Fig. 4. Dll1 overexpression induces neuronal differentiation in a non-cell-autonomous manner. (A) Primary NPCs were prepared from 3-day sphere cultures (3 DIV) of the neocortical cells of E12.5 ICR mice, infected with a retrovirus encoding GFP (pMX-GFP, control), or both GFP and Dll1 (pMX-Dll1-IG), at a high titer and analyzed as in Fig. 3C. (B) Primary NPCs were prepared from 3-day sphere cultures (3 DIV) of the neocortical cells of E12.5 ICR mice and plated at different cell densities (0.26x, 0.52x and 1.04x10⁵ cells/cm²). These cells were infected with a retrovirus encoding GFP (pMX-GFP, control), or both GFP and Dll1 (pMX-Dll1-IG), at a low titer and analyzed as in Fig. 3B (clonal analysis). ^*P<0.05. (C) Primary NPCs were prepared from 3-day sphere cultures (3 DIV) of the neocortical cells of E12.5 ICR mice and infected with a retrovirus encoding GFP (pMX-GFP, control), or both GFP and the delta-like 1 intracellular domain (pMX-DICD-IG), at a low titer and analyzed as in Fig. 3B (clonal analysis).