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Transgenic Overexpression (transgenic + overexpression)
Selected AbstractsDrosophila multiplexin (Dmp) modulates motor axon pathfinding accuracyDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 5 2009Frauke Meyer Multiplexins are multidomain collagens typically composed of an N-terminal thrombospondin-related domain, an interrupted triple helix and a C-terminal endostatin domain. They feature a clear regulatory function in the development of different tissues, which is chiefly conveyed by the endostatin domain. This domain can be found in proteolytically released monomeric and trimeric versions, and their diverse and opposed effects on the migratory behavior of epithelial and endothelial cell types have been demonstrated in cell culture experiments. The only Drosophila multiplexin displays specific features of both vertebrate multiplexins, collagens XV and XVIII. We characterized the Drosophila multiplexin (dmp) gene and found that three main isoforms are expressed from it, one of which is the monomeric endostatin version. Generation of dmp deletion alleles revealed that Dmp plays a role in motor axon pathfinding, as the mutants exhibit ventral bypass defects of the intersegmental nerve b (ISNb) similar to other motor axon guidance mutants. Transgenic overexpression of monomeric endostatin as well as of full-length Dmp, but not trimeric endostatin, were able to rescue these defects. In contrast, trimeric endostatin increased axon pathfinding accuracy in wild type background. We conclude that Dmp plays a modulating role in motor axon pathfinding and may be part of a buffering system that functions to avoid innervation errors. [source] The tyrosine kinase Syk is required for light chain isotype exclusion but dispensable for the negative selection of B,cellsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 4 2004Josephine Meade Abstract In this study we set out to test whether Syk was required for negative selection of immature B,cells. B,cells expressing a B,cell antigen receptor (BCR) transgene (3,83, anti-H-2Kk) underwent negative selection independently of Syk in both fetal liver organ culture and radiation chimera models. Furthermore, Syk-independent negative selection was not reversed by transgenic overexpression of Bcl-2. Receptor editing was not apparent in Syk-deficient B,cells, presumably as a consequence of the failure of mature edited B,cells to develop in the absence of Syk. Interestingly, light chain isotype exclusion by the BCR transgene failed in the absence of Syk. We observed a dramatic reduction in the overall BCR-mediated tyrosine phosphorylation of cellular proteins in Syk-deficient immature B,cells. However, the tyrosine phosphorylation of a number of substrates including phospholipase,C,2, although reduced, was not completely abrogated. BCR ligation triggered an increase in calcium flux in the absence of Syk. Thus signaling events that mediate negative selection can still occur in the absence of Syk. This may be due to redundancy with zeta-associated protein,70 (ZAP-70), which we demonstrate to be expressed in immature B,cells. [source] Rescue of ,2 subunit-deficient mice by transgenic overexpression of the GABAA receptor ,2S or ,2L subunit isoformsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2000Kristin Baer Abstract The ,2 subunit is an important functional determinant of GABAA receptors and is essential for formation of high-affinity benzodiazepine binding sites and for synaptic clustering of major GABAA receptor subtypes along with gephyrin. There are two splice variants of the ,2 subunit, ,2 short (,2S) and ,2 long (,2L), the latter carrying in the cytoplasmic domain an additional eight amino acids with a putative phosphorylation site. Here, we show that transgenic mice expressing either the ,2S or ,2L subunit on a ,2 subunit-deficient background are phenotypically indistinguishable from wild-type. They express nearly normal levels of ,2 subunit protein and [3H]flumazenil binding sites. Likewise, the distribution, number and size of GABAA receptor clusters colocalized with gephyrin are similar to wild-type in both juvenile and adult mice. Our results indicate that the two ,2 subunit splice variants can substitute for each other and fulfil the basic functions of GABAA receptors, allowing in vivo studies that address isoform-specific roles in phosphorylation-dependent regulatory mechanisms. [source] Knockin Animal Models of Inherited Arrhythmogenic Diseases: What Have We Learned From Them?JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2007KATHY M NILLES B.S. Mouse models are becoming an increasingly accepted method of studying human diseases. Knockin and knockout techniques have several advantages over traditional transgenic overexpression, and the versatility of the knockin mouse allows the study of both gain of function mutations through targeted mutagenesis, as well as the replacement of one gene by another functional gene. Here, we will review the methods available to generate knockin mice; provide an overview of the techniques used to study electrophysiology in the mice at the cellular, organ, and whole animal level; and highlight knockin mice that have implications for inherited arrhythmias. Specifically, we will focus on models that used knockin mice to clarify gene expression, identify similarities and differences between related genes, and model human arrhythmia syndromes. Our goal is to provide the reader with a general understanding of studies done on knockin mouse models of inherited arrhythmias as well as ideas for future directions. [source] Oxidative stress and antioxidant enzyme upregulation in SOD1-G93A mouse skeletal muscleMUSCLE AND NERVE, Issue 6 2006Douglas J. Mahoney PhD Abstract Amyotrophic lateral sclerosis (ALS) is caused by motor neuron loss in the spinal cord, but the mechanisms responsible are not known. Ubiquitous transgenic overexpression of copper/zinc superoxide dismutase (SOD1) mutations causing familial ALS (SOD1mut) leads to an ALS phenotype in mice; however, restricted expression of SOD1mut in neurons alone is not sufficient to cause this phenotype, suggesting that non-neuronal SOD1mut expression is also required for disease manifestation. Recently, several investigators have suggested that SOD1mut -mediated oxidative stress in skeletal muscle may contribute to ALS pathogenesis. The purpose of this study was to examine oxidative stress and antioxidant enzyme adaptation in 95-day-old SOD1-G93A skeletal muscle. We observed significant elevations in both malondialdehyde (22% and 31% in red and white gastrocnemius, respectively) and protein carbonyls (53% in red gastrocnemius) in SOD1-G93A mice. Copper/zinc SOD activity was higher in red and white SOD1-G93A gastrocnemius (7- and 10-fold, respectively), as was manganese SOD (4- and 5-fold, respectively) and catalase (2- and 2.5-fold, respectively). Taken together, our data demonstrate oxidative stress and compensatory antioxidant enzyme upregulation in SOD1-G93A skeletal muscle. Muscle Nerve, 2006 [source] The transcription factor Fra-2 regulates the production of extracellular matrix in systemic sclerosisARTHRITIS & RHEUMATISM, Issue 1 2010Nicole Reich Objective Fra-2 belongs to the activator protein 1 family of transcription factors. Mice transgenic for Fra-2 develop a systemic fibrotic disease with vascular manifestations similar to those of systemic sclerosis (SSc). The aim of the present study was to investigate whether Fra-2 plays a role in the pathogenesis of SSc and to identify the molecular mechanisms by which Fra-2 induces fibrosis. Methods Dermal thickness and the number of myofibroblasts were determined in skin sections from Fra-2,transgenic and wild-type mice. The expression of Fra-2 in SSc patients and in animal models of SSc was analyzed by real-time polymerase chain reaction and immunohistochemistry. Fra-2, transforming growth factor , (TGF,), and ERK signaling in SSc fibroblasts were inhibited using small interfering RNA, neutralizing antibodies, and small-molecule inhibitors. Results Fra-2,transgenic mice developed a skin fibrosis with increases in dermal thickness and increased myofibroblast differentiation starting at age 12 weeks. The expression of Fra-2 was up-regulated in SSc patients and in different mouse models of SSc. Stimulation with TGF, and platelet-derived growth factor (PDGF) significantly increased the expression of Fra-2 in SSc fibroblasts and induced DNA binding of Fra-2 in an ERK-dependent manner. Knockdown of Fra-2 potently reduced the stimulatory effects of TGF, and PDGF and decreased the release of collagen from SSc fibroblasts. Conclusion We demonstrate that Fra-2 is overexpressed in SSc and acts as a novel downstream mediator of the profibrotic effects of TGF, and PDGF. Since transgenic overexpression of Fra-2 causes not only fibrosis but also vascular disease, Fra-2 might be an interesting novel candidate for molecular-targeted therapies for SSc. [source] Transgenic disruption of glucocorticoid signaling in mature osteoblasts and osteocytes attenuates K/BxN mouse serum,induced arthritis in vivoARTHRITIS & RHEUMATISM, Issue 7 2009Frank Buttgereit Objective Endogenous glucocorticoids (GCs) modulate numerous biologic systems involved in the initiation and maintenance of arthritis. Bone cells play a critical role in the progression of arthritis, and some of the effects of GCs on inflammation may be mediated via these cells. The aim of this study was to investigate the impact of osteoblast-targeted disruption of GC signaling on joint inflammation, cartilage damage, and bone metabolism in the K/BxN mouse serum transfer model of autoimmune arthritis. Methods Intracellular GC signaling was disrupted in osteoblasts through transgenic overexpression of 11,-hydroxysteroid dehydrogenase type 2 under the control of a type I collagen promoter. Arthritis was induced in 5-week-old male transgenic mice and their wild-type (WT) littermates, and paw swelling was assessed daily until the mice were killed. The mice were examined by histology, histomorphometry, and microfocal computed tomography, and serum was analyzed for cytokines, adrenocorticotropic hormone, and corticosterone. Results Acute arthritis developed in both transgenic and WT mice treated with K/BxN mouse serum. However, the arthritis and local inflammatory activity were significantly attenuated in transgenic mice, as judged by clinical and histologic indices of inflammation and cartilage damage. Bone turnover and bone volume remained unchanged in arthritic transgenic mice, while WT mice exhibited stimulated bone resorption, suppressed osteoblast activity, and significantly reduced bone volume, compatible with the known effects of active inflammation on bone. Circulating levels of proinflammatory cytokines tended to be lower in arthritic transgenic mice than in control transgenic mice. Conclusion Disruption of GC signaling in osteoblasts significantly attenuates K/BxN mouse serum,induced autoimmune arthritis in mice. These data suggest that osteoblasts modulate the immune-mediated inflammatory response via a GC-dependent pathway. [source] Wet-wrap treatment using dilutions of tacrolimus ointment and fluticasone propionate cream in human APOC1 (+/+) mice with atopic dermatitisBRITISH JOURNAL OF DERMATOLOGY, Issue 1 2009A.P. Oranje Summary Background, Wet-wrap treatment (WWT) with diluted topical steroids is widely used in atopic dermatitis (AD). Mice with transgenic overexpression of human apolipoprotein C1 (APOC1) in the liver and the skin are not only characterized by hyperlipidaemia and raised IgE levels, but also by pruritic dermatitis and a disturbed skin barrier function, providing a novel in vivo mouse model for AD. Objectives, We investigated an adapted WWT method in the AD model in APOC1 mice in order to establish its efficacy. Methods, The effect of topical 0·1% and 0·03% tacrolimus ointment, tacrolimus base ointment, different dilutions of 0·05% fluticasone propionate (FP) cream and emollient on the development of dermatitis in APOC1 mice was investigated. WWT was performed with 0·03% tacrolimus ointment or 0·017% FP cream. Results, AD in APOC1 mice responded to topical treatment with tacrolimus or FP. In contrast to tacrolimus treatment, FP treatment was associated with loss of body weight. WWT reinforced several therapeutic aspects, notably improvements in transepidermal water loss and in epidermal thickness. WWT using tacrolimus 0·03% ointment was more effective than WWT using FP 0·017% cream. Conclusions, AD in APOC1 mice responds to treatment with (diluted) tacrolimus or FP; treatment with FP cream, but not tacrolimus ointment, was associated with weight loss. In this study, the adapted WWT using tacrolimus or FP in mice had a limited improving effect as compared with open application of tacrolimus or FP. [source] IMPLICATIONS OF CROSS-TALK BETWEEN TUMOUR NECROSIS FACTOR AND INSULIN-LIKE GROWTH FACTOR-1 SIGNALLING IN SKELETAL MUSCLECLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 7 2008Miranda D Grounds SUMMARY 1Inflammation, particularly the pro-inflammatory cytokine tumour necrosis factor (TNF), increases necrosis of skeletal muscle. Depletion of inflammatory cells, such as neutrophils, cromolyn blockade of mast cell degranulation or pharmacological blockade of TNF reduces necrosis of dystrophic myofibres in the mdx mouse model of the lethal childhood disease Duchenne muscular dystrophy (DMD). 2Insulin-like growth factor-1 (IGF-1) is a very important cytokine for maintenance of skeletal muscle mass and the transgenic overexpression of IGF-1 within muscle cells reduces necrosis of dystrophic myofibres in mdx mice. Thus, IGF-1 usually has the opposite effect to TNF. 3Activation of TNF signalling via the c-Jun N-terminal kinase (JNK) can inhibit IGF-1 signalling by phosphorylation and conformational changes in insulin receptor substrate (IRS)-1 downstream of the IGF-1 receptor. Such silencing of IGF-1 signalling in situations where inflammatory cytokines are elevated has many implications for skeletal muscle in vivo. 4The basis for these interactions between TNF and IGF-1 is discussed with specific reference to clinical consequences for myofibre necrosis in DMD and also for the wasting (atrophy) of skeletal muscles that occurs in very old people and in cachexia associated with inflammatory disorders. [source] | |||||||||||||