Extended Data Figure 10. Intranasal HB-EGF accelerates oligodendrocyte maturation in WM after Hyp by preventing Notch activation.

a, Microdissected WM was probed for activated Notch Intracellular Domain (NICD) and its ligand Delta1. Western blot analysis obtained from microdissected WM at P11, P14.5 and P18 with actin as a loading control. Histograms represent quantification of the density of NICD (b) and Delta1 (c) signal normalized to actin. b, At P11 and P14.5, there was a significant increase in the amount of NICD in the Hyp group. No significant difference was evident at P18. The Hyp HB-EGF treated mice had no significant increase at P14.5 compared to Nx, and significantly less than the Hyp Saline group (n=4 mice for each group and age; One way ANOVA, Bonferroni post hoc test for individual comparisons). c, Delta1 was increased at P14.5 only in the Hyp Saline group (P11: n=4 for each group; P14.5 and P18: n=5 for each group and age; One way ANOVA, Bonferroni post hoc test for individual comparisons). d–g, Representative 40x confocal images of subcortical WM in the transgenic Notch reporter (TNR) mice, where EGFP is expressed upon activation of Notch-effector C-promoter binding factor 1 (CBF1), a downstream transcriptional target of Notch. h, Histogram represents the number of EGFP⁺Olig2⁺ cells at P14.5 in the WM. The Hyp Saline group displayed a significant increase in EGFP⁺Olig2⁺ cells, corresponding to enhanced Notch activation in OL lineage cells. This contributes to delayed maturation of OL lineage cells observed after Hyp (n=4 mice per group; One-way ANOVA, Bonferroni post hoc test for individual comparisons). Histogram is presented as means ± s.e.m. Scale bars, 50μm (d–g). *P<0.05; **P<0.01.