Cell surface protein dynamics in neural circuit assembly

PROJECT SUMMARY/ABSTRACT The central nervous system contains an enormous number of neurons that are interconnected to form the circuits governing all brain functions. Neural circuits are built following a series of developmental steps such as neurite guidance, target selection, and synapse formation. Cell surface proteins (CSPs) enable neurites to connect with the correct synaptic partners. CSPs are not static within the membrane. They undergo dynamics and can be cycled on and off of the membrane which influences how they respond to and control the physiological and signaling events underlying neurodevelopment. Endocytosis internalizes CSPs from the membrane into the cytosol and has dramatic effects on CSP signaling and function. However, CSP endocytosis has largely been investigated in the context of a few known dynamic CSPs and mostly in culture systems. Though these approaches are informative, we still do not know the identity and number of endocytosed CSPs within a given developmental context or how their dynamics impact circuit assembly in vivo. The Drosophila olfactory system displays stereotyped wiring and high genetic tractability, making it a powerful in vivo system to elucidate the role and regulators of dynamic CSPs in circuit assembly. Here, ~57 distinct types of olfactory receptor neurons (ORNs) project their axons from the periphery into the brain to make one-to-one synaptic connections with the dendrites of ~57 corresponding types of projection neurons (PNs). This one-ORN-type-to-one-PN-type motif creates ~57 distinct and invariant information relay channels called glomeruli. In fact, impairing CSP dynamics disrupts olfactory circuit assembly, as well as the development of other sensory systems. The proposal will provide foundational insight into how CSP dynamics govern olfactory circuit assembly and enable the candidate to build an independent research direction to pursue in her own lab. Specifically, the K99 phase of this application focuses on: 1) employing cutting-edge quantitative proteomics to profile dynamic CSPs in ORNs and PNs in the developing brain; and 2) performing functional analyses to determine how CSP endocytosis impacts circuit formation. This work will be completed under the guidance of world-renowned neuroscientist, Dr. Liqun Luo (mentor), expert cell biologist, Dr. Kang Shen (co-mentor) and in collaboration with leaders in proximity labeling, Dr. Alice Ting, and mass-spectrometry, Dr. Steven Carr. The R00 phase of this proposal seeks to evaluate the intracellular mechanisms that control CSP dynamics by building upon expertise gained from the mentored phase of this proposal. The research in the mentored and independent portions of this application is directly in line with NIDCD’s mission to understand chemo-sensation and treat chemosensory disorders because elucidating the cellular mechanisms controlling olfactory circuit assembly could enable us to ameliorate sensory circuit defects that arise from disorders, injury, disease, or ageing.