稳定表达hHCN2基因 HEK293细胞系的建立

目的：培育稳定表达hHCN2基因的细胞系,建立一种表达研究心肌离子通道的有效模型。方法：通过脂质体转染的方法,将重组pcDNA3-hHCN2真核表达载体导入人胚肾细胞（HEK293细胞）,以G418压力筛选转染细胞,并对其进行全细胞膜片钳记录。结果：经600μg／ml压力筛选后,获得抗性细胞克隆,并用全细胞膜片钳技术记录到克隆hHCN2通道编码电流。结论：本实验采用脂质体转染法成功地培育出G418抗性HEK293细胞。为进一步研究克隆离子通道结构和功能的关系奠定基础。     

稳定表达人SidT2基因细胞系的建立及其dsRNA转运功能的研究

目的:构建稳定表达人SidT2基因的BHK及MDCK细胞系,探讨SidT2基因过表达与细胞转运双链RNA(dsRNA)能力的关系。方法:根据人SidT2基因序列设计引物,克隆其编码区序列,经双酶切后与pEGFP-N3载体连接,构建其真核表达载体,分别瞬时转染BHK及MDCK细胞,并使用G418筛选稳定表达细胞系;在此基础上,体外转录合成绿色荧光蛋白(GFP)dsRNA,以GFP基因为报告基因,进一步分析过表达人SidT2基因对BHK及MDCK细胞转运dsRNA能力的影响。结果:经基因克隆、酶切、连接后,构建了人SidT2基因真核表达载体pEGFP-SidT2;经瞬时转染及G418筛选,获得稳定过表达人SidT2基因的BHK及MDCK细胞系,实时荧光定量RT-PCR分析表明,其SidT2基因转录水平分别提高71、64.5倍;稳定表达SidT2基因后,在培养液中添加GFP dsRNA,GFP荧光强度较对照细胞分别降低88.1%、73.7%,表明稳定表达SidT2基因的BHK、MDCK细胞转运dsRNA的能力显著增强。结论:构建了稳定表达人SidT2基因的BHK及MDCK细胞系,SidT2基因过表达可显著提高外源性dsRNA的转运能力。     

G418抗性HEK293细胞的培育

目的　培育具有G418抗性的HEK2 93细胞 ,用于建立猪内源性反转录病毒感染人HEK2 93细胞的模型。方法　通过脂质体转染的方法 ,将含有neo基因的质粒pIRESneo导入HEK2 93细胞中 ,利用G418的选择特性 ,对转染细胞进行压力筛选 ,并对其进行了PCR鉴定。结果　经 6 0 0 μg ml的G418压力筛选后 ,获得了抗性细胞克隆。抗性细胞的形态和生长速度与筛选前细胞没有差异 ,特异性核苷酸引物检测抗性细胞基因组DNA ,可以扩增出对应的核苷酸片段。结论　成功地培育了G418抗性HEK2 93细胞 ,为建立猪内源性反转录病毒感染人HEK2 93细胞的模型奠定了基础。     

BHK-21-derived cell lines that produce basic fibroblast growth factor, but not parental BHK-21 cells, initiate neuronal differentiation of neural crest progenitors.

We present evidence that basic fibroblast growth factor (bFGF)-producing cells stimulate primary differentiation of neurons from neural crest progenitors. Baby hamster kidney (BHK-21) cells were stably cotransfected with plasmid pSV2/neo, which contains the gene conferring resistance to the neomycin analog G418 and expression vectors containing the human bFGF cDNA. Various clones, which differed in their bFGF production levels, were isolated. Homogeneous neural crest cells were cultured on monolayers of bFGF-producing, BHK-21-derived cell lines. While the parental BHK-21 cells, which do not produce detectable bFGF, had poor neurogenic ability, the various bFGF-producing clones promoted a 1.5- to 4-fold increase in neuronal cell number compared to the parental cells. This increase was correlated with the levels of bFGF produced by the different transfected clones, which ranged between 2.3 and 140 ng/mg protein. In contrast, no stimulation of neuronal differentiation was observed when neural crest cells were grown on monolayers of parental BHK cells transfected with plasmid pSV2/neo alone, or on a parental BHK-derived clone, which secretes high amounts of recombinant vascular endothelial growth factor (VEGF). Furthermore, the neuron-promoting ability of bFGF-producing cells could be mimicked by addition of exogenous bFGF to neural crest cells grown on the parental BHK line. A similar treatment of neural crest cells grown on laminin substrata, instead of BHK cells, resulted in increased survival of non-neuronal cells, but not of neurons (see also Kalcheim, C. 1989, Dev. Biol. 134, 1-10). Taken together, these results suggest that bFGF stimulates neuronal differentiation of neural crest cells by a cell-mediated signalling mechanism.     

Transfection of a human gene for the repair of X-ray- and EMS-induced DNA damage

EM9 cells are a line of Chinese hamster ovary cells that are sensitive to killing by ethylmethanesulfonate (EMS) and X ray, since they are unable to repair the DNA damage inflicted by these agents. Through DNA-mediated gene transfer, human DNA and a selectable marker gene, pSV2neo, were transfected into EM9 cells. Resistant clones of transfected cells were selected for by growth in EMS and G418 (an antibiotic lethal to mammalian cells not containing the transfected neo gene). One primary clone (APEX1) and one secondary clone (TEMS2) were shown to contain both marker and human DNA sequences by Southern blot. In cell survival studies, APEX1 was shown to be as resistant to EMS and X ray as the parental cell type AA8 (CHO cells). TEMS2 cells were found to be partially resistant to EMS and X ray, displaying an intermediate phenotype more sensitive than AA8 cells but more resistant than EM9 cells. Alkaline elution was used to assess the DNA strand-break rejoining ability of these cells at 23 degrees C. APEX1 cells showed DNA repair capacity equal to that of AA8 cells; 75% of the strand breaks were repaired with a rejoining T 1/2 of 3 min. TEMS2 showed similar levels of repair but a T 1/2 for repair of 9 min. EM9 cells repaired only 25% of the breaks and showed a T 1/2 for repair of 16 min. The DNA repair data are consistent with the survival data in that the more resistant cell lines showed a greater capacity for DNA repair. The data support the conclusion that APEX1 and TEMS2 cells contain a human DNA repair gene.     

组织专一性表达自杀基因治疗人结肠癌的研究

构建了以癌胚抗原(CEA)基因启动子控制的HSV-TK和ECCD的表达质粒PCEA-TK和pCEA-CD. 将它们分别与pSV2-neo共转染人结肠癌细胞株LoVo和人宫颈癌细胞株HeLa. G418筛选得到细胞克隆LoVo/CEA-TK、toVo/CEA-CD、HeLa/CEA-TK和HeLa/CEA-CD. 与野生型LoVo细胞相比, LoVo/CEA-TK和LoVo/CEA-CD形态无明显改变, 生长曲线也相似, 但对GCV或5-FC的细胞毒的敏感性分别提高了2000倍或700倍.而HeLa/CEA-TK(或HeLa/CEA-CD)仍对低浓度GCV(或5-FC)不敏感. 以上结果显示了应用组织专一性表达的自杀基因治疗人结肠癌的可能性.     

Gene activation mediated by protein kinase C in human macrophage and teratocarcinoma cells expressing aminoglycoside phosphotransferase activity.

The bacterial neomycin phosphotransferase gene driven by the Moloney mouse leukemia virus long terminal repeat (LTR) or SV40 early region promoter was introduced into the human promonocyte-macrophage cell line, U937, and into the pluripotential human embryonic teratocarcinoma cell line, NT2/D1. Clonally derived cell lines capable of growing in 2-4 mg/ml of the aminoglycoside antibiotic, G418 (Geneticin), were established and transfected with pHIVCat, a plasmid expressing the bacterial chloramphenicol acetyl transferase (CAT) activity under the control of the human immunodeficiency virus (HIV-1) LTR. All of the G418 resistant (neo(r)) U937 cell lines and 10 of 14 neo(r) NT2/D1 cell lines exhibited reduced basal levels of CAT expression or impaired responses to activation of the HIV-1 LTR by phorbol 12-myristate 13-acetate (PMA) when compared to the parental lines. Other differences included inhibition of tat activation of the HIV-1 LTR and increased sensitivity of U937 cells to human tumor necrosis factor alpha. The expression of other eukaryotic promoters including the HTLV-1 LTR, SV40 ori sequences, and the human beta-actin gene promoter was similarly affected. However, differentiation of the neo(r) U937 cells into macrophages was neither delayed nor impaired. Because PMA is an activator of protein kinase C (PKC) and a potent inducer of HIV-1 directed gene expression, the amounts, sensitivity to G418, and cytosol to membrane translocation of this enzyme were determined in the wild type and neo(r) U937 cells. G418 at concentrations too low to affect cell growth (12-150 micrograms/ml) inhibited PMA-induced transactivation responses in wild type cells but did not inhibit PKC-dependent protein phosphorylation in vitro. PKC activities in the wild type and neo(r) cells were similar in absolute amounts and in the cytosol-membrane distribution of the enzyme. In contrast with wild type cells, however, all of the cytosolic Ca(2+)-phospholipid-dependent form of PKC disappeared from the neo(r) cells within 30 min after PMA induction. The results suggested that, depending upon the cell type, gene cotransfer using aminoglycoside resistance as a selectable marker may seriously perturb important cellular control mechanisms such as the PKC pathway leading to activation of gene expression.     

Selection of transgenic Xenopus laevis using antibiotic resistance

We previously established lines of transgenic Xenopus laevis expressing green fluorescent protein (GFP) or GFP fusion proteins in the rod photoreceptors of their retinas under control of the X. laevis opsin promoter, which permits easy identification of transgenic animals by fluorescence microscopy. However, GFP tags can alter the properties of fusion partners, and in many circumstances a second selectable marker would be useful. The transgene constructs we used also encode a gene that confers resistance to the antibiotic G418 in cultured mammalian cells. In this study, we show that F2 transgenic offspring of these animals are more resistant to G418 toxicity than their non-transgenic siblings, as are primary transgenic X. laevis. G418 resistance can be used as a selectable marker in transgenic X. laevis, and possibly other aquatic transgenic animals.     

稳定表达乙脑病毒结构蛋白的细胞系的建立

以乙型脑炎病毒SA14-14-2疫苗株全长基因组克隆质粒pBR-JTF为模板,通过PCR分别扩增prM-E及C-prM-E基因片段,构建表达乙型脑炎病毒结构蛋白的真核表达质粒pCJE-ME及pCJE-CME。将这2种重组质粒用脂质体法转染BHK-21细胞后,质粒pCJE-ME表现明显的细胞毒性,转染细胞不能存活;质粒pCJE-cME可导致筛选到表达JEV结构蛋白的稳定细胞系,这种稳定表达JEV结构蛋白的细胞系通过PCR扩增细胞系基因组、ELISA、Western Blot、间接免疫荧光等方法得到鉴定。研究结果表明在C蛋白存在下,乙型脑炎病毒C-prM-E蛋白可以在BHK细胞中稳定表达,为研制JEV新型复制子颗粒疫苗提供了便利工具。     

Circular YAC vectors containing short mammalian origin sequences are maintained under selection as HeLa episomes

pYACneo, a 15.8-kb plasmid, contains a bacterial origin, G418-resistance gene, and yeast ARS, CEN, and TEL elements. Three mammalian origins have been cloned into this circular vector: 343, a 448-bp chromosomal origin from a transcribed region of human chromosome 6q; X24, a 4.3-kb element containing the hamster DHFR origin of bidirectional replication (oribeta), and S3, a 1.1-kb human anti-cruciform purified autonomously replicating sequence. The resulting constructs have been transfected into HeLa cells, and G418-resistant subcultures were isolated. The frequency of G418-resistant transformation was 1.7-8.7 times higher with origin-containing YACneo than with vector alone. After >45 generations under G418 selection, the presence of episomal versus integrated constructs was assessed by fluctuation assay and by PCR of supercoiled, circular, and linear genomic cellular DNAs separated on ethidium bromide-cesium chloride gradients. In stable G418-resistant subcultures transfected with vector alone or with linearized constructs, as well as in some subcultures transfected with circular origin-containing constructs, resistance was conferred by integration into the host genome. However, several examples were found of G418-resistant transfectants maintaining the Y.343 and the YAC.S3 circular constructs in a strictly episomal state after long-term culture in selective medium, with 80-90% stability per cell division. The episomes were found to replicate semiconservatively in a bromodeoxyuridine pulse-labeling assay for 相似文献   

Adeno-associated virus vector for high-frequency integration, expression, and rescue of genes in mammalian cells.

We describe the construction of an adeno-associated virus (AAV) vector in which the coding sequence of the procaryotic gene neo is expressed under the control of the major AAV promoter p40. This AAV-neo vector allowed stable expression of neo as a dominant selective marker in mammalian cells by selection of cells which were resistant to the antibiotic geneticin (G418). When the vector was introduced into human (293 or HeLa) cell lines by a DNA transfection procedure, stable geneticin-resistant colonies were obtained. When the vector was first packaged into AAV particles and then introduced into cells via particle infection, geneticin-resistant cells were obtained at higher frequencies than those obtained by DNA transfection. In geneticin-resistant cells the AAV-neo vector was integrated at low copy number and could be rescued by subsequent infection with wild-type AAV and the helper adenovirus or, in some cases, by infection with adenovirus alone. The rescued AAV-neo vector could then be recovered as amplified unintegrated DNA from a Hirt lysate. These results demonstrate that AAV can be used as a transducing viral vector for stable integration and expression of a foreign gene in mammalian cells. The high frequency of integration and the ability to rescue the integrated vector suggest that this vector system may be useful for selecting genes from cDNA libraries. This vector may also be useful for introduction of genes into cells which are refractory to transfection in procedures such as those involving the use of CaPO4 or DEAE-dextran.     

The effects of G418 on the growth and metabolism of recombinant mammalian cell lines

It is widely reported that the growth of recombinant bacteria and yeast is adversely affected by increased metabolic load caused by the maintenance of plasmid copy number and recombinant protein expression. Reports suggest that recombinant mammalian systems are similarly affected by increased metabolic load. However, in comparison to bacterial systems relatively little information exists. It was the aim of this study to test the effects of recombinant gene expression on the growth and metabolism of two industrially important cell lines. A BHK and CHO cell line were stably transfected with the human gastric inhibitory peptide (h-GIP)and glucagon receptor respectively. Selection was by way of the neomycin resistance (neo ^r) gene using G418.The growth and metabolism of both cell lines was affected by the presence of G418 in a manner indicative of increased metabolic load and which appeared to be caused by over-expression of the neomycin resistance protein. The two cell lines differed in their metabolic response to G418, which suggested that some cell lines or clones may be better able to tolerate a metabolic load than others. Growth under increased metabolic load was affected by medium composition with serum, insulin and glutamine concentration as influencing factors. Implications for the use of G418 are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

SV 40-transformed normal and DNA-repair-deficient human fibroblasts can be transfected with high frequency but retain only limited amounts of integrated DNA

The ability of simian virus 40-transformed human fibroblasts to integrate and maintain transfected genomic DNA has been investigated in two normal and six DNA-repair-deficient human cell lines. These cell lines were transfected with DNA containing two selective markers (G418 and hygromycin (Hyg) resistance) separated by random pieces of human DNA of 0-40 kb in length. The transfection frequency for the selected (G418R) marker was between 2 x 10(-4) and 2 x 10(-3) for all cell lines, comparable to many other mammalian systems. About 50% of the G418R colonies were also initially resistant to Hyg. Analysis of the DNA from individual clones expanded for a further month revealed, however, that about one to three copies of the selected marker but only about 0.1 copy per cell of the unselected marker were maintained. Our results were broadly similar for all eight cell lines. Thus the amount of integrated DNA that is stably maintained in these cells is in general very small (less than 50 kb). This may provide an explanation for the difficulties encountered in many laboratories in attempts to correct the defect in DNA-repair-deficient human cells by transfection with genomic DNA. Our results also show that none of several defects in DNA repair has any obvious effect on either the transfection frequency or the amount of stably integrated foreign DNA.     

人GLP-1R基因转染BHK细胞及重组细胞的应用

为了构建表达人胰高血糖素样肽-1受体(GLP-1R)基因的BHK细胞株,并利用该重组细胞对GLP-1等相关肽进行活性测定,首先通过酶切、连接方式将人GLP-1R基因克隆至真核表达载体pCDNA3.(1 )中,然后用脂质体转染法将重组质粒转染至BHK-21细胞,转染后的细胞经G418加压筛选、细胞有限稀释等方法获得克隆细胞株。经过该细胞株RT-PCR验证,结果证实目的基因已整合至BHK-21细胞基因组中,并获得成功转录和表达。活性检测实验表明该重组细胞株经过GLP-1的刺激后,其细胞中的cAMP含量得到明显提升。该细胞株的构建为GLP-1及相关肽的活性测定奠定了基础。     

The role of human globin gene promoters in the expression of hybrid genes in erythroid and non-erythroid cells

Hybrid genes containing human gamma or beta globin gene promoters linked to a neomycin resistance (neoR) gene were transfected into erythroid (K562) and nonerythroid (HeLa) cells. The number of clones resistant to G418, a neomycin analogue, was used to assay promoter strength. The results indicate that in K562 cells both promoters are active, and the gamma gene promoter is much stronger than the beta. By contrast, neither gene promoter is active in HeLa cells. These experiments indicate that these globin gene promoters are tissue-specific and sufficient for activity.     

嘌呤霉素抗性基因捕获载体的构建及在细胞中的功能验证

目的构建具有嘌呤霉素抗性基因捕获载体,扩大基因捕获载体的应用范围。方法用经改造的捕获载体（gene trapping vector）稳定转染HepG2．2．15肝癌细胞系,经嘌呤霉素筛选,制作单克隆细胞株。用PCR方法验证该载体的在细胞染色体中的整合,ELISA方法证明捕获载体捕获基因后的细胞的功能改变。结果嘌呤霉素抗性基因捕获载体整合在HepG2．2．15肝癌细胞的染色体上,并能影响细胞HBsAg和HBeAg的分泌。结论新构建的嘌呤霉素抗性基因捕获载体能在具有G418抗性的细胞中捕获有意义的目的基因。     

稳定表达乙型肝炎病毒G145R变异表面抗原细胞系的建立

构建可以在真核细胞表达G145R HBsAg的重组质粒PCI-HBs145。用此质粒转染Hela细胞,经克隆化培养 以及G418筛选,建立稳定表达G145R HBsAg的细胞系。ELISA检测表明表达G145R HBsAg与野生型HBsAg 在免疫反应性上有较大的差异。生物学性状研究结果表明稳定表达G145R HBsAg的2A8细胞纯度好,遗传性状 稳定。     

Induced recombination between duplicated neo genes stably integrated in the genome of CHO cells

Homologous recombination between 2 truncated neo genes stably integrated in the genome of Chinese hamster ovary (CHO) cells was studied. A vector containing a functional gpt gene and 2 tandemly arranged G418 resistance (neo) gene fragments with about 400 bp of sequence homology was transfected into CHO cells. Clonal cell lines were established from transfected cultures and the spontaneous frequency of G418-resistant revertants was found to range between 1 x 10(-4) and 5 x 10(-4). The ability of the alkylating agents MMS and HN2 to induce recombination of the transfected neo genes was studied in 2 of the cell lines. After treatment with MMS at doses that reduced survival to 10% of the control these cell lines showed a dose-dependent increase in the frequency of G418-resistant revertants. No effect was observed after treatment with HN2. All G418-resistant subclones contained a new restriction fragment indicating that a whole neo gene had been formed by rearrangement in pairs of truncated neo genes. Hence, this system can be used to study molecular mechanisms and chemical inducibility of homologous recombination in mammalian cells.     

Immortalization of bovine germ line stem cells by c-myc and hTERT

The limited life span of bovine germ line stem cells in vitro is one of the obstacles to spermatogenesis analysis, genetic manipulation and generating transgenic animal. The aim of this study is to establish immortalized bovine germ line stem cells by c-myc or hTERT. We constructed pEMY and pETE expression vectors and transfected germ line cells from 5-month-old bovine. After G418 screening, four types of positive clones were obtained. The results showed that they expressed exogenous genes c-myc or hTERT at mRNA and protein level by RT-PCR and Western blotting detection. Presumable cell lines GM7, GT3, GMT5 all expressed germ-line-stem-cell-specific makers by immunocytochemical analysis, such as c-kit, Oct-4 and GFR-1. The putative cell lines also had higher capacity of proliferation than freshly isolated bovine spermatogonial stem cells. So we can conclude that exogenous genes c-myc or hTERT have integrated into the genome of bovine germ cells and upregulated the expression of telomerase.