2001 — 2003 |
Williams, Megan E |
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.). |
A Role For the Netrin Receptor Unc5h1 in Apoptosis @ University of California Santa Cruz
DESCRIPTION: The nervous system is composed of an integrated network of neurons and synaptic connections. To function properly the nervous system requires neuronal cells and their axons to be correctly positioned at a precise time. To accomplish this, cells sample the surrounding environment and are guided by a variety of long and short range cues. One long range guidance cue, netrin- 1, functions in both axonal attraction and repulsion. Attraction is mediated through the netrin-1 receptor, DCC, and repulsion through a receptor complex of DCC and UNC5H. Recently, a second function involving apoptosis has begun to emerge for the netrin-1 receptors. I propose to understand how cells distinguish between guidance and apoptosis by investigating the mechanism by which UNC5H1 relays the apoptotic signal into the cell and identifying molecules downstream of UNC5H1. UNC5H1 may be a central link between the cellular processes of axon guidance and apoptosis during development and depending on the state of the cell, a disruption in UNC5H1 could affect either of these cellular processes resulting in various neurological disorders.
|
0.976 |
2014 — 2018 |
Williams, Megan Elise |
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. |
The Intellectual Disability-Associated Gene Kirrel3 in Synapse Development
DESCRIPTION (provided by applicant): Synapses are specialized neuronal junctions required for nearly all neurotransmission in the brain. Most synapses contain many of the same basic molecular components but there are also specificity molecules that instruct neurons to make different types of synapses with different types of synaptic partners. Thus far, research has largely focused on understanding basic molecules found at all synapses and we have little mechanistic understanding of how neurons develop specificity. Nonetheless, mutations in putative synaptic specificity molecules are emerging as key susceptibility genes for cognitive disorders. In particular, mutations in the gene Kirrel3 are repeatedly found in patients with intellectual disabilities but the role of Kirrel3 in synapse formation in the mammalian brain has not been investigated. Here, we present evidence that Kirrel3 is a novel synaptic specificity molecule at hippocampal mossy fiber synapses. In this proposal, we will define the role of Kirrel3 in mossy fiber synapse formation at an ultrastructural level, elucidate Kirrel3 signaling mechanisms, and its role in learning-dependent synaptic plasticity. Importantly, we will determine whether Kirrel3 point mutations identified in patients with autism and intellectual disability have an attenuated synaptic function. Our results will increase our understanding in several intersecting areas of neuroscience including the cellular basis of neurological disorders, learning and memory, and molecular mechanisms of synaptic specificity.
|
1 |
2020 |
Williams, Megan Elise |
R56Activity Code Description: To provide limited interim research support based on the merit of a pending R01 application while applicant gathers additional data to revise a new or competing renewal application. This grant will underwrite highly meritorious applications that if given the opportunity to revise their application could meet IC recommended standards and would be missed opportunities if not funded. Interim funded ends when the applicant succeeds in obtaining an R01 or other competing award built on the R56 grant. These awards are not renewable. |
Molecular Mechanisms of Target-Specific Synapse Formation
Proper brain function requires that neurons make specific types of synapses with specific types of target neurons. Defects in this process of synapse specficity can alter brain activity and may underlie many types of mental illnesses but we know little about the mechanisms by which synapse specificity develops. We recently discovered that the cell adhesion molecule Kirrel3, which is a risk factor for autism and intellectual disability and other mental illnesses, is selectively required for formation of a specific type of hippocampal synapse that connects DG neurons to GABA neurons. This synapse provides feed-forward inhibition to CA3 and Kirrel3 null mice have significantly elevated CA3 neuron activity. This established Kirrel3 as a functionally relevant target-specific synaptogenic molecule but we still do not know the mechanism of how it functions. Through a series of in vitro assays, our new preliminary data suggests that Kirrel3 binds other Kirrel3 molecules in cis and trans, functions directly in pre- and post-synapse formation, and requires yet to be identified neuron-specific binding partner(s). In the hippocampus, Kirrel3 is only expressed by DG and GABA neuron. Thus, we will test the central hypothesis that homophilic, trans-cellular Kirrel3 interactions nucleate DG-to-GABA synapses by sending bi-directional signals to actively recruit pre- and post-synaptic proteins. In Aim 1, we will determine if Kirrel3 function requires trans-cellular binding in vivo by determining precisely where, when, and how much Kirrel3 is required to build hippocampal DG-to-GABA synapses. In Aim 2, we will define the role of Kirrel3 in adhesion versus synapse formation and identify binding partners and downstream signaling mechanisms mediated by Kirrel3. Kirrel3 provides a new approach to identify the still elusive mechanisms of target-specific synapse formation and, given its links to disease, our results will provide basic insight to the etiology of cognitive and mental illnesses.
|
1 |
2021 |
Williams, Megan Elise |
R21Activity Code Description: To encourage the development of new research activities in categorical program areas. (Support generally is restricted in level of support and in time.) |
Localizing Endogenous Synaptic Proteins in Vivo
PROJECT SUMMARY Determining the subcellular localization of a protein under different cellular states is a critical aspect of assessing protein function and dysfunction. This is especially important in neuroscience as neurons are complex, polarized cells with distinct functional compartments, including synapses. Synapse dysfunction underlies many neural and psychiatric disorders. Interestingly, synapses connecting different neurons develop unique structural and functional properties that differentially modulate circuit function. This structural and functional diversity is mediated by molecular differences. However, our understanding of the proteins located at different types of synapses is very limited. Suitable antibodies are simply not available for many proteins and protein overexpression drives mis-localization. Therefore, methods to localize endogenous synaptic proteins in brain tissue are urgently needed. Here, we developed a CRISPR gene editing strategy that, in one seamless genetic modification, inserts an epitope tag onto a protein of interest and drives expression of a cell marker in postmitotic neurons using a single AAV. Our innovative new method is the first to provide an integrated means for selectively identifying only those neurons that correctly integrated the protein tag and provide a cell filling, structural reference necessary for determining the synapse-specific localization of a protein. Our method is highly flexible for a variety of proteins, tags, and cell markers. Preliminary data indicate that our method correctly tags the synaptic protein N-cadherin in cultured neurons but it requires further optimization and expansion in vitro (Aim 1) and in vivo (Aim 2). Successful completion of our proposal will yield new technologies that allow the study of endogenously expressed, synapse-specific proteins in the brain. As an example, we will test the hypothesis that different cadherins associated with distinct mental illnesses localize to different types of synapses in vivo. Taken together, our results are expected to result in a new technology that can be broadly applied to study synapse formation and function and provide new molecular insight to mechanisms underlying synapse diversity.
|
1 |