RESUMO
The linearized plasmid pEGFP-N3 was electroporated into three different mouse ES cell lines MESPU-13, MESPU-35 and MESPU-62 derived from 129/ter, C57BL/6J and BALB/c mouse strains respectively. Resistant clones were selected in the presence of G418 and then were identified under the fluorescence microscope through blue exciting light. Positive green clones were primarily expanded and further sorted using FACS(fluorescence activated cell sorter). Finally five EGFP stable integrated cell strains were obtained and were expanded (2 strains from 129/ter, 1 strain from C57BL/6J and 2 strains from BALB/c). Each of the five cell strains presents high proliferation growth rate and typical morphology characters of ES cells and their colonies. More than 85% cells of each cell strain contain normal diploid karyotype. Then some analysis such as the AP (alkaline phosphatase) staining, oct4 gene expression assay, embryonic body formation and differentiated test in vivo and in vitro were made. The results indicated that the stable labeled ES cell strains had the normal karyotypes and maintained the ES cell typical characteristics.
Assuntos
Embrião de Mamíferos/metabolismo , Proteínas Luminescentes/metabolismo , Coloração e Rotulagem/métodos , Células-Tronco/metabolismo , Fatores de Transcrição , Fosfatase Alcalina/metabolismo , Animais , Diferenciação Celular/genética , Divisão Celular/genética , Linhagem Celular , Proteínas de Ligação a DNA/genética , Eletroporação , Embrião de Mamíferos/citologia , Citometria de Fluxo/métodos , Expressão Gênica , Proteínas de Fluorescência Verde , Cariotipagem , Proteínas Luminescentes/genética , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos , Fator 3 de Transcrição de Octâmero , Plasmídeos/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Transplante de Células-Tronco , Células-Tronco/citologia , Transfecção/métodosRESUMO
RNA interference is a phenomenon of gene silencing directed by double-stranded RNA. It can specifically inhibit gene expression by degrading mRNA efficiently and has been widely used to knockdown gene expression in Caenorhabditis elegans, Drosophila melanogaster, etc. For mammalian cells, dsRNA directed RNAi was detected only in murine undifferentiated ES or embryonic carcinoma (EC) cells. Our previous work proved the existence of RNAi effect for reporter gene GFP and endogenous gene Oct4 in undifferentiated murine ES cells. Yet in other kinds of mammalian cells, because of the existence of interferon pathway, long dsRNA will induce the cells to shutdown global protein translation and go to apoptosis. Therefore, dsRNA longer than 30 bp cannot be used to induce specific gene knockdown effect in these cells. Elbashir et al found that in vitro synthesized small interfering RNA (siRNA) (19-23 nt) could induce potent RNAi as effective as long dsRNA without showing unspecific effect, so that the interferon pathway could be bypassed. It was shown that during RNAi process, long dsRNA was first degraded into 19-23 nt siRNA and then recruited into RISC (RNA induced silencing complex) to degrade corresponding mRNA. However, the synthesis of siRNA is expensive and the effect is transient because the knockdown effect can only be maintained for about a week. Recently, it has been shown that U6 promoter directed small hairpin RNA (shRNA) can induce potent gene knockdown effect in murine P19 Embryonic Carcinoma cell. The RNAi effect of U6 promoter-driven shRNA corresponding to Green Fluorescence Protein (GFP) in COS-7 cells was checked. And it was found that the U6 promoter-driven shRNA for GFP can specifically and potently knockdown the GFP's expression in COS-7 cells. The result established the feasibility of using RNAi technique directed by U6 promoter-driven shRNA to study genes' function in COS-7 cell line.