Figure 5. Retroviral-Cre mediated deletion of Rb does not affect neurogenesis in the adult OB.

2-month-old animals were injected with a mixture of CAG-RFP (control) and CAG-Cre/GFP retroviruses in the SVZ and sacrificed 28 d later. (A–C′) Double labeling with anti-GFP and anti-RFP on sagittal sections in the OB. (D–F′) and (G–I′) are co-labeling with (GFP, NeuN) and (GFP, CR), respectively (n = 3Ct and 3Mut). Insets in (C,C′,F,F′,I,I′) are higher magnifications showing double-labeled cells. Quantification of positive cells showed no increase in OB neurogenesis in Rb−/− mice compared with Rb+/− mice at this age (A–C′; yellow arrows, J,K). Terminal differentiation (L) was also similar between genotypes with the majority of GFP+ cells (87–97%) co-expressing NeuN and a subpopulation (25–28%) co-expressing calretinin (CR). The absence of enhanced neurogenesis may be explained by a dramatic increase in cell death observed in Rb-null OBs (N) compared with controls (M). Arrowheads indicate (AC3+Hoechst+) cells and insets in M and N show higher magnification images of selected cells. (O) Quantification of data shown in (M,N). Error bars represent SD of measurements from n = 3 per genotype and asterisks indicate a statistically significant difference between genotypes using independent samples t-tests. Scale bar = 100 uM.