Fig. 7. NS-divisions induced by retrovirus-mediated Ngn2 expression. (A) Retroviral vectors used in this study. (B-D) Section of an E14 cerebral wall infected with the control-GFP virus 48 hours earlier, doubly stained with anti-GFP and anti-pH3 showing two GFP⁺ mitoses at the ventricular surface (arrows). (E-G) Section of an E14 cerebral wall infected with the ngn2/GFP virus 48 hours earlier showing two GFP⁺ mitoses in the NS position (arrows). (H) Retroviral infection leads to expression of Ngn2 by a GFP⁺ mitosis at the NS position of a ngn2-introduced cerebral wall. (I) NS mitoses are significantly increased (P<0.001 compared with control) in ngn2 retrovirus-treated samples (n=7 for control-GFP, n=9 for ngn2/GFP; mean±s.e.m.). Scale bars: 10 µm in B,C,E,F,H. CMV, cytomegalovirus promoter; IRES, internal ribosomal entry site; GFP, green fluorescent protein; LTR, long terminal repeat.