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Zhu M, Wang J, Zhu L, Zhu M. Investigations of forgetting in Caenorhabditis elegans. Neurobiol Learn Mem 2025; 220:108061. [PMID: 40350072 DOI: 10.1016/j.nlm.2025.108061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2024] [Revised: 04/17/2025] [Accepted: 05/01/2025] [Indexed: 05/14/2025]
Abstract
The traditional view considered forgetting as a passive process where memory traces gradually fade due to the natural weakening of neural connections. However, studies on olfactory memory in Drosophila have revealed that forgetting is an active process controlled by specific neural circuits. Caenorhabditis elegans is a widely used model organism in neurobiological research due to its relatively simple nervous system. Despite its simplicity, C. elegans exhibits complex behaviors influenced by environmental factors and prior experiences. Similar to Drosophila, C. elegans can actively initiate neural circuits based on the type of memory that needs to be forgotten, which supports using C. elegans as a model for studying forgetting. These characteristics facilitate the identification of genes and pathways involved in forgetting in C. elegans. In this review, we discuss recent advances in understanding forgetting mechanisms in C. elegans through three well-characterized olfactory learning paradigms. The insights derived from C. elegans offer a valuable framework for understanding the molecular and cellular mechanisms underlying forgetting, with potentially broader implications for memory regulation in more complex organisms.
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Affiliation(s)
- Man Zhu
- College of Biological and Food Engineering, Qujing Normal University, Qujing 655011, China
| | - Jiayi Wang
- College of Biological and Food Engineering, Qujing Normal University, Qujing 655011, China
| | - Ling Zhu
- College of Biological and Food Engineering, Qujing Normal University, Qujing 655011, China
| | - Man Zhu
- College of Biological and Food Engineering, Qujing Normal University, Qujing 655011, China.
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2
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Park G, Jin Z, Lu H, Du J. Clearing Amyloid-Beta by Astrocytes: The Role of Rho GTPases Signaling Pathways as Potential Therapeutic Targets. Brain Sci 2024; 14:1239. [PMID: 39766438 PMCID: PMC11674268 DOI: 10.3390/brainsci14121239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2024] [Revised: 12/05/2024] [Accepted: 12/07/2024] [Indexed: 01/11/2025] Open
Abstract
Astrocytes, vital support cells in the central nervous system (CNS), are crucial for maintaining neuronal health. In neurodegenerative diseases such as Alzheimer's disease (AD), astrocytes play a key role in clearing toxic amyloid-β (Aβ) peptides. Aβ, a potent neuroinflammatory trigger, stimulates astrocytes to release excessive glutamate and inflammatory factors, exacerbating neuronal dysfunction and death. Recent studies underscore the role of Rho GTPases-particularly RhoA, Rac1, and Cdc42-in regulating Aβ clearance and neuroinflammation. These key regulators of cytoskeletal dynamics and intracellular signaling pathways function independently through distinct mechanisms but may converge to modulate inflammatory responses. Their influence on astrocyte structure and function extends to regulating endothelin-converting enzyme (ECE) activity, which modulates vasoactive peptides such as endothelin-1 (ET-1). Through these processes, Rho GTPases impact vascular permeability and neuroinflammation, contributing to AD pathogenesis by affecting both Aβ clearance and cerebrovascular interactions. Understanding the interplay between Rho GTPases and the cerebrovascular system provides fresh insights into AD pathogenesis. Targeting Rho GTPase signaling pathways in astrocytes could offer a promising therapeutic approach to mitigate neuroinflammation, enhance Aβ clearance, and slow disease progression, ultimately improving cognitive outcomes in AD patients.
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Affiliation(s)
- Gyeongah Park
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA;
| | - Zhen Jin
- Department of Pharmaceutical Sciences, University of Tennessee Health Science Center, Memphis, TN 38163, USA;
| | - Hui Lu
- Department of Pharmacology and Physiology, School of Medicine, The George Washington University, Washington, DC 20037, USA;
| | - Jianyang Du
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA;
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3
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Kim S, Park H, Kang J, Choi S, Sadra A, Huh SO. β-PIX-d, a Member of the ARHGEF7 Guanine Nucleotide Exchange Factor Family, Activates Rac1 and Induces Neuritogenesis in Primary Cortical Neurons. Exp Neurobiol 2024; 33:215-224. [PMID: 39568178 PMCID: PMC11581827 DOI: 10.5607/en24026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2024] [Revised: 10/30/2024] [Accepted: 10/30/2024] [Indexed: 11/22/2024] Open
Abstract
β-PIX, a Rac1/Cdc42-specific guanine nucleotide exchange factor, is known to regulate actin cytoskeleton remodeling during cell migration. In this study, we investigated the effects of β-PIX-d, an isoform of β-PIX, on neocortical development and neuritogenesis. Overexpression of β-PIX-d in the embryonic neocortex induced increased cell clusters and enhanced neurite outgrowth in cortical neurons. Following in utero electroporation of β-PIX-d expression vectors into neuronal progenitor cells at embryonic day 13.5 (E13.5), histological analysis at postnatal day 0 (P0) revealed the presence of clustered neurons and neurites outside of the marginal zone (MZ). Immunofluorescence staining with the neuronal marker TuJ1 confirmed that the clustered structures were predominantly composed of neurons. Layer-specific marker analysis further demonstrated the misplacement of layer V-VI neurons into layer I and the subarachnoid space. In primary neocortical cultures, β-PIX-d overexpression promoted neuritogenesis and increased Rac1 activity, as detected by pull-down assays. These findings suggest that β-PIX-d and Rac1 interactions play a critical role in the formation of neocortical clustering and the regulation of neuritogenesis.
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Affiliation(s)
- Seunghyuk Kim
- Department of Pharmacology, Institute of Natural Medicine, College of Medicine, Hallym University, Chuncheon 24252, Korea
| | - Heeyoung Park
- Department of Pharmacology, Institute of Natural Medicine, College of Medicine, Hallym University, Chuncheon 24252, Korea
| | - Jieun Kang
- Department of Pharmacology, Institute of Natural Medicine, College of Medicine, Hallym University, Chuncheon 24252, Korea
| | - Seunghyuk Choi
- Department of Pharmacology, Institute of Natural Medicine, College of Medicine, Hallym University, Chuncheon 24252, Korea
| | - Ali Sadra
- Department of Pharmacology, Institute of Natural Medicine, College of Medicine, Hallym University, Chuncheon 24252, Korea
| | - Sung-Oh Huh
- Department of Pharmacology, Institute of Natural Medicine, College of Medicine, Hallym University, Chuncheon 24252, Korea
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4
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Zhang Y, Yang YS, Chen WC, Wang CM, He HF. Constructing and Validating a Network of Potential Olfactory Sheathing Cell Transplants Regulating Spinal Cord Injury Progression. Mol Neurobiol 2023; 60:6883-6895. [PMID: 37515671 DOI: 10.1007/s12035-023-03510-9] [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: 04/14/2023] [Accepted: 07/10/2023] [Indexed: 07/31/2023]
Abstract
The pathology of spinal cord injury (SCI), including primary and secondary injuries, primarily involves hemorrhage, ischemia, edema, and inflammatory responses. Cell transplantation has been the most promising treatment for SCI in recent years; however, its specific molecular mechanism remains unclear. In this study, bioinformatics analysis verified by experiment was used to elucidate the hub genes associated with SCI and to discover the underlying molecular mechanisms of cell intervention. GSE46988 data were downloaded from the Gene Expression Omnibus dataset. In our study, differentially expressed genes (DEGs) were reanalyzed using the "R" software (R v4.2.1). Functional enrichment and protein-protein interaction network analyses were performed, and key modules and hub genes were identified. Network construction was performed for the hub genes and their associated miRNAs. Finally, a semi-quantitative analysis of hub genes and pathways was performed using quantitative real-time polymerase chain reaction. In total, 718 DEGs were identified, mainly enriched in immune and inflammation-related functions. We found that Cd4, Tp53, Rac2, and Akt3 differed between vehicle and transplanted groups, suggesting that these genes may play an essential role in the transplantation of olfactory ensheathing cells, while a toll-like receptor signaling pathway was significantly enriched in Gene set enrichment analysis, and then, the differences were statistically significant by experimentally verifying the expression of their associated molecules (Tlr4, Nf-κb, Ikkβ, Cxcl2, and Tnf-α). In addition, we searched for upstream regulatory molecules of these four central genes and constructed a regulatory network. This study is the first to construct a regulatory network for olfactory ensheathing cell transplantation in treating SCI, providing a new idea for SCI cell therapy.
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Affiliation(s)
- Yan Zhang
- Department of Anesthesiology, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, Fujian Province, China
| | - Yu-Shen Yang
- Department of Anesthesiology, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, Fujian Province, China
| | - Wei-Can Chen
- Department of Anesthesiology, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, Fujian Province, China
| | - Cong-Mei Wang
- Department of Anesthesiology, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, Fujian Province, China
| | - He-Fan He
- Department of Anesthesiology, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, Fujian Province, China.
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5
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Kounoupa Z, Tivodar S, Theodorakis K, Kyriakis D, Denaxa M, Karagogeos D. Rac1 and Rac3 GTPases and TPC2 are required for axonal outgrowth and migration of cortical interneurons. J Cell Sci 2023; 136:286920. [PMID: 36744839 DOI: 10.1242/jcs.260373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 01/31/2023] [Indexed: 02/07/2023] Open
Abstract
Rho GTPases, among them Rac1 and Rac3, are major transducers of extracellular signals and are involved in multiple cellular processes. In cortical interneurons, the neurons that control the balance between excitation and inhibition of cortical circuits, Rac1 and Rac3 are essential for their development. Ablation of both leads to a severe reduction in the numbers of mature interneurons found in the murine cortex, which is partially due to abnormal cell cycle progression of interneuron precursors and defective formation of growth cones in young neurons. Here, we present new evidence that upon Rac1 and Rac3 ablation, centrosome, Golgi complex and lysosome positioning is significantly perturbed, thus affecting both interneuron migration and axon growth. Moreover, for the first time, we provide evidence of altered expression and localization of the two-pore channel 2 (TPC2) voltage-gated ion channel that mediates Ca2+ release. Pharmacological inhibition of TPC2 negatively affected axonal growth and migration of interneurons. Our data, taken together, suggest that TPC2 contributes to the severe phenotype in axon growth initiation, extension and interneuron migration in the absence of Rac1 and Rac3.
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Affiliation(s)
- Zouzana Kounoupa
- Institute of Molecular Biology and Biotechnology (IMBB, FORTH), Heraklion 71110, Greece.,Department of Basic Science, Faculty of Medicine, University of Crete, Heraklion 71110, Greece
| | - Simona Tivodar
- Institute of Molecular Biology and Biotechnology (IMBB, FORTH), Heraklion 71110, Greece.,Department of Basic Science, Faculty of Medicine, University of Crete, Heraklion 71110, Greece
| | - Kostas Theodorakis
- Institute of Molecular Biology and Biotechnology (IMBB, FORTH), Heraklion 71110, Greece.,Department of Basic Science, Faculty of Medicine, University of Crete, Heraklion 71110, Greece
| | - Dimitrios Kyriakis
- Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxembourg, L-4365 Esch-sur-Alzette, Luxembourg
| | - Myrto Denaxa
- Institute for Fundamental Biomedical Research, Biomedical Sciences Research Centre 'Al. Fleming', Vari, 16672, Greece
| | - Domna Karagogeos
- Institute of Molecular Biology and Biotechnology (IMBB, FORTH), Heraklion 71110, Greece.,Department of Basic Science, Faculty of Medicine, University of Crete, Heraklion 71110, Greece
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6
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Bonnet M, Roche F, Fagotto-Kaufmann C, Gazdagh G, Truong I, Comunale F, Barbosa S, Bonhomme M, Nafati N, Hunt D, Rodriguez MP, Chaudhry A, Shears D, Madruga M, Vansenne F, Curie A, Kajava AV, Baralle D, Fassier C, Debant A, Schmidt S. Pathogenic TRIO variants associated with neurodevelopmental disorders perturb the molecular regulation of TRIO and axon pathfinding in vivo. Mol Psychiatry 2023; 28:1527-1544. [PMID: 36717740 DOI: 10.1038/s41380-023-01963-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 12/26/2022] [Accepted: 01/13/2023] [Indexed: 01/31/2023]
Abstract
The RhoGEF TRIO is known to play a major role in neuronal development by controlling actin cytoskeleton remodeling, primarily through the activation of the RAC1 GTPase. Numerous de novo mutations in the TRIO gene have been identified in individuals with neurodevelopmental disorders (NDDs). We have previously established the first phenotype/genotype correlation in TRIO-associated diseases, with striking correlation between the clinical features of the individuals and the opposite modulation of RAC1 activity by TRIO variants targeting different domains. The mutations hyperactivating RAC1 are of particular interest, as they are recurrently found in patients and are associated with a severe form of NDD and macrocephaly, indicating their importance in the etiology of the disease. Yet, it remains unknown how these pathogenic TRIO variants disrupt TRIO activity at a molecular level and how they affect neurodevelopmental processes such as axon outgrowth or guidance. Here we report an additional cohort of individuals carrying a pathogenic TRIO variant that reinforces our initial phenotype/genotype correlation. More importantly, by performing conformation predictions coupled to biochemical validation, we propose a model whereby TRIO is inhibited by an intramolecular fold and NDD-associated variants relieve this inhibition, leading to RAC1 hyperactivation. Moreover, we show that in cultured primary neurons and in the zebrafish developmental model, these gain-of-function variants differentially affect axon outgrowth and branching in vitro and in vivo, as compared to loss-of-function TRIO variants. In summary, by combining clinical, molecular, cellular and in vivo data, we provide compelling new evidence for the pathogenicity of novel genetic variants targeting the TRIO gene in NDDs. We report a novel mechanism whereby the fine-tuned regulation of TRIO activity is critical for proper neuronal development and is disrupted by pathogenic mutations.
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Affiliation(s)
- Maxime Bonnet
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), University of Montpellier, CNRS, Montpellier, France
| | - Fiona Roche
- Institut de la Vision, Sorbonne University, CNRS, INSERM, Paris, France
| | - Christine Fagotto-Kaufmann
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), University of Montpellier, CNRS, Montpellier, France
| | - Gabriella Gazdagh
- Faculty of Medicine, University of Southampton, Southampton, SO16 5YA, UK.,Wessex Clinical Genetics Service, University Hospital Southampton National Health Service Foundation Trust, Southampton, SO16 5YA, UK
| | - Iona Truong
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), University of Montpellier, CNRS, Montpellier, France.,Institut de Génomique Fonctionnelle (IGF), Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Franck Comunale
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), University of Montpellier, CNRS, Montpellier, France
| | - Sonia Barbosa
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), University of Montpellier, CNRS, Montpellier, France
| | - Marion Bonhomme
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), University of Montpellier, CNRS, Montpellier, France
| | - Nicolas Nafati
- Montpellier Ressources Imagerie, BioCampus, University of Montpellier, CNRS, INSERM, 34293, Montpellier, France
| | - David Hunt
- Wessex Clinical Genetics Service, Princess Anne Hospital, Southampton, SO16 5YA, UK
| | | | - Ayeshah Chaudhry
- Department of Laboratory Medicine and Genetics, Trillium Health Partners, Mississauga, ON, Canada.,Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - Deborah Shears
- Oxford Centre for Genomic Medicine, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Marcos Madruga
- Hospital Viamed Santa Ángela De la Cruz, Sevilla, 41014, Spain
| | - Fleur Vansenne
- Department of Clinical Genetics, University Medical Center, Groningen, 9713 GZ, Groningen, The Netherlands
| | - Aurore Curie
- Reference Center for Intellectual Disability from rare causes, Department of Child Neurology, Woman Mother and Child Hospital, Hospices Civils de Lyon, Lyon Neuroscience Research Centre, CNRS UMR5292, INSERM U1028, Université de Lyon, Bron, France
| | - Andrey V Kajava
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), University of Montpellier, CNRS, Montpellier, France
| | - Diana Baralle
- Faculty of Medicine, University of Southampton, Southampton, SO16 5YA, UK
| | - Coralie Fassier
- Institut de la Vision, Sorbonne University, CNRS, INSERM, Paris, France
| | - Anne Debant
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), University of Montpellier, CNRS, Montpellier, France.
| | - Susanne Schmidt
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), University of Montpellier, CNRS, Montpellier, France.
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7
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Bu F, Munshi Y, Furr JW, Min JW, Qi L, Patrizz A, Spahr ZR, Urayama A, Kofler JK, McCullough LD, Li J. Activation of neuronal Ras-related C3 botulinum toxin substrate 1 (Rac1) improves post-stroke recovery and axonal plasticity in mice. J Neurochem 2020; 157:1366-1376. [PMID: 32964455 DOI: 10.1111/jnc.15195] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 08/18/2020] [Accepted: 09/10/2020] [Indexed: 12/13/2022]
Abstract
Long-term disability after stroke is common but the mechanisms of post-stroke recovery remain unclear. Cerebral Ras-related C3 botulinum toxin substrate (Rac) 1 contributes to functional recovery after ischemic stroke in mice. As Rac1 plays divergent roles in individual cell types after central neural system injury, we herein examined the specific role of neuronal Rac1 in post-stroke recovery and axonal regeneration. Young male mice were subjected to 60-min of middle cerebral artery occlusion (MCAO). Inducible deletion of neuronal Rac1 by daily intraperitoneal injection of tamoxifen (2 mg/40 g) into Thy1-creER/Rac1-floxed mice day 7-11 after MCAO worsened cognitive (assayed by novel object recognition test) and sensorimotor (assayed by adhesive removal and pellet reaching tests) recovery day 14-28 accompanied with the reduction of neurofilament-L (NFL) and myelin basic protein (MBP) and the elevation of glial fibrillary acidic protein (GFAP) in the peri-infarct zone assessed by immunostaining. Whereas the brain tissue loss was not altered assayed by cresyl violet staining. In another approach, delayed overexpression of neuronal Rac1 by injection of lentivirus encoding Rac1 with neuronal promotor into both the cortex and striatum (total 4 μl at 1 × 109 transducing units/mL) of stroke side in C57BL/6J mice day 7 promoted stroke outcome, NFL and MBP regrowth and alleviated GFAP invasion. Furthermore, neuronal Rac1 over-expression led to the activation of p21 activating kinases (PAK) 1, mitogen-activated protein kinase kinase (MEK) 1/2 and extracellular signal-regulated kinase (ERK) 1/2, and the elevation of brain-derived neurotrophic factor (BDNF) day 14 after stroke. Finally, we observed higher counts of neuronal Rac1 in the peri-infarct zone of subacute/old ischemic stroke subjects. This work identified a neuronal Rac1 signaling in improving functional recovery and axonal regeneration after stroke, suggesting a potential therapeutic target in the recovery stage of stroke.
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Affiliation(s)
- Fan Bu
- Department of Neurology, University of Texas Health Science Center, Houston, TX, USA
| | - Yashasvee Munshi
- Department of Neurology, University of Texas Health Science Center, Houston, TX, USA
| | - J Weldon Furr
- Department of Neurology, University of Texas Health Science Center, Houston, TX, USA
| | - Jia-Wei Min
- Department of Neurology, University of Texas Health Science Center, Houston, TX, USA
| | - Li Qi
- Department of Neurology, University of Texas Health Science Center, Houston, TX, USA
| | - Anthony Patrizz
- Department of Neurology, University of Texas Health Science Center, Houston, TX, USA
| | - Zachary R Spahr
- Department of Neurology, University of Texas Health Science Center, Houston, TX, USA
| | - Akihiko Urayama
- Department of Neurology, University of Texas Health Science Center, Houston, TX, USA
| | - Julia K Kofler
- Division of Neuropathology, University of Pittsburg, PA, USA
| | - Louise D McCullough
- Department of Neurology, University of Texas Health Science Center, Houston, TX, USA
| | - Jun Li
- Department of Neurology, University of Texas Health Science Center, Houston, TX, USA
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8
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Mechanisms of axon polarization in pyramidal neurons. Mol Cell Neurosci 2020; 107:103522. [PMID: 32653476 DOI: 10.1016/j.mcn.2020.103522] [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: 11/22/2019] [Revised: 06/19/2020] [Accepted: 06/29/2020] [Indexed: 01/19/2023] Open
Abstract
Neurons are highly polarized cells that have specialized regions for synaptic input, the dendrites, and synaptic output, the axons. This polarity is critical for appropriate neural circuit formation and function. One of the central gaps in our knowledge is understanding how developing neurons initiate axon polarity. Given the critical nature of this polarity on neural circuit formation and function, neurons have evolved multiple mechanisms comprised of extracellular and intracellular cues that allow them to initiate and form axons. These mechanisms engage a variety of signaling cascades that provide positive and negative cues to ensure axon polarization. This review highlights our current knowledge of the molecular underpinnings of axon polarization in pyramidal neurons and their relevance to the development of the brain.
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9
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Yang S, Weske A, Du Y, Valera JM, Jones KL, Johnson AN. FGF signaling directs myotube guidance by regulating Rac activity. Development 2020; 147:dev.183624. [PMID: 31932350 DOI: 10.1242/dev.183624] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 12/27/2019] [Indexed: 01/25/2023]
Abstract
Nascent myotubes undergo a dramatic morphological transformation during myogenesis, in which the myotubes elongate over several cell diameters and are directed to the correct muscle attachment sites. Although this process of myotube guidance is essential to pattern the musculoskeletal system, the mechanisms that control myotube guidance remain poorly understood. Using transcriptomics, we found that components of the Fibroblast Growth Factor (FGF) signaling pathway were enriched in nascent myotubes in Drosophila embryos. Null mutations in the FGF receptor heartless (htl), or its ligands, caused significant myotube guidance defects. The FGF ligand Pyramus is expressed broadly in the ectoderm, and ectopic Pyramus expression disrupted muscle patterning. Mechanistically, Htl regulates the activity of Rho/Rac GTPases in nascent myotubes and effects changes in the actin cytoskeleton. FGF signals are thus essential regulators of myotube guidance that act through cytoskeletal regulatory proteins to pattern the musculoskeletal system.
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Affiliation(s)
- Shuo Yang
- Department of Developmental Biology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Allison Weske
- Department of Developmental Biology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Yingqiu Du
- Department of Developmental Biology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Juliana M Valera
- Department of Developmental Biology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Kenneth L Jones
- Hematology, Oncology, and Bone Marrow Transplant, Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Aaron N Johnson
- Department of Developmental Biology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
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10
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Johnson A, Nasser TIN, Spencer GE. Inhibition of Rho GTPases in Invertebrate Growth Cones Induces a Switch in Responsiveness to Retinoic Acid. Biomolecules 2019; 9:biom9090460. [PMID: 31500289 PMCID: PMC6769630 DOI: 10.3390/biom9090460] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 08/29/2019] [Accepted: 09/04/2019] [Indexed: 12/24/2022] Open
Abstract
During development, growth cones are essential for axon pathfinding by sensing numerous guidance cues in their environment. Retinoic acid, the metabolite of vitamin A, is important for neurite outgrowth during vertebrate development, but may also play a role in axon guidance, though little is known of the cellular mechanisms involved. Our previous studies showed that retinoid-induced growth cone turning of invertebrate motorneurons requires local protein synthesis and calcium influx. However, the signalling pathways that link calcium influx to cytoskeletal dynamics involved in retinoid-mediated growth cone turning are not currently known. The Rho GTPases, Cdc42 and Rac, are known regulators of the growth cone cytoskeleton. Here, we demonstrated that inhibition of Cdc42 or Rac not only prevented growth cone turning toward retinoic acid but could also induce a switch in growth cone responsiveness to chemorepulsion or growth cone collapse. However, the effects of Cdc42 or Rac inhibition on growth cone responsiveness differed, depending on whether the turning was induced by the all-trans or 9-cis retinoid isomer. The effects also differed depending on whether the growth cones maintained communication with the cell body. These data strongly suggest that Cdc42 and Rac are downstream effectors of retinoic acid during growth cone guidance.
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Affiliation(s)
- Alysha Johnson
- Department of Biological Sciences, Brock University, 1812 Sir Isaac Brock Way, St Catharines, ON L2S 3A1, Canada
| | - Tamara I N Nasser
- Department of Biological Sciences, Brock University, 1812 Sir Isaac Brock Way, St Catharines, ON L2S 3A1, Canada
| | - Gaynor E Spencer
- Department of Biological Sciences, Brock University, 1812 Sir Isaac Brock Way, St Catharines, ON L2S 3A1, Canada.
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11
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Wang T, Wu B, Zhang X, Zhang M, Zhang S, Huang W, Liu T, Yu W, Li J, Yu X. Identification of gene coexpression modules, hub genes, and pathways related to spinal cord injury using integrated bioinformatics methods. J Cell Biochem 2019; 120:6988-6997. [PMID: 30657608 DOI: 10.1002/jcb.27908] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 09/25/2018] [Indexed: 01/24/2023]
Abstract
Spinal cord injury (SCI) is characterized by dramatic neurons loss and axonal regeneration suppression. The underlying mechanism associated with SCI-induced immune suppression is still unclear. Weighted gene coexpression network analysis (WGCNA) is now widely applied for the identification of the coexpressed modules, hub genes, and pathways associated with clinic traits of diseases. We performed this study to identify hub genes associated with SCI development. Gene Expression Omnibus (GEO) data sets GSE45006 and GSE20907 were downloaded and the significant correlativity and connectivity between them were detected using WGCNA. Three significant consensus modules, including 567 eigengenes, were identified from the master GSE45006 data following the preconditions of approximate scale-free topology for WGCNA. Further bioinformatics analysis showed these eigengenes were involved in inflammatory and immune responses in SCI. Three hub genes Rac2, Itgb2, and Tyrobp and one pathway "natural killer cell-mediated cytotoxicity" were identified following short time-series expression miner, protein-protein interaction network, and functional enrichment analysis. Gradually upregulated expression patterns of Rac2, Itgb2, and Tyrobp genes at 0, 3, 7, and 14 days after SCI were confirmed based on GSE45006 and GSE20907 data set. Finally, we found that Rac2, Itgb2, and Tyrobp genes might take crucial roles in SCI development through the "natural killer cell-mediated cytotoxicity" pathway.
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Affiliation(s)
- Tienan Wang
- Department of Orthopaedics, Zhongshan Hospital of Dalian University, Dalian, China
| | - Baolin Wu
- Department of Orthopaedics, Zhongshan Hospital of Dalian University, Dalian, China
| | - Xiuzhi Zhang
- Department of Orthopaedics, Zhongshan Hospital of Dalian University, Dalian, China
| | - Meng Zhang
- Department of Orthopaedics, Zhongshan Hospital of Dalian University, Dalian, China
| | - Shuo Zhang
- Department of Orthopaedics, Zhongshan Hospital of Dalian University, Dalian, China
| | - Wei Huang
- Department of Orthopaedics, Zhongshan Hospital of Dalian University, Dalian, China
| | - Tao Liu
- Department of Orthopaedics, Zhongshan Hospital of Dalian University, Dalian, China
| | - Weiting Yu
- Department of Orthopaedics, Zhongshan Hospital of Dalian University, Dalian, China
| | - Junlei Li
- Department of Orthopaedics, Zhongshan Hospital of Dalian University, Dalian, China
| | - Xiaobing Yu
- Department of Orthopaedics, Zhongshan Hospital of Dalian University, Dalian, China
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Gujar MR, Sundararajan L, Stricker A, Lundquist EA. Control of Growth Cone Polarity, Microtubule Accumulation, and Protrusion by UNC-6/Netrin and Its Receptors in Caenorhabditis elegans. Genetics 2018; 210:235-255. [PMID: 30045855 PMCID: PMC6116952 DOI: 10.1534/genetics.118.301234] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 07/23/2018] [Indexed: 11/18/2022] Open
Abstract
UNC-6/Netrin has a conserved role in dorsal-ventral axon guidance, but the cellular events in the growth cone regulated by UNC-6/Netrin signaling during outgrowth are incompletely understood. Previous studies showed that, in growth cones migrating away from UNC-6/Netrin, the receptor UNC-5 regulates growth cone polarity, as observed by polarized F-actin, and limits the extent of growth cone protrusion. It is unclear how UNC-5 inhibits protrusion, and how UNC-40 acts in concert with UNC-5 to regulate polarity and protrusion. New results reported here indicate that UNC-5 normally restricts microtubule (MT) + end accumulation in the growth cone. Tubulin mutant analysis and colchicine treatment suggest that stable MTs are necessary for robust growth cone protrusion. Thus, UNC-5 might inhibit protrusion in part by restricting growth cone MT accumulation. Previous studies showed that the UNC-73/Trio Rac GEF and UNC-33/CRMP act downstream of UNC-5 in protrusion. Here, we show that UNC-33/CRMP regulates both growth cone dorsal asymmetric F-actin accumulation and MT accumulation, whereas UNC-73/Trio Rac GEF activity only affects F-actin accumulation. This suggests an MT-independent mechanism used by UNC-5 to inhibit protrusion, possibly by regulating lamellipodial and filopodial actin. Furthermore, we show that UNC-6/Netrin and the receptor UNC-40/DCC are required for excess protrusion in unc-5 mutants, but not for loss of F-actin asymmetry or MT + end accumulation, indicating that UNC-6/Netrin and UNC-40/DCC are required for protrusion downstream of, or in parallel to, F-actin asymmetry and MT + end entry. F-actin accumulation might represent a polarity mark in the growth cone where protrusion will occur, and not protrusive lamellipodial and filopodial actin per se Our data suggest a model in which UNC-6/Netrin first polarizes the growth cone via UNC-5, and then regulates protrusion based upon this polarity (the polarity/protrusion model). UNC-6/Netrin inhibits protrusion ventrally via UNC-5, and stimulates protrusion dorsally via UNC-40, resulting in dorsally-directed migration. The polarity/protrusion model represents a novel conceptual paradigm in which to understand axon guidance and growth cone migration away from UNC-6/Netrin.
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Affiliation(s)
- Mahekta R Gujar
- Program in Molecular, Cellular, and Developmental Biology, Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66046
| | - Lakshmi Sundararajan
- Program in Molecular, Cellular, and Developmental Biology, Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66046
| | - Aubrie Stricker
- Program in Molecular, Cellular, and Developmental Biology, Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66046
| | - Erik A Lundquist
- Program in Molecular, Cellular, and Developmental Biology, Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66046
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13
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Alan JK, Robinson SK, Magsig KL, Demarco RS, Lundquist EA. The Atypical Rho GTPase CHW-1 Works with SAX-3/Robo To Mediate Axon Guidance in Caenorhabditis elegans. G3 (BETHESDA, MD.) 2018; 8:1885-1895. [PMID: 29653940 PMCID: PMC5982818 DOI: 10.1534/g3.118.200148] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 03/26/2018] [Indexed: 01/12/2023]
Abstract
During development, neuronal cells extend an axon toward their target destination in response to a cue to form a properly functioning nervous system. Rho proteins, Ras-related small GTPases that regulate cytoskeletal organization and dynamics, cell adhesion, and motility, are known to regulate axon guidance. Despite extensive knowledge about canonical Rho proteins (RhoA/Rac1/Cdc42), little is known about the Caenorhabditis elegans (C. elegans) atypical Cdc42-like family members CHW-1 and CRP-1 in regards to axon pathfinding and neuronal migration. chw-1(Chp/Wrch) encodes a protein that resembles human Chp (Wrch-2/RhoV) and Wrch-1 (RhoU), and crp-1 encodes for a protein that resembles TC10 and TCL. Here, we show that chw-1 works redundantly with crp-1 and cdc-42 in axon guidance. Furthermore, proper levels of chw-1 expression and activity are required for proper axon guidance. When examining CHW-1 GTPase mutants, we found that the native CHW-1 protein is likely partially activated, and mutations at a conserved residue (position 12 using Ras numbering, position 18 in CHW-1) alter axon guidance and neural migration. Additionally, we showed that chw-1 genetically interacts with the guidance receptor sax-3 in PDE neurons. Finally, in VD/DD motor neurons, chw-1 works downstream of sax-3 to control axon guidance. In summary, this is the first study implicating the atypical Rho GTPases chw-1 and crp-1 in axon guidance. Furthermore, this is the first evidence of genetic interaction between chw-1 and the guidance receptor sax-3 These data suggest that chw-1 is likely acting downstream and/or in parallel to sax-3 in axon guidance.
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Affiliation(s)
- Jamie K Alan
- Department of Pharmacology and Toxicology; Michigan State University; East Lansing, MI 48824
| | - Sara K Robinson
- College of Medicine; Central Michigan University; Mount Pleasant, MI 48859
| | - Katie L Magsig
- College of Medicine; Central Michigan University; Mount Pleasant, MI 48859
| | - Rafael S Demarco
- Department of Molecular Biosciences; University of Kansas; Lawrence, KS 60045
| | - Erik A Lundquist
- Department of Molecular Biosciences; University of Kansas; Lawrence, KS 60045
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14
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Li W, Tam KMV, Chan WWR, Koon AC, Ngo JCK, Chan HYE, Lau KF. Neuronal adaptor FE65 stimulates Rac1-mediated neurite outgrowth by recruiting and activating ELMO1. J Biol Chem 2018; 293:7674-7688. [PMID: 29615491 DOI: 10.1074/jbc.ra117.000505] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 03/12/2018] [Indexed: 12/25/2022] Open
Abstract
Neurite outgrowth is a crucial process in developing neurons for neural network formation. Understanding the regulatory mechanisms of neurite outgrowth is essential for developing strategies to stimulate neurite regeneration after nerve injury and in neurodegenerative disorders. FE65 is a brain-enriched adaptor that stimulates Rac1-mediated neurite elongation. However, the precise mechanism by which FE65 promotes the process remains elusive. Here, we show that ELMO1, a subunit of ELMO1-DOCK180 bipartite Rac1 guanine nucleotide exchange factor (GEF), interacts with the FE65 N-terminal region. Overexpression of FE65 and/or ELMO1 enhances, whereas knockdown of FE65 or ELMO1 inhibits, neurite outgrowth and Rac1 activation. The effect of FE65 alone or together with ELMO1 is attenuated by an FE65 double mutation that disrupts FE65-ELMO1 interaction. Notably, FE65 is found to activate ELMO1 by diminishing ELMO1 intramolecular autoinhibitory interaction and to promote the targeting of ELMO1 to the plasma membrane, where Rac1 is activated. We also show that FE65, ELMO1, and DOCK180 form a tripartite complex. Knockdown of DOCK180 reduces the stimulatory effect of FE65-ELMO1 on Rac1 activation and neurite outgrowth. Thus, we identify a novel mechanism by which FE65 stimulates Rac1-mediated neurite outgrowth by recruiting and activating ELMO1.
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Affiliation(s)
- Wen Li
- From the School of Life Sciences, Faculty of Science, Chinese University of Hong Kong, Shatin New Territories, Hong Kong
| | - Ka Ming Vincent Tam
- From the School of Life Sciences, Faculty of Science, Chinese University of Hong Kong, Shatin New Territories, Hong Kong
| | - Wai Wa Ray Chan
- From the School of Life Sciences, Faculty of Science, Chinese University of Hong Kong, Shatin New Territories, Hong Kong
| | - Alex Chun Koon
- From the School of Life Sciences, Faculty of Science, Chinese University of Hong Kong, Shatin New Territories, Hong Kong
| | - Jacky Chi Ki Ngo
- From the School of Life Sciences, Faculty of Science, Chinese University of Hong Kong, Shatin New Territories, Hong Kong
| | - Ho Yin Edwin Chan
- From the School of Life Sciences, Faculty of Science, Chinese University of Hong Kong, Shatin New Territories, Hong Kong
| | - Kwok-Fai Lau
- From the School of Life Sciences, Faculty of Science, Chinese University of Hong Kong, Shatin New Territories, Hong Kong
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15
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Pandey A, Yadav V, Sharma A, Khurana JP, Pandey GK. The unc-53 gene negatively regulates rac GTPases to inhibit unc-5 activity during Distal tip cell migrations in C. elegans. Cell Adh Migr 2017; 12:195-203. [PMID: 28678595 DOI: 10.1080/19336918.2017.1345413] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
The unc-53/NAV2 gene encodes for an adaptor protein required for cell migrations along the anteroposterior (AP) axes of C. elegans. This study identifies unc-53 as a novel component of signaling pathways regulating Distal tip cell (DTC) migrations along the AP and dorsoventral (DV) axes. unc-53 negatively regulates and functions downstream of ced-10/Rac pathway genes; ced-10/Rac and mig-2/RhoG, which are required for proper DTC migration. Moreover, unc-53 exhibits genetic interaction with abl-1 and unc-5, the 2 known negative regulators of ced-10/Rac signaling. Our genetic analysis supports the model, where abl-1 negatively regulates unc-53 during DTC migrations and requirement of unc-53 function during both AP and DV DTC migrations could be due to unc-53 mediated regulation of unc-5 activity.
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Affiliation(s)
- Amita Pandey
- a Department of Plant Molecular Biology , University of Delhi South Campus , New Delhi , India
| | - Vipul Yadav
- b Department of Genetics , University of Delhi South Campus , New Delhi , India
| | - Aditi Sharma
- a Department of Plant Molecular Biology , University of Delhi South Campus , New Delhi , India
| | - Jitendra P Khurana
- a Department of Plant Molecular Biology , University of Delhi South Campus , New Delhi , India
| | - Girdhar K Pandey
- a Department of Plant Molecular Biology , University of Delhi South Campus , New Delhi , India
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16
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Gugliandolo A, Diomede F, Cardelli P, Bramanti A, Scionti D, Bramanti P, Trubiani O, Mazzon E. Transcriptomic analysis of gingival mesenchymal stem cells cultured on 3D bioprinted scaffold: A promising strategy for neuroregeneration. J Biomed Mater Res A 2017; 106:126-137. [PMID: 28879677 DOI: 10.1002/jbm.a.36213] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 08/02/2017] [Accepted: 08/22/2017] [Indexed: 01/01/2023]
Abstract
The combined approach of mesenchymal stem cells (MSCs) and scaffolds has been proposed as a potential therapeutic tool for the treatment of neurodegenerative diseases. Indeed, even if MSCs can promote neuronal regeneration, replacing lost neurons or secreting neurotrophic factors, many limitations still exist for their application in regenerative medicine, including the low survival and differentiation rate. The scaffolds, by mimicking the endogenous microenvironment, have shown to promote cell survival, proliferation, and differentiation. In this work, gingival mesenchymal stem cells (GMSCs), isolated from healthy donors, were expanded in vitro, by culturing them adherent in plastic dishes (CTR-GMSCs) or on a poly(lactic acid) scaffold (SC-GMSCs). In order to evaluate the survival and the neurogenic differentiation potential, we performed a comparative transcriptomic analysis between CTR-GMSCs and SC-GMSCs by next generation sequencing. We found that SC-GMSCs showed an increased expression of neurogenic and prosurvival genes. In particular, genes involved in neurotrophin signaling and PI3K/Akt pathways were upregulated. On the contrary, proapoptotic and negative regulator of neuronal growth genes were downregulated. Moreover, nestin and GAP-43 protein levels increased in SC-GMSCs, confirming the neurogenic commitment of these cells. In conclusion, the scaffold, providing a trophic support for MSCs, may promote GMSCs differentiation toward a neuronal phenotype and survival. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 126-137, 2018.
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Affiliation(s)
- Agnese Gugliandolo
- IRCCS Centro Neurolesi "Bonino-Pulejo," Via Provinciale Palermo, Contrada Casazza, 98124 Messina, Italy
| | - Francesca Diomede
- Stem Cells and Regenerative Medicine Laboratory, Department of Medical, Oral and Biotechnological Sciences, University "G. D'Annunzio," Chieti-Pescara, via dei Vestini, 31, 66100, Chieti, Italy
| | - Paolo Cardelli
- Stem Cells and Regenerative Medicine Laboratory, Department of Medical, Oral and Biotechnological Sciences, University "G. D'Annunzio," Chieti-Pescara, via dei Vestini, 31, 66100, Chieti, Italy
| | - Alessia Bramanti
- IRCCS Centro Neurolesi "Bonino-Pulejo," Via Provinciale Palermo, Contrada Casazza, 98124 Messina, Italy.,Institute of Applied Science and Intelligent Systems "ISASI Eduardo Caianiello,", National Research Council of Italy, Messina, Italy
| | - Domenico Scionti
- IRCCS Centro Neurolesi "Bonino-Pulejo," Via Provinciale Palermo, Contrada Casazza, 98124 Messina, Italy
| | - Placido Bramanti
- IRCCS Centro Neurolesi "Bonino-Pulejo," Via Provinciale Palermo, Contrada Casazza, 98124 Messina, Italy
| | - Oriana Trubiani
- Stem Cells and Regenerative Medicine Laboratory, Department of Medical, Oral and Biotechnological Sciences, University "G. D'Annunzio," Chieti-Pescara, via dei Vestini, 31, 66100, Chieti, Italy
| | - Emanuela Mazzon
- IRCCS Centro Neurolesi "Bonino-Pulejo," Via Provinciale Palermo, Contrada Casazza, 98124 Messina, Italy
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17
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Zhang S, Liang Z, Sun W, Pei L. Repeated propofol anesthesia induced downregulation of hippocampal miR-132 and learning and memory impairment of rats. Brain Res 2017; 1670:156-164. [PMID: 28465226 DOI: 10.1016/j.brainres.2017.04.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2016] [Revised: 04/10/2017] [Accepted: 04/15/2017] [Indexed: 12/15/2022]
Abstract
Several studies have reported that neonatal exposure to propofol may cause neurotoxicity in the hippocampus, involving long-term neurodevelopmental impairments. We aimed to detect real-time changes of miR-132 of neonatal rats exposed to propofol anesthesia and to characterize subsequent changes in learning and memory. Seven-day-old Sprague-Dawley rats were injected intraperitoneally with 40mg/kg propofol at 0, 120, and 240 min or with isotonic fat emulsion as controls. Expression levels of miR-132 were assessed, and the mRNA and protein expression levels of p250GAP, a prominent target for miR-132, were evaluated at different time points during development. Dendritic spines were counted, and the learning and memory abilities were also investigated. We found that repeated propofol anesthesia resulted in a significant downregulation of miR-132 levels and a decrease in the number of dendritic spines in the hippocampus leading to learning and memory dysfunction. Therefore, repeated propofol anesthesia induces downregulation of miR-132 and learning and memory impairment in the hippocampus of rats.
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Affiliation(s)
- Shuo Zhang
- Department of Anesthesiology, the First Affiliated Hospital of China Medical University, Shenyang, Liaoning, China
| | - Zuodi Liang
- Department of Anesthesiology, the First Affiliated Hospital of China Medical University, Shenyang, Liaoning, China
| | - Wenchong Sun
- Department of Anesthesiology, the First Affiliated Hospital of China Medical University, Shenyang, Liaoning, China
| | - Ling Pei
- Department of Anesthesiology, the First Affiliated Hospital of China Medical University, Shenyang, Liaoning, China.
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18
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GEFs and Rac GTPases control directional specificity of neurite extension along the anterior-posterior axis. Proc Natl Acad Sci U S A 2016; 113:6973-8. [PMID: 27274054 DOI: 10.1073/pnas.1607179113] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Although previous studies have identified many extracellular guidance molecules and intracellular signaling proteins that regulate axonal outgrowth and extension, most were conducted in the context of unidirectional neurite growth, in which the guidance cues either attract or repel growth cones. Very few studies addressed how intracellular signaling molecules differentially specify bidirectional outgrowth. Here, using the bipolar PLM neurons in Caenorhabditis elegans, we show that the guanine nucleotide exchange factors (GEFs) UNC-73/Trio and TIAM-1 promote anterior and posterior neurite extension, respectively. The Rac subfamily GTPases act downstream of the GEFs; CED-10/Rac1 is activated by TIAM-1, whereas CED-10 and MIG-2/RhoG act redundantly downstream of UNC-73. Moreover, these two pathways antagonize each other and thus regulate the directional bias of neuritogenesis. Our study suggests that directional specificity of neurite extension is conferred through the intracellular activation of distinct GEFs and Rac GTPases.
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19
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Zhao Z, Xu J, Chen J, Kim S, Reimers M, Bacanu SA, Yu H, Liu C, Sun J, Wang Q, Jia P, Xu F, Zhang Y, Kendler KS, Peng Z, Chen X. Transcriptome sequencing and genome-wide association analyses reveal lysosomal function and actin cytoskeleton remodeling in schizophrenia and bipolar disorder. Mol Psychiatry 2015; 20:563-572. [PMID: 25113377 PMCID: PMC4326626 DOI: 10.1038/mp.2014.82] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 05/23/2014] [Accepted: 06/17/2014] [Indexed: 12/20/2022]
Abstract
Schizophrenia (SCZ) and bipolar disorder (BPD) are severe mental disorders with high heritability. Clinicians have long noticed the similarities of clinic symptoms between these disorders. In recent years, accumulating evidence indicates some shared genetic liabilities. However, what is shared remains elusive. In this study, we conducted whole transcriptome analysis of post-mortem brain tissues (cingulate cortex) from SCZ, BPD and control subjects, and identified differentially expressed genes in these disorders. We found 105 and 153 genes differentially expressed in SCZ and BPD, respectively. By comparing the t-test scores, we found that many of the genes differentially expressed in SCZ and BPD are concordant in their expression level (q⩽0.01, 53 genes; q⩽0.05, 213 genes; q⩽0.1, 885 genes). Using genome-wide association data from the Psychiatric Genomics Consortium, we found that these differentially and concordantly expressed genes were enriched in association signals for both SCZ (P<10(-7)) and BPD (P=0.029). To our knowledge, this is the first time that a substantially large number of genes show concordant expression and association for both SCZ and BPD. Pathway analyses of these genes indicated that they are involved in the lysosome, Fc gamma receptor-mediated phagocytosis, regulation of actin cytoskeleton pathways, along with several cancer pathways. Functional analyses of these genes revealed an interconnected pathway network centered on lysosomal function and the regulation of actin cytoskeleton. These pathways and their interacting network were principally confirmed by an independent transcriptome sequencing data set of the hippocampus. Dysregulation of lysosomal function and cytoskeleton remodeling has direct impacts on endocytosis, phagocytosis, exocytosis, vesicle trafficking, neuronal maturation and migration, neurite outgrowth and synaptic density and plasticity, and different aspects of these processes have been implicated in SCZ and BPD.
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Affiliation(s)
- Zhongming Zhao
- Departments of Biomedical Informatics and Psychiatry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Jiabao Xu
- Beijing Genomics Institute (BGI), Shenzhen, Guangdong, 518083, China
| | - Jingchun Chen
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Sanghyeon Kim
- Stanley Laboratory of Brain Research, 9800 Medical Center Drive, Rockville, MD 20850, USA
| | - Mark Reimers
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Silviu-Alin Bacanu
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Hui Yu
- Departments of Biomedical Informatics and Psychiatry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Chunyu Liu
- Department of Psychiatry, University of Illinois at Chicago, Chicago, IL 60637, USA
| | - Jingchun Sun
- Departments of Biomedical Informatics and Psychiatry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Quan Wang
- Departments of Biomedical Informatics and Psychiatry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Peilin Jia
- Departments of Biomedical Informatics and Psychiatry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Fengping Xu
- Beijing Genomics Institute (BGI), Shenzhen, Guangdong, 518083, China
| | - Yong Zhang
- Beijing Genomics Institute (BGI), Shenzhen, Guangdong, 518083, China
| | - Kenneth S. Kendler
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Zhiyu Peng
- Beijing Genomics Institute (BGI), Shenzhen, Guangdong, 518083, China
| | - Xiangning Chen
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, VA 23298, USA
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20
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Stiles TL, Kapiloff MS, Goldberg JL. The role of soluble adenylyl cyclase in neurite outgrowth. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1842:2561-8. [PMID: 25064589 PMCID: PMC4262618 DOI: 10.1016/j.bbadis.2014.07.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 07/11/2014] [Accepted: 07/15/2014] [Indexed: 12/25/2022]
Abstract
Axon regeneration in the mature central nervous system is limited by extrinsic inhibitory signals and a postnatal decline in neurons' intrinsic growth capacity. Neuronal levels of the second messenger cAMP are important in regulating both intrinsic growth capacity and neurons' responses to extrinsic factors. Approaches which increase intracellular cAMP in neurons enhance neurite outgrowth and facilitate regeneration after injury. Thus, understanding the factors which affect cAMP in neurons is of potential therapeutic importance. Recently, soluble adenylyl cyclase (sAC, ADCY10), the ubiquitous, non-transmembrane adenylyl cyclase, was found to play a key role in neuronal survival and axon growth. sAC is activated by bicarbonate and cations and may translate physiologic signals from metabolism and electrical activity into a neuron's decision to survive or regenerate. Here we critically review the literature surrounding sAC and cAMP signaling in neurons to further elucidate the potential role of sAC signaling in neurite outgrowth and regeneration. This article is part of a Special Issue entitled: The role of soluble adenylyl cyclase in health and disease.
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Affiliation(s)
- Travis L Stiles
- Shiley Eye Center, University of California, San Diego, CA 92093, USA
| | - Michael S Kapiloff
- Departments of Pediatrics and Medicine, Leonard M. Miller School of Medicine, University of Miami, Miami, FL 33136, USA
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21
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Abstract
A crucial step in the development of the vertebrate visual system is the branching of retinal ganglion cell (RGC) axons within their target, the superior colliculus/tectum. A major player in this process is the neurotrophin brain-derived neurotrophic factor (BDNF). However, the molecular basis for the signaling pathways mediating BDNF action is less well understood. As BDNF exerts some of its functions by controlling the expression of microRNAs (miRNAs), we investigated whether miRNAs are also involved in BDNF-mediated retinal axon branching. Here, we demonstrate that the expression pattern of miRNA-132 in the retina is consistent with its involvement in this process, and that BDNF induces the upregulation of miRNA-132 in retinal cultures. Furthermore, in vitro gain-of-function and loss-of-function approaches in retinal cultures reveal that miRNA-132 mediates axon branching downstream of BDNF. A known target of miRNA-132 is the Rho family GTPase-activating protein, p250GAP. We find that p250GAP is expressed in RGC axons and mediates the effects of miRNA-132 in BDNF-induced branching. BDNF treatment or overexpression of miRNA-132 leads to a reduction in p250GAP protein levels in retinal cultures, whereas the overexpression of p250GAP abolishes BDNF-induced branching. Finally, we used a loss-of-function approach to show that miRNA-132 affects the maturation of RGC termination zones in the mouse superior colliculus in vivo, while their topographic targeting remains intact. Together, our data indicate that BDNF promotes RGC axon branching during retinocollicular/tectal map formation via upregulation of miRNA-132, which in turn downregulates p250GAP.
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22
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Tivodar S, Kalemaki K, Kounoupa Z, Vidaki M, Theodorakis K, Denaxa M, Kessaris N, de Curtis I, Pachnis V, Karagogeos D. Rac-GTPases Regulate Microtubule Stability and Axon Growth of Cortical GABAergic Interneurons. Cereb Cortex 2014; 25:2370-82. [PMID: 24626607 PMCID: PMC4537417 DOI: 10.1093/cercor/bhu037] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Cortical interneurons are characterized by extraordinary functional and morphological diversity. Although tremendous progress has been made in uncovering molecular and cellular mechanisms implicated in interneuron generation and function, several questions still remain open. Rho-GTPases have been implicated as intracellular mediators of numerous developmental processes such as cytoskeleton organization, vesicle trafficking, transcription, cell cycle progression, and apoptosis. Specifically in cortical interneurons, we have recently shown a cell-autonomous and stage-specific requirement for Rac1 activity within proliferating interneuron precursors. Conditional ablation of Rac1 in the medial ganglionic eminence leads to a 50% reduction of GABAergic interneurons in the postnatal cortex. Here we examine the additional role of Rac3 by analyzing Rac1/Rac3 double-mutant mice. We show that in the absence of both Rac proteins, the embryonic migration of medial ganglionic eminence-derived interneurons is further impaired. Postnatally, double-mutant mice display a dramatic loss of cortical interneurons. In addition, Rac1/Rac3-deficient interneurons show gross cytoskeletal defects in vitro, with the length of their leading processes significantly reduced and a clear multipolar morphology. We propose that in the absence of Rac1/Rac3, cortical interneurons fail to migrate tangentially towards the pallium due to defects in actin and microtubule cytoskeletal dynamics.
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Affiliation(s)
- Simona Tivodar
- Institute of Molecular Biology and Biotechnology (IMBB, FORTH), Heraklion, Greece Department of Basic Science, Faculty of Medicine, University of Crete, Heraklion, Greece
| | - Katerina Kalemaki
- Institute of Molecular Biology and Biotechnology (IMBB, FORTH), Heraklion, Greece Department of Basic Science, Faculty of Medicine, University of Crete, Heraklion, Greece
| | - Zouzana Kounoupa
- Institute of Molecular Biology and Biotechnology (IMBB, FORTH), Heraklion, Greece Department of Basic Science, Faculty of Medicine, University of Crete, Heraklion, Greece
| | - Marina Vidaki
- Institute of Molecular Biology and Biotechnology (IMBB, FORTH), Heraklion, Greece Department of Basic Science, Faculty of Medicine, University of Crete, Heraklion, Greece Current Address: Koch Institute for Integrative Cancer Research at MIT, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Kostas Theodorakis
- Institute of Molecular Biology and Biotechnology (IMBB, FORTH), Heraklion, Greece Department of Basic Science, Faculty of Medicine, University of Crete, Heraklion, Greece
| | - Myrto Denaxa
- Division of Molecular Neurobiology, Medical Research Council, National Institute for Medical Research, London, UK
| | - Nicoletta Kessaris
- Wolfson Institute for Biomedical Research and Department of Cell and Developmental Biology, University College London, UK
| | - Ivan de Curtis
- Cell Adhesion Unit, Dibit, San Raffaele Scientific Institute, 20132 Milano, Italy
| | - Vassilis Pachnis
- Division of Molecular Neurobiology, Medical Research Council, National Institute for Medical Research, London, UK
| | - Domna Karagogeos
- Institute of Molecular Biology and Biotechnology (IMBB, FORTH), Heraklion, Greece Department of Basic Science, Faculty of Medicine, University of Crete, Heraklion, Greece
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Doi M, Minematsu H, Kubota Y, Nishiwaki K, Miyamoto M. The novel Rac effector RIN-1 regulates neuronal cell migration and axon pathfinding in C. elegans. Development 2013; 140:3435-44. [PMID: 23900541 DOI: 10.1242/dev.089722] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Cell migration and axon guidance require proper regulation of the actin cytoskeleton in response to extracellular guidance cues. Rho/Rac small GTPases are essential regulators of actin remodeling. Caenorhabditis elegans CED-10 is a Rac1 homolog that is required for various cellular morphological changes and migration events and is under the control of several guidance signaling pathways. There is still considerable uncertainty regarding events following the activation of guidance receptors by extracellular signals and the regulation of actin dynamics based on spatiotemporally restricted Rac activity. Here we show that the VPS9 domain protein RIN-1 acts as a novel effector for CED-10 in C. elegans. The orthologous mammalian Rin1 protein has previously been identified as an effector for Ras GTPase and is now known to function as a guanine nucleotide exchange factor for Rab5 GTPase. We found that RIN-1 specifically binds to the GTP-bound form of CED-10 and that mutations in rin-1 cause significant defects in migration and axon guidance of restricted neuronal cell types including AVM and HSN neurons, in contrast to the various defects observed in ced-10 mutants. Our analyses place RIN-1 in the Slit-Robo genetic pathway that regulates repulsive signaling for dorsoventral axon guidance. In rin-1 mutants, actin accumulated on both the ventral and dorsal sides of the developing HSN neuron, in contrast to its ventral accumulation in wild type. These results strongly suggest that RIN-1 acts as an effector for CED-10/Rac1 and regulates actin remodeling in response to restricted guidance cues.
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Affiliation(s)
- Motomichi Doi
- Biomedical Research Institute, AIST, Tsukuba, Ibaraki 305-8566, Japan.
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24
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Alan JK, Struckhoff EC, Lundquist EA. Multiple cytoskeletal pathways and PI3K signaling mediate CDC-42-induced neuronal protrusion in C. elegans. Small GTPases 2013; 4:208-20. [PMID: 24149939 PMCID: PMC4011816 DOI: 10.4161/sgtp.26602] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Revised: 09/23/2013] [Accepted: 09/25/2013] [Indexed: 12/30/2022] Open
Abstract
Rho GTPases are key regulators of cellular protrusion and are involved in many developmental events including axon guidance during nervous system development. Rho GTPase pathways display functional redundancy in developmental events, including axon guidance. Therefore, their roles can often be masked when using simple loss-of-function genetic approaches. As a complement to loss-of-function genetics, we constructed a constitutively activated CDC-42(G12V) expressed in C. elegans neurons. CDC-42(G12V) drove the formation of ectopic lamellipodial and filopodial protrusions in the PDE neurons, which resembled protrusions normally found on migrating growth cones of axons. We then used a candidate gene approach to identify molecules that mediate CDC-42(G12V)-induced ectopic protrusions by determining if loss of function of the genes could suppress CDC-42(G12V). Using this approach, we identified 3 cytoskeletal pathways previously implicated in axon guidance, the Arp2/3 complex, UNC-115/abLIM, and UNC-43/Ena. We also identified the Nck-interacting kinase MIG-15/NIK and p21-activated kinases (PAKs), also implicated in axon guidance. Finally, PI3K signaling was required, specifically the Rictor/mTORC2 branch but not the mTORC1 branch that has been implicated in other aspects of PI3K signaling including stress and aging. Our results indicate that multiple pathways can mediate CDC-42-induced neuronal protrusions that might be relevant to growth cone protrusions during axon pathfinding. Each of these pathways involves Rac GTPases, which might serve to integrate the pathways and coordinate the multiple CDC-42 pathways. These pathways might be relevant to developmental events such as axon pathfinding as well as disease states such as metastatic melanoma.
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Affiliation(s)
| | - Eric C Struckhoff
- Department of Molecular Biosciences; University of Kansas; Lawrence, KS USA
| | - Erik A Lundquist
- Department of Molecular Biosciences; University of Kansas; Lawrence, KS USA
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25
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Cheung HNM, Dunbar C, Mórotz GM, Cheng WH, Chan HYE, Miller CCJ, Lau KF. FE65 interacts with ADP-ribosylation factor 6 to promote neurite outgrowth. FASEB J 2013; 28:337-49. [PMID: 24056087 DOI: 10.1096/fj.13-232694] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
FE65 is an adaptor protein that binds to the amyloid precursor protein (APP). As such, FE65 has been implicated in the pathogenesis of Alzheimer's disease. In addition, evidence suggests that FE65 is involved in brain development. It is generally believed that FE65 participates in these processes by recruiting various interacting partners to form functional complexes. Here, we show that via its first phosphotyrosine binding (PTB) domain, FE65 binds to the small GTPase ADP-ribosylation factor 6 (ARF6). FE65 preferentially binds to ARF6-GDP, and they colocalize in neuronal growth cones. Interestingly, FE65 stimulates the activation of both ARF6 and its downstream GTPase Rac1, a regulator of actin dynamics, and functions in growth cones to stimulate neurite outgrowth. We show that transfection of FE65 and/or ARF6 promotes whereas small interfering RNA knockdown of FE65 or ARF6 inhibits neurite outgrowth in cultured neurons as compared to the mock-transfected control cells. Moreover, knockdown of ARF6 attenuates FE65 stimulation of neurite outgrowth and defective neurite outgrowth seen in FE65-deficient neurons is partially corrected by ARF6 overexpression. Notably, the stimulatory effect of FE65 and ARF6 on neurite outgrowth is abrogated either by dominant-negative Rac1 or knockdown of Rac1. Thus, we identify FE65 as a novel regulator of neurite outgrowth via controlling ARF6-Rac1 signaling.
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Affiliation(s)
- Hei Nga Maggie Cheung
- 1School of Life Sciences, Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR, China.
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26
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Hou X, Katahira T, Ohashi K, Mizuno K, Sugiyama S, Nakamura H. Coactosin accelerates cell dynamism by promoting actin polymerization. Dev Biol 2013; 379:53-63. [DOI: 10.1016/j.ydbio.2013.04.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Revised: 03/05/2013] [Accepted: 04/09/2013] [Indexed: 01/25/2023]
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27
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Nelson JC, Stavoe AKH, Colón-Ramos DA. The actin cytoskeleton in presynaptic assembly. Cell Adh Migr 2013; 7:379-87. [PMID: 23628914 DOI: 10.4161/cam.24803] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Dramatic morphogenetic processes underpin nearly every step of nervous system development, from initial neuronal migration and axon guidance to synaptogenesis. Underlying this morphogenesis are dynamic rearrangements of cytoskeletal architecture. Here we discuss the roles of the actin cytoskeleton in the development of presynaptic terminals, from the elaboration of terminal arbors to the recruitment of presynaptic vesicles and active zone components. The studies discussed here underscore the importance of actin regulation at every step in neuronal circuit assembly.
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Affiliation(s)
- Jessica C Nelson
- Program in Cellular Neuroscience, Neurodegeneration and Repair; Department of Cell Biology; Yale University; New Haven, CT USA
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28
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Stavoe AKH, Nelson JC, Martínez-Velázquez LA, Klein M, Samuel ADT, Colón-Ramos DA. Synaptic vesicle clustering requires a distinct MIG-10/Lamellipodin isoform and ABI-1 downstream from Netrin. Genes Dev 2012; 26:2206-21. [PMID: 23028145 DOI: 10.1101/gad.193409.112] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The chemotrophic factor Netrin can simultaneously instruct different neurodevelopmental programs in individual neurons in vivo. How neurons correctly interpret the Netrin signal and undergo the appropriate neurodevelopmental response is not understood. Here we identify MIG-10 isoforms as critical determinants of individual cellular responses to Netrin. We determined that distinct MIG-10 isoforms, varying only in their N-terminal motifs, can localize to specific subcellular domains and are differentially required for discrete neurodevelopmental processes in vivo. We identified MIG-10B as an isoform uniquely capable of localizing to presynaptic regions and instructing synaptic vesicle clustering in response to Netrin. MIG-10B interacts with Abl-interacting protein-1 (ABI-1)/Abi1, a component of the WAVE complex, to organize the actin cytoskeleton at presynaptic sites and instruct vesicle clustering through SNN-1/Synapsin. We identified a motif in the MIG-10B N-terminal domain that is required for its function and localization to presynaptic sites. With this motif, we engineered a dominant-negative MIG-10B construct that disrupts vesicle clustering and animal thermotaxis behavior when expressed in a single neuron in vivo. Our findings indicate that the unique N-terminal domains confer distinct MIG-10 isoforms with unique capabilities to localize to distinct subcellular compartments, organize the actin cytoskeleton at these sites, and instruct distinct Netrin-dependent neurodevelopmental programs.
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Affiliation(s)
- Andrea K H Stavoe
- Program in Cellular Neuroscience, Neurodegeneration, and Repair, Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06536, USA
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29
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Demarco RS, Struckhoff EC, Lundquist EA. The Rac GTP exchange factor TIAM-1 acts with CDC-42 and the guidance receptor UNC-40/DCC in neuronal protrusion and axon guidance. PLoS Genet 2012; 8:e1002665. [PMID: 22570618 PMCID: PMC3343084 DOI: 10.1371/journal.pgen.1002665] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 03/07/2012] [Indexed: 11/19/2022] Open
Abstract
The mechanisms linking guidance receptors to cytoskeletal dynamics in the growth cone during axon extension remain mysterious. The Rho-family GTPases Rac and CDC-42 are key regulators of growth cone lamellipodia and filopodia formation, yet little is understood about how these molecules interact in growth cone outgrowth or how the activities of these molecules are regulated in distinct contexts. UNC-73/Trio is a well-characterized Rac GTP exchange factor in Caenorhabditis elegans axon pathfinding, yet UNC-73 does not control CED-10/Rac downstream of UNC-6/Netrin in attractive axon guidance. Here we show that C. elegans TIAM-1 is a Rac-specific GEF that links CDC-42 and Rac signaling in lamellipodia and filopodia formation downstream of UNC-40/DCC. We also show that TIAM-1 acts with UNC-40/DCC in axon guidance. Our results indicate that a CDC-42/TIAM-1/Rac GTPase signaling pathway drives lamellipodia and filopodia formation downstream of the UNC-40/DCC guidance receptor, a novel set of interactions between these molecules. Furthermore, we show that TIAM-1 acts with UNC-40/DCC in axon guidance, suggesting that TIAM-1 might regulate growth cone protrusion via Rac GTPases in response to UNC-40/DCC. Our results also suggest that Rac GTPase activity is controlled by different GEFs in distinct axon guidance contexts, explaining how Rac GTPases can specifically control multiple cellular functions. Axons extend great distances to make precise synaptic connections in the developing nervous system. Axons are guided to their targets by the growth cone, a dynamic structure at the axon distal tip that senses extracellular cues telling the axon where to go. In response to guidance cues, growth cones alter their shape and motility resulting in outgrowth and turning. The cytoskeleton (actin and microtubules) underlies growth cone motility and guidance. The signaling mechanisms linking guidance receptors to cytoskeletal change remain mysterious. Here, we define a new signaling mechanism downstream of the guidance receptor UNC-40/DCC involving the GTPases CDC-42 and Rac, which have long been known to control growth cone protrusion. We show that CDC-42 and Rac act in a linear pathway in axon guidance; CDC-42 acts upstream of the GTPase regulatory molecule TIAM-1, which is a GTP exchange factor specific for Rac and which activates Rac signaling. We also show that TIAM-1 acts with UNC-40/DCC signaling in protrusion and axon guidance. Our results imply that Rac GTPase function in axon guidance is complex and that distinct GEFs (TIAM-1 and UNC-73/Trio) might control Rac GTPases in different aspects of axon guidance.
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Affiliation(s)
- Rafael S. Demarco
- Programs in Genetics and Molecular, Cellular, and Developmental Biology, Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
| | - Eric C. Struckhoff
- Programs in Genetics and Molecular, Cellular, and Developmental Biology, Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
| | - Erik A. Lundquist
- Programs in Genetics and Molecular, Cellular, and Developmental Biology, Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
- * E-mail:
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30
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Dobrin SE, Fahrbach SE. Rho GTPase activity in the honey bee mushroom bodies is correlated with age and foraging experience. JOURNAL OF INSECT PHYSIOLOGY 2012; 58:228-234. [PMID: 22108023 PMCID: PMC3256268 DOI: 10.1016/j.jinsphys.2011.11.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 11/08/2011] [Accepted: 11/09/2011] [Indexed: 05/31/2023]
Abstract
Foraging experience is correlated with structural plasticity of the mushroom bodies of the honey bee brain. While several neurotransmitter and intracellular signaling pathways have been previously implicated as mediators of these structural changes, none interact directly with the cytoskeleton, the ultimate effector of changes in neuronal morphology. The Rho family of GTPases are small, monomeric G proteins that, when activated, initiate a signaling cascade that reorganizes the neuronal cytoskeleton. In this study, we measured activity of two members of the Rho family of GTPases, Rac and RhoA, in the mushroom bodies of bees with different durations of foraging experience. A transient increase in Rac activity coupled with a transient decrease in RhoA activity was found in honey bees with 4 days foraging experience compared with same-aged new foragers. These observations are in accord with previous reports based on studies of other species of a growth supporting role for Rac and a growth opposing role for RhoA. This is the first report of Rho GTPase activation in the honey bee brain.
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Affiliation(s)
- Scott E Dobrin
- Neuroscience Program, Wake Forest University, Graduate School of Arts and Sciences, Winston-Salem, NC 27157, USA.
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31
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Marcus-Gueret N, Schmidt KL, Stringham EG. Distinct cell guidance pathways controlled by the Rac and Rho GEF domains of UNC-73/TRIO in Caenorhabditis elegans. Genetics 2012; 190:129-42. [PMID: 21996675 PMCID: PMC3249371 DOI: 10.1534/genetics.111.134429] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2011] [Accepted: 09/27/2011] [Indexed: 11/18/2022] Open
Abstract
The cytoskeleton regulator UNC-53/NAV2 is required for both the anterior and posterior outgrowth of several neurons as well as that of the excretory cell while the kinesin-like motor VAB-8 is essential for most posteriorly directed migrations in Caenorhabditis elegans. Null mutations in either unc-53 or vab-8 result in reduced posterior excretory canal outgrowth, while double null mutants display an enhanced canal extension defect, suggesting the genes act in separate pathways to control this posteriorly directed outgrowth. Genetic analysis of putative interactors of UNC-53 or VAB-8, and cell-specific rescue experiments suggest that VAB-8, SAX-3/ROBO, SLT-1/Slit, and EVA-1 are functioning together in the outgrowth of the excretory canals, while UNC-53 appears to function in a parallel pathway with UNC-71/ADAM. The known VAB-8 interactor, the Rac/Rho GEF UNC-73/TRIO operates in both pathways, as isoform specific alleles exhibit enhancement of the phenotype in double-mutant combination with either unc-53 or vab-8. On the basis of these results, we propose a bipartite model for UNC-73/TRIO activity in excretory canal extension: a cell autonomous function that is mediated by the Rho-specific GEF domain of the UNC-73E isoform in conjunction with UNC-53 and UNC-71 and a cell nonautonomous function that is mediated by the Rac-specific GEF domain of the UNC-73B isoform, through partnering with VAB-8 and the receptors SAX-3 and EVA-1.
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Affiliation(s)
- Nancy Marcus-Gueret
- Department of Biology, Trinity Western University, Langley, BC V2Y 1Y1, Canada
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Kristopher L. Schmidt
- Department of Biology, Trinity Western University, Langley, BC V2Y 1Y1, Canada
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Eve G. Stringham
- Department of Biology, Trinity Western University, Langley, BC V2Y 1Y1, Canada
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
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32
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UNC-73/trio RhoGEF-2 activity modulates Caenorhabditis elegans motility through changes in neurotransmitter signaling upstream of the GSA-1/Galphas pathway. Genetics 2011; 189:137-51. [PMID: 21750262 DOI: 10.1534/genetics.111.131227] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Rho-family GTPases play regulatory roles in many fundamental cellular processes. Caenorhabditis elegans UNC-73 RhoGEF isoforms function in axon guidance, cell migration, muscle arm extension, phagocytosis, and neurotransmission by activating either Rac or Rho GTPase subfamilies. Multiple differentially expressed UNC-73 isoforms contain a Rac-specific RhoGEF-1 domain, a Rho-specific RhoGEF-2 domain, or both domains. The UNC-73E RhoGEF-2 isoform is activated by the G-protein subunit Gαq and is required for normal rates of locomotion; however, mechanisms of UNC-73 and Rho pathway regulation of locomotion are not clear. To better define UNC-73 function in the regulation of motility we used cell-specific and inducible promoters to examine the temporal and spatial requirements of UNC-73 RhoGEF-2 isoform function in mutant rescue experiments. We found that UNC-73E acts within peptidergic neurons of mature animals to regulate locomotion rate. Although unc-73 RhoGEF-2 mutants have grossly normal synaptic morphology and weak resistance to the acetylcholinesterase inhibitor aldicarb, they are significantly hypersensitive to the acetylcholine receptor agonist levamisole, indicating alterations in acetylcholine neurotransmitter signaling. Consistent with peptidergic neuron function, unc-73 RhoGEF-2 mutants exhibit a decreased level of neuropeptide release from motor neuron dense core vesicles (DCVs). The unc-73 locomotory phenotype is similar to those of rab-2 and unc-31, genes with distinct roles in the DCV-mediated secretory pathway. We observed that constitutively active Gαs pathway mutations, which compensate for DCV-mediated signaling defects, rescue unc-73 RhoGEF-2 and rab-2 lethargic movement phenotypes. Together, these data suggest UNC-73 RhoGEF-2 isoforms are required for proper neurotransmitter signaling and may function in the DCV-mediated neuromodulatory regulation of locomotion rate.
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Kusano K, Enomoto M, Hirai T, Wakabayashi Y, Itoh S, Ichinose S, Okabe S, Shinomiya K, Okawa A. Enhancement of sciatic nerve regeneration by adenovirus-mediated expression of dominant negative RhoA and Rac1. Neurosci Lett 2011; 492:64-9. [DOI: 10.1016/j.neulet.2011.01.058] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Revised: 01/19/2011] [Accepted: 01/24/2011] [Indexed: 10/18/2022]
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34
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Demarco RS, Lundquist EA. “RACK”-ing up the effectors. Small GTPases 2011; 2:47-50. [DOI: 10.4161/sgtp.2.1.15062] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 02/03/2011] [Accepted: 02/04/2011] [Indexed: 11/19/2022] Open
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35
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Demarco RS, Lundquist EA. RACK-1 acts with Rac GTPase signaling and UNC-115/abLIM in Caenorhabditis elegans axon pathfinding and cell migration. PLoS Genet 2010; 6:e1001215. [PMID: 21124943 PMCID: PMC2987834 DOI: 10.1371/journal.pgen.1001215] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2010] [Accepted: 10/21/2010] [Indexed: 12/21/2022] Open
Abstract
Migrating cells and growth cones extend lamellipodial and filopodial protrusions that are required for outgrowth and guidance. The mechanisms of cytoskeletal regulation that underlie cell and growth cone migration are of much interest to developmental biologists. Previous studies have shown that the Arp2/3 complex and UNC-115/abLIM act redundantly to mediate growth cone lamellipodia and filopodia formation and axon pathfinding. While much is known about the regulation of Arp2/3, less is known about regulators of UNC-115/abLIM. Here we show that the Caenorhabditis elegans counterpart of the Receptor for Activated C Kinase (RACK-1) interacts physically with the actin-binding protein UNC-115/abLIM and that RACK-1 is required for axon pathfinding. Genetic interactions indicate that RACK-1 acts cell-autonomously in the UNC-115/abLIM pathway in axon pathfinding and lamellipodia and filopodia formation, downstream of the CED-10/Rac GTPase and in parallel to MIG-2/RhoG. Furthermore, we show that RACK-1 is involved in migration of the gonadal distal tip cells and that the signaling pathways involved in this process might be distinct from those involved in axon pathfinding. In sum, these studies pinpoint RACK-1 as a component of a novel signaling pathway involving Rac GTPases and UNC-115/abLIM and suggest that RACK-1 might be involved in the regulation of the actin cytoskeleton and lamellipodia and filopodia formation in migrating cells and growth cones. In the developing nervous system, the growth cone guides axons of neurons to their correct targets in the organism. The growth cone is a highly dynamic specialization at the tip of the axon that senses cues and responds by crawling toward its target, leaving the axon behind. Key to growth cone motility are dynamic cellular protrusions called lamellipodia and filopodia. These protrusions are required for growth cone movement and steering. The genes that are involved in lamellipodia and filopodia formation in the growth cone are still being discovered, and studies to understand how these genes act together in cell signaling events that control growth cone movement are in their infancy. Here we report discovery of a new gene necessary for growth cone movement in Caenorhabditis elegans called rack-1. This gene is conserved in vertebrates and is involved in cellular signaling. We show that it interacts in a novel manner with other cell signaling genes (the Rac GTPase genes) and a gene involved in lamellipodia and filopodia formation, called unc-115/abLIM. We think that rack-1 is involved in a novel cellular signaling event involving Rac GTPases that regulates lamellipodia and filopodia protrusion in the growth cone during nervous system development.
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Affiliation(s)
- Rafael S. Demarco
- Programs in Genetics and Molecular, Cellular, and Developmental Biology, Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
| | - Erik A. Lundquist
- Programs in Genetics and Molecular, Cellular, and Developmental Biology, Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
- * E-mail:
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36
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Hall A, Lalli G. Rho and Ras GTPases in axon growth, guidance, and branching. Cold Spring Harb Perspect Biol 2010; 2:a001818. [PMID: 20182621 DOI: 10.1101/cshperspect.a001818] [Citation(s) in RCA: 328] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The establishment of precise neuronal cell morphology provides the foundation for all aspects of neurobiology. During development, axons emerge from cell bodies after an initial polarization stage, elongate, and navigate towards target regions guided by a range of environmental cues. The Rho and Ras families of small GTPases have emerged as critical players at all stages of axonogenesis. Their ability to coordinately direct multiple signal transduction pathways with precise spatial control drives many of the activities that underlie this morphogenetic program: the dynamic assembly, disassembly, and reorganization of the actin and microtubule cytoskeletons, the interaction of the growing axon with other cells and extracellular matrix, the delivery of lipids and proteins to the axon through the exocytic machinery, and the internalization of membrane and proteins at the leading edge of the growth cone through endocytosis. This article highlights the contribution of Rho and Ras GTPases to axonogenesis.
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Affiliation(s)
- Alan Hall
- Memorial Sloan-Kettering Cancer Center, Cell Biology Program, New York, New York 10065, USA
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37
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Regulation of axonal development by the nuclear protein hindsight (pebbled) in the Drosophila visual system. Dev Biol 2010; 344:911-21. [PMID: 20541542 DOI: 10.1016/j.ydbio.2010.06.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2010] [Revised: 05/14/2010] [Accepted: 06/03/2010] [Indexed: 11/24/2022]
Abstract
The molecules and networks involved in the process of acquisition and maintenance of the form of a mature neuron are not completely known. Using a misexpression screen we identified the gene hindsight as a gene involved in the process of acquisition of the neuronal morphogenesis in the Drosophila adult nervous system. hindsight encodes a transcription factor known for its role in early developmental processes such as embryonic germ band retraction and dorsal closure, as well as in the establishment of cell morphology, planar cell polarity, and epithelial integrity during retinal development. We describe here a novel function for HNT by showing that both loss and gain of function of HNT affects the pathfinding of the photoreceptors axons. By manipulating the timing and level of HNT expression, together with the number of cells manipulated we show here that the function of HNT in axonal guidance is independent of the HNT functions previously reported in retinal cells. Based on genetic interaction experiments we show that part of HNT function in axonal development is exerted through the regulation of genes involved in the dynamics of the actin cytoskeleton.
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38
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Tannoury H, Rodriguez V, Kovacevic I, Ibourk M, Lee M, Cram EJ. CACN-1/Cactin interacts genetically with MIG-2 GTPase signaling to control distal tip cell migration in C. elegans. Dev Biol 2010; 341:176-85. [PMID: 20188721 PMCID: PMC2854247 DOI: 10.1016/j.ydbio.2010.02.025] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Revised: 02/05/2010] [Accepted: 02/16/2010] [Indexed: 01/31/2023]
Abstract
The two specialized C. elegans distal tip cells (DTCs) provide an in vivo model system for the study of developmentally regulated cell migration. We identified cacn-1/cactin, a well-conserved, novel regulator of cell migration in a genome-wide RNAi screen for regulators of DTC migration. RNAi depletion experiments and analysis of the hypomorphic allele cacn-1(tm3126) indicate that CACN-1 is required during DTC migration for proper pathfinding and for cessation of DTC migration at the end of larval morphogenesis. Strong expression of CACN-1 in the DTCs, and data from cell-specific RNAi depletion experiments, suggest that CACN-1 is required cell-autonomously to control DTC migration. Importantly, genetic interaction data with Rac GTPase activators and effectors suggest that CACN-1 acts specifically to inhibit the mig-2/Rac pathway, and in parallel to ced-10/Rac, to control DTC pathfinding.
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Affiliation(s)
- Hiba Tannoury
- Department of Biology, Northeastern University, 360 Huntington Ave, 134 Mugar Hall, Boston, MA, 02115
| | - Varenka Rodriguez
- Department of Biology, Northeastern University, 360 Huntington Ave, 134 Mugar Hall, Boston, MA, 02115
| | - Ismar Kovacevic
- Department of Biology, Northeastern University, 360 Huntington Ave, 134 Mugar Hall, Boston, MA, 02115
| | - Mouna Ibourk
- Department of Biology, Northeastern University, 360 Huntington Ave, 134 Mugar Hall, Boston, MA, 02115
| | - Myeongwoo Lee
- Department of Biology, Baylor University, One Bear Place 97388, Waco, TX 76798
| | - Erin J. Cram
- Department of Biology, Northeastern University, 360 Huntington Ave, 134 Mugar Hall, Boston, MA, 02115
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Schmidt KL, Marcus-Gueret N, Adeleye A, Webber J, Baillie D, Stringham EG. The cell migration molecule UNC-53/NAV2 is linked to the ARP2/3 complex by ABI-1. Development 2009; 136:563-74. [PMID: 19168673 DOI: 10.1242/dev.016816] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The shape changes that are required to position a cell to migrate or grow out in a particular direction involve a coordinated reorganization of the actin cytoskeleton. Although it is known that the ARP2/3 complex nucleates actin filament assembly, exactly how the information from guidance cues is integrated to elicit ARP2/3-mediated remodeling during outgrowth remains vague. Previous studies have shown that C. elegans UNC-53 and its vertebrate homolog NAV (Neuronal Navigators) are required for the migration of cells and neuronal processes. We have identified ABI-1 as a novel molecular partner of UNC-53/NAV2 and have found that a restricted calponin homology (CH) domain of UNC-53 is sufficient to bind ABI-1. ABI-1 and UNC-53 have an overlapping expression pattern, and display similar cell migration phenotypes in the excretory cell, and in mechanosensory and motoneurons. Migration defects were also observed after RNAi of proteins known to function with abi-1 in actin dynamics, including nck-1, wve-1 and arx-2. We propose that UNC-53/NAV2, through its CH domain, acts as a scaffold that links ABI-1 to the ARP2/3 complex to regulate actin cytoskeleton remodeling.
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Abstract
Regeneration following axonal injury of the adult peripheral sensory nervous system is heavily influenced by factors located in a neuron's extracellular environment. These factors include neurotrophins, such as Nerve Growth Factor (NGF) and the extracellular matrix, such as laminin. The presence of these molecules in the peripheral nervous system (PNS) is a major contributing factor for the dichotomy between regenerative capacities of central vs. peripheral neurons. Although PNS neurons are capable of spontaneous regeneration, this response is critically dependent on many different factors including the type, location and severity of the injury. In this article, we will focus on the plasticity of adult dorsal root ganglion (DRG) sensory neurons and how trophic factors and the extracellular environment stimulate the activation of intracellular signaling cascades that promote axonal growth in adult dorsal root ganglion neurons.
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Quinn CC, Wadsworth WG. Axon guidance: asymmetric signaling orients polarized outgrowth. Trends Cell Biol 2008; 18:597-603. [PMID: 18951796 PMCID: PMC2871313 DOI: 10.1016/j.tcb.2008.09.005] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2008] [Revised: 09/25/2008] [Accepted: 09/26/2008] [Indexed: 11/22/2022]
Abstract
A network of connections is established as neural circuits form between neurons. To make these connections, neurons initiate asymmetric axon outgrowth in response to extracellular guidance cues. Within the specialized growth cones of migrating axons, F-actin and microtubules asymmetrically accumulate where an axon projects forward. Although many guidance cues, receptors and intracellular signaling components that are required for axon guidance have been identified, the means by which the asymmetry is established and maintained is unclear. Here, we discuss recent studies in invertebrate and vertebrate organisms that define a signaling module comprising UNC-6 (the Caenorhabditis elegans ortholog of netrin), UNC-40 (the C. elegans ortholog of DCC), PI3K, Rac and MIG-10 (the C. elegans ortholog of lamellipodin) and we consider how this module could establish polarized outgrowth in response to guidance cues.
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Affiliation(s)
- Christopher C Quinn
- Department of Pathology, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, NJ 08854-5635, USA.
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The Arp2/3 activators WAVE and WASP have distinct genetic interactions with Rac GTPases in Caenorhabditis elegans axon guidance. Genetics 2008; 179:1957-71. [PMID: 18689885 DOI: 10.1534/genetics.108.088963] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In the developing nervous system, axons are guided to their targets by the growth cone. Lamellipodial and filopodial protrusions from the growth cone underlie motility and guidance. Many molecules that control lamellipodia and filopodia formation, actin organization, and axon guidance have been identified, but it remains unclear how these molecules act together to control these events. Experiments are described here that indicate that, in Caenorhabditis elegans, two WH2-domain-containing activators of the Arp2/3 complex, WVE-1/WAVE and WSP-1/WASP, act redundantly in axon guidance and that GEX-2/Sra-1 and GEX-3/Kette, molecules that control WAVE activity, might act in both pathways. WAVE activity is controlled by Rac GTPases, and data are presented here that suggest WVE-1/WAVE and CED-10/Rac act in parallel to a pathway containing WSP-1/WASP and MIG-2/RhoG. Furthermore, results here show that the CED-10/WVE-1 and MIG-2/WSP-1 pathways act in parallel to two other molecules known to control lamellipodia and filopodia and actin organization, UNC-115/abLIM and UNC-34/Enabled. These results indicate that at least three actin-modulating pathways act in parallel to control actin dynamics and lamellipodia and filopodia formation during axon guidance (WASP-WAVE, UNC-115/abLIM, and UNC-34/Enabled).
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Timing differences of signaling response in neuron cultures activated by glutamate analogue or free radicals. Brain Res 2008; 1191:20-9. [DOI: 10.1016/j.brainres.2007.11.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2007] [Revised: 10/30/2007] [Accepted: 11/01/2007] [Indexed: 11/19/2022]
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Veldman MB, Bemben MA, Thompson RC, Goldman D. Gene expression analysis of zebrafish retinal ganglion cells during optic nerve regeneration identifies KLF6a and KLF7a as important regulators of axon regeneration. Dev Biol 2007; 312:596-612. [PMID: 17949705 DOI: 10.1016/j.ydbio.2007.09.019] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Revised: 09/11/2007] [Accepted: 09/13/2007] [Indexed: 01/07/2023]
Abstract
Unlike mammals, teleost fish are able to mount an efficient and robust regenerative response following optic nerve injury. Although it is clear that changes in gene expression accompany axonal regeneration, the extent of this genomic response is not known. To identify genes involved in successful nerve regeneration, we analyzed gene expression in zebrafish retinal ganglion cells (RGCs) regenerating their axons following optic nerve injury. Microarray analysis of RNA isolated by laser capture microdissection from uninjured and 3-day post-optic nerve injured RGCs identified 347 up-regulated and 29 down-regulated genes. Quantitative RT-PCR and in situ hybridization were used to verify the change in expression of 19 genes in this set. Gene ontological analysis of the data set suggests regenerating neurons up-regulate genes associated with RGC development. However, not all regeneration-associated genes are expressed in differentiating RGCs indicating the regeneration is not simply a recapitulation of development. Knockdown of six highly induced regeneration-associated genes identified two, KLF6a and KLF7a, that together were necessary for robust RGC axon re-growth. These results implicate KLF6a and KLF7a as important mediators of optic nerve regeneration and suggest that not all induced genes are essential to mount a regenerative response.
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Affiliation(s)
- Matthew B Veldman
- Neuroscience Program, University of Michigan, 5045 Biomedical Sciences Research Building, 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA
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45
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Causeret F, Jacobs T, Terao M, Heath O, Hoshino M, Nikolić M. Neurabin-I is phosphorylated by Cdk5: implications for neuronal morphogenesis and cortical migration. Mol Biol Cell 2007; 18:4327-42. [PMID: 17699587 PMCID: PMC2043560 DOI: 10.1091/mbc.e07-04-0372] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The correct morphology and migration of neurons, which is essential for the normal development of the nervous system, is enabled by the regulation of their cytoskeletal elements. We reveal that Neurabin-I, a neuronal-specific F-actin-binding protein, has an essential function in the developing forebrain. We show that gain and loss of Neurabin-I expression affect neuronal morphology, neurite outgrowth, and radial migration of differentiating cortical and hippocampal neurons, suggesting that tight regulation of Neurabin-I function is required for normal forebrain development. Importantly, loss of Neurabin-I prevents pyramidal neurons from migrating into the cerebral cortex, indicating its essential role during early stages of corticogenesis. We demonstrate that in neurons Rac1 activation is affected by the expression levels of Neurabin-I. Furthermore, the Cdk5 kinase, a key regulator of neuronal migration and morphology, directly phosphorylates Neurabin-I and controls its association with F-actin. Mutation of the Cdk5 phosphorylation site reduces the phenotypic consequences of Neurabin-I overexpression both in vitro and in vivo, suggesting that Neurabin-I function depends, at least in part, on its phosphorylation status. Together our findings provide new insight into the signaling pathways responsible for controlled changes of the F-actin cytoskeleton that are required for normal development of the forebrain.
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Affiliation(s)
- Frédéric Causeret
- *Department of Cellular and Molecular Neuroscience, Imperial College School of Medicine, Charing Cross Campus, London W6 8RP, United Kingdom; and
| | - Tom Jacobs
- *Department of Cellular and Molecular Neuroscience, Imperial College School of Medicine, Charing Cross Campus, London W6 8RP, United Kingdom; and
| | - Mami Terao
- Department of Pathology and Tumor Biology, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Owen Heath
- *Department of Cellular and Molecular Neuroscience, Imperial College School of Medicine, Charing Cross Campus, London W6 8RP, United Kingdom; and
| | - Mikio Hoshino
- Department of Pathology and Tumor Biology, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Margareta Nikolić
- *Department of Cellular and Molecular Neuroscience, Imperial College School of Medicine, Charing Cross Campus, London W6 8RP, United Kingdom; and
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Nur-E-Kamal A, Meiners S, Ahmed I, Azarova A, Lin CP, Lyu YL, Liu LF. Role of DNA topoisomerase IIβ in neurite outgrowth. Brain Res 2007; 1154:50-60. [PMID: 17493591 DOI: 10.1016/j.brainres.2007.04.029] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2006] [Revised: 03/26/2007] [Accepted: 04/03/2007] [Indexed: 10/23/2022]
Abstract
Failure to establish neuromuscular junctions is a major phenotype of top2beta knockout mice. However, the precise mechanism for this defect is not known. In the current study, we have investigated the role of TopIIbeta in cultured neurons. We showed that the TopII inhibitor ICRF-193 significantly blocked neurite outgrowth and growth cone formation in cultured cerebellar granule neurons (CGNs), dorsal root ganglions (DRGs) and cortical neurons (CNs). In addition, ICRF-193 also blocked neurite outgrowth and growth cone formation of PC12 cells undergoing NGF-induced differentiation. Isolated cortical neurons from top2beta knockout embryos elaborated shorter neurites than did those from their wild type counterparts, confirming the role of TopIIbeta in neurite outgrowth. Together, these results demonstrate a critical role of TopIIbeta in neurite outgrowth in cultured neurons. Furthermore, we demonstrated that neurons derived from top2beta knockout mice failed to form contacts with muscle cells in co-cultures. These results suggest that the defect in establishing neuromuscular junctions in top2beta knockout mice could be due to the lack of TopIIbeta-mediated neurite outgrowth.
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Affiliation(s)
- Alam Nur-E-Kamal
- Department of Biology, MEC-CUNY, 1150 Carroll Street, Brooklyn, NY 11225, USA.
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Srahna M, Leyssen M, Choi CM, Fradkin LG, Noordermeer JN, Hassan BA. A signaling network for patterning of neuronal connectivity in the Drosophila brain. PLoS Biol 2007; 4:e348. [PMID: 17032066 PMCID: PMC1592317 DOI: 10.1371/journal.pbio.0040348] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2005] [Accepted: 08/21/2006] [Indexed: 01/22/2023] Open
Abstract
The precise number and pattern of axonal connections generated during brain development regulates animal behavior. Therefore, understanding how developmental signals interact to regulate axonal extension and retraction to achieve precise neuronal connectivity is a fundamental goal of neurobiology. We investigated this question in the developing adult brain of Drosophila and find that it is regulated by crosstalk between Wnt, fibroblast growth factor (FGF) receptor, and Jun N-terminal kinase (JNK) signaling, but independent of neuronal activity. The Rac1 GTPase integrates a Wnt-Frizzled-Disheveled axon-stabilizing signal and a Branchless (FGF)-Breathless (FGF receptor) axon-retracting signal to modulate JNK activity. JNK activity is necessary and sufficient for axon extension, whereas the antagonistic Wnt and FGF signals act to balance the extension and retraction required for the generation of the precise wiring pattern.
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Affiliation(s)
- Mohammed Srahna
- Laboratory of Neurogenetics, Department of Molecular and Developmental Genetics, Flanders Interuniversity Institute for Biotechnology (VIB), University of Leuven School of Medicine, Leuven, Belgium
| | - Maarten Leyssen
- Laboratory of Neurogenetics, Department of Molecular and Developmental Genetics, Flanders Interuniversity Institute for Biotechnology (VIB), University of Leuven School of Medicine, Leuven, Belgium
| | - Ching Man Choi
- Laboratory of Neurogenetics, Department of Molecular and Developmental Genetics, Flanders Interuniversity Institute for Biotechnology (VIB), University of Leuven School of Medicine, Leuven, Belgium
| | - Lee G Fradkin
- Laboratory of Developmental Neurobiology, Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, Netherlands
| | - Jasprina N Noordermeer
- Laboratory of Developmental Neurobiology, Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, Netherlands
| | - Bassem A Hassan
- Laboratory of Neurogenetics, Department of Molecular and Developmental Genetics, Flanders Interuniversity Institute for Biotechnology (VIB), University of Leuven School of Medicine, Leuven, Belgium
- * To whom correspondence should be addressed. E-mail:
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Yang Y, Lu J, Rovnak J, Quackenbush SL, Lundquist EA. SWAN-1, a Caenorhabditis elegans WD repeat protein of the AN11 family, is a negative regulator of Rac GTPase function. Genetics 2006; 174:1917-32. [PMID: 16980389 PMCID: PMC1698646 DOI: 10.1534/genetics.106.063115] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2006] [Accepted: 09/03/2006] [Indexed: 11/18/2022] Open
Abstract
Rac GTPases are key regulators of cell shape and cytoskeletal organization. While some regulators of Rac activity are known, such as GTPase-activating proteins (GAPs) that repress Rac activity, other Rac regulators remain to be identified. The novel Caenorhabditis elegans WD-repeat protein SWAN-1 was identified in a yeast two-hybrid screen with the LIM domains of the Rac effector UNC-115/abLIM. SWAN-1 was found to also associate physically with Rac GTPases. The swan-1(ok267) loss-of-function mutation suppressed defects caused by the hypomorphic ced-10(n1993) allele and enhanced ectopic lamellipodia and filopodia formation induced by constitutively active Rac in C. elegans neurons. Furthermore, SWAN-1(+) transgenic expression suppressed the effects of overactive Rac, including ectopic lamellipodia and filopodia formation in C. elegans neurons, ectopic lamellipodia formation in cultured mammalian fibroblasts, and cell polarity and actin cytoskeleton defects in yeast. These studies indicate that SWAN-1 is an inhibitor of Rac GTPase function in cellular morphogenesis and cytoskeletal organization. While broadly conserved across species, SWAN-1 family members show no sequence similarity to previously known Rac inhibitors.
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Affiliation(s)
- Yieyie Yang
- Department of Molecular Biosciences, University of Kansas, Lawrence 66045, USA
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Lucanic M, Kiley M, Ashcroft N, L'etoile N, Cheng HJ. The Caenorhabditis elegans P21-activated kinases are differentially required for UNC-6/netrin-mediated commissural motor axon guidance. Development 2006; 133:4549-59. [PMID: 17050621 DOI: 10.1242/dev.02648] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
P21 activated kinases (PAKs) are major downstream effectors of rac-related small GTPases that regulate various cellular processes. We have identified the new PAK gene max-2 in a screen for mutants disrupted in UNC-6/netrin-mediated commissural axon guidance. There are three Caenorhabditis elegans PAKs. We find that each C. elegans PAK represents a distinct group previously identified in other species. Here we examine their roles in the postembryonic migration of the P cell neuroblasts and the axon guidance of the ventral cord commissural motoneurons (VCCMNs). We find that the two PAKs, max-2 and pak-1, are redundantly required for P cell migration and function with UNC-73/Trio and the rac GTPases (CED-10 and MIG-2). During axon guidance of the VCCMNs, PAK-1 also acts with the rac GTPases, CED-10 and MIG-2, and is completely redundant with MAX-2. Interestingly, we find that unlike MAX-2 activity during P cell migration, for motoneuron axon guidance max-2 is also required in parallel to this PAK-1 pathway, independent of rac GTPase signaling. Finally, we provide evidence that MAX-2 functions downstream of the UNC-6/netrin receptor UNC-5 during axon repulsion and is an integral part of its signaling.
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Affiliation(s)
- Mark Lucanic
- Center for Neuroscience, and Cell and Developmental Biology Graduate Group, University of California, Davis, CA 95616, USA
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50
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Shakir MA, Gill JS, Lundquist EA. Interactions of UNC-34 Enabled with Rac GTPases and the NIK kinase MIG-15 in Caenorhabditis elegans axon pathfinding and neuronal migration. Genetics 2006; 172:893-913. [PMID: 16204220 PMCID: PMC1456253 DOI: 10.1534/genetics.105.046359] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Accepted: 09/21/2005] [Indexed: 01/20/2023] Open
Abstract
Many genes that affect axon pathfinding and cell migration have been identified. Mechanisms by which these genes and the molecules they encode interact with one another in pathways and networks to control developmental events are unclear. Rac GTPases, the cytoskeletal signaling molecule Enabled, and NIK kinase have all been implicated in regulating axon pathfinding and cell migration. Here we present evidence that, in Caenorhabditis elegans, three Rac GTPases, CED-10, RAC-2, and MIG-2, define three redundant pathways that each control axon pathfinding, and that the NIK kinase MIG-15 acts in each Rac pathway. Furthermore, we show that the Enabled molecule UNC-34 defines a fourth partially redundant pathway that acts in parallel to Rac/MIG-15 signaling in axon pathfinding. Enabled and the three Racs also act redundantly to mediate AQR and PQR neuronal cell migration. The Racs and UNC-34 Ena might all control the formation of actin-based protrusive structures (lamellipodia and filopodia) that mediate growth cone outgrowth and cell migration. MIG-15 does not act with the three Racs in execution of cell migration. Rather, MIG-15 affects direction of PQR neuronal migration, similar to UNC-40 and DPY-19, which control initial Q cell polarity, and Wnt signaling, which acts later to control Q cell-directed migration. MIG-2 Rac, which acts with CED-10 Rac, RAC-2 Rac, and UNC-34 Ena in axon pathfinding and cell migration, also acts with MIG-15 in PQR directional migration.
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Affiliation(s)
- M Afaq Shakir
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045, USA
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