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Bassett EA, Tokarew N, Allemano EA, Mazerolle C, Morin K, Mears AJ, McNeill B, Ringuette R, Campbell C, Smiley S, Pokrajac NT, Dubuc AM, Ramaswamy V, Northcott PA, Remke M, Monnier PP, Potter D, Paes K, Kirkpatrick LL, Coker KJ, Rice DS, Perez-Iratxeta C, Taylor MD, Wallace VA. Norrin/Frizzled4 signalling in the preneoplastic niche blocks medulloblastoma initiation. eLife 2016; 5. [PMID: 27823583 PMCID: PMC5100999 DOI: 10.7554/elife.16764] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 10/07/2016] [Indexed: 12/25/2022] Open
Abstract
The tumor microenvironment is a critical modulator of carcinogenesis; however, in many tumor types, the influence of the stroma during preneoplastic stages is unknown. Here we explored the relationship between pre-tumor cells and their surrounding stroma in malignant progression of the cerebellar tumor medulloblastoma (MB). We show that activation of the vascular regulatory signalling axis mediated by Norrin (an atypical Wnt)/Frizzled4 (Fzd4) inhibits MB initiation in the Ptch+/− mouse model. Loss of Norrin/Fzd4-mediated signalling in endothelial cells, either genetically or by short-term blockade, increases the frequency of pre-tumor lesions and creates a tumor-permissive microenvironment at the earliest, preneoplastic stages of MB. This pro-tumor stroma, characterized by angiogenic remodelling, is associated with an accelerated transition from preneoplasia to malignancy. These data expose a stromal component that regulates the earliest stages of tumorigenesis in the cerebellum, and a novel role for the Norrin/Fzd4 axis as an endogenous anti-tumor signal in the preneoplastic niche. DOI:http://dx.doi.org/10.7554/eLife.16764.001
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Affiliation(s)
- Erin A Bassett
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada
| | - Nicholas Tokarew
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada.,Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada
| | - Ema A Allemano
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada
| | - Chantal Mazerolle
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada
| | - Katy Morin
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada
| | - Alan J Mears
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada
| | - Brian McNeill
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada
| | - Randy Ringuette
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada.,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Canada
| | - Charles Campbell
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada.,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Canada
| | - Sheila Smiley
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada
| | - Neno T Pokrajac
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.,Donald K. Johnson Eye Institute, Krembil Research Institute, University Health Network, Toronto, Canada
| | - Adrian M Dubuc
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.,Developmental and Stem Cell Biology Program, Arthur and Sonia Labatt Brain Tumor Research Centre, The Hospital for Sick Children, Toronto, Canada
| | - Vijay Ramaswamy
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.,Developmental and Stem Cell Biology Program, Arthur and Sonia Labatt Brain Tumor Research Centre, The Hospital for Sick Children, Toronto, Canada.,Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Canada.,Division of Haematology/Oncology, The Hospital for Sick Children, Toronto, Canada
| | - Paul A Northcott
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.,Developmental and Stem Cell Biology Program, Arthur and Sonia Labatt Brain Tumor Research Centre, The Hospital for Sick Children, Toronto, Canada
| | - Marc Remke
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.,Developmental and Stem Cell Biology Program, Arthur and Sonia Labatt Brain Tumor Research Centre, The Hospital for Sick Children, Toronto, Canada
| | - Philippe P Monnier
- Genetics and Development Division, Krembil Research Institute, University Health Network, Toronto, Canada.,Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Canada
| | - David Potter
- Department of Ophthalmology, Lexicon Pharmaceuticals Inc., The Woodlands, United States
| | - Kim Paes
- Department of Ophthalmology, Lexicon Pharmaceuticals Inc., The Woodlands, United States
| | - Laura L Kirkpatrick
- Department of Ophthalmology, Lexicon Pharmaceuticals Inc., The Woodlands, United States
| | - Kenneth J Coker
- Department of Ophthalmology, Lexicon Pharmaceuticals Inc., The Woodlands, United States
| | - Dennis S Rice
- Department of Ophthalmology, Lexicon Pharmaceuticals Inc., The Woodlands, United States
| | - Carol Perez-Iratxeta
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada.,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Canada
| | - Michael D Taylor
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.,Developmental and Stem Cell Biology Program, Arthur and Sonia Labatt Brain Tumor Research Centre, The Hospital for Sick Children, Toronto, Canada.,Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Canada
| | - Valerie A Wallace
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Canada.,Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada.,Donald K. Johnson Eye Institute, Krembil Research Institute, University Health Network, Toronto, Canada.,Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Canada
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Campbell C, Beug S, Nickerson PEB, Peng J, Mazerolle C, Bassett EA, Ringuette R, Jama FA, Morales C, Christ A, Wallace VA. Sortilin regulates sorting and secretion of Sonic hedgehog. Development 2016. [DOI: 10.1242/dev.145870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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3
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Campbell C, Beug S, Nickerson PEB, Peng J, Mazerolle C, Bassett EA, Ringuette R, Jama FA, Morales C, Christ A, Wallace VA. Sortilin regulates sorting and secretion of Sonic hedgehog. J Cell Sci 2016; 129:3832-3844. [PMID: 27632999 DOI: 10.1242/jcs.183541] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 08/26/2016] [Indexed: 01/03/2023] Open
Abstract
Sonic Hedgehog (Shh) is a secreted morphogen that is an essential regulator of patterning and growth. The Shh full-length protein undergoes autocleavage in the endoplasmic reticulum to generate the biologically active N-terminal fragment (ShhN), which is destined for secretion. We identified sortilin (Sort1), a member of the VPS10P-domain receptor family, as a new Shh trafficking receptor. We demonstrate that Sort-Shh interact by performing coimmunoprecipitation and proximity ligation assays in transfected cells and that they colocalize at the Golgi. Sort1 overexpression causes re-distribution of ShhN and, to a lesser extent, of full-length Shh to the Golgi and reduces Shh secretion. We show loss of Sort1 can partially rescue Hedgehog-associated patterning defects in a mouse model that is deficient in Shh processing, and we show that Sort1 levels negatively regulate anterograde Shh transport in axons in vitro and Hedgehog-dependent axon-glial interactions in vivo Taken together, we conclude that Shh and Sort1 can interact at the level of the Golgi and that Sort1 directs Shh away from the pathways that promote its secretion.
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Affiliation(s)
- Charles Campbell
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario, Canada K1H 8L6 Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, Canada K1H 8M5
| | - Shawn Beug
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario, Canada K1H 8L6 Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, Canada K1H 8M5
| | - Philip E B Nickerson
- Vision Science Division, Krembil Research Institute, University Health Network and Department of Ophthalmology and Vision Sciences, University of Toronto, 60 Leonard Street, Toronto ON M5T 2S8
| | - Jimmy Peng
- Department of Biology, McGill University, 1205 Ave Docteur Penfield Room W4/8, Montreal, Quebec, Canada H3A 1B1 Institut de recherches cliniques de Montréal (IRCM), 110 Avenue des Pins Ouest, Montréal, Quebec, Canada H2W 1R7
| | - Chantal Mazerolle
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario, Canada K1H 8L6
| | - Erin A Bassett
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario, Canada K1H 8L6
| | - Randy Ringuette
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario, Canada K1H 8L6 Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, Canada K1H 8M5
| | - Fadumo A Jama
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario, Canada K1H 8L6 Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, Canada K1H 8M5
| | - Carlos Morales
- Department of Anatomy and Cell Biology, McGill University, 3640 Rue University, Montréal, Quebec, Canada H3A 0C7
| | - Annabel Christ
- Max-Delbrück-Center for Molecular Medicine, Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Valerie A Wallace
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario, Canada K1H 8L6 Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, Canada K1H 8M5 Vision Science Division, Krembil Research Institute, University Health Network and Department of Ophthalmology and Vision Sciences, University of Toronto, 60 Leonard Street, Toronto ON M5T 2S8
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Ringuette R, Atkins M, Lagali PS, Bassett EA, Campbell C, Mazerolle C, Mears AJ, Picketts DJ, Wallace VA. A Notch-Gli2 axis sustains Hedgehog responsiveness of neural progenitors and Müller glia. Dev Biol 2016; 411:85-100. [PMID: 26795056 DOI: 10.1016/j.ydbio.2016.01.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 01/05/2016] [Accepted: 01/11/2016] [Indexed: 11/18/2022]
Abstract
Neurogenesis is regulated by the dynamic and coordinated activity of several extracellular signalling pathways, but the basis for crosstalk between these pathways remains poorly understood. Here we investigated regulatory interactions between two pathways that are each required for neural progenitor cell maintenance in the postnatal retina; Hedgehog (Hh) and Notch signalling. Both pathways are activated in progenitor cells in the postnatal retina based on the co-expression of fluorescent pathway reporter transgenes at the single cell level. Disrupting Notch signalling, genetically or pharmacologically, induces a rapid downregulation of all three Gli proteins and inhibits Hh-induced proliferation. Ectopic Notch activation, while not sufficient to promote Hh signalling or proliferation, increases Gli2 protein. We show that Notch regulation of Gli2 in Müller glia renders these cells competent to proliferate in response to Hh. These data suggest that Notch signalling converges on Gli2 to prime postnatal retinal progenitor cells and Müller glia to proliferate in response to Hh.
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Affiliation(s)
- Randy Ringuette
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada K1H 8L6; Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5
| | - Michael Atkins
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada K1H 8L6
| | - Pamela S Lagali
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada K1H 8L6
| | - Erin A Bassett
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada K1H 8L6
| | - Charles Campbell
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada K1H 8L6; Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5
| | - Chantal Mazerolle
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada K1H 8L6
| | - Alan J Mears
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada K1H 8L6
| | - David J Picketts
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada K1H 8L6; Department of Biochemistry, Microbiology and Immunology, Department of Ophthalmology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5
| | - Valerie A Wallace
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada K1H 8L6; Department of Biochemistry, Microbiology and Immunology, Department of Ophthalmology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5; Vision Research Division, Krembil Research Institute, University Health Network and Department of Ophthalmology and Vision Science, University of Toronto, Toronto, Ontario, Canada.
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McNeill B, Mazerolle C, Bassett EA, Mears AJ, Ringuette R, Lagali P, Picketts DJ, Paes K, Rice D, Wallace VA. Hedgehog regulates Norrie disease protein to drive neural progenitor self-renewal. Hum Mol Genet 2012. [PMID: 23201751 DOI: 10.1093/hmg/dds505] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Norrie disease (ND) is a congenital disorder characterized by retinal hypovascularization and cognitive delay. ND has been linked to mutations in 'Norrie Disease Protein' (Ndp), which encodes the secreted protein Norrin. Norrin functions as a secreted angiogenic factor, although its role in neural development has not been assessed. Here, we show that Ndp expression is initiated in retinal progenitors in response to Hedgehog (Hh) signaling, which induces Gli2 binding to the Ndp promoter. Using a combination of genetic epistasis and acute RNAi-knockdown approaches, we show that Ndp is required downstream of Hh activation to induce retinal progenitor proliferation in the retina. Strikingly, Ndp regulates the rate of cell-cycle re-entry and not cell-cycle kinetics, thereby uncoupling the self-renewal and cell-cycle progression functions of Hh. Taken together, we have uncovered a cell autonomous function for Ndp in retinal progenitor proliferation that is independent of its function in the retinal vasculature, which could explain the neural defects associated with ND.
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Affiliation(s)
- Brian McNeill
- Vision Program, Ottawa Hospital Research Institute, Ottawa, Ont. K1H 8L6, Canada
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6
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Haque ME, Mount MP, Safarpour F, Abdel-Messih E, Callaghan S, Mazerolle C, Kitada T, Slack RS, Wallace V, Shen J, Anisman H, Park DS. Inactivation of Pink1 gene in vivo sensitizes dopamine-producing neurons to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and can be rescued by autosomal recessive Parkinson disease genes, Parkin or DJ-1. J Biol Chem 2012; 287:23162-70. [PMID: 22511790 DOI: 10.1074/jbc.m112.346437] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mutations in the mitochondrial PTEN-induced kinase 1 (Pink1) gene have been linked to Parkinson disease (PD). Recent reports including our own indicated that ectopic Pink1 expression is protective against toxic insult in vitro, suggesting a potential role for endogenous Pink1 in mediating survival. However, the role of endogenous Pink1 in survival, particularly in vivo, is unclear. To address this critical question, we examined whether down-regulation of Pink1 affects dopaminergic neuron loss following 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the adult mouse. Two model systems were utilized: virally delivered shRNA-mediated knockdown of Pink1 and germ line-deficient mice. In both instances, loss of Pink1 generated significant sensitivity to damage induced by systemic MPTP treatment. This sensitivity was associated with greater loss of dopaminergic neurons in the Substantia Nigra pars compacta and terminal dopamine fiber density in the striatum region. Importantly, we also show that viral mediated expression of two other recessive PD-linked familial genes, DJ-1 and Parkin, can protect dopaminergic neurons even in the absence of Pink1. This evidence not only provides strong evidence for the role of endogenous Pink1 in neuronal survival, but also supports a role of DJ-1 and Parkin acting parallel or downstream of endogenous Pink1 to mediate survival in a mammalian in vivo context.
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Affiliation(s)
- M Emdadul Haque
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
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7
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McNeill B, Perez-Iratxeta C, Mazerolle C, Furimsky M, Mishina Y, Andrade-Navarro MA, Wallace VA. Comparative genomics identification of a novel set of temporally regulated hedgehog target genes in the retina. Mol Cell Neurosci 2012; 49:333-40. [PMID: 22281533 DOI: 10.1016/j.mcn.2011.12.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Revised: 11/07/2011] [Accepted: 12/15/2011] [Indexed: 11/26/2022] Open
Abstract
The hedgehog (Hh) signaling pathway is involved in numerous developmental and adult processes with many links to cancer. In vertebrates, the activity of the Hh pathway is mediated primarily through three Gli transcription factors (Gli1, 2 and 3) that can serve as transcriptional activators or repressors. The identification of Gli target genes is essential for the understanding of the Hh-mediated processes. We used a comparative genomics approach using the mouse and human genomes to identify 390 genes that contained conserved Gli binding sites. RT-qPCR validation of 46 target genes in E14.5 and P0.5 retinal explants revealed that Hh pathway activation resulted in the modulation of 30 of these targets, 25 of which demonstrated a temporal regulation. Further validation revealed that the expression of Bok, FoxA1, Sox8 and Wnt7a was dependent upon Sonic Hh (Shh) signaling in the retina and their regulation is under positive and negative controls by Gli2 and Gli3, respectively. We also show using chromatin immunoprecipitation that Gli2 binds to the Sox8 promoter, suggesting that Sox8 is an Hh-dependent direct target of Gli2. Finally, we demonstrate that the Hh pathway also modulates the expression of Sox9 and Sox10, which together with Sox8 make up the SoxE group. Previously, it has been shown that Hh and SoxE group genes promote Müller glial cell development in the retina. Our data are consistent with the possibility for a role of SoxE group genes downstream of Hh signaling on Müller cell development.
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Affiliation(s)
- Brian McNeill
- Vision Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario, Canada K1H 8L6
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8
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Wall DS, Mears AJ, McNeill B, Mazerolle C, Thurig S, Wang Y, Kageyama R, Wallace VA. Progenitor cell proliferation in the retina is dependent on Notch-independent Sonic hedgehog/Hes1 activity. ACTA ACUST UNITED AC 2009; 184:101-12. [PMID: 19124651 PMCID: PMC2615087 DOI: 10.1083/jcb.200805155] [Citation(s) in RCA: 152] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Sonic hedgehog (Shh) is an indispensable, extrinsic cue that regulates progenitor and stem cell behavior in the developing and adult mammalian central nervous system. Here, we investigate the link between the Shh signaling pathway and Hes1, a classical Notch target. We show that Shh-driven stabilization of Hes1 is independent of Notch signaling and requires the Shh effector Gli2. We identify Gli2 as a primary mediator of this response by showing that Gli2 is required for Hh (Hedgehog)-dependent up-regulation of Hes1. We also show using chromatin immunoprecipitation that Gli2 binds to the Hes1 promoter, which suggests that Hes1 is a Hh-dependent direct target of Gli2 signaling. Finally, we show that Shh stimulation of progenitor proliferation and cell diversification requires Gli2 and Hes1 activity. This paper is the first demonstration of the mechanistic and functional link between Shh, Gli, and Hes1 in the regulation of progenitor cell behavior.
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Affiliation(s)
- Dana S Wall
- Ottawa Health Research Institute, Ottawa, Ontario, Canada
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Medina CF, Mazerolle C, Wang Y, Bérubé NG, Coupland S, Gibbons RJ, Wallace VA, Picketts DJ. Altered visual function and interneuron survival in Atrx knockout mice: inference for the human syndrome. Hum Mol Genet 2008; 18:966-77. [DOI: 10.1093/hmg/ddn424] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Dakubo GD, Mazerolle C, Furimsky M, Yu C, St-Jacques B, McMahon AP, Wallace VA. Indian hedgehog signaling from endothelial cells is required for sclera and retinal pigment epithelium development in the mouse eye. Dev Biol 2008; 320:242-55. [PMID: 18582859 DOI: 10.1016/j.ydbio.2008.05.528] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2007] [Revised: 05/02/2008] [Accepted: 05/08/2008] [Indexed: 01/21/2023]
Abstract
The development of extraocular orbital structures, in particular the choroid and sclera, is regulated by a complex series of interactions between neuroectoderm, neural crest and mesoderm derivatives, although in many instances the signals that mediate these interactions are not known. In this study we have investigated the function of Indian hedgehog (Ihh) in the developing mammalian eye. We show that Ihh is expressed in a population of non-pigmented cells located in the developing choroid adjacent to the RPE. The analysis of Hh mutant mice demonstrates that the RPE and developing scleral mesenchyme are direct targets of Ihh signaling and that Ihh is required for the normal pigmentation pattern of the RPE and the condensation of mesenchymal cells to form the sclera. Our findings also indicate that Ihh signals indirectly to promote proliferation and photoreceptor specification in the neural retina. This study identifies Ihh as a novel choroid-derived signal that regulates RPE, sclera and neural retina development.
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Affiliation(s)
- Gabriel D Dakubo
- University of Ottawa Eye Institute, 451 Smyth Road, Ottawa, ON, Canada K1H 8M5
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11
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Liu H, Xu S, Wang Y, Mazerolle C, Thurig S, Coles BLK, Ren JC, Taketo MM, van der Kooy D, Wallace VA. Ciliary margin transdifferentiation from neural retina is controlled by canonical Wnt signaling. Dev Biol 2007; 308:54-67. [PMID: 17574231 DOI: 10.1016/j.ydbio.2007.04.052] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2006] [Revised: 04/09/2007] [Accepted: 04/30/2007] [Indexed: 11/30/2022]
Abstract
The epithelial layers of the ciliary body (CB) and iris are non-neural structures that differentiate from the anterior region of the eyecup, the ciliary margin (CM). We show here that activation of the canonical Wnt signaling pathway is sufficient and necessary for the normal development of anterior eye structures. Pharmacological activation of beta-catenin signaling with lithium (Li(+)) treatment in retinal explants in vitro induced the ectopic expression of the CM markers Otx1 and Msx1. Cre-mediated stabilization of beta-catenin expression in the peripheral retina in vivo induced a cell autonomous upregulation of CM markers at the expense of neural retina (NR) markers and inhibited neurogenesis. Consistent with a cell autonomous conversion to peripheral eye fates, the proliferation index in the region of the retina that expressed stabilized beta-catenin was identical to the wild-type CM and there was an expansion of CB-like structures at later stages. Conversely, Cre-mediated inactivation of beta-catenin reduced CM marker expression as well as the size of the CM and CB/iris. Aberrant CB development in both mouse models was also associated with a reduction in the number of retinal stem cells in vitro. In summary, activation of canonical Wnt signaling is sufficient to promote the development of peripheral eyecup fates at the expense of the NR and is also required for the normal development of anterior eyecup structures.
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Affiliation(s)
- Hong Liu
- Molecular Medicine Program, Ottawa Health Research Institute, 501 Smyth Road, Ottawa, Ontario, Canada K1H 8L6
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12
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Dakubo GD, Wang YP, Mazerolle C, Campsall K, McMahon AP, Wallace VA. Retinal ganglion cell-derived sonic hedgehog signaling is required for optic disc and stalk neuroepithelial cell development. Development 2003; 130:2967-80. [PMID: 12756179 DOI: 10.1242/dev.00515] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The development of optic stalk neuroepithelial cells depends on Hedgehog (Hh) signaling, yet the source(s) of Hh protein in the optic stalk is unknown. We provide genetic evidence that sonic hedgehog (Shh) from retinal ganglion cells (RGCs) promotes the development of optic disc and stalk neuroepithelial cells. We demonstrate that RGCs express Shh soon after differentiation, and cells at the optic disc in close proximity to the Shh-expressing RGCs upregulate Hh target genes, which suggests they are responding to RGC-derived Shh signaling. Conditional ablation of Shh in RGCs caused a complete loss of optic disc astrocyte precursor cells, resulting in defective axon guidance in the retina, as well as conversion of the neuroepithelial cells in the optic stalk to pigmented cells. We further show that Shh signaling modulates the size of the Pax2(+) astrocyte precursor cell population at the optic disc in vitro. Together, these data provide a novel insight into the source of Hh that promotes neuroepithelial cell development in the mammalian optic disc and stalk.
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Affiliation(s)
- Gabriel D Dakubo
- Molecular Medicine Program, Ottawa Health Research Institute, 501 Smyth Road, Ottawa, ON K1H 8L6, Canada
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