| Summary: | (A-H) Aversive olfactory conditioning experiments were conducted with Aβ 42 Arctic expressing flies. (A, B) Pan-neuronal expression of Aβ 42 Arctic impaired memory measured immediately (0 h) after training in 7- to 9-day-old flies (A) 4- to 5-day-old nSyb>Aβ 42 Arctic flies (B), n ≥ 12. (C, D) Flies expressing Aβ 42 Arctic in the MB using Ok107-Gal4 did not perform differently from parental controls for 0-h memory (C; n ≥ 12) but showed a significantly lower 2-h memory performance (D; n ≥ 12). (E, F) Flies expressing the nontoxic Aβ 40 in the MB have no significant memory impairment 0 h (E) or 2 h (F) after conditioning (n ≥ 12). (G, H) The GeneSwitch Gal4 system was used to restrict the expression of Aβ 42 Arctic to the adult stage, by feeding flies RU486 after the hatching for 8 days until the conditioning experiments. (G) elav - Gal4 GS Aβ 42 Arctic flies fed with RU486 showed a lower performance index than vehicle-treated flies 2 h after training (n ≥ 12). (H) Induction of Aβ 42 Arctic expression after hatching in MB cells using MB - Gal4 GS resulted in a slightly reduced 2-h memory performance (n ≥ 12). (I-N) Appetitive olfactory conditioning experiments were performed with flies expressing Aβ 42 Arctic in the brain or specifically in the MB. (I, J) Expression of Aβ 42 Arctic in the whole brain impaired memory measured immediately (I; n ≥ 12) and 24 h after conditioning (J; n ≥ 12). (K-N) MB-specific expression of Aβ 42 Arctic using OK107-Gal4 did not affect 0-h memory (K), whereas 2-h (L), 6-h (M), and 24-h (N) memory performances were reduced in AD flies compared to parental control flies (n ≥ 12). See S1 – S3 Figs for sensory controls and S1 Table for the data. Bar graphs represent the mean, and error bars represent the standard error of the mean. Asterisks denote significant difference between groups (* p < 0.05, ** p < 0.005, *** p < 0.001). AD, Alzheimer disease; MB, mushroom body.
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