Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Methylation profiling by array of human cell line HCT116 after treatment with demethylating drugs azacytidine or decitabine.

ABSTRACT: array-based analysis of genome-wide DNA methylation changes induced by the demethylating drugs azacytidine and decitabine on HCT116 cells for 24 hours

ORGANISM(S): Homo sapiens

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PROVIDER: E-MTAB-210 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Epigenetic methyl-CpG silencing of the ribosomal RNA (rRNA) genes is thought to down-regulate rRNA synthesis in mammals. In contrast, we now show that CpG methylation in fact positively influences rRNA synthesis and processing. Human HCT116 cells, inactivated for DNMT1 and DNMT3b or treated with aza-dC, lack CpG methylation and reactivate a large fraction of normally silent rRNA genes. Unexpectedly, these cells display reduced rRNA synthesis and processing, and accumulate unprocessed 45S rRNA. Reactivation of the rRNA genes is associated with their cryptic transcription by RNA polymerase II. Ectopic expression of cryptic rRNA gene transcripts recapitulates the defects associated with loss of CpG methylation. The data demonstrate that rRNA gene silencing prevents cryptic RNA polymerase II transcription of these genes. Lack of silencing leads to the partial disruption of rRNA synthesis and rRNA processing, providing an unexpected explanation for the cytotoxic effects of loss of CpG methylation. Agilent custom microarray analyses of transcripts from sense and antisense strands of the human rRNA genes present in total nuclear RNA from HCT116-DNMT1-/-;DNMT3b-/- (DKO) and HCT116 (PS) cells. The DKO/PS RNA ratio was normalized within the 5â region of the 45S ribosomal RNA, since this sense coding region was found by quantitative Northern and S1-mapping analyses to equally present in the RNA pools from both cells (as compared to total RNA levels and 18S and 28S levels). The distribution for sense RNAs from the coding region is strongly influenced by the predominant RPI 45S rRNA transcript and hence peaks at 0, the DKO and PS 45S rRNA signals having been normalized. 60-mer probes were designed to tile Human rDNA (GenBank accession U13369) on both strands using ArrayOligoSelector (Wardle et al., 2006). A total of 1,146 different non-overlapping probes (573 for each DNA strand) were designed to cover the 43 kb of human rDNA and each printed in triplicate on the array. The experiment was performed using a dye-swap duplicate analysis. The microarrays were scanned on a G2565CA DNA microarray scanner (Agilent Technologies) and the quantification performed using the Feature Extraction software (Agilent technologies). The data were analyzed using the LIMMA software package in R (Smyth and Speed, 2003).

Project description:T cell receptor (TCR) αβ+ CD4- CD8- double negative T cells represent a rare T cell subset implicated in the pathogenesis of several autoimmune diseases. In this study, we investigated the DNA methylation signature of double negative T cells to gain insight into the epigenetic architecture and transcriptional capacity of peripheral blood primary human double negative T cells compared to autologous CD4+ and CD8+ T cells. We identified 2,984 CG sites across the genome with unique loss of DNA methylation in double negative T cells, and showed significant reduction in mRNA expression of DNA methyltransferases DNMT1, DNMT3A, and DNMT3B. DNA methylation was increased in CD8A/CD8B and CD4 consistent with epigenetic repression of both the CD8 and CD4 genetic loci in double negative T cells. Curiously, we show consistent increase in non-CG methylation in double negative T cells, a finding suggestive of pluripotency and previously only known to occur in embryonic stem cells and developing brain tissue. Network analyses of genes hypomethylated in double negative compared to CD4+ and CD8+ T cells indicate a strong relationship between double negative T cells and functions related to cell-cell interaction, cell adhesion, and cell activation pathways. Our data also suggest a robust pro-inflammatory epigenetic signature in double negative T cells, consistent with a transcriptional permissiveness to produce key inflammatory cytokines including IFNγ, IL-17F, IL-12B, IL-5, IL-18, TNFSF11 (RANKL), and TNFSF13B (BLYS or BAFF). These findings highlight an epigenetic basis for a role of double negative T cells in autoimmunity and extend the potential pathogenic transcriptional capacity of this unique T cell subset. Peripheral blood mononuclear cells (PBMCs) were isolated from fresh blood samples of 7 unrelated healthy women (age range 25-60) (Supplementary Table 1) by Ficoll-gradient centrifugation (GE Healthcare Bio-Sciences AB, Uppsala, Sweden). Subsequently, T cells were negatively-selected using the Human Pan T Cell Isolation II kit (Miltenyi Biotec, Cambridge, MA). T cells were then analyzed and sorted into TCRαβ+ CD4+ T cells, TCRαβ+ CD8+ T cells, and TCRαβ+ DN T cell subsets by flow cytometry. DNA was isolated from CD4+, CD8+, and DN T cell subsets using the DNeasy Blood and Tissue Kit (Qiagen, Valencia, CA), then bisulfite-converted using the EZ DNA Methylation kit (Zymo Research, Irvine, CA) for DNA methylation studies.

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Methylation profiling by array of human cell line HCT116 after treatment with demethylating drugs azacytidine or decitabine.

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