Base editing technology enables the generation of precisely genome‐modified animal models. In this study, we applied base editing to chicken, an important livestock animal in the fields of agriculture, nutrition, and research through primordial germ cell (PGC)‐mediated germline transmission. Using this approach, we successfully produced two genome‐modified chicken lines harboring mutations in the genes encoding ovotransferrin (TF) and myostatin (MSTN); however, only 55.5% and 35.7% of genome‐modified chickens had the desired base substitutions in TF and MSTN, respectively. To explain the low base‐editing activity, we performed molecular analysis to compare DNA repair pathways between PGCs and the chicken fibroblast cell line DF‐1. The results revealed that base excision repair (BER)‐related genes were significantly elevated in PGCs relative to DF‐1 cells. Subsequent functional studies confirmed that the editing activity could be regulated by modulating the expression of uracil N‐glycosylase (UNG), an upstream gene of the BER pathway. Collectively, our findings indicate that the distinct DNA repair property of chicken PGCs causes low editing activity during genome modification, however, modulation of BER functions could promote the production of genome‐modified organisms with the desired genotypes.

中文翻译：

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原始生殖细胞中高度升高的碱基切除修复途径导致鸡的碱基编辑活性低

碱基编辑技术能够生成精确基因组修饰的动物模型。在这项研究中，我们通过原始生殖细胞 (PGC) 介导的生殖系传递将碱基编辑应用于农业、营养和研究领域的重要家畜鸡鸡。使用这种方法，我们成功地生产了两个基因组修饰的鸡系，它们在编码卵转铁蛋白（TF）和肌生长抑制素（MSTN）的基因中含有突变；然而，分别只有 55.5% 和 35.7% 的基因组修饰鸡在 TF 和 MSTN 中具有所需的碱基替换。为了解释低碱基编辑活性，我们进行了分子分析以比较 PGC 和鸡成纤维细胞系 DF-1 之间的 DNA 修复途径。结果显示，相对于 DF-1 细胞，PGC 中碱基切除修复 (BER) 相关基因显着升高。随后的功能研究证实，可以通过调节 BER 通路上游基因尿嘧啶 N-糖基化酶 (UNG) 的表达来调节编辑活性。总的来说，我们的研究结果表明，鸡 PGC 独特的 DNA 修复特性导致基因组修饰过程中的编辑活性较低，然而，BER 功能的调节可以促进具有所需基因型的基因组修饰生物的产生。