Rôle du phosphatidylinositol 5-phosphate dans la survie et la migration cellulaires : implication dans la dynamique des membranes et du cytosquelette

Les phosphoinositides jouent un rôle essentiel dans le contrôle spatio-temporel de grandes voies de signalisation impliquées dans la prolifération, la survie, la dynamique du cytosquelette, le trafic ou la migration. Le phosphatidylinositol 5-phosphate (PtdIns5P) est le dernier membre de la famille à avoir été caractérisé et ses fonctions ne sont pas encore totalement connues. Dans ce travail, nous avons étudié le rôle de ce second messager lipidique dans la signalisation en relation avec la survie (régulation de la voie PI3-kinase/Akt) et la migration (activation des GTPases de la famille Rho). Dans un premier modèle, nous avons étudié les processus invasifs des lymphomes anaplasiques à grandes cellules exprimant la protéine chimérique NPM-ALK au fort pouvoir transformant. Nous avons montré que la dissémination de ces lymphomes dépendait de la GTPase Rac1 qui orchestre la structuration d'invadopodes fonctionnels en régulant la formation du complexe CD44/MMP-9/Hsp90 sur la surface des cellules NPM-ALK(+). CD44 ancre le complexe à la surface des cellules et Hsp90 est requise pour l'activation extracellulaire de MMP-9. De façon intéressante, nous avons mesuré des taux élevés de PtdIns5P dans les cellules NPM-ALK(+), qui dans ce modèle est produit par la lipide kinase PIKfyve activée par NPM-ALK. L'inhibition de PIKfyve conduit à un blocage de l'invasion associé à une modification de la répartition de MMP-9 à la surface cellulaire, ainsi qu'à un défaut de sa maturation, suggérant que le PtdIns5P serait central à l'invasion des lymphomes NPM-ALK(+). En parallèle, nous avons étudié le PtdIns5P dans l'infection par la bactérie pathogène Shigella flexneri responsable de la dysenterie chez l'homme. L'équipe avait montré que le facteur de virulence IpgD transformait le PtdIns(4,5)P2 en PtdIns5P, ce qui conduisait à une activation de la voie de survie PI 3-Kinase/Akt. Nous avons montré que le PtdIns5P active le récepteur à l'EGF (EGFR)indépendamment de son ligand, et que ce dernier est requis pour l'activation d'Akt. De plus, le PtdIns5P agit en perturbant le trafic de l'EGFR qui n'est plus dégradé suite à son activation mais plutôt recyclé pour maintenir la cellule activée. Dans ce modèle, le PtdIns5P modulerait les propriétés de diffusion de la membrane plasmique pour conduire à l'activation du récepteur. Par ailleurs, nous avons montré que le PtdIns5P activait les GTPases Rac1 (en liant directement son facteur d'échange Tiam1)et Cdc42 en périphérie cellulaire où cette dernière pourrait jouer un rôle dans la dynamique des membranes requises pour l'activation sans ligand du récepteur. Le module Tiam1/Rac1 répond par ailleurs à des taux élevés de PtdIns5P en activant la dynamique de l'actine de façon polarisée et en se localisant au niveau des endosomes précoces où nous mesurons une accumulation de PtdIns5P, ce qui induit un chimiotactisme fort en réponse à un gradient de sérum. Ces données permettent de proposer un rôle du PtdIns5P dans l'intégration entre le trafic et la dynamique de l'actine pour favoriser les voies de recyclage de récepteurs pour réguler la survie et l'invasion.Phosphoinositides are key regulators of signalling pathway involved in proliferation, survival, cytoskeleton organization, vesicular trafficking and migration. Phosphatidylinositol 5-phosphate (PtdIns5P) is the last characterized and its metabolism and cellular functions are still elusive. In this work, we focused on the potential role of this lipid second messenger in signalling regulating survival (regulation of the PI 3-Kinase pathway) and migration (activation of Rho family GTPases). In a first model, we studied the invasiveness of anaplastic large cell lymphomas (ALCL) expressing the chimeric tyrosine kinase oncogene NPM-ALK, which drives malignant transformation of 75% of ALCLs. We showed that dissemination of these lymphomas is dependent on the GTPase Rac1, which promotes the structuration of functional invadopodia by regulating the formation of the CD44/MMP-9/Hsp90 complex at the surface of NPM-ALK(+) cells. CD44 anchors the complex on the cell surface, and Hsp90 is required for the extracellular activation of MMP-9. Interestingly, we measured elevated levels of PtdIns5P in NPM-ALK(+) cells and its production is dependent on the NPM-ALK-activated PtdIns 5-Kinase, PIKfyve. Inhibition of PIKfyve strongly reduces the invasive capacities by disturbing MMP-9 cell surface distribution, which leads to defects in its activation, suggesting that PtdIns5P plays a central role in the srpeading of NPM-ALK(+) lymphomas. In parallel, we studied the role of PtdIns5P during Shigella flexneri infection, which is responsible for the dysentery in humans. Our group previously showed that the virulence effector IpgD transforms the PtdIns(4,5)P2 into PtdIns5P, and that this conversion drives the activation of the PI 3-Kinase/Akt survival pathway. We found that the EGF receptor is the key intermediate between PtdIns5P and Akt activation. PtdIns5P, that we found accumulated on early endosomes, induces modifications of trafficking, which abolishes EGFR degradation and promotes its recycling towards the plasma membrane. In this model, PtdIns5P modulates the diffusion properties of the plasma membrane to promote receptor activation without ligand. In addition, we showed that PtdIns5P activates the Rac1 GTPases, by binding to the PH domain of its exchange factor Tiam1. Cdc42 also gets activated at the cell periphery where it could be involved in the membrane dynamic required for the activation of receptors without ligands and the subsequent internalization. The Tiam1/Rac1 module responds to elevated levels of PtdIns5P by inducing a strong polarized actin dynamics, leading to chimiotactism in response to serum gradients, and is an important component of anaplastic lymphomas metastatic process. This work points to a crucial role of PtdIns5P in the integration between traffic and actin dynamic to favour the recycling pathway of receptors to regulate the survival and invasion

Mecagenius : An Innovative Learning Game for Mechanical Engineering.

International audienceThe present paper provides a description of Mecagenius, a learning game to teach mechanical engineering at an engineering faculty. Firstly, the Mecagenius game and learning content are introduced before practical ways of integrating this application in educational activities are explored in relation to the skills the teacher seeks to transmit knowledge. This is followed by a review of the literature on the educational effectiveness of serious games. Secondly, the learning game experience of Mecagenius on a course is reported, providing evaluations from both students and teachers. Interviews with teacher and students together with the collected computer records allow for an assessment of the advantages and drawbacks of teaching and learning with this kind of tool.Through a qualitative analysis of students’ game reports, the different strategies used in this educational environment are assessed

Multi-scale agglomerates: relationship between morphology and optical properties.

International audienceMulti-scale solid particle aggregates designate aggregates of clusters, which are composed of smaller clusters, themselves composed by aggregated solid particles. There are usually 3 or 4 relevant scale levels of agglomeration. The final aim of this study is to define the relationships between the geometrical and optical characteristics of different aggregates. Indeed, a previous work of Gruy and Jacquier in 2008 [1] and [2] showed the existence of a narrow link between these two aggregate characterizations. The first step consists in modeling multi-scale aggregates with specific geometrical shape and optical properties. Thereafter, the aggregate characterization is performed. Following the Xu theory called GMM (Generalized Multiparticle Mie solution) exposed in his paper [3], the studied optical parameter is the scattering cross section, denoted, Csca in (µm2). In addition, the optical analysis is focused on aggregates with a high optical index. Concerning the geometrical characterization, several parameters are studied: the compactness, the number of the primary particles and the volume of the aggregates, successively. Using different 2D joint (geometrical/optical) representations, the correlation between the Csca values and the geometry of the aggregate is analyzed

Caractérisation géométrique et optique de plusieurs types d'agrégats.

National audienceLes agrégats multi-échelles résultent de l'agglomération de clusters de petites particules, elles-mêmes résultant de l'agrégation de particules encore plus fines. Il existe en général 3 ou 4 niveaux d'agglomération. La géométrie de ces agrégats leur confère des propriétés physiques et chimiques (support catalytique, absorbant) très recherchées par divers industries. Le but de ce travail est de caractériser ces agrégats multi-échelles de deux façons : d'une part par une méthode optique, et d'autre part par une étude morphologique. Le but final est de trouver un lien possible entre ces deux types de caractérisations. L'étude optique est réalisée par la théorie de Xu YL (1995) appelée GMM (Generalized Multiparticle Mie solution), et une analyse de paramètres optiques (sections efficaces, paramètre d'asymétrie). De plus, nous examinons les caractéristiques morphologiques de ces agrégats grâce à l'analyse d'image. Afin de faire le lien entre les deux études, nous modélisons les agrégats par la géométrie de leur enveloppe convexe que nous fixons tout d'abord simple (sphère, cube, cylindre). A partir de cette modélisation, nous étudions les paramètres optiques avec la méthode GMM, et le but est d'extraire des lois générales suivant la géométrie des agrégats étudiés

Geometrical Characterization of Various Shaped 3D-Aggregates of Primary Spherical Particules by Radial Distribution Functions

International audienceMulti-scale aggregates are composed of particles which results themselves of agglomeration of other primary particles. If particles are modeled by their centers, the geometrical characterization of aggregates refers to point pattern analysis. Radial distribution and function of pairs allow a description of the point pattern to be performed. They describe how points are radially packed around each other. In this paper, the characterization of different simulated aggregates are computed and compared

Water vapor Raman-lidar observations from multiple sites in the framework of WaLiNeAs

During the Water Vapor Lidar Network Assimilation (WaLiNeAs) campaign, 8 lidars specifically designed to measure water vapor mixing ratio (WVMR) profiles were deployed on the western Mediterranean coast. The main objectives were to investigate the water vapor content during case studies of heavy precipitation events in the coastal Western Mediterranean and assess the impact of high spatio-temporal WVMR data on numerical weather prediction forecasts by means of state–of–the–art assimilation techniques. Given the increasing occurrence of extreme events due to climate change, WaLiNeAs is the first program in Europe to provide network–like, simultaneous and continuous water vapor profile measurements. This paper focuses on the WVMR profiling datasets obtained from three of the lidars managed by the French component of the WaLiNeAs team. These lidars were deployed in the towns of Coursan, Grau du Roi and Cannes. This measurement setup enabled monitoring of the water vapor content within the low troposphere along a period of three months over autumn – winter 2022 and four months in summer 2023. The lidars measured the WVMR profiles from the surface up to approximately 6–10 km at night, and 1–2 km during daytime; with a vertical resolution of 100 m and a time sampling between 15 – 30 min, selected to meet the needs of weather forecasting with an uncertainty lower than 0.4 g kg-1. The paper presents details about the instruments, the experimental strategy, as well as the datasets given in NETcdf format. The final dataset is divided in two datasets, the first with a time resolution of 15 min, which contains a total of 26 423 WVMR vertical profiles and the second with a time resolution of 30 min to improve the signal to noise ratio and signal altitude range

Transcriptome profiling of the feeding-to-fasting transition in chicken liver

<p>Abstract</p> <p>Background</p> <p>Starvation triggers a complex array of adaptative metabolic responses including energy-metabolic responses, a process which must imply tissue specific alterations in gene expression and in which the liver plays a central role. The present study aimed to describe the evolution of global gene expression profiles in liver of 4-week-old male chickens during a 48 h fasting period using a chicken 20 K oligoarray.</p> <p>Results</p> <p>A large number of genes were modulated by fasting (3532 genes with a pvalue corrected by Benjamini-Hochberg < 0.01); 2062 showed an amplitude of variation higher than +/- 40% among those, 1162 presented an human ortholog, allowing to collect functional information. Notably more genes were down-regulated than up-regulated, whatever the duration of fasting (16 h or 48 h). The number of genes differentially expressed after 48 h of fasting was 3.5-fold higher than after 16 h of fasting. Four clusters of co-expressed genes were identified by a hierarchical cluster analysis. Gene Ontology, KEGG and Ingenuity databases were then used to identify the metabolic processes associated to each cluster. After 16 h of fasting, genes involved in ketogenesis, gluconeogenesis and mitochondrial or peroxisomal fatty acid beta-oxidation, were up-regulated (cluster-1) whereas genes involved in fatty acid and cholesterol synthesis were down-regulated (cluster-2). For all genes tested, the microarray data was confirmed by quantitative RT-PCR. Most genes were altered by fasting as already reported in mammals. A notable exception was the <it>HMG-CoA synthase 1 </it>gene, which was up-regulated following 16 and 48 h of fasting while the other genes involved in cholesterol metabolism were down-regulated as reported in mammalian studies. We further focused on genes not represented on the microarray and candidates for the regulation of the target genes belonging to cluster-1 and -2 and involved in lipid metabolism. Data are provided concerning PPARa, SREBP1, SREBP2, NR1H3 transcription factors and two desaturases (FADS1, FADS2).</p> <p>Conclusion</p> <p>This study evidences numerous genes altered by starvation in chickens and suggests a global repression of cellular activity in response to this stressor. The central role of lipid and acetyl-CoA metabolisms and its regulation at transcriptional level are confirmed in chicken liver in response to short-term fasting. Interesting expression modulations were observed for <it>NR1H3, FADS1 </it>and <it>FADS2 </it>genes. Further studies are needed to precise their role in the complex regulatory network controlling lipid metabolism.</p

Why, What and How to help each Citizen to Understand Artificial Intelligence?

International audienceA critical understanding of digital technologies is an empowering competence for citizens of all ages. In this paper we introduce an open educational approach of artificial intelligence (AI) for everyone. Through a hybrid and participative MOOC we aim to develop a critical and creative perspective about the way AI is integrated in the different domains of our lives. We have built and now operate a MOOC in AI for all the citizens from 15 years old. The MOOC aims to help understanding AI foundations and applications, intended for a large public beyond the school domain, with more than 20000 participants engaged in the MOOC after nine months. This study addresses the pedagogical methods for designing and evaluating the MOOC in AI. Through this study we raise four questions regarding citizen education in AI: Why (i.e., to which aim) sharing such citizen formation ? What is the disciplinary knowledge to be shared? What are the competencies to develop ? How can it be shared and evaluated? We finally share learning analytics, quantitative and qualitative evaluations and explain to which extent educational science research helps enlighten such large scale initiatives. The analysis of the MOOC in AI helps to identify that the main feedback related to AI is “fear”, because AI is unknown and mysterious to the participants. After developing playful AI simulations, the AI mechanisms become familiar for the MOOC participants and they can overcome their misconception on AI to develop a more critical point of view. This contribution describes a K-12 AI educational project or initiatives of a considerable impact, via the formation of teachers and other educators

Layers response to a suboptimal diet through phenotype and transcriptome changes in four tissues

Poultry meat and eggs are major sources of nutrients in the human diet. The long production career of laying hens expose them to biotic or abiotic stressors, lowering their production. Understanding the mechanisms of adaptation to stress is crucial for selecting robust animals and meeting the needs of a growing human population. In this study, financed by the French ChickStress and the European Feed-a-Gene (grant agreement no. 633531) programs, we compared the effects of a 15%-energy-reduced diet (feed stress, FS) vs a commercial diet (control, CT) on phenotypic traits and adipose, blood, hypothalamus and liver transcriptomes in two feed-efficiency-diverging lines. Phenotypic traits showed differences between lines or diets, but no line × diet interaction. In the FS group, feed intake (FI) increased and hens had lower body- and abdominal adipose weight, compared to CT group. We found no differences in egg production or quality. At the transcriptomic level, 16,461 genes were expressed in one or more tissues, 41% of which were shared among tissues. We found differentially expressed genes between lines or diet in all tissues, and almost no line × diet interactions. Focusing on diet, adipose and liver transcriptomes were unaffected. In blood, pathways linked to amino acids, monosaccharides, and steroid metabolism were affected, while in the hypothalamus, changes were observed in fatty acid metabolism and endocannabinoid signalling. Given the similarities in egg production, the FS animals seem to have adapted to the stress by increasing FI and by mobilizing adipose reserves. Increase in FI did not appear to affect liver metabolism, and the mobilization of adipose reserves was apparently not driven at the transcriptomic level. In blood, the pathways linked to metabolic processes suggest a metabolic role for this tissue in chicken, whose erythrocytes are nucleated and contain mitochondria. FI increase might be linked to the hypothalamic pathway of endocannabinoid signalling, which are lipid-based neurotransmitters, notably involved in the regulation of appetite

Understanding Intelligently Artificial Intelligence : a citizens' open formation

International audienceOur whole society is and will be deeply impacted by digital science and this takes a new qualitative and quantitative turn with what is named artificial intelligence (AI). We must allow everyone to master, thus understand how all this works. This means computational thinking discovery and machine learning initiation. Directly inspired by the Finnish initiative to train 1% of its population on these subjects and after our success in providing a hybrid formation on computational thinking for teachers and citizens not familiar with computer science where more 45000 persons have been reached, yielding a satisfaction level higher than 90%, we have built and now operate a citizen training in AI in the broad sense, intended to a large public beyond the school domain, with the goal of giving rise to an ubiquitary citizen university in digital science and cultur