Although it is fundamentally a simple synapse, the formation and maturation of the neuromuscular junction (NMJ) involves a complex molecular and activity-dependent crosstalk among presynaptic terminals, postsynaptic muscle fibres and glial cells. This crosstalk results in the tight assembly of an efficient and reliable communication unit.
The maturation of the NMJ involves precise and highly regulated molecular mechanisms. These mechanisms promote the clustering and stabilization of nicotinic acetylcholine receptors at the crest of postjunctional folds, as well as the differentiation of the presynaptic element to form active zones with proper synaptic proteins and clustered synaptic vesicles.
Presynaptic and postsynaptic maturation are interdependent and coordinated by common molecular and regulatory mechanisms. Glial cells also participate in synaptic maturation, which is dependent on both pre- and postsynaptic elements.
The NMJ undergoes activity-dependent maturation, which involves a drastic reduction in the number of presynaptic terminals via synaptic competition. The superseding nerve terminal is the one that delivers the most efficient synaptic communication (the strongest input) and that is in the best position to benefit from interactions with the muscle fibre and glial cells.
Glial cells at the NMJ regulate synaptic competition by clearing debris and participating in the elimination of supernumerary nerve terminals. They also actively decode the ongoing synaptic competition, discriminating competing inputs by detecting the levels of transmitter released from each competing nerve terminal. This enables these cells to then actively enhance the synaptic properties of a particular input to promote its survival.
The formation of highly efficient and reliable synapses at the neuromuscular junction (NMJ) relies on dynamic molecular interactions. Studies of the development and maturation of the NMJ have focused on events that are dependent on synaptic activity and that require the coordinated actions of nerve- and muscle-derived molecules with different targets and effects. More recently, perisynaptic Schwann cells — the glial cells at NMJs — have become an important focus of research. These glia concomitantly contribute to pre- and postsynaptic maturation while undergoing maturation themselves. Thus, an intricate 'danse à trois' regulates the maturation of the NMJ to form a highly efficient communication unit, in which fine glial processes lie in close proximity to a highly concentrated population of postsynaptic receptors and perfectly aligned presynaptic release sites.
This is a preview of subscription content, access via your institution
Open Access articles citing this article.
Hydrogen peroxide induced by nerve injury promotes axon regeneration via connective tissue growth factor
Acta Neuropathologica Communications Open Access 25 December 2022
Scientific Reports Open Access 09 December 2022
Involvement of the Voltage-Gated Calcium Channels L- P/Q- and N-Types in Synapse Elimination During Neuromuscular Junction Development
Molecular Neurobiology Open Access 27 April 2022
Subscribe to this journal
Receive 12 print issues and online access
$189.00 per year
only $15.75 per issue
Rent or buy this article
Prices vary by article type
Prices may be subject to local taxes which are calculated during checkout
Bonanomi, D. & Pfaff, S. L. Motor axon pathfinding. Cold Spring Harb. Perspect. Biol. 2, a001735 (2010).
O'Donnell, M., Chance, R. K. & Bashaw, G. J. Axon growth and guidance: receptor regulation and signal transduction. Annu. Rev. Neurosci. 32, 383–412 (2009).
Desaki, J. & Uehara, Y. The overall morphology of neuromuscular junctions as revealed by scanning electron microscopy. J. Neurocytol. 10, 101–110 (1981).
Redfern, P. A. Neuromuscular transmission in new-born rats. J. Physiol. 209, 701–709 (1970).
Sanes, J. R. & Lichtman, J. W. Development of the vertebrate neuromuscular junction. Annu. Rev. Neurosci. 22, 389–442 (1999).
Patton, B. L. et al. Properly formed but improperly localized synaptic specializations in the absence of laminin α4. Nature Neurosci. 4, 597–604 (2001).
Wu, H., Xiong, W. C. & Mei, L. To build a synapse: signaling pathways in neuromuscular junction assembly. Development 137, 1017–1033 (2010).
Sanes, J. R. & Lichtman, J. W. Induction, assembly, maturation and maintenance of a postsynaptic apparatus. Nature Rev. Neurosci. 2, 791–805 (2001).
Koirala, S., Reddy, L. V. & Ko, C. P. Roles of glial cells in the formation, function, and maintenance of the neuromuscular junction. J. Neurocytol. 32, 987–1002 (2003).
Reddy, L. V., Koirala, S., Sugiura, Y., Herrera, A. A. & Ko, C. P. Glial cells maintain synaptic structure and function and promote development of the neuromuscular junction in vivo. Neuron 40, 563–580 (2003). This study demonstrates that selective ablation of PSCs at the developing and mature frog NMJ results in major structural, developmental and functional defects of the synapse.
Yang, J.-f. et al. Schwann cells express active agrin and enhance aggregation of acetylcholine receptors on muscle fibers. J. Neurosci. 21, 9572–9584 (2001).
Feng, Z. & Ko, C. P. Schwann cells promote synaptogenesis at the neuromuscular junction via transforming growth factor-β1. J. Neurosci. 28, 9599–9609 (2008).
Fuentes-Medel, Y. et al. Integration of a retrograde signal during synapse formation by glia-secreted TGF-β ligand. Curr. Biol. 22, 1831–1838 (2012).
Kerr, K. S. et al. Glial Wingless/Wnt regulates glutamate receptor clustering and synaptic physiology at the Drosophila neuromuscular junction. J. Neurosci. 34, 2910–2920 (2014).
Escher, P. et al. Synapses form in skeletal muscles lacking neuregulin receptors. Science 308, 1920–1923 (2005).
Lin, W. et al. Aberrant development of motor axons and neuromuscular synapses in erbB2-deficient mice. Proc. Natl Acad. Sci. USA 97, 1299–1304 (2000).
Wolpowitz, D. et al. Cysteine-rich domain isoforms of the neuregulin-1 gene are required for maintenance of peripheral synapses. Neuron 25, 79–91 (2000).
Darabid, H., Arbour, D. & Robitaille, R. Glial cells decipher synaptic competition at the mammalian neuromuscular junction. J. Neurosci. 33, 1297–1313 (2013). By combining confocal calcium-imaging techniques and electrophysiological recordings at dually innervated mouse NMJs, this study shows that PSCs can differentially decode synaptic activity from competing nerve terminals at developing NMJs.
Patton, B. L., Chiu, A. Y. & Sanes, J. R. Synaptic laminin prevents glial entry into the synaptic cleft. Nature 393, 698–701 (1998).
Yang, D. et al. Coordinate control of axon defasciculation and myelination by laminin-2 and -8. J. Cell Biol. 168, 655–666 (2005).
Bishop, D. L., Misgeld, T., Walsh, M. K., Gan, W. B. & Lichtman, J. W. Axon branch removal at developing synapses by axosome shedding. Neuron 44, 651–661 (2004). Using time-lapse imaging and serial electron microscopy of mouse NMJs, this paper describes the changes in the PSC coverage of nerve terminals, providing new insights into the mechanisms of synapse elimination and the shedding of axon terminals by SCs.
Smith, I. W., Mikesh, M., Lee, Y. & Thompson, W. J. Terminal Schwann cells participate in the competition underlying neuromuscular synapse elimination. J. Neurosci. 33, 17724–17736 (2013). This research shows that PSCs actively participate in axon removal during synaptic competition in the developing NMJ.
Lin, W. et al. Distinct roles of nerve and muscle in postsynaptic differentiation of the neuromuscular synapse. Nature 410, 1057–1064 (2001).
Sheard, P. W. & Duxson, M. J. The transient existence of 'en passant' nerve terminals in normal embryonic rat skeletal muscle. Brain Res. Dev. Brain Res. 98, 259–264 (1997).
Landmesser, L. The development of motor projection patterns in the chick hind limb. J. Physiol. 284, 391–414 (1978).
Landmesser, L. The distribution of motoneurones supplying chick hind limb muscles. J. Physiol. 284, 371–389 (1978).
Landmesser, L. T. The acquisition of motoneuron subtype identity and motor circuit formation. Int. J. Dev. Neurosci. 19, 175–182 (2001).
Jessell, T. M. Neuronal specification in the spinal cord: inductive signals and transcriptional codes. Nature Rev. Genet. 1, 20–29 (2000).
Lance-Jones, C. Motoneuron axon guidance: development of specific projections to two muscles in the embryonic chick limb. Brain Behav. Evol. 31, 209–217 (1988).
Tripodi, M. & Arber, S. Regulation of motor circuit assembly by spatial and temporal mechanisms. Curr. Opin. Neurobiol. 22, 615–623 (2012).
Phelan, K. A. & Hollyday, M. Axon guidance in muscleless chick wings: the role of muscle cells in motoneuronal pathway selection and muscle nerve formation. J. Neurosci. 10, 2699–2716 (1990).
Tessier-Lavigne, M. & Goodman, C. S. The molecular biology of axon guidance. Science 274, 1123–1133 (1996).
Hanson, M. G. & Landmesser, L. T. Normal patterns of spontaneous activity are required for correct motor axon guidance and the expression of specific guidance molecules. Neuron 43, 687–701 (2004).
Yang, X. et al. Patterning of muscle acetylcholine receptor gene expression in the absence of motor innervation. Neuron 30, 399–410 (2001).
Yang, X., Li, W., Prescott, E. D., Burden, S. J. & Wang, J. C. DNA topoisomerase IIβ and neural development. Science 287, 131–134 (2000).
Yampolsky, P. et al. Time lapse in vivo visualization of developmental stabilization of synaptic receptors at neuromuscular junctions. J. Biol. Chem. 285, 34589–34596 (2010).
Flanagan-Steet, H., Fox, M. A., Meyer, D. & Sanes, J. R. Neuromuscular synapses can form in vivo by incorporation of initially aneural postsynaptic specializations. Development 132, 4471–4481 (2005).
Panzer, J. A., Song, Y. & Balice-Gordon, R. J. In vivo imaging of preferential motor axon outgrowth to and synaptogenesis at prepatterned acetylcholine receptor clusters in embryonic zebrafish skeletal muscle. J. Neurosci. 26, 934–947 (2006).
Anderson, M. J. & Cohen, M. W. Nerve-induced and spontaneous redistribution of acetylcholine receptors on cultured muscle cells. J. Physiol. 268, 757–773 (1977).
Frank, E. & Fischbach, G. D. Early events in neuromuscular junction formation in vitro: induction of acetylcholine receptor clusters in the postsynaptic membrane and morphology of newly formed synapses. J. Cell Biol. 83, 143–158 (1979).
Kim, N. & Burden, S. J. MuSK controls where motor axons grow and form synapses. Nature Neurosci. 11, 19–27 (2008).
Vock, V. M., Ponomareva, O. N. & Rimer, M. Evidence for muscle-dependent neuromuscular synaptic site determination in mammals. J. Neurosci. 28, 3123–3130 (2008).
Tapia, J. C. et al. Pervasive synaptic branch removal in the mammalian neuromuscular system at birth. Neuron 74, 816–829 (2012).
Wyatt, R. M. & Balice-Gordon, R. J. Activity-dependent elimination of neuromuscular synapses. J. Neurocytol. 32, 777–794 (2003).
Chung, W. S. & Barres, B. A. Selective remodeling: refining neural connectivity at the neuromuscular junction. PLoS Biol. 7, e1000185 (2009).
Gautam, M. et al. Defective neuromuscular synaptogenesis in agrin-deficient mutant mice. Cell 85, 525–535 (1996).
Bezakova, G., Helm, J. P., Francolini, M. & Lomo, T. Effects of purified recombinant neural and muscle agrin on skeletal muscle fibers in vivo. J. Cell Biol. 153, 1441–1452 (2001).
Bezakova, G. & Lomo, T. Muscle activity and muscle agrin regulate the organization of cytoskeletal proteins and attached acetylcholine receptor (AchR) aggregates in skeletal muscle fibers. J. Cell Biol. 153, 1453–1463 (2001).
Jones, G. et al. Induction by agrin of ectopic and functional postsynaptic-like membrane in innervated muscle. Proc. Natl Acad. Sci. USA 94, 2654–2659 (1997).
Gesemann, M., Denzer, A. J. & Ruegg, M. A. Acetylcholine receptor-aggregating activity of agrin isoforms and mapping of the active site. J. Cell Biol. 128, 625–636 (1995).
Burgess, R. W., Nguyen, Q. T., Son, Y. J., Lichtman, J. W. & Sanes, J. R. Alternatively spliced isoforms of nerve- and muscle-derived agrin: their roles at the neuromuscular junction. Neuron 23, 33–44 (1999).
Bowen, D. C., Sugiyama, J., Ferns, M. & Hall, Z. W. Neural agrin activates a high-affinity receptor in C2 muscle cells that is unresponsive to muscle agrin. J. Neurosci. 16, 3791–3797 (1996).
Ferns, M. J., Campanelli, J. T., Hoch, W., Scheller, R. H. & Hall, Z. The ability of agrin to cluster AChRs depends on alternative splicing and on cell surface proteoglycans. Neuron 11, 491–502 (1993).
DeChiara, T. M. et al. The receptor tyrosine kinase MuSK is required for neuromuscular junction formation in vivo. Cell 85, 501–512 (1996).
Valenzuela, D. M. et al. Receptor tyrosine kinase specific for the skeletal muscle lineage: expression in embryonic muscle, at the neuromuscular junction, and after injury. Neuron 15, 573–584 (1995).
Weatherbee, S. D., Anderson, K. V. & Niswander, L. A. LDL-receptor-related protein 4 is crucial for formation of the neuromuscular junction. Development 133, 4993–5000 (2006).
Zhang, B. et al. LRP4 serves as a coreceptor of agrin. Neuron 60, 285–297 (2008).
Kim, N. et al. Lrp4 is a receptor for Agrin and forms a complex with MuSK. Cell 135, 334–342 (2008). This is the first study to demonstrate that LRP4 is the agrin co-receptor that is required for MUSK activation.
Burden, S. J., Yumoto, N. & Zhang, W. The role of MuSK in synapse formation and neuromuscular disease. Cold Spring Harb. Perspect. Biol. 5, a009167 (2013).
Gautam, M. et al. Failure of postsynaptic specialization to develop at neuromuscular junctions of rapsyn-deficient mice. Nature 377, 232–236 (1995).
Zhang, B. et al. Wnt proteins regulate acetylcholine receptor clustering in muscle cells. Mol. Brain 5, 7 (2012).
Korkut, C. & Budnik, V. WNTs tune up the neuromuscular junction. Nature Rev. Neurosci. 10, 627–634 (2009).
Budnik, V. & Salinas, P. C. Wnt signaling during synaptic development and plasticity. Curr. Opin. Neurobiol. 21, 151–159 (2011).
Jing, L., Lefebvre, J. L., Gordon, L. R. & Granato, M. Wnt signals organize synaptic prepattern and axon guidance through the zebrafish unplugged/MuSK receptor. Neuron 61, 721–733 (2009).
Henriquez, J. P. et al. Wnt signaling promotes AChR aggregation at the neuromuscular synapse in collaboration with agrin. Proc. Natl Acad. Sci. USA 105, 18812–18817 (2008).
Wang, J. et al. Wnt/β-catenin signaling suppresses rapsyn expression and inhibits acetylcholine receptor clustering at the neuromuscular junction. J. Biol. Chem. 283, 21668–21675 (2008).
Castelo-Branco, G. et al. Ventral midbrain glia express region-specific transcription factors and regulate dopaminergic neurogenesis through Wnt-5a secretion. Mol. Cell Neurosci. 31, 251–262 (2006).
Rimer, M., Cohen, I., Lomo, T., Burden, S. J. & McMahan, U. J. Neuregulins and erbB receptors at neuromuscular junctions and at agrin-induced postsynaptic-like apparatus in skeletal muscle. Mol. Cell Neurosci. 12, 1–15 (1998).
Lemke, G. Glial control of neuronal development. Annu. Rev. Neurosci. 24, 87–105 (2001).
Jo, S. A., Zhu, X., Marchionni, M. A. & Burden, S. J. Neuregulins are concentrated at nerve–muscle synapses and activate ACh-receptor gene expression. Nature 373, 158–161 (1995).
Sandrock, A. W. Jr et al. Maintenance of acetylcholine receptor number by neuregulins at the neuromuscular junction in vivo. Science 276, 599–603 (1997).
Riethmacher, D. et al. Severe neuropathies in mice with targeted mutations in the ErbB3 receptor. Nature 389, 725–730 (1997).
Ngo, S. T., Cole, R. N., Sunn, N., Phillips, W. D. & Noakes, P. G. Neuregulin-1 potentiates agrin-induced acetylcholine receptor clustering through muscle-specific kinase phosphorylation. J. Cell Sci. 125, 1531–1543 (2012).
Jaworski, A. & Burden, S. J. Neuromuscular synapse formation in mice lacking motor neuron- and skeletal muscle-derived neuregulin-1. J. Neurosci. 26, 655–661 (2006).
Ponomareva, O. N. et al. Defective neuromuscular synaptogenesis in mice expressing constitutively active ErbB2 in skeletal muscle fibers. Mol. Cell Neurosci. 31, 334–345 (2006).
Garratt, A. N., Britsch, S. & Birchmeier, C. Neuregulin, a factor with many functions in the life of a schwann cell. Bioessays 22, 987–996 (2000).
St John, P. A. & Gordon, H. Agonists cause endocytosis of nicotinic acetylcholine receptors on cultured myotubes. J. Neurobiol. 49, 212–223 (2001).
Misgeld, T., Kummer, T. T., Lichtman, J. W. & Sanes, J. R. Agrin promotes synaptic differentiation by counteracting an inhibitory effect of neurotransmitter. Proc. Natl Acad. Sci. USA 102, 11088–11093 (2005). This elegant study uses double-mutant mice (lacking both ChAT and agrin) to show that synaptic transmission regulates NMJ maturation and counters the effects of agrin.
Misgeld, T. et al. Roles of neurotransmitter in synapse formation: development of neuromuscular junctions lacking choline acetyltransferase. Neuron 36, 635–648 (2002).
Brandon, E. P. et al. Aberrant patterning of neuromuscular synapses in choline acetyltransferase-deficient mice. J. Neurosci. 23, 539–549 (2003).
Singhal, N. & Martin, P. T. Role of extracellular matrix proteins and their receptors in the development of the vertebrate neuromuscular junction. Dev. Neurobiol. 71, 982–1005 (2011).
VanSaun, M., Herrera, A. A. & Werle, M. J. Structural alterations at the neuromuscular junctions of matrix metalloproteinase 3 null mutant mice. J. Neurocytol. 32, 1129–1142 (2003).
VanSaun, M. & Werle, M. J. Matrix metalloproteinase-3 removes agrin from synaptic basal lamina. J. Neurobiol. 44, 369 (2000).
Werle, M. J. Cell-to-cell signaling at the neuromuscular junction: the dynamic role of the extracellular matrix. Ann. NY Acad. Sci. 1132, 13–18 (2008).
Werle, M. J. & VanSaun, M. Activity dependent removal of agrin from synaptic basal lamina by matrix metalloproteinase 3. J. Neurocytol. 32, 905–913 (2003).
Nagase, H. & Woessner, J. F. Jr. Matrix metalloproteinases. J. Biol. Chem. 274, 21491–21494 (1999).
Knight, D., Tolley, L. K., Kim, D. K., Lavidis, N. A. & Noakes, P. G. Functional analysis of neurotransmission at β2-laminin deficient terminals. J. Physiol. 546, 789–800 (2003).
Noakes, P. G., Gautam, M., Mudd, J., Sanes, J. R. & Merlie, J. P. Aberrant differentiation of neuromuscular junctions in mice lacking s-laminin/laminin β 2. Nature 374, 258–262 (1995).
Nishimune, H., Sanes, J. R. & Carlson, S. S. A synaptic laminin–calcium channel interaction organizes active zones in motor nerve terminals. Nature 432, 580–587 (2004).
Urbano, F. J., Rosato-Siri, M. D. & Uchitel, O. D. Calcium channels involved in neurotransmitter release at adult, neonatal and P/Q-type deficient neuromuscular junctions (review). Mol. Membr. Biol. 19, 293–300 (2002).
Chen, J., Billings, S. E. & Nishimune, H. Calcium channels link the muscle-derived synapse organizer laminin β2 to Bassoon and CAST/Erc2 to organize presynaptic active zones. J. Neurosci. 31, 512–525 (2011).
Umemori, H., Linhoff, M. W., Ornitz, D. M. & Sanes, J. R. FGF22 and its close relatives are presynaptic organizing molecules in the mammalian brain. Cell 118, 257–270 (2004).
Fox, M. A. et al. Distinct target-derived signals organize formation, maturation, and maintenance of motor nerve terminals. Cell 129, 179–193 (2007). This elegant study uncovers the role of FGFs, laminin β2 and type IV collagen α chains using specific in vivo genetic manipulations to describe their sequential role in presynaptic maturation.
Zhang, X. et al. Receptor specificity of the fibroblast growth factor family. The complete mammalian FGF family. J. Biol. Chem. 281, 15694–15700 (2006).
Miner, J. H. & Sanes, J. R. Collagen IV α 3, α 4, and α 5 chains in rodent basal laminae: sequence, distribution, association with laminins, and developmental switches. J. Cell Biol. 127, 879–891 (1994).
Latvanlehto, A. et al. Muscle-derived collagen XIII regulates maturation of the skeletal neuromuscular junction. J. Neurosci. 30, 12230–12241 (2010).
Umemori, H. & Sanes, J. R. Signal regulatory proteins (SIRPS) are secreted presynaptic organizing molecules. J. Biol. Chem. 283, 34053–34061 (2008).
Henderson, C. E. et al. GDNF: a potent survival factor for motoneurons present in peripheral nerve and muscle. Science 266, 1062–1064 (1994).
Wright, D. E. & Snider, W. D. Focal expression of glial cell line-derived neurotrophic factor in developing mouse limb bud. Cell Tissue Res. 286, 209–217 (1996).
Yan, Q., Matheson, C. & Lopez, O. T. In vivo neurotrophic effects of GDNF on neonatal and adult facial motor neurons. Nature 373, 341–344 (1995).
Nguyen, Q. T. Hyperinnervation of neuromuscular junctions caused by GDNF overexpression in muscle. Science 279, 1725–1729 (1998).
Je, H. S. et al. ProBDNF and mature BDNF as punishment and reward signals for synapse elimination at mouse neuromuscular junctions. J. Neurosci. 33, 9957–9962 (2013).
Chao, M. V. & Bothwell, M. Neurotrophins: to cleave or not to cleave. Neuron 33, 9–12 (2002).
Je, H. S. et al. Role of pro-brain-derived neurotrophic factor (proBDNF) to mature BDNF conversion in activity-dependent competition at developing neuromuscular synapses. Proc. Natl Acad. Sci. USA 109, 15924–15929 (2012).
Nishimune, H. et al. Laminins promote postsynaptic maturation by an autocrine mechanism at the neuromuscular junction. J. Cell Biol. 182, 1201–1215 (2008).
Jacobson, C., Cote, P. D., Rossi, S. G., Rotundo, R. L. & Carbonetto, S. The dystroglycan complex is necessary for stabilization of acetylcholine receptor clusters at neuromuscular junctions and formation of the synaptic basement membrane. J. Cell Biol. 152, 435–450 (2001).
Cote, P. D., Moukhles, H., Lindenbaum, M. & Carbonetto, S. Chimaeric mice deficient in dystroglycans develop muscular dystrophy and have disrupted myoneural synapses. Nature Genet. 23, 338–342 (1999).
Arikawa-Hirasawa, E., Rossi, S. G., Rotundo, R. L. & Yamada, Y. Absence of acetylcholinesterase at the neuromuscular junctions of perlecan-null mice. Nature Neurosci. 5, 119–123 (2002).
Zhang, W., Coldefy, A. S., Hubbard, S. R. & Burden, S. J. Agrin binds to the N-terminal region of Lrp4 protein and stimulates association between Lrp4 and the first immunoglobulin-like domain in muscle-specific kinase (MuSK). J. Biol. Chem. 286, 40624–40630 (2011).
Yumoto, N., Kim, N. & Burden, S. J. Lrp4 is a retrograde signal for presynaptic differentiation at neuromuscular synapses. Nature 489, 438–442 (2012).
Huijbers, M. G. et al. MuSK IgG4 autoantibodies cause myasthenia gravis by inhibiting binding between MuSK and Lrp4. Proc. Natl Acad. Sci. USA 110, 20783–20788 (2013).
Wu, H. et al. Distinct roles of muscle and motoneuron LRP4 in neuromuscular junction formation. Neuron 75, 94–107 (2012). This study describes, using cell-specific mutations, a potential role of motor neuron LRP4, in addition to muscular LRP4, in the maturation of the NMJ.
Packard, M. et al. The Drosophila Wnt, wingless, provides an essential signal for pre- and postsynaptic differentiation. Cell 111, 319–330 (2002).
Liebl, F. L. et al. Derailed regulates development of the Drosophila neuromuscular junction. Dev. Neurobiol. 68, 152–165 (2008).
Wells, D. G., McKechnie, B. A., Kelkar, S. & Fallon, J. R. Neurotrophins regulate agrin-induced postsyn aptic differentiation. Proc. Natl Acad. Sci. USA 96, 1112–1117 (1999).
Shelton, D. L. et al. Human TRKs: molecular cloning, tissue distribution, and expression of extracellular domain immunoadhesins. J. Neurosci. 15, 477–491 (1995).
Gonzalez, M. et al. Disruption of Trkb-mediated signaling induces disassembly of postsynaptic receptor clusters at neuromuscular junctions. Neuron 24, 567–583 (1999).
Yang, L. X. & Nelson, P. G. Glia cell line-derived neurotrophic factor regulates the distribution of acetylcholine receptors in mouse primary skeletal muscle cells. Neuroscience 128, 497–509 (2004).
Todd, K. J., Auld, D. S. & Robitaille, R. Neurotrophins modulate neuron-glia interactions at a vertebrate synapse. Eur. J. Neurosci. 25, 1287–1296 (2007).
Mirsky, R. et al. Schwann cells as regulators of nerve development. J. Physiol. Paris 96, 17–24 (2002).
Davies, A. M. Neuronal survival: early dependence on Schwann cells. Curr. Biol. 8, R15–R18 (1998).
Halstead, S. K. et al. Anti-disialosyl antibodies mediate selective neuronal or Schwann cell injury at mouse neuromuscular junctions. Glia 52, 177–189 (2005).
Halstead, S. K. et al. Anti-disialoside antibodies kill perisynaptic Schwann cells and damage motor nerve terminals via membrane attack complex in a murine model of neuropathy. Brain 127, 2109–2123 (2004).
Balice-Gordon, R. J., Chua, C. K., Nelson, C. C. & Lichtman, J. W. Gradual loss of synaptic cartels precedes axon withdrawal at developing neuromuscular junctions. Neuron 11, 801–815 (1993).
Walsh, M. K. & Lichtman, J. W. In vivo time-lapse imaging of synaptic takeover associated with naturally occurring synapse elimination. Neuron 37, 67–73 (2003). This is a detailed analysis using confocal and in vivo imaging that describes the morphological changes that take place in the NMJ during synaptic competition and elimination in development.
Cai, D., Cohen, K. B., Luo, T., Lichtman, J. W. & Sanes, J. R. Improved tools for the Brainbow toolbox. Nature Methods 10, 540–547 (2013).
Lu, J., Tapia, J. C., White, O. L. & Lichtman, J. W. The interscutularis muscle connectome. PLoS Biol. 7, e32 (2009).
Gan, W. B. & Lichtman, J. W. Synaptic segregation at the developing neuromuscular junction. Science 282, 1508–1511 (1998).
Turney, S. G. & Lichtman, J. W. Reversing the outcome of synapse elimination at developing neuromuscular junctions in vivo: evidence for synaptic competition and its mechanism. PLoS Biol. 10, e1001352 (2012). Using specific ablation of individual nerve terminals during NMJ formation, this study shows that active nerve terminals can innervate vacated territories, underlining the notion that competition at developing NMJs is an active process.
Colman, H., Nabekura, J. & Lichtman, J. W. Alterations in synaptic strength preceding axon withdrawal. Science 275, 356–361 (1997).
Buffelli, M. et al. Genetic evidence that relative synaptic efficacy biases the outcome of synaptic competition. Nature 424, 430–434 (2003). This study uses genetic tools to show that inputs that release more neurotransmitter are favoured during synapse elimination at the developing NMJ.
Kopp, D. M., Perkel, D. J. & Balice-Gordon, R. J. Disparity in neurotransmitter release probability among competing inputs during neuromuscular synapse elimination. J. Neurosci. 20, 8771–8779 (2000).
Personius, K. E. & Balice-Gordon, R. J. Book review: activity-dependent synaptic plasticity: insights from neuromuscular junctions. Neuroscientist 8, 414–422 (2002).
Callaway, E. M., Soha, J. M. & Van Essen, D. C. Competition favouring inactive over active motor neurons during synapse elimination. Nature 328, 422–426 (1987).
Costanzo, E. M., Barry, J. A. & Ribchester, R. R. Co-regulation of synaptic efficacy at stable polyneuronally innervated neuromuscular junctions in reinnervated rat muscle. J. Physiol. 521 (Pt. 2), 365–374 (1999).
Costanzo, E. M., Barry, J. A. & Ribchester, R. R. Competition at silent synapses in reinnervated skeletal muscle. Nature Neurosci. 3, 694–700 (2000).
Favero, M., Busetto, G. & Cangiano, A. Spike timing plays a key role in synapse elimination at the neuromuscular junction. Proc. Natl Acad. Sci. USA 109, E1667–E1675 (2012).
Balice-Gordon, R. J. & Lichtman, J. W. Long-term synapse loss induced by focal blockade of postsynaptic receptors. Nature 372, 519–524 (1994).
Personius, K. E. & Balice-Gordon, R. J. Loss of correlated motor neuron activity during synaptic competition at developing neuromuscular synapses. Neuron 31, 395–408 (2001). This study uses in vivo electrophysiology techniques to study the patterns of changes in the activity of motor neurons during synaptic competition and elimination.
Ribchester, R. R. & Taxt, T. Motor unit size and synaptic competition in rat lumbrical muscles reinnervated by active and inactive motor axons. J. Physiol. 344, 89–111 (1983).
Ridge, R. M. & Betz, W. J. The effect of selective, chronic stimulation on motor unit size in developing rat muscle. J. Neurosci. 4, 2614–2620 (1984).
Buffelli, M., Busetto, G., Cangiano, L. & Cangiano, A. Perinatal switch from synchronous to asynchronous activity of motoneurons: link with synapse elimination. Proc. Natl Acad. Sci. USA 99, 13200–13205 (2002).
Marques, M. J., Conchello, J. A. & Lichtman, J. W. From plaque to pretzel: fold formation and acetylcholine receptor loss at the developing neuromuscular junction. J. Neurosci. 20, 3663–3675 (2000).
Neukomm, L. J. & Freeman, M. R. Diverse cellular and molecular modes of axon degeneration. Trends Cell Biol. 24, 1–9 (2014).
Pfrieger, F. W. Roles of glial cells in synapse development. Cell. Mol. Life Sci. 66, 2037–2047 (2009).
Song, J. W. et al. Lysosomal activity associated with developmental axon pruning. J. Neurosci. 28, 8993–9001 (2008).
Corty, M. M. & Freeman, M. R. Cell biology in neuroscience: architects in neural circuit design: glia control neuron numbers and connectivity. J. Cell Biol. 203, 395–405 (2013).
Fuentes-Medel, Y. et al. Glia and muscle sculpt neuromuscular arbors by engulfing destabilized synaptic boutons and shed presynaptic debris. PLoS Biol. 7, e1000184 (2009).
Brill, M. S., Lichtman, J. W., Thompson, W., Zuo, Y. & Misgeld, T. Spatial constraints dictate glial territories at murine neuromuscular junctions. J. Cell Biol. 195, 293–305 (2011). This paper shows that following the ablation of individual SCs, changes in PSC-territory dynamics at developing and mature NMJs are under spatial constraints.
Hirata, K., Zhou, C., Nakamura, K. & Kawabuchi, M. Postnatal development of Schwann cells at neuromuscular junctions, with special reference to synapse elimination. J. Neurocytol. 26, 799–809 (1997).
Love, F. M. & Thompson, W. J. Schwann cells proliferate at rat neuromuscular junctions during development and regeneration. J. Neurosci. 18, 9376–9385 (1998).
Jahromi, B. S., Robitaille, R. & Charlton, M. P. Transmitter release increases intracellular calcium in perisynaptic Schwann cells in situ. Neuron 8, 1069–1077 (1992).
Robitaille, R. Modulation of synaptic efficacy and synaptic depression by glial cells at the frog neuromuscular junction. Neuron 21, 847–855 (1998).
Rochon, D., Rousse, I. & Robitaille, R. Synapse–glia interactions at the mammalian neuromuscular junction. J. Neurosci. 21, 3819–3829 (2001).
Todd, K. J., Darabid, H. & Robitaille, R. Perisynaptic glia discriminate patterns of motor nerve activity and influence plasticity at the neuromuscular junction. J. Neurosci. 30, 11870–11882 (2010). This study combines electrophysiological recordings, PSC Ca2+-imaging and alteration of the activity of specific PSCs using photo-activatable molecules to show that PSCs regulate synaptic plasticity by discerning patterns of motor nerve activity.
Clarke, L. E. & Barres, B. A. Emerging roles of astrocytes in neural circuit development. Nature Rev. Neurosci. 14, 311–321 (2013).
Eroglu, C. & Barres, B. A. Regulation of synaptic connectivity by glia. Nature 468, 223–231 (2010).
Allen, N. J. et al. Astrocyte glypicans 4 and 6 promote formation of excitatory synapses via GluA1 AMPA receptors. Nature 486, 410–414 (2012).
Christopherson, K. S. et al. Thrombospondins are astrocyte-secreted proteins that promote CNS synaptogenesis. Cell 120, 421–433 (2005).
Kucukdereli, H. et al. Control of excitatory CNS synaptogenesis by astrocyte-secreted proteins Hevin and SPARC. Proc. Natl Acad. Sci. USA 108, E440–449 (2011).
Murai, K. K. & Pasquale, E. B. Eph receptors and ephrins in neuron-astrocyte communication at synapses. Glia 59, 1567–1578 (2011).
Jessen, K. R. & Mirsky, R. The origin and development of glial cells in peripheral nerves. Nature Rev. Neurosci. 6, 671–682 (2005).
Georgiou, J., Robitaille, R. & Charlton, M. P. Muscarinic control of cytoskeleton in perisynaptic glia. J. Neurosci. 19, 3836–3846 (1999).
Fawcett, J. W. & Keynes, R. J. Peripheral nerve regeneration. Annu. Rev. Neurosci. 13, 43–60 (1990).
Kang, H., Tian, L. & Thompson, W. Terminal Schwann cells guide the reinnervation of muscle after nerve injury. J. Neurocytol 32, 975–985 (2003).
Miledi, R. & Slater, C. R. Electrophysiology and electron-microscopy of rat neuromuscular junctions after nerve degeneration. Proc. R. Soc. Lond. B Biol. Sci. 169, 289–306 (1968).
Miledi, R. & Slater, C. R. On the degeneration of rat neuromuscular junctions after nerve section. J. Physiol. 207, 507–528 (1970).
Reynolds, M. L. & Woolf, C. J. Terminal Schwann cells elaborate extensive processes following denervation of the motor endplate. J. Neurocytol. 21, 50–66 (1992).
O'Malley, J. P., Waran, M. T. & Balice-Gordon, R. J. In vivo observations of terminal Schwann cells at normal, denervated, and reinnervated mouse neuromuscular junctions. J. Neurobiol. 38, 270–286 (1999).
Gantus, M. A., Nasciutti, L. E., Cruz, C. M., Persechini, P. M. & Martinez, A. M. Modulation of extracellular matrix components by metalloproteinases and their tissue inhibitors during degeneration and regeneration of rat sural nerve. Brain Res. 1122, 36–46 (2006).
Rich, M. M. & Lichtman, J. W. In vivo visualization of pre- and postsynaptic changes during synapse elimination in reinnervated mouse muscle. J. Neurosci. 9, 1781–1805 (1989).
Kang, H. & Lichtman, J. W. Motor axon regeneration and muscle reinnervation in young adult and aged animals. J. Neurosci. 33, 19480–19491 (2013).
Magill, C. K. et al. Reinnervation of the tibialis anterior following sciatic nerve crush injury: a confocal microscopic study in transgenic mice. Exp. Neurol. 207, 64–74 (2007).
Laskowski, M. B., Colman, H., Nelson, C. & Lichtman, J. W. Synaptic competition during the reformation of a neuromuscular map. J. Neurosci. 18, 7328–7335 (1998).
Lindstrom, J. M., Seybold, M. E., Lennon, V. A., Whittingham, S. & Duane, D. D. Antibody to acetylcholine receptor in myasthenia gravis. Prevalence, clinical correlates, and diagnostic value. Neurology 26, 1054–1059 (1976).
Hoch, W. et al. Auto-antibodies to the receptor tyrosine kinase MuSK in patients with myasthenia gravis without acetylcholine receptor antibodies. Nature Med. 7, 365–368 (2001).
Plomp, J. J., Huijbers, M. G., van der Maarel, S. M. & Verschuuren, J. J. Pathogenic IgG4 subclass autoantibodies in MuSK myasthenia gravis. Ann. NY Acad. Sci. 1275, 114–122 (2012).
Mori, S. et al. Antibodies against muscle-specific kinase impair both presynaptic and postsynaptic functions in a murine model of myasthenia gravis. Am. J. Pathol. 180, 798–810 (2012).
Higuchi, O., Hamuro, J., Motomura, M. & Yamanashi, Y. Autoantibodies to low-density lipoprotein receptor-related protein 4 in myasthenia gravis. Ann. Neurol. 69, 418–422 (2011).
Shen, C. et al. Antibodies against low-density lipoprotein receptor-related protein 4 induce myasthenia gravis. J. Clin. Invest. 123, 5190–5202 (2013).
Huijbers, M. G. et al. Pathogenic immune mechanisms at the neuromuscular synapse: the role of specific antibody-binding epitopes in myasthenia gravis. J. Intern. Med. 275, 12–26 (2014).
Maselli, R. A., Arredondo, J., Ferns, M. J. & Wollmann, R. L. Synaptic basal lamina-associated congenital myasthenic syndromes. Ann. NY Acad. Sci. 1275, 36–48 (2012).
Musarella, M. et al. Expression of Nav1.6 sodium channels by Schwann cells at neuromuscular junctions: role in the motor endplate disease phenotype. Glia 53, 13–23 (2006).
Caillol, G. et al. Motor endplate disease affects neuromuscular junction maturation. Eur. J. Neurosci. 36, 2400–2408 (2012).
Lin, W. et al. Neurotransmitter acetylcholine negatively regulates neuromuscular synapse formation by a Cdk5-dependent mechanism. Neuron 46, 569–579 (2005).
Son, Y. J. et al. The synaptic vesicle protein SV2 is complexed with an α 5-containing laminin on the nerve terminal surface. J. Biol. Chem. 275, 451–460 (2000).
Xu, P. et al. Nerve injury induces glial cell line-derived neurotrophic factor (GDNF) expression in Schwann cells through purinergic signaling and the PKC–PKD pathway. Glia 61, 1029–1040 (2013).
The authors thank S. Carbonetto and A. Llobet for reading the manuscript and providing useful comments. This work was supported by grants from the Canadian Institutes for Health Research to R.R. (MOP-14137 and MOP-111070), a Leader Opportunity Fund from the Canadian Foundation of Innovation and an infrastructure grant from Fonds Recherche Québec-Santé (FRQ-S) to the GRSNC (Groupe de Recherche sur le Système Nerveux Central). At the time of writing, H.D. held a FRQ-S studentship.
The authors declare no competing financial interests.
- Neuromuscular junction
(NMJ). A unitary functional structure composed of a single axon terminal innervating a muscle fibre. The presynaptic terminal is covered by specialized glial cells called perisynaptic Schwann cells.
- Perisynaptic Schwann cells
(PSCs). Non-myelinating glial cells at the neuromuscular junction. They originate from the neural crest but differ structurally and phenotypically from axonal myelinating or axonal non-myelinating Schwann cells.
- Active zones
Areas on the surface of the presynaptic terminal that are characterized by their electron-dense appearance owing to the high concentration of proteins involved in Ca2+-dependent synaptic-vesicle exocytosis and recycling.
- Motor columns
Groups of motor neurons that innervate selective sets of muscles.
A nerve-independent phenomenon that occurs prior to the arrival of motor axons whereby acetylcholine receptors cluster in the central region of the muscle fibres (along the longitudinal axis), purportedly defining the location of nerve–muscle contact.
- AChR clustering
The gathering of acetylcholine receptors (AChRs), which is regulated by molecular mechanisms. It is one of the initial steps of synapse maturation.
- Synapse elimination
A reduction in the number of synaptic contacts that results from activity-dependent synaptic competition.
Member of a family of oligoglycosylceramide plasma-membrane lipids that was originally discovered after its isolation from ganglion cells and which is predominantly found in the nervous system. Antibodies against some disialosyl epitopes of gangliosides can be used to specifically ablate perisynaptic Schwann cells at the mammalian neuromuscular junction.
- Retraction bulb
Enlarged distal part of the axon undergoing retraction (that is, axosomal shedding); it is commonly observed during synapse elimination.
- Spike timing
Pattern of temporal correlation between presynaptic and postsynaptic activities. Synchronous and asynchronous patterns of activity are observed during early and late phases of synapse elimination, respectively.
- Asynchronous activity
Uncorrelated timing of synaptic inputs onto the muscle fibre, leading to an out-of-phase activation.
- PSC-receptor segregation
Spatial grouping and separation of receptors on the surface of perisynaptic Schwann cell (PSC) processes. Presumably, this grouping enables the PSC to detect neurotransmitter release from each competing terminal at dually innervated neuromuscular junctions. This segregation was described for purinergic type 2Y receptors, which mediate intra-PSC calcium activity during synaptic competition.
- Muscle-twitch tension
Tension elicited by a muscle contraction that is evoked by a suprathreshold stimulation of the muscle or the nerve input.
About this article
Cite this article
Darabid, H., Perez-Gonzalez, A. & Robitaille, R. Neuromuscular synaptogenesis: coordinating partners with multiple functions. Nat Rev Neurosci 15, 703–718 (2014). https://doi.org/10.1038/nrn3821
This article is cited by
Hydrogen peroxide induced by nerve injury promotes axon regeneration via connective tissue growth factor
Acta Neuropathologica Communications (2022)
Scientific Reports (2022)
Involvement of the Voltage-Gated Calcium Channels L- P/Q- and N-Types in Synapse Elimination During Neuromuscular Junction Development
Molecular Neurobiology (2022)
Can the Imbalance between Neurotrophic and Apoptotic Proteins Be the “Beware the Ides of March” for Unaffected Relatives of Schizophrenia Patients?
Molecular Neurobiology (2022)
Stem Cell Research & Therapy (2021)