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Cintrón-Rivera LG, Oulette G, Prakki A, Burns NM, Patel R, Cyr R, Plavicki J. Exposure to the persistent organic pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) disrupts development of the zebrafish inner ear. Aquat Toxicol 2023; 259:106539. [PMID: 37086653 PMCID: PMC10519160 DOI: 10.1016/j.aquatox.2023.106539] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 04/07/2023] [Accepted: 04/09/2023] [Indexed: 05/03/2023]
Abstract
Dioxins are a class of highly toxic and persistent environmental pollutants that have been shown through epidemiological and laboratory-based studies to act as developmental teratogens. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most potent dioxin congener, has a high affinity for the aryl hydrocarbon receptor (AHR), a ligand activated transcription factor. TCDD-induced AHR activation during development impairs nervous system, cardiac, and craniofacial development. Despite the robust phenotypes previously reported, the characterization of developmental malformations and our understanding of the molecular targets mediating TCDD-induced developmental toxicity remains limited. In zebrafish, TCDD-induced craniofacial malformations are produced, in part, by the downregulation of SRY-box transcription factor 9b (sox9b), a member of the SoxE gene family. sox9b, along with fellow SoxE gene family members sox9a and sox10, have important functions in the development of the otic placode, the otic vesicle, and, ultimately, the inner ear. Given that sox9b is a known target of TCDD and that transcriptional interactions exist among SoxE genes, we asked whether TCDD exposure impaired the development of the zebrafish auditory system, specifically the otic vesicle, which gives rise to the sensory components of the inner ear. Using immunohistochemistry, in vivo confocal imaging, and time-lapse microscopy, we assessed the impact of TCDD exposure on zebrafish otic vesicle development. We found exposure resulted in structural deficits, including incomplete pillar fusion and altered pillar topography, leading to defective semicircular canal development. The observed structural deficits were accompanied by reduced collagen type II expression in the ear. Together, our findings reveal the otic vesicle as a novel target of TCDD-induced toxicity, suggest that the function of multiple SoxE genes may be affected by TCDD exposure, and provide insight into how environmental contaminants contribute to congenital malformations.
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Affiliation(s)
- Layra G Cintrón-Rivera
- Department of Pathology and Laboratory Medicine, Brown University, 70 Ship St, Providence, RI, 02903, USA
| | - Gabrielle Oulette
- Department of Pathology and Laboratory Medicine, Brown University, 70 Ship St, Providence, RI, 02903, USA
| | - Aishwarya Prakki
- Department of Pathology and Laboratory Medicine, Brown University, 70 Ship St, Providence, RI, 02903, USA
| | - Nicole M Burns
- Department of Pathology and Laboratory Medicine, Brown University, 70 Ship St, Providence, RI, 02903, USA
| | - Ratna Patel
- Department of Pathology and Laboratory Medicine, Brown University, Providence, RI, USA
| | - Rachel Cyr
- Department of Pathology and Laboratory Medicine, Brown University, Providence, RI, USA
| | - Jessica Plavicki
- Department of Pathology and Laboratory Medicine, Brown University, 70 Ship St, Providence, RI, 02903, USA.
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2
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Cintr N-Rivera LG, Oulette G, Prakki A, Burns NM, Patel R, Cyr R, Plavicki J. Exposure to the persistent organic pollutant 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD, dioxin) disrupts development of the zebrafish inner ear. bioRxiv 2023:2023.03.14.532434. [PMID: 36993549 PMCID: PMC10054988 DOI: 10.1101/2023.03.14.532434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/28/2023]
Abstract
Dioxins are a class of highly toxic and persistent environmental pollutants that have been shown through epidemiological and laboratory-based studies to act as developmental teratogens. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most potent dioxin congener, has a high affinity for the aryl hydrocarbon receptor (AHR), a ligand activated transcription factor. TCDD-induced AHR activation during development impairs nervous system, cardiac, and craniofacial development. Despite the robust phenotypes previously reported, the characterization of developmental malformations and our understanding of the molecular targets mediating TCDD-induced developmental toxicity remains limited. In zebrafish, TCDD-induced craniofacial malformations are produced, in part, by the downregulation of SRY-box transcription factor 9b ( sox9b ), a member of the SoxE gene family. sox9b , along with fellow SoxE gene family members sox9a and sox10 , have important functions in the development of the otic placode, the otic vesicle, and, ultimately, the inner ear. Given that sox9b in a known target of TCDD and that transcriptional interactions exist among SoxE genes, we asked whether TCDD exposure impaired the development of the zebrafish auditory system, specifically the otic vesicle, which gives rise to the sensory components of the inner ear. Using immunohistochemistry, in vivo confocal imaging, and time-lapse microscopy, we assessed the impact of TCDD exposure on zebrafish otic vesicle development. We found exposure resulted in structural deficits, including incomplete pillar fusion and altered pillar topography, leading to defective semicircular canal development. The observed structural deficits were accompanied by reduced collagen type II expression in the ear. Together, our findings reveal the otic vesicle as a novel target of TCDD-induced toxicity, suggest that the function of multiple SoxE genes may be affected by TCDD exposure, and provide insight into how environmental contaminants contribute to congenital malformations. Highlights The zebrafish ear is necessary to detect changes in motion, sound, and gravity.Embryos exposed to TCDD lack structural components of the developing ear.TCDD exposure impairs formation of the fusion plate and alters pillar topography.The semicircular canals of the ear are required to detect changes in movement.Following TCDD exposure embryos fail to establish semicircular canals.
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3
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Laureano AS, Flaherty K, Hinman AM, Jadali A, Nakamura T, Higashijima SI, Sabaawy HE, Kwan KY. shox2 is required for vestibular statoacoustic neuron development. Biol Open 2023; 11:286143. [PMID: 36594417 PMCID: PMC9838637 DOI: 10.1242/bio.059599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 11/22/2022] [Indexed: 01/04/2023] Open
Abstract
Homeobox genes act at the top of genetic hierarchies to regulate cell specification and differentiation during embryonic development. We identified the short stature homeobox domain 2 (shox2) transcription factor that is required for vestibular neuron development. shox2 transcripts are initially localized to the otic placode of the developing inner ear where neurosensory progenitors reside. To study shox2 function, we generated CRISPR-mediated mutant shox2 fish. Mutant embryos display behaviors associated with vestibular deficits and showed reduced number of anterior statoacoustic ganglion neurons that innervate the utricle, the vestibular organ in zebrafish. Moreover, a shox2-reporter fish showed labeling of developing statoacoustic ganglion neurons in the anterior macula of the otic vesicle. Single cell RNA-sequencing of cells from the developing otic vesicle of shox2 mutants revealed altered otic progenitor profiles, while single molecule in situ assays showed deregulated levels of transcripts in developing neurons. This study implicates a role for shox2 in development of vestibular but not auditory statoacoustic ganglion neurons.
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Affiliation(s)
- Alejandra S. Laureano
- Department of Cell Biology & Neuroscience, Rutgers University, Piscataway, NJ 08854, USA,Stem Cell Research Center and Keck Center for Collaborative Neuroscience, Rutgers University, NJ 08854, USA
| | - Kathleen Flaherty
- Department of Comparative Medicine Resources, Rutgers University, Piscataway, NJ 08854, USA
| | - Anna-Maria Hinman
- Department of Cell Biology & Neuroscience, Rutgers University, Piscataway, NJ 08854, USA,Stem Cell Research Center and Keck Center for Collaborative Neuroscience, Rutgers University, NJ 08854, USA
| | - Azadeh Jadali
- Department of Cell Biology & Neuroscience, Rutgers University, Piscataway, NJ 08854, USA,Stem Cell Research Center and Keck Center for Collaborative Neuroscience, Rutgers University, NJ 08854, USA
| | - Tetsuya Nakamura
- Department of Genetics, Rutgers University, Piscataway, NJ 08854, USA
| | - Shin-ichi Higashijima
- Institutes of Natural Sciences, Exploratory Research Center on Life and Living Systems, Okazaki, Aichi 444-8787, Japan
| | - Hatim E. Sabaawy
- Department of Medicine, Division of Medical Oncology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA,Department of Medicine RBHS-Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ 08854, USA
| | - Kelvin Y. Kwan
- Department of Cell Biology & Neuroscience, Rutgers University, Piscataway, NJ 08854, USA,Stem Cell Research Center and Keck Center for Collaborative Neuroscience, Rutgers University, NJ 08854, USA,Author for correspondence ()
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Tan AL, Mohanty S, Guo J, Lekven AC, Riley BB. Pax2a, Sp5a and Sp5l act downstream of Fgf and Wnt to coordinate sensory-neural patterning in the inner ear. Dev Biol 2022; 492:139-153. [PMID: 36244503 DOI: 10.1016/j.ydbio.2022.10.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 07/22/2022] [Revised: 09/25/2022] [Accepted: 10/10/2022] [Indexed: 01/21/2023]
Abstract
In zebrafish, sensory epithelia and neuroblasts of the inner ear form simultaneously in abutting medial and lateral domains, respectively, in the floor of the otic vesicle. Previous studies support regulatory roles for Fgf and Wnt, but how signaling is coordinated is poorly understood. We investigated this problem using pharmacological and transgenic methods to alter Fgf or Wnt signaling from early placodal stages to evaluate later changes in growth and patterning. Blocking Fgf at any stage reduces proliferation of otic tissue and terminates both sensory and neural specification. Wnt promotes proliferation in the otic vesicle but is not required for sensory or neural development. However, sustained overactivation of Wnt laterally expands sensory epithelia and blocks neurogenesis. pax2a, sp5a and sp5l are coregulated by Fgf and Wnt and show overlapping expression in the otic placode and vesicle. Gain- and loss-of-function studies show that these genes are together required for Wnt's suppression of neurogenesis, as well as some aspects of sensory development. Thus, pax2a, sp5a and sp5l are critical for mediating Fgf and Wnt signaling to promote spatially localized sensory and neural development.
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Affiliation(s)
- Amy L Tan
- Biology Department, Texas A&M University, College Station, TX, United States
| | - Saurav Mohanty
- Department of Biology and Biochemistry, University of Houston, Houston, TX, United States
| | - Jinbai Guo
- Biology Department, Texas A&M University, College Station, TX, United States
| | - Arne C Lekven
- Department of Biology and Biochemistry, University of Houston, Houston, TX, United States
| | - Bruce B Riley
- Biology Department, Texas A&M University, College Station, TX, United States.
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Riley BB. Comparative assessment of Fgf's diverse roles in inner ear development: A zebrafish perspective. Dev Dyn 2021; 250:1524-1551. [PMID: 33830554 DOI: 10.1002/dvdy.343] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [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: 02/09/2021] [Revised: 03/26/2021] [Accepted: 03/26/2021] [Indexed: 01/21/2023] Open
Abstract
Progress in understanding mechanisms of inner ear development has been remarkably rapid in recent years. The research community has benefited from the availability of several diverse model organisms, including zebrafish, chick, and mouse. The complexity of the inner ear has proven to be a challenge, and the complexity of the mammalian cochlea in particular has been the subject of intense scrutiny. Zebrafish lack a cochlea and exhibit a number of other differences from amniote species, hence they are sometimes seen as less relevant for inner ear studies. However, accumulating evidence shows that underlying cellular and molecular mechanisms are often highly conserved. As a case in point, consideration of the diverse functions of Fgf and its downstream effectors reveals many similarities between vertebrate species, allowing meaningful comparisons the can benefit the entire research community. In this review, I will discuss mechanisms by which Fgf controls key events in early otic development in zebrafish and provide direct comparisons with chick and mouse.
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Affiliation(s)
- Bruce B Riley
- Biology Department, Texas A&M University, College Station, Texas, USA
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Mackowetzky K, Yoon KH, Mackowetzky EJ, Waskiewicz AJ. Development and evolution of the vestibular apparatuses of the inner ear. J Anat 2021; 239:801-828. [PMID: 34047378 PMCID: PMC8450482 DOI: 10.1111/joa.13459] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 04/07/2021] [Accepted: 05/06/2021] [Indexed: 12/16/2022] Open
Abstract
The vertebrate inner ear is a labyrinthine sensory organ responsible for perceiving sound and body motion. While a great deal of research has been invested in understanding the auditory system, a growing body of work has begun to delineate the complex developmental program behind the apparatuses of the inner ear involved with vestibular function. These animal studies have helped identify genes involved in inner ear development and model syndromes known to include vestibular dysfunction, paving the way for generating treatments for people suffering from these disorders. This review will provide an overview of known inner ear anatomy and function and summarize the exciting discoveries behind inner ear development and the evolution of its vestibular apparatuses.
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Affiliation(s)
- Kacey Mackowetzky
- Department of Biological SciencesUniversity of AlbertaEdmontonAlbertaCanada
| | - Kevin H. Yoon
- Department of Biological SciencesUniversity of AlbertaEdmontonAlbertaCanada
| | | | - Andrew J. Waskiewicz
- Department of Biological SciencesUniversity of AlbertaEdmontonAlbertaCanada
- Women & Children’s Health Research InstituteUniversity of AlbertaEdmontonAlbertaCanada
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Sun P, Zhang Y, Zhao F, Wu JP, Pun SH, Peng C, Du M, Vai MI, Liu D, Chen F. An Assay for Systematically Quantifying the Vestibulo-Ocular Reflex to Assess Vestibular Function in Zebrafish Larvae. Front Cell Neurosci 2018; 12:257. [PMID: 30186115 PMCID: PMC6113563 DOI: 10.3389/fncel.2018.00257] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [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: 01/21/2018] [Accepted: 07/27/2018] [Indexed: 12/25/2022] Open
Abstract
Zebrafish (Danio rerio) larvae are widely used to study otic functions because they possess all five typical vertebrate senses including hearing and balance. Powerful genetic tools and the transparent body of the embryo and larva also make zebrafish a unique vertebrate model to study otic development. Due to its small larval size and moisture requirement during experiments, accurately acquiring the vestibulo-ocular reflex (VOR) of zebrafish larva is challenging. In this report, a new VOR testing device has been developed for quantifying linear VOR (LVOR) in zebrafish larva, evoked by the head motion about the earth horizontal axis. The system has a newly designed larva-shaped chamber, by which live fish can be steadily held without anesthesia, and the system is more compact and easier to use than its predecessors. To demonstrate the efficacy of the system, the LVORs in wild-type (WT), dlx3b and dlx4b morphant zebrafish larvae were measured and the results showed that LVOR amplitudes were consistent with the morphological changes of otoliths induced by morpholino oligonucleotides (MO). Our study represents an important advance to obtain VOR and predict the vestibular conditions in zebrafish.
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Affiliation(s)
- Peng Sun
- State Key Laboratory of Analog and Mixed-Signal VLSI, University of Macau, Taipa, China.,Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Taipa, China.,Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen, China
| | - Yingla Zhang
- School of Life Sciences, Peking University, Beijing, China
| | - Feng Zhao
- Department of Biology, Southern University of Science and Technology, Shenzhen, China
| | - Jian-Ping Wu
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen, China.,SUSTech Academy for Advanced Interdisciplinary Studies, Southern University of Science and Technology, Shenzhen, China
| | - Sio Hang Pun
- State Key Laboratory of Analog and Mixed-Signal VLSI, University of Macau, Taipa, China
| | - Cheng Peng
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen, China
| | - Meide Du
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen, China
| | - Mang I Vai
- State Key Laboratory of Analog and Mixed-Signal VLSI, University of Macau, Taipa, China.,Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Taipa, China
| | - Dong Liu
- School of Life Sciences, Peking University, Beijing, China.,Department of Biology, Southern University of Science and Technology, Shenzhen, China
| | - Fangyi Chen
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen, China
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Gou Y, Guo J, Maulding K, Riley BB. sox2 and sox3 cooperate to regulate otic/epibranchial placode induction in zebrafish. Dev Biol 2018; 435:84-95. [PMID: 29355522 DOI: 10.1016/j.ydbio.2018.01.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [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: 10/27/2017] [Revised: 01/15/2018] [Accepted: 01/15/2018] [Indexed: 12/16/2022]
Abstract
Expression of sox3 is one of the earliest markers of Fgf-dependent otic/epibranchial placode induction. We report here that sox2 is also expressed in the early otic/epibranchial placode in zebrafish. To address functions of sox2 and sox3, we generated knockouts and heat shock-inducible transgenes. Mutant analysis, and low-level misexpression, showed that sox2 and sox3 act redundantly to establish a full complement of otic/epibranchial cells. Disruption of pax8, another early regulator, caused similar placodal deficiencies to sox3 mutants or pax8-sox3 double mutants, suggesting that sox3 and pax8 operate in the same pathway. High-level misexpression of sox2 or sox3 during early stages cell-autonomously blocked placode induction, whereas misexpression several hours later could not reverse placodal differentiation. In an assay for ectopic placode-induction, we previously showed that misexpression of fgf8 induces a high level of ectopic sox3, but not pax8. Partial knockdown of sox3 significantly enhanced ectopic induction of pax8, whereas full knockdown of sox3 inhibited this process. Together these findings show that sox2 and sox3 are together required for proper otic induction, but the level of expression must be tightly regulated to avoid suppression of differentiation and maintenance of pluripotency.
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Affiliation(s)
- Yunzi Gou
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, United States
| | - Jinbai Guo
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, United States
| | - Kirstin Maulding
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, United States
| | - Bruce B Riley
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, United States.
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9
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Schwarzer S, Spieß S, Brand M, Hans S. Dlx3b/4b is required for early-born but not later-forming sensory hair cells during zebrafish inner ear development. Biol Open 2017; 6:1270-1278. [PMID: 28751305 PMCID: PMC5612237 DOI: 10.1242/bio.026211] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [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] [Indexed: 12/15/2022] Open
Abstract
Morpholino-mediated knockdown has shown that the homeodomain transcription factors Dlx3b and Dlx4b are essential for proper induction of the otic-epibranchial progenitor domain (OEPD), as well as subsequent formation of sensory hair cells in the developing zebrafish inner ear. However, increasing use of reverse genetic approaches has revealed poor correlation between morpholino-induced and mutant phenotypes. Using CRISPR/Cas9-mediated mutagenesis, we generated a defined deletion eliminating the entire open reading frames of dlx3b and dlx4b (dlx3b/4b) and investigated a potential phenotypic difference between mutants and morpholino-mediated knockdown. Consistent with previous findings obtained by morpholino-mediated knockdown of Dlx3b and Dlx4b, dlx3b/4b mutants display compromised otic induction, the development of smaller otic vesicles and an elimination of all indications of otic specification when combined with loss of foxi1, a second known OEPD competence factor in zebrafish. Furthermore, sensorigenesis is also affected in dlx3b/4b mutants. However, we find that only early-born sensory hair cells (tether cells), that seed and anchor the formation of otoliths, are affected. Later-forming sensory hair cells are present, indicating that two genetically distinct pathways control the development of early-born and later-forming sensory hair cells. Finally, impairment of early-born sensory hair cell formation in dlx3b/4b mutant embryos reverses the common temporal sequence of neuronal and sensory hair cell specification in zebrafish, resembling the order of cell specification in amniotes; Neurog1 expression before Atoh1 expression. We conclude that the Dlx3b/4b-dependent pathway has been either acquired newly in the fish lineage or lost in other vertebrate species during evolution, and that the events during early inner ear development are remarkably similar in fish and amniotes in the absence of this pathway. Summary: The transcription factors Dlx3b and Dlx4b control the formation of early-born sensory hair cells or tether cells in the developing zebrafish inner ear.
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Affiliation(s)
- Simone Schwarzer
- Technische Universität Dresden, Biotechnology Center and DFG-Center for Regenerative Therapies Dresden Cluster of Excellence, Tatzberg 47-49, 01307 Dresden, Germany
| | - Sandra Spieß
- Technische Universität Dresden, Biotechnology Center and DFG-Center for Regenerative Therapies Dresden Cluster of Excellence, Tatzberg 47-49, 01307 Dresden, Germany
| | - Michael Brand
- Technische Universität Dresden, Biotechnology Center and DFG-Center for Regenerative Therapies Dresden Cluster of Excellence, Tatzberg 47-49, 01307 Dresden, Germany
| | - Stefan Hans
- Technische Universität Dresden, Biotechnology Center and DFG-Center for Regenerative Therapies Dresden Cluster of Excellence, Tatzberg 47-49, 01307 Dresden, Germany
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10
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Anwar M, Tambalo M, Ranganathan R, Grocott T, Streit A. A gene network regulated by FGF signalling during ear development. Sci Rep 2017; 7:6162. [PMID: 28733657 DOI: 10.1038/s41598-017-05472-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 05/31/2017] [Indexed: 02/08/2023] Open
Abstract
During development cell commitment is regulated by inductive signals that are tightly controlled in time and space. In response, cells activate specific programmes, but the transcriptional circuits that maintain cell identity in a changing signalling environment are often poorly understood. Specification of inner ear progenitors is initiated by FGF signalling. Here, we establish the genetic hierarchy downstream of FGF by systematic analysis of many ear factors combined with a network inference approach. We show that FGF rapidly activates a small circuit of transcription factors forming positive feedback loops to stabilise otic progenitor identity. Our predictive network suggests that subsequently, transcriptional repressors ensure the transition of progenitors to mature otic cells, while simultaneously repressing alternative fates. Thus, we reveal the regulatory logic that initiates ear formation and highlight the hierarchical organisation of the otic gene network.
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11
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McCarthy N, Sidik A, Bertrand JY, Eberhart JK. An Fgf-Shh signaling hierarchy regulates early specification of the zebrafish skull. Dev Biol 2016; 415:261-277. [PMID: 27060628 PMCID: PMC4967541 DOI: 10.1016/j.ydbio.2016.04.005] [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] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 03/30/2016] [Accepted: 04/05/2016] [Indexed: 02/03/2023]
Abstract
The neurocranium generates most of the craniofacial skeleton and consists of prechordal and postchordal regions. Although development of the prechordal is well studied, little is known of the postchordal region. Here we characterize a signaling hierarchy necessary for postchordal neurocranial development involving Fibroblast growth factor (Fgf) signaling for early specification of mesodermally-derived progenitor cells. The expression of hyaluron synthetase 2 (has2) in the cephalic mesoderm requires Fgf signaling and Has2 function, in turn, is required for postchordal neurocranial development. While Hedgehog (Hh)-deficient embryos also lack a postchordal neurocranium, this appears primarily due to a later defect in chondrocyte differentiation. Inhibitor studies demonstrate that postchordal neurocranial development requires early Fgf and later Hh signaling. Collectively, our results provide a mechanistic understanding of early postchordal neurocranial development and demonstrate a hierarchy of signaling between Fgf and Hh in the development of this structure.
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Affiliation(s)
- Neil McCarthy
- Department of Molecular Biosciences; Institute of Cell and Molecular Biology, Waggoner Center for Alcohol and Alcohol Addiction Research, University of Texas, Austin, TX, United States
| | - Alfire Sidik
- Department of Molecular Biosciences; Institute of Cell and Molecular Biology, Waggoner Center for Alcohol and Alcohol Addiction Research, University of Texas, Austin, TX, United States
| | - Julien Y Bertrand
- Department of Pathology and Immunology, University of Geneva Medical School, Geneva, Switzerland
| | - Johann K Eberhart
- Department of Molecular Biosciences; Institute of Cell and Molecular Biology, Waggoner Center for Alcohol and Alcohol Addiction Research, University of Texas, Austin, TX, United States; Department of Molecular Biosciences; Institute of Neurobiology, University of Texas, Austin, TX, United States.
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12
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Uribe RA, Buzzi AL, Bronner ME, Strobl-Mazzulla PH. Histone demethylase KDM4B regulates otic vesicle invagination via epigenetic control of Dlx3 expression. J Cell Biol 2016; 211:815-27. [PMID: 26598618 PMCID: PMC4657164 DOI: 10.1083/jcb.201503071] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In vertebrate embryos, the histone demethylase KDM4B affects otic placode proliferation, intercellular adhesion, and invagination by directly regulating Dlx3 expression. In vertebrates, the inner ear arises from the otic placode, a thickened swathe of ectoderm that invaginates to form the otic vesicle. We report that histone demethylase KDM4B is dynamically expressed during early stages of chick inner ear formation. A loss of KDM4B results in defective invagination and striking morphological changes in the otic epithelium, characterized by abnormal localization of adhesion and cytoskeletal molecules and reduced expression of several inner ear markers, including Dlx3. In vivo chromatin immunoprecipitation reveals direct and dynamic occupancy of KDM4B and its target, H3K9me3, at regulatory regions of the Dlx3 locus. Accordingly, coelectroporations of DLX3 or KDM4B encoding constructs, but not a catalytically dead mutant of KDM4B, rescue the ear invagination phenotype caused by KDM4B knockdown. Moreover, a loss of DLX3 phenocopies a loss of KDM4B. Collectively, our findings suggest that KDM4B play a critical role during inner ear invagination via modulating histone methylation of the direct target Dlx3.
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Affiliation(s)
- Rosa A Uribe
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125
| | - Ailín L Buzzi
- Laboratory of Developmental Biology, Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús (CONICET-UNSAM), 7130 Chascomús, Argentina
| | - Marianne E Bronner
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125
| | - Pablo H Strobl-Mazzulla
- Laboratory of Developmental Biology, Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús (CONICET-UNSAM), 7130 Chascomús, Argentina
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He Y, Tang D, Li W, Chai R, Li H. Histone deacetylase 1 is required for the development of the zebrafish inner ear. Sci Rep 2016; 6:16535. [PMID: 26832938 DOI: 10.1038/srep16535] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 09/29/2015] [Indexed: 11/09/2022] Open
Abstract
Histone deacetylase 1 (HDAC1) has been reported to be important for multiple aspects of normal embryonic development, but little is known about its function in the development of mechanosensory organs. Here, we first confirmed that HDAC1 is expressed in the developing otic vesicles of zebrafish by whole-mount in situ hybridization. Knockdown of HDAC1 using antisense morpholino oligonucleotides in zebrafish embryos induced smaller otic vesicles, abnormal otoliths, malformed or absent semicircular canals, and fewer sensory hair cells. HDAC1 loss of function also caused attenuated expression of a subset of key genes required for otic vesicle formation during development. Morpholino-mediated knockdown of HDAC1 resulted in decreased expression of members of the Fgf family in the otic vesicles, suggesting that HDAC1 is involved in the development of the inner ear through regulation of Fgf signaling pathways. Taken together, our results indicate that HDAC1 plays an important role in otic vesicle formation.
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14
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Abstract
Cranial placodes are thickenings in the ectoderm that give rise to sensory organs and peripheral ganglia of the vertebrate head. At gastrula and neurula stages, placodal precursors are intermingled in the neural plate border with future neural and neural crest cells. Here, we show that the epigenetic modifier, DNA methyl transferase (DNMT) 3A, expressed in the neural plate border region, influences development of the otic placode which will contribute to the ear. DNMT3A is expressed in the presumptive otic region at gastrula through neurula stages and later in the otic placode itself. Whereas neural plate border and non-neural ectoderm markers Erni, Dlx5, Msx1 and Six1 are unaltered, DNMT3A loss of function leads to early reduction in the expression of the key otic placode specifier genes Pax2 and Gbx2 and later otic markers Sox10 and Soho1. Reduction of Gbx2 was first observed at HH7, well before loss of other otic markers. Later, this translates to significant reduction in the size of the otic vesicle. Based on these results, we propose that DNMT3A is important for enabling the activation of Gbx2 expression, necessary for normal development of the inner ear.
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Affiliation(s)
- Daniela Roellig
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
| | - Marianne E Bronner
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
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Birol O, Ohyama T, Edlund RK, Drakou K, Georgiades P, Groves AK. The mouse Foxi3 transcription factor is necessary for the development of posterior placodes. Dev Biol 2015; 409:139-151. [PMID: 26550799 DOI: 10.1016/j.ydbio.2015.09.022] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [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: 09/16/2015] [Accepted: 09/22/2015] [Indexed: 02/01/2023]
Abstract
The inner ear develops from the otic placode, one of the cranial placodes that arise from a region of ectoderm adjacent to the anterior neural plate called the pre-placodal domain. We have identified a Forkhead family transcription factor, Foxi3, that is expressed in the pre-placodal domain and down-regulated when the otic placode is induced. We now show that Foxi3 mutant mice do not form otic placodes as evidenced by expression changes in early molecular markers and the lack of thickened placodal ectoderm, an otic cup or otocyst. Some preplacodal genes downstream of Foxi3-Gata3, Six1 and Eya1-are not expressed in the ectoderm of Foxi3 mutant mice, and the ectoderm exhibits signs of increased apoptosis. We also show that Fgf signals from the hindbrain and cranial mesoderm, which are necessary for otic placode induction, are received by pre-placodal ectoderm in Foxi3 mutants, but do not initiate otic induction. Finally, we show that the epibranchial placodes that develop in close proximity to the otic placode and the mandibular division of the trigeminal ganglion are missing in Foxi3 mutants. Our data suggest that Foxi3 is necessary to prime pre-placodal ectoderm for the correct interpretation of inductive signals for the otic and epibranchial placodes.
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Affiliation(s)
- Onur Birol
- Program in Developmental Biology, Baylor College of Medicine, BCM295, 1 Baylor Plaza, Houston, TX 77030, USA
| | - Takahiro Ohyama
- USC Caruso Department of Otolaryngology - Head & Neck Surgery, Keck Medicine of USC, University of Southern California, 1501 San Pablo Street, Los Angeles, CA 90033-4503, USA; Zilkha Neurogenetic Institute, Keck Medicine of USC, University of Southern California, 1501 San Pablo Street, Los Angeles, CA 90033-4503, USA
| | - Renée K Edlund
- Program in Developmental Biology, Baylor College of Medicine, BCM295, 1 Baylor Plaza, Houston, TX 77030, USA
| | - Katerina Drakou
- Department of Biological Sciences, University of Cyprus, 1 University Avenue, P.O. Box 20537, 1678 Nicosia, Cyprus
| | - Pantelis Georgiades
- Department of Biological Sciences, University of Cyprus, 1 University Avenue, P.O. Box 20537, 1678 Nicosia, Cyprus
| | - Andrew K Groves
- Program in Developmental Biology, Baylor College of Medicine, BCM295, 1 Baylor Plaza, Houston, TX 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, BCM295, 1 Baylor Plaza, Houston, TX 77030, USA; Department of Neurosc ience, Baylor College of Medicine, BCM295, 1 Baylor Plaza, Houston, TX 77030, USA.
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16
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Shida H, Mende M, Takano-Yamamoto T, Osumi N, Streit A, Wakamatsu Y. Otic placode cell specification and proliferation are regulated by Notch signaling in avian development. Dev Dyn 2015; 244:839-51. [PMID: 25970828 DOI: 10.1002/dvdy.24291] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [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: 10/16/2014] [Revised: 04/26/2015] [Accepted: 05/01/2015] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND The entire inner ear including the cochlear-vestibular ganglion arises from a simple epithelium, the otic placode. Precursors for the placode originate from a pool of progenitors located in ectoderm next to the future hindbrain, the pre-otic field, where they are intermingled with future epibranchial and epidermal cells. While the importance of secreted proteins, such as FGFs and Wnts, in imparting otic identity has been well studied, how precursors for these different fates segregate locally is less well understood. RESULTS (1) The Notch ligand Delta1 and the Notch target Hes5-2 are expressed in a part of pre-otic field before otic commitment, indicative of active Notch signaling, and this is confirmed using a Notch reporter. (2) Loss and gain-of-function approaches reveal that Notch signaling regulates both proliferation and specification of pre-otic progenitors. CONCLUSIONS Our results identify a novel function of Notch signaling in cell fate determination in the pre-otic field of avian embryos.
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Affiliation(s)
- Hiroko Shida
- Department of Developmental Neuroscience, Center for Translational and Advanced Animal Research, Tohoku University Graduate School of Medicine, Miyagi, Japan.,Division of Orthodontics and Dentofacial Orthopedics, Tohoku University Graduate School of Dentistry, Miyagi, Japan
| | - Michael Mende
- Department of Craniofacial Development and Stem Cell Biology, King's College London
| | - Teruko Takano-Yamamoto
- Division of Orthodontics and Dentofacial Orthopedics, Tohoku University Graduate School of Dentistry, Miyagi, Japan
| | - Noriko Osumi
- Department of Developmental Neuroscience, Center for Translational and Advanced Animal Research, Tohoku University Graduate School of Medicine, Miyagi, Japan
| | - Andrea Streit
- Department of Craniofacial Development and Stem Cell Biology, King's College London
| | - Yoshio Wakamatsu
- Department of Developmental Neuroscience, Center for Translational and Advanced Animal Research, Tohoku University Graduate School of Medicine, Miyagi, Japan
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Wu D, Mandal S, Choi A, Anderson A, Prochazkova M, Perry H, Gil-Da-Silva-Lopes VL, Lao R, Wan E, Tang PLF, Kwok PY, Klein O, Zhuan B, Slavotinek AM. DLX4 is associated with orofacial clefting and abnormal jaw development. Hum Mol Genet 2015; 24:4340-52. [PMID: 25954033 DOI: 10.1093/hmg/ddv167] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 05/05/2015] [Indexed: 01/10/2023] Open
Abstract
Cleft lip and/or palate (CL/P) are common structural birth defects in humans. We used exome sequencing to study a patient with bilateral CL/P and identified a single nucleotide deletion in the patient and her similarly affected son—c.546_546delG, predicting p.Gln183Argfs*57 in the Distal-less 4 (DLX4) gene. The sequence variant was absent from databases, predicted to be deleterious and was verified by Sanger sequencing. In mammals, there are three Dlx homeobox clusters with closely located gene pairs (Dlx1/Dlx2, Dlx3/Dlx4, Dlx5/Dlx6). In situ hybridization showed that Dlx4 was expressed in the mesenchyme of the murine palatal shelves at E12.5, prior to palate closure. Wild-type human DLX4, but not mutant DLX4_c.546delG, could activate two murine Dlx conserved regulatory elements, implying that the mutation caused haploinsufficiency. We showed that reduced DLX4 expression after short interfering RNA treatment in a human cell line resulted in significant up-regulation of DLX3, DLX5 and DLX6, with reduced expression of DLX2 and significant up-regulation of BMP4, although the increased BMP4 expression was demonstrated only in HeLa cells. We used antisense morpholino oligonucleotides to target the orthologous Danio rerio gene, dlx4b, and found reduced cranial size and abnormal cartilaginous elements. We sequenced DLX4 in 155 patients with non-syndromic CL/P and CP, but observed no sequence variants. From the published literature, Dlx1/Dlx2 double homozygous null mice and Dlx5 homozygous null mice both have clefts of the secondary palate. This first finding of a DLX4 mutation in a family with CL/P establishes DLX4 as a potential cause of human clefts.
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Affiliation(s)
- Di Wu
- Department of Pediatrics, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Shyamali Mandal
- Department of Pediatrics, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Alex Choi
- Department of Pediatrics, University of California, San Francisco, San Francisco, CA 94143, USA
| | - August Anderson
- Department of Pediatrics, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Michaela Prochazkova
- Division of Craniofacial Anomalies, Department of Orofacial Sciences, University of California, San Francisco, San Francisco, CA, USA, Laboratory of Transgenic Models of Diseases, Institute of Molecular Genetics of the ASCR, v. v.i., Prague, Czech Republic, Program in Craniofacial Biology, University of California, San Francisco, San Francisco, CA 94114, USA
| | - Hazel Perry
- Division of Craniofacial Anomalies, Department of Orofacial Sciences, University of California, San Francisco, San Francisco, CA, USA
| | | | - Richard Lao
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, USA and
| | - Eunice Wan
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, USA and
| | - Paul Ling-Fung Tang
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, USA and
| | - Pui-yan Kwok
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, USA and Institute for Human Genetics, University of California, San Francisco, San Francisco, CA, USA
| | - Ophir Klein
- Department of Pediatrics, University of California, San Francisco, San Francisco, CA 94143, USA, Division of Craniofacial Anomalies, Department of Orofacial Sciences, University of California, San Francisco, San Francisco, CA, USA, Institute for Human Genetics, University of California, San Francisco, San Francisco, CA, USA, Program in Craniofacial Biology, University of California, San Francisco, San Francisco, CA 94114, USA
| | - Bian Zhuan
- Key Laboratory of Oral Biomedicine, Ministry of Education, School and Hospital of Stomatology, Wuhan University, China
| | - Anne M Slavotinek
- Department of Pediatrics, University of California, San Francisco, San Francisco, CA 94143, USA, Institute for Human Genetics, University of California, San Francisco, San Francisco, CA, USA,
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18
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Wang J, Wu Y, Zhao F, Wu Y, Dong W, Zhao J, Zhu Z, Liu D. Fgf-signaling-dependent Sox9a and Atoh1a regulate otic neural development in zebrafish. J Neurosci 2015; 35:234-44. [PMID: 25568117 DOI: 10.1523/JNEUROSCI.3353-14.2015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Fibroblast growth factors (Fgfs) play important roles in developmental processes of the inner ear, including the ontogeny of the statoacoustic ganglia (SAG) and hair cells. However, the detailed genetic mechanism(s) underlying Fgf/Fgfr-dependent otic neural development remains elusive. Using conditional genetic approaches and inhibitory small molecules, we have revealed that Fgfr-PI3K/Akt signaling is mainly responsible for zebrafish SAG development and have determined that Sox9a and Atoh1a act downstream of Fgfr-Akt signaling to specify and/or maintain the otic neuron fate during the early segmentation stage. Sox9a and Atoh1a coregulate numerous downstream factors identified through our ChIP-seq analyses, including Tlx2 and Eya2. Fgfr-Erk1/2 signaling contributes to ultricular hair cell development during a critical period between 9 and 15 hours postfertilization. Our work reveals that a genetic network of the previously known sensory determinant Atoh1 and the neural crest determinant Sox9 plays critical roles in SAG development. These newly uncovered roles for Atoh1and Sox9 in zebrafish otic development may be relevant to study in other species.
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Hartman BH, Durruthy-Durruthy R, Laske RD, Losorelli S, Heller S. Identification and characterization of mouse otic sensory lineage genes. Front Cell Neurosci 2015; 9:79. [PMID: 25852475 PMCID: PMC4365716 DOI: 10.3389/fncel.2015.00079] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [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: 12/19/2014] [Accepted: 02/22/2015] [Indexed: 11/23/2022] Open
Abstract
Vertebrate embryogenesis gives rise to all cell types of an organism through the development of many unique lineages derived from the three primordial germ layers. The otic sensory lineage arises from the otic vesicle, a structure formed through invagination of placodal non-neural ectoderm. This developmental lineage possesses unique differentiation potential, giving rise to otic sensory cell populations including hair cells, supporting cells, and ganglion neurons of the auditory and vestibular organs. Here we present a systematic approach to identify transcriptional features that distinguish the otic sensory lineage (from early otic progenitors to otic sensory populations) from other major lineages of vertebrate development. We used a microarray approach to analyze otic sensory lineage populations including microdissected otic vesicles (embryonic day 10.5) as well as isolated neonatal cochlear hair cells and supporting cells at postnatal day 3. Non-otic tissue samples including periotic tissues and whole embryos with otic regions removed were used as reference populations to evaluate otic specificity. Otic populations shared transcriptome-wide correlations in expression profiles that distinguish members of this lineage from non-otic populations. We further analyzed the microarray data using comparative and dimension reduction methods to identify individual genes that are specifically expressed in the otic sensory lineage. This analysis identified and ranked top otic sensory lineage-specific transcripts including Fbxo2, Col9a2, and Oc90, and additional novel otic lineage markers. To validate these results we performed expression analysis on select genes using immunohistochemistry and in situ hybridization. Fbxo2 showed the most striking pattern of specificity to the otic sensory lineage, including robust expression in the early otic vesicle and sustained expression in prosensory progenitors and auditory and vestibular hair cells and supporting cells.
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Affiliation(s)
- Byron H Hartman
- Department of Otolaryngology, Head and Neck Surgery, Stanford University School of Medicine Stanford, CA, USA
| | - Robert Durruthy-Durruthy
- Department of Otolaryngology, Head and Neck Surgery, Stanford University School of Medicine Stanford, CA, USA
| | - Roman D Laske
- Department of Otolaryngology, Head and Neck Surgery, Stanford University School of Medicine Stanford, CA, USA
| | - Steven Losorelli
- Department of Otolaryngology, Head and Neck Surgery, Stanford University School of Medicine Stanford, CA, USA
| | - Stefan Heller
- Department of Otolaryngology, Head and Neck Surgery, Stanford University School of Medicine Stanford, CA, USA
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20
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Park BY. Sox9 regulates development of neural crest and otic placode in a time- and dose-dependent fashion. J Biomed Res 2015. [DOI: 10.12729/jbr.2015.16.1.013] [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: 11/17/2022] Open
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21
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Abstract
Cranial sensory placodes derive from discrete patches of the head ectoderm and give rise to numerous sensory structures. During gastrulation, a specialized "neural border zone" forms around the neural plate in response to interactions between the neural and nonneural ectoderm and signals from adjacent mesodermal and/or endodermal tissues. This zone subsequently gives rise to two distinct precursor populations of the peripheral nervous system: the neural crest and the preplacodal ectoderm (PPE). The PPE is a common field from which all cranial sensory placodes arise (adenohypophyseal, olfactory, lens, trigeminal, epibranchial, otic). Members of the Six family of transcription factors are major regulators of PPE specification, in partnership with cofactor proteins such as Eya. Six gene activity also maintains tissue boundaries between the PPE, neural crest, and epidermis by repressing genes that specify the fates of those adjacent ectodermally derived domains. As the embryo acquires anterior-posterior identity, the PPE becomes transcriptionally regionalized, and it subsequently becomes subdivided into specific placodes with distinct developmental fates in response to signaling from adjacent tissues. Each placode is characterized by a unique transcriptional program that leads to the differentiation of highly specialized cells, such as neurosecretory cells, sensory receptor cells, chemosensory neurons, peripheral glia, and supporting cells. In this review, we summarize the transcriptional and signaling factors that regulate key steps of placode development, influence subsequent sensory neuron specification, and discuss what is known about mutations in some of the essential PPE genes that underlie human congenital syndromes.
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Affiliation(s)
- Sally A Moody
- Department of Anatomy and Regenerative Biology, The George Washington University, School of Medicine and Health Sciences, Washington, DC, USA; George Washington University Institute for Neuroscience, Washington, DC, USA.
| | - Anthony-Samuel LaMantia
- George Washington University Institute for Neuroscience, Washington, DC, USA; Department of Pharmacology and Physiology, The George Washington University, School of Medicine and Health Sciences, Washington, DC, USA
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22
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Abstract
The mammalian outer, middle, and inner ears have different embryonic origins and evolved at different times in the vertebrate lineage. The outer ear is derived from first and second branchial arch ectoderm and mesoderm, the middle ear ossicles are derived from neural crest mesenchymal cells that invade the first and second branchial arches, whereas the inner ear and its associated vestibule-acoustic (VIIIth) ganglion are derived from the otic placode. In this chapter, we discuss recent findings in the development of these structures and describe the contributions of members of a Forkhead transcription factor family, the Foxi family to their formation. Foxi transcription factors are critical for formation of the otic placode, survival of the branchial arch neural crest, and developmental remodeling of the branchial arch ectoderm.
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Affiliation(s)
- Renée K Edlund
- Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, USA
| | - Onur Birol
- Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, USA
| | - Andrew K Groves
- Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA; Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA.
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23
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Yan B, Neilson KM, Ranganathan R, Maynard T, Streit A, Moody SA. Microarray identification of novel genes downstream of Six1, a critical factor in cranial placode, somite, and kidney development. Dev Dyn 2014; 244:181-210. [PMID: 25403746 DOI: 10.1002/dvdy.24229] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [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: 06/05/2014] [Revised: 11/03/2014] [Accepted: 11/12/2014] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND Six1 plays an important role in the development of several vertebrate organs, including cranial sensory placodes, somites, and kidney. Although Six1 mutations cause one form of branchio-otic syndrome (BOS), the responsible gene in many patients has not been identified; genes that act downstream of Six1 are potential BOS candidates. RESULTS We sought to identify novel genes expressed during placode, somite and kidney development by comparing gene expression between control and Six1-expressing ectodermal explants. The expression patterns of 19 of the significantly up-regulated and 11 of the significantly down-regulated genes were assayed from cleavage to larval stages. A total of 28/30 genes are expressed in the otocyst, a structure that is functionally disrupted in BOS, and 26/30 genes are expressed in the nephric mesoderm, a structure that is functionally disrupted in the related branchio-otic-renal (BOR) syndrome. We also identified the chick homologues of five genes and show that they have conserved expression patterns. CONCLUSIONS Of the 30 genes selected for expression analyses, all are expressed at many of the developmental times and appropriate tissues to be regulated by Six1. Many have the potential to play a role in the disruption of hearing and kidney function seen in BOS/BOR patients.
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Affiliation(s)
- Bo Yan
- Department of Anatomy and Regenerative Biology, The George Washington University, School of Medicine and Health Sciences, Washington, DC
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24
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Maier EC, Whitfield TT. RA and FGF signalling are required in the zebrafish otic vesicle to pattern and maintain ventral otic identities. PLoS Genet 2014; 10:e1004858. [PMID: 25473832 PMCID: PMC4256275 DOI: 10.1371/journal.pgen.1004858] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 10/29/2014] [Indexed: 12/12/2022] Open
Abstract
During development of the zebrafish inner ear, regional patterning in the ventral half of the otic vesicle establishes zones of gene expression that correspond to neurogenic, sensory and non-neural cell fates. FGF and Retinoic acid (RA) signalling from surrounding tissues are known to have an early role in otic placode induction and otic axial patterning, but how external signalling cues are translated into intrinsic patterning during otic vesicle (OV) stages is not yet understood. FGF and RA signalling pathway members are expressed in and around the OV, suggesting important roles in later patterning or maintenance events. We have analysed the temporal requirement of FGF and RA signalling for otic development at stages after initial anteroposterior patterning has occurred. We show that high level FGF signalling acts to restrict sensory fates, whereas low levels favour sensory hair cell development; in addition, FGF is both required and sufficient to promote the expression of the non-neural marker otx1b in the OV. RA signalling has opposite roles: it promotes sensory fates, and restricts otx1b expression and the development of non-neural fates. This is surprisingly different from the earlier requirement for RA signalling in specification of non-neural fates via tbx1 expression, and highlights the shift in regulation that takes place between otic placode and vesicle stages in zebrafish. Both FGF and RA signalling are required for the development of the otic neurogenic domain and the generation of otic neuroblasts. In addition, our results indicate that FGF and RA signalling act in a feedback loop in the anterior OV, crucial for pattern refinement. The vertebrate inner ear is a complex three-dimensional structure with hearing and balance functions. To form a functional ear in the embryo, it is crucial that the right cells develop at the right time and in the right place. These cells include the sensory hair cells that detect sound and movement, neurons that relay sensory information to the brain, and structural cells. We have investigated patterning and maintenance events in the developing ear of the zebrafish embryo. We show that two signalling pathways, FGF and Retinoic Acid (RA), act in an antagonistic manner to regulate the numbers of sensory hair cells that develop, together with the expression of a key gene, otx1b, required for the development of structural cells. However, the two signalling pathways act in concert to regulate the emergence of neuronal cells. Our data also indicate that FGF and RA signalling form a feedback loop, placing them at the heart of the regulatory network that ensures correct patterning is maintained in the ear. Both FGF and RA signalling are employed to generate hair cells and neurons for replacement therapies to treat hearing loss. Understanding the roles of FGF and RA signalling underpins the development of such therapies.
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Affiliation(s)
- Esther C. Maier
- MRC Centre for Developmental and Biomedical Genetics, Bateson Centre and Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Tanya T. Whitfield
- MRC Centre for Developmental and Biomedical Genetics, Bateson Centre and Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
- * E-mail:
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25
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Maulding K, Padanad MS, Dong J, Riley BB. Mesodermal Fgf10b cooperates with other fibroblast growth factors during induction of otic and epibranchial placodes in zebrafish. Dev Dyn 2014; 243:1275-85. [PMID: 24677486 PMCID: PMC4313390 DOI: 10.1002/dvdy.24119] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [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: 11/04/2013] [Revised: 01/27/2014] [Accepted: 02/16/2014] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Vertebrate otic and epibranchial placodes develop in close proximity in response to localized fibroblast growth factor (Fgf) signaling. Although less is known about epibranchial induction, the process of otic induction in highly conserved, with important roles for Fgf3 and Fgf8 reported in all species examined. Fgf10 is also critical for otic induction in mouse, but the only zebrafish ortholog examined to date, fgf10a, is not expressed early enough to play such a role. A second zebrafish ortholog, fgf10b, has not been previously examined. RESULTS We find that zebrafish fgf10b is expressed at tailbud stage in paraxial cephalic mesoderm beneath prospective epibranchial tissue, lateral to the developing otic placode. Knockdown of fgf10b does not affect initial otic induction but impairs subsequent accumulation of otic cells. Formation of epibranchial placodes and ganglia are also moderately impaired. Combinatorial disruption of fgf10b and fgf3 exacerbates the deficiency of otic cells and eliminates epibranchial induction entirely. Disruption of fgf10b and fgf24 also strongly reduces, but does not eliminate, epibranchial induction. CONCLUSIONS fgf10b participates in a late phase of otic induction and, in combination with fgf3, is especially critical for epibranchial induction.
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Affiliation(s)
- Kirstin Maulding
- Biology Department, Texas A&M University, College Station, TX 77843-3258
| | - Mahesh S. Padanad
- Biology Department, Texas A&M University, College Station, TX 77843-3258
| | - Jennifer Dong
- Biology Department, Texas A&M University, College Station, TX 77843-3258
| | - Bruce B. Riley
- Biology Department, Texas A&M University, College Station, TX 77843-3258
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26
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Yao D, Zhao F, Wu Y, Wang J, Dong W, Zhao J, Zhu Z, Liu D. Dissecting the differentiation process of the preplacodal ectoderm in zebrafish. Dev Dyn 2014; 243:1338-51. [DOI: 10.1002/dvdy.24160] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 06/21/2014] [Accepted: 06/23/2014] [Indexed: 01/13/2023] Open
Affiliation(s)
- Di Yao
- The Education Ministry Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Bio-membrane and Membrane Bio-engineering; School of Life Sciences; Peking University; Beijing China
| | - Feng Zhao
- The Education Ministry Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Bio-membrane and Membrane Bio-engineering; School of Life Sciences; Peking University; Beijing China
| | - Ying Wu
- The Education Ministry Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Bio-membrane and Membrane Bio-engineering; School of Life Sciences; Peking University; Beijing China
| | - Jialiang Wang
- The Education Ministry Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Bio-membrane and Membrane Bio-engineering; School of Life Sciences; Peking University; Beijing China
| | - Wei Dong
- The Education Ministry Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Bio-membrane and Membrane Bio-engineering; School of Life Sciences; Peking University; Beijing China
| | - Jue Zhao
- The Education Ministry Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Bio-membrane and Membrane Bio-engineering; School of Life Sciences; Peking University; Beijing China
| | - Zuoyan Zhu
- The Education Ministry Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Bio-membrane and Membrane Bio-engineering; School of Life Sciences; Peking University; Beijing China
| | - Dong Liu
- The Education Ministry Key Laboratory of Cell Proliferation and Differentiation and the State Key Laboratory of Bio-membrane and Membrane Bio-engineering; School of Life Sciences; Peking University; Beijing China
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Khatri SB, Edlund RK, Groves AK. Foxi3 is necessary for the induction of the chick otic placode in response to FGF signaling. Dev Biol 2014; 391:158-69. [PMID: 24780628 DOI: 10.1016/j.ydbio.2014.04.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 03/19/2014] [Accepted: 04/20/2014] [Indexed: 01/06/2023]
Abstract
Vertebrate cranial sensory organs are derived from region at the border of the anterior neural plate called the pre-placodal region (PPR). The otic placode, the anlagen of the inner ear, is induced from PPR ectoderm by FGF signaling. We have previously shown that competence of embryonic ectoderm to respond to FGF signaling during otic placode induction correlates with the expression of PPR genes, but the molecular basis of this competence is poorly understood. Here, we characterize the function of a transcription factor, Foxi3 that is expressed at very early stages in the non-neural ectoderm and later in the PPR of chick embryos. Ablation experiments showed that the underlying hypoblast is necessary for the initiation of Foxi3 expression. Mis-expression of Foxi3 was sufficient to induce markers of non-neural ectoderm such as Dlx5, and the PPR such as Six1 and Eya2. Electroporation of Dlx5, or Six1 together with Eya1 also induced Foxi3, suggesting direct or indirect positive regulation between non-neural ectoderm genes and PPR genes. Knockdown of Foxi3 in chick embryos prevented the induction of otic placode markers, and was able to prevent competent cranial ectoderm from expressing otic markers in response to FGF2. In contrast, Foxi3 expression alone was not sufficient to confer competence to respond to FGF on embryonic ectoderm. Our analysis of PPR and FGF-responsive genes after Foxi3 knockdown at gastrula stages suggests it is not necessary for the expression of PPR genes at these stages, nor for the transduction of FGF signals. The early expression but late requirement for Foxi3 in ear induction suggests it may have some of the properties associated with pioneer transcription factors.
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Saint-Jeannet JP, Moody SA. Establishing the pre-placodal region and breaking it into placodes with distinct identities. Dev Biol 2014; 389:13-27. [PMID: 24576539 DOI: 10.1016/j.ydbio.2014.02.011] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Revised: 02/13/2014] [Accepted: 02/14/2014] [Indexed: 11/17/2022]
Abstract
Specialized sensory organs in the vertebrate head originate from thickenings in the embryonic ectoderm called cranial sensory placodes. These placodes, as well as the neural crest, arise from a zone of ectoderm that borders the neural plate. This zone separates into a precursor field for the neural crest that lies adjacent to the neural plate, and a precursor field for the placodes, called the pre-placodal region (PPR), that lies lateral to the neural crest. The neural crest domain and the PPR are established in response to signaling events mediated by BMPs, FGFs and Wnts, which differentially activate transcription factors in these territories. In the PPR, members of the Six and Eya families, act in part to repress neural crest specific transcription factors, thus solidifying a placode developmental program. Subsequently, in response to environmental cues the PPR is further subdivided into placodal territories with distinct characteristics, each expressing a specific repertoire of transcription factors that provide the necessary information for their progression to mature sensory organs. In this review we summarize recent advances in the characterization of the signaling molecules and transcriptional effectors that regulate PPR specification and its subdivision into placodal domains with distinct identities.
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Affiliation(s)
- Jean-Pierre Saint-Jeannet
- Department of Basic Science and Craniofacial Biology, New York University, College of Dentistry, 345 East 24th Street, New York City, NY 10010, USA.
| | - Sally A Moody
- Department of Anatomy and Regenerative Biology, The George Washington University, School of Medicine and Health Sciences, 2300 I (eye) Street, NW, Washington, DC 20037, USA.
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29
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Hans S, Irmscher A, Brand M. Zebrafish Foxi1 provides a neuronal ground state during inner ear induction preceding the Dlx3b/4b-regulated sensory lineage. Development 2013; 140:1936-45. [PMID: 23571216 DOI: 10.1242/dev.087718] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Vertebrate inner ear development is a complex process that involves the induction of a common territory for otic and epibranchial precursors and their subsequent segregation into otic and epibranchial cell fates. In zebrafish, the otic-epibranchial progenitor domain (OEPD) is induced by Fgf signaling in a Foxi1- and Dlx3b/4b-dependent manner, but the functional differences of Foxi1 and Dlx3b/4b in subsequent cell fate specifications within the developing inner ear are poorly understood. Based on pioneer tracking (PioTrack), a novel Cre-dependent genetic lineage tracing method, and genetic data, we show that the competence to embark on a neuronal or sensory fate is provided sequentially and very early during otic placode induction. Loss of Foxi1 prevents neuronal precursor formation without affecting hair cell specification, whereas loss of Dlx3b/4b inhibits hair cell but not neuronal precursor formation. Consistently, in Dlx3b/4b- and Sox9a-deficient b380 mutants almost all otic epithelial fates are absent, including sensory hair cells, and the remaining otic cells adopt a neuronal fate. Furthermore, the progenitors of the anterior lateral line ganglia also arise from the OEPD in a Foxi1-dependent manner but are unaffected in the absence of Dlx3b/4b or in b380 mutants. Thus, in addition to otic fate Foxi1 provides neuronal competence during OEPD induction prior to and independently of the Dlx3b/4b-mediated sensory fate of the developing inner ear.
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Affiliation(s)
- Stefan Hans
- Technische Universität Dresden, Biotechnology Center and DFG-Center for Regenerative Therapies Dresden Cluster of Excellence, Tatzberg 47-49, Dresden, Germany.
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30
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Economou A, Datta P, Georgiadis V, Cadot S, Frenz D, Maconochie M. Gata3 directly regulates early inner ear expression of Fgf10. Dev Biol 2013; 374:210-22. [DOI: 10.1016/j.ydbio.2012.11.028] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 11/23/2012] [Accepted: 11/26/2012] [Indexed: 01/19/2023]
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Abstract
Despite its complexity in the adult, during development the inner ear arises from a simple epithelium, the otic placode. Placode specification is a multistep process that involves the integration of various signalling pathways and downstream transcription factors in time and space. Here we review the molecular events that successively commit multipotent ectodermal precursors to the otic lineage. The first step in this hierarchy is the specification of sensory progenitor cells, which can contribute to all sensory placodes, followed by the induction of a common otic-epibranchial field and finally the establishment the otic territory. In recent years, some of the molecular components that control this process have been identified, and begin to reveal complex interactions. Future studies will need to unravel how this information is integrated and encoded in the genome. This will form the blueprint for stem cell differentiation towards otic fates and generate a predictive gene regulatory network that models the earliest steps of otic specification.
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Affiliation(s)
- Jingchen Chen
- Department of Craniofacial Development and Stem Cell Biology, King's College London, Guy's Tower Wing, Floor 27, London SE1 9RT, UK
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32
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Bhat N, Kwon HJ, Riley BB. A gene network that coordinates preplacodal competence and neural crest specification in zebrafish. Dev Biol 2013; 373:107-17. [PMID: 23078916 DOI: 10.1016/j.ydbio.2012.10.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2012] [Revised: 09/23/2012] [Accepted: 10/09/2012] [Indexed: 11/20/2022]
Abstract
Preplacodal ectoderm (PPE) and neural crest (NC) are specified at the interface of neural and nonneural ectoderm and together contribute to the peripheral nervous system in all vertebrates. Bmp activates early steps for both fates during late blastula stage. Low Bmp activates expression of transcription factors Tfap2a and Tfap2c in the lateral neural plate, thereby specifying neural crest fate. Elevated Bmp establishes preplacodal competence throughout the ventral ectoderm by coinducing Tfap2a, Tfap2c, Foxi1 and Gata3. PPE specification occurs later at the end of gastrulation and requires complete attenuation of Bmp, yet expression of PPE competence factors continues well past gastrulation. Here we show that competence factors positively regulate each other's expression during gastrulation, forming a self-sustaining network that operates independently of Bmp. Misexpression of Tfap2a in embryos blocked for Bmp from late blastula stage can restore development of both PPE and NC. However, Tfap2a alone is not sufficient to activate any other competence factors nor does it rescue individual placodes. On the other hand, misexpression of any two competence factors in Bmp-blocked embryos can activate the entire transcription factor network and support the development of NC, PPE and some individual placodes. We also show that while these factors are partially redundant with respect to PPE specification, they later provide non-redundant functions needed for development of specific placodes. Thus, we have identified a gene regulatory network that coordinates development of NC, PPE and individual placodes in zebrafish.
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Magariños M, Contreras J, Aburto MR, Varela-Nieto I. Early development of the vertebrate inner ear. Anat Rec (Hoboken) 2012; 295:1775-90. [PMID: 23044927 DOI: 10.1002/ar.22575] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Accepted: 07/24/2012] [Indexed: 12/12/2022]
Abstract
This is a review of the biological processes and the main signaling pathways required to generate the different otic cell types, with particular emphasis on the actions of insulin-like growth factor I. The sensory organs responsible of hearing and balance have a common embryonic origin in the otic placode. Lineages of neural, sensory, and support cells are generated from common otic neuroepithelial progenitors. The sequential generation of the cell types that will form the adult inner ear requires the coordination of cell proliferation with cell differentiation programs, the strict regulation of cell survival, and the metabolic homeostasis of otic precursors. A network of intracellular signals operates to coordinate the transcriptional response to the extracellular input. Understanding the molecular clues that direct otic development is fundamental for the design of novel treatments for the protection and repair of hearing loss and balance disorders.
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Affiliation(s)
- Marta Magariños
- Instituto de Investigaciones Biomédicas, Alberto Sols, CSIC-UAM, Madrid, Spain
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34
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Grocott T, Tambalo M, Streit A. The peripheral sensory nervous system in the vertebrate head: a gene regulatory perspective. Dev Biol 2012; 370:3-23. [PMID: 22790010 DOI: 10.1016/j.ydbio.2012.06.028] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [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] [Received: 04/17/2012] [Revised: 06/28/2012] [Accepted: 06/29/2012] [Indexed: 02/06/2023]
Abstract
In the vertebrate head, crucial parts of the sense organs and sensory ganglia develop from special regions, the cranial placodes. Despite their cellular and functional diversity, they arise from a common field of multipotent progenitors and acquire distinct identity later under the influence of local signalling. Here we present the gene regulatory network that summarises our current understanding of how sensory cells are specified, how they become different from other ectodermal derivatives and how they begin to diversify to generate placodes with different identities. This analysis reveals how sequential activation of sets of transcription factors subdivides the ectoderm over time into smaller domains of progenitors for the central nervous system, neural crest, epidermis and sensory placodes. Within this hierarchy the timing of signalling and developmental history of each cell population is of critical importance to determine the ultimate outcome. A reoccurring theme is that local signals set up broad gene expression domains, which are further refined by mutual repression between different transcription factors. The Six and Eya network lies at the heart of sensory progenitor specification. In a positive feedback loop these factors perpetuate their own expression thus stabilising pre-placodal fate, while simultaneously repressing neural and neural crest specific factors. Downstream of the Six and Eya cassette, Pax genes in combination with other factors begin to impart regional identity to placode progenitors. While our review highlights the wealth of information available, it also points to the lack information on the cis-regulatory mechanisms that control placode specification and of how the repeated use of signalling input is integrated.
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Affiliation(s)
- Timothy Grocott
- Department of Craniofacial Development and Stem Cell Biology, King's College London, Guy's Tower Wing, Floor 27, London SE1 9RT, UK
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35
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Padanad MS, Bhat N, Guo B, Riley BB. Conditions that influence the response to Fgf during otic placode induction. Dev Biol 2012; 364:1-10. [PMID: 22327005 DOI: 10.1016/j.ydbio.2012.01.022] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [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] [Received: 11/07/2011] [Revised: 01/22/2012] [Accepted: 01/26/2012] [Indexed: 01/04/2023]
Abstract
Despite the vital importance of Fgf for otic induction, previous attempts to study otic induction through Fgf misexpression have yielded widely varying and contradictory results. There are also discrepancies regarding the ability of Fgf to induce otic tissue in ectopic locations, raising questions about the sufficiency of Fgf and the degree to which other local factors enhance or restrict otic potential. Using heat shock-inducible transgenes to misexpress Fgf3 or Fgf8 in zebrafish, we found that the stage, distribution and level of misexpression strongly influence the response to Fgf. Fgf misexpression during gastrulation can inhibit or promote otic development, depending on context, whereas misexpression after gastrulation leads to expansion of otic markers throughout preplacodal ectoderm surrounding the head. Elevated Fgf also expands expression of the putative competence factor Foxi1, which is required for Fgf to expand other otic markers. Misexpression of downstream factors Pax2a or Pax8 also expands otic markers but cannot bypass the requirement for Fgf or Foxi1. Co-misexpression of Pax2/8 with Fgf8 potentiates formation of ectopic otic vesicles expressing a full range of otic markers. These findings document the variables critically affecting the response to Fgf and clarify the roles of foxi1 and pax2/8 in the otic response.
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Affiliation(s)
- Mahesh S Padanad
- Biology Department, Texas A&M University, College Station, TX 77843-3258, USA
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36
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Hammond KL, Whitfield TT. Fgf and Hh signalling act on a symmetrical pre-pattern to specify anterior and posterior identity in the zebrafish otic placode and vesicle. Development 2011; 138:3977-87. [PMID: 21831919 PMCID: PMC3160093 DOI: 10.1242/dev.066639] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [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] [Accepted: 07/01/2011] [Indexed: 11/20/2022]
Abstract
Specification of the otic anteroposterior axis is one of the earliest patterning events during inner ear development. In zebrafish, Hedgehog signalling is necessary and sufficient to specify posterior otic identity between the 10 somite (otic placode) and 20 somite (early otic vesicle) stages. We now show that Fgf signalling is both necessary and sufficient for anterior otic specification during a similar period, a function that is completely separable from its earlier role in otic placode induction. In lia(-/-) (fgf3(-/-)) mutants, anterior otic character is reduced, but not lost altogether. Blocking all Fgf signalling at 10-20 somites, however, using the pan-Fgf inhibitor SU5402, results in the loss of anterior otic structures and a mirror image duplication of posterior regions. Conversely, overexpression of fgf3 during a similar period, using a heat-shock inducible transgenic line, results in the loss of posterior otic structures and a duplication of anterior domains. These phenotypes are opposite to those observed when Hedgehog signalling is altered. Loss of both Fgf and Hedgehog function between 10 and 20 somites results in symmetrical otic vesicles with neither anterior nor posterior identity, which, nevertheless, retain defined poles at the anterior and posterior ends of the ear. These data suggest that Fgf and Hedgehog act on a symmetrical otic pre-pattern to specify anterior and posterior otic identity, respectively. Each signalling pathway has instructive activity: neither acts simply to repress activity of the other, and, together, they appear to be key players in the specification of anteroposterior asymmetries in the zebrafish ear.
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Affiliation(s)
- Katherine L. Hammond
- MRC Centre for Developmental and Biomedical Genetics and Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK
| | - Tanya T. Whitfield
- MRC Centre for Developmental and Biomedical Genetics and Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK
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37
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Sinkkonen ST, Starlinger V, Galaiya DJ, Laske RD, Myllykangas S, Oshima K, Heller S. Serial analysis of gene expression in the chicken otocyst. J Assoc Res Otolaryngol 2011; 12:697-710. [PMID: 21853378 DOI: 10.1007/s10162-011-0286-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Accepted: 08/02/2011] [Indexed: 10/17/2022] Open
Abstract
The inner ear arises from multipotent placodal precursors that are gradually committed to the otic fate and further differentiate into all inner ear cell types, with the exception of a few immigrating neural crest-derived cells. The otocyst plays a pivotal role during inner ear development: otic progenitor cells sub-compartmentalize into non-sensory and prosensory domains, giving rise to individual vestibular and auditory organs and their associated ganglia. The genes and pathways underlying this progressive subdivision and differentiation process are not entirely known. The goal of this study was to identify a comprehensive set of genes expressed in the chicken otocyst using the serial analysis of gene expression (SAGE) method. Our analysis revealed several hundred transcriptional regulators, potential signaling proteins, and receptors. We identified a substantial collection of genes that were previously known in the context of inner ear development, but we also found many new candidate genes, such as SOX4, SOX5, SOX7, SOX8, SOX11, and SOX18, which previously were not known to be expressed in the developing inner ear. Despite its limitation of not being all-inclusive, the generated otocyst SAGE library is a practical bioinformatics tool to study otocyst gene expression and to identify candidate genes for developmental studies.
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Affiliation(s)
- Saku T Sinkkonen
- Departments of Otolaryngology-Head & Neck Surgery and Molecular & Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5739, USA
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38
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Betancur P, Sauka-Spengler T, Bronner M. A Sox10 enhancer element common to the otic placode and neural crest is activated by tissue-specific paralogs. Development 2011; 138:3689-98. [PMID: 21775416 DOI: 10.1242/dev.057836] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The otic placode, a specialized region of ectoderm, gives rise to components of the inner ear and shares many characteristics with the neural crest, including expression of the key transcription factor Sox10. Here, we show that in avian embryos, a highly conserved cranial neural crest enhancer, Sox10E2, also controls the onset of Sox10 expression in the otic placode. Interestingly, we show that different combinations of paralogous transcription factors (Sox8, Pea3 and cMyb versus Sox9, Ets1 and cMyb) are required to mediate Sox10E2 activity in the ear and neural crest, respectively. Mutating their binding motifs within Sox10E2 greatly reduces enhancer activity in the ear. Moreover, simultaneous knockdown of Sox8, Pea3 and cMyb eliminates not only the enhancer-driven reporter expression, but also the onset of endogenous Sox10 expression in the ear. Rescue experiments confirm that the specific combination of Myb together with Sox8 and Pea3 is responsible for the onset of Sox10 expression in the otic placode, as opposed to Myb plus Sox9 and Ets1 for neural crest Sox10 expression. Whereas SUMOylation of Sox8 is not required for the initial onset of Sox10 expression, it is necessary for later otic vesicle formation. This new role of Sox8, Pea3 and cMyb in controlling Sox10 expression via a common otic/neural crest enhancer suggests an evolutionarily conserved function for the combination of paralogous transcription factors in these tissues of distinct embryological origin.
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Affiliation(s)
- Paola Betancur
- Division of Biology 139-74, California Institute of Technology, Pasadena, CA 91125, USA
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Padanad MS, Riley BB. Pax2/8 proteins coordinate sequential induction of otic and epibranchial placodes through differential regulation of foxi1, sox3 and fgf24. Dev Biol 2011; 351:90-8. [PMID: 21215261 DOI: 10.1016/j.ydbio.2010.12.036] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Revised: 12/15/2010] [Accepted: 12/17/2010] [Indexed: 11/24/2022]
Abstract
Vertebrate cranial placodes contribute vitally to development of sensory structures of the head. Amongst posterior placodes, the otic placode forms the inner ear whereas nearby epibranchial placodes produce sensory ganglia within branchial clefts. Though diverse in fate, these placodes show striking similarities in their early regulation. In zebrafish, both are initiated by localized Fgf signaling plus the ubiquitous competence factor Foxi1, and both express pax8 and sox3 in response. It has been suggested that Fgf initially induces a common otic/epibranchial field, which later subdivides in response to other signals. However, we find that otic and epibranchial placodes form at different times and by distinct mechanisms. Initially, Fgf from surrounding tissues induces otic expression of pax8 and sox3, which cooperate synergistically to establish otic fate. Subsequently, pax8 works with related genes pax2a/pax2b to downregulate otic expression of foxi1, a necessary step for further otic development. Additionally, pax2/8 activate otic expression of fgf24, which induces epibranchial expression of sox3. Knockdown of fgf24 or sox3 causes severe epibranchial deficiencies but has little effect on otic development. These findings clarify the roles of pax8 and sox3 and support a model whereby the otic placode forms first and induces epibranchial placodes through an Fgf-relay.
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Affiliation(s)
- Mahesh S Padanad
- Biology Department, Texas A&M University, College Station, TX 77843-3258, USA
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40
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Kwon HJ, Bhat N, Sweet EM, Cornell RA, Riley BB. Identification of early requirements for preplacodal ectoderm and sensory organ development. PLoS Genet 2010; 6:e1001133. [PMID: 20885782 PMCID: PMC2944784 DOI: 10.1371/journal.pgen.1001133] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Accepted: 08/22/2010] [Indexed: 11/25/2022] Open
Abstract
Preplacodal ectoderm arises near the end of gastrulation as a narrow band of cells surrounding the anterior neural plate. This domain later resolves into discrete cranial placodes that, together with neural crest, produce paired sensory structures of the head. Unlike the better-characterized neural crest, little is known about early regulation of preplacodal development. Classical models of ectodermal patterning posit that preplacodal identity is specified by readout of a discrete level of Bmp signaling along a DV gradient. More recent studies indicate that Bmp-antagonists are critical for promoting preplacodal development. However, it is unclear whether Bmp-antagonists establish the proper level of Bmp signaling within a morphogen gradient or, alternatively, block Bmp altogether. To begin addressing these issues, we treated zebrafish embryos with a pharmacological inhibitor of Bmp, sometimes combined with heat shock-induction of Chordin and dominant-negative Bmp receptor, to fully block Bmp signaling at various developmental stages. We find that preplacodal development occurs in two phases with opposing Bmp requirements. Initially, Bmp is required before gastrulation to co-induce four transcription factors, Tfap2a, Tfap2c, Foxi1, and Gata3, which establish preplacodal competence throughout the nonneural ectoderm. Subsequently, Bmp must be fully blocked in late gastrulation by dorsally expressed Bmp-antagonists, together with dorsally expressed Fgf and Pdgf, to specify preplacodal identity within competent cells abutting the neural plate. Localized ventral misexpression of Fgf8 and Chordin can activate ectopic preplacodal development anywhere within the zone of competence, whereas dorsal misexpression of one or more competence factors can activate ectopic preplacodal development in the neural plate. Conversely, morpholino-knockdown of competence factors specifically ablates preplacodal development. Our work supports a relatively simple two-step model that traces regulation of preplacodal development to late blastula stage, resolves two distinct phases of Bmp dependence, and identifies the main factors required for preplacodal competence and specification. Cranial placodes, which produce sensory structures in the head, arise from a contiguous band of preplacodal ectoderm surrounding the anterior neural plate during gastrulation. Little is known about early regulation of preplacodal ectoderm, but modulation of signaling through Bone Morphogenetic Protein (Bmp) is clearly involved. Recent studies show that dorsally expressed Bmp-antagonists help establish preplacodal ectoderm, but it is not clear whether antagonists titrate Bmp to a discrete low level that actively induces preplacodal fate or, alternatively, whether Bmp must be fully blocked to permit preplacodal development. We show that in zebrafish preplacodal development occurs in distinct phases with differing Bmp requirements. Initially, Bmp is required before gastrulation to render all ventral ectoderm competent to form preplacodal tissue. We further show that four transcription factors, Foxi1, Gata3, Tfap2a, and Tfap2c, specifically mediate preplacodal competence. Once induced, these factors no longer require Bmp. Thereafter, Bmp must be fully blocked by dorsally expressed Bmp-antagonists to permit preplacodal development. In addition, dorsally expressed Fgf and/or Pdgf are also required, activating preplacodal development in competent cells abutting the neural plate. Thus, we have resolved the role of Bmp and traced the regulation of preplacodal development to pre-gastrula stage.
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Affiliation(s)
- Hye-Joo Kwon
- Biology Department, Texas A&M University, College Station, Texas, United States of America
| | - Neha Bhat
- Biology Department, Texas A&M University, College Station, Texas, United States of America
| | - Elly M. Sweet
- Biology Department, Texas A&M University, College Station, Texas, United States of America
| | - Robert A. Cornell
- Department of Anatomy and Cell Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Bruce B. Riley
- Biology Department, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
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41
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Talbot JC, Johnson SL, Kimmel CB. hand2 and Dlx genes specify dorsal, intermediate and ventral domains within zebrafish pharyngeal arches. Development 2010; 137:2507-17. [PMID: 20573696 DOI: 10.1242/dev.049700] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The ventrally expressed secreted polypeptide endothelin1 (Edn1) patterns the skeleton derived from the first two pharyngeal arches into dorsal, intermediate and ventral domains. Edn1 activates expression of many genes, including hand2 and Dlx genes. We wanted to know how hand2/Dlx genes might generate distinct domain identities. Here, we show that differential expression of hand2 and Dlx genes delineates domain boundaries before and during cartilage morphogenesis. Knockdown of the broadly expressed genes dlx1a and dlx2a results in both dorsal and intermediate defects, whereas knockdown of three intermediate-domain restricted genes dlx3b, dlx4b and dlx5a results in intermediate-domain-specific defects. The ventrally expressed gene hand2 patterns ventral identity, in part by repressing dlx3b/4b/5a. The jaw joint is an intermediate-domain structure that expresses nkx3.2 and a more general joint marker, trps1. The jaw joint expression of trps1 and nkx3.2 requires dlx3b/4b/5a function, and expands in hand2 mutants. Both hand2 and dlx3b/4b/5a repress dorsal patterning markers. Collectively, our work indicates that the expression and function of hand2 and Dlx genes specify major patterning domains along the dorsoventral axis of zebrafish pharyngeal arches.
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Ladher RK, O'Neill P, Begbie J. From shared lineage to distinct functions: the development of the inner ear and epibranchial placodes. Development 2010; 137:1777-85. [PMID: 20460364 DOI: 10.1242/dev.040055] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The inner ear and the epibranchial ganglia constitute much of the sensory system in the caudal vertebrate head. The inner ear consists of mechanosensory hair cells, their neurons, and structures necessary for sound and balance sensation. The epibranchial ganglia are knots of neurons that innervate and relay sensory signals from several visceral organs and the taste buds. Their development was once thought to be independent, in line with their independent functions. However, recent studies indicate that both systems arise from a morphologically distinct common precursor domain: the posterior placodal area. This review summarises recent studies into the induction, morphogenesis and innervation of these systems and discusses lineage restriction and cell specification in the context of their common origin.
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Affiliation(s)
- Raj K Ladher
- RIKEN Center for Developmental Biology, Chuoku, Kobe 650-0047, Japan.
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Urness LD, Paxton CN, Wang X, Schoenwolf GC, Mansour SL. FGF signaling regulates otic placode induction and refinement by controlling both ectodermal target genes and hindbrain Wnt8a. Dev Biol 2010; 340:595-604. [PMID: 20171206 PMCID: PMC2854211 DOI: 10.1016/j.ydbio.2010.02.016] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [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: 01/13/2010] [Revised: 02/10/2010] [Accepted: 02/10/2010] [Indexed: 12/25/2022]
Abstract
The inner ear epithelium, with its complex array of sensory, non-sensory, and neuronal cell types necessary for hearing and balance, is derived from a thickened patch of head ectoderm called the otic placode. Mouse embryos lacking both Fgf3 and Fgf10 fail to initiate inner ear development because appropriate patterns of gene expression fail to be specified within the pre-otic field. To understand the transcriptional "blueprint" initiating inner ear development, we used microarray analysis to identify prospective placode genes that were differentially expressed in control and Fgf3(-)(/)(-);Fgf10(-)(/)(-) embryos. Several genes in the down-regulated class, including Hmx3, Hmx2, Foxg1, Sox9, Has2, and Slc26a9 were validated by in situ hybridization. We also assayed candidate target genes suggested by other studies of otic induction. Two placode markers, Fgf4 and Foxi3, were down-regulated in Fgf3(-)(/)(-);Fgf10(-)(/)(-) embryos, whereas Foxi2, a cranial epidermis marker, was expanded in double mutants, similar to its behavior when WNT responses are blocked in the otic placode. Assays of hindbrain Wnt genes revealed that only Wnt8a was reduced or absent in FGF-deficient embryos, and that even some Fgf3(-)(/)(-);Fgf10(-)(/+) and Fgf3(-)(/)(-) embryos failed to express Wnt8a, suggesting a key role for Fgf3, and a secondary role for Fgf10, in Wnt8a expression. Chick explant assays showed that FGF3 or FGF4, but not FGF10, were sufficient to induce Wnt8a. Collectively, our results suggest that Wnt8a provides the link between FGF-induced formation of the pre-otic field and restriction of the otic placode to ectoderm adjacent to the hindbrain.
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Affiliation(s)
- Lisa D. Urness
- Department of Human Genetics, University of Utah, 15 N 2030 E, RM 2100, Salt Lake City, UT 84112-5330, USA
| | - Christian N. Paxton
- Department of Neurobiology and Anatomy, University of Utah, 30 N 1900 E, RM 2R066 SOM, Salt Lake City, UT 84132-3401, USA
| | - Xiaofen Wang
- Department of Human Genetics, University of Utah, 15 N 2030 E, RM 2100, Salt Lake City, UT 84112-5330, USA
| | - Gary C. Schoenwolf
- Department of Neurobiology and Anatomy, University of Utah, 30 N 1900 E, RM 2R066 SOM, Salt Lake City, UT 84132-3401, USA
| | - Suzanne L. Mansour
- Department of Human Genetics, University of Utah, 15 N 2030 E, RM 2100, Salt Lake City, UT 84112-5330, USA
- Department of Neurobiology and Anatomy, University of Utah, 30 N 1900 E, RM 2R066 SOM, Salt Lake City, UT 84132-3401, USA
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Abstract
The transcription factor Sox9 has been implicated in inner ear formation in several species. To investigate the long-term consequences of Sox9 depletion on inner ear development we analyzed the inner ear architecture of Sox9-depleted Xenopus tadpoles generated by injection of increasing amounts of Sox9 morpholino antisense oligonucleotides. We found that Sox9-depletion resulted in major defects in the development of vestibular structures, semicircular canals and utricle, while the ventrally located saccule was less severely affected in these embryos. Consistent with this phenotype, we observed a specific loss of the dorsal expression of Wnt3a expression in the otic vesicle of Sox9 morphants, associated with an increase in cell death and a reduction in cell proliferation in the region of the presumptive otic epithelium. We propose that, in addition to its early role in placode specification, Sox9 is also required for the maintenance of progenitors in the otic epithelium.
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Affiliation(s)
- Byung-Yong Park
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104, USA
| | - Jean-Pierre Saint-Jeannet
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104, USA
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Feng Y, Xu Q. Pivotal role of hmx2 and hmx3 in zebrafish inner ear and lateral line development. Dev Biol 2010; 339:507-18. [DOI: 10.1016/j.ydbio.2009.12.028] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Revised: 12/17/2009] [Accepted: 12/18/2009] [Indexed: 10/20/2022]
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Abstract
Cranial placodes (which include the adenohypophyseal, olfactory, lens, otic, lateral line, profundal/trigeminal, and epibranchial placodes) give rise to many sense organs and ganglia of the vertebrate head. Recent evidence suggests that all cranial placodes may be developmentally related structures, which originate from a common panplacodal primordium at neural plate stages and use similar regulatory mechanisms to control developmental processes shared between different placodes such as neurogenesis and morphogenetic movements. After providing a brief overview of placodal diversity, the present review summarizes current evidence for the existence of a panplacodal primordium and discusses the central role of transcription factors Six1 and Eya1 in the regulation of processes shared between different placodes. Upstream signaling events and transcription factors involved in early embryonic induction and specification of the panplacodal primordium are discussed next. I then review how individual placodes arise from the panplacodal primordium and present a model of multistep placode induction. Finally, I briefly summarize recent advances concerning how placodal neurons and sensory cells are specified, and how morphogenesis of placodes (including delamination and migration of placode-derived cells and invagination) is controlled.
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Affiliation(s)
- Gerhard Schlosser
- Zoology, School of Natural Sciences & Martin Ryan Institute, National University of Ireland, Galway, Ireland
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Abbas L, Whitfield TT. The zebrafish inner ear. ACTA ACUST UNITED AC 2010. [DOI: 10.1016/s1546-5098(10)02904-3] [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: 03/07/2023]
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Paxton CN, Bleyl SB, Chapman SC, Schoenwolf GC. Identification of differentially expressed genes in early inner ear development. Gene Expr Patterns 2009; 10:31-43. [PMID: 19913109 DOI: 10.1016/j.gep.2009.11.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Revised: 10/30/2009] [Accepted: 11/05/2009] [Indexed: 01/06/2023]
Abstract
To understand the etiology of congenital hearing loss, a comprehensive understanding of the molecular genetic mechanisms underlying normal ear development is required. We are identifying genes involved in otogenesis, with the longer term goal of studying their mechanisms of action, leading to inner ear induction and patterning. Using Agilent microarrays, we compared the differential expression of a test domain (which consisted of the pre-otic placodal ectoderm with the adjacent hindbrain ectoderm and the underlying mesendodermal tissues) with a rostral control domain (which included tissue that is competent, but not specified, to express inner ear markers in explant assays). We identified 1261 transcripts differentially expressed between the two domains at a 2-fold or greater change: 463 were upregulated and 798 were downregulated in the test domain. We validated the differential expression of several signaling molecules and transcription factors identified in this array using in situ hybridization. Furthermore, the expression patterns of the validated group of genes from the test domain were explored in detail to determine how the timing of their expression relates to specific events of otic induction and development. In conclusion, we identified a number of novel candidate genes for otic placode induction.
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Affiliation(s)
- Christian N Paxton
- University of Utah, Dept. of Neurobiology and Anatomy, Salt Lake City, UT 84132-3401, USA
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Kwon HJ, Riley BB. Mesendodermal signals required for otic induction: Bmp-antagonists cooperate with Fgf and can facilitate formation of ectopic otic tissue. Dev Dyn 2009; 238:1582-94. [PMID: 19418450 DOI: 10.1002/dvdy.21955] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Induction of otic placodes requires Fgf from surrounding tissues. We tested the hypothesis that mesendodermally derived Bmp-antagonists Chordin, Follistatin-a, and Crossveinless-2 cooperate in this process. Injecting morpholinos for all three genes, or treatment with the Nodal inhibitor SB431542 to block mesoderm-formation, reduces otic induction and strongly enhances the effects of disrupting fgf3 or fgf8. In contrast, using a lower dose of SB431542, combined with partial loss of Fgf, causes a dramatic medial expansion of otic tissue and formation of a single, large otic vesicle spanning the width of the hindbrain. Under these conditions, paraxial cephalic mesoderm forms ectopically at the midline, migrates into the head, and later transfates to form otic tissue beneath the hindbrain. Blocking expression of Bmp-antagonists blocks formation of medial otic tissue. These data show the importance of mesendodermal Bmp-antagonists for otic induction and that paraxial cephalic mesendoderm can facilitate its own otic differentiation under certain circumstances. Developmental Dynamics 238:1582-1594, 2009. (c) 2009 Wiley-Liss, Inc.
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Affiliation(s)
- Hye-Joo Kwon
- Biology Department, Texas A&M University, College Station, Texas, USA
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Abstract
The Wnt family of signalling proteins is known to participate in multiple developmental decisions during embryogenesis. We misexpressed Wnt1 in medaka embryos and observed anterior truncations, similar to those described for ectopic activation of canonical Wnt signalling in other species. Interestingly, when we induced a heat-shock Wnt1 transgenic line exactly at 30% epiboly, we observed multiple ectopic otic vesicles in the truncated embryos. The vesicles then fused, forming a single large ear structure. These "cyclopic ears" filled the complete anterior region of the embryos. The ectopic induction of otic development can be explained by the juxtaposition of hindbrain tissue with anterior ectoderm. Fibroblast growth factor (Fgf) ligands are thought to mediate the otic-inducing properties of the hindbrain. However, signals different from Fgf3 and Fgf8 are necessary to explain the formation of the ectopic ear structures, suggesting that Wnt signalling is involved in the otic induction process in medaka.
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Affiliation(s)
- Baubak Bajoghli
- Department for Biomedical Sciences, University of Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria
- Present Address: Max-Planck Institute of Immunobiology, Stuebeweg 51, 79108 Freiburg, Germany
| | - Narges Aghaallaei
- Department for Biomedical Sciences, University of Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria
- Present Address: Max-Planck Institute of Immunobiology, Stuebeweg 51, 79108 Freiburg, Germany
| | - Gerlinde Jung
- Department for Applied Life Sciences, University of Applied Sciences, FH Campus Wien, Viehmarktgasse 2A, 1030 Vienna, Austria
| | - Thomas Czerny
- Department for Biomedical Sciences, University of Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria
- Department for Applied Life Sciences, University of Applied Sciences, FH Campus Wien, Viehmarktgasse 2A, 1030 Vienna, Austria
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