The main mechanism underlying AD is that β-amyloid precursor protein (APP) produces significant levels of neurotoxic Aβ42 through the amyloid degradation pathway; then, neurotoxic Aβ42 can induce tau protein aggregation and hyperphosphorylation, and hyperphosphorylated tau and normal tau compete for binding to tubulin, disrupting the dynamic balance of microtubule assembly and decomposition, and ultimately form NFTs [71], causing region-specific synaptic degeneration and neuronal loss and leading to dementia [72]. The gene discussed is MAPT; the disease is Alzheimer disease.