Studying karyoptosis: Cell death in the context of EV-mediated neuron-glia signalling

During neurodegeneration, dying neuronal cells may influence or inform neighboring glial cells of their dying status by releasing extracellular vesicles (EVs). During a recently characterized cell death, Karyoptosis, EVs are released, and it is yet to be understood what role they play in neurodegeneration. This project sits at the nexus of understanding neuronal cell death in neurodegeneration and exploring EVs as messengers in neuron-microglia signaling. Using ex vivo brain sections from DRPLA mice we validated the anatomical correlation between areas with high Karyoptosis and microglia activation in those areas. To further study the link between neuronal cell death and specifically the effect of the Karyoptotic EVs, we moved to an in vitro model to purify the secreted EVs, dissect their contents, and observe their uptake and effect in microglia-like cells. The initial work in DRPLA mice shows a possible relationship between Karyoptosis and microglia activation. In disease-relevant anatomical areas of the DRPLA cerebellum, microglia are increased in number, have larger somas, and fewer, shorter branches compared to age-matched controls. These morphological observations suggest that the microglia in these DRPLA mice are activated, perhaps in response to the EVs released from neighboring neurons dying from Karyoptosis. The in vitro part of the project enabled the examination of Karyoptotic EVs and reveal that these are large, protein- and DNA-rich, membrane-bound vesicles that when applied onto BV2 cells are more readily taken-up, and their effect are not pro-inflammatory, but instead lead to membrane rupture and non-apoptotic cell death.