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Shirakawa Y, Li H, Inoue Y, Izumi H, Kaga Y, Goto YI, Inoue K, Inagaki M. Abnormality in GABAergic postsynaptic transmission associated with anxiety in Bronx waltzer mice with an Srrm4 mutation. IBRO Neurosci Rep 2024; 16:67-77. [PMID: 38229888 PMCID: PMC10790029 DOI: 10.1016/j.ibneur.2023.12.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 12/13/2023] [Accepted: 12/22/2023] [Indexed: 01/18/2024] Open
Abstract
The homozygous Bronx waltzer (bv) mouse, which shows hearing impairment, also exhibits anxiety accompanied by a reduction in cortical parvalbumin (PV)-positive GABAergic interneurons. Recently, a mutation in splicing factor Ser/Arg repetitive matrix 4 (Srrm4) was found in bv mice. However, the cellular consequences of the Srrm4 mutation for anxiety remain unknown. Here, we tested our hypothesis that bv mutant primarily affects interneurons through a cell-intrinsic pathology that leads to a reduction of interneurons and consequently causes anxiety. We found that the anxiety becomes apparent at 6 weeks of age in bv/bv mice. However, in situ hybridization revealed that Srrm4 is not expressed in interneurons, but rather dominates in pyramidal neurons. In addition, the PV-positive GABAergic interneurons were not reduced in number in the bv/bv cortex when anxiety became evident. However, electrophysiological abnormality of GABAergic transmission from interneurons was concomitantly present. Pharmacological blockage of GABAA receptors revealed increased excitability in bv/bv mice, although no gross change occurred in the expression of an Srrm4-downstream gene, Kcc2, which regulates chloride flux upon GABAergic transmission. These findings suggest that the bv-associated Srrm4 mutation mainly involves post-synaptic GABAergic transmission in the central nervous system, which may be associated with the anxiety phenotype in bv/bv mice.
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Affiliation(s)
- Yuka Shirakawa
- Department of Developmental Disorders, National Institute of Mental Health, National Center of Neurology and Psychiatry, 4–1-1 Ogawa Higashi, Kodaira, Tokyo 187–8553, Japan
| | - Heng Li
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4–1-1 Ogawa Higashi, Kodaira, Tokyo 187–8553, Japan
| | - Yuki Inoue
- Department of Developmental Disorders, National Institute of Mental Health, National Center of Neurology and Psychiatry, 4–1-1 Ogawa Higashi, Kodaira, Tokyo 187–8553, Japan
| | - Hitomi Izumi
- Department of Developmental Disorders, National Institute of Mental Health, National Center of Neurology and Psychiatry, 4–1-1 Ogawa Higashi, Kodaira, Tokyo 187–8553, Japan
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4–1-1 Ogawa Higashi, Kodaira, Tokyo 187–8553, Japan
| | - Yoshimi Kaga
- Department of Developmental Disorders, National Institute of Mental Health, National Center of Neurology and Psychiatry, 4–1-1 Ogawa Higashi, Kodaira, Tokyo 187–8553, Japan
| | - Yu-ichi Goto
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4–1-1 Ogawa Higashi, Kodaira, Tokyo 187–8553, Japan
| | - Ken Inoue
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4–1-1 Ogawa Higashi, Kodaira, Tokyo 187–8553, Japan
| | - Masumi Inagaki
- Department of Developmental Disorders, National Institute of Mental Health, National Center of Neurology and Psychiatry, 4–1-1 Ogawa Higashi, Kodaira, Tokyo 187–8553, Japan
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Emerging Roles of RNA-Binding Proteins in Inner Ear Hair Cell Development and Regeneration. Int J Mol Sci 2022; 23:ijms232012393. [PMID: 36293251 PMCID: PMC9604452 DOI: 10.3390/ijms232012393] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 10/07/2022] [Accepted: 10/14/2022] [Indexed: 11/05/2022] Open
Abstract
RNA-binding proteins (RBPs) regulate gene expression at the post-transcriptional level. They play major roles in the tissue- and stage-specific expression of protein isoforms as well as in the maintenance of protein homeostasis. The inner ear is a bi-functional organ, with the cochlea and the vestibular system required for hearing and for maintaining balance, respectively. It is relatively well documented that transcription factors and signaling pathways are critically involved in the formation of inner ear structures and in the development of hair cells. Accumulating evidence highlights emerging functions of RBPs in the post-transcriptional regulation of inner ear development and hair cell function. Importantly, mutations of splicing factors of the RBP family and defective alternative splicing, which result in inappropriate expression of protein isoforms, lead to deafness in both animal models and humans. Because RBPs are critical regulators of cell proliferation and differentiation, they present the potential to promote hair cell regeneration following noise- or ototoxin-induced damage through mitotic and non-mitotic mechanisms. Therefore, deciphering RBP-regulated events during inner ear development and hair cell regeneration can help define therapeutic strategies for treatment of hearing loss. In this review, we outline our evolving understanding of the implications of RBPs in hair cell formation and hearing disease with the aim of promoting future research in this field.
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Nakano Y, Wiechert S, Fritzsch B, Bánfi B. Inhibition of a transcriptional repressor rescues hearing in a splicing factor-deficient mouse. Life Sci Alliance 2020; 3:3/12/e202000841. [PMID: 33087486 PMCID: PMC7652395 DOI: 10.26508/lsa.202000841] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Revised: 10/09/2020] [Accepted: 10/12/2020] [Indexed: 11/26/2022] Open
Abstract
The vital role of the splicing factor SRRM4 in vestibular and inner hair cells of the ear is inactivation of the gene repressor REST; however, in outer hair cells, SRRM4 is dispensable for REST inactivation, which SRRM3 accomplishes independently. In mechanosensory hair cells (HCs) of the ear, the transcriptional repressor REST is continuously inactivated by alternative splicing of its pre-mRNA. This mechanism of REST inactivation is crucial for hearing in humans and mice. Rest is one of many pre-mRNAs whose alternative splicing is regulated by the splicing factor SRRM4; Srrm4 loss-of-function mutation in mice (Srrm4bv/bv) causes deafness, balance defects, and degeneration of all HC types other than the outer HCs (OHCs). The specific splicing alterations that drive HC degeneration in Srrm4bv/bv mice are unknown, and the mechanism underlying SRRM4-independent survival of OHCs is undefined. Here, we show that transgenic expression of a dominant-negative REST fragment in Srrm4bv/bv mice is sufficient for long-term rescue of hearing, balancing, HCs, alternative splicing of Rest, and expression of REST target genes including the Srrm4 paralog Srrm3. We also show that in HCs, SRRM3 regulates many of the same exons as SRRM4; OHCs are unique among HCs in that they transiently down-regulate Rest transcription as they mature to express Srrm3 independently of SRRM4; and simultaneous SRRM4–SRRM3 deficiency causes complete HC loss by preventing inactivation of REST in all HCs. Thus, our data reveal that REST inactivation is the primary and essential role of SRRM4 in the ear, and that OHCs differ from other HCs in the SRRM4-independent expression of the functionally SRRM4-like splicing factor SRRM3.
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Affiliation(s)
- Yoko Nakano
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA.,Inflammation Program, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Susan Wiechert
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA.,Inflammation Program, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Bernd Fritzsch
- Department of Biology, College of Liberal Arts and Sciences, University of Iowa, Iowa City, IA, USA
| | - Botond Bánfi
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA .,Inflammation Program, Carver College of Medicine, University of Iowa, Iowa City, IA, USA.,Department of Otolaryngology-Head and Neck Surgery, Carver College of Medicine, University of Iowa, Iowa City, IA, USA.,Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
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Ding D, Jiang H, Chen GD, Longo-Guess C, Muthaiah VPK, Tian C, Sheppard A, Salvi R, Johnson KR. N-acetyl-cysteine prevents age-related hearing loss and the progressive loss of inner hair cells in γ-glutamyl transferase 1 deficient mice. Aging (Albany NY) 2017; 8:730-50. [PMID: 26977590 PMCID: PMC4925825 DOI: 10.18632/aging.100927] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2016] [Accepted: 02/18/2016] [Indexed: 02/07/2023]
Abstract
Genetic factors combined with oxidative stress are major determinants of age-related hearing loss (ARHL), one of the most prevalent disorders of the elderly. Dwarf grey mice, Ggt1dwg/dwg, are homozygous for a loss of function mutation of the γ-glutamyl transferase 1 gene, which encodes an important antioxidant enzyme critical for the resynthesis of glutathione (GSH). Since GSH reduces oxidative damage, we hypothesized that Ggt1dwg/dwg mice would be susceptible to ARHL. Surprisingly, otoacoustic emissions and cochlear microphonic potentials, which reflect cochlear outer hair cell (OHC) function, were largely unaffected in mutant mice, whereas auditory brainstem responses and the compound action potential were grossly abnormal. These functional deficits were associated with an unusual and selective loss of inner hair cells (IHC), but retention of OHC and auditory nerve fibers. Remarkably, hearing deficits and IHC loss were completely prevented by N-acetyl-L-cysteine, which induces de novo synthesis of GSH; however, hearing deficits and IHC loss reappeared when treatment was discontinued. Ggt1dwg/dwgmice represent an important new model for investigating ARHL, therapeutic interventions, and understanding the perceptual and electrophysiological consequences of sensory deprivation caused by the loss of sensory input exclusively from IHC.
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Affiliation(s)
- Dalian Ding
- Center for Hearing and Deafness, University at Buffalo, Buffalo, NY 14214, USA
| | - Haiyan Jiang
- Center for Hearing and Deafness, University at Buffalo, Buffalo, NY 14214, USA
| | - Guang-Di Chen
- Center for Hearing and Deafness, University at Buffalo, Buffalo, NY 14214, USA
| | | | | | - Cong Tian
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
| | - Adam Sheppard
- Center for Hearing and Deafness, University at Buffalo, Buffalo, NY 14214, USA
| | - Richard Salvi
- Center for Hearing and Deafness, University at Buffalo, Buffalo, NY 14214, USA
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Abstract
Alternative precursor-mRNA splicing is a key mechanism for regulating gene expression in mammals and is controlled by specialized RNA-binding proteins. The misregulation of splicing is implicated in multiple neurological disorders. We describe recent mouse genetic studies of alternative splicing that reveal its critical role in both neuronal development and the function of mature neurons. We discuss the challenges in understanding the extensive genetic programmes controlled by proteins that regulate splicing, both during development and in the adult brain.
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Affiliation(s)
- Celine K Vuong
- Molecular Biology Interdepartmental Graduate Program, University of California at Los Angeles, Los Angeles, California 90095, USA
| | - Douglas L Black
- Department of Microbiology, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
| | - Sika Zheng
- Division of Biomedical Sciences, University of California at Riverside, Riverside, California 92521, USA
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Wang Y, Liu Y, Nie H, Ma X, Xu Z. Alternative splicing of inner-ear-expressed genes. Front Med 2016; 10:250-7. [PMID: 27376950 DOI: 10.1007/s11684-016-0454-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Accepted: 05/11/2016] [Indexed: 11/26/2022]
Abstract
Alternative splicing plays a fundamental role in the development and physiological function of the inner ear. Inner-ear-specific gene splicing is necessary to establish the identity and maintain the function of the inner ear. For example, exon 68 of Cadherin 23 (Cdh23) gene is subject to inner-ear-specific alternative splicing, and as a result, Cdh23(+ 68) is only expressed in inner ear hair cells. Alternative splicing along the tonotopic axis of the cochlea contributes to frequency tuning, particularly in lower vertebrates, such as chickens and turtles. Differential splicing of Kcnma1, which encodes for the α subunit of the Ca(2+)-activated K(+) channel (BK channel), has been suggested to affect the channel gating properties and is important for frequency tuning. Consequently, deficits in alternative splicing have been shown to cause hearing loss, as we can observe in Bronx Waltzer (bv) mice and Sfswap mutant mice. Despite the advances in this field, the regulation of alternative splicing in the inner ear remains elusive. Further investigation is also needed to clarify the mechanism of hearing loss caused by alternative splicing deficits.
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Affiliation(s)
- Yanfei Wang
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan, 250100, China
| | - Yueyue Liu
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan, 250100, China
| | - Hongyun Nie
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan, 250100, China
| | - Xin Ma
- School of Control Science and Engineering, Shandong University, Jinan, 250061, China
| | - Zhigang Xu
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan, 250100, China.
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Sensational placodes: neurogenesis in the otic and olfactory systems. Dev Biol 2014; 389:50-67. [PMID: 24508480 PMCID: PMC3988839 DOI: 10.1016/j.ydbio.2014.01.023] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 01/27/2014] [Accepted: 01/28/2014] [Indexed: 11/22/2022]
Abstract
For both the intricate morphogenetic layout of the sensory cells in the ear and the elegantly radial arrangement of the sensory neurons in the nose, numerous signaling molecules and genetic determinants are required in concert to generate these specialized neuronal populations that help connect us to our environment. In this review, we outline many of the proteins and pathways that play essential roles in the differentiation of otic and olfactory neurons and their integration into their non-neuronal support structures. In both cases, well-known signaling pathways together with region-specific factors transform thickened ectodermal placodes into complex sense organs containing numerous, diverse neuronal subtypes. Olfactory and otic placodes, in combination with migratory neural crest stem cells, generate highly specialized subtypes of neuronal cells that sense sound, position and movement in space, odors and pheromones throughout our lives.
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The candidate splicing factor Sfswap regulates growth and patterning of inner ear sensory organs. PLoS Genet 2014; 10:e1004055. [PMID: 24391519 PMCID: PMC3879212 DOI: 10.1371/journal.pgen.1004055] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 11/08/2013] [Indexed: 12/15/2022] Open
Abstract
The Notch signaling pathway is thought to regulate multiple stages of inner ear development. Mutations in the Notch signaling pathway cause disruptions in the number and arrangement of hair cells and supporting cells in sensory regions of the ear. In this study we identify an insertional mutation in the mouse Sfswap gene, a putative splicing factor, that results in mice with vestibular and cochlear defects that are consistent with disrupted Notch signaling. Homozygous Sfswap mutants display hyperactivity and circling behavior consistent with vestibular defects, and significantly impaired hearing. The cochlea of newborn Sfswap mutant mice shows a significant reduction in outer hair cells and supporting cells and ectopic inner hair cells. This phenotype most closely resembles that seen in hypomorphic alleles of the Notch ligand Jagged1 (Jag1). We show that Jag1; Sfswap compound mutants have inner ear defects that are more severe than expected from simple additive effects of the single mutants, indicating a genetic interaction between Sfswap and Jag1. In addition, expression of genes involved in Notch signaling in the inner ear are reduced in Sfswap mutants. There is increased interest in how splicing affects inner ear development and function. Our work is one of the first studies to suggest that a putative splicing factor has specific effects on Notch signaling pathway members and inner ear development.
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A mutation in the Srrm4 gene causes alternative splicing defects and deafness in the Bronx waltzer mouse. PLoS Genet 2012; 8:e1002966. [PMID: 23055939 PMCID: PMC3464207 DOI: 10.1371/journal.pgen.1002966] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2012] [Accepted: 08/08/2012] [Indexed: 11/19/2022] Open
Abstract
Sensory hair cells are essential for hearing and balance. Their development from epithelial precursors has been extensively characterized with respect to transcriptional regulation, but not in terms of posttranscriptional influences. Here we report on the identification and functional characterization of an alternative-splicing regulator whose inactivation is responsible for defective hair-cell development, deafness, and impaired balance in the spontaneous mutant Bronx waltzer (bv) mouse. We used positional cloning and transgenic rescue to locate the bv mutation to the splicing factor-encoding gene Ser/Arg repetitive matrix 4 (Srrm4). Transcriptome-wide analysis of pre–mRNA splicing in the sensory patches of embryonic inner ears revealed that specific alternative exons were skipped at abnormally high rates in the bv mice. Minigene experiments in a heterologous expression system confirmed that these skipped exons require Srrm4 for inclusion into the mature mRNA. Sequence analysis and mutagenesis experiments showed that the affected transcripts share a novel motif that is necessary for the Srrm4-dependent alternative splicing. Functional annotations and protein–protein interaction data indicated that the encoded proteins cluster in the secretion and neurotransmission pathways. In addition, the splicing of a few transcriptional regulators was found to be Srrm4 dependent, and several of the genes known to be targeted by these regulators were expressed at reduced levels in the bv mice. Although Srrm4 expression was detected in neural tissues as well as hair cells, analyses of the bv mouse cerebellum and neocortex failed to detect splicing defects. Our data suggest that Srrm4 function is critical in the hearing and balance organs, but not in all neural tissues. Srrm4 is the first alternative-splicing regulator to be associated with hearing, and the analysis of bv mice provides exon-level insights into hair-cell development. The identification of novel deafness-causing mutations has been instrumental in revealing unexpected mechanisms that are required for development of the sound- and gravity-sensing hair cells of the inner ear. The Bronx waltzer (bv) mouse is characterized by defects in hair-cell development, as well as by deafness and impaired balance. Here, we report on our identification of a mutation in the Ser/Arg repetitive matrix 4 (Srrm4) gene as the source of these defects. The encoded protein, Srrm4, belongs to a family of RNA splicing factors that regulate the inclusion of certain genetic information (i.e. alternative exons) into the transcribed RNA. We analyzed the molecular function of Srrm4 by comparing the exon composition of RNAs in the inner ear of bv and control mice. This approach revealed that, in the bv mice, specific alternative exons were omitted from protein-encoding RNAs. The affected transcripts shared two features: they contained a short sequence motif that was required for Srrm4-dependent splicing, and they encoded proteins that were related predominantly to secretion and neurotransmission. In addition, RNAs of a few gene expression regulators contained Srrm4-regulated exons. Our data suggest that Srrm4-dependent alternative splicing has a profound effect on the developmental program of hair cells.
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Matsuda Y, Inoue Y, Izumi H, Kaga M, Inagaki M, Goto YI. Fewer GABAergic interneurons, heightened anxiety and decreased high-frequency electroencephalogram components in Bronx waltzer mice, a model of hereditary deafness. Brain Res 2010; 1373:202-10. [PMID: 21146505 DOI: 10.1016/j.brainres.2010.12.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Revised: 12/01/2010] [Accepted: 12/02/2010] [Indexed: 11/16/2022]
Abstract
The homozygous Bronx waltzer mutation (bv/bv) results in the degeneration of most but not all of the primary auditory receptors, the inner hair cells and their afferent neurons, and leads to perceptive deafness. However, the influence of the mutation on the central nervous system (CNS) remains largely unclear. In this study, we have conducted behavioral, morphological and electrophysiological investigations to clarify the CNS dysfunction in bv/bv mice. These mutant mice exhibited heightened levels of anxiety with normal levels of motor activity. Immunohistochemical analysis revealed a significant reduction in parvalbumin-containing GABAergic interneurons in the anterior cingulate, somatosensory and auditory cortices of bv/bv mice. The current results suggest that interneuron development may be disrupted in the bv/bv cerebrum. Moreover, the high-frequency electroencephalogram components of the cortical activity, including the frequency range containing high gamma, were markedly decreased in bv/bv mice compared with controls, probably indicating a disturbance in cortical inhibitory function. Together, these results suggest that the cortical development of interneurons and their electrophysiological profiles are altered in bv/bv mice. We propose that these novel phenotypes identified in bv/bv mice provide new perspectives on the basic neuronal mechanisms of developmental disorders.
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Affiliation(s)
- Yoshiki Matsuda
- Department of Developmental Disorders, National Institute of Mental Health, National Center of Neurology and Psychiatry, 4-1-1 Ogawa Higashi, Kodaira, Tokyo 187-8553, Japan
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Zou D, Erickson C, Kim EH, Jin D, Fritzsch B, Xu PX. Eya1 gene dosage critically affects the development of sensory epithelia in the mammalian inner ear. Hum Mol Genet 2008; 17:3340-56. [PMID: 18678597 DOI: 10.1093/hmg/ddn229] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Haploinsufficiency of the transcription co-activator EYA1 causes branchio-oto-renal syndrome, congenital birth defects that account for as many as 2% of profoundly deaf children; however, the underlying cause for its dosage requirement and its specific role in sensory cell development of the inner ear are unknown. Here, an allelic series of Eya1 were generated to study the basis of Eya1 dosage requirements for sensory organ development. Our results show different threshold requirements for the level of Eya1 in different regions of the inner ear. Short and disorganized hair cell sterocilia was observed in wild-type/null heterozygous or hypomorphic/hypomorphic homozygous cochleae. Patterning and gene-marker analyses indicate that in Eya1 hypomorphic/null heterozygous mice, a reduction of Eya1 expression to 21% of normal level causes an absence of cochlear and vestibular sensory formation. Eya1 is initially expressed in the progenitors throughout the epithelium of all six sensory regions, and later on during sensory cell differentiation, its expression becomes restricted to the differentiating hair cells. We provide genetic evidence that Eya1 activity, in a concentration-dependent manner, plays a key role in the regulation of genes known to be important for sensory development. Furthermore, we show that Eya1 co-localizes with Sox2 in the sensory progenitors and both proteins physically interact. Together, our results indicate that Eya1 appears to be upstream of very early events during the sensory organ development, hair cell differentiation and inner-ear patterning. These results also provide a molecular mechanism for understanding how hypomorphic levels of EYA1 cause inner-ear defects in humans.
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Affiliation(s)
- Dan Zou
- McLaughlin Research Institute for Biomedical Sciences, Great Falls, MT 59405, USA
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Inagaki M, Kon K, Suzuki S, Kobayashi N, Kaga M, Nanba E. Characteristic findings of auditory brainstem response and otoacoustic emission in the Bronx waltzer mouse. Brain Dev 2006; 28:617-24. [PMID: 16730938 DOI: 10.1016/j.braindev.2006.04.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2006] [Revised: 04/01/2006] [Accepted: 04/10/2006] [Indexed: 10/24/2022]
Abstract
Auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs) were evaluated serially from 1 to 22 months in Bronx waltzer homozygotes (bv/bv), heterozygotes (+/bv) and control (+/+) mice, which were differentiated by means of PCR of marker DNA (D5Mit209). The wave IV threshold of the click-evoked ABR was higher than the DPOAE threshold with the DP growth method in each bv/bv, although the two thresholds were almost the same in the +/+ group. The DP value at 2f(1) - f(2) in the bv/bv showed an apparent decrease at 2 to 3 months of age with 80 dB SPL stimulation using f(2) frequency 7996 Hz and frequency ratio f(2)/f(1) = 1.22, compared to control or heterozygote mice. It was characteristic that the 2f(2) - f(1) DP signal-to-noise ratio (SNR) value was more preserved from 80 to 60 dB SPL than the 2f(1) - f(2) DP value at f(2) frequency 7996 Hz in most bv/bv, however, control mice showed almost the same levels of 2f(1) - f(2) and 2f(2) - f(1) SNR value at both f(2) frequencies of 6006 and 7996 Hz. The preservation of a substantial 2f(2) - f(1) DP suggested that it would be generated basal to the primary-tone place on the basilar membrane and there might be a reflection of the unique function of the remaining outer hair cells in the Bronx waltzer mice. These findings suggest that combination of ABR with DPOAE could offer useful information about differentiating the mechanism of hair cell dysfunction of the hereditary hearing impairment in the clinical fields.
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Affiliation(s)
- Masumi Inagaki
- Department of Developmental Disorders, National Institute of Mental Health, National Center of Neurology and Psychiatry (NCNP), 4-1-1 Ogawa Higashi, Kodaira 187-8553, Japan.
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Sterbing SJ, Schrott-Fischer A. Neuronal responses in the inferior colliculus of mutant mice (Bronx waltzer) with hereditary inner hair cell loss. Hear Res 2003; 177:91-9. [PMID: 12618321 DOI: 10.1016/s0378-5955(02)00805-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Bronx waltzer mice lose a great proportion of their cochlear inner hair cells during early development. Hair cell counts revealed that these mice lacked on average 86% of their inner hair cells. Outer hair cells were present in a normal number, but appeared disarranged. The effect of this inner hair cell loss on the properties of central auditory neurons was investigated by recording neuronal responses in the inferior colliculus. Neuronal thresholds were on average elevated by 40 dB compared to CBA controls. The frequency tuning curves of the mutants were broad, and in part (18.5%) multi-peaked. The tonotopy found in the inferior colliculus of the Bronx waltzer mice appeared diffuse. Both the driven and spontaneous discharge rates were not statistically significantly different from the controls. However, the average first spike latency was significantly longer in the Bronx waltzer mice.
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Affiliation(s)
- S J Sterbing
- Department of Zoology and Neurobiology, Ruhr University, Bochum, Germany.
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Sobkowicz HM, August BK, Slapnick SM. Influence of neurotrophins on the synaptogenesis of inner hair cells in the deaf Bronx waltzer (bv) mouse organ of Corti in culture. Int J Dev Neurosci 2002; 20:537-54. [PMID: 12485622 DOI: 10.1016/s0736-5748(02)00084-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
UNLABELLED The Bronx waltzer (bv) deaf mouse is characterized by massive degeneration of the primary auditory receptors, the inner hair cells, which occurs during the time of expected afferent synaptogenesis. The process is associated with degeneration and protracted division of the normally postmitotic afferent spiral ganglion neurons. To investigate the potential role of neurotrophins in the afferent synaptogenesis of inner hair cells, we exposed bv newborn cochleas in organotypic culture to brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) and nerve growth factor (NGF), and also to gamma aminobutyric acid (GABA), for up to 8 days. The study was done using light and electron microscopy. Only about 20% of the inner hair cells survived in culture, regardless of the treatment, similar to the number in the intact mutant in our colony. Depending on the exogenous treatment, this population consisted of either innervated ultrastructurally normal cells or denervated dedifferentiated cells wrapped-in lieu of nerve endings-by the supporting inner phalangeal and border cells. In the control and GABA cultures, inner hair cells were mostly denervated. BDNF and NT-3 alone or combined increased synaptogenesis and hair cell survival only during the first 3 days (by about 10%); however, the cells became denervated by 8 postnatal (PN). Only NGF induced stable innervation and differentiation of neurosensory relationships, including supernumerary innervation characteristic of the intact bv. Denervation among the remaining 20% of inner hair cells induced a reactive wrapping by inner phalangeal and border cells which evidently extended inner hair cell survival. Immunocytochemical studies of these reactive supporting cells were done in the intact (8 PN) mutant cochlea. The supporting cells that provide sustenance to the denervated inner hair cells displayed strong BDNF (and possibly NT-3) immunoreactivity. Subsequently, we revealed the presence of all three neurotrophins in the inner hair cell region of the developing (1-8 PN) cochlea of the normal ICR mouse. The inner hair cells expressed all three neurotrophins; BDNF prevailed in the inner phalangeal cells, NT-3 in the pillar cells and inner phalangeal cells, and NGF in the pillar cells. IN CONCLUSION initially, the 80% loss of inner hair cells is apparently caused by their failed afferent synaptogenesis. Exogenous neurotrophins influence synaptogenesis in the bv in culture, but NGF alone is successful in promoting stable neurosensory relationships. The presence of neurotrophins in supporting cells in the normal and degenerating cochlea indicates their role in the sustenance of inner hair cells.
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MESH Headings
- Aging/drug effects
- Aging/physiology
- Animals
- Animals, Newborn
- Brain-Derived Neurotrophic Factor/pharmacology
- Cell Count
- Cell Differentiation/drug effects
- Cell Line
- Cell Survival
- Deafness/physiopathology
- Hair Cells, Auditory, Inner/abnormalities
- Hair Cells, Auditory, Inner/drug effects
- Hair Cells, Auditory, Inner/physiopathology
- Hair Cells, Auditory, Inner/ultrastructure
- Mice
- Mice, Mutant Strains
- Nerve Degeneration/drug therapy
- Nerve Degeneration/embryology
- Nerve Degeneration/pathology
- Nerve Growth Factor/pharmacology
- Nerve Growth Factors/pharmacology
- Neurotrophin 3/pharmacology
- Organ of Corti/abnormalities
- Organ of Corti/drug effects
- Organ of Corti/ultrastructure
- Reference Values
- Synapses/drug effects
- Synapses/physiology
- Synapses/ultrastructure
- gamma-Aminobutyric Acid/pharmacology
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Affiliation(s)
- Hanna M Sobkowicz
- Neurology Department, University of Wisconsin, 1300 University Avenue, Room 75 MSC, Madison 53706, USA.
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15
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Erven A, Skynner MJ, Okumura K, Takebayashi SI, Brown SDM, Steel KP, Allen ND. A novel stereocilia defect in sensory hair cells of the deaf mouse mutant Tasmanian devil. Eur J Neurosci 2002; 16:1433-41. [PMID: 12405956 DOI: 10.1046/j.1460-9568.2002.02213.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Stereocilia are specialized actin-filled, finger-like processes arrayed in rows of graded heights to form a crescent or W-shape on the apical surface of sensory hair cells. The stereocilia are deflected by the vibration of sound, which opens transduction channels and allows an influx of ions to depolarize the hair cell, in turn triggering synaptic activity. The specialized morphology and organization of the stereocilia bundle is crucial in the process of sensory transduction in the inner ear. However, we know little about the development of stereocilia in the mouse and few molecules that are involved in stereocilia maturation are known. We describe here a new mouse mutant with abnormal stereocilia development. The Tasmanian devil (tde) mouse mutation arose by insertional mutagenesis and has been mapped to the middle of chromosome 5. Homozygotes show head-tossing and circling and have raised thresholds for cochlear nerve responses to sound. The gross morphology of the inner ear was normal, but the stereocilia of cochlear and vestibular hair cells are abnormally thin, and they become progressively disorganized with increasing age. Ultimately, the hair cells die. This is the first report of a mutant showing thin stereocilia. The association of thin stereocilia with cochlear dysfunction emphasizes the critical role of stereocilia in auditory transduction, and the discovery of the Tasmanian devil mutant provides a resource for the identification of an essential molecule in hair cell function.
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Affiliation(s)
- Alexandra Erven
- MRC Institute of Hearing Research, University of Nottingham, Nottingham NG7 2RD, UK
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16
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Li S, Price SM, Cahill H, Ryugo DK, Shen MM, Xiang M. Hearing loss caused by progressive degeneration of cochlear hair cells in mice deficient for the Barhl1 homeobox gene. Development 2002; 129:3523-32. [PMID: 12091321 DOI: 10.1242/dev.129.14.3523] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The cochlea of the mammalian inner ear contains three rows of outer hair cells and a single row of inner hair cells. These hair cell receptors reside in the organ of Corti and function to transduce mechanical stimuli into electrical signals that mediate hearing. To date, the molecular mechanisms underlying the maintenance of these delicate sensory hair cells are unknown. We report that targeted disruption of Barhl1, a mouse homolog of the Drosophila BarH homeobox genes, results in severe to profound hearing loss, providing a unique model for the study of age-related human deafness disorders. Barhl1 is expressed in all sensory hair cells during inner ear development, 2 days after the onset of hair cell generation. Loss of Barhl1 function in mice results in age-related progressive degeneration of both outer and inner hair cells in the organ of Corti, following two reciprocal longitudinal gradients. Our data together indicate an essential role for Barhl1 in the long-term maintenance of cochlear hair cells, but not in the determination or differentiation of these cells.
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MESH Headings
- Animals
- Deafness/genetics
- Deafness/pathology
- Disease Models, Animal
- Evoked Potentials, Auditory, Brain Stem/genetics
- Gene Expression Regulation, Developmental
- Genes, Homeobox
- Hair Cells, Auditory/growth & development
- Hair Cells, Auditory/pathology
- Hair Cells, Auditory, Inner/growth & development
- Hair Cells, Auditory, Inner/pathology
- Homeodomain Proteins/genetics
- Homeodomain Proteins/physiology
- Lac Operon
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Nerve Tissue Proteins/deficiency
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/physiology
- Repressor Proteins
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Affiliation(s)
- Shengguo Li
- Center for Advanced Biotechnology and Medicine and Department of Pediatrics, UMDNJ-Robert Wood Johnson Medical School, 679 Hoes Lane, Piscataway, NJ 08854, USA
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17
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Kong WJ, Scholtz AW, Hussl B, Kammen-Jolly K, Schrott-Fischer A. Localization of efferent neurotransmitters in the inner ear of the homozygous Bronx waltzer mutant mouse. Hear Res 2002; 167:136-55. [PMID: 12117537 DOI: 10.1016/s0378-5955(02)00382-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Naturally occurring mutant mice provide an excellent model for the study of genetic malformations of the inner ear. Mice homozygous for the Bronx waltzer (bv/bv) mutation are severely hearing impaired or deaf and exhibit a 'waltzing' gait. Functional aspects of cochlear and vestibular efferents in the bv/bv mutant mouse are not well known. The present study was designed to evaluate several candidates of efferent neurotransmitters or neuromodulators including choline acetyltransferase (ChAT), gamma-aminobutyric acid (GABA), and calcitonin gene-related peptide (CGRP) in the inner ear of the bv/bv mutant mouse. Ultrastructural investigations at both light and electron microscopic level were performed. Ultrastructural morphologic evaluations of the cochlea and the vestibular end-organs were also undertaken. It is demonstrated that ChAT, GABA and CGRP immunoreactivities are present in the cochlea and in vestibular end-organs of bv/bv mutant mice. In the organ of Corti, immunoreactivity of ChAT, GABA and CGRP is confined to the inner spiral fibers, tunnel-crossing fibers, and the vesiculated nerve endings synapsing with outer hair cells. Interestingly, immunoreactivity was detectable even where inner hair cells appeared missing. Results also revealed malformations of the outer hair cells with synaptic contacts to efferent nerve endings consistently intact. In the neurosensory epithelia of the vestibular end-organs, the presence of ChAT, GABA, and CGRP immunoreactivity was localized at the vestibular efferents, with the exception of the macula of saccule. In one 8-month-old macula of utricle where the depletion of hair cells appeared highest, ChAT immunostaining was still discernible. Ultrastructural investigation demonstrated that vesiculated efferent nerve endings make synaptic contact with the outer hair cells in the organ of Corti and with type II hair cells in the vestibular end-organs. The present study provides further support that the efferent system in the bv/bv mutant inner ear is morphologically as well as functionally mature. These findings also demonstrate that if and when the onset of efferent degeneration in the bv/bv mutant inner ear occurs, it transpires subsequent to pathological conditions in the hair cells. The present findings give further indication that the efferent systems of the bv/bv mutant inner ear are independent of the afferent systems in many aspects including development, maturation as well as degeneration.
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MESH Headings
- Animals
- Auditory Pathways/metabolism
- Calcitonin Gene-Related Peptide/metabolism
- Choline O-Acetyltransferase/metabolism
- Cochlea/metabolism
- Cochlea/ultrastructure
- Ear, Inner/abnormalities
- Ear, Inner/metabolism
- Ear, Inner/ultrastructure
- Efferent Pathways/metabolism
- Female
- Hair Cells, Auditory, Inner/abnormalities
- Hair Cells, Auditory, Inner/metabolism
- Hair Cells, Auditory, Inner/ultrastructure
- Hair Cells, Auditory, Outer/abnormalities
- Hair Cells, Auditory, Outer/metabolism
- Hair Cells, Auditory, Outer/ultrastructure
- Immunohistochemistry
- Male
- Mice
- Mice, Inbred CBA
- Mice, Mutant Strains
- Microscopy, Electron
- Neurotransmitter Agents/metabolism
- Vestibule, Labyrinth/abnormalities
- Vestibule, Labyrinth/metabolism
- Vestibule, Labyrinth/ultrastructure
- gamma-Aminobutyric Acid/metabolism
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Affiliation(s)
- W J Kong
- Department of Otolaryngology, Union Hospital of Tongji Medical College, Hua-Zhong University of Science and Technology, Hua-Zhong, PR China
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18
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Abstract
In bronx waltzer mouse mutants, inner hair cells die at an early stage in their development, from around 17.5 days of gestation onwards. In contrast, outer hair cells appear to develop normally. Vestibular hair cells also degenerate, but the earliest signs of vestibular abnormalities have not yet been described. We looked at prenatal and early postnatal stages of vestibular development by scanning electron microscopy in the mutants, and established that vestibular hair cells (types I and II) never reach beyond the middle stages of differentiation (at least up to P2) and instead show signs of degeneration. Thus, it appears that the bronx waltzer gene product is required for the continued survival and differentiation of inner and vestibular hair cells past a set point in their development.
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MESH Headings
- Animals
- Animals, Newborn
- Female
- Genotype
- Gestational Age
- Hair Cells, Auditory/embryology
- Hair Cells, Auditory/growth & development
- Hair Cells, Auditory/pathology
- Hair Cells, Auditory, Inner/embryology
- Hair Cells, Auditory, Inner/growth & development
- Hair Cells, Auditory, Inner/pathology
- Male
- Mice
- Mice, Mutant Strains/anatomy & histology
- Mice, Mutant Strains/embryology
- Mice, Mutant Strains/growth & development
- Microscopy, Electron, Scanning
- Pregnancy
- Vestibule, Labyrinth/embryology
- Vestibule, Labyrinth/growth & development
- Vestibule, Labyrinth/pathology
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Affiliation(s)
- Michael A Cheong
- MRC Institute of Hearing Research, University of Nottingham, University Park, NG7 2RD, UK
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19
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Zhang N, Martin GV, Kelley MW, Gridley T. A mutation in the Lunatic fringe gene suppresses the effects of a Jagged2 mutation on inner hair cell development in the cochlea. Curr Biol 2000; 10:659-62. [PMID: 10837254 DOI: 10.1016/s0960-9822(00)00522-4] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recent studies have demonstrated that the Notch signaling pathway regulates the differentiation of sensory hair cells in the vertebrate inner ear [1] [2] [3] [4] [5] [6] [7] [8] [9]. We have shown previously that in mice homozygous for a targeted null mutation of the Jagged2 (Jag2) gene, which encodes a Notch ligand, supernumerary hair cells differentiate in the cochlea of the inner ear [7]. Other components of the Notch pathway, including the Lunatic fringe (Lfng) gene, are also expressed during differentiation of the inner ear in mice [6] [7] [8] [9] [10]. In contrast to the Jag2 gene, which is expressed in hair cells, the Lfng gene is expressed in non-sensory supporting cells in the mouse cochlea [10]. Here we demonstrate that a mutation in the Lfng gene partially suppresses the effects of the Jag2 mutation on hair cell development. In mice homozygous for targeted mutations of both Jag2 and Lfng, the generation of supernumerary hair cells in the inner hair cell row is suppressed, while supernumerary hair cells in the outer hair cell rows are unaffected. We also demonstrate that supernumerary hair cells are generated in mice heterozygous for a Notch1 mutation. We suggest a model for the action of the Notch signaling pathway in regulating hair cell differentiation in the cochlear sensory epithelium.
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Affiliation(s)
- N Zhang
- The Jackson Laboratory, Bar Harbor,ME 04609, USA
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20
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Abstract
Tenascin-C is a glycoprotein of the extracellular matrix that acts in vitro as both a permissive and a nonpermissive substrate for neurite growth. We analyzed, by immunocytochemistry, the distribution of tenascin-C along neural growth pathways in the developing mouse cochlea. In the spiral lamina, tenascin-C coexists in a region where nerve bundles arborize. In the organ of Corti, tenascin-C lines the neural pathways along pillar and Deiters' cells before and during the time of nerve fiber ingrowth. By embryonic day 16, tenascin-C is abundant on the pillar side of the inner hair cell but does not accumulate on the modiolar side until about birth, a time after the arrival of afferent fibers. The synaptic zones beneath outer hair cells are strongly labeled during the time when early events in afferent synaptogenesis are progressing but not during the time of efferent synaptogenesis. At the age when most neural growth ceases, tenascin-C immunoreactivity disappears. Faint tenascin-C immunolabeling of normal hair cells, strong tenascin immunolabeling in pathological hair cells of Bronx waltzer (bv/bv) mice, and staining for beta-galactosidase, whose gene replaces tenascin in a "knockout" mouse, indicate that hair cells supply at least part of the tenascin-C. The changing composition of the extracellular matrix in the synaptic region during afferent and efferent synaptogenesis is consistent with a role for tenascin in synaptogenesis. The presence of tenascin-C along the growth routes of nerve fibers, particularly toward the outer hair cells, raises the possibility that growth cone interactions with tenascin-C helps to guide nerve fibers in the cochlea.
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Affiliation(s)
- D S Whitlon
- Audiology and Hearing Sciences Program and Institute for Neuroscience, Northwestern University, Evanston, Illinois 60208, USA.
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21
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Sobkowicz HM, August BK, Slapnick SM, Luthy DF. Terminal dendritic sprouting and reactive synaptogenesis in the postnatal organ of Corti in culture. J Comp Neurol 1998; 397:213-30. [PMID: 9658285 DOI: 10.1002/(sici)1096-9861(19980727)397:2<213::aid-cne5>3.0.co;2-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Synaptogenesis in the organ of Corti between the primary receptors, the inner hair cells, and the peripheral processes of their afferent spiral ganglion neurons in the mouse lasts for 5 days postnatally (Sobkowicz et al. [1986] J. Neurocytol. 15:693-714). The transplantation of the organ into culture at the fifth postnatal day induces a reactive sprouting of dendritic terminals and an extensive formation of new ribbon synapses within 24 hours. This reactive synaptogenesis differs strikingly from the primary synaptogenesis and has been seen thus far only in the inner hair cells. The synaptically engaged neuronal endings sprout a multitude of filopodia that intussuscept the inner hair cells. The filopodial tips contain a heavy electron-dense matter that appears to attract the synaptic ribbons, which form new synaptic contacts with the growing processes. The intensity of the filopodial growth and synaptogenesis subsides in about 3 days; the filopodia undergo resorption, leaving behind fibrous cytoplasmic plaques mostly stored in the supranuclear part of the hair cells. However, occasional filopodial growth and formation of new synaptic connections continued. The data demonstrate that any disruption or disturbance of the initial synaptic contacts between the inner hair cells and their afferent neurons caused by transplantation results in prompt synaptic reacquisition. Furthermore, we suggest that the transitory phase of terminal sprouting and multiribbon synapse formation manifests a trophic dependence that develops postnatally between the synaptic cells.
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Affiliation(s)
- H M Sobkowicz
- Department of Neurology, University of Wisconsin, Madison 53706, USA.
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