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See detailExpression of zebrafish pax6b in pancreas is regulated by two enhancers containing highly conserved cis-elements bound by PDX1, PBX and PREP factors
Delporte, F. M.; Pasque, Vincent; Devos, Nathalie et al

in BMC Developmental Biology (2008), 8

BACKGROUND: PAX6 is a transcription factor playing a crucial role in the development of the eye and in the differentiation of the pancreatic endocrine cells as well as of enteroendocrine cells. Studies on ... [more ▼]

BACKGROUND: PAX6 is a transcription factor playing a crucial role in the development of the eye and in the differentiation of the pancreatic endocrine cells as well as of enteroendocrine cells. Studies on the mouse Pax6 gene have shown that sequences upstream from the P0 promoter are required for expression in the lens and the pancreas; but there remain discrepancies regarding the precise location of the pancreatic regulatory elements. RESULTS: Due to genome duplication in the evolution of ray-finned fishes, zebrafish has two pax6 genes, pax6a and pax6b. While both zebrafish pax6 genes are expressed in the developing eye and nervous system, only pax6b is expressed in the endocrine cells of the pancreas. To investigate the cause of this differential expression, we used a combination of in silico, in vivo and in vitro approaches. We show that the pax6b P0 promoter targets expression to endocrine pancreatic cells and also to enteroendocrine cells, retinal neurons and the telencephalon of transgenic zebrafish. Deletion analyses indicate that strong pancreatic expression of the pax6b gene relies on the combined action of two conserved regulatory enhancers, called regions A and C. By means of gel shift assays, we detected binding of the homeoproteins PDX1, PBX and PREP to several cis-elements of these regions. In constrast, regions A and C of the zebrafish pax6a gene are not active in the pancreas, this difference being attributable to sequence divergences within two cis-elements binding the pancreatic homeoprotein PDX1. CONCLUSION: Our data indicate a conserved role of enhancers A and C in the pancreatic expression of pax6b and emphasize the importance of the homeoproteins PBX and PREP cooperating with PDX1, in activating pax6b expression in endocrine pancreatic cells. This study also provides a striking example of how adaptative evolution of gene regulatory sequences upon gene duplication progressively leads to subfunctionalization of the paralogous gene pair. [less ▲]

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See detailInhibition of tumor growth and metastasis establishment by adenovirus-mediated gene transfer delivery of the antiangiogenic factor 16K hPRL
Nguyen, Ngoc-Quynh-Nhu ULg; Cornet, Anne ULg; Blacher, Silvia ULg et al

in Molecular Therapy : The Journal of the American Society of Gene Therapy (2007), 15(12), 2094-2100

Tumor metastases, the most fearsome aspect of cancer, are generally resistant to conventional therapies. Angiogenesis is a crucial aspect of tumor growth and metastatic dissemination. Antiangiogenic ... [more ▼]

Tumor metastases, the most fearsome aspect of cancer, are generally resistant to conventional therapies. Angiogenesis is a crucial aspect of tumor growth and metastatic dissemination. Antiangiogenic therapy, therefore, holds potential as an attractive strategy for inhibiting metastasis development. Human 16K PRL (16K hPRL), a potent inhibitor of angiogenesis, has been demonstrated to prevent tumor growth in two xenograft mouse models, but whether it also affects tumor metastasis is unknown. In this study we will investigate the ability of 16K hPRL to prevent the establishment of metastasis. We demonstrate that 16K hPRL administered via adenovirus-mediated gene transfer, inhibits tumor growth by 86% in a subcutaneous (SC) B16-F10 mouse melanoma model. Computer-assisted image analysis shows that 16K hPRL treatment results in a reduction of tumor-vessel length and width, leading to a 57% reduction of average vessel size. In a pre-established tumor model, moreover, 16K hPRL can significantly delay tumor development. Finally, for the first time, we provide evidence that 16K hPRL considerably reduces the establishment of B16-F10 metastasis in an experimental lung metastasis model. Both the number and size of metastases are reduced by 50% in 16K hPRL-treated mice. These results highlight a potential role for 16K hPRL in anticancer therapy for both primary tumors and metastases. [less ▲]

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See detailThe expression of prolactin and its cathepsin D-mediated cleavage in the bovine corpus luteum vary with the estrous cycle
Erdmann, S.; Ricken, A.; Merkwitz, C. et al

in American Journal of Physiology - Endocrinology and Metabolism (2007), 293(5), 1365-1377

In the corpus luteum (CL), blood vessels develop, stabilize, and regress. This process depends on the ratio of pro-and antiangiogenic factors, which change during the ovarian cycle. The present study ... [more ▼]

In the corpus luteum (CL), blood vessels develop, stabilize, and regress. This process depends on the ratio of pro-and antiangiogenic factors, which change during the ovarian cycle. The present study focuses on the possible roles of 23,000 (23K) prolactin (PRL) in the bovine CL and its antiangiogenic NH2-terminal fragments after extracellular cleavage by cathepsin D (Cath D). PRL RNA and protein were demonstrated in the CL tissue, in luteal endothelial cells, and in steroidogenic cells. Cath D was detected in CL tissue, cell extracts, and corresponding cell supernatants. In the intact CL, 23K PRL levels decreased gradually, whereas Cath D levels concomitantly increased between early and late luteal stages. In vitro, PRL cleavage occurred in the presence of acidified homogenates of CL tissue, cells, and corresponding cell supernatants. Similar fragments were obtained with purified Cath D, and their appearance was inhibited by pepstatin A. The aspartic protease specific substrate MOCAc-GKPILF similar to FRLK(Dnp)-D-R-NH2 was cleaved by CL cell supernatants, providing further evidence for Cath D activity. The 16,000 PRL inhibited proliferation of luteal endothelial cells accompanied by an increase in cleaved caspase-3. In conclusion, 1) the bovine CL is able to produce PRL and to process it into antiangiogenic fragments by Cath D activity and 2) PRL cleavage might mediate angioregression during luteolysis. [less ▲]

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See detailTIM crystals grown by capillary counterdiffusion: Statistical evidence of quality improvement in microgravity
Evrard, Christine ULg; Maes, D.; Zegers, I. et al

in Crystal Growth & Design (2007), 7(11), 2161-2166

The capillary counterdiffusion method is a very efficient crystallization technique for obtaining high-quality protein crystals. This technique requires a convection-free environment, which can be ... [more ▼]

The capillary counterdiffusion method is a very efficient crystallization technique for obtaining high-quality protein crystals. This technique requires a convection-free environment, which can be achieved using either gelled solutions, very thin capillaries, or microgravity conditions. To study the influence of a convection-free environment on protein crystal quality and to evaluate two different experimental implementations to achieve it, we have made a comparative analysis of crystals grown by capillary counterdiffusion in agarose, a convective-free environment on Earth, and crystals grown in microgravity at the International Space Station. Thermotoga maritima triose phosphate isomerase (TIM) was chosen as a model for this study. The statistical analysis reveals a significant improvement for the crystals grown in microgravity in terms of their R-merge, B-value, and mosaicity, but the statistical evidence is insufficient to show a similar benefit for the resolution and mean intensity parameters. These results are quite surprising because it is known that, unlike gels, the noisy microgravity scenario offered by the ISS cannot sustain a convection-free environment on the time scale of days required for protein crystallization experiments. [less ▲]

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See detailDetection of micro-RNA/gene interactions involved in angiogenesis using machine learning techniques
Huynh-Thu, Vân Anh ULg; Hiard, Samuel ULg; Geurts, Pierre ULg et al

Poster (2007, September)

Motivation: Angiogenesis is the process responsible for the growth of new blood vessels from existing ones. It is also associated with the development of cancer, as tumors need to be irrigated by blood ... [more ▼]

Motivation: Angiogenesis is the process responsible for the growth of new blood vessels from existing ones. It is also associated with the development of cancer, as tumors need to be irrigated by blood vessels for growing. New cancer therapies appear that exploit angiogenesis inhibitors, also called angiostatic agents, to asphyxiate and starve the tumors. Better understanding the regulatory mechanisms that control angiogenesis is thus fundamental. Recently, short non-coding RNA molecules, called micro-RNAs, have been discovered that are involved in post- transcriptional regulation of gene expressions. These molecules bind to RNA messengers following the base pairing rules, preventing them from being translated into proteins and/or tagging them for degradation. The main goal of this work is to use computational approaches to identify micro-RNAs involved in angiogenesis. Method: In order to identify genes involved in angiogenesis, bovine endothelial cells were treated by a known angiogenesis inhibitor [1], prolactin 16K, and their gene expression profile was compared to the profile of untreated cells. The genes were then divided into three classes: up-regulated, down-regulated, and unaffected genes. The 3'UTR regions of these genes were then analysed by machine learning techniques. Different approaches were considered. First, we described each gene by a vector of motif counts in their 3'UTR regions and used machine learning techniques to rank the motifs according to their relevance for separating the genes into the different classes. We considered successively motifs corresponding to the seeds of known micro- RNAs and also all possible motifs of a given length. To rank the motifs, we compared ensemble of decision trees and linear support vector machines. Second, we considered an approach called Segment and Combine that was proposed in [2]. Finally, we also carried out an exhaustive search of all motifs of a given length that satisfy some constraints on specificity and coverage with respect to a given gene category. Results: The ability of the different approaches at identifying relevant motifs was first assessed on genes predicted to be the target of some known miRNAs. In this simple setting, most methods were able to identify the micro-RNA seed. The results obtained on the genes regulated by prolactin 16K are also very encouraging. We were able to identify one micro-RNA already known to play a role in angiogenesis and several motifs are predicted by different approaches as very specific of up- or down-regulation by prolactin 16K. Their relationship with known micro-RNAs is certainly worth exploring. Conclusion: Machine learning approaches are promising techniques for the identification of micro-RNA/gene interactions. Future work will concern the application of the same kind of techniques on promoters for the identification of transcription factor binding sites. [less ▲]

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See detailSox4b is required for pituitary expression of gata2 and specification of thyrotrope cells in zebrafish
Muller, Marc ULg; Mavropoulos, A.; Nica, G. et al

in Developmental Biology (2007, June 01), 306(1), 438-439

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See detailAntiangiogenic peptides
Martial, Joseph ULg; Struman, Ingrid ULg; Nguyen, Ngoc-Quynh-Nhu ULg et al

Patent (2007)

The present invention refers to antiangiogenic peptides, especially to tilted peptides having antiangiogenic properties and peptides from the prolactin/growth hormone familiy having antiangiogenic ... [more ▼]

The present invention refers to antiangiogenic peptides, especially to tilted peptides having antiangiogenic properties and peptides from the prolactin/growth hormone familiy having antiangiogenic properties. [less ▲]

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See detailReciprocal endoderm-mesoderm interactions mediated by fgf24 and fgf10 govern pancreas development
Manfroid, Isabelle ULg; Delporte, F.; Baudhuin, A. et al

in Development (2007), 134(22), 4011-21

In amniotes, the pancreatic mesenchyme plays a crucial role in pancreatic epithelium growth, notably through the secretion of fibroblast growth factors. However, the factors involved in the formation of ... [more ▼]

In amniotes, the pancreatic mesenchyme plays a crucial role in pancreatic epithelium growth, notably through the secretion of fibroblast growth factors. However, the factors involved in the formation of the pancreatic mesenchyme are still largely unknown. In this study, we characterize, in zebrafish embryos, the pancreatic lateral plate mesoderm, which is located adjacent to the ventral pancreatic bud and is essential for its specification and growth. We firstly show that the endoderm, by expressing the fgf24 gene at early stages, triggers the patterning of the pancreatic lateral plate mesoderm. Based on the expression of isl1, fgf10 and meis genes, this tissue is analogous to the murine pancreatic mesenchyme. Secondly, Fgf10 acts redundantly with Fgf24 in the pancreatic lateral plate mesoderm and they are both required to specify the ventral pancreas. Our results unveil sequential signaling between the endoderm and mesoderm that is critical for the specification and growth of the ventral pancreas, and explain why the zebrafish ventral pancreatic bud generates the whole exocrine tissue. [less ▲]

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See detailEvaluation of the antitumor activity of 16K prolactin
Kinet, Virginie; Nguyen, Ngoc-Quynh-Nhu ULg; Cornet, Anne ULg et al

Poster (2007)

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See detailProtein crystallisation under microgravity conditions: What did we learn on TIM crystallisation from the Soyuz missions?
MAES, D.; DECANNIERE, K.; ZEGERS, I. et al

in Microgravity Science and Technology (2007), XIX(5/6), 90-94

The protein Triose Phosphate Isomerase from the hyperthermophilic organism Thermotoga maritima was crystallised on board of the International Space Station in the framework of the Soyuz missions. In this ... [more ▼]

The protein Triose Phosphate Isomerase from the hyperthermophilic organism Thermotoga maritima was crystallised on board of the International Space Station in the framework of the Soyuz missions. In this paper we report on the scientific results obtained during these flights. Firstly it qas shown that different crystal forms for the same protein in the same crystallisation conditions, what is presumably due to a change in the rate at which supersaturation is achieved. Secondly, the X-ray qualité of the crystals grown in the ISS is superior to their ground control crystals. Mimicking microgravity on ground, by adding a small amourt of gel to avoid convection, also results in an improvement of X-ray quality. Nevertheless our analysis shows that the crystals obtained in this gelled ground environment are of inferior quality as compared to their space homologues. Finally we observed movement of crystals grown in the International Space Station, not only because of g-jitters but also due to residual accelerations. This has an important effect on concentration gradients of precipiants and therefore on the solubility of the protein. [less ▲]

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See detailThe angiostatic 16K human prolactin overcomes endothelial cell anergy and promotes leukocyte infiltration via nuclear factor-kappaB activation
Tabruyn, Sébastien ULg; Sabatel, Céline ULg; Nguyen, Ngoc-Quynh-Nhu ULg et al

in Molecular Endocrinology (2007), 21(6), 1422-9

The 16-kDa N-terminal fragment of human prolactin (16K hPRL) is a potent angiostatic factor that inhibits tumor growth in mouse models. Using microarray experiments, we have dissected how the endothelial ... [more ▼]

The 16-kDa N-terminal fragment of human prolactin (16K hPRL) is a potent angiostatic factor that inhibits tumor growth in mouse models. Using microarray experiments, we have dissected how the endothelial-cell genome responds to 16K hPRL treatment. We found 216 genes that show regulation by 16K hPRL, of which a large proportion turned out to be associated with the process of immunity. 16K hPRL induces expression of various chemokines and endothelial adhesion molecules. These expressions, under the control of nuclear factor-kappaB, result in an enhanced leukocyte-endothelial cell interaction. Furthermore, analysis of B16-F10 tumor tissues reveals a higher expression of adhesion molecules (intercellular adhesion molecule 1, vascular cell adhesion molecule 1, or E-selectin) in endothelial cells and a significantly higher number of infiltrated leukocytes within the tumor treated with 16K hPRL compared with the untreated ones. In conclusion, this study describes a new antitumor mechanism of 16K hPRL. Because cellular immunity against tumor cells is a crucial step in therapy, the discovery that treatment with 16K hPRL overcomes tumor-induced anergy may become important for therapeutic perspectives. [less ▲]

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See detailCrystallization of ornithine acetyltransferase from yeast by counter-diffusion and preliminary X-ray study
Maes, D.; Crabeel, M.; Van de Weerdt, Cécile ULg et al

in Acta Crystallographica Section F-Structural Biology and Crystallization Communications (2006), 62(Part 12), 1294-1297

A study is presented on the crystallization of ornithine acetyltransferase from yeast, which catalyzes the fifth step in microbial arginine synthesis. The use of the counter-diffusion technique removes ... [more ▼]

A study is presented on the crystallization of ornithine acetyltransferase from yeast, which catalyzes the fifth step in microbial arginine synthesis. The use of the counter-diffusion technique removes the disorder present in one dimension in crystals grown by either the batch or hanging-drop techniques. This makes the difference between useless crystals and crystals that allow successful determination of the structure of the protein. The crystals belong to space group P4, with unit-cell parameters a = b = 66.98, c = 427.09 angstrom, and a data set was collected to 2.76 angstrom. [less ▲]

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See detailMolecular profiling of 16K PRL treated tumours by an antibody-array approach
Cornet, Anne ULg; Nguyen, Ngoc-Quynh-Nhu ULg; Lion, Michelle ULg et al

Poster (2006, May)

Tumour development is often accompanied by the formation of new blood vessels from existing vasculature. This new intratumoral blood network is driven by the process of angiogenesis, providing the ... [more ▼]

Tumour development is often accompanied by the formation of new blood vessels from existing vasculature. This new intratumoral blood network is driven by the process of angiogenesis, providing the essential nutrients for growth, invasion and metastasis. At the present time, it is well established that inhibitors of angiogenesis prevent the growth and progression of tumours, offering a new therapeutic approach for treatment of cancer. Several studies have already showed that the N-terminal fragment of the human prolactin, 16k-Da PRL, has a potent anti-angiogenic activity. Recently, research groups have demonstrated that the 16k-Da PRL inhibits tumour development in animal models. Despite the fact that several studies leading to improve our knowledge of 16k-Da PRL action were performed, little is known about its role played to prevent tumour growth in vivo. In this study, we first tested the ability of the 16k-Da PRL to inhibit the growth of established HCT116 tumours in nude mice, using an adenovirus approach. As expected, we found that the tumour progression was tightly reduced by the expression of the 16k-Da PRL into the tumours. This antitumour activity was also associated with a slight tumour vascularization. To discover biomarkers that contribute in 16k-Da PRL tumour suppressive effects, we used one of the most powerful multiplexed detection techonologies: the antibody-microarray proposed by Eurogentec. These protein-chips allow to identify multiple proteins from small amounts of samples within a single experiment. Three independent sets of antibody array from samples of 16k-Da PRL treated tumours and controls were analysed. Experimental and analysis optimisations were applied to ensure the correct interpretation of the fluorescent signals from the antibody arrays. In addition, significant results were confirmed by Western blot analysis. Our study allowed to identify several proteins which could be implicated in the tumour dormancy induced by 16k-Da PRL treatment. Additional analysis will provide important biological information for discovering of the new cancer biomarkers and their relationship with the 16k-Da PRL effects on cancer development. [less ▲]

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See detailExpression of the somatolactin beta gene during zebrafish embryonic development
Lopez, Mauricio; Nica, G.; Motte, Patrick ULg et al

in Gene Expression Patterns (2006), 6(2), 156-161

Somatolactin (Sl) is a pituitary hormone closely related to prolactin (Prl) and growth hormone that was until now only found in various fish species. We isolated the cDNA coding for zebrafish Sl beta and ... [more ▼]

Somatolactin (Sl) is a pituitary hormone closely related to prolactin (Prl) and growth hormone that was until now only found in various fish species. We isolated the cDNA coding for zebrafish Sl beta and we identified the gene encoding this hormone. We also obtained a 1 kb genomic fragment corresponding to the sl beta upstream promoter region. Furthermore, the sl beta expression pattern was examined during zebrafish embryogenesis using whole-mount in situ hybridization. Sl beta mRNA is first detected in a single cell at the anterior border of the neural plate starting at 23 h post fertilization (hpf). Sl beta-expressing cells also express the transcription factor pit1 and are located close to prl-expressing cells. Using combined fluorescent in situ hybridization, we show that sl beta- and prl-expressing cells are clearly distinct at 29 hpf. Starting at 30 hpf, the number of sl beta positive cells increases and their location becomes more clearly distinct from lactotrope cells, in a more posterior position. At later stages (48 hpf), sl beta expression was observed posterior to growth hormone expression, again in a distinct cell type. We show that zebrafish mutants aal, as well as mutants in the pit1 gene, are deficient in sl beta expression. In conclusion, sl beta expression defines a new, additional cell type in zebrafish pituitary that depends on pit1 and aal for its differentiation. (C) 2005 Elsevier B.V. All rights reserved. [less ▲]

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