Fig. 2

Overexpressing hTau in ChAT-neurons induces spatial memory deficit and cholinergic loss. A Carton shown infusion of AAV-DIO-hTau-EGFP or the empty vector control in the MS of ChAT-Cre mice. B, C Representative co-immunofluorescence images confirmed cholinergic-specific expression of the exogenously infused hTau in the MS (B), and quantitative analysis for the percentage of ChAT +- and hTau +- neurons (C). Scale bar, 15 μm. N = 6 mice. D-G Overexpressing hTau for 3 m in ChAT + -neurons caused cholinergic neuron loss (D scale bar, 100 μm) in the MS and in its cholinergic projection to hippocampal CA1 (E scale bar, 200 μm or 50 μm in enlarged images) measured by ChAT immunohistochemical staining. N = 6 mice per group. ChAT + cell number (F unpaired t test, t = 7.686 df = 10, P < 0.01). ChAT + fiber intensity (G unpaired t test, t = 6.382 df = 10, P < 0.01). **P < 0.01 vs Vec group. H-Q MS-ChAT-hTau mice displayed long-term spatial memory deficits measured by BM test. During spatial learning trials, no difference of latency (H two–way ANOVA group × days, escape latency: F [3,76] = 0.1017, P > 0.05) and error number (I two–way ANOVA group × days, number of errors: F [3,76] = 0.2126, P > 0.05) were found between MS-ChAT-hTau mice and the controls. In probe test carried out 24 h after the last training trial (J-L), MS-ChAT-hTau mice showed longer time to reach the target area (J unpaired t test, t = 5.063, df = 19, P < 0.01), with less poking to the target hole (K unpaired t test, t = 3.522 df = 19, P < 0.01) and less staying time in the target area (L unpaired t test, t = 2.439 df = 19, P < 0.05) than the controls. After one week (N-P), the MS-ChAT-hTau mice still showed an increased latency to the target (N unpaired t test, t = 2.483, df = 19, P < 0.05) with decreased correct pokes (O unpaired t test, t = 2.763 df = 19, P < 0.05) and time staying in the target (P unpaired t test, t = 2.556 df = 19, P < 0.05) compared with control mice. No difference of distance moved was shown between groups (M unpaired t test, t = 1.061 df = 19, P > 0.05; Q unpaired t test, t = 0.3439 df = 19, P > 0.05). N = 10, 11 mice per group. *P < 0.05, **P < 0.01 vs Vec group. Data were presented as mean ± SEM