Regeneration and reinnervation of the dystrophic mouse soleus muscle

Summers, Philip; Ashmore, C. R.

doi:10.1007/bf00703205

Cited by 4 publications

(4 citation statements)

References 46 publications

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“…Thus, regulation of cellular morphology and survival by laminin-2 (or, ␣2) is largely redundant to other molecular signals in embryos. Nerves and muscles regenerate in ␣2-deficient mice (Bray et al, 1983;Parry, 1979;Summers and Ashmore, 1983), suggesting some of the redundant factors are present in ␣2-deficient adults, as well. One candidate is laminin-8 (␣4␤1␥1), which is widely expressed in embryonic muscle and endoneurium, and is re-expressed in ␣2-deficient adult muscles and nerves .…”

Section: Functions In Extrasynaptic Blsmentioning

confidence: 99%

“…This suggests that laminin-␤2 is required to correctly target nerve terminals during reinnervation in adults. Laminin-11 is the most likely active isoform, because functional reinnervation occurs in ␣2-deficient mice (Bray et al, 1983;Parry, 1979;Summers and Ashmore, 1983) that lack laminin-4 at the NMJ , and synaptic defects in ␣4-deficient mice are limited (Patton et al, 1999b). Although normal innervation of ␤2-deficient embryonic muscles occurs without overgrowth, this likely occurs as a consequence of development.…”

Section: Functions In Synaptic Blsmentioning

confidence: 99%

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Laminins of the neuromuscular system

Patton

2000

Microsc. Res. Tech.

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The mammalian neuromuscular system expresses seven laminin genes (α1, α2, α4, α5, β1, β2, and γ1), produces seven isoforms of the laminin trimer (laminins 1, 2, 4, 8, 9, 10, and 11), and distributes these trimers to at least seven distinct basal laminae (perineurial, endoneurial, terminal Schwann cell, myotendinous junction, synaptic cleft, synaptic fold, and extrajunctional muscle). The patterns of expression, assembly, and distribution are regulated during development, and primary and secondary changes in laminin expression occur in several neuromuscular genetic disorders. Functional studies using knockout and transgenic mice, and purified laminins and cell types, demonstrate that laminins are required components of basal laminae in the neuromuscular system. Collectively, laminins have both structural and signaling functions; individually, laminin isoforms have unique roles in regulating the behavior of nerve, muscle, and Schwann cell. Among them, laminin‐2 (α2β1γ1) plays an important structural role in supporting the muscle plasma membrane, laminin‐4 regulates adhesion and differentiation of the myotendinous junction, and laminin‐11 regulates nerve terminal differentiation and Schwann cell motility. Together, these observations reveal remarkable diversity in the formation and function of laminins and basal laminae, and suggest avenues for addressing some neuromuscular diseases. Microsc. Res. Tech. 51:247–261, 2000. © 2000 Wiley‐Liss, Inc.

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Section: Functions In Extrasynaptic Blsmentioning

confidence: 99%

Section: Functions In Synaptic Blsmentioning

confidence: 99%

Laminins of the neuromuscular system

Patton

2000

Microsc. Res. Tech.

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“…Muscle injury results in sprouting of the neuromuscular junction, resulting in polyneuronal innervation of muscle (Huang and Keynes, 1983;Summers and Ashmore, 1983;PecotDechavassine, 1986). The factors involved in neuromuscular junction sprouting have not been identified.…”

Section: Extracellular Myosin II Promotes Axon Formation 443mentioning

confidence: 96%

Extracellular Muscle Myosin II Promotes Sensory Axon Formation

Silver

Gallo²

2005

DNA and Cell Biology

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Myosin II is an intracellular force-generating enzyme with no known extracellular action. In the course of experiments involving trituration loading of skeletal myosin II into embryonic sensory neurons we observed that extracellular application of myosin II to neurons resulted in a robust increase in the number of axons initiated by each neuron, but did not alter the rate of axon extension. Substratum bound myosin II in the presence of laminin was sufficient to elicit increases in axon formation. However, in the absence of laminin, extracellular myosin II alone was not sufficient to promote axon formation, although it allowed neuron survival in the presence of neurotrophin. Myosin II promoted the attachment of neurons to the substratum in the absence or presence of laminin. In addition to promoting the initiation of axons, extracellular myosin II also increased the frequency of axon collateral branching. Finally, extracellular myosin II did not affect growth cone collapse in response to semaphorin-IIIA, but attenuated the inhibitory action of chondroitin sulfate proteoglycans on axon extension. Surprisingly, these results demonstrate that extracellular myosin II promotes attachment of neurons and increases axon formation and branching. The potential significance of these observations is discussed in the context of myosin II release from injured muscle and a previous demonstration of extracellular myosin II association with the extracellular matrix.

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“…These muscle fibers were classified as functionally denervated (Law et al, 1976), a condition in which a n axon, in close apposition to the motor fibers, is still able to supply sufficient trophic influence to prevent denervation but is not healthy enough to maintain electrophysiologically efficient synapses. The hypothesis of less efficient junctions is sustained by the presence of elongated nerve terminals with collateral sprouting (Harris and Ribchester, 1979;Summers and Ashmore, 1983). Less complex and more shallow postjunctional folds have also been re-ported in some studies (Ragab, 1971;Gilbert et al, 1973;Pachte et al, 1974) but these modifications of the subneural apparatus were attributed to degeneration of the subjacent muscle fiber.…”

Section: Introductionmentioning

confidence: 97%

Reduction of postjunctional fold density and depth in dystrophic mice

Tremblay

Grégoire

Sasseville

et al. 1988

Synapse

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A total of 769 neuromuscular junction profiles (on 221 muscle fibers) from 21 normal (C57BL/6J +/+), 6 heterozygous (C57BL/6J dy2J/+) and 22 homozygous dystrophic (C57BL/6J dy2J/dy2J) gastrocnemius were photographed in electron microscopy. The fast and slow twitch muscle fibers were differentiated by the width of the Z lines. The number of secondary postjunctional folds per unit length of synaptic cleft was lower in dystrophic than in normal animals. Intermediate values were obtained in heterozygous animals. The length of the postsynaptic membrane was measured and normalized by dividing it by the length of the cross-section through the synaptic cleft. This normalized length of postjunctional membrane was significantly reduced by 45% in dystrophic animals relative to normal animals and by 41% relative to heterozygous animals. The depth of the secondary folds was also significantly reduced in dystrophic animals relative to normal animals in both fast and slow twitch fibers. These morphometric changes of the postjunctional membrane were observed on NMJs whose nerve terminals were not significantly modified by the dystrophic process and were sometimes observed on apparently normal muscle fibers.

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Regeneration and reinnervation of the dystrophic mouse soleus muscle

Cited by 4 publications

References 46 publications

Laminins of the neuromuscular system

Laminins of the neuromuscular system

Extracellular Muscle Myosin II Promotes Sensory Axon Formation

Reduction of postjunctional fold density and depth in dystrophic mice

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