MAPT and Alzheimer disease: Based on the reported Tau alterations observed in individuals with DS [5,13,77,78,79], the current study was focused on the following two central questions: (1) Do neuron-derived EVs (NDEVs) isolated from the plasma of persons with DS-AD contain Tau species that have seeding capacity in the WT mouse brain, and (2) If so, to which cell types in the CNS do the toxic species of Tau spread?