A029 Extracellular vesicle remodeling in response to mutant Huntingtin

<h3>Background</h3> Extracellular vesicles (EVs) mediate cell-to-cell communication via several mechanisms including extracellular ligand/receptor-mediated signaling and fusion with the target cell membrane to deliver bioactive cargos to recipient cells. EVs may either gang up against cells or contribute to cell protection, which may involve a variety of EV subtypes. However, several questions remain unanswered about the role of EV subtypes in nervous systems in normal or disease conditions, e.g. in neurodegenerative diseases. We study these questions in Huntington’s disease (HD) as a well-characterized neurodegenerative and repeat expansion disease. To characterize EV remodeling in self-renewal/neurogenesis, we analyzed the features of small EVs (SEVs) secreted by mouse striatal cells derived from HD knock-in mice and by human HD iPSC-derived neural stem cells (NSCs). <h3>Methods</h3> We purified SEVs using differential ultracentrifugation or size exclusion chromatography. SEVs were characterized using electron microscopy, quantification of soluble mutant huntingtin, nanoparticle tracking analysis, total protein dosage, western blot analysis using a panel of EV markers and functional assays. <h3>Results</h3> Changes in protein composition of human SEVs were analyzed using label-free quantitative proteomics. To characterize EV remodeling in neuronal circuits that are known to be affected by HD, we analyzed EV trafficking in cortico-striatal connections isolated from HD knock-in mice and reconstituted in microfluidic devices. <h3>Conclusion</h3> Our data reveal several changes in SEVs secreted by NSCs and mature neurons. We will discuss the implications of our findings for understanding the role of EV remodeling in neural stem cell niches and neuronal circuits that are exposed to chronic neurodegenerative insults.