AD is the most common form of dementia in the elderly and is characterized by two neuropathological hallmarks: intracellular neurofibrillary tangles, that are mainly composed of an aberrantly high phosphorylated and thus aggregate-prone protein called Tau, and extracellular amyloid plaques, which are mainly formed by the Aβ peptide, which results from aberrant cleavage of the amyloid precursor protein (APP). Here, APP is linked to Alzheimer disease.