Soluble tau levels are reduced in AD brains compared to control brains (Ksiezak-Reding et al., 1988; Shin et al., 1992; Khatoon et al., 1994; Zhukareva et al., 2001, 2003; van Eersel et al., 2009); which might result from tau deposition into insoluble aggregates during the disease progress (Khatoon et al., 1994). This evidence concerns the gene MAPT and Alzheimer disease.