Highly bovine spongiform encephalopathy-sensitive transgenic mice confirm the essential restriction of infectivity to the nervous system in clinically diseased cattle

Transgenic mice expressing bovine prion protein (PrP)(C) (Tgbov XV mice) display remarkably shorter incubation times for cattle-derived bovine spongiform encephalopathy (BSE) infectivity than do nontransgenic mice. To verify that this phenomenon reflects increased sensitivity, we challenged Tgbov XV mice and conventional RIII mice with a BSE brain-stem homogenate of known infectivity titer in cattle. An end-point titration experiment in Tgbov XV mice revealed their superior sensitivity, which exceeded that of RIII mice by at least 10,000-fold and even that of cattle by approximately10-fold. Moreover, Tgbov XV mice were challenged with various tissues from cattle with end-stage clinical BSE, and infectivity was found only in the central and peripheral nervous system and not in lymphatic tissues; the only exception was the Peyer's patches of the distal ileum, which most likely are the site of entry for BSE infectivity. These results provide further indication that the pathogenesis of BSE in cattle is fundamentally different from that in sheep and mice, due to an exclusive intraneuronal spread of infectivity from the gut to the central nervous system.     

Conditional transgenic technologies

Transgenic technology has been revolutionised by the development of techniques that allow temporo-spatial control of gene deletion or expression in transgenic animals. The ability to switch gene expression 'on' or 'off' in restricted tissues at specific times allows unprecedented flexibility for exploring gene function in both health and disease. As use of these techniques grows in all areas of biomedical research, an understanding of this topic is essential. In this review we examine the theory, application and limitations of these strategies, with particular reference to endocrine research.     

丙型肝炎病毒转基因小鼠模型的研究

0引言丙型肝炎病毒(HCV)是1989年美国Chooetal[1]利用逆转录-聚合酶链反应(RT-PCR)技术分离鉴定的一种新型肝炎病毒,属黄病毒科丙型肝炎病毒属.其基因组为单股正链RNA,长9.4kb左右,两侧分别为5’和3’非编码区(NCR),中间为单一的开放读码框(ORF),可分为核壳蛋白区(C区)、包膜蛋白区(E区)和非结构蛋白区(NS区).其中,5’NCR区变异较小,内含内部核糖体进入位点(IRES),在病毒蛋白的翻译中有重要的调控功能.C区与E1/E2区构成结构基因,分别编码衣壳蛋白和包膜糖蛋白,内含重要的中和抗原表位与细胞免疫抗原表位,与HCV的免疫致病及防…     

转基因蚊最新研究进展

利用转基因技术对蚊虫进行遗传修饰,通过降低野生种群数量或以不能传播寄生虫的蚊虫替代现有种群,达到控制疾病传播的目的。本文对近2年转基因蚊虫的培育和转基因蚊在野生群体中的适应性等方面的主要研究进展作一简要介绍。     

Heterologous expression in transgenic mosquitoes

Arthropod-borne diseases such as malaria and dengue virus afflict billions of people worldwide imposing major economic and social burdens. Control of such pathogens is mainly performed by vector management and treatment of affected individuals with drugs. The failure of these conventional approaches due to emergence of insecticide-resistant insects and drug-resistant parasites demonstrate the need of novel and efficacious control strategies to combat these diseases. Genetic modification (GM) of mosquito vectors to impair their ability to be infected and transmit pathogens has emerged as a new strategy to reduce transmission of many vector-borne diseases and deliver public health gains. Several advances in developing transgenic mosquitoes unable to transmit pathogens have gained support, some of them attempt to manipulate the naturally occurring endogenous refractory mechanisms, while others initiate the identification of an exogenous foreign gene which disrupt the pathogen development in insect vectors. Heterologous expression of transgenes under a native or heterologous promoter is important for the screening and effecting of the transgenic mosquitoes. The effect of the transgene on mosquito fitness is a crucial parameter influencing the success of this transgenic approach. This review examines these two aspects and describes the basic research work that has been accomplished towards understanding the complex relation between the parasite and its vector and focuses on recent advances and perspectives towards construction of transgenic mosquitoes refractory to vector-borne disease transmission.     

Cardiovascular research in transgenic animals

The ability to alter specifically the expression or activity of known gene products in intact animals provides a powerful experimental system to study pathophysiology. These animal models can now be readily generated using transgenic technology. Traditional transgenic approaches rely on gain-of-function alterations, and several experimental paradigms have recently been established based on this attribute. These include assessment of promoter function, overexpression of physiologically important gene products, targeted oncogenesis, and insertional mutagenesis. Technical and practical issues relevant to the generation of such models are discussed here. In addition, several recent transgenic models germane to the cardiovascular system are presented. These experiments provide exciting new model systems to study clinical issues that heretofore have been difficult, if not impossible, to address.     

Pulmonary carcinogenesis in transgenic mice

Use of genetically engineered mice offers a unique approach to identifying and investigating factors that may influence tumor development. We have used conventional histopathologic and ultrastructural techniques to characterize lung tumors in three lines of transgenic mice bearing an albumin enhancer/promoter linked to a mutated human H-ras gene. Mice in all three lines developed multiple alveolar-bronchiolar (A/B) adenocarcinomas that are eventually lethal. The large diversity in tumor morphological features and differential tumor growth rates suggests that secondary events contribute to tumor phenotype and biological behavior. Two of the transgenic lines developed numerous A/B neoplasms within 6 to 8 weeks and thus may be useful animal models for testing potential anticancer chemotherapeutic agents. The other line lived for approximately 10 months, had fewer A/B tumors, but also developed bronchiogenic tumors. All three transgenic lines may be useful models for studying factors that affect lung tumor development.     

骨髓干细胞移植促进ctnt^R141W转基因小鼠心肌组织再生

目的观察骨髓干细胞移植对ctnt^R141W转基因小鼠心脏组织结构的重建和病变心脏的泵血功能的影响。方法放射线9Gy照射ctnt^R141W转基因小鼠,将绿色荧光蛋白转基因小鼠的骨髓细胞尾静脉注射入ctnt^R141W转基因小鼠体内,替换ctnt^R141W转基因小鼠自身的骨髓细胞。流式细胞仪分析移植后的ctnt^R141W转基因小鼠绿色荧光骨髓干细胞所占的百分比。用免疫荧光双染方法探测移植后的ctnt^R141W转基因小鼠心肌组织中绿色荧光心肌细胞所占的比例,M型超声检测ctnt^R141W转基因小鼠心脏功能变化。结果相对于野生型对照小鼠ctnt^R141W转基因小鼠心肌组织中绿色荧光心肌细胞显著增加,左心室内径缩小,室壁变厚,收缩期末期和舒张末期左室容积缩小,心脏泵血功能增强。结论移植后的骨髓干细胞参与ctnt^R141W转基因小鼠心肌组织的损伤后重建,有助于改善病变心脏的泵血功能。研究提示扩张型心肌病心肌组织损伤重建增加,移植后的骨髓干细胞在受损心肌组织再生过程中起重要作用。     

HLA-B27 transgenic rats model

To investigate the role of HLA-B27 in the pathogenesis of spondylarthropathies, rats transgenic for HLA-B27 and human beta 2-microglobulin were produced. Several lines of B27 transgenic rats spontaneously develop a multisystem inflammatory disorder reminiscent of human spondylarthropathies, with gut, joint, skin and male genital lesions. The role of HLA-B27 in this model was studied and it was found that a high expression level of the transgene in cells of hematopoietic origin was critical to induce inflammatory manifestations. Furthermore, a combined implication of CD4+ T cells and antigen presenting cells in this model is suspected, based on passive transfer studies, although a specific influence of HLA-B27 upon T cell education in the thymus is unlikely to be important. Beside the immune system, bacterial flora exerts an important influence in this model, as a triggering agent of gut and joint inflammation. Finally, endogenous rat genetic factors are suspected to be involved in this model.     

Immunologic relations between cattle and ticks, specifically between cattle and Boophilus microplus]

In the present investigation, it has been demonstrated that cattle become resistant to ticks after several heavy infestations, particularly with B. microplus. During development of the infestations, antibodies against salivary glands of B. microplus were detected using 2 techniques: indirect immunofluorescence and immunoelectrophoresis. There is a positive causal relationship between antibody titer and resistance development. Two precipitating systems against B. microplus in infested cattle and 7 systems in immunized rabbits were studied. The systems 1 and 2 are similar in cattle and rabbits, but system 2 does not show any specificity, as it has been detected in cattle completely lacking tick infestations. Two one-day calves were treated with the antigen of B. microplus by injection of salivary glands and repeated infestations with a small number of larvae. They developed a pronounced resistance to the usual subsequent infestations by the ticks of the same species. Specific antibodies were found before the first usual infestation. This suggests that they might be responsible for resistance.     

Lessons in obesity from transgenic animals

Many genetic manipulations have created models of obesity, leanness or resistance to dietary obesity in mice, often providing insights into molecular mechanisms that affect energy balance, and new targets for anti-obesity drugs. Since many genes can affect energy balance in mice, polymorphisms in many genes may also contribute to obesity in humans, and there may be many causes of primary leptin resistance. Secondary leptin resistance (due to high leptin levels) can be investigated by combining the ob mutation with other obesity genes. Some transgenic mice have failed to display the expected phenotype, or have even been obese when leanness was expected. Compensatory changes in the expression of other genes during development, or opposing influences of the gene on energy balance, especially in global knockout mice, may offer explanations for such findings. Obesity has been separated from insulin resistance in some transgenic strains, providing new insights into the mechanisms that usually link these phenotypes. It has also been shown that in some transgenic mice, obesity develops without hyperphagia, or leanness without hypophagia, demonstrating that generalised physiological explanations for obesity in individual humans may be inappropriate. Possibly the most important transgenic model of obesity so far created is the Type 1 11beta-hydroxysteroid dehydrogenase over-expressing mouse, since this models the metabolic syndrome in humans. The perspectives into obesity offered by transgenic mouse models should assist clinical researchers in the design and interpretation of their studies in human obesity.