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Heiman MG, Bülow HE. Dendrite morphogenesis in Caenorhabditis elegans. Genetics 2024; 227:iyae056. [PMID: 38785371 PMCID: PMC11151937 DOI: 10.1093/genetics/iyae056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 04/02/2024] [Indexed: 05/25/2024] Open
Abstract
Since the days of Ramón y Cajal, the vast diversity of neuronal and particularly dendrite morphology has been used to catalog neurons into different classes. Dendrite morphology varies greatly and reflects the different functions performed by different types of neurons. Significant progress has been made in our understanding of how dendrites form and the molecular factors and forces that shape these often elaborately sculpted structures. Here, we review work in the nematode Caenorhabditis elegans that has shed light on the developmental mechanisms that mediate dendrite morphogenesis with a focus on studies investigating ciliated sensory neurons and the highly elaborated dendritic trees of somatosensory neurons. These studies, which combine time-lapse imaging, genetics, and biochemistry, reveal an intricate network of factors that function both intrinsically in dendrites and extrinsically from surrounding tissues. Therefore, dendrite morphogenesis is the result of multiple tissue interactions, which ultimately determine the shape of dendritic arbors.
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Affiliation(s)
- Maxwell G Heiman
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, USA
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Hannes E Bülow
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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2
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Yadav DK, Chang AC, Grooms NWF, Chung SH, Gabel CV. O-GlcNAc signaling increases neuron regeneration through one-carbon metabolism in Caenorhabditis elegans. eLife 2024; 13:e86478. [PMID: 38334260 PMCID: PMC10857789 DOI: 10.7554/elife.86478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Accepted: 11/17/2023] [Indexed: 02/10/2024] Open
Abstract
Cellular metabolism plays an essential role in the regrowth and regeneration of a neuron following physical injury. Yet, our knowledge of the specific metabolic pathways that are beneficial to neuron regeneration remains sparse. Previously, we have shown that modulation of O-linked β-N-acetylglucosamine (O-GlcNAc) signaling, a ubiquitous post-translational modification that acts as a cellular nutrient sensor, can significantly enhance in vivo neuron regeneration. Here, we define the specific metabolic pathway by which O-GlcNAc transferase (ogt-1) loss of function mediates increased regenerative outgrowth. Performing in vivo laser axotomy and measuring subsequent regeneration of individual neurons in C. elegans, we find that glycolysis, serine synthesis pathway (SSP), one-carbon metabolism (OCM), and the downstream transsulfuration metabolic pathway (TSP) are all essential in this process. The regenerative effects of ogt-1 mutation are abrogated by genetic and/or pharmacological disruption of OCM and the SSP linking OCM to glycolysis. Testing downstream branches of this pathway, we find that enhanced regeneration is dependent only on the vitamin B12 independent shunt pathway. These results are further supported by RNA sequencing that reveals dramatic transcriptional changes by the ogt-1 mutation, in the genes involved in glycolysis, OCM, TSP, and ATP metabolism. Strikingly, the beneficial effects of the ogt-1 mutation can be recapitulated by simple metabolic supplementation of the OCM metabolite methionine in wild-type animals. Taken together, these data unearth the metabolic pathways involved in the increased regenerative capacity of a damaged neuron in ogt-1 animals and highlight the therapeutic possibilities of OCM and its related pathways in the treatment of neuronal injury.
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Affiliation(s)
- Dilip Kumar Yadav
- Department of Pharmacology, Physiology and Biophysics, Chobanian & Avedisian School of Medicine, Boston UniversityBostonUnited States
| | - Andrew C Chang
- Department of Pharmacology, Physiology and Biophysics, Chobanian & Avedisian School of Medicine, Boston UniversityBostonUnited States
| | - Noa WF Grooms
- Department of Bioengineering, Northeastern UniversityBostonUnited States
| | - Samuel H Chung
- Department of Bioengineering, Northeastern UniversityBostonUnited States
| | - Christopher V Gabel
- Department of Pharmacology, Physiology and Biophysics, Chobanian & Avedisian School of Medicine, Boston UniversityBostonUnited States
- Neurophotonics Center, Boston UniversityBostonUnited States
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3
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Sun J, Noss S, Banerjee D, Das M, Girirajan S. Strategies for dissecting the complexity of neurodevelopmental disorders. Trends Genet 2024; 40:187-202. [PMID: 37949722 PMCID: PMC10872993 DOI: 10.1016/j.tig.2023.10.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 09/20/2023] [Accepted: 10/16/2023] [Indexed: 11/12/2023]
Abstract
Neurodevelopmental disorders (NDDs) are associated with a wide range of clinical features, affecting multiple pathways involved in brain development and function. Recent advances in high-throughput sequencing have unveiled numerous genetic variants associated with NDDs, which further contribute to disease complexity and make it challenging to infer disease causation and underlying mechanisms. Herein, we review current strategies for dissecting the complexity of NDDs using model organisms, induced pluripotent stem cells, single-cell sequencing technologies, and massively parallel reporter assays. We further highlight single-cell CRISPR-based screening techniques that allow genomic investigation of cellular transcriptomes with high efficiency, accuracy, and throughput. Overall, we provide an integrated review of experimental approaches that can be applicable for investigating a broad range of complex disorders.
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Affiliation(s)
- Jiawan Sun
- Molecular, Cellular, and Integrative Biosciences Graduate Program, The Huck Institutes of Life Sciences, University Park, PA 16802, USA
| | - Serena Noss
- Molecular, Cellular, and Integrative Biosciences Graduate Program, The Huck Institutes of Life Sciences, University Park, PA 16802, USA
| | - Deepro Banerjee
- Bioinformatics and Genomics Graduate Program, The Huck Institutes of Life Sciences, University Park, PA 16802, USA
| | - Maitreya Das
- Molecular, Cellular, and Integrative Biosciences Graduate Program, The Huck Institutes of Life Sciences, University Park, PA 16802, USA
| | - Santhosh Girirajan
- Molecular, Cellular, and Integrative Biosciences Graduate Program, The Huck Institutes of Life Sciences, University Park, PA 16802, USA; Bioinformatics and Genomics Graduate Program, The Huck Institutes of Life Sciences, University Park, PA 16802, USA; Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA; Department of Anthropology, Pennsylvania State University, University Park, PA 16802, USA.
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4
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Li Y, Chen S, Liu W, Zhao D, Gao Y, Hu S, Liu H, Li Y, Qu L, Liu X. A full-body transcription factor expression atlas with completely resolved cell identities in C. elegans. Nat Commun 2024; 15:358. [PMID: 38195740 PMCID: PMC10776613 DOI: 10.1038/s41467-023-42677-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 10/18/2023] [Indexed: 01/11/2024] Open
Abstract
Invariant cell lineage in C. elegans enables spatiotemporal resolution of transcriptional regulatory mechanisms controlling the fate of each cell. Here, we develop RAPCAT (Robust-point-matching- And Piecewise-affine-based Cell Annotation Tool) to automate cell identity assignment in three-dimensional image stacks of L1 larvae and profile reporter expression of 620 transcription factors in every cell. Transcription factor profile-based clustering analysis defines 80 cell types distinct from conventional phenotypic cell types and identifies three general phenotypic modalities related to these classifications. First, transcription factors are broadly downregulated in quiescent stage Hermaphrodite Specific Neurons, suggesting stage- and cell type-specific variation in transcriptome size. Second, transcription factor expression is more closely associated with morphology than other phenotypic modalities in different pre- and post-differentiation developmental stages. Finally, embryonic cell lineages can be associated with specific transcription factor expression patterns and functions that persist throughout postembryonic life. This study presents a comprehensive transcription factor atlas for investigation of intra-cell type heterogeneity.
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Affiliation(s)
- Yongbin Li
- College of Life Sciences, Capital Normal University, Beijing, 100048, China
| | - Siyu Chen
- School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Weihong Liu
- School of Life Sciences, Tsinghua University, Beijing, 100084, China
- Intelligent Perception Lab, Hanwang Technology Co., Ltd, Beijing, 100193, China
| | - Di Zhao
- School of Life Sciences, Tsinghua University, Beijing, 100084, China
- Tianjin Key Laboratory of Exercise Physiology and Sports Medicine, Institute of Sport, Exercise & Health, Tianjin University of Sport, Tianjin, 300381, China
| | - Yimeng Gao
- College of Life Sciences, Capital Normal University, Beijing, 100048, China
| | - Shipeng Hu
- College of Life Sciences, Capital Normal University, Beijing, 100048, China
| | - Hanyu Liu
- College of Life Sciences, Capital Normal University, Beijing, 100048, China
| | - Yuanyuan Li
- Ministry of Education Key Laboratory of Intelligent Computation & Signal Processing, Information Materials and Intelligent Sensing Laboratory of Anhui Province, School of Electronics and Information Engineering, Anhui University, Hefei, 230039, China
| | - Lei Qu
- Ministry of Education Key Laboratory of Intelligent Computation & Signal Processing, Information Materials and Intelligent Sensing Laboratory of Anhui Province, School of Electronics and Information Engineering, Anhui University, Hefei, 230039, China
| | - Xiao Liu
- College of Life Sciences, Capital Normal University, Beijing, 100048, China.
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5
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Puri D, Sharma S, Samaddar S, Ravivarma S, Banerjee S, Ghosh-Roy A. Muscleblind-1 interacts with tubulin mRNAs to regulate the microtubule cytoskeleton in C. elegans mechanosensory neurons. PLoS Genet 2023; 19:e1010885. [PMID: 37603562 PMCID: PMC10470942 DOI: 10.1371/journal.pgen.1010885] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 08/31/2023] [Accepted: 07/26/2023] [Indexed: 08/23/2023] Open
Abstract
Regulation of the microtubule cytoskeleton is crucial for the development and maintenance of neuronal architecture, and recent studies have highlighted the significance of regulated RNA processing in the establishment and maintenance of neural circuits. In a genetic screen conducted using mechanosensory neurons of C. elegans, we identified a mutation in muscleblind-1/mbl-1 as a suppressor of loss of kinesin-13 family microtubule destabilizing factor klp-7. Muscleblind-1(MBL-1) is an RNA-binding protein that regulates the splicing, localization, and stability of RNA. Our findings demonstrate that mbl-1 is required cell-autonomously for axon growth and proper synapse positioning in the posterior lateral microtubule (PLM) neuron. Loss of mbl-1 leads to increased microtubule dynamics and mixed orientation of microtubules in the anterior neurite of PLM. These defects are also accompanied by abnormal axonal transport of the synaptic protein RAB-3 and reduction of gentle touch sensation in mbl-1 mutant. Our data also revealed that mbl-1 is genetically epistatic to mec-7 (β tubulin) and mec-12 (α tubulin) in regulating axon growth. Furthermore, mbl-1 is epistatic to sad-1, an ortholog of BRSK/Brain specific-serine/threonine kinase and a known regulator of synaptic machinery, for synapse formation at the correct location of the PLM neurite. Notably, the immunoprecipitation of MBL-1 resulted in the co-purification of mec-7, mec-12, and sad-1 mRNAs, suggesting a direct interaction between MBL-1 and these transcripts. Additionally, mbl-1 mutants exhibited reduced levels and stability of mec-7 and mec-12 transcripts. Our study establishes a previously unknown link between RNA-binding proteins and cytoskeletal machinery, highlighting their crucial roles in the development and maintenance of the nervous system.
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Affiliation(s)
- Dharmendra Puri
- National Brain Research Centre, Manesar, Gurgaon, Haryana, India
| | - Sunanda Sharma
- National Brain Research Centre, Manesar, Gurgaon, Haryana, India
| | - Sarbani Samaddar
- National Brain Research Centre, Manesar, Gurgaon, Haryana, India
| | - Sruthy Ravivarma
- National Brain Research Centre, Manesar, Gurgaon, Haryana, India
| | - Sourav Banerjee
- National Brain Research Centre, Manesar, Gurgaon, Haryana, India
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Li Z, Fouad AD, Bowlin PD, Fan Y, He S, Chang MC, Du A, Teng C, Kassouni A, Ji H, Raizen DM, Fang-Yen C. A robotic system for automated genetic manipulation and analysis of Caenorhabditis elegans. PNAS NEXUS 2023; 2:pgad197. [PMID: 37416871 PMCID: PMC10321491 DOI: 10.1093/pnasnexus/pgad197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 04/04/2023] [Accepted: 06/06/2023] [Indexed: 07/08/2023]
Abstract
The nematode Caenorhabditis elegans is one of the most widely studied organisms in biology due to its small size, rapid life cycle, and manipulable genetics. Research with C. elegans depends on labor-intensive and time-consuming manual procedures, imposing a major bottleneck for many studies, especially for those involving large numbers of animals. Here, we describe a general-purpose tool, WormPicker, a robotic system capable of performing complex genetic manipulations and other tasks by imaging, phenotyping, and transferring C. elegans on standard agar media. Our system uses a motorized stage to move an imaging system and a robotic arm over an array of agar plates. Machine vision tools identify animals and assay developmental stage, morphology, sex, expression of fluorescent reporters, and other phenotypes. Based on the results of these assays, the robotic arm selectively transfers individual animals using an electrically self-sterilized wire loop, with the aid of machine vision and electrical capacitance sensing. Automated C. elegans manipulation shows reliability and throughput comparable with standard manual methods. We developed software to enable the system to autonomously carry out complex protocols. To validate the effectiveness and versatility of our methods, we used the system to perform a collection of common C. elegans procedures, including genetic crossing, genetic mapping, and genomic integration of a transgene. Our robotic system will accelerate C. elegans research and open possibilities for performing genetic and pharmacological screens that would be impractical using manual methods.
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Affiliation(s)
- Zihao Li
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Anthony D Fouad
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Peter D Bowlin
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Yuying Fan
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Siming He
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Meng-Chuan Chang
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Angelica Du
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Christopher Teng
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Alexander Kassouni
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Hongfei Ji
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - David M Raizen
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Christopher Fang-Yen
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH 43210, USA
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7
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Cook SJ, Kalinski CA, Hobert O. Neuronal contact predicts connectivity in the C. elegans brain. Curr Biol 2023:S0960-9822(23)00553-5. [PMID: 37236179 DOI: 10.1016/j.cub.2023.04.071] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Revised: 01/26/2023] [Accepted: 04/27/2023] [Indexed: 05/28/2023]
Abstract
Axons must project to particular brain regions, contact adjacent neurons, and choose appropriate synaptic targets to form a nervous system. Multiple mechanisms have been proposed to explain synaptic partnership choice. In a "lock-and-key" mechanism, first proposed by Sperry's chemoaffinity model,1 a neuron selectively chooses a synaptic partner among several different, adjacent target cells, based on a specific molecular recognition code.2 Alternatively, Peters' rule posits that neurons indiscriminately form connections with other neuron types in their proximity; hence, neighborhood choice, determined by initial neuronal process outgrowth and position, is the main predictor of connectivity.3,4 However, whether Peters' rule plays an important role in synaptic wiring remains unresolved.5 To assess the nanoscale relationship between neuronal adjacency and connectivity, we evaluate the expansive set of C. elegans connectomes. We find that synaptic specificity can be accurately modeled as a process mediated by a neurite adjacency threshold and brain strata, offering strong support for Peters' rule as an organizational principle of C. elegans brain wiring.
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Affiliation(s)
- Steven J Cook
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY, USA.
| | - Cristine A Kalinski
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY, USA
| | - Oliver Hobert
- Department of Biological Sciences, Howard Hughes Medical Institute, Columbia University, New York, NY, USA.
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8
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Janssen R, Budd GE. Expression of netrin and its receptors uncoordinated-5 and frazzled in arthropods and onychophorans suggests conserved and diverged functions in neuronal pathfinding and synaptogenesis. Dev Dyn 2023; 252:172-185. [PMID: 35112412 DOI: 10.1002/dvdy.459] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2021] [Revised: 01/30/2022] [Accepted: 01/30/2022] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Development of the nervous system and the correct connection of nerve cells require coordinated axonal pathfinding through an extracellular matrix. Outgrowing axons exhibit directional growth toward or away from external guidance cues such as Netrin. Guidance cues can be detected by growth cones that are located at the end of growing axons through membrane-bound receptors such as Uncoordianted-5 and Frazzled. Binding of Netrin causes reformation of the cytoskeleton and growth of the axon toward (or away from) the source of Netrin production. RESULTS Here, we investigate the embryonic mRNA expression patterns of netrin genes and their potential receptors, uncoordinated-5 and frazzled in arthropod species that cover all main branches of Arthropoda, that is, Pancrustacea, Myriapoda, and Chelicerata. We also studied the expression patterns in a closely related outgroup species, the onychophoran Euperipatoides kanangrensis, and provide data on expression profiles of these genes in larval tissues of the fly Drosophila melanogaster including the brain and the imaginal disks. CONCLUSION Our data reveal conserved and diverged aspects of neuronal guidance in Drosophila with respect to the other investigated species and suggest a conserved function in nervous system patterning of the developing appendages.
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Affiliation(s)
- Ralf Janssen
- Department of Earth Sciences, Palaeobiology, Uppsala University, Uppsala, Sweden
| | - Graham E Budd
- Department of Earth Sciences, Palaeobiology, Uppsala University, Uppsala, Sweden
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Kokan N, Witt S, Sandhu S, Hutter H. lron-11 guides axons in the ventral nerve cord of Caenorhabditis elegans. PLoS One 2022; 17:e0278258. [PMID: 36449480 PMCID: PMC9710760 DOI: 10.1371/journal.pone.0278258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 11/13/2022] [Indexed: 12/02/2022] Open
Abstract
For the nervous system to develop properly, neurons must connect in a precise way to form functional networks. This requires that outgrowing neuronal processes (axons) navigate to their target areas, where they establish proper synaptic connections. The molecular basis of this navigation process is not firmly understood. A candidate family containing putative receptors acting in various aspects of neuronal development including axon navigation are transmembrane proteins of the extracellular Leucine-Rich Repeat family (eLRRs). We systematically tested members of this family in C. elegans for a role in axon navigation in the ventral nerve cord (VNC). We found that lron-11 mutants showed VNC navigation defects in several classes of neurons, including a pioneer neuron and various classes of interneurons and motoneurons. This suggests that while most members of the lron-family do not seem to have a role in axon navigation in the VNC, lron-11 is likely to be a receptor required for correct navigation of axons in the VNC of C. elegans.
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Affiliation(s)
- Nikolas Kokan
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
| | - Skyla Witt
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
| | - Saru Sandhu
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
| | - Harald Hutter
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
- * E-mail:
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Lauziere A, Christensen R, Shroff H, Balan R. An Exact Hypergraph Matching algorithm for posture identification in embryonic C. elegans. PLoS One 2022; 17:e0277343. [PMID: 36445888 PMCID: PMC9707761 DOI: 10.1371/journal.pone.0277343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 10/25/2022] [Indexed: 12/03/2022] Open
Abstract
The nematode Caenorhabditis elegans (C. elegans) is a model organism used frequently in developmental biology and neurobiology [White, (1986), Sulston, (1983), Chisholm, (2016) and Rapti, (2020)]. The C. elegans embryo can be used for cell tracking studies to understand how cell movement drives the development of specific embryonic tissues. Analyses in late-stage development are complicated by bouts of rapid twitching motions which invalidate traditional cell tracking approaches. However, the embryo possesses a small set of cells which may be identified, thereby defining the coiled embryo's posture [Christensen, 2015]. The posture serves as a frame of reference, facilitating cell tracking even in the presence of twitching. Posture identification is nevertheless challenging due to the complete repositioning of the embryo between sampled images. Current approaches to posture identification rely on time-consuming manual efforts by trained users which limits the efficiency of subsequent cell tracking. Here, we cast posture identification as a point-set matching task in which coordinates of seam cell nuclei are identified to jointly recover the posture. Most point-set matching methods comprise coherent point transformations that use low order objective functions [Zhou, (2016) and Zhang, (2019)]. Hypergraphs, an extension of traditional graphs, allow more intricate modeling of relationships between objects, yet existing hypergraphical point-set matching methods are limited to heuristic algorithms which do not easily scale to handle higher degree hypergraphs [Duchenne, (2010), Chertok, (2010) and Lee, (2011)]. Our algorithm, Exact Hypergraph Matching (EHGM), adapts the classical branch-and-bound paradigm to dynamically identify a globally optimal correspondence between point-sets under an arbitrarily intricate hypergraphical model. EHGM with hypergraphical models inspired by C. elegans embryo shape identified posture more accurately (56%) than established point-set matching methods (27%), correctly identifying twice as many sampled postures as a leading graphical approach. Posterior region seeding empowered EHGM to correctly identify 78% of postures while reducing runtime, demonstrating the efficacy of the method on a cutting-edge problem in developmental biology.
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Affiliation(s)
- Andrew Lauziere
- Department of Mathematics, University of Maryland, College Park, MD, United States of America
- Laboratory of High Resolution Optical Imaging, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, United States of America
- * E-mail:
| | - Ryan Christensen
- Laboratory of High Resolution Optical Imaging, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, United States of America
| | - Hari Shroff
- Laboratory of High Resolution Optical Imaging, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, United States of America
| | - Radu Balan
- Department of Mathematics, University of Maryland, College Park, MD, United States of America
- Center for Scientific Computation and Mathematical Modeling (CSCAMM), University of Maryland, College Park, MD, United States of America
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11
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Miranda-Negrón Y, García-Arrarás JE. Radial glia and radial glia-like cells: Their role in neurogenesis and regeneration. Front Neurosci 2022; 16:1006037. [PMID: 36466166 PMCID: PMC9708897 DOI: 10.3389/fnins.2022.1006037] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 10/21/2022] [Indexed: 01/25/2024] Open
Abstract
Radial glia is a cell type traditionally associated with the developing nervous system, particularly with the formation of cortical layers in the mammalian brain. Nonetheless, some of these cells, or closely related types, called radial glia-like cells are found in adult central nervous system structures, functioning as neurogenic progenitors in normal homeostatic maintenance and in response to injury. The heterogeneity of radial glia-like cells is nowadays being probed with molecular tools, primarily by the expression of specific genes that define cell types. Similar markers have identified radial glia-like cells in the nervous system of non-vertebrate organisms. In this review, we focus on adult radial glia-like cells in neurogenic processes during homeostasis and in response to injury. We highlight our results using a non-vertebrate model system, the echinoderm Holothuria glaberrima where we have described a radial glia-like cell that plays a prominent role in the regeneration of the holothurian central nervous system.
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Affiliation(s)
| | - José E. García-Arrarás
- Department of Biology, College of Natural Sciences, University of Puerto Rico, San Juan, Puerto Rico
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12
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Harreguy MB, Tanvir Z, Shah E, Simprevil B, Tran TS, Haspel G. Semaphorin signaling restricts neuronal regeneration in C. elegans. Front Cell Dev Biol 2022; 10:814160. [PMID: 36325362 PMCID: PMC9618706 DOI: 10.3389/fcell.2022.814160] [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: 11/12/2021] [Accepted: 09/23/2022] [Indexed: 11/13/2022] Open
Abstract
Extracellular signaling proteins serve as neuronal growth cone guidance molecules during development and are well positioned to be involved in neuronal regeneration and recovery from injury. Semaphorins and their receptors, the plexins, are a family of conserved proteins involved in development that, in the nervous system, are axonal guidance cues mediating axon pathfinding and synapse formation. The Caenorhabditis elegans genome encodes for three semaphorins and two plexin receptors: the transmembrane semaphorins, SMP-1 and SMP-2, signal through their receptor, PLX-1, while the secreted semaphorin, MAB-20, signals through PLX-2. Here, we evaluate the locomotion behavior of knockout animals missing each of the semaphorins and plexins and the neuronal morphology of plexin knockout animals; we described the cellular expression pattern of the promoters of all plexins in the nervous system of C. elegans; and we evaluated their effect on the regrowth and reconnection of motoneuron neurites and the recovery of locomotion behavior following precise laser microsurgery. Regrowth and reconnection were more prevalent in the absence of each plexin, while recovery of locomotion surpassed regeneration in all genotypes.
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Affiliation(s)
- Maria B Harreguy
- New Jersey Institute of Technology, Department of Biological Sciences, Newark, NJ, United States
- Rutgers University, Department of Biological Sciences, Newark, NJ, United States
| | - Zainab Tanvir
- New Jersey Institute of Technology, Department of Biological Sciences, Newark, NJ, United States
- Rutgers University, Department of Biological Sciences, Newark, NJ, United States
| | - Esha Shah
- New Jersey Institute of Technology, Department of Biological Sciences, Newark, NJ, United States
| | - Blandine Simprevil
- New Jersey Institute of Technology, Department of Biological Sciences, Newark, NJ, United States
- City College of New York (CUNY), New York, NY, United States
| | - Tracy S Tran
- New Jersey Institute of Technology, Department of Biological Sciences, Newark, NJ, United States
- Rutgers University, Department of Biological Sciences, Newark, NJ, United States
| | - Gal Haspel
- New Jersey Institute of Technology, Department of Biological Sciences, Newark, NJ, United States
- Rutgers University, Department of Biological Sciences, Newark, NJ, United States
- Mercer University School of Medicine, Department of Biomedical Sciences, Columbus, GA, United States
- *Correspondence: Gal Haspel, ,
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13
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Godini R, Fallahi H, Pocock R. The regulatory landscape of neurite development in Caenorhabditis elegans. Front Mol Neurosci 2022; 15:974208. [PMID: 36090252 PMCID: PMC9453034 DOI: 10.3389/fnmol.2022.974208] [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: 06/20/2022] [Accepted: 07/26/2022] [Indexed: 11/18/2022] Open
Abstract
Neuronal communication requires precise connectivity of neurite projections (axons and dendrites). Developing neurites express cell-surface receptors that interpret extracellular cues to enable correct guidance toward, and connection with, target cells. Spatiotemporal regulation of neurite guidance molecule expression by transcription factors (TFs) is critical for nervous system development and function. Here, we review how neurite development is regulated by TFs in the Caenorhabditis elegans nervous system. By collecting publicly available transcriptome and ChIP-sequencing data, we reveal gene expression dynamics during neurite development, providing insight into transcriptional mechanisms governing construction of the nervous system architecture.
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Affiliation(s)
- Rasoul Godini
- Development and Stem Cells Program, Department of Anatomy and Developmental Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
- *Correspondence: Rasoul Godini,
| | - Hossein Fallahi
- Department of Biology, School of Sciences, Razi University, Kermanshah, Iran
| | - Roger Pocock
- Development and Stem Cells Program, Department of Anatomy and Developmental Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
- Roger Pocock,
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14
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Hansen J, Siddiq MM, Yadaw AS, Tolentino RE, Rabinovich V, Jayaraman G, Jain MR, Liu T, Li H, Xiong Y, Goldfarb J, Iyengar R. Whole cell response to receptor stimulation involves many deep and distributed subcellular biochemical processes. J Biol Chem 2022; 298:102325. [PMID: 35926710 PMCID: PMC9520007 DOI: 10.1016/j.jbc.2022.102325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 07/26/2022] [Accepted: 07/27/2022] [Indexed: 11/28/2022] Open
Abstract
Neurite outgrowth is an integrated whole cell response triggered by the cannabinoid-1 receptor. We sought to identify the many different biochemical pathways that contribute to this whole cell response. To understand underlying mechanisms, we identified subcellular processes (SCPs) composed of one or more biochemical pathways and their interactions required for this response. Differentially expressed genes and proteins were obtained from bulk transcriptomics and proteomic analysis of extracts from cells stimulated with a cannabinoid-1 receptor agonist. We used these differentially expressed genes and proteins to build networks of interacting SCPs by combining the expression data with prior pathway knowledge. From these SCP networks, we identified additional genes that when ablated, experimentally validated the SCP involvement in neurite outgrowth. Our experiments and informatics modeling allowed us to identify diverse SCPs such as those involved in pyrimidine metabolism, lipid biosynthesis, and mRNA splicing and stability, along with more predictable SCPs such as membrane vesicle transport and microtubule dynamics. We find that SCPs required for neurite outgrowth are widely distributed among many biochemical pathways required for constitutive cellular functions, several of which are termed ‘deep’, since they are distal to signaling pathways and the key SCPs directly involved in extension of the neurite. In contrast, ‘proximal’ SCPs are involved in microtubule growth and membrane vesicle transport dynamics required for neurite outgrowth. From these bioinformatics and dynamical models based on experimental data, we conclude that receptor-mediated regulation of subcellular functions for neurite outgrowth is both distributed, that is, involves many different biochemical pathways, and deep.
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Affiliation(s)
- Jens Hansen
- Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States
| | - Mustafa M Siddiq
- Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States
| | - Arjun Singh Yadaw
- Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States
| | - Rosa E Tolentino
- Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States
| | - Vera Rabinovich
- Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States
| | - Gomathi Jayaraman
- Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States
| | - Mohit Raja Jain
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers University, New Jersey Medical School, Newark, NY, 07103, United States
| | - Tong Liu
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers University, New Jersey Medical School, Newark, NY, 07103, United States
| | - Hong Li
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers University, New Jersey Medical School, Newark, NY, 07103, United States
| | - Yuguang Xiong
- Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States
| | - Joseph Goldfarb
- Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States
| | - Ravi Iyengar
- Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States.
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15
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Nelson JC, Granato M. Zebrafish behavior as a gateway to nervous system assembly and plasticity. Development 2022; 149:275367. [PMID: 35552393 PMCID: PMC9148562 DOI: 10.1242/dev.177998] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Nervous system assembly relies on a diversity of cellular processes ranging from dramatic tissue reorganization to local, subcellular changes all driven by precise molecular programs. Combined, these processes culminate in an animal's ability to plan and execute behaviors. Animal behavior can, therefore, serve as a functional readout of nervous system development. Benefitting from an expansive and growing set of molecular and imaging tools paired with an ever-growing number of assays of diverse behaviors, the zebrafish system has emerged as an outstanding platform at the intersection of nervous system assembly, plasticity and behavior. Here, we summarize recent advancements in the field, including how developing neural circuits are refined to shape complex behaviors and plasticity.
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Affiliation(s)
- Jessica C. Nelson
- Department of Cell and Developmental Biology, University of Colorado, Anschutz Medical Campus, Aurora, CO 80045, USA,Department of Cell and Developmental Biology, University of Pennsylvania, Perelman School of Medicine, 421 Curie Blvd, Philadelphia, PA 19104, USA,Authors for correspondence (; )
| | - Michael Granato
- Department of Cell and Developmental Biology, University of Pennsylvania, Perelman School of Medicine, 421 Curie Blvd, Philadelphia, PA 19104, USA,Authors for correspondence (; )
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16
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Vijayaraghavan T, Dhananjay S, Neumann B. DYN-1/dynamin regulates microtubule dynamics after axon injury. MICROPUBLICATION BIOLOGY 2022; 2022:10.17912/micropub.biology.000549. [PMID: 35622508 PMCID: PMC9005196 DOI: 10.17912/micropub.biology.000549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 03/25/2022] [Accepted: 04/04/2022] [Indexed: 11/14/2022]
Abstract
Microtubules play essential roles in the regeneration of axons after injury, but precisely how their growth is regulated remains to be resolved. Here, we studied the influence of the
C. elegans
DYN-1/dynamin GTPase protein on microtubule growth after axon injury. Before injury, loss of DYN-1 had no effect on microtubule dynamics compared to wild-type animals. However, significant increases in microtubule dynamics were observed after axotomy in animals lacking DYN-1. Moreover, a greater proportion of these animals displayed microtubule growth in the retrograde direction compared to wild-type controls. These data establish a role for DYN-1 in regulating microtubule dynamics after injury in
C. elegans
.
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Affiliation(s)
- Tarika Vijayaraghavan
- Neuroscience Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria 3800, Australia
| | - Samiksha Dhananjay
- Neuroscience Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria 3800, Australia
| | - Brent Neumann
- Neuroscience Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria 3800, Australia
,
Correspondence to: Brent Neumann (
)
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17
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Juanez K, Ghose P. Repurposing the Killing Machine: Non-canonical Roles of the Cell Death Apparatus in Caenorhabditis elegans Neurons. Front Cell Dev Biol 2022; 10:825124. [PMID: 35237604 PMCID: PMC8882910 DOI: 10.3389/fcell.2022.825124] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 01/31/2022] [Indexed: 12/29/2022] Open
Abstract
Here we highlight the increasingly divergent functions of the Caenorhabditis elegans cell elimination genes in the nervous system, beyond their well-documented roles in cell dismantling and removal. We describe relevant background on the C. elegans nervous system together with the apoptotic cell death and engulfment pathways, highlighting pioneering work in C. elegans. We discuss in detail the unexpected, atypical roles of cell elimination genes in various aspects of neuronal development, response and function. This includes the regulation of cell division, pruning, axon regeneration, and behavioral outputs. We share our outlook on expanding our thinking as to what cell elimination genes can do and noting their versatility. We speculate on the existence of novel genes downstream and upstream of the canonical cell death pathways relevant to neuronal biology. We also propose future directions emphasizing the exploration of the roles of cell death genes in pruning and guidance during embryonic development.
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18
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Kulkarni SS, Sabharwal V, Sheoran S, Basu A, Matsumoto K, Hisamoto N, Ghosh-Roy A, Koushika SP. UNC-16 alters DLK-1 localization and negatively regulates actin and microtubule dynamics in Caenorhabditis elegans regenerating neurons. Genetics 2021; 219:6359182. [PMID: 34740241 DOI: 10.1093/genetics/iyab139] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 08/13/2021] [Indexed: 11/13/2022] Open
Abstract
Neuronal regeneration after injury depends on the intrinsic growth potential of neurons. Our study shows that UNC-16, a Caenorhabditis elegans JIP3 homolog, inhibits axonal regeneration by regulating initiation and rate of regrowth. This occurs through the inhibition of the regeneration-promoting activity of the long isoform of DLK-1 and independently of the inhibitory short isoform of DLK-1. We show that UNC-16 promotes DLK-1 punctate localization in a concentration-dependent manner limiting the availability of the long isoform of DLK-1 at the cut site, minutes after injury. UNC-16 negatively regulates actin dynamics through DLK-1 and microtubule dynamics partially via DLK-1. We show that post-injury cytoskeletal dynamics in unc-16 mutants are also partially dependent on CEBP-1. The faster regeneration seen in unc-16 mutants does not lead to functional recovery. Our data suggest that the inhibitory control by UNC-16 and the short isoform of DLK-1 balances the intrinsic growth-promoting function of the long isoform of DLK-1 in vivo. We propose a model where UNC-16's inhibitory role in regeneration occurs through both a tight temporal and spatial control of DLK-1 and cytoskeletal dynamics.
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Affiliation(s)
- Sucheta S Kulkarni
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, 560065, India
| | - Vidur Sabharwal
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, Maharashtra 400005, India
| | - Seema Sheoran
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, 560065, India
| | - Atrayee Basu
- Department of Biotechnology National Brain Research Centre, Manesar 122052, India
| | - Kunihiro Matsumoto
- Department of Molecular Biology, Nagoya University, Nagoya 4648601, Japan
| | - Naoki Hisamoto
- Department of Molecular Biology, Nagoya University, Nagoya 4648601, Japan
| | - Anindya Ghosh-Roy
- Department of Biotechnology National Brain Research Centre, Manesar 122052, India
| | - Sandhya P Koushika
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, Maharashtra 400005, India
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19
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Imaging of Actin Cytoskeleton in the Nematode Caenorhabditis elegans. Methods Mol Biol 2021. [PMID: 34542852 DOI: 10.1007/978-1-0716-1661-1_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
The nematode Caenorhabditis elegans is one of the major model organisms in cell and developmental biology. This organism is easy to culture in laboratories and suitable for microscopic investigation of the cytoskeleton. Because the worms are small and transparent, the actin cytoskeleton in many tissues and cells can be observed with appropriate visualization techniques without sectioning or dissection. This chapter describes the introduction to representative methods for imaging the actin cytoskeleton in C. elegans and a protocol for staining worms with fluorescent phalloidin.
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20
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Basu A, Behera S, Bhardwaj S, Dey S, Ghosh-Roy A. Regulation of UNC-40/DCC and UNC-6/Netrin by DAF-16 promotes functional rewiring of the injured axon. Development 2021; 148:268990. [PMID: 34109380 DOI: 10.1242/dev.198044] [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: 10/26/2020] [Accepted: 05/04/2021] [Indexed: 01/02/2023]
Abstract
The adult nervous system has a limited capacity to regenerate after accidental damage. Post-injury functional restoration requires proper targeting of the injured axon to its postsynaptic cell. Although the initial response to axonal injury has been studied in great detail, it is rather unclear what controls the re-establishment of a functional connection. Using the posterior lateral microtubule neuron in Caenorhabditis elegans, we found that after axotomy, the regrowth from the proximal stump towards the ventral side and accumulation of presynaptic machinery along the ventral nerve cord correlated to the functional recovery. We found that the loss of insulin receptor DAF-2 promoted 'ventral targeting' in a DAF-16-dependent manner. We further showed that coordinated activities of DAF-16 in neuron and muscle promoted 'ventral targeting'. In response to axotomy, expression of the Netrin receptor UNC-40 was upregulated in the injured neuron in a DAF-16-dependent manner. In contrast, the DAF-2-DAF-16 axis contributed to the age-related decline in Netrin expression in muscle. Therefore, our study revealed an important role for insulin signaling in regulating the axon guidance molecules during the functional rewiring process.
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Affiliation(s)
- Atrayee Basu
- Department of Cellular and Molecular Neuroscience, National Brain Research Centre, Manesar, Nainwal Mode, Gurgaon, Haryana 122051, India
| | - Sibaram Behera
- Department of Cellular and Molecular Neuroscience, National Brain Research Centre, Manesar, Nainwal Mode, Gurgaon, Haryana 122051, India
| | - Smriti Bhardwaj
- Department of Cellular and Molecular Neuroscience, National Brain Research Centre, Manesar, Nainwal Mode, Gurgaon, Haryana 122051, India
| | - Shirshendu Dey
- Fluorescence Microscopy Division, Bruker India Scientific PvT Ltd, International Trade Tower, Nehru Place, New Delhi 110019, India
| | - Anindya Ghosh-Roy
- Department of Cellular and Molecular Neuroscience, National Brain Research Centre, Manesar, Nainwal Mode, Gurgaon, Haryana 122051, India
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21
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Abstract
Establishment of neural circuits requires reproducible and precise interactions between growing axons, dendrites and their tissue environment. Cell adhesion molecules and guidance factors are involved in the process, but how specificity is achieved remains poorly understood. Glycans are the third major class of biopolymers besides nucleic acids and proteins, and are usually covalently linked to proteins to form glycoconjugates. Common to most glycans is an extraordinary level of molecular diversity, making them attractive candidates to contribute specificity during neural development. Indeed, many genes important for neural development encode glycoproteins, or enzymes involved in synthesizing or modifying glycans. Glycoconjugates are classified based on both the types of glycans and type of attachment that link them to proteins. Here I discuss progress in understanding the function of glycans, glycan modifications and glycoconjugates during neural development in Caenorhabditis elegans. I will also highlight relevance to human disease and known roles of glycoconjugates in regeneration.
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Affiliation(s)
- Hannes E Bülow
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY, United States; Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, United States.
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22
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Zhao J, Wang X, Meng X, Zou W, Xu S. Rapid and efficient wounding for in vivo studies of neuronal dendrite regeneration and degeneration. J Genet Genomics 2021; 48:163-166. [PMID: 33483295 DOI: 10.1016/j.jgg.2020.10.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 09/24/2020] [Accepted: 10/17/2020] [Indexed: 11/18/2022]
Affiliation(s)
- Jianzhi Zhao
- Center for Stem Cell and Regenerative Medicine and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058 China
| | - Xiaojie Wang
- The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu 322000, China; Institute of Translational Medicine, Zhejiang University, Hangzhou 310058, China
| | - Xinan Meng
- Center for Stem Cell and Regenerative Medicine and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058 China
| | - Wei Zou
- The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu 322000, China; Institute of Translational Medicine, Zhejiang University, Hangzhou 310058, China.
| | - Suhong Xu
- Center for Stem Cell and Regenerative Medicine and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058 China.
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23
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Abstract
During multicellular organism development, complex structures are sculpted to form organs and tissues, which are maintained throughout adulthood. Many of these processes require cells to fuse with one another, or with themselves. These plasma membrane fusions merge endoplasmic cellular content across external, exoplasmic, space. In the nematode Caenorhabditis elegans, such cell fusions serve as a unique sculpting force, involved in the embryonic morphogenesis of the skin-like multinuclear hypodermal cells, but also in refining delicate structures, such as valve openings and the tip of the tail. During post-embryonic development, plasma membrane fusions continue to shape complex neuron structures and organs such as the vulva, while during adulthood fusion participates in cell and tissue repair. These processes rely on two fusion proteins (fusogens): EFF-1 and AFF-1, which are part of a broader family of structurally related membrane fusion proteins, encompassing sexual reproduction, viral infection, and tissue remodeling. The established capabilities of these exoplasmic fusogens are further expanded by new findings involving EFF-1 and AFF-1 in endocytic vesicle fission and phagosome sealing. Tight regulation by cell-autonomous and non-cell autonomous mechanisms orchestrates these diverse cell fusions at the correct place and time-these processes and their significance are discussed in this review.
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24
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Wnt Signaling Regulates Ipsilateral Pathfinding in the Zebrafish Forebrain through slit3. Neuroscience 2020; 449:9-20. [DOI: 10.1016/j.neuroscience.2020.09.028] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 09/03/2020] [Accepted: 09/09/2020] [Indexed: 12/21/2022]
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25
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Harnessing the power of genetics: fast forward genetics in Caenorhabditis elegans. Mol Genet Genomics 2020; 296:1-20. [PMID: 32888055 DOI: 10.1007/s00438-020-01721-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Accepted: 08/27/2020] [Indexed: 12/23/2022]
Abstract
Forward genetics is a powerful tool to unravel molecular mechanisms of diverse biological processes. The success of genetic screens primarily relies on the ease of genetic manipulation of an organism and the availability of a plethora of genetic tools. The roundworm Caenorhabditis elegans has been one of the favorite models for genetic studies due to its hermaphroditic lifestyle, ease of maintenance, and availability of various genetic manipulation tools. The strength of C. elegans genetics is highlighted by the leading role of this organism in the discovery of several conserved biological processes. In this review, the principles and strategies for forward genetics in C. elegans are discussed. Further, the recent advancements that have drastically accelerated the otherwise time-consuming process of mutation identification, making forward genetic screens a method of choice for understanding biological functions, are discussed. The emphasis of the review has been on providing practical and conceptual pointers for designing genetic screens that will identify mutations, specifically disrupting the biological processes of interest.
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26
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cnd-1/NeuroD1 Functions with the Homeobox Gene ceh-5/Vax2 and Hox Gene ceh-13/labial To Specify Aspects of RME and DD Neuron Fate in Caenorhabditis elegans. G3-GENES GENOMES GENETICS 2020; 10:3071-3085. [PMID: 32601060 PMCID: PMC7466980 DOI: 10.1534/g3.120.401515] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Identifying the mechanisms behind neuronal fate specification are key to understanding normal neural development in addition to neurodevelopmental disorders such as autism and schizophrenia. In vivo cell fate specification is difficult to study in vertebrates. However, the nematode Caenorhabditis elegans, with its invariant cell lineage and simple nervous system of 302 neurons, is an ideal organism to explore the earliest stages of neural development. We used a comparative transcriptome approach to examine the role of cnd-1/NeuroD1 in C. elegans nervous system development and function. This basic helix-loop-helix transcription factor is deeply conserved across phyla and plays a crucial role in cell fate specification in both the vertebrate nervous system and pancreas. We find that cnd-1 controls expression of ceh-5, a Vax2-like homeobox class transcription factor, in the RME head motorneurons and PVQ tail interneurons. We also show that cnd-1 functions redundantly with the Hox gene ceh-13/labial in defining the fate of DD1 and DD2 embryonic ventral nerve cord motorneurons. These data highlight the utility of comparative transcriptomes for identifying transcription factor targets and understanding gene regulatory networks.
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27
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Synaptic Protein Degradation Controls Sexually Dimorphic Circuits through Regulation of DCC/UNC-40. Curr Biol 2020; 30:4128-4141.e5. [PMID: 32857970 PMCID: PMC7658809 DOI: 10.1016/j.cub.2020.08.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 07/13/2020] [Accepted: 08/03/2020] [Indexed: 12/27/2022]
Abstract
Sexually dimorphic circuits underlie behavioral differences between the sexes, yet the molecular mechanisms involved in their formation are poorly understood. We show here that sexually dimorphic connectivity patterns arise in C. elegans through local ubiquitin-mediated protein degradation in selected synapses of one sex but not the other. Specifically, synaptic degradation occurs via binding of the evolutionary conserved E3 ligase SEL-10/FBW7 to a phosphodegron binding site of the netrin receptor UNC-40/DCC (Deleted in Colorectal Cancer), resulting in degradation of UNC-40. In animals carrying an undegradable unc-40 gain-of-function allele, synapses were retained in both sexes, compromising the activity of the circuit without affecting neurite guidance. Thus, by decoupling the synaptic and guidance functions of the netrin pathway, we reveal a critical role for dimorphic protein degradation in controlling neuronal connectivity and activity. Additionally, the interaction between SEL-10 and UNC-40 is necessary not only for sex-specific synapse pruning, but also for other synaptic functions. These findings provide insight into the mechanisms that generate sex-specific differences in neuronal connectivity, activity, and function. Sex-specific synapse pruning during development is regulated by the ubiquitin pathway The E3 ligase SEL-10 targets the UNC-40 netrin receptor via binding to a CPD motif UNC-40 degradation leads to synapse removal only in hermaphrodites, not males CPD mutations disrupt synaptic functions of UNC-40, leaving axon guidance intact
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28
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Abay-Nørgaard S, Attianese B, Boreggio L, Salcini AE. Regulators of H3K4 methylation mutated in neurodevelopmental disorders control axon guidance in Caenorhabditis elegans. Development 2020; 147:dev.190637. [PMID: 32675280 PMCID: PMC7420840 DOI: 10.1242/dev.190637] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 07/10/2020] [Indexed: 12/11/2022]
Abstract
Post-translational histone modifications regulate chromatin compaction and gene expression to control many aspects of development. Mutations in genes encoding regulators of H3K4 methylation are causally associated with neurodevelopmental disorders characterized by intellectual disability and deficits in motor functions. However, it remains unclear how H3K4 methylation influences nervous system development and contributes to the aetiology of disease. Here, we show that the catalytic activity of set-2, the Caenorhabditis elegans homologue of the H3K4 methyltransferase KMT2F/G (SETD1A/B) genes, controls embryonic transcription of neuronal genes and is required for establishing proper axon guidance, and for neuronal functions related to locomotion and learning. Moreover, we uncover a striking correlation between components of the H3K4 regulatory machinery mutated in neurodevelopmental disorders and the process of axon guidance in C. elegans. Thus, our study supports an epigenetic-based model for the aetiology of neurodevelopmental disorders, based on an aberrant axon guidance process originating from deregulated H3K4 methylation. Summary: Analysis of mutants lacking many known H3K4 regulators reveals the role of H3K4 methylation in C. elegans neuronal functions and suggests that aberrant axon guidance is a shared trait in neurodevelopmental diseases.
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Affiliation(s)
- Steffen Abay-Nørgaard
- BRIC, University of Copenhagen, Biotech Research and Innovation Centre, Ole Maaloes vej 5, 2200, Copenhagen, Denmark
| | - Benedetta Attianese
- BRIC, University of Copenhagen, Biotech Research and Innovation Centre, Ole Maaloes vej 5, 2200, Copenhagen, Denmark
| | - Laura Boreggio
- BRIC, University of Copenhagen, Biotech Research and Innovation Centre, Ole Maaloes vej 5, 2200, Copenhagen, Denmark
| | - Anna Elisabetta Salcini
- BRIC, University of Copenhagen, Biotech Research and Innovation Centre, Ole Maaloes vej 5, 2200, Copenhagen, Denmark
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29
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Gordon KL, Zussman JW, Li X, Miller C, Sherwood DR. Stem cell niche exit in C. elegans via orientation and segregation of daughter cells by a cryptic cell outside the niche. eLife 2020; 9:e56383. [PMID: 32692313 PMCID: PMC7467730 DOI: 10.7554/elife.56383] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 07/17/2020] [Indexed: 12/17/2022] Open
Abstract
Stem cells reside in and rely upon their niche to maintain stemness but must balance self-renewal with the production of daughters that leave the niche to differentiate. We discovered a mechanism of stem cell niche exit in the canonical C. elegans distal tip cell (DTC) germ stem cell niche mediated by previously unobserved, thin, membranous protrusions of the adjacent somatic gonad cell pair (Sh1). A disproportionate number of germ cell divisions were observed at the DTC-Sh1 interface. Stem-like and differentiating cell fates segregated across this boundary. Spindles polarized, pairs of daughter cells oriented between the DTC and Sh1, and Sh1 grew over the Sh1-facing daughter. Impeding Sh1 growth by RNAi to cofilin and Arp2/3 perturbed the DTC-Sh1 interface, reduced germ cell proliferation, and shifted a differentiation marker. Because Sh1 membrane protrusions eluded detection for decades, it is possible that similar structures actively regulate niche exit in other systems.
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Affiliation(s)
- Kacy L Gordon
- Department of Biology, The University of North Carolina at Chapel HillChapel HillUnited States
| | - Jay W Zussman
- Department of Biology, Duke UniversityDurhamUnited States
| | - Xin Li
- Department of Biology, The University of North Carolina at Chapel HillChapel HillUnited States
| | - Camille Miller
- Department of Biology, The University of North Carolina at Chapel HillChapel HillUnited States
| | - David R Sherwood
- Department of Biology, Duke UniversityDurhamUnited States
- Regeneration Next, Duke UniversityDurhamUnited States
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30
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Chang C, Hisamoto N. Engulfment Genes Promote Neuronal Regeneration in
Caenorhabditis Elegans
: Two Divergent But Complementary Views. Bioessays 2020; 42:e1900185. [DOI: 10.1002/bies.201900185] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 04/23/2020] [Indexed: 12/25/2022]
Affiliation(s)
- Chieh Chang
- Department of Biological Sciences University of Illinois at Chicago Chicago Illinois 60607 USA
| | - Naoki Hisamoto
- Dept. of Biological Science Graduate School of Science Nagoya University Furo‐cho, Chikusa‐ku, Aichi Prefecture Nagoya 464‐8602 Japan
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31
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The netrin receptor UNC-40/DCC assembles a postsynaptic scaffold and sets the synaptic content of GABA A receptors. Nat Commun 2020; 11:2674. [PMID: 32471987 PMCID: PMC7260190 DOI: 10.1038/s41467-020-16473-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 04/28/2020] [Indexed: 01/11/2023] Open
Abstract
Increasing evidence indicates that guidance molecules used during development for cellular and axonal navigation also play roles in synapse maturation and homeostasis. In C. elegans the netrin receptor UNC-40/DCC controls the growth of dendritic-like muscle cell extensions towards motoneurons and is required to recruit type A GABA receptors (GABAARs) at inhibitory neuromuscular junctions. Here we show that activation of UNC-40 assembles an intracellular synaptic scaffold by physically interacting with FRM-3, a FERM protein orthologous to FARP1/2. FRM-3 then recruits LIN-2, the ortholog of CASK, that binds the synaptic adhesion molecule NLG-1/Neuroligin and physically connects GABAARs to prepositioned NLG-1 clusters. These processes are orchestrated by the synaptic organizer CePunctin/MADD-4, which controls the localization of GABAARs by positioning NLG-1/neuroligin at synapses and regulates the synaptic content of GABAARs through the UNC-40-dependent intracellular scaffold. Since DCC is detected at GABA synapses in mammals, DCC might also tune inhibitory neurotransmission in the mammalian brain. The netrin receptor UNC-40/DCC is required to recruit GABAAR at neuromuscular junctions in C. elegans. Here, the authors show that UNC-40/DCC assembles an intracellular synaptic scaffold, regulating the content of GABAAR and inhibitory neurotransmission.
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32
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Gokuladhas S, Schierding W, Cameron-Smith D, Wake M, Scotter EL, O’Sullivan J. Shared Regulatory Pathways Reveal Novel Genetic Correlations Between Grip Strength and Neuromuscular Disorders. Front Genet 2020; 11:393. [PMID: 32391060 PMCID: PMC7194178 DOI: 10.3389/fgene.2020.00393] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 03/30/2020] [Indexed: 12/13/2022] Open
Abstract
Muscle weakness is a common consequence of both aging (sarcopenia) and neuromuscular disorders (NMD). Whilst genome-wide association (GWA) studies have identified genetic variants associated with grip strength (GS; measure of muscle strength/weakness) and NMDs, including multiple sclerosis (MS), myasthenia gravis (MG) and amyotrophic lateral sclerosis (ALS), it is not known whether there are common mechanisms between these phenotypes. To examine this, we have integrated GS and NMD associated genetic variants (single nucleotide polymorphisms; SNPs) in a multimorbid analysis that leverages high-throughput chromatin interaction (Hi-C) data and expression quantitative trait loci data to identify target genes (i.e., SNP-mediated gene regulation). Biological pathways enriched by these genes were then identified using next-generation pathway enrichment analysis. Lastly, druggable genes were identified using drug gene interaction (DGI) database. We identified gene regulatory mechanisms associated with GS, MG, MS, and ALS. The SNPs associated with GS regulate a subset of genes that are also regulated by the SNPs of MS, MG, and ALS. Yet, we did not find any genes commonly regulated by all four phenotype associated SNPs. By contrast, we identified significant enrichment in three pathways (mTOR signaling, axon guidance, and alcoholism) that are commonly affected by the gene regulatory mechanisms associated with all four phenotypes. 13% of the genes we identified were known drug targets, and GS shares at least one druggable gene and pathway with each of the NMD phenotypes. We have identified significant biological overlaps between GS and NMD, demonstrating the potential for spatial genetic analysis to identify common mechanisms between potential multimorbid phenotypes. Collectively, our results form the foundation for a shift from a gene to a pathway-based approach to the rationale design of therapeutic interventions and treatments for NMD.
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Affiliation(s)
| | | | - David Cameron-Smith
- Liggins Institute, The University of Auckland, Auckland, New Zealand
- Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research (ASTAR), Singapore, Singapore
| | - Melissa Wake
- Murdoch Children’s Research Institute, The University of Melbourne, Parkville, VIC, Australia
| | - Emma L. Scotter
- Department of Pharmacology and Clinical Pharmacology, The University of Auckland, Auckland, New Zealand
- Centre for Brain Research, The University of Auckland, Auckland, New Zealand
| | - Justin O’Sullivan
- Liggins Institute, The University of Auckland, Auckland, New Zealand
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33
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Long-term activity drives dendritic branch elaboration of a C. elegans sensory neuron. Dev Biol 2020; 461:66-74. [PMID: 31945343 PMCID: PMC7170766 DOI: 10.1016/j.ydbio.2020.01.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 01/07/2020] [Accepted: 01/08/2020] [Indexed: 12/13/2022]
Abstract
Neuronal activity often leads to alterations in gene expression and cellular architecture. The nematode Caenorhabditis elegans, owing to its compact translucent nervous system, is a powerful system in which to study conserved aspects of the development and plasticity of neuronal morphology. Here we focus on one pair of sensory neurons, termed URX, which the worm uses to sense and avoid high levels of environmental oxygen. Previous studies have reported that the URX neuron pair has variable branched endings at its dendritic sensory tip. By controlling oxygen levels and analyzing mutants, we found that these microtubule-rich branched endings grow over time as a consequence of neuronal activity in adulthood. We also find that the growth of these branches correlates with an increase in cellular sensitivity to particular ranges of oxygen that is observable in the behavior of older worms. Given the strengths of C. elegans as a model organism, URX may serve as a potent system for uncovering genes and mechanisms involved in activity-dependent morphological changes in neurons and possible adaptive changes in the aging nervous system. The dendritic tip of an oxygen-sensing neuron grows elaborate microtubule-rich processes in adult C. elegans. Dendritic tip elaboration depends on the long-term activity of the neuron and calcium. The elaboration correlates with increased sensitivity of the neuron to certain ranges of oxygen as well as higher avoidance of oxygen during bordering behavior. The dendritic tip changes may reflect adaptive changes in physiology and behavior during adulthood.
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34
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Cravo J, van den Heuvel S. Tissue polarity and PCP protein function: C. elegans as an emerging model. Curr Opin Cell Biol 2019; 62:159-167. [PMID: 31884395 DOI: 10.1016/j.ceb.2019.11.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 11/14/2019] [Accepted: 11/19/2019] [Indexed: 12/14/2022]
Abstract
Polarity is the basis for the generation of cell diversity, as well as the organization, morphogenesis, and functioning of tissues. Studies in Caenorhabditis elegans have provided much insight into PAR-protein mediated polarity; however, the molecules and mechanisms critical for cell polarization within the plane of epithelia have been identified in other systems. Tissue polarity in C. elegans is organized by Wnt-signaling with some resemblance to the Wnt/planar cell polarity (PCP) pathway, but lacking core PCP protein functions. Nonetheless, recent studies revealed that conserved PCP proteins regulate directed cell migratory events in C. elegans, such as convergent extension movements and neurite formation and guidance. Here, we discuss the latest insights and use of C. elegans as a PCP model.
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Affiliation(s)
- Janine Cravo
- Developmental Biology, Department of Biology, Faculty of Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, the Netherlands
| | - Sander van den Heuvel
- Developmental Biology, Department of Biology, Faculty of Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, the Netherlands.
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35
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The C. elegans BRCA2-ALP/Enigma Complex Regulates Axon Regeneration via a Rho GTPase-ROCK-MLC Phosphorylation Pathway. Cell Rep 2019; 24:1880-1889. [PMID: 30110643 DOI: 10.1016/j.celrep.2018.07.049] [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: 11/24/2017] [Revised: 05/28/2018] [Accepted: 07/16/2018] [Indexed: 12/11/2022] Open
Abstract
The ability of specific neurons to regenerate their axons after injury is governed by cell-intrinsic regeneration pathways. However, the mechanisms regulating axon regeneration are not well understood. Here, we identify the brc-2 gene encoding a homolog of the mammalian BRCA2 tumor suppressor as a regulator of axon regeneration in Caenorhabditis elegans motor neurons. We show that the RHO-1/Rho GTPase-LET-502/ROCK (Rho-associated coiled-coil kinase)-regulatory non-muscle myosin light-chain (MLC-4/MLC) phosphorylation signaling pathway regulates axon regeneration. BRC-2 functions between RHO-1 and LET-502, suggesting that BRC-2 is required for the activation of LET-502 by RHO-1-GTP. We also find that one component that interacts with BRC-2, the ALP (α-actinin-associated LIM protein)/Enigma protein ALP-1, is required for regeneration and acts between LET-502 and MLC-4 phosphorylation. Furthermore, we demonstrate that ALP-1 associates with LET-502 and MLC-4. Thus, ALP-1 serves as a platform to activate MLC-4 phosphorylation mediated by the RHO-1-LET-502 signaling pathway.
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36
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Hodgkin J. Nematode Autotomy Requires Molting and Entails Tissue Healing without Obvious Regeneration. J Dev Biol 2019; 7:jdb7040021. [PMID: 31771156 PMCID: PMC6955759 DOI: 10.3390/jdb7040021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 10/30/2019] [Accepted: 11/21/2019] [Indexed: 11/16/2022] Open
Abstract
Autotomy in C. elegans, which results in the severing of the body into two fragments, has been observed as a response to late larval worm-star formation after exposure to a bacterial surface pathogen. It was found that autotomy can occur in both hermaphroditic and gonochoristic nematode species, and during either the L3 or the L4 molt. Severing was hypothesized to be driven by a ‘balloon-twisting’ mechanism during molting but was found to be independent of lethargus-associated flipping. Extensive healing and apparent tissue fusion were seen at the site of scission. No obvious regeneration of lost body parts was seen in either L4 or adult truncated worms. A variety of mutants defective in processes of cell death, healing, regeneration, responses to damage, stress or pathogens were found to be competent to autotomize. Mutants specifically defective in autotomy have yet to be found. Autotomy may represent a modification of the essential normal process of molting.
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Affiliation(s)
- Jonathan Hodgkin
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
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37
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Wang G, Sun L, Reina CP, Song I, Gabel CV, Driscoll M. CED-4 CARD domain residues can modulate non-apoptotic neuronal regeneration functions independently from apoptosis. Sci Rep 2019; 9:13315. [PMID: 31527664 PMCID: PMC6746752 DOI: 10.1038/s41598-019-49633-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 06/20/2019] [Indexed: 12/31/2022] Open
Abstract
A major challenge in regenerative medicine is the repair of injured neurons. Regeneration of laser-cut C. elegans neurons requires early action of core apoptosis activator CED-4/Apaf1 and CED-3/caspase. While testing models for CED-4 as a candidate calcium-sensitive activator of repair, we unexpectedly discovered that amino acid substitutions affecting alpha-helix-6 within the CED-4 caspase recruitment domain (CARD) confer a CED-4 gain-of-function (gf) activity that increases axonal regrowth without disrupting CED-4 apoptosis activity. The in vivo caspase reporter CA-GFP reveals a rapid localized increase in caspase activity upon axotomy, which is absent in ced-4 and ced-3 loss-of-function mutants but present in the ced-4(gf) mutant. The ced-3 loss-of-function mutation can significantly suppress the axonal regrowth of the ced-4(gf) mutant, indicating that CED-4(gf) regeneration depends on CED-3 caspase. Thus, we identified a subdomain within the CED-4 CARD that regulates the dynamic and controlled caspase activity required for efficient regeneration.
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Affiliation(s)
- Guoqiang Wang
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ, 08854, USA
| | - Lin Sun
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA, 02118, USA
| | - Christopher P Reina
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ, 08854, USA
| | - Isaac Song
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ, 08854, USA
| | - Christopher V Gabel
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA, 02118, USA
| | - Monica Driscoll
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, NJ, 08854, USA.
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38
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Integrins Have Cell-Type-Specific Roles in the Development of Motor Neuron Connectivity. J Dev Biol 2019; 7:jdb7030017. [PMID: 31461926 PMCID: PMC6787651 DOI: 10.3390/jdb7030017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 08/11/2019] [Accepted: 08/22/2019] [Indexed: 01/16/2023] Open
Abstract
Formation of the nervous system requires a complex series of events including proper extension and guidance of neuronal axons and dendrites. Here we investigate the requirement for integrins, a class of transmembrane cell adhesion receptors, in regulating these processes across classes of C. elegans motor neurons. We show α integrin/ina-1 is expressed by both GABAergic and cholinergic motor neurons. Despite this, our analysis of hypomorphic ina-1(gm144) mutants indicates preferential involvement of α integrin/ina-1 in GABAergic commissural development, without obvious involvement in cholinergic commissural development. The defects in GABAergic commissures of ina-1(gm144) mutants included both premature termination and guidance errors and were reversed by expression of wild type ina-1 under control of the native ina-1 promoter. Our results also show that α integrin/ina-1 is important for proper outgrowth and guidance of commissures from both embryonic and post-embryonic born GABAergic motor neurons, indicating an ongoing requirement for integrin through two phases of GABAergic neuron development. Our findings provide insights into neuron-specific roles for integrin that would not be predicted based solely upon expression analysis.
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39
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Abstract
Permanent disabilities following CNS injuries result from the failure of injured axons to regenerate and rebuild functional connections with their original targets. By contrast, injury to peripheral nerves is followed by robust regeneration, which can lead to recovery of sensory and motor functions. This regenerative response requires the induction of widespread transcriptional and epigenetic changes in injured neurons. Considerable progress has been made in recent years in understanding how peripheral axon injury elicits these widespread changes through the coordinated actions of transcription factors, epigenetic modifiers and, to a lesser extent, microRNAs. Although many questions remain about the interplay between these mechanisms, these new findings provide important insights into the pivotal role of coordinated gene expression and chromatin remodelling in the neuronal response to injury.
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Affiliation(s)
- Marcus Mahar
- Department of Neuroscience, Hope Center for Neurological Disorders and Center of Regenerative Medicine, Washington University School of Medicine, St Louis, MO, USA
| | - Valeria Cavalli
- Department of Neuroscience, Hope Center for Neurological Disorders and Center of Regenerative Medicine, Washington University School of Medicine, St Louis, MO, USA.
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40
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Abstract
While PIWI-interacting RNAs (piRNAs) are primarily recognized as guardians of genome integrity, new functions of these small non-coding RNAs are emerging. In this issue, Kim et al. (2018) describe a piRNA-based mechanism that limits axon regeneration in C. elegans.
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Affiliation(s)
- Cláudio Gouveia Roque
- The Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University, New York, NY 10032, USA
| | - Ulrich Hengst
- The Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University, New York, NY 10032, USA; Department of Pathology and Cell Biology, Columbia University, New York, NY 10032, USA.
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41
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Yamanashi T, Maki M, Kojima K, Shibukawa A, Tsukamoto T, Chowdhury S, Yamanaka A, Takagi S, Sudo Y. Quantitation of the neural silencing activity of anion channelrhodopsins in Caenorhabditis elegans and their applicability for long-term illumination. Sci Rep 2019; 9:7863. [PMID: 31133660 PMCID: PMC6536681 DOI: 10.1038/s41598-019-44308-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Accepted: 05/14/2019] [Indexed: 11/15/2022] Open
Abstract
Ion pumps and channels are responsible for a wide variety of biological functions. Ion pumps transport only one ion during each stimulus-dependent reaction cycle, whereas ion channels conduct a large number of ions during each cycle. Ion pumping rhodopsins such as archaerhodopsin-3 (Arch) are often utilized as light-dependent neural silencers in animals, but they require a high-density light illumination of around 1 mW/mm2. Recently, anion channelrhodopsins -1 and -2 (GtACR1 and GtACR2) were discovered as light-gated anion channels from the cryptophyte algae Guillardia theta. GtACRs are therefore expected to silence neural activity much more efficiently than Arch. In this study, we successfully expressed GtACRs in neurons of the nematode Caenorhabditis elegans (C. elegans) and quantitatively evaluated how potently GtACRs can silence neurons in freely moving C. elegans. The results showed that the light intensity required for GtACRs to cause locomotion paralysis was around 1 µW/mm2, which is three orders of magnitude smaller than the light intensity required for Arch. As attractive features, GtACRs are less harmfulness to worms and allow stable neural silencing effects under long-term illumination. Our findings thus demonstrate that GtACRs possess a hypersensitive neural silencing activity in C. elegans and are promising tools for long-term neural silencing.
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Affiliation(s)
- Taro Yamanashi
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, 700-8530, Japan
| | - Misayo Maki
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, 700-8530, Japan
| | - Keiichi Kojima
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, 700-8530, Japan
| | - Atsushi Shibukawa
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, 700-8530, Japan
| | - Takashi Tsukamoto
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, 700-8530, Japan.,Faculty of Advanced Life Science and Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Kita-10 Nishi-8, Kita-ku, Sapporo, 060-0810, Japan
| | - Srikanta Chowdhury
- Department of Neuroscience II, Research Institute of Environmental Medicine, Nagoya University, Nagoya, 464-8601, Japan
| | - Akihiro Yamanaka
- Department of Neuroscience II, Research Institute of Environmental Medicine, Nagoya University, Nagoya, 464-8601, Japan
| | - Shin Takagi
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, 464-8602, Japan
| | - Yuki Sudo
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, 700-8530, Japan.
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42
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C. elegans Tensin Promotes Axon Regeneration by Linking the Met-like SVH-2 and Integrin Signaling Pathways. J Neurosci 2019; 39:5662-5672. [PMID: 31109965 DOI: 10.1523/jneurosci.2059-18.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 05/07/2019] [Accepted: 05/08/2019] [Indexed: 01/04/2023] Open
Abstract
Axon regeneration is a conserved mechanism induced by axon injury that initiates a neuronal response leading to regrowth of the axon. In Caenorhabditis elegans, the initiation of axon regeneration is regulated by the JNK MAP kinase (MAPK) pathway. We have previously identified a number of genes affecting the JNK pathway using an RNAi-based screen. Analysis of these genes, called the svh genes, has shed new light on the regulation of axon regeneration, revealing the involvement of a signaling cascade consisting of a growth factor SVH-1 and its receptor, the tyrosine kinase SVH-2. Here, we characterize the svh-6/tns-1 gene, which is a homolog of mammalian tensin, and show that it is a positive regulator of axon regeneration in motor neurons. We demonstrate that TNS-1 interacts with tyrosine-autophosphorylated SVH-2 and the integrin β subunit PAT-3 via its SH2 and PTB domains, respectively, to promote axon regeneration. These results suggest that TNS-1 acts as an adaptor to link the SVH-2 and integrin signaling pathways.SIGNIFICANCE STATEMENT The Caenorhabditis elegans JNK MAPK pathway regulates the initiation of axon regeneration. Previously, we showed that a signaling cascade consisting of the HGF-like growth factor SVH-1 and its Met-like receptor tyrosine kinase SVH-2 promotes axon regeneration through activation of the JNK pathway. In this study, we show that the C. elegans tensin, TNS-1, is required for efficient regeneration after axon injury. Phosphorylation of SVH-2 on tyrosine mediates its interaction with the SH2 domain of TNS-1 to positively regulate axon regeneration. Furthermore, TNS-1 interacts via its PTB domain with the integrin β subunit PAT-3. These results suggest that TNS-1 plays a critical role in the regulation of axon regeneration by linking the SVH-2 and integrin signaling pathways.
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43
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Sales EC, Heckman EL, Warren TL, Doe CQ. Regulation of subcellular dendritic synapse specificity by axon guidance cues. eLife 2019; 8:43478. [PMID: 31012844 PMCID: PMC6499537 DOI: 10.7554/elife.43478] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Accepted: 04/18/2019] [Indexed: 11/13/2022] Open
Abstract
Neural circuit assembly occurs with subcellular precision, yet the mechanisms underlying this precision remain largely unknown. Subcellular synaptic specificity could be achieved by molecularly distinct subcellular domains that locally regulate synapse formation, or by axon guidance cues restricting access to one of several acceptable targets. We address these models using two Drosophila neurons: the dbd sensory neuron and the A08a interneuron. In wild-type larvae, dbd synapses with the A08a medial dendrite but not the A08a lateral dendrite. dbd-specific overexpression of the guidance receptors Unc-5 or Robo-2 results in lateralization of the dbd axon, which forms anatomical and functional monosynaptic connections with the A08a lateral dendrite. We conclude that axon guidance cues, not molecularly distinct dendritic arbors, are a major determinant of dbd-A08a subcellular synapse specificity.
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Affiliation(s)
- Emily C Sales
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, United States.,Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Emily L Heckman
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, United States.,Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Timothy L Warren
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, United States.,Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Chris Q Doe
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, United States.,Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
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44
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Abstract
How the nervous system is wired has been a central question of neuroscience since the inception of the field, and many of the foundational discoveries and conceptual advances have been made through the study of invertebrate experimental organisms, including Caenorhabditis elegans and Drosophila melanogaster. Although many guidance molecules and receptors have been identified, recent experiments have shed light on the many modes of action for these pathways. Here, we summarize the recent progress in determining how the physical and temporal constraints of the surrounding environment provide instructive regulations in nervous system wiring. We use Netrin and its receptors as an example to analyze the complexity of how they guide neurite outgrowth. In neurite repair, conserved injury detection and response-signaling pathways regulate gene expression and cytoskeletal dynamics. We also describe recent developments in the research on molecular mechanisms of neurite regeneration in worms and flies.
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Affiliation(s)
- Claire E Richardson
- Department of Biology, Stanford University, Stanford, California 94305, USA;
| | - Kang Shen
- Department of Biology, Stanford University, Stanford, California 94305, USA; .,Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
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45
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Multiple Pathways Act Together To Establish Asymmetry of the Ventral Nerve Cord in Caenorhabditis elegans. Genetics 2019; 211:1331-1343. [PMID: 30792268 DOI: 10.1534/genetics.119.301999] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 02/15/2019] [Indexed: 01/30/2023] Open
Abstract
The central nervous system of most animals is bilaterally symmetrical. Closer observation often reveals some functional or anatomical left-right asymmetries. In the nematode Caenorhabditis elegans, the most obvious asymmetry in the nervous system is found in the ventral nerve cord (VNC), where most axons are in the right axon tract. The asymmetry is established when axons entering the VNC from the brain switch from the left to the right side at the anterior end of the VNC. In genetic screens we identified several mutations compromising VNC asymmetry. This includes alleles of col-99 (encoding a transmembrane collagen), unc-52/perlecan and unc-34 (encoding the actin modulator Enabled/Vasodilator-stimulated phosphoproteins). In addition, we evaluated mutants in known axon guidance pathways for asymmetry defects and used genetic interaction studies to place the genes into genetic pathways. In total we identified four different pathways contributing to the establishment of VNC asymmetry, represented by UNC-6/netrin, SAX-3/Robo, COL-99, and EPI-1/laminin. The combined inactivation of these pathways in triple and quadruple mutants leads to highly penetrant VNC asymmetry defects, suggesting these pathways are important contributors to the establishment of VNC asymmetry in C. elegans.
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46
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Donato A, Kagias K, Zhang Y, Hilliard MA. Neuronal sub-compartmentalization: a strategy to optimize neuronal function. Biol Rev Camb Philos Soc 2019; 94:1023-1037. [PMID: 30609235 PMCID: PMC6617802 DOI: 10.1111/brv.12487] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 11/21/2018] [Accepted: 11/23/2018] [Indexed: 12/14/2022]
Abstract
Neurons are highly polarized cells that consist of three main structural and functional domains: a cell body or soma, an axon, and dendrites. These domains contain smaller compartments with essential roles for proper neuronal function, such as the axonal presynaptic boutons and the dendritic postsynaptic spines. The structure and function of these compartments have now been characterized in great detail. Intriguingly, however, in the last decade additional levels of compartmentalization within the axon and the dendrites have been identified, revealing that these structures are much more complex than previously thought. Herein we examine several types of structural and functional sub-compartmentalization found in neurons of both vertebrates and invertebrates. For example, in mammalian neurons the axonal initial segment functions as a sub-compartment to initiate the action potential, to select molecules passing into the axon, and to maintain neuronal polarization. Moreover, work in Drosophila melanogaster has shown that two distinct axonal guidance receptors are precisely clustered in adjacent segments of the commissural axons both in vivo and in vitro, suggesting a cell-intrinsic mechanism underlying the compartmentalized receptor localization. In Caenorhabditis elegans, a subset of interneurons exhibits calcium dynamics that are localized to specific sections of the axon and control the gait of navigation, demonstrating a regulatory role of compartmentalized neuronal activity in behaviour. These findings have led to a number of new questions, which are important for our understanding of neuronal development and function. How are these sub-compartments established and maintained? What molecular machinery and cellular events are involved? What is their functional significance for the neuron? Here, we reflect on these and other key questions that remain to be addressed in this expanding field of biology.
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Affiliation(s)
- Alessandra Donato
- Clem Jones Centre for Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| | - Konstantinos Kagias
- Department of Organismic and Evolutionary Biology, Center for Brain Science, Harvard University, Cambridge, MA 02138, U.S.A
| | - Yun Zhang
- Department of Organismic and Evolutionary Biology, Center for Brain Science, Harvard University, Cambridge, MA 02138, U.S.A
| | - Massimo A Hilliard
- Clem Jones Centre for Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
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Hutter H. Formation of longitudinal axon pathways in Caenorhabditis elegans. Semin Cell Dev Biol 2019; 85:60-70. [DOI: 10.1016/j.semcdb.2017.11.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 11/10/2017] [Indexed: 10/18/2022]
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Mecklenburg KL, Weghorst FP, Freed SA, O'Tousa JE. Discordant Responses to MAPK Pathway Stimulation Include Axonal Growths in Adult Drosophila Photoreceptors. Front Mol Neurosci 2018; 11:441. [PMID: 30564098 PMCID: PMC6288290 DOI: 10.3389/fnmol.2018.00441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 11/14/2018] [Indexed: 11/22/2022] Open
Abstract
Wallenda (WND) is the Drosophila member of a conserved family of dual leucine-zipper kinases (DLK) active in both neuronal regeneration and degeneration. We examined the role of WND over-expression on sensory neuron morphology by driving WND in multiple subtypes of Drosophila photoreceptors. WND overexpression under control of the pan-retinal GAL4 driver GMR causes multiple photoreceptor defects including cell death, rhabdomere degeneration, and axonal sprouting. Individual photoreceptor subtypes were assayed using GAL4 drivers specific for each photoreceptor class. Many R7 and R8 cells exhibit axonal sprouting while some show cell degeneration. Delaying the onset of WND overexpression until 20 days of age showed that older adult R7 cells retain the ability to initiate new axon growth. R1–6 photoreceptor cells degenerate in response to WND expression and exhibit rhodopsin loss and rhabdomere degeneration. RNAi knockdown of the MAPK signaling components Kayak (KAY) and Hemipterous (HEP) attenuates the WND-induced loss of Rh1 rhodopsin. UAS-induced HEP expression is similar to WND expression, causing degeneration in R1–6 photoreceptors and axonal sprouting in R7 photoreceptors. These results demonstrate that WND in adult Drosophila photoreceptor cells acts through MAPK signaling activity with both regenerative and degenerative responses. These photoreceptors provide a tractable experimental model to reveal cellular mechanisms driving contradictory WND signaling responses.
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Affiliation(s)
- Kirk L Mecklenburg
- Department of Biology, Indiana University South Bend, South Bend, IN, United States
| | - Forrest P Weghorst
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States
| | - Stephanie A Freed
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States
| | - Joseph E O'Tousa
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States
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Sphingosine Kinase Regulates Neuropeptide Secretion During the Oxidative Stress-Response Through Intertissue Signaling. J Neurosci 2018; 38:8160-8176. [PMID: 30082417 DOI: 10.1523/jneurosci.0536-18.2018] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 07/19/2018] [Accepted: 07/20/2018] [Indexed: 12/12/2022] Open
Abstract
The Nrf2 antioxidant transcription factor promotes redox homeostasis in part through reciprocal signaling between neurons and neighboring cells, but the signals involved in intertissue signaling in response to Nrf2 activation are not well defined. In Caenorhabditis elegans, activation of SKN-1/Nrf2 in the intestine negatively regulates neuropeptide secretion from motor neurons. Here, we show that sphingosine kinase (SPHK-1) functions downstream of SKN-1/Nrf2 in the intestine to regulate neuropeptide secretion from motor neurons during the oxidative stress response in C. elegans hermaphrodites. SPHK-1 localizes to mitochondria in the intestine and SPHK-1 mitochondrial localization and kinase activity are essential for its function in regulating motor neuron function. SPHK-1 is recruited to mitochondria from cytosolic pools and its mitochondrial abundance is negatively regulated by acute or chronic SKN-1 activation. Finally, the regulation of motor function by SKN-1 requires the activation of the p38 MAPK cascade in the intestine and occurs through controlling the biogenesis or maturation of dense core vesicles in motor neurons. These findings show that the inhibition of SPHK-1 in the intestine by SKN-1 negatively regulates neuropeptide secretion from motor neurons, revealing a new mechanism by which SPHK-1 signaling mediates its effects on neuronal function in response to oxidative stress.SIGNIFICANCE STATEMENT Neurons are highly susceptible to damage by oxidative stress, yet have limited capacity to activate the SKN-1/Nrf2 oxidative stress response, relying instead on astrocytes to provide redox homeostasis. In Caenorhabditis elegans, intertissue signaling from the intestine plays a key role in regulating neuronal function during the oxidative stress response. Here, through a combination of genetic, behavioral, and fluorescent imaging approaches, we found that sphingosine kinase functions in the SKN-1/Nrf2 pathway in the intestine to regulate neuropeptide biogenesis and secretion in motor neurons. These results implicate sphingolipid signaling as a new component of the oxidative stress response and suggest that C. elegans may be a genetically tractable model to study non-cell-autonomous oxidative stress signaling to neurons.
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McLachlan IG, Beets I, de Bono M, Heiman MG. A neuronal MAP kinase constrains growth of a Caenorhabditis elegans sensory dendrite throughout the life of the organism. PLoS Genet 2018; 14:e1007435. [PMID: 29879119 PMCID: PMC6007932 DOI: 10.1371/journal.pgen.1007435] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 06/19/2018] [Accepted: 05/18/2018] [Indexed: 02/07/2023] Open
Abstract
Neurons develop elaborate morphologies that provide a model for understanding cellular architecture. By studying C. elegans sensory dendrites, we previously identified genes that act to promote the extension of ciliated sensory dendrites during embryogenesis. Interestingly, the nonciliated dendrite of the oxygen-sensing neuron URX is not affected by these genes, suggesting it develops through a distinct mechanism. Here, we use a visual forward genetic screen to identify mutants that affect URX dendrite morphogenesis. We find that disruption of the MAP kinase MAPK-15 or the βH-spectrin SMA-1 causes a phenotype opposite to what we had seen before: dendrites extend normally during embryogenesis but begin to overgrow as the animals reach adulthood, ultimately extending up to 150% of their normal length. SMA-1 is broadly expressed and acts non-cell-autonomously, while MAPK-15 is expressed in many sensory neurons including URX and acts cell-autonomously. MAPK-15 acts at the time of overgrowth, localizes at the dendrite ending, and requires its kinase activity, suggesting it acts locally in time and space to constrain dendrite growth. Finally, we find that the oxygen-sensing guanylate cyclase GCY-35, which normally localizes at the dendrite ending, is localized throughout the overgrown region, and that overgrowth can be suppressed by overexpressing GCY-35 or by genetically mimicking elevated cGMP signaling. These results suggest that overgrowth may correspond to expansion of a sensory compartment at the dendrite ending, reminiscent of the remodeling of sensory cilia or dendritic spines. Thus, in contrast to established pathways that promote dendrite growth during early development, our results reveal a distinct mechanism that constrains dendrite growth throughout the life of the animal, possibly by controlling the size of a sensory compartment at the dendrite ending.
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Affiliation(s)
- Ian G McLachlan
- Department of Genetics, Harvard Medical School and Boston Children's Hospital, Boston MA, United States of America
| | - Isabel Beets
- Division of Cell Biology, Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Mario de Bono
- Division of Cell Biology, Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Maxwell G Heiman
- Department of Genetics, Harvard Medical School and Boston Children's Hospital, Boston MA, United States of America
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