APP and Alzheimer disease: Familial AD involves a number of single-gene mutations on chromosomes 1, 14 and 21, which corresponds to the abnormal presenilin 2, presenilin 1 and amyloid precursor protein production respectively [13,14,15,16,17], and each of these mutations is believed to play a very important role in the cleavage of APP and thus affect Aβ production.