Fig. 1

a Nuclear immunoreactivity specific for 5 methylated cytosine (5mC, green) and OLIG2 (red) in adult mouse spinal cord sections. Scale bar = 10 µm. b Bar graphs showing the relative proportion of OLIG2 + cells with low, medium, or high levels of 5mC immunoreactivity in the neonatal (P7) and adult (P60) spinal cord. Error bars represent SEM for n = 4 mice (*p < 0.05 and ***p < 0.001, two-way ANOVA, for age and 5mC immunoreactivity). c Nuclear immunoreactivity specific for hydroxymethylated cytosines (5hmC, green) and for OLIG2 (red) in adult mouse spinal cord sections. Scale bar = 10 µm. d Bar graphs showing the relative proportion of OLIG2 + cells with low, medium, or high levels of 5hmC immunoreactivity in the neonatal (P7) and adult (P60) spinal cord. Error bars represent SEM for n = 4 mice (**p < 0.01 and ***p < 0.001, two-way ANOVA, for age and 5hmC immunoreactivity). e Schematic experimental timeline of lysolecithin lesion experiment in young and old mice. f Electron micrographs of lesioned spinal cord sections from young (P60) and old (P540) mice at 21 days post-lesion (21dpl). Remyelination in young and old adult samples shown by white arrowheads. Scale bar = 5 µm. g Data indicate the average remyelinated axons in young and old spinal cord 21dpl. Error bars represent SEM for n = 5 young mice and n = 4 old mice (***p = 0.0002, Student’s t test two-tailed). h, i Quantification of the percentage of OLIG2 + cells with high levels of 5hmC in spinal cord lesions at 7dpl, 14dpl, and 21dpl, in young (h) and old (i) mice. Dotted line indicates the relative percentage of OLIG2 + cells with high level of 5hmC in unlesioned white matter tracts (NWM). Data represent the average of 3 sections/mouse. Error bars represent SEM for n = 5 young mice and n = 4 old mice (**p < 0.01 and ***p < 0.001, one-way ANOVA, for time after lesion). j, k Quantification of the percentage of CC1 + cells with high level of 5hmC in spinal cord lesions in young (j) and old (k) mice analyzed at 7dpl, 14dpl, and 21dpl. Dotted line indicates the relative percentage of CC1 + cells with high level of 5hmC in unlesioned white matter tracts (NWM). Data points indicate the average 3 sections/mouse. Error bars represent SEM for n = 5 young mice and n = 4 old mice (***p < 0.001, one-way ANOVA, time after lesion).