Through the genetic research on the families of patients with AD, the researchers found three main pathogenic genes, namely, β-amyloid precursor protein (APP) gene, presenilin 1 (PS1) gene, and presenilin 2 (PS2) gene, which laid the foundation for the formation of Aβ to play an important role in the pathogenesis of AD (5). Here, PSEN2 is linked to Alzheimer disease.