Immunocytochemistry has revealed localization of Ras and P-ERK in neurons proximal to plaques and tangles in AD brains, while Western blot analysis has shown increased expression of components of the MAPK signaling cascade in conjunction with increased Aβ levels and phosphorylated tau (Trojanowski et al. 1993; Hyman et al. 1994; Arendt et al. 1995; Gärtner et al. 1995, 1999; McShea et al. 1999; Ferrer et al. 2001). Here, MAPT is linked to Alzheimer disease.