10 research outputs found

    Evolutionary history of the iroquois/Irx genes in metazoans

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    <p>Abstract</p> <p>Background</p> <p>The <it>iroquois </it>(<it>iro/Irx</it>) genes encode transcriptional regulators that belong to the TALE superclass of homeodomain proteins and have key functions during development in both vertebrates and insects. The <it>Irx </it>genes occur in one or two genomic clusters containing three genes each within the <it>Drosophila </it>and several vertebrate genomes, respectively. The similar genomic organization in <it>Drosophila </it>and vertebrates is widely considered as a result of convergent evolution, due to independent tandem gene duplications. In this study, we investigate the evolutionary history of the <it>Irx </it>genes at the scale of the whole metazoan kingdom.</p> <p>Results</p> <p>We identified <it>in silico </it>the putative full complement of <it>Irx </it>genes in the sequenced genomes of 36 different species representative of the main metazoan lineages, including non bilaterian species, several arthropods, non vertebrate chordates, and a basal vertebrate, the sea lamprey. We performed extensive phylogenetic analyses of the identified <it>Irx </it>genes and defined their genomic organizations. We found that, in most species, there are several <it>Irx </it>genes, these genes form two to four gene clusters, and the <it>Irx </it>genes are physically linked to a structurally and functionally unrelated gene known as <it>CG10632 </it>in <it>Drosophila</it>.</p> <p>Conclusion</p> <p>Three main conclusions can be drawn from our study. First, an <it>Irx </it>cluster composed of two genes, <it>araucan/caupolican </it>and <it>mirror</it>, is ancestral to the crustaceans+insects clade and has been strongly conserved in this clade. Second, three <it>Irx </it>genes were probably present in the last common ancestor of vertebrates and the duplication that has given rise to the six genes organized into two clusters found in most vertebrates, likely occurred in the gnathostome lineage after its separation from sea lampreys. Third, the clustered organization of the <it>Irx </it>genes in various evolutionary lineages may represent an exceptional case of convergent evolution or may point to the existence of an <it>Irx </it>gene cluster ancestral to bilaterians.</p

    Identification and In Vivo Characterization of NvFP-7R, a Developmentally Regulated Red Fluorescent Protein of Nematostella vectensis

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    In recent years, the sea anemone Nematostella vectensis has emerged as a critical model organism for comparative genomics and developmental biology. Although Nematostella is a member of the anthozoan cnidarians (known for producing an abundance of diverse fluorescent proteins (FPs)), endogenous patterns of Nematostella fluorescence have not been described and putative FPs encoded by the genome have not been characterized.We described the spatiotemporal expression of endogenous red fluorescence during Nematostella development. Spatially, there are two patterns of red fluorescence, both restricted to the oral endoderm in developing polyps. One pattern is found in long fluorescent domains associated with the eight mesenteries and the other is found in short fluorescent domains situated between tentacles. Temporally, the long domains appear simultaneously at the 12-tentacle stage. In contrast, the short domains arise progressively between the 12- and 16-tentacle stage. To determine the source of the red fluorescence, we used bioinformatic approaches to identify all possible putative Nematostella FPs and a Drosophila S2 cell culture assay to validate NvFP-7R, a novel red fluorescent protein. We report that both the mRNA expression pattern and spectral signature of purified NvFP-7R closely match that of the endogenous red fluorescence. Strikingly, the red fluorescent pattern of NvFP-7R exhibits asymmetric expression along the directive axis, indicating that the nvfp-7r locus senses the positional information of the body plan. At the tissue level, NvFP-7R exhibits an unexpected subcellular localization and a complex complementary expression pattern in apposed epithelia sheets comprising each endodermal mesentery.These experiments not only identify NvFP-7R as a novel red fluorescent protein that could be employed as a research tool; they also uncover an unexpected spatio-temporal complexity of gene expression in an adult cnidarian. Perhaps most importantly, our results define Nematostella as a new model organism for understanding the biological function of fluorescent proteins in vivo

    Analyse de la spécificité fonctionnelle et de l'histoire évolutive des gènes du complexe iroquois de Drosophila melanogaster

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    Chez la drosophile, les trois gènes paralogues du complexe iroquois(araucan, caupolican et mirror) codent des facteurs de transcription à homéodomaine . Les homologues de ces gènes ont été identifiés dans toutes les espèces animales où ils ont été recherchés et constituent la famille des gènes iroquois. Ils sont généralement organisés en complexe (s). Le rôle particulier de chacun de ces gènes est un peu documenté. Mes travaux de thèse sur les trois gènes iroquois de la drosophile ont consisté à mettre en place les outils génétiques nécessaires pour étudier cette question. J ai ainsi pu montrer que, contrairement à l idée généralement admise, ces gènes jouent des rôles biologiques différents , notamment durant la mise en place du système nerveux périphérique, processus auquel je me suis particulièrement intéressé. J ai réussi à monter que les différents rôles observés de ces gènes ne sont pas seulement dus pour partie à des différences de profils d expression mais principalement à des spécificités fonctionnelles intrinsèques à chacune des protéines codées par ces gènes. D un point de vue évolutif, cela suggère que les trois gènes paralogues du complexe iroquois soient en cours de diversification fonctionnelle.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

    Feeding-dependent tentacle development in the sea anemone Nematostella vectensis

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    How the developmental capacity of long-lived animals copes with fluctuations in the food supply is unclear. Here, the authors show using the sea anemone Nematostella vectensis that the crosstalk between Target of Rapamycin and fibroblast growth factor signalling in ring muscles links postembryonic tentacle patterning with food availability

    Muscular hydraulics drive larva-polyp morphogenesis

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    Development is a highly dynamic process in which organisms often experience changes in both form and behavior, which are typically coupled to each other. However, little is known about how organismal-scale behaviors such as body contractility and motility impact morphogenesis. Here, we use the cnidarian Nematostella vectensis as a developmental model to uncover a mechanistic link between organismal size, shape, and behavior. Using quantitative live imaging in a large population of developing animals, combined with molecular and biophysical experiments, we demonstrate that the muscular-hydraulic machinery that controls body movement also drives larva-polyp morphogenesis. We show that organismal size largely depends on cavity inflation through fluid uptake, whereas body shape is constrained by the organization of the muscular system. The generation of ethograms identifies different trajectories of size and shape development in sessile and motile animals, which display distinct patterns of body contractions. With a simple theoretical model, we conceptualize how pressures generated by muscular hydraulics can act as a global mechanical regulator that coordinates tissue remodeling. Altogether, our findings illustrate how organismal contractility and motility behaviors can influence morphogenesis
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