The ordered part of each monomer in the fibril comprises residues306–378, corresponding closely to the shorter of two stabletau peptide fragments (9.5 and 12 kDa) identified in PHFs extractedfrom AD patient brains.30 Tau proteolysis,resulting in a variety of aggregation-prone tau fragments, is knownto occur in tauopathies,31,32 and recently, a recombinantfragment (residues 297–391) was reported to form highly orderedPHFs, although a detailed mechanistic understanding of its aggregationwas not described.33,34. This evidence concerns the gene MAPT and Alzheimer disease.