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Speciation, the formation of new species, is an essential evolutionary process that causes species diversity on the Earth. At the beginning of this process is the separation of two populations by a reproductive barrier that prevents gene flow between these populations. One of the mechanisms, which enable reproductive isolation, is hybrid sterility (HS). It is a mechanism of postzygotic isolation that is described in a number of eukaryotes. The first discovered gene of hybrid sterility in vertebrates is the mice gene Hst1, later identified as gene Prdm9. By genetic and molecular analysis the locus on the X chromosome was determined, whose interaction with Prdm9 causes sterility or reduced fitness in male hybrids. This locus contains two genetic factors: Hstx1, causing an abnormal morphology of spermatozoa, and Hstx2, causing an arrest in spermatogenesis in pachytene spermatocytes and sterility. In my thesis I focus on the effect of deletion of a candidate hybrid sterility gene Fmr1nb on the X chromosome. The analysis of males B6N.Fmr1nbmut with deletion variants of the Fmr1nb gene showed that Fmr1nb is one of the factors influencing spermatogenesis. An increase in morphologic abnormalities in spermatozoa occurred in males with Fmr1nb gene deletion. This phenotype is identical with Hstx1. The effect...

A compensação da dosagem gênica entre fêmeas XX e machos XY em mamíferos é adquirida através de um complexo mecanismo epigenético que resulta na inativação de grande parte de um dos cromossomos X nas células femininas. O processo de inativação do cromossomo X (XCI) se inicia cedo durante a embriogênese, concomitantemente à diferenciação celular, e envolve a aquisição de modificações epigenéticas características do cromossomo X inativo (Xi). Uma estabelecido, o padrão de inativação é estavelmente mantido através de todas as mitoses celulares subsequentes e por toda a vida do organismo (exceto para células germinativas que sofrem reativação do Xi). Os mecanismos envolvidos na iniciação e estabelecimento da XCI foram extensivamente estudados, especialmente em camundongos. Embora algumas características epigenéticas associadas à manutenção da XCI tenham sido descritas, a identidade e modo específico de ação de fatores envolvidos durante essa fase da XCI são aspectos ainda não bem compreendidos. Além disso, o processo de XCI apresenta diferenças importantes entre humanos e camundongos e estudos direcionados para a identificação de novos componentes envolvidos na manutenção da XCI em humanos tornam-se de fundamental importância. Triagens funcionais genômicas por bibliotecas de shRNAs constituem uma ferramenta poderosa para a identificação de genes envolvidos em diferentes mecanismos celulares e vias bioquímicas. Sendo assim, utilizamos essa ferramenta para triar genes envolvidos na manutenção da XCI em humanos. Células somáticas femininas primárias HPRT+/-/HPRT- foram transduzidas com uma biblioteca lentiviral de shRNAs e posteriormente tratadas em meio de cultura contendo a droga HAT para seleção de células HPRT+ nas quais esperava-se que o cromossomo Xi presente tivesse sofrido reativação em decorrência do knockdown de genes envolvidos na manutenção da XCI. Essa estratégia nos permitiu identificar 20 novos genes candidatos a estarem envolvidos na manutenção da XCI. Esses candidatos deverão ser avaliados individualmente para confirmar seu papel no processo de controle epigenético do cromossomo X / Transcriptional dosage compensation between mammalian XX females and XY males is acquired through a complex epigenetic mechanism that leads to the inactivation of most part of one of the X chromosomes in the female cells. The X chromosome inactivation (XCI) process takes place early during embryogenesis and involves the acquisition of epigenetic modifications that are characteristic of the inactive X chromosome (Xi). Once silencing is established, the inactivation pattern is maintained in through all the subsequent mitosis and the same X chromosome remains stably silenced in all the descendant cells and throughout the life of the organism (except for the germ line cells that undergo X chromosome reactivation). The initiation of XCI has been studied extensively, especially in mice. Although some epigenetic features associated with the maintenance of XCI have already been described, the identity and specific mode of action of the factors involved in this phase of XCI are largely unknown. Moreover, the XCI process presents important differences between mice and humans, and studies directed to the identification of new players involved in the maintenance of human XCI are fundamentally important. Functional genome-wide screens using multiplex shRNA libraries are a powerful tool for the identification of genes involved in different cellular mechanisms and biochemical pathways. In order to screen for genes involved in the maintenance of XCI in humans, a population of HPRT+/-/HPRT- primary somatic female cells were transduced with a multiplex lentiviral shRNA library and subsequently treated in HAT medium to select for HPRT+ cells in which we expected that the Xi would undergo reactivation as a result of the knockdown of genes involved in the maintenance of XCI. As a result, we identified 20 new candidate genes that could potentially be involved in the maintenance of XCI. These candidates should be individually evaluated in order to confirm their role in the epigenetic control of the X chromosome

Estudos relacionando a síndrome de Turner com o estado nutricional relativo aos micronutrientes, em especial o zinco e selênio, são praticamente inexistentes. Portanto, o presente estudo teve como objetivo avaliar o estado nutricional relativo ao zinco e ao selênio dessa população, considerando as diferentes fases de vida. A avaliação antropométrica das crianças mostrou que 55,6% estavam eutróficas e 44,4% com sobrepeso, de acordo com o índice de peso/estatura. As adolescentes foram classificadas segundo o percentil de IMC ajustado para a idade, onde 73,7% estavam eutróficas e 26,3% com sobrepeso. Em relação ao grupo das adultas, 42,9% estavam com sobrepeso e 14,3% com obesidade, considerando o IMC (kg/(m)2). A avaliação do consumo alimentar foi realizada por meio do software Nutwin, mostrando que a ingestão de zinco dietético de 35,7% das participantes do estudo estava abaixo da EAR. Em relação à ingestão de selênio, observou-se que 100% das pacientes consumiram quantidades deste mineral acima da EAR. Na avaliação da concentração de zinco plasmático foi demonstrado que 22,2%, 68,4% e 14,3% das crianças, adolescentes e adultas estavam deficientes em zinco. A concentração de zinco eritrocitário apresentou-se deficiente em 66,7% das crianças, 57,9% das adolescentes e 28,6% das adultas. Na avaliação da excreção urinária de zinco observou-se que mais de 50% da população estudada estavam eliminando baixas concentrações desse mineral. Em relação ao estado nutricional de selênio, 77,8% das crianças, 78,9% das adolescentes e 85,7% das adultas encontravam-se deficientes em selênio plasmático e 55,6%, 52,6% e 57,1% das crianças, adolescentes e adultas, respectivamente, estavam deficientes em selênio eritrocitário. Opercentual de crianças, adolescentes e adultas com baixas concentrações de selênio na urina foi de 100%, 94,7% e 100%, respectivamente. A determinação da concentração de selênio nas unhas mostrou que 100% das crianças, 93,8% das adolescentes e 66,7% das adultas se encontravam com valores reduzidos neste compartimento. Os resultados da atividade da glutationa peroxidase se mostraram dentro dos limites de normalidade nas três fases de desenvolvimento. Assim, pode se concluir que o estado nutricional relativo ao zinco e ao selênio está deficiente para grande parte das pacientes, visto que as concentrações desses micronutrientes encontram-se reduzidos para a maioria dos parâmetros utilizados. / Studies relating to Turner Syndrome with the nutritional status on micronutrients, in particular zinc and selenium are practically non-existent. This study aimed to assess the nutritional status on zinc and selenium in this population, considering the different stages of life. Anthropometric evaluation of the children showed that 55.6% were eutrophic and 44.4% with overweight, according to the rate of weight/height. The adolescents were c1assified according to the percentile of BMI adjusted for age, where 73.7% were eutrophic and 26.3% with overweight. Regarding the group of adults, 42.9% were overweight and 14.3% with obesity, according BMI (kg/m2). The assessment of food consumption was made through the software Nutwin, demonstrating that the intake of dietary zinc, 35.7% of participants in the study were below the EAR. Regarding the intake of selenium, it was observed that 100% of patients consumed quantities of this mineral above the EAR. In assessing the plasma concentration of zinc has been shown that 22.2%, 68.4% e 14.3% of children, adolescents and adults were deficient in zinco The concentrations of zinc in erythrocyte were deficient 66.7% of children, 57.9% of adolescents and 28.6% of adults. In assessing the urinary excretion of zinc observed that 55.6%,57.9% and 66.7% of children, adolescents and adults, respectively, eliminate low concentrations of this mineral. The nutritional status of selenium, 77.8% of children, 78.9% of adolescents and 85.7% of adults were found deficient in plasmatic selenium and 55.6%, 52.6% and 57.1% of children, adolescents and adults, respectively, were deficient for selenium in erythrocyte. The percentage of children, adolescents and adults with low concentrations of selenium in urine was 100%, 94.7% and 100% respectively. The determination of the concentration of selenium Nail showed that 100% of children, adolescents and 93.8% from 66.7% of adults with values were reduced in this compartment. The results of the activity of glutathione peroxidase were within the limits of normality in the three stages of development. Thus, it can be concluded that the nutritional status on the zinc and selenium is deficient for most patients, because the concentrations of these micronutrients, are reduced for most of the parameters used.

<p>Kratki uzastopni ponovci predstavljaju klasu mikrosatelitskih segmenata DNK, rasprostranjenih &scaron;irom genoma čoveka. Građeni su od uzastopno ponavljajućih sekvenci dužine 2-6 parova nukleotida. Zahvaljujući različitom broju ponavljanja repetitivne jedinice, većina mikrosatelitskih markera pokazuje visok stepen polimorfizma dužine, koji je moguće ispitati primenom tehnike lančane reakcije polimeraze. Pored utvrđivanja spornih srodničkih odnosa, analiza X hromozom mikrosatelitskih markera može se uspe&scaron;no koristiti i u oblastima kriminalistike, humane identifikacije, populaciono-genetičkim i demografskim istraživanjima i dr. Cilj istraživanja je izrada populacione studije, iz koje će se izračunati broj i frekvencija alela, struktura i frekvencija haplotipova, utvrditi vrednosti relevantnih statističkih parametara, oceniti mogućnost primene analize X-STR markera u slučajevima iz oblasti medicinske kriminalistike, humane identifikacije i ve&scaron;tačenja spornih srodničkih odnosa u populaciji Vojvodine. Istraživanjem je obuhvaćeno 200 odraslih, međusobno nesrodnih osoba. Izolacija DNK materijala iz krvnih mrlja vr&scaron;ena je Chelex metodom, a amplifikacija dobijenih uzoraka DNK metodom PCR, uz kori&scaron;ćenje komercijalnog Mentype&reg; Argus X-12 PCR Amplification Kit &ndash; a. Razdvajanje i detekcija dobijenih fragmenata izvr&scaron;eno je kapilarnom elektroforezom GeneScan i Genotyper programom. Statististička obrada rezultata izvr&scaron;ena je pomoću Arlequin i GENEPOP programa. Za vizuelizaciju interpopulacionih genetičkih odnosa, upotrebljen je program POPTREE2 i koordinatna analiza (Principal Coordinate Analysis - PCoA). Dobijeni rezultati ukazuju da se analiza ispitivanih X-STR markera može uspe&scaron;no primeniti u slučajevima iz oblasti medicinske kriminalistike, humane identifikacije i ve&scaron;tačenja spornih srodničkih odnosa u populaciji Vojvodine, kao i da mogu poslužiti kao osnova za dalja istraživanja u&nbsp; populacionogenetičkim, antropolo&scaron;kim, demografskim i drugim oblastima.</p> / <p>Short tandem repeats (STR) represent a class of microsatellites, widely spread throughout the human genome, consisting of tandemly repeated sequences of 2-6 bp. Related to variation in the number of repeat unit displayed, most of microsatellites show a high degree of length polymorphism, investigated by the PCR techniques. The aim of this research is to create a population study, which will be used to calculate allele and haplotype frequencies, determine the value of relevant statistical parameters and assess the possibility of applying X-STR markers analysis in the fields of forensics, human identification and kinship testing. The study included 200 unrelated adults. DNA isolation was performed by Chelex method and DNA amplification by PCR, using commercial Mentype Argus X-12 PCR Amplification Kit. Separation and detection of fragments was obtained by capillary electrophoresis using Gene Scanand Genotyper program. Statistical analysis of the result was performed using Arlequin and GENEPOP program. For visualization of inter population genetic distances POPTREE2 program and coordinate analysis (PCoA) was used. The results show that the analysis of X-STR markers can be successfully applied in the field of forensics, human identification and kinship testing in the population of Vojvodina, as well as to serve as a basis for further research in population genetic, anthropological, demographic and other scientific areas.</p>

Este trabalho teve o objetivo de identificar genes candidatos para deficiência mental de herança ligada ao cromossomo X (DMLX). Foram investigadas quatro famílias, nas quais a deficiência mental de causa desconhecida segregava num padrão típico de herança ligada ao X, e 24 irmandades que incluíam pelo menos dois afetados do sexo masculino. O padrão de inativação do cromossomo X foi determinado nas mães dos afetados, pois desvios extremos no padrão de inativação são frequentes em mulheres portadoras de mutações no cromossomo X que causam DMLX. Nas famílias com padrão de herança ligada ao X, a deficiência mental foi mapeada, usando marcadores moleculares do tipo microssatélite, localizados ao longo do cromossomo X. Desequilíbrios cromossômicos submicroscópicos foram investigados por hibridação genômica comparativa baseada em array (array-CGH). Genes candidatos posicionais que já haviam sido associados a deficiência mental foram sequenciados pelo método de Sanger, em busca de mutações patogênicas. Em três famílias com DMLX, o probando teve seu exoma sequenciado. Nas três famílias com DMLX em que o sequenciamento do exoma foi realizado, foram detectadas mutações missense, levando à substituição de resíduos de aminoácidos conservados, que segregavam com a deficiência mental. Essas mutações foram consideradas como prováveis causas dos fenótipos nessas famílias: c.12378C>G no gene HUWE1 (HECT, UBA and WWE domain containing 1, E3 ubiquitin protein ligase); c.1413C>A no gene SHROOM4 (shroom family member 4) e c.262G>A no gene KIAA2022. As mulheres heterozigóticas quanto a essas mutações apresentaram desvio completo de inativação do cromossomo X (100:0). Mutações de ponto ou interrupção desses genes por rearranjos cromossômicos foram previamente descritas em alguns pacientes com deficiência mental. Em uma família, em que a DMLX estava associada a microcefalia e malformação de Dandy-Walker, uma microduplicação de aproximadamente 300 kb em Xq28 (ChrX :153,578,110-153,880,794;Hg19) foi detectada segregando com a doença. As mulheres heterozigóticas quanto a essa duplicação apresentaram desvios de inativação do X (80:20 e 90:10). Duplicações semelhantes foram anteriormente descritas em três famílias europeias e em um caso esporádico; a malformação de Dandy-Walker foi documentada em alguns desses pacientes. No estudo das 24 irmandades com pelo menos dois indivíduos do sexo masculino apresentando deficiência mental, o padrão de inativação do cromossomo X de suas mães foi determinado. Quatro mulheres (16,7%) apresentaram desvio total de inativação do cromossomo X (100:0), frequência significativamente maior do que a descrita para população geral de mulheres adultas (cerca de 2 %). Considerando que desvios extremos de inativação do cromossomo X são observados em aproximadamente 30% das portadoras de mutações que causam DMLX, concluiu-se que as quatro mães de homens que apresentam deficiência mental eram provavelmente portadores de mutações no cromossomo X, causadoras da deficiência mental em seus filhos. Não foram encontradas microdeleções ou microduplicações no cromossomo X nos probandos das quatro irmandades. / This study aimed at identifying candidate genes for X-linked intellectual disability (ID). Four families in which ID of unknown cause segregated as an X-linked trait, and 24 sibships with at least two affected males were investigated. The pattern of X-inactivation was determined in the mothers of affected males, taking into account that extremely skewing of X-inactivation is frequently found in women carrying mutations causative of X-linked intellectual disability (XLID). In the XLID families, ID was mapped by the genotyping of microsatellite markers localized throughout the X chromosome. Cryptic X-chromosome imbalances were investigated by array-based comparative genomic hybridization (a-CGH). Positional candidate genes that had been associated with ID were directly sequenced in the search for causative mutations. In three XLID families, the propositus had their exome sequenced. In three XLID families missense mutations that led to substitutions of conservative aminoacid residues were found that segregated with ID, and were probably causative of the clinical phenotypes: c.12378C>G in HUWE1 (HECT, UBA and WWE domain containing 1, E3 ubiquitin protein ligase) gene; c.1413C>A in the SHROOM4 (shroom family member 4) gene; c.262G>A in the KIAA2022 gene. Heterozygotes for these mutations had completely skewed X-inactivation (100:0 inactivation ratio). Point mutations or disruption of these genes by rearrangement breakpoints have been previously described in a few patients with ID. In one family in which XLID was associated with microcephaly and Dandy-Walker malformation, a duplication of approximately 300 kb at Xq28 (ChrX:153,578,110-153,880,794 - Hg19) was found segregating with the disease. Heterozygotes for this duplication had skewed X-inactivation (80:20 and 90:10 inactivation ratios). Similar duplications have been described in three European families and one sporadic case, Dandy-Walker malformation being documented in some patients. In the study of the 24 sibships with at least two males presenting with ID, the maternal pattern of X-inactivation was determined. Four women (16.7%) showed completely skewing of X-inactivation (100:0 inactivation ratio), a frequency significantly higher than the reported frequency of skewing >= 95% in women from the general population (about 2%). Considering this finding and that extremely skewed X-inactivation have been reported in about 30% of carriers of mutations causing XLID, it was assumed that the four mothers of males presenting with ID were most probably carriers of the mutations causative of ID in their sons. Chromosome X microimbalances were not found in the propositus, in these four sibships.

Human pluripotent stem cells (hPSCs) exist in multiple states of pluripotency, broadly categorised as naïve and primed states. These provide an important model to investigate the earliest stages of human embryonic development. Naïve cells can be obtained through primed-to-naïve reprogramming; however, there are no reliable methods to prospectively isolate unmodified naïve cells during this process. Moreover, the current isolation strategies are incompatible for enrichment of naïve hPSCs early during reprogramming. Consequently, we know very little about the temporal dynamics of transcriptional changes and remodelling of the epigenetic landscape that occurs during the reprogramming process. To address this knowledge gap, I sought to develop an isolation strategy capable of identifying nascent naïve hPSCs early during reprogramming. Comprehensive profiling of cell-surface markers by flow cytometry in naïve and primed hPSCs revealed pluripotent state-specific antibodies. By compiling the identified state-specific markers into a multiplexed antibody panel, I was able to distinguish naïve and primed hPSCs. Moreover, the antibody panel was able to track the dynamics of primed-to-naïve reprogramming, as the state-specific surface markers collectively reflect the change in pluripotent states. Through using the newly identified surface markers, I found that naïve cells are formed at a much earlier time point than previously realised, and could be subsequently isolated from a heterogeneous cell population early during reprogramming. This allowed me to perform the first molecular characterisation of nascent naïve hPSCs, which revealed distinct transcriptional changes associated with early and late stage naïve cell formation. Analysis of the DNA methylation landscape showed that nascent naïve cells are globally hypomethylated, whilst imprint methylation is largely preserved. Moreover, the loss of DNA methylation precedes X-chromosome reactivation, which occurs primarily during the late-stage of primed-to-naïve reprogramming, and is therefore a hallmark of mature naïve cells. Using the antibody panel at discrete time points throughout reprogramming has allowed an unprecedented insight into the early molecular events leading to naïve cell formation, and permits the direct comparison between different naïve reprogramming methods. Taken together, the identified state-specific surface markers provide a robust and straightforward method to unambiguously define human PSC states, and reveal for the first time the order of transcriptional and epigenetic changes associated with primed to naïve reprogramming.

Produzidos pela inserção ou deleção de um ou mais nucleotídeos em um ou ambos os cromossomos homólogos, os marcadores InDel são os polimorfismos mais abundantes depois dos SNPs. Apresentam baixa taxa de mutação quando comparados a outros polimorfismos, ampla distribuição no genoma, simples e rápida genotipagem e frequências alélicas diferentes entre populações distintas. Além disso, uma aplicação relevante dos InDel é a possibilidade de se direcionar a amplificação de sequências alvo específicas, através do desenho de primers que se ligam com regiões de interesse e amplifiquem alelos específicos em um lócus, capacidade esta que melhora a detecção e quantificação do DNA, inclusive do DNA fetal na circulação materna. Apesar de marcadores autossômicos serem os mais utilizados para estudos de mistura em populações, o cromossomo X tem ganhado significativa importância em estudos populacionais e de genética forense, graças ao seu padrão especial de transmissão, a uma deriva genética menor e à sua menor taxa de recombinação. Dessa forma, marcadores genéticos do cromossomo X têm potencial de apresentar parâmetros forenses mais eficientes do que autossômicos em casos de investigação complexa de parentesco, complementar informações fornecidas pelos autossomos e permitir identificar haplótipos com mais facilidade. Neste trabalho, propomos a seleção e descrição formal de um número adequado de lócus do tipo InDel bialélicos ligados ao cromossomo X que possam ser aplicados em estudos de análises populacionais, a fim de complementar os trabalhos de padronização de conjuntos de InDel autossômicos anteriormente desenvolvidos neste laboratório. Foram selecionados sete lócus do cromossomo X que formam dois blocos de haplótipos. Primers flanqueadores e inserção-específicos desenhados para estes lócus tiveram suas condições de PCR convencional padronizadas e foram aplicados na análise fenotípica de uma amostra da população urbana brasileira, composta por 80 trios (Mãe-Filha(o)-Pai), para estimar parâmetros populacionais e de interesse forense. A estimativa das frequências alélicas dos lócus revelou que o alelo inserção é mais frequente para todos os lócus estudados, com exceção do lócus MIDX550. Foram encontrados 60 haplótipos, com o mais frequente correspondendo a 7,5%. Os parâmetros forenses gerados com base nestes lócus estudados mostraram-se eficazes, todos com heterozigose acima de 0,2. Não é possível fornecer afirmações definitivas sobre a paternidade com estes lócus, uma vez que não foi encontrado nenhuma Probabilidade Média de Paternidade W > 99,99%. Entretanto, se combinados com outras informações que aumentem seu poder de discriminação, integrados em painéis e combinados com marcadores autossômicos, os lócus analisados neste trabalho são capazes de fornecer alta informatividade na identificação humana, ancestralidade e quantificação e dosagem de misturas desbalanceadas de DNA. / Originated by the insertion or deletion of one or more nucleotides in one or both homologous chromosomes, InDel markers are the polymorphisms more abundant after SNPs. They have a low mutation rate when compared to other polymorphisms, wide spreading in the genome, simple and rapid genotyping and distinct allelic frequencies between different populations. In addition, a relevant application of the InDel is the possibility to target a specific sequence in PCR, by designing primers that anneal to the regions of interest and amplify specifics alleles in that locus, which improves the DNA detection and quantification in DNA mixtures situations, including fetal DNA in the maternal circulation. Despite being the autosomic markers the most used for DNA mixtures in populations studies, the X chromosome has significant importance in population and forensic genetics studies, thanks to its special transmission pattern, to a lesser genetic drift and to the lower recombination rate. Thus, the genetic markers of the X chromosome have the potential to generate more efficient parameters than the autosomal ones in cases of complex kinship invetigation, adding information in that provided by the autosomes and allow haplotypes with more easily identification. In this work, we propose the selection and formal description of a set of biallelic X-InDel loci that can be applied in population analysis, to complement the standardization work of autosomes InDel sets previously developed in this laboratory. Seven loci of the X chromosome forming two haplotypes blocks were selected. We standardized flanking and insertion-specific primers designed for these loci in conventional PCR conditions. Then, these primers were applied in the phenotypic analysis of a brazilian urban population sample, composed of 80 trios (MotherChild-Father), to estimate the population and forensic interest parameters. The estimation of allele frequencies of loci showed that the insertion allele is more frequent for all the loci studied, with the exception of the MIDX550 locus. Sixty haplotypes were found, most frequently corresponding to 7.5%. The forensic parameters generated for these loci were effective, all with heterozygosis above 0.2. It was not possible to provide statements about paternity with these loci, since no Average Paternity Probability W> 99.99% was found. However, combined with other information that increase its power of discrimination, integrated in panels and combined with the autosomal markers, the analyzed loci in this work are able to provide high informativity for human identification, ancestrality and quantification and dosage of unbalanced DNA mixtures.

Les femmes développent une réponse immunitaire plus forte que celle des hommes. Ceci les protège vis-à-vis des infections virales ou bactériennes, mais augmente également leur risque de développer une pathologie auto-immune. Le lupus érythemateux systémique (LES) est une pathologie auto-immune prototypique à fort dimorphisme sexuel, avec 9 femmes affectées pour 1 homme. TLR7 (Toll-like receptor 7) est un TLR endosomal spécifique de l'ARN simple brin. Ce récepteur joue un rôle crucial dans la réponse antivirale mais aussi dans la rupture de tolérance à la base de la pathologie lupique. Sa surexpression dans un modèle murin suffit à induire le développement spontané d'un lupus. Au contraire, son invalidation dans des souches de souris développant un lupus spontané, est protectrice. Chez l'Homme, TLR7 est exprimé dans les cellules dendritiques plasmacytoïdes (pDC), les monocytes, ainsi que dans les lymphocytes B (LB). Son engagement induit la production de médiateurs pro-inflammatoires par les pDC et les monocytes, et la maturation et la production d'anticorps par les LB. Le gène TLR7 est porté sur le bras court du chromosome X. Un mécanisme compensatoire du dosage des gènes portés sur les gonosomes intervient dans les cellules des mammifères, où un des deux chromosomes X est aléatoirement inactivé pendant le développement embryonnaire. Or ce mécanisme est imparfait et, chez les femmes, au minimum 15% des gènes portés sur l'X sont susceptibles d'échapper à son inactivation. Vu l'effet du dosage de Tlr7 dans les modèles murins du lupus, et de la localisation de TLR7 sur le chromosome X humain, nous avons cherché à déterminer si TLR7 serait sujet à l'échappement à l'inactivation de l'X chez les femmes. Pour cela nous avons développé une approche basée sur l'analyse sur cellule unique de l'expression d'un marqueur allélique au niveau des transcrits de TLR7. Nos résultats démontrent que ce gène échappe à l'inactivation du chromosome X dans 30% environ des LB, monocytes et pDC de femmes saines. De plus, nous avons observé par une technique d'hybridation in situ la transcription simultanée des deux allèles. L'expression bi-allélique de TLR7 est associée à une augmentation significative de l'ARNm de TLR7 dans les LB naïfs. Enfin, nos résultats démontrent que les LB naïfs exprimant les deux allèles de TLR7 sont préférentiellement enrichis dans les cellules différentiées dont la commutation de classe a été induite par un ligand de TLR7. De la même façon, les cellules plasmocytaires où TLR7 échappe à l'inactivation de l'X sont enrichies parmi les cellules prolifératrices en réponse à l'engagement de TLR7. En conclusion, ce travail démontre que le gène TLR7 échappe à l'inactivation de l'X chez plusieurs types de cellules immunitaires, que le dosage des transcrits du gène s'en trouve augmenté chez les lymphocytes B, et que la réponse biologique à l'engagement TLR7 est plus importante chez les lymphocytes B à expression bi-allélique. Par ailleurs, de premiers résultats mettent en évidence l'échappement de TLR7 à l'inactivation de l'X chez des hommes atteints du syndrome de Klinefelter (47, XXY). Ceci pourrait expliquer leur susceptibilité équivalente à celle des femmes au développement du lupus. / Women develop stronger immune responses than men, with positive effects on the resistance to viral or bacterial infections but magnifying also the susceptibility to autoimmune diseases like systemic lupus erythematosus (SLE), which affects 9 women per 1 man. Toll-like receptor 7 (TLR7) is an endosomal single-stranded RNA sensor that plays a key role in the initiation of the antiviral response. TLR7 dosage, however, is also a crucial determinant in SLE, and Tlr7 overexpression suffices to induce spontaneous lupus-like disease. Conversely, Tlr7 knock-out abolishes SLE development in lupus-prone mice. In humans, TLR7 is expressed in plasmacytoid dendritic cells (pDCs), monocytes and B lymphocytes. TLR7 engagement increases B cell maturation and production of antibodies, but also the production of pro-inflammatory cytokines by pDCs and monocytes. Human TLR7 is encoded on the short arm of the X chromosome. The cells of female mammals randomly inactivate one X chromosome in the course of embryonic development to equalize gene dosage between the sexes. However, 15% of X-linked human genes consistently escape inactivation so that both alleles are expressed in individual cells. Because increased dosage of TLR7 expression due to non-inactivation could contribute to autoimmunity, we investigated allelic expression of TLR7 in individual immune cells from women using a TLR7 allelic marker observable on mRNA molecules. Our results show that TLR7 escapes X chromosome inactivation in about 30% of B cells, pDCs and monocytes. TLR7 bi-allelic expression was observed also in situ by RNA-FISH. Naive B cell TLR7 bi-allelic expression is accompanied by higher TLR7 mRNA expression. Our results demonstrate that TLR7 escape from X-inactivation is associated with an enhanced plasma cell proliferative response to TLR7 ligands, and promotes immunoglobulin class switch induced by T cell help and TLR7 engagement. Our study provides proof of principle that TLR7 escapes from X chromosome inactivation in several types of immune cells of women and results in greater transcriptional expression, and shows also that cellular function in bi-allelic B cells is augmented in a TLR7-specific manner. Bi-allelic expression of TLR7 in women is thus a potential risk factor in the pathogenesis of SLE. Our initial results show also that TLR7 escapes from X inactivation in the immune cells of men with Klinefelter syndrome (47, XXY), which may explain a risk of SLE equivalent to women's.

Peu d’hommes sont touchés par les maladies auto-immunes (MAI), maladies où la réponse immune est très forte et attaque l’hôte. La polyarthrite rhumatoïde (PR), une maladie inflammatoire chronique, suit cette règle avec 3 femmes pour 1 homme atteint. Dans cette thèse, nous analysons les différences en fonction du sexe et les raisons d’un tel biais. D’après des observations chez l’animal, nous nous sommes demandés si les rares hommes atteints de PR ont une augmentation du nombre de copies d’un gène impliqué dans la réponse immune et porté par le chromosome (Chr) X. Contrairement aux femmes, les hommes n’ont qu’un Chr X et de ce fait qu’une copie de ce gène. Cependant, nous avons montré par différentes techniques, que ces patients avaient 10% de cellules portant 2 copies de ce gène, et que cette augmentation venait de cellules ayant 2 Chr X. Nos recherches soulignent l’importance du Chr X dans l’auto-immunité et ouvrent un nouveau champ d'investigation pour les hommes atteints de MAI. / Few men are affected by autoimmune diseases (AID), diseases where the immune response is very strong and attacks the host. Rheumatoid arthritis (RA), a chronic inflammatory disease, follows this rule with 3 women affected for 1 man. In this thesis, we analyse gender differences and the reasons for such bias. Based on observations in animals, we wondered whether the rare men with RA have an increased copy number of a gene involved in the immune response and carried by the X chromosome (Chr). Unlike women, men have only one X Chr and one copy of this gene. However, we showed by different techniques that these patients had 10% of cells carrying 2 copies of this gene, and that this increase came from cells with 2 X Chr. Our research emphasizes the importance of the X Chr in autoimmunity and opens up a new field of investigation for men with AID.