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Goodyear RJ, Richardson GP. Structure, Function, and Development of the Tectorial Membrane: An Extracellular Matrix Essential for Hearing. Curr Top Dev Biol 2018; 130:217-244. [PMID: 29853178 DOI: 10.1016/bs.ctdb.2018.02.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The tectorial membrane is an extracellular matrix that lies over the apical surface of the auditory epithelia in the inner ears of reptiles, birds, and mammals. Recent studies have shown it is composed of a small set of proteins, some of which are only produced at high levels in the ear and many of which are the products of genes that, when mutated, cause nonsyndromic forms of human hereditary deafness. Quite how the proteins of the tectorial membrane are assembled within the lumen of the inner ear to form a structure that is precisely regulated in its size and physical properties along the length of a tonotopically organized hearing organ is a question that remains to be fully answered. In this brief review we will summarize what is known thus far about the structure, protein composition, and function of the tectorial membrane in birds and mammals, describe how the tectorial membrane develops, and discuss major events that have occurred during the evolution of this extracellular matrix.
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Affiliation(s)
- Richard J Goodyear
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, United Kingdom
| | - Guy P Richardson
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, United Kingdom.
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2
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Xu Y, Zhang Y, Lundberg YW. Spatiotemporal differences in otoconial gene expression. Genesis 2016; 54:613-625. [PMID: 27792272 DOI: 10.1002/dvg.22990] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 10/02/2016] [Accepted: 10/26/2016] [Indexed: 11/06/2022]
Abstract
Otoconia are minute biocrystals composed of glycoproteins, proteoglycans, and CaCO3 , and are indispensable for sensory processing in the utricle and saccule. Otoconia abnormalities and degeneration can cause or facilitate crystal dislocation to the ampulla, leading to vertigo and imbalance in humans. In order to better understand the molecular mechanism controlling otoconia formation and maintenance, we have examined the spatial and temporal expression differences of otoconial genes in the mouse inner ear at developmental, mature and aging stages using whole transcriptome sequencing (RNA-Seq) and quantitative RT-PCR. We show that the expression levels of most otoconial genes are much higher in the utricle and saccule compared with other inner ear tissues before postnatal stages in C57Bl/6J mice, and the expression of a few of these genes is restricted to the embryonic utricle and saccule. After the early postnatal stages, expression of all otoconial genes in the utricle and saccule is drastically reduced, while a few genes gain expression dominance in the aging ampulla, indicating a potential for ectopic debris formation in the latter tissue at old ages. The data suggest that the expression of otoconial genes is tightly regulated spatially and temporally during developmental stages and can become unregulated at aging stages. Birth Defects Research (Part A) 106:613-625, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Yinfang Xu
- Vestibular Genetics Laboratory, Center for Sensory Neuroscience, Boys Town National Research Hospital, Omaha, Nebraska, 68131, USA.,Cell Electrophysiology Laboratory, Shanghai Research Center of Acupuncture and Meridians, Shanghai, 201203, China
| | - Yan Zhang
- Vestibular Genetics Laboratory, Center for Sensory Neuroscience, Boys Town National Research Hospital, Omaha, Nebraska, 68131, USA
| | - Yunxia Wang Lundberg
- Vestibular Genetics Laboratory, Center for Sensory Neuroscience, Boys Town National Research Hospital, Omaha, Nebraska, 68131, USA
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3
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van Beelen E, Schraders M, Huygen P, Oostrik J, Plantinga R, van Drunen W, Collin R, Kooper D, Pennings R, Cremers C, Kremer H, Kunst H. Clinical aspects of an autosomal dominantly inherited hearing impairment linked to the DFNA60 locus on chromosome 2q23.1–2q23.3. Hear Res 2013; 300:10-7. [DOI: 10.1016/j.heares.2013.03.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 02/07/2013] [Accepted: 03/09/2013] [Indexed: 11/26/2022]
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Davies D. Temporal and spatial regulation of alpha6 integrin expression during the development of the cochlear-vestibular ganglion. J Comp Neurol 2007; 502:673-82. [PMID: 17436285 DOI: 10.1002/cne.21302] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The neurons of the cochlear-vestibular ganglion (CVG) that innervate the sensory hair cells of the inner ear are derived from the otic epithelium early in development. Neuroblasts detach from neighboring cells, migrate into the mesenchyme where they coalesce to form the ganglion complex, then send processes back into the epithelium. Cell migration and neuronal process formation involve changes in cellular interactions with other cells and proteins in the extracellular matrix that are orchestrated by cell surface-expressed adhesion molecules, including the integrins. I studied the expression pattern of the alpha6 integrin subunit during the early development of the CVG using immunohistochemistry and reverse-transcriptase polymerase chain reaction (RT-PCR) in murine tissue sections, otocyst, and ganglion explants. At embryonic day (E)10.5 alpha6 integrin was expressed in the otic epithelium but not in migrating neuroblasts. Importantly, the loss of alpha6 was associated with exit from the epithelium, not neuronal determination, revealing differentiation cues acutely associated with the cellular environment. Markers of glial and neuronal phenotype showed that alpha6-expressing cells present in the CVG at this stage were glia of neural crest origin. By E12.5 alpha6 expression in the ganglion increased alongside the elaboration of neuronal processes. Immunohistochemistry applied to otocyst cultures in the absence of glia revealed that neuronal processes remained alpha6-negative at this developmental stage and confirmed that alpha6 was expressed by closely apposed glia. The spatiotemporal modulation of alpha6 expression suggests changing roles for this integrin during the early development of inner ear innervation.
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Affiliation(s)
- Dawn Davies
- Department of Physiology, University of Bristol, School of Medical Sciences, University Walk, Bristol, BS8 1TD, UK.
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5
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Hildebrand MS, de Silva MG, Klockars T, Campbell CA, Smith RJH, Dahl HHM. Gene expression profiling analysis of the inner ear. Hear Res 2007; 225:1-10. [PMID: 17300888 DOI: 10.1016/j.heares.2007.01.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2006] [Revised: 01/01/2007] [Accepted: 01/02/2007] [Indexed: 11/20/2022]
Abstract
Recent developments in molecular genetics, including progress in the human genome project, have allowed identification of genes at an unprecedented rate. To date gene expression profiling studies have focused on identifying transcripts that are specifically or preferentially enriched within the inner ear on the assumption that they are more likely to be important for auditory and vestibular function. It is now apparent that some genes preferentially expressed in the cochleo-vestibular system are not crucial for hearing or balance or their functions are compensated for by other genes. In addition, transcripts expressed at low abundance in the inner ear are generally under-represented in gene profiling studies. In this review, we highlight the limitations of current gene expression profiling strategies as a discovery tool for genes involved in cochleo-vestibular development and function. We argue that expression profiling based on hierarchical clustering of transcripts by gene ontology, combined with tissue enrichment data, is more effective for inner ear gene discovery. This approach also provides a framework to assist and direct the functional characterization of gene products.
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Affiliation(s)
- Michael S Hildebrand
- Department of Otolaryngology - Head and Neck Surgery, University of Iowa, Iowa City, IA 52242, USA.
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6
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Abstract
The innervation of the cochlear sensory epithelium is intricately organized, allowing the tonotopy established by the auditory hair cells to be maintained along the ascending auditory pathways. These auditory projections are patterned by several gene families that regulate neurite attraction and repulsion, known as axon guidance cues. In this review, the roles of various axon guidance molecules, including fibroblast growth factor, ephs, semaphorins, netrins and slits, are examined in light of their known contribution to auditory development. Additionally, morphogens are discussed in the context of their recently described influence on axonal pathfinding in other sensory systems. The elucidation of these various mechanisms may guide the development of therapies aimed at maximizing the connectivity of auditory neurons in the context of congenital or acquired sensorineural hearing loss, especially as pertains to cochlear implants. Further afield, improved understanding of the molecular processes which regulate innervation of the organ of Corti during normal development may prove useful in connecting regenerated hair cells to the central nervous system.
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Affiliation(s)
- Audra Webber
- Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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Toyama K, Ozeki M, Hamajima Y, Lin J. Expression of the integrin genes in the developing cochlea of rats. Hear Res 2005; 201:21-6. [PMID: 15721557 DOI: 10.1016/j.heares.2004.04.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2004] [Accepted: 04/12/2004] [Indexed: 10/26/2022]
Abstract
Integrins play an important role in the development of the cochlea. However, little is known about the expression pattern of integrins in the developing cochlear tissue. In this study, we investigated the dynamic expression profile of the integrin genes in the developing cochlear tissue of rats by Affymetrix microarrays and explored the role of the integrin genes in vitro by using antisense oligonucleotides. It was demonstrated that the alpha1, alpha7, alphav, beta3, and beta4 genes were expressed in the developing cochlear tissue of rats. Inhibition of the integrin expression with antisense oligonucleotides against alphav, alpha7, beta3, and beta4, respectively, in cochlear sensorineural epithelial cells significantly decreased the [3H]thymidine incorporation, suggesting that these integrins are involved in cell growth and proliferation. Inhibition of the alphav and beta4 integrins significantly decreased the transcription of nuclear factor-kappa B (NF-kappaB, a signal molecule involved in cell growth and proliferation) induced by epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF), respectively. It suggests that EGF-induced cell growth is dependent upon the alphav integrin whereas bFGF-induced cell growth is dependent upon the beta4 integrin in the cochlear tissue during the development of the inner ear.
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Affiliation(s)
- Katsuhiro Toyama
- Auditory Molecular Biology Laboratory, Department of Otolaryngology, University of Minnesota School of Medicine, Minneapolis, MN, USA
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Doetzlhofer A, White PM, Johnson JE, Segil N, Groves AK. In vitro growth and differentiation of mammalian sensory hair cell progenitors: a requirement for EGF and periotic mesenchyme. Dev Biol 2004; 272:432-47. [PMID: 15282159 DOI: 10.1016/j.ydbio.2004.05.013] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2003] [Revised: 03/22/2004] [Accepted: 05/05/2004] [Indexed: 11/19/2022]
Abstract
The sensory hair cells and supporting cells of the organ of Corti are generated by a precise program of coordinated cell division and differentiation. Since no regeneration occurs in the mature organ of Corti, loss of hair cells leads to deafness. To investigate the molecular basis of hair cell differentiation and their lack of regeneration, we have established a dissociated cell culture system in which sensory hair cells and supporting cells can be generated from mitotic precursors. By incorporating a Math1-GFP transgene expressed exclusively in hair cells, we have used this system to characterize the conditions required for the growth and differentiation of hair cells in culture. These conditions include a requirement for epidermal growth factor, as well as the presence of periotic mesenchymal cells. Lastly, we show that early postnatal cochlear tissue also contains cells that can divide and generate new sensory hair cells in vitro.
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Affiliation(s)
- Angelika Doetzlhofer
- Gonda Department of Cell and Molecular Biology, House Ear Institute, Los Angeles, CA 90057, USA
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9
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Simonneau L, Gallego M, Pujol R. Comparative expression patterns of T-, N-, E-cadherins, beta-catenin, and polysialic acid neural cell adhesion molecule in rat cochlea during development: implications for the nature of Kölliker's organ. J Comp Neurol 2003; 459:113-26. [PMID: 12640664 DOI: 10.1002/cne.10604] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
We investigated the expression patterns of several cell adhesion molecules (CAMs) during rat cochlea ontogeny, from embryo day 16 to adulthood, with the use of immunohistochemistry: neural cadherin (N-cad) and polysialic acid neural CAM (PSA-NCAM) as two different neural CAM paradigms; epithelial cadherin (E-cad), which was restricted to the epitheloid phenotype; and the cytoplasmic domain-free truncated-cadherin (T-cad). We made the following observations. (1) T-cad was present in all types of fibrocyte and in subdomains within the pillar cells. (2) E- and N-cad were expressed with mutually exclusive patterns and did not overlap with T-cad. All cochlear epithelial cells, including the sensory outer hair cells (OHCs), were E-cad-positive, except for the negative inner hair cells (IHCs) and the nonsensory Kölliker's organ domain close to the IHCs. N-cad expression appeared first in the developing IHCs and then in the neighboring Kölliker's organ in an increasingly mediolateral gradient in opposition to the E-cad gradient. The OHCs, which are never N-cad positive, intensively expressed E-cad, as did the Hensen cells at the beginning of their differentiation. (3) The cadherin-linked molecule beta-catenin, absent in fibrocytes, was detected in all epithelial cell membranes and was prominent in the E-cad-rich modiolar extremity of Kölliker's organ. (4) Gradual PSA-NCAM expression was observed in the lateral portion of Kölliker's organ, and the intense PSA-NCAM expression was seen surrounding the IHCs. As development proceeded, PSA-NCAM immunoreactivity progressively became restricted to the basal poles of the IHCs, where it remained in the adult rat cochlea, suggesting a synaptic plasticity. Synaptic plasticity in rat cochlea and hypotheses about T-cad functions and neosensory features of the Kölliker's organ are discussed.
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Affiliation(s)
- Lionel Simonneau
- Laboratoire de Neurobiologie de l'Audition-Plasticité Synaptique, Institut National de la Santé et de la Recherche Médicale U254, Université Montpellier I, 34090 Montpellier, France.
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Abstract
The neurons of the cochlear ganglion transmit acoustic information between the inner ear and the brain. These placodally derived neurons must produce a topographically precise pattern of connections in both the inner ear and the brain. In this review, we consider the current state of knowledge concerning the development of these neurons, their peripheral and central connections, and their influences on peripheral and central target cells. Relatively little is known about the cellular and molecular regulation of migration or the establishment of precise topographic connection to the hair cells or cochlear nucleus (CN) neurons. Studies of mice with neurotrophin deletions are beginning to yield increasing understanding of variations in ganglion cell survival and resulting innervation patterns, however. Finally, existing evidence suggests that while ganglion cells have little influence on the differentiation of their hair cell targets, quite the opposite is true in the brain. Ganglion cell innervation and synaptic activity are essential for normal development of neurons in the cochlear nucleus.
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Affiliation(s)
- Edwin W Rubel
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology/Head and Neck Surgery, University of Washington, Seattle 98195-7923, USA.
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11
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Davies D, Holley MC. Differential expression of alpha 3 and alpha 6 integrins in the developing mouse inner ear. J Comp Neurol 2002; 445:122-32. [PMID: 11891657 DOI: 10.1002/cne.10161] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The development of the mammalian inner ear involves a complex series of cell-cell and cell-extracellular matrix interactions. These interactions are likely to be mediated by families of adhesion molecules, including the integrins. We have studied the expression of three integrin subunits known to be expressed on epithelia in a number of tissues (namely, alpha3, alpha6, and beta4) during the development of the murine inner ear. At E10.5, both alpha3 and alpha6 were expressed in the epithelial layers of the otocyst. The expression of alpha6 was concentrated in an anterioventral region of the epithelium and in a proportion of the cells forming the cochlear-vestibular and facial ganglia. By E12.5, alpha6 showed a more restricted expression, confined mainly to the pro-sensory epithelia and the neural processes from the cochlear-vestibular ganglion. In contrast, alpha3 was expressed in epithelia adjacent to the pro-sensory areas. This reciprocal expression pattern was maintained until birth. Between birth and P6, a switch in expression occurred such that alpha3 was upregulated and alpha6 was downregulated in the sensory epithelia of both the auditory and vestibular systems. At this stage, alpha3 was expressed in all the epithelia lining the scala media, thus defining the endolymph compartment. The expression of beta4 was restricted to epithelial/mesenchymal borders throughout the developmental stages studied, suggesting that alpha6 expression observed within the epithelium and neuronal tissue was alpha6beta1. The early expression and changing pattern of alpha3 and alpha6 integrins during development of the mammalian inner ear suggests that they may be involved in the molecular processes that define epithelial boundaries and guide sensory innervation.
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MESH Headings
- Animals
- Animals, Newborn/embryology
- Animals, Newborn/genetics
- Animals, Newborn/metabolism
- Antigens, CD/biosynthesis
- Antigens, CD/genetics
- Ear, Inner/embryology
- Ear, Inner/growth & development
- Ear, Inner/metabolism
- Embryo, Mammalian/metabolism
- Embryo, Mammalian/physiology
- Female
- Gene Expression Regulation, Developmental/physiology
- Integrin alpha3
- Integrin alpha6
- Integrins/biosynthesis
- Integrins/genetics
- Male
- Mice
- Mice, Inbred C57BL
- Pregnancy
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Affiliation(s)
- Dawn Davies
- Department of Physiology, University of Bristol, School of Medical Sciences, Bristol BS8 1TD, United Kingdom.
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12
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Malgrange B, Belachew S, Thiry M, Nguyen L, Rogister B, Alvarez ML, Rigo JM, Van De Water TR, Moonen G, Lefebvre PP. Proliferative generation of mammalian auditory hair cells in culture. Mech Dev 2002; 112:79-88. [PMID: 11850180 DOI: 10.1016/s0925-4773(01)00642-6] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Hair cell (HC) and supporting cell (SC) productions are completed during early embryonic development of the mammalian cochlea. This study shows that acutely dissociated cells from the newborn rat organ of Corti, developed into so-called otospheres consisting of 98% nestin (+) cells when plated on a non-adherent substratum in the presence of either epidermal growth factor (EGF) or fibroblast growth factor (FGF2). Within cultured otospheres, nestin (+) cells were shown to express EGF receptor (EGFR) and FGFR2 and rapidly give rise to newly formed myosin VIIA (+) HCs and p27(KIP1) (+) SCs. Myosin VIIA (+) HCs had incorporated bromodeoxyuridine (BrdU) demonstrating that they were generated by a mitotic process. Ultrastructural studies confirmed that HCs had differentiated within the otosphere, as defined by the presence of both cuticular plates and stereocilia. This work raises the hypothesis that nestin (+) cells might be a source of newly generated HCs and SCs in the injured postnatal organ of Corti.
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Affiliation(s)
- Brigitte Malgrange
- Center for Cellular and Molecular Neurobiology, University of Liège, 17 Place Delcour, B-4020, Liège, Belgium.
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Abstract
Usher syndrome (USH) is defined by the association of sensorineural deafness and visual impairment due to retinitis pigmentosa. The syndrome has three distinct clinical subtypes, referred to as USH1, USH2, and USH3. Each subtype is genetically heterogeneous, and 12 loci have been detected so far. Four genes have been identified, namely, USH1B, USH1C, USH1D, and USH2A. USH1B, USH1C, and USH1D encode an unconventional myosin (myosin VIIA), a PDZ domain-containing protein (harmonin), and a cadherin-like protein (cadherin-23), respectively. Mutations of these genes cause primary defects of the sensory cells in the inner ear, and probably also in the retina. In the inner ear, the USH1 genes, I propose, are involved in the same signaling pathway, which may control development and/or maintenance of the hair bundles of sensory cells via an adhesion force (a) at the junctions between these cells and supporting cells and (b) at the level of the lateral links that interconnect the stereocilia. In contrast, the molecular pathogenesis of USH2A, which is owing to a defect of a novel extracellular matrix protein, is likely to be different from that of USH1.
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Affiliation(s)
- C Petit
- Unité de Génétique des Déficits Sensoriels, CNRS URA 1968 Institut Pasteur, Paris, Cedex 15, 75724 France.
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14
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Jovine L, Litscher ES, Wassarman PM. Egg zona pellucida, egg vitelline envelope, and related extracellular glycoproteins. GENE EXPRESSION AT THE BEGINNING OF ANIMAL DEVELOPMENT 2002. [DOI: 10.1016/s1569-1799(02)12023-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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15
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Bolz H, Ramírez A, von Brederlow B, Kubisch C. Characterization of ADAMTS14, a novel member of the ADAMTS metalloproteinase family. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1522:221-5. [PMID: 11779638 DOI: 10.1016/s0167-4781(01)00329-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
ADAMTS (a disintegrin-like and metalloproteinase domain with thrombospondin type 1 modules) proteins constitute a family of zinc metalloproteinases which target and process extracellular matrix proteins. We cloned and characterized a novel human ADAMTS gene, ADAMTS14, which is located on human chromosome 10q2. ADAMTS14 exhibits the characteristic multidomain structure of ADAMTS proteins including four thrombospondin modules and shows highest similarity to ADAMTS3 and ADAMTS2. By RT-PCR analysis we demonstrated that ADAMTS14 is expressed in human retina and also at low levels in adult brain, lung and placenta.
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Affiliation(s)
- H Bolz
- Institut für Hmangentik, Universitäts-Klinikum Eppendorf, Hamburg, Germany.
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16
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Lee MJ, Calle E, Brennan A, Ahmed S, Sviderskaya E, Jessen KR, Mirsky R. In early development of the rat mRNA for the major myelin protein P(0) is expressed in nonsensory areas of the embryonic inner ear, notochord, enteric nervous system, and olfactory ensheathing cells. Dev Dyn 2001; 222:40-51. [PMID: 11507768 DOI: 10.1002/dvdy.1165] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The myelin protein P(0) has a major structural role in Schwann cell myelin, and the expression of P(0) protein and mRNA in the Schwann cell lineage has been extensively documented. We show here, using in situ hybridization, that the P(0) gene is also activated in a number of other tissues during embryonic development. P(0) mRNA is first detectable in 10-day-old embryos (E10) and is at this time seen only in cells in the cephalic neural crest and in the otic placode/pit. P(0) expression continues in the otic vesicle and at E12 P(0) expression in this structure largely overlaps with expression of another myelin gene, proteolipid protein. In the developing ear at E14, P(0) expression is complementary to expression of serrate and c-ret mRNAs, which later are expressed in sensory areas of the inner ear, while expression of bone morphogenetic protein (BMP)-4 and P(0), though largely complementary, shows small areas of overlap. P(0) mRNA and protein are detectable in the notochord from E10 to at least E13. In addition to P(0) expression in a subpopulation of trunk crest cells at E11/E12 and in Schwann cell precursors thereafter, P(0) mRNA is also present transiently in a subpopulation of cells migrating in the enteric neural crest pathway, but is down-regulated in these cells at E14 and thereafter. P(0) is also detected in the placode-derived olfactory ensheathing cells from E13 and is maintained in the adult. No signal is seen in cells in the melanocyte migration pathway or in TUJ1 positive neuronal cells in tissue sections. The activation of the P(0) gene in specific tissues outside the nervous system was unexpected. It remains to be determined whether this is functionally significant, or whether it is an evolutionary relic, perhaps reflecting ancestral use of P(0) as an adhesion molecule.
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Affiliation(s)
- M J Lee
- Department of Anatomy and Developmental Biology, University College London, London, United Kingdom
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17
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Mothe AJ, Brown IR. Expression of mRNA encoding extracellular matrix glycoproteins SPARC and SC1 is temporally and spatially regulated in the developing cochlea of the rat inner ear. Hear Res 2001; 155:161-74. [PMID: 11335086 DOI: 10.1016/s0378-5955(01)00246-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
SPARC is a multifunctional extracellular matrix (ECM) glycoprotein that shares partial sequence homology with SC1/hevin. These ECM molecules exhibit calcium-binding properties and modulate cellular interactions. This study examines the expression of SC1 and SPARC mRNA in the developing cochlea of the rat inner ear prior to and after the onset of hearing. At all ages examined, SC1 mRNA is highly expressed in neurons of the spiral ganglion. In contrast, SPARC transcripts are not detected in the spiral ganglion but are enriched in the temporal bone and cartilaginous otic capsule surrounding the cochlea. Both SC1 and SPARC mRNA are expressed in connective tissue elements involved in maintaining ionic homeostasis of cochlear fluids. SC1 mRNA is localized to type III fibrocytes of the spiral ligament (slg) and marginal cells of the stria vascularis, while SPARC mRNA is apparent in the spiral limbus and type I fibrocytes of the slg. At postnatal day 10, SPARC mRNA shows a dramatic change in expression. High levels of SPARC transcripts are induced in Deiters cells (dc) of the organ of Corti. Interestingly, this induction of SPARC mRNA correlates with the onset of hearing. This suggests that SPARC may play a role in calcium regulation in dc when functional maturation of the cochlea is attained and rapid changes in calcium levels are required.
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Affiliation(s)
- A J Mothe
- Department of Zoology, University of Toronto at Scarborough, M1C 1A4, Toronto, ON, Canada
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18
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Bolz H, von Brederlow B, Ramírez A, Bryda EC, Kutsche K, Nothwang HG, Seeliger M, del C-Salcedó Cabrera M, Vila MC, Molina OP, Gal A, Kubisch C. Mutation of CDH23, encoding a new member of the cadherin gene family, causes Usher syndrome type 1D. Nat Genet 2001; 27:108-12. [PMID: 11138009 DOI: 10.1038/83667] [Citation(s) in RCA: 350] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Usher syndrome type I (USH1) is an autosomal recessive disorder characterized by congenital sensorineural hearing loss, vestibular dysfunction and visual impairment due to early onset retinitis pigmentosa (RP). So far, six loci (USH1A-USH1F) have been mapped, but only two USH1 genes have been identified: MYO7A for USH1B and the gene encoding harmonin for USH1C. We identified a Cuban pedigree linked to the locus for Usher syndrome type 1D (MIM 601067) within the q2 region of chromosome 10). Affected individuals present with congenital deafness and a highly variable degree of retinal degeneration. Using a positional candidate approach, we identified a new member of the cadherin gene superfamily, CDH23. It encodes a protein of 3,354 amino acids with a single transmembrane domain and 27 cadherin repeats. In the Cuban family, we detected two different mutations: a severe course of the retinal disease was observed in individuals homozygous for what is probably a truncating splice-site mutation (c.4488G-->C), whereas mild RP is present in individuals carrying the homozygous missense mutation R1746Q. A variable expression of the retinal phenotype was seen in patients with a combination of both mutations. In addition, we identified two mutations, Delta M1281 and IVS51+5G-->A, in a German USH1 patient. Our data show that different mutations in CDH23 result in USH1D with a variable retinal phenotype. In an accompanying paper, it is shown that mutations in the mouse ortholog cause disorganization of inner ear stereocilia and deafness in the waltzer mouse.
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Affiliation(s)
- H Bolz
- Institut für Humangenetik, UniversitätsKlinikum Hamburg-Eppendorf, Hamburg, Germany
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Rendtorff ND, Frödin M, Attié-Bitach T, Vekemans M, Tommerup N. Identification and characterization of an inner ear-expressed human melanoma inhibitory activity (MIA)-like gene (MIAL) with a frequent polymorphism that abolishes translation. Genomics 2001; 71:40-52. [PMID: 11161796 DOI: 10.1006/geno.2000.6409] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To discover new cochlea-specific genes as candidate genes for nonsyndromic hearing impairment, we searched in The Institute of Genome Research database for expressed sequence tags isolated from the cochlea only. This led to the cloning and characterization of a human gene named melanoma inhibitory activity-like (MIAL; HGMW-approved symbol OTOR alias MIAL) gene. In situ hybridization revealed MIAL expression in a cell layer beneath the sensory epithelium of cochlea and vestibule of human fetal inner ear. No other human tissue, except fetal brain, showed expression of MIAL when analyzed by in situ hybridization or reverse transcription-polymerase chain reaction. The cDNA of the mouse homologue was also cloned and mapped about 80 cM from the top of mouse chromosome 2. In mouse, Mial was also expressed in the cochlea and the vestibule of the inner ear, as well as in brain, eye, limb, and ovary. Expression in mammalian cell cultures showed that MIAL is translated as an approximately 15-kDa polypeptide that is assembled into a covalently linked homodimer, modified by sulfation, and secreted from the cells via the Golgi apparatus. In the human MIAL gene, a frequent polymorphism was discovered in the translation initiation codon (ACG instead of ATG). Of 505 individuals, 48 (9.5%) were ATG/ACG heterozygous and 1 (0.2%) was homozygous for ACG. No MIAL protein was synthesized in cells transfected with cDNA of the ACG allele. The inner ear-restricted expression pattern and the existence of an inactive allele suggest that MIAL may contribute to inner-ear dysfunction in humans.
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MESH Headings
- Alleles
- Amino Acid Sequence
- Animals
- Base Sequence
- Brain/embryology
- Brefeldin A/pharmacology
- COS Cells
- Chromosome Mapping
- Cloning, Molecular
- DNA, Complementary/metabolism
- Databases, Factual
- Ear, Inner/embryology
- Ear, Inner/metabolism
- Electrophoresis, Polyacrylamide Gel
- Expressed Sequence Tags
- Extracellular Matrix Proteins
- Extremities/embryology
- Eye/embryology
- Female
- Humans
- Immunoblotting
- Immunohistochemistry
- In Situ Hybridization
- Mice
- Models, Genetic
- Molecular Sequence Data
- Neoplasm Proteins/biosynthesis
- Neoplasm Proteins/genetics
- Ovary/embryology
- Polymorphism, Genetic
- Precipitin Tests
- Protein Biosynthesis
- Protein Processing, Post-Translational
- Protein Synthesis Inhibitors/pharmacology
- Proteins/genetics
- Proteins/physiology
- RNA, Messenger/metabolism
- Radiation Hybrid Mapping
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Homology, Amino Acid
- Tissue Distribution
- Transfection
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Affiliation(s)
- N D Rendtorff
- Department of Medical Genetics, Institute of Medical Biochemistry and Genetics, University of Copenhagen, N, 2200, Denmark
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Littlewood Evans A, Müller U. Stereocilia defects in the sensory hair cells of the inner ear in mice deficient in integrin alpha8beta1. Nat Genet 2000; 24:424-8. [PMID: 10742111 DOI: 10.1038/74286] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The mammalian inner ear contains organs for the detection of sound and acceleration, the cochlea and the vestibule, respectively. Mechanosensory hair cells within the neuroepithelia of these organs transduce mechanical force generated by sound waves or head movements into neuronal signals. Defects in hair cells lead to deafness and balance defects. Hair cells have stereocilia that are indispensable for mechanosensation, but the molecular mechanisms regulating stereocilia formation are poorly understood. We show here that integrin alpha8beta1, its ligand fibronectin and the integrin-regulated focal adhesion kinase (FAK) co-localize to the apical hair-cell surface where stereocilia are forming. In mice homozygous for a targeted mutation of Itga8 (encoding the alphabeta8 subunit), this co-localization is perturbed and hair cells in the utricle, a vestibular subcompartment, lack stereocilia or contain malformed stereocilia. Most integrin alpha-8beta1-deficient mice die soon after birth due to kidney defects. Many of the survivors have difficulty balancing, consistent with the structural defects of the inner ear. Our data suggest that integrin alpha8beta1, and potentially other integrins, regulates hair-cell differentiation and stereocilia maturation. Mutations affecting matrix molecules cause inherited forms of inner ear disease and integrins may mediate some effects of matrix molecules in the ear; thus, mutations in integrin genes may lead to inner-ear diseases as well.
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