PSEN1 and Alzheimer disease: The combination of stem cell technology and gene editing technology has yielded some results in AD therapy, but many problems remain.CRISPR/Cas9 technology repaired the pathogenic mutant gene in APP/PS1 mutant iPSCs, and the abnormal accumulation of Aβ and tau protein was significantly reduced when they were re-differentiated into neural cells, which improved cognitive function in AD model mice.