Abstracts - Deutsche Zoologische Gesellschaft

14 Key Lectures of the SymposiaS DB.1 (Su) - ENNovel genes control species-specific morphological traits in the genus HydraKonstantin Khalturin, Friederike Anton-Erxleben, Jörg Wittlieb, Georg Hemmrich, Thomas C.G.BoschZoological Institute, University of KielUnderstanding the molecular events that underlie the evolution of morphological diversity is a majorchallenge in biology. To identify genes whose expression correlates with species-specific morphologieswe compared transcriptoms of two closely related Hydra species. We found that developmentof species-specific structures is correlated with expression of taxonomically restricted genes (TRGs).We functionally analyzed the role of one of the TRGs in affecting tentacle formation in Hydra. Weshow that gain-of-function induces changes in morphology which mirror phenotypic differencesobserved between species. Thus, taxonomically restricted genes are involved in the generation ofspecies-specific morphological traits.S DB.2 (Su) - ENMolecular mechanisms of tectal development in vertebratesDorothea Schulte, Anja Badde, Antje Vennemann, Zsuzsa AgostonAbteilung Neuroanatomie, Max-Planck-Institut für Hirnforschung, Frankfurt a.M.The fundamental plan of the vertebrate brain is laid down as a series of vesicles by the time the neuraltube closes. The mesencephalic vesicle is the embryonic precursor of the adult midbrain structuresincluding the tectum, whereas the anterior hindbrain gives rise to the adult cerebellum. Earlydevelopment of the mid-hindbrain region is governed by the mid-hindbrain boundary (MHB) organizer,a signaling center located at the boundary between the mid- and hindbrain vesicles. Its activityis regulated by an interdependent network of nuclear factors and secreted proteins, which includesmembers of the Fgf- and Wnt-families. We provide evidence for a new player in this network, theReceptor Tyrosine Phosphatase lambda (RPTPlambda). Using gain-of-function and loss-of-functionapproaches in chick embryos we show that this molecule impacts on midbrain development in a dualway: it negatively regulates the expression of the secreted protein Wnt1, an important mediator ofMHB organizer function. This helps to confine Wnt1 activity to its characteristic narrow domain atthe MHB organizer. In addition, RPTPlambda binds to and can presumably sequester b-catenin, acentral component of the canonical Wnt signaling pathway, and thereby controls the growth of thefuture midbrain.S EB.1 (Sa) - ENBiogeographical and evolutionary importance of the European high mountainsystemsThomas SchmittBiogeographie, Universität TrierEurope is characterised by several high mountain systems over major parts of its surface, and thesestructures have strongly influenced the evolution of taxa. For species now restricted to these highmountain systems, characteristic patterns of differentiation exist. (i) Populations of taxa with widedistributions in the Alps often have two or more genetic lineages, which in some cases even have the