Embryonic stem cells (ESCs) are characterized by their unlimited capacity for self-renewal and the ability to contribute to every lineage of the developing embryo. The promoters of developmentally regulated loci within these cells are marked by coincident epigenetic modifications of gene activation and repression, termed bivalent domains. Trithorax group (TrxG) and Polycomb Group (PcG) proteins respectively place these epigenetic marks on chromatin and extensively colocalize with Oct4 in ESCs. Although it appears that these cells are poised and ready for differentiation, the switch that permits this transition is critically held in check. The derepression of bivalent domains upon knockdown of Oct4 or PcG underscores their respective roles in maintaining the pluripotent state through epigenetic regulation of chromatin structure. The mechanisms that facilitate the recruitment and retention of Oct4, TrxG, and PcG proteins at developmentally regulated loci to maintain the pluripotent state, however, remain unknown. Oct4 may function as either a transcriptional activator or repressor. Prevailing thought holds that both of these activities are required to maintain the pluripotent state through activation of genes implicated in pluripotency and cell-cycle control with concomitant repression of genes required for differentiation and lineage-specific differentiation. More recent evidence however, suggests that the activator function of Oct4 may play a more critical role in maintaining the pluripotent state (Hammachi et al., 2012). The purpose of the studies described in this dissertation was to clarify the underlying mechanisms by which Oct4 functions in transcriptional activation and repression. By so doing, we wished to contextualize its role in pluripotent cells, and to provide insight into how changes in Oct4 function might account for its ability to facilitate cell fate transitions. As a result of our studies we find that Oct4 function is dependent upon post-translational modifications (PTMs). We find through a combination of experimental approaches, including genome-wide microarray analysis, bioinformatics, chromatin immunoprecipitation, functional molecular, and biochemical analyses, that in the pluripotent state Oct4, Akt, and Hmgb2 participate in a regulatory feedback loop. Akt-mediated phosphorylation of Oct4 facilitates interaction with PcG recruiter Hmgb2. Consequently, Hmgb2 functions as a context dependent modulator of Akt and Oct4 function, promoting transcriptional poise at Oct4 bound loci. Sumoylation of Oct4 is then required to maintain Hmgb2 enrichment at repressed loci and to transmit the H3K27me3 mark in daughter progeny. The expression of Oct4 phosphorylation mutants however, leads to Akt inactivation and initiates the DNA Damage Checkpoint response. Our results suggest that this may subsequently facilitate chromatin reorganization and cell fate transitions. In summary, our results suggest that controlled modulation of Oct4, Akt, and Hmgb2 function is required to maintain pluripotency and for the faithful induction of transcriptional programs required for lineage specific differentiation.

Tot i que es coneix l’involucrament de les cèl·lules pancreàtiques acinars en patologies exocrines (pancreatitis i càncer de pàncrees), la manca de models normals basats en cèl·lules ha limitat l’estudi de les alteracions que succeeixen en el programa de diferenciació pancreàtica. Hem demostrat prèviament que les cèl·lules mare embrionàries murines, que són pluripotents, poden adquirir un fenotip acinar in vitro. Això es va aconseguir, en part, amb una combinació de senyals que provenien del cultiu de pàncrees fetals que no era, però, específic del llinatge pancreàtic. L’objectiu d’aquest treball ha estat el de desenvolupar un protocol selectiu pel llinatge acinar basat en l’activació seqüencial de vies de senyalització que recapitulin el desenvolupament pancreàtic in vivo, a través de la formació definitiva de l’endoderm, l’especificació pancreàtica i acinar i l’expansió/diferenciació de progenitors acinars. El tractament de cossos embrionaris amb Activina A va promoure l’expressió de gens d’endoderm com està prèviament descrit. El tractament subsegüent amb àcid Retinoic, FGF10 i Ciclopamina, un inhibidor de la via de Hedgehog, va resutar en la inducció dels marcadors de progenitors pancreàtics Pdx1, Ptf1a i Cpa1 però també d’aquells expressats en el llinatge pancreàtic, que van ser reduïts amb la inhibició de BMPs. Les cèl·lules van ser a continuació cultivades en Matrigel utilitzant un sistema de cultiu en 3D en presència de fol·listatina, dexametasona i KGF comportant una inducció significativa dels nivells de mRNA i proteïna de marcadors acinars i una disminució de l’expressió dels de marcadors acinars. A més, es va veure que Amyl es secretava en el medi. Aquestes dades indiquen que l’activació selectiva del programa de diferenciació acinar en cèl·lules mare embrionàries es pot dur a terme mitjançant una inducció esgraonada de vies de senyalització involucrades en el desenvolupament pancreàtic exocrí proporcionant una eina potencial per estudiar la diferenciació pancreàtica i malalties relacionades amb el pàncrees. / Despite known involvement of pancreatic acinar cells in exocrine pathologies (pancreatitis and pancreatic cancer), the lack of normal cell-based models has limited the study of the alterations that occur in the acinar differentiation program. We have previously shown that mESC (murine embryonic stem cells), which are pluripotent, can acquire an acinar phenotype in vitro. This was achieved, in part, by a combination of signals provided by the culture of foetal pancreases which was, however, no specific for the acinar lineage. The aim of this work was to develop a protocol selective for the acinar lineage based on the sequential activation of signaling pathways that recapitulate pancreatic development in vivo, through the definitive endoderm formation, the pancreatic and acinar specification and the expansion/differentiation of acinar progenitors. Treatment of embryoid bodies with Activin A enhanced the expression of endodermal genes as previously described. Subsequent treatment with Retinoic acid, FGF10 and Cyclopamine, an inhibitor of the Hedgehog pathway, resulted in the enhancement of pancreatic progenitor markers Pdx1, Ptf1a and Cpa1 but also of those expressed in the hepatic lineage, which were reduced by BMPs inhibition. Cells were further cultured in Matrigel using a 3D culture system in the presence of follistatin, dexamethasone, and KGF leading to a significant enhancement of the mRNA and protein levels of acinar markers while decreasing the expression of endocrine ones. Moreover, active Amyl was released into the medium. These data indicate that the selective activation of the acinar differentiation program in ES cells can be achieved by stepwise induction of signaling pathways involved in pancreatic exocrine development providing a potential tool for studying pancreatic differentiation and pancreas-related diseases.

Notre génome est constamment attaqué par des facteurs endogènes et exogènes qui menacent son intégrité et conduisent à différents types de dommages. Les cassures double brins (CDBs) font partie des dommages les plus nuisibles car elles peuvent entraîner la perte d'information génétique, des translocations chromosomiques et la mort cellulaire. Tous les processus de réparation se déroulent dans le cadre d'une chromatine hautement organisée et compartimentée. Cette chromatine peut être divisée en un compartiment ouvert transcriptionnellement actif (euchromatine) et un compartiment compacté transcriptionnellement inactif (hétérochromatine). Ces différents degrés de compaction jouent un rôle dans la régulation de la réponse aux dommages à l’ADN. L'objectif de mon premier projet était de comprendre l'influence de l'organisation 3D du génome sur la réparation de l'ADN. Pour cela, j’ai utilisé deux approches complémentaires dans le but d’induire et de cartographier les CDBs dans le génome de souris. Mes résultats ont mis en évidence un enrichissement de γH2AX, facteur de réparation des dommages à l’ADN, sur différentes régions du génome de cellules souches embryonnaires de souris, et ont également montré que les dommages persistent dans l’hétérochromatine, contrairement à l’euchromatine qui est protégée des dommages. Pour mon deuxième projet, j'ai cartographié l'empreinte génomique de 53BP1, facteur impliqué dans la réparation des CDBs, dans des cellules U2OS asynchrones et des cellules bloquées en G1 afin d’identifier de nouveaux sites de liaison de 53BP1. Mes résultats ont permis d’identifier de nouveaux domaines de liaison de 53BP1 couvrant de larges régions du génome, et ont montré que ces domaines de liaison apparaissent dans des régions de réplication moyenne et tardive. / Our genome is constantly under attack by endogenous and exogenous factors which challenge its integrity and lead to different types of damages. Double strand breaks (DSBs) constitute the most deleterious type of damage since they maylead to loss of genetic information, translocations and cell death. All the repair processes happen in the context of a highly organized and compartmentalized chromatin. Chromatin can be divided into an open transcriptionally active compartment (euchromatin) and a compacted transcriptionally inactive compartment (heterochromatin). These different degrees of compaction play important roles in regulating the DNA damage response. The goal of my first project was to understand the influence of 3D genome organization on DNA repair. I used two complementary approaches to induce and map DSBs in the mouse genome. My results have shown that enrichment of the DNA damage repair factor γH2AX occurs at distinct loci in the mouse embryonic stem cell genome and that the damage persists in the heterochromatin compartment while the euchromatin compartment is protected from DNA damage. For my second project, I mapped the genomic footprint of 53BP1, a factor involved in DSBs repair, in asynchronous and G1 arrested U2OS cells to identify novel 53BP1 binding sites. My results have identified novel 53BP1 binding domains which cover broad regions of the genome and occur in mid to late replicating regions of the genome.

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Made available in DSpace on 2016-08-18T18:55:12Z (GMT). No. of bitstreams: 1 ANA ZELIA JANSEN SARAIVA GOMES.pdf: 382708 bytes, checksum: d4a06d04b79581bd8bab21baebc7e467 (MD5) Previous issue date: 2010-04-14 / A review the decision of the Supreme Court ruled as a constitutional law 11.105/05 (Biosafety Law) concerning the possibility of using embryonic stem cells for scientific research derived from the manipulation of frozen embryos more than three years or impractical for human reproduction. The decision became historic because it can generate the 1st public hearing held by the Supreme Court that, besides having to deal with issues that at first escaped legal issues, such as the beginning of human life in a biomedical perspective. Throughout the analysis, there is a new insight into the legal issues is becoming increasingly a social need, particularly when discussing issues related to human life and ethics, as these create a number of consequences that impact directly the legal environment. The search for solutions to such problems is presented as urgent in view of social harmony, which is necessary to rescue the constitutional principles as a means able to balance tensions between science presented, Law and Ethics. Thus, they are justified in the light of Biolaw and Democratic State of Brazil, the advantages, disadvantages and consequences of permitting such research, so that we can finally analyze the favorable decision of the Supreme Court for the research, which allows, in the near future, be formulated and implemented policies regarding the issues under investigation. / A análise da decisão do Supremo Tribunal Federal que julgou constitucional a lei 11.105/05 (Lei de Biossegurança), referente à possibilidade de utilização de célulastronco embrionárias para pesquisas científicas obtidas a partir da manipulação de embriões congelados há mais de três anos ou inviáveis para a reprodução humana. A decisão se tornou histórica em virtude de ter gerado a 1ª audiência pública realizada por aquela Corte Suprema, além de ter que enfrentar temas que, a princípio, fugiam ao âmbito jurídico, como por exemplo, o início da vida humana em uma perspectiva biomédica. Ao longo da análise, observa-se que uma nova visão sobre as questões jurídicas constitui-se cada vez mais uma necessidade social, especialmente quando se discute temas relacionados à vida humana e sua ética, visto que estas criam diversas conseqüências que repercutem de forma direta no âmbito jurídico. A busca de soluções para tais situações apresenta-se como urgência tendo em vista a harmonia social, o que faz necessário o resgate dos princípios constitucionais como meio capaz de equilibrar tensões apresentadas entre Ciência, Direito e Ética. Assim, são fundamentadas, à luz do Biodireito e do Estado Democrático do Brasil, as vantagens, desvantagens e consequências da permissão de tais pesquisas, para que se possa, por fim, analisar a decisão favorável do Supremo Tribunal Federal para as pesquisas, o que permite, em um futuro próximo, serem formuladas e implementadas políticas públicas referentes à tematica em questão.

Dans la première partie de cette thèse effectuée en collaboration avec le groupe expérimental de C. Chazaud (Clermont Université), nous avons étudié théoriquement un processus de différenciation cellulaire intervenant avant l’implantation de l’embryon dans l’utérus. Il s’agit de la spécification des cellules de la masse cellulaire interne (MCI) en épiblaste (EPI) et en endoderme primitif (EPr), processus dans lequel les facteurs de transcription Nanog et Gata6 jouent un rôle essentiel. En effet, en absence de Nanog, les cellules de la MCI acquièrent toutes une identité EPr, tandis qu’en absence de Gata6, elles se différencient toutes en EPI. De plus, la voie de signalisation Fgf/Erk active l’expression de Gata6 et inhibe celle de Nanog. Enfin, Nanog active la sécrétion dans le milieu extracellulaire de Fgf4, une molécule qui active la voie de signalisation Fgf/Erk en se liant au FgfR2. Nous avons développé un modèle mathématique pour ce réseau de régulations, fondé sur des équations différentielles ordinaires décrivant l’évolution temporelle des niveaux de protéines Nanog, Gata6, Fgf4 et Fgfr2 et de l’activité de la voie Fgf-Erk. Nous avons validé ce modèle en montrant qu’il récapitule les résultats expérimentaux obtenus in vivo, dans les embryons wild-type et dans les mutants Nanog-/- et Gata6-/-. De plus, l’analyse des résultats du modèle permet de proposer un nouveau mécanisme pour l’émergence d’une population mixte de cellules EPI et EPr au sein de la MCI. Ce mécanisme repose sur le fait que le système décrit par notre modèle peut présenter trois états stationnaires stables, dont les niveaux d’expression de Nanog et Gata6 correspondent à l’EPI, l’EPr et la MCI non-différenciée, respectivement. De plus, le modèle a été utilisé afin d’interpréter des résultats expérimentaux récents et contre-intuitifs, concernant les embryons hétérozygotes Gata6+/-. Enfin, nous avons établi des prédictions théoriques, dont certaines ont été ultérieurement vérifiées en laboratoire. <p>Dans la seconde partie de la thèse, effectuée dans le laboratoire d’O. Pourquié (Université de Strasbourg), nous avons étudié un processus de différenciation in vitro, par une approche expérimentale. Il s’agit de la différenciation des cellules souches embryonnaires (ES) en cellules de mésoderme paraxial, un tissu dont dérivent –au cours du développement embryonnaire– les cellules formant notamment les vertèbres, les côtes, la peau et les muscles squelettiques du dos.<p> / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished

Recent genome-wide sequencing projects revealed the pervasive transcription of intergenic long noncoding RNAs (lincRNAs) in eukaryotic genomes (reviewed in Ponting et al. 2009). For the vast majority of lincRNAs, their mechanisms of function remain largely unrecognized. However, the genome-wide signatures of functionality associated with many lincRNAs, including apparent evolutionary sequence conservation, spatial and temporal-restricted expression patterns, strong associations with epigenetic marks, and reported molecular and cellular functions, reinforce their biological relevance. My work investigates lincRNAs that post-transcriptionally regulate gene abundance by competing for the binding of common microRNAs (miRNAs) with protein-coding transcripts, termed competitive endogenous RNAs (ceRNAs) acting lincRNAs (lnceRNAs). First, I examine the biological relevance of this post-transcriptional regulation of gene abundance by ceRNAs. Next, I estimate the genome-wide prevalence of lnceRNAs in mouse embryonic stem cells (mESCs) and characterize their properties. Finally, using two specific examples of lnceRNAs, I show the contributions of lnceRNAs to human monogenic and complex trait diseases. Collectively, these results illustrate that lnceRNAs provide a novel layer of post-transcriptional regulation via a miRNA-mediated mechanism that contributes to organismal and cellular biology.

Embryonic stem cells (ESCs) are characterized by their unlimited capacity for self-renewal and the ability to contribute to every lineage of the developing embryo. The promoters of developmentally regulated loci within these cells are marked by coincident epigenetic modifications of gene activation and repression, termed bivalent domains. Trithorax group (TrxG) and Polycomb Group (PcG) proteins respectively place these epigenetic marks on chromatin and extensively colocalize with Oct4 in ESCs. Although it appears that these cells are poised and ready for differentiation, the switch that permits this transition is critically held in check. The derepression of bivalent domains upon knockdown of Oct4 or PcG underscores their respective roles in maintaining the pluripotent state through epigenetic regulation of chromatin structure. The mechanisms that facilitate the recruitment and retention of Oct4, TrxG, and PcG proteins at developmentally regulated loci to maintain the pluripotent state, however, remain unknown. Oct4 may function as either a transcriptional activator or repressor. Prevailing thought holds that both of these activities are required to maintain the pluripotent state through activation of genes implicated in pluripotency and cell-cycle control with concomitant repression of genes required for differentiation and lineage-specific differentiation. More recent evidence however, suggests that the activator function of Oct4 may play a more critical role in maintaining the pluripotent state (Hammachi et al., 2012). The purpose of the studies described in this dissertation was to clarify the underlying mechanisms by which Oct4 functions in transcriptional activation and repression. By so doing, we wished to contextualize its role in pluripotent cells, and to provide insight into how changes in Oct4 function might account for its ability to facilitate cell fate transitions. As a result of our studies we find that Oct4 function is dependent upon post-translational modifications (PTMs). We find through a combination of experimental approaches, including genome-wide microarray analysis, bioinformatics, chromatin immunoprecipitation, functional molecular, and biochemical analyses, that in the pluripotent state Oct4, Akt, and Hmgb2 participate in a regulatory feedback loop. Akt-mediated phosphorylation of Oct4 facilitates interaction with PcG recruiter Hmgb2. Consequently, Hmgb2 functions as a context dependent modulator of Akt and Oct4 function, promoting transcriptional poise at Oct4 bound loci. Sumoylation of Oct4 is then required to maintain Hmgb2 enrichment at repressed loci and to transmit the H3K27me3 mark in daughter progeny. The expression of Oct4 phosphorylation mutants however, leads to Akt inactivation and initiates the DNA Damage Checkpoint response. Our results suggest that this may subsequently facilitate chromatin reorganization and cell fate transitions. In summary, our results suggest that controlled modulation of Oct4, Akt, and Hmgb2 function is required to maintain pluripotency and for the faithful induction of transcriptional programs required for lineage specific differentiation.

Chez la souris, le Leukemia Inhibitory Factor (LIF) joue un rôle clé dans le maintien des cellules souches embryonnaires (ES) à l’état pluripotent. Le LIF agit en activant le facteur de transcription STAT3 via les kinases Jak. Cette activation est nécessaire et suffisante au maintien des cellules ES en autorenouvellement en présence de sérum. Une étude du transcriptome de STAT3 réalisée au laboratoire a permis d’identifier plusieurs gènes cibles de ce facteur, parmi lesquels plusieurs gènes inconnus. L’un d’eux, le gène 1456160_at, est fortement exprimé dans les cellules ES de souris et son expression diminue après induction de la différenciation. Ce gène a été appelé Asgard pour Another Self-renewal GuARDian. La caractérisation et le séquençage de ce gène ont permis de mettre en évidence qu'Asgard code pour un microARN. De nombreux microARNs jouent un rôle clé dans le maintien de l'autorenouvellement des cellules ES et dans le contrôle de la différenciation. Des expériences d’inhibition et de surexpression ont permis de montrer que Asgard est impliqué dans la régulation de la différenciation endoderme versus mésoderme. Des analyses préliminaires ont permis d’identifier Pbx3, FoxA2 et Sox17 comme cibles potentielles. Bien que les mécanismes d’action du microARN Asgard restent à confirmer, ce travail a permis d’identifier un nouveau gène clé de l'autorenouvellement des cellules ES de souris / The Leukemia Inhibitory Factor (LIF) activates the transcription factor STAT3, which results in the maintenance of mouse embryonic stem cells in the undifferentiated state by inhibiting mesodermal and endodermal differentiation. We identified several target genes of STAT3 by transcriptomic analysis. Among them, we focused on an unknown gene referred as 1456160_at on Affymetrix array. This gene is highly expressed in embryonic stem cells and its expression level decreases during differentiation. We named this gene Asgard for Another Self-renewal GuARDian. Its characterization and sequencing revealed that Asgard encodes for a microRNA sequence. Several microRNAs have been shown to play key role in the maintenance of self-renewal of mouse ES cells and in the control of differentiation. Inhibition and overexpression assays showed that Asgard inhibits endodermal differentiation in order to maintain self-renewal. Through preliminary analysis, we identified Pbx3, FoxA2 and Sox17 as potential targets of the microRNA Asgard. Our work enables us to identify a new key gene of self-renewal of mouse ES cells

Fontes alternativas de células &#946; têm sido estudadas para o tratamento de Diabetes mellitus tipo 1, dentre as quais a mais promissora consiste das células-tronco diferenciadas em células produtoras de insulina (IPCs). Alguns trabalhos demonstram a capacidade de células-tronco embrionárias murinas (mESCs) de formarem estruturas semelhantes a ilhotas pancreáticas, porém, os níveis de produção de insulina são insuficientes para a reversão do diabetes em camundongos diabetizados. Este trabalho visa desenvolver um protocolo adequado para geração de IPCs e contribuir para a identificação e caracterização funcional de novos genes associados à organogênese pancreática. Logo no início da diferenciação das mESCs em IPCs, foi possível verificar o surgimento de células progenitoras, evidenciado pela expressão de marcadores importantes da diferenciação beta-pancreática. Ao final do processo de diferenciação in vitro, ocorreu a formação de agrupamentos (clusters) semelhantes a ilhotas, corando positivamente por ditizona, que é específica para células &#946;-pancreáticas. Para avaliar seu potencial in vivo, estes clusters foram microencapsulados em Biodritina® e transplantados em camundongos diabetizados. Apesar dos níveis de insulina produzidos não serem suficientes para estabelecer a normoglicemia, os animais tratados com IPCs apresentaram melhores condições, quando comparados ao grupo controle, tendo melhor controle glicêmico, ganho de massa corpórea e melhor aparência da pelagem, na ausência de apatia. Além disso, análise dos clusters transplantados nestes animais indicou aumento da expressão de genes relacionados à maturação das células &#946;. Porém, quando estes clusters foram microencapsuladas em Bioprotect® e submetidos à maturação in vivo em animais normais, ocorreu um aumento drástico na expressão de todos os genes analisados, indicando sua maturação completa em células beta. O transplante destas células completamente maturadas em animais diabetizados, tornou-os normoglicêmicos e capazes de responder ao teste de tolerância à glicose (OGTT) de forma semelhante aos animais normais. A segunda parte do trabalho visou analisar genes diferencialmente expressos identificados em estudo anterior do nosso grupo, comparando, através de DNA microarray, mESCs indiferenciadas e diferenciadas em IPCs. Um dos genes diferencialmente expressos é aquele que codifica para a Purkinge cell protein 4 (Pcp4), sendo 3.700 vezes mais expresso em IPCs. Para investigar o possível papel do gene Pcp4 em células &#946; e no processo de diferenciação &#946;-pancreática, adotou-se o enfoque de genômica funcional, superexpressando e inibindo sua expressão em células MIN-6 e mESCs. Apesar da alteração na expressão de Pcp4 em células MIN-6 não ter interferido de forma expressiva na expressão dos genes analisados, quando inibido, modificou o perfil da curva de crescimento celular, aumentando seu tempo de dobramento de forma significativa e diminuindo da viabilidade celular em ensaios de indução de apoptose. Já na diferenciação de mESCs em IPCs, a superexpressão de Pcp4 interferiu de forma positiva apresentando uma tendência a aumentar a expressão dos genes relacionado à diferenciação&#946;-pancreática. Concluindo, desenvolvemos um novo protocolo de diferenciação de mESCs em IPCs as quais foram capazes de reverter o diabetes em camundongos diabetizados e descrevemos, pela primeira vez, o gene Pcp4 como sendo expresso em células &#946;-pancreáticas, podendo estar relacionado à manutenção da viabilidade celular e maturação destas células. / New cellular sources for type 1 Diabetes mellitus treatment have been previously investigated, the most promising of which seems to be the insulin producing cells (IPCs), obtained by stem cells differentiation. Some reports show that murine embryonic stem cells (mESCs) are able to form islet-like structures, however, their insulin production is insufficient to render diabetic mice normoglycemic. This work aims at developing an adequate protocol for generation of IPCs and searching for new genes which could be involved in the pancreatic organogenesis process. Early on during mESCs differentiation into IPCs, we observed the presence of progenitor cells, which were able to express pancreatic &#946;-cell markers. At the end of the differentiation process, the islet-like clusters positively stained for the insulin-specific dithizone. These clusters were microencapsulated in Biodritin® microcapsules, and then transplanted into diabetized mice. Although the levels of insulin production were insufficient for the animals to achieve normoglycemia, those which received IPCs displayed improved conditions, when compared to the control group, as judged by a better glycemic control, body weight gain and healthy fur appearance, in the absence of apathy. In addition, when these transplantated clusters were retrieved, high levels of expression of the genes related to &#946;-cell maturation were detected. IPCs were also microencapsulated in Bioprotect® and subjected to in vivo maturation in normal animals. A dramatic increase of the analyzed genes expression was observed, indicating complete maturation of the differentiated cells. When these cells were transplanted into diabetized mice, these animals achieved normoglycemia and were able to display glucose tolerance test (OGTT) response very similar to that of normal mice. In the second part of this work, we analyzed upregulated genes described in previous work from our group, comparing undifferentiated mESCs to IPCs using a microarray platform. One of these genes is that coding for the Purkinje cell protein 4 (Pcp4), which is 3,700 more expressed than in undifferentiated mESC cells. We adopted a functional genomics approach to investigate the role played by the Pcp4 gene in &#946;-cells and in &#946;-cell differentiation, by inducing overexpression and knocking down this gene in MIN-6 and mESC cells. Although the differential expression of Pcp4 in MIN-6 was not able to interfere with the expression of the genes analyzed, we observed different cell growth rates, with increased doubling time and decreased cell viability when its expression was knocked down. In addition, overexpression of Pcp4 in mESCs subjected to differentiation into IPCs apparently increases the expression of genes related to &#946;-cell differentiation. In conclusion, we developed a new protocol for ESCs differentiation into IPCs, which is able to revert diabetes in diabetized mice, and we also describe here, for the first time, the Pcp4 gene as being expressed in pancreatic &#946;-cells and possibly being related to maintenance of cell viability and &#946;-cell maturation.