Figure 10.
Phosphorylation and aggregation of Tau is reduced after switching off the expression of TauRD/ΔK280. A, Representative immunoblots of Sarkosyl-soluble and Sarkosyl-insoluble fractions from cortex homogenates of young proaggregation mice: lanes 1–3, Sarkosyl-soluble fractions; and lanes 4–6, Sarkosyl-insoluble fractions of wild-type mice; proaggregation mutant mice 4.5 months ON; or proaggregation mutant mice 3 months ON and 1.5 months OFF. B, Immunoblot analysis of Sarkosyl-soluble fractions (lanes 1–3) and Sarkosyl-insoluble fractions (lanes 4–6) from cortex homogenates in the case of older proaggregation mice. Lanes 1 and 4 show wild type; lanes 2 and 5 show proaggregation mutant, 11.5 months expression ON; and lanes 3 and 6 show proaggregation mutant, 10 months ON and 1.5 months OFF. Note that after switch-off for 1.5 months, the insoluble human TauRD disappears, whereas the insoluble mouse Tau stays aggregated (lane 6 in A and B; red boxes). C, Phosphorylation at KXGS motifs in Tau repeats seen by the 12E8 antibody in the cortex of proaggregation mutant at 4.5 months TauRD/ΔK280 gene expression and (D) loss of 12E8 immunoreactivity after 1.5 months switching off gene expression (3 months ON and 1.5 months OFF). E, F, 12E8 immunoreactivity in proaggregation transgenic mice at 11.5 months gene expression (E) was reversible after suppression of TauRD/ΔK280 gene for 1.5 months (10 months ON and 1.5 months OFF) (F). G, Tangles at 4.5 months of TauRD/ΔK280 gene expression in entorhinal cortex (Gallyas staining). H, I, Two examples of reduction (H) or persistence (I) of tangles in the entorhinal cortex after switching off TauRD/ΔK280 gene expression for 1.5 months in mice with initial 3 months gene expression (3 months ON and 1.5 months OFF). J, NFTs in entorhinal cortex of proaggregation mutant at 11.5 months TauRD/ΔK280 expression. K, L, Two examples of switch off experiments: after 1.5 month suppression of TauRD/ΔK280 gene expression, the tangle pathology decreased (K) or partly persisted (L) in proaggregation mice initially induced for 10 months (10 months ON and 1.5 months OFF). M–P, Entorhinal neurons in the brain of proaggregation mice after 1.5 months of switch off of the TauRD/ΔK280 transgene (10 months ON and 1.5 months OFF) were positive for Gallyas staining (M), and at the same time were stained by antibodies against the first N-terminal insert of Tau with antibody SA4473 (N), against Tau phosphorylated at S46 (O) and at T231 (P). Note that full-length mouse Tau is present in the persisting tangles after switching off exogenous TauRD. Scale bars: C–P, 50 μm.