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Wyart C, Carbo-Tano M. Design of mechanosensory feedback during undulatory locomotion to enhance speed and stability. Curr Opin Neurobiol 2023; 83:102777. [PMID: 37666012 DOI: 10.1016/j.conb.2023.102777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 08/08/2023] [Accepted: 08/08/2023] [Indexed: 09/06/2023]
Abstract
Undulatory locomotion relies on the propagation of a wave of excitation in the spinal cord leading to consequential activation of segmental skeletal muscles along the body. Although this process relies on self-generated oscillations of motor circuits in the spinal cord, mechanosensory feedback is crucial to entrain the underlying oscillatory activity and thereby, to enhance movement power and speed. This effect is achieved through directional projections of mechanosensory neurons either sensing stretching or compression of the trunk along the rostrocaudal axis. Different mechanosensory feedback pathways act in concert to shorten and fasten the excitatory wave propagating along the body. While inhibitory mechanosensory cells feedback inhibition on excitatory premotor interneurons and motor neurons, excitatory mechanosensory cells feedforward excitation to premotor excitatory interneurons. Together, diverse mechanosensory cells coordinate the activity of skeletal muscles controlling the head and tail to optimize speed and stabilize balance during fast locomotion.
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Affiliation(s)
- Claire Wyart
- Sorbonne Université, INSERM U1127, UMR CNRS 7225, Institut du Cerveau (ICM), 47 bld de l'hôpital, Paris 75013, France.
| | - Martin Carbo-Tano
- Sorbonne Université, INSERM U1127, UMR CNRS 7225, Institut du Cerveau (ICM), 47 bld de l'hôpital, Paris 75013, France. https://twitter.com/martincarbotano
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2
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Katz HR, Hamlet CL. Mechanosensory Feedback in Lamprey Swimming Models and Applications in the Field of Spinal Cord Regeneration. Integr Comp Biol 2023; 63:464-473. [PMID: 37355775 DOI: 10.1093/icb/icad079] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 05/31/2023] [Accepted: 06/15/2023] [Indexed: 06/26/2023] Open
Abstract
The central pattern generator (CPG) in anguilliform swimming has served as a model for examining the neural basis of locomotion. This system has been particularly valuable for the development of mathematical models. As our biological understanding of the neural basis of locomotion has expanded, so too have these models. Recently, there have been significant advancements in our understanding of the critical role that mechanosensory feedback plays in robust locomotion. This work has led to a push in the field of mathematical modeling to incorporate mechanosensory feedback into CPG models. In this perspective piece, we review advances in the development of these models and discuss how newer complex models can support biological investigation. We highlight lamprey spinal cord regeneration as an area that can both inform these models and benefit from them.
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Affiliation(s)
- Hilary R Katz
- Department of Biology, Western Kentucky University, Bowling Green, KY, 42101, USA
| | - Christina L Hamlet
- Department of Mathematics, Bucknell University, Lewisburg, PA, 17837, USA
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3
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Dubuc R, Cabelguen JM, Ryczko D. Locomotor pattern generation and descending control: a historical perspective. J Neurophysiol 2023; 130:401-416. [PMID: 37465884 DOI: 10.1152/jn.00204.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 07/11/2023] [Accepted: 07/12/2023] [Indexed: 07/20/2023] Open
Abstract
The ability to generate and control locomotor movements depends on complex interactions between many areas of the nervous system, the musculoskeletal system, and the environment. How the nervous system manages to accomplish this task has been the subject of investigation for more than a century. In vertebrates, locomotion is generated by neural networks located in the spinal cord referred to as central pattern generators. Descending inputs from the brain stem initiate, maintain, and stop locomotion as well as control speed and direction. Sensory inputs adapt locomotor programs to the environmental conditions. This review presents a comparative and historical overview of some of the neural mechanisms underlying the control of locomotion in vertebrates. We have put an emphasis on spinal mechanisms and descending control.
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Affiliation(s)
- Réjean Dubuc
- Groupe de Recherche en Activité Physique Adaptée, Département des Sciences de l'Activité Physique, Université du Québec à Montréal, Montreal, Quebec, Canada
- Groupe de Recherche sur le Système Nerveux Central, Département de Neurosciences, Université de Montréal, Montreal, Quebec, Canada
| | - Jean-Marie Cabelguen
- Institut National de la Santé et de la Recherche Médicale (INSERM) U 1215-Neurocentre Magendie, Université de Bordeaux, Bordeaux Cedex, France
| | - Dimitri Ryczko
- Département de Pharmacologie-Physiologie, Université de Sherbrooke, Sherbrooke, Quebec, Canada
- Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, Quebec, Canada
- Neurosciences Sherbrooke, Sherbrooke, Quebec, Canada
- Institut de Pharmacologie de Sherbrooke, Sherbrooke, Quebec, Canada
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Maxson Jones K, Morgan JR. Lampreys and spinal cord regeneration: "a very special claim on the interest of zoologists," 1830s-present. Front Cell Dev Biol 2023; 11:1113961. [PMID: 37228651 PMCID: PMC10203415 DOI: 10.3389/fcell.2023.1113961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 04/24/2023] [Indexed: 05/27/2023] Open
Abstract
Employing history of science methods, including analyses of the scientific literature, archival documents, and interviews with scientists, this paper presents a history of lampreys in neurobiology from the 1830s to the present. We emphasize the lamprey's roles in helping to elucidate spinal cord regeneration mechanisms. Two attributes have long perpetuated studies of lampreys in neurobiology. First, they possess large neurons, including multiple classes of stereotypically located, 'identified' giant neurons in the brain, which project their large axons into the spinal cord. These giant neurons and their axonal fibers have facilitated electrophysiological recordings and imaging across biological scales, ranging from molecular to circuit-level analyses of nervous system structures and functions and including their roles in behavioral output. Second, lampreys have long been considered amongst the most basal extant vertebrates on the planet, so they have facilitated comparative studies pointing to conserved and derived characteristics of vertebrate nervous systems. These features attracted neurologists and zoologists to studies of lampreys between the 1830s and 1930s. But, the same two attributes also facilitated the rise of the lamprey in neural regeneration research after 1959, when biologists first wrote about the spontaneous, robust regeneration of some identified CNS axons in larvae after spinal cord injuries, coupled with recovery of normal swimming. Not only did large neurons promote fresh insights in the field, enabling studies incorporating multiple scales with existing and new technologies. But investigators also were able to attach a broad scope of relevance to their studies, interpreting them as suggesting conserved features of successful, and sometimes even unsuccessful, CNS regeneration. Lamprey research demonstrated that functional recovery takes place without the reformation of the original neuronal connections, for instance, by way of imperfect axonal regrowth and compensatory plasticity. Moreover, research performed in the lamprey model revealed that factors intrinsic to neurons are integral in promoting or hindering regeneration. As this work has helped illuminate why basal vertebrates accomplish CNS regeneration so well, whereas mammals do it so poorly, this history presents a case study in how biological and medical value have been, and could continue to be, gleaned from a non-traditional model organism for which molecular tools have been developed only relatively recently.
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Affiliation(s)
- Kathryn Maxson Jones
- Center for Medical Ethics and Health Policy, Baylor College of Medicine, Houston, TX, United States
- Department of History, Purdue University, West Lafayette, IN, United States
- Marine Biological Laboratory, The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Woods Hole, MA, United States
| | - Jennifer R. Morgan
- Marine Biological Laboratory, The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Woods Hole, MA, United States
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5
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Lacroix-Ouellette P, Dubuc R. Brainstem neural mechanisms controlling locomotion with special reference to basal vertebrates. Front Neural Circuits 2023; 17:910207. [PMID: 37063386 PMCID: PMC10098025 DOI: 10.3389/fncir.2023.910207] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 03/13/2023] [Indexed: 04/03/2023] Open
Abstract
Over the last 60 years, the basic neural circuitry responsible for the supraspinal control of locomotion has progressively been uncovered. Initially, significant progress was made in identifying the different supraspinal structures controlling locomotion in mammals as well as some of the underlying mechanisms. It became clear, however, that the complexity of the mammalian central nervous system (CNS) prevented researchers from characterizing the detailed cellular mechanisms involved and that animal models with a simpler nervous system were needed. Basal vertebrate species such as lampreys, xenopus embryos, and zebrafish became models of choice. More recently, optogenetic approaches have considerably revived interest in mammalian models. The mesencephalic locomotor region (MLR) is an important brainstem region known to control locomotion in all vertebrate species examined to date. It controls locomotion through intermediary cells in the hindbrain, the reticulospinal neurons (RSNs). The MLR comprises populations of cholinergic and glutamatergic neurons and their specific contribution to the control of locomotion is not fully resolved yet. Moreover, the downward projections from the MLR to RSNs is still not fully understood. Reporting on discoveries made in different animal models, this review article focuses on the MLR, its projections to RSNs, and the contribution of these neural elements to the control of locomotion. Excellent and detailed reviews on the brainstem control of locomotion have been recently published with emphasis on mammalian species. The present review article focuses on findings made in basal vertebrates such as the lamprey, to help direct new research in mammals, including humans.
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Affiliation(s)
| | - Réjean Dubuc
- Department of Neurosciences, Université de Montréal, Montréal, QC, Canada
- Department of Physical Activity Sciences, Université du Québec à Montréal, Montréal, QC, Canada
- Research Group for Adapted Physical Activity, Université du Québec à Montréal, Montréal, QC, Canada
- *Correspondence: Réjean Dubuc,
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Abstract
Myelination of axons provides the structural basis for rapid saltatory impulse propagation along vertebrate fiber tracts, a well-established neurophysiological concept. However, myelinating oligodendrocytes and Schwann cells serve additional functions in neuronal energy metabolism that are remarkably similar to those of axon-ensheathing glial cells in unmyelinated invertebrates. Here we discuss myelin evolution and physiological glial functions, beginning with the role of ensheathing glia in preventing ephaptic coupling, axoglial metabolic support, and eliminating oxidative radicals. In both vertebrates and invertebrates, axoglial interactions are bidirectional, serving to regulate cell fate, nerve conduction, and behavioral performance. One key step in the evolution of compact myelin in the vertebrate lineage was the emergence of the open reading frame for myelin basic protein within another gene. Several other proteins were neofunctionalized as myelin constituents and help maintain a healthy nervous system. Myelination in vertebrates became a major prerequisite of inhabiting new ecological niches.
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Affiliation(s)
- Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, D-37075 Göttingen, Germany; ,
| | - Hauke B Werner
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, D-37075 Göttingen, Germany; ,
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7
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Zhang G, Rodemer W, Sinitsa I, Hu J, Selzer ME. Source of Early Regenerating Axons in Lamprey Spinal Cord Revealed by Wholemount Optical Clearing with BABB. Cells 2020; 9:cells9112427. [PMID: 33172031 PMCID: PMC7694618 DOI: 10.3390/cells9112427] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 11/04/2020] [Accepted: 11/04/2020] [Indexed: 12/22/2022] Open
Abstract
Many studies of axon regeneration in the lamprey focus on 18 pairs of large identified reticulospinal (RS) neurons, whose regenerative abilities have been individually quantified. Their axons retract during the first 2 weeks after transection (TX), and many grow back to the site of injury by 4 weeks. However, locomotor movements begin before 4 weeks and the lesion is invaded by axons as early as 2 weeks post-TX. The origins of these early regenerating axons are unknown. Their identification could be facilitated by studies in central nervous system (CNS) wholemounts, particularly if spatial resolution and examination by confocal microscopy were not limited by light scattering. We have used benzyl alcohol/benzyl benzoate (BABB) clearing to enhance the resolution of neuronal perikarya and regenerated axons by confocal microscopy in lamprey CNS wholemounts, and to assess axon regeneration by retrograde and anterograde labeling with fluorescent dye applied to a second TX caudal or rostral to the original lesion, respectively. We found that over 50% of the early regenerating axons belonged to small neurons in the brainstem. Some propriospinal neurons located close to the TX also contributed to early regeneration. The number of early regenerating propriospinal neurons decreased with distance from the original lesion. Descending axons from the brainstem were labeled anterogradely by application of tracer to a second TX close to the spinal-medullary junction. This limited contamination of the data by regenerating spinal axons whose cell bodies are located rostral or caudal to the TX and confirmed the regeneration of many small RS axons as early as 2 weeks post-TX. Compared with the behavior of axotomized giant axons, the early regenerating axons were of small caliber and showed little retraction, probably because they resealed rapidly after injury.
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Affiliation(s)
- Guixin Zhang
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), Philadelphia, PA 19140, USA; (G.Z.); (W.R.); (J.H.)
| | - William Rodemer
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), Philadelphia, PA 19140, USA; (G.Z.); (W.R.); (J.H.)
| | - Isabelle Sinitsa
- College of Science and Technology, Temple University, Philadelphia, PA 19122, USA;
| | - Jianli Hu
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), Philadelphia, PA 19140, USA; (G.Z.); (W.R.); (J.H.)
| | - Michael E. Selzer
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), Philadelphia, PA 19140, USA; (G.Z.); (W.R.); (J.H.)
- Department of Neurology, the Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA 19140, USA
- Correspondence:
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Jin LQ, John BH, Hu J, Selzer ME. Activated Erk Is an Early Retrograde Signal After Spinal Cord Injury in the Lamprey. Front Neurosci 2020; 14:580692. [PMID: 33250705 PMCID: PMC7674770 DOI: 10.3389/fnins.2020.580692] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 10/16/2020] [Indexed: 12/12/2022] Open
Abstract
We previously reported that spinal cord transection (TX) in the lamprey causes mRNA to accumulate in the injured tips of large reticulospinal (RS) axons. We sought to determine whether this mRNA accumulation results from phosphorylation and transport of retrograde signals, similar to what has been reported in mammalian peripheral nerve. Extracellular signal-regulated protein kinase (Erk), mediates the neurite outgrowth-promoting effects of many neurotrophic factors. To assess the role of Erk in retrograde signaling of RS axon injury, we used immunoblot and immunohistochemistry to determine the changes in phosphorylated Erk (p-Erk) in the spinal cord after spinal cord TX. Immunostaining for p-Erk increased within axons and local cell bodies, most heavily within the 1-2 mm closest to the TX site, at between 3 and 6 h post-TX. In axons, p-Erk was concentrated in 3-5 μm granules that became less numerous with distance from the TX. The retrograde molecular motor dynein colocalized with p-Erk, but vimentin, which in peripheral nerve was reported to participate with p-Erk as part of a retrograde signal complex, did not colocalize with p-Erk, even though vimentin levels were elevated post-TX. The results suggest that p-Erk, but not vimentin, may function as a retrograde axotomy signal in lamprey central nervous system neurons, and that this signal may induce transcription of mRNA, which is then transported down the axon to its injured tip.
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Affiliation(s)
- Li-Qing Jin
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Brittany H. John
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Jianli Hu
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Michael E. Selzer
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
- Department of Neurology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
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Ryczko D, Grätsch S, Alpert MH, Cone JJ, Kasemir J, Ruthe A, Beauséjour PA, Auclair F, Roitman MF, Alford S, Dubuc R. Descending Dopaminergic Inputs to Reticulospinal Neurons Promote Locomotor Movements. J Neurosci 2020; 40:8478-8490. [PMID: 32998974 PMCID: PMC7605428 DOI: 10.1523/jneurosci.2426-19.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 09/01/2020] [Accepted: 09/24/2020] [Indexed: 01/25/2023] Open
Abstract
Meso-diencephalic dopaminergic neurons are known to modulate locomotor behaviors through their ascending projections to the basal ganglia, which in turn project to the mesencephalic locomotor region, known to control locomotion in vertebrates. In addition to their ascending projections, dopaminergic neurons were found to increase locomotor movements through direct descending projections to the mesencephalic locomotor region and spinal cord. Intriguingly, fibers expressing tyrosine hydroxylase (TH), the rate-limiting enzyme of dopamine synthesis, were also observed around reticulospinal neurons of lampreys. We now examined the origin and the role of this innervation. Using immunofluorescence and tracing experiments, we found that fibers positive for dopamine innervate reticulospinal neurons in the four reticular nuclei of lampreys. We identified the dopaminergic source using tracer injections in reticular nuclei, which retrogradely labeled dopaminergic neurons in a caudal diencephalic nucleus (posterior tuberculum [PT]). Using voltammetry in brain preparations isolated in vitro, we found that PT stimulation evoked dopamine release in all four reticular nuclei, but not in the spinal cord. In semi-intact preparations where the brain is accessible and the body moves, PT stimulation evoked swimming, and injection of a D1 receptor antagonist within the middle rhombencephalic reticular nucleus was sufficient to decrease reticulospinal activity and PT-evoked swimming. Our study reveals that dopaminergic neurons have access to command neurons that integrate sensory and descending inputs to activate spinal locomotor neurons. As such, our findings strengthen the idea that dopamine can modulate locomotor behavior both via ascending projections to the basal ganglia and through descending projections to brainstem motor circuits.SIGNIFICANCE STATEMENT Meso-diencephalic dopaminergic neurons play a key role in modulating locomotion by releasing dopamine in the basal ganglia, spinal networks, and the mesencephalic locomotor region, a brainstem region that controls locomotion in a graded fashion. Here, we report in lampreys that dopaminergic neurons release dopamine in the four reticular nuclei where reticulospinal neurons are located. Reticulospinal neurons integrate sensory and descending suprareticular inputs to control spinal interneurons and motoneurons. By directly modulating the activity of reticulospinal neurons, meso-diencephalic dopaminergic neurons control the very last instructions sent by the brain to spinal locomotor circuits. Our study reports on a new direct descending dopaminergic projection to reticulospinal neurons that modulates locomotor behavior.
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Affiliation(s)
- Dimitri Ryczko
- Department of Neuroscience, Université de Montréal, Montréal, Québec H3C 3J7, Canada
- Department of Pharmacology-Physiology, Université de Sherbrooke, Sherbrooke J1H 5N4, Québec Canada
- Centre de recherche du CHUS, Sherbrooke, J1H 5N4, Québec, Canada
| | - Swantje Grätsch
- Department of Neuroscience, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Michael H Alpert
- Department of Biological Sciences, University of Illinois at Chicago, Chicago IL 60607, Illinois
| | - Jackson J Cone
- Department of Psychology, University of Illinois at Chicago, Chicago IL 60607, Illinois
| | - Jacquelin Kasemir
- Department of Neuroscience, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Angelina Ruthe
- Department of Neuroscience, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | | | - François Auclair
- Department of Neuroscience, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Mitchell F Roitman
- Department of Psychology, University of Illinois at Chicago, Chicago IL 60607, Illinois
| | - Simon Alford
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago IL 60612-7308, Illinois
| | - Réjean Dubuc
- Department of Neuroscience, Université de Montréal, Montréal, Québec H3C 3J7, Canada
- Groupe de Recherche en Activité Physique Adaptée, Department of Exercise Science, Université du Québec à Montréal, Montréal, Québec H3C 3P8, Canada
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10
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Rodemer W, Zhang G, Sinitsa I, Hu J, Jin LQ, Li S, Selzer ME. PTPσ Knockdown in Lampreys Impairs Reticulospinal Axon Regeneration and Neuronal Survival After Spinal Cord Injury. Front Cell Neurosci 2020; 14:61. [PMID: 32265663 PMCID: PMC7096546 DOI: 10.3389/fncel.2020.00061] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 03/02/2020] [Indexed: 01/10/2023] Open
Abstract
Traumatic spinal cord injury (SCI) results in persistent functional deficits due to the lack of axon regeneration within the mammalian CNS. After SCI, chondroitin sulfate proteoglycans (CSPGs) inhibit axon regrowth via putative interactions with the LAR-family protein tyrosine phosphatases, PTPσ and LAR, localized on the injured axon tips. Unlike mammals, the sea lamprey, Petromyzon marinus, robustly recovers locomotion after complete spinal cord transection (TX). Behavioral recovery is accompanied by heterogeneous yet predictable anatomical regeneration of the lamprey's reticulospinal (RS) system. The identified RS neurons can be categorized as "good" or "bad" regenerators based on the likelihood that their axons will regenerate. Those neurons that fail to regenerate their axons undergo a delayed form of caspase-mediated cell death. Previously, this lab reported that lamprey PTPσ mRNA is selectively expressed in "bad regenerator" RS neurons, preceding SCI-induced caspase activation. Consequently, we hypothesized that PTPσ deletion would reduce retrograde cell death and promote axon regeneration. Using antisense morpholino oligomers (MOs), we knocked down PTPσ expression after TX and assessed the effects on axon regeneration, caspase activation, intracellular signaling, and behavioral recovery. Unexpectedly, PTPσ knockdown significantly impaired RS axon regeneration at 10 weeks post-TX, primarily due to reduced long-term neuron survival. Interestingly, cell loss was not preceded by an increase in caspase or p53 activation. Behavioral recovery was largely unaffected, although PTPσ knockdowns showed mild deficits in the recovery of swimming distance and latency to immobility during open field swim assays. Although the mechanism underlying the cell death following TX and PTPσ knockdown remains unknown, this study suggests that PTPσ is not a net negative regulator of long tract axon regeneration in lampreys.
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Affiliation(s)
- William Rodemer
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Guixin Zhang
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Isabelle Sinitsa
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
- College of Science and Technology, Temple University, Philadelphia, PA, United States
| | - Jianli Hu
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Li-qing Jin
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Shuxin Li
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
- Department of Anatomy and Cell Biology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Michael E. Selzer
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
- Department of Neurology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
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11
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Rodemer W, Hu J, Selzer ME, Shifman MI. Heterogeneity in the regenerative abilities of central nervous system axons within species: why do some neurons regenerate better than others? Neural Regen Res 2020; 15:996-1005. [PMID: 31823869 PMCID: PMC7034288 DOI: 10.4103/1673-5374.270298] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Some neurons, especially in mammalian peripheral nervous system or in lower vertebrate or in vertebrate central nervous system (CNS) regenerate after axotomy, while most mammalian CNS neurons fail to regenerate. There is an emerging consensus that neurons have different intrinsic regenerative capabilities, which theoretically could be manipulated therapeutically to improve regeneration. Population-based comparisons between “good regenerating” and “bad regenerating” neurons in the CNS and peripheral nervous system of most vertebrates yield results that are inconclusive or difficult to interpret. At least in part, this reflects the great diversity of cells in the mammalian CNS. Using mammalian nervous system imposes several methodical limitations. First, the small sizes and large numbers of neurons in the CNS make it very difficult to distinguish regenerating neurons from non-regenerating ones. Second, the lack of identifiable neurons makes it impossible to correlate biochemical changes in a neuron with axonal damage of the same neuron, and therefore, to dissect the molecular mechanisms of regeneration on the level of single neurons. This review will survey the reported responses to axon injury and the determinants of axon regeneration, emphasizing non-mammalian model organisms, which are often under-utilized, but in which the data are especially easy to interpret.
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Affiliation(s)
- William Rodemer
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), the Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
| | - Jianli Hu
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), the Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
| | - Michael E Selzer
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation); Department of Neurology, the Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
| | - Michael I Shifman
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), the Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
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12
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Chen J, Shifman MI. Inhibition of neogenin promotes neuronal survival and improved behavior recovery after spinal cord injury. Neuroscience 2019; 408:430-447. [PMID: 30943435 DOI: 10.1016/j.neuroscience.2019.03.055] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 03/22/2019] [Accepted: 03/26/2019] [Indexed: 01/09/2023]
Abstract
Following spinal cord trauma, axonal regeneration in the mammalian spinal cord does not occur and functional recovery may be further impeded by retrograde neuronal death. By contrast, lampreys recover after spinal cord injury (SCI) and axons re-connected to their targets in spinal cord. However, the identified reticulospinal (RS) neurons located in the lamprey brain differ in their regenerative capacities - some are good regenerators, and others are bad regenerators - despite the fact that they have analogous projection pathways. Previously, we reported that axonal guidance receptor Neogenin involved in regulation of axonal regeneration after SCI and downregulation of Neogenin synthesis by morpholino oligonucleotides (MO) enhanced the regeneration of RS neurons. Incidentally, the bad regenerating RS neurons often undergo a late retrograde apoptosis after SCI. Here we report that, after SCI, expression of RGMa mRNA was upregulated around the transection site, while its receptor Neogenin continued to be synthesized almost inclusively in the "bad-regenerating" RS neurons. Inhibition of Neogenin by MO prohibited activation of caspases and improved the survival of RS neurons at 10 weeks after SCI. These data provide new evidence in vivo that Neogenin is involved in retrograde neuronal death and failure of axonal regeneration after SCI.
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Affiliation(s)
- Jie Chen
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), Philadelphia, PA 19140, USA
| | - Michael I Shifman
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), Philadelphia, PA 19140, USA; Department of Neuroscience, Temple University School of Medicine, 3500 North Broad Street, Philadelphia, PA 19140, USA.
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Hanslik KL, Allen SR, Harkenrider TL, Fogerson SM, Guadarrama E, Morgan JR. Regenerative capacity in the lamprey spinal cord is not altered after a repeated transection. PLoS One 2019; 14:e0204193. [PMID: 30699109 PMCID: PMC6353069 DOI: 10.1371/journal.pone.0204193] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 12/21/2018] [Indexed: 01/19/2023] Open
Abstract
The resilience of regeneration in vertebrates is not very well understood. Yet understanding if tissues can regenerate after repeated insults, and identifying limitations, is important for elucidating the underlying mechanisms of tissue plasticity. This is particularly challenging in tissues, such as the nervous system, which possess a large number of terminally differentiated cells and often exhibit limited regeneration in the first place. However, unlike mammals, which exhibit very limited regeneration of spinal cord tissues, many non-mammalian vertebrates, including lampreys, bony fishes, amphibians, and reptiles, regenerate their spinal cords and functionally recover even after a complete spinal cord transection. It is well established that lampreys undergo full functional recovery of swimming behaviors after a single spinal cord transection, which is accompanied by tissue repair at the lesion site, as well as axon and synapse regeneration. Here we begin to explore the resilience of spinal cord regeneration in lampreys after a second spinal transection (re-transection). We report that by all functional and anatomical measures tested, lampreys regenerate after spinal re-transection just as robustly as after single transections. Recovery of swimming, synapse and cytoskeletal distributions, axon regeneration, and neuronal survival were nearly identical after spinal transection or re-transection. Only minor differences in tissue repair at the lesion site were observed in re-transected spinal cords. Thus, regenerative potential in the lamprey spinal cord is largely unaffected by spinal re-transection, indicating a greater persistent regenerative potential than exists in some other highly regenerative models. These findings establish a new path for uncovering pro-regenerative targets that could be deployed in non-regenerative conditions.
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Affiliation(s)
- Kendra L Hanslik
- The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, Massachusetts, United States of America
| | - Scott R Allen
- The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, Massachusetts, United States of America
| | - Tessa L Harkenrider
- The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, Massachusetts, United States of America
| | - Stephanie M Fogerson
- The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, Massachusetts, United States of America
| | - Eduardo Guadarrama
- The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, Massachusetts, United States of America
| | - Jennifer R Morgan
- The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, Massachusetts, United States of America
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14
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A Brainstem Neural Substrate for Stopping Locomotion. J Neurosci 2018; 39:1044-1057. [PMID: 30541913 DOI: 10.1523/jneurosci.1992-18.2018] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 11/20/2018] [Accepted: 12/03/2018] [Indexed: 01/04/2023] Open
Abstract
Locomotion occurs sporadically and needs to be started, maintained, and stopped. The neural substrate underlying the activation of locomotion is partly known, but little is known about mechanisms involved in termination of locomotion. Recently, reticulospinal neurons (stop cells) were found to play a crucial role in stopping locomotion in the lamprey: their activation halts ongoing locomotion and their inactivation slows down the termination process. Intracellular recordings of these cells revealed a distinct activity pattern, with a burst of action potentials at the beginning of a locomotor bout and one at the end (termination burst). The termination burst was shown to be time linked to the end of locomotion, but the mechanisms by which it is triggered have remained unknown. We studied this in larval sea lampreys (Petromyzon marinus; the sex of the animals was not taken into account). We found that the mesencephalic locomotor region (MLR), which is known to initiate and control locomotion, stops ongoing locomotion by providing synaptic inputs that trigger the termination burst in stop cells. When locomotion is elicited by MLR stimulation, a second MLR stimulation stops the locomotor bout if it is of lower intensity than the initial stimulation. This occurs for MLR-induced, sensory-evoked, and spontaneous locomotion. Furthermore, we show that glutamatergic and, most likely, monosynaptic projections from the MLR activate stop cells during locomotion. Therefore, activation of the MLR not only initiates locomotion, but can also control the end of a locomotor bout. These results provide new insights onto the neural mechanisms responsible for stopping locomotion.SIGNIFICANCE STATEMENT The mesencephalic locomotor region (MLR) is a brainstem region well known to initiate and control locomotion. Since its discovery in cats in the 1960s, the MLR has been identified in all vertebrate species tested from lampreys to humans. We now demonstrate that stimulation of the MLR not only activates locomotion, but can also stop it. This is achieved through a descending glutamatergic signal, most likely monosynaptic, from the MLR to the reticular formation that activates reticulospinal stop cells. Together, our findings have uncovered a neural mechanism for stopping locomotion and bring new insights into the function of the MLR.
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Zhang G, Rodemer W, Lee T, Hu J, Selzer ME. The Effect of Axon Resealing on Retrograde Neuronal Death after Spinal Cord Injury in Lamprey. Brain Sci 2018; 8:E65. [PMID: 29661988 PMCID: PMC5924401 DOI: 10.3390/brainsci8040065] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 04/02/2018] [Accepted: 04/11/2018] [Indexed: 02/05/2023] Open
Abstract
Failure of axon regeneration in the central nervous system (CNS) of mammals is due to both extrinsic inhibitory factors and to neuron-intrinsic factors. The importance of intrinsic factors is illustrated in the sea lamprey by the 18 pairs of large, individually identified reticulospinal (RS) neurons, whose axons are located in the same spinal cord tracts but vary greatly in their ability to regenerate after spinal cord transection (TX). The neurons that are bad regenerators also undergo very delayed apoptosis, signaled early by activation of caspases. We noticed that the neurons with a low probability of axon regeneration tend to be larger than the good regenerators. We postulate that the poorly regenerating larger neurons have larger caliber axons, which reseal more slowly, allowing more prolonged entry of toxic signals (e.g., Ca++) into the axon at the injury site. To test this hypothesis, we used a dye-exclusion assay, applying membrane-impermeable dyes to the cut ends of spinal cords at progressively longer post-TX intervals. Axons belonging to the very small neurons (not individually identified) of the medial inferior RS nucleus resealed within 15 min post-TX. Almost 75% of axons belonging to the medium-sized identified RS neurons resealed within 3 h. At this time, only 36% of the largest axons had resealed, often taking more than 24 h to exclude the dye. There was an inverse relationship between an RS neuron's size and the probability that its axon would regenerate (r = -0.92) and that the neuron would undergo delayed apoptosis, as indicated by staining with a fluorescently labeled inhibitor of caspases (FLICA; r = 0.73). The artificial acceleration of resealing with polyethylene glycol (PEG) reduced retrograde neuronal apoptosis by 69.5% at 2 weeks after spinal cord injury (SCI), suggesting that axon resealing is a critical determinant of cell survival. Ca++-free Ringer's solution with EGTA prolonged the sealing time and increased apoptotic signaling, suggesting that factors other than Ca++ diffusion into the injured tip contribute to retrograde death signaling. A longer distance of the lesion from the cell body reduced apoptotic signaling independent of the axon sealing time.
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Affiliation(s)
- Guixin Zhang
- Shriners Hospital Pediatric Research Center (Center for Neural Repair and Rehabilitation), Philadelphia, PA 19140, USA.
| | - William Rodemer
- Shriners Hospital Pediatric Research Center (Center for Neural Repair and Rehabilitation), Philadelphia, PA 19140, USA.
| | - Taemin Lee
- Shriners Hospital Pediatric Research Center (Center for Neural Repair and Rehabilitation), Philadelphia, PA 19140, USA.
| | - Jianli Hu
- Shriners Hospital Pediatric Research Center (Center for Neural Repair and Rehabilitation), Philadelphia, PA 19140, USA.
| | - Michael E Selzer
- Shriners Hospital Pediatric Research Center (Center for Neural Repair and Rehabilitation), Philadelphia, PA 19140, USA.
- Department of Neurology, the Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA 19140, USA.
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16
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Nigral Glutamatergic Neurons Control the Speed of Locomotion. J Neurosci 2017; 37:9759-9770. [PMID: 28924005 DOI: 10.1523/jneurosci.1810-17.2017] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 08/08/2017] [Accepted: 08/26/2017] [Indexed: 01/16/2023] Open
Abstract
The mesencephalic locomotor region (MLR) plays a crucial role in locomotor control. In vertebrates, stimulation of the MLR at increasing intensities elicits locomotion of growing speed. This effect has been presumed to result from higher brain inputs activating the MLR like a dimmer switch. Here, we show in lampreys (Petromyzon marinus) of either sex that incremental stimulation of a region homologous to the mammalian substantia nigra pars compacta (SNc) evokes increasing activation of MLR cells with a graded increase in the frequency of locomotor movements. Neurons co-storing glutamate and dopamine were found to project from the primal SNc to the MLR. Blockade of glutamatergic transmission largely diminished MLR cell responses and locomotion. Local blockade of D1 receptors in the MLR decreased locomotor frequency, but did not disrupt the SNc-evoked graded control of locomotion. Our findings revealed the presence of a glutamatergic input to the MLR originating from the primal SNc that evokes graded locomotor movements.SIGNIFICANCE STATEMENT The mesencephalic locomotor region (MLR) plays a crucial role in the control of locomotion. It projects downward to reticulospinal neurons that in turn activate the spinal locomotor networks. Increasing the intensity of MLR stimulation produces a growing activation of reticulospinal cells and a progressive increase in the speed of locomotor movements. Since the discovery of the MLR some 50 years ago, it has been presumed that higher brain regions activate the MLR in a graded fashion, but this has not been confirmed yet. Here, using a combination of techniques from cell to behavior, we provide evidence of a new glutamatergic pathway activating the MLR in a graded fashion, and consequently evoking a progressive increase in locomotor output.
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17
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Abstract
Paralysis following spinal cord injury (SCI) is due to failure of axonal regeneration. It is believed that the capacities of neurons to regrow their axons are due partly to their intrinsic characteristics, which in turn are greatly influenced by several types of inhibitory molecules that are present, or even increased in the extracellular environment of the injured spinal cord. Many of these inhibitory molecules have been studied extensively in recent years. It has been suggested that the small GTPase RhoA is an intracellular convergence point for signaling by these extracellular inhibitory molecules, but due to the complexity of the central nervous system (CNS) in mammals, and the limitation of pharmacological tools, the specific roles of RhoA are unclear. By exploiting the anatomical and technical advantages of the lamprey CNS, we recently demonstrated that RhoA knockdown promotes true axon regeneration through the lesion site after SCI. In addition, we found that RhoA knockdown protects the large, identified reticulospinal neurons from apoptosis after their axons were axotomized in spinal cord. Therefore, manipulation of the RhoA signaling pathway may be an important approach in the development of treatments that are both neuroprotective and axon regeneration-promoting, to enhance functional recovery after SCI.
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Affiliation(s)
- Jianli Hu
- Shriners Hospitals for Children, Pediatric Research Center (Center for Neural Repair and Rehabilitation), Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
| | - Michael E Selzer
- Shriners Hospitals for Children, Pediatric Research Center (Center for Neural Repair and Rehabilitation), Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA.,Department of Neurology, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
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18
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Chen J, Laramore C, Shifman MI. The expression of chemorepulsive guidance receptors and the regenerative abilities of spinal-projecting neurons after spinal cord injury. Neuroscience 2016; 341:95-111. [PMID: 27890825 DOI: 10.1016/j.neuroscience.2016.11.020] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 11/14/2016] [Accepted: 11/16/2016] [Indexed: 12/31/2022]
Abstract
Spinal cord injury (SCI) in mammals leads to permanent loss of function because axons do not regenerate in the central nervous system (CNS). To date, treatments based on neutralizing inhibitory environmental cues, such as the myelin-associated growth inhibitors and chondroitin sulfate proteoglycans, or on adding neurotrophic factors, have had limited success in enhancing regeneration. Published studies suggested that multiple axon guidance cues (repulsive guidance molecule (RGM) family, semaphorins, ephrins, and netrins) persist in adult animals, and that their expression is upregulated after CNS injury. Moreover, many adult CNS neurons continue to express axon guidance receptors. We used the advantages of the lamprey CNS to test the hypotheses that the regenerative abilities of spinal-projecting neurons depend upon their expression of chemorepulsive guidance receptors. After complete spinal transection, lampreys recover behaviorally, and injured axons grow selectively in their correct paths. However, the large identified reticulospinal (RS) neurons in the lamprey brain are heterogeneous in their regenerative abilities - some are high regeneration capacity neurons (probability of axon regeneration >50%), others are low regeneration capacity neurons (<30%). Here we report that the RGM receptor Neogenin is expressed preferentially in the low regeneration capacity RS neurons that regenerate poorly, and that downregulation of Neogenin by morpholino antisense oligonucleotides enhances regeneration of RS axons after SCI. Moreover, lamprey CNS neurons co-express multiple guidance receptors (Neogenin, UNC5 and PlexinA), suggesting that the regenerative abilities of spinal-projecting neurons might reflect the summed influences of the chemorepulsive guidance receptors that they express.
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Affiliation(s)
- Jie Chen
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), USA
| | - Cindy Laramore
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), USA
| | - Michael I Shifman
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), USA; Department of Neuroscience, Temple University School of Medicine, 3500 North Broad Street, Philadelphia, PA 19140, USA.
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19
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Hu J, Zhang G, Rodemer W, Jin LQ, Shifman M, Selzer ME. The role of RhoA in retrograde neuronal death and axon regeneration after spinal cord injury. Neurobiol Dis 2016; 98:25-35. [PMID: 27888137 DOI: 10.1016/j.nbd.2016.11.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 10/24/2016] [Accepted: 11/20/2016] [Indexed: 01/13/2023] Open
Abstract
Paralysis following spinal cord injury (SCI) is due to interruption of axons and their failure to regenerate. It has been suggested that the small GTPase RhoA may be an intracellular signaling convergence point for several types of growth-inhibiting extracellular molecules. Even if this is true in vitro, it is not clear from studies in mammalian SCI, whether the effects of RhoA manipulations on axon growth in vivo are due to a RhoA-mediated inhibition of true regeneration or only of collateral sprouting from spared axons, since work on SCI generally is performed with partial injury models. RhoA also has been implicated in local neuronal apoptosis after SCI, but whether this reflects an effect on axotomy-induced cell death or an effect on other pathological mechanisms is not known. In order to resolve these ambiguities, we studied the effects of RhoA knockdown in the sea lamprey central nervous system (CNS), where after complete spinal cord transection (TX), robust but incomplete regeneration of large axons belonging to individually identified reticulospinal (RS) neurons occurs, and where some RS neurons show unambiguous delayed retrograde apoptosis after axotomy. RhoA protein was detected in neurons and axons of the lamprey brain and spinal cord, and its expression was increased post-TX. Knockdown of RhoA in vivo by retrogradely-delivered morpholino antisense oligonucleotides (MOs) to the RS neurons significantly reduced retrograde apoptosis signaling in identified RS neurons post-SCI, as indicated by Fluorochrome Labeled Inhibitor of Caspases (FLICA) in brain wholemounts. In individual RS neurons, the reduction of caspase activation by RhoA knockdown began at 2weeks post-TX and was still seen at 8weeks. RhoA knockdown slowed axon retraction and possibly increased early axon regeneration in the proximal stump. The number of axons regenerating beyond the lesion more than 5mm at 10weeks post-TX also was increased. Thus RhoA knockdown both enhanced true axon regeneration and inhibited retrograde apoptosis signaling after SCI.
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Affiliation(s)
- Jianli Hu
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA 19140, USA
| | - Guixin Zhang
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA 19140, USA
| | - William Rodemer
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA 19140, USA
| | - Li-Qing Jin
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA 19140, USA
| | - Michael Shifman
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA 19140, USA
| | - Michael E Selzer
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA 19140, USA; Dept. of Neurology, Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA 19140, USA.
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20
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Hsu LJ, Zelenin PV, Orlovsky GN, Deliagina TG. Supraspinal control of spinal reflex responses to body bending during different behaviours in lampreys. J Physiol 2016; 595:883-900. [PMID: 27589479 DOI: 10.1113/jp272714] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 08/22/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Spinal reflexes are substantial components of the motor control system in all vertebrates and centrally driven reflex modifications are essential to many behaviours, but little is known about the neuronal mechanisms underlying these modifications. To study this issue, we took advantage of an in vitro brainstem-spinal cord preparation of the lamprey (a lower vertebrate), in which spinal reflex responses to spinal cord bending (caused by signals from spinal stretch receptor neurons) can be evoked during different types of fictive behaviour. Our results demonstrate that reflexes observed during fast forward swimming are reversed during escape behaviours, with the reflex reversal presumably caused by supraspinal commands transmitted by a population of reticulospinal neurons. NMDA receptors are involved in the formation of these commands, which are addressed primarily to the ipsilateral spinal networks. In the present study the neuronal mechanisms underlying reflex reversal have been characterized for the first time. ABSTRACT Spinal reflexes can be modified during different motor behaviours. However, our knowledge about the neuronal mechanisms underlying these modifications in vertebrates is scarce. In the lamprey, a lower vertebrate, body bending causes activation of intraspinal stretch receptor neurons (SRNs) resulting in spinal reflexes: activation of motoneurons (MNs) with bending towards either the contralateral or ipsilateral side (a convex or concave response, respectively). The present study had two main aims: (i) to investigate how these spinal reflexes are modified during different motor behaviours, and (ii) to reveal reticulospinal neurons (RSNs) transmitting commands for the reflex modification. For this purpose in in vitro brainstem-spinal cord preparation, RSNs and reflex responses to bending were recorded during different fictive behaviours evoked by supraspinal commands. We found that during fast forward swimming MNs exhibited convex responses. By contrast, during escape behaviours, MNs exhibited concave responses. We found RSNs that were activated during both stimulation causing reflex reversal without initiation of any specific behaviour, and stimulation causing reflex reversal during escape behaviour. We suggest that these RSNs transmit commands for the reflex modification. Application of the NMDA antagonist (AP-5) to the brainstem significantly decreased the reversed reflex, suggesting involvement of NMDA receptors in the formation of these commands. Longitudinal split of the spinal cord did not abolish the reflex reversal caused by supraspinal commands, suggesting an important role for ipsilateral networks in determining this type of motor response. This is the first study to reveal the neuronal mechanisms underlying supraspinal control of reflex reversal.
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Affiliation(s)
- Li-Ju Hsu
- Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden
| | - Pavel V Zelenin
- Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden
| | - Grigori N Orlovsky
- Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden
| | - Tatiana G Deliagina
- Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden
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21
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Hale ME, Katz HR, Peek MY, Fremont RT. Neural circuits that drive startle behavior, with a focus on the Mauthner cells and spiral fiber neurons of fishes. J Neurogenet 2016; 30:89-100. [DOI: 10.1080/01677063.2016.1182526] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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22
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Chen J, Laramore C, Shifman MI. Differential expression of HDACs and KATs in high and low regeneration capacity neurons during spinal cord regeneration. Exp Neurol 2016; 280:50-9. [DOI: 10.1016/j.expneurol.2016.04.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 03/11/2016] [Accepted: 04/03/2016] [Indexed: 12/12/2022]
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23
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Jin LQ, Pennise CR, Rodemer W, Jahn KS, Selzer ME. Protein synthetic machinery and mRNA in regenerating tips of spinal cord axons in lamprey. J Comp Neurol 2016; 524:3614-3640. [PMID: 27120118 DOI: 10.1002/cne.24020] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 04/11/2016] [Accepted: 04/12/2016] [Indexed: 02/03/2023]
Abstract
Polyribosomes, mRNA, and other elements of translational machinery have been reported in peripheral nerves and in elongating injured axons of sensory neurons in vitro, primarily in growth cones. Evidence for involvement of local protein synthesis in regenerating central nervous system (CNS) axons is less extensive. We monitored regeneration of back-labeled lamprey spinal axons after spinal cord transection and detected mRNA in axon tips by in situ hybridization and microaspiration of their axoplasm. Poly(A)+mRNA was present in the axon tips, and was more abundant in actively regenerating tips than in static or retracting ones. Target-specific polymerase chain reaction (PCR) and in situ hybridization revealed plentiful mRNA for the low molecular neurofilament subunit and β-tubulin, but very little for β-actin, consistent with the morphology of their tips, which lack filopodia and lamellipodia. Electron microscopy showed ribosomes/polyribosomes in the distal parts of axon tips and in association with vesicle-like membranes, primarily in the tip. In one instance, there were structures with the appearance of rough endoplasmic reticulum. Immunohistochemistry showed patches of ribosomal protein S6 positivity in a similar distribution. The results suggest that local protein synthesis might be involved in the mechanism of axon regeneration in the lamprey spinal cord. J. Comp. Neurol. 524:3614-3640, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Li-Qing Jin
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA, 19140.
| | - Cynthia R Pennise
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA, 19140
| | - William Rodemer
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA, 19140
| | - Kristen S Jahn
- The Children's Hospital of Philadelphia, 1108 Pine Street, Philadelphia, PA, 19107
| | - Michael E Selzer
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA, 19140. .,Department of Neurology, Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA, 19140.
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24
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Daghfous G, Green WW, Alford ST, Zielinski BS, Dubuc R. Sensory Activation of Command Cells for Locomotion and Modulatory Mechanisms: Lessons from Lampreys. Front Neural Circuits 2016; 10:18. [PMID: 27047342 PMCID: PMC4801879 DOI: 10.3389/fncir.2016.00018] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 03/07/2016] [Indexed: 11/13/2022] Open
Abstract
Sensorimotor transformation is one of the most fundamental and ubiquitous functions of the central nervous system (CNS). Although the general organization of the locomotor neural circuitry is relatively well understood, less is known about its activation by sensory inputs and its modulation. Utilizing the lamprey model, a detailed understanding of sensorimotor integration in vertebrates is emerging. In this article, we explore how the vertebrate CNS integrates sensory signals to generate motor behavior by examining the pathways and neural mechanisms involved in the transformation of cutaneous and olfactory inputs into motor output in the lamprey. We then review how 5-hydroxytryptamine (5-HT) acts on these systems by modulating both sensory inputs and motor output. A comprehensive review of this fundamental topic should provide a useful framework in the fields of motor control, sensorimotor integration and neuromodulation.
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Affiliation(s)
- Gheylen Daghfous
- Groupe de Recherche en Activité Physique Adaptée, Département des Sciences de l'Activité Physique, Université du Québec à MontréalMontréal, QC, Canada; Groupe de Recherche sur le Système Nerveux Central, Département de Neurosciences, Université de MontréalMontréal, QC, Canada
| | - Warren W Green
- Department of Biological Sciences and Great Lakes Institute for Environmental Research, University of Windsor Windsor, ON, Canada
| | - Simon T Alford
- Laboratory of Integrative Neuroscience, Department of Biological Sciences, University of Illinois at Chicago Chicago, IL, USA
| | - Barbara S Zielinski
- Department of Biological Sciences and Great Lakes Institute for Environmental Research, University of Windsor Windsor, ON, Canada
| | - Réjean Dubuc
- Groupe de Recherche en Activité Physique Adaptée, Département des Sciences de l'Activité Physique, Université du Québec à MontréalMontréal, QC, Canada; Groupe de Recherche sur le Système Nerveux Central, Département de Neurosciences, Université de MontréalMontréal, QC, Canada
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25
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Fogerson SM, van Brummen AJ, Busch DJ, Allen SR, Roychaudhuri R, Banks SML, Klärner FG, Schrader T, Bitan G, Morgan JR. Reducing synuclein accumulation improves neuronal survival after spinal cord injury. Exp Neurol 2016; 278:105-15. [PMID: 26854933 DOI: 10.1016/j.expneurol.2016.02.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Revised: 01/29/2016] [Accepted: 02/04/2016] [Indexed: 11/25/2022]
Abstract
Spinal cord injury causes neuronal death, limiting subsequent regeneration and recovery. Thus, there is a need to develop strategies for improving neuronal survival after injury. Relative to our understanding of axon regeneration, comparatively little is known about the mechanisms that promote the survival of damaged neurons. To address this, we took advantage of lamprey giant reticulospinal neurons whose large size permits detailed examination of post-injury molecular responses at the level of individual, identified cells. We report here that spinal cord injury caused a select subset of giant reticulospinal neurons to accumulate synuclein, a synaptic vesicle-associated protein best known for its atypical aggregation and causal role in neurodegeneration in Parkinson's and other diseases. Post-injury synuclein accumulation took the form of punctate aggregates throughout the somata and occurred selectively in dying neurons, but not in those that survived. In contrast, another synaptic vesicle protein, synaptotagmin, did not accumulate in response to injury. We further show that the post-injury synuclein accumulation was greatly attenuated after single dose application of either the "molecular tweezer" inhibitor, CLR01, or a translation-blocking synuclein morpholino. Consequently, reduction of synuclein accumulation not only improved neuronal survival, but also increased the number of axons in the spinal cord proximal and distal to the lesion. This study is the first to reveal that reducing synuclein accumulation is a novel strategy for improving neuronal survival after spinal cord injury.
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Affiliation(s)
- Stephanie M Fogerson
- Marine Biological Laboratory, The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Woods Hole, MA 02543, United States
| | - Alexandra J van Brummen
- Marine Biological Laboratory, The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Woods Hole, MA 02543, United States; Section of Molecular Cell and Developmental Biology, The University of Texas at Austin, Austin, TX 78712, United States
| | - David J Busch
- Section of Molecular Cell and Developmental Biology, The University of Texas at Austin, Austin, TX 78712, United States
| | - Scott R Allen
- Marine Biological Laboratory, The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Woods Hole, MA 02543, United States
| | - Robin Roychaudhuri
- Department of Neurology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, United States
| | - Susan M L Banks
- Marine Biological Laboratory, The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Woods Hole, MA 02543, United States
| | - Frank-Gerrit Klärner
- Institute of Organic Chemistry, University of Duisburg-Essen, Essen 45117, Germany
| | - Thomas Schrader
- Institute of Organic Chemistry, University of Duisburg-Essen, Essen 45117, Germany
| | - Gal Bitan
- Department of Neurology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, United States; Brain Research Institute and Molecular Biology Institute, University of California at Los Angeles, Los Angeles, CA 90095, United States
| | - Jennifer R Morgan
- Marine Biological Laboratory, The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Woods Hole, MA 02543, United States.
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Evolution of rapid nerve conduction. Brain Res 2016; 1641:11-33. [PMID: 26879248 DOI: 10.1016/j.brainres.2016.02.015] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 02/04/2016] [Accepted: 02/05/2016] [Indexed: 01/29/2023]
Abstract
Rapid conduction of nerve impulses is a priority for organisms needing to react quickly to events in their environment. While myelin may be viewed as the crowning innovation bringing about rapid conduction, the evolution of rapid communication mechanisms, including those refined and enhanced in the evolution of myelin, has much deeper roots. In this review, a sequence is traced starting with diffusional communication, followed by transport-facilitated communication, the rise of electrical signaling modalities, the invention of voltage-gated channels and "all-or-none" impulses, the emergence of elongate nerve axons specialized for communication and their fine-tuning to enhance impulse conduction speeds. Finally within the evolution of myelin itself, several innovations have arisen and have been interactively refined for speed enhancement, including the addition and sealing of layers, their limitation by space availability, and the optimization of key parameters: channel density, lengths of exposed nodes and lengths of internodes. We finish by suggesting several design principles that appear to govern the evolution of rapid conduction. This article is part of a Special Issue entitled SI: Myelin Evolution.
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The evolution of vertebrate and invertebrate myelin: a theoretical computational study. J Comput Neurosci 2015; 38:521-38. [PMID: 25832903 DOI: 10.1007/s10827-015-0552-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 02/20/2015] [Accepted: 03/04/2015] [Indexed: 01/11/2023]
Abstract
Multilayered, lipid-rich myelin increases nerve impulse conduction velocity, contributes to compact nervous systems, and reduces metabolic costs of neural activity. Based on the hypothesis that increased impulse conduction velocity provides a selective advantage that drives the evolution of myelin, we simulated a sequence of plausible intermediate stages of myelin evolution, each of which providing an enhancement of conduction speed. We started with the expansion of insulating glial coverage, which led first to a single layer of myelin surrounding the axon and then to multiple myelin wraps with well-organized nodes. The myelinated fiber was modeled at three levels of complexity as the hypothesized evolutionary progression became more quantitatively exacting: 1) representing the fiber as a mathematically-tractable uniform active cylinder with the effect of myelination approximated by changing its specific capacitance (C(m)); 2) representing it as a chain of simple, cable-model compartments having alternating nodal and internodal parameters subject to optimization, and 3) representing it in a double cable model with the axon and myelin sheath treated separately. Conduction velocity was optimized at each stage. To maintain optimal conduction velocities, increased myelin coverage of axonal surface must be accompanied by an increase in channel density at the evolving nodes, but along with increases in myelin thickness, a reduction in overall average channel density must occur. Leakage under the myelin sheath becomes more of a problem with smaller fiber diameters, which may help explain the tendency for myelin to occur preferentially in larger nerve fibers in both vertebrates and invertebrates.
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Gelman S. Heterogeneous release probabilities and activity-dependent short-term synaptic depression. Commun Integr Biol 2014. [DOI: 10.4161/cib.16752] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Zhang G, Hu J, Li S, Huang L, Selzer ME. Selective expression of CSPG receptors PTPσ and LAR in poorly regenerating reticulospinal neurons of lamprey. J Comp Neurol 2014; 522:2209-29. [DOI: 10.1002/cne.23529] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Revised: 12/16/2013] [Accepted: 12/17/2013] [Indexed: 12/26/2022]
Affiliation(s)
- Guixin Zhang
- Center for Neural Repair and Rehabilitation; Shriners Hospitals Pediatric Research Center; Philadelphia Pennsylvania 19140
| | - Jianli Hu
- Center for Neural Repair and Rehabilitation; Shriners Hospitals Pediatric Research Center; Philadelphia Pennsylvania 19140
| | - Shuxin Li
- Center for Neural Repair and Rehabilitation; Shriners Hospitals Pediatric Research Center; Philadelphia Pennsylvania 19140
| | - Lisa Huang
- Center for Neural Repair and Rehabilitation; Shriners Hospitals Pediatric Research Center; Philadelphia Pennsylvania 19140
| | - Michael E. Selzer
- Center for Neural Repair and Rehabilitation; Shriners Hospitals Pediatric Research Center; Philadelphia Pennsylvania 19140
- Department of Neurology; Temple University School of Medicine; 3500 North Broad Street Philadelphia Pennsylvania 19140
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Hsu LJ, Orlovsky GN, Zelenin PV. Different forms of locomotion in the spinal lamprey. Eur J Neurosci 2014; 39:2037-49. [PMID: 24641591 DOI: 10.1111/ejn.12553] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Accepted: 02/12/2014] [Indexed: 11/28/2022]
Abstract
Forward locomotion has been extensively studied in different vertebrate animals, and the principal role of spinal mechanisms in the generation of this form of locomotion has been demonstrated. Vertebrate animals, however, are capable of other forms of locomotion, such as backward walking and swimming, sideward walking, and crawling. Do the spinal mechanisms play a principal role in the generation of these forms of locomotion? We addressed this question in lampreys, which are capable of five different forms of locomotion - fast forward swimming, slow forward swimming, backward swimming, forward crawling, and backward crawling. To induce locomotion in lampreys spinalised at the second gill level, we used either electrical stimulation of the spinal cord at different rostrocaudal levels, or tactile stimulation of specific cutaneous receptive fields from which a given form of locomotion could be evoked in intact lampreys. We found that any of the five forms of locomotion could be evoked in the spinal lamprey by electrical stimulation of the spinal cord, and some of them by tactile stimulation. These results suggest that spinal mechanisms in the lamprey, in the absence of phasic supraspinal commands, are capable of generating the basic pattern for all five forms of locomotion observed in intact lampreys. In spinal lampreys, the direction of swimming did not depend on the site of spinal cord stimulation, but on the stimulation strength. The direction of crawling strongly depended on the body configuration. The spinal structures presumably activated by spinal cord stimulation and causing different forms of locomotion are discussed.
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Affiliation(s)
- Li-Ju Hsu
- Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden
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Villar-Cerviño V, Fernández-López B, Celina Rodicio M, Anadón R. Aspartate-containing neurons of the brainstem and rostral spinal cord of the sea lampreyPetromyzon marinus: Distribution and comparison with γ-aminobutyric acid. J Comp Neurol 2014; 522:1209-31. [DOI: 10.1002/cne.23493] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 10/29/2013] [Accepted: 10/29/2013] [Indexed: 12/26/2022]
Affiliation(s)
- Verona Villar-Cerviño
- Departamento de Biología Celular y Ecología; Facultad de Biología, Universidad de Santiago de Compostela; Santiago de Compostela 15782 Spain
| | - Blanca Fernández-López
- Departamento de Biología Celular y Ecología; Facultad de Biología, Universidad de Santiago de Compostela; Santiago de Compostela 15782 Spain
| | - María Celina Rodicio
- Departamento de Biología Celular y Ecología; Facultad de Biología, Universidad de Santiago de Compostela; Santiago de Compostela 15782 Spain
| | - Ramón Anadón
- Departamento de Biología Celular y Ecología; Facultad de Biología, Universidad de Santiago de Compostela; Santiago de Compostela 15782 Spain
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Liu YC, Hale ME. Alternative forms of axial startle behaviors in fishes. ZOOLOGY 2014; 117:36-47. [DOI: 10.1016/j.zool.2013.10.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 10/08/2013] [Accepted: 10/09/2013] [Indexed: 10/25/2022]
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Cyclic AMP promotes axon regeneration, lesion repair and neuronal survival in lampreys after spinal cord injury. Exp Neurol 2013; 250:31-42. [PMID: 24041988 DOI: 10.1016/j.expneurol.2013.09.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Revised: 09/03/2013] [Accepted: 09/08/2013] [Indexed: 01/10/2023]
Abstract
Axon regeneration after spinal cord injury in mammals is inadequate to restore function, illustrating the need to design better strategies for improving outcomes. Increasing the levels of the second messenger cyclic adenosine monophosphate (cAMP) after spinal cord injury enhances axon regeneration across a wide variety of species, making it an excellent candidate molecule that has therapeutic potential. However, several important aspects of the cellular and molecular mechanisms by which cAMP enhances axon regeneration are still unclear, such as how cAMP affects axon growth patterns, the molecular components within growing axon tips, the lesion scar, and neuronal survival. To address these points, we took advantage of the large, identified reticulospinal (RS) neurons in lamprey, a vertebrate that exhibits robust axon regeneration after a complete spinal cord transection. Application of a cAMP analog, db-cAMP, at the time of spinal cord transection increased the number of axons that regenerated across the lesion site. Db-cAMP also promoted axons to regenerate in straighter paths, prevented abnormal axonal growth patterns, increased the levels of synaptotagmin within axon tips, and increased the number of axotomized neurons that survived after spinal cord injury, thereby increasing the pool of neurons available for regeneration. There was also a transient increase in the number of microglia/macrophages and improved repair of the lesion site. Taken together, these data reveal several new features of the cellular and molecular mechanisms underlying cAMP-mediated enhancement of axon regeneration, further emphasizing the positive roles for this conserved pathway.
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Villar-Cerviño V, Barreiro-Iglesias A, Fernández-López B, Mazan S, Rodicio MC, Anadón R. Glutamatergic neuronal populations in the brainstem of the sea lamprey, Petromyzon marinus: an in situ hybridization and immunocytochemical study. J Comp Neurol 2013; 521:522-57. [PMID: 22791297 DOI: 10.1002/cne.23189] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Accepted: 07/06/2012] [Indexed: 12/27/2022]
Abstract
Glutamate is the major excitatory neurotransmitter in vertebrates, and glutamatergic cells probably represent a majority of neurons in the brain. Physiological studies have demonstrated a wide presence of excitatory (glutamatergic) neurons in lampreys. The present in situ hybridization study with probes for the lamprey vesicular glutamate transporter (VGLUT) provides an anatomical basis for the general distribution and precise localization of glutamatergic neurons in the sea lamprey brainstem. Most glutamatergic neurons were found within the periventricular gray layer throughout the brainstem, with the following regions being of particular interest: the optic tectum, torus semicircularis, isthmus, dorsal and medial nuclei of the octavolateral area, dorsal column nucleus, solitary tract nucleus, motoneurons, and reticular formation. The reticular population revealed a high degree of cellular heterogeneity including small, medium-sized, large, and giant glutamatergic neurons. We also combined glutamate immunohistochemistry with neuronal tract-tracing methods or γ-aminobutyric acid (GABA) immunohistochemistry to better characterize the glutamatergic populations. Injection of Neurobiotin into the spinal cord revealed that retrogradely labeled small and medium-sized cells of some reticulospinal-projecting groups were often glutamate-immunoreactive, mostly in the hindbrain. In contrast, the large and giant glutamatergic reticulospinal perikarya mostly lacked glutamate immunoreactivity. These results indicate that glutamate immunoreactivity did not reveal the entire set of glutamatergic populations. Some spinal-projecting octaval populations lacked both VGLUT and glutamate. As regards GABA and glutamate, their distribution was largely complementary, but colocalization of glutamate and GABA was observed in some small neurons, suggesting that glutamate immunohistochemistry might also detect non-glutamatergic cells or neurons that co-release both GABA and glutamate.
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Affiliation(s)
- Verona Villar-Cerviño
- Departamento de Biología Celular y Ecología, Facultad de Biología, Universidad de Santiago de Compostela, Santiago de Compostela 15782, Spain
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Barreiro-Iglesias A, Laramore C, Shifman MI. The sea lamprey UNC5 receptors: cDNA cloning, phylogenetic analysis and expression in reticulospinal neurons at larval and adult stages of development. J Comp Neurol 2013; 520:4141-56. [PMID: 22592960 DOI: 10.1002/cne.23143] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
UNC5 receptors mediate repulsive signaling of netrin on neurons. Although only one UNC5 receptor has been identified in invertebrates, four members of the UNC5 family have been identified in gnathostomes. Lampreys, together with mixynes, belong to the oldest branch of extant vertebrates, and their phylogenetic position near to the vertebrate root makes them an interesting model for understanding molecular evolution. Here, we cloned three sea lamprey UNC5 (UNC5L) receptors, and phylogenetic analyses indicated that the first two duplications of the ancestral UNC5 gene occurred before the separation of jawless and jawed vertebrates. UNC5 receptors play important roles during early development, but expression studies have also suggested that UNC5 receptors play roles in the mature nervous system. Here, we report the expression of the different UNC5L receptor transcripts in identified reticulospinal neurons of mature larval or adult sea lampreys detected by in situ hybridization in wholemounted brain preparations. In addition, an extensive expression of the UNC5 receptors was also observed in most brain regions of the adult lamprey. An increase in the types of identifiable reticulospinal neurons expressing the UNC5L receptors was observed in adults compared with larvae. Expression of UNC5 receptors at late developmental stages appears to be a shared characteristic of lampreys and mammals. In larvae, expression of UNC5L receptors was observed in reticulospinal neurons that when axotomized are known to be "bad regenerators." Results in lampreys and mammals suggest that the UNC5-Netrin axonal guidance system may play a role in limiting axonal regeneration after spinal cord injury.
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Affiliation(s)
- Antón Barreiro-Iglesias
- Shriners Hospitals Pediatric Research Center (Center for Neural Repair and Rehabilitation), Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
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The "Lillie transition": models of the onset of saltatory conduction in myelinating axons. J Comput Neurosci 2013; 34:533-46. [PMID: 23306554 DOI: 10.1007/s10827-012-0435-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Revised: 10/29/2012] [Accepted: 12/03/2012] [Indexed: 10/27/2022]
Abstract
Almost 90 years ago, Lillie reported that rapid saltatory conduction arose in an iron wire model of nerve impulse propagation when he covered the wire with insulating sections of glass tubing equivalent to myelinated internodes. This led to his suggestion of a similar mechanism explaining rapid conduction in myelinated nerve. In both their evolution and their development, myelinating axons must make a similar transition between continuous and saltatory conduction. Achieving a smooth transition is a potential challenge that we examined in computer models simulating a segmented insulating sheath surrounding an axon having Hodgkin-Huxley squid parameters. With a wide gap under the sheath, conduction was continuous. As the gap was reduced, conduction initially slowed, owing to the increased extra-axonal resistance, then increased (the "rise") up to several times that of the unmyelinated fiber, as saltatory conduction set in. The conduction velocity slowdown was little affected by the number of myelin layers or modest changes in the size of the "node," but strongly affected by the size of the "internode" and axon diameter. The steepness of the rise of rapid conduction was greatly affected by the number of myelin layers and axon diameter, variably affected by internode length and little affected by node length. The transition to saltatory conduction occurred at surprisingly wide gaps and the improvement in conduction speed persisted to surprisingly small gaps. The study demonstrates that the specialized paranodal seals between myelin and axon, and indeed even the clustering of sodium channels at the nodes, are not necessary for saltatory conduction.
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Busch DJ, Morgan JR. Synuclein accumulation is associated with cell-specific neuronal death after spinal cord injury. J Comp Neurol 2012; 520:1751-71. [PMID: 22120153 DOI: 10.1002/cne.23011] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Spinal cord injury axotomizes neurons and induces many of them to die, whereas others survive. Therefore, it is important to identify factors that lead to neuronal death after injury as a first step toward developing better strategies for increasing neuronal survival and functional recovery. However, the intrinsic molecular pathways that govern whether an injured neuron lives or dies remain surprisingly unclear. To address this question, we took advantage of the large size of giant reticulospinal (RS) neurons in the brain of the lamprey, Petromyzon marinus. We report that axotomy of giant RS neurons induces a select subset of them to accumulate high levels of synuclein, a synaptic vesicle-associated protein whose abnormal accumulation is linked to Parkinson's disease. Injury-induced synuclein accumulation occurred only in neurons that were classified as "poor survivors" by both histological and Fluoro-Jade C staining. In contrast, post-injury synuclein immunofluorescence remained at control levels in neurons that were identified as "good survivors." Synuclein accumulation appeared in the form of aggregated intracellular inclusions. Cells that accumulated synuclein also exhibited more ubiquitin-containing inclusions, similar to what occurs during disease states. When synuclein levels and cell vitality were measured in the same neurons, it became clear that synuclein accumulation preceded and strongly correlated with subsequent neuronal death. Thus, synuclein accumulation is identified as a marker and potential risk factor for forthcoming neuronal death after axotomy, expanding its implications beyond the neurodegenerative diseases.
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Affiliation(s)
- David J Busch
- Section of Molecular Cell and Developmental Biology, Institute for Cell and Molecular Biology, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78712, USA
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Valle-Maroto S, Fernández-López B, Villar-Cerviño V, Barreiro-Iglesias A, Anadón R, Rodicio MC. Inhibitory descending rhombencephalic projections in larval sea lamprey. Neuroscience 2011; 194:1-10. [DOI: 10.1016/j.neuroscience.2011.08.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Revised: 07/29/2011] [Accepted: 08/06/2011] [Indexed: 10/17/2022]
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Gelman S. Heterogeneous release probabilities and activity-dependent short-term synaptic depression. Commun Integr Biol 2011; 4:603-5. [PMID: 22046475 DOI: 10.4161/cib.4.5.16752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Accepted: 06/01/2011] [Indexed: 11/19/2022] Open
Abstract
Synaptic transmission is a major mechanism by which neurons communicate with each other. Basic steps in neurotransmitter release are similar in all synapses. However, many properties of release vary between synapses and reflect specific structural and functional requirements, endowing synapses with specialized functions. Recently, Gelman et al.1 described properties of release and short-term depression at specialized nicotinic synapses in the brainstem of goldfish, Carassius auratus (Linnaeus). These axo-axonic synapses between the Mauthner cell collaterals and their targets, cranial relay neurons (CRNs), exhibit strong short-term depression, even at stimulation frequencies as low as 0.33 Hz. In short, amplitudes of post-synaptic responses, evoked by presynaptic trains of action potentials, were depressed with a time course approximated by a sum of two exponential functions. Initially, fast depression reduced the amplitude of EPSP(2) (response after the second stimulus), to less than 50% of EPSP(1) (response after the first stimulus). This was followed by a slow component of depression that produced an additional 10-30% amplitude reduction over a time-span of tens to hundreds of seconds. Interestingly, depressed EPSPs exhibited longer latencies than that of the "undepressed" EPSP1. Additionally, fast and slow calcium chelators (BAPTA and EGTA), injected pre-synaptically, were equally potent in reducing release. These data are consistent with a previously proposed general mechanism that assumes a change in release probability after the initial release. However, in an alternative interpretation the results could be coherently explained by postulating two releasable pools of vesicles, with high and low release probabilities, and a generally accepted depletion scheme. This latter interpretation will be discussed in this article.
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Affiliation(s)
- Simon Gelman
- Dominick P. Purpura Department of Neuroscience; Albert Einstein College of Medicine; Bronx, NY USA
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Buchanan JT. Spinal locomotor inputs to individually identified reticulospinal neurons in the lamprey. J Neurophysiol 2011; 106:2346-57. [PMID: 21832033 DOI: 10.1152/jn.01100.2010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Locomotor feedback signals from the spinal cord to descending brain stem neurons were examined in the lamprey using the uniquely identifiable reticulospinal neurons, the Müller and Mauthner cells. The same identified reticulospinal neurons were recorded in several preparations, under reduced conditions, to address whether an identified reticulospinal neuron shows similar locomotor-related oscillation timing from animal to animal and whether these timing signals can differ significantly from other identified reticulospinal neurons. Intracellular recordings of membrane potential in identified neurons were made in an isolated brain stem-spinal cord preparation with a high-divalent cation solution on the brain stem to suppress indirect neural pathways and with D-glutamate perfusion to the spinal cord to induce fictive swimming. Under these conditions, the identified reticulospinal neurons show significant clustering of the timings of the peaks and troughs of their locomotor-related oscillations. Whereas most identified neurons oscillated in phase with locomotor bursting in ipsilateral ventral roots of the rostral spinal cord, the B1 Müller cell, which has an ipsilateral descending axon, and the Mauthner cell, which has a contralateral descending axon, both had oscillation peaks that were out of phase with the ipsilateral ventral roots. The differences in oscillation timing appear to be due to differences in synaptic input sources as shown by cross-correlations of fast synaptic activity in pairs of Müller cells. Since the main source of the locomotor input under these experimental conditions is ascending neurons in the spinal cord, these experiments suggest that individual reticulospinal neurons can receive locomotor signals from different subsets of these ascending neurons. This result may indicate that the locomotor feedback signals from the spinal locomotor networks are matched in some way to the motor output functions of the individual reticulospinal neurons, which include command signals for turning and for compensatory movements.
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Affiliation(s)
- James T Buchanan
- Dept. of Biological Sciences, 530 N. 15th St., Marquette Univ., Milwaukee, WI 53233, USA.
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Smith J, Morgan JR, Zottoli SJ, Smith PJ, Buxbaum JD, Bloom OE. Regeneration in the era of functional genomics and gene network analysis. THE BIOLOGICAL BULLETIN 2011; 221:18-34. [PMID: 21876108 PMCID: PMC4109899 DOI: 10.1086/bblv221n1p18] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
What gives an organism the ability to regrow tissues and to recover function where another organism fails is the central problem of regenerative biology. The challenge is to describe the mechanisms of regeneration at the molecular level, delivering detailed insights into the many components that are cross-regulated. In other words, a broad, yet deep dissection of the system-wide network of molecular interactions is needed. Functional genomics has been used to elucidate gene regulatory networks (GRNs) in developing tissues, which, like regeneration, are complex systems. Therefore, we reason that the GRN approach, aided by next generation technologies, can also be applied to study the molecular mechanisms underlying the complex functions of regeneration. We ask what characteristics a model system must have to support a GRN analysis. Our discussion focuses on regeneration in the central nervous system, where loss of function has particularly devastating consequences for an organism. We examine a cohort of cells conserved across all vertebrates, the reticulospinal (RS) neurons, which lend themselves well to experimental manipulations. In the lamprey, a jawless vertebrate, there are giant RS neurons whose large size and ability to regenerate make them particularly suited for a GRN analysis. Adding to their value, a distinct subset of lamprey RS neurons reproducibly fail to regenerate, presenting an opportunity for side-by-side comparison of gene networks that promote or inhibit regeneration. Thus, determining the GRN for regeneration in RS neurons will provide a mechanistic understanding of the fundamental cues that lead to success or failure to regenerate.
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Affiliation(s)
- Joel Smith
- The Eugene Bell Center for Regenerative Biology and Tissue Engineering and The Josephine Bay Pau Center for Comparative Molecular Biology and Evolution, The Marine Biological Laboratory, 7 MBL Street, Woods Hole, Massachusetts 02543
- Co-corresponding authors: and obloom@ nshs.edu
| | - Jennifer R. Morgan
- Section of Molecular Cell and Developmental Biology, Institute for Cell and Molecular Biology, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78712
| | - Steven J. Zottoli
- Department of Biology, 59 Lab Campus Drive, Williams College, Williamstown, Massachusetts 01267 and Cellular Dynamics Program, The Marine Biological Laboratory, 7 MBL Street, Woods Hole, Massachusetts 02453
| | - Peter J. Smith
- The Biocurrents Research Center, Cellular Dynamics Program, The Marine Biological Laboratory, 7 MBL Street, Woods Hole, Massachusetts 02543
| | - Joseph D. Buxbaum
- Department of Psychiatry and the Friedman Brain Institute, Mount Sinai School of Medicine, One Gustave L Levy Plc, Box 1668, New York, New York 10029
| | - Ona E. Bloom
- The Center for Autoimmune and Musculoskeletal Disease, The Feinstein Institute for Medical Research, 350 Community Drive, Manhasset, New York 11030
- Co-corresponding authors: and obloom@ nshs.edu
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Buchanan JT. Flexibility in the patterning and control of axial locomotor networks in lamprey. Integr Comp Biol 2011; 51:869-78. [PMID: 21743089 DOI: 10.1093/icb/icr077] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
In lower vertebrates, locomotor burst generators for axial muscles generally produce unitary bursts that alternate between the two sides of the body. In lamprey, a lower vertebrate, locomotor activity in the axial ventral roots of the isolated spinal cord can exhibit flexibility in the timings of bursts to dorsally-located myotomal muscle fibers versus ventrally-located myotomal muscle fibers. These episodes of decreased synchrony can occur spontaneously, especially in the rostral spinal cord where the propagating body waves of swimming originate. Application of serotonin, an endogenous spinal neurotransmitter known to presynaptically inhibit excitatory synapses in lamprey, can promote decreased synchrony of dorsal-ventral bursting. These observations suggest the possible existence of dorsal and ventral locomotor networks with modifiable coupling strength between them. Intracellular recordings of motoneurons during locomotor activity provide some support for this model. Pairs of motoneurons innervating myotomal muscle fibers of similar ipsilateral dorsoventral location tend to have higher correlations of fast synaptic activity during fictive locomotion than do pairs of motoneurons innervating myotomes of different ipsilateral dorsoventral locations, suggesting their control by different populations of premotor interneurons. Further, these different motoneuron pools receive different patterns of excitatory and inhibitory inputs from individual reticulospinal neurons, conveyed in part by different sets of premotor interneurons. Perhaps, then, the locomotor network of the lamprey is not simply a unitary burst generator on each side of the spinal cord that activates all ipsilateral body muscles simultaneously. Instead, the burst generator on each side may comprise at least two coupled burst generators, one controlling motoneurons innervating dorsal body muscles and one controlling motoneurons innervating ventral body muscles. The coupling strength between these two ipsilateral burst generators may be modifiable and weakening when greater swimming maneuverability is required. Variable coupling of intrasegmental burst generators in the lamprey may be a precursor to the variable coupling of burst generators observed in the control of locomotion in the joints of limbed vertebrates.
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Affiliation(s)
- James T Buchanan
- Department of Biological Sciences, Marquette University, 530 N. 15th Street, Milwaukee WI 53233, USA.
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Zottoli SJ, Wong TW, Agostini MA, Meyers JR. Axon cap morphology of the sea robin (Prionotus carolinus): mauthner cell is correlated with the presence of “signature” field potentials and a C-Type startle response. J Comp Neurol 2011; 519:1979-98. [DOI: 10.1002/cne.22617] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Zelenin PV. Reticulospinal neurons controlling forward and backward swimming in the lamprey. J Neurophysiol 2011; 105:1361-71. [DOI: 10.1152/jn.00887.2010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Most vertebrates are capable of two forms of locomotion, forward and backward, strongly differing in the patterns of motor coordination. Basic mechanisms generating these patterns are located in the spinal cord; they are activated and regulated by supraspinal commands. In the lamprey, these commands are transmitted by reticulospinal (RS) neurons. The aim of this study was to reveal groups of RS neurons controlling different aspects of forward (FS) and backward (BS) swimming in the lamprey. Activity of individual larger RS neurons in intact lampreys was recorded during FS and BS by chronically implanted electrodes. It was found that among the neurons activated during locomotion, 27% were active only during FS, 3% only during BS, and 70% during both FS and BS. In a portion of RS neurons, their mean firing frequency was correlated with frequency of body undulations during FS (8%), during BS (34%), or during both FS and BS (22%), suggesting their involvement in control of locomotion intensity. RS activity was phasically modulated by the locomotor rhythm during FS (20% of neurons), during BS (29%), or during both FS and BS (16%). The majority of RS neurons responding to vestibular stimulation (and presumably involved in control of body orientation) were active mainly during FS. This explains the absence of stabilization of the body orientation observed during BS. We discuss possible functions of different groups of RS neurons, i.e., activation of the spinal locomotor CPG, inversion of the direction of propagation of locomotor waves, and postural control.
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Affiliation(s)
- P. V. Zelenin
- Department of Neuroscience, Karolinska Institute, Stockholm, Sweden
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Mullins OJ, Hackett JT, Buchanan JT, Friesen WO. Neuronal control of swimming behavior: comparison of vertebrate and invertebrate model systems. Prog Neurobiol 2011; 93:244-69. [PMID: 21093529 PMCID: PMC3034781 DOI: 10.1016/j.pneurobio.2010.11.001] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Revised: 11/01/2010] [Accepted: 11/08/2010] [Indexed: 01/26/2023]
Abstract
Swimming movements in the leech and lamprey are highly analogous, and lack homology. Thus, similarities in mechanisms must arise from convergent evolution rather than from common ancestry. Despite over 40 years of parallel investigations into this annelid and primitive vertebrate, a close comparison of the approaches and results of this research is lacking. The present review evaluates the neural mechanisms underlying swimming in these two animals and describes the many similarities that provide intriguing examples of convergent evolution. Specifically, we discuss swim initiation, maintenance and termination, isolated nervous system preparations, neural-circuitry, central oscillators, intersegmental coupling, phase lags, cycle periods and sensory feedback. Comparative studies between species highlight mechanisms that optimize behavior and allow us a broader understanding of nervous system function.
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Affiliation(s)
- Olivia J. Mullins
- Dept. of Biology University of Virginia Charlottesville, VA 22904-4328
- Neuroscience Graduate Program University of Virginia Charlottesville, VA 22904-4328
| | - John T. Hackett
- Neuroscience Graduate Program University of Virginia Charlottesville, VA 22904-4328
- Dept. of Molecular Physiology and Biological Physics University of Virginia Charlottesville, VA 22904-4328
| | - James T. Buchanan
- Dept. of Biological Sciences Marquette University Milwaukee, WI 53233
| | - W. Otto Friesen
- Dept. of Biology University of Virginia Charlottesville, VA 22904-4328
- Neuroscience Graduate Program University of Virginia Charlottesville, VA 22904-4328
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Le Ray D, Juvin L, Ryczko D, Dubuc R. Supraspinal control of locomotion. PROGRESS IN BRAIN RESEARCH 2011; 188:51-70. [DOI: 10.1016/b978-0-444-53825-3.00009-7] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Jin LQ, Zhang G, Pennicooke B, Laramore C, Selzer ME. Multiple neurofilament subunits are present in lamprey CNS. Brain Res 2010; 1370:16-33. [PMID: 21081119 DOI: 10.1016/j.brainres.2010.11.037] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2010] [Revised: 10/07/2010] [Accepted: 11/08/2010] [Indexed: 10/18/2022]
Abstract
In mammals, there are three neurofilament (NF) subunits (NF-L, NF-M, and NF-H), but it was thought that only a single NF, NF180, exists in lamprey. However, NF180 lacked the ability to self-assemble, suggesting that like mammalian NFs, lamprey NFs are heteropolymers, and that additional NF subunits may exist. The present study provides evidence for the existence of a lamprey NF-L homolog (L-NFL). Genes encoding two new NF-M isoforms (NF132 and NF95) also have been isolated and characterized. With NF180, this makes three NF-M-like isoforms. In situ hybridization showed that all three newly cloned NFs are expressed in spinal cord neurons and in spinal-projecting neurons of the brainstem. Like NF180, there were no KSP multiphosphorylation repeat motifs in the tail regions of NF132 or NF95. NF95 was highly identical to homologous parts of NF180, sharing 2 common pieces of DNA with it. Northern blots suggested that NF95 may be expressed at very low levels in older larvae. The presence of L-NFL in lamprey CNS may support the hypothesis that as in mammals, NFs in lamprey are obligate heteropolymers, in which NF-L is a required subunit.
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Affiliation(s)
- Li-Qing Jin
- Shriners Hospitals Pediatric Research Center, Temple University School of Medicine, 3500 N. Broad Street, Philadelphia, PA 19140-5104, USA.
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Kaul S, Stach T. Ontogeny of the collar cord: neurulation in the hemichordate Saccoglossus kowalevskii. J Morphol 2010; 271:1240-59. [PMID: 20665533 DOI: 10.1002/jmor.10868] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The chordate body plan is characterized by a central notochord, a pharynx perforated by gill pores, and a dorsal central nervous system. Despite progress in recent years, the evolutionary origin of each of theses characters remains controversial. In the case of the nervous system, two contradictory hypotheses exist. In the first, the chordate nervous system is derived directly from a diffuse nerve net; whereas, the second proposes that a centralized nervous system is found in hemichordates and, therefore, predates chordate evolution. Here, we document the ontogeny of the collar cord of the enteropneust Saccoglossus kowalevskii using transmission electron microscopy and 3D-reconstruction based on completely serially sectioned stages. We demonstrate that the collar cord develops from a middorsal neural plate that is closed in a posterior to anterior direction. Transversely oriented ependymal cells possessing myofilaments mediate this morphogenetic process and surround the remnants of the neural canal in juveniles. A mid-dorsal glandular complex is present in the collar. The collar cord in juveniles is clearly separated into a dorsal saddle-like region of somata and a ventral neuropil. We characterize two cell types in the somata region, giant neurons and ependymal cells. Giant neurons connect via a peculiar cell junction that seems to function in intercellular communication. Synaptic junctions containing different vesicle types are present in the neuropil. These findings support the hypotheses that the collar cord constitutes a centralized element of the nervous system and that the morphogenetic process in the ontogeny of the collar cord is homologous to neurulation in chordates. Moreover, we suggest that these similarities are indicative of a close phylogenetic relationship between enteropneusts and chordates.
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Affiliation(s)
- Sabrina Kaul
- Department of Zoology, Systematics and Evolutionary Research, Faculty of Biology, Chemistry, and Pharmacy, Freie Universität Berlin, Königin-Luise-Strasse 1-3, 14195 Berlin, Germany
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Oliphint PA, Alieva N, Foldes AE, Tytell ED, Lau BYB, Pariseau JS, Cohen AH, Morgan JR. Regenerated synapses in lamprey spinal cord are sparse and small even after functional recovery from injury. J Comp Neurol 2010; 518:2854-72. [PMID: 20506479 DOI: 10.1002/cne.22368] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Despite the potential importance that synapse regeneration plays in restoring neuronal function after spinal cord injury (SCI), even the most basic questions about the morphology of regenerated synapses remain unanswered. Therefore, we set out to gain a better understanding of central synapse regeneration by examining the number, distribution, molecular composition, and ultrastructure of regenerated synapses under conditions in which behavioral recovery from SCI was robust. To do so, we used the giant reticulospinal (RS) neurons of lamprey spinal cord because they readily regenerate, are easily identifiable, and contain large synapses that serve as a classic model for vertebrate excitatory neurotransmission. Using a combination of light and electron microscopy, we found that regenerated giant RS synapses regained the basic structures and presynaptic organization observed at control giant RS synapses at a time when behavioral recovery was nearly complete. However, several obvious differences remained. Most strikingly, regenerated giant RS axons produced very few synapses. In addition, presynaptic sites within regenerated axons were less complex, had fewer vesicles, and had smaller active zones than normal. In contrast, the densities of presynapses and docked vesicles were nearly restored to control values. Thus, robust functional recovery from SCI can occur even when the structures of regenerated synapses are sparse and small, suggesting that functional recovery is due to a more complex set of compensatory changes throughout the spinal network.
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Affiliation(s)
- Paul A Oliphint
- Section of Molecular Cell and Developmental Biology; Institute for Cell and Molecular Biology, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78712, USA
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Shaw AC, Jackson AW, Holmes T, Thurman S, Davis GR, McClellan AD. Descending brain neurons in larval lamprey: spinal projection patterns and initiation of locomotion. Exp Neurol 2010; 224:527-41. [PMID: 20510243 DOI: 10.1016/j.expneurol.2010.05.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Revised: 05/18/2010] [Accepted: 05/20/2010] [Indexed: 01/14/2023]
Abstract
In larval lamprey, partial lesions were made in the rostral spinal cord to determine which spinal tracts are important for descending activation of locomotion and to identify descending brain neurons that project in these tracts. In whole animals and in vitro brain/spinal cord preparations, brain-initiated spinal locomotor activity was present when the lateral or intermediate spinal tracts were spared but usually was abolished when the medial tracts were spared. We previously showed that descending brain neurons are located in eleven cell groups, including reticulospinal (RS) neurons in the mesenecephalic reticular nucleus (MRN) as well as the anterior (ARRN), middle (MRRN), and posterior (PRRN) rhombencephalic reticular nuclei. Other descending brain neurons are located in the diencephalic (Di) as well as the anterolateral (ALV), dorsolateral (DLV), and posterolateral (PLV) vagal groups. In the present study, the Mauthner and auxillary Mauthner cells, most neurons in the Di, ALV, DLV, and PLV cell groups, and some neurons in the ARRN and PRRN had crossed descending axons. The majority of neurons projecting in medial spinal tracts included large identified Müller cells and neurons in the Di, MRN, ALV, and DLV. Axons of individual descending brain neurons usually did not switch spinal tracts, have branches in multiple tracts, or cross the midline within the rostral cord. Most neurons that projected in the lateral/intermediate spinal tracts were in the ARRN, MRRN, and PRRN. Thus, output neurons of the locomotor command system are distributed in several reticular nuclei, whose neurons project in relatively wide areas of the cord.
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Affiliation(s)
- Albert C Shaw
- Division of Biological Sciences, University of Missouri, Columbia, MO 65211-6190, USA
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