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This is an independent research group at the Institute of Neurobiology at the Free University of Berlin, funded in the Emmy Noether program of the Deutsche ForschungsgemeinschaftThe group started December, 2000, is planned for 4 years and is led by Dr. Carsten DuchTopic:The postembryonic acquisition of behavior requires alterations in neural circuitry, which ultimately must be understood as specific changes in neuronal structure, membrane properties, and synaptic connectivity. We use the holometabolous insects Manduca sexta and Drosophila melanogaster as model systems to unravel the mechanisms for behaviorally relevant modifications of structural and physiological properties of neurons. To address the mechanisms and the behavioral relevance of postembryonic plasticity on the level of single identified neurons, we make use of developmental changes in the excitability and the morphology of an identified motoneuron, MN5. During the metamorphosis of Manduca sexta MN5 changes from a slow motoneuron that is involved in larval crawling behavior into a fast adult flight motoneuron. To accommodate the new behavior in the adult, dendritic shape, synaptic input, membrane properties, and calcium signaling of MN5 are modified dramatically (Duch and Levine, J Neurosci 20, 2000; Duch and Levine, J Neurophysiol 87, 2002). The homologous MN5 in Drosophila undergoes many similar developmental changes (Consoulas et al., J Neurosci 22, 2002). Concerning the signals for structural and physiological remodeling of neurons we currently focus on the role of activity- and calcium-dependent signals. Concerning the behavioral relevance of postembryonic neuronal plasticity we currently focus on the functions of developmental alterations in dendritic shape and in active and passive membrane properties in motoneurons for adult motor output.Team:Dr. Carsten Duch (Group Leader)Dipl.-Biol. Andree Czjzek (Technical Assistant) Dipl.-Biol. Jan-Felix Evers (Graduate Student; project Du 331-2/2,3) Dipl.-Biol. Peter Burkert (Graduate Student; project SFB 515, A7) VACANCIESDiploma thesis (several projects for diploma thesis are always available in the lab. Topics can be individually discussed with applicants but must always be related to the research described below) Student work (SHK; student projects are available in the lab for most of the time, some funds are available for paid student projects)Projects:What is the role of developmental changes in neuronal calcium signaling for dendritic shape and synaptogenesis?(Peter Burkert, SFB 515, A7) In the motoneuron MN5 developmental changes in the dendritic calcium signaling (Duch and Levine, J Neurophysiol 87, 2002) correlate with distinct phases of dendritic growth (Libersat and Duch, J Comp Neurol 450, 2002). To address the possible link between calcium concentration and structural changes the activity of calcium-dependent enzymes is measured by phosphorylation assays at critical developmental stages. In a next step, promising candidates will be inhibited pharmacologically followed by an analysis of dendritic structure. The long term goal is to identify downstream targets of such enzymes and to determine by which mechanisms they cause structural changes. In a parallel approach calcium influx by will be prevented during critical developmental stages by suppression of calcium channel expression using dsRNA interference followed by an analysis of dendrite structure.What is the role of activity for dendritic remodeling?(Jan-Felix Evers, Tim Mentel, Carsten Duch, Du 331-2/2, 3, SFB 515, A7) The developmental function of normally occurring changes in motoneuron spiking patterns during metamorphosis is investigated with three approaches. First chronic extracellular electrode implantations allow to measure and to manipulate spiking activity of identified motoneurons in vivo during specific periods of normal development (Duch and Mentel, European J Neurosci 17, 2003). Second pharmacological manipulations of activity are used during Manduca development. Third, in collaboration with Dr. C Consoulas activity will be manipulated genetically during critical periods of Drosophila development. In all three approaches our assay is to compare membrane properties and dendritic structure in manipulated animals with our wildtype databases.How does dendritic growth relate to dendritic synapse distribution?(Jan-Felix Evers, Samanta Maphumo, Andree Czjzek, Du 331-2/2, 3) Two approaches are used to assess the role of dendritic growth for synaptic changes during development. First, presynaptic neurons to MN5 are being identified to follow the synaptic connections of specific neurons through the phases of dendritic retraction and growth (Samanta Maphumo, Andree Czjzik). Second, the synapse distribution throughout the entire dendritic tree of MN5 is followed through development (Jan-Felix Evers). Manipulating pre-or postsynaptic activity and calcium signaling etc. (see 1) will address the mechanisms underlying synapse formation during the integration of MN5 into the newly formed flight motor network.What are the functions of developmental changes in membrane properties and in dendritic morphology for the adult behavior?(Carsten Duch, Du 331-2/2, 3) Structural changes in dendritic morphology might underlie the integration of MN5 into the newly formed motor network. We study the contribution of dendritic modifications to developmental changes in synaptic connectivity. Moreover, the functional role of the adult-specific membrane current composition of MN5 will be addressed by recordings and pharmacological experiments during 'fictive' flight behavior in an isolated CNS preparation. In collaboration with S Schönknecht and M Scholz (TU Berlin), we have most recently started to create compartment models to address the role of developmentally altered dendritic shape for adult motor output.Technical expertise:We apply a broad spectrum of techniques, covering electrophysiological recordings in voltage clamp-, current clamp-, and bridge-mode, neuroanatomical approaches including automatic 3-dimensional reconstructions and metric analysis from stacks of optical sections, immun-histochemistry, intracellular and retrograde labeling, and biochemical and molecular techniques.Collaborators:Prof. Dr. RB Levine (University of Arizona, USA)Prof. Dr. C Consoulas (University of Athens, Greece) Prof Dr. F Libersat (University of the Negev, Beer Sheva, Israel) Prof. Dr. HJ Pflüger (Free University of Berlin) Dr. M Scholz(Technical University of Berlin)Selected publications:Duch C, Levine RB (2000) Remodeling of membrane properties and dendritic architecture accompany the postembryonic conversion of a ‘slow’ into a ‘fast’ motoneuron. J Neurosci 20:6950-6961. Consoulas C, Duch C, Bayline RJ, Levine RB (2000) Behavioral transformations during metamorphosis: remodeling of neural and motor systems.Brain Res Bulletin53:571-583. Bayline RJ, Duch C, Levine RB (2001) Nerve-muscle interactions regulate motor terminal growth and myoblast distribution during muscle development. Dev Biol 231:348-363. Duch C, Levine RB (2002) Changes of calcium signaling during postembryonic dendritic growth in Manduca sexta. J Neurophysiol 87:1415-1425. Libersat F, Duch C (2002) Morphometric analysis of dendritic remodeling in an identified motoneuron during postembryonic development. J Comp Neurol 450:153-166. Duch C, Mentel T (2003) Motoneuron terminal retraction and outgrowth depend on stage-specific activity patterns during the metamorphosis of Manduca sexta. European J Neurosci, 17:1-18.Complete list of publications
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