Human α-Synuclein is strongly expressed in immature neurons in a region-specific pattern. Immunofluorescent labeling of hα-Syn (green channel) in different regions of the brain shows strong expression of transgenic α-Syn (arrowheads) in immature neurons in the rostral migratory stream (RMS) (A, D, G) and in the ventricular zone (VZ) (B, C, E, F). We found no coexpression with either GAD67 or TH (A, B, C), whereas many hα-Syn-positive cells were immunoreactive for doublecortin (DCX) in the RMS (D) and the VZ (E), indicating that hα-Syn is expressed in subpopulations of immature migrating neurons. (F) We also found co-expression of hα-Syn and ErbB4 in the VZ (open arrowhead in F) and the RMS (G), whereas hα-Syn was not expressed in microglia immunoreactive for Iba1 (arrow in F). The VZ and the RMS were identified by immunoreactivity for DCX, ErbB4, or PSA-NCAM (G). (H) In contrast to the VZ and RMS, we found no indication for expression of either hα-Syn (arrowhead) or ErbB4 (open arrowhead) in DCX-positive immature neurons (arrow) in the subgranular layer (sgl) of the hippocampal dentate gyrus (DG). Single channel images are rotated clockwise in panel H. Abbreviations: caudate/putamen (CPu), corpus callosum (cc), glutamic acid decarboxylase 67 kD (GAD67), hilus (hi), lateral ventricle (lv), olfactory bulb (Olf), stratum granulosum (sg), stratum moleculare (sm), tyrosine hydroxylase (TH), doublecortin (DCX). Scale bar = 50 μm (A-E, H), 70 μm (F, G).