Fig 2: Experimental design of tamoxifen-induced conditional deletion of Fgfr1 in oligodendrocytes and EAE induction with the MOG35-55 peptide. (A) In 4-week-old female B6.Cg-Tg(PLP1-cre/ERT)3Pop Fgfr1tm5.1Sor mice, tamoxifen was administered to induce nuclear translocation of the Cre recombinase fusion protein and subsequent deletion of floxed gene alleles. (B) Confirmation of FGFR1 lox and PLP-Cre expression in mutant mice by PCR and agarose gel electrophoresis. EAE was induced with the MOG35-55 peptide at 8–12 weeks of age, and samples were collected on day 62 p.i.

Fig 3: Quantitative assessment of myelin-related protein densities at 16 days of age. (A) Western blot analysis of MBP, PLP1, HMGCS1, MAG, and MOG protein (blue font) expression in tissue isolated from the PFCWM, CC-Genu, CC-Body, and CC-Splenium of control (C) and germ-free (GF) animals at P16. Loading controls: β-Actin for MBP, GAPDH for PLP1, HMGCS1, MAG, and MOG. (B) Quantification of protein expression normalized to respective loading controls. Individual male and female animals are marked by orange triangles and circles, respectively. Data expressed as mean ± SEM, n = 3 animals/group. No significant differences determined by unpaired student’s t-test or Mann-Whitney U test. PLP1, proteolipid protein; HMGCS1, Hydroxymethylglutaryl-CoA synthase; MAG, myelin-associated glycoprotein; MOG, myelin oligodendrocyte glycoprotein.

Fig 4: FGFR1 downstream protein expression in the cerebellum at day 62 p.i. (A,B). Phosphorylation of Akt was increased in Fgfr1ind−/− mice. ERK, P38 and JNK phosphorylation was not different between Fgfr1ind−/− mice and controls. n = 3–4/group. Data are expressed as the mean ± SEM. ns = not significant, * p < 0.05. Graphical abstract (C): deletion of FGFR1 leads to increase of the myelin protein PLP via increasing phosphorylation of Akt, TrkB and BDNF expression.

Fig 5: RNF220 knockout leads to myelination defects in mice.(A) Representative T2-weighted mouse brain MRI scanning of P60 RNF220-WT (n = 3), RNF220-cHet (n = 3), and RNF220-cKO (n = 3) mice. The arrows indicate the corpus callosum. (B) Representative images showing myelin staining (BG) in corpus callosum regions of P60 RNF220-WT (n = 3), RNF220-cHet (n = 3), and RNF220-cKO (n = 3) mice. (C) Electron microscopy images of the corpus callosum transverse sections from P60 RNF220-WT (n = 8), RNF220-cHet (n = 8), and RNF220-cKO (n = 8) mice with indicated magnifications. Scale bars, 5 μm for upper panels and 2 μm for lower panels. Bar graphs (mean ± SD) show quantification of the total fiber number and the number or percentage of myelinated axons, and scatterplots show g-ratios relative to axon diameter. (D) WB analyses of protein expression of RNF220, MBP, PLP, MAG, and MOG in the cerebral cortex of P21 RNF220-WT (n = 3), RNF220-cHet (n = 3), and RNF220-cKO (n = 3) mice. α-Tubulin was used as the internal controls. Bar graphs (mean ± SD) show the relative levels normalized against indicated proteins expression in the respective wild-type (WT) controls. IB, immunoblotting. Statistical analyses are compared to respective control with Mann-Whitney U test with Bonferroni correction. n.s. (not significant), P > 0.05; **P < 0.01.