Figure 1.
Structure of the six tau isoforms expressed in the adult human brain
Human MAPT is located on chromosome 17q21.31 and has two main haplotypes: H1 (direct orientation) and H2 (inverse orientation). The gene contains 15 exons, including exon 0, which encodes the 5’ untranslated region (UTR). Tau isoforms can have zero, one, or two amino-terminal inserts based on alternative splicing of exons 2 and 3 (0N, 1N, 2N; shown in blue), The insertion of exon 3 is dependent on the presence of exon 2. Tau isoforms can also include three or four microtubule-binding repeats, depending on splicing of exon 10 (3R or 4R; shown in orange). Exon 4A corresponds to the alternative exon located between exons 4 and 5, and is expressed outside of the brain. Exon 6 is also expressed outside the brain, while exon 8 insertion has not been reported in humans.