MAPT and early-onset autosomal dominant Alzheimer disease: With the recent convergence of scientific evidence that many, if not most, neurodegenerative diseases are caused by proteins that become prions [74], [75], the identification of organisms expressing Aβ, tau, or α-synuclein proteins that exhibit an increased propensity to misfold may facilitate studies on the transmissibility of Alzheimer's disease and Parkinson's disease.