中文摘要：

通过相应再结合的指向的点 mutagenesis 广泛地在基因研究被使用了并且为在病人修理引起疾病的变化保持可观的诺言。然而，象 mosaicism 那样的问题和低 mutagenesis 效率继续提出挑战到如此的途径的临床的申请。最近，一个基础编辑器() 在 cytidine (C) 脱氨基酶上造的系统和 CRISPR/Cas9 技术在植物，酵母，和人的房间为指向的点 mutagenesis 作为一个其他的方法被开发。然而，基础编辑器高效地在 deamination 窗口中把 C 变换成 thymidine (T) 是否指向了在鼠标胚胎的基础编辑，仍然保持不清楚是可行的。在这份报告，我们产生了基础编辑的一个修改高保真版本 2 (HF2-BE2 ) ，并且调查了它在老鼠胚胎编辑功效的底。我们发现 HF2-BE2 能高效地把 C 变换成 T，与直到在老鼠胚胎的 100% biallelic 变化效率。不同于 BE3， HF2-BE2 能在目标和非目标海滨上把 C 变换成 T，扩展基础编辑器的编辑范围。令人惊讶地，我们发现 HF2-BE2 能也使脱去氨基对 gRNA 有约束力的区域近似的 C。一起拿，我们的工作表明由基础编辑，和下划线在鼠标产生点变化的可行性小心地优化编辑系统以便消除近似地点的 deamination 的底的需要。

英文摘要：

Targeted point mutagenesis through homologous recombination has been widely used in genetic studies and holds considerable promise for repairing disease- causing mutations in patients. However, problems such as mosaicism and low mutagenesis efficiency continue to pose challenges to clinical applicaUon of such approaches. Recently, a base editor （BE） system built on cytidine （C） deaminase and CRISPR/Cas9 technology was developed as an alternative method for targeted point mutagenesis in plant, yeast, and human cells. Base editors convert C in the deamination window to thymidine （T） efficiently, however, it remains unclear whether targeted base editing in mouse embryos is feasible. In this report, we generated a modified high- fidelity version of base editor 2 （HF2-BE2）, and investigated its base editing efficacy in mouse embryos. We found that HF2-BE2 could convert C to T efficiently, with up to 100% biallelic mutation efficiency in mouse embryos. Unlike BE3, HF2-BE2 could convert C to T on both the target and non-target strand, expanding the editing scope of base editors. Surprisingly, we found HF2-BE2 could also deaminate C that was proximal to the gRNA-binding region. Taken together, our work demonstrates the feasibility of generating point mutations in mouse by base editing, and underscores the need to carefully optimize base editing systems in order to eliminate proximal-site deamination.