This system has demonstrated promise in gene function research and disease models, such as targeting the promoter of amyloid precursor protein (APP) via dCas9-Dnmt3a treatment to alter its DNA methylation for Alzheimer’s disease (AD) [11] and removing the 5mC target at the FLOWERING WAGENINGEN (FWA) promoter in the genome of Arabidopsis [17]. This evidence concerns the gene DNMT3A and Alzheimer disease.