Single extracellular vesicle detection assay identifies membrane-associated α-synuclein as an early-stage biomarker in Parkinson’s disease
Publication date: 18/05/2025
Authors: Yan S., Zhang W., Li X., Dutta S., Castle A. R., Liu Y., Sahoo A., Lai Lam C., Gatford N. J. F., Hu M. T., Li C., Jiang C., Shu B., and Tofaris G. K.
Journal: Cell Reports Medicine
Commentary: The diagnosis of Parkinson's disease (PD) still relies largely on the onset of motor symptoms, by which time substantial neurodegeneration has already occurred. This limitation highlights the urgent need for biomarkers capable of identifying the disease during its prodromal phase, when disease-modifying interventions may be most effective. Because PD is causally linked to the misfolding and aggregation of α-synuclein, considerable effort has been devoted to evaluating α-synuclein as a biomarker. However, measurements of free α-synuclein in plasma or serum have yielded inconsistent and often contradictory results. In this context, neuronally derived L1CAM-positive extracellular vesicles (L1EVs) have emerged as a promising source of biomarkers, as they may mirror pathological processes occurring within the nervous system. In this study, Tofaris and colleagues developed an ultrasensitive microfluidic platform for the detection and quantification of EV membrane-associated proteins at single-EV resolution. The assay combines immunocapture of L1EVs with on-chip droplet compartmentalization of individual EV-bead complexes, enabling the analysis of rare neuronal EV populations from minimal serum volumes. Using conditioned media derived from neuroblastoma cells expressing α-synuclein mutants, as well as iPSC-derived neurons from a patient carrying an α-synuclein gene triplication, the authors demonstrate that membrane-associated α-synuclein is increased under pathological conditions. They further show that this association is partly determined by the membrane-binding affinity of PD-associated mutations. Notably, the authors show that membrane-associated α-synuclein distinguishes both patients with PD and with isolated REM sleep behaviour disorder (iRBD) from healthy controls with high diagnostic accuracy (AUC > 0.93). Since iRBD is a prodromal stage of α-synucleinopathies, this finding suggests that the biomarker may identify disease-related changes before the onset of classical motor symptoms. Furthermore, by employing antibodies recognizing either monomeric or aggregated conformations, the authors demonstrate that a fraction of membrane-associated α-synuclein displays pathological features. Overall, this work identifies L1EV membrane-associated α-synuclein as a promising blood-based biomarker for early α-synucleinopathy and introduces a powerful technological platform for its detection.
Commented by: Deborah Di Martino
DOI: https://doi.org/10.1016/j.xcrm.2025.101999
