51
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Adachi C, Kakinuma N, Jo SH, Ishii T, Arai Y, Arai S, Kitaguchi T, Takeda S, Inoue T. Sonic hedgehog enhances calcium oscillations in hippocampal astrocytes. J Biol Chem 2019; 294:16034-16048. [PMID: 31506300 DOI: 10.1074/jbc.ra119.007883] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Revised: 09/04/2019] [Indexed: 01/05/2023] Open
Abstract
Sonic hedgehog (SHH) is important for organogenesis during development. Recent studies have indicated that SHH is also involved in the proliferation and transformation of astrocytes to the reactive phenotype. However, the mechanisms underlying these are unknown. Involvement of SHH signaling in calcium (Ca) signaling has not been extensively studied. Here, we report that SHH and Smoothened agonist (SAG), an activator of the signaling receptor Smoothened (SMO) in the SHH pathway, activate Ca oscillations in cultured murine hippocampal astrocytes. The response was rapid, on a minute time scale, indicating a noncanonical pathway activity. Pertussis toxin blocked the SAG effect, indicating an involvement of a Gi coupled to SMO. Depletion of extracellular ATP by apyrase, an ATP-degrading enzyme, inhibited the SAG-mediated activation of Ca oscillations. These results indicate that SAG increases extracellular ATP levels by activating ATP release from astrocytes, resulting in Ca oscillation activation. We hypothesize that SHH activates SMO-coupled Gi in astrocytes, causing ATP release and activation of Gq/11-coupled P2 receptors on the same cell or surrounding astrocytes. Transcription factor activities are often modulated by Ca patterns; therefore, SHH signaling may trigger changes in astrocytes by activating Ca oscillations. This enhancement of Ca oscillations by SHH signaling may occur in astrocytes in the brain in vivo because we also observed it in hippocampal brain slices. In summary, SHH and SAG enhance Ca oscillations in hippocampal astrocytes, Gi mediates SAG-induced Ca oscillations downstream of SMO, and ATP-permeable channels may promote the ATP release that activates Ca oscillations in astrocytes.
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Affiliation(s)
- Chihiro Adachi
- Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Tokyo 1628480, Japan
| | - Naoto Kakinuma
- Department of Anatomy and Cell Biology, Interdisciplinary School of Medicine & Engineering, University of Yamanashi, Yamanashi 4093898, Japan
| | - Soo Hyun Jo
- Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Tokyo 1628480, Japan
| | - Takayuki Ishii
- Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Tokyo 1628480, Japan
| | - Yusuke Arai
- Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Tokyo 1628480, Japan
| | - Satoshi Arai
- Cell Signaling Group, Waseda Bioscience Research Institute in Singapore (WABIOS), Singapore 138667.,Research Institute for Science and Engineering, Waseda University, Tokyo 1698555, Japan
| | - Tetsuya Kitaguchi
- Cell Signaling Group, Waseda Bioscience Research Institute in Singapore (WABIOS), Singapore 138667.,Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Tokyo 2268503, Japan
| | - Sen Takeda
- Department of Anatomy and Cell Biology, Interdisciplinary School of Medicine & Engineering, University of Yamanashi, Yamanashi 4093898, Japan
| | - Takafumi Inoue
- Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Tokyo 1628480, Japan
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52
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Escartin C, Guillemaud O, Carrillo-de Sauvage MA. Questions and (some) answers on reactive astrocytes. Glia 2019; 67:2221-2247. [PMID: 31429127 DOI: 10.1002/glia.23687] [Citation(s) in RCA: 168] [Impact Index Per Article: 33.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Revised: 06/12/2019] [Accepted: 06/28/2019] [Indexed: 02/06/2023]
Abstract
Astrocytes are key cellular partners for neurons in the central nervous system. Astrocytes react to virtually all types of pathological alterations in brain homeostasis by significant morphological and molecular changes. This response was classically viewed as stereotypical and is called astrogliosis or astrocyte reactivity. It was long considered as a nonspecific, secondary reaction to pathological conditions, offering no clues on disease-causing mechanisms and with little therapeutic value. However, many studies over the last 30 years have underlined the crucial and active roles played by astrocytes in physiology, ranging from metabolic support, synapse maturation, and pruning to fine regulation of synaptic transmission. This prompted researchers to explore how these new astrocyte functions were changed in disease, and they reported alterations in many of them (sometimes beneficial, mostly deleterious). More recently, cell-specific transcriptomics revealed that astrocytes undergo massive changes in gene expression when they become reactive. This observation further stressed that reactive astrocytes may be very different from normal, nonreactive astrocytes and could influence disease outcomes. To make the picture even more complex, both normal and reactive astrocytes were shown to be molecularly and functionally heterogeneous. Very little is known about the specific roles that each subtype of reactive astrocytes may play in different disease contexts. In this review, we have interrogated researchers in the field to identify and discuss points of consensus and controversies about reactive astrocytes, starting with their very name. We then present the emerging knowledge on these cells and future challenges in this field.
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Affiliation(s)
- Carole Escartin
- Commissariat à l'Energie Atomique et aux Energies Alternatives, Département de la Recherche Fondamentale, Institut de Biologie François Jacob, MIRCen, Fontenay-aux-Roses, France.,Centre National de la Recherche Scientifique, Univ. Paris Sud, Univ. Paris-Saclay, UMR 9199, Neurodegenerative Disease Laboratory, Fontenay-aux-Roses, France
| | - Océane Guillemaud
- Commissariat à l'Energie Atomique et aux Energies Alternatives, Département de la Recherche Fondamentale, Institut de Biologie François Jacob, MIRCen, Fontenay-aux-Roses, France.,Centre National de la Recherche Scientifique, Univ. Paris Sud, Univ. Paris-Saclay, UMR 9199, Neurodegenerative Disease Laboratory, Fontenay-aux-Roses, France
| | - Maria-Angeles Carrillo-de Sauvage
- Commissariat à l'Energie Atomique et aux Energies Alternatives, Département de la Recherche Fondamentale, Institut de Biologie François Jacob, MIRCen, Fontenay-aux-Roses, France.,Centre National de la Recherche Scientifique, Univ. Paris Sud, Univ. Paris-Saclay, UMR 9199, Neurodegenerative Disease Laboratory, Fontenay-aux-Roses, France
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53
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Hill SA, Blaeser AS, Coley AA, Xie Y, Shepard KA, Harwell CC, Gao WJ, Garcia ADR. Sonic hedgehog signaling in astrocytes mediates cell type-specific synaptic organization. eLife 2019; 8:45545. [PMID: 31194676 PMCID: PMC6629371 DOI: 10.7554/elife.45545] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2019] [Accepted: 06/13/2019] [Indexed: 01/08/2023] Open
Abstract
Astrocytes have emerged as integral partners with neurons in regulating synapse formation and function, but the mechanisms that mediate these interactions are not well understood. Here, we show that Sonic hedgehog (Shh) signaling in mature astrocytes is required for establishing structural organization and remodeling of cortical synapses in a cell type-specific manner. In the postnatal cortex, Shh signaling is active in a subpopulation of mature astrocytes localized primarily in deep cortical layers. Selective disruption of Shh signaling in astrocytes produces a dramatic increase in synapse number specifically on layer V apical dendrites that emerges during adolescence and persists into adulthood. Dynamic turnover of dendritic spines is impaired in mutant mice and is accompanied by an increase in neuronal excitability and a reduction of the glial-specific, inward-rectifying K+ channel Kir4.1. These data identify a critical role for Shh signaling in astrocyte-mediated modulation of neuronal activity required for sculpting synapses. A central system of neurons in the spinal cord and brain coordinate most of our body’s actions, ranging from regulating our heart rate to controlling our movement and thoughts. As the brain develops, neurons form specialized contacts with one another known as synapses. If the number of synapses is not properly regulated this can disrupt communication between the neurons, leading to diseases like schizophrenia and autism. As the brain develops, it first forms an excess of synapses and later eliminates unnecessary or weak connections. Various factors, such gene expression or a neuron’s level of activity, regulate this turnover process. However, neurons cannot do this alone, and rely on other types of cells to help regulate their behavior. In the central nervous system, for example, a cell called an astrocyte is known to support the formation and activity of synapses. Now, Hill and Blaeser et al. show that astrocytes also exert influence over synaptic turnover during development, leading to long lasting changes in the number of synapses. Hill, Blaeser et al. revealed that disrupting activity of the signaling pathway known as Sonic hedgehog, or Shh for short, in the astrocytes of mice led to disordered synaptic connections. Notably, neurons produce Shh, suggesting that neurons use this signaling pathway to communicate to specific astrocyte partners. Further experiments showed that reducing astrocyte’s ability to respond to Shh impaired synaptic turnover as the brain developed, leading to an overabundance of synapses. Importantly, these effects were only found to influence neuron populations associated with astrocytes that actively use Shh signaling. This suggests that distinct populations of neurons and astrocytes interact in specialized ways to build the connections within the nervous system. To address how astrocytes use Shh signaling to regulate synaptic turnover, Hill, Blaeser et al. examined gene expression changes in astrocytes that lack Shh signaling. Astrocytes with a reduced capacity to respond to Shh were found to have lower levels of a protein responsible for transporting potassium ions into and out of the cell. This impairs astrocyte’s ability to regulate neuronal activity, which may lead to a failure in eliminating unnecessary synapses. Understanding how synapses are controlled and organized by astrocytes could help identify new ways to treat diseases of the developing nervous system. However, further studies would be needed to improve our understanding of how this process works.
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Affiliation(s)
- Steven A Hill
- Department of Biology, Drexel University, Philadelphia, United States
| | - Andrew S Blaeser
- Department of Biology, Drexel University, Philadelphia, United States
| | - Austin A Coley
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, United States
| | - Yajun Xie
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | | | - Corey C Harwell
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Wen-Jun Gao
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, United States
| | - A Denise R Garcia
- Department of Biology, Drexel University, Philadelphia, United States.,Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, United States
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54
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Rivell A, Petralia RS, Wang YX, Clawson E, Moehl K, Mattson MP, Yao PJ. Sonic hedgehog expression in the postnatal brain. Biol Open 2019; 8:bio.040592. [PMID: 30837226 PMCID: PMC6451348 DOI: 10.1242/bio.040592] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Beyond its role in patterning the neural tube during embryogenesis, additional functions of Sonic hedgehog (Shh) in post-embryonic and mature brains have been coming into focus. However, the question of the abundance of endogenous Shh - the ligand of the signaling pathway - and its changes over time in post-embryonic and mature brains are less well understood. Here we find that while the amounts of Shh transcript and protein in rat brains are nearly undetectable at birth, they increase continuously during postnatal development and remain at readily detectable levels in young adults. This developmental age-associated increase in Shh levels is also seen in hippocampal neurons grown in culture, in which very young neurons produce minimal amounts of Shh protein but, as neurons grow and form synapses, the amounts of Shh increase significantly. Using immunolabeling with antibodies to different residues of Shh, we observed that the N-terminal fragment and the C-terminal fragment of Shh are present in hippocampal neurons, and that these two Shh forms co-exist in most compartments of the neuron. Our findings provide a better understanding of Shh expression in the brain, laying the groundwork for further comprehending the biogenesis of Shh protein in the young and mature brain and neurons.
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Affiliation(s)
- Aileen Rivell
- Laboratory of Neurosciences, NIA/NIH, Baltimore, MD 21224, USA
| | | | - Ya-Xian Wang
- Advanced Imaging Core, NIDCD/NIH, Bethesda, MD 20892, USA
| | - Ellie Clawson
- Laboratory of Neurosciences, NIA/NIH, Baltimore, MD 21224, USA
| | - Keelin Moehl
- Laboratory of Neurosciences, NIA/NIH, Baltimore, MD 21224, USA
| | - Mark P Mattson
- Laboratory of Neurosciences, NIA/NIH, Baltimore, MD 21224, USA.,Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Pamela J Yao
- Laboratory of Neurosciences, NIA/NIH, Baltimore, MD 21224, USA
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55
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Nicaise C, Marneffe C, Bouchat J, Gilloteaux J. Osmotic Demyelination: From an Oligodendrocyte to an Astrocyte Perspective. Int J Mol Sci 2019; 20:E1124. [PMID: 30841618 PMCID: PMC6429405 DOI: 10.3390/ijms20051124] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 02/26/2019] [Accepted: 02/27/2019] [Indexed: 12/15/2022] Open
Abstract
Osmotic demyelination syndrome (ODS) is a disorder of the central myelin that is often associated with a precipitous rise of serum sodium. Remarkably, while the myelin and oligodendrocytes of specific brain areas degenerate during the disease, neighboring neurons and axons appear unspoiled, and neuroinflammation appears only once demyelination is well established. In addition to blood‒brain barrier breakdown and microglia activation, astrocyte death is among one of the earliest events during ODS pathology. This review will focus on various aspects of biochemical, molecular and cellular aspects of oligodendrocyte and astrocyte changes in ODS-susceptible brain regions, with an emphasis on the crosstalk between those two glial cells. Emerging evidence pointing to the initiating role of astrocytes in region-specific degeneration are discussed.
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Affiliation(s)
| | - Catherine Marneffe
- Laboratory of Glia Biology (VIB-KU Leuven Center for Brain & Disease Research), Department of Neuroscience, KU Leuven, 3000 Leuven, Belgium.
| | - Joanna Bouchat
- URPhyM-NARILIS, Université de Namur, 5000 Namur, Belgium.
| | - Jacques Gilloteaux
- URPhyM-NARILIS, Université de Namur, 5000 Namur, Belgium.
- Department of Anatomical Sciences, St George's University School of Medicine, Newcastle upon Tyne NE1 8ST, UK.
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56
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Razumilava N, Shiota J, Mohamad Zaki NH, Ocadiz-Ruiz R, Cieslak CM, Zakharia K, Allen BL, Gores GJ, Samuelson LC, Merchant JL. Hedgehog Signaling Modulates Interleukin-33-Dependent Extrahepatic Bile Duct Cell Proliferation in Mice. Hepatol Commun 2019; 3:277-292. [PMID: 30766964 PMCID: PMC6357834 DOI: 10.1002/hep4.1295] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 11/14/2018] [Indexed: 01/11/2023] Open
Abstract
Hedgehog (HH) signaling participates in hepatobiliary repair after injury and is activated in patients with cholangiopathies. Cholangiopathies are associated with bile duct (BD) hyperplasia, including expansion of peribiliary glands, the niche for biliary progenitor cells. The inflammation-associated cytokine interleukin (IL)-33 is also up-regulated in cholangiopathies, including cholangiocarcinoma. We hypothesized that HH signaling synergizes with IL-33 in acute inflammation-induced BD hyperplasia. We measured extrahepatic BD (EHBD) thickness and cell proliferation with and without an IL-33 challenge in wild-type mice, mice overexpressing Sonic HH (pCMV-Shh), and mice with loss of the HH pathway effector glioma-associated oncogene 1 (Gli1lacZ/lacZ ). LacZ reporter mice were used to map the expression of HH effector genes in mouse EHBDs. An EHBD organoid (BDO) system was developed to study biliary progenitor cells in vitro. EHBDs from the HH overexpressing pCMV-Shh mice showed increased epithelial cell proliferation and hyperplasia when challenged with IL-33. In Gli1lacZ/lacZ mice, we observed a decreased proliferative response to IL-33 and decreased expression of Il6. The HH ligands Shh and Indian HH (Ihh) were expressed in epithelial cells, whereas the transcriptional effectors Gli1, Gli2, and Gli3 and the HH receptor Patched1 (Ptch1) were expressed in stromal cells, as assessed by in situ hybridization and lacZ reporter mice. Although BDO cells lacked canonical HH signaling, they expressed the IL-33 receptor suppression of tumorigenicity 2. Accordingly, IL-33 treatment directly induced BDO cell proliferation in a nuclear factor κB-dependent manner. Conclusion: HH ligand overexpression enhances EHBD epithelial cell proliferation induced by IL-33. This proproliferative synergism of HH and IL-33 involves crosstalk between HH ligand-producing epithelial cells and HH-responding stromal cells.
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Affiliation(s)
| | - Junya Shiota
- Department of Internal Medicine University of Michigan Ann Arbor MI
| | | | | | | | - Kais Zakharia
- Department of Internal Medicine University of Michigan Ann Arbor MI
| | - Benjamin L Allen
- Department of Cell and Developmental Biology University of Michigan Ann Arbor MI
| | | | - Linda C Samuelson
- Department of Internal Medicine University of Michigan Ann Arbor MI
- Molecular and Integrative Physiology University of Michigan Ann Arbor MI
| | - Juanita L Merchant
- Department of Internal Medicine University of Michigan Ann Arbor MI
- Molecular and Integrative Physiology University of Michigan Ann Arbor MI
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57
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Allahyari RV, Clark KL, Shepard KA, Garcia ADR. Sonic hedgehog signaling is negatively regulated in reactive astrocytes after forebrain stab injury. Sci Rep 2019; 9:565. [PMID: 30679745 PMCID: PMC6345977 DOI: 10.1038/s41598-018-37555-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 12/07/2018] [Indexed: 12/19/2022] Open
Abstract
Following injury to the central nervous system, astrocytes perform critical and complex functions that both promote and antagonize neural repair. Understanding the molecular signaling pathways that coordinate their diverse functional properties is key to developing effective therapeutic strategies. In the healthy, adult CNS, Sonic hedgehog (Shh) signaling is active in mature, differentiated astrocytes. Shh has been shown to undergo injury-induced upregulation and promote neural repair. Here, we investigated whether Shh signaling mediates astrocyte response to injury. Surprisingly, we found that following an acute, focal injury, reactive astrocytes exhibit a pronounced reduction in Shh activity in a spatiotemporally-defined manner. Shh signaling is lost in reactive astrocytes at the lesion site, but persists in mild to moderately reactive astrocytes in distal tissues. Nevertheless, local pharmacological activation of the Shh pathway in astrocytes mitigates inflammation, consistent with a neuroprotective role for Shh signaling after injury. Interestingly, we find that Shh signaling is restored to baseline levels two weeks after injury, a time during which acute inflammation has largely subsided and lesions have matured. Taken together, these data suggest that endogenous Shh signaling in astrocytes is dynamically regulated in a context dependent manner. In addition, exogenous activation of the Shh pathway promotes neuroprotection mediated by reactive astrocytes.
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Affiliation(s)
- R Vivian Allahyari
- Departments of Biology and Neurobiology and Anatomy, Drexel University, Philadelphia, PA, 19104, USA
| | - K Lyles Clark
- Departments of Biology and Neurobiology and Anatomy, Drexel University, Philadelphia, PA, 19104, USA
- Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; and Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Katherine A Shepard
- Departments of Biology and Neurobiology and Anatomy, Drexel University, Philadelphia, PA, 19104, USA
| | - A Denise R Garcia
- Departments of Biology and Neurobiology and Anatomy, Drexel University, Philadelphia, PA, 19104, USA.
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58
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Verkhratsky A, Ho MS, Vardjan N, Zorec R, Parpura V. General Pathophysiology of Astroglia. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1175:149-179. [PMID: 31583588 PMCID: PMC7188602 DOI: 10.1007/978-981-13-9913-8_7] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Astroglial cells are involved in most if not in all pathologies of the brain. These cells can change the morpho-functional properties in response to pathology or innate changes of these cells can lead to pathologies. Overall pathological changes in astroglia are complex and diverse and often vary with different disease stages. We classify astrogliopathologies into reactive astrogliosis, astrodegeneration with astroglial atrophy and loss of function, and pathological remodelling of astrocytes. Such changes can occur in neurological, neurodevelopmental, metabolic and psychiatric disorders as well as in infection and toxic insults. Mutation in astrocyte-specific genes leads to specific pathologies, such as Alexander disease, which is a leukodystrophy. We discuss changes in astroglia in the pathological context and identify some molecular entities underlying pathology. These entities within astroglia may repent targets for novel therapeutic intervention in the management of brain pathologies.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Oxford Road, Manchester, M13 9PT, UK.
- Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark.
- Achucarro Center for Neuroscience, IKERBASQUE, Basque Foundation for Science, 48011, Bilbao, Spain.
| | - Margaret S Ho
- School of Life Science and Technology, ShanghaiTech University, 201210, Shanghai, China
| | - Nina Vardjan
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia
- Celica BIOMEDICAL, Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia
- Celica BIOMEDICAL, Ljubljana, Slovenia
| | - Vladimir Parpura
- Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL, USA
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59
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Martinez-Chavez E, Scheerer C, Wizenmann A, Blaess S. The zinc-finger transcription factor GLI3 is a regulator of precerebellar neuronal migration. Development 2018; 145:dev.166033. [PMID: 30470704 DOI: 10.1242/dev.166033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 11/15/2018] [Indexed: 01/24/2023]
Abstract
Hindbrain precerebellar neurons arise from progenitor pools at the dorsal edge of the embryonic hindbrain: the caudal rhombic lip. These neurons follow distinct migratory routes to establish nuclei that provide climbing or mossy fiber inputs to the cerebellum. Gli3, a zinc-finger transcription factor in the Sonic hedgehog signaling pathway, is an important regulator of dorsal brain development. We demonstrate that in Gli3-null mutant mice, disrupted neuronal migratory streams lead to a disorganization of precerebellar nuclei. Precerebellar progenitors are properly established in Gli3-null embryos and, using conditional gene inactivation, we provide evidence that Gli3 does not play a cell-autonomous role in migrating precerebellar neurons. Thus, GLI3 likely regulates the development of other hindbrain structures, such as non-precerebellar nuclei or cranial ganglia and their respective projections, which may in turn influence precerebellar migration. Although the organization of non-precerebellar hindbrain nuclei appears to be largely unaffected in absence of Gli3, trigeminal ganglia and their central descending tracts are disrupted. We show that rostrally migrating precerebellar neurons are normally in close contact with these tracts, but are detached in Gli3-null embryos.
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Affiliation(s)
- Erick Martinez-Chavez
- Institute of Reconstructive Neurobiology, University of Bonn Medical Center, 53127 Bonn, Germany
| | - Claudia Scheerer
- Institute of Reconstructive Neurobiology, University of Bonn Medical Center, 53127 Bonn, Germany
| | - Andrea Wizenmann
- Institute of Clinical Anatomy and Cell Analysis, Department of Anatomy, University of Tübingen, 72074 Tübingen, Germany
| | - Sandra Blaess
- Institute of Reconstructive Neurobiology, University of Bonn Medical Center, 53127 Bonn, Germany
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60
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Yang Y, Jackson R. Astrocyte identity: evolutionary perspectives on astrocyte functions and heterogeneity. Curr Opin Neurobiol 2018; 56:40-46. [PMID: 30529823 DOI: 10.1016/j.conb.2018.11.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 11/18/2018] [Accepted: 11/21/2018] [Indexed: 10/27/2022]
Abstract
The development of new animal models, in vivo isolation approaches, and improvements in genome-wide RNA expression methods have greatly propelled molecular profiling of astrocytes and the characterization of astrocyte heterogeneity in the central nervous system (CNS). Several recent reviews have comprehensively discussed the molecular and functional diversity of mammalian astrocytes. In this brief review, we emphasize interspecies comparisons and an evolutionary perspective regarding the astro(glia) of vertebrates and invertebrates which are similar in form and function. This analysis has revealed conserved astrocyte transcriptomes in the fly, mouse and human. We also offer opinions about the pattern and origin of astrocyte heterogeneity in the CNS.
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Affiliation(s)
- Yongjie Yang
- Department of Neuroscience, Tufts University School of Medicine, 136 Harrison Ave, Boston, MA, 02111, United States; Sackler School of Biomedical Sciences, Tufts University, 145 Harrison Ave, Boston, MA, 02111, United States.
| | - Rob Jackson
- Department of Neuroscience, Tufts University School of Medicine, 136 Harrison Ave, Boston, MA, 02111, United States; Sackler School of Biomedical Sciences, Tufts University, 145 Harrison Ave, Boston, MA, 02111, United States.
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61
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Keller D, Erö C, Markram H. Cell Densities in the Mouse Brain: A Systematic Review. Front Neuroanat 2018; 12:83. [PMID: 30405363 PMCID: PMC6205984 DOI: 10.3389/fnana.2018.00083] [Citation(s) in RCA: 198] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 09/20/2018] [Indexed: 11/29/2022] Open
Abstract
The mouse brain is the most extensively studied brain of all species. We performed an exhaustive review of the literature to establish our current state of knowledge on cell numbers in mouse brain regions, arguably the most fundamental property to measure when attempting to understand a brain. The synthesized information, collected in one place, can be used by both theorists and experimentalists. Although for commonly-studied regions cell densities could be obtained for principal cell types, overall we know very little about how many cells are present in most brain regions and even less about cell-type specific densities. There is also substantial variation in cell density values obtained from different sources. This suggests that we need a new approach to obtain cell density datasets for the mouse brain.
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Affiliation(s)
- Daniel Keller
- Blue Brain Project, École Polytechnique Fédérale de Lausanne, Geneva, Switzerland
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62
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Antonelli F, Casciati A, Tanori M, Tanno B, Linares-Vidal MV, Serra N, Bellés M, Pannicelli A, Saran A, Pazzaglia S. Alterations in Morphology and Adult Neurogenesis in the Dentate Gyrus of Patched1 Heterozygous Mice. Front Mol Neurosci 2018; 11:168. [PMID: 29875630 PMCID: PMC5974030 DOI: 10.3389/fnmol.2018.00168] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 05/03/2018] [Indexed: 01/06/2023] Open
Abstract
Many genes controlling neuronal development also regulate adult neurogenesis. We investigated in vivo the effect of Sonic hedgehog (Shh) signaling activation on patterning and neurogenesis of the hippocampus and behavior of Patched1 (Ptch1) heterozygous mice (Ptch1+/−). We demonstrated for the first time, that Ptch1+/− mice exhibit morphological, cellular and molecular alterations in the dentate gyrus (DG), including elongation and reduced width of the DG as well as deregulations at multiple steps during lineage progression from neural stem cells to neurons. By using stage-specific cellular markers, we detected reduction of quiescent stem cells, newborn neurons and astrocytes and accumulation of proliferating intermediate progenitors, indicative of defects in the dynamic transition among neural stages. Phenotypic alterations in Ptch1+/− mice were accompanied by expression changes in Notch pathway downstream components and TLX nuclear receptor, as well as perturbations in inflammatory and synaptic networks and mouse behavior, pointing to complex biological interactions and highlighting cooperation between Shh and Notch signaling in the regulation of neurogenesis.
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Affiliation(s)
- Francesca Antonelli
- Laboratory of Biomedical Technologies, Agenzia Nazionale per le Nuove Tecnologie, l'Energia e lo Sviluppo Economico Sostenibile (ENEA), Rome, Italy
| | - Arianna Casciati
- Laboratory of Biomedical Technologies, Agenzia Nazionale per le Nuove Tecnologie, l'Energia e lo Sviluppo Economico Sostenibile (ENEA), Rome, Italy
| | - Mirella Tanori
- Laboratory of Biomedical Technologies, Agenzia Nazionale per le Nuove Tecnologie, l'Energia e lo Sviluppo Economico Sostenibile (ENEA), Rome, Italy
| | - Barbara Tanno
- Laboratory of Biomedical Technologies, Agenzia Nazionale per le Nuove Tecnologie, l'Energia e lo Sviluppo Economico Sostenibile (ENEA), Rome, Italy
| | - Maria V Linares-Vidal
- Laboratory of Toxicology and Environmental Health, School of Medicine, Institut d'Investigació Sanitària Pere Virgili (IISPV), Rovira I Virgili University (URV), Reus, Spain.,Physiology Unit, School of Medicine, Institut d'Investigació Sanitària Pere Virgili (IISPV), Universitat Rovira i Virgili, Tarragona, Spain
| | - Noemi Serra
- Laboratory of Toxicology and Environmental Health, School of Medicine, Institut d'Investigació Sanitària Pere Virgili (IISPV), Rovira I Virgili University (URV), Reus, Spain.,Physiology Unit, School of Medicine, Institut d'Investigació Sanitària Pere Virgili (IISPV), Universitat Rovira i Virgili, Tarragona, Spain
| | - Monserrat Bellés
- Laboratory of Toxicology and Environmental Health, School of Medicine, Institut d'Investigació Sanitària Pere Virgili (IISPV), Rovira I Virgili University (URV), Reus, Spain.,Physiology Unit, School of Medicine, Institut d'Investigació Sanitària Pere Virgili (IISPV), Universitat Rovira i Virgili, Tarragona, Spain
| | - Alessandro Pannicelli
- Technical Unit of Energetic Efficiency, Agenzia Nazionale per le Nuove Tecnologie, l'Energia e lo Sviluppo Economico Sostenibile (ENEA), Rome, Italy
| | - Anna Saran
- Laboratory of Biomedical Technologies, Agenzia Nazionale per le Nuove Tecnologie, l'Energia e lo Sviluppo Economico Sostenibile (ENEA), Rome, Italy
| | - Simonetta Pazzaglia
- Laboratory of Biomedical Technologies, Agenzia Nazionale per le Nuove Tecnologie, l'Energia e lo Sviluppo Economico Sostenibile (ENEA), Rome, Italy
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63
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Ma W, Wu M, Zhou S, Tao Y, Xie Z, Zhong Y. Reduced Smoothened level rescues Aβ-induced memory deficits and neuronal inflammation in animal models of Alzheimer's disease. J Genet Genomics 2018; 45:237-246. [PMID: 29807798 DOI: 10.1016/j.jgg.2018.05.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 05/06/2018] [Accepted: 05/07/2018] [Indexed: 12/30/2022]
Abstract
Emerging evidence suggests that neuro-inflammation begins early and drives the pathogenesis of Alzheimer's disease (AD), and anti-inflammatory therapies are under clinical development. However, several anti-inflammatory compounds failed to improve memory in clinical trials, indicating that reducing inflammation alone might not be enough. On the other hand, neuro-inflammation is implicated in a number of mental disorders which share the same therapeutic targets. Based on these observations, we screened a batch of genes related with mental disorder and neuro-inflammation in a classical olfactory conditioning in an amyloid beta (Aβ) overexpression fly model. A Smoothened (SMO) mutant was identified as a genetic modifier of Aβ toxicity in 3-min memory and downregulation of SMO rescued Aβ-induced 3-min and 1-h memory deficiency. Also, Aβ activated innate inflammatory response in fly by increasing the expression of antimicrobial peptides, which were alleviated by downregulating SMO. Furthermore, pharmaceutical administration of a SMO antagonist LDE rescued Aβ-induced upregulation of SMO in astrocytes of mouse hippocampus, improved memory in Morris water maze (MWM), and reduced expression of astrocyte secreting pro-inflammatory factors IL-1β, TNFα and the microglia marker IBA-1 in an APP/PS1 transgenic mouse model. Our study suggests that SMO is an important conserved modulator of Aβ toxicity in both fly and mouse models of AD.
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Affiliation(s)
- Weiwei Ma
- School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Mengnan Wu
- School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Siyan Zhou
- School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Ye Tao
- Suzhou Joekai Biotechnology LLC, Suzhou 215347, China
| | - Zuolei Xie
- Beijing Joekai Biotechnology LLC, Beijing 100094, China
| | - Yi Zhong
- School of Life Sciences, Tsinghua University, Beijing 100084, China.
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64
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Lanjakornsiripan D, Pior BJ, Kawaguchi D, Furutachi S, Tahara T, Katsuyama Y, Suzuki Y, Fukazawa Y, Gotoh Y. Layer-specific morphological and molecular differences in neocortical astrocytes and their dependence on neuronal layers. Nat Commun 2018; 9:1623. [PMID: 29691400 PMCID: PMC5915416 DOI: 10.1038/s41467-018-03940-3] [Citation(s) in RCA: 175] [Impact Index Per Article: 29.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2017] [Accepted: 03/23/2018] [Indexed: 12/22/2022] Open
Abstract
Non-pial neocortical astrocytes have historically been thought to comprise largely a nondiverse population of protoplasmic astrocytes. Here we show that astrocytes of the mouse somatosensory cortex manifest layer-specific morphological and molecular differences. Two- and three-dimensional observations revealed that astrocytes in the different layers possess distinct morphologies as reflected by differences in cell orientation, territorial volume, and arborization. The extent of ensheathment of synaptic clefts by astrocytes in layer II/III was greater than that by those in layer VI. Moreover, differences in gene expression were observed between upper-layer and deep-layer astrocytes. Importantly, layer-specific differences in astrocyte properties were abrogated in reeler and Dab1 conditional knockout mice, in which neuronal layers are disturbed, suggesting that neuronal layers are a prerequisite for the observed morphological and molecular differences of neocortical astrocytes. This study thus demonstrates the existence of layer-specific interactions between neurons and astrocytes, which may underlie their layer-specific functions.
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Affiliation(s)
- Darin Lanjakornsiripan
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 113-0033, Japan
| | - Baek-Jun Pior
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 113-0033, Japan
| | - Daichi Kawaguchi
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 113-0033, Japan
| | - Shohei Furutachi
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 113-0033, Japan. .,Sainsbury Wellcome Centre for Neural Circuits and Behaviour, University College London, London, W1T 4JG, UK.
| | - Tomoaki Tahara
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 113-0033, Japan
| | - Yu Katsuyama
- Department of Anatomy, Shiga University of Medical Science, Otsu, 520-2192, Japan
| | - Yutaka Suzuki
- Department of Computational Biology, Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, 277-8561, Japan
| | - Yugo Fukazawa
- Graduate School of Medical Sciences, University of Fukui, Fukui, 910-1193, Japan
| | - Yukiko Gotoh
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 113-0033, Japan.
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65
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Sanchez MA, Sullivan GM, Armstrong RC. Genetic detection of Sonic hedgehog (Shh) expression and cellular response in the progression of acute through chronic demyelination and remyelination. Neurobiol Dis 2018; 115:145-156. [PMID: 29627579 DOI: 10.1016/j.nbd.2018.04.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 02/26/2018] [Accepted: 04/01/2018] [Indexed: 01/20/2023] Open
Abstract
Multiple sclerosis is a demyelinating disease in which neurological deficits result from damage to myelin, axons, and neuron cell bodies. Prolonged or repeated episodes of demyelination impair remyelination. We hypothesized that augmenting Sonic hedgehog (Shh) signaling in chronically demyelinated lesions could enhance oligodendrogenesis and remyelination. Shh regulates oligodendrocyte development during postnatal myelination, and maintains adult neural stem cells. We used genetic approaches to detect Shh expression and Shh responding cells in vivo. ShhCreERT2 or Gli1CreERT2 mice were crossed to reporter mice for genetic fate-labeling of cells actively transcribing Shh or Gli1, an effective readout of canonical Shh signaling. Tamoxifen induction enabled temporal control of recombination at distinct stages of acute and chronic cuprizone demyelination of the corpus callosum. Gli1 fate-labeled cells were rarely found in the corpus callosum with tamoxifen given during acute demyelination stages to examine activated microglia, reactive astrocytes, or remyelinating cells. Gli1 fate-labeled cells, mainly reactive astrocytes, were observed in the corpus callosum with tamoxifen given after chronic demyelination. However, Shh expressing cells were not detected in the corpus callosum during acute or chronic demyelination. Finally, SAG, an agonist of both canonical and type II non-canonical Hedgehog signaling pathways, was microinjected into the corpus callosum after chronic demyelination. Significantly, SAG delivery increased proliferation and enhanced remyelination. SAG did not increase Gli1 fate-labeled cells in the corpus callosum, which may indicate signaling through the non-canonical Hedgehog pathway. These studies demonstrate that Hedgehog pathway interventions may have therapeutic potential to modulate astrogliosis and to promote remyelination after chronic demyelination.
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Affiliation(s)
- Maria A Sanchez
- Program in Neuroscience, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA; Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA
| | - Genevieve M Sullivan
- Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA; Center for Neuroscience and Regenerative Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA
| | - Regina C Armstrong
- Program in Neuroscience, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA; Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA; Center for Neuroscience and Regenerative Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA.
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66
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BMP-Responsive Protease HtrA1 Is Differentially Expressed in Astrocytes and Regulates Astrocytic Development and Injury Response. J Neurosci 2018; 38:3840-3857. [PMID: 29483282 DOI: 10.1523/jneurosci.2031-17.2018] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 01/23/2018] [Accepted: 01/29/2018] [Indexed: 11/21/2022] Open
Abstract
Astrocytes perform a wide array of physiological functions, including structural support, ion exchange, and neurotransmitter uptake. Despite this diversity, molecular markers that label subpopulations of astrocytes are limited, and mechanisms that generate distinct astrocyte subtypes remain unclear. Here we identified serine protease high temperature requirement A 1 (HtrA1), a bone morphogenetic protein 4 signaling regulated protein, as a novel marker of forebrain astrocytes, but not of neural stem cells, in adult mice of both sexes. Genetic deletion of HtrA1 during gliogenesis accelerates astrocyte differentiation. In addition, ablation of HtrA1 in cultured astrocytes leads to altered chondroitin sulfate proteoglycan expression and inhibition of neurite extension, along with elevated levels of transforming growth factor-β family proteins. Brain injury induces HtrA1 expression in reactive astrocytes, and loss of HtrA1 leads to an impairment in wound closure accompanied by increased proliferation of endothelial and immune cells. Our findings demonstrate that HtrA1 is differentially expressed in adult mouse forebrain astrocytes, and that HtrA1 plays important roles in astrocytic development and injury response.SIGNIFICANCE STATEMENT Astrocytes, an abundant cell type in the brain, perform a wide array of physiological functions. Although characterized as morphologically and functionally diverse, molecular markers that label astrocyte subtypes or signaling pathways that lead to their diversity remain limited. Here, after examining the expression profile of astrocytes generated in response to bone morphogenetic protein signaling, we identify high temperature requirement A 1 (HtrA1) as an astrocyte-specific marker that is differentially expressed in distinct adult mouse brain regions. HtrA1 is a serine protease that has been linked to cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy, a small blood vessel disease in humans. Understanding the role of HtrA1 during development and after injury will provide insights into how distinct astrocyte populations are generated and their unique roles in injury and disease.
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67
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Yamada Y, Ohazama A, Maeda T, Seo K. The Sonic Hedgehog signaling pathway regulates inferior alveolar nerve regeneration. Neurosci Lett 2018; 671:114-119. [PMID: 29428403 DOI: 10.1016/j.neulet.2017.12.051] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 12/16/2017] [Accepted: 12/22/2017] [Indexed: 02/08/2023]
Abstract
Activation of Shh signaling is known to be observed following injury of the peripheral nerves such as the sciatic nerve. However, the precise role of Shh signaling during peripheral nerve regeneration is not fully understood. The inferior alveolar nerve (IAN) is most commonly injured during oral surgery. Unlike the sciatic nerve, the IAN is isolated from other craniofacial tissues, as it resides in a long bony canal within the mandible. The IAN is thus an excellent experimental model for investigating peripheral nerve regeneration. In this study, the role of Shh signaling in peripheral nerve regeneration was investigated using the mouse IAN transection model. During regeneration, Shh signaling was activated within the entire distal region of the IAN and proximal stumps. Inhibition of Shh signaling by cyclopamine application at the transection site led to abnormal axon growth in random directions, a reduced number of macrophages, and an increase in myelin debris within the distal region. Shh signaling is thus involved in peripheral nerve regeneration via the regulation of myelin degradation.
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Affiliation(s)
- Yurie Yamada
- Center for Advanced Oral Science, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan; Division of Oral Anatomy, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Atsushi Ohazama
- Division of Oral Anatomy, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Takeyasu Maeda
- Center for Advanced Oral Science, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Kenji Seo
- Division of Dental Anesthesiology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
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68
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Postnatal Sonic hedgehog (Shh) responsive cells give rise to oligodendrocyte lineage cells during myelination and in adulthood contribute to remyelination. Exp Neurol 2018; 299:122-136. [DOI: 10.1016/j.expneurol.2017.10.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 09/23/2017] [Accepted: 10/13/2017] [Indexed: 12/21/2022]
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69
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Farmer WT, Murai K. Resolving Astrocyte Heterogeneity in the CNS. Front Cell Neurosci 2017; 11:300. [PMID: 29021743 PMCID: PMC5623685 DOI: 10.3389/fncel.2017.00300] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 09/11/2017] [Indexed: 01/30/2023] Open
Abstract
Astrocytes play essential roles in nearly all aspects of brain function from modulating synapses and neurovasculature to preserving appropriate extracellular solute concentrations. To meet the complex needs of the central nervous system (CNS), astrocytes possess highly specialized properties that are optimized for their surrounding neural circuitry. Precisely how these diverse astrocytes types are generated in vivo, however, remains poorly understood. Key to this process is a critical balance of intrinsic developmental patterning and context-dependent environmental signaling events that configures astrocyte phenotype. Indeed, emerging lines of evidence indicate that persistent cues from neighboring cells in the mature CNS cooperate with early patterning events to promote astrocyte diversity. Consistent with this, manipulating Sonic hedgehog (Shh), Notch and fibroblast growth factor (FGF) signaling in the adult brain, have profound effects on the structural, morphological and physiological state of mature astrocytes. These pathways may become disrupted in various neurological diseases and contribute to CNS pathology. This mini-review article focuses on how context-dependent environmental cues cooperate with intrinsic developmental patterning events to control astrocyte diversity in vivo in order to promote healthy brain function.
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Affiliation(s)
- W Todd Farmer
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Center, Montreal General Hospital, Montreal, QC, Canada
| | - Keith Murai
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Center, Montreal General Hospital, Montreal, QC, Canada
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70
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Verkhratsky A, Zorec R, Parpura V. Stratification of astrocytes in healthy and diseased brain. Brain Pathol 2017; 27:629-644. [PMID: 28805002 PMCID: PMC5599174 DOI: 10.1111/bpa.12537] [Citation(s) in RCA: 153] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 06/03/2017] [Accepted: 06/06/2017] [Indexed: 12/11/2022] Open
Abstract
Astrocytes, a subtype of glial cells, come in variety of forms and functions. However, overarching role of these cell is in the homeostasis of the brain, be that regulation of ions, neurotransmitters, metabolism or neuronal synaptic networks. Loss of homeostasis represents the underlying cause of all brain disorders. Thus, astrocytes are likely involved in most if not all of the brain pathologies. We tabulate astroglial homeostatic functions along with pathological condition that arise from dysfunction of these glial cells. Classification of astrocytes is presented with the emphasis on evolutionary trails, morphological appearance and numerical preponderance. We note that, even though astrocytes from a variety of mammalian species share some common features, human astrocytes appear to be the largest and most complex of all astrocytes studied thus far. It is then an imperative to develop humanized models to study the role of astrocytes in brain pathologies, which is perhaps most abundantly clear in the case of glioblastoma multiforme.
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Affiliation(s)
- Alexei Verkhratsky
- Division of Neuroscience & Experimental PsychologyThe University of ManchesterManchesterUnited Kingdom
- Achúcarro Basque Center for NeuroscienceIKERBASQUE, Basque Foundation for Science48011 BilbaoSpain
- Department of NeuroscienceUniversity of the Basque Country UPV/EHU and CIBERNED48940 LeioaSpain
| | - Robert Zorec
- Laboratory of Cell EngineeringCelica BIOMEDICAL, Tehnološki park 24, Ljubljana 1000SloveniaEurope
- Laboratory of Neuroendocrinology‐Molecular Cell PhysiologyInstitute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, Ljubljana 1000SloveniaEurope
| | - Vladimir Parpura
- Department of Neurobiology, Civitan International Research Center and Center for Glial Biology in Medicine, Evelyn F. McKnight Brain Institute, Atomic Force Microscopy & Nanotechnology Laboratories, 1719 6th Avenue South, CIRC 429University of Alabama at BirminghamBirminghamAL 35294‐0021
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71
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Transplanted Adult Neural Stem Cells Express Sonic Hedgehog In Vivo and Suppress White Matter Neuroinflammation after Experimental Traumatic Brain Injury. Stem Cells Int 2017; 2017:9342534. [PMID: 29081811 PMCID: PMC5610817 DOI: 10.1155/2017/9342534] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 04/19/2017] [Accepted: 06/05/2017] [Indexed: 01/05/2023] Open
Abstract
Neural stem cells (NSCs) delivered intraventricularly may be therapeutic for diffuse white matter pathology after traumatic brain injury (TBI). To test this concept, NSCs isolated from adult mouse subventricular zone (SVZ) were transplanted into the lateral ventricle of adult mice at two weeks post-TBI followed by analysis at four weeks post-TBI. We examined sonic hedgehog (Shh) signaling as a candidate mechanism by which transplanted NSCs may regulate neuroregeneration and/or neuroinflammation responses of endogenous cells. Mouse fluorescent reporter lines were generated to enable in vivo genetic labeling of cells actively transcribing Shh or Gli1 after transplantation and/or TBI. Gli1 transcription is an effective readout for canonical Shh signaling. In ShhCreERT2;R26tdTomato mice, Shh was primarily expressed in neurons and was not upregulated in reactive astrocytes or microglia after TBI. Corroborating results in Gli1CreERT2;R26tdTomato mice demonstrated that Shh signaling was not upregulated in the corpus callosum, even after TBI or NSC transplantation. Transplanted NSCs expressed Shh in vivo but did not increase Gli1 labeling of host SVZ cells. Importantly, NSC transplantation significantly reduced reactive astrogliosis and microglial/macrophage activation in the corpus callosum after TBI. Therefore, intraventricular NSC transplantation after TBI significantly attenuated neuroinflammation, but did not activate host Shh signaling via Gli1 transcription.
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72
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Ding S, Yang J, Huang X, Liu L, Hu J, Xu Z, Zhuge Q. Dopamine Burden Induced the Inactivation of Sonic Hedgehog Signaling to Cognitive Decline in Minimal Hepatic Encephalopathy. Aging Dis 2017; 8:442-457. [PMID: 28840059 PMCID: PMC5524807 DOI: 10.14336/ad.2016.1123] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2016] [Accepted: 11/23/2016] [Indexed: 12/20/2022] Open
Abstract
Minimal hepatic encephalopathy (MHE) is induced by elevated intracranial dopamine (DA). The relationship of the Shh pathway with memory loss in MHE, however, is elusive. In the current study, rats with MHE induced with DA displayed downregulation of the Shh pathway. Additionally, injection of Shh into MHE/DA-treated rats reversed downregulation of BDNF/NT3, whereas administration of cyclopamine (Cyc) enhanced the inhibition of expression of BDNF/NT3. Furthermore, naringin (Nrg) substantially prevented cognitive impairment in MHE/DA-treated rats and upregulated the Shh pathway, paralleling the elevated expression of BDNF/NT3. Overall, our results indicate that the Shh pathway can induce the expression of BDNF/NT3, and DA causes memory loss by inactivation of Shh pathway signaling to BDNF/NT3 in MHE rats, which is reversed by Nrg. Our study may provide new theory basis of pathogenesis and therapeutic target of MHE.
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Affiliation(s)
- Saidan Ding
- 1Zhejiang Provincial Key Laboratory of Aging and Neurological Disease Research, Department of Surgery Laboratory, the First Affiliated Hospital, Wenzhou Medical University, Zhejiang 325000, China
| | - Jianjing Yang
- 2Department of Neurosurgery, the First Affiliated Hospital, Wenzhou Medical University, Zhejiang 325000, China
| | - Xueli Huang
- 3School of Pharmaceutical Sciences, Wenzhou Medical University, Zhejiang 325000, China
| | - Leping Liu
- 1Zhejiang Provincial Key Laboratory of Aging and Neurological Disease Research, Department of Surgery Laboratory, the First Affiliated Hospital, Wenzhou Medical University, Zhejiang 325000, China
| | - Jiangnan Hu
- 4Institute for Healthy Aging, University of North Texas Health Science Center, Fort Worth, Texas 76107, USA
| | - Zhu Xu
- 2Department of Neurosurgery, the First Affiliated Hospital, Wenzhou Medical University, Zhejiang 325000, China
| | - Qichuan Zhuge
- 2Department of Neurosurgery, the First Affiliated Hospital, Wenzhou Medical University, Zhejiang 325000, China
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73
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Ugbode CI, Smith I, Whalley BJ, Hirst WD, Rattray M. Sonic hedgehog signalling mediates astrocyte crosstalk with neurons to confer neuroprotection. J Neurochem 2017; 142:429-443. [PMID: 28485896 PMCID: PMC5575469 DOI: 10.1111/jnc.14064] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 04/18/2017] [Accepted: 05/03/2017] [Indexed: 01/10/2023]
Abstract
Sonic hedgehog (SHH) is a glycoprotein associated with development that is also expressed in the adult CNS and released after brain injury. Since the SHH receptors patched homolog‐1 and Smoothened are highly expressed on astrocytes, we hypothesized that SHH regulates astrocyte function. Primary mouse cortical astrocytes derived from embryonic Swiss mouse cortices, were treated with two chemically distinct agonists of the SHH pathway, which caused astrocytes to elongate and proliferate. These changes are accompanied by decreases in the major astrocyte glutamate transporter‐1 and the astrocyte intermediate filament protein glial fibrillary acidic protein. Multisite electrophysiological recordings revealed that the SHH agonist, smoothened agonist suppressed neuronal firing in astrocyte‐neuron co‐cultures and this was abolished by the astrocyte metabolic inhibitor ethylfluoroacetate, revealing that SHH stimulation of metabolically active astrocytes influences neuronal firing. Using three‐dimensional co‐culture, MAP2 western blotting and immunohistochemistry, we show that SHH‐stimulated astrocytes protect neurons from kainate‐induced cell death. Altogether the results show that SHH regulation of astrocyte function represents an endogenous neuroprotective mechanism. ![]()
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Affiliation(s)
- Christopher I Ugbode
- School of Pharmacy, University of Bradford, Bradford, UK.,School of Chemistry, Food & Pharmacy, University of Reading, Reading, UK.,Department of Biology, University of York, Heslington, UK
| | - Imogen Smith
- School of Chemistry, Food & Pharmacy, University of Reading, Reading, UK.,Portsmouth Brain Tumour Research Centre, University of Portsmouth, Portsmouth, UK
| | - Benjamin J Whalley
- School of Chemistry, Food & Pharmacy, University of Reading, Reading, UK
| | - Warren D Hirst
- Neurodegeneration and Neurologic Diseases, Pfizer Neuroscience Research Unit, Cambridge, Massachusetts, USA
| | - Marcus Rattray
- School of Pharmacy, University of Bradford, Bradford, UK
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74
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Lee JH, Chung YC, Bok E, Lee H, Huh SH, Lee JE, Jin BK, Ko HW. Injury-stimulated Sonic hedgehog expression in microglia contributes to neuroinflammatory response in the MPTP model of Parkinson's disease. Biochem Biophys Res Commun 2017; 482:980-986. [DOI: 10.1016/j.bbrc.2016.11.144] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2016] [Accepted: 11/26/2016] [Indexed: 01/20/2023]
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75
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76
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Wang IE, Lapan SW, Scimone ML, Clandinin TR, Reddien PW. Hedgehog signaling regulates gene expression in planarian glia. eLife 2016; 5:e16996. [PMID: 27612382 PMCID: PMC5055395 DOI: 10.7554/elife.16996] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2016] [Accepted: 09/02/2016] [Indexed: 12/23/2022] Open
Abstract
Hedgehog signaling is critical for vertebrate central nervous system (CNS) development, but its role in CNS biology in other organisms is poorly characterized. In the planarian Schmidtea mediterranea, hedgehog (hh) is expressed in medial cephalic ganglia neurons, suggesting a possible role in CNS maintenance or regeneration. We performed RNA sequencing of planarian brain tissue following RNAi of hh and patched (ptc), which encodes the Hh receptor. Two misregulated genes, intermediate filament-1 (if-1) and calamari (cali), were expressed in a previously unidentified non-neural CNS cell type. These cells expressed orthologs of astrocyte-associated genes involved in neurotransmitter uptake and metabolism, and extended processes enveloping regions of high synapse concentration. We propose that these cells are planarian glia. Planarian glia were distributed broadly, but only expressed if-1 and cali in the neuropil near hh+ neurons. Planarian glia and their regulation by Hedgehog signaling present a novel tractable system for dissection of glia biology.
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Affiliation(s)
- Irving E Wang
- Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, United States
- Whitehead Institute, Massachusetts Institute of Technology, Cambridge, United States
- Department of Neurobiology, Stanford University, Stanford, United States
| | - Sylvain W Lapan
- Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, United States
- Whitehead Institute, Massachusetts Institute of Technology, Cambridge, United States
| | - M Lucila Scimone
- Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, United States
- Whitehead Institute, Massachusetts Institute of Technology, Cambridge, United States
| | - Thomas R Clandinin
- Department of Neurobiology, Stanford University, Stanford, United States
| | - Peter W Reddien
- Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, United States
- Whitehead Institute, Massachusetts Institute of Technology, Cambridge, United States
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77
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Choe S, Bond CW, Harrington DA, Stupp SI, McVary KT, Podlasek CA. Peptide amphiphile nanofiber hydrogel delivery of sonic hedgehog protein to the cavernous nerve to promote regeneration and prevent erectile dysfunction. NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE 2016; 13:95-101. [PMID: 27609775 DOI: 10.1016/j.nano.2016.08.032] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 08/22/2016] [Indexed: 11/15/2022]
Abstract
Erectile dysfunction (ED) has high impact on quality of life in prostatectomy, diabetic and aging patients. An underlying mechanism is cavernous nerve (CN) injury, which causes ED in up to 80% of prostatectomy patients. We examine how sonic hedgehog (SHH) treatment with innovative peptide amphiphile nanofiber hydrogels (PA), promotes CN regeneration after injury. SHH and its receptors patched (PTCH1) and smoothened (SMO) are localized in PG neurons and glia. SMO undergoes anterograde transport to signal to downstream targets. With crush injury, PG neurons degenerate and undergo apoptosis. SHH protein decreases, SMO localization changes to the neuronal cell surface, and anterograde transport stops. With SHH treatment SHH is taken up at the injury site and undergoes retrograde transport to PG neurons, allowing SMO transport to occur, and neurons remain intact. SHH treatment prevents neuronal degeneration, maintains neuronal, glial and downstream target signaling, and is significant as a regenerative therapy.
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Affiliation(s)
- Shawn Choe
- Department of Urology, University of Illinois at Chicago, Chicago, IL, USA
| | - Christopher W Bond
- Department of Allergy/Immunology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | | | - Samuel I Stupp
- Simpson-Querrey Institute for BioNanotechnology, Department of Chemistry, Department of Materials Science and Engineering, and Biomedical Engineering, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | - Kevin T McVary
- Division of Urology, Southern Illinois University School of Medicine, Springfield, IL, USA
| | - Carol A Podlasek
- Departments of Urology, Physiology and Bioengineering, University of Illinois at Chicago, Chicago, IL, USA.
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78
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Disrupted hippocampal network physiology following PTEN deletion from newborn dentate granule cells. Neurobiol Dis 2016; 96:105-114. [PMID: 27597527 DOI: 10.1016/j.nbd.2016.09.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 08/04/2016] [Accepted: 09/01/2016] [Indexed: 01/28/2023] Open
Abstract
Abnormal hippocampal granule cells are present in patients with temporal lobe epilepsy, and are a prominent feature of most animal models of the disease. These abnormal cells are hypothesized to contribute to epileptogenesis. Isolating the specific effects of abnormal granule cells on hippocampal physiology, however, has been difficult in traditional temporal lobe epilepsy models. While epilepsy induction in these models consistently produces abnormal granule cells, the causative insults also induce widespread cell death among hippocampal, cortical and subcortical structures. Recently, we demonstrated that introducing morphologically abnormal granule cells into an otherwise normal mouse brain - by selectively deleting the mTOR pathway inhibitor PTEN from postnatally-generated granule cells - produced hippocampal and cortical seizures. Here, we conducted acute slice field potential recordings to assess the impact of these cells on hippocampal function. PTEN deletion from a subset of granule cells reproduced aberrant responses present in traditional epilepsy models, including enhanced excitatory post-synaptic potentials (fEPSPs) and multiple, rather than single, population spikes in response to perforant path stimulation. These findings provide new evidence that abnormal granule cells initiate a process of epileptogenesis - in the absence of widespread cell death - which culminates in an abnormal dentate network similar to other models of temporal lobe epilepsy. Findings are consistent with the hypothesis that accumulation of abnormal granule cells is a common mechanism of temporal lobe epileptogenesis.
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79
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Wang GH, Liu Y, Wu XB, Lu Y, Liu J, Qin YR, Li T, Duan HF. Neuroprotective effects of human umbilical cord-derived mesenchymal stromal cells combined with nimodipine against radiation-induced brain injury through inhibition of apoptosis. Cytotherapy 2016; 18:53-64. [PMID: 26719199 DOI: 10.1016/j.jcyt.2015.10.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Revised: 09/30/2015] [Accepted: 10/05/2015] [Indexed: 12/21/2022]
Abstract
BACKGROUND AIMS Mesenchymal stromal cells (MSCs) possess the ability to repair brain injuries. Additionally, nimodipine is a neuroprotective agent that increases cerebral blood flow and may help with the homing of MSCs to the injury site. Here we investigate the effectiveness of a combined human umbilical cord-derived MSCs and nimodipine therapy in radiation-induced brain injury (RIBI). METHODS Female mice received whole brain irradiation (WBI) and were treated with saline, nimodipine, hUC-MSCs, or hUC-MSCs combined with nimodipine. Body weight was measured weekly. An open field test for locomotor activity and a step-down avoidance test for learning and memory function were conducted at week 4 and week 12 post-WBI. The histological damage was evaluated by hematoxylin and eosin staining and glial fibrillary acidic protein immunohistochemistry. Quantitative polymerase chain reaction and Western blotting were used to detect apoptosis-related mediators (p53, Bax and Bcl-2). RESULTS In mice receiving the hUC-MSCs or the combined treatment, their body weight recovered, their locomotor and cognitive ability improved, and the percentage of necrotic neurons and astrocytes was reduced. The combined therapy was significantly (P < 0.05) more effective than hUC-MSCs alone; these mice showed decreased expression of pro-apoptotic indicators (p53, Bax) and increased expression of an anti-apoptotic indicator (Bcl-2), which may protect brain cells. CONCLUSIONS We demonstrated that hUC-MSCs therapy helps recover body weight loss and behavior dysfunction in a mice model of RIBI. Moreover, the effectiveness of the combined hUC-MSCs and nimodipine therapy is due to apoptosis inhibition and enhancing homing of MSCs to the injured brain.
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Affiliation(s)
- Gui-Hua Wang
- Department of Neurology, the First Affiliated Hospital of Xinxiang Medical University, Xinxiang, Henan, China; Beijing Institute of Radiation Medicine, Beijing, China
| | - Yang Liu
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, China
| | - Xiao-Bing Wu
- Beijing Institute of Radiation Medicine, Beijing, China
| | - Ying Lu
- No. 307 Hospital of the Chinese People's Liberation Army, Beijing, China
| | - Jin Liu
- Beijing Institute of Radiation Medicine, Beijing, China
| | - Ya-Ru Qin
- Beijing Institute of Radiation Medicine, Beijing, China
| | - Tong Li
- Department of Neurology, the First Affiliated Hospital of Xinxiang Medical University, Xinxiang, Henan, China.
| | - Hai-Feng Duan
- Beijing Institute of Radiation Medicine, Beijing, China.
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80
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Eitan E, Petralia RS, Wang YX, Indig FE, Mattson MP, Yao PJ. Probing extracellular Sonic hedgehog in neurons. Biol Open 2016; 5:1086-92. [PMID: 27387534 PMCID: PMC5004615 DOI: 10.1242/bio.019422] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 06/20/2016] [Indexed: 01/02/2023] Open
Abstract
The bioactivity of Sonic hedgehog (Shh) depends on specific lipid modifications; a palmitate at its N-terminus and a cholesterol at its C-terminus. This dual-lipid modification makes Shh molecules lipophilic, which prevents them from diffusing freely in extracellular space. Multiple lines of evidence indicate that Shh proteins are carried by various forms of extracellular vesicles (EVs). It also has been shown, for instance, that in some tissues Shh proteins are transported to neighboring cells directly via filopodia. We have previously reported that Shh proteins are expressed in hippocampal neurons. In this study we show that, in the hippocampus and cerebellum of postnatal day (P)2 rats, Shh is mostly found near or on the membrane surface of small neurites or filopodia. We also examined cultured hippocampal neurons where we observed noticeable and widespread Shh-immunolabeled vesicles located outside neurons. Through immunoelectron microscopy and biochemical analysis, we find Shh-containing EVs with a wide range of sizes. Unlike robust Shh activity in EVs isolated from cells overexpressing an N-terminal Shh fragment construct, we did not detect measurable Shh activity in EVs purified from the medium of cultured hippocampal neurons. These results suggest the complexity of the transcellular Shh signaling mechanisms in neurons.
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Affiliation(s)
- Erez Eitan
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD 21224, USA
| | | | - Ya-Xian Wang
- Advanced Imaging Core, NIDCD/NIH, Bethesda, MD 20892, USA
| | - Fred E Indig
- Confocal Imaging Facility, Laboratory of Clinical Investigation, National Institute on Aging Intramural Research Program, Baltimore, MD 21224, USA
| | - Mark P Mattson
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD 21224, USA
| | - Pamela J Yao
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD 21224, USA
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81
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Honsa P, Valny M, Kriska J, Matuskova H, Harantova L, Kirdajova D, Valihrach L, Androvic P, Kubista M, Anderova M. Generation of reactive astrocytes from NG2 cells is regulated by sonic hedgehog. Glia 2016; 64:1518-31. [DOI: 10.1002/glia.23019] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 05/10/2016] [Accepted: 05/26/2016] [Indexed: 11/10/2022]
Affiliation(s)
- Pavel Honsa
- Department of Cellular Neurophysiology; Institute of Experimental Medicine, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Martin Valny
- Department of Cellular Neurophysiology; Institute of Experimental Medicine, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Jan Kriska
- Department of Cellular Neurophysiology; Institute of Experimental Medicine, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Hana Matuskova
- Department of Cellular Neurophysiology; Institute of Experimental Medicine, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Lenka Harantova
- Department of Cellular Neurophysiology; Institute of Experimental Medicine, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Denisa Kirdajova
- Department of Cellular Neurophysiology; Institute of Experimental Medicine, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Lukas Valihrach
- Laboratory of Gene Expression; Institute of Biotechnology, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Peter Androvic
- Laboratory of Gene Expression; Institute of Biotechnology, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Mikael Kubista
- Laboratory of Gene Expression; Institute of Biotechnology, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Miroslava Anderova
- Department of Cellular Neurophysiology; Institute of Experimental Medicine, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
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82
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Smoothened Agonist Reduces Human Immunodeficiency Virus Type-1-Induced Blood-Brain Barrier Breakdown in Humanized Mice. Sci Rep 2016; 6:26876. [PMID: 27241024 PMCID: PMC4886511 DOI: 10.1038/srep26876] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 05/10/2016] [Indexed: 11/09/2022] Open
Abstract
Human Immunodeficiency Virus type-1 (HIV)-associated neurocognitive disorder is characterized by recruitment of activated/infected leukocytes into the CNS via disrupted Blood Brain Barrier (BBB) that contributes to persistent neuro-inflammation. In this report, humanized NOD/scid-IL2Rγcnull mice were used to establish that impaired Sonic hedgehog (Shh) signaling is associated with loss of BBB function and neurological damage, and that modulating Shh signaling can rescue these detrimental effects. Plasma viral load, p24 levels and CD4+ T cells were measured as markers of productive HIV infection. These mice also showed impaired exclusion of Evans blue dye from the brain, increased plasma levels of S100B, an astrocytic protein, and down-regulation of tight junction proteins Occludin and Claudin5, collectively indicating BBB dysfunction. Further, brain tissue from HIV+ mice indicated reduced synaptic density, neuronal atrophy, microglial activation, and astrocytosis. Importantly, reduced expression of Shh and Gli1 was also observed in these mice, demonstrating diminished Shh signaling. Administration of Shh mimetic, smoothened agonist (SAG) restored BBB integrity and also abated the neuropathology in infected mice. Together, our results suggest a neuroprotective role for Shh signaling in the context of HIV infection, underscoring the therapeutic potential of SAG in controlling HAND pathogenesis.
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83
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Abstract
Stroke not only causes initial cell death, but also a limited process of repair and recovery. As an overall biological process, stroke has been most often considered from the perspective of early phases of ischemia, how these inter-relate and lead to expansion of the infarct. However, just as the biology of later stages of stroke becomes better understood, the clinical realities of stroke indicate that it is now more a chronic disease than an acute killer. As an overall biological process, it is now more important to understand how early cell death leads to the later, limited recovery so as develop an integrative view of acute to chronic stroke. This progression from death to repair involves sequential stages of primary cell death, secondary injury events, reactive tissue progenitor responses, and formation of new neuronal circuits. This progression is radial: from the tissue that suffers the infarct secondary injury signals, including free radicals and inflammatory cytokines, radiate out from the stroke core to trigger later regenerative events. Injury and repair processes occur not just in the local stroke site, but are also triggered in the connected networks of neurons that had existed in the stroke center: damage signals are relayed throughout a brain network. From these relayed, distributed damage signals, reactive astrocytosis, inflammatory processes, and the formation of new connections occur in distant brain areas. In short, emerging data in stroke cell death studies and the development of the field of stroke neural repair now indicate a continuum in time and in space of progressive events that can be considered as the 3 Rs of stroke biology: radial, relayed, and regenerative.
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Affiliation(s)
- S Thomas Carmichael
- Departments of Neurology and Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
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84
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Farmer WT, Abrahamsson T, Chierzi S, Lui C, Zaelzer C, Jones EV, Bally BP, Chen GG, Théroux JF, Peng J, Bourque CW, Charron F, Ernst C, Sjöström PJ, Murai KK. Neurons diversify astrocytes in the adult brain through sonic hedgehog signaling. Science 2016; 351:849-54. [PMID: 26912893 DOI: 10.1126/science.aab3103] [Citation(s) in RCA: 186] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Astrocytes are specialized and heterogeneous cells that contribute to central nervous system function and homeostasis. However, the mechanisms that create and maintain differences among astrocytes and allow them to fulfill particular physiological roles remain poorly defined. We reveal that neurons actively determine the features of astrocytes in the healthy adult brain and define a role for neuron-derived sonic hedgehog (Shh) in regulating the molecular and functional profile of astrocytes. Thus, the molecular and physiological program of astrocytes is not hardwired during development but, rather, depends on cues from neurons that drive and sustain their specialized properties.
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Affiliation(s)
- W Todd Farmer
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Therése Abrahamsson
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Sabrina Chierzi
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Christopher Lui
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Cristian Zaelzer
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Emma V Jones
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Blandine Ponroy Bally
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Gary G Chen
- Department of Psychiatry, McGill University, Montreal, Quebec, Canada. McGill Group for Suicide Studies, Douglas Hospital, Montreal, Quebec, Canada
| | - Jean-Francois Théroux
- Department of Psychiatry, McGill University, Montreal, Quebec, Canada. McGill Group for Suicide Studies, Douglas Hospital, Montreal, Quebec, Canada
| | - Jimmy Peng
- Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal, Department of Medicine, University of Montreal, Montreal, Quebec, Canada. Department of Biology, McGill University, Montreal, Quebec, Canada
| | - Charles W Bourque
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Frédéric Charron
- Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal, Department of Medicine, University of Montreal, Montreal, Quebec, Canada. Department of Biology, McGill University, Montreal, Quebec, Canada
| | - Carl Ernst
- Department of Psychiatry, McGill University, Montreal, Quebec, Canada. McGill Group for Suicide Studies, Douglas Hospital, Montreal, Quebec, Canada. Department of Human Genetics, McGill University, Montreal, Quebec, Canada. Douglas Hospital Research Institute, Verdun, Quebec, Canada
| | - P Jesper Sjöström
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Keith K Murai
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada.
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85
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Astrocytes: a central element in neurological diseases. Acta Neuropathol 2016; 131:323-45. [PMID: 26671410 DOI: 10.1007/s00401-015-1513-1] [Citation(s) in RCA: 531] [Impact Index Per Article: 66.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Revised: 10/28/2015] [Accepted: 11/21/2015] [Indexed: 12/18/2022]
Abstract
The neurone-centred view of the past disregarded or downplayed the role of astroglia as a primary component in the pathogenesis of neurological diseases. As this concept is changing, so is also the perceived role of astrocytes in the healthy and diseased brain and spinal cord. We have started to unravel the different signalling mechanisms that trigger specific molecular, morphological and functional changes in reactive astrocytes that are critical for repairing tissue and maintaining function in CNS pathologies, such as neurotrauma, stroke, or neurodegenerative diseases. An increasing body of evidence shows that the effects of astrogliosis on the neural tissue and its functions are not uniform or stereotypic, but vary in a context-specific manner from astrogliosis being an adaptive beneficial response under some circumstances to a maladaptive and deleterious process in another context. There is a growing support for the concept of astrocytopathies in which the disruption of normal astrocyte functions, astrodegeneration or dysfunctional/maladaptive astrogliosis are the primary cause or the main factor in neurological dysfunction and disease. This review describes the multiple roles of astrocytes in the healthy CNS, discusses the diversity of astroglial responses in neurological disorders and argues that targeting astrocytes may represent an effective therapeutic strategy for Alexander disease, neurotrauma, stroke, epilepsy and Alzheimer's disease as well as other neurodegenerative diseases.
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86
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De Luca A, Cerrato V, Fucà E, Parmigiani E, Buffo A, Leto K. Sonic hedgehog patterning during cerebellar development. Cell Mol Life Sci 2016; 73:291-303. [PMID: 26499980 PMCID: PMC11108499 DOI: 10.1007/s00018-015-2065-1] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Revised: 10/06/2015] [Accepted: 10/08/2015] [Indexed: 01/30/2023]
Abstract
The morphogenic factor sonic hedgehog (Shh) actively orchestrates many aspects of cerebellar development and maturation. During embryogenesis, Shh signaling is active in the ventricular germinal zone (VZ) and represents an essential signal for proliferation of VZ-derived progenitors. Later, Shh secreted by Purkinje cells sustains the amplification of postnatal neurogenic niches: the external granular layer and the prospective white matter, where excitatory granule cells and inhibitory interneurons are produced, respectively. Moreover, Shh signaling affects Bergmann glial differentiation and promotes cerebellar foliation during development. Here we review the most relevant functions of Shh during cerebellar ontogenesis, underlying its role in physiological and pathological conditions.
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Affiliation(s)
- Annarita De Luca
- Department of Neuroscience Rita Levi-Montalcini, University of Turin, 10126, Turin, Italy
- Neuroscience Institute Cavalieri Ottolenghi, Regione Gonzole 10, 10043, Orbassano, Turin, Italy
| | - Valentina Cerrato
- Department of Neuroscience Rita Levi-Montalcini, University of Turin, 10126, Turin, Italy
- Neuroscience Institute Cavalieri Ottolenghi, Regione Gonzole 10, 10043, Orbassano, Turin, Italy
| | - Elisa Fucà
- Department of Neuroscience Rita Levi-Montalcini, University of Turin, 10126, Turin, Italy
- Neuroscience Institute Cavalieri Ottolenghi, Regione Gonzole 10, 10043, Orbassano, Turin, Italy
| | - Elena Parmigiani
- Department of Neuroscience Rita Levi-Montalcini, University of Turin, 10126, Turin, Italy
- Neuroscience Institute Cavalieri Ottolenghi, Regione Gonzole 10, 10043, Orbassano, Turin, Italy
| | - Annalisa Buffo
- Department of Neuroscience Rita Levi-Montalcini, University of Turin, 10126, Turin, Italy
- Neuroscience Institute Cavalieri Ottolenghi, Regione Gonzole 10, 10043, Orbassano, Turin, Italy
| | - Ketty Leto
- Department of Neuroscience Rita Levi-Montalcini, University of Turin, 10126, Turin, Italy.
- Neuroscience Institute Cavalieri Ottolenghi, Regione Gonzole 10, 10043, Orbassano, Turin, Italy.
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87
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Hedgehog Signaling Modulates the Release of Gliotransmitters from Cultured Cerebellar Astrocytes. Neurochem Res 2015; 41:278-89. [PMID: 26694649 DOI: 10.1007/s11064-015-1791-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2015] [Revised: 11/24/2015] [Accepted: 11/24/2015] [Indexed: 10/22/2022]
Abstract
Sonic hedgehog (Shh), a member of the Hedgehog (Hh) family, plays essential roles in the development of the central nervous system. Recent studies suggest that the Hh signaling pathway also functions in mature astrocytes under physiological conditions. We first examined the expression of genes encoding Hh signaling molecules in the adult mouse cerebellum by in situ hybridization histochemistry. mRNA for Patched homolog 1 (Ptch1), a receptor for Hh family members, was expressed in S100β-positive astrocytes and Shh mRNA was expressed in HuC/D-positive neurons, implying that the Hh signaling pathway contributes to neuro-glial interactions. To test this hypothesis, we next examined the effects of recombinant SHH N-terminal protein (rSHH-N) on the functions of cultured cerebellar astrocytes. rSHH-N up-regulated Hh signal target genes such as Ptch1 and Gli-1, a key transcription factor of the Hh signaling pathway. Although activation of Hh signaling by rSHH-N or purmorphamine influenced neither glutamate uptake nor gliotransmitters release, inhibition of the Hh signaling pathway by cyclopamine, neutralizing antibody against SHH or intracellular Ca(2+) chelation decreased glutamate and ATP release from cultured cerebellar astrocytes. On the other hand, cyclopamine, neutralizing antibody against SHH or Ca(2+) chelator hardly affected D-serine secretion. Various kinase inhibitors attenuated glutamate and ATP release, while only U0126 reduced D-serine secretion from the astrocytes. These results suggested that the Hh signaling pathway sustains the release of glutamate and ATP and participates in neuro-glial interactions in the adult mouse brain. We also propose that signaling pathways distinct from the Hh pathway govern D-serine secretion from adult cerebellar astrocytes.
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88
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Kharebava G, Rashid MA, Lee JW, Sarkar S, Kevala K, Kim HY. N-docosahexaenoylethanolamine regulates Hedgehog signaling and promotes growth of cortical axons. Biol Open 2015; 4:1660-70. [PMID: 26545965 PMCID: PMC4736029 DOI: 10.1242/bio.013425] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Axonogenesis, a process for the establishment of neuron connectivity, is central to brain function. The role of metabolites derived from docosahexaenoic acid (DHA, 22:6n-3) that is specifically enriched in the brain, has not been addressed in axon development. In this study, we tested if synaptamide (N-docosahexaenoylethanolamine), an endogenous metabolite of DHA, affects axon growth in cultured cortical neurons. We found that synaptamide increased the average axon length, inhibited GLI family zinc finger 1 (GLI1) transcription and sonic hedgehog (Shh) target gene expression while inducing cAMP elevation. Similar effects were produced by cyclopamine, a regulator of the Shh pathway. Conversely, Shh antagonized elevation of cAMP and blocked synaptamide-mediated increase in axon length. Activation of Shh pathway by a smoothened (SMO) agonist (SAG) or overexpression of SMO did not inhibit axon growth mediated by synaptamide or cyclopamine. Instead, adenylate cyclase inhibitor SQ22536 abolished synaptamide-mediated axon growth indicating requirement of cAMP elevation for this process. Our findings establish that synaptamide promotes axon growth while Shh antagonizes synaptamide-mediated cAMP elevation and axon growth by a SMO-independent, non-canonical pathway. Summary: Synaptamide, an omega-3 fatty acid metabolite, promotes axon growth while Shh antagonizes synaptamide-mediated axon growth by a SMO-independent, non-canonical pathway.
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Affiliation(s)
- Giorgi Kharebava
- Laboratory of Molecular Signaling, Division of Intramural Clinical and Biological Research, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20852, USA
| | - Mohammad A Rashid
- Laboratory of Molecular Signaling, Division of Intramural Clinical and Biological Research, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20852, USA
| | - Ji-Won Lee
- Laboratory of Molecular Signaling, Division of Intramural Clinical and Biological Research, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20852, USA
| | - Sarmila Sarkar
- Laboratory of Molecular Signaling, Division of Intramural Clinical and Biological Research, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20852, USA
| | - Karl Kevala
- Laboratory of Molecular Signaling, Division of Intramural Clinical and Biological Research, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20852, USA
| | - Hee-Yong Kim
- Laboratory of Molecular Signaling, Division of Intramural Clinical and Biological Research, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20852, USA
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89
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Choe Y, Huynh T, Pleasure SJ. Epithelial cells supply Sonic Hedgehog to the perinatal dentate gyrus via transport by platelets. eLife 2015; 4. [PMID: 26457609 PMCID: PMC4600762 DOI: 10.7554/elife.07834] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 09/12/2015] [Indexed: 12/14/2022] Open
Abstract
Dentate neural stem cells produce neurons throughout life in mammals. Sonic hedgehog (Shh) is critical for maintenance of these cells; however, the perinatal source of Shh is enigmatic. In the present study, we examined the role of Shh expressed by hair follicles (HFs) that expand perinatally in temporal concordance with the proliferation of Shh-responding dentate stem cells. Specific inhibition of Shh from HFs or from epithelial sources in general hindered development of Shh-responding dentate stem cells. We also found that the blood–brain barrier (BBB) of the perinatal dentate gyrus (DG) is leaky with stem cells in the dentate exposed to blood-born factors. In attempting to identify how Shh might be transported in blood, we found that platelets contain epithelial Shh, provide Shh to the perinatal DG and that inhibition of platelet generation reduced hedgehog-responsive dentate stem cells. DOI:http://dx.doi.org/10.7554/eLife.07834.001 Although most of the neurons in the brain have been made by the time we are born, new neurons develop throughout life in part of the brain called the hippocampus. These neurons are thought to help with learning and forming memories. Conditions such as depression and Alzheimer's disease have been linked to not being able to produce enough new neurons. The neurons develop from a pool of stem cells in part of the hippocampus. A protein called Sonic Hedgehog (Shh) helps to ensure there are enough stem cells and control when they develop into new neurons. The brain cells that produce Shh in adult mice do not appear until a week after birth, by which point the stem cells are already present and generating neurons. This has led scientists to question where these cells get Shh from around the time of birth. One idea is that cells outside of the brain contribute the Shh such as hair follicles—the structures that hairs grow out of—in the scalp. Hair follicles produce Shh, develop at around the same time as the brain stem cells, and are known to regulate the development of other nearby stem cells. So, Choe et al. conducted a series of experiments in genetically engineered newborn mice and found that the brain stem cells multiply at around the same time that the hair follicles start to produce Shh. Furthermore, reducing the amount of Shh produced by the hair follicles hampered the growth of these stem cells and caused fewer neurons to develop from the stem cell pool. These results raised the question of how Shh gets from the hair follicles to the stem cell pool in the developing brain. In adult animals, a barrier exists between the brain and the blood supply to protect the brain from infection. However, parts of this barrier are still leaky before birth, which might allow blood cells to carry Shh to the brain. Cloe et al. found that platelets—the blood cells responsible for clotting—are able to carry Shh to the brain stem cell pool. Further experiments showed that preventing platelets from forming caused fewer stem cells to develop. The suggestion that Shh from the epithelium—the tissue layer that hair follicles are found in—is able to signal to the brain during a specific window of time raises several questions that require further study. Does epithelial Shh also signal to other organs during embryonic or postnatal development? Does injury to the nervous system that increases the permeability of the blood–brain barrier lead to the delivery of Shh to the brain via the circulation in adult animals? DOI:http://dx.doi.org/10.7554/eLife.07834.002
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Affiliation(s)
- Youngshik Choe
- Department of Neurology, University of California, San Francisco, San Francisco, United States.,Department of Neural Development and Disease, Korea Brain Research Institute, Daegu, Republic of Korea
| | - Trung Huynh
- Department of Neurology, University of California, San Francisco, San Francisco, United States
| | - Samuel J Pleasure
- Department of Neurology, University of California, San Francisco, San Francisco, United States.,Program in Neuroscience, University of California, San Francisco, San Francisco, United States.,Program in Developmental Stem Cell Biology, University of California, San Francisco, San Francisco, United States.,Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, United States
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90
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Inhibition of Gli1 mobilizes endogenous neural stem cells for remyelination. Nature 2015; 526:448-52. [PMID: 26416758 PMCID: PMC4970518 DOI: 10.1038/nature14957] [Citation(s) in RCA: 125] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2015] [Accepted: 07/15/2015] [Indexed: 02/08/2023]
Abstract
Enhancing repair of myelin is an important, but still elusive therapeutic goal in many neurological disorders1. In Multiple Sclerosis (MS), an inflammatory demyelinating disease, endogenous remyelination does occur but is frequently insufficient to restore function. Both parenchymal oligodendrocyte progenitor cells (OPCs) and endogenous adult neural stem cells (NSCs) resident within the subventricular zone (SVZ) are known sources of remyelinating cells2. Here, we characterize the contribution to remyelination of a subset of adult NSCs, identified by their expression of Gli1, a transcriptional effector of the Sonic Hedgehog (Shh) pathway. We show that these cells are recruited from the SVZ to populate demyelinated lesions in the forebrain but never enter healthy, white matter tracts. Unexpectedly, recruitment of this pool of NSCs, and their differentiation into oligodendrocytes, is significantly enhanced by genetic or pharmacological inhibition of Gli1. Importantly, complete inhibition of canonical hedgehog signaling was ineffective indicating that Gli1’s role in both augmenting hedgehog signaling and retarding myelination is specialized. Indeed, inhibition of Gli1 improves the functional outcome in a relapsing/remitting model of experimental autoimmune encephalomyelitis (RR-EAE) and is neuroprotective. Thus, endogenous NSCs can be mobilized for the repair of demyelinated lesions by inhibiting Gli1, identifying a new therapeutic avenue for the treatment of demyelinating disorders.
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91
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Diversity of astrocyte functions and phenotypes in neural circuits. Nat Neurosci 2015; 18:942-52. [PMID: 26108722 DOI: 10.1038/nn.4043] [Citation(s) in RCA: 742] [Impact Index Per Article: 82.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 05/04/2015] [Indexed: 12/11/2022]
Abstract
Astrocytes tile the entire CNS. They are vital for neural circuit function, but have traditionally been viewed as simple, homogenous cells that serve the same essential supportive roles everywhere. Here, we summarize breakthroughs that instead indicate that astrocytes represent a population of complex and functionally diverse cells. Physiological diversity of astrocytes is apparent between different brain circuits and microcircuits, and individual astrocytes display diverse signaling in subcellular compartments. With respect to injury and disease, astrocytes undergo diverse phenotypic changes that may be protective or causative with regard to pathology in a context-dependent manner. These new insights herald the concept that astrocytes represent a diverse population of genetically tractable cells that mediate neural circuit-specific roles in health and disease.
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92
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Allahyari RV, Garcia ADR. Triggering Reactive Gliosis In Vivo by a Forebrain Stab Injury. J Vis Exp 2015:e52825. [PMID: 26167674 DOI: 10.3791/52825] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Following injury to the CNS, astrocytes undergo a broad range of biochemical, morphological, and molecular changes collectively referred to as reactive astrogliosis. Reactive astrocytes exert both inflammatory and protective effects that inhibit and promote, respectively, neural repair. The mechanisms underlying the diverse functional properties of reactive astrogliosis are not well understood. Achieving a greater understanding of these mechanisms is critical to developing therapeutic strategies to treat the injured CNS. Here we demonstrate a method to trigger reactive astrogliosis in the adult mouse forebrain using a forebrain stab lesion. This lesion model is simple, reliable, and requires only a stereotaxic device and a scalpel blade to produce the injury. The use of stab lesions as an injury model in the forebrain is well established and amenable to studies addressing a broad range of neuropathological outcomes, such as neuronal degeneration, neuroinflammation, and disruptions in the blood brain barrier (BBB). Thus, the forebrain stab injury model serves as a powerful tool that can be applied for a broad range of studies on the CNS response to trauma.
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93
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Todd L, Fischer AJ. Hedgehog signaling stimulates the formation of proliferating Müller glia-derived progenitor cells in the chick retina. Development 2015; 142:2610-22. [PMID: 26116667 DOI: 10.1242/dev.121616] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Accepted: 06/15/2015] [Indexed: 12/29/2022]
Abstract
Müller glia can be stimulated to de-differentiate and become proliferating progenitor cells that regenerate neurons in the retina. The signaling pathways that regulate the formation of proliferating Müller glia-derived progenitor cells (MGPCs) are beginning to be revealed. The purpose of this study was to investigate whether Hedgehog (Hh) signaling influences the formation of MGPCs in the chick retina. We find that Hh signaling is increased in damaged retinas where MGPCs are known to form. Sonic Hedgehog (Shh) is normally present in the axons of ganglion cells, but becomes associated with Müller glia and MGPCs following retinal damage. Activation of Hh signaling with recombinant human SHH (rhShh) or smoothened agonist (SAG) increased levels of Ptch1, Gli1, Gli2, Gli3, Hes1 and Hes5, and stimulated the formation of proliferating MGPCs in damaged retinas. In undamaged retinas, SAG or rhShh had no apparent effect upon the Müller glia. However, SAG combined with FGF2 potentiated the formation of MGPCs, whereas SAG combined with IGF1 stimulated the nuclear migration of Müller glia, but not the formation of MGPCs. Conversely, inhibition of Hh signaling with KAAD-cyclopamine, Gli antagonists or antibody to Shh reduced numbers of proliferating MGPCs in damaged and FGF2-treated retinas. Hh signaling potentiates Pax6, Klf4 and cFos expression in Müller glia during the formation of MGPCs. We find that FGF2/MAPK signaling recruits Hh signaling into the signaling network that drives the formation of proliferating MGPCs. Our findings implicate Hh signaling as a key component of the network of signaling pathways that promote the de-differentiation of Müller glia and proliferation of MGPCs.
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Affiliation(s)
- Levi Todd
- Department of Neuroscience, College of Medicine, The Ohio State University, 4190 Graves Hall, 333 West 10th Ave, Columbus, OH 43210, USA
| | - Andy J Fischer
- Department of Neuroscience, College of Medicine, The Ohio State University, 4190 Graves Hall, 333 West 10th Ave, Columbus, OH 43210, USA
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94
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Chechneva OV, Deng W. Empowering sonic hedgehog to rescue brain cells after ischemic stroke. Neural Regen Res 2015; 10:360-2. [PMID: 25878576 PMCID: PMC4396090 DOI: 10.4103/1673-5374.153677] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/30/2015] [Indexed: 11/04/2022] Open
Affiliation(s)
- Olga V Chechneva
- Department of Biochemistry and Molecular Medicine, University of California, Davis, CA 95616, USA
| | - Wenbin Deng
- Department of Biochemistry and Molecular Medicine, University of California, Davis, CA 95616, USA ; Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children, 2425 Stockton Blvd, Sacramento, CA 95817, USA
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95
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Haddad-Tóvolli R, Paul FA, Zhang Y, Zhou X, Theil T, Puelles L, Blaess S, Alvarez-Bolado G. Differential requirements for Gli2 and Gli3 in the regional specification of the mouse hypothalamus. Front Neuroanat 2015; 9:34. [PMID: 25859185 PMCID: PMC4373379 DOI: 10.3389/fnana.2015.00034] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 03/09/2015] [Indexed: 11/13/2022] Open
Abstract
Secreted protein Sonic hedgehog (Shh) ventralizes the neural tube by modulating the crucial balance between activating and repressing functions (GliA, GliR) of transcription factors Gli2 and Gli3. This balance—the Shh-Gli code—is species- and context-dependent and has been elucidated for the mouse spinal cord. The hypothalamus, a forebrain region regulating vital functions like homeostasis and hormone secretion, shows dynamic and intricate Shh expression as well as complex regional differentiation. Here we asked if particular combinations of Gli2 and Gli3 and of GliA and GliR functions contribute to the variety of hypothalamic regions, i.e., we wanted to approach the question of a possible hypothalamic version of the Shh-Gli code. Based on mouse mutant analysis, we show that: (1) hypothalamic regional heterogeneity is based in part on differentially stringent requirements for Gli2 or Gli3; (2) another source of diversity are differential requirements for Shh of neural vs. non-neural origin; (3) the medial progenitor domain known to depend on Gli2 for its development generates several essential hypothalamic nuclei plus the pituitary and median eminence; (4) the suppression of Gli3R by neural and non-neural Shh is essential for hypothalamic specification. Finally, we have mapped our results on a recent model which considers the hypothalamus as a transverse region with alar and basal portions. Our data confirm the model and are explained by it.
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Affiliation(s)
- Roberta Haddad-Tóvolli
- Department of Medical Cell Biology and Neuroanatomy, University of Heidelberg Heidelberg, Germany
| | - Fabian A Paul
- Laboratory of Neurodevelopmental Genetics, Institute of Reconstructive Neurobiology, Life and Brain Center, University of Bonn Bonn, Germany
| | - Yuanfeng Zhang
- Department of Medical Cell Biology and Neuroanatomy, University of Heidelberg Heidelberg, Germany
| | - Xunlei Zhou
- Department of Medical Cell Biology and Neuroanatomy, University of Heidelberg Heidelberg, Germany
| | - Thomas Theil
- Centre for Integrative Physiology, University of Edinburgh Edinburgh, UK
| | - Luis Puelles
- Department of Morphology, Instituto Murciano de Investigación Biosanitaria, School of Medicine, University of Murcia Murcia, Spain ; Facultad de Medicina, University of Murcia Murcia, Spain
| | - Sandra Blaess
- Laboratory of Neurodevelopmental Genetics, Institute of Reconstructive Neurobiology, Life and Brain Center, University of Bonn Bonn, Germany
| | - Gonzalo Alvarez-Bolado
- Department of Medical Cell Biology and Neuroanatomy, University of Heidelberg Heidelberg, Germany
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96
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Mizeracka K, Heiman MG. The many glia of a tiny nematode: studying glial diversity using Caenorhabditis elegans. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2015; 4:151-60. [PMID: 25611728 DOI: 10.1002/wdev.171] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Revised: 11/20/2014] [Accepted: 12/02/2014] [Indexed: 11/06/2022]
Abstract
UNLABELLED Glia constitute a major, understudied population of cells in the nervous system. Currently, it is appreciated that these cells exhibit vast morphological, functional, and molecular diversity, but our understanding of glial biology is limited. Some key unanswered questions include how glial diversity is generated during development and what functions distinct glial subtypes serve in the mature nervous system. The nematode Caenorhabditis elegans contains a defined set of glia, which have clear morphological and molecular differences, and thus provides a simplified model for understanding glial diversity. In addition, recent experiments suggest that the molecular mechanisms underlying the generation of glial diversity in C. elegans are conserved with those in mammals. In this review, we summarize the surprising diversity of glial subtypes present in this simple organism, and highlight current thinking about what roles they perform in the nervous system. We emphasize how genetic approaches may be used to identify the mechanistic origins of glial diversity, which is key to understanding how glia function in health and disease. For further resources related to this article, please visit the WIREs website. CONFLICT OF INTEREST The authors have declared no conflicts of interest for this article.
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Affiliation(s)
- Karolina Mizeracka
- Division of Genetics, Boston Children's Hospital, Boston, MA, USA; Department of Genetics, Harvard Medical School, Boston, MA, USA
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97
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Urbán N, Guillemot F. Neurogenesis in the embryonic and adult brain: same regulators, different roles. Front Cell Neurosci 2014; 8:396. [PMID: 25505873 PMCID: PMC4245909 DOI: 10.3389/fncel.2014.00396] [Citation(s) in RCA: 319] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 11/05/2014] [Indexed: 12/12/2022] Open
Abstract
Neurogenesis persists in adult mammals in specific brain areas, known as neurogenic niches. Adult neurogenesis is highly dynamic and is modulated by multiple physiological stimuli and pathological states. There is a strong interest in understanding how this process is regulated, particularly since active neuronal production has been demonstrated in both the hippocampus and the subventricular zone (SVZ) of adult humans. The molecular mechanisms that control neurogenesis have been extensively studied during embryonic development. Therefore, we have a broad knowledge of the intrinsic factors and extracellular signaling pathways driving proliferation and differentiation of embryonic neural precursors. Many of these factors also play important roles during adult neurogenesis, but essential differences exist in the biological responses of neural precursors in the embryonic and adult contexts. Because adult neural stem cells (NSCs) are normally found in a quiescent state, regulatory pathways can affect adult neurogenesis in ways that have no clear counterpart during embryogenesis. BMP signaling, for instance, regulates NSC behavior both during embryonic and adult neurogenesis. However, this pathway maintains stem cell proliferation in the embryo, while it promotes quiescence to prevent stem cell exhaustion in the adult brain. In this review, we will compare and contrast the functions of transcription factors (TFs) and other regulatory molecules in the embryonic brain and in adult neurogenic regions of the adult brain in the mouse, with a special focus on the hippocampal niche and on the regulation of the balance between quiescence and activation of adult NSCs in this region.
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Affiliation(s)
- Noelia Urbán
- Department of Molecular Neurobiology, MRC National Institute for Medical Research London, UK
| | - François Guillemot
- Department of Molecular Neurobiology, MRC National Institute for Medical Research London, UK
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98
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Abstract
In addition to their many functions in the healthy central nervous system (CNS), astrocytes respond to CNS damage and disease through a process called astrogliosis. For many decades, astrogliosis was sparsely studied and enigmatic. This article examines recent evidence supporting a definition of astrogliosis as a spectrum of heterogeneous potential changes in astrocytes that occur in a context-specific manner as determined by diverse signaling events that vary with the nature and severity of different CNS insults. Astrogliosis is associated with essential beneficial functions, but under specific circumstances can lead to harmful effects. Potential dysfunctions of astrocytes and astrogliosis are being identified that can contribute to, or be primary causes of, CNS disorders, leading to the notion of astrocytopathies. A conceptual framework is presented that allows consideration of normally occurring and dysfunctional astrogliosis and their different roles in CNS disorders.
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Affiliation(s)
- Michael V Sofroniew
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, California 90095
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99
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Chew LJ, DeBoy CA, Senatorov VV. Finding degrees of separation: experimental approaches for astroglial and oligodendroglial cell isolation and genetic targeting. J Neurosci Methods 2014; 236:125-47. [PMID: 25169049 PMCID: PMC4171043 DOI: 10.1016/j.jneumeth.2014.08.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 08/15/2014] [Accepted: 08/18/2014] [Indexed: 12/20/2022]
Abstract
The study of CNS glial cell function requires experimental methods to detect, purify, and manipulate each cell population with fidelity and specificity. With the identification and cloning of cell- and stage-specific markers, glial cell analysis techniques have grown beyond physical methods of tissue dissociation and cell culture, and become highly specific with immunoselection of cell cultures in vitro and genetic targeting in vivo. The unique plasticity of glial cells offers the potential for cell replacement therapies in neurological disease that utilize neural cells derived from transplanted neural stem and progenitor cells. In this mini-review, we outline general physical and genetic approaches for macroglial cell generation. We summarize cell culture methods to obtain astrocytes and oligodendrocytes and their precursors, from developing and adult tissue, as well as approaches to obtain human neural progenitor cells through the establishment of stem cells. We discuss popular targeting rodent strains designed for cell-specific detection, selection and manipulation of neuroglial cell progenitors and their committed progeny. Based on shared markers between astrocytes and stem cells, we discuss genetically modified mouse strains with overlapping expression, and highlight SOX-expressing strains available for targeting of stem and progenitor cell populations. We also include recently established mouse strains for detection, and tag-assisted RNA and miRNA analysis. This discussion aims to provide a brief overview of the rapidly expanding collection of experimental approaches and genetic resources for the isolation and targeting of macroglial cells, their sources, progeny and gene products to facilitate our understanding of their properties and potential application in pathology.
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Affiliation(s)
- Li-Jin Chew
- Center for Neuroscience Research, Children's Research Institute, Children's National Medical Center, Washington, DC, United States.
| | - Cynthia A DeBoy
- Biology Department, Trinity Washington University, Washington, DC, United States
| | - Vladimir V Senatorov
- Helen Wills Neuroscience Institute, University of California, Berkeley, CA, United States
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100
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Petrova R, Joyner AL. Roles for Hedgehog signaling in adult organ homeostasis and repair. Development 2014; 141:3445-57. [PMID: 25183867 DOI: 10.1242/dev.083691] [Citation(s) in RCA: 285] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The hedgehog (HH) pathway is well known for its mitogenic and morphogenic functions during development, and HH signaling continues in discrete populations of cells within many adult mammalian tissues. Growing evidence indicates that HH regulates diverse quiescent stem cell populations, but the exact roles that HH signaling plays in adult organ homeostasis and regeneration remain poorly understood. Here, we review recently identified functions of HH in modulating the behavior of tissue-specific adult stem and progenitor cells during homeostasis, regeneration and disease. We conclude that HH signaling is a key factor in the regulation of adult tissue homeostasis and repair, acting via multiple different routes to regulate distinct cellular outcomes, including maintenance of plasticity, in a context-dependent manner.
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Affiliation(s)
- Ralitsa Petrova
- Developmental Biology Program, Sloan-Kettering Institute, 1275 York Avenue, New York, NY 10065, USA BCMB Graduate Program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA
| | - Alexandra L Joyner
- Developmental Biology Program, Sloan-Kettering Institute, 1275 York Avenue, New York, NY 10065, USA BCMB Graduate Program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA
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