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Keuenhof KS, Kohler V, Broeskamp F, Panagaki D, Speese SD, Büttner S, Höög JL. Nuclear envelope budding and its cellular functions. Nucleus 2023; 14:2178184. [PMID: 36814098 PMCID: PMC9980700 DOI: 10.1080/19491034.2023.2178184] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 02/03/2023] [Indexed: 02/24/2023] Open
Abstract
The nuclear pore complex (NPC) has long been assumed to be the sole route across the nuclear envelope, and under normal homeostatic conditions it is indeed the main mechanism of nucleo-cytoplasmic transport. However, it has also been known that e.g. herpesviruses cross the nuclear envelope utilizing a pathway entitled nuclear egress or envelopment/de-envelopment. Despite this, a thread of observations suggests that mechanisms similar to viral egress may be transiently used also in healthy cells. It has since been proposed that mechanisms like nuclear envelope budding (NEB) can facilitate the transport of RNA granules, aggregated proteins, inner nuclear membrane proteins, and mis-assembled NPCs. Herein, we will summarize the known roles of NEB as a physiological and intrinsic cellular feature and highlight the many unanswered questions surrounding these intriguing nuclear events.
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Affiliation(s)
| | - Verena Kohler
- Institute of Molecular Biosciences, University of Graz, Austria
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Sweden
| | - Filomena Broeskamp
- Department for Chemistry and Molecular biology, University of Gothenburg, Sweden
| | - Dimitra Panagaki
- Department for Chemistry and Molecular biology, University of Gothenburg, Sweden
| | - Sean D. Speese
- Knight Cancer Early Detection Advanced Research Center, Oregon Health and Science University, 2720 S Moody Ave, Portland, OR, 97201, USA
| | - Sabrina Büttner
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Sweden
| | - Johanna L. Höög
- Department for Chemistry and Molecular biology, University of Gothenburg, Sweden
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2
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Abstract
Axon degeneration elicits a range of immune responses from local glial cells, including striking changes in glial gene expression, morphology, and phagocytic activity. Here, we describe a detailed set of protocols to assess discrete components of the glial reaction to axotomy in the adult nervous system of Drosophila melanogaster. These methods allow one to visualize and quantify transcriptional, morphological, and functional responses of glia to degenerating axons in a model system that is highly amenable to genetic manipulation.
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Affiliation(s)
- Mary A Logan
- Jungers Center for Neurosciences Research, Department of Neurology, Oregon Health and Science University, Portland, OR, USA.
| | - Sean D Speese
- Jungers Center for Neurosciences Research, Department of Neurology, Oregon Health and Science University, Portland, OR, USA
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3
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Purice MD, Ray A, Münzel EJ, Pope BJ, Park DJ, Speese SD, Logan MA. A novel Drosophila injury model reveals severed axons are cleared through a Draper/MMP-1 signaling cascade. eLife 2017; 6. [PMID: 28825401 PMCID: PMC5565368 DOI: 10.7554/elife.23611] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 07/25/2017] [Indexed: 02/06/2023] Open
Abstract
Neural injury triggers swift responses from glia, including glial migration and phagocytic clearance of damaged neurons. The transcriptional programs governing these complex innate glial immune responses are still unclear. Here, we describe a novel injury assay in adult Drosophila that elicits widespread glial responses in the ventral nerve cord (VNC). We profiled injury-induced changes in VNC gene expression by RNA sequencing (RNA-seq) and found that responsive genes fall into diverse signaling classes. One factor, matrix metalloproteinase-1 (MMP-1), is induced in Drosophila ensheathing glia responding to severed axons. Interestingly, glial induction of MMP-1 requires the highly conserved engulfment receptor Draper, as well as AP-1 and STAT92E. In MMP-1 depleted flies, glia do not properly infiltrate neuropil regions after axotomy and, as a consequence, fail to clear degenerating axonal debris. This work identifies Draper-dependent activation of MMP-1 as a novel cascade required for proper glial clearance of severed axons.
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Affiliation(s)
- Maria D Purice
- Jungers Center for Neurosciences Research, Department of Neurology, Oregon Health and Science University, Portland, United States
| | - Arpita Ray
- Jungers Center for Neurosciences Research, Department of Neurology, Oregon Health and Science University, Portland, United States
| | - Eva Jolanda Münzel
- Jungers Center for Neurosciences Research, Department of Neurology, Oregon Health and Science University, Portland, United States
| | - Bernard J Pope
- Melbourne Informatics, The University of Melbourne, Melbourne, Australia
| | - Daniel J Park
- Melbourne Informatics, The University of Melbourne, Melbourne, Australia
| | - Sean D Speese
- Jungers Center for Neurosciences Research, Department of Neurology, Oregon Health and Science University, Portland, United States
| | - Mary A Logan
- Jungers Center for Neurosciences Research, Department of Neurology, Oregon Health and Science University, Portland, United States
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Winfree LM, Speese SD, Logan MA. Protein phosphatase 4 coordinates glial membrane recruitment and phagocytic clearance of degenerating axons in Drosophila. Cell Death Dis 2017; 8:e2623. [PMID: 28230857 PMCID: PMC5386485 DOI: 10.1038/cddis.2017.40] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 01/06/2017] [Accepted: 01/09/2017] [Indexed: 12/15/2022]
Abstract
Neuronal damage induced by injury, stroke, or neurodegenerative disease elicits swift immune responses from glial cells, including altered gene expression, directed migration to injury sites, and glial clearance of damaged neurons through phagocytic engulfment. Collectively, these responses hinder further cellular damage, but the mechanisms that underlie these important protective glial reactions are still unclear. Here, we show that the evolutionarily conserved trimeric protein phosphatase 4 (PP4) serine/threonine phosphatase complex is a novel set of factors required for proper glial responses to nerve injury in the adult Drosophila brain. Glial-specific knockdown of PP4 results in reduced recruitment of glia to severed axons and delayed glial clearance of degenerating axonal debris. We show that PP4 functions downstream of the the glial engulfment receptor Draper to drive glial morphogenesis through the guanine nucleotide exchange factor SOS and the Rho GTPase Rac1, revealing that PP4 molecularly couples Draper to Rac1-mediated cytoskeletal remodeling to ensure glial infiltration of injury sites and timely removal of damaged neurons from the CNS.
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Affiliation(s)
- Lilly M Winfree
- Jungers Center for Neurosciences Research, Department of Neurology, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Sean D Speese
- Jungers Center for Neurosciences Research, Department of Neurology, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Mary A Logan
- Jungers Center for Neurosciences Research, Department of Neurology, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
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Musashe DT, Purice MD, Speese SD, Doherty J, Logan MA. Insulin-like Signaling Promotes Glial Phagocytic Clearance of Degenerating Axons through Regulation of Draper. Cell Rep 2016; 16:1838-50. [PMID: 27498858 DOI: 10.1016/j.celrep.2016.07.022] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Revised: 05/23/2016] [Accepted: 07/09/2016] [Indexed: 01/15/2023] Open
Abstract
Neuronal injury triggers robust responses from glial cells, including altered gene expression and enhanced phagocytic activity to ensure prompt removal of damaged neurons. The molecular underpinnings of glial responses to trauma remain unclear. Here, we find that the evolutionarily conserved insulin-like signaling (ILS) pathway promotes glial phagocytic clearance of degenerating axons in adult Drosophila. We find that the insulin-like receptor (InR) and downstream effector Akt1 are acutely activated in local ensheathing glia after axotomy and are required for proper clearance of axonal debris. InR/Akt1 activity, it is also essential for injury-induced activation of STAT92E and its transcriptional target draper, which encodes a conserved receptor essential for glial engulfment of degenerating axons. Increasing Draper levels in adult glia partially rescues delayed clearance of severed axons in glial InR-inhibited flies. We propose that ILS functions as a key post-injury communication relay to activate glial responses, including phagocytic activity.
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Affiliation(s)
- Derek T Musashe
- Department of Neurology, Jungers Center for Neurosciences Research, Oregon Health and Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR 97239, USA
| | - Maria D Purice
- Department of Neurology, Jungers Center for Neurosciences Research, Oregon Health and Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR 97239, USA
| | - Sean D Speese
- Department of Neurology, Jungers Center for Neurosciences Research, Oregon Health and Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR 97239, USA
| | - Johnna Doherty
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, 55 North Lake Avenue, Worcester, MA 01605, USA
| | - Mary A Logan
- Department of Neurology, Jungers Center for Neurosciences Research, Oregon Health and Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR 97239, USA.
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Speese SD, Ashley J, Jokhi V, Nunnari J, Barria R, Li Y, Ataman B, Koon A, Chang YT, Li Q, Moore MJ, Budnik V. Nuclear envelope budding enables large ribonucleoprotein particle export during synaptic Wnt signaling. Cell 2012; 149:832-46. [PMID: 22579286 DOI: 10.1016/j.cell.2012.03.032] [Citation(s) in RCA: 249] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Revised: 12/08/2011] [Accepted: 03/14/2012] [Indexed: 01/25/2023]
Abstract
Localized protein synthesis requires assembly and transport of translationally silenced ribonucleoprotein particles (RNPs), some of which are exceptionally large. Where in the cell such large RNP granules first assemble was heretofore unknown. We previously reported that during synapse development, a fragment of the Wnt-1 receptor, DFrizzled2, enters postsynaptic nuclei where it forms prominent foci. Here we show that these foci constitute large RNP granules harboring synaptic protein transcripts. These granules exit the nucleus by budding through the inner and the outer nuclear membranes in a nuclear egress mechanism akin to that of herpes viruses. This budding involves phosphorylation of A-type lamin, a protein linked to muscular dystrophies. Thus nuclear envelope budding is an endogenous nuclear export pathway for large RNP granules.
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Affiliation(s)
- Sean D Speese
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, 01605, USA
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Logan MA, Hackett R, Doherty J, Sheehan A, Speese SD, Freeman MR. Negative regulation of glial engulfment activity by Draper terminates glial responses to axon injury. Nat Neurosci 2012; 15:722-30. [PMID: 22426252 PMCID: PMC3337949 DOI: 10.1038/nn.3066] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Accepted: 02/13/2012] [Indexed: 12/16/2022]
Abstract
Neuronal injury elicits potent cellular responses from glia, but molecular pathways modulating glial activation, phagocytic function, and termination of reactive responses remain poorly defined. Here we show that positive or negative regulation of glial reponses to axon injury are molecularly encoded by unique isoforms of the Drosophila engulfment receptor Draper. Draper-I promotes engulfment of axonal debris through an immunoreceptor tyrosine-based activation motif (ITAM). In contrast, Draper-II, an alternative splice variant, potently inhibits glial engulfment function. Draper-II suppresses Draper-I signaling through a novel immunoreceptor tyrosine-based inhibitory motif (ITIM)-like domain and the tyrosine phosphatase Corkscrew (Csw). Intriguingly, loss of Draper-II/Csw signaling prolongs expression of glial engulfment genes after axotomy and reduces the ability of glia to respond to secondary axotomy. Our work highlights a novel role for Draper-II in inhibiting glial responses to neurodegeneration, and indicates a balance of opposing Draper-I/-II signaling events is essential to maintain glial sensitivity to brain injury.
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Affiliation(s)
- Mary A Logan
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
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Abstract
Synaptic development, function and plasticity are highly regulated processes requiring a precise coordination of pre- and postsynaptic events. Recent studies have begun to highlight Wingless-Int (Wnt) signaling as a key player in synapse differentiation and function. Emerging roles of Wnts include the differentiation of synaptic specializations, microtubule dynamics, architecture of synaptic protein organization, modulation of synaptic efficacy and regulation of gene expression. These processes are driven by a variety of Wnt transduction pathways. Combined with a myriad of Wnts and Frizzled receptor family members, these pathways highlight the versatility of Wnt signaling and the potential for combinatorial use of these pathways in different aspects of synapse development and function. The identification of neurons secreting Wnt and those containing molecular components downstream of Frizzled receptors indicates that Wnts can function both as anterograde and retrograde signals. These studies open new avenues for understanding how embryonic morphogens are utilized during the development and function of synaptic networks.
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Affiliation(s)
- Sean D Speese
- Department of Neurobiology, Aaron Lazare Biomedical Research Building, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01601, USA
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9
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Huang FD, Matthies HJG, Speese SD, Smith MA, Broadie K. Rolling blackout, a newly identified PIP2-DAG pathway lipase required for Drosophila phototransduction. Nat Neurosci 2004; 7:1070-8. [PMID: 15361878 DOI: 10.1038/nn1313] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2004] [Accepted: 07/19/2004] [Indexed: 11/08/2022]
Abstract
The rolling blackout (rbo) gene encodes an integral plasma membrane lipase required for Drosophila phototransduction. Photoreceptors are enriched for the RBO protein, and temperature-sensitive rbo mutants show reversible elimination of phototransduction within minutes, demonstrating an acute requirement for the protein. The block is activity dependent, indicating that the action of RBO is use dependent. Conditional rbo mutants show activity-dependent depletion of diacylglycerol and concomitant accumulation of phosphatidylinositol phosphate and phosphatidylinositol 4,5-bisphosphate within minutes of induction, suggesting rapid downregulation of phospholipase C (PLC) activity. The RBO requirement identifies an essential regulatory step in G-protein-coupled, PLC-dependent inositol lipid signaling mediating activation of TRP and TRPL channels during phototransduction.
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Affiliation(s)
- Fu-De Huang
- Department of Biological Sciences, Vanderbilt Kennedy Center, Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee 37235-1634, USA
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10
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Speese SD, Trotta N, Rodesch CK, Aravamudan B, Broadie K. The ubiquitin proteasome system acutely regulates presynaptic protein turnover and synaptic efficacy. Curr Biol 2003; 13:899-910. [PMID: 12781128 DOI: 10.1016/s0960-9822(03)00338-5] [Citation(s) in RCA: 193] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
BACKGROUND The ubiquitin proteasome system (UPS) mediates regulated protein degradation and provides a mechanism for closely controlling protein abundance in spatially restricted domains within cells. We hypothesized that the UPS may acutely determine the local concentration of key regulatory proteins at neuronal synapses as a means for locally modulating synaptic efficacy and the strength of neurotransmission communication. RESULTS We investigated this hypothesis at the Drosophila neuromuscular synapse by using an array of genetic and pharmacological tools. This study demonstrates that UPS components are present in presynaptic boutons and that the UPS functions locally in the presynaptic compartment to rapidly eliminate a conditional transgenic reporter of proteasome activity. We assayed a panel of synaptic proteins to determine whether the UPS acutely regulates the local abundance of native synaptic targets. Both acute pharmacological inhibition of the proteasome (<1 hr) and targeted genetic perturbation of proteasome function in the presynaptic neuron cause the specific accumulation of the essential synaptic vesicle-priming protein DUNC-13. Most importantly, acute pharmacological inhibition of the proteasome (<1 hr) causes a rapid strengthening of neurotransmission (an approximately 50% increase in evoked amplitude) because of increased presynaptic efficacy. The proteasome-dependent regulation of presynaptic protein abundance, both of the exogenous reporter and native DUNC-13, and the modulation of presynaptic neurotransmitter release occur on an intermediate, rapid (tens of minutes) timescale. CONCLUSIONS Taken together, these studies demonstrate that the UPS functions locally within synaptic boutons to acutely control levels of presynaptic protein and that the rate of UPS-dependent protein degradation is a primary determinant of neurotransmission strength.
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Affiliation(s)
- Sean D Speese
- Department of Biology, 257 South 1400 East, University of Utah, Salt Lake City, UT 84112-0840, USA
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Zhang YQ, Bailey AM, Matthies HJ, Renden RB, Smith MA, Speese SD, Rubin GM, Broadie K. Drosophila fragile X-related gene regulates the MAP1B homolog Futsch to control synaptic structure and function. Cell 2001; 107:591-603. [PMID: 11733059 DOI: 10.1016/s0092-8674(01)00589-x] [Citation(s) in RCA: 511] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Fragile X mental retardation gene (FMR1) encodes an RNA binding protein that acts as a negative translational regulator. We have developed a Drosophila fragile X syndrome model using loss-of-function mutants and overexpression of the FMR1 homolog (dfxr). dfxr nulls display enlarged synaptic terminals, whereas neuronal overexpression results in fewer and larger synaptic boutons. Synaptic structural defects are accompanied by altered neurotransmission, with synapse type-specific regulation in central and peripheral synapses. These phenotypes mimic those observed in mutants of microtubule-associated Futsch. Immunoprecipitation of dFXR shows association with futsch mRNA, and Western analyses demonstrate that dFXR inversely regulates Futsch expression. dfxr futsch double mutants restore normal synaptic structure and function. We propose that dFXR acts as a translational repressor of Futsch to regulate microtubule-dependent synaptic growth and function.
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Affiliation(s)
- Y Q Zhang
- Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
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12
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Sánchez D, Ganfornina MD, Torres-Schumann S, Speese SD, Lora JM, Bastiani MJ. Characterization of two novel lipocalins expressed in the Drosophila embryonic nervous system. Int J Dev Biol 2000; 44:349-59. [PMID: 10949044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
We have found two novel lipocalins in the fruit fly Drosophila melanogaster that are homologous to the grasshopper Lazarillo, a singular lipocalin within this protein family which functions in axon guidance during nervous system development. Sequence analysis suggests that the two Drosophila proteins are secreted and possess peptide regions unique in the lipocalin family. The mRNAs of DNLaz (for Drosophila neural Lazarillo) and DGLaz (for Drosophila glial Lazarillo) are expressed with different temporal patterns during embryogenesis. They show low levels of larval expression and are highly expressed in pupa and adult flies. DNLaz mRNA is transcribed in a subset of neurons and neuronal precursors in the embryonic CNS. DGLaz mRNA is found in a subset of glial cells of the CNS: the longitudinal glia and the medial cell body glia. Both lipocalins are also expressed outside the nervous system in the developing gut, fat body and amnioserosa. The DNLaz protein is detected in a subset of axons in the developing CNS. Treatment with a secretion blocker enhances the antibody labeling, indicating the DNLaz secreted nature. These findings make the embryonic nervous system expression of lipocalins a feature more widespread than previously thought. We propose that DNLaz and DGLaz may have a role in axonal outgrowth and pathfinding, although other putative functions are also discussed.
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Affiliation(s)
- D Sánchez
- Department of Biology, University of Utah, Salt Lake City 84112-0840, USA.
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