Prolonged antiretroviral therapy initiated at seroconversion is associated with a polyfunctional HIV-1-specific T-cell profile comparable to that of long-term non-progressors (LTNPs)

Background: Early initiation of antiretroviral therapy (ART) may dramatically curtail cumulative immunological damage allowing maximal levels of immune preservation/reconstitution and induce an immunovirological status similar to that of HIV-1 LTNPs with low viral reservoirs and polyfunctional HIV-1 specific T cell responses.Methods: We performed a cross-sectional study of an HIV-1 seroconverter cohort on long-term ART (LTTS) and compared it to one of LTNPs. Inclusion criteria for 20 LTTS were: (a) ?4 years ART; (b) long-term aviremia and (c) absence of treatment failure and for 15 LTNPs: (a) ?7 years of documented HIV-1 infection; (b) <1000 HIV-1 RNA copies/mL and ?500 CD4+ T-cells/mm3 in >90% of measurements; (d) absence of AIDS-defining conditions; (e) ART-naı¨ve except for temporary ART for prevention of MTCT. In both cohorts, we analysed residual viral replication and reservoirs in peripheral blood, as measured by cellassociated HIV-1 RNA and DNA in PBMCs, respectively and used polychromatic flow cytometry to analyse HIV-1-specific CD4+ and CD8+ T-cell functional profile in terms of cytokine production using IFN-c, IL-2, TNF-a production.Results: Cell-associated DNA [47.7 (4.8-583.2) in LTTS and 19.7 (0.5-295.5) in LTNPS, p=0.10], and RNA [3.9 (0-36) and 5.8 (0-10.3), respectively] were shown to be similarly low in both cohorts. We identified 103 CD8 T cell epitope-specific responses, all subjects responding to ?1 epitope. Mean responding number of responding epitopes per patient was 2 and 4 in LTTS and LTNPS, respectively. Mean% of cytokine-secreting CD8 T cells was 0.37% and 0.50% (p=0.06), of these 43% and 39% (p=0.12) were secreting simultaneously IFN-c, IL-2 and TNF-a. Respective values for CD4 T cells were 0.28% and 0.33% (p=0.28) of which 33% and 30% (0.32) were secreting these 3 cytokines simultaneously.Conclusions: Long-term aviremia after very early ART initiation is associated with low levels of reservoirs saturation ad residual replication. Although less broad CD8 T cell responses were found in LTTS, HIV-1 specific CD4 and CD8 T cell responses showed similar magnitude and functional profile in the 2 cohorts. Our results indicate that prolonged ART initiated at the time of HIV-1 seroconversion is associated with immuno-virological features which resemble those of LTNPs. (BHIVA Research Award Winner 2008: Anna Garcia-Diaz.)

Aplicació web per a un casino online

L'objectiu del projecte es basa principalment en la realització d'una aplicació fent servir els coneixements adquirits al llarg de la carrera, emmarcats dins l'àmbit de les tecnologies oferides per la plataforma Microsoft .NET. Més concretament i d'acord amb l'àrea escollida, l'objectiu funcional es centra en una aplicació web per a un casino virtual, que permeti el registre, l'autenticació i el manteniment d'usuaris, i ofereixi a aquests un àrea de jocs.Com a objectius no funcionals, es planteja la utilització de la tecnologia ASP.NET, la plataforma Silverlight, i AJAX com a tècnica de desenvolupament web.

MAPI: towards the integrated exploitation of bioinformatics Web Services.

BACKGROUND. Bioinformatics is commonly featured as a well assorted list of available web resources. Although diversity of services is positive in general, the proliferation of tools, their dispersion and heterogeneity complicate the integrated exploitation of such data processing capacity. RESULTS. To facilitate the construction of software clients and make integrated use of this variety of tools, we present a modular programmatic application interface (MAPI) that provides the necessary functionality for uniform representation of Web Services metadata descriptors including their management and invocation protocols of the services which they represent. This document describes the main functionality of the framework and how it can be used to facilitate the deployment of new software under a unified structure of bioinformatics Web Services. A notable feature of MAPI is the modular organization of the functionality into different modules associated with specific tasks. This means that only the modules needed for the client have to be installed, and that the module functionality can be extended without the need for re-writing the software client. CONCLUSIONS. The potential utility and versatility of the software library has been demonstrated by the implementation of several currently available clients that cover different aspects of integrated data processing, ranging from service discovery to service invocation with advanced features such as workflows composition and asynchronous services calls to multiple types of Web Services including those registered in repositories (e.g. GRID-based, SOAP, BioMOBY, R-bioconductor, and others).

Early and Prolonged Antiretroviral Therapy Is Associated with an HIV-1-Specific T-Cell Profile Comparable to That of Long-Term Non-Progressors.

Background: Intervention with antiretroviral treatment (ART) and control of viral replication at the time of HIV-1 seroconversion may curtail cumulative immunological damage. We have therefore hypothesized that ART maintenance over a very prolonged period in HIV-1 seroconverters could induce an immuno-virological status similar to that of HIV-1 long-term non-progressors (LTNPs).Methodology/Principal Findings: We have investigated a cohort of 20 HIV-1 seroconverters on long-term ART (LTTS) and compared it to one of 15 LTNPs. Residual viral replication and reservoirs in peripheral blood, as measured by cell-associated HIV-1 RNA and DNA, respectively, were demonstrated to be similarly low in both cohorts. These two virologically matched cohorts were then comprehensively analysed by polychromatic flow cytometry for HIV-1-specific CD4(+) and CD8(+) T-cell functional profile in terms of cytokine production and cytotoxic capacity using IFN-gamma, IL-2, TNF-alpha production and perforin expression, respectively. Comparable levels of highly polyfunctional HIV-1-specific CD4(+) and CD8(+) T-cells were found in LTTS and LTNPs, with low perforin expression on HIV-1-specific CD8+ T-cells, consistent with a polyfunctional/non-cytotoxic profile in a context of low viral burden.Conclusions: Our results indicate that prolonged ART initiated at the time of HIV-1 seroconversion is associated with immuno-virological features which resemble those of LTNPs, strengthening the recent emphasis on the positive impact of early treatment initiation and paving the way for further interventions to promote virological control after treatment interruption.

Functional multidisciplinary rehabilitation versus outpatient physiotherapy for non specific low back pain: randomized controlled trial.

INTRODUCTION: In recent decades the treatment of non-specific low back pain has turned to active modalities, some of which were based on cognitive-behavioural principles. Non-randomised studies clearly favour functional multidisciplinary rehabilitation over outpatient physiotherapy. However, systematic reviews and meta-analysis provide contradictory evidence regarding the effects on return to work and functional status. The aim of the present randomised study was to compare long-term functional and work status after 3-week functional multidisciplinary rehabilitation or 18 supervised outpatient physiotherapy sessions. METHODS: 109 patients with non-specific low back pain were randomised to either a 3-week functional multidisciplinary rehabilitation programme, including physical and ergonomic training, psychological pain management, back school and information, or 18 sessions of active outpatient physiotherapy over 9 weeks. Primary outcomes were functional disability (Oswestry) and work status. Secondary outcomes were lifting capacity (Spinal Function Sort and PILE test), lumbar range-of-motion (modified-modified Schöber and fingertip-to-floor tests), trunk muscle endurance (Shirado and Biering-Sörensen tests) and aerobic capacity (modified Bruce test). RESULTS: Oswestry disability index was improved to a significantly greater extent after functional multidisciplinary rehabilitation compared to outpatient physiotherapy at follow-up of 9 weeks (P = 0.012), 9 months (P = 0.023) and 12 months (P = 0.011). Work status was significantly improved after functional multidisciplinary rehabilitation only (P = 0.012), resulting in a significant difference compared to outpatient physiotherapy at 12 months' follow-up (P = 0.012). Secondary outcome results were more contrasted. CONCLUSIONS: Functional multidisciplinary rehabilitation was better than outpatient physiotherapy in improving functional and work status. From an economic point of view, these results should be backed up by a cost-effectiveness study.

Autologous adult cortical cell transplantation enhances functional recovery following unilateral lesion of motor cortex in primates: a pilot study.

BACKGROUND:: Although cell therapy is a promising approach after cerebral cortex lesion, few studies assess quantitatively its behavioral gain in non-human primates. Furthermore, implantations of fetal grafts of exogenous stem cells are limited by safety and ethical issues. OBJECTIVE:: To test in non-human primates the transplantation of autologous adult neural progenitor cortical cells with assessment of functional outcome. METHODS:: Seven adult macaque monkeys were trained to perform a manual dexterity task, before the hand representation in motor cortex was chemically lesioned unilaterally. Five monkeys were used as control, compared to two monkeys subjected to different autologous cells transplantation protocols performed at different time intervals. RESULTS:: After lesion, there was a complete loss of manual dexterity in the contralesional hand. The five "control" monkeys recovered progressively and spontaneously part of their manual dexterity, reaching a unique and definitive plateau of recovery, ranging from 38% to 98% of pre-lesion score after 10 to 120 days. The two "treated" monkeys reached a first spontaneous recovery plateau at about 25 and 40 days post-lesion, representing 35% and 61% of the pre-lesion performance, respectively. In contrast to the controls, a second recovery plateau took place 2-3 months after cell transplantation, corresponding to an additional enhancement of functional recovery, representing 24 and 37% improvement, respectively. CONCLUSIONS:: These pilot data, derived from two monkeys treated differently, suggest that, in the present experimental conditions, autologous adult brain progenitor cell transplantation in non-human primate is safe and promotes enhancement of functional recovery.

From SNPs to pathways: integration of functional effect of sequence variations on models of cell signalling pathways

Background: Single nucleotide polymorphisms (SNPs) are the most frequent type of sequence variation between individuals, and represent a promising tool for finding genetic determinants of complex diseases and understanding the differences in drug response. In this regard, it is of particular interest to study the effect of non-synonymous SNPs in the context of biological networks such as cell signalling pathways. UniProt provides curated information about the functional and phenotypic effects of sequence variation, including SNPs, as well as on mutations of protein sequences. However, no strategy has been developed to integrate this information with biological networks, with the ultimate goal of studying the impact of the functional effect of SNPs in the structure and dynamics of biological networks. Results: First, we identified the different challenges posed by the integration of the phenotypic effect of sequence variants and mutations with biological networks. Second, we developed a strategy for the combination of data extracted from public resources, such as UniProt, NCBI dbSNP, Reactome and BioModels. We generated attribute files containing phenotypic and genotypic annotations to the nodes of biological networks, which can be imported into network visualization tools such as Cytoscape. These resources allow the mapping and visualization of mutations and natural variations of human proteins and their phenotypic effect on biological networks (e.g. signalling pathways, protein-protein interaction networks, dynamic models). Finally, an example on the use of the sequence variation data in the dynamics of a network model is presented. Conclusion: In this paper we present a general strategy for the integration of pathway and sequence variation data for visualization, analysis and modelling purposes, including the study of the functional impact of protein sequence variations on the dynamics of signalling pathways. This is of particular interest when the SNP or mutation is known to be associated to disease. We expect that this approach will help in the study of the functional impact of disease-associated SNPs on the behaviour of cell signalling pathways, which ultimately will lead to a better understanding of the mechanisms underlying complex diseases.

A context-based methodology for integrating Web 2.0 services in learning scenarios

The emergence of the Web 2.0 technologies in the last years havechanged the way people interact with knowledge. Services for cooperation andcollaboration have placed the user in the centre of a new knowledge buildingspace. The development of new second generation learning environments canbenefit from the potential of these Web 2.0 services when applied to aneducational context. We propose a methodology for designing learningenvironments that relates Web 2.0 services with the functional requirements ofthese environments. In particular, we concentrate on the design of the KRSMsystem to discuss the components of this methodology and its application.

Record keeping by Swiss physiotherapists--a national survey of knowledge regarding legal requirements.

A national survey conducted in Switzerland aimed to evaluate the knowledge of physiotherapists regarding the legal requirements for record keeping and to collect their feedback about record keeping in general. Three physiotherapists from various professional practice groups and a lawyer specialised in health law developed a questionnaire that was sent to the 7,753 members of two existing national associations of physiotherapists. The questionnaire evaluated the participants' knowledge by calculating a score of legal knowledge, which had a maximum of 30 points. We included 825 questionnaires in the analysis. The large majority (83.4%) of participants confessed an ignorance of the legal requirements concerning record keeping prior to the survey. The average score of legal compatibility was 8 points. The younger age of the physiotherapists was a significant predictor of having knowledge of the legal requirements for record keeping (p <0.001). The participants had an appreciation of the value of records, but they did not have the relevant knowledge regarding the legal requirements for keeping records. The participants blamed a lack of time and remuneration for their failure to keep records according to known requirements. All practising allied health professionals should keep up-to-date and accurate records that conform to active legal requirements and existing international guidelines. In addition to the existing legal requirements, the emergence of e-health and the electronic era will trigger major changes in patient record management by physiotherapists.

Integrability and non-integrability of periodic non-autonomous Lyness recurrences

This paper studies non-autonomous Lyness type recurrences of the form x_{n+2}=(a_n+x_n)/x_{n+1}, where a_n is a k-periodic sequence of positive numbers with prime period k. We show that for the cases k in {1,2,3,6} the behavior of the sequence x_n is simple(integrable) while for the remaining cases satisfying k not a multiple of 5 this behavior can be much more complicated(chaotic). The cases k multiple of 5 are studied separately.

Integrability and non-integrability of periodic non-autonomous Lyness recurrences (revised and enlarged version)

This paper studies non-autonomous Lyness type recurrences of the form xn+2 = (an+xn+1)=xn, where fang is a k-periodic sequence of positive numbers with primitive period k. We show that for the cases k 2 f1; 2; 3; 6g the behavior of the sequence fxng is simple (integrable) while for the remaining cases satisfying this behavior can be much more complicated (chaotic). We also show that the cases where k is a multiple of 5 present some di erent features.

Multimodal MRI analysis of structural and functional networks in the human brain : application to two clinical studies : driving abilities under THC intoxication and early white matter changes in FXTAS

Les approches multimodales dans l'imagerie cérébrale non invasive sont de plus en plus considérées comme un outil indispensable pour la compréhension des différents aspects de la structure et de la fonction cérébrale. Grâce aux progrès des techniques d'acquisition des images de Resonance Magnetique et aux nouveaux outils pour le traitement des données, il est désormais possible de mesurer plusieurs paramètres sensibles aux différentes caractéristiques des tissues cérébraux. Ces progrès permettent, par exemple, d'étudier les substrats anatomiques qui sont à la base des processus cognitifs ou de discerner au niveau purement structurel les phénomènes dégénératifs et développementaux. Cette thèse met en évidence l'importance de l'utilisation d'une approche multimodale pour étudier les différents aspects de la dynamique cérébrale grâce à l'application de cette approche à deux études cliniques: l'évaluation structurelle et fonctionnelle des effets aigus du cannabis fumé chez des consommateurs réguliers et occasionnels, et l'évaluation de l'intégrité de la substance grise et blanche chez des jeunes porteurs de la prémutations du gène FMR1 à risque de développer le FXTAS (Fragile-X Tremor Ataxia Syndrome). Nous avons montré que chez les fumeurs occasionnels de cannabis, même à faible concentration du principal composant psychoactif (THC) dans le sang, la performance lors d'une tâche visuo-motrice est fortement diminuée, et qu'il y a des changements dans l'activité des trois réseaux cérébraux impliqués dans les processus cognitifs: le réseau de saillance, le réseau du contrôle exécutif, et le réseau actif par défaut (Default Mode). Les sujets ne sont pas en mesure de saisir les saillances dans l'environnement et de focaliser leur attention sur la tâche. L'augmentation de la réponse hémodynamique dans le cortex cingulaire antérieur suggère une augmentation de l'activité introspective. Une investigation des ef¬fets au niveau cérébral d'une exposition prolongée au cannabis, montre des changements persistants de la substance grise dans les régions associées à la mémoire et au traitement des émotions. Le niveau d'atrophie dans ces structures corrèle avec la consommation de cannabis au cours des trois mois précédant l'étude. Dans la deuxième étude, nous démontrons des altérations structurelles des décennies avant l'apparition du syndrome FXTAS chez des sujets jeunes, asymptomatiques, et porteurs de la prémutation du gène FMR1. Les modifications trouvées peuvent être liées à deux mécanismes différents. Les altérations dans le réseau moteur du cervelet et dans la fimbria de l'hippocampe, suggèrent un effet développemental de la prémutation. Elles incluent aussi une atrophie de la substance grise du lobule VI du cervelet et l'altération des propriétés tissulaires de la substance blanche des projections afférentes correspondantes aux pédoncules cérébelleux moyens. Les lésions diffuses de la substance blanche cérébrale peu¬vent être un marquer précoce du développement de la maladie, car elles sont liées à un phénomène dégénératif qui précède l'apparition des symptômes du FXTAS. - Multimodal brain imaging is becoming a leading tool for understanding different aspects of brain structure and function. Thanks to the advances in Magnetic Resonance imaging (MRI) acquisition schemes and data processing techniques, it is now possible to measure different parameters sensitive to different tissue characteristics. This allows for example to investigate anatomical substrates underlying cognitive processing, or to disentangle, at a pure structural level degeneration and developmental processes. This thesis highlights the importance of using a multimodal approach for investigating different aspects of brain dynamics by applying this approach to two clinical studies: functional and structural assessment of the acute effects of cannabis smoking in regular and occasional users, and grey and white matter assessment in young FMR1 premutation carriers at risk of developing FXTAS. We demonstrate that in occasional smokers cannabis smoking, even at low concentration of the main psychoactive component (THC) in the blood, strongly decrease subjects' performance on a visuo-motor tracking task, and globally alters the activity of the three brain networks involved in cognitive processing: the Salience, the Control Executive, and the Default Mode networks. Subjects are unable to capture saliences in the environment and to orient attention to the task; the increase in Hemodynamic Response in the Anterior Cingulate Cortex suggests an increase in self-oriented mental activity. A further investigation on long term exposure to cannabis, shows a persistent grey matter modification in brain regions associated with memory and affective processing. The degree of atrophy in these structures also correlates with the estimation of drug use in the three months prior the participation to the study. In the second study we demonstrate structural changes in young asymptomatic premutation carriers decades before the onset of FXTAS that might be related to two different mechanisms. Alteration of the cerebellar motor network and of the hippocampal fimbria/ fornix, may reflect a potential neurodevelopmental effect of the premutation. These include grey matter atrophy in lobule VI and modification of white matter tissue property in the corresponding afferent projections through the Middle Cerebellar Peduncles. Diffuse hemispheric white matter lesions that seem to appear closer to the onset of FXTAS and be related to a neurodegenerative phenomenon may mark the imminent onset of FXTAS.

Functional importance of cardiac enhancer-associated noncoding RNAs in heart development and disease.

The key information processing units within gene regulatory networks are enhancers. Enhancer activity is associated with the production of tissue-specific noncoding RNAs, yet the existence of such transcripts during cardiac development has not been established. Using an integrated genomic approach, we demonstrate that fetal cardiac enhancers generate long noncoding RNAs (lncRNAs) during cardiac differentiation and morphogenesis. Enhancer expression correlates with the emergence of active enhancer chromatin states, the initiation of RNA polymerase II at enhancer loci and expression of target genes. Orthologous human sequences are also transcribed in fetal human hearts and cardiac progenitor cells. Through a systematic bioinformatic analysis, we identified and characterized, for the first time, a catalog of lncRNAs that are expressed during embryonic stem cell differentiation into cardiomyocytes and associated with active cardiac enhancer sequences. RNA-sequencing demonstrates that many of these transcripts are polyadenylated, multi-exonic long noncoding RNAs. Moreover, knockdown of two enhancer-associated lncRNAs resulted in the specific downregulation of their predicted target genes. Interestingly, the reactivation of the fetal gene program, a hallmark of the stress response in the adult heart, is accompanied by increased expression of fetal cardiac enhancer transcripts. Altogether, these findings demonstrate that the activity of cardiac enhancers and expression of their target genes are associated with the production of enhancer-derived lncRNAs.

BioSuper: A web tool for the superimposition of biomolecules and assemblies with rotational symmetry

Background Most of the proteins in the Protein Data Bank (PDB) are oligomeric complexes consisting of two or more subunits that associate by rotational or helical symmetries. Despite the myriad of superimposition tools in the literature, we could not find any able to account for rotational symmetry and display the graphical results in the web browser. Results BioSuper is a free web server that superimposes and calculates the root mean square deviation (RMSD) of protein complexes displaying rotational symmetry. To the best of our knowledge, BioSuper is the first tool of its kind that provides immediate interactive visualization of the graphical results in the browser, biomolecule generator capabilities, different levels of atom selection, sequence-dependent and structure-based superimposition types, and is the only web tool that takes into account the equivalence of atoms in side chains displaying symmetry ambiguity. BioSuper uses ICM program functionality as a core for the superimpositions and displays the results as text, HTML tables and 3D interactive molecular objects that can be visualized in the browser or in Android and iOS platforms with a free plugin. Conclusions BioSuper is a fast and functional tool that allows for pairwise superimposition of proteins and assemblies displaying rotational symmetry. The web server was created after our own frustration when attempting to superimpose flexible oligomers. We strongly believe that its user-friendly and functional design will be of great interest for structural and computational biologists who need to superimpose oligomeric proteins (or any protein). BioSuper web server is freely available to all users at http://ablab.ucsd.edu/BioSuper webcite.

Role of an LRR receptor-like kinase in the establishment of a functional root endodermal barrier

The endodermis is a highly conserved cell layer present in the root of all vascular plants, except Lycophytes. This tissue layer establishes a protective diffusion barrier surrounding the vasculature and is expected to prevent passive, uncontrolled flow of nutrients through the root. This barrier property is achieved by the production of Casparian strips (CS), a localized cell wall impregnation of lignin in the anticlinal walls of each endodermal cell, forming a belt-like structure sealing the extracellular space. The CS act as a selective barrier between the external cell layers and the vascular cylinder and are thought to be important in many aspects of root function. For instance, selective nutrient uptake and sequestration from the soil, resistance to different abiotic and biotic stresses are expected to involve functional CS. Although discovered 150 years ago, nothing was known about the genes involved in CS establishment until recently. The use of the model plant Arabidopsis thaliana together with both reverse and forward genetic approaches led to the discovery of an increasing number of genes involved in different steps of CS formation during the last few years. One of these genes encodes SCHENGEN3 (SGN3), a leucine-rich repeat receptor-like kinase (LRR-RLK). SGN3 was discovered first by reverse genetic due to its endodermis-enriched expression, and the corresponding mutant displays strong endodermal permeability of the apoplastic tracer Propidium Iodide (PI) indicative of defective CS. One aim of this thesis is to study the role of SGN3 at the molecular level in order to understand its involvement in establishing an impermeable CS. The endodermal permeability of sgn3 is shown to be the result of incorrect localization of key proteins involved in CS establishment (the "Casparian strip domain proteins", CASPs), leading to non-functional CS interrupted by discontinuities. CASPs localize in the plasma membrane domain subjacent to the CS, named the Casparian Strip membrane Domain (CSD). The CSD discontinuities in sgn3 together with SGN3 localization in close proximity to the CASPs lead to the assumption that SGN3 is involved in the formation of a continuous CSD. In addition, SGN3 might have a second role, acting as a kinase reporting CSD integrity leading to lignin and suberin production in CSD/CS defective plants. Up to now, sgn3 is the strongest and most specific CS mutant available, displaying tracer penetration along the whole length of the seedling root. For this reason, this mutant is well suited in order to characterize the physiological behaviour of CS affected plants. Due to the lack of such mutants in the past, it was not possible to test the presumed functions of CS by using plants lacking this structure. We decided to use sgn3 for this purpose. Surprisingly, sgn3 overall growth is only slightly affected. Nevertheless, processes expected to rely on functional CS, such as water transport through the root, nutrient homeostasis, salt tolerance and resistance to an excess of some nutrients are altered in this mutant. On the other hand, homeostasis for most elements and drought tolerance are not affected in sgn3. It is surprising to observe that homeostatic defects are specific, with a decrease in potassium and an increase in magnesium levels. It indicates a backup system, set up by the plant in order to counteract free diffusion of nutrients into the stele. For instance, potassium shortage in sgn3 upregulates the transcription of potassium influx transport proteins and genes known to be induced by potassium starvation. Moreover, sgn3 mutant is hypersensitive to low potassium conditions. Hopefully, these results about SGN3 will help our understanding of CS establishment at the molecular level. In addition, physiological experiments using sgn3 should give us a framework for future experiments and help us to understand the different roles of CS and their involvement during nutrient radial transport through the root. -- L'endoderme est un tissu présent dans les racines de toutes les plantes vasculaires à l'exception des Lycophytes. Ce tissu établit une barrière protectrice entourant les tissus vasculaires dans le but d'éviter la diffusion passive et incontrôlée des nutriments au travers de la racine. Cette propriété de barrière provient de la production des cadres de Caspary, une imprégnation localisée de lignine des parties anticlinales de la paroi de chaque cellule d'endoderme. Cela donne naissance à un anneau/cadre qui rend étanche l'espace extracellulaire. Les cadres de Caspary agissent comme une barrière sélective entre les couches externes de la racine et le cylindre central et sont supposés être importants dans beaucoup d'aspects du fonctionnement de la racine. Par exemple, l'absorption sélective de nutriments et leur séquestration à partir du sol ainsi que la résistance contre différents stress abiotiques et biotiques sont supposés impliquer des cadres de Caspary fonctionnels. Bien que découverts il y a 150 ans, rien n'était connu concernant les gènes impliqués dans Ja formation des cadres de Caspary jusqu'à récemment. Durant ces dernière années, l'utilisation de la plante modèle Arabidopsis thaliana ainsi que des approches de génétique inverse et classique ont permis la découverte d'un nombre croissant de gènes impliqués à différentes étapes de la formation de cette structure. Un des ces gènes code pour SCHENGEN3 (SGN3), un récepteur kinase "leucine-rich repeat receptor-like kinase" (LRR-RLK). SGN3 a été découvert en premier par génétique inverse grâce à son expression enrichie dans l'endoderme. Les cadres de Caspary ne sont pas fonctionnels dans le mutant correspondant, ce qui est visible à cause de la perméabilité de l'endoderme au traceur apoplastique Propidium Iodide (PI). Un des objectifs de cette thèse est d'étudier la fonction de SGN3 au niveau moléculaire dans le but de comprendre son rôle dans la formation des cadres de Caspary. J'ai pu démontrer que la perméabilité de l'endoderme du mutant sgn3 est le résultat de la localisation incorrecte de protéines impliquées dans la formation des cadres de Caspary, les "Casparian strip domain proteins" (CASPs). Cela induit des cadres de Caspary non fonctionnels, contenant de nombreuses interruptions. Les CASPs sont localisés à la membrane plasmique dans un domaine sous-jacent les cadres de Caspary appelé Casparian Strip membrane Domain (CSD). Les interruptions du CSD dans le mutant sgn3, ainsi que la localisation de SGN3 à proximité des CASPs nous font penser à un rôle de SGN3 dans l'élaboration d'un CSD ininterrompu. De plus, SGN3 pourrait avoir un second rôle, agissant en tant que kinase reportant l'intégrité du CSD et induisant la production de lignine et de subérine dans des plantes contenant des cadres de Caspary non fonctionnels. Jusqu'à ce jour, sgn3 est le mutant en notre possession le plus fort et le plus spécifique, ayant un endoderme perméable tout le long de la racine. Pour cette raison, ce mutant est adéquat dans le but de caractériser la physiologie de plantes ayant des cadres de Caspary affectés. De manière surprenante, la croissance de sgn3 est seulement peu affectée. Néanmoins, des processus censés nécessiter des cadres de Caspary fonctionnels, comme le transport de l'eau au travers de la racine, l'homéostasie des nutriments, la tolérance au sel et la résistance à l'excès de certains nutriments sont altérés dans ce mutant. Malgré tout, l'homéostasie de la plupart des nutriments ainsi que la résistance au stress hydrique ne sont pas affectés dans sgn3. De manière surprenante, les altérations de l'ionome de sgn3 sont spécifiques, avec une diminution de potassium et un excès de magnésium. Cela implique un système de compensation établi par la plante dans le but d'éviter la diffusion passive des nutriments en direction du cylindre central. Par exemple, le manque de potassium dans sgn3 augmente la transcription de transporteurs permettant l'absorption de cet élément. De plus, des gènes connus pour être induits en cas de carence en potassium sont surexprimés dans sgn3 et la croissance de ce mutant est sévèrement affectée dans un substrat pauvre en potassium. Ces résultats concernant SGN3 vont, espérons-le, aider à la compréhension du processus de formation des cadres de Caspary au niveau moléculaire. De plus, les expériences de physiologie utilisant sgn3 présentées dans cette thèse devraient nous donner une base pour des expériences futures et nous permettre de comprendre mieux le rôle des cadres de Caspary, et plus particulièrement leur implication dans le transport radial des nutriments au travers de la racine. -- Les plantes terrestres sont des organismes puisant l'eau et les nutriments dont elles ont besoin pour leur croissance dans le sol grâce à leurs racines. De par leur immobilité, elles doivent s'adapter à des sols contenant des quantités variables de nutriments et il leur est crucial de sélectionner ce dont elles ont besoin afin de ne pas s'intoxiquer. Cette sélection est faite grâce à un filtre formé d'un tissu racinaire interne appelé endoderme. L'endoderme fabrique une barrière imperméable entourant chaque cellule appelée "cadre de Caspary". Ces cadres de Caspary empêchent le libre passage des nutriments, permettant un contrôle précis de leur passage. De plus, ils sont censés permettre de résister contre différents stress environnementaux comme la sécheresse, la salinité du sol ou l'excès de nutriments. Bien que découverts il y a 150 ans, rien n'était connu concernant les gènes impliqués dans la formation des cadres de Caspary jusqu'à récemment. Durant ces dernière années, l'utilisation de la plante modèle Arabidopsis thaliana a permis la découverte d'un nombre croissant de gènes impliqués à différentes étapes de la formation de cette structure. Un de ces gènes code pour SCHENGEN3 (SGN3), un récepteur kinase "leucine-rich repeat receptor-like kinase" (LRR- RLK). Nous montrons dans cette étude que le gène SGN3 est impliqué dans la formation des cadres de Caspary, et que le mutant correspondant sgn3 a des cadres de Caspary interrompus. Ces interruptions rendent l'endoderme perméable, l'empêchant de bloquer le passage des molécules depuis le sol vers le centre de la racine. En utilisant ce mutant, nous avons pu caractériser la physiologie de plantes ayant des cadres de Caspary affectés. Cela a permis de découvrir que le transport de l'eau au travers de la racine était affecté dans le mutant sgn3. De plus, l'accumulation de certains éléments dans les feuilles de ce mutant est altérée. Nous avons également pu montrer une sensibilité de ce mutant à un excès de sel ou de certains nutriments comme le fer et le manganèse.