DYT-TOR1A genotype alters extracellular vesicle composition in murine cell model and shows potential for biomarker discovery

Introduction: Biomarkers that can be used to identify patient subgroups with shared pathophysiology and/or that can be used as pharmacodynamic readouts of disease state are valuable assets for successful clinical trial design. In translational research for brain diseases, extracellular vesicles (EVs) have become a high-priority target for biomarker discovery because of their ubiquity in peripheral biofluids and potential to indicate brain state.Materials and methods: Here, we applied unbiased quantitative proteomics of EVs isolated from DYT-TOR1A knockin mouse embryonic fibroblasts and littermate controls to discover candidates for protein biomarkers. We further examined the response of genotype perturbations to drug treatment conditions to determine their pharmacodynamic properties.Results: We found that many DYT-TOR1A MEF EV differences were significantly corrected by ritonavir, a drug recently shown to correct DYT-TOR1A phenotypes in cell and mouse disease models. We also used tool compounds to explore the effect of the integrated stress response (ISR), which regulates protein synthesis and is implicated in dystonia pathogenesis. Integrated stress response inhibition in WT cells partially phenocopied the effects of DYT-TOR1A on EV proteome composition, and ISR potentiation in DYT-TOR1A caused changes that paralleled ritonavir treatment.Conclusion: These results collectively show that DYT-TOR1A genotype alters EV protein composition, and these changes can be dynamically modulated by a candidate therapeutic drug and ISR activity state. These mouse model findings provide proof-of-concept that EVs may be a useful source of biomarkers in human populations and further suggest specific homologs to evaluate in cross-species validation.