MAPT and Alzheimer disease: Progressive impairment of episodic memory and other cognitive functions are the characteristic features of AD, and the diagnosis is supported by biomarkers, in particular, increased total tau (t-tau) and phosphorylated 181 P tau (p-tau) levels with low amyloid-beta 1–42 (Aβ42) levels in the cerebrospinal fluid (CSF), and positive amyloid PET9,11,12.