We detected the expression of cystatin F in 5XFAD transgenic mice, which express human APP and PSEN1 transgenes with a total of five AD-linked mutations, namely, the Swedish (K670N/M671L), Florida (I716V), and London (V717I) mutations in APP and the M146L and L286V mutations in PSEN1 [57]. This evidence concerns the gene PSEN1 and Alzheimer disease.