Measuring Technology Achievement of Nations and the Capacity to Participate in the Network Age

human development, democracy

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Version anglaise disponible dans la Bibliothèque numérique du CRDI: Science and technology serving developmen

Tissue-Specific Transcriptomes Reveal Gene Expression Trajectories in Two Maturing Skin Epithelial Layers in Zebrafish Embryos.

Epithelial cells are the building blocks of many organs, including skin. The vertebrate skin initially consists of two epithelial layers, the outer periderm and inner basal cell layers, which have distinct properties, functions, and fates. The embryonic periderm ultimately disappears during development, whereas basal cells proliferate to form the mature, stratified epidermis. Although much is known about mechanisms of homeostasis in mature skin, relatively little is known about the two cell types in pre-stratification skin. To define the similarities and distinctions between periderm and basal skin epithelial cells, we purified them from zebrafish at early development stages and deeply profiled their gene expression. These analyses identified groups of genes whose tissue enrichment changed at each stage, defining gene flow dynamics of maturing vertebrate epithelia. At each of 52 and 72 hr post-fertilization (hpf), more than 60% of genes enriched in skin cells were similarly expressed in both layers, indicating that they were common epithelial genes, but many others were enriched in one layer or the other. Both expected and novel genes were enriched in periderm and basal cell layers. Genes encoding extracellular matrix, junctional, cytoskeletal, and signaling proteins were prominent among those distinguishing the two epithelial cell types. In situ hybridization and BAC transgenes confirmed our expression data and provided new tools to study zebrafish skin. Collectively, these data provide a resource for studying common and distinguishing features of maturing epithelia

A conserved morphogenetic mechanism for epidermal ensheathment of nociceptive sensory neurites.

Interactions between epithelial cells and neurons influence a range of sensory modalities including taste, touch, and smell. Vertebrate and invertebrate epidermal cells ensheath peripheral arbors of somatosensory neurons, including nociceptors, yet the developmental origins and functional roles of this ensheathment are largely unknown. Here, we describe an evolutionarily conserved morphogenetic mechanism for epidermal ensheathment of somatosensory neurites. We found that somatosensory neurons in Drosophila and zebrafish induce formation of epidermal sheaths, which wrap neurites of different types of neurons to different extents. Neurites induce formation of plasma membrane phosphatidylinositol 4,5-bisphosphate microdomains at nascent sheaths, followed by a filamentous actin network, and recruitment of junctional proteins that likely form autotypic junctions to seal sheaths. Finally, blocking epidermal sheath formation destabilized dendrite branches and reduced nociceptive sensitivity in Drosophila. Epidermal somatosensory neurite ensheathment is thus a deeply conserved cellular process that contributes to the morphogenesis and function of nociceptive sensory neurons

Is international agricultural research a global public good? : The case of rice biofortification

The status of international agricultural research as a global public good (GPG) has been widely accepted since the Green Revolution of the 1960s and 1970s. While the term was not used at the time of its creation, the Consultative Group on International Agricultural Research (CGIAR) system that evolved at that time has been described as a 'prime example of the promise, performance and perils of an international approach to providing GPGs'. Contemporary literature on international agricultural research as a GPG tends to support this view and focuses on how to operationalize the concept. This paper adopts a different starting point and questions this conceptualization of the CGIAR and its outputs. It questions the appropriateness of such a 'neutral' concept to a system born of the imperatives of Cold War geopolitics, and shaped by a history of attempts to secure its relevance in a changing world. This paper draws on a multi-sited, ethnographic study of a research effort highlighted by the CGIAR as an exemplar of GPG-oriented research. Behind the ubiquitous language of GPGs, 'partnership' and 'consensus', however, new forms of exclusion and restriction are emerging within everyday practice, reproducing North-South inequalities and undermining the ability of these programmes to respond to the needs of projected beneficiaries

Hydrogen Peroxide Promotes Injury-Induced Peripheral Sensory Axon Regeneration in the Zebrafish Skin

Production of H2O2 by injured zebrafish skin cells promotes the regeneration of nearby somatosensory axon terminals, thus coordinating wound healing of the skin with sensory reinnervation

Chromatin signature of embryonic pluripotency is established during genome activation

available in PMC 2011 April 8.After fertilization the embryonic genome is inactive until transcription is initiated during the maternal–zygotic transition. This transition coincides with the formation of pluripotent cells, which in mammals can be used to generate embryonic stem cells. To study the changes in chromatin structure that accompany pluripotency and genome activation, we mapped the genomic locations of histone H3 molecules bearing lysine trimethylation modifications before and after the maternal–zygotic transition in zebrafish. Histone H3 lysine 27 trimethylation (H3K27me3), which is repressive, and H3K4me3, which is activating, were not detected before the transition. After genome activation, more than 80% of genes were marked by H3K4me3, including many inactive developmental regulatory genes that were also marked by H3K27me3. Sequential chromatin immunoprecipitation demonstrated that the same promoter regions had both trimethylation marks. Such bivalent chromatin domains also exist in embryonic stem cells and are thought to poise genes for activation while keeping them repressed. Furthermore, we found many inactive genes that were uniquely marked by H3K4me3. Despite this activating modification, these monovalent genes were neither expressed nor stably bound by RNA polymerase II. Inspection of published data sets revealed similar monovalent domains in embryonic stem cells. Moreover, H3K4me3 marks could form in the absence of both sequence-specific transcriptional activators and stable association of RNA polymerase II, as indicated by the analysis of an inducible transgene. These results indicate that bivalent and monovalent domains might poise embryonic genes for activation and that the chromatin profile associated with pluripotency is established during the maternal–zygotic transition.National Institutes of Health (U.S.) (grant 1R01 HG004069)National Institutes of Health (U.S.) (grant 5R01 GM56211)Human Frontier Science Program (Strasbourg, France) (LT-00090/2007)European Molecular Biology Organization (fellowship