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Wakizono T, Nakashima H, Yasui T, Noda T, Aoyagi K, Okada K, Yamada Y, Nakagawa T, Nakashima K. Growth factors with valproic acid restore injury-impaired hearing by promoting neuronal regeneration. JCI Insight 2021; 6:139171. [PMID: 34806649 PMCID: PMC8663787 DOI: 10.1172/jci.insight.139171] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Spiral ganglion neurons (SGNs) are primary auditory neurons in the spiral ganglion that transmit sound information from the inner ear to the brain and play an important role in hearing. Impairment of SGNs causes sensorineural hearing loss (SNHL), and it has been thought until now that SGNs cannot be regenerated once lost. Furthermore, no fundamental therapeutic strategy for SNHL has been established other than inserting devices such as hearing aids and cochlear implants. Here we show that the mouse spiral ganglion contains cells that are able to proliferate and indeed differentiate into neurons in response to injury. We suggest that SRY-box transcription factor 2/SRY-box transcription factor 10-double-positive (Sox2/Sox10-double-positive) Schwann cells sequentially started to proliferate, lost Sox10 expression, and became neurons, although the number of new neurons generated spontaneously was very small. To increase the abundance of new neurons, we treated mice with 2 growth factors in combination with valproic acid, which is known to promote neuronal differentiation and survival. This treatment resulted in a dramatic increase in the number of SGNs, accompanied by a partial recovery of the hearing loss induced by injury. Taken together, our findings offer a step toward developing strategies for treatment of SNHL.
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Affiliation(s)
- Takahiro Wakizono
- Department of Stem Cell Biology and Medicine and.,Department of Otorhinolaryngology, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
| | | | - Tetsuro Yasui
- Department of Otorhinolaryngology, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
| | - Teppei Noda
- Department of Otorhinolaryngology, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
| | - Kei Aoyagi
- Department of Stem Cell Biology and Medicine and.,Department of Otorhinolaryngology, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
| | - Kanako Okada
- Department of Stem Cell Biology and Medicine and
| | - Yasuhiro Yamada
- Division of Stem Cell Pathology, Center for Experimental Medicine and Systems Biology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan
| | - Takashi Nakagawa
- Department of Otorhinolaryngology, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
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2
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Law S, Stout M, Rensch A, Rowsell JM. Expression of MYOSIN VIIA in developing mouse cochleovestibular ganglion neurons. Gene Expr Patterns 2020; 35:119092. [PMID: 31918020 DOI: 10.1016/j.gep.2019.119092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 12/23/2019] [Accepted: 12/24/2019] [Indexed: 10/25/2022]
Abstract
Myosins make up a large super family of motor proteins responsible for actin-based motility in most eukaryotic cells. Myosin VIIA is essential for the development and function of sensory hair cells in the inner ear. The role of Myosin VIIA in the development of cochleovestibular ganglion (CVG) neurons in the mouse is largely unknown. Neurons of the CVG innervate sensory hair cells of the cochlea and vestibular organs to transmit hearing and balance information respectively to the brain. The aim of this study was to characterize the expression of MYOSIN VIIA in the CVG of mouse embryos. Spatiotemporal expression of MYOSIN VIIA was characterized in embryonic (E) mouse inner ear neurons from E9.5 to postnatal (P) day 0. At early stages, when otic neurons begin to delaminate to form the CVG, MYOSIN VIIA was co-expressed with TuJ1, ISLET1 and NEUROD in the otic epithelium and CVG. When CVG neurons were migrating and exiting mitosis, MYSOSIN VIIA was downregulated in a subset of neurons, which were NEUROD-negative and GATA3-positive. After segregation of the CVG, MYOSIN VIIA was observed in a subset of vestibular neurons marked by TUJ1 and absent in cochlear neurons, marked by GATA3. The differential expression of MYOSIN VIIA may indicate a role in inner ear neuron migration and specific labeling of vestibular neurons.
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Affiliation(s)
- Sarah Law
- Department of Biology, Saint Mary's College, Notre Dame, IN, 46556, USA.
| | - Molly Stout
- Department of Biology, Saint Mary's College, Notre Dame, IN, 46556, USA.
| | - Amanda Rensch
- Department of Biology, Saint Mary's College, Notre Dame, IN, 46556, USA.
| | - Jennifer M Rowsell
- Department of Biology, Saint Mary's College, Notre Dame, IN, 46556, USA.
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3
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Washausen S, Knabe W. Lateral line placodes of aquatic vertebrates are evolutionarily conserved in mammals. Biol Open 2018; 7:bio.031815. [PMID: 29848488 PMCID: PMC6031350 DOI: 10.1242/bio.031815] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Placodes are focal thickenings of the surface ectoderm which, together with neural crest, generate the peripheral nervous system of the vertebrate head. Here we examine how, in embryonic mice, apoptosis contributes to the remodelling of the primordial posterior placodal area (PPA) into physically separated otic and epibranchial placodes. Using pharmacological inhibition of apoptosis-associated caspases, we find evidence that apoptosis eliminates hitherto undiscovered rudiments of the lateral line sensory system which, in fish and aquatic amphibia, serves to detect movements, pressure changes or electric fields in the surrounding water. Our results refute the evolutionary theory, valid for more than a century that the whole lateral line was completely lost in amniotes. Instead, those parts of the PPA which, under experimental conditions, escape apoptosis have retained the developmental potential to produce lateral line placodes and the primordia of neuromasts that represent the major functional units of the mechanosensory lateral line system. Summary: Inhibition of apoptosis in mouse embryos reveals rudiments of the lateral line system, a sensory system common to fish and aquatic amphibia, but hypothesized to be completely lost in amniotes.
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Affiliation(s)
- Stefan Washausen
- Department Prosektur Anatomie, Westfälische Wilhelms-University, 48149 Münster, Germany
| | - Wolfgang Knabe
- Department Prosektur Anatomie, Westfälische Wilhelms-University, 48149 Münster, Germany
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4
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Wu JS, Vyas P, Glowatzki E, Fuchs PA. Opposing expression gradients of calcitonin-related polypeptide alpha (Calca/Cgrpα) and tyrosine hydroxylase (Th) in type II afferent neurons of the mouse cochlea. J Comp Neurol 2017; 526:425-438. [PMID: 29055051 DOI: 10.1002/cne.24341] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 10/04/2017] [Accepted: 10/10/2017] [Indexed: 12/20/2022]
Abstract
Type II spiral ganglion neurons (SGNs) are small caliber, unmyelinated afferents that extend dendritic arbors hundreds of microns along the cochlear spiral, contacting many outer hair cells (OHCs). Despite these many contacts, type II afferents are insensitive to sound and only weakly depolarized by glutamate release from OHCs. Recent studies suggest that type II afferents may be cochlear nociceptors, and can be excited by ATP released during tissue damage, by analogy to somatic pain-sensing C-fibers. The present work compares the expression patterns among cochlear type II afferents of two genes found in C-fibers: calcitonin-related polypeptide alpha (Calca/Cgrpα), specific to pain-sensing C-fibers, and tyrosine hydroxylase (Th), specific to low-threshold mechanoreceptive C-fibers, which was shown previously to be a selective biomarker of type II versus type I cochlear afferents (Vyas et al., ). Whole-mount cochlear preparations from 3-week- to 2-month-old CGRPα-EGFP (GENSAT) mice showed expression of Cgrpα in a subset of SGNs with type II-like peripheral dendrites extending beneath OHCs. Double labeling with other molecular markers confirmed that the labeled SGNs were neither type I SGNs nor olivocochlear efferents. Cgrpα starts to express in type II SGNs before hearing onset, but the expression level declines in the adult. The expression patterns of Cgrpα and Th formed opposing gradients, with Th being preferentially expressed in apical and Cgrpα in basal type II afferent neurons, indicating heterogeneity among type II afferent neurons. The expression of Th and Cgrpα was not mutually exclusive and co-expression could be observed, most abundantly in the middle cochlear turn.
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Affiliation(s)
- Jingjing Sherry Wu
- Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, Maryland.,The Center for Hearing and Balance and the Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Pankhuri Vyas
- The Center for Hearing and Balance and the Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland.,Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Elisabeth Glowatzki
- Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, Maryland.,The Center for Hearing and Balance and the Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland.,Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Paul Albert Fuchs
- Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, Maryland.,The Center for Hearing and Balance and the Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland.,Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland
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5
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Nguyen K, Hall AL, Jones JM. Expression of myosin VIIA in the developing chick inner ear neurons. Gene Expr Patterns 2015. [DOI: 10.1016/j.gep.2015.07.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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6
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Chow CL, Guo W, Trivedi P, Zhao X, Gubbels SP. Characterization of a unique cell population marked by transgene expression in the adult cochlea of nestin-CreER(T2)/tdTomato-reporter mice. J Comp Neurol 2015; 523:1474-87. [PMID: 25611038 DOI: 10.1002/cne.23747] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 10/18/2014] [Accepted: 01/13/2015] [Indexed: 02/06/2023]
Abstract
Hair cells in the adult mammalian cochlea cannot spontaneously regenerate after damage, resulting in the permanency of hearing loss. Stem cells have been found to be present in the cochlea of young rodents; however, there has been little evidence for their existence into adulthood. We used nestin-CreER(T2)/tdTomato-reporter mice to trace the lineage of putative nestin-expressing cells and their progeny in the cochleae of adult mice. Nestin, an intermediate filament found in neural progenitor cells during early development and adulthood, is regarded as a multipotent and neural stem cell marker. Other investigators have reported its presence in postnatal and young adult rodents; however, there are discrepancies among these reports. Using lineage tracing, we documented a robust population of tdTomato-expressing cells and evaluated these cells at a series of adult time points. Upon activation of the nestin promoter, tdTomato was observed just below and medial to the inner hair cell layer. All cells colocalized with the stem cell and cochlear-supporting-cell marker Sox2 as well as the supporting cell and Schwann cell marker Sox10; however, they did not colocalize with the Schwann cell marker Krox20, spiral ganglion marker NF200, nor glial fibrillary acidic acid (GFAP)-expressing supporting cell marker. The cellular identity of this unique population of tdTomato-expressing cells in the adult cochlea of nestin-CreER(T2)/tdTomato mice remains unclear; however, these cells may represent a type of supporting cell on the neural aspect of the inner hair cell layer.
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Affiliation(s)
- Cynthia L Chow
- Department of Communication Sciences and Disorders, University of Wisconsin-Madison, Madison, Wisconsin, 53706.,Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, 53705
| | - Weixiang Guo
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, 53705
| | - Parul Trivedi
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, 53705
| | - Xinyu Zhao
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, 53705.,Department of Neuroscience, University of Wisconsin-Madison, Madison, Wisconsin, 53706
| | - Samuel P Gubbels
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, 53705.,Department of Surgery, Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin-Madison, Madison, Wisconsin, 53792
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7
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Comparative expression analysis of POU4F1, POU4F2 and ISL1 in developing mouse cochleovestibular ganglion neurons. Gene Expr Patterns 2014; 15:31-7. [PMID: 24709358 DOI: 10.1016/j.gep.2014.03.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 03/10/2014] [Accepted: 03/13/2014] [Indexed: 12/26/2022]
Abstract
POU-homeodomain and LIM-homeodomain transcription factors are expressed in developing projection neurons within retina, inner ear, dorsal root ganglion, and trigeminal ganglion, and play synergistic roles in their differentiation and survival. Here, using immunohistochemistry, we present a comparative analysis of the spatiotemporal expression pattern of POU4F1, POU4F2, and ISL1 during the development of cochleovestibular ganglion (CVG) neurons in mouse inner ear. At early stages, when otic neurons are first detected in the otic epithelium (OE) and migrate into periotic mesenchyme to form the CVG, POU4F1 and ISL1 are co-expressed in a majority of the delaminated CVG neurons, which are marked by NEUROD1 expression, but POU4F1 is absent in the otic epithelium. The onset of POU4F2 expression starts after that of POU4F1 and ISL1, and is observed in the NEUROD1-negative, post-mitotic CVG neurons. When the CVG neurons innervate the vestibular and cochlear sensory organs, the expression of POU4F1, POU4F2, and ISL1 continues in both vestibular and spiral ganglion cells. Later in development, POU4F1 expression becomes down-regulated in a majority of spiral ganglion (SG) neurons and more neurons express POU4F2 expression while ISL1 expression is maintained. The differential as well as overlapping expression of POU4F1, POU4F2, and ISL1 combined with previous studies suggests possible functional interaction and regulatory relationship of these transcription factors in the development of inner ear neurons.
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8
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Lassiter RNT, Stark MR, Zhao T, Zhou CJ. Signaling mechanisms controlling cranial placode neurogenesis and delamination. Dev Biol 2013; 389:39-49. [PMID: 24315854 DOI: 10.1016/j.ydbio.2013.11.025] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2013] [Revised: 11/22/2013] [Accepted: 11/23/2013] [Indexed: 01/17/2023]
Abstract
The neurogenic cranial placodes are a unique transient epithelial niche of neural progenitor cells that give rise to multiple derivatives of the peripheral nervous system, particularly, the sensory neurons. Placode neurogenesis occurs throughout an extended period of time with epithelial cells continually recruited as neural progenitor cells. Sensory neuron development in the trigeminal, epibranchial, otic, and olfactory placodes coincides with detachment of these neuroblasts from the encompassing epithelial sheet, leading to delamination and ingression into the mesenchyme where they continue to differentiate as neurons. Multiple signaling pathways are known to direct placodal development. This review defines the signaling pathways working at the finite spatiotemporal period when neuronal selection within the placodes occurs, and neuroblasts concomitantly delaminate from the epithelium. Examining neurogenesis and delamination after initial placodal patterning and specification has revealed a common trend throughout the neurogenic placodes, which suggests that both activated FGF and attenuated Notch signaling activities are required for neurogenesis and changes in epithelial cell adhesion leading to delamination. We also address the varying roles of other pathways such as the Wnt and BMP signaling families during sensory neurogenesis and neuroblast delamination in the differing placodes.
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Affiliation(s)
- Rhonda N T Lassiter
- Institute for Pediatric Regenerative Medicine at Shriners Hospitals for Children-Northern California, CA 95817, USA; Department of Cell Biology and Human Anatomy, University of California Davis, School of Medicine, Sacramento, CA 95817, USA.
| | - Michael R Stark
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT 84602, USA.
| | - Tianyu Zhao
- Institute for Pediatric Regenerative Medicine at Shriners Hospitals for Children-Northern California, CA 95817, USA; Department of Cell Biology and Human Anatomy, University of California Davis, School of Medicine, Sacramento, CA 95817, USA
| | - Chengji J Zhou
- Institute for Pediatric Regenerative Medicine at Shriners Hospitals for Children-Northern California, CA 95817, USA; Department of Cell Biology and Human Anatomy, University of California Davis, School of Medicine, Sacramento, CA 95817, USA; Department of Biochemistry and Molecular Medicine, University of California Davis, School of Medicine, Sacramento, CA 95817, USA.
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9
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Sandell LL, Butler Tjaden NE, Barlow AJ, Trainor PA. Cochleovestibular nerve development is integrated with migratory neural crest cells. Dev Biol 2013; 385:200-10. [PMID: 24252775 DOI: 10.1016/j.ydbio.2013.11.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 11/01/2013] [Accepted: 11/08/2013] [Indexed: 02/04/2023]
Abstract
The cochleovestibular (CV) nerve, which connects the inner ear to the brain, is the nerve that enables the senses of hearing and balance. The aim of this study was to document the morphological development of the mouse CV nerve with respect to the two embryonic cells types that produce it, specifically, the otic vesicle-derived progenitors that give rise to neurons, and the neural crest cell (NCC) progenitors that give rise to glia. Otic tissues of mouse embryos carrying NCC lineage reporter transgenes were whole mount immunostained to identify neurons and NCC. Serial optical sections were collected by confocal microscopy and were compiled to render the three dimensional (3D) structure of the developing CV nerve. Spatial organization of the NCC and developing neurons suggest that neuronal and glial populations of the CV nerve develop in tandem from early stages of nerve formation. NCC form a sheath surrounding the CV ganglia and central axons. NCC are also closely associated with neurites projecting peripherally during formation of the vestibular and cochlear nerves. Physical ablation of NCC in chick embryos demonstrates that survival or regeneration of even a few individual NCC from ectopic positions in the hindbrain results in central projection of axons precisely following ectopic pathways made by regenerating NCC.
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Affiliation(s)
- Lisa L Sandell
- University of Louisville, Department of Molecular, Cellular and Craniofacial Biology, Louisville, KY 40201, USA.
| | - Naomi E Butler Tjaden
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA; Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Amanda J Barlow
- Department of Surgery, University of Wisconsin, Madison, WI 53792, USA
| | - Paul A Trainor
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA; Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
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10
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Shi F, Edge ASB. Prospects for replacement of auditory neurons by stem cells. Hear Res 2013; 297:106-12. [PMID: 23370457 DOI: 10.1016/j.heares.2013.01.017] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 01/16/2013] [Accepted: 01/18/2013] [Indexed: 02/07/2023]
Abstract
Sensorineural hearing loss is caused by degeneration of hair cells or auditory neurons. Spiral ganglion cells, the primary afferent neurons of the auditory system, are patterned during development and send out projections to hair cells and to the brainstem under the control of largely unknown guidance molecules. The neurons do not regenerate after loss and even damage to their projections tends to be permanent. The genesis of spiral ganglion neurons and their synapses forms a basis for regenerative approaches. In this review we critically present the current experimental findings on auditory neuron replacement. We discuss the latest advances with a focus on (a) exogenous stem cell transplantation into the cochlea for neural replacement, (b) expression of local guidance signals in the cochlea after loss of auditory neurons, (c) the possibility of neural replacement from an endogenous cell source, and (d) functional changes from cell engraftment.
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Affiliation(s)
- Fuxin Shi
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA 02114, USA
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11
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Magariños M, Contreras J, Aburto MR, Varela-Nieto I. Early development of the vertebrate inner ear. Anat Rec (Hoboken) 2012; 295:1775-90. [PMID: 23044927 DOI: 10.1002/ar.22575] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Accepted: 07/24/2012] [Indexed: 12/12/2022]
Abstract
This is a review of the biological processes and the main signaling pathways required to generate the different otic cell types, with particular emphasis on the actions of insulin-like growth factor I. The sensory organs responsible of hearing and balance have a common embryonic origin in the otic placode. Lineages of neural, sensory, and support cells are generated from common otic neuroepithelial progenitors. The sequential generation of the cell types that will form the adult inner ear requires the coordination of cell proliferation with cell differentiation programs, the strict regulation of cell survival, and the metabolic homeostasis of otic precursors. A network of intracellular signals operates to coordinate the transcriptional response to the extracellular input. Understanding the molecular clues that direct otic development is fundamental for the design of novel treatments for the protection and repair of hearing loss and balance disorders.
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Affiliation(s)
- Marta Magariños
- Instituto de Investigaciones Biomédicas, Alberto Sols, CSIC-UAM, Madrid, Spain
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12
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Aburto MR, Sánchez-Calderón H, Hurlé JM, Varela-Nieto I, Magariños M. Early otic development depends on autophagy for apoptotic cell clearance and neural differentiation. Cell Death Dis 2012; 3:e394. [PMID: 23034329 PMCID: PMC3481121 DOI: 10.1038/cddis.2012.132] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Autophagy is a highly regulated program of self-degradation of the cytosolic constituents that has key roles during early development and in adult cell growth and homeostasis. To investigate the role of autophagy in otic neurogenesis, we studied the expression of autophagy genes in early stages of chicken (Gallus gallus) inner ear development and the consequences of inhibiting the autophagic pathway in organotypic cultures of explanted chicken otic vesicles (OVs). Here we show the expression of autophagy-related genes (Atg) Beclin-1 (Atg6), Atg5 and LC3B (Atg8) in the otocyst and the presence of autophagic vesicles by using transmission electron microscopy in the otic neurogenic zone. The inhibition of the transcription of LC3B by using antisense morpholinos and of class III phosphatidylinositol 3-kinase with 3-methyladenine causes an aberrant morphology of the OV with accumulation of apoptotic cells. Moreover, inhibition of autophagy provokes the misregulation of the cell cycle in the otic epithelium, impaired neurogenesis and poor axonal outgrowth. Finally, our results indicate that autophagy provides the energy required for the clearing of neuroepithelial dying cells and suggest that it is required for the migration of otic neuronal precursors. Taken together, our results show for the first time that autophagy is an active and essential process during early inner ear development.
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Affiliation(s)
- M R Aburto
- Instituto de Investigaciones Biomédicas 'Alberto Sols', CSIC-UAM, Madrid, Spain
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13
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Aburto MR, Magariños M, Leon Y, Varela-Nieto I, Sanchez-Calderon H. AKT signaling mediates IGF-I survival actions on otic neural progenitors. PLoS One 2012; 7:e30790. [PMID: 22292041 PMCID: PMC3264639 DOI: 10.1371/journal.pone.0030790] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Accepted: 12/29/2011] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Otic neurons and sensory cells derive from common progenitors whose transition into mature cells requires the coordination of cell survival, proliferation and differentiation programmes. Neurotrophic support and survival of post-mitotic otic neurons have been intensively studied, but the bases underlying the regulation of programmed cell death in immature proliferative otic neuroblasts remains poorly understood. The protein kinase AKT acts as a node, playing a critical role in controlling cell survival and cell cycle progression. AKT is activated by trophic factors, including insulin-like growth factor I (IGF-I), through the generation of the lipidic second messenger phosphatidylinositol 3-phosphate by phosphatidylinositol 3-kinase (PI3K). Here we have investigated the role of IGF-dependent activation of the PI3K-AKT pathway in maintenance of otic neuroblasts. METHODOLOGY/PRINCIPAL FINDINGS By using a combination of organotypic cultures of chicken (Gallus gallus) otic vesicles and acoustic-vestibular ganglia, Western blotting, immunohistochemistry and in situ hybridization, we show that IGF-I-activation of AKT protects neural progenitors from programmed cell death. IGF-I maintains otic neuroblasts in an undifferentiated and proliferative state, which is characterised by the upregulation of the forkhead box M1 (FoxM1) transcription factor. By contrast, our results indicate that post-mitotic p27(Kip)-positive neurons become IGF-I independent as they extend their neuronal processes. Neurons gradually reduce their expression of the Igf1r, while they increase that of the neurotrophin receptor, TrkC. CONCLUSIONS/SIGNIFICANCE Proliferative otic neuroblasts are dependent on the activation of the PI3K-AKT pathway by IGF-I for survival during the otic neuronal progenitor phase of early inner ear development.
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Affiliation(s)
- Maria R Aburto
- Instituto de Investigaciones Biomedicas Alberto Sols, CSIC-UAM, Madrid, Spain
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14
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Davies D. Cell-extracellular matrix versus cell-cell interactions during the development of the cochlear-vestibular ganglion. J Neurosci Res 2011; 89:1375-87. [PMID: 21557292 DOI: 10.1002/jnr.22664] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Revised: 01/31/2011] [Accepted: 03/17/2011] [Indexed: 11/06/2022]
Abstract
Cells destined to become the neurones of the cochlear-vestibular ganglion (CVG) originate within the otic epithelium. Early in development they detach from their neighbors and migrate out of the epithelium, where they coalesce to form the CVG. To accomplish this process, the neuroblasts must modify their interactions with other cells within the epithelium and with proteins in the extracellular matrix to allow for repositioning. The aim of this study was to investigate the roles of the major families of adhesion molecules that mediate cellular interactions with the extracellular matrix, the integrins, and with other cells, the cadherins, in neuroblast segregation from the otic epithelium. The expression of classical cadherins increased in migrating neuroblasts compared with the otic epithelium. Quantitative RT-PCR revealed that this was concomitant with down-regulation of E-cadherin and up-regulation of N-cadherin in the migrating cells. In contrast, the level of β1 integrin expression by the epithelium was maintained in migrating neuroblasts. However, although multiple integrin ligands were expressed within the otic basement membrane at this stage of development, only fibronectin (FN) supported neuroblast migration along the substrate in vitro. Inhibition of β1 integrins resulted in significantly reduced linear migration on FN. Importantly, neuroblasts retained the ability to segregate from the epithelium but remained compacted immediately adjacent to the originating tissue, suggesting dominance of cell-cell over cell-matrix interactions. These data suggest that the balance between cell-cell and cell-substratum interactions directs otic neuroblast migration and gangliogenesis.
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Affiliation(s)
- Dawn Davies
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom.
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15
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Yang T, Kersigo J, Jahan I, Pan N, Fritzsch B. The molecular basis of making spiral ganglion neurons and connecting them to hair cells of the organ of Corti. Hear Res 2011; 278:21-33. [PMID: 21414397 DOI: 10.1016/j.heares.2011.03.002] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2010] [Revised: 03/01/2011] [Accepted: 03/07/2011] [Indexed: 11/28/2022]
Abstract
The bipolar spiral ganglion neurons apparently delaminate from the growing cochlear duct and migrate to Rosenthal's canal. They project radial fibers to innervate the organ of Corti (type I neurons to inner hair cells, type II neurons to outer hair cells) and also project tonotopically to the cochlear nuclei. The early differentiation of these neurons requires transcription factors to regulate migration, pathfinding and survival. Neurog1 null mice lack formation of neurons. Neurod1 null mice show massive neuronal death combined with aberrant central and peripheral projections. Prox1 protein is necessary for proper type II neuron process navigation, which is also affected by the neurotrophins Bdnf and Ntf3. Neurotrophin null mutants show specific patterns of neuronal loss along the cochlea but remaining neurons compensate by expanding their target area. All neurotrophin mutants have reduced radial fiber growth proportional to the degree of loss of neurotrophin alleles. This suggests a simple dose response effect of neurotrophin concentration. Keeping overall concentration constant, but misexpressing one neurotrophin under regulatory control of another one results in exuberant fiber growth not only of vestibular fibers to the cochlea but also of spiral ganglion neurons to outer hair cells suggesting different effectiveness of neurotrophins for spiral ganglion neurite growth. Finally, we report here for the first time that losing all neurons in double null mutants affects extension of the cochlear duct and leads to formation of extra rows of outer hair cells in the apex, possibly by disrupting the interaction of the spiral ganglion with the elongating cochlea.
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Affiliation(s)
- Tian Yang
- Department of Biology, College of Liberal Arts and Sciences, University of Iowa, 143 BB, Iowa City, IA 52242, USA
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Appler JM, Goodrich LV. Connecting the ear to the brain: Molecular mechanisms of auditory circuit assembly. Prog Neurobiol 2011; 93:488-508. [PMID: 21232575 DOI: 10.1016/j.pneurobio.2011.01.004] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 12/09/2010] [Accepted: 01/03/2011] [Indexed: 12/21/2022]
Abstract
Our sense of hearing depends on precisely organized circuits that allow us to sense, perceive, and respond to complex sounds in our environment, from music and language to simple warning signals. Auditory processing begins in the cochlea of the inner ear, where sounds are detected by sensory hair cells and then transmitted to the central nervous system by spiral ganglion neurons, which faithfully preserve the frequency, intensity, and timing of each stimulus. During the assembly of auditory circuits, spiral ganglion neurons establish precise connections that link hair cells in the cochlea to target neurons in the auditory brainstem, develop specific firing properties, and elaborate unusual synapses both in the periphery and in the CNS. Understanding how spiral ganglion neurons acquire these unique properties is a key goal in auditory neuroscience, as these neurons represent the sole input of auditory information to the brain. In addition, the best currently available treatment for many forms of deafness is the cochlear implant, which compensates for lost hair cell function by directly stimulating the auditory nerve. Historically, studies of the auditory system have lagged behind other sensory systems due to the small size and inaccessibility of the inner ear. With the advent of new molecular genetic tools, this gap is narrowing. Here, we summarize recent insights into the cellular and molecular cues that guide the development of spiral ganglion neurons, from their origin in the proneurosensory domain of the otic vesicle to the formation of specialized synapses that ensure rapid and reliable transmission of sound information from the ear to the brain.
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Affiliation(s)
- Jessica M Appler
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
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Harlow DE, Yang H, Williams T, Barlow LA. Epibranchial placode-derived neurons produce BDNF required for early sensory neuron development. Dev Dyn 2011; 240:309-23. [PMID: 21246648 DOI: 10.1002/dvdy.22527] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2010] [Indexed: 12/20/2022] Open
Abstract
In mice, BDNF provided by the developing taste epithelium is required for gustatory neuron survival following target innervation. However, we find that expression of BDNF, as detected by BDNF-driven β-galactosidase, begins in the cranial ganglia before its expression in the central (hindbrain) or peripheral (taste papillae) targets of these sensory neurons, and before gustatory ganglion cells innervate either target. To test early BDNF function, we examined the ganglia of bdnf null mice before target innervation, and found that while initial neuron survival is unaltered, early neuron development is disrupted. In addition, fate mapping analysis in mice demonstrates that murine cranial ganglia arise from two embryonic populations, i.e., epibranchial placodes and neural crest, as has been described for these ganglia in non-mammalian vertebrates. Only placodal neurons produce BDNF, however, which indicates that prior to innervation, early ganglionic BDNF produced by placode-derived cells promotes gustatory neuron development.
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Affiliation(s)
- Danielle E Harlow
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
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Magariños M, Aburto MR, Sánchez-Calderón H, Muñoz-Agudo C, Rapp UR, Varela-Nieto I. RAF kinase activity regulates neuroepithelial cell proliferation and neuronal progenitor cell differentiation during early inner ear development. PLoS One 2010; 5:e14435. [PMID: 21203386 PMCID: PMC3010996 DOI: 10.1371/journal.pone.0014435] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2010] [Accepted: 11/24/2010] [Indexed: 12/21/2022] Open
Abstract
Background Early inner ear development requires the strict regulation of cell proliferation, survival, migration and differentiation, coordinated by the concerted action of extrinsic and intrinsic factors. Deregulation of these processes is associated with embryonic malformations and deafness. We have shown that insulin-like growth factor I (IGF-I) plays a key role in embryonic and postnatal otic development by triggering the activation of intracellular lipid and protein kinases. RAF kinases are serine/threonine kinases that regulate the highly conserved RAS-RAF-MEK-ERK signaling cascade involved in transducing the signals from extracellular growth factors to the nucleus. However, the regulation of RAF kinase activity by growth factors during development is complex and still not fully understood. Methodology/Principal Findings By using a combination of qRT-PCR, Western blotting, immunohistochemistry and in situ hybridization, we show that C-RAF and B-RAF are expressed during the early development of the chicken inner ear in specific spatiotemporal patterns. Moreover, later in development B-RAF expression is associated to hair cells in the sensory patches. Experiments in ex vivo cultures of otic vesicle explants demonstrate that the influence of IGF-I on proliferation but not survival depends on RAF kinase activating the MEK-ERK phosphorylation cascade. With the specific RAF inhibitor Sorafenib, we show that blocking RAF activity in organotypic cultures increases apoptosis and diminishes the rate of cell proliferation in the otic epithelia, as well as severely impairing neurogenesis of the acoustic-vestibular ganglion (AVG) and neuron maturation. Conclusions/Significance We conclude that RAF kinase activity is essential to establish the balance between cell proliferation and death in neuroepithelial otic precursors, and for otic neuron differentiation and axonal growth at the AVG.
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Affiliation(s)
- Marta Magariños
- Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, Madrid, Spain.
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Schwartz CM, Cheng A, Mughal MR, Mattson MP, Yao PJ. Clathrin assembly proteins AP180 and CALM in the embryonic rat brain. J Comp Neurol 2010; 518:3803-18. [PMID: 20653035 DOI: 10.1002/cne.22425] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Clathrin-coated vesicles are known to play diverse and pivotal roles in cells. The proper formation of clathrin-coated vesicles is dependent on, and highly regulated by, a large number of clathrin assembly proteins. These assembly proteins likely determine the functional specificity of clathrin-coated vesicles, and together they control a multitude of intracellular trafficking pathways, including those involved in embryonic development. In this study, we focus on two closely related clathrin assembly proteins, AP180 and CALM (clathrin assembly lymphoid myeloid leukemia protein), in the developing embryonic rat brain. We find that AP180 begins to be expressed at embryonic day 14 (E14), but only in postmitotic cells that have acquired a neuronal fate. CALM, on the other hand, is expressed as early as E12, by both neural stem cells and postmitotic neurons. In vitro loss-of-function studies using RNA interference (RNAi) indicate that AP180 and CALM are dispensable for some aspects of embryonic neurogenesis but are required for the growth of postmitotic neurons. These results identify the developmental stage of AP180 and CALM expression and suggest that each protein has distinct functions in neural development.
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Affiliation(s)
- Catherine M Schwartz
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, Maryland 21224, USA
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Hu L, Yang H, Chen J, Li X, Ben Z, He X, Zhang F, Tao T, Cheng C, Shen A. β-1,4-Galactosyltransferase-involved in lipopolysaccharide-induced adhesion of schwann cells. Inflamm Res 2010; 60:169-74. [DOI: 10.1007/s00011-010-0251-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2009] [Revised: 02/23/2010] [Accepted: 09/06/2010] [Indexed: 12/25/2022] Open
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Liu Z, Owen T, Zhang L, Zuo J. Dynamic expression pattern of Sonic hedgehog in developing cochlear spiral ganglion neurons. Dev Dyn 2010; 239:1674-83. [PMID: 20503364 DOI: 10.1002/dvdy.22302] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Sonic hedgehog (Shh) signaling plays important roles in the formation of the auditory epithelium. However, little is known about the detailed expression pattern of Shh and the cell sources from which Shh is secreted. By analyzing Shh(CreEGFP/+) mice, we found that Shh was first expressed in all cochlear spiral ganglion neurons by embryonic day 13.5, after which its expression gradually decreased from base to apex. By postnatal day 0, it was not detected in any spiral ganglion neurons. Genetic cell fate mapping results also confirmed that Shh was exclusively expressed in all spiral ganglion neurons and not in surrounding glia cells. The basal-to-apical wave of Shh decline strongly resembles that of hair cell differentiation, supporting the idea that Shh signaling inhibits hair cell differentiation. Furthermore, this Shh(CreEGFP/+) mouse is a useful Cre line in which to delete floxed genes specifically in spiral ganglion neurons of the developing cochlea.
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Affiliation(s)
- Zhiyong Liu
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
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PC3 is involved in the shift from proliferation to differentiation and maturation in spiral ganglion neurons. Neuroreport 2010; 21:90-3. [PMID: 19997037 DOI: 10.1097/wnr.0b013e328332c4d7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PC3 is a member of the BTG/Tob family of antiproliferative genes. Here, we report the results of an analysis of PC3 protein expression in spiral ganglion neurons of the rat cochlea at embryonic days 16 (E16) and 20 (E20), and postnatal days 4 (P4) and 7 (P7). PC3 expression was observed in the cytoplasm of ganglion neurons at E16 and E20, and this protein had translocated to the nucleus by P4. The expression of Ki-67, a nuclear antigen expressed by dividing cells, was detected in ganglion neurons at E16 and E20, but not at P4 or P7. These results suggest that PC3 is involved in the shift from proliferation to differentiation and maturation in the ganglion neurons of the rat cochlea.
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