MAPT and semantic dementia: Mis-splicing of exon 10 is a cause of that form of FTLD-tau, known as Frontotemporal Dementia with parkinsonism linked to chromosome 17 (FTDP-17) in which there is increased use of this splice site leading to an imbalance in the ratio of 3-repeat and 4-repeat tau isoforms, in favour of 4-repeat tau, with aggregation of the excess 4-repeat tau into neurofibrillary tangle-like structures [15, 29].