Novel Experimental Models to Study the Effect of Extracellular Vesicles on Neurons

Extracellular vesicles (EVs) have taken center stage in almost every area of biological research, including neurobiology. EVs are secreted vesicles that transport lipids, RNA/DNA, and proteins from a donor to a recipient cell, including pathogenic peptides and proteins such as Aβ, tau, and synuclein. Therefore, spreading of pathogenic factors by EVs in Alzheimer’s disease (AD) and Parkinson’s Disease (PD) is the focus of many recent studies. However, the physiological significance of endogenously generated EVs and mechanism of function are largely unknown. A critical knowledge gap and barrier to progress is our lack of understanding of the physiological and pathological function of EVs due to the scarcity of in vivo models. We showed that EVs secreted by astrocytes and enriched with the sphingolipid ceramide (“astrosomes”) are taken up by neurons and transported to mitochondria. We discovered that genetic deficiency of neutral sphingomyelinase 2 (nSMase2), an enzyme generating ceramide by hydrolysis of sphingomyelin, reduces astrosomes and upregulates transcript clusters associated with neuronal development and signal transduction, suggesting that astrosomes regulate neuronal function. To test the regulation of neurons by astrosomes, we propose to establish novel techniques and models for EV functional analysis. We developed mouse models with-astrocyte specific nSMase2 deficiency (loss-of- function) models and secretion of fluorescently labeled astrosomes (reporter models). We will primarily use these models to understand the significance of endogenous astrosomes for normal neuronal function. We will incorporate pilot studies to understand the function of astrosomes in (changing) physiological conditions (e.g., aging). Our overall goal is to establish novel techniques to determine the in vivo function of astrosomes. Once established, these techniques can be adapted to determine the function of EVs from other cell types (neurons, microglia, or any other tissue and cell type) as well