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Neuromuscular synapse integrity requires linkage of acetylcholine receptors to postsynaptic intermediate filament networks via rapsyn-plectin 1f complexes.

Mihailovska E, Raith M, Valencia RG, Fischer I, Al Banchaabouchi M, Herbst R, Wiche G - Mol. Biol. Cell (2014)

Bottom Line: Live imaging of acetylcholine receptors (AChRs) in cultured myotubes differentiated ex vivo from immortalized plectin-deficient myoblasts revealed them to be highly mobile and unable to coalesce into stable clusters, in contrast to wild-type cells.In their phenotypic behavior, mutant mice closely mimicked EBS-MD-MyS patients, including impaired body balance, severe muscle weakness, and reduced life span.Our study demonstrates that linkage to desmin IF networks via plectin is crucial for formation and maintenance of AChR clusters, postsynaptic NMJ organization, and body locomotion.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria.

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Electron microscopy of NMJs in wt and plectin-deficient soleus muscle. (A) Cross-sectioned NMJs show numerous densely assembled synaptic folds of comparable length and upright orientation in wt myofibers, contrasting the mere two or three (mostly curved and disoriented) infoldings formed per presynaptic membrane in mutant mice (left and middle, top vs. bottom row). Middle, 3× magnification of boxed areas in left. Right, survey views showing lower frequency of postsynaptic mitochondria in plectin-deficient compared with wt muscle. Outlining (red), synaptic folds; green, presynaptic membranes. Arrowheads, selected mitochondria. Note disoriented Z-disks in lower right. Bars, 1 μm. (B, C) Numerical evaluation of infoldings (B) and NMJ-associated mitochondria (C), normalized to presynaptic membrane length. Wt, n = 34; Pax7-Cre/cKO, n = 36. Mean ± SEM, two experiments. ***p < 0.001, unpaired Student's t-test.
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Figure 8: Electron microscopy of NMJs in wt and plectin-deficient soleus muscle. (A) Cross-sectioned NMJs show numerous densely assembled synaptic folds of comparable length and upright orientation in wt myofibers, contrasting the mere two or three (mostly curved and disoriented) infoldings formed per presynaptic membrane in mutant mice (left and middle, top vs. bottom row). Middle, 3× magnification of boxed areas in left. Right, survey views showing lower frequency of postsynaptic mitochondria in plectin-deficient compared with wt muscle. Outlining (red), synaptic folds; green, presynaptic membranes. Arrowheads, selected mitochondria. Note disoriented Z-disks in lower right. Bars, 1 μm. (B, C) Numerical evaluation of infoldings (B) and NMJ-associated mitochondria (C), normalized to presynaptic membrane length. Wt, n = 34; Pax7-Cre/cKO, n = 36. Mean ± SEM, two experiments. ***p < 0.001, unpaired Student's t-test.

Mentions: To investigate whether plectin deficiency affected the ultrastructure of NMJs, in particular the typical infoldings of the sarcolemma, we subjected epoxy resin–embedded ultrathin sections of soleus muscle from adult wt and Pax7-Cre/cKO mice to electron microscopy. Whereas in wt mice, the postsynaptic region was characterized by numerous, evenly distributed infoldings of uniform depth, in Pax7-Cre/cKO mice, synaptic infoldings were strikingly rare and of uneven shape (Figure 8, A, left and center, and B). In addition, a dearth of postsynaptic mitochondria was noticeable (Figure 8, A, right, and C).


Neuromuscular synapse integrity requires linkage of acetylcholine receptors to postsynaptic intermediate filament networks via rapsyn-plectin 1f complexes.

Mihailovska E, Raith M, Valencia RG, Fischer I, Al Banchaabouchi M, Herbst R, Wiche G - Mol. Biol. Cell (2014)

Electron microscopy of NMJs in wt and plectin-deficient soleus muscle. (A) Cross-sectioned NMJs show numerous densely assembled synaptic folds of comparable length and upright orientation in wt myofibers, contrasting the mere two or three (mostly curved and disoriented) infoldings formed per presynaptic membrane in mutant mice (left and middle, top vs. bottom row). Middle, 3× magnification of boxed areas in left. Right, survey views showing lower frequency of postsynaptic mitochondria in plectin-deficient compared with wt muscle. Outlining (red), synaptic folds; green, presynaptic membranes. Arrowheads, selected mitochondria. Note disoriented Z-disks in lower right. Bars, 1 μm. (B, C) Numerical evaluation of infoldings (B) and NMJ-associated mitochondria (C), normalized to presynaptic membrane length. Wt, n = 34; Pax7-Cre/cKO, n = 36. Mean ± SEM, two experiments. ***p < 0.001, unpaired Student's t-test.
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Related In: Results  -  Collection

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Figure 8: Electron microscopy of NMJs in wt and plectin-deficient soleus muscle. (A) Cross-sectioned NMJs show numerous densely assembled synaptic folds of comparable length and upright orientation in wt myofibers, contrasting the mere two or three (mostly curved and disoriented) infoldings formed per presynaptic membrane in mutant mice (left and middle, top vs. bottom row). Middle, 3× magnification of boxed areas in left. Right, survey views showing lower frequency of postsynaptic mitochondria in plectin-deficient compared with wt muscle. Outlining (red), synaptic folds; green, presynaptic membranes. Arrowheads, selected mitochondria. Note disoriented Z-disks in lower right. Bars, 1 μm. (B, C) Numerical evaluation of infoldings (B) and NMJ-associated mitochondria (C), normalized to presynaptic membrane length. Wt, n = 34; Pax7-Cre/cKO, n = 36. Mean ± SEM, two experiments. ***p < 0.001, unpaired Student's t-test.
Mentions: To investigate whether plectin deficiency affected the ultrastructure of NMJs, in particular the typical infoldings of the sarcolemma, we subjected epoxy resin–embedded ultrathin sections of soleus muscle from adult wt and Pax7-Cre/cKO mice to electron microscopy. Whereas in wt mice, the postsynaptic region was characterized by numerous, evenly distributed infoldings of uniform depth, in Pax7-Cre/cKO mice, synaptic infoldings were strikingly rare and of uneven shape (Figure 8, A, left and center, and B). In addition, a dearth of postsynaptic mitochondria was noticeable (Figure 8, A, right, and C).

Bottom Line: Live imaging of acetylcholine receptors (AChRs) in cultured myotubes differentiated ex vivo from immortalized plectin-deficient myoblasts revealed them to be highly mobile and unable to coalesce into stable clusters, in contrast to wild-type cells.In their phenotypic behavior, mutant mice closely mimicked EBS-MD-MyS patients, including impaired body balance, severe muscle weakness, and reduced life span.Our study demonstrates that linkage to desmin IF networks via plectin is crucial for formation and maintenance of AChR clusters, postsynaptic NMJ organization, and body locomotion.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria.

Show MeSH
Related in: MedlinePlus