Figure 4 |. Region-specific differences in oligodendrogenesis correlate with transcriptional heterogeneity.

a) Oligodendrogenesis (cyan) over 4 weeks in layer 5 of the PPC. b) Cumulative OL gain curves for individual mice in the entire depth of the GM. c) Oligodendrogenesis (cyan) from weeks 3–6 in the dorsal corpus callosum. d) Cumulative OL gain curves for individual mice in the WM. e) The WM gained substantially more OLs per imaging volume at a faster rate than the GM (p=0.013 for total gain at 66d; p=0.005 for mean rate). f) The GM population experienced greater percentage growth than the WM. Significance asterisks refer to data in (g) and (h). g) Total population gain was increased in the GM vs. the WM (p=0.022). h) The rate of OL gain during the fifth week of imaging (~P100) was increased in the GM vs. WM (p=0.020). i) The time at half-maximum of the mechanistic growth curves did not differ between GM and WM. j) The rate of WM population gain decreased more rapidly with age than in the GM (p=0.037, Weeks 5–6 vs. 1–2; p=0.022, Weeks 9–10 vs. 1–2). k-m) Images of MOL1+ (EGFP/Egr1+), MOL2/3+ (EGFP/Klk6+), and MOL5/6+ (EGFP/Ptgds+) oligodendrocyte populations in the PPC and WM at P60 (left) and P140 (right). n) No age-related changes in the population proportions of OL subtypes between P60 and P140. o) Differences in transcriptional heterogeneity between the GM and WM. MOL1+ OLs represented a higher proportion of the OL population in the GM vs. WM (p=0.002), while MOL2 and MOL5/6-OLs were more abundant in the WM (p=0.018, MOL2/3; p=0.005, MOL5/6). Data in h,i were calculated from the mechanistic growth curves. Data in a–f,h,j represent n=6 mice / group, g,i, n=5 mice, n–o represent n=6 mice (P60) and n=8 mice (P140), two sections per mouse. *p<0.05, **p<0.01, n.s., not significant; for growth curves, cubic splines approximate the measure of center and error bars are 95% confidence intervals; box plots represent the median, interquartile ranges and the minimum/maximum values. Line plots connect the mean at each time point. Statistical tests were unpaired, two-sided Student’s t-tests for equal or unequal variance (e,g,h,o), Dunnett’s multiple comparisons with control (j), or two-sided Wilcoxon rank sum (o). For detailed statistics, see Supplementary Table 3.