Epithelial ovarian cancer (EOC) is a leading cause of morbidity and mortality among women in the United States, and the etiology is incompletely understood. Common, low penetrant genetic variants such as single nucleotide polymorphisms (SNPs) likely contribute to a significant proportion of EOC. We examined whether SNPs in two understudied yet biologically important types of genes, mitochondrial-related and miRNA-related genes, may contribute to EOC susceptibility using data from a large, homogeneous study population of 1,815 EOC cases and 1,900 controls (frequency-matched on age-group and race/ethnicity) genotyped through stage 1 of an ongoing genome-wide association study. Inter-individual variation in genes involved in mitochondrial biogenesis was strongly associated with EOC risk (empirical P=0.050), especially for genes NRF1, PPARGC1A, MTERF, ESRRA, and CAMK2D. SNPs in several genes involved in the biogenesis of miRNAs (LIN28, LIN28B, AGO2, DICER, and DROSHA) also demonstrated associations with EOC risk; a joint meta-analysis and in vitro investigations reinforced evidence for a protective role of LIN28B rs12194974 (combined OR= 0.90, 95% CI: 0.82-0.98), a G>A SNP predicted to reside in a transcription factor binding site in the highly conserved LIN28B promoter. Our findings provide valuable insight into the pathogenesis of EOC, and support the consideration of variants in these genes as candidates when building risk prediction models. Most importantly, this work has provided a strong foundation for further lines of research that may aid in reducing the burden of this disease.

Background: Meat consumption is associated with an elevated risk of colorectal cancer (CRC); exposure to heterocyclic aromatic amines (HAAs), carcinogens produced when meat is cooked at high temperatures, is one hypothesized explanation for this relationship. HAAs form adducts with DNA; left unrepaired, DNA adducts can induce mutations which may initiate and/or promote the development of colorectal adenomas, precursors to the vast majority of CRCs. Along this continuum, genetic differences in the ability to biotransform or metabolize HAAs and repair DNA is postulated to modify the HAA-CRC relationship. Methods: This thesis examined the HAA-CRC relationship in two studies (Phase 1 and 2). In a cross-sectional study of 99 healthy volunteers, Phase 1 investigated the relationship between dietary exposure to HAAs and the levels of bulky DNA adducts in blood leukocytes. In Phase 2, a cross-sectional study examined the relationships between dietary exposures to: a) HAAs and; b) meat mutagenicity, and the prevalence of colorectal adenomas among 342 patients undergoing a screening colonoscopy. Both Phase 1 and 2 examined potential gene-diet interactions between dietary HAAs and genetic factors relevant to the biotransformation of HAAs and DNA repair. Results: In Phase 1, an interaction was observed for dietary HAAs and NAT1 polymorphisms where a positive association between HAA intakes and bulky DNA adduct levels was found among those with the NAT1 slow acetylator genotype, hypothesized to confer a lower ability to biotransform HAAs. In Phase 2, polymorphisms in genes involved in the biotransformation of HAAs (CYP1B1 rs10012 and rs1056827) and DNA repair (XPC rs2228001) were found to determine colorectal adenoma risk. As well, gene-diet interactions were observed for dietary HAAs/meat mutagenicity exposures and polymorphisms in CYP1B1 and XPD (rs13181 and rs1799793). Overall, a higher risk of colorectal adenoma was observed with higher HAA and/or meat mutagenicity exposures among those with polymorphisms which confer a greater activity to biotransform HAAs and/or a lower ability to repair DNA. Conclusion: This research supports the contribution of dietary HAAs and genetic susceptibility to the risk of developing colorectal adenomas and highlighted bulky DNA adduct formation as a potential biologic pathway through which HAAs may influence cancer risk. / Thesis (Ph.D, Community Health & Epidemiology) -- Queen's University, 2014-04-25 11:32:30.392

No description available.

No description available.

La maladie de Crohn (MC) et la colite ulcéreuse (CU) sont des maladies inflammatoires chroniques du tube digestif qu’on regroupe sous le terme maladies inflammatoires de l’intestin (MII). Les mécanismes moléculaires menant au développement des MII ne sont pas entièrement connus, mais des études génétiques et fonctionnelles ont permis de mettre en évidence des interactions entre des prédispositions génétiques et des facteurs environnementaux - notamment la flore intestinale – qui contribuent au développement d’une dérégulation de la réponse immunitaire menant à l’inflammation de la muqueuse intestinale. Des études d’association pangénomiques et ciblées ont permis d’identifier plusieurs gènes de susceptibilité aux MII mais les estimations de la contribution de ces gènes à l’héritabilité suggèrent que plusieurs gènes restent à découvrir. Certains d’entre eux peuvent se trouver dans les régions identifiées par des études de liaison génétique. L’objectif de mon projet de doctorat était d’identifier un ou des facteurs de risque génétique dans la région chromosomale 19p (identifiée comme région de liaison IBD6) et de le/les caractériser au niveau fonctionnel. Nous avons d’abord entrepris une cartographie d’association de la région 19p. À la suite du génotypage successif de deux cohortes indépendantes, nous avons identifié un SNP intronique et quatre SNP codants dont un non-synonyme, rs8108738, tous localisés dans le gène microtubule associated serine threonine kinase gene-3 (MAST3) et associés aux MII. Peu d’information fonctionnelle sur MAST3 était disponible. Par contre MAST2, une protéine encodée par un gène de la même famille, régule l’activité du facteur de transcription inflammatoire NF-kappaB. Nous avons confirmé l’implication de MAST3 dans l’activité de NF-kappaB via un knockdown de MAST3 et des essais gène-rapporteur. Pour poursuivre la caractérisation fonctionnelle de MAST3, nous avons choisi une approche non ciblée pour étudier les effets de la variation des niveaux d’expression de MAST3 sur la cellule. C’est-à-dire que nous avons créé un 1er modèle cellulaire de surexpression du gène MAST3 dans les cellules HEK293 et analysé l’expression pangénomique endogène. La validation de l’expression génique dans un 2e modèle cellulaire de knockdown et de type cellulaire différent (THP1), nous a permis d’identifier et de contrer les effets non-spécifiques dus aux niveaux non-physiologiques. Notre étude d’expression a mené à l’identification d’un groupe de gènes dont l’expression est régulée par MAST3. Ces gènes sont majoritairement impliqués dans des fonctions immunitaires (cytokines pro-inflammatoires, régulateurs de NF-kappaB, migration cellulaire, etc.) et une forte proportion est régulée par NF-kappaB. Nous avons évalué l’importance du groupe de gènes régulés par MAST3 dans la présentation clinique des MII à travers des études d’expression dans des biopsies intestinales de patients atteints de CU. Nous avons constaté que l’expression de ces gènes est significativement supérieure dans les régions enflammées par rapport aux régions saines de la muqueuse intestinale des patients atteints de CU. Globalement, les résultats de nos études suggèrent que le facteur de risque aux MII MAST3 agit via la voie du facteur de transcription NF-kappaB pour influencer l’expression d’un groupe de gènes impliqués dans l’inflammation intestinale typique des MII. Chaque étude génétique sur les MII a le potentiel d’orienter les recherches fonctionnelles vers de nouvelles voies biologiques causales. Le dévoilement des mécanismes moléculaires sous-jacents à ces voies permet d’augmenter les connaissances sur le développement de ces maladies vers une compréhension plus complète de la pathogenèse qui permettra d’optimiser le diagnostic et le traitement de ces maladies. / Inflammatory bowel diseases (IBD) refer to different chronic inflammatory diseases of the digestive tract mainly Crohn’s disease (CD) and ulcerative colitis (UC). Mechanisms leading to the pathogenesis of IBD are not completely understood, but genetic and functional studies have highlighted interactions between genetic predispositions and environmental factors, such as the intestinal microbiota, as contributors to the deregulation of the immune response that leads to inflammation of the intestinal mucosa. Genome-wide and targeted association studies have identified several IBD susceptibility genes. However, estimations of the contribution of these genes to heritability of the disease suggest that more are to be discovered. Some of these genes may be in previously identified IBD linkage regions. The objective of my doctoral project was first, to identify risk factors in the 19p chromosomal region (IBD6), previously identified following a genome-wide linkage study, then to characterise them functionally. We first performed a comprehensive association mapping study of the 19p region. Our two-stage genotyping strategy led to the identification of one intronic SNP and four coding SNP –including one non-synonymous SNP, rs8108738 – all located in the microtubule associated serine threonine kinase gene 3 (MAST3) and associated to IBD. Very limited functional information on MAST3 was available at that time. However MAST2 (a gene in the same family as MAST3), is involved in the regulation of inflammation master switch, transcription factor NF-B. We confirmed the involvement of MAST3 in the modulation of NF-B via a knockdown of MAST3 and gene reporter assays. In order to further characterize the function of MAST3, we chose a non-targeted approach to study the effects of the modulation of MAST3 levels on the cell. More specifically, we created a 1st cell model of MAST3 overexpression in HEK293 cells and analysed the resulting genome-wide endogenous gene expression. Validation in a 2nd cell model consisting of a knockdown of MAST3 in THP1 cells, allowed to identify non-specific gene expression due to non-physiological MAST3 levels. Our expression study led to the identification of a group of genes whose expression is modulated by MAST3. These genes are mainly involved in immune functions (pro-inflammatory cytokines, NF-B regulation, cellular migration, etc) and a majority is regulated by transcription factor NF-B. We evaluated the importance of this MAST3-regulated gene set in the clinical manifestation of IBD through an expression study on biopsies of UC patients. We found that the expression the MAST3-regulated gene set was significantly enriched in inflamed region of the intestinal mucosa of UC patients compared to healthy region. Taken together, the results of our study suggest that IBD risk factor MAST3 acts on the NF-B pathway to influence the expression of a group of genes involved in intestinal inflammation typical of IBD. Every genetic study on IBD has the potential to lead functional research towards new causal biological pathways. The unravelling of the molecular mechanisms underlying these pathways aims to improve the comprehension of the pathogenesis of IBD and hopefully will allow for optimization of diagnostic and treatment of these diseases.

Submitted by admin tede (tede@pucgoias.edu.br) on 2016-10-07T13:26:52Z No. of bitstreams: 1 SIMONE SOUZA FAGUNDES.pdf: 1864838 bytes, checksum: 28db816101558781ede4b2fb42be7695 (MD5) / Made available in DSpace on 2016-10-07T13:26:52Z (GMT). No. of bitstreams: 1 SIMONE SOUZA FAGUNDES.pdf: 1864838 bytes, checksum: 28db816101558781ede4b2fb42be7695 (MD5) Previous issue date: 2016-06-27 / Breast cancer is the most frequent in the world and Brazilian women, except for cases of skin cancer nonmelanoma. It is a complex disease that has no single cause, results from the interaction of multiple risk factors (environmental, hormonal, lifestyle) with an individual genome (Pruthi et al., 2007). Polymorphism of codon 72 of TP53 gene is well studied because of the impact on the coding sequence of the gene is also associated with increased risk for the development of some cancers. The TP53 polymorphism in exon 4 of the 72 codon results in the substitution of arginine (Arg) or proline (Pro), which may encode an arginine (p53Arg) or a proline (p53Pro). This is a job that made the update meta-analysis on the association between the R72P polymorphism of the TP53 gene in patients with breast cancer considering a broad sample obtained from studies with conflicting data, making a statistical method that combines results of relevant studies to answer a question, search available evidence and points out the areas where there is need for more research. After search of the articles surveyed in multiple databases were selected for performing the metaanalysis a total of 47 articles totaling 27,068 cases and 28,065 controls. The organization of the articles was according to the year of publication, covering studies from 2002 to 2015. The results found worldwide about codon 72 polymorphism in p53 are quite conflicting, suggesting that it is due to ethnic and geographic factors that impact each continent evident. Although several studies show the wide variety can occur between genotypes and codon 72 alleles, identifying significant results for Arg / Arg genotype and allele arginine suggesting that this meta-analysis corroborates for therapies, diagnostics and more studies in this area. / O câncer de mama é o mais incidente na população feminina mundial e brasileira, excetuando-se os casos de câncer de pele não melanoma. É uma doença complexa que não tem causa única, resulta da interação de múltiplos fatores de risco (ambientais, hormonais, estilo de vida) com um genoma individual (Pruthi et al., 2007). O polimorfismo do códon 72 do gene TP53 é bastante estudado devido ao impacto na sequência codificadora do gene, além de estar associado ao maior risco para o desenvolvimento de alguns tipos de câncer. O polimorfismo do gene TP53 no éxon 4 do códon 72, resulta na substituição de Arginina (Arg) ou Prolina (Pro), que pode codificar um aminoácido arginina (p53Arg) ou uma prolina (p53Pro). Este é um trabalho que fez a atualização de metanálise sobre associação entre o polimorfismo R72P do gene TP53 em pacientes com câncer de mama considerando uma ampla amostragem obtidos de estudos com dados conflitantes, fazendo uma abordagem estatística que combina resultados de estudos relevantes para responder a uma questão, busca evidências disponíveis e aponta as áreas onde há necessidade de mais pesquisas. Após busca dos artigos pesquisados em várias bases de dados foram selecionados para a realização da metanálise um total de 47 artigos somando 27.068 casos e 28.065 controles. A organização dos artigos foi de acordo com o ano de publicação, contemplando estudos de 2002 a 2015. Os resultados encontrados mundialmente a respeito do polimorfismo do códon 72 na p53 são bastantes conflitantes, sugerindo que seja devido a fatores étnicos e geográficos que impactam em cada continente de forma evidente. Apesar de vários estudos mostrarem a grande variedade pode ocorrer entre os genótipos e alelos do códon 72, identificando resultados significativos para o genótipo Arg/Arg e o alelo arginina sugerindo que esta metanálise corrobora para terapias, diagnósticos e mais estudos nesta área.

Made available in DSpace on 2016-01-26T12:51:30Z (GMT). No. of bitstreams: 1 nataliaguelfifurlani_dissert.pdf: 2586696 bytes, checksum: c66f56a5e70e155d3ec22d8e0643f53a (MD5) Previous issue date: 2011-07-27 / The Brazilian population is mainly composed of three parental populations: Native Americans, Europeans and Africans. Significant levels of tri-hybrid admixture have been detected in all regions and socioeconomic levels within the country. Recent statistical methods allied to the ability to genotype a large number of markers permit the estimate of the admixture at the individual level. In epidemiological studies with case-control design, ethnic heterogeneity between subgroups can produce false positive results. Therefore, for this type of study, it is important to evaluate individual admixture, as well as to measureits influence on the genetic structure of diverse subgroups within the Brazilian populations. Ancestry Informative Markers (AIMs), which frequencies show large differences between parental populations are suitable for tracking the effect of mixing, in order to avoid spurious associations in case control studies. This knowledge could help to further define the levels of population structure in groups and subgroups that constitute the subject of epidemiological studies, optimizing their designto avoid false positive results. Among these groups are particularly relevant studies addressing genetic factors that modulate susceptibility to malaria in regions where the population is exposed to endemic levels, for example, those residing in the municipality of Porto Velho (RO), Brazilian amazon region and surroundings. Objectives: a) to describe the Amerindian, European and African individual genomic ancestry in healthy individuals and patients with falciparum malaria in Porto Velho, RO (Western Amazonia) and assess its impact on the design of epidemiological studies and b) to determine, from the genotyped markers, the genetic structure of populations of falciparum malaria patients and healthy individuals from the same region, depending on the admixture levels . / A população brasileira é formada majoritariamente por três populações parentais: Nativos Americanos, Europeus e Africanos. Níveis significativos de miscigenação tri-híbrida já foram detectados em todas as regiões e níveis sócio-econômicos do País. Métodos estatísticos recentes aliados à possibilidade de genotipagem de um grande número de marcadores permitem estimar a miscigenação em nível individual. Em estudos epidemiológicos com desenho de caso-controle, a heterogeneidade étnica entre estas categorias pode produzir resultados falso-positivos. Por este motivo, para este tipo de estudo, é importante estudar a miscigenação individual, assim como avaliar como a miscigenação neste nível influencia a estrutura genética dos diferentes subgrupos das populações brasileiras. O controle do efeito da miscigenação, para evitar as associações espúrias em estudos do tipo caso-controle pode ser feito estudando Marcadores Informativos de Ancestralidade (MIAs), os quais apresentam grandes diferenças de freqüência entre as populações parentais. Este conhecimento poderá contribuir para a futura definição dos níveis de estruturação populacional em grupos e subgrupos que constituirão alvo de estudos epidemiológicos, permitindo a otimização dos mesmos, a fim de evitar resultados falso-positivos. Dentre estes grupos, são de particular relevância estudos que abordem os fatores genéticos que modulam a suscetibilidade à malária em regiões onde a população se encontra exposta em nível endêmico como, por exemplo, a que reside no município de Porto Velho (RO) e região. Objetivos: a) descrever a ancestralidade genômica individual Ameríndia, Européia e Africana em indivíduos sadios e portadores de malária por Plasmodium falciparum da cidade de Porto Velho, RO (Amazônia Ocidental), Brasil, e avaliar seu impacto no desenho de estudos epidemiológicos e b) determinar, a partir dos marcadores genotipados, a estrutura genética das populações de portadores de malária falciparum e indivíduos sadios da mesma região, em função dos níveis de miscigenação.

Les protéines kinases de la voie de signalisation de l’Epidermal Growth Factor Receptor sont l’objet d’une dérégulation au cours des cancers broncho-pulmonaires. Les gènes encodant ces protéines sont porteurs de mutations oncogéniques mutuellement exclusives induisant la transformation tumorale des cellules de l’épithélium respiratoire. Ces mutations définissent autant de sous-groupes moléculaires spécifiques caractérisés sur le plan clinique, histologique, et biologique. Notre travail a consisté en l’étude de ces mutations dans trois situations cliniques spécifiques, les cancers broncho-pulmonaires du non-fumeur, les cancers bronchopulmonaires multiples, et les tumeurs thymiques. L’évaluation des polymorphismes génétiques chez les patients non-fumeurs atteints de cancer broncho-pulmonaire suggère le rôle de gènes spécifiques, différents de ceux impliqués chez le patient fumeur. L’étude génomique des cancers broncho-pulmonaires multiples montre la possibilité d’utiliser les mutations oncogéniques pour évaluer le degré de clonalité des lésions tumorales multiples, avec une corrélation significative avec leur analyse histo-pathologique détaillée. L’analyse génomique intégrative des tumeurs thymiques indique l’existence de sous-groupes moléculaires spécifiques, corrélés à la classification histologique, et caractérisés par des mutations oncogéniques prédictives de l’efficacité de certains traitements ciblés. Nos données illustrent les principes de la médecine personnalisée en oncologie thoracique, consistant en l’analyse des caractéristiques moléculaires de chaque tumeur individuelle, pour permettre une meilleure personnalisation de la prise en charge des patients / Oncogenic mutations may be identified in several genes of the Epidermal Growth Factor Receptor signaling pathway in non-small cell lung cancer. These mutations are transforming for epithelial cells of the respiratory tract through deregulation of the encoded proteins. These mutations are mutually exclusive and thus define molecular subsets of lung cancer with specific clinical, histological, and biological relevance. Here we integrated the use of mutation genotyping for the analysis of 3 specific clinical issues, including lung cancer occurring in never-smokers, multiple lung cancers, and thymic malignancies. Our results indicate that genetic polymophisms in never-smokers with lung cancer differ from those observed in smokers. Genomic profiling of multiple lung cancers suggests the feasibility of mutational profiling as a surrogate marker to evaluate the clonal relationships among multiple lung tumors, with a strong correlation with comprehensive histologic subtyping. Integrated genomic analysis of thymic malignancies identified specific molecular subsets, associated with histologic subtypes and oncogenic mutations predicting response to specific inhibitors. Taken together, our results illustrate the concept of personalized medicine in thoracic oncology, consisting of the individual analysis of molecular features of tumors to better tailor the therapeutic management of patients

La maladie de Crohn (MC) et la colite ulcéreuse (CU) sont des maladies inflammatoires chroniques du tube digestif qu’on regroupe sous le terme maladies inflammatoires de l’intestin (MII). Les mécanismes moléculaires menant au développement des MII ne sont pas entièrement connus, mais des études génétiques et fonctionnelles ont permis de mettre en évidence des interactions entre des prédispositions génétiques et des facteurs environnementaux - notamment la flore intestinale – qui contribuent au développement d’une dérégulation de la réponse immunitaire menant à l’inflammation de la muqueuse intestinale. Des études d’association pangénomiques et ciblées ont permis d’identifier plusieurs gènes de susceptibilité aux MII mais les estimations de la contribution de ces gènes à l’héritabilité suggèrent que plusieurs gènes restent à découvrir. Certains d’entre eux peuvent se trouver dans les régions identifiées par des études de liaison génétique. L’objectif de mon projet de doctorat était d’identifier un ou des facteurs de risque génétique dans la région chromosomale 19p (identifiée comme région de liaison IBD6) et de le/les caractériser au niveau fonctionnel. Nous avons d’abord entrepris une cartographie d’association de la région 19p. À la suite du génotypage successif de deux cohortes indépendantes, nous avons identifié un SNP intronique et quatre SNP codants dont un non-synonyme, rs8108738, tous localisés dans le gène microtubule associated serine threonine kinase gene-3 (MAST3) et associés aux MII. Peu d’information fonctionnelle sur MAST3 était disponible. Par contre MAST2, une protéine encodée par un gène de la même famille, régule l’activité du facteur de transcription inflammatoire NF-kappaB. Nous avons confirmé l’implication de MAST3 dans l’activité de NF-kappaB via un knockdown de MAST3 et des essais gène-rapporteur. Pour poursuivre la caractérisation fonctionnelle de MAST3, nous avons choisi une approche non ciblée pour étudier les effets de la variation des niveaux d’expression de MAST3 sur la cellule. C’est-à-dire que nous avons créé un 1er modèle cellulaire de surexpression du gène MAST3 dans les cellules HEK293 et analysé l’expression pangénomique endogène. La validation de l’expression génique dans un 2e modèle cellulaire de knockdown et de type cellulaire différent (THP1), nous a permis d’identifier et de contrer les effets non-spécifiques dus aux niveaux non-physiologiques. Notre étude d’expression a mené à l’identification d’un groupe de gènes dont l’expression est régulée par MAST3. Ces gènes sont majoritairement impliqués dans des fonctions immunitaires (cytokines pro-inflammatoires, régulateurs de NF-kappaB, migration cellulaire, etc.) et une forte proportion est régulée par NF-kappaB. Nous avons évalué l’importance du groupe de gènes régulés par MAST3 dans la présentation clinique des MII à travers des études d’expression dans des biopsies intestinales de patients atteints de CU. Nous avons constaté que l’expression de ces gènes est significativement supérieure dans les régions enflammées par rapport aux régions saines de la muqueuse intestinale des patients atteints de CU. Globalement, les résultats de nos études suggèrent que le facteur de risque aux MII MAST3 agit via la voie du facteur de transcription NF-kappaB pour influencer l’expression d’un groupe de gènes impliqués dans l’inflammation intestinale typique des MII. Chaque étude génétique sur les MII a le potentiel d’orienter les recherches fonctionnelles vers de nouvelles voies biologiques causales. Le dévoilement des mécanismes moléculaires sous-jacents à ces voies permet d’augmenter les connaissances sur le développement de ces maladies vers une compréhension plus complète de la pathogenèse qui permettra d’optimiser le diagnostic et le traitement de ces maladies. / Inflammatory bowel diseases (IBD) refer to different chronic inflammatory diseases of the digestive tract mainly Crohn’s disease (CD) and ulcerative colitis (UC). Mechanisms leading to the pathogenesis of IBD are not completely understood, but genetic and functional studies have highlighted interactions between genetic predispositions and environmental factors, such as the intestinal microbiota, as contributors to the deregulation of the immune response that leads to inflammation of the intestinal mucosa. Genome-wide and targeted association studies have identified several IBD susceptibility genes. However, estimations of the contribution of these genes to heritability of the disease suggest that more are to be discovered. Some of these genes may be in previously identified IBD linkage regions. The objective of my doctoral project was first, to identify risk factors in the 19p chromosomal region (IBD6), previously identified following a genome-wide linkage study, then to characterise them functionally. We first performed a comprehensive association mapping study of the 19p region. Our two-stage genotyping strategy led to the identification of one intronic SNP and four coding SNP –including one non-synonymous SNP, rs8108738 – all located in the microtubule associated serine threonine kinase gene 3 (MAST3) and associated to IBD. Very limited functional information on MAST3 was available at that time. However MAST2 (a gene in the same family as MAST3), is involved in the regulation of inflammation master switch, transcription factor NF-B. We confirmed the involvement of MAST3 in the modulation of NF-B via a knockdown of MAST3 and gene reporter assays. In order to further characterize the function of MAST3, we chose a non-targeted approach to study the effects of the modulation of MAST3 levels on the cell. More specifically, we created a 1st cell model of MAST3 overexpression in HEK293 cells and analysed the resulting genome-wide endogenous gene expression. Validation in a 2nd cell model consisting of a knockdown of MAST3 in THP1 cells, allowed to identify non-specific gene expression due to non-physiological MAST3 levels. Our expression study led to the identification of a group of genes whose expression is modulated by MAST3. These genes are mainly involved in immune functions (pro-inflammatory cytokines, NF-B regulation, cellular migration, etc) and a majority is regulated by transcription factor NF-B. We evaluated the importance of this MAST3-regulated gene set in the clinical manifestation of IBD through an expression study on biopsies of UC patients. We found that the expression the MAST3-regulated gene set was significantly enriched in inflamed region of the intestinal mucosa of UC patients compared to healthy region. Taken together, the results of our study suggest that IBD risk factor MAST3 acts on the NF-B pathway to influence the expression of a group of genes involved in intestinal inflammation typical of IBD. Every genetic study on IBD has the potential to lead functional research towards new causal biological pathways. The unravelling of the molecular mechanisms underlying these pathways aims to improve the comprehension of the pathogenesis of IBD and hopefully will allow for optimization of diagnostic and treatment of these diseases.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Horse breeding industry is an activity in ascension worldwide, and is responsible for generating jobs and income. In Brazil, especially in Rio Grande do Sul state, there are several horse breeding farms with high-standard equines. Although these herds are under strict sanitary control, the occurrence of respiratory diseases is an important cause of mortality in foals and reduced athletic performance. Among the respiratory diseases, equine rhodococcosis, caused by the bacterium Rhodococcus equi, is the major cause of pneumonia in foals. Rhodococcus equi is worldwide distributed, and have emerged as an important cause of economic losses due to pneumonia in young animals. However, preventive measures and effective control of the disease are still challenges to be reached. In R. equi infection, iron (Fe) is classified as an essential element not only for the bacterium multiplication, but also as a key for the expression of virulence factors. Studies have shown the presence of specific Fe uptake mechanisms in R. equi, which have been determining its survival in both saprophytic and pathogenic life styles. However, as a type of nutritional immunity, mammals, including horses, reduce the plasmatic concentration of Fe through its binding in proteins, including the transferrin (Tf). In this context, the present thesis was developed to study aspects related to metabolism and acquisition of Fe by R. equi and Fe importance in the pathogenesis of equine rhodococcosis (manuscript 1), control and treatment of infections caused by R. equi through drugs with capability to reduce the availability of intracellular Fe (manuscript 2), and genetic susceptibility to R. equi pneumonia (manuscript 3), including the assessment of polymorphisms in the equine Tf gene as risk factors related to susceptibility and/or resistance to equine rhodococcosis (manuscript 4 ). We conclude that R. equi is evolving to specialize it in the acquisition and utilization of Fe from the host, skills that should be considered as key points for the development of chemotherapeutic agents. Once R. equi encodes redundant mechanisms of acquisition and utilization of Fe, it is likely that chemotherapeutic agents will need act on multiple cellular mechanisms or be used in combination. Furthermore, the term "nutritional immunity" may be considered an important strategy to minimize antimicrobial resistance observed in R. equi. As an example of chemotherapy associated with iron metabolism, we observed that chloroquine inhibits the intracellular multiplication of R. equi, most likely due to intracellular iron deprivation. However, further studies are necessary to evaluate the chloroquine therapeutic potential against R. equi infections. We also observed important chromosomal regions positively associated with R. equi pneumonia, which seem to possess genes associated with immune response against intracellular pathogens. This observation allows us to classify the equine rhodococcosis as a disease of polygenic basis, as postulated by previous studies. Finally, we found that polymorphisms in the Tf gene, including some not described yet in the literature, occur in Brazilian Sport Horses and Brazilian Thoroughbred Horses. There is the occurrence of two alleles between the breeds studied, including heterozygosis for these alleles. We believe that there is a relationship between equine Tf variants, and genetic susceptibility to R. equi pneumonia in the breeds evaluated. Summarizing, we have demonstrated that the modulation of Fe availability may be a useful approach to control the disease. / A equideocultura é uma atividade em ascensão mundial, responsável pela geração de empregos e renda. No Brasil, em especial no Rio Grande do Sul, encontram-se diversos locais de criação de equinos de alto padrão zootécnico. Embora estes rebanhos estejam sob rigoroso controle sanitário, a ocorrência de doenças respiratórias é causa importante de mortalidade em potros e redução de seu desempenho atlético. Dentre as doenças respiratórias, a rodococose equina, causada pela bactéria Rhodococcus equi, é a principal causa de pneumonia nesta categoria animal. R. equi está distribuído mundialmente, e cresce como causa de perdas econômicas devido à pneumonia observada em animais jovens. No entanto, medidas preventivas e efetivo controle da enfermidade são ainda desafios a serem alcançados. Na infecção por R. equi, o ferro (Fe) apresenta-se como um elemento fundamental não somente para multiplicação da bactéria, mas também, como um determinante para a expressão de fatores de virulência. Estudos têm demonstrado a presença de mecanismos específicos de captação de Fe em R. equi, os quais determinam sua sobrevivência tanto durante seu estilo de vida saprófito quanto patogênico. Em contrapartida, como uma forma de imunidade nutricional, mamíferos, entre eles os equinos, diminuem a concentração plasmática de Fe através de sua ligação em proteínas, entre elas, a transferrina (Tf). Neste contexto, esta tese foi elaborada visando contemplar aspectos relacionados ao metabolismo e aquisição de Fe por R. equi e sua importância para patogenia da rodococose equina (manuscrito 1), controle e tratamento de infecções por R. equi através de drogas com capacidade de modular a disponibilidade de Fe intracelular (manuscrito 2), e susceptibilidade genética à pneumonia por R. equi (manuscrito 3), incluindo a avaliação de polimorfismos no gene da Tf equina como fatores de risco relacionados à susceptibilidade e/ou resistência genética à rodococose equina (manuscrito 4). Concluímos que R. equi está evoluindo de forma a especializar-se na aquisição e utilização de Fe a partir do hospedeiro, habilidades que devem ser consideradas como pontos chave no desenvolvimento de agentes quimioterápicos. Uma vez que R. equi codifica redundantes mecanismos de aquisição e utilização de Fe, é provável que agentes quimioterápicos deverão inibir múltiplos mecanismos ou ser utilizados em combinação. Além disso, o conceito de imunidade nutricional pode considerado uma importante estratégia para minimizar a resistência antimicrobiana observada em R. equi. Como um exemplo de quimioterápicos associados ao metabolismo de Fe, observados que chloroquine inibir a multiplicação intracelular de R. equi, muito provavelmente devido à deprivação de Fe intracelular. No entanto, ainda são necessários estudos avaliando o potencial terapêutico de chloroquine como tratamento alternativo de infecções por R. equi. Observou-se, também, importantes regiões cromossômicas positivamente associadas à pneumonia por R. equi, as quais parecem possuir genes associados à resposta imune contra patógenos intracelulares. Esta observação nos permite classificar a rodococose equina como uma enfermidade de base poligênica, como postulado por estudos anteriores. Por fim, verificamos que polimorfismos no gene da Tf, inclusive polimorfismos ainda não descritos na literatura, ocorrem em equinos das raças Brasileiro de Hipismo e Puro Sangue de Corrida, criados no Brasil. Existe a ocorrência de dois alelos entre as raças estudas, incluindo animais heterozigotos para estes alelos. Acredita-se que exista uma relação entre variantes de Tf equina e susceptibilidade genética à pneumonia por R. equi nas raças analisadas. Em suma, demonstrou-se através de diferentes estudos que a modulação da disponibilidade de Fe pode ser uma forma de controle da rodococose equina.