APP and Alzheimer disease: AD neuropathology is underpinned by two molecular hallmarks; intracellular neurofibrillary tangles (NFTs) composed of hyper-phosphorylated Tau and extracellular amyloid beta (Aβ) plaques, composed of Aβ peptides derived from the amyloid precursor protein (APP) (Nixon and Yang, 2011; Cai et al., 2012).