Fig. 7. Dll1 deletion in a small number of NPCs in the developing mouse neocortex suppresses neuronal differentiation. Retroviruses encoding GFP alone (pMX-SV40-GFP, control), or both GFP and Cre recombinase (pMX-Cre-SV40-GFP), were injected into the lateral ventricle of Dll1^flox/flox mice at E12.5. Under these conditions, only a small proportion of cortical NPCs were infected. Brains were excised 3 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 five independent littermates. (D) Brain sections were stained with anti-GFP and anti-Pax6, and the percentage of Pax6-positive cells among GFP-positive cells in the whole neocortex was determined. Data are the mean±s.e.m. of values from six sections of each brain compared between littermates. Similar results were obtained from three independent brains. ^*P<0.005, ^**P<0.0005. VZ, ventricular zone; SVZ, subventricular zone; IZ, intermediate zone; CP, cortical plate. Scale bars: 200 µm.