Fig 2: Qk deletion in oligodendrocyte precursor cells leads to defective myelinogenesis without impairing differentiation of Aspa+ myelinating oligodendrocytes.(A) Schema of the generation of Qk-Plp-iCKO mice. (B) Representative images of severe hind limb paresis in Qk-Plp-iCKO mice 2 weeks after tamoxifen injection. (C) Latency of mice falling off the rotarod at a constant speed (5 rpm). n = 3 mice in the Qk-Plp-iCKO group; n = 7 mice in the control group. (D) Body weights of Qk-Plp-iCKO mice (n = 12) and control mice (n = 18) 2 weeks after tamoxifen injection. (E) Kaplan–Meier curves of and log-rank test results for overall survival in Qk-Plp-iCKO mice (n = 32) and control mice (n = 59). (F) Representative images of and quantification of immunofluorescent staining of MBP, GFP, and Iba1 in the corpus callosum tissues in Qk-Plp-iCKO mice (n = 6) and control mice (n = 3) 2 weeks after tamoxifen injection. Scale bars, 50 µm. (G) Representative images of and quantification of staining of FluoroMyelin in the corpus callosum tissues in Qk-Plp-iCKO mice (n = 3) and control mice (n = 4) 2 weeks after tamoxifen injection. Scale bars, 50 µm. (H) Representative electron micrographs of and quantification of the percentage of myelinated axons in the optic nerves in Qk-Plp-iCKO mice (n = 3) and control mice (n = 5) 2 weeks after tamoxifen injection. Scale bars, 500 nm. (I) Representative images of and quantification of immunofluorescent staining of Aspa and Qki in the corpus callosum tissues in Qk-Plp-iCKO mice (n = 3) and control mice (n = 4) 2 weeks after tamoxifen injection. Scale bars, 50 µm. Data are shown as mean ± s.d. and were analyzed using Student's t test (C,D, F–H) or one-way ANOVA with Tukey’s multiple comparisons test (I). **p<0.01; ****p<0.0001; ns: not significant.Figure 4—source data 1.Exact p-values for statistical analysis.

Fig 3: Neonatal CD11c+ microglia are a major source of myelinogenic Igf1 A, BExpression of Igf1 relative to 18S rRNA in MACS‐sorted microglia, OPC, astrocytes and neurons (n = 4) (A) as well as FACS‐sorted CD11c+ and CD11c− microglia (n = 6) (B) from brains of PN4‐7 mice.CRepresentative micrographs showing patches of Cre‐GFP, CD11b double‐positive cells in corpus callosum from PN4‐5 CD11c Cre‐GFP Igf1fl/fl brains (n = 3), Scale bar = 50 μm.DGenomic PCR analysis of Cre recombination in MACS‐sorted splenic dendritic cells (DC) from Igf1wt/fl and microglia, OPC, astrocytes, and neurons from CD11cCre‐GFP Igf1fl/fl. Wild‐type Igf1 gene is detected as an ˜1‐kb band; Cre‐induced recombination is detected as an ˜0.2‐kb band, while the Igf1/flox locus cannot be amplified under the assay condition (Liu et al, 1998).EExpression of Igf1 relative to 18S rRNA in FACS‐sorted splenic CD11c+ cells (n = 5), CD11c+ microglia (n = 5), and CD11c− microglia (n = 5) from Igf1fl/fl mice and Cre+ microglia (n = 4, each n represents a pool of 2 brains) from CD11cCre‐GFP Igf1fl/fl mice.FBar graph showing weights of brains from PN21 Igf1fl/fl (blue) (n = 8) and CD11cCre‐GFP Igf1fl/fl (red) (n = 4) mice.GExpression of Igf1, Mog, Plp, and Mbp relative to 18S rRNA in brain tissue from PN21 CD11cCre‐GFP Igf1fl/fl and Igf1fl/fl mice (F) n = 6.H, IRepresentative micrographs (H) and quantification of PLP staining intensity (I) in corpus callosum of CD11cCre‐GFP Igf1fl/fl (red) (n = 4) and Igf1fl/fl (blue) (n = 6) PN21 brains.J–MRepresentative electron microscopy micrographs (J), mean G‐ratios (K), and distribution of G‐ratios (L, M) in corpus callosum from Igf1fl/fl (blue) (n = 8) and CD11c CD11cCre‐GFP Igf1fl/fl (red) (n = 6) PN21 brains. Scale bar = 1 μm.Data information: Data are based on at least two experimental repeats. Data are presented as means ± SEM; each n represents an individual mouse. P‐values were determined by two‐tailed Mann‐Whitney U‐test (A, B, E, G, I), Welch's t‐test (F, K, M) (distribution was normal) or two‐way ANOVA with Sidak's multiple comparisons test (L) (variances were similar, and distribution was normal); ns, not significant; *P < 0.05; **P < 0.01; ***P < 0.001.Source data are available online for this figure.

Fig 4: Qki loss leads to defective myelin membrane assembly.(A) Representative images of immunofluorescent staining of MBP in the corpus callosum tissues in Qk-Nestin-iCKO mice and control mice 2 weeks after tamoxifen injection. (B, C) Representative images of and quantification of the co-localization rates of immunofluorescent staining of MBP-PLP (B) and MBP-MAG (C) in the corpus callosum tissues in Qk-Nestin-iCKO mice and control mice 2 weeks after tamoxifen injection. (D) Representative images of and quantification of staining of FluoroMyelin in the corpus callosum tissues in Qk-Nestin-iCKO mice and control mice 2 weeks after tamoxifen injection. (E) Quantification of the relative ratio of FluoroMyelin to PLP in the corpus callosum tissues in Qk-Nestin-iCKO mice (n = 3) and control mice (n = 4) 2 weeks after tamoxifen injection. Scale bars, 50 µm. Data are shown as mean ± s.d. and were analyzed using Student's t test. The r values in the scatter plots (B, C) were calculated using Pearson’s correlation. ****p<0.0001.Figure 3—source data 1.Exact p-values for statistical analysis.

Fig 5: Deletion of Qk in mouse neural stem cells leads to hypomyelination in the central nervous system.(A) Schema of the generation of Qk-Nestin-iCKO mice. (B) Representative images of severe hind limb paralysis in Qk-Nestin-iCKO mice 2 weeks after tamoxifen injection. Ctrl: control. (C) Latency of mice falling off the rotarod at a constant speed (5 rpm). n = 6 mice in the Qk-Nestin-iCKO group; n = 9 mice in the control group. (D) Body weights of Qk-Nestin-iCKO mice (n = 29) and control mice (n = 22) 12 days after tamoxifen injection. (E) Kaplan–Meier curves of and log-rank test results for overall survival in Qk-Nestin-iCKO mice (n = 157) and control mice (n = 153). (F) Representative images of and quantification of immunofluorescent staining of MBP, PLP, MAG, GFP, and Iba1 in the corpus callosum tissues in Qk-Nestin-iCKO mice (n = 3) and control mice (n = 4) 2 weeks after tamoxifen injection. Scale bars, 50 µm. (G) Representative images of and quantification of immunofluorescent staining of MBP and Iba1 in the optic nerves in Qk-Nestin-iCKO mice (n = 3) and control mice (n = 4) 2 weeks after tamoxifen injection. Scale bars, 50 µm. (H) Representative electron micrographs of the optic nerves in Qk-Nestin-iCKO mice and control mice with quantification of the percentage of myelinated axons and g-ratios 2 weeks after tamoxifen injection (n = 3 mice/group). Scale bars, 500 nm. (I) Representative images and quantification of immunofluorescent staining of amyloid precursor protein (App) in the corpus callosum tissues in Qk-Nestin-iCKO mice (n = 3) and control mice (n = 4) 2 weeks after tamoxifen injection. Scale bars, 50 µm. Data are shown as mean ± s.d. and were analyzed using Student's t test. ***p<0.001; ****p<0.0001; ns: not significant.Figure 1—source data 1.Exact p-values for statistical analysis.