Lijie Wang, Wei Xue, Hongxia Zhang, Runze Gao, Houyuan Qiu, Jia Wei, Lina Zhou, Yun-Ni Lei, Xiaocheng Wu, Xiao Li, Chengfang Liu, Jing Wu, Qiubing Chen, Hanhui Ma, Xingxu Huang, Cheguo Cai, Ying Zhang, Bei Yang, Hao Yin, Li Yang and Jia Chen
The fusion of CRISPR–Cas9 with cytidine deaminases leads to base editors (BEs) capable of programmable C-to-T editing, which has potential in clinical applications but suffers from off-target (OT) mutations. Here, we used a cleavable deoxycyti-dine deaminase inhibitor (dCDI) domain to construct a transformer BE (tBE) system that induces efficient editing with only background levels of genome-wide and transcriptome-wide OT mutations. After being produced, the tBE remains inactive at OT sites with the fusion of a cleavable dCDI, therefore eliminating unintended mutations. When binding at on-target sites, the
tBE is transformed to cleave off the dCDI domain and catalyses targeted deamination for precise base editing. After delivery into mice through a dual-adeno-associated virus (AAV) system, the tBE system created a premature stop codon in Pcsk9 and significantly reduced serum PCSK9, resulting in a ~30–40% decrease in total cholesterol. The development of tBE establishes a highly specific base editing system and its in vivo efficacy has potential for therapeutic applications.
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