Fig. 1

Preparation of human preformed fibrils (PFF) α-syn and validation of endogenous mouse α-syn inclusions in in vitro mouse primary neurons. a Thioflavin T assay showed the conversion of purified monomeric α-syn into PFF α-syn. b Representative electron microscopy images of PFF α-syn (left) and sonicated PFF α-syn (right). c Distribution of α-syn PFF length after sonication as determined by values obtained from the analysis of aggregates in electron microscopy images. Mean length of mouse PFF seeds are 21.74 nm ± 0.41 (n = 400). d Immunocytochemistry images of primary mouse neurons using antibodies against p-α-syn (green), MAP-2 (purple), and human α-syn Syn204 (red) to confirm PFF α-syn seeding and transduction capacity. On day 7 of neuronal culture, neurons were treated with PBS, 1 μg/mL of monomer α-syn, non-sonicated PFF α-syn, or sonicated PFF α-syn for 7 days, then were fixed on day 14. Scale bars are 20 μm