Abstract
Recently, a rationally engineered SpCas9 variant (SpCas9-NG) that can recognize a minimal NG protospacer adjacent motif (PAM) was reported to expand the targeting scope in genome editing. However, increased genome-wide off-target mutations with this variant compared with SpCas9 were reported in previous studies. In addition, lower base editing frequencies and higher unintended off-target mutations were also found in Hoxc13-ablated rabbits generated by NG-BE4max in our study. Here, a high-fidelity base editor, NG-HiFi, in comparison to NG-BE4max, showed retention of on-target activity while exhibiting significantly decreased off-target activity in Hoxc13-ablated rabbits. Collectively, the improved specificity and reduced off-target effect of SpCas9-NG assisted in cytidine base editing with the NG-HiFi system, providing a promising tool to precisely model human diseases in rabbits.