Tauopathies are, therefore, classified into three main categories based on the predominant tau isoform in their aggregates: 3R tauopathies (e.g., FTD), 4R tauopathies (e.g., PSP and CBD), and mixed 3R/4R tauopathies such as AD and chronic traumatic encephalopathy. This evidence concerns the gene MAPT and Alzheimer disease.