RP1: Ras-MAPK signalling and cognitive function -
The significance of activating mutations in human mental retardation.

Prof. Martin Zenker

Activating germline mutations in various genes encoding components or modulators of the Ras-MAPK signalling pathway have been found to cause a group of clinically overlapping syndromes (including Noonan, CFC and Costello syndrome). Cognitive deficits of variable expression are part of all these diseases and are considered to reflect dysregulated Ras-MAPK signalling in the nervous system. We hypothesize that mutations in other modulators of the pathway, that are preferentially expressed in neuronal cells, may be responsible for mental retardation without the typical physical symptoms of Noonan syndrome and related disorders. We therefore intend to screen the genes for neuronal components / modulators of this pathway in a large cohort of patients with non-syndromic or non-specific mental retardation using new sequencing technologies. Sequence variants detected by this approach will be further validated and functionally evaluated.

Literature:

    Schubbert S, Zenker M, Rowe SL, Boll S, Klein C, Bollag G, van der Burgt I, Musante L, Kalscheuer V, Wehner LE, Nguyen H, West B, Zhang KY, Sistermans E, Rauch A, Niemeyer CM, Shannon K, Kratz CP (2006) Germline KRAS mutations cause Noonan syndrome. Nat Genet 38:331-336.

    Zenker M et al. (2007) SOS1 is the second most common Noonan gene but plays no major role in cardio-facio-cutaneous syndrome. J Med Genet 44:651-656.

    Cirstea IC et al. (2010) A restricted spectrum of NRAS mutations causes Noonan syndrome. Nat Genet 42:27-29.

    Martinelli S et al. (2010) Heterozygous germline mutations in the CBL tumor-suppressor gene cause a Noonan syndrome-like phenotype. Am J Hum Genet 87:250-257.

RP2: Imaging Genetics of Cognitive Functions - Significance of the Ras-MAP kinase signalling pathway for cognitive functions - influence of genetic polymorphisms on learning processes in humans

Dr. Björn H. Schott & PD Dr. Constanze I. Seidenbecher

We want to study the influence of single nucleotide polymorphisms (SNP) in genes encoding molecules of the Ras signalling pathway on human learning and memory performance. A large cohort of approx. 700 healthy human subjects shall be studied in hippocampus- and striatum-dependent cognitive processes using neuropsychological testing and multimodal non-invasive brain imaging.  With fMRI measurements of the BOLD response we will elucidate the functional anatomy of these cognitive processes. The temporal dynamics shall be investigated with EEG. We will focus on candidate genes of the RAS pathway and, besides the SNPs, also look for copy number variations in these genes.

Literature:

    Schott BH, Niehaus L, Wittmann BC, Schutze H, Seidenbecher CI, Heinze HJ, Duzel E (2007) Ageing and early-stage Parkinson's disease affect separable neural mechanisms of mesolimbic reward processing. Brain 130:2412-2424.

    Schott BH, Seidenbecher CI, Richter S, Wustenberg T, Debska-Vielhaber G, Schubert H, Heinze HJ, Richardson-Klavehn A, Duzel E (2011) Genetic variation of the serotonin 2a receptor affects hippocampal novelty processing in humans. PLoS One 6:e15984.

    Schott BH, Seidenbecher CI, Fenker DB, Lauer CJ, Bunzeck N, Bernstein HG, Tischmeyer W, Gundelfinger ED, Heinze HJ, Duzel E (2006) The dopaminergic midbrain participates in human episodic memory formation: evidence from genetic imaging. J Neurosci 26:1407-1417.

    Schott BH, Minuzzi L, Krebs RM, Elmenhorst D, Lang M, Winz OH, Seidenbecher CI, Coenen HH, Heinze HJ, Zilles K, Duzel E, Bauer A (2008) Mesolimbic functional magnetic resonance imaging activations during reward anticipation correlate with reward-related ventral striatal dopamine release. J Neurosci 28:14311-14319.

RP3: Emotions, learning and memory: What roles does Grb2 play in hippocampal signalling?

Prof. Mario Engelmann & Prof. Klaus Dieter Fischer

Neurotrophins such as BDNF activate the Ras signalling cascade downstream of receptor tyrosine kinases and are critical to the induction of neuronal plasticity. Grb2 is an intracellular adaptor molecule that mediates Ras signalling upon receptor tyrosine kinase stimulation. We will study the relevance of Grb2 in the generation of emotions and to learning and memory using conditional Grb2 knockout mice. Manipulated mutant mice will be exposed to mild chronic stress and to the application of anti-depressants, both of which are known to trigger neurotrophin action resulting in neurogenesis and increased hippocampal plasticity.

Literature:

    Noack J, Richter K, Laube G, Haghgoo HA, Veh RW, Engelmann M (2010) Different importance of the volatile and non-volatile fractions of an olfactory signature for individual social recognition in rats versus mice and short-term versus long-term memory. Neurobiol Learn Mem 94:568-575.

     Tobin VA, Hashimoto H, Wacker DW, Takayanagi Y, Langnaese K, Caquineau C, Noack J, Landgraf R, Onaka T, Leng G, Meddle SL, Engelmann M, Ludwig M (2010) An intrinsic vasopressin system in the olfactory bulb is involved in social recognition. Nature 464:413-417.

    Zelena D, Langnaese K, Domokos A, Pinter O, Landgraf R, Makara GB, Engelmann M (2009) Vasopressin administration into the paraventricular nucleus normalizes plasma oxytocin and corticosterone levels in Brattleboro rats. Endocrinology 150:2791-2798.

    Missy K, Hu B, Schilling K, Harenberg A, Sakk V, Kuchenbecker K, Kutsche K, Fischer KD (2008) AlphaPIX Rho GTPase guanine nucleotide exchange factor regulates lymphocyte functions and antigen receptor signaling. Mol Cell Biol 28:3776-3789.

    Tedford K, Nitschke L, Girkontaite I, Charlesworth A, Chan G, Sakk V, Barbacid M, Fischer KD (2001) Compensation between Vav-1 and Vav-2 in B cell development and antigen receptor signaling. Nat Immunol 2:548-555.

RP4: GABAergic interneurons in fear conditioning: Role of synaptic GAD expression

Prof. Oliver Stork

Groups of GABAergic interneurons filter sensory input to the amygdala, determine its principle neuron excitability  and control network activity patterns involved in information processing. These cell populations mediate different aspects of the acquisition, consolidation, and extinciton of fear memories. In this project we will investigate the particular role of synaptic vs non-synaptic forms of the key enzyme of GABA synthesis, glutamic acid decarboxylase (GAD)65 and GAD67. Both enzymes are specifically expressed in amygdalar GABA interneurons, albeit at different levels in different subpopulations. Using constitutive and conditional mutant mice as well as lentiviral gene transfer we will locally inactivate GAD65 or GAD67 in selected GABAergic subpopulations and investigate the consequences for fear memory formation. Our findings can be expected to help understanding critical mechanisms of both physiological and pathological fear memory storage through the amygdala.

Literature:

    Sangha S, Narayanan RT, Bergado-Acosta JR, Stork O, Seidenbecher T, Pape HC (2009) Deficiency of the 65 kDa isoform of glutamic acid decarboxylase impairs extinction of cued but not contextual fear memory. J Neurosci 29:15713-15720.

    Kluge C, Stoppel C, Szinyei C, Stork O, Pape HC (2008) Role of the somatostatin system in contextual fear memory and hippocampal synaptic plasticity. Learn Mem 15:252-260.

    Bergado-Acosta JR, Sangha S, Narayanan RT, Obata K, Pape HC, Stork O (2008) Critical role of the 65-kDa isoform of glutamic acid decarboxylase in consolidation and generalization of Pavlovian fear memory. Learn Mem 15:163-171.

    Stork O, Yamanaka H, Stork S, Kume N, Obata K (2003) Altered conditioned fear behavior in glutamate decarboxylase 65 null mutant mice. Genes Brain Behav 2:65-70.

RP5: Interactions between amyloid

Jun.-Prof. Tanja Brigadski & Prof. Volkmar Lessmann

A neuropathological characteristic of Alzheimer’s disease is the atropic change in the hippocampus, a brain region known to be important for formation of spatial memories. Despite the typical neurodegeneration during Alzheimer’s disease recent studies suggest an enhanced neurogenesis in the hippocampus of Alzheimer patients and genetic mouse models of Alzheimer‘s disease which is accompanied by an incomplete neuronal differentiation of hippocampal neurons. While the increased proliferation is supposed to be mediated by the amyloid b-protein, which is a central protein in the pathogenesis of Alzheimer’s disease, the incomplete neuronal differentiation could be mediated by a lack of the neurotrophic factor BDNF.

This project will analyse the interaction between amyloid b-protein and BDNF signalling during hippocampal neurogenesis. The project will involve confocal microscopy, electrophysiology, cell biology and molecular biology techniques, to analyse the consequences of altered amyloid b-protein and BDNF-levels in generation and maturation of hippocampal neurons.

Literature:

    Brigadski T, Hartmann M, Lessmann V (2005) Differential vesicular targeting and time course of synaptic secretion of the mammalian neurotrophins. J Neurosci 25:7601-7614.

    Kolarow R, Brigadski T, Lessmann V (2007) Postsynaptic secretion of BDNF and NT-3 from hippocampal neurons depends on calcium calmodulin kinase II signaling and proceeds via delayed fusion pore opening. J Neurosci 27:10350-10364.

    Lessmann V, Brigadski T (2009) Mechanisms, locations, and kinetics of synaptic BDNF secretion: an update. Neurosci Res 65:11-22.

RP6: Genetics of presynaptic scaffold proteins: Redundant and exclusive roles of Bassoon and Piccolo in synaptic assembly, function and plasticity

Dr. Anna Fejtova & Prof. Eckart D. Gundelfinger

Bassoon und Piccolo are presynaptic scaffold proteins controlling synapse assembly, maturation, stability and function. They share a high sequence homology, which is mirrored in a number of common interaction partners, and highly overlapping subcellular localization patterns. The fact that animals lacking both Bassoon and Piccolo are in contrast to single mutants not viable also suggests the functional redundancy of these two proteins. However, we recently identified a number of cellular processes (e.g. axonal vesicle transport, neuronal morphogenesis, dispersion of vesicles during synaptic activity and modulation of neuronal activity at systemic level), where Bassoon or Piccolo have an exclusive function. The molecular basis of this functional redundancy and exclusivity is absolutely unclear up to date and its elucidation is the main goal of our project.

Literature:

    Hallermann S, Fejtova A, Schmidt H, Weyhersmuller A, Silver RA, Gundelfinger ED, Eilers J (2010) Bassoon speeds vesicle reloading at a central excitatory synapse. Neuron 68:710-723.

    Fejtova A, Davydova D, Bischof F, Lazarevic V, Altrock WD, Romorini S, Schone C, Zuschratter W, Kreutz MR, Garner CC, Ziv NE, Gundelfinger ED (2009) Dynein light chain regulates axonal trafficking and synaptic levels of Bassoon. J Cell Biol 185:341-355.

    Ghiglieri V, Picconi B, Sgobio C, Bagetta V, Barone I, Paille V, Di Filippo M, Polli F, Gardoni F, Altrock W, Gundelfinger ED, De Sarro G, Bernardi G, Ammassari-Teule M, Di Luca M, Calabresi P (2009) Epilepsy-induced abnormal striatal plasticity in Bassoon mutant mice. Eur J Neurosci 29:1979-1993.

    Leal-Ortiz S, Waites CL, Terry-Lorenzo R, Zamorano P, Gundelfinger ED, Garner CC (2008) Piccolo modulation of Synapsin1a dynamics regulates synaptic vesicle exocytosis. J Cell Biol 181:831-846.

RP7: The role of neuron-glia communication during synaptogenesis in Drosophila melanogaster: Cell-specific proteome dynamics using transgenic cell-select click chemistry

Dr. Daniela C. Dieterich

The emerging concept of the “Tripartite synapse” points to the importance of glia cells for neuronal function and development. Although it is well established that astrocytes are important for the formation and maintenance of synaptic contacts, sense neuronal activity and actively participate in homeostatic scaling, it is unclear if the astroglial proteome is as dynamic as the neuronal. In this project we aim to decipher the communication of neurons with astrocytes at the synaptic level in Drosophila larvae and adult flies using cell-selective labeling of newly synthesized priteins via click chemistry. In more detail we ask the following questions: Do characteristic signature proteomes for different stages during development of the neuromascular junction exist in neurons, in muscle cells and also in glia cells? Where in the cell are these proteins synthesized – only in the cell somata or also locally in cellular processes? Do glial cells react as dynamic as neurons to changes in the neuronal activity pattern?

Literature:

    Dieterich DC, Link AJ, Graumann J, Tirrell DA, Schuman EM (2006) Selective identification of newly synthesized proteins in mammalian cells using bioorthogonal noncanonical amino acid tagging (BONCAT). Proc Natl Acad Sci U S A 103:9482-9487.

    Dieterich DC, Lee JJ, Link AJ, Graumann J, Tirrell DA, Schuman EM (2007) Labeling, detection and identification of newly synthesized proteomes with bioorthogonal non-canonical amino-acid tagging. Nat Protoc 2:532-540.

    Dieterich DC, Hodas JJ, Gouzer G, Shadrin IY, Ngo JT, Triller A, Tirrell DA, Schuman EM (2010) In situ visualization and dynamics of newly synthesized proteins in rat hippocampal neurons. Nat Neurosci 13:897-905.

    Ngo JT, Champion JA, Mahdavi A, Tanrikulu IC, Beatty KE, Connor RE, Yoo TH, Dieterich DC, Schuman EM, Tirrell DA (2009) Cell-selective metabolic labeling of proteins. Nat Chem Biol 5:715-717.

RP8: The control of synaptic stabilization and destabilization by scaffold and adhesion molecules in Drosophila

Dr. Ulrich Thomas

Synapse remodeling involves the well-controlled destabilization of synaptic protein complexes balanced by stabilizing mechansims, which warrant the maintenance of synaptic connectivity. Disrupting this balance interferes with the striking capacity of neural networks to undergo use-dependent adjustments at the level of synaptic junctions. In fact, mental disorders such as autism and some forms of neural degeneration may result from such disturbancies. Our recent studies imply, that the highly conserved Dlg-scaffold protein complex controls the stability of glutamatergic neuromuscular junctions in Drosophila,possibly through interactions with synaptic cell adhesion molecules (CAMs) such as Neurexin and Neuroligin-1. Based on the versatility of Drosophila genetics, this project is aimed at deciphering the regulation and dynamics of the Dlg complex and associated cell adhesion complexes in controlling synaptic stability under various conditions (e.g. during activity-induced synaptic terminal growth). A broad range of methods including classical and molecular genetics, confocal microscopy and life imaging techniques will be employed.

Literature:

    Thomas U, Kobler O, Gundelfinger ED (2010) The Drosophila larval neuromuscular junction as a model for scaffold complexes at glutamatergic synapses: benefits and limitations. J Neurogenet 24:109-119.

    Bachmann A, Kobler O, Kittel RJ, Wichmann C, Sierralta J, Sigrist SJ, Gundelfinger ED, Knust E, Thomas U (2010) A perisynaptic menage a trois between Dlg, DLin-7, and Metro controls proper organization of Drosophila synaptic junctions. J Neurosci 30:5811-5824.

    Mendoza-Topaz C, Urra F, Barria R, Albornoz V, Ugalde D, Thomas U, Gundelfinger ED, Delgado R, Kukuljan M, Sanxaridis PD, Tsunoda S, Ceriani MF, Budnik V, Sierralta J (2008) DLGS97/SAP97 is developmentally upregulated and is required for complex adult behaviors and synapse morphology and function. J Neurosci 28:304-314.

    Bachmann A, Timmer M, Sierralta J, Pietrini G, Gundelfinger ED, Knust E, Thomas U (2004) Cell type-specific recruitment of Drosophila Lin-7 to distinct MAGUK-based protein complexes defines novel roles for Sdt and Dlg-S97. J Cell Sci 117:1899-1909.