Investigating novel mechanisms that underlie glial-mediated synapse elimination in development and aging

项目总结

Project Summary Formation and maintenance of synaptic connections between appropriate neuronal partners is essential for proper nervous system function. Indeed, impairments in either initial synapse formation or in subsequent developmental synapse elimination underlie many neurodevelopmental disorders. Synapse elimination that occurs outside of appropriate developmental contexts underlies synaptic loss associated with age-related cognitive decline and in neurodegenerative diseases. Thus, defining the mechanisms that underlie the regulation of synapse number will provide insight into how appropriate connections are formed during development, and these pathologies of synapse elimination. Despite its essential role in nervous system development and function throughout life, we still know little about the mechanisms underlying this process. We do know, however, that glia are required. In order to identify novel glial regulators of synapse development, I completed a forward genetic screen in Drosophila, and identified 91 molecules that, when knocked down in glia, alter synapse number. Among these molecules is the immune receptor Crq, which I found is required for glial elimination of synapses in development. This proposal will focus on understanding Crq’s role in synapse elimination, in order to gain insight into the larger questions of which synapses undergo developmental synapse elimination, the mechanisms underlying the specificity of this process, and whether these same mechanisms are re-used in pathological synapse loss associated with aging. Aim 1 will address the question of which synapses undergo developmental elimination across the nervous system and evaluate which of these are Crq-dependent. I have recently developed an inducible pre-synaptic label that makes this work possible, and will generate inducible postsynaptic labels as part of this aim. Aim 2 will use proximity labeling to identify the neuronal ligand(s) for Crq that act to specify which synapses undergo elimination, and will identify how expression and localization of these ligands are regulated. Aim 3 will define which synapses are lost with aging, and identify whether Crq acts as a common mediator of synaptic loss in development and aging. I will also perform a targeted screen based on a recent transcriptional profiling experiment I completed to identify additional glial regulators of age-related synaptic loss. Together, these studies will address the mechanisms by which synapses are targeted for elimination and how. This is a key question in achieving the larger goal of understanding how neurons and glia work together to create and maintain appropriate synaptic connections throughout life. Dissecting these mechanisms will also provide insight into the process of age-related synaptic loss that underlies age-related cognitive decline. In addition, performing this work will allow me to address existing gaps in my technical skills that will allow me to carry out my long-term research goals as an independent invesitigator.