Fig. 9. Ablation of radial glia by diphtheria toxin (DT) disrupts the inner and outer barriers of the developing brain. (A-L) Each vector was introduced into the telencephalic cells by electroporation at E13, and the sections were examined at E15. When pCL-GFP was introduced (A-C), both cells in the ventricular zone (nestin⁺) and the outer layers were found to express GFP. No dying cells (TUNEL⁺) were detected (C). When pNes-DT-A was introduced (E-G), many cells underwent apoptosis in the ventricular zone (TUNEL⁺, G). When pNes-GFP was introduced, only nestin⁺ ventricular cells (I,J), but not NeuN⁺ neurons (K), expressed GFP. The schematic structures of the vectors are shown in D,H,L. (M-Z) Each vector was introduced into the telencephalic cells by electroporation at E13, and the sections were examined at E18. When pCL-GFP was introduced (M-S), GFP was expressed in both radial glia and neurons (O) and did not affect radial glia (nestin⁺, P), the apical junction (ZO-1⁺, Q, arrowheads), the basal lamina (Laminin 1⁺, N, arrowheads) or neurons (NeuN⁺, R). Cell arrangement was not disturbed (DAPI, S). The indicated region in M is enlarged in O-S. When pNes-DT-A was introduced (T-Z), GFP⁺ cells were almost undetectable (T,T'). Only a small number of GFP⁺ neurons is detectable, which shows the electroporated region (T,T'). pNes-DT-A specifically killed nestin⁺ radial glia, which disappeared from the electroporated region (V,V', arrowheads). This region lost ZO-1 expression at the apical side (W, arrowheads, compare with the normal expression indicated by arrows). The electroporated region also lost laminin 1 at the basal side (X, between the two arrowheads). In this region, the cortical lamination is destroyed with rosette-like structures, and some neurons protrude into the outer region and the lumen (Y,Y',Z, arrowheads). The indicated region in (T) and (U) is enlarged in (T') and (V',W,Y',Z), respectively. Scale bars: 100 µm in A-C,E-G,I-K,N S,T',V',W,Y',Z; 200 µm M,T-V,X,Y.