In AD brain, tau is abnormally hyperphosphorylated (Ksiezak-Reding et al., 1992; Köpke et al., 1993), which leads to the loss of biological activity, the gain of toxic activity, and the aggregation into paired helical filaments (PHFs; Iqbal et al., 1986; Alonso et al., 1994, 1996, 2001; Lucas et al., 2001; Fath et al., 2002; Jackson et al., 2002; Pérez et al., 2002). The gene discussed is MAPT; the disease is Alzheimer disease.