MAPT and semantic dementia: Mutations in tau have been shown to cause frontotemporal dementia with parkinsonism linked to tau mutations on chromosome 17 (FTDP-17T) and neurofibrillary tangles which mainly consist of hyperphosphorylated tau are a pathological hallmark of Alzheimer's disease (Grundke-Iqbal et al., 1986; reviewed in Iqbal et al., 2016).