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L’un des domaines clés de la recherche en neurosciences modernes consiste à comprendre les interactions complexes entre le stress et la génétique qui conduisent à la manifestation de troubles tels que la dépression, l’anxiété et le dysfonctionnement cognitif. Des preuves de plus en plus nombreuses suggèrent que le système glutamatergique peut être une cible thérapeutique pertinente pour de tels troubles. Le glutamate est le neurotransmetteur utilisé par la grande majorité des synapses excitatrices dans le cerveau. Et les sous-types des récepteurs métabotropique au glutamate (mGluR1 – mGluR8) agissent avant tout comme d’importants régulateurs postsynaptiques de la neurotransmission dans le système nerveux central (SNC), en fournissant un mécanisme par lequel les réponses synaptiques rapides à travers des canaux cationiques dépendants du glutamate peuvent être affinées. Ainsi, les récepteurs mGluR participent à une grande variété de fonctions du système nerveux central. Au sein dela famille des récepteurs métabotropiques au glutamate, le récepteur présynaptique mGluR7 montre la conservation évolutive la plus élevée et on pense qu'il agit comme un régulateur de la libération de neurotransmetteurs. Le récepteur mGluR7 est également le plus largement distribué des récepteurs présynaptiques mGluR, présent sur une large gamme de synapses démontrées comme critiques à la fois dans le fonctionnement normal du système nerveux central, mais également dans une large gamme de troubles psychiatriques et neurologiques. De plus, un nombre croissant de preuves expérimentales suggèrent que le récepteur mGluR7 est non seulement un acteur clé dans l’élaboration de réponses synaptiques au niveau des synapses glutamatergiques, mais qu’il est également un régulateur clé de la transmission GABAergique inhibitrice. Le développement d’outils pharmacologiques et génétiques sélectifs a permis le démantèlement de la fonction du récepteur mGluR7 dans une multitude de processus physiologiques et comportementaux. Ainsi les souris knock-out ont mis en évidence un rôle du récepteur mGluR7 dans l’anxiété, le conditionnement de la peur, l’aversion, l’apprentissage et la mémoire spatiale. De plus, ces souris dépourvues du récepteur métabrotrope mGluR7 démontrent une sensibilité accrue aux crises épileptiques suggérant un rôle unique de ce récepteur dans la régulation de l’excitabilité neuronale. De même, une altération de la plasticité synaptique à court terme dans les souris transgéniques dépourvues du récepteur métabotrope au glutamate mGluR7 démontre que l’absence de récepteurs mGluR7 engendre des altérations de la plasticité synaptique à court terme dans l’hippocampe. En outre, la découverte et la caractérisation récente du premier antagoniste allostérique agissant sur le domaine VFTD de l’extrémité N-terminale du récepteur mGluR7 potentialise définitivement les observations effectuées sur les souris mGluR7 knock-out quant à la fonction de ce récepteur dans l’anxiété et la dépression. Ensemble, ces données suggèrent que le récepteur mGluR7 est un important régulateur de la fonction glutamatergique, de la peur, de l’aversion et de la cognition et donc ce récepteur représente une cible thérapeutique innovante pour les troubles liés au stress à l’interface de la cognition et de l’anxiété. / Metabotropic glutamate receptors (mGluRs) consist of eight different subtypes and exert their effects on second messengers and ion channels via G-proteins. The function of individual mGluR subtypes in the CNS, however, largely remains to be clarified. To study the role of mGluR7 receptors, we used homologous recombination to generate mice lacking this metabotropic receptor subtype (mGluR7). Immunohistochemical and immunoelectron-microscopic analyses showed that mGluR7 is highly expressed in amygdala and preferentially localized at the presynaptic axon terminals of glutamatergic neurons, suggesting strongly that mGluR7 is involved in neural processes subserving amygdala-dependent averse responses. To examine amygdala-dependent behavior, we examined first the fear response of freezing after electric shock in wild-type and mGluR7 (mGluR7-/-) knockout littermates. Wild-type mice displayed freezing immediately after footshock. In comparison, mGluR7 knockout mice showed significantly reduced levels in both immediate postshock and delayed freezing responses. However, the knockout mice exhibited no abnormalities in pain sensitivity and locomotor activity. Secondly, we performed conditioned taste aversion (CTA) experiments. In wild-type mice, the administration of saccharin followed by intraperitoneal injection of the malaise-inducing agent LiCl resulted in an association between saccharin and LiCl. This association caused strong CTA toward saccharin. In contrast, mGluR7 knockout mice failed to associate between the taste and the negative reinforcer in CTA experiments. Again, the knockout mice showed no abnormalities in taste preference and in the sensitivity to LiCl toxicity. These results indicated that mGluR7 deficiency causes an impairment of two distinct amygdala-dependent behavioral paradigms. Because the amygdale function is essential for these two distinct behavioral paradigms, our results suggest that mGluR7 is critical in amygdale function. The amygdale is a brain region that is known to be critical for the manifestation of anxiolysis and antidepressant action and glutamatergic neurotransmission has been strongly implicated in the pathophysiology of affective disorders. To this end we analyzed the behavioral profiles of mGluR7-/- mice in animal models of depression and anxiety. mGluR7-/- mice were compared to wildtype littermates and showed substantially less behavioural immobility in both the forced swim test and the tail suspension test. Both behavioural paradigms are widely used to predict antidepressant-like activity. Further, mGluR7-/- mice displayed anxiolytic activity in four different behavioural tests namely the light-dark box, the elevated plus maze, the staircase test, and the stress-induced hyperthermia test, while their cognitive performance was normal in the passive avoidance paradigm. [...]

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid metabolite and an important signaling molecule that plays a significant role in fibrosis. S1P synthesis is catalyzed by sphingosine kinases (SphKs), which phosphorylate sphingosine into S1P. The present study tested the hypothesis that SphK1-S1P signaling pathway participates in the kidney damage in unilateral ureteral obstruction (UUO) model. Wild type and SphK1 knockout mice were subjected to UUO for 7 days or 14 days and then four groups of kidneys were collected: wild type control group (WT-C), wild type UUO group (WT-UUO), SphK1-/- control group (KO-C) and SphK1-/- UUO group (KO-UUO). The mRNA level of SphK1 in WT-UUO was increased by 6.1 folds compared to WT-C. The fibrotic markers α-smooth muscle actin (α-SMA) and collagen I were both upregulated in UUO groups, whereas the levels of these two markers were significant lower in KO-UUO than that in WT-UUO. The immunohistochemistry analyses showed that the distribution of α-SMA and collagen was located in the interstitial space and that the infiltration of immune cells was more in UUO groups than that in control groups, but there was no significant difference between KO-UUO and WT-UUO, suggesting a direct effect of SphK1 deletion on renal fibrotic markers independent of immune regulation. Further, the morphological examination showed that UUO-induced tubular injury and glomerular damage were significantly reduced in KO-UUO compared with WT-UUO. Our study suggests that SphK1-S1P signaling pathway mediates kidney damage in UUO mice. Manipulating SphK1-S1P signaling pathway may be used as a therapeutic strategy in renal interstitial fibrosis.

No presente estudo realizamos uma análise ultraestrutural e imuhistoquímica da organização das fibrilas de colágeno no endométrio durante a gestação de camundongos silvestres e deficientes em decorim. Os resultados mostraram que as fibrilas de colágeno em ambos os genótipos sofrem grande variação de forma e tamanho. Observou-se variação significante, na percentagem de distribuição dos diâmetros das fibrilas de colágeno existentes na região decidualizada em ambos os genótipos, porém foi maior nos animais Dcn-/-. Estes animais também apresentam maior percentagem de fibrilas finas quando comparados aos animais Dcn+/+. Observamos ainda que biglicam é expresso no endométrio não decidualizado dos animais Dcn-/-, no 3º dia de gestação. A expressão de lumicam mostrou-se nítida no estroma decidualizado e não decidualizado nos animais Dcn-/- no 7º dia de gestação e foi ausente nos animais Dcn-/-. Estes resultados mostraram que a ausência do decorim promove distúrbios no processo de agregação lateral das fibrilas espessas de colágeno. / The present study is an ultrastructural investigation into the organization of collagen fibrils in the pregnant endometrium of wild-type and decorin-deficient mice. Our results showed that collagen fibrils from both genotypes present a great variability of shape and size in cross section. Significant variation in the diameter of collagen fibrils exists in the decidualized endometrium from both groups of animals. In the decidualized endometrium, the diameter of collagen fibrils increases in both genotypes were higher in Dcn-/- than in Dcn+/+ animals. In the Dcn-/- animals the percentage of thin fibrils with diameter is also higher, when compared with Dcn+/+ animals. We also showed that Bgn is expressed in the non decidualized endometrium in the Dcn-/- animals, on day 3 of pregnancy. The expression of lumican showed a very sharp labeling in the decidualized stroma from day 7, and in the non decidualized estroma from Dcn-/- animals. These results suggest that the deficience of decorin may play a role on collagen fibrillogenesis in different stages of pregnancy.

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Le système nerveux somatosensoriel permet l'interaction entre l'organisme et son environnement. Ce système collecte, via des récepteurs périphériques, les stimuli extérieurs et les transmet au système nerveux central par les neurones sensoriels primaires, dont les corps cellulaires sont situés dans les ganglions rachidiens dorsaux. Ces neurones primaires sont spécifiques des différentes sensations et ont, pour y répondre, des récepteurs, des modalités sensorielles, des caractéristiques moléculaires différentes. Ils sont généralement séparés en 3 grandes familles: les propriocepteurs, les mécanocepteurs et les nocicepteurs, chacune de ces familles se séparant à son tour en une multitude de sous familles. Ces neurones dérivent de la crête neurale, une structure spécifique des vertébrés. Au cours de leur migration vers les ganglions rachidiens dorsaux, les cellules vont être soumises à un grand nombre de facteurs et de voies de signalisation, qui vont entrainer leur survie, leur mort ou leur différenciation. Le facteur de transcription Meis2 a été isolé par l'équipe comme un candidat pouvant intervenir dans cette différentiation des cellules en neurones différenciés. Chez les souris, son expression est spécifique de sous populations mécanoceptives et proprioceptives, et s'étend des stades précoces de développement jusqu'à l'âge adulte. La lignée conditionnelle de souris Knock Out pour Meis2, croisée avec la lignée Wnt1cre, permet l'abolition de Meis2 dans toutes les cellules de la crête neurale et ses dérivés. Le mutant issu de ce croisement meurt à la naissance, avec de nombreux problèmes phénotypiques. Cette lignée cKOMeis2 a alors été croisée avec la lignée Islet1cre, ce qui permet d'invalider le gène Meis2 dans les neurones post-mitotiques des ganglions rachidiens dorsaux. Cette souris m'a servi de modèle afin de déterminer les conséquences éventuelles de la perte de Meis2 dans les neurones sensoriels du ganglion rachidien dorsal par analyse comportementale. / The somatosensory nervous system allows the interaction between the organism and the environment. This system receives from peripheral receptors some exterior stimuli which are transmitted to the central nervous system by sensory primary neurons. Their cell bodies are located in the dorsal root ganglions (DRG). These primary neurons are specific to various sensations and are characterized by specific receptors, sensory modalities and molecular characteristics involved in their response. They are usually defined as belonging to one of three main families: proprioceptors, mecanoceptors and nociceptors, and each family is composed of a large number of subgroups. These neurons are derived from the neural crest cells to form the DRG. The cells are exposed to a number of key pathways and factors, which permit their survival, death or differentiation. The transcription factor Meis2 was isolated by our team as a good candidate to act in the differentiation or specification of these cells into sensory neurons. The expression pattern of Meis2 is shown to be specific to the mecanoceptor and proprioceptor subgroups and starts, in mice, from the early stages of development up to the adult age. To investigate the role of Meis2 the conditional strain mice Meis2 Knock Out (cKOMeis2) were crossed with the strain Wnt1cre which invalidates the gene Meis2 in all the neural crest and derived cells. The new born mice die at birth with most showing phenotypic dysfunctions. Finally, this cKOMeis2 strain was crossed with Islet1cre which specifically disrupts the Meis2 gene in post-mitotic DRG neurons. This thesis characterises the Islet1cre/+cKOMeis2LoxP/LoxP strain in order to determine the behavioural consequences of the loss of the Meis2 protein in DRG sensory neurons.

A insuficiência cardíaca (IC) é uma síndrome clínica de alta incidência e mau prognóstico, caracterizada por fadiga, dispnéia e grande limitação aos esforços físicos. Essas alterações não estão apenas limitadas ao comprometimento cardíaco, mas em parte, são decorrentes também de alterações morfo-funcionais da musculatura esquelética. Para a dissertação foram utilizados camundongos com deleção dos genes para os receptores ?2A e ?2C adrenérgicos (KO) que desenvolvem cardiomiopatia induzida por hiperatividade simpática, associada à sinais clínicos de IC e 50% de mortalidade aos sete meses de idade. Foi objetivo desse estudo realizar a caracterização fenotípica do músculo esquelético por meio de avaliações funcionais e morfológicas em camundongos KO previamente ao desenvolvimento da IC (três meses de idade), e ao longo de sua progressão (cinco e sete meses de idade). Somente na faixa etária de sete meses de idades foi constatado o estabelecimento da miopatia muscular esquelética. Nessa fase, observou-se rarefação vascular, atrofia muscular, aumento na porcentagem de fibras glicolíticas e redução na atividade máxima da enzima citrato sintase, que em conjunto, contribuem para a antecipação da fadiga observada nesse modelo, e como conseqüência, para a redução da tolerância aos esforços. Os resultados sugerem que os camundongos KO apresentam alterações morfo-funcionais da musculatura esquelética semelhantes às observadas nos demais modelos de IC e em indivíduos portadores dessa síndrome. Portanto, sendo um ótimo modelo experimental para estudos de futuras estratégias terapêuticas que visem minimizar as alterações na musculatura esquelética decorrentes da IC / Heart failure (HF) is a clinical syndrome with high incidence and bad prognostic, characterized by fatigue, dyspnea, and increased intolerance to exercise. These changes are not only related to the cardiovascular tissue, but are at least in part, consequence of morphofunctional alterations in skeletal muscles. To the present study it was used mice lacking both ?2A/?2C AR subtypes (KO) which develop cardiomyopathy induced by sympathetic hyperactivity, associated to clinical signals of HF and 50% of mortality at seven months of age. The aim of the present study was characterize the phenotype of skeletal muscle by functional and morphological evaluations in KO before (three months of age) and during the HF progression (five and seven months of age). Skeletal muscle alterations due HF were observed only at seven months of age. The alterations were characterized by vascular rarefaction, muscular atrophy, increase in glycolitic fibers percentage and reduction of maximal activity of citrate synthase and contributed with early fatigue observed in this model, and consequently, exercise intolerance. The results of present study suggest that KO mice present morphofunctional changes in skeletal muscles in a similarly to others models of HF and in patients that have this syndrome. Therefore, consisting in an excellent experimental model to future studies related to therapeutic strategies to minimize the skeletal muscle changes due HF