MAPT and early-onset autosomal dominant Alzheimer disease: Alzheimer’s disease (AD) is a neurodegenerative diseases characterized by decreased levels of amyloid-beta (Aβ) (reduced levels of Aβ in the cerebrospinal fluid due to deposition of Aβ in the brain), increased levels of total tau or phosphorylated tau, and a reduction in the number and function of synapses (Palop et al., 2006).