MAPT and Alzheimer disease: Until now, changes in the level of Tau protein and the processes of its phosphorylation have been intensively studied in neurodegenerative diseases, in particular in Alzheimer’s disease (AD), in which hyperphosphorylated Tau protein is deposited in the brain in the form of neurofibrillary tangles (NFTs) and is involved in the molecular mechanisms of neuronal death [33,35,37,38,39].