Azimuthal anisotropy of charged jet production in root s(NN)=2.76 TeV Pb-Pb collisions

We present measurements of the azimuthal dependence of charged jet production in central and semi-central root s(NN) = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as nu(ch)(2) (jet). Jet finding is performed employing the anti-k(T) algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero nu(ch)(2) (jet) is observed in semi-central collisions (30-50% centrality) for 20 <p(T)(ch) (jet) <90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the nu(2) of single charged particles at high p(T). Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

Forward-central two-particle correlations in p-Pb collisions at root s(NN)=5.02 TeV

Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 2GeV/c. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B. V.Peer reviewe

Event-shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions at root(NN)-N-S=2.76 TeV

Peer reviewe

Pseudorapidity and transverse-momentum distributions of charged particles in proton-proton collisions at root s=13 TeV

The pseudorapidity (eta) and transverse-momentum (p(T)) distributions of charged particles produced in proton-proton collisions are measured at the centre-of-mass energy root s = 13 TeV. The pseudorapidity distribution in vertical bar eta vertical bar <1.8 is reported for inelastic events and for events with at least one charged particle in vertical bar eta vertical bar <1. The pseudorapidity density of charged particles produced in the pseudorapidity region vertical bar eta vertical bar <0.5 is 5.31 +/- 0.18 and 6.46 +/- 0.19 for the two event classes, respectively. The transverse-momentum distribution of charged particles is measured in the range 0.15 <p(T) <20 GeV/c and vertical bar eta vertical bar <0.8 for events with at least one charged particle in vertical bar eta vertical bar <1. The evolution of the transverse momentum spectra of charged particles is also investigated as a function of event multiplicity. The results are compared with calculations from PYTHIA and EPOS Monte Carlo generators. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Elliptic flow of muons from heavy-flavour hadron decays at forward rapidity in Pb-Pb collisions at root s(NN)=2.76TeV

The elliptic flow, v(2), of muons from heavy-flavour hadron decays at forward rapidity (2.5 <y <4) is measured in Pb-Pb collisions at root s(NN)= 2.76TeVwith the ALICE detector at the LHC. The scalar product, two- and four-particle Q cumulants and Lee-Yang zeros methods are used. The dependence of the v(2) of muons from heavy-flavour hadron decays on the collision centrality, in the range 0-40%, and on transverse momentum, p(T), is studied in the interval 3 <p(T)<10 GeV/c. A positive v(2) is observed with the scalar product and two-particle Q cumulants in semi-central collisions (10-20% and 20-40% centrality classes) for the p(T) interval from 3 to about 5GeV/c with a significance larger than 3 sigma, based on the combination of statistical and systematic uncertainties. The v(2) magnitude tends to decrease towards more central collisions and with increasing pT. It becomes compatible with zero in the interval 6 <p(T)<10 GeV/c. The results are compared to models describing the interaction of heavy quarks and open heavy-flavour hadrons with the high-density medium formed in high-energy heavy-ion collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V.Peer reviewe

Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb-Pb collisions at root s(NN)=2.76TeV

Peer reviewe

An interactive network between ERRα-LSD1 promotes gene transcription via H3K9 demethylation

Les récepteurs nucléaires sont des facteurs de transcription qui exercent leur fonction via le contrôle de la transcription de leurs gènes cibles, une régulation qui est dépendante de cofacteurs associés. Les complexes transcriptionnels ainsi formés dialogueront avec l’environnement chromatinien (méthylation de l’ADN, remodelage des nucléosomes, modifications post-traductionnelles des histones) afin de promouvoir la répression ou l’activation transcriptionnelle des cibles géniques de ces récepteurs. Ce projet a identifié une interaction entre la lysine déméthylase LSD1 et le récepteur nucléaire orphelin ERRα dans des cellules humaines de cancers du sein. LSD1 protège ERRα d’une dégradation protéasomale de manière indépendante de son activité catalytique. Par ailleurs, LSD1 déméthyle H3K9 et H3K4 in vivo, mais est incapable in vitro de déméthyler H3K9. La présence de ERRα révèle cette activité de LSD1 sur H3K9, suggérant que le complexe ERRα -LSD1 agit comme un régulateur positif de la transcription. En ce sens, ERRα et LSD1 régulent un nombre important de gènes communs identifiés par RNAseq. Ainsi, 10 gènes activés ont été sélectionnés et le recrutement de ERRα et LSD1 a été examiné sur ces cibles géniques. En association avec les résultats obtenus in vitro, nous avons observé in vivo qu’en absence de ERRα ou LSD1, les gènes activés par ces deux partenaires présentent une augmentation de la marque répressive H3K9me2 sans affecter H3K4me2 au niveau du site d’initiation de la transcription. En conclusion, LSD1 interagit avec ERRα et inhibe sa dégradation, conduisant à une coopération transcriptionnelle de ces protéines. Pour la première fois, un rôle direct de ERRα sur l’environnement chromatinien a été identifié via l’activité de LSD1 sur des marques répressives d’histones.Nuclear receptors are transcription factors that cooperate with chromatin associated factors to promote their activities. These transcriptional complexes are able to modulate the chromatin landscape to repress or promote transcription. Interestingly, there is an intricate cross-talk between these complexes and the chromatin environment that can influence each other to coordinate gene expression led by nuclear receptors. Post-translational modifications of histones regulate in part, DNA accessibility and the activities of nuclear receptors. One of these histone modifiers is LSD1, which is known to demethylate lysines 4 (H3K4) and 9 (H3K9) on histone 3. This manuscript focuses on the discovered LSD1-ERRα complex in human cancer cell lines. LSD1 interacts with ERRα, hence, modulates ERRα protein stability via a demethylation independent manner. Moreover, LSD1 is able to demethylate H3K4me2 in vitro but not H3K9me2. Interestingly, we observed that ERRα is able to switch LSD1 activity toward H3K9me2 to promote gene transcription without any additional cofactor in vitro. To confirm this effect in vivo, a transcriptomic analysis on mammary cancer cells was performed and highlights common target genes between ERRα and LSD1. We selected 10 genes activated by both and verified ERRα and LSD1 recruitment on these targets. Moreover, upon knock-down of ERRα or LSD1, the transcriptional start sites of activated genes -bound and regulated by both proteins- are enriched in the repressive mark H3K9me2. Altogether, these results describe a positive regulation of ERRα by LSD1 which in turn, drives the demethylase activity on H3K9me2 to promote transcription. Finally, these data highlight a direct function of ERRα on chromatin landscape

Closing the gap: a roadmap to single‐cell regulatory genomics

Studying the spatiotemporal control of gene regulatory networks at the single‐cell level is still a challenge, yet it is key to understanding the mechanisms driving cellular identity. In their recent study, Aerts and colleagues (González‐Blas et al, 2020) develop a new strategy to spatially map and integrate single‐cell transcriptome and epigenome profiles in the Drosophila eye‐antennal disc and to deduce in each cell precise enhancer‐to‐gene activity relationships. This opens a new era in the transcriptional regulation field, as it allows extracting from each of the thousands of cells forming a tissue the critical features driving their identity, from enhancer sequences to transcription factors to gene regulatory networks

Hox dosage and morphological diversification during development and evolution

International audienceHox genes encode for evolutionary conserved transcription factors that have long fascinated biologists since the observation of the first homeotic transformations in flies. Hox genes are developmental architects that instruct the formation of various and precise morphologies along the body axes in cnidarian and bilaterian species. In contrast to these highly specific developmental functions, Hox genes encode for proteins that display poorly selective DNA-binding properties in vitro. This “Hox paradox” has been partially solved with the discovery of the TALE-class cofactors, which interact with all Hox members and form versatile Hox/TALE protein complexes on DNA. Here, we describe the role of the Hox dosage as an additional molecular strategy contributing to further resolve the Hox paradox. We present several cases where the Hox dosage is involved in the formation of different morphologies in invertebrates and vertebrates, with a particular emphasis on flight appendages in insects. We also discuss how the Hox dosage could be interpreted in different types of target enhancers within the nuclear environment in vivo. Altogether our survey underlines the Hox dosage as a key mechanism for shaping Hox molecular function during development and evolution