PSEN1 and Alzheimer disease: In AD research, many CRISPR/Cas9 systems have been tested in mouse models and iPSCs, and there are newer variants of the traditional CRISPR/Cas9 system, like base editing and Prime editing included, such as in mouse models, where CRISPR/Cas9 has been used to accurately knock-in and knock-out AD-related genes (e.g., APP and PSEN1), which results in a model that more closely resembles the human AD pathological condition.