Search tips
Search criteria

Results 1-10 (10)

Clipboard (0)

Select a Filter Below

Year of Publication
Document Types
1.  Portraying breast cancers with long noncoding RNAs 
Science Advances  2016;2(9):e1600220.
Comprehensive analysis of the lncRNA landscape in breast cancers and its relationship with key clinical features and functional pathways.
Evidence is emerging that long noncoding RNAs (lncRNAs) may play a role in cancer development, but this role is not yet clear. We performed a genome-wide transcriptional survey to explore the lncRNA landscape across 995 breast tissue samples. We identified 215 lncRNAs whose genes are aberrantly expressed in breast tumors, as compared to normal samples. Unsupervised hierarchical clustering of breast tumors on the basis of their lncRNAs revealed four breast cancer subgroups that correlate tightly with PAM50-defined mRNA-based subtypes. Using multivariate analysis, we identified no less than 210 lncRNAs prognostic of clinical outcome. By analyzing the coexpression of lncRNA genes and protein-coding genes, we inferred potential functions of the 215 dysregulated lncRNAs. We then associated subtype-specific lncRNAs with key molecular processes involved in cancer. A correlation was observed, on the one hand, between luminal A–specific lncRNAs and the activation of phosphatidylinositol 3-kinase, fibroblast growth factor, and transforming growth factor–β pathways and, on the other hand, between basal-like–specific lncRNAs and the activation of epidermal growth factor receptor (EGFR)–dependent pathways and of the epithelial-to-mesenchymal transition. Finally, we showed that a specific lncRNA, which we called CYTOR, plays a role in breast cancer. We confirmed its predicted functions, showing that it regulates genes involved in the EGFR/mammalian target of rapamycin pathway and is required for cell proliferation, cell migration, and cytoskeleton organization. Overall, our work provides the most comprehensive analyses for lncRNA in breast cancers. Our findings suggest a wide range of biological functions associated with lncRNAs in breast cancer and provide a foundation for functional investigations that could lead to new therapeutic approaches.
PMCID: PMC5010371  PMID: 27617288
Epigenetics; long non-coding RNA; breast cancer
2.  Genome-wide hydroxymethylcytosine pattern changes in response to oxidative stress 
Scientific Reports  2015;5:12714.
The TET enzymes convert methylcytosine to the newly discovered base hydroxymethylcytosine. While recent reports suggest that TETs may play a role in response to oxidative stress, this role remains uncertain, and results lack in vivo models. Here we show a global decrease of hydroxymethylcytosine in cells treated with buthionine sulfoximine, and in mice depleted for the major antioxidant enzymes GPx1 and 2. Furthermore, genome-wide profiling revealed differentially hydroxymethylated regions in coding genes, and intriguingly in microRNA genes, both involved in response to oxidative stress. These results thus suggest a profound effect of in vivo oxidative stress on the global hydroxymethylome.
PMCID: PMC4523844  PMID: 26239807
3.  Citrullination of DNMT3A by PADI4 regulates its stability and controls DNA methylation 
Nucleic Acids Research  2014;42(13):8285-8296.
DNA methylation is a central epigenetic modification in mammals, with essential roles in development and disease. De novo DNA methyltransferases establish DNA methylation patterns in specific regions within the genome by mechanisms that remain poorly understood. Here we show that protein citrullination by peptidylarginine deiminase 4 (PADI4) affects the function of the DNA methyltransferase DNMT3A. We found that DNMT3A and PADI4 interact, from overexpressed as well as untransfected cells, and associate with each other's enzymatic activity. Both in vitro and in vivo, PADI4 was shown to citrullinate DNMT3A. We identified a sequence upstream of the PWWP domain of DNMT3A as its primary region citrullinated by PADI4. Increasing the PADI4 level caused the DNMT3A protein level to increase as well, provided that the PADI4 was catalytically active, and RNAi targeting PADI4 caused reduced DNMT3A levels. Accordingly, pulse-chase experiments revealed stabilization of the DNMT3A protein by catalytically active PADI4. Citrullination and increased expression of native DNMT3A by PADI4 were confirmed in PADI4-knockout MEFs. Finally, we showed that PADI4 overexpression increases DNA methyltransferase activity in a catalytic-dependent manner and use bisulfite pyrosequencing to demonstrate that PADI4 knockdown causes significant reduction of CpG methylation at the p21 promoter, a known target of DNMT3A and PADI4. Protein citrullination by PADI4 thus emerges as a novel mechanism for controlling a de novo DNA methyltransferase. Our results shed new light on how post-translational modifications might contribute to shaping the genomic CpG methylation landscape.
PMCID: PMC4117755  PMID: 24957603
4.  Dietary Flavanols Modulate the Transcription of Genes Associated with Cardiovascular Pathology without Changes in Their DNA Methylation State 
PLoS ONE  2014;9(4):e95527.
In a recent intervention study, the daily supplementation with 200 mg monomeric and oligomeric flavanols (MOF) from grape seeds for 8 weeks revealed a vascular health benefit in male smokers. The objective of the present study was to determine the impact of MOF consumption on the gene expression profile of leukocytes and to assess changes in DNA methylation.
Methodology/Principal Findings
Gene expression profiles were determined using whole genome microarrays (Agilent) and DNA methylation was assessed using HumanMethylation450 BeadChips (Illumina). MOF significantly modulated the expression of 864 genes. The majority of the affected genes are involved in chemotaxis, cell adhesion, cell infiltration or cytoskeleton organisation, suggesting lower immune cell adhesion to endothelial cells. This was corroborated by in vitro experiments showing that MOF exposure of monocytes attenuates their adhesion to TNF-α-stimulated endothelial cells. Nuclear factor kappa B (NF-κB) reporter gene assays confirmed that MOF decrease the activity of NF-κB. Strong inter-individual variability in the leukocytes' DNA methylation was observed. As a consequence, on group level, changes due to MOF supplementation could not be found.
Our study revealed that an 8 week daily supplementation with 200 mg MOF modulates the expression of genes associated with cardiovascular disease pathways without major changes of their DNA methylation state. However, strong inter-individual variation in leukocyte DNA methylation may obscure the subtle epigenetic response to dietary flavanols. Despite the lack of significant changes in DNA methylation, the modulation of gene expression appears to contribute to the observed vascular health effect of MOF in humans.
PMCID: PMC3998980  PMID: 24763279
5.  A comprehensive overview of Infinium HumanMethylation450 data processing 
Briefings in Bioinformatics  2013;15(6):929-941.
Infinium HumanMethylation450 beadarray is a popular technology to explore DNA methylomes in health and disease, and there is a current explosion in the use of this technique. Despite experience acquired from gene expression microarrays, analyzing Infinium Methylation arrays appeared more complex than initially thought and several difficulties have been encountered, as those arrays display specific features that need to be taken into consideration during data processing. Here, we review several issues that have been highlighted by the scientific community, and we present an overview of the general data processing scheme and an evaluation of the different normalization methods available to date to guide the 450K users in their analysis and data interpretation.
PMCID: PMC4239800  PMID: 23990268
Epigenomics; Genome-wide DNA methylation technology
6.  TET2 and TET3 regulate GlcNAcylation and H3K4 methylation through OGT and SET1/COMPASS 
The EMBO Journal  2013;32(5):645-655.
This paper identifies the N-acetylglucosamine transferase OGT as binding partner for TET2/3 proteins. Their genome-wide chromatin binding and the characterization of the Set1/COMPASS complex as OGT target implies coordinated gene regulation.
TET proteins convert 5-methylcytosine to 5-hydroxymethylcytosine, an emerging dynamic epigenetic state of DNA that can influence transcription. Evidence has linked TET1 function to epigenetic repression complexes, yet mechanistic information, especially for the TET2 and TET3 proteins, remains limited. Here, we show a direct interaction of TET2 and TET3 with O-GlcNAc transferase (OGT). OGT does not appear to influence hmC activity, rather TET2 and TET3 promote OGT activity. TET2/3–OGT co-localize on chromatin at active promoters enriched for H3K4me3 and reduction of either TET2/3 or OGT activity results in a direct decrease in H3K4me3 and concomitant decreased transcription. Further, we show that Host Cell Factor 1 (HCF1), a component of the H3K4 methyltransferase SET1/COMPASS complex, is a specific GlcNAcylation target of TET2/3–OGT, and modification of HCF1 is important for the integrity of SET1/COMPASS. Additionally, we find both TET proteins and OGT activity promote binding of the SET1/COMPASS H3K4 methyltransferase, SETD1A, to chromatin. Finally, studies in Tet2 knockout mouse bone marrow tissue extend and support the data as decreases are observed of global GlcNAcylation and also of H3K4me3, notably at several key regulators of haematopoiesis. Together, our results unveil a step-wise model, involving TET–OGT interactions, promotion of GlcNAcylation, and influence on H3K4me3 via SET1/COMPASS, highlighting a novel means by which TETs may induce transcriptional activation.
PMCID: PMC3590984  PMID: 23353889
chromatin; epigenetics; TET proteins
7.  Aberrant Promoter Methylation and Expression of UTF1 during Cervical Carcinogenesis 
PLoS ONE  2012;7(8):e42704.
Promoter methylation profiles are proposed as potential prognosis and/or diagnosis biomarkers in cervical cancer. Up to now, little is known about the promoter methylation profile and expression pattern of stem cell (SC) markers during tumor development. In this study, we were interested to identify SC genes methylation profiles during cervical carcinogenesis. A genome-wide promoter methylation screening revealed a strong hypermethylation of Undifferentiated cell Transcription Factor 1 (UTF1) promoter in cervical cancer in comparison with normal ectocervix. By direct bisulfite pyrosequencing of DNA isolated from liquid-based cytological samples, we showed that UTF1 promoter methylation increases with lesion severity, the highest level of methylation being found in carcinoma. This hypermethylation was associated with increased UTF1 mRNA and protein expression. By using quantitative RT-PCR and Western Blot, we showed that both UTF1 mRNA and protein are present in epithelial cancer cell lines, even in the absence of its two main described regulators Oct4A and Sox2. Moreover, by immunofluorescence, we confirmed the nuclear localisation of UTF1 in cell lines. Surprisingly, direct bisulfite pyrosequencing revealed that the inhibition of DNA methyltransferase by 5-aza-2′-deoxycytidine was associated with decreased UTF1 gene methylation and expression in two cervical cancer cell lines of the four tested. These findings strongly suggest that UTF1 promoter methylation profile might be a useful biomarker for cervical cancer diagnosis and raise the questions of its role during epithelial carcinogenesis and of the mechanisms regulating its expression.
PMCID: PMC3411846  PMID: 22880087
8.  The histone demethylase Kdm3a is essential to progression through differentiation 
Nucleic Acids Research  2012;40(15):7219-7232.
Histone demethylation has important roles in regulating gene expression and forms part of the epigenetic memory system that regulates cell fate and identity by still poorly understood mechanisms. Here, we examined the role of histone demethylase Kdm3a during cell differentiation, showing that Kdm3a is essential for differentiation into parietal endoderm-like (PE) cells in the F9 mouse embryonal carcinoma model. We identified a number of target genes regulated by Kdm3a during endoderm differentiation; among the most dysregulated were the three developmental master regulators Dab2, Pdlim4 and FoxQ1. We show that dysregulation of the expression of these genes correlates with Kdm3a H3K9me2 demethylase activity. We further demonstrate that either Dab2 depletion or Kdm3a depletion prevents F9 cells from fully differentiating into PE cells, but that ectopic expression of Dab2 cannot compensate for Kdm3a knockdown; Dab2 is thus necessary, but insufficient on its own, to promote complete terminal differentiation. We conclude that Kdm3a plays a crucial role in progression through PE differentiation by regulating expression of a set of endoderm differentiation master genes. The emergence of Kdm3a as a key modulator of cell fate decision strengthens the view that histone demethylases are essential to cell differentiation.
PMCID: PMC3424556  PMID: 22581778
9.  DNA methylation profiling identifies epigenetic dysregulation in pancreatic islets from type 2 diabetic patients 
The EMBO Journal  2012;31(6):1405-1426.
DNA methylation profiling identifies epigenetic dysregulation in pancreatic islets from type 2 diabetic patients
The first genome-scale DNA methylation study on pancreatic islets from type 2 diabetic patients identifies disease-associated DNA methylation pattern that translate into aberrant gene expression in novel factors relevant for β-cell function and survival.
In addition to genetic predisposition, environmental and lifestyle factors contribute to the pathogenesis of type 2 diabetes (T2D). Epigenetic changes may provide the link for translating environmental exposures into pathological mechanisms. In this study, we performed the first comprehensive DNA methylation profiling in pancreatic islets from T2D and non-diabetic donors. We uncovered 276 CpG loci affiliated to promoters of 254 genes displaying significant differential DNA methylation in diabetic islets. These methylation changes were not present in blood cells from T2D individuals nor were they experimentally induced in non-diabetic islets by exposure to high glucose. For a subgroup of the differentially methylated genes, concordant transcriptional changes were present. Functional annotation of the aberrantly methylated genes and RNAi experiments highlighted pathways implicated in β-cell survival and function; some are implicated in cellular dysfunction while others facilitate adaptation to stressors. Together, our findings offer new insights into the intricate mechanisms of T2D pathogenesis, underscore the important involvement of epigenetic dysregulation in diabetic islets and may advance our understanding of T2D aetiology.
PMCID: PMC3321176  PMID: 22293752
DNA methylation; pancreatic islets; type 2 diabetes
10.  DNA methylation profiling reveals a predominant immune component in breast cancers 
EMBO Molecular Medicine  2011;3(12):726-741.
Breast cancer is a molecularly, biologically and clinically heterogeneous group of disorders. Understanding this diversity is essential to improving diagnosis and optimizing treatment. Both genetic and acquired epigenetic abnormalities participate in cancer, but the involvement of the epigenome in breast cancer and its contribution to the complexity of the disease are still poorly understood. By means of DNA methylation profiling of 248 breast tissues, we have highlighted the existence of previously unrecognized breast cancer groups that go beyond the currently known ‘expression subtypes’. Interestingly, we showed that DNA methylation profiling can reflect the cell type composition of the tumour microenvironment, and in particular a T lymphocyte infiltration of the tumours. Further, we highlighted a set of immune genes having high prognostic value in specific tumour categories. The immune component uncovered here by DNA methylation profiles provides a new perspective for the importance of the microenvironment in breast cancer, holding implications for better management of breast cancer patients.
PMCID: PMC3377115  PMID: 21910250
breast cancer; DNA methylation; epigenetics; epigenomics; microenvironment

Results 1-10 (10)