Fig. 4: Isoform-specific seeding pattern is independent of isoform-composition.

a Experimental paradigm showing how human tau strains were converted into AD-3R, AD-4R, PiD-3R, or PSP-4R tau strains through in vivo propagation in mice expressing only 3R tau (T44mTauKO) or only 4R tau (WT). b Immunoblots of the transformed tau strains using 3R (RD3) or 4R isoform-selective antibody (4RTau), respectively. Equal proportion of sarkosyl-soluble fractions were loaded, and twofold fraction from T44mTauKO mice or 20-fold from WT mice were loaded as sarkosyl-insoluble fractions. c Representative IHC staining with AT8 on brain sections from 6hTau mice injected with 3R tau control lysate extracted from non-injected T44mTauKO mice or 4R tau control lysate extracted from non-injected WT mice at 3 m.p.i. d Representative IHC staining with AT8, RD3, and RD4 on adjacent brain sections from 6hTau mice injected with similar amount of AD-3R, AD-4R, PiD-3R, and PSP-4R tau. e Immunoblots of the induced tau pathologies in 6hTau mice by different tau strains with isoform-specific tau antibodies. Equal proportion of sarkosyl-soluble fraction and 7.5-fold for AD_3R, 52.5-fold for PiD_3R, 40-fold for AD_4R, and 52.5-fold for PSP_4R induced sarkosyl-insoluble fraction samples were loaded. rhT44 and rhT40 are recombinant human 0N3R and 2N4R tau isoforms, respectively. 3R tau-positive bands, open arrowheads; 4R tau-positive bands, solid arrowheads. Asterisks indicate non-specific blot bands. f Quantification of AT8-, RD3- and RD4-positive neurons in the 6hTau mice injected with distinct lysates as shown in d. n = 3 mice per group. One-way ANOVA with multiple t-tests were performed. g IHC staining with AT8 in the WT mice injected with similar amounts of AD-3R and PiD-3R tau, and in the T44mTauKO mice injected with similar amounts of AD-4R and PSP-4R tau. Quantification of AT8-positive tau pathologies in h AD-3R and PiD-3R tau injected 4R tau mice, and i AD-4R and PiD-4R tau injected 3R tau mice. Three mice per group were quantified. Data are presented as mean ± s.e.m. and each dot represents a mouse. One-tailed Mann–Whitney tests were performed. Only ipsilateral hippocampus (iHpx) were quantified for each mouse.