1
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Willshaw DJ, Gale NM. Reanalysis of EphA3 Knock-In Double Maps in Mouse Suggests That Stochasticity in Topographic Map Formation Acts at the Retina Rather than between Competing Mechanisms at the Colliculus. eNeuro 2023; 10:ENEURO.0135-23.2023. [PMID: 37852780 PMCID: PMC10668230 DOI: 10.1523/eneuro.0135-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 09/05/2023] [Accepted: 09/08/2023] [Indexed: 10/20/2023] Open
Abstract
It has been suggested that stochasticity acts in the formation of topographically ordered maps in the visual system through the opposing chemoaffinity and neural activity forces acting on the innervating nerve fibers being held in an unstable equilibrium. Evidence comes from the Islet2-EphA3 knock-in mouse, in which ∼50% of the retinal ganglion cells, distributed across the retina, acquire the EphA3 receptor, thus having an enhanced density of EphA which specifies retinotopic order along the rostrocaudal (RC) axis of the colliculus. Sampling EphA3 knock-in maps in heterozygotes at different positions along the mediolateral (ML) extent of the colliculus had found single 1D maps [as in wild types (WTs)], double maps (as in homozygous knock-ins) or both single and double maps. We constructed full 2D maps from the same mouse dataset. We found either single maps or maps where the visual field projects rostrally, with a part-projection more caudally to form a double map, the extent and location of this duplication varying considerably. Contrary to previous analyses, there was no strict demarcation between heterozygous and homozygous maps. These maps were replicated in a computational model where, as the level of EphA3 was increased, there was a smooth transition from single to double maps. Our results suggest that the diversity in these retinotopic maps has its origin in a variability over the retina in the effective amount of EphA3, such as through variability in gene expression or the proportion of EphA3+ retinal ganglion cells, rather than the result of competing mechanisms acting at the colliculus.
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Affiliation(s)
- David J Willshaw
- Institute for Adaptive and Neural Computation, School of Informatics, University of Edinburgh, Edinburgh EH8 9AB, United Kingdom
| | - Nicholas M Gale
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, United Kingdom
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2
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Kutsarova E, Schohl A, Munz M, Wang A, Zhang YY, Bilash OM, Ruthazer ES. BDNF signaling in correlation-dependent structural plasticity in the developing visual system. PLoS Biol 2023; 21:e3002070. [PMID: 37011100 PMCID: PMC10101647 DOI: 10.1371/journal.pbio.3002070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 04/13/2023] [Accepted: 03/08/2023] [Indexed: 04/05/2023] Open
Abstract
During development, patterned neural activity instructs topographic map refinement. Axons with similar patterns of neural activity converge onto target neurons and stabilize their synapses with these postsynaptic partners, restricting exploratory branch elaboration (Hebbian structural plasticity). On the other hand, non-correlated firing in inputs leads to synapse weakening and increased exploratory growth of axons (Stentian structural plasticity). We used visual stimulation to control the correlation structure of neural activity in a few ipsilaterally projecting (ipsi) retinal ganglion cell (RGC) axons with respect to the majority contralateral eye inputs in the optic tectum of albino Xenopus laevis tadpoles. Multiphoton live imaging of ipsi axons, combined with specific targeted disruptions of brain-derived neurotrophic factor (BDNF) signaling, revealed that both presynaptic p75NTR and TrkB are required for Stentian axonal branch addition, whereas presumptive postsynaptic BDNF signaling is necessary for Hebbian axon stabilization. Additionally, we found that BDNF signaling mediates local suppression of branch elimination in response to correlated firing of inputs. Daily in vivo imaging of contralateral RGC axons demonstrated that p75NTR knockdown reduces axon branch elongation and arbor spanning field volume.
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Affiliation(s)
- Elena Kutsarova
- Montreal Neurological Institute-Hospital, McGill University, Montreal, Canada
- Max Planck Institute for Brain Research, Frankfurt, Germany
| | - Anne Schohl
- Montreal Neurological Institute-Hospital, McGill University, Montreal, Canada
| | - Martin Munz
- Montreal Neurological Institute-Hospital, McGill University, Montreal, Canada
- Institute of Molecular and Clinical Ophthalmology Basel, Basel, Switzerland
- Department of Ophthalmology, University of Basel, Basel, Switzerland
| | - Alex Wang
- Montreal Neurological Institute-Hospital, McGill University, Montreal, Canada
- Interdepartmental Neuroscience, Yale University, New Haven, Connecticut, United States of America
| | - Yuan Yuan Zhang
- Montreal Neurological Institute-Hospital, McGill University, Montreal, Canada
- Faculty of Medicine, University of Ottawa, Ottawa, Canada
| | - Olesia M Bilash
- Montreal Neurological Institute-Hospital, McGill University, Montreal, Canada
- NYU Neuroscience Institute, New York University, New York, New York, United States of America
| | - Edward S Ruthazer
- Montreal Neurological Institute-Hospital, McGill University, Montreal, Canada
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Bajar BT, Phi NT, Isaacman-Beck J, Reichl J, Randhawa H, Akin O. A discrete neuronal population coordinates brain-wide developmental activity. Nature 2022; 602:639-646. [PMID: 35140397 DOI: 10.1038/s41586-022-04406-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Accepted: 01/05/2022] [Indexed: 11/09/2022]
Abstract
In vertebrates, stimulus-independent activity accompanies neural circuit maturation throughout the developing brain1,2. The recent discovery of similar activity in the developing Drosophila central nervous system suggests that developmental activity is fundamental to the assembly of complex brains3. How such activity is coordinated across disparate brain regions to influence synaptic development at the level of defined cell types is not well understood. Here we show that neurons expressing the cation channel transient receptor potential gamma (Trpγ) relay and pattern developmental activity throughout the Drosophila brain. In trpγ mutants, activity is attenuated globally, and both patterns of activity and synapse structure are altered in a cell-type-specific manner. Less than 2% of the neurons in the brain express Trpγ. These neurons arborize throughout the brain, and silencing or activating them leads to loss or gain of brain-wide activity. Together, these results indicate that this small population of neurons coordinates brain-wide developmental activity. We propose that stereotyped patterns of developmental activity are driven by a discrete, genetically specified network to instruct neural circuit assembly at the level of individual cells and synapses. This work establishes the fly brain as an experimentally tractable system for studying how activity contributes to synapse and circuit formation.
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Affiliation(s)
- Bryce T Bajar
- Department of Biological Chemistry, Medical Scientist Training Program, David Geffen School of Medicine at UCLA, University of California, Los Angeles, Los Angeles, CA, USA
| | - Nguyen T Phi
- Molecular, Cellular, and Integrative Physiology Interdepartmental Graduate Program, University of California, Los Angeles, Los Angeles, CA, USA
| | - Jesse Isaacman-Beck
- Department of Neurobiology, Stanford University School of Medicine, Stanford University, Stanford, CA, USA
| | - Jun Reichl
- Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, Los Angeles, CA, USA
| | - Harpreet Randhawa
- Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, Los Angeles, CA, USA
| | - Orkun Akin
- Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, Los Angeles, CA, USA.
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4
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Choi BJ, Chen YCD, Desplan C. Building a circuit through correlated spontaneous neuronal activity in the developing vertebrate and invertebrate visual systems. Genes Dev 2021; 35:677-691. [PMID: 33888564 PMCID: PMC8091978 DOI: 10.1101/gad.348241.121] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
During the development of the vertebrate nervous systems, genetic programs assemble an immature circuit that is subsequently refined by neuronal activity evoked by external stimuli. However, prior to sensory experience, the intrinsic property of the developing nervous system also triggers correlated network-level neuronal activity, with retinal waves in the developing vertebrate retina being the best documented example. Spontaneous activity has also been found in the visual system of Drosophila Here, we compare the spontaneous activity of the developing visual system between mammalian and Drosophila and suggest that Drosophila is an emerging model for mechanistic and functional studies of correlated spontaneous activity.
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Affiliation(s)
- Ben Jiwon Choi
- Department of Biology, New York University, New York, New York 10003, USA
| | | | - Claude Desplan
- Department of Biology, New York University, New York, New York 10003, USA
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5
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Sasaki K, Arimoto K, Kankawa K, Terada C, Yamamori T, Watakabe A, Yamamoto N. Rho Guanine Nucleotide Exchange Factors Regulate Horizontal Axon Branching of Cortical Upper Layer Neurons. Cereb Cortex 2020; 30:2506-2518. [PMID: 31768529 DOI: 10.1093/cercor/bhz256] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 08/23/2019] [Indexed: 11/14/2022] Open
Abstract
Axon branching is a crucial process for cortical circuit formation. However, how the cytoskeletal changes in axon branching are regulated is not fully understood. In the present study, we investigated the role of RhoA guanine nucleotide exchange factors (RhoA-GEFs) in branch formation of horizontally elongating axons (horizontal axons) in the mammalian cortex. In situ hybridization showed that more than half of all known RhoA-GEFs were expressed in the developing rat cortex. These RhoA-GEFs were mostly expressed in the macaque cortex as well. An overexpression study using organotypic cortical slice cultures demonstrated that several RhoA-GEFs strongly promoted horizontal axon branching. Moreover, branching patterns were different between overexpressed RhoA-GEFs. In particular, ARHGEF18 markedly increased terminal arbors, whereas active breakpoint cluster region-related protein (ABR) increased short branches in both distal and proximal regions of horizontal axons. Rho kinase inhibitor treatment completely suppressed the branch-promoting effect of ARHGEF18 overexpression, but only partially affected that of ABR, suggesting that these RhoA-GEFs employ distinct downstream pathways. Furthermore, knockdown of either ARHGEF18 or ABR considerably suppressed axon branching. Taken together, the present study revealed that subsets of RhoA-GEFs differentially promote axon branching of mammalian cortical neurons.
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Affiliation(s)
- Kensuke Sasaki
- Cellular and Molecular Neurobiology Group, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Kei Arimoto
- Cellular and Molecular Neurobiology Group, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Kento Kankawa
- Cellular and Molecular Neurobiology Group, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Chikayo Terada
- Cellular and Molecular Neurobiology Group, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Tetsuo Yamamori
- Laboratory for Molecular Analysis of Higher Brain Function, RIKEN Center for Brain Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Akiya Watakabe
- Laboratory for Molecular Analysis of Higher Brain Function, RIKEN Center for Brain Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Nobuhiko Yamamoto
- Cellular and Molecular Neurobiology Group, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
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6
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Cioni JM, Wong HHW, Bressan D, Kodama L, Harris WA, Holt CE. Axon-Axon Interactions Regulate Topographic Optic Tract Sorting via CYFIP2-Dependent WAVE Complex Function. Neuron 2019. [PMID: 29518358 PMCID: PMC5855093 DOI: 10.1016/j.neuron.2018.01.027] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The axons of retinal ganglion cells (RGCs) are topographically sorted before they arrive at the optic tectum. This pre-target sorting, typical of axon tracts throughout the brain, is poorly understood. Here, we show that cytoplasmic FMR1-interacting proteins (CYFIPs) fulfill non-redundant functions in RGCs, with CYFIP1 mediating axon growth and CYFIP2 specifically involved in axon sorting. We find that CYFIP2 mediates homotypic and heterotypic contact-triggered fasciculation and repulsion responses between dorsal and ventral axons. CYFIP2 associates with transporting ribonucleoprotein particles in axons and regulates translation. Axon-axon contact stimulates CYFIP2 to move into growth cones where it joins the actin nucleating WAVE regulatory complex (WRC) in the periphery and regulates actin remodeling and filopodial dynamics. CYFIP2’s function in axon sorting is mediated by its binding to the WRC but not its translational regulation. Together, these findings uncover CYFIP2 as a key regulatory link between axon-axon interactions, filopodial dynamics, and optic tract sorting. CYFIP1 and CYFIP2 serve non-redundant functions in retinal axon growth and guidance CYFIP2 regulates growth cone filopodial dynamics and axon-axon responses CYFIP2 interacts with RNPs and the WRC in distinct cellular compartments Axon sorting is mediated by CYFIP2’s interaction with the WRC
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Affiliation(s)
- Jean-Michel Cioni
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3DY, UK
| | - Hovy Ho-Wai Wong
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3DY, UK
| | - Dario Bressan
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Robinson Way, Cambridge, CB2 0RE, UK
| | - Lay Kodama
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3DY, UK
| | - William A Harris
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3DY, UK
| | - Christine E Holt
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3DY, UK.
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7
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Cao M, Ouyang J, Liang H, Guo J, Lin S, Yang S, Xie T, Chen S. Regional Gene Expression Profile Comparison Reveals the Unique Transcriptome of the Optic Fissure. Invest Ophthalmol Vis Sci 2019; 59:5773-5784. [PMID: 30521666 DOI: 10.1167/iovs.18-23962] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose The optic fissure (OF) is a transient opening in the ventral optic cup (OC) that acts as a passage for blood vessels and retinal ganglion cell axons during early eye development. Failure to close the OF is the developmental basis for uveal coloboma, a congenital blinding eye disease that significantly contributes to childhood blindness. Genes specifically expressed in the OF region may play important roles in OF development and function. The aim of this study was to characterize the transcriptome of OC cells in the OF region and investigate the function of OF-specific genes during OF closure. Methods Laser-assisted microdissection was used to collect different regions of OC tissues. Microarray analysis was used to obtain and compare gene expression profiles of different OC regions. RNA in situ hybridization (ISH) was used to further characterize OF-specific gene expression patterns. Morpholino knockdown in zebrafish was used to study the function of a newly discovered OF-specific gene during OF closure. Results Microarray comparison revealed that the OC at the OF region exhibited a unique gene expression profile. OC expression patterns of a number of newly discovered OF-specific genes were confirmed by ISH. Morpholino knockdown and downstream target expression and function analysis demonstrated that afap1l2, a newly discovered OF-specific gene, controls OF closure by regulating pax2a expression. Conclusions Our study characterized the unique transcriptome of the OF region of the OC and demonstrated the essential role of a newly discovered OF-specific gene in OF closure. This study provides a valuable foundation for future mechanism dissection in OF development and physiology, and for human coloboma etiology exploration.
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Affiliation(s)
- Mingzhe Cao
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Jiamin Ouyang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Huilin Liang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Jingyi Guo
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Siyuan Lin
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Shulan Yang
- Translational Medicine Centre, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Ting Xie
- Stowers Institute for Medical Research, Kansas City, Missouri, United States
| | - Shuyi Chen
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.,Guangdong Province Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
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8
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Wu Y, Ma L, Duyck K, Long CC, Moran A, Scheerer H, Blanck J, Peak A, Box A, Perera A, Yu CR. A Population of Navigator Neurons Is Essential for Olfactory Map Formation during the Critical Period. Neuron 2018; 100:1066-1082.e6. [PMID: 30482691 DOI: 10.1016/j.neuron.2018.09.051] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 08/10/2018] [Accepted: 09/27/2018] [Indexed: 11/29/2022]
Abstract
In the developing brain, heightened plasticity during the critical period enables the proper formation of neural circuits. Here, we identify the "navigator" neurons, a group of perinatally born olfactory sensory neurons, as playing an essential role in establishing the olfactory map during the critical period. The navigator axons project circuitously in the olfactory bulb and traverse multiple glomeruli before terminating in perspective glomeruli. These neurons undergo a phase of exuberant axon growth and exhibit a shortened lifespan. Single-cell transcriptome analyses reveal distinct molecular signatures for the navigators. Extending their lifespan prolongs the period of exuberant growth and perturbs axon convergence. Conversely, a genetic ablation experiment indicates that, despite postnatal neurogenesis, only the navigators are endowed with the ability to establish a convergent map. The presence and the proper removal of the navigator neurons are both required to establish tight axon convergence into the glomeruli.
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Affiliation(s)
- Yunming Wu
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Limei Ma
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Kyle Duyck
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Carter C Long
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Andrea Moran
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Hayley Scheerer
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Jillian Blanck
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Allison Peak
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Andrew Box
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Anoja Perera
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - C Ron Yu
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA; Department of Anatomy and Cell Biology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA.
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Protein Tyrosine Phosphatase Receptor Type J (PTPRJ) Regulates Retinal Axonal Projections by Inhibiting Eph and Abl Kinases in Mice. J Neurosci 2018; 38:8345-8363. [PMID: 30082414 DOI: 10.1523/jneurosci.0128-18.2018] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 07/05/2018] [Accepted: 07/30/2018] [Indexed: 12/28/2022] Open
Abstract
Eph receptors play pivotal roles in the axon guidance of retinal ganglion cells (RGCs) at the optic chiasm and the establishment of the topographic retinocollicular map. We previously demonstrated that protein tyrosine phosphatase receptor type O (PTPRO) is specifically involved in the control of retinotectal projections in chicks through the dephosphorylation of EphA and EphB receptors. We subsequently revealed that all the mouse R3 subfamily members (PTPRB, PTPRH, PTPRJ, and PTPRO) of the receptor protein tyrosine phosphatase (RPTP) family inhibited Eph receptors as their substrates in cultured mammalian cells. We herein investigated the functional roles of R3 RPTPs in the projection of mouse retinal axon of both sexes. Ptpro and Ptprj were expressed in mouse RGCs; however, Ptprj expression levels were markedly higher than those of Ptpro Consistent with their expression levels, Eph receptor activity was significantly enhanced in Ptprj-knock-out (Ptprj-KO) retinas. In Ptprj-KO and Ptprj/Ptpro-double-KO (DKO) mice, the number of retinal axons that projected ipsilaterally or to the contralateral eye was significantly increased. Furthermore, retinal axons in Ptprj-KO and DKO mice formed anteriorly shifted ectopic terminal zones in the superior colliculus (SC). We found that c-Abl (Abelson tyrosine kinase) was downstream of ephrin-Eph signaling for the repulsion of retinal axons at the optic chiasm and in the SC. c-Abl was identified as a novel substrate for PTPRJ and PTPRO, and the phosphorylation of c-Abl was upregulated in Ptprj-KO and DKO retinas. Thus, PTPRJ regulates retinocollicular projections in mice by controlling the activity of Eph and c-Abl kinases.SIGNIFICANCE STATEMENT Correct retinocollicular projection is a prerequisite for proper vision. Eph receptors have been implicated in retinal axon guidance at the optic chiasm and the establishment of the topographic retinocollicular map. We herein demonstrated that protein tyrosine phosphatase receptor type J (PTPRJ) regulated retinal axonal projections by controlling Eph activities. The retinas of Ptprj-knock-out (KO) and Ptpro/Ptprj double-KO mice exhibited significantly enhanced Eph activities over those in wild-type mice, and their axons showed defects in pathfinding at the chiasm and retinocollicular topographic map formation. We also revealed that c-Abl (Abelson tyrosine kinase) downstream of Eph receptors was regulated by PTPRJ. These results indicate that the regulation of the ephrin-Eph-c-Abl axis by PTPRJ plays pivotal roles in the proper central projection of retinal axons during development.
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10
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Abstract
The formation of the nervous system is a multistep process that yields a mature brain. Failure in any of the steps of this process may cause brain malfunction. In the early stages of embryonic development, neural progenitors quickly proliferate and then, at a specific moment, differentiate into neurons or glia. Once they become postmitotic neurons, they migrate to their final destinations and begin to extend their axons to connect with other neurons, sometimes located in quite distant regions, to establish different neural circuits. During the last decade, it has become evident that Zic genes, in addition to playing important roles in early development (e.g., gastrulation and neural tube closure), are involved in different processes of late brain development, such as neuronal migration, axon guidance, and refinement of axon terminals. ZIC proteins are therefore essential for the proper wiring and connectivity of the brain. In this chapter, we review our current knowledge of the role of Zic genes in the late stages of neural circuit formation.
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11
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Kung FH, Sillitti D, Shreiber DI, Zahn JD, Firestein BL. Microfluidic device-assisted etching of p-HEMA for cell or protein patterning. Biotechnol Prog 2017; 34:243-248. [PMID: 29086494 DOI: 10.1002/btpr.2576] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 10/16/2017] [Indexed: 11/09/2022]
Abstract
The construction of biomaterials with which to limit the growth of cells or to limit the adsorption of proteins is essential for understanding biological phenomena. Here, we describe a novel method to simply and easily create thin layers of poly (2-hydroxyethyl methacrylate) (p-HEMA) for protein and cellular patterning via etching with ethanol and microfluidic devices. First, a cell culture surface or glass coverslip is coated with p-HEMA. Next, a polydimethylsiloxane (PDMS) microfluidic is placed onto the p-HEMA surface, and ethanol is aspirated through the device. The PDMS device is removed, and the p-HEMA surface is ready for protein adsorption or cell plating. This method allows for the fabrication of 0.3 µm thin layers of p-HEMA, which can be etched to 10 µm wide channels. Furthermore, it creates regions of differential protein adhesion, as shown by Coomassie staining and fluorescent labeling, and cell adhesion, as demonstrated by C2C12 myoblast growth. This method is simple, versatile, and allows biologists and bioengineers to manipulate regions for cell culture adhesion and growth. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:243-248, 2018.
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Affiliation(s)
- Frank H Kung
- Dept. of Cell Biology and Neuroscience, Rutgers University, 604 Allison Road, Piscataway, NJ, 08854
| | - David Sillitti
- Dept. of Biomedical Engineering, Rutgers University, 599 Taylor Road, Piscataway, NJ, 08854
| | - David I Shreiber
- Dept. of Biomedical Engineering, Rutgers University, 599 Taylor Road, Piscataway, NJ, 08854.,Graduate Faculty in Biomedical Engineering, Rutgers University, 599 Taylor Road, Piscataway, NJ, 08854
| | - Jeffrey D Zahn
- Dept. of Biomedical Engineering, Rutgers University, 599 Taylor Road, Piscataway, NJ, 08854.,Graduate Faculty in Biomedical Engineering, Rutgers University, 599 Taylor Road, Piscataway, NJ, 08854
| | - Bonnie L Firestein
- Dept. of Cell Biology and Neuroscience, Rutgers University, 604 Allison Road, Piscataway, NJ, 08854.,Graduate Faculty in Biomedical Engineering, Rutgers University, 599 Taylor Road, Piscataway, NJ, 08854
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12
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Reinhard J, Roll L, Faissner A. Tenascins in Retinal and Optic Nerve Neurodegeneration. Front Integr Neurosci 2017; 11:30. [PMID: 29109681 PMCID: PMC5660115 DOI: 10.3389/fnint.2017.00030] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 10/03/2017] [Indexed: 02/04/2023] Open
Abstract
Tenascins represent key constituents of the extracellular matrix (ECM) with major impact on central nervous system (CNS) development. In this regard, several studies indicate that they play a crucial role in axonal growth and guidance, synaptogenesis and boundary formation. These functions are not only important during development, but also for regeneration under several pathological conditions. Additionally, tenascin-C (Tnc) represents a key modulator of the immune system and inflammatory processes. In the present review article, we focus on the function of Tnc and tenascin-R (Tnr) in the diseased CNS, specifically after retinal and optic nerve damage and degeneration. We summarize the current view on both tenascins in diseases such as glaucoma, retinal ischemia, age-related macular degeneration (AMD) or diabetic retinopathy. In this context, we discuss their expression profile, possible functional relevance, remodeling of the interacting matrisome and tenascin receptors, especially under pathological conditions.
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Affiliation(s)
- Jacqueline Reinhard
- Department of Cell Morphology and Molecular Neurobiology, Faculty of Biology and Biotechnology, Ruhr-University Bochum, Bochum, Germany
| | - Lars Roll
- Department of Cell Morphology and Molecular Neurobiology, Faculty of Biology and Biotechnology, Ruhr-University Bochum, Bochum, Germany
| | - Andreas Faissner
- Department of Cell Morphology and Molecular Neurobiology, Faculty of Biology and Biotechnology, Ruhr-University Bochum, Bochum, Germany
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13
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Pratt KG, Hiramoto M, Cline HT. An Evolutionarily Conserved Mechanism for Activity-Dependent Visual Circuit Development. Front Neural Circuits 2016; 10:79. [PMID: 27818623 PMCID: PMC5073143 DOI: 10.3389/fncir.2016.00079] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 09/26/2016] [Indexed: 12/01/2022] Open
Abstract
Neural circuit development is an activity-dependent process. This activity can be spontaneous, such as the retinal waves that course across the mammalian embryonic retina, or it can be sensory-driven, such as the activation of retinal ganglion cells (RGCs) by visual stimuli. Whichever the source, neural activity provides essential instruction to the developing circuit. Indeed, experimentally altering activity has been shown to impact circuit development and function in many different ways and in many different model systems. In this review, we contemplate the idea that retinal waves in amniotes, the animals that develop either in ovo or utero (namely reptiles, birds and mammals) could be an evolutionary adaptation to life on land, and that the anamniotes, animals whose development is entirely external (namely the aquatic amphibians and fish), do not display retinal waves, most likely because they simply don’t need them. We then review what is known about the function of both retinal waves and visual stimuli on their respective downstream targets, and predict that the experience-dependent development of the tadpole visual system is a blueprint of what will be found in future studies of the effects of spontaneous retinal waves on instructing development of retinorecipient targets such as the superior colliculus (SC) and the lateral geniculate nucleus.
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Affiliation(s)
- Kara G Pratt
- Program in Neuroscience, Department of Zoology and Physiology, University of Wyoming Laramie, WY, USA
| | - Masaki Hiramoto
- Department of Molecular and Cellular Neuroscience and The Dorris Neuroscience Center, The Scripps Research Institute La Jolla, CA, USA
| | - Hollis T Cline
- Department of Molecular and Cellular Neuroscience and The Dorris Neuroscience Center, The Scripps Research Institute La Jolla, CA, USA
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Hasegawa Y, Takata N, Okuda S, Kawada M, Eiraku M, Sasai Y. Emergence of dorsal-ventral polarity in ESC-derived retinal tissue. Development 2016; 143:3895-3906. [PMID: 27633992 DOI: 10.1242/dev.134601] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Accepted: 09/01/2016] [Indexed: 01/08/2023]
Abstract
We previously demonstrated that mouse embryonic stem cell (mESC)-derived retinal epithelium self-forms an optic cup-like structure. In the developing retina, the dorsal and ventral sides differ in terms of local gene expression and morphological features. This aspect has not yet been shown in vitro Here, we demonstrate that mESC-derived retinal tissue spontaneously acquires polarity reminiscent of the dorsal-ventral (D-V) patterning of the embryonic retina. Tbx5 and Vax2 were expressed in a mutually exclusive manner, as seen in vivo Three-dimensional morphometric analysis showed that the in vitro-formed optic cup often contains cleft structures resembling the embryonic optic fissure. To elucidate the mechanisms underlying the spontaneous D-V polarization of mESC-derived retina, we examined the effects of patterning factors, and found that endogenous BMP signaling plays a predominant role in the dorsal specification. Further analysis revealed that canonical Wnt signaling, which was spontaneously activated at the proximal region, acts upstream of BMP signaling for dorsal specification. These observations suggest that D-V polarity could be established within the self-formed retinal neuroepithelium by intrinsic mechanisms involving the spatiotemporal regulation of canonical Wnt and BMP signals.
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Affiliation(s)
- Yuiko Hasegawa
- Laboratory for Organogenesis and Neurogenesis, RIKEN Center for Developmental Biology, 2-2-3, Minatojima-Minamimachi, Chuo, Kobe 650-0047, Japan.,Laboratory for in vitro Histogenesis, RIKEN Center for Developmental Biology, 2-2-3, Minatojima-Minamimachi, Chuo, Kobe 650-0047, Japan
| | - Nozomu Takata
- Laboratory for Organogenesis and Neurogenesis, RIKEN Center for Developmental Biology, 2-2-3, Minatojima-Minamimachi, Chuo, Kobe 650-0047, Japan.,Laboratory for in vitro Histogenesis, RIKEN Center for Developmental Biology, 2-2-3, Minatojima-Minamimachi, Chuo, Kobe 650-0047, Japan
| | - Satoru Okuda
- Laboratory for Organogenesis and Neurogenesis, RIKEN Center for Developmental Biology, 2-2-3, Minatojima-Minamimachi, Chuo, Kobe 650-0047, Japan.,Laboratory for in vitro Histogenesis, RIKEN Center for Developmental Biology, 2-2-3, Minatojima-Minamimachi, Chuo, Kobe 650-0047, Japan
| | - Masako Kawada
- Laboratory for Organogenesis and Neurogenesis, RIKEN Center for Developmental Biology, 2-2-3, Minatojima-Minamimachi, Chuo, Kobe 650-0047, Japan.,Laboratory for in vitro Histogenesis, RIKEN Center for Developmental Biology, 2-2-3, Minatojima-Minamimachi, Chuo, Kobe 650-0047, Japan
| | - Mototsugu Eiraku
- Laboratory for Organogenesis and Neurogenesis, RIKEN Center for Developmental Biology, 2-2-3, Minatojima-Minamimachi, Chuo, Kobe 650-0047, Japan .,Laboratory for in vitro Histogenesis, RIKEN Center for Developmental Biology, 2-2-3, Minatojima-Minamimachi, Chuo, Kobe 650-0047, Japan
| | - Yoshiki Sasai
- Laboratory for Organogenesis and Neurogenesis, RIKEN Center for Developmental Biology, 2-2-3, Minatojima-Minamimachi, Chuo, Kobe 650-0047, Japan
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Abstract
Compelling new findings have revealed that receptor tyrosine kinases of the Eph family, along with their ephrin ligands, play an essential role in regulating the properties of developing mature excitatory synapses in the central nervous system. The cell surface localization of both the Eph receptors and the ephrins enables these proteins to signal bidirectionally at sites of cell-to-cell contact, such as synapses. Eph receptors and ephrins have indeed been implicated in multiple aspects of synaptic function, including clustering and modulating N-methyl-D-aspartate receptors, modifying the geometry of postsynaptic terminals, and influencing long-term synaptic plasticity and memory. In this review, we discuss how Eph receptors and ephrins are integrated into the molecular machinery that supports synaptic function.
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Affiliation(s)
- Keith K Murai
- Centre for Research in Neuroscience, McGill University Health Centre, Montreal General Hospital, Montreal, Canada
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16
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Inverse Expression Levels of EphrinA3 and EphrinA5 Contribute to Dopaminergic Differentiation of Human SH-SY5Y Cells. J Mol Neurosci 2016; 59:483-92. [PMID: 27217159 DOI: 10.1007/s12031-016-0759-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 04/22/2016] [Indexed: 10/21/2022]
Abstract
Two key principles underlying successful cellular therapies for Parkinson's disease (PD) are appropriate differentiation of dopaminergic (DA) neurons from transplanted cells and precise axon growth. EphrinAs, a subclass of ephrins, act as axon guidance molecules and are highly expressed in DA brain regions. Existing evidences indicate that they act as either repulsion or attraction signals to guide axon growth. This study investigated whether ephrinAs are involved in DA neuron differentiation. Data from miRCURY™ LNA mRNAs/microRNAs microarrays and quantitative real-time polymerase chain reaction (qRT-PCR) showed upregulated ephrinA3 mRNA (EFNA3) and downregulated ephrinA5 mRNA (EFNA5) during DA neuron differentiation. In addition, hsa-miR-4271 was downregulated, which could influence EFNA3 translation. Furthermore, immunofluorescence (IF) and western blotting confirmed the mRNA results and showed increased ephrinA3 and decreased ephrinA5 protein levels in differentiating DA neurons. Taken together, our results indicate that inverse expression levels of ephrinA3 and ephrinA5, which are possibly influenced by microRNAs, contribute to DA neuron differentiation by guiding axon growth.
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Rapid Changes in Cortical and Subcortical Brain Regions after Early Bilateral Enucleation in the Mouse. PLoS One 2015; 10:e0140391. [PMID: 26452243 PMCID: PMC4599918 DOI: 10.1371/journal.pone.0140391] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 09/24/2015] [Indexed: 01/09/2023] Open
Abstract
Functional sensory and motor areas in the developing mammalian neocortex are formed through a complex interaction of cortically intrinsic mechanisms, such as gene expression, and cortically extrinsic mechanisms such as those mediated by thalamic input from the senses. Both intrinsic and extrinsic mechanisms are believed to be involved in cortical patterning and the establishment of areal boundaries in early development; however, the nature of the interaction between intrinsic and extrinsic processes is not well understood. In a previous study, we used a perinatal bilateral enucleation mouse model to test some aspects of this interaction by reweighting sensory input to the developing cortex. Visual deprivation at birth resulted in a shift of intraneocortical connections (INCs) that aligned with ectopic ephrin A5 expression in the same location ten days later at postnatal day (P) 10. A prevailing question remained: Does visual deprivation first induce a change in gene expression, followed by a shift in INCs, or vice versa? In the present study, we address this question by investigating the neuroanatomy and patterns of gene expression in post-natal day (P) 1 and 4 mice following bilateral enucleation at birth. Our results demonstrate a rapid reduction in dorsal lateral geniculate nucleus (dLGN) size and ephrin A5 gene expression 24-hours post-enucleation, with more profound effects apparent at P4. The reduced nuclear size and diminished gene expression mirrors subtle changes in ephrin A5 expression evident in P1 and P4 enucleated neocortex, 11 and 8 days prior to natural eye opening, respectively. Somatosensory and visual INCs were indistinguishable between P1 and P4 mice bilaterally enucleated at birth, indicating that perinatal bilateral enucleation initiates a rapid change in gene expression (within one day) followed by an alteration of sensory INCs later on (second postnatal week). With these results, we gain a deeper understanding of how gene expression and sensory input together regulate cortical arealization and plasticity during early development.
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King BA, Parra C, Li Y, Helton KJ, Qaddoumi I, Wilson MW, Ogg RJ. Spatiotemporal Patterns of Tumor Occurrence in Children with Intraocular Retinoblastoma. PLoS One 2015; 10:e0132932. [PMID: 26230335 PMCID: PMC4521796 DOI: 10.1371/journal.pone.0132932] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 06/21/2015] [Indexed: 01/11/2023] Open
Abstract
PURPOSE To accurately map the retinal area covered by tumor in a prospectively enrolled cohort of children diagnosed with retinoblastoma. METHODS Orbital MRI in 106 consecutive retinoblastoma patients (44 bilateral) was analyzed. For MRI-visible tumors, the polar angle and angle of eccentricity of points defining tumor perimeter on the retina were determined by triangulation from images in three orthogonal planes. The centroid of the mapped area was calculated to approximate tumor origin, and the location and cumulative tumor burden were analyzed in relation to mutation type (germline vs. somatic), tumor area, and patient age at diagnosis. Location of small tumors undetected by MRI was approximated with fundoscopic images. RESULTS Mapping was successful for 129 tumors in 91 eyes from 67 patients (39 bilateral, 43 germline mutation). Cumulative tumor burden was highest within the macula and posterior pole and was asymmetrically higher within the inferonasal periphery. Tumor incidence was lowest in the superotemporal periphery. Tumor location varied with age at diagnosis in a complex pattern. Tumor location was concentrated in the macula and superonasal periphery in patients <5.6 months, in the inferotemporal quadrant of the posterior pole in patients 5.6-8.8 months, in the inferonasal quadrant in patients 8.8-13.2 months, and in the nasal and superotemporal periphery in patients >13.2 months. The distribution of MRI-invisible tumors was consistent with the asymmetry of mapped tumors. CONCLUSIONS MRI-based mapping revealed a previously unrecognized pattern of retinoblastoma localization that evolves with age at diagnosis. The structured spatiotemporal distribution of tumors may provide valuable clues about cellular or molecular events associated with tumorigenesis in the developing retina.
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Affiliation(s)
- Benjamin A. King
- Department of Ophthalmology, Hamilton Eye Institute, University of Tennessee Health Sciences Center, Memphis, Tennessee, United States of America
- Department of Radiological Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Carlos Parra
- Department of Radiological Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
- Department of Biomedical Engineering, University of Memphis, Memphis, Tennessee, United States of America
| | - Yimei Li
- Department of Biostatistics, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Kathleen J. Helton
- Department of Radiological Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Ibrahim Qaddoumi
- Department of Oncology, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Matthew W. Wilson
- Department of Ophthalmology, Hamilton Eye Institute, University of Tennessee Health Sciences Center, Memphis, Tennessee, United States of America
- Department of Surgery, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Robert J. Ogg
- Department of Radiological Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
- * E-mail:
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Reinhard J, Joachim SC, Faissner A. Extracellular matrix remodeling during retinal development. Exp Eye Res 2015; 133:132-40. [DOI: 10.1016/j.exer.2014.07.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 06/30/2014] [Accepted: 07/01/2014] [Indexed: 10/25/2022]
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Abstract
The visual system is beautifully crafted to transmit information of the external world to visual processing and cognitive centers in the brain. For visual information to be relayed to the brain, a series of axon pathfinding events must take place to ensure that the axons of retinal ganglion cells, the only neuronal cell type in the retina that sends axons out of the retina, find their way out of the eye to connect with targets in the brain. In the past few decades, the power of molecular and genetic tools, including the generation of genetically manipulated mouse lines, have multiplied our knowledge about the molecular mechanisms involved in the sculpting of the visual system. Here, we review major advances in our understanding of the mechanisms controlling the differentiation of RGCs, guidance of their axons from the retina to the primary visual centers, and the refinement processes essential for the establishment of topographic maps and eye-specific axon segregation. Human disorders, such as albinism and achiasmia, that impair RGC axon growth and guidance and, thus, the establishment of a fully functioning visual system will also be discussed.
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Affiliation(s)
- Lynda Erskine
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Scotland, UK
| | - Eloisa Herrera
- Instituto de Neurosciencias de Alicante, CSIC-UMH, San Juan de Alicante, Spain
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21
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Hjorth JJJ, Sterratt DC, Cutts CS, Willshaw DJ, Eglen SJ. Quantitative assessment of computational models for retinotopic map formation. Dev Neurobiol 2014; 75:641-66. [PMID: 25367067 PMCID: PMC4497816 DOI: 10.1002/dneu.22241] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 10/27/2014] [Accepted: 10/28/2014] [Indexed: 11/10/2022]
Abstract
Molecular and activity-based cues acting together are thought to guide retinal axons to their terminal sites in vertebrate optic tectum or superior colliculus (SC) to form an ordered map of connections. The details of mechanisms involved, and the degree to which they might interact, are still not well understood. We have developed a framework within which existing computational models can be assessed in an unbiased and quantitative manner against a set of experimental data curated from the mouse retinocollicular system. Our framework facilitates comparison between models, testing new models against known phenotypes and simulating new phenotypes in existing models. We have used this framework to assess four representative models that combine Eph/ephrin gradients and/or activity-based mechanisms and competition. Two of the models were updated from their original form to fit into our framework. The models were tested against five different phenotypes: wild type, Isl2-EphA3(ki/ki), Isl2-EphA3(ki/+), ephrin-A2,A3,A5 triple knock-out (TKO), and Math5(-/-) (Atoh7). Two models successfully reproduced the extent of the Math5(-/-) anteromedial projection, but only one of those could account for the collapse point in Isl2-EphA3(ki/+). The models needed a weak anteroposterior gradient in the SC to reproduce the residual order in the ephrin-A2,A3,A5 TKO phenotype, suggesting either an incomplete knock-out or the presence of another guidance molecule. Our article demonstrates the importance of testing retinotopic models against as full a range of phenotypes as possible, and we have made available MATLAB software, we wrote to facilitate this process.
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Affiliation(s)
- J J Johannes Hjorth
- Cambridge Computational Biology Institute, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, CB3 0WA, United Kingdom
| | - David C Sterratt
- Institute for Adaptive and Neural Computation, School of Informatics, University of Edinburgh, Edinburgh, EH8 9AB, United Kingdom
| | - Catherine S Cutts
- Cambridge Computational Biology Institute, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, CB3 0WA, United Kingdom
| | - David J Willshaw
- Institute for Adaptive and Neural Computation, School of Informatics, University of Edinburgh, Edinburgh, EH8 9AB, United Kingdom
| | - Stephen J Eglen
- Cambridge Computational Biology Institute, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, CB3 0WA, United Kingdom
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Sharma A, LeVaillant CJ, Plant GW, Harvey AR. Changes in expression of Class 3 Semaphorins and their receptors during development of the rat retina and superior colliculus. BMC DEVELOPMENTAL BIOLOGY 2014; 14:34. [PMID: 25062604 PMCID: PMC4121511 DOI: 10.1186/s12861-014-0034-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 07/15/2014] [Indexed: 12/28/2022]
Abstract
Background Members of the Semaphorin 3 family (Sema3s) influence the development of the central nervous system, and some are implicated in regulating aspects of visual system development. However, we lack information about the timing of expression of the Sema3s with respect to different developmental epochs in the mammalian visual system. In this time-course study in the rat, we document for the first time changes in the expression of RNAs for the majority of Class 3 Semaphorins (Sema3s) and their receptor components during the development of the rat retina and superior colliculus (SC). Results During retinal development, transcript levels changed for all of the Sema3s examined, as well as Nrp2, Plxna2, Plxna3, and Plxna4a. In the SC there were also changes in transcript levels for all Sema3s tested, as well as Nrp1, Nrp2, Plxna1, Plxna2, Plxna3, and Plxna4a. These changes correlate with well-established epochs, and our data suggest that the Sema3s could influence retinal ganglion cell (RGC) apoptosis, patterning and connectivity in the maturing retina and SC, and perhaps guidance of RGC and cortical axons in the SC. Functionally we found that SEMA3A, SEMA3C, SEMA3E, and SEMA3F proteins collapsed purified postnatal day 1 RGC growth cones in vitro. Significantly this is a developmental stage when RGCs are growing into and within the SC and are exposed to Sema3 ligands. Conclusion These new data describing the overall temporal regulation of Sema3 expression in the rat retina and SC provide a platform for further work characterising the functional impact of these proteins on the development and maturation of mammalian visual pathways.
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Affiliation(s)
- Anil Sharma
- School of Anatomy, Physiology and Human Biology, The University of Western Australia, 35 Stirling Highway, Crawley 6009, WA, Australia.
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Hamodi AS, Pratt KG. Region-specific regulation of voltage-gated intrinsic currents in the developing optic tectum of the Xenopus tadpole. J Neurophysiol 2014; 112:1644-55. [PMID: 24990560 DOI: 10.1152/jn.00068.2014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Across the rostrocaudal (RC) axis of the Xenopus tadpole optic tectum exists a developmental gradient. This gradient has served as a useful model to study many aspects of synapse and dendrite maturation. To compliment these studies, we characterized how the intrinsic excitability, the ease in which a neuron can fire action potentials, might also be changing across the same axis. Whole-cell recordings from tectal neurons at different points along the RC axis revealed a graded increase in intrinsic excitability: compared with neurons at the caudal end of the tectum, neurons at the rostral end fired more action potentials in response to current injection and expressed greater peak Na⁺ and K⁺ currents, the major intrinsic currents in these neurons that underlie the action potential. We also observed, along the same axis and in the same direction, a previously described increase in the amount of synaptic drive received by individual neurons (Wu GY, Malinow R, Cline HT. Science 274: 972-976, 1996). Thus as synaptic activity ramps up across the RC axis, so does intrinsic excitability. The reduction of overall circuit activity induced a compensatory scaling up of peak Na⁺ and K⁺ currents only in the caudal portion of the tectum, suggesting a region-specific, compensatory form of plasticity.
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Affiliation(s)
- Ali S Hamodi
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming
| | - Kara G Pratt
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming
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Abstract
We previously identified SPARC-related protein-containing immunoglobulin domains 1 (SPIG1, also known as Follistatin-like protein 4) as one of the dorsal-retina-specific molecules expressed in the developing chick retina. We here demonstrated that the knockdown of SPIG1 in the retinal ganglion cells (RGCs) of developing chick embryos induced the robust ectopic branching of dorsal RGC axons and failed to form a tight terminal zone at the proper position on the tectum. The knockdown of SPIG1 in RGCs also led to enhanced axon branching in vitro. However, this was canceled by the addition of a neutralizing antibody against brain-derived neurotrophic factor (BDNF) to the culture medium. SPIG1 and BDNF were colocalized in vesicle-like structures in cells. SPIG1 bound with the proform of BDNF (proBDNF) but very weakly with mature BDNF in vitro. The expression and secretion of mature BDNF were significantly decreased when SPIG1 was exogenously expressed with BDNF in HEK293T or PC12 cells. The amount of mature BDNF proteins as well as the tyrosine phosphorylation level of the BDNF receptor, tropomyosin-related kinase B (TrkB), in the hippocampus were significantly higher in SPIG1-knockout mice than in wild-type mice. Here the spine density of CA1 pyramidal neurons was consistently increased. Together, these results suggest that SPIG1 negatively regulated BDNF maturation by binding to proBDNF, thereby suppressing axonal branching and spine formation.
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Abstract
We introduce the Lattice Method for the quantitative assessment of the topographic order within the pattern of connections between two structures. We apply this method to published visuocollicular mapping data obtained by Fourier-based intrinsic imaging of mouse colliculus. We find that, in maps from wild types and β2 knock-outs, at least 150 points on the colliculus are represented in the visual field in the correct relative order. In maps from animals with knock-out of the three ephrinA ligands (TKO), thought to specify the rostrocaudal axis of the map, the projection on the colliculus of each small circular area of visual field is elongated approximately rostrocaudally. Of these projections, 9% are made up of two distinct regions lying along the direction of ingrowth of retinal fibers. These are similar to the ectopic projections found in other ephrinA knock-out data. Coexisting with the ectopic projections, each TKO map contains a submap where neighbor-neighbor relations are preserved, which is ordered along both rostrocaudal and mediolateral axes, in the orientation found in wild-type maps. The submaps vary in size with order well above chance level, which can approach the order in wild-type maps. Knock-out of both β2 and two of the three ephrinAs yields maps with some order. The ordered TKO maps cannot be produced by correlated neural activity acting alone, as this mechanism is unable to specify map orientation. These results invite reassessment of the role of molecular signaling, particularly that of ephrinAs, in the formation of ordered nerve connections.
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Tai AX, Cassidy RM, Kromer LF. EphA7 expression identifies a unique neuronal compartment in the rat striatum. J Comp Neurol 2014; 521:2663-79. [PMID: 23348681 DOI: 10.1002/cne.23308] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Revised: 01/03/2013] [Accepted: 01/17/2013] [Indexed: 01/26/2023]
Abstract
Prior studies have identified two anatomically and neurochemically distinct cellular compartments within the mammalian striatum, termed striosomes and matrix, which express μ-opioid receptors (μOR) and EphA4, respectively. Here we identify and characterize an additional compartment in the rat striatum composed of neurons that express EphA7. In situ hybridization and immunohistochemical data indicate that neurons expressing EphA7 mRNA and protein are arranged in a banded "matrisome-like" pattern confined to the matrix in the dorsal striatum. Within the ventral striatum, EphA7-positive (+) neurons have a less organized mosaic pattern that partially overlaps areas expressing μOR. Immunolabeling data demonstrate that EphA7+ striatofugal axons form distinct fascicles leaving the striatum. Within the globus pallidus, EphA7+ axons terminate primarily within ventromedial areas of the nucleus and along its striatal border. EphA7+ axons avoid regions containing dopamine neurons within the substantia nigra and preferentially innervate areas near the rostral and caudal margins of the nucleus. Within both nuclei, EphA7+ axons have similar but more restricted terminal fields than the entire population of EphA4+ matrix axons, indicating that EphA7+ axons comprise a subpopulation of matrix axons. Ligand binding data demonstrate that ephrin-A5 selectively binds areas of the striatum, globus pallidus, and substantia nigra containing EphA7+ neurons and axons, but not areas expressing only EphA4. Our findings demonstrate that EphA7 expression identifies a novel "matrisome" compartment within the matrix that binds ephrin-A5 and possesses unique axonal projections. Our findings also suggest that EphA7 and ephrin-A5 may participate in the formation of this matrisome subcompartment and its striatofugal projections.
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Affiliation(s)
- Alexander X Tai
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC 20007, USA
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27
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Yates N, Robertson D, Martin-Iverson M, Rodger J. Auditory brainstem responses of ephrin-A2, ephrin-A5(-/-) and ephrin-A2A5(-/-) mice. Audiol Neurootol 2014; 19:115-26. [PMID: 24457350 DOI: 10.1159/000357029] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Accepted: 10/30/2013] [Indexed: 01/04/2023] Open
Abstract
Eph receptors and ephrin ligands are large families of cell surface proteins which have established roles in axonal growth and guidance. These are well characterized in the visual and somatosensory systems but are less well documented in the auditory pathway. We examined the possible functional role of two ephrin genes (ephrin-A2 and ephrin-A5) in the auditory system by measuring auditory brainstem responses (ABR) to tone bursts from 6 to 30 kHz in ephrin-A2(-/-), ephrin-A5(-/-) and ephrin-A2A5(-/-) (knockout) mice. At high frequencies, the ephrin-A2A5(-/-) mice exhibited thresholds that were significantly lower than in wild-type mice by approximately 20 dB, suggesting ephrin-A2 and ephrin-A5 may have frequency-specific effects on the auditory system. There were also alterations in ABR wave peak amplitudes that were specific to each mouse strain which suggested both peripheral and central involvement of EphA-ephrin-A signalling in auditory function.
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Affiliation(s)
- Nathanael Yates
- School of Animal Biology, University of Western Australia, Crawley, W.A., Australia
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Butt GF, Habib A, Mahgoub K, Sofela A, Tilley M, Guo L, Cordeiro MF. Optic nerve regeneration. EXPERT REVIEW OF OPHTHALMOLOGY 2014. [DOI: 10.1586/eop.12.66] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Abstract
Classic studies have proposed that genetically encoded programs and spontaneous activity play complementary but independent roles in the development of neural circuits. Recent evidence, however, suggests that these two mechanisms could interact extensively, with spontaneous activity affecting the expression and function of guidance molecules at early developmental stages. Here, using the developing chick spinal cord and the mouse visual system to ectopically express the inwardly rectifying potassium channel Kir2.1 in individual embryonic neurons, we demonstrate that cell-intrinsic blockade of spontaneous activity in vivo does not affect neuronal identity specification, axon pathfinding, or EphA/ephrinA signaling during the development of topographic maps. However, intrinsic spontaneous activity is critical for axon branching and pruning once axonal growth cones reach their correct topographic position in the target tissues. Our experiments argue for the dissociation of spontaneous activity from hard-wired developmental programs in early phases of neural circuit formation.
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Restricted perinatal retinal degeneration induces retina reshaping and correlated structural rearrangement of the retinotopic map. Nat Commun 2013; 4:1938. [PMID: 23733098 PMCID: PMC3709497 DOI: 10.1038/ncomms2926] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 04/24/2013] [Indexed: 02/05/2023] Open
Abstract
The formation of the retinotopic map depends on the action of axon guidance molecules, activity-dependent mechanisms and axonal competition. However, little is known about the plasticity potential of the system and the effects on the remodelling of retinocollicular connections upon retinal insults. Here we create a mouse model in which retinal ganglion cells that project to anterior and posterior superior colliculus undergo cell death during topographic map formation. We show that the remaining retinal ganglion cells expand the targeted area in the superior colliculus and at the same time increase their spatial coverage in the retina in a correlated fashion. The resulting contralateral topographic map is overall maintained but less precise, while ipsilateral retinal ganglion cell axons are abnormally distributed in anterior and posterior superficial superior colliculus. These results suggest the presence of plastic mechanisms in the developing mammalian visual system to adjust retinal space and its target coverage and ensure a uniform map.
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Furman M, Xu HP, Crair MC. Competition driven by retinal waves promotes morphological and functional synaptic development of neurons in the superior colliculus. J Neurophysiol 2013; 110:1441-54. [PMID: 23741047 PMCID: PMC3763158 DOI: 10.1152/jn.01066.2012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 06/03/2013] [Indexed: 11/22/2022] Open
Abstract
Prior to eye opening, waves of spontaneous activity sweep across the developing retina. These "retinal waves," together with genetically encoded molecular mechanisms, mediate the formation of visual maps in the brain. However, the specific role of wave activity in synapse development in retino-recipient brain regions is unclear. Here we compare the functional development of synapses and the morphological development of neurons in the superior colliculus (SC) of wild-type (WT) and transgenic (β2-TG) mice in which retinal wave propagation is spatially truncated (Xu HP, Furman M, Mineur YS, Chen H, King SL, Zenisek D, Zhou ZJ, Butts DA, Tian N, Picciotto MR, Crair MC. Neuron 70: 1115-1127, 2011). We use two recently developed brain slice preparations to examine neurons and synapses in the binocular vs. mainly monocular SC. We find that retinocollicular synaptic strength is reduced whereas the number of retinal inputs is increased in the binocular SC of β2-TG mice compared with WT mice. In contrast, in the mainly monocular SC the number of retinal inputs is normal in β2-TG mice, but, transiently, synapses are abnormally strong, possibly because of enhanced activity-dependent competition between local, "small" retinal wave domains. These findings demonstrate that retinal wave size plays an instructive role in the synaptic and morphological development of SC neurons, possibly through a competitive process among retinofugal axons.
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Affiliation(s)
- Moran Furman
- Department of Neurobiology, Yale University School of Medicine, New Haven, Connecticut
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Zhang R, Huang H, Cao P, Wang Z, Chen Y, Pan Y. Sma- and Mad-related protein 7 (Smad7) is required for embryonic eye development in the mouse. J Biol Chem 2013; 288:10275-85. [PMID: 23426374 PMCID: PMC3624411 DOI: 10.1074/jbc.m112.416719] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 02/19/2013] [Indexed: 01/16/2023] Open
Abstract
Smad7 is an intracellular inhibitory protein that antagonizes the signaling of TGF-β family members. Deletion of Smad7 in the mouse leads to an abnormality in heart development. However, whether Smad7 has a functional role in the development of other organs has been elusive. Here we present evidence that Smad7 imparts a role to eye development in the mouse. Smad7 is expressed in both the lens and retina in the developing embryonic eye. Depletion of Smad7 caused various degrees of coloboma and microphthalmia with alterations in cell apoptosis and proliferation in eyes. Smad7 was implicated in lens differentiation but was not required for the induction of the lens placode. The development of the periocular mesenchyme was retarded with the down-regulation of Bmp7 and Pitx2 in mutant mice. Retinal spatial patterning was affected by Smad7 deletion and was accompanied by altered bone morphogenetic protein (BMP) signaling. At late gestation stages, TGF-β signaling was up-regulated in the differentiating retina. Smad7 mutant mice displayed an expanded optic disc with increasing of sonic hedgehog (SHH) signaling. Furthermore, loss of Smad7 led to a temporal change in retinal neurogenesis. In conclusion, our study suggests that Smad7 is essential for eye development. In addition, our data indicate that alterations in the signaling of BMP, TGF-β, and SHH likely underlie the defects in eye development caused by Smad7 deletion.
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Affiliation(s)
- Rui Zhang
- From the Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Heng Huang
- From the Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Peijuan Cao
- From the Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Zhenzhen Wang
- From the Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Yan Chen
- From the Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Yi Pan
- From the Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
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Adaptation of the central retina for high acuity vision: cones, the fovea and the avascular zone. Prog Retin Eye Res 2013; 35:63-81. [PMID: 23500068 DOI: 10.1016/j.preteyeres.2013.01.005] [Citation(s) in RCA: 179] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 01/25/2013] [Accepted: 01/25/2013] [Indexed: 12/31/2022]
Abstract
Presence of a fovea centralis is directly linked to molecular specification of an avascular area in central retina, before the fovea (or 'pit') begins to form. Modelling suggests that mechanical forces, generated within the eye, initiate formation of a pit within the avascular area, and its later remodelling in the postnatal period. Within the avascular area the retina is dominated by 'midget' circuitry, in which signals are transferred from a single cone to a single bipolar cell, then a single ganglion cell. Thus in inner, central retina there are relatively few lateral connections between neurons. This renders the region adaptable to tangential forces, that translocate of ganglion cells laterally/centrifugally, to form the fovea. Optical coherence tomography enables live imaging of the retina, and shows that there is greater variation in the morphology of foveae in humans than previously thought. This variation is associated with differences in size of the avascular area and appears to be genetically based, but can be modified by environmental factors, including prematurity. Even when the fovea is absent (foveal hypoplasia), cones in central retina adopt an elongated and narrow morphology, enabling them to pack more densely to increase the sampling rate, and to act as more effective waveguides. Given these findings, what then is the adaptive advantage of a fovea? We suggest that the advantages of having a pit in central retina are relatively few, and minor, but together work to enhance acuity.
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Roy J, Kennedy TE, Costantino S. Engineered cell culture substrates for axon guidance studies: moving beyond proof of concept. LAB ON A CHIP 2013; 13:498-508. [PMID: 23288417 DOI: 10.1039/c2lc41002h] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Promoting axon regeneration following injury is one of the ultimate challenges of neuroscience, and understanding the mechanisms that regulate axon growth and guidance is essential to achieve this goal. During development axons are directed over relatively long distances by a precise extracellular distribution of chemical signals in the embryonic nervous system. Multiple guidance proteins, including netrins, slits, semaphorins, ephrins and neurotrophins have been identified as key players in this process. During the last decade, engineered cell culture substrates have been developed to investigate the cellular and molecular mechanisms underlying axon guidance. This review is focused on the biological insights that have been achieved using new techniques that attempt to mimic in vitro the spatial patterns of proteins that growth cones encounter in vivo.
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Affiliation(s)
- Joannie Roy
- Maisonneuve-Rosemont Hospital, University of Montreal, Montreal, Canada
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Higenell V, Han SM, Feldheim DA, Scalia F, Ruthazer ES. Expression patterns of Ephs and ephrins throughout retinotectal development in Xenopus laevis. Dev Neurobiol 2012; 72:547-63. [PMID: 21656698 DOI: 10.1002/dneu.20930] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The Eph family of receptor tyrosine kinases and their ligands the ephrins play an essential role in the targeting of retinal ganglion cell axons to topographically correct locations in the optic tectum during visual system development. The African claw-toed frog Xenopus laevis is a popular animal model for the study of retinotectal development because of its amenability to live imaging and electrophysiology. Its visual system undergoes protracted growth continuing beyond metamorphosis, yet little is known about ephrin and Eph expression patterns beyond stage 39 when retinal axons first arrive in the tectum. We used alkaline phosphatase fusion proteins of EphA3, ephrin-A5, EphB2, and ephrin-B1 as affinity probes to reveal the expression patterns of ephrin-As, EphAs, ephrin-Bs, and EphBs, respectively. Analysis of brains from stage 40 to adult frog revealed that ephrins and Eph receptors are expressed throughout development. As observed in other species, staining for ephrin-As displayed a high caudal to low rostral expression pattern across the tectum, roughly complementary to the expression of EphAs. In contrast with the prevailing model, EphBs were found to be expressed in the tectum in a high dorsal to low ventral gradient in young animals. In animals with induced binocular tectal innervation, ocular dominance bands of alternating input from the two eyes formed in the tectum; however, ephrin-A and EphA expression patterns were unmodulated and similar to those in normal frogs, confirming that the segregation of axons into eye-specific stripes is not the consequence of a respecification of molecular guidance cues in the tectum.
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Affiliation(s)
- Valerie Higenell
- Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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Kruse-Bend R, Rosenthal J, Quist TS, Veien ES, Fuhrmann S, Dorsky RI, Chien CB. Extraocular ectoderm triggers dorsal retinal fate during optic vesicle evagination in zebrafish. Dev Biol 2012; 371:57-65. [PMID: 22921921 DOI: 10.1016/j.ydbio.2012.08.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 07/10/2012] [Accepted: 08/09/2012] [Indexed: 01/30/2023]
Abstract
Dorsal retinal fate is established early in eye development, via expression of spatially restricted dorsal-specific transcription factors in the optic vesicle; yet the events leading to initiation of dorsal fate are not clear. We hypothesized that induction of dorsal fate would require an extraocular signal arising from a neighboring tissue to pattern the prospective dorsal retina, however no such signal has been identified. We used the zebrafish embryo to determine the source, timing, and identity of the dorsal retina-inducing signal. Extensive cell movements occur during zebrafish optic vesicle morphogenesis, however the location of prospective dorsal cells within the early optic vesicle and their spatial relationship to early dorsal markers is currently unknown. Our mRNA expression and fate mapping analyses demonstrate that the dorsolateral optic vesicle is the earliest region to express dorsal specific markers, and cells from this domain contribute to the dorsal retinal pole at 24 hpf. We show that three bmp genes marking dorsal retina at 25 hpf are also expressed extraocularly before retinal patterning begins. We identified gdf6a as a dorsal initiation signal acting from the extraocular non-neural ectoderm during optic vesicle evagination. We find that bmp2b is involved in dorsal retina initiation, acting upstream of gdf6a. Together, this work has identified the nature and source of extraocular signals required to pattern the dorsal retina.
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Affiliation(s)
- Renee Kruse-Bend
- Department of Neurobiology and Anatomy, 20 North 1900 East, Room 401 MREB, University of Utah, Salt Lake City, UT 84132, USA
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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] [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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Maiorano NA, Hindges R. Non-coding RNAs in retinal development. Int J Mol Sci 2012; 13:558-578. [PMID: 22312272 PMCID: PMC3269706 DOI: 10.3390/ijms13010558] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2011] [Revised: 12/20/2011] [Accepted: 12/21/2011] [Indexed: 12/22/2022] Open
Abstract
Retinal development is dependent on an accurately functioning network of transcriptional and translational regulators. Among the diverse classes of molecules involved, non-coding RNAs (ncRNAs) play a significant role. Members of this family are present in the cell as transcripts, but are not translated into proteins. MicroRNAs (miRNAs) are small ncRNAs that act as post-transcriptional regulators. During the last decade, they have been implicated in a variety of biological processes, including the development of the nervous system. On the other hand, long-ncRNAs (lncRNAs) represent a different class of ncRNAs that act mainly through processes involving chromatin remodeling and epigenetic mechanisms. The visual system is a prominent model to investigate the molecular mechanisms underlying neurogenesis or circuit formation and function, including the differentiation of retinal progenitor cells to generate the seven principal cell classes in the retina, pathfinding decisions of retinal ganglion cell axons in order to establish the correct connectivity from the eye to the brain proper, and activity-dependent mechanisms for the functionality of visual circuits. Recent findings have associated ncRNAs in several of these processes and uncovered a new level of complexity for the existing regulatory mechanisms. This review summarizes and highlights the impact of ncRNAs during the development of the vertebrate visual system, with a specific focus on the role of miRNAs and a synopsis regarding recent findings on lncRNAs in the retina.
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Affiliation(s)
- Nicola A. Maiorano
- MRC Centre for Developmental Neurobiology, King’s College London, New Hunt’s House, Guy’s Campus, London, SE1 1UL, UK; E-Mail:
| | - Robert Hindges
- MRC Centre for Developmental Neurobiology, King’s College London, New Hunt’s House, Guy’s Campus, London, SE1 1UL, UK; E-Mail:
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Atkinson-Leadbeater K, McFarlane S. Extrinsic factors as multifunctional regulators of retinal ganglion cell morphogenesis. Dev Neurobiol 2011; 71:1170-85. [DOI: 10.1002/dneu.20924] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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40
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Singh A, Tare M, Puli OR, Kango-Singh M. A glimpse into dorso-ventral patterning of the Drosophila eye. Dev Dyn 2011; 241:69-84. [PMID: 22034010 DOI: 10.1002/dvdy.22764] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/06/2011] [Indexed: 12/15/2022] Open
Abstract
During organogenesis in all multi-cellular organisms, axial patterning is required to transform a single layer organ primordium into a three-dimensional organ. The Drosophila eye model serves as an excellent model to study axial patterning. Dorso-ventral (DV) axis determination is the first lineage restriction event during axial patterning of the Drosophila eye. The early Drosophila eye primordium has a default ventral fate, and the dorsal eye fate is established by onset of dorsal selector gene pannier (pnr) expression in a group of cells on the dorsal eye margin. The boundary between dorsal and ventral compartments called the equator is the site for Notch (N) activation, which triggers cell proliferation and differentiation. This review will focus on (1) chronology of events during DV axis determination; (2) how early division of eye into dorsal and ventral compartments contributes towards the growth and patterning of the fly retina, and (3) functions of DV patterning genes.
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Affiliation(s)
- Amit Singh
- Department of Biology, University of Dayton, Dayton, Ohio 45469, USA.
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41
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Chan KC, Cheng JS, Fan S, Zhou IY, Yang J, Wu EX. In vivo evaluation of retinal and callosal projections in early postnatal development and plasticity using manganese-enhanced MRI and diffusion tensor imaging. Neuroimage 2011; 59:2274-83. [PMID: 21985904 DOI: 10.1016/j.neuroimage.2011.09.055] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Revised: 08/22/2011] [Accepted: 09/22/2011] [Indexed: 12/14/2022] Open
Abstract
The rodents are an excellent model for understanding the development and plasticity of the visual system. In this study, we explored the feasibility of Mn-enhanced MRI (MEMRI) and diffusion tensor imaging (DTI) at 7 T for in vivo and longitudinal assessments of the retinal and callosal pathways in normal neonatal rodent brains and after early postnatal visual impairments. Along the retinal pathways, unilateral intravitreal Mn2+ injection resulted in Mn2+ uptake and transport in normal neonatal visual brains at postnatal days (P) 1, 5 and 10 with faster Mn2+ clearance than the adult brains at P60. The reorganization of retinocollicular projections was also detected by significant Mn2+ enhancement by 2%-10% in the ipsilateral superior colliculus (SC) of normal neonatal rats, normal adult mice and adult rats after neonatal monocular enucleation (ME) but not in normal adult rats or adult rats after monocular deprivation (MD). DTI showed a significantly higher fractional anisotropy (FA) by 21% in the optic nerve projected from the remaining eye of ME rats compared to normal rats at 6 weeks old, likely as a result of the retention of axons from the ipsilaterally uncrossed retinal ganglion cells, whereas the anterior and posterior retinal pathways projected from the enucleated or deprived eyes possessed lower FA after neonatal binocular enucleation (BE), ME and MD by 22%-56%, 18%-46% and 11%-15% respectively compared to normal rats, indicative of neurodegeneration or immaturity of white matter tracts. Along the visual callosal pathways, intracortical Mn2+ injection to the visual cortex of BE rats enhanced a larger projection volume by about 74% in the V1/V2 transition zone of the contralateral hemisphere compared to normal rats, without apparent DTI parametric changes in the splenium of corpus callosum. This suggested an adaptive change in interhemispheric connections and spatial specificity in the visual cortex upon early blindness. The results of this study may help determine the mechanisms of axonal uptake and transport, microstructural reorganization and functional activities in the living visual brains during development, diseases, plasticity and early interventions in a global and longitudinal setting.
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Affiliation(s)
- Kevin C Chan
- Laboratory of Biomedical Imaging and Signal Processing, Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
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42
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Developmental sculpting of dendritic morphology of layer 4 neurons in visual cortex: influence of retinal input. J Neurosci 2011; 31:7456-70. [PMID: 21593329 DOI: 10.1523/jneurosci.5222-10.2011] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Dendritic morphology determines the kinds of input a neuron receives, having a profound impact on neural information processing. In the mammalian cerebral cortex, excitatory neurons have been ascribed to one of two main dendritic morphologies, either pyramidal or stellate, which differ mainly on the extent of the apical dendrite. Developmental mechanisms regulating the emergence and refinement of dendritic morphologies have been studied for cortical pyramidal neurons, but little is known for spiny stellate neurons. Using biolistics to label single cells on acute brain slices of the ferret primary visual cortex, we show that neurons in layer 4 develop in a two-step process: initially, all neurons appear pyramidal, growing a prominent apical dendrite and few small basal dendrites. Later, a majority of these neurons show a change in the relative extent of basal and apical dendrites that results in a gradual sculpting into a stellate morphology. We also find that ∼ 22% of neurons maintain the proportionality of their dendritic arbors, remaining as pyramidal cells at maturity. When ferrets were deprived of retinal input at early stages of postnatal development by binocular enucleation, a significant proportion of layer 4 spiny neurons failed to remodel their apical dendrites, and ∼ 55% remained as pyramidal neurons. Our results demonstrate that cortical spiny stellate neurons emerge by differential sculpting of the dendritic arborizations of an initial pyramidal morphology and that sensory input plays a fundamental role in this process.
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43
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Simpson HD, Giacomantonio CE, Goodhill GJ. Computational modeling of neuronal map development: insights into disease. FUTURE NEUROLOGY 2011. [DOI: 10.2217/fnl.11.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The study of the formation of neuronal maps in the brain has greatly increased our understanding of how the brain develops and, in some cases, regenerates. Computational modeling of neuronal map development has been invaluable in integrating complex biological phenomena and synthesizing them into quantitative and predictive frameworks. These models allow us to investigate how neuronal map development is perturbed under conditions of altered development, disease and regeneration. In this article, we use examples of activity-dependent and activity-independent models of retinotopic map formation to illustrate how they can aid our understanding of developmental and acquired disease processes. We note that fully extending these models to specific clinically relevant problems is a largely unexplored domain and suggest future work in this direction. We argue that this type of modeling will be necessary in furthering our understanding of the pathophysiology of neurological diseases and in developing treatments for them. Furthermore, we discuss how the nature of computational and theoretical approaches uniquely places them to bridge the gap between the bench and the clinic.
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Affiliation(s)
- Hugh D Simpson
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Clare E Giacomantonio
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Geoffrey J Goodhill
- School of Mathematics & Physics, The University of Queensland, Brisbane, Queensland 4072, Australia
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44
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Stanic K, Montecinos H, Caprile T. Subdivisions of chick diencephalic roof plate: implication in the formation of the posterior commissure. Dev Dyn 2011; 239:2584-93. [PMID: 20730872 DOI: 10.1002/dvdy.22387] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The subcommissural organ (SCO) is a roof plate differentiation located in the caudal diencephalon under the posterior commissure (PC). A role for SCO and its secretory product, SCO-spondin, in the formation of the PC has been proposed. Here, we provide immunohistochemical evidence to suggest that SCO is anatomically divided in a bilateral region positive for SCO-spondin that surrounds a negative medial region. Remarkably, axons contacting the lateral region are highly fasciculated, in sharp contrast with the defasciculated axons of the medial region. In addition, lateral axon fascicles run toward the midline inside of tunnels limited by the basal prolongations of SCO cells and extracellular SCO-spondin. Our in vitro data in collagen gel matrices show that SCO-spondin induces axonal growth and fasciculation of pretectal explants. Together, our findings support the idea that SCO-spondin participates in the guidance and fasciculation of axons of the PC.
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Affiliation(s)
- Karen Stanic
- Department of Cell Biology, University of Concepción, Chile
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45
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Dent EW, Gupton SL, Gertler FB. The growth cone cytoskeleton in axon outgrowth and guidance. Cold Spring Harb Perspect Biol 2011; 3:cshperspect.a001800. [PMID: 21106647 DOI: 10.1101/cshperspect.a001800] [Citation(s) in RCA: 394] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Axon outgrowth and guidance to the proper target requires the coordination of filamentous (F)-actin and microtubules (MTs), the dynamic cytoskeletal polymers that promote shape change and locomotion. Over the past two decades, our knowledge of the many guidance cues, receptors, and downstream signaling cascades involved in neuronal outgrowth and guidance has increased dramatically. Less is known, however, about how those cascades of information converge and direct appropriate remodeling and interaction of cytoskeletal polymers, the ultimate effectors of movement and guidance. During development, much of the communication that occurs between environmental guidance cues and the cytoskeleton takes place at the growing tip of the axon, the neuronal growth cone. Several articles on this topic focus on the "input" to the growth cone, the myriad of receptor types, and their corresponding cognate ligands. Others investigate the signaling cascades initiated by receptors and propagated by second messenger pathways (i.e., kinases, phosphatases, GTPases). Ultimately, this plethora of information converges on proteins that associate directly with the actin and microtubule cytoskeletons. The role of these cytoskeletal-associated proteins, as well as the cytoskeleton itself in axon outgrowth and guidance, is the subject of this article.
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Affiliation(s)
- Erik W Dent
- Department of Anatomy, University of Wisconsin-Madison, 53706, USA
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Tsigankov D, Koulakov AA. Sperry versus Hebb: topographic mapping in Isl2/EphA3 mutant mice. BMC Neurosci 2010; 11:155. [PMID: 21190559 PMCID: PMC3019204 DOI: 10.1186/1471-2202-11-155] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Accepted: 12/29/2010] [Indexed: 11/19/2022] Open
Abstract
Background In wild-type mice, axons of retinal ganglion cells establish topographically precise projection to the superior colliculus of the midbrain. This means that axons of neighboring retinal ganglion cells project to the proximal locations in the target. The precision of topographic projection is a result of combined effects of molecular labels, such as Eph receptors and ephrins, and correlated neural activity. In the Isl2/EphA3 mutant mice the expression levels of molecular labels are changed. As a result the topographic projection is rewired so that the neighborhood relationships between retinal cell axons are disrupted. Results Here we study the computational model for retinocollicular connectivity formation that combines the effects of molecular labels and correlated neural activity. We argue that the effects of correlated activity presenting themselves in the form of Hebbian learning rules can facilitate the restoration of the topographic connectivity even when the molecular labels carry conflicting instructions. This occurs because the correlations in electric activity carry information about retinal cells' origin that is independent on molecular labels. We argue therefore that partial restoration of the topographic property of the retinocollicular projection observed in Isl2/EphA3 heterozygous knockin mice may be explained by the effects of correlated neural activity. We address the maps observed in Isl2/EphA3 knockin/EphA4 knockout mice in which the levels of retinal labels are uniformly reduced. These maps can be explained by either the saturation of EphA receptor mapping leading to the relative signaling model or by the reverse signaling conveyed by ephrin-As expressed by retinal axons. Conclusion According to our model, experiments in Isl2/EphA3 knock-in mice test the interactions between effects of molecular labels and correlated activity during the development of neural connectivity. Correlated activity can partially restore topographic order even when molecular labels carry conflicting information.
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Affiliation(s)
- Dmitry Tsigankov
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
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CHAN KEVINC, CHEUNG MATTHEWM, WU EDX. IN VIVOMULTIPARAMETRIC MAGNETIC RESONANCE IMAGING AND SPECTROSCOPY OF RODENT VISUAL SYSTEM. J Integr Neurosci 2010; 9:477-508. [DOI: 10.1142/s0219635210002524] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 11/04/2010] [Indexed: 01/27/2023] Open
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Matejů K, Sumová A, Bendová Z. Expression and light sensitivity of clock genes Per1 and Per2 and immediate-early gene c-fos within the retina of early postnatal Wistar rats. J Comp Neurol 2010; 518:3630-44. [PMID: 20589906 DOI: 10.1002/cne.22421] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Mammalian retina contains a circadian clock that is composed of components similar to those of the master circadian clock within the suprachiasmatic nuclei of the hypothalamus. The aim of the present study was to elucidate whether, when, and where the transcripts of the clock genes Per1 and Per2 and the immediate early gene c-fos are spontaneously expressed and/or induced by light in the newborn rat retina. At postnatal day 1 (P1), P3, P5, and P10, Wistar rat pups were released into constant darkness, and a 30-minute light pulse was administered during the subjective day or during the first or second part of subjective night. Gene expression was determined 30 minutes, 1 hour, 2 hours, and 4 hours after the light pulse by in situ hybridization followed by emulsion autoradiography. Endogenous expression of Per1 was detected in the neuroblastic retina, and Per2 expression was detected in the inner part of the neuroblastic retina from birth. Light pulses induced c-fos expression in ganglion cells from P1. Until P5, the cells were localized in the dorsal part of the retina, but, at P10, they were already distributed across the entire retinal circumference. Light pulses also induced the expression of c-fos and Per1 in the retinal pigment epithelium until P3, but not afterward. Expression of the Per2 gene was not photoresponsive until P10. These data demonstrate that the rat retina is light-sensitive immediately after birth. During early postnatal development, the spatial distribution of spontaneous and light-induced gene expression within the retinal layers changes gradually.
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Affiliation(s)
- Kristýna Matejů
- Department of Neurohumoral Regulations, Institute of Physiology, Academy of Sciences of the Czech Republic v.v.i., Prague 14220, Czech Republic
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Feldheim DA, O'Leary DDM. Visual map development: bidirectional signaling, bifunctional guidance molecules, and competition. Cold Spring Harb Perspect Biol 2010; 2:a001768. [PMID: 20880989 DOI: 10.1101/cshperspect.a001768] [Citation(s) in RCA: 150] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Topographic maps are a two-dimensional representation of one neural structure within another and serve as the main strategy to organize sensory information. The retina's projection via axons of retinal ganglion cells to midbrain visual centers, the optic tectum/superior colliculus, is the leading model to elucidate mechanisms of topographic map formation. Each axis of the retina is mapped independently using different mechanisms and sets of axon guidance molecules expressed in gradients to achieve the goal of representing a point in the retina onto a point within the target. An axon's termination along the temporal-nasal mapping axis is determined by opposing gradients of EphAs and ephrin-As that act through their forward and reverse signaling, respectively, within the projecting axons, each of which inhibits interstitial branching, cooperating with a branch-promoting activity, to generate topographic specific branching along the shaft of the parent axons that overshoot their correct termination zone along the anterior-posterior axis of the target. The dorsal-ventral termination position is then determined using a gradient of ephrin-B that can act as a repellent or attractant depending on the ephrin-B concentration relative to EphB levels on the interstitial branches to guide them along the medial-lateral axis of the target to their correct termination zone, where they arborize. In both cases, axon-axon competition results in axon mapping based on relative rather than absolute levels of repellent or attractant activity. The map is subsequently refined through large-scale pruning driven in large part by patterned retinal activity.
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Affiliation(s)
- David A Feldheim
- MCD Biology, University of California, Santa Cruz, Santa Cruz, California 95064, USA.
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Erickson T, French CR, Waskiewicz AJ. Meis1 specifies positional information in the retina and tectum to organize the zebrafish visual system. Neural Dev 2010; 5:22. [PMID: 20809932 PMCID: PMC2939508 DOI: 10.1186/1749-8104-5-22] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2009] [Accepted: 09/01/2010] [Indexed: 01/17/2023] Open
Abstract
Background During visual system development, multiple signalling pathways cooperate to specify axial polarity within the retina and optic tectum. This information is required for the topographic mapping of retinal ganglion cell axons on the tectum. Meis1 is a TALE-class homeodomain transcription factor known to specify anterior-posterior identity in the hindbrain, but its role in visual system patterning has not been investigated. Results meis1 is expressed in both the presumptive retina and tectum. An analysis of retinal patterning reveals that Meis1 is required to correctly specify both dorsal-ventral and nasal-temporal identity in the zebrafish retina. Meis1-knockdown results in a loss of smad1 expression and an upregulation in follistatin expression, thereby causing lower levels of Bmp signalling and a partial ventralization of the retina. Additionally, Meis1-deficient embryos exhibit ectopic Fgf signalling in the developing retina and a corresponding loss of temporal identity. Meis1 also positively regulates ephrin gene expression in the tectum. Consistent with these patterning phenotypes, a knockdown of Meis1 ultimately results in retinotectal mapping defects. Conclusions In this work we describe a novel role for Meis1 in regulating Bmp signalling and in specifying temporal identity in the retina. By patterning both the retina and tectum, Meis1 plays an important role in establishing the retinotectal map and organizing the visual system.
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Affiliation(s)
- Timothy Erickson
- Department of Biological Sciences, University of Alberta, CW405, Biological Sciences Bldg, Edmonton T6G 2E9, Canada
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