Fig. 1

Overexpressing hTau in MS induces MS-dCA1 cholinergic loss and spatial memory deficit. A The exogenously overexpressed hTau detected by confocal imaging (A) and Western blotting (B) at 3 and 6 m after MS infusion of pAAV-CAG-MAPT-EGFP-3flag or pAAV-CAG-EGFP-3flag, respectively. The antibody pT231, pT205, Tau5 and HT7 reacts with phosphorylated tau and total tau proteins. The bands at 110 kDa and 55 kDa indicate exogenously expressed hTau and endogenously expressed mouse tau respectively. C-E Overexpressing hTau in the MS for 6 m but not 3 m significantly reduced cholinergic neuron number measured by ChAT immunohistochemical staining. N = 6 mice per group. ChAT + cell number: unpaired t test, t = 0.7513 df = 10, P > 0.05 (3 m); t = 5.802 df = 10, P < 0.01 (6 m). Scale bar, 100 μm. F–H Overexpressing hTau for 6 m but not 3 m decreased cholinergic projection intensity in hippocampal CA1 measured by ChAT immunohistochemical staining. N = 6 mice per group. ChAT + fiber intensity (H): unpaired t test, t = 0.6429 df = 10, P > 0.05 (3 m); t = 5.178 df = 10, P < 0.01 (6 m). Scale bar, 200 μm or 50 μm in enlarged image. I-N Overexpressing hTau in the MS for 3 m had no effects on spatial learning (I, J) and memory (K-N) detected by Barnes maze (BM) test. I two–way ANOVA group × days, escape latency: F [3,80] = 0.7710, P > 0.05; J Number of errors: F [3,80] = 0.5044, P > 0.05; K first escape latency, unpaired t test, t = 0.06583 df = 20, P > 0.05; L percentage of time in target, unpaired t test, t = 0.2421 df = 20, P > 0.05; M percentage of correct pokes, unpaired t test, t = 0.2261 df = 20, P > 0.05; N distance moved, unpaired t test, t = 0.3920 df = 20, P > 0.05). N = 11 mice per group. O-T Overexpressing hTau in MS for 6 m impaired spatial memory (Q-T) without changing learning ability (O, P) in BM test. O Two–way ANOVA group × days, escape latency: F [3,80] = 0.2125, P > 0.05; P two–way ANOVA group × days, number of errors: F [3,80] = 1.124, P > 0.05; Q unpaired t test, t = 2.714 df = 20, P < 0.05; R percentage of time in target, unpaired t test, t = 2.906 df = 20, P < 0.01; S percentage of correct pokes, unpaired t test, t = 2.530 df = 20, P < 0.05; T distance moved, unpaired t test, t = 0.3526 df = 20, P > 0.05. *P < 0.05, **P < 0.01. N = 11 mice per group, and data were presented as mean ± SEM