PSEN1 and Alzheimer disease: These models are characterized by the presence of AD-related human mutations in the APP gene alone or in combination with mutations on the presenilin 1 or 2 genes, all involved in the release of the \documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\beta$$\end{document}βA peptide.