Using well-characterized clinical cohorts, we recently reported that serum levels of DDE, the metabolite of the organochlorine pesticide DDT is significantly higher in the serum of Alzheimer Disease (AD) cases and is associated with increased risk of AD diagnosis. Further, individuals harboring a polymorphism in APOE and having high serum levels of DDE performed worse on a cognitive task than either those with just the polymorphism or high DDE levels. Finally, we identified that DDT and DDE increase levels of amyloid precursor protein (APP), suggesting a possible mechanism by which DDT exposure may contribute to ADBased on our initial findings, the goals of this project include: (1) identifying the mechanism by which DDT exposure increases APP levels; (2) determining the effect of APOE genetic status on the effects of DDT on Aβ accumulation and oligomerization; and (3) assessing the effects of DDT exposure on AD pathology and behavioral dysfunction in transgenic mouse models humanized for APOE polymorphisms. We will achieve these goals using a combination of cutting edge techniques including epigenetic analysis, patient-specific stem cells, and transgenic mice harboring human polymorphisms.