Misfolded tau seeds have been proposed to propagate trans-synaptically, moving between functionally connected neurons via exosomes, but also through vesicle-free mechanisms (Polanco and Gotz, 2022), while elevated Aβ oligomer levels have been found in exosomes isolated from AD brains (Sardar Sinha et al., 2018). This evidence concerns the gene MAPT and Alzheimer disease.