2% ± 4.1% myelinated, <i>p</i> = 0.0034) and for spinal cord in F (0.3–0.4 μm: WT = 34.0% ± 4.4%, cKO = 9.3% ± 3.7% myelinated, <i>p</i> = 0.039; 0.4–0.5μm: WT = 47.5% ± 4.5%, cKO = 22.3% ± 2.5% myelinated, <i>p</i> = 0.033) Numerical results here and below are presented as mean ± SEM. Two-way ANOVA with Bonferroni's multiple comparisons test was used. <i>n</i> = 3 animals per genotype. At least 200 axons were analysed per animal, per region. G–I; Axons that are myelinated in cKOs have thicker myelin sheaths than do axons of similar diameters in wild-type littermates, as decreased mean g-ratios were observed in both optic nerve and spinal cord (G; optic nerve: WT = 0.755 ± 0.004, cKO = 0.704 ± 0.016, <i>p</i> = 0.012; spinal cord: WT = 0.760 ± 0.010, cKO = 0.702 ± 0.008; <i>p</i> = 0.018; Student's <i>t</i> test was used to compare means from each animal. At least 100 g-ratios were analysed per animal, per region.). The best fit lines obtained by linear regression differed significantly between cKO and wild-type datasets in both optic nerve (H; WT: slope = 0.063 ± 0.012, intercept = 0.720 ± 0.007, cKO: slope = 0.075 ± 0.015, intercept = 0.666 ± 0.010; <i>p</i> = 0.548 [slope], <i>p</i> < 0.0001 [intercept]) and spinal cord (I; WT: slope = 0.027 ± 0.004, intercept = 0.728 ± 0.006, cKO: slope = 0.012 ± 0.005, intercept = 0.688 ± 0.007; <i>p</i> = 0.022 [slope]). J–L; Increased abundance of phosphorylated ERK1/2 relative to total ERK1/2 was observed in western blots of lysates of optic nerve and spinal cord from Scribble conditional mutants (J). The ratio of phospho-ERK/ERK densitometry is provided in arbitrary units for optic nerve (K): p44ERK/ERK1: WT: 0.306 ± 0.064, cKO: 0.666 ± 0.027, <i>p</i> = 0.0066; p42ERK/ERK2: WT: 1.511 ± 0.025 cKO: 5.391 ± 0.924, <i>p</i> = 0.014; and spinal cord (L): p44ERK/ERK1: WT: 0.127 ± 0.046 cKO: 0.335 ± 0.051, <i>p</i> = 0.038; p42ERK/ERK2: WT: 0.997 ± 0.069, cKO: 5.218 ± 1.278, <i>p</i> = 0.030, Student's <i>t</i> test was used. A,B: Scale bar = 1 um. E,F: Scale bar = 1.5 um. * <i>p</i> < 0.05, ** <i>p</i> < 0.01, *** <i>p</i> < 0.005 versus Scrib WT.