Autosomal-dominant variants of AD are associated with mutations in the genes that encode proteins involved in the generation of Aβ, including the APP gene, encoding amyloid-beta precursor protein (APP), as well as the PSEN1 and PSEN2 genes, encoding presenilin-1 (PS1) and presenilin-2 (PS2). Here, PSEN2 is linked to Alzheimer disease.