MAPT and Alzheimer disease: Recently, we used biochemical extraction and mass spectrometry (MS) to show that specific tau fragments, such as the residues 243–254 (MTBR-tau243; R1), 299–317 (MTBR-tau299; R2-R3) and 354–369 (MTBR-tau354; R4), differentially enriched in AD brains with disease progression19.