MAPT and Alzheimer disease: However, in the brains of people with AD, tau becomes hyperphosphorylated, which means that the protein detaches from microtubules and clings to other tau molecules forming fibers that accumulate as neurofibrillary tangles (NFTs) (Umeda et al., 2014, Hurtado et al., 2010, Serrano-Pozo et al., 2011).