Developing CRISPR/Cas9-Mediated Fluorescent Reporter Human Pluripotent Stem-Cell Lines for High-Content Screening

Application of the CRISPR/Cas9 system to knock in fluorescent proteins to endogenous genes of interest in human pluripotent stem cells (hPSCs) has the potential to facilitate hPSC-based disease modeling, drug screening, and optimization of transplantation therapy. To evaluate the capability of fluorescent reporter hPSC lines for high-content screening approaches, we targeted EGFP to the endogenous OCT4 locus. Resulting hPSC–OCT4–EGFP lines generated expressed EGFP coincident with pluripotency markers and could be adapted to multi-well formats for high-content screening (HCS) campaigns. However, after long-term culture, hPSCs transiently lost their EGFP expression. Alternatively, through EGFP knock-in to the AAVS1 locus, we established a stable and consistent EGFP-expressing hPSC–AAVS1–EGFP line that maintained EGFP expression during in vitro hematopoietic and neural differentiation. Thus, hPSC–AAVS1–EGFP-derived sensory neurons could be adapted to a high-content screening platform that can be applied to high-throughput small-molecule screening and drug discovery campaigns. Our observations are consistent with recent findings indicating that high-frequency on-target complexities appear following CRISPR/Cas9 genome editing at the OCT4 locus. In contrast, we demonstrate that the AAVS1 locus is a safe genomic location in hPSCs with high gene expression that does not impact hPSC quality and differentiation. Our findings suggest that the CRISPR/Cas9-integrated AAVS1 system should be applied for generating stable reporter hPSC lines for long-term HCS approaches, and they underscore the importance of careful evaluation and selection of the applied reporter cell lines for HCS purposes.     

增强型绿色荧光蛋白的色谱分离和纯化

增强型绿色荧光蛋白(EGFP)是生物领域常用的标记物。在前期成功克隆表达EGFP的基础上,本实验建立了两步分离纯化EGFP的色谱方法,并验证其分离纯化效果,检验EGFP的活性。首先用金属螯合亲和色谱柱HisTrap HP对EGFP的重组菌体破碎上清液进行初步分离,再用葡聚糖凝胶排阻色谱柱Sephadex G-10 HR对其进行脱盐纯化。采用丙烯葡聚糖凝胶排阻色谱柱Sephacryl S-300 HR和十二烷基磺酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)检测分离纯化后的EGFP纯度。最后通过荧光分光检测器和非变性聚丙烯酰胺凝胶电泳(Native-PAGE)验证分离纯化后的EGFP是否具有荧光活性。结果表明该方法可以简便快速地分离纯化EGFP,纯度超过98%,同时保持了EGFP的荧光活性。     

稳定表达egfp基因细胞的构建与克隆

将增强的绿色荧光蛋白（enhanced green fluorescent pprotein,EGFP）基因插在HCMV（humancytomegolovirus）启动子下游,构建了表达质粒pCA13-eG,用脂质体Lipofectin介导分别转染HeLa细胞、Vero细胞,仅通过细胞传代,就最能稳定高效表达EGFP的绿色细胞,比较发现,质粒pCS13-eG转染后,产生能高效表达EGFP的HeLa细胞其比率高于Vero细胞;EGFP高效表达对Vero细胞的毒性大于对HeLa细胞的毒性,本研究表明,绿色细胞轮廓清晰,由于其特有的性质,在用于细胞的形态观察、细胞分裂等研究时会有所作为。     

慢病毒载体转染离体兔角膜基质细胞的实验研究

目的：观察慢病毒载体转染离体兔角膜基质细胞的有效性及对细胞活性的影响。方法：转染组用慢病毒携带增强型绿色荧光蛋白（Lentivirus-enhanced green fluorescent proteins,Lenti-EGFP）转染细胞,对照组则加入空白培养液,在不同感染复数（multiplicity of infection,MOI）及感染后不同时间段在倒置荧光显微镜下观察绿色荧光蛋白的表达情况并计算转染率;RT-PCR检测EGFP mRNA的表达;MTT比色法和流式细胞技术（Flow cytometer,FCM）检测病毒对细胞增殖和凋亡的影响。结果：Lenti-EGFP转染细胞后从48h开始可见绿色荧光,在MOI=500时,转染后第5天转染率可达51%;RT-PCR检测转染组有EGFP的mRNA表达;MTT结果显示在MOI为1~500时,漫病毒不影响细胞的增殖;在MOI=500时,FCM检测慢病毒载体对细胞凋亡无影响。结论：慢病毒载体可以在体外稳定有效转染兔角膜基质细胞且不影响细胞活性,是角膜基质细胞理想的基因转染载体。     

污染水产去甲基化表观遗传毒性EGFP评价方法

pEGFP-C3质粒经过体外人工甲基化处理后,被转染进入HepG2细胞以构建重组细胞株．以5-AZA为阳性去甲基化毒物与重组细胞共培养,通过亚硫酸氢钠测序法定量检测EGFP基因启动子区甲基化状态,通过实时定量PCR检测EGFP基因表达,借助流式细胞术和荧光摄片定量检测共培养细胞的绿色荧光强度,在DNA甲基化、EGFP基因mRNA表达、GFP蛋白等多个层次研究5-AZA染毒处理与其去甲基化能力和荧光表达改变的响应关系．对天津污染水产的去甲基化能力进行了实际样品测试．结果表明,5-AZA与重组细胞的DNA甲基化、基因表达、蛋白产物变化之间存在显著关联,具有较低的检出浓度和良好的重复性．天津污染海域的水产去甲基化能力较强．本文初步建立了一种污染物去甲基化表观遗传毒性评价方法．