Accelerated turnover of taste bud cells in mice deficient for the cyclin-dependent kinase inhibitor p27Kip1

Background: Mammalian taste buds contain several specialized cell types that coordinately respond to tastants and communicate with sensory nerves. While it has long been appreciated that these cells undergo continual turnover, little is known concerning how adequate numbers of cells are generated and maintained. The cyclin-dependent kinase inhibitor p27Kip1 has been shown to influence cell number in several developing tissues, by coordinating cell cycle exit during cell differentiation. Here, we investigated its involvement in the control of taste cell replacement by examining adult mice with targeted ablation of the p27Kip1 gene.Results: Histological and morphometric analyses of fungiform and circumvallate taste buds reveal no structural differences between wild-type and p27Kip1-null mice. However, when examined in functional assays, mutants show substantial proliferative changes. In BrdU incorporation experiments, more S-phase-labeled precursors appear within circumvallate taste buds at 1 day post-injection, the earliest time point examined. After 1 week, twice as many labeled intragemmal cells are present, but numbers return to wild-type levels by 2 weeks. Mutant taste buds also contain more TUNEL-labeled cells and 50% more apoptotic bodies than wild-type controls. In normal mice, p27 Kip1 is evident in a subset of receptor and presynaptic taste cells beginning about 3 days post-injection, correlating with the onset of taste cell maturation. Loss of gene function, however, does not alter the proportions of distinct immunohistochemically-identified cell types.Conclusions: p27Kip1 participates in taste cell replacement by regulating the number of precursor cells available for entry into taste buds. This is consistent with a role for the protein in timing cell cycle withdrawal in progenitor cells. The equivalence of mutant and wild-type taste buds with regard to cell number, cell types and general structure contrasts with the hyperplasia and tissue disruption seen in certain developing p27Kip1-null sensory organs, and may reflect a compensatory capability inherent in the regenerative taste system

Les Arts et les Lettres en Provence au temps du roi René

C’est à l’occasion du 600e anniversaire de la naissance de René, duc d’Anjou, comte de Provence et de la fondation d’Aix que s’est tenu à Aix-en-Provence, du 18 au 21 novembre 2009, le colloque international « Les arts et les lettres en Provence au temps du roi René : analyses, rayonnement, mémoire » dont ce volume constitue les Actes. Littéraires, historiens et historiens de l’art ont offert des approches nouvelles de ce prince, «  faisant contre mauvaise fortune bon cœur ». Ses écrits (Mortifiement de Vaine Plaisance, Livre du Cœur d’Amour épris, Livre des tournois) sont ici analysés tant pour leur valeur intrinsèque que pour leur influence sur la littérature du temps et au-delà, en France et en Italie. Ses relations avec l’Italie et la Flandre sont ici l’objet de découvertes essentielles pour comprendre sa politique culturelle en Provence. On voit par ailleurs comment les artistes et écrivains dont il s’entoure servent son goût pour la vie spirituelle, mais aussi pour la théâtralisation ou mise en spectacle festive de l’image qu’il entend donner de lui et du rôle princier. En ce XVe siècle finissant, René d’Anjou est délibérément tourné vers la modernité