Many genetic diseases are caused by single-nucleotide polymorphisms (SNPs). Base editors can correct SNPs at single-nucleotide resolution, but until recently, only allowed for C:G to T:A and A:T to G:C transition edits, addressing four out of twelve possible DNA base substitutions. Here we developed a novel class of C:G to G:C Base Editors (CGBEs) to create single-base genomic transversions in human cells. Our CGBEs consist of a nickase CRISPR-Cas9 (nCas9) fused to a cytosine deaminase and base excision repair (BER) proteins. Characterization of >30 CGBE candidates and 27 guide RNAs (gRNAs) revealed that CGBEs predominantly perform C:G to G:C editing (up to 90% purity), with rAPOBEC-nCas9-rXRCC1 being the most efficient (mean C:G to G:C edits at 15% and up to 37%). CGBEs target cytosine in WCW, ACC or GCT sequence contexts and within a precise two-nucleotide window of the target protospacer. We further targeted genes linked to dyslipidemia, hypertrophic cardiomyopathy, and deafness, showing the therapeutic potential of CGBE in interrogating and correcting human genetic diseases.

中文翻译：

---

基因组DNA的精确和可编程C：G到G：C碱基编辑

许多遗传疾病是由单核苷酸多态性（SNP）引起的。碱基编辑者可以单核苷酸分辨率校正SNP，但直到最近，才允许C：G到T：A和A：T到G：C的过渡编辑，解决了十二种可能的DNA碱基取代中的四种。在这里，我们开发了新颖的C：G到G：C基础编辑器（CGBE）类，以在人类细胞中创建单碱基基因组转化。我们的CGBE由与胞嘧啶脱氨酶和碱基切除修复（BER）蛋白融合的切口酶CRISPR-Cas9（nCas9）组成。表征> 30种CGBE候选物和27种引导RNA（gRNA）显示，CGBE主要执行C：G到G：C的编辑（纯度高达90％），其中rAPOBEC-nCas9-rXRCC1效率最高（平均C：G至G：C编辑比例为15％至37％）。CGBE靶向WCW中的胞嘧啶，ACC或GCT序列上下文，并在目标原型间隔子的精确两个核苷酸窗口内。我们进一步靶向与血脂异常，肥厚型心肌病和耳聋相关的基因，显示了CGBE在审讯和纠正人类遗传疾病中的治疗潜力。