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Age-Related Changes in Pre- and Postsynaptic Partners of the Cholinergic C-Boutons in Wild-Type and SOD1G93A Lumbar Motoneurons.

Milan L, Courtand G, Cardoit L, Masmejean F, Barrière G, Cazalets JR, Garret M, Bertrand SS - PLoS ONE (2015)

Bottom Line: In WT motoneurons, both C-bouton terminals and associated M2 postsynaptic receptors presented a complex age-related dynamic that appeared completely disrupted in SOD1 motoneurons.Finally, we showed that early C-bouton system alterations have no physiological impact on the cholinergic neuromodulation of newborn motoneurons.Altogether, these data suggest a complete reconfiguration of the spinal cholinergic system in SOD1 spinal networks that could be part of the compensatory mechanisms established during spinal development.

View Article: PubMed Central - PubMed

Affiliation: INCIA, Université de Bordeaux, CNRS UMR5287, Bordeaux, France.

ABSTRACT
Large cholinergic synaptic terminals known as C-boutons densely innervate the soma and proximal dendrites of motoneurons that are prone to neurodegeneration in amyotrophic lateral sclerosis (ALS). Studies using the Cu/Zn-superoxide dismutase (SOD1) mouse model of ALS have generated conflicting data regarding C-bouton alterations exhibited during ALS pathogenesis. In the present work, a longitudinal study combining immunohistochemistry, biochemical approaches and extra- and intra-cellular electrophysiological recordings revealed that the whole spinal cholinergic system is modified in the SOD1 mouse model of ALS compared to wild type (WT) mice as early as the second postnatal week. In WT motoneurons, both C-bouton terminals and associated M2 postsynaptic receptors presented a complex age-related dynamic that appeared completely disrupted in SOD1 motoneurons. Indeed, parallel to C-bouton morphological alterations, analysis of confocal images revealed a clustering process of M2 receptors during WT motoneuron development and maturation that was absent in SOD1 motoneurons. Our data demonstrated for the first time that the lamina X cholinergic interneurons, the neuronal source of C-boutons, are over-abundant in high lumbar segments in SOD1 mice and are subject to neurodegeneration in the SOD1 animal model. Finally, we showed that early C-bouton system alterations have no physiological impact on the cholinergic neuromodulation of newborn motoneurons. Altogether, these data suggest a complete reconfiguration of the spinal cholinergic system in SOD1 spinal networks that could be part of the compensatory mechanisms established during spinal development.

No MeSH data available.


Related in: MedlinePlus

M2 receptor expression is decreased in presymptomatic stages in the SOD1 ventral spinal cord.(A) Representative protein levels of the M2 muscarinic receptor detected by western blot in wild type (WT) and SOD1 (SOD) mice at different postnatal (P) stages. All blots were reprobed for β-actin as a loading control. The molecular weight in kDa is shown on the left side of the picture. (B) Mean M2 receptor/β-actin expression ratio as a function of animal age in WT (black bars) and SOD1 (white bars) mice. At least four WT and four SOD1 mice were tested in each group. Comparisons between groups were made with two-way ANOVA with Sidak’s multiple comparison tests. Asterisks indicate positive significance (p<0.05).
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pone.0135525.g003: M2 receptor expression is decreased in presymptomatic stages in the SOD1 ventral spinal cord.(A) Representative protein levels of the M2 muscarinic receptor detected by western blot in wild type (WT) and SOD1 (SOD) mice at different postnatal (P) stages. All blots were reprobed for β-actin as a loading control. The molecular weight in kDa is shown on the left side of the picture. (B) Mean M2 receptor/β-actin expression ratio as a function of animal age in WT (black bars) and SOD1 (white bars) mice. At least four WT and four SOD1 mice were tested in each group. Comparisons between groups were made with two-way ANOVA with Sidak’s multiple comparison tests. Asterisks indicate positive significance (p<0.05).

Mentions: Anatomical studies have shown accumulations of M2 receptors in the PSM of C-boutons [25] and electrophysiological experiments have further demonstrated the role of these muscarinic receptors in Mn cholinergic modulation [10,26]. As C-boutons exhibit morphological alterations in SOD1 lumbar Mns compared to WT, we addressed the question of whether the postsynaptic partners of these synapses were also modified. For this purpose, a western blot analysis was first performed to compare M2 receptor expression in the ventral spinal cord of WT and SOD1 mice from birth to presymptomatic stages (P100). Fig 3 shows that the M2 protein level was similar in the ventral spinal cord of WT and SOD1 mice from P1 to P21 (Fig 3A and 3B). In P40 animals, the M2 protein content in SOD1 cords tended to decrease compared to WT and became significantly smaller at P75 and P100 (Fig 3A and 3B). These results suggest that the global M2 protein level begins to decrease in presymptomatic stages in the ventral spinal cord of SOD1 mice.


Age-Related Changes in Pre- and Postsynaptic Partners of the Cholinergic C-Boutons in Wild-Type and SOD1G93A Lumbar Motoneurons.

Milan L, Courtand G, Cardoit L, Masmejean F, Barrière G, Cazalets JR, Garret M, Bertrand SS - PLoS ONE (2015)

M2 receptor expression is decreased in presymptomatic stages in the SOD1 ventral spinal cord.(A) Representative protein levels of the M2 muscarinic receptor detected by western blot in wild type (WT) and SOD1 (SOD) mice at different postnatal (P) stages. All blots were reprobed for β-actin as a loading control. The molecular weight in kDa is shown on the left side of the picture. (B) Mean M2 receptor/β-actin expression ratio as a function of animal age in WT (black bars) and SOD1 (white bars) mice. At least four WT and four SOD1 mice were tested in each group. Comparisons between groups were made with two-way ANOVA with Sidak’s multiple comparison tests. Asterisks indicate positive significance (p<0.05).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4549056&req=5

pone.0135525.g003: M2 receptor expression is decreased in presymptomatic stages in the SOD1 ventral spinal cord.(A) Representative protein levels of the M2 muscarinic receptor detected by western blot in wild type (WT) and SOD1 (SOD) mice at different postnatal (P) stages. All blots were reprobed for β-actin as a loading control. The molecular weight in kDa is shown on the left side of the picture. (B) Mean M2 receptor/β-actin expression ratio as a function of animal age in WT (black bars) and SOD1 (white bars) mice. At least four WT and four SOD1 mice were tested in each group. Comparisons between groups were made with two-way ANOVA with Sidak’s multiple comparison tests. Asterisks indicate positive significance (p<0.05).
Mentions: Anatomical studies have shown accumulations of M2 receptors in the PSM of C-boutons [25] and electrophysiological experiments have further demonstrated the role of these muscarinic receptors in Mn cholinergic modulation [10,26]. As C-boutons exhibit morphological alterations in SOD1 lumbar Mns compared to WT, we addressed the question of whether the postsynaptic partners of these synapses were also modified. For this purpose, a western blot analysis was first performed to compare M2 receptor expression in the ventral spinal cord of WT and SOD1 mice from birth to presymptomatic stages (P100). Fig 3 shows that the M2 protein level was similar in the ventral spinal cord of WT and SOD1 mice from P1 to P21 (Fig 3A and 3B). In P40 animals, the M2 protein content in SOD1 cords tended to decrease compared to WT and became significantly smaller at P75 and P100 (Fig 3A and 3B). These results suggest that the global M2 protein level begins to decrease in presymptomatic stages in the ventral spinal cord of SOD1 mice.

Bottom Line: In WT motoneurons, both C-bouton terminals and associated M2 postsynaptic receptors presented a complex age-related dynamic that appeared completely disrupted in SOD1 motoneurons.Finally, we showed that early C-bouton system alterations have no physiological impact on the cholinergic neuromodulation of newborn motoneurons.Altogether, these data suggest a complete reconfiguration of the spinal cholinergic system in SOD1 spinal networks that could be part of the compensatory mechanisms established during spinal development.

View Article: PubMed Central - PubMed

Affiliation: INCIA, Université de Bordeaux, CNRS UMR5287, Bordeaux, France.

ABSTRACT
Large cholinergic synaptic terminals known as C-boutons densely innervate the soma and proximal dendrites of motoneurons that are prone to neurodegeneration in amyotrophic lateral sclerosis (ALS). Studies using the Cu/Zn-superoxide dismutase (SOD1) mouse model of ALS have generated conflicting data regarding C-bouton alterations exhibited during ALS pathogenesis. In the present work, a longitudinal study combining immunohistochemistry, biochemical approaches and extra- and intra-cellular electrophysiological recordings revealed that the whole spinal cholinergic system is modified in the SOD1 mouse model of ALS compared to wild type (WT) mice as early as the second postnatal week. In WT motoneurons, both C-bouton terminals and associated M2 postsynaptic receptors presented a complex age-related dynamic that appeared completely disrupted in SOD1 motoneurons. Indeed, parallel to C-bouton morphological alterations, analysis of confocal images revealed a clustering process of M2 receptors during WT motoneuron development and maturation that was absent in SOD1 motoneurons. Our data demonstrated for the first time that the lamina X cholinergic interneurons, the neuronal source of C-boutons, are over-abundant in high lumbar segments in SOD1 mice and are subject to neurodegeneration in the SOD1 animal model. Finally, we showed that early C-bouton system alterations have no physiological impact on the cholinergic neuromodulation of newborn motoneurons. Altogether, these data suggest a complete reconfiguration of the spinal cholinergic system in SOD1 spinal networks that could be part of the compensatory mechanisms established during spinal development.

No MeSH data available.


Related in: MedlinePlus