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VDR/RXR and TCF4/beta-Catenin Cistromes in Colonic Cells of Colorectal Tumor Origin: Impact on c-FOS and c-MYC Gene Expression

ABSTRACT: Many of the transcriptional and growth regulating activities of 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) in the intestine and colon are recapitulated in the human colorectal cancer cell LS180. We therefore used this line together with ChIP-seq and gene expression analyses to identify the vitamin D receptor (VDR)/retinoid x receptor (RXR) and TCF7L2(TCF4)/β-catenin cistromes and the genes that they regulate. VDR and RXR co-localized to predominantly promoter distal, VDRE-containing sites in a largely ligand-dependent manner. These regulatory sites control the expression of both known as well as novel 1,25(OH)2D3 target genes. TCF4 and β-catenin cistromes partially overlapped, contained TCF/LEF consensus elements, and were only modestly influenced by 1,25(OH)2D3. However, the two heterodimer complexes co-localized at sites near a limited set of genes that included c-FOS and c-MYC; the expression of both genes was modulated by 1,25(OH)2D3. At the c-FOS gene, both VDR/RXR and TCF4/β-catenin bound to a single distal enhancer located 24 kb upstream of the transcriptional start site. At the c-MYC locus, however, binding was noted at a cluster of sites between -139 and -165 kb and at a site located -335 kb upstream. Examined as isolated enhancer fragments, these regions exhibited basal and 1,25(OH)2D3-inducible activities that were interlinked to both VDR and β-catenin activation. These data reveal additional complexity in the regulation of target genes by 1,25(OH)2D3 and support a direct action of both VDR and the TCF4/β-catenin regulatory complex at c-FOS and c-MYC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE31939 | GEO | 2011/11/22

SECONDARY ACCESSION(S): PRJNA145015

REPOSITORIES: GEO

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Project description:The biological effects of 1?,25-dihydroxyvitamin D3 (1,25(OH)2D3) on osteoblast differentiation and function differ significantly depending upon the cellular state of maturation. To explore this phenomenon mechanistically, we examined the impact of 1,25(OH)2D3 on the transcriptomes of both pre-osteoblastic (POBs) and differentiated osteoblastic (OBs) MC3T3-E1 cells, and assessed localization of the vitamin D receptor (VDR) at sites of action on a genome-scale using ChIP-seq analysis. We observed that the 1,25(OH)2D3-induced transcriptomes of POBs and OBs were quantitatively and qualitatively different, supporting not only the altered biology observed but the potential for a change in VDR interaction at the genome as well. This idea was confirmed through discovery that VDR cistromes in POBs and OBs were also strikingly different. Depletion of VDR binding sites in OBs, due in part to reduced VDR expression, was the likely cause of the loss of VDR-target gene interaction. Continued novel regulation by 1,25(OH)2D3, however, suggested that factors in addition to the VDR might also be involved. Accordingly, we show that transcriptomic modifications are also accompanied by changes in genome binding of the master osteoblast regulator RUNX2 and the chromatin remodeler C/EBP?. Importantly, genome occupancy was also highlighted by the presence of epigenetic enhancer signatures which were selectively changed in response to both differentiation and 1,25(OH)2D3. The impact of VDR, RUNX2, and C/EBP? on osteoblast differentiation is exemplified by their actions at the Runx2 and Sp7 gene loci. We conclude that each of these mechanisms may contribute to the diverse actions of 1,25(OH)2D3 on differentiating osteoblasts. 4 transcription factors and 5 histone modifications were examined in undifferentiated MC3T3-E1 cells as well as post 15 day osteogenic differentiation MC3T3-E1 cells, which were treated for 3 hours prior to ChIP assay with ethanol vehicle or with 10-7M 1,25(OH)2D3. For the vehicle matched samples for RUNX2, CEBP beta and histones, please refer to study GSE41955. The samples were completed in biological replicate and examined separately.

Project description:The biological effects of 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) on osteoblast differentiation and function differ significantly depending upon the cellular state of maturation. To explore this phenomenon mechanistically, we examined the impact of 1,25(OH)2D3 on the transcriptomes of both pre-osteoblastic (POBs) and differentiated osteoblastic (OBs) MC3T3-E1 cells, and assessed localization of the vitamin D receptor (VDR) at sites of action on a genome-scale using ChIP-seq analysis. We observed that the 1,25(OH)2D3-induced transcriptomes of POBs and OBs were quantitatively and qualitatively different, supporting not only the altered biology observed but the potential for a change in VDR interaction at the genome as well. This idea was confirmed through discovery that VDR cistromes in POBs and OBs were also strikingly different. Depletion of VDR binding sites in OBs, due in part to reduced VDR expression, was the likely cause of the loss of VDR-target gene interaction. Continued novel regulation by 1,25(OH)2D3, however, suggested that factors in addition to the VDR might also be involved. Accordingly, we show that transcriptomic modifications are also accompanied by changes in genome binding of the master osteoblast regulator RUNX2 and the chromatin remodeler C/EBPβ. Importantly, genome occupancy was also highlighted by the presence of epigenetic enhancer signatures which were selectively changed in response to both differentiation and 1,25(OH)2D3. The impact of VDR, RUNX2, and C/EBPβ on osteoblast differentiation is exemplified by their actions at the Runx2 and Sp7 gene loci. We conclude that each of these mechanisms may contribute to the diverse actions of 1,25(OH)2D3 on differentiating osteoblasts. RNA was isolated and applied to gene expression microarrays in undifferentiated MC3T3-E1 cells as well as post 15 day osteogenic differentiation MC3T3-E1 cells, which were treated for 24 hours with 10-7M 1,25(OH)2D3. For the vehicle matched samples, please refer to study GSE41955. The samples were completed in biological triplicate.

Project description:Osteocytes are derived from osteoblast lineage cells that become progressively embedded in mineralized bone. Development of the osteocytogenic cell line IDG-SW3 has enabled a temporal and mechanistic investigation of this process. Through RNA-seq analyses, we show that while substantial changes in gene expression occur during the osteoblast to osteocyte transition, the majority of the transcriptome remains qualitatively osteoblast-like. Genes either up-regulated or expressed uniquely in the osteocyte include local and systemic factors such as Sost and Fgf23 as well as genes implicated in neuronal, muscle, vascular, or regulatory function. As assessed by ChIP-seq, numerous changes in epigenetic histone modifications also occur during osteocytogenesis; these are largely qualitative rather than quantitative. Specific epigenetic changes correlate with altered gene expression patterns that are observed during the transition. These genomic changes likely influence the highly restricted transcriptomic response to 1,25(OH)2D3 that occurs during differentiation. VDR binding in osteocytes revealed an extensive cistrome co-occupied by RXR and located predominantly at sites distal to regulated genes. Although sites of VDR binding were apparent near many 1,25(OH)2D3-regulated genes, the expression of others adjacent to VDR binding sites were unaffected; lack of VDR binding was particularly prevalent at down-regulated genes. Interestingly, 1,25(OH)2D3 was found to induce the Boc and Cdon co-receptors that are active in hedgehog signaling in osteocytes. We conclude that osteocytogenesis is accompanied by changes in gene expression that may be driven by both genetic and epigenetic components. These changes are likely responsible for the osteocyte phenotype and may contribute to reduced sensitivity to 1,25(OH)2D3. ChIP-seq was performed on differentiated IDGSW3 cells at day 35 for VDR and RXR following 3 hour vehicle or 1,25(OH)2d3 treatment in biological replicate. ChIP-seq was also performed for H3K4me1, H3K4me2, H3K4me3, H3K27Ac, H4K5Ac, H3K9Ac, H4K20me1, H3K36me3, or H3K9me3 at day 3 and day 35 of differentiation in the basal condition.

Project description:Heterogeneous nuclear ribonucleoprotein (hnRNP) C1/C2 plays a pivotal role in vitamin D receptor (VDR) signaling by acting as a vitamin D response element (VDRE)-binding protein (VDRE-BP). Transcriptional regulation by active 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) involves occupancy of VDRE by VDRE-BP or 1,25(OH)2D3 bound-VDR. This relationship is disrupted by over-expression of VDRE-BP and can cause a form of human hereditary vitamin D-resistant rickets (HVDRR). DNA array analyses using B-cells from an HVDRR patient and matched control defined a sub-cluster of genes where 1,25(OH)2D3-regulated transcription was abrogated by over-expression of VDRE-BP. Amongst these, the DNA-damage-inducible transcript 4 (DDIT4), an inhibitor of mammalian target of rapamycin (mTOR) signaling, was also induced by 1,25(OH)2D3 in human osteoblasts. Chromatin immunoprecipitation using 1,25(OH)2D3-treated osteoblasts confirmed that liganded VDR and VDRE-BP compete for binding to the proximal promoter of the DDIT4 gene in a similar fashion to other known 1,25(OH)2D3-target genes. Treatment of osteoblasts with 1,25(OH)2D3 induced DDIT4 expression and suppressed phosphorylated S6K1T389 protein (a downstream target of mTOR). The functional importance of this for 1,25(OH)2D3 responses in osteoblasts was underlined by the fact that siRNA knockdown of DDIT4 expression suppressed antiproliferative and cell growth responses to 1,25(OH)2D3. These data confirm that VDRE-BP is required for normal 1,25(OH)2D3-mediated transcription and cell function in osteoblasts. Conversely over-expression of VDRE-BP exerts a dominant-negative effect on transcription of 1,25(OH)2D3-target genes. Characterization of VDRE-BP action in 1,25(OH)2D3-treated osteoblasts highlights an entirely novel role for vitamin D as a regulator of mTOR – a known ‘master regulator’ of cell function. We performed gene expression microarray analysis in HVDRR EBV-transformed B-cells and control cells in the presence or absence of vitamin D.

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VDR/RXR and TCF4/beta-Catenin Cistromes in Colonic Cells of Colorectal Tumor Origin: Impact on c-FOS and c-MYC Gene Expression

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