MAPT and semantic dementia: The discovery of mutations in the tau gene and their cosegregation with the disease in the inherited frontotemporal dementia with parkinsonism linked to chromosome-17 (FTDP-17) has established that abnormalities in tau protein as a primary event can lead to neurodegeneration and dementia (Hutton et al. 1998; Poorkaj et al. 1998; Spillantini et al. 1998).