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McClain J, Grubišić V, Fried D, Gomez-Suarez RA, Leinninger GM, Sévigny J, Parpura V, Gulbransen BD. Ca2+ responses in enteric glia are mediated by connexin-43 hemichannels and modulate colonic transit in mice. Gastroenterology 2014; 146:497-507.e1. [PMID: 24211490 PMCID: PMC3935238 DOI: 10.1053/j.gastro.2013.10.061] [Citation(s) in RCA: 148] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 10/18/2013] [Accepted: 10/30/2013] [Indexed: 12/17/2022]
Abstract
BACKGROUND & AIMS In the enteric nervous system, neurotransmitters initiate changes in calcium (Ca(2+) responses) in glia, but it is not clear how this process affects intestinal function. We investigated whether Ca(2+)-mediated responses in enteric glia are required to maintain gastrointestinal function. METHODS We used in situ Ca(2+) imaging to monitor glial Ca(2+) responses, which were manipulated with pharmacologic agents or via glia-specific disruption of the gene encoding connexin-43 (Cx43) (hGFAP::CreER(T2+/-)/Cx43(f/f) mice). Gastrointestinal function was assessed based on pellet output, total gut transit, colonic bead expulsion, and muscle tension recordings. Proteins were localized and quantified by immunohistochemistry, immunoblot, and reverse transcription polymerase chain reaction analyses. RESULTS Ca(2+) responses in enteric glia of mice were mediated by Cx43 hemichannels. Cx43 immunoreactivity was confined to enteric glia within the myenteric plexus of the mouse colon; the Cx43 inhibitors carbenoxolone and 43Gap26 inhibited the ability of enteric glia to propagate Ca(2+) responses. In vivo attenuation of Ca(2+) responses in the enteric glial network slowed gut transit overall and delayed colonic transit--these changes are also observed during normal aging. Altered motility with increasing age was associated with reduced glial Ca(2+)-mediated responses and changes in glial expression of Cx43 messenger RNA and protein. CONCLUSIONS Ca(2+)-mediated responses in enteric glia regulate gastrointestinal function in mice. Altered intercellular signaling between enteric glia and neurons might contribute to motility disorders.
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Affiliation(s)
- Jonathon McClain
- Neuroscience Program and Department of Physiology, Michigan State University, 567 Wilson Road, East Lansing, MI, 48824 USA
| | - Vladimir Grubišić
- Department of Neurobiology, Center for Glial Biology in Medicine, Atomic Force Microscopy and Nanotechnology Laboratories, Civitan International Research Center, Evelyn F. McKnight Brain Institute, University of Alabama, Birmingham, AL 35294, USA
| | - David Fried
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI 48824
| | - Roberto A Gomez-Suarez
- Department of Neurobiology, Center for Glial Biology in Medicine, Atomic Force Microscopy and Nanotechnology Laboratories, Civitan International Research Center, Evelyn F. McKnight Brain Institute, University of Alabama, Birmingham, AL 35294, USA.,Department of Pediatrics Division of Pediatric Gastroenterology Hepatology And Nutrition at Nemours Chlidren's Hospital. Orlando, FL 32827, USA
| | - Gina M Leinninger
- Neuroscience Program and Department of Physiology, Michigan State University, 567 Wilson Road, East Lansing, MI, 48824 USA
| | - Jean Sévigny
- Département de microbiologie-infectiologie et d'immunologie, Faculté de Médecine, Université Laval, Québec, QC, Canada.,Centre de recherche du CHU de Québec, Québec, QC, G1V 4G2 Canada
| | - Vladimir Parpura
- Department of Neurobiology, Center for Glial Biology in Medicine, Atomic Force Microscopy and Nanotechnology Laboratories, Civitan International Research Center, Evelyn F. McKnight Brain Institute, University of Alabama, Birmingham, AL 35294, USA.,Department of Biotechnology, University of Rijeka, 51000 Rijeka, Croatia
| | - Brian D Gulbransen
- Neuroscience Program and Department of Physiology, Michigan State University, 567 Wilson Road, East Lansing, MI, 48824 USA
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Davila D, Thibault K, Fiacco TA, Agulhon C. Recent molecular approaches to understanding astrocyte function in vivo. Front Cell Neurosci 2013; 7:272. [PMID: 24399932 PMCID: PMC3871966 DOI: 10.3389/fncel.2013.00272] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 12/06/2013] [Indexed: 12/11/2022] Open
Abstract
Astrocytes are a predominant glial cell type in the nervous systems, and are becoming recognized as important mediators of normal brain function as well as neurodevelopmental, neurological, and neurodegenerative brain diseases. Although numerous potential mechanisms have been proposed to explain the role of astrocytes in the normal and diseased brain, research into the physiological relevance of these mechanisms in vivo is just beginning. In this review, we will summarize recent developments in innovative and powerful molecular approaches, including knockout mouse models, transgenic mouse models, and astrocyte-targeted gene transfer/expression, which have led to advances in understanding astrocyte biology in vivo that were heretofore inaccessible to experimentation. We will examine the recently improved understanding of the roles of astrocytes – with an emphasis on astrocyte signaling – in the context of both the healthy and diseased brain, discuss areas where the role of astrocytes remains debated, and suggest new research directions.
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Affiliation(s)
- David Davila
- Glia-Glia and Glia-Neuron Interactions Group, National Center for Scientific Research, UFR Biomedicale, Paris Descartes University Paris, France
| | - Karine Thibault
- Glia-Glia and Glia-Neuron Interactions Group, National Center for Scientific Research, UFR Biomedicale, Paris Descartes University Paris, France
| | - Todd A Fiacco
- Department of Cell Biology and Neuroscience, and Center for Glial-Neuronal Interactions and Program in Cellular, Molecular and Developmental Biology, University of California at Riverside Riverside, CA, USA
| | - Cendra Agulhon
- Glia-Glia and Glia-Neuron Interactions Group, National Center for Scientific Research, UFR Biomedicale, Paris Descartes University Paris, France
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Abstract
The use of cultures has informed us of functions and regulation of astrocytes that were previously unknown. This chapter details the methods that result in such cultures.
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54
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Mishra PK, Hsuchou H, Ouyang S, Kastin AJ, Wu X, Pan W. Loss of astrocytic leptin signaling worsens experimental autoimmune encephalomyelitis. Brain Behav Immun 2013; 34:98-107. [PMID: 23916894 PMCID: PMC3818286 DOI: 10.1016/j.bbi.2013.07.176] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2013] [Revised: 07/19/2013] [Accepted: 07/28/2013] [Indexed: 11/30/2022] Open
Abstract
Leptin is commonly thought to play a detrimental role in exacerbating experimental autoimmune encephalomyelitis (EAE) and multiple sclerosis. Paradoxically, we show here that astrocytic leptin signaling has beneficial effects in reducing disease severity. In the astrocyte specific leptin receptor knockout (ALKO) mouse in which leptin signaling is absent in astrocytes, there were higher EAE scores (more locomotor deficits) than in the wildtype counterparts. The difference mainly occurred at a late stage of EAE when wildtype mice showed signs of recovery whereas ALKO mice continued to deteriorate. The more severe symptoms in ALKO mice coincided with more infiltrating cells in the spinal cord and perivascular brain parenchyma, more demyelination, more infiltrating CD4 cells, and a lower percent of neutrophils in the spinal cord 28 days after EAE induction. Cultured astrocytes from wildtype mice showed increased adenosine release in response to interleukin-6 and the hippocampus of wildtype mice had increased adenosine production 28 days after EAE induction, but the ALKO mutation abolished the increase in both conditions. This indicates a role of astrocytic leptin in normal gliotransmitter release and astrocyte functions. The worsening of EAE in the ALKO mice in the late stage suggests that astrocytic leptin signaling helps to clear infiltrating leukocytes and reduce autoimmune destruction of the CNS.
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Affiliation(s)
| | | | | | | | | | - Weihong Pan
- Corresponding author: Weihong Pan, MD, PhD, Blood-Brain Barrier Group, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808, Tel. 225-763-2715; Fax 225-763-0261,
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55
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Li D, Agulhon C, Schmidt E, Oheim M, Ropert N. New tools for investigating astrocyte-to-neuron communication. Front Cell Neurosci 2013; 7:193. [PMID: 24194698 PMCID: PMC3810613 DOI: 10.3389/fncel.2013.00193] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 10/07/2013] [Indexed: 12/24/2022] Open
Abstract
Gray matter protoplasmic astrocytes extend very thin processes and establish close contacts with synapses. It has been suggested that the release of neuroactive gliotransmitters at the tripartite synapse contributes to information processing. However, the concept of calcium (Ca2+)-dependent gliotransmitter release from astrocytes, and the release mechanisms are being debated. Studying astrocytes in their natural environment is challenging because: (i) astrocytes are electrically silent; (ii) astrocytes and neurons express an overlapping repertoire of transmembrane receptors; (iii) the size of astrocyte processes in contact with synapses are below the resolution of confocal and two-photon microscopes (iv) bulk-loading techniques using fluorescent Ca2+ indicators lack cellular specificity. In this review, we will discuss some limitations of conventional methodologies and highlight the interest of novel tools and approaches for studying gliotransmission. Genetically encoded Ca2+ indicators (GECIs), light-gated channels, and exogenous receptors are being developed to selectively read out and stimulate astrocyte activity. Our review discusses emerging perspectives on: (i) the complexity of astrocyte Ca2+ signaling revealed by GECIs; (ii) new pharmacogenetic and optogenetic approaches to activate specific Ca2+ signaling pathways in astrocytes; (iii) classical and new techniques to monitor vesicle fusion in cultured astrocytes; (iv) possible strategies to express specifically reporter genes in astrocytes.
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Affiliation(s)
- Dongdong Li
- Biophysics of Gliotransmitter Release Team, Laboratory of Neurophysiology and New Microscopies, INSERM U603, CNRS UMR 8154, University Paris Descartes Paris, France
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Abstract
Glioblastoma (GBM), the most common brain malignancy, remains fatal with no effective treatment. Analyses of common aberrations in GBM suggest major regulatory pathways associated with disease etiology. However, 90% of GBMs are diagnosed at an advanced stage (primary GBMs), providing no access to early disease stages for assessing disease progression events. As such, both understanding of disease mechanisms and the development of biomarkers and therapeutics for effective disease management are limited. Here, we describe an adult-inducible astrocyte-specific system in genetically engineered mice that queries causation in disease evolution of regulatory networks perturbed in human GBM. Events yielding disease, both engineered and spontaneous, indicate ordered grade-specific perturbations that yield high-grade astrocytomas (anaplastic astrocytomas and GBMs). Impaired retinoblastoma protein RB tumor suppression yields grade II histopathology. Additional activation of v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) network drives progression to grade III disease, and further inactivation of phosphatase and tensin homolog (PTEN) yields GBM. Spontaneous missense mutation of tumor suppressor Trp53 arises subsequent to KRAS activation, but before grade III progression. The stochastic appearance of mutations identical to those observed in humans, particularly the same spectrum of p53 amino acid changes, supports the validity of engineered lesions and the ensuing interpretations of etiology. Absence of isocitrate dehydrogenase 1 (IDH1) mutation, asymptomatic low grade disease, and rapid emergence of GBM combined with a mesenchymal transcriptome signature reflect characteristics of primary GBM and provide insight into causal relationships.
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57
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β-Catenin is critical for cerebellar foliation and lamination. PLoS One 2013; 8:e64451. [PMID: 23691221 PMCID: PMC3656863 DOI: 10.1371/journal.pone.0064451] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Accepted: 04/15/2013] [Indexed: 11/19/2022] Open
Abstract
The cerebellum has a conserved foliation pattern and a well-organized layered structure. The process of foliation and lamination begins around birth. β-catenin is a downstream molecule of Wnt signaling pathway, which plays a critical role in tissue organization. Lack of β-catenin at early embryonic stages leads to either prenatal or neonatal death, therefore it has been difficult to resolve its role in cerebellar foliation and lamination. Here we used GFAP-Cre to ablate β-catenin in neuronal cells of the cerebellum after embryonic day 12.5, and found an unexpected role of β-catenin in determination of the foliation pattern. In the mutant mice, the positions of fissure formation were changed, and the meninges were improperly incorporated into fissures. At later stages, some lobules were formed by Purkinje cells remaining in deep regions of the cerebellum and the laminar structure was dramatically altered. Our results suggest that β-catenin is critical for cerebellar foliation and lamination. We also found a non cell-autonomous role of β-catenin in some developmental properties of major cerebellar cell types during specific stages.
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58
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Jayaram B, Pan W, Wang Y, Hsuchou H, Mace A, Cornelissen-Guillaume GG, Mishra PK, Koza RA, Kastin AJ. Astrocytic leptin-receptor knockout mice show partial rescue of leptin resistance in diet-induced obesity. J Appl Physiol (1985) 2013; 114:734-41. [PMID: 23329815 DOI: 10.1152/japplphysiol.01499.2012] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
To determine how astrocytic leptin signaling regulates the physiological response of mice to diet-induced obesity (DIO), we performed metabolic analyses and hypothalamic leptin signaling assays on astrocytic leptin-receptor knockout (ALKO) mice in which astrocytes lack functional leptin receptor (ObR) signaling. ALKO mice and wild-type (WT) littermate controls were studied at different stages of DIO with measurement of body wt, percent fat, metabolic activity, and biochemical parameters. When fed regular chow, the ALKO mice had similar body wt, percent fat, food intake, heat dissipation, respiratory exchange ratio, and activity as their WT littermates. There was no change in blood concentrations of triglyceride, soluble leptin receptor (sObR), mRNA for leptin and uncoupling protein 1 (UCP1) in adipose tissue, and insulin sensitivity. Unexpectedly, in response to a high-fat diet the ALKO mice had attenuated hyperleptinemia and sObR, a lower level of leptin mRNA in subcutaneous fat, and a paradoxical increase in UCP1 mRNA. Thus, ALKO mice did not show the worsening of obesity that occurs with normal WT mice and the neuronal ObR mutation that results in morbid obesity. The findings are consistent with a competing, counterregulatory model between neuronal and astrocytic leptin signaling.
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Affiliation(s)
- Bhavaani Jayaram
- Pennington Biomedical Research Center, Baton Rouge, Louisiana 70808, USA
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59
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Suppression of neuroinflammation by astrocytic dopamine D2 receptors via αB-crystallin. Nature 2012; 494:90-4. [PMID: 23242137 DOI: 10.1038/nature11748] [Citation(s) in RCA: 316] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 11/07/2012] [Indexed: 01/05/2023]
Abstract
Chronic neuroinflammation is a common feature of the ageing brain and some neurodegenerative disorders. However, the molecular and cellular mechanisms underlying the regulation of innate immunity in the central nervous system remain elusive. Here we show that the astrocytic dopamine D2 receptor (DRD2) modulates innate immunity through αB-crystallin (CRYAB), which is known to suppress neuroinflammation. We demonstrate that knockout mice lacking Drd2 showed remarkable inflammatory response in multiple central nervous system regions and increased the vulnerability of nigral dopaminergic neurons to neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity. Astrocytes null for Drd2 became hyper-responsive to immune stimuli with a marked reduction in the level of CRYAB. Preferential ablation of Drd2 in astrocytes robustly activated astrocytes in the substantia nigra. Gain- or loss-of-function studies showed that CRYAB is critical for DRD2-mediated modulation of innate immune response in astrocytes. Furthermore, treatment of wild-type mice with the selective DRD2 agonist quinpirole increased resistance of the nigral dopaminergic neurons to MPTP through partial suppression of inflammation. Our study indicates that astrocytic DRD2 activation normally suppresses neuroinflammation in the central nervous system through a CRYAB-dependent mechanism, and provides a new strategy for targeting the astrocyte-mediated innate immune response in the central nervous system during ageing and disease.
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60
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Glioblastoma, a Brief Review of History, Molecular Genetics, Animal Models and Novel Therapeutic Strategies. Arch Immunol Ther Exp (Warsz) 2012; 61:25-41. [DOI: 10.1007/s00005-012-0203-0] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Accepted: 11/22/2012] [Indexed: 01/06/2023]
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61
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Local generation of glia is a major astrocyte source in postnatal cortex. Nature 2012; 484:376-80. [PMID: 22456708 DOI: 10.1038/nature10959] [Citation(s) in RCA: 335] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Accepted: 02/14/2012] [Indexed: 12/21/2022]
Abstract
Glial cells constitute nearly 50% of the cells in the human brain. Astrocytes, which make up the largest glial population, are crucial to the regulation of synaptic connectivity during postnatal development. Because defects in astrocyte generation are associated with severe neurological disorders such as brain tumours, it is important to understand how astrocytes are produced. Astrocytes reportedly arise from two sources: radial glia in the ventricular zone and progenitors in the subventricular zone, with the contribution from each region shifting with time. During the first three weeks of postnatal development, the glial cell population, which contains predominantly astrocytes, expands 6-8-fold in the rodent brain. Little is known about the mechanisms underlying this expansion. Here we show that a major source of glia in the postnatal cortex in mice is the local proliferation of differentiated astrocytes. Unlike glial progenitors in the subventricular zone, differentiated astrocytes undergo symmetric division, and their progeny integrate functionally into the existing glial network as mature astrocytes that form endfeet with blood vessels, couple electrically to neighbouring astrocytes, and take up glutamate after neuronal activity.
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62
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Abstract
Astroglial cells, due to their passive electrical properties, were long considered subservient to neurons and to merely provide the framework and metabolic support of the brain. Although astrocytes do play such structural and housekeeping roles in the brain, these glial cells also contribute to the brain's computational power and behavioural output. These more active functions are endowed by the Ca2+-based excitability displayed by astrocytes. An increase in cytosolic Ca2+ levels in astrocytes can lead to the release of signalling molecules, a process termed gliotransmission, via the process of regulated exocytosis. Dynamic components of astrocytic exocytosis include the vesicular-plasma membrane secretory machinery, as well as the vesicular traffic, which is governed not only by general cytoskeletal elements but also by astrocyte-specific IFs (intermediate filaments). Gliotransmitters released into the ECS (extracellular space) can exert their actions on neighbouring neurons, to modulate synaptic transmission and plasticity, and to affect behaviour by modulating the sleep homoeostat. Besides these novel physiological roles, astrocytic Ca2+ dynamics, Ca2+-dependent gliotransmission and astrocyte–neuron signalling have been also implicated in brain disorders, such as epilepsy. The aim of this review is to highlight the newer findings concerning Ca2+ signalling in astrocytes and exocytotic gliotransmission. For this we report on Ca2+ sources and sinks that are necessary and sufficient for regulating the exocytotic release of gliotransmitters and discuss secretory machinery, secretory vesicles and vesicle mobility regulation. Finally, we consider the exocytotic gliotransmission in the modulation of synaptic transmission and plasticity, as well as the astrocytic contribution to sleep behaviour and epilepsy.
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63
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Benneyworth MA, Li Y, Basu AC, Bolshakov VY, Coyle JT. Cell selective conditional null mutations of serine racemase demonstrate a predominate localization in cortical glutamatergic neurons. Cell Mol Neurobiol 2012; 32:613-24. [PMID: 22362148 DOI: 10.1007/s10571-012-9808-4] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 01/19/2012] [Indexed: 11/25/2022]
Abstract
D-serine, which is synthesized by the enzyme serine racemase (SR), is a co-agonist at the N-methyl-D-aspartate receptor (NMDAR). Crucial to an understanding of the signaling functions of D-serine is defining the sites responsible for its synthesis and release. In order to quantify the contributions of astrocytes and neurons to SR and D-serine localization, we used recombinant DNA techniques to effect cell type selective suppression of SR expression in astrocytes (aSRCKO) and in forebrain glutamatergic neurons (nSRCKO). The majority of SR is expressed in neurons: SR expression was reduced by ~65% in nSRCKO cerebral cortex and hippocampus, but only ~15% in aSRCKO as quantified by western blots. In contrast, nSRCKO is associated with only modest decreases in D-serine levels as quantified by HPLC, whereas D-serine levels were unaffected in aSRCKO mice. Liver expression of SR was increased by 35% in the nSRCKO, suggesting a role for peripheral SR in the maintenance of brain D-serine. Electrophysiologic studies of long-term potentiation (LTP) at the Schaffer collateral-CA1 pyramidal neuron synapse revealed no alterations in the aSRCKO mice versus wild-type. LTP induced by a single tetanic stimulus was reduced by nearly 70% in the nSRCKO mice. Furthermore, the mini-excitatory post-synaptic currents mediated by NMDA receptors but not by AMPA receptors were significantly reduced in nSRCKO mice. Our findings indicate that in forebrain, where D-serine appears to be the endogenous co-agonist at NMDA receptors, SR is predominantly expressed in glutamatergic neurons, and co-release of glutamate and D-serine is required for optimal activation of post-synaptic NMDA receptors.
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64
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Transgenic techniques for cell ablation or molecular deletion to investigate functions of astrocytes and other GFAP-expressing cell types. Methods Mol Biol 2012; 814:531-44. [PMID: 22144330 DOI: 10.1007/978-1-61779-452-0_35] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Genetic tools are enabling the molecular dissection of the functions and mechanisms of many biological processes. Transgenic manipulations provide powerful tools with which to test hypotheses regarding functions of specific cell types and molecules in vivo in combination with different types of experimental models. Various techniques are available that can target genetic manipulations specifically to astrocytes and that are enabling the molecular dissection of astrocyte biology in vivo. This article summarizes procedures and experience from our laboratory using transgenic strategies that enable either the ablation of proliferating astrocytes and related cells, or the deletion of specific molecules selectively from astrocytes, to study the functions of astrocytes and related cell types in health and disease in vivo using different experimental mouse models.
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65
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Pfrieger FW, Slezak M. Genetic approaches to study glial cells in the rodent brain. Glia 2011; 60:681-701. [PMID: 22162024 DOI: 10.1002/glia.22283] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Accepted: 11/18/2011] [Indexed: 01/02/2023]
Abstract
The development, function, and pathology of the brain depend on interactions of neurons and different types of glial cells, namely astrocytes, oligodendrocytes, microglia, and ependymal cells. Understanding neuron-glia interactions in vivo requires dedicated experimental approaches to manipulate each cell type independently. In this review, we first summarize techniques that allow for cell-specific gene modification including targeted mutagenesis and viral transduction. In the second part, we describe the genetic models that allow to target the main glial cell types in the central nervous system. The existing arsenal of approaches to study glial cells in vivo and its expansion in the future are key to understand neuron-glia interactions under normal and pathologic conditions.
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Affiliation(s)
- Frank W Pfrieger
- CNRS UPR 3212, University of Strasbourg, Institute of Cellular and Integrative Neurosciences (INCI), 67084 Strasbourg, France.
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66
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Yu T, Shakkottai VG, Chung C, Lieberman AP. Temporal and cell-specific deletion establishes that neuronal Npc1 deficiency is sufficient to mediate neurodegeneration. Hum Mol Genet 2011; 20:4440-51. [PMID: 21856732 DOI: 10.1093/hmg/ddr372] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Niemann-Pick type C (NPC) disease is an autosomal recessive lysosomal storage disorder caused by mutations in the NPC1 or NPC2 genes. Loss of function mutations in either gene disrupt intracellular lipid trafficking and lead to a clinically heterogeneous phenotype that invariably includes neurological dysfunction and early death. The mechanism by which impaired lipid transport leads to neurodegeneration is poorly understood. Here we used mice with a conditional null allele to establish the timing and cell type that underlie neurodegeneration due to Npc1 deficiency. We show that global deletion of Npc1 in adult mice leads to progressive weight loss, impaired motor function and early death in a time course similar to that resulting from germline deletion. These phenotypes are associated with the occurrence of characteristic neuropathology including patterned Purkinje cell loss, axonal spheroids and reactive gliosis, demonstrating that there is not a significant developmental component to NPC neurodegeneration. Furthermore, we show that these same changes occur when Npc1 is specifically deleted only in neurons, establishing that neuronal deficiency is sufficient to mediate central nervous system (CNS) disease. In contrast, astrocyte-specific deletion does not impact behavioral phenotypes, CNS histopathology or synaptic function. We conclude that defects arising in neurons, but not in astrocytes, are the determining factor in the development of NPC neuropathology.
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Affiliation(s)
- Ting Yu
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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67
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Hsuchou H, Kastin AJ, Tu H, Markadakis EN, Stone KP, Wang Y, Heymsfield SB, Chua SS, Obici S, Magrisso IJ, Pan W. Effects of cell-type specific leptin receptor mutation on leptin transport across the BBB. Peptides 2011; 32:1392-9. [PMID: 21616110 PMCID: PMC3137692 DOI: 10.1016/j.peptides.2011.05.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Revised: 05/09/2011] [Accepted: 05/09/2011] [Indexed: 11/19/2022]
Abstract
The functions of leptin receptors (LRs) are cell-type specific. At the blood-brain barrier, LRs mediate leptin transport that is essential for its CNS actions, and both endothelial and astrocytic LRs may be involved. To test this, we generated endothelia specific LR knockout (ELKO) and astrocyte specific LR knockout (ALKO) mice. ELKO mice were derived from a cross of Tie2-cre recombinase mice with LR-floxed mice, whereas ALKO mice were generated by a cross of GFAP-cre with LR-floxed mice, yielding mutant transmembrane LRs without signaling functions in endothelial cells and astrocytes, respectively. The ELKO mutation did not affect leptin half-life in blood or apparent influx rate to the brain and spinal cord, though there was an increase of brain parenchymal uptake of leptin after in situ brain perfusion. Similarly, the ALKO mutation did not affect blood-brain barrier permeation of leptin or its degradation in blood and brain. The results support our observation from cellular studies that membrane-bound truncated LRs are fully efficient in transporting leptin, and that basal levels of astrocytic LRs do not affect leptin transport across the endothelial monolayer. Nonetheless, the absence of leptin signaling at the BBB appears to enhance the availability of leptin to CNS parenchyma. The ELKO and ALKO mice provide new models to determine the dynamic regulation of leptin transport in metabolic and inflammatory disorders where cellular distribution of LRs is shifted.
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Affiliation(s)
- Hung Hsuchou
- Pennington Biomedical Research Center, Baton Rouge, LA 70808
| | - Abba J. Kastin
- Pennington Biomedical Research Center, Baton Rouge, LA 70808
| | - Hong Tu
- Pennington Biomedical Research Center, Baton Rouge, LA 70808
| | | | | | - Yuping Wang
- Pennington Biomedical Research Center, Baton Rouge, LA 70808
| | | | | | - Silvana Obici
- Obesity Research Center, University of Cincinnati, Cincinnati, Ohio 45237
| | - I. Jack Magrisso
- Obesity Research Center, University of Cincinnati, Cincinnati, Ohio 45237
| | - Weihong Pan
- Pennington Biomedical Research Center, Baton Rouge, LA 70808
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68
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Lioy DT, Garg SK, Monaghan CE, Raber J, Foust KD, Kaspar BK, Hirrlinger PG, Kirchhoff F, Bissonnette JM, Ballas N, Mandel G. A role for glia in the progression of Rett's syndrome. Nature 2011; 475:497-500. [PMID: 21716289 DOI: 10.1038/nature10214] [Citation(s) in RCA: 367] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Accepted: 05/18/2011] [Indexed: 11/09/2022]
Abstract
Rett's syndrome (RTT) is an X-chromosome-linked autism spectrum disorder caused by loss of function of the transcription factor methyl-CpG-binding protein 2 (MeCP2). Although MeCP2 is expressed in most tissues, loss of MeCP2 expression results primarily in neurological symptoms. Earlier studies suggested the idea that RTT is due exclusively to loss of MeCP2 function in neurons. Although defective neurons clearly underlie the aberrant behaviours, we and others showed recently that the loss of MECP2 from glia negatively influences neurons in a non-cell-autonomous fashion. Here we show that in globally MeCP2-deficient mice, re-expression of Mecp2 preferentially in astrocytes significantly improved locomotion and anxiety levels, restored respiratory abnormalities to a normal pattern, and greatly prolonged lifespan compared to globally null mice. Furthermore, restoration of MeCP2 in the mutant astrocytes exerted a non-cell-autonomous positive effect on mutant neurons in vivo, restoring normal dendritic morphology and increasing levels of the excitatory glutamate transporter VGLUT1. Our study shows that glia, like neurons, are integral components of the neuropathology of RTT, and supports the targeting of glia as a strategy for improving the associated symptoms.
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Affiliation(s)
- Daniel T Lioy
- Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239, USA
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69
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Genetically engineered mouse models of diffuse gliomas. Brain Res Bull 2011; 88:72-9. [PMID: 21684324 DOI: 10.1016/j.brainresbull.2011.06.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Accepted: 06/05/2011] [Indexed: 01/06/2023]
Abstract
Over the last decade, genetically engineered mouse models have been extensively used to dissect the genetic requirements for neoplastic initiation and progression of diffuse gliomas. While these models faithfully recapitulate the histopathological features of human gliomas, comparative genomic analyses are increasingly being utilized to comprehensively assess their fidelity to recently identified molecular subtypes of these tumors. Future progress with these models will rely on incorporating insights not only from oncogenomics studies of cancer, but also from the developmental neuroscience and stem cell biology fields to design accurate and experimentally tractable models for use in translational cancer research, particularly for experimental therapeutics studies of molecularly defined subtypes of gliomas.
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70
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Weber T, Baier V, Pauly R, Sahay A, Baur M, Herrmann E, Ciccolini F, Hen R, Kronenberg G, Bartsch D. Inducible gene expression in GFAP+ progenitor cells of the SGZ and the dorsal wall of the SVZ-A novel tool to manipulate and trace adult neurogenesis. Glia 2011; 59:615-26. [PMID: 21294160 DOI: 10.1002/glia.21129] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Accepted: 11/25/2010] [Indexed: 01/07/2023]
Abstract
In the adult mammalian brain, neurogenesis originates from astrocyte-like stem cells. We generated a transgenic mouse line in which the tetracycline dependent transactivator (tTA) is expressed under the control of the murine GFAP promoter. In this mouse line, inducible gene expression targets virtually all GFAP-expressing stem-like cells in the dentate gyrus and a subset of GFAP-expressing progenitors located primarily in the dorsal wall/dorsolateral corner of the subventricular zone. Outside the neurogenic zones, astrocytes are infrequently targeted. We introduce a panel of transgenic mice which allow both inducible expression of candidate genes under control of the murine GFAP promoter and, at the same time, lineage tracing of all cells descendant from the original GFAP-positive cell. This new mouse line represents a versatile tool for functional analysis of neurogenesis and lineage tracing.
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Affiliation(s)
- Tillmann Weber
- Department of Molecular Biology, Central Institute of Mental Health, Heidelberg University, Medical Faculty Mannheim, Mannheim, Germany
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71
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Abstract
Gene targeting in ES cells is extensively used to generate designed mouse mutants and to study gene function in vivo. Knockout mice that harbor a null allele in their germline provide appropriate genetic models of inherited diseases and often exhibit embryonic or early postnatal lethality. To study gene function in adult mice and in selected cell types, a refined strategy for conditional gene inactivation has been developed that relies on the DNA recombinase Cre and its recognition (loxP) sites. For conditional mutagenesis, a target gene is modified by the insertion of two loxP sites that enable to excise the flanked (floxed) gene segment through Cre-mediated recombination. Conditional mutant mice are obtained by crossing the floxed strain with a Cre transgenic line such that the target gene becomes inactivated in vivo within the expression domain of Cre. A large collection of Cre transgenic lines has been generated over time and can be used in a combinatorial manner to achieve gene inactivation in many different cell types. A growing number of CreER(T2) transgenic mice further allows for inducible inactivation of floxed alleles in adult mice upon administration of tamoxifen. This chapter covers the design and construction of loxP flanked alleles and refers to the vectors, ES cells, and mice generated by the European conditional mouse mutagenesis (EUCOMM) project. We further describe the design and use of Cre and CreER(T2) transgenic mice and a convenient breeding strategy to raise conditional mutants and controls for phenotype analysis.
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72
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Dhara SK, Gerwe BA, Majumder A, Dodla MC, Boyd NL, Machacek DW, Hasneen K, Stice SL. Genetic manipulation of neural progenitors derived from human embryonic stem cells. Tissue Eng Part A 2010; 15:3621-34. [PMID: 19795983 DOI: 10.1089/ten.tea.2009.0155] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Human embryonic stem cell-derived neural progenitors (NP) present an important tool for understanding human development and disease. Optimal utilization of NP cells, however, requires an enhanced ability to monitor these cells in vitro and in vivo. Here we report production of the first genetically modified self-renewing human embryonic stem cell-derived NP cells that express fluorescent proteins under constitutive as well as lineage-specific promoters, enabling tracking and monitoring of cell fate. Nucleofection, transfection, and lentiviral transduction were compared for optimal gene delivery to NP cells. Transduction was most efficient in terms of transgene expression (37%), cell viability (39%), and long-term reporter expression (>3 months). Further, the constitutive gene promoters, cytomegalovirus, elongation factor 1alpha, and ubiquitin-C, exhibited comparable silencing (20-30%) in NP cells over a 2-month period, suggesting their suitability for long-term reporter expression studies. Transduced NP cells maintained their progenitor state and differentiation potential, as demonstrated by expression of endogenous NP markers and neuronal markers after differentiation. We also detected reporter expression in astrocytes generated from NP cells transduced with an astrocyte-specific gene promoter, glial fibrillary acidic protein, demonstrating the usefulness of this approach. The genetically manipulated NP cells described here offer great potential for live cell-tracking experiments, and a similar approach can as well be used for expression of proteins other than reporters.
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Affiliation(s)
- Sujoy K Dhara
- Regenerative Bioscience Center, University of Georgia, Athens, Georgia 30602, USA
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73
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Abstract
Understanding how cells are assembled in three dimensions to generate an organ, or a whole organism, is a pivotal question in developmental biology. Similarly, it is critical to understand how adult stem cells integrate into an existing organ during regeneration or in response to injury. Key to discovering the answers to these questions is being able to study the various behaviors of distinct cell types during development or regeneration. Fate mapping techniques are fundamental to studying cell behaviors such as proliferation, movement, and lineage segregation, as the techniques allow precursor cells to be marked and their descendants followed and characterized over time. The generation of transgenic mice, combined with the use of site-specific recombinases (SSR) in the mouse genome, has provided a means to develop powerful genetic fate mapping approaches. A key advantage of genetic fate mapping is that it allows cells to be genetically marked, and therefore the mark is transmitted to all the descendants of the initially marked cells. By making modifications to the SSRs that render their enzymatic activity inducible, and the development of an assortment of reporter alleles for marking cells, increasingly sophisticated genetic fate mapping studies can be performed. In this chapter, we review the four main genetic fate mapping methods that utilize intrachromosomal recombination to mark cells (cumulative, inducible, clonal, and intersectional) and one interchromosomal method, the tools required to carry out each approach, and the practical considerations that have to be taken into account before embarking on each type of genetic fate mapping study.
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Affiliation(s)
- Emilie Legué
- Memorial Sloan-Kettering Cancer Center, New York, USA
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74
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Sofroniew MV. Molecular dissection of reactive astrogliosis and glial scar formation. Trends Neurosci 2009; 32:638-47. [PMID: 19782411 DOI: 10.1016/j.tins.2009.08.002] [Citation(s) in RCA: 1874] [Impact Index Per Article: 124.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Revised: 08/11/2009] [Accepted: 08/31/2009] [Indexed: 02/07/2023]
Abstract
Reactive astrogliosis, whereby astrocytes undergo varying molecular and morphological changes, is a ubiquitous but poorly understood hallmark of all central nervous system pathologies. Genetic tools are now enabling the molecular dissection of the functions and mechanisms of reactive astrogliosis in vivo. Recent studies provide compelling evidence that reactive astrogliosis can exert both beneficial and detrimental effects in a context-dependent manner determined by specific molecular signaling cascades. Reactive astrocytes can have both loss of normal functions and gain of abnormal effects that could feature prominently in a variety of disease processes. This article reviews developments in the signaling mechanisms that regulate specific aspects of reactive astrogliosis and highlights the potential to identify novel therapeutic molecular targets for diverse neurological disorders.
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Affiliation(s)
- Michael V Sofroniew
- Department of Neurobiology, University of California Los Angeles, Los Angeles, CA 90095-1763, USA.
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75
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Abstract
The Cre/lox site-specific recombination system has emerged as an important tool for the generation of conditional somatic mouse mutants. This method allows one to control gene activity in space and time in almost any tissue of the mouse, thus opening new avenues for studying gene function and for establishing sophisticated animal models of human diseases. A major technical advance in terms of in vivo inducibility was the development of ligand-dependent Cre recombinases that can be activated by administration of tamoxifen to the animal. Here we describe how tamoxifen-dependent Cre recombinases, so-called CreER recombinases, work and how they can be used to generate time- and tissue-specific mouse mutants. The focus will be on the CreER(T2) recombinase, which is currently the most successful CreER version. We will give an overview of available CreER(T2) transgenic mouse lines and present protocols that detail the generation of experimental mice for inducible gene knockout studies, the induction of recombination by tamoxifen treatment, and the analysis of the quality and quantity of recombination by reporter gene and target gene studies. Most of the protocols can also be used as general guidelines for the generation and characterization of Cre/lox-mediated genome modifications in mice.
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76
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Hall ED, Traystman RJ. Role of animal studies in the design of clinical trials. FRONTIERS OF NEUROLOGY AND NEUROSCIENCE 2009; 25:10-33. [PMID: 19478492 DOI: 10.1159/000209470] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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77
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Havekes R, Abel T. Genetic dissection of neural circuits and behavior in Mus musculus. ADVANCES IN GENETICS 2009; 65:1-38. [PMID: 19615530 DOI: 10.1016/s0065-2660(09)65001-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
One of the major challenges in the field of neurobiology is to elucidate the molecular machinery that underlies the formation and storage of memories. For many decades, genetic studies in the fruit fly (Drosophila melanogaster) have provided insight into the role of specific genes underlying memory storage. Although these pioneering studies were groundbreaking, a transition to a mammalian system more closely resembling the human brain is critical for the translation of basic research findings into therapeutic strategies in humans. Because the mouse (Mus musculus) shares the complex genomic and neuroanatomical organization of mammals and there is a wealth of molecular tools that are available to manipulate gene function in mice, the mouse has become the primary model for research into the genetic basis of mammalian memory. Another major advantage of mouse research is the ability to examine in vivo electrophysiological processes, such as synaptic plasticity and neuronal firing patterns during behavior (e.g., the analysis of place cell activity). The focus on mouse models for memory research has led to the development of sophisticated behavioral protocols capable of exploring the role of particular genes in distinct phases of learning and memory formation, which is one of the major accomplishments of the past decade. In this chapter, we will give an overview of several state of the art genetic approaches to study gene function in the mouse brain in a spatially and temporally restricted fashion.
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Affiliation(s)
- Robbert Havekes
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - Ted Abel
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
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78
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Breunig JJ, Arellano JI, Macklis JD, Rakic P. Everything that glitters isn't gold: a critical review of postnatal neural precursor analyses. Cell Stem Cell 2008; 1:612-27. [PMID: 18371403 DOI: 10.1016/j.stem.2007.11.008] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Adult neurogenesis research has made enormous strides in the last decade but has been complicated by several failures to replicate promising findings. Prevalent use of highly sensitive methods with inherent sources of error has led to extraordinary conclusions without adequate crossvalidation. Perhaps the biggest culprit is the reliance on molecules involved in DNA synthesis and genetic markers to indicate neuronal neogenesis. In this Protocol Review, we present an overview of common methodological issues in the field and suggest alternative approaches, including viral vectors, siRNA, and inducible transgenic/knockout mice. A multipronged approach will enhance the overall rigor of research on stem cell biology and related fields by allowing increased replication of findings between groups and across systems.
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Affiliation(s)
- Joshua J Breunig
- Department of Neurobiology, Yale University School of Medicine, New Haven, CT 06510, USA
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79
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STAT3 is a critical regulator of astrogliosis and scar formation after spinal cord injury. J Neurosci 2008; 28:7231-43. [PMID: 18614693 DOI: 10.1523/jneurosci.1709-08.2008] [Citation(s) in RCA: 690] [Impact Index Per Article: 43.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Signaling mechanisms that regulate astrocyte reactivity and scar formation after spinal cord injury (SCI) are not well defined. We used the Cre recombinase (Cre)-loxP system under regulation of the mouse glial fibrillary acidic protein (GFAP) promoter to conditionally delete the cytokine and growth factor signal transducer, signal transducer and activator of transcription 3 (STAT3), from astrocytes. After SCI in GFAP-Cre reporter mice, >99% of spinal cord cells that exhibited Cre activity as detected by reporter protein expression were GFAP-expressing astrocytes. Conditional deletion (or knock-out) of STAT3 (STAT3-CKO) from astrocytes in GFAP-Cre-loxP mice was confirmed in vivo and in vitro. In uninjured adult STAT3-CKO mice, astrocytes appeared morphologically similar to those in STAT3+/+ mice except for a partially reduced expression of GFAP. In STAT3+/+ mice, phosphorylated STAT3 (pSTAT3) was not detectable in astrocytes in uninjured spinal cord, and pSTAT3 was markedly upregulated after SCI in astrocytes and other cell types near the injury. Mice with STAT3-CKO from astrocytes exhibited attenuated upregulation of GFAP, failure of astrocyte hypertrophy, and pronounced disruption of astroglial scar formation after SCI. These changes were associated with increased spread of inflammation, increased lesion volume and partially attenuated motor recovery over the first 28 d after SCI. These findings indicate that STAT3 signaling is a critical regulator of certain aspects of reactive astrogliosis and provide additional evidence that scar-forming astrocytes restrict the spread of inflammatory cells after SCI.
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80
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Chow LML, Zhang J, Baker SJ. Inducible Cre recombinase activity in mouse mature astrocytes and adult neural precursor cells. Transgenic Res 2008; 17:919-28. [PMID: 18483774 PMCID: PMC2522290 DOI: 10.1007/s11248-008-9185-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2008] [Accepted: 04/24/2008] [Indexed: 11/28/2022]
Abstract
Two transgenic mouse lines expressing an inducible form of the Cre recombinase (CreER) under the control of the human GFAP promoter have been generated and characterized. In adult mice, expression of the fusion protein is largely confined to astrocytes in all regions of the central nervous system. Minimal spontaneous Cre activity was detected and recombination was efficiently induced by intraperitoneal administration of tamoxifen in adult mice. The pattern of recombination closely mirrored that of transgene expression. The percentage of astrocytes undergoing recombination varied from region to region ranging from 35% to 70% while a much smaller portion (<1%) of oligodendrocytes and neural precursor cells showed evidence of Cre activity. These mouse lines will provide important tools to dissect gene function in glial cells and in gliomagenesis.
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Affiliation(s)
- Lionel M L Chow
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, 332 North Lauderdale Street, Memphis, TN, 38105, USA
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81
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Luan H, White BH. Combinatorial methods for refined neuronal gene targeting. Curr Opin Neurobiol 2007; 17:572-80. [DOI: 10.1016/j.conb.2007.10.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Revised: 10/01/2007] [Accepted: 10/04/2007] [Indexed: 01/13/2023]
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