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Mature Astrocytes (mature + astrocyte)
Selected AbstractsMixed primary culture and clonal analysis provide evidence that NG2 proteoglycan-expressing cells after spinal cord injury are glial progenitorsDEVELOPMENTAL NEUROBIOLOGY, Issue 7 2007Soonmoon Yoo Abstract NG2+ cells in the adult rat spinal cord proliferate after spinal cord injury (SCI) and are postulated to differentiate into mature glia to replace some of those lost to injury. To further study these putative endogenous precursors, tissue at 3 days after SCI or from uninjured adults was dissociated, myelin partially removed and replicate cultures grown in serum-containing or serum-free medium with or without growth factors for up to 7 days in vitro (DIV). Cell yield after SCI was 5,6 times higher than from the normal adult. Most cells were OX42+ microglia/macrophages but there were also more than twice the normal number of NG2+ cells. Most of these coexpressed A2B5 or nestin, as would be expected for glial progenitors. Few cells initially expressed mature astrocyte (GFAP) or oligodendrocyte (CC1) markers, but more did at 7 DIV, suggesting differentiation of glial precursors in vitro. To test the hypothesis that NG2+ cells after SCI express progenitor-like properties, we prepared free-floating sphere and single cell cultures from purified suspension of NG2+ cells from injured spinal cord. We found that sphere cultures could be passaged in free-floating subcultures, and upon attachment the spheres clonally derived from an acutely purified single cell differentiated into oligodendrocytes and rarely astrocytes. Taken together, these data support the hypothesis that SCI stimulates proliferation of NG2+ cells that are glial progenitor cells. Better understanding the intrinsic properties of the NG2+ cells stimulated by SCI may permit future therapeutic manipulations to improve recovery after SCI. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007. [source] Cortical radial glial cells in human fetuses: Depth-correlated transformation into astrocytesDEVELOPMENTAL NEUROBIOLOGY, Issue 3 2003Leonardo C. deAzevedo Abstract In the human brain, the transformation of radial glial cells (RGC) into astrocytes has been studied only rarely. In this work, we were interested in studying the morphologic aspects underlying this transformation during the fetal/perinatal period, particularly emphasizing the region-specific glial fiber anatomy in the medial cortex. We have used carbocyanine dyes (DiI/DiA) to identify the RGC transitional forms and glial fiber morphology. Immunocytochemical markers such as vimentin and glial fibrillary acidic protein (GFAP) were also employed to label the radial cells of glial lineage and to reveal the early pattern of astrocyte distribution. Neuronal markers such as neuronal-specific nuclear protein (NeuN) and microtubule-associated protein (MAP-2) were employed to discern whether or not these radial cells could, in fact, be neurons or neuronal precursors. The main findings concern the beginning of RGC transformation showing loss of the ventricular fixation in most cases, followed by transitional figures and the appearance of mature astrocytes. In addition, diverse fiber morphology related to depth within the cortical mantle was clearly demonstrated. We concluded that during the fetal/perinatal period the cerebral cortex is undergoing the final stages of radial neuronal migration, followed by involution of RGC ventricular processes and transformation into astrocytes. None of the transitional or other radial glia were positive for neuronal markers. Furthermore, the differential morphology of RGC fibers according to depth suggests that factors may act locally in the subplate and could have a role in the process of cortical RGC transformation and astrocyte localization. The early pattern of astrocyte distribution is bilaminar, sparing the cortical plate. Few astrocytes (GFAP+) in the upper band could be found with radial processes at anytime. This suggests that astrocytes in the marginal zone could be derived from different precursors than those that differentiate from RGCs during this period. © 2003 Wiley Periodicals, Inc. J Neurobiol 55: 288,298, 2003 [source] Heterogeneity of Kir4.1 channel expression in glia revealed by mouse transgenesisGLIA, Issue 16 2009Xiaofang Tang Abstract The weakly inwardly rectifying K+ channel Kir4.1 is found in many glial cells including astrocytes. However, questions remain regarding the relative contribution of Kir4.1 to the resting K+ conductance of mature astrocytes in situ. We employed a bacterial artificial chromosome transgenic approach in mice to visualize Kir4.1 expression in vivo. These mice (Kir4.1-EGFP) express enhanced green fluorescent protein (EGFP) under the transcriptional control of the Kir4.1 promoter. The brains of adult Kir4.1-EGFP transgenic mice showed co-expression of EGFP and Kir4.1 in astrocytes. In addition, weaker expression of EGFP was detected in NG2+ glial cells when compared with EGFP expression in GFAP+ glial cells. Whole-cell voltage clamp recordings of EGFP+ glial cells in the CA1 area of the adult mouse hippocampus indicated astrocytes displaying properties consistent with both the "passive" and "complex" subpopulations. EGFP+ cells with bright fluorescence had the linear current,voltage (I,V) relationships and extensive gap junctional coupling characteristic of passive astrocytes. However, EGFP+ glia with weaker fluorescence displayed properties associated with complex astrocytes including nonlinear I,V relationships and lack of intercellular gap junctional coupling. Pharmacological blockade of inward currents implied that Kir4.1 channels constitute the dominant resting K+ conductance in both glial cell types and are more highly expressed in passive astrocytes. These results suggest differential expression of Kir4.1 in glia and that this channel likely underlies the resting K+ conductance in passive and complex astrocytes. © 2009 Wiley-Liss, Inc. [source] Ca2+ - and thromboxane-dependent distribution of MaxiK channels in cultured astrocytes: From microtubules to the plasma membraneGLIA, Issue 12 2009J. W. Ou Abstract Large-conductance, voltage- and Ca2+ -activated K+ channels (MaxiK) are broadly expressed ion channels minimally assembled by four pore-forming ,-subunits (MaxiK,) and typically observed as plasma membrane proteins in various cell types. In murine astrocyte primary cultures, we show that MaxiK, is predominantly confined to the microtubule network. Distinct microtubule distribution of MaxiK, was visualized by three independent labeling approaches: (1) MaxiK,-specific antibodies, (2) expressed EGFP-labeled MaxiK,, and (3) fluorophore-conjugated iberiotoxin, a specific MaxiK pore-blocker. This MaxiK, association with microtubules was further confirmed by in vitro His-tag pulldown, co-immunoprecipitation from brain lysates, and microtubule depolymerization experiments. Changes in intracellular Ca2+ elicited by general pharmacological agents, caffeine or thapsigargin, resulted in increased MaxiK, labeling at the plasma membrane. More notably, U46619, an analog of thromboxane A2 (TXA2), which triggers Ca2+ -release pathways and whose levels increase during cerebral hemorrhage/trauma, also elicits a similar increase in MaxiK, surface labeling. Whole-cell patch clamp recordings of U46619-stimulated cells develop a ,3-fold increase in current amplitude indicating that TXA2 stimulation results in the recruitment of additional, functional MaxiK channels to the surface membrane. While microtubules are largely absent in mature astrocytes, immunohistochemistry results in brain slices show that cortical astrocytes in the newborn mouse (P1) exhibit a robust expression of microtubules that significantly colocalize with MaxiK,. The results of this study provide the novel insight that suggests that Ca2+ released from intracellular stores may play a key role in regulating the traffic of intracellular, microtubule-associated MaxiK, stores to the plasma membrane of developing murine astrocytes. © 2009 Wiley-Liss, Inc. [source] An FGF-responsive astrocyte precursor isolated from the neonatal forebrainGLIA, Issue 6 2009Grace Lin Abstract Gliogenesis in the mammalian CNS continues after birth, with astrocytes being generated well into the first two postnatal weeks. In this study, we have isolated an A2B5+ astrocyte precursor (APC) from the postnatal rat forebrain, which is capable of differentiating into mature astrocytes in serum-free medium without further trophic support. Exposure to basic fibroblast growth factor (bFGF) selectively induces the APCs to proliferate, forming clusters of vimentin+ cells, which, within 2 weeks, differentiate into GFAP+ astrocytes. While bFGF functions as a potent mitogen, neither is it necessary to induce or maintain astrocyte differentiation, nor is it capable of maintaining the precursors in an immature, proliferative state. APCs exit the cell cycle and differentiate, even in the continued presence of fibroblast growth factor alone or in combination with other mitogenic factors such as platelet-derived growth factor. Under the culture conditions used, it was not possible to cause the astrocytes to re-enter cell cycle. After transplantation into the neonatal forebrain, APCs differentiated exclusively into astrocytes, regardless of brain region. Initially distributed widely within the forebrain, the precursors are most greatly concentrated within the subventricular zone (SVZ) and subcortical white matter, where they are maintained throughout postnatal development. APCs can be isolated from the SVZ and white matter of animals as late as 4 weeks after birth. © 2008 Wiley-Liss, Inc. [source] Ultrastructural and antigenic properties of neural stem cells and their progeny in adult rat subventricular zoneGLIA, Issue 2 2009Alexandre I. Danilov Abstract Neural stem cells (NSCs) in the subventricular zone (SVZ) continuously generate olfactory bulb interneurons in the adult rodent brain. Based on their ultrastructural and antigenic properties, NSCs, transient amplifying precursor cells, and neuroblasts (B, C, and A cells, respectively) have been distinguished in mouse SVZ. Here, we aimed to identify these cell types in rat SVZ ultrastructurally and at the light microscopy level, and to determine the antigenic properties of each cell type using gold and fluorescence immunolabeling. We found astrocytes with single cilia (NSCs, correspond to B cells) and neuroblasts (A cells). We also observed mitotic cells, ependymal cells, displaced ependymal cells, and mature astrocytes. In contrast, transient amplifying precursor cells (C cells) were not detected. The NSCs and neuroblasts had epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor alpha (PDGFR,) expressed on the ciliary apparatus and were the only cell types incorporating the proliferation marker BrdU. Throughout mitosis, EGFR and PDGFR, were associated with the microtubule of the mitotic spindle. Ependymal and displaced ependymal cells also expressed EGFR and PDGFR, on their cilia but did not incorporate BrdU. Our findings indicate that the NSCs in adult rat SVZ give rise directly to neuroblasts. During mitosis, the NSCs disassemble the primary cilium and symmetrically distribute EGFR and PDGFR, among their progeny. © 2008 Wiley-Liss, Inc. [source] A role for Connexin43 during neurodevelopmentGLIA, Issue 7 2007Amy E. Wiencken-Barger Abstract Connexin43 (Cx43) is the predominant gap junction protein expressed in premitotic radial glial cells and mature astrocytes. It is thought to play a role in many aspects of brain development and physiology, including intercellular communication, the release of neuroactive substances, and neural and glial proliferation and migration. To investigate the role of Cx43 in brain physiology, we generated a conditional knockout (cKO) mouse expressing Cre recombinase driven by the human GFAP promoter and a floxed Cx43 gene. The removal of Cx43 from GFAP-expressing cells affects the behavior of the mice and the development of several brain structures; however, the severity of the phenotype varies depending on the mouse background. One mouse subline, hereafter termed Shuffler, exhibits cellular disorganization of the cortex, hippocampus, and cerebellum, accompanied by ataxia and motor deficits. The Shuffler cerebellum is most affected and displays altered distribution and lamination of glia and neurons suggestive of cell migration defects. In all Shuffler mice by postnatal day two (P2), the hippocampus, cortex, and cerebellum are smaller. Disorganization of the ventricular and subventricular zone of the cortex is also evident. Given that these are sites of early progenitor cell proliferation, we suspect production and migration of neural progenitors may be altered. In conclusion, neurodevelopment of Shuffler/Cx43 cKO mice is abnormal, and the observed cellular phenotype may explain behavioral disturbances seen in these animals as well as in humans carrying Cx43 mutations. © 2007 Wiley-Liss, Inc. [source] NG2 proteoglycan-expressing cells of the adult rat brain: Possible involvement in the formation of glial scar astrocytes following stab woundGLIA, Issue 3 2005G. Alonso Abstract Stab wound lesion to the adult central nervous system induces strong proliferative response that is followed by the formation of a dense astroglial scar. In order to determine the origin of those astrocytes composing the glial scar, the cell proliferation marker bromodeoxyuridine (BrdU) was administered to lesioned rats that were fixed 3 h or 6 days later. At 3 h after the BrdU administration, labeled nuclei were frequently associated with either NG2+ cells or microglia/macrophages, but rarely with astrocytes expressing glial fibrillary acidic protein (GFAP). Six days later, by contrast, numerous BrdU-labeled nuclei were associated with astrocytes located along the lesion borders. After the injection of a viral vector of the green fluorescent protein (GFP) into the lesional cavity, GFP was preferentially detected within NG2- or GFAP-labeled cells when lesioned animals were fixed 1 or 6 days after the injections, respectively. The combined detection of glial markers within cells present in the lesioned area indicated that, although they rarely express GFAP, the marker of mature astrocytes, NG2+ cells located along the lesion borders frequently express nestin and vimentin, i.e., two markers of immature astrocytes. Lastly, chronic treatment of lesioned rats with dexamethasone was found to inhibit the proliferation of NG2+ cells present within the lesioned area and to subsequently alter the formation of a dense astroglial scar. Taken together, these data strongly suggest that following a surgical lesion, at least a portion of the astrocytes that constitute the glial scar are issued from resident NG2+ cells. © 2004 Wiley-Liss, Inc. [source] GFAP: Functional implications gleaned from studies of genetically engineered miceGLIA, Issue 1 2003Albee Messing Abstract GFAP is the major intermediate filament of mature astrocytes, and its relatively specific expression in these cells suggests an important function. To study the role of the GFAP gene, mice have been created carrying null alleles (no protein), modified alleles (altered protein), or added wild type alleles (elevated protein). Surprisingly, absence of GFAP has relatively subtle effects on development. On the other hand, over-expression can be lethal, and led to the discovery that GFAP coding mutations are responsible for most cases of Alexander disease, a devastating neurodegenerative disorder. Here we review what the various GFAP mouse models reveal about GFAP and astrocyte function. GLIA 43:87,90, 2003. © 2003 Wiley-Liss, Inc. [source] Regulation of glial development by cystatin CJOURNAL OF NEUROCHEMISTRY, Issue 1 2007Akiko Hasegawa Abstract Cystatin C (CysC) is an endogenous cysteine proteases inhibitor produced by mature astrocytes in the adult brain. Previously we isolated CysC as a factor activating the glial fibrillary acidic protein (GFAP) promoter, and showed that CysC is expressed in astrocyte progenitors during development. Here we show that protease inhibitor activity increased daily in conditioned medium, and that this activity was mainly a result of CysC released from primary cultured cells. Human CysC added to the culture medium of primary brain cells increased the number of GFAP-positive and nestin-positive cells. Human CysC also increased the number of neurospheres formed from embryonic brain, and thus it increases the number of neural stem/precursor cells in a manner similar to glycosylated rat CysC. The addition of a neutralizing antibody, on the other hand, greatly decreased the number of GFAP and glutamate aspartate transporter (GLAST)-positive astrocytes. This decrease was reversed by the addition of CysC but not by another cysteine protease inhibitor. Thus, the promotion of astrocyte development by CysC appears to be independent of its protease inhibitor activity. The antibody increased the number of oligodendrocytes and their precursors. Therefore, CysC modifies glial development in addition to its activity against neural stem/precursor cells. [source] Low-density lipoprotein receptor-related protein (LRP)-2/megalin is transiently expressed in a subpopulation of neural progenitors in the embryonic mouse spinal cordTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 2 2005Grzegorz Wicher Abstract The lipoprotein receptor LRP2/megalin is expressed by absorptive epithelia and involved in receptor-mediated endocytosis of a wide range of ligands. Megalin is expressed in the neuroepithelium during central nervous system (CNS) development. Mice with homozygous deletions of the megalin gene show severe forebrain abnormalities. The possible role of megalin in the developing spinal cord, however, is unknown. Here we examined the spatial and temporal expression pattern of megalin in the embryonic mouse spinal cord using an antibody that specifically recognizes the cytoplasmic part of the megalin molecule. In line with published data, we show expression of megalin in ependymal cells of the central canal from embryonic day (E)11 until birth. In addition, from E11 until E15 a population of cells was found in the dorsal part of the developing spinal cord strongly immunoreactive against megalin. Double labeling showed that most of these cells express vimentin, a marker for immature astrocytes and radial glia, but not brain lipid binding protein (BLBP), a marker for radial glial cells, or glial fibrillary acidic protein (GFAP), a marker for mature astrocytes. These findings indicate that the majority of the megalin-positive cells are astroglial precursors. Megalin immunoreactivity was mainly localized in the nuclei of these cells, suggesting that the cytoplasmic part of the megalin molecule can be cleaved following ligand binding and translocated to the nucleus to act as a transcription factor or regulate other transcription factors. These findings suggest that megalin has a crucial role in the development of astrocytes of the spinal cord. J. Comp. Neurol. 492:123,131, 2005. © 2005 Wiley-Liss, Inc. [source] | ||||||||||