Complementary mass spectrometry based detection of gangliosides within the brain

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Rationale: Gangliosides are a major class of glycosphingolipids and are enriched within the central nervous system (CNS). Gangliosides have a wide range of CNS functions including membrane function, axon stability and regeneration, differentiation and neurodegeneration. Using NSERC funding, our lab has shown that neurons are highly sensitive to changes within the lipid micro-environment. Specifically, we've published that harmful gangliosides GM2 and GM3, which are both precursors and breakdown products of GM1, are transiently increased following stressful stimuli to neurons in the mouse and rat and brain. Furthermore, we have recently published that exogenously delivered GM1 can protect primary neurons from excitotoxicity. Based on these published and preliminary studies we hypothesize that gangliosides GM2 and GM3 are transiently increased following neuronal stress. We further predict that preventing the breakdown of GM1 into GM2 and GM3 can prevent neurodegeneration.******Objectives: This proposal builds upon our current NSERC funding with the following objectives:******1) Use pharmacological and siRNA approaches both in vitro and in vivo to target enzymes within the ganglioside synthetic and degradation pathways to increase GM1 within neurons. This will allow us to test the hypothesis that intrinsically increasing GM1 can protect neurons against cell death.******2) Continue to develop methodology to enhance the capabilities of imaging mass spectrometry (IMS) based detection of gangliosides and other lipids, specifically in fixed rodent and human brain samples. To date, IMS within formaldehyde and/or formalin fixed tissues has been met with limited success. The ability to overlay IMS images with histopathological findings would be a significant contribution to the field of IMS. ******Approach: Gangliosides, like other lipids, are contained within different cellular compartments of the brain and have the ability to change their structure to meet their external and internal environmental demands. This ability to change structure makes lipids both fascinating and technologically challenging targets to identify and understand. To meet this challenge, we employ complementary mass spectrometry (MS) techniques, including IMS to detect and image gangliosides directly within brain tissue. We will use pharmacological and siRNA mediated intervention to prevent the breakdown of GM1 into GM2 and GM3 to further validate that GM2 and GM3 are fundamental mediators of neurodegeneration. Finally, we push the boundaries of IMS technology by developing methodology to image gangliosides within formalin-fixed tissue samples. ******Significance: This proposal will add knowledge on the role of gangliosides and other lipids in mediating neuronal vulnerability and neurodegeneration. This proposal will also push the boundaries of IMS based detection of lipids within intact tissue samples. **