Alginates along the filament of the brown alga Ectocarpus help cells cope with stress

International audienceEctocarpus is a filamentous brown alga, which cell wall is composed mainly of alginates and fucans (80%), two non-crystalline polysaccharide classes. Alginates are linear chains of epimers of 1,4-linked uronic acids, β-d-mannuronic acid (M) and α-l-guluronic acid (G). Previous physico-chemical studies showed that G-rich alginate gels are stiffer than M-rich alginate gels when prepared in vitro with calcium. In order to assess the possible role of alginates in Ectocarpus, we first immunolocalised M-rich or G-rich alginates using specific monoclonal antibodies along the filament. As a second step, we calculated the tensile stress experienced by the cell wall along the filament, and varied it with hypertonic or hypotonic solutions. As a third step, we measured the stiffness of the cell along the filament, using cell deformation measurements and atomic force microscopy. Overlapping of the three sets of data allowed to show that alginates co-localise with the stiffest and most stressed areas of the filament, namely the dome of the apical cell and the shanks of the central round cells. In addition, no major distinction between M-rich and G-rich alginate spatial patterns could be observed. Altogether, these results support that both M-rich and G-rich alginates play similar roles in stiffening the cell wall where the tensile stress is high and exposes cells to bursting, and that these roles are independent from cell growth and differentiation

Alginates along the filament of the brown alga Ectocarpus help cells cope with stress.

Ectocarpus is a filamentous brown alga, which cell wall is composed mainly of alginates and fucans (80%), two non-crystalline polysaccharide classes. Alginates are linear chains of epimers of 1,4-linked uronic acids, β-D-mannuronic acid (M) and α-L-guluronic acid (G). Previous physico-chemical studies showed that G-rich alginate gels are stiffer than M-rich alginate gels when prepared in vitro with calcium. In order to assess the possible role of alginates in Ectocarpus, we first immunolocalised M-rich or G-rich alginates using specific monoclonal antibodies along the filament. As a second step, we calculated the tensile stress experienced by the cell wall along the filament, and varied it with hypertonic or hypotonic solutions. As a third step, we measured the stiffness of the cell along the filament, using cell deformation measurements and atomic force microscopy. Overlapping of the three sets of data allowed to show that alginates co-localise with the stiffest and most stressed areas of the filament, namely the dome of the apical cell and the shanks of the central round cells. In addition, no major distinction between M-rich and G-rich alginate spatial patterns could be observed. Altogether, these results support that both M-rich and G-rich alginates play similar roles in stiffening the cell wall where the tensile stress is high and exposes cells to bursting, and that these roles are independent from cell growth and differentiation

Development and physiology of the brown alga Ectocarpus siliculosus: two centuries of research

International audienceBrown algae share several important features with land plants, such as their photoautotrophic nature and their cellulose‐containing wall, but the two groups are distantly related from an evolutionary point of view. The heterokont phylum, to which the brown algae belong, is a eukaryotic crown group that is phylogenetically distinct not only from the green lineage, but also from the red algae and the opisthokont phylum (fungi and animals). As a result of this independent evolutionary history, the brown algae exhibit many novel features and, moreover, have evolved complex multicellular development independently of the other major groups already mentioned. In 2004, a consortium of laboratories, including the Station Biologique in Roscoff and Genoscope, initiated a project to sequence the genome of Ectocarpus siliculosus, a small filamentous brown alga that is found in temperate, coastal environments throughout the globe. The E. siliculosus genome, which is currently being annotated, is expected to be the first completely characterized genome of a multicellular alga. In this review we look back over two centuries of work on this brown alga and highlight the advances that have led to the choice of E. siliculosus as a genomic and genetic model organism for the brown algae

Normalisation genes for expression analyses in the brown alga model Ectocarpus siliculosus

<p>Abstract</p> <p>Background</p> <p>Brown algae are plant multi-cellular organisms occupying most of the world coasts and are essential actors in the constitution of ecological niches at the shoreline. <it>Ectocarpus siliculosus </it>is an emerging model for brown algal research. Its genome has been sequenced, and several tools are being developed to perform analyses at different levels of cell organization, including transcriptomic expression analyses. Several topics, including physiological responses to osmotic stress and to exposure to contaminants and solvents are being studied in order to better understand the adaptive capacity of brown algae to pollution and environmental changes. A series of genes that can be used to normalise expression analyses is required for these studies.</p> <p>Results</p> <p>We monitored the expression of 13 genes under 21 different culture conditions. These included genes encoding proteins and factors involved in protein translation (ribosomal protein 26S, EF1alpha, IF2A, IF4E) and protein degradation (ubiquitin, ubiquitin conjugating enzyme) or folding (cyclophilin), and proteins involved in both the structure of the cytoskeleton (tubulin alpha, actin, actin-related proteins) and its trafficking function (dynein), as well as a protein implicated in carbon metabolism (glucose 6-phosphate dehydrogenase). The stability of their expression level was assessed using the Ct range, and by applying both the geNorm and the Normfinder principles of calculation.</p> <p>Conclusion</p> <p>Comparisons of the data obtained with the three methods of calculation indicated that EF1alpha (EF1a) was the best reference gene for normalisation. The normalisation factor should be calculated with at least two genes, alpha tubulin, ubiquitin-conjugating enzyme or actin-related proteins being good partners of EF1a. Our results exclude actin as a good normalisation gene, and, in this, are in agreement with previous studies in other organisms.</p

Analysis of gap junctional intercellular communications using a dielectrophoresis-based microchip

Gap junctions are transmembrane structures that directly connect the cytoplasm of adjacent cells, making intercellular communications possible. It has been shown that the behaviour of several tumours – such as bone tumours – is related to gap junction intercellular communications (GJIC). Several methodologies are available for studying GJIC, based on measuring different parameters that are useful for multiple applications, such as the study of carcinogenesis for example. These methods nevertheless have several limitations. The present manuscript describes the setting up of a DEP-based lab-on-a-chip platform for the real-time study of Gap Junctional Intercellular Communication between osteosarcoma cells and the main cells accessible to their microenvironment. We conclude that using the DEParray technology for the GJIC assessment has several advantages comparing to current techniques. This methodology is less harmful for cells integrity; cells can be recovered after interaction to make further molecular analysis; it is possible to study GJIC in real time; we can promote cell interactions using up to five different populations. The setting up of this new methodology overcomes several difficulties to perform experiments for solving questions about GJIC process that we are not able to do with current technics

Inhibition of BET proteins and epigenetic signaling as a potential treatment for osteoporosis

International audienceHistone modifications are important for maintaining the transcription program. BET proteins, an important class of " histone reading proteins " , have recently been described as essential in bone biology. This study presents the therapeutic opportunity of BET protein inhibition in osteoporosis. We find that the pharmacological BET protein inhibitor JQ1 rescues pathologic bone loss in a post-ovariectomy osteoporosis model by increasing the trabecular bone volume and restoring mechanical properties. The BET protein inhibition suppresses osteoclast differentiation and activity as well as the osteoblastogenesis in vitro. Moreover, we show that treated non-resorbing osteoclasts could still activate osteoblast differentiation. In addition, specific inhibition of BRD4 using RNA interference inhibits osteoclast differentiation but strongly activates osteoblast mineralization activity. Mechanistically, JQ1 inhibits expression of the master osteoclast transcription factor NFATc1 and the transcription factor of osteoblast Runx2. These findings strongly support that targeting epigenetic chromatin regulators such as BET proteins may offer a promising alternative for the treatment of bone-related disorders such as osteoporosis

Exploration des différents modes d'implication au sein d'un pôle de santé pluriprofessionnel : une étude qualitative sur le vécu du personnel du pôle de santé de Saint-Martin-d'Hères

Background : Health centers represent a public health issue for the years to come, in order to facilitate access to care. The purpose of this study was to focus on the various ways in which the members of a health center are involved in its functioning and development. Method : A qualitative study was carried out amongst the members of the Saint-Martin-d’Hères health center using semi-structured individual interviews. A thematic analysis of all the interviews was made by the 2 investigators. Results : Eighteen medical and paramedical members took part in the interviews. The study revealed 3 differerent degrees of commitment depending on the level of involvement in projects or structure organisation. The interviewees mobilised moral resources and strong convictions regarding equal access to health and the benefits of interprofessional practice. They brought along the personnal skills that they had acquired through their personal and professional history, or during their time in the health center. Despite their efforts, the relationships still seemed to be based on a hierarchic model. All the efforts and time dedicated to the good functioning of the health center often clashed with a time consuming administration which seemed far from their vision of care. Time was taken on their personnal activities or on their time of care. Financial recognition was seen as insufficient and unpredictable. Conclusion : Our study shows a great variety of means and energy put toward the right functioning of a health center, by commited professionals who share a common vision of care. It also questions the human difficulties and above all the adminstrative and financial obstacles faced by the professionals working in those structures.Contexte : Les pôles de santé représentent un enjeu de santé publique dans les années à venir pour faciliter l’accès au soin. Le but de ce travail était d’étudier les différentes manières dont les membres d’un pôle de santé s’impliquent dans son fonctionnement et son développement. Méthode : Étude qualitative par entretiens semi dirigés auprès des membres du pôle de santé de Saint-Martin-d’Hères. Une analyse thématique de l'ensemble des entretiens a été réalisée par les 2 enquêtrices. Résultats : Dix-huit professionnels médicaux et paramédicaux ont participé. L’étude montrait 3 grands degrés d’implication en fonction de la participation aux projets ou aux instances du pôle. Les membres mobilisaient des ressources morales et des convictions fortes pour l’équité en santé et les bénéfices du travail interprofessionnel. Ils apportaient leurs compétences inhérentes à leur parcours personnel et professionnel ou acquises dans le pôle. Malgré leur volonté, les relations étaient encore perçues comme hiérarchiques. Les efforts et le temps déployés pour le fonctionnement du pôle se heurtaient à une gestion chronophage considérée comme éloignée de l’activité de soin. Le temps était pris sur leurs activités personnelles ou leur temps soignant. La reconnaissance financière de leur travail supplémentaire était vécue comme insuffisante et incertaine. Conclusion : Notre travail montre la richesse des moyens et l’énergie dédiée au fonctionnement d’un pôle, par des professionnels engagés partageant une vision commune du soin. Elle interroge également sur les difficultés humaines mais surtout administratives et financières auxquelles sont soumis les professionnels de ces structures

Morphogenèse précoce de l'algue brune Ectocarpus siliculosus

Cette thèse initie l étude de la morphogenèse de l algue brune modèle Ectocarpus siliculosus, qui est formée d un filament primaire unisérié comportant des embranchements. Dans un premier temps, l étude du patron de développement précoce a mis en évidence une croissance apicale des filaments suivie d une différenciation cellulaire centripète aboutissant à deux types de cellules. Ces données ont ensuite été utilisées pour modéliser le développement d E. siliculosus grâce à une approche par simulation informatique, révélant qu aux stades très précoces, la connaissance par chaque cellule de l identité des cellules voisines est suffisante pour créer des filaments identiques à ceux observés en culture. Cette hypothèse est appuyée par l étude du mutant de morphogenèse étoile, qui possède une capacité de prolifération cellulaire accrue et met en évidence l importance de protéines transmembranaires à domaine Notch dans la mise en place du patron de développement. En parallèle, la phytohormone auxine a été détectée dans les filaments avec une concentration maximale aux apices, et semble jouer un rôle dans la morphogenèse de l algue en procurant aux cellules une information de position globale permettant la mise en place du patron d embranchements. De plus, l analyse du génome a permis de montrer qu E. siliculosus possède la machinerie enzymatique nécessaire à la synthèse de l acide indole-3-acétique. La morphogenèse d E. siliculosus pourrait ainsi requérir l intervention de deux types de mécanismes, une signalisation paracrine faisant intervenir des protéines transmembranaires à domaine Notch, et une signalisation à distance par l intermédiaire d un gradient d auxine.PARIS-BIUSJ-Physique recherche (751052113) / SudocROSCOFF-Observ.Océanol. (292393008) / SudocSudocFranceF

Shift to 3D growth during embryogenesis of <i>Saccharina latissima</i>

These are the raw data and measurements for our paper on the embryonic development of Saccharina latissima and specifically, during the third phase where the first layers of tissue emerge on the previously monostromatic embryo. The methodology is described on our article (see link on related materials). The data and the different measurements inside the zip file are organised per figure or table as set on our publication. Please read the readme.txt files before proceeding with interpreting our data.</p