Plateforme d’imagerie Cellulaire et Tissulaire

Publications

Année de publication : 2018

Antoine Hocher, Myriam Ruault, Petra Kaferle, Marc Descrimes, Mickaël Garnier, Antonin Morillon, Angela Taddei (2018 Oct 26)

Expanding heterochromatin reveals discrete subtelomeric domains delimited by chromatin landscape transitions.

Genome research : DOI : gr.236554.118 En savoir plus
Résumé

The eukaryotic genome is divided into chromosomal domains of heterochromatin and euchromatin. Transcriptionally silent heterochromatin is found at subtelomeric regions, leading to the telomeric position effect (TPE) in yeast fly and human. Heterochromatin generally initiates and spreads from defined loci, and diverse mechanisms prevent the ectopic spread of heterochromatin into euchromatin. Here, we overexpressed the silencing factor Sir3 at varying levels in yeast and found that Sir3 spreads into Extended Silent Domains (ESDs), eventually reaching saturation at subtelomeres. We observed the spread of Sir3 into subtelomeric domains associated with specific histone marks in wild-type cells and stopping at zones of histone mark transitions including H3K79 tri-methylation levels. Our study shows that the conserved H3K79 methyltransferase Dot1 is essential in restricting Sir3 spread beyond ESDs, thus ensuring viability upon overexpression of Sir3. Lastly, our analyses of published data demonstrate how ESDs unveil uncharacterized discrete domains isolating structural and functional subtelomeric features from the rest of the genome. Our work offers a new approach on how to separate subtelomeres from the core chromosome.

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Marine Fanny Garrido, Nicolas Jp Martin, Matthieu Bertrand, Catherine Gaudin, Frederic Commo, Nassif El Kalaany, Nader Al Nakouzi, Ladan Fazli, Elaine Del Nery, Jacques Camonis, Franck Perez, Stéphanie Lerondel, Alain LE Pape, Martin E Gleave, Yohann Loriot, Laurent Desaubry, Stephan Vagner, Karim Fizazi, Anne Chauchereau (2018 Oct 15)

Regulation of eIF4F translation initiation complex by the peptidyl prolyl isomerase FKBP7 in taxane-resistant prostate cancer.

Clinical cancer research : an official journal of the American Association for Cancer Research : DOI : clincanres.0704.2018 En savoir plus
Résumé

Targeted therapies that use the signaling pathways involved in prostate cancer are required to overcome chemoresistance and improve treatment outcomes for men. Molecular chaperones play a key role in the regulation of protein homeostasis and are potential targets for overcoming chemoresistance.

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Géraldine Gentric, Yann Kieffer, Virginie Mieulet, Oumou Goundiam, Claire Bonneau, Fariba Nemati, Ilse Hurbain, Graca Raposo, Tatiana Popova, Marc-Henri Stern, Valérie Lallemand-Breitenbach, Sebastian Müller, Tatiana Cañeque, Raphaël Rodriguez, Anne Vincent-Salomon, Hugues de Thé, Rodrigue Rossignol, Fatima Mechta-Grigoriou (2018 Sep 25)

PML-Regulated Mitochondrial Metabolism Enhances Chemosensitivity in Human Ovarian Cancers.

Cell metabolism : 156-173.e10 : DOI : S1550-4131(18)30567-9 En savoir plus
Résumé

High-grade serous ovarian cancer (HGSOC) remains an unmet medical challenge. Here, we unravel an unanticipated metabolic heterogeneity in HGSOC. By combining proteomic, metabolomic, and bioergenetic analyses, we identify two molecular subgroups, low- and high-OXPHOS. While low-OXPHOS exhibit a glycolytic metabolism, high-OXPHOS HGSOCs rely on oxidative phosphorylation, supported by glutamine and fatty acid oxidation, and show chronic oxidative stress. We identify an important role for the PML-PGC-1α axis in the metabolic features of high-OXPHOS HGSOC. In high-OXPHOS tumors, chronic oxidative stress promotes aggregation of PML-nuclear bodies, resulting in activation of the transcriptional co-activator PGC-1α. Active PGC-1α increases synthesis of electron transport chain complexes, thereby promoting mitochondrial respiration. Importantly, high-OXPHOS HGSOCs exhibit increased response to conventional chemotherapies, in which increased oxidative stress, PML, and potentially ferroptosis play key functions. Collectively, our data establish a stress-mediated PML-PGC-1α-dependent mechanism that promotes OXPHOS metabolism and chemosensitivity in ovarian cancer.

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Jérôme Boulanger, Nelly Pustelnik, Laurent Condat, Lucie Sengmanivong, Tristan Piolot (2018 Aug 8)

Nonsmooth Convex Optimization for Structured Illumination Microscopy Image Reconstruction.

Inverse problems : 095004 : DOI : 10.1088/1361-6420/aaccca En savoir plus
Résumé

In this paper, we propose a new approach for structured illumination microscopy image reconstruction. We first introduce the principles of this imaging modality and describe the forward model. We then propose the minimization of nonsmooth convex objective functions for the recovery of the unknown image. In this context, we investigate two data-fitting terms for Poisson-Gaussian noise and introduce a new patch-based regularization method. This approach is tested against other regularization approaches on a realistic benchmark. Finally, we perform some test experiments on images acquired on two different microscopes.

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Verweij Frederik J, Revenu Celine, Arras Guillaume, Dingli Florent, Loew Damarys, Follain Gautier, Allio Guillaume, Goetz Jacky G., Herbomel Philippe, Del Bene Filippo, Raposo Graça, van Niel Guillaume (2018 Jul 30)

Live tracking of inter-organ communication by endogenous exosomes in vivo

BioRxiv : DOI : 10.1101/380311 En savoir plus
Résumé

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Alexandre Beber, Maryam Alqabandi, Coline Prevost, Fanny Viars, Daniel Levy, Patricia Bassereau, Aurélie Bertin*, Stéphanie Mangenot* (2018 Jul 16)

Septin-based readout of PI(4,5)P2 incorporation into membranes of giant unilamellar vesicles

Cytoskeleton : DOI : 10.1002/cm.21480 En savoir plus
Résumé

Septins constitute a novel class of cytoskeletal proteins. Budding yeast septins self-assemble into non-polar filaments bound to the inner plasma membrane through specific interactions with L- α-phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2). Biomimetic in vitro assays using Giant Unilamellar Vesicles (GUVs) are relevant tools to dissect and reveal insights in proteins-lipids interactions, membrane mechanics and curvature sensitivity. GUVs doped with PI(4,5)P2 are challenging to prepare. This report is dedicated to optimize the incorporation of PI(4,5)P2 lipids into GUVs by probing the proteins-PI(4,5)P2 GUVs interactions. We show that the interaction between budding yeast septins and PI(4,5)P2 is more specific than using usual reporters (phospholipase  Cd1). Septins have thus been chosen as reporters to probe the proper incorporation of PI(4,5)P2 into giant vesicles. We have shown that electro-formation on platinum wires is the most appropriate method to achieve an optimal septin-lipid interaction resulting from an optimal PI(4,5)P2 incorporation for which, we have optimized the growth conditions. Finally, we have shown that PI(4,5)P2 GUVs have to be used within a few hours after their preparation. Indeed, over time, PI(4,5)P2 is expelled from he GUV membrane and the PI(4,5)P2 concentration in the bilayer decreases .

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Sara El Hoss, Michaël Dussiot, Olivier Renaud, Valentine Brousse, Wassim El Nemer (2018 Jun 9)

A novel non-invasive method to measure splenic filtration function in humans.

Haematologica : e436-e439 : DOI : 10.3324/haematol.2018.188920 En savoir plus
Résumé

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Léa Ripoll, Xavier Heiligenstein, Ilse Hurbain, Lia Domingues, Florent Figon, Karl J Petersen, Megan K Dennis, Anne Houdusse, Michael S Marks, Graça Raposo, Cédric Delevoye (2018 Jun 8)

Myosin VI and branched actin filaments mediate membrane constriction and fission of melanosomal tubule carriers.

The Journal of cell biology : 2709-2726 : DOI : 10.1083/jcb.201709055 En savoir plus
Résumé

Vesicular and tubular transport intermediates regulate organellar cargo dynamics. Transport carrier release involves local and profound membrane remodeling before fission. Pinching the neck of a budding tubule or vesicle requires mechanical forces, likely exerted by the action of molecular motors on the cytoskeleton. Here, we show that myosin VI, together with branched actin filaments, constricts the membrane of tubular carriers that are then released from melanosomes, the pigment containing lysosome-related organelles of melanocytes. By combining superresolution fluorescence microscopy, correlative light and electron microscopy, and biochemical analyses, we find that myosin VI motor activity mediates severing by constricting the neck of the tubule at specific melanosomal subdomains. Pinching of the tubules involves the cooperation of the myosin adaptor optineurin and the activity of actin nucleation machineries, including the WASH and Arp2/3 complexes. The fission and release of these tubules allows for the export of components from melanosomes, such as the SNARE VAMP7, and promotes melanosome maturation and transfer to keratinocytes. Our data reveal a new myosin VI- and actin-dependent membrane fission mechanism required for organelle function.

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Anna M Lilja, Veronica Rodilla, Mathilde Huyghe, Edouard Hannezo, Camille Landragin, Olivier Renaud, Olivier Leroy, Steffen Rulands, Benjamin D Simons, Silvia Fre (2018 May 23)

Clonal analysis of Notch1-expressing cells reveals the existence of unipotent stem cells that retain long-term plasticity in the embryonic mammary gland.

Nature cell biology : DOI : 10.1038/s41556-018-0108-1 En savoir plus
Résumé

Recent lineage tracing studies have revealed that mammary gland homeostasis relies on unipotent stem cells. However, whether and when lineage restriction occurs during embryonic mammary development, and which signals orchestrate cell fate specification, remain unknown. Using a combination of in vivo clonal analysis with whole mount immunofluorescence and mathematical modelling of clonal dynamics, we found that embryonic multipotent mammary cells become lineage-restricted surprisingly early in development, with evidence for unipotency as early as E12.5 and no statistically discernable bipotency after E15.5. To gain insights into the mechanisms governing the switch from multipotency to unipotency, we used gain-of-function Notch1 mice and demonstrated that Notch activation cell autonomously dictates luminal cell fate specification to both embryonic and basally committed mammary cells. These functional studies have important implications for understanding the signals underlying cell plasticity and serve to clarify how reactivation of embryonic programs in adult cells can lead to cancer.

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Année de publication : 2017

France Rose, Sreetama Basu, Elton Rexhepaj, Anne Chauchereau, Elaine Del Nery, Auguste Genovesio (2017 Nov 5)

Compound Functional Prediction Using Multiple Unrelated Morphological Profiling Assays.

SLAS technology : 243-251 : DOI : 10.1177/2472630317740831 En savoir plus
Résumé

Phenotypic cell-based assays have proven to be efficient at discovering first-in-class therapeutic drugs mainly because they allow for scanning a wide spectrum of possible targets at once. However, despite compelling methodological advances, posterior identification of a compound’s mechanism of action (MOA) has remained difficult and highly refractory to automated analyses. Methods such as the cell painting assay and multiplexing fluorescent dyes to reveal broadly relevant cellular components were recently suggested for MOA prediction. We demonstrated that adding fluorescent dyes to a single assay has limited impact on MOA prediction accuracy, as monitoring only the nuclei stain could reach compelling levels of accuracy. This observation suggested that multiplexed measurements are highly correlated and nuclei stain could possibly reflect the general state of the cell. We then hypothesized that combining unrelated and possibly simple cell-based assays could bring a solution that would be biologically and technically more relevant to predict a drug target than using a single assay multiplexing dyes. We show that such a combination of past screen data could rationally be reused in screening facilities to train an ensemble classifier to predict drug targets and prioritize a possibly large list of unknown compound hits at once.

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Stéphanie Miserey-Lenkei, Hugo Bousquet, Olena Pylypenko, Sabine Bardin, Ariane Dimitrov, Gaëlle Bressanelli, Raja Bonifay, Vincent Fraisier, Catherine Guillou, Cécile Bougeret, Anne Houdusse, Arnaud Echard, Bruno Goud (2017 Nov 3)

Coupling fission and exit of RAB6 vesicles at Golgi hotspots through kinesin-myosin interactions.

Nature communications : 1254 : DOI : 10.1038/s41467-017-01266-0 En savoir plus
Résumé

The actin and microtubule cytoskeletons play important roles in Golgi structure and function, but how they are connected remain poorly known. In this study, we investigated whether RAB6 GTPase, a Golgi-associated RAB involved in the regulation of several transport steps at the Golgi level, and two of its effectors, Myosin IIA and KIF20A participate in the coupling between actin and microtubule cytoskeleton. We have previously shown that RAB6-Myosin IIA interaction is critical for the fission of RAB6-positive transport carriers from Golgi/TGN membranes. Here we show that KIF20A is also involved in the fission process and serves to anchor RAB6 on Golgi/TGN membranes near microtubule nucleating sites. We provide evidence that the fission events occur at a limited number of hotspots sites. Our results suggest that coupling between actin and microtubule cytoskeletons driven by Myosin II and KIF20A ensures the spatial coordination between RAB6-positive vesicles fission from Golgi/TGN membranes and their exit along microtubules.

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Charlène Delestre-Delacour, Ophélie Carmon, Fanny Laguerre, Catherine Estay-Ahumada, Maïté Courel, Salah Elias, Lydie Jeandel, Margarita Villar Rayo, Juan R Peinado, Lucie Sengmanivong, Stéphane Gasman, Evelyne Coudrier, Youssef Anouar, Maité Montero-Hadjadje (2017 Jul 14)

Myosin 1b and F-actin are involved in the control of secretory granule biogenesis.

Scientific reports : 5172 : DOI : 10.1038/s41598-017-05617-1 En savoir plus
Résumé

Hormone secretion relies on secretory granules which store hormones in endocrine cells and release them upon cell stimulation. The molecular events leading to hormone sorting and secretory granule formation at the level of the TGN are still elusive. Our proteomic analysis of purified whole secretory granules or secretory granule membranes uncovered their association with the actomyosin components myosin 1b, actin and the actin nucleation complex Arp2/3. We found that myosin 1b controls the formation of secretory granules and the associated regulated secretion in both neuroendocrine cells and chromogranin A-expressing COS7 cells used as a simplified model of induced secretion. We show that F-actin is also involved in secretory granule biogenesis and that myosin 1b cooperates with Arp2/3 to recruit F-actin to the Golgi region where secretory granules bud. These results provide the first evidence that components of the actomyosin complex promote the biogenesis of secretory granules and thereby regulate hormone sorting and secretion.

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Jérémy Magescas, Lucie Sengmanivong, Amandine Viau, Adeline Mayeux, Tien Dang, Martine Burtin, Ulf J Nilsson, Hakon Leffler, Françoise Poirier, Fabiola Terzi, Delphine Delacour (2017 May 5)

Spindle pole cohesion requires glycosylation-mediated localization of NuMA.

Scientific reports : 1474 : DOI : 10.1038/s41598-017-01614-6 En savoir plus
Résumé

Glycosylation is critical for the regulation of several cellular processes. One glycosylation pathway, the unusual O-linked β-N-acetylglucosamine glycosylation (O-GlcNAcylation) has been shown to be required for proper mitosis, likely through a subset of proteins that are O-GlcNAcylated during metaphase. As lectins bind glycosylated proteins, we asked if specific lectins interact with mitotic O-GlcNAcylated proteins during metaphase to ensure correct cell division. Galectin-3, a small soluble lectin of the Galectin family, is an excellent candidate, as it has been previously described as a transient centrosomal component in interphase and mitotic epithelial cells. In addition, it has recently been shown to associate with basal bodies in motile cilia, where it stabilizes the microtubule-organizing center (MTOC). Using an experimental mouse model of chronic kidney disease and human epithelial cell lines, we investigate the role of Galectin-3 in dividing epithelial cells. Here we find that Galectin-3 is essential for metaphase where it associates with NuMA in an O-GlcNAcylation-dependent manner. We provide evidence that the NuMA-Galectin-3 interaction is important for mitotic spindle cohesion and for stable NuMA localization to the spindle pole, thus revealing that Galectin-3 is a novel contributor to epithelial mitotic progress.

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Perrine Paul-Gilloteaux, Xavier Heiligenstein, Martin Belle, Marie-Charlotte Domart, Banafshe Larijani, Lucy Collinson, Graça Raposo, Jean Salamero (2017 Feb 1)

eC-CLEM: flexible multidimensional registration software for correlative microscopies.

Nature methods : 102-103 : DOI : 10.1038/nmeth.4170 En savoir plus
Résumé

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Claire François-Martin, James E Rothman, Frederic Pincet (2017 Jan 25)

Low energy cost for optimal speed and control of membrane fusion.

Proceedings of the National Academy of Sciences of the United States of America : 1238-1241 : DOI : 10.1073/pnas.1621309114 En savoir plus
Résumé

Membrane fusion is the cell’s delivery process, enabling its many compartments to receive cargo and machinery for cell growth and intercellular communication. The overall activation energy of the process must be large enough to prevent frequent and nonspecific spontaneous fusion events, yet must be low enough to allow it to be overcome upon demand by specific fusion proteins [such as soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs)]. Remarkably, to the best of our knowledge, the activation energy for spontaneous bilayer fusion has never been measured. Multiple models have been developed and refined to estimate the overall activation energy and its component parts, and they span a very broad range from 20 kBT to 150 kBT, depending on the assumptions. In this study, using a bulk lipid-mixing assay at various temperatures, we report that the activation energy of complete membrane fusion is at the lowest range of these theoretical values. Typical lipid vesicles were found to slowly and spontaneously fully fuse with activation energies of ∼30 kBT Our data demonstrate that the merging of membranes is not nearly as energy consuming as anticipated by many models and is ideally positioned to minimize spontaneous fusion while enabling rapid, SNARE-dependent fusion upon demand.

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