Growth cones (GCs) are structures associated with growing neurons. GC membrane expansion, which necessitates protein-lipid interactions, is critical to axonal elongation in development and in adult neuritogenesis. We present a multi-omic analysis that integrates proteomics and lipidomics data for the identification of GC pathways, cell phenotypes, and lipid-protein interactions, with an analytic platform to facilitate the visualization of these data. We combine lipidomic data from GC and adult axonal regeneration following optic nerve crush. Our results reveal significant molecular variability in GCs across developmental ages that aligns with the upregulation and downregulation of lipid metabolic processes and correlates with distinct changes in the lipid composition of GC plasmalemma. We find that these processes also define the transition into a growth-permissive state in the adult central nervous system. The insight derived from these analyses will aid in promoting adult regeneration and functional innervation in devastating neurodegenerative diseases.

Elevated intraocular pressure (IOP) is a risk factor in glaucoma, a group of irreversible blinding diseases. Endogenous lipids may be involved in regulation of IOP homeostasis. We present comparative fold analysis of phospholipids and sphingolipids of aqueous humour and trabecular meshwork from human control vs primary openangle glaucoma and mouse control (normotensive) vs ocular hypertensive state. The fold analysis in control vs disease state was based on ratiometric mass spectrometric data for above classes of lipids. We standardized in vitro assays for rapid characterization of lipids undergoing significant diminishment in disease state. Evaluation of lipids using in vitro assays helped select a finite number of lipids that may potentially expand cellular interstitial space embedded in an artificial matrix or increase fluid flow across a layer of cells. These assays reduced a number of lipids for initial evaluation using a mouse model, DBA/2J with spontaneous IOP elevation. These lipids were then used in other mouse models for confirmation of IOP lowering potential of a few lipids that were found promising in previous assessments. Our results provide selected lipid molecules that can be pursued for further evaluation and studies that may provide insight into their function. K E Y W O R D Saqueous humour, glaucoma, lipidomics, lipids, trabecular meshwork | 3857 EDWARDS Et Al.

The optic nerve transfers visual information from the retina to the brain through the axons of retinal ganglion cells (RGCs). In adult mammals, optic nerve injuries and progressive degenerative diseases lead to the irreversible loss of RGCs, resulting in vision loss and blindness. Optogenetic models have proved useful in manipulating the growth of RGCs through expression and stimulation of channelrhodopsins (Chr2) in RGCs using the RGC-specific thy-1 promoter. Using transgenic Chr2 mouse (Thy1-ChR2-EYFP) as a model of regeneration, we profile the lipid changes which occur after traumatic optic nerve crush, light stimulation and forced RGC axonal growth. Thy1-ChR2-EYFP and control (C57BL/6) mice were divided in four groups each – 1) no crush and no stimulation, 2) no crush with stimulation, 3) crush and without stimulation, and 4) crush with stimulation. After euthanasia, the optic nerves were collected for lipidomic analysis. The Bligh and Dyer method was used for lipid extraction, followed by mass spectrometry lipid profiling with a Q-Exactive Orbitrap Liquid Chromatography-Mass Spectrometer (LC MS-MS). The raw scans were analysed with LipidSearch 4.1.3 and the statistical analysis was conducted through Metaboanalyst 4.0. This data is available at Metabolomics Workbench, study ID ST001381: [ https://www.metabolomicsworkbench.org/data/DRCCMetadata.php?Mode=Study&StudyID=ST001381&StudyType=MS&ResultType=5 ].

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