MAPT and early-onset autosomal dominant Alzheimer disease: Notably, a cross-seeding activity for α-synuclein with other aggregating proteins has already been described: α-synuclein accelerates the aggregation of tau and amyloid-β, proteins implicated in Alzheimer’s disease (AD), and huntingtin, a protein involved in Huntington’s disease [45, 46, 50–53].