{"title":"Satellite glial cells: more than just 'rings around the neuron'.","authors":"Menachem Hanani","doi":"10.1017/S1740925X10000104","DOIUrl":"https://doi.org/10.1017/S1740925X10000104","url":null,"abstract":"When most neuroscientists discuss peripheral glia, it is usually about Scwhann cells. However, the peripheral nervous system includes a large number of ganglia – sensory and autonomic – which contain specialized glial cells termed ‘satellite glial cells’ (SGCs). (The enteric nervous system has its own specialized glial cells.) SGCs surround the neurons and form a tight envelope around them. In tissue sections SGCs appear like a ring around the neuron, which is mostly very thin and occasionally can even be invisible under the light microscope. These cells could be regarded as a special type of Schwann cells, but their development, and especially their unique organization with respect to the neurons, make them a distinct cell type. The collection of articles in this issue is not meant to be the definitive word on SGCs. We are currently several years away from having a comprehensive understanding of these cells. Rather, these articles can serve as an introduction to this topic and for pointing to potentially important research directions. In the first article Pannese (2010) describes the ultrastructure of SGCs. That this article will open this issue is appropriate at least for two reasons. First, Prof. Pannese has pioneered the research on SGCs, and his first article on this topic appeared over 50 years ago (Pannese, 1956). His 1981 monograph on SGCs is a must reading for anyone interested in this field, and is a classic of beauty, precision and clarity (Pannese, 1981). Second, structure is the best way to approach any study in biology because structure gives us important clues on function. Pannese’s article emphasizes the unique arrangement of SGC as a tight sheath around the neurons, which results in the formation of a discrete unit consisting of a neuronal cell body and the SGCs surrounding it. This organization distinguishes SGCs from Scwhann cells and astrocytes, and has obvious functional implications, because even if the molecular and pharmacological properties of SGCs were similar to those of these other cell types, the functions of SGCs are very likely to be unique due to this special arrangement. Pannese also highlights the striking morphological changes that SGCs undergo after nerve injury, which include hypertrophy and the formation of bridges with other SGCs, which contain numerous newly formed gap junctions. Obviously, SGCs can sense injury-related changes in sensory neurons. Garrett and Durham (2010) investigated the postnatal temporal and spatial morphological changes in trigeminal ganglia that lead to formation of neuron–SGC units described by Pannese. They found that the expression of the inwardly rectifying K+ channel Kir4.1, the vesicle docking protein SNAP-25 and the neuropeptide CGRP correlate with the formation of these units. Thippeswamy and his co-workers (e.g. Thippeswamy and Morris, 1997) were among the first to report the presence of two-way neuron–SGC chemical signaling, which involves the secretion nitric oxide (NO) fro","PeriodicalId":19153,"journal":{"name":"Neuron glia biology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1017/S1740925X10000104","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"29104030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Konstantina Psachoulia, Francoise Jamen, Kaylene M Young, William D Richardson
{"title":"Cell cycle dynamics of NG2 cells in the postnatal and ageing brain.","authors":"Konstantina Psachoulia, Francoise Jamen, Kaylene M Young, William D Richardson","doi":"10.1017/S1740925X09990354","DOIUrl":"https://doi.org/10.1017/S1740925X09990354","url":null,"abstract":"<p><p>Oligodendrocyte precursors (OLPs or 'NG2 cells') are abundant in the adult mouse brain, where they continue to proliferate and generate new myelinating oligodendrocytes. By cumulative BrdU labelling, we estimated the cell cycle time TC and the proportion of NG2 cells that is actively cycling (the growth fraction) at approximately postnatal day 6 (P6), P60, P240 and P540. In the corpus callosum, TC increased from <2 days at P6 to approximately 9 days at P60 to approximately 70 days at P240 and P540. In the cortex, TC increased from approximately 2 days to >150 days over the same period. The growth fraction remained relatively invariant at approximately 50% in both cortex and corpus callosum - that is, similar numbers of mitotically active and inactive NG2 cells co-exist at all ages. Our data imply that a stable population of quiescent NG2 cells appears before the end of the first postnatal week and persists throughout life. The mitotically active population acts as a source of new oligodendrocytes during adulthood, while the biological significance of the quiescent population remains to be determined. We found that the mitotic status of adult NG2 cells is unrelated to their developmental site of origin in the ventral or dorsal telencephalon. We also report that new oligodendrocytes continue to be formed at a slow rate from NG2 cells even after P240 (8 months of age).</p>","PeriodicalId":19153,"journal":{"name":"Neuron glia biology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2009-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1017/S1740925X09990354","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"28884186","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Neuron glia biologyPub Date : 2009-11-01Epub Date: 2009-09-29DOI: 10.1017/S1740925X09990342
Susan M Staugaitis, Bruce D Trapp
{"title":"NG2-positive glia in the human central nervous system.","authors":"Susan M Staugaitis, Bruce D Trapp","doi":"10.1017/S1740925X09990342","DOIUrl":"https://doi.org/10.1017/S1740925X09990342","url":null,"abstract":"<p><p>Cells that express the NG2 chondroitin sulfate proteoglycan and platelet-derived growth factor receptor alpha (NG2 glia) are widespread in the adult human cerebral cortex and white matter and represent 10-15% of non-neuronal cells. The morphology and distribution of NG2 glia are similar to, but distinct from, both microglia and astrocytes. They are present as early as 17 weeks gestation and persist throughout life. NG2 glia can be detected in a variety of human central nervous system (CNS) diseases, of which multiple sclerosis is the best studied. NG2 glia show morphological changes in the presence of pathology and can show expression of the Ki-67 proliferation antigen. The antigenic profile and morphology of NG2 glia in human tissues are consistent with an oligodendrocyte progenitor function that has been well established in rodent models. Most antibodies to NG2 do not stain formalin-fixed paraffin-embedded tissues. Advances in our understanding of NG2 glia in human tissues will require the development of more robust markers for their detection in routinely processed human specimens.</p>","PeriodicalId":19153,"journal":{"name":"Neuron glia biology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2009-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1017/S1740925X09990342","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40040433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Neuron glia biologyPub Date : 2009-11-01Epub Date: 2009-10-07DOI: 10.1017/S1740925X09990317
Fraser J Sim, Martha S Windrem, Steven A Goldman
{"title":"Fate determination of adult human glial progenitor cells.","authors":"Fraser J Sim, Martha S Windrem, Steven A Goldman","doi":"10.1017/S1740925X09990317","DOIUrl":"https://doi.org/10.1017/S1740925X09990317","url":null,"abstract":"<p><p>Glial progenitor cells (GPCs) comprise the most abundant population of progenitor cells in the adult human brain. They are responsible for central nervous system (CNS) remyelination, and likely contribute to the astrogliotic response to brain injury and degeneration as well. Adult human GPCs are biased to differentiate as oligodendrocytes and elaborate new myelin, and yet they retain multilineage plasticity, and can give rise to neurons as well as astrocytes and oligodendrocytes once removed from the adult parenchymal environment. GPCs retain strong mechanisms for cell-autonomous self-renewal, and yet both their phenotype and fate may be dictated by their microenvironment. Using the transcriptional profiles of acutely isolated GPCs, we have begun to understand the operative ligand-receptor interactions involved in these processes, and have identified several key signaling pathways by which adult human GPCs may be reliably instructed to either oligodendrocytic or astrocytic fate. In addition, we have noted significant differences between the expressed genes and dominant signaling pathways of fetal and adult human GPCs, as well as between rodent and human GPCs. The latter data in particular call into question therapeutic strategies predicated solely upon data obtained using rodents, while perhaps highlighting the extent to which evolution has been attended by the phylogenetic modification of glial phenotype and function.</p>","PeriodicalId":19153,"journal":{"name":"Neuron glia biology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2009-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1017/S1740925X09990317","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"28421309","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Neuron glia biologyPub Date : 2009-05-01Epub Date: 2009-09-29DOI: 10.1017/S1740925X09990329
Rebekah Wigley, Arthur M Butt
{"title":"Integration of NG2-glia (synantocytes) into the neuroglial network.","authors":"Rebekah Wigley, Arthur M Butt","doi":"10.1017/S1740925X09990329","DOIUrl":"10.1017/S1740925X09990329","url":null,"abstract":"<p><p>NG2-glia are a distinct class of CNS glial cells that are generally classed as oligodendrocyte progenitor cells. However, in the adult CNS a large fraction of NG2 cells does not appear to divide or generate oligodendrocytes. The functions of these adult NG2-glia, which we have termed synantocytes, are unknown. NG2-glia (synantocytes) form interactive domains with astrocytes and neurons. Within their domains, NG2-glia and astrocytes contact the same neurons, form multiple heterologous contacts with each other, and contact pericytes which regulate cerebral blood flow. NG2-glia receive presynaptic input from neurons and respond to neurotransmitters released at synapses. In addition, NG2-glia are intimately associated with astroglia and respond to astroglial signals, a hitherto neglected aspect of NG2-glial cell physiology. The non-overlapping domain organisation of astrocytes is believed to be important in isolating and integrating activity at the synapses and blood vessels within their domains. The domains of NG2-glia overlap with astrocytes, suggesting they could play a role in integrating non-overlapping astrocyte domains.</p>","PeriodicalId":19153,"journal":{"name":"Neuron glia biology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2009-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40040431","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Neuron glia biologyPub Date : 2009-05-01Epub Date: 2009-09-29DOI: 10.1017/S1740925X09990330
Fredrik Ullén
{"title":"Is activity regulation of late myelination a plastic mechanism in the human nervous system?","authors":"Fredrik Ullén","doi":"10.1017/S1740925X09990330","DOIUrl":"https://doi.org/10.1017/S1740925X09990330","url":null,"abstract":"<p><p>Studies on various animal models have established that neuronal activity can influence the myelination process. Are such mechanisms present in humans, and do they mediate experience-driven white matter plasticity not only during early development but also in adolescents and adults? While there is as yet no direct evidence for this, a number of findings - reviewed here - are consistent with this idea. First, postmortem and neuroimaging studies show that the human white matter development is a protracted process that continues well into adulthood. Second, developmental changes and individual differences in white matter structure are related to differences in neural activity and behavior. Finally, studies on effects of long-term training, in particular in musicians, show strong relations between training and white matter structure. I conclude by briefly discussing possible types of white matter plasticity that could underlie these findings, emphasizing a distinction between indirect myelination plasticity, where the myelin sheath grows in parallel with the axon itself, and direct myelination plasticity, where the myelin sheath thickness is modulated independently of axonal diameter.</p>","PeriodicalId":19153,"journal":{"name":"Neuron glia biology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2009-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1017/S1740925X09990330","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40040432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Neuron glia biologyPub Date : 2009-05-01Epub Date: 2009-12-22DOI: 10.1017/S1740925X09990081
Maria Kukley, Dirk Dietrich
{"title":"Kainate receptors and signal integration by NG2 glial cells.","authors":"Maria Kukley, Dirk Dietrich","doi":"10.1017/S1740925X09990081","DOIUrl":"https://doi.org/10.1017/S1740925X09990081","url":null,"abstract":"<p><p>It is well established that NG2 cells throughout the young and adult brain consistently detect the release of single vesicles filled with glutamate from nearby axons. The released neurotransmitter glutamate electrically excites NG2 cells via non-NMDA (N-methyl-D-aspartic acid) glutamate receptors but the individual contribution of AMPA and kainate receptors to neuron-NG2 cell signalling, is not well understood. Here we pharmacologically block AMPA-type glutamate receptors and investigate whether hippocampal NG2 cells also express the kainate subtype of glutamate receptors and what may be their contribution to synaptic connectivity. It has been shown previously that vesicular glutamate release does not lead to a detectable activation of kainate receptors on NG2 cells. Here we report that while bath application of 250 nM-1 muM kainate does not have a major effect on NG2 cells it consistently induces a small and persistent depolarising current. This current was not mimicked by ATPA, suggesting that this current is carried by non-GluR5 containing kainate receptors. In addition to this inward current, nanomolar concentrations of kainate also produced a dramatic increase in the frequency of spontaneous GABA-A receptor-mediated synaptic currents (IPSCs) in NG2 cells. This increase in spontaneous IPSC frequency was even more pronounced on application of the GluR5-specific agonist ATPA (approximately 15-fold increase in frequency). In contrast, mono-synaptic stimulated IPSCs recorded in NG2 cells were unaffected by kainate receptor activation. Those and further experiments show that the occurrence of the high frequency of IPSCs is due to action potential firing of hippocampal interneurons caused by activation of GluR5 receptors on the somatodendritic membrane of the interneurons. Our data suggest that hippocampal kainate receptors are not only important for communication between neurons but may also play a dual and subtype-specific role for neuron-glia signalling: Firstly, extra-synaptic non-GluR5 kainate receptors in the membrane of NG2 cells are ideally suited to instruct NG2 cells on the population activity of local excitatory neurons via ambient glutamate. Secondly, based on the known importance of GluR5 receptors on hippocampal interneurons for the generation of network rhythms and based on our finding that these interneurons heavily project onto NG2 cells, it appears that synaptic activation of interneuronal GluR5 receptors triggers signalling to NG2 cells which transmits the phase and frequency of ongoing network oscillations in the developing hippocampus.</p>","PeriodicalId":19153,"journal":{"name":"Neuron glia biology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2009-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1017/S1740925X09990081","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"28606893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Neuron glia biologyPub Date : 2009-05-01Epub Date: 2009-08-13DOI: 10.1017/S1740925X09990202
Yamina Bakiri, David Attwell, Ragnhildur Káradóttir
{"title":"Electrical signalling properties of oligodendrocyte precursor cells.","authors":"Yamina Bakiri, David Attwell, Ragnhildur Káradóttir","doi":"10.1017/S1740925X09990202","DOIUrl":"10.1017/S1740925X09990202","url":null,"abstract":"<p><p>Oligodendrocyte precursor cells (OPCs) have become the focus of intense research, not only because they generate myelin-forming oligodendrocytes in the normal CNS, but because they may be suitable for transplantation to treat disorders in which myelin does not form or is damaged, and because they have stem-cell-like properties in that they can generate astrocytes and neurons as well as oligodendrocytes. In this article we review the electrical signalling properties of OPCs, including the synaptic inputs they receive and their use of voltage-gated channels to generate action potentials, and we describe experiments attempting to detect output signalling from OPCs. We discuss controversy over the existence of different classes of OPC with different electrical signalling properties, and speculate on the lineage relationship and myelination potential of these different classes of OPC. Finally, we point out that, since OPCs are the main proliferating cell type in the mature brain, the discovery that they can develop into neurons raises the question of whether more neurons are generated in the mature brain from the classical sites of neurogenesis in the subventricular zone of the lateral ventricle and the hippocampal dentate gyrus or from the far more widely distributed OPCs.</p>","PeriodicalId":19153,"journal":{"name":"Neuron glia biology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2009-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1017/S1740925X09990202","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"28336368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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