Publications by authors named "Stephane Avner"

13 Publications

  • Page 1 of 1

Nuclear accumulation of MKL1 in luminal breast cancer cells impairs genomic activity of ERα and is associated with endocrine resistance.

Biochim Biophys Acta Gene Regul Mech 2020 05 27;1863(5):194507. Epub 2020 Feb 27.

Univ Rennes, Inserm, EHESP, Irset (Institut de Recherche en Santé, Environnement et Travail) - UMR_S 1085, F-35000 Rennes, France. Electronic address:

Estrogen receptor (ERα) is central in driving the development of hormone-dependent breast cancers. A major challenge in treating these cancers is to understand and overcome endocrine resistance. The Megakaryoblastic Leukemia 1 (MKL1, MRTFA) protein is a master regulator of actin dynamic and cellular motile functions, whose nuclear translocation favors epithelial-mesenchymal transition. We previously demonstrated that nuclear accumulation of MKL1 in estrogen-responsive breast cancer cell lines promotes hormonal escape. In the present study, we confirm through tissue microarray analysis that nuclear immunostaining of MKL1 is associated with endocrine resistance in a cohort of breast cancers and we decipher the underlining mechanisms using cell line models. We show through gene expression microarray analysis that the nuclear accumulation of MKL1 induces dedifferentiation leading to a mixed luminal/basal phenotype and suppresses estrogen-mediated control of gene expression. Chromatin immunoprecipitation of DNA coupled to high-throughput sequencing (ChIP-Seq) shows a profound reprogramming in ERα cistrome associated with a massive loss of ERα binding sites (ERBSs) generally associated with lower ERα-binding levels. Novel ERBSs appear to be associated with EGF and RAS signaling pathways. Collectively, these results highlight a major role of MKL1 in the loss of ERα transcriptional activity observed in certain cases of endocrine resistances, thereby contributing to breast tumor cells malignancy.
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http://dx.doi.org/10.1016/j.bbagrm.2020.194507DOI Listing
May 2020

The hydroxymethylome of multiple myeloma identifies FAM72D as a 1q21 marker linked to proliferation.

Haematologica 2020 03 20;105(3):774-783. Epub 2019 Jun 20.

SPARTE, IGDR, CNRS UMR6290, University Rennes 1, Rennes, France

Cell identity relies on the cross-talk between genetics and epigenetics and their impact on gene expression. Oxidation of 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC) is the first step of an active DNA demethylation process occurring mainly at enhancers and gene bodies and, as such, participates in processes governing cell identity in normal and pathological conditions. Although genetic alterations are well documented in multiple myeloma (MM), epigenetic alterations associated with this disease have not yet been thoroughly analyzed. To gain insight into the biology of MM, genome-wide 5hmC profiles were obtained and showed that regions enriched in this modified base overlap with MM enhancers and super enhancers and are close to highly expressed genes. Through the definition of a MM-specific 5hmC signature, we identified FAM72D as a poor prognostic gene located on 1q21, a region amplified in high risk myeloma. We further uncovered that FAM72D functions as part of the FOXM1 transcription factor network controlling cell proliferation and survival and we evidenced an increased sensitivity of cells expressing high levels of FOXM1 and FAM72 to epigenetic drugs targeting histone deacetylases and DNA methyltransferases.
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http://dx.doi.org/10.3324/haematol.2019.222133DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7049362PMC
March 2020

Interplay between transcription regulators RUNX1 and FUBP1 activates an enhancer of the oncogene c-KIT and amplifies cell proliferation.

Nucleic Acids Res 2018 11;46(21):11214-11228

Univ Rennes, CNRS, IGDR (Institut de Génétique et Développement de Rennes) - UMR 6290, F-35000 Rennes, France.

Runt-related transcription factor 1 (RUNX1) is a well-known master regulator of hematopoietic lineages but its mechanisms of action are still not fully understood. Here, we found that RUNX1 localizes on active chromatin together with Far Upstream Binding Protein 1 (FUBP1) in human B-cell precursor lymphoblasts, and that both factors interact in the same transcriptional regulatory complex. RUNX1 and FUBP1 chromatin localization identified c-KIT as a common target gene. We characterized two regulatory regions, at +700 bp and +30 kb within the first intron of c-KIT, bound by both RUNX1 and FUBP1, and that present active histone marks. Based on these regions, we proposed a novel FUBP1 FUSE-like DNA-binding sequence on the +30 kb enhancer. We demonstrated that FUBP1 and RUNX1 cooperate for the regulation of the expression of the oncogene c-KIT. Notably, upregulation of c-KIT expression by FUBP1 and RUNX1 promotes cell proliferation and renders cells more resistant to the c-KIT inhibitor imatinib mesylate, a common therapeutic drug. These results reveal a new mechanism of action of RUNX1 that implicates FUBP1, as a facilitator, to trigger transcriptional regulation of c-KIT and to regulate cell proliferation. Deregulation of this regulatory mechanism may explain some oncogenic function of RUNX1 and FUBP1.
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http://dx.doi.org/10.1093/nar/gky756DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6265458PMC
November 2018

Cytosine modifications modulate the chromatin architecture of transcriptional enhancers.

Genome Res 2017 06 10;27(6):947-958. Epub 2017 Apr 10.

CNRS UMR6290, Equipe SP@RTE, Institut de Génétique et Développement de Rennes, Campus de Beaulieu, 35042 Rennes Cedex, France.

Epigenetic mechanisms are believed to play key roles in the establishment of cell-specific transcription programs. Accordingly, the modified bases 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) have been observed in DNA of genomic regulatory regions such as enhancers, and oxidation of 5mC into 5hmC by Ten-eleven translocation (TET) proteins correlates with enhancer activation. However, the functional relationship between cytosine modifications and the chromatin architecture of enhancers remains elusive. To gain insights into their function, 5mC and 5hmC levels were perturbed by inhibiting DNA methyltransferases and TETs during differentiation of mouse embryonal carcinoma cells into neural progenitors, and chromatin characteristics of enhancers bound by the pioneer transcription factors FOXA1, MEIS1, and PBX1 were interrogated. In a large fraction of the tested enhancers, inhibition of DNA methylation was associated with a significant increase in monomethylation of H3K4, a characteristic mark of enhancer priming. In addition, at some specific enhancers, 5mC oxidation by TETs facilitated chromatin opening, a process that may stabilize MEIS1 binding to these genomic regions.
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http://dx.doi.org/10.1101/gr.211466.116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5453328PMC
June 2017

Changes in Gene Expression and Estrogen Receptor Cistrome in Mouse Liver Upon Acute E2 Treatment.

Mol Endocrinol 2016 Jul 10;30(7):709-32. Epub 2016 May 10.

Equipe Spatio-Temporal Regulation of Transcription in Eukaryotes (SP@RTE) (G.P., C.L.P., S.A., G.S., R.M.), Unité Mixte de Recherche 6290 Centre National de la Recherche Scientifique (Institut de Genétique et Développement de Rennes), Université de Rennes 1, Campus de Beaulieu, and Equipe Transcription, Environment and Cancer (TREC) (G.F.), Inserm U1085-Institut de Recherche en Santé, Environnement et Travail, Rennes 35042 Cedex, France; and Equipe 9 "Estrogen Receptor: In Vivo Dissection and Modulation" (A.F., R.S., F.L., C.F., J.-F.A.), Inserm Unité 1048 (Institut des Maladies Métaboliques et Cardiovasculaires), Toulouse 31432 Cedex 4, France.

Transcriptional regulation by the estrogen receptor-α (ER) has been investigated mainly in breast cancer cell lines, but estrogens such as 17β-estradiol (E2) exert numerous extrareproductive effects, particularly in the liver, where E2 exhibits both protective metabolic and deleterious thrombotic actions. To analyze the direct and early transcriptional effects of estrogens in the liver, we determined the E2-sensitive transcriptome and ER cistrome in mice after acute administration of E2 or placebo. These analyses revealed the early induction of genes involved in lipid metabolism, which fits with the crucial role of ER in the prevention of liver steatosis. Characterization of the chromatin state of ER binding sites (BSs) in mice expressing or not ER demonstrated that ER is not required per se for the establishment and/or maintenance of chromatin modifications at the majority of its BSs. This is presumably a consequence of a strong overlap between ER and hepatocyte nuclear factor 4α BSs. In contrast, 40% of the BSs of the pioneer factor forkhead box protein a (Foxa2) were dependent upon ER expression, and ER expression also affected the distribution of nucleosomes harboring dimethylated lysine 4 of Histone H3 around Foxa2 BSs. We finally show that, in addition to a network of liver-specific transcription factors including CCAAT/enhancer-binding protein and hepatocyte nuclear factor 4α, ER might be required for proper Foxa2 function in this tissue.
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http://dx.doi.org/10.1210/me.2015-1311DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5426578PMC
July 2016

Single-CpG resolution mapping of 5-hydroxymethylcytosine by chemical labeling and exonuclease digestion identifies evolutionarily unconserved CpGs as TET targets.

Genome Biol 2016 Mar 29;17:56. Epub 2016 Mar 29.

CNRS UMR6290, Equipe SP@RTE, Institut de Génétique et Développement de Rennes, Campus de Beaulieu, Rennes cedex, 35042, France.

Conventional techniques for single-base resolution mapping of epigenetic modifications of DNA such as 5-hydroxymethylcytosine (5hmC) rely on the sequencing of bisulfite-modified DNA. Here we present an alternative approach called SCL-exo which combines selective chemical labeling (SCL) of 5hmC in genomic DNA with exonuclease (exo) digestion of the bead-trapped modified DNA molecules. Associated with a straightforward bioinformatic analysis, this new procedure provides an unbiased and fast method for mapping this epigenetic mark at high resolution. Implemented on mouse genomic DNA from in vitro-differentiated neural precursor cells, SCL-exo sheds light on an intrinsic lack of conservation of hydroxymethylated CpGs across vertebrates.
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http://dx.doi.org/10.1186/s13059-016-0919-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4810514PMC
March 2016

Cell-Cycle-Dependent Reconfiguration of the DNA Methylome during Terminal Differentiation of Human B Cells into Plasma Cells.

Cell Rep 2015 Nov 22;13(5):1059-71. Epub 2015 Oct 22.

INSERM, UMR917, Equipe labellisée Ligue contre le Cancer, Rennes 35043, France; Pôle de Biologie, Centre Hospitalier Universitaire (CHU), Rennes 35033, France; Université de Rennes 1, Rennes 35065, France; Etablissement Français du Sang de Bretagne, Rennes 35016, France. Electronic address:

Molecular mechanisms underlying terminal differentiation of B cells into plasma cells are major determinants of adaptive immunity but remain only partially understood. Here we present the transcriptional and epigenomic landscapes of cell subsets arising from activation of human naive B cells and differentiation into plasmablasts. Cell proliferation of activated B cells was linked to a slight decrease in DNA methylation levels, but followed by a committal step in which an S phase-synchronized differentiation switch was associated with an extensive DNA demethylation and local acquisition of 5-hydroxymethylcytosine at enhancers and genes related to plasma cell identity. Downregulation of both TGF-?1/SMAD3 signaling and p53 pathway supported this final step, allowing the emergence of a CD23-negative subpopulation in transition from B cells to plasma cells. Remarkably, hydroxymethylation of PRDM1, a gene essential for plasma cell fate, was coupled to progression in S phase, revealing an intricate connection among cell cycle, DNA (hydroxy)methylation, and cell fate determination.
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http://dx.doi.org/10.1016/j.celrep.2015.09.051DOI Listing
November 2015

Dynamic estrogen receptor interactomes control estrogen-responsive trefoil Factor (TFF) locus cell-specific activities.

Mol Cell Biol 2014 Jul 21;34(13):2418-36. Epub 2014 Apr 21.

Equipe SP@RTE, UMR CNRS 6290, Equipe Labellisée Ligue contre le Cancer, Université de Rennes I, Rennes, France

Estradiol signaling is ideally suited for analyzing the molecular and functional linkages between the different layers of information directing transcriptional regulations: the DNA sequence, chromatin modifications, and the spatial organization of the genome. Hence, the estrogen receptor (ER) can bind at a distance from its target genes and engages timely and spatially coordinated processes to regulate their expression. In the context of the coordinated regulation of colinear genes, identifying which ER binding sites (ERBSs) regulate a given gene still remains a challenge. Here, we investigated the coordination of such regulatory events at a 2-Mb genomic locus containing the estrogen-sensitive trefoil factor (TFF) cluster of genes in breast cancer cells. We demonstrate that this locus exhibits a hormone- and cohesin-dependent reduction in the plasticity of its three-dimensional organization that allows multiple ERBSs to be dynamically brought to the vicinity of estrogen-sensitive genes. Additionally, by using triplex-forming oligonucleotides, we could precisely document the functional links between ER engagement at given ERBSs and the regulation of particular genes. Hence, our data provide evidence of a formerly suggested cooperation of enhancers toward gene regulation and also show that redundancy between ERBSs can occur.
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http://dx.doi.org/10.1128/MCB.00918-13DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4054307PMC
July 2014

Peroxisome proliferator-activated receptor γ regulates genes involved in insulin/insulin-like growth factor signaling and lipid metabolism during adipogenesis through functionally distinct enhancer classes.

J Biol Chem 2014 Jan 27;289(2):708-22. Epub 2013 Nov 27.

From INSERM UMR U1011, F-59000 Lille, France.

The nuclear receptor peroxisome proliferator-activated receptor (PPAR) is a transcription factor whose expression is induced during adipogenesis and that is required for the acquisition and control of mature adipocyte functions. Indeed, PPAR induces the expression of genes involved in lipid synthesis and storage through enhancers activated during adipocyte differentiation. Here, we show that PPAR also binds to enhancers already active in preadipocytes as evidenced by an active chromatin state including lower DNA methylation levels despite higher CpG content. These constitutive enhancers are linked to genes involved in the insulin/insulin-like growth factor signaling pathway that are transcriptionally induced during adipogenesis but to a lower extent than lipid metabolism genes, because of stronger basal expression levels in preadipocytes. This is consistent with the sequential involvement of hormonal sensitivity and lipid handling during adipocyte maturation and correlates with the chromatin structure dynamics at constitutive and activated enhancers. Interestingly, constitutive enhancers are evolutionary conserved and can be activated in other tissues, in contrast to enhancers controlling lipid handling genes whose activation is more restricted to adipocytes. Thus, PPAR utilizes both broadly active and cell type-specific enhancers to modulate the dynamic range of activation of genes involved in the adipogenic process.
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http://dx.doi.org/10.1074/jbc.M113.526996DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3887199PMC
January 2014

Dynamic hydroxymethylation of deoxyribonucleic acid marks differentiation-associated enhancers.

Nucleic Acids Res 2012 Sep 22;40(17):8255-65. Epub 2012 Jun 22.

Université de Rennes 1, CNRS UMR6290, Team SP@RTE, Campus de Beaulieu, Rennes F-35042, France.

Enhancers are developmentally controlled transcriptional regulatory regions whose activities are modulated through histone modifications or histone variant deposition. In this study, we show by genome-wide mapping that the newly discovered deoxyribonucleic acid (DNA) modification 5-hydroxymethylcytosine (5hmC) is dynamically associated with transcription factor binding to distal regulatory sites during neural differentiation of mouse P19 cells and during adipocyte differentiation of mouse 3T3-L1 cells. Functional annotation reveals that regions gaining 5hmC are associated with genes expressed either in neural tissues when P19 cells undergo neural differentiation or in adipose tissue when 3T3-L1 cells undergo adipocyte differentiation. Furthermore, distal regions gaining 5hmC together with H3K4me2 and H3K27ac in P19 cells behave as differentiation-dependent transcriptional enhancers. Identified regions are enriched in motifs for transcription factors regulating specific cell fates such as Meis1 in P19 cells and PPARγ in 3T3-L1 cells. Accordingly, a fraction of hydroxymethylated Meis1 sites were associated with a dynamic engagement of the 5-methylcytosine hydroxylase Tet1. In addition, kinetic studies of cytosine hydroxymethylation of selected enhancers indicated that DNA hydroxymethylation is an early event of enhancer activation. Hence, acquisition of 5hmC in cell-specific distal regulatory regions may represent a major event of enhancer progression toward an active state and participate in selective activation of tissue-specific genes.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3458548PMC
http://dx.doi.org/10.1093/nar/gks595DOI Listing
September 2012

Epigenetic switch involved in activation of pioneer factor FOXA1-dependent enhancers.

Genome Res 2011 Apr 13;21(4):555-65. Epub 2011 Jan 13.

Université de Rennes 1, Rennes, France.

Transcription factors (TFs) bind specifically to discrete regions of mammalian genomes called cis-regulatory elements. Among those are enhancers, which play key roles in regulation of gene expression during development and differentiation. Despite the recognized central regulatory role exerted by chromatin in control of TF functions, much remains to be learned regarding the chromatin structure of enhancers and how it is established. Here, we have analyzed on a genomic-scale enhancers that recruit FOXA1, a pioneer transcription factor that triggers transcriptional competency of these cis-regulatory sites. Importantly, we found that FOXA1 binds to genomic regions showing local DNA hypomethylation and that its cell-type-specific recruitment to chromatin is linked to differential DNA methylation levels of its binding sites. Using neural differentiation as a model, we showed that induction of FOXA1 expression and its subsequent recruitment to enhancers is associated with DNA demethylation. Concomitantly, histone H3 lysine 4 methylation is induced at these enhancers. These epigenetic changes may both stabilize FOXA1 binding and allow for subsequent recruitment of transcriptional regulatory effectors. Interestingly, when cloned into reporter constructs, FOXA1-dependent enhancers were able to recapitulate their cell type specificity. However, their activities were inhibited by DNA methylation. Hence, these enhancers are intrinsic cell-type-specific regulatory regions of which activities have to be potentiated by FOXA1 through induction of an epigenetic switch that includes notably DNA demethylation.
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http://dx.doi.org/10.1101/gr.111534.110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3065703PMC
April 2011

CoBaltDB: Complete bacterial and archaeal orfeomes subcellular localization database and associated resources.

BMC Microbiol 2010 Mar 23;10:88. Epub 2010 Mar 23.

CNRS UMR 6026, ICM, Equipe B@SIC, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes, France.

Background: The functions of proteins are strongly related to their localization in cell compartments (for example the cytoplasm or membranes) but the experimental determination of the sub-cellular localization of proteomes is laborious and expensive. A fast and low-cost alternative approach is in silico prediction, based on features of the protein primary sequences. However, biologists are confronted with a very large number of computational tools that use different methods that address various localization features with diverse specificities and sensitivities. As a result, exploiting these computer resources to predict protein localization accurately involves querying all tools and comparing every prediction output; this is a painstaking task. Therefore, we developed a comprehensive database, called CoBaltDB, that gathers all prediction outputs concerning complete prokaryotic proteomes.

Description: The current version of CoBaltDB integrates the results of 43 localization predictors for 784 complete bacterial and archaeal proteomes (2.548.292 proteins in total). CoBaltDB supplies a simple user-friendly interface for retrieving and exploring relevant information about predicted features (such as signal peptide cleavage sites and transmembrane segments). Data are organized into three work-sets ("specialized tools", "meta-tools" and "additional tools"). The database can be queried using the organism name, a locus tag or a list of locus tags and may be browsed using numerous graphical and text displays.

Conclusions: With its new functionalities, CoBaltDB is a novel powerful platform that provides easy access to the results of multiple localization tools and support for predicting prokaryotic protein localizations with higher confidence than previously possible. CoBaltDB is available at http://www.umr6026.univ-rennes1.fr/english/home/research/basic/software/cobalten.
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http://dx.doi.org/10.1186/1471-2180-10-88DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2850352PMC
March 2010

OxyGene: an innovative platform for investigating oxidative-response genes in whole prokaryotic genomes.

BMC Genomics 2008 Dec 31;9:637. Epub 2008 Dec 31.

CNRS UMR 6026, Interactions Cellulaires et Moléculaires, Equipe B@SIC, Université de Rennes 1, IFR140 GFAS, Campus de Beaulieu, Av. du Général Leclerc, 35042 Rennes, France.

Background: Oxidative stress is a common stress encountered by living organisms and is due to an imbalance between intracellular reactive oxygen and nitrogen species (ROS, RNS) and cellular antioxidant defence. To defend themselves against ROS/RNS, bacteria possess a subsystem of detoxification enzymes, which are classified with regard to their substrates. To identify such enzymes in prokaryotic genomes, different approaches based on similarity, enzyme profiles or patterns exist. Unfortunately, several problems persist in the annotation, classification and naming of these enzymes due mainly to some erroneous entries in databases, mistake propagation, absence of updating and disparity in function description.

Description: In order to improve the current annotation of oxidative stress subsystems, an innovative platform named OxyGene has been developed. It integrates an original database called OxyDB, holding thoroughly tested anchor-based signatures associated to subfamilies of oxidative stress enzymes, and a new anchor-driven annotator, for ab initio detection of ROS/RNS response genes. All complete Bacterial and Archaeal genomes have been re-annotated, and the results stored in the OxyGene repository can be interrogated via a Graphical User Interface.

Conclusion: OxyGene enables the exploration and comparative analysis of enzymes belonging to 37 detoxification subclasses in 664 microbial genomes. It proposes a new classification that improves both the ontology and the annotation of the detoxification subsystems in prokaryotic whole genomes, while discovering new ORFs and attributing precise function to hypothetical annotated proteins. OxyGene is freely available at: http://www.umr6026.univ-rennes1.fr/english/home/research/basic/software.
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http://dx.doi.org/10.1186/1471-2164-9-637DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2631583PMC
December 2008