Thioflavin T is a fluorescent dye that binds to beta sheet-rich structures, such as those in alpha synuclein fibrils. Upon binding, the emission spectrum of the dye experiences a red-shift and increased fluorescence intensity. Thioflavin T emission curves show increased fluorescence (correlated to alpha synuclein protein aggregation) over time when 10 µM of Type 1 alpha synuclein pre-formed fibrils (SPR-322) is combined with 100 µM of Type 1 alpha synuclein monomer (SPR-321), compared to 10 µM of Type 1 alpha synuclein pre-formed fibrils (SPR-322) combined with 100 µM Type 2 alpha synuclein monomer (SPR-316). Type 2 fibrils (SPR-317) do not seed type 2 monomers (SPR-316) (data not shown). Thioflavin T ex = 450 nm, em = 485 nm.

Type 2 monomers (SPR-316) are currently undergoing testing in a Real-Time Quaking-Induced Conversion (RT-QuIC) assay. At 10 μg/well there was discrimination between positive and negative CSF samples, and the unseeded reaction occurred later than either the LB BH or the positive CSF sample. This suggests Type 2 monomers could potentially be used as a substrate for alpha synuclein RT-QuIC. Further testing/optimization is underway. LB BH: 10% Lewy body disease; CSF +: CSF from patient with neuropathologically confirmed alpha-synucleinopathy; CSF -: CSF from patient with no evidence of alpha-synuclein deposition at postmortem. Image source: Alison Green, Graham Fairfoul

Evaluation of a-syn toxicity on primary mouse cortical neurons. Lactate dehydrogenase (LDH) is a soluble enzyme present in the cytosol that is released upon cell death. Toxicity was assessed with an LDH assay and displayed as % of vehicle control (VC). Data are presented as bar graphs and standard deviation. For statistical analysis One-way ANOVA followed by Bonferroni post-hoc test (vs VC) was used. *** p<0.001. Treatment with alpha synuclein monomers did not significantly impact LDH release. Data courtesy of QPS.

Evaluation of a-syn toxicity on primary mouse cortical neurons. Mitochondrial dehydrogenase activity reduces yellow MTT to dark blue formazan crystals, a reaction catalyzed in living cells. Cell viability was assessed with an MTT assay and displayed as % of vehicle control (VC). Data are presented as bar graphs and standard deviation. For statistical analysis One-way ANOVA followed by Bonferroni post-hoc test (vs VC) was used. ** p<0.01, *** p<0.001. Treatment with alpha synuclein monomers did not significantly impact cell viability. Data courtesy of QPS.