Scott H. Soderling - US grants

[unreadable] DESCRIPTION (provided by applicant): Several genes implicated in neurological disease are thought to regulate Rho GTPase signaling, yet there is a limited understanding of how these signaling proteins function. WRP (WAVE associated Rac GAP protein), which was identified by positional cloning as a gene disrupted in 3p-syndrome mental retardation (MR), is one such protein. WRP regulates actin remodeling by binding to the Rac effector WAVE-1 and by stimulating Rac GTP hydrolysis. WAVE-1 null mice exhibit dramatic behavioral impairments in learning and memory tests. Importantly, the phenotype of WAVE-1 null mice overlaps well with those of 3p-syndrome retardation, supporting a link between WRP regulated signaling and MR. The objective of this application is to examine the molecular mechanisms regulating WRP and whether loss of WRP affects specific neuronal functions that contribute to behavioral impairments. Our central hypothesis is that one cellular function of WRP is to regulate actin signaling in spines. Thus loss of WRP would lead to spine abnormalities and cognitive impairments. This hypothesis is guided by strong preliminary data based on 1) structure/function and imaging data defining a WRP targeting domain and 2) data linking WRP and WAVE-1 to spinogenesis, synaptic plasticity and cognitive behavior. The specific aims of this grant are: 1) Identify the mechanisms that spatially target and regulate WRP. We will use a combination of biochemical and imaging approaches designed to address how WRP is regulated and may be targeted to subcellular compartments. 2) Delineate the cellular role of anchored WRP. Because WRP regulates Rac and WAVE-1, we hypothesize targeting of WRP is a salient feature of this signaling pathway in spines. We will use imaging and cellular assays to quantify the role of WRP targeting in synapse function. 3) Test the in vivo function of WRP in regulating cognitive behavior and synapse function. Using a conditional WRP null mouse model we will analyze aspects of synapse function in vivo and in vitro. We will also examine these mice for abnormalities in a range of behaviors related to 3p-syndrome retardation. Because this proposal utilizes a multidisciplinary approach to analyze WRP signaling, a fundamental advance in understanding the mechanisms linking actin signaling to neuronal dysfunction can be anticipated. PUBLIC HEALTH RELEVANCE: This research is relevant to the mission of NIH because it examines the functional role of a gene implicated in mental retardation at the molecular, cellular and organismal level. Thus, important advances in understanding the etiology of mental retardation could be anticipated. It is also expected that knowledge gained in these studies will shed light on other forms of neuropathologies that involve abnormal Rho-GTPase signaling and mechanisms that normally regulate neuronal connectivity. [unreadable] [unreadable]

Actins; Affect; Area; Behavioral; Binding; Binding (Molecular Function); Brain; C 1 Esterase; C1 Esterase; C1 s; C1s; CRISP; Cell Communication and Signaling; Cell Signaling; Cellular Matrix; Central Nervous System; Collaborations; Complement; Complement 1 Esterase; Complement 1s; Complement Proteins; Complement component C1s; Computer Retrieval of Information on Scientific Projects Database; Cytoskeletal System; Cytoskeleton; Data; Dendritic Spines; Development; Encephalon; Encephalons; Family; Family member; Funding; GAP Proteins; GDP Dissociation Factor; GDP Dissociation Stimulators; GDP Exchange Factors; GDP-GTP Exchange Protein; GDP-GTP Reversing Factors; GEF; GTP GDP exchange factor; GTPase-Activating Proteins; General Population; General Public; Genes; Grant; Guanine Nucleotide Exchange Factors; Guanine Nucleotide Exchange Protein; Guanine Nucleotide Releasing Factors; Guanyl-Nucleotide Exchange Factor; Guanyl-Nucleotide Releasing Factor; Histology; Individual; Institution; Intracellular Communication and Signaling; Investigators; Knockout Mice; Lateral Ventricle of Brain; Lateral Ventricles; Lateral ventricle structure; Magnetic Resonance; Mammals, Mice; Measurement; Mental Retardation; Mice; Mice, Knock-out; Mice, Knockout; Microscopy; Molecular Genetic; Molecular Genetics; Molecular Interaction; Morphology; Murine; Mus; NIH; National Institutes of Health; National Institutes of Health (U.S.); Nerve Cells; Nerve Unit; Nervous System, Brain; Nervous System, CNS; Neural Cell; Neuraxis; Neurocyte; Neurons; Null Mouse; Numbers; Pathway interactions; Play; Radial; Reeler Mouse; Research; Research Personnel; Research Resources; Researchers; Resources; Role; Scar1 protein; Signal Transduction; Signal Transduction Systems; Signaling; Source; Structure; Testing; Thinking; Thinking, function; United States National Institutes of Health; WAS protein family, member 1; WASF1; WAVE protein; WAVE1 protein; axonal guidance; biological signal transduction; cognitive function; dendrite spine; exchange factor; guanosinetriphosphatase activating protein; in vivo; intracellular skeleton; lateral ventricle; member; migration; mouse model; nervous system development; neuroimaging; neuronal; pathway; rho; rho G-Proteins; rho GTP-Binding Proteins; rho GTPase-activating protein; rho GTPases; rho Protein P21; rho Small GTP-Binding Proteins; rhoGAP; shape analysis; shape description; social role

DESCRIPTION (provided by applicant): To appreciate how cells migrate, establish polarity, and adopt cell shape is fundamental to understanding cancer biology. Almost one percent of the human proteome is dedicated to Rho GTPase signaling, which regulates key aspects of each of these processes. It is well known that Rho GTPases are "signaling switches" that are turned "on" or "off" by GEF (Guanine nucleotide Exchange Factors) and GAP (GTPase Activating Proteins) proteins. What is not known are the molecular mechanisms that determine Rho GEF and GAP specificity. Because GEFs and GAPs regulate Rho-GTPases in specific cellular contexts, they are promising candidates for future therapeutic interventions to modulate GTPase activity in different types of cancers. This proposal develops an innovative and integrated approach to map the architecture of Rho GTPase signaling in vivo. Multiple independent methods will be used, including novel proteomic screens using cellular proteins with unnatural amino acids as well as high throughput binding assays and informatics- based experiments. We have recently established this approach in our laboratory and our preliminary data validates our rationale that this approach will uncover novel links between Rho GTPase signaling and cancer biology. At the conclusion of this pilot project we expect to demonstrate that this approach can work on a larger scale to map interaction networks for regulators of this pathway. These results will fundamentally advance our understanding of how Rho GTPases are modulated to regulate processes such as migration, polarity, and cell morphology. It can also be expected to provide the basic information necessary for the future development of therapeutic strategies to alter cancer outcomes.

DESCRIPTION (provided by applicant): The small size of dendritic spines belies the elaborate role they play in excitatory synaptic transmission and ultimately complex behaviors. The cytoskeletal architecture of the spine is predominately composed of actin filaments. These filaments, which at first glance might appear simple, are also surprisingly complex. They dynamically assemble into different structures and serve as a platform for orchestrating the elaborate responses of the spine during spinogenesis and experience-dependent plasticity. Mutations in pathways that regulate synaptic actin in humans and mice are associated with neurological disorders (humans) and related endophenotypes (mice). My laboratory studies a signaling pathway that drives de novo actin polymerization in spines by the activation of WAVE1 downstream of Rac. The objective of this application is to analyze epistasis between Fmr1, the causative gene in Fragile X Syndrome, and WAVE1. Our central hypothesis is that elevated WAVE1 and dysregulation of actin significantly contributes to the synaptic and behavioral phenotypes of Fragile X Syndrome. This hypothesis is guided by strong preliminary data based on: 1) In Fmr1 null mice, Rac activity is elevated and inhibition of Rac normalizes LTD. 2) Our previous work showing that loss of WAVE1 results in synaptic phenotypes opposite those of Fmr1 loss. 3) WAVE1 mRNA is a direct target of FMRP and our preliminary data shows an increase in WAVE1 protein in Fmr1 null mice. 4) Our data that demonstrates that mGluR activation reorganizes spine actin and that synaptic actin dynamics are significantly altered in a mouse model of FXS. 5) Our preliminary data showing Fmr1 null memory impairments are rescued in mice also heterozygous for Wave1. The specific aims of this grant are: 1) Quantitatively analyze the link between spine actin dynamics and loss of FMRP. 2) Test if genetic reduction of WAVE1 normalizes Fmr1 null deficits. 3) Test for mimicry of Fmr1 null phenotypes by WAVE1 overexpression in vivo. Because this proposal utilizes a multidisciplinary approach to analyze how loss of Fmr1 results in abnormal WAVE1 levels, altered spine actin dynamics, synaptic plasticity, and behavioral deficits, a fundamental advance in understanding the mechanisms linking actin signaling to neuronal dysfunction in a model of Fragile X Syndrome can be anticipated. Thus the proposed research is relevant to that part of NIH's mission that pertains to the investigation of the mechanisms linking genetic mutations to mechanisms of neurological disease.

DESCRIPTION (provided by applicant): Neuropsychiatric disorders are the leading cause of disease burden in the United States and Canada, far outpacing other maladies such as cardiovascular disease and cancer (WHO statistics). Progress in treating neuropsychiatric disorders is severely hampered by our lack of basic knowledge related to their underlying causes. Defects in dendritic spine morphogenesis, a process regulated by dynamic actin remodeling, is a common feature of these disorders and is also associated with stress, which may precipitate disorders such as schizophrenia. Moreover, it is increasingly clear that disruptions in genes that regulate signaling to excitatory synaptic actin are risk factors for schizophrenia, autism, and intellectual disability. Arp2/3 complex is enriched in dendritic spines and stimulates the formation of branched actin downstream of many genes implicated neuropsychiatric disorders. Recently we published that the conditional loss of Arp2/3 in mice leads to the progressive development of multiple synaptic and behavioral phenotypes relevant to models of schizophrenia. Many of the schizophrenia-related behaviors are normalized by the antipsychotics clozapine and haloperidol. The specific aims of this grant build on these exciting findings to address fundamental questions of how SZ-related phenotypes evolve at the synaptic and circuit level and how this is influenced by chronic stress. We anticipate the results of these aims will bridge our knowledge gap regarding how SZ-like phenotypes emerge in vivo, leading to new future directions for the prevention and possible treatments of the disorder.

? DESCRIPTION (provided by applicant): Mutations affecting inhibitory transmission are also linked to many of our most devastating neurodevelopmental disorders, including autism spectrum disorders (ASD), epilepsy, neonatal hyperekplexia, and intellectual disability (formally mental retardation). Yet in contrast with the excitatory synapse, the symmetric (inhibitory) postsynaptic complex does not have a morphological landmark and its purification using classical strategies is intractable. Thus, the biochemical nature of the symmetric synapse has largely eluded neuroscientists, and remains to this day a relative black box. This basic lack of fundamental knowledge concerning the signaling apparatus of the symmetric synapse poses a critical barrier to understanding how symmetric synapses develop, are modified by activity, or are affected by neurodevelopmental disorders. This proposal will utilize a highly innovative approach to unveil the symmetric synaptic complex, revealing the internal machinery that governs inhibitory synapse development and function.

Epilepsy affects approximately 2.3 million adults and 450,000 children in the US. Each year, 150,000 citizens are newly diagnosed with epilepsy. The estimated cost associated with epilepsies is approximately 15.5 billion in medical expenses and lost earnings (NINDS). Progress in treating disorders associated with epilepsies is severely hampered by our lack of basic knowledge related to the molecular mechanisms underlying the disorder. Our recently published work in Science, used a novel in vivo chemico-genetic approach to identify the proteome of the inhibitory postsynapse (iPSD). This study was supported by an R21 and identified a large complex of proteins that are enriched at the iPSD of GABAergic synapses of excitatory neurons. Several of these are novel proteins encoded by genes for which human mutations are known to cause epilepsies. The specific aims of this grant build on these exciting findings and follow up on our recent study by focusing on the testable hypothesis that epilepsy-associated mutations in genes encoding proteins of the iPSD lead to seizures by impairing inhibition. We anticipate the results of these aims will bridge our knowledge gap regarding molecular mechanisms of how epilepsies emerge in vivo from abnormalities of inhibition, leading to new future directions for the prevention and possible treatments of these disorders.

ABSTRACT Synapses are the most abundant and distinguishing feature of the brain, providing enormous functional diversity and plasticity to neural circuits. These structures are incredibly small, less than 1 femtoliter in volume, and remarkably plastic in their functional properties. Unique ensembles of protein networks that are enriched within postsynaptic structures orchestrate the development, maintenance, and plasticity of synapses. Genetic mutations associated with risk for intellectual disability, schizophrenia, autism, and other developmental brain disorders (DBDs) are predominated by genes encoding synaptic proteins. These observations have led to the hypothesis that many DBDs are synaptopathologies that alter synaptic development and function. However, while histological evidence in human postmortem samples and mouse models supports this theory, the molecular mechanisms of synaptic pathology remain poorly understood. This proposal will address this gap in knowledge by combining recent advances in CRISPR-genome editing paired with two highly innovative proteomics approaches we have developed to enable: 1) the discovery of synaptic protein complexes in vivo that are associated with DBDs and 2) how these complexes are disrupted in diverse models of DBD. This will significantly advance our understanding of potential synaptopathic mechanisms that may be comorbid across DBD mutations. Uncovering these molecular mechanisms of synaptopathology can be expected to lead to better insights of disorder etiology and potential therapeutic approaches.

ABSTRACT Synaptic transmission and its modulation by various mechanisms of synaptic plasticity are foundations of the performance of neural circuits that produce complex behaviors. Synaptic plasticity is required for healthy learning and memory as well as the development of adult nervous systems. Critically, dysfunction of synaptic plasticity is now unequivocally linked to a large number of neuropsychiatric, developmental and neurodegenerative/cognitive disorders. Accordingly, interest in this field has intensified dramatically and continuously over the past two decades. New tools for imaging the molecules involved in synaptic transmission and plasticity, for manipulating synaptic transmission, and for assessing and controlling neural circuit function are reaching a new, more powerful maturity in synchrony with one another. Thus, this is an ideal time to bring new and established investigators in this field together to share perspectives and to search for new ways to collaborate on difficult but central questions. We propose to hold a Workshop on Current Trends and Future Directions of Synaptic Plasticity.? This Workshop will bring together neuroscientists from Japan and the US who have contributed significantly to the mechanisms underlying synaptic structural and functional plasticity, and to the plasticity of neural circuits underlying healthy and diseased cognitive performance. The participants will present overviews and new findings, and specially tailored discussion sessions will be conducted to leverage the diversity of the group to identify and encourage collaborative endeavors. Through such exchanges of views and discussion, the goal of this workshop is to foster new collaborations, ultimately leading to better understanding of the molecular mechanisms and functional impact of synaptic plasticity. Importantly, the workshop will prioritize the participation of young promising scientists from the US and Japan that will lead the field in the next decade, and we will highlight work from trainees in a dedicated session. Also, a well-balanced and representative number of women and under-represented minorities has been considered. The organizers are Scott Soderling (Duke University SOM) and Masanori Murayama (RIKEN Center for Brain Science, Japan). The workshop will be held in Japan at the Gotemba Kogen Resort outside of Tokyo Japan (http://gotembakogenresort.com) during the days of September 3rd - 6th, 2019. We request funding to support this workshop, including travel and lodging of the invited participants residing in the US.!

ABSTRACT Astrocytes are the most abundant glial cells in the human brain. Interactions of astrocytes with synapses via thin perisynaptic astrocytic processes are critical for proper synaptic connectivity and function. Each mouse astrocyte sends out an extensive array of processes that are estimated to contact over 100,000 synapses. The number of astrocytes and the extent of their interactions with synapses have increased throughout evolution, indicating a close link between astrocytes and cognition. Moreover, emerging evidence suggests that dysfunction of astrocyte-synapse interactions contributes to a variety of brain disorders. In contrast to neuronal synaptic structures, however, we are largely blind to the molecular composition and mechanisms of the astrocytic perisynaptic structures. Moreover, there is currently very little understanding of how mutations that disrupt astrocyte-synapse interactions lead to synaptic pathologies. This is in large part because, unlike neuronal synaptic structures, it has not been possible to purify and identify proteins enriched at subcellular regions of astrocytes. In this project, we will develop and utilize innovative proteomic and genome editing approaches to solve these problems, revealing the proteins and inner workings of astrocyte processes that associate with and modulate synapses. We anticipate these data will provide a new and unparalleled molecular framework for future studies on astrocyte- neuron interactions.

ABSTRACT The microscope we propose in this application is the new Zeiss Elyra 7 system, which combines multiple modes of super-resolution imaging. The new Lattice SIM technology of the Elyra 7 enables structured illumination super-resolution imaging of common fluorescent proteins and labels, even in tissue samples, due to the increased signal to noise imaging with the lattice pattern. Increased light efficiency allows 2x diffraction limited imaging at high speed with less phototoxicity and bleaching ? up to 255 fps. One can examine the fastest processes in living samples ? in large fields of view, in 3D, over long time periods, and with multiple colors. The Elyra 7 also has single molecule localization microscopy (SMLM) capabilities for techniques such as photoactivation localization microscopy (PALM), direct stochastic optical reconstruction microscopy (dSTORM) and points accumulation for imaging in nanoscale topography (PAINT) with high power laser lines and dual camera functionality. The new Apotome mode gives superfast optical sectioning of 3D samples with minimal photobleaching. We note PALM/STORM and lattice-structured illumination of the Elyra 7 includes Zeiss software solutions for the analysis of images acquired in each of these modes and thus adds capabilities in super-resolution imaging that currently do not exist on Duke campus. The flexibility and new technologies of the ELYRA 7 will significantly contribute to new research capabilities related to NIH funded developmental biology, neuroscience, and cell biology questions relevant to human disorders as outlined in the research statement. The instrument would be housed in a large shared resource serving the entire research base at Duke University and Duke School of Medicine where the impact and use would be widespread. The LCMF Director has experience with these forms of imaging and has general high-levels of imaging expertise and so is well placed to immediately and effectively help implement these methods for an important array of basic research. Additionally, as part of our broad long-term objectives with institutional support, the ELYRA 7 works seamlessly with ZEISS SEMs in a correlative light-EM imaging workflow via integrated software solutions that enable the precise landmarking of light imaging regions of interest to be automatically recalled from the same sample for electron microscopy. This added benefit will be paradigm shifting for many research programs in our user group.

ABSTRACT The molecular mechanisms of plasticity within the presynapse and its role in behaviors such as learning and memory are still poorly understood, mainly due to a lack of knowledge of the signaling molecules of the presynaptic cytomatrix and tools to spatially and temporally manipulate presynaptic plasticity. This gap in knowledge is a fundamental barrier to the field. In this project, we will develop and utilize innovative proteomic, genome editing, and optogenetic approaches to solve these problems, revealing the proteins and inner workings of the cytomatrix of presynapses from distinct neuronal cell types and their roles in learning and memory. We anticipate these data will provide a new and unparalleled molecular framework for future studies on presynaptic physiology as well as insights into how forms of presynaptic plasticity modulate behavior.