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Bui KC, Kamiyama D. Adjacent Neuronal Fascicle Guides Motoneuron 24 Dendritic Branching and Axonal Routing Decisions through Dscam1 Signaling. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.08.588591. [PMID: 38645010 PMCID: PMC11030417 DOI: 10.1101/2024.04.08.588591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
The formation and precise positioning of axons and dendrites are crucial for the development of neural circuits. Although juxtracrine signaling via cell-cell contact is known to influence these processes, the specific structures and mechanisms regulating neuronal process positioning within the central nervous system (CNS) remain to be fully identified. Our study investigates motoneuron 24 (MN24) in the Drosophila embryonic CNS, which is characterized by a complex yet stereotyped axon projection pattern, known as 'axonal routing.' In this motoneuron, the primary dendritic branches project laterally toward the midline, specifically emerging at the sites where axons turn. We observed that Scp2-positive neurons contribute to the lateral fascicle structure in the ventral nerve cord (VNC) near MN24 dendrites. Notably, the knockout of the Down syndrome cell adhesion molecule (dscam1) results in the loss of dendrites and disruption of proper axonal routing in MN24, while not affecting the formation of the fascicle structure. Through cell-type specific knockdown and rescue experiments of dscam1, we have determined that the interaction between MN24 and Scp2-positive fascicle, mediated by Dscam1, promotes the development of both dendrites and axonal routing. Our findings demonstrate that the holistic configuration of neuronal structures, such as axons and dendrites, within single motoneurons can be governed by local contact with the adjacent neuron fascicle, a novel reference structure for neural circuitry wiring.
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Affiliation(s)
- Kathy Clara Bui
- Department of Cellular Biology, University of Georgia, Athens, GA 30605, USA
| | - Daichi Kamiyama
- Department of Cellular Biology, University of Georgia, Athens, GA 30605, USA
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Morant L, Petrovic-Erfurth ML, Jordanova A. An Adapted GeneSwitch Toolkit for Comparable Cellular and Animal Models: A Proof of Concept in Modeling Charcot-Marie-Tooth Neuropathy. Int J Mol Sci 2023; 24:16138. [PMID: 38003325 PMCID: PMC10670994 DOI: 10.3390/ijms242216138] [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: 09/29/2023] [Revised: 10/23/2023] [Accepted: 10/25/2023] [Indexed: 11/26/2023] Open
Abstract
Investigating the impact of disease-causing mutations, their affected pathways, and/or potential therapeutic strategies using disease modeling often requires the generation of different in vivo and in cellulo models. To date, several approaches have been established to induce transgene expression in a controlled manner in different model systems. Several rounds of subcloning are, however, required, depending on the model organism used, thus bringing labor-intensive experiments into the technical approach and analysis comparison. The GeneSwitch™ technology is an adapted version of the classical UAS-GAL4 inducible system, allowing the spatial and temporal modulation of transgene expression. It consists of three components: a plasmid encoding for the chimeric regulatory pSwitch protein, Mifepristone as an inducer, and an inducible plasmid. While the pSwitch-containing first plasmid can be used both in vivo and in cellulo, the inducible second plasmid can only be used in cellulo. This requires a specific subcloning strategy of the inducible plasmid tailored to the model organism used. To avoid this step and unify gene expression in the transgenic models generated, we replaced the backbone vector with standard pUAS-attB plasmid for both plasmids containing either the chimeric GeneSwitch™ cDNA sequence or the transgene cDNA sequence. We optimized this adapted system to regulate transgene expression in several mammalian cell lines. Moreover, we took advantage of this new system to generate unified cellular and fruit fly models for YARS1-induced Charco-Marie-Tooth neuropathy (CMT). These new models displayed the expected CMT-like phenotypes. In the N2a neuroblastoma cells expressing YARS1 transgenes, we observed the typical "teardrop" distribution of the synthetase that was perturbed when expressing the YARS1CMT mutation. In flies, the ubiquitous expression of YARS1CMT induced dose-dependent developmental lethality and pan-neuronal expression caused locomotor deficit, while expression of the wild-type allele was harmless. Our proof-of-concept disease modeling studies support the efficacy of the adapted transgenesis system as a powerful tool allowing the design of studies with optimal data comparability.
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Affiliation(s)
- Laura Morant
- Center for Molecular Neurology, VIB, University of Antwerp, 2610 Antwerpen, Belgium; (L.M.); (M.-L.P.-E.)
- Department of Biomedical Sciences, University of Antwerp, 2610 Antwerpen, Belgium
| | - Maria-Luise Petrovic-Erfurth
- Center for Molecular Neurology, VIB, University of Antwerp, 2610 Antwerpen, Belgium; (L.M.); (M.-L.P.-E.)
- Department of Biomedical Sciences, University of Antwerp, 2610 Antwerpen, Belgium
| | - Albena Jordanova
- Center for Molecular Neurology, VIB, University of Antwerp, 2610 Antwerpen, Belgium; (L.M.); (M.-L.P.-E.)
- Department of Biomedical Sciences, University of Antwerp, 2610 Antwerpen, Belgium
- Molecular Medicine Center, Department of Medical Chemistry and Biochemistry, Faculty of Medicine, Medical University-Sofia, 1431 Sofia, Bulgaria
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Feng L, Shu HP, Sun LL, Tu YC, Liao QQ, Yao LJ. Role of the SLIT-ROBO signaling pathway in renal pathophysiology and various renal diseases. Front Physiol 2023; 14:1226341. [PMID: 37497439 PMCID: PMC10366692 DOI: 10.3389/fphys.2023.1226341] [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: 05/21/2023] [Accepted: 06/30/2023] [Indexed: 07/28/2023] Open
Abstract
SLIT ligand and its receptor ROBO were initially recognized for their role in axon guidance in central nervous system development. In recent years, as research has advanced, the role of the SLIT-ROBO signaling pathway has gradually expanded from axonal repulsion to cell migration, tumor development, angiogenesis, and bone metabolism. As a secreted protein, SLIT regulates various pathophysiological processes in the kidney, such as proinflammatory responses and fibrosis progression. Many studies have shown that SLIT-ROBO is extensively involved in various aspects of kidney development and maintenance of structure and function. The SLIT-ROBO signaling pathway also plays an important role in different types of kidney disease. This article reviews the advances in the study of the SLIT-ROBO pathway in various renal pathophysiological and kidney disorders and proposes new directions for further research in this field.
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Dong H, Yang X, Wu L, Zhang S, Zhang J, Guo P, Du Y, Pan C, Fu Y, Li L, Shi J, Zhu Y, Ma H, Bian L, Xu B, Li G, Shi F, Huang J, He H, Jin Y. A systematic CRISPR screen reveals redundant and specific roles for Dscam1 isoform diversity in neuronal wiring. PLoS Biol 2023; 21:e3002197. [PMID: 37410725 DOI: 10.1371/journal.pbio.3002197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2023] [Accepted: 06/13/2023] [Indexed: 07/08/2023] Open
Abstract
Drosophila melanogaster Down syndrome cell adhesion molecule 1 (Dscam1) encodes 19,008 diverse ectodomain isoforms via the alternative splicing of exon 4, 6, and 9 clusters. However, whether individual isoforms or exon clusters have specific significance is unclear. Here, using phenotype-diversity correlation analysis, we reveal the redundant and specific roles of Dscam1 diversity in neuronal wiring. A series of deletion mutations were performed from the endogenous locus harboring exon 4, 6, or 9 clusters, reducing to 396 to 18,612 potential ectodomain isoforms. Of the 3 types of neurons assessed, dendrite self/non-self discrimination required a minimum number of isoforms (approximately 2,000), independent of exon clusters or isoforms. In contrast, normal axon patterning in the mushroom body and mechanosensory neurons requires many more isoforms that tend to associate with specific exon clusters or isoforms. We conclude that the role of the Dscam1 diversity in dendrite self/non-self discrimination is nonspecifically mediated by its isoform diversity. In contrast, a separate role requires variable domain- or isoform-related functions and is essential for other neurodevelopmental contexts, such as axonal growth and branching. Our findings shed new light on a general principle for the role of Dscam1 diversity in neuronal wiring.
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Affiliation(s)
- Haiyang Dong
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Xi Yang
- Cancer Center and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Lili Wu
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Shixin Zhang
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Jian Zhang
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Pengjuan Guo
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Yiwen Du
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Changkun Pan
- Cancer Center and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Ying Fu
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Lei Li
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Jilong Shi
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Yanda Zhu
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Hongru Ma
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Lina Bian
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Bingbing Xu
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Guo Li
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Feng Shi
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Jianhua Huang
- Institute of Insect Sciences, Zhejiang University, Hangzhou, Zhejiang, China, PR China
| | - Haihuai He
- Department of Neurosurgery, Cancer Center and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Yongfeng Jin
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
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Zhang S, Yang X, Dong H, Xu B, Wu L, Zhang J, Li G, Guo P, Li L, Fu Y, Du Y, Zhu Y, Shi J, Shi F, Huang J, He H, Jin Y. Cis mutagenesis in vivo reveals extensive noncanonical functions of Dscam1 isoforms in neuronal wiring. PNAS NEXUS 2023; 2:pgad135. [PMID: 37152679 PMCID: PMC10156172 DOI: 10.1093/pnasnexus/pgad135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 04/04/2023] [Accepted: 04/06/2023] [Indexed: 05/09/2023]
Abstract
Drosophila Down syndrome cell adhesion molecule 1 (Dscam1) encodes tens of thousands of cell recognition molecules via alternative splicing, which are required for neural function. A canonical self-avoidance model seems to provide a central mechanistic basis for Dscam1 functions in neuronal wiring. Here, we reveal extensive noncanonical functions of Dscam1 isoforms in neuronal wiring. We generated a series of allelic cis mutations in Dscam1, encoding a normal number of isoforms, but with an altered isoform composition. Despite normal dendritic self-avoidance and self-/nonself-discrimination in dendritic arborization (da) neurons, which is consistent with the canonical self-avoidance model, these mutants exhibited strikingly distinct spectra of phenotypic defects in the three types of neurons: up to ∼60% defects in mushroom bodies, a significant increase in branching and growth in da neurons, and mild axonal branching defects in mechanosensory neurons. Remarkably, the altered isoform composition resulted in increased dendrite growth yet inhibited axon growth. Moreover, reducing Dscam1 dosage exacerbated axonal defects in mushroom bodies and mechanosensory neurons but reverted dendritic branching and growth defects in da neurons. This splicing-tuned regulation strategy suggests that axon and dendrite growth in diverse neurons cell-autonomously require Dscam1 isoform composition. These findings provide important insights into the functions of Dscam1 isoforms in neuronal wiring.
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Affiliation(s)
| | | | - Haiyang Dong
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou ZJ310058, People's Republic of China
| | - Bingbing Xu
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou ZJ310058, People's Republic of China
| | - Lili Wu
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou ZJ310058, People's Republic of China
| | - Jian Zhang
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou ZJ310058, People's Republic of China
| | - Guo Li
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou ZJ310058, People's Republic of China
| | - Pengjuan Guo
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou ZJ310058, People's Republic of China
| | - Lei Li
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou ZJ310058, People's Republic of China
| | - Ying Fu
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou ZJ310058, People's Republic of China
| | - Yiwen Du
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou ZJ310058, People's Republic of China
| | - Yanda Zhu
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou ZJ310058, People's Republic of China
| | - Jilong Shi
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou ZJ310058, People's Republic of China
| | - Feng Shi
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou ZJ310058, People's Republic of China
| | - Jianhua Huang
- Institute of Insect Sciences, Zhejiang University, Hangzhou ZJ310058, People’s Republic of China
| | - Haihuai He
- To whom correspondence should be addressed: (H.H.); (Y.J.)
| | - Yongfeng Jin
- To whom correspondence should be addressed: (H.H.); (Y.J.)
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Hernández K, Godoy L, Newquist G, Kellermeyer R, Alavi M, Mathew D, Kidd T. Dscam1 overexpression impairs the function of the gut nervous system in Drosophila. Dev Dyn 2023; 252:156-171. [PMID: 36454543 PMCID: PMC9812936 DOI: 10.1002/dvdy.554] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 11/04/2022] [Accepted: 11/22/2022] [Indexed: 12/05/2022] Open
Abstract
BACKGROUND Down syndrome (DS) patients have a 100-fold increase in the risk of Hirschsprung syndrome of the colon and rectum (HSCR), a lack of enteric neurons in the colon. The leading DS candidate gene is trisomy of the Down syndrome cell adhesion molecule (DSCAM). RESULTS We find that Dscam1 protein is expressed in the Drosophila enteric/stomatogastric nervous system (SNS). Axonal Dscam1 phenotypes can be rescued equally by diverse isoforms. Overexpression of Dscam1 resulted in frontal and hindgut nerve overgrowth. Expression of dominant negative Dscam1-ΔC led to a truncated frontal nerve and increased branching of the hindgut nerve. Larval locomotion is influenced by feeding state, and we found that the average speed of larvae with Dscam1 SNS expression was reduced, whereas overexpression of Dscam1-ΔC significantly increased the speed. Dscam1 overexpression reduced the efficiency of food clearance from the larval gut. CONCLUSION Our work demonstrates that overexpression of Dscam1 can perturb gut function in a model system.
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Affiliation(s)
| | - Luis Godoy
- Biology/MS 314, University of Nevada, Reno, NV 89557, USA
| | | | | | - Maryam Alavi
- Biology/MS 314, University of Nevada, Reno, NV 89557, USA
| | - Dennis Mathew
- Biology/MS 314, University of Nevada, Reno, NV 89557, USA
| | - Thomas Kidd
- Biology/MS 314, University of Nevada, Reno, NV 89557, USA
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7
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Hou S, Li G, Xu B, Dong H, Zhang S, Fu Y, Shi J, Li L, Fu J, Shi F, Meng Y, Jin Y. Trans-splicing facilitated by RNA pairing greatly expands sDscam isoform diversity but not homophilic binding specificity. SCIENCE ADVANCES 2022; 8:eabn9458. [PMID: 35857463 PMCID: PMC9258826 DOI: 10.1126/sciadv.abn9458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 05/21/2022] [Indexed: 06/15/2023]
Abstract
The Down syndrome cell adhesion molecule 1 (Dscam1) gene can generate tens of thousands of isoforms via alternative splicing, which is essential for nervous and immune functions. Chelicerates generate approximately 50 to 100 shortened Dscam (sDscam) isoforms by alternative promoters, similar to mammalian protocadherins. Here, we reveal that trans-splicing markedly increases the repository of sDscamβ isoforms in Tetranychus urticae. Unexpectedly, every variable exon cassette engages in trans-splicing with constant exons from another cluster. Moreover, we provide evidence that competing RNA pairing not only governs alternative cis-splicing but also facilitates trans-splicing. Trans-spliced sDscam isoforms mediate cell adhesion ability but exhibit the same homophilic binding specificity as their cis-spliced counterparts. Thus, we reveal a single sDscam locus that generates diverse adhesion molecules through cis- and trans-splicing coupled with alternative promoters. These findings expand understanding of the mechanism underlying molecular diversity and have implications for the molecular control of neuronal and/or immune specificity.
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Affiliation(s)
- Shouqing Hou
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Guo Li
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Bingbing Xu
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Haiyang Dong
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Shixin Zhang
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Ying Fu
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Jilong Shi
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Lei Li
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Jiayan Fu
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Feng Shi
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Yijun Meng
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, Zhejiang ZJ310018, P. R. China
| | - Yongfeng Jin
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
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Nguyen MQ, Taniguchi M, Yasumura M, Iguchi T, Sato M. Cytoneme-like protrusion formation induced by LAR is promoted by receptor dimerization. Biol Open 2022; 11:276051. [PMID: 35735010 PMCID: PMC9346286 DOI: 10.1242/bio.059024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 06/20/2022] [Indexed: 11/20/2022] Open
Abstract
Actin-based protrusions called cytonemes are reported to function in cell communication by supporting events such as morphogen gradient establishment and pattern formation. Despite the crucial roles of cytonemes in cell signaling, the molecular mechanism for cytoneme establishment remains elusive. In this study, we showed that the leukocyte common antigen-related (LAR) receptor protein tyrosine phosphatase plays an important role in cytoneme-like protrusion formation. Overexpression of LAR in HEK293T cells induced the formation of actin-based protrusions, some of which exceeded 200 µm in length and displayed a complex morphology with branches. Upon focusing on the regulation of LAR dimerization or clustering and the resulting regulatory effects on LAR phosphatase activity, we found that longer and more branched protrusions were formed when LAR dimerization was artificially induced and when heparan sulfate was applied. Interestingly, although the truncated form of LAR lacking phosphatase-related domains promoted protrusion formation, the phosphatase-inactive forms did not show clear changes, suggesting that LAR dimerization triggers the formation of cytoneme-like protrusions in a phosphatase-independent manner. Our results thus emphasize the importance of LAR and its dimerization in cell signaling. This article has an associated First Person interview with the first author of the paper. Summary: We showed that the formation of cytoneme-like protrusions, which function in cell signaling, is induced by LAR and clarified that it is LAR dimerization which promotes protrusion formation.
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Affiliation(s)
- Mai Quynh Nguyen
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Manabu Taniguchi
- Department of Anatomy and Neuroscience, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Misato Yasumura
- Department of Anatomy and Neuroscience, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Tokuichi Iguchi
- Department of Anatomy and Neuroscience, Graduate School of Medicine, Osaka University, Osaka, Japan.,Department of Nursing, Faculty of Health Science, Fukui Health Science University, Fukui, Japan
| | - Makoto Sato
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan.,Department of Anatomy and Neuroscience, Graduate School of Medicine, Osaka University, Osaka, Japan.,Division of Developmental Neuroscience, Department of Child Development, United Graduate School of Child Development, Osaka University, Kanazawa University, Hamamatsu University School of Medicine, Chiba University and University of Fukui (UGSCD), Osaka University, Osaka, Japan
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9
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Self-avoidance alone does not explain the function of Dscam1 in mushroom body axonal wiring. Curr Biol 2022; 32:2908-2920.e4. [PMID: 35659864 DOI: 10.1016/j.cub.2022.05.030] [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: 12/29/2021] [Revised: 02/28/2022] [Accepted: 05/11/2022] [Indexed: 11/24/2022]
Abstract
Alternative splicing of Drosophila Dscam1 into 38,016 isoforms provides neurons with a unique molecular code for self-recognition and self-avoidance. A canonical model suggests that the homophilic binding of identical Dscam1 isoforms on the sister branches of mushroom body (MB) axons supports segregation with high fidelity, even when only a single isoform is expressed. Here, we generated a series of mutant flies with a single exon 4, 6, or 9 variant, encoding 1,584, 396, or 576 potential isoforms, respectively. Surprisingly, most of the mutants in the latter two groups exhibited obvious defects in the growth, branching, and segregation of MB axonal sister branches. This demonstrates that the repertoires of 396 and 576 Dscam1 isoforms were not sufficient for the normal patterning of axonal branches. Moreover, reducing Dscam1 levels largely reversed the defects caused by reduced isoform diversity, suggesting a functional link between Dscam1 expression levels and isoform diversity. Taken together, these results indicate that canonical self-avoidance alone does not explain the function of Dscam1 in MB axonal wiring.
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10
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Neurons Induce Tiled Astrocytes with Branches That Avoid Each Other. Int J Mol Sci 2022; 23:ijms23084161. [PMID: 35456979 PMCID: PMC9028504 DOI: 10.3390/ijms23084161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Revised: 04/02/2022] [Accepted: 04/06/2022] [Indexed: 12/10/2022] Open
Abstract
Neurons induce astrocyte branches that approach synapses. Each astrocyte tiles by expanding branches in an exclusive territory, with limited entries for the neighboring astrocyte branches. However, how astrocytes form exclusive territories is not known. For example, the extensive branching of astrocytes may sterically interfere with the penetration of other astrocyte branches. Alternatively, astrocyte branches may actively avoid each other or remove overlapped branches to establish a territory. Here, we show time-lapse imaging of the multi-order branching process of GFP-labeled astrocytes. Astrocyte branches grow in the direction where other astrocyte branches do not exist. Neurons that had just started to grow dendrites were able to induce astrocyte branching and tiling. Upon neuronal loss by glutamate excitotoxicity, astrocytes’ terminal processes retracted and more branches went over other branches. Our results indicate that neurons induce astrocyte branches and make them avoid each other.
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11
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Jiang L, Sun J, Huang D. Role of Slit/Robo Signaling pathway in Bone Metabolism. Int J Biol Sci 2022; 18:1303-1312. [PMID: 35173554 PMCID: PMC8771833 DOI: 10.7150/ijbs.66931] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 12/26/2021] [Indexed: 11/12/2022] Open
Abstract
Slit/Robo signals were initially found to play an essential role in nerve development as axonal guidance molecules. In recent years, with in-depth study, the role of Slit/Robo in other life activities, such as tumor development, angiogenesis, cell migration, and bone homeostasis, has gradually been revealed. Bone is an organ with an active metabolism. Bone resorption and bone formation are closely related through precise spatiotemporal coordination. There is much evidence that slit, as a new bone coupling factor, can regulate bone formation and resorption. For example, Slit3 can promote bone formation and inhibit bone resorption through Robo receptors, which has excellent therapeutic potential in metabolic bone diseases. Although the conclusions of some studies are contradictory, they all affirm the vital role of Slit/Robo signaling in regulating bone metabolism. This paper reviews the research progress of Slit/Robo signaling in bone metabolism, briefly discusses the contradictions in the existing research, and puts forward the research direction of Slit/Robo in the field of bone metabolism in the future.
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Affiliation(s)
- Lingyu Jiang
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China
- Department of Conservative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China
| | - Jianxun Sun
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China
- Department of Conservative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China
| | - Dingming Huang
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China
- Department of Conservative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China
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12
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The RNA-binding protein Musashi controls axon compartment-specific synaptic connectivity through ptp69D mRNA poly(A)-tailing. Cell Rep 2021; 36:109713. [PMID: 34525368 DOI: 10.1016/j.celrep.2021.109713] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 08/24/2020] [Accepted: 08/24/2021] [Indexed: 10/20/2022] Open
Abstract
Synaptic targeting with subcellular specificity is essential for neural circuit assembly. Developing neurons use mechanisms to curb promiscuous synaptic connections and to direct synapse formation to defined subcellular compartments. How this selectivity is achieved molecularly remains enigmatic. Here, we discover a link between mRNA poly(A)-tailing and axon collateral branch-specific synaptic connectivity within the CNS. We reveal that the RNA-binding protein Musashi binds to the mRNA encoding the receptor protein tyrosine phosphatase Ptp69D, thereby increasing poly(A) tail length and Ptp69D protein levels. This regulation specifically promotes synaptic connectivity in one axon collateral characterized by a high degree of arborization and strong synaptogenic potential. In a different compartment of the same axon, Musashi prevents ectopic synaptogenesis, revealing antagonistic, compartment-specific functions. Moreover, Musashi-dependent Ptp69D regulation controls synaptic connectivity in the olfactory circuit. Thus, Musashi differentially shapes synaptic connectivity at the level of individual subcellular compartments and within different developmental and neuron type-specific contexts.
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Izadifar A, Courchet J, Virga DM, Verreet T, Hamilton S, Ayaz D, Misbaer A, Vandenbogaerde S, Monteiro L, Petrovic M, Sachse S, Yan B, Erfurth ML, Dascenco D, Kise Y, Yan J, Edwards-Faret G, Lewis T, Polleux F, Schmucker D. Axon morphogenesis and maintenance require an evolutionary conserved safeguard function of Wnk kinases antagonizing Sarm and Axed. Neuron 2021; 109:2864-2883.e8. [PMID: 34384519 DOI: 10.1016/j.neuron.2021.07.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 05/24/2021] [Accepted: 07/08/2021] [Indexed: 12/13/2022]
Abstract
The molecular and cellular mechanisms underlying complex axon morphogenesis are still poorly understood. We report a novel, evolutionary conserved function for the Drosophila Wnk kinase (dWnk) and its mammalian orthologs, WNK1 and 2, in axon branching. We uncover that dWnk, together with the neuroprotective factor Nmnat, antagonizes the axon-destabilizing factors D-Sarm and Axundead (Axed) during axon branch growth, revealing a developmental function for these proteins. Overexpression of D-Sarm or Axed results in axon branching defects, which can be blocked by overexpression of dWnk or Nmnat. Surprisingly, Wnk kinases are also required for axon maintenance of adult Drosophila and mouse cortical pyramidal neurons. Requirement of Wnk for axon maintenance is independent of its developmental function. Inactivation of dWnk or mouse Wnk1/2 in mature neurons leads to axon degeneration in the adult brain. Therefore, Wnk kinases are novel signaling components that provide a safeguard function in both developing and adult axons.
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Affiliation(s)
- Azadeh Izadifar
- Life and Medical Sciences Institute (LIMES), Bonn, Germany; VIB Center for Brain & Disease Research, Leuven, Belgium; Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Julien Courchet
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR-5310, INSERM U-1217, Institut NeuroMyoGène, 69622 Villeurbanne, France; Department of Neuroscience, Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY, USA.
| | - Daniel M Virga
- Department of Neuroscience, Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY, USA
| | - Tine Verreet
- VIB Center for Brain & Disease Research, Leuven, Belgium; Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Stevie Hamilton
- Department of Neuroscience, Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY, USA
| | - Derya Ayaz
- VIB Center for Brain & Disease Research, Leuven, Belgium; Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Anke Misbaer
- VIB Center for Brain & Disease Research, Leuven, Belgium; Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Sofie Vandenbogaerde
- VIB Center for Brain & Disease Research, Leuven, Belgium; Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Laloe Monteiro
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR-5310, INSERM U-1217, Institut NeuroMyoGène, 69622 Villeurbanne, France
| | - Milan Petrovic
- VIB Center for Brain & Disease Research, Leuven, Belgium; Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Sonja Sachse
- VIB Center for Brain & Disease Research, Leuven, Belgium; Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Bing Yan
- VIB Center for Brain & Disease Research, Leuven, Belgium; Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Maria-Luise Erfurth
- VIB Center for Brain & Disease Research, Leuven, Belgium; Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Dan Dascenco
- VIB Center for Brain & Disease Research, Leuven, Belgium; Department of Neurosciences, KU Leuven, Leuven, Belgium
| | | | - Jiekun Yan
- VIB Center for Brain & Disease Research, Leuven, Belgium; Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Gabriela Edwards-Faret
- Life and Medical Sciences Institute (LIMES), Bonn, Germany; VIB Center for Brain & Disease Research, Leuven, Belgium; Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Tommy Lewis
- Department of Neuroscience, Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY, USA; Aging & Metabolism Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Franck Polleux
- Department of Neuroscience, Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY, USA; Kavli Institute for Brain Science, Columbia University, New York, NY, USA.
| | - Dietmar Schmucker
- Life and Medical Sciences Institute (LIMES), Bonn, Germany; VIB Center for Brain & Disease Research, Leuven, Belgium; Department of Neurosciences, KU Leuven, Leuven, Belgium.
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14
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Abstract
Neurons develop dendritic morphologies that bear cell type-specific features in dendritic field size and geometry, branch placement and density, and the types and distributions of synaptic contacts. Dendritic patterns influence the types and numbers of inputs a neuron receives, and the ways in which neural information is processed and transmitted in the circuitry. Even subtle alterations in dendritic structures can have profound consequences on neuronal function and are implicated in neurodevelopmental disorders. In this chapter, I review how growing dendrites acquire their exquisite patterns by drawing examples from diverse neuronal cell types in vertebrate and invertebrate model systems. Dendrite morphogenesis is shaped by intrinsic and extrinsic factors such as transcriptional regulators, guidance and adhesion molecules, neighboring cells and synaptic partners. I discuss molecular mechanisms that regulate dendrite morphogenesis with a focus on five aspects of dendrite patterning: (1) Dendritic cytoskeleton and cellular machineries that build the arbor; (2) Gene regulatory mechanisms; (3) Afferent cues that regulate dendritic arbor growth; (4) Space-filling strategies that optimize dendritic coverage; and (5) Molecular cues that specify dendrite wiring. Cell type-specific implementation of these patterning mechanisms produces the diversity of dendrite morphologies that wire the nervous system.
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15
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Mitsogiannis MD, Pancho A, Aerts T, Sachse SM, Vanlaer R, Noterdaeme L, Schmucker D, Seuntjens E. Subtle Roles of Down Syndrome Cell Adhesion Molecules in Embryonic Forebrain Development and Neuronal Migration. Front Cell Dev Biol 2021; 8:624181. [PMID: 33585465 PMCID: PMC7876293 DOI: 10.3389/fcell.2020.624181] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 12/22/2020] [Indexed: 12/26/2022] Open
Abstract
Down Syndrome (DS) Cell Adhesion Molecules (DSCAMs) are transmembrane proteins of the immunoglobulin superfamily. Human DSCAM is located within the DS critical region of chromosome 21 (duplicated in Down Syndrome patients), and mutations or copy-number variations of this gene have also been associated to Fragile X syndrome, intellectual disability, autism, and bipolar disorder. The DSCAM paralogue DSCAM-like 1 (DSCAML1) maps to chromosome 11q23, implicated in the development of Jacobsen and Tourette syndromes. Additionally, a spontaneous mouse DSCAM deletion leads to motor coordination defects and seizures. Previous research has revealed roles for DSCAMs in several neurodevelopmental processes, including synaptogenesis, dendritic self-avoidance, cell sorting, axon growth and branching. However, their functions in embryonic mammalian forebrain development have yet to be completely elucidated. In this study, we revealed highly dynamic spatiotemporal patterns of Dscam and Dscaml1 expression in definite cortical layers of the embryonic mouse brain, as well as in structures and ganglionic eminence-derived neural populations within the embryonic subpallium. However, an in-depth histological analysis of cortical development, ventral forebrain morphogenesis, cortical interneuron migration, and cortical-subcortical connectivity formation processes in Dscam and Dscaml1 knockout mice (Dscam del17 and Dscaml1 GT ) at several embryonic stages indicated that constitutive loss of Dscam and Dscaml1 does not affect these developmental events in a significant manner. Given that several Dscam- and Dscaml1-linked neurodevelopmental disorders are associated to chromosomal region duplication events, we furthermore sought to examine the neurodevelopmental effects of Dscam and Dscaml1 gain of function (GOF). In vitro, ex vivo, and in vivo GOF negatively impacted neural migration processes important to cortical development, and affected the morphology of maturing neurons. Overall, these findings contribute to existing knowledge on the molecular etiology of human neurodevelopmental disorders by elucidating how dosage variations of genes encoding adhesive cues can disrupt cell-cell or cell-environment interactions crucial for neuronal migration.
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Affiliation(s)
- Manuela D. Mitsogiannis
- Developmental Neurobiology Group, Animal Physiology and Neurobiology Division, Department of Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Anna Pancho
- Developmental Neurobiology Group, Animal Physiology and Neurobiology Division, Department of Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Tania Aerts
- Developmental Neurobiology Group, Animal Physiology and Neurobiology Division, Department of Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Sonja M. Sachse
- Neuronal Wiring Laboratory, Department of Neurosciences, VIB-KU Leuven Center for Brain & Disease Research, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Ria Vanlaer
- Developmental Neurobiology Group, Animal Physiology and Neurobiology Division, Department of Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Lut Noterdaeme
- Developmental Neurobiology Group, Animal Physiology and Neurobiology Division, Department of Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Dietmar Schmucker
- Neuronal Wiring Laboratory, Department of Neurosciences, VIB-KU Leuven Center for Brain & Disease Research, Katholieke Universiteit Leuven, Leuven, Belgium
- Neuronal Wiring Group, Life & Medical Sciences Institute, University of Bonn, Bonn, Germany
| | - Eve Seuntjens
- Developmental Neurobiology Group, Animal Physiology and Neurobiology Division, Department of Biology, Katholieke Universiteit Leuven, Leuven, Belgium
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16
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Zang Y, Chaudhari K, Bashaw GJ. New insights into the molecular mechanisms of axon guidance receptor regulation and signaling. Curr Top Dev Biol 2021; 142:147-196. [PMID: 33706917 DOI: 10.1016/bs.ctdb.2020.11.008] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
As the nervous system develops, newly differentiated neurons need to extend their axons toward their synaptic targets to form functional neural circuits. During this highly dynamic process of axon pathfinding, guidance receptors expressed at the tips of motile axons interact with soluble guidance cues or membrane tethered molecules present in the environment to be either attracted toward or repelled away from the source of these cues. As competing cues are often present at the same location and during the same developmental period, guidance receptors need to be both spatially and temporally regulated in order for the navigating axons to make appropriate guidance decisions. This regulation is exerted by a diverse array of molecular mechanisms that have come into focus over the past several decades and these mechanisms ensure that the correct complement of surface receptors is present on the growth cone, a fan-shaped expansion at the tip of the axon. This dynamic, highly motile structure is defined by a lamellipodial network lining the periphery of the growth cone interspersed with finger-like filopodial projections that serve to explore the surrounding environment. Once axon guidance receptors are deployed at the right place and time at the growth cone surface, they respond to their respective ligands by initiating a complex set of signaling events that serve to rearrange the growth cone membrane and the actin and microtubule cytoskeleton to affect axon growth and guidance. In this review, we highlight recent advances that shed light on the rich complexity of mechanisms that regulate axon guidance receptor distribution, activation and downstream signaling.
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Affiliation(s)
- Yixin Zang
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Karina Chaudhari
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Greg J Bashaw
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States.
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17
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Hoersting AK, Schmucker D. Axonal branch patterning and neuronal shape diversity: roles in developmental circuit assembly: Axonal branch patterning and neuronal shape diversity in developmental circuit assembly. Curr Opin Neurobiol 2020; 66:158-165. [PMID: 33232861 DOI: 10.1016/j.conb.2020.10.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 10/21/2020] [Accepted: 10/26/2020] [Indexed: 02/06/2023]
Abstract
Recent progress in human genetics and single cell sequencing rapidly expands the list of molecular factors that offer important new contributions to our understanding of brain wiring. Yet many new molecular factors are being discovered that have never been studied in the context of neuronal circuit development. This is clearly asking for increased efforts to better understand the developmental mechanisms of circuit assembly [1]. Moreover, recent studies characterizing the developmental causes of some psychiatric diseases show impressive progress in reaching cellular resolution in their analysis. They provide concrete support emphasizing the importance of axonal branching and synapse formation as a hotspot for potential defects. Inspired by these new studies we will discuss progress but also challenges in understanding how neurite branching and neuronal shape diversity itself impacts on specificity of neuronal circuit assembly. We discuss the idea that neuronal shape acquisition itself is a key specificity factor in neuronal circuit assembly.
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Affiliation(s)
| | - Dietmar Schmucker
- Life and Medical Sciences Institute (LIMES), University Bonn, Bonn, Germany; Center for Brain and Disease Research, VIB Leuven, University Leuven, Belgium.
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18
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Kellermeyer R, Heydman LM, Gillis T, Mastick GS, Song M, Kidd T. Proteolytic cleavage of Slit by the Tolkin protease converts an axon repulsion cue to an axon growth cue in vivo. Development 2020; 147:dev.196055. [PMID: 32994163 PMCID: PMC7648596 DOI: 10.1242/dev.196055] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 09/18/2020] [Indexed: 12/27/2022]
Abstract
Slit is a secreted protein that has a canonical function of repelling growing axons from the CNS midline. The full-length Slit (Slit-FL) is cleaved into Slit-N and Slit-C fragments, which have potentially distinct functions via different receptors. Here, we report that the BMP-1/Tolloid family metalloprotease Tolkin (Tok) is responsible for Slit proteolysis in vivo and in vitro. In Drosophilatok mutants lacking Slit cleavage, midline repulsion of axons occurs normally, confirming that Slit-FL is sufficient to repel axons. However, longitudinal axon guidance is highly disrupted in tok mutants and can be rescued by midline expression of Slit-N, suggesting that Slit is the primary substrate for Tok in the embryonic CNS. Transgenic restoration of Slit-N or Slit-C does not repel axons in Slit-null flies. Slit-FL and Slit-N are both biologically active cues with distinct axon guidance functions in vivo Slit signaling is used in diverse biological processes; therefore, differentiating between Slit-FL and Slit fragments will be essential for evaluating Slit function in broader contexts.
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Affiliation(s)
| | | | | | | | | | - Thomas Kidd
- Department of Biology/MS 314, University of Nevada, 1664 North Virginia Street, Reno, NV 89557, USA
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19
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Brown HE, Evans TA. Minimal structural elements required for midline repulsive signaling and regulation of Drosophila Robo1. PLoS One 2020; 15:e0241150. [PMID: 33091076 PMCID: PMC7580999 DOI: 10.1371/journal.pone.0241150] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 10/08/2020] [Indexed: 02/07/2023] Open
Abstract
The Roundabout (Robo) family of axon guidance receptors has a conserved ectodomain arrangement of five immunoglobulin-like (Ig) domains plus three fibronectin type III (Fn) repeats. Based on the strong evolutionary conservation of this domain structure among Robo receptors, as well as in vitro structural and domain-domain interaction studies of Robo family members, this ectodomain arrangement is predicted to be important for Robo receptor signaling in response to Slit ligands. Here, we define the minimal ectodomain structure required for Slit binding and midline repulsive signaling in vivo by Drosophila Robo1. We find that the majority of the Robo1 ectodomain is dispensable for both Slit binding and repulsive signaling. We show that a significant level of midline repulsive signaling activity is retained when all Robo1 ectodomain elements apart from Ig1 are deleted, and that the combination of Ig1 plus one additional ectodomain element (Ig2, Ig5, or Fn3) is sufficient to restore midline repulsion to wild type levels. Further, we find that deleting four out of five Robo1 Ig domains (ΔIg2-5) does not affect negative regulation of Robo1 by Commissureless (Comm) or Robo2, while variants lacking all three fibronectin repeats (ΔFn1-3 and ΔIg2-Fn3) are insensitive to regulation by both Comm and Robo2, signifying a novel regulatory role for Robo1's Fn repeats. Our results provide an in vivo perspective on the importance of the conserved 5+3 ectodomain structure of Robo receptors, and suggest that specific biochemical properties and/or ectodomain structural conformations observed in vitro for domains other than Ig1 may have limited significance for in vivo signaling in the context of midline repulsion.
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Affiliation(s)
- Haley E. Brown
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, United States of America
| | - Timothy A. Evans
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, United States of America
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20
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Zhang Z, So K, Peterson R, Bauer M, Ng H, Zhang Y, Kim JH, Kidd T, Miura P. Elav-Mediated Exon Skipping and Alternative Polyadenylation of the Dscam1 Gene Are Required for Axon Outgrowth. Cell Rep 2020; 27:3808-3817.e7. [PMID: 31242415 PMCID: PMC7092717 DOI: 10.1016/j.celrep.2019.05.083] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2018] [Revised: 04/18/2019] [Accepted: 05/22/2019] [Indexed: 12/19/2022] Open
Abstract
Many metazoan genes express alternative long 3′ UTR isoforms in the nervous system, but their functions remain largely unclear. In Drosophila melanogaster, the Dscam1 gene generates short and long (Dscam1-L) 3′ UTR isoforms because of alternative polyadenylation (APA). Here, we found that the RNA-binding protein Embryonic Lethal Abnormal Visual System (Elav) impacts Dscam1 biogenesis at two levels, including regulation of long 3′ UTR biogenesis and skipping of an upstream exon (exon 19). MinION long-read sequencing confirmed the connectivity of this alternative splicing event to the long 3′ UTR. Knockdown or CRISPR deletion of Dscam1-L impaired axon outgrowth in Drosophila. The Dscam1 long 3′ UTR was found to be required for correct Elav-mediated skipping of exon 19. Elav thus co-regulates APA and alternative splicing to generate specific Dscam1 transcripts that are essential for neural development. This coupling of APA to alternative splicing might represent a new class of regulated RNA processing. Like most metazoan genes, Dscam1 expresses alternative short and long 3′ UTR mRNAs. Zhang et al. find that loss of Dscam1 long 3′ UTR transcripts impairs axon outgrowth in Drosophila. Long-read sequencing reveals that these long 3′ UTR mRNAs preferentially skip an upstream exon, altering Dscam1 amino acid sequence.
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Affiliation(s)
- Zhiping Zhang
- Department of Biology, University of Nevada, Reno, Reno, NV, USA
| | - Kevin So
- Department of Biology, University of Nevada, Reno, Reno, NV, USA
| | - Ryan Peterson
- Department of Biology, University of Nevada, Reno, Reno, NV, USA
| | - Matthew Bauer
- Department of Biology, University of Nevada, Reno, Reno, NV, USA
| | - Henry Ng
- Department of Biology, University of Nevada, Reno, Reno, NV, USA
| | - Yong Zhang
- Department of Biology, University of Nevada, Reno, Reno, NV, USA
| | - Jung Hwan Kim
- Department of Biology, University of Nevada, Reno, Reno, NV, USA
| | - Thomas Kidd
- Department of Biology, University of Nevada, Reno, Reno, NV, USA
| | - Pedro Miura
- Department of Biology, University of Nevada, Reno, Reno, NV, USA.
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21
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Expression of Genes Involved in Axon Guidance: How Much Have We Learned? Int J Mol Sci 2020; 21:ijms21103566. [PMID: 32443632 PMCID: PMC7278939 DOI: 10.3390/ijms21103566] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 05/15/2020] [Accepted: 05/16/2020] [Indexed: 12/20/2022] Open
Abstract
Neuronal axons are guided to their target during the development of the brain. Axon guidance allows the formation of intricate neural circuits that control the function of the brain, and thus the behavior. As the axons travel in the brain to find their target, they encounter various axon guidance cues, which interact with the receptors on the tip of the growth cone to permit growth along different signaling pathways. Although many scientists have performed numerous studies on axon guidance signaling pathways, we still have an incomplete understanding of the axon guidance system. Lately, studies on axon guidance have shifted from studying the signal transduction pathways to studying other molecular features of axon guidance, such as the gene expression. These new studies present evidence for different molecular features that broaden our understanding of axon guidance. Hence, in this review we will introduce recent studies that illustrate different molecular features of axon guidance. In particular, we will review literature that demonstrates how axon guidance cues and receptors regulate local translation of axonal genes and how the expression of guidance cues and receptors are regulated both transcriptionally and post-transcriptionally. Moreover, we will highlight the pathological relevance of axon guidance molecules to specific diseases.
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22
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Sanes JR, Zipursky SL. Synaptic Specificity, Recognition Molecules, and Assembly of Neural Circuits. Cell 2020; 181:536-556. [DOI: 10.1016/j.cell.2020.04.008] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 03/23/2020] [Accepted: 04/06/2020] [Indexed: 01/02/2023]
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23
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Chen B, Carr L, Dun XP. Dynamic expression of Slit1-3 and Robo1-2 in the mouse peripheral nervous system after injury. Neural Regen Res 2020; 15:948-958. [PMID: 31719262 PMCID: PMC6990781 DOI: 10.4103/1673-5374.268930] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The Slit family of axon guidance cues act as repulsive molecules for precise axon pathfinding and neuronal migration during nervous system development through interactions with specific Robo receptors. Although we previously reported that Slit1-3 and their receptors Robo1 and Robo2 are highly expressed in the adult mouse peripheral nervous system, how this expression changes after injury has not been well studied. Herein, we constructed a peripheral nerve injury mouse model by transecting the right sciatic nerve. At 14 days after injury, quantitative real-time polymerase chain reaction was used to detect mRNA expression of Slit1-3 and Robo1-2 in L4-5 spinal cord and dorsal root ganglia, as well as the sciatic nerve. Immunohistochemical analysis was performed to examine Slit1-3, Robo1-2, neurofilament heavy chain, F4/80, and vimentin in L4-5 spinal cord, L4 dorsal root ganglia, and the sciatic nerve. Co-expression of Slit1-3 and Robo1-2 in L4 dorsal root ganglia was detected by in situ hybridization. In addition, Slit1-3 and Robo1-2 protein expression in L4-5 spinal cord, L4 dorsal root ganglia, and sciatic nerve were detected by western blot assay. The results showed no significant changes of Slit1-3 or Robo1-2 mRNA expression in the spinal cord within 14 days after injury. In the dorsal root ganglion, Slit1-3 and Robo1-2 mRNA expression were initially downregulated within 4 days after injury; however, Robo1-2 mRNA expression returned to the control level, while Slit1-3 mRNA expression remained upregulated during regeneration from 4-14 days after injury. In the sciatic nerve, Slit1-3 and their receptors Robo1-2 were all expressed in the proximal nerve stump; however, Slit1, Slit2, and Robo2 were barely detectable in the nerve bridge and distal nerve stump within 14 days after injury. Slit3 was highly ex-pressed in macrophages surrounding the nerve bridge and slightly downregulated in the distal nerve stump within 14 days after injury. Robo1 was upregulated in vimentin-positive cells and migrating Schwann cells inside the nerve bridge. Robo1 was also upregulated in Schwann cells of the distal nerve stump within 14 days after injury. Our findings indicate that Slit3 is the major ligand expressed in the nerve bridge and distal nerve stump during peripheral nerve regeneration, and Slit3/Robo signaling could play a key role in peripheral nerve repair after injury. This study was approved by Plymouth University Animal Welfare Ethical Review Board (approval No. 30/3203) on April 12, 2014.
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Affiliation(s)
- Bing Chen
- Department of Neurology, The Affiliated Huaian No.1 People's Hospital of Nanjing Medical University, Huai'an, Jiangsu Province, China
| | - Lauren Carr
- Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth, UK
| | - Xin-Peng Dun
- Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth, UK; The Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu Province, China
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24
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Roig-Puiggros S, Vigouroux RJ, Beckman D, Bocai NI, Chiou B, Davimes J, Gomez G, Grassi S, Hoque A, Karikari TK, Kiffer F, Lopez M, Lunghi G, Mazengenya P, Meier S, Olguín-Albuerne M, Oliveira MM, Paraíso-Luna J, Pradhan J, Radiske A, Ramos-Hryb AB, Ribeiro MC, Schellino R, Selles MC, Singh S, Theotokis P, Chédotal A. Construction and reconstruction of brain circuits: normal and pathological axon guidance. J Neurochem 2019; 153:10-32. [PMID: 31630412 DOI: 10.1111/jnc.14900] [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: 08/16/2019] [Revised: 10/14/2019] [Accepted: 10/17/2019] [Indexed: 02/06/2023]
Abstract
Perception of our environment entirely depends on the close interaction between the central and peripheral nervous system. In order to communicate each other, both systems must develop in parallel and in coordination. During development, axonal projections from the CNS as well as the PNS must extend over large distances to reach their appropriate target cells. To do so, they read and follow a series of axon guidance molecules. Interestingly, while these molecules play critical roles in guiding developing axons, they have also been shown to be critical in other major neurodevelopmental processes, such as the migration of cortical progenitors. Currently, a major hurdle for brain repair after injury or neurodegeneration is the absence of axonal regeneration in the mammalian CNS. By contrasts, PNS axons can regenerate. Many hypotheses have been put forward to explain this paradox but recent studies suggest that hacking neurodevelopmental mechanisms may be the key to promote CNS regeneration. Here we provide a seminar report written by trainees attending the second Flagship school held in Alpbach, Austria in September 2018 organized by the International Society for Neurochemistry (ISN) together with the Journal of Neurochemistry (JCN). This advanced school has brought together leaders in the fields of neurodevelopment and regeneration in order to discuss major keystones and future challenges in these respective fields.
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Affiliation(s)
| | - Robin J Vigouroux
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, Paris, France
| | - Danielle Beckman
- California National Primate Research Center, UC Davis, Davis, California, USA
| | - Nadia I Bocai
- Laboratory of Amyloidosis and Neurodegeneration, Fundación Instituto Leloir, Buenos Aires, Argentina.,Instituto de Investigaciones Bioquímicas de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Brian Chiou
- Department of Pediatrics, University of California - San Francisco, San Francisco, California, USA
| | - Joshua Davimes
- Faculty of Health Sciences School of Anatomical Sciences, University of the Witwatersrand, Parktown Johannesburg, South Africa
| | - Gimena Gomez
- Laboratorio de Parkinson Experimental, Instituto de Investigaciones Farmacológicas (ININFA-CONICET-UBA), Ciudad Autónoma de Buenos Aires, Argentina
| | - Sara Grassi
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy
| | - Ashfaqul Hoque
- Metabolic Signalling Laboratory, St Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia
| | - Thomas K Karikari
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden.,School of Life Sciences, University of Warwick, Coventry, UK.,Midlands Integrative Biosciences Training Partnership, University of Warwick, Coventry, UK
| | - Frederico Kiffer
- Division of Radiation Health, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.,Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.,Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Mary Lopez
- Institute for Stroke and Dementia Research, LMU Munich, Munich, Germany
| | - Giulia Lunghi
- Department of Medical Biotechnology and Translational Medicin, University of Milano, Segrate, Italy
| | - Pedzisai Mazengenya
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Sonja Meier
- Queensland Brain Institute, The University of Queensland, St Lucia, Queensland, Australia
| | - Mauricio Olguín-Albuerne
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, México
| | - Mauricio M Oliveira
- Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Juan Paraíso-Luna
- Ramón y Cajal Institute of Health Research (IRYCIS), Department of Biochemistry and Molecular Biology and University Research Institute in Neurochemistry (IUIN), Complutense University, Madrid, Spain.,Network Center for Biomedical Research in Neurodegenerative Diseases (CIBERNED), Madrid, Spain
| | - Jonu Pradhan
- Faculty of Medicine, School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Andressa Radiske
- Memory Research Laboratory, Brain Institute, Federal University of Rio Grande do Norte, Natal, Brazil
| | - Ana Belén Ramos-Hryb
- Instituto de Biología y Medicina Experimental (IBYME)-CONICET, Buenos Aires, Argentina.,Grupo de Neurociencia de Sistemas, Instituto de Fisiología y Biofísica (IFIBIO) Bernardo Houssay, Universidad de Buenos Aires, CONICET, Buenos Aires, Argentina
| | - Mayara C Ribeiro
- Department of Biology, Program in Neuroscience, Syracuse University, Syracuse, New York, USA
| | - Roberta Schellino
- Neuroscience Department "Rita Levi-Montalcini" and Neuroscience Institute Cavalieri Ottolenghi, University of Torino, Torino, Italy
| | - Maria Clara Selles
- Institute of Medical Biochemistry Leopoldo de Meis, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Shripriya Singh
- System Toxicology and Health Risk Assessment Group, CSIR-Indian Institute of Toxicology Research, Lucknow, India
| | - Paschalis Theotokis
- Department of Neurology, Laboratory of Experimental Neurology and Neuroimmunology, AHEPA University Hospital, Thessaloniki, Macedonia, Greece
| | - Alain Chédotal
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, Paris, France
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25
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Meijers R, Smock RG, Zhang Y, Wang JH. Netrin Synergizes Signaling and Adhesion through DCC. Trends Biochem Sci 2019; 45:6-12. [PMID: 31704057 DOI: 10.1016/j.tibs.2019.10.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 10/09/2019] [Accepted: 10/14/2019] [Indexed: 01/08/2023]
Abstract
Netrin is a prototypical axon guidance cue. Structural studies have revealed how netrin interacts with the deleted in colorectal cancer (DCC) receptor, other receptors, and co-factors for signaling. Recently, genetic studies suggested that netrin is involved in neuronal haptotaxis, which requires a reversible adhesion process. Structural data indicate that netrin can also mediate trans-adhesion between apposing cells decorated with its receptors on the condition that the auxiliary guidance cue draxin is present. Here, we propose that netrin is involved in conditional adhesion, a reversible and localized process that can contribute to cell adhesion and migration. We suggest that netrin-mediated adhesion and signaling are linked, and that local environmental factors in the ventricular zone, the floor plate, or other tissues coordinate its function.
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Affiliation(s)
- Rob Meijers
- European Molecular Biology Laboratory (EMBL), Hamburg Outstation, Notkestrasse 85, D-22607 Hamburg, Germany.
| | - Robert G Smock
- European Molecular Biology Laboratory (EMBL), Hamburg Outstation, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Yan Zhang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871 China
| | - Jia-Huai Wang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871 China; Department of Medical Oncology and Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA.
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26
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Koohini Z, Koohini Z, Teimourian S. Slit/Robo Signaling Pathway in Cancer; a New Stand Point for Cancer Treatment. Pathol Oncol Res 2019; 25:1285-1293. [PMID: 30610466 DOI: 10.1007/s12253-018-00568-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 12/17/2018] [Indexed: 10/27/2022]
Abstract
Angiogenesis and metastasis are two critical steps for cancer cells survival and migration. The microenvironment of tumor sphere induces new blood vessels formation for enhancing tumor mass. Preexisting capillaries and postcapillary venules in tumors bring about new blood vessels. ROBO1-ROBO4 are transmembrane receptors family which act as guidance molecules of the nervous system. The SLITs family is secreted glycoproteins that bind to these receptors. SLIT-ROBO signaling pathway plays an important role in neurogenesis and immune response. Linkage between ROBOs and their ligands (SLITs) induce chemorepllent signal for regulation of axon guidance and leukocyte cell migration, recent finding shows that it is also involved in endothelial cell migration and angiogenesis in various type of cancers. In this article we review recent finding of SLIT-ROBO pathway in angiogenesis and metastasis.
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Affiliation(s)
- Zahra Koohini
- Department of Medical Genetics, School of Medicine, Iran University of Medical Sciences, Tehran, Iran
| | - Zohreh Koohini
- Department of Immunology, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran
| | - Shahram Teimourian
- Department of Medical Genetics, School of Medicine, Iran University of Medical Sciences, Tehran, Iran.
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27
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Jiang Z, Liang G, Xiao Y, Qin T, Chen X, Wu E, Ma Q, Wang Z. Targeting the SLIT/ROBO pathway in tumor progression: molecular mechanisms and therapeutic perspectives. Ther Adv Med Oncol 2019; 11:1758835919855238. [PMID: 31217826 PMCID: PMC6557020 DOI: 10.1177/1758835919855238] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 05/07/2019] [Indexed: 01/14/2023] Open
Abstract
The SLITs (SLIT1, SLIT2, and SLIT3) are a family of secreted proteins that mediate positional interactions between cells and their environment during development by signaling through ROBO receptors (ROBO1, ROBO2, ROBO3, and ROBO4). The SLIT/ROBO signaling pathway has been shown to participate in axonal repulsion, axon guidance, and neuronal migration in the nervous system and the formation of the vascular system. However, the role of the SLIT/ROBO pathway has not been thoroughly clarified in tumor development. The SLIT/ROBO pathway can produce both beneficial and detrimental effects in the growth of malignant cells. It has been confirmed that SLIT/ROBO play contradictory roles in tumorigenesis. Here, we discuss the tumor promotion and tumor suppression roles of the SLIT/ROBO pathway in tumor growth, angiogenesis, migration, and the tumor microenvironment. Understanding these roles will help us develop more effective cancer therapies.
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Affiliation(s)
- Zhengdong Jiang
- Department of Hepatobiliary Surgery, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Gang Liang
- Department of Hepatobiliary Surgery, No. 215 Hospital of Shaanxi Nuclear Industry, Xianyang, Shaanxi, China
| | - Ying Xiao
- Department of Hepatobiliary Surgery, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Tao Qin
- Department of Hepatobiliary Surgery, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Xin Chen
- Department of Hepatobiliary Surgery, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Erxi Wu
- Department of Neurosurgery, Neuroscience Institute, Baylor Scott and White Health, Temple, TX, USA
| | - Qingyong Ma
- Department of Hepatobiliary Surgery, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710061, China
| | - Zheng Wang
- Department of Hepatobiliary Surgery, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710061, China
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28
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Tong M, Jun T, Nie Y, Hao J, Fan D. The Role of the Slit/Robo Signaling Pathway. J Cancer 2019; 10:2694-2705. [PMID: 31258778 PMCID: PMC6584916 DOI: 10.7150/jca.31877] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 04/28/2019] [Indexed: 12/25/2022] Open
Abstract
The Slit family is a family of secreted proteins that play important roles in various physiologic and pathologic activities via interacting with Robo receptors. Slit/Robo signaling was first identified in the nervous system, where it functions in neuronal axon guidance; nevertheless, an increasing number of studies have shown that Slit/Robo signaling even regulates other activities, such as angiogenesis, inflammatory cell chemotaxis, tumor cell migration and metastasis. Although the precise role of the ligand-receptor in organisms has been obscure and the conclusions drawn are sometimes paradoxical, tremendous advances in understanding the Slit/Robo signaling pathway have been made. As such, our review summarizes the characteristics of the Slit/Robo signaling pathway and its role in various cell types.
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Affiliation(s)
- Mingfu Tong
- Department of Gastroenterology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, China.,State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
| | - Tie Jun
- State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
| | - Yongzhan Nie
- State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
| | - Jianyu Hao
- Department of Gastroenterology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, China
| | - Daiming Fan
- State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
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29
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Urwyler O, Izadifar A, Vandenbogaerde S, Sachse S, Misbaer A, Schmucker D. Branch-restricted localization of phosphatase Prl-1 specifies axonal synaptogenesis domains. Science 2019; 364:364/6439/eaau9952. [DOI: 10.1126/science.aau9952] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Accepted: 03/29/2019] [Indexed: 01/21/2023]
Abstract
Central nervous system (CNS) circuit development requires subcellular control of synapse formation and patterning of synapse abundance. We identified the Drosophila membrane-anchored phosphatase of regenerating liver (Prl-1) as an axon-intrinsic factor that promotes synapse formation in a spatially restricted fashion. The loss of Prl-1 in mechanosensory neurons reduced the number of CNS presynapses localized on a single axon collateral and organized as a terminal arbor. Flies lacking all Prl-1 protein had locomotor defects. The overexpression of Prl-1 induced ectopic synapses. In mechanosensory neurons, Prl-1 modulates the insulin receptor (InR) signaling pathway within a single contralateral axon compartment, thereby affecting the number of synapses. The axon branch–specific localization and function of Prl-1 depend on untranslated regions of the prl-1 messenger RNA (mRNA). Therefore, compartmentalized restriction of Prl-1 serves as a specificity factor for the subcellular control of axonal synaptogenesis.
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30
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Barak R, Yom-Tov G, Guez-Haddad J, Gasri-Plotnitsky L, Maimon R, Cohen-Berkman M, McCarthy AA, Perlson E, Henis-Korenblit S, Isupov MN, Opatowsky Y. Structural Principles in Robo Activation and Auto-inhibition. Cell 2019; 177:272-285.e16. [PMID: 30853216 DOI: 10.1016/j.cell.2019.02.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Revised: 12/06/2018] [Accepted: 02/06/2019] [Indexed: 01/28/2023]
Abstract
Proper brain function requires high-precision neuronal expansion and wiring, processes controlled by the transmembrane Roundabout (Robo) receptor family and their Slit ligands. Despite their great importance, the molecular mechanism by which Robos' switch from "off" to "on" states remains unclear. Here, we report a 3.6 Å crystal structure of the intact human Robo2 ectodomain (domains D1-8). We demonstrate that Robo cis dimerization via D4 is conserved through hRobo1, 2, and 3 and the C. elegans homolog SAX-3 and is essential for SAX-3 function in vivo. The structure reveals two levels of auto-inhibition that prevent premature activation: (1) cis blocking of the D4 dimerization interface and (2) trans interactions between opposing Robo receptors that fasten the D4-blocked conformation. Complementary experiments in mouse primary neurons and C. elegans support the auto-inhibition model. These results suggest that Slit stimulation primarily drives the release of Robo auto-inhibition required for dimerization and activation.
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Affiliation(s)
- Reut Barak
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Israel
| | - Galit Yom-Tov
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Israel
| | - Julia Guez-Haddad
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Israel
| | | | - Roy Maimon
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Israel
| | - Moran Cohen-Berkman
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Israel
| | | | - Eran Perlson
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Israel
| | | | | | - Yarden Opatowsky
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Israel.
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31
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Sachse SM, Lievens S, Ribeiro LF, Dascenco D, Masschaele D, Horré K, Misbaer A, Vanderroost N, De Smet AS, Salta E, Erfurth ML, Kise Y, Nebel S, Van Delm W, Plaisance S, Tavernier J, De Strooper B, De Wit J, Schmucker D. Nuclear import of the DSCAM-cytoplasmic domain drives signaling capable of inhibiting synapse formation. EMBO J 2019; 38:embj.201899669. [PMID: 30745319 DOI: 10.15252/embj.201899669] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 01/04/2019] [Accepted: 01/09/2019] [Indexed: 11/09/2022] Open
Abstract
DSCAM and DSCAML1 are immunoglobulin and cell adhesion-type receptors serving important neurodevelopmental functions including control of axon growth, branching, neurite self-avoidance, and neuronal cell death. The signal transduction mechanisms or effectors of DSCAM receptors, however, remain poorly characterized. We used a human ORFeome library to perform a high-throughput screen in mammalian cells and identified novel cytoplasmic signaling effector candidates including the Down syndrome kinase Dyrk1a, STAT3, USP21, and SH2D2A. Unexpectedly, we also found that the intracellular domains (ICDs) of DSCAM and DSCAML1 specifically and directly interact with IPO5, a nuclear import protein of the importin beta family, via a conserved nuclear localization signal. The DSCAM ICD is released by γ-secretase-dependent cleavage, and both the DSCAM and DSCAML1 ICDs efficiently translocate to the nucleus. Furthermore, RNA sequencing confirms that expression of the DSCAM as well as the DSCAML1 ICDs alone can profoundly alter the expression of genes associated with neuronal differentiation and apoptosis, as well as synapse formation and function. Gain-of-function experiments using primary cortical neurons show that increasing the levels of either the DSCAM or the DSCAML1 ICD leads to an impairment of neurite growth. Strikingly, increased expression of either full-length DSCAM or the DSCAM ICD, but not the DSCAML1 ICD, significantly decreases synapse numbers in primary hippocampal neurons. Taken together, we identified a novel membrane-to-nucleus signaling mechanism by which DSCAM receptors can alter the expression of regulators of neuronal differentiation and synapse formation and function. Considering that chromosomal duplications lead to increased DSCAM expression in trisomy 21, our findings may help uncover novel mechanisms contributing to intellectual disability in Down syndrome.
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Affiliation(s)
- Sonja M Sachse
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Sam Lievens
- VIB Center for Medical Biotechnology, Ghent, Belgium.,Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Luís F Ribeiro
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Dan Dascenco
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Delphine Masschaele
- VIB Center for Medical Biotechnology, Ghent, Belgium.,Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Katrien Horré
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Anke Misbaer
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Nele Vanderroost
- VIB Center for Medical Biotechnology, Ghent, Belgium.,Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Anne Sophie De Smet
- VIB Center for Medical Biotechnology, Ghent, Belgium.,Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Evgenia Salta
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | | | - Yoshiaki Kise
- VIB Center for Brain & Disease Research, Leuven, Belgium
| | - Siegfried Nebel
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | | | | | - Jan Tavernier
- VIB Center for Medical Biotechnology, Ghent, Belgium.,Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Bart De Strooper
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium.,Dementia Research Institute, University College London, London, UK
| | - Joris De Wit
- VIB Center for Brain & Disease Research, Leuven, Belgium.,Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Dietmar Schmucker
- VIB Center for Brain & Disease Research, Leuven, Belgium .,Department of Neurosciences, KU Leuven, Leuven, Belgium
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32
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Jin Y, Li H. Revisiting Dscam diversity: lessons from clustered protocadherins. Cell Mol Life Sci 2019; 76:667-680. [PMID: 30343321 PMCID: PMC11105660 DOI: 10.1007/s00018-018-2951-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 10/13/2018] [Accepted: 10/15/2018] [Indexed: 12/14/2022]
Abstract
The complexity of neuronal wiring relies on the extraordinary recognition diversity of cell surface molecules. Drosophila Dscam1 and vertebrate clustered protocadherins (Pcdhs) are two classic examples of the striking diversity from a complex genomic locus, wherein the former encodes more than 10,000 distinct isoforms via alternative splicing, while the latter employs alternative promoters to attain isoform diversity. These structurally unrelated families show remarkably striking molecular parallels and even similar functions. Recent studies revealed a novel Dscam gene family with tandemly arrayed 5' cassettes in Chelicerata (e.g., the scorpion Mesobuthus martensii and the tick Ixodes scapularis), similar to vertebrate clustered Pcdhs. Likewise, octopus shows a more remarkable expansion of the Pcdh isoform repertoire than human. These discoveries of Dscam and Pcdh diversification reshape the evolutionary landscape of recognition molecule diversity and provide a greater understanding of convergent molecular strategies for isoform diversity. This article reviews new insights into the evolution, regulatory mechanisms, and functions of Dscam and Pcdh isoform diversity. In particular, the convergence of clustered Dscams and Pcdhs is highlighted.
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Affiliation(s)
- Yongfeng Jin
- Institute of Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou, 310058, Zhejiang (ZJ), People's Republic of China.
| | - Hao Li
- Institute of Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou, 310058, Zhejiang (ZJ), People's Republic of China
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33
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Abstract
The creation of complex neuronal networks relies on ligand-receptor interactions that mediate attraction or repulsion towards specific targets. Roundabouts comprise a family of single-pass transmembrane receptors facilitating this process upon interaction with the soluble extracellular ligand Slit protein family emanating from the midline. Due to the complexity and flexible nature of Robo receptors , their overall structure has remained elusive until now. Recent structural studies of the Robo 1 and Robo 2 ectodomains have provided the basis for a better understanding of their signalling mechanism. These structures reveal how Robo receptors adopt an auto-inhibited conformation on the cell surface that can be further stabilised by cis and/or trans oligmerisation arrays. Upon Slit -N binding Robo receptors must undergo a conformational change for Ig4 mediated dimerisation and signaling, probably via endocytosis. Furthermore, it's become clear that Robo receptors do not only act alone, but as large and more complex cell surface receptor assemblies to manifest directional and growth effects in a concerted fashion. These context dependent assemblies provide a mechanism to fine tune attractive and repulsive signals in a combinatorial manner required during neuronal development. While a mechanistic understanding of Slit mediated Robo signaling has advanced significantly further structural studies on larger assemblies are required for the design of new experiments to elucidate their role in cell surface receptor complexes. These will be necessary to understand the role of Slit -Robo signaling in neurogenesis, angiogenesis, organ development and cancer progression. In this chapter, we provide a review of the current knowledge in the field with a particular focus on the Roundabout receptor family.
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Affiliation(s)
- Francesco Bisiak
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue Des Martyrs, 38042, Grenoble, France.
| | - Andrew A McCarthy
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue Des Martyrs, 38042, Grenoble, France.
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34
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Abstract
Proper neuronal wiring is central to all bodily functions, sensory perception, cognition, memory, and learning. Establishment of a functional neuronal circuit is a highly regulated and dynamic process involving axonal and dendritic branching and navigation toward appropriate targets and connection partners. This intricate circuitry includes axo-dendritic synapse formation, synaptic connections formed with effector cells, and extensive dendritic arborization that function to receive and transmit mechanical and chemical sensory inputs. Such complexity is primarily achieved by extensive axonal and dendritic branch formation and pruning. Fundamental to neuronal branching are cytoskeletal dynamics and plasma membrane expansion, both of which are regulated via numerous extracellular and intracellular signaling mechanisms and molecules. This review focuses on recent advances in understanding the biology of neuronal branching.
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Affiliation(s)
- Shalini Menon
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Stephanie Gupton
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, Chapel Hill, NC, 27599, USA.,Neuroscience Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.,Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
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35
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The Role of Apoptotic Signaling in Axon Guidance. J Dev Biol 2018; 6:jdb6040024. [PMID: 30340315 PMCID: PMC6316149 DOI: 10.3390/jdb6040024] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2018] [Revised: 10/16/2018] [Accepted: 10/16/2018] [Indexed: 12/28/2022] Open
Abstract
Navigating growth cones are exposed to multiple signals simultaneously and have to integrate competing cues into a coherent navigational response. Integration of guidance cues is traditionally thought to occur at the level of cytoskeletal dynamics. Drosophila studies indicate that cells exhibit a low level of continuous caspase protease activation, and that axon guidance cues can activate or suppress caspase activity. We base a model for axon guidance on these observations. By analogy with other systems in which caspase signaling has non-apoptotic functions, we propose that caspase signaling can either reinforce repulsion or negate attraction in response to external guidance cues by cleaving cytoskeletal proteins. Over the course of an entire trajectory, incorrectly navigating axons may pass the threshold for apoptosis and be eliminated, whereas axons making correct decisions will survive. These observations would also explain why neurotrophic factors can act as axon guidance cues and why axon guidance systems such as Slit/Robo signaling may act as tumor suppressors in cancer.
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36
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Abstract
During nervous system development, neurons extend axons to reach their targets and form functional circuits. The faulty assembly or disintegration of such circuits results in disorders of the nervous system. Thus, understanding the molecular mechanisms that guide axons and lead to neural circuit formation is of interest not only to developmental neuroscientists but also for a better comprehension of neural disorders. Recent studies have demonstrated how crosstalk between different families of guidance receptors can regulate axonal navigation at choice points, and how changes in growth cone behaviour at intermediate targets require changes in the surface expression of receptors. These changes can be achieved by a variety of mechanisms, including transcription, translation, protein-protein interactions, and the specific trafficking of proteins and mRNAs. Here, I review these axon guidance mechanisms, highlighting the most recent advances in the field that challenge the textbook model of axon guidance.
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Affiliation(s)
- Esther T Stoeckli
- University of Zurich, Institute of Molecular Life Sciences, Neuroscience Center Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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37
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Zhao J, Mommersteeg MTM. Slit-Robo signalling in heart development. Cardiovasc Res 2018; 114:794-804. [PMID: 29538649 PMCID: PMC5909645 DOI: 10.1093/cvr/cvy061] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2017] [Revised: 01/16/2018] [Accepted: 03/09/2018] [Indexed: 02/06/2023] Open
Abstract
The Slit ligands and their Robo receptors are well-known for their roles during axon guidance in the central nervous system but are still relatively unknown in the cardiac field. However, data from different animal models suggest a broad involvement of the pathway in many aspects of heart development, from cardiac cell migration and alignment, lumen formation, chamber formation, to the formation of the ventricular septum, semilunar and atrioventricular valves, caval veins, and pericardium. Absence of one or more of the genes in the pathway results in defects ranging from bicuspid aortic valves to ventricular septal defects and abnormal venous connections to the heart. Congenital heart defects are the most common congenital malformations found in life new-born babies and progress in methods for large scale human genetic testing has significantly enhanced the identification of new causative genes involved in human congenital heart disease. Recently, loss of function variants in ROBO1 have also been linked to ventricular septal defects and tetralogy of Fallot in patients. Here, we will give an overview of the role of the Slit-Robo signalling pathway in Drosophila, zebrafish, and mouse heart development. The extent of these data warrant further attention on the SLIT-ROBO signalling pathway as a candidate for an array of human congenital heart defects.
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Affiliation(s)
- Juanjuan Zhao
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Burdon Sanderson Cardiac Science Centre, University of Oxford, South Parks Road, Oxford OX1 3PT, UK
| | - Mathilda T M Mommersteeg
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Burdon Sanderson Cardiac Science Centre, University of Oxford, South Parks Road, Oxford OX1 3PT, UK
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38
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Liu Y, Bhowmick T, Liu Y, Gao X, Mertens HDT, Svergun DI, Xiao J, Zhang Y, Wang JH, Meijers R. Structural Basis for Draxin-Modulated Axon Guidance and Fasciculation by Netrin-1 through DCC. Neuron 2018; 97:1261-1267.e4. [PMID: 29503192 PMCID: PMC5871715 DOI: 10.1016/j.neuron.2018.02.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 10/19/2017] [Accepted: 02/05/2018] [Indexed: 11/25/2022]
Abstract
Axon guidance involves the spatiotemporal interplay between guidance cues and membrane-bound cell-surface receptors, present on the growth cone of the axon. Netrin-1 is a prototypical guidance cue that binds to deleted in colorectal cancer (DCC), and it has been proposed that the guidance cue Draxin modulates this interaction. Here, we present structural snapshots of Draxin/DCC and Draxin/Netrin-1 complexes, revealing a triangular relationship that affects Netrin-mediated haptotaxis and fasciculation. Draxin interacts with DCC through the N-terminal four immunoglobulin domains, and Netrin-1 through the EGF-3 domain, in the same region where DCC binds. Netrin-1 and DCC bind to adjacent sites on Draxin, which appears to capture Netrin-1 and tether it to the DCC receptor. We propose the conformational flexibility of the single-pass membrane receptor DCC is used to promote fasciculation and regulate axon guidance through concerted Netrin-1/Draxin binding. Video Abstract
Crystal structure of cysteine knot domain of Draxin in complex with DCC Crystal structure of Netrin-1 in complex with a Draxin fragment Netrin-1 contains a competing binding site for DCC and Draxin on the EGF-3 domain Draxin tethers Netrin-1 and DCC together to promote fasciculation
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Affiliation(s)
- Ying Liu
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Tuhin Bhowmick
- European Molecular Biology Laboratory (EMBL), Hamburg Outstation, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Yiqiong Liu
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China; PKU-IDG/McGovern Institute for Brain Research, Peking University, 100871 Beijing, China
| | - Xuefan Gao
- European Molecular Biology Laboratory (EMBL), Hamburg Outstation, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Haydyn D T Mertens
- European Molecular Biology Laboratory (EMBL), Hamburg Outstation, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Dmitri I Svergun
- European Molecular Biology Laboratory (EMBL), Hamburg Outstation, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Junyu Xiao
- State Key Laboratory of Protein and Plant Gene Research, School of Life Science and Peking-Tsinghua Centre for Life Sciences, Peking University, 100871 Beijing, China.
| | - Yan Zhang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China; PKU-IDG/McGovern Institute for Brain Research, Peking University, 100871 Beijing, China.
| | - Jia-Huai Wang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China; Department of Medical Oncology and Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA.
| | - Rob Meijers
- European Molecular Biology Laboratory (EMBL), Hamburg Outstation, Notkestrasse 85, D-22607 Hamburg, Germany.
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Howard LJ, Brown HE, Wadsworth BC, Evans TA. Midline axon guidance in the Drosophila embryonic central nervous system. Semin Cell Dev Biol 2017; 85:13-25. [PMID: 29174915 DOI: 10.1016/j.semcdb.2017.11.029] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 11/13/2017] [Accepted: 11/21/2017] [Indexed: 02/02/2023]
Abstract
Studies in the fruit fly Drosophila melanogaster have provided many fundamental insights into the genetic regulation of neural development, including the identification and characterization of evolutionarily conserved axon guidance pathways and their roles in important guidance decisions. Due to its highly organized and fast-developing embryonic nervous system, relatively small number of neurons, and molecular and genetic tools for identifying, labeling, and manipulating individual neurons or small neuronal subsets, studies of axon guidance in the Drosophila embryonic CNS have allowed researchers to dissect these genetic mechanisms with a high degree of precision. In this review, we discuss the major axon guidance pathways that regulate midline crossing of axons and the formation and guidance of longitudinal axon tracts, two processes that contribute to the development of the precise three-dimensional structure of the insect nerve cord. We focus particularly on recent insights into the roles and regulation of canonical midline axon guidance pathways, and on additional factors and pathways that have recently been shown to contribute to axon guidance decisions at and near the midline.
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Affiliation(s)
- LaFreda J Howard
- Department of Biological Sciences, University of Arkansas, Fayetteville AR 72701, USA
| | - Haley E Brown
- Department of Biological Sciences, University of Arkansas, Fayetteville AR 72701, USA
| | - Benjamin C Wadsworth
- Department of Biological Sciences, University of Arkansas, Fayetteville AR 72701, USA
| | - Timothy A Evans
- Department of Biological Sciences, University of Arkansas, Fayetteville AR 72701, USA.
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40
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Protein O-Mannosyltransferases Affect Sensory Axon Wiring and Dynamic Chirality of Body Posture in the Drosophila Embryo. J Neurosci 2017; 38:1850-1865. [PMID: 29167399 DOI: 10.1523/jneurosci.0346-17.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 11/01/2017] [Accepted: 11/06/2017] [Indexed: 02/06/2023] Open
Abstract
Genetic defects in protein O-mannosyltransferase 1 (POMT1) and POMT2 underlie severe muscular dystrophies. POMT genes are evolutionarily conserved in metazoan organisms. In Drosophila, both male and female POMT mutants show a clockwise rotation of adult abdominal segments, suggesting a chirality of underlying pathogenic mechanisms. Here we described and analyzed a similar phenotype in POMT mutant embryos that shows left-handed body torsion. Our experiments demonstrated that coordinated muscle contraction waves are associated with asymmetric embryo rolling, unveiling a new chirality marker in Drosophila development. Using genetic and live-imaging approaches, we revealed that the torsion phenotype results from differential rolling and aberrant patterning of peristaltic waves of muscle contractions. Our results demonstrated that peripheral sensory neurons are required for normal contractions that prevent the accumulation of torsion. We found that POMT mutants show abnormal axonal connections of sensory neurons. POMT transgenic expression limited to sensory neurons significantly rescued the torsion phenotype, axonal connectivity defects, and abnormal contractions in POMT mutant embryos. Together, our data suggested that protein O-mannosylation is required for normal sensory feedback to control coordinated muscle contractions and body posture. This mechanism may shed light on analogous functions of POMT genes in mammals and help to elucidate the etiology of neurological defects in muscular dystrophies.SIGNIFICANCE STATEMENT Protein O-mannosyltransferases (POMTs) are evolutionarily conserved in metazoans. Mutations in POMTs cause severe muscular dystrophies associated with pronounced neurological defects. However, neurological functions of POMTs remain poorly understood. We demonstrated that POMT mutations in Drosophila result in abnormal muscle contractions and cause embryo torsion. Our experiments uncovered a chirality of embryo movements and a unique POMT-dependent mechanism that maintains symmetry of a developing system affected by chiral forces. Furthermore, POMTs were found to be required for proper axon connectivity of sensory neurons, suggesting that O-mannosylation regulates the sensory feedback controlling muscle contractions. This novel POMT function in the peripheral nervous system may shed light on analogous functions in mammals and help to elucidate pathomechanisms of neurological abnormalities in muscular dystrophies.
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Abstract
Alternative pre-mRNA splicing provides an effective means for expanding coding capacity of eukaryotic genomes. Recent studies suggest that co-expression of different splice isoforms may increase diversity of RNAs and proteins at a single-cell level. A pertinent question in the field is whether such co-expression is biologically meaningful or, rather, represents insufficiently stringent splicing regulation. Here we argue that isoform co-expression may produce functional outcomes that are difficult and sometimes impossible to achieve using other regulation strategies. Far from being a ‘splicing noise’, co-expression is often established through co-ordinated activity of specific cis-elements and trans-acting factors. Further work in this area may uncover new biological functions of alternative splicing (AS) and generate important insights into mechanisms allowing different cell types to attain their unique molecular identities.
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42
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Regulation of Drosophila Brain Wiring by Neuropil Interactions via a Slit-Robo-RPTP Signaling Complex. Dev Cell 2017; 39:267-278. [PMID: 27780041 PMCID: PMC5084709 DOI: 10.1016/j.devcel.2016.09.028] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 03/29/2016] [Accepted: 08/25/2016] [Indexed: 11/05/2022]
Abstract
The axonal wiring molecule Slit and its Round-About (Robo) receptors are conserved regulators of nerve cord patterning. Robo receptors also contribute to wiring brain circuits. Whether molecular mechanisms regulating these signals are modified to fit more complex brain wiring processes is unclear. We investigated the role of Slit and Robo receptors in wiring Drosophila higher-order brain circuits and identified differences in the cellular and molecular mechanisms of Robo/Slit function. First, we find that signaling by Robo receptors in the brain is regulated by the Receptor Protein Tyrosine Phosphatase RPTP69d. RPTP69d increases membrane availability of Robo3 without affecting its phosphorylation state. Second, we detect no midline localization of Slit during brain development. Instead, Slit is enriched in the mushroom body, a neuronal structure covering large areas of the brain. Thus, a divergent molecular mechanism regulates neuronal circuit wiring in the Drosophila brain, partly in response to signals from the mushroom body. In the Drosophila brain, mushroom bodies are a source of the Slit guidance cue Slit regulates axon growth in the vicinity of mushroom bodies via Robo receptors The phosphatase RPTP69D regulates Robo signaling in the brain RPTP69D regulates Robo3 membrane presentation independent of its enzymatic activity
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43
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Wu MF, Liao CY, Wang LY, Chang JT. The role of Slit-Robo signaling in the regulation of tissue barriers. Tissue Barriers 2017; 5:e1331155. [PMID: 28598714 PMCID: PMC5501134 DOI: 10.1080/21688370.2017.1331155] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 05/11/2017] [Accepted: 05/11/2017] [Indexed: 01/12/2023] Open
Abstract
The role of Slit/Robo signaling has extended from initial axon repulsion in the developing nervous system to organ morphogenesis, cancer development and angiogenesis. Slit/Robo signaling regulates similar pathways within these processes. Slit/Robo ensures the homeostasis of the dynamic interaction between cell-cell and cell-matrix interactions. The dysregulation of Slit/Robo signaling damages the tissue barrier, resulting in developmental abnormalities or disease. Here, we summarize how Slit/Robo controls kidney morphogenesis and describe the dual roles of Slit/Robo signaling in the regulation of tumorigenesis and angiogenesis.
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Affiliation(s)
- Ming-Fang Wu
- School of Medicine, Chung Shan Medical University, Taichung, Taiwan, R.O.C.
- Divisions of Medical Oncology and Pulmonary Medicine, Chung Shan Medical University Hospital, Taichung, Taiwan, R.O.C.
| | - Chen-Yi Liao
- Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan, R.O.C.
| | - Ling-Yi Wang
- Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan, R.O.C.
| | - Jinghua Tsai Chang
- Divisions of Medical Oncology and Pulmonary Medicine, Chung Shan Medical University Hospital, Taichung, Taiwan, R.O.C.
- Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan, R.O.C.
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44
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Carr L, Parkinson DB, Dun XP. Expression patterns of Slit and Robo family members in adult mouse spinal cord and peripheral nervous system. PLoS One 2017; 12:e0172736. [PMID: 28234971 PMCID: PMC5325304 DOI: 10.1371/journal.pone.0172736] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 02/08/2017] [Indexed: 11/19/2022] Open
Abstract
The secreted glycoproteins, Slit1-3, are classic axon guidance molecules that act as repulsive cues through their well characterised receptors Robo1-2 to allow precise axon pathfinding and neuronal migration. The expression patterns of Slit1-3 and Robo1-2 have been most characterized in the rodent developing nervous system and the adult brain, but little is known about their expression patterns in the adult rodent peripheral nervous system. Here, we report a detailed expression analysis of Slit1-3 and Robo1-2 in the adult mouse sciatic nerve as well as their expression in the nerve cell bodies within the ventral spinal cord (motor neurons) and dorsal root ganglion (sensory neurons). Our results show that, in the adult mouse peripheral nervous system, Slit1-3 and Robo1-2 are expressed in the cell bodies and axons of both motor and sensory neurons. While Slit1 and Robo2 are only expressed in peripheral axons and their cell bodies, Slit2, Slit3 and Robo1 are also expressed in satellite cells of the dorsal root ganglion, Schwann cells and fibroblasts of peripheral nerves. In addition to these expression patterns, we also demonstrate the expression of Robo1 in blood vessels of the peripheral nerves. Our work gives important new data on the expression patterns of Slit and Robo family members within the peripheral nervous system that may relate both to nerve homeostasis and the reaction of the peripheral nerves to injury.
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Affiliation(s)
- Lauren Carr
- Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth, Devon, United Kingdom
| | - David B. Parkinson
- Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth, Devon, United Kingdom
| | - Xin-peng Dun
- Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth, Devon, United Kingdom
- Hubei University of Science and Technology, Xian-Ning City, Hubei, China
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45
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Oliva C, Hassan BA. Receptor Tyrosine Kinases and Phosphatases in Neuronal Wiring: Insights From Drosophila. Curr Top Dev Biol 2016; 123:399-432. [PMID: 28236973 DOI: 10.1016/bs.ctdb.2016.10.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Tyrosine phosphorylation is at the crossroads of many signaling pathways. Brain wiring is not an exception, and several receptor tyrosine kinases (RTKs) and tyrosine receptor phosphates (RPTPs) have been involved in this process. Considerable work has been done on RTKs, and for many of them, detailed molecular mechanisms and functions in several systems have been characterized. In contrast, RPTPs have been studied considerably less and little is known about their ligands and substrates. In both families, we find redundancy between different members to accomplish particular wiring patterns. Strikingly, some RTKs and RPTPs have lost their catalytic activity during evolution, but not their importance in biological processes. In this regard, we have to keep in mind that these proteins have multiple domains and some of their functions are independent of tyrosine phosphorylation/dephosphorylation. Since RTKs and RPTPs are enzymes involved not only in early stages of axon and dendrite pathfinding but also in synapse formation and physiology, they have a potential as drug targets. Drosophila has been a key model organism in the search of a better understanding of brain wiring, and its sophisticated toolbox is very suitable for studying the function of genes with pleiotropic functions such as RTKs and RPTPs, from wiring to synaptic formation and function. In these review, we mainly cover findings from this model organism and complement them with discoveries in vertebrate systems.
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Affiliation(s)
- Carlos Oliva
- Biomedical Neuroscience Institute, Faculty of Medicine, Universidad of Chile, Santiago, Chile.
| | - Bassem A Hassan
- Sorbonne Universités, UPMC Univ Paris 06, Inserm, CNRS, AP-HP, Institut du Cerveau et la Moelle (ICM)-Hôpital Pitié-Salpêtrière, Boulevard de l'Hôpital, Paris, France.
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46
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Raza Q, Jacobs JR. Guidance signalling regulates leading edge behaviour during collective cell migration of cardiac cells in Drosophila. Dev Biol 2016; 419:285-297. [PMID: 27618756 DOI: 10.1016/j.ydbio.2016.09.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 09/04/2016] [Accepted: 09/05/2016] [Indexed: 01/31/2023]
Abstract
Collective cell migration is the coordinated movement of cells, which organize tissues during morphogenesis, repair and some cancers. The motile cell membrane of the advancing front in collective cell migration is termed the Leading Edge. The embryonic development of the vertebrate and Drosophila hearts are both characterized by the coordinated medial migration of a bilateral cluster of mesodermal cells. In Drosophila, the cardioblasts form cohesive bilateral rows that migrate collectively as a unit towards the dorsal midline to form the dorsal vessel. We have characterized the collective cell migration of cardioblasts as an in vivo quantitative model to study the behaviour of the Leading Edge. We investigated whether guidance signalling through Slit and Netrin pathways plays a role in cell migration during heart development. Through time-lapse imaging and quantitative assessment of migratory behaviour of the cardioblasts in loss-of-function mutants, we demonstrate that both Slit and Netrin mediated signals are autonomously and concomitantly required to maximize migration velocity, filopodial and lamellipodial activities. Additionally, we show that another Slit and Netrin receptor, Dscam1, the role of which during heart development was previously unknown, is required for both normal migration of cardioblasts and luminal expansion. Leading edge behaviour analysis revealed a dosage dependent genetic interaction between Slit and Netrin receptors suggesting that downstream signalling through these receptors converge on a common output that increases leading edge activity of the cardioblasts. Finally, we found that guidance signalling maintains the balance between epithelial and mesenchymal characteristics of the migrating cardioblasts.
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Affiliation(s)
- Qanber Raza
- Department of Biology, McMaster University, 1280 Main St W, Hamilton, ON, Canada L8S 4L8
| | - J Roger Jacobs
- Department of Biology, McMaster University, 1280 Main St W, Hamilton, ON, Canada L8S 4L8.
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47
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Ordan E, Volk T. Amontillado is required for Drosophila Slit processing and for tendon-mediated muscle patterning. Biol Open 2016; 5:1530-1534. [PMID: 27628033 PMCID: PMC5087687 DOI: 10.1242/bio.020636] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Slit cleavage into N-terminal and C-terminal polypeptides is essential for restricting the range of Slit activity. Although the Slit cleavage site has been characterized previously and is evolutionally conserved, the identity of the protease that cleaves Slit remains elusive. Our previous analysis indicated that Slit cleavage is essential to immobilize the active Slit-N at the tendon cell surfaces, mediating the arrest of muscle elongation. In an attempt to identify the protease required for Slit cleavage we performed an RNAi-based assay in the ectoderm and followed the process of elongation of the lateral transverse muscles toward tendon cells. The screen led to the identification of the Drosophila homolog of pheromone convertase 2 (PC2), Amontillado (Amon), as an essential protease for Slit cleavage. Further analysis indicated that Slit mobility on SDS polyacrylamide gel electrophoresis (SDS-PAGE) is slightly up-shifted in amon mutants, and its conventional cleavage into the Slit-N and Slit-C polypeptides is attenuated. Consistent with the requirement for amon to promote Slit cleavage and membrane immobilization of Slit-N, the muscle phenotype of amon mutant embryos was rescued by co-expressing a membrane-bound form of full-length Slit lacking the cleavage site and knocked into the slit locus. The identification of a novel protease component essential for Slit processing may represent an additional regulatory step in the Slit signaling pathway. Summary: The Drosophila homolog of pheromone convertase 2 (PC2), amontillado (Amon), is shown to contribute to Slit processing and further cleavage into an N-Slit, essential for Slit activity in directing muscle patterning.
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Affiliation(s)
- Elly Ordan
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Talila Volk
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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48
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Alavi M, Song M, King GLA, Gillis T, Propst R, Lamanuzzi M, Bousum A, Miller A, Allen R, Kidd T. Dscam1 Forms a Complex with Robo1 and the N-Terminal Fragment of Slit to Promote the Growth of Longitudinal Axons. PLoS Biol 2016; 14:e1002560. [PMID: 27654876 PMCID: PMC5031454 DOI: 10.1371/journal.pbio.1002560] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2016] [Accepted: 08/23/2016] [Indexed: 11/19/2022] Open
Abstract
The Slit protein is a major midline repellent for central nervous system (CNS) axons. In vivo, Slit is proteolytically cleaved into N- and C-terminal fragments, but the biological significance of this is unknown. Analysis in the Drosophila ventral nerve cord of a slit allele (slit-UC) that cannot be cleaved revealed that midline repulsion is still present but longitudinal axon guidance is disrupted, particularly across segment boundaries. Double mutants for the Slit receptors Dscam1 and robo1 strongly resemble the slit-UC phenotype, suggesting they cooperate in longitudinal axon guidance, and through biochemical approaches, we found that Dscam1 and Robo1 form a complex dependent on Slit-N. In contrast, Robo1 binding alone shows a preference for full-length Slit, whereas Dscam1 only binds Slit-N. Using a variety of transgenes, we demonstrated that Dscam1 appears to modify the output of Robo/Slit complexes so that signaling is no longer repulsive. Our data suggest that the complex is promoting longitudinal axon growth across the segment boundary. The ability of Dscam1 to modify the output of other receptors in a ligand-dependent fashion may be a general principle for Dscam proteins.
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Affiliation(s)
- Maryam Alavi
- Department of Biology, University of Nevada, Reno, Nevada, United States of America
| | - Minmin Song
- Department of Biology, University of Nevada, Reno, Nevada, United States of America
| | | | - Taylor Gillis
- Department of Biology, University of Nevada, Reno, Nevada, United States of America
| | - Robert Propst
- Department of Biology, University of Nevada, Reno, Nevada, United States of America
| | - Matthew Lamanuzzi
- Department of Biology, University of Nevada, Reno, Nevada, United States of America
| | - Adam Bousum
- Department of Biology, University of Nevada, Reno, Nevada, United States of America
| | - Amanda Miller
- Department of Biology, University of Nevada, Reno, Nevada, United States of America
| | - Ryan Allen
- Department of Biology, University of Nevada, Reno, Nevada, United States of America
| | - Thomas Kidd
- Department of Biology, University of Nevada, Reno, Nevada, United States of America
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49
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Abstract
Slits are secreted proteins that bind to Roundabout (Robo) receptors. Slit-Robo signaling is best known for mediating axon repulsion in the developing nervous system. However, in recent years the functional repertoire of Slits and Robo has expanded tremendously and Slit-Robo signaling has been linked to roles in neurogenesis, angiogenesis and cancer progression among other processes. Likewise, our mechanistic understanding of Slit-Robo signaling has progressed enormously. Here, we summarize new insights into Slit-Robo evolutionary and system-dependent diversity, receptor-ligand interactions, signaling crosstalk and receptor activation.
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Affiliation(s)
- Heike Blockus
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 Rue Moreau, Paris 75012, France Ecole des Neurosciences de Paris, Paris F-75005, France
| | - Alain Chédotal
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 Rue Moreau, Paris 75012, France
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50
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Tadros W, Xu S, Akin O, Yi CH, Shin GJE, Millard SS, Zipursky SL. Dscam Proteins Direct Dendritic Targeting through Adhesion. Neuron 2016; 89:480-93. [PMID: 26844831 DOI: 10.1016/j.neuron.2015.12.026] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 11/11/2015] [Accepted: 12/07/2015] [Indexed: 11/17/2022]
Abstract
Cell recognition molecules are key regulators of neural circuit assembly. The Dscam family of recognition molecules in Drosophila has been shown to regulate interactions between neurons through homophilic repulsion. This is exemplified by Dscam1 and Dscam2, which together repel dendrites of lamina neurons, L1 and L2, in the visual system. By contrast, here we show that Dscam2 directs dendritic targeting of another lamina neuron, L4, through homophilic adhesion. Through live imaging and genetic mosaics to dissect interactions between specific cells, we show that Dscam2 is required in L4 and its target cells for correct dendritic targeting. In a genetic screen, we identified Dscam4 as another regulator of L4 targeting which acts with Dscam2 in the same pathway to regulate this process. This ensures tiling of the lamina neuropil through heterotypic interactions. Thus, different combinations of Dscam proteins act through distinct mechanisms in closely related neurons to pattern neural circuits.
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Affiliation(s)
- Wael Tadros
- Department of Biological Chemistry, Howard Hughes Medical Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Shuwa Xu
- Department of Biological Chemistry, Howard Hughes Medical Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Orkun Akin
- Department of Biological Chemistry, Howard Hughes Medical Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Caroline H Yi
- Department of Biological Chemistry, Howard Hughes Medical Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Grace Ji-Eun Shin
- School of Biomedical Sciences, The University of Queensland, Brisbane QLD 4072, Australia
| | - S Sean Millard
- School of Biomedical Sciences, The University of Queensland, Brisbane QLD 4072, Australia
| | - S Lawrence Zipursky
- Department of Biological Chemistry, Howard Hughes Medical Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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