Demyelination-induced recruitment of oligodendrocyte precursor cells (OPCs) is impaired in CX3CR1^−/− mice. Complementary histological markers were used to measure OPC proliferation and recruitment in the corpus callosum. (A and B) Platelet-derived growth factor receptor α (PDGFR-α) mRNA hybridization signal in the corpus callosum of mice killed 4 wk after being fed with a cuprizone-supplemented diet. (C) Representative Olig2-immunoreactive staining in the corpus callosum of WT and CX3CR1^−/− mice 5 wk after a cuprizone treatment or normal show. (D) Stereologic quantification of Olig2-immunoreactive cells in the corpus callosum of WT and CX3CR1^−/− after 5 wk of cuprizone or normal feeding. High expression of this protein is specific to OPCs and preoligodendrocytes (Levine et al., 2001). (E) Immunoreactive signal for Olig2 (red)/Ki67 (green), PDGFRα (red), and IGF-1 (red). One representative experiment out of two is shown. n = 3–6 mice/group. (B) **, P = 0.0083; ****, P < 0.0001; **, P = 0.0022; (D) ***, P = 0.0009; ***, P = 0.0003. Bars: (C) 100 µm; (E) 20 µm.