MAPT and neurodegenerative disease: Abnormal processing, modification, and aggregation of tau protein in neurons and glial cells is central to the pathogenesis of several major neurodegenerative diseases, collectively known as “tauopathies.” Defined by the inclusion or exclusion of exon 10 of the tau microtubule‐binding region, tauopathies are often categorized into three repeats (3R), four repeats (4R), and 3R/4R tauopathies according to the tau isoform present in aggregates.