O câncer de mama é um importante problema de saúde pública, sendo o mais frequente em mulheres no mundo. A alimentação influencia diretamente o desenvolvimento do câncer de mama. Assim, por exemplo, dietas ricas em ácidos graxos poliinsaturados ômega 3 (AGPI &#969;-3), flavonóides, vitaminas A e E, bem como em minerais, incluindo selênio e zinco, têm sido associadas a redução de risco desta neoplasia. Neste contexto, zinco tem-se destacado por regular mecanismos celulares e moleculares como reparo de DNA, controle de ciclo celular e controle de fatores transcricionais. Uma hipótese pouco descrita na literatura, ainda que biologicamente plausível, aponta a origem do câncer de mama já na vida intrauterina, período em que a glândula mamária estaria mais suscetível à influência da alimentação e níveis hormonais maternos. A dieta materna no período gestacional parece ter importante influência na modulação do ambiente intrauterino e, consequentemente, na programação do risco de desenvolvimento do câncer de mama na progênie. Assim, fatores dietéticos e níveis hormonais poderiam induzir modificações na morfologia da glândula mamária durante as fases iniciais do desenvolvimento, alterando, assim, o risco para o desenvolvimento do câncer de mama. Do ponto de vista molecular, a modulação inadequada do epigenoma no início da vida pode ter implicações para os descendentes ao longo da vida, modificando a suscetibilidade ao risco de doenças crônicas não transmissíveis, incluindo o câncer de mama. Sugere-se que a exposição, durante o período fetal, ao zinco parece também modular a suscetibilidade ao desenvolvimento de doenças crônicas não transmissíveis. Dessa forma, propôs-se avaliar se o zinco representa fator dietético que modula o risco de câncer de mama já no início da vida. Camundongos fêmeas C57BL/6 foram expostas, durante a gestação, a dieta controle (AIN-93G; grupo CO); dieta deficiente em zinco (8 ppm; grupo ZND) e dieta suplementada com zinco (45 ppm; grupo ZnS). Neoplasias mamárias foram induzidas na prole feminina com 6 semanas de idade com a administração subcutânea de 15 mg de medroxiprogesterona, seguida pela administração oral de 1 mg 7,12-dimetilbenz [a] antraceno uma vez por semana durante 4 semanas. As glândulas mamarias da prole feminina com 7 semanas de idade não iniciadas, de todos os grupos, foram usadas para análise morfológica, proliferação celular, apoptose e análise molecular. Em relação a prole feminina do grupo CO, a do ZnS apresentou aumento (p<0,05) da incidência final de neoplasias mamária, proliferação celular (Ki67) e apoptose. A expressão da proteína p21 foi maior (p=0,06) no grupo ZnS em relação ao grupo CO. Em relação a prole do grupo ZnD, ZnS apresentou maior (p<0,05) nível de expressão da proteína p53. Sem diferença (p>0,05) em relação a estas variáveis entre o grupo CO e ZnD. Em relação a prole femina do grupo CO, ZnS apresentou aumento (p=0,08) marginal da expressão dos genes RASSF1 e STAT3. Em relação a prole feminina do grupo ZnD, ZnS apresentou maior (p=0,02) expressão de ZPF382. H3K9me3 e H4K20me3 foram regulados positivamente (p<0,05) na glândula mamária da prole feminina do grupo ZnD em relação aos grupos CO e ZnS. A suplementação com zinco, mas não a deficiência, no início de vida foi associado com aumento da susceptibilidade de câncer de mama na vida adulta. / Breast cancer is an important public health problem, representing the main cause of women death worldwide. Dietetic factors, such as omega-3 fatty-acids, flavonoids, vitamins A and E, and micronutrients have been associated with the reduction of breast cancer risk. Zinc is a micronutrient of remarkable importance for health, essential for several cellular mechanisms, which may influence the development of breast cancer through epigenetic mechanisms, among others. A hypothesis not frequently addressed in the literature, although biologically plausible, considers the fetal origin of breast cancer, a developmental stage in which the mammary gland would be more sensitive to the influence of maternal diet and hormone levels. The maternal diet during pregnancy seems to have significant influence in the modulation of the intrauterine environment and, consequently, in programming the risk of development of breast cancer in offspring through the induction of morphological and molecular changes. The inadequate modulation of the epigenome in early life may have implications for the offspring throughout life, modulating the susceptibility to the risk of chronic diseases, including breast cancer. The exposure during the fetal period, to zinc, seems also to modulate the susceptibility to the development of chronic diseases, such as cardiovascular diseases and renal dysfunctions. Thereby, it would be interesting to evaluate the effects of zinc deficiency or supplementation in maternal diet during pregnancy period in the susceptibility of breast cancer in offspring. In this context, we propose to evaluate if zinc is a dietary factor that may modify the risk of breast cancer during early life, by modulation of morphological, molecular and epigenetic events. C57BL/6 female mice consumed during pregnancy control diet (AIN-93G; CO group); zinc-deficient diet (8 ppm; ZnD group) and zinc-supplemented diet (45 ppm; ZnS group). Mammary tumors were induced by subcutaneous administration of 15mg of medroxyprogesterone to 6-week-old female offspring, followed by oral administration of 1mg 7, 12-dimethylbenz[a]anthracene once-a-week for 4 weeks. Non-initiated mammary glands of 7-week-old female offspring from all groups were used to morphological, cell proliferation, apoptosis and molecular analysis. Compared to CO group offspring, ZnS presented increased (p<0.05) mammary tumor incidence, cell proliferation (Ki67) and apoptosis. Expression levels of p21 protein was higher (p=0.06) in ZnS compared to the CO group. Compared to ZnD group offspring, ZnS showed higher (p<0.05) expression level of p53 protein. There were no differences (p&#8805;0.05) concerning these variables between CO and ZnD group. Compared to CO offspring group, ZnS also showed marginal increased (p=0.08) expression of RASSF1 and STAT3 genes. Compared to ZnD offspring group, ZnS showed higher (p=0.02) expression of ZPF382. H3K9me3 and H4K20me3 were upregulated (p<0.05) in the mammary gland of ZnD female offspring compared to CO and ZnS groups. Thereby, zinc-supplementation, but not zinc-deficiency, in early-life was associated with an increased susceptibility to breast cancer development in adulthood.

O câncer de mama representa problema mundial de saúde pública e a causa mais frequente de morte por câncer entre as mulheres. A identificação de agentes moduladores de marcas epigenéticas, tais como metilação global do DNA e modificações pós-tradução em histonas, compreende alternativa promissora para estabelecimento de estratégias de controle da carcinogênese mamária. Dentre os nutrientes, o elemento traço essencial selênio (Se) pode ser destacado como agente dietético com potencial anti-câncer de mama e que poderia atuar modulando processos epigenéticos. Entretanto seus mecanismos de ação são pouco elucidados. Este estudo objetivou, assim, identificar efeitos do tratamento com selênio no crescimento e marcas epigenéticas de células de adenocarcinoma mamário humano MCF-7. Células MCF-7, positivas para o receptor de estrógeno, foram tratadas com ácido metilselenínico (MSA) ou selenito de sódio (ST) por diferentes tempos e em diferentes concentrações. Foram avaliados: padrão de proliferação (ensaio cristal violeta) e viabilidade celular (método de exclusão azul de tripan); integridade de membrana plasmática (citometria de fluxo); níveis de fragmentação do DNA (citometria de fluxo), distribuição das fases do ciclo celular (citometria de fluxo); apoptose (citometria de fluxo/ marcação dupla com Anexina V - Iodeto de propídio); níveis de lisina 9 acetilada (H3K9ac) e trimetilada (H3K9me3) em histona H3; níveis de lisina 16 acetilada (H4K16ac) em histona H4 (Western blot); padrão de metilação global do DNA (HPLC-DAD); expressão de gene supressor de tumor (RASSF1a; qPCR) e padrão de metilação da região promotora (RASSF1a e RAR&#946;; MS-PCR); expressão da enzima DNA metilstransferase 1 (DNMT1) (Western Blotting). Comparado ao grupo controle de células não tratadas (GC), ambos os tratamentos com MSA ou ST inibiram a proliferação e viabilidade de células MCF-7 de forma dose e tempo dependente. Ambas as formas químicas de Se induziram a parada do ciclo celular, aumentando (p< 0,05) a proporção de células na fase G2/M e reduzindo (p< 0,05) a proporção daquelas nas fases G0/G1 e S. Os tratamentos com MSA favoreceram a morte celular por apoptose, que foi associada com nível de fragmentação de DNA aumentado (p< 0,05), e reduzida ruptura da membrana plasmática associada com a exposição aumentada (p< 0,05) de fostadilserina. Por outro lado, o ST aumentou (p< 0,05) a fragmentação do DNA e (p< 0,05) a positividade ao iodeto de propídio associado à indução de necrose (p< 0,05). Dentre os mecanismos epigenéticos investigados, 1,6&#181;M e 2&#181;M reduziram a acetilação de H3K9ac (72h; p< 0,05) e aumentaram a de H4K16ac (96h; p< 0,05). O tratamento por 96h com 2&#181;M de MSA reduziu (p< 0,05) a metilação de H3K9me3. Ambos MSA e ST não alteraram o padrão de metilação global do DNA, mas reduziram a expressão de DNMT1, após 96h com 2&#181;M de MSA (p< 0,001; 88%) e após 120h com 10&#181;M de ST (p< 0,001; 96%). ST, mas não o MSA, aumentou (p< 0,05; 45%) a expressão do gene RASSF1a. Em ambos os grupos tratados com MSA ou ST, bem como no GC, a região promotora dos genes RASSF1a e RAR estavam predominantemente metiladas. Estes resultados fornecem evidências de que as ações anti-câncer de mama de compostos do selênio dependem de sua forma química. Além disso, a modulação de processos epigenéticos parecem ser relevantes para as ações inibitórias do MSA em células de câncer de mama. / Breast cancer is a global public health problem and the most frequent cause of cancer death among women. The identification of agents able to modulate epigenetic marks, such as global DNA methylation and histone post-translational modifications, comprises promising alternative for establishing control strategies on mammary carcinogenesis. Among the nutrients, the essential trace element selenium (Se) can be highlighted as a dietary agent with potential anti-breast cancer and could act by modulating epigenetic processes. However its mechanisms of action are poorly understood. This study aimed, therefore, to identify the effects of selenium treatment on growth and epigenetic marks of MCF-7 human breast adenocarcinoma cells. MCF-7 cells, positive for estrogen receptor, were treated with methylseleninic acid (MSA) or sodium selenite (ST) for different times and in different concentrations. Evaluated parameters included: cell proliferation (crystal violet assay) and cell viability (trypan blue exclusion assay); plasma membrane integrity (flow cytometry); levels of DNA fragmentation (flow cytometry), apoptosis (flow cytometry - double labeling with Annexin V - propidium iodide); distribution of cell cycle phases (flow cytometry); acetylated (H3K9ac) and trimethylated (H3K9me3) lysine 9 levels on histone H3; acetylated (H4K16ac) lysine 16 level on histone H4 (Western blot); global DNA methylation (HPLC-DAD); tumor suppressor gene expression (RASSF1a; qPCR) and promoter methylation (RASSF1a, RAR&#946;; MS-PCR); DNA methyltransferase 1 (DNMT1) expression (Western blot). Compared to untreated cells (controls), both MSA and ST inhibited (p< 0.05) MCF-7 cell proliferation and viability in a dose- and time-dependent manner. Treatments with MSA favored cell death by apoptosis, that was associated with increased (p< 0.05) DNA fragmentation level, reduced plasma membrane rupture associated with high (p< 0.05) phosphatidylserine exposure. On the other hand, ST increased (p< 0.05) DNA fragmentation, enhanced (p< 0.05) propidium iodide positivity associated to necrosis induction (p< 0,05). Both chemical forms of Se induced nduced cell cycle arrest, increasing (p< 0.05) the proportion of cells in G2/M phase and reducing (p< 0.05) the proportion of those in G0/G1 and S phases. Among the epigenetic mechanisms investigated, 1.6&#181;M and 2&#181;M of MSA reduced acetylation of H3K9ac (72h, p< 0.05) and increased the H4K16ac (96h, p< 0.05). The treatment for 96h with 2&#181;M of MSA reduced (p< 0.05) the H3K9me3 methylation. Neither MSA nor ST altered (p> 0.05) global DNA methylation, while both compounds reduced (p< 0.05) DNMT1 protein expression, after 96h with 2&#181;M of MSA (p< 0.001; 88%) and after 120h with 10&#181;m of ST (p< 0.001; 94%). ST, but not MSA, increased (p< 0.05; 45%) RASSF1a gene expression. In control and Se-treated cells promoter regions of RASSF1a and RAR&#946; were predominantly methylated. These results provide evidence that the anti-breast cancer actions of selenium compounds depend on its chemical form. Additionally, modulation of epigenetic processes seems to represent a relevant feature of MSA inhibitory effects in breast cancer cells.

Em fêmeas de mamíferos, um dos cromossomos X é inativado proporcionando compensação de dose entre os produtos gênicos de machos e fêmeas. A inativação do cromossomo X (ICX) ocorre no embrião em desenvolvimento, e se caracteriza pela aquisição de marcas heterocromáticas no cromossomo X inativado (Xi), que são mantidas nas células somáticas ao longo das divisões celulares. O melhor modelo para estudo do início da ICX são as células-tronco embrionárias femininas. Provenientes da massa celular interna de blastocistos, elas representam um embrião em desenvolvimento e possuem os dois X ativos; a diferenciação das células promove a ICX in vitro, o que permite a identificação dos fatores e mecanismos moleculares envolvidos. A derivação de linhagens de célulastronco embrionárias humanas (human embryonic stem cells - hESCs) em 1998 permitiu novas possibilidades de estudo da ICX, pois a maioria dos trabalhos procurou esclarecer o mecanismo da ICX no modelo murino. Tradicionalmente, a manutenção da ICX em humanos tem sido investigada em células somáticas híbridas ou transformadas; porém, sabe-se que estas não representam um contexto celular natural. Assim, o presente trabalho teve como objetivos principais explorar a potencialidade de hESCs no estudo do início da ICX, e ainda investigar a função de três fatores na manutenção da ICX em células humanas imortalizadas: DNMT1 (enzima responsável pela manutenção da metilação do DNA), SMCHD1 (proteína da família de coesinas/condensinas), e XIST (um RNA não-codificador que inicia o processo de heterocromatinização do futuro Xi) foram selecionados para este estudo, uma vez que todos participam da manutenção da ICX em camundongos. Até o momento foram derivadas em nosso laboratório quatro linhagens de hESCs, as primeiras da América Latina. A caracterização das linhagens mostrou que, apesar de se manterem indiferenciadas, as hESCs femininas encontram-se em estágio pós-ICX, pois mesmo indiferenciadas já apresentam um dos X inativado. Nossos dados indicam que, submetidas às atuais condições de cultivo, as hESCs não são bons modelos para o estudo do início da ICX, e é possível que a inativação de um cromossomo X durante o cultivo confira alguma vantagem seletiva às células. A estratégia utilizada no estudo da manutenção da ICX foi o silenciamento dos três genes por interferência de RNA (RNAi). Não foi possível diminuir significativamente a expressão dos genes XIST e SMCHD1. Porém, o silenciamento de DNMT1 foi expressivo, e em resposta foi observada reativação do gene MAOA, localizado no cromossomo X e submetido à inativação. Apesar de nossas análises mostrarem que os efeitos da diminuição de DNMT1 foram restritos ao gene MAOA, estes resultados sugerem a existência de diferentes hierarquias de controle epigenético dos genes submetidos à ICX em células humanas / In female mammals, one of the X chromosomes is inactivated to achieve dosage compensation between males and females. The X chromosome inactivation (XCI) occurs early during embryogenesis and is characterized by the acquisition of heterochromatic features on the inactive X (Xi), which are maintained during all the subsequent cell divisions. Embryonic stem cells are the most suitable cells to study the establishment of XCI. They are obtained from the inner cell mass (ICM) of blastocysts, and can represent a developing female embryo, possessing two active X-chromosomes; when differentiated, these cells recapitulate XCI in vitro, and thus one can identify XCI regulators and factors involved. The derivation of human embryonic stem cells (hESCs) in 1998 offered new possibilities to study XCI, since most of the mechanistic studies of XCI have so far been investigated in the mouse model system. Traditionally, maintenance of XCI in humans has been addressed in somatic cell hybrids or transformed cells; however, they do not represent a natural cellular context. The main goals of the present work were to verify the potential of hESCs as models of XCI, and also to study the function of three important factors in XCI maintenance in immortalized human cells. DNMT1 (DNA-methyltransferase 1), SMCHD1 (a cohesin/condensin protein family member) and the XIST gene (a non-coding RNA which triggers XCI and promotes X heterochromatin formation on the future Xi) were selected, as they are key factors in XCI maintenance in the mouse. Until now four hESCs lines were derived in our lab. Their characterization showed that, in spite of been undifferentiated, the female hESCs have already undergone XCI. Our data suggest that, under the actual culture conditions, hESCs are not good models to study XCI, and it is also possible that X inactivation confers selective advantage to hESCs. Knockdown by RNA interference was used to study the roles of three genes in XCI maintenance. We could not efficiently knockdown XIST or SMCHD1. However, the DNMT1 silencing was substantial, and led to the reactivation of MAOA, an X-linked gene subjected to XCI. Although the effect of DNMT1 silencing was restricted to MAOA, our data suggest that there are different epigenetic hierarchies to control the expression of the genes subjected to XCI in human cells.

Os programas de melhoramento de figueira (Ficus carica L.) por métodos convencionais tais como cruzamentos dirigidos, para a obtenção de novos cultivares, são inviáveis em muitos países, como no Brasil, principalmente pela pequena variabilidade genética encontrada, e pela dificuldade de obtenção de plantas originadas pela fusão de gametas, uma vez que a vespa Blastophaga psenes, responsável pela polinização natural, não existe no país. Desse modo, o melhoramento genético, com o uso de mutagênicos, se torna uma linha de pesquisa importante para a melhoria da cultura, sendo necessário reunir informações sobre essa espécie, principalmente, em relação à sua variabilidade genética, para que projetos de propagação e manejo adequados sejam realizados. Diante do exposto, o objetivo do presente trabalho foi verificar a existência de variabilidade epigenética devido à metilação do DNA em seleções irradiadas de figueiras, entre si e quando comparadas ao principal cultivar comercial, Roxo-de-Valinhos, utilizando as técnicas de MSAP e ELISA, e posterior sequenciamento do DNA, tratado com bissulfito de sódio, para detecção do posicionamento das regiões polimórficas, analisado por ferramentas de bioinformática. Amostras do DNA genômico foram duplamente digeridas com a enzima HpaII (sensível à metilação) ou com o seu isoesquizomero MspI (não sensível à metilação), juntamente com a enzima EcoRI. Foram testadas 14 combinações de primers e obteve-se 87.9%, 10.1% e 2.0%, respectivamente, de regiões não metiladas CCGG, regiões metiladas CmCGG e regiões hemimetiladas hmCCGG, de um total de 553 produtos de amplificação, demostrando que a técnica MSAP é eficiente para detecção de sítios diferencialmente metilados no material genômico estudado, evidenciando sua divergência epigenética. Com o sequenciamento do DNA isolado desses sítios diferencialmente metilados, foi possível verificar diferentes padrões de metilação nos mesmos pelo sequenciamento dos DNAs tratados com bissulfito de sódio, em regiões codificadoras de genes regulatórios do desenvolvimento e amadurecimento dos frutos, além de terem sido encontrados no DNA mitocondrial dos tratamentos, o qual regula o fornecimento de energia em forma de ATP para as plantas, estando intimamente relacionado com o desenvolvimento das mesmas, justificando os diferentes fenótipos encontrados, tanto nos frutos, quanto no crescimento das plantas que sofreram estresse devido à exposição à radiação gama. Pela técnica de imunoquímica (ELISA), utilizando anticorpos anti 5-mC, foram observadas diferenças significativas pelo teste de Tukey, a 95 % de confiabilidade, no conteúdo global de metilação dos DNAs dos tratamentos, indicando que este fator abiótico foi responsável pelas alterações no epigenoma das plantas. Como o material utilizado como controle se encontrou também metilado, uma possível desmetilação dos materiais genômicos pode ser a responsável pela variação fenotípica entre os tratamentos. Diante disso, o estudo futuro da expressão gênica entre os tratamentos torna-se uma estratégia de extrema importância para o entendimento dos complexos sistemas regulatórios, levando à identificação de genes de interesse agronômico para a cultura da figueira, possibilitando a sua manipulação subsequente e propagação de cultivares melhorados para fins comerciais. / The fig tree (Ficus carica L.) breeding programs by conventional methods such as directed crosses, in order to obtain new cultivars, are unworkable in many countries, as in Brazil, mainly by small genetic variability found, and by the difficulty for obtaining plants originated from the fusion of gametes, since the wasp Blastophaga psenes, responsible for natural pollination, doesn`t exist in the country. In this way, the genetic breeding, with the use of mutagenic, becomes an important research line for the improvement of culture, being necessary to gather information about this species, mainly in relation to its genetic variability, for perform propagation projects and appropriate management. Given the above, The objective of this study was to verify the existence of epigenetic variability due to DNA methylation in irradiated fig selections, with each other and when compared to the main commercial cultivar, Roxo-de-Valinhos, using MSAP and ELISA techniques, and subsequent DNA sequencing, treated with sodium bisulfite, for detection of the position of the polymorphic regions, analyzed by bioinformatics tools. Samples of genomic DNA were double-digested with the HpaII enzyme (sensitive to methylation) with its isoschizomer MspI (insensitive to methylation), together with the EcoRI enzyme. Fourteen primer combinations were tested and it was obtained 87.9%, 10.1% e 2.0%, respectively, unmethylated CCGG, methylated CmCGG and hemimethylated regions hmCCGG, from a total of 553 amplification products, displaying, the MSAP technique, efficient for detection of differentially methylated sites in the genomic material studied, demonstrating their epigenetic divergence. With the sequencing of DNA isolated of these differentially methylated sites, it was possible to verify different patterns of methylation in them by sequencing the DNA treated with sodium bisulfite, in coding regions of regulatory genes of the development and fruits ripening, besides they have been found in the mitochondrial DNA of treatments, which regulates the supply of energy in ATP form for the plants, being closely related to their development, justifying the different phenotypes found in both fruits and plant growth that suffered stress due to exposure to gamma radiation. By the technique of immunochemistry (ELISA), using 5-mC antibodies, significant differences were observed by Tukey test, at 95% of trustworthiness, in the global content methylation of the treatments DNA, indicating that this abiotic factor was responsible for the changes in the epigenome of the plants. Since the material used as control was found also methylated, a supposed demethylation of the genomic material may be responsible for phenotypic variation among treatments. Considering this, future study of gene expression between treatments becomes an extreme important strategy for understanding the complex regulatory systems, leading to the identification of genes with agronomic interest for the fig culture, allowing its subsequent manipulation and propagation of improved cultivars for commercial purposes.

Cytotoxicity is the capacity for immune cells to kill infected or malignant cells in order to eliminate pathogens and tumours through different mechanisms including the exocytosis of perforin-containing cytosolic granules. This crucial property is usually restricted to specialized innate and adaptive lymphocytes such as natural killer (NK) cells and CD8 T cells. T lymphocytes differentiate in the thymus and are delivered to the peripheral blood as naive T cells committed to either the CD8 or the CD4 lineage. CD8 T cells are programmed to acquire cytotoxic effector functions under the control of the transcription factor (TF) Runx3. The fate of CD4 T cells is to acquire multiple helper functions through the action of the TF ThPOK that promotes CD4 helper functions and restricts the CD8 cytotoxic program. However, this restriction is not absolute as cytotoxic CD4 (CD4CTX) T cells differentiate in vivo, indicating that the multipotency of human naive CD4 T cells includes the ability to acquire perforin expression and potent cytotoxicity in vitro and ex vivo. This cytotoxic potential correlates with outcome in human pathology and mediates protection against viral challenge and tumour eradication in murine models. CD4CTX T cells are terminally differentiated effector memory T cells that accumulate during cytomegalovirus chronic infection and ageing. They are phenotypically and functionally related to T helper type 1 (Th1)-effector memory cells. However, whether they belong to the Th1 pathway or constitute a separate specialized helper T cell subset is unknown. In this work, we show that CD4CTX T cell differentiation is an integral part of the Th1 pathway. Indeed, CD4 T cells acquire cytotoxic potential early in the memory differentiation process as central memory Th1 but not Th2 and Th17 cells are epigenetically primed to develop a cytotoxic program. The expression of perforin and other cytotoxic genes present a stepwise increase profile that is specific of the Th1 differentiation pathway. This profile has been recapitulated in an in vitro model of effector CD4 T cell differentiation in which naive CD4 T cells acquire cytotoxicity one to two weeks after polyclonal stimulation when cultured in presence of Th1 cytokines. The molecular regulation of CD4CTX T cells is poorly understood and most available data have been generated in mice. These data include the observation of intraepithelial CD4CTX T cells in the mouse gut after loss of ThPOK expression and subsequent up-regulation of a Runx3-dependent cytotoxic program. Other candidate regulators of CD4 T cell cytotoxic function include the TF regulating Th1 and CD8CTX T cells differentiation such as Runx3, T-bet and Eomesodermin (Eomes). We show that the transcriptional program of human CD4CTX T cells is enriched in CD8-lineage genes. However, by contrast to CD4CTX T cells from the mouse intestine, human circulating CD4CTX T cells maintain the expression of ThPOK and even up-regulate this TF upon differentiation from naive CD4 T cells. Surprisingly, this sustained expression of ThPOK was compatible with the establishment of a T-bet- and Runx3-dependent cytotoxic transcriptional program. The specific knockdown of T-bet or Runx3 but not Eomes resulted in impaired cytotoxic differentiation whereas ThPOK knockdown enhanced perforin expression and cytotoxicity. We propose that CD4CTX T cells constitute the terminal stage of Th1 memory differentiation and that ThPOK, Runx3 and T-bet co-regulate this process by instructing a cytotoxic transcriptional network largely shared with CD8CTX T cells. The modulation of this network is a potential target for novel immunotherapeutic strategies in viral infections and cancer. / Doctorat en Sciences médicales (Médecine) / info:eu-repo/semantics/nonPublished

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Les protéines du groupe Polycomb sont des régulateurs épigénétiques impliqués dans divers processus développementaux et cellulaires. Le complexe Polycomb Répressif 1 (PRC1) est bien caractérisé chez les animaux, cependant sa composition et sa fonction restent énigmatiques dans les plantes. Sur base d'homologie de séquences trois homologues de la sous-unité de base BMI1 du complexe PRC1 animal ont été identifiés dans Arabidopsis: AtBMI1a, AtBMI1b et AtBMI1c. L'interaction de ces trois protéines avec les composantes PRC1 connues (i.e. AtRING1ab, et LHP1) a été démontrée. Des analyses génétiques et moléculaires ont permis d'attribuer aux protéines AtBMI1ab et AtRING1ab un rôle essentiel dans la répression des caractères embryonnaire lors de la croissance végétative. Un nouvel interactant d'AtRING1a, une protéine à domaine PHD de la famille AL (Alfine-Like) a été identifiée dans criblage d'une banque de ADNc. Par différentes techniques l'association entre les protéines de la famille AL et les membres de bases du complexe PRC1 (i.e. AtBMI1ab, AtRING1ab et LHP1) a été démontrée. Les protéines AL sont nucléaires et se lient in vitro à H3k4me3, une marque active de la chromatine. Des analyses génétiques ont révélé que les protéines AL et AtBMI1ab régulent la germination en réprimant l'expression de gènes impliqués dans le développement de la graine. Au niveau chromatinien, les protéines PRC1 interviennent dans la transition d'une chromatine active, marquée par du H3K4me3 vers une chromatine répressive enrichie en H3K27me3. Nous proposons que les protéines AL reconnaissent la marque active et recrutent la fonction répressive des protéines à domaine RING du complexe PRC1 afin d'induire la répression transcriptionelle. / Polycomb group (PcG) proteins are critical epigenetic repressors implicated in various developmental and cellular processes. While the Polycomb Repressive Complex 2 (PRC2) is evolutionary conserved and its functions extensively studied in Arabidopsis, the PRC1 complex composition and function remain still enigmatic in plants. Our work focuses on several Arabidopsis RING-domain proteins to unravel PRC1-like functions in the regulation of various processes during plant development. Based on sequence similarity we identified three homologues of the animal PRC1 core subunit BMI1: AtBMI1a, AtBMI1b and AtBMI1c. These proteins were found to interact with other PRC1-like components, AtRING1a, AtRING1b and LHP1. Genetic and molecular analyses demonstrated that AtBMI1a/b and AtRING1a/b play crucial roles in stable repression of embryonic traits to allow proper somatic growth. Comparative transcriptome analyses were performed to uncover genetic networks underlying seedling growth and the flower development defects of several different PRC1-like and PRC2 Arabidopsis mutants. Our data revealed overlapping and non-overlapping gene categories of misregulated genes in Atring1a/b, Atbmi1a/b and lhp1 mutants. The Atring1a/b mutant showed particular disturbed expression of flower developmental genes. Accordingly, phenotypic and molecular analyses of the mutant flowers confirmed that AtRING1a/b play a critical role in cell fate determination and in different aspects of flower development. To better understand the broad function of AtRING1a/b, we performed yeast two-hybrid screen and identified PHD-domain proteins of the ALFIN-LIKE (AL) family as binding partners. In vitro AL proteins bind the active mark for gene transcription, H3K4me3. By various methods, both in vitro and in planta, we provided strong evidence for the physical interaction between AL and PRC1 RING-domain proteins. We uncovered that al6/7 similar to Atbmi1a/b mutants exhibit seed germination defects, which are associated with the derepression of several seed related genes. Consistently on the corresponding chromatin a delay of the remodeling from active H3K4me3 labeled to a repressive H3K27me3 marked chromatin could be detected. We propose that through binding to H3K4me3 AL6/7 function as scaffold proteins to target PRC1 RING-domain proteins to active chromatin in order to establish gene silencing. Taken together, the presented work contributes significantly to the knowledge of PRC1 complex(es) in Arabidopsis at both biological function and complex composition levels. It opens several exciting perspectives for future research in the field.

La 5-hydroxymethylcytosine (5hmC) est une base modifiée de l'ADN. Chez le mammifère, cette base était considérée jusqu'à récemment comme une espèce mineure produite par des dommages oxydatifs. Cependant, des travaux publiés en 2009 ont profondément changé cette vision. En effet, d'une part, la 5hmC est abondante dans certains types cellulaires, d'autre part la formation de 5hmC est un processus actif, dirigé par des enzymes spécialisées (TET1-3) à partir d'une autre base modifiée de l'ADN, la 5-méthylcytosine. Ces découvertes récentes posent naturellement la question du rôle biologique de la 5hmC. En effet, le rôle biologique de la 5hmC est en cours d'exploration et nécessite donc le développement de méthodes dédiées à son étude. Nous avons pris part au développement de méthodes pour l'étude de l'hydroxyméthylation de l'ADN et des protéines partenaires de cette base en proposant des outils chimiques, biochimiques et analytiques. Nous avons adapté une méthode utilisant la chromatographie liquide couplée à la spectrométrie de masse à l'étude de l'hydroxyméthylation. Nous avons également participé au développement de méthodes de marquage spécifique des 5hmC selon deux stratégies : (i) une stratégie enzymatique basée sur l'utilisation d'une glucosyltransférase et d'un donneur de glucose (uridine diphosphate glucose) modifié chimiquement; (ii) une stratégie chimique basée sur l'oxydation sélective de l'alcool allylique de la 5hmC. Enfin, nous avons conçu, synthétisé et étudié les propriétés de différentes sondes oligonucléotidiques photoactivables destinées à l'identification de protéines interagissant spécifiquement avec la 5hmC. / 5-hydroxymethylcytosine (5hmC) is a modified DNA base, who was until recently believed be a minor modification, resulting of oxidative damage. However, results published in 2009 have challenged this understanding. Indeed, 5hmC is abundant in some cell types and its formation is an active process, mediated by specific enzymes (TET1-3) using another modified DNA base, 5-methylcytosine (5mC). These recent discoveries raise the question of the biological role of 5hmC. Indeed, if the role of 5mC in gene expression regulation is established, the biological role of 5hmC is still in study and require the development of specific methods. We participated in the development of methods to study 5hmC and its partner proteins using chemical, biochemical and analytical tools. We showed that mass spectrometry is a powerful tool to quantify global methylation levels and adapted a method, using liquid chromatography coupled to tandem mass spectrometry to study hydroxymethylation. We have also taken part in the development of two 5hmC specific labeling methods: (i) an enzymatic strategy, using a glucosyltransferase and a chemically modified glucose donor, allowing the introduction of a probe by a bio-orthogonal reaction; (ii) a chemical strategy based on the selective oxidation of the 5hmC allylic alcohol. Finally, we have designed, synthesized and assessed the properties of photoactivable oligonucleotidic probes in order to identify proteins interacting with 5hmC.

Issues d'un gène ancestral commun, les molécules CD5 et CD6 sont présentes à la surface de tous les lymphocytes T (LT) matures ainsi qu'à la surface de certains lymphocytes B (LB). Ces deux protéines font partie de la famille des « Scavenger Receptor Cystein Rich » (SRCR) protéines mais la régulation, l'expression et les fonctions de ces deux molécules ne sont pas totalement résolues. Ainsi, CD5 est impliquée dans la régulation du récepteur à l’antigène des LB et des LT, dans la tolérance des LB et elle est présente à la surface des LB régulateurs. A l’opposé, CD6 possède un rôle dans la prolifération des lymphocytes, la survie, la migration et l’adhésion cellulaire. Les expressions de CD5 et CD6 diffèrent au sein des LB normaux ainsi qu'en pathologie. Dans le cadre du lupus érythémateux systémique (LES), le nombre de molécules CD5 à la surface des LB CD5+ est réduit. Dans une autre maladie auto-immune (MAI), le Syndrome de Gougerot Sjögren (SGS), l'expression de CD6 à la membrane des LB n'est pas affectée mais la distribution des LB mémoires CD6+, mais pas des LB naïfs, est modifiée par rapport aux témoins sains. En effet, les LB CD6+ sont sous représentés dans le sang périphérique et ce, en raison de leur délocalisation dans les glandes salivaires (GS) des patients. Cette délocalisation est liée à la surexpression d’ALCAM, le ligand naturel de CD6, par les cellules épithéliales au cours du SGS. L'étude de la diminution de l'expression de CD5 à la surface des LB de patients atteints de LES a permis de montrer qu'il existait un défaut dans le processus de la méthylation de l'ADN chez ces patients. Ce même défaut a été retrouvé dans les GS de patients atteints de SGS. Enfin, les LB de patients atteints de leucémie lymphoïde chronique (LLC) sont porteurs des deux molécules à leur membrane. Nous avons testé l'effet in vitro et in vivo d'un l'anticorps monoclonal (Acm) humanisé anti-CD6, T1H, dans la LLC. De façon intéressante, il s’avère que cet Acm favorise la lyse des LB de LLC et ceci, de façon équivalente au rituximab dans un modèle murin in vivo. T1H est internalisé par les LT et est donc inefficace sur ces cellules. Ces résultats nous permettent de conclure que même si les molécules CD5 et CD6 sont proches phylogénétiquement, elles possèdent des fonctions et des modes de régulation différents entre les LB et les LT mais aussi au sein des différentes populations de LB. Une meilleure compréhension des fonctions et des modes d'actions de ces deux protéines ouvre des perspectives thérapeutiques dans le traitement des MAI et de la LLC. / Derived from a common ancestral gene, CD5 and CD6 molecules are present on the surface of all mature T lymphocytes (LT) and some B lymphocytes (LB). These two proteins are members of the "Scavenger Receptor Cystein Rich" family proteins (SRCR) but the regulation, the expression and the function of these molecules is not totally resolved. CD5 is involved in the regulation of antigen receptor in LB and in LT, in the LB tolerance and is present on the surface of regulator B cells. In contrast, CD6 plays a role in lymphocyte proliferation, survival, migration, and cell adhesion. Expressions of CD5 and CD6 differ within normal LB and and LB present in different in pathologies. In the context of systemic lupus erythematosus (LES), the number of CD5 molecules on the surface of CD5+ LB is reduced. In another autoimmune disease (MAI), the Sjogren Syndrome (SS), the expression of CD6 at the membrane of B cells is not affected but the distribution of CD6 + memory LB but not naive LB is changed compared to healthy controls. Indeed, LB CD6 + are underrepresented in the peripheral blood and, it’s due to their relocation in the salivary glands (GS) of patients. This relocation is related to overexpression of ALCAM, the natural ligand of CD6, by epithelial cells in SS. The study of the decreased expression of CD5 on the surface of LB SLE patients has shown that there was a defect in the process of DNA methylation in these patients. The same defect was found in the GS of SS patients. Finally, B cells from chronic lymphocytic leukemia patients (CLL) are holders of the two molecules on their membrane. We tested the effect in vitro and in vivo of a humanized monoclonal antibody (mAb) anti-CD6, T1H, in the CLL. Interestingly, it appears that this mAb promotes lysis of CLL LB and this effect is equivalent to the one that rituximab was shown to have in an in vivo mouse model. T1H is internalized by LT and is therefore ineffective on these cells. These results allow us to conclude that even if the CD5 and CD6 molecules are phylogenetically close, they have different functions and modes of regulation between LB and LT but also within different populations of LB. A better understanding of their functions and action pathway of these two proteins opens up therapeutic perspectives for the treatment of MAI and CLL.

Les troubles de l’humeur font partie des problèmes de santé majeurs dans le monde, du fait de leur forte incidence et récurrence dans la population générale, de la nuisance pour la qualité de vie des patients ainsi que la répercussion majeure sur les systèmes de santé. A ce jour, l’étiologie ainsi que les mécanismes biologiques sous-jacents les troubles de l’humeur sous encore très mal connus. Un nombre grandissant de preuves suggère qu’une interaction complexe entre les gènes et l’environnement serait a l’origine de la mise en place et évolution des épisodes dépressifs majeurs – un des troubles de l’humeur les plus répandus. Par conséquent, des régulations épigénétiques complexes, qui consistent en des mécanismes clefs par lesquels l’environnement induit des changements persistant sur l’expression des gènes (sans modifier le code génétique), joueraient un rôle prépondérant dans la pathophysiologie de la dépression. De manière plus spécifique, la répression épigénétique du gène codant pour le brain-derived neurotrophic factor (BDNF) – un facteur de croissance impliqué dans la plasticité neuronale et développement du système nerveux central – serait un mécanisme clef dans la mise en place de la dépression et autres troubles de l’humeur. Dans ce contexte, les travaux de recherche présentés dans cette thèse visent à explorer le rôle des régulations épigénétiques au niveau de la signalisation BDNF/TrkB dans la physiopathologie et traitement des troubles de l’humeur. Les résultats montrent que les régulations épigénétiques au niveau de la signalisation BDNF/TrkB sont fortement impliquées dans la mise en place et maintenance de la plasticité neuronale. De plus, les variations environnementales, particulièrement au cours du développement, sont capables d’induire une reprogrammation épigénétique stable et persistante au niveau du complexe BDNF/TrkB ainsi qu’une altération de la neuroplasticité, conduisant à une augmentation de la vulnérabilité au stress et troubles de l’humeur. De manière intéressante, la signalisation du récepteur TrkB est nécessaire pour les effets neurobiologiques et comportementaux des antidépresseurs. De ce fait, une approche pharmocologique ciblée sur le complexe BDNF/TrkB et ses régulations épigénétiques sous-jacentes apparaît comme stratégie thérapeutique prometteuse pour le traitement des troubles de l’humeur tel que la dépression. / Mood disorders are among the major health problems worldwide due to the high prevalence and recurrence in the general population, and the significant burden for individual life quality and the repercussion on healthcare systems and society. Up to date, the etiology and biological mechanisms underlying mood disorders are still poorly understood. Mounting evidences suggest that a complex interaction between genes and environment might account in the development and course of major depression i.e. one of the most prevalent affective disorders. Accordingly, complex epigenetic regulations - consisting of key mechanisms by which environmental factors induce enduring changes in gene expression without altering the DNA code - have been suspected to plays a pivotal role in the pathophysiology of depression. More specifically, epigenetic repression of the gene encoding for brain-derived neurotrophic factor (BDNF) - a small-secreted growth factor implicated in brain development and neuronal plasticity - may have a preponderant role in the onset of depression and other mood disorders. In this context, the research presented in this thesis aimed at exploring the role of BDNF signaling and its downstream epigenetic regulations in the pathophysiology and treatment of mood disorders. Our findings indicate that epigenetic regulation at BDNF/TrkB signaling is critically important in the establishment and maintenance of neuronal plasticity. Moreover, environmental variations, especially when occurring in development, are able to induce stable and enduring epigenetic reprogramming involving aberrant BDNF/TrkB signaling and impaired neuroplasticity, thereby increasing vulnerability to stress and mood disorders. Interestingly, antidepressants require TrkB to exert some of their neurochemical and behavioral effects. Hence, targeting the BDNF receptor TrkB to restore a normal epigenetic regulation and neuronal functioning appears to be a promising strategy for the treatment of mood disorders.