目的：运用CRISPR/Cas9基因编辑技术，在人恶性横纹肌样瘤细胞株G401中敲除p21基因。方法通过反转录定量PCR（RT-qPCR）及Western blot检测各瘤细胞株中p21的表达，针对p21基因作用的功能域，设计了靶向人p21基因第3个外显子的向导RNA（sgRNA），克隆入lentiCRISPR v2载体。将测序及酶切鉴定正确的重组质粒在293T工具细胞中制备慢病毒颗粒并感染G401细胞，使用嘌呤霉素进行阳性细胞筛选，显微镜下挑取单克隆细胞团并继续培养获得G401单克隆细胞株。提取单克隆细胞株RNA及蛋白，利用RT-qPCR及Western blot方法检测细胞株中p21的敲除效果。结果 p21在人横纹肌样瘤细胞中高表达。成功构建靶向p21基因的lentiCRISPR v2-sgRNA重组慢病毒质粒。与对照组相比，筛选得到的G401亚克隆细胞系中p21蛋白表达缺失。结论针对难转染的G401细胞，应用CRISPR/Cas9系统成功构建了p21基因敲除的稳定株，为后续深入研究p21在人恶性横纹肌样瘤中的作用机制奠定了基础。%Objective To knock out p21 gene in human malignant rhab doid tumor(MRT)cell line G401 by using CRISPR/Cas9 genome engineering technology. Methods The expression of p21 was detected by reverse transcription quantitative PCR (RT-qPCR) and Western blot assay in several MRT cell lines. The guide RNA was designed by targeting the third exon of p21 gene,which encoded its home domains, and then subcloned into lentiCRISPR v2 vector and validated sequencing. The validated plasmids were further used to package and produce the lentivirus in 293T cells, and the G401 cells were infected, then puromycin was used to screen positive cells, and the clusters of G401 monoclonal cells, were obtained by selecting monoclonal cells and culturing under the microscope. The RNA and protein of new clonal cell line were extracted, and RT-qPCR and Western blot assay were applied to confirm whether p21 was successfully knocked out. Results The p21 was highly expressed in MRT tumor cells. The CRISPR/Cas9 lentivirus plasmids, targeted p21 gene were successfully constructed. Compared with negative control group,the expression of p21 was not detected in G401 monoclonal cells, which were successfully screened. Conclusion In view of the difficult transfection of cells such as G401, p21 knockout stable cell line has been successfully constructed by using CRISPR/Cas9 system, which lays the foundation for further study of the mechanism of p21 in MRT tumors .
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