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Rodríguez-Pérez LM, López-de-San-Sebastián J, de Diego I, Smith A, Roales-Buján R, Jiménez AJ, Paez-Gonzalez P. A selective defect in the glial wedge as part of the neuroepithelium disruption in hydrocephalus development in the mouse hyh model is associated with complete corpus callosum dysgenesis. Front Cell Neurosci 2024; 18:1330412. [PMID: 38450283 PMCID: PMC10915275 DOI: 10.3389/fncel.2024.1330412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 02/08/2024] [Indexed: 03/08/2024] Open
Abstract
Introduction Dysgenesis of the corpus callosum is present in neurodevelopmental disorders and coexists with hydrocephalus in several human congenital syndromes. The mechanisms that underlie the etiology of congenital hydrocephalus and agenesis of the corpus callosum when they coappear during neurodevelopment persist unclear. In this work, the mechanistic relationship between both disorders is investigated in the hyh mouse model for congenital hydrocephalus, which also develops agenesis of the corpus callosum. In this model, hydrocephalus is generated by a defective program in the development of neuroepithelium during its differentiation into radial glial cells. Methods In this work, the populations implicated in the development of the corpus callosum (callosal neurons, pioneering axons, glial wedge cells, subcallosal sling and indusium griseum glial cells) were studied in wild-type and hyh mutant mice. Immunohistochemistry, mRNA in situ hybridization, axonal tracing experiments, and organotypic cultures from normal and hyh mouse embryos were used. Results Our results show that the defective program in the neuroepithelium/radial glial cell development in the hyh mutant mouse selectively affects the glial wedge cells. The glial wedge cells are necessary to guide the pioneering axons as they approach the corticoseptal boundary. Our results show that the pioneering callosal axons arising from neurons in the cingulate cortex can extend projections to the interhemispheric midline in normal and hyh mice. However, pioneering axons in the hyh mutant mouse, when approaching the area corresponding to the damaged glial wedge cell population, turned toward the ipsilateral lateral ventricle. This defect occurred before the appearance of ventriculomegaly. Discussion In conclusion, the abnormal development of the ventricular zone, which appears to be inherent to the etiology of several forms of congenital hydrocephalus, can explain, in some cases, the common association between hydrocephalus and corpus callosum dysgenesis. These results imply that further studies may be needed to understand the corpus callosum dysgenesis etiology when it concurs with hydrocephalus.
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Affiliation(s)
- Luis-Manuel Rodríguez-Pérez
- Departamento de Fisiología Humana, Histología Humana, Anatomía Patológica y Educación Física y Deportiva, Universidad de Málaga, Malaga, Spain
- Instituto de Investigación Biomédica de Málaga (IBIMA), Malaga, Spain
| | | | - Isabel de Diego
- Departamento de Anatomía y Medicina Legal e Historia de la Ciencia, Universidad de Málaga, Malaga, Spain
| | - Aníbal Smith
- Departamento de Anatomía y Medicina Legal e Historia de la Ciencia, Universidad de Málaga, Malaga, Spain
| | - Ruth Roales-Buján
- Departamento de Biología Celular, Genética y Fisiología, Universidad de Málaga, Malaga, Spain
| | - Antonio J. Jiménez
- Instituto de Investigación Biomédica de Málaga (IBIMA), Malaga, Spain
- Departamento de Biología Celular, Genética y Fisiología, Universidad de Málaga, Malaga, Spain
| | - Patricia Paez-Gonzalez
- Instituto de Investigación Biomédica de Málaga (IBIMA), Malaga, Spain
- Departamento de Biología Celular, Genética y Fisiología, Universidad de Málaga, Malaga, Spain
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Lynton Z, Suárez R, Fenlon LR. Brain plasticity following corpus callosum agenesis or loss: a review of the Probst bundles. Front Neuroanat 2023; 17:1296779. [PMID: 38020213 PMCID: PMC10657877 DOI: 10.3389/fnana.2023.1296779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2023] [Accepted: 10/11/2023] [Indexed: 12/01/2023] Open
Abstract
The corpus callosum is the largest axonal tract in the human brain, connecting the left and right cortical hemipheres. This structure is affected in myriad human neurodevelopmental disorders, and can be entirely absent as a result of congenital or surgical causes. The age when callosal loss occurs, for example via surgical section in cases of refractory epilepsy, correlates with resulting brain morphology and neuropsychological outcomes, whereby an earlier loss generally produces relatively improved interhemispheric connectivity compared to a loss in adulthood (known as the "Sperry's paradox"). However, the mechanisms behind these age-dependent differences remain unclear. Perhaps the best documented and most striking of the plastic changes that occur due to developmental, but not adult, callosal loss is the formation of large, bilateral, longitudinal ectopic tracts termed Probst bundles. Despite over 100 years of research into these ectopic tracts, which are the largest and best described stereotypical ectopic brain tracts in humans, much remains unclear about them. Here, we review the anatomy of the Probst bundles, along with evidence for their faciliatory or detrimental function, the required conditions for their formation, patterns of etiology, and mechanisms of development. We provide hypotheses for many of the remaining mysteries of the Probst bundles, including their possible relationship to preserved interhemispheric communication following corpus callosum absence. Future research into naturally occurring plastic tracts such as Probst bundles will help to inform the general rules governing axon plasticity and disorders of brain miswiring.
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Affiliation(s)
- Zorana Lynton
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, St Lucia, QLD, Australia
- Queensland Brain Institute, The University of Queensland, St Lucia, QLD, Australia
| | - Rodrigo Suárez
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, St Lucia, QLD, Australia
- Queensland Brain Institute, The University of Queensland, St Lucia, QLD, Australia
| | - Laura R. Fenlon
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, St Lucia, QLD, Australia
- Queensland Brain Institute, The University of Queensland, St Lucia, QLD, Australia
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Lindenmaier LB, Parmentier N, Guo C, Tissir F, Wright KM. Dystroglycan is a scaffold for extracellular axon guidance decisions. eLife 2019; 8:42143. [PMID: 30758284 PMCID: PMC6395066 DOI: 10.7554/elife.42143] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 02/13/2019] [Indexed: 12/13/2022] Open
Abstract
Axon guidance requires interactions between extracellular signaling molecules and transmembrane receptors, but how appropriate context-dependent decisions are coordinated outside the cell remains unclear. Here we show that the transmembrane glycoprotein Dystroglycan interacts with a changing set of environmental cues that regulate the trajectories of extending axons throughout the mammalian brain and spinal cord. Dystroglycan operates primarily as an extracellular scaffold during axon guidance, as it functions non-cell autonomously and does not require signaling through its intracellular domain. We identify the transmembrane receptor Celsr3/Adgrc3 as a binding partner for Dystroglycan, and show that this interaction is critical for specific axon guidance events in vivo. These findings establish Dystroglycan as a multifunctional scaffold that coordinates extracellular matrix proteins, secreted cues, and transmembrane receptors to regulate axon guidance.
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Affiliation(s)
| | - Nicolas Parmentier
- Institiute of Neuroscience, Université Catholique de Louvain, Brussels, Belgium
| | - Caiying Guo
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Fadel Tissir
- Institiute of Neuroscience, Université Catholique de Louvain, Brussels, Belgium
| | - Kevin M Wright
- Vollum Institute, Oregon Health & Science University, Portland, United States
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4
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Collette JC, Choubey L, Smith KM. -Glial and stem cell expression of murine Fibroblast Growth Factor Receptor 1 in the embryonic and perinatal nervous system. PeerJ 2017; 5:e3519. [PMID: 28674667 PMCID: PMC5493973 DOI: 10.7717/peerj.3519] [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: 01/13/2017] [Accepted: 06/08/2017] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Fibroblast growth factors (FGFs) and their receptors (FGFRs) are involved in the development and function of multiple organs and organ systems, including the central nervous system (CNS). FGF signaling via FGFR1, one of the three FGFRs expressed in the CNS, stimulates proliferation of stem cells during prenatal and postnatal neurogenesis and participates in regulating cell-type ratios in many developing regions of the brain. Anomalies in FGFR1 signaling have been implicated in certain neuropsychiatric disorders. Fgfr1 expression has been shown, via in situ hybridization, to vary spatially and temporally throughout embryonic and postnatal development of the brain. However, in situ hybridization lacks sufficient resolution to identify which cell-types directly participate in FGF signaling. Furthermore, because antibodies raised against FGFR1 commonly cross-react with other members of the FGFR family, immunocytochemistry is not alone sufficient to accurately document Fgfr1 expression. Here, we elucidate the identity of Fgfr1 expressing cells in both the embryonic and perinatal mouse brain. METHODS To do this, we utilized a tgFGFR1-EGFPGP338Gsat BAC line (tgFgfr1-EGFP+) obtained from the GENSAT project. The tgFgfr1-EGFP+ line expresses EGFP under the control of a Fgfr1 promoter, thereby causing cells endogenously expressing Fgfr1 to also present a positive GFP signal. Through simple immunostaining using GFP antibodies and cell-type specific antibodies, we were able to accurately determine the cell-type of Fgfr1 expressing cells. RESULTS This technique revealed Fgfr1 expression in proliferative zones containing BLBP+ radial glial stem cells, such as the cortical and hippocampal ventricular zones, and cerebellar anlage of E14.5 mice, in addition to DCX+ neuroblasts. Furthermore, our data reveal Fgfr1 expression in proliferative zones containing BLBP+ cells of the anterior midline, hippocampus, cortex, hypothalamus, and cerebellum of P0.5 mice, in addition to the early-formed GFAP+ astrocytes of the anterior midline. DISCUSSION Understanding when during development and where Fgfr1 is expressed is critical to improving our understanding of its function during neurodevelopment as well as in the mature CNS. This information may one day provide an avenue of discovery towards understanding the involvement of aberrant FGF signaling in neuropsychiatric disorders.
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Affiliation(s)
- Jantzen C Collette
- Department of Biology, University of Louisiana at Lafayette, Lafayette, LA, United States of America
| | - Lisha Choubey
- Department of Biology, University of Louisiana at Lafayette, Lafayette, LA, United States of America
| | - Karen Müller Smith
- Department of Biology, University of Louisiana at Lafayette, Lafayette, LA, United States of America
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Woerly S, Ulbrich K, Chytrý V, Smetana K, Petrovický P, Říhová B, Morassutti D. Synthetic Polymer Matrices for Neural Cell Transplantation. Cell Transplant 2017; 2:229-239. [DOI: 10.1177/096368979300200307] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
This study proposes a strategy to promote the integration of a neural graft into the host brain tissue. It involves the attachment of donor cells to a polymeric matrix, and the implantation of this cell-polymer matrix. We have synthesized hydrogels based on N-(2-hydroxypropyl)-methacrylamide (HPMA) to produce highly porous matrices. As preliminary steps, we have examined: 1) The response of the brain tissue to the implantation of PHPMA/collagen hydrogels; 2) adhesion, growth, differentiation, and viability of embryonic neuronal cells, and embryonal carcinoma-derived neurons seeded onto PHPMA substrates containing hexosamine residues (glucosamine and N-acetylglucosamine), and after entrapment of cells within the hydrogels. Histological analysis seven wk after implantation showed the tolerance of PHPMA hydrogels, and the penetration of host cells into the pore structures. However, cellular ingrowth requires the presence of collagen, and is dependent upon porosity. In vitro data showed that PHPMA substrates supported neuronal cell attachment and neuritic growth, but the biocompatibility of the substrate was enhanced after incorporation of N-acetylglucosamine into the hydrogel. The data also showed the feasibility of entrapping cells into the polymer matrices, and that these “cellular” hydrogel matrices could be maintained in vitro with preservation of cell viability and differentiation. These findings suggest that PHPMA-based hydrogels can serve as carriers for neural transplant, and as a support to guide tissue ingrowth and organization.
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Affiliation(s)
- S. Woerly
- Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Prague 6, Czech Republic
| | - K. Ulbrich
- Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Prague 6, Czech Republic
| | - V. Chytrý
- Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Prague 6, Czech Republic
| | - K. Smetana
- Department of Anatomy, First Faculty of Medicine, Charles University, Prague 2, Czech Republic
| | - P. Petrovický
- Department of Anatomy, First Faculty of Medicine, Charles University, Prague 2, Czech Republic
| | - B. Říhová
- Institute of Microbiology, Academy of Sciences of the Czech Republic, Prague 6, Czech Republic
| | - D.J. Morassutti
- Departments of Biology and Neurosurgery, University of Ottawa, Ottawa, Canada
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6
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Silver J. The glial scar is more than just astrocytes. Exp Neurol 2016; 286:147-149. [PMID: 27328838 DOI: 10.1016/j.expneurol.2016.06.018] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 06/14/2016] [Accepted: 06/17/2016] [Indexed: 01/06/2023]
Affiliation(s)
- Jerry Silver
- Case Western Reserve University, School of Medicine, Department of Neurosciences, Cleveland, OH 44106, USA.
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Stewart CE, Corella KM, Samberg BD, Jones PT, Linscott ML, Chung WCJ. Perinatal midline astrocyte development is impaired in fibroblast growth factor 8 hypomorphic mice. Brain Res 2016; 1646:287-296. [PMID: 27291295 DOI: 10.1016/j.brainres.2016.06.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 05/27/2016] [Accepted: 06/09/2016] [Indexed: 12/31/2022]
Abstract
Our previous studies showed that Fgf8 mutations can cause Kallmann syndrome (KS), a form of congenital hypogonadotropic hypogonadism, in which patients do not undergo puberty and are infertile. Interestingly, some KS patients also have agenesis of the corpus callosum (ACC) suggesting that KS pathology is not limited to reproductive function. Here, we asked whether FGF8 dysfunction is the underlying cause of ACC in some KS patients. Indeed, early studies in transgenic mice with Fgf8 mutations reported the presence of failed or incomplete corpus callosum formation. Additional studies in transgenic mice showed that FGF8 function most likely prevents the prenatal elimination of glial fibrillary acidic protein (GFAP)-immunoreactive (IR) glial cells in the indusium griseum (IG) and midline zipper (MZ), two anterior-dorsal midline regions required for corpus callosum formation (i.e., between embryonic days (E) 15.5-18.5). Here, we tested the hypothesis that FGF8 function is critical for the survival of the GFAP-IR midline glial cells. First, we measured the incidence of apoptosis in the anterior-dorsal midline region in Fgf8 hypomorphic mice during embryonic corpus callosum formation. Second, we quantified the GFAP expression in the anterior-dorsal midbrain region during pre- and postnatal development, in order to study: 1) how Fgf8 hypomorphy disrupts prenatal GFAP-IR midline glial cell development, and 2) whether Fgf8 hypomorphy continues to disrupt postnatal GFAP-IR midline glial cell development. Our results indicate that perinatal FGF8 signaling is important for the timing of the onset of anterior-dorsal Gfap expression in midline glial cells suggesting that FGF8 function regulates midline GFAP-IR glial cell development, which when disrupted by Fgf8 deficiency prevents the formation of the corpus callosum. These studies provide an experimentally-based mechanistic explanation as to why corpus callosum formation may fail in KS patients with deficits in FGF signaling.
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Affiliation(s)
- Courtney E Stewart
- School of Biomedical Sciences, Kent State University, Kent, OH 44242, USA
| | - Kristina M Corella
- School of Biomedical Sciences, Kent State University, Kent, OH 44242, USA
| | - Brittany D Samberg
- Department of Biological Sciences, Kent State University, Kent, OH 44242, USA
| | - Paula T Jones
- Department of Biological Sciences, Kent State University, Kent, OH 44242, USA
| | - Megan L Linscott
- Department of Biological Sciences, Kent State University, Kent, OH 44242, USA
| | - Wilson C J Chung
- School of Biomedical Sciences, Kent State University, Kent, OH 44242, USA; Department of Biological Sciences, Kent State University, Kent, OH 44242, USA.
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8
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Nulty J, Alsaffar M, Barry D. Radial glial cells organize the central nervous system via microtubule dependant processes. Brain Res 2015; 1625:171-9. [DOI: 10.1016/j.brainres.2015.08.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 08/21/2015] [Accepted: 08/22/2015] [Indexed: 11/16/2022]
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9
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Hakanen J, Salminen M. Defects in neural guidepost structures and failure to remove leptomeningeal cells from the septal midline behind the interhemispheric fusion defects in Netrin1 deficient mice. Int J Dev Neurosci 2015; 47:206-15. [PMID: 26397040 DOI: 10.1016/j.ijdevneu.2015.08.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 08/19/2015] [Accepted: 08/19/2015] [Indexed: 11/18/2022] Open
Abstract
Corpus callosum (CC) is the largest commissural tract in mammalian brain and it acts to coordinate information between the two cerebral hemispheres. During brain development CC forms at the boundary area between the cortex and the septum and special transient neural and glial guidepost structures in this area are thought to be critical for CC formation. In addition, it is thought that the fusion of the two hemispheres in the septum area is a prerequisite for CC formation. However, very little is known of the molecular mechanisms behind the fusion of the two hemispheres. Netrin1 (NTN1) acts as an axon guidance molecule in the developing central nervous system and Ntn1 deficiency leads to the agenesis of CC in mouse. Here we have analyzed Ntn1 deficient mice to better understand the reasons behind the observed lack of CC. We show that Ntn1 deficiency leads to defects in neural, but not in glial guidepost structures that may contribute to the agenesis of CC. In addition, Nnt1 was expressed by the leptomeningeal cells bordering the two septal walls prior to fusion. Normally these cells are removed when the septal fusion occurs. At the same time, the Laminin containing basal lamina produced by the leptomeningeal cells is disrupted in the midline area to allow the cells to mix and the callosal axons to cross. In Ntn1 deficient embryos however, the leptomeninges and the basal lamina were not removed properly from the midline area and the septal fusion did not occur. Thus, NTN1 contributes to the formation of the CC by promoting the preceding removal of the midline leptomeningeal cells and interhemispheric fusion.
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Affiliation(s)
- Janne Hakanen
- Department of Veterinary Biosciences, University of Helsinki, Finland.
| | - Marjo Salminen
- Department of Veterinary Biosciences, University of Helsinki, Finland.
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Squarzoni P, Thion MS, Garel S. Neuronal and microglial regulators of cortical wiring: usual and novel guideposts. Front Neurosci 2015; 9:248. [PMID: 26236185 PMCID: PMC4505395 DOI: 10.3389/fnins.2015.00248] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 06/30/2015] [Indexed: 12/17/2022] Open
Abstract
Neocortex functioning relies on the formation of complex networks that begin to be assembled during embryogenesis by highly stereotyped processes of cell migration and axonal navigation. The guidance of cells and axons is driven by extracellular cues, released along by final targets or intermediate targets located along specific pathways. In particular, guidepost cells, originally described in the grasshopper, are considered discrete, specialized cell populations located at crucial decision points along axonal trajectories that regulate tract formation. These cells are usually early-born, transient and act at short-range or via cell-cell contact. The vast majority of guidepost cells initially identified were glial cells, which play a role in the formation of important axonal tracts in the forebrain, such as the corpus callosum, anterior, and post-optic commissures as well as optic chiasm. In the last decades, tangential migrating neurons have also been found to participate in the guidance of principal axonal tracts in the forebrain. This is the case for several examples such as guideposts for the lateral olfactory tract (LOT), corridor cells, which open an internal path for thalamo-cortical axons and Cajal-Retzius cells that have been involved in the formation of the entorhino-hippocampal connections. More recently, microglia, the resident macrophages of the brain, were specifically observed at the crossroads of important neuronal migratory routes and axonal tract pathways during forebrain development. We furthermore found that microglia participate to the shaping of prenatal forebrain circuits, thereby opening novel perspectives on forebrain development and wiring. Here we will review the last findings on already known guidepost cell populations and will discuss the role of microglia as a potentially new class of atypical guidepost cells.
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Affiliation(s)
- Paola Squarzoni
- Centre National de la Recherche Scientifique UMR8197, Ecole Normale Supérieure, Institut de Biologie, Institut National de la Santé et de la Recherche Médicale U1024 Paris, France
| | - Morgane S Thion
- Centre National de la Recherche Scientifique UMR8197, Ecole Normale Supérieure, Institut de Biologie, Institut National de la Santé et de la Recherche Médicale U1024 Paris, France
| | - Sonia Garel
- Centre National de la Recherche Scientifique UMR8197, Ecole Normale Supérieure, Institut de Biologie, Institut National de la Santé et de la Recherche Médicale U1024 Paris, France
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Nkx2.1-derived astrocytes and neurons together with Slit2 are indispensable for anterior commissure formation. Nat Commun 2015; 6:6887. [PMID: 25904499 PMCID: PMC4423212 DOI: 10.1038/ncomms7887] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2014] [Accepted: 02/19/2015] [Indexed: 12/16/2022] Open
Abstract
Guidepost cells present at and surrounding the midline provide guidance cues that orient the growing axons through commissures. Here we show that the transcription factor Nkx2.1 known to control the specification of GABAergic interneurons also regulates the differentiation of astroglia and polydendrocytes within the mouse anterior commissure (AC). Nkx2.1-positive glia were found to originate from three germinal regions of the ventral telencephalon. Nkx2.1-derived glia were observed in and around the AC region by E14.5. Thereafter, a selective cell ablation strategy showed a synergistic role of Nkx2.1-derived cells, both GABAergic interneurons and astroglia, towards the proper formation of the AC. Finally, our results reveal that the Nkx2.1-regulated cells mediate AC axon guidance through the expression of the repellent cue, Slit2. These results bring forth interesting insights about the spatial and temporal origin of midline telencephalic glia, and highlight the importance of neurons and astroglia towards the formation of midline commissures. Guidepost cells provide guidance cues that orient growing axons in the brain but little is known about the midline guidepost cells that populate the mouse anterior commissure (AC). Here, the authors show that the transcription factor Nkx2.1 regulates the differentiation of astroglia and neurons that cooperate to guide AC axons through the expression of Slit2.
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Silver J, Schwab ME, Popovich PG. Central nervous system regenerative failure: role of oligodendrocytes, astrocytes, and microglia. Cold Spring Harb Perspect Biol 2014; 7:a020602. [PMID: 25475091 DOI: 10.1101/cshperspect.a020602] [Citation(s) in RCA: 219] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Animal studies are now showing the exciting potential to achieve significant functional recovery following central nervous system (CNS) injury by manipulating both the inefficient intracellular growth machinery in neurons, as well as the extracellular barriers, which further limit their regenerative potential. In this review, we have focused on the three major glial cell types: oligodendrocytes, astrocytes, and microglia/macrophages, in addition to some of their precursors, which form major extrinsic barriers to regrowth in the injured CNS. Although axotomized neurons in the CNS have, at best, a limited capacity to regenerate or sprout, there is accumulating evidence that even in the adult and, especially after boosting their growth motor, neurons possess the capacity for considerable circuit reorganization and even lengthy regeneration when these glial obstacles to neuronal regrowth are modified, eliminated, or overcome.
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Affiliation(s)
- Jerry Silver
- Department of Neurosciences, Case Western Reserve University, Cleveland, Ohio 44140
| | - Martin E Schwab
- Brain Research Institute, University of Zurich and Department of Health Sciences and Technology, ETH Zurich, 8057 Zurich, Switzerland
| | - Phillip G Popovich
- Center for Brain and Spinal Cord Repair, Ohio State University, Columbus, Ohio 43210
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Suárez R, Gobius I, Richards LJ. Evolution and development of interhemispheric connections in the vertebrate forebrain. Front Hum Neurosci 2014; 8:497. [PMID: 25071525 PMCID: PMC4094842 DOI: 10.3389/fnhum.2014.00497] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 06/19/2014] [Indexed: 12/20/2022] Open
Abstract
Axonal connections between the left and right sides of the brain are crucial for bilateral integration of lateralized sensory, motor, and associative functions. Throughout vertebrate species, forebrain commissures share a conserved developmental plan, a similar position relative to each other within the brain and similar patterns of connectivity. However, major events in the evolution of the vertebrate brain, such as the expansion of the telencephalon in tetrapods and the origin of the six-layered isocortex in mammals, resulted in the emergence and diversification of new commissural routes. These new interhemispheric connections include the pallial commissure, which appeared in the ancestors of tetrapods and connects the left and right sides of the medial pallium (hippocampus in mammals), and the corpus callosum, which is exclusive to eutherian (placental) mammals and connects both isocortical hemispheres. A comparative analysis of commissural systems in vertebrates reveals that the emergence of new commissural routes may have involved co-option of developmental mechanisms and anatomical substrates of preexistent commissural pathways. One of the embryonic regions of interest for studying these processes is the commissural plate, a portion of the early telencephalic midline that provides molecular specification and a cellular scaffold for the development of commissural axons. Further investigations into these embryonic processes in carefully selected species will provide insights not only into the mechanisms driving commissural evolution, but also regarding more general biological problems such as the role of developmental plasticity in evolutionary change.
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Affiliation(s)
- Rodrigo Suárez
- Queensland Brain Institute, The University of QueenslandBrisbane, QLD, Australia
| | - Ilan Gobius
- Queensland Brain Institute, The University of QueenslandBrisbane, QLD, Australia
| | - Linda J. Richards
- Queensland Brain Institute, The University of QueenslandBrisbane, QLD, Australia
- School of Biomedical Sciences, The University of QueenslandBrisbane, QLD, Australia
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Edwards TJ, Sherr EH, Barkovich AJ, Richards LJ. Clinical, genetic and imaging findings identify new causes for corpus callosum development syndromes. ACTA ACUST UNITED AC 2014; 137:1579-613. [PMID: 24477430 DOI: 10.1093/brain/awt358] [Citation(s) in RCA: 221] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The corpus callosum is the largest fibre tract in the brain, connecting the two cerebral hemispheres, and thereby facilitating the integration of motor and sensory information from the two sides of the body as well as influencing higher cognition associated with executive function, social interaction and language. Agenesis of the corpus callosum is a common brain malformation that can occur either in isolation or in association with congenital syndromes. Understanding the causes of this condition will help improve our knowledge of the critical brain developmental mechanisms required for wiring the brain and provide potential avenues for therapies for callosal agenesis or related neurodevelopmental disorders. Improved genetic studies combined with mouse models and neuroimaging have rapidly expanded the diverse collection of copy number variations and single gene mutations associated with callosal agenesis. At the same time, advances in our understanding of the developmental mechanisms involved in corpus callosum formation have provided insights into the possible causes of these disorders. This review provides the first comprehensive classification of the clinical and genetic features of syndromes associated with callosal agenesis, and provides a genetic and developmental framework for the interpretation of future research that will guide the next advances in the field.
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Affiliation(s)
- Timothy J Edwards
- 1 Queensland Brain Institute, The University of Queensland, Brisbane, 4072, Australia2 Departments of Neurology and Pediatrics, The University of California and the Benioff Children's Hospital, CA, 94158, USA
| | - Elliott H Sherr
- 3 Departments of Pediatrics and Neurosurgery, Radiology and Biomedical Imaging, The University of California Children's Hospital, CA 94143, USA
| | - A James Barkovich
- 3 Departments of Pediatrics and Neurosurgery, Radiology and Biomedical Imaging, The University of California Children's Hospital, CA 94143, USA4 Departments of Paediatrics and Neurosurgery, Radiology and Biomedical Imaging, The University of California San Francisco and The Benioff Children's Hospital, CA 94143-0628 USA
| | - Linda J Richards
- 1 Queensland Brain Institute, The University of Queensland, Brisbane, 4072, Australia5 School of Biomedical Sciences, The University of Queensland, Brisbane, 4072, Australia
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Abstract
Roundabout receptors (Robo) and their Slit ligands were discovered in the 1990s and found to be key players in axon guidance. Slit was initially described s an extracellular matrix protein that was expressed by midline glia in Drosophila. A few years later, it was shown that, in vertebrates and invertebrates, Slits acted as chemorepellents for axons crossing the midline. Robo proteins were originally discovered in Drosophila in a mutant screen for genes involved in the regulation of midline crossing. This ligand-receptor pair has since been implicated in a variety of other neuronal and non-neuronal processes ranging from cell migration to angiogenesis, tumourigenesis and even organogenesis of tissues such as kidneys, lungs and breasts.
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Niquille M, Minocha S, Hornung JP, Rufer N, Valloton D, Kessaris N, Alfonsi F, Vitalis T, Yanagawa Y, Devenoges C, Dayer A, Lebrand C. Two specific populations of GABAergic neurons originating from the medial and the caudal ganglionic eminences aid in proper navigation of callosal axons. Dev Neurobiol 2013; 73:647-72. [PMID: 23420573 DOI: 10.1002/dneu.22075] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Revised: 02/10/2013] [Accepted: 02/11/2013] [Indexed: 12/22/2022]
Abstract
The corpus callosum (CC) plays a crucial role in interhemispheric communication. It has been shown that CC formation relies on the guidepost cells located in the midline region that include glutamatergic and GABAergic neurons as well as glial cells. However, the origin of these guidepost GABAergic neurons and their precise function in callosal axon pathfinding remain to be investigated. Here, we show that two distinct GABAergic neuronal subpopulations converge toward the midline prior to the arrival of callosal axons. Using in vivo and ex vivo fate mapping we show that CC GABAergic neurons originate in the caudal and medial ganglionic eminences (CGE and MGE) but not in the lateral ganglionic eminence (LGE). Time lapse imaging on organotypic slices and in vivo analyses further revealed that CC GABAergic neurons contribute to the normal navigation of callosal axons. The use of Nkx2.1 knockout (KO) mice confirmed a role of these neurons in the maintenance of proper behavior of callosal axons while growing through the CC. Indeed, using in vitro transplantation assays, we demonstrated that both MGE- and CGE-derived GABAergic neurons exert an attractive activity on callosal axons. Furthermore, by combining a sensitive RT-PCR technique with in situ hybridization, we demonstrate that CC neurons express multiple short and long range guidance cues. This study strongly suggests that MGE- and CGE-derived interneurons may guide CC axons by multiple guidance mechanisms and signaling pathways.
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Affiliation(s)
- Mathieu Niquille
- Département des neurosciences fondamentales, University of Lausanne, Rue du Bugnon 9, CH-1005 Lausanne, Switzerland
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17
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Grondona JM, Hoyo-Becerra C, Visser R, Fernández-Llebrez P, López-Ávalos MD. The subcommissural organ and the development of the posterior commissure. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 296:63-137. [PMID: 22559938 DOI: 10.1016/b978-0-12-394307-1.00002-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Growing axons navigate through the developing brain by means of axon guidance molecules. Intermediate targets producing such signal molecules are used as guideposts to find distal targets. Glial, and sometimes neuronal, midline structures represent intermediate targets when axons cross the midline to reach the contralateral hemisphere. The subcommissural organ (SCO), a specialized neuroepithelium located at the dorsal midline underneath the posterior commissure, releases SCO-spondin, a large glycoprotein belonging to the thrombospondin superfamily that shares molecular domains with axonal pathfinding molecules. Several evidences suggest that the SCO could be involved in the development of the PC. First, both structures display a close spatiotemporal relationship. Second, certain mutants lacking an SCO present an abnormal PC. Third, some axonal guidance molecules are expressed by SCO cells. Finally, SCO cells, the Reissner's fiber (the aggregated form of SCO-spondin), or synthetic peptides from SCO-spondin affect the neurite outgrowth or neuronal aggregation in vitro.
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Affiliation(s)
- Jesús M Grondona
- Departamento de Biología Celular, Genética y Fisiología, Facultad de Ciencias, Universidad de Málaga, Spain.
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18
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Benadiba C, Magnani D, Niquille M, Morlé L, Valloton D, Nawabi H, Ait-Lounis A, Otsmane B, Reith W, Theil T, Hornung JP, Lebrand C, Durand B. The ciliogenic transcription factor RFX3 regulates early midline distribution of guidepost neurons required for corpus callosum development. PLoS Genet 2012; 8:e1002606. [PMID: 22479201 PMCID: PMC3315471 DOI: 10.1371/journal.pgen.1002606] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 02/03/2012] [Indexed: 01/28/2023] Open
Abstract
The corpus callosum (CC) is the major commissure that bridges the cerebral hemispheres. Agenesis of the CC is associated with human ciliopathies, but the origin of this default is unclear. Regulatory Factor X3 (RFX3) is a transcription factor involved in the control of ciliogenesis, and Rfx3-deficient mice show several hallmarks of ciliopathies including left-right asymmetry defects and hydrocephalus. Here we show that Rfx3-deficient mice suffer from CC agenesis associated with a marked disorganisation of guidepost neurons required for axon pathfinding across the midline. Using transplantation assays, we demonstrate that abnormalities of the mutant midline region are primarily responsible for the CC malformation. Conditional genetic inactivation shows that RFX3 is not required in guidepost cells for proper CC formation, but is required before E12.5 for proper patterning of the cortical septal boundary and hence accurate distribution of guidepost neurons at later stages. We observe focused but consistent ectopic expression of Fibroblast growth factor 8 (Fgf8) at the rostro commissural plate associated with a reduced ratio of GLIoma-associated oncogene family zinc finger 3 (GLI3) repressor to activator forms. We demonstrate on brain explant cultures that ectopic FGF8 reproduces the guidepost neuronal defects observed in Rfx3 mutants. This study unravels a crucial role of RFX3 during early brain development by indirectly regulating GLI3 activity, which leads to FGF8 upregulation and ultimately to disturbed distribution of guidepost neurons required for CC morphogenesis. Hence, the RFX3 mutant mouse model brings novel understandings of the mechanisms that underlie CC agenesis in ciliopathies.
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Affiliation(s)
- Carine Benadiba
- Département de Biologie Cellulaire et de Morphologie, University of Lausanne, Lausanne, Switzerland
- Centre de Génétique et de Physiologie Moléculaire et Cellulaire, CNRS UMR 5534, Université Claude Bernard Lyon 1, Lyon, France
| | - Dario Magnani
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, United Kingdom
| | - Mathieu Niquille
- Département de Biologie Cellulaire et de Morphologie, University of Lausanne, Lausanne, Switzerland
| | - Laurette Morlé
- Centre de Génétique et de Physiologie Moléculaire et Cellulaire, CNRS UMR 5534, Université Claude Bernard Lyon 1, Lyon, France
| | - Delphine Valloton
- Département de Biologie Cellulaire et de Morphologie, University of Lausanne, Lausanne, Switzerland
| | - Homaira Nawabi
- Centre de Génétique et de Physiologie Moléculaire et Cellulaire, CNRS UMR 5534, Université Claude Bernard Lyon 1, Lyon, France
| | - Aouatef Ait-Lounis
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Centre Médical Universitaire, Geneva, Switzerland
| | - Belkacem Otsmane
- Département de Biologie Cellulaire et de Morphologie, University of Lausanne, Lausanne, Switzerland
| | - Walter Reith
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Centre Médical Universitaire, Geneva, Switzerland
| | - Thomas Theil
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, United Kingdom
| | - Jean-Pierre Hornung
- Département de Biologie Cellulaire et de Morphologie, University of Lausanne, Lausanne, Switzerland
| | - Cécile Lebrand
- Département de Biologie Cellulaire et de Morphologie, University of Lausanne, Lausanne, Switzerland
- National Center of Competence in Research Robotics, Ecole Polytechnique Fédérale, Lausanne, Switzerland
| | - Bénédicte Durand
- Centre de Génétique et de Physiologie Moléculaire et Cellulaire, CNRS UMR 5534, Université Claude Bernard Lyon 1, Lyon, France
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Bilasy SE, Satoh T, Terashima T, Kataoka T. RA-GEF-1 (Rapgef2) is essential for proper development of the midline commissures. Neurosci Res 2011; 71:200-9. [PMID: 21864586 DOI: 10.1016/j.neures.2011.08.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Revised: 08/02/2011] [Accepted: 08/04/2011] [Indexed: 12/22/2022]
Abstract
The cerebral hemispheres are directly connected by three major interhemispheric fibers: the corpus callosum, the anterior commissure, and the hippocampal commissure. RA-GEF-1 (also termed Rapgef2) is a guanine nucleotide exchange factor responsible for sustained activation of Rap1. We previously reported anatomical defects of the major forebrain commissures in the adult dorsal telencephalon-specific RA-GEF-1 conditional knockout (cKO) mice. In this study, we use neuroanatomical tracing and immunohistochemistry to study the formation of the commissural fibers during early postnatal development. DiI anterograde tracing reveals the inability of the callosal axons to cross the midline in cKO mice, thereby forming Probst bundles on the ipsilateral side, which is associated with the absence of the indusium griseum glia and the glial sling at the cortical midline. Wheat germ agglutinin-conjugated horseradish peroxidase retrograde tracing verifies the agenesis of the anterior commissure in cKO mice, and DiI anterograde tracing confirms the deviation of the fibers from their original tract. As for the hippocampal commissure, agenesis and hypoplasia are observed in its dorsal and ventral parts, respectively. These results indicate the essential role of RA-GEF-1 in the proper formation of the cerebral midline commissures.
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Affiliation(s)
- Shymaa E Bilasy
- Division of Molecular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
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20
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Sánchez-Camacho C, Ortega JA, Ocaña I, Alcántara S, Bovolenta P. Appropriate Bmp7 levels are required for the differentiation of midline guidepost cells involved in corpus callosum formation. Dev Neurobiol 2011; 71:337-50. [PMID: 21485009 DOI: 10.1002/dneu.20865] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Guidepost cells are essential structures for the establishment of major axonal tracts. How these structures are specified and acquire their axon guidance properties is still poorly understood. Here, we show that in mouse embryos appropriate levels of Bone Morphogenetic Protein 7 (Bmp7), a member of the TGF-β superfamily of secreted proteins, are required for the correct development of the glial wedge, the indusium griseum, and the subcallosal sling, three groups of cells that act as guidepost cells for growing callosal axons. Bmp7 is expressed in the region occupied by these structures and its genetic inactivation in mouse embryos caused a marked reduction and disorganization of these cell populations. On the contrary, infusion of recombinant Bmp7 in the developing forebrain induced their premature differentiation. In both cases, changes were associated with the disruption of callosal axon growth and, in most animals fibers did not cross the midline forming typical Probst bundles. Addition of Bmp7 to cortical explants did not modify the extent of their outgrowth nor their directionality, when explants were exposed to a focalized source of the protein. Together, these results indicate that Bmp7 is indirectly required for corpus callosum formation by controlling the timely differentiation of its guidepost cells.
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Affiliation(s)
- Cristina Sánchez-Camacho
- Departamento de Neurobiología Molecular, Celular y del Desarrollo, Instituto Cajal (CSIC) and CIBER de Enfermedades Raras (CIBERER), Madrid, Spain
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21
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Gobius I, Richards L. Creating Connections in the Developing Brain: Mechanisms Regulating Corpus Callosum Development. ACTA ACUST UNITED AC 2011. [DOI: 10.4199/c00038ed1v01y201107dbr002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Ilan Gobius
- Queensland Brain Institute, University of Queensland, Australia
| | - Linda Richards
- Queensland Brain Institute, University of Queensland, Australia
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Ueno M, Yamashita T. Strategies for regenerating injured axons after spinal cord injury - insights from brain development. Biologics 2011; 2:253-64. [PMID: 19707358 PMCID: PMC2721354 DOI: 10.2147/btt.s2715] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Axonal regeneration does not occur easily after an adult central nervous system (CNS) injury. Various attempts have partially succeeded in promoting axonal regeneration after the spinal cord injury (SCI). Interestingly, several recent therapeutic concepts have emerged from or been tightly linked to the researches on brain development. In a developing brain, remarkable and dynamic axonal elongation and sprouting occur even after the injury; this finding is essential to the development of a therapy for SCI. In this review, we overview the revealed mechanism of axonal tract formation and plasticity in the developing brain and compare the differences between a developing brain and a lesion site in an adult brain. One of the differences is that mature glial cells participate in the repair process in the case of adult injuries. Interestingly, these cells express inhibitory molecules that impede axonal regeneration such as myelin-associated proteins and the repulsive guidance molecules found originally in the developing brain for navigating axons to specific routes. Some reports have clearly elucidated that any treatment designed to suppress these inhibitory cues is beneficial for promoting regeneration and plasticity after an injury. Thus, understanding the developmental process will provide us with an important clue for designing therapeutic strategies for recovery from SCI.
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Affiliation(s)
- Masaki Ueno
- Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, 2-2, Yamadaoka, Suita-shi, Osaka 565-0871, Japan
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23
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Heparan sulfate sugar modifications mediate the functions of slits and other factors needed for mouse forebrain commissure development. J Neurosci 2011; 31:1955-70. [PMID: 21307234 DOI: 10.1523/jneurosci.2579-10.2011] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Heparan sulfate proteoglycans are cell surface and secretory proteins that modulate intercellular signaling pathways including Slit/Robo and FGF/FGFR. The heparan sulfate sugar moieties on HSPGs are subject to extensive postsynthetic modification, generating enormous molecular complexity that has been postulated to provide increased diversity in the ability of individual cells to respond to specific signaling molecules. This diversity could help explain how a relatively small number of axon guidance molecules are able to instruct the extremely complex connectivity of the mammalian brain. Consistent with this hypothesis, we previously showed that mutant mice lacking the heparan sulfotransferases (Hsts) Hs2st or Hs6st1 display major axon guidance defects at the developing optic chiasm. Here we further explore the role of these Hsts at the optic chiasm and investigate their function in corpus callosum development. Each Hst is expressed in a distinct pattern and each mutant displays a specific spectrum of axon guidance defects. Particular Hs2st(-/-) and Hs6st1(-/-) phenotypes closely match those of Slit1(-/-) and Slit2(-/-) embryos respectively, suggesting possible functional relationships. To test functional interactions between Hs2st or Hs6st1 and Slits we examined optic chiasm and corpus callosum phenotypes in a panel of genotypes where Hs2st or Hs6st1 and Slit1 or Slit2 function were simultaneously reduced or absent. We find examples of Hs2st and Hs6st1 having epistatic, synergistic, and antagonistic genetic relationships with Slit1 and/or Slit2 depending on the context. At the corpus callosum we find that Hs6st1 has Slit-independent functions and our data indicate additional roles in FGF signaling.
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Zhao H, Maruyama T, Hattori Y, Sugo N, Takamatsu H, Kumanogoh A, Shirasaki R, Yamamoto N. A molecular mechanism that regulates medially oriented axonal growth of upper layer neurons in the developing neocortex. J Comp Neurol 2011; 519:834-48. [DOI: 10.1002/cne.22536] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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The corpus callosum, the other great forebrain commissures, and the septum pellucidum: anatomy, development, and malformation. Neuroradiology 2010; 52:447-77. [PMID: 20422408 DOI: 10.1007/s00234-010-0696-3] [Citation(s) in RCA: 184] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Accepted: 03/29/2010] [Indexed: 12/13/2022]
Abstract
There are three telencephalic commissures which are paleocortical (the anterior commissure), archicortical (the hippocampal commissure), and neocortical. In non-placental mammals, the neocortical commissural fibers cross the midline together with the anterior and possibly the hippocampal commissure, across the lamina reuniens (joining plate) in the upper part of the lamina terminalis. In placental mammals, a phylogenetically new feature emerged, which is the corpus callosum: it results from an interhemispheric fusion line with specialized groups of mildline glial cells channeling the commissural axons through the interhemispheric meninges toward the contralateral hemispheres. This concerns the frontal lobe mainly however: commissural fibers from the temporo-occipital neocortex still use the anterior commissure to cross, and the posterior occipito-parietal fibers use the hippocampal commissure, forming the splenium in the process. The anterior callosum and the splenium fuse secondarily to form the complete commissural plate. Given the complexity of the processes involved, commissural ageneses are many and usually associated with other diverse defects. They may be due to a failure of the white matter to develop or to the commissural neurons to form or to migrate, to a global failure of the midline crossing processes or to a selective failure of commissuration affecting specific commissural sites (anterior or hippocampal commissures, anterior callosum), or specific sets of commissural axons (paleocortical, hippocampal, neocortical commissural axons). Severe hemispheric dysplasia may prevent the axons from reaching the midline on one or both sides. Besides the intrinsically neural defects, midline meningeal factors may prevent the commissuration as well (interhemispheric cysts or lipoma). As a consequence, commissural agenesis is a malformative feature, not a malformation by itself. Good knowledge of the modern embryological data may allow for a good understanding of a specific pattern in a given individual patient, paving the way for better clinical correlation and genetic counseling.
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Transient neuronal populations are required to guide callosal axons: a role for semaphorin 3C. PLoS Biol 2009; 7:e1000230. [PMID: 19859539 PMCID: PMC2762166 DOI: 10.1371/journal.pbio.1000230] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2009] [Accepted: 09/18/2009] [Indexed: 11/19/2022] Open
Abstract
The corpus callosum (CC) is the main pathway responsible for interhemispheric communication. CC agenesis is associated with numerous human pathologies, suggesting that a range of developmental defects can result in abnormalities in this structure. Midline glial cells are known to play a role in CC development, but we here show that two transient populations of midline neurons also make major contributions to the formation of this commissure. We report that these two neuronal populations enter the CC midline prior to the arrival of callosal pioneer axons. Using a combination of mutant analysis and in vitro assays, we demonstrate that CC neurons are necessary for normal callosal axon navigation. They exert an attractive influence on callosal axons, in part via Semaphorin 3C and its receptor Neuropilin-1. By revealing a novel and essential role for these neuronal populations in the pathfinding of a major cerebral commissure, our study brings new perspectives to pathophysiological mechanisms altering CC formation.
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Yara T, Kato Y, Kataoka H, Kanchiku T, Suzuki H, Gondo T, Yoshii S, Taguchi T. Environmental factors involved in axonal regeneration following spinal cord transection in rats. Med Mol Morphol 2009; 42:150-4. [PMID: 19784741 DOI: 10.1007/s00795-009-0454-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Accepted: 05/01/2009] [Indexed: 10/20/2022]
Abstract
A recent study of a rat model treated with grafted collagen filament (CF) after spinal cord transection showed dramatic recovery of motor function but did not report on the acute-stage phenomenon. In the present study, we describe molecular and histological aspects of the axonal regeneration process during the acute stage following spinal cord transection. The spinal cord of 8-week-old rats was completely transected, and a scaffold of almost the same size as the resected portion was implanted in the gap. Changes in the mRNA expression of four neurotrophic factors [nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), NT-3, and glial cell-derived neurotrophic factor (GDNF)] were analyzed after 72 h. The expression of BDNF and NT-3 mRNA increased significantly in the CF-grafted group compared to the nongrafted group. Immunostaining for BDNF and NT-3 revealed that cells positive for these neurotrophic factors extended along the collagen filaments in the CF-grafted group. Similarly, astrocytes extended into the collagen filament scaffold together with the neurotrophic factors and partly across a border line. These findings indicate that collagen filament helps to reduce scar tissue, supports the expression of neurotrophic factors, and serves as a scaffold for the outgrowth of regenerating axons.
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Affiliation(s)
- Takahiro Yara
- Department of Orthopaedic Surgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi 755-8505, Japan
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Understanding the mechanisms of callosal development through the use of transgenic mouse models. Semin Pediatr Neurol 2009; 16:127-42. [PMID: 19778710 DOI: 10.1016/j.spen.2009.07.003] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The cerebral cortex is the area of the brain where higher-order cognitive processing occurs. The 2 hemispheres of the cerebral cortex communicate through one of the largest fiber tracts in the brain, the corpus callosum. Malformation of the corpus callosum in human beings occurs in 1 in 4000 live births, and those afflicted experience an extensive range of neurologic disorders, from relatively mild to severe cognitive deficits. Understanding the molecular and cellular processes involved in these disorders would therefore assist in the development of prognostic tools and therapies. During the past 3 decades, mouse models have been used extensively to determine which molecules play a role in the complex regulation of corpus callosum development. This review provides an update on these studies, as well as highlights the value of using mouse models with the goal of developing therapies for human acallosal syndromes.
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29
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Jovanov-Milosević N, Culjat M, Kostović I. Growth of the human corpus callosum: modular and laminar morphogenetic zones. Front Neuroanat 2009; 3:6. [PMID: 19562029 PMCID: PMC2697006 DOI: 10.3389/neuro.05.006.2009] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Accepted: 05/21/2009] [Indexed: 01/15/2023] Open
Abstract
The purpose of this focused review is to present and discuss recent data on the changing organization of cerebral midline structures that support the growth and development of the largest commissure in humans, the corpus callosum. We will put an emphasis on the callosal growth during the period between 20 and 45 postconceptual weeks (PCW) and focus on the advantages of a correlated histological/magnetic resonance imaging (MRI) approach. The midline structures that mediate development of the corpus callosum in rodents, also mediate its early growth in humans. However, later phases of callosal growth in humans show additional medial transient structures: grooves made up of callosal septa and the subcallosal zone. These modular (septa) and laminar (subcallosal zone) structures enable the growth of axons along the ventral callosal tier after 18 PCW, during the rapid increase in size of the callosal midsagittal cross-section area. Glial fibrillary acidic protein positive cells, neurons, guidance molecule semaphorin3A in cells and extracellular matrix (ECM), and chondroitin sulfate proteoglycan in the ECM have been identified along the ventral callosal tier in the protruding septa and subcallosal zone. Postmortem MRI at 3 T can demonstrate transient structures based on higher water content in ECM, and give us the possibility to follow the growth of the corpus callosum in vivo, due to the characteristic MR signal. Knowledge about structural properties of midline morphogenetic structures may facilitate analysis of the development of interhemispheric connections in the normal and abnormal fetal human brain.
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JONES N, HALL S. Evaluation of a new method of neural anastomosis using nitrocellulose paper*. Clin Otolaryngol 2009. [DOI: 10.1111/j.1365-2273.1991.tb02075.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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31
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Smeal RM, Tresco PA. The influence of substrate curvature on neurite outgrowth is cell type dependent. Exp Neurol 2008; 213:281-92. [DOI: 10.1016/j.expneurol.2008.05.026] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Revised: 05/29/2008] [Accepted: 05/30/2008] [Indexed: 01/04/2023]
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32
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Lu W, Quintero-Rivera F, Fan Y, Alkuraya FS, Donovan DJ, Xi Q, Turbe-Doan A, Li QG, Campbell CG, Shanske AL, Sherr EH, Ahmad A, Peters R, Rilliet B, Parvex P, Bassuk AG, Harris DJ, Ferguson H, Kelly C, Walsh CA, Gronostajski RM, Devriendt K, Higgins A, Ligon AH, Quade BJ, Morton CC, Gusella JF, Maas RL. NFIA haploinsufficiency is associated with a CNS malformation syndrome and urinary tract defects. PLoS Genet 2007; 3:e80. [PMID: 17530927 PMCID: PMC1877820 DOI: 10.1371/journal.pgen.0030080] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2006] [Accepted: 04/05/2007] [Indexed: 11/23/2022] Open
Abstract
Complex central nervous system (CNS) malformations frequently coexist with other developmental abnormalities, but whether the associated defects share a common genetic basis is often unclear. We describe five individuals who share phenotypically related CNS malformations and in some cases urinary tract defects, and also haploinsufficiency for the NFIA transcription factor gene due to chromosomal translocation or deletion. Two individuals have balanced translocations that disrupt NFIA. A third individual and two half-siblings in an unrelated family have interstitial microdeletions that include NFIA. All five individuals exhibit similar CNS malformations consisting of a thin, hypoplastic, or absent corpus callosum, and hydrocephalus or ventriculomegaly. The majority of these individuals also exhibit Chiari type I malformation, tethered spinal cord, and urinary tract defects that include vesicoureteral reflux. Other genes are also broken or deleted in all five individuals, and may contribute to the phenotype. However, the only common genetic defect is NFIA haploinsufficiency. In addition, previous analyses of Nfia−/− knockout mice indicate that Nfia deficiency also results in hydrocephalus and agenesis of the corpus callosum. Further investigation of the mouse Nfia+/− and Nfia−/− phenotypes now reveals that, at reduced penetrance, Nfia is also required in a dosage-sensitive manner for ureteral and renal development. Nfia is expressed in the developing ureter and metanephric mesenchyme, and Nfia+/− and Nfia−/− mice exhibit abnormalities of the ureteropelvic and ureterovesical junctions, as well as bifid and megaureter. Collectively, the mouse Nfia mutant phenotype and the common features among these five human cases indicate that NFIA haploinsufficiency contributes to a novel human CNS malformation syndrome that can also include ureteral and renal defects. Central nervous system (CNS) and urinary tract abnormalities are common human malformations, but their variability and genetic complexity make it difficult to identify the responsible genes. Analysis of human chromosomal abnormalities associated with such disorders offers one approach to this problem. In five individuals described herein, a novel human syndrome that involves both CNS and urinary tract defects is associated with chromosomal disruption or deletion of NFIA, encoding a member of the Nuclear Factor I (NFI) family of transcription factors. This syndrome includes brain abnormalities (abnormal corpus callosum, hydrocephalus, ventriculomegaly, and Chiari type I malformation), spinal abnormalities (tethered spinal cord), and urinary tract abnormalities (vesicoureteral reflux). Nfia disruption in mice was already known to cause hydrocephalus and abnormal corpus callosum, and is now shown to exhibit renal defects and disturbed ureteral development. Other genes besides NFIA are also disrupted or deleted and may contribute to the observed phenotype. However, loss of one copy of NFIA is the only genetic defect common to all five patients. The authors thus provide evidence that genetic loss of NFIA contributes to a distinct CNS malformation syndrome with urinary tract defects of variable penetrance.
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Affiliation(s)
- Weining Lu
- Genetics Division, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
- Renal Section, Boston University Medical Center, Boston, Massachusetts, United States of America
| | - Fabiola Quintero-Rivera
- Center for Human Genetic Research, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Yanli Fan
- Genetics Division, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Fowzan S Alkuraya
- Genetics Division, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Diana J Donovan
- Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Qiongchao Xi
- Genetics Division, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Annick Turbe-Doan
- Genetics Division, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Qing-Gang Li
- Renal Section, Boston University Medical Center, Boston, Massachusetts, United States of America
| | - Craig G Campbell
- Division of Neurology, Children's Hospital of Western Ontario, London, Ontario, Canada
| | - Alan L Shanske
- Children's Hospital at Montefiore, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Elliott H Sherr
- Department of Neurology, University of California San Francisco, San Francisco, California, United States of America
| | - Ayesha Ahmad
- Division of Genetic and Metabolic Disorders, Department of Pediatrics, Wayne State University, Detroit, Michigan, United States of America
| | - Roxana Peters
- Genetics Division, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Benedict Rilliet
- Department of Neurosurgery, University Hospital, Geneva, Switzerland
| | - Paloma Parvex
- Department of Nephrology, University Hospital, Geneva, Switzerland
| | - Alexander G Bassuk
- Departments of Pediatrics and Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America
| | - David J Harris
- Genetics Division, Children's Hospital Boston and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Heather Ferguson
- Department of Obstetrics, Gynecology and Reproductive Biology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Chantal Kelly
- Department of Obstetrics, Gynecology and Reproductive Biology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Christopher A Walsh
- Genetics Division, Children's Hospital Boston and Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States of America
- Howard Hughes Medical Institute, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Richard M Gronostajski
- Department of Biochemistry, State University of New York at Buffalo, Buffalo, New York, United States of America
| | | | - Anne Higgins
- Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Azra H Ligon
- Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Bradley J Quade
- Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Cynthia C Morton
- Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Obstetrics, Gynecology and Reproductive Biology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - James F Gusella
- Center for Human Genetic Research, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Richard L Maas
- Genetics Division, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
- * To whom correspondence should be addressed. E-mail:
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Sánchez-Soriano N, Tear G, Whitington P, Prokop A. Drosophila as a genetic and cellular model for studies on axonal growth. Neural Dev 2007; 2:9. [PMID: 17475018 PMCID: PMC1876224 DOI: 10.1186/1749-8104-2-9] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2007] [Accepted: 05/02/2007] [Indexed: 11/10/2022] Open
Abstract
One of the most fascinating processes during nervous system development is the establishment of stereotypic neuronal networks. An essential step in this process is the outgrowth and precise navigation (pathfinding) of axons and dendrites towards their synaptic partner cells. This phenomenon was first described more than a century ago and, over the past decades, increasing insights have been gained into the cellular and molecular mechanisms regulating neuronal growth and navigation. Progress in this area has been greatly assisted by the use of simple and genetically tractable invertebrate model systems, such as the fruit fly Drosophila melanogaster. This review is dedicated to Drosophila as a genetic and cellular model to study axonal growth and demonstrates how it can and has been used for this research. We describe the various cellular systems of Drosophila used for such studies, insights into axonal growth cones and their cytoskeletal dynamics, and summarise identified molecular signalling pathways required for growth cone navigation, with particular focus on pathfinding decisions in the ventral nerve cord of Drosophila embryos. These Drosophila-specific aspects are viewed in the general context of our current knowledge about neuronal growth.
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Affiliation(s)
- Natalia Sánchez-Soriano
- The Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, The University of Manchester, Manchester, UK
| | - Guy Tear
- MRC Centre for Developmental Neurobiology, Guy's Campus, King's College, London, UK
| | - Paul Whitington
- Department of Anatomy and Cell Biology, University of Melbourne, Victoria, Australia
| | - Andreas Prokop
- The Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, The University of Manchester, Manchester, UK
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Paul LK, Brown WS, Adolphs R, Tyszka JM, Richards LJ, Mukherjee P, Sherr EH. Agenesis of the corpus callosum: genetic, developmental and functional aspects of connectivity. Nat Rev Neurosci 2007; 8:287-99. [PMID: 17375041 DOI: 10.1038/nrn2107] [Citation(s) in RCA: 554] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Agenesis of the corpus callosum (AgCC), a failure to develop the large bundle of fibres that connect the cerebral hemispheres, occurs in 1:4000 individuals. Genetics, animal models and detailed structural neuroimaging are now providing insights into the developmental and molecular bases of AgCC. Studies using neuropsychological, electroencephalogram and functional MRI approaches are examining the resulting impairments in emotional and social functioning, and have begun to explore the functional neuroanatomy underlying impaired higher-order cognition. The study of AgCC could provide insight into the integrated cerebral functioning of healthy brains, and may offer a model for understanding certain psychiatric illnesses, such as schizophrenia and autism.
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Affiliation(s)
- Lynn K Paul
- California Institute of Technology, MC 228-77 Pasadena, California 91125, USA.
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Lindwall C, Fothergill T, Richards LJ. Commissure formation in the mammalian forebrain. Curr Opin Neurobiol 2007; 17:3-14. [PMID: 17275286 DOI: 10.1016/j.conb.2007.01.008] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2006] [Accepted: 01/18/2007] [Indexed: 01/06/2023]
Abstract
Commissural formation in the mammalian brain is highly organised and regulated both by the cell-autonomous expression of transcription factors, and by non-cell-autonomous mechanisms including the formation of midline glial structures and their expression of specific axon guidance molecules. These mechanisms channel axons into the correct path and enable the subsequent connection of specific brain areas to their appropriate targets. Several key findings have been made over the past two years, including the discovery of novel mechanisms of action that 'classical' guidance factors such as the Slits, Netrins, and their receptors have in axon guidance. Moreover, novel guidance factors such as members of the Wnt family, and extracellular matrix components such as heparan sulphate proteoglycans, have been shown to be important for mammalian brain commissure formation. Additionally, there have been significant discoveries regarding the role of FGF signalling in the formation of midline glial structures. In this review, we discuss the most recent advances in the field that have contributed to our current understanding of commissural development in the telencephalon.
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Affiliation(s)
- Charlotta Lindwall
- The University of Queensland, School of Biomedical Sciences and The Queensland Brain Institute, St Lucia, Queensland 4072, Australia
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Sarnat HB. Embryology and malformations of the forebrain commissures. MALFORMATIONS OF THE NERVOUS SYSTEM 2007; 87:67-87. [DOI: 10.1016/s0072-9752(07)87005-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Jubinsky PT, Shanske AL, Pixley FJ, Montagna C, Short MK. A syndrome of holoprosencephaly, recurrent infections, and monocytosis. Am J Med Genet A 2006; 140:2742-8. [PMID: 17103456 DOI: 10.1002/ajmg.a.31542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We describe three siblings with holoprosencephaly, recurrent infections, and increased peripheral blood monocytes. These children were born to apparently healthy parents in a family with one unaffected child. Affected individuals had microcephaly, severe developmental delay, failure to thrive, and brachydactyly. The clinical courses were complicated by endocrine dysfunction, multiple respiratory, and skin infections. Laboratory studies showed normal karyotypes, normal lymphocyte function, and a peripheral blood monocytosis with markedly abnormal morphology. Mutation analysis of the seven genes (SHH, ZIC2, SIX3, TGI, FTDGF1, GLI2, and PTCH) known to be involved in holoprosencephaly was normal. This is the first report demonstrating an association between abnormal mononuclear phagocytes and holoprosencephaly.
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Affiliation(s)
- Paul T Jubinsky
- Pediatric Hematology/Oncology, Albert Einstein College of Medicine and Children's Hospital at Montefiore, Bronx, New York, USA.
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38
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Polikov VS, Block ML, Fellous JM, Hong JS, Reichert WM. In vitro model of glial scarring around neuroelectrodes chronically implanted in the CNS. Biomaterials 2006; 27:5368-76. [PMID: 16842846 DOI: 10.1016/j.biomaterials.2006.06.018] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2006] [Accepted: 06/22/2006] [Indexed: 11/17/2022]
Abstract
A novel in vitro model of glial scarring was developed by adapting a primary cell-based system previously used for studying neuroinflammatory processes in neurodegenerative disease. Midbrains from embryonic day 14 Fischer 344 rats were mechanically dissociated and grown on poly-D-lysine coated 24 well plates to a confluent layer of neurons, astrocytes, and microglia. The culture was injured with either a mechanical scrape or foreign-body placement (segments of 50 microm diameter stainless steel microwire), fixed at time points from 6 h to 10 days, and assessed by immunocytochemistry. Microglia invaded the scraped wound area at early time points and hypertrophied activated astrocytes repopulated the wound after 7 days. The chronic presence of microwire resulted in a glial scar forming at 10 days, with microglia forming an inner layer of cells coating the microwire, while astrocytes surrounded the microglial core with a network of cellular processes containing upregulated GFAP. Vimentin expressing cells and processes were present in the scrape at early times and within the astrocyte processes forming the glial scar. Neurons within the culture did not repopulate the scrape wound and did not respond to the microwire, although they were determined to be electrically active through patch clamp recording. The time course and relative positions of the glia in response to the different injury paradigms correlated well with stereotypical in vivo responses and warrant further work in the development of a functional in vitro test bed.
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Affiliation(s)
- Vadim S Polikov
- Department of Biomedical Engineering, Duke University, Durham NC 27708-0281, USA
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39
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Wahlsten D, Bishop KM, Ozaki HS. Recombinant inbreeding in mice reveals thresholds in embryonic corpus callosum development. GENES BRAIN AND BEHAVIOR 2006; 5:170-88. [PMID: 16507008 DOI: 10.1111/j.1601-183x.2005.00153.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The inbred strains BALB/cWah1 and 129P1/ReJ both show incomplete penetrance for absent corpus callosum (CC); about 14% of adult mice have no CC at all. Their F(1) hybrid offspring are normal, which proves that the strains differ at two or more loci pertinent to absent CC. Twenty-three recombinant inbred lines were bred from the F(2) cross of BALB/c and 129, and several of these expressed a novel and severe phenotype after only three or four generations of inbreeding - total absence of the CC and severe reduction of the hippocampal commissure (HC) in every adult animal. As inbreeding progressed, intermediate sizes of the CC and the HC remained quite rare. This striking phenotypic distribution in adults arose from developmental thresholds in the embryo. CC axons normally cross to the opposite hemisphere via a tissue bridge in the septal region at midline, where the HC forms before CC axons arrive. The primary defect in callosal agenesis in the BALB/c and 129 strains is severe retardation of fusion of the hemispheres in the septal region, and failure to form a CC is secondary to this defect. The putative CC axons arrive at midline at the correct time and place in all groups, but in certain genotypes, the bridge is not yet present. The relative timing of axon growth and delay of the septal bridge create a narrow critical period for forming a normal brain.
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Affiliation(s)
- D Wahlsten
- Department of Psychology, University of Alberta, Edmonton, Canada.
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Smith KM, Ohkubo Y, Maragnoli ME, Rasin MR, Schwartz ML, Sestan N, Vaccarino FM. Midline radial glia translocation and corpus callosum formation require FGF signaling. Nat Neurosci 2006; 9:787-97. [PMID: 16715082 DOI: 10.1038/nn1705] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Accepted: 04/24/2006] [Indexed: 12/11/2022]
Abstract
Midline astroglia in the cerebral cortex develop earlier than other astrocytes through mechanisms that are still unknown. We show that radial glia in dorsomedial cortex retract their apical endfeet at midneurogenesis and translocate to the overlaying pia, forming the indusium griseum. These cells require the fibroblast growth factor receptor 1 (Fgfr1) gene for their precocious somal translocation to the dorsal midline, as demonstrated by inactivating the Fgfr1 gene in radial glial cells and by RNAi knockdown of Fgfr1 in vivo. Dysfunctional astroglial migration underlies the callosal dysgenesis in conditional Fgfr1 knockout mice, suggesting that precise targeting of astroglia to the cortex has unexpected roles in axon guidance. FGF signaling is sufficient to induce somal translocation of radial glial cells throughout the cortex; furthermore, the targeting of astroglia to dorsolateral cortex requires FGFr2 signaling after neurogenesis. Hence, FGFs have an important role in the transition from radial glia to astrocytes by stimulating somal translocation of radial glial cells.
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Affiliation(s)
- Karen Müller Smith
- Child Study Center, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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41
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Ren T, Anderson A, Shen WB, Huang H, Plachez C, Zhang J, Mori S, Kinsman SL, Richards LJ. Imaging, anatomical, and molecular analysis of callosal formation in the developing human fetal brain. ACTA ACUST UNITED AC 2006; 288:191-204. [PMID: 16411247 DOI: 10.1002/ar.a.20282] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
A complex set of axonal guidance mechanisms are utilized by axons to locate and innervate their targets. In the developing mouse forebrain, we previously described several midline glial populations as well as various guidance molecules that regulate the formation of the corpus callosum. Since agenesis of the corpus callosum is associated with over 50 different human congenital syndromes, we wanted to investigate whether these same mechanisms also operate during human callosal development. Here we analyze midline glial and commissural development in human fetal brains ranging from 13 to 20 weeks of gestation using both diffusion tensor magnetic resonance imaging and immunohistochemistry. Through our combined radiological and histological studies, we demonstrate the morphological development of multiple forebrain commissures/decussations, including the corpus callosum, anterior commissure, hippocampal commissure, and the optic chiasm. Histological analyses demonstrated that all the midline glial populations previously described in mouse, as well as structures analogous to the subcallosal sling and cingulate pioneering axons, that mediate callosal axon guidance in mouse, are also present during human brain development. Finally, by Northern blot analysis, we have identified that molecules involved in mouse callosal development, including Slit, Robo, Netrin1, DCC, Nfia, Emx1, and GAP-43, are all expressed in human fetal brain. These data suggest that similar mechanisms and molecules required for midline commissure formation operate during both mouse and human brain development. Thus, the mouse is an excellent model system for studying normal and pathological commissural formation in human brain development.
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Affiliation(s)
- Tianbo Ren
- Department of Anatomy and Neurobiology and Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland, USA
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Mihrshahi R. The corpus callosum as an evolutionary innovation. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2006; 306:8-17. [PMID: 16116611 DOI: 10.1002/jez.b.21067] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The corpus callosum (CC) is the major interhemispheric fibre bundle in the eutherian brain and has been described as a true evolutionary innovation. This paper reviews the current literature with regard to functional, developmental and genetic concepts that may help elucidate the evolutionary origin of this structure. It has been suggested that the CC arose in the eutherian brain as a more direct and, therefore, more effective system for the interhemispheric integration of topographically organized sensory cortices than the anterior commissure (AC) and hippocampal commissure (HC) already present in nonplacental mammals. It can also be argued, however, that the ability of the CC to integrate the newly evolving motor cortices of placental mammals may have played a role in the evolutionary fixation of this structure. Investigations into the developmental mechanism involved in the formation of the CC and their underlying patterns of gene expression make it possible to formulate a tentative hypothesis about the evolutionary origin of this commissure. This paper suggests that changes in the developmental patterns of the expression of certain regulatory genes may have allowed a first group of callosal pioneering axons to cross the cortical midline. These pioneering fibres may have used the axons of the HC to find their way across the midline. Additional callosal fibres may then have fasciculated with these pioneers. Once the CC had formed in this way, more complex systems of axonal guidance may have evolved over time, thus enabling a gradual increase in the size and complexity of the CC.
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Affiliation(s)
- Robin Mihrshahi
- Department of Biological Sciences, Macquarie University, Sydney, North Ryde 2109, Australia.
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Barresi MJF, Hutson LD, Chien CB, Karlstrom RO. Hedgehog regulated Slit expression determines commissure and glial cell position in the zebrafish forebrain. Development 2005; 132:3643-56. [PMID: 16033800 DOI: 10.1242/dev.01929] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Three major axon pathways cross the midline of the vertebrate forebrain early in embryonic development: the postoptic commissure (POC), the anterior commissure (AC) and the optic nerve. We show that a small population of Gfap+ astroglia spans the midline of the zebrafish forebrain in the position of, and prior to, commissural and retinal axon crossing. These glial ;bridges' form in regions devoid of the guidance molecules slit2 and slit3, although a subset of these glial cells express slit1a. We show that Hh signaling is required for commissure formation, glial bridge formation, and the restricted expression of the guidance molecules slit1a, slit2, slit3 and sema3d, but that Hh does not appear to play a direct role in commissural and retinal axon guidance. Reducing Slit2 and/or Slit3 function expanded the glial bridges and caused defasciculation of the POC, consistent with a ;channeling' role for these repellent molecules. By contrast, reducing Slit1a function led to reduced midline axon crossing, suggesting a distinct role for Slit1a in midline axon guidance. Blocking Slit2 and Slit3, but not Slit1a, function in the Hh pathway mutant yot (gli2DR) dramatically rescued POC axon crossing and glial bridge formation at the midline, indicating that expanded Slit2 and Slit3 repellent function is largely responsible for the lack of midline crossing in these mutants. This analysis shows that Hh signaling helps to pattern the expression of Slit guidance molecules that then help to regulate glial cell position and axon guidance across the midline of the forebrain.
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Abstract
The human brain assembles an incredible network of over a billion neurons. Understanding how these connections form during development in order for the brain to function properly is a fundamental question in biology. Much of this wiring takes place during embryonic development. Neurons are generated in the ventricular zone, migrate out, and begin to differentiate. However, neurons are often born in locations some distance from the target cells with which they will ultimately form connections. To form connections, neurons project long axons tipped with a specialized sensing device called a growth cone. The growing axons interact directly with molecules within the environment through which they grow. In order to find their targets, axonal growth cones use guidance molecules that can either attract or repel them. Understanding what these guidance cues are, where they are expressed, and how the growth cone is able to transduce their signal in a directionally specific manner is essential to understanding how the functional brain is constructed. In this chapter, we review what is known about the mechanisms involved in axonal guidance. We discuss how the growth cone is able to sense and respond to its environment and how it is guided by pioneering cells and axons. As examples, we discuss current models for the development of the spinal cord, the cerebral cortex, and the visual and olfactory systems.
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Affiliation(s)
- Céline Plachez
- Department of Anatomy and Neurobiology, University of Maryland, School of Medicine, Baltimore, Maryland 21201, USA
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Ha HY, Cho IH, Lee KW, Lee KW, Song JY, Kim KS, Yu YM, Lee JK, Song JS, Yang SD, Shin HS, Han PL. The axon guidance defect of the telencephalic commissures of the JSAP1-deficient brain was partially rescued by the transgenic expression of JIP1. Dev Biol 2005; 277:184-99. [PMID: 15572149 DOI: 10.1016/j.ydbio.2004.09.019] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2004] [Revised: 09/12/2004] [Accepted: 09/13/2004] [Indexed: 11/17/2022]
Abstract
The JNK interacting protein, JSAP1, has been identified as a scaffold protein for mitogen-activated protein kinase (MAPK) signaling pathways and as a linker protein for the cargo transport along the axons. To investigate the physiological function of JSAP1 in vivo, we generated mice lacking JSAP1. The JSAP1 null mutation produced various developmental deficits in the brain, including an axon guidance defect of the corpus callosum, in which phospho-FAK and phospho-JNK were distributed at reduced levels. The axon guidance defect of the corpus callosum in the jsap1-/- brain was correlated with the misplacement of glial sling cells, which reverted to their normal position after the transgenic expression of JNK interacting protein 1(JIP1). The transgenic JIP1 partially rescued the axon guidance defect of the corpus callosum and the anterior commissure of the jsap1-/- brain. The JSAP1 null mutation impaired the normal distribution of the Ca+2 regulating protein, calretinin, but not the synaptic vesicle marker, SNAP-25, along the axons of the thalamocortical tract. These results suggest that JSAP1 is required for the axon guidance of the telencephalic commissures and the distribution of cellular protein(s) along axons in vivo, and that the signaling network organized commonly by JIP1 and JSAP1 regulates the axon guidance in the developing brain.
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Affiliation(s)
- Hye-Yeong Ha
- Department of Neuroscience, Neuroscience Research Center and Medical Research Institute, Ewha Womans University School of Medicine, Seoul 110-783, Korea
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Iseda T, Nishio T, Kawaguchi S, Yamanoto M, Kawasaki T, Wakisaka S. Spontaneous regeneration of the corticospinal tract after transection in young rats: a key role of reactive astrocytes in making favorable and unfavorable conditions for regeneration. Neuroscience 2004; 126:365-74. [PMID: 15207354 DOI: 10.1016/j.neuroscience.2004.03.056] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/29/2004] [Indexed: 11/29/2022]
Abstract
We demonstrated the occurrence of marked regeneration of the corticospinal tract (CST) after a single transection and failure of regeneration after a repeated transection in young rats. To provide convincing evidence for the complete transection and regeneration we used retrograde neuronal double labeling. Double-labeled neurons that took up the first tracer from the transection site and the second tracer from the injection site caudal to the transection site were observed in the sensorimotor cortex. The anterograde tracing method revealed various patterns of regeneration. In the most successful cases the vast majority of regenerated fibers descended in the normal tract and terminated normally whereas a trace amount of fibers coursed aberrantly. In the less successful cases fibers descended partly normally and partly aberrantly or totally aberrantly. To clarify the role of astrocytes in determining the success or failure of regeneration we compared expression of glial fibrillary acidic protein (GFAP), vimentin and neurofilament (NF) immunoreactivity (IR) in the lesion between single and repeated transections. In either transection, astrocytes disappeared from the CST near the lesion site as early as 3 h after lesioning. However, by 24 h after a single transection, immature astrocytes coexpressing GFAP- and vimentin-IR appeared in the former astrocyte-free area and NF-positive axons crossed the lesion. By contrast, after a repeated transection the astrocyte-free area spread and NF-positive axons never crossed the lesion. It appears likely that the major sign, and possibly cause of failure of regeneration is the prolonged disappearance of astrocytes in the lesioned tract area.
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Affiliation(s)
- T Iseda
- Department of Integrative Brain Science, Graduate School of Medicine, Kyoto University, Yoshida-Konoe, Sakyo, Kyoto 606-8501, Japan
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Sundaresan V, Mambetisaeva E, Andrews W, Annan A, Knöll B, Tear G, Bannister L. Dynamic expression patterns of Robo (Robo1 and Robo2) in the developing murine central nervous system. J Comp Neurol 2004; 468:467-81. [PMID: 14689480 DOI: 10.1002/cne.10984] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The Robo family of molecules is important for axon guidance across the midline during central nervous system (CNS) development in invertebrates and vertebrates. Here we describe the patterns of Robo protein expression in the developing mouse CNS from embryonic day (E) 9.5 to postnatal day (P) 4, as determined by immunohistochemical labeling with an antibody (S3) raised against a common epitope present in the Robo ectodomain of Robos 1 and 2. In the spinal cord, midline-crossing axons are initially (at E11) S3-positive. At later times, midline Robo expression disappears, but is strongly upregulated in longitudinally running postcrossing axons. It is also strongly expressed in noncrossing longitudinal axons. Differential expression of Robo along axons was also found in axons cultured from E14 spinal cord. These findings resemble those from the Drosophila ventral nerve cord and indicate that in vertebrates a low level of Robo expression occurs in the initial crossing of the midline, while a high level of expression in the postcrossing fibers prevents recrossing. Likewise, Robo-positive ipsilateral axons are prevented from crossing at all. However, in the brain different rules appear to apply. Most commissural axons including those of the corpus callosum are strongly S3-positive along their whole length from their time of formation to postnatal life, but some have more complex age-dependent expression patterns. S3 labeling of the optic pathway is also complex, being initially strong in the retinal ganglion cells, optic tract, and chiasma but thereafter being lost except in a proportion of postchiasmal axons. The corticospinal tract is strongly positive throughout its course at all stages examined, including its decussation, formed at about P2 in the central part of the medulla oblongata.
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Affiliation(s)
- Vasi Sundaresan
- Medical Research Council Centre for Developmental Neurobiology, Guys Hospital Campus, Kings College London, London Bridge, SE1 1UL, UK.
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Iseda T, Nishio T, Kawaguchi S, Kawasaki T, Wakisaka S. Spontaneous regeneration of the corticospinal tract after transection in young rats: collagen type IV deposition and astrocytic scar in the lesion site are not the cause but the effect of failure of regeneration. J Comp Neurol 2003; 464:343-55. [PMID: 12900928 DOI: 10.1002/cne.10786] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In young rats the corticospinal tract regenerated after a single transection of the spinal cord with a sharp blade, but regeneration failed if the transection was repeated to make a more traumatic injury. To identify cells and associated molecules that promote or impede regeneration, we compared expression of collagen type IV, glial fibrillary acidic protein (GFAP), and vimentin immunoreactivity (IR) at the lesion sites in combination with anterograde axonal tracing between animals with two types of transection. Axonal regeneration occurred as early as 18 hours after transection; regenerating axons penetrated vessel-like structures with collagen type IV-IR at the lesion site, while reactive astrocytes coexpressing GFAP- and vimentin-IR appeared in the lesioned white matter. In contrast, when regeneration failed astrocytes were absent near the lesion. By 7 days sheet-like structures with collagen type IV-IR and astrocytic scar appeared in the lesioned white matter and persisted until the end of the observation period (31 days). On the basis of their spatiotemporal appearance, collagen type IV-IR sheet-like structures and the astrocytic scar follow, rather than cause, the failure of regeneration. The major sign, and perhaps cause, of failure of axonal regeneration is likely the prolonged disappearance of astrocytes around the lesion site in the early postinjury period.
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Affiliation(s)
- Tsutomu Iseda
- Department of Integrative Brain Science, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
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Judas M, Milosević NJ, Rasin MR, Heffer-Lauc M, Kostović I. Complex patterns and simple architects: molecular guidance cues for developing axonal pathways in the telencephalon. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2003; 32:1-32. [PMID: 12827969 DOI: 10.1007/978-3-642-55557-2_1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- M Judas
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Salata 12, 10000 Zagreb, Croatia
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Shu T, Li Y, Keller A, Richards LJ. The glial sling is a migratory population of developing neurons. Development 2003; 130:2929-37. [PMID: 12756176 PMCID: PMC2810520 DOI: 10.1242/dev.00514] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
For two decades the glial sling has been hypothesized to act as a guidance substratum for developing callosal axons. However, neither the cellular nature of the sling nor its guidance properties have ever been clearly identified. Although originally thought to be glioblasts, we show here that the subventricular zone cells forming the sling are in fact neurons. Sling cells label with a number of neuronal markers and display electrophysiological properties characteristic of neurons and not glia. Furthermore, sling cells are continuously generated until early postnatal stages and do not appear to undergo widespread cell death. These data indicate that the sling may be a source of, or migratory pathway for, developing neurons in the rostral forebrain, suggesting additional functions for the sling independent of callosal axon guidance.
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