Limits...
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.

Show MeSH

Related in: MedlinePlus

Progressive impairment of Ca++ regulation in mossy fiber boutons in slices of TauRDΔ. (a1) The photomicrograph shows a magnification of stratum lucidum in a hippocampal slice culture from a control mouse. The slice was labeled with the Ca++ indicator dye Oregon Green BAPTA-1-AM (OGB-1) at DIV 5. After labeling it was possible to locate “giant” mossy fiber boutons loaded with OGB (white arrow). (a2) After membrane depolarization with high KCl Ca++ is flowing into the bouton (white arrow). The increase of intracellular calcium is false-color coded as indicated on the right column. (b1) Analogue to (a1-2) a bouton (white arrow) in a pro-aggregant slice is depicted before and after (b2) membrane depolarization (white arrow). (c1) At DIV 10 a stronger Ca++ influx in boutons (white arrow) after membrane depolarization (c2) compared to boutons in DIV 5 slices (a1-a2) was observed. (d1) A strong decrease in Ca++ influx after depolarization (d2) is observed in boutons from pro-aggregant TauRDΔ slices compared to control slices at DIV 10. (e) Quantification of maximum intracellular Ca++ increase after high KCl application in mossy fiber boutons from control littermate slices (white column) and from pro-aggregant TauRDΔ slices (red column) at DIV 5. Note that the maximum intracellular Ca++ concentration did not change in comparison to boutons from control littermate DIV 5 slices. (f) Comparison of maximum intracellular Ca++ concentration in boutons from control littermate slices (white column) and from pro-aggregant TauRDΔ slices (red column) at DIV10. At DIV 10 the pro-aggregant TauRDΔ slices show a severe impairment in Ca++ influx after membrane depolarization. Note that the maximum intracellular Ca++ peak in control boutons increases with maturation of slices (compare e and f control). Error bars represent SEM. *** p-value < 0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4384391&req=5

Fig7: Progressive impairment of Ca++ regulation in mossy fiber boutons in slices of TauRDΔ. (a1) The photomicrograph shows a magnification of stratum lucidum in a hippocampal slice culture from a control mouse. The slice was labeled with the Ca++ indicator dye Oregon Green BAPTA-1-AM (OGB-1) at DIV 5. After labeling it was possible to locate “giant” mossy fiber boutons loaded with OGB (white arrow). (a2) After membrane depolarization with high KCl Ca++ is flowing into the bouton (white arrow). The increase of intracellular calcium is false-color coded as indicated on the right column. (b1) Analogue to (a1-2) a bouton (white arrow) in a pro-aggregant slice is depicted before and after (b2) membrane depolarization (white arrow). (c1) At DIV 10 a stronger Ca++ influx in boutons (white arrow) after membrane depolarization (c2) compared to boutons in DIV 5 slices (a1-a2) was observed. (d1) A strong decrease in Ca++ influx after depolarization (d2) is observed in boutons from pro-aggregant TauRDΔ slices compared to control slices at DIV 10. (e) Quantification of maximum intracellular Ca++ increase after high KCl application in mossy fiber boutons from control littermate slices (white column) and from pro-aggregant TauRDΔ slices (red column) at DIV 5. Note that the maximum intracellular Ca++ concentration did not change in comparison to boutons from control littermate DIV 5 slices. (f) Comparison of maximum intracellular Ca++ concentration in boutons from control littermate slices (white column) and from pro-aggregant TauRDΔ slices (red column) at DIV10. At DIV 10 the pro-aggregant TauRDΔ slices show a severe impairment in Ca++ influx after membrane depolarization. Note that the maximum intracellular Ca++ peak in control boutons increases with maturation of slices (compare e and f control). Error bars represent SEM. *** p-value < 0.001.

Mentions: Normal Ca++ signaling during resting and active neuronal states is essential for neuronal survival and synaptic plasticity [41]. In the present study we wanted to know if depolarization dependent Ca++ dysregulation at the mossy fiber presynapse could be responsible for the described effects of pro-aggregant TauRDΔ on transmission and plasticity. Therefore we imaged Ca++ influx in mossy fiber boutons in s.l. of area CA3 in slice cultures loaded with Oregon green bapta (OGB, Figure 7). After membrane depolarization, we observed an increase of intracellular Ca++ concentration in axons with a peak in bouton-like structures compared with Ca++ influx at the axonal shaft (data not shown), indicating that functional ion channels are enriched on the bouton membrane. At DIV 5 the KCl-induced Ca ++ influx was comparable in boutons from pro-aggregant TauRDΔ slices and control littermates (pro-aggregant: 222.1 ± 12.4%, n = 10 and control: 249.7 ± 32.8% of baseline, n = 9; prepared from at least 5 animals per group, Figure 7a-b and e). However at a later time point (DIV 10) there was a pronounced reduction by 106.4% in pro-aggregant TauRDΔ expressing slices, compared with controls (control: 302.3 ± 21.1% of baseline, n = 20 and pro-aggregant: 195.9 ± 18.2% of baseline, n = 17; prepared from at least 5 animals per group) Figure 7c-d and f).Figure 7


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)

Progressive impairment of Ca++ regulation in mossy fiber boutons in slices of TauRDΔ. (a1) The photomicrograph shows a magnification of stratum lucidum in a hippocampal slice culture from a control mouse. The slice was labeled with the Ca++ indicator dye Oregon Green BAPTA-1-AM (OGB-1) at DIV 5. After labeling it was possible to locate “giant” mossy fiber boutons loaded with OGB (white arrow). (a2) After membrane depolarization with high KCl Ca++ is flowing into the bouton (white arrow). The increase of intracellular calcium is false-color coded as indicated on the right column. (b1) Analogue to (a1-2) a bouton (white arrow) in a pro-aggregant slice is depicted before and after (b2) membrane depolarization (white arrow). (c1) At DIV 10 a stronger Ca++ influx in boutons (white arrow) after membrane depolarization (c2) compared to boutons in DIV 5 slices (a1-a2) was observed. (d1) A strong decrease in Ca++ influx after depolarization (d2) is observed in boutons from pro-aggregant TauRDΔ slices compared to control slices at DIV 10. (e) Quantification of maximum intracellular Ca++ increase after high KCl application in mossy fiber boutons from control littermate slices (white column) and from pro-aggregant TauRDΔ slices (red column) at DIV 5. Note that the maximum intracellular Ca++ concentration did not change in comparison to boutons from control littermate DIV 5 slices. (f) Comparison of maximum intracellular Ca++ concentration in boutons from control littermate slices (white column) and from pro-aggregant TauRDΔ slices (red column) at DIV10. At DIV 10 the pro-aggregant TauRDΔ slices show a severe impairment in Ca++ influx after membrane depolarization. Note that the maximum intracellular Ca++ peak in control boutons increases with maturation of slices (compare e and f control). Error bars represent SEM. *** p-value < 0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4384391&req=5

Fig7: Progressive impairment of Ca++ regulation in mossy fiber boutons in slices of TauRDΔ. (a1) The photomicrograph shows a magnification of stratum lucidum in a hippocampal slice culture from a control mouse. The slice was labeled with the Ca++ indicator dye Oregon Green BAPTA-1-AM (OGB-1) at DIV 5. After labeling it was possible to locate “giant” mossy fiber boutons loaded with OGB (white arrow). (a2) After membrane depolarization with high KCl Ca++ is flowing into the bouton (white arrow). The increase of intracellular calcium is false-color coded as indicated on the right column. (b1) Analogue to (a1-2) a bouton (white arrow) in a pro-aggregant slice is depicted before and after (b2) membrane depolarization (white arrow). (c1) At DIV 10 a stronger Ca++ influx in boutons (white arrow) after membrane depolarization (c2) compared to boutons in DIV 5 slices (a1-a2) was observed. (d1) A strong decrease in Ca++ influx after depolarization (d2) is observed in boutons from pro-aggregant TauRDΔ slices compared to control slices at DIV 10. (e) Quantification of maximum intracellular Ca++ increase after high KCl application in mossy fiber boutons from control littermate slices (white column) and from pro-aggregant TauRDΔ slices (red column) at DIV 5. Note that the maximum intracellular Ca++ concentration did not change in comparison to boutons from control littermate DIV 5 slices. (f) Comparison of maximum intracellular Ca++ concentration in boutons from control littermate slices (white column) and from pro-aggregant TauRDΔ slices (red column) at DIV10. At DIV 10 the pro-aggregant TauRDΔ slices show a severe impairment in Ca++ influx after membrane depolarization. Note that the maximum intracellular Ca++ peak in control boutons increases with maturation of slices (compare e and f control). Error bars represent SEM. *** p-value < 0.001.
Mentions: Normal Ca++ signaling during resting and active neuronal states is essential for neuronal survival and synaptic plasticity [41]. In the present study we wanted to know if depolarization dependent Ca++ dysregulation at the mossy fiber presynapse could be responsible for the described effects of pro-aggregant TauRDΔ on transmission and plasticity. Therefore we imaged Ca++ influx in mossy fiber boutons in s.l. of area CA3 in slice cultures loaded with Oregon green bapta (OGB, Figure 7). After membrane depolarization, we observed an increase of intracellular Ca++ concentration in axons with a peak in bouton-like structures compared with Ca++ influx at the axonal shaft (data not shown), indicating that functional ion channels are enriched on the bouton membrane. At DIV 5 the KCl-induced Ca ++ influx was comparable in boutons from pro-aggregant TauRDΔ slices and control littermates (pro-aggregant: 222.1 ± 12.4%, n = 10 and control: 249.7 ± 32.8% of baseline, n = 9; prepared from at least 5 animals per group, Figure 7a-b and e). However at a later time point (DIV 10) there was a pronounced reduction by 106.4% in pro-aggregant TauRDΔ expressing slices, compared with controls (control: 302.3 ± 21.1% of baseline, n = 20 and pro-aggregant: 195.9 ± 18.2% of baseline, n = 17; prepared from at least 5 animals per group) Figure 7c-d and f).Figure 7

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