ΔNp63 Is Essential for Epidermal Commitment of Embryonic Stem Cells

In vivo studies have demonstrated that p63 plays complex and pivotal roles in pluristratified squamous epithelial development, but its precise function and the nature of the isoform involved remain controversial. Here, we investigate the role of p63 in epithelial differentiation, using an in vitro ES cell model that mimics the early embryonic steps of epidermal development. We show that the ΔNp63 isoform is activated soon after treatment with BMP-4, a morphogen required to commit differentiating ES cells from a neuroectodermal to an ectodermal cell fate. ΔNp63 gene expression remains high during epithelial development. P63 loss of function drastically prevents ectodermal cells to commit to the K5/K14-positive stratified epithelial pathway while gain of function experiments show that ΔNp63 allows this commitment. Interestingly, other epithelial cell fates are not affected, allowing the production of K5/K18-positive epithelial cells. Therefore, our results demonstrate that ΔNp63 may be dispensable for some epithelial differentiation, but is necessary for the commitment of ES cells into K5/K14-positive squamous stratified epithelial cells

Hypoxia-inducible factor 1α is a new target of microphthalmia-associated transcription factor (MITF) in melanoma cells

In melanocytes and melanoma cells α-melanocyte stimulating hormone (α-MSH), via the cAMP pathway, elicits a large array of biological responses that control melanocyte differentiation and influence melanoma development or susceptibility. In this work, we show that cAMP transcriptionally activates Hif1a gene in a melanocyte cell–specific manner and increases the expression of a functional hypoxia-inducible factor 1α (HIF1α) protein resulting in a stimulation of Vegf expression. Interestingly, we report that the melanocyte-specific transcription factor, microphthalmia-associated transcription factor (MITF), binds to the Hif1a promoter and strongly stimulates its transcriptional activity. Further, MITF “silencing” abrogates the cAMP effect on Hif1a expression, and overexpression of MITF in human melanoma cells is sufficient to stimulate HIF1A mRNA. Our data demonstrate that Hif1a is a new MITF target gene and that MITF mediates the cAMP stimulation of Hif1a in melanocytes and melanoma cells. Importantly, we provide results demonstrating that HIF1 plays a pro-survival role in this cell system. We therefore conclude that the α-MSH/cAMP pathway, using MITF as a signal transducer and HIF1α as a target, might contribute to melanoma progression

Implication de la voie GSK3b/béta caténine dans la sortie de l'état souche vers un état plus différencié des cellules initatrices de gliome

Les glioblastomes sont les tumeurs cérébrales primaires les plus fréquentes chez l adulte caractérisées par une forte capacité d infiltration. Ces tumeurs demeurent incurables en raison de leur résistance aux traitements conventionnels. Des populations de cellules tumorales à propriétés souches, appelées cellules souches cancéreuses ou cellules initiatrices de gliome (CiGs) dans le cas des gliomes, ont été décrites pour leur contribution à cette résistance. Cibler ces CiGs en forçant la sortie de l état souche vers un état plus différencié semble donc être une stratégie efficace pour inhiber leur tumorigénicité. Dans cette étude, nous avons démontré que GSK3-béta et Béta-caténine, plutôt connues pour leur implication dans le maintien des propriétés souches, sont cruciales non seulement pour induire mais aussi pour maintenir les CiGs dans un état plus différencié. En effet, nous avons trouvé que la GSK3-béta est responsable de la localisation nucléaire de Béta-caténine et de l expression de DOCK4. La Béta-caténine, transcriptionnellement active, est donc capable de se fixer sur son propre promoteur et sur celui de DOCK4, permettant leur expression constitutive. DOCK4 est en retour requis pour stabiliser Béta-caténine et conduire à une boucle de rétroaction positive, nécessaire à une différenciation effective des CiGs. En accord avec ces résultats, le profil d expression de DOCK4 est restreint aux territoires différenciés de glioblastomes, confirmant son rôle majeur dans le processus de sortie de l état souche. La Béta-caténine est également responsable de l expression du cluster-miR-302-367, qui constitue un effecteur clé de la perte de tumorigénicité des CiGs.Glioblastomas multiforme (GBM) are the most frequent primary brain tumors in the adult, highly infiltrative and characterized by an extensive vascularization. These tumors are considered incurable owing to their strong resistance towards conventional treatments. Subpopulations of cancer stem-like cells, so called glioma initiating cells (GiCs) in the case of gliomas, have been implicated in the resistance to drugs and radiotherapy. Targeting GiCs by forcing their exit from stemness towards a more differentiated state seems to be an efficient way to inhibit glioma cell tumorigenicity. In the present study we have demonstrated that GSK3-beta and Beta-catenin, previously well known for their contribution in maintaining cancer stem cells properties, are crucial for inducing not only GiC differentiation but also the stability of this more differentiated state. Mechanistically, we found that GSK3-beta is responsible for nuclear Beta-catenin localization and DOCK4 expression. Nuclear Beta-catenin binds to its own promoter as well as the DOCK4 promoter, thus enabling their transcriptional activity. DOCK4 protein is in turn required for Beta-catenin stabilization and nuclear transcriptional activity, thus orchestrating efficient GiC differentiation. Accordingly, DOCK4 protein is strongly expressed only in differentiated territories of GBM, confirming its major role in glioma stem cell differentiation. In such a mechanism, nuclear Beta-catenin is responsible for miR-302-367 cluster expression, which constitutes key effector for GiC differentiation and loss of tumorigenicity.NICE-BU Sciences (060882101) / SudocSudocFranceF

Bioconversion of agricultural lignocellulosic residues into branched-chain fatty acids using

Two lignocellulosic agricultural residues, sunflower stalks and rape straw, were investigated as potential low-cost, non-food substrates for the production of triacylglycerols by the oleaginous, lignocellulolytic bacteria Streptomyces lividans. Chemical analysis of each type of residue revealed similar cell wall compositions in the polysaccharides and lignins of the two feedstocks, with high lignin β-O-4 bond content compared to other angiosperms’ lignin. Growing tests of Streptomyces lividans TK 24 were performed before and after sequential water and ethanol extraction by assessing bacterial fatty acid accumulation. All extracted and non-extracted samples were found to be substrates of the bacteria with fatty acid production ranging between 19% and 44% of the production obtained with arabinose as a reference substrate. The maximum conversion rate was obtained with the less lignified, non-extracted sample. This study suggests that lignocellulosic residues from oleaginous crops could be advantageously valorized by microbial bioconversion processes for the production of lipids of interest

Bioconversion of agricultural lignocellulosic residues into branched-chain fatty acids using Streptomyces lividans

Two lignocellulosic agricultural residues, sunflower stalks and rape straw, were investigated as potential low-cost, non-food substrates for the production of triacylglycerols by the oleaginous, lignocellulolytic bacteria Streptomyces lividans. Chemical analysis of each type of residue revealed similar cell wall compositions in the polysaccharides and lignins of the two feedstocks, with high lignin β-O-4 bond content compared to other angiosperms’ lignin. Growing tests of Streptomyces lividans TK 24 were performed before and after sequential water and ethanol extraction by assessing bacterial fatty acid accumulation. All extracted and non-extracted samples were found to be substrates of the bacteria with fatty acid production ranging between 19% and 44% of the production obtained with arabinose as a reference substrate. The maximum conversion rate was obtained with the less lignified, non-extracted sample. This study suggests that lignocellulosic residues from oleaginous crops could be advantageously valorized by microbial bioconversion processes for the production of lipids of interest

SETMAR Shorter Isoform: A New Prognostic Factor in Glioblastoma

International audienceRecent evidence suggests that the chimeric protein SETMAR is a factor of interest in cancer, especially in glioblastoma. However, little is known about the expression of this protein in glioblastoma tissues, and no study has been done to assess if SETMAR could be a prognostic and/or diagnostic marker of glioblastoma. We analyzed protein extracts of 47 glioblastoma samples coming from a local and a national cohort of patients. From the local cohort, we obtained localized biopsies from the central necrosis area, the tumor, and the perilesional brain. From the French Glioblastoma Biobank (FGB), we obtained three types of samples: from the same tumors before and after treatment, from long survivors, and from very short survivors. We studied the correlations between SETMAR amounts, clinical profiles of patients and other associated proteins (PTN, snRNP70 and OLIG2). In glioblastoma tissues, the shorter isoform of SETMAR (S-SETMAR) was predominant over the full-length isoform (FL-SETMAR), and the expression of both SETMAR variants was higher in the tumor compared to the perilesional tissues. Data from the FGB showed that SETMAR amounts were not different between the initial tumors and tumor relapses after treatment. These data also showed a trend toward higher amounts of S-SETMAR in long survivors. In localized biopsies, we found a positive correlation between good prognosis and large amounts of S-SETMAR in the perilesional area. This is the main result presented here: survival in Glioblastoma is correlated with amounts of S-SETMAR in perilesional brain, which should be considered as a new relevant prognosis marker