APP and Alzheimer disease: Such physiological humanised knock-in models include those for studying AD, whereby finescale humanisation of only a handful of mouse amino acids in the amyloid precursor protein (APP) encoded by the mouse App gene, resulted in a fully human amyloid beta peptide; and recreating unique human biochemistry, such that these mice provide an excellent physiological model of human amyloid beta protein deposition (Saito et al. 2014).