MAPT and Alzheimer disease: The SAMP8 substrain is an ideal strain for the study of early age-related diseases as it closely resembles the age-related changes found in AD patients, such as cognitive impairment, learning and memory deficits, β-amyloid (Aβ) peptide aggregates, hyperphosphorylated tau, gliosis in astrocytes, alterations in the cholinergic system, and epigenetic modifications.