Transmissible spongiform encephalopathies (TSEs), such as scrapie and variant Creutzfeldt-Jakob disease are infectious, fatal, neurodegenerative diseases. Following peripheral infection TSE agents usually accumulate in lymhoid tissues before spreading to the central nervous system. In mice, follicular dendritic cells (FDCs) expressing the host prion protein (PrPC) are essential for scrapie agent accumulation in lymphoid tissues. The accumulation of the scrapie agent on FDCs is critical for the efficient spread of infection to the brain. However, it is unknown whether FDCs themselves actively replicate the scrapie agent, or simply accumulate it following production by other cells types such as neurones, lymphocytes or other stromal cell populations. To definitively address this issue a transgenic mouse model was created in which PrPC is switched on or off exclusively on FDCs. Expression of cre-recombinase (Cre) under the action of cell-specific gene promoters can be used to induce or delete the expression of a target gene in specific cell populations. In this model, Cre expression is driven by the complement receptor type 2 gene (Cr2/CD21) which is expressed by FDCs and mature B lymphocytes. Characterisation of the CD21-cre mouse line was achieved by crossing with a ROSA26 reporter strain. The CD21-cre mouse line was subsequently crossed with floxed-PrP mouse lines to produce compound transgenic mouse lines in which PrPC expression was switched on or off, only in FDCs. Cre expression by B lymphocytes was eliminated by γ-irradiation and grafting recipient mice with Cre-deficient bone marrow. Immunohistochemical analysis confirmed the expression PrPC had been switched on or off exclusively on FDCs. Subsequently, the mice were challenged with scrapie by intra-peritoneal injection to determine the precise role of FDCs in the accumulation of scrapie in lymphoid tissues. Switching off PrPC expression exclusively on FDCs prevented the accumulation of TSE agent specific disease-associated PrPSc in the spleen after i.p inoculation. Conversely, in mice in which PrPC was expressed only on FDC, successful replication of the agent occurred on the FDC network in the spleen. Taken together, these data show PrPC-expressing FDCs alone are sufficient to support the accumulation of the scrapie agent within lymphoid tissues. Furthermore, these data suggest FDC replicate the TSE agent and do not simply accumulate it following synthesis by other cell types.

Transmissible spongiform encephalopathies (TSEs), or prion diseases, are fatal neurodegenerative diseases that affect several species, such as scrapie in sheep or goats and CJD in humans. In several species, neurological disease is preceded by TSE agent accumulation in lymphoid tissues prior to neuroinvasion. While oral transmission is considered the most common route for scrapie, transmission can also occur through lesions to the skin or mucosa, for example in the mouth or gastrointestinal tract due to rough feed, or birth associated skin damage. Scrapie has also been experimentally transmitted through skin scarification in mice. Following scrapie infection via skin scarification, PrPSc accumulates in the draining lymph node (LN) before spreading to other organs in the lymphoreticular system. It is not yet known by what means the scrapie agent is transported from the skin to the draining LN. Dendritic cells (DCs) in the skin have been found to transport viruses, such as HIV or Dengue, from the skin, thereby raising the question whether DCs or Langerhans cells (LCs), located within the epidermis, play a role in the uptake and transport of the TSE agent from the skin to the draining LN. CD11c is a cell surface marker traditionally used to identify or isolate DCs from other cell types. Mice and rats are naturally resistant to Diphtheria toxin (DTX). A transgenic mouse line was created where the Diphtheria toxin receptor (DTR) was expressed on CD11c+ cells. The presence of this receptor on CD11c+ cells allowed for the temporary conditional depletion of CD11c+ cells following a single injection of DTX. The cells repopulate the tissues within a time frame specific to the tissues the cells are located in. These mice were used to determine whether the absence of CD11c+ cells at the time of scrapie infection via the skin had an effect on the early accumulation of PrPSc within the lymphoid tissues and on disease progression. Immunohistochemical analysis demonstrated that early PrPSc accumulation in the draining LNs was delayed following depletion of CD11c+ cells, indicating that their potential role in the transport of the scrapie agent from the skin. Scrapie incubation period was not affected by the absence of the CD11c+ cells at the time of infection. Recent findings show that CD11c is not exclusive to DCs and is also expressed on macrophage populations. Following DTX-mediated depletion, DCs repopulate the tissues much faster than CD11c+ macrophages. Scrapie infection was carried out in the skin in DTX treated mice after DCs had repopulated the tissues but before macrophage numbers had returned, to determine whether macrophages rather than DCs played a role in the early accumulation of PrPSc in the draining LNs. No differences in PrPSc accumulation were observed in mice depleted of macrophages compared to controls and there was no effect on disease incubation period. Another transgenic mouse line was used, where DTX expression on langerin+ cells (LCs and langerin+ DCs in the dermis), allowed for their temporary depletion through DTX treatment. Following langerin+ cell depletion, increased PrPSc accumulation was observed in the draining LNs 7 weeks post infection, but did not affect the incubation period of disease. These results indicate that the absence of LCs somehow accelerated PrPSc accumulation, and that LCs might play a preventative role in early stages after infection. Histopathological analysis was used to complement microarray studies aimed to determine what immune responses were associated with scarification and DTXmediated depletion of cells within the skin and whether these responses might be linked to disease transmission. DCs and LCs in the skin appear to play different roles in the early stages following scrapie infection via the skin, but the lack of effect on incubation period does not rule out the involvement of other cell types or cell-free mechanisms of scrapie agent spread from the skin.

The Transmissible Spongiform Encephalopathies (TSEs) or “prion” diseases are a group of fatal neurodegenerative diseases the aetiology of which is not fully understood. These diseases are characterised by a number of pathological changes in the central nervous system (CNS) including; vacuolation of the neuropil, gliosis and deposition of PrPSc; the abnormal form of the host glycoprotein PrP. Although the major pathology in these diseases is associated with the CNS the immune system is central to the pathogenesis of many natural and experimental TSEs including natural scrapie in sheep, chronic wasting disease in free ranging and captive deer and variant CJD (vCJD) in humans. Unlike many infectious diseases where deficiencies in immune function are opportunistic for the invading pathogen a competent immune system is required for efficient TSE infection via peripheral routes. As infection of the lymphoid tissues in many TSEs can occur many months before the detection of infectivity in the CNS, the determination of those cells in the lymphoid system has been the focus of much research and a number of studies now point towards the importance of the follicular dendritic cell (FDC), a long-lived radio resistant cell, in TSE pathogenesis. The involvement of FDCs in peripheral TSE pathogenesis relates to the inability of ionising radiation to influence pathogenesis, the association of PrP protein with FDCs in both uninfected and infected lymphoid tissues, and the demonstration that TSE pathogenesis is severely impaired in mice devoid of these cells. The aims of this thesis were to further understand the role of FDCs in the pathogenesis of a range of mouse-adapted experimental TSE strains and to determine if peripherally acquired TSE infections are influenced by host age or by stimulation of the immune system. Using chimaeric mouse models where a mismatch in the expression of PrP protein between FDCs and lymphoid/myeloid cells was produced, further evidence for a critical role for in the pathogenesis of the ME7 TSE strain was produced. Although these findings produced strong evidence that FDCs were important for the ME7 strain the possibility that different TSE strains may target different cell types in the peripheral lymphoid system was explored using a range of mice with specific immunological defects. Infection of these mice with several experimental TSE strains showed that the presence of mature FDCs was also important for the pathogenesis of the strains tested. Clinical cases of vCJD have been confined almost exclusively to young adults, although the reasons behind this apparent age-related susceptibility are not fully understood. The capacity of the immune system to mediate immune responses to pathogens declines with age as a result of impaired lymphocyte and FDC function. As FDCs are critically involved in the pathogenesis of many TSEs, including vCJD, it was hypothesised that an aging immune system may impair disease pathogenesis. Peripheral infection of senescent mice failed to produce clinical disease during lifespan, although evidence of disease transmission, was detected in a proportion of aged mice. These findings demonstrate that this inefficient disease transmission, as a consequence of age, may lead to considerable levels of sub-clinical disease within the population. Finally the influence of immune system stimulation, by the generation of a humoral immune response, on peripheral TSE pathogenesis was investigated. These findings demonstrated that immunisation can influence pathogenesis, but only during the early stages of infection prior to spread to the CNS. These data imply that modulation of the immune system does not alter TSE pathogenesis once disease has been initiated in the CNS. Finally, these studies have found some preliminary evidence that TSE infection may induce FDC activation suggesting that TSE infection may influence the immune response. Together, these data show that a functional immune system and specifically, the presence of mature FDCs, are central to the pathogenesis of peripherally acquired TSE infections.

<p>Calcium (Ca2+) is a known important second messenger. Calcium/Calmodulin (CaM) dependent protein kinase kinase 2 (CaMKK2) is a crucial kinase in the calcium signaling cascade. Activated by Ca2+/CaM, CaMKK2 can phosphorylate other CaM kinases and AMP-activated protein kinase (AMPK) to regulate cell differentiation, energy balance, metabolism and inflammation. Outside of the brain, CaMKK2 can only be detected in hematopoietic stem cells and progenitors, and in the subsets of mature myeloid cells. CaMKK2 has been noted to facilitate tumor cell proliferation in prostate cancer, breast cancer, and hepatic cancer. However, whethter CaMKK2 impacts the tumor microenvironment especially in hematopoietic malignancies remains unknown. Due to the relevance of myeloid cells in tumor growth, we hypothesized that CaMKK2 has a critical role in the tumor microenvironment, and tested this hyopothesis in murine models of hematological and solid cancer malignancies. </p><p>We found that CaMKK2 ablation in the host suppressed the growth of E.G7 murine lymphoma, Vk*Myc myeloma and E0771 mammary cancer. The selective ablation of CaMKK2 in myeloid cells was sufficient to restrain tumor growth, of which could be reversed by CD8 cell depletion. In the lymphoma microenvironment, ablating CaMKK2 generated less myeloid-derived suppressor cells (MDSCs) in vitro and in vivo. Mechanistically, CaMKK2 deficient dendritic cells showed higher Major Histocompatibility Class II (MHC II) and costimulatory factor expression, higher chemokine and IL-12 secretion when stimulated by LPS, and have higher potent in stimulating T-cell activation. AMPK, an anti-inflammatory kinase, was found as the relevant downstream target of CaMKK2 in dendritic cells. Treatment with CaMKK2 selective inhibitor STO-609 efficiently suppressed E.G7 and E0771 tumor growth, and reshaped the tumor microenvironment by attracting more immunogenic myeloid cells and infiltrated T cells.</p><p>In conclusion, we demonstrate that CaMKK2 expressed in myeloid cells is an important checkpoint in tumor microenvironment. Ablating CaMKK2 suppresses lymphoma growth by promoting myeloid cells development thereby decreasing MDSCs while enhancing the anti-tumor immune response. CaMKK2 inhibition is an innovative strategy for cancer therapy through reprogramming the tumor microenvironment.</p> / Dissertation

La zone marginale de la rate apparaît comme un lieu stratégique de détection des antigènes et agents pathogènes véhiculés par le sang. Ces propriétés sont principalement liées à la présence de cellules appartenant au système immunitaire inné parmi lesquelles se trouvent des nombreuses cellules présentatrices d’antigènes (APC), comme les macrophages, les lymphocytes B de la zone marginale (MZB) ou encore les cellules dendritiques (DC). Ces cellules représentent une première ligne de défense contre les pathogènes véhiculés par le sang et sont importantes pour l’initiation des réponses immunes. Il a fortement était suggéré la localisation dans la zone marginale d’une autre population appartenant au système immunitaire inné : les lymphocytes T Natural Killer invariants ou iNKT. Ces lymphocytes T non conventionnels sont caractérisés par l’expression de marqueurs de cellules NK et de lymphocytes T conventionnels notamment le TCR. Contrairement aux lymphocytes T conventionnels, les iNKT reconnaissent des antigènes (Ag) lipidiques (d’origine exogène ou endogène) présentés par l’intermédiaire de la molécule CD1d exprimée à la surface des APC, notamment les DC. En réponse à ces lipides, et notamment l’&#945;-galactosylceramide (&#945;-GalCer), les cellules iNKT ont la capacité unique de sécréter rapidement de grandes quantités de cytokines immunomodulatrices comme l’IFN-&#947; et/ou l’IL-4 qui, en retour, permettent l’activation d’autres populations immunes telles que les DC, les cellules NK, les lymphocytes B et lymphocytes T conventionnels. Les DC, en tant qu’APC professionnelles, sont de puissantes cellules activatrices des lymphocytes T conventionnels mais également des iNKT. Cependant, bien que souvent souligné dans la littérature, le rôle des autres APC dans l’activation des lymphocytes T conventionnels mais surtout des iNKT restait relativement obscur lorsque ce travail de thèse a débuté. Parmi les APC, les MZB représentaient des cibles idéales puisqu’elles ont la particularité d’exprimer fortement les molécules de présentation telle que les molécules du CMH de classe II, la molécule CD1d mais aussi les molécules de co-stimulation. Nous avons donc débuté notre travail par l’étude du rôle des MZB dans l’activation des lymphocytes conventionnels et des iNKT. Nous montrons que les MZB sensibilisés avec un peptide de l’ovalbumine sont capables d’activer les lymphocytes T CD4+, dont la réponse est orientée vers un profil Th1 après l’activation des MZB par le CpG-ODN (agoniste du TLR-9). Ainsi, les MZB se comportent comme de véritables APC. Nous avons ensuite étudié l’activation des iNKT en réponse à l&#945;’-GalCer. De façon surprenante, bien que les MZB expriment fortement la molécule CD1d, elles sont incapables d’activer in vitro les iNKT primaires en réponse l’&#945;-GalCer libre. Elles sont cependant capables de présenter l’&#945;-GalCer aux iNKT suggérant qu’il manque aux MZB des facteurs (solubles ou non) pour induire l’activation des iNKT. De façon intéressante, l’ajout de DC non sensibilisées restaure la production d’IFN-&#947; et d’IL-4 par les iNKT co-cultivés en présence de MZB sensibilisés avec l’&#945;-GalCer. Nous montrons que les DC participent à cette activation via un mécanisme de présentation croisée mais également via l’apport de facteurs nécessaires aux MZB pour induire l’activation des iNKT. Il existe une réelle coopération entre ces deux types d’APC pour une activation optimale des iNKT. Finalement, nous montrons que les MZB sensibilisés avec l’&#945;-GalCer induisent l’activation des lymphocytes iNKT et NK in vivo. Nous nous sommes ensuite concentrés sur les DC qui comme indiqué ci-dessus, sont des APC professionnelles. Cependant, dans la rate, les DC représentent une population très hétérogène dont le rôle de chaque sous-population notamment dans l’activation des iNKT était également très peu connu lorsque ce travail a débuté. / The spleen, with its highly specialized lymphoid compartments, plays a central role in clearing blood-borne pathogens. Innate immune cells, that are mainly present in the marginal zone of the spleen, are strategically located to respond to blood-borne microorganisms and viruses. Among innate cells, macrophages and marginal zone B (MZB) cells represent the first line of defense against blood-borne pathogens and with dendritic cells (DC) are important for initiation of the immune response. Along with these populations of antigen-presenting cells (APC), it was also suggested that invariant Natural Killer T (iNKT), a population of innate-like T lymphocytes, were also located in the marginal zone of the spleen. Unlike conventional T lymphocytes, iNKT cells recognize exogenous and self (glyco)lipid antigens (Ag) presented by the non-classical class I Ag presenting molecule CD1d expressed on APC, in particular DC. Upon lipid recognition, in particular in response to the non-mammalian glycolipid, &#945;-galactosylceramide (&#945;-GalCer), iNKT cells have the unique capacity to rapidly produce large amounts of immunoregulatory cytokines, including IFN-&#947; and IL-4, which lead to downstream activation of other immune populations (DC, NK cells, B cells and conventional T cells). Through this property, iNKT cells influence the strength and quality of the ensuing immune response. Dendritic cells, as professional APC, are potent activators of conventional T lymphocytes and iNKT cells. When we started our PhD, the role of APC other than DC in the priming of T lymphocytes including iNKT cells remained unclear. Among them, MZB cells represented good candidates since they express high levels of MHC class II and CD1d molecules and their ability to activate and orientate conventional and innate-like T lymphocytes, such as iNKT cells, were elusive. We show that MZB cells, when loaded OVA peptide promote the release of IFN-&#947; and IL-4 by antigen specific CD4+ T lymphocytes and their stimulation with CpG-ODN biases them toward more Th1 inducers. Surprisingly, although able to activate iNKT hybridomas, MZB cells sensitized with free &#945;-GalCer do not directly activate ex vivo sorted iNKT cells unless DC are added to the culture system. Dendritic cells help MZB cells to promote iNKT cell activation in part through &#945;-GalCer cross-presentation and also through DC-expressed co-factors. Interestingly, MZB cells amplify the DC-mediated activation of iNKT cells and depletion of MZB cells from total splenocytes strongly reduces iNKT cell activation in response to &#945;-GalCer. Thus, DC and MZB cells provide help to each other to optimize iNKT cell stimulation. Finally, in vivo transfer of &#945;-GalCer-loaded MZB cells potently activates iNKT and NK cells. Thus, we show for the first time a role of MZB cell in iNKT cell activation in response to free &#945;-GalCer, an important finding to better understand the modalities of iNKT cell activation. As mentioned above, DC are professional APC and thus are strong activators of conventional and unconventional T lymphocytes. However, DC in the spleen represent an heterogeneous cell population and when we started our study, the role of DC subsets in T lymphocyte priming was still unclear. Among DC subsets, we concentrated on the major splenic DC subset located in the marginal zone, the CD8&#945;- DC. This DC subset was further subdivided in CD4+ and CD4- subtypes. We provide evidences that CD4+ and CD4- DC are equally efficient at priming CD4+ T lymphocytes when loaded with OVA peptide and whole OVA, leading to a mixed Th1/Th2 response, and also CD8+ T lymphocytes when pulsed with OVA peptide (but not whole OVA).

Activity-dependent dendritic development is an important process in the maturation of neuronal circuits. The precise morphology of a neuron’s dendritic tree dictates which other cells it is able to interact with and how it will receive and process synaptic information. The aim of this Thesis was to investigate the mechanisms by which dendrites grow and, in particular, how changes in intracellular ion concentrations contribute to these mechanisms. One important activity-dependent signal is calcium as it can translate neuronal activity into morphological changes. Despite this, very little is known about calcium signalling during the period of dendritic development. Using single-cell electroporation of immature CA1 hippocampal pyramidal neurons, I characterised the spatial and temporal properties of local calcium transients in growing dendrites. This revealed a high frequency of transients at shaft filopodia and stable branchpoints, but an almost complete absence from the tips of dendritic branches. Another important factor during development is the intracellular chloride concentration because this regulates neuronal excitability. Prematurely lowering intracellular chloride by expressing the chloride co-transporter KCC2 led to less stable dendritic filopodia and stunted dendritic growth. These effects were independent of local calcium signalling and suggested that chloride regulation itself may be fundamental to normal dendritic growth. To examine this further I developed imaging techniques to measure the spatial and temporal dynamics of chloride in growing dendrites. This work revealed a somatodendritic gradient of increasing intracellular chloride, whereby the highest concentrations were found at sites of growth. Further analysis suggested a close link between local chloride regulation and morphological changes. The dendritic tips that exhibited high intracellular chloride levels and the potential to rapidly modulate these levels, also exhibited the greatest morphological dynamics. These findings have important implications for understanding the mechanisms of dendritic growth and establish the spatiotemporal regulation of chloride as a key parameter.

The primary aim of this thesis is to explore the immunostimulatory properties of a family of layered, crystalline, inorganic materials known as layered double hydroxides (LDHs). <strong>Chapter One</strong> provides an introduction to relevant aspects of the immune system, and the context for investigating the immunostimulatory properties of inorganic materials in terms of vaccine/adjuvant formulations. The possible mechanisms of action of commercial adjuvant materials are also reviewed, and the structure, synthesis methods and applications of LDHs are discussed. <strong>Chapter Two</strong> details the controlled synthesis and characterisation of LDHs in specific particle sizes. A series of MgAl-CO3 LDHs with precisely controlled particle sizes ranging from 20 to 10000 nm were successfully synthesised, then the techniques used were extended to other compositions to create a panel of LDHs for use in subsequent Chapters. In <strong>Chapter Three</strong>, the responses of monocyte-derived dendritic cells (Mo-DC) to the LDH particle sizes discussed in Chapter Two are assessed in terms of viability, surface molecule expression, and cytokine secretion. A statistical modelling approach using the physicochemical properties of the LDHs as explanatory variables for immune responses was employed to evaluate the validity of the model formulated in the previous work, and to establish if particle size could be used to improve its predictive ability. It was found that strong relationships between LDH particle size and certain Mo-DC responses exist, and that these responses could be predicted with a high degree of accuracy. <strong>Chapter Four</strong> is concerned with the investigation of T cell responses to LDH-stimulated allogeneic Mo-DC. Various methods were used for assessing T cell division and proliferation, and a protocol for intracellular cytokine staining was developed to probe T cell polarisation. Five LDHs, which have elicited potentially interesting T cell responses in previous work, were selected for investigation. However, using the assays described, no discernible improvement in proliferation or polarisation was observed with any of the LDHs tested. <strong>Chapter Five</strong> presents an initial exploration of the interactions between LDH particles and cells. Experiments have shown that LDH particles both adhere to and are internalised by Mo-DC. Variations in the extent of internalisation with both particle size and composition were highlighted by confocal microscopy studies. Through investigations into interactions between LDH particles and the plasma membrane using protease enzymes, it was revealed that adhesion of LDH particles is partly protein-dependent. Further studies have also demonstrated a pH-dependent element to particle association with Mo-DC. Details of the experimental procedures employed are included in <strong>Chapter Six</strong>. Supplementary information referred to in the main thesis may be found in the <strong>Appendices</strong>.

Excitotoxic calcium influx and activation of calcium-regulated systems is a common event in several types of neuronal injury. This mechanism has been the focus of intense research, with the hope that a more complete understanding of how neuronal injury affects calcium-regulated systems will provide effective treatment options. This study examines one such calcium-stimulated enzyme, calcineurin, in the context of two common neurological pathologies, status epilepticus and traumatic brain injury.Status epilepticus was induced by pilocarpine injection. NMDA-dependent increases in calcineurin activity were observed in cortical and hippocampal homogenates. Upon closer examination, the most profound increases in activity were found to be present in crude synaptoplasmic membrane fractions isolated from cortex and hippocampus. A concurrent status epilepticus-induced increase in calcineurin concentration was observed in membrane fractions from cortex and hippocampus. Immunohistochemical analysis revealed an increase in calcineurin immunoreactivity in apical dendrites of hippocampal pyramidal neurons. We examined a cellular effect of increased dendritic calcineurin activity by characterizing a calcineurin-dependent loss of dendritic spines. Increased dendritic calcineurin led to increased dephosphorylation and activation of cofilin, an actin-depolymerizing factor. Calcineurin-activated cofilin induced an increase in actin depolymerization, a mechanism shown to cause spine loss in other models. Finally, via Golgi impregnation, we demonstrated that status epilepticus-induced spine loss is blocked by calcineurin inhibitors.To demonstrate that the increase in dendritic calcineurin activity was not model-specific, we examined a moderate fluid-percussion model of brain injury. Calcineurin activity was significantly increased in hippocampal and cortical homogenates. This increased activity persisted for several weeks post-injury, and may be involved in injury-induced neuronal pathologies. Also similar to the SE model, calcineurin immunoreactivity was dramatically increased in synaptoplasmic membrane fractions from cortex and hippocampus, and immunohistochemistry revealed increased calcineurin content in dendrites of hippocampal CA1-3 pyramidal neurons. These changes in calcineurin distribution also persisted for several weeks post-injury.These studies demonstrate a novel, cellular mechanism of calcium-mediated pathology in two models of neuronal injury. Elucidation of cellular events involved in the acute and chronic effects of brain trauma is essential for the development of more effective treatment options.

La cellule de Purkinje (PC) est l'élément central du réseau neuronal du cortex cérébelleux et possède un arbre dendritique très développé qui se développe au cours des trois premières semaines post-natales chez la souris. Cette arborisation nécessite de nombreux réarrangement du cytosquelette, un processus contrôlé par les GTPases et leurs régulateurs, les GEFs et les GAPs, dans de nombreux types cellulaires. Au cours de ma thèse, j'ai étudié l'implication de la signalisation des RhoGTPases dans le développement post-natal du cervelet, et plus particulièrement des PCs chez la souris. Afin d'identifier de nouveaux acteurs de la signalisation des RhoGTPases impliqués dans la différenciation des PCs, nous avons établi le profil d'expression de toutes les GTPases et des GEFs de la famille DOCK à différents stades de développement de ces cellules (P3, P7, P15, P20) par Q-PCR en temps réel. Cette approche globale nous a permis d'identifier une GTPase, RhoQ, et un GEF, DOCK10, dont l'expression est très fortement augmentée au cours du développement des PCs. Nous avons montré que l'extinction de leur expression par infection lentivirale dans un modèle de coupes organotypiques de cervelet ou dans des neurones d'hippocampe entraine une très forte diminution du nombre d'épines dendritiques, révélant un rôle crucial de ces protéines dans la différenciation des PCs. / Purkinje cell (PC) occupy a central and integrative position in the synaptic network of the cerebellum and have the most elaborate dendritic tree among CNS neurons, which develops remarkably in the first three postnatal weeks in mice. This arborization requires intensive actin cytoskeleton remodeling, a process known in many cell types to be controlled by Rho GTPases and their regulators, GEFs and GAPs. During my thesis, I investigated the importance of Rho signaling during postnatal mouse cerebellar development, focusing on PC differentiation.In order to identify novel regulators of PC differentiation among members of the Rho signaling pathway, I undertook a global approach, comparing gene expression profiles of all mammalian Rho GTPases and all GEFs of the DOCK family at various stages of postnatal PC differentiation (P3, P7, P15 and P20) using real-time quantitative PCR. My global approach has allowed the identification of two Rho signaling actors, the GTPase RhoQ and the RhoGEF DOCK10, whose expressions increase dramatically during cerebellar development. Lentiviral shRNA-mediated knock down of their expression in organotypic cerebellar cultures and in hippocampal neurons showed strong dendritic spine defects, revealing an essential role for these proteins in PC differentiation.

The main goal of this tesis is to describe changes in representation of various subpopulations dendritic cells (myelogenic and plasmocytoigenic) in peripheral blood after intense physical stress and to review their activation status. Early count changes and changes of function of basic elements of cellular immunity after a sport load was described, whereas a behaviour of circulating dendritic cells hasn't been studied yet. The amount and the stage of differentation of dendritic cells was specified by analysis of blood samples taken before and after the load. According to the result of the tesis the reaction to extreme physical load had two effects. The amount of dendritic cells was increased, whilst the expression of kostimulative molecules (their activation) was decreased. Described changes support an opinion, that physical load initates reaction to a danger of body damage. Powered by TCPDF (www.tcpdf.org)