Université PSL



Laboratoire :
Auteur :
Revue :
Année :
mTOR and S6K1 drive polycystic kidney by the control of Afadin-dependent oriented cell division
Laboratoire Biologie cellulaire systémique de la polarité et de la division - Martina Bonucci, Nicolas Kuperwasser, Serena Barbe, Vonda Koka, Delphine de Villeneuve, Chi Zhang, Nishit Srivastava, Xiaoying Jia, Matthew P Stokes, Frank Bienaimé, Virginie Verkarre, Jean Baptiste Lopez, Fanny Jaulin, Marco Pontoglio, Fabiola Terzi, Be
Nature Communications - - DOI : 10.1038/s41467-020-16978-z - 2020
mTOR activation is essential and sufficient to cause polycystic kidneys in Tuberous Sclerosis Complex (TSC) and other genetic disorders. In disease models, a sharp increase of proliferation and cyst formation correlates with a dramatic loss of oriented cell division (OCD). We find that OCD distortion is intrinsically due to S6 kinase 1 (S6K1) activation. The concomitant loss of S6K1 in Tsc1-mutant mice restores OCD but does not decrease hyperproliferation, leading to non-cystic harmonious hyper growth of kidneys. Mass spectrometry-based phosphoproteomics for S6K1 substrates revealed Afadin, a known component of cell-cell junctions required to couple intercellular adhesions and cortical cues to spindle orientation. Afadin is directly phosphorylated by S6K1 and abnormally decorates the apical surface of Tsc1-mutant cells with E-cadherin and α-catenin. Our data reveal that S6K1 hyperactivity alters centrosome positioning in mitotic cells, affecting oriented cell division and promoting kidney cysts in conditions of mTOR hyperactivity.
Mechanochemical Crosstalk Produces Cell-Intrinsic Patterning of the Cortex to Orient the Mitotic Spindle.
Laboratoire Biologie cellulaire systémique de la polarité et de la division - Andrea Dimitracopoulos, Pragya Srivastava, Agathe Chaigne, Zaw Win, Roie Shlomovitz, Oscar M Lancaster, Maël Le Berre, Matthieu Piel, Kristian Franze, Guillaume Salbreux, Buzz Baum
Current biology - - DOI : S0960-9822(20)30984-2 - 2020
Proliferating animal cells are able to orient their mitotic spindles along their interphase cell axis, setting up the axis of cell division, despite rounding up as they enter mitosis. This has previously been attributed to molecular memory and, more specifically, to the maintenance of adhesions and retraction fibers in mitosis [1-6], which are thought to act as local cues that pattern cortical Gαi, LGN, and nuclear mitotic apparatus protein (NuMA) [3, 7-18]. This cortical machinery then recruits and activates Dynein motors, which pull on astral microtubules to position the mitotic spindle. Here, we reveal a dynamic two-way crosstalk between the spindle and cortical motor complexes that depends on a Ran-guanosine triphosphate (GTP) signal [12], which is sufficient to drive continuous monopolar spindle motion independently of adhesive cues in flattened human cells in culture. Building on previous work [1, 12, 19-23], we implemented a physical model of the system that recapitulates the observed spindle-cortex interactions. Strikingly, when this model was used to study spindle dynamics in cells entering mitosis, the chromatin-based signal was found to preferentially clear force generators from the short cell axis, so that cortical motors pulling on astral microtubules align bipolar spindles with the interphase long cell axis, without requiring a fixed cue or a physical memory of interphase shape. Thus, our analysis shows that the ability of chromatin to pattern the cortex during the process of mitotic rounding is sufficient to translate interphase shape into a cortical pattern that can be read by the spindle, which then guides the axis of cell division.
ATR is essential for preservation of cell mechanics and nuclear integrity during interstitial migration
Laboratoire Biologie cellulaire systémique de la polarité et de la division - Gururaj Rao Kidiyoor, Qingsen Li, Giulia Bastianello, Christopher Bruhn, Irene Giovannetti, Adhil Mohamood, Galina V. Beznoussenko, Alexandre Mironov, Matthew Raab, Matthieu Piel, Umberto Restuccia, Vittoria Matafora, Angela Bachi, Sara
Nature Communications - 11 4828 - https://doi.org/10.1038/s41467-020-18580-9 - 2020
ATR responds to mechanical stress at the nuclear envelope and mediates envelope-associated repair of aberrant topological DNA states. By combining microscopy, electron microscopic analysis, biophysical and in vivo models, we report that ATR-defective cells exhibit altered nuclear plasticity and YAP delocalization. When subjected to mechanical stress or undergoing interstitial migration, ATR-defective nuclei collapse accumulating nuclear envelope ruptures and perinuclear cGAS, which indicate loss of nuclear envelope integrity, and aberrant perinuclear chromatin status. ATR-defective cells also are defective in neuronal migration during development and in metastatic dissemination from circulating tumor cells. Our findings indicate that ATR ensures mechanical coupling of the cytoskeleton to the nuclear envelope and accompanying regulation of envelope-chromosome association. Thus the repertoire of ATR-regulated biological processes extends well beyond its canonical role in triggering biochemical implementation of the DNA damage response.

The nucleus acts as a ruler tailoring cell responses to spatial constraints
Laboratoire Biologie cellulaire systémique de la polarité et de la division - A. J. Lomakin, C. J. Cattin, D. Cuvelier, Z. Alraies, M. Molina. Nader, N. Sri
Science - 6514 370 - DOI: 10.1126/science.aba2894 - 2020
Single cells continuously experience and react to mechanical challenges in three-dimensional tissues. Spatial constraints in dense tissues, physical activity, and injury all impose changes in cell shape. How cells can measure shape deformations to ensure correct tissue development and homeostasis remains largely unknown (see the Perspective by Shen and Niethammer). Working independently, Venturini et al. and Lomakin et al. now show that the nucleus can act as an intracellular ruler to measure cellular shape variations. The nuclear envelope provides a gauge of cell deformation and activates a mechanotransduction pathway that controls actomyosin contractility and migration plasticity. The cell nucleus thereby allows cells to adapt their behavior to the local tissue microenvironment.
The impact of frost-damage on the quality and quantity of the secreted antigen-specific IgG repertoire
Laboratoire Colloïdes et Matériaux Divisés - Author links open overlay panelMagdaRybczynskaaJeanBaudryaEyerKlaus
Vaccine - 38(33) 5337-5342 - https://doi.org/10.1016/j.vaccine.2020.05.066 - 2020
Freezing of alum-based vaccines drastically alters their colloidal composition and leads to irreversible cluster formation. The loss of stability is well described, but the impact of frost damage on the functionality of the induced and secreted antibody repertoire has not been studied in detail. We therefore applied our single-cell measurement platform to extract the frequencies of Immunoglobulin G-secreting cells in combination with individual secretion rates and affinities. We showed that, frost-damaged or not, the tested vaccine was able to generate similar frequencies of total and antigen-affine IgG-secreting cells. Additionally, the frost-damaged vaccine stimulated a similar T-cell cytokine secretion pattern when compared to the regularly stored vaccine. However, frost-damaged vaccines induced no efficient affinity maturation and a complete collapse of the affinity distribution was observed. This study unveiled the impact of frost-damage to alum-based vaccines on the induced secreted antibody repertoire, and illustrated the power of functional single-antibody analysis.

Dynamic single-cell phenotyping of immune cells using the microfluidic platform DropMap
Laboratoire Colloïdes et Matériaux Divisés - Yacine Bounab, Klaus Eyer, Sophie Dixneuf, Magda Rybczynska, Cécile Chauvel, Maxime Mistretta, Trang Tran, Nathan Aymerich, Guilhem Chenon, Jean-François Llitjos, Fabienne Venet, Guillaume Monneret, Iain A. Gillespie, Pierre Cortez, Virginie Moucadel, Al
Nature Protocols - 15 2920–2955 - https://www.nature.com/articles/s41596-020-0354-0 - 2020
Characterization of immune responses is currently hampered by the lack of systems enabling quantitative and dynamic phenotypic characterization of individual cells and, in particular, analysis of secreted proteins such as cytokines and antibodies. We recently developed a simple and robust microfluidic platform, DropMap, to measure simultaneously the kinetics of secretion and other cellular characteristics, including endocytosis activity, viability and expression of cell-surface markers, from tens of thousands of single immune cells. Single cells are compartmentalized in 50-pL droplets and analyzed using fluorescence microscopy combined with an immunoassay based on fluorescence relocation to paramagnetic nanoparticles aligned to form beadlines in a magnetic field. The protocol typically takes 8–10 h after preparation of microfluidic chips and chambers, which can be done in advance. By contrast, enzyme-linked immunospot (ELISPOT), flow cytometry, time-of-flight mass cytometry (CyTOF), and single-cell sequencing enable only end-point measurements and do not enable direct, quantitative measurement of secreted proteins. We illustrate how this system can be used to profile downregulation of tumor necrosis factor-α (TNF-α) secretion by single monocytes in septic shock patients, to study immune responses by measuring rates of cytokine secretion from single T cells, and to measure affinity of antibodies secreted by single B cells.
The Quantitative Assessment of the Secreted IgG Repertoire after Recall to Evaluate the Quality of Immunizations
Laboratoire Colloïdes et Matériaux Divisés - Klaus Eyer, Carlos Castrillon, Guilhem Chenon, Jérôme Bibette, Pierre Bruhns, Andrew D. Griffiths and Jean Baudry
The Journal of Immunology - 205 8 - DOI: https://doi.org/10.4049/jimmunol.2000112 - 2020
One of the major goals of vaccination is to prepare the body to rapidly secrete specific Abs during an infection. Assessment of the vaccine quality is often difficult to perform, as simple measurements like Ab titer only partly correlate with protection. Similarly, these simple measurements are not always sensitive to changes in the preceding immunization scheme. Therefore, we introduce in this paper a new, to our knowledge, method to assay the quality of immunization schemes for mice: shortly after a recall with pure Ag, we analyze the frequencies of IgG-secreting cells (IgG-SCs) in the spleen, as well as for each cells, the Ag affinity of the secreted Abs. We observed that after recall, appearance of the IgG-SCs within the spleen of immunized mice was fast (<24 h) and this early response was free of naive IgG-SCs. We further confirmed that our phenotypic analysis of IgG-SCs after recall strongly correlated with the different employed immunization schemes. Additionally, a phenotypic comparison of IgG-SCs presented in the spleen during immunization or after recall revealed similarities but also significant differences. The developed approach introduced a novel (to our knowledge), quantitative, and functional highly resolved alternative to study the quality of immunizations.
Metabolic cost of rapid adaptation of single yeast cells
Laboratoire Macromolécules et Microsystèmes en Biologie et Médecine - Gabrielle Woronoff, Philippe Nghe, Jean Baudry, Laurent Boitard, Erez Braun, Andrew D. Griffiths, and Jérôme Bibette
PNAS - 117 (20) 10660-10666 - https://doi.org/10.1073/pnas.1913767117 - 2020
Cells can rapidly adapt to changing environments through nongenetic processes; however, the metabolic cost of such adaptation has never been considered. Here we demonstrate metabolic coupling in a remarkable, rapid adaptation process (1 in 1,000 cells adapt per hour) by simultaneously measuring metabolism and division of thousands of individual Saccharomyces cerevisiae cells using a droplet microfluidic system: droplets containing single cells are immobilized in a two-dimensional (2D) array, with osmotically induced changes in droplet volume being used to measure cell metabolism, while simultaneously imaging the cells to measure division. Following a severe challenge, most cells, while not dividing, continue to metabolize, displaying a remarkably wide diversity of metabolic trajectories from which adaptation events can be anticipated. Adaptation requires a characteristic amount of energy, indicating that it is an active process. The demonstration that metabolic trajectories predict a priori adaptation events provides evidence of tight energetic coupling between metabolism and regulatory reorganization in adaptation. This process allows S. cerevisiae to adapt on a physiological timescale, but related phenomena may also be important in other processes, such as cellular differentiation, cellular reprogramming, and the emergence of drug resistance in cancer.
High-throughput single-cell activity-based screening and sequencing of antibodies using droplet microfluidics
Laboratoire Macromolécules et Microsystèmes en Biologie et Médecine - Annabelle Gérard, Adam Woolfe, […]Colin Brenan
Nat Biotechnol. - 38 715–721 - https://doi.org/10.1038/s41587-020-0466-7 - 2020
Mining the antibody repertoire of plasma cells and plasmablasts could enable the discovery of useful antibodies for therapeutic or research purposes1. We present a method for high-throughput, single-cell screening of IgG-secreting primary cells to characterize antibody binding to soluble and membrane-bound antigens. CelliGO is a droplet microfluidics system that combines high-throughput screening for IgG activity, using fluorescence-based in-droplet single-cell bioassays2, with sequencing of paired antibody V genes, using in-droplet single-cell barcoded reverse transcription. We analyzed IgG repertoire diversity, clonal expansion and somatic hypermutation in cells from mice immunized with a vaccine target, a multifunctional enzyme or a membrane-bound cancer target. Immunization with these antigens yielded 100–1,000 IgG sequences per mouse. We generated 77 recombinant antibodies from the identified sequences and found that 93% recognized the soluble antigen and 14% the membrane antigen. The platform also allowed recovery of ~450–900 IgG sequences from ~2,200 IgG-secreting activated human memory B cells, activated ex vivo, demonstrating its versatility.
Quantitative modeling of the effect of antigen dosage on B-cell affinity distributions in maturating germinal centers
Laboratoire Macromolécules et Microsystèmes en Biologie et Médecine - Marco Molari, Klaus Eyer, Jean Baudry, Simona Cocco, Rémi Monasson
e-Life - 1 619 - DOI: 10.7554/eLife.55678 - 2020
Affinity maturation is a complex dynamical process allowing the immune system to generate antibodies capable of recognizing antigens. We introduce a model for the evolution of the distribution of affinities across the antibody population in germinal centers. The model is amenable to detailed mathematical analysis and gives insight on the mechanisms through which antigen availability controls the rate of maturation and the expansion of the antibody population. It is also capable, upon maximum-likelihood inference of the parameters, to reproduce accurately the distributions of affinities of IgG-secreting cells we measure in mice immunized against Tetanus Toxoid under largely varying conditions (antigen dosage, delay between injections). Both model and experiments show that the average population affinity depends non-monotonically on the antigen dosage. We show that combining quantitative modeling and statistical inference is a concrete way to investigate biological processes underlying affinity maturation (such as selection permissiveness), hardly accessible through measurements.

430 publications.