Third, artificial elimination of one copy of BACE2 by CRISPR/Cas9 editing in the trisomy-21 iPSCs caused an extremely accelerated presence of a triad of AD-like neuropathological signs: amyloid plaque–like deposits, pathologically conformed intraneuronal tau, and progressive neuronal loss (20). The gene discussed is BACE2; the disease is Alzheimer disease.