MAPT and Alzheimer disease: Altered synaptic functions and loss of synapses underlie the cognitive impairment seen in Alzheimer ́s disease (AD) [2–6], which is a progressive neurodegenerative brain disorder characterized by depositions of extracellular amyloid-beta (Aβ) plaques and intracellular accumulation of tau neurofibrillary tangles (NFTs) [7, 8].