MAPT and early-onset autosomal dominant Alzheimer disease: In healthy neurons, the tau protein stabilizes axonal microtubules that are necessary for proper neuronal function, but in Alzheimer’s disease and tauopathies, there is an abnormal accumulation of tau protein in somatodendritic compartments, associated with axonal and synaptic dysfunction, neuronal loss, atrophy, and cognitive decline (Lee et al., 2001).