绿色荧光蛋白与H-2K~b融合基因的构建及表达

目的　构建GFP与H 2Kb 融合基因 ,并分析融合基因在活细胞中的表达。方法　应用基因工程技术构建H 2Kb 与绿色荧光蛋白 (GFP)的融合基因。RT PCR和Western印迹分析基因表达 ;激光共聚焦荧光显微镜观察活细胞内荧光布局。结果　RT PCR和Western印迹分析表明融合基因获得了正确表达。激光共聚焦荧光显微镜观察结果表明 ,Kb GFP融合分子象天然Kb 分子一样表达在细胞膜表面 ,且胞外区域可被Kb 分子特异性单克隆抗体所识别 ,表明Kb GFP融合分子可在细胞内正确折叠和装配。Kb GFP融合基因的瞬间和稳定表达均获得了相同结果。结论　Kb GFP融合蛋白具有GFP的自发荧光特性 ,且不影响Kb 分子在细胞内的正确表达。     

Gene disruption in Cryptococcus neoformans and Cryptococcus gattii by in vitro transposition

Cryptococcus neoformans and Cryptococcus gattii are basidiomycetous fungi that infect immunocompromised and immunocompetent people. We developed an insertional mutagenesis strategy for these species based on in vitro transposition and we tested the method by disrupting the URA5 gene in a strain of C. neoformans and the CAP10 gene in three strains of C. gattii. We targeted plasmid DNA containing the URA5 gene or plasmid DNA containing the CAP10 gene from genomic libraries from the shotgun sequencing project for the C. gatti strain WM276. In the latter case, the availability of the end sequences of the clones from the assembled genomic sequence allows rapid selection of target genes for disruption. Modified transposons containing the nourseothricin (NAT) or neomycin (Neo) resistance cassettes were randomly inserted into the target DNA by in vitro transposition. The disrupted genes were used for biolistic transformation and homologous integration was subsequently confirmed by PCR and Southern blot analysis. These results demonstrate that the emerging genomic resources, combined with in vitro transposition into plasmid DNAs from shotgun sequencing libraries or cloned PCR products, will facilitate high-throughput genetic analysis in Cryptococcus species.     

Destabilized green fluorescent protein for monitoring transient changes in mycobacterial gene expression

The green fluorescent protein (GFP) is a useful reporter for the study of gene expression and protein localisation within living cells. The stability of GFP permits its intracellular accumulation and detection, but renders it less useful for assessing transient changes in gene expression. We have developed a destabilized form of GFP for monitoring gene expression in mycobacteria. By fusing to the C-terminal end of GFP an 11 amino acid peptide encoded by the E. coli ssrA gene, we have developed a form of GFP that exhibits gradual, time-dependent degradation within the fast-growing species Mycobacterium smegmatis. This unstable variant of GFP detected transient changes in the activity of the stress-induced Mycobacterium tuberculosis sigE promoter; by contrast, unmodified GFP only detected a delayed 'switch-on' of this promoter upon exposure to acid stress. Both forms of the protein displayed equivalent stability in the slow-growing species Mycobacterium bovis bacille Calmette-Guerin (BCG), suggesting differing recognition of the ssrA-encoded peptides in slow- and fast-growing mycobacteria. This system will facilitate studies exploring dynamic changes in mycobacterial gene expression.     

In vivo and in vitro tissue-specific expression of green fluorescent protein using the cre-lox system in mouse embryonic stem cells

Embryonic stem cells (ES) are pluripotent and may therefore serve as a source for the generation of specific cell types required for future therapies based on cell replacement. The isolation of defined cell populations from a certain lineage or tissue is a prerequisite for the analysis of the potential of such ES-derived cells in animal transplantation studies. Here, using the Cre/loxP system, we report the generation of murine ES cells conditionally expressing the hrGFP gene at the cell surface. Such ES cells can be differentiated in vitro into neurons displaying GFP activity in neurites. Transgenic mice derived from these ES cells permit the targeting of GFP-expression to specific tissues and provide material from the three germ layers suitable for molecular and biochemical analysis.     

携带增强型绿色荧光蛋白基因的shRNA真核表达载体的构建

目的：构建携带EGFP的shRNA真核表达载体。 方法: 应用PCR的方法从pBSK/U6质粒上扩增出U6启动子及其下游的Xbal、SalI和BamHI酶切位点，并增加NotI位点。将扩增的产物连入pEGFP-C1载体MluI位点处，构建成携带EGFP的siRNA真核表达载体。应用该载体介导针对EGFP的短发夹环RNA（pEGFP/U6/EGFP），转染U251细胞，通过荧光显微镜和流式细胞仪检测EGFP的表达，验证所构建载体在细胞内产生RNA干扰的效果。 结果: 与对照组比较pEGFP/U6/EGFP在细胞内对EGFP的抑制效果达89.8%。 结论: 成功构建携带EGFP的shRNA真核表达载体。     

Receptor-mediated clearance of Cryptococcus neoformans capsular polysaccharide in vivo

Cryptococcus neoformans capsular glucuronoxylomannan (GXM) is shed during cryptococcosis and taken up by macrophages. The roles of the putative GXM receptors CD14, CD18, Toll-like receptor 2 (TLR2), and TLR4 in GXM clearance from serum and deposition in the liver and spleen in receptor-deficient mice were studied. While alterations in the kinetics of GXM redistribution were seen in the mutant mice, none of the receptors was absolutely required for serum clearance or hepatosplenic accumulation.     

Laccase expression in murine pulmonary Cryptococcus neoformans infection

Cryptococcus neoformans laccase expression during murine infection was investigated in lung tissue by immunohistochemistry and immunogold electron microscopy. Laccase was detected in the fungal cell cytoplasm, cell wall, and capsule in vivo. The amount of laccase found in different sites varied as a function of the time of infection.     

Detection of Cryptococcus neoformans gene in patients with pulmonary cryptococcosis.

Pulmonary cryptococcosis was diagnosed by nested PCR. Extraction of DNA was performed by mechanical destruction of the capsules of Cryptococcus neoformans by the glass bead technique. Nested PCR was positive for 4 of 5 culture-positive specimens but negative for 1 culture-positive specimen, 10 culture-negative specimens, and 1 specimen with undetermined culture results.     

携EGFP的人Synoviolin基因慢病毒表达载体的构建与鉴定

目的构建携EGFP的人Synoviolin基因慢病毒表达载体。方法应用基因重组手段,SalⅠ/NotⅠ双酶切质粒pIRES2-EGFP-syno,得到含EGFP和人Synoviolin的基因片段,将其亚克隆至入门载体pENTR1A的多克隆位点内得到入门质粒pENTR1A-syno-egfp。采用LR重组酶将pENTR1A-syno-egfp和目的载体pLenti4/TO/V5-DEST进行重组反应,形成慢病毒表达载体pLenti4/TO/V5-DEST-syno-egfp。将pLenti4/TO/V5-DEST-syno-egfp与包装质粒混合,利用脂质体共转染293FT细胞,包装产生慢病毒,以293FT细胞GFP蛋白的表达水平测定病毒滴度。结果PCR,酶切及测序结果表明慢病毒表达载体pLenti4/TO/V5-DEST-syno-egfp构建成功,转染后的293FT细胞在荧光显微镜下观察可见强绿色荧光。包装的慢病毒原液滴度为1×10~8TU/ml。结论成功构建了EGFP和Synoviolin基因共表达的慢病毒表达载体,为Synoviolin基因的功能研究提供了高效稳定的转基因技术平台。     

Cryptococcus neoformans capsule structure evolution in vitro and during murine infection

Cryptococcus neoformans capsule structure modifications after prolonged in vitro growth or in vivo passaging have been reported previously. However, nothing is known about the dynamics of these modifications or about their environmental specificities. In this study, capsule structure modifications after mouse passaging and prolonged in vitro culturing were analyzed by flow cytometry using the glucuronoxylomannan-specific monoclonal antibody E1. The capsule structures of strains recovered after 0, 1, 8, and 35 days were compared by using the level of E1-specific epitope expression and its cell-to-cell heterogeneity within a given cell population. In vitro, according to these parameters, the diversity of the strains was higher on day 35 than it was initially, suggesting the absence of selection during in vitro culturing. In contrast, the diversity of the strains recovered from the brain tended to decrease over time, suggesting that selection of more adapted strains had occurred. The strains recovered on day 35 from the spleen and the lungs had different phenotypes than the strains isolated from the brain of the same mouse on the same day, thus strongly suggesting that there is organ specificity for C. neoformans strain selection. Fingerprinting of the strains recovered in vitro and in vivo over time confirmed that genotypes evolved very differently in vitro and in vivo, depending on the environment. Overall, our results suggest that organ-specific selection can occur during cryptococcosis.     

绿色荧光蛋白转基因小鼠来源肌卫星细胞的体外培养及体内示踪

目的:从绿色荧光蛋白转基因小鼠中分离培养肌卫星细胞(MSCs)并进行体内示踪.方法:利用差速贴壁结合克隆分选方法,分离了MSCs,并于体外进行培养传代、鉴定及分化.检测所获MSCs的生长曲线及细胞周期并与来源于野生型鼠的同代MSCs进行比较.将绿色荧光蛋白标记的MSCs注射到裸鼠胫前肌,于注射后当时、注射后1周、2周、3周和4周利用二维荧光成像平台进行体内示踪.结果:MSCs被成功分离、传代及鉴定.来源于绿色荧光蛋白(GFP)标记或未标记小鼠MSCs的生长曲线、细胞周期及肌原性分化等无差别.MSCs注射后4周内可以动态观察到注射部位的绿色荧光信号并获得组织学证实.结论:来源于GFP转基因小鼠的MSCs在生长和增殖特性上与未转基因来源的MSCs相似,在体内可以通过二维荧光成像平台进行可靠的、无创性的示踪.     

Constitutive and inducible expression of green fluorescent protein in Brucella suis

A gene fusion system based on plasmid pBBR1MCS and the expression of green fluorescent protein was developed for Brucella suis, allowing isolation of constitutive and inducible genes. Bacteria containing promoter fusions of chromosomal DNA to gfp were visualized by fluorescence microscopy and examined by flow cytometry. Twelve clones containing gene fragments induced inside J774 murine macrophages were isolated and further characterized.     

In vitro interactions of immune lymphocytes and Cryptococcus neoformans.

CBA/J mice immunized subcutaneously with emulsions of heat-killed Cryptococcus neoformans in complete Freund adjuvant displayed delayed-type hypersensitivity to cryptococcal culture filtrate antigen and developed sensitized splenic lymphoid cells which inhibited the growth of C. neoformans in vitro. The in vitro assay of growth inhibition served to investigate further the kinetics of the effect of sensitized lymphoid cells on the pathogen. There was a close correlation between the delayed-type hypersensitivity response in mice and inhibition of growth of C. neoformans by lymphoid cells. Sensitized splenic lymphocytes capable of inhibiting the growth of the cryptococci were detected at day 6 after immunization and reached maximum levels by days 8 through 16. Inhibition of growth was highest with effector-to-target cell ratios of 300:1 or greater. Inhibition of growth of C. neoformans by sensitized lymphoid cells was detectable as early as 4 h after effector and target cells were mixed and increased gradually, reaching a maximum at 24 h, but dropped significantly by 48 h. By supplementing the reaction mixtures with fresh medium or additional sensitized effector cells during incubation, the inhibition of growth of C. neoformans could be maintained through 48 h. C. neoformans-sensitized effector lymphoid populations not only inhibited the growth of the pathogen in vitro but also restricted C. neoformans proliferation in various vital organs upon transfer to naive recipient animals, indicating that the in vitro growth inhibition assay may be a means of assessing the resistance of animals to C. neoformans. The effector cells from sensitized animals were nylon wool-nonadherent Thy-1+ and Ia+ lymphocytes.     

In vitro synergistic effect of minocycline combined with antifungals against Cryptococcus neoformans

BackgroundCryptococcus neoformans infections occur in immunocompromised patients, especially those with HIV infection, chemoradiotherapy after cancer, and organ transplantation. Infection can cause pneumonia and meningoencephalitis in severe cases with a high mortality rate if not treated. Although fluconazole and amphotericin B are the first-line treatments for cryptococcosis, the rate of fluconazole resistance has increased significantly due to long-term use. Minocycline is a derivative of tetracycline that exerts its antibacterial effect through inhibition of bacterial protein synthesis. It is also able to pass the blood-brain barrier to act on the central nervous system. The present study investigates the effects of minocycline in combination with antifungals in treating C. neoformans.ObjectiveTo determine in vitro interactions of minocycline combined with itraconazole, voriconazole, posaconazole, fluconazole and amphotericin B against C. neoformans.MethodsThe minimum inhibitory concentrations (MIC) of the antifungals were determined by the CLSI Clinical and Laboratory Standards Institute M27-A3 microdilution method. The in vitro synergistic effects of minocycline combined with itraconazole, voriconazole, posaconazole, fluconazole, and amphotericin B on C. neoformans were detected by the broth microdilution checkerboard technique and disk diffusion testing.Results and ConclusionThe working concentration ranges were 0.125–4 µg/mL for itraconazole, 0.03–0.125 µg/ml for voriconazole, 0.03–1 µg/ml for posaconazole, 0.25–16 µg/ml for fluconazole, and 0.125–2 µg/ml for amphotericin B. The synergistic rates of minocycline combinations against C. neoformans were 55% with itraconazole, 10% with voriconazole, 85% with posaconazole, 20% with fluconazole, and 70% with amphotericin B. The effective MIC value of minocycline in the synergistic combination decreased to 2–32 µg/ml, while the MIC of itraconazole decreased to 0.03–0.125 µg/ml, voriconazole 0.03–0.125 µg/ml, posaconazole 0.03–0.125 µg/ml, 0.125–4 µg/ml fluconazole, and 0.06–0.50 µg/ml amphotericin B. The disk diffusion assay showed that the plates containing minocycline and antifungal drugs produced inhibition zones with diameters larger than the single drug plates. Minocycline showed no antagonistic effect in the combinations. In conclusion, the combination of minocycline and azoles or amphotericin B has synergistic effects against C. neoformans in vitro.     

Role of alternative oxidase gene in pathogenesis of Cryptococcus neoformans

We identified a homologue of the alternative oxidase gene in a screen to identify genes that are preferentially transcribed in response to a shift to 37 degrees C in the human-pathogenic yeast Cryptococcus neoformans. Alternative oxidases are nucleus-encoded mitochondrial proteins that have two putative roles: they can function in parallel with the classic cytochrome oxidative pathway to produce ATP, and they may counter oxidative stress within the mitochondria. The C. neoformans alternative oxidase gene (AOX1) was found to exist as a single copy in the genome, and it encodes a putative protein of 401 amino acids. An aox1 mutant strain was created using targeted gene disruption, and the mutant strain was reconstituted to wild type using a full-length AOX1. Compared to both the wild-type and reconstituted strains, the aox1 mutant strain was not temperature sensitive but did have significant impairment of both respiration and growth when treated with inhibitors of the classic cytochrome oxidative pathway. The aox1 mutant strain was also found to be more sensitive to the oxidative stressor tert-butyl hydroperoxide. The aox1 mutant strain was significantly less virulent than both the wild type and the reconstituted strain in the murine inhalational model, and it also had significantly impaired growth within a macrophage-like cell line. These data demonstrate that the alternative oxidase of C. neoformans can make a significant contribution to metabolism, has a role in the yeast's defense against exogenous oxidative stress, and contributes to the virulence composite of this organism, possibly by improving survival within phagocytic cells.     

绿色荧光蛋白腺病毒表达载体在大鼠肌源性干细胞标记中的应用

目的:对大鼠肌源性干细胞转染携带绿色荧光蛋白基因的腺病毒表达载体,为进一步行标记细胞移植治疗实验奠定基础。方法:复苏并培养人胚胎肾293细胞,进行包装重组及大规模扩增腺病毒;原代培养大鼠肌源性干细胞并进行GFP基因转染,荧光显微镜观察转染情况并计算转染率。结果:人胚胎肾293细胞在普通培养条件下生长良好,加入Ad-GFP病毒液后48h荧光显微镜观察绝大多数细胞呈悬浮状态,带有较强的绿色荧光;转染肌源性干细胞后呈Desmin免疫组织化学显色阳性;48h荧光转染率为83.14%,4d为78.35%,8d为75.12%。结论:采用携带绿色荧光蛋白基因的腺病毒表达载体标记肌源性干细胞的方法安全可靠、简便有效,且能保持肌源性干细胞原有生物学特性。     

组织因子途径抑制因子/绿色荧光蛋白双顺反子真核表达载体构建及其在NIH 3T3细胞中表达

目的构建含人组织因子途径抑制因子(TFPI)和绿色荧光蛋白(GFP)基因的双顺反子真核表达载体,并验证其在NIH 3T3细胞中的表达,为血管再狭窄的防治提供一个具有示踪和治疗双重作用的有效载体。方法以含有全长cDNA的pIRES-TFPI为模板,多聚酶链反应(PCR)扩增TFPI全长cDNA,经酶切后插入到pIRES2-AcGFP1-Nuc载体中,构建成双顺反子真核表达载体,重组质粒经酶切图谱分析、PCR扩增及测序鉴定后命名为pIRES2-AcGFP1-Nuc-TFPI。将其转染NIH3T3细胞,采用荧光显微镜观察GFP在细胞中的表达,以RT-PCR检测TFPI在细胞内的表达。结果经酶切图谱分析、PCR扩增及DNA测序证实双顺反子真核表达载体构建正确;荧光显微镜可观察到细胞内GFP的表达;RT-PCR证实经TFPI基因转染的细胞内TFPI mRNA表达增高。结论成功构建了包括TFPI和GFP的真核双表达载体,并使其在NIH3T3细胞中顺利表达。     

新型隐球菌与肺泡上皮细胞的体外相互作用

目的研究新型隐球菌与肺泡上皮细胞的体外相互作用,探讨隐球菌肺部感染的发病机制。方法体外培养Ⅱ型肺泡上皮细胞A549(ATCC CCL-185),检测新型隐球菌2种变种对细胞的时间/浓度黏附率、通过率;检测新型隐球菌对细胞的损伤作用;透射电镜观察相互作用的超微结构。结果2种变种的新型隐球菌可以对A549细胞产生黏附与侵袭,黏附率与侵袭率呈现时间依赖性;同时还可以使A549细胞凋亡率升高,对其造成损伤,这与菌体的活力相关。超微结构可见隐球菌与肺泡上皮细胞的黏附与侵袭过程。2种变种之间在黏附率、通过率及对细胞的损伤作用方面差异无统计学意义。结论活的隐球菌黏附与侵袭肺泡上皮细胞是隐球菌感染肺部的重要条件,不同变种对肺部的易感性可能不存在差异。进一步明确二者的作用机制对隐球菌的发病机制研究具有重要意义。