APP and Alzheimer disease: A decrease in the expression of APP, APLP1, APLP2, and their various binding partners, such as APBB1 and PSENEN, in elderly individuals with AD compared with aged but healthy individuals may contribute to the negative enrichment of pathways and gene ontologies related to neurodegeneration and AD because the APP gene encodes a precursor protein that generates various peptides after cleavage by secretases.