Recently, Woodruff et al. demonstrated that PSEN1 mutations disrupted γ-secretase activity and the mutation acted dominantly to execute toxic effects [28]. We hypothesized that a reduction in the level of endogenous mutated PSEN1 expression in AD-NPCs might be able to correct premature neuronal differentiation of AD-NPCs. To this end, shRNA sequences specific to PSEN1 were introduced into A15-NPC-3 (Figure 5a). Amazingly, knocking down the expression of PSEN1 in AD-NPCs abrogated the phenotype of faster appearance of neurites observed in AD-NPCs at day 28 of differentiation (Figure 5b). Moreover, immunofluorescence staining results revealed that the knock down of PSEN1 in AD-NPCs brought the percentage of MAP+ and Nestin+ cells closer to those in N-NPCs at day 28 of differentiation (Figure 5c-5e). Importantly, the number of Nestin+ NPCs and the percentage of proliferative cells were increased after PSEN1 knock down (Figure 5e-5g). These results indicated that reduction of the mutant PSEN1 expression in AD-NPCs could attenuate the abnormal neuronal differentiation.
