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Extracellular matrix deposition controls early differentiation patterns in human cardiac gastruloids
No full textInternational audienceABSTRACT Amongst the various factors that affect differentiation and tissue organization, the autonomous deposition of extracellular matrix (ECM) has hardly been considered in the context of gastruloids. Using biofunctionalized colloidal particles as artificial organizing centers (aOCs), we patterned differentiation loci within 3D embryonic bodies. Our findings reveal that the spatial distribution of the aOCs induces various pattern organizations, mediated by endogenous deposition of ECM. We investigated how the interplay between meso-endoderm cell epithelial-to-mesenchymal transition, migration into germ layers, and the prolonged maintenance of local stem-cell niches orchestrates gastruloid structure and composition. These factors collectively regulate the complexity of emergent cardiac structures observed at later time points. This work uncovers a critical feedback loop between cell differentiation rates and endogenous ECM deposition patterns, which governs the differentiation paths in scaffolded cardiac gastruloids
Introducción – Masculinidades y violencias en representaciones culturales de latinoamérica
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La diversification des activités économiques de montagne
No full textInternational audienceLa diversification de l'économie de la montagne est aujourd'hui présentée comme une absolue nécessité. Les stations d'altitude avaient pu générer des ressources financières considérables dans les années 1980 qui sont nécessairement appelées à disparaître. La limite pluie-neige ne cesse de remonter en altitude. Avec un réchauffement des températures sur les pentes montagneuses voisinant avec le double (+2 degrés C.) de la moyenne du territoire national (+1,4 degrés C.), les Alpes ont perdu trente-six jours de couverture neigeuse par an. Une étude publiée dans la revue Nature Climate Change l'été 2024 pronostique qu'une station sur trois est menacée si la configuration actuelle de réchauffement à plus 2 degrés se confirme. Neuf sur dix sont vouées à disparaître avec un réchauffement global de plus 3 degrés.Pourtant, à prendre connaissance avec le sujet, deux considérations ponctuelles viennent à l'esprit qui permettront un regard plus distancié avec les réalités actuelles. Fermement annoncée comme le principal défi de l'économie locale, cette diversification n'est pourtant pas une préoccupation nouvelle d'une part et elle est très relativement mise en oeuvre d'autre part.1)En premier lieu, on ne saurait tenir la volonté de développer et diversifier les activités économiques en zone de montagne pour une nouveauté qui serait liée à la pénurie de ressource en neige en corrélation avec l'accélération actuelle du réchauffement climatique. En effet, « l'exode montagnard » ne date pas d'aujourd'hui et le déclin de la mono-activité qui a toujours caractérisé l'économie de la montagne (agriculture, mono-industrie) est un phénomène observable depuis au moins un demi-siècle. Soucieux de la situation, les collectivités territoriales de montagne ont de longue date consenti l'effort de mobiliser leurs moyens financiers et juridiques pour diversifier leurs activités. L'ouvrage sur « L'action économique locale » (J.-C.Douence, dir., Economica 1988) révélait déjà comment ces collectivités situées dans les Pyrénées, généralement à l'écart des grands axes régionaux et fortes d'une tradition rurale, s'étaient emparées de leurs nouvelles compétences issues de la grande réforme décentralisatrice des années 1980 pour favoriser l'encrage de leur population sur place par le soutien au développement de leur économie. Elles ont ainsi pu aider les exploitations agricoles à augmenter leur taille, accorder des exonérations fiscales à des entreprises locales diversifiant leurs activités, se doter d'un programme d'amélioration de l'habitat et de construction de logements, créer un bâtiment communal érigé en lieu d'animation commerciale, favoriser l'exploitation de la forêt… Les décennies antérieures (1960-1970) avaient d'ailleurs connu une amorce de diversification économique dans des cas de mono-industrie déclinante sous l'impulsion des communes, pour défricher des terres louées ensuite à des exploitations agricoles ou pour créer une salle polyvalente servant de marché aux bestiaux. Le développement de l'activité économique s'est, en fait, toujours inscrit dans la vocation des communes et de leurs élus à prendre en charge les besoins de leurs habitants en mobilisant, à cette cause, tous les acteurs locaux, publics et privés. Sur la base de cette considération, ces communes ont</div
Robust Optimization for Multi-Energy Microgrid Sizing and Energy Management under Load Uncertainty with Demand Response
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The RING1 subunit of Polycomb Repressive Complex 1 monoubiquitinates histone H2A and mediates repression independently of Polycomb Repressive Complex 2 in the model diatom Phaeodactylum tricornutum
No full textInternational audiencePolycomb Repressive Complex 1 (PRC1) and its associated mark, H2A monoubiquitination (H2Aub), cooperate with PRC2 for transcriptional silencing in multicellular organisms. However, PRC1 is absent from many unicellular lineages, leaving its functional conservation and relationship with PRC2 unclear. In the model diatom Phaeodactylum tricornutum , the role of the PRC1 subunit RING1 was investigated to assess whether PRC1‐mediated repression is evolutionary conserved and how it interacts with PRC2. RING1 knockout mutants were generated to investigate H2Aub deposition. Genome‐wide H2Aub profiles were integrated with existing H3K27me3 maps, and transcriptome analyses were performed to compare RING1 and the PRC2 catalytic subunit Enhancer of Zeste mutants, thereby evaluating their respective contributions to gene and transposable elements (TEs) repression. Loss of RING1 abolished H2Aub and revealed that H2Aub predominantly marks repressed genes lacking H3K27me3, while both marks colocalize on TEs. Transcriptome data indicate that H2Aub primarily mediates repression of genes with high H2Aub enrichment, whereas TEs marked by both H2Aub and H3K27me3 are mainly regulated by H3K27me3. These results demonstrate that PRC1 and PRC2, which originated before multicellularity, act independently to establish transcriptional silencing in P. tricornutum . PRC1 is functionally conserved in this diatom, with H2Aub and H3K27me3 fulfilling distinct yet complementary regulatory roles
Nitrogen concentration shapes the size structure and the functional diversity of phytoplankton communities in the southern Indian Ocean
No full textInternational audiencePhytoplankton are fundamental to marine ecosystems, biogeochemical cycling and climate regulation. Their community structure and productivity are shaped by biotic and abiotic factors, notably temperature and macronutrient concentrations. Climate change is altering ocean vertical stratification and nutrient dynamics, with complex and often poorly understood impacts on phytoplankton communities and global primary production. To contribute characterizing these relationships, we analysed planktonic community composition using 18S rRNA amplicon sequencing and imaging f low cytometry in the southern Indian Ocean across a strong environmental gradient from warm, stratified, N-depleted (but relativ ely P-repleted) waters in the north to cold, mixed, macronutrient-replete waters in the south. Phytoplankton composition and local diversity correlated primarily with temperature and macronutrient concentrations, but smaller cells (<3 μm) were less affected than larger ones (>3 μm). To disentangle the relative inf luence of temperature and macronutrients, we applied a model of dissolved macronutrient diffusion, suggesting that nutrient limitation, primarily nitrogen, likely c onstrains the growth of osmotrophic phytoplankton with cell sizes exceeding 2-15 μm in the nutrient-depleted region. We show that smaller cells, with higher surface area-to-volume ratios, are likely to evade this limitation, explaining their lower sensitivity to nitrogen concentrations, both in their taxonomic composition and diversity. Imaging f low cytometry confirmed that larger cells persisting in nitrogen-depleted waters predominantly employ alternative nitrogen acquisition strategies such as diazotrophy or mixotrophy, fostering functional local diversity. Notably, three Prymnesiophyceae taxa exhibited partial limitation by nitrogen diffusion, raising questions about their potential for mixotrophy or diazotrophy, akin to Braarudosphaera bigelowii. Other environmental factors, such as trace metal concentrations, showed weaker corr elations with community structure metrics. Overall, our results are consistent with N concentration gradients and N:P imbalances driving a great share of planktonic diversity by constraining large-cell nutrient acquisition strategies and fostering functional diversification in oligotrophic regions of the Ocean.</div
Réseau d'antennes à photomélange large bande en bande W basé sur technologie PCB multicouche
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13C position-specific isotopic analysis of fatty acid methyl esters using NMR with intramolecular isotopic referencing
No full textInternational audienceAmong stable isotope measurement strategies at natural abundance, Position-Specific Isotope Analysis (PSIA) is a valuable approach for food authentication and metabolism understanding. In this context, carbon-13 Nuclear Magnetic Resonance spectroscopy (irm-13C NMR) has emerged as an efficient tool It enables the determination of the absolute 13C intramolecular composition (δ13Ci) when all NMR signals are well-resolved and the global 13C content (δ13Cg) is known. However, in the case of fatty acids with eight carbons or more, 13C-NMR can only resolve six carbon signals. δ13Ci values are thus not attainable without specialized methods. To overcome this limitation, we developed a novel methodology that leverages the concept of isotopic intramolecular referencing by using the methoxy group in the fatty acid methyl esters (FAMEs) as a reference. We thus determined δ13Ci values with improved trueness and repeatability without requiring δ13Cg measurement. Combining this enhancement with the acquisition of 13C NMR spectra using an adiabatic INEPT pulse sequence offered a more time-efficient, sample-efficient, and sustainable approach, rendering the entire process greener. We successfully applied this approach to FAMEs from butter and coconut oil. Subsequent studies will evaluate the effectiveness of the novel isotopomic biomarkers derived from our method in authenticating foodstuffs and elucidating metabolic differences among fatty acids. Additionally, the same intramolecular isotope referencing approach will be of interest for studying other molecules and isotopes