scholarly journals Antibodies that bind specifically to synaptic sites on muscle fiber basal lamina.

1979 ◽  
Vol 83 (2) ◽  
pp. 357-370 ◽  
Author(s):  
J R Sanes ◽  
Z W Hall
Keyword(s):  
Skeletal Muscle ◽  
Neuromuscular Junction ◽  
Basal Lamina ◽  
Muscle Fiber ◽  
Differential Susceptibility ◽  
Synaptic Cleft ◽  
Lens Capsule ◽  
Anterior Lens Capsule ◽  
Basement Membrane Collagen ◽  
Immunohistochemical Techniques

Basal lamina (BL) ensheathes each skeletal muscle fiber and passes through the synaptic cleft at the neuromuscular junction. Synaptic portions of the BL are known to play important roles in the formation, function, and maintenance of the neuromuscular junction. Here we demonstrate molecular differences between synaptic and extrasynaptic BL. We obtained antisera to immunogens that might be derived from or share determinants with muscle fiber BL, and used immunohistochemical techniques to study the binding of antibodies to rat skeletal muscle. Four antisera contained antibodies that distinguished synaptic from extrasynaptic portions of the muscle fiber's surface. They were anti-anterior lens capsule, anti-acetylcholinesterase, anti-lens capsule collagen, and anti-muscle basement membrane collagen; the last two sera were selective only after antibodies binding to extrasynaptic areas had been removed by adsorption with connective tissue from endplate-free regions of muscle. Synaptic antigens revealed by each of the four sera were present on the external cell surface and persisted after removal of nerve terminal. Schwann cell, and postsynaptic plasma membrane. Thus, the antigens are contained in or connected to BL of the synaptic cleft. Details of staining patterns, differential susceptibility of antigens to proteolysis, and adsorption experiments showed that the antibodies define at least three different determinants that are present in synaptic but not extrasynaptic BL.

scholarly journals Laminin, fibronectin, and collagen in synaptic and extrasynaptic portions of muscle fiber basement membrane.

1982 ◽  
Vol 93 (2) ◽  
pp. 442-451 ◽  
Author(s):  
J R Sanes
Keyword(s):  
Skeletal Muscle ◽  
Electron Microscope ◽  
Basement Membrane ◽  
Basal Lamina ◽  
Muscle Fiber ◽  
Synaptic Cleft ◽  
Neuromuscular Function ◽  
Collagen Iv ◽  
Rat Skeletal Muscle ◽  
Immunohistochemical Methods

Light and electron microscope immunohistochemical methods were used to study the distribution of several proteins in rat skeletal muscle. The aims were to identify components of muscle fiber basement membrane and to compare the small fraction (0.1%) of the basement membrane that extends through the synaptic cleft at the neuromuscular junction with the remaining, extrasynaptic portion. Synaptic basement membrane is functionally specialized and plays important roles in neuromuscular function and regeneration. Laminin, fibronectin, collagen IV, collagen V, and a collagenous protein (high-salt-soluble protein [HSP]) are all present in muscle fiber basement membrane. Laminin and collagen IV are concentrated in basal lamina (the feltlike, inner layer of the basement membrane) and are shared by synaptic and extrasynaptic regions. Fibronectin, also present synaptically and extrasynaptically, is present in basal lamina and in the overlying reticular lamina. Collagen V and HSP are present throughout extrasynaptic basement membrane but are absent from synaptic sites; HSP is concentrated in the reticular lamina and on the outer surface of the basal lamina. These results, together with experiments reported previously (Sanes and Hall, 1979. J. Cell Biol: 83:357--370), provide examples of three classes of components in muscle fiber basement membrane--synaptic, extrasynaptic, and shared.

scholarly journals Basal lamina directs acetylcholinesterase accumulation at synaptic sites in regenerating muscle.

1985 ◽  
Vol 101 (3) ◽  
pp. 735-743 ◽  
Author(s):  
L Anglister ◽  
U J McMahan
Keyword(s):  
Plasma Membrane ◽  
Neuromuscular Junction ◽  
Basal Lamina ◽  
Acetylcholine Receptors ◽  
Skeletal Muscles ◽  
Ache Activity ◽  
Neuromuscular Junctions ◽  
Muscle Fibers ◽  
Synaptic Cleft

In skeletal muscles that have been damaged in ways which spare the basal lamina sheaths of the muscle fibers, new myofibers develop within the sheaths and neuromuscular junctions form at the original synaptic sites on them. At the regenerated neuromuscular junctions, as at the original ones, the muscle fibers are characterized by junctional folds and accumulations of acetylcholine receptors and acetylcholinesterase (AChE). The formation of junctional folds and the accumulation of acetylcholine receptors is known to be directed by components of the synaptic portion of the myofiber basal lamina. The aim of this study was to determine whether or not the synaptic basal lamina contains molecules that direct the accumulation of AChE. We crushed frog muscles in a way that caused disintegration and phagocytosis of all cells at the neuromuscular junction, and at the same time, we irreversibly blocked AChE activity. New muscle fibers were allowed to regenerate within the basal lamina sheaths of the original muscle fibers but reinnervation of the muscles was deliberately prevented. We then stained for AChE activity and searched the surface of the new muscle fibers for deposits of enzyme they had produced. Despite the absence of innervation, AChE preferentially accumulated at points where the plasma membrane of the new muscle fibers was apposed to the regions of the basal lamina that had occupied the synaptic cleft at the neuromuscular junctions. We therefore conclude that molecules stably attached to the synaptic portion of myofiber basal lamina direct the accumulation of AChE at the original synaptic sites in regenerating muscle. Additional studies revealed that the AChE was solubilized by collagenase and that it remained adherent to basal lamina sheaths after degeneration of the new myofibers, indicating that it had become incorporated into the basal lamina, as at normal neuromuscular junctions.

scholarly journals Reinnervation of muscle fiber basal lamina after removal of myofibers. Differentiation of regenerating axons at original synaptic sites.

1978 ◽  
Vol 78 (1) ◽  
pp. 176-198 ◽  
Author(s):  
J R Sanes ◽  
L M Marshall ◽  
U J McMahan
Keyword(s):  
Skeletal Muscle ◽  
Basal Lamina ◽  
Muscle Fiber ◽  
Nerve Terminal ◽  
Synaptic Vesicles ◽  
Muscle Fibers ◽  
Nerve Terminals ◽  
Morphological Criteria ◽  
Histological Criteria ◽  
Active Zones

Axons regenerate to reinnervate denervated skeletal muscle fibers precisely at original synaptic sites, and they differentiate into nerve terminals where they contact muscle fibers. The aim of this study was to determine the location of factors that influence the growth and differentiation of the regenerating axons. We damaged and denervated frog muscles, causing myofibers and nerve terminals to degenerate, and then irradiated the animals to prevent regeneration of myofibers. The sheath of basal lamina (BL) that surrounds each myofiber survives these treatments, and original synaptic sites on BL can be recognized by several histological criteria after nerve terminals and muscle cells have been completely removed. Axons regenerate into the region of damage within 2 wk. They contact surviving BL almost exclusively at original synaptic sites; thus, factors that guide the axon's growth are present at synaptic sites and stably maintained outside of the myofiber. Portions of axons that contact the BL acquire active zones and accumulations of synaptic vesicles; thus by morphological criteria they differentiate into nerve terminals even though their postsynaptic targets, the myofibers, are absent. Within the terminals, the synaptic organelles line up opposite periodic specializations in the myofiber's BL, demonstrating that components associated with the BL play a role in organizing the differentiation of the nerve terminal.

scholarly journals Agrin-like molecules at synaptic sites in normal, denervated, and damaged skeletal muscles.

1987 ◽  
Vol 105 (6) ◽  
pp. 2457-2469 ◽  
Author(s):  
N E Reist ◽  
C Magill ◽  
U J McMahan
Keyword(s):  
Monoclonal Antibodies ◽  
Neuromuscular Junction ◽  
Basal Lamina ◽  
Skeletal Muscles ◽  
Neuromuscular Junctions ◽  
Electric Organ ◽  
Synaptic Cleft ◽  
Cellular Components ◽  
Term Maintenance

Several lines of evidence have led to the hypothesis that agrin, a protein extracted from the electric organ of Torpedo, is similar to the molecules in the synaptic cleft basal lamina at the neuromuscular junction that direct the formation of acetylcholine receptor and acetylcholinesterase aggregates on regenerating myofibers. One such finding is that monoclonal antibodies against agrin stain molecules concentrated in the synaptic cleft of neuromuscular junctions in rays. In the studies described here we made additional monoclonal antibodies against agrin and used them to extend our knowledge of agrin-like molecules at the neuromuscular junction. We found that anti-agrin antibodies intensely stained the synaptic cleft of frog and chicken as well as that of rays, that denervation of frog muscle resulted in a reduction in staining at the neuromuscular junction, and that the synaptic basal lamina in frog could be stained weeks after degeneration of all cellular components of the neuromuscular junction. We also describe anti-agrin staining in nonjunctional regions of muscle. We conclude the following: (a) agrin-like molecules are likely to be common to all vertebrate neuromuscular junctions; (b) the long-term maintenance of such molecules at the junction is nerve dependent; (c) the molecules are, indeed, a component of the synaptic basal lamina; and (d) they, like the molecules that direct the formation of receptor and esterase aggregates on regenerating myofibers, remain associated with the synaptic basal lamina after muscle damage.

scholarly journals ARIA is concentrated in the synaptic basal lamina of the developing chick neuromuscular junction.

1995 ◽  
Vol 130 (6) ◽  
pp. 1423-1434 ◽  
Author(s):  
A D Goodearl ◽  
A G Yee ◽  
A W Sandrock ◽  
G Corfas ◽  
G D Fischbach
Keyword(s):  
Neuromuscular Junction ◽  
Basal Lamina ◽  
Motor Neurons ◽  
Neuromuscular Junctions ◽  
Primary Cultures ◽  
Cholinergic Neurons ◽  
Synaptic Cleft ◽  
Motor Axons ◽  
Amino Terminal

ARIA is a member of a family of polypeptide growth and differentiation factors that also includes glial growth factor (GGF), neu differentiation factor, and heregulin. ARIA mRNA is expressed in all cholinergic neurons of the central nervous systems of rats and chicks, including spinal cord motor neurons. In vitro, ARIA elevates the rate of acetylcholine receptor incorporation into the plasma membrane of primary cultures of chick myotubes. To study whether ARIA may regulate the synthesis of junctional synaptic acetylcholine receptors in chick embryos, we have developed riboprobes and polyclonal antibody reagents that recognize isoforms of ARIA that include an amino-terminal immunoglobulin C2 domain and examined the expression and distribution of ARIA in motor neurons and at the neuromuscular junction. We detected significant ARIA mRNA expression in motor neurons as early as embryonic day 5, around the time that motor axons are making initial synaptic contacts with their target muscle cells. In older embryos and postnatal animals, we found ARIA protein concentrated in the synaptic cleft at neuromuscular junctions, consistent with transport down motor axons and release at nerve terminals. At high resolution using immunoelectron microscopy, we detected ARIA immunoreactivity exclusively in the synaptic basal lamina in a pattern consistent with binding to synapse specific components on the presynaptic side of the basal lamina. These results support a role for ARIA as a trophic factor released by motor neuron terminals that may regulate the formation of mature neuromuscular synapses.

scholarly journals The Neuromuscular Junction: Roles in Aging and Neuromuscular Disease

2021 ◽  
Vol 22 (15) ◽  
pp. 8058
Author(s):  
Shama R. Iyer ◽  
Sameer B. Shah ◽  
Richard M. Lovering
Keyword(s):  
Skeletal Muscle ◽  
Neuromuscular Junction ◽  
Motor Neuron ◽  
Muscle Fiber ◽  
Short Review ◽  
Muscle Disease ◽  
Contributing Factors ◽  
Functional Changes ◽  
Disease Modifier ◽  
Electrical Impulses

The neuromuscular junction (NMJ) is a specialized synapse that bridges the motor neuron and the skeletal muscle fiber and is crucial for conversion of electrical impulses originating in the motor neuron to action potentials in the muscle fiber. The consideration of contributing factors to skeletal muscle injury, muscular dystrophy and sarcopenia cannot be restricted only to processes intrinsic to the muscle, as data show that these conditions incur denervation-like findings, such as fragmented NMJ morphology and corresponding functional changes in neuromuscular transmission. Primary defects in the NMJ also influence functional loss in motor neuron disease, congenital myasthenic syndromes and myasthenia gravis, resulting in skeletal muscle weakness and heightened fatigue. Such findings underscore the role that the NMJ plays in neuromuscular performance. Regardless of cause or effect, functional denervation is now an accepted consequence of sarcopenia and muscle disease. In this short review, we provide an overview of the pathologic etiology, symptoms, and therapeutic strategies related to the NMJ. In particular, we examine the role of the NMJ as a disease modifier and a potential therapeutic target in neuromuscular injury and disease.

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