2,046 Projects, page 1 of 410
The skin is a complex tissue, capable of controlling infections through efficient immune responses while maintaining its own integrity. Dendritic cells (DCs) constitute sentinels of the immune system that contribute to elicit and control skin immune responses. Using innovative mouse models (LangEGFP and LangEGFPDTR), we studied the Langerhans cells (LCs) located in the epidermis, we discovered a new DC subset in the dermis (Poulin, 2007) and described five different DC subsets in the skin (LCs, CD207+ CD103-, CD207+ CD103+, CD207- CD11b-, and CD207- CD11b+ dermal DCs (DDCs)). We hypothesized that this phenotypic heterogeneity is associated with functional differences. Accordingly, the main objective of the present project is to understand the biological role of these different skin DC subsets by focussing mainly on tolerance mechanisms such as clonal deletion of self-specific T cells and induction of regulatory T cells (Treg). Four lines of research will be developed : 1. We will take advantage of our ability to discriminate homogeneous skin DC subsets to develop a comparative transcriptomic analysis of such five skin DC subsets. Such approach should provide us important hints on the functional specialization of those various skin DC subsets. 2. Using a transgenic mice where a model antigen (OVA) is expressed in keratinocytes (K5-mOVA), we have showed that the CD207+ CD103+ DDC subset was the only one capable of cross-presenting such self-antigen to OVA-specific OT-I CD8+ T cells (Henri, 2009). One aim of the present proposal is thus to elucidate the mechanism underlying the capacity of the CD207+ CD103+ DDCs to cross-present antigens. More specifically, we will determine whether this cross-presenting capacity is due to their enhanced capacity to encounter OT-I CD8+ T cells via XCR1 chemokine receptor expression. Moreover, the K5-mOVA model should allow us to further understand the mechanism of peripheral tolerance that is based on clonal deletion. 3. Treg cells could be induced by DCs producing retinoic acid (RA) through the oxidation of retinaldehyde by retinaldehyde dehydrogenase (ALDH). We have recently showed that in the skin, only the CD207- CD11b+ DDC was expressing the ALDH at the protein level and was able to induce Treg cells in vitro (Guilliams, in press). We hypothesized that this important property also extends in vivo. To determine if the high frequency of Treg cells found in the skin is the consequence of the inductive function of the RA-producing CD207- CD11b+ skin DDC subset, we will develop an innovative knock-in mouse model allowing to track and ablate RA production by CD207- CD11b+ DCs in vivo. 4. Finally, we will attempt to visualize the interactions of DCs with T cells using confocal and intravital microscopy. To track DDCs both in the dermis and in the CLNs, we intend to use mice that co-express the Cre recombinase under the control of either the CD11c or the Langerin gene and a LoxP-STOP-LoxP-RFP red reporter cassette within the Rosa locus. Adoptive transfer of green (GFP+) OT-I T cells into Langerin-Cre x LoxP-STOP-LoxP-RFP x K5-mOVA recipient will give us the unique possibility to determine by confocal and 2 photon microscopy whether the GFP+ OT-I T cells colocalize with the cross-presenting RFPbright CD207+ DDCs that have captured OVA in the skin. If the expression of XCR1 chemokine receptor is of importance in such cross-talk, developing a K5-mOVA x Lang-Cre x LoxP-STOP-LoxP-RFP x B6.129P2-Xcr1/J mouse line will allow us to visualize whether XCR1-deficient CD207+ DDCs have lost their ability to contact CD8+ T cells. In conclusion, this research proposal aims to unravel if the phenotypic diversity of the skin DCs is associated with specialized functions in vivo. A better understanding of the mechanisms of tolerance contributing to maintain skin homeostasis will allow the selection of the most optimal DC target for therapy intended to intensify or dampen skin immune responses.
Gene therapies offer great therapeutic perspectives toward personalized medicine. However, despite considerable efforts, translation of these technologies into clinical applications remains slow and is often hampered by the issue of gene delivery. The intracellular delivery of oligonucleotides is indeed a daunting task due their poor ability to cross biological membranes and their rapid degradation by endogenous nucleases. Viruses are remarkable at performing efficient gene delivery: they ensure chemical stability of the viral gene by its encapsulation within a capsid which actively transports the material to its biological target. Since viral gene delivery can cause severe adverse effects, small molecules able to mimic this process would therefore open new perspectives in gene delivery. The present research project lays out a general methodology to identify synthetic compounds that dynamically encapsulate oligonucleotides and may thus serve as gene carriers. The nanoencapsulation within a synthetic capsid is expected to stabilize oligonucleotides against enzymatic degradation. Furthermore, chemical engineering of the supramolecular carriers will enable active and targeted delivery of unmodified oligonucleotides. The long-term goal of the project is to develop a molecular toolbox for the supramolecular engineering of various oligonucleotides (ssDNA, dsDNA, microRNA, siRNA) with a selective molecular carrier for each application (eg. delivery of antisense DNA to cancer cells) and an extremely straightforward protocol to produce the bioassembly.
L'étonnante capacité d'adaptation et de survie de M. tuberculosis (M. tb) dans l'hôte infecté est grandement liée à la structure singulière de sa paroi. En dépit de leur rôle dans les interactions avec l'hôte et la physiopathologie tuberculeuse, les mécanismes gouvernant l'expression des composants de la paroi au cours de l'infection restent peu connus. Nos travaux suggèrent que les Ser/Thr protéines kinases participeraient aux mécanismes d'adaptation mis en place par M. tb. Ainsi, la phosphorylation par PknH ou PknL de deux régulateurs transcriptionnels, EmbR et Rv2175c, modulerait l'expression des composants de paroi et/ou de la division cellulaire. Ce projet consiste donc à i) décrire de quelle façon la phosphorylation de EmbR et Rv2175c affecterait les constituants de la paroi, ii) examiner la contribution relative de la phosphorylation de ces régulateurs dans la physiologie et la virulence de M. tb et iii) identifier les régulons directement contrôlés in vivo par ces régulateurs.
The SNS project, which implies L2C, NEEL, IES, and ICG, intends to develop a broadband optical spin noise detection setup, for probing the spin dynamics of either localized paramagnetic impurities or itinerant carriers in semiconductors. The setup will be tested on Mn spins embedded in CdTe, an ideal model system for broadband optical spin noise detection. The optical setup to be developed will benefit from the recently developed Spin Noise Spectroscopy (SNS) technique. SNS is based on fast sampling of Faraday rotation fluctuations, which faithfully reproduce those of the spins being probed with the laser beam. One gets by FFT a spin noise spectrum equivalent to a spin resonance spectrum. In semiconductors the case of transition metals differs from conduction electrons, by their complex spectra spreading over 1 GHz in case of manganese, the weakness of expected signal, and the necessity to apply a magnetic field of several kOe in order to limit the number of spectral components. This implies a bandwidth of the detection system of several GHz. Thus, the project plans to develop a specific setup, based on either optical heterodyne mixing of the spin noise signal. In addition to the already put forward advantages of SNS over other methods, such as being a “perturbation-free” method, sensitive to a small number of spins, optical heterodyne mixing will extend the spectrum of accessible spin fluctuations in arbitrary magnetic field. Thus this method will outperform Electronic Paramagnetic Resonance (EPR) in terms of sensitivity, but also Optically Detected Magnetic Resonance (ODMR) in terms of bandwidth. It has a strong potential for studying spin noise and spin dynamics in arbitrarily large magnetic field of, not only localized spins, but also itinerant carriers including the regime of short spin relaxation times. The final outcome of the project should be the validation of the method as an optical technique for investigating broadband spin noise of paramagnetic impurities or itinerant carriers in semiconductors. It will be demonstrated by obtaining manganese noise spectra exhibiting fine and hyperfine structures complying with EPR, and will be used for solving some pending questions on Mn spin coherence lifetimes.
One of the major scientific challenges in modern evolutionary biology concerns the existence of non-genetic heritability and its importance in adaptive explanations. In particular, questions regarding the relationship between biological evolution and cultural evolution have become fundamental in biology as well as in social sciences. The purpose of this project of fundamental research is to shed light on these questions by establishing a new methodology for the study of cultural evolution. By culture, we mean the set of objects, ideas and behaviours that are transmitted from individual to individual by non-genetic means. In recent years, important theoretical advances have clarified the relationship between biological and cultural evolution and raised the question of the balance between selection and attraction (i.e. directed transformations occurring during transmission). Ideally, transmission chains experiments, in which the results of one individual’s action are passed on to another individual, should easily provide an accurate estimation of cultural selection and attraction. However, transmission chains conducted so far have remained severely limited in this respect and there is to our knowledge no convincing experimental paradigm that can quantify some basic properties of cultural evolution such as the degree of fidelity of transmission, the power of cultural selection or the strength of attraction. The experimental system that we need to develop should overcome these limitations and have the properties that make experiments in biological evolution successful. To succeed, we propose to take advantage of the unique opportunity offered by a recently developed research platform of the Laboratoire de Psychologie Cognitive (UMR 7290), that comprises fully automatized operant conditioning stations. This world unique structure offers the ideal environment to study social learning and cultural evolution and in order to study the feasibility of our proposal, we carried out a first pilot experiment with baboons that addressed the main technical challenges that we aim to overcome (large number of trials, repeatability of the experiment and the use of a non-verbal task). This pilot study, which was designed to demonstrate the potential of the approach taken, has been extremely successful. Accordingly, we will estimate the balance between attraction and selection by applying our new methodology to 4 challenging questions in the field. Firstly, we will extend our pilot work by developing, carrying out and analysing transmission chains with non-human primates. Secondly, we will study the impact of social influence on social learning and cultural evolution, which, surprisingly, has never been studied in detail. Thirdly, building on previous studies showing that precursors of fundamental aspects of language can be found in non-human primates, we will address the question of the evolution of compositionality in non-human primates. Finally, we will also aim to demonstrate the strength of our approach to study cognitive capacities that are specific to humans by studying the cultural evolution of arguments. The new experimental system that we have described opens the door to many questions that were, until now, impossible to address experimentally and we therefore expect to produce important methodological, analytical and theoretical advances in the field. The study of cultural evolution and social learning remains under-represented in France compared to other European countries. We aim to bring researchers from various institutions and disciplines together to create a core network of collaborations that will strengthen the domain, promote its development and facilitate the future emergence of research teams dedicated to this topic in France. This will open the way to a broad range of research opportunities that will facilitate the development of long term projects (5-10 years) and the prospect of employment for the coordinator.