MAPT and early-onset autosomal dominant Alzheimer disease: Alzheimer’s disease (AD) is the most common form of age-related neurodegenerative disorder characterized by the presence of extracellular amyloid plaques consisting of β-amyloid peptides (Aβ) and intracellular neurofibrillary tangles (NFT) composed of hyperphosphorylated tau (p-tau) protein in diseased brains.