Fig. 3
AQP4 and vimentin immunoreactivity in a control sample of 21 PCW. a Schematic representation (modified from Allen atlas) at 21 PCW showing localization of the corpus callosum and the fornix. b Panoramic view from a parietooccipital section of a 21 PCW brain. AQP4 expression is restricted to VZ and the main white matter tracts (corpus callosum and fornix). c Magnification of the square in B showing staining for glial radial cell-like cells associated with white matter tracts (arrowheads). d Schematic representation of the area of study. e Magnification of the square in c, showing basal processes that curve to follow the fiber tracts of the fornix (arrowhead) and do not progress radially toward the cortical plate. f Magnification of the square in c showing expression in VZ and radial glial cell-like cells (arrowhead) specific to the corpus callosum with progression toward the cortical plate (asterisk). G; Vimentin expression in a parallel slide from F showing immunoreactivity in the VZ, cell processes of the corpus callosum (arrowhead), and glial radial cell processes that project to the cortical plate (arrow). h–j Immunofluorescence for AQP4 (red) and vimentin (green) in a parallel slide from c, showing colocalization (yellow) in the cells with basal processes, suggesting that these cells are a subtype of glial radial cells that do not project to the cortical plate, instead restricted to the white matter tracts associated with gliogenic phenomena. Immunohistochemistry for AQP4 (k) and vimentin (l) in the subventricular zone shows expression in glial radial cells with apical and basal processes (arrow) and glial radial cells with single basal processes (arrowhead). M; Detail of basal projections of the SVZ indicating glial radial cell functionality as a scaffold to guide cells toward white matter tracts (nuclei labeled with DAPI in blue). Immunohistochemistry for AQP4 (n) and vimentin (o) in VZ showing expression in undifferentiated intermediate progenitor cell-like cells. P; Double labeling against vimentin and AQP4 at the VZ. Intermediate progenitor cell-like cells stain for vimentin only (arrowhead) and colocalizing with AQP4 (arrow). LV, lateral ventricle; VZ, ventricular zone; SVZ, Subventricular zone. Scale bars: b 500 µm; c–j 160 µm; k, l 30 µm; m–p 40 µm