101
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Hertle D, Schleichert M, Steup A, Kirsch M, Hofmann HD. Regulation of cytokine signaling components in developing rat retina correlates with transient inhibition of rod differentiation by CNTF. Cell Tissue Res 2008; 334:7-16. [PMID: 18665395 DOI: 10.1007/s00441-008-0651-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Accepted: 05/20/2008] [Indexed: 10/21/2022]
Abstract
Ciliary neurotrophic factor (CNTF) is known to inhibit the differentiation of rod photoreceptors from postmitotic precursor cells. During early postnatal development, photoreceptor precursors lose their responsiveness to CNTF. The underlying events causing this change in responsiveness are unknown. Moreover, whether rods express CNTF receptor alpha, a prerequisite for a direct response to the factor, is controversial. Since morphological studies have previously produced conflicting results, we have analyzed the expression of cytokine receptor components and potential ligands in the rat photoreceptor layer by real-time reverse transcription with the polymerase chain reaction after laser microdissection and by immunoblotting. Cytokine effects on rods were studied in explant cultures from newborn rat retina. CNTF receptor alpha (CNTFR alpha) and leukemia inhibitory factor receptor ss (LIFRss) were expressed in immature photoreceptors. Expression of the CNTF-specific alpha-subunit (but not of LIFRss) was downregulated specifically in the photoreceptor layer in parallel with the appearance of opsin-positive rods. The decrease of CNTFR alpha levels in explant cultures was closely correlated with the loss of precursor cell responsiveness to CNTF. Increasing the CNTF concentration in the culture medium led to prolonged CNTFR alpha expression and, concomitantly, to persistent inhibition of rod differentiation. Application of CNTF and LIF in vitro induced phosphorylation of STAT3. Inducibility of STAT3 activation by CNTF decreased with photoreceptor maturation, whereas the LIF effect persisted. Our results thus indicate that CNTF acts directly on photoreceptor precursors inhibiting their differentiation via activation of the JAK/STAT3 signal transduction pathway, and that this effect is temporally limited because of the downregulation of CNTFR alpha.
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Affiliation(s)
- Daniel Hertle
- Institute of Anatomy and Cell Biology, University of Freiburg, P.O. Box 111, 79001, Freiburg, Germany
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102
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Fuhrmann S, Riesenberg AN, Mathiesen AM, Brown EC, Vetter ML, Brown NL. Characterization of a transient TCF/LEF-responsive progenitor population in the embryonic mouse retina. Invest Ophthalmol Vis Sci 2008; 50:432-40. [PMID: 18599572 DOI: 10.1167/iovs.08-2270] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE High mobility group (HMG) transcription factors of the T-cell-specific transcription factor/lymphoid enhancer binding factor (TCF/LEF) family are a class of intrinsic regulators that are dynamically expressed in the embryonic mouse retina. Activation of TCF/LEFs is a hallmark of the Wnt/beta-catenin pathway; however, the requirement for Wnt/beta-catenin and noncanonical Wnt signaling during mammalian retinal development remains unclear. The goal of the study was to characterize more fully a TCF/LEF-responsive retinal progenitor population in the mouse embryo and to correlate this with Wnt/beta-catenin signaling. METHODS TCF/LEF activation was analyzed in the TOPgal (TCF optimal promoter) reporter mouse at embryonic ages and compared to Axin2 mRNA expression, an endogenous readout of Wnt/beta-catenin signaling. Reporter expression was also examined in embryos with a retina-specific deletion of the beta-catenin gene (Ctnnb1), using Six3-Cre transgenic mice. Finally, the extent to which TOPgal cells coexpress cell cycle proteins, basic helix-loop-helix (bHLH) transcription factors, and other retinal cell markers was tested by double immunohistochemistry. RESULTS TOPgal reporter activation occurred transiently in a subpopulation of embryonic retinal progenitor cells. Axin2 was not expressed in the central retina, and TOPgal reporter expression persisted in the absence of beta-catenin. Although a proportion of TOPgal-labeled cells were proliferative, most coexpressed the cyclin-dependent kinase inhibitor p27/Kip1. CONCLUSIONS TOPgal cells give rise to the four earliest cell types: ganglion, amacrine, horizontal, and photoreceptor. TCF/LEF activation in the central retina does not correlate with Wnt/beta-catenin signaling, pointing to an alternate role for this transcription factor family during retinal development.
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Affiliation(s)
- Sabine Fuhrmann
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, Utah 84132, USA.
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103
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Edqvist PHD, Lek M, Boije H, Lindbäck SM, Hallböök F. Axon-bearing and axon-less horizontal cell subtypes are generated consecutively during chick retinal development from progenitors that are sensitive to follistatin. BMC DEVELOPMENTAL BIOLOGY 2008; 8:46. [PMID: 18439241 PMCID: PMC2386784 DOI: 10.1186/1471-213x-8-46] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Accepted: 04/25/2008] [Indexed: 11/12/2022]
Abstract
BACKGROUND Horizontal cells are retinal interneurons that modulate the output from photoreceptors. A rich literature on the morphological classification and functional properties of HCs in different animals exists, however, the understanding of the events underlying their development is still limited. In most vertebrates including chicken, two main horizontal cell (HC) subtypes are identified based on the presence or absence of an axon. RESULTS In this work we have molecularly characterized three HC subtypes based on Lim1, Isl1, GABA and TrkA, a classification that is consistent with three chick HC subtypes previously defined by morphology. The axon-bearing and axon-less HC subpopulations molecularly defined by Lim1 and Isl1, are born consecutively on embryonic day (E) 3-4 and E4-5, respectively, and exhibit temporally distinguishable periods of migration. Their relative numbers are not adjusted by apoptosis. A sharp decrease of high endogenous levels of the activin-inhibitor follistatin at E3 coincides with the appearance of the Lim1 positive cells. Extending the follistatin exposure of the HC retinal progenitor cells by injection of follistatin at E3 increased the number of both Lim1- and Isl1 positive HCs when analysed at E9. CONCLUSION The results imply that the axon-bearing and axon-less HC subgroups are defined early and are generated consecutively from a retinal progenitor cell population that is sensitive to the inhibitory action of follistatin. The results are consistent with a model wherein added follistatin causes HC-generating progenitors to proliferate beyond the normal period of HC generation, thus producing extra HCs of both types that migrate to the HC layer.
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Affiliation(s)
- Per-Henrik D Edqvist
- Department of Neuroscience, Unit of Developmental Neuroscience, Biomedical Centre, Uppsala University, S-751 23, Uppsala, Sweden
| | - Madelen Lek
- Department of Neuroscience, Unit of Developmental Neuroscience, Biomedical Centre, Uppsala University, S-751 23, Uppsala, Sweden
| | - Henrik Boije
- Department of Neuroscience, Unit of Developmental Neuroscience, Biomedical Centre, Uppsala University, S-751 23, Uppsala, Sweden
| | - Sarah M Lindbäck
- Department of Neuroscience, Unit of Developmental Neuroscience, Biomedical Centre, Uppsala University, S-751 23, Uppsala, Sweden
| | - Finn Hallböök
- Department of Neuroscience, Unit of Developmental Neuroscience, Biomedical Centre, Uppsala University, S-751 23, Uppsala, Sweden
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Abstract
In the vertebrate retina, stem cells with prolonged proliferative capacities reside in the most peripheral region, the ciliary marginal zone (CMZ), and they persist even after the functional eye has formed. These stem cells contribute to the formation of the retinal structures during the postnatal period in vivo, or can expand as neurospheres in vitro. Despite the wealth of anatomical descriptions of the characteristics of CMZ cells, molecular mechanisms for their specification or maintenance have long been uncharacterized. Recent studies provide evidence that certain secreted signaling molecules act as key regulators at multiple steps during these processes. In this review, we discuss the molecular basis for the regulation of retinal stem cells and their related cell types, especially focusing on the role of Wnt signaling.
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Affiliation(s)
- Fumi Kubo
- RIKEN Frontier Research System, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
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105
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Vsx2/Chx10 ensures the correct timing and magnitude of Hedgehog signaling in the mouse retina. Dev Biol 2008; 317:560-75. [PMID: 18417110 DOI: 10.1016/j.ydbio.2008.02.055] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2007] [Revised: 02/07/2008] [Accepted: 02/29/2008] [Indexed: 12/27/2022]
Abstract
Vertebrate retinal progenitor cells (RPCs) undergo a robust proliferative expansion to produce enough cells for the retina to form appropriately. Vsx2 (formerly Chx10), a homeodomain protein expressed in RPCs, is required for sufficient proliferation to occur. Sonic Hedgehog protein (SHH), secreted by retinal ganglion cells (RGCs), activates Hedgehog (Hh) signaling in RPCs and is also required for sufficient proliferation to occur. Therefore, we sought to determine if reduced Hh signaling is a contributing factor to the proliferation changes that occur in the absence of Vsx2. To do this, we examined Shh expression and Hh signaling activity in the homozygous ocular retardation J (orJ) mouse, which harbors a recessive null allele in the Vsx2 gene. We found that Shh expression and Hh signaling activity are delayed during early retinal development in orJ mice and this correlates with a delay in the onset of RGC differentiation. At birth, reduced expression of genes regulated by Hh signaling was observed despite the production of SHH ligand. orJ RPCs respond to pre-processed recombinant SHH ligand (SHH-N) in explant culture as evidenced by increased proliferation and expression of Hh target genes. Interestingly, proliferation in the orJ retina is further inhibited by cyclopamine, an antagonist of Hh signaling. Our results suggest that reduced Hh signaling contributes to the reduced level of RPC proliferation in the orJ retina, thereby revealing a role for Vsx2 in mediating mitogen signaling.
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106
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Okamoto M, Tomonari S, Naito Y, Saigo K, Noji S, Ui-Tei K, Ohuchi H. Introduction of silencing-inducing transgene against Fgf19 does not affect expression of Tbx5 and beta3-tubulin in the developing chicken retina. Dev Growth Differ 2008; 50:159-68. [PMID: 18312426 DOI: 10.1111/j.1440-169x.2008.00996.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Fgf19 is known to be expressed in the developing chicken eye but its functions during retinal development have remained elusive. Since Fgf19 is expressed in the dorsal portion of the optic cup, it is intriguing to know whether FGF19 is required for expression of dorso-ventral morphogenetic genes in the eye. To clarify this, expression patterns of Tbx5 and Vax were examined in the developing eye after in ovo RNA interference targeted against Fgf19. Quantitative polymerase chain reaction (PCR) analysis showed that the short-hairpin RNAs (shRNAs) targeted against Fgf19 could reduce its expression in the eye to less than 50% of a relative amount of mRNA, compared with contralateral or untreated control eyes. However, no obvious alteration in expression domains of Tbx5 or Vax was observed. Misexpression of Tbx5 or Tbx5-RNAi did not alter the Fgf19 expression either. Furthermore, although Fgf19 is expressed in the central retina before neurogenesis occurs, beta3-tubulin, a marker for early retinal differentiation was still detected in the central retina after knockdown of Fgf19. Thus, knockdown of Fgf19 supports no obvious regulations between Fgf19 and Tbx5, or exhibits no phenotypes that perturb early retinal differentiation.
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Affiliation(s)
- Mayumi Okamoto
- Department of Life Systems, Institute of Technology and Science, The University of Tokushima, 2-1 Minami-Josanjima-cho, Tokushima City 770-8506, Japan
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107
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Schulte D, Bumsted-O'Brien KM. Molecular mechanisms of vertebrate retina development: Implications for ganglion cell and photoreceptor patterning. Brain Res 2008; 1192:151-64. [PMID: 17553468 DOI: 10.1016/j.brainres.2007.04.079] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2007] [Revised: 04/05/2007] [Accepted: 04/20/2007] [Indexed: 12/20/2022]
Abstract
Although the neural retina appears as a relatively uniform tissue when viewed from its surface, it is in fact highly patterned along its anterior-posterior and dorso-ventral axes. The question of how and when such patterns arise has been the subject of intensive investigations over several decades. Most studies aimed at understanding retinal pattern formation have used the retinotectal map, the ordered projections of retinal ganglion cells to the brain, as a functional readout of the pattern. However, other cell types are also topographically organized in the retina. The most commonly recognized example of such a topographic cellular organization is the differential distribution of photoreceptor types across the retina. Photoreceptor patterns are highly species-specific and may represent an important adaptation to the visual niche a given species occupies. Nevertheless, few studies have addressed this functional readout of pattern to date and our understanding of its development has remained superficial. Here, we review recent advances in understanding the molecular cascades that control regionalization of the eye anlage, relate these findings to the development of photoreceptor patterns and discuss common and unique strategies involved in both aspects of retinal pattern formation.
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Affiliation(s)
- Dorothea Schulte
- Max Planck Institute for Brain Research, Department of Neuroanatomy, Deutschordenst. 46, D-60218 Frankfurt, Germany.
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108
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Yi H, Nakamura REI, Mohamed O, Dufort D, Hackam AS. Characterization of Wnt signaling during photoreceptor degeneration. Invest Ophthalmol Vis Sci 2008; 48:5733-41. [PMID: 18055826 DOI: 10.1167/iovs.07-0097] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
PURPOSE The Wnt pathway is an essential signaling cascade that regulates multiple processes in developing and adult tissues, including differentiation, cellular survival, and stem cell proliferation. The authors recently demonstrated altered expression of Wnt pathway genes during photoreceptor death in rd1 mice, suggesting an involvement for Wnt signaling in the disease process. In this study, the authors investigated the role of Wnt signaling in retinal degeneration. METHODS The Wnt signaling reporter mouse line Tcf-LacZ was crossed with retinal degeneration rd1 mice, and beta-galactosidase expression was used to localize Wnt signaling during photoreceptor death. To analyze the role of Wnt signaling activation, primary mixed retinal cultures were prepared, and XTT and TUNEL assays were used to quantify cell death. Luciferase reporter assays were used to measure Wnt signaling. RESULTS The canonical Wnt signaling pathway was activated in Müller glia and the ganglion cell layer during rod photoreceptor degeneration in rd1/Tcf-LacZ mice. Wnt signaling was confirmed in cultured primary Müller glia. Furthermore, Wnt signaling activators protected photoreceptors in primary retinal cultures from H(2)O(2)-induced oxidative stress. The Wnt ligands Wnt5a, Wnt5b, Wnt10a, and Wnt13 were expressed in the degenerating retina and are candidate Wnt signaling activators in vivo. CONCLUSIONS This study is the first demonstration that Wnt signaling is activated in the degenerating retina and that it protects retinal cultures from oxidative stress. These data suggest that Wnt signaling is a component of the glial protective response during photoreceptor injury. Therefore, inducing Wnt activation, alone or in combination with growth factors, may increase the threshold for apoptosis and halt or delay further photoreceptor degeneration.
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Affiliation(s)
- Hyun Yi
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, FL 33136, USA
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109
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Djojosubroto MW, Arsenijevic Y. Retinal stem cells: promising candidates for retina transplantation. Cell Tissue Res 2007; 331:347-57. [PMID: 17912553 DOI: 10.1007/s00441-007-0501-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2007] [Accepted: 08/29/2007] [Indexed: 12/12/2022]
Abstract
Stem cell transplantation is widely considered as a promising therapeutic approach for photoreceptor degeneration, one of the major causes of blindness. In this review, we focus on the biology of retinal stem cells (RSCs) and progenitor cells (RPCs) isolated from fetal, postnatal, and adult animals, with emphasis on those from rodents and humans. We discuss the origin of RSCs/RPCs, the markers expressed by these cells and the conditions for the isolation, culture, and differentiation of these cells in vitro or in vivo by induction with exogenous stimulation.
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Affiliation(s)
- Meta W Djojosubroto
- Unit of Gene Therapy & Stem Cell Biology, Jules-Gonin Eye Hospital, Ophthalmology Department, University of Lausanne, 15 Avenue de France, 1004, Lausanne, Switzerland
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110
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McGlinn AM, Baldwin DA, Tobias JW, Budak MT, Khurana TS, Stone RA. Form-deprivation myopia in chick induces limited changes in retinal gene expression. Invest Ophthalmol Vis Sci 2007; 48:3430-6. [PMID: 17652709 PMCID: PMC1983368 DOI: 10.1167/iovs.06-1538] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
PURPOSE Evidence has implicated the retina as a principal controller of refractive development. In the present study, the retinal transcriptome was analyzed to identify alterations in gene expression and potential signaling pathways involved in form-deprivation myopia of the chick. METHODS One-week-old white Leghorn chicks wore a unilateral image-degrading goggle for 6 hours or 3 days (n = 6 at each time). Total RNA from the retina/(retinal pigment epithelium) was used for expression profiling with chicken gene microarrays (Chicken GeneChips; Affymetrix, Santa Clara, CA). To identify gene expression level differences between goggled and contralateral nongoggled eyes, normalized microarray signal intensities were analyzed by the significance analysis of microarrays (SAM) approach. Differentially expressed genes were validated by real-time quantitative reverse transcription-polymerase chain reaction (qPCR) in independent biological replicates. RESULTS Small changes were detected in differentially expressed genes in form-deprived eyes. In chickens that had 6 hours of goggle wear, downregulation of bone morphogenetic protein 2 and connective tissue growth factor was validated. In those with 3 days of goggle wear, downregulation of bone morphogenetic protein 2, vasoactive intestinal peptide, preopro-urotensin II-related peptide and mitogen-activated protein kinase phosphatase 2 was validated, and upregulation of endothelin receptor type B and interleukin-18 was validated. CONCLUSIONS Form-deprivation myopia, in its early stages, is associated with only minimal changes in retinal gene expression at the level of the transcriptome. While the list of validated genes is short, each merits further study for potential involvement in the signaling cascade mediating myopia development.
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Affiliation(s)
- Alice M. McGlinn
- From the Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| | - Donald A. Baldwin
- From the Departments of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| | - John W. Tobias
- From the Department of the Bioinformatics Core, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
- From the Department of the Pennsylvania Muscle Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| | - Murat T. Budak
- From the Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| | - Tejvir S. Khurana
- From the Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| | - Richard A. Stone
- From the Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
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111
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Abstract
Progenitor and stem cell transplantation represent therapeutic strategies for retinal disorders that are accompanied by photoreceptor degeneration. The transplanted cells may either replace degenerating photoreceptors or secrete beneficial factors that halt the processes of photoreceptor degeneration. The present study analyzes whether rat retinal progenitor cells differentiated into photoreceptor phenotypic cells in neurospheres have a potential to interact with rat retinal explants. Immunocytochemistry for rhodopsin and synaptophysin indicated photoreceptor cell-like differentiation in neurospheres that were stimulated by basic fibroblast growth factor and epidermal growth factor. Differentiation into neural phenotypes including photoreceptor cells was effectively blocked by an addition of leukemia inhibitory factor. Grafting of neurospheres onto retinal explants demonstrated a consistent penetration of glial cell processes into the explanted tissue. On the other hand, the incorporation of donor cells into explants was very low. A general finding was that neurospheres grafting was associated with local decrease in Müller cell activation in the explants. Further characterization of these effect(s) could provide further insight into progenitor cell-based therapies of retinal degenerative disorders.
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112
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Harada T, Harada C, Parada LF. Molecular regulation of visual system development: more than meets the eye. Genes Dev 2007; 21:367-78. [PMID: 17322396 DOI: 10.1101/gad.1504307] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Vertebrate eye development has been an excellent model system to investigate basic concepts of developmental biology ranging from mechanisms of tissue induction to the complex patterning and bidimensional orientation of the highly specialized retina. Recent advances have shed light on the interplay between numerous transcriptional networks and growth factors that are involved in the specific stages of retinogenesis, optic nerve formation, and topographic mapping. In this review, we summarize this recent progress on the molecular mechanisms underlying the development of the eye, visual system, and embryonic tumors that arise in the optic system.
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Affiliation(s)
- Takayuki Harada
- Department of Developmental Biology, Kent Waldrep Foundation Center for Basic Neuroscience Research on Nerve Growth and Regeneration, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA
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113
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Hegde GV, James J, Das AV, Zhao X, Bhattacharya S, Ahmad I. Characterization of early retinal progenitor microenvironment: Presence of activities selective for the differentiation of retinal ganglion cells and maintenance of progenitors. Exp Eye Res 2007; 84:577-90. [PMID: 17227675 DOI: 10.1016/j.exer.2006.11.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2006] [Revised: 10/28/2006] [Accepted: 11/09/2006] [Indexed: 11/21/2022]
Abstract
The maintenance and differentiation of retinal progenitors take place in the context of the microenvironment in which they reside at a given time during retinal histogenesis. To understand the nature of the microenvironment in the developing retina, we have examined the influence of activities present during the early stage of retinal histogenesis on enriched retinal progenitors, using the neurosphere model. Early and late retinal progenitors, enriched as neurospheres from embryonic day 14 (E14) and E18 rat retina, respectively, were cultured in embryonic day 3 (E3) chick retinal conditioned medium, simulating the microenvironment present during early retinal histogenesis. Examination of the differentiation and proliferation of retinal progenitors revealed that the early microenvironment contains at least three regulatory activities, which are partitioned in different size fractions of the conditioned medium with different heat sensitivity. First, it is characterized by activities, present in heat stable <30 kDa fraction, that promote the differentiation of retinal ganglion cells (RGCs), the early born neurons. Second, it contains activities, present in heat-sensitive >30 kDa fraction, that regulate the number of early born neurons and maintain the pool of retinal progenitors. Third, it possesses activities, present in heat-sensitive <30 kDa fraction, that prevent the premature differentiation of early retinal progenitors into the late born neurons. Thus, our observations demonstrate the regulatory influence of microenvironment on the maintenance and differentiation of retinal progenitors and establish neurospheres as a viable model system for the examination of such influences.
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Affiliation(s)
- Ganapati V Hegde
- Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE 68198, USA
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114
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Ramunas J, Illman M, Kam A, Farn K, Kelly L, Morshead CM, Jervis EJ. True monolayer cell culture in a confined 3D microenvironment enables lineage informatics. Cytometry A 2007; 69:1202-11. [PMID: 17066473 DOI: 10.1002/cyto.a.20341] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
BACKGROUND There is a need for methods to (1) track cells continuously to generate lineage trees; (2) culture cells in in vivo-like microenvironments; and (3) measure many biological parameters simultaneously and noninvasively. Herein, we present a novel imaging culture chamber that facilitates "lineage informatics," a lineage-centric approach to cytomics. METHODS We cultured cells in a confined monolayer using a novel "gap chamber" that produces images with confocal-like qualities using standard DIC microscopy. Lineage and other cytometric data were semiautomatically extracted from image sets of neural stem and progenitor cells and analyzed using lineage informatics. RESULTS Cells imaged in the chamber every 3 min could be tracked for at least 6 generations allowing for the construction of extensive lineage trees with multiparameter data sets at hundreds of time points for each cell. The lineage informatics approach reveals relationships between lineage, phenotype, and microenvironment. Mass transfer characteristics and 3D geometry make the chamber more in vivo-like than traditional culture systems. CONCLUSIONS The gap chamber allows cells to be cultured, imaged, and tracked in true monolayers permitting detailed informatics analysis of cell lineage, phenotype, and fate determinants. The chamber is biomimetic and straightforward to build and use, and should find many applications in long-term cell imaging.
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Affiliation(s)
- John Ramunas
- Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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115
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Roger J, Goureau O, Sahel JA, Guillonneau X. Use of suppression subtractive hybridization to identify genes regulated by ciliary neurotrophic factor in postnatal retinal explants. Mol Vis 2007; 13:206-19. [PMID: 17327826 PMCID: PMC2610405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
PURPOSE The retinal progenitors are multipotential, and the decision taken by a progenitor to differentiate along a particular path depends on both cell-intrinsic and cell-extrinsic factors. Ciliary neurotrophic factor (CNTF), a member of the interleukin-6 (IL-6) family, added to rat postnatal retinal progenitors inhibits rod photoreceptor cell differentiation, promotes Müller glia genesis and enhances the expression of bipolar neuron markers. We hypothesized that those transcripts regulated during CNTF-influenced retinal differentiation may be involved in the choice of progenitor cell fate. Our aim was to isolate these genes, characterize their expression in the retina, and to subsequently focus on candidates that may promote photoreceptor cell differentiation. METHODS Retinas were cultured in vitro as explants at postnatal day 0 (P0) in the absence or presence of CNTF for six days. Transcripts regulated by CNTF after six days in vitro (DIV) were selected by subtraction suppressive hybridization (SSH) and cloned as two libraries. The UC6 and DC6 libraries contained those genes upregulated and downregulated, respectively, in the presence of CNTF at 6DIV. RESULTS In the first library, UC6, eight clones representing seven different genes were isolated as up-regulated by CNTF. In the DC6 library, 21 clones, representing 17 different genes appeared as down-regulated by CNTF. Genes were classified in six categories, such as protein modification, signal transduction, and regulation of transcription according to the Gene Ontology Annotation. CONCLUSIONS Among the 24 selected genes, our study revealed 11 genes (two upregulated and nine downregulated) potentially involved in CNTF biological effects.
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Affiliation(s)
- Jérôme Roger
- INSERM U592, Paris, France,Université Pierre et Marie Curie-Paris 6 UMR-S592, Paris, F-75012
| | - Olivier Goureau
- INSERM U592, Paris, France,Université Pierre et Marie Curie-Paris 6 UMR-S592, Paris, F-75012
| | - José-Alain Sahel
- INSERM U592, Paris, France,Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, Paris, France,Université Pierre et Marie Curie-Paris 6 UMR-S592, Paris, F-75012
| | - Xavier Guillonneau
- INSERM U592, Paris, France,Université Pierre et Marie Curie-Paris 6 UMR-S592, Paris, F-75012
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116
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Adler R, Canto-Soler MV. Molecular mechanisms of optic vesicle development: complexities, ambiguities and controversies. Dev Biol 2007; 305:1-13. [PMID: 17335797 PMCID: PMC1927083 DOI: 10.1016/j.ydbio.2007.01.045] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Revised: 01/26/2007] [Accepted: 01/30/2007] [Indexed: 12/31/2022]
Abstract
Optic vesicle formation, transformation into an optic cup and integration with neighboring tissues are essential for normal eye formation, and involve the coordinated occurrence of complex cellular and molecular events. Perhaps not surprisingly, these complex phenomena have provided fertile ground for controversial and even contradictory results and conclusions. After presenting an overview of current knowledge of optic vesicle development, we will address conceptual and methodological issues that complicate research in this field. This will be done through a review of the pertinent literature, as well as by drawing on our own experience, gathered through recent studies of both intra- and extra-cellular regulation of optic vesicle development and patterning. Finally, and without attempting to be exhaustive, we will point out some important aspects of optic vesicle development that have not yet received enough attention.
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Affiliation(s)
- Ruben Adler
- Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD 21287-9257, USA.
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117
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Bao ZZ. Intraretinal projection of retinal ganglion cell axons as a model system for studying axon navigation. Brain Res 2007; 1192:165-77. [PMID: 17320832 PMCID: PMC2267003 DOI: 10.1016/j.brainres.2007.01.116] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2006] [Revised: 01/24/2007] [Accepted: 01/26/2007] [Indexed: 01/19/2023]
Abstract
The initial step of retinal ganglion cell (RGC) axon pathfinding involves directed growth of RGC axons toward the center of the retina, the optic disc, a process termed "intraretinal guidance". Due to the accessibility of the system, and with various embryological, molecular and genetic approaches, significant progress has been made in recent years toward understanding the mechanisms involved in the precise guidance of the RGC axons. As axons are extending from RGCs located throughout the retina, a multitude of factors expressed along with the differentiation wave are important for the guidance of the RGC axons. To ensure that the RGC axons are oriented correctly, restricted to the optic fiber layer (OFL) of the retina, and exit the eye properly, different sets of positive and negative factors cooperate in the process. Fasciculation mediated by a number of cell adhesion molecules (CAMs) and modulation of axonal response to guidance factors provide additional mechanisms to ensure proper guidance of the RGC axons. The intraretinal axon guidance thus serves as an excellent model system for studying how different signals are regulated, modulated and integrated for guiding a large number of axons in three-dimensional space.
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Affiliation(s)
- Zheng-Zheng Bao
- Department of Medicine and Cell Biology, Program in Neuroscience, University of Massachusetts Medical School, Worcester, MA 01605, USA.
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118
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Bharti K, Nguyen MTT, Skuntz S, Bertuzzi S, Arnheiter H. The other pigment cell: specification and development of the pigmented epithelium of the vertebrate eye. ACTA ACUST UNITED AC 2006; 19:380-94. [PMID: 16965267 PMCID: PMC1564434 DOI: 10.1111/j.1600-0749.2006.00318.x] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Vertebrate retinal pigment epithelium (RPE) cells are derived from the multipotent optic neuroepithelium, develop in close proximity to the retina, and are indispensible for eye organogenesis and vision. Recent advances in our understanding of RPE development provide evidence for how critical signaling factors operating in dorso-ventral and distal-proximal gradients interact with key transcription factors to specify three distinct domains in the budding optic neuroepithelium: the distal future retina, the proximal future optic stalk/optic nerve, and the dorsal future RPE. Concomitantly with domain specification, the eye primordium progresses from a vesicle to a cup, RPE pigmentation extends towards the ventral side, and the future ciliary body and iris form from the margin zone between RPE and retina. While much has been learned about the molecular networks controlling RPE cell specification, key questions concerning the cell proliferative parameters in RPE and the subsequent morphogenetic events still need to be addressed in greater detail.
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Affiliation(s)
- Kapil Bharti
- Mammalian Development Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
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119
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Morcillo J, Martínez-Morales JR, Trousse F, Fermin Y, Sowden JC, Bovolenta P. Proper patterning of the optic fissure requires the sequential activity of BMP7 and SHH. Development 2006; 133:3179-90. [PMID: 16854970 DOI: 10.1242/dev.02493] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The optic disc develops at the interface between optic stalk and retina,and enables both the exit of visual fibres and the entrance of mesenchymal cells that will form the hyaloid artery. In spite of the importance of the optic disc for eye function, little is known about the mechanisms that control its development. Here, we show that in mouse embryos, retinal fissure precursors can be recognised by the expression of netrin 1 and the overlapping distribution of both optic stalk (Pax2, Vax1) and ventral neural retina markers (Vax2, Raldh3). We also show that in the absence of Bmp7, fissure formation is not initiated. This absence is associated with a reduced cell proliferation and apoptosis in the proximoventral quadrant of the optic cup, lack of the hyaloid artery, optic nerve aplasia, and intra-retinal misrouting of RGC axons. BMP7 addition to organotypic cultures of optic vesicles from Bmp7-/- embryos rescues Pax2 expression in the ventral region, while follistatin, a BMP7 antagonist, prevents it in early, but not in late, optic vesicle cultures from wild-type embryos. The presence of Pax2-positive cells in late optic cup is instead abolished by interfering with Shh signalling. Furthermore, SHH addition re-establishes Pax2 expression in late optic cups derived from ocular retardation (or) embryos, where optic disc development is impaired owing to the near absence of SHH-producing RGC. Collectively, these data indicate that BMP7 is required for retinal fissure formation and that its activity is needed, before SHH signalling, for the generation of PAX2-positive cells at the optic disc.
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Affiliation(s)
- Julian Morcillo
- Departamento de Neurobiología del Desarrollo, Instituto Cajal, CSIC, Dr Arce 37, Madrid 28002, Spain
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120
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Turner BA, Sparrow J, Cai B, Monroe J, Mikawa T, Hempstead BL. TrkB/BDNF signaling regulates photoreceptor progenitor cell fate decisions. Dev Biol 2006; 299:455-65. [PMID: 17005175 PMCID: PMC2623246 DOI: 10.1016/j.ydbio.2006.08.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Revised: 08/07/2006] [Accepted: 08/09/2006] [Indexed: 10/24/2022]
Abstract
Neurotrophins, via activation of Trk receptor tyrosine kinases, serve as mitogens, survival factors and regulators of arborization during retinal development. Brain-derived neurotrophic factor (BDNF) and TrkB regulate neuronal arborization and survival in late retinal development. However, TrkB is expressed during early retinal development where its functions are unclear. To assess TrkB/BDNF actions in the early chick retina, replication-incompetent retroviruses were utilized to over-express a dominant negative truncated form of TrkB (trunc TrkB), or BDNF and effects were assessed at E15. Clones expressing trunc TrkB were smaller than controls, and proliferation and apoptosis assays suggest that decreased clone size correlated with increased cell death when BDNF/TrkB signaling was impaired. Analysis of clonal composition revealed that trunc TrkB over-expression decreased photoreceptor numbers (41%) and increased cell numbers in the middle third of the inner nuclear layer (INL) (23%). Conversely, BDNF over-expression increased photoreceptor numbers (25%) and decreased INL numbers (17%). Photoreceptors over-expressing trunc TrkB demonstrated no increase in apoptosis nor abnormalities in lamination suggesting that TrkB activation is not required for photoreceptor cell survival or migration. These studies suggest that TrkB signaling regulates commitment to and/or differentiation of photoreceptor cells from retinal progenitor cells, identifying a novel role for TrkB/BDNF in regulating cell fate decisions.
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Affiliation(s)
- Brian A. Turner
- Department of Medicine, Weill Medical College of Cornell University, New York, New York, 10021
| | - Janet Sparrow
- Department of Ophthalmology, Columbia University, New York, New York, 10032
| | - Bolin Cai
- Department of Ophthalmology, Columbia University, New York, New York, 10032
| | - Julie Monroe
- Department of Medicine, Weill Medical College of Cornell University, New York, New York, 10021
| | - Takashi Mikawa
- Department of Cell Biology, Weill Medical College of Cornell University, New York, New York, 10021
| | - Barbara L. Hempstead
- Department of Medicine, Weill Medical College of Cornell University, New York, New York, 10021
- *Author to whom to address correspondence: Barbara L. Hempstead, Department of Medicine, Weill Medical College of Cornell University, 1300 York Avenue, Room C606, New York, New York, 10021, phone: 212-746-6215, fax: 212-746-8647,
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121
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Gulati-Leekha A, Goldman D. A reporter-assisted mutagenesis screen using α1-tubulin-GFP transgenic zebrafish uncovers missteps during neuronal development and axonogenesis. Dev Biol 2006; 296:29-47. [PMID: 16784739 DOI: 10.1016/j.ydbio.2006.03.024] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2005] [Revised: 03/07/2006] [Accepted: 03/20/2006] [Indexed: 12/30/2022]
Abstract
Alpha1-tubulin expression occurs in a neural-specific, temporally regulated, and regeneration-inducible fashion in zebrafish. A GFP reporter driven by the alpha1-tubulin promoter in transgenic zebrafish acts as a stable, in vivo molecular tag that follows neuronal development from birth/specification through postmitotic differentiation to axonal outgrowth and synaptogenesis. We exploited this transgenic system in a reporter expression-dependent (morphology-independent) mutagenesis screen to identify disruptions in genetic loci essential for neuronogenesis and axon elaboration, which would manifest as visually appreciable perturbations in GFP fluorescence. Thirty-two such recessive mutations were obtained, a subset of which was screened through a secondary RNA quantification-based assay to eliminate housekeeping gene defects. Three representative loci, when characterized in detail, were found to exhibit missteps in discrete, sequential stages of embryonic neuronal development. Mutation in sookshma panneurally diminishes the neural precursor pool by affecting cell proliferation in the developing embryo while patterning along the neuraxis remains unperturbed. Disruption of drishti on the other hand ameliorates the mitotic neural population by affecting cell cycle exit of progenitors and stalling their progression to the postmitotic neuronal stage, without impairing subsequent cell fate determination or differentiation. Finally, dhruva is required during neuronal differentiation for axonal branching and terminal innervation in spinal motoaxons and the retinotectal projection. Molecular identification of these loci and analysis of the remaining mutational repertoire will offer unique insights into the genetic inputs that go on to make a mature, differentiated neuron.
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Affiliation(s)
- Abhilasha Gulati-Leekha
- Molecular and Behavioral Neuroscience Institute, Department of Biological Chemistry, University of Michigan, 205 Zina Pitcher Place, Ann Arbor, MI 48109-070, USA
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122
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Le TT, Wroblewski E, Patel S, Riesenberg AN, Brown NL. Math5 is required for both early retinal neuron differentiation and cell cycle progression. Dev Biol 2006; 295:764-78. [PMID: 16690048 DOI: 10.1016/j.ydbio.2006.03.055] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2006] [Revised: 03/10/2006] [Accepted: 03/30/2006] [Indexed: 01/10/2023]
Abstract
CNS progenitors choose a fate, exit mitosis and differentiate. Basic helix-loop-helix (bHLH) transcription factors are key regulators of neurogenesis, but their molecular mechanisms remain unclear. In the mouse retina, removal of the bHLH factor Math5 (Atoh7) causes the loss of retinal ganglion cells (RGCs) and appearance of excess cone photoreceptors. Here, we show a simultaneous requirement for Math5 in retinal neuron formation and cell cycle progression. At embryonic day E11.5, Math5-/- cells are unable to assume the earliest fates, particularly that of an RGC, and instead adopt the last fate as Müller glia. Concurrently, the loss of Math5 causes mitotically active retinal progenitors to undergo aberrant cell cycles. The drastic fate shift of Math5-/- cells correlates with age-specific alterations in p27/Kip1 expression and an inability to become fully postmitotic. Finally, Math5 normally suppresses NeuroD1 within Math5-expressing cells and inhibits Ngn2 expression and cone photoreceptor genesis within separate cell populations. Thus, Math5 orchestrates neurogenesis in multiple ways, regulating both intrinsic and extrinsic processes.
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Affiliation(s)
- Tien T Le
- Division of Developmental Biology, Children's Hospital Research Foundation, Departments of Pediatrics and Ophthalmology University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229-7007, USA
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123
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Moreira EF, Adler R. Effects of follistatin overexpression on cell differentiation in the chick embryo retina. Dev Biol 2006; 298:272-84. [PMID: 16872597 DOI: 10.1016/j.ydbio.2006.06.035] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2006] [Revised: 06/21/2006] [Accepted: 06/22/2006] [Indexed: 11/19/2022]
Abstract
Although activin is expressed in the embryonic central nervous system (CNS), its possible functions in the regulation of CNS neuronal differentiation remain largely unknown. We have investigated this question in the retina, a well-characterized CNS structure previously shown to respond to activin in vitro, and to express activin subunits and receptors in vivo. RCAS retroviruses were used to overexpress in the chick retina in ovo either follistatin (FS), an activin-binding protein and inhibitor, or alkaline phosphatase (AP), as control. FS-treated retinas appeared normal until ED 8, when they showed a reduction of the inner plexiform layer, accompanied by a marked decrease in the frequency of amacrine cells. The territory lacking amacrine cells showed downregulation of transcription factors necessary for amacrine cell differentiation, such as Pax6 and AP2alpha, accompanied by ectopic expression of transcription factors associated with the development of horizontal or bipolar neurons, such as Prox1, Chx10 and NeuroM. Increases in cell death were also observed in FS-treated retinas. Taken together with previous in vitro studies, our results suggest that activin is a powerful regulator of neuronal differentiation in the central nervous system.
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Affiliation(s)
- Ernesto F Moreira
- Department of Opthalmology, The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21287-9257, USA
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124
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Li M, Sipe CW, Hoke K, August LL, Wright MA, Saha MS. The role of early lineage in GABAergic and glutamatergic cell fate determination in Xenopus laevis. J Comp Neurol 2006; 495:645-57. [PMID: 16506195 DOI: 10.1002/cne.20900] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Proper functioning of the adult nervous system is critically dependent on neurons adopting the correct neurotransmitter phenotype during early development. Whereas the importance of cell-cell communication in fate determination is well documented for a number of neurotransmitter phenotypes, the contributions made by early lineage to this process remain less clear. This is particularly true for gamma-aminobutyric acid (GABA)ergic and glutamatergic neurons, which are present as the most abundant inhibitory and excitatory neurons, respectively, in the central nervous system of all vertebrates. In the present study, we have investigated the role of early lineage in the determination of these two neurotransmitter phenotypes by constructing a fate map of GABAergic and glutamatergic neurons for the 32-cell stage Xenopus embryo with the goal of determining whether early lineage influences the acquisition of these two neurotransmitter phenotypes. To examine these phenotypes, we have cloned xGAT-1, a molecular marker for the GABAergic phenotype in Xenopus, and described its expression pattern over the course of development. Although we have identified isolated examples of a blastomere imparting a statistically significant bias, when taken together, our results suggest that blastomere lineage does not impart a widespread bias for subsequent GABAergic or glutamatergic fate determination. In addition, the fate map presented here suggests a general dorsal-anterior to ventral-posterior patterning progression of the nervous system for the 32-cell stage Xenopus embryo.
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Affiliation(s)
- Mei Li
- Department of Biology, College of William and Mary, Williamsburg, Virginia 23187, USA
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125
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Hashimoto T, Zhang XM, Yi-kuang Chen B, Yang XJ. VEGF activates divergent intracellular signaling components to regulate retinal progenitor cell proliferation and neuronal differentiation. Development 2006; 133:2201-10. [PMID: 16672338 PMCID: PMC7060787 DOI: 10.1242/dev.02385] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
During vertebrate neurogenesis, multiple extracellular signals influence progenitor cell fate choices. The process by which uncommitted progenitor cells interpret and integrate signals is not well understood. We demonstrate here that in the avascular chicken retina, vascular endothelial growth factor (VEGF) secreted by postmitotic neurons acts through the FLK1 receptor present on progenitor cells to influence cell proliferation and commitment. Augmenting VEGF signals increases progenitor cell proliferation and decreases retinal ganglion cell genesis. Conversely, absorbing endogenous VEGF ligand or disrupting FLK1 activity attenuates cell proliferation and enhances retinal ganglion cell production. In addition, we provide evidence that VEGF signals transmitted by the FLK1 receptor activate divergent intracellular signaling components, which regulate different responses of progenitor cells. VEGF-induced proliferation is influenced by the MEK-ERK pathway, as well as by the basic helix-loop-helix factor HES1. By contrast, VEGF-dependent ganglion cell suppression does not require MEK-ERK activation, but instead relies on VEGF-stimulated HES1 activity, which is independent of NOTCH signaling. Moreover, elevated HES1 expression promotes progenitor cell proliferation and prevents overproduction of retinal ganglion cells owing to the loss of VEGF or sonic hedgehog (SHH), another signal that suppresses ganglion cell development. Based on previous and current findings, we propose that HES1 serves as a convergent signaling node within early retinal progenitor cells to integrate various cell-extrinsic cues, including VEGF and SHH, in order to control cell proliferation and neuronal specification.
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Affiliation(s)
- Takao Hashimoto
- Jules Stein Eye Institute and Department of Ophthalmology, Molecular Biology Institute, University of California, David Geffen School of Medicine, 100 Stein Plaza Los Angeles, CA 90095, USA
| | - Xiang-Mei Zhang
- Jules Stein Eye Institute and Department of Ophthalmology, Molecular Biology Institute, University of California, David Geffen School of Medicine, 100 Stein Plaza Los Angeles, CA 90095, USA
| | | | - Xian-Jie Yang
- Jules Stein Eye Institute and Department of Ophthalmology, Molecular Biology Institute, University of California, David Geffen School of Medicine, 100 Stein Plaza Los Angeles, CA 90095, USA
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126
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Lupo G, Harris WA, Lewis KE. Mechanisms of ventral patterning in the vertebrate nervous system. Nat Rev Neurosci 2006; 7:103-14. [PMID: 16429120 DOI: 10.1038/nrn1843] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Dorsoventral patterning of the neural tube has a crucial role in shaping the functional organization of the CNS. It is well established that hedgehog signalling plays a key role in specifying ventral cell types throughout the neuroectoderm, and major progress has been made in elucidating how hedgehog signalling works in this ventral specification. In addition, other molecular pathways, including nodal, retinoic acid and fibroblast growth factor signalling, have been identified as important molecular cues for ventral patterning of the spinal cord, telencephalon and eye. Here, we discuss recent advances in this field, highlighting the emerging interplay of these signalling pathways in the molecular specification of ventral patterning at different rostrocaudal levels of the CNS.
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Affiliation(s)
- Giuseppe Lupo
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
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127
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Dinet V, Girard-Naud N, Voisin P, Bernard M. Melatoninergic differentiation of retinal photoreceptors: activation of the chicken hydroxyindole-O-methyltransferase promoter requires a homeodomain-binding element that interacts with Otx2. Exp Eye Res 2006; 83:276-90. [PMID: 16563383 DOI: 10.1016/j.exer.2005.12.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2005] [Revised: 12/06/2005] [Accepted: 12/13/2005] [Indexed: 11/28/2022]
Abstract
The gene encoding the last enzyme of the melatonin-synthesis pathway, hydroxyindole-O-methyltransferase (HIOMT), is selectively expressed in retinal photoreceptors and pineal cells. Here, we analysed the promoter of the chicken HIOMT gene and we found that a homeodomain-binding element located in the proximal region of this promoter was essential for its activation in primary cultures of embryonic chicken retinal cells. This homeodomain-regulatory element interacted with a protein expressed in the chicken retina and pineal gland, which was recognized by an anti-Otx2 antiserum. Recombinant Otx2 expressed in vitro was able to bind this DNA element and to directly transactivate the chicken HIOMT promoter. This promoter was also transactivated by another member of the Otx family, Otx5, but the amplitude of stimulation was lower than with Otx2. The spatio-temporal pattern of Otx2 expression was compatible with a possible role of this transcription factor in HIOMT gene activation. In adult chicken, Otx2 mRNA was found to be present in those two tissues that express HIOMT: the retina and the pineal gland. During development, a burst of Otx2 mRNA closely matched the timing of HIOMT gene activation in these two tissues. In the pineal, Otx2 immunolabelling was specifically localized in the nuclei of photoreceptor cells. In the neural retina, Otx2 immunoreactivity brightly decorated the photoreceptor nuclei and extended more faintly to the outer half of the inner nuclear layer. Together, the data support a role of Otx2 in the onset of HIOMT expression in developing chicken photoreceptors.
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Affiliation(s)
- Virginie Dinet
- Institut de Physiologie et Biologie Cellulaires, UMR CNRS 6187, Neurobiologie Cellulaire, 40 avenue du Recteur Pineau, 86022 Poitiers Cedex, France
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128
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Esteve P, Bovolenta P. Secreted inducers in vertebrate eye development: more functions for old morphogens. Curr Opin Neurobiol 2006; 16:13-9. [PMID: 16413771 DOI: 10.1016/j.conb.2006.01.001] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Accepted: 01/04/2006] [Indexed: 02/04/2023]
Abstract
Cell signaling molecules secreted from strategically localized positions coordinate cell behavior to enable progressive specification of embryonic tissues. These molecules converge on a few signaling pathways that are reiteratively used in different tissues at different times for generating cell type-specific patterns of gene expression. Although our current knowledge of the system is fragmentary, eye development seems to follow this general strategy. In line with this idea, recent studies have added new information on how Fgf and Wnt signaling participates in the formation of the eye field. In addition, later on in development, Fgf controls the onset of retinal neurogenesis and Shh and GDF11 control its feedback regulation.
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Affiliation(s)
- Pilar Esteve
- Departamento de Neurobiología del Desarrollo, Instituto Cajal, Consejo Superior de Investigaciones Cientificas, Doctor Arce 37, Madrid 28002, Spain
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129
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Abstract
Progress in the study of the molecular mechanisms that regulate neuronal differentiation has been quite impressive in recent years, and promises to continue to an equally fast pace. This should not lead us into a sense of complacency, however, because there are still significant barriers that cannot be overcome by simply conducting the same type of experiments that we have been performing thus far. This article will describe some of these challenges, while highlighting the conceptual and methodological breakthroughs that will be necessary to overcome them.
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Affiliation(s)
- Ruben Adler
- Department of Ophthalmology and Neuroscience The Johns Hopkins University School of Medicine Baltimore, MD 21287-9257, USA.
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130
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Picker A, Brand M. Fgf signals from a novel signaling center determine axial patterning of the prospective neural retina. Development 2005; 132:4951-62. [PMID: 16236770 DOI: 10.1242/dev.02071] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Axial eye patterning determines the positional code of retinal ganglion cells (RGCs), which is crucial for their topographic projection to the midbrain. Several asymmetrically expressed determinants of retinal patterning are known, but it is unclear how axial polarity is first established. We find that Fgf signals, including Fgf8, determine retinal patterning along the nasotemporal (NT) axis during early zebrafish embryogenesis: Fgf8 induces nasal and/or suppresses temporal retinal cell fates; and inhibition of all Fgf-receptor signaling leads to complete retinal temporalization and concomitant loss of all nasal fates. Misprojections of RGCs with Fgf-dependent alterations in retinal patterning to the midbrain demonstrate the importance of this early patterning process for late topographic map formation. The crucial period of Fgf-dependent patterning is at the onset of eye morphogenesis. Fgf8 expression, the restricted temporal requirement for Fgf-receptor signaling and target gene expression at this stage suggests that the telencephalic primordium is the source of Fgf8 and acts as novel signaling center for non-autonomous axial patterning of the prospective neural retina.
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Affiliation(s)
- Alexander Picker
- University of Technology, Department of Genetics, c/o Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauer Strasse 108, 01307 Dresden, Germany.
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131
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Yamaguchi M, Tonou-Fujimori N, Komori A, Maeda R, Nojima Y, Li H, Okamoto H, Masai I. Histone deacetylase 1 regulates retinal neurogenesis in zebrafish by suppressing Wnt and Notch signaling pathways. Development 2005; 132:3027-43. [PMID: 15944187 DOI: 10.1242/dev.01881] [Citation(s) in RCA: 174] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In the developing vertebrate retina, progenitor cells initially proliferate but begin to produce postmitotic neurons when neuronal differentiation occurs. However, the mechanism that determines whether retinal progenitor cells continue to proliferate or exit from the cell cycle and differentiate is largely unknown. Here, we report that histone deacetylase 1 (Hdac1) is required for the switch from proliferation to differentiation in the zebrafish retina. We isolated a zebrafish mutant, ascending and descending (add), in which retinal cells fail to differentiate into neurons and glial cells but instead continue to proliferate. The cloning of the add gene revealed that it encodes Hdac1. Furthermore, the ratio of the number of differentiating cells to that of proliferating cells increases in proportion to Hdac activity, suggesting that Hdac proteins regulate a crucial step of retinal neurogenesis in zebrafish. Canonical Wnt signaling promotes the proliferation of retinal cells in zebrafish, and Notch signaling inhibits neuronal differentiation through the activation of a neurogenic inhibitor, Hairy/Enhancer-of-split (Hes). We found that both the Wnt and Notch/Hes pathways are activated in the add mutant retina. The cell-cycle progression and the upregulation of Hes expression in the add mutant retina can be inhibited by the blockade of Wnt and Notch signaling, respectively. These data suggest that Hdac1 antagonizes these pathways to promote cell-cycle exit and the subsequent neurogenesis in zebrafish retina. Taken together, these data suggest that Hdac1 functions as a dual switch that suppresses both cell-cycle progression and inhibition of neurogenesis in the zebrafish retina.
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Affiliation(s)
- Masahiro Yamaguchi
- Masai Initiative Research Unit, RIKEN (The Institute of Physical and Chemical Research
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132
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Goureau O, Rhee KD, Yang XJ. Ciliary neurotrophic factor promotes muller glia differentiation from the postnatal retinal progenitor pool. Dev Neurosci 2005; 26:359-70. [PMID: 15855765 PMCID: PMC7050730 DOI: 10.1159/000082278] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2004] [Accepted: 06/23/2004] [Indexed: 12/20/2022] Open
Abstract
Ciliary neurotrophic factor (CNTF) exhibits multiple biological effects during vertebrate retinal development, including regulating the differentiation of photoreceptor cells and promoting the survival and axonal growth of ganglion cells. We report here that in addition to affecting the differentiation of retinal neurons, CNTF also promotes Muller glia genesis in the postnatal mouse retina. In both retinal monolayer and explant cultures, CNTF increases the number of progenitor cells adopting the Muller cell fate. Exogenous CNTF induces phosphorylation of signal transducers and activators of transcription (STAT)3 and extracellular signal-regulated kinase (ERK) among neonatal progenitor cells and newborn Muller cells. In addition, increased levels of endogenous STAT3 and ERK phosphorylation have been observed at around postnatal day 5, coinciding with the peak of Muller glia genesis. Perturbation of STAT and ERK signaling using protein kinase inhibitors and a dominant-negative STAT3 mutant demonstrates that both CNTF-induced STAT and ERK activation are involved in promoting Muller cell production. Moreover, absorbing epidermal growth factor (EGF) signals with a neutralizing antibody did not affect CNTF-induced Muller glial genesis, indicating that the effect of CNTF is not mediated by the known Muller-enhancing activity of EGF. Together, these results support a novel function of CNTF-like cytokines in retinal gliogenesis.
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Affiliation(s)
- Olivier Goureau
- Laboratoire de Physiopathologie Cellulaire et Moléculaire de la Rétine, INSERM U592, Hôpital Saint-Antoine, Paris, France
| | - Kun Do Rhee
- Department of Ophthalmology, Jules Stein Eye Institute, David Geffen School of Medicine, Molecular Biology Institute, University of California, Los Angeles, Calif., USA
| | - Xian-Jie Yang
- Department of Ophthalmology, Jules Stein Eye Institute, David Geffen School of Medicine, Molecular Biology Institute, University of California, Los Angeles, Calif., USA
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Lupo G, Liu Y, Qiu R, Chandraratna RAS, Barsacchi G, He RQ, Harris WA. Dorsoventral patterning of the Xenopus eye: a collaboration of Retinoid, Hedgehog and FGF receptor signaling. Development 2005; 132:1737-48. [PMID: 15753216 DOI: 10.1242/dev.01726] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
In the developing spinal cord and telencephalon, ventral patterning involves the interplay of Hedgehog (Hh), Retinoic Acid (RA) and Fibroblast Growth Factor (FGF) signaling. In the eye, ventral specification involves Hh signaling, but the roles of RA and FGF signaling are less clear. By overexpression assays in Xenopus embryos, we found that both RA and FGF receptor (FGFR) signaling ventralize the eye, by expanding optic stalk and ventral retina, and repressing dorsal retina character. Co-overexpression experiments show that RA and FGFR can collaborate with Hh signaling and reinforce its ventralizing activity. In loss-of-function experiments, a strong eye dorsalization was observed after triple inhibition of Hh, RA and FGFR signaling, while weaker effects were obtained by inhibiting only one or two of these pathways. These results suggest that the ventral regionalization of the eye is specified by interactions of Hh, RA and FGFR signaling. We argue that similar mechanisms might control ventral neural patterning throughout the central nervous system.
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Affiliation(s)
- Giuseppe Lupo
- Department of Anatomy, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
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Masai I, Yamaguchi M, Tonou-Fujimori N, Komori A, Okamoto H. The hedgehog-PKA pathway regulates two distinct steps of the differentiation of retinal ganglion cells: the cell-cycle exit of retinoblasts and their neuronal maturation. Development 2005; 132:1539-53. [PMID: 15728672 DOI: 10.1242/dev.01714] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In the developing zebrafish retina, neurogenesis is initiated in cells adjacent to the optic stalk and progresses to the entire neural retina. It has been reported that hedgehog (Hh) signalling mediates the progression of the differentiation of retinal ganglion cells (RGCs) in zebrafish. However, the progression of neurogenesis seems to be only mildly delayed by genetic or chemical blockade of the Hh signalling pathway. Here, we show that cAMP-dependent protein kinase (PKA) effectively inhibits the progression of retinal neurogenesis in zebrafish. Almost all retinal cells continue to proliferate when PKA is activated, suggesting that PKA inhibits the cell-cycle exit of retinoblasts. A cyclin-dependent kinase (cdk) inhibitor p27 inhibits the PKA-induced proliferation, suggesting that PKA functions upstream of cyclins and cdk inhibitors. Activation of the Wnt signalling pathway induces the hyperproliferation of retinal cells in zebrafish. The blockade of Wnt signalling inhibits the PKA-induced proliferation, but the activation of Wnt signalling promotes proliferation even in the absence of PKA activity. These observations suggest that PKA inhibits exit from the Wnt-mediated cell cycle rather than stimulates Wnt-mediated cell-cycle progression. PKA is an inhibitor of Hh signalling, and Hh signalling molecule morphants show severe defects in cell-cycle exit of retinoblasts. Together, these data suggest that Hh acts as a short-range signal to induce the cell-cycle exit of retinoblasts. The pulse inhibition of Hh signalling revealed that Hh signalling regulates at least two distinct steps of RGC differentiation: the cell-cycle exit of retinoblasts and RGC maturation. This dual requirement of Hh signalling in RGC differentiation implies that the regulation of a neurogenic wave is more complex in the zebrafish retina than in the Drosophila eye.
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Affiliation(s)
- Ichiro Masai
- Masai Initiative Research Unit, RIKEN (The Institute of Physical and Chemical Research, Hirosawa, Saitama, Japan.
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135
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Rhee KD, Goureau O, Chen S, Yang XJ. Cytokine-induced activation of signal transducer and activator of transcription in photoreceptor precursors regulates rod differentiation in the developing mouse retina. J Neurosci 2004; 24:9779-88. [PMID: 15525763 PMCID: PMC6730236 DOI: 10.1523/jneurosci.1785-04.2004] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2004] [Revised: 09/17/2004] [Accepted: 09/18/2004] [Indexed: 11/21/2022] Open
Abstract
Ciliary neurotrophic factor (CNTF) exhibits multiple biological effects during vertebrate retinogenesis, including regulation of photoreceptor cell differentiation. In the early postnatal mouse retina, CNTF induces rapid and transient phosphorylation of signal transducer and activator of transcription (STAT) 1 and STAT3 and the extracellular signal-regulated kinase (ERK). Although both proliferating progenitor cells and postmitotic neurons respond directly to cytokine signals, CNTF elicits distinct phosphorylation patterns of STAT3 and ERK. CNTF stimulation induces low levels of STAT3 phosphorylation in progenitors and differentiated neurons but a robust STAT3 activation among postmitotic photoreceptor precursors expressing the cone-rod homeobox gene Crx and newly differentiated rod photoreceptors. In contrast, CNTF causes preferential phosphorylation of ERK in progenitor cells and photoreceptor precursors. Inhibition of the cytokine receptor gp130 using neutralizing antibodies reveals that gp130 is required for both CNTF-induced STAT3 and ERK phosphorylation. Perturbation of STAT signaling by a STAT inhibitor peptide or a dominant-negative STAT3 mutant causes enhanced production of rod photoreceptors in the absence of exogenous cytokines, whereas inhibiting ERK activation by a MEK (mitogen-activated protein kinase kinase)-specific inhibitor has no effect on rod photoreceptor differentiation in vitro. Furthermore, disrupting the function of epidermal growth factor (EGF) receptors, which modulate rod development in vivo, indicates that the EGF family of ligands does not mediate the inhibitory effect of cytokine on rod differentiation. These results demonstrate that cytokine signal transduction is dynamic and heterogeneous in the developing retina, and that endogenous ligand-induced STAT activation in retinal progenitor and/or photoreceptor precursor cells plays an important role in regulating photoreceptor development.
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Affiliation(s)
- Kun Do Rhee
- Department of Ophthalmology, Jules Stein Eye Institute, David Geffen School of Medicine, Molecular Biology Institute, University of California, Los Angeles, California 90095, USA
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