2nd FSER meeting - version publique

2nd meeting of the FSER laureates and their teams

Oct 10-11, 2017 Imagine Institute, Paris

Hover the stars to see the detail about social activities

Hover names and titles to read the abstract

DAY 2

DAY 1

Tuesday, October 10th

#FSER2017 - @CercleFSER

Role of the Fidgetin-Like-1/AAA-ATPase and it's interacting protein (FLIP) in repairing DNA double strand breaks Rajeev Kumar1 2*, Joiselle FERNANDES1 2, Chloe Girard1 2, Marine Duhamel1 2, Sandrine Choinard1 2, and Raphael Mercier1 2 PRIVATE 1 INRA Institut Jean-Pierre Bourgin UMR1318 ERL CNRS 3559 Saclay Plant Sciences RD10 78000 Versailles France 2 AgroParisTech Institut Jean-Pierre Bourgin UMR 1318 ERL CNRS 3559 Saclay Plant Sciences RD10 78000 Versailles France

Deregulation of Centriole Length is Widespread in Cancer and Promotes Centriole Amplification and Chromosome Missegregation Gaëlle Marteil1; Adan Guerrero1 2; André F. Vieira3; Pedro Machado1 4; Susana Mendonça1; Marta Mesquita5; Beth Villarreal6; Irina Fonseca1; Maria Eugenia Francia1 7; Katharina Dores 1; Erin Tranfield8; Joana Paredes3; David Pellman9; Susana A. Godinho9 10; Mónica Bettencourt-Dias1 PRIVATE 1 Instituto Gulbenkian de Ciência Oeiras 2780-156 Portugal. 2 Present Address: Universidad Nacional Autónoma de México (UNAM) Cuernavaca Morelos 62210 México. 3 Instituto de Patologia e Imunologia Molecular da Universidade do Porto Porto 4200-135 Portugal. 4 Present address: European Molecular Biology Laboratory Heidelberg 69117 Germany. 5 Barrett's Esophagus Study Group Instituto Português de Oncologia de Lisboa Lisbon 1099-023 Portugal. 6 Novartis Institutes for BioMedical Research Boston MA 02139 USA. 7 Present Address: Institut Pasteur de Montevideo Montevideo 11400 Uruguay 8 Electron Microscopy Facility Instituto Gulbenkian de Ciência Oeiras 2780-156 Portugal. 9 The Pellman Lab Dana-Faber Cancer Institute Boston MA 02215-5450 USA. 10 Present Address: Molecular Oncology Barts Cancer Institute Queen Mary University of London London EC1M 6BQ United Kingdom.

IFT proteins spatially control the geometry of cleavage furrow ingression and lumen positioning Nicolas TAULET Benjamin VITRE Christelle ANGUILLE Audrey DOUANIER Murielle ROCANCOURT Michael TASCHNER Esben LORENTZEN Arnaud ECHARD and Benedicte DELAVAL PRIVATE CRBM-CNRS UMR 5237 Montpellier France - Institut PASTEUR CNRS UMR 3691 Paris France - Aarhus University Aarhus Denmark

Molecular determinants of cell size planar cell polarity epileptogenesis: link between the mTOR pathway and the primary cilium. Manuela Barilari, Mario Pende PRIVATE Laboratory of Cell growth control by nutrients Inserm U1151/CNRS UMR 8253 Necker Enfants Malades Institute (INEM) Faculté de Médecine Paris Descartes

Polarized dynamics of intermediate filaments in glial cells Cecile Leduc and Sandrine Etienne-Manneville Institut Pasteur, Paris PRIVATE

Oxidation of F-actin controls the terminal steps of cytokinesis Stéphane Frémont1,2, Hussein Hammich4, Hugo Wioland3, Kerstin Klinkert1,2, Murielle Rocancourt1,2, Carlos Kikuti3, Olena Pylypenko4, Anne Houdusse4, Guillaume Romet-Lemonne3 and Arnaud Echard1,2 At the end of each division, the mother cell is physically cleaved into two new daughter cells by a mechanism known as cytokinesis. Failure in cytokinesis leads to genetic instability and can promote tumorigenesis in vivo. Cytokinetic abscission, the final stage of cytokinesis, corresponds to the severing of the intercellular bridge connecting the two daughter cells. The mechanism mediating the final scission event crucially depends on the local constriction of ESCRT-III helices after complete cytoskeleton disassembly. While the ESCRT-associated enzyme Spastin cuts the microtubules of the intercellular bridge, the mechanism that actively clears F-actin at the abscission site is unknown. We found that oxidation-mediated depolymerization of actin by the redox enzyme MICAL1 (Molecules Interacting with CasL) is key for cytokinetic abscission. We observed that the depletion of MICAL1 delays cytokinetic abscission in human cells, due to a dramatic increase of F-actin within the intercellular bridges that impairs ESCRT-III recruitment to the abscission site. MICAL1 is recruited to the abscission site by the Rab35 GTPase through a direct interaction with a flat three-helix domain found in MICAL1 C-terminus. Mechanistically, in vitro single filament assays show that MICAL1 is activated by Rab35. Moreover, we demonstrate that MICAL1 is not a severing enzyme as previously thought, but induces F-actin depolymerization from both ends. We propose that MICAL1 oxidation weakens longitudinal interactions between actin subunits within the filaments, making the filaments more fragile and leading to enhanced F-actin depolymerization rates. Our work thus reveals an unexpected role for oxidoreduction in triggering local actin depolymerization to control a fundamental step of cell division. 1 Membrane Traffic and Cell Division Lab, Cell Biology and Infection department Institut Pasteur, 25–28 rue du Dr Roux, 75724 Paris cedex 15, France 2 CNRS UMR3691, 75015 Paris, France 3 Institut Jacques Monod, Paris 75013, France 4 CNRS UMR 144, Structural Motility Lab, Institut Curie, 75005 Paris, France

Unraveling mechanisms in vascular patterning during tumor angiogenesis using in vivo multi-photon imaging in mouse glioblastoma. Thomas Mathivet; Holger Gerhardt Anne Eichmann PRIVATE PARCC - HEGP - INSERM U970; 56 rue Leblanc; 75015 Paris; France

Role of Netrin-1 in the migration of precerebellar neurons Sergi Roig Puiggros*1 Juan Antonio Moreno-Bravo*1 Chloé Dominici1 Heike Blockus1 Pavol Zelina1 Patrick Mehlen2 and Alain Chédotal1. PRIVATE 1Sorbonne Universités UPMC Paris 06 INSERM CNRS Institut de la Vision 17 Rue Moreau 75012 Paris France. 2 Apoptosis Cancer and Development Laboratory Equipe labellisée La Ligue', LabEx DEVweCAN Centre de Recherche en Cancérologie de Lyon INSERM U1052-CNRS UMR5286 Université de Lyon Centre Léon Bérard 69008 Lyon France.

Gut microbiota: A potent modulator of adult neurogenesis and mood states Eleni Siopi, Pierre-Marie Lledo PRIVATE CNRS UMR 3571 Institut Pasteur

Imaging and modelling signaling pathways dynamics in striatal projection neurons. Nicolas Gervasi 1, Lu Li 2 and Jean-Antoine Girault 1 PRIVATE 1 Institut du Fer à Moulin INSERM UPMC-Sorbonne-Universités UMR-S 839 Paris France. 2 Babraham Institute Cambridge UK.

A pair of serotonergic neurons controls long-term memory consolidation in Drosophila Lisa Scheunemann, Pierre-Yves Placais Yann Dromard and Thomas Preat The formation of memory as an adaptive behavior is crucial for the fitness and survival of any organism. However memory and especially long-term memory (LTM) has a cost that can impact the physiology of an animal fundamentally. Therefore mechanisms that restrict LTM formation are required that integrate the animals' state together with the salience of the received stimulus. We previously showed that in Drosophila such a gate is controlled by a single pair of dopaminergic neurons MP1 that changes its Ca2+ oscillatory activity specifically during LTM consolidation. To date the identity of regulatory inputs for the oscillatory activity of MP1 is not known. Here we discovered that a bilateral neuron located in the gnathal ganglia (GNG) a brain region associated with gustatory inputs and control of feeding behavior can modulate MP1 oscillations. Our investigations revealed that the neuron is serotonergic and sends projections toward the mushroom body (MB) the olfactory memory center where it synapses with MP1 at the level of the MB peduncle. Activation of this serotonergic projection neuron (SPN) induced oscillatory activity in MP1 and facilitated LTM formation. Additionally conditional knock-down of 5HT in the SPN as well as the 5HT-2A receptor in MP1 interfered with both long-term memory formation and MP1 oscillations. Our study thus identifies a major regulatory input for MP1 that regulates calcium oscillations and LTM formation. Genes and Dynamics of Memory Systems Brain Plasticity Unit CNRS ESPCI Paris PSL Research University 10 rue de Vauquelin 75005 Paris France

How do you see your prospects ? Mood fluctuations and decision making Fabien Vinckier, Mathias Pessiglione PRIVATE

INTERPOL: INTERaction and POLarization of human Hematopoietic Stem and Progenitor Cell in artificial niches Thomas Bessy, Benoit Vianay Stephane Brunet Jérôme Larghero Manuel Théry PRIVATE

Unraveling the complexity of somatic mutation in aging adult intestinal stem cells Kasia Siudeja Nick Riddiford Marius van den Beek and Allison J. Bardin PRIVATE Stem Cell and Tissue Homeostasis Group UMR 3215/ U934 Institut Curie Paris France

SUV4-20 activity in the preimplantation mouse embryo controls timely replication André Eid, Diego Rodriguez-Terrones, Adam Burton and Maria-Elena Torres-Padilla PRIVATE IGBMC-Univesite de Strasbourg Helmholtz-Zentum Munchen The Francis Crick Institute

Fetal EMP hematopoiesis in the mouse embryo Lorea Iturri, Yvan Lallemand and Elisa Gomez-Perdiguero PRIVATE Macrophages and Endothelial Cells Unit CNRS UMR3738 Paris 6

A novel auto-regulatory module controls body fat in C. elegans Cornelia Habacher1,2, Yanwu Guo1, Pooja Kumari1, Richard Venz1, Anca Neagu1, Dimos Gaidazis1,3, Heinz Gut1, Rafal Ciosk1 PRIVATE 1 Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland2 University of Basel, Petersplatz 1, 4003 Basel, Switzerland3 Swiss Institute of Bioinformatics, 4058 Basel, Switzerland

Molecular determinants of cell size planar cell polarity epileptogenesis: link between the mTOR pathway and the primary cilium. Manuela Barilari, Mario Pende The mTOR signaling pathway plays an essential role in cell growth and proliferation. It integrates numerous cellular and environmental signals which modulate its actions and results in a complex regulation of metabolism protein synthesis and cellular survival. Its deregulation is associated with numerous pathologies. In the brain mTOR modulates neurogenesis neural differentiation neuronal plasticity and memory. Its abnormal activation in the tuberous sclerosis complex disorder or in other neurological diseases is known for inducing epileptic seizures but the molecular mechanism is still unclear. The purpose of our project is to clarify the molecular mechanisms linking mTOR and epilepsy. Our hypothesis is that the kinases S6K activated by mTOR are major effectors in the development of the epilepsy induced by mTOR and that they act by regulating primary cilia dynamics as we observed in other systems. Laboratory of Cell growth control by nutrients Inserm U1151/CNRS UMR 8253 Necker Enfants Malades Institute (INEM) Faculté de Médecine Paris Descartes

Contribution of oocyte-inherited DNA methylation to the early embryo transcriptome R Pérez-Palacios 1 A Teissandier1 J Iranzo1 R Duffié 2 and D Bourc'his 1 In mammals the sperm and the oocyte genomes are strikingly different in terms of DNA methylation content and distribution. In consequence the embryo inherits two parental sets of chromosomes with remarkably asymmetric methylomes. Abolition of oocyte-inherited DNA methylation as exemplified by the Dnmt3L maternal mutation in mice results in an obligate lethality at mid-gestation illustrating the key role of maternal imprinting on embryonic development and in particular on the establishment of the foeto-maternal interface through the placenta. However the role of oocyte-inherited DNA methylation right after fertilization on the control of the transcriptome and cell fate of the early embryo is unknown. By combining high throughput sequencing with detailed developmental analyses of models of maternal methylation deficiency we assessed the net effect of oocyte-inherited DNA methylation on the regulation of the transcriptome and development of the early preimplantation embryo. Our results highlight the sensitivity of specific cleavage stages to the lack of maternal DNA methylation which influence the normal developmental timing and cell fate of the early embryo. Moreover we provide a panorama of the multifaceted role of DNA methylation on transcription regulation during this key period of initial cellular decisions. 1 Institut Curie- Department of Genetics and Developmental Biology - Paris France; 2 Columbia University-Department of Pathology and Cell Biology- New York USA

Hippocampal autophagy controls memory acquisition and counteracts age-related memory decline Mélissa Glatigny*1 Stéphanie Moriceau*1 Mariana Ramos-Brossier$1 Anna C. Nascimbeni$2 Mary R. Shanley4 Manon Rivagorda1 Nadir Boudarene1 Audrey Rousseaud1 Carmine Settembre3 Gérard Friedlander2 Allyson K. Friedman4 Etienne Morel2 Patrice Codogno£2 Franck Oury£1 Normal brain aging is characterized by a progressive decline in cognitive functions. One of the most common brain regions affected by aging is the hippocampus leading to memory decline. With the increase in life expectancy the number of individuals affected by age-related cognitive decline is bound to dramatically increase. Because physiological aging is a complex and multifactorial process it is now essential to deeply understand how brain ages at the cellular level. Autophagy is a lysosomal catabolic process that regulates protein homeostasis and organelle turnover. Autophagy also plays a fundamental role in tissue homeostasis notably mediating cellular adaptive response to various physiological stimuli. Accordingly a decrease in autophagy has been associated with accelerated aging. Recent studies suggest that autophagy may contribute to neuronal synapse formation and growth. However very little is known about the physiological role of autophagy during normal neuronal function and behavior. Here we show that memory stimulations induce autophagy in the mouse hippocampus while local pharmacological and genetic modulations of hippocampal autophagy strongly influence memory acquisition. These effects were associated with induction of neuronal synaptic plasticity and dendritic spines formation in response to memory stimuli. Moreover we observed that increasing autophagy in hippocampi of old animals can reverse the age-related decline in memory. Our results reveal a novel physiological role of autophagy in regulating hippocampal-dependent memory functions and demonstrate the potential therapeutic benefits of modulating autophagy in order to prevent and/or reverse the deleterious effects of aging on cognitive function. 1 Institut National de la Santé et de la Recherche Médicale (INSERM) U1151 Institut Necker Enfants Malades (INEM) Depart: Cell growth and signaling Team 14 Université Paris Descartes - Sorbone ? Paris Cité 75014 Paris France. 2 Institut National de la Santé et de la Recherche Médicale (INSERM) U1151 Institut Necker Enfants Malades (INEM) Depart: Cell growth and signaling Team 1 Université Paris Descartes - Sorbone ? Paris Cité 75014 Paris France. 3 Telethon Institut of Genetics and Medicine Department of Cell Biology and Disease Mechanisms Naples Italy 4 City University of New York ? Hunter College Department of Biological Sciences 695 Park Avenue New York NY 10065 USA

Unraveling the complexity of somatic mutation in aging adult intestinal stem cells Kasia Siudeja Nick Riddiford Marius van den Beek and Allison J. Bardin During aging adult stem cells may acquire somatic mutations capable of modifying cellular behavior leading to a functional decline or to a competitive advantage resulting in a premalignant state. However the mechanisms phenotypic impact and frequency of spontaneous mutation in adult stem cells are currently unclear. We have recently reported that aging adult Drosophila intestinal stem cells (ISCs) accumulate spontaneous mutation leading to phenotypic alteration in the intestine (Siudeja et al Cell Stem Cell 2015). We showed that somatic inactivation of the X-linked tumor-suppressor gene Notch in ISCs is leading to spontaneously arising neoplasias in about 10% of wild-type males. Here we use whole genome sequencing of spontaneous neoplasia and bioinformatics tools to identify complex mechanisms driving somatic genetic variation in the aging ISCs. As it was observed for human cancers we detect deletions and complex genomic rearrangements across neoplastic genomes mostly associated with Notch but also affecting other loci. Interestingly we find evidence for frequent involvement of Transposable Elements (TEs) in the somatic variation. De novo TE insertions are often found at breakpoints and germline insertions can mediate Non-Allelic Homologous Recombination. Furtermore de novo somatic insertions not linked to structural variants are also detected along the genome and could influence tissue physiology. This results show that our model system is suitable for addressing complex mechanisms of somatic mutations in aging self-renewing tissues. Stem Cell and Tissue Homeostasis Group UMR 3215/ U934 Institut Curie Paris France

D-Alanine esterification of teichoic acids contributes to Lactobacillus plantarum mediated Drosophila growth promotion upon chronic undernutrition Renata C. Matos1 Martin Schwarzer1 Hugo Gervais1 Pauline Joncour1 Benjamin Gillet1 Anne-Laure Bulteau1 Dali Ma1 Maria Elena Martino1 Pascal Courtin2 Sandrine Hughes1 Marie-Pierre Chapot-Chartier2 and François Leulier1 The microbial environment influence animal physiology. However the underlying molecular mechanisms of such functional interactions are largely undefined. Previously we showed that upon chronic undernutrition strains of Lactobacillus plantarum a dominant commensal partner of Drosophila promote host juvenile growth and maturation partly via enhanced expression of intestinal peptidases. By screening a transposon insertion library of Lactobacillus plantarum in gnotobiotic Drosophila larvae we identify a bacterial cell wall modifying machinery encoded by the pbpX2-dltXABCD operon that is critical to enhance host digestive capabilities and promote growth and maturation. Deletion of this operon leads to bacterial cell wall alteration with a complete loss of teichoic acids D-alanylation. We thus conclude that teichoic acids modifications participate in commensal-host molecular dialogue and specifically D-alanine esterification of teichoic acids contributes to optimal L. plantarum mediated intestinal peptidase expression and Drosophila juvenile growth upon chronic undernutrition. 1Institut de Génomique Fonctionnelle de Lyon UMR5242 CNRS ENS-Lyon UCBL-1 France; 2Micalis Institute INRA AgroParisTech Université Paris-Saclay 78350 Jouy-en-Josas France

Fetal EMP hematopoiesis in the mouse embryo Lorea Iturri, Yvan Lallemand and Elisa Gomez-Perdiguero Two lineages of macrophages coexist in most mouse tissues "infiltrating" vs "resident" macrophages which can be distinguished by their ontogeny and mechanism of maintenance. In contrast to infiltrating macrophages that are short-lived and renew from hematopoietic stem cells (HSCs) resident macrophages develop from embryonic progenitors called EMPs and do not renew from HSCs. However the development and contribution of this erythromyeloid progenitors (EMPs) to the definitive macrophage pool is poorly understood. In my project I try to characterise the dynamics of this progenitors and of resident macrophages during development. Macrophages and Endothelial Cells Unit CNRS UMR3738 Paris 6

TBA Rafal Ciosk lab

You are what you experience: The impact of environment on cellular identity S.F. Becker M.C. Morin S. Mangold and S. Jarriault The cells of the organs and tissues of multicellular organisms require to maintain their specialized identity over time. However under certain circumstances cells can change their identity a process known as Transdifferentiation or Td to the benefits of the animal. The balance between maintenance of cellular identity and cellular plasticity (as the potential for a change in identity at the functional and morphological levels) is a major challenge for tissues inside an organism. Uncontrolled cell fate changes can cause several dysfunctional cellular behaviors such as cancer and degenerative diseases. Unraveling the mechanisms behind cell type conversion will help to develop a safe environment for regenerative medicine. Here we describe how several external factors can impact on cellular identity and increase its plasticity potential. We use a natural cell identity conversion in the worm to determine how a cell can change or maintain its identity. C. elegans rectal to neuronal Y-to-PDA transition is a bona fide transdifferentiation event: During L2 larval stage the epithelial identity of the Y rectal cell is erased completely followed by a very robust and unipotent redifferentiation into a fully functional motoneuron PDA. We previously described a subset of essential factors that are crucial for the initiation of Td such as egl-27/MTA sem-4/SALL ceh-6/OCT and sox-2 whose loss-of-function lead to severe defects in PDA formation. We identified two novel regulators of Td: lin-15A and lin-56 that appear to act as licensers of the process. Their null mutants show a lower penetrance of PDA defects and are highly variable under different environmental conditions. We found starvation and caloric restriction as well as virulence or different food sources to decrease PDA defects in these mutants and thus to increase the potential of cellular plasticity of the Y cell. We will present our detailed analysis of the impact of the environment on cellular plasticity and our evidence that a general mechanism may underlie the effect of these various external factors. Environmental impact - an often neglected aspect - might have more general implications to the use of cell identity conversions as a tool in regenerative medicine - and the worm might lead us the way to understand these. IGBMC CNRS UMR7104 INSERM U964 UdS Strasbourg France

Neck morphogenesis of Drosophila melanogaster: Collective cell behaviors promoting tissue folding and translocation Aurélien Villedieu, Yohanns Bellaïche Epithelial folding and collective cell migration are two basic mechanisms underlying morphogenesis in Metazoa. Making use of the genetic toolkit available for Drosophila melanogaster we have described at the tissue scale and with a cellular resolution the morphogenetic events shaping the neck and the anterior thorax of Drosophila during metamorphosis. Interestingly neck invagination is coordinated with a highly directional translocation of the thorax cells. Preventing neck invagination by laser ablation does not abrogate the translocation of the thorax tissue suggesting that thorax cells actively migrate in a collective manner. Taken together our data unveil possible new mechanisms underlying epithelial folding and collective cell migration. Polarity Division and Morphogenesis (Institut Curie Paris)

SUV4-20 activity in the preimplantation mouse embryo controls timely replication André Eid, Diego Rodriguez-Terrones, Adam Burton and Maria-Elena Torres-Padilla Extensive chromatin remodeling after fertilization is thought to take place to allow a new developmental program to start. This includes dynamic changes in histone methylation and in particular the remodeling of constitutive heterochromatic marks such as histone H4 Lys20 trimethylation (H4K20me3). While the essential function of H4K20me1 in preimplantation mouse embryos is well established the role of the additional H4K20 methylation states through the action of the SUV4-20 methyltransferases has not been addressed. Here we show that Suv4-20h1/h2 are mostly absent in mouse embryos before implantation underscoring a rapid decrease of H4K20me3 from the two-cell stage onward. We addressed the functional significance of this remodeling by introducing Suv4-20h1 and Suv4-20h2 in early embryos. Ectopic expression of Suv4-20h2 leads to sustained levels of H4K20me3 developmental arrest and defects in S-phase progression. The developmental phenotype can be partially overcome through inhibition of the ATR pathway suggesting that the main function for the remodeling of H4K20me3 after fertilization is to allow the timely and coordinated progression of replication. This is in contrast to the replication program in somatic cells where H4K20me3 has been shown to promote replication origin licensing and anticipates a different regulation of replication during this early developmental time window. IGBMC-Univesite de Strasbourg Helmholtz-Zentum Munchen The Francis Crick Institute

INTERPOL: INTERaction and POLarization of human Hematopoietic Stem and Progenitor Cell in artificial niches Thomas Bessy, Benoit Vianay Stephane Brunet Jérôme Larghero Manuel Théry Stem cells Cytoskeleton ;Objectives: In sight of the interest Hematopoietic Stem Cells (HSCs) have in the therapy of blood related diseases it is important to understand HSC differentiation and how they could be amplified and maintained in vitro. For a time now we know that the complex in vivo HSC environment (or niche) plays a critical role both at the cellular and molecular level on the control of their behaviour be it proliferation migration or differentiation. Observing intercellular interactions in the bone marrow is made very difficult because of various experimental constraints starting from localizing HSCs to observing them with the high number of proximal cell present in a complex 3D niche. Also HSCs can have various specific interactions with numerous cell types making their identification difficult even without considering combined interactions. In this study we propose to isolate interactions into single elements in vitro with a view to simplify their observation and to characterize specific interactions for each cell type of the niche. Method: In order to answer this question we here propose an in vitro model of minimal niche: microwells that represents a physical constraint allowing us to generate and analyse specific heterotypic cell-cell interactions between a cell of the niche and a HSC. Results: The material for the construction of the wells has been selected based on its biological properties. Among several hydrogels we selected a mix of PolyEthylene Glycol diacrylate which allowed the creation of biocompatible wells with a controlled shape and size adherent at the bottom but cell-repellent on their side and top surfaces. We then plated a single cell of the niche in these wells followed by HSCs seeded homogenously with an average of one HSC per well. Preliminary coculture experiments showed that HSCs where adhering to feeder cell. Cell adhesion and cytoskeleton organisation were therefore analysed as the primary response before functional effects. We found out that endothelial cells and osteoblast induced HSC adhesion as well as a strong polarization of the centrosome and microtubule network toward the feeder cell contrasting isolated HSCs. Conclusion: Our microwell system allowed us to observe specific polarization of HSCs in contact with cells of the niche reminiscent of T Lymphocytes engaged in the immune synapse. We now need to find out the mechanism of the polarization the adhesion receptor involved and the consequence such an interaction has on HSC behaviour.

Division of labor in Rho1 signaling during epithelial morphogenesis Alain Garcia De Las Bayonas Jean-Marc Philippe and Thomas Lecuit Small RhoGTPases control precise cell shape changes and movements to orchestrate morphogenesis. Their activity must be tightly regulated in time and space to specify appropriate patterns of activation of the downstream actomyosin meshwork a key element in epithelial remodeling. Little is known about how Rho regulators (RhoGEFs and RhoGAPs) control RhoGTPases in vivo. During early Drosophila embryogenesis the ventro-lateral ectoderm extends posteriorly as a consequence of epithelial cell intercalation a process called germ-band extension (GBE). Myosin-II molecular motors drive this process via pulsatile medial-apical and planar polarized junctional pools. Despite a clear involvement of Rho1 mechanisms driving localized Rho1 activity both in the medial-apical and junctional subcellular compartments are not well understood. Taking advantage of Drosophila RNAi lines I have characterized two RhoGEFs RhoGEF2 and Wireless as the main medial-apical and junctional Rho1 activators respectively. We are currently investigating how Rhogef2 and Wireless are controlled in space and time during this morphogenetic process. IBDM UMR 7288 Aix-Marseille Université and CNRS 13009 Marseille France

Networking lunch Enjoy informal discussions about five topics around lunch: - choosing your postdoc - getting your first grant - a PI's life - non academic careers - outreach, why, how?

Drinks, good mood and music to dance and socialize !

Discover the social events!

2nd meeting of the FSER laureates and their teams

Oct 10-11, 2017 Imagine Institute, Paris

Outreach activity (limited to 10)

DAY 2

DAY 1

Wednesday, October 11th

Hover names and titles to read abstracts

#FSER2017 - @CercleFSER

During 1h30, scientists will interact with those students in a speed meeting set up. If you wish to participate, sign up here ! You have nothing to prepare, just to be open to discuss with the students !

This meeting will be an exciting time for the participants to exchange on their projects and views. But it will also be the opportunity to share with a younger audience our interest for research. Indeed, it includes a session on Wednesday during lunch with high school students, and thus will be a "Meeting in Science Open to the Public" (MSOP), a label which supports scientific conferences bringing together researchers and a lay audience. Practically speaking, the Imagine Institute will welcome students from a neighbouring high school Wednesday. During 1h30, scientists will interact with those students in a speed meeting set up. If you wish to participate, sign up here ! You have nothing to prepare, just to be open to discuss with the students ! Most of the exchanges will be in French. However, if you do not speak French, you are welcome to join in! Experience shows that even if their English level is limited, students are engaged by motivated English speakers: it is both very informative and surprising for them to experience first hand that science is very international. Due to space limitation, only 10 researchers will be able to participate, so sign up fast!

Division of labor in Rho1 signaling drives epithelial morphogenesis Alain Garcia De Las Bayonas Jean-Marc Philippe and Thomas Lecuit Small RhoGTPases control precise cell shape changes and movements to orchestrate morphogenesis. Their activity must be tightly regulated in time and space to specify appropriate patterns of activation of the downstream actomyosin meshwork a key element in epithelial remodeling. Little is known about how Rho regulators (RhoGEFs and RhoGAPs) control RhoGTPases in vivo. During early Drosophila embryogenesis the ventro-lateral ectoderm extends posteriorly as a consequence of epithelial cell intercalation a process called germ-band extension (GBE). Myosin-II molecular motors drive this process via pulsatile medial-apical and planar polarized junctional pools. Despite a clear involvement of Rho1, mechanisms driving localized Rho1 activity both in the medial-apical and junctional subcellular compartments are not well understood. Taking advantage of Drosophila RNAi lines I have characterized two RhoGEFs RhoGEF2 and Wireless as the main medial-apical and junctional Rho1 activators respectively. We are currently investigating how Rhogef2 and Wireless are controlled in space and time during this morphogenetic process. IBDM UMR 7288 Aix-Marseille Université and CNRS 13009 Marseille France

Communication between distinct infection associated compartments drives the intracellular lifestyle of Salmonella Virginie Stévenin1 Yuen Yan Chang1 Magalie Duchateau2 Quentin Giai Gianetto2 Victoria Sohst3 Jennifer Fredlund1 Mariette Matondo2 Norbert Reiling3 Jost Enninga1 PRIVATE 1: Institut Pasteur Dynamics of Host-Pathogen Interactions Unit 25 rue du Dr. Roux 75724 Paris France. 2: Institut Pasteur Structural Mass Spectrometry and Proteomics Unit 25 rue du Dr. Roux 75724 Paris France. 3: German Center for Infection Research (DZIF) Partner Site Hamburg-Lübeck-Borstel Parkallee 1-40 23845 Borstel Germany.

Defining the cell populations responsible for skin cancer initiation and relapse following therapy Adriana Sánchez-Danés & Cédric Blanpain PRIVATE (1) Sánchez-Danés A Hannezo E Larsimont JC Liagre M Youssef KK Simons BD Blanpain C. Defining the clonal dynamics leading to mouse skin tumour initation. Nature. 2016 Jul 8;536(7616):298-303. doi: 10.1038/nature19069 Université Libre de Bruxelles (ULB) Belgium

STING, a critical innate sensor also functions intrisically in cells of the adaptative immune system to inhibit proliferation S. Cerboni1 # N. Jeremiah1 # M. Gentili1 # U. Gehrmann1 £ # C. Conrad1 MC. Stolzenberg3 C. Picard3 B. Neven2 4 A. Fischer2 4 S. Amigorena1 F. Rieux-Laucat2 * N. Manel1 * PRIVATE 1Immunity and Cancer Department Institut Curie PSL Research University INSERM U932 75005 Paris France. 2Laboratory of Immunogenetics of Pediatric autoimmune Diseases INSERM UMR 1163 Paris Descartes-Sorbonne Paris Cité University Imagine Institute 75015 Paris France 3Center for Primary Immunodeficiencies Hopital Necker Enfants-Malades Assistance Publique-Hôpitaux de Paris 75015 Paris France 4Pediatric Immunology Haematology and Rheumatology Unit Necker Children's Hospital Assistance Publique-Hôpitaux de Paris; #These authors contributed equally to the work. *These authors contributed equally to the work.

Importance of cancer-associated fibroblasts (CAFs) in promoting cancer stemness via Netrin-1 and its receptors Peggy Sung, Patrick Mehlen PRIVATE

Modulation of translation efficiency: a new player in dendritic cell function Marisa Reverendo1 Rafael Argüello1 Evelina Gatti1 2 Philippe Pierre1 2 PRIVATE 1 CNRS INSERM CIML Aix Marseille University Marseille France 2 Institute for Research in Biomedicine iBiMED and Aveiro Health Sciences Program University of Aveiro Aveiro Portugal

ZNF341 orchestrates anti-fungal and allergic immunity by regulating STAT3 transcription Vivien Béziat1 2 Juan Li3 Jian-Xin Lin4 Cindy S. Ma5 6 Peng Li4 Aziz Bousfiha7 Isabelle Pellier8 Samaneh Zoghi9 10 Safa Baris11 Sevgi Keles12 Ning Du4 Yi Wang 1 2 Yoann Zerbib1 2 Romain Lévy1 2 Thibaut Leclercq1 2 Frédégonde About1 2 Ai Ing Lim13 14 Geetha Rao5 6 Kathryn Payne5 6 Simon J Pelham5 6 Danielle T Avery5 Elissa K Deenick5 6 Janet Chou15 16 Romain Guery1 2 17 Aziz Belkadi1 2 Antoine Guérin1 2 Mélanie Migaud1 2 Vimel Rattina1 2 Fatima Ailal7 Ibtihal Benhsaien7 Mathieu Bouaziz1 2 Habib Tanwir18 Damien Chaussabel18 Nico Marr18 Jacinta Bustamante1 2 3 19 Bertrand Boisson1 2 3 Ingrid Müller-Fleckenstein20 Bernhard Fleckenstein20 Marie-Olivia Chandesris21 22 Matthias Titeux2 23 Sylvie Fraitag24 Marie-Alexandra Alyanakian25 Marianne Leruez-Ville26 Capucine Picard 1 2 19 Isabelle Meyts27 James P. Di Santo13 14 Alain Hovnanian 2 23 28 Ayper Somer29 Ahmet Ozen11 Nima Rezaei9 10 Talal Chatila15 16 Laurent Abel1 2 3 Warren J. Leonard4 Stuart G. Tangye5 6 Anne Puel1 2 3 and Jean-Laurent Casanova1 2 3 30 31 PRIVATE 1. Laboratory of Human Genetics of Infectious Diseases Necker Branch INSERM U1163 75015 Paris France EU. 2. Paris Descartes University Imagine Institute 75015 Paris France EU. 3. St. Giles Laboratory of Human Genetics of Infectious Diseases Rockefeller Branch The Rockefeller University New York NY 10065 USA. 4. Laboratory of Molecular Immunology and the Immunology Center NHLBI NIH Bethesda MD 20892-1674 USA. 5. Immunology Division Garvan Institute of Medical Research Darlinghurst Sydney NSW 2010 Australia. 6. St. Vincent's Clinical School UNSW Sydney Sydney NSW 2052 Australia. 7. Clinical Immunology Unit Casablanca Children's Hospital Ibn Rochd Medical School King Hassan II University Casablanca Morocco. 8. Pediatric Hemato-Oncology Unit University Hospital of Angers 49933 Angers France EU. 9. Research Center for Immunodeficiencies Children's Medical Center Tehran University of Medical Sciences 1417613151 Tehran Iran. 10. Network of Immunity in Infection Malignancy and Autoimmunity (NIIMA) Universal Scientific Education and Research Network (USERN) 1419733151 Tehran Iran. 11. Marmara University Division of Pediatric Allergy/Immunology 34722 Istanbul Turkey. 12. Necmettin Erbakan University Meram Medical Faculty Division of Pediatric Allergy and Immunology 42060 Konya Turkey. 13. Innate Immunity Unit Institut Pasteur 75015 Paris France EU. 14. INSERM U1223 75015 Paris France EU. 15. Division of Immunology Boston Children's Hospital Boston MA 02115 USA. 16. Department of Pediatrics Harvard Medical School Boston MA 02115 USA. 17. Unit of Tropical and Infectious Diseases Necker Hospital for Sick Children AP-HP 75015 Paris France EU. 18. Sidra Medical and Research Center Doha Qatar. 19. Study Center for Immunodeficiency Necker Hospital for Sick Children AP-HP 75015 Paris France EU. 20. Institute of Clinical and Molecular Virology University of Erlangen-Nürnberg D-91054 Erlangen Germany EU. 21. Department of Hematology Necker Hospital for Sick Children AP-HP 75015 Paris France EU. 22. Referral Center for Immunodeficiency Necker Hospital for Sick Children AP-HP 75015 Paris France EU. 23. Laboratory of Genetic Skin Diseases: from Disease Mechanism to Therapies INSERM U1163 75015 Paris France EU. 24. Department of Pathology Necker Hospital for Sick Children AP-HP 75015 Paris France EU. 25. Immunology Laboratory Necker Hospital for Sick Children AP-HP 75015 Paris France EU. 26. Virology Laboratory Necker Hospital for Sick Children AP-HP 75015 Paris Descartes University EA 73-28 75015 Paris France EU. 27. Department of Immunology and Microbiology Childhood Immunology Department of Pediatrics University Hospitals Leuven and KU Leuven 3000 Leuven Belgium EU. 28. Department of Genetics Necker Hospital for Sick Children AP-HP 75015 Paris France EU. 29. Istanbul University Istanbul Medical Faculty Division of Infectious Diseases and Immunology 34452 Istanbul Turkey. 30. Pediatric Hematology-Immunology Unit Necker Hospital for Sick Children AP-HP 75015 Paris France EU. 31. Howard Hughes Medical Institute New York 10065 USA.

You are what you experience: The impact of environment on cellular identity S.F. Becker M.C. Morin S. Mangold and S. Jarriault PRIVATE IGBMC CNRS UMR7104 INSERM U964 UdS Strasbourg France

The role of chromatin organization in DNA double strand break repair in mouse embryonic stem cells Lyuba Chechik, Michail Amoiridis and Evi Soutoglou Thousands acts of DNA damage happen in multicellular organisms every day. This makes the process of DNA repair particularly of double strand breaks extremely important to study. Evidence grow to support the hypothesis that chromatin organization plays a notable role in repair pathway choice. We want to further investigate its impact using mouse embryonic stem cells as a model. This would allow us to compare the process of repair of the same loci in different chromatin states. We are using CRISPR-Cas9 system to create double strand breaks in specific loci and then study dynamics of repair as well as a pathway choice depending on a chromatin state. We are particularly interested in a stem cell-specific chromatin phenomenon: bivalency. We are also interested in the impact of specific chromatin state on DNA repair. Our preliminary data suggest that more open chromatin found in ES cells could lead to changes in the outcome of NHEJ as an error-prone pathway. Institut de Genetique et de Biologie Moleculaire et Cellulaire 67404 Illkirch France; Institut National de la Sante et de la Recherche Medicale U964 67404 Illkirch France; Centre National de Recherche Scientifique UMR7104 67404 Illkirch France ; Universite de Strasbourg 67081 Strasbourg France

Epigenetic Roadmap for Transcriptional Silencing: A Tale of Two X's Jan Jakub Zylicz Aurélie Bousard Laurène Syx Edith Heard PRIVATE Institut Curie Paris France; University of Cambridge UK

Long non-coding RNAs in nuclear organization of mouse ES cells Alexandra TACHTSIDI Pablo NAVARRO PRIVATE Institut Pasteur

Dissecting the functional importance of Polycomb Response Element (PRE) interactions for the formation of epigenetic chromatin domains in Drosophila Bernd Schuettengruber Yuki Ogiyama Giacomo Cavalli Polycomb group (PcG) proteins dynamically define cellular identities through the epigenetic repression of key developmental genes. In Drosophila cis-regulatory regions termed Polycomb response elements (PREs) act as nucleation sites for PcG proteins to create large repressive Polycomb domains that are marked by trimethylation of lysine 27 on histone H3 (H3K27me3). Recent advances in HiC technologies have revealed that PREs can form looping interactions within Polycomb domains leading to the clustering of PcG target genes and their regulatory regions. However the functional importance of these 3D chromatin interactions is largely unknown. Therefore we are using the CRISPR/Cas9 technology to mutate PREs in their endogenous chromatin context and study the functional importance of PRE interactions for the formation of Polycomb domains and PcG target gene regulation. IGH CNRS UMR9002 141 Rue de la cardonille 34396 Montpellier

Regulation of PAMP-triggered transcriptional reprogramming by active DNA demethylation in Arabidopsis T. Halter J. Wang D. Amesefe A. Pérez Quintero E. Lastrucci M. Charvin and L. Navarro PRIVATE Institut de Biologie de l'Ecole Normale Supérieure (IBENS) Paris France

Proteolytic balance in intestinal epithelium Céline Deraison, Chrystelle Bonnart, Frederic Barreau, Mireille Sebbag, Claire Rolland, Nuria Sola-Tapias, Alexandre Denadaï-Souza, Corinne Rolland, Muriel Quaranta, Jean-Paul Motta, Nathalie Vergnolle PRIVATE

Functional characterization of a novel IgH locus enhancer during B cell development Rocio Amoretti-Villa Mélanie Rogier Isabelle Robert Vincent Heyer and Bernardo Reina-San-Martin PRIVATE Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC) Illkirch-Graffenstaden France

Paf1 complex is required for the phyllotactic regularity in Arabidopsis Kateryna Fal1 Mengying Liu1 Assem Duisembekova1 Yassin Refahi2 Elizabeth S. Haswell3 Olivier Hamant1 In plants shoot apical meristems (SAMs) are groups of dividing cells that are responsible for the generation of all aerial organs. SAM activity is associated with a well-established choreography of gene expression patterns and a stereotypical spatial pattern of organ initiation also called phyllotaxis. As in most plants new aerial organs appear sequentially with a divergence angle of ca. 137° in Arabidopsis. To investigate the molecular basis behind such regularity several mutants with altered architecture have been isolated. Here we provide evidence that phyllotaxis can become non stereotypical and that phyllotactic robustness depends on the function of VIP3 a member of the PolII-associating factor 1 (Paf1) complex. Increased variance in phyllotaxis in vip3 was related to increased variability in spatial patterns of auxin activity at the meristem. We thus demonstrate that the control of phyllotaxis robustness involves a Paf1C-dependent regulation of meristem function. Notably we previously showed that Paf1C is required for plant touch responses opening the path for an integration of mechanical cues in the control of phyllotaxis robustness. 1 - Laboratoire Reproduction et Développement des Plantes Univ Lyon ENS de Lyon UCB Lyon 1 CNRS INRA F-69342 Lyon France; 2 - Sainsbury Laboratory University of Cambridge Bateman Street Cambridge CB2 1LR United Kingdom; 3 - Department of Biology Mailbox 1137 Washington University in Saint Louis Saint Louis MO USA 63130

The role of chromatin in the establishment of a cell-specific splicing program. Segelle A Oldfield A and Luco R Classically chromatin has been involved in the regulation of purely DNA-related processes. However it has become more and more evident that regulation of gene expression is a much more complex and multifactorial process in which epigenetics is intimately implicated at multiple levels from the DNA to the RNA. One of such processes is alternative splicing a very general process which misregulation can lead to disease such as cancer. Unfortunately the mechanisms behind cell-specific splicing regulation are still largely unknown. We have shown in the past that non-coding RNAs and histone marks can talk to the splicing machinery via recruitment of chromatin/splicing-adaptor complexes. We want now to better understand the role of chromatin and lncRNAs in the onset and maintenance of cell-specific splicing programs using as an inducible cell reprogramming model the epithelial-to-mesenchymal transition. For that purpose we will use state-of-the-art genome-wide deep sequencing approaches combined with innovative molecular biology tools to depict the mechanisms of splicing regulation in a cancer-relevant model system. IGH-UMR9002

TBA Rafal Ciosk lab

2nd meeting of the FSER laureates and their teams

Oct 10-11, 2017 Imagine Institute, Paris

Poster sessions

DAY 1

Poster session A: Tuesday, Oct. 10th, 18h00 - 20h00

Poster session B: Wednesday, Oct. 11th, 12h05 - 14h00

Details of poster sessions

Innate immune responses of human dendritic cells to the MVA vaccine Marius Döring1,2, Takeshi Satoh1,2, Matteo Gentilli1, Xavier Lahaye1 and Nicolas Manel1,2 The activation of dendritic cells (DCs) by vaccines is critical for the induction of protective immune responses. Modied vaccinia virus Ankara (MVA), a promising candidate live attenuated vaccine vector, induces potent target antigen-specic immune responses. It replicates in human cells but does not produce viral progeny. In DCs, MVA infection leads to vaccine antigen expression, but paradoxically also to cell death. How human DCs sense and respond to MVA infection remains incompletely understood. We aim to unravel how the course of MVA infection and innate sensing pathways intersect in DCs. To this end, we generated monocyte-derived DCs (MDDCs), overexpressed a dominant-negative IRF3 (IRF3DN) and silenced cGAS using lentivectors. We noted that CD86 was induced on uninfected bystander DCs, while it was downregulated on MVA-infected DCs. IRF3DN inhibited DC activation by MVA and HIV. In contrast, cGAS depletion only modestly decreased DC response to MVA, while it abrogated the DC response to HIV. Cross-talk between MVA-infected and bystander DCs partially required type I IFN, and also additional JAK/STAT pathways. Unexpectedly, we noted that MVA did not replicate in DCs, while it did in control HeLa cells. We identified a restriction factor responsible for blocking MVA replication in DCs. Alleviating this restriction allows for MVA replication and enhances antigen expression in DCs. 1 Immunity and Cancer Department, LABEX DCBIOL Institut Curie, PSL Research, University, INSERM U932, 75005 Paris, France, 2 LABEX Vaccine Research Institute (VRI), Créteil, Paris, France

Class III PI3K in metabolic control and circadian clock regulation Anton Iershov, Chantal Alkhoury, Ivan Nemazanyy, Catherine Caillaud, Mario Pende, Ganna Panasyuk Continuous coordination of nutrient sensing and signal transduction is essential for achieving metabolic homeostasis. Class III phosphoinositide 3-kinase (PI3K) is a conserved enzymatic complex involved in autophagy and trafficking. Currently we found that loss of PI3K-III in liver led to striking metabolic phenotypes including dysfunctional mitochondria. We will present biochemical and genetic evidence that PI3K-III in addition to its essential role in autophagy also controls mitochondrial metabolism having a potent effect on cellular pathways of clearance. We also found that PI3K-III is required for circadian clock function. Knockdown of its regulatory subunit Vps15 disrupted circadian expression of core clock components in vivo and in vitro. We showed that PI3K-III binds chromatin and we now study its nuclear function and whether it might be connected to its novel role in circadian rhythm regulation. The relevance of our findings to the human pathologies will be discussed. Necker Enfants Malades Institute (INEM) 14 Rue Maria Helena Vieira da Silva CS61431 75993 Paris cedex 14 France

New insights into commissural identity by NGS sequencing Manuela Argentini, François Friocourt, Sergi Roig, Alain Chedotal Commissural neurons connect the two CNS halves by extending axons from one side to the other. Spinal cord and hindbrain commissural axons extend dorsoventrally towards the ventral midline and cross it to reach their final targets contralaterally. Although some underlying guidance pathways are known, a transcriptomic and proteomic analysis of developing commissural neurons is lacking. Here, we performed a transcriptomic screen to seek for genes specifying commissural neuron identity and novel modulators of midline crossing. We used the RiboTag mouse line to specifically purify RNA from different neuronal populations. This line expresses a HA-tagged ribosomal protein (Rpl22-HA) upon Cre-mediated recombination. We used the Robo3Cre line and the NestinCre line to drive the expression of Rpl22-HA in commissural neurons or all neural-derivatives, respectively. We performed Translating Ribosome Affinity Purification experiments (TRAP) and submitted ribosomal-associated RNA samples to NGS sequencing. Differential analyses between Robo3Cre and NestinCre samples highlight 240 genes potentially involved in the specification of commissural neuron identity. We are currently investigating the functional relevance of some of these candidates. Institut de la Vision (IdV) CNRS : UMRS968, Centre de Recherche Inserm, Université Pierre et Marie Curie [UPMC] - Paris VI

Regulation of skeletal muscle differentiation Anne-Sophie Armand, Mario Pende Skeletal muscle formation adult muscle regeneration and growth requires the recruitment of embryonic or adult stem cells. Upon injury these muscle adult stem cells also called satellite cells are activated and proliferate before fusing with each other to form myotubes or with existing muscle fibers. Each step of muscle differentiation is regulated by a complex network of transcription factors such as YAP (Yes-associated protein) or the NFAT (Nuclear Factors of Activated T-cells) family of proteins.

LINCing the Nuclear Envelope to HIV infection: focus on SUN Anvita Bhargava, Nicolas Manel HIV replication requires the successful orchestration of reverse transcription nuclear entry and integration while avoiding various antiviral factors and innate immune sensors during early steps of infection. The viral capsid and its interactions with cellular factors play a major role during all of these steps. Furthermore the virus passes seemingly undetected through the nuclear envelope (NE) to invade the host genome. It is currently thought that HIV gets access to the nuclear interior by passing through the nuclear pore complex. However this process remains poorly understood. The lab has recently discovered that HIV uses SUN2 a protein of the LINC complex in the NE for infection. Interestingly SUN2 is embedded is the inner membrane of the NE but does not associate with the NPC. In this work I illustrate how over-expression of both SUN2 and its homolog SUN1 leads to reduced infection by HIV-1 and HIV-2 in HeLa cells. I show that this effect is linked to the lamin-binding rather than the nesprin-binding domains of SUN proteins. I also explore whether further disruption of these associated NE factors further impacts HIV infection. Overall results suggest that other NE factors besides the NPC likely play crucial roles in HIV infection.

Strangling nuclei: Nuclear deformation correlates with microtubules bundles formation and chromatin reorganization in human hematopoietic stem cells. S. Biedzinski, B. Vianay, S. Brunet, J. Larghero and M. Théry Chromatin state is highly influenced by nuclear envelope architecture. Modulating nuclear geometry can affect chromatin organization and thus potentially affect gene expression. It has been demonstrated in adherent cells that actin cytoskeleton is the main actor responsible of nuclear deformation via its ability to transmit forces but this phenomenon has never been addressed in non-adherent cells. Also the role of these deformations on stem cell differentiation has never been fully has never been explored before. Our study aims to understand the parameters controlling nucleus shape change and its impact on cellular differentiation using a non-adherent stem cell model the hematopoietic stem cell (HSC). To address this question nuclear morphology and cytoskeleton organization have been quantitatively analyzed in two different populations of HSCs: one which represents naïve stem cells identified with the presence of the surface marker CD34 and the absence of the CD38 marker opposed to early-stage differentiated cells expressing CD38. We show that both size and shape of the nucleus are strikingly different in these two populations. Mainly the nucleus of naïve cells is spherical while it displays concave surfaces in differentiated cells. These differences correlate with changes in heterochromatin spatial distribution indicative of chromatin reorganization which in turn is known to occur during differentiation. Furthermore cytoskeleton organization was analyzed and main differences were observed for the microtubules. Interestingly in contrast to naïve cella differentiated cells exhibit bundling microtubules tightly apposed to the nuclear envelope. This reorganization suggests strong interaction between microtubules and the nuclear envelope that may be the cause of its deformation. Taken together these observations suggest that microtubules may monitor nuclear shape changes during early steps of differentiation of HSCs allowing the cell to change its expression program. Modulation of microtubules dynamics and/or interaction with the nucleus could be a key point in controlling HSCs' stemness over time. CEA Grolenoble AP-HP

mTOR and the regulation of primary cilium through S6K Martina Bonucci, Manuela Barilari, Nicolas Kuperwasser, Mario Pende Aberrant activation of mTOR and its substrate S6K1 via genetic inactivation of either component of the TSC complex (Tsc1 or Tsc2) leads to the formation of benign tumors with the brain and kidney being strongly affected. We have developed two conditional Tsc-knockout models in the brain and in the kidney of mice to investigate the contributions of mTOR and S6K in disease progression. Virus-mediated Tsc1 inactivation in the brain leads to epilepsy and the formation of dysmorphic and hypertrophic neurons and epithelial-specific inactivation of Tsc1 in the kidney gives rise to polycystic kidneys. Both of these phenotypes are reversed in the absence of S6K. Interestingly both epilepsy and polycystic kidney disease are associated with defects in primary cilium and planar cell polarity. Here we show evidence for a new mechanism of regulation of primary cilium length through S6K which will help dissect their roles in the development of the pathology. 1. Institut Necker-Enfants Malades CS 61431 Paris France 2. Institut National de la Santé et de la Recherche Médicale U1151 F-75014 Paris France 3. Université Paris Descartes Sorbonne Paris Cité 75006 Paris France

DNA repair and genome instability in aging stem cells Benjamin Boumard, Katarzyna Siudeja and Allison Bardin Genome integrity in long-lived tissue stem cells is essential to maintain tissue function and prevent cancer initiation. How stem cells cope with DNA lesions determines their mutation rate susceptibility to cancer and likely age-related functional decline. Here we aim to understand the mechanisms acting in adult stem cells to prevent spontaneous mutation. Our previous work in Drosophila demonstrated that in aging intestinal stem cells frequent gene inactivation leads to neoplastic growth. Using whole-genome sequencing we determined that the gene Notch becomes inactivated by small and large deletions that can be accompanied by more complex structural rearrangements. Using gene Knockdown in the Drosophila stem cells we are currently investigating the role of DNA damage response and DNA repair pathways on genome instability and more specifically on the deletion events we characterized. In addition the study of GFP-reporter lines will provide insight into the molecular pathways used in vivo in adult stem cells. Finally we are exploring the contribution of replication stress to stem cell genome instability. Institut Curie 26 rue d'Ulm F-75248 Paris France

The Reissner's fiber and motile cilia control body axis development in zebrafish. Y. Cantaut-Belarif 1, O. Thouvenin 2, J. R. Sternberg 1, C. Boccara 2 C. Wyart #1 and P. L. Bardet #1 Cerebrospinal fluid (CSF) properties are critical for the adult nervous system homeostasis. However its role during development is poorly understood. Reissner's fiber (RF) bathing in the CSF is formed via the polymerization of the secreted sco-spondin protein. Due animal models lack its contribution in vertebrates development remains enigmatic. We have now generated zebrafish sco-spondin mutants to study the role of RF. Mutations leading to the absence of RF result in an abnormal curvature of the embryonic posterior axis. Our mutant phenotype recalls the curled-down phenotype observed in ciliary mutants suggesting a link between cilia and body morphogenesis. Thus we analyzed ependymal ciliogenesis and motility in our mutants and found no disruption. Reciprocally we analyzed four ciliary mutants and observed abnormally developed Reissner structures. As both RF and cilia motility have been suggested regulating CSF flow we finally show a disturbed local CSF flow in RF lacking embryos. This phenotype would recall a scoliotic one observed in adult zebrafish following a CSF flow disruption at juvenile stage. 1: Sorbonne Universités UPMC Univ Paris 06 INSERM CNRS Institut du Cerveau et la Moelle (ICM ; Brain and Spine Institute) ; 75013 Paris ; France 2: Institut Langevin ESPCI Paris PSL Research University ; 75005 Paris ; France #: co-corresponding authors equal contributors.

Exploring Stage-dependent Properties in Neural Stem Cells Marion Coolen, Rosaria Esposito, Emmanuel Than-Trong and Laure Bally-Cuif Brain development and homeostasis require life-long control of neural progenitors division activity. In our laboratory we are using the zebrafish model system to study the molecular mechanisms underlying this control. During vertebrate development a major progenitor type radial glia cells (RGCs) is at the top of the clonal hierarchy generating neurons and macroglia. While in rodents RGCs disappear in most brain regions at post-natal stages in zebrafish RGCs are widespread in the adult brain lining all brain ventricles and functioning as adult neural stem cells (NSCs). A critical difference between embryonic and adult RGCs is that the latter enter infrequently into the cell cycle and mostly reside in a quiescent state. However little is known on the timing and molecular regulation of the emergence of a quiescent state in NSCs and more generally on the changing properties of RGCs between embryonic and adult stages. I will present our current investigations on this issue. Zebrafish Neurogenetics Unit Institut Pasteur/CNRS UMR 3738

Searching for loopholes to the limitations of DNA-Fluorescence In Situ Hybridization. Philippe Clerc, Florian Mueller, Samy Gobaa, Audrey Salles, Christophe Zimmer and Pablo Navarro Despite tremendous progress in the comprehension of spatial genome organization questions remain concerning chromatin condensation TAD organization and enhancer-promoter looping in regard with the dynamics of transcription. Only high-throughput high-resolution single-cell analytical tools could address these issues. DNA-FISH (Fluorescent In Situ Hybridization) as a microscope-based method can measure physical distances between DNA loci at the single-cell level but it has limitations. The necessity of DNA denaturation at elevated temperature produces mechanical constraints on chromatin structure. In general only 2 or 3 loci can be analysed at a time although probes made of oligonucleotides (oligopaint) should permit multiplexing through barcoding . However single-copy DNA loci can be detected with satisfactory frequencies when using as many as 100 oligonucleotides or more thus hampering genomic resolution. Fixed chromatin the biochemical sample used in DNA-FISH is a likely cause for the limited DNA accessibility the non-specific binding of oligonucleotides (background) and the topological alteration by temperature. To examine the role of chromatin during DNA-FISH we are currently attempting to perform DNA-FISH with oligonucleotides on naked nuclear DNA obtained by both embedding cells within a hydrogel and removing proteins by complete proteolysis. We report on the level of conservation of DNA topology on the signal-to-background ratio and on the efficiency of detection of single-copy loci in this experimental setting.

Regulation of neural crest mesenchymal differentiation potentials by Hox genes Barbara F. FONSECA and Elisabeth DUPIN The neural crest (NC) is a multipotent structure of vertebrate embryos at the origin of peripheral nervous system and skin pigment cells. In addition cephalic NC (CNC) not trunk NC (TNC) yields mesenchymal cells in craniofacial skeleton dermis and fat tissue. Albeit in a dormant state in vivo mesenchymal potentials of TNC cells can be disclosed after in vitro culture. The mechanisms that regulate NC mesenchymal potentials along rostro-caudal axis are still elusive. We used the avian embryo and in vitro NC cultures to investigate the influence of Hox transcription factor genes on NC mesenchymal fate. In CNC cells ectopic expression of Hoxa2 strongly reduced the production of osteoblasts while neural and melanocytic phenotypes were unaffected. In CNT cells overexpression of Hoxa2 resulted in largely impaired in vitro differentiation into bone cells chondrocytes and adipocytes without change in other NC derivatives. These results suggest that mesenchymal potentials of the CNC and TNC are controlled at least in part via a common mechanism that involves inhibition of Hoxa2 gene. Sorbonne Universités Institut de la Vision Centre de Recherche UMR INSERM S968/ CNRS 7210/ UPMC

Pyk2 a tyrosine kinase essential for synaptic plasticity Benoit de Pins, Albert Giralt and Jean-Antoine Girault Pyk2 is a non-receptor tyrosine kinase activated by Ca2+ and highly expressed in forebrain neurons especially in the hippocampus. We tested its role in vivo using mutant mice. We observed that Pyk2 mutation impairs dendritic spines post-synaptic density proteins synaptic plasticity and spatial memory. We also found that Pyk2 was decreased in the hippocampus of patients with Huntington's disease (HD) an inherited neurodegenerative disorder and in a mouse model of the disease. These mice display an hippocampal phenotype similar to that observed in Pyk2 mutant mice which was partly rescued by restoring Pyk2 levels. In addition Pyk2 gene PTK2B is associated with Alzheimer's disease but its potential role is not known. We found that Pyk2 activation was altered in an Alzheimer mouse model whereas its overexpression improved the behavioral phenotype. This work reveals that Pyk2 is important for synaptic organization and plasticity and that its alteration can reversibly contribute to the phenotype of neurodegenerative diseases. Institut du Fer à Moulin INSERM UPMC-Sorbonne-Universités UMR-S 839 Paris France.

Immune functions of the nuclear envelope in vivo Nilushi De Silva, Nicolas Manel A key property of DCs is their capacity to migrate within tissues to sample antigen and reach sites of infection. Recent in vitro work has revealed that DNA is transiently accessible to the cytosol in DCs undergoing constricted migration due to rupture of the nuclear envelope (NE) and is detected by the antiviral cytosolic DNA sensor cGAS. The in vivo relevance of this finding especially in regards to whether there is an immune response to NE rupture remains unknown. To address this question we are investigating the immune consequences of NE modulation by perturbing several factors that regulate the structure and integrity of the NE including SUN1/2 of the LINC complex and lamin A of the nuclear lamina in mouse models. We will present the results of our initial immunophenotyping analysis of several of these genetic lines. We have also developed a genetic tool to trace cGAS expression within these mice and we will present our analysis of cGAS expression within the immune system.

Chromatin regulation and the stability of Nanog transcription states Agnes DUBOIS Pablo NAVARRO-GIL Embryonic Stem (ES) cells self-renewal is controlled by a gene regulatory network (GRN) at the center of which lie 3 transcription factors : Nanog Oct4 and Sox2. While Oct4 and Sox2 need to be expressed within strict levels for self-renewal to occur Nanog displays a wide range of expression levels associated with distinct propensities to self-renew (high Nanog) or undergo differentiation (low Nanog). Two complementary models have been proposed to explain Nanog heterogeneity. In the first model Nanog fluctuations are encoded within the topology and architecture of the GRN itself. In the second model extrinsic noise associated to FGF/ERK and GSK3b signaling potent repressor pathways of Nanog play a preponderant role. Here we show that Nanog regulation follows two independent regimes: whilst Nanog fluctuations between low and high expression states are largely independent of FGF/ERK and GSK3b signaling Nanog-negative cells are strictly dependent. We then focus on the Nanog-negative state which has been recently shown to be epigenetically propagated throughout several cell divisions. In order to identify the molecular nature of this epigenetic memory we have analyzed the distribution of repressive histone marks across the Nanog locus in several biological conditions. We will show that (1) H3K9me3 is enriched at the Nanog locus in Nanog-negative cells; (2) H3K9me3 at Nanog requires FGF/ERK signaling; (3) H3K9me3 at Nanog is mitotically stable. Therefore we propose that H3K9me3 at Nanog acts as a canonical epigenetic mark conveying the information required to maintain FGF/ERK-mediated Nanog silencing across several divisions. Finally using Dicer and Ago2 knock-out cells we further suggest that the RNA interference (RNAi) machinery may be involved in H3K9 tri-methylation of the Nanog locus.

Mitotic preservation of regulatory architectures Nicola Festuccia, Inmaculada Gonzalez, Nick Owens and Pablo Navarro The preservation of cell identity depends on the maintenance of gene expression programs through mitosis. Mitosis is accompanied by chromatin compaction displacement of many regulators from the chromatin and a halt in transcription: as such it is thought to lead to the transient collapse of regulatory architectures. Generally resumption of the appropriate expression programmes in daughter cells is believed to be guided by mitotically stable covalent modifications of the chromatin such as DNA and histone modifications. We present evidence that in Embryonic Stem Cells regulatory control by transcription factors persists throughout mitosis rather than being re-established after cell division. Chromatin accessibility is largely maintained at regulatory regions which are dynamically occupied by several pluripotency factors a process known as "bookmarking". We have identified one crucial mitotic regulator Esrrb which through direct recognition of its DNA binding sites occupies a large group of crucial pluripotency enhancers during division. We further show that Sox2 although not as robustly as Esrrb is also capable of binding mitotic DNA. Oct4 the chief pluripotency factor during interphase is instead almost totally excluded from the chromatin as is Nanog. We propose that the pluripotency network is not extinguished but restructured during cell division with certain bookmarking factors gaining central importance in its mitotic preservation. Our findings corroborated by recent reports in other cell types call for redefining our view of the mechanisms governing the transmission of cell identity through division. Epigenetics of Stem Cells Department of Developmental and Stem Cell Biology Pasteur Institute Paris France

Déclics: meet high-school students to share the hows and whys of your science Tania Louis, Héloïse Dufour In a post-truth era, where the difference between knowledge and belief is increasingly blurred, scientific reasoning and research mechanisms represent useful conceptual tools for young minds to apprehend our complex society. However, even in large metropolis, more than 2/3 of high-schoolers have never encountered scientists. On the other end, it has been shown that under a third of biologists participate at least yearly to outreach actions, although our studies show that up to 90% of researchers are willing to do so. Déclics (Développer les Echanges entre Chercheurs et Lycéens pour les Intéresser à la Construction des Savoirs) is a program bridging this gap, by organizing the encounter of research scientists and high-schoolers in personalized, memorable settings. In the speed-meeting at the core of the program, scientists have nothing to prepare and are present in a high school for a couple of hours, discussing with successive small groups of students. Each students thus meets with 7 researchers, for 10 minutes each. Despite their brevity, the variety offered and the personalised contacts those encounters provide is highly impactful for those young minds, in terms of career orientation, but also on discovering how research is practiced and finally in terms of citizenship by giving tools to understand how knowledge is produced. Assessments indeed show that the number of students knowing about research jobs is multiplied by 3. The proportion of students understanding what basic research is multiplied by 2.3. Finally there is an increase of 64% in terms of the number of students understanding how knowledge is produced and verified. Whatever your position in the lab is, might it be PI, technician, PhD student or else, join the more than 99% of research scientists who have already participated were happy about it! Sign up on www.declics2017.org Cercle FSER

Shigella hijacks Ago2 function to promote rupture of its vacuole Didier Filopon1, Mariette Bonnet2, Lionel Schiavolin1, Philippe Sansonetti3, Guy Tran Van Nhieu2 & Lionel Navarro1 MicroRNAs (miRNAs) have emerged as critical fine-tuners of host immune responses in both plants and mammals [1-2]. However, their functional relevance in antibacterial defence is still poorly understood. Furthermore, unlike in plants, there is no evidence of the implication of human miRNA pathway in the control of host-bacterial interactions [3-5]. Here, we used Shigella and HeLa cells as an in vitro infection model system to study the localization and functional relevance of human Ago2 during host-bacterial interactions. Shigella is known to induce its host cell internalization and further rapidly escapes from its phagocytic vacuole to reach the cytosol, a step that is critical for its intracellular life cycle [6]. Using live microscopy, we showed that Ago2 is transiently recruited at Shigella entry foci and that Ago2 deficient cells exhibit a pronounced delay in Shigella vacuole rupture. Using a complementation assay in Ago2 knock-out cells, we further showed that miRNA-mediated translation inhibition activity of Ago2 or its binding to GW protein TNRC6 is essential for rapid Shigella-induced vacuole rupture, while its slicing activity is dispensable for this process. Moreover, infections using a bacterial mutant strain during Ago2 KO rescue experiments suggest that Shigella targets Ago2 to promote rupture of its vacuoles. Altogether, this study demonstrates for the first time a critical role of Ago2, and of the human miRNA pathway, in host-bacterial interactions. This work also provides novel insights into the mechanism of Shigella-induced vacuole rupture, a phenomenon that remains poorly characterized at the mechanistic level. 1. Staiger et al., New Phytol., 20132. Maudet et al., Nat Commun., 20143. Navarro et al., Science., 20084. Li et al., Plant Physiol., 20105. Thiébeauld et al., under review6. Valencia-Gallardo et al., Cell Microbiol. , 2015 1 Institut de Biologie de L’Ecole Normale Supérieure (IBENS), Paris, France 2 Centre de Recherche Interdisciplinaire en Biologie(CIRB), Collège de France, Paris, France 3 Institut Pasteur, Paris, France

Nutrient sensing and metabolic control by class III PI3K Anton Iershov, Chantal Alkhoury, Ivan Nemazanyy, Catherine Caillaud, Mario Pende, Ganna Panasyuk In cell, metabolic changes are continuously sensed and decoded into the coordination of pro-growth and degrative activities. The molecular mechanisms of these processes are complex and are not fully understood. Class III phosphoinositide 3-kinase (PI3K) is an essential and remarkably conserved enzyme complex. Its lipid kinase activity is important for nutrient uptake and metabolism through control of endocytic trafficking, autophagy and lysosomal activities. Importantly, in physiology, core metabolic processes and trafficking are controlled transcriptionally in a circadian manner. The poster will summarize our advances on two projects that address the role of class III PI3K signalling in (1) specific metabolic activities in liver and (2) circadian clock regulation: (1) Recently, we have revealed a novel crosstalk between PI3K-III and insulin transduction contributing to whole body metabolic control (Nemazanyy et al., Nat. Comm., 2015). In our current work, have made a discovery that loss of functional class III PI3K in liver results in striking metabolic phenotypes. However, less is known about which metabolic activities and how those are controlled by class III PI3K in vivo. The metabolomic analyses of liver tissue have pointed to dysfunctional mitochondria in hepatic mutants of class III PI3K. These observations were further confirmed by molecular and biochemical analyses upon short-term and chronic depletion of a regulatory subunit of class III PI3K complex, Vps15 protein. Mechanistically, expression and activity of transcription factor of nuclear receptor superfamily - Peroxisome Proliferator Activated Receptor alpha (PPARa), a known regulator of mitochondrial catabolic metabolism, was defective in liver mutants of Vps15. Importantly, the pharmacological reactivation of PPARa by a synthetic ligand resulted in a restoration of mitochondrial function, suggesting that PPARa acts downstream of class III PI3K. Strikingly, activation of PPARa was also sufficient to clear accumulated lysosomes, endosomes and autophagosomes in class III PI3K deficient liver. In sum, we will present biochemical and genetic evidence that class III PI3K, in addition to its essential role in autophagy, also controls mitochondrial metabolism having a potent effect on cellular pathways of clearance. (2) Our very recent observations in vivo and in vitro show that class III PI3K is required for circadian clock function. In vivo, in liver mutants of class III PI3K, it is reflected in a loss of circadian expression of core components of the clock. Those observations are also reproduced in vitro upon acute Vps15 depletion. Furthermore, we have discovered that class III PI3K subunits including a regulatory subunit Vps15 are chromatin bound proteins. Currently, we are addressing what is the function of class III PI3K in nucleus and whether it might be connected to its novel role in circadian rhythm regulation. The relevance of the finding on both projects to the human pathologies will be discussed. Necker Enfants Malades Institute (INEM), 14 Rue Maria Helena Vieira da Silva, CS61431, 75993 Paris cedex 14, France

Activation versus silencing: a dual function for H3K9me3 in transcription Mathilde Gauchier Sophie Kan and Jérôme Déjardin1 Most of the mammalian genome is composed of repetitive sequences such as satellite DNA telomeric DNA and transposable elements which are regulated and organized into heterochromatin. The trimethylation of the lysine 9 on histone H3 (H3K9me3) mediated by specific Histone-methyl-transferase (HMTase) is a specific hallmark of constitutive heterochromatin. The SETDB1 HMTase installs H3K9me3 across transposable element such as Intracisternal-A-Particle IAP retrotransposons and we found that SETDB1 is also essential to maintain H3K9me3 on telomeres in mouse ES cells. Whereas the mark is critical for transcriptional silencing at retrotransposons our results show that aberrant heterochromatin formation stimulates rather than inhibits transcriptional elongation at telomeric regions. To better understand the dual function of H3K9me3 on transcriptional activities across the genome we are improving the PICh (Proteomics of Isolated Chromatin segments) approach to purify and characterize the global chromatin associated to the IAP retrotransposons necessary for its silencing. 1: Institute of Human Genetics CNRS UPR1142. 141 rue de la Cardonille. 34000 Montpellier France

"Molecular Mechanisms of mitotic bookmarking"- How to maintain permissive chromatin during mitosis Inma Gonzalez, Nicola Festuccia, Nick Owens and Pablo NAVARRO GIL Embryonic stem cells (ESCs) can efficiently maintain their cellular identity and developmental potential over virtually infinite cell generations. This phenomenon referred as self-renewal depends on a network of sequence-specific transcription factors (TFs) and requires daughter cells to accurately reproduce the gene expression pattern of the mother. The high degree of condensation of the mitotic chromosomes generally leads to the eviction of TFs from the chromatin during cell division. However some TFs have emerged to remain bound to select sites within mitotic chromatin. This so-called mitotic bookmarking has been proposed to be important for the prompt reactivation of a specific set of genes early in interphase which is in turn essential for the maintenance of cell identity. Recently our lab has shown that Estrogen-related receptor B (Esrrb) a key pluripotency TF acts as a mitotic bookmarking factor in mouse ESCs and preliminary data suggests a similar role of the pluripotency TFs OCT4 and SOX2 as bookmarking transcription factors. I also assessed chromatin accessibility using ATAC-seq in interphase and mitosis revealing that the pattern of accessibility is strikingly stable and therefore maintained during mitosis. Hence we want to identify and characterize factors responsible to maintain this pattern of accessibility and the specific properties of the mitotic chromosomes of ESCs thereby enabling this chromatin "fluidity" of bookmarking TF. Our working hypothesis is that that reciprocal stimulations of PTFs recruitment by remodellers and of remodellers by PTFs would constitute a positive feedback loop resulting in the high occupancy observed for PTFs and remodellers at ES cell regulatory elements to the maintain chromatin accessibility. Therefore we want to study the chromatin accessibility in interphase and mitosis upon loss of function of pluripotency factors and chromatin remodelers factors. Pasteur

The Chromatin Remodeling Factor Kismet/CHD7 Controls INTESTINAL Stem Cell Proliferation Louis Gervais, Carolina Perdigoto, Patricia Skorski, Allison Bardin Replacement of specialized cells occurs in most adult tissues and relies on the activity of resident adult stem cells. Increasing evidences highlights the importance of the regulation of chromatin structure both in the maintenance of stem cell identity and in their commitment to differentiation yet the importance of such regulation in adult stem cells is poorly understood. Using the Drosophila intestine as a model to identify new factors regulating tissue homeostasis and adult stem cell activity we found that clonal inactivation of the chromatin remodeling factor Kismet results in a strong increase in relative number and density of intestinal stem cells (ISC) in the gut. This is due to an abnormal division rate of kismet mutant stem cells compared to wild-type stem cells. Kismet is a member of the chromodomain-helicase-DNA binding (CHD) subfamily of ATP-dependent chromatin remodeling factors. CHD proteins are thought to function in the nucleus via binding to the DNA and thus regulate gene transcription. Mutations in CHD7 are a common genetic cause of CHARGE Syndrome. Although most of the disorders affecting individuals with CHARGE are due to defects during embryonic development recent published work points toward essential functions of CHD7 in adult tissues. We then established the gene bound by Kismet in the ISC using genome wide mapping of Kismet protein. This combined with an aberrant activation of EGFR and Jak/Stat pathways in mutant conditions helped us to determined that Kismet is a major regulator of ISC proliferation upstream of these pathways. Consistent with this inactivation of these pathways suppresses kismet phenotypes indicating that Kismet is maintaining intestinal stem cell proliferation at a basal level in order to properly control gut homeostasis. Institut Curie CNRS - INSERM Paris France 26 rue d'Ulm 75005 Paris - France

The commensal bacterium Lactobacillus plantarum rescues the developmental delay of Drosophila melanogaster due to limiting amino acids Théodore Grenier, François Leulier The association formed by Drosophila melanogaster and the bacterium Lactobacillus plantarum is a model of mutualistic interaction between microbes and animal hosts. Previous data show that upon nutrient scarcity, certain strains of L. plantarum are able to rescue the developmental delay of Drosophila larvae. However, the exact mechanism underlying this growth promoting effect of L. plantarum remains elusive. In this study, we replaced our commonly used complex diet based on inactivated yeast with a chemically defined diet, which allow us to finely control its nutritional composition. Using this experimental diet we performed developmental timing experiments using Germ-Free larvae and larvae mono-associated with L. plantarum and we now show that L. plantarum is specifically able to compensate for amino acids scarcity. Comparing the effect of L. plantarum on other chemically defined diets led us to the conclusion that L. plantarum can rescue scarcity in specific limiting amino acids, such as arginine, possibly by producing them and providing them to the larva. Our study provides an interesting model to finely understand how commensal bacteria increase their host's ability to cope with nutritional challenges. Institut de Génomique Fonctionnelle de Lyon (IGFL), CNRS : UMR5242, Université Claude Bernard - Lyon I (UCBL), École Normale Supérieure (ENS) - Lyon

Screening for non-coding regulators of ES cell self-renewal: a CRISPR-ON story Victor Heurtier and Pablo Navarro Mouse Embryonic Stem (ES) cells are derived from the inner cell mass of blastocysts. They are able to self-renew and maintain pluripotency through division. Protein factors behind these properties have been widely studied and operate through a highly interconnected network called "pluripotency network". Its three core transcription factors Oct4 Sox2 and Nanog integrate external signals and orchestrate a broad variety of internal components. In particular Nanog targets are enriched of self-renewal regulatory factors. However little is known about the role of long non-coding RNAs (lncRNAs) in mouse ES cell biology. LncRNAs represent a wide class of transcripts (several thousands in mice) and remain poorly explored. It is now established that they can display gene regulatory functions. But if some of them have such major functions in self-renewal is not yet demonstrated. In order to find lncRNAs involved in the regulation of the pluripotency network of ES cells we adopted a two-step strategy: - A/ we determined a list of non-coding transcripts regulated by Nanog and reinforced in the "naïve" ES cell state - B/ we are now conducting a functional screening on this limited number of transcripts using a new mouse ES cell line expressing an inducible CRISPR-based technology of transcription activation. CNRS Institut Pasteur

Systemic rejuvenation of the aged brain Lida Katsimpardi, Nicolas Kuperwasser, Claire Camus, Carine Moigneu, Virginie Tolle and Pierre-Marie Lledo During aging the interaction between the immune metabolic and endocrine systems results in deregulation of the equilibrium affecting all levels of the organism. Although aging has long been thought to be an irreversible process recent advances in the field have shown that there are ways of slowing down or even reversing aging by systemic manipulations leading to amelioration of functional decline but also increase in lifespan. GDF11 has been previously shown to be a circulating factor that mimics the effects of heterochronic parabiosis. Here we show that GDF11 treatment has effects on multiple targets in the aging organism and that it can act both systemically and directly in the brain to promote its anti-aging potential thereby opening new possibilities for novel therapies for age-related diseases.

Floor plate-derived netrin-1 is dispensable for commissural axon guidance Juan Antonio Moreno-Bravo1, Sergi Roig Puiggros1 2, Chloé Dominici1, Nicolas Rama2, Patrick Mehlen2 and Alain Chédotal1 Netrin-1 is an evolutionarily conserved secreted extracellular matrix protein expressed by cells localized at CNS midline such as the floor plate (fp) in vertebrate embryos. Different in vitro assays showed that netrin-1 can attract commissural axons. Loss-of-function experiments demonstrated that commissural axon extension to the midline is severely impaired in absence of netrin-1. These data support a model in which commissural axons are attracted by a netrin-1 gradient diffusing from the fp. We selectively ablated netrin-1 in fp cells using a Netrin-1 conditional line. We found that hindbrain and spinal cord commissural axons develop normally in absence of fp-derived netrin-1. We show that netrin-1 is highly expressed by cells in the ventricular zone (vz) with the potential to release it at the pial surface where it binds to commissural axons. Netrin-1 deletion from the vz phenocopies guidance defects previously described in Netrin-1 k.o mice. These results show that the view that attraction of commissural axons is mediated by a gradient of fp-derived netrin-1 is inaccurate and that netrin-1 primarily acts locally by promoting growth cone adhesion. 1 Sorbonne Universités UPMC Univ Paris 06 INSERM CNRS Institut de la Vision 17 Rue Moreau 75012 Paris France. 2 Apoptosis Cancer and Development Laboratory Equipe labellisée ?La Ligue' LabEx DEVweCAN Centre de Recherche en Cancérologie de Lyon INSERM U1052-CNRS UMR5286 Université de Lyon Centre Léon Bérard 69008 Lyon France

Identification of novel partners for Activation Induced Cytidine Deaminase using BioID Moritz Jacques, Gaudot Léa, Robert Isabelle, Heyer Vincent, Reina-San-Martin Bernardo During immune responses activation-induced cytidine deaminase (AID) is required for a diversifying immunoglobulin (Ig) mechanism called class switch recombination (CSR). AID acts by deaminating cytidine residues in single-stranded DNA ultimately generating double-stranded breaks required for CSR. Due to this mutagenic effect AID has a strong oncogenic potential. Thus it is crucial to understand how AID action is controlled so that it can play its physiological role without threatening B cell genomic integrity. In order to find AID cofactors that could regulate its function we use BioID. In this approach AID is fused to BirA* a mutated biotin ligase that biotinylates all proteins in its surroundings. After a streptavidin-based purification AID partners can be identified by mass spectrometry. Amongst the purified proteins identified in primary B cells we find new potential interesting partners which we plan to characterize by generating knockouts and study their effects on CSR. Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC) 1 rue Laurent Fries Illkirch

Developing transgenic tools to study Notch signaling in intact neural stem cell niches of the adult vertebrate brain in vivo Sara Ortica Gatti, Nicolas Dray, Sébastien Bedu, Isabelle Foucher, Laure Bally-Cuif In the adult vertebrate brain neurons and glia are generated by a pool of adult Neural Stem Cells (aNSCs). The zebrafish dorsal telencephalon is enriched in aNSCs exposed at the brain surface in a monolayer and that can be imaged through the skull of live animals. aNSCs are mainly quiescent but can be activated and re-enter the cell cycle to maintain the aNSC pool and to permit neuronal production. The balance between quiescence and activation is tightly controlled by Notch3 signaling. We aim to test whether and how Notch3 signaling fluctuations correlate with the spatiotemporal pattern of aNSC activation at the population level. To do this we are generating transgenic lines where the Notch3 receptor is tagged with fluorescent proteins to follow its activation and the corresponding nuclear translocation of its intracellular domain. I will present our approaches either via CRISPR/Cas9 and homology directed repair or with a recombined BAC harboring the tagged version of Notch3. Zebrafish Neurogenetics Unit Developmental and Stem Cell Biology Dept Pasteur Institute Paris

Quantitative Interpretation of pluripotency transcription factor occupancy with ChIP-seq Nick Owens, Inma Gonzalez, Nicola Festuccia, Pablo Navarro Chromatin binding can be explored in great detail through high-throughput sequencing using technologies such as ChIP-seq. The correct interpretation of changes in this data over multiple conditions requires an understanding of the quantitative signal available. Here in the context of pluripotency transcription factor binding in interphase and mitosis in mouse ES cells we show how statistical models of the quantitative aspects of ChIP-seq can gain insight into changes in transcription factor occupancy. Epigenetics of Stem Cells Department of Developmental and Stem Cell Biology Institut Pasteur

Replication effects in chromatin structure and TF binding in pluripotent ES cells Thaleia Papadopoulou and Pablo Navarro Embryonic stem cells (ES) are characterized by their ability to indefinitely self-renew while being responsive to external cues leading to their differentiation into specialized cell types. As the maintenance of ES cell identity relies on the activity of pluripotency transcription factors (TFs) rather than on epigenetic silencing mechanisms it is crucial to understand the specific mechanisms which ensure the expression and activity of these factors. This question is important to be addressed in the context of replication an event which takes place permanently in ES cells and challenges their chromatin structure and TF occupancy. We are planning to establish the technique for in vivo mapping of nascent chromatin (MINCE-seq) in ES cells and use it in combination with proteomic analysis in order to study the TF binding behind the replication fork. We expect to identify amongst our candidates TFs which are essential for the fast re-assembly of the appropriate pluripotency landscape. Institut Pasteur

Investigation of the diversity of neurosecretory compounds released in the cerebrospinal fluid by contacting neurons Feng Quan, Hugo Marnas, Sara Zeppilli, Lydia Djenoune, Andrew Prendergast, Laura Desban, Pierre-Luc Bardet and Claire Wyart Arousal locomotion varies as a function of our inner states as well as cues from the environment. The initiation of locomotion relies on descending command from the brain as well as the excitability of spinal circuits themselves. The mechanisms allowing the CNS to monitor the interplay between generating motor activity and integrating sensory inputs during locomotion remain unclear. Our team investigates a novel interoceptive pathway relying on spinal sensory neurons called cerebrospinal fluid contacting neurons (CSF-cNs) which were described by Kolmer and Agduhr in more than 200 vertebrates species. Due to their location at the interface between the cerebrospinal fluid (CSF) and the central nervous system these neurons are good candidate for a sensorimotor loop in the spinal cord. CSF-cNs are GABAergic neurons expressing the transient receptor potential PKD2L1. We have evidence that CSF-cNs respond to variations of CSF pH and flow and modulate locomotion and posture via projections on spinal targets. Recently we performed a transcriptome analysis of CSF-cNs and identified a wide repertoire of peptides and secreted proteins. We took advantage of the zebrafish embryo transparency to validate the expression of peptides and small proteins by fluorescent in situ hybridization coupled with immunohistochemistry using PKD2L1 as a CSF-cNs marker. We showed that peptide expression was mainly localized in the spinal cord in the embryonic and larval stages. Few peptides remain expressed around the central canal in the spinal cord in adult zebrafish possibly in adult CSF-cNs. To investigate the putative CSF-cNs peptides contributing to the modulation of locomotion and posture our team developed tools to monitor endogeneous peptidic release in vivo and generated mutants for all peptides and key elements of the neurosecretory machine. We currently investigate the phenotypes of such neurosecretory mutants in multiple behavioral assays. Altogether our data indicate that secreted peptides released by CSF-cNs in the cerebrospinal fluid could modulate widely physiology via regulating the molecular content of the CSF in addition to locally impact locomotion and posture. Institut du Cerveau et de la Moelle épinière (ICM) 47 bld hospital 75013 Paris France.

ER-mitochondrial stress in the lipin1 deficient myopathy Talha Rashid, Ivan Nemazanyy, Karim Nadra, Timothy Wai, Pacale de Lonlay, Hélène de Foucauld, Mario Pende Hereditary Rhabdomyolysis are rare diseases caused by mutations in metabolic enzymes involved in important metabolic functions such as Glycolysis Glycogenolysis Fatty Acids beta-Oxidation leading to a depletion of ATP. The Lpin1 gene encodes for the phosphatidate phosphatase enzyme Lipin1. Lipin1 can also function as a transcriptional co-regulator after nutrient/mTOR-regulated nuclear translocation. Mutations in Lpin1 are associated with recurrent episodes of Rhabdomyloysis in early childhood but to date the biological mechanisms linking Lipin1 deficiency and Rhabdomyolysis are unclear. One of the Rhabdomyolysis etiologies is Fatty Acids beta-Oxidation deficiency that can be due to dysfunctional mitochondria. We hypothesized that Lipin1 is an important actor of ER/Mitochondria coupling homeostasis which is most probably impaired in Lipin1 deficiency resulting in mitochondrial dysfunction that could in fine triggers Rhabdomyolysis. Institut Necker des Enfants Malades Paris - Sanofi Chilly-Mazarin

Assessing the potential of Host Induced Gene Silencing against a bacterial pathogen Meenu S RASTOGI (1) Magali CHARVIN (1) Venugopal MENDU (2) Lionel NAVARRO (1) During the last decade small RNAs have emerged as critical fine-tuners of immune responses in both plants and animals. For example our laboratory has shown that a dozens of Arabidopsis miRNAs are differentially expressed to orchestrate antibacterial defence. In addition we have reported a major role of the Arabidopsis miRNA pathway in basal immunity and as a corollary have identified bacterial effectors that suppress this small RNA pathway. In the present work we want to extent these findings and investigate whether plant small RNAs could not only fine-tune immune responses but also reprogram bacterial gene expression as part of a natural antibacterial defence. As a first step towards reaching this objective I have investigated whether in planta expression of artificial small RNAs directed against two major pathogenicity factors of a Pseudomonas syringae strain DC3000 could result in host-induced gene silencing (HIGS) and protection against this pathogen. I will present results suggesting that antibacterial HIGS is indeed effective and discuss the potential implication of these findings. (1) RNA interference and plant immunity lab Institut de Biologie de l'École Normale Supérieure (IBENS) Paris 75005 (2) Texas Tech University Department of Plant and Soil Science Box 42122 Lubboc

Maintenance of genome integrity by the DNA damage-dependent PARPs during immunoglobulin class switch recombination Isabelle Robert 1, Léa Gaudot 1, Mélanie Rogier 1, Vincent Heyer 1, Aurélia Noll 2, Françoise Dantzer 2 and Bernardo Reina-San-Martin 1 To mount specific and adapted immune responses B cells assemble and diversify their antibody repertoire through mechanisms involving the formation of programmed DNA damage. Immunoglobulin class switch recombination (CSR) is triggered by DNA lesions induced by activation-induced cytidine deaminase which are processed to double-stranded DNA breaks (DSB). These DSBs activate the DNA damage response and mobilize DNA repair factors including poly(ADP-ribose) polymerases Parp1 Parp2 and Parp3 to promote appropriate DNA repair and efficient long-range recombination. The mechanisms by which Parps protect the recombining immunoglobulin locus against illegitimate recombinations are still elusive. To gain insight we aim to identify their specific cofactors and the targets they modify. By fusing Parps to a promiscuous biotin ligase in primary B cells this proximity-dependent biotinylation strategy gives us an unique opportunity to identify Parp-specific PARylome and interactome during CSR. 1 : Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC) Strasbourg France. 2 : Intégrité du Génome UMR 7175 Ecole Supérieure de Biotechnologie de Strasbourg (ESBS) Strasbourg France.

Identification of genes involved during Class Switch Recombination by Genome-scale CRISPR/Cas9 KnockOut Screen (GeCKO). Mélanie Rogier, Isabelle Robert, Aurore Frey and Bernardo Reina-San-Martin During immune responses immunoglobulin (Ig) class switch recombination (CSR) is initiated by the recruitment of activation-induced cytidine deaminase (AID) to single strand DNA followed by generation of DNA lesions. These lesions are then processed into double-stranded breaks which eventually lead to antibody diversification. However if AID deaminates cytosines at non-Ig loci or if DNA repair is aberrant this can give rise to widespread mutagenesis and cancer development. To understand the regulation of AID activity and CSR mechanisms in an unbiased manner we suggest performing a genome-wide loss-of-function screening using CRISPR/Cas9. We did the proof of principle using a small-scale experiment and data shows that our model is functional. Setting up the genome wide screen using the GeCKO library would allow us to identify the genes involved during CSR and characterize their role. IGBMC

Transcriptional control of immune-responsive genes by DNA methylation and demethylation during Shigella infection L. Schiavolin1, D. Filopon1, C. Bonamy2, B. Sperandio2, P. Sansonetti2, L. Navarro1 Whereas the molecular mechanisms orchestrating the establishment and maintenance of DNA methylation are now relatively well understood little is known about their role and dynamics in biologically relevant processes such as antibacterial defense. In plants recent studies have however filled in some gaps by showing a tight negative control of the plant immune system by DNA methylation. Conversely active DNA demethylation was shown to facilitate the transcriptional activation of functionally relevant immune-responsive genes and to restrict the growth of virulent bacteria in planta. In humans some key immune-responsive genes have also been identified as primary targets of DNA methylation and changes in this epigenetic mark have recently been unraveled at the whole genome level in response to different bacterial pathogens. However very little is known about the impact of DNA methylation and demethylation on the transcriptional regulation of immune-responsive genes during bacterial infection and on the control of bacterial pathogenesis. To address these questions we have used Shigella flexneri and intestinal Caco2/TC7 cell line as a model system of host-bacterial interaction. We first showed that basal expression of a subset of functionally relevant immune-responsive genes is constitutively repressed by DNA methylation as treatment with the demethylating agent 5-Aza-2'-deoxycytidine (5-Aza) triggers their derepression in TC7 cells. Some of these genes require demethylation treatment in order to be induced in response to Shigella others were synergistically activated by 5-Aza and Shigella infection. These results suggest that antibacterial immune responses are finely regulated by DNA methylation and that demethylation could contribute to the transcriptional activation of defense genes during bacterial infection. Consistent with this hypothesis we found that the promoters of several candidate genes were targeted by active DNA demethylase Ten-eleven Translocation (TET) enzymes particularly in regions containing stress-responsive cis-regulatory elements. These observations suggest that removal of DNA methylation might be required to ensure a rapid and pervasive transcription of these genes during Shigella infection potentially by facilitating the recruitment of transcriptional activators onto the chromatin. I will present the experimental approach that we are currently using to test this intriguing hypothesis. Furthermore I will report the ongoing analyses that we are conducting to determine the role of DNA methylation and demethylation in the control of Shigella pathogenesis and to assess whether Shigella type-III effectors could have evolved to interfere with these epigenetic regulatory processes. 1Environmental and evolutionary genomics Immune response & RNA silencing IBENS Paris France 2Unité de Pathogénie Microbienne Moléculaire Institut Pasteur Paris France

The role of epigenetics in the regulation of an EMT-specific alternative splicing program. Alexandre Segelle Reini Fernandez de Luco Alternative splicing is a key mechanism to achieve cell identity that increases the protein diversity with a limited coding genome. Cancer-specific splice variants have been involved in tumour progression. Interestingly emerging evidence suggest an important new role for chromatin conformation and histone modifications in regulating alternative splicing. Even though the mechanisms and real biological impact of this new regulatory layer are still not fully understood. To address the dynamic role of chromatin in establishing and maintaining a new cell-specific splicing program I will use as an inducible model system the well-established epithelial-to-mesenchymal transition (EMT) a paradigm of cell reprogramming relevant to tumour progression and metastasis. Analysis of accurate time-courses during EMT have shown that EMT-specific alternative splicing changes perfectly correlate in time with changes in histone modification enrichment levels along alternatively spliced genes such as FGFR2 CTNND1 and TCF7L2 all involved in key process for EMT progression. Moreover the observed changes in histone mark levels are sequential in time with changes in H3K27me3 and H3K27Ac levels very early in time and a later change in H3K36me3 and H3K4me1 levels when the changes in splicing are well established. Strikingly those very early changes in splicing cannot be explained by changes in expression levels of the splicing regulators involved suggesting that chromatin is playing a role in inducing highly dynamic changes in splicing. To test this hypothesis we are now testing more genes that change splicing early during EMT. Finally to address the biological impact of chromatin in EMT-specific splicing I am adapting the CRISPR/dCas9 system to edit the epigenome and test the effect on splicing of changing gene specifically the levels of specific histone marks. Since the genes I am studying are known to play important roles in EMT progression I will also test the effect of editing splicing-specific histone modifications in the EMT process itself. This research will open new perspectives in the role of histone modifications in the establishment of a new cell-specific alternative splicing program that will finally address whether chromatin's impact on the final splicing outcome is truly biologically meaningful. Institut de Génétique Humaine Laboratoire Composante Epigénétique de l'Epissage Alternatif UMR9002 CNRS Université de Montpellier Montpellier France

A novel reporter system to study siRNA-directed transmission of epigenetic states in Arabidopsis Diep T. N. Tran 1, Magali Charvin 1, Delase Amesefe 1, Venugopal Mendu 1 2, Gersende Lepère 1, Emmanuelle Lastrucci 1, Lionel Navarro 1 In plants RNA-directed DNA methylation (RdDM) is a key epigenetic process that triggers DNA methylation through small interfering RNAs (siRNAs). Although the molecular basis of RdDM establishment maintenance and removal have been extensively studied in plants very little is known about the mechanisms that control siRNA-directed transmission of epigenetic states. We generated a reporter system to monitor siRNA-directed transmission of epigenetic states in the model plant Arabidopsis thaliana. This sensor namely IR-CHL expresses an inverted repeat targeting a specific promoter region of a gene involved in chlorophyll biosynthesis. Constitutive expression of the IR-CHL hairpin in A. thaliana results in primary transformants (T1) having leaves with variegated pattern of chlorosis. We found several evidences indicating the role of RdDM factors in the establishment and maintenance of the chl epiallele. Both siRNAs and DNA methylation at all three contexts (CG CHG and CHH) highly accumulated in the T1 plants carrying 35S::IR-CHL. Non-CG marks and siRNA accumulation are increased in the chlorotic sectors compared to the green sectors of T1 plants suggesting a threshold of siRNAs/DNA methylation to initiate chlorosis. To further investigate the genetic requirements of the IR-CHL-mediated gene silencing we have transformed the hairpin into Arabidopsis mutants impaired in various components of the RdDM pathways. Quantification of the chlorosis showed that several RdDM factors such as NRPE1 are important to produce the variegated phenotype. The contribution of other RdDM components as well as molecular basis for this gene silencing phenomenon will be presented. In addition many leaf chlorotic sectors emerge from the base of petioles suggesting vegetative shoot apical meristem (SAM) as a starting site of the phenotype. Because the hairpin-derived siRNA accumulation is strand-biased we propose that asymmetric siRNA profile in SAM cells is a primary trigger of the chlorotic sectors. To this end IR-CHL will be expressed under a SAM-specific promoter to verify the tissue origin of the silencing. I will also present a scheme of forward genetic screen that will be conducted in an inducible IR-CHL system to identify mutations that prevent de novo epiallelism initiated from vegetative meristems and/or during reproduction. 1. Institut de Biologie de l'Ecole Normale Supérieure 46 rue d'Ulm 75005 Paris France; 2. Current address: Department of Plant and Soil Science Texas Tech University Lubbock Texas USA

Contribution of the Intraflagellar Transport machinery to extra centrosome clustering Benjamin Vitre, Nicolas Taulet, Mélanie Cisnéros, Justine Maurin, Audrey Douanier, Christelle Anguille, Simon Descamps & Bénédicte Delaval. Intraflagellar Transport (IFT) machinery proteins have been well characterized so far for their role in cilia where they act as adaptors between motors and cargos to allow for proper assembly and function of cilia. Interestingly recent evidences introduce new perspectives on cellular processes involving IFT proteins beyond their role in cilia. Indeed studies described roles of IFTs in immune synapse establishment in the regulation of cytoplasmic MT dynamics and in mitosis. In mitotic cells IFTs were shown to be necessary for proper spindle assembly and positioning both in cells and in vivo and a fine characterization of IFT 88 functions during mitosis revealed its importance for the assembly of a robust mitotic spindle by contributing to peripheral microtubules cluster relocalization toward the poles together with dynein. Here we are investigating how IFTs contribute to centrosome clustering in cells harboring supernumerary centrosomes. Overall our work is revealing an important contribution of IFTs to centrosome clustering potentially through interactions with mitotic motors known for their role in clustering. Centre de Recherche de Biologie Cellulaire de Montpellier CNRS - UMR 5237 Montpellier France.

CDK1 unscheduled PLK4-STIL complex assembly in centriole biogenesis Sihem Zitouni1, Maria E Francia, Filipe Leal, Susana-Montenegro, Gouveia Paulo Duarte1 Catarina Nabais, Samuel Gilberto, Daniela Brito, Tyler Moyer, Steffi Kandels-Lewis, Midori Ohta, Daiju Kitagawa, Andrew J Holland, Eric Karsenti, Thierry Lorca, Mariana Lince-Faria1, Monica Bettencourt-Dias1 Centrioles are essential for the assembly of both centrosomes and cilia. The number of centrioles per cell is tightly controlled: cells have either two or four centrioles and their duplication only occurs once per cell cycle in S-phase.A pre-existent "mother" centriole guides the assembly of one "daughter". Mother and daughter centrioles remain physically close to each other until the end of mitosis. This physical proximity is thought to prevent re-duplication. However it was recently shown that in prometaphase the physical constraint imposed in S- phase begins to be relieved by an increased distance between mother and daughter centrioles nonetheless the potential for untimely reduplication is somehow countered. Here we uncover that an additional layer of regulation prevents centriole reduplication in mitosis. We show that CDK1/CyclinB the major mitotic kinase inhibits premature formation of the complex that initiates centriole biogenesis the PLK4- STIL complex by competitively binding STIL and preventing PLK4 from binding it until the end of mitosis. We uncovered this biochemical regulation in two systems: Xenopus egg extracts which are naturally devoid of centrioles and in human cells suggesting that this regulatory mechanism is conserved across species and independent of physical constraints imposed by the presence of centrioles. Additionally our findings can be paralleled in some aspects with DNA replication and centromere specification licensing in which premature initiation and loading respectively is prevented by CDK1 by interfering with the formation of protein complexes critical for triggering these processes. 1- Instituto Gulbenkian de Ciencia

Role of PlexinB2 in Cerebellar Granule Neuron Development Eljo van Battum, Céline Heitz, Alain Chédotal The stereotypical developmental sequence of proliferation migration and differentiation of Cerebellar Granule Neurons (CGNs) the most abundant neurons in the mouse brain mainly takes place during the first postnatal weeks. PlexinB2 (PlxnB2) is expressed exclusively in proliferating CGNs in the outer external granule layer (EGL). PlxnB2-knockout mice show a disrupted lobular and laminar organization of the cerebellum and ectopic proliferating CGNs. It is unknown how PlxnB2 regulates the transition between CGN proliferation and migration. To date research into the role of PlxnB2 in postnatal cerebellar development was difficult due to lethality of PlxnB2-/- mice. Using a novel conditional line (and cerebellum-specific cre-lines) and novel 3D imaging techniques we show for the first time a patch-like residual EGL and a ruffled IGL. Also we discovered that mutant CGNs both in vitro and in vivo display abnormal migration and axon outgrowth. Besides in vivo electroporation 3D-imaging and culturing techniques we perform live-imaging and biochemistry to study how PlxnB2 is involved in CGN maturation and localization during cerebellar development. Sorbonne Universités UPMC Paris 06 INSERM CNRS Institut de la Vision 17 Rue Moreau 75012 Paris France

Identifying the role of DCC in the postnatal visual system Robin Vigouroux, Alain Chedotal, Kim Nguyen-Ba-Charvet A major goal in neuroscience is to understand how sensory information is processed. The mammalian visual system is an ideal model to address this question. The retina is a highly organized structure divided into 3 distinct nuclear layers and 2 synaptic areas. Light is converted by photoreceptors into an electrical signal collected by bipolar cells and then relayed to Retinal Ganglion Cells (RGC) which exit the retina and innervate different brain targets. RGCs from the retina project to multiple visual brain nuclei via a single tract the optic nerve. The transmembrane receptor Deleted in Colorectal Cancer (DCC) is expressed by RGCs and has been shown to be critical for the formation of the optic nerve by responding to its ligand Netrin-1 expressed at the optic disc. Indeed both Netrin-1 hypomorphs and DCC knockout mice show optic nerve hypoplasia. Due to the lethality of both mutants the study of these molecules has been restricted to embryonic stages. However at birth the visual system is far from being fully developped. Indeed half of the retinal cell types still have to differentiate. Moreover axonal arborization and refinement in brain nuclei all occur in the first postnatal week. Our data shows that contrary to what was previously described DCC expression within the retina is much broader. Indeed DCC expression is initially restricted to differentiating RGCs but is then highly expressed in both nuclear layers as well as both synaptic layers of the retina in early postnatal stages. To understand the role of DCC within the retina we created a conditional deletion of DCC under the Dickopf-3 (Dkk3) promoter which is expressed in retinal progenitors cells Dkk3:Cre;DCClox/lox. These mutants are viable and adult mice show a dramatic thinning of the retina characterized by the absence of an RGC layer as well as photoreceptor degeneration. We are currently adopting both genetic and viral approaches to remove DCC in particular retinal neurons to study the precise mechanism responsible for the degeneration of both RGCs and Photoreceptors. Institut de la Vision Université Pierre et Marie Curie Paris

TBA Rafal Ciosk lab

2nd FSER meeting - version publique

More creations to inspire you

ASTL

TOM DOLAN

BASIL RESTAURANT PRESENTATION

AC/DC

ENGLISH IRREGULAR VERBS

ALL THE THINGS

SANTIAGOVR_EN

Transcript