Distinct Impacts of Eda and Edar Loss of Function on the Mouse Dentition

The Eda-A1-Edar signaling pathway is involved in the development of organs with an ectodermal origin, including teeth. In mouse, mutants are known for both the ligand, Eda-A1 (Tabby), and the receptor, Edar (Downless). The adult dentitions of these two mutants have classically been considered to be similar. However, previous studies mentioned differences in embryonic dental development between EdaTa and Edardl-J mutants. A detailed study of tooth morphology in mutants bearing losses of functions of these two genes thus appears necessary to test the pattern variability induced by the developmental modifications. 3D-reconstructions of the cheek teeth have been performed at the ESRF (Grenoble, France) by X-ray synchrotron microtomography to assess dental morphology. The morphological variability observed in EdaTa and Edardl-J mutants have then been compared in detail. Despite patchy similarities, our detailed work on cheek teeth in EdaTa and Edardl-J mice show that all dental morphotypes defined in Edardl-J mice resolutely differ from those of EdaTa mice. This study reveals that losses of function of Eda and Edar have distinct impacts on the tooth size and morphology, contrary to what has previously been thought. The results indicate that unknown mechanisms of the Eda pathway are implicated in tooth morphogenesis. Three hypotheses could explain our results; an unexpected role of the Xedar pathway (which is influenced by the Eda gene product but not that of Edar), a more complex connection than has been appreciated between Edar and another protein, or a ligand-independent activity for Edar. Further work is necessary to test these hypotheses and improve our understanding of the mechanisms of development

Un centre communal d’action sociale et des personnes âgées dépendantes. Quand la « prise en charge » cherche à faire une place à la « prise en compte » !

INTRODUCTION Vivement encouragé par l’équipe municipale à étendre son rôle de prévention et d’animation auprès des personnes âgées dépendantes, le Centre Communal d’Action Sociale (CCAS) dont il est ici question a considéré que pour mieux s’investir dans la prise en charge de ceux et celles qui en ont besoin, il convenait au préalable de les connaître davantage en procédant à un état des lieux de ce qu’ils pensent, ressentent et attendent. Dans cette perspective, une enquête par entretiens a ..

Looking beyond the genes: the interplay between signaling pathways and mechanics in the shaping and diversification of epithelial tissues

The core of Evo-Devo lies in the intuition that the way tissues grow during embryonic development, the way they sustain their structure and function throughout lifetime, and the way they evolve are closely linked. Epithelial tissues are ubiquitous in metazoans, covering the gut and internal branched organs, as well as the skin and its derivatives (ie, teeth). Here, we discuss in vitro, in vivo, and in silico studies on epithelial tissues to illustrate the conserved, dynamical, and complex aspects of their development. We then explore the implications of the dynamical and nonlinear nature of development on the evolution of their size and shape at the phenotypic and genetic levels. In rare cases, when the interplay between signaling and mechanics is well understood at the cell level, it is becoming clear that the structure of development leads to covariation of characters, an integration which in turn provides some predictable structure to evolutionary changes. We suggest that such nonlinear systems are prone to genetic drift, cryptic genetic variation, and context-dependent mutational effects. We argue that experimental and theoretical studies at the cell level are critical to our understanding of the phenotypic and genetic evolution of epithelial tissues, including carcinomas

What sharks and mammals share

International audienceThe tooth shape of sharks and mice are regulated by a similar signaling center despite their teeth having very different geometries

Les insulines des invertébrés sèment le trouble

Des travaux récents ont démontré la forte conservation de la voie de réponse aux peptides de type insuline/IGF (insulin growth factor) depuis les invertébrés jusqu’aux mammifères. Les études génétiques menées sur la drosophile ou le ver C. elegans ont en particulier démontré le rôle de cette voie dans la croissance tissulaire et la longévité. Très récemment, une famille importante de peptides insuliniques a été découverte dans ces deux organismes, suggérant de nouvelles fonctions associées à ces peptides ainsi que l’existence, chez les mammifères, d’autres membres de cette famille encore à découvrir

Contrôle génétique de la croissance tissulaire chez la drosophile (caractérisation de deux nouveaux régulateurs)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

A new genetic locus controlling growth and proliferation in Drosophila melanogaster.

Multicellular organisms grow through both proliferation and growth of their individual cells. We have conducted a P-element-based misexpression screen for genes whose upregulation alters wing disc growth during development. One particular group of four P elements, all inserted at cytological location 61C7-8, exhibited specific overgrowth upon misexpression in proliferating imaginal tissues. Clonal analysis revealed that upon misexpression, cell number was increased but cell size was not affected, indicating that cell growth and proliferation were induced in a coordinate manner. Loss of function at the locus produced small flies with reduced cell number, consistent with the presence of a gene encoding a positive growth regulator. We characterized a new transcription unit initiating in a region adjacent to the P insertions, which generated a complex series of polyadenylated transcripts. Although these RNAs were induced in response to misexpression, none was sufficient by itself to recapitulate overgrowth when overexpressed. This suggested either that a particular combination of these transcripts was necessary or that other sequences are involved