Fig. 5. Dll1 overexpression in a small number of NPCs in the developing mouse neocortex induces neuronal differentiation. Retroviruses encoding GFP alone (pMX-GFP, control), or both GFP and Dll1 (pMX-Dll1-IG), were injected into the lateral ventricle of ICR mice at E12.5. Under these conditions, only a small proportion of cortical NPCs were infected. Brains were excised 2 days later and examined. (A,B) The location of the GFP-positive cells was determined by immunohistochemistry with anti-GFP and TO-PRO-3 (nuclear staining). Typical results are shown. (C) Quantification of the distribution of GFP-positive cells in the neocortex. Data are the mean±s.e.m. of values from eight sections of each brain compared between littermates. Similar results were obtained from seven independent littermates. (D) Brain sections were stained with anti-GFP and TuJ1, and the percentage of TuJ1-positive cells among GFP-positive cells in the whole neocortex was determined. Data are the mean±s.e.m. of values from eight sections of each brain compared between littermates. Similar results were obtained from three independent brains. ^*P<0.01, ^**P<0.0001. VZ, ventricular zone; SVZ, subventricular zone; IZ, intermediate zone; CP, cortical plate. Scale bars: 200 µm.