Figure 1.

Schematic representation of tau isoforms in human adult brain. Tau isoforms (0N3R, 1N3R, 2N3R, 0N4R, 1N4R, 2N4R) are generated by alternative splicing of exons 2, 3, and 10. Two inserts N1 and N2 (brown boxes) near the N-terminus of tau are produced by exons 2 and 3, respectively. Absence of N1 and N2 gives rise to 0N isoforms, whereas inclusion of N1 produces 1N isoforms and inclusion of both N1 and N2 results in 2N isoforms. The proline-rich region is indicated in yellow. R1–R4 (orange boxes) represent the four microtubule- binding repeats, R2 being encoded by exon 10. The exclusion or inclusion of exon 10 results in isoforms with three or four microtubule-binding repeats named 3R and 4R isoforms.