Multiple missense and deletion mutations of tau gene coding region and intron have been found in chromosome 17 of FTDP-17 patients, which will lead to changes in tau function, excessive phosphorylation, aggregation of insoluble Tau in brain tissue, destruction of microtubule system, degeneration of nerve cells, deletion and eventually frontotemporal dementia, and Parkinson's syndrome. The gene discussed is MAPT; the disease is semantic dementia.