Unknown,Transcriptomics,Genomics,Proteomics

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DNA methylome profiling of human tissues identifies global and tissue-specific methylation patterns

ABSTRACT: Background: DNA epigenetic modifications, such as methylation, are important regulators of tissue differentiation, contributing to processes of both development and cancer. Profiling the tissue-specific DNA methylome patterns will provide novel insights into normal and pathogenic mechanisms, as well as help in future epigenetic therapies. In this study, 17 somatic tissues from four autopsied humans were subjected to functional genome analysis using the Illumina Infinium HumanMethylation450 BeadChip, covering 486 428 CpG sites. Results: Only 2% of the CpGs analyzed are hypermethylated in all 17 tissue specimens; these permanently methylated CpG sites are located predominantly in gene-body regions. In contrast, 15% of the CpGs are hypomethylated in all specimens and are primarily located in regions proximal to transcription start sites. A vast number of tissue-specific differentially methylated regions are identified and considered likely mediators of tissue-specific gene regulatory mechanisms since the hypomethylated regions are closely related to known functions of the corresponding tissue. Finally, a clear inverse correlation is observed between promoter methylation within CpG islands and gene expression data obtained from publicly available databases. Conclusions: This genome-wide methylation profiling study identified tissue-specific differentially methylated regions in 17 human somatic tissues. Many of the genes corresponding to these differentially methylated regions contribute to tissue-specific functions. Future studies may use these data as a reference to identify markers of perturbed differentiation and disease-related pathogenic mechanisms. DNA methylation analysis of the total 72 tissue samples and controls was performed with the Illumina Infinium HumanMethylation450 BeadChip. The 17 post-mortem human somatic tissues used in this study were collected at the time of autopsy. Controls for unmethylated and methylated DNA were represented, respectively, by whole-genome amplified DNA from subcutaneous adipose tissue (using the GenomiPhi DNA amplification kit; GE Healthcare, Piscataway, NJ, USA) and the universal methylated human DNA standard (Zymo Research). We had two technical and two biological replicates processed by chip technique.

ORGANISM(S): Homo sapiens

SUBMITTER: Kaie Lokk

PROVIDER: E-GEOD-50192 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Cancer is characterised by DNA hypermethylation and gene silencing of CpG island-associated promoters, including tumour suppressor genes The methyl-CpG-binding domain (MBD) family of proteins bind to methylated DNA and can aid in the meditation of gene silencing by interaction with histone deacetylases and histone methyltransferases. However the mechanisms responsible for eliciting CpG island hypermethylation in cancer, and the potential role that MBD may proteins play in modulation of the methylome remain unclear. Our previous work demonstrated that MBD2 preferentially binds to the hypermethylated GSTP1 promoter CpG island in prostate cancer cells. Here, we use functional genetic approaches to investigate if MBD2 plays an active role in promoting DNA methylation. First, we show that loss of MBD2 results in inhibition of both maintenance and spread of de novo methylation of a transfected construct containing the GSTP1 promoter CpG island in prostate cancer cells and Mbd2-/- mouse fibroblasts. De novo methylation was rescued by transient expression of Mbd2 in Mbd2-/- cells. Second, we show that MBD2 depletion triggers significant hypomethylation genome-wide in prostate cancer cells with concomitant loss of MBD2 binding at promoter and enhancer regulatory regions. Finally, CpG islands and shores that become hypomethylated after MBD2 depletion in LNCaP cancer cells show significant hypermethylation in clinical prostate cancer, highlighting a potential active role of MBD2 in promoting cancer specific hypermethylation. Importantly, co-immunoprecipiation of MBD2 reveals that MBD2 associates with DNA methyltransferase (DNMT) enzymes 1 and 3A. Together our results demonstrate that MBD2 plays a critical role in â??rewritingâ?? the cancer methylome at specific regulatory regions. LNCaP prostate cancer cell line clones with reduced MBD2 expression were establised by using shRNA to MBD2 and scrambled control clones were established with scrambled control shRNA. To interrogate methylation changes induced by MBD2 knock-down we profiled three stably transfected scrambled control clones and three MBD2 knockdown clones on Illumina HumanMethylation450K arrays. Differential methylation analysis was carried out to identified CpG sites hypo-/hyper-methylated as a result of MBD2 knockdown.

Project description:To further our understanding of the role of DNA methylation in development, Methylated DNA Immunoprecipitation (MeDIP) was used in conjunction with a NimbleGen promoter plus CpG island array to identify Tissue and Developmental Stage specific Differentially Methylated DNA Regions (T-DMRs and DS-DMRs) on a genome-wide basis. Four tissues (brain, heart, liver, and testis) from C57BL/6J mice were analyzed at three developmental stages (15 day embryo, E15; new born, NB; 12 week adult, AD). Almost 5,000 adult T-DMRs and 10,000 DS-DMRs were identified. Surprisingly, almost all DS-DMRs were tissue specific (i.e., methylated and ummenthylated in one or more non-overlapping tissues), indicating that the vast majority of unique sequence DNA methylation has tissue specificity. Also, many DS-DMRs were methylated at early development stages (E15 and NB) but unmethylated in adult, indicating “demethylation” has a prominent role in tissue differentiation. The pattern of DNA methylation in adult testis was dramatically different from somatic tissues in many aspects, mostly notably with a very strong bias of methylation in non-CpGi (CpG island) promoter regions (94%). Although the majority of T-DMRs and DS-DMRs tended to be in non-CpGi promoter regions, a relatively large number were also located in CpGi in promoter, intra-genic and inter-genic regions (>15% of all CpGi). Gene Ontology analysis of genes with methylation in non-CpGi promoters indicates enrichment of genes related to membrane proteins and G-protein coupled receptors. Our data also suggest regulatory roles of DNA methylation outside of promoter regions and in alternative promoter selection. Overall, our studies indicate that change in DNA methylation during development is a dynamic, widespread and tissue-specific process involving both DNA methylation and demethylation. Comparison of DNA methylation across 3 developmental stages (15 day embryo, newborn, and adult) for four tissues (brain, heart, liver and testis)

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DNA methylome profiling of human tissues identifies global and tissue-specific methylation patterns

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