First, the presence of mutations in the genes encoding presenilin 1 (PS1), amyloid precursor protein (APP), and tau (MAPT) have been identified as causing familial AD (PS1M146V, APPSWE) or tauopathies including frontotemporal dementia and parkinsonism linked to chromosome 17 (MAPTP301L) [49]. The gene discussed is MAPT; the disease is semantic dementia.