MAPT and Alzheimer disease: One of the present authors (M.H.)had found that the asparagine residue at position 279 (N279), located in the RD4 epitope, was detected mostly as aspartic acid owing to deamidation of asparagine when PHF-tau in AD brains was subjected to protein sequencing and LC/MS/MS analysis after digestion with lysyl endopeptidase [8].