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Mariano V, Domínguez-Iturza N, Neukomm LJ, Bagni C. Maintenance mechanisms of circuit-integrated axons. Curr Opin Neurobiol 2018; 53:162-173. [PMID: 30241058 DOI: 10.1016/j.conb.2018.08.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Accepted: 08/14/2018] [Indexed: 12/21/2022]
Abstract
Adult, circuit-integrated neurons must be maintained and supported for the life span of their host. The attenuation of either maintenance or plasticity leads to impaired circuit function and ultimately to neurodegenerative disorders. Over the last few years, significant discoveries of molecular mechanisms were made that mediate the formation and maintenance of axons. Here, we highlight intrinsic and extrinsic mechanisms that ensure the health and survival of axons. We also briefly discuss examples of mutations associated with impaired axonal maintenance identified in specific neurological conditions. A better understanding of these mechanisms will therefore help to define targets for therapeutic interventions.
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Affiliation(s)
- Vittoria Mariano
- Department of Fundamental Neurosciences, University of Lausanne, Switzerland; Department of Neurosciences KU Leuven, VIB Center for Brain and Disease Research, Leuven, Belgium
| | - Nuria Domínguez-Iturza
- Department of Fundamental Neurosciences, University of Lausanne, Switzerland; Department of Neurosciences KU Leuven, VIB Center for Brain and Disease Research, Leuven, Belgium
| | - Lukas J Neukomm
- Department of Fundamental Neurosciences, University of Lausanne, Switzerland.
| | - Claudia Bagni
- Department of Fundamental Neurosciences, University of Lausanne, Switzerland; Department of Biomedicine and Prevention, University of Rome Tor Vergata, Italy.
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2
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Turner MB, Szabo-Maas TM, Poyer JC, Zoran MJ. Regulation and restoration of motoneuronal synaptic transmission during neuromuscular regeneration in the pulmonate snail Helisoma trivolvis. THE BIOLOGICAL BULLETIN 2011; 221:110-125. [PMID: 21876114 PMCID: PMC4459755 DOI: 10.1086/bblv221n1p110] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Regeneration of motor systems involves reestablishment of central control networks, reinnervation of muscle targets by motoneurons, and reconnection of neuromodulatory circuits. Still, how these processes are integrated as motor function is restored during regeneration remains ill defined. Here, we examined the mechanisms underlying motoneuronal regeneration of neuromuscular synapses related to feeding movements in the pulmonate snail Helisoma trivolvis. Neurons B19 and B110, although activated during different phases of the feeding pattern, innervate similar sets of muscles. However, the percentage of muscle fibers innervated, the efficacy of excitatory junction potentials, and the strength of muscle contractions were different for each cell's specific connections. After peripheral nerve crush, a sequence of transient electrical and chemical connections formed centrally within the buccal ganglia. Neuromuscular synapse regeneration involved a three-phase process: the emergence of spontaneous synaptic transmission (P1), the acquisition of evoked potentials of weak efficacy (P2), and the establishment of functional reinnervation (P3). Differential synaptic efficacy at muscle contacts was recapitulated in cell culture. Differences in motoneuronal presynaptic properties (i.e., quantal content) were the basis of disparate neuromuscular synapse function, suggesting a role for retrograde target influences. We propose a homeostatic model of molluscan motor system regeneration. This model has three restoration events: (1) transient central synaptogenesis during axonal outgrowth, (2) intermotoneuronal inhibitory synaptogenesis during initial neuromuscular synapse formation, and (3) target-dependent regulation of neuromuscular junction formation.
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Affiliation(s)
- M. B. Turner
- Department of Cellular Biology, University of Georgia, Athens, Georgia 30602
| | - T. M. Szabo-Maas
- Department of Biology, Brandeis University, Waltham, Massachusetts 02453
| | - J. C. Poyer
- Department of Biology, Texas A&M University, College Station, Texas 77843
| | - M. J. Zoran
- Department of Biology, Texas A&M University, College Station, Texas 77843
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3
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Colby GP, Sung YJ, Ambron RT. mRNAs encoding theAplysia homologues of fasciclin-I and β-thymosin are expressed only in the second phase of nerve injury and are differentially segregated in axons regenerating in vitro and in vivo. J Neurosci Res 2005; 82:484-98. [PMID: 16237720 DOI: 10.1002/jnr.20645] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Studies using Aplysia californica have demonstrated that transcription after nerve injury occurs during a rapid, transient first phase and a delayed, prolonged second phase. Although the second phase is especially important for regeneration, the mRNAs produced during this phase have not been identified. We characterized two such mRNAs following axotomy. One encodes a novel fasciclin-I homologue, Aplysia fasciclin-like protein (apFasP), and the other encodes Aplysia beta-thymosin (apbetaT). In addition to mRNA synthesis, proteins required for regeneration must be available at the site of growth, and the transport and local translation of certain extrasomatic mRNAs aids in this process. We found apbetaT and apFasP proteins and mRNA at growth cones in vitro. However, only the mRNA for apbetaT was present in regenerating axons in vivo. This implies that the membrane protein apFasP is supplied by rapid transport from the soma, whereas the soluble apbetaT is synthesized locally.
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MESH Headings
- Animals
- Aplysia
- Axons/metabolism
- Blotting, Northern/methods
- Blotting, Western/methods
- Cell Adhesion Molecules, Neuronal/genetics
- Cell Adhesion Molecules, Neuronal/metabolism
- Cell Count/methods
- Cloning, Molecular
- Functional Laterality
- Ganglia, Invertebrate/pathology
- Gene Expression/physiology
- Gene Expression Regulation/physiology
- Immunohistochemistry/methods
- In Situ Hybridization/methods
- In Vitro Techniques
- Models, Neurological
- Nerve Crush/methods
- Nerve Regeneration/physiology
- Neurons/metabolism
- Neurons/pathology
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction/methods
- Sequence Analysis, Protein
- Sequence Homology
- Thymosin/genetics
- Thymosin/metabolism
- Time Factors
- Trauma, Nervous System/metabolism
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Affiliation(s)
- Geoffrey P Colby
- Department of Anatomy and Cell Biology, Columbia University, New York, NY 10032, USA
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Lin H, Bao J, Sung YJ, Walters ET, Ambron RT, Ying JS. Rapid electrical and delayed molecular signals regulate the serum response element after nerve injury: convergence of injury and learning signals. ACTA ACUST UNITED AC 2003; 57:204-20. [PMID: 14556286 DOI: 10.1002/neu.10275] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Axotomy elicits changes in gene expression, but little is known about how information from the site of injury is communicated to the cell nucleus. We crushed nerves in Aplysia californica and the sciatic nerve in the mouse and found short- and long-term activation of an Elk1-SRF transcription complex that binds to the serum response element (SRE). The enhanced short-term binding appeared rapidly and was attributed to the injury-induced activation of an Elk1 kinase that phosphorylates Elk1 at ser383. This kinase is the previously described Aplysia (ap) ERK2 homologue, apMAPK. Nerve crush evoked action potentials that propagated along the axon to the cell soma. Exposing axons to medium containing high K(+), which evoked a similar burst of spikes, or bathing the ganglia in 20 microM serotonin (5HT) for 20 min, activated the apMAPK and enhanced SRE binding. Since 5HT is released in response to electrical activity, our data indicate that the short-term process is initiated by an injury-induced electrical discharge that causes the release of 5HT which activates apMAPK. 5HT is also released in response to noxious stimuli for aversive learning. Hence, apMAPK is a point of convergence for injury signals and learning signals. The delay before the onset of the long-term SRE binding was reduced when the crush was closer to the ganglion and was attributed to an Elk1 kinase that is activated by injury in the axon and retrogradely transported to the cell body. Although this Elk1 kinase phosphorylates mammalian rElk1 at ser383, it is distinct from apMAPK.
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Affiliation(s)
- Hana Lin
- Department of Anatomy and Cell Biology, 1201 Black Building, Columbia University, West 168th Street, New York, New York 10032, USA
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5
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Díaz-Ríos M, Oyola E, Miller MW. Colocalization of gamma-aminobutyric acid-like immunoreactivity and catecholamines in the feeding network of Aplysia californica. J Comp Neurol 2002; 445:29-46. [PMID: 11891652 DOI: 10.1002/cne.10152] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Functional consequences of neurotransmitter coexistence and cotransmission can be readily studied in certain experimentally favorable invertebrate motor systems. In this study, whole-mount histochemical methods were used to identify neurons in which gamma-aminobutyric acid (GABA)-like immunoreactivity (GABAli) was colocalized with catecholamine histofluorescence (CAh; FaGlu method) and tyrosine hydroxylase (TH)-like immunoreactivity (THli) in the feeding motor circuitry (buccal and cerebral ganglia) of the marine mollusc Aplysia californica. In agreement with previous reports, five neurons in the buccal ganglia were found to exhibit CAh. These included the paired B20 buccal-cerebral interneurons (BCIs), the paired B65 buccal interneurons, and an unpaired cell with projections to both cerebral-buccal connectives (CBCs). Experiments in which the FaGlu method was combined with the immunohistochemical detection of GABA revealed double labeling of all five of these neurons. An antibody generated against TH, the rate-limiting enzyme in the biosynthesis of catecholamines, was used to obtain an independent determination of GABA-CA colocalization. Biocytin backfills of the CBC performed in conjunction with TH immunohistochemistry revealed labeling of the rostral B20 cell pair and the unpaired CBI near the caudal surface of the right hemiganglion. THli was also present in a prominent bilateral pair of caudal neurons that were not stained with CBC backfills. On the basis of their position, size, shape, and lack of CBC projections, the lateral THli neurons were identified as B65. Double-labeling immunohistochemical experiments revealed GABAli in all five buccal THli neurons. Finally, GABAli was observed in individual B20 and B65 neurons that were identified using electrophysiological criteria and injected with a marker (neurobiotin). Similar methods were used to demonstrate that a previously identified catecholaminergic cerebral-buccal interneuron (CBI) designated CBI-1 contained THli but did not contain GABAli. Although numerous THli and GABAli neurons and fibers were present in the cerebral and buccal ganglia, additional instances of their colocalization were not observed. These findings indicate that GABA and a catecholamine (probably dopamine) are colocalized in a limited number of interneurons within the central pattern generator circuits that control feeding-related behaviors in Aplysia.
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Affiliation(s)
- Manuel Díaz-Ríos
- Institute of Neurobiology, Department of Anatomy, University of Puerto Rico, 201 Blvd. del Valle, San Juan, Puerto Rico 00901
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Zelenin PV, Panchin YV. Projection pattern and target selection ofClione limacina motoneurons sprouting within an intact environment. J Comp Neurol 2000. [DOI: 10.1002/1096-9861(20000724)423:2<220::aid-cne3>3.0.co;2-m] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
Gastropod research is providing many insights into mechanisms of neural regeneration. These observations were made possible by the pioneering work of individuals who described the nervous systems of gastropods, mapped prominent neurons and determined their roles and connections, and developed the techniques for culturing them. This information has allowed questions about injury responses, target selection, and pathway cues to be explored at the level of individually identified neurons. Because of gastropod studies, more is known about axon sealing, growth cone formation and behavior, signals that travel from the site of axotomy to the soma, and the second messengers that are activated there. The responses in neurons and non-neuronal cells during neural development and injury are coordinated by chemical messenger systems that are highly conserved, including neurotransmitters, cytokines, and neurotrophins. The nervous system is modified in learning paradigms by some of the same messenger systems activated by injury, because learning and injury both challenge neurons to change. The conservation of basic mechanisms that coordinate neuronal plasticity allows us to approach basic questions in relatively simple nervous systems with reasonable confidence that the findings will be relevant for other nervous systems, including possible applications to the mammalian nervous system.
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Affiliation(s)
- S B Moffett
- School of Biological Sciences, Washington State University, Pullman, Washington 99164, USA.
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8
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Panchin YV, Zelenin PV, Popova LB. Axotomized neurons of the pteropod mollusc Clione limacina develop novel sites of transmitter release in the absence of their normal muscle target. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART C, PHARMACOLOGY, TOXICOLOGY & ENDOCRINOLOGY 1999; 123:185-91. [PMID: 10442827 DOI: 10.1016/s0742-8413(99)00026-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Neural network for rhythmic wing movements in the swimming mollusc Clione limacina is a well-studied system. After nerve transection the efferent wing neurons cannot reach muscles and consequently display intensive central sprouting. In the present work it was shown that two types of efferent neurons with different neurotransmitters: acethylcholinergic locomotor motoneurons and serotonergic modulatory efferent neurons when deprived of their normal targets, release their neurotransmitter intended for peripheral muscles, in the unusual compartment--neuropile. Such 'unauthorized' release of neurotransmitter may cause nervous system dysfunctions in the damaged brain of other animals.
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Affiliation(s)
- Y V Panchin
- Institute of Problems of Information Transmission, Russian Academy Sciences, Moscow, Russian Federation
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9
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Johnson SL, Schroeder ML, Sánchez JA, Kirk MD. Axonal regeneration in the central nervous system of aplysia californica determined by anterograde transport of biocytin. J Comp Neurol 1999; 406:476-86. [PMID: 10205024 DOI: 10.1002/(sici)1096-9861(19990419)406:4<476::aid-cne5>3.0.co;2-i] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Rhythmic biting, a component of consummatory feeding behavior in the sea hare Aplysia californica, is eliminated following bilateral cerebral-buccal connective (CBC) crushes and recovers within 14 days postlesion. To assess axonal regeneration after CBC lesions, we used biocytin backfills of CBCs followed by fluorescence labeling with streptavidin-lissamine rhodamine. Anterograde transport of biocytin showed up to 1 mm of outgrowth by regenerating axons at 3 days postlesion. At 7 days postlesion, the regenerated axons approached or had entered the ipsilateral buccal neuropil and exhibited numerous varicosities; the average rate of axonal growth was 326 microm/day for the longest, most rapidly growing axons labeled in the CBC. The number of varicosities on labeled axons, suggestive of intercellular interactions, was increased dramatically at all times postlesion. At 14 and 20 days postlesion, regenerated axons branched extensively in the ipsilateral buccal neuropil, entered the contralateral buccal neuropil, and entered peripheral nerves on both sides of the midline. At these later times postlesion, some labeled axons encircled unlabeled buccal cell bodies and exhibited branches containing numerous varicosities, indicative of axosomatic contacts. Some regenerating axons were observed in the sheath of the CBC, but the vast majority of labeled axons remained confined to the connective core, as in control preparations. The bilateral projections within the buccal ganglia of labeled cerebral-to-buccal axons and the large number of varicosities present on these processes are indicative of regenerating axons and synapses that likely contribute to the functional recovery of rhythmic biting.
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Affiliation(s)
- S L Johnson
- Division of Biological Sciences, University of Missouri-Columbia, 65211, USA
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Scott ML, Danzer SC, Govind CK, Kirk MD. Morphological correlates of neural regeneration in the feeding system ofAplysia californica after central nervous system lesions. J Comp Neurol 1997. [DOI: 10.1002/(sici)1096-9861(19971020)387:2<279::aid-cne9>3.0.co;2-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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11
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Regeneration of central and peripheral synaptic connections in the locomotor system of the pteropod molluscClione limacina. INVERTEBRATE NEUROSCIENCE 1997. [DOI: 10.1007/bf02481712] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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