Figure 8.

MT binding of human tau in KI and Tg mice. MT-bound and NT-unbound tau were prepared from adult non-Tg and P301L-Tg (A), P301L KI (C), or V337M-KI mouse brains (E) as described in the Materials and Methods and detected in Western blotting using anti-total tau (BD anti-tau), anti-human tau (H-150), or anti-mouse tau (RTM47) antibodies. Human and mouse tau in Tg mouse brains are indicated by closed and open arrowheads, respectively. Samples in a single gel were prepared in a single experiment, and multiple samples prepared from different animals are shown. Immunoreactive bands of interest were quantified using known amounts of recombinant tau as standards. The proportions of MT-unbound (solid) and MT-bound (open) endogenous (endo) and exogenous (exo) tau are shown in B, D, and F for A, C, and E, respectively. The averages of the unbound fraction were compared in each experiment using two-way ANOVA with Sidak post hoc test because the preservation of MTs and the level of MT-bound tau differ in every experiment. We therefore made comparisons only within each experimental set. The level of unbound human tau was significantly higher than that of endogenous tau in the Tg mice and in WT (non-Tg) mice (F_(2,9) = 427.7, p < 0.0001). By contrast, there was no significant difference in the levels of unbound tau for KI mice (F_(2,8) = 0.9127, p = 0.4395 for D; F_(2,9) = 3.879, p = 0.061 for F).