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Gandhi JM, Sankhe S, Udmale P. Pontine Tegmental Cap Dysplasia- the Role of MRI and DTI in Diagnosis. Neurol India 2020; 68:691-693. [PMID: 32643691 DOI: 10.4103/0028-3886.289019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Affiliation(s)
| | - Shilpa Sankhe
- Department of Radiology, Neuroradiology Unit, KEM Hosiptal, Mumbai, Maharastra, India
| | - Prasad Udmale
- Department of Radiology, Neuroradiology Unit, KEM Hosiptal, Mumbai, Maharastra, India
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Beyeler SA, Hodges MR, Huxtable AG. Impact of inflammation on developing respiratory control networks: rhythm generation, chemoreception and plasticity. Respir Physiol Neurobiol 2020; 274:103357. [PMID: 31899353 DOI: 10.1016/j.resp.2019.103357] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 11/17/2019] [Accepted: 12/02/2019] [Indexed: 10/25/2022]
Abstract
The respiratory control network in the central nervous system undergoes critical developmental events early in life to ensure adequate breathing at birth. There are at least three "critical windows" in development of respiratory control networks: 1) in utero, 2) newborn (postnatal day 0-4 in rodents), and 3) neonatal (P10-13 in rodents, 2-4 months in humans). During these critical windows, developmental processes required for normal maturation of the respiratory control network occur, thereby increasing vulnerability of the network to insults, such as inflammation. Early life inflammation (induced by LPS, chronic intermittent hypoxia, sustained hypoxia, or neonatal maternal separation) acutely impairs respiratory rhythm generation, chemoreception and increases neonatal risk of mortality. These early life impairments are also greater in young males, suggesting sex-specific impairments in respiratory control. Further, neonatal inflammation has a lasting impact on respiratory control by impairing adult respiratory plasticity. This review focuses on how inflammation alters respiratory rhythm generation, chemoreception and plasticity during each of the three critical windows. We also highlight the need for additional mechanistic studies and increased investigation into how glia (such as microglia and astrocytes) play a role in impaired respiratory control after inflammation. Understanding how inflammation during critical windows of development disrupt respiratory control networks is essential for developing better treatments for vulnerable neonates and preventing adult ventilatory control disorders.
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Affiliation(s)
- Sarah A Beyeler
- Department of Human Physiology, University of Oregon, Eugene, OR, 97403, United States
| | - Matthew R Hodges
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226, United States
| | - Adrianne G Huxtable
- Department of Human Physiology, University of Oregon, Eugene, OR, 97403, United States.
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Abstract
PURPOSE OF REVIEW Recent advances in experimental studies of optic nerve regeneration to better understand the pathophysiology of axon regrowth and provide insights into the future treatment of numerous optic neuropathies. RECENT FINDINGS The optic nerve is part of the central nervous system and cannot regenerate if injured. There are several steps that regenerating axons of retinal ganglion cells (RGCs) must take following optic nerve injury that include: maximizing the intrinsic growth capacity of RGCs, overcoming the extrinsic growth-inhibitory environment of the optic nerve, and optimizing the reinnervation of regenerated axons to their targets in the brain. Recently, some degree of experimental optic nerve regeneration has been achieved by factors associated with inducing intraocular inflammation, providing exogenous neurotrophic factors, reactivating intrinsic growth capacity of mature RGCs, or by modifying the extrinsic growth-inhibitory environment of the optic nerve. In some experiments, regenerating axons have been shown to reinnervate their central targets in the brain. SUMMARY Further approaches to the combination of aforementioned treatments will be necessary to develop future therapeutic strategy to promote ultimate regeneration of the optic nerve and functional vision recovery after optic nerve injury.
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Nagai T, Ikegami Y, Mizumachi H, Shirakigawa N, Ijima H. Development of an in situ evaluation system for neural cells using extracellular matrix-modeled gel culture. J Biosci Bioeng 2017; 124:430-438. [DOI: 10.1016/j.jbiosc.2017.04.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 04/21/2017] [Indexed: 01/21/2023]
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Feng L, Zhou D, Zhang Z, He L, Liu Y, Yang Y. Exome sequencing identifies a novel UNC5D mutation in a severe myopic anisometropia family: A case report. Medicine (Baltimore) 2017; 96:e7138. [PMID: 28614238 PMCID: PMC5478323 DOI: 10.1097/md.0000000000007138] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
INTRODUCTION Severe myopic anisometropia has been identified to have heritability, but the pathogenesis of anisometropia still remains obscure. CASE DESCRIPTION Here, we presented a Chinese severe myopic anisometropia family with 5 members affected. Though using the exome sequencing, we identified a novel mutation in the UNC5D gene (c.1297C>T, p.R433C), which was predicted to have a damage effect on the protein function and kept highly conserved throughout evolution across species. As previously described, the UNC5D gene belongs to the UNC5 protein family and may have functions to regulate neuronal migration, axon guidance, and cell survival. The expression of UNC5D was also co-located at the visual areas of the mouse cortical regions at early postnatal ages. CONCLUSION Our data provide the first evidence for involvement of UNC5D gene in the severe myopic anisometropia.
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Affiliation(s)
- Lei Feng
- Eye Center, The Second Affiliated Hospital of Zhejiang University School of Medicine
| | - Daizhan Zhou
- Department of General Surgery, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou
- Bio-X Center, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders (Ministry of Education), Shanghai Jiao Tong University
| | - Zhou Zhang
- Bio-X Center, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders (Ministry of Education), Shanghai Jiao Tong University
| | - Lin He
- Bio-X Center, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders (Ministry of Education), Shanghai Jiao Tong University
| | - Yun Liu
- Institutes of Biomedical Sciences, Fudan University
- Key Laboratory of Molecular Medicine, The Ministry of Education, Department of Biochemistry and Molecular Biology, Fudan University Shanghai Medical College, Shanghai, PR China
| | - Yabo Yang
- Eye Center, The Second Affiliated Hospital of Zhejiang University School of Medicine
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6
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Black BJ, Gu L, Mohanty SK. Highly effective photonic cue for repulsive axonal guidance. PLoS One 2014; 9:e86292. [PMID: 24717339 PMCID: PMC3981697 DOI: 10.1371/journal.pone.0086292] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Accepted: 12/11/2013] [Indexed: 01/03/2023] Open
Abstract
In vivo nerve repair requires not only the ability to regenerate damaged axons, but most importantly, the ability to guide developing or regenerating axons along paths that will result in functional connections. Furthermore, basic studies in neuroscience and neuro-electronic interface design require the ability to construct in vitro neural circuitry. Both these applications require the development of a noninvasive, highly effective tool for axonal growth-cone guidance. To date, a myriad of technologies have been introduced based on chemical, electrical, mechanical, and hybrid approaches (such as electro-chemical, optofluidic flow and photo-chemical methods). These methods are either lacking in desired spatial and temporal selectivity or require the introduction of invasive external factors. Within the last fifteen years however, several attractive guidance cues have been developed using purely light based cues to achieve axonal guidance. Here, we report a novel, purely optical repulsive guidance technique that uses low power, near infrared light, and demonstrates the guidance of primary goldfish retinal ganglion cell axons through turns of up to 120 degrees and over distances of ∼90 µm.
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Affiliation(s)
- Bryan J Black
- Biophysics and Physiology Group, Department of Physics, The University of Texas at Arlington, Arlington, Texas, United States of America
| | - Ling Gu
- Biophysics and Physiology Group, Department of Physics, The University of Texas at Arlington, Arlington, Texas, United States of America
| | - Samarendra K Mohanty
- Biophysics and Physiology Group, Department of Physics, The University of Texas at Arlington, Arlington, Texas, United States of America
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7
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Renin–angiotensin system involvement in the oxidative stress-induced neurodegeneration of cultured retinal ganglion cells. Jpn J Ophthalmol 2012; 57:126-32. [DOI: 10.1007/s10384-012-0204-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 08/28/2012] [Indexed: 02/03/2023]
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Abstract
The failure of the optic nerve to regenerate after injury or in neurodegenerative disease remains a major clinical and scientific problem. Retinal ganglion cell (RGC) axons course through the optic nerve and carry all the visual information to the brain, but after injury, they fail to regrow through the optic nerve and RGC cell bodies typically die, leading to permanent loss of vision. There are at least 4 hurdles to overcome in preserving RGCs and regenerating their axons: 1) increase RGC survival, 2) overcome the inhibitory environment of the optic nerve, 3) enhance RGC intrinsic axon growth potential, and 4) optimize the mapping of RGC connections back into their targets in the brain.
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Conway CD, Price DJ, Pratt T, Mason JO. Analysis of axon guidance defects at the optic chiasm in heparan sulphate sulphotransferase compound mutant mice. J Anat 2011; 219:734-42. [PMID: 21951307 DOI: 10.1111/j.1469-7580.2011.01432.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
During embryonic development of the visual system, retinal ganglion cells (RGCs) project their axons towards the brain, passing through the optic chiasm. Axons are guided on this journey by molecular cues in the environment. The heparan sulphate sulphotransferase (Hst) enzymes Hs2st and Hs6st1 are each known to be required for specific aspects of axon guidance in the developing visual system, as revealed by studies of Hs2st(-/-) and Hs6st1(-/-) mutant embryos. However, it remained possible that these two enzymes have additional, overlapping, functions in RGC axon guidance; but that no effect is manifest in single mutant embryos, because the other enzyme is sufficient to fulfil the shared function. To investigate this possibility, we generated a set of Hs2st;Hs6st1 double mutant embryos that had reduced gene dosage of each of these Hsts, reasoning that any additional phenotypes in these animals would indicate the presence of functional overlap. We first characterised the structure of the mutant Hs6st1 locus, identifying the insertion site of the gene trap vector, to allow us to genotype compound mutants reliably. We found that Hs2st(-/-) ;Hs6st1(-/-) mutants that lack both enzymes died prior to E15.5. As the optic chiasm has not formed by this stage, we were unable to determine the effect of complete loss of Hs2st and Hs6st1 on chiasm formation. However, compound mutant embryos lacking one Hst and heterozygous for the other were viable. We found that RGC axon guidance defects in such compound mutants were no more severe than those found in the single mutant embryos. We also found that expression of the Hs6st1 isoform Hs6st3 overlaps with that of Hs6st1 in the developing visual system, suggesting that some Hs6st activity remains present in this region of Hs6st1(-/-) mutant embryos.
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Affiliation(s)
- Christopher D Conway
- Genes and Development Group, Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, George Square, Edinburgh, UK
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Ogata-Iwao M, Inatani M, Iwao K, Takihara Y, Nakaishi-Fukuchi Y, Irie F, Sato S, Furukawa T, Yamaguchi Y, Tanihara H. Heparan sulfate regulates intraretinal axon pathfinding by retinal ganglion cells. Invest Ophthalmol Vis Sci 2011; 52:6671-9. [PMID: 21743013 DOI: 10.1167/iovs.11-7559] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
PURPOSE. Heparan sulfate (HS) is abundantly expressed in the developing neural retina; however, its role in the intraretinal axon guidance of retinal ganglion cells (RGCs) remains unclear. In this study, the authors examined whether HS was essential for the axon guidance of RGCs toward the optic nerve head. METHODS. The authors conditionally ablated the gene encoding the exostosin-1 (Ext1) enzyme, using the dickkopf homolog 3 (Dkk3)-Cre transgene, which disrupted HS expression in the mouse retina during directed pathfinding by RGC axons toward the optic nerve head. In situ hybridization, immunohistochemistry, DiI tracing, binding assay, and retinal explant assays were performed to evaluate the phenotypes of the mutants and the roles of HS in intraretinal axon guidance. RESULTS. Despite no gross abnormality in RGC distribution, the mutant RGC axons exhibited severe intraretinal guidance errors, including optic nerve hypoplasia, ectopic axon penetration through the full thickness of the neural retina and into the subretinal space, and disturbance of the centrifugal projection of RGC axons toward the optic nerve head. These abnormal phenotypes shared similarities with the RGC axon misguidance caused by mutations of genes encoding Netrin-1 and Slit-1/2. Explant assays revealed that the mutant RGCs exhibited disturbed Netrin-1-dependent axon outgrowth and Slit-2-dependent repulsion. CONCLUSIONS. The present study demonstrated that RGC axon projection toward the optic nerve head requires the expression of HS in the neural retina, suggesting that HS in the retina functions as an essential modulator of Netrin-1 and Slit-mediated intraretinal RGC axon guidance.
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Affiliation(s)
- Minako Ogata-Iwao
- Department of Ophthalmology and Visual Science, Kumamoto University Graduate School of Medical Sciences, Japan
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Yamamoto H, Agata K. Optic chiasm formation in planarian I: Cooperative netrin- and robo-mediated signals are required for the early stage of optic chiasm formation. Dev Growth Differ 2011; 53:300-11. [PMID: 21428985 DOI: 10.1111/j.1440-169x.2010.01234.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Freshwater planarians can regenerate a brain, including eyes, from the anterior blastema, and coordinately form an optic chiasm during eye and brain regeneration. To investigate the role of the netrin- and slit-signaling systems during optic chiasm formation, we cloned three receptor genes (Djunc5A, Djdcc and DjroboA) expressed in visual neurons and their ligand genes (DjnetB and Djslit) and analyzed their functions by RNA interference (RNAi). Although each of DjroboA(RNAi), Djunc5A(RNAi) and DjnetB(RNAi) showed a weak phenotype and Djslit(RNAi) showed a severe defect of eye formation, we did not observe any defect of crossing of visual axons over the midline among single knockdown planarians. However, among double knockdown planarians, some of DjnetB(RNAi);DjroboA(RNAi) and Djunc5A(RNAi);DjroboA(RNAi) showed complete disconnection between the visual axons from the two sides, suggesting that some combination of netrin- and robo-mediated signals may be required for crossing over the midline. Finally, we carefully investigated the distribution patterns of cells expressing DjNetB protein, DjnetB, and Djslit at the early stage of regeneration, and found that visual axons projected along a path sandwiched between DjNetB protein and Djslit-positive cells. These results suggest that two different collaborative or combinatory signals may be required for midline crossing at the early stage of chiasm formation during eye and brain regeneration.
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Affiliation(s)
- Hiroshi Yamamoto
- Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto 606-8502, Japan
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Concerted action of CB1 cannabinoid receptor and deleted in colorectal cancer in axon guidance. J Neurosci 2011; 31:1489-99. [PMID: 21273433 DOI: 10.1523/jneurosci.4134-09.2011] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Endocannabinoids (eCBs) are retrograde neurotransmitters that modulate the function of many types of synapses. The presence of eCBs, their CB1 receptor (CB1R), and metabolizing enzymes at embryonic and early postnatal periods have been linked to developmental processes such as neuronal proliferation, differentiation, and migration, axon guidance, and synaptogenesis. Here, we demonstrate the presence of a functional eCB system in the developing visual system and the role of CB1R during axon growth and retinothalamic development. Pharmacological treatment of retinal explants and primary cortical neuron cultures with ACEA, a selective CB1R agonist, induced a collapse of the growth cone (GC). Furthermore the application of AM251, a CB1R inverse agonist, to the neuronal cultures increased the surface area of GC. In vivo, intraocular injection of ACEA diminished retinal projection growth, while AM251 promoted growth and caused aberrant projections. In addition, compared with their wild-type littermates, CB1R-deficient adult mice revealed a lower level of eye-specific segregation of retinal projections in the dorsal lateral geniculate nucleus. Finally, we found that pharmacological modulation of CB1R affected the trafficking of Deleted in colorectal cancer (DCC) receptor to the plasma membrane in a PKA-dependent manner. Moreover, pharmacological inhibition or genetic inactivation of DCC abolished the CB1R-induced reorganization of the GC. Overall, these findings establish a mechanism by which the CB1R influences GC behavior and nervous system development in concerted action with DCC.
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Liu JB, Jiang YQ, Gong AH, Zhang ZJ, Jiang Q, Chu XP. Expression of Slit2 and Robo1 after traumatic lesions of the rat spinal cord. Acta Histochem 2011; 113:43-8. [PMID: 19783284 DOI: 10.1016/j.acthis.2009.08.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Revised: 08/03/2009] [Accepted: 08/06/2009] [Indexed: 02/02/2023]
Abstract
We have used semi-quantitative RT-PCR, Western blot, and immunofluorescence imaging approaches to detect the expression levels of Slit2 and its receptor Robo1 in the rat spinal cord after traumatic lesions. Our results revealed that both the mRNA and protein levels of Slit2 were up-regulated in the injured spinal cord. The Slit2 expression level was increased at day 7 until day 14, and then returned to normal level at day 21 after injury. A double-immunolabelling study showed that Slit2 and neurofilament (NF) proteins were both localized in neurons of spinal corda cinerea. Slit2 immunopositivity was detected in neuronal plasma membranes but not in the axonal fibers. In contrast, the immunolabelling of Robo1 in the normal spinal cord was at a low level, mostly in the neurons of spinal corda cinerea, and remained unchanged at all time points following spinal cord injury (SCI). The regulation levels of Slit2 and Robo1 after traumatic lesions in the rat spinal cord are different. Our results indicate that Slit2-Robo1 might not be involved in the inhibitory environment after SCI.
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Affiliation(s)
- Jin-Bo Liu
- Department of Orthopedics, The Third Affiliated Hospital, Suzhou University, Changzhou, China.
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Reese BE. Development of the retina and optic pathway. Vision Res 2010; 51:613-32. [PMID: 20647017 DOI: 10.1016/j.visres.2010.07.010] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Revised: 07/04/2010] [Accepted: 07/13/2010] [Indexed: 12/30/2022]
Abstract
Our understanding of the development of the retina and visual pathways has seen enormous advances during the past 25years. New imaging technologies, coupled with advances in molecular biology, have permitted a fuller appreciation of the histotypical events associated with proliferation, fate determination, migration, differentiation, pathway navigation, target innervation, synaptogenesis and cell death, and in many instances, in understanding the genetic, molecular, cellular and activity-dependent mechanisms underlying those developmental changes. The present review considers those advances associated with the lineal relationships between retinal nerve cells, the production of retinal nerve cell diversity, the migration, patterning and differentiation of different types of retinal nerve cells, the determinants of the decussation pattern at the optic chiasm, the formation of the retinotopic map, and the establishment of ocular domains within the thalamus.
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Affiliation(s)
- Benjamin E Reese
- Neuroscience Research Institute and Department of Psychology, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, USA.
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Jissendi-Tchofo P, Doherty D, McGillivray G, Hevner R, Shaw D, Ishak G, Leventer R, Barkovich AJ. Pontine tegmental cap dysplasia: MR imaging and diffusion tensor imaging features of impaired axonal navigation. AJNR Am J Neuroradiol 2008; 30:113-9. [PMID: 18842761 DOI: 10.3174/ajnr.a1305] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Malformations of the brain stem are uncommon. We present MR imaging and diffusion tensor imaging (DTI) features of 6 patients with pontine tegmental cap dysplasia, characterized by ventral pontine hypoplasia and a dorsal "bump," and speculate on potential mechanisms by which it forms. MATERIALS AND METHODS Birth and developmental records of 6 patients were reviewed. We reviewed MR imaging studies of all patients and DTIs of patient 3. Potential developmental causes were evaluated. RESULTS All patients were born uneventfully after normal pregnancies except patient 6 (in utero growth retardation). They presented with multiple cranial neuropathies and evidence of cerebellar dysfunction. Variable hypotonia and motor dysfunction were present. Imaging revealed ventral pontine hypoplasia and mild cerebellar vermian hypoplasia, in addition to an unusual rounded to beaklike "bump" on the dorsal surface of the pons, extending into the fourth ventricle. Color fractional anisotropy maps showed the bump to consist of a bundle of axons directed horizontally (left-right). The bump appeared, on morphologic images, to be continuous with the middle cerebellar peduncles (MCPs), which were slightly diminished in size compared with those in healthy infants. Analysis of the DTI was, however, inconclusive regarding the connections of these axons. The decussation of the MCPs, transverse pontine fibers, and longitudinal brain stem axonal pathways was also abnormal. CONCLUSIONS Our data suggest that the dorsal transverse axonal band in these disorders results from abnormal axonal pathfinding, abnormal neuronal migration, or a combination of the 2 processes.
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Affiliation(s)
- P Jissendi-Tchofo
- Department of Radiology, University of California, San Francisco, CA, USA.
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Zhao J, Yoneda M, Takeyama M, Inoue Y, Kataoka T, Ohno-Jinno A, Isogai Z, Iwaki M, Zako M. Competitive binding of heparin with hyaluronan to a specific motif in SPACR. J Neurochem 2008; 107:823-31. [PMID: 18786170 DOI: 10.1111/j.1471-4159.2008.05669.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The critical hyaluronan binding motif (HABM) in sialoprotein associated with cones and rods (SPACR) has already been determined. As sialoproteoglycan associated with cones and rods, another interphotoreceptor matrix molecule, binds to chondroitin sulfate and heparin with or without the employment of HABMs, respectively, we evaluated and compared the binding of these glycosaminoglycans to SPACR. A western blotting study in combination with inhibition assays showed that heparin bound specifically to SPACR. A series of GST fusion proteins covering the whole SPACR molecule narrowed down the region responsible for the binding. Finally, a site-directed mutagenesis assay demonstrated that the critical HABM also acts as a specific binding site for heparin. These results were supported with mutual inhibitions by hyaluronan and heparin in analyses using GST fusion proteins and native SPACR derived from retina. Thus, these glycosaminoglycans bind to SPACR in a different manner than to sialoproteoglycan associated with cones and rods. The competitive binding between hyaluronan and heparin to SPACR, mediated through the identical HABM, may dominate the functions of SPACR, in turn involving physiological and pathological processes involved in retinal development, aging and other related disorders.
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Affiliation(s)
- Jinsong Zhao
- Department of Ophthalmology, Aichi Medical University, Nagakute, Aichi, Japan
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Becker CG, Becker T. Growth and pathfinding of regenerating axons in the optic projection of adult fish. J Neurosci Res 2008; 85:2793-9. [PMID: 17131420 DOI: 10.1002/jnr.21121] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In contrast to mammals, teleost fish are able to regrow severed long-range projection axons in the central nervous system (CNS), leading to recovery of function. The optic projection in teleost fish is used to study neuron-intrinsic and environmental molecular factors that determine successful axon regrowth and navigation through a complex CNS pathway back to original targets. Here we review evidence for regeneration-specific regulation and robust expression of growth- and pathfinding-associated genes in regenerating retinal ganglion cell (RGC) axons of adult fish. The environment of the CNS in fish appears to contain few inhibitory molecules and at the same time a number of promoting molecules for axon regrowth. Finally, some environmental cues that are used as guidance cues for developing RGC axons are also present in continuously growing adult animals. These molecules may serve as guidance cues for the precise navigation of axons from newly generated RGCs in adult animals as well as of regenerating RGC axons after a lesion. The application of new molecular techniques especially to adult zebrafish, is likely to produce new insights into successful axonal regeneration in the CNS of fish and the absence thereof in mammals.
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Affiliation(s)
- Catherina G Becker
- Centre for Neuroscience Research, University of Edinburgh, Summerhall, Edinburgh, United Kingdom
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Cebrià F. Regenerating the central nervous system: how easy for planarians! Dev Genes Evol 2007; 217:733-48. [PMID: 17999079 DOI: 10.1007/s00427-007-0188-6] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2007] [Accepted: 10/03/2007] [Indexed: 11/29/2022]
Abstract
The regenerative capabilities of freshwater planarians (Platyhelminthes) are very difficult to match. A fragment as tiny as 1/279th of the planarian body is able to regenerate a whole animal within very few days [Morgan. Arch Entwm 7:364-397 (1898)]. Although the planarian central nervous system (CNS) may appear quite morphologically simple, recent studies have shown it to be more complex at the molecular level, revealing a high degree of molecular compartmentalization in planarian cephalic ganglia. Planarian neural genes include homologues of well-known transcription factors and genes involved in human diseases, neurotransmission, axon guidance, signaling pathways, and RNA metabolism. The availability of hundreds of genes expressed in planarian neurons coupled with the ability to silence them through the use of RNA interference makes it possible to start unraveling the molecular mechanisms underlying CNS regeneration. In this review, I discuss current knowledge on the planarian nervous system and the genes involved in its regeneration, and I discuss some of the important questions that remain to be answered.
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Affiliation(s)
- Francesc Cebrià
- Departament de Genètica, Facultat de Biologia, Institut de Biomedicina de la Universitat de Barcelona (IBUB), Barcelona, Catalunya, Spain.
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Benowitz LI, Yin Y. Combinatorial treatments for promoting axon regeneration in the CNS: strategies for overcoming inhibitory signals and activating neurons' intrinsic growth state. Dev Neurobiol 2007; 67:1148-65. [PMID: 17514713 DOI: 10.1002/dneu.20515] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In general, neurons in the mature mammalian central nervous system (CNS) are unable to regenerate injured axons, and neurons that remain uninjured are unable to form novel connections that might compensate for ones that have been lost. As a result of this, victims of CNS injury, stroke, or certain neurodegenerative diseases are unable to fully recover sensory, motor, cognitive, or autonomic functions. Regenerative failure is related to a host of inhibitory signals associated with the extracellular environment and with the generally low intrinsic potential of mature CNS neurons to regenerate. Most research to date has focused on extrinsic factors, particularly the identification of inhibitory proteins associated with myelin, the perineuronal net, glial cells, and the scar that forms at an injury site. However, attempts to overcome these inhibitors have resulted in relatively limited amounts of CNS regeneration. Using the optic nerve as a model system, we show that with appropriate stimulation, mature neurons can revert to an active growth state and that when this occurs, the effects of overcoming inhibitory signals are enhanced dramatically. Similar conclusions are emerging from studies in other systems, pointing to a need to consider combinatorial treatments in the clinical setting.
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Affiliation(s)
- Larry I Benowitz
- Laboratories for Neuroscience Research in Neurosurgery and Neurobiology Program, Children's Hospital, Boston, Massachusetts, USA.
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Chehrehasa F, Key B, St John JA. The shape of the olfactory bulb influences axon targeting. Brain Res 2007; 1169:17-23. [PMID: 17698047 DOI: 10.1016/j.brainres.2007.06.073] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2006] [Revised: 06/26/2007] [Accepted: 06/26/2007] [Indexed: 11/17/2022]
Abstract
Each primary olfactory neuron in the mouse expresses a single type of odorant receptor. All neurons expressing the same odorant receptor gene typically project to two topographically fixed glomeruli, one each on the medial and lateral surfaces of the olfactory bulb. While topographic gradients of guidance receptors and their ligands help to establish the retinotectal projection, similar orthogonal distributions of cues have not yet been detected within the olfactory system. While odorant receptors are crucial for the final targeting of axons to glomeruli, it is unclear whether the olfactory bulb itself provides instructive cues for the establishment of the topographic map. To begin to understand the role of the olfactory bulb in the formation of the olfactory nerve pathway, we developed a model whereby the gross shape of the bulb in the P2-IRES-tau-LacZ line of mice was radically altered during postnatal development. We have shown here that the topography of axons expressing the P2 odorant receptor is dependent on the shape of the olfactory bulb. When the dorsoventral axis of the olfactory bulb was compressed during the early postnatal period, newly developing P2 axons projected to multiple inappropriate glomeruli surrounding their normal target site. These results suggest that the distribution of local guidance cues within the olfactory bulb is influenced by the shape of the olfactory bulb and that these cues contribute to the topographic positioning of glomeruli.
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Affiliation(s)
- Fatemeh Chehrehasa
- Brain Growth and Regeneration Lab, Discipline of Anatomy and Developmental Biology, School of Biomedical Sciences, The University of Queensland, Brisbane 4072, Australia
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Abstract
Albinism is associated with a misrouting of fibers at the optic chiasm where the majority of fibers cross to the contralateral side. The cause of this abnormal decussation pattern reflects a disturbance of cell cycle regulation in the development of the retina which is in part controlled by melanin. Growing axons from retinal ganglion cells therefore arrive later than usual at the optic chiasm and are misrouted contralaterally. This atypical decussation leads to morphological changes of the optic chiasm including a reduced chiasm width with larger angles between optic nerves and tracts which can be shown by magnetic resonance imaging.
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Affiliation(s)
- B Schmitz
- Klinik für Diagnostische und Interventionelle Radiologie, Universitätskliniken Ulm, Steinhövelstrasse 9, 89075, Ulm, Deutschland.
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Cebrià F, Newmark PA. Morphogenesis defects are associated with abnormal nervous system regeneration following roboA RNAi in planarians. Development 2007; 134:833-7. [PMID: 17251262 DOI: 10.1242/dev.02794] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The process by which the proper pattern is restored to newly formed tissues during metazoan regeneration remains an open question. Here, we provide evidence that the nervous system plays a role in regulating morphogenesis during anterior regeneration in the planarian Schmidtea mediterranea. RNA interference (RNAi) knockdown of a planarian ortholog of the axon-guidance receptor roundabout (robo) leads to unexpected phenotypes during anterior regeneration, including the development of a supernumerary pharynx (the feeding organ of the animal) and the production of ectopic, dorsal outgrowths with cephalic identity. We show that Smed-roboA RNAi knockdown disrupts nervous system structure during cephalic regeneration: the newly regenerated brain and ventral nerve cords do not re-establish proper connections. These neural defects precede, and are correlated with, the development of ectopic structures. We propose that, in the absence of proper connectivity between the cephalic ganglia and the ventral nerve cords, neurally derived signals promote the differentiation of pharyngeal and cephalic structures. Together with previous studies on regeneration in annelids and amphibians, these results suggest a conserved role of the nervous system in pattern formation during blastema-based regeneration.
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Affiliation(s)
- Francesc Cebrià
- Department of Cell and Developmental Biology, Neuroscience Program, University of Illinois at Urbana-Champaign, B107 Chemical and Life Sciences Laboratory, 601 South Goodwin Avenue, Urbana, IL 61801, USA
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Yi XN, Zheng LF, Zhang JW, Zhang LZ, Xu YZ, Luo G, Luo XG. Dynamic changes in Robo2 and Slit1 expression in adult rat dorsal root ganglion and sciatic nerve after peripheral and central axonal injury. Neurosci Res 2006; 56:314-21. [PMID: 16979769 DOI: 10.1016/j.neures.2006.07.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Revised: 07/16/2006] [Accepted: 07/31/2006] [Indexed: 11/26/2022]
Abstract
Robos are transmembrane receptors that mediate Slit signaling to repel growth cone outgrowth and neural migration in the developing central nervous system. Their distribution and function in the peripheral nervous system remains unclear. In the present study, we examined expression of Slit1 and Robo2 in adult rat dorsal root ganglion (DRG), spinal cord and sciatic nerve after peripheral nerve injury (axotomy). In control rats, Slit1 and Robo2 mRNA and protein were expressed at basic levels in the L5 and L6 DRGs. Sciatic transection resulted in a significant up-regulation of both Robo2 and Slit1 mRNA and protein (p<0.05 versus control). The peak of Slit1 and Robo2 expression occurred at days 7 and 14, respectively, and returned to control levels at days 28 and 21 post-axotomy, respectively. By contrast, injury to the central axons of the DRG by dorsal rhizotomy did not up-regulate Slit1 and Robo2 expression. Robo2 staining was stronger in small diameter neurons than in large diameter neurons in control DRG. Interestingly, post-axotomy, Robo2 immunostaining increased in the large diameter neurons and the number of Robo2 positive large diameter neurons increased significantly relative to controls. Non-neuronal cells surrounding the primary sensory neurons, including the satellite cells, were Slit1-positive, and Slit1 protein was expressed in the myelin sheath and non-neural cells in both intact and degenerating sciatic nerve axons. Sciatic nerve transection also led to an accumulation of Slit1 protein in peripheral region of the traumatic neuroma. In conclusion, we report an altered expression and redistribution of Robo2 and Slit1 in the DRG and sciatic nerve trunk after peripheral axotomy. Our results indicate that Slit1 and Robo2 likely play an important role in regeneration after peripheral nerve injury.
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Affiliation(s)
- Xi-Nan Yi
- Department of Anatomy & Neurobiology, Xiangya School of Medicine, Central South University, No. 172, Tongzipo Road, Changsha, Hunan 410013, China
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