MAPT and Alzheimer disease: The hippocampus plays a key role in learning and memory (Morris et al., 1982; Burgess et al., 2002; Neves et al., 2008), and is one of the first brain regions affected by AD pathological hallmarks, i.e., amyloid beta (Aβ) plaques composed of Aβ peptide and neurofibrillary tangles composed of abnormally hyperphosphorylated tau protein (Braak and Braak, 1991, 1995, 1996; Morrison and Hof, 2002).