Recent studies suggest that telomerase promotes cell growth by mechanisms that extend beyond the rescue of critically short telomeres. The in vitro model of mTert overexpressing MEFs recapitulates fundamental aspects of the growth-promoting effects of mTert in vivo. First, in Terc-proficient cells, mTert overexpression favors escape from replicative senescence and enhances anchorage-independent growth in response to oncogenic stress, which fits well with previous data showing that mTert overexpression promotes tumor formation. Second, in Terc-deficient cells, retroviral transduction with mTert results in a delayed onset of immortalization and impairs colony formation in response to oncogenic stress, which is in agreement with the inhibitory effect of mTert overexpression on tumorigenesis in a Terc null mouse background. To unravel the molecular targets of telomerase that impact on cell growth, we compared the transcriptome of MEFs, before and after mTert introduction. We found that ectopic expression of mTert was associated with detectable gene expression changes (greater than 1.5-fold; validated by qRT-PCR) of 26 transcripts. Analysis of the observed transcriptional changes indicates that ectopic expression of mTert suppresses in a coordinated manner functionally related genes with overlapping roles in growth arrest, resistance to transformation, and apoptosis. We show that the majority of the telomerase target genes are growth-inhibitory, transforming growth factor-beta (TGF-beta) -inducible genes and provide functional evidence for the potential of telomerase to abrogate TGF-beta -mediated growth inhibition. Thus, in line with the current view that the diversity of TGF-beta responses is not so much a consequence of the use of different signaling pathways but caused by different ways of reading the output from the same basic pathway, we propose that the telomerase status of a cell creates a gene expression pattern that determines how cells read growth inhibitory signals, among them signals propagated through the TGF-beta pathway.
Expression of mTert in primary murine cells links the growth-promoting effects of telomerase to transforming growth factor-beta signaling.
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View SamplesFTLD-U is the most common pathological correlate of the neurodegenerative dementia frontotemporal dementia
Variations in the progranulin gene affect global gene expression in frontotemporal lobar degeneration.
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View SamplesTyrosine phosphorylation is a hallmark for activation of Signal Transducer and Activator of Transcription (STAT) proteins, but their transcriptional activity also depends on other secondary modifications. Type I interferons (IFNs) can activate both the ISGF3 (STAT1:STAT2:IRF9) complex and STAT3, but with cell-specific, selective triggering of only the ISGF3 transcriptional program. Following a genome-wide RNAi screen, we identified the Sin3a complex as an important mediator of this STAT3 transcriptional repression. Sin3a directly interacts with the DNA-binding domain of STAT3 and alters its acetylation status. SIN3A silencing enhances recruitment of STAT3 and enhanceosome components to the SOCS3 promoter, resulting in histone hyperacetylation and enhanced transcription. Conversely, Sin3a is required for ISGF3-dependent gene transcription and for an efficient IFN-mediated antiviral protection against Influenza A and hepatitis C viruses. The Sin3a complex therefore acts as a context-dependent STAT1/3 transcriptional switch.
The Sin3a repressor complex is a master regulator of STAT transcriptional activity.
Cell line, Treatment
View SamplesBipolar disorder (BPD) is a debilitating heritable psychiatric disorder. Contemporary models for the manic pole of BPD have primarily utilized either single locus transgenics or treatment with psychostimulants. Our lab recently characterized a mouse strain, termed Madison (MSN), which naturally displays a manic phenotype, exhibiting elevated locomotor activity, increased sexual behavior, and higher forced swimming relative to control strains. Lithium chloride and olanzapine treatments attenuate this phenotype. In this study, we replicated our locomotor activity experiment, showing that MSN mice display generationally-stable mania relative to their outbred ancestral strain, hsd:ICR (ICR). We then performed a gene expression microarray experiment to compare hippocampus of MSN and ICR mice. We found dysregulation of multiple transcripts whose human orthologs are associated with BPD and other psychiatric disorders including schizophrenia and ADHD, including: Epor, Smarca4, Cmklr1, Cat, Tac1, Npsr1, Fhit, and P2rx7. RT-qPCR confirmed dysregulation for all of seven transcripts tested. Using a network analysis, we found dysregulation of a gene system related to chromatin packaging, a result convergent with recent human findings on BPD. Using a novel genomic enrichment algorithm, we found enrichment in genome regions homologous to human loci implicated in BPD in replicated linkage studies including homologs of human cytobands 1p36, 3p14, 3q29, 6p21-22, 12q24, 16q24, and 17q25. Our findings suggest that MSN mice represent a polygenic model for the manic pole of BPD showing much of the genetic systems complexity of the corresponding human disorder. Further, the high degree of convergence between our findings and the human literature on BPD brings up novel questions about evolution by analogy in mammalian genomes.
A new mouse model for mania shares genetic correlates with human bipolar disorder.
Sex, Specimen part
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Divergent whole-genome methylation maps of human and chimpanzee brains reveal epigenetic basis of human regulatory evolution.
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View SamplesWe identified human-specific gene expression patterns in the brain by comparing expression with chimpanzee and rhesus macaque
Divergent whole-genome methylation maps of human and chimpanzee brains reveal epigenetic basis of human regulatory evolution.
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View SamplesThe intestine is composed of an epithelial layer, containing rapidly proliferating cells that mature into two distinct anatomic regions, the small and the large intestine. Although previous studies have identified stem cells as the cell-of-origin for the whole intestine, no studies have compared stem cells derived from the small and large intestine. Here, we report intrinsic differences between these two populations of cells. Primary epithelial cells isolated from human fetal small and large intestine and expanded with Wnt agonist, R-spondin 2, displayed differential expression of stem cell markers and separate hierarchical clustering of gene expression involved in differentiation, proliferation and disease pathways. Using a three-dimensional in vitro differentiation assay, single cells derived from small and large intestine formed distinct organoid architecture with cellular hierarchy similar to that found in primary tissue. Our characterization of human fetal intestinal stem cells defies the classical definition proposed by most where small and large intestine are repopulated by an identical epithelial stem cell and raises the question of the importance of intrinsic and extrinsic cues in the development of intestinal diseases.
Distinct human stem cell populations in small and large intestine.
Specimen part
View SamplesDespite the well-established role of the frontal and posterior peri-sylvian cortices in many facets of human-cognitive specializations, including language, little is known about the developmental patterning of these regions in human brain. We performed a genome-wide analysis of human cerebral patterning during mid-gestation, a critical epoch in cortical regionalization. A total of 345 genes were identified as differentially expressed (DE) between superior temporal gyrus (STG) and the remaining cerebral cortex (CTX). GO categories representing transcription factors were enriched in STG, while cell-adhesion and extracellular matrix molecules, were enriched in the other cortical regions. Q-PCR or in situ hybridization were performed to validate differential expression in a subset of 32 genes, most of which were confirmed. LIM domain binding 1 (LDB1), which we show to be enriched in the STG, is a recently identified interactor of LIM domain only 4 (LMO4), a gene known to be involved in the asymmetric pattering of the peri-sylvian region in the developing human brain. Protocadherin 17 (PCDH17), a neuronal cell adhesion molecule, was highly enriched in focal regions of the human prefrontal cortex. Contactin Associated Protein-Like 2 (CNTNAP2), in which mutations are known to cause autism, epilepsy and language delay, showed a remarkable pattern of anterior enriched expression in cortical regions important for human higher cognition. Importantly, a similar pattern was not observed in the mouse or rat. These data highlight the importance of expression analysis of human brain and the utility of cross-species comparisons of gene expression. Genes identified here provide a foundation for understanding molecular aspects of human-cognitive specializations and disorders that disrupt them.
Genome-wide analyses of human perisylvian cerebral cortical patterning.
Sex, Age
View SamplesThis SuperSeries is composed of the SubSeries listed below.
Mechanisms of epigenetic and cell-type specific regulation of Hey target genes in ES cells and cardiomyocytes.
Specimen part
View SamplesWe used an in vitro cardiomyocyte differentiation system with inducible Hey1 or Hey2 expression to study target gene regulation in cardiomyocytes (CM) generated from murine embryonic stem cells (ESC). The effects of Hey1 and Hey2 are largely redundant, but cell type specific. The number of regulated genes is comparable between ESC and CM, but the total number of binding sites is much higher, especially in ESC, targeting mainly genes involved in transcriptional regulation and developmental processes. Repression by Hey generally correlates with the extent of Hey-binding to target promoters, subsequent Hdac recruitment and lower histone acetylation. Functionally, treatment with the Hdac inhibitor TSA abolished Hey target gene regulation. However, in CM the repressive effect of Hey-binding is lost for a subset of genes. These lack Hey-dependent histone deacetylation in CM and are enriched for binding sites of cardiac specific activators like Srf, Nkx2-5, and Gata4.
Mechanisms of epigenetic and cell-type specific regulation of Hey target genes in ES cells and cardiomyocytes.
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