Optical Measurements of Presynaptic Release in Mutant Zebrafish Lacking Postsynaptic Receptors

Li, Weiyan; Ono, Fumihito; Brehm, Paul

doi:10.1523/jneurosci.23-33-10467.2003

Cited by 24 publications

(22 citation statements)

References 40 publications

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“…Our data suggest that the presence of pre-patterned AChR clusters is not required for initiating pre-synaptic differentiation. These results are consistent with studies in zebrafish NMJ previously reported: presynaptic nerve terminals develop normally in mutants lacking functional AChRs in zebrafish NMJ (Li et al, 2003;Ono et al, 2001;Panzer et al, 2006;Westerfield et al, 1990).…”

Section: Fig 10 Increased Motoneuron Survival In γsupporting

confidence: 93%

Essential roles of the acetylcholine receptor γ-subunit in neuromuscular synaptic patterning

et al. 2008

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Formation of the vertebrate neuromuscular junction (NMJ) takes place in a stereotypic pattern in which nerves terminate at select sarcolemmal sites often localized to the central region of the muscle fibers. Several lines of evidence indicate that the muscle fibers may initiate postsynaptic differentiation independent of the ingrowing nerves. For example, nascent acetylcholine receptors (AChRs) are pre-patterned at select regions of the muscle during the initial stage of neuromuscular synaptogenesis. It is not clear how these pre-patterned AChR clusters are assembled, and to what extent they contribute to pre-and post-synaptic differentiation during development. Here, we show that genetic deletion of the AChR γ-subunit gene in mice leads to an absence of pre-patterned AChR clusters during initial stages of neuromuscular synaptogenesis. The absence of pre-patterned AChR clusters was associated with excessive nerve branching, increased motoneuron survival, as well as aberrant distribution of acetylcholinesterase (AChE) and rapsyn. However, clustering of muscle specific kinase (MuSK) proceeded normally in the γ-null muscles. AChR clusters emerged at later stages owing to the expression of the AChR epsilon-subunit, but these delayed AChR clusters were broadly distributed and appeared at lower level compared with the wild-type muscles. Interestingly, despite the abnormal pattern, synaptic vesicle proteins were progressively accumulated at individual nerve terminals, and neuromuscular synapses were ultimately established in γ-null muscles. These results demonstrate that the γ-subunit is required for the formation of pre-patterned AChR clusters, which in turn play an essential role in determining the subsequent pattern of neuromuscular synaptogenesis.

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Section: Fig 10 Increased Motoneuron Survival In γsupporting

confidence: 93%

Essential roles of the acetylcholine receptor γ-subunit in neuromuscular synaptic patterning

et al. 2008

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“…These results indicate that although agrin-MuSK signaling is necessary for both expression of AChR in postsynaptic clusters and specialization of presynaptic nerve terminals, expression of AChR in clusters per se is not an essential intermediary in this process. Interestingly, synaptic vesicles are also clustered in zebrafish AChR cluster mutants nic-1 (29) and sop, which are deficient in the AChRδ subunit (34,35). Although AChRs are required for the postsynaptic clustering of several of the proteins observed in the NMJ such as acetylcholinesterase (AChE), syntrophin isoforms, and rapsyn (36-38), we found that AChE and MuSK are, whereas rapsyn is not, clustered at the postsynaptic membrane (Fig.…”

Section: Loss Of Muscle Receptors Results In Increased Nerve Branchinmentioning

confidence: 92%

Acetylcholine negatively regulates development of the neuromuscular junction through distinct cellular mechanisms

Lin²,

Yang

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Emerging evidence suggests that the neurotransmitter acetylcholine (ACh) negatively regulates the development of the neuromuscular junction, but it is not clear if ACh exerts its effects exclusively through muscle ACh receptors (AChRs). Here, we used genetic methods to remove AChRs selectively from muscle. Similar to the effects of blocking ACh biosynthesis, eliminating postsynaptic AChRs increased motor axon branching and expanded innervation territory, suggesting that ACh negatively regulates synaptic growth through postsynaptic AChRs. However, in contrast to the effects of blocking ACh biosynthesis, eliminating postsynaptic AChRs in agrin-deficient mice failed to restore deficits in pre- and postsynaptic differentiation, suggesting that ACh negatively regulates synaptic differentiation through nonpostsynaptic receptors. Consistent with this idea, the ACh agonist carbachol inhibited presynaptic specialization of motorneurons in vitro. Together, these data suggest that ACh negatively regulates axon growth and presynaptic specialization at the neuromuscular junction through distinct cellular mechanisms.

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“…As a result, knock-out of either subunit will only prevent expression of the adult or embryonic form of the receptor. Consequently, zebrafish mutant lines provide a unique vertebrate system in which neuromuscular development can be studied in the absence of AChRs (Westerfield et al, 1990;Ono et al, 2001;Li et al, 2003).…”

Section: Discussionmentioning

confidence: 99%

Acetylcholine Receptors Direct Rapsyn Clusters to the Neuromuscular Synapse in Zebrafish

Ono¹,

Mandel²,

Brehm³

2004

J. Neurosci.

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Clustering of nicotinic muscle acetylcholine receptors (AChRs) requires association with intracellular rapsyn, a protein with an intrinsic ability to self-cluster. Previous studies on sofa potato (sop), an AChR null line of zebrafish, have suggested that AChRs may play an active role in subsynaptic localization of rapsyn clusters. To test this proposal directly, we identified and cloned the gene responsible for the sop phenotype and then attempted to rescue subsynaptic localization of the receptor-rapsyn complex in mutant fish. sop contains a leucine to proline mutation at position 28, near the N terminus of the zebrafish AChR ␦ subunit. Transient expression of mutant ␦ subunit in sop fish was unable to restore surface expression of muscle AChRs. In contrast, expression of wild-type ␦ subunit restored the ability of muscle to assemble surface receptors along with the ability of fish to swim. Most importantly, the ability of rapsyn clusters to localize effectively to subsynaptic sites also was rescued in large part. Our results point to direct involvement of the AChR molecule in restricting receptor-rapsyn clusters to the synapse.

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Optical Measurements of Presynaptic Release in Mutant Zebrafish Lacking Postsynaptic Receptors

Cited by 24 publications

References 40 publications

Essential roles of the acetylcholine receptor γ-subunit in neuromuscular synaptic patterning

Essential roles of the acetylcholine receptor γ-subunit in neuromuscular synaptic patterning

Acetylcholine negatively regulates development of the neuromuscular junction through distinct cellular mechanisms

Acetylcholine Receptors Direct Rapsyn Clusters to the Neuromuscular Synapse in Zebrafish

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