APP and Alzheimer disease: Myelin perturbation was shown to increase the risk of developing or exacerbating AD—for example, by altering components of the Aβ-generating machinery, including the amyloid precursor protein (APP) and the APP-cleaving enzyme BACE1 (refs. 32,57), or by distracting microglia-mediated breakdown of Aβ due to redeployment of these cells to sites of myelin damage32.