The retrovirus-based “single-cell genetic” approach is not best suited to investigate the proliferation phase of adult neurogenesis in vivo because of the delay in transgene/shRNA expression after stable viral integration into the host genome and rapid cell cycle exit of infected transient amplifying cells (Ge et al., 2006). However, such approach has been shown to be effective in affecting the fate choice of adult neural progenitors in vivo (Jessberger et al., 2008). To ensure that our genetic manipulations of the AKT signaling pathway do not perturb neuronal subtype differentiation of adult neural progenitors, we examined the expression of Prox-1, a dentate granule cell marker, and Parvalbumin, an interneuron marker (Duan et al., 2007). Immunostaining showed that at 14 dpi, all GFP+ neurons expressing KIAA1212 or CA-AKT also expressed Prox-1, but not Parvalbumin (Figure S6). Thus, the observed defects on soma hypertrophy and ectopic dendrites under these conditions were not due to changes in neuronal subtype differentiation of adult neural progenitors in the adult brain.
