MAPT and Alzheimer disease: Tau plays major roles in the assembly of microtubules, the stabilization of microtubules against dynamic instability, and in bridging these polymers with other cytoskeletal filaments.[4] In AD, NFTs are formed by hyperphosphorylated tau.[5] In normal brain, the equilibrium between phosphorylations and dephosphorylation of tau modulates the stability of the cytoskeleton and consequently axonal morphology.