MAPT and Alzheimer disease: MTBR tau fragments, a proxy for neurofibrillary tangle presence, were substantially increased in AD, with + 8,579% increases for MTBR tau243-254 (p = 0.0006, Fig. 2O) and + 19,534% increases for MTBR tau354-369 (p = 0.0003, Fig. 2P).