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Singh N, Kaushik R, Prakash A, Singh Saini S, Garg S, Adhikary A, Ladher RK. Mosaic Atoh1 deletion in the chick auditory epithelium reveals a homeostatic mechanism to restore hair cell number. Dev Biol 2024; 516:35-46. [PMID: 39074652 DOI: 10.1016/j.ydbio.2024.07.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2024] [Revised: 07/16/2024] [Accepted: 07/26/2024] [Indexed: 07/31/2024]
Abstract
The mechanosensory hair cell of the vertebrate inner ear responds to the mechanical deflections that result from hearing or change in the acceleration due to gravity, to allow us to perceive and interpret sounds, maintain balance and spatial orientation. In mammals, ototoxic compounds, disease, and acoustic trauma can result in damage and extrusion of hair cells, without replacement, resulting in hearing loss. In contrast, non-mammalian vertebrates can regenerate sensory hair cells. Upon damage, hair cells are extruded and an associated cell type, the supporting cell is transformed into a hair cell. The mechanisms that can trigger regeneration are not known. Using mosaic deletion of the hair cell master gene, Atoh1, in the embryonic avian inner ear, we find that despite hair cells depletion at E9, by E12, hair cell number is restored in sensory epithelium. Our study suggests a homeostatic mechanism can restores hair cell number in the basilar papilla, that is activated when juxtracrine signalling is disrupted. Restoration of hair cell numbers during development may mirror regenerative processes, and our work provides insights into the mechanisms that trigger regeneration.
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Affiliation(s)
- Nishant Singh
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, GKVK PO, Bellary Road, Bangalore, 560065, India; The University of Trans-Disciplinary Health Sciences and Technology, Yelahanka, Bangalore, 560064, India
| | - Raman Kaushik
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, GKVK PO, Bellary Road, Bangalore, 560065, India
| | - Anubhav Prakash
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, GKVK PO, Bellary Road, Bangalore, 560065, India; Ashoka University, Sonipat, Haryana, 131029, India
| | - Surjit Singh Saini
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, GKVK PO, Bellary Road, Bangalore, 560065, India
| | - Sonal Garg
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, GKVK PO, Bellary Road, Bangalore, 560065, India
| | - Adrija Adhikary
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, GKVK PO, Bellary Road, Bangalore, 560065, India
| | - Raj K Ladher
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, GKVK PO, Bellary Road, Bangalore, 560065, India.
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2
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Żak M, Støle TP, Plagnol V, Daudet N. Regulation of otic neurosensory specification by Notch and Wnt signalling: insights from RNA-seq screenings in the embryonic chicken inner ear. Front Cell Dev Biol 2023; 11:1245330. [PMID: 37900277 PMCID: PMC10600479 DOI: 10.3389/fcell.2023.1245330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 09/25/2023] [Indexed: 10/31/2023] Open
Abstract
The Notch and Wnt signalling pathways play key roles in the formation of inner ear sensory organs, but little is known about their transcriptional effectors and targets in this context. Here, we perturbed Notch and Wnt activities in the embryonic chicken otic vesicle using pharmacological treatment or in ovo electroporation of plasmid DNA, and used RNA-Seq to analyse the resulting changes in gene expression. Compared to pharmacological treatments, in ovo electroporation changed the expression of fewer genes, a likely consequence of the variability and mosaicism of transfection. The pharmacological inhibition of Notch activity induced a rapid change in the expression of known effectors of this pathway and genes associated with neurogenesis, consistent with a switch towards an otic neurosensory fate. The Wnt datasets contained many genes associated with a neurosensory biological function, confirming the importance of this pathway for neurosensory specification in the otocyst. Finally, the results of a preliminary gain-of-function screening of selected transcription factors and Wnt signalling components suggest that the endogenous programs of otic neurosensory specification are very robust, and in general unaffected by the overexpression of a single factor. Altogether this work provides new insights into the effectors and candidate targets of the Notch and Wnt pathways in the early developing inner ear and could serve as a useful reference for future functional genomics experiments in the embryonic avian inner ear.
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Affiliation(s)
- Magdalena Żak
- UCL Ear Institute, University College London, London, United Kingdom
| | - Thea P. Støle
- UCL Ear Institute, University College London, London, United Kingdom
| | - Vincent Plagnol
- Genetics Institute, University College London, London, United Kingdom
| | - Nicolas Daudet
- UCL Ear Institute, University College London, London, United Kingdom
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3
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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: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [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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4
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Maková B, Mik V, Lišková B, Gonzalez G, Vítek D, Medvedíková M, Monfort B, Ručilová V, Kadlecová A, Khirsariya P, Gándara Barreiro Z, Havlíček L, Zatloukal M, Soural M, Paruch K, D'Autréaux B, Hajdúch M, Strnad M, Voller J. Cytoprotective activities of kinetin purine isosteres. Bioorg Med Chem 2021; 33:115993. [PMID: 33497938 DOI: 10.1016/j.bmc.2021.115993] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 12/31/2020] [Indexed: 01/23/2023]
Abstract
Kinetin (N6-furfuryladenine), a plant growth substance of the cytokinin family, has been shown to modulate aging and various age-related conditions in animal models. Here we report the synthesis of kinetin isosteres with the purine ring replaced by other bicyclic heterocycles, and the biological evaluation of their activity in several in vitro models related to neurodegenerative diseases. Our findings indicate that kinetin isosteres protect Friedreich́s ataxia patient-derived fibroblasts against glutathione depletion, protect neuron-like SH-SY5Y cells from glutamate-induced oxidative damage, and correct aberrant splicing of the ELP1 gene in fibroblasts derived from a familial dysautonomia patient. Although the mechanism of action of kinetin derivatives remains unclear, our data suggest that the cytoprotective activity of some purine isosteres is mediated by their ability to reduce oxidative stress. Further, the studies of permeation across artificial membrane and model gut and blood-brain barriers indicate that the compounds are orally available and can reach central nervous system. Overall, our data demonstrate that isosteric replacement of the kinetin purine scaffold is a fruitful strategy for improving known biological activities of kinetin and discovering novel therapeutic opportunities.
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Affiliation(s)
- Barbara Maková
- Department of Experimental Biology, Faculty of Science, Palacký University, Šlechtitelů 27, Olomouc CZ-78371, Czech Republic
| | - Václav Mik
- Department of Experimental Biology, Faculty of Science, Palacký University, Šlechtitelů 27, Olomouc CZ-78371, Czech Republic
| | - Barbora Lišková
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacký University, Hněvotínská 3, Olomouc CZ-77515, Czech Republic
| | - Gabriel Gonzalez
- Department of Experimental Biology, Faculty of Science, Palacký University, Šlechtitelů 27, Olomouc CZ-78371, Czech Republic; Department of Neurology, Palacký University Olomouc, Faculty of Medicine and Dentistry and University Hospital, Olomouc, Czech Republic
| | - Dominik Vítek
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacký University, Hněvotínská 3, Olomouc CZ-77515, Czech Republic
| | - Martina Medvedíková
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacký University, Hněvotínská 3, Olomouc CZ-77515, Czech Republic
| | - Beata Monfort
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Veronika Ručilová
- Department of Organic Chemistry, Faculty of Science, Palacký University, 17. listopadu 1192/12, Olomouc CZ-783-71, Czech Republic
| | - Alena Kadlecová
- Department of Experimental Biology, Faculty of Science, Palacký University, Šlechtitelů 27, Olomouc CZ-78371, Czech Republic
| | - Prashant Khirsariya
- Department of Chemistry, CZ Openscreen, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Zoila Gándara Barreiro
- Department of Experimental Biology, Faculty of Science, Palacký University, Šlechtitelů 27, Olomouc CZ-78371, Czech Republic
| | - Libor Havlíček
- Isotope Laboratory, The Czech Academy of Science, Institute of Experimental Botany, Vídeňská 1083, Praha 4 CZ-14220, Czech Republic
| | - Marek Zatloukal
- Department of Chemical Biolology and Genetics, Centre of the Region Hana for Biotechnological and Agricultural Research, Palacký University, Šlechtitelů 27, Olomouc CZ-78371, Czech Republic
| | - Miroslav Soural
- Department of Organic Chemistry, Faculty of Science, Palacký University, 17. listopadu 1192/12, Olomouc CZ-783-71, Czech Republic
| | - Kamil Paruch
- Department of Chemistry, CZ Openscreen, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Benoit D'Autréaux
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Marián Hajdúch
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacký University, Hněvotínská 3, Olomouc CZ-77515, Czech Republic
| | - Miroslav Strnad
- Department of Experimental Biology, Faculty of Science, Palacký University, Šlechtitelů 27, Olomouc CZ-78371, Czech Republic
| | - Jiří Voller
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacký University, Hněvotínská 3, Olomouc CZ-77515, Czech Republic; Laboratory of Growth Regulators, Palacký University & Institute of Experimental Botany AS CR, Šlechtitelů 27, Olomouc CZ-78371, Czech Republic.
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5
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Thawani A, Sammudin NH, Reygaerts HS, Wozniak AN, Munnamalai V, Kuhn RJ, Fekete DM. Zika virus can directly infect and damage the auditory and vestibular components of the embryonic chicken inner ear. Dev Dyn 2020; 249:867-883. [PMID: 32384225 DOI: 10.1002/dvdy.176] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 04/03/2020] [Accepted: 04/04/2020] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Sensorineural hearing loss is an understudied consequence of congenital Zika syndrome, and balance disorders are essentially unreported to date. Also lacking is information about the susceptibility and the pathogenesis of the developing inner ear following Zika virus (ZIKV) exposure. To address this, ZIKV was delivered directly into the otic cup/otocyst of chicken embryos and infection of inner ear tissues was evaluated using immunohistochemistry. RESULTS After injections on embryonic days 2 to 5, ZIKV infection was observed in 90% of the samples harvested 2 to 8 days later; however, the degree of infection was highly variable across individuals. ZIKV was detected in all regions of the inner ear, associated ganglia, and in the surrounding periotic mesenchyme. Detection of virus peaked earlier in the ganglion and vestibular compartments, and later in the cochlea. ZIKV infection increased cell death robustly in the auditory ganglion, and modestly in the auditory sensory organ. Macrophage accumulation was found to overlap with dense viral infection in some tissues. Additionally, dysmorphogenesis of the semicircular canals and ganglion was observed for a subset of injection conditions. CONCLUSIONS This article presents evidence of direct ZIKV infection of developing inner ear epithelium and shows previously unknown inner ear dysmorphogenesis phenotypes.
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Affiliation(s)
- Ankita Thawani
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, USA.,Purdue Institute of Integrative Neuroscience, Purdue University, West Lafayette, Indiana, USA.,Purdue Institute of Inflammation Immunology and Infectious Disease, Purdue University, West Lafayette, Indiana, USA
| | - Nabilah H Sammudin
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, USA.,Purdue Institute of Integrative Neuroscience, Purdue University, West Lafayette, Indiana, USA
| | - Hannah S Reygaerts
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, USA
| | - Alexis N Wozniak
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, USA
| | | | - Richard J Kuhn
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, USA.,Purdue Institute of Inflammation Immunology and Infectious Disease, Purdue University, West Lafayette, Indiana, USA
| | - Donna M Fekete
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, USA.,Purdue Institute of Integrative Neuroscience, Purdue University, West Lafayette, Indiana, USA.,Purdue Institute of Inflammation Immunology and Infectious Disease, Purdue University, West Lafayette, Indiana, USA.,Purdue University Center for Cancer Research, Purdue University, West Lafayette, Indiana, USA
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6
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Sánchez-Guardado LÓ, Puelles L, Hidalgo-Sánchez M. Origin of acoustic-vestibular ganglionic neuroblasts in chick embryos and their sensory connections. Brain Struct Funct 2019; 224:2757-2774. [PMID: 31396696 DOI: 10.1007/s00429-019-01934-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Accepted: 07/31/2019] [Indexed: 01/03/2023]
Abstract
The inner ear is a complex three-dimensional sensory structure with auditory and vestibular functions. It originates from the otic placode, which generates the sensory elements of the membranous labyrinth and all the ganglionic neuronal precursors. Neuroblast specification is the first cell differentiation event. In the chick, it takes place over a long embryonic period from the early otic cup stage to at least stage HH25. The differentiating ganglionic neurons attain a precise innervation pattern with sensory patches, a process presumably governed by a network of dendritic guidance cues which vary with the local micro-environment. To study the otic neurogenesis and topographically-ordered innervation pattern in birds, a quail-chick chimaeric graft technique was used in accordance with a previously determined fate-map of the otic placode. Each type of graft containing the presumptive domain of topologically-arranged placodal sensory areas was shown to generate neuroblasts. The differentiated grafted neuroblasts established dendritic contacts with a variety of sensory patches. These results strongly suggest that, rather than reverse-pathfinding, the relevant role in otic dendritic process guidance is played by long-range diffusing molecules.
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Affiliation(s)
| | - Luis Puelles
- Department of Human Anatomy and Psychobiology, School of Medicine, University of Murcia, E30100, Murcia, Spain.,Instituto Murciano de Investigaciones Biosanitarias (IMIB-Arrixaca), E30100, Murcia, Spain
| | - Matías Hidalgo-Sánchez
- Department of Cell Biology, School of Science, University of Extremadura, E06071, Badajoz, Spain.
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7
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The Key Transcription Factor Expression in the Developing Vestibular and Auditory Sensory Organs: A Comprehensive Comparison of Spatial and Temporal Patterns. Neural Plast 2018; 2018:7513258. [PMID: 30410537 PMCID: PMC6205106 DOI: 10.1155/2018/7513258] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 07/31/2018] [Accepted: 09/06/2018] [Indexed: 11/17/2022] Open
Abstract
Inner ear formation requires that a series of cell fate decisions and morphogenetic events occur in a precise temporal and spatial pattern. Previous studies have shown that transcription factors, including Pax2, Sox2, and Prox1, play important roles during the inner ear development. However, the temporospatial expression patterns among these transcription factors are poorly understood. In the current study, we present a comprehensive description of the temporal and spatial expression profiles of Pax2, Sox2, and Prox1 during auditory and vestibular sensory organ development in mice. Using immunohistochemical analyses, we show that Sox2 and Pax2 are both expressed in the prosensory cells (the developing hair cells), but Sox2 is later restricted to only the supporting cells of the organ of Corti. In the vestibular sensory organ, however, the Pax2 expression is localized in hair cells at postnatal day 7, while Sox2 is still expressed in both the hair cells and supporting cells at that time. Prox1 was transiently expressed in the presumptive hair cells and developing supporting cells, and lower Prox1 expression was observed in the vestibular sensory organ compared to the organ of Corti. The different expression patterns of these transcription factors in the developing auditory and vestibular sensory organs suggest that they play different roles in the development of the sensory epithelia and might help to shape the respective sensory structures.
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8
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Mann ZF, Gálvez H, Pedreno D, Chen Z, Chrysostomou E, Żak M, Kang M, Canden E, Daudet N. Shaping of inner ear sensory organs through antagonistic interactions between Notch signalling and Lmx1a. eLife 2017; 6:e33323. [PMID: 29199954 PMCID: PMC5724992 DOI: 10.7554/elife.33323] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 12/02/2017] [Indexed: 12/19/2022] Open
Abstract
The mechanisms of formation of the distinct sensory organs of the inner ear and the non-sensory domains that separate them are still unclear. Here, we show that several sensory patches arise by progressive segregation from a common prosensory domain in the embryonic chicken and mouse otocyst. This process is regulated by mutually antagonistic signals: Notch signalling and Lmx1a. Notch-mediated lateral induction promotes prosensory fate. Some of the early Notch-active cells, however, are normally diverted from this fate and increasing lateral induction produces misshapen or fused sensory organs in the chick. Conversely Lmx1a (or cLmx1b in the chick) allows sensory organ segregation by antagonizing lateral induction and promoting commitment to the non-sensory fate. Our findings highlight the dynamic nature of sensory patch formation and the labile character of the sensory-competent progenitors, which could have facilitated the emergence of new inner ear organs and their functional diversification in the course of evolution.
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Affiliation(s)
- Zoe F Mann
- The Ear InstituteUniversity College LondonLondonUnited Kingdom
| | - Héctor Gálvez
- The Ear InstituteUniversity College LondonLondonUnited Kingdom
| | - David Pedreno
- The Ear InstituteUniversity College LondonLondonUnited Kingdom
| | - Ziqi Chen
- The Ear InstituteUniversity College LondonLondonUnited Kingdom
| | | | - Magdalena Żak
- The Ear InstituteUniversity College LondonLondonUnited Kingdom
| | - Miso Kang
- The Ear InstituteUniversity College LondonLondonUnited Kingdom
| | | | - Nicolas Daudet
- The Ear InstituteUniversity College LondonLondonUnited Kingdom
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9
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Nguyen K, Hall AL, Jones JM. Expression of myosin VIIA in the developing chick inner ear neurons. Gene Expr Patterns 2015. [DOI: 10.1016/j.gep.2015.07.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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10
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Nakajima Y. Signaling regulating inner ear development: cell fate determination, patterning, morphogenesis, and defects. Congenit Anom (Kyoto) 2015; 55:17-25. [PMID: 25040109 DOI: 10.1111/cga.12072] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2014] [Accepted: 06/07/2014] [Indexed: 12/28/2022]
Abstract
The membranous labyrinth of the inner ear is a highly complex organ that detects sound and balance. Developmental defects in the inner ear cause congenital hearing loss and balance disorders. The membranous labyrinth consists of three semicircular ducts, the utricle, saccule, and endolymphatic ducts, and the cochlear duct. These complex structures develop from the simple otic placode, which is established in the cranial ectoderm adjacent to the neural crest at the level of the hindbrain at the early neurula stage. During development, the otic placode invaginates to form the otic vesicle, which subsequently gives rise to neurons for the vestibulocochlear ganglion, the non-sensory and sensory epithelia of the membranous labyrinth that includes three ampullary crests, two maculae, and the organ of Corti. Combined paracrine and autocrine signals including fibroblast growth factor, Wnt, retinoic acid, hedgehog, and bone morphogenetic protein regulate fate determination, axis formation, and morphogenesis in the developing inner ear. Juxtacrine signals mediated by Notch pathways play a role in establishing the sensory epithelium, which consists of mechanosensory hair cells and supporting cells. The highly differentiated organ of Corti, which consists of uniformly oriented inner/outer hair cells and specific supporting cells, develops during fetal development. Developmental alterations/arrest causes congenital malformations in the inner ear in a spatiotemporal-restricted manner. A clearer understanding of the mechanisms underlying inner ear development is important not only for the management of patients with congenital inner ear malformations, but also for the development of regenerative therapy for impaired function.
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Affiliation(s)
- Yuji Nakajima
- Department of Anatomy and Cell Biology, Graduate School of Medicine, Osaka City University, Osaka, Japan
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11
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Abstract
The loss of auditory hair cells triggers repair responses within the population of nonsensory supporting cells. When hair cells are irreversibly lost from the mammalian cochlea, supporting cells expand to fill the resulting lesions in the sensory epithelium, an initial repair process that is dependent on gap junctional intercellular communication (GJIC). In the chicken cochlea (the basilar papilla or BP), dying hair cells are extruded from the epithelium and supporting cells expand to fill the lesions and then replace hair cells via mitotic and/or conversion mechanisms. Here, we investigated the involvement of GJIC in the initial epithelial repair process in the aminoglycoside-damaged BP. Gentamicin-induced hair cell loss was associated with a decrease of chicken connexin43 (cCx43) immunofluorescence, yet cCx30-labeled gap junction plaques remained. Fluorescence recovery after photobleaching experiments confirmed that the GJIC remained robust in gentamicin-damaged explants, but regionally asymmetric coupling was no longer evident. Dye injections in slice preparations from undamaged BP explants identified cell types with characteristic morphologies along the neural-abneural axis, but these were electrophysiologically indistinct. In gentamicin-damaged BP, supporting cells expanded to fill space formerly occupied by hair cells and displayed more variable electrophysiological phenotypes. When GJIC was inhibited during the aminoglycoside damage paradigm, the epithelial repair response halted. Dying hair cells were retained within the sensory epithelium and supporting cells remained unexpanded. These observations suggest that repair of the auditory epithelium shares common mechanisms across vertebrate species and emphasize the importance of functional gap junctions in maintaining a homeostatic environment permissive for subsequent hair cell regeneration.
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12
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Mulvaney JF, Amemiya Y, Freeman SD, Ladher RK, Dabdoub A. Molecular cloning and functional characterisation of chicken Atonal homologue 1: a comparison with human Atoh1. Biol Cell 2015; 107:41-60. [PMID: 25412697 DOI: 10.1111/boc.201400078] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 11/20/2014] [Indexed: 12/19/2022]
Abstract
BACKGROUND INFORMATION The vertebrate basic helix-loop-helix transcription factor Atoh1 is essential for maturation and survival of mechanosensory hair cells of the inner ear, neurogenesis, differentiation of the intestine, homeostasis of the colon and is implicated in cancer progression. Given that mutations in Atoh1 are detected in malignant tumours, study of functionally different Atoh1 alleles and homologues might yield useful avenues for investigation. The predicted sequence of chicken Atoh1 (cAtoh1) has large regions of dissimilarity to that of mammalian Atoh1 homologues. We hypothesise that cAtoh1 might have intrinsic functional differences to mammalian Atoh1. RESULTS In this study, we cloned and sequenced the full open reading frame of cAtoh1. In overexpression experiments, we show that this sequence is sufficient to generate a cAtoh1 protein capable of inducing hair cell markers when expressed in nonsensory regions of the developing inner ear, and that morpholino-mediated knock-down using a section of the sequence 5' to the start codon inhibits differentiation of hair cells in the chicken basilar papilla. Furthermore, we compare the behaviour of cAtoh1 and human Atoh1 (hAtoh1) in embryonic mouse cochlear explants, showing that cAtoh1 is a potent inducer of hair cell differentiation and that it can overcome Sox2-mediated repression of hair cell differentiation more effectively than hAtoh1. CONCLUSIONS cAtoh1 is both necessary and sufficient for avian mechanosensory hair cell differentiation. The non-conserved regions of the cAtoh1 coding region have functional consequences on its behaviour.
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Affiliation(s)
- Joanna F Mulvaney
- Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, ON, M4N 3M5, Canada
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13
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Comparative expression analysis of POU4F1, POU4F2 and ISL1 in developing mouse cochleovestibular ganglion neurons. Gene Expr Patterns 2014; 15:31-7. [PMID: 24709358 DOI: 10.1016/j.gep.2014.03.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 03/10/2014] [Accepted: 03/13/2014] [Indexed: 12/26/2022]
Abstract
POU-homeodomain and LIM-homeodomain transcription factors are expressed in developing projection neurons within retina, inner ear, dorsal root ganglion, and trigeminal ganglion, and play synergistic roles in their differentiation and survival. Here, using immunohistochemistry, we present a comparative analysis of the spatiotemporal expression pattern of POU4F1, POU4F2, and ISL1 during the development of cochleovestibular ganglion (CVG) neurons in mouse inner ear. At early stages, when otic neurons are first detected in the otic epithelium (OE) and migrate into periotic mesenchyme to form the CVG, POU4F1 and ISL1 are co-expressed in a majority of the delaminated CVG neurons, which are marked by NEUROD1 expression, but POU4F1 is absent in the otic epithelium. The onset of POU4F2 expression starts after that of POU4F1 and ISL1, and is observed in the NEUROD1-negative, post-mitotic CVG neurons. When the CVG neurons innervate the vestibular and cochlear sensory organs, the expression of POU4F1, POU4F2, and ISL1 continues in both vestibular and spiral ganglion cells. Later in development, POU4F1 expression becomes down-regulated in a majority of spiral ganglion (SG) neurons and more neurons express POU4F2 expression while ISL1 expression is maintained. The differential as well as overlapping expression of POU4F1, POU4F2, and ISL1 combined with previous studies suggests possible functional interaction and regulatory relationship of these transcription factors in the development of inner ear neurons.
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14
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Neves J, Abelló G, Petrovic J, Giraldez F. Patterning and cell fate in the inner ear: a case for Notch in the chicken embryo. Dev Growth Differ 2012; 55:96-112. [PMID: 23252974 DOI: 10.1111/dgd.12016] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 10/09/2012] [Accepted: 10/09/2012] [Indexed: 01/08/2023]
Abstract
The development of the inner ear provides a beautiful example of one basic problem in development, that is, to understand how different cell types are generated at specific times and domains throughout embryonic life. The functional unit of the inner ear consists of hair cells, supporting cells and neurons, all deriving from progenitor cells located in the neurosensory competent domain of the otic placode. Throughout development, the otic placode resolves into the complex inner ear labyrinth, which holds the auditory and vestibular sensory organs that are innervated in a highly specific manner. How does the early competent domain of the otic placode give rise to the diverse specialized cell types of the different sensory organs of the inner ear? We review here our current understanding on the role of Notch signaling in coupling patterning and cell fate determination during inner ear development, with a particular emphasis on contributions from the chicken embryo as a model organism. We discuss further the question of how these two processes rely on two modes of operation of the Notch signaling pathway named lateral induction and lateral inhibition.
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Affiliation(s)
- Joana Neves
- CEXS, Universitat Pompeu Fabra, Parc de Recerca Biomèdica de Barcelona, Barcelona, Spain
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15
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Artificial induction of Sox21 regulates sensory cell formation in the embryonic chicken inner ear. PLoS One 2012; 7:e46387. [PMID: 23071561 PMCID: PMC3468625 DOI: 10.1371/journal.pone.0046387] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Accepted: 08/29/2012] [Indexed: 12/26/2022] Open
Abstract
During embryonic development, hair cells and support cells in the sensory epithelia of the inner ear derive from progenitors that express Sox2, a member of the SoxB1 family of transcription factors. Sox2 is essential for sensory specification, but high levels of Sox2 expression appear to inhibit hair cell differentiation, suggesting that factors regulating Sox2 activity could be critical for both processes. Antagonistic interactions between SoxB1 and SoxB2 factors are known to regulate cell differentiation in neural tissue, which led us to investigate the potential roles of the SoxB2 member Sox21 during chicken inner ear development. Sox21 is normally expressed by sensory progenitors within vestibular and auditory regions of the early embryonic chicken inner ear. At later stages, Sox21 is differentially expressed in the vestibular and auditory organs. Sox21 is restricted to the support cell layer of the auditory epithelium, while it is enriched in the hair cell layer of the vestibular organs. To test Sox21 function, we used two temporally distinct gain-of-function approaches. Sustained over-expression of Sox21 from early developmental stages prevented prosensory specification, and abolished the formation of both hair cells and support cells. However, later induction of Sox21 expression at the time of hair cell formation in organotypic cultures of vestibular epithelia inhibited endogenous Sox2 expression and Notch activity, and biased progenitor cells towards a hair cell fate. Interestingly, Sox21 did not promote hair cell differentiation in the immature auditory epithelium, which fits with the expression of endogenous Sox21 within mature support cells in this tissue. These results suggest that interactions among endogenous SoxB family transcription factors may regulate sensory cell formation in the inner ear, but in a context-dependent manner.
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16
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Lu MH, Huang CC, Pan MR, Chen HH, Hung WC. Prospero homeobox 1 promotes epithelial-mesenchymal transition in colon cancer cells by inhibiting E-cadherin via miR-9. Clin Cancer Res 2012; 18:6416-25. [PMID: 23045246 DOI: 10.1158/1078-0432.ccr-12-0832] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
PURPOSE Prospero homeobox 1 (PROX1) has been shown to function as a tumor suppressor in various types of cancer. However, it promotes colon cancer progression. The aim of this study is to clarify the underlying mechanism by which PROX1 regulates tumorigenicity of colon cancer. EXPERIMENTAL DESIGN Association of PROX1 and clinicopathological features was studied by immunohistochemical staining. Pri-miR-9-2 and miR-9 were detected by quantitative real-time PCR. Assays of cell invasion, adhesion, and matrix metalloproteinase activity were used to study PROX1-mediated epithelial-mesenchymal transition (EMT). RESULTS PROX1 was overexpressed in 43% (59/136) of colon cancer tissues and its expression was correlated with E-cadherin downregulation (P = 0.00005), advanced tumor staging (P = 0.005), and lymph node metastasis (P = 0.000009). Enforced expression of PROX1 in DLD-1 cells caused downregulation of E-cadherin and integrins and attenuated cell adhesion. These cells showed increase of matrix metalloproteinase activity and invasive ability. Conversely, knockdown of PROX1 in SW620 cells restored E-cadherin protein expression and reduced invasiveness. Unexpectedly, repression of E-cadherin by PROX1 was not mediated by transcriptional inhibition. We found that PROX1 bound to miR-9-2 promoter and triggered its expression to suppress E-cadherin 3'UTR reporter activity and protein expression. Anti-miR-9 restored E-cadherin in SW620 cells, whereas precursor miR-9 inhibited E-cadherin in PROX1-knockdown cells. The miR-9 level was higher in tumor tissues with high PROX1/low E-cadherin than that of tumor tissues with low PROX1/high E-cadherin. CONCLUSIONS Our results provide mechanistic insights by which PROX1 promotes EMT and colon cancer progression. Targeting of PROX1-mediated oncogenic activity may be helpful for the treatment of colon cancer.
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Affiliation(s)
- Mei-Hsuan Lu
- Institute of Biomedical Sciences, National Sun Yat-Sen University, Taiwan
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17
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Jacques BE, Dabdoub A, Kelley MW. Fgf signaling regulates development and transdifferentiation of hair cells and supporting cells in the basilar papilla. Hear Res 2012; 289:27-39. [PMID: 22575790 DOI: 10.1016/j.heares.2012.04.018] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 04/24/2012] [Accepted: 04/24/2012] [Indexed: 11/17/2022]
Abstract
The avian basilar papilla (BP) is a likely homolog of the auditory sensory epithelium of the mammalian cochlea, the organ of Corti. During mammalian development Fibroblast growth factor receptor-3 (Fgfr3) is known to regulate the differentiation of auditory mechanosensory hair cells (HCs) and supporting cells (SCs), both of which are required for sound detection. Fgfr3 is expressed in developing progenitor cells (PCs) and SCs of both the BP and the organ of Corti; however its role in BP development is unknown. Here we utilized an in vitro whole organ embryonic culture system to examine the role of Fgf signaling in the developing avian cochlea. SU5402 (an antagonist of Fgf signaling) was applied to developing BP cultures at different stages to assay the role of Fgf signaling during HC formation. Similar to the observed effects of inhibition of Fgfr3 in the mammalian cochlea, Fgfr inhibition in the developing BP increased the number of HCs that formed. This increase was not associated with increased proliferation, suggesting that inhibition of the Fgf pathway leads to the direct conversion of PCs or supporting cells into HCs, a process known as transdifferentiation. This also implies that Fgf signaling is required to prevent the conversion of PCs and SCs into HCs. The ability of Fgf signaling to inhibit transdifferentiation suggests that its down-regulation may be essential for the initial steps of HC formation, as well as for the maintenance of SC phenotypes.
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Affiliation(s)
- Bonnie E Jacques
- Laboratory of Cochlear Development, NIDCD, NIH, Porter Neuroscience Research Center, 35 Convent Dr, Room 2A-100, Bethesda, MD 20892-3729, USA.
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18
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Appler JM, Goodrich LV. Connecting the ear to the brain: Molecular mechanisms of auditory circuit assembly. Prog Neurobiol 2011; 93:488-508. [PMID: 21232575 DOI: 10.1016/j.pneurobio.2011.01.004] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 12/09/2010] [Accepted: 01/03/2011] [Indexed: 12/21/2022]
Abstract
Our sense of hearing depends on precisely organized circuits that allow us to sense, perceive, and respond to complex sounds in our environment, from music and language to simple warning signals. Auditory processing begins in the cochlea of the inner ear, where sounds are detected by sensory hair cells and then transmitted to the central nervous system by spiral ganglion neurons, which faithfully preserve the frequency, intensity, and timing of each stimulus. During the assembly of auditory circuits, spiral ganglion neurons establish precise connections that link hair cells in the cochlea to target neurons in the auditory brainstem, develop specific firing properties, and elaborate unusual synapses both in the periphery and in the CNS. Understanding how spiral ganglion neurons acquire these unique properties is a key goal in auditory neuroscience, as these neurons represent the sole input of auditory information to the brain. In addition, the best currently available treatment for many forms of deafness is the cochlear implant, which compensates for lost hair cell function by directly stimulating the auditory nerve. Historically, studies of the auditory system have lagged behind other sensory systems due to the small size and inaccessibility of the inner ear. With the advent of new molecular genetic tools, this gap is narrowing. Here, we summarize recent insights into the cellular and molecular cues that guide the development of spiral ganglion neurons, from their origin in the proneurosensory domain of the otic vesicle to the formation of specialized synapses that ensure rapid and reliable transmission of sound information from the ear to the brain.
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Affiliation(s)
- Jessica M Appler
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
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19
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Id gene regulation and function in the prosensory domains of the chicken inner ear: a link between Bmp signaling and Atoh1. J Neurosci 2010; 30:11426-34. [PMID: 20739564 DOI: 10.1523/jneurosci.2570-10.2010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Bone morphogenetic proteins (Bmps) regulate the expression of the proneural gene Atoh1 and the generation of hair cells in the developing inner ear. The present work explored the role of Inhibitor of Differentiation genes (Id1-3) in this process. The results show that Id genes are expressed in the prosensory domains of the otic vesicle, along with Bmp4 and Bmp7. Those domains exhibit high levels of the phosphorylated form of Bmp-responding R-Smads (P-Smad1,5,8), and of Bmp-dependent Smad transcriptional activity as shown by the BRE-tk-EGFP reporter. Increased Bmp signaling induces the expression of Id1-3 along with the inhibition of Atoh1. Conversely, the Bmp antagonist Noggin or the Bmp-receptor inhibitor Dorsomorphin elicit opposite effects, indicating that Bmp signaling is necessary for Id expression and Atoh1 regulation in the otocyst. The forced expression of Id3 is sufficient to reduce Atoh1 expression and to prevent the expression of hair cell differentiation markers. Together, these results suggest that Ids are part of the machinery that mediates the regulation of hair cell differentiation exerted by Bmps. In agreement with that, during hair cell differentiation Bmp4 expression, P-Smad1,5,8 levels and Id expression are downregulated from hair cells. However, Ids are also downregulated from the supporting cells which contrarily to hair cells exhibit high levels of Bmp4 expression, P-Smad1,5,8, and BRE-tk-EGFP activity, suggesting that in these cells Ids escape from Bmp/Smad signaling. The differential regulation of Ids in time and space may underlie the multiple functions of Bmp signaling during sensory organ development.
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20
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Fritzsch B, Dillard M, Lavado A, Harvey NL, Jahan I. Canal cristae growth and fiber extension to the outer hair cells of the mouse ear require Prox1 activity. PLoS One 2010; 5:e9377. [PMID: 20186345 PMCID: PMC2826422 DOI: 10.1371/journal.pone.0009377] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Accepted: 02/04/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The homeobox gene Prox1 is required for lens, retina, pancreas, liver, and lymphatic vasculature development and is expressed in inner ear supporting cells and neurons. METHODOLOGY/PRINCIPAL FINDINGS We have investigated the role of Prox1 in the developing mouse ear taking advantage of available standard and conditional Prox1 mutant mouse strains using Tg(Pax2-Cre) and Tg(Nes-Cre). A severe reduction in the size of the canal cristae but not of other vestibular organs or the cochlea was identified in the E18.5 Prox1(Flox/Flox); Tg(Pax2-Cre) mutant ear. In these mutant embryos, hair cell differentiated; however, their distribution pattern was slightly disorganized in the cochlea where the growth of type II nerve fibers to outer hair cells along Prox1 expressing supporting cells was severely disrupted. In the case of Nestin-Cre, we found that newborn Prox1(Flox/Flox); Tg(Nestin-Cre) exhibit only a disorganized innervation of outer hair cells despite apparently normal cellular differentiation of the organ of Corti, suggesting a cell-autonomous function of Prox1 in neurons. CONCLUSIONS/SIGNIFICANCE These results identify a dual role of Prox1 during inner ear development; growth of the canal cristae and fiber guidance of Type II fibers along supporting cells in the cochlea.
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MESH Headings
- Animals
- Animals, Newborn
- Cell Differentiation
- Cochlea/embryology
- Cochlea/metabolism
- Ear, Inner/embryology
- Ear, Inner/metabolism
- Ear, Inner/ultrastructure
- Embryo, Mammalian/embryology
- Embryo, Mammalian/metabolism
- Epithelium/embryology
- Epithelium/metabolism
- Female
- Gene Expression Regulation, Developmental
- Hair Cells, Auditory, Outer/metabolism
- Homeodomain Proteins/genetics
- Homeodomain Proteins/metabolism
- Immunohistochemistry
- In Situ Hybridization
- Male
- Mice
- Mice, Knockout
- Mice, Transgenic
- Microscopy, Confocal
- Microscopy, Electron, Transmission
- Mutation
- Pregnancy
- Time Factors
- Tumor Suppressor Proteins/genetics
- Tumor Suppressor Proteins/metabolism
- Vestibule, Labyrinth/embryology
- Vestibule, Labyrinth/metabolism
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Affiliation(s)
- Bernd Fritzsch
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America.
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21
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Sienknecht UJ, Fekete DM. Mapping of Wnt, frizzled, and Wnt inhibitor gene expression domains in the avian otic primordium. J Comp Neurol 2010; 517:751-64. [PMID: 19842206 DOI: 10.1002/cne.22169] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Wnt signaling activates at least three different pathways involved in development and disease. Interactions of secreted ligands and inhibitors with cell-surface receptors result in the activation or regulation of particular downstream intracellular cascades. During the developmental stages of otic vesicle closure and beginning morphogenesis, the forming inner ear transcribes a plethora of Wnt-related genes. We report expression of 23 genes out of 25 tested in situ hybridization probes on tissue serial sections. Sensory primordia and Frizzled gene expression share domains, with Fzd1 being a continuous marker. Prospective nonsensory domains express Wnts, whose transcripts mainly flank prosensory regions. Finally, Wnt inhibitor domains are superimposed over both prosensory and nonsensory otic regions. Three Wnt antagonists, Dkk1, SFRP2, and Frzb are prominent. Their gene expression patterns partly overlap and change over time, which adds to the diversity of molecular microenvironments. Strikingly, prosensory domains express Wnts transiently. This includes: 1) the prosensory otic region of high proliferation, neuroblast delamination, and programmed cell death at stage 20/21 (Wnt3, -5b, -7b, -8b, -9a, and -11); and 2) sensory primordia at stage 25 (Wnt7a and Wnt9a). In summary, robust Wnt-related gene expression shows both spatial and temporal tuning during inner ear development as the otic vesicle initiates morphogenesis and prosensory cell fate determination.
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Affiliation(s)
- Ulrike J Sienknecht
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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22
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Pistocchi A, Feijóo CG, Cabrera P, Villablanca EJ, Allende ML, Cotelli F. The zebrafish prospero homolog prox1 is required for mechanosensory hair cell differentiation and functionality in the lateral line. BMC DEVELOPMENTAL BIOLOGY 2009; 9:58. [PMID: 19948062 PMCID: PMC2794270 DOI: 10.1186/1471-213x-9-58] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Accepted: 11/30/2009] [Indexed: 11/20/2022]
Abstract
Background The lateral line system in zebrafish is composed of a series of organs called neuromasts, which are distributed over the body surface. Neuromasts contain clusters of hair cells, surrounded by accessory cells. Results In this report we describe zebrafish prox1 mRNA expression in the migrating primordium and in the neuromasts of the posterior lateral line. Furthermore, using an antibody against Prox1 we characterize expression of the protein in different cell types within neuromasts, and we show distribution among the supporting cells and hair cells. Conclusion Functional analysis using antisense morpholinos indicates that prox1 activity is crucial for the hair cells to differentiate properly and acquire functionality, while having no role in development of other cell types in neuromasts.
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Affiliation(s)
- Anna Pistocchi
- Department of Biology, Università degli Studi di Milano, Milan, Italy.
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23
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Jones JM, Warchol ME. Expression of the Gata3 transcription factor in the acoustic ganglion of the developing avian inner ear. J Comp Neurol 2009; 516:507-18. [PMID: 19673002 DOI: 10.1002/cne.22128] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
During the development of the inner ear, auditory and vestibular ganglion neurons are generated in a highly regulated sequential process. First, neuroblasts are specified, delaminate from the epithelium of the otocyst, and migrate to form the auditory-vestibular ganglion (AVG). These neuroblasts then undergo proliferation and differentiate into afferent neurons of the auditory and vestibular ganglia. The zinc finger transcription factor Gata3 has been shown to play a role in cell proliferation and differentiation in various regions of the inner ear. Here we profile the spatiotemporal expression pattern of Gata3 in the developing auditory and vestibular ganglia of the chick embryo. Gata3 is expressed in a distinct population of sensorineural precursor cells within the otic epithelium, but is not expressed in migrating or proliferating neuroblasts. Following terminal mitosis, Gata3 expression is restricted to very few cells in the auditory ganglion and is not expressed in any cells of the vestibular ganglion. Gata3 expression levels then increase in auditory neurons as they mature. The increase of Gata3 in auditory ganglion neurons is accompanied by decreased expression of NeuroD. Our results suggest that Gata3 may be specifically involved in the differentiation of auditory ganglion neurons.
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Affiliation(s)
- Jennifer M Jones
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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24
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Molecular cloning and gene expression of the prox1a and prox1b genes in the medaka, Oryzias latipes. Gene Expr Patterns 2009; 9:341-7. [DOI: 10.1016/j.gep.2009.02.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 01/29/2009] [Accepted: 02/04/2009] [Indexed: 11/18/2022]
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25
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Collado MS, Burns JC, Hu Z, Corwin JT. Recent advances in hair cell regeneration research. Curr Opin Otolaryngol Head Neck Surg 2009; 16:465-71. [PMID: 18797290 DOI: 10.1097/moo.0b013e32830f4ab5] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
PURPOSE OF REVIEW This review discusses recent progress in research that seeks to understand the regeneration of hair cells and highlights findings that may hold importance for the eventual development of regenerative therapies for hearing and balance impairments. RECENT FINDINGS Signaling via the Notch receptor and the basic helix-loop-helix transcription factors has important roles in the development and regeneration of hair cells. The cytoskeletal properties and cell-matrix interactions of supporting cells in mice of different ages may hold part of the explanation for the age-related differences in their proliferative responses to damage and the differences between mammals and nonmammals in hair cell regeneration. Progress also has been made in deriving stem cells from inner ear tissues and other sources and in the evaluation of their potential uses as sources of new hair cells and as tools for biomedical research. SUMMARY Much has been accomplished since the discovery of postembryonic hair cell production and hair cell regeneration in nonmammals decades ago. No therapies for hair cell regeneration are under clinical trials, but research is yielding potentially important discoveries that are likely to lead to the development of therapeutic methods for inducing hair cell regeneration in the mammalian inner ear.
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Affiliation(s)
- Maria Sol Collado
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
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26
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Cafaro J, Lee GS, Stone JS. Atoh1 expression defines activated progenitors and differentiating hair cells during avian hair cell regeneration. Dev Dyn 2007; 236:156-70. [PMID: 17096404 DOI: 10.1002/dvdy.21023] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
In the avian inner ear, nonsensory supporting cells give rise to new sensory hair cells through two distinct processes: mitosis and direct transdifferentiation. Regulation of supporting cell behavior and cell fate specification during avian hair cell regeneration is poorly characterized. Expression of Atoh1, a proneural transcription factor necessary and sufficient for developmental hair cell specification, was examined using immunofluorescence in quiescent and regenerating hair cell epithelia of mature chickens. In untreated birds, Atoh1 protein was not detected in the auditory epithelium, which is quiescent. In contrast, numerous Atoh1-positive nuclei were seen in the utricular macula, which undergoes continual hair cell turnover. Atoh1-positive nuclei emerged in the auditory epithelium by 15 hr post-ototoxin administration, before overt hair cell damage and supporting cell re-entry into the cell cycle. Subsequently, Atoh1 labeling was seen in 15% of dividing supporting cells. During cell division, Atoh1 was distributed symmetrically to daughter cells, but Atoh1 levels were dramatically regulated shortly thereafter. After cellular differentiation, Atoh1 labeling was confined to hair cells regenerated through either mitosis or direct transdifferentiation. However, Atoh1 expression in dividing progenitors did not necessarily predict hair cell fate specification in daughter cells. Finally, predominant modes of hair cell regeneration varied significantly across the radial axis of the auditory epithelium, with mitosis most frequent neurally and direct transdifferentiation most frequent abneurally. These observations suggest a role for Atoh1 in re-specifying supporting cells and in biasing postmitotic cells toward the hair cell fate during hair cell regeneration in the mature chicken ear.
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Affiliation(s)
- Jon Cafaro
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology and Head and Neck Surgery, University of Washington, Seattle, Washington 98195-7923, USA
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27
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Fischer AJ, Stanke JJ, Aloisio G, Hoy H, Stell WK. Heterogeneity of horizontal cells in the chicken retina. J Comp Neurol 2007; 500:1154-71. [PMID: 17183536 DOI: 10.1002/cne.21236] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Despite numerous reports that different markers are expressed by horizontal cells in the avian retina, it remains unknown whether different types of horizontal cells can be defined by differences in their immunocytochemical profiles. The purpose of this study was to rectify this deficiency. We identified horizontal cells by indirect immunofluorescence with antibodies to calretinin, trkA, GABA, Prox1, AP2alpha, Pax6, islet1, and Lim1 + 2. We found two major groups of horizontal cells, those that express trkA and those that express calretinin. The trkA-immunoreactive (-IR) horizontal cells had small, round somata and robust, bulbous dendritic endings, whereas calretinin-IR horizontal cells had large, polygonal cell bodies and fine, diffuse dendritic endings, both contacting the calbindin-IR pedicles of double cones. Weak gamma-aminobutyric acid (GABA) immunoreactivity was observed only in a few of the trkA-IR horizontal cells, whereas the overlap of calretinin and GABA immunoreactivities was 100%. The majority of trkA-IR horizontal cells expressed islet1, and the majority of calretinin-IR horizontal cells expressed Lim1 + 2, AP2alpha, and Pax6. Islet1 immunoreactivity was observed in a small fraction of calretinin-IR/non-trkA-IR cells. In agreement with previous reports, we detected Prox1 immunoreactivity in all types of horizontal cells. These immunolabeling profiles suggest that there are four immunochemically distinct subtypes of horizontal cells in the postnatal chick retina, which may match the four types that have been observed in Golgi-impregnated pigeon and turtle retinas.
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Affiliation(s)
- Andy J Fischer
- Department of Neuroscience, The Ohio State University, Columbus, Ohio 43210, USA.
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28
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Warchol ME. Characterization of supporting cell phenotype in the avian inner ear: implications for sensory regeneration. Hear Res 2006; 227:11-8. [PMID: 17081713 DOI: 10.1016/j.heares.2006.08.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2006] [Revised: 04/26/2006] [Accepted: 08/30/2006] [Indexed: 10/24/2022]
Abstract
The avian inner ear possesses a remarkable capacity for the regeneration of sensory receptors after acoustic trauma or ototoxicity. Most replacement hair cells are created by renewed cell division within the sensory epithelium, although some new hair cells may also arise through nonmitotic mechanisms. Current data indicate that epithelial supporting cells play an essential role in regeneration, by serving as progenitor cells. In order to become progenitors, however, supporting cells may need to undergo partial dedifferentiation. In this review, I describe molecules that are expressed by supporting cells in the avian ear. Although a number of these molecules are likely to be critical to the maintenance of the supporting cell phenotype, we presently know very little about phenotypic changes in supporting cells during the early phase of regeneration.
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Affiliation(s)
- Mark E Warchol
- Department of Otolaryngology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
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29
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Bermingham-McDonogh O, Oesterle EC, Stone JS, Hume CR, Huynh HM, Hayashi T. Expression of Prox1 during mouse cochlear development. J Comp Neurol 2006; 496:172-86. [PMID: 16538679 PMCID: PMC2572724 DOI: 10.1002/cne.20944] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We carried out an analysis of the expression of Prox1, a homeo-domain transcription factor, during mouse inner ear development with particular emphasis on the auditory system. Prox1 is expressed in the otocyst beginning at embryonic day (E)11, in the developing vestibular sensory patches. Expression is down regulated in maturing (myosin VIIA immunoreactive) vestibular hair cells and subsequently in the underlying support cell layer by E16.5. In the auditory sensory epithelium, Prox1 is initially expressed at embryonic day 14.5 in a narrow stripe of cells at the base of the cochlea. This stripe encompasses the full thickness of the sensory epithelium, including developing hair cells and support cells. Over the next several days the stripe of expression extends to the apex, and as the sensory epithelium differentiates Prox1 becomes restricted to a subset of support cells. Double labeling for Prox1 and cell-type-specific markers revealed that the outer hair cells transiently express Prox1. After E18, Prox1 protein is no longer detectable in hair cells, but it continues to be expressed in support cells for the rest of embryogenesis and into the second postnatal week. During this time, Prox1 is not expressed in all support cell types in the organ of Corti, but is restricted to developing Deiters' and pillar cells. The expression is maintained in these cells into the second week of postnatal life, at which time Prox1 is dynamically down regulated. These studies form a baseline from which we can analyze the role of Prox1 in vertebrate sensory development.
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Affiliation(s)
- Olivia Bermingham-McDonogh
- Virginia Merrill Bloedel Hearing Research Center and Department of Otolaryngology, University of Washington School of Medicine, Seattle, Washington 98195, USA.
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Sekerková G, Zheng L, Mugnaini E, Bartles JR. Differential expression of espin isoforms during epithelial morphogenesis, stereociliogenesis and postnatal maturation in the developing inner ear. Dev Biol 2006; 291:83-95. [PMID: 16413524 PMCID: PMC2586395 DOI: 10.1016/j.ydbio.2005.12.021] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2005] [Revised: 12/02/2005] [Accepted: 12/06/2005] [Indexed: 01/23/2023]
Abstract
The espins are a family of multifunctional actin cytoskeletal proteins. They are present in hair cell stereocilia and are the target of mutations that cause deafness and vestibular dysfunction. Here, we demonstrate that the different espin isoforms are expressed in complex spatiotemporal patterns during inner ear development. Espin 3 isoforms were prevalent in the epithelium of the otic pit, otocyst and membranous labyrinth as they underwent morphogenesis. This espin was down-regulated ahead of hair cell differentiation and during neuroblast delamination. Espin also accumulated in the epithelium of branchial clefts and pharyngeal pouches and during branching morphogenesis in other embryonic epithelial tissues, suggesting general roles for espins in epithelial morphogenesis. Espin reappeared later in inner ear development in differentiating hair cells. Its levels and compartmentalization to stereocilia increased during the formation and maturation of stereociliary bundles. Late in embryonic development, espin was also present in a tail-like process that emanated from the hair cell base. Increases in the levels of espin 1 and espin 4 isoforms correlated with stereocilium elongation and maturation in the vestibular system and cochlea, respectively. Our results suggest that the different espin isoforms play specific roles in actin cytoskeletal regulation during epithelial morphogenesis and hair cell differentiation.
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MESH Headings
- Animals
- Animals, Newborn
- Cell Differentiation
- Cochlea/embryology
- Cochlea/growth & development
- Cochlea/metabolism
- Cytoskeleton/metabolism
- Ear, Inner/embryology
- Ear, Inner/growth & development
- Ear, Inner/metabolism
- Epithelium/embryology
- Epithelium/growth & development
- Epithelium/metabolism
- Hair Cells, Auditory/embryology
- Hair Cells, Auditory/growth & development
- Hair Cells, Auditory/metabolism
- Lacrimal Apparatus/embryology
- Lacrimal Apparatus/growth & development
- Lacrimal Apparatus/metabolism
- Lung/embryology
- Lung/growth & development
- Lung/metabolism
- Mice
- Microfilament Proteins/metabolism
- Morphogenesis
- Protein Isoforms/metabolism
- Rats
- Rats, Sprague-Dawley
- Vestibule, Labyrinth/embryology
- Vestibule, Labyrinth/growth & development
- Vestibule, Labyrinth/metabolism
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Affiliation(s)
- Gabriella Sekerková
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, IL 60611, USA
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Kil SH, Streit A, Brown ST, Agrawal N, Collazo A, Zile MH, Groves AK. Distinct roles for hindbrain and paraxial mesoderm in the induction and patterning of the inner ear revealed by a study of vitamin-A-deficient quail. Dev Biol 2005; 285:252-71. [PMID: 16039643 DOI: 10.1016/j.ydbio.2005.05.044] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2005] [Revised: 05/25/2005] [Accepted: 05/25/2005] [Indexed: 01/22/2023]
Abstract
The hindbrain and cranial paraxial mesoderm have been implicated in the induction and patterning of the inner ear, but the precise role of the two tissues in these processes is still not clear. We have addressed these questions using the vitamin-A-deficient (VAD) quail model, in which VAD embryos lack the posterior half of the hindbrain that normally lies next to the inner ear. Using a battery of molecular markers, we show that the anlagen of the inner ear, the otic placode, is induced in VAD embryos in the absence of the posterior hindbrain. By performing grafting and ablation experiments in chick embryos, we also show that cranial paraxial mesoderm which normally lies beneath the presumptive otic placode is necessary for otic placode induction and that paraxial mesoderm from other locations cannot induce the otic placode. Two members of the fibroblast growth factor family, FGF3 and FGF19, continue to be expressed in this mesodermal population in VAD embryos, and these may be responsible for otic placode induction in the absence of the posterior hindbrain. Although the posterior hindbrain is not required for otic placode induction in VAD embryos, the subsequent patterning of the inner ear is severely disrupted. Several regional markers of the inner ear, such as Pax2, EphA4, SOHo1 and Wnt3a, are incorrectly expressed in VAD otocysts, and the sensory patches and vestibulo-acoustic ganglia are either greatly reduced or absent. Exogenous application of retinoic acid prior to 30 h of development is able rescue the VAD phenotype. By performing such rescue experiments before and after 30 h of development, we show that the inner ear defects of VAD embryos correlate with the absence of the posterior hindbrain. These results show that induction and patterning of the inner ear are governed by separate developmental processes that can be experimentally uncoupled from each other.
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Affiliation(s)
- Sung-Hee Kil
- Gonda Department of Cell and Molecular Biology, House Ear Institute, 2100 West 3rd Street, Los Angeles, CA 90057, USA
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Satoh T, Fekete DM. Clonal analysis of the relationships between mechanosensory cells and the neurons that innervate them in the chicken ear. Development 2005; 132:1687-97. [PMID: 15743876 DOI: 10.1242/dev.01730] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In vertebrates, hair-cell-bearing mechanosensory organs and the neurons that innervate them share a common placodal origin. In the inner ear, the peripheral neurons for both auditory and vestibular systems emigrate from the otic placode as neuroblasts, and divide, differentiate and innervate only one of six to eight distinct sensory organs. How these neurons find their correct target is unknown, although one suggestion is that they synapse with clonally related cells. To test this idea for both the middle and inner ears of chicken embryos, lineage analysis was initiated at the time of neuroblast delamination by labeling progenitors with replication-defective retroviruses. The vast majority (89%) of clones were restricted to a single anatomical subdivision of the sensory periphery or its associated ganglia, indicating limited clonal dispersion. Among the remaining clones, we found evidence of a shared neurosensory lineage in the middle ear. Likewise, in the inner ear, neurons could be related to cells of the otic epithelium, although the latter cells were not widely distributed. Rather, they were restricted to a region in or near the utricular macula. None of the other seven sensory organs was related to the ganglion neurons, suggesting that a common lineage between neurons and their targets is not a general mechanism of establishing synaptic connections in the inner ear. This conclusion is further strengthened by finding a shared lineage between the vestibular and acoustic ganglia, revealing the presence of a common progenitor for the two functional classes of neurons.
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Affiliation(s)
- Takunori Satoh
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
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RADDE-GALLWITZ KRISTEN, PAN LING, GAN LIN, LIN XI, SEGIL NEIL, CHEN PING. Expression of Islet1 marks the sensory and neuronal lineages in the mammalian inner ear. J Comp Neurol 2004; 477:412-21. [PMID: 15329890 PMCID: PMC4158841 DOI: 10.1002/cne.20257] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Several basic helix-loop-helix (bHLH) genes have been shown to be essential for the generation of the auditory sensory hair cells or the spiral ganglion (SG) neurons that innervate the hair cells in the cochlea, as well as a variety of cell types in the other nervous systems. However, it remains elusive what cellular context-dependent mechanisms confer the inner ear-specific neuronal or sensory competency/identities. We explored the possibility that one of the mechanisms responsible for generating cellular diversity in the nervous system through cooperative action of bHLH and LIM-homeodomain (LIM-HD) transcriptional factors might also contribute to the inner ear-specific sensory and/or neuronal competency. Here, we show that Islet1 (Isl1), a LIM-HD protein, is expressed early in the otocyst in the region that gives rise to both the auditory sensory organ, the organ of Corti, and SG neurons. Subsequently, the expression of Isl1 is maintained in SG neurons but is transitory in the sensory lineage. At embryonic day 12 (E12) in mice, the expression of Isl1 marks distinctively the ventral portion of the nascent cochlear epithelium encompassing the primordial organ of Corti. At E13, Isl1 is maintained at relatively high levels in the sensory primordium while down-regulated in the other regions of the cochlear duct. As the sensory epithelium starts to differentiate, it is down-regulated in the entire cochlear epithelium. The expression of Isl1 in the developing inner ear reveals an early and likely a common step in the development of both sensory and neuronal lineages of the inner ear, and suggests its potential role in the inner ear-specific sensory and neuronal cell development.
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Affiliation(s)
| | - LING PAN
- Center for Aging and Developmental Biology, University of Rochester, Rochester, New York 14642
| | - LIN GAN
- Center for Aging and Developmental Biology, University of Rochester, Rochester, New York 14642
| | - XI LIN
- Department of Otolaryngology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - NEIL SEGIL
- Department of Cell and Molecular Biology, House Ear Institute, Los Angeles, California 90057
| | - PING CHEN
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322
- Department of Otolaryngology, Emory University School of Medicine, Atlanta, Georgia 30322
- Department of Cell and Molecular Biology, House Ear Institute, Los Angeles, California 90057
- Correspondence to: Ping Chen, Department of Cell Biology, Emory University School of Medicine, 615 Michael Street, Atlanta, GA.
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Li H, Liu H, Sage C, Huang M, Chen ZY, Heller S. Islet-1 expression in the developing chicken inner ear. J Comp Neurol 2004; 477:1-10. [PMID: 15281076 DOI: 10.1002/cne.20190] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The cell types of the inner ear originate from the otic placode, a thickened layer of ectoderm adjacent to the developing hindbrain. The placode invaginates and forms the otic pit, which pinches off as a small vesicle called the otocyst. Presumptive cochleovestibular neurons delaminate from the anterior ventral part of the otocyst and form the cochleovestibular ganglion of the inner ear. Here we show that the LIM/homeodomain protein islet-1 is expressed in cells of the ventral part of the otic placode and that this ventral expression is maintained at the otic pit and the otocyst stages. Auditory and vestibular neurons originate from this islet-1-positive zone of the otocyst, and these neurons maintain islet-1 expression until adulthood. We also demonstrate that islet-1 becomes up-regulated in the presumptive sensory epithelia of the inner ear in regions that are defined by the expression domains of BMP4. The up-regulation of islet-1 in developing inner ear hair and supporting cells is accompanied by down-regulation of Pax-2 in these cell types. Islet-1 expression in hair and supporting cells persists until early postnatal stages, when the transcriptional regulator is down-regulated in hair cells. Our data is consistent with a role for islet-1 in differentiating inner ear neurons and sensory epithelia cells, perhaps in the specification of cellular subtypes in conjunction with other LIM/homeodomain proteins.
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Affiliation(s)
- Huawei Li
- Department of Otolaryngology and Program in Neuroscience, Harvard Medical School, and Eaton Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts 02114, USA
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Abstract
The highly orchestrated processes that generate the vertebrate inner ear from the otic placode provide an excellent and circumscribed testing ground for fundamental cellular and molecular mechanisms of development. The recent pace of discovery in developmental auditory biology has been unusually rapid,with hundreds of papers published in the past 4 years. This review summarizes studies addressing several key issues that shape our current thinking about inner ear development, with particular emphasis on early patterning events,sensory hair cell specification and planar cell polarity.
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Affiliation(s)
- Kate F Barald
- Department of Cell and Developmental Biology, Program in Neuroscience, Cell and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI 48109-0616, USA
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36
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Alsina B, Abelló G, Ulloa E, Henrique D, Pujades C, Giraldez F. FGF signaling is required for determination of otic neuroblasts in the chick embryo. Dev Biol 2004; 267:119-34. [PMID: 14975721 DOI: 10.1016/j.ydbio.2003.11.012] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2003] [Revised: 10/01/2003] [Accepted: 11/10/2003] [Indexed: 10/26/2022]
Abstract
The interplay between intrinsic and extrinsic factors is essential for the transit into different cell states during development. We have analyzed the expression and function of FGF10 and FGF-signaling during the early stages of the development of otic neurons. FGF10 is expressed in a highly restricted domain overlapping the presumptive neurogenic region of the chick otic placode. A detailed study of the expression pattern of FGF10, proneural, and neurogenic genes revealed the following temporal sequence for the onset of gene expression: FGF10>Ngn1/Delta1/Hes5>NeuroD/NeuroM. FGF10 and FGF receptor inhibition cause opposed effects on cell determination and cell proliferation. Ectopic expression of FGF10 in vivo promotes an increase in NeuroD and NeuroM expression. BrdU incorporation experiments showed that the increase in NeuroD-expressing cells is not due to an increase in cell proliferation. Inhibition of FGF receptor signaling in otic explants causes a severe reduction in Neurogenin1, NeuroD, Delta1, and Hes5 expression with no change in non-neural genes like Lmx1. However, it does not interfere with NeuroD expression within the CVG or with neuroblast delamination. The loss of proneural gene expression caused by FGF inhibition is not caused by decreased cell proliferation or by increased cell death. We suggest that FGF signaling in the otic epithelium is required for neuronal precursors to withdraw from cell division and irreversibly commit to neuronal fate.
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Affiliation(s)
- Berta Alsina
- Biologia del Desenvolupament, Departament de Ciéncies Experimentals i de la Salut (DCEXS), Universitat Pompeu Fabra, 08003, Barcelona, Spain.
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Stone JS, Shang JL, Tomarev S. cProx1 immunoreactivity distinguishes progenitor cells and predicts hair cell fate during avian hair cell regeneration. Dev Dyn 2004; 230:597-614. [PMID: 15254895 DOI: 10.1002/dvdy.20087] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
In birds, mature sensory hair cells are regenerated continually in vestibular epithelia and after damage in the auditory basilar papilla. Molecular mechanisms governing the cellular processes associated with hair cell regeneration are poorly understood. Transcription factors are critical regulators of cell proliferation and differentiation in developing tissues. We examined immunoreactivity for cProx1 during both ongoing and damage-induced hair cell regeneration in chickens. Homologues of this divergent homeobox transcription factor are required for cell cycle withdrawal and differentiation in several vertebrate and invertebrate tissues. In the mitotically quiescent basilar papilla, a population of resting progenitor cells (supporting cells) shows faint nuclear immunoreactivity for cProx1. When auditory hair cell regeneration is triggered by experimental damage, nuclear cProx1 immunolabel is highly elevated in approximately 50% of dividing progenitor cells. Shortly after cytokinesis, all sibling pairs show symmetric patterns of nuclear cProx1 labeling, but pairs with asymmetric labeling emerge shortly thereafter. Strongly immunoreactive cells acquire the hair cell fate, whereas cells with low nuclear immunoreactivity differentiate as supporting cells. By contrast, cProx1 is not detected in any dividing progenitor cells during ongoing regeneration in the utricle. However, nuclear cProx1 immunoreactivity becomes asymmetric in postmitotic sibling cells, and as in the basilar papilla, cells with elevated cProx1 label differentiate as hair cells. In conclusion, cProx1 immunolabeling varies across sensory epithelial progenitors and distinguishes early differentiating hair cells from supporting cells. cProx1 may regulate the proliferative or differentiative capacities of progenitor cells and specify hair cell fate in postmitotic cells during avian hair cell regeneration.
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Affiliation(s)
- Jennifer S Stone
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology and Head and Neck Surgery, University of Washington, Seattle, 98195-7923, USA.
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