Given that the catalysis of tau aggregation by Aβ42 is observed at physiological low nanomolar concentrations of Aβ42, the finding suggests that such aggregation catalysis of tau by Aβ42 can be a molecular mechanism underlying the pathological tau aggregation process associated with the onset and development of Alzheimer’s disease. The gene discussed is MAPT; the disease is early-onset autosomal dominant Alzheimer disease.