51
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Anazi S, Maddirevula S, Faqeih E, Alsedairy H, Alzahrani F, Shamseldin HE, Patel N, Hashem M, Ibrahim N, Abdulwahab F, Ewida N, Alsaif HS, Al Sharif H, Alamoudi W, Kentab A, Bashiri FA, Alnaser M, AlWadei AH, Alfadhel M, Eyaid W, Hashem A, Al Asmari A, Saleh MM, AlSaman A, Alhasan KA, Alsughayir M, Al Shammari M, Mahmoud A, Al-Hassnan ZN, Al-Husain M, Osama Khalil R, Abd El Meguid N, Masri A, Ali R, Ben-Omran T, El Fishway P, Hashish A, Ercan Sencicek A, State M, Alazami AM, Salih MA, Altassan N, Arold ST, Abouelhoda M, Wakil SM, Monies D, Shaheen R, Alkuraya FS. Clinical genomics expands the morbid genome of intellectual disability and offers a high diagnostic yield. Mol Psychiatry 2017; 22:615-624. [PMID: 27431290 DOI: 10.1038/mp.2016.113] [Citation(s) in RCA: 159] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 06/02/2016] [Accepted: 06/06/2016] [Indexed: 12/13/2022]
Abstract
Intellectual disability (ID) is a measurable phenotypic consequence of genetic and environmental factors. In this study, we prospectively assessed the diagnostic yield of genomic tools (molecular karyotyping, multi-gene panel and exome sequencing) in a cohort of 337 ID subjects as a first-tier test and compared it with a standard clinical evaluation performed in parallel. Standard clinical evaluation suggested a diagnosis in 16% of cases (54/337) but only 70% of these (38/54) were subsequently confirmed. On the other hand, the genomic approach revealed a likely diagnosis in 58% (n=196). These included copy number variants in 14% (n=54, 15% are novel), and point mutations revealed by multi-gene panel and exome sequencing in the remaining 43% (1% were found to have Fragile-X). The identified point mutations were mostly recessive (n=117, 81%), consistent with the high consanguinity of the study cohort, but also X-linked (n=8, 6%) and de novo dominant (n=19, 13%). When applied directly on all cases with negative molecular karyotyping, the diagnostic yield of exome sequencing was 60% (77/129). Exome sequencing also identified likely pathogenic variants in three novel candidate genes (DENND5A, NEMF and DNHD1) each of which harbored independent homozygous mutations in patients with overlapping phenotypes. In addition, exome sequencing revealed de novo and recessive variants in 32 genes (MAMDC2, TUBAL3, CPNE6, KLHL24, USP2, PIP5K1A, UBE4A, TP53TG5, ATOH1, C16ORF90, SLC39A14, TRERF1, RGL1, CDH11, SYDE2, HIRA, FEZF2, PROCA1, PIANP, PLK2, QRFPR, AP3B2, NUDT2, UFC1, BTN3A2, TADA1, ARFGEF3, FAM160B1, ZMYM5, SLC45A1, ARHGAP33 and CAPS2), which we highlight as potential candidates on the basis of several lines of evidence, and one of these genes (SLC39A14) was biallelically inactivated in a potentially treatable form of hypermanganesemia and neurodegeneration. Finally, likely causal variants in previously published candidate genes were identified (ASTN1, HELZ, THOC6, WDR45B, ADRA2B and CLIP1), thus supporting their involvement in ID pathogenesis. Our results expand the morbid genome of ID and support the adoption of genomics as a first-tier test for individuals with ID.
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Affiliation(s)
- S Anazi
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - S Maddirevula
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - E Faqeih
- Department of Pediatric Subspecialties, Children's Hospital, King Fahad Medical City, Riyadh, Saudi Arabia
| | - H Alsedairy
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - F Alzahrani
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - H E Shamseldin
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - N Patel
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - M Hashem
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - N Ibrahim
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - F Abdulwahab
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - N Ewida
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - H S Alsaif
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - H Al Sharif
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - W Alamoudi
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - A Kentab
- Department of Pediatrics, College of Medicine & King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia
| | - F A Bashiri
- Department of Pediatrics, College of Medicine & King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia
| | - M Alnaser
- Department of Pediatrics, College of Medicine & King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia
| | - A H AlWadei
- Pediatric Neurology Department, National Neuroscience Institute, King Fahad Medical City, Riyadh, Saudi Arabia
| | - M Alfadhel
- Department of Pediatrics, King Saud bin Abdulaziz University for Health Science, King Abdulaziz Medical City, Riyadh, Saudi Arabia
| | - W Eyaid
- Department of Pediatrics, King Saud bin Abdulaziz University for Health Science, King Abdulaziz Medical City, Riyadh, Saudi Arabia
| | - A Hashem
- Department of Pediatrics, Prince Sultan Military Medical City, Riyadh, Saudi Arabia
| | - A Al Asmari
- Department of Pediatric Subspecialties, Children's Hospital, King Fahad Medical City, Riyadh, Saudi Arabia
| | - M M Saleh
- Department of Pediatric Subspecialties, Children's Hospital, King Fahad Medical City, Riyadh, Saudi Arabia
| | - A AlSaman
- Pediatric Neurology Department, National Neuroscience Institute, King Fahad Medical City, Riyadh, Saudi Arabia
| | - K A Alhasan
- Department of Pediatrics, College of Medicine & King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia
| | - M Alsughayir
- Department of Psychiatry, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - M Al Shammari
- Department of Pediatrics, College of Medicine & King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia
| | - A Mahmoud
- Pediatric Neurology Department, National Neuroscience Institute, King Fahad Medical City, Riyadh, Saudi Arabia
| | - Z N Al-Hassnan
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - M Al-Husain
- Department of Pediatrics, College of Medicine & King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia
| | - R Osama Khalil
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA, USA.,National Research Center, Cairo, Egypt
| | | | - A Masri
- Department of Pediatrics, Faculty of Medicine, The University of Jordan, Amman, Jordan
| | - R Ali
- Clinical & Metabolic Genetics, Pediatrics, Hamad Medical Corporation, Doha, Qatar
| | - T Ben-Omran
- Clinical & Metabolic Genetics, Pediatrics, Hamad Medical Corporation, Doha, Qatar
| | - P El Fishway
- Department of Neurosurgery, Program on Neurogenetics, Yale University School of Medicine, New Haven, CT, USA
| | - A Hashish
- National Research Center, Cairo, Egypt
| | - A Ercan Sencicek
- Department of Neurosurgery, Program on Neurogenetics, Yale University School of Medicine, New Haven, CT, USA
| | - M State
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA, USA
| | - A M Alazami
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - M A Salih
- Department of Pediatrics, College of Medicine & King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia
| | - N Altassan
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - S T Arold
- King Abdullah University of Science and Technology (KAUST), Computational Bioscience Research Center (CBRC), Division of Biological and Environmental Sciences and Engineering (BESE), Thuwal, Saudi Arabia
| | - M Abouelhoda
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - S M Wakil
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - D Monies
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - R Shaheen
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - F S Alkuraya
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.,Department of Anatomy and Cell Biology, College of Medicine, Alfaisal University, Riyadh, Saudi Arabia
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52
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Huang GH, Sun ZL, Li HJ, Feng DF. Rho GTPase-activating proteins: Regulators of Rho GTPase activity in neuronal development and CNS diseases. Mol Cell Neurosci 2017; 80:18-31. [PMID: 28163190 DOI: 10.1016/j.mcn.2017.01.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 01/06/2017] [Accepted: 01/29/2017] [Indexed: 12/22/2022] Open
Abstract
The Rho family of small GTPases was considered as molecular switches in regulating multiple cellular events, including cytoskeleton reorganization. The Rho GTPase-activating proteins (RhoGAPs) are one of the major families of Rho GTPase regulators. RhoGAPs were initially considered negative mediators of Rho signaling pathways via their GAP domain. Recent studies have demonstrated that RhoGAPs also regulate numerous aspects of neuronal development and are related to various neurodegenerative diseases in GAP-dependent and GAP-independent manners. Moreover, RhoGAPs are regulated through various mechanisms, such as phosphorylation. To date, approximately 70 RhoGAPs have been identified; however, only a small portion has been thoroughly investigated. Thus, the characterization of important RhoGAPs in the central nervous system is crucial to understand their spatiotemporal role during different stages of neuronal development. In this review, we summarize the current knowledge of RhoGAPs in the brain with an emphasis on their molecular function, regulation mechanism and disease implications in the central nervous system.
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Affiliation(s)
- Guo-Hui Huang
- Department of Neurosurgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201900, China
| | - Zhao-Liang Sun
- Department of Neurosurgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201900, China
| | - Hong-Jiang Li
- Department of Neurosurgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201900, China
| | - Dong-Fu Feng
- Department of Neurosurgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201900, China; Institute of Traumatic Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai 201900, China.
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53
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Xu Y, Quinn CC. SYD-1 Promotes Multiple Developmental Steps Leading to Neuronal Connectivity. Mol Neurobiol 2016; 53:6768-6773. [PMID: 26660112 PMCID: PMC5841450 DOI: 10.1007/s12035-015-9592-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 12/01/2015] [Indexed: 11/30/2022]
Abstract
The establishment of neuronal connectivity requires precise orchestration of multiple developmental steps, including axon specification, axon guidance, selection of synaptic target sites, and development of synaptic specializations. Although these are separate developmental steps, evidence indicates that some of the signaling molecules that regulate these steps are shared. In this review, we focus on SYD-1, a RhoGAP-like protein that has been implicated in each step of axonal development. We discuss interactions between SYD-1, UNC-40(DCC) and RhoGTPases and highlight both similarities and differences in how SYD-1 functions to regulate the different steps of axonal development. These observations reveal an example of how a signaling protein can be repurposed across sequential developmental steps.
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Affiliation(s)
- Yan Xu
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, 53211, USA
| | - Christopher C Quinn
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, 53211, USA.
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54
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Xu Y, Quinn CC. Transition between synaptic branch formation and synaptogenesis is regulated by the lin-4 microRNA. Dev Biol 2016; 420:60-66. [PMID: 27746167 PMCID: PMC5841448 DOI: 10.1016/j.ydbio.2016.10.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 07/25/2016] [Accepted: 10/12/2016] [Indexed: 11/29/2022]
Abstract
Axonal branch formation and synaptogenesis are sequential events that are required for the establishment of neuronal connectivity. However, little is known about how the transition between these two events is regulated. Here, we report that the lin-4 microRNA can regulate the transition between branch formation and synaptogenesis in the PLM axon of C. elegans. The PLM axon grows a collateral branch during the early L1 stage and undergoes synaptogenesis during the late L1 stage. Loss of the lin-4 microRNA disrupts synaptogenesis during the late L1 stage, suggesting that lin-4 promotes synaptogenesis. Conversely, the target of lin-4, the LIN-14 transcription factor, promotes PLM branch formation and inhibits synaptogenesis during the early L1 stage. Moreover, we present genetic evidence suggesting that synaptic vesicle transport is required for PLM branch formation and that the role of LIN-14 is to promote transport of synaptic vesicles to the region of future branch growth. These observations provide a novel mechanism whereby lin-4 promotes the transition from branch formation to synaptogenesis by repressing the branch-promoting and synaptogenesis-inhibiting activities of LIN-14.
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Affiliation(s)
- Yan Xu
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA
| | - Christopher C Quinn
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA.
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55
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Huang RYJ, Kuay KT, Tan TZ, Asad M, Tang HM, Ng AHC, Ye J, Chung VY, Thiery JP. Functional relevance of a six mesenchymal gene signature in epithelial-mesenchymal transition (EMT) reversal by the triple angiokinase inhibitor, nintedanib (BIBF1120). Oncotarget 2016; 6:22098-113. [PMID: 26061747 PMCID: PMC4673149 DOI: 10.18632/oncotarget.4300] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 05/22/2015] [Indexed: 11/25/2022] Open
Abstract
Epithelial-mesenchymal transition (EMT), a crucial mechanism in carcinoma progression, describes the process whereby epithelial cells lose their apico-basal polarity and junctional complexes and acquire a mesenchymal-like morphology. Several markers are considered to be authentic indicators of an epithelial or mesenchymal status; however, there is currently no comprehensive or systematic method with which to determine their functional relevance. Previously, we identified a 33-gene EMT signature comprising 25 epithelial and 6 mesenchymal genes that best describe this concept of the EMT spectrum. Here, we designed small-scale siRNA screens targeting these six mesenchymal signature genes (CD99L2, EMP3, ITGA5, SYDE1, VIM, ZEB1) to explore their functional relevance and their roles during EMT reversal by nintedanib (BIBF1120) in a mesenchymal-like SKOV3 ovarian cancer cell line. We found that neither cell proliferation nor cytotoxicity was affected by silencing any of these genes. SKOV3 cells expressing siRNA against mesenchymal genes (ZEB1, EMP3, CD99L2, ITGA5, and SYDE1) showed enhanced colony compaction (reduced inter-nuclear distance). Inductions of E-cadherin expression were only observed in SYDE1- and ZEB1-silenced SKOV3 cells. In addition, only SYDE1-silenced SKOV3 cells showed increased anoikis. Finally, we identified that SYDE1 and ZEB1 were down-regulated in nintedanib-treated SKOV3 cells and SYDE1- and ZEB1-silenced SKOV3 cells showed enhanced nintedanib-induced up-regulation of E-cadherin. Nintedanib-treated SKOV3 cells also showed colony compaction and decreases in EMT scores both in vitro and in vivo. We conclude that SYDE1 and ZEB1 are functionally relevant in EMT reversal. This study thus provides a proof-of-concept for the use of in vitro siRNA screening to explore the EMT-related functions of selected genes and their potential relevance in the discovery of EMT reversing drugs.
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Affiliation(s)
- Ruby Yun-Ju Huang
- Department of Obstetrics and Gynaecology, National University Health System, Singapore.,Cancer Science Institute of Singapore, National University of Singapore, Singapore
| | - Kuee Theng Kuay
- Cancer Science Institute of Singapore, National University of Singapore, Singapore
| | - Tuan Zea Tan
- Cancer Science Institute of Singapore, National University of Singapore, Singapore
| | - Mohammad Asad
- Department of Obstetrics and Gynaecology, National University Health System, Singapore
| | - Hei Mui Tang
- Cancer Science Institute of Singapore, National University of Singapore, Singapore
| | - Aloysius Hsien Chun Ng
- Dean's Office, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Jieru Ye
- Cancer Science Institute of Singapore, National University of Singapore, Singapore.,Dean's Office, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Vin Yee Chung
- Cancer Science Institute of Singapore, National University of Singapore, Singapore
| | - Jean Paul Thiery
- Cancer Science Institute of Singapore, National University of Singapore, Singapore.,Institute of Molecular and Cell Biology, A*STAR, Singapore.,Department of Biochemistry, National University of Singapore, Singapore
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56
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Gupta VK, Pech U, Bhukel A, Fulterer A, Ender A, Mauermann SF, Andlauer TFM, Antwi-Adjei E, Beuschel C, Thriene K, Maglione M, Quentin C, Bushow R, Schwärzel M, Mielke T, Madeo F, Dengjel J, Fiala A, Sigrist SJ. Spermidine Suppresses Age-Associated Memory Impairment by Preventing Adverse Increase of Presynaptic Active Zone Size and Release. PLoS Biol 2016; 14:e1002563. [PMID: 27684064 PMCID: PMC5042543 DOI: 10.1371/journal.pbio.1002563] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Accepted: 08/26/2016] [Indexed: 01/24/2023] Open
Abstract
Memories are assumed to be formed by sets of synapses changing their structural or functional performance. The efficacy of forming new memories declines with advancing age, but the synaptic changes underlying age-induced memory impairment remain poorly understood. Recently, we found spermidine feeding to specifically suppress age-dependent impairments in forming olfactory memories, providing a mean to search for synaptic changes involved in age-dependent memory impairment. Here, we show that a specific synaptic compartment, the presynaptic active zone (AZ), increases the size of its ultrastructural elaboration and releases significantly more synaptic vesicles with advancing age. These age-induced AZ changes, however, were fully suppressed by spermidine feeding. A genetically enforced enlargement of AZ scaffolds (four gene-copies of BRP) impaired memory formation in young animals. Thus, in the Drosophila nervous system, aging AZs seem to steer towards the upper limit of their operational range, limiting synaptic plasticity and contributing to impairment of memory formation. Spermidine feeding suppresses age-dependent memory impairment by counteracting these age-dependent changes directly at the synapse.
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Affiliation(s)
- Varun K. Gupta
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure, Charité, Berlin, Germany
| | - Ulrike Pech
- Georg-August-Universität Göttingen, Molecular Neurobiology of Behavior, Göttingen, Germany
| | - Anuradha Bhukel
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure, Charité, Berlin, Germany
| | - Andreas Fulterer
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure, Charité, Berlin, Germany
| | - Anatoli Ender
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Stephan F. Mauermann
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure, Charité, Berlin, Germany
| | | | | | - Christine Beuschel
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Kerstin Thriene
- Centre for Systems Biological Analysis, University of Freiburg, Freiburg, Germany
| | - Marta Maglione
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure, Charité, Berlin, Germany
| | - Christine Quentin
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure, Charité, Berlin, Germany
| | - René Bushow
- Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Martin Schwärzel
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Thorsten Mielke
- Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Frank Madeo
- Institute for Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
- BioTechMed Graz, Graz, Austria
| | - Joern Dengjel
- Centre for Systems Biological Analysis, University of Freiburg, Freiburg, Germany
| | - André Fiala
- Georg-August-Universität Göttingen, Molecular Neurobiology of Behavior, Göttingen, Germany
| | - Stephan J. Sigrist
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure, Charité, Berlin, Germany
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57
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Böhme MA, Beis C, Reddy-Alla S, Reynolds E, Mampell MM, Grasskamp AT, Lützkendorf J, Bergeron DD, Driller JH, Babikir H, Göttfert F, Robinson IM, O'Kane CJ, Hell SW, Wahl MC, Stelzl U, Loll B, Walter AM, Sigrist SJ. Active zone scaffolds differentially accumulate Unc13 isoforms to tune Ca2+ channel–vesicle coupling. Nat Neurosci 2016; 19:1311-20. [DOI: 10.1038/nn.4364] [Citation(s) in RCA: 136] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 07/20/2016] [Indexed: 01/05/2023]
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58
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Mechanisms controlling assembly and plasticity of presynaptic active zone scaffolds. Curr Opin Neurobiol 2016; 39:69-76. [DOI: 10.1016/j.conb.2016.04.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 04/08/2016] [Accepted: 04/15/2016] [Indexed: 11/18/2022]
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59
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Miller KG. Keeping Neuronal Cargoes on the Right Track: New Insights into Regulators of Axonal Transport. Neuroscientist 2016; 23:232-250. [PMID: 27154488 DOI: 10.1177/1073858416648307] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In neurons, a single motor (dynein) transports large organelles as well as synaptic and dense core vesicles toward microtubule minus ends; however, it is unclear why dynein appears more active on organelles, which are generally excluded from mature axons, than on synaptic and dense core vesicles, which are maintained at high levels. Recent studies in Zebrafish and Caenorhabditis elegans have shown that JIP3 promotes dynein-mediated retrograde transport to clear some organelles (lysosomes, early endosomes, and Golgi) from axons and prevent their potentially harmful accumulation in presynaptic regions. A JIP3 mutant suppressor screen in C. elegans revealed that JIP3 promotes the clearance of organelles from axons by blocking the action of the CSS system (Cdk5, SAD Kinase, SYD-2/Liprin). A synthesis of results in vertebrates with the new findings suggests that JIP3 blocks the CSS system from disrupting the connection between dynein and organelles. Most components of the CSS system are enriched at presynaptic active zones where they normally contribute to maintaining optimal levels of captured synaptic and dense core vesicles, in part by inhibiting dynein transport. The JIP3-CSS system model explains how neurons selectively regulate a single minus-end motor to exclude specific classes of organelles from axons, while at the same time ensuring optimal levels of synaptic and dense core vesicles.
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Affiliation(s)
- Kenneth G Miller
- 1 Genetic Models of Disease Laboratory, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
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60
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Han KA, Jeon S, Um JW, Ko J. Emergent Synapse Organizers: LAR-RPTPs and Their Companions. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 324:39-65. [PMID: 27017006 DOI: 10.1016/bs.ircmb.2016.01.002] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Leukocyte common antigen-related receptor tyrosine phosphatases (LAR-RPTPs) have emerged as key players that organize various aspects of neuronal development, including axon guidance, neurite extension, and synapse formation and function. Recent research has highlighted the roles of LAR-RPTPs at neuronal synapses in mediating distinct synaptic adhesion pathways through interactions with a host of extracellular ligands and in governing a variety of intracellular signaling cascades through binding to various scaffolds and signaling proteins. In this chapter, we review and update current research progress on the extracellular ligands of LAR-RPTPs, regulation of their extracellular interactions by alternative splicing and heparan sulfates, and their intracellular signaling machineries. In particular, we review structural insights on complexes of LAR-RPTPs with their various ligands. These studies lend support to general molecular mechanisms underlying LAR-RPTP-mediated synaptic adhesion and signaling pathways.
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Affiliation(s)
- K A Han
- Department of Physiology and BK21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea
| | - S Jeon
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, South Korea
| | - J W Um
- Department of Physiology and BK21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea
| | - J Ko
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, South Korea.
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61
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Sulkowski MJ, Han TH, Ott C, Wang Q, Verheyen EM, Lippincott-Schwartz J, Serpe M. A Novel, Noncanonical BMP Pathway Modulates Synapse Maturation at the Drosophila Neuromuscular Junction. PLoS Genet 2016; 12:e1005810. [PMID: 26815659 PMCID: PMC4729469 DOI: 10.1371/journal.pgen.1005810] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 12/22/2015] [Indexed: 12/21/2022] Open
Abstract
At the Drosophila NMJ, BMP signaling is critical for synapse growth and homeostasis. Signaling by the BMP7 homolog, Gbb, in motor neurons triggers a canonical pathway—which modulates transcription of BMP target genes, and a noncanonical pathway—which connects local BMP/BMP receptor complexes with the cytoskeleton. Here we describe a novel noncanonical BMP pathway characterized by the accumulation of the pathway effector, the phosphorylated Smad (pMad), at synaptic sites. Using genetic epistasis, histology, super resolution microscopy, and electrophysiology approaches we demonstrate that this novel pathway is genetically distinguishable from all other known BMP signaling cascades. This novel pathway does not require Gbb, but depends on presynaptic BMP receptors and specific postsynaptic glutamate receptor subtypes, the type-A receptors. Synaptic pMad is coordinated to BMP’s role in the transcriptional control of target genes by shared pathway components, but it has no role in the regulation of NMJ growth. Instead, selective disruption of presynaptic pMad accumulation reduces the postsynaptic levels of type-A receptors, revealing a positive feedback loop which appears to function to stabilize active type-A receptors at synaptic sites. Thus, BMP pathway may monitor synapse activity then function to adjust synapse growth and maturation during development. Synaptic activity and synapse development are intimately linked, but our understanding of the coupling mechanisms remains limited. Anterograde and retrograde signals together with trans-synaptic complexes enable intercellular communications. How synapse activity status is monitored and relayed across the synaptic cleft remains poorly understood. The Drosophila NMJ is a very powerful genetic system to study synapse development. BMP signaling modulates NMJ growth via a canonical, Smad-dependent pathway, but also synapse stability, via a noncanonical, Smad-independent pathway. Here we describe a novel, noncanonical BMP pathway, which is genetically distinguishable from all other known BMP pathways. This pathway does not contribute to NMJ growth and instead influences synapse formation and maturation in an activity-dependent manner. Specifically, phosphorylated Smad (pMad in flies) accumulates at active zone in response to active postsynaptic type-A glutamate receptors, a specific receptor subtype. In turn, synaptic pMad functions to promote the recruitment of type-A receptors at synaptic sites. This positive feedback loop provides a molecular switch controlling which flavor of glutamate receptors will be stabilized at synaptic locations as a function of synapse status. Since BMP signaling also controls NMJ growth and stability, BMP pathway offers an exquisite means to monitor the status of synapse activity and coordinate NMJ growth with synapse maturation and stabilization.
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Affiliation(s)
- Mikolaj J. Sulkowski
- Program in Cellular Regulation and Metabolism, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, Maryland, United States of America
| | - Tae Hee Han
- Program in Cellular Regulation and Metabolism, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, Maryland, United States of America
| | - Carolyn Ott
- Cellular Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, Maryland, United States of America
| | - Qi Wang
- Program in Cellular Regulation and Metabolism, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, Maryland, United States of America
| | - Esther M. Verheyen
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Jennifer Lippincott-Schwartz
- Cellular Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, Maryland, United States of America
| | - Mihaela Serpe
- Program in Cellular Regulation and Metabolism, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, Maryland, United States of America
- * E-mail:
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62
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Muhammad K, Reddy-Alla S, Driller JH, Schreiner D, Rey U, Böhme MA, Hollmann C, Ramesh N, Depner H, Lützkendorf J, Matkovic T, Götz T, Bergeron DD, Schmoranzer J, Goettfert F, Holt M, Wahl MC, Hell SW, Scheiffele P, Walter AM, Loll B, Sigrist SJ. Presynaptic spinophilin tunes neurexin signalling to control active zone architecture and function. Nat Commun 2015; 6:8362. [PMID: 26471740 PMCID: PMC4633989 DOI: 10.1038/ncomms9362] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 08/13/2015] [Indexed: 11/17/2022] Open
Abstract
Assembly and maturation of synapses at the Drosophila neuromuscular junction
(NMJ) depend on trans-synaptic neurexin/neuroligin signalling, which is promoted by
the scaffolding protein Syd-1 binding to neurexin. Here we report that the scaffold
protein spinophilin binds to the C-terminal portion of neurexin and is needed to
limit neurexin/neuroligin signalling by acting antagonistic to Syd-1. Loss of
presynaptic spinophilin results in the formation of excess, but atypically small
active zones. Neuroligin-1/neurexin-1/Syd-1 levels are increased at
spinophilin mutant NMJs, and removal of single copies of the
neurexin-1, Syd-1 or neuroligin-1 genes suppresses the
spinophilin-active zone phenotype. Evoked transmission is strongly reduced at
spinophilin terminals, owing to a severely reduced release probability at
individual active zones. We conclude that presynaptic spinophilin fine-tunes
neurexin/neuroligin signalling to control active zone number and functionality,
thereby optimizing them for action potential-induced exocytosis. Synaptic assembly depends on trans-synaptic Neurexin/Neuroligin
signalling. Here, Muhammad et al. show that Spinophilin, a pre-synaptic
scaffolding protein, interacts with Neurexin, in competition with Syd-1, to regulate the
formation and function of synaptic active zones at Drosophila neuromuscular
junctions.
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Affiliation(s)
- Karzan Muhammad
- Freie Universität Berlin, Institute for Biology/Genetics, Takustrasse 6, Berlin 14195, Germany.,NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany
| | - Suneel Reddy-Alla
- Freie Universität Berlin, Institute for Biology/Genetics, Takustrasse 6, Berlin 14195, Germany.,NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany
| | - Jan H Driller
- Freie Universität Berlin, Institut für Chemie und Biochemie /Strukturbiochmie, Takustrasse 6, Berlin D-14195, Germany
| | - Dietmar Schreiner
- Biozentrum, University of Basel, Klingelbergstrasse 50-70, Basel 4056, Switzerland
| | - Ulises Rey
- NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany
| | | | | | - Niraja Ramesh
- Freie Universität Berlin, Institute for Biology/Genetics, Takustrasse 6, Berlin 14195, Germany
| | - Harald Depner
- Freie Universität Berlin, Institute for Biology/Genetics, Takustrasse 6, Berlin 14195, Germany.,NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany
| | | | - Tanja Matkovic
- Freie Universität Berlin, Institute for Biology/Genetics, Takustrasse 6, Berlin 14195, Germany.,NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany
| | - Torsten Götz
- Freie Universität Berlin, Institute for Biology/Genetics, Takustrasse 6, Berlin 14195, Germany.,NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany
| | | | - Jan Schmoranzer
- Freie Universität Berlin, Institut für Chemie und Biochemie /Strukturbiochmie, Takustrasse 6, Berlin D-14195, Germany.,Leibniz Institut für Molekulare Pharmakologie, Robert-Roessle-Strasse 10, Berlin 13125, Germany
| | - Fabian Goettfert
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen 37077, Germany
| | - Mathew Holt
- VIB Center for the Biology of Disease, Herestraat 49, Leuven 3000, Belgium
| | - Markus C Wahl
- Freie Universität Berlin, Institut für Chemie und Biochemie /Strukturbiochmie, Takustrasse 6, Berlin D-14195, Germany
| | - Stefan W Hell
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen 37077, Germany
| | - Peter Scheiffele
- Biozentrum, University of Basel, Klingelbergstrasse 50-70, Basel 4056, Switzerland
| | - Alexander M Walter
- NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany.,Leibniz Institut für Molekulare Pharmakologie, Robert-Roessle-Strasse 10, Berlin 13125, Germany
| | - Bernhard Loll
- Freie Universität Berlin, Institut für Chemie und Biochemie /Strukturbiochmie, Takustrasse 6, Berlin D-14195, Germany
| | - Stephan J Sigrist
- Freie Universität Berlin, Institute for Biology/Genetics, Takustrasse 6, Berlin 14195, Germany.,NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany
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63
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Harris KP, Littleton JT. Transmission, Development, and Plasticity of Synapses. Genetics 2015; 201:345-75. [PMID: 26447126 PMCID: PMC4596655 DOI: 10.1534/genetics.115.176529] [Citation(s) in RCA: 119] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 05/28/2015] [Indexed: 01/03/2023] Open
Abstract
Chemical synapses are sites of contact and information transfer between a neuron and its partner cell. Each synapse is a specialized junction, where the presynaptic cell assembles machinery for the release of neurotransmitter, and the postsynaptic cell assembles components to receive and integrate this signal. Synapses also exhibit plasticity, during which synaptic function and/or structure are modified in response to activity. With a robust panel of genetic, imaging, and electrophysiology approaches, and strong evolutionary conservation of molecular components, Drosophila has emerged as an essential model system for investigating the mechanisms underlying synaptic assembly, function, and plasticity. We will discuss techniques for studying synapses in Drosophila, with a focus on the larval neuromuscular junction (NMJ), a well-established model glutamatergic synapse. Vesicle fusion, which underlies synaptic release of neurotransmitters, has been well characterized at this synapse. In addition, studies of synaptic assembly and organization of active zones and postsynaptic densities have revealed pathways that coordinate those events across the synaptic cleft. We will also review modes of synaptic growth and plasticity at the fly NMJ, and discuss how pre- and postsynaptic cells communicate to regulate plasticity in response to activity.
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Affiliation(s)
- Kathryn P Harris
- Department of Biology and Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - J Troy Littleton
- Department of Biology and Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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64
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Siebert M, Böhme MA, Driller JH, Babikir H, Mampell MM, Rey U, Ramesh N, Matkovic T, Holton N, Reddy-Alla S, Göttfert F, Kamin D, Quentin C, Klinedinst S, Andlauer TF, Hell SW, Collins CA, Wahl MC, Loll B, Sigrist SJ. A high affinity RIM-binding protein/Aplip1 interaction prevents the formation of ectopic axonal active zones. eLife 2015; 4. [PMID: 26274777 PMCID: PMC4536467 DOI: 10.7554/elife.06935] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 07/24/2015] [Indexed: 12/17/2022] Open
Abstract
Synaptic vesicles (SVs) fuse at active zones (AZs) covered by a protein scaffold, at Drosophila synapses comprised of ELKS family member Bruchpilot (BRP) and RIM-binding protein (RBP). We here demonstrate axonal co-transport of BRP and RBP using intravital live imaging, with both proteins co-accumulating in axonal aggregates of several transport mutants. RBP, via its C-terminal Src-homology 3 (SH3) domains, binds Aplip1/JIP1, a transport adaptor involved in kinesin-dependent SV transport. We show in atomic detail that RBP C-terminal SH3 domains bind a proline-rich (PxxP) motif of Aplip1/JIP1 with submicromolar affinity. Pointmutating this PxxP motif provoked formation of ectopic AZ-like structures at axonal membranes. Direct interactions between AZ proteins and transport adaptors seem to provide complex avidity and shield synaptic interaction surfaces of pre-assembled scaffold protein transport complexes, thus, favouring physiological synaptic AZ assembly over premature assembly at axonal membranes. DOI:http://dx.doi.org/10.7554/eLife.06935.001 To pass on information, the neurons that make up the nervous system connect at structures known as synapses. Chemical messengers called neurotransmitters are released from one neuron, and travel across the synapse to trigger a response in the neighbouring cell. The formation of new synapses plays an important role in learning and memory, but many aspects of this process are not well understood. In a specific region of the synapse called the active zone, a scaffold of proteins helps to release the neurotransmitters. These proteins are made in the cell body of the neuron, and are then transported to the end of the long, thin axons that protrude from the cell body. This presents a challenge for the cell, because the components of the active zone scaffold must be correctly targeted to the synapse at the end of the axon, ensuring the active zone scaffold assembles only at its proper location. Siebert, Böhme et al. studied how some of the proteins that are found in the active zone scaffold of the fruit fly Drosophila are transported along axons. Labelling the proteins with fluorescent markers allowed their movement to be examined under a microscope in living Drosophila larvae. The results showed that two of the proteins—known as BRP and RBP—are transported along the axons together. Further investigation revealed that a transport adaptor protein called Aplip1, which binds to RBP, is required for this movement. Siebert, Böhme et al. established the structure of the part of RBP where this interaction occurs, and found that mutating this region causes premature active zone scaffold assembly in the axonal part of the neuron. The interaction between RBP and Aplip1 is very strong, and this helps to prevent the scaffold assembling before it has reached the correct part of the neuron. Exactly how the transport adaptor and active zone protein are separated once they reach their final destination (the synapse) remains to be discovered. DOI:http://dx.doi.org/10.7554/eLife.06935.002
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Affiliation(s)
- Matthias Siebert
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Mathias A Böhme
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Jan H Driller
- Institute of Chemistry and Biochemisty/Structural Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Husam Babikir
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Malou M Mampell
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Ulises Rey
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Niraja Ramesh
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Tanja Matkovic
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Nicole Holton
- Institute of Chemistry and Biochemisty/Structural Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Suneel Reddy-Alla
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Fabian Göttfert
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Dirk Kamin
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Christine Quentin
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Susan Klinedinst
- Department of Molecular Cellular and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Till Fm Andlauer
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Stefan W Hell
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Catherine A Collins
- Department of Molecular Cellular and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Markus C Wahl
- Institute of Chemistry and Biochemisty/Structural Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Bernhard Loll
- Institute of Chemistry and Biochemisty/Structural Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Stephan J Sigrist
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
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65
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Abstract
To create a presynaptic terminal, molecular signaling events must be orchestrated across a number of subcellular compartments. In the soma, presynaptic proteins need to be synthesized, packaged together, and attached to microtubule motors for shipment through the axon. Within the axon, transport of presynaptic packages is regulated to ensure that developing synapses receive an adequate supply of components. At individual axonal sites, extracellular interactions must be translated into intracellular signals that can incorporate mobile transport vesicles into the nascent presynaptic terminal. Even once the initial recruitment process is complete, the components and subsequent functionality of presynaptic terminals need to constantly be remodeled. Perhaps most remarkably, all of these processes need to be coordinated in space and time. In this review, we discuss how these dynamic cellular processes occur in neurons of the central nervous system in order to generate presynaptic terminals in the brain.
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Affiliation(s)
- Luke A D Bury
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Shasta L Sabo
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH, USA Department of Neuroscience, Case Western Reserve University School of Medicine, Cleveland, OH, USA
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66
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Ackermann F, Waites CL, Garner CC. Presynaptic active zones in invertebrates and vertebrates. EMBO Rep 2015; 16:923-38. [PMID: 26160654 DOI: 10.15252/embr.201540434] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 06/19/2015] [Indexed: 11/09/2022] Open
Abstract
The regulated release of neurotransmitter occurs via the fusion of synaptic vesicles (SVs) at specialized regions of the presynaptic membrane called active zones (AZs). These regions are defined by a cytoskeletal matrix assembled at AZs (CAZ), which functions to direct SVs toward docking and fusion sites and supports their maturation into the readily releasable pool. In addition, CAZ proteins localize voltage-gated Ca(2+) channels at SV release sites, bringing the fusion machinery in close proximity to the calcium source. Proteins of the CAZ therefore ensure that vesicle fusion is temporally and spatially organized, allowing for the precise and reliable release of neurotransmitter. Importantly, AZs are highly dynamic structures, supporting presynaptic remodeling, changes in neurotransmitter release efficacy, and thus presynaptic forms of plasticity. In this review, we discuss recent advances in the study of active zones, highlighting how the CAZ molecularly defines sites of neurotransmitter release, endocytic zones, and the integrity of synapses.
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Affiliation(s)
- Frauke Ackermann
- German Center for Neurodegenerative Disease, Charité Medical University, Berlin, Germany
| | - Clarissa L Waites
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Craig C Garner
- German Center for Neurodegenerative Disease, Charité Medical University, Berlin, Germany
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67
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Tian X, Wu C. Active zone stability: insights from fly neuromuscular junction. Neural Regen Res 2015; 10:677-8. [PMID: 26109929 PMCID: PMC4468746 DOI: 10.4103/1673-5374.156942] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/20/2015] [Indexed: 11/23/2022] Open
Abstract
The presynaptic active zone is a dynamic structure that orchestrates regulated release of neurotransmitters. Developmental and aging processes, and changes in neuronal network activity can all modulate the number, size and composition of active zone and thereby synaptic efficacy. However, very little is known about the mechanism that controls the structural stability of active zone. By studying a model synapse, the Drosophila neuromuscular junction, our recent work shed light on how two scaffolding proteins at the active zone regulate active zone stability by promoting a localized dephosphorylation event at the nerve terminal. Here we discuss the major insights from our findings and their implications for future research.
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Affiliation(s)
- Xiaolin Tian
- Neuroscience Center of Excellence, Department of Cell Biology and Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA
| | - Chunlai Wu
- Neuroscience Center of Excellence, Department of Cell Biology and Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA
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68
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Mosca TJ. On the Teneurin track: a new synaptic organization molecule emerges. Front Cell Neurosci 2015; 9:204. [PMID: 26074772 PMCID: PMC4444827 DOI: 10.3389/fncel.2015.00204] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 05/11/2015] [Indexed: 11/16/2022] Open
Abstract
To achieve proper synaptic development and function, coordinated signals must pass between the pre- and postsynaptic membranes. Such transsynaptic signals can be comprised of receptors and secreted ligands, membrane associated receptors, and also pairs of synaptic cell adhesion molecules. A critical open question bridging neuroscience, developmental biology, and cell biology involves identifying those signals and elucidating how they function. Recent work in Drosophila and vertebrate systems has implicated a family of proteins, the Teneurins, as a new transsynaptic signal in both the peripheral and central nervous systems. The Teneurins have established roles in neuronal wiring, but studies now show their involvement in regulating synaptic connections between neurons and bridging the synaptic membrane and the cytoskeleton. This review will examine the Teneurins as synaptic cell adhesion molecules, explore how they regulate synaptic organization, and consider how some consequences of human Teneurin mutations may have synaptopathic origins.
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Affiliation(s)
- Timothy J Mosca
- Department of Biology, Stanford University Stanford, CA, USA
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69
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Li T, Tian Y, Li Q, Chen H, Lv H, Xie W, Han J. The Neurexin/N-Ethylmaleimide-sensitive Factor (NSF) Interaction Regulates Short Term Synaptic Depression. J Biol Chem 2015; 290:17656-17667. [PMID: 25953899 DOI: 10.1074/jbc.m115.644583] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Indexed: 11/06/2022] Open
Abstract
Although Neurexins, which are cell adhesion molecules localized predominantly to the presynaptic terminals, are known to regulate synapse formation and synaptic transmission, their roles in the regulation of synaptic vesicle release during repetitive nerve stimulation are unknown. Here, we show that nrx mutant synapses exhibit rapid short term synaptic depression upon tetanic nerve stimulation. Moreover, we demonstrate that the intracellular region of NRX is essential for synaptic vesicle release upon tetanic nerve stimulation. Using a yeast two-hybrid screen, we find that the intracellular region of NRX interacts with N-ethylmaleimide-sensitive factor (NSF), an enzyme that mediates soluble NSF attachment protein receptor (SNARE) complex disassembly and plays an important role in synaptic vesicle release. We further map the binding sites of each molecule and demonstrate that the NRX/NSF interaction is critical for both the distribution of NSF at the presynaptic terminals and SNARE complex disassembly. Our results reveal a previously unknown role of NRX in the regulation of short term synaptic depression upon tetanic nerve stimulation and provide new mechanistic insights into the role of NRX in synaptic vesicle release.
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Affiliation(s)
- Tao Li
- Institute of Life Sciences, Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing 210096
| | - Yao Tian
- Institute of Life Sciences, Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing 210096
| | - Qian Li
- Institute of Life Sciences, Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing 210096
| | - Huiying Chen
- Institute of Life Sciences, Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing 210096
| | - Huihui Lv
- Institute of Life Sciences, Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing 210096
| | - Wei Xie
- Institute of Life Sciences, Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing 210096; Co-innovation Center of Neuroregeneration, Nantong University, Nantong, JS 226001, China
| | - Junhai Han
- Institute of Life Sciences, Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing 210096; Co-innovation Center of Neuroregeneration, Nantong University, Nantong, JS 226001, China.
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70
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Bloch-Gallego E. Mechanisms controlling neuromuscular junction stability. Cell Mol Life Sci 2015; 72:1029-43. [PMID: 25359233 PMCID: PMC11113273 DOI: 10.1007/s00018-014-1768-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 10/06/2014] [Accepted: 10/17/2014] [Indexed: 01/01/2023]
Abstract
The neuromuscular junction (NMJ) is the synaptic connection between motor neurons and muscle fibers. It is involved in crucial processes such as body movements and breathing. Its proper development requires the guidance of motor axons toward their specific targets, the development of multi-innervated myofibers, and a selective synapse stabilization. It first consists of the removal of excessive motor axons on myofibers, going from multi-innervation to a single innervation of each myofiber. Whereas guidance cues of motor axons toward their specific muscular targets are well characterized, only few molecular and cellular cues have been reported as clues for selecting and stabilizing specific neuromuscular junctions. We will first provide a brief summary on NMJ development. We will then review molecular cues that are involved in NMJ stabilization, in both pre- and post-synaptic compartments, considering motor neurons and Schwann cells on the one hand, and muscle on the other hand. We will provide links with pathologies and highlight advances that can be brought both by basic research on NMJ development and clinical data resulting from the analyses of neurodegeneration of synaptic connections to obtain a better understanding of this process. The goal of this review is to highlight the findings toward understanding the roles of poly- or single-innervations and the underlying mechanisms of NMJ stabilization.
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Affiliation(s)
- Evelyne Bloch-Gallego
- Institut Cochin, INSERM U. 1016, CNRS UMR 8104, University Paris Descartes 24, rue du Fbg St-Jacques, 75014, Paris, France,
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71
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Abstract
The neurexin family of cell adhesion proteins consists of three members in
vertebrates and has homologs in several invertebrate species. In mammals, each
neurexin gene encodes an α-neurexin in which the extracellular portion is long,
and a β-neurexin in which the extracellular portion is short. As a result of
alternative splicing, both major isoforms can be transcribed in many variants,
contributing to distinct structural domains and variability. Neurexins act
predominantly at the presynaptic terminal in neurons and play essential roles in
neurotransmission and differentiation of synapses. Some of these functions require
the formation of trans-synaptic complexes with postsynaptic proteins such as
neuroligins, LRRTM proteins or cerebellin. In addition, rare mutations and
copy-number variations of human neurexin genes have been linked to autism and
schizophrenia, indicating that impairments of synaptic function sustained by
neurexins and their binding partners may be relevant to the pathomechanism of these
debilitating diseases.
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72
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Abstract
Synapses are specialized asymmetric cell-cell connections permitting the controlled transfer of an electrical or chemical signal between a presynaptic neuronal cell and a postsynaptic target cell (e.g. neuron or muscle). Adequate synapse function is an essential prerequisite of all neuronal processing, including higher cognitive functions, such as learning and memory. At synapses, neurotransmitters (e.g. amino acids, amines, peptides, and acetylcholine) are released from synaptic vesicles into the synaptic cleft in response to action potentials. The Nobel Prize for Physiology and Medicine in 2013 was awarded to James E. Rothman, Randy W. Schekman and Thomas C. Südhof "for their discoveries of the machinery regulating vesicle traffic, a major transport system in our cells". This included crucial revelations, such as the identification of the core machinery of synaptic vesicle fusion. However, in contrast to the advances concerning the organization of the core functions of the synapse, our current understanding of the processes of synapse formation and maintenance--i.e. 'synaptogenesis'--is still somewhat fragmentary. Here, we will outline the current status and future directions of the field of synaptogenesis, primarily from the perspective of the presynaptic release site.
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Affiliation(s)
- Astrid G Petzoldt
- Neurogenetik, Institut für Biologie, Freie Universität Berlin, 14195 Berlin, Germany; Cluster of Excellence NeuroCure, Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany
| | - Stephan J Sigrist
- Neurogenetik, Institut für Biologie, Freie Universität Berlin, 14195 Berlin, Germany; Cluster of Excellence NeuroCure, Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany.
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73
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Andlauer TFM, Scholz-Kornehl S, Tian R, Kirchner M, Babikir HA, Depner H, Loll B, Quentin C, Gupta VK, Holt MG, Dipt S, Cressy M, Wahl MC, Fiala A, Selbach M, Schwärzel M, Sigrist SJ. Drep-2 is a novel synaptic protein important for learning and memory. eLife 2014; 3. [PMID: 25392983 PMCID: PMC4229683 DOI: 10.7554/elife.03895] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Accepted: 10/13/2014] [Indexed: 12/16/2022] Open
Abstract
CIDE-N domains mediate interactions between the DNase Dff40/CAD and its inhibitor Dff45/ICAD. In this study, we report that the CIDE-N protein Drep-2 is a novel synaptic protein important for learning and behavioral adaptation. Drep-2 was found at synapses throughout the Drosophila brain and was strongly enriched at mushroom body input synapses. It was required within Kenyon cells for normal olfactory short- and intermediate-term memory. Drep-2 colocalized with metabotropic glutamate receptors (mGluRs). Chronic pharmacological stimulation of mGluRs compensated for drep-2 learning deficits, and drep-2 and mGluR learning phenotypes behaved non-additively, suggesting that Drep 2 might be involved in effective mGluR signaling. In fact, Drosophila fragile X protein mutants, shown to benefit from attenuation of mGluR signaling, profited from the elimination of drep-2. Thus, Drep-2 is a novel regulatory synaptic factor, probably intersecting with metabotropic signaling and translational regulation. DOI:http://dx.doi.org/10.7554/eLife.03895.001 Synapses are specialized structures that connect nerve cells to one another and allow information to be transmitted between the cells. Synapses are essential for learning and storing memories. Many proteins that regulate how signals are transmitted at synapses have already been studied. In this manner, much has been learned about their function in learning and memory. Cells can commit suicide by a process called apoptosis, also known as programmed cell death. Apoptosis is not only triggered in damaged cells but is also necessary for an organism to develop correctly. In fruit flies, the protein Drep-2 is a member of a family of proteins that degrade the DNA of cells that undergo apoptosis. Andlauer et al. found no evidence that Drep-2 plays a role in apoptosis, but have now found Drep-2 at the synapses of the brain of the fruit fly Drosophila. Drep-2 could be observed in close proximity to another type of protein called metabotropic glutamate receptors. Metabotropic glutamate receptors and their signaling pathways are important for regulating certain changes to the synapses that mediate learning processes. Indeed, Andlauer et al. found that flies that have lost the gene that produces Drep-2 were unable to remember smells when these were paired with a punishment. Stimulating the regulatory glutamate receptors with drugs helped to overcome learning deficits that result from the lack of Drep-2. Alterations in the production of a protein called FMRP cause fragile X syndrome in humans, the most common form of hereditary mental disability originating from a single gene defect. Flies lacking the FMRP protein show learning deficits that are very similar to the ones seen in flies that cannot produce Drep-2. However, Andlauer et al. observed that flies lacking both Drep-2 and FMRP can learn normally. Exactly how Drep-2 works in synapses to help with memory formation remains to be discovered, although there are indications that it boosts the effects of signaling from the glutamate receptors and counteracts FMRP. Further research will be needed to establish whether the mammalian proteins related to Drep-2 perform similar roles in the brains of mammals. DOI:http://dx.doi.org/10.7554/eLife.03895.002
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Affiliation(s)
- Till F M Andlauer
- Genetics, Institute of Biology, Freie Universität Berlin, Berlin, Germany
| | | | - Rui Tian
- Genetics, Institute of Biology, Freie Universität Berlin, Berlin, Germany
| | - Marieluise Kirchner
- Department of Cell Signalling and Mass Spectrometry, Max-Delbrück-Centrum für Molekulare Medizin, Berlin-Buch, Germany
| | - Husam A Babikir
- Genetics, Institute of Biology, Freie Universität Berlin, Berlin, Germany
| | - Harald Depner
- Genetics, Institute of Biology, Freie Universität Berlin, Berlin, Germany
| | - Bernhard Loll
- Institute of Chemistry and Biochemisty, Freie Universität Berlin, Berlin, Germany
| | - Christine Quentin
- Genetics, Institute of Biology, Freie Universität Berlin, Berlin, Germany
| | - Varun K Gupta
- Genetics, Institute of Biology, Freie Universität Berlin, Berlin, Germany
| | - Matthew G Holt
- Department Laboratory of Glia Biology, Vlaams Instituut voor Biotechnologie (VIB) Center for the Biology of Disease, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Shubham Dipt
- Department of Molecular Neurobiology of Behavior, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Michael Cressy
- Department of Neuroscience, Cold Spring Harbor Laboratory, Cold Spring Harbor, United States
| | - Markus C Wahl
- Institute of Chemistry and Biochemisty, Freie Universität Berlin, Berlin, Germany
| | - André Fiala
- Department of Molecular Neurobiology of Behavior, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Matthias Selbach
- Department of Cell Signalling and Mass Spectrometry, Max-Delbrück-Centrum für Molekulare Medizin, Berlin-Buch, Germany
| | - Martin Schwärzel
- Genetics, Institute of Biology, Freie Universität Berlin, Berlin, Germany
| | - Stephan J Sigrist
- Genetics, Institute of Biology, Freie Universität Berlin, Berlin, Germany
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Depner H, Lützkendorf J, Babkir HA, Sigrist SJ, Holt MG. Differential centrifugation-based biochemical fractionation of the Drosophila adult CNS. Nat Protoc 2014; 9:2796-808. [PMID: 25393777 DOI: 10.1038/nprot.2014.192] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Drosophila is widely used as a genetic model in questions of development, cellular function and disease. Genetic screens in flies have proven to be incredibly powerful in identifying crucial components for synapse formation and function, particularly in the case of the presynaptic release machinery. Although modern biochemical methods can identify individual proteins and lipids (and their binding partners), they have typically been excluded from use in Drosophila for technical reasons. To bridge this essential gap between genetics and biochemistry, we developed a fractionation method to isolate various parts of the synaptic machinery from Drosophila, thus allowing it to be studied in unprecedented biochemical detail. This is only possible because our protocol has unique advantages in terms of enriching and preserving endogenous protein complexes. The procedure involves decapitation of adult flies, homogenization and differential centrifugation of fly heads, which allow subsequent purification of presynaptic (and to a limited degree postsynaptic) components. It is designed to require only a rudimentary knowledge of biochemical fractionation, and it takes ∼3.5 h. The yield is typically 4 mg of synaptic membrane protein per gram of Drosophila heads.
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Affiliation(s)
- Harald Depner
- Institute for Biology - Genetics, Freie Universität Berlin, Berlin, Germany
| | - Janine Lützkendorf
- Institute for Biology - Genetics, Freie Universität Berlin, Berlin, Germany
| | - Husam A Babkir
- Institute for Biology - Genetics, Freie Universität Berlin, Berlin, Germany
| | - Stephan J Sigrist
- 1] Institute for Biology - Genetics, Freie Universität Berlin, Berlin, Germany. [2] NeuroCure Cluster of Excellence, Charité, Berlin, Germany
| | - Matthew G Holt
- Laboratory of Glia Biology, Vlaams Instituut voor Biotechnologie (VIB) Center for the Biology of Disease, Katholieke Universiteit (KU) Leuven, Leuven, Belgium
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75
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Jepson JEC, Shahidullah M, Liu D, le Marchand SJ, Liu S, Wu MN, Levitan IB, Dalva MB, Koh K. Regulation of synaptic development and function by the Drosophila PDZ protein Dyschronic. Development 2014; 141:4548-57. [PMID: 25359729 DOI: 10.1242/dev.109538] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Synaptic scaffold proteins control the localization of ion channels and receptors, and facilitate molecular associations between signaling components that modulate synaptic transmission and plasticity. Here, we define novel roles for a recently described scaffold protein, Dsychronic (DYSC), at the Drosophila larval neuromuscular junction. DYSC is the Drosophila homolog of whirlin/DFNB31, a PDZ domain protein linked to Usher syndrome, the most common form of human deaf-blindness. We show that DYSC is expressed presynaptically and is often localized adjacent to the active zone, the site of neurotransmitter release. Loss of DYSC results in marked alterations in synaptic morphology and cytoskeletal organization. Moreover, active zones are frequently enlarged and misshapen in dysc mutants. Electrophysiological analyses further demonstrate that dysc mutants exhibit substantial increases in both evoked and spontaneous synaptic transmission. We have previously shown that DYSC binds to and regulates the expression of the Slowpoke (SLO) BK potassium channel. Consistent with this, slo mutant larvae exhibit similar alterations in synapse morphology, active zone size and neurotransmission, and simultaneous loss of dysc and slo does not enhance these phenotypes, suggesting that dysc and slo act in a common genetic pathway to modulate synaptic development and output. Our data expand our understanding of the neuronal functions of DYSC and uncover non-canonical roles for the SLO potassium channel at Drosophila synapses.
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Affiliation(s)
- James E C Jepson
- Department of Neuroscience, The Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, PA 19107, USA UCL Institute of Neurology, London WC1N 3BG, UK
| | - Mohammed Shahidullah
- Department of Neuroscience, The Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Die Liu
- Department of Neuroscience, The Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Sylvain J le Marchand
- Department of Neuroscience, The Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Sha Liu
- Department of Neurology, John Hopkins University, Baltimore, MD 21287, USA
| | - Mark N Wu
- Department of Neurology, John Hopkins University, Baltimore, MD 21287, USA
| | - Irwin B Levitan
- Department of Neuroscience, The Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Matthew B Dalva
- Department of Neuroscience, The Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Kyunghee Koh
- Department of Neuroscience, The Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, PA 19107, USA
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76
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Mosca TJ, Luo L. Synaptic organization of the Drosophila antennal lobe and its regulation by the Teneurins. eLife 2014; 3:e03726. [PMID: 25310239 PMCID: PMC4194450 DOI: 10.7554/elife.03726] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 09/18/2014] [Indexed: 12/11/2022] Open
Abstract
Understanding information flow through neuronal circuits requires knowledge of their synaptic organization. In this study, we utilized fluorescent pre- and postsynaptic markers to map synaptic organization in the Drosophila antennal lobe, the first olfactory processing center. Olfactory receptor neurons (ORNs) produce a constant synaptic density across different glomeruli. Each ORN within a class contributes nearly identical active zone number. Active zones from ORNs, projection neurons (PNs), and local interneurons have distinct subglomerular and subcellular distributions. The correct number of ORN active zones and PN acetylcholine receptor clusters requires the Teneurins, conserved transmembrane proteins involved in neuromuscular synapse organization and synaptic partner matching. Ten-a acts in ORNs to organize presynaptic active zones via the spectrin cytoskeleton. Ten-m acts in PNs autonomously to regulate acetylcholine receptor cluster number and transsynaptically to regulate ORN active zone number. These studies advanced our ability to assess synaptic architecture in complex CNS circuits and their underlying molecular mechanisms.
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Affiliation(s)
- Timothy J Mosca
- Department of Biology, Howard Hughes Medical Institute, Stanford University, Stanford, United States
| | - Liqun Luo
- Department of Biology, Howard Hughes Medical Institute, Stanford University, Stanford, United States
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77
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Chua JJE. Macromolecular complexes at active zones: integrated nano-machineries for neurotransmitter release. Cell Mol Life Sci 2014; 71:3903-16. [PMID: 24912984 PMCID: PMC11113288 DOI: 10.1007/s00018-014-1657-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 05/22/2014] [Accepted: 05/23/2014] [Indexed: 02/06/2023]
Abstract
The release of neurotransmitters from synaptic vesicles exocytosing at presynaptic nerve terminals is a critical event in the initiation of synaptic transmission. This event occurs at specialized sites known as active zones. The task of faithfully executing various steps in the process is undertaken by careful orchestration of overlapping sets of molecular nano-machineries upon a core macromolecular scaffold situated at active zones. However, their composition remains incompletely elucidated. This review provides an overview of the role of the active zone in mediating neurotransmitter release and summarizes the recent progress using neuroproteomic approaches to decipher their composition. Key proteins of these nano-machineries are highlighted.
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Affiliation(s)
- John Jia En Chua
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany,
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78
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McDermott SM, Yang L, Halstead JM, Hamilton RS, Meignin C, Davis I. Drosophila Syncrip modulates the expression of mRNAs encoding key synaptic proteins required for morphology at the neuromuscular junction. RNA (NEW YORK, N.Y.) 2014; 20:1593-606. [PMID: 25171822 PMCID: PMC4174441 DOI: 10.1261/rna.045849.114] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2014] [Accepted: 06/09/2014] [Indexed: 05/24/2023]
Abstract
Localized mRNA translation is thought to play a key role in synaptic plasticity, but the identity of the transcripts and the molecular mechanism underlying their function are still poorly understood. Here, we show that Syncrip, a regulator of localized translation in the Drosophila oocyte and a component of mammalian neuronal mRNA granules, is also expressed in the Drosophila larval neuromuscular junction, where it regulates synaptic growth. We use RNA-immunoprecipitation followed by high-throughput sequencing and qRT-PCR to show that Syncrip associates with a number of mRNAs encoding proteins with key synaptic functions, including msp-300, syd-1, neurexin-1, futsch, highwire, discs large, and α-spectrin. The protein levels of MSP-300, Discs large, and a number of others are significantly affected in syncrip null mutants. Furthermore, syncrip mutants show a reduction in MSP-300 protein levels and defects in muscle nuclear distribution characteristic of msp-300 mutants. Our results highlight a number of potential new players in localized translation during synaptic plasticity in the neuromuscular junction. We propose that Syncrip acts as a modulator of synaptic plasticity by regulating the translation of these key mRNAs encoding synaptic scaffolding proteins and other important components involved in synaptic growth and function.
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Affiliation(s)
- Suzanne M McDermott
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Lu Yang
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - James M Halstead
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Russell S Hamilton
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Carine Meignin
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Ilan Davis
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
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79
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Petzoldt A, Lee YH, Khorramshahi O, Reynolds E, Plested A, Herzel H, Sigrist S. Gating Characteristics Control Glutamate Receptor Distribution and Trafficking In Vivo. Curr Biol 2014; 24:2059-65. [DOI: 10.1016/j.cub.2014.07.051] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 06/20/2014] [Accepted: 07/18/2014] [Indexed: 11/29/2022]
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80
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Drosophila Syd-1, liprin-α, and protein phosphatase 2A B' subunit Wrd function in a linear pathway to prevent ectopic accumulation of synaptic materials in distal axons. J Neurosci 2014; 34:8474-87. [PMID: 24948803 DOI: 10.1523/jneurosci.0409-14.2014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
During synaptic development, presynaptic differentiation occurs as an intrinsic property of axons to form specialized areas of plasma membrane [active zones (AZs)] that regulate exocytosis and endocytosis of synaptic vesicles. Genetic and biochemical studies in vertebrate and invertebrate model systems have identified a number of proteins involved in AZ assembly. However, elucidating the molecular events of AZ assembly in a spatiotemporal manner remains a challenge. Syd-1 (synapse defective-1) and Liprin-α have been identified as two master organizers of AZ assembly. Genetic and imaging analyses in invertebrates show that Syd-1 works upstream of Liprin-α in synaptic assembly through undefined mechanisms. To understand molecular pathways downstream of Liprin-α, we performed a proteomic screen of Liprin-α-interacting proteins in Drosophila brains. We identify Drosophila protein phosphatase 2A (PP2A) regulatory subunit B' [Wrd (Well Rounded)] as a Liprin-α-interacting protein, and we demonstrate that it mediates the interaction of Liprin-α with PP2A holoenzyme and the Liprin-α-dependent synaptic localization of PP2A. Interestingly, loss of function in syd-1, liprin-α, or wrd shares a common defect in which a portion of synaptic vesicles, dense-core vesicles, and presynaptic cytomatrix proteins ectopically accumulate at the distal, but not proximal, region of motoneuron axons. Strong genetic data show that a linear syd-1/liprin-α/wrd pathway in the motoneuron antagonizes glycogen synthase kinase-3β kinase activity to prevent the ectopic accumulation of synaptic materials. Furthermore, we provide data suggesting that the syd-1/liprin-α/wrd pathway stabilizes AZ specification at the nerve terminal and that such a novel function is independent of the roles of syd-1/liprin-α in regulating the morphology of the T-bar structural protein BRP (Bruchpilot).
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81
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Bury LA, Sabo SL. Dynamic mechanisms of neuroligin-dependent presynaptic terminal assembly in living cortical neurons. Neural Dev 2014; 9:13. [PMID: 24885664 PMCID: PMC4049477 DOI: 10.1186/1749-8104-9-13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 05/12/2014] [Indexed: 12/23/2022] Open
Abstract
Background Synapse formation occurs when synaptogenic signals trigger coordinated development of pre and postsynaptic structures. One of the best-characterized synaptogenic signals is trans-synaptic adhesion. However, it remains unclear how synaptic proteins are recruited to sites of adhesion. In particular, it is unknown whether synaptogenic signals attract synaptic vesicle (SV) and active zone (AZ) proteins to nascent synapses or instead predominantly function to create sites that are capable of forming synapses. It is also unclear how labile synaptic proteins are at developing synapses after their initial recruitment. To address these issues, we used long-term, live confocal imaging of presynaptic terminal formation in cultured cortical neurons after contact with the synaptogenic postsynaptic adhesion proteins neuroligin-1 or SynCAM-1. Results Surprisingly, we find that trans-synaptic adhesion does not attract SV or AZ proteins nor alter their transport. In addition, although neurexin (the presynaptic partner of neuroligin) typically accumulates over the entire region of contact between axons and neuroligin-1-expressing cells, SV proteins selectively assemble at spots of enhanced neurexin clustering. The arrival and maintenance of SV proteins at these sites is highly variable over the course of minutes to hours, and this variability correlates with neurexin levels at individual synapses. Conclusions Together, our data support a model of synaptogenesis where presynaptic proteins are trapped at specific axonal sites, where they are stabilized by trans-synaptic adhesion signaling.
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Affiliation(s)
| | - Shasta L Sabo
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.
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82
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Lüthy K, Ahrens B, Rawal S, Lu Z, Tarnogorska D, Meinertzhagen IA, Fischbach KF. The irre cell recognition module (IRM) protein Kirre is required to form the reciprocal synaptic network of L4 neurons in the Drosophila lamina. J Neurogenet 2014; 28:291-301. [PMID: 24697410 DOI: 10.3109/01677063.2014.883390] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Each neuropil module, or cartridge, in the fly's lamina has a fixed complement of cells. Of five types of monopolar cell interneurons, only L4 has collaterals that invade neighboring cartridges. In the proximal lamina, these collaterals form reciprocal synapses with both the L2 of their own cartridge and the L4 collateral branches from two other neighboring cartridges. During synaptogenesis, L4 collaterals strongly express the cell adhesion protein Kirre, a member of the irre cell recognition module (IRM) group of proteins ( Fischbach et al., 2009 , J Neurogenet, 23, 48-67). The authors show by mutant analysis and gene knockdown techniques that L4 neurons develop their lamina collaterals in the absence of this cell adhesion protein. Using electron microscopy (EM), the authors demonstrate, however, that without Kirre protein these L4 collaterals selectively form fewer synapses. The collaterals of L4 neurons of various genotypes reconstructed from serial-section EM revealed that the number of postsynaptic sites was dramatically reduced in the absence of Kirre, almost eliminating any synaptic input to L4 neurons. A significant reduction of presynaptic sites was also detected in kirre(0) mutants and gene knockdown flies using RNA interference. L4 neuron reciprocal synapses are thus almost eliminated. A presynaptic marker, Brp-short(GFP) confirmed these data using confocal microscopy. This study reveals that removing Kirre protein specifically disrupts the functional L4 synaptic network in the Drosophila lamina.
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Affiliation(s)
- Kevin Lüthy
- Faculty of Biology, Albert-Ludwigs University Freiburg , Germany
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83
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New approaches for studying synaptic development, function, and plasticity using Drosophila as a model system. J Neurosci 2013; 33:17560-8. [PMID: 24198346 DOI: 10.1523/jneurosci.3261-13.2013] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The fruit fly Drosophila melanogaster has been established as a premier experimental model system for neuroscience research. These organisms are genetically tractable, yet their nervous systems are sufficiently complex to study diverse processes that are conserved across metazoans, including neural cell fate determination and migration, axon guidance, synaptogenesis and function, behavioral neurogenetics, and responses to neuronal injury. For several decades, Drosophila neuroscientists have taken advantage of a vast toolkit of genetic and molecular techniques to reveal fundamental principles of neuroscience illuminating to all systems, including the first behavioral mutants from Seymour Benzer's pioneering work in the 1960s and 1970s, the cloning of the first potassium channel in the 1980s, and the identification of the core genes that orchestrate axon guidance and circadian rhythms in the 1990s. Over the past decade, new tools and innovations in genetic, imaging, and electrophysiological technologies have enabled the visualization, in vivo, of dynamic processes in synapses with unprecedented resolution. We will review some of the fresh insights into synaptic development, function, and plasticity that have recently emerged in Drosophila with an emphasis on the unique advantages of this model system.
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84
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Chia PH, Li P, Shen K. Cell biology in neuroscience: cellular and molecular mechanisms underlying presynapse formation. ACTA ACUST UNITED AC 2013; 203:11-22. [PMID: 24127213 PMCID: PMC3798257 DOI: 10.1083/jcb.201307020] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Synapse formation is a highly regulated process that requires the coordination of many cell biological events. Decades of research have identified a long list of molecular components involved in assembling a functioning synapse. Yet how the various steps, from transporting synaptic components to adhering synaptic partners and assembling the synaptic structure, are regulated and precisely executed during development and maintenance is still unclear. With the improvement of imaging and molecular tools, recent work in vertebrate and invertebrate systems has provided important insight into various aspects of presynaptic development, maintenance, and trans-synaptic signals, thereby increasing our understanding of how extrinsic organizers and intracellular mechanisms contribute to presynapse formation.
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Affiliation(s)
- Poh Hui Chia
- Department of Biology, Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305
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85
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Gokce O, Südhof TC. Membrane-tethered monomeric neurexin LNS-domain triggers synapse formation. J Neurosci 2013; 33:14617-28. [PMID: 24005312 PMCID: PMC3761060 DOI: 10.1523/jneurosci.1232-13.2013] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Revised: 07/10/2013] [Accepted: 08/03/2013] [Indexed: 12/20/2022] Open
Abstract
Neurexins are presynaptic cell-adhesion molecules that bind to postsynaptic cell-adhesion molecules such as neuroligins and leucine-rich repeat transmembrane proteins (LRRTMs). When neuroligins or LRRTMs are expressed in a nonneuronal cell, cocultured neurons avidly form heterologous synapses onto that cell. Here we show that knockdown of all neurexins in cultured hippocampal mouse neurons did not impair synapse formation between neurons, but blocked heterologous synapse formation induced by neuroligin-1 or LRRTM2. Rescue experiments demonstrated that all neurexins tested restored heterologous synapse formation in neurexin-deficient neurons. Neurexin-deficient neurons exhibited a decrease in the levels of the PDZ-domain protein CASK (a calcium/calmodulin-activated serine/threonine kinase), which binds to neurexins, and mutation of the PDZ-domain binding sequence of neurexin-3β blocked its transport to the neuronal surface and impaired heterologous synapse formation. However, replacement of the C-terminal neurexin sequence with an unrelated PDZ-domain binding sequence that does not bind to CASK fully restored surface transport and heterologous synapse formation in neurexin-deficient neurons, suggesting that no particular PDZ-domain protein is essential for neurexin surface transport or heterologous synapse formation. Further mutagenesis revealed, moreover, that the entire neurexin cytoplasmic tail was dispensable for heterologous synapse formation in neurexin-deficient neurons, as long as the neurexin protein was transported to the neuronal cell surface. Furthermore, the single LNS-domain (for laminin/neurexin/sex hormone-binding globulin-domain) of neurexin-1β or neurexin-3β, when tethered to the presynaptic plasma membrane by a glycosylinositolphosphate anchor, was sufficient for rescuing heterologous synapse formation in neurexin-deficient neurons. Our data suggest that neurexins mediate heterologous synapse formation via an extracellular interaction with presynaptic and postsynaptic ligands without the need for signal transduction by the neurexin cytoplasmic tail.
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Affiliation(s)
- Ozgun Gokce
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University Medical School, Stanford, California 94305-5453
| | - Thomas C. Südhof
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University Medical School, Stanford, California 94305-5453
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86
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Wentzel C, Sommer JE, Nair R, Stiefvater A, Sibarita JB, Scheiffele P. mSYD1A, a mammalian synapse-defective-1 protein, regulates synaptogenic signaling and vesicle docking. Neuron 2013; 78:1012-23. [PMID: 23791195 DOI: 10.1016/j.neuron.2013.05.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/13/2013] [Indexed: 10/26/2022]
Abstract
Structure and function of presynaptic terminals are critical for the transmission and processing of neuronal signals. Trans-synaptic signaling systems instruct the differentiation and function of presynaptic release sites, but their downstream mediators are only beginning to be understood. Here, we identify the intracellular mSYD1A (mouse Synapse-Defective-1A) as a regulator of presynaptic function in mice. mSYD1A forms a complex with presynaptic receptor tyrosine phosphatases and controls tethering of synaptic vesicles at synapses. mSYD1A function relies on an intrinsically disordered domain that interacts with multiple structurally unrelated binding partners, including the active zone protein liprin-α2 and nsec1/munc18-1. In mSYD1A knockout mice, synapses assemble in normal numbers but there is a significant reduction in synaptic vesicle docking at the active zone and an impairment of synaptic transmission. Thus, mSYD1A is a regulator of presynaptic release sites at central synapses.
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87
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Spangler SA, Schmitz SK, Kevenaar JT, de Graaff E, de Wit H, Demmers J, Toonen RF, Hoogenraad CC. Liprin-α2 promotes the presynaptic recruitment and turnover of RIM1/CASK to facilitate synaptic transmission. ACTA ACUST UNITED AC 2013; 201:915-28. [PMID: 23751498 PMCID: PMC3678157 DOI: 10.1083/jcb.201301011] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Liprin-α2 is required for the presynaptic recruitment and turnover of RIM1 and CASK, components of the release machinery, and facilitates synaptic output by regulating synaptic vesicle pool size. The presynaptic active zone mediates synaptic vesicle exocytosis, and modulation of its molecular composition is important for many types of synaptic plasticity. Here, we identify synaptic scaffold protein liprin-α2 as a key organizer in this process. We show that liprin-α2 levels were regulated by synaptic activity and the ubiquitin–proteasome system. Furthermore, liprin-α2 organized presynaptic ultrastructure and controlled synaptic output by regulating synaptic vesicle pool size. The presence of liprin-α2 at presynaptic sites did not depend on other active zone scaffolding proteins but was critical for recruitment of several components of the release machinery, including RIM1 and CASK. Fluorescence recovery after photobleaching showed that depletion of liprin-α2 resulted in reduced turnover of RIM1 and CASK at presynaptic terminals, suggesting that liprin-α2 promotes dynamic scaffolding for molecular complexes that facilitate synaptic vesicle release. Therefore, liprin-α2 plays an important role in maintaining active zone dynamics to modulate synaptic efficacy in response to changes in network activity.
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Affiliation(s)
- Samantha A Spangler
- Department of Neuroscience, Erasmus Medical Center, 3015GE Rotterdam, Netherlands
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88
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Protein tyrosine phosphatases PTPδ, PTPσ, and LAR: presynaptic hubs for synapse organization. Trends Neurosci 2013; 36:522-34. [PMID: 23835198 DOI: 10.1016/j.tins.2013.06.002] [Citation(s) in RCA: 197] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 06/03/2013] [Accepted: 06/11/2013] [Indexed: 02/04/2023]
Abstract
Synapse development requires differentiation of presynaptic neurotransmitter release sites and postsynaptic receptive apparatus coordinated by synapse organizing proteins. In addition to the well-characterized neurexins, recent studies identified presynaptic type IIa receptor-type protein tyrosine phosphatases (RPTPs) as mediators of presynaptic differentiation and triggers of postsynaptic differentiation, thus extending the roles of RPTPs from axon outgrowth and guidance. Similarly to neurexins, RPTPs exist in multiple isoforms generated by alternative splicing that interact in a splice-selective code with diverse postsynaptic partners. The parallel RPTP and neurexin hub design facilitates synapse self-assembly through cooperation, pairs presynaptic similarity with postsynaptic diversity, and balances excitation with inhibition. Upon mutation of individual genes in neuropsychiatric disorders, imbalance of this synaptic organizing network may contribute to impaired cognitive function.
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89
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Ruiz S, Ferreiro MJ, Menhert KI, Casanova G, Olivera A, Cantera R. Rhythmic changes in synapse numbers in Drosophila melanogaster motor terminals. PLoS One 2013; 8:e67161. [PMID: 23840613 PMCID: PMC3695982 DOI: 10.1371/journal.pone.0067161] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Accepted: 05/15/2013] [Indexed: 11/18/2022] Open
Abstract
Previous studies have shown that the morphology of the neuromuscular junction of the flight motor neuron MN5 in Drosophila melanogaster undergoes daily rhythmical changes, with smaller synaptic boutons during the night, when the fly is resting, than during the day, when the fly is active. With electron microscopy and laser confocal microscopy, we searched for a rhythmic change in synapse numbers in this neuron, both under light:darkness (LD) cycles and constant darkness (DD). We expected the number of synapses to increase during the morning, when the fly has an intense phase of locomotion activity under LD and DD. Surprisingly, only our DD data were consistent with this hypothesis. In LD, we found more synapses at midnight than at midday. We propose that under LD conditions, there is a daily rhythm of formation of new synapses in the dark phase, when the fly is resting, and disassembly over the light phase, when the fly is active. Several parameters appeared to be light dependent, since they were affected differently under LD or DD. The great majority of boutons containing synapses had only one and very few had either two or more, with a 70∶25∶5 ratio (one, two and three or more synapses) in LD and 75∶20∶5 in DD. Given the maintenance of this proportion even when both bouton and synapse numbers changed with time, we suggest that there is a homeostatic mechanism regulating synapse distribution among MN5 boutons.
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Affiliation(s)
- Santiago Ruiz
- Departamento de Biología del Neurodesarrollo, Instituto de Investigaciones Biológicas Clemente
- Estable, Montevideo, Uruguay
| | - Maria Jose Ferreiro
- Departamento de Biología del Neurodesarrollo, Instituto de Investigaciones Biológicas Clemente
- Estable, Montevideo, Uruguay
| | | | - Gabriela Casanova
- Unidad de Microscopía Electrónica de Transmisión, Facultad de Ciencias, UdelaR, Montevideo, Uruguay
| | - Alvaro Olivera
- Unidad de Microscopía Electrónica de Transmisión, Facultad de Ciencias, UdelaR, Montevideo, Uruguay
| | - Rafael Cantera
- Departamento de Biología del Neurodesarrollo, Instituto de Investigaciones Biológicas Clemente
- Estable, Montevideo, Uruguay
- Zoology Department, Stockholm University, Stockholm, Sweden
- * E-mail:
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90
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Long JB, Van Vactor D. Embryonic and larval neural connectivity: progressive changes in synapse form and function at the neuromuscular junction mediated by cytoskeletal regulation. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2013; 2:747-65. [PMID: 24123935 DOI: 10.1002/wdev.114] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
During development, precise formation of millions of synaptic connections is critical for the formation of a functional nervous system. Synaptogenesis is a complex multistep process in which axons follow gradients of secreted and cell surface guidance cues to reach their target area, at which point they must accurately distinguish their specific target. Upon target recognition, the axonal growth cone undergoes rapid growth and morphological changes, ultimately forming a functional synapse that continues to remodel during activity-dependent plasticity. Significant evidence suggests that the underlying actin and microtubule (MT) cytoskeletons are key effectors throughout synaptogenesis downstream of numerous receptors and signaling pathways. An increasing number of cytoskeletal-associated proteins have been shown to influence actin and MT stability and dynamics and many of these regulators have been implicated during synaptic morphogenesis using both mammalian and invertebrate model systems. In this review, we present an overview of the role cytoskeletal regulators play during the formation of the Drosophila neuromuscular junction.
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Affiliation(s)
- Jennifer B Long
- Department of Cell Biology and Program in Neuroscience, Harvard Medical School, Boston, MA, USA
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91
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Abstract
Genetic analyses in both worm and fly have identified the RhoGAP-like protein Syd-1 as a key positive regulator of presynaptic assembly. In worm, loss of syd-1 can be fully rescued by overexpressing wild-type Liprin-α, suggesting that the primary function of Syd-1 in this process is to recruit Liprin-α. We show that loss of syd-1 from Drosophila R7 photoreceptors causes two morphological defects that occur at distinct developmental time points. First, syd-1 mutant R7 axons often fail to form terminal boutons in their normal M6 target layer. Later, those mutant axons that do contact M6 often project thin extensions beyond it. We find that the earlier defect coincides with a failure to localize synaptic vesicles, suggesting that it reflects a failure in presynaptic assembly. We then analyze the relationship between syd-1 and Liprin-α in R7s. We find that loss of Liprin-α causes a stronger early R7 defect and provide a possible explanation for this disparity: we show that Liprin-α promotes Kinesin-3/Unc-104/Imac-mediated axon transport independently of Syd-1 and that Kinesin-3/Unc-104/Imac is required for normal R7 bouton formation. Unlike loss of syd-1, loss of Liprin-α does not cause late R7 extensions. We show that overexpressing Liprin-α partly rescues the early but not the late syd-1 mutant R7 defect. We therefore conclude that the two defects are caused by distinct molecular mechanisms. We find that Trio overexpression rescues both syd-1 defects and that trio and syd-1 have similar loss- and gain-of-function phenotypes, suggesting that the primary function of Syd-1 in R7s may be to promote Trio activity.
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92
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Menon KP, Carrillo RA, Zinn K. Development and plasticity of the Drosophila larval neuromuscular junction. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2013; 2:647-70. [PMID: 24014452 DOI: 10.1002/wdev.108] [Citation(s) in RCA: 163] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The Drosophila larval neuromuscular system is relatively simple, containing only 32 motor neurons in each abdominal hemisegment, and its neuromuscular junctions (NMJs) have been studied extensively. NMJ synapses exhibit developmental and functional plasticity while displaying stereotyped connectivity. Drosophila Type I NMJ synapses are glutamatergic, while the vertebrate NMJ uses acetylcholine as its primary neurotransmitter. The larval NMJ synapses use ionotropic glutamate receptors (GluRs) that are homologous to AMPA-type GluRs in the mammalian brain, and they have postsynaptic scaffolds that resemble those found in mammalian postsynaptic densities. These features make the Drosophila neuromuscular system an excellent genetic model for the study of excitatory synapses in the mammalian central nervous system. The first section of the review presents an overview of NMJ development. The second section describes genes that regulate NMJ development, including: (1) genes that positively and negatively regulate growth of the NMJ, (2) genes required for maintenance of NMJ bouton structure, (3) genes that modulate neuronal activity and alter NMJ growth, (4) genes involved in transsynaptic signaling at the NMJ. The third section describes genes that regulate acute plasticity, focusing on translational regulatory mechanisms. As this review is intended for a developmental biology audience, it does not cover NMJ electrophysiology in detail, and does not review genes for which mutations produce only electrophysiological but no structural phenotypes.
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Affiliation(s)
- Kaushiki P Menon
- Broad Center, Division of Biology, California Institute of Technology, Pasadena, CA, USA
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