The use of specific assays designed to amplify and detect minute amounts of aggregated aSyn in biological samples, termed collectively as aSyn seed amplification assays (aSyn SAAs), (e.g., real-time quaking-induced conversion (RT-QuIC) and protein-misfolding cyclic amplification (PMCA)), have consistently shown the presence of seeding-competent aSyn species in CSF and peripheral tissue biopsies (e.g., from the skin and colon), which could serve as a reliable diagnostic marker for PD with higher accuracy, sensitivity and specificity35,72,83–87. The gene discussed is PCSK1N; the disease is Parkinson disease.