How organ size and form are controlled during development is a major question of biology. Blood vessels have been shown to be essential for early development of the liver and pancreas, and are fundamental to normal and pathological tissue growth. Here we report that non-nutritional signals from blood vessels surprisingly act to restrain pancreas growth. Elimination of endothelial cells increases the size of embryonic pancreatic buds. Conversely, VEGF-induced hypervascularization decreases pancreas size. The growth phenotype results from vascular restriction of pancreatic tip cell formation, lateral branching and differentiation of the pancreatic epithelium into endocrine and acinar cells. The effects are seen both in vivo and ex vivo, indicating a perfusion-independent mechanism. Thus the vasculature controls pancreas morphogenesis and growth by reducing branching and differentiation of primitive epithelial cells.
Blood vessels restrain pancreas branching, differentiation and growth.
Specimen part
View SamplesAmong the multiple mechanisms that control the intensity and duration of macrophage activation, the development of a state of refractoriness to a second stimulation in cells treated with LPS has long been recognized. Release of inhibitory cytokines and alterations in intracellular signaling pathways may be involved in the development of LPS tolerance. Although a number of molecules have been implicated, a detailed picture of the molecular changes in LPS tolerance is still missing. We have used a genome-wide gene expression analysis approach to (i) define which fraction of LPS target genes are subject to tolerance induction and (ii) identify genes that are expressed at high levels in tolerant macrophages. Our data show that in LPS tolerant macrophages the vast majority of LPS-induced gene expression is abrogated. The extent of tolerance induction varies for individual genes, and a small subset appears to be excepted. Compared to other negative control mechanisms of macrophages, e.g. IL-10-induced deactivation, LPS-tolerance inhibits a much wider range of transcriptional targets. Some previously described negative regulators of TLR-signaling (e.g. IRAK-M) were confirmed as expressed at higher levels in LPS-tolerant macrophages. In addition, we discuss other potential players in LPS tolerance identified in this group of genes.
A genome-wide analysis of LPS tolerance in macrophages.
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View SamplesPre-leukemic mutations are thought to promote clonal expansion of hematopoietic stem cells (HSCs) by increasing self-renewal and competitiveness. However, mutations that increase HSC proliferation tend to reduce competitiveness and self-renewal potential, raising the question of how a mutant HSC can sustainably outcompete wild-type HSCs. Activating mutations in NRAS are prevalent in human myeloproliferative disease and leukemia. Here we show that a single allele of oncogenic NrasG12D increases HSC proliferation but also increases reconstituting and self-renewal potential upon serial transplantation in irradiated mice, all without immortalizing HSCs or causing leukemia in our experiments. NrasG12D also confers long-term self-renewal potential upon multipotent progenitors. To explore the mechanism by which NrasG12D promotes HSC proliferation and self-renewal we assessed HSC cell cycle kinetics using H2B-GFP label retention. We found that NrasG12D had a bimodal effect on HSCs, increasing the proliferation of some HSCs while increasing the quiescence and competitiveness of other HSCs. One signal can therefore increase HSC proliferation, competitiveness, and self-renewal through a bimodal effect that promotes proliferation in some HSCs and quiescence in others.
Oncogenic Nras has bimodal effects on stem cells that sustainably increase competitiveness.
Specimen part
View SamplesMycobacterium avium infection in mice induces granuloma necrosis in the lung which is dependent on IFNg. IRF1 is a transcription factor activated by IFNg signaling. The effect of IFNg and IRF1 on immunopathology and transcriptional changes in the lung were analysed using gene-deficient mice.
Mycobacteria-induced granuloma necrosis depends on IRF-1.
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View SamplesChlamydia pneumoniae, an obligate intracellular bacterium, causes pneumonia in humans and mice. Toll-like receptors and the key adaptor molecule MyD88 play a critical role in inducing immunity against this microorganism and are crucial to survive the infection. To explore the influence of MyD88 on induction of immune responses in vivo on a genome wide level, WT or MyD88-/- mice were infected with C. pneumoniae upon anesthesia and the pulmonary transcriptome was analyzed three days later by microarrays. We find that the infection induced the transcription of 360 genes and repressed 18 genes in WT mice. Of these, 221 genes were not or weakly induced in lungs of MyD88-/- mice. This cluster contains primarily genes encoding for chemokines, cytokines and other immune effector molecules. Genes induced by interferons were abundant in a cluster of 102 genes which were only partially MyD88-dependent. Interestingly, a set of 37 genes were induced more strongly in MyD88-/- mice and most of them are involved in the regulation of cellular replication. In summary, ex vivo analysis of the pulmonary transcriptome upon infection with C. pneumoniae demonstrated a major impact of MyD88 on inflammatory responses but not on interferon-type responses, and identified MyD88-independent genes involved in cellular replication
MyD88-dependent changes in the pulmonary transcriptome after infection with Chlamydia pneumoniae.
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View SamplesAlthough several markers have been associated with the characterization of regulatory T cells (Treg) and their function, no studies have investigated the dynamics of their phenotype during infection. Since the necessity of Treg to control immunopathology has been demonstrated, we used the chronic helminth infection model S. mansoni to address the impact on the Treg gene repertoire. Before gene expression profiling we first chose to study the localization and antigen-specific suppressive nature of classically defined Treg during infection. Presence of Foxp3+ cells were found especially in the periphery of granulomas and isolated CD4+CD25hiFoxp3+ Treg from infected mice blocked IFN-gamma and IL-10 cytokine secretion from infected CD4+CD25- effector T cells (Teff). Furthermore the gene expression patterns of Treg and Teff showed that in total 474 genes were significantly regulated during chronic schistosomiasis. Upon k-means clustering we identified genes exclusively regulated in all four populations including Foxp3, CD103, GITR, OX40 and CTLA-4: classical Treg markers. During infection however, several non-classical genes were up-regulated solely within the Treg population such as Slpi, Gzmb, Mt1, Fabp5, Nfil3, Socs2, Gpr177 and Klrg1. Using RT-PCR we confirmed aspects of the microarray data and in addition showed that the expression profile of Treg from S. mansoni-infected mice is simultaneously unique and comparative with Treg derived from other infections
Pronounced phenotype in activated regulatory T cells during a chronic helminth infection.
Specimen part
View SamplesThis experiment is an additional experiment to GSE6688. Mouse macrophages (ANA-1 cells) were infected in vitro with C. pneumoniae with a M.O.I. of 10. Twenty two genes were significantly upregulated. Examples of the most upregulated genes in mouse macrophages after C. pneumoniae infection are serum amyloid A3 (saa3), a protein that is mainly produced by activated macrophages during tissue injury or inflammation, MIP-2 (cxcl2) and irg1. Expression levels of all genes induced by C. pneumoniae in macrophages in vitro correlated with the results obtained from infected lungs from wild type mice (GSE6688), suggesting that this cell type participates in host defense in vivo against C. pneumoniae.
MyD88-dependent changes in the pulmonary transcriptome after infection with Chlamydia pneumoniae.
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View SamplesThis SuperSeries is composed of the SubSeries listed below.
Gene expression signature for biliary atresia and a role for interleukin-8 in pathogenesis of experimental disease.
Specimen part, Time
View SamplesLiver biopsy samples were obtained from 64 infants with biliary atresia at the time of intraoperative cholangiogram. Liver biopsy samples were obtained from 14 age-matched infants with other causes of intrahepatic cholestasis, and from 7 deceased-donor children. GeneChip Human Gene 1.0 ST Array (Affymetrix, CA) were used to screen mRNAs whose expression was specifically regulated in the livers from patients with biliary atresia.
Gene expression signature for biliary atresia and a role for interleukin-8 in pathogenesis of experimental disease.
Specimen part
View SamplesNewborn Balb/c mice were injected intraperitoneally with 1.5x10^6 fluorescent-forming units (ffu) of type- A Rhesus Rotavirus (RRV) or 0.9% normal saline (NS; control) within 24 hours of birth to induce experimental model of biliary atresia. Extrahepatic bile ducts including gallbladder were microdissected en bloc at 3, 7 and 14 days after RRV or saline injections. GeneChip Mouse Gene 1.0 ST Array (Affymetrix, CA) were used to screen mRNAs whose expression was differently regulated after RRV challenge compared to normal saline controls.
Gene expression signature for biliary atresia and a role for interleukin-8 in pathogenesis of experimental disease.
Specimen part, Time
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