For example, alternative spicing of tau (12, 13, 14, 15), which forms NFTs and is mutated in frontotemporal dementia (16, 17, 18, 19, 20, 21, 22, 23), leads to expression of tau isoforms with three or four microtubule-binding domains (3R and 4R, respectively). This evidence concerns the gene MAPT and frontotemporal dementia.