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Ujita S, Sasaki T, Asada A, Funayama K, Gao M, Mikoshiba K, Matsuki N, Ikegaya Y. cAMP-Dependent Calcium Oscillations of Astrocytes: An Implication for Pathology. Cereb Cortex 2018; 27:1602-1614. [PMID: 26803165 DOI: 10.1093/cercor/bhv310] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Astrocytes in various brain regions exhibit spontaneous intracellular calcium elevations both in vitro and in vivo; however, neither the temporal pattern underlying this activity nor its function has been fully evaluated. Here, we utilized a long-term optical imaging technique to analyze the calcium activity of more than 4000 astrocytes in acute hippocampal slices as well as in the neocortex and hippocampus of head-restrained mice. Although astrocytic calcium activity was largely sparse and irregular, we observed a subset of cells in which the fluctuating calcium oscillations repeated at a regular interval of ∼30 s. These intermittent oscillations i) depended on type 2 inositol 1,4,5-trisphosphate receptors; ii) consisted of a complex reverberatory interaction between the soma and processes of individual astrocytes; iii) did not synchronize with those of other astrocytes; iv) did not require neuronal firing; v) were modulated through cAMP-protein kinase A signaling; vi) were facilitated under pathological conditions, such as energy deprivation and epileptiform hyperexcitation; and vii) were associated with enhanced hypertrophy in astrocytic processes, an early hallmark of reactive gliosis, which is observed in ischemia and epilepsy. Therefore, calcium oscillations appear to be associated with a pathological state in astrocytes.
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Affiliation(s)
- Sakiko Ujita
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Takuya Sasaki
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Akiko Asada
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Kenta Funayama
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Mengxuan Gao
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Katsuhiko Mikoshiba
- Laboratory for Developmental Neurobiology, Riken Brain Science Institute, Saitama, Japan
| | - Norio Matsuki
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Yuji Ikegaya
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan.,Center for Information and Neural Networks, Suita City, Osaka, Japan
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Tassoni A, Gutteridge A, Barber AC, Osborne A, Martin KR. Molecular Mechanisms Mediating Retinal Reactive Gliosis Following Bone Marrow Mesenchymal Stem Cell Transplantation. Stem Cells 2015; 33:3006-16. [PMID: 26175331 PMCID: PMC4832383 DOI: 10.1002/stem.2095] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 06/15/2015] [Accepted: 06/21/2015] [Indexed: 01/09/2023]
Abstract
A variety of diseases lead to degeneration of retinal ganglion cells (RGCs) and their axons within the optic nerve resulting in loss of visual function. Although current therapies may delay RGC loss, they do not restore visual function or completely halt disease progression. Regenerative medicine has recently focused on stem cell therapy for both neuroprotective and regenerative purposes. However, significant problems remain to be addressed, such as the long-term impact of reactive gliosis occurring in the host retina in response to transplanted stem cells. The aim of this work was to investigate retinal glial responses to intravitreally transplanted bone marrow mesenchymal stem cells (BM-MSCs) to help identify factors able to modulate graft-induced reactive gliosis. We found in vivo that intravitreal BM-MSC transplantation is associated with gliosis-mediated retinal folding, upregulation of intermediate filaments, and recruitment of macrophages. These responses were accompanied by significant JAK/STAT3 and MAPK (ERK1/2 and JNK) cascade activation in retinal Muller glia. Lipocalin-2 (Lcn-2) was identified as a potential new indicator of graft-induced reactive gliosis. Pharmacological inhibition of STAT3 in BM-MSC cocultured retinal explants successfully reduced glial fibrillary acidic protein expression in retinal Muller glia and increased BM-MSC retinal engraftment. Inhibition of stem cell-induced reactive gliosis is critical for successful transplantation-based strategies for neuroprotection, replacement, and regeneration of the optic nerve.
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Affiliation(s)
- Alessia Tassoni
- Department of Clinical Neurosciences, John van Geest Centre for Brain Repair, University of Cambridge, Cambridge, United Kingdom
| | | | - Amanda C Barber
- Department of Clinical Neurosciences, John van Geest Centre for Brain Repair, University of Cambridge, Cambridge, United Kingdom
| | - Andrew Osborne
- Department of Clinical Neurosciences, John van Geest Centre for Brain Repair, University of Cambridge, Cambridge, United Kingdom
| | - Keith R Martin
- Department of Clinical Neurosciences, John van Geest Centre for Brain Repair, University of Cambridge, Cambridge, United Kingdom
- Cambridge NIHR Biomedical Research Centre, Cambridge, United Kingdom
- Eye Department, Addenbrooke's Hospital, Cambridge, United Kingdom
- Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, Cambridge, United Kingdom
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Adornetto A, Pagliara V, Renzo GD, Arcone R. Polychlorinated biphenyls impair dibutyryl cAMP-induced astrocytic differentiation in rat C6 glial cell line. FEBS Open Bio 2013; 3:459-66. [PMID: 24251112 PMCID: PMC3829991 DOI: 10.1016/j.fob.2013.10.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 10/20/2013] [Accepted: 10/22/2013] [Indexed: 02/04/2023] Open
Abstract
In the central nervous system, alteration of glial cell differentiation can affect brain functions. Polychlorinated biphenyls (PCBs) are persistent environmental chemical contaminants that exert neurotoxic effects in glial and neuronal cells. We examined the effects of a commercial mixture of PCBs, Aroclor1254 (A1254) on astrocytic differentiation of glial cells, using the rat C6 cell line as in vitro model. The exposure for 24 h to sub-toxic concentrations of A1254 (3 or 9 μM) impaired dibutyryl cAMP-induced astrocytic differentiation as showed by the decrease of glial fibrillary acidic protein (GFAP) protein levels and inhibition in change of cell morphology toward an astrocytic phenotype. The A1254 inhibition was restored by the addition of a protein kinase C (PKC) inhibitor, bisindolylmaleimide (bis), therefore indicating that PCBs disturbed the cAMP-induced astrocytic differentiation of C6 cells via the PKC pathway. The phosphorylation of signal transducer and activator of transcription 3 (STAT3) is essential for cAMP-induced transcription of GFAP promoter in C6 cells. Our results indicated that the exposure to A1254 (3 or 9 μM) for 24 h suppressed cAMP-induced STAT3 phosphorylation. Moreover, A1254 reduced cAMP-dependent phosphorylation of STAT3 requires inhibition of PKC activity. Together, our results suggest that PCBs induce perturbation in cAMP/PKA and PKC signaling pathway during astrocytic differentiation of glial cells.
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Key Words
- A1254, Aroclor 1254
- Aroclor1254
- Astrocytic differentiation
- C6 glial cell line
- CNS, central nervous system
- CRE, cAMP responsive element
- CREB, cAMP-response element binding protein
- DAPI, 4′,6-diamidino-2-phenylindole
- DMEM, Dulbecco’s Modified Eagle’s Medium
- DMSO, dimethyl sulfoxide
- GAPDH, glyceraldehyde-3-phosphate dehydrogenase
- GFAP, glial fibrillary acidic protein
- Glial fibrillary acidic protein (GFAP)
- MTT, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide
- NMDA, N-methyl-d-aspartate
- PCBs, polychlorinated biphenyls
- PKA, protein kinase A
- PKC, protein kinase C
- Protein kinase C (PKC)
- ROS, reactive oxygen species
- STAT3, signal transducer and activator of transcription 3
- Signal transducer and activator of transcription 3 (STAT3)
- TRE, CRE transcriptional response element
- bis, 2-[1-(3-dimethylamino-propyl)indol-3-yl]-3-(indol-3-yl) maleimide
- dbcAMP, N6,2′-O-dibutyryl cAMP
- nNOS, neuronal nitric oxide
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Affiliation(s)
- Annagrazia Adornetto
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Via P. Bucci, Arcavacata di Rende, Cosenza (CS) 87036, Italy
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Liu Y, Zhu H, Liu M, Du J, Qian Y, Wang Y, Ding F, Gu X. Downregulation of Pax3 expression correlates with acquired GFAP expression during NSC differentiation towards astrocytes. FEBS Lett 2011; 585:1014-20. [PMID: 21371476 DOI: 10.1016/j.febslet.2011.02.034] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 02/21/2011] [Accepted: 02/24/2011] [Indexed: 10/18/2022]
Abstract
Glial fibrillary acidic protein (GFAP) is a principal intermediate filament in mature astrocytes of the central nervous system (CNS), and the regulation of GFAP transcription has not been well understood yet. In the present study, we reported paired box 3 protein (Pax3) as a novel regulator of GFAP transcription, which could bind the promoter region of GFAP and down regulate the GFAP level during the serum-induced astrocyte differentiation of neural stem cells (NSCs). Moreover, the overexpression and suppression of Pax3 could inhibit and promote NSC differentiation, respectively. These data suggest that Pax3 negatively regulates GFAP expression during astrocyte differentiation in vitro.
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Affiliation(s)
- Yan Liu
- Jiangsu Key Laboratory of Neuroregeneration, Nantong University, Nantong, Jiangsu Province 226001, PR China
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Bringmann A, Iandiev I, Pannicke T, Wurm A, Hollborn M, Wiedemann P, Osborne NN, Reichenbach A. Cellular signaling and factors involved in Müller cell gliosis: neuroprotective and detrimental effects. Prog Retin Eye Res 2009; 28:423-51. [PMID: 19660572 DOI: 10.1016/j.preteyeres.2009.07.001] [Citation(s) in RCA: 512] [Impact Index Per Article: 34.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Müller cells are active players in normal retinal function and in virtually all forms of retinal injury and disease. Reactive Müller cells protect the tissue from further damage and preserve tissue function by the release of antioxidants and neurotrophic factors, and may contribute to retinal regeneration by the generation of neural progenitor/stem cells. However, Müller cell gliosis can also contribute to neurodegeneration and impedes regenerative processes in the retinal tissue by the formation of glial scars. This article provides an overview of the neuroprotective and detrimental effects of Müller cell gliosis, with accounts on the cellular signal transduction mechanisms and factors which are implicated in Müller cell-mediated neuroprotection, immunomodulation, regulation of Müller cell proliferation, upregulation of intermediate filaments, glial scar formation, and the generation of neural progenitor/stem cells. A proper understanding of the signaling mechanisms implicated in gliotic alterations of Müller cells is essential for the development of efficient therapeutic strategies that increase the supportive/protective and decrease the destructive roles of gliosis.
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Affiliation(s)
- Andreas Bringmann
- Department of Ophthalmology and Eye Hospital, University of Leipzig, Liebigstrasse 10-14, D-04103 Leipzig, Germany.
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Morita K, Arimochi H, Itoh H, Her S. Possible involvement of 5α-reduced neurosteroids in adrenergic and serotonergic stimulation of GFAP gene expression in rat C6 glioma cells. Brain Res 2006; 1085:49-56. [PMID: 16581042 DOI: 10.1016/j.brainres.2006.02.033] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2005] [Revised: 02/01/2006] [Accepted: 02/07/2006] [Indexed: 11/16/2022]
Abstract
Influence of adrenergic and serotonergic stimulation on glial fibrillary acidic protein (GFAP) gene expression in rat C6 glioma cells was first examined as an in vitro model experiment for investigating the neuronal regulation of glial cell differentiation. Stimulation of these cells with isoproterenol and serotonin elevated GFAP mRNA levels followed by an increase in its protein contents, thus suggesting that both adrenergic and serotonergic stimulation might induce the differentiation of the glioma cells. In addition, progesterone and its 5alpha-reduced metabolite dihydroprogesterone also elevated GFAP mRNA levels in rat C6 glioma cells, consistent with their stimulatory actions on GFAP gene expression observed in rat astrocytes. Further studies showed that the elevation of GFAP mRNA levels induced by isoproterenol and serotonin as well as progesterone was abolished by pretreatment of the glioma cells with finasteride, an inhibitor of 5alpha-reduced steroid production. Moreover, the stimulatory actions of isoproterenol and serotonin on GFAP gene expression were inhibited by pretreatment with a GABA(A) receptor antagonist bicuculline and a progesterone receptor antagonist RU486. These findings suggest that both adrenergic and serotonergic stimulation may indirectly activate GFAP gene expression probably through the production of 5alpha-reduced steroid metabolites in rat C6 glioma cells, proposing the possibility that 5alpha-reduced neurosteroids may play a potential role in the neuronal regulation of glial cell differentiation.
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Affiliation(s)
- Kyoji Morita
- Department of Pharmacology, Tokushima University School of Medicine, 3-18-15 Kuramoto, Tokushima 770-8503, Japan.
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Kase S, Yoshida K, Harada T, Harada C, Namekata K, Suzuki Y, Ohgami K, Shiratori K, Nakayama KI, Ohno S. Phosphorylation of extracellular signal-regulated kinase and p27(KIP1) after retinal detachment. Graefes Arch Clin Exp Ophthalmol 2005; 244:352-8. [PMID: 16075224 DOI: 10.1007/s00417-005-0016-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Revised: 02/18/2005] [Accepted: 04/15/2005] [Indexed: 10/25/2022] Open
Abstract
PURPOSE The roles of the extracellular signal-regulated kinase (ERK) pathway in the expression of cyclin D1 and p27(KIP1), the phosphorylation of p27(KIP1), and proliferation activity were examined after retinal detachment. METHODS Normal eyes and eyes at 15 min, 2 and 4 days after retinal detachment in C57Bl6 mice were examined by immunohistochemistry using anti-phosphorylated (p) ERK1/2, anti-cyclin D1, anti-p27(KIP1), anti-p27(KIP1) phosphorylated at serine 10 (S10-phospho-p27), and anti-proliferating cell nuclear antigen (PCNA) antibodies with or without treatment with a specific ERK inhibitor, PD98059. Mouse Müller cells were isolated and examined for alteration of p27(KIP1) and cyclin D1 after exposure of basic fibroblast growth factor (bFGF) with and without treatment of PD98059 using Western blotting. RESULTS In the normal retina, nuclear immunoreactivity for p27(KIP1), but not S10-phospho-p27 or pERK1/2, was observed in the middle sublayer of the inner nuclear layer (INL), where Müller glial cells are situated. At 15 min after the retinal detachment, p27(KIP1), S10-phospho-p27 and pERK1/2-positive nuclei were noted in the INL, whereas immunoreactivity for pERK1/2 or S10-phospho-p27 was not observed after treatment with PD98095. Cyclin D1 was induced in the INL 2 days after the retinal detachment, and the induction was inhibited by PD98059. At 4 days after the detachment, p27(KIP1) immunoreactivity was not observed, and cyclin D1 and PCNA were expressed. The disappearance of p27(KIP1) was suppressed, whereas expression of cyclin D1 and PCNA was not observed in mice treated with PD98059. Exposure of bFGF relatively decreased the expression level of p27(KIP1) and increased the level of cyclin D1 in mouse Müller cells, compared with control level. Induction of cyclin D1 and decrease in p27(KIP1) were inhibited with treatment of PD98059. CONCLUSION Phosphorylation of ERK and expression of p27(KIP1) and cyclin D1 are involved in the proliferation of Müller cells after retinal detachment.
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Affiliation(s)
- Satoru Kase
- Department of Ophthalmology and Visual Sciences, Hokkaido University Graduate School of Medicine, N15 W7, Kita-ku, Sapporo, 060-8638, Japan
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Nicole O, Goldshmidt A, Hamill CE, Sorensen SD, Sastre A, Lyuboslavsky P, Hepler JR, McKeon RJ, Traynelis SF. Activation of protease-activated receptor-1 triggers astrogliosis after brain injury. J Neurosci 2005; 25:4319-29. [PMID: 15858058 PMCID: PMC6725104 DOI: 10.1523/jneurosci.5200-04.2005] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We have studied the involvement of the thrombin receptor [protease-activated receptor-1 (PAR-1)] in astrogliosis, because extravasation of PAR-1 activators, such as thrombin, into brain parenchyma can occur after blood-brain barrier breakdown in a number of CNS disorders. PAR1-/- animals show a reduced astrocytic response to cortical stab wound, suggesting that PAR-1 activation plays a key role in astrogliosis associated with glial scar formation after brain injury. This interpretation is supported by the finding that the selective activation of PAR-1 in vivo induces astrogliosis. The mechanisms by which PAR-1 stimulates glial proliferation appear to be related to the ability of PAR-1 receptor signaling to induce sustained extracellular receptor kinase (ERK) activation. In contrast to the transient activation of ERK by cytokines and growth factors, PAR-1 stimulation induces a sustained ERK activation through its coupling to multiple G-protein-linked signaling pathways, including Rho kinase. This sustained ERK activation appears to regulate astrocytic cyclin D1 levels and astrocyte proliferation in vitro and in vivo. We propose that this PAR-1-mediated mechanism underlying astrocyte proliferation will operate whenever there is sufficient injury-induced blood-brain barrier breakdown to allow extravasation of PAR-1 activators.
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Affiliation(s)
- Olivier Nicole
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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Singh R, Nielsen AL, Johansen MG, Jørgensen AL. Genetic polymorphism and sequence evolution of an alternatively spliced exon of the glial fibrillary acidic protein gene, GFAP. Genomics 2003; 82:185-93. [PMID: 12837269 DOI: 10.1016/s0888-7543(03)00106-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Isoform GFAPepsilon of the human cytoskeletal protein GFAP carries, as the result of alternative splicing of exon 7a of GFAP, a novel 42-amino-acid-long C-terminal region with binding capacity for the presenilin proteins. Here we show that exon 7a is present in a variety of mammals but absent from GFAP of chicken and fish. Comparison of the mouse and human GFAP exons showed an increased rate of nonsynonymous nucleotide substitutions in exon 7a compared to the other exons. This resulted in 10 nonconservative and 2 conservative amino acid substitutions and suggests that exon 7a has evolved under different functional constraints. Exons 7a of humans and higher primates are 100% identical apart from alanine codon 426, which is conserved in only 9% of the human alleles, while 21 and 70% of the alleles, respectively, have a valine or a threonine codon at that position. Threonine represents a potential phosphorylation site, and positive selection of that effect could explain the high allele frequency.
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Affiliation(s)
- Ripudaman Singh
- Institute of Human Genetics, University of Aarhus, DK-8000 Aarhus C, Denmark
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Logan A, Berry M. Cellular and molecular determinants of glial scar formation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 513:115-58. [PMID: 12575819 DOI: 10.1007/978-1-4615-0123-7_4] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Ann Logan
- Molecular Neuroscience, Department of Medicine, Wolfson Research Laboratories, Queen Elizabeth Hospital, Edgbaston, Birmingham, B15 2TH, UK
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Hermanson O, Jepsen K, Rosenfeld MG. N-CoR controls differentiation of neural stem cells into astrocytes. Nature 2002; 419:934-9. [PMID: 12410313 DOI: 10.1038/nature01156] [Citation(s) in RCA: 217] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2002] [Accepted: 09/23/2002] [Indexed: 11/09/2022]
Abstract
Understanding the gene programmes that regulate maintenance and differentiation of neural stem cells is a central question in stem cell biology. Virtually all neural stem cells maintain an undifferentiated state and the capacity to self-renew in response to fibroblast growth factor-2 (FGF2). Here we report that a repressor of transcription, the nuclear receptor co-repressor (N-CoR), is a principal regulator in neural stem cells, as FGF2-treated embryonic cortical progenitors from N-CoR gene-disrupted mice display impaired self-renewal and spontaneous differentiation into astroglia-like cells. Stimulation of wild-type neural stem cells with ciliary neurotrophic factor (CNTF), a differentiation-inducing cytokine, results in phosphatidylinositol-3-OH kinase/Akt1 kinase-dependent phosphorylation of N-CoR, and causes a temporally correlated redistribution of N-CoR to the cytoplasm. We find that this is a critical strategy for cytokine-induced astroglia differentiation and lineage-characteristic gene expression. Recruitment of protein phosphatase-1 to a specific binding site on N-CoR exerts a reciprocal effect on the cellular localization of N-CoR. We propose that repression by N-CoR, modulated by opposing enzymatic activities, is a critical mechanism in neural stem cells that underlies the inhibition of glial differentiation.
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Affiliation(s)
- Ola Hermanson
- Howard Hughes Medical Institute, Department of Molecular Medicine, University of California, San Diego, School of Medicine, 9500 Gilman Drive, Room 345, La Jolla, California 92093-0648, USA
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Nielsen AL, Holm IE, Johansen M, Bonven B, Jørgensen P, Jørgensen AL. A new splice variant of glial fibrillary acidic protein, GFAP epsilon, interacts with the presenilin proteins. J Biol Chem 2002; 277:29983-91. [PMID: 12058025 DOI: 10.1074/jbc.m112121200] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We describe a new human isoform, GFAP epsilon, of the intermediary filament protein GFAP (glial fibrillary acidic protein). GFAP epsilon mRNA is the result of alternative splicing and a new polyadenylation signal, and thus GFAP epsilon has a new C-terminal protein sequence. This provides GFAP epsilon with the capacity for specific binding of presenilin proteins in yeast and in vitro. Our observations suggest a direct link between the presenilins and the cytoskeleton where GFAP epsilon is incorporated. Mutations in GFAP and presenilins are associated with Alexander disease and Alzheimer's disease, respectively. Accordingly, GFAP epsilon should be taken into consideration when studying neurodegenerative diseases.
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Huber G, März W, Martin JR, Malherbe P, Richards JG, Sueoka N, Ohm T, Hoffmann MM. Characterization of transgenic mice expressing apolipoprotein E4(C112R) and apolipoprotein E4(L28P; C112R). Neuroscience 2001; 101:211-8. [PMID: 11068149 DOI: 10.1016/s0306-4522(00)00341-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Apolipoprotein E (ApoE), which is genetically polymorphic, is a constituent of different lipoproteins. Two variants, ApoE4(C112R) and ApoE4(L28P; C112R) have been linked to the risk of developing Alzheimer's disease. Transgenic mice carrying ApoE4(C112R) (AD71) and ApoE4(L28P; C112R) (AD61) were generated and compared to wild-type mice. The use of glial fibrillary acidic protein as promoter led to transgene expression mainly in glial cells but also in neurons. Transgene protein levels were approximately three-and-a-half-fold that of endogenous ApoE in the glial fibrillary acidic protein-ApoE4(C112R) (AD71) and nearly twofold in the glial fibrillary acidic protein-ApoE4(L28P; C112R) (AD61) mouse lines. Neither transgenic mouse differed from wild-type in cognitive tests at the age of approximately one-and-a-half years. The locomotor activity of AD61 mice was similar to controls, whereas AD71 mice exhibited a clearly reduced level of motor activity. Immunohistological and biochemical brain protein analyses revealed no difference between strains.Thus, in the absence of morphological changes over-expression of ApoE4(C112R) on a background of endogenous mouse ApoE, may result in behavioral deficits while for the ApoE4(L28P; C112R) transgene higher expression might be required or some compensatory mechanisms might protect these animals from the behavioral abnormalities.
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Affiliation(s)
- G Huber
- Pharma Division, Preclinical CNS Research, F. Hoffmann-La Roche Ltd, 4070 Basel, Switzerland.
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Barresi V, Condorelli DF, Giuffrida Stella AM. GFAP gene methylation in different neural cell types from rat brain. Int J Dev Neurosci 1999; 17:821-8. [PMID: 10593618 DOI: 10.1016/s0736-5748(99)00059-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
It is generally believed that specific demethylation processes take place in the promoter of tissue-specific genes during development. It has been suggested that hypomethylation of the -1500/-1100 domain of the 5' flanking regulatory region of the rat glial fibrillary acidic protein gene may be specific for neuroectodermal derivatives such as neurons and astrocytes. In the present work the methylation status of one of those seven CG sites (the -1176) of the 'neuroectoderm-specific domain' was analyzed. In agreement with the neuroectoderm hypothesis, the -1176 site is highly demethylated in astroglial, oligodendroglial and neuronal cells, but heavily methylated in microglial and fibroblast cells. The three different glial population are derived from the same tissue (cerebral hemispheres of newborn rats) but have a different embryological origin: oligodendrocytes and astrocytes originate from neuroectoderm, while microglia is of mesodermal origin. It is not clear if GFAP-negative neuronal cells maintain such demethylation in the advanced stage of maturation or if they undergo a second phase of de novo methylation. In order to clarify this point we used a subcellular fractionation method which allowed us to separate two different nuclear populations from adult rat cerebral hemispheres: one enriched in neuronal nuclei (called N1) and the other enriched in glial nuclei (N2). A higher methylation level of the -1176 site was detected in the N1 fraction, suggesting the GFAP gene undergo a de novo methylation process during neuronal maturation. This observation is in agreement with recent results showing a de novo methylation of the -1176 site during postnatal brain development. We hypothesize that a DNA demethylation process takes place in neuroectodermal precursor cells and that the -1176 site persists demethylated at the earlier stages of neuronal differentiation (immature neurons) and becomes fully methylated at more advanced stages of differentiation.
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Affiliation(s)
- V Barresi
- Dipartimento di Scienze Chimiche, Facoltà di Medicina, Università di Catania, Italy
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Astroglial differentiation of cortical precursor cells triggered by activation of the cAMP-dependent signaling pathway. J Neurosci 1999. [PMID: 10516318 DOI: 10.1523/jneurosci.19-20-09004.1999] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In the developing brain, differentiation of neural precursors into neurons or glial cells occurs in response to neurotrophic factors acting on the cell surface. Intracellular signaling mechanisms that relay information to initiate differentiative responses of neural precursor cells are poorly understood. To investigate whether stimulation of the cAMP-dependent signaling pathway participates in differentiative responses of cells in the developing CNS, we performed experiments using both conditionally immortalized neural precursor cells (RC2.E10 cells) and primary cultures of cells from developing rat cortex. Initially, we determined that RC2.E10 cells retain phenotypic features of neural precursors after inactivation of the immortalizing oncogene, a temperature-sensitive mutant of the simian virus 40 large-T antigen (SV40T). We found that, once SV40T is inactivated, RC2.E10 cells cease to divide and die. However, RC2. E10 cells can proliferate in the presence of basic fibroblast growth factor. In addition, they express nestin, a marker of neural precursor cells. Both RC2.E10 cells and primary cortical precursor cells undergo astroglial differentiation in response to cAMP stimulation by treatment with 8-bromo-cAMP. In both cases, cAMP-induced astrocyte differentiation is characterized by morphological changes, stimulation of glial fibrillary acidic protein expression, downregulation of nestin expression, and decreased proliferation. No increases in the expression of neuronal or oligodendrocytic markers were observed. Our results support the notion that the developing CNS contains neural precursor cells with the capacity of undergoing astrocyte differentiation in response to increased intracellular cAMP concentrations.
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McManus MF, Chen LC, Vallejo I, Vallejo M. Astroglial differentiation of cortical precursor cells triggered by activation of the cAMP-dependent signaling pathway. J Neurosci 1999; 19:9004-15. [PMID: 10516318 PMCID: PMC6782746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023] Open
Abstract
In the developing brain, differentiation of neural precursors into neurons or glial cells occurs in response to neurotrophic factors acting on the cell surface. Intracellular signaling mechanisms that relay information to initiate differentiative responses of neural precursor cells are poorly understood. To investigate whether stimulation of the cAMP-dependent signaling pathway participates in differentiative responses of cells in the developing CNS, we performed experiments using both conditionally immortalized neural precursor cells (RC2.E10 cells) and primary cultures of cells from developing rat cortex. Initially, we determined that RC2.E10 cells retain phenotypic features of neural precursors after inactivation of the immortalizing oncogene, a temperature-sensitive mutant of the simian virus 40 large-T antigen (SV40T). We found that, once SV40T is inactivated, RC2.E10 cells cease to divide and die. However, RC2. E10 cells can proliferate in the presence of basic fibroblast growth factor. In addition, they express nestin, a marker of neural precursor cells. Both RC2.E10 cells and primary cortical precursor cells undergo astroglial differentiation in response to cAMP stimulation by treatment with 8-bromo-cAMP. In both cases, cAMP-induced astrocyte differentiation is characterized by morphological changes, stimulation of glial fibrillary acidic protein expression, downregulation of nestin expression, and decreased proliferation. No increases in the expression of neuronal or oligodendrocytic markers were observed. Our results support the notion that the developing CNS contains neural precursor cells with the capacity of undergoing astrocyte differentiation in response to increased intracellular cAMP concentrations.
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Affiliation(s)
- M F McManus
- Reproductive Endocrine Unit, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA
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18
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Abstract
Glial cells constitute one of the most common cell types in the brain. They play critical roles in central nervous system (CNS) development. Recent evidence demonstrates that glial cells are profoundly affected by prenatal alcohol exposure, suggesting that alterations in these cells may participate in CNS abnormalities associated with ethanol-induced teratogenesis. In vivo studies show that prenatal exposure to alcohol hampers myelinogenesis and is associated with neuroglial heterotopias and abnormal astrogliogenesis. Studies using primary cultures of rat cortical astrocytes show that ethanol affects DNA, RNA, and protein synthesis, decreases the number of mitotic cells, alters the content and distribution of several cytoskeletal proteins including the astroglial marker, glial fibrillary acidic protein (GFAP), and the levels of plasma-membrane glycoproteins, reduces the capacity of astrocytes to secrete growth factors, and induces oxidative stress. Furthermore, ethanol exposure during early embryogenesis alters the normal development of radial glia cells (the main astrocytic precursors), delays the onset of GFAP expression, and decreases mRNA GFAP levels in fetal and postnatal brains and in radial glia and astrocytes in primary culture. Recent evidence suggests that ethanol interferes with the transcription process of GFAP, thus leading to a reduction in GFAP-gene expression during astrogliogenesis. However, brief exposure of rats to high levels of ethanol during the neonatal period (the period of astrocyte differentiation) causes a transient gliosis, with an increase in GFAP and its mRNA levels. These findings indicate that astroglial cells are an important target of ethanol toxicity during central nervous system (CNS) development.
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Affiliation(s)
- C Guerri
- Instituto Investigaciones Citológicas (FVIB), Amadeo de Saboya, Valencia
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19
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Anciaux K, Van Dommelen K, Nicola� S, Van Mechelen E, Slegers H. Cyclic AMP-mediated induction of the glial fibrillary acidic protein is independent of protein kinase A activation in rat C6 glioma. J Neurosci Res 1997. [DOI: 10.1002/(sici)1097-4547(19970515)48:4<324::aid-jnr4>3.0.co;2-d] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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20
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Teter B, Rozovsky I, Krohn K, Anderson C, Osterburg H, Finch C. Methylation of the glial fibrillary acidic protein gene shows novel biphasic changes during brain development. Glia 1996; 17:195-205. [PMID: 8840161 DOI: 10.1002/(sici)1098-1136(199607)17:3<195::aid-glia2>3.0.co;2-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The gene for glial fibrillary acidic protein (GFAP) was analyzed in the rat for developmental changes in methylation of cytosine at CpG sequences as a correlate of the onset of GFAP mRNA expression and for the effect of methylation on GFAP promoter activity. The methylation of nine CpG sites in the GFAP promoter and ten sites in exon 1 was analyzed in F344 rats by a quantitative application of ligation-mediated polymerase chain reaction. Whole rat brain poly(A)+ RNA showed an exponential increase of GFAP mRNA after embryo day 14 that reached stable adult levels by postnatal day 10. During development, only the seven CpG sites in the far-upstream promoter showed large changes in methylation; these sites constitute the brain-specific domain of methylation described in adult rats (Teter et al: J Neurosci Res 39:680, 1994). These seven CpG sites showed a cycle of demethylation during the onset of GFAP transcription in the embryo (between embryonic day 14 and postnatal day 10) followed by remethylation at later postnatal ages when GFAP mRNA remains prevalent. The minimum levels of methylation across these CpG sites displayed a gradient with the lowest minima at the 3' sites. This demethylation/remethylation cycle is a novel phenomenon in DNA methylation during perinatal development. The demethylation/remethylation cycle during development was also shown by the opposite-strand cytosines. Two cytosines in this region that are conserved in rat and mouse also undergo the same demethylation/remethylation cycle in the mouse GFAP gene during development, implying evolutionary conservation and functional significance. As a further test of functional significance, a Luciferase reporter gene assay was evaluated in primary cultured astrocytes; the activity of the GFAP promoter was reduced when it was methylated at one or all CpG sites. Therefore, the GFAP promoter may be activated in rodent development by transient demethylation of a conserved brain-specific methylation domain.
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Affiliation(s)
- B Teter
- Neurogerontology Division, Andrus Gerontology Center, University of Southern California, Los Angeles 90089-0191, USA
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21
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Hagiwara N, Sueoka N. Regulation of the rat S100 beta gene expression: the role of the 2 kb 5'-upstream sequence in glial specific expression. J Neurosci Res 1995; 42:603-12. [PMID: 8600292 DOI: 10.1002/jnr.490420502] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We have studied the role of the 2047 bp 5'-upstream region and 232 bp first exon sequence of the rat S100 beta gene in glial specific expression. S100 beta luciferase expression vectors carrying serial deletions of the S100 beta 5' upstream sequence were constructed and transiently transfected into the peripheral nervous system (PNS) glial-type cell line RT4-D6, the PNS neuronal-type cell line RT4-E5, and the central nervous system (CNS) glial-type cell line C6. The hepatoma cell line HTC was also transfected as a nonneural control. From this functional analysis, we found a glial-specific positive regulatory sequence(s) mapped between -583 and -106 relative to the transcriptional start site. This region confers a significantly higher level of luciferase expression in the glial-type cell lines RT4-D6 and C6 than in the neuronal cell line RT4-E5 and the hepatoma cell line HTC. Also, a non-cell type specific positive regulatory element was identified in the first exon sequence between +78 and +232. Though non-cell type-specific, it was found to have a predominant effect in glial cells. From these observations, we have concluded that the 2047 bp 5'-upstream region and 232 bp of the first exon sequence confers the high levels of S100 beta expression in glial cells through these two positive elements.
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Affiliation(s)
- N Hagiwara
- Department of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder 80309, USA
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22
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Johnson WB, Ruppe MD, Rockenstein EM, Price J, Sarthy VP, Verderber LC, Mucke L. Indicator expression directed by regulatory sequences of the glial fibrillary acidic protein (GFAP) gene: in vivo comparison of distinct GFAP-lacZ transgenes. Glia 1995; 13:174-84. [PMID: 7782103 DOI: 10.1002/glia.440130304] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
An increase in the expression of the glial fibrillary acidic protein (GFAP) gene by astrocytes appears to constitute a crucial component of the brain's response to injury because it is seen in many different species and features prominently in diverse neurological diseases. Previously, we have used a modified GFAP gene (C-339) to target the expression of beta-galactosidase (beta-gal) to astrocytes in transgenic mice (Mucke et al.; New Biol 3:465-474 1991). To determine to what extent the in vivo expression of GFAP-driven fusion genes is influenced by intragenic GFAP sequences, the E. coli lacZ reporter gene was either placed downstream of approximately 2 kb of murine GFAP 5' flanking region (C-259) or ligated into exon 1 of the entire murine GFAP gene (C-445). Transgenic mice expressing C-259 versus C-445 showed similar levels and distributions of beta-gal activity in their brains. Exclusion of intragenic GFAP sequences from the GFAP-lacZ fusion gene did not diminish injury-induced upmodulation of astroglial beta-gal expression or increase beta-gal expression in non-astrocytic brain cells. These results demonstrate that 2 kb of murine GFAP 5' flanking region is sufficient to restrict transgene expression primarily to astrocytes and to mediate injury-responsiveness in vivo. This sequence therefore constitutes a critical target for mediators of reactive astrocytosis. While acute penetrating brain injuries induced focal increases in beta-gal expression around the lesion sites in C-259, C-445, and C-339 transgenic mice, infection of C-339 transgenic mice with scrapie led to a widespread upmodulation of astroglial beta-gal expression. Hence, GFAP-lacZ transgenic mice can be used to monitor differential patterns of astroglial activation in vivo. These and related models should facilitate the assessment of strategies aimed at the in vivo manipulation of GFAP expression and astroglial activation.
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Affiliation(s)
- W B Johnson
- Department of Neuropharmacology, Scripps Research Institute, La Jolla, California 92037, USA
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23
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Teter B, Finch CE, Condorelli DF. DNA methylation in the glial fibrillary acidic protein gene: map of CpG methylation sites and summary of analysis by restriction enzymes and by LMPCR. J Neurosci Res 1994; 39:708-9. [PMID: 7897705 DOI: 10.1002/jnr.490390611] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- B Teter
- Neurogerontology Division, Andrus Gerontology Center, University of Southern California, Los Angeles 90089-0191
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Teter B, Osterburg HH, Anderson CP, Finch CE. Methylation of the rat glial fibrillary acidic protein gene shows tissue-specific domains. J Neurosci Res 1994; 39:680-93. [PMID: 7897703 DOI: 10.1002/jnr.490390609] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The gene for glial fibrillary acidic protein (GFAP) was compared for CpG sites that are potential locations of methylated cytosine (mC). GFAP sequences in the 5'-upstream promoter and in exon 1 of rat, mouse, and human showed extensive similarity in the locations of CpG sites in the promoter and in exon 1, implying conservation. The methylation of mC at 9 CpG sites in the promoter and 10 sites in exon 1 was analyzed in F344 male rats by a quantitative application of ligation-mediated polymerase chain reaction (LMPCR). CpG sites with varying mC in different tissues were found in the GFAP promoter and in a CpG island in exon 1. In the brain, the promoter had about 40% less mC than in testis and liver. The degree of methylation varied strikingly between adjacent sites within and between tissues. Testis GFAP exon 1 had a gradient of mC from 5' to 3' across the exon that was absent in liver, brain, and cultured neurons and astrocytes. Among brain regions, the hippocampus had 10-40% less mC at 12 CpG sites than in hypothalamus; the other sites (7/19) showed smaller differences between these brain regions. In DNA from primary cultures, astrocytes had slightly less mC than neurons at all sites. Because neuron-rich hippocampal subregions and primary neurons cultures had less methylation than nonneural tissues, we hypothesize that neuroectodermal derivatives tend to be less methylated, whether or not GFAP is expressed. Four domains of methylated CpG sites are proposed on the basis of tissue and cell-type distribution: I) a constitutively methylated domain in the mid-upstream promoter; II) a testis-specific gradient of methylation in exon 1; III) a hypomethylated domain found in neuroectodermal derivatives; and IV) subsets of sites in the promoter and in exon 1 that have the least methylation in astrocytes, and therefore may be astrocyte-specific domains.
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Affiliation(s)
- B Teter
- Neurogerontology Division, Andrus Gerontology Center, University of Southern California, Los Angeles 90089-0191
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25
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Laping NJ, Teter B, Anderson CP, Osterburg HH, O'Callaghan JP, Johnson SA, Finch CE. Age-related increases in glial fibrillary acidic protein do not show proportionate changes in transcription rates or DNA methylation in the cerebral cortex and hippocampus of male rats. J Neurosci Res 1994; 39:710-7. [PMID: 7897706 DOI: 10.1002/jnr.490390612] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Age-related increases in the expression of glial fibrillary acidic protein (GFAP) in many brain regions are observed in short- and long-lived mammals. Possible genomic mechanisms for the increase of GFAP mRNA and protein were studied in the hippocampus and cortex of male F344 rats and a longer-lived hybrid F1 (F344 x Brown Norway). No age-related changes were found in the extent of cytosine methylation at 19 CpG sites in the 5'-upstream GFAP promoter and in exon 1. With the nuclear runon assay, no change was found in the transcription rate of GFAP in the cerebral cortex or hippocampus. Thus, age-related increases in GFAP are not associated with proportionate changes in transcription rates or DNA methylation. However, the transcription of glutamine synthetase was increased by about 60%. These findings contrast with age-related loss of bulk tissue DNA methylation and decreased transcription rates of other genes reported in non-neural tissues.
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Affiliation(s)
- N J Laping
- Renal Pharmacology Department, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania
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26
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Condorelli DF, Nicoletti VG, Barresi V, Caruso A, Conticello S, de Vellis J, Giuffrida Stella AM. Tissue-specific DNA methylation patterns of the rat glial fibrillary acidic protein gene. J Neurosci Res 1994; 39:694-707. [PMID: 7897704 DOI: 10.1002/jnr.490390610] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The glial fibrillary acidic protein (GFAP) is an intermediate filament protein, specific of the cytoskeleton of astrocytes in the central nervous system. In the present work, as a preliminary step to the study of glial-specific gene expression, we cloned the rat GFAP gene, and we report the sequence of 1.9 kb of the 5' flanking region, exon 1, and the majority of the first intron. By digestion with methylation-sensitive restriction enzymes followed by Southern blot analysis, the methylation status of various CpG sites was examined in this genomic segment. We tested whether structural modification of the GFAP gene, such as DNA methylation, could be related to its tissue-specific transcriptional activity. Therefore, we compared a GFAP-expressing cell population (primary culture of astroglial cells), a mixed population of GFAP-expressing and -nonexpressing cells (adult rat cerebral hemispheres), and a GFAP-nonexpressing tissue (liver). In the 5' flanking region we identified a CpG site at position -1176 whose level of methylation is inversely correlated to GFAP expression. In primary cultured astrocytes, 75% of the GFAP gene alleles were demethylated at this site, while the corresponding value obtained for the cerebral hemispheres was 45%, and for liver only 9%. On the basis of the sequence data, a CpG-rich region (putative CpG island) was identified extending from -38 to +347 and overlapping 80% of the first exon. HhaI and HpaII sites located in the putative CpG island showed a relatively high level of methylation in all the cell populations examined, and did not show any clear correlation with the level of GFAP gene expression or with the methylation status of the -1176 site. Further in vivo developmental studies and in vitro differentiation studies are necessary to better understand the functional differences of the various methylatable CpG sites in the 5' end of the GFAP gene.
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Affiliation(s)
- D F Condorelli
- Institute of Biochemistry, Faculty of Medicine, University of Catania, Italy
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27
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Laping NJ, Teter B, Nichols NR, Rozovsky I, Finch CE. Glial fibrillary acidic protein: regulation by hormones, cytokines, and growth factors. Brain Pathol 1994; 4:259-75. [PMID: 7952267 DOI: 10.1111/j.1750-3639.1994.tb00841.x] [Citation(s) in RCA: 178] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Levels of glial fibrillary acidic protein (GFAP), an astrocyte-specific intermediate filament protein, are altered during development and aging, GFAP also responds dynamically to neurodegenerative lesions. Changes in GFAP expression can occur at both transcriptional and translational levels. Modulators of GFAP expression include steroids, cytokines, and growth factors. GFAP expression also shows brain region-specific responses to sex steroids and of astrocyte-neuronal interactions. The 5'-upstream sequences of rat, mouse, and human are compared for the presence of response elements that are candidates for transcriptional regulation of GFAP. We propose that the regulation of the GFAP gene has evolved a system of controls that allow integrated responses to neuroendocrine and inflammatory modulators.
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Affiliation(s)
- N J Laping
- Neurogerontology Division, Andrus Gerontology Center, University of Southern California, Los Angeles 90089-0191
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28
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Abstract
Transcriptional regulation of the GFAP gene is intimately connected with astrocyte function: its initial activation marks the differentiation of astrocytes, and its up-regulation accompanies the reactive response to CNS injury. Studies of GFAP transcription should thus provide insights into multiple regulatory pathways operating in these cells. In addition, they should identify DNA elements that could be used to direct synthesis of other proteins to astrocytes in transgenic animals, permitting creation of disease models, and the testing of cause and effect relationships. This review describes several GFAP cDNA and genomic clones that have been isolated, including homology comparisons of the encoded RNAs and proteins. Cell transfection studies by several laboratories are summarized that have identified a DNA segment immediately upstream of the RNA start site that is essential for transcriptional activity, but which have yielded conflicting results concerning the importance of other segments located both further upstream and downstream of the RNA start site. Two procedures are recounted that have led to the successful expression of GFAP-transgenes in astrocytes in mice. One of these incorporates the transgene into the first exon of a fragment spanning the entire GFAP gene, while the other links it to a 2 kb 5'-flanking segment. Results already produced by GFAP-transgenic studies include demonstration of a neurotoxic effect of the HIV-1 gp120 coat protein, and creation of a hydrocephalic mouse model.
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Affiliation(s)
- M Brenner
- Stroke Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
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