Identification of a key lysine residue in heat shock protein 90 required for azole and echinocandin resistance in Aspergillus fumigatus.

Heat shock protein 90 (Hsp90) is an essential chaperone involved in the fungal stress response that can be harnessed as a novel antifungal target for the treatment of invasive aspergillosis. We previously showed that genetic repression of Hsp90 reduced Aspergillus fumigatus virulence and potentiated the effect of the echinocandin caspofungin. In this study, we sought to identify sites of posttranslational modifications (phosphorylation or acetylation) that are important for Hsp90 function in A. fumigatus. Phosphopeptide enrichment and tandem mass spectrometry revealed phosphorylation of three residues in Hsp90 (S49, S288, and T681), but their mutation did not compromise Hsp90 function. Acetylation of lysine residues of Hsp90 was recovered after treatment with deacetylase inhibitors, and acetylation-mimetic mutations (K27A and K271A) resulted in reduced virulence in a murine model of invasive aspergillosis, supporting their role in Hsp90 function. A single deletion of lysine K27 or an acetylation-mimetic mutation (K27A) resulted in increased susceptibility to voriconazole and caspofungin. This effect was attenuated following a deacetylation-mimetic mutation (K27R), suggesting that this site is crucial and should be deacetylated for proper Hsp90 function in antifungal resistance pathways. In contrast to previous reports in Candida albicans, the lysine deacetylase inhibitor trichostatin A (TSA) was active alone against A. fumigatus and potentiated the effect of caspofungin against both the wild type and an echinocandin-resistant strain. Our results indicate that the Hsp90 K27 residue is required for azole and echinocandin resistance in A. fumigatus and that deacetylase inhibition may represent an adjunctive anti-Aspergillus strategy.

Ultrahigh dose-rate FLASH irradiation increases the differential response between normal and tumor tissue in mice.

In vitro studies suggested that sub-millisecond pulses of radiation elicit less genomic instability than continuous, protracted irradiation at the same total dose. To determine the potential of ultrahigh dose-rate irradiation in radiotherapy, we investigated lung fibrogenesis in C57BL/6J mice exposed either to short pulses (≤ 500 ms) of radiation delivered at ultrahigh dose rate (≥ 40 Gy/s, FLASH) or to conventional dose-rate irradiation (≤ 0.03 Gy/s, CONV) in single doses. The growth of human HBCx-12A and HEp-2 tumor xenografts in nude mice and syngeneic TC-1 Luc(+) orthotopic lung tumors in C57BL/6J mice was monitored under similar radiation conditions. CONV (15 Gy) triggered lung fibrosis associated with activation of the TGF-β (transforming growth factor-β) cascade, whereas no complications developed after doses of FLASH below 20 Gy for more than 36 weeks after irradiation. FLASH irradiation also spared normal smooth muscle and epithelial cells from acute radiation-induced apoptosis, which could be reinduced by administration of systemic TNF-α (tumor necrosis factor-α) before irradiation. In contrast, FLASH was as efficient as CONV in the repression of tumor growth. Together, these results suggest that FLASH radiotherapy might allow complete eradication of lung tumors and reduce the occurrence and severity of early and late complications affecting normal tissue.

MAF1: a new target of mTORC1.

Yeast and mammalian MAF1 are both regulated by the TOR (target of rapamycin) pathway. However, the exact mechanisms of regulation diverge at TOR, with yeast Maf1 phosphorylated mainly by the TORC1 (TOR complex 1) substrate Sch9 kinase and mammalian MAF1 by mTORC1 (mammalian target of rapamycin complex 1) itself. Sch9 phosphorylation of yeast Maf1 regulates Maf1 localization, but it is less clear whether phosphorylation of human MAF1 regulates its localization. Replacement of phosphosites with alanine decreases Pol III (RNA polymerase III) transcription, but the effect is much more pronounced for human MAF1 than for the yeast protein. In both cases, Pol III repression can be further increased by rapamycin treatment or, in mammalian cells, serum starvation, suggesting that the TOR pathway controls another aspect of Pol III transcription that is closely linked to MAF1, as it depends on the presence of MAF1.

PPARgamma but not PPARalpha ligands are potent repressors of major histocompatibility complex class II induction in atheroma-associated cells.

Peroxisome proliferator-activated receptors (PPARs) are essential in glucose and lipid metabolism and are implicated in metabolic disorders predisposing to atherosclerosis, such as diabetes and dyslipidemia. Conversely, antidiabetic glitazones and hypolipidemic fibrate drugs, known as PPARgamma and PPARalpha ligands, respectively, reduce the process of atherosclerotic lesion formation, which involves chronic immunoinflammatory processes. Major histocompatibility complex class II (MHC-II) molecules, expressed on the surface of specialized cells, are directly involved in the activation of T lymphocytes and in the control of the immune response. Interestingly, expression of MHC-II has recently been observed in atherosclerotic plaques, and it can be induced by the proinflammatory cytokine interferon-gamma (IFN-gamma) in vascular cells. To explore a possible role for PPAR ligands in the regulation of the immune response, we investigated whether PPAR activation affects MHC-II expression in atheroma-associated cells. In the present study, we demonstrate that PPARgamma but not PPARalpha ligands act as inhibitors of IFN-gamma-induced MHC-II expression and thus as repressors of MHC-II-mediated T-cell activation. All different types of PPARgamma ligands tested inhibit MHC-II. This effect of PPARgamma ligands is due to a specific inhibition of promoter IV of CIITA and does not concern constitutive expression of MHC-II. Thus, the beneficial effects of antidiabetic PPARgamma activators on atherosclerotic plaque development may be partly explained by their repression of MHC-II expression and subsequent inhibition of T-lymphocyte activation.

GENETIC AND BIOCHEMICAL ANALYSIS OF THE TESTIS-SPECIFIC ZINC FINGER PROTEIN CTCFL/BORIS

Abstract en FrançaisCTCFL a d'abord été identifié comme un paralogue de la protéine ubiquitaire CTCF en raison de sa forte homologie entre leurs onze « zinc fingers », un domaine de liaison à l'ADN. Parmi ses nombreux rôles, la liaison des zinc fingers de CTCF à la région de contrôle de l'empreinte (ICR) maternelle non-méthylée Igf2/H19, contrôle l'expression empreinte (monoallélique) de H19 et IGF2 dans les cellules somatiques. La méthylation de l'ICR Igf2/H19 paternelle est nécessaire à l'expression empreinte de ces deux gènes. Bien que le mécanisme par lequel l'ICR est méthylé soit mal compris, il est connu que l'établissement de la méthylation se produit pendant le développement des cellules germinales mâles et que les ADN méthyltransférases de novo DNMT3A et DNMT3L sont essentiels. Par conséquent, CTCFL fournit un bon candidat pour un rôle dans la méthylation de l'ICR paternelle Igf2/H19 en raison de son expression restreinte à certains types de cellules où la méthylation de l'ICR a lieu (spermatogonies et spermatocytes) ainsi qu'en raison sa capacité à lier les ICR lgf2/HÎ9 dans ces cellules. Les premiers travaux expérimentaux de cette thèse portent sur le rôle possible des mutations de CTCFL chez les patients atteints du syndrome de Silver-Russell (SRS), où une diminution de la méthylation de l'ICR IGF2/H19 a été observée chez 60% d'entre eux. Admettant que CTCFL pourrait être muté chez ces patients, j'ai examiné les mutations possibles de CTCFL chez 35 d'entre eux par séquençage de l'ADN et analyse du nombre de copies d'exons. N'ayant trouvé aucune mutation chez ces patients, cela suggère que les mutations de CTCFL ne sont pas associées au SRS. Les travaux expérimentaux suivants ont porté sur les modifications post-traductionnelles de CTCFL par la protéine SU MO « small ubiquitin-like modifier » (SUMO). La modification de protéines par SU MO change les interactions avec d'autres molécules (ADN ou protéines). Comme CTCFL régule sans doute l'expression d'un certain nombre de gènes dans le cancer et que plusieurs facteurs de transcription sont régulés par SUMO, j'ai mené des expériences pour déterminer si CTCFL est sumoylé. En effet, j'ai observé que CTCFL est sumoylated in vitro et in vivo et j'ai déterminé les deux résidus d'attachement de SUMO aux lysines 181 et 645. Utilisant les mutants de CTCFL K181R et K645R ne pouvant pas être sumoylated, j'ai évalué les conséquences fonctionnelles de la modification par SUMO. Je n'ai trouvé aucun changement significatif dans la localisation subcellulaire, la demi-vie ou la liaison à l'ADN, mais ai constaté que la sumoylation module à la fois {'activation CTCFL-dépendante et la répression de l'expression génique. Il s'agit de la première modification post-traductionnelle décrite pour CTCFL et les conséquences possibles de cette modification sont discutées pour le cancer et les testicules normaux. Avec cette thèse, j'espère avoir ajouté des résultats importants à l'étude de CTCFL et donné quelques idées pour de futures recherches.AbstractJeremiah Bernier-Latmani, Institute of Pathology, University of Lausanne, CHUVCTCFL was first identified as a paralog of the ubiquitous protein CTCF because of high homology between their respective eleven zinc fingers, a DNA binding domain. Among its many roles, CTCF zinc finger-mediated binding to the unmethylated maternal Igf2/H19 imprinting control region (ICR), controls the imprinted (monoallelic) expression of Igf2 and H19 in somatic cells. Methylation of the paternal Igf2/H19 ICR is necessary for the imprinted expression of the two genes. Although the mechanism by which the ICR is methylated is incompletely understood, it is known that establishment of methylation occurs during male germ cell development and the de novo DNA methyltransferases DNMT3A and DNMT3L are essential. Therefore, CTCFL provided a good candidate to play a role in methylation of the paternal Igf2/H19 ICR because of its restricted expression to cell types where ICR methylation takes place (spermatogonia and spermatocytes) and its ability to bind the Igf2/H19 ICR in these cells. The first experimental work of this thesis investigated the possible role of CTCFL mutations in Silver-Russell syndrome (SRS) patients, where it has been observed that 60% of the patients have reduced methylation of the IGF2/HÎ9 ICR. Reasoning that CTCFL could be mutated in these patients, I screened 35 patients for mutations in CTCFL by DNA sequencing and exon copy number analysis, I did not find any mutations in these patients suggesting that mutations of CTCFL are not associated with SRS. The next experimental work of my thesis focused on posttranslational modification of CTCFL by small ubiquitin-like modifier (SUMO) protein. SUMO modification of proteins changes the interactions with other molecules (DNA or protein). As CTCFL arguably regulates the expression of a number of genes in cancer and many transcription factors are regulated by SUMO, I conducted experiments to assess whether CTCFL is sumoylated. I found that CTCFL is sumoylated in vitro and in vivo and determined the two residues of SUMO attachment to be lysines 181 and 645. Using K181R, K645R mutated CTCFL- which cannot be detected to be sumoylated-1 assessed the functional consequences of SUMO modification. I found no significant changes in subcellular localization, half-life or DNA binding, but found that sumoylation modulates both CTCFL-dependent activation and repression of gene expression. This is the first posttranslational modification described for CTCFL and possible consequences of this modification are discussed in both cancer and normal testis. With this thesis, I hope I have added important findings to the study of CTCFL and provide some ideas for future research.

EWS-FLI-1 modulates miRNA145 and SOX2 expression to initiate mesenchymal stem cell reprogramming toward Ewing sarcoma cancer stem cells.

Cancer stem cells (CSCs) display plasticity and self-renewal properties reminiscent of normal tissue stem cells, but the events responsible for their emergence remain obscure. We recently identified CSCs in Ewing sarcoma family tumors (ESFTs) and showed that they retain mesenchymal stem cell (MSC) plasticity. In the present study, we addressed the mechanisms that underlie ESFT CSC development. We show that the EWS-FLI-1 fusion gene, associated with 85%-90% of ESFTs and believed to initiate their pathogenesis, induces expression of the embryonic stem cell (ESC) genes OCT4, SOX2, and NANOG in human pediatric MSCs (hpMSCs) but not in their adult counterparts. Moreover, under appropriate culture conditions, hpMSCs expressing EWS-FLI-1 generate a cell subpopulation displaying ESFT CSC features in vitro. We further demonstrate that induction of the ESFT CSC phenotype is the result of the combined effect of EWS-FLI-1 on its target gene expression and repression of microRNA-145 (miRNA145) promoter activity. Finally, we provide evidence that EWS-FLI-1 and miRNA-145 function in a mutually repressive feedback loop and identify their common target gene, SOX2, in addition to miRNA145 itself, as key players in ESFT cell differentiation and tumorigenicity. Our observations provide insight for the first time into the mechanisms whereby a single oncogene can reprogram primary cells to display a CSC phenotype.

A role for Yin Yang-1 (YY1) in the assembly of snRNA transcription complexes.

The RNA polymerase (pol) II and III human small nuclear RNA (snRNA) genes have very similar promoters and recruit a number of common factors. In particular, both types of promoters utilize the small nuclear RNA activating protein complex (SNAP(c)) and the TATA box binding protein (TBP) for basal transcription, and are activated by Oct-1. We find that SNAP(c) purified from cell lines expressing tagged SNAP(c) subunits is associated with Yin Yang-1 (YY1), a factor implicated in both activation and repression of transcription. Recombinant YY1 accelerates the binding of SNAP(c) to the proximal sequence element, its target within snRNA promoters. Moreover, it enhances the formation of a complex on the pol III U6 snRNA promoter containing all the factors (SNAP(c), TBP, TFIIB-related factor 2 (Brf2), and B double prime 1 (Bdp1)) that are sufficient to direct in vitro U6 transcription when complemented with purified pol III, as well as that of a subcomplex containing TBP, Brf2, and Bdp1. YY1 is found on both the RNA polymerase II U1 and the RNA polymerase III U6 promoters as determined by chromatin immunoprecipitations. Thus, YY1 represents a new factor that participates in transcription complexes formed on both pol II and III promoters.

Interest rate restrictions in a natural experiment: loan allocation and the change in the usury laws in 1714

This article studies the effects of interest rate restrictions on loan allocation. The British governmenttightened the usury laws in 1714, reducing the maximum permissible interest rate from 6% to5%. A sample of individual loan transactions reveals that average loan size and minimum loan sizeincreased strongly, while access to credit worsened for those with little social capital. Collateralisedcredits, which had accounted for a declining share of total lending, returned to their former role ofprominence. Our results suggest that the usury laws distorted credit markets significantly; we findno evidence that they offered a form of Pareto-improving social insurance.

Three small RNAs jointly ensure secondary metabolism and biocontrol in Pseudomonas fluorescens CHA0.

In many Gram-negative bacteria, the GacS/GacA two-component system positively controls the expression of extracellular products or storage compounds. In the plant-beneficial rhizosphere bacterium Pseudomonas fluorescens CHA0, the GacS/GacA system is essential for the production of antibiotic compounds and hence for biological control of root-pathogenic fungi. The small (119-nt) RNA RsmX discovered in this study, together with RsmY and RsmZ, forms a triad of GacA-dependent small RNAs, which sequester the RNA-binding proteins RsmA and RsmE and thereby antagonize translational repression exerted by these proteins in strain CHA0. This small RNA triad was found to be both necessary and sufficient for posttranscriptional derepression of biocontrol factors and for protection of cucumber from Pythium ultimum. The same three small RNAs also positively regulated swarming motility and the synthesis of a quorum-sensing signal, which is unrelated to N-acyl-homoserine lactones, and which autoinduces the Gac/Rsm cascade. Expression of RsmX and RsmY increased in parallel throughout cell growth, whereas RsmZ was produced during the late growth phase. This differential expression is assumed to facilitate fine tuning of GacS/A-controlled cell population density-dependent regulation in P. fluorescens.

State and industry in the 1940s: The Spanish automobile industry

The decade of the 1940s was one of the darkest periods in the country's history, with years of famine, repression, general misery, and impoverishment of all aspects of national life ranging from culture to the economy. During those years plans were made to establish a Spanish motor industry once the Civil War had come to an end in 1939. It seemed a propitious moment for private enterprise and various foreign motor companies presented proposals for manufacturing their entire vehicle range, from cars to trucks. However, the government plans were for a State monopoly, a policy which meant that any private projects which did not contemplate the regime taking management decisions were rejected out of hand. From 1941 onwards, any new initiative was required to meet the plans set by INI. The main argument running through this paper is that one can only understand the development of the modern Spanish motor industry if one grasps the haggling between motor companies and government regarding market entry and the impact of the regime's autarchic policies in the 1940s.

The p63 target HBP1 is required for skin differentiation and stratification.

Genetic experiments established that p63 is crucial for the development and maintenance of pluristratified epithelia. In the RNA interference (RNAi) screening for targets of p63 in keratinocytes, we identified the transcription factor, High Mobility Group (HMG) box protein 1 (HBP1). HBP1 is an HMG-containing repressor transiently induced during differentiation of several cell lineages. We investigated the relationship between the two factors: using RNAi, overexpression, chromatin immunoprecipitations and transient transfections with reporter constructs, we established that HBP1 is directly repressed by p63. This was further confirmed in vivo by evaluating expression in p63 knockout mice and in transgenics expressing p63 in basal keratinocytes. Consistent with these findings, expression of HBP1 increases upon differentiation of primary keratinocytes and HaCaT cells in culture, and it is higher in the upper layers of human skin. Inactivation of HBP1 by RNAi prevents differentiation of keratinocytes and stratification of organotypic skin cultures. Finally, we analyzed the keratinocyte transcriptomes after HBP1 RNAi; in addition to repression of growth-promoting genes, unexpected activation of differentiation genes was uncovered, coexisting with repression of other genes involved in epithelial cornification. Our data indicate that suppression of HBP1 is part of the growth-promoting strategy of p63 in the lower layers of epidermis and that HBP1 temporally coordinates expression of genes involved in stratification, leading to the formation of the skin barrier.

RNA pentaloop structures as effective targets of regulators belonging to the RsmA/CsrA protein family.

In the Gac/Rsm signal transduction pathway of Pseudomonas fluorescens CHA0, the dimeric RNA-binding proteins RsmA and RsmE, which belong to the vast bacterial RsmA/CsrA family, effectively repress translation of target mRNAs containing a typical recognition sequence near the translation start site. Three small RNAs (RsmX, RsmY, RsmZ) with clustered recognition sequences can sequester RsmA and RsmE and thereby relieve translational repression. According to a previously established structural model, the RsmE protein makes optimal contacts with an RNA sequence 5'- (A)/(U)CANGGANG(U)/(A)-3', in which the central ribonucleotides form a hexaloop. Here, we questioned the relevance of the hexaloop structure in target RNAs. We found that two predicted pentaloop structures, AGGGA (in pltA mRNA encoding a pyoluteorin biosynthetic enzyme) and AAGGA (in mutated pltA mRNA), allowed effective interaction with the RsmE protein in vivo. By contrast, ACGGA and AUGGA were poor targets. Isothermal titration calorimetry measurements confirmed the strong binding of RsmE to the AGGGA pentaloop structure in an RNA oligomer. Modeling studies highlighted the crucial role of the second ribonucleotide in the loop structure. In conclusion, a refined structural model of RsmE-RNA interaction accommodates certain pentaloop RNAs among the preferred hexaloop RNAs.

Perceptual and semantic contributions to repetition priming of environmental sounds.

Repetition of environmental sounds, like their visual counterparts, can facilitate behavior and modulate neural responses, exemplifying plasticity in how auditory objects are represented or accessed. It remains controversial whether such repetition priming/suppression involves solely plasticity based on acoustic features and/or also access to semantic features. To evaluate contributions of physical and semantic features in eliciting repetition-induced plasticity, the present functional magnetic resonance imaging (fMRI) study repeated either identical or different exemplars of the initially presented object; reasoning that identical exemplars share both physical and semantic features, whereas different exemplars share only semantic features. Participants performed a living/man-made categorization task while being scanned at 3T. Repeated stimuli of both types significantly facilitated reaction times versus initial presentations, demonstrating perceptual and semantic repetition priming. There was also repetition suppression of fMRI activity within overlapping temporal, premotor, and prefrontal regions of the auditory "what" pathway. Importantly, the magnitude of suppression effects was equivalent for both physically identical and semantically related exemplars. That the degree of repetition suppression was irrespective of whether or not both perceptual and semantic information was repeated is suggestive of a degree of acoustically independent semantic analysis in how object representations are maintained and retrieved.

SOCS3 Transactivation by PPARγ Prevents IL-17-Driven Cancer Growth.

Activation of the transcription factor PPARγ by the n-3 fatty acid docosahexaenoic acid (DHA) is implicated in controlling proinflammatory cytokine secretion, but the intracellular signaling pathways engaged by PPARγ are incompletely characterized. Here, we identify the adapter-encoding gene SOCS3 as a critical transcriptional target of PPARγ. SOCS3 promoter binding and gene transactivation by PPARγ was associated with a repression in differentiation of proinflammatory T-helper (TH)17 cells. Accordingly, TH17 cells induced in vitro displayed increased SOCS3 expression and diminished capacity to produce interleukin (IL)-17 following activation of PPARγ by DHA. Furthermore, naïve CD4 T cells derived from mice fed a DHA-enriched diet displayed less capability to differentiate into TH17 cells. In two different mouse models of cancer, DHA prevented tumor outgrowth and angiogenesis in an IL-17-dependent manner. Altogether, our results uncover a novel molecular pathway by which PPARγ-induced SOCS3 expression prevents IL-17-mediated cancer growth. Cancer Res; 73(12); 3578-90. ©2013 AACR.

Role of the REST/RE-1 system in beta-cell life, function and differentiation

SUMMARYDiabetes is characterized by insulin deficiency that results from the destruction of insulin-secreting pancreatic beta-cells (Type 1), or in part from beta-cell death and insulin secretion defects (Type 2). Therefore, understanding the mechanisms of beta cell neogenesis (to generate unlimited supply of beta cells for T1D transplantation] or identifying the specific genes that favors insulin secretion or beta-cell survival is of great importance for the management of diabetes. The transcriptional repressor RE-1 Silencing Transcription Factor (REST) restricts the expression of a large number of genes containing its binding element, called Repressor Element-1 (RE-1), to neurons and beta cells. To do so, REST is ubiquitously expressed but in neurons and beta cells. To identify these essential genes and their functional significance in beta cells, we have generated transgenic mice that express REST specifically in beta cells under the control of the rat insulin promoter (RIP-REST mice). This resulted in the repression of the RE-1- containing genes in beta cells, and we analyzed the consequences.We first showed that RIP-REST mice were glucose-intolerant because of a defective insulin secretion. To explain this defect, we identified that a subset of the REST target genes were necessary for insulin exocytosis, such as Snap25, Synaptotagmin (Syt) IX, Complexin II, and Ica512, and we further demonstrated that among the identified REST targets, Syt IV and VII were also involved in insulin release. We next analyzed a novel RIP-REST mouse line that featured diabetes and we showed that this defect was due to a major loss of beta-cell mass. To explain this phenotype, we identified REST target genes that were involved in beta-cell survival, such as Ibl, Irs2, Ica512 and Connexin36, and revealed that another REST target, Cdk5r2 is also involved in beta-cell protection. In a third part, we finally suggest that REST may be important for pancreatic endocrine differentiation, since transgenic mice expressing constitutive REST in pancreatic multipotent progenitors show impaired formation of Ngn3-expressing endocrine- committed precursors, and impaired formation of differentiated endocrine cells. Mapping the pattern of REST expression in wild type animals indicates that it is expressed in multipotent progenitors to become then excluded from endocrine cells. Preliminary results suggest that a downregulation of REST would result in relieved expression of at least the Mytl target, favoring subsequent acquisition of the endocrine competence by endocrine precursor cells.Thus, we propose that the REST/RE-1 system is an important feature for beta-cell neogenesis, function and survivalRESUMELe diabète se caractérise par une déficience en insuline qui résulte d'une destruction des cellules bêta (β) pancréatiques sécrétant l'insuline [Type 1], ou à un défaut de sécrétion d'insuline qui peut être associé à la mort des cellules β (Type 2). La compréhension des mécanismes de néogenèse des cellules β, ainsi que l'identification de gènes impliqués dans leur survie et dans le contrôle de la sécrétion d'insuline est donc importante pour le traitement du diabète. Le facteur de transcription de type répresseur, RE-1 Silencing Transcription Factor [REST], contribue à la spécificité d'expression dans les neurones et les cellules β, d'un grand nombre de gènes portant son motif de fixation, le Repressor Element-1 (RE-1). Pour cela, REST est exprimé dans toutes les cellules, sauf dans les neurones et les cellules β. Afin d'identifier les gènes cibles de REST ainsi que leur fonction au sein de la cellule β, nous avons généré des souris transgéniques qui expriment REST spécifiquement dans ces cellules, sous la dépendance du promoteur de l'insuline (souris RIP-REST]. Cette expression ectopique de REST a permis de diminuer l'expression des gènes contrôlés par REST, et d'en analyser les conséquences. Nous avons montré que les souris RIP-REST étaient intolérantes au glucose et que ceci était du à un défaut de sécrétion d'insuline. Pour expliquer ce phénotype, nous avons mis en évidence le fait que des gènes cibles de REST codent pour des protéines importantes pour l'exocytose de l'insuline, comme SNAP25, Synaptotagmin (Syt) IX, Complexin II ou ICA512. De plus, nous avons découvert deux nouvelles cibles de REST impliquées dans la sécrétion d'insuline, Syt IV et Syt VII. Par la suite, nous avons démontré qu'une nouvelle lignée de souris RIP-REST étaient atteintes d'un diabète sévère à cause d'une perte massive des cellules β. La disparition de ces cellules a été expliquée par l'identification de gènes cibles de REST impliqués dans la survie des cellules β, comme Ibl, Irs2, Ica512 ou la Connexine36. De plus, nous avons découvert qu'une nouvelle cible, Cdk5r2, était aussi impliquée dans la survie des cellules β. Dans une dernière partie, nous suggérons, grâce à l'analyse de nouvelles souris transgéniques exprimant constitutivement REST dans les cellules progénitrices du pancréas embryonnaire, que REST empêche la formation des précurseurs de cellules endocrines ainsi que la différenciation de ces cellules. L'analyse de l'expression de REST au cours du développement embryonnaire du pancréas indique que la diminution de l'expression de REST conduit en partie, à l'induction d'un de ses gènes cible Mytl, qui favorise la formation de précurseurs endocrines. Nous proposons donc que le système REST/RE-1 est important pour la génération, la fonction et la survie des cellules β.