AD, whose diagnosis is firmly established post-mortem, is defined by the extracellular accumulation of amyloid -β (Aβ) peptides into extracellular amyloid plaques (Checler, 1995) and the presence of neuronal neurofibrillary tangles (NFT) made up of intraneuronal fibrillar aggregates of hyper- and/or abnormally phosphorylated Tau proteins (« Tau pathology »), a common feature of other neurodegenerative disorders called tauopathies (Sergeant et al., 2008). The gene discussed is MAPT; the disease is tauopathy.