2006 — 2008 |
Howard, Mackenzie A |
F31Activity Code Description: To provide predoctoral individuals with supervised research training in specified health and health-related areas leading toward the research degree (e.g., Ph.D.). |
Development of Inhibition in the Avian Cochlear Nucleus @ University of Washington
[unreadable] DESCRIPTION (provided by applicant): The auditory system localizes sound in azimuth by computing interaural time delays. In the avian auditory brainstem, nucleus magnocellularis (NM) is the first central nucleus in this temporal coding pathway. NM contains highly specialized anatomic, synaptic, and intrinsic properties that play key roles in shaping inhibitory responses and maintaining temporal fidelity in NM. The development of these specializations is poorly understood. The first aim is to describe the time-course of the development of inhibition in chick NM using in vitro electrophysiological techniques.. The second aim is to understand the developmental importance of afferent excitatory inputs in the development of inhibition using otocyst removal followed by physiological recordings. The third aim will examine role of Kv1.1 in developing the normal NM phenotype using RNA interference techniques. Plasmids encoding RNAs designed to interfere with the Kcnal, the Kv1.1 gene, and an EGFP reporter gene will be electroporated in ovo in early embryos. The physiology of transfected cells will be examined through development. These manipulations are hypothesized to alter the normal development of NM anatomy and physiological responses to excitatory and inhibitory inputs. [unreadable] [unreadable] [unreadable]
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0.958 |
2010 — 2012 |
Howard, Mackenzie A |
F32Activity Code Description: To provide postdoctoral research training to individuals to broaden their scientific background and extend their potential for research in specified health-related areas. |
Molecular Mechanisms Underlying Psd-Maguk/Nmda Receptor Interactions @ University of California, San Francisco
DESCRIPTION (provided by applicant): The overall objectives of my proposal are to understand the molecular mechanisms by which glutamate receptors, particularly NMDA receptors (NMDARs), interact with synaptic scaffolding proteins and how these interactions shape synaptic transmission. Specifically, I will study how the postsynaptic density-95-like membrane associated guanylate kinase (PSD-MAGUK) protein family, in particular the protein SAP97, traffic NMDA receptors subunits and change their physiology. PSD-MAGUKs and NMDA receptors play a critical role in basal synaptic transmission and learning and memory, and have been implicated in a wide variety of neurological diseases, ranging from developmental disorders such as autism, schizophrenia, to degenerative diseases such as Alzheimer's. My research goals are outlined in two Specific Aims: Specific Aim 1: SAP97 controls AMPA and NMDA receptor trafficking and synaptic morphology. I hypothesize that SAP97 traffics AMPA and NMDARs to synapses during early development and specifically promotes GluN2A-containing NMDARs. Second, I hypothesize that SAP97-mediated signaling also controls dendrite and synapse morphology in developing neurons. I will manipulate SAP97 protein levels in vivo and use electrophysiology and confocal imaging to measure the role of this protein in synaptic transmission and neuronal anatomy. Specific Aim 2: Molecular differences in PSD-MAGUKs underlie NMDAR kinetics and subunit switching. First, I hypothesize that specific protein binding domains shared by PSD-93, -95, and SAP97 promote synaptic trafficking of GluN2A-containing NMDARs while different motifs in SAP102 promote GluN2B- containing receptors. Second, I hypothesize that PSD-MAGUKs also directly influence NMDAR physiology, with each PSD-MAGUK differentially interacting with NMDARs and shaping synaptic currents. I will design and overexpress chimeric PSD-MAGUK proteins in vivo, in NMDAR subunit conditional knockout mice, and measure the effect on NMDARs using electrophysiology. I will also use a heterologous expression system to measure direct interactions between these proteins. Thus, I will define the protein domains responsible for PSD-MAGUK/NMDAR interactions and how these interactions alter NMDAR physiology. These experiments take a multi-dimensional approach to a vital scientific question, combining cutting edge molecular genetic, physiologocial, and anatomical techniques and will enhance our understanding of fundamental molecular mechanisms of synaptic transmission and learning and memory. PUBLIC HEALTH RELEVANCE: My experiments study the interactions between glutamate receptors and the family of proteins that organize them at synapses. These studies will uncover fundamental mechanisms of glutamatergic synaptic transmission, the major form of neural signaling, and synaptic plasticity, the cellular basis of learning and memory. Deficits in synaptic transmission are symptomatic of most neurological diseases. Thus, my results will be relevant both to basic scientists and to clinicians and will guide the way for future studies of learning and memory and the genetic causes of and pharmacological therapies for the alleviation of a variety of neurological diseases.
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0.943 |
2020 |
Howard, Mackenzie A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Mechanisms of Altered Synaptic Integration and Plasticity Underlying Cellular and Circuit Dysfunction in Genetic Epilepsy Disorders @ University of Texas, Austin
PROJECT SUMMARY. Synaptic integration and plasticity are the cellular mechanisms of information pro- cessing, learning, and memory. How these fundamental processes are disrupted in epilepsy is not understood. Generalized Epilepsy with Febrile Seizures Plus/Dravet syndrome (GEFS+/DS) is a spectrum of epilepsy disor- ders linked to mutations of the SCN1B gene which cause seizures, neurodevelopmental delays, and early death. To develop treatments for seizures/cognitive deficits of GEFS+/DS epilepsies, there is a critical need to identify mechanisms by which SCN1B mutations disrupt cellular-level information processing and learning. Our long- term goal is to define general principles linking genes to disrupted synaptic integration and plasticity in such neurodevelopmental disorders. The overall objective of our proposal is to define how the interplay between syn- apses, dendritic physiology, and somatic physiology impair synaptic integration and plasticity in the Scn1b knock- out (KO) mouse model of GEFS+/DS. Our central hypothesis is loss of Scn1b dysregulates ion channels and dendrite excitability, disturbing integration and plasticity. To test this hypothesis, we will complete three Aims: Aim 1: Determine the mechanisms of somatic and dendritic hyperexcitability in Scn1b KO neurons. Based on preliminary data, our hypothesis is that both dendrites and somata of Scn1b KO CA1 pyramidal neu- rons exhibit intrinsic hyperexcitability in part due to abnormal HCN channel activity. We will test this hypothesis with whole cell somatic and dendritic recordings, immunohistochemistry, and cell morphology analyses. Aim 2: Determine the mechanisms of altered synaptic integration in Scn1b KO neurons. Based on our preliminary data, our hypothesis is that loss of Scn1b fundamentally alters the translation of inputs into outputs, with both temporal and spatial synaptic integration abnormally enhanced due to dendritic hyperexcitability and disrupted synaptic physiology. We will use whole cell recordings to test how temporal and spatial features of input/output functions are altered in Scn1b KO neurons in response to naturalistic patterns of synaptic inputs. Aim 3: Test the hypothesis that Scn1b disruption alters synaptic learning rules and gating by GABA that dictate plasticity. Based on our preliminary data, our hypothesis is that synaptic learning rules governing LTP and LTD induction are re-shaped due to interplay between suppressed excitation, hyperexcitable intrinsic properties, and abnormal gating by aberrant depolarizing inhibition after loss of Scn1b. We will test how input patterns that evoke LTP and LTD shift after loss of Scn1b, and how inhibition influences this plasticity. Upon successful completion of the proposed research, we will have defined detailed mechanisms by which changes in neuron intrinsic and synaptic physiology and their interactions re-shape the cellular forms of neural processing and learning in the Scn1b KO mouse model of GEFS+/DS. This contribution will provide mechanistic links between genetic changes, primary neurophysiology phenotypes, and neuronal processing deficits underly- ing seizures and the learning, memory, and cognition impairments in GEFS+/DS epilepsies.
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