Abstract

Glycosylase base editor (GBE) can induce C‐to‐G transversion in mammalian cells, showing great promise for the treatment of human genetic disorders. However, the limited efficiency of transversion and the possibility of off‐target effects caused by Cas9 restrict its potential clinical applications. In our recent study, we have successfully developed TaC9‐CBE and TaC9‐ABE by separating nCas9 and deaminase, which eliminates the Cas9‐dependent DNA off‐target effects without compromising editing efficiency. We developed a novel GBE called TaC9‐GBE YE1 , which utilizes the deaminase and UNG‐nCas9 guided by TALE and sgRNA, respectively. TaC9‐GBE YE1 showed comparable levels of on‐target editing efficiency to traditional GBE at 19 target sites, without any off‐target effects caused by Cas9 or TALE. The TaC9‐GBE YE1 is a safe tool for gene therapy.