scholarly journals Evidence for a Conserved Function in Synapse Formation Reveals Phr1 as a Candidate Gene for Respiratory Failure in Newborn Mice

2004 ◽  
Vol 24 (3) ◽  
pp. 1096-1105 ◽  
Author(s):  
Robert W. Burgess ◽  
Kevin A. Peterson ◽  
Michael J. Johnson ◽  
Jeffrey J. Roix ◽  
Ian C. Welsh ◽  
...  
Keyword(s):  
Respiratory Distress ◽  
Candidate Gene ◽  
Synapse Formation ◽  
Neuromuscular Junctions ◽  
Genomic Region ◽  
Neuronal Morphology ◽  
Nerve Terminals ◽  
Newborn Mice ◽  
C Elegans ◽  
Neuron Terminals

ABSTRACT Genetic studies using a set of overlapping deletions centered at the piebald locus on distal mouse chromosome 14 have defined a genomic region associated with respiratory distress and lethality at birth. We have isolated and characterized the candidate gene Phr1 that is located within the respiratory distress critical genomic interval. Phr1 is the ortholog of the human Protein Associated with Myc as well as Drosophila highwire and Caenorhabditis elegans regulator of presynaptic morphology 1. Phr1 is expressed in the embryonic and postnatal nervous system. In mice lacking Phr1, the phrenic nerve failed to completely innervate the diaphragm. In addition, nerve terminal morphology was severely disrupted, comparable with the synaptic defects seen in the Drosophila hiw and C. elegans rpm-1 mutants. Although intercostal muscles were completely innervated, they also showed dysmorphic nerve terminals. In addition, sensory neuron terminals in the diaphragm were abnormal. The neuromuscular junctions showed excessive sprouting of nerve terminals, consistent with inadequate presynaptic stimulation of the muscle. On the basis of the abnormal neuronal morphology seen in mice, Drosophila, and C. elegans, we propose that Phr1 plays a conserved role in synaptic development and is a candidate gene for respiratory distress and ventilatory disorders that arise from defective neuronal control of breathing.

scholarly journals Semaphorin signaling restricts neuronal regeneration in C. elegans

2021 ◽  
Author(s):  
Maria Belen Harreguy ◽  
Esha Shah ◽  
Zainab Tanvir ◽  
Blandine Simprevil ◽  
Tracy S. Tran ◽  
...  
Keyword(s):  
Nervous System ◽  
Synapse Formation ◽  
Neuronal Morphology ◽  
Axonal Guidance ◽  
Axon Pathfinding ◽  
Neuronal Regeneration ◽  
C Elegans ◽  
Locomotion Behavior ◽  
Neuronal Growth Cone ◽  
Knockout Animals

Extracellular signaling proteins serve as neuronal growth cone guidance molecules during development and are well positioned to be involved in neuronal regeneration and recovery from injury. Semaphorins and their receptors, the plexins, are a family of conserved proteins involved in development that, in the nervous system, are axonal guidance cues mediating axon pathfinding and synapse formation. The Caenorhabditis elegans genome encodes for three semaphorins and two plexin receptors: the transmembrane semaphorins, SMP-1 and SMP-2, signal through their receptor, PLX-1, while the secreted semaphorin, MAB-20, signals through PLX-2. Here, we determined the neuronal morphology and locomotion behavior of knockout animals missing each of the semaphorins and plexins; we described the expression pattern of all plexins in the nervous system of C. elegans; and we evaluated their effect on the regeneration of motoneuron neurites and the recovery of locomotion behavior following precise laser microsurgery.

scholarly journals Specific heparan sulfate modifications stabilize the synaptic organizer MADD-4/Punctin at C. elegans neuromuscular junctions

Genetics ◽  
2021 ◽  
Author(s):  
Mélissa Cizeron ◽  
Laure Granger ◽  
Hannes E BÜlow ◽  
Jean-Louis Bessereau
Keyword(s):  
Heparan Sulfate ◽  
Matrix Protein ◽  
Neuromuscular Junctions ◽  
Core Protein ◽  
Extracellular Matrix Protein ◽  
Inhibitory Synapses ◽  
Single Chain ◽  
C Elegans ◽  
Sugar Chains

Abstract Heparan sulfate proteoglycans contribute to the structural organization of various neurochemical synapses. Depending on the system, their role involves either the core protein or the glycosaminoglycan chains. These linear sugar chains are extensively modified by heparan sulfate modification enzymes, resulting in highly diverse molecules. Specific modifications of glycosaminoglycan chains may thus contribute to a sugar code involved in synapse specificity. Caenorhabditis elegans is particularly useful to address this question because of the low level of genomic redundancy of these enzymes, as opposed to mammals. Here, we systematically mutated the genes encoding heparan sulfate modification enzymes in C. elegans and analyzed their impact on excitatory and inhibitory neuromuscular junctions. Using single chain antibodies that recognize different heparan sulfate modification patterns, we show in vivo that these two heparan sulfate epitopes are carried by the SDN-1 core protein, the unique C. elegans syndecan orthologue, at neuromuscular junctions. Intriguingly, these antibodies differentially bind to excitatory and inhibitory synapses, implying unique heparan sulfate modification patterns at different neuromuscular junctions. Moreover, while most enzymes are individually dispensable for proper organization of neuromuscular junctions, we show that 3-O-sulfation of SDN-1 is required to maintain wild-type levels of the extracellular matrix protein MADD-4/Punctin, a central synaptic organizer that defines the identity of excitatory and inhibitory synaptic domains at the plasma membrane of muscle cells.

scholarly journals Genetic Mapping and Molecular Characterization of a Broad-spectrum Phytophthora sojae Resistance Gene in Chinese Soybean

2019 ◽  
Vol 20 (8) ◽  
pp. 1809 ◽  
Author(s):  
Chao Zhong ◽  
Yinping Li ◽  
Suli Sun ◽  
Canxing Duan ◽  
Zhendong Zhu
Keyword(s):  
Genetic Mapping ◽  
Candidate Gene ◽  
Broad Spectrum ◽  
Genomic Region ◽  
Phytophthora Sojae ◽  
Genetic Population ◽  
Phytophthora Root Rot ◽  
Different Origins ◽  
Lrr Domain

Phytophthora root rot (PRR) causes serious annual soybean yield losses worldwide. The most effective method to prevent PRR involves growing cultivars that possess genes conferring resistance to Phytophthora sojae (Rps). In this study, QTL-sequencing combined with genetic mapping was used to identify RpsX in soybean cultivar Xiu94-11 resistance to all P. sojae isolates tested, exhibiting broad-spectrum PRR resistance. Subsequent analysis revealed RpsX was located in the 242-kb genomic region spanning the RpsQ locus. However, a phylogenetic investigation indicated Xiu94-11 carrying RpsX is distantly related to the cultivars containing RpsQ, implying RpsX and RpsQ have different origins. An examination of candidate genes revealed RpsX and RpsQ share common nonsynonymous SNP and a 144-bp insertion in the Glyma.03g027200 sequence encoding a leucine-rich repeat (LRR) region. Glyma.03g027200 was considered to be the likely candidate gene of RpsQ and RpsX. Sequence analyses confirmed that the 144-bp insertion caused by an unequal exchange resulted in two additional LRR-encoding fragments in the candidate gene. A marker developed based on the 144-bp insertion was used to analyze the genetic population and germplasm, and proved to be useful for identifying the RpsX and RpsQ alleles. This study implies that the number of LRR units in the LRR domain may be important for PRR resistance in soybean.

scholarly journals Acetylcholinesterase from the motor nerve terminal accumulates on the synaptic basal lamina of the myofiber.

1991 ◽  
Vol 115 (3) ◽  
pp. 755-764 ◽  
Author(s):  
L Anglister
Keyword(s):  
Basal Lamina ◽  
Ache Activity ◽  
Neuromuscular Junctions ◽  
Motor Nerve ◽  
Synaptic Cleft ◽  
Motor Nerve Terminal ◽  
Nerve Terminals ◽  
Axon Terminals ◽  
Muscle Nerve ◽  
Almost All

Acetylcholinesterase (AChE) in skeletal muscle is concentrated at neuromuscular junctions, where it is found in the synaptic cleft between muscle and nerve, associated with the synaptic portion of the myofiber basal lamina. This raises the question of whether the synaptic enzyme is produced by muscle, nerve, or both. Studies on denervated and regenerating muscles have shown that myofibers can produce synaptic AChE, and that the motor nerve may play an indirect role, inducing myofibers to produce synaptic AChE. The aim of this study was to determine whether some of the AChE which is known to be made and transported by the motor nerve contributes directly to AChE in the synaptic cleft. Frog muscles were surgically damaged in a way that caused degeneration and permanent removal of all myofibers from their basal lamina sheaths. Concomitantly, AChE activity was irreversibly blocked. Motor axons remained intact, and their terminals persisted at almost all the synaptic sites on the basal lamina in the absence of myofibers. 1 mo after the operation, the innervated sheaths were stained for AChE activity. Despite the absence of myofibers, new AChE appeared in an arborized pattern, characteristic of neuromuscular junctions, and its reaction product was concentrated adjacent to the nerve terminals, obscuring synaptic basal lamina. AChE activity did not appear in the absence of nerve terminals. We concluded therefore, that the newly formed AChE at the synaptic sites had been produced by the persisting axon terminals, indicating that the motor nerve is capable of producing some of the synaptic AChE at neuromuscular junctions. The newly formed AChE remained adherent to basal lamina sheaths after degeneration of the terminals, and was solubilized by collagenase, indicating that the AChE provided by nerve had become incorporated into the basal lamina as at normal neuromuscular junctions.

scholarly journals Post-synaptic morphology of mouse neuromuscular junctions is linked to muscle fibre type

2020 ◽  
Author(s):  
Aleksandra M. Mech ◽  
Anna-Leigh Brown ◽  
Giampietro Schiavo ◽  
James N. Sleigh
Keyword(s):  
Motor Neuron ◽  
Muscle Fibre ◽  
Fibre Type ◽  
Neuromuscular Junctions ◽  
Fibre Diameter ◽  
Neuromuscular Diseases ◽  
Neuronal Morphology ◽  
Muscle Fibre Type ◽  
Muscle Membrane ◽  
Muscle Fibres

AbstractThe neuromuscular junction (NMJ) is the highly specialised peripheral synapse formed between lower motor neuron terminals and muscle fibres. Post-synaptic acetylcholine receptors (AChRs), which are found in high density in the muscle membrane, bind to acetylcholine released into the synaptic cleft of the NMJ, ultimately facilitating the conversion of motor action potentials to muscle contractions. NMJs have been studied for many years as a general model for synapse formation, development and function, and are known to be early sites of pathological changes in many neuromuscular diseases. However, information is limited on the diversity of NMJs in different muscles, whether muscle fibre type impacts NMJ morphology and growth, and the relevance of these parameters to neuropathology. Here, this crucial gap was addressed using a robust and standardised semi-automated workflow called NMJ-morph to quantify features of pre- and post-synaptic NMJ architecture in an unbiased manner. Five wholemount muscles from wild-type mice were dissected and compared at immature (post-natal day, P7) and early adult (P31-32) timepoints. Post-synaptic AChR morphology was found to be more variable between muscles than that of the motor neuron terminal and there were greater differences in the developing NMJ than at the mature synapse. Post-synaptic architecture, but not neuronal morphology or post-natal synapse growth, correlates with fibre type and is largely independent of muscle fibre diameter. Counter to previous observations, this study indicates that smaller NMJs tend to innervate muscles with higher proportions of fast twitch fibres and that NMJ growth rate is not conserved across all muscles. Furthermore, healthy pre- and post-synaptic NMJ morphological parameters were collected for five anatomically and functionally distinct mouse muscles, generating reference data that will be useful for the future assessment of neuromuscular disease models.Graphical Abstract

Multiple Presynaptic and Postsynaptic Sites of Inhibitory Modulation by Myomodulin at ARC Neuromuscular Junctions ofAplysia

2003 ◽  
Vol 89 (3) ◽  
pp. 1488-1502 ◽  
Author(s):  
Irina V. Orekhova ◽  
Vera Alexeeva ◽  
Paul J. Church ◽  
Klaudiusz R. Weiss ◽  
Vladimir Brezina
Keyword(s):  
Motor Neuron ◽  
Motor Neurons ◽  
Neuromuscular Junctions ◽  
Definitive Evidence ◽  
Multiple Parameters ◽  
Intact Muscle ◽  
Single Arc ◽  
Excitatory Junction Potentials ◽  
K Current ◽  
Neuron Terminals

The functional activity of even simple cellular ensembles is often controlled by surprisingly complex networks of neuromodulators. One such network has been extensively studied in the accessory radula closer (ARC) neuromuscular system of Aplysia. The ARC muscle is innervated by two motor neurons, B15 and B16, which release modulatory peptide cotransmitters to shape ACh-mediated contractions of the muscle. Previous analysis has shown that key to the combinatorial ability of B15 and B16 to control multiple parameters of the contraction is an asymmetry in their peptide modulatory actions. B16, but not B15, releases myomodulin, which, among other actions, inhibits the contraction. Work in single ARC muscle fibers has identified a distinctive myomodulin-activated K current as a candidate postsynaptic mechanism of the inhibition. However, definitive evidence for this mechanism has been lacking. Here, working with the single fibers and then motor neuron-elicited excitatory junction potentials (EJPs) and contractions of the intact ARC muscle, we have confirmed two central predictions of the K-current hypothesis: the myomodulin inhibition of contraction is associated with a correspondingly large inhibition of the underlying depolarization, and the inhibition of both contraction and depolarization is blocked by 4-aminopyridine (4-AP), a potent and selective blocker of the myomodulin-activated K current. However, in the intact muscle, the experiments revealed a second, 4-AP-resistant component of myomodulin inhibition of both B15- and B16-elicited EJPs. This component resembles, and mutually occludes with, inhibition of the EJPs by another peptide modulator released from both B15 and B16, buccalin, which acts by a presynaptic mechanism, inhibition of ACh release from the motor neuron terminals. Direct measurements of peptide release showed that myomodulin also inhibits buccalin release from B15 terminals. At the level of contractions, nevertheless, the postsynaptic K-current mechanism is responsible for much of the myomodulin inhibition of peak contraction amplitude. The presynaptic mechanism, which is most evident during the initial build-up of the EJP waveform, underlies instead an increase of contraction latency.

scholarly journals Genetic Analysis of Collagen Q: Roles in Acetylcholinesterase and Butyrylcholinesterase Assembly and in Synaptic Structure and Function

1999 ◽  
Vol 144 (6) ◽  
pp. 1349-1360 ◽  
Author(s):  
Guoping Feng ◽  
Eric Krejci ◽  
Jordi Molgo ◽  
Jeanette M. Cunningham ◽  
Jean Massoulié ◽  
...  
Keyword(s):  
Neuromuscular Junctions ◽  
Synaptic Cleft ◽  
Neuromuscular Function ◽  
Nerve Terminals ◽  
Compensatory Mechanisms ◽  
Structural Mechanism ◽  
Synaptic Structure ◽  
Cardiac Muscles ◽  
And Function ◽  
Early Phases

Acetylcholinesterase (AChE) occurs in both asymmetric forms, covalently associated with a collagenous subunit called Q (ColQ), and globular forms that may be either soluble or membrane associated. At the skeletal neuromuscular junction, asymmetric AChE is anchored to the basal lamina of the synaptic cleft, where it hydrolyzes acetylcholine to terminate synaptic transmission. AChE has also been hypothesized to play developmental roles in the nervous system, and ColQ is also expressed in some AChE-poor tissues. To seek roles of ColQ and AChE at synapses and elsewhere, we generated ColQ-deficient mutant mice. ColQ−/− mice completely lacked asymmetric AChE in skeletal and cardiac muscles and brain; they also lacked asymmetric forms of the AChE homologue, butyrylcholinesterase. Thus, products of the ColQ gene are required for assembly of all detectable asymmetric AChE and butyrylcholinesterase. Surprisingly, globular AChE tetramers were also absent from neonatal ColQ−/− muscles, suggesting a role for the ColQ gene in assembly or stabilization of AChE forms that do not themselves contain a collagenous subunit. Histochemical, immunohistochemical, toxicological, and electrophysiological assays all indicated absence of AChE at ColQ−/− neuromuscular junctions. Nonetheless, neuromuscular function was initially robust, demonstrating that AChE and ColQ do not play obligatory roles in early phases of synaptogenesis. Moreover, because acute inhibition of synaptic AChE is fatal to normal animals, there must be compensatory mechanisms in the mutant that allow the synapse to function in the chronic absence of AChE. One structural mechanism appears to be a partial ensheathment of nerve terminals by Schwann cells. Compensation was incomplete, however, as animals lacking ColQ and synaptic AChE failed to thrive and most died before they reached maturity.

scholarly journals Deletion of the Nucleotide Exchange Factor Vav3 Enhances Axonal Complexity and Synapse Formation but Tampers Activity of Hippocampal Neuronal Networks In Vitro

2020 ◽  
Vol 21 (3) ◽  
pp. 856
Author(s):  
David Wegrzyn ◽  
Christine Wegrzyn ◽  
Kerry Tedford ◽  
Klaus-Dieter Fischer ◽  
Andreas Faissner
Keyword(s):  
Hippocampal Neurons ◽  
Synapse Formation ◽  
Synergistic Effects ◽  
Neuronal Morphology ◽  
Network Activity ◽  
Nucleotide Exchange ◽  
Double Knockout ◽  
Nucleotide Exchange Factor ◽  
Key Events

Vav proteins activate GTPases of the RhoA subfamily that regulate the cytoskeleton and are involved in adhesion, migration, differentiation, polarity and the cell cycle. While the importance of RhoA GTPases for neuronal morphology is undisputed, their regulation is less well understood. In this perspective, we studied the consequences of the deletion of Vav2, Vav3 and Vav2 and 3 (Vav2−/−, Vav3−/−, Vav2−/−/3−/−) for the development of embryonic hippocampal neurons in vitro. Using an indirect co-culture system of hippocampal neurons with primary wild-type (WT) cortical astrocytes, we analysed axonal and dendritic parameters, structural synapse numbers and the spontaneous network activity via immunocytochemistry and multielectrode array analysis (MEA). Here, we observed a higher process complexity in Vav3−/−, but not in Vav2−/− neurons after three and five days in vitro (DIV). Furthermore, an enhanced synapse formation was observed in Vav3−/− after 14 days in culture. Remarkably, Vav2−/−/3−/− double knockout neurons did not display synergistic effects. Interestingly, these differences were transient and compensated after a cultivation period of 21 days. Network analysis revealed a diminished number of spontaneously occurring action potentials in Vav3−/− neurons after 21 DIV. Based on these results, it appears that Vav3 participates in key events of neuronal differentiation.

scholarly journals Interaction between Calcium Chelators and the Activity of P2X7 Receptors in Mouse Motor Synapses

2020 ◽  
Vol 21 (6) ◽  
pp. 2034 ◽  
Author(s):  
Anna Miteva ◽  
Alexander Gaydukov ◽  
Olga Balezina
Keyword(s):  
Neuromuscular Junctions ◽  
Motor Nerve ◽  
Control Level ◽  
Nerve Terminals ◽  
Quantal Content ◽  
Ach Release ◽  
P2x7 Receptors ◽  
Motor Nerve Terminals ◽  
Pannexin 1 ◽  
End Plate

The ability of P2X7 receptors to potentiate rhythmically evoked acetylcholine (ACh) release through Ca2+ entry via P2X7 receptors and via L-type voltage-dependent Ca2+ channels (VDCCs) was compared by loading Ca2+ chelators into motor nerve terminals. Neuromuscular preparations of the diaphragms of wild-type (WT) mice and pannexin-1 knockout (Panx1−/−) mice, in which ACh release is potentiated by the disinhibition of the L-type VDCCs upon the activation of P2X7 receptors, were used. Miniature end-plate potentials (MEPPs) and evoked end-plate potentials (EPPs) were recorded when the motor terminals were loaded with slow or fast Ca2+ chelators (EGTA-AM or BAPTA-AM, respectively, 50 μM). In WT and Panx1−/− mice, EGTA-AM did not change either spontaneous or evoked ACh release, while BAPTA-AM inhibited synaptic transmission by suppressing the quantal content of EPPs throughout the course of the short rhythmic train (50 Hz, 1 s). In the motor synapses of either WT or Panx1−/− mice in the presence of BAPTA-AM, the activation of P2X7 receptors by BzATP (30 μM) returned the EPP quantal content to the control level. In the neuromuscular junctions (NMJs) of Panx1−/− mice, EGTA-AM completely prevented the BzATP-induced increase in EPP quantal content. After Panx1−/− NMJs were treated with BAPTA-AM, BzATP lost its ability to enhance the EPP quantal content to above the control level. Nitrendipine (1 μM), an inhibitor of L-type VDCCs, was unable to prevent this BzATP-induced enhancement of EPP quantal content to the control level. We propose that the activation of P2X7 receptors may provide additional Ca2+ entry into motor nerve terminals, which, independent of the modulation of L-type VDCC activity, can partially reduce the buffering capacity of Ca2+ chelators, thereby providing sufficient Ca2+ signals for ACh secretion at the control level. However, the activity of both Ca2+ chelators was sufficient to eliminate Ca2+ entry via L-type VDCCs activated by P2X7 receptors and increase the EPP quantal content in the NMJs of Panx1−/− mice to above the control level.

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