Fig. 3: Sarkosyl-insoluble (SI) fractions and brain homogenate (BH) exhibit increased tau PTMs in MF-ADNC compared to MF-PART.
a Representative seeding activity endpoint analysis of MF-ADNC and MF-PART brain homogenates (BH) and BH equivalents of sarkosyl-insoluble (SI) extracts. Normalized Thioflavin T (ThT) fluorescence readouts of indicate seed amplification of 10-3-10-9 BH and SI dilutions. b Schematic of select tau post-translational modifications (PTMs) investigated and their relative location on tau primary structure. Regions used to characterize the tau sequence are included: N-terminal inserts (green), proline-rich domain (blue), and microtubule binding repeats (purple). Phosphorylation events are marked at S202/T205 and T217. The C-terminal (C-term) region of interest is marked near D430. c Western blots representing MF-PART, MF-ADNC, and MF-high ADNC (Braak VI) pS202/pT205, pT217, and C-terminal immunoreactivity in BH (5% w/v) and SI extracts (0.1 mg/ml). Similar results have been obtained across 3+ technical replicates. d Representative BH (5% w/v) dot blot pS202/pT205, pT217, and C-terminal immunoreactivity (greyscale) of 3 cases of both HP and MF regions of ADNC and PART and total protein staining (Ponceau S, pink). e–g Quantitation of BH dot blot immunoreactivity relative to total protein staining in HP and MF regions of all ADNC (n = 21) and PART (n = 17) cases. Each point represents the average of an individual case across 3 replicates, bars represent the group means, and error bars represent standard deviations across the averaged replicate values. MF-ADNC cases had significantly higher immunoreactivity compared to MF-PART cases for each pS202/pT205, pT217, and C-terminal antibodies (unequal variance t-test). In contrast, HP-ADNC and HP-PART did not differ across these epitopes (p > 0.05, unequal variance t-test). All statistical tests in this figure are two-sided.
