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Baldera D, Baxendale S, van Hateren NJ, Marzo M, Glendenning E, Geng F, Yokoya K, Knight RD, Whitfield TT. Enhancer trap lines with GFP driven by smad6b and frizzled1 regulatory sequences for the study of epithelial morphogenesis in the developing zebrafish inner ear. J Anat 2023; 243:78-89. [PMID: 36748120 PMCID: PMC10273346 DOI: 10.1111/joa.13845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/23/2023] [Accepted: 01/23/2023] [Indexed: 02/08/2023] Open
Abstract
Live imaging in the zebrafish embryo using tissue-specific expression of fluorescent proteins can yield important insights into the mechanisms that drive sensory organ morphogenesis and cell differentiation. Morphogenesis of the semicircular canal ducts of the vertebrate inner ear requires a complex rearrangement of epithelial cells, including outgrowth, adhesion, fusion and perforation of epithelial projections to generate pillars of tissue that form the hubs of each canal. We report the insertion sites and expression patterns of two enhancer trap lines in the developing zebrafish embryo, each of which highlight different aspects of epithelial cell morphogenesis in the inner ear. A membrane-linked EGFP driven by smad6b regulatory sequences is expressed throughout the otic epithelium, most strongly on the lateral side of the ear and in the sensory cristae. A second enhancer trap line, with cytoplasmic EGFP driven by frizzled1 (fzd1) regulatory sequences, specifically marks cells of the ventral projection and pillar in the developing ear, and marginal cells in the sensory cristae, together with variable expression in the retina and epiphysis, and neurons elsewhere in the developing central nervous system. We have used a combination of methods to identify the insertion sites of these two transgenes, which were generated through random insertion, and show that Targeted Locus Amplification is a rapid and reliable method for the identification of insertion sites of randomly inserted transgenes.
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Affiliation(s)
- Davide Baldera
- School of BiosciencesUniversity of SheffieldSheffieldUK
- Present address:
CeSASt, University of CagliariCagliariItaly
| | | | | | - Mar Marzo
- School of BiosciencesUniversity of SheffieldSheffieldUK
| | | | - Fan‐Suo Geng
- Brain and Mind Research Institute, University of SydneySydneyNew South WalesAustralia
- Present address:
Data Science Institute, The University of Technology SydneySydneyAustralia
| | - Kazutomo Yokoya
- Centre for Craniofacial and Regenerative Biology, King's College London, Guy's HospitalLondonUK
| | - Robert D. Knight
- Centre for Craniofacial and Regenerative Biology, King's College London, Guy's HospitalLondonUK
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2
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Gibaja A, Aburto MR, Pulido S, Collado M, Hurle JM, Varela-Nieto I, Magariños M. TGFβ2-induced senescence during early inner ear development. Sci Rep 2019; 9:5912. [PMID: 30976015 PMCID: PMC6459823 DOI: 10.1038/s41598-019-42040-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 03/21/2019] [Indexed: 01/16/2023] Open
Abstract
Embryonic development requires the coordinated regulation of apoptosis, survival, autophagy, proliferation and differentiation programs. Senescence has recently joined the cellular processes required to master development, in addition to its well-described roles in cancer and ageing. Here, we show that senescent cells are present in a highly regulated temporal pattern in the developing vertebrate inner ear, first, surrounding the otic pore and, later, in the otocyst at the endolymphatic duct. Cellular senescence is associated with areas of increased apoptosis and reduced proliferation consistent with the induction of the process when the endolymphatic duct is being formed. Modulation of senescence disrupts otic vesicle morphology. Transforming growth factor beta (TGFβ) signaling interacts with signaling pathways elicited by insulin-like growth factor type 1 (IGF-1) to jointly coordinate cellular dynamics required for morphogenesis and differentiation. Taken together, these results show that senescence is a natural occurring process essential for early inner ear development.
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Affiliation(s)
- Alejandro Gibaja
- Instituto de Investigaciones Biomédicas "Alberto Sols" (CSIC-UAM), Madrid, Spain
| | - María R Aburto
- Instituto de Investigaciones Biomédicas "Alberto Sols" (CSIC-UAM), Madrid, Spain
| | - Sara Pulido
- Instituto de Investigaciones Biomédicas "Alberto Sols" (CSIC-UAM), Madrid, Spain.,CIBERER, Instituto de Salud Carlos III, Madrid, Spain
| | - Manuel Collado
- Instituto de Investigación Sanitaria de Santiago de Compostela, Santiago de Compostela, Spain
| | - Juan M Hurle
- Departamento de Anatomía y Biología Celular and IDIVAL, Universidad de Cantabria, Santander, Spain
| | - Isabel Varela-Nieto
- Instituto de Investigaciones Biomédicas "Alberto Sols" (CSIC-UAM), Madrid, Spain.,CIBERER, Instituto de Salud Carlos III, Madrid, Spain.,Instituto de Investigación Sanitaria del Hospital Universitario La Paz (IdiPAZ), Madrid, Spain
| | - Marta Magariños
- Instituto de Investigaciones Biomédicas "Alberto Sols" (CSIC-UAM), Madrid, Spain. .,CIBERER, Instituto de Salud Carlos III, Madrid, Spain. .,Departamento de Biología, Universidad Autónoma de Madrid, Madrid, Spain.
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Clément A, Blanco-Sánchez B, Peirce JL, Westerfield M. Cog4 is required for protrusion and extension of the epithelium in the developing semicircular canals. Mech Dev 2018; 155:1-7. [PMID: 30287385 DOI: 10.1016/j.mod.2018.09.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 09/06/2018] [Accepted: 09/22/2018] [Indexed: 11/17/2022]
Abstract
The semicircular canals in the inner ear sense angular acceleration. In zebrafish, the semicircular canals develop from epithelial projections that grow toward each other and fuse to form pillars. The growth of the epithelial projections is driven by the production and secretion of extracellular matrix components by the epithelium. The conserved oligomeric Golgi 4 protein, Cog4, functions in retrograde vesicle transport within the Golgi and mutations can lead to sensory neural hearing loss. In zebrafish cog4 mutants, the inner ear is smaller and the number of hair cells is reduced. Here, we show that formation of the pillars is delayed and that secretion of extracellular matrix components (ECM) is impaired in cog4-/- mutants. These results show that Cog4 is required for secretion of ECM molecules essential to drive the growth of the epithelial projections and thus regulates morphogenesis of the semicircular canals.
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Affiliation(s)
- Aurélie Clément
- Institute of Neuroscience, University of Oregon, Eugene, OR 97403, USA
| | | | - Judy L Peirce
- Institute of Neuroscience, University of Oregon, Eugene, OR 97403, USA
| | - Monte Westerfield
- Institute of Neuroscience, University of Oregon, Eugene, OR 97403, USA.
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Ohta S, Schoenwolf GC. Dorsoventral differences in cAMP levels and correlated changes in the subcellular distribution of the PKA catalytic domain, provide further evidence that PKA signaling coordinates dorsoventral patterning of the otocyst. Dev Growth Differ 2018; 60:431-441. [PMID: 29920660 DOI: 10.1111/dgd.12543] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 05/09/2018] [Accepted: 05/10/2018] [Indexed: 01/22/2023]
Abstract
Dorsoventral (DV) patterning of the otocyst gives rise to formation of the morphologically and functionally complex membranous labyrinth composed of unique dorsal and ventral sensory organs. DV patterning results from extracellular signaling by secreted growth factors, which presumably form reciprocal concentration gradients across the DV axis of the otocyst. Previous work suggested a model in which two important growth factors, bone morphogenetic protein (BMP) and SHH, undergo crosstalk through an intersecting pathway to coordinate DV patterning. cAMP-dependent protein kinase A (PKA) lies at the heart of this pathway. Here, we provide further evidence that PKA signaling coordinates DV patterning, showing that both BMPs and SHH regulate cAMP levels, with BMPs increasing levels in the dorsal otocyst and SHH decreasing levels in the ventral otocyst. This, in turn, results in regional changes in the subcellular distribution of the catalytic domain of PKA, as well as DV regulation of PKA activity, increasing it dorsally and decreasing it ventrally. These new results fill an important gap in our previous understanding of how ligand signaling acts intracellularly during otocyst DV patterning and early morphogenesis, thereby initiating the series of events leading to formation of the inner ear sensory organs that function in balance and hearing.
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Affiliation(s)
- Sho Ohta
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah
| | - Gary C Schoenwolf
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah
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Jiang L, Xu J, Jin R, Bai H, Zhang M, Yang S, Zhang X, Zhang X, Han Z, Zeng S. Transcriptomic analysis of chicken cochleae after gentamicin damage and the involvement of four signaling pathways (Notch, FGF, Wnt and BMP) in hair cell regeneration. Hear Res 2018; 361:66-79. [DOI: 10.1016/j.heares.2018.01.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 06/22/2017] [Accepted: 01/06/2018] [Indexed: 10/18/2022]
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Ohta S, Schoenwolf GC. Hearing crosstalk: the molecular conversation orchestrating inner ear dorsoventral patterning. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2017; 7. [PMID: 29024472 DOI: 10.1002/wdev.302] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 08/08/2017] [Accepted: 08/28/2017] [Indexed: 11/10/2022]
Abstract
The inner ear is a structurally and functionally complex organ that functions in balance and hearing. It originates during neurulation as a localized thickened region of rostral ectoderm termed the otic placode, which lies adjacent to the developing caudal hindbrain. Shortly after the otic placode forms, it invaginates to delineate the otic cup, which quickly pinches off of the surface ectoderm to form a hollow spherical vesicle called the otocyst; the latter gives rise dorsally to inner ear vestibular components and ventrally to its auditory component. Morphogenesis of the otocyst is regulated by secreted proteins, such as WNTs, BMPs, and SHH, which determine its dorsoventral polarity to define vestibular and cochlear structures and sensory and nonsensory cell fates. In this review, we focus on the crosstalk that occurs among three families of secreted molecules to progressively polarize and pattern the developing otocyst. WIREs Dev Biol 2018, 7:e302. doi: 10.1002/wdev.302 This article is categorized under: Establishment of Spatial and Temporal Patterns > Gradients Signaling Pathways > Cell Fate Signaling Vertebrate Organogenesis > From a Tubular Primordium: Non-Branched.
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Affiliation(s)
- Sho Ohta
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Gary C Schoenwolf
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, UT, USA
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7
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Sculpting the labyrinth: Morphogenesis of the developing inner ear. Semin Cell Dev Biol 2017; 65:47-59. [DOI: 10.1016/j.semcdb.2016.09.015] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 07/26/2016] [Accepted: 09/25/2016] [Indexed: 01/23/2023]
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SHH ventralizes the otocyst by maintaining basal PKA activity and regulating GLI3 signaling. Dev Biol 2016; 420:100-109. [PMID: 27720745 DOI: 10.1016/j.ydbio.2016.10.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 10/04/2016] [Accepted: 10/04/2016] [Indexed: 02/07/2023]
Abstract
During development of the inner ear, secreted morphogens act coordinately to establish otocyst dorsoventral polarity. Among these, Sonic hedgehog (SHH) plays a critical role in determining ventral polarity. However, how this extracellular signal is transduced intracellularly to establish ventral polarity is unknown. In this study, we show that cAMP dependent protein kinase A (PKA) is a key intracellular factor mediating SHH signaling through regulation of GLI3 processing. Gain-of-function experiments using targeted gene transfection by sonoporation or electroporation revealed that SHH signaling inactivates PKA, maintaining a basal level of PKA activity in the ventral otocyst. This, in turn, suppresses partial proteolytic processing of GLI3FL, resulting in a low GLI3R/GLI3FL ratio in the ventral otocyst and the expression of ventral-specific genes required for ventral otocyst morphogenesis. Thus, we identify a molecular mechanism that links extracellular and intracellular signaling, determines early ventral polarity of the inner ear, and has implications for understanding the integration of polarity signals in multiple organ rudiments regulated by gradients of signaling molecules.
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Ohta S, Wang B, Mansour SL, Schoenwolf GC. BMP regulates regional gene expression in the dorsal otocyst through canonical and non-canonical intracellular pathways. Development 2016; 143:2228-37. [PMID: 27151948 DOI: 10.1242/dev.137133] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 04/27/2016] [Indexed: 12/13/2022]
Abstract
The inner ear consists of two otocyst-derived, structurally and functionally distinct components: the dorsal vestibular and ventral auditory compartments. BMP signaling is required to form the vestibular compartment, but how it complements other required signaling molecules and acts intracellularly is unknown. Using spatially and temporally controlled delivery of signaling pathway regulators to developing chick otocysts, we show that BMP signaling regulates the expression of Dlx5 and Hmx3, both of which encode transcription factors essential for vestibular formation. However, although BMP regulates Dlx5 through the canonical SMAD pathway, surprisingly, it regulates Hmx3 through a non-canonical pathway involving both an increase in cAMP-dependent protein kinase A activity and the GLI3R to GLI3A ratio. Thus, both canonical and non-canonical BMP signaling establish the precise spatiotemporal expression of Dlx5 and Hmx3 during dorsal vestibular development. The identification of the non-canonical pathway suggests an intersection point between BMP and SHH signaling, which is required for ventral auditory development.
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Affiliation(s)
- Sho Ohta
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, UT 84132-3401, USA
| | - Baolin Wang
- Department of Cell and Developmental Biology and Genetic Medicine, Weill Cornell Medical College, New York, NY 10065, USA
| | - Suzanne L Mansour
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, UT 84132-3401, USA Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT 84112-5330, USA
| | - Gary C Schoenwolf
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, UT 84132-3401, USA
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Tfap2a promotes specification and maturation of neurons in the inner ear through modulation of Bmp, Fgf and notch signaling. PLoS Genet 2015; 11:e1005037. [PMID: 25781991 PMCID: PMC4364372 DOI: 10.1371/journal.pgen.1005037] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 01/28/2015] [Indexed: 11/23/2022] Open
Abstract
Neurons of the statoacoustic ganglion (SAG) transmit auditory and vestibular information from the inner ear to the hindbrain. SAG neuroblasts originate in the floor of the otic vesicle. New neuroblasts soon delaminate and migrate towards the hindbrain while continuing to proliferate, a phase known as transit amplification. SAG cells eventually come to rest between the ear and hindbrain before terminally differentiating. Regulation of these events is only partially understood. Fgf initiates neuroblast specification within the ear. Subsequently, Fgf secreted by mature SAG neurons exceeds a maximum threshold, serving to terminate specification and delay maturation of transit-amplifying cells. Notch signaling also limits SAG development, but how it is coordinated with Fgf is unknown. Here we show that transcription factor Tfap2a coordinates multiple signaling pathways to promote neurogenesis in the zebrafish inner ear. In both zebrafish and chick, Tfap2a is expressed in a ventrolateral domain of the otic vesicle that includes neurogenic precursors. Functional studies were conducted in zebrafish. Loss of Tfap2a elevated Fgf and Notch signaling, thereby inhibiting SAG specification and slowing maturation of transit-amplifying cells. Conversely, overexpression of Tfap2a inhibited Fgf and Notch signaling, leading to excess and accelerated SAG production. However, most SAG neurons produced by Tfap2a overexpression died soon after maturation. Directly blocking either Fgf or Notch caused less dramatic acceleration of SAG development without neuronal death, whereas blocking both pathways mimicked all observed effects of Tfap2a overexpression, including apoptosis of mature neurons. Analysis of genetic mosaics showed that Tfap2a acts non-autonomously to inhibit Fgf. This led to the discovery that Tfap2a activates expression of Bmp7a, which in turn inhibits both Fgf and Notch signaling. Blocking Bmp signaling reversed the effects of overexpressing Tfap2a. Together, these data support a model in which Tfap2a, acting through Bmp7a, modulates Fgf and Notch signaling to control the duration, amount and speed of SAG neural development. Neurons of the statoacoustic ganglion (SAG) transmit impulses from the inner ear necessary for hearing and balance. SAG cells exhibit a complex pattern of development, regulation of which remains poorly understood. Here we show that transcription factor Tfap2a coordinates multiple cell signaling pathways needed to regulate the quantity and pace of SAG neuron production. SAG progenitors originate within the developing inner ear and then migrate out of the ear towards the hindbrain before forming mature neurons. We showed previously that Fgf initiates formation of SAG progenitors in the inner ear, but rising levels of Fgf signaling eventually terminate this process. Elevated Fgf also stimulates proliferation of SAG progenitors outside the ear and delays their maturation. Notch signaling is also known to limit SAG development. Tfap2a governs the strength of Fgf and Notch signaling by activating expression of Bmp7a, which inhibits Fgf and Notch. Together these signals stabilize the pool of SAG progenitors outside the ear by equalizing rates of maturation and proliferation. This balance is critical for sustained accumulation of SAG neurons during larval growth as well as regeneration following neural damage. These findings could inform development of stem cell therapies to correct auditory neuropathies in humans.
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Sai X, Ladher RK. Early steps in inner ear development: induction and morphogenesis of the otic placode. Front Pharmacol 2015; 6:19. [PMID: 25713536 PMCID: PMC4322616 DOI: 10.3389/fphar.2015.00019] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Accepted: 01/21/2015] [Indexed: 01/09/2023] Open
Abstract
Various cellular replacement therapies using in vitro generated cells to replace damaged tissue have been proposed as strategies to alleviate hearing loss. All such therapies must involve a complete understanding of the earliest steps in inner ear development; its induction as a thickened plate of cells in the non-neural, surface ectoderm of the embryo, to its internalization as an otocyst embedded in the head mesenchyme of the embryo. Such knowledge informs researchers addressing the feasibility of the proposed strategy and present alternatives if needed. In this review we describe the mechanisms of inner ear induction, concentrating on the factors that steer the fate of ectoderm into precursors of the inner ear. Induction then leads to inner ear morphogenesis and we describe the cellular changes that occur as the inner ear is converted from a superficial placode to an internalized otocyst, and how they are coordinated with a particular emphasis on how the signaling environment surrounding the inner ear influences these processes.
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Affiliation(s)
- Xiaorei Sai
- Laboratory for Sensory Development, RIKEN Center for Developmental Biology Kobe, Japan
| | - Raj K Ladher
- Laboratory for Sensory Development, RIKEN Center for Developmental Biology Kobe, Japan
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Freeman SD, Keino-Masu K, Masu M, Ladher RK. Expression of the heparan sulfate 6-O-endosulfatases, Sulf1 and Sulf2, in the avian and mammalian inner ear suggests a role for sulfation during inner ear development. Dev Dyn 2014; 244:168-80. [PMID: 25370455 DOI: 10.1002/dvdy.24223] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Revised: 10/21/2014] [Accepted: 10/21/2014] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Inner ear morphogenesis is tightly regulated by the temporally and spatially coordinated action of signaling ligands and their receptors. Ligand-receptor interactions are influenced by heparan sulfate proteoglycans (HSPGs), cell surface molecules that consist of glycosaminoglycan chains bound to a protein core. Diversity in the sulfation pattern within glycosaminoglycan chains creates binding sites for numerous cell signaling factors, whose activities and distribution are modified by their association with HSPGs. RESULTS Here we describe the expression patterns of two extracellular 6-O-endosulfatases, Sulf1 and Sulf2, whose activity modifies the 6-O-sulfation pattern of HSPGs. We use in situ hybridization to determine the temporal and spatial distribution of transcripts during the development of the chick and mouse inner ear. We also use immunocytochemistry to determine the cellular localization of Sulf1 and Sulf2 within the sensory epithelia. Furthermore, we analyze the organ of Corti in Sulf1/Sulf2 double knockout mice and describe an increase in the number of mechanosensory hair cells. CONCLUSIONS Our results suggest that the tuning of intracellular signaling, mediated by Sulf activity, plays an important role in the development of the inner ear.
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Affiliation(s)
- Stephen D Freeman
- Laboratory for Sensory Development, RIKEN Center for Developmental Biology, Chuo-ku, Kobe-shi, Japan
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Abstract
The inner ear is a structurally complex vertebrate organ built to encode sound, motion, and orientation in space. Given its complexity, it is not surprising that inner ear dysfunction is a relatively common consequence of human genetic mutation. Studies in model organisms suggest that many genes currently known to be associated with human hearing impairment are active during embryogenesis. Hence, the study of inner ear development provides a rich context for understanding the functions of genes implicated in hearing loss. This chapter focuses on molecular mechanisms of inner ear development derived from studies of model organisms.
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Affiliation(s)
- Doris K Wu
- National Institute on Deafness and Other Communication Disorders, Rockville, Maryland 20850, USA.
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Lin H, Wang L, Jiang M, Huang J, Qi L. P-glycoprotein(ABCB1)inhibited network of mitochondrion transport along microtubule and BMP signal-induced cell shape in chimpanzee left cerebrum by systems-theoretical analysis. Cell Biochem Funct 2012; 30:582-7. [DOI: 10.1002/cbf.2837] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2011] [Revised: 03/01/2012] [Accepted: 04/02/2012] [Indexed: 12/20/2022]
Affiliation(s)
- Hong Lin
- Biomedical Center, School of Electronic Engineering; Beijing University of Posts and Telecommunications; Beijing; China
| | - Lin Wang
- Biomedical Center, School of Electronic Engineering; Beijing University of Posts and Telecommunications; Beijing; China
| | - Minghu Jiang
- Lab of Computational Linguistics, School of Humanities and Social Sciences; Tsinghua University; Beijing; China
| | - Juxiang Huang
- Biomedical Center, School of Electronic Engineering; Beijing University of Posts and Telecommunications; Beijing; China
| | - Lianxiu Qi
- Biomedical Center, School of Electronic Engineering; Beijing University of Posts and Telecommunications; Beijing; China
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15
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Redundant functions of Rac GTPases in inner ear morphogenesis. Dev Biol 2011; 362:172-86. [PMID: 22182523 DOI: 10.1016/j.ydbio.2011.12.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Revised: 11/10/2011] [Accepted: 12/02/2011] [Indexed: 11/21/2022]
Abstract
Development of the mammalian inner ear requires coordination of cell proliferation, cell fate determination and morphogenetic movements. While significant progress has been made in identifying developmental signals required for inner ear formation, less is known about how distinct signals are coordinated by their downstream mediators. Members of the Rac family of small GTPases are known regulators of cytoskeletal remodeling and numerous other cellular processes. However, the function of Rac GTPases in otic development is largely unexplored. Here, we show that Rac1 and Rac3 redundantly regulate many aspects of inner ear morphogenesis. While no morphological defects were observed in Rac3(-/-) mice, Rac1(CKO); Rac3(-/-) double mutants displayed enhanced vestibular and cochlear malformations compared to Rac1(CKO) single mutants. Moreover, in Rac1(CKO); Rac3(-/-) mutants, we observed compromised E-cadherin-mediated cell adhesion, reduced cell proliferation and increased cell death in the early developing otocyst, leading to a decreased size and malformation of the membranous labyrinth. Finally, cochlear extension was severely disrupted in Rac1(CKO); Rac3(-/-) mutants, accompanied by a loss of epithelial cohesion and formation of ectopic sensory patches underneath the cochlear duct. The compartmentalized expression of otic patterning genes within the Rac1(CKO); Rac3(-/-) mutant otocyst was largely normal, however, indicating that Rac proteins regulate inner ear morphogenesis without affecting cell fate specification. Taken together, our results reveal an essential role for Rac GTPases in coordinating cell adhesion, cell proliferation, cell death and cell movements during otic development.
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Noda T, Oki S, Kitajima K, Harada T, Komune S, Meno C. Restriction of Wnt signaling in the dorsal otocyst determines semicircular canal formation in the mouse embryo. Dev Biol 2011; 362:83-93. [PMID: 22166339 DOI: 10.1016/j.ydbio.2011.11.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Revised: 11/27/2011] [Accepted: 11/28/2011] [Indexed: 01/07/2023]
Abstract
The mouse inner ear develops from a simple epithelial pouch, the otocyst, with the dorsal and ventral portions giving rise to the vestibule and cochlea, respectively. The otocyst undergoes a morphological change to generate flattened saclike structures, known as outpocketings, in the dorsal and lateral regions. The semicircular canals of the vestibule form from the periphery of the outpocketings, with the central region (the fusion plate) undergoing de-epithelialization and disappearing. However, little is known of the mechanism that orchestrates formation of the semicircular canals. We now show that the area of canonical Wnt signaling changes dynamically in the dorsal otocyst during its morphogenesis. The genes for several Wnt ligands were found to be expressed in the dorsal otocyst according to specific patterns, whereas those for secreted inhibitors of Wnt ligands were expressed exclusively in the ventral otocyst. With the use of whole-embryo culture in combination with potent modulators of canonical Wnt signaling, we found that forced persistence of such signaling resulted in impaired formation both of the lateral outpocketing and of the fusion plates of the dorsal outpocketing. Canonical Wnt signaling was found to suppress Netrin1 expression and to preserve the integrity of the outpocketing epithelium. In addition, inhibition of canonical Wnt signaling reduced the size of the otocyst, likely through suppression of cell proliferation and promotion of apoptosis. Our stage-specific functional analysis suggests that strict regulation of canonical Wnt signaling in the dorsal otocyst orchestrates the process of semicircular canal formation.
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Affiliation(s)
- Teppei Noda
- Department of Developmental Biology, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
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17
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Developmental profiling of spiral ganglion neurons reveals insights into auditory circuit assembly. J Neurosci 2011; 31:10903-18. [PMID: 21795542 DOI: 10.1523/jneurosci.2358-11.2011] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The sense of hearing depends on the faithful transmission of sound information from the ear to the brain by spiral ganglion (SG) neurons. However, how SG neurons develop the connections and properties that underlie auditory processing is largely unknown. We catalogued gene expression in mouse SG neurons from embryonic day 12, when SG neurons first extend projections, up until postnatal day 15, after the onset of hearing. For comparison, we also analyzed the closely related vestibular ganglion (VG). Gene ontology analysis confirmed enriched expression of genes associated with gene regulation and neurite outgrowth at early stages, with the SG and VG often expressing different members of the same gene family. At later stages, the neurons transcribe more genes related to mature function, and exhibit a dramatic increase in immune gene expression. Comparisons of the two populations revealed enhanced expression of TGFβ pathway components in SG neurons and established new markers that consistently distinguish auditory and vestibular neurons. Unexpectedly, we found that Gata3, a transcription factor commonly associated with auditory development, is also expressed in VG neurons at early stages. We therefore defined new cohorts of transcription factors and axon guidance molecules that are uniquely expressed in SG neurons and may drive auditory-specific aspects of their differentiation and wiring. We show that one of these molecules, the receptor guanylyl cyclase Npr2, is required for bifurcation of the SG central axon. Hence, our dataset provides a useful resource for uncovering the molecular basis of specific auditory circuit assembly events.
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