Absence of atrn protein in oligodendrocyte lineage. Characterization of atrn-expressing cells in the early postnatal forebrain at P2 (A, B), P7 (C, D), and in the 2-months-old adult brain (E-H). A, B, Confocal images of double immunofluorescence labeling of the subventricular zone (SVZ) surrounding the dorso-lateral corner of the lateral ventricle of wild-type rats, using antibodies against PDGFR-α (red) and atrn (green). Atrn expression was not detected in PDGFR-α-positive cells (arrows). C, D, Confocal images of the wild-type SVZ immunostained for A2B5 (red) and atrn (green). Cell nuclei were visualized by TOPRO-3 staining (blue). Insets show an enlarged view of the SVZ. Arrowhead depicts A2B5-positive but atrn-negative OPCs among the densely packed cells in the SVZ. E, Atrn-positive cells (DAB, brown) in the gray matter (layer V) of the adult cerebral neocortex. Atrn expression was observed in neurons including typical pyramidal neurons. F, Atrn-positive cell (DAB, brown) in the corpus callosum of the adult forebrain was indicated by arrow. G, H, Confocal images of double immunofluorescent labeling with antibodies to atrn (green) and CNPase (red) in the adult cerebral cortex (layers II-III) (G) or the internal granule cell layer of the adult cerebellum (H), respectively. Atrn expression was observed in many pyramidal or granule neurons, but not in CNPase-positive oligodendrocytes (arrows). I, J, Immunohistochemical analysis for specificity of anti-atrn antibody in rat brain. Coronal sections through the adult cerebral cortex were immunostained with anti-atrn antibody. Atrn-immunoreactivity in wild-type SD (I) and zi/zi (J) rats. Scale bars: 20 μm (A, B); 100 μm (C, D); 10 μm (E, F); 10 μm (F); 20 μm (G); 100 μm (I, J). lv, lateral ventricle.