In patients without AD, normal tau protein plays a role in microtubule-mediated axonal transport in neurons; however, in AD, hyperphosphorylated tau misfolds to form intraneuronal tangles that disrupt both axonal transport and synaptic function (Medeiros et al., 2011; Ashraf et al., 2014; Ittner et al., 2010). Here, MAPT is linked to Alzheimer disease.