In the second part of the study water-soluble extracts from AD, DLB and Pick’s disease (PiD) brain induced neurotoxic effects dependent on the presence of specific protein aggregates, and immunoprecipitation of single protein Aβ for AD brain extract, α-syn for DLB and tau for PiD nullified the respective toxicity and the elimination of PrPc from the neuronal cells (iPS-derived) completely antagonized it; furthermore the extract from neurodegeneration-free brain was not toxic at all. The gene discussed is MAPT; the disease is Alzheimer disease.