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Hooper KM, Lundquist EA. Short- and long-range roles of UNC-6/Netrin in dorsal-ventral axon guidance in vivo in Caenorhabditis elegans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.23.590737. [PMID: 38712249 PMCID: PMC11071391 DOI: 10.1101/2024.04.23.590737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
Recent studies in vertebrates and Caenorhabditis elegans have reshaped models of how the axon guidance cue UNC-6/Netrin functions in dorsal-ventral axon guidance, which was traditionally thought to form a ventral-to-dorsal concentration gradient that was actively sensed by growing axons. In the vertebrate spinal cord, floorplate Netrin1 was shown to be largely dispensable for ventral commissural growth. Rather, short range interactions with Netrin1 on the ventricular zone radial glial stem cells was shown to guide ventral commissural axon growth. In C. elegans, analysis of dorsally-migrating growth cones during outgrowth has shown that growth cone polarity of filopodial extension is separable from the extent of growth cone protrusion. Growth cones are first polarized by UNC-6/Netrin, and subsequent regulation of protrusion by UNC-6/Netrin is based on this earlier-established polarity (the Polarity/Protrusion model). In both cases, short-range or even haptotactic mechanisms are invoked: in vertebrate spinal cord, interactions of growth cones with radial glia expressing Netrin-1; and in C. elegans, a potential close-range interaction that polarizes the growth cone. To explore potential short-range and long-range functions of UNC-6/Netrin, a potentially membrane-anchored transmembrane UNC-6 (UNC-6(TM)) was generated by genome editing. Unc-6(tm) was hypomorphic for dorsal VD/DD axon pathfinding, indicating that it retained some unc-6 function. Polarity of VD growth cone filopodial protrusion was initially established in unc-6(tm), but was lost as the growth cones migrated away from the unc-6(tm) source in the ventral nerve cord. In contrast, ventral guidance of the AVM and PVM axons was equally severe in unc-6(tm) and unc-6(null). Together, these results suggest that unc-6(tm) retains short-range functions but lacks long-range functions. Finally, ectopic unc-6(+) expression from non-ventral sources could rescue dorsal and ventral guidance defects in unc-6(tm) and unc-6(null). Thus, a ventral directional source of UNC-6 was not required for dorsal-ventral axon guidance, and UNC-6 can act as a permissive, not instructive, cue for dorsal-ventral axon guidance. Possibly, UNC-6 is a permissive signal that activates cell-intrinsic polarity; or UNC-6 acts with another signal that is required in a directional manner. In either case, the role of UNC-6 is to polarize the pro-protrusive activity of UNC-40/DCC in the direction of outgrowth.
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Affiliation(s)
- Kelsey M. Hooper
- University of Kansas, Department of Molecular Biosciences, Program in Molecular, Cellular, and Developmental Biology
| | - Erik A. Lundquist
- University of Kansas, Department of Molecular Biosciences, Program in Molecular, Cellular, and Developmental Biology
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Chisholm AD, Hutter H, Jin Y, Wadsworth WG. The Genetics of Axon Guidance and Axon Regeneration in Caenorhabditis elegans. Genetics 2016; 204:849-882. [PMID: 28114100 PMCID: PMC5105865 DOI: 10.1534/genetics.115.186262] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 09/06/2016] [Indexed: 11/18/2022] Open
Abstract
The correct wiring of neuronal circuits depends on outgrowth and guidance of neuronal processes during development. In the past two decades, great progress has been made in understanding the molecular basis of axon outgrowth and guidance. Genetic analysis in Caenorhabditis elegans has played a key role in elucidating conserved pathways regulating axon guidance, including Netrin signaling, the slit Slit/Robo pathway, Wnt signaling, and others. Axon guidance factors were first identified by screens for mutations affecting animal behavior, and by direct visual screens for axon guidance defects. Genetic analysis of these pathways has revealed the complex and combinatorial nature of guidance cues, and has delineated how cues guide growth cones via receptor activity and cytoskeletal rearrangement. Several axon guidance pathways also affect directed migrations of non-neuronal cells in C. elegans, with implications for normal and pathological cell migrations in situations such as tumor metastasis. The small number of neurons and highly stereotyped axonal architecture of the C. elegans nervous system allow analysis of axon guidance at the level of single identified axons, and permit in vivo tests of prevailing models of axon guidance. C. elegans axons also have a robust capacity to undergo regenerative regrowth after precise laser injury (axotomy). Although such axon regrowth shares some similarities with developmental axon outgrowth, screens for regrowth mutants have revealed regeneration-specific pathways and factors that were not identified in developmental screens. Several areas remain poorly understood, including how major axon tracts are formed in the embryo, and the function of axon regeneration in the natural environment.
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Affiliation(s)
| | - Harald Hutter
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - Yishi Jin
- Section of Neurobiology, Division of Biological Sciences, and
- Department of Cellular and Molecular Medicine, School of Medicine, University of California, San Diego, La Jolla, California 92093
- Department of Pathology and Laboratory Medicine, Howard Hughes Medical Institute, Chevy Chase, Maryland, and
| | - William G Wadsworth
- Department of Pathology, Rutgers Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
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Yu J, Li X, Yang J, Wu Y, Li B. Effects of Simazine Exposure on Neuronal Development-Related Factors in MN9D Cells. Med Sci Monit 2016; 22:2831-8. [PMID: 27513680 PMCID: PMC4987066 DOI: 10.12659/msm.896460] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Background Simazine is a triazine herbicide used worldwide in both agricultural and non-agricultural fields that is frequently detected in surface water and groundwater. Due to its widespread use, an increasing amount of research has focused on the potentially serious environmental and health risks. Material/Methods We used Western blotting and real-time quantitative PCR to analyze the effects of simazine on dopamine neuronal development-related factors in MN9D dopaminergic cells. Results The expression of tyrosine hydroxylase (TH) mRNA was significantly increased after treatment with 300 and 600 μmol L−1 simazine after 24 and 48 h. Levels of nuclear-related receptor 1 (Nurr1) mRNA after 24- and 48-h exposure were decreased with 50 μmol L−1 simazine, but increased with 600 μmol L−1 simazine. Significant increases in TH and Nurr1 protein were observed in all simazine-treated groups at 24 and 48 h. The expression of neurogenin 2 and LIM homeobox transcription factor 1 beta (Lmx1b) mRNA were significantly increased after exposure to 600 μmol L−1 simazine for 48 h, while the expression of wingless-type MMTV integration site family member 1 (Wnt1) mRNA was increased by all doses of simazine. Conclusions Simazine may have an impact on TH in MN9D cells through 2 mechanisms; one mechanism is through the Lmx1a/Ngn2 pathway, and the other mechanism is through the Lmx1b-pitx3/Wnt1-Nurr1 pathway. These 2 pathways likely do not operate in isolation, but rather together, during the cellular response to simazine exposure.
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Affiliation(s)
- Jia Yu
- Department of Toxicology, College of Public Health, Harbin Medical University, Harbin, Heilongjiang, China (mainland)
| | - Xueting Li
- Department of Toxicology, College of Public Health, Harbin Medical University, Harbin, Heilongjiang, China (mainland)
| | - Junwei Yang
- Department of Toxicology, College of Public Health, Harbin Medical University, Harbin, Heilongjiang, China (mainland)
| | - Yanping Wu
- Department of Toxicology, College of Public Health, Harbin Medical University, Harbin, Heilongjiang, China (mainland)
| | - Baixiang Li
- Department of Toxicology, College of Public Health, Harbin Medical University, Harbin, Heilongjiang, China (mainland)
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4
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Rella L, Fernandes Póvoa EE, Korswagen HC. The Caenorhabditis elegans Q neuroblasts: A powerful system to study cell migration at single-cell resolution in vivo. Genesis 2016; 54:198-211. [PMID: 26934462 DOI: 10.1002/dvg.22931] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 02/09/2016] [Accepted: 02/25/2016] [Indexed: 11/08/2022]
Abstract
During development, cell migration plays a central role in the formation of tissues and organs. Understanding the molecular mechanisms that drive and control these migrations is a key challenge in developmental biology that will provide important insights into disease processes, including cancer cell metastasis. In this article, we discuss the Caenorhabditis elegans Q neuroblasts and their descendants as a tool to study cell migration at single-cell resolution in vivo. The highly stereotypical migration of these cells provides a powerful system to study the dynamic cytoskeletal processes that drive migration as well as the evolutionarily conserved signaling pathways (including different Wnt signaling cascades) that guide the cells along their specific trajectories. Here, we provide an overview of what is currently known about Q neuroblast migration and highlight the live-cell imaging, genome editing, and quantitative gene expression techniques that have been developed to study this process.
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Affiliation(s)
- Lorenzo Rella
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT, Utrecht, the Netherlands
| | - Euclides E Fernandes Póvoa
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT, Utrecht, the Netherlands
| | - Hendrik C Korswagen
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT, Utrecht, the Netherlands
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Dong B, Moseley-Alldredge M, Schwieterman AA, Donelson CJ, McMurry JL, Hudson ML, Chen L. EFN-4 functions in LAD-2-mediated axon guidance in Caenorhabditis elegans. Development 2016; 143:1182-91. [PMID: 26903502 DOI: 10.1242/dev.128934] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 02/12/2016] [Indexed: 11/20/2022]
Abstract
During development of the nervous system, growing axons rely on guidance molecules to direct axon pathfinding. A well-characterized family of guidance molecules are the membrane-associated ephrins, which together with their cognate Eph receptors, direct axon navigation in a contact-mediated fashion. InC. elegans, the ephrin-Eph signaling system is conserved and is best characterized for their roles in neuroblast migration during early embryogenesis. This study demonstrates a role for the C. elegans ephrin EFN-4 in axon guidance. We provide both genetic and biochemical evidence that is consistent with the C. elegans divergent L1 cell adhesion molecule LAD-2 acting as a non-canonical ephrin receptor to EFN-4 to promote axon guidance. We also show that EFN-4 probably functions as a diffusible factor because EFN-4 engineered to be soluble can promote LAD-2-mediated axon guidance. This study thus reveals a potential additional mechanism for ephrins in regulating axon guidance and expands the repertoire of receptors by which ephrins can signal.
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Affiliation(s)
- Bingyun Dong
- Department of Genetics, Cell Biology & Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Melinda Moseley-Alldredge
- Department of Genetics, Cell Biology & Development, University of Minnesota, Minneapolis, MN 55455, USA Developmental Biology Center, University of Minnesota, Minneapolis, MN 55455, USA
| | - Alicia A Schwieterman
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, GA 30144, USA
| | - Cory J Donelson
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, GA 30144, USA
| | - Jonathan L McMurry
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, GA 30144, USA
| | - Martin L Hudson
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, GA 30144, USA
| | - Lihsia Chen
- Department of Genetics, Cell Biology & Development, University of Minnesota, Minneapolis, MN 55455, USA Developmental Biology Center, University of Minnesota, Minneapolis, MN 55455, USA
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Basement Membranes in the Worm: A Dynamic Scaffolding that Instructs Cellular Behaviors and Shapes Tissues. CURRENT TOPICS IN MEMBRANES 2015; 76:337-71. [PMID: 26610919 DOI: 10.1016/bs.ctm.2015.08.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The nematode worm Caenorhabditis elegans has all the major basement membrane proteins found in vertebrates, usually with a smaller gene family encoding each component. With its powerful forward genetics, optical clarity, simple tissue organization, and the capability to functionally tag most basement membrane components with fluorescent proteins, C. elegans has facilitated novel insights into the assembly and function of basement membranes. Although basement membranes are generally thought of as static structures, studies in C. elegans have revealed their active properties and essential functions in tissue formation and maintenance. Here, we review discoveries from C. elegans development that highlight dynamic aspects of basement membrane assembly, function, and regulation during organ growth, tissue polarity, cell migration, cell invasion, and tissue attachment. These studies have helped transform our view of basement membranes from static support structures to dynamic scaffoldings that play broad roles in regulating tissue organization and cellular behavior that are essential for development and have important implications in human diseases.
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Mentink RA, Middelkoop TC, Rella L, Ji N, Tang CY, Betist MC, van Oudenaarden A, Korswagen HC. Cell intrinsic modulation of Wnt signaling controls neuroblast migration in C. elegans. Dev Cell 2014; 31:188-201. [PMID: 25373777 DOI: 10.1016/j.devcel.2014.08.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 07/11/2014] [Accepted: 08/07/2014] [Indexed: 01/25/2023]
Abstract
Members of the Wnt family of secreted signaling proteins are key regulators of cell migration and axon guidance. In the nematode C. elegans, the migration of the QR neuroblast descendants requires multiple Wnt ligands and receptors. We found that the migration of the QR descendants is divided into three sequential phases that are each mediated by a distinct Wnt signaling mechanism. Importantly, the transition from the first to the second phase, which is the main determinant of the final position of the QR descendants along the anteroposterior body axis, is mediated through a cell-autonomous process in which the time-dependent expression of a Wnt receptor turns on the canonical Wnt/β-catenin signaling response that is required to terminate long-range anterior migration. Our results show that, in addition to direct guidance of cell migration by Wnt morphogenic gradients, cell migration can also be controlled indirectly through cell-intrinsic modulation of Wnt signaling responses.
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Affiliation(s)
- Remco A Mentink
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
| | - Teije C Middelkoop
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
| | - Lorenzo Rella
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
| | - Ni Ji
- Department of Physics and Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Chung Yin Tang
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
| | - Marco C Betist
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
| | - Alexander van Oudenaarden
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands; Department of Physics and Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Hendrik C Korswagen
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
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8
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Kulkarni G, Xu Z, Mohamed AM, Li H, Tang X, Limerick G, Wadsworth WG. Experimental evidence for UNC-6 (netrin) axon guidance by stochastic fluctuations of intracellular UNC-40 (DCC) outgrowth activity. Biol Open 2013; 2:1300-12. [PMID: 24337114 PMCID: PMC3863414 DOI: 10.1242/bio.20136346] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
How the direction of axon guidance is determined is not understood. In Caenorhabditis elegans the UNC-40 (DCC) receptor mediates a response to the UNC-6 (netrin) guidance cue that directs HSN axon development. UNC-40 becomes asymmetrically localized within the HSN neuron to the site of axon outgrowth. Here we provide experimental evidence that the direction of guidance can be explained by the stochastic fluctuations of UNC-40 asymmetric outgrowth activity. We find that the UNC-5 (UNC5) receptor and the cytoskeletal binding protein UNC-53 (NAV2) regulate the induction of UNC-40 localization by UNC-6. If UNC-40 localization is induced without UNC-6 by using an unc-53 mutation, the direction of UNC-40 localization undergoes random fluctuations. Random walk models describe the path made by a succession of randomly directed movement. This model was experimentally tested using mutations that affect Wnt/PCP signaling. These mutations inhibit UNC-40 localization in the anterior and posterior directions. As the axon forms in Wnt/PCP mutants, the direction of UNC-40 localization randomly fluctuates; it can localize in either the anterior, posterior, or ventral direction. Consistent with a biased random walk, over time the axon will develop ventrally in response to UNC-6, even though at a discrete time UNC-40 localization and outgrowth can be observed anterior or posterior. Also, axon formation is slower in the mutants than in wild-type animals. This is also consistent with a random walk since this model predicts that the mean square displacement (msd) will increase only linearly with time, whereas the msd increases quadratically with time for straight-line motion.
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Affiliation(s)
- Gauri Kulkarni
- Department of Pathology, Robert Wood Johnson Medical School, Rutgers University, 675 Hoes Lane West, Piscataway, NJ 08854, USA
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9
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Barsi-Rhyne BJ, Miller KM, Vargas CT, Thomas AB, Park J, Bremer M, Jarecki JL, VanHoven MK. Kinesin-1 acts with netrin and DCC to maintain sensory neuron position in Caenorhabditis elegans. Genetics 2013; 194:175-87. [PMID: 23475988 PMCID: PMC3632465 DOI: 10.1534/genetics.113.149310] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 02/24/2013] [Indexed: 11/18/2022] Open
Abstract
The organization of neurons and the maintenance of that arrangement are critical to brain function. Failure of these processes in humans can lead to severe birth defects, mental retardation, and epilepsy. Several kinesins have been shown to play important roles in cell migration in vertebrate systems, but few upstream and downstream pathway members have been identified. Here, we utilize the genetic model organism Caenorhabditis elegans to elucidate the pathway by which the C. elegans Kinesin-1 Heavy Chain (KHC)/KIF5 ortholog UNC-116 functions to maintain neuronal cell body position in the PHB sensory neurons. We find that UNC-116/KHC acts in part with the cell and axon migration molecules UNC-6/Netrin and UNC-40/DCC in this process, but in parallel to SAX-3/Robo. We have also identified several potential adaptor, cargo, and regulatory proteins that may provide insight into the mechanism of UNC-116/KHC's function in this process. These include the cargo receptor UNC-33/CRMP2, the cargo adaptor protein UNC-76/FEZ and its regulator UNC-51/ULK, the cargo molecule UNC-69/SCOCO, and the actin regulators UNC-44/Ankyrin and UNC-34/Enabled. These genes also act in cell migration and axon outgrowth; however, many proteins that function in these processes do not affect PHB position. Our findings suggest an active posterior cell migration mediated by UNC-116/KHC occurs throughout development to maintain proper PHB cell body position and define a new pathway that mediates maintenance of neuronal cell body position.
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Affiliation(s)
| | - Kristine M. Miller
- Department of Biological Sciences, San José State University, San José, California 95192
| | - Christopher T. Vargas
- Department of Biological Sciences, San José State University, San José, California 95192
| | - Anthony B. Thomas
- Department of Biological Sciences, San José State University, San José, California 95192
| | - Joori Park
- Department of Biological Sciences, San José State University, San José, California 95192
| | - Martina Bremer
- Department of Mathematics, San José State University, San José, California 95192
| | - Jessica L. Jarecki
- Department of Biological Sciences, San José State University, San José, California 95192
| | - Miri K. VanHoven
- Department of Biological Sciences, San José State University, San José, California 95192
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10
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Chai Y, Li W, Feng G, Yang Y, Wang X, Ou G. Live imaging of cellular dynamics during Caenorhabditis elegans postembryonic development. Nat Protoc 2012; 7:2090-102. [PMID: 23138350 DOI: 10.1038/nprot.2012.128] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Postembryonic development is an important process of organismal maturation after embryonic growth. Despite key progress in recent years in understanding embryonic development via fluorescence time-lapse microscopy, comparatively less live-cell imaging of postembryonic development has been done. Here we describe a protocol to image larval development in the nematode Caenorhabditis elegans. Our protocol describes the construction of fluorescent transgenic C. elegans, immobilization of worm larvae and time-lapse microscopy analysis. To improve the throughput of imaging, we developed a C. elegans triple-fluorescence imaging approach with a worm-optimized blue fluorescent protein (TagBFP), green fluorescent protein (GFP) and mCherry. This protocol has been previously applied to time-lapse imaging analysis of Q neuroblast asymmetric division, migration and apoptosis, and we show here that it can also be used to image neuritogenesis in the L1 larvae. Other applications are also possible. The protocol can be completed within 3 h and may provide insights into understanding postembryonic development.
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Affiliation(s)
- Yongping Chai
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
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11
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Abstract
This review is focusing on a critical mediator of embryonic and postnatal development with multiple implications in inflammation, neoplasia, and other pathological situations in brain and peripheral tissues. These morphogenetic guidance and dependence processes are involved in several malignancies targeting the epithelial and immune systems including the progression of human colorectal cancers. We consider the most important findings and their impact on basic, translational, and clinical cancer research. Expected information can bring new cues for innovative, efficient, and safe strategies of personalized medicine based on molecular markers, protagonists, signaling networks, and effectors inherent to the Netrin axis in pathophysiological states.
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12
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Rabe Bernhardt N, Memic F, Gezelius H, Thiebes AL, Vallstedt A, Kullander K. DCC mediated axon guidance of spinal interneurons is essential for normal locomotor central pattern generator function. Dev Biol 2012; 366:279-89. [DOI: 10.1016/j.ydbio.2012.03.017] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2011] [Revised: 03/21/2012] [Accepted: 03/27/2012] [Indexed: 11/16/2022]
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13
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Wang X, Zhang W, Cheever T, Schwarz V, Opperman K, Hutter H, Koepp D, Chen L. The C. elegans L1CAM homologue LAD-2 functions as a coreceptor in MAB-20/Sema2 mediated axon guidance. ACTA ACUST UNITED AC 2008; 180:233-46. [PMID: 18195110 PMCID: PMC2213605 DOI: 10.1083/jcb.200704178] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The L1 cell adhesion molecule (L1CAM) participates in neuronal development. Mutations in the human L1 gene can cause the neurological disorder CRASH (corpus callosum hypoplasia, retardation, adducted thumbs, spastic paraplegia, and hydrocephalus). This study presents genetic data that shows that L1-like adhesion gene 2 (LAD-2), a Caenorhabditis elegans L1CAM, functions in axon pathfinding. In the SDQL neuron, LAD-2 mediates dorsal axon guidance via the secreted MAB-20/Sema2 and PLX-2 plexin receptor, the functions of which have largely been characterized in epidermal morphogenesis. We use targeted misexpression experiments to provide in vivo evidence that MAB-20/Sema2 acts as a repellent to SDQL. Coimmunoprecipitation assays reveal that MAB-20 weakly interacts with PLX-2; this interaction is increased in the presence of LAD-2, which can interact independently with MAB-20 and PLX-2. These results suggest that LAD-2 functions as a MAB-20 coreceptor to secure MAB-20 coupling to PLX-2. In vertebrates, L1 binds neuropilin1, the obligate receptor to the secreted Sema3A. However, invertebrates lack neuropilins. LAD-2 may thus function in the semaphorin complex by combining the roles of neuropilins and L1CAMs.
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Affiliation(s)
- Xuelin Wang
- Department of Genetics, Cell Biology, and Development, Developmental Biology Center, University of Minnesota, Minneapolis, MN 55455, USA
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14
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Abstract
Recent findings indicate that the embryonic motor neurons act as gatekeepers to regulate midline crossing during development of the nematode Caenorhabditis elegans. The newly identified protein WRK-1 and ephrins cooperate to prevent longitudinal axons from crossing the midline.
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Affiliation(s)
- Christopher C Quinn
- UMDNJ-Robert Wood Johnson Medical School, Department of Pathology, 675 Hoes Lane, Piscataway, New Jersey 08854-5635, USA.
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15
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Abstract
How axons in the developing nervous system successfully navigate to their correct targets is a fundamental problem in neurobiology. Understanding the mechanisms that mediate axon guidance will give important insight into how the nervous system is correctly wired during development and may have implications for therapeutic approaches to developmental brain disorders and nerve regeneration. Achieving this understanding will require unraveling the molecular logic that ensures the proper expression and localization of axon guidance cues and receptors, and elucidating the signaling events that regulate the growth cone cytoskeleton in response to guidance receptor activation. Studies of axon guidance at the midline of many experimental systems, from the ventral midline of Drosophila to the vertebrate spinal cord, have led to important mechanistic insights into the complex problem of wiring the nervous system. Here we review recent advances in understanding the regulation of midline axon guidance, with a particular emphasis on the contributions made from molecular genetic studies of invertebrate model systems.
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Affiliation(s)
- David S Garbe
- Department of Neuroscience, University of Pennsylvania, School of Medicine, Philadelphia, PA 19104, USA
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16
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Qin H, Powell-Coffman JA. The Caenorhabditis elegans aryl hydrocarbon receptor, AHR-1, regulates neuronal development. Dev Biol 2004; 270:64-75. [PMID: 15136141 DOI: 10.1016/j.ydbio.2004.02.004] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2003] [Revised: 02/11/2004] [Accepted: 02/11/2004] [Indexed: 11/24/2022]
Abstract
The mammalian aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates the toxic effects of dioxins and related compounds. Dioxins have been shown to cause a range of neurological defects, but the role of AHR during normal neuronal development is not known. Here we investigate the developmental functions of ahr-1, the Caenorhabditis elegans aryl hydrocarbon receptor homolog. We show that ahr-1:GFP is expressed in a subset of neurons, and we demonstrate that animals lacking ahr-1 function have specific defects in neuronal differentiation, as evidenced by changes in gene expression, aberrant cell migration, axon branching, or supernumerary neuronal processes. In ahr-1-deficient animals, the touch receptor neuron AVM and its sister cell, the interneuron SDQR, exhibit cell and axonal migration defects. We show that dorsal migration of SDQR is mediated by UNC-6/Netrin, SAX-3/Robo, and UNC-129/TGFbeta, and this process requires the functions of both ahr-1 and its transcription factor dimerization partner aha-1. We also document a role for ahr-1 during the differentiation of the neurons that contact the pseudocoelomic fluid. In ahr-1-deficient animals, these neurons are born but they do not express the cell-type-specific markers gcy-32:GFP and npr-1:GFP at appropriate levels. Additionally, we show that ahr-1 expression is regulated by the UNC-86 transcription factor. We propose that the AHR-1 transcriptional complex acts in combination with other intrinsic and extracellular factors to direct the differentiation of distinct neuronal subtypes. These data, when considered with the neurotoxic effects of AHR-activating pollutants, support the hypothesis that AHR has an evolutionarily conserved role in neuronal development.
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Affiliation(s)
- Hongtao Qin
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA 50011-3260, USA
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Manitt C, Kennedy TE. Where the rubber meets the road: netrin expression and function in developing and adult nervous systems. PROGRESS IN BRAIN RESEARCH 2002; 137:425-42. [PMID: 12440385 DOI: 10.1016/s0079-6123(02)37034-1] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Netrins are a family of secreted proteins that direct the migration of cells and axonal growth cones during neural development. They are bifunctional cues, attracting some cell types and repelling others. Netrins function as either short- or long-range cues, in some circumstances acting close to the surface of the cells that produce them and in other cases at a distance. Two classes of receptors mediate the response to netrin-1, the deleted in colorectal cancer family and the UNC-5 homolog family. Although netrin function has been extensively studied in the embryonic nervous system, netrin-1 is expressed in the adult mammalian spinal cord at a level similar to that in the embryonic CNS. In the adult and embryonic CNS, the majority of netrin-1 protein is not freely soluble but is associated with membranes and extracellular matrix. This distribution is consistent with netrin-1 acting as a short-range cue. Here we present a model whereby netrin-1 in the embryonic neural epithelium could act as a membrane-associated long-range cue. Netrin-1 is expressed in the adult by multiple types of neurons and by myelinating glia: oligodendrocytes in the CNS and Schwann cells in the PNS. In the white matter of the adult CNS, netrin-1 protein is absent from compact myelin but enriched in periaxonal myelin at the interface between axons and oligodendrocytes. This distribution suggests that in the adult nervous system netrin-1 may function to mediate cell-cell interactions. Furthermore, netrin receptor expression persists in neurons following injury, raising the possibility that netrin-1 may influence axonal regeneration.
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Affiliation(s)
- Colleen Manitt
- Centre for Neuronal Survival, Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, QC H3A 2B4, Canada
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18
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Yu TW, Hao JC, Lim W, Tessier-Lavigne M, Bargmann CI. Shared receptors in axon guidance: SAX-3/Robo signals via UNC-34/Enabled and a Netrin-independent UNC-40/DCC function. Nat Neurosci 2002; 5:1147-54. [PMID: 12379860 DOI: 10.1038/nn956] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2002] [Accepted: 11/09/2002] [Indexed: 11/09/2022]
Abstract
The C. elegans SAX-3/Robo receptor acts in anterior-posterior, dorsal-ventral and midline guidance decisions. Here we show that SAX-3 signaling involves the C. elegans Enabled protein UNC-34 and an unexpected Netrin-independent function of the Netrin receptor UNC-40/DCC. Genetic interactions with gain- and loss-of-function mutations suggest that unc-34 and unc-40 act together with sax-3 in several guidance decisions, but the C. elegans Netrin gene unc-6 does not act in the same genetic pathways. Within the migrating axon, sax-3, unc-34 and unc-40 all act cell-autonomously. Our results support a role for UNC-34/Enabled proteins in SAX-3-mediated repulsion, and show that UNC-40/DCC can potentiate SAX-3/Robo signaling via a mechanism that may involve direct binding of the two guidance receptors. A combinatorial logic dictates alternative functions for UNC-40/DCC, which can act in attraction to UNC-6/Netrin, repulsion from Netrin (with UNC-5), or repulsion from Slit (with SAX-3).
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Affiliation(s)
- Timothy W Yu
- Howard Hughes Medical Institute, Program in Neuroscience, Department of Anatomy and of Biochemistry and Biophysics, The University of California, San Francisco, California 94143, USA
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Kindt KS, Tam T, Whiteman S, Schafer WR. Serotonin promotes G(o)-dependent neuronal migration in Caenorhabditis elegans. Curr Biol 2002; 12:1738-47. [PMID: 12401168 DOI: 10.1016/s0960-9822(02)01199-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
BACKGROUND The directed migration of neurons during development requires attractive and repulsive cues that control the direction of migration as well as permissive cues that potentiate cell motility and responsiveness to guidance molecules. RESULTS Here, we show that the neurotransmitter serotonin functions as a permissive signal for embryonic and postembryonic neuronal migration in the nematode C. elegans. In serotonin-deficient mutants, the migrations of the ALM, BDU, SDQR, and AVM neurons were often foreshortened or misdirected, indicating a serotonin requirement for normal migration. Moreover, exogenous serotonin could restore motility to AVM neurons in serotonin-deficient mutants as well as induce AVM-like migrations in the normally nonmotile neuron PVM; this indicates that serotonin was functioning as a permissive cue to enable neuronal motility. The migration defects of serotonin-deficient mutants were mimicked by ablations of serotonergic neuroendocrine cells, implicating humoral release of serotonin in these processes. Mutants defective in G(q) and G(o) signaling, or in N-type voltage-gated calcium channels, showed migration phenotypes similar to serotonin-deficient mutants, and these molecules appeared to genetically function downstream of serotonin in the control of neuronal migration. CONCLUSIONS Thus, serotonin is important for promoting directed neuronal migration in the developing C. elegans nervous system. We hypothesize that serotonin may promote cell motility through G protein-dependent modulation of voltage-gated calcium channels in the migrating cell.
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Affiliation(s)
- Katie S Kindt
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0349, USA
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20
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Wadsworth WG. Moving around in a worm: netrin UNC-6 and circumferential axon guidance in C. elegans. Trends Neurosci 2002; 25:423-9. [PMID: 12127760 DOI: 10.1016/s0166-2236(02)02206-3] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
How does an extracellular guidance molecule direct multiple growth cones to different positions? The answer is important for understanding the development of complex neural connections. UNC-6 is a member of the netrin family of guidance proteins. It has phylogenetically conserved domains that mediate its different guidance and branching activities. In the Caenorhabditis elegans embryo, UNC-6 is secreted ventrally and a pattern of circumferential axon tracts develops as pioneer growth cones bearing UNC-5 and UNC-40 receptors are directed towards, or away from, the ventral sources. Following the first migrations, UNC-6 from additional sources allows more complex migration patterns to emerge. In addition, at specific dorsoventral positions, locally restricted extracellular molecules alter growth cone responses to UNC-6, causing circumferentially migrating growth cones to turn and longitudinal nerves to develop. These observations show that extracellular guidance molecules can direct complex arrangements of migrating growth cones in vivo by eliciting different types of responses, by spatially and temporally regulating their expression and by working in concert with other extracellular molecules.
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Affiliation(s)
- William G Wadsworth
- Department of Pathology, Robert Wood Johnson Medical School, 675 Hoes Lane West, Piscataway, NJ 08854-5635, USA.
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Honigberg L, Kenyon C. Establishment of left/right asymmetry in neuroblast migration by UNC-40/DCC, UNC-73/Trio and DPY-19 proteins in C. elegans. Development 2000; 127:4655-68. [PMID: 11023868 DOI: 10.1242/dev.127.21.4655] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The bilateral C. elegans neuroblasts QL and QR are born in the same anterior/posterior (A/P) position, but polarize and migrate left/right asymmetrically: QL migrates toward the posterior and QR migrates toward the anterior. After their migrations, QL but not QR switches on the Hox gene mab-5. We find that the UNC-40/netrin receptor and a novel transmembrane protein DPY-19 are required to orient these cells correctly. In unc-40 or dpy-19 mutants, the Q cells polarize randomly; in fact, an individual Q cell polarizes in multiple directions over time. In addition, either cell can express MAB-5. Both UNC-40 and DPY-19, as well as the Trio/GTPase exchange factor homolog UNC-73, are required for full polarization and migration. Thus, these proteins appear to participate in a signaling system that orients and polarizes these migrating cells in a left/right asymmetrical fashion during development. The C. elegans netrin UNC-6, which guides many cells and axons along the dorsoventral axis, is not involved in Q cell polarization, suggesting that a different netrin-like ligand serves to polarize these cells along the anteroposterior axis.
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Affiliation(s)
- L Honigberg
- Program in Neuroscience and Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143-0448, USA
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22
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Koch M, Murrell JR, Hunter DD, Olson PF, Jin W, Keene DR, Brunken WJ, Burgeson RE. A novel member of the netrin family, beta-netrin, shares homology with the beta chain of laminin: identification, expression, and functional characterization. J Cell Biol 2000; 151:221-34. [PMID: 11038171 PMCID: PMC2192657 DOI: 10.1083/jcb.151.2.221] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The netrins are a family of laminin-related molecules. Here, we characterize a new member of the family, beta-netrin. beta-Netrin is homologous to the NH(2) terminus of laminin chain short arms; it contains a laminin-like domain VI and 3.5 laminin EGF repeats and a netrin C domain. Unlike other netrins, this new netrin is more related to the laminin beta chains, thus, its name beta-netrin. An initial analysis of the tissue distribution revealed that kidney, heart, ovary, retina, and the olfactory bulb were tissues of high expression. We have expressed the molecule in a eukaryotic cell expression system and made antibodies to the expressed product. Both in situ hybridization and immunohistochemistry were used to describe the cellular source of beta-netrin and where beta-netrin is deposited. beta-Netrin is a basement membrane component; it is present in the basement membranes of the vasculature, kidney, and ovaries. In addition, beta-netrin is expressed in a limited set of fiber tracts within the brain, including the lateral olfactory tract and the vomeronasal nerve. Functional studies were performed and show that beta-netrin promotes neurite elongation from olfactory bulb explants. Together, these data suggest that beta-netrin is important in neural, kidney, and vascular development.
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Affiliation(s)
- M Koch
- Cutaneous Biology Research Center, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, USA
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Nash B, Colavita A, Zheng H, Roy PJ, Culotti JG. The forkhead transcription factor UNC-130 is required for the graded spatial expression of the UNC-129 TGF-beta guidance factor in C. elegans. Genes Dev 2000; 14:2486-500. [PMID: 11018016 PMCID: PMC316974 DOI: 10.1101/gad.831500] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Secreted proteins required for cellular movements along the circumference of the body wall in Caenorhabditis elegans include UNC-6/netrin and the novel TGF-beta UNC-129. Expression of these proteins is graded along the dorsoventral (D/V) axis, providing polarity information to guide migrations. Here we show that the graded expression of UNC-129 in dorsal but not ventral body muscles depends on unc-130, which encodes a Forkhead transcription factor. The phenotype of unc-130 mutants closely mimics the reported effects of ectopically expressing unc-129 in both dorsal and ventral body muscles (). This fits our present finding that unc-130 cell autonomously represses unc-129 expression in the ventral body muscles. Thus the cell-specific effects of unc-130 on ventral, but not dorsal, body muscle expression of unc-129 accounts for the D/V polarity information required for UNC-129-mediated guidance. Genetic interactions between unc-130 and other guidance genes show that several molecular pathways function in parallel to guide the ventral to dorsal migration of distal tip cells (DTCs) and axonal growth cones in C. elegans. Genetic interactions confirm that UNC-129 does not require the only known type II TGF-beta receptor in C. elegans (DAF-4) for its guidance functions. Also, unc-130 is partially required for male tail morphogenesis and for embryogenesis.
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Affiliation(s)
- B Nash
- Department of Molecular and Medical Genetics, University of Toronto, Toronto M5S 1A8, Canada
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Tam T, Mathews E, Snutch TP, Schafer WR. Voltage-gated calcium channels direct neuronal migration in Caenorhabditis elegans. Dev Biol 2000; 226:104-17. [PMID: 10993677 DOI: 10.1006/dbio.2000.9854] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Calcium signaling is known to be important for regulating the guidance of migrating neurons, yet the molecular mechanisms underlying this process are not well understood. We have found that two different voltage-gated calcium channels are important for the accurate guidance of postembryonic neuronal migrations in the nematode Caenorhabditis elegans. In mutants carrying loss-of-function alleles of the calcium channel gene unc-2, the touch receptor neuron AVM and the interneuron SDQR often migrated inappropriately, leading to misplacement of their cell bodies. However, the AVM neurons in unc-2 mutant animals extended axons in a wild-type pattern, suggesting that the UNC-2 calcium channel specifically directs migration of the neuronal cell body and is not required for axonal pathfinding. In contrast, mutations in egl-19, which affect a different voltage-gated calcium channel, affected the migration of the AVM and SDQR bodies, as well as the guidance of the AVM axon. Thus, cell migration and axonal pathfinding in the AVM neurons appear to involve distinct calcium channel subtypes. Mutants defective in the unc-43/CaM kinase gene showed a defect in SDQR and AVM positioning that resembled that of unc-2 mutants; thus, CaM kinase may function as an effector of the UNC-2-mediated calcium influx in guiding cell migration.
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Affiliation(s)
- T Tam
- Department of Biology, University of California at San Diego, La Jolla, California 92093-0349, USA
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25
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Abstract
Basement membranes can help determine pathways of migrating axons. Although members of the nidogen (entactin) protein family are structural components of basement membranes, we find that nidogen is not required for basement membrane assembly in the nematode Caenorhabditis elegans. Nidogen is localized to body wall basement membranes and is required to direct longitudinal nerves dorsoventrally and to direct axons at the midlines. By examining migration of a single axon in vivo, we show that nidogen is required for the axon to switch from circumferential to longitudinal migration. Specialized basement membranes may thus regulate nerve position.
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Affiliation(s)
- S Kim
- Department of Pathology, Robert Wood Johnson Medical School, Piscataway, NJ 08854-5635, USA
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