气道内微量雾化机对质粒DNA完整性和基因转染效率的影响

目的:探索新型气道内微量雾化机对质粒DNA(pDNA)完整性和整体动物基因转染效率的影响。方法:首先,研究新型气道内微量雾化机对pDNA破坏程度。分别向新型气道内微量雾化机和目前临床普遍使用的机械喷射式雾化机的加药池内加入2ml pDNA(20μg/ml),在开始雾化后第1min、3min、5min分别收集两种雾化机嘴处的雾化液滴,用琼脂糖凝胶电泳观察比较质粒的完整性。其次,研究整新型气道内微量雾化机在整体动物上对基因转染效率的影响。分别用新型气道内微量雾化机和目前临床普遍使用的机械喷射式雾化机,给大鼠雾化经多聚乙烯亚胺(polyethylenimine,PEI)修饰的相同量的绿色荧光蛋白质粒(plasmid DNA of green fluorescent protein gene, pEGFP)3.3μg(PEI/pEGFP),24h后提取动物肺组织进行反转录,用real time PCR及琼脂糖凝胶电泳观察分析绿色荧光蛋白(green fluorescent protein, GFP)的mRNA表达情况。结果:新型气道内微量雾化机在雾化第1min、第3min、第5min后完整的质粒比例分别为(99.6±0.7)%、(100±1.2)%、(99.6±0.7)%,与未雾化对照相比(P>0.05,n=3),无统计学差异,新型雾化机对质粒破坏性可以忽略。临床常用的喷射式雾化机在相同时间段内完整的质粒比例分别为(70.3±1.5)%、(49.3±1.5)%、(32.7±0.6)%。与未雾化对照相比(P<0.05,n=3)有统计学差异,并且随雾化时间增加临床常用的喷射式雾化机对质粒的完整性破坏程度逐渐增加;新型气道内微量雾化机的基因转染效率高于临床普遍使用的机械喷射式雾化机转染效率的(382.1±101.1)倍(P<0.01,n=3)。结论:新型气道内微量雾化机对质粒没有破坏性,能显著增加雾化吸入基因转染效率。为雾化基因治疗提供了一种合适的工具。     

The Absence of Cruciform Structures from pA03 Plasmid DNA In vivo

Abstract

We extracted pA03 plasmid DNA from E. coli cells, having “frozen” the transitions between cruciform and double-helical conformations in DNA. The characteristic feature of the DNA isolation procedure is that all steps were carried out at temperature between 0 and 4 C and no phenol deproteinization was used, since it has been discovered that phenol destabilizes cruciform structures in pA03 DNA. Two-dimensional gel electrophoresis has revealed no cruciform structures in the pA03 DNA preparations obtained this way, although the superhelical density of DNA was sufficient for them. Cruciform structures are absent from intracellular pA03 DNA at all growth stages of the bacterial culture: stationary and logarithmic, and under the induction of pA03 DNA replication in chloramphenicol-treated cells.     

钠米颗粒介导质粒DNA转染体外真核细胞

DNA传递是基因表达与功能研究及其医学应用的重要技术,安全高效的DNA传递一直是研究者期待的目标。利用一种新的阳离子多聚物脱乙酰甲壳胺16介导重组质粒pcDNA3vp1转染COS7细胞,RTPCR可检测到目的基因vp1在mRNA水平的表达,实时定量PCR结果表明其转染效率介于脂质体与磷酸钙法之间,同时还对转染条件进行了探讨。DNA结合分析发现脱乙酰甲壳胺16能够与DNA形成核酸纳米颗粒,提高DNA稳定性,促进真核细胞转染效率的提高。这些结果表明脱乙酰甲壳胺16确能做为一种新型的非病毒纳米DNA传递载体,并将可能在基因表达与功能研究及基因治疗等领域发挥重要作用 。     

Influence of Plasmid Concentration on DNA Electrotransfer In Vitro Using High-Voltage and Low-Voltage Pulses

DNA electrotransfer in vivo for gene therapy is a promising method. For further clinical developments, the efficiency of the method should be increased. It has been shown previously that high efficiency of gene electrotransfer in vivo can be achieved using high-voltage (HV) and low-voltage (LV) pulses. In this study we evaluated whether HV and LV pulses could be optimized in vitro for efficient DNA electrotransfer. Experiments were performed using Chinese hamster ovary (CHO) cells. To evaluate the efficiency of DNA electrotransfer, two different plasmids coding for GFP and luciferase were used. For DNA electrotransfer experiments 50 μl of CHO cell suspension containing 100, 10 or 1 μg/ml of the plasmid were placed between plate electrodes and subjected to various combinations of HV and LV pulses. The results showed that at 100 μg/ml plasmid concentration LV pulse delivered after HV pulse increased neither the percentage of transfected cells nor the total transfection efficiency (luciferase activity). The contribution of the LV pulse was evident only at reduced concentration (10 and 1 μg/ml) of the plasmid. In comparison to HV (1,200 V/cm, 100 μs) pulse, addition of LV (100 V/cm, 100 ms) pulse increased transfection efficiency severalfold at 10 μg/ml and fivefold at 1 μg/ml. At 10 μg/ml concentration of plasmid, application of four LV pulses after HV pulse increased transfection efficiency by almost 10-fold. Thus, these results show that contribution of electrophoretic forces to DNA electrotransfer can be investigated in vitro using HV and LV pulses.     

Multiple Tissue Transformation in Adult Zebrafish by Gene Gun Bombardment and Muscular Injection of Naked DNA

The efficiency of two direct gene transfer methods, gene gun (or particle bombardment) and intramuscular injection, in transforming adult zebrafish tissues in vivo was examined by a noninvasive approach using green fluorescent protein (GFP) reporter gene driven by the ubiquitously expressed human cytomegalovirus promoter. Particle bombardment of adult zebrafish caused internalization and expression of the plasmid only in the superficial layer such as epithelial cells, pigment cells, endothelial cells, and neurons, whereas direct injection primarily transformed muscle fibers of several bundles near or around the injection site. Expression was also evident in several nonmuscle tissues, such as skin epithelia, pigment cells, blood vessel cells, and neuron-like cells. GFP expression persisted for more than 50 days with both methods. These observations indicate the potential of these methods for functional analysis of tissue-specific promoters, delivery of DNA vaccine, and muscular expression of other useful genes. Received June 12, 2000; accepted September 12, 2000     

牛胎儿成纤维细胞的组织块贴附法分离培养与电穿孔法基因转染

为获得转基因克隆牛的供体细胞,采用组织块贴附培养的方法分离培养牛胎儿皮肤成纤维细胞,经2～3次传代纯化,绘制生长曲线,分别分析体外传代培养10代以内和20代以上细胞的核型特征。分别采用800、900、1000V／cm和1、5、10、15和20ms的参数组合,将线性化的带有新霉素抗性和绿色荧光蛋白双重筛选标记的人胰岛素原乳腺特异表达载体pNEI电穿孔转入体外培养的牛胎儿成纤维细胞,经800μg／mLG418筛选2周,继续以300μg／mLG418扩大培养2～3代,取部分筛选后的细胞进行PCR检测结果表明,体外培养的牛胎儿成纤维细胞生长旺盛,体外传代20次后核型未发生改变;转染后24～48h在荧光镜下检测各组均可观察到绿色荧光表达,筛选后各组克隆形成数以900V／cm和5ms组最多;PCR检测得到了预期条带,说明目的基因已经成功导入。分离得到的牛胎儿耳成纤维细胞有可能作为体细胞核移植的供体,进行转基因克隆研究。     

氨基葡甘聚糖的质粒DNA转染载体作用的研究

目的 :发展一种新的半人工合成的质粒DNA转染载体。方法 :用氨基化方法将纯化的葡甘聚糖阳离子化 ,用凝胶阻滞检测法 (gelretardationassayforcomplexformation)观察氨基葡甘聚糖 DNA复合物的形成 ,以及用氨基葡甘聚糖作报告基因质粒pEGFP Cl的载体 ,转染HEK2 93细胞 ,观察转染效率。结果 :葡甘聚糖氨基化后溶液离子强度增大 2 0倍左右 ,氨基葡甘聚糖可与质粒DNA形成复合物 ,形成的复合物转染HEK2 93细胞后 ,报告基因pEGFP Cl获得阳性表达。氨基葡甘聚糖最大至 1 0 %仍未显示细胞毒性。结论 :氨基葡甘聚糖可发展为DNA载体系统 ,在HEK2 93细胞中获得理想的目的基因表达。     

Tumors Induced in Mice by Direct Inoculation of Plasmid DNA Expressing Both Activated H-ras and c-myc

Vaccines contain residual DNA derived from the cells used to produce them. As part of our investigation to assess the risk of this cellular DNA, we are developing a quantitative in vivo assay to assess the oncogenicity of DNA. In an earlier study, we had generated expression plasmids for two oncogenes - human activated T24-H-ras and murine c-myc - and had shown that these two plasmids, pMSV-T24-H-ras and pMSV-c-myc, could act in concert to induce tumors in mice, although the efficiency was low. In this study, we took two approaches to increase the oncogenic efficiency: 1) both oncogene-expression cassettes were placed on the same plasmid; 2) transfection facilitators, which increase DNA uptake and expression in vitro, were tested. The dual-expression plasmid, pMSV-T24-H-ras/MSV-c-myc, is about 20-fold more efficient at tumor induction in newborn NIH Swiss mice than the separate expression plasmids, with tumors being induced with 1 µg of the dual-expression plasmid DNA. However, none of the transfection facilitators tested increased the efficiency of tumor induction. Based on these data, the dual-expression plasmid pMSV-T24-H-ras/MSV-c-myc will be used as the positive control to develop a sensitive and quantitative animal assay that can be used to assess the oncogenic activity of DNA.     

DNA Transfection of Bone Marrow Stromal Cells Using Microbubble-Mediated Ultrasound and Polyethylenimine: An In Vitro Study

Non-viral vector transfection efficiency is an issue affecting the clinical application of stem cell gene therapy. This study makes use of the synergistic effect of combining ultrasound (US) with microbubbles (MB) and polyethylenimine (PEI) to increase DNA transfection efficiency, which will enhance the efficiency of gene transfer to bone marrow stromal cells (BMSCs). The optimal parameters for primary-cultured rat-BMSC DNA transfection were examined. The study was arranged based on uniform design. Using a construct containing hepatocyte growth factor (HGF) tagged with enhanced green fluorescent protein (pEGFP-HGF) as example, the mixture of BMSCs, MB, and PEI:DNA complex were exposed to US with frequency of 1 MHz and 10 % duty cycle pulses. Other factors such as acoustic intensity (Q), MB dosage, and total treatment time (T) were also tested. The results were analyzed by regression analysis. Using the best match of parameters, Q = 0.6 W/cm², MB = 10⁶/ml, T = 30 s, different groups were compared. The cooperativity of MB-mediated US and PEI enhanced the gene transfection efficiency by nearly 38-times compared to the DNA without US group. Furthermore, the expression of HGF protein was confirmed by Western blot. The eGFP could be not only seen mainly at the cytoplasm, but also seen in the nucleus in a small proportion of the cells (<10 %) for up to 7 observed days. The transfected BMSCs maintained their capability of multi-directional differentiation and reproductive activity. Our results provide useful information in establishing a novel non-viral transfection method, which may be applied to clinical application in stem cell gene therapy.     

重叠延伸PCR对DNA片段进行定点双突变

探讨如何利用重叠延伸PCR对同一靶DNA片段中的两个不同位点实施联合突变。先用野生型DNA作模板,通过一轮重叠延伸PCR,获得突变一个预期位点的DNA片段,再用此突变DNA片段作模板,通过另一轮重叠延伸PCR获得两个预期位点均突变的DNA片段。重叠延伸PCR能对DNA片段进行双突变甚至多点突变,具有简便、快速、经济等特点,在阐明基因的调控机理、改造蛋白质结构等分子生物学领域中具有极大的应用价值。     

Plasmid DNA Vaccine Co-Immunisation Modulates Cellular and Humoral Immune Responses Induced by Intranasal Inoculation in Mice

Background

An effective HIV vaccine will likely require induction of both mucosal and systemic cellular and humoral immune responses. We investigated whether intramuscular (IM) delivery of electroporated plasmid DNA vaccine and simultaneous protein vaccinations by intranasal (IN) and IM routes could be combined to induce mucosal and systemic cellular and humoral immune responses to a model HIV-1 CN54 gp140 antigen in mice.

Results

Co-immunisation of DNA with intranasal protein successfully elicited both serum and vaginal IgG and IgA responses, whereas DNA and IM protein co-delivery did not induce systemic or mucosal IgA responses. Cellular IFNγ responses were preserved in co-immunisation protocols compared to protein-only vaccination groups. The addition of DNA to IN protein vaccination reduced the strong Th2 bias observed with IN protein vaccination alone. Luminex analysis also revealed that co-immunisation with DNA and IN protein induced expression of cytokines that promote B-cell function, generation of T_FH cells and CCR5 ligands that can reduce HIV infectivity.

Significance

These data suggest that while IN inoculation alone elicits both cellular and humoral responses, co-administration with homologous DNA vaccination can tailor these towards a more balanced Th1/Th2 phenotype modulating the cellular cytokine profile while eliciting high-levels of antigen-specific antibody. This work provides insights on how to generate differential immune responses within the same vaccination visit, and supports co-immunisation with DNA and protein by a mucosal route as a potential delivery strategy for HIV vaccines.     

In vivo control of CpG and non-CpG DNA methylation by DNA methyltransferases

The enzymatic control of the setting and maintenance of symmetric and non-symmetric DNA methylation patterns in a particular genome context is not well understood. Here, we describe a comprehensive analysis of DNA methylation patterns generated by high resolution sequencing of hairpin-bisulfite amplicons of selected single copy genes and repetitive elements (LINE1, B1, IAP-LTR-retrotransposons, and major satellites). The analysis unambiguously identifies a substantial amount of regional incomplete methylation maintenance, i.e. hemimethylated CpG positions, with variant degrees among cell types. Moreover, non-CpG cytosine methylation is confined to ESCs and exclusively catalysed by Dnmt3a and Dnmt3b. This sequence position-, cell type-, and region-dependent non-CpG methylation is strongly linked to neighboring CpG methylation and requires the presence of Dnmt3L. The generation of a comprehensive data set of 146,000 CpG dyads was used to apply and develop parameter estimated hidden Markov models (HMM) to calculate the relative contribution of DNA methyltransferases (Dnmts) for de novo and maintenance DNA methylation. The comparative modelling included wild-type ESCs and mutant ESCs deficient for Dnmt1, Dnmt3a, Dnmt3b, or Dnmt3a/3b, respectively. The HMM analysis identifies a considerable de novo methylation activity for Dnmt1 at certain repetitive elements and single copy sequences. Dnmt3a and Dnmt3b contribute de novo function. However, both enzymes are also essential to maintain symmetrical CpG methylation at distinct repetitive and single copy sequences in ESCs.     

Transfection of liver in vivo by biolistic particle delivery

We describe the delivery of reporter gene constructs to rat liver through the use of the Helios Gene Gun system. The effectiveness of this transfection method is illustrated by describing its use for determining in vivo the role of a DNA element that regulates cytochrome P450 2B1 (CYP2B1) gene expression in response to xenobiotics. DNA was delivered to the liver of an anesthetized animal via DNA-coated gold microcarriers. The highest level of reporter gene expression was obtained about six hours posttransfection; however, at this time endogenous CYP2B1 mRNA is transiently induced by the anesthetic treatment. The optimal time for investigating expression of a reporter gene under the control of CYP2B1 regulatory elements was 24 h after transfection, by which time the inductive effect of the anesthetic had ceased. Reporter gene expression subsequently declined rapidly to a low level by 48 h. In the transfected liver the heterologous SV40 promoter was about eight-fold stronger than the minimal CYP2B1 promoter. However, when attached to the phenobarbital response element both promoters give the same fold-induction of reporter activity in response to phenobarbital.     

In Vivo Transfection of Animals by Intravenous Injection of Cationic Liposome: DNA Complexes

Abstract

Cationic liposome:DNA complex (CLDC)-mediated gene transfer by intravenous injection results in expression of genes of interest in a variety of animal tissues. Large multilamellar vesicles transfect more efficiently than small unilamellar vesicles when complexed to plasmid DNA, and higher ratios of liposome to DNA result in higher transfection levels. Inclusion of the neutral lipid cholesterol enhances gene expression in animals, and our most efficient liposome formulation to date (DOTIM:cholesterol MLV) produced significant levels of gene expression in a sheep for a period of up to 5 months following a single intravenous injection. In addition, the normal vascular cells surrounding melanoma-induced tumors in mice can be transfected by intravenous injection of CLDC, suggesting sanguine prospects for the possibility of anti-cancer gene therapy by CLDC-mediated intravenous gene transfer.     

Site-Specific Mutations in the TraI Relaxase and Upstream Region of Plasmid RP4

The relaxase of RP4 nicks the double-stranded plasmid at the oriT site and binds covalently to DNA at the 5′ end of the nick. The 80-kDa relaxase (TraI) is encoded on an operon with several overlapping open reading frames (ORFs). The importance in conjugation of a short ORF (traX) with a start site overlapping the 5′ terminus of traI was investigated, as well as the effects of specific mutations in the relaxase. Elimination of TraX reduced the transfer efficiency by approximately 50% in several intergeneric matings, especially when Escherichia coli was the donor. While TraI was essential for transfer to occur, deletion of the C-terminus of TraI decreased, but did not eliminate plasmid transfer. Mutation of the active site tyrosine resulted in residual transfer associated with amino acid misincorporation.     

质粒DNA抗原芯片检测抗双链DNA抗体的初步研究

目的:建立以质粒DNA作为抗原的检测血清中抗双链DNA(dsDNA)抗体的芯片方法,并与酶联免疫吸附实验比较,初步探讨用芯片法检测抗dsDNA抗体的临床价值。方法:将原核表达载体质粒pcDNAⅡ用质粒DNA快速抽提试剂盒提取纯化DNA后按1∶2稀释,用点样仪点在经3-氨丙基三乙氧基硅烷(APES)修饰的玻片上,温孵后用含有1%小牛血清白蛋白和2.5%蔗糖的PBST封闭,以Cy3标记的人IgG为二抗,建立检测dsDNA抗体的芯片方法,并与德国欧蒙公司生产的抗双链DNA检测ELISA试剂盒做比较,对包括58例系统性红斑狼疮(SLE)、25例干燥综合征(SS)、10例皮肌炎(DM)和7例类风湿关节炎(RA)在内的病人和60例健康人对照进行了抗dsDNA的对比检测。结果:对阳性标本的检测,与现用常规检测方法ELISA相比,芯片检测抗dsDNA的灵敏度为91.3%,特异度为90.7%,阳性预测值为89.3%,阴性预测值为92.5%;对健康对照的检测,2种方法均为阴性,符合率为100%。结论:与ELISA相比,用质粒DNA作为抗原建立的芯片方法的灵敏度和特异度较高,为今后建立同时检测多个自身抗体的芯片奠定了基础。     

In vivo Imaging of Optic Nerve Fiber Integrity by Contrast-Enhanced MRI in Mice

The rodent visual system encompasses retinal ganglion cells and their axons that form the optic nerve to enter thalamic and midbrain centers, and postsynaptic projections to the visual cortex. Based on its distinct anatomical structure and convenient accessibility, it has become the favored structure for studies on neuronal survival, axonal regeneration, and synaptic plasticity. Recent advancements in MR imaging have enabled the in vivo visualization of the retino-tectal part of this projection using manganese mediated contrast enhancement (MEMRI). Here, we present a MEMRI protocol for illustration of the visual projection in mice, by which resolutions of (200 µm)³ can be achieved using common 3 Tesla scanners. We demonstrate how intravitreal injection of a single dosage of 15 nmol MnCl₂ leads to a saturated enhancement of the intact projection within 24 hr. With exception of the retina, changes in signal intensity are independent of coincided visual stimulation or physiological aging. We further apply this technique to longitudinally monitor axonal degeneration in response to acute optic nerve injury, a paradigm by which Mn²⁺ transport completely arrests at the lesion site. Conversely, active Mn²⁺ transport is quantitatively proportionate to the viability, number, and electrical activity of axon fibers. For such an analysis, we exemplify Mn²⁺ transport kinetics along the visual path in a transgenic mouse model (NF-κB p50^KO) displaying spontaneous atrophy of sensory, including visual, projections. In these mice, MEMRI indicates reduced but not delayed Mn²⁺ transport as compared to wild type mice, thus revealing signs of structural and/or functional impairments by NF-κB mutations.In summary, MEMRI conveniently bridges in vivo assays and post mortem histology for the characterization of nerve fiber integrity and activity. It is highly useful for longitudinal studies on axonal degeneration and regeneration, and investigations of mutant mice for genuine or inducible phenotypes.     

Transfection of siRNAs can alter miRNA levels and trigger non-specific protein degradation in mammalian cells

Sequence-non-specific effects of siRNAs that alter the expression of non-targeted genes have been reported, including competition of siRNAs with endogenous RISC components. However, the detailed mechanisms and subsequent effects of such competition are not well documented. Here we analyze the competition of miRNAs in mammalian cells with low concentrations of siRNAs, and found that: 1) transfection of different siRNAs in the low nanomolar range used to deplete target RNAs can reduce the levels of miRNAs in different cell types, 2) siRNA transfection results in rapid reduction of Ago2-associated miRNAs concurrent with accumulation of Ago2-bound siRNAs and a significant change in the expression levels of many miRNAs, 3) competition largely depends on Ago2 and not Dicer, 4) microarray analysis showed that the majority of highly expressed miRNAs are reduced, in a siRNA concentration dependent manner, and low abundant miRNAs may be unchanged or repressed and a few miRNAs appear to have increased levels, and 5) consistent with previous studies, the expression levels of mRNAs that are targeted by highly repressed miRNAs are preferentially increased. As a consequence of such competition, we observed that α-tubulin, a substrate of two up-regulated proteases, granzyme B and granzyme M, was rapidly degraded at the protein level upon siRNA transfection. Our results support a model in which transfection of siRNAs can change the levels of many miRNAs by competition for Ago2, leading to altered expression of many miRNA target genes, which can in turn affect downstream gene expression even at the protein level.