51
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Kaplan C, Steinmann M, Zapiorkowska NA, Ewers H. Functional Redundancy of Septin Homologs in Dendritic Branching. Front Cell Dev Biol 2017; 5:11. [PMID: 28265560 PMCID: PMC5316521 DOI: 10.3389/fcell.2017.00011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Accepted: 02/06/2017] [Indexed: 01/02/2023] Open
Abstract
Septins are cytoskeletal GTPases present in nonpolar heteromeric complexes that assemble in a palindromic fashion from two to eight subunits. Mammalian septins function in several fundamental cellular processes at the membrane-cytoskeleton interface including dendritic branching in neurons. Sequence homology divides the 13 mammalian septin genes into four homology groups. Experimental findings suggest that septin function is redundant among septins from one homology group. This is best understood for the isoforms of the SEPT2 group, which form a homodimer at the center of septin complexes. In vitro, all SEPT2-group septins form recombinant hexameric complexes with two copies of SEPT6 and SEPT7. However, it remains unclear to what extent homologs septins can substitute for each other in specific cellular processes. Here, we use the experimental paradigm of dendritic branching in hippocampal rat neurons to ask, to what extent septins of the SEPT2-group are functionally redundant. Dendritic branching is significantly reduced when SEPT5 is downregulated. In neurons expressing SEPT5-shRNA, simultaneously expressed SEPT2-GFP, and SEPT4-GFP colocalize with SEPT7 at dendritic spine necks and rescue dendritic branching. In contrast, SEPT1-GFP is diffusely distributed in the cytoplasm in SEPT5 downregulated neurons and cannot rescue dendritic branching. Our findings provide a basis for the study of septin-specific functions in cells.
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Affiliation(s)
- Charlotte Kaplan
- Department of Biology, Institute of Biochemistry, University of ZurichZurich, Switzerland; Laboratory of Physical Chemistry, University of ZurichZurich, Switzerland
| | - Mayra Steinmann
- Department of Biology, Institute of Biochemistry, University of ZurichZurich, Switzerland; Laboratory of Physical Chemistry, University of ZurichZurich, Switzerland
| | - Natalia A Zapiorkowska
- Department of Biology, Institute of Biochemistry, University of ZurichZurich, Switzerland; Laboratory of Physical Chemistry, University of ZurichZurich, Switzerland
| | - Helge Ewers
- Department of Biology, Institute of Biochemistry, University of ZurichZurich, Switzerland; Laboratory of Physical Chemistry, University of ZurichZurich, Switzerland
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52
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Miermans CA, Kusters RPT, Hoogenraad CC, Storm C. Biophysical model of the role of actin remodeling on dendritic spine morphology. PLoS One 2017; 12:e0170113. [PMID: 28158194 PMCID: PMC5291493 DOI: 10.1371/journal.pone.0170113] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Accepted: 12/29/2016] [Indexed: 11/24/2022] Open
Abstract
Dendritic spines are small membranous structures that protrude from the neuronal dendrite. Each spine contains a synaptic contact site that may connect its parent dendrite to the axons of neighboring neurons. Dendritic spines are markedly distinct in shape and size, and certain types of stimulation prompt spines to evolve, in fairly predictable fashion, from thin nascent morphologies to the mushroom-like shapes associated with mature spines. It is well established that the remodeling of spines is strongly dependent upon the actin cytoskeleton inside the spine. A general framework that details the precise role of actin in directing the transitions between the various spine shapes is lacking. We address this issue, and present a quantitative, model-based scenario for spine plasticity validated using realistic and physiologically relevant parameters. Our model points to a crucial role for the actin cytoskeleton. In the early stages of spine formation, the interplay between the elastic properties of the spine membrane and the protrusive forces generated in the actin cytoskeleton propels the incipient spine. In the maturation stage, actin remodeling in the form of the combined dynamics of branched and bundled actin is required to form mature, mushroom-like spines. Importantly, our model shows that constricting the spine-neck aids in the stabilization of mature spines, thus pointing to a role in stabilization and maintenance for additional factors such as ring-like F-actin structures. Taken together, our model provides unique insights into the fundamental role of actin remodeling and polymerization forces during spine formation and maturation.
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Affiliation(s)
- C A Miermans
- Theory of Polymers and Soft Matter, Department of Applied Physics, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - R P T Kusters
- Theory of Polymers and Soft Matter, Department of Applied Physics, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - C C Hoogenraad
- Cell Biology, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - C Storm
- Theory of Polymers and Soft Matter, Department of Applied Physics, Eindhoven University of Technology, Eindhoven, The Netherlands
- Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, The Netherlands
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53
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Yadav S, Oses-Prieto JA, Peters CJ, Zhou J, Pleasure SJ, Burlingame AL, Jan LY, Jan YN. TAOK2 Kinase Mediates PSD95 Stability and Dendritic Spine Maturation through Septin7 Phosphorylation. Neuron 2017; 93:379-393. [PMID: 28065648 DOI: 10.1016/j.neuron.2016.12.006] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 10/11/2016] [Accepted: 11/23/2016] [Indexed: 01/09/2023]
Abstract
Abnormalities in dendritic spines are manifestations of several neurodevelopmental and psychiatric diseases. TAOK2 is one of the genes in the 16p11.2 locus, copy number variations of which are associated with autism and schizophrenia. Here, we show that the kinase activity of the serine/threonine kinase encoded by TAOK2 is required for spine maturation. TAOK2 depletion results in unstable dendritic protrusions, mislocalized shaft-synapses, and loss of compartmentalization of NMDA receptor-mediated calcium influx. Using chemical-genetics and mass spectrometry, we identified several TAOK2 phosphorylation targets. We show that TAOK2 directly phosphorylates the cytoskeletal GTPase Septin7, at an evolutionary conserved residue. This phosphorylation induces translocation of Septin7 to the spine, where it associates with and stabilizes the scaffolding protein PSD95, promoting dendritic spine maturation. This study provides a mechanistic basis for postsynaptic stability and compartmentalization via TAOK2-Sept7 signaling, with implications toward understanding the potential role of TAOK2 in neurological deficits associated with the 16p11.2 region.
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Affiliation(s)
- Smita Yadav
- Departments of Physiology, Biochemistry, and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Juan A Oses-Prieto
- Mass Spectrometry Facility, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Christian J Peters
- Departments of Physiology, Biochemistry, and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Jing Zhou
- Department of Neurology, Programs in Neuroscience and Developmental Biology, Institute for Regenerative Medicine, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Samuel J Pleasure
- Department of Neurology, Programs in Neuroscience and Developmental Biology, Institute for Regenerative Medicine, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Alma L Burlingame
- Mass Spectrometry Facility, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Lily Y Jan
- Departments of Physiology, Biochemistry, and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Yuh-Nung Jan
- Departments of Physiology, Biochemistry, and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA.
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54
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Yamada S, Isogai T, Tero R, Tanaka-Takiguchi Y, Ujihara T, Kinoshita M, Takiguchi K. Septin Interferes with the Temperature-Dependent Domain Formation and Disappearance of Lipid Bilayer Membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:12823-12832. [PMID: 27934514 DOI: 10.1021/acs.langmuir.6b03452] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Domain formation or compartmentalization in a lipid bilayer membrane has been thought to take place dynamically in cell membranes and play important roles in the spatiotemporal regulation of their physiological functions. In addition, the membrane skeleton, which is a protein assembly beneath the cell membrane, also regulates the properties as well as the morphology of membranes because of its role as a diffusion barrier against constitutive molecules of the membrane or as a scaffold for physiological reactions. Therefore, it is important to study the relationship between lipid bilayer membranes and proteins that form the membrane skeleton. Among cytoskeletal systems, septin is unique because it forms arrays on liposomes that contain phosphoinositides, and this property is thought to contribute to the formation of the annulus in sperm flagellum. In this study, a supported lipid bilayer (SLB) was used to investigate the effect of septin on lipid bilayers because SLBs rather than liposomes are suitable for observation of the membrane domains formed. We found that SLBs containing phosphatidylinositol (PI) reversibly form domains by decreasing the temperature and that septin affects both the formation and the disappearance of the cooling-induced domain. Septin inhibits the growth of cooling-induced domains during decreases in temperature and inhibits the dispersion and the disappearance of those domains during increases in temperature. These results indicate that septin complexes, i.e., filaments or oligomers assembling on the surface of lipid bilayer membranes, can regulate the dynamics of domain formation via their behavior as an anchor for PI molecules.
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Affiliation(s)
| | | | - Ryugo Tero
- The Electronics-Inspired Interdisciplinary Research Institute, Toyohashi University of Technology , Toyohashi 441-8580, Japan
| | | | | | | | - Kingo Takiguchi
- Structural Biology Research Center, Nagoya University , Nagoya 464-8601, Japan
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55
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Bär J, Kobler O, van Bommel B, Mikhaylova M. Periodic F-actin structures shape the neck of dendritic spines. Sci Rep 2016; 6:37136. [PMID: 27841352 PMCID: PMC5107894 DOI: 10.1038/srep37136] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 10/25/2016] [Indexed: 11/17/2022] Open
Abstract
Most of the excitatory synapses on principal neurons of the forebrain are located on specialized structures called dendritic spines. Their morphology, comprising a spine head connected to the dendritic branch via a thin neck, provides biochemical and electrical compartmentalization during signal transmission. Spine shape is defined and tightly controlled by the organization of the actin cytoskeleton. Alterations in synaptic strength correlate with changes in the morphological appearance of the spine head and neck. Therefore, it is important to get a better understanding of the nanoscale organization of the actin cytoskeleton in dendritic spines. A periodic organization of the actin/spectrin lattice was recently discovered in axons and a small fraction of dendrites using super-resolution microscopy. Here we use a small probe phalloidin-Atto647N, to label F-actin in mature hippocampal primary neurons and in living hippocampal slices. STED nanoscopy reveals that in contrast to β-II spectrin antibody labelling, phalloidin-Atto647N stains periodic actin structures in all dendrites and the neck of nearly all dendritic spines, including filopodia-like spines. These findings extend the current view on F-actin organization in dendritic spines and may provide new avenues for understanding the structural changes in the spine neck during induction of synaptic plasticity, active organelle transport or tethering.
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Affiliation(s)
- Julia Bär
- DFG Emmy Noether Group 'Neuronal Protein Transport', Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Oliver Kobler
- Combinatorial Neuroimaging Core Facility (CNI), Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany
| | - Bas van Bommel
- DFG Emmy Noether Group 'Neuronal Protein Transport', Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Marina Mikhaylova
- DFG Emmy Noether Group 'Neuronal Protein Transport', Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
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56
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Alexandre C, Baillard S, Tavet J, Nüsse O. [The diffusional barrier, a new window for exclusion]. Med Sci (Paris) 2016; 32:827-830. [PMID: 27758743 DOI: 10.1051/medsci/20163210012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
| | | | - Julien Tavet
- M1 Biologie Santé, Université Paris-Saclay, 91405 Orsay, France
| | - Oliver Nüsse
- Laboratoire de chimie physique, UMR8000, Université Paris-Sud, CNRS, Université Paris-Saclay, 91405 Orsay, France
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57
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Albrecht D, Winterflood CM, Sadeghi M, Tschager T, Noé F, Ewers H. Nanoscopic compartmentalization of membrane protein motion at the axon initial segment. J Cell Biol 2016; 215:37-46. [PMID: 27697928 PMCID: PMC5057285 DOI: 10.1083/jcb.201603108] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 09/16/2016] [Indexed: 12/31/2022] Open
Abstract
A diffusion barrier impeding membrane molecule motion between the axon and the somatodendritic compartment develops as neurons mature and the axon initial segment (AIS) is enriched in specific molecules. Albrecht et al. analyze the mobility of lipid-anchored molecules in the AIS using single-particle tracking time course experiments and propose a new mechanistic model for the AIS diffusion barrier. The axon initial segment (AIS) is enriched in specific adaptor, cytoskeletal, and transmembrane molecules. During AIS establishment, a membrane diffusion barrier is formed between the axonal and somatodendritic domains. Recently, an axonal periodic pattern of actin, spectrin, and ankyrin forming 190-nm-spaced, ring-like structures has been discovered. However, whether this structure is related to the diffusion barrier function is unclear. Here, we performed single-particle tracking time-course experiments on hippocampal neurons during AIS development. We analyzed the mobility of lipid-anchored molecules by high-speed single-particle tracking and correlated positions of membrane molecules with the nanoscopic organization of the AIS cytoskeleton. We observe a strong reduction in mobility early in AIS development. Membrane protein motion in the AIS plasma membrane is confined to a repetitive pattern of ∼190-nm-spaced segments along the AIS axis as early as day in vitro 4, and this pattern alternates with actin rings. Mathematical modeling shows that diffusion barriers between the segments significantly reduce lateral diffusion along the axon.
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Affiliation(s)
- David Albrecht
- Institute for Chemistry and Biochemistry, Free University Berlin, 14195 Berlin, Germany Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, England, UK Institute for Biochemistry, ETH Zurich, 8093 Zurich, Switzerland
| | - Christian M Winterflood
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, England, UK Institute for Biochemistry, ETH Zurich, 8093 Zurich, Switzerland
| | - Mohsen Sadeghi
- Department of Mathematics and Computer Science, Free University Berlin, 14195 Berlin, Germany
| | - Thomas Tschager
- Institute for Biochemistry, ETH Zurich, 8093 Zurich, Switzerland
| | - Frank Noé
- Department of Mathematics and Computer Science, Free University Berlin, 14195 Berlin, Germany
| | - Helge Ewers
- Institute for Chemistry and Biochemistry, Free University Berlin, 14195 Berlin, Germany Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, England, UK Institute for Biochemistry, ETH Zurich, 8093 Zurich, Switzerland
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58
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Partial Functional Diversification of Drosophila melanogaster Septin Genes Sep2 and Sep5. G3-GENES GENOMES GENETICS 2016; 6:1947-57. [PMID: 27172205 PMCID: PMC4938648 DOI: 10.1534/g3.116.028886] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The septin family of hetero-oligomeric complex-forming proteins can be divided into subgroups, and subgroup members are interchangeable at specific positions in the septin complex. Drosophila melanogaster has five septin genes, including the two SEPT6 subgroup members Sep2 and Sep5. We previously found that Sep2 has a unique function in oogenesis, which is not performed by Sep5. Here, we find that Sep2 is uniquely required for follicle cell encapsulation of female germline cysts, and that Sep2 and Sep5 are redundant for follicle cell proliferation. The five D. melanogaster septins localize similarly in oogenesis, including as rings flanking the germline ring canals. Pnut fails to localize in Sep5; Sep2 double mutant follicle cells, indicating that septin complexes fail to form in the absence of both Sep2 and Sep5. We also find that mutations in septins enhance the mutant phenotype of bazooka, a key component in the establishment of cell polarity, suggesting a link between septin function and cell polarity. Overall, this work suggests that Sep5 has undergone partial loss of ancestral protein function, and demonstrates redundant and unique functions of septins.
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59
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Finnigan GC, Duvalyan A, Liao EN, Sargsyan A, Thorner J. Detection of protein-protein interactions at the septin collar in Saccharomyces cerevisiae using a tripartite split-GFP system. Mol Biol Cell 2016; 27:2708-25. [PMID: 27385335 PMCID: PMC5007091 DOI: 10.1091/mbc.e16-05-0337] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 06/30/2016] [Indexed: 01/22/2023] Open
Abstract
A tripartite split-GFP system faithfully reports the order of the subunits in septin hetero-octamers (and thus can serve as a “molecular ruler”), conversely yields little or no false signal even with very highly expressed cytosolic proteins, and detects authentic interactions of other cellular proteins that are bona fide septin-binding proteins. Various methods can provide a readout of the physical interaction between two biomolecules. A recently described tripartite split-GFP system has the potential to report by direct visualization via a fluorescence signal the intimate association of minimally tagged proteins expressed at their endogenous level in their native cellular milieu and can capture transient or weak interactions. Here we document the utility of this tripartite split-GFP system to assess in living cells protein–protein interactions in a dynamic cytoskeletal structure—the septin collar at the yeast bud neck. We show, first, that for septin–septin interactions, this method yields a robust signal whose strength reflects the known spacing between the subunits in septin filaments and thus serves as a “molecular ruler.” Second, the method yields little or no spurious signal even with highly abundant cytosolic proteins readily accessible to the bud neck (including molecular chaperone Hsp82 and glycolytic enzyme Pgk1). Third, using two proteins (Bni5 and Hsl1) that have been shown by other means to bind directly to septins at the bud neck in vivo, we validate that the tripartite split-GFP method yields the same conclusions and further insights about specificity. Finally, we demonstrate the capacity of this approach to uncover additional new information by examining whether three other proteins reported to localize to the bud neck (Nis1, Bud4, and Hof1) are able to interact physically with any of the subunits in the septin collar and, if so, with which ones.
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Affiliation(s)
- Gregory C Finnigan
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3202
| | - Angela Duvalyan
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3202
| | - Elizabeth N Liao
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3202
| | - Aspram Sargsyan
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3202
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3202
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60
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Kang H, Lew DJ. How do cells know what shape they are? Curr Genet 2016; 63:75-77. [PMID: 27313005 DOI: 10.1007/s00294-016-0623-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 06/07/2016] [Accepted: 06/09/2016] [Indexed: 10/21/2022]
Abstract
Studies on a yeast cell cycle checkpoint that can delay mitosis depending on whether cells have built a bud have identified a "sensor" that seems to recognize the organization of filament-forming septin proteins. Innovative work applying correlative light and platinum replica electron microscopy suggests that the informative septin organization involves parallel alignment of septin filaments, and another striking study shows that septin filaments prefer to populate membranes that have positive micron-scale curvature. Together, these findings suggest a model for how cells may monitor aspects of their own shape to influence cell behavior.
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Affiliation(s)
- Hui Kang
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Daniel J Lew
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, 27710, USA.
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61
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Kaplan C, Yu C, Ewers H. Ashbya gossypii as a model system to study septin organization by single-molecule localization microscopy. Methods Cell Biol 2016; 136:161-82. [PMID: 27473909 DOI: 10.1016/bs.mcb.2016.04.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Heteromeric complexes of GTP-binding proteins from the septin family assemble into higher order structures that are essential for cell division in many organisms. The correct organization of the subunits into filaments, gauzes, and rings is the basis of septin function in this process. Electron microscopy and polarization fluorescence microscopy contributed greatly to the understanding of the dynamics and organization of such structures. However, both methods show technical limitations in resolution and specificity that do not allow the identification of individual septin complexes in assemblies in intact cells. Single-molecule localization-based fluorescence superresolution microscopy methods combine the resolution of cellular structures at the nanometer level with highest molecular specificity and excellent contrast. Here, we provide a protocol that enables the investigation of the organization of septin complexes in higher order structures in cells by combining advantageous features of the model organism Ashbya gossypii with single-molecule localization microscopy. Our assay is designed to investigate the general assembly mechanism of septin complexes in cells and is applicable to many cell types.
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Affiliation(s)
| | - C Yu
- ETH Zurich, Zurich, Switzerland
| | - H Ewers
- ETH Zurich, Zurich, Switzerland
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62
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Kähne T, Richter S, Kolodziej A, Smalla KH, Pielot R, Engler A, Ohl FW, Dieterich DC, Seidenbecher C, Tischmeyer W, Naumann M, Gundelfinger ED. Proteome rearrangements after auditory learning: high-resolution profiling of synapse-enriched protein fractions from mouse brain. J Neurochem 2016; 138:124-38. [PMID: 27062398 PMCID: PMC5089584 DOI: 10.1111/jnc.13636] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 03/23/2016] [Accepted: 04/01/2016] [Indexed: 01/09/2023]
Abstract
Learning and memory processes are accompanied by rearrangements of synaptic protein networks. While various studies have demonstrated the regulation of individual synaptic proteins during these processes, much less is known about the complex regulation of synaptic proteomes. Recently, we reported that auditory discrimination learning in mice is associated with a relative down-regulation of proteins involved in the structural organization of synapses in various brain regions. Aiming at the identification of biological processes and signaling pathways involved in auditory memory formation, here, a label-free quantification approach was utilized to identify regulated synaptic junctional proteins and phosphoproteins in the auditory cortex, frontal cortex, hippocampus, and striatum of mice 24 h after the learning experiment. Twenty proteins, including postsynaptic scaffolds, actin-remodeling proteins, and RNA-binding proteins, were regulated in at least three brain regions pointing to common, cross-regional mechanisms. Most of the detected synaptic proteome changes were, however, restricted to individual brain regions. For example, several members of the Septin family of cytoskeletal proteins were up-regulated only in the hippocampus, while Septin-9 was down-regulated in the hippocampus, the frontal cortex, and the striatum. Meta analyses utilizing several databases were employed to identify underlying cellular functions and biological pathways. Data are available via ProteomeExchange with identifier PXD003089. How does the protein composition of synapses change in different brain areas upon auditory learning? We unravel discrete proteome changes in mouse auditory cortex, frontal cortex, hippocampus, and striatum functionally implicated in the learning process. We identify not only common but also area-specific biological pathways and cellular processes modulated 24 h after training, indicating individual contributions of the regions to memory processing.
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Affiliation(s)
- Thilo Kähne
- Institute of Experimental Internal Medicine, Medical School, Otto von Guericke University, Magdeburg, Germany
| | - Sandra Richter
- Institute of Experimental Internal Medicine, Medical School, Otto von Guericke University, Magdeburg, Germany
| | - Angela Kolodziej
- Leibniz Institute for Neurobiology (LIN), Magdeburg, Germany.,Institute of Biology, Otto von Guericke University, Magdeburg, Germany
| | - Karl-Heinz Smalla
- Leibniz Institute for Neurobiology (LIN), Magdeburg, Germany.,Center for Behavioral Brain Sciences, Magdeburg, Germany
| | - Rainer Pielot
- Leibniz Institute for Neurobiology (LIN), Magdeburg, Germany
| | | | - Frank W Ohl
- Leibniz Institute for Neurobiology (LIN), Magdeburg, Germany.,Institute of Biology, Otto von Guericke University, Magdeburg, Germany.,Center for Behavioral Brain Sciences, Magdeburg, Germany
| | - Daniela C Dieterich
- Center for Behavioral Brain Sciences, Magdeburg, Germany.,Institute of Pharmacology and Toxicology, Medical School, Otto von Guericke University, Magdeburg, Germany
| | - Constanze Seidenbecher
- Leibniz Institute for Neurobiology (LIN), Magdeburg, Germany.,Center for Behavioral Brain Sciences, Magdeburg, Germany
| | - Wolfgang Tischmeyer
- Leibniz Institute for Neurobiology (LIN), Magdeburg, Germany.,Center for Behavioral Brain Sciences, Magdeburg, Germany
| | - Michael Naumann
- Institute of Experimental Internal Medicine, Medical School, Otto von Guericke University, Magdeburg, Germany
| | - Eckart D Gundelfinger
- Leibniz Institute for Neurobiology (LIN), Magdeburg, Germany.,Center for Behavioral Brain Sciences, Magdeburg, Germany.,Molecular Neuroscience, Medical School, Otto von Guericke University, Magdeburg, Germany.,German Center for Neurodegenerative Diseases, Magdeburg, Germany
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63
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Abstract
Septins are highly conserved and essential eukaryotic cytoskeletal proteins that interact with the inner plasma membrane. They are involved in essential functions requiring cell membrane remodeling and compartmentalization, such as cell division and dendrite morphogenesis, and have been implicated in numerous diseases. Depending on the organisms and on the type of tissue, a specific set of septins genes are expressed, ranging from 2 to 13. Septins self-assemble into linear, symmetric rods that can further organize into linear filaments several microns in length. Only a subset of human septins has been described at high resolution by X-ray crystallography (Sirajuddin et al., 2007). Electron microscopy (EM) has proven to be a method of choice for analyzing the molecular organization of septins. It is possible to localize each septin subunit within the rod complex using genetic tags, such as maltose-binding protein or green fluorescent protein, to generate a visible label of a specific septin subunit in EM images that are processed using single-particle EM methodology. In this chapter we present, in detail, the methods that we have used to analyze the molecular organization of budding yeast septins (Bertin et al., 2008). These methods include purification of septin complexes, sample preparation for EM, and image processing procedures. Such methods can be generalized to analyze the organization of septins from any organism.
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64
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Wang L, Dumoulin A, Renner M, Triller A, Specht CG. The Role of Synaptopodin in Membrane Protein Diffusion in the Dendritic Spine Neck. PLoS One 2016; 11:e0148310. [PMID: 26840625 PMCID: PMC4739495 DOI: 10.1371/journal.pone.0148310] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 01/15/2016] [Indexed: 12/21/2022] Open
Abstract
The dynamic exchange of neurotransmitter receptors at synapses relies on their lateral diffusion in the plasma membrane. At synapses located on dendritic spines this process is limited by the geometry of the spine neck that restricts the passage of membrane proteins. Biochemical compartmentalisation of the spine is believed to underlie the input-specificity of excitatory synapses and to set the scale on which functional changes can occur. Synaptopodin is located predominantly in the neck of dendritic spines, and is thus ideally placed to regulate the exchange of synaptic membrane proteins. The central aim of our study was to assess whether the presence of synaptopodin influences the mobility of membrane proteins in the spine neck and to characterise whether this was due to direct molecular interactions or to spatial constraints that are related to the structural organisation of the neck. Using single particle tracking we have identified a specific effect of synaptopodin on the diffusion of metabotropic mGluR5 receptors in the spine neck. However, super-resolution STORM/PALM imaging showed that this was not due to direct interactions between the two proteins, but that the presence of synaptopodin is associated with an altered local organisation of the F-actin cytoskeleton, that in turn could restrict the diffusion of membrane proteins with large intracellular domains through the spine neck. This study contributes new data on the way in which the spine neck compartmentalises excitatory synapses. Our data complement models that consider the impact of the spine neck as a function of its shape, by showing that the internal organisation of the neck imposes additional physical barriers to membrane protein diffusion.
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Affiliation(s)
- Lili Wang
- Biologie Cellulaire de la Synapse, Inserm U1024, CNRS 8197, Institute of Biology, Ecole Normale Supérieure (ENS), Paris, France
| | - Andréa Dumoulin
- Biologie Cellulaire de la Synapse, Inserm U1024, CNRS 8197, Institute of Biology, Ecole Normale Supérieure (ENS), Paris, France
| | - Marianne Renner
- Biologie Cellulaire de la Synapse, Inserm U1024, CNRS 8197, Institute of Biology, Ecole Normale Supérieure (ENS), Paris, France
| | - Antoine Triller
- Biologie Cellulaire de la Synapse, Inserm U1024, CNRS 8197, Institute of Biology, Ecole Normale Supérieure (ENS), Paris, France
- * E-mail:
| | - Christian G. Specht
- Biologie Cellulaire de la Synapse, Inserm U1024, CNRS 8197, Institute of Biology, Ecole Normale Supérieure (ENS), Paris, France
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Polarity Determinants in Dendritic Spine Development and Plasticity. Neural Plast 2015; 2016:3145019. [PMID: 26839714 PMCID: PMC4709733 DOI: 10.1155/2016/3145019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Revised: 10/16/2015] [Accepted: 11/01/2015] [Indexed: 11/17/2022] Open
Abstract
The asymmetric distribution of various proteins and RNAs is essential for all stages of animal development, and establishment and maintenance of this cellular polarity are regulated by a group of conserved polarity determinants. Studies over the last 10 years highlight important functions for polarity proteins, including apical-basal polarity and planar cell polarity regulators, in dendritic spine development and plasticity. Remarkably, many of the conserved polarity machineries function in similar manners in the context of spine development as they do in epithelial morphogenesis. Interestingly, some polarity proteins also utilize neuronal-specific mechanisms. Although many questions remain unanswered in our understanding of how polarity proteins regulate spine development and plasticity, current and future research will undoubtedly shed more light on how this conserved group of proteins orchestrates different pathways to shape the neuronal circuitry.
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66
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Platonova E, Winterflood CM, Junemann A, Albrecht D, Faix J, Ewers H. Single-molecule microscopy of molecules tagged with GFP or RFP derivatives in mammalian cells using nanobody binders. Methods 2015; 88:89-97. [PMID: 26123185 DOI: 10.1016/j.ymeth.2015.06.018] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Revised: 06/03/2015] [Accepted: 06/24/2015] [Indexed: 10/23/2022] Open
Abstract
With the recent development of single-molecule localization-based superresolution microscopy, the imaging of cellular structures at a resolution below the diffraction-limit of light has become a widespread technique. While single fluorescent molecules can be resolved in the nanometer range, the delivery of these molecules to the authentic structure in the cell via traditional antibody-mediated techniques can add substantial error due to the size of the antibodies. Accurate and quantitative labeling of cellular molecules has thus become one of the bottlenecks in the race for highest resolution of target structures. Here we illustrate in detail how to use small, high affinity nanobody binders against GFP and RFP family proteins for highly generic labeling of fusion constructs with bright organic dyes. We provide detailed protocols and examples for their application in superresolution imaging and single particle tracking and demonstrate advantages over conventional labeling approaches.
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Affiliation(s)
- Evgenia Platonova
- Randall Division of Cell and Molecular Biophysics, King's College London, SE1 1UL, United Kingdom; Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | - Christian M Winterflood
- Randall Division of Cell and Molecular Biophysics, King's College London, SE1 1UL, United Kingdom; Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | | | - David Albrecht
- Randall Division of Cell and Molecular Biophysics, King's College London, SE1 1UL, United Kingdom; Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | - Jan Faix
- Hannover Medical School, Hannover, Germany
| | - Helge Ewers
- Randall Division of Cell and Molecular Biophysics, King's College London, SE1 1UL, United Kingdom; Institute of Biochemistry, ETH Zurich, Zurich, Switzerland; Institut für Biochemie und Chemie, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany.
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Abstract
The small size of dendritic spines belies the elaborate role they play in excitatory synaptic transmission and ultimately complex behaviors. The cytoskeletal architecture of the spine is predominately composed of actin filaments. These filaments, which at first glance might appear simple, are also surprisingly complex. They dynamically assemble into different structures and serve as a platform for orchestrating the elaborate responses of the spine during spinogenesis and experience-dependent plasticity. Multiple mutations associated with human neurodevelopmental and psychiatric disorders involve genes that encode regulators of the synaptic cytoskeleton. A major, unresolved question is how the disruption of specific actin filament structures leads to the onset and progression of complex synaptic and behavioral phenotypes. This review will cover established and emerging mechanisms of actin cytoskeletal remodeling and how this influences specific aspects of spine biology that are implicated in disease.
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Affiliation(s)
| | - Scott H Soderling
- From the Departments of Cell Biology and Neurobiology, Duke University, School of Medicine, Durham, North Carolina 27710
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Abstract
The structural plasticity of dendritic spines is considered to be essential for various forms of synaptic plasticity, learning, and memory. The process is mediated by a complex signaling network consisting of numerous species of molecules. Furthermore, the spatiotemporal dynamics of the biochemical signaling are regulated in a complicated manner because of geometrical restrictions from the unique morphology of the dendritic branches and spines. Recent advances in optical techniques have enabled the exploration of the spatiotemporal aspects of the signal regulations in spines and dendrites and have provided many insights into the principle of the biochemical computation that underlies spine structural plasticity.
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Affiliation(s)
- Jun Nishiyama
- Max Planck Florida Institute for Neuroscience, One Max Planck Way, Jupiter, FL 33458, USA
| | - Ryohei Yasuda
- Max Planck Florida Institute for Neuroscience, One Max Planck Way, Jupiter, FL 33458, USA.
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Alp M, Parihar VK, Limoli CL, Cucinotta FA. Irradiation of Neurons with High-Energy Charged Particles: An In Silico Modeling Approach. PLoS Comput Biol 2015; 11:e1004428. [PMID: 26252394 PMCID: PMC4529238 DOI: 10.1371/journal.pcbi.1004428] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2015] [Accepted: 07/03/2015] [Indexed: 11/19/2022] Open
Abstract
In this work, a stochastic computational model of microscopic energy deposition events is used to study for the first time damage to irradiated neuronal cells of the mouse hippocampus. An extensive library of radiation tracks for different particle types is created to score energy deposition in small voxels and volume segments describing a neuron's morphology that later are sampled for given particle fluence or dose. Methods included the construction of in silico mouse hippocampal granule cells from neuromorpho.org with spine and filopodia segments stochastically distributed along the dendritic branches. The model is tested with high-energy (56)Fe, (12)C, and (1)H particles and electrons. Results indicate that the tree-like structure of the neuronal morphology and the microscopic dose deposition of distinct particles may lead to different outcomes when cellular injury is assessed, leading to differences in structural damage for the same absorbed dose. The significance of the microscopic dose in neuron components is to introduce specific local and global modes of cellular injury that likely contribute to spine, filopodia, and dendrite pruning, impacting cognition and possibly the collapse of the neuron. Results show that the heterogeneity of heavy particle tracks at low doses, compared to the more uniform dose distribution of electrons, juxtaposed with neuron morphology make it necessary to model the spatial dose painting for specific neuronal components. Going forward, this work can directly support the development of biophysical models of the modifications of spine and dendritic morphology observed after low dose charged particle irradiation by providing accurate descriptions of the underlying physical insults to complex neuron structures at the nano-meter scale.
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Affiliation(s)
- Murat Alp
- Department of Health Physics and Diagnostic Sciences, University of Nevada, Las Vegas, Las Vegas, Nevada, United States of America
| | - Vipan K. Parihar
- Department of Radiation Oncology, University of California, Irvine, Irvine, California, United States of America
| | - Charles L. Limoli
- Department of Radiation Oncology, University of California, Irvine, Irvine, California, United States of America
| | - Francis A. Cucinotta
- Department of Health Physics and Diagnostic Sciences, University of Nevada, Las Vegas, Las Vegas, Nevada, United States of America
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The Carboxy-Terminal Tails of Septins Cdc11 and Shs1 Recruit Myosin-II Binding Factor Bni5 to the Bud Neck in Saccharomyces cerevisiae. Genetics 2015; 200:843-62. [PMID: 25971666 DOI: 10.1534/genetics.115.176503] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 05/08/2015] [Indexed: 12/20/2022] Open
Abstract
UNLABELLED Septins are a conserved family of GTP-binding proteins that form heterooctameric complexes that assemble into higher-order structures. In yeast, septin superstructure at the bud neck serves as a barrier to separate a daughter cell from its mother and as a scaffold to recruit the proteins that execute cytokinesis. However, how septins recruit specific factors has not been well characterized. In the accompanying article in this issue, (Finnigan et al. 2015), we demonstrated that the C-terminal extensions (CTEs) of the alternative terminal subunits of septin heterooctamers, Cdc11 and Shs1, share a role required for optimal septin function in vivo. Here we describe our use of unbiased genetic approaches (both selection of dosage suppressors and analysis of synthetic interactions) that pinpointed Bni5 as a protein that interacts with the CTEs of Cdc11 and Shs1. Furthermore, we used three independent methods-construction of chimeric proteins, noncovalent tethering mediated by a GFP-targeted nanobody, and imaging by fluorescence microscopy-to confirm that a physiologically important function of the CTEs of Cdc11 and Shs1 is optimizing recruitment of Bni5 and thereby ensuring efficient localization at the bud neck of Myo1, the type II myosin of the actomyosin contractile ring.Related article in GENETICS Finnigan, G. C. et al., 2015 Comprehensive Genetic Analysis of Paralogous Terminal Septin Subunits Shs1 and Cdc11 in Saccharomyces cerevisiae. Genetics 200: 841-861.
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Albrecht D, Winterflood CM, Ewers H. Dual color single particle tracking via nanobodies. Methods Appl Fluoresc 2015; 3:024001. [DOI: 10.1088/2050-6120/3/2/024001] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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MacGillavry HD, Hoogenraad CC. The internal architecture of dendritic spines revealed by super-resolution imaging: What did we learn so far? Exp Cell Res 2015; 335:180-6. [PMID: 25746722 DOI: 10.1016/j.yexcr.2015.02.024] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 02/26/2015] [Indexed: 12/21/2022]
Abstract
The molecular architecture of dendritic spines defines the efficiency of signal transmission across excitatory synapses. It is therefore critical to understand the mechanisms that control the dynamic localization of the molecular constituents within spines. However, because of the small scale at which most processes within spines take place, conventional light microscopy techniques are not adequate to provide the necessary level of resolution. Recently, super-resolution imaging techniques have overcome the classical barrier imposed by the diffraction of light, and can now resolve the localization and dynamic behavior of proteins within small compartments with nanometer precision, revolutionizing the study of dendritic spine architecture. Here, we highlight exciting new findings from recent super-resolution studies on neuronal spines, and discuss how these studies revealed important new insights into how protein complexes are assembled and how their dynamic behavior shapes the efficiency of synaptic transmission.
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Affiliation(s)
- Harold D MacGillavry
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands.
| | - Casper C Hoogenraad
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands.
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