Enriched preparations of PHF from extracts of homogenates from AD brains by using N-lauroylsarcosine (sarkosyl) and 2-mercaptoethanol, after removal of aggregates by microfiltration, sucrose density centrifugation and immunoblotting, revealed three tau bands of 60, 64, and 69 kDa ([49]; a minor fourth band of 72 kDa being described later by Mulot et al. [50]). This evidence concerns the gene MAPT and Alzheimer disease.