Fig. 9.

Synapse loss and neurodegeneration in hTau40^AT mice. a Western blots of hippocampus and cortex extracts showing expression levels of synaptic proteins (synaptophysin and PSD-95) of 12 months old hTau40^AT and WT mice. β-actin serves as loading control. Decreased levels of pre-synaptic (synaptophysin) and post-synaptic (PSD-95) markers are detected in hTau40^AT mice compared to WT. b Quantification of (a), normalized to ß-actin. Red bars indicate a reduction of pre-synaptic (synaptophysin) and postsynaptic (PSD-95) markers in hTau40^AT mice. Bars show mean ± SEM; n = 5. Statistics: two-sided t test indicates significant differences between WT and hTau40^AT mice (*:p < 0.05). c Dendritic spine density analyzed by Golgi-staining. (c1) Overview of Golgi-stained CA1 neurons of WT mouse with highlighted region of interest (box). (c2-c5) Higher magnification of CA1 and CA3 apical dendrites of hTau40^AT mice compared to WT at 20 months of age. Scale bar c1, 50 μm; c2-5, 2 μm. d Quantification of (c). A highly significant reduction of dendritic spines is detected in 20 months old hTau40^AT mice (red bar, CA1: ~35 %; CA3: ~25 %) compared to WT mice (grey bars). Bars show mean values ± SEM; n = 2-3 mice per group. Statistics: two-sided t test, ****:p < 0.0001. e Fluoro Jade C staining of floating sections from 12 months old hTau40^AT and WT mice to visualize neurodegenerative processes. Note the intense neurodegeneration in the CA3 region (e2) and cortex of hTau40^AT mice (e4) compared to WT mice (e1, e3). Arrows in the overviews indicate the location of higher magnified neurons (inserts). f Western blots of cortex extracts show NeuN expression levels in 12 and 20 months old hTau40^AT and WT mice. GAPDH serves as loading control. Note the dramatic loss of NeuN (especially ~66 kDa) in 20 months old hTau40^AT mice compared to 12 months old hTau40^AT and 20 months old WT mice. g Quantification of (f), normalized to GAPDH. Red bar indicates neuronal loss of ~40 % in 20 months old hTau40^AT mice compared to age-matched WT mice. Data represent mean values ± SEM; n = 4. Statistical comparisons were accomplished by one-way ANOVA followed by a post hoc Newman-Keuls multiple comparison test using Prism 5.0 (GraphPad Software). Asterisk indicates significant difference between WT and 20 months old hTau40^AT mice (*:p < 0.05). WT: wildtype; A152T: hTau40^AT transgenic mouse strain; CA: cornu ammonis; Ctx: cortex; mo: months; Scale bars: 2 μm (c2-5), 20 μm (inserts of e3-4), 50 μm (e1-4; inserts of e1-2)