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Ortalli AL, Fiore L, Di Napoli J, Rapacioli M, Salierno M, Etchenique R, Flores V, Sanchez V, Carri NG, Scicolone G. EphA3 expressed in the chicken tectum stimulates nasal retinal ganglion cell axon growth and is required for retinotectal topographic map formation. PLoS One 2012; 7:e38566. [PMID: 22685584 PMCID: PMC3369860 DOI: 10.1371/journal.pone.0038566] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 05/07/2012] [Indexed: 11/29/2022] Open
Abstract
Background Retinotopic projection onto the tectum/colliculus constitutes the most studied model of topographic mapping and Eph receptors and their ligands, the ephrins, are the best characterized molecular system involved in this process. Ephrin-As, expressed in an increasing rostro-caudal gradient in the tectum/colliculus, repel temporal retinal ganglion cell (RGC) axons from the caudal tectum and inhibit their branching posterior to their termination zones. However, there are conflicting data regarding the nature of the second force that guides nasal axons to invade and branch only in the caudal tectum/colliculus. The predominant model postulates that this second force is produced by a decreasing rostro-caudal gradient of EphA7 which repels nasal optic fibers and prevents their branching in the rostral tectum/colliculus. However, as optic fibers invade the tectum/colliculus growing throughout this gradient, this model cannot explain how the axons grow throughout this repellent molecule. Methodology/Principal Findings By using chicken retinal cultures we showed that EphA3 ectodomain stimulates nasal RGC axon growth in a concentration dependent way. Moreover, we showed that nasal axons choose growing on EphA3-expressing cells and that EphA3 diminishes the density of interstitial filopodia in nasal RGC axons. Accordingly, in vivo EphA3 ectodomain misexpression directs nasal optic fibers toward the caudal tectum preventing their branching in the rostral tectum. Conclusions We demonstrated in vitro and in vivo that EphA3 ectodomain (which is expressed in a decreasing rostro-caudal gradient in the tectum) is necessary for topographic mapping by stimulating the nasal axon growth toward the caudal tectum and inhibiting their branching in the rostral tectum. Furthermore, the ability of EphA3 of stimulating axon growth allows understanding how optic fibers invade the tectum growing throughout this molecular gradient. Therefore, opposing tectal gradients of repellent ephrin-As and of axon growth stimulating EphA3 complement each other to map optic fibers along the rostro-caudal tectal axis.
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Affiliation(s)
- Ana Laura Ortalli
- Laboratory of Developmental Neurobiology, Institute of Cell Biology and Neurosciences “Prof. E. De Robertis” (UBA-CONICET), School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | - Luciano Fiore
- Laboratory of Developmental Neurobiology, Institute of Cell Biology and Neurosciences “Prof. E. De Robertis” (UBA-CONICET), School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | - Jennifer Di Napoli
- Laboratory of Developmental Neurobiology, Institute of Cell Biology and Neurosciences “Prof. E. De Robertis” (UBA-CONICET), School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | - Melina Rapacioli
- Interdisciplinary Group in Theoretical Biology, Department of Bioestructural Sciences, Favaloro University, Buenos Aires, Argentina
| | - Marcelo Salierno
- Department of Inorganic, Analytical and Physical Chemistry (INQUIMAE), Faculty of Exact and Natural Sciences, University of Buenos Aires, Buenos Aires, Argentina
| | - Roberto Etchenique
- Department of Inorganic, Analytical and Physical Chemistry (INQUIMAE), Faculty of Exact and Natural Sciences, University of Buenos Aires, Buenos Aires, Argentina
| | - Vladimir Flores
- Laboratory of Developmental Neurobiology, Institute of Cell Biology and Neurosciences “Prof. E. De Robertis” (UBA-CONICET), School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
- Interdisciplinary Group in Theoretical Biology, Department of Bioestructural Sciences, Favaloro University, Buenos Aires, Argentina
| | - Viviana Sanchez
- Laboratory of Developmental Neurobiology, Institute of Cell Biology and Neurosciences “Prof. E. De Robertis” (UBA-CONICET), School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | | | - Gabriel Scicolone
- Laboratory of Developmental Neurobiology, Institute of Cell Biology and Neurosciences “Prof. E. De Robertis” (UBA-CONICET), School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
- * E-mail:
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Jayasena CS, Flood WD, Koblar SA. High EphA3 expressing ophthalmic trigeminal sensory axons are sensitive to ephrin-A5-Fc: Implications for lobe specific axon guidance. Neuroscience 2005; 135:97-109. [PMID: 16054765 DOI: 10.1016/j.neuroscience.2005.05.052] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2005] [Revised: 05/16/2005] [Accepted: 05/16/2005] [Indexed: 11/17/2022]
Abstract
The ophthalmic, maxillary and mandibular axon branches of the trigeminal ganglion provide cutaneous sensory innervation to the vertebrate face. In the chick embryo, the trigeminal ganglion is bilobed, with ophthalmic axons projecting from the ophthalmic lobe, while maxillary and mandibular projections emerge from the maxillomandibular lobe. To date, target tissue specific guidance cues that discriminately guide the axon projections from the two trigeminal ganglion lobes are unknown. EphA receptor tyrosine kinases and ephrin-A ligands are excellent candidates for this process as they are known to mediate axon guidance in the developing nervous system. Accordingly, the expression of EphAs and ephrin-As was investigated at stages 13, 15, 20 of chick embryogenesis when peripheral axons from the trigeminal ganglion are pathfinding. EphA3 is expressed highly in the ophthalmic trigeminal ganglion lobe neurons in comparison to maxillomandibular trigeminal ganglion lobe neurons. Furthermore, from stages 13-20 ephrin-A2 and ephrin-A5 ligands are only localized to the mesenchyme of the first branchial arch (maxillary and mandibular processes), the target fields for maxillomandibular trigeminal ganglion axons. We found that ophthalmic and not maxillomandibular lobe axons were responsive to ephrin-A5-Fc utilizing a substratum choice assay. The implication of these results is that EphA3 forward signaling in ophthalmic sensory axons may be an important mechanism in vivo for lobe specific guidance of trigeminal ganglion ophthalmic projections.
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Affiliation(s)
- C S Jayasena
- ARC Centre for Molecular Genetics of Development (CMGD), School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, South Australia 5005, Australia
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Abstract
BACKGROUND We examine results of gain-of-function experiments on retinocollicular maps in knock-in mice [Brown et al. (2000) Cell 102:77]. In wild-type mice the temporal-nasal axis of retina is mapped to the rostral-caudal axis of superior colliculus. The established map is single-valued, which implies that each point in retina maps to a unique termination zone in superior colliculus. In homozygous Isl2/EphA3 knock-in mice the map is double-valued, which means that each point on retina maps to two termination zones in superior colliculus. This is because about 50 percent of cells in retina express Isl2, and two types of projections, wild-type and Isl2/EphA3 positive, form two branches of the map. In heterozygous Isl2/EphA3 knock-ins the map is intermediate between the homozygous and wild-type: it is single-valued in temporal and double-valued in the nasal parts of retina. In this study we address possible reasons for such a bifurcation of the map. RESULTS We study the map formation using stochastic model based on Markov chains. In our model the map undergoes a series of reconstructions with probabilities dependent upon a set of chemical cues. Our model suggests that the map in heterozygotes is single-valued in temporal region of retina for two reasons. First, the inhomogeneous gradient of endogenous receptor in retina makes the impact of exogenous receptor less significant in temporal retina. Second, the gradient of ephrin in the corresponding region of superior colliculus is smaller, which reduces the chemical signal-to-noise ratio. We predict that if gradient of ephrin is reduced by a genetic manipulation, the single-valued region of the map should extend to a larger portion of temporal retina, i.e. the point of transition between single-and double-valued maps should move to a more nasal position in Isl2-EphA3 heterozygotes. CONCLUSIONS We present a theoretical model for retinocollicular map development, which can account for intriguing behaviors observed in gain-of-function experiments by Brown et al., including bifurcation in heterozygous Isl2/EphA3 knock-ins. The model is based on known chemical labels, axonal repulsion/competition, and stochasticity. Possible mapping in Isl2/EphB knock-ins is also discussed.
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Affiliation(s)
- Alexei A Koulakov
- Cold Spring Harbor Laboratory, One Bungtown Road, Cold Spring Harbor, NY, 11724, USA
| | - Dmitry N Tsigankov
- Cold Spring Harbor Laboratory, One Bungtown Road, Cold Spring Harbor, NY, 11724, USA
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Feldheim DA, Nakamoto M, Osterfield M, Gale NW, DeChiara TM, Rohatgi R, Yancopoulos GD, Flanagan JG. Loss-of-function analysis of EphA receptors in retinotectal mapping. J Neurosci 2004; 24:2542-50. [PMID: 15014130 PMCID: PMC6729493 DOI: 10.1523/jneurosci.0239-03.2004] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
EphA tyrosine kinases are thought to act as topographically specific receptors in the well-characterized projection map from the retina to the tectum. Here, we describe a loss-of-function analysis of EphA receptors in retinotectal mapping. Expressing patches of a cytoplasmically truncated EphA3 receptor in chick retina caused temporal axons to have reduced responsiveness to posterior tectal repellent activity in vitro and to shift more posteriorly within the map in vivo. A gene disruption of mouse EphA5, replacing the intracellular domain with beta-galactosidase, reduced in vitro responsiveness of temporal axons to posterior target membranes. It also caused map abnormalities in vivo, with temporal axons shifted posteriorly and nasal axons anteriorly, but with the entire target still filled by retinal axons. The anterior shift of nasal axons was not accompanied by increased responsiveness to tectal repellent activity, in contrast to the comparable anterior shift in ephrin-A knock-outs, helping to resolve a previous ambiguity in interpreting the ephrin gene knock-outs. The results show the functional requirement for endogenous EphA receptors in retinotectal mapping, show that the receptor intracellular domain is required for a forward signaling response to topographic cues, and provide new evidence for a role of axon competition in topographic mapping.
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MESH Headings
- Animals
- Axons/metabolism
- Axons/physiology
- Chick Embryo
- Gene Targeting
- Genes, Reporter
- Genetic Vectors/administration & dosage
- Genetic Vectors/genetics
- Mice
- Mice, Mutant Strains
- Receptor, EphA3/biosynthesis
- Receptor, EphA3/genetics
- Receptor, EphA3/physiology
- Receptor, EphA5/biosynthesis
- Receptor, EphA5/genetics
- Receptor, EphA5/physiology
- Receptors, Eph Family/deficiency
- Receptors, Eph Family/genetics
- Receptors, Eph Family/physiology
- Retinal Ganglion Cells/cytology
- Retinal Ganglion Cells/metabolism
- Sequence Deletion
- Superior Colliculi/cytology
- Superior Colliculi/metabolism
- Visual Pathways/cytology
- Visual Pathways/metabolism
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Affiliation(s)
- David A Feldheim
- Department of Cell Biology and Program in Neuroscience, Harvard Medical School, Boston, Massachusetts 02115, USA
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Xu B, Li S, Brown A, Gerlai R, Fahnestock M, Racine RJ. EphA/ephrin-A interactions regulate epileptogenesis and activity-dependent axonal sprouting in adult rats. Mol Cell Neurosci 2004; 24:984-99. [PMID: 14697663 DOI: 10.1016/j.mcn.2003.08.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The Eph family of tyrosine kinase receptors and their ligands, ephrins, are distributed in gradients and serve as molecular guidance cues for axonal patterning during neuronal development. Most of these molecules are also expressed in mature brain. Thus, we examine here the potential roles of such molecules in plasticity and activity-dependent mossy fiber sprouting of adult CNS. We show that the ligand ephrin-A3 and the receptor EphA5 are expressed in complementary gradients in the adult rat mossy fiber system. Using the kindling model, we demonstrate that exogenous immunoadhesins that affect the interaction of endogenous EphA receptors and ephrin-A ligands modulate the development of kindling, one type of long-term plasticity, in mature rat brain. These immunoadhesins, combined with epileptogenic stimulations, alter both the extent and the pattern of collateral axonal sprouting in the mossy fiber pathway. Our results suggest that EphA receptors and ephrin-A ligands modify neuronal plasticity and may serve as spatial cues that modulate the development and pattern of activation-dependent axonal growth in adult CNS.
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Affiliation(s)
- B Xu
- Department of Psychology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4K1
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Abstract
Neural maps in the vertebrate central nervous system often show discontinuously segregated, domain-to-domain patterns. However, the molecular mechanism that establishes such maps is not well understood. Here we show that in the chicken olivocerebellar system, EphA receptors and ephrin-As are expressed with distinct levels and combinations in mapping domains. When ephrin-A2 is retrovirally overexpressed in the cerebellum, the olivocerebellar map is disrupted, excluding axons with high receptor activity from ectopic expression domains. Conversely, overexpression of a truncated EphA3 receptor in the cerebellum reduces endogenous ligand activity to undetectable levels and causes aberrant mapping, with high receptor axons invading high ligand domains. In vitro, ephrin-A2 inhibits outgrowth of inferior olive axons in a region-specific manner. These results suggest that Eph receptors and ephrins constitute domain-specific positional information, and the spatially accurate receptor-ligand interaction is essential to guide inferior olive axons to their correct target domains.
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Affiliation(s)
- Kazuhiko Nishida
- Department of Neurosciences, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, OH 44195, USA
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