Biomedical subjects

Alain Vincent

Publications and source records attributed to Alain Vincent.

11 recordsLinked to original sources

PubMed2005

Protein interaction mapping: a Drosophila case study.

The Drosophila (fruit fly) model system has been instrumental in our current understanding of human biology, development, and diseases. Here, we used a high-throughput yeast two-hybrid (Y2H)-based technology to screen 102 bait proteins from Drosophila melanogaster, most of them orthologous to human cancer-related and/or signaling proteins, against high-complexity fly cDNA libraries. More than 2300 protein-protein interactions (PPI) were identified, of which 710 are of high confidence. The computation of a reliability score for each protein-protein interaction and the systematic identification of the interacting domain combined with a prediction of structural/functional motifs allow the elaboration of known complexes and the identification of new ones. The full data set can be visualized using a graphical Web interface, the PIMRider (http://pim.hybrigenics.com), and is also accessible in the PSI standard Molecular Interaction data format. Our fly Protein Interaction Map (PIM) is surprisingly different from the one recently proposed by Giot et al. with little overlap between the two data sets. Analysis of the differences in data sets and methods suggests alternative strategies to enhance the accuracy and comprehensiveness of the post-genomic generation of broad-scale protein interaction maps.

Animals↗

PubMed2005

Shifted, the Drosophila ortholog of Wnt inhibitory factor-1, controls the distribution and movement of Hedgehog.

We here identify and characterize an extracellular modulator of Hedgehog signaling in Drosophila, Shifted. Shifted is required for high levels of long-range signaling in the developing wing imaginal disc. Surprisingly, shifted encodes the only Drosophila ortholog of the secreted vertebrate protein Wnt Inhibitory Factor-1 (WIF-1), whose known role is to bind to extracellular Wnts and inhibit their activity. However, Shifted does not regulate Hedgehog signaling by affecting Wingless or Wnt signaling. We show instead that Shifted is a secreted protein that acts over a long distance and is required for the normal accumulation of Hh protein and its movement in the wing. Our data further indicate that Shf interacts with Hh and the heparan sulfate proteoglycans. Therefore, we propose that Shf stabilizes the interaction between Hh and the proteoglycans, an unexpected role for a member of the WIF-1 family.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Cellular immune response to parasitization in Drosophila requires the EBF orthologue collier.

Drosophila immune response involves three types of hemocytes ('blood cells'). One cell type, the lamellocyte, is induced to differentiate only under particular conditions, such as parasitization by wasps. Here, we have investigated the mechanisms underlying the specification of lamellocytes. We first show that collier (col), the Drosophila orthologue of the vertebrate gene encoding early B-cell factor (EBF), is expressed very early during ontogeny of the lymph gland, the larval hematopoietic organ. In this organ, Col expression prefigures a specific posterior region recently proposed to act as a signalling centre, the posterior signalling centre (PSC). The complete lack of lamellocytes in parasitized col mutant larvae revealed the critical requirement for Col activity in specification of this cell type. In wild-type larvae, Col expression remains restricted to the PSC following parasitization, despite the massive production of lamellocytes. We therefore propose that Col endows PSC cells with the capacity to relay an instructive signal that orients hematopoietic precursors towards the lamellocyte fate in response to parasitization. Considered together with the role of EBF in lymphopoiesis, these findings suggest new parallels in cellular immunity between Drosophila and vertebrates. Further investigations on Col/EBF expression and function in other phyla should provide fresh insight into the evolutionary origin of lymphoid cells.

Animals↗

PubMed2004

Preoperative F-18 fluorodeoxyglucose-positron emission tomography maximal standardized uptake value predicts survival after lung cancer resection.

PURPOSE: A retrospective review of surgically treated lung cancer patients imaged preoperatively by F-18 fluorodeoxyglucose-positron emission tomography ([(18)F]FDG-PET) to determine if the primary tumor standardized uptake value (SUV) predicts survival. PATIENTS AND METHODS: Non-small-cell lung cancer or carcinoid pT1-4, N0-2, M0 patients treated by R0 surgical resection alone were imaged with computed tomography scan and PET within 90 days before surgery. Prognostic variables were assessed by log-rank test; survival was assessed by the method of Kaplan and Meier. RESULTS: One hundred consecutive patients (48 men, 52 women) were retrospectively reviewed. Median follow-up for surviving patients was 28 months (range, 16 to 81 months). Median maximal SUV (SUV(MAX)) was 9. The 2-year survival for patients with SUV(MAX) more than 9 was 68% and for those with SUV(MAX) less than 9, it was 96% (P <.01, log-rank test). In a multivariate analysis including pathologic tumor size, involved nodes, histology, and SUV(MAX), only tumor size (T) more than 3 cm and SUV(MAX) more than 9 and their interaction were significant predictors of survival (P =.01, 0.02, and < 0.01, respectively). The 3-year survivals for patients with both T less than 3 cm and SUV(MAX) less than 9 was 97%; for those with T less than 3 cm and SUV(MAX) more than 9, it was 94%; for those with T more than 3 cm and SUV(MAX) less than 9, it was 93%; and for those with T more than 3 cm and SUV(MAX) more than 9, it was 47% (P <.01). CONCLUSION: In surgically managed lung cancer patients, SUV is a predictor of overall survival after resection. The addition of SUV(MAX) to pathologic tumor size identifies a subgroup of patients at highest risk for death as a result of recurrent disease after resection.

Adult↗

PubMed2004

Expression patterns of the coe/ebf transcription factor genes during chicken and mouse limb development.

The COE (Collier/Olf/EBF) family of transcription factors comprises a single member in Drosophila and four members in human and mice. We have examined by in situ hybridization the expression patterns of each ebf/coe gene during limb development in mouse and chicken embryos. Expression of mouse ebf1, 2 and 3 is detected in mesenchymal cells from stages E10.5-11, expression of ebf2 being restricted to the presumptive zeugopod. Cross sections of mouse and chicken limb buds at several stages reveal that ebfs are specifically expressed in the connective tissues surrounding chondrogenic condensations and forming tendons. They thus represent useful new markers for studying vertebrate limb development, particularly formation of ligaments.

Animals↗

PubMed2004

Patterns in evolution: veins of the Drosophila wing.

The development of the Drosophila wing is a classical model for studying the genetic control of tissue size, shape and patterning. A detailed picture of how positional information is interpreted by cells in the imaginal disc and translated into the adult wing vein pattern has recently emerged. It highlights the central role of dose-dependent activation of distinct cell transcription programs in response to the Hedgehog (Hh) and Decapentaplegic (Dpp) morphogens, as well as an early role of Notch signalling, in connecting the positioning of vein primordia and vein differentiation proper. The biochemical basis of the cross-talk that operates between these different signalling pathways is less well understood. New strategies made possible by the genome sequencing of several insect models should provide an important complement to the knowledge obtained from >60 years of genetic studies.

Animals↗

PubMed2003

Vein-positioning in the Drosophila wing in response to Hh; new roles of Notch signaling.

The Drosophila wing is a classical model for studying the generation of developmental patterns. Previous studies have suggested that vein primordia form at boundaries between discrete sectors of gene expression along the antero-posterior (A/P) axis in the larval wing imaginal disc. Observation that the vein marker rhomboid (rho) is expressed at the centre of wider vein-competent domains led to propose that narrow vein primordia form first, and produce secondary short-range signals activating provein genes in neighbouring cells (see Curr. Opin. Genet. Dev. 10 (2000) 393). Here, we examined how the central L3 and L4 veins are positioned relative to the limits of expression of Collier (Col), a dose-dependent Hedgehog (Hh) target activated in the wing A/P organiser. We found that rho expression is first activated in broad domains adjacent to Col-expressing cells and secondarily restricted to the centre of these domains. This restriction which depends upon Notch (N) signaling sets the L3 and L4 vein primordia off the boundaries of Col expression. N activity is also required to fix the anterior limit of Col expression by locally antagonising Hh activation, thus precisely positioning the L3 vein primordium relative to the A/P compartment boundary. Experiments using Nts mutants further indicated that these two activities of N could be temporally uncoupled. Together, these observations highlight new roles of N in topologically linking the position of veins to prepattern gene expression.

Animals↗

PubMed2003

The dual function of ovo/shavenbaby in germline and epidermis differentiation is conserved between Drosophila melanogaster and the olive fruit fly Bactrocera oleae.

The olive fruit fly Bactrocera oleae (B. oleae) is a major olive damaging pest in the Mediterranean area. As a first molecular analysis of a developmental gene in this insect, we characterised the ovo/shavenbaby (ovo/svb) gene. In Drosophila, ovo/svb encodes a family of transcription regulators with two distinct functions: ovo is required for female germline differentiation and svb controls morphogenesis of epidermal cells. Here, we report the cloning and characterisation of ovo/svb in B. oleae, showing that the ovo genomic organisation and complex pattern of germline transcription have been conserved between distantly related Dipterae. We further show that B. oleae svb embryonic expression precisely prefigures the pattern of larval trichomes, supporting the conclusion that regulatory changes in svb transcription underlie evolutionary diversification of trichome patterns seen among Dipterae.

Amino Acid Sequence↗

PubMed2002

A germline-specific splicing generates an extended ovo protein isoform required for Drosophila oogenesis.

Most regulatory genes are employed multiple times to control different processes during development. The Drosophila Ovo/Shavenbaby (Svb) transcription factor is required both for germline and epidermal differentiation, two roles also found for its ortholog m-ovo1 in mice. In Drosophila, these two distinct functions are contributed by separate control regions directing the expression of Ovo/Svb in the germline (ovo) and soma (svb), respectively. We report here that alternative splicing represents an additional level of the regulation of Ovo/Svb functional specificity. Characterization of the ovo(D1rv23) mutation revealed that the intragenic insertion of a novel retrotransposon, romano, inactivates ovo without altering svb. We provide evidence that this insertion disrupts a germline-specific alternative exon, exon 2b, which encodes a 178-amino-acid internal extension (2B). While both isoforms, Ovo+2B and Ovo-2B, accumulate during oogenesis, only Ovo+2B is able to fulfill germinal ovo functions. Ovo-2B is unable, even when overexpressed, to fully rescue oogenic defects resulting from the absence of wild type ovo product. By contrast, either Ovo+2B or Ovo-2B germline protein can substitute for Svb in the epidermis. Our results emphasize the specific features of splicing in the germline, and reveal its functional importance for the control of ovo/svb-dependent ovarian and epidermal differentiation.

Alternative Splicing↗

PubMed2002

A P-insertion screen identifying novel X-linked essential genes in Drosophila.

The recent determination and annotation of the entire euchromatic sequence of the Drosophila melanogaster genome predicted the existence of about 13600 different genes (Science 287 (2000) 2185; http://www.fruitfly.org/annot/index.html). In parallel, the Berkeley Drosophila Genome Project (BDGP) has undertaken systematic P-insertion screens, to isolate new lethals and misexpressing lines. To date, however, the genes of the X chromosome have been under-represented in the screens performed. In order both to characterize several X-linked genes of prime interest to our laboratories and contribute to the collection of lethal P-insertions available to the community, we performed a P-insertion mutagenesis of the X chromosome. Using the PlacW and PGawB P-elements as mutagens, we generated two complementary sets of enhancer-trap lines, l(1)(T)PL and l(1)(T)PG, respectively, which both contain a reporter gene whose developmental expression can be monitored when driven by nearby enhancer sequences. We report here the characterization of 260 new insertions, mapping to 133 different genes or predicted CGs. Of these, 83 correspond to genes for which no lethal mutation had yet been reported. For 64 of those, we could confirm that lethality was solely due to the P-element insertion. The primary molecular data, reporter gene expression patterns (observed in embryos, third instar larvae and adult ovaries) and proposed CG assignment for each strain can be accessed and updated on our website at the following address: http://www-cbd.ups-tlse.fr:8080/screen.

Animals↗

PubMed2002

Connecting Hh, Dpp and EGF signalling in patterning of the Drosophila wing; the pivotal role of collier/knot in the AP organiser.

Hedgehog (Hh) signalling from posterior (P) to anterior (A) cells is the primary determinant of AP polarity in the limb field in insects and vertebrates. Hh acts in part by inducing expression of Decapentaplegic (Dpp), but how Hh and Dpp together pattern the central region of the Drosophila wing remains largely unknown. We have re-examined the role played by Collier (Col), a dose-dependent Hh target activated in cells along the AP boundary, the AP organiser in the imaginal wing disc. We found that col mutant wings are smaller than wild type and lack L4 vein, in addition to missing the L3-L4 intervein and mis-positioning of the anterior L3 vein. We link these phenotypes to col requirement for the local upregulation of both emc and N, two genes involved in the control of cell proliferation, the EGFR ligand Vein and the intervein determination gene blistered. We further show that attenuation of Dpp signalling in the AP organiser is also col dependent and, in conjunction with Vein upregulation, required for formation of L4 vein. A model recapitulating the molecular interplay between the Hh, Dpp and EGF signalling pathways in the wing AP organiser is presented.

Animals↗