Protein sequence analysis of the three major bands at 7, 12 and 15 kDa from AD brains revealed that all these bands contained two fragments of both 3R and 4R tau isoforms with the N-terminal sequences, HQPGGGKVQIVY (268–279 of 3R tau) and HVPGGGSVQIVY (299–310 of 4R tau) (Suppl Fig. 3b). This evidence concerns the gene MAPT and Alzheimer disease.