Fig 1: Abnormal densities of oligodendrocyte progenitor cells are accompanied by normal oligodendrocyte densities in the developing mdx corpus callosum. a Oligodendrocyte progenitor cells (OPCs) in the developing corpus callosum white matter tract were visualized using PDGFRa immunohistochemistry. Representative confocal microscopy images of postnatal day 14 (p14) mdx and control callosa are shown, b quantification of mean PDGFRa+ cells (OPCs) per mm2 in confocal images from p8, p14, p21, and 2 months corpus callosum. Abnormally high OPC densities were observed in mdx mice relative to that in controls. ***p < 0.01, c oligodendrocytes in the developing corpus callosum white matter tract were visualized using CC1 (oligodendrocyte) and olig2 (oligodendrocyte lineage) immunohistochemistry. Representative confocal microscopy images of p21 mdx and control callosa are shown, d quantification of mean CC1+ Olig2+ cells (oligodendrocytes) per mm2 in confocal images from p8, p14, p21, and 2 months corpus callosum. Oligodendrocyte densities were similar in mdx and control mice, e Enpp6 immunohistochemistry of mdx and control coronal floating brain sections at postnatal day 14 (p14) and p8. Tiled confocal microscopy images reveal less Enpp6 immunoreactivity in mdx cerebral cortices, f quantification of Enppp6 intensity per mm2 in confocal images from p8 and p14 corpus callosum. Abnormally low Enppp6 intensity was observed in mdx mice relative to that in control mice. **p < 0.01, g proliferating OPCs in the developing corpus callosum white matter tract were visualized using PDGFRa and Ki67 immunohistochemistry. Representative confocal microscopy images of p8 mdx and control callosa are shown, h quantification of mean Ki67+ cells per mm2 in confocal images from p8 mdx and control corpus callosum. Ki67+ cell densities were significantly increased in mdx callosa relative to that in controls (*p < 0.05). Scale bars 50 microns