Les comportements olfactifs nécessitent de reconnaitre les odeurs sur une large gamme de concentration tout en restant sensible aux changements de concentration. Pour accomplir cette tâche paradoxale, le système olfactif doit façonner des représentations des odeurs qui soient à la fois dépendantes et indépendantes de leurs concentrations.Nous avons combiné des techniques de génétique murine, microscopie biphotonique, et enregistrements neurophysiologiques extracellulaires pour caractériser l’activité neuronale en réponse aux odeurs dans le bulbe olfactif et le cortex olfactif (piriforme) de la souris. En utilisant une souris au « nez monoclonal », nous montrons que les circuits du bulbe olfactif sont capables d’amplifier les entrées sensorielles très faibles, et d’atténuer les entrées envahissantes. En revanche, nous observons que le niveau d’activité neuronale induite par les odeurs dans le cortex piriforme est globalement indépendant de leurs concentrations. En outre, nous avons identifié une sous-population de neurones du cortex piriforme encodant l’identité d’une odeur indépendamment de sa concentration. Nos résultats d’imagerie calcique in vivo et d’enregistrement neurophysiologiques suggèrent que cette invariance à la concentration dans le cortex piriforme est assurée par les interneurones positifs à la paravalbumine, une sous-population de neurones inhibiteurs.Ces résultats mettent en évidence deux étapes différenciées du traitement de l’information dans les voies neurales de l’olfaction : tandis que le bulbe olfactif normalise les entrées sensorielles, les microcircuits du cortex piriforme intègrent cette information en composantes sensorielles distinctes. / Olfactory behaviors require the identification of odors across a large range of different concentrations, yet are exquisitely sensitive to changes in odor concentrations. To accomplish this seemingly paradoxical task the olfactory system must generate odor representations that are, at once, both concentration-dependent and concentration-invariant.We have used a combination of mouse genetics, in vivo two-photon microscopy, and extracellular multielectrode recording techniques to characterize odor-evoked activity in the olfactory bulb and olfactory (piriform) cortex of mice. Taking advantage of a mouse with a “monoclonal nose” in which the sensory input map is strongly perturbed, we show that olfactory bulb circuits are able to amplify very weak sensory inputs, and to suppress pervasive input.In contrast, we found that the overall level of odor-evoked neural activity in the piriform cortex is largely concentration-invariant. Moreover, we identified a small subpopulation of odor-responsive piriform neurons, which encodes odor identity independent of concentration. In vivo calcium imaging and extracellular multielectrode recordings suggest that parvalbumin-expressing interneurons, a subpopulation of inhibitory neurons, mediate concentration invariance in the piriform cortex.These results highlight contrasting processing mechanisms of sensory information along the olfactory pathway: while the olfactory bulb normalizes sensory inputs, microcircuits of the piriform cortex integrate this information into distinct sensory features. This process may allow for the simultaneous representation of identity and intensity in the olfactory system.

Habituation is a filter that optimizes the processing of information by our brain in all sensory modalities. It results in an unconscious reduced responsiveness to continuous or repetitive stimulation. In olfaction, the main question is whether habituation works the same way for any odorant or whether we habituate differently to each odorant? In particular, whether chemical, physical or perceptual cues can limit or increase habituation. To test this, the odour intensity of 32 odorants differing in physicochemical characteristics was rated by 58 participants continuously during 120s. Each odorant was delivered at a constant concentration. Results showed odorants differed significantly in habituation, highlighting the multifactoriality of habituation. Additionally habituation was predicted from 15 physico-chemical and perceptual characteristics of the odorants. The analysis highlighted the importance of trigeminality which is highly correlated to intensity and pleasantness. The vapour pressure, the molecular weight, the Odor Activity Value (OAV) and the number of double bonds mostly contributed to the modulation of habituation. Moreover, length of the carbon chain, number of conformers and hydrophobicity contributed to a lesser extent to the modulation of habituation. These results highlight new principles involved in the fundamental process of habituation, notably trigeminality and the physicochemical characteristics associated.

The clinical diagnostics of olfactory dysfunction in children turns out to be challenging due to low attention span, insufficient linguistic development and lack of odor experiences. Several smell tests have been developed for adults. Most of these examinations take a relatively long time and require a high level of concentration. Therefore, the aim of the current study was to evaluate an odor discrimination and olfactory threshold test using the frequently used “Sniffin’ Sticks” in children and adolescents in a simplified two-alternative-forced-choice version (2AFC) and compare it to the original three-alternative-forced-choice test (3AFC). One-hundred-twenty-one healthy participants aged between 5 and 17 years took part in this study. Within each of the two sessions participants underwent olfactory testing using the modified 2AFC as well as the standard 3AFC method. A better test-retest reliability was achieved using the original 3AFC method compared to the modified 2AFC. This was true for the odor discrimination as well as the olfactory threshold. Age had a significant influence on both tests, which should be considered when testing young children. We discuss these findings with relation to the existing norms and recommend using the 3AFC version due to a better test-retest reliability to measure olfactory function in children.

La résistance pléiotropique (MDR) est une propriété de certaines cellules relative à la capacité de rejeter ou d’évacuer une très large variété de substances potentiellement toxiques. Les pompes à l’origine de ce rejet sont des protéines membranaires appartenant à la superfamille ABC (ATP-Binding Cassette). Deux membres de cette famille ABC confèrent la propriété de résistance pléiotropique, P-gp (P-glycoprotein) et MRP1 (Multidrug Resistance-associated Protein). Nous avons mené une étude fonctionnelle sur l’activité de ces deux transporteurs dans la muqueuse olfactive à la fois chez le rat et la souris. Nous avons employé le test fluorométrique à la calcéine-AM sur des tranches coronales de la muqueuse olfactive incubées en présence d’inhibiteurs spécifiques des transporteurs de la résistance pléiotropique, vérapamil et cyclosporine A comme inhibiteurs de Pgp ainsi que probénécide et MK571 comme inhibiteurs de MRP1. Chacun de ces quatre inhibiteurs provoque une augmentation significative de l’intensité de la fluorescence.Afin de savoir si les transporteurs de la résistance pléiotropique peuvent être impliqués dans la réponse olfactive nous avons examiné les réponses évoquées par des odorants seuls ou mélangés à l’aide d’enregistrements d’électro-olfactogrammes (EOG). En présence des deux inhibiteurs de MRP1, l’amplitude maximale des EOG est significativement réduite pour chaque stimulus odorant testé, tandis que les inhibiteurs de Pgp n’ont qu’un effet modéré ou nul. L’expression des gènes codant pour Pgp et MRP1 dans l’épithélium olfactif ont ensuite été confirmées par RT-PCR. L’ensemble de ces résultats suggère que les transporteurs MRP1 et Pgp sont présents et fonctionnels dans l’épithélium olfactif principal des rongeurs et sont impliqués dans la réponse aux odorants. Leur fonction précise dans l’olfaction reste à élucider / Multidrug resistance (MDR) is a property of various cells associated with the capacity to reject or efflux a wide range of potentially harmful substances out of the cell. Pumps that effect such efflux are membrane proteins and belong to the ATP- binding cassette (ABC) superfamily. Among the members of the ABC family two are conferring MDR, P-glycoprotein (Pgp) and the multidrug resistance-associated protein (MRP1). In this study we investigated the functional activity of MDR transporters in olfactory mucosa of two species, rat and mouse. We used the fluorometric calcein-AM uptake assay on olfactory mucosal slices incubated with specific inhibitors of the MDR-transporters, verapamil and cyclosporin A as Pgp-inhibitors, and probenecid and MK571 as MRP-inhibitors. All four inhibitors caused significant increases in fluorescence intensities. To test if MDR transporters may be involved in the olfactory response we examined odorant evoked responses to single and mixed odorants by means of electro-olfactograms recordings (EOG). In the presence of the two MRP inhibitors, maximum EOG amplitudes were significantly reduced for all odorants tested, while Pgp inhibitors had only a moderate or no effect. Expression of Pgp and MRP1 encoding genes in the olfactory epithelium was further confirmed by RT-PCR. The results together suggest that MRP and Pgp transporters are present and functional in the main olfactory epithelium of rodents and are implicated in the olfactory response. The precise functional role in olfaction remains to be elucidated.

Dans la schizophrénie, de nombreux patients présentent un manque de soins d’hygiène personnelle, caractéristique du versant négatif de la symptomatologie. Cette négligence donne naissance à une odeur corporelle nauséabonde, qui d’antan fut un élément déterminant du diagnostic. Les prises en charge de ce symptôme, focalisées sur les soins fondamentaux de la toilette, sont souvent une gageure et échouent. En nous inscrivant dans une démarche pluridisciplinaire, nous tentons de donner du sens aux odeurs corporelles dans la schizophrénie. Notre hypothèse est que les comportements d’hygiène personnelle pourraient être conditionnés par les capacités du système olfactif des patients, sujet tout juste effleuré jusqu’ici. Une épreuve d’identification d’échantillons odorants au moyen d’images photographiques des sources d’odeurs potentielles a été normalisée : le test olfacto-visuel (TOV). L’application du TOV a permis de montrer un défaut des capacités d’identification olfactive chez les patients, sa relation avec la symptomatologie et les compétences sociales des patients. La mise en place d’un atelier thérapeutique à médiation olfactive a conduit à montrer les conséquences bénéfiques de la prise en charge de la sensorialité olfactive sur l’évolution des capacités olfactives, la symptomatologie, les comportements hygiéniques et alimentaires ainsi que sur le vécu affectif des patients atteints de schizophrénie. Ces derniers montrent aussi des dysfonctionnements de la sphère émotionnelle. Nous avons d’abord réanalysé les liens existants entre la caractéristique hédonique des odorants et les émotions dans la population générale, puis repoussé leurs simplifications habituelles. Les liens entre odeurs perçues et émotions évoquées par les échantillons odorants apparaissent perturbés chez les patients. Ce travail de recherche propose une relecture de la perception olfactive dans la schizophrénie et montre l’intérêt thérapeutique de son exploitation. L’évolution clinique positive des comportements d’hygiène personnelle, après la prise en charge olfactive, valide l’hypothèse du rôle de l’odeur corporelle en tant que gardien de l’existence. L’ « être-au-monde odorant » des patients possède une fonction identitaire dans la schizophrénie. / In the case of schizophrenia, numerous patients have poor personal hygiene, which is typical of negative symptomatology. This self-neglect engenders offensive body odor which also was in the past a crucial element for the diagnosis. Attempts to address the manifestations of that symptom by focusing on the principles of basic grooming often prove a losing battle and fail. Thanks to an interdisciplinary approach, our endeavor is to try and give meaning to body odor for schizophrenics. Our hypothesis is that personal hygiene behavior could be conditioned by the patients’ olfactory system capacities – a domain which has barely been studied to this day. An olfactory stimuli identification test of potential odor sources via photographic images has been standardized: the olfacto-visual test (OVT). The OVT’s application has permitted to reveal an olfactory identification deficit in the patients, its relation to symptomatology and the patients’ social skills. The setting up of a therapeutic workshop through olfactory mediation has led to show the beneficial consequences of the caring for the sense of smell on the evolution of olfactory skills, symptomatology, hygiene and dietary patterns, as well as on the patients’ emotional life. Patients suffering from schizophrenia also present emotion-management troubles. We have first analyzed the existing links between the hedonic characteristics of odorants and the emotions among the general population anew, and then questioned the usual simplifications about them. The links between perceived odors and emotions produced by the odor samples appeared as blurred for the patients. This research offers a new approach of the olfactory perception in schizophrenia and shows the therapeutic interest of its exploitation. The positive clinical evolution of personal hygiene behavior after the olfactory caring confirms the hypothesis of the role of body odor as a token of existence. The patients’ bad body odor reveals an identity function in schizophrenia.

L'objectif de cette thèse est d'utiliser MEMRI (manganese-enhanced magnetic resonance imaging) pour étudier le traitement d'odeurs signifiantes dans le cortex olfactif primaire de rats dans les conditions les plus proches de la perception naturelle. MEMRI est une méthode fondée sur la détection d'un agent de contraste fonctionnel et rémanent de l'activité neuronale, le manganèse, qui a prouvé son efficacité pour montrer le traitement différencié d'odeurs dans le bulbe olfactif chez l'animal vigile. Cependant, cette technique a été surtout utilisée pour tracer les voies neuronales, mais relativement peu pour explorer des fonctions sensorielles. C'est pourquoi nous avons conduit deux études visant l'une à définir les conditions d'application du manganèse et l'autre à optimiser le traitement des images MEMRI, avant d'aborder la question biologique proprement dite. S'appuyant sur ces développement méthodologiques, nous avons ensuite utilisé MEMRI pour étudier les variations du traitement d'odeurs signifiantes (odeurs de nourriture et de prédateur comparées à une situation de contrôle) dans le cortex olfactif primaire de rats. Nous avons montré que le traitement cérébral d'une odeur de prédateur est différent de celui de la situation de contrôle dans le cortex olfactif primaire. Nous avons confirmé ce résultat par immunomarquage Fos dans le cortex piriforme. Mis ensemble, les résultats de MEMRI et Fos suggèrent que le traitement cérébral d'une odeur peut varier en terme de taille de populations de neurone recrutés ainsi qu'en termes d'intensité de l'activation de ces neurones. Enfin, les résultats MEMRI montrent qu'un message olfactif crucial, pour la survie, est traité asymétriquement dans le cerveau. Les avancées méthodologiques et scientifiques qu'apporte cette thèse ouvrent la voie à une meilleure compréhension du traitement cérébral des odeurs. / The aim of this thesis was to use MEMRI (manganese-enhanced magnetic resonance imaging) for studying the processing of behaviorally significant odors in the rat primary olfactory cortex, under conditions close to natural perception in awake animals. MEMRI is a method based on the detection of o functional and remanent contrast agent, manganese, which has proved to be valuable dor studying odor processing in the olfactory bulb. However , this method has mainly been used to trace neuronal pathways, but seldom to explore sensory functions. Here, we have conducted two studies to define the conditions of application of manganese and to optimize processing of MEMRI images. Based on these methodological developments, we have then used MEMRI to investigate the activation of central olfactory structures following exposure of awake rats to biologically relevant odors (food and predator odors compared to a control situation). MEMRI revealed that a predator is processed differently from the control situation in the primary olfactory cortex. Fos immunolabeling in the anterior piriform cortex corroborated this result. Altogether, MEMRI and Fos results suggest that olfactory processing may rely on both the intensity of activation and the size of neuronal populations recruited. Finally, MEMRI revealed that the olfactory message, crucial for survival, is asymmetrically processed in the brain. Methodological and scientific advances brought by this thesis will be useful for better understanding brain olfactory processing.

Le bulbe olfactif est le siège d'une neurogenèse adulte pouvant jouer un rôle dans les apprentissages olfactifs. Nous nous sommes intéressés à son rôle dans un type d'apprentissage olfactif : l'apprentissage perceptif. Tout d'abord, l'enrichissement permet d'améliorer la discrimination d'odeurs proches : c'est l'apprentissage perceptif. En étudiant les effets de la suppression de la neurogenèse pendant l'enrichissement nous avons montré que la neurogenèse était nécessaire à l'apprentissage perceptif en modulant l'inhibition des cellules mitrales par les cellules granulaires. Ensuite, nous avons étudié le rôle de la noradrénaline dans cet apprentissage. La noradrénaline est nécessaire à l'apprentissage perceptif et suffisante pour en mimer les effets. De plus, nous avons montré que la neurogenèse bulbaire était essentielle à l'action de la noradrénaline pour permettre l'apprentissage perceptif. Enfin, nous nous sommes intéressés à l'effet du vieillissement sur l'apprentissage perceptif. Nous avons trouvé qu'il existait un défaut d'apprentissage perceptif chez la souris âgée en lien avec une diminution de la neurogenèse. En revanche, une stimulation noradrénergique permet de restaurer l'apprentissage perceptif sans modulation de la neurogenèse bulbaire suggérant l'existence de mécanismes compensatoires. L'apprentissage perceptif est sous-tendu par la neurogenèse bulbaire, via le système noradrénergique, pour permettre une hausse d'inhibition des cellules mitrales par les cellules granulaires améliorant la discrimination des odeurs proches. Avec l'âge, l'apprentissage perceptif peut être restauré suggérant une plasticité toujours présente dans un système olfactif vieillissant / The olfactory bulb is the target of a well described adult neurogenesis which has been involved in different kinds of learning. We focused on the role of adult neurogenesis on olfactory perceptual learning which consists on an improvement of olfactory discrimination after odor enrichment. We found that experience-driven improvement in olfactory discrimination (perceptual learning) requires the addition of newborn neurons in the olfactory bulb. More specifically, we showed that adult-born neurons are required for perceptual learning by modulating the inhibition of mitral cells by granule cells. Then, we studied the role of noradrenaline on perceptual learning. Direct manipulation of noradrenergic transmission significantly effect on adult-born neuron survival and perceptual learning. Finally, we investigated the effect of aging on perceptual learning. We found that perceptual learning was impaired by aging in line with an alteration of neurogenesis. However, noradrenergic stimulation restores perceptual learning without modulating neurogenesis suggesting compensatory mechanisms. Neural mechanisms underlying perceptual learning involve neurogenesis and noradrenergic system to allow an increase of mitral cell inhibition thanks to the granule cells leading to an improvement of odor discrimination. During aging, perceptual learning can be restored suggesting that the olfactory system is still plastic

Orientador: Fabio Papes / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-27T05:41:39Z (GMT). No. of bitstreams: 1 Souza_MateusAugustodeAndrade_M.pdf: 6121419 bytes, checksum: a603ea19d560e8cfebddccca9b7d824a (MD5) Previous issue date: 2015 / Resumo: Em mamíferos, os neurônios sensoriais do Sistema Olfatório (OSNs) se encontram no interior da cavidade nasal, mas estão diretamente expostos ao ambiente externo. Por um lado, tal localização permite a esses neurônios o acesso imediato aos estímulos químicos ambientais, tomando vantagem do fluxo respiratório. Por outro lado, esses neurônios estão constantemente sujeitos a injúrias por agentes nocivos, como toxinas e patógenos, capazes de destruir essas células sensoriais. Sua perda constante, contudo, é contrabalanceada pela geração de novos OSNs durante toda a vida do indivíduo, fato que torna o Sistema Olfatório um dos poucos locais do organismo com neurogênese contínua na idade adulta. A regeneração dos OSNs tem atraído a atenção da comunidade científica tanto pelo seu potencial uso como modelo de estudo do Sistema Nervoso quanto pela sua potencial aplicação para o tratamento de doenças neurodegenerativas. Nesse sentido, muito conhecimento já foi produzido sobre a dinâmica de fatores de transcrição que acompanha a diferenciação dos progenitores neuronais olfatórios em OSNs. Porém, uma grande lacuna no conhecimento diz respeito a outros elementos capazes de coordenar esse processo, como os fatores moduladores da cromatina. Diante desse cenário, escolhemos como objeto de estudo as proteínas do Grupo Polycomb (PcG), que constituem uma maquinaria de controle transcricional relacionada a modificações na organização da cromatina. Neste trabalho, genes PcG selecionados foram caracterizados molecular e funcionalmente no epitélio olfatório principal de camundongos (MOE). Através de ensaios de hibridação in situ, cinco dos seis genes avaliados apresentaram expressão ubíqua por todo o epitélio (Cbx2, Cbx4, Phc2, Ezh1, Bcl6), enquanto um (Ezh2) mostrou-se expresso somente nos estratos basais do MOE. Em ensaios de colocalização, provamos que Ezh2 é expresso exclusivamente nos progenitores olfatórios, onde o processo de diferenciação se inicia, e em parte dos OSNs recém-diferenciados, ainda não funcionais. Esta foi a primeira vez que a expressão de um gene PcG foi analisada detalhadamente no Sistema Olfatório. O interessante perfil de expressão de Ezh2 foi sugestivo de um possível papel funcional relacionado à diferenciação dos progenitores olfatórios. Para investigar essa hipótese, utilizamos como ferramenta experimental a habilidade do MOE em se regenerar após a indução de injúrias específicas. Para isso, o MOE de camundongos foi lesionado quimicamente com o composto diclobenil, que leva à perda abrupta de OSNs, estimulando a proliferação e a diferenciação dos progenitores olfatórios para repovoar as regiões lesionadas. Os animais assim tratados receberam, por via intranasal, o fármaco GSK126, uma molécula inibidora específica da atividade da proteína EZH2. Acompanhando a regeneração subsequente do MOE, observamos que a inibição da atividade de EZH2 levou ao incremento de OSNs no epitélio, favorecendo a sua regeneração. Interessantemente, esse incremento também foi observado em MOEs não lesionados, mostrando que o efeito de GSK126 não é dependente da indução de injúrias prévias. Através dessa investigação molecular e funcional, buscamos contribuir para o melhor entendimento da diferenciação neuronal do MOE, e apontamos as proteína PcG como elementos importantes para esse processo / Abstract: In mammals, the olfactory sensory neurons (OSNs) are located inside the nasal cavity, but they are directly exposed to the external environment. Taking advantage of the respiratory flux, this location favors the access to the chemical stimuli presented by the environment. On the other hand, it leads OSNs to be continually damaged by pathogens and toxic substances carried by the inhaled air. However, the persistence of neuronal progenitors in the olfactory epithelium makes the constant reposition of the OSNs possible. This unique ability of regeneration makes the Olfactory System one of the few sites of neurogenesis throughout the adult life. Olfactory regeneration has attracted the attention scientific community because of its potential as a model of study of the Nervous System and application in the treatment of neurodegenerative diseases. A great amount of knowledge has been accumulated about the transcription factor dynamics that follows the differentiation of neuronal progenitors into OSNs. However, there is a great gap about other elements that could coordinate this process, such as chromatin modulator factors. In this scenario, we decided to study the Polycomb Group (PcG) proteins, a transcription control machinery involved in chromatin structure organization. In the present study, selected PcG genes were molecular and functionally analyzed in the mouse main olfactory epithelium (MOE). Using in situ hybridization assays, we characterized the expression of six PcG genes. Five of them were shown to be expressed throughout the MOE (Cbx2, Cbx4, Phc2, Ezh1, Bcl6), while one (Ezh2) was found only in the basal layers of this epithelium. Using colocalization strategies, we proved that Ezh2 gene is expressed exclusively in the olfactory progenitor cells, where the differentiation process begins, and in part of the newly differentiated OSNs that are still not functional. It was the first time that a PcG gene expression profile was finely analyzed in the Olfactory System. This interesting expression profile presented by Ezh2 suggested a possible involvement with the MOE neuronal progenitor differentiation. For this functional investigation, we used MOE¿s neuronal regeneration after specific injuries as an experimental tool. For this purpose, the MOE was chemically damaged by the compound dichlobenil, which causes a great loss of OSNs, stimulating proliferation and differentiation of neuronal progenitor cells, leading to the repopulation of the damaged tissue. Next, mice received by intranasal route the pharmacological inhibitor GSK126, which blocks EZH2 protein activity. The observation of the MOE regeneration that followed showed us that GSK126 application resulted in an increased number of OSNs, improving MOE regeneration. Interestingly, this increase was also found in intact MOEs, pointing that GSK126¿s effects do not depend on previous olfactory injuries. By this molecular and functional investigation, we aimed at a better understanding of olfactory neuronal differentiation, and we targeted the PcG proteins as relevant elements to this process / Mestrado / Genetica Animal e Evolução / Mestre em Genética e Biologia Molecular

O gene, uma seqüência de nucleotídeos necessária para a síntese de moléculas funcionais, é transcrito e regulado por um conjunto de processos e fatores extremamente complexos. Entender o momento e o tecido em que os genes são expressos, as isoformas funcionais, as regiões controladoras e os fatores envolvidos na regulação da expressão de cada gene é um dos grandes desafios da biologia molecular moderna. Hoje, com a enorme quantidade de informações de seqüências genômicas e de transcriptomas, aliado ao desenvolvimento de métodos computacionais para agrupar e analisar estes dados em larga escala, o estudo dos fenômenos relacionados à transcrição e regulação gênica está passando por uma revolução. Por exemplo, é possível medir, concomitantemente, a expressão gênica de milhares de genes em diferentes tecidos, assim como identificar diversos fenômenos que atuam nestes genes. Neste trabalho nós desenvolvemos e aplicamos métodos computacionais no estudo de quatro temas envolvendo aspectos chave da transcrição e regulação gênica. No primeiro trabalho, nós abordamos a expressão gênica tecido-específica através do estudo dos genes expressos no cérebro e em dez regiões cerebrais de camundongo. No segundo trabalho, nós identificamos seqüências potencialmente envolvidas no controle da transcrição gênica através do estudo de motivos sobre representados na região promotora dos genes de receptores olfativos. No terceiro trabalho, analisamos o transcriptoma humano quanto a presença de eventos de retenção de intron, um tipo de splicing alternativo. No quarto trabalho, nós abordamos a complexidade do transcriptoma e a regulação da expressão gênica através do estudo de pares de genes senso-antisenso em humanos e camundongos. Em todos os trabalhos, obtivemos resultados que nos permitiram tirar conclusões específicas sobre cada fenômeno estudado e nos mostraram a importância de estudá-los através de uma abordagem em larga escala. Adicionalmente, verificamos que os nossos métodos computacionais foram eficientes e adequados para o estudo da transcrição e regulação gênica em Homo sapiens e Mus musculus. / Genes, nucleotide sequences necessary for the synthesis of functional molecules, are transcribed and regulated by extremely complex cellular and molecular processes. To understand when and in which tissues the genes are expressed, their functional isoforms, control regions and the factors involved in gene regulation is one of major challenges of modern molecular biology. Today, the availability of complete genome sequences and transcriptomes, together with the development of new computational methods allows the study of phenomena related to the transcription and gene regulation in a large scale. For example, it is possible to quantify, concomitantly, gene expression of thousands of genes in different tissues and analyze different aspects of their regulation. In this work we developed and applied computational methods to the study of four key aspects of gene transcription and regulation. In the first study, we addressed tissue specific gene expression through the study of genes that are preferentially expressed in the brain and ten different mouse brain regions. In the second study, we identified sequences that are potentially involved in the control of gene transcription through the study of motifs that are over represented in the promoter region of olfactory receptor genes. In the third study, we browsed the human for the presence of intron retention, a type of alternative splicing. In the fourth study, we addressed the transcriptoma complexity and gene expression regulation through the study of pair of sense-antisense genes in human and mouse. In all studies, our results allowed us to make specific conclusions about each phenomenon analyzed which showed us the importance of a large scale approach. In addition, we verified that our computational methods can be efficiently applied to the study of transcription and gene regulation in Homo sapiens and Mus musculus.

La période périnatale est une période sensible pendant laquelle la neurophysiologie et neurocircuiterie à l’origine de nombreux comportements, notamment sexuels, se mettent en place. La gestation et la lactation sont également des périodes critiques pour les femelles qui subissent de grands remaniements physiologiques, permettant la mise en place des comportements maternels nécessaires à la survie de la descendance. Les modifications ayant lieu pendant la gestation et la lactation vont être sensibles à de nombreux facteurs, comme le stress ou l’environnement chimique, dont les perturbateurs endocriniens. L’objectif de ma thèse a été de caractériser les conséquences d’une exposition périnatale lors de la gestation et la lactation au glyphosate, herbicide très largement utilisé à travers le monde. L’exposition maternelle pendant la gestation et la lactation à une faible dose (5mg/kg pc/j soit 1/10ème de la NOAEL) a permis de mettre en évidence pour la première fois une altération des comportements maternels, de la neurogénèse hippocampale et du gyrus cingulaire, et de la plasticité synaptique par la molécule active seule mais également en formulation. Cette exposition induit également une dysbiose intestinale chez les mères. Chez la descendance, nous avons mis en évidence une hypoactivité induite chez le mâle suite au traitement de la mère par le glyphosate seul. Dans une moindre mesure, nous avons également montré une altération des comportements sexuels et de préférence olfactive des mâles exposés au glyphosate. Aucune altération de la neuroplasticité hippocampale des mâles n’a pu être observée dans nos conditions expérimentales. Chez la descendance femelle, les comportements sexuels et locomoteurs, ainsi que la neuroplasticité ne sont pas modifiés par l’exposition maternelle. L’ensemble des résultats obtenus nous a permis de mettre en évidence pour la première fois une vulnérabilité de la neurophysiologie, des comportements maternels et du microbiome suite à l’exposition à de faibles doses de glyphosate seul ou en formulation. De manière intéressante, seules les mères et la descendance mâle sont impactées au niveau comportemental. Nos résultats ont également mis en évidence pour la première fois une absence d’effets sur le comportement sexuel chez la descendance femelle. Enfin nos travaux sont les premiers à montrer des effets différentiels du glyphosate seul et de la formulation chez les mammifères. / Perinatal period is sensitive for offspring as neurophysiology and circuitry underlying behaviors take place. This period includes formation of the sexual behavior circuitry. Perinatal period is also essential for pregnant or lactating females. Indeed, females undergo major physiological changes involved in maternal behaviors. Perinatal modifications are altered by several parameters like stress or chemicals, including endocrine disruptors. The aim of my thesis was to characterize the outcomes of a perinatal exposure to glyphosate, a widely use herbicide across the world. Maternal exposure during pregnancy and lactation to a low dose of glyphosate (5mg/kg bw/d corresponding to 1/10th of the NOAEL) highlighted that maternal behavior, hippocampal neurogenesis and synaptic plasticity were altered by glyphosate alone and in formulation. Maternal exposure also induced gut dysbiosis on the dams. We showed that glyphosate alone induced hypoactivity on males offspring. To a lesser extent, males sexual behavior and olfactory preference were altered after glyphosate exposure. There was no effect on hippocampal plasticity on males. Sexual behavior, locomotor activity and neuroplasticity were not impacted in female offspring after maternal exposure. Together, these results highlight for the first time effects on neurophysiology, maternal behaviors and maternal gut microbiota after low doses exposure of glyphosate alone or in formulation. Interestingly, only males offspring had behavioral outcomes. Our study was the first to investigated sexual behavior of female offspring and showed no effect of glyphosate on this parameter. Finally, our work is the first that showed differential effect between active compound and formulation in mammals.