Overview of dominantly inherited mutations in the amyloid precursor protein. Amyloid precursor protein (APP) is a type I integral membrane protein inserted in the cell membrane (upper part). The APP mutations are all clustered in or around the amyloid-beta (Aβ) peptide sequence, and this region is therefore displayed enlarged using the single amino acid code. White circles, mutations found; red font, resulting amino acid substitutions. Mutations cluster around the α-secretase, β-secretase and γ-secretase sites as indicated. They have various effects on the generation of Aβ as indicated, but their overall effect is an increased tendency to generate toxic species.