Frédéric Biemar
University of Liège
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Publication
Featured researches published by Frédéric Biemar.
Journal of Cell Biology | 2003
Bart De Cat; S Muyldermans; Christien Coomans; Gisèle Degeest; Bernadette Vanderschueren; John Creemers; Frédéric Biemar; Bernard Peers; Guido David
Glypican (GPC)-3 inhibits cell proliferation and regulates cell survival during development. This action is demonstrated by GPC3 loss-of-function mutations in humans and mice. Here, we show that the GPC3 core protein is processed by a furinlike convertase. This processing is essential for GPC3 modulating Wnt signaling and cell survival in vitro and for supporting embryonic cell movements in zebrafish. The processed GPC3 core protein is necessary and sufficient for the cell-specific induction of apoptosis, but in vitro effects on canonical and noncanonical Wnt signaling additionally require substitution of the core protein with heparan sulfate. Wnt 5A physically associates only with processed GPC3, and only a form of GPC3 that can be processed by a convertase is able to rescue epiboly and convergence/extension movements in GPC3 morphant embryos. Our data imply that the Simpson–Golabi–Behmel syndrome may in part result from a loss of GPC3 controls on Wnt signaling, and suggest that this function requires the cooperation of both the protein and the heparan sulfate moieties of the proteoglycan.
FEBS Letters | 2000
Alfredo Molina; Frédéric Biemar; Ferenc Müller; Arati Iyengar; Patrick Prunet; Norman Maclean; Joseph A. Martial; Marc Muller
We isolated and characterized the tilapia (Oreochromis mossambicus) HSP70 gene, highly homologous to other HSP70 genes. A dramatic increase of tilapia HSP70 mRNA levels was observed after heat shock of whole animals in all organs tested. Reporter constructs were tested for transient expression in carp cells and in microinjected zebrafish embryos. The entire isolated regulatory region (−851/+157) was able to mediate heat shock inducible expression of the reporter gene, with no preference for a particular tissue. Our studies represent the first transcriptional analysis of a HSP70 promoter from fish, revealing a powerful tool to direct controlled, tissue‐independent gene expression in fish.
Mechanisms of Development | 2002
Nathalie Devos; Gianluca Deflorian; Frédéric Biemar; Marino Bortolussi; Joseph Martial; Bernard Peers; Francesco Argenton
We have identified the cDNAs of two new zebrafish preprosomatostatins, PPSS1 and PPSS3, in addition to the previously cloned PPSS2 (Argenton et al., 1999). PPSS1 is the orthologue of mammalian PPSSs, with a conserved C-terminal SS-14 sequence, PPSS2 is a divergent SS precursor and PPSS3 is a cortistatin-like prohormone. Using whole-mount in situ hybridisation, we have analysed the expression of PPSS1 and PPSS2 in zebrafish embryos up to 5 days post fertilisation. PPSS1 was expressed in the developing pancreas and central nervous system (CNS), whereas PPSS2 expression was exclusively pancreatic. In the CNS, PPSS1 was detected in several areas, in particular in the vagal motor nucleus and in cells that pioneer the tract of the postoptic commissure. PPSS1 was also expressed transiently in the telencephalon and spinal motor neurons. In all areas but the telencephalon PPSS1 was coexpressed with islet-1.
BMC Developmental Biology | 2008
François M Delporte; Vincent Pasque; Nathalie Devos; Isabelle Manfroid; Marianne Voz; Patrick Motte; Frédéric Biemar; Joseph Martial; Bernard Peers
BackgroundPAX6 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.ResultsDue 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.ConclusionOur 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.
Mechanisms of Development | 2001
Frédéric Biemar; Nathalie Devos; Joseph Martial; Wolfgang Driever; Bernard Peers
Meis and Prep/Pknox (MEINOX family) proteins, together with Pbx (PBC family) proteins, belong to the TALE superfamily characterized by an atypical homeodomain containing three additional amino acids between helix 1 and helix 2. Members of the MEINOX and PBC families have been isolated in Caenorhabditis elegans, Drosophila, Xenopus, chick, mouse and human, and play crucial roles in many aspects of embryogenesis. Here, we report the isolation of meis2 in zebrafish. Expression of meis2 is first detected at the beginning of gastrulation. Later during embryogenesis, meis2 transcripts are found in distinct domains of the central nervous system with the strongest expression in the hindbrain. Expression was also detected in the isthmus, along the spinal cord and in the lateral mesoderm. As development proceeds, meis2 is also expressed in the developing retina, pharyngeal arches, and in the vicinity of the gut tube.
Developmental Dynamics | 2006
Elin Ellertsdottir; Julia Ganz; Katrin Dürr; Niki T. Loges; Frédéric Biemar; Franziska Seifert; Anne Katrin Ettl; Albrecht Kramer-Zucker; Roland Nitschke; Wolfgang Driever
While there is a good conceptual framework of dorsoventral and anterioposterior axes formation in most vertebrate groups, understanding of left‐right axis initiation is fragmentary. Diverse mechanisms have been implied to contribute to the earliest steps of left‐right asymmetry, including small molecule signals, gap junctional communication, membrane potential, and directional flow of extracellular liquid generated by monocilia in the node region. Here we demonstrate that a mutation in the zebrafish Na,K‐ATPase subunit atp1a1a causes left‐right defects including isomerism of internal organs at the anatomical level. The normally left‐sided Nodal signal spaw as well as its inhibitor lefty are expressed bilaterally, while pitx2 may appear random or bilateral. Monocilia movement and fluid circulation in Kupffers vesicle are normal in atp1a1am883 mutant embryos. Therefore, the Na,K‐ATPase is required downstream or in parallel to monocilia function during initiation of left‐right asymmetry in zebrafish. Developmental Dynamics 235:1794–1808, 2006.
Journal of Biological Chemistry | 2010
Vincianne Verbruggen; Olivier Ek; Daphne Georlette; François M Delporte; Virginie Von Berg; Nathalie Detry; Frédéric Biemar; Pedro Coutinho; Joseph Martial; Marianne Voz; Isabelle Manfroid; Bernard Peers
Pax6 is a well conserved transcription factor that contains two DNA-binding domains, a paired domain and a homeodomain, and plays a key role in the development of eye, brain, and pancreas in vertebrates. The recent identification of the zebrafish sunrise mutant, harboring a mutation in the pax6b homeobox and presenting eye abnormalities but no obvious pancreatic defects, raised a question about the role of pax6b in zebrafish pancreas. We show here that pax6b does play an essential role in pancreatic endocrine cell differentiation, as revealed by the phenotype of a novel zebrafish pax6b null mutant and of embryos injected with pax6b morpholinos. Pax6b-depleted embryos have almost no β cells, a strongly reduced number of δ cells, and a significant increase of ϵ cells. Through the use of various morpholinos targeting intron-exon junctions, pax6b RNA splicing was perturbed at several sites, leading either to retention of intronic sequences or to deletion of exonic sequences in the pax6b transcript. By this strategy, we show that deletion of the Pax6b homeodomain in zebrafish embryos does not disturb pancreas development, whereas lens formation is strongly affected. These data thus provide the explanation for the lack of pancreatic defects in the sunrise pax6b mutants. In addition, partial reduction of Pax6b function in zebrafish embryos performed by injection of small amounts of pax6b morpholinos caused a clear rise in α cell number and in glucagon expression, emphasizing the importance of the fine tuning of the Pax6b level to its biological activity.
Biochimica et Biophysica Acta | 2001
Alfredo Molina; Arati Iyengar; Luis F. Marins; Frédéric Biemar; Sean Hanley; Norman Maclean; Terry J. Smith; Joseph Martial; Marc Muller
We have cloned and characterized a tilapia (Oreochromis mossambicus) L18 ribosomal protein gene, including the complete transcribed region and 488 bp of upstream regulatory sequences. We have also isolated two L18 cDNAs from another tilapia (Oreochromis niloticus) with a few conservative nucleotide differences. Our results suggest the presence of two genes in both species. Reporter constructs were tested for transient expression in CV1 cells and in microinjected zebrafish and tilapia embryos. The tilapia L18 promoter was able to drive expression of the reporter gene in all three experiments, with no apparent preference for a particular tissue. The tilapia L18 promoter is therefore likely to be a powerful tool to drive tissue-independent gene expression in fish.
Developmental Biology | 2001
Frédéric Biemar; Francesco Argenton; Regine Schmidtke; Simone Epperlein; Bernard Peers; Wolfgang Driever
Journal of Biological Chemistry | 1999
Ghylène Goudet; Sylvie Delhalle; Frédéric Biemar; Joseph Martial; Bernard Peers