Depletion of neural progenitor cells in the PS cDKO embryonic brain. (A-F) Proliferating (S-pahse) neural progenitors are identified by BrdU labeling at E13.5, E14.5 and E17.5. While the BrdU staining pattern does not differ between PS cDKO and control embryonic brains at E13.5 (A, B), severe morphological abnormalities of BrdU stained progenitor cells are present in PS cDKO brains at E14.5 (C, D). By E17.5, only a few proliferating neural progenitor cells remain in the lateral ganglionic eminence (GE, black arrowheads), whereas in the ventricular zone of the telencephalon neural progenitor cells are almost completely depleted in the PS cDKO mice brain. Many non-neuronal, unnucleated, clotted and small staining are found in the PS cDKO brain (opened arrow heads and inset in F). The lateral ventricle (labeled with an asterisk in the control brain) is missing in PS cDKO brains (E, F). The insets in E, F are the high power view of boxed area. Scale bar: 500 μm. (G) Quantification of BrdU-labeled S-phase cells. BrdU-positive cells were counted at E12.5, E13.5, E14.5, and E15.5, and the percentage of BrdU-positive cells in PS cDKO embryos to that in the control is shown. Significant reductions of BrdU-positive cells are detected at E14.5 and E15.5 in PS cDKO mice (**, p < 0.01; ***, p < 0.001).