Interestingly, exosomes isolated from the CSF of patients with mild (Braak stage 3) and established neurodegeneration (Braak stage 5) are strongly positive for Tau protein, specifically Tau phosphorylated at threonine 181, and the proportion of pTau in the exosomal fraction is significantly higher in mild/moderate AD groups than in controls [76]. Here, MAPT is linked to Alzheimer disease.