中文摘要：

能识别特定基因组DNA序列的核酸酶是基因编辑的重要工具。在单链RNA引导下。来源于一种产脓链球菌的成簇规律间隔短回文重复（clusteredregularly imerspaced short palindromic repeats，CRISPR）关联蛋白（CRISPR．associatedprotein9，Cas9）能够发挥其核酸酶功能对基因纽特定序列进行剪切。这种功能依赖于单链引导RNA（single—guideRNAs，sgRNAs或gRNAs）中20nt的核心靶向序列。在该研究中，作者对已有的CRISPR／Cas9系统载体进行了优化，简化了gRNA表达载体的构建。运用优化后的CRISPR／Cas9系统，我们敲除了HEK93T细胞HtrA2基因的第一个外显子。这一改进大幅度降低了CRISPR／Cas9技术的使用成本。

英文摘要：

Sequence-specific nucleases are powerful tools for genome editing. The RNA-guided Cas9 nuclease from Streptococcus pyogenes can be effectively targeted to genomic loci and generate DNA breaks. The site-specific DNA cleavages of Cas9 rely on the core 20 nt targeting sequences within its guide RNA （sgRNA or gRNA）. In this paper, we describe a modified version of the CRISPR/Cas9 system, which significantly simplifies the construction of gRNA expression vectors. Using this system, we have efficiently generated HtrA2 knockout HEK293T cells by removing the first exon of the gene. This improvement significantly reduces the cost associated with the genome editing using CRISPR/CAS9 system.