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Recruitment of MYC to target genes in ramos and mutu3 cells

ABSTRACT: Follicular lymphomas and diffuse large B-cell lymphomas have markedly different biological phenotypes and yet all originate from mature, germinal center B-cells. We hypothesized that alterations in DNA methylation patterning might help explain the clinical heterogeneity of these diseases. We report that intra- and inter-individual patient heterogeneity in cytosine methylation is associated with disease severity, and that methylation heterogeneity originates in germinal centers and is amplified during disease progression. Abnormal methylation patterns differ between chromosomal regions and depend on local gene density and the methylation status of neighboring genes. Lymphomagenic transcriptional regulators, such as BCL6, MYC and EZH2, perturb DNA methylation in a target gene-specific manner. Furthermore, aberrant epigenetic states – especially hypomethylation – tend to spread along DNA in a non-specific manner while insulator elements like CTCF inhibit such spreading. Our findings suggest mechanisms through which altered cytosine methylation contributes to the distinct phenotypes of tumors derived from mature B-cells.

ORGANISM(S): Homo sapiens

PROVIDER: GSE31110 | GEO | 2012/11/27

SECONDARY ACCESSION(S): PRJNA144677

REPOSITORIES: GEO

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Recruitment of MYC to target genes in ramos and mutu3 cells

Project description:Follicular lymphomas and diffuse large B-cell lymphomas have markedly different biological phenotypes and yet all originate from mature, germinal center B-cells. We hypothesized that alterations in DNA methylation patterning might help explain the clinical heterogeneity of these diseases. We report that intra- and inter-individual patient heterogeneity in cytosine methylation is associated with disease severity, and that methylation heterogeneity originates in germinal centers and is amplified during disease progression. Abnormal methylation patterns differ between chromosomal regions and depend on local gene density and the methylation status of neighboring genes. Lymphomagenic transcriptional regulators, such as BCL6, MYC and EZH2, perturb DNA methylation in a target gene-specific manner. Furthermore, aberrant epigenetic states – especially hypomethylation – tend to spread along DNA in a non-specific manner while insulator elements like CTCF inhibit such spreading. Our findings suggest mechanisms through which altered cytosine methylation contributes to the distinct phenotypes of tumors derived from mature B-cells. Identification of MYC target genes in Burkitt lymphomas by ChIP-on-chip. MYC ChIP-on-chip was done in two Burkitt Lymphoma (BL) cell lines (ramos and mutu3) in duplicate. This submission represents the ChIP-chip component of the study.

2012-11-27 | E-GEOD-31110 | biostudies-arrayexpress

AICDA-induced epigenetic plasticity accelerates germinal center-derived lymphomagenesis

Project description:Epigenetic heterogeneity is emerging as a significant phenotypic feature of tumors. In diffuse large B-cell lymphomas (DLBCLs), increased cytosine methylation heterogeneity is associated with poor clinical outcome, yet the biological mechanisms driving epigenetic heterogeneity remain unclear. Activation-induced cytidine deaminase (AICDA), an enzyme that deaminates and facilitates demethylation of DNA methyl-cytosines in germinal center (GC) B-cells, is required for DLBCL pathogenesis and linked to inferior clinical outcomes. Here, we show that overexpression of AICDA causes more aggressive disease and worse outcome in BCL2-driven murine lymphomas. This phenotype was associated with significantly increased focal inter-tumor and intra-tumor cytosine methylation heterogeneity as compared to control lymphomas, but not with increased mutational burden. AICDA-mediated epigenetic heterogeneity was accompanied by DNA hypomethylation. Reciprocally, we observed that the focal inter-individual and intra-individual cytosine methylation heterogeneity characteristic of normal GC B-cells was lost upon depletion of AICDA. There was significant overlap of AICDA-induced methylation heterogeneity foci in GC B-cells and murine lymphomas. These observations are relevant to human patients, since DLBCLs with high AICDA expression likewise manifest extensive increases in focal inter-patient and intra-patient heterogeneity as compared to DLBCLs with low AICDA expression. Affected regions significantly overlapped with those found in murine AICDA-overexpressing lymphomas. Our results identify AICDA as a novel source of epigenetic plasticity and heterogeneity in B-cell lymphomas with potential significance for other tumors that express cytosine deaminases.

2018-01-19 | GSE95013 | GEO

Small-RNA expression in normal and malignant mature B cells

Project description:Small-RNA profiles were generated for normal mature germinal center (GC) B cells and GC-derived lymphomas.

2014-06-01 | GSE56354 | GEO

Small-RNA expression in normal and malignant mature B cells

Project description:Small-RNA profiles were generated for normal mature germinal center (GC) B cells and GC-derived lymphomas. Normal and tumor samples are derived from different donors.

2014-06-01 | E-GEOD-56354 | biostudies-arrayexpress

Pivotal role for S-nitrosylation of DNA methyltransferase in epigenetic regulation

Project description:DNMTs catalyze the methylation of cytosine with SAM. DNA methylation affects key cellular processes by regulating gene expression, thus serving a variety of physiological and pathophysiological roles. However, the chemical mechanisms of DNA methylation by which its enzymatic activity is regulated have not been fully elucidated. We found that a critical cysteine residue in DNMT is the target of protein S-nitrosylation, leading to the attenuation of DNMT enzymatic activity and consequent aberrant regulation of gene expression during neoplastic cell proliferation. Our results demonstrate that de novo DNA methylation mediated by DNMT3 is regulated by NO, which is involved in tumor formation.

2023-03-11 | PXD039437 | Pride

Identification of N6-adenine methylation in C. elegans DNA

Project description:In mammalian cells, DNA methylation on the 5th position of cytosine (5mC) plays an important role as an epigenetic mark. However, DNA methylation was considered to be absent in C. elegans because of the lack of detectable 5mC as well as homologs of the cytosine DNA methyltransferases. Here, using multiple approaches, we demonstrate the presence of adenine N6-methylation (6mA) in C. elegans DNA. We further demonstrate that this modification increases trans-generationally in a paradigm of epigenetic inheritance. Importantly, we identify a DNA demethylase, NMAD-1, and a potential DNA methyltransferase, DAMT-1, which regulate 6mA levels and crosstalk between methylation of histone H3K4me2 and 6mA, and control the epigenetic inheritance of phenotypes associated with the loss of the H3K4me2 demethylase spr-5. Together, these data identify a novel DNA modification in C. elegans and raise the exciting possibility that 6mA may be a carrier of heritable epigenetic information in eukaryotes. SMRT-sequencing for a mixed cell population of wildtype worms 6mA ChIP-Seq for a mixed cell population of wildtype worms

2015-05-05 | E-GEOD-66504 | biostudies-arrayexpress

Active DNA Demethylation by DNMT3A and DNMT3B - Mechanistic Aspect and In Vivo Evidence

Project description:The DNA methylation program is at the bottom layer of the epigenetic regulatory cascade of vertebrate development. While the methylation at C-5 position of the cytosine (C) residues on the vertebrate genomes is achieved through the catalytic activities of the DNA methyltransferases (DNMTs), the conversion of the methylated cytosine (5mC) could be accomplished by the combined actions of the TET enzyme and DNA repair. Interestingly, it has been found recently that the mouse and human DNMTs also possess active DNA demethylation activity in vitro in a Ca2+- and redox condition-dependent manner. We report here the study of tracking down the fate of the methyl group removed from 5mC on DNA during in vitro demethylation reaction by mouse de novo DNMTs, i.e. DNMT3A and DNMT3B. Remarkably, the methyl group becomes covalently linked to the catalytic cysteines utilized by the two de novo DNMTs in their DNA methylation reactions. Thus, the forward and reverse reactions of DNA methylations by the DNMTs may utilize the same cysteine residue(s) as the active site despite of their distinctive pathways. Secondly, we demonstrate that active DNA demethylation of a heavily methylated GFP reporter plasmid by ectopically expressed DNMT3A or DNMT3B occurs in vivo in transfected human HEK 293 cells in culture. Furthermore, the extent of DNA demethylation by the DNMTs in this cell-based system is affected by Ca2+ homeostasis as well as by mutation of their putative active cysteines. These findings substantiate the roles of the vertebrate DNMTs as double-edged swords in DNA methylation-demethylation in vitro as well as in a cellular context.

2022-02-24 | PXD003401 | Pride

Single molecule DNA methylation reveals unique epigenetic identity profiles of T helper cells

Project description:Identity and plasticity of CD4 T helper (Th) cells are regulated in part by epigenetic mechanisms. Cytosine methylation in CpG context (5mCpG) and cytosine hydroxymethylation (5hmCpG) are DNA modifications that identify stable cell phenotypes. To assess transition states in Th cells, we developed a method based on Cas9-targeted single molecule nanopore sequencing and found that 5mCpG can be used as markers of cellular identity. Targeting as few as 10 mouse selected genomic loci, we were able to distinguish major differentiated T cell subtypes as well as intermediate phenotypes by their native DNA 5mCpG patterns. Moreover, by using off-target sequences we were able to infer transcription factor activities relevant to each cell subtype. Our data highlight the potential to exploit native DNA methylation profiling to study physiological and pathological Th transition states.

2024-01-08 | GSE248540 | GEO

The DNA methylomes of hyper-IgM syndrome type 2 B cells provide insights into the roles of activation-induced deaminase prior to the germinal center reaction

Project description:Inactivating mutations in activation induced deaminase (AID) lead to hyper-IgM syndrome type 2 (HIGM2), a rare primary antibody deficiency. AID-mediated cytosine deamination has been proposed as mediating active demethylation, although there is evidence both to support and cast doubt on such a role. We here made use of HIGM2 B cells to investigate direct AID involvement in active DNA demethylation. HIGM2 naïve and memory B cells both display widespread DNA methylation defects. For genes that undergo demethylation in the transition from naïve to memory B cells but not in HIGM2 individuals, we did not observe AID involvement but a participation of TET enzymes. DNA methylation alterations in HIGM2 naïve B cells are related to premature overstimulation of the B-cell receptor prior to the germinal center reaction. Our data supports a role for AID in B cell central tolerance in preventing the expansion of autoreactive cell clones, affecting the correct establishment of DNA methylation patterns without involvement of its cytosine deaminase activity.

2020-12-31 | GSE134664 | GEO

Single-cell transcriptomic analysis of human germinal center B cells

Project description:In response to T cell-dependent antigens, mature B cells are stimulated to form germinal centers, which are the place of B cell affinity maturation and selection. Here, we dissected the heterogeneity of germinal center B cells and reconstructed their pathway of differentiation using single-cell transcriptomic analysis.

2020-06-17 | GSE139891 | GEO

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