MAPT and tauopathy: The core of tau protofilaments found in the 4R tauopathy is made of residues spanning from the last amino acid of R1, the whole of R2, R3, and R4 and 12 amino acids after the R4 region (K274-E380 of full-length tau), where a total of 11 β-sheet secondary structures of the protein are stacked together in four layers and connected to each other by turns and arcs.