51
|
Glenn TD, Talbot WS. Analysis of Gpr126 function defines distinct mechanisms controlling the initiation and maturation of myelin. Development 2013; 140:3167-75. [PMID: 23804499 PMCID: PMC3931731 DOI: 10.1242/dev.093401] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/14/2013] [Indexed: 01/29/2023]
Abstract
In peripheral nerves, Schwann cells form the myelin sheath, which allows the efficient propagation of action potentials along axons. The transcription factor Krox20 regulates the initiation of myelination in Schwann cells and is also required to maintain mature myelin. The adhesion G protein-coupled receptor (GPCR) Gpr126 is essential for Schwann cells to initiate myelination, but previous studies have not addressed the role of Gpr126 signaling in myelin maturation and maintenance. Through analysis of Gpr126 in zebrafish, we define two distinct mechanisms controlling the initiation and maturation of myelin. We show that gpr126 mutant Schwann cells elaborate mature myelin sheaths and maintain krox20 expression for months, provided that the early signaling defect is bypassed by transient elevation of cAMP. At the onset of myelination, Gpr126 and protein kinase A (PKA) function as a switch that allows Schwann cells to initiate krox20 expression and myelination. After myelination is initiated, krox20 expression is maintained and myelin maturation proceeds independently of Gpr126 signaling. Transgenic analysis indicates that the Krox20 cis-regulatory myelinating Schwann cell element (MSE) becomes active at the onset of myelination and that this activity is dependent on Gpr126 signaling. Activity of the MSE declines after initiation, suggesting that other elements are responsible for maintaining krox20 expression in mature nerves. We also show that elevated cAMP does not initiate myelination in the absence of functional Neuregulin 1 (Nrg1) signaling. These results indicate that the mechanisms regulating the initiation of myelination are distinct from those mediating the maturation and maintenance of myelin.
Collapse
Affiliation(s)
- Thomas D. Glenn
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - William S. Talbot
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| |
Collapse
|
52
|
SWI/SNF enzymes promote SOX10- mediated activation of myelin gene expression. PLoS One 2013; 8:e69037. [PMID: 23874858 PMCID: PMC3712992 DOI: 10.1371/journal.pone.0069037] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 06/04/2013] [Indexed: 12/21/2022] Open
Abstract
SOX10 is a Sry-related high mobility (HMG)-box transcriptional regulator that promotes differentiation of neural crest precursors into Schwann cells, oligodendrocytes, and melanocytes. Myelin, formed by Schwann cells in the peripheral nervous system, is essential for propagation of nerve impulses. SWI/SNF complexes are ATP dependent chromatin remodeling enzymes that are critical for cellular differentiation. It was recently demonstrated that the BRG1 subunit of SWI/SNF complexes activates SOX10 expression and also interacts with SOX10 to activate expression of OCT6 and KROX20, two transcriptional regulators of Schwann cell differentiation. To determine the requirement for SWI/SNF enzymes in the regulation of genes that encode components of myelin, which are downstream of these transcriptional regulators, we introduced SOX10 into fibroblasts that inducibly express dominant negative versions of the SWI/SNF ATPases, BRM or BRG1. Dominant negative BRM and BRG1 have mutations in the ATP binding site and inhibit gene activation events that require SWI/SNF function. Ectopic expression of SOX10 in cells derived from NIH 3T3 fibroblasts led to the activation of the endogenous Schwann cell specific gene, myelin protein zero (MPZ) and the gene that encodes myelin basic protein (MBP). Thus, SOX10 reprogrammed these cells into myelin gene expressing cells. Ectopic expression of KROX20 was not sufficient for activation of these myelin genes. However, KROX20 together with SOX10 synergistically activated MPZ and MBP expression. Dominant negative BRM and BRG1 abrogated SOX10 mediated activation of MPZ and MBP and synergistic activation of these genes by SOX10 and KROX20. SOX10 was required to recruit BRG1 to the MPZ locus. Similarly, in immortalized Schwann cells, BRG1 recruitment to SOX10 binding sites at the MPZ locus was dependent on SOX10 and expression of dominant negative BRG1 inhibited expression of MPZ and MBP in these cells. Thus, SWI/SNF enzymes cooperate with SOX10 to directly activate genes that encode components of peripheral myelin.
Collapse
|
53
|
Sox10 cooperates with the mediator subunit 12 during terminal differentiation of myelinating glia. J Neurosci 2013; 33:6679-90. [PMID: 23575864 DOI: 10.1523/jneurosci.5178-12.2013] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Several transcription factors are essential for terminal differentiation of myelinating glia, among them the high-mobility-group-domain-containing protein Sox10. To better understand how these factors exert their effects and shape glial expression programs, we identified and characterized a physical and functional link between Sox10 and the Med12 subunit of the Mediator complex that serves as a conserved multiprotein interphase between transcription factors and the general transcription machinery. We found that Sox10 bound with two of its conserved domains to the C-terminal region of Med12 and its close relative, Med12-like. In contrast to Med12-like, substantial amounts of Med12 were detected in both Schwann cells and oligodendrocytes. Its conditional glia-specific deletion in mice led to terminal differentiation defects that were highly reminiscent of those obtained after Sox10 deletion. In support of a functional cooperation, both proteins were jointly required for Krox20 induction and were physically associated with the critical regulatory region of the Krox20 gene in myelinating Schwann cells. We conclude that Sox10 functions during terminal differentiation of myelinating glia, at least in part by Med12-dependent recruitment of the Mediator complex.
Collapse
|
54
|
Doddrell RDS, Dun XP, Shivane A, Feltri ML, Wrabetz L, Wegner M, Sock E, Hanemann CO, Parkinson DB. Loss of SOX10 function contributes to the phenotype of human Merlin-null schwannoma cells. ACTA ACUST UNITED AC 2013; 136:549-63. [PMID: 23413263 PMCID: PMC3572932 DOI: 10.1093/brain/aws353] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Loss of the Merlin tumour suppressor causes abnormal de-differentiation and proliferation of Schwann cells and formation of schwannoma tumours in patients with neurofibromatosis type 2. Within the mature peripheral nerve the normal development, differentiation and maintenance of myelinating and non-myelinating Schwann cells is regulated by a network of transcription factors that include SOX10, OCT6 (now known as POU3F1), NFATC4 and KROX20 (also known as Egr2). We have examined for the first time how their regulation of Schwann cell development is disrupted in primary human schwannoma cells. We find that induction of both KROX20 and OCT6 is impaired, whereas enforced expression of KROX20 drives both myelin gene expression and cell cycle arrest in Merlin-null cells. Importantly, we show that human schwannoma cells have reduced expression of SOX10 protein and messenger RNA. Analysis of mouse SOX10-null Schwann cells shows they display many of the characteristics of human schwannoma cells, including increased expression of platelet derived growth factor receptor beta (PDGFRB) messenger RNA and protein, enhanced proliferation, increased focal adhesions and schwannoma-like morphology. Correspondingly, reintroduction of SOX10 into human Merlin-null cells restores the ability of these cells to induce KROX20 and myelin protein zero (MPZ), localizes NFATC4 to the nucleus, reduces cell proliferation and suppresses PDGFRB expression. Thus, we propose that loss of the SOX10 protein, which is vital for normal Schwann cell development, is also key to the pathology of Merlin-null schwannoma tumours.
Collapse
Affiliation(s)
- Robin D S Doddrell
- Peninsula School of Medicine and Dentistry, University of Plymouth, Devon, PL6 8BU, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
55
|
Ueda H, Matsunaga H, Olaposi OI, Nagai J. Lysophosphatidic acid: Chemical signature of neuropathic pain. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1831:61-73. [DOI: 10.1016/j.bbalip.2012.08.014] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Revised: 08/21/2012] [Accepted: 08/21/2012] [Indexed: 02/07/2023]
|
56
|
Kipanyula MJ, Woodhoo A, Rahman M, Payne D, Jessen KR, Mirsky R. Calcineurin-nuclear factor of activated T cells regulation of Krox-20 expression in Schwann cells requires elevation of intracellular cyclic AMP. J Neurosci Res 2013; 91:105-15. [PMID: 23073893 PMCID: PMC5722200 DOI: 10.1002/jnr.23131] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Revised: 07/09/2012] [Accepted: 07/20/2012] [Indexed: 12/13/2022]
Abstract
The transcription factor Krox-20 (Egr2) is a master regulator of Schwann cell myelination. In mice from which calcineurin B had been excised in cells of the neural crest lineage, calcineurin-nuclear factor of activated T cells (NFAT) signaling was required for neuregulin-related Schwann cell myelination (Kao et al. [2009] Immunity 12:359-372). Whether NFAT signaling required simultaneous elevation of intracellular cAMP levels was not explored. In vivo, Krox-20 expression requires continuous axon-Schwann cell signaling that in Schwann cell cultures can be mimicked by elevation of intracellular cAMP. We have investigated the role of the calcineurin-NFAT pathway in Krox-20 induction in purified rat Schwann cell cultures. Activation of this pathway requires elevation of intracellular Ca(2+) levels. The calcium ionophore A23187 or ionomycin was used to increase intracellular Ca(2+) levels in Schwann cell cultures that had been treated with dibutyryl cAMP to induce Krox-20. Increase in Ca(2+) levels significantly potentiated Krox-20 induction, determined by Krox-20 immunolabeling of individual cells and Western blotting. Levels of the myelin proteins periaxin and P(0) were also elevated. The potentiating effect was blocked by cyclosporin A, a specific blocker of the calcineurin-NFAT pathway. We found that, in the absence of cAMP elevation, treatment with A23187 alone failed to induce Krox-20 expression, indicating that NFAT upregulation of Krox-20 requires elevation of cAMP levels in Schwann cells. P-VIVIT, another specific inhibitor of calcineurin-NFAT interaction, blocked Krox-20 induction in response to dibutyryl cAMP and ionophore. HA-NFAT1 (1-460)-GFP translocated to the nucleus on treatment with dibutyryl cAMP with or without added ionophore. NFAT isoforms 1-4 were detected in purified Schwann cells by quantitative RT-PCR.
Collapse
Affiliation(s)
- Maulilio J. Kipanyula
- Department of Veterinary Anatomy, Sokoine University of Agriculture, Chuo Kikuu, Morogoro, Tanzania
| | - Ashwin Woodhoo
- Metabolomics Unit, CICbioGune, Parque Tecnológico de Bizcaia, Derio, Bizcaia, Spain
| | - Mary Rahman
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Donna Payne
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Kristján R. Jessen
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Rhona Mirsky
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| |
Collapse
|
57
|
Weider M, Küspert M, Bischof M, Vogl MR, Hornig J, Loy K, Kosian T, Müller J, Hillgärtner S, Tamm ER, Metzger D, Wegner M. Chromatin-remodeling factor Brg1 is required for Schwann cell differentiation and myelination. Dev Cell 2012; 23:193-201. [PMID: 22814607 DOI: 10.1016/j.devcel.2012.05.017] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 04/12/2012] [Accepted: 05/22/2012] [Indexed: 10/28/2022]
Abstract
Schwann cells produce myelin sheaths and thereby permit rapid saltatory conductance in the vertebrate peripheral nervous system. Their stepwise differentiation from neural crest cells is driven by a defined set of transcription factors. How this is linked to chromatin changes is not well understood. Here we show that the glial transcription factor Sox10 functions in Schwann cells by recruiting Brg1-containing chromatin-remodeling complexes via Baf60a to regulatory regions of Oct6 and Krox20 genes. It thereby stimulates expression of these transcriptional regulators that then cooperate with Sox10 to convert immature into myelinating Schwann cells. The functional interaction between Sox10 and Brg1 is evident from gain- and loss-of-function studies, similar neuropathies in the corresponding mouse mutants, and an aggravated neuropathy in compound mutants. Our results demonstrate that the transcription factor-mediated recruitment of the chromatin-remodeling machinery to specific genomic loci is an essential driving force for Schwann cell differentiation and myelination.
Collapse
Affiliation(s)
- Matthias Weider
- Institut für Biochemie, Emil-Fischer-Zentrum, Universität Erlangen-Nürnberg, Erlangen, Germany
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
58
|
Doddrell RDS, Dun XP, Moate RM, Jessen KR, Mirsky R, Parkinson DB. Regulation of Schwann cell differentiation and proliferation by the Pax-3 transcription factor. Glia 2012; 60:1269-78. [PMID: 22532290 PMCID: PMC5722199 DOI: 10.1002/glia.22346] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2011] [Accepted: 03/30/2012] [Indexed: 12/13/2022]
Abstract
Pax-3 is a paired domain transcription factor that plays many roles during vertebrate development. In the Schwann cell lineage, Pax-3 is expressed at an early stage in Schwann cells precursors of the embryonic nerve, is maintained in the nonmyelinating cells of the adult nerve, and is upregulated in Schwann cells after peripheral nerve injury. Consistent with this expression pattern, Pax-3 has previously been shown to play a role in repressing the expression of the myelin basic protein gene in Schwann cells. We have studied the role of Pax-3 in Schwann cells and have found that it controls not only the regulation of cell differentiation but also the survival and proliferation of Schwann cells. Pax-3 expression blocks both the induction of Oct-6 and Krox-20 (K20) by cyclic AMP and completely inhibits the ability of K20, the physiological regulator of myelination in the peripheral nervous system, to induce myelin gene expression in Schwann cells. In contrast to other inhibitors of myelination, we find that Pax-3 represses myelin gene expression in a c-Jun-independent manner. In addition to this, we find that Pax-3 expression alone is sufficient to inhibit the induction of apoptosis by TGFβ1 in Schwann cells. Expression of Pax-3 is also sufficient to induce the proliferation of Schwann cells in the absence of added growth factors and to reverse K20-induced exit from the cell cycle. These findings indicate new roles for the Pax-3 transcription factor in controlling the differentiation and proliferation of Schwann cells during development and after peripheral nerve injury.
Collapse
Affiliation(s)
- Robin D. S. Doddrell
- Peninsula College of Medicine and Dentistry, University of Exeter, Plymouth, Devon, United Kingdom
| | - Xin-Peng Dun
- Peninsula College of Medicine and Dentistry, University of Exeter, Plymouth, Devon, United Kingdom
| | - Roy M. Moate
- School of Biomedical and Biological Sciences, University of Plymouth, Plymouth, Devon, United Kingdom
| | - Kristjan R. Jessen
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Rhona Mirsky
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - David B. Parkinson
- Peninsula College of Medicine and Dentistry, University of Exeter, Plymouth, Devon, United Kingdom
| |
Collapse
|
59
|
Srinivasan R, Sun G, Keles S, Jones EA, Jang SW, Krueger C, Moran JJ, Svaren J. Genome-wide analysis of EGR2/SOX10 binding in myelinating peripheral nerve. Nucleic Acids Res 2012; 40:6449-60. [PMID: 22492709 PMCID: PMC3413122 DOI: 10.1093/nar/gks313] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Revised: 03/25/2012] [Accepted: 03/26/2012] [Indexed: 11/17/2022] Open
Abstract
Myelin is essential for the rapidity of saltatory nerve conduction, and also provides trophic support for axons to prevent axonal degeneration. Two critical determinants of myelination are SOX10 and EGR2/KROX20. SOX10 is required for specification of Schwann cells from neural crest, and is required at every stage of Schwann cell development. Egr2/Krox20 expression is activated by axonal signals in myelinating Schwann cells, and is required for cell cycle arrest and myelin formation. To elucidate the integrated function of these two transcription factors during peripheral nerve myelination, we performed in vivo ChIP-Seq analysis of myelinating peripheral nerve. Integration of these binding data with loss-of-function array data identified a range of genes regulated by these factors. In addition, although SOX10 itself regulates Egr2/Krox20 expression, leading to coordinate activation of several major myelin genes by the two factors, there is a large subset of genes that are activated independent of EGR2. Finally, the results identify a set of SOX10-dependent genes that are expressed in early Schwann cell development, but become subsequently repressed by EGR2/KROX20.
Collapse
Affiliation(s)
- Rajini Srinivasan
- Waisman Center, Department of Statistics, Department of Biostatistics and Medical Informatics, Program in Cellular and Molecular Biology and, Department of Comparative Biosciences, University of Wisconsin, Madison, WI, USA
| | - Guannan Sun
- Waisman Center, Department of Statistics, Department of Biostatistics and Medical Informatics, Program in Cellular and Molecular Biology and, Department of Comparative Biosciences, University of Wisconsin, Madison, WI, USA
| | - Sunduz Keles
- Waisman Center, Department of Statistics, Department of Biostatistics and Medical Informatics, Program in Cellular and Molecular Biology and, Department of Comparative Biosciences, University of Wisconsin, Madison, WI, USA
| | - Erin A. Jones
- Waisman Center, Department of Statistics, Department of Biostatistics and Medical Informatics, Program in Cellular and Molecular Biology and, Department of Comparative Biosciences, University of Wisconsin, Madison, WI, USA
| | - Sung-Wook Jang
- Waisman Center, Department of Statistics, Department of Biostatistics and Medical Informatics, Program in Cellular and Molecular Biology and, Department of Comparative Biosciences, University of Wisconsin, Madison, WI, USA
| | - Courtney Krueger
- Waisman Center, Department of Statistics, Department of Biostatistics and Medical Informatics, Program in Cellular and Molecular Biology and, Department of Comparative Biosciences, University of Wisconsin, Madison, WI, USA
| | - John J. Moran
- Waisman Center, Department of Statistics, Department of Biostatistics and Medical Informatics, Program in Cellular and Molecular Biology and, Department of Comparative Biosciences, University of Wisconsin, Madison, WI, USA
| | - John Svaren
- Waisman Center, Department of Statistics, Department of Biostatistics and Medical Informatics, Program in Cellular and Molecular Biology and, Department of Comparative Biosciences, University of Wisconsin, Madison, WI, USA
| |
Collapse
|
60
|
Abstract
Schwann cells are the main glial cell type in the PNS. They develop along nerves during embryogenesis and rely on the HMG domain containing Sox10 transcription factor for specification, lineage progression, and terminal differentiation. Sox10 deletion in immature Schwann cells caused peripheral nerve defects in mice that were not restricted to this glial cell type, although expression in the nerve and gene loss were. Formation of the perineurium as the protecting sheath was, for instance, heavily compromised. This resembled the defect observed after loss of Desert hedgehog (Dhh) in mice. Here we show that Sox10 activates Dhh expression in Schwann cells via an enhancer that is located in intron 1 of the Dhh gene. Sox10 binds this enhancer in monomeric form via several sites. Mutation of these sites abolishes both Schwann-cell-specific activity and Sox10 responsiveness in vitro and in transgenic mouse embryos. This argues that Sox10 activates Dhh expression by direct binding to the enhancer and by increasing Dhh levels promotes formation of the perineurial sheath. This represents the first mechanism for a non-cell-autonomous function of Sox10 during peripheral nerve development.
Collapse
|
61
|
Hossain S, de la Cruz-Morcillo MA, Sanchez-Prieto R, Almazan G. Mitogen-activated protein kinase p38 regulates krox-20 to direct schwann cell differentiation and peripheral myelination. Glia 2012; 60:1130-44. [DOI: 10.1002/glia.22340] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Accepted: 03/16/2012] [Indexed: 12/24/2022]
|
62
|
Fröb F, Bremer M, Finzsch M, Kichko T, Reeh P, Tamm ER, Charnay P, Wegner M. Establishment of myelinating schwann cells and barrier integrity between central and peripheral nervous systems depend on Sox10. Glia 2012; 60:806-19. [DOI: 10.1002/glia.22310] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2011] [Accepted: 01/24/2012] [Indexed: 11/05/2022]
|
63
|
Pereira JA, Lebrun-Julien F, Suter U. Molecular mechanisms regulating myelination in the peripheral nervous system. Trends Neurosci 2011; 35:123-34. [PMID: 22192173 DOI: 10.1016/j.tins.2011.11.006] [Citation(s) in RCA: 181] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Revised: 11/17/2011] [Accepted: 11/18/2011] [Indexed: 12/21/2022]
Abstract
Glial cells and neurons are engaged in a continuous and highly regulated bidirectional dialog. A remarkable example is the control of myelination. Oligodendrocytes in the central nervous system (CNS) and Schwann cells (SCs) in the peripheral nervous system (PNS) wrap their plasma membranes around axons to organize myelinated nerve fibers that allow rapid saltatory conduction. The functionality of this system is critical, as revealed by numerous neurological diseases that result from deregulation of the system, including multiple sclerosis and peripheral neuropathies. In this review we focus on PNS myelination and present a conceptual framework that integrates crucial signaling mechanisms with basic SC biology. We will highlight signaling hubs and overarching molecular mechanisms, including genetic, epigenetic, and post-translational controls, which together regulate the interplay between SCs and axons, extracellular signals, and the transcriptional network.
Collapse
Affiliation(s)
- Jorge A Pereira
- Institute of Cell Biology, Department of Biology, Swiss Federal Institute of Technology, ETH Zürich, Zürich, Switzerland
| | | | | |
Collapse
|