(A) Representative Western blot of P14 cortical lysates (Top) and extracts of proliferating OPCs and differentiated OLs (2 DIV) from WT and Gde2KOs. Arrow highlights GDE2 protein, * marks nonspecific band. (B). Representative images of WT and Gde2KO OLs. Graphs quantifying the percentage of MBP+Olig2+ OLs (***p = 0.0008) and Olig2+ cells (ns p=0.9385) normalized to WT, n = 3 WT, 3 Gde2KO. (C) Representative images of 3 stages of OL maturation in vitro. Graph quantifying the percentage of MBP+Olig2+ OLs. 2-way ANOVA ***p < 0.0001 (Bonferroni correction) ns p >0.05; **p <0.01; n = 3 WT, 3 Gde2KO. (D) Schematic of neuron-OPC co-culture. (E) Representative images of WT and Gde2KO OPCs co-cultured with WT neurons. Insets show higher magnification of myelinated axons. Arrows highlight myelinated axons. Graph quantifying the numbers of MBP+ segments (normalized to WT OLs) **p = 0.0037, n = 3 WT, 3 Gde2KO. All graphs: Mean ± sem. (B, E) two-tailed unpaired Students t-test; Scale bars: (B, E) 100 μm, inset: 10 μm (C) 50 μm.