Triangles bridge the scales: Quantifying cellular contributions to tissue deformation

In this article, we propose a general framework to study the dynamics and topology of cellular networks that capture the geometry of cell packings in two-dimensional tissues. Such epithelia undergo large-scale deformation during morphogenesis of a multicellular organism. Large-scale deformations emerge from many individual cellular events such as cell shape changes, cell rearrangements, cell divisions, and cell extrusions. Using a triangle-based representation of cellular network geometry, we obtain an exact decomposition of large-scale material deformation. Interestingly, our approach reveals contributions of correlations between cellular rotations and elongation as well as cellular growth and elongation to tissue deformation. Using this Triangle Method, we discuss tissue remodeling in the developing pupal wing of the fly Drosophila melanogaster.Comment: 26 pages, 18 figure

Active dynamics of tissue shear flow

We present a hydrodynamic theory to describe shear flows in developing epithelial tissues. We introduce hydrodynamic fields corresponding to state properties of constituent cells as well as a contribution to overall tissue shear flow due to rearrangements in cell network topology. We then construct a generic linear constitutive equation for the shear rate due to topological rearrangements and we investigate a novel rheological behaviour resulting from memory effects in the tissue. We identify two distinct active cellular processes: generation of active stress in the tissue, and actively driven topological rearrangements. We find that these two active processes can produce distinct cellular and tissue shape changes, depending on boundary conditions applied on the tissue. Our findings have consequences for the understanding of tissue morphogenesis during development

Surdités hérédtaires (rôles de la myosine VIIa dans le développement de la cellule sensorielle auditive)

La myosine VIIa, dont le déficit est à l'origine du syndrome de Usher de type IB (USH1B), associe surdité profonde et rétinopathie pigmentaire. Son expression, au sein de l'oreille interne, est restreinte aux cellules sensorielles (cellules ciliées). La myosine VIIa et la myosine 1c ont été impliquées dans le processus d'adaptation du courant de transduction, dans les cellules ciliées de l oreille interne, en réponse à la stimulation sonore. J'ai entrepris la recherche de nouvelles molécules impliquées dans ce processus par un crible double-hybride chez la levure. J'ai identifié PHR1, une protéine transmembranaire à domaine Pleckstrin Homology, comme partenaire de liaison commun aux myosines 1c et VIIa. En supposant que PHR1 soit localisé dans les stéréocils, il pourrait ancrer les deux myosines à la membrane, et jouer lui aussi un rôle dans le processus d'adaptation. je me suis ensuite concentré sur le rôle de la myosine VIIa aux jonctions apicales entre les cellules ciliées et leurs cellules de soutien. Ces jonctions jouent notamment un rôle crucial dans le maintien du potentiel endocochléaire, qui contribue à la dépolarisation cellulaire en réponse à une stimulation sonore. Par une approche biochimique, j ai montré que la myosine VIIa se lie à shroom2, une protéine à domaine PDZ, qui se lie à ZO1 et à l actine. L'abondance de shroom2 aux jonctions serrées des cellules ciliées, continuellement soumises à des forces de cisaillement en réponse à la stimulation sonore, incite à penser que shroom2, en conjonction avec la myosine VIIa, est impliquée dans le renforcement des jonctions serrées.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Extracting multiple surfaces from 3D microscopy images in complex biological tissues with the Zellige software tool

International audienceBackgroundEfficient tools allowing the extraction of 2D surfaces from 3D-microscopy data are essential for studies aiming to decipher the complex cellular choreography through which epithelium morphogenesis takes place during development. Most existing methods allow for the extraction of a single and smooth manifold of sufficiently high signal intensity and contrast, and usually fail when the surface of interest has a rough topography or when its localization is hampered by other surrounding structures of higher contrast. Multiple surface segmentation entails laborious manual annotations of the various surfaces separately.ResultsAs automating this task is critical in studies involving tissue-tissue or tissue-matrix interaction, we developed the Zellige software, which allows the extraction of a non-prescribed number of surfaces of varying inclination, contrast, and texture from a 3D image. The tool requires the adjustment of a small set of control parameters, for which we provide an intuitive interface implemented as a Fiji plugin.ConclusionsAs a proof of principle of the versatility of Zellige, we demonstrate its performance and robustness on synthetic images and on four different types of biological samples, covering a wide range of biological contexts

Extracting multiple surfaces from 3D microscopy images in complex biological tissues with the Zellige software tool

International audienceBackgroundEfficient tools allowing the extraction of 2D surfaces from 3D-microscopy data are essential for studies aiming to decipher the complex cellular choreography through which epithelium morphogenesis takes place during development. Most existing methods allow for the extraction of a single and smooth manifold of sufficiently high signal intensity and contrast, and usually fail when the surface of interest has a rough topography or when its localization is hampered by other surrounding structures of higher contrast. Multiple surface segmentation entails laborious manual annotations of the various surfaces separately.ResultsAs automating this task is critical in studies involving tissue-tissue or tissue-matrix interaction, we developed the Zellige software, which allows the extraction of a non-prescribed number of surfaces of varying inclination, contrast, and texture from a 3D image. The tool requires the adjustment of a small set of control parameters, for which we provide an intuitive interface implemented as a Fiji plugin.ConclusionsAs a proof of principle of the versatility of Zellige, we demonstrate its performance and robustness on synthetic images and on four different types of biological samples, covering a wide range of biological contexts

SARS-CoV-2 infection induces the dedifferentiation of multiciliated cells and impairs mucociliary clearance

SARS-CoV-2 infection damages the airways. Here the authors show that SARS-CoV-2 infection induces the rapid loss of airway motile cilia, resulting in altered cilia clearance function. Cilia loss is preceded by reduced expression of the ciliogenesis regulator Foxj1