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Pro-aggregant Tau impairs mossy fiber plasticity due to structural changes and Ca(++) dysregulation.

Decker JM, Krüger L, Sydow A, Zhao S, Frotscher M, Mandelkow E, Mandelkow EM - Acta Neuropathol Commun (2015)

Bottom Line: Both pre-and postsynaptic structural deficits are preventable by inhibition of Tau(RDΔ) aggregation.In N2a cells we observed this even in cells without tangle load, whilst in primary hippocampal neurons transient Tau(RDΔ) expression alone caused similar Ca(++) dysregulation.We conclude that oligomer formation by Tau(RDΔ) causes pre- and postsynaptic structural deterioration and Ca(++) dysregulation which leads to synaptic plasticity deficits.

View Article: PubMed Central - PubMed

ABSTRACT

Introduction: We used an inducible mouse model expressing the Tau repeat domain with the pro-aggregant mutation ΔK280 to analyze presynaptic Tau pathology in the hippocampus.

Results: Expression of pro-aggregant Tau(RDΔ) leads to phosphorylation, aggregation and missorting of Tau in area CA3. To test presynaptic pathophysiology we used electrophysiology in the mossy fiber tract. Synaptic transmission was severely disturbed in pro-aggregant Tau(RDΔ) and Tau-knockout mice. Long-term depression of the mossy fiber tract failed in pro-aggregant Tau(RDΔ) mice. We observed an increase in bouton size, but a decline in numbers and presynaptic markers. Both pre-and postsynaptic structural deficits are preventable by inhibition of Tau(RDΔ) aggregation. Calcium imaging revealed progressive calcium dysregulation in boutons of pro-aggregant Tau(RDΔ) mice. In N2a cells we observed this even in cells without tangle load, whilst in primary hippocampal neurons transient Tau(RDΔ) expression alone caused similar Ca(++) dysregulation. Ultrastructural analysis revealed a severe depletion of synaptic vesicles pool in accordance with synaptic transmission impairments.

Conclusions: We conclude that oligomer formation by Tau(RDΔ) causes pre- and postsynaptic structural deterioration and Ca(++) dysregulation which leads to synaptic plasticity deficits.

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Related in: MedlinePlus

Expression of TauRDΔcauses morphological changes of mossy fiber boutons in hippocampal slice cultures. Photomicrographs of slice cultures from control (Ctrl) or pro-aggregant-mice (Pro) at DIV5 (a1-b3) and DIV10 (c1-d9); area CA3-immunostaining against pan-Tau (K9JA, a1,b1,c1,d1), phospho-Tau (12E8, a2,b2,c2,d2) and merged (a3,b3,c3,d3) pictures are depicted. (a1) No 12E8-immunoreactivity is present in control slices at DIV5 (a1-a3) and DIV10 (c1-c3). (b1) In contrast, in pro-aggregant slices 12E8-immunoreactivity is observed in pyramidal cell somata and dendrites at DIV5 (b1-b3) and DIV10 (d1-d3). (c4-c6) Zoom-in images (from (c1)) showing mossy fiber boutons filled with Tau. No 12E8 phosphorylation was detected in control slices. (d4-d6, zoom-in from d1) In contrast, boutons in pro-aggregant slices contain phosphorylated Tau. (c7-c9 + d7-d9) Immunostaining against pan-Tau (green), synaptophysin (S’physin, red) and merged picture is shown in control (c7-c9) and pro-aggregant slices (d7-d9). Arrows mark the axon shaft; boutons are marked by dotted line. (e) Higher magnification of single mossy fiber boutons (stained with DiI) in slices from control mice, pro-aggregant mice and pro-aggregant slices treated with compound bb14. (f) The bouton diameter was increased by ~42% in pro-aggregant slices in comparison to control and by only ~18% when compared to bb14-treated pro-aggregant slices. (g) The bouton surface was larger in pro-aggregant slices (by ~75%) vs. control and by only 32% vs. bb14-treated pro-aggregant slice cultures. (h) The average distance between boutons was increased by ~50% in pro-aggregant slices compared to control and bb14-treated pro-aggregant cultures. (i) Numbers of filopodia (control: 1.56; pro-aggregant: 1.89; pro-aggregant + bb14: 1.77) per bouton was only slightly affected in pro-aggregant slices. (j) The length of filopodia (control: 1.66 μm; pro-aggregant: 1.39 μm; pro-aggregant + bb14: 1.69 μm) was not changed in pro-aggregant slices. One way ANOVA followed by Tukey’s post-hoc test *** p- value < 0.001; * p-value < 0.05). Error bars represent SEM.
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Fig5: Expression of TauRDΔcauses morphological changes of mossy fiber boutons in hippocampal slice cultures. Photomicrographs of slice cultures from control (Ctrl) or pro-aggregant-mice (Pro) at DIV5 (a1-b3) and DIV10 (c1-d9); area CA3-immunostaining against pan-Tau (K9JA, a1,b1,c1,d1), phospho-Tau (12E8, a2,b2,c2,d2) and merged (a3,b3,c3,d3) pictures are depicted. (a1) No 12E8-immunoreactivity is present in control slices at DIV5 (a1-a3) and DIV10 (c1-c3). (b1) In contrast, in pro-aggregant slices 12E8-immunoreactivity is observed in pyramidal cell somata and dendrites at DIV5 (b1-b3) and DIV10 (d1-d3). (c4-c6) Zoom-in images (from (c1)) showing mossy fiber boutons filled with Tau. No 12E8 phosphorylation was detected in control slices. (d4-d6, zoom-in from d1) In contrast, boutons in pro-aggregant slices contain phosphorylated Tau. (c7-c9 + d7-d9) Immunostaining against pan-Tau (green), synaptophysin (S’physin, red) and merged picture is shown in control (c7-c9) and pro-aggregant slices (d7-d9). Arrows mark the axon shaft; boutons are marked by dotted line. (e) Higher magnification of single mossy fiber boutons (stained with DiI) in slices from control mice, pro-aggregant mice and pro-aggregant slices treated with compound bb14. (f) The bouton diameter was increased by ~42% in pro-aggregant slices in comparison to control and by only ~18% when compared to bb14-treated pro-aggregant slices. (g) The bouton surface was larger in pro-aggregant slices (by ~75%) vs. control and by only 32% vs. bb14-treated pro-aggregant slice cultures. (h) The average distance between boutons was increased by ~50% in pro-aggregant slices compared to control and bb14-treated pro-aggregant cultures. (i) Numbers of filopodia (control: 1.56; pro-aggregant: 1.89; pro-aggregant + bb14: 1.77) per bouton was only slightly affected in pro-aggregant slices. (j) The length of filopodia (control: 1.66 μm; pro-aggregant: 1.39 μm; pro-aggregant + bb14: 1.69 μm) was not changed in pro-aggregant slices. One way ANOVA followed by Tukey’s post-hoc test *** p- value < 0.001; * p-value < 0.05). Error bars represent SEM.

Mentions: Next, we made use of organotypic slice cultures, since this system is particularly advantageous for long distance granule cell-CA3 axonal connections [38,39]. With DiI labeling we detected granule cell-CA3 mossy fiber connections in DIV 10 slices (Figure 4a and b), a time point when we already detected phosphorylated and mislocalized Tau in TauRDΔ slices (Figure 5d1-6), well comparable with results from acute slices. It was possible to label boutons as well as thorny excrescences in area CA3 (Figure 4c). In pro-aggregant slices the dendritic spine density (1.26 ± 0.07 spines/μm) was reduced by ~20% compared to control littermate slices (1.56 ± 0.07 spines/μm). This reduction was prevented by adding the Tau aggregation inhibitor bb14 [31] to pro-aggregant slices at DIV 0 (1.49 ± 0.05 spines/μm; F(2/81) = 5.851; p = 0.0042; Figure 4d,e).Figure 4


Pro-aggregant Tau impairs mossy fiber plasticity due to structural changes and Ca(++) dysregulation.

Decker JM, Krüger L, Sydow A, Zhao S, Frotscher M, Mandelkow E, Mandelkow EM - Acta Neuropathol Commun (2015)

Expression of TauRDΔcauses morphological changes of mossy fiber boutons in hippocampal slice cultures. Photomicrographs of slice cultures from control (Ctrl) or pro-aggregant-mice (Pro) at DIV5 (a1-b3) and DIV10 (c1-d9); area CA3-immunostaining against pan-Tau (K9JA, a1,b1,c1,d1), phospho-Tau (12E8, a2,b2,c2,d2) and merged (a3,b3,c3,d3) pictures are depicted. (a1) No 12E8-immunoreactivity is present in control slices at DIV5 (a1-a3) and DIV10 (c1-c3). (b1) In contrast, in pro-aggregant slices 12E8-immunoreactivity is observed in pyramidal cell somata and dendrites at DIV5 (b1-b3) and DIV10 (d1-d3). (c4-c6) Zoom-in images (from (c1)) showing mossy fiber boutons filled with Tau. No 12E8 phosphorylation was detected in control slices. (d4-d6, zoom-in from d1) In contrast, boutons in pro-aggregant slices contain phosphorylated Tau. (c7-c9 + d7-d9) Immunostaining against pan-Tau (green), synaptophysin (S’physin, red) and merged picture is shown in control (c7-c9) and pro-aggregant slices (d7-d9). Arrows mark the axon shaft; boutons are marked by dotted line. (e) Higher magnification of single mossy fiber boutons (stained with DiI) in slices from control mice, pro-aggregant mice and pro-aggregant slices treated with compound bb14. (f) The bouton diameter was increased by ~42% in pro-aggregant slices in comparison to control and by only ~18% when compared to bb14-treated pro-aggregant slices. (g) The bouton surface was larger in pro-aggregant slices (by ~75%) vs. control and by only 32% vs. bb14-treated pro-aggregant slice cultures. (h) The average distance between boutons was increased by ~50% in pro-aggregant slices compared to control and bb14-treated pro-aggregant cultures. (i) Numbers of filopodia (control: 1.56; pro-aggregant: 1.89; pro-aggregant + bb14: 1.77) per bouton was only slightly affected in pro-aggregant slices. (j) The length of filopodia (control: 1.66 μm; pro-aggregant: 1.39 μm; pro-aggregant + bb14: 1.69 μm) was not changed in pro-aggregant slices. One way ANOVA followed by Tukey’s post-hoc test *** p- value < 0.001; * p-value < 0.05). Error bars represent SEM.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Fig5: Expression of TauRDΔcauses morphological changes of mossy fiber boutons in hippocampal slice cultures. Photomicrographs of slice cultures from control (Ctrl) or pro-aggregant-mice (Pro) at DIV5 (a1-b3) and DIV10 (c1-d9); area CA3-immunostaining against pan-Tau (K9JA, a1,b1,c1,d1), phospho-Tau (12E8, a2,b2,c2,d2) and merged (a3,b3,c3,d3) pictures are depicted. (a1) No 12E8-immunoreactivity is present in control slices at DIV5 (a1-a3) and DIV10 (c1-c3). (b1) In contrast, in pro-aggregant slices 12E8-immunoreactivity is observed in pyramidal cell somata and dendrites at DIV5 (b1-b3) and DIV10 (d1-d3). (c4-c6) Zoom-in images (from (c1)) showing mossy fiber boutons filled with Tau. No 12E8 phosphorylation was detected in control slices. (d4-d6, zoom-in from d1) In contrast, boutons in pro-aggregant slices contain phosphorylated Tau. (c7-c9 + d7-d9) Immunostaining against pan-Tau (green), synaptophysin (S’physin, red) and merged picture is shown in control (c7-c9) and pro-aggregant slices (d7-d9). Arrows mark the axon shaft; boutons are marked by dotted line. (e) Higher magnification of single mossy fiber boutons (stained with DiI) in slices from control mice, pro-aggregant mice and pro-aggregant slices treated with compound bb14. (f) The bouton diameter was increased by ~42% in pro-aggregant slices in comparison to control and by only ~18% when compared to bb14-treated pro-aggregant slices. (g) The bouton surface was larger in pro-aggregant slices (by ~75%) vs. control and by only 32% vs. bb14-treated pro-aggregant slice cultures. (h) The average distance between boutons was increased by ~50% in pro-aggregant slices compared to control and bb14-treated pro-aggregant cultures. (i) Numbers of filopodia (control: 1.56; pro-aggregant: 1.89; pro-aggregant + bb14: 1.77) per bouton was only slightly affected in pro-aggregant slices. (j) The length of filopodia (control: 1.66 μm; pro-aggregant: 1.39 μm; pro-aggregant + bb14: 1.69 μm) was not changed in pro-aggregant slices. One way ANOVA followed by Tukey’s post-hoc test *** p- value < 0.001; * p-value < 0.05). Error bars represent SEM.
Mentions: Next, we made use of organotypic slice cultures, since this system is particularly advantageous for long distance granule cell-CA3 axonal connections [38,39]. With DiI labeling we detected granule cell-CA3 mossy fiber connections in DIV 10 slices (Figure 4a and b), a time point when we already detected phosphorylated and mislocalized Tau in TauRDΔ slices (Figure 5d1-6), well comparable with results from acute slices. It was possible to label boutons as well as thorny excrescences in area CA3 (Figure 4c). In pro-aggregant slices the dendritic spine density (1.26 ± 0.07 spines/μm) was reduced by ~20% compared to control littermate slices (1.56 ± 0.07 spines/μm). This reduction was prevented by adding the Tau aggregation inhibitor bb14 [31] to pro-aggregant slices at DIV 0 (1.49 ± 0.05 spines/μm; F(2/81) = 5.851; p = 0.0042; Figure 4d,e).Figure 4

Bottom Line: Both pre-and postsynaptic structural deficits are preventable by inhibition of Tau(RDΔ) aggregation.In N2a cells we observed this even in cells without tangle load, whilst in primary hippocampal neurons transient Tau(RDΔ) expression alone caused similar Ca(++) dysregulation.We conclude that oligomer formation by Tau(RDΔ) causes pre- and postsynaptic structural deterioration and Ca(++) dysregulation which leads to synaptic plasticity deficits.

View Article: PubMed Central - PubMed

ABSTRACT

Introduction: We used an inducible mouse model expressing the Tau repeat domain with the pro-aggregant mutation ΔK280 to analyze presynaptic Tau pathology in the hippocampus.

Results: Expression of pro-aggregant Tau(RDΔ) leads to phosphorylation, aggregation and missorting of Tau in area CA3. To test presynaptic pathophysiology we used electrophysiology in the mossy fiber tract. Synaptic transmission was severely disturbed in pro-aggregant Tau(RDΔ) and Tau-knockout mice. Long-term depression of the mossy fiber tract failed in pro-aggregant Tau(RDΔ) mice. We observed an increase in bouton size, but a decline in numbers and presynaptic markers. Both pre-and postsynaptic structural deficits are preventable by inhibition of Tau(RDΔ) aggregation. Calcium imaging revealed progressive calcium dysregulation in boutons of pro-aggregant Tau(RDΔ) mice. In N2a cells we observed this even in cells without tangle load, whilst in primary hippocampal neurons transient Tau(RDΔ) expression alone caused similar Ca(++) dysregulation. Ultrastructural analysis revealed a severe depletion of synaptic vesicles pool in accordance with synaptic transmission impairments.

Conclusions: We conclude that oligomer formation by Tau(RDΔ) causes pre- and postsynaptic structural deterioration and Ca(++) dysregulation which leads to synaptic plasticity deficits.

Show MeSH
Related in: MedlinePlus