Polarité, division et morphogenèse

Publications de l’équipe

Année de publication : 2015

Boris Guirao, Stéphane U Rigaud, Floris Bosveld, Anaïs Bailles, Jesús López-Gay, Shuji Ishihara, Kaoru Sugimura, François Graner, Yohanns Bellaïche (2015 Dec 15)

Unified quantitative characterization of epithelial tissue development.

eLife : DOI : 10.7554/eLife.08519 En savoir plus
Résumé

Understanding the mechanisms regulating development requires a quantitative characterization of cell divisions, rearrangements, cell size and shape changes, and apoptoses. We developed a multiscale formalism that relates the characterizations of each cell process to tissue growth and morphogenesis. Having validated the formalism on computer simulations, we quantified separately all morphogenetic events in the Drosophila dorsal thorax and wing pupal epithelia to obtain comprehensive statistical maps linking cell and tissue scale dynamics. While globally cell shape changes, rearrangements and divisions all significantly participate in tissue morphogenesis, locally, their relative participations display major variations in space and time. By blocking division we analyzed the impact of division on rearrangements, cell shape changes and tissue morphogenesis. Finally, by combining the formalism with mechanical stress measurement, we evidenced unexpected interplays between patterns of tissue elongation, cell division and stress. Our formalism provides a novel and rigorous approach to uncover mechanisms governing tissue development.

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Floris Bosveld, Boris Guirao, Zhimin Wang, Mathieu Rivière, Isabelle Bonnet, François Graner, Yohanns Bellaïche (2015 Jul 5)

Modulation of junction tension by tumor suppressors and proto-oncogenes regulates cell-cell contacts.

Development (Cambridge, England) : 623-34 : DOI : 10.1242/dev.127993 En savoir plus
Résumé

Tumor suppressors and proto-oncogenes play crucial roles in tissue proliferation. Furthermore, de-regulation of their functions is deleterious to tissue architecture and can result in the sorting of somatic rounded clones minimizing their contact with surrounding wild-type (wt) cells. Defects in the shape of somatic clones correlate with defects in proliferation, cell affinity, cell-cell adhesion, oriented cell division and cortical contractility. Combining genetics, live-imaging, laser ablation and computer simulations, we aim to analyze whether distinct or similar mechanisms can account for the common role of tumor suppressors and proto-oncogenes in cell-cell contact regulation. In Drosophila epithelia, the tumor suppressors Fat (Ft) and Dachsous (Ds) regulate cell proliferation, tissue morphogenesis, planar cell polarity and junction tension. By analyzing the evolution over time of ft mutant cells and clones, we show that ft clones reduce their cell-cell contacts with the surrounding wt tissue in the absence of concomitant cell divisions and over-proliferation. This contact reduction depends on opposed changes of junction tensions in the clone bulk and its boundary with neighboring wt tissue. More generally, either clone bulk or boundary junction tension is modulated by the activation of Yorkie, Myc and Ras, yielding similar contact reductions with wt cells. Together, our data highlight mechanical roles for proto-oncogene and tumor suppressor pathways in cell-cell interactions.

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Maria-Dolores Martín-Bermudo, Pierre-Luc Bardet, Yohanns Bellaïche, Marianne Malartre (2015 Mar 28)

The vav oncogene antagonises EGFR signalling and regulates adherens junction dynamics during Drosophila eye development.

Development (Cambridge, England) : 1492-501 : DOI : 10.1242/dev.110585 En savoir plus
Résumé

Organ shaping and patterning depends on the coordinated regulation of multiple processes. The Drosophila compound eye provides an excellent model to study the coordination of cell fate and cell positioning during morphogenesis. Here, we find that loss of vav oncogene function during eye development is associated with a disorganised retina characterised by the presence of additional cells of all types. We demonstrate that these defects result from two distinct roles of Vav. First, and in contrast to its well-established role as a positive effector of the EGF receptor (EGFR), we show that readouts of the EGFR pathway are upregulated in vav mutant larval eye disc and pupal retina, indicating that Vav antagonises EGFR signalling during eye development. Accordingly, decreasing EGFR signalling in vav mutant eyes restores retinal organisation and rescues most vav mutant phenotypes. Second, using live imaging in the pupal retina, we observe that vav mutant cells do not form stable adherens junctions, causing various defects, such as recruitment of extra primary pigment cells. In agreement with this role in junction dynamics, we observe that these phenotypes can be exacerbated by lowering DE-Cadherin or Cindr levels. Taken together, our findings establish that Vav acts at multiple times during eye development to prevent excessive cell recruitment by limiting EGFR signalling and by regulating junction dynamics to ensure the correct patterning and morphogenesis of the Drosophila eye.

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Marisa M Merino, Christa Rhiner, Jesus M Lopez-Gay, David Buechel, Barbara Hauert, Eduardo Moreno (2015 Jan 21)

Elimination of unfit cells maintains tissue health and prolongs lifespan.

Cell : 461-76 : DOI : 10.1016/j.cell.2014.12.017 En savoir plus
Résumé

Viable yet damaged cells can accumulate during development and aging. Although eliminating those cells may benefit organ function, identification of this less fit cell population remains challenging. Previously, we identified a molecular mechanism, based on « fitness fingerprints » displayed on cell membranes, which allows direct fitness comparison among cells in Drosophila. Here, we study the physiological consequences of efficient cell selection for the whole organism. We find that fitness-based cell culling is naturally used to maintain tissue health, delay aging, and extend lifespan in Drosophila. We identify a gene, azot, which ensures the elimination of less fit cells. Lack of azot increases morphological malformations and susceptibility to random mutations and accelerates tissue degeneration. On the contrary, improving the efficiency of cell selection is beneficial for tissue health and extends lifespan.

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Année de publication : 2014

Anaïs Bouissou, Christel Vérollet, Hélène de Forges, Laurence Haren, Yohanns Bellaïche, Franck Perez, Andreas Merdes, Brigitte Raynaud-Messina (2014 Jan 15)

γ-Tubulin Ring Complexes and EB1 play antagonistic roles in microtubule dynamics and spindle positioning.

The EMBO journal : 114-28 : DOI : 10.1002/embj.201385967 En savoir plus
Résumé

γ-Tubulin is critical for microtubule (MT) assembly and organization. In metazoa, this protein acts in multiprotein complexes called γ-Tubulin Ring Complexes (γ-TuRCs). While the subunits that constitute γ-Tubulin Small Complexes (γ-TuSCs), the core of the MT nucleation machinery, are essential, mutation of γ-TuRC-specific proteins in Drosophila causes sterility and morphological abnormalities via hitherto unidentified mechanisms. Here, we demonstrate a role of γ-TuRCs in controlling spindle orientation independent of MT nucleation activity, both in cultured cells and in vivo, and examine a potential function for γ-TuRCs on astral MTs. γ-TuRCs locate along the length of astral MTs, and depletion of γ-TuRC-specific proteins increases MT dynamics and causes the plus-end tracking protein EB1 to redistribute along MTs. Moreover, suppression of MT dynamics through drug treatment or EB1 down-regulation rescues spindle orientation defects induced by γ-TuRC depletion. Therefore, we propose a role for γ-TuRCs in regulating spindle positioning by controlling the stability of astral MTs.

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Sophie Herszterg, Diana Pinheiro, Yohanns Bellaïche (2014 Jan 2)

A multicellular view of cytokinesis in epithelial tissue.

Trends in cell biology : 285-93 : DOI : 10.1016/j.tcb.2013.11.009 En savoir plus
Résumé

The study of cytokinesis in single-cell systems provided a wealth of knowledge on the molecular and biophysical mechanisms controlling daughter cell separation. In this review, we outline recent advances in the understanding of cytokinesis in epithelial tissues. These findings provide evidence for how the cytokinetic machinery adapts to a multicellular context and how the cytokinetic machinery is itself exploited by the tissue for the preservation of tissue function and architecture during proliferation. We propose that cytokinesis in epithelia should be viewed as a multicellular process, whereby the biochemical and mechanical interactions between the dividing cell and its neighbors are essential for successful daughter cell separation while defining epithelial tissue organization and preserving tissue integrity.

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Année de publication : 2013

Joffrey L Degoutin, Claire C Milton, Eefang Yu, Marla Tipping, Floris Bosveld, Liu Yang, Yohanns Bellaiche, Alexey Veraksa, Kieran F Harvey (2013 Aug 20)

Riquiqui and minibrain are regulators of the hippo pathway downstream of Dachsous.

Nature cell biology : 1176-85 : DOI : 10.1038/ncb2829 En savoir plus
Résumé

The atypical cadherins Fat (Ft) and Dachsous (Ds) control tissue growth through the Salvador-Warts-Hippo (SWH) pathway, and also regulate planar cell polarity and morphogenesis. Ft and Ds engage in reciprocal signalling as both proteins can serve as receptor and ligand for each other. The intracellular domains (ICDs) of Ft and Ds regulate the activity of the key SWH pathway transcriptional co-activator protein Yorkie (Yki). Signalling from the FtICD is well characterized and controls tissue growth by regulating the abundance of the Yki-repressive kinase Warts (Wts). Here we identify two regulators of the Drosophila melanogaster SWH pathway that function downstream of the DsICD: the WD40 repeat protein Riquiqui (Riq) and the DYRK-family kinase Minibrain (Mnb). Ds physically interacts with Riq, which binds to both Mnb and Wts. Riq and Mnb promote Yki-dependent tissue growth by stimulating phosphorylation-dependent inhibition of Wts. Thus, we describe a previously unknown branch of the SWH pathway that controls tissue growth downstream of Ds.

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Bertrand Jauffred, Flora Llense, Bernhard Sommer, Zhimin Wang, Charlotte Martin, Yohanns Bellaïche (2013 May 31)

Regulation of centrosome movements by numb and the collapsin response mediator protein during Drosophila sensory progenitor asymmetric division.

Development (Cambridge, England) : 2657-68 : DOI : 10.1242/dev.087338 En savoir plus
Résumé

Asymmetric cell division generates cell fate diversity during development and adult life. Recent findings have demonstrated that during stem cell divisions, the movement of centrosomes is asymmetric in prophase and that such asymmetry participates in mitotic spindle orientation and cell polarization. Here, we have investigated the dynamics of centrosomes during Drosophila sensory organ precursor asymmetric divisions and find that centrosome movements are asymmetric during cytokinesis. We demonstrate that centrosome movements are controlled by the cell fate determinant Numb, which does not act via its classical effectors, Sanpodo and α-Adaptin, but via the Collapsin Response Mediator Protein (CRMP). Furthermore, we find that CRMP is necessary for efficient Notch signalling and that it regulates the duration of the pericentriolar accumulation of Rab11-positive endosomes, through which the Notch ligand, Delta is recycled. Our work characterizes an additional mode of asymmetric centrosome movement during asymmetric divisions and suggests a model whereby the asymmetry in centrosome movements participates in differential Notch activation to regulate cell fate specification.

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Carl-Philipp Heisenberg, Yohanns Bellaïche (2013 May 28)

Forces in tissue morphogenesis and patterning.

Cell : 948-62 : DOI : 10.1016/j.cell.2013.05.008 En savoir plus
Résumé

During development, mechanical forces cause changes in size, shape, number, position, and gene expression of cells. They are therefore integral to any morphogenetic processes. Force generation by actin-myosin networks and force transmission through adhesive complexes are two self-organizing phenomena driving tissue morphogenesis. Coordination and integration of forces by long-range force transmission and mechanosensing of cells within tissues produce large-scale tissue shape changes. Extrinsic mechanical forces also control tissue patterning by modulating cell fate specification and differentiation. Thus, the interplay between tissue mechanics and biochemical signaling orchestrates tissue morphogenesis and patterning in development.

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Pierre-Luc Bardet, Boris Guirao, Camille Paoletti, Fanny Serman, Valentine Léopold, Floris Bosveld, Yûki Goya, Vincent Mirouse, François Graner, Yohanns Bellaïche (2013 May 28)

PTEN controls junction lengthening and stability during cell rearrangement in epithelial tissue.

Developmental cell : 534-46 : DOI : 10.1016/j.devcel.2013.04.020 En savoir plus
Résumé

Planar cell rearrangements control epithelial tissue morphogenesis and cellular pattern formation. They lead to the formation of new junctions whose length and stability determine the cellular pattern of tissues. Here, we show that during Drosophila wing development the loss of the tumor suppressor PTEN disrupts cell rearrangements by preventing the lengthening of newly formed junctions that become unstable and keep on rearranging. We demonstrate that the failure to lengthen and to stabilize is caused by the lack of a decrease of Myosin II and Rho-kinase concentration at the newly formed junctions. This defect results in a heterogeneous cortical contractility at cell junctions that disrupts regular hexagonal pattern formation. By identifying PTEN as a specific regulator of junction lengthening and stability, our results uncover how a homogenous distribution of cortical contractility along the cell cortex is restored during cell rearrangement to control the formation of epithelial cellular pattern.

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Shuji Ishihara, Kaoru Sugimura, Simon J. Cox, Isabelle Bonnet, Yohanns Bellaïche, François Graner (2013 Apr 26)

Comparative study of non-invasive force and stress inference methods in tissue.

The European physical journal. E, Soft matter : 9859 : DOI : 10.1140/epje/i2013-13045-8 En savoir plus
Résumé

In the course of animal development, the shape of tissue emerges in part from mechanical and biochemical interactions between cells. Measuring stress in tissue is essential for studying morphogenesis and its physical constraints. For that purpose, a possible new approach is force inference (up to a single prefactor) from cell shapes and connectivity. It is non-invasive and can provide space-time maps of stress in a whole tissue, unlike existing methods. To validate this approach, three force-inference methods, which differ in their approach of treating indefiniteness in an inverse problem between cell shapes and forces, were compared. Tests using two artificial and two experimental data sets consistently indicate that our Bayesian force inference, by which cell-junction tensions and cell pressures are simultaneously estimated, performs best in terms of accuracy and robustness. Moreover, by measuring the stress anisotropy and relaxation, we cross-validated the force inference and the global annular ablation of tissue, each of which relies on different prefactors. A practical choice of force-inference methods in different systems of interest is discussed.

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F Etoc, D Lisse, Y Bellaiche, J Piehler, M Coppey, M Dahan (2013 Mar 5)

Subcellular control of Rac-GTPase signalling by magnetogenetic manipulation inside living cells.

Nature nanotechnology : 193-8 : DOI : 10.1038/nnano.2013.23 En savoir plus
Résumé

Many cell functions rely on the coordinated activity of signalling pathways at a subcellular scale. However, there are few tools capable of probing and perturbing signalling networks with a spatial resolution matching the intracellular dimensions of their activity patterns. Here we present a generic magnetogenetic approach based on the self-assembly of signalling complexes on the surface of functionalized magnetic nanoparticles inside living cells. The nanoparticles act as nanoscopic hot spots that can be displaced by magnetic forces and trigger signal transduction pathways that bring about a cell response. We applied this strategy to Rho-GTPases, a set of molecular switches known to regulate cell morphology via complex spatiotemporal patterns of activity. We demonstrate that the nanoparticle-mediated activation of signalling pathways leads to local remodelling of the actin cytoskeleton and to morphological changes.

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Sophie Herszterg, Andrea Leibfried, Floris Bosveld, Charlotte Martin, Yohanns Bellaiche (2013 Feb 16)

Interplay between the dividing cell and its neighbors regulates adherens junction formation during cytokinesis in epithelial tissue.

Developmental cell : 256-70 : DOI : 10.1016/j.devcel.2012.11.019 En savoir plus
Résumé

How adherens junctions (AJs) are formed upon cell division is largely unexplored. Here, we found that AJ formation is coordinated with cytokinesis and relies on an interplay between the dividing cell and its neighbors. During contraction of the cytokinetic ring, the neighboring cells locally accumulate Myosin II and produce the cortical tension necessary to set the initial geometry of the daughter cell interface. However, the neighboring cell membranes impede AJ formation. Upon midbody formation and concomitantly to neighboring cell withdrawal, Arp2/3-dependent actin polymerization oriented by the midbody maintains AJ geometry and regulates AJ final length and the epithelial cell arrangement upon division. We propose that cytokinesis in epithelia is a multicellular process, whereby the cooperative actions of the dividing cell and its neighbors define a two-tiered mechanism that spatially and temporally controls AJ formation while maintaining tissue cohesiveness.

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Année de publication : 2012

Floris Bosveld, Isabelle Bonnet, Boris Guirao, Sham Tlili, Zhimin Wang, Ambre Petitalot, Raphaël Marchand, Pierre-Luc Bardet, Philippe Marcq, François Graner, Yohanns Bellaïche (2012 Apr 14)

Mechanical control of morphogenesis by Fat/Dachsous/Four-jointed planar cell polarity pathway.

Science (New York, N.Y.) : 724-7 : DOI : 10.1126/science.1221071 En savoir plus
Résumé

During animal development, several planar cell polarity (PCP) pathways control tissue shape by coordinating collective cell behavior. Here, we characterize by means of multiscale imaging epithelium morphogenesis in the Drosophila dorsal thorax and show how the Fat/Dachsous/Four-jointed PCP pathway controls morphogenesis. We found that the proto-cadherin Dachsous is polarized within a domain of its tissue-wide expression gradient. Furthermore, Dachsous polarizes the myosin Dachs, which in turn promotes anisotropy of junction tension. By combining physical modeling with quantitative image analyses, we determined that this tension anisotropy defines the pattern of local tissue contraction that contributes to shaping the epithelium mainly via oriented cell rearrangements. Our results establish how tissue planar polarization coordinates the local changes of cell mechanical properties to control tissue morphogenesis.

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Bertrand Jauffred, Yohanns Bellaiche (2012 Jan 6)

Analyzing frizzled signaling using fixed and live imaging of the asymmetric cell division of the Drosophila sensory organ precursor cell.

Methods in molecular biology (Clifton, N.J.) : 19-25 : DOI : 10.1007/978-1-61779-510-7_2 En savoir plus
Résumé

When you look at the dorsal thorax of a fruitfly, you can easily get fascinated by the high degree of alignment of the bristles that show a strong polarization in their surface organization. This organization of cells in the plane of the epithelium is known as planar cell polarity (PCP), and was initially characterized in Drosophila melanogaster. This process is important in a broad variety of morphological cellular asymmetries in various organisms. In Drosophila, genetic studies of PCP mutants showed that the asymmetric division of the sensory organ precursor cell (pI cell) is polarized along the anterior-posterior axis by Frizzled receptor signaling. Here, we described two methods to image and analyze the PCP in the pI cell model.

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