Wt1 is required for cardiovascular progenitor cell formation through transcriptional control of Snail and E-cadherin

Epicardial epithelial-mesenchymal transition (EMT) is hypothesized to generate cardiovascular progenitor cells that differentiate into various cell types, including coronary smooth muscle and endothelial cells, perivascular and cardiac interstitial fibroblasts and cardiomyocytes. Here we show that an epicardial-specific knockout of Wt1 leads to a reduction of mesenchymal progenitor cells and their derivatives. We demonstrate that Wt1 is essential for repression of the epithelial phenotype in epicardial cells and during Embryonic Stem (ES) cell differentiation, through direct transcriptional regulation of Snail (Snai1) and E-cadherin (Cdh1), two of the major mediators of EMT. Some mesodermal lineages fail to form in Wt1 null embryoid bodies but this effect is rescued by the expression of Snai1, underlining the importance of EMT in generating these differentiated cells. These new insights into the molecular mechanisms regulating cardiovascular progenitor cells and EMT will shed light on the pathogenesis of heart diseases and may help the development of cell based therapies

A Wt1-Controlled Chromatin Switching Mechanism Underpins Tissue-Specific Wnt4 Activation and Repression

SummaryWt1 regulates the epithelial-mesenchymal transition (EMT) in the epicardium and the reverse process (MET) in kidney mesenchyme. The mechanisms underlying these reciprocal functions are unknown. Here, we show in both embryos and cultured cells that Wt1 regulates Wnt4 expression dichotomously. In kidney cells, Wt1 recruits Cbp and p300 as coactivators; in epicardial cells it enlists Basp1 as a corepressor. Surprisingly, in both tissues, Wt1 loss reciprocally switches the chromatin architecture of the entire Ctcf-bounded Wnt4 locus, but not the flanking regions; we term this mode of action “chromatin flip-flop.” Ctcf and cohesin are dispensable for Wt1-mediated chromatin flip-flop but essential for maintaining the insulating boundaries. This work demonstrates that a developmental regulator coordinates chromatin boundaries with the transcriptional competence of the flanked region. These findings also have implications for hierarchical transcriptional regulation in development and disease

Genomics Meets Glycomics—The First GWAS Study of Human N-Glycome Identifies HNF1α as a Master Regulator of Plasma Protein Fucosylation

Over half of all proteins are glycosylated, and alterations in glycosylation have been observed in numerous physiological and pathological processes. Attached glycans significantly affect protein function; but, contrary to polypeptides, they are not directly encoded by genes, and the complex processes that regulate their assembly are poorly understood. A novel approach combining genome-wide association and high-throughput glycomics analysis of 2,705 individuals in three population cohorts showed that common variants in the Hepatocyte Nuclear Factor 1α (HNF1α) and fucosyltransferase genes FUT6 and FUT8 influence N-glycan levels in human plasma. We show that HNF1α and its downstream target HNF4α regulate the expression of key fucosyltransferase and fucose biosynthesis genes. Moreover, we show that HNF1α is both necessary and sufficient to drive the expression of these genes in hepatic cells. These results reveal a new role for HNF1α as a master transcriptional regulator of multiple stages in the fucosylation process. This mechanism has implications for the regulation of immunity, embryonic development, and protein folding, as well as for our understanding of the molecular mechanisms underlying cancer, coronary heart disease, and metabolic and inflammatory disorders

Development of HIS to improve technical knowledge on the reservoir and hydrodynamic functioning of the Rmel aquifer (Morocco)

La majorité des centres urbains et ruraux du bassin du Bas-Loukkos (nord du Maroc) sont généralement situés sur la côte et les plaines côtières. L'augmentation de la demande en eau due à la démographie et au développement agricole est accompagnée par une pression sur les eaux souterraines. Cette situation a entraîné une baisse significative du niveau piézométrique et peut éventuellement causer un déficit du bilan hydrique de la nappe en provoquant une dégradation de la qualité de l'eau douce par invasion des eaux marines. La zone d'étude de Rmel-Oulad Ogbane, couvrant une superficie de 305 km2, est située dans le bassin du Bas-Loukkos au sud de la ville de Larache. Afin de fournir une meilleure caractérisation de l’aquifère, il a été décidé d'organiser toutes les données dans des formats standard stockés dans une base de données numérique SIH (Système d'information hydrogéologique). Cette base de données SIH développée englobe un menu très varié relatif aux réservoirs et aux fonctionnements hydrodynamiques des ressources en eau. Les données issues de plusieurs sources et sur différents supports ont été traitées et organisées dans une base de données commune avec des coordonnées spatiales référencées. Une application Visual Basic a été aussi développée pour une meilleure utilisation et gestion de cette base de données sous SIH. Ainsi, plusieurs cartes thématiques relatives aux réservoirs et aux ressources en eau ont été produites pour être exploitées par le décideur. Ces produits de la base de données SIH ont permis l’actualisation du bilan hydrique de la nappe, la construction d’un bon modèle conceptuel des aquifères conduisant au développement d’un modèle mathématique en régimes permanent et transitoire, ainsi qu’un modèle de transport simulant l'intrusion de l'eau de mer dans ces aquifères.The majority of urban and rural centres of Low-Loukkos basin (Northern Morocco) are generally located on the coast and coastal plains. Due to demographic and agricultural development, increase in water demand has led to pressure on groundwater resources. This situation has caused significant drops in groundwater level and may eventually lead to a deficit in the water balance of the aquifer, as well as a degradation of the freshwater quality by seawater intrusion. The study area of Rmel-Ouled Ogbane aquifers covers approximately 305 km2 and is located in Low-Loukkos basin to the south of the city of Larache. In order to improve the characterization of the aquifers, we chose to organize all data in standard formats stored in a digital HIS (Hydrogeological Information System) database. This HIS database presents a varied menu related to reservoir aquifers and water resources. Data have been obtained from different sources on different supports and have been processed and organized in a single database with spatial coordinates. A Visual Basic application has also been developed for a better use and management of this HIS database. Several thematic maps of the aquifers and hydrodynamic functioning of water resources have been produced to be exploited by decision makers. These products of HIS database allowed to update the water balance and to build a good conceptual model of the aquifers conducting to the development of a set of groundwater numerical simulation models consisting in a mathematical model in steady state and transient flows, and a pollutant transport model to simulate seawater intrusion in these aquifers

Développement d’un sih pour l’amélioration des connaissances techniques sur le réservoir et le fonctionnement hydrodynamique de la nappe de Rmel (Maroc)

La majorité des centres urbains et ruraux du bassin du Bas-Loukkos (nord du Maroc) sont généralement situés sur la côte et les plaines côtières. L'augmentation de la demande en eau due à la démographie et au développement agricole est accompagnée par une pression sur les eaux souterraines. Cette situation a entraîné une baisse significative du niveau piézométrique et peut éventuellement causer un déficit du bilan hydrique de la nappe en provoquant une dégradation de la qualité de l'eau douce par invasion des eaux marines. La zone d'étude de Rmel-Oulad Ogbane, couvrant une superficie de 305 km2, est située dans le bassin du Bas-Loukkos au sud de la ville de Larache. Afin de fournir une meilleure caractérisation de l’aquifère, il a été décidé d'organiser toutes les données dans des formats standard stockés dans une base de données numérique SIH (Système d'information hydrogéologique). Cette base de données SIH développée englobe un menu très varié relatif aux réservoirs et aux fonctionnements hydrodynamiques des ressources en eau. Les données issues de plusieurs sources et sur différents supports ont été traitées et organisées dans une base de données commune avec des coordonnées spatiales référencées. Une application Visual Basic a été aussi développée pour une meilleure utilisation et gestion de cette base de données sous SIH. Ainsi, plusieurs cartes thématiques relatives aux réservoirs et aux ressources en eau ont été produites pour être exploitées par le décideur. Ces produits de la base de données SIH ont permis l’actualisation du bilan hydrique de la nappe, la construction d’un bon modèle conceptuel des aquifères conduisant au développement d’un modèle mathématique en régimes permanent et transitoire, ainsi qu’un modèle de transport simulant l'intrusion de l'eau de mer dans ces aquifères.The majority of urban and rural centres of Low-Loukkos basin (Northern Morocco) are generally located on the coast and coastal plains. Due to demographic and agricultural development, increase in water demand has led to pressure on groundwater resources. This situation has caused significant drops in groundwater level and may eventually lead to a deficit in the water balance of the aquifer, as well as a degradation of the freshwater quality by seawater intrusion. The study area of Rmel-Ouled Ogbane aquifers covers approximately 305 km2 and is located in Low-Loukkos basin to the south of the city of Larache. In order to improve the characterization of the aquifers, we chose to organize all data in standard formats stored in a digital HIS (Hydrogeological Information System) database. This HIS database presents a varied menu related to reservoir aquifers and water resources. Data have been obtained from different sources on different supports and have been processed and organized in a single database with spatial coordinates. A Visual Basic application has also been developed for a better use and management of this HIS database. Several thematic maps of the aquifers and hydrodynamic functioning of water resources have been produced to be exploited by decision makers. These products of HIS database allowed to update the water balance and to build a good conceptual model of the aquifers conducting to the development of a set of groundwater numerical simulation models consisting in a mathematical model in steady state and transient flows, and a pollutant transport model to simulate seawater intrusion in these aquifers

Induction of Mxi1-SRα by FOXO3a Contributes to Repression of Myc-Dependent Gene Expression▿ †

Forkhead transcription factors of the O class (FOXOs) are important targets of the phosphatidylinositol 3-kinase (PI3-kinase)/Akt pathway. FOXOs have been implicated in the regulation of cell cycle progression, oxidative stress resistance, and apoptosis. Using DNA microarrays, we analyzed the transcriptional response to FOXO3a activation by gene expression analysis in DLD-1 colon cancer cells stably expressing a FOXO3a.A3-ER fusion protein. We found that activation of FOXO3a resulted in repression of a number of previously identified Myc target genes. Furthermore, FOXO3a activation induced expression of several members of the Mad/Mxd family of transcriptional repressors, most notably Mxi1. The induction of Mxi1 by FOXO3a was specific to the Mxi1-SRα isoform and was mediated by three highly conserved FOXO binding sites within the first intron of the gene. Activation of FOXO3a in response to inhibition of Akt also resulted in activation of Mxi1-SRα expression. Silencing of Mxi1 by small interfering RNA (siRNA) reduced FOXO3a-mediated repression of a number of Myc target genes. We also observed that FOXO3a activation induced a switch in promoter occupancy from Myc to Mxi1 on the E-box containing promoter regions of two Myc target genes, APEX and FOXM1. siRNA-mediated transient silencing of Mxi1 or all Mad/Mxd proteins reduced exit from S phase in response to FOXO3a activation, and stable silencing of Mxi1 or Mad1 reduced the growth inhibitory effect of FOXO3a. We conclude that induction of Mad/Mxd proteins contributes to the inhibition of proliferation in response to FOXO3a activation. Our results provide evidence of direct regulation of Mxi1 by FOXO3a and imply an additional mechanism through which the PI3-kinase/Akt/FOXO pathway can modulate Myc function

Studying the subcellular localization and DNA-binding activity of FoxO transcription factors, downstream effectors of PI3K/Akt

This chapter describes methods for studying downstream events of the PI3K/Akt signaling cascade, focusing on the FoxO transcription factors. These approaches also represent alternative means for gauging the phosphoinositide-3 kinase/Akt activity. We describe protocols for the fractionation of cytoplasmic and nuclear protein extracts and for studying transcription factor DNA-binding activity in vitro and in vivo

Epstein-Barr Virus Represses the FoxO1 Transcription Factor through Latent Membrane Protein 1 and Latent Membrane Protein 2A

Epstein-Barr virus (EBV) infection is associated with the development of many B-cell lymphomas, including Burkitt's lymphoma, Hodgkin's lymphoma, and posttransplant lymphoproliferative disease. The virus alters a diverse range of cellular molecules, which leads to B-cell growth and immortalization. This study was initiated to investigate the interplay between EBV and a proapoptotic transcription factor target, FoxO1. In this report, we show that EBV infection of B cells leads to the downregulation of FoxO1 expression by phosphatidylinositol 3-kinase-mediated nuclear export, by inhibition of FoxO1 mRNA expression, and by alteration of posttranslational modifications. This repression directly correlates with the expression of the FoxO1 target gene Bcl-6 and inversely correlates with the FoxO1-regulated gene Cyclin D2. Expression of the EBV genes for latent membrane protein 1 and latent membrane protein 2A decreases FoxO1 expression. Thus, our data elucidate distinct mechanisms for the regulation of the proapoptotic transcription factor FoxO1 by EBV