Detailed information about stage-specific changes in gene expression is crucial for understanding the gene regulatory networks underlying development and the various signal transduction pathways contributing to morphogenesis. Here, we describe the global gene expression dynamics during early murine limb development, when cartilage, tendons, muscle, joints, vasculature, and nerves are specified and the musculoskeletal system of the limbs is established. We used whole-genome microarrays to identify genes with differential expression at 5 stages of limb development (E9.5 to 13.5), during fore-limb and hind-limb patterning. We found that the onset of limb formation is characterized by an up-regulation of transcription factors, which is followed by a massive activation of genes during E10.5 and E11.5 which tampers off at later time points. Among 3520 genes identified as significantly up-regulated in the limb, we find ~30% to be novel, dramatically expanding the repertoire of candidate genes likely to function in the limb. Hierarchical and stage-specific clustering identified expression profiles that correlate with functional programs during limb development and are likely to provide new insights into specific tissue patterning processes. Here we provide for the first time, a comprehensve analysis of developmentally regulated genes during murine limb development, and provide some novel insights into the expression dynamics governing limb morphogenesis.
Global gene expression analysis of murine limb development.
Specimen part
View SamplesWe developed a mouse model that captures radiation effects on host biology by transplanting unirradiated Trp53 null mammary tissue to sham or irradiated hosts. Gene expression profiles of tumors that arose in irradiated mice are distinct from those that arose in nave hosts.
Murine microenvironment metaprofiles associate with human cancer etiology and intrinsic subtypes.
Specimen part
View SamplesWe previously generated genetically engineered mouse (GEM) models based on perturbation of Tp53, Rb with or without Brca1 or Brca2 that develop serous epithelial ovarian cancer (SEOC) closely resembling the human disease on histologic and molecular levels. We have adapted these GEM models to orthotopic allografts that uniformly develop tumors with short latency in immunocompetent recipients and are ideally suited for routine preclinical studies. To monitor passaged tumors at the molecular level, we analyzed transcriptional profiles of a set of primary SEOC and matching derived passaged tumors. We have merged this dataset with previously published ( doi: 10.1158/0008-5472.CAN-11-3834; PMID 22617326) dataset of murine primary ovarian tumors from our GEM models (GSE46169) and merged and compared them to expression profiles of human dataset published previously (doi: 10.1038/nature10166).
Pathway-specific engineered mouse allograft models functionally recapitulate human serous epithelial ovarian cancer.
Specimen part
View SamplesHigh-fat diets are associated with increased obesity and metabolic disease in mice and humans. Here we used analysis of variance (ANOVA) to scrutinize a microarray data set consisting of 10 inbred strains of mice from both sexes fed atherogenic high-fat and control chow diets. An overall F-test was applied to the 40 unique groups of strain-diet-sex to identify 15,288 genes with altered transcription. Bootstrapping k-means clustering separated these changes into four strain-dependent expression patterns, including two sex-related profiles and two diet-related profiles. Sex-induced effects correspond to secretion (males) or fat and energy metabolism (females), whereas diet-induced changes relate to neurological processes (chow) or immune response (high-fat). The full set of pairwise contrasts for differences between strains within sex (90 different statistical tests) uncovered 32,379 total changes. These differences were unevenly distributed across strains and between sexes, indicating that strain-specific responses to high-fat diet differ between sexes. Correlations between expression levels and 8 obesity-related traits identified 5,274 associations between transcript abundance and measured phenotypic endpoints. From this number, 2,678 genes are positively correlated with total cholesterol levels and associate with immune-related categories while 2,596 genes are negatively correlated with cholesterol and connect to cholesterol synthesis.
Practical applications of the bioinformatics toolbox for narrowing quantitative trait loci.
Sex
View SamplesIn this study that was specifically designed to identify early stages of glaucoma in DBA/2J mice, we used genome-wide expression profiling and a series of computational methods. Our methods successfully subdivided eyes with no detectable glaucoma by conventional assays into molecularly defined stages of disease. These stages represent a temporally ordered sequence of glaucoma states. Using an array of tools, we then determined networks and biological processes that are altered at these early stages. Our strategy proved very sensitive, suggesting that similar approaches will be valuable for uncovering early processes in other complex, later-onset diseases. Early changes included upregulation of both the complement cascade and endothelin system, and so we tested the therapeutic value of separately inhibiting them. Mice with a mutation in the complement component 1a gene (C1qa) were robustly protected from glaucoma with the protection being among the greatest reported. Similarly, inhibition of the endothelin system was strongly protective. Since EDN2 is potently vasoconstrictive and was produced by microglial/macrophages, our data provide a novel link between these cell types and vascular dysfunction in glaucoma. Targeting early events such as the upregulation of the complement and endothelin pathways may provide effective new treatments for human glaucoma.
Molecular clustering identifies complement and endothelin induction as early events in a mouse model of glaucoma.
Sex, Age, Specimen part
View SamplesWe used a novel probe-level microarray analysis, revealing connections between mRNA processing and lymphoid neoplasia, in a mouse leukemia model. Characteristic differences in mRNA processing, primarily in the 3-untranslated region, distinguished histologically similar tumor subtypes with different survival characteristics. Gene sets with specific processing in each tumor subtype defined signatures useful for tumor subclassification, as demonstrated by internal cross-validation with up to 80% discrimination accuracy. A combination of mRNA expression and sequence analysis suggested that differences in isoform abundance likely arose from both alternative polyadenylation and differential degradation.
Global changes in processing of mRNA 3' untranslated regions characterize clinically distinct cancer subtypes.
Specimen part
View SamplesRosiglitazone (Rosi), a member of the thiazolidinedione class of drugs used to treat type 2 diabetes, activates the adipocyte-specific transcription factor peroxisome proliferator-activated receptor gamma (PPARg). This activation causes bone loss in animals and humans, at least in part due to suppression of osteoblast differentiation from marrow mesenchymal stem cells (MSC). In order to identify mechanisms by which PPARg2 suppresses osteoblastogenesis and promotes adipogenesis in MSC, we have analyzed the PPARg2 transcriptome in response to Rosi. A total of 4,252 transcriptional changes resulted when Rosi (1 uM) was applied to the U-33 marrow stromal cell line, stably transfected with PPARg2 (U-33/g2), as compared to non-induced U-33/g2 cells. Differences between U-33/g2 and U-33 cells stably transfected with empty vector (U-33/c) comprised 7,928 transcriptional changes, independent of Rosi. Cell type-, time- and treatment-specific gene clustering uncovered distinct patterns of PPARg2 transcriptional control of MSC lineage commitment. The earliest changes accompanying Rosi activation of PPARg2 included adjustments in morphogenesis, Wnt signaling, and immune responses, as well as sustained induction of lipid metabolism. Expression signatures influenced by longer exposure to Rosi provided evidence for distinct mechanisms governing the repression of osteogenesis and stimulation of adipogenesis. Our results suggest interactions that could lead to the identification of a master regulatory scheme controlling osteoblast differentiation.
No associated publication
Compound, Time
View SamplesThe recent identification of cancer stem cells (CSCs) in multiple human cancers provides a new inroad to understanding tumorigenesis at the cellular level. CSCs are defined by their characteristics of self-renewal, multipotentiality, and tumor initiation upon transplantation. By testing for these defining characteristics, we provide evidence for the existence of CSCs in a transgenic mouse model of glioma, S100-verbB;Trp53. In this glioma model, CSCs are enriched in the side-population (SP) cells. These SP cells have enhanced tumor-initiating capacity, self-renewal, and multipotentiality compared to non-SP cells from the same tumors. Furthermore, gene expression analysis comparing FACS-sorted cancer SP cells to non-SP cancer cells and normal neural SP cells identified 45 candidate genes that are differentially expressed in glioma stem cells. We validated the expression of two genes from this list (S100a4 and S100a6) in primary mouse gliomas and human glioma samples. Analyses of xenografted human GBM (glioblatoma multiforme) cell lines and primary human glioma tissues show that S100A4 and S100A6 are expressed in a small subset of cancer cells and that their abundance is positively correlated to tumor grade. In conclusion, this study shows that CSCs exist in a mouse glioma model, suggesting that this model can be used to study the molecular and cellular characteristics of CSCs in vivo and to further test the cancer stem cell hypothesis.
Cancer stem cells are enriched in the side population cells in a mouse model of glioma.
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View SamplesMutations in the membrane frizzled-related gene (Mfrp) are linked to posterior microphthalmia, retinitis pigmentosa and nanophthalmia in humans. In homozygous Mfrprd6 mice, a splice site mutation causes a slow photoreceptor degeneration characterized by shortening and disorganization of outer segments with eventual photoreceptor loss. To better understand the function of MFRP in the retina, microarray analysis was carried out in mutant and control mice at postnatal day14 (P14), prior to the loss of photoreceptors. Analysis of the data revealed differentially expressed RPE and neuroretina transcripts. Although the analysis of the microarray data from Mfrprd6 mutant mice compared to age-matched wild-type controls identified some transcripts with relative fold change > 5.0, most of the differentially expressed genes showed a relative fold change between1.5 - 2.0. Global gene expression analysis using Ingenuity Pathway Analysis software identified decreased levels of transcripts in phototransduction and visual pathways in Mfrprd6 mutants. Select candidate transcripts were validated by quantitative real-time PCR analyses. The expression of RPE-specific visual transduction protein, RPE65, was significantly decreased in Mfrprd6 mutants. As an indirect consequence of the primary RPE cell defect due to the Mfrprd6 mutation, retinal specific transcripts Rgr, Pde6a, GuCa1b, and Rgs9 were also significantly decreased. We also confirmed the significantly elevated levels of Prss56, a gene previously associated with myopia and open angle glaucoma. In the Mfrprd6 mutant, a progressive increase in Prss56 mRNA levels from 14- to 70-fold was observed from P7 to P21, respectively. In situ hybridization and glutamine synthetase staining of mutant eyes indirectly identified Mller glia in the inner nuclear layer of retina as the cell type expressing the Prss56 transcript.
No associated publication
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View SamplesThe BCR-ABL oncogene, generated by Philadelphia chromosome, is present in about 95% human Chronic myeloid leukemia (CML) and 20~30% acute lymphoblastic leukemia (ALL). One of BCR-ABL isoforms, P210, is more often detected in CML and ALL patients. Although BCR-ABL kinase inhibitors are effective in controlling the diseases, they do not provide cure due to the development of drug resistance and the insensitivity of leukemia stem cells to these drugs. Identification of new therapeutic targets is critical. To identify potential target against leukemia stem cells, we studied gene expression in leukemia stem cells, which were identified in mice in our lab (Hu Y, Swerdlow S, Duffy TM, Weinmann R, Lee FY, Li S. 2006. Targeting multiple kinase pathways in leukemic progenitors and stem cells is essential for improved treatment of Ph+ leukemia. Proc Natl Acad Sci USA 103(45):16870-16875.). The sorted leukemia stem cells that expressed BCR-ABL were used for isolation of RNA, followed by the analysis of gene expression using the DNA microarray. The same lineage of non-BCR-ABL-expressing normal hematopoietic stem cells was used as control. We have identified some interesting genes that are up- or down-regulated by BCR-ABL in these leukemia stem cells. We are currently studying the functions of these identified genes.
Loss of the Alox5 gene impairs leukemia stem cells and prevents chronic myeloid leukemia.
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