1
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Fontenas L. Glial plasticity at nervous system transition zones. Biol Open 2023; 12:bio060037. [PMID: 37787575 PMCID: PMC10562931 DOI: 10.1242/bio.060037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/04/2023] Open
Abstract
The central and peripheral nervous systems (CNS and PNS, respectively) are two separate yet connected domains characterized by molecularly distinct cellular components that communicate via specialized structures called transition zones to allow information to travel from the CNS to the periphery, and vice versa. Until recently, nervous system transition zones were thought to be selectively permeable only to axons, and the establishment of the territories occupied by glial cells at these complex regions remained poorly described and not well understood. Recent work now demonstrates that transition zones are occupied by dynamic glial cells and are precisely regulated over the course of nervous system development. This review highlights recent work on glial cell migration in and out of the spinal cord, at motor exit point (MEP) and dorsal root entry zone (DREZ) transition zones, in the physiological and diseased nervous systems. These cells include myelinating glia (oligodendrocyte lineage cells, Schwann cells and motor exit point glia), exit glia, perineurial cells that form the perineurium along spinal nerves, as well as professional and non-professional phagocytes (microglia and neural crest cells).
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Affiliation(s)
- Laura Fontenas
- Department of Biological Sciences, Florida Atlantic University, Jupiter, FL 33458, USA
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2
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Smith CJ. Evolutionarily conserved concepts in glial cell biology. Curr Opin Neurobiol 2023; 78:102669. [PMID: 36577179 PMCID: PMC9845142 DOI: 10.1016/j.conb.2022.102669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 11/17/2022] [Accepted: 11/28/2022] [Indexed: 12/28/2022]
Abstract
The evolutionary conservation of glial cells has been appreciated since Ramon y Cajal and Del Rio Hortega first described the morphological features of cells in the nervous system. We now appreciate that glial cells have essential roles throughout life in most nervous systems. The field of glial cell biology has grown exponentially in the last ten years. This new wealth of knowledge has been aided by seminal findings in non-mammalian model systems. Ultimately, such concepts help us to understand glia in mammalian nervous systems. Rather than summarizing the field of glial biology, I will first briefly introduce glia in non-mammalian models systems. Then, highlight seminal findings across the glial field that utilized non-mammalian model systems to advance our understanding of the mammalian nervous system. Finally, I will call attention to some recent findings that introduce new questions about glial cell biology that will be investigated for years to come.
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Affiliation(s)
- Cody J Smith
- Department of Biological Sciences, IN, USA; The Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN, USA.
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3
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Arena KA, Zhu Y, Kucenas S. Transforming growth factor-beta signaling modulates perineurial glial bridging following peripheral spinal motor nerve injury in zebrafish. Glia 2022; 70:1826-1849. [PMID: 35616185 PMCID: PMC9378448 DOI: 10.1002/glia.24220] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Revised: 05/06/2022] [Accepted: 05/11/2022] [Indexed: 11/12/2022]
Abstract
Spinal motor nerves are necessary for organismal locomotion and survival. In zebrafish and most vertebrates, these peripheral nervous system structures are composed of bundles of axons that naturally regenerate following injury. However, the cellular and molecular mechanisms that mediate this process are still only partially understood. Perineurial glia, which form a component of the blood-nerve barrier, are necessary for the earliest regenerative steps by establishing a glial bridge across the injury site as well as phagocytosing debris. Without perineurial glial bridging, regeneration is impaired. In addition to perineurial glia, Schwann cells, the cells that ensheath and myelinate axons within the nerve, are essential for debris clearance and axon guidance. In the absence of Schwann cells, perineurial glia exhibit perturbed bridging, demonstrating that these two cell types communicate during the injury response. While the presence and importance of perineurial glial bridging is known, the molecular mechanisms that underlie this process remain a mystery. Understanding the cellular and molecular interactions that drive perineurial glial bridging is crucial to unlocking the mechanisms underlying successful motor nerve regeneration. Using laser axotomy and in vivo imaging in zebrafish, we show that transforming growth factor-beta (TGFβ) signaling modulates perineurial glial bridging. Further, we identify connective tissue growth factor-a (ctgfa) as a downstream effector of TGF-β signaling that works in a positive feedback loop to mediate perineurial glial bridging. Together, these studies present a new signaling pathway involved in the perineurial glial injury response and further characterize the dynamics of the perineurial glial bridge.
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Affiliation(s)
- Kimberly A. Arena
- Department of BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
- Program in Fundamental NeuroscienceUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - Yunlu Zhu
- Department of BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - Sarah Kucenas
- Department of BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
- Program in Fundamental NeuroscienceUniversity of VirginiaCharlottesvilleVirginiaUSA
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4
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Limbach LE, Penick RL, Casseday RS, Hyland MA, Pontillo EA, Ayele AN, Pitts KM, Ackerman SD, Harty BL, Herbert AL, Monk KR, Petersen SC. Peripheral nerve development in zebrafish requires muscle patterning by tcf15/paraxis. Dev Biol 2022; 490:37-49. [PMID: 35820658 DOI: 10.1016/j.ydbio.2022.07.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 06/29/2022] [Accepted: 07/01/2022] [Indexed: 11/03/2022]
Abstract
The vertebrate peripheral nervous system (PNS) is an intricate network that conveys sensory and motor information throughout the body. During development, extracellular cues direct the migration of axons and glia through peripheral tissues. Currently, the suite of molecules that govern PNS axon-glial patterning is incompletely understood. To elucidate factors that are critical for peripheral nerve development, we characterized the novel zebrafish mutant, stl159, that exhibits abnormalities in PNS patterning. In these mutants, motor and sensory nerves that develop adjacent to axial muscle fail to extend normally, and neuromasts in the posterior lateral line system, as well as neural crest-derived melanocytes, are incorrectly positioned. The stl159 genetic lesion lies in the basic helix-loop-helix (bHLH) transcription factor tcf15, which has been previously implicated in proper development of axial muscles. We find that targeted loss of tcf15 via CRISPR-Cas9 genome editing results in the PNS patterning abnormalities observed in stl159 mutants. Because tcf15 is expressed in developing muscle prior to nerve extension, rather than in neurons or glia, we predict that tcf15 non-cell-autonomously promotes peripheral nerve patterning in zebrafish through regulation of extracellular patterning cues. Our work underscores the importance of muscle-derived factors in PNS development.
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Affiliation(s)
| | - Rocky L Penick
- Department of Neuroscience, Kenyon College, Gambier, OH, USA
| | - Rudy S Casseday
- Department of Neuroscience, Kenyon College, Gambier, OH, USA
| | | | | | - Afomia N Ayele
- Department of Neuroscience, Kenyon College, Gambier, OH, USA
| | | | - Sarah D Ackerman
- Department of Developmental Biology, Washington University in St. Louis, MO, USA
| | - Breanne L Harty
- Department of Developmental Biology, Washington University in St. Louis, MO, USA
| | - Amy L Herbert
- Department of Developmental Biology, Washington University in St. Louis, MO, USA
| | - Kelly R Monk
- Department of Developmental Biology, Washington University in St. Louis, MO, USA
| | - Sarah C Petersen
- Department of Neuroscience, Kenyon College, Gambier, OH, USA; Department of Biology, Kenyon College, Gambier, OH, USA; Department of Developmental Biology, Washington University in St. Louis, MO, USA.
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5
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Abstract
Schwann cells in the peripheral nervous system (PNS) are essential for the support and myelination of axons, ensuring fast and accurate communication between the central nervous system and the periphery. Schwann cells and related glia accompany innervating axons in virtually all tissues in the body, where they exhibit remarkable plasticity and the ability to modulate pathology in extraordinary, and sometimes surprising, ways. Here, we provide a brief overview of the various glial cell types in the PNS and describe the cornerstone cellular and molecular processes that enable Schwann cells to perform their canonical functions. We then dive into discussing exciting noncanonical functions of Schwann cells and related PNS glia, which include their role in organizing the PNS, in regulating synaptic activity and pain, in modulating immunity, in providing a pool of stem cells for different organs, and, finally, in influencing cancer.
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Affiliation(s)
- Carla Taveggia
- Axo-Glial Interaction Unit, Division of Neuroscience, IRCCS Ospedale San Raffaele, Milan, Italy;
| | - M. Laura Feltri
- Institute for Myelin and Glia Exploration, Departments of Biochemistry and Neurology, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, New York, USA
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6
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Green LA, O'Dea MR, Hoover CA, DeSantis DF, Smith CJ. The embryonic zebrafish brain is seeded by a lymphatic-dependent population of mrc1 + microglia precursors. Nat Neurosci 2022; 25:849-864. [PMID: 35710983 PMCID: PMC10680068 DOI: 10.1038/s41593-022-01091-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 05/06/2022] [Indexed: 02/02/2023]
Abstract
Microglia are the resident macrophages of the CNS that serve critical roles in brain construction. Although human brains contain microglia by 4 weeks gestation, an understanding of the earliest microglia that seed the brain during its development remains unresolved. Using time-lapse imaging in zebrafish, we discovered a mrc1a+ microglia precursor population that seeds the brain before traditionally described microglia. These early microglia precursors are dependent on lymphatic vasculature that surrounds the brain and are independent of pu1+ yolk sac-derived microglia. Single-cell RNA-sequencing datasets reveal Mrc1+ microglia in the embryonic brains of mice and humans. We then show in zebrafish that these early mrc1a+ microglia precursors preferentially expand during pathophysiological states in development. Taken together, our results identify a critical role of lymphatics in the microglia precursors that seed the early embryonic brain.
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Affiliation(s)
- Lauren A Green
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
- The Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN, USA
| | - Michael R O'Dea
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - Camden A Hoover
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
- The Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN, USA
| | - Dana F DeSantis
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
- The Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN, USA
| | - Cody J Smith
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA.
- The Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN, USA.
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7
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Wiltbank AT, Steinson ER, Criswell SJ, Piller M, Kucenas S. Cd59 and inflammation regulate Schwann cell development. eLife 2022; 11:e76640. [PMID: 35748863 PMCID: PMC9232220 DOI: 10.7554/elife.76640] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 06/01/2022] [Indexed: 11/13/2022] Open
Abstract
Efficient neurotransmission is essential for organism survival and is enhanced by myelination. However, the genes that regulate myelin and myelinating glial cell development have not been fully characterized. Data from our lab and others demonstrates that cd59, which encodes for a small GPI-anchored glycoprotein, is highly expressed in developing zebrafish, rodent, and human oligodendrocytes (OLs) and Schwann cells (SCs), and that patients with CD59 dysfunction develop neurological dysfunction during early childhood. Yet, the function of Cd59 in the developing nervous system is currently undefined. In this study, we demonstrate that cd59 is expressed in a subset of developing SCs. Using cd59 mutant zebrafish, we show that developing SCs proliferate excessively and nerves may have reduced myelin volume, altered myelin ultrastructure, and perturbed node of Ranvier assembly. Finally, we demonstrate that complement activity is elevated in cd59 mutants and that inhibiting inflammation restores SC proliferation, myelin volume, and nodes of Ranvier to wildtype levels. Together, this work identifies Cd59 and developmental inflammation as key players in myelinating glial cell development, highlighting the collaboration between glia and the innate immune system to ensure normal neural development.
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Affiliation(s)
- Ashtyn T Wiltbank
- Neuroscience Graduate Program, University of VirginiaCharlottesvilleUnited States
- Program in Fundamental Neuroscience, University of VirginiaCharlottesvilleUnited States
| | - Emma R Steinson
- Department of Biology, University of VirginiaCharlottesvilleUnited States
| | - Stacey J Criswell
- Department of Cell Biology, University of VirginiaCharlottesvilleUnited States
| | - Melanie Piller
- Department of Biology, University of VirginiaCharlottesvilleUnited States
| | - Sarah Kucenas
- Neuroscience Graduate Program, University of VirginiaCharlottesvilleUnited States
- Program in Fundamental Neuroscience, University of VirginiaCharlottesvilleUnited States
- Department of Biology, University of VirginiaCharlottesvilleUnited States
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8
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Green LA, Gallant RM, Brandt JP, Nichols EL, Smith CJ. A Subset of Oligodendrocyte Lineage Cells Interact With the Developing Dorsal Root Entry Zone During Its Genesis. Front Cell Neurosci 2022; 16:893629. [PMID: 35734217 PMCID: PMC9207214 DOI: 10.3389/fncel.2022.893629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 05/11/2022] [Indexed: 11/29/2022] Open
Abstract
Oligodendrocytes are the myelinating cell of the CNS and are critical for the functionality of the nervous system. In the packed CNS, we know distinct profiles of oligodendrocytes are present. Here, we used intravital imaging in zebrafish to identify a distinct oligodendrocyte lineage cell (OLC) that resides on the dorsal root ganglia sensory neurons in the spinal cord. Our profiling of OLC cellular dynamics revealed a distinct cell cluster that interacts with peripheral sensory neurons at the dorsal root entry zone (DREZ). With pharmacological, physical and genetic manipulations, we show that the entry of dorsal root ganglia pioneer axons across the DREZ is important to produce sensory located oligodendrocyte lineage cells. These oligodendrocyte lineage cells on peripherally derived sensory neurons display distinct processes that are stable and do not express mbpa. Upon their removal, sensory behavior related to the DRG neurons is abolished. Together, these data support the hypothesis that peripheral neurons at the DREZ can also impact oligodendrocyte development.
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Affiliation(s)
- Lauren A. Green
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States
- Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN, United States
| | - Robert M. Gallant
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States
| | - Jacob P. Brandt
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States
| | - Ev L. Nichols
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States
| | - Cody J. Smith
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States
- Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN, United States
- *Correspondence: Cody J. Smith,
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9
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Fu H, Hu D, Chen J, Wang Q, Zhang Y, Qi C, Yu T. Repair of the Injured Spinal Cord by Schwann Cell Transplantation. Front Neurosci 2022; 16:800513. [PMID: 35250447 PMCID: PMC8891437 DOI: 10.3389/fnins.2022.800513] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Accepted: 01/27/2022] [Indexed: 01/12/2023] Open
Abstract
Spinal cord injury (SCI) can result in sensorimotor impairments or disability. Studies of the cellular response to SCI have increased our understanding of nerve regenerative failure following spinal cord trauma. Biological, engineering and rehabilitation strategies for repairing the injured spinal cord have shown impressive results in SCI models of both rodents and non-human primates. Cell transplantation, in particular, is becoming a highly promising approach due to the cells’ capacity to provide multiple benefits at the molecular, cellular, and circuit levels. While various cell types have been investigated, we focus on the use of Schwann cells (SCs) to promote SCI repair in this review. Transplantation of SCs promotes functional recovery in animal models and is safe for use in humans with subacute SCI. The rationales for the therapeutic use of SCs for SCI include enhancement of axon regeneration, remyelination of newborn or sparing axons, regulation of the inflammatory response, and maintenance of the survival of damaged tissue. However, little is known about the molecular mechanisms by which transplanted SCs exert a reparative effect on SCI. Moreover, SC-based therapeutic strategies face considerable challenges in preclinical studies. These issues must be clarified to make SC transplantation a feasible clinical option. In this review, we summarize the recent advances in SC transplantation for SCI, and highlight proposed mechanisms and challenges of SC-mediated therapy. The sparse information available on SC clinical application in patients with SCI is also discussed.
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Affiliation(s)
- Haitao Fu
- Department of Sports Medicine, The Affiliated Hospital of Qingdao University, Qingdao University, Qingdao, China
| | - Die Hu
- State Key Laboratory Cultivation Base, Shandong Provincial Key Laboratory of Ophthalmology, Qingdao Eye Hospital, Shandong Eye Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Qingdao, China
| | - Jinli Chen
- Department of Sports Medicine, The Affiliated Hospital of Qingdao University, Qingdao University, Qingdao, China
| | - Qizun Wang
- Department of Orthopedics, The Affiliated Hospital of Qingdao University, Qingdao, China
| | - Yingze Zhang
- Key Laboratory of Biomechanics of Hebei Province, Department of Trauma Emergency Center, The Third Hospital of Hebei Medical University, Orthopaedics Research Institution of Hebei Province, Shijiazhuang, China
| | - Chao Qi
- Department of Sports Medicine, The Affiliated Hospital of Qingdao University, Qingdao University, Qingdao, China
- *Correspondence: Chao Qi,
| | - Tengbo Yu
- Department of Sports Medicine, The Affiliated Hospital of Qingdao University, Qingdao University, Qingdao, China
- Tengbo Yu,
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10
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Brown RI, Kawakami K, Kucenas S. A novel gene trap line for visualization and manipulation of erbb3b + neural crest and glial cells in zebrafish. Dev Biol 2022; 482:114-123. [PMID: 34932993 DOI: 10.1016/j.ydbio.2021.12.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 12/08/2021] [Accepted: 12/16/2021] [Indexed: 12/22/2022]
Abstract
Glia are a diverse and essential cell type in the vertebrate nervous system. Transgenic tools and fluorescent reporter lines are critical resources to investigate how glial subtypes develop and function. However, despite the many lines available in zebrafish, the community still lacks the ability to label all unique stages of glial development and specific subpopulations of cells. To address this issue, we screened zebrafish gene and enhancer trap lines to find a novel reporter for peripheral glial subtypes. From these, we generated the gSAIzGFFD37A transgenic line that expresses GFP in neural crest cells and central and peripheral glia. We found that the gene trap construct is located within an intron of erbb3b, a gene essential for glial development. Additionally, we confirmed that GFP+ cells express erbb3b along with sox10, a known glial marker. From our screen, we have identified the gSAIzGFFD37A line as a novel and powerful tool for studying glia in the developing zebrafish, as well as a new resource to manipulate erbb3b+ cells.
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Affiliation(s)
- Robin Isadora Brown
- Department of Biology, University of Virginia, Charlottesville, VA, 22904, USA; Program in Fundamental Neuroscience, University of Virginia, Charlottesville, VA, 22904, USA
| | - Koichi Kawakami
- Laboratory of Molecular and Developmental Biology, National Institute of Genetics, and Department of Genetics, SOKENDAI The Graduate University for Advanced Studies, Mishima, Shizuoka, 444-8540, Japan
| | - Sarah Kucenas
- Department of Biology, University of Virginia, Charlottesville, VA, 22904, USA; Program in Fundamental Neuroscience, University of Virginia, Charlottesville, VA, 22904, USA.
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11
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Petersen SC. Open-Ended Inquiry into Zebrafish Nerve Development Using Image Analysis. JOURNAL OF UNDERGRADUATE NEUROSCIENCE EDUCATION : JUNE : A PUBLICATION OF FUN, FACULTY FOR UNDERGRADUATE NEUROSCIENCE 2021; 20:A73-A82. [PMID: 35540941 PMCID: PMC9053433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 09/07/2021] [Accepted: 09/20/2021] [Indexed: 06/14/2023]
Abstract
Open-ended laboratory projects increase student success and retention in the sciences. However, developing organismal-based research projects is a challenge for students with restricted laboratory access, such as those attending courses remotely. Here I describe the use of image analysis of zebrafish neural development for authentic research projects in an introductory biology laboratory course. Zebrafish are a vertebrate model that produce large numbers of externally and rapidly developing embryos. Because zebrafish larvae are transparent, fluorescent reporters marking nervous system structures can be imaged over time and analyzed by undergraduate scientists. In the pilot of this project, remote first-year college students independently developed biological questions based on an image collection comparing zebrafish mutants and wild-type siblings. Students created and mastered techniques to analyze position, organization, and other morphological features of developing neurons and glia in the images to directly test their biological questions. At the end of the course, students communicated their project results in journal article format and oral presentations. Students were able to hone skills in organismal observation and data collection while studying remotely, and they reported excitement at applying lecture-based knowledge to their own independent questions. This module can be adapted by other instructors for both students on- and off-campus to teach principles of neural development, data collection, data analysis, and scientific communication.
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Affiliation(s)
- Sarah C Petersen
- Department of Neuroscience and Department of Biology, Kenyon College, Gambier, OH 43022
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12
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Hines JH. Evolutionary Origins of the Oligodendrocyte Cell Type and Adaptive Myelination. Front Neurosci 2021; 15:757360. [PMID: 34924932 PMCID: PMC8672417 DOI: 10.3389/fnins.2021.757360] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Accepted: 10/29/2021] [Indexed: 12/23/2022] Open
Abstract
Oligodendrocytes are multifunctional central nervous system (CNS) glia that are essential for neural function in gnathostomes. The evolutionary origins and specializations of the oligodendrocyte cell type are among the many remaining mysteries in glial biology and neuroscience. The role of oligodendrocytes as CNS myelinating glia is well established, but recent studies demonstrate that oligodendrocytes also participate in several myelin-independent aspects of CNS development, function, and maintenance. Furthermore, many recent studies have collectively advanced our understanding of myelin plasticity, and it is now clear that experience-dependent adaptations to myelination are an additional form of neural plasticity. These observations beg the questions of when and for which functions the ancestral oligodendrocyte cell type emerged, when primitive oligodendrocytes evolved new functionalities, and the genetic changes responsible for these evolutionary innovations. Here, I review recent findings and propose working models addressing the origins and evolution of the oligodendrocyte cell type and adaptive myelination. The core gene regulatory network (GRN) specifying the oligodendrocyte cell type is also reviewed as a means to probe the existence of oligodendrocytes in basal vertebrates and chordate invertebrates.
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Affiliation(s)
- Jacob H. Hines
- Biology Department, Winona State University, Winona, MN, United States
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13
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Scott K, O'Rourke R, Winkler CC, Kearns CA, Appel B. Temporal single-cell transcriptomes of zebrafish spinal cord pMN progenitors reveal distinct neuronal and glial progenitor populations. Dev Biol 2021; 479:37-50. [PMID: 34303700 PMCID: PMC8410680 DOI: 10.1016/j.ydbio.2021.07.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 07/19/2021] [Accepted: 07/21/2021] [Indexed: 11/20/2022]
Abstract
Ventral spinal cord progenitor cells, which express the basic helix loop helix transcription factor Olig2, sequentially produce motor neurons and oligodendrocyte precursor cells (OPCs). Following specification some OPCs differentiate as myelinating oligodendrocytes while others persist as OPCs. Though a considerable amount of work has described the molecular profiles that define motor neurons, OPCs, and oligodendrocytes, less is known about the progenitors that produce them. To identify the developmental origins and transcriptional profiles of motor neurons and OPCs, we performed single-cell RNA sequencing on isolated pMN cells from embryonic zebrafish trunk tissue at stages that encompassed motor neurogenesis, OPC specification, and initiation of oligodendrocyte differentiation. Downstream analyses revealed two distinct pMN progenitor populations: one that appears to produce neurons and one that appears to produce OPCs. This latter population, called Pre-OPCs, is marked by expression of GS Homeobox 2 (gsx2), a gene that encodes a homeobox transcription factor. Using fluorescent in situ hybridizations, we identified gsx2-expressing Pre-OPCs in the spinal cord prior to expression of canonical OPC marker genes. Our data therefore reveal heterogeneous gene expression profiles among pMN progenitors, supporting prior fate mapping evidence.
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Affiliation(s)
- Kayt Scott
- Department of Pediatrics, Section of Developmental Biology, Colorado, 80045, USA; Cell Biology, Stem Cells and Development Training Program, Colorado, 80045, USA
| | - Rebecca O'Rourke
- Department of Pediatrics, Section of Developmental Biology, Colorado, 80045, USA
| | - Caitlin C Winkler
- Department of Pediatrics, Section of Developmental Biology, Colorado, 80045, USA; RNA Bioscience Initiative and Department of Biochemistry and Molecular Genetics, Colorado, 80045, USA
| | - Christina A Kearns
- Department of Pediatrics, Section of Developmental Biology, Colorado, 80045, USA
| | - Bruce Appel
- Department of Pediatrics, Section of Developmental Biology, Colorado, 80045, USA; Children's Hospital Colorado, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA.
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14
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DeSantis DF, Smith CJ. Tetris in the Nervous System: What Principles of Neuronal Tiling Can Tell Us About How Glia Play the Game. Front Cell Neurosci 2021; 15:734938. [PMID: 34512272 PMCID: PMC8430210 DOI: 10.3389/fncel.2021.734938] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 08/09/2021] [Indexed: 11/14/2022] Open
Abstract
The precise organization and arrangement of neural cells is essential for nervous system functionality. Cellular tiling is an evolutionarily conserved phenomenon that organizes neural cells, ensuring non-redundant coverage of receptive fields in the nervous system. First recorded in the drawings of Ramon y Cajal more than a century ago, we now have extensive knowledge of the biochemical and molecular mechanisms that mediate tiling of neurons. The advent of live imaging techniques in both invertebrate and vertebrate model organisms has enhanced our understanding of these processes. Despite advancements in our understanding of neuronal tiling, we know relatively little about how glia, an essential non-neuronal component of the nervous system, tile and contribute to the overall spatial arrangement of the nervous system. Here, we discuss lessons learned from neurons and apply them to potential mechanisms that glial cells may use to tile, including cell diversity, contact-dependent repulsion, and chemical signaling. We also discuss open questions in the field of tiling and what new technologies need to be developed in order to better understand glial tiling.
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Affiliation(s)
- Dana F DeSantis
- Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN, United States.,Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States
| | - Cody J Smith
- Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN, United States.,Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States
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15
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Solovieva T, Bronner M. Reprint of: Schwann cell precursors: Where they come from and where they go. Cells Dev 2021; 168:203729. [PMID: 34456178 DOI: 10.1016/j.cdev.2021.203729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Revised: 04/29/2021] [Accepted: 04/30/2021] [Indexed: 10/20/2022]
Abstract
Schwann cell precursors (SCPs) are a transient population in the embryo, closely associated with nerves along which they migrate into the periphery of the body. Long considered to be progenitors that only form Schwann cells-the myelinating cells of nerves, current evidence suggests that SCPs have much broader developmental potential. Indeed, different cell marking techniques employed over the past 20 years have identified multiple novel SCP derivatives throughout the body. It is now clear that SCPs represent a multipotent progenitor population, which also display a level of plasticity in response to injury. Moreover, they originate from multiple origins in the embryo and may reflect several distinct subpopulations in terms of molecular identity and fate. Here we review SCP origins, derivatives and plasticity in development, growth and repair.
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Affiliation(s)
- Tatiana Solovieva
- Division of Biology and Biological Engineering, California Institute of Technology, United States of America.
| | - Marianne Bronner
- Division of Biology and Biological Engineering, California Institute of Technology, United States of America
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16
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Piller M, Werkman IL, Brown RI, Latimer AJ, Kucenas S. Glutamate Signaling via the AMPAR Subunit GluR4 Regulates Oligodendrocyte Progenitor Cell Migration in the Developing Spinal Cord. J Neurosci 2021; 41:5353-5371. [PMID: 33975920 PMCID: PMC8221590 DOI: 10.1523/jneurosci.2562-20.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 04/28/2021] [Accepted: 05/03/2021] [Indexed: 11/21/2022] Open
Abstract
Oligodendrocyte progenitor cells (OPCs) are specified from discrete precursor populations during gliogenesis and migrate extensively from their origins, ultimately distributing throughout the brain and spinal cord during early development. Subsequently, a subset of OPCs differentiates into mature oligodendrocytes, which myelinate axons. This process is necessary for efficient neuronal signaling and organism survival. Previous studies have identified several factors that influence OPC development, including excitatory glutamatergic synapses that form between neurons and OPCs during myelination. However, little is known about how glutamate signaling affects OPC migration before myelination. In this study, we use in vivo, time-lapse imaging in zebrafish in conjunction with genetic and pharmacological perturbation to investigate OPC migration and myelination when the GluR4A ionotropic glutamate receptor subunit is disrupted. In our studies, we observed that gria4a mutant embryos and larvae displayed abnormal OPC migration and altered dorsoventral distribution in the spinal cord. Genetic mosaic analysis confirmed that these effects were cell-autonomous, and we identified that voltage-gated calcium channels were downstream of glutamate receptor signaling in OPCs and could rescue the migration and myelination defects we observed when glutamate signaling was perturbed. These results offer new insights into the complex system of neuron-OPC interactions and reveal a cell-autonomous role for glutamatergic signaling in OPCs during neural development.SIGNIFICANCE STATEMENT The migration of oligodendrocyte progenitor cells (OPCs) is an essential process during development that leads to uniform oligodendrocyte distribution and sufficient myelination for central nervous system function. Here, we demonstrate that the AMPA receptor (AMPAR) subunit GluR4A is an important driver of OPC migration and myelination in vivo and that activated voltage-gated calcium channels are downstream of glutamate receptor signaling in mediating this migration.
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Affiliation(s)
- Melanie Piller
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904
| | - Inge L Werkman
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904
| | - Robin Isadora Brown
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904
| | - Andrew J Latimer
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904
| | - Sarah Kucenas
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904
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17
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Pioneer Axons Utilize a Dcc Signaling-Mediated Invasion Brake to Precisely Complete Their Pathfinding Odyssey. J Neurosci 2021; 41:6617-6636. [PMID: 34131031 DOI: 10.1523/jneurosci.0212-21.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 06/01/2021] [Accepted: 06/08/2021] [Indexed: 11/21/2022] Open
Abstract
Axons navigate through the embryo to construct a functional nervous system. A missing part of the axon navigation puzzle is how a single axon traverses distinct anatomic choice points through its navigation. The dorsal root ganglia (DRG) neurons experience such choice points. First, they navigate to the dorsal root entry zone (DREZ), then halt navigation in the peripheral nervous system to invade the spinal cord, and then reinitiate navigation inside the CNS. Here, we used time-lapse super-resolution imaging in zebrafish DRG pioneer neurons to investigate how embryonic axons control their cytoskeleton to navigate to and invade at the correct anatomic position. We found that invadopodia components form in the growth cone even during filopodia-based navigation, but only stabilize when the axon is at the spinal cord entry location. Further, we show that intermediate levels of DCC and cAMP, as well as Rac1 activation, subsequently engage an axon invasion brake. Our results indicate that actin-based invadopodia components form in the growth cone and disruption of the invasion brake causes axon entry defects and results in failed behavioral responses, thereby demonstrating the importance of regulating distinct actin populations during navigational challenges.SIGNIFICANCE STATEMENT Correct spatiotemporal navigation of neuronal growth cones is dependent on extracellular navigational cues and growth cone dynamics. Here, we link dcc-mediated signaling to actin-based invadopodia and filopodia dynamics during pathfinding and entry into the spinal cord using an in vivo model of dorsal root ganglia (DRG) sensory axons. We reveal a molecularly-controlled brake on invadopodia stabilization until the sensory neuron growth cone is present at the dorsal root entry zone (DREZ), which is ultimately essential for growth cone entry into the spinal cord and behavioral response.
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18
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Solovieva T, Bronner M. Schwann cell precursors: Where they come from and where they go. Cells Dev 2021; 166:203686. [PMID: 33994354 DOI: 10.1016/j.cdev.2021.203686] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Revised: 04/29/2021] [Accepted: 04/30/2021] [Indexed: 11/30/2022]
Abstract
Schwann cell precursors (SCPs) are a transient population in the embryo, closely associated with nerves along which they migrate into the periphery of the body. Long considered to be progenitors that only form Schwann cells-the myelinating cells of nerves, current evidence suggests that SCPs have much broader developmental potential. Indeed, different cell marking techniques employed over the past 20 years have identified multiple novel SCP derivatives throughout the body. It is now clear that SCPs represent a multipotent progenitor population, which also display a level of plasticity in response to injury. Moreover, they originate from multiple origins in the embryo and may reflect several distinct subpopulations in terms of molecular identity and fate. Here we review SCP origins, derivatives and plasticity in development, growth and repair.
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Affiliation(s)
- Tatiana Solovieva
- Division of Biology and Biological Engineering, California Institute of Technology, United States of America.
| | - Marianne Bronner
- Division of Biology and Biological Engineering, California Institute of Technology, United States of America
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19
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Zebrafish Neural Crest: Lessons and Tools to Study In Vivo Cell Migration. Methods Mol Biol 2021. [PMID: 32939715 DOI: 10.1007/978-1-0716-0779-4_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
The study of cell migration has been greatly enhanced by the development of new model systems and analysis protocols to study this process in vivo. Zebrafish embryos have been a principal protagonist because they are easily accessible, genetically tractable, and optically transparent. Neural crest cells, on the other hand, are the ideal system to study cell migration. These cells migrate extensively, using different modalities of movement and sharing many traits with metastatic cancer cells. In this chapter, we present new tools and protocols that allow the study of NC development and migration in vivo.
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20
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Fontenas L, Kucenas S. Spinal cord precursors utilize neural crest cell mechanisms to generate hybrid peripheral myelinating glia. eLife 2021; 10:64267. [PMID: 33554855 PMCID: PMC7886336 DOI: 10.7554/elife.64267] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Accepted: 02/05/2021] [Indexed: 12/11/2022] Open
Abstract
During development, oligodendrocytes and Schwann cells myelinate central and peripheral nervous system axons, respectively, while motor exit point (MEP) glia are neural tube-derived, peripheral glia that myelinate axonal territory between these populations at MEP transition zones. From which specific neural tube precursors MEP glia are specified, and how they exit the neural tube to migrate onto peripheral motor axons, remain largely unknown. Here, using zebrafish, we found that MEP glia arise from lateral floor plate precursors and require foxd3 to delaminate and exit the spinal cord. Additionally, we show that similar to Schwann cells, MEP glial development depends on axonally derived neuregulin1. Finally, our data demonstrate that overexpressing axonal cues is sufficient to generate additional MEP glia in the spinal cord. Overall, these studies provide new insight into how a novel population of hybrid, peripheral myelinating glia are generated from neural tube precursors and migrate into the periphery.
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Affiliation(s)
- Laura Fontenas
- Department of Biology, University of Virginia, Charlottesville, United States
| | - Sarah Kucenas
- Department of Biology, University of Virginia, Charlottesville, United States
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21
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Feltri ML, Weaver MR, Belin S, Poitelon Y. The Hippo pathway: Horizons for innovative treatments of peripheral nerve diseases. J Peripher Nerv Syst 2021; 26:4-16. [PMID: 33449435 DOI: 10.1111/jns.12431] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 12/16/2020] [Accepted: 12/20/2020] [Indexed: 12/19/2022]
Abstract
Initially identified in Drosophila, the Hippo signaling pathway regulates how cells respond to their environment by controlling proliferation, migration and differentiation. Many recent studies have focused on characterizing Hippo pathway function and regulation in mammalian cells. Here, we present a brief overview of the major components of the Hippo pathway, as well as their regulation and function. We comprehensively review the studies that have contributed to our understanding of the Hippo pathway in the function of the peripheral nervous system and in peripheral nerve diseases. Finally, we discuss innovative approaches that aim to modulate Hippo pathway components in diseases of the peripheral nervous system.
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Affiliation(s)
- M Laura Feltri
- Hunter James Kelly Research Institute, Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York, USA.,Department of Neurology, Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York, USA
| | - Michael R Weaver
- Hunter James Kelly Research Institute, Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York, USA
| | - Sophie Belin
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, USA
| | - Yannick Poitelon
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, USA
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22
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Lago-Baldaia I, Fernandes VM, Ackerman SD. More Than Mortar: Glia as Architects of Nervous System Development and Disease. Front Cell Dev Biol 2020; 8:611269. [PMID: 33381506 PMCID: PMC7767919 DOI: 10.3389/fcell.2020.611269] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 11/17/2020] [Indexed: 12/12/2022] Open
Abstract
Glial cells are an essential component of the nervous system of vertebrates and invertebrates. In the human brain, glia are as numerous as neurons, yet the importance of glia to nearly every aspect of nervous system development has only been expounded over the last several decades. Glia are now known to regulate neural specification, synaptogenesis, synapse function, and even broad circuit function. Given their ubiquity, it is not surprising that the contribution of glia to neuronal disease pathogenesis is a growing area of research. In this review, we will summarize the accumulated evidence of glial participation in several distinct phases of nervous system development and organization-neural specification, circuit wiring, and circuit function. Finally, we will highlight how these early developmental roles of glia contribute to nervous system dysfunction in neurodevelopmental and neurodegenerative disorders.
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Affiliation(s)
- Inês Lago-Baldaia
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Vilaiwan M. Fernandes
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Sarah D. Ackerman
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR, United States
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23
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Muppirala AN, Limbach LE, Bradford EF, Petersen SC. Schwann cell development: From neural crest to myelin sheath. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2020; 10:e398. [PMID: 33145925 DOI: 10.1002/wdev.398] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 10/06/2020] [Accepted: 10/07/2020] [Indexed: 12/16/2022]
Abstract
Vertebrate nervous system function requires glial cells, including myelinating glia that insulate axons and provide trophic support that allows for efficient signal propagation by neurons. In vertebrate peripheral nervous systems, neural crest-derived glial cells known as Schwann cells (SCs) generate myelin by encompassing and iteratively wrapping membrane around single axon segments. SC gliogenesis and neurogenesis are intimately linked and governed by a complex molecular environment that shapes their developmental trajectory. Changes in this external milieu drive developing SCs through a series of distinct morphological and transcriptional stages from the neural crest to a variety of glial derivatives, including the myelinating sublineage. Cues originate from the extracellular matrix, adjacent axons, and the developing SC basal lamina to trigger intracellular signaling cascades and gene expression changes that specify stages and transitions in SC development. Here, we integrate the findings from in vitro neuron-glia co-culture experiments with in vivo studies investigating SC development, particularly in zebrafish and mouse, to highlight critical factors that specify SC fate. Ultimately, we connect classic biochemical and mutant studies with modern genetic and visualization tools that have elucidated the dynamics of SC development. This article is categorized under: Signaling Pathways > Cell Fate Signaling Nervous System Development > Vertebrates: Regional Development.
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Affiliation(s)
- Anoohya N Muppirala
- Program in Neuroscience, Harvard Medical School, Boston, Massachusetts, USA.,Department of Neuroscience, Kenyon College, Gambier, Ohio, USA
| | | | | | - Sarah C Petersen
- Department of Neuroscience, Kenyon College, Gambier, Ohio, USA.,Department of Biology, Kenyon College, Gambier, Ohio, USA
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24
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Lee DW, Kim E, Jeong I, Kim HK, Kim S, Park HC. Schwann cells selectively myelinate primary motor axons via neuregulin-ErbB signaling. Glia 2020; 68:2585-2600. [PMID: 32589818 DOI: 10.1002/glia.23871] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2019] [Revised: 05/20/2020] [Accepted: 05/26/2020] [Indexed: 11/06/2022]
Abstract
Spinal motor neurons project their axons out of the spinal cord via the motor exit point (MEP) and regulate their target muscle fibers for diverse behaviors. Several populations of glial cells including Schwann cells, MEP glia, and perineurial glia are tightly associated with spinal motor axons in nerve fascicles. Zebrafish have two types of spinal motor neurons, primary motor neurons (PMNs) and secondary motor neurons (SMNs). PMNs are implicated in the rapid response, whereas SMNs are implicated in normal and slow movements. However, the precise mechanisms mediating the distinct functions of PMNs and SMNs in zebrafish are unclear. In this study, we found that PMNs were myelinated by MEP glia and Schwann cells, whereas SMNs remained unmyelinated at the examined stages. Immunohistochemical analysis revealed that myelinated PMNs solely innervated fast muscle through a distributed neuromuscular junction (NMJ), whereas unmyelinated SMNs innervated both fast and slow muscle through distributed and myoseptal NMJs, respectively, indicating that myelinated PMNs could provide rapid responses for startle and escape movements, while unmyelinated SMNs regulated normal, slow movement. Further, we demonstrate that neuregulin 1 (Nrg1) type III-ErbB signaling provides a key instructive signal that determines the myelination of primary motor axons by MEP glia and Schwann cells. Perineurial glia ensheathed unmyelinated secondary motor axons and myelinated primary motor nerves. Ensheathment required interaction with both MEP glia and Schwann cells. Collectively, these data suggest that primary and secondary motor neurons contribute to the regulation of movement in zebrafish with distinct patterns of myelination.
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Affiliation(s)
- Dong-Won Lee
- Department of Biomedical Sciences, College of Medicine, Korea University, Ansan, Republic of Korea
| | - Eunmi Kim
- Department of Biomedical Sciences, College of Medicine, Korea University, Ansan, Republic of Korea
| | - Inyoung Jeong
- Department of Biomedical Sciences, College of Medicine, Korea University, Ansan, Republic of Korea
| | - Hwan-Ki Kim
- Department of Biomedical Sciences, College of Medicine, Korea University, Ansan, Republic of Korea
| | - Suhyun Kim
- Department of Biomedical Sciences, College of Medicine, Korea University, Ansan, Republic of Korea
| | - Hae-Chul Park
- Department of Biomedical Sciences, College of Medicine, Korea University, Ansan, Republic of Korea
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25
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Fontenas L, Welsh TG, Piller M, Coughenour P, Gandhi AV, Prober DA, Kucenas S. The Neuromodulator Adenosine Regulates Oligodendrocyte Migration at Motor Exit Point Transition Zones. Cell Rep 2020; 27:115-128.e5. [PMID: 30943395 DOI: 10.1016/j.celrep.2019.03.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 01/27/2019] [Accepted: 03/02/2019] [Indexed: 12/30/2022] Open
Abstract
During development, oligodendrocyte progenitor cells (OPCs) migrate extensively throughout the spinal cord. However, their migration is restricted at transition zones (TZs). At these specialized locations, unique glial cells in both zebrafish and mice play a role in preventing peripheral OPC migration, but the mechanisms of this regulation are not understood. To elucidate the mechanisms that mediate OPC segregation at motor exit point (MEP) TZs, we performed an unbiased small-molecule screen. Using chemical screening and in vivo imaging, we discovered that inhibition of A2a adenosine receptors (ARs) causes ectopic OPC migration out of the spinal cord. We provide in vivo evidence that neuromodulation, partially mediated by adenosine, influences OPC migration specifically at the MEP TZ. This work opens exciting possibilities for understanding how OPCs reach their final destinations during development and identifies mechanisms that could promote their migration in disease.
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Affiliation(s)
- Laura Fontenas
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Taylor G Welsh
- Neuroscience Graduate Program, University of Virginia, Charlottesville, VA 22904, USA
| | - Melanie Piller
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Patricia Coughenour
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Avni V Gandhi
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - David A Prober
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Sarah Kucenas
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA; Neuroscience Graduate Program, University of Virginia, Charlottesville, VA 22904, USA.
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26
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Suter TACS, Jaworski A. Cell migration and axon guidance at the border between central and peripheral nervous system. Science 2020; 365:365/6456/eaaw8231. [PMID: 31467195 DOI: 10.1126/science.aaw8231] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 07/22/2019] [Indexed: 12/13/2022]
Abstract
The central and peripheral nervous system (CNS and PNS, respectively) are composed of distinct neuronal and glial cell types with specialized functional properties. However, a small number of select cells traverse the CNS-PNS boundary and connect these two major subdivisions of the nervous system. This pattern of segregation and selective connectivity is established during embryonic development, when neurons and glia migrate to their destinations and axons project to their targets. Here, we provide an overview of the cellular and molecular mechanisms that control cell migration and axon guidance at the vertebrate CNS-PNS border. We highlight recent advances on how cell bodies and axons are instructed to either cross or respect this boundary, and present open questions concerning the development and plasticity of the CNS-PNS interface.
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Affiliation(s)
- Tracey A C S Suter
- Department of Neuroscience, Division of Biology and Medicine, Brown University, Providence, RI 02912, USA.,Robert J. and Nancy D. Carney Institute for Brain Science, Providence, RI 02912, USA
| | - Alexander Jaworski
- Department of Neuroscience, Division of Biology and Medicine, Brown University, Providence, RI 02912, USA. .,Robert J. and Nancy D. Carney Institute for Brain Science, Providence, RI 02912, USA
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27
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Oligodendrocytes in Development, Myelin Generation and Beyond. Cells 2019; 8:cells8111424. [PMID: 31726662 PMCID: PMC6912544 DOI: 10.3390/cells8111424] [Citation(s) in RCA: 278] [Impact Index Per Article: 55.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 11/07/2019] [Accepted: 11/07/2019] [Indexed: 02/06/2023] Open
Abstract
Oligodendrocytes are the myelinating cells of the central nervous system (CNS) that are generated from oligodendrocyte progenitor cells (OPC). OPC are distributed throughout the CNS and represent a pool of migratory and proliferative adult progenitor cells that can differentiate into oligodendrocytes. The central function of oligodendrocytes is to generate myelin, which is an extended membrane from the cell that wraps tightly around axons. Due to this energy consuming process and the associated high metabolic turnover oligodendrocytes are vulnerable to cytotoxic and excitotoxic factors. Oligodendrocyte pathology is therefore evident in a range of disorders including multiple sclerosis, schizophrenia and Alzheimer’s disease. Deceased oligodendrocytes can be replenished from the adult OPC pool and lost myelin can be regenerated during remyelination, which can prevent axonal degeneration and can restore function. Cell population studies have recently identified novel immunomodulatory functions of oligodendrocytes, the implications of which, e.g., for diseases with primary oligodendrocyte pathology, are not yet clear. Here, we review the journey of oligodendrocytes from the embryonic stage to their role in homeostasis and their fate in disease. We will also discuss the most common models used to study oligodendrocytes and describe newly discovered functions of oligodendrocytes.
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28
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Bradley EC, Cunningham RL, Wilde C, Morgan RK, Klug EA, Letcher SM, Schöneberg T, Monk KR, Liebscher I, Petersen SC. In vivo identification of small molecules mediating Gpr126/Adgrg6 signaling during Schwann cell development. Ann N Y Acad Sci 2019; 1456:44-63. [PMID: 31529518 DOI: 10.1111/nyas.14233] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 07/30/2019] [Accepted: 08/26/2019] [Indexed: 12/13/2022]
Abstract
Gpr126/Adgrg6, an adhesion family G protein-coupled receptor (aGPCR), is required for the development of myelinating Schwann cells in the peripheral nervous system. Myelin supports and insulates vertebrate axons to permit rapid signal propagation throughout the nervous system. In mammals and zebrafish, mutations in Gpr126 arrest Schwann cells at early developmental stages. We exploited the optical and pharmacological tractability of larval zebrafish to uncover drugs that mediate myelination by activating Gpr126 or functioning in parallel. Using a fluorescent marker of mature myelinating glia (Tg[mbp:EGFP-CAAX]), we screened hypomorphic gpr126 mutant larvae for restoration of myelin basic protein (mbp) expression along peripheral nerves following small molecule treatment. Our screens identified five compounds sufficient to promote mbp expression in gpr126 hypomorphs. Using an allelic series of gpr126 mutants, we parsed the ability of small molecules to restore mbp, suggesting differences in drug efficacy dependent on Schwann cell developmental state. Finally, we identify apomorphine hydrochloride as a direct small molecule activator of Gpr126 using combined in vivo/in vitro assays and show that aporphine class compounds promote Schwann cell development in vivo. Our results demonstrate the utility of in vivo screening for aGPCR modulators and identify small molecules that interact with the gpr126-mediated myelination program.
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Affiliation(s)
| | - Rebecca L Cunningham
- Department of Developmental Biology, Washington University in St. Louis School of Medicine, St. Louis, Missouri
| | - Caroline Wilde
- Rudolf Schönheimer Institute of Biochemistry, Medical Faculty, University of Leipzig, Leipzig, Germany
| | - Rory K Morgan
- Vollum Institute, Oregon Health & Science University, Portland, Oregon
| | - Emma A Klug
- Department of Neuroscience, Kenyon College, Gambier, Ohio
| | | | - Torsten Schöneberg
- Rudolf Schönheimer Institute of Biochemistry, Medical Faculty, University of Leipzig, Leipzig, Germany
| | - Kelly R Monk
- Department of Developmental Biology, Washington University in St. Louis School of Medicine, St. Louis, Missouri.,Vollum Institute, Oregon Health & Science University, Portland, Oregon
| | - Ines Liebscher
- Rudolf Schönheimer Institute of Biochemistry, Medical Faculty, University of Leipzig, Leipzig, Germany
| | - Sarah C Petersen
- Department of Neuroscience, Kenyon College, Gambier, Ohio.,Department of Developmental Biology, Washington University in St. Louis School of Medicine, St. Louis, Missouri
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29
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Zhu Y, Crowley SC, Latimer AJ, Lewis GM, Nash R, Kucenas S. Migratory Neural Crest Cells Phagocytose Dead Cells in the Developing Nervous System. Cell 2019; 179:74-89.e10. [PMID: 31495570 DOI: 10.1016/j.cell.2019.08.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Revised: 07/16/2019] [Accepted: 08/01/2019] [Indexed: 12/20/2022]
Abstract
During neural tube closure and spinal cord development, many cells die in both the central and peripheral nervous systems (CNS and PNS, respectively). However, myeloid-derived professional phagocytes have not yet colonized the trunk region during early neurogenesis. How apoptotic cells are removed from this region during these stages remains largely unknown. Using live imaging in zebrafish, we demonstrate that neural crest cells (NCCs) respond rapidly to dying cells and phagocytose cellular debris around the neural tube. Additionally, NCCs have the ability to enter the CNS through motor exit point transition zones and clear debris in the spinal cord. Surprisingly, NCCs phagocytosis mechanistically resembles macrophage phagocytosis and their recruitment toward cellular debris is mediated by interleukin-1β. Taken together, our results reveal a role for NCCs in phagocytosis of debris in the developing nervous system before the presence of professional phagocytes.
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Affiliation(s)
- Yunlu Zhu
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Samantha C Crowley
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Andrew J Latimer
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Gwendolyn M Lewis
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Rebecca Nash
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Sarah Kucenas
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA.
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30
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Green LA, Nebiolo JC, Smith CJ. Microglia exit the CNS in spinal root avulsion. PLoS Biol 2019; 17:e3000159. [PMID: 30794533 PMCID: PMC6402705 DOI: 10.1371/journal.pbio.3000159] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 03/06/2019] [Accepted: 02/06/2019] [Indexed: 12/31/2022] Open
Abstract
Microglia are central nervous system (CNS)-resident cells. Their ability to migrate outside of the CNS, however, is not understood. Using time-lapse imaging in an obstetrical brachial plexus injury (OBPI) model, we show that microglia squeeze through the spinal boundary and emigrate to peripheral spinal roots. Although both macrophages and microglia respond, microglia are the debris-clearing cell. Once outside the CNS, microglia re-enter the spinal cord in an altered state. These peripheral nervous system (PNS)-experienced microglia can travel to distal CNS areas from the injury site, including the brain, with debris. This emigration is balanced by two mechanisms—induced emigration via N-methyl-D-aspartate receptor (NMDA) dependence and restriction via contact-dependent cellular repulsion with macrophages. These discoveries open the possibility that microglia can migrate outside of their textbook-defined regions in disease states. Microglia are normally assumed to be confined to the central nervous system (CNS), but this study shows show that after spinal root injury, microglia can exit the CNS to clear debris. Upon re-entry, the emigrated microglia are altered and can travel to distal areas such as the brain. Cells are precisely organized in specific anatomical domains to ensure normal functioning of the nervous system. One such cell type, microglia, is usually considered to be confined to the central nervous system (CNS). Using time-lapse imaging to capture microglia as they migrate, we show that their characteristic CNS-residency can be altered after spinal root injury. After such injury, the microglia exit the spinal root to the periphery, where they clear debris at the injury site and then carry that debris back into the CNS. In addition, microglia that leave the CNS after spinal root injury become distinct from those that remain within the CNS. This emigration event of microglia after injury is driven by two mechanisms—dependence on glutamatergic signaling that induces their emigration to the injury and interactions with macrophages that prevent their ectopic exit from the spinal cord. Together, these discoveries raise the possibility that microglia could override their CNS-residency in certain disease contexts.
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Affiliation(s)
- Lauren A Green
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America.,Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Julia C Nebiolo
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Cody J Smith
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America.,Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, Indiana, United States of America
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Pioneer axons employ Cajal's battering ram to enter the spinal cord. Nat Commun 2019; 10:562. [PMID: 30718484 PMCID: PMC6362287 DOI: 10.1038/s41467-019-08421-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 01/09/2019] [Indexed: 01/17/2023] Open
Abstract
Sensory axons must traverse a spinal cord glia limitans to connect the brain with the periphery. The fundamental mechanism of how these axons enter the spinal cord is still debatable; both Ramon y Cajal’s battering ram hypothesis and a boundary cap model have been proposed. To distinguish between these hypotheses, we visualized the entry of pioneer axons into the dorsal root entry zone (DREZ) with time-lapse imaging in zebrafish. Here, we identify that DRG pioneer axons enter the DREZ before the arrival of neural crest cells at the DREZ. Instead, actin-rich invadopodia in the pioneer axon are necessary and sufficient for DREZ entry. Using photoactivable Rac1, we demonstrate cell-autonomous functioning of invasive structures in pioneer axon spinal entry. Together these data support the model that actin-rich invasion structures dynamically drive pioneer axon entry into the spinal cord, indicating that distinct pioneer and secondary events occur at the DREZ. The fundamental mechanism of how sensory axons traverse a spinal cord glia limitans remains debatable, with some suggesting a role for boundary cap cells at the dorsal root entry zone (DREZ). Here, authors use time-lapse imaging of DRG axons at the DREZ to show that pioneer axons enter the DREZ before the presence of boundary cap cells, and that this entry is critically dependent on the development of actin-rich invasion structures reminiscent of invadopodia.
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Treichel AJ, Hines JH. Development of an Embryonic Zebrafish Oligodendrocyte-Neuron Mixed Coculture System. Zebrafish 2018; 15:586-596. [PMID: 30300571 DOI: 10.1089/zeb.2018.1625] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
During vertebrate neural development, oligodendrocytes insulate nerve axons with myelin sheaths. Zebrafish (Danio rerio) has emerged as a useful model organism for studying oligodendrocyte development. However, the absence of an in vitro culture system necessitates in vivo manipulations and analyses, which, in some instances, limits the questions that can be addressed. To fill this gap we developed a mixed coculture system for embryonic zebrafish neurons and oligodendrocyte-lineage cells. Cultures harvested from embryos ≥30 hours postfertilization (hpf) yielded oligodendrocyte progenitor cells (OPCs) positive for olig2 and sox10 transgenic reporters. Cultured OPCs exhibited dynamic, exploratory membrane processes, and cell morphologies resembled those established in vivo. Cells harvested from advanced stage embryos possessed more arborized processes than those from early stage embryos. Advanced stage (>60 hpf) embryo culture produced differentiated, mbp+ oligodendrocytes. Genetically tractable neuron subtypes extended neurites when harvested from embryos ≥19 hpf. Coculture produced juxtaposed oligodendrocytes and neurons, demonstrating the practical usefulness of this technique for future studies examining axon-oligodendrocyte interactions under defined conditions. We expect that zebrafish oligodendrocyte culture will complement existing in vivo strengths and may facilitate future studies elucidating the mechanisms of oligodendrocyte specification, proliferation, differentiation, motility, and axon-oligodendrocyte interactions that shape adult myelination patterns.
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Affiliation(s)
| | - Jacob H Hines
- Department of Biology, Winona State University , Winona, Minnesota
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Fontenas L, Kucenas S. Motor Exit Point (MEP) Glia: Novel Myelinating Glia That Bridge CNS and PNS Myelin. Front Cell Neurosci 2018; 12:333. [PMID: 30356886 PMCID: PMC6190867 DOI: 10.3389/fncel.2018.00333] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2018] [Accepted: 09/11/2018] [Indexed: 12/12/2022] Open
Abstract
Oligodendrocytes (OLs) and Schwann cells (SCs) have traditionally been thought of as the exclusive myelinating glial cells of the central and peripheral nervous systems (CNS and PNS), respectively, for a little over a century. However, recent studies demonstrate the existence of a novel, centrally-derived peripheral glial population called motor exit point (MEP) glia, which myelinate spinal motor root axons in the periphery. Until recently, the boundaries that exist between the CNS and PNS, and the cells permitted to cross them, were mostly described based on fixed histological collections and static lineage tracing. Recent work in zebrafish using in vivo, time-lapse imaging has shed light on glial cell interactions at the MEP transition zone and reveals a more complex picture of myelination both centrally and peripherally.
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Affiliation(s)
- Laura Fontenas
- Department of Biology, University of Virginia, Charlottesville, VA, United States
| | - Sarah Kucenas
- Department of Biology, University of Virginia, Charlottesville, VA, United States
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Yuan T, York JR, McCauley DW. Gliogenesis in lampreys shares gene regulatory interactions with oligodendrocyte development in jawed vertebrates. Dev Biol 2018; 441:176-190. [DOI: 10.1016/j.ydbio.2018.07.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 07/02/2018] [Accepted: 07/02/2018] [Indexed: 01/09/2023]
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Nichols EL, Green LA, Smith CJ. Ensheathing cells utilize dynamic tiling of neuronal somas in development and injury as early as neuronal differentiation. Neural Dev 2018; 13:19. [PMID: 30121077 PMCID: PMC6098834 DOI: 10.1186/s13064-018-0115-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 07/27/2018] [Indexed: 12/18/2022] Open
Abstract
Background Glial cell ensheathment of specific components of neuronal circuits is essential for nervous system function. Although ensheathment of axonal segments of differentiated neurons has been investigated, ensheathment of neuronal cell somas, especially during early development when neurons are extending processes and progenitor populations are expanding, is still largely unknown. Methods To address this, we used time-lapse imaging in zebrafish during the initial formation of the dorsal root ganglia (DRG). Results Our results show that DRG neurons are ensheathed throughout their entire lifespan by a progenitor population. These ensheathing cells dynamically remodel during development to ensure axons can extend away from the neuronal cell soma into the CNS and out to the skin. As a population, ensheathing cells tile each DRG neuron to ensure neurons are tightly encased. In development and in experimental cell ablation paradigms, the oval shape of DRG neurons dynamically changes during partial unensheathment. During longer extended unensheathment neuronal soma shifting is observed. We further show the intimate relationship of these ensheathing cells with the neurons leads to immediate and choreographed responses to distal axonal damage to the neuron. Conclusion We propose that the ensheathing cells dynamically contribute to the shape and position of neurons in the DRG by their remodeling activity during development and are primed to dynamically respond to injury of the neuron. Electronic supplementary material The online version of this article (10.1186/s13064-018-0115-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Evan L Nichols
- Department of Biological Sciences, University of Notre Dame, 015 Galvin Life Sciences Building, Notre Dame, IN, 46556, USA
| | - Lauren A Green
- Department of Biological Sciences, University of Notre Dame, 015 Galvin Life Sciences Building, Notre Dame, IN, 46556, USA.,Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN, USA
| | - Cody J Smith
- Department of Biological Sciences, University of Notre Dame, 015 Galvin Life Sciences Building, Notre Dame, IN, 46556, USA. .,Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN, USA.
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Abstract
Animal and plant tissue is composed of distinct populations of cells. These cells interact over time to build and maintain the tissue and can cause disease when disrupted. Scientists have developed clever techniques to investigate characteristics and natural dynamics of these cells within intact tissue by expressing fluorescent proteins in subsets of cells. However, at times, experiments require more selected visualization of cells within the tissue, sometimes at the single-cell or population-of-cells manner. To achieve this and visualize single cells within a population of cells, scientists have utilized single-cell photoconversion of fluorescent proteins. To demonstrate this technique, we show here how to direct UV light to an Eos-expressing cell of interest in an intact, living zebrafish. We then image those photoconverted Eos+ cells 24 h later to determine how they changed in the tissue. We describe two techniques: single cell photoconversion and photoconversions of populations of cell. These techniques can be used to visualize cell-cell interactions, cell-fate and differentiation, and cell migrations, making it a technique that is applicable in numerous biological questions.
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Affiliation(s)
- Lauren Green
- Department of Biological Sciences, University of Notre Dame; Center for Stem Cells and Regenerative Medicine, University of Notre Dame
| | - Cody J Smith
- Department of Biological Sciences, University of Notre Dame; Center for Stem Cells and Regenerative Medicine, University of Notre Dame;
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Boundary cap cells in development and disease. Curr Opin Neurobiol 2017; 47:209-215. [DOI: 10.1016/j.conb.2017.11.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 10/10/2017] [Accepted: 11/03/2017] [Indexed: 01/18/2023]
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Dynein/dynactin is necessary for anterograde transport of Mbp mRNA in oligodendrocytes and for myelination in vivo. Proc Natl Acad Sci U S A 2017; 114:E9153-E9162. [PMID: 29073112 PMCID: PMC5664533 DOI: 10.1073/pnas.1711088114] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Oligodendrocytes in the brain insulate neuronal axons in layers of fatty myelin to facilitate fast electrical signaling. Myelin basic protein (MBP), an important myelin component, is transported as mRNA away from the cell body before being translated into protein. In zebrafish, the anterograde motor kinesin transports mbp mRNA away from the cell body. We now identify myelination defects in zebrafish caused by a mutation in the retrograde motor complex dynein/dynactin, which normally transports cargos back toward the cell body. However, this mutant displays defects in anterograde mbp mRNA transport. We confirm in mammalian oligodendrocyte cultures that drug inhibition of dynein arrests transport in both directions and decreases MBP protein levels. Thus, dynein/dynactin is paradoxically required for anterograde mbp mRNA transport. Oligodendrocytes in the central nervous system produce myelin, a lipid-rich, multilamellar sheath that surrounds axons and promotes the rapid propagation of action potentials. A critical component of myelin is myelin basic protein (MBP), expression of which requires anterograde mRNA transport followed by local translation at the developing myelin sheath. Although the anterograde motor kinesin KIF1B is involved in mbp mRNA transport in zebrafish, it is not entirely clear how mbp transport is regulated. From a forward genetic screen for myelination defects in zebrafish, we identified a mutation in actr10, which encodes the Arp11 subunit of dynactin, a critical activator of the retrograde motor dynein. Both the actr10 mutation and pharmacological dynein inhibition in zebrafish result in failure to properly distribute mbp mRNA in oligodendrocytes, indicating a paradoxical role for the retrograde dynein/dynactin complex in anterograde mbp mRNA transport. To address the molecular mechanism underlying this observation, we biochemically isolated reporter-tagged Mbp mRNA granules from primary cultured mammalian oligodendrocytes to show that they indeed associate with the retrograde motor complex. Next, we used live-cell imaging to show that acute pharmacological dynein inhibition quickly arrests Mbp mRNA transport in both directions. Chronic pharmacological dynein inhibition also abrogates Mbp mRNA distribution and dramatically decreases MBP protein levels. Thus, these cell culture and whole animal studies demonstrate a role for the retrograde dynein/dynactin motor complex in anterograde mbp mRNA transport and myelination in vivo.
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Livin' On The Edge: glia shape nervous system transition zones. Curr Opin Neurobiol 2017; 47:44-51. [PMID: 28957729 DOI: 10.1016/j.conb.2017.09.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 09/11/2017] [Indexed: 11/21/2022]
Abstract
The vertebrate nervous system is divided into two functional halves; the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which consists of nerves and ganglia. Incoming peripheral stimuli transmitted from the periphery to the CNS and subsequent motor responses created because of this information, require efficient communication between the two halves that make up this organ system. Neurons and glial cells of each half of the nervous system, which are the main actors in this communication, segregate across nervous system transition zones and never mix, allowing for efficient neurotransmission. Studies aimed at understanding the cellular and molecular mechanisms governing the development and maintenance of these transition zones have predominantly focused on mammalian models. However, zebrafish has emerged as a powerful model organism to study these structures and has allowed researchers to identify novel glial cells and mechanisms essential for nervous system assembly. This review will highlight recent advances into the important role that glial cells play in building and maintaining the nervous system and its boundaries.
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Perineurial Glial Plasticity and the Role of TGF-β in the Development of the Blood-Nerve Barrier. J Neurosci 2017; 37:4790-4807. [PMID: 28389474 DOI: 10.1523/jneurosci.2875-16.2017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 03/29/2017] [Accepted: 03/31/2017] [Indexed: 12/28/2022] Open
Abstract
Precisely orchestrated interactions between spinal motor axons and their ensheathing glia are vital for forming and maintaining functional spinal motor nerves. Following perturbations to peripheral myelinating glial cells, centrally derived oligodendrocyte progenitor cells (OPCs) ectopically exit the spinal cord and myelinate peripheral nerves in myelin with CNS characteristics. However, whether remaining peripheral ensheathing glia, such as perineurial glia, properly encase the motor nerve despite this change in glial cell and myelin composition, remains unknown. Using zebrafish mutants in which OPCs migrate out of the spinal cord and myelinate peripheral motor axons, we assayed perineurial glial development, maturation, and response to injury. Surprisingly, in the presence of OPCs, perineurial glia exited the CNS normally. However, aspects of their development, response to injury, and function were altered compared with wildtype larvae. In an effort to better understand the plasticity of perineurial glia in response to myelin perturbations, we identified transforming growth factor-β1 as a partial mediator of perineurial glial development. Together, these results demonstrate the incredible plasticity of perineurial glia in the presence of myelin perturbations.SIGNIFICANCE STATEMENT Peripheral neuropathies can result from damage or dysregulation of the insulating myelin sheath surrounding spinal motor axons, causing pain, inefficient nerve conduction, and the ectopic migration of oligodendrocyte progenitor cells (OPCs), the resident myelinating glial cell of the CNS, into the periphery. How perineurial glia, the ensheathing cells that form the protective blood-nerve barrier, are impacted by this myelin composition change is unknown. Here, we report that certain aspects of perineurial glial development and injury responses are mostly unaffected in the presence of ectopic OPCs. However, perineurial glial function is disrupted along nerves containing centrally derived myelin, demonstrating that, although perineurial glial cells display plasticity despite myelin perturbations, the blood-nerve barrier is compromised in the presence of ectopic OPCs.
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Smith CJ, Wheeler MA, Marjoram L, Bagnat M, Deppmann CD, Kucenas S. TNFa/TNFR2 signaling is required for glial ensheathment at the dorsal root entry zone. PLoS Genet 2017; 13:e1006712. [PMID: 28379965 PMCID: PMC5397050 DOI: 10.1371/journal.pgen.1006712] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Revised: 04/19/2017] [Accepted: 03/22/2017] [Indexed: 01/09/2023] Open
Abstract
Somatosensory information from the periphery is routed to the spinal cord through centrally-projecting sensory axons that cross into the central nervous system (CNS) via the dorsal root entry zone (DREZ). The glial cells that ensheath these axons ensure rapid propagation of this information. Despite the importance of this glial-axon arrangement, how this afferent nerve is assembled during development is unknown. Using in vivo, time-lapse imaging we show that as centrally-projecting pioneer axons from dorsal root ganglia (DRG) enter the spinal cord, they initiate expression of the cytokine TNFalpha. This induction coincides with ensheathment of these axons by associated glia via a TNF receptor 2 (TNFR2)-mediated process. This work identifies a signaling cascade that mediates peripheral glial-axon interactions and it functions to ensure that DRG afferent projections are ensheathed after pioneer axons complete their navigation, which promotes efficient somatosensory neural function.
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Affiliation(s)
- Cody J. Smith
- Department of Biology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Michael A. Wheeler
- Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia, United States of America
| | - Lindsay Marjoram
- Department of Cell Biology, Duke University, Durham, North Carolina, United States of America
| | - Michel Bagnat
- Department of Cell Biology, Duke University, Durham, North Carolina, United States of America
| | - Christopher D. Deppmann
- Department of Biology, University of Virginia, Charlottesville, Virginia, United States of America
- Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia, United States of America
| | - Sarah Kucenas
- Department of Biology, University of Virginia, Charlottesville, Virginia, United States of America
- Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia, United States of America
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Singhal A, Shaham S. Infrared laser-induced gene expression for tracking development and function of single C. elegans embryonic neurons. Nat Commun 2017; 8:14100. [PMID: 28098184 PMCID: PMC5253673 DOI: 10.1038/ncomms14100] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 11/28/2016] [Indexed: 11/09/2022] Open
Abstract
Visualizing neural-circuit assembly in vivo requires tracking growth of optically resolvable neurites. The Caenorhabditis elegans embryonic nervous system, comprising 222 neurons and 56 glia, is attractive for comprehensive studies of development; however, embryonic reporters are broadly expressed, making single-neurite tracking/manipulation challenging. We present a method, using an infrared laser, for reproducible heat-dependent gene expression in small sublineages (one to four cells) without radiation damage. We go beyond proof-of-principle, and use our system to label and track single neurons during early nervous-system assembly. We uncover a retrograde extension mechanism for axon growth, and reveal the aetiology of axon-guidance defects in sax-3/Robo and vab-1/EphR mutants. We also perform cell-specific rescues, determining DAF-6/patched-related site of action during sensory-organ development. Simultaneous ablation and labelling of cells using our system reveals roles for glia in dendrite extension. Our method can be applied to other optically/IR-transparent organisms, and opens the door to high-resolution systematic analyses of C. elegans morphogenesis.
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Affiliation(s)
- Anupriya Singhal
- Laboratory of Developmental Genetics, The Rockefeller University, 1230 York Avenue, New York, New York 10065, USA
| | - Shai Shaham
- Laboratory of Developmental Genetics, The Rockefeller University, 1230 York Avenue, New York, New York 10065, USA
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Fontenas L, De Santis F, Di Donato V, Degerny C, Chambraud B, Del Bene F, Tawk M. Neuronal Ndrg4 Is Essential for Nodes of Ranvier Organization in Zebrafish. PLoS Genet 2016; 12:e1006459. [PMID: 27902705 PMCID: PMC5130175 DOI: 10.1371/journal.pgen.1006459] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 11/03/2016] [Indexed: 11/19/2022] Open
Abstract
Axon ensheathment by specialized glial cells is an important process for fast propagation of action potentials. The rapid electrical conduction along myelinated axons is mainly due to its saltatory nature characterized by the accumulation of ion channels at the nodes of Ranvier. However, how these ion channels are transported and anchored along axons is not fully understood. We have identified N-myc downstream-regulated gene 4, ndrg4, as a novel factor that regulates sodium channel clustering in zebrafish. Analysis of chimeric larvae indicates that ndrg4 functions autonomously within neurons for sodium channel clustering at the nodes. Molecular analysis of ndrg4 mutants shows that expression of snap25 and nsf are sharply decreased, revealing a role of ndrg4 in controlling vesicle exocytosis. This uncovers a previously unknown function of ndrg4 in regulating vesicle docking and nodes of Ranvier organization, at least through its ability to finely tune the expression of the t-SNARE/NSF machinery. Myelination is an important process that enables fast propagation of action potential along the axons. Schwann cells (SCs) are the specialized glial cells that ensure the ensheathment of the corresponding axons in the Peripheral Nervous System. In order to do so, SCs and axons need to communicate to organize the myelinating segments and the clustering of sodium channels at the nodes of Ranvier. We have investigated the early events of myelination in the zebrafish embryo. We here identify ndrg4 as a novel neuronal factor essential for sodium channel clustering at the nodes. Immuno-labeling analysis show defective vesicle patterning along the axons of ndrg4 mutants, while timelapse experiments monitoring the presence and the transport of these vesicles reveal a normal behavior. Molecular analysis unravels a novel function of ndrg4 in controlling the expression of the t-SNARE/NSF machinery required for vesicle docking and release. However, inhibiting specifically regulated synaptic vesicle release does not lead to sodium channel clustering defects. We thus propose that ndrg4 can regulate this process, at least partially, through its ability to regulate the expression of key components of the t-SNARE/NSF machinery, responsible for clustering of sodium channels along myelinated axons.
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Affiliation(s)
- Laura Fontenas
- U1195, Inserm, University Paris Sud, University Paris-Saclay, Kremlin-Bicêtre, France
| | | | | | - Cindy Degerny
- U1195, Inserm, University Paris Sud, University Paris-Saclay, Kremlin-Bicêtre, France
| | - Béatrice Chambraud
- U1195, Inserm, University Paris Sud, University Paris-Saclay, Kremlin-Bicêtre, France
| | | | - Marcel Tawk
- U1195, Inserm, University Paris Sud, University Paris-Saclay, Kremlin-Bicêtre, France
- * E-mail:
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Smith CJ, Johnson K, Welsh TG, Barresi MJF, Kucenas S. Radial glia inhibit peripheral glial infiltration into the spinal cord at motor exit point transition zones. Glia 2016; 64:1138-53. [PMID: 27029762 DOI: 10.1002/glia.22987] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 03/12/2016] [Accepted: 03/14/2016] [Indexed: 11/09/2022]
Abstract
In the mature vertebrate nervous system, central and peripheral nervous system (CNS and PNS, respectively) GLIA myelinate distinct motor axon domains at the motor exit point transition zone (MEP TZ). How these cells preferentially associate with and myelinate discrete, non-overlapping CNS versus PNS axonal segments, is unknown. Using in vivo imaging and genetic cell ablation in zebrafish, we demonstrate that radial glia restrict migration of PNS glia into the spinal cord during development. Prior to development of radial glial endfeet, peripheral cells freely migrate back and forth across the MEP TZ. However, upon maturation, peripherally located cells never enter the CNS. When we ablate radial glia, peripheral glia ectopically migrate into the spinal cord during developmental stages when they would normally be restricted. These findings demonstrate that radial glia contribute to both CNS and PNS development and control the unidirectional movement of glial cell types across the MEP TZ early in development. GLIA 2016. GLIA 2016;64:1138-1153.
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Affiliation(s)
- Cody J Smith
- Department of Biology, University of Virginia, Charlottesville, Virginia, 22904
| | - Kimberly Johnson
- Department of Biological Sciences, Smith College, Northampton, Massachusetts, 01003
| | - Taylor G Welsh
- Department of Biology, University of Virginia, Charlottesville, Virginia, 22904.,Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia, 22904
| | - Michael J F Barresi
- Department of Biological Sciences, Smith College, Northampton, Massachusetts, 01003.,Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, Massachusetts, 01003
| | - Sarah Kucenas
- Department of Biology, University of Virginia, Charlottesville, Virginia, 22904.,Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia, 22904
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Genetically targeted magnetic control of the nervous system. Nat Neurosci 2016; 19:756-761. [PMID: 26950006 PMCID: PMC4846560 DOI: 10.1038/nn.4265] [Citation(s) in RCA: 147] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 02/09/2016] [Indexed: 12/14/2022]
Abstract
Optogenetic and chemogenetic actuators are critical for deconstructing the neural correlates of behavior. However, these tools have several limitations, including invasive modes of stimulation or slow on/off kinetics. We have overcome these disadvantages by synthesizing a single-component, magnetically sensitive actuator, "Magneto," comprising the cation channel TRPV4 fused to the paramagnetic protein ferritin. We validated noninvasive magnetic control over neuronal activity by demonstrating remote stimulation of cells using in vitro calcium imaging assays, electrophysiological recordings in brain slices, in vivo electrophysiological recordings in the brains of freely moving mice, and behavioral outputs in zebrafish and mice. As proof of concept, we used Magneto to delineate a causal role of striatal dopamine receptor 1 neurons in mediating reward behavior in mice. Together our results present Magneto as an actuator capable of remotely controlling circuits associated with complex animal behaviors.
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Abstract
In the nervous system, axons transmit information in the form of electrical impulses over long distances. The speed of impulse conduction is enhanced by myelin, a lipid-rich membrane that wraps around axons. Myelin also is required for the long-term health of axons by providing metabolic support. Accordingly, myelin deficiencies are implicated in a wide range of neurodevelopmental and neuropsychiatric disorders, intellectual disabilities, and neurodegenerative conditions. Central nervous system myelin is formed by glial cells called oligodendrocytes. During development, oligodendrocyte precursor cells migrate from their origins to their target axons, extend long membrane processes that wrap axons, and produce the proteins and lipids that provide myelin membrane with its unique characteristics. Myelination is a dynamic process that involves intricate interactions between multiple cell types. Therefore, an in vivo myelination model, such as the zebrafish, which allows for live observation of cell dynamics and cell-to-cell interactions, is well suited for investigating oligodendrocyte development. Zebrafish offer several advantages to investigating myelination, including the use of transgenic reporter lines, live imaging, forward genetic screens, chemical screens, and reverse genetic approaches. This chapter will describe how these tools and approaches have provided new insights into the regulatory mechanisms that guide myelination.
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Affiliation(s)
- E S Mathews
- University of Colorado School of Medicine, Aurora, CO, United States
| | - B Appel
- University of Colorado School of Medicine, Aurora, CO, United States
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The scales and tales of myelination: using zebrafish and mouse to study myelinating glia. Brain Res 2015; 1641:79-91. [PMID: 26498880 DOI: 10.1016/j.brainres.2015.10.011] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 10/01/2015] [Accepted: 10/05/2015] [Indexed: 01/06/2023]
Abstract
Myelin, the lipid-rich sheath that insulates axons to facilitate rapid conduction of action potentials, is an evolutionary innovation of the jawed-vertebrate lineage. Research efforts aimed at understanding the molecular mechanisms governing myelination have primarily focused on rodent models; however, with the advent of the zebrafish model system in the late twentieth century, the use of this genetically tractable, yet simpler vertebrate for studying myelination has steadily increased. In this review, we compare myelinating glial cell biology during development and regeneration in zebrafish and mouse and enumerate the advantages and disadvantages of using each model to study myelination. This article is part of a Special Issue entitled SI: Myelin Evolution.
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Czopka T. Insights into mechanisms of central nervous system myelination using zebrafish. Glia 2015; 64:333-49. [PMID: 26250418 DOI: 10.1002/glia.22897] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 07/14/2015] [Accepted: 07/15/2015] [Indexed: 12/12/2022]
Abstract
Myelin is the multi-layered membrane that surrounds most axons and is produced by oligodendrocytes in the central nervous system (CNS). In addition to its important role in enabling rapid nerve conduction, it has become clear in recent years that myelin plays additional vital roles in CNS function. Myelinating oligodendrocytes provide metabolic support to axons and active myelination is even involved in regulating forms of learning and memory formation. However, there are still large gaps in our understanding of how myelination by oligodendrocytes is regulated. The small tropical zebrafish has become an increasingly popular model organism to investigate many aspects of nervous system formation, function, and regeneration. This is mainly due to two approaches for which the zebrafish is an ideally suited vertebrate model--(1) in vivo live cell imaging using vital dyes and genetically encoded reporters, and (2) gene and target discovery using unbiased screens. This review summarizes how the use of zebrafish has helped understand mechanisms of oligodendrocyte behavior and myelination in vivo and discusses the potential use of zebrafish to shed light on important future questions relating to myelination in the context of CNS development, function and repair.
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Affiliation(s)
- Tim Czopka
- Institute of Neuronal Cell Biology, Technische Universität München, Munich, Germany
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Affiliation(s)
- Sarah Kucenas
- University of Virginia, Charlottesville, Virginia, United States of America
- * E-mail:
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