MAPT and Alzheimer disease: At present, AD diagnosis is based on the existence of dementia, brain volume changes detected by magnetic resonance imaging (MRI), and brain amyloid β-protein (Aβ) or Tau deposition detected by positron emission tomography (PET), together with an Aβ42 decrease and a phosphorylated/total Tau increase in the cerebrospinal fluid (CSF) [6].