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Yersinia pestis, l'agent de la peste, est une bactérie à Gram-négatif classée comme agent pathogène ré-émergent et potentielle arme de bioterrorisme. De plus, l'apparition d'une souche multi-résistance de cette bactérie souligne la nécessité de mieux comprendre comment cette bactérie hyper-virulente interagit avec son hôte. Afin d'identifier des facteurs génétiques de vulnérabilité à la peste, notre laboratoire travaille sur la réponse de souris résistantes versus sensibles à Y. pestis. Notre stratégie pour identifier les facteurs génétiques impliqués dans la résistance/sensibilité à la peste combine une approche de cartographie de QTL (Quantitative Trait Locus) et d'analyse d'expression génique. Nous avons précédemment décrit la lignée SEG/Pas, issue de Mus spretus, comme la première résistante à une souche virulente de Y. pestis, alors que la plupart des lignées murines de laboratoire, telle que la lignée C57BL/6J, sont extrêmement sensible à la bactérie. Des croisements entre SEG/Pas et C57BL/6J nous ont permis d'identifier trois QTL impliqués dans la résistance à Y. pestis, localisés sur les chromosomes 3, 4 et 6. Deux des QTL (situés sur les chromosomes 4 et 6) ont pu être confirmés par l'analyse de lignées congéniques. Plus de 40 % des femelles bi-congéniques hétérozygotes pour ces deux QTL ont survécu à l'infection, alors que tous les témoins C57BL/6J ont succombé. La dissection de ces deux QTL par l'analyse de lignées sous-congéniques, nous a permis d'affiner l'architecture génétique de la résistance à la peste chez SEG/Pas. Nous avons conclu qu'un minimum de quatre facteurs génétiques, au sein de ces deux QTL, sont nécessaires pour augmenter la résistance à Y. pestis chez la Souris. Cependant, la production de plusieurs lignées congéniques portant le QTL situé sur le chromosome 3, dont une lignée triple congénique, ne nous a pas permis de confirmer l'existence de ce QTL. En parallèle de l'analyse génétique, nous avons déterminé que les macrophages de SEG/Pas et de C57BL/6J présentaient des caractéristiques différentes après exposition à Y. pestis. Une analyse différentielle du profil transcriptionnel des macrophages de ces deux lignées a été réalisée à l'aide de puces à ADN. Nos résultats montrent une forte activation de la production cytokinique dans les macrophages de SEG/Pas en réponse à la bactérie, activation qui n'est pas observée dans la lignée C57BL/6J. Ces résultats suggèrent que les souris SEG/Pas sont capables de mettre en place une réponse immune innée plus forte ou peut-être plus précoce que C57BL/6J. Nous avons ensuite étudié par qRT-PCR l'expression en cinétique de 44 gènes dans des macrophages de SEG/Pas, C57BL/6J et des bi-congéniques portant les QTL sur les chromosomes 4 et 6. Cette étude nous a permis de confirmer que les souris SEG/Pas sont capables se mettre en place une forte réponse inflammatoire lors de l'infection. Cependant, aucune différence significative n'a été observée entre la lignée bicongénique et la lignée parentale C57BL/6J. D'autres expériences seront nécessaires afin de mieux comprendre les mécanismes biologiques impliqués dans la résistance intermédiaire de cette lignée. La dissection génétique associée à l'analyse de l'expression génique de ces lignées résistante et sensible permet d'augmenter notre compréhension de la réponse de l'hôte à Y. pestis. / Yersinia pestis, the agent of plague, is a deadly gram-negative bacterium classified as a re-emerging pathogen and class A biological weapon. The appearance of a multi-resistant strain highlights the need to better understand how this pathogen kills its host. To identify genetic factors of host susceptibility to plague, our laboratory is investigating the response of resistant versus susceptible mice to Y. pestis. Our strategy to decipher genetic determinants involved in resistance to plague combines Quantitative Trait Loci (QTL) mapping with gene expression analysis. We previously described the Mus spretus-derived SEG/Pas strain as the first to resist fully virulent Y. pestis, while most inbred strains, such as C57BL/6, are highly susceptible. Crosses between these two strains identified three QTLs (located on chromosome 3, 4 and 6) contributing to resistance. Two of the QTLs (on chromosome 4 and 6) were confirmed through creation of congenic mice. Up to 40% of the congenic mice heterozygous at these two QTLs, on a C57BL/6J background, survived the infection while all C57BL/6J mice died. Further dissection of these two QTLs, through the use of subcongenic strains, enabled us to refine the genetic architecture of resistance to plague in SEG/Pas mice. We concluded that a minimum of four genetic factors, within these two QTLs, are required to increased resistance to Y. pestis in mice. Despite production of numerous congenic strains, including triple congenic mice, we were not able to confirm the existence of the third QTL identified on chromosome 3. In parallel to genetic studies, we determined that SEG/Pas and C57BL/6J macrophages exhibit distinct characteristics upon in vitro exposure to Y. pestis. The underlying molecular differences were investigated by using microarrays. Our results show strong activation of cytokines in SEG/Pas macrophages in response to Y. pestis, which is not found in C57BL/6J macrophages. These results suggest that SEG/Pas mice are able to better activate innate immune response to Y. pestis than C57BL/6J mice.We further studied the expression of 44 genes in a kinetic study on macrophages in vitro of SEG/Pas, C57BL/6J and bicongenic mice (carrying QTLs on chromosome 4 and 6). This study confirmed that SEG/Pas mice are able to build a stronger inflammatory response at early time of infection. Nevertheless no significant differences were observed in the bicongenic strain compared to C57BL/6J. Further studies will be required to understand the mechanisms involved in the intermediate resistance of this strain. This combination of genetic dissection and gene expression analysis of resistant and susceptible mouse strains will enhance our ability to better understand the host response to plague.

Metabolic syndrome (MetS) is a complex condition with a number of interacting genes, epigenetic and environmental factors underlying its pathogenesis. The analysis of genetic component of MetS showed that number of defining parameters of the syndrome is linked to regions of rat chromosome 4. In order to verify these quantitative trait loci (QTL), a double congenic strain was derived with parts of chromosome 4 of spontaneously hypertensive rat (SHR, an inbred MetS model) origin introgressed onto genomic background of congenic Brown Norway strain (BN-Lx). The aim of the proposed thesis is comprise detail genetic mapping of differential segments of the above mentioned double congenic strain BN-Lx.SHR4 and comparison of its metabolic profile under different dietary conditions with varying carbohydrate and fat content. Utilizing DNA sequence and gene expression comparisons, candidate genes or polymorphisms for the MetS aspects and potential nutrigenetic interactions will be identified. Key words: nutrigenetics, experimental models, metabolic syndrome, congenic strain, genotyping, rat

Metabolic syndrome is a prevalent disease characterized by concurrent manifestation of insulin resistance, obesity, dyslipidemia, hypertension and other hemodynamic and metabolic disorders. It has multifactorial type of inheritance and its resultant phenotype is determined by both environmental and genetic factors as well as their interactions. That is the main reason why comprehensive analysis of the genetic component of this syndrome is complicated in human population. Genetically designed experimental animal models are significant tools for analysis of genetic architecture of human complex conditions including the metabolic syndrome. The aim of this Thesis is utilization of functional and comparative genomic tools to uncover pathogenesis of metabolic syndrome aspects and their genetic determinants. We also studied pharmacogenetic interactions of these genetic determinants with drugs affecting particular components of the metabolic syndrome. Establishing and utilizing several genetically designed congenic rat strains, we undertook four different research projects focusing on pharmacogenetic interaction of all-trans retinoic acid and ondansetron with differential segment of rat chromosome 8, pharmacogenetic interaction of differential segment of rat chromosome 4 and dexamethasone, determining Plzf...

Metabolic syndrome is a prevalent disease characterized by concurrent manifestation of insulin resistance, obesity, dyslipidemia, hypertension and other hemodynamic and metabolic disorders. It has multifactorial type of inheritance and its resultant phenotype is determined by both environmental and genetic factors as well as their interactions. That is the main reason why comprehensive analysis of the genetic component of this syndrome is complicated in human population. Genetically designed experimental animal models are significant tools for analysis of genetic architecture of human complex conditions including the metabolic syndrome. The aim of this Thesis is utilization of functional and comparative genomic tools to uncover pathogenesis of metabolic syndrome aspects and their genetic determinants. We also studied pharmacogenetic interactions of these genetic determinants with drugs affecting particular components of the metabolic syndrome. Establishing and utilizing several genetically designed congenic rat strains, we undertook four different research projects focusing on pharmacogenetic interaction of all-trans retinoic acid and ondansetron with differential segment of rat chromosome 8, pharmacogenetic interaction of differential segment of rat chromosome 4 and dexamethasone, determining Plzf...