Figure 7.

Inter-MT distance in MT bundles in the presence of Tau mutants. A–C, Electron micrographs of cross-sections of MT pellets polymerized in vitro with Tau WT (A), 3A (B), or 3D (C). Scale bar, 100 nm. D, The wall-to-wall distances between nearest-neighbor MTs were measured and expressed as the percentage of the total number of counted MTs. The mean distance was 11.7 ± 1.7 nm for Tau WT (n = 48), 11.8 ± 2.1 nm for Tau 3A (n = 51), and 11.9 ± 1.6 nm for Tau 3D (n = 69). E–G, Electron micrographs of processes of Sf9 cells [untreated (−)] expressing Tau WT (E), 3A (F), or 3D (G). H, Inter-MT distances were measured between nearest-neighbor MTs and expressed as the percentage of the total number of counts. The mean distance was 15.7 ± 2.2 nm for Tau WT (n = 30), 17.5 ± 2.7 nm for Tau 3A (n = 27), and 16.3 ± 2.2 nm for Tau 3D (n = 28). I–K, Electron micrographs of processes of latrunculin B-treated (+) Sf9 cells expressing Tau WT (I), 3A (J), or 3D (K). Sf9 cells were treated with 0.5 μg/ml latrunculin B for 72 h after infection with baculovirus expressing each Tau. L, Inter-MT distances were measured and expressed as the relative ratio of the total number of counts. The mean distance was 26.8 ± 2.7 nm for Tau WT (n = 60), 27.2 ± 2.0 nm for Tau 3A (n = 80), and 37.1 ± 2.3 nm for Tau 3D (n = 75). M, Immunostaining of Sf9 cells overexpressing Tau 3D (top), Tau 3A (middle), or WT (bottom) with anti-Tau. Scale bar, 20 μm. N, O, Sf9 cells overexpressing Tau 3D formed longer and wider processes compared to those expressing Tau WT or 3A. N, The length distribution of Sf9 cell processes overexpressing Tau constructs. The mean length was 106.5 ± 3.7 μm for Tau WT, 97.2 ± 5.3 μm for Tau 3A, and 119.1 ± 4.3 μm for Tau 3D (n = 20 for each Tau construct). O, The width distribution of Sf9 cell processes overexpressing Tau constructs. The mean width was 1.09 ± 0.04 μm for Tau WT, 1.04 ± 0.09 μm for Tau 3A, and 1.39 ± 0.07 μm for Tau 3D (n = 20 for each Tau construct).