APOE and Alzheimer disease: In order to understand the regional and dosage effects of APOE4 allelic expression, we studied APOE3/3, APOE3/4, and APOE4/4 mice (n = 8 mice per group) and extracted lipids from two brain regions: the EC, which is one of the first brain regions where neurofibrillary tangles (NFTs) accumulate in AD, and the PVC, which develops tangle pathology at a later stage [46].