Figure 2. The D664A Point Mutation Rescues Aβ-Mediated Synaptic Dysfunction.

(A) Representative dendritic spine images of hippocampal OTSCs from APP WT and D664A KI mice. The OTSCs were incubated in 7PA2-conditioned media containing 150 pM Aβ₄₂ for 5 days in vitro. GFP-expressing Sindbis virus was injected 1 day prior to experiment endpoint. Scale bar, 20 μm. (B) Quantification of dendritic spine densities in OTSCs shown in (A). 7PA2 containing 150 pM or 250 pM Aβ₄₂ significantly reduced spine density; however, spine density was unchanged in D664A KI mice. n = 50 neurons (CHO media), n = 37 neurons (150 Aβ₄₂), n = 30 neurons (250 Aβ₄₂) from 9 APP D664AKI mice; n = 43 neurons (CHO media), n = 40 neurons (150 pM Aβ₄₂), n = 31 neurons (250 pM Aβ₄₂) from 10 WT littermate control mice. *p ≤ 0.05, **p ≤ 0.01 by two-way ANOVA followed by Tukey’s multiple comparisons test. Aβ-immunodepleted 7PA2-conditioned medium showed no significant reduction in spine density. n = 10 neurons from 4 APP D664A KI mice and n = 10 neurons from 4 WT littermate controls. NS, not significant by Student’s t test. (C) 7PA2-conditioned media depressed LTP as compared to untransfected CHO media. This impairment was rescued in APP D664A KI mice. n = 11 slices for each of four conditions. **p ≤ 0.01 by two-tailed Student’s t test comparing WT-7PA2 versus D664A-7PA2.