1
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Anselmi C, Fuller GK, Stolfi A, Groves AK, Manni L. Sensory cells in tunicates: insights into mechanoreceptor evolution. Front Cell Dev Biol 2024; 12:1359207. [PMID: 38550380 PMCID: PMC10973136 DOI: 10.3389/fcell.2024.1359207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Accepted: 03/04/2024] [Indexed: 04/04/2024] Open
Abstract
Tunicates, the sister group of vertebrates, offer a unique perspective for evolutionary developmental studies (Evo-Devo) due to their simple anatomical organization. Moreover, the separation of tunicates from vertebrates predated the vertebrate-specific genome duplications. As adults, they include both sessile and pelagic species, with very limited mobility requirements related mainly to water filtration. In sessile species, larvae exhibit simple swimming behaviors that are required for the selection of a suitable substrate on which to metamorphose. Despite their apparent simplicity, tunicates display a variety of mechanoreceptor structures involving both primary and secondary sensory cells (i.e., coronal sensory cells). This review encapsulates two decades of research on tunicate mechanoreception focusing on the coronal organ's sensory cells as prime candidates for understanding the evolution of vertebrate hair cells of the inner ear and the lateral line organ. The review spans anatomical, cellular and molecular levels emphasizing both similarity and differences between tunicate and vertebrate mechanoreception strategies. The evolutionary significance of mechanoreception is discussed within the broader context of Evo-Devo studies, shedding light on the intricate pathways that have shaped the sensory system in chordates.
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Affiliation(s)
- Chiara Anselmi
- Hopkins Marine Station, Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Pacific Grove, CA, United States
- Wu Tsai Neurosciences Institute, Stanford University, Stanford, CA, United States
| | - Gwynna K. Fuller
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
| | - Alberto Stolfi
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States
| | - Andrew K. Groves
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, United States
| | - Lucia Manni
- Dipartimento di Biologia, Università degli Studi di Padova, Padova, Italy
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2
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Schlosser G. From "self-differentiation" to organoids-the quest for the units of development. Dev Genes Evol 2023:10.1007/s00427-023-00711-z. [PMID: 37815616 DOI: 10.1007/s00427-023-00711-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 09/29/2023] [Indexed: 10/11/2023]
Abstract
As proposed by Wilhelm Roux in 1885, the key goal of experimental embryology ("Entwicklungsmechanik") was to elucidate whether organisms or their parts develop autonomously ("self-differentiation") or require interactions with other parts or the environment. However, experimental embryologists soon realized that concepts like "self-differentiation" only make sense when applied to particular parts or units of the developing embryo as defined both in time and space. Whereas the formation of tissues or organs may initially depend on interactions with surrounding tissues, they later become independent of such interactions or "determined." Moreover, the determination of a particular tissue or organ primordium has to be distinguished from the spatially coordinated determination of its parts-what we now refer to as "patterning." While some primordia depend on extrinsic influences (e.g., signals from adjacent tissues) for proper patterning, others rely on intrinsic mechanisms. Such intrinsically patterned units may behave as "morphogenetic fields" that can compensate for lost parts and regulate their size and proper patterning. While these insights were won by experimental embryologists more than 100 years ago, they retain their relevance today. To enable the generation of more life-like organoids in vitro for studying developmental processes and diseases in a dish, questions about the spatiotemporal units of development (when and how tissues and organs are determined and patterned) need to be increasingly considered. This review briefly sketches this conceptual history and its continued relevance by focusing on the determination and patterning of the inner ear with a specific emphasis on some studies published in this journal.
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Affiliation(s)
- Gerhard Schlosser
- School of Biological and Chemical Sciences, University of Galway, Biomedical Sciences Building, Second Floor North, Newcastle Road, Galway, H91 W2TY, Ireland.
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3
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Origin of Neuroblasts in the Avian Otic Placode and Their Distributions in the Acoustic and Vestibular Ganglia. BIOLOGY 2023; 12:biology12030453. [PMID: 36979145 PMCID: PMC10045822 DOI: 10.3390/biology12030453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 03/09/2023] [Accepted: 03/13/2023] [Indexed: 03/18/2023]
Abstract
The inner ear is a complex three-dimensional sensorial structure with auditory and vestibular functions. This intricate sensory organ originates from the otic placode, which generates the sensory elements of the membranous labyrinth, as well as all the ganglionic neuronal precursors. How auditory and vestibular neurons establish their fate identities remains to be determined. Their topological origin in the incipient otic placode could provide positional information before they migrate, to later segregate in specific portions of the acoustic and vestibular ganglia. To address this question, transplants of small portions of the avian otic placode were performed according to our previous fate map study, using the quail/chick chimeric graft model. All grafts taking small areas of the neurogenic placodal domain contributed neuroblasts to both acoustic and vestibular ganglia. A differential distribution of otic neurons in the anterior and posterior lobes of the vestibular ganglion, as well as in the proximal, intermediate, and distal portions of the acoustic ganglion, was found. Our results clearly show that, in birds, there does not seem to be a strict segregation of acoustic and vestibular neurons in the incipient otic placode.
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4
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Song H, Morrow BE. Tbx2 and Tbx3 regulate cell fate progression of the otic vesicle for inner ear development. Dev Biol 2023; 494:71-84. [PMID: 36521641 PMCID: PMC9870991 DOI: 10.1016/j.ydbio.2022.12.003] [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: 10/05/2022] [Revised: 12/05/2022] [Accepted: 12/10/2022] [Indexed: 12/14/2022]
Abstract
The morphogenesis of the otic vesicle (OV) to form inner ear organs serves as an excellent model system to understand cell fate acquisition on a single cell level. Tbx2 and Tbx3 (Tbx2/3) encode closely related T-box transcription factors that are expressed widely in the mammalian OV. Inactivation of both genes in the OV (Tbx2/3cKO) results in failed morphogenesis into inner ear organs. To understand the basis of these defects, single cell RNA-sequencing (scRNA-seq) was performed on the OV lineage, in controls versus Tbx2/3cKO embryos. We identified a multipotent population termed otic progenitors in controls that are marked by expression of the known otic placode markers Eya1, Sox2, and Sox3 as well as new markers Fgf18, Cxcl12, and Pou3f3. The otic progenitor population was increased three-fold in Tbx2/3cKO embryos, concomitant with dysregulation of genes in these cells as well as reduced progression to more differentiated states of prosensory and nonsensory cells. An ectopic neural population of cells was detected in the posterior OV of Tbx2/3cKO embryos but had reduced maturation to delaminated neural cells. As all three cell fates were affected in Tbx2/3cKO embryos, we suggest that Tbx2/3 promotes progression of multipotent otic progenitors to more differentiated cell types in the OV.
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Affiliation(s)
- Hansoo Song
- Department of Genetics, Albert Einstein College of Medicine, 1301 Morris Park Ave., Bronx, NY, USA
| | - Bernice E Morrow
- Department of Genetics, Albert Einstein College of Medicine, 1301 Morris Park Ave., Bronx, NY, USA.
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5
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Osaki D, Ouji Y, Sakagami M, Kitamura T, Misu M, Kitahara T, Yoshikawa M. Culture of organoids with vestibular cell-derived factors promotes differentiation of embryonic stem cells into inner ear vestibular hair cells. J Biosci Bioeng 2023; 135:143-150. [PMID: 36503871 DOI: 10.1016/j.jbiosc.2022.11.005] [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: 08/16/2022] [Revised: 11/07/2022] [Accepted: 11/15/2022] [Indexed: 12/13/2022]
Abstract
Vestibular hair cells (V-HCs) residing in the inner ear have important roles related to balance. Although differentiation of pluripotent stem cells into HCs has been shown, an effective method has yet to be established. We previously reported that use of vestibular cell-derived conditioned medium (V-CM) was helpful to induce embryonic stem (ES) cells to differentiate into V-HC-like cells in two-dimensional (2D) cultures of ES-derived embryoid bodies (EBs). In the present report, V-CM was used with three-dimensional (3D) cultures of EBs, which resulted in augmented expression of V-HC-related markers (Math1, Myosin6, Brn3c, Dnah5), but not of the cochlear HC-related marker Lmod3. Gene expression analyses of both 2D and 3D EBs cultured for two weeks revealed a greater level of augmented induction of HC-related markers in the 3D-cultured EBs. These results indicate that a 3D culture in combination with use of V-CM is an effective method for producing V-HCs.
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Affiliation(s)
- Daisuke Osaki
- Department of Pathogen, Infection and Immunity, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8521, Japan; Department of Otolaryngology - Head and Neck Surgery, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8521, Japan.
| | - Yukiteru Ouji
- Department of Pathogen, Infection and Immunity, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8521, Japan.
| | - Masaharu Sakagami
- Department of Pathogen, Infection and Immunity, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8521, Japan; Department of Otolaryngology - Head and Neck Surgery, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8521, Japan.
| | - Tomotaka Kitamura
- Department of Pathogen, Infection and Immunity, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8521, Japan.
| | - Masayasu Misu
- Department of Pathogen, Infection and Immunity, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8521, Japan.
| | - Tadashi Kitahara
- Department of Otolaryngology - Head and Neck Surgery, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8521, Japan.
| | - Masahide Yoshikawa
- Department of Pathogen, Infection and Immunity, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8521, Japan.
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Cardeña-Núñez S, Callejas-Marín A, Villa-Carballar S, Rodríguez-Gallardo L, Sánchez-Guardado LÓ, Hidalgo-Sánchez M. CRABP-I Expression Patterns in the Developing Chick Inner Ear. BIOLOGY 2023; 12:biology12010104. [PMID: 36671796 PMCID: PMC9855850 DOI: 10.3390/biology12010104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 12/30/2022] [Accepted: 01/03/2023] [Indexed: 01/12/2023]
Abstract
The vertebrate inner ear is a complex three-dimensional sensorial structure with auditory and vestibular functions, regarded as an excellent system for analyzing events that occur during development, such as patterning, morphogenesis, and cell specification. Retinoic acid (RA) is involved in all these development processes. Cellular retinoic acid-binding proteins (CRABPs) bind RA with high affinity, buffering cellular free RA concentrations and consequently regulating the activation of precise specification programs mediated by particular regulatory genes. In the otic vesicle, strong CRABP-I expression was detected in the otic wall's dorsomedial aspect, where the endolymphatic apparatus develops, whereas this expression was lower in the ventrolateral aspect, where part of the auditory system forms. Thus, CRABP-I proteins may play a role in the specification of the dorsal-to-ventral and lateral-to-medial axe of the otic anlagen. Regarding the developing sensory patches, a process partly involving the subdivision of a ventromedial pro-sensory domain, the CRABP-I gene displayed different levels of expression in the presumptive territory of each sensory patch, which was maintained throughout development. CRABP-I was also relevant in the acoustic-vestibular ganglion and in the periotic mesenchyme. Therefore, CRABP-I could protect RA-sensitive cells in accordance with its dissimilar concentration in specific areas of the developing chick inner ear.
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7
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Laureano AS, Flaherty K, Hinman AM, Jadali A, Nakamura T, Higashijima SI, Sabaawy HE, Kwan KY. shox2 is required for vestibular statoacoustic neuron development. Biol Open 2023; 11:286143. [PMID: 36594417 PMCID: PMC9838637 DOI: 10.1242/bio.059599] [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: 08/24/2022] [Accepted: 11/22/2022] [Indexed: 01/04/2023] Open
Abstract
Homeobox genes act at the top of genetic hierarchies to regulate cell specification and differentiation during embryonic development. We identified the short stature homeobox domain 2 (shox2) transcription factor that is required for vestibular neuron development. shox2 transcripts are initially localized to the otic placode of the developing inner ear where neurosensory progenitors reside. To study shox2 function, we generated CRISPR-mediated mutant shox2 fish. Mutant embryos display behaviors associated with vestibular deficits and showed reduced number of anterior statoacoustic ganglion neurons that innervate the utricle, the vestibular organ in zebrafish. Moreover, a shox2-reporter fish showed labeling of developing statoacoustic ganglion neurons in the anterior macula of the otic vesicle. Single cell RNA-sequencing of cells from the developing otic vesicle of shox2 mutants revealed altered otic progenitor profiles, while single molecule in situ assays showed deregulated levels of transcripts in developing neurons. This study implicates a role for shox2 in development of vestibular but not auditory statoacoustic ganglion neurons.
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Affiliation(s)
- Alejandra S. Laureano
- Department of Cell Biology & Neuroscience, Rutgers University, Piscataway, NJ 08854, USA,Stem Cell Research Center and Keck Center for Collaborative Neuroscience, Rutgers University, NJ 08854, USA
| | - Kathleen Flaherty
- Department of Comparative Medicine Resources, Rutgers University, Piscataway, NJ 08854, USA
| | - Anna-Maria Hinman
- Department of Cell Biology & Neuroscience, Rutgers University, Piscataway, NJ 08854, USA,Stem Cell Research Center and Keck Center for Collaborative Neuroscience, Rutgers University, NJ 08854, USA
| | - Azadeh Jadali
- Department of Cell Biology & Neuroscience, Rutgers University, Piscataway, NJ 08854, USA,Stem Cell Research Center and Keck Center for Collaborative Neuroscience, Rutgers University, NJ 08854, USA
| | - Tetsuya Nakamura
- Department of Genetics, Rutgers University, Piscataway, NJ 08854, USA
| | - Shin-ichi Higashijima
- Institutes of Natural Sciences, Exploratory Research Center on Life and Living Systems, Okazaki, Aichi 444-8787, Japan
| | - Hatim E. Sabaawy
- Department of Medicine, Division of Medical Oncology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA,Department of Medicine RBHS-Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ 08854, USA
| | - Kelvin Y. Kwan
- Department of Cell Biology & Neuroscience, Rutgers University, Piscataway, NJ 08854, USA,Stem Cell Research Center and Keck Center for Collaborative Neuroscience, Rutgers University, NJ 08854, USA,Author for correspondence ()
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8
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Hou S, Zhang J, Wu Y, Junmin C, Yuyu H, He B, Yang Y, Hong Y, Chen J, Yang J, Li S. FGF22 deletion causes hidden hearing loss by affecting the function of inner hair cell ribbon synapses. Front Mol Neurosci 2022; 15:922665. [PMID: 35966010 PMCID: PMC9366910 DOI: 10.3389/fnmol.2022.922665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 07/04/2022] [Indexed: 12/04/2022] Open
Abstract
Ribbon synapses are important structures in transmitting auditory signals from the inner hair cells (IHCs) to their corresponding spiral ganglion neurons (SGNs). Over the last few decades, deafness has been primarily attributed to the deterioration of cochlear hair cells rather than ribbon synapses. Hearing dysfunction that cannot be detected by the hearing threshold is defined as hidden hearing loss (HHL). The relationship between ribbon synapses and FGF22 deletion remains unknown. In this study, we used a 6-week-old FGF22 knockout mice model (Fgf22–/–) and mainly focused on alteration in ribbon synapses by applying the auditory brainstem response (ABR) test, the immunofluorescence staining, the patch-clamp recording, and quantitative real-time PCR. In Fgf22–/– mice, we found the decreased amplitude of ABR wave I, the reduced vesicles of ribbon synapses, and the decreased efficiency of exocytosis, which was suggested by a decrease in the capacitance change. Quantitative real-time PCR revealed that Fgf22–/– led to dysfunction in ribbon synapses by downregulating SNAP-25 and Gipc3 and upregulating MEF2D expression, which was important for the maintenance of ribbon synapses’ function. Our research concluded that FGF22 deletion caused HHL by affecting the function of IHC ribbon synapses and may offer a novel therapeutic target to meet an ever-growing demand for deafness treatment.
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Affiliation(s)
- Shule Hou
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Jifang Zhang
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Yan Wu
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Chen Junmin
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Huang Yuyu
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Baihui He
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Yan Yang
- Liaoning Medical Device Test Institute, Shenyang, China
| | - Yuren Hong
- Laboratory of Electron Microscope Center, Shanghai Medical College, Fudan University, Shanghai, China
| | - Jiarui Chen
- Department of Otorhinolaryngology-Head and Neck Surgery, Shanghai Children’s Hospital, Shanghai Jiao Tong University, Shanghai, China
- *Correspondence: Jiarui Chen,
| | - Jun Yang
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
- Jun Yang,
| | - Shuna Li
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
- Shuna Li,
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9
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Elliott KL, Pavlinkova G, Chizhikov VV, Yamoah EN, Fritzsch B. Neurog1, Neurod1, and Atoh1 are essential for spiral ganglia, cochlear nuclei, and cochlear hair cell development. Fac Rev 2021; 10:47. [PMID: 34131657 PMCID: PMC8170689 DOI: 10.12703/r/10-47] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
We review the molecular basis of three related basic helix–loop–helix (bHLH) genes (Neurog1, Neurod1, and Atoh1) and upstream regulators Eya1/Six1, Sox2, Pax2, Gata3, Fgfr2b, Foxg1, and Lmx1a/b during the development of spiral ganglia, cochlear nuclei, and cochlear hair cells. Neuronal development requires early expression of Neurog1, followed by its downstream target Neurod1, which downregulates Atoh1 expression. In contrast, hair cells and cochlear nuclei critically depend on Atoh1 and require Neurod1 and Neurog1 expression for various aspects of development. Several experiments show a partial uncoupling of Atoh1/Neurod1 (spiral ganglia and cochlea) and Atoh1/Neurog1/Neurod1 (cochlear nuclei). In this review, we integrate the cellular and molecular mechanisms that regulate the development of auditory system and provide novel insights into the restoration of hearing loss, beyond the limited generation of lost sensory neurons and hair cells.
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Affiliation(s)
- Karen L Elliott
- Department of Biology, University of Iowa, Iowa City, IA, USA
| | - Gabriela Pavlinkova
- Institute of Biotechnology of the Czech Academy of Sciences, Vestec, Czechia
| | - Victor V Chizhikov
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Ebenezer N Yamoah
- Department of Physiology and Cell Biology, University of Nevada, Reno, NV, USA
| | - Bernd Fritzsch
- Department of Biology, University of Iowa, Iowa City, IA, USA
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10
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Kaiser M, Wojahn I, Rudat C, Lüdtke TH, Christoffels VM, Moon A, Kispert A, Trowe MO. Regulation of otocyst patterning by Tbx2 and Tbx3 is required for inner ear morphogenesis in the mouse. Development 2021; 148:dev.195651. [PMID: 33795231 DOI: 10.1242/dev.195651] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2020] [Accepted: 03/23/2021] [Indexed: 12/21/2022]
Abstract
All epithelial components of the inner ear, including sensory hair cells and innervating afferent neurons, arise by patterning and differentiation of epithelial progenitors residing in a simple sphere, the otocyst. Here, we identify the transcriptional repressors TBX2 and TBX3 as novel regulators of these processes in the mouse. Ablation of Tbx2 from the otocyst led to cochlear hypoplasia, whereas loss of Tbx3 was associated with vestibular malformations. The loss of function of both genes (Tbx2/3cDKO) prevented inner ear morphogenesis at midgestation, resulting in indiscernible cochlear and vestibular structures at birth. Morphogenetic impairment occurred concomitantly with increased apoptosis in ventral and lateral regions of Tbx2/3cDKO otocysts around E10.5. Expression analyses revealed partly disturbed regionalisation, and a posterior-ventral expansion of the neurogenic domain in Tbx2/3cDKO otocysts at this stage. We provide evidence that repression of FGF signalling by TBX2 is important to restrict neurogenesis to the anterior-ventral otocyst and implicate another T-box factor, TBX1, as a crucial mediator in this regulatory network.
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Affiliation(s)
- Marina Kaiser
- Institute for Molecular Biology, Medizinische Hochschule Hannover, 30625 Hannover, Germany
| | - Irina Wojahn
- Institute for Molecular Biology, Medizinische Hochschule Hannover, 30625 Hannover, Germany
| | - Carsten Rudat
- Institute for Molecular Biology, Medizinische Hochschule Hannover, 30625 Hannover, Germany
| | - Timo H Lüdtke
- Institute for Molecular Biology, Medizinische Hochschule Hannover, 30625 Hannover, Germany
| | - Vincent M Christoffels
- Department of Anatomy, Embryology and Physiology, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands
| | - Anne Moon
- Department of Molecular and Functional Genomics, Weis Center for Research, Geisinger Clinic, Danville, PA 17822, USA.,Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| | - Andreas Kispert
- Institute for Molecular Biology, Medizinische Hochschule Hannover, 30625 Hannover, Germany
| | - Mark-Oliver Trowe
- Institute for Molecular Biology, Medizinische Hochschule Hannover, 30625 Hannover, Germany
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11
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Liu H, Giffen KP, Grati M, Morrill SW, Li Y, Liu X, Briegel KJ, He DZ. Transcription co-factor LBH is necessary for the survival of cochlear hair cells. J Cell Sci 2021; 134:237781. [PMID: 33674448 DOI: 10.1242/jcs.254458] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 02/11/2021] [Indexed: 11/20/2022] Open
Abstract
Hearing loss affects ∼10% of adults worldwide. Most sensorineural hearing loss is caused by the progressive loss of mechanosensitive hair cells (HCs) in the cochlea. The molecular mechanisms underlying HC maintenance and loss remain poorly understood. LBH, a transcription co-factor implicated in development, is abundantly expressed in outer hair cells (OHCs). We used Lbh-null mice to identify its role in HCs. Surprisingly, Lbh deletion did not affect differentiation and the early development of HCs, as nascent HCs in Lbh knockout mice had normal looking stereocilia. The stereocilia bundle was mechanosensitive and OHCs exhibited the characteristic electromotility. However, Lbh-null mice displayed progressive hearing loss, with stereocilia bundle degeneration and OHC loss as early as postnatal day 12. RNA-seq analysis showed significant gene enrichment of biological processes related to transcriptional regulation, cell cycle, DNA damage/repair and autophagy in Lbh-null OHCs. In addition, Wnt and Notch pathway-related genes were found to be dysregulated in Lbh-deficient OHCs. Our study implicates, for the first time, loss of LBH function in progressive hearing loss, and demonstrates a critical requirement of LBH in promoting HC survival in adult mice.
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Affiliation(s)
- Huizhan Liu
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
| | - Kimberlee P Giffen
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
| | - M'Hamed Grati
- Department of Otorhinolaryngology-Head and Neck Surgery, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Seth W Morrill
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
| | - Yi Li
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA.,Department of Otorhinolaryngology-Head and Neck Surgery, Beijing Tongren Hospital, Capital Medical University, 100730 Beijing, China
| | - Xuezhong Liu
- Department of Otorhinolaryngology-Head and Neck Surgery, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Karoline J Briegel
- Department of Surgery, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - David Z He
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
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12
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van der Valk WH, Steinhart MR, Zhang J, Koehler KR. Building inner ears: recent advances and future challenges for in vitro organoid systems. Cell Death Differ 2020; 28:24-34. [PMID: 33318601 PMCID: PMC7853146 DOI: 10.1038/s41418-020-00678-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 11/04/2020] [Accepted: 11/05/2020] [Indexed: 02/07/2023] Open
Abstract
While inner ear disorders are common, our ability to intervene and recover their sensory function is limited. In vitro models of the inner ear, like the organoid system, could aid in identifying new regenerative drugs and gene therapies. Here, we provide a perspective on the status of in vitro inner ear models and guidance on how to improve their applicability in translational research. We highlight the generation of inner ear cell types from pluripotent stem cells as a particularly promising focus of research. Several exciting recent studies have shown how the developmental signaling cues of embryonic and fetal development can be mimicked to differentiate stem cells into “inner ear organoids” containing otic progenitor cells, hair cells, and neurons. However, current differentiation protocols and our knowledge of embryonic and fetal inner ear development in general, have a bias toward the sensory epithelia of the inner ear. We propose that a more holistic view is needed to better model the inner ear in vitro. Moving forward, attention should be made to the broader diversity of neuroglial and mesenchymal cell types of the inner ear, and how they interact in space or time during development. With improved control of epithelial, neuroglial, and mesenchymal cell fate specification, inner ear organoids would have the ability to truly recapitulate neurosensory function and dysfunction. We conclude by discussing how single-cell atlases of the developing inner ear and technical innovations will be critical tools to advance inner ear organoid platforms for future pre-clinical applications.
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Affiliation(s)
- Wouter H van der Valk
- Department of Otorhinolaryngology and Head & Neck Surgery, Leiden University Medical Center, Leiden, Netherlands.,Department of Otolaryngology, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Matthew R Steinhart
- Department of Otolaryngology, Boston Children's Hospital, Boston, MA, 02115, USA.,Department of Otolaryngology-Head and Neck Surgery, Indiana University School of Medicine, Indianapolis, IN, 46202, USA.,Medical Neuroscience Graduate Program, Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Jingyuan Zhang
- Department of Otolaryngology, Boston Children's Hospital, Boston, MA, 02115, USA.,Department of Plastic and Oral Surgery, Boston Children's Hospital, Boston, MA, 02115, USA.,F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, 02115, USA.,Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, 02115, USA
| | - Karl R Koehler
- Department of Otolaryngology, Boston Children's Hospital, Boston, MA, 02115, USA. .,Department of Otolaryngology-Head and Neck Surgery, Indiana University School of Medicine, Indianapolis, IN, 46202, USA. .,Department of Plastic and Oral Surgery, Boston Children's Hospital, Boston, MA, 02115, USA. .,F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, 02115, USA. .,Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, 02115, USA.
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13
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Combined Atoh1 and Neurod1 Deletion Reveals Autonomous Growth of Auditory Nerve Fibers. Mol Neurobiol 2020; 57:5307-5323. [PMID: 32880858 DOI: 10.1007/s12035-020-02092-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Accepted: 08/24/2020] [Indexed: 12/24/2022]
Abstract
Ear development requires the transcription factors ATOH1 for hair cell differentiation and NEUROD1 for sensory neuron development. In addition, NEUROD1 negatively regulates Atoh1 gene expression. As we previously showed that deletion of the Neurod1 gene in the cochlea results in axon guidance defects and excessive peripheral innervation of the sensory epithelium, we hypothesized that some of the innervation defects may be a result of abnormalities in NEUROD1 and ATOH1 interactions. To characterize the interdependency of ATOH1 and NEUROD1 in inner ear development, we generated a new Atoh1/Neurod1 double null conditional deletion mutant. Through careful comparison of the effects of single Atoh1 or Neurod1 gene deletion with combined double Atoh1 and Neurod1 deletion, we demonstrate that NEUROD1-ATOH1 interactions are not important for the Neurod1 null innervation phenotype. We report that neurons lacking Neurod1 can innervate the flat epithelium without any sensory hair cells or supporting cells left after Atoh1 deletion, indicating that neurons with Neurod1 deletion do not require the presence of hair cells for axon growth. Moreover, transcriptome analysis identified genes encoding axon guidance and neurite growth molecules that are dysregulated in the Neurod1 deletion mutant. Taken together, we demonstrate that much of the projections of NEUROD1-deprived inner ear sensory neurons are regulated cell-autonomously.
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14
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Notch-mediated lateral induction is necessary to maintain vestibular prosensory identity during inner ear development. Dev Biol 2020; 462:74-84. [PMID: 32147304 DOI: 10.1016/j.ydbio.2020.02.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 02/27/2020] [Indexed: 01/24/2023]
Abstract
The five vestibular organs of the inner ear derive from patches of prosensory cells that express the transcription factor SOX2 and the Notch ligand JAG1. Previous work suggests that JAG1-mediated Notch signaling is both necessary and sufficient for prosensory formation and that the separation of developing prosensory patches is regulated by LMX1a, which antagonizes Notch signaling. We used an inner ear-specific deletion of the Rbpjκ gene in which Notch signaling is progressively lost from the inner ear to show that Notch signaling, is continuously required for the maintenance of prosensory fate. Loss of Notch signaling in prosensory patches causes them to shrink and ultimately disappear. We show this loss of prosensory fate is not due to cell death, but rather to the conversion of prosensory tissue into non-sensory tissue that expresses LMX1a. Notch signaling is therefore likely to stabilize, rather than induce prosensory fate.
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15
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Brown R, Groves AK. Hear, Hear for Notch: Control of Cell Fates in the Inner Ear by Notch Signaling. Biomolecules 2020; 10:biom10030370. [PMID: 32121147 PMCID: PMC7175228 DOI: 10.3390/biom10030370] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 02/24/2020] [Accepted: 02/26/2020] [Indexed: 02/08/2023] Open
Abstract
The vertebrate inner ear is responsible for detecting sound, gravity, and head motion. These mechanical forces are detected by mechanosensitive hair cells, arranged in a series of sensory patches in the vestibular and cochlear regions of the ear. Hair cells form synapses with neurons of the VIIIth cranial ganglion, which convey sound and balance information to the brain. They are surrounded by supporting cells, which nourish and protect the hair cells, and which can serve as a source of stem cells to regenerate hair cells after damage in non-mammalian vertebrates. The Notch signaling pathway plays many roles in the development of the inner ear, from the earliest formation of future inner ear ectoderm on the side of the embryonic head, to regulating the production of supporting cells, hair cells, and the neurons that innervate them. Notch signaling is re-deployed in non-mammalian vertebrates during hair cell regeneration, and attempts have been made to manipulate the Notch pathway to promote hair cell regeneration in mammals. In this review, we summarize the different modes of Notch signaling in inner ear development and regeneration, and describe how they interact with other signaling pathways to orchestrate the fine-grained cellular patterns of the ear.
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Affiliation(s)
- Rogers Brown
- Program in Developmental Biology; Baylor College of Medicine, Houston, TX 77030, USA;
| | - Andrew K. Groves
- Program in Developmental Biology; Baylor College of Medicine, Houston, TX 77030, USA;
- Department of Neuroscience; Baylor College of Medicine, Houston, TX 77030, USA
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Correspondence: ; Tel.: +1-713-798-8743
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16
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Notch Signalling: The Multitask Manager of Inner Ear Development and Regeneration. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1218:129-157. [DOI: 10.1007/978-3-030-34436-8_8] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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17
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Cardeña-Núñez S, Sánchez-Guardado LÓ, Hidalgo-Sánchez M. Cyp1B1 expression patterns in the developing chick inner ear. Dev Dyn 2019; 249:410-424. [PMID: 31400045 DOI: 10.1002/dvdy.99] [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: 06/24/2019] [Revised: 07/26/2019] [Accepted: 07/26/2019] [Indexed: 11/07/2022] Open
Abstract
BACKGROUND Retinoic acid (RA) plays an important role in organogenesis as a paracrine signal through transcriptional regulation of an increasing number of known downstream target genes, regulating cell proliferation, and differentiation. During the development of the inner ear, RA directly governs the morphogenesis and specification processes mainly by means of RA-synthesizing retinaldehyde dehydrogenase (RALDH) enzymes. Interestingly, CYP1B1, a cytochrome P450 enzyme, is able to mediate the oxidative metabolisms also leading to RA generation, its expression patterns being associated with many known sites of RA activity. RESULTS This study describes for the first time the presence of CYP1B1 in the developing chick inner ear as a RALDH-independent RA-signaling mechanism. In our in situ hybridization analysis, Cyp1B1 expression was first observed in a domain located in the ventromedial wall of the otic anlagen, being included within the rostralmost aspect of an Fgf10-positive pan-sensory domain. As development proceeds, all identified Fgf10-positive areas were Cyp1B1 stained, with all sensory patches being Cyp1B1 positive at stage HH34, except the macula neglecta. CONCLUSIONS Cyp1B1 expression suggested a possible contribution of CYP1B1 action in the specification of the lateral-to-medial and dorsal-to-ventral axes of the developing chick inner ear.
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Affiliation(s)
- Sheila Cardeña-Núñez
- Department of Cell Biology, School of Science, University of Extremadura, Badajoz, Spain
| | - Luis Ó Sánchez-Guardado
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California
| | - Matías Hidalgo-Sánchez
- Department of Cell Biology, School of Science, University of Extremadura, Badajoz, Spain
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18
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Sánchez-Guardado LÓ, Puelles L, Hidalgo-Sánchez M. Origin of acoustic-vestibular ganglionic neuroblasts in chick embryos and their sensory connections. Brain Struct Funct 2019; 224:2757-2774. [PMID: 31396696 DOI: 10.1007/s00429-019-01934-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Accepted: 07/31/2019] [Indexed: 01/03/2023]
Abstract
The inner ear is a complex three-dimensional sensory structure with auditory and vestibular functions. It originates from the otic placode, which generates the sensory elements of the membranous labyrinth and all the ganglionic neuronal precursors. Neuroblast specification is the first cell differentiation event. In the chick, it takes place over a long embryonic period from the early otic cup stage to at least stage HH25. The differentiating ganglionic neurons attain a precise innervation pattern with sensory patches, a process presumably governed by a network of dendritic guidance cues which vary with the local micro-environment. To study the otic neurogenesis and topographically-ordered innervation pattern in birds, a quail-chick chimaeric graft technique was used in accordance with a previously determined fate-map of the otic placode. Each type of graft containing the presumptive domain of topologically-arranged placodal sensory areas was shown to generate neuroblasts. The differentiated grafted neuroblasts established dendritic contacts with a variety of sensory patches. These results strongly suggest that, rather than reverse-pathfinding, the relevant role in otic dendritic process guidance is played by long-range diffusing molecules.
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Affiliation(s)
| | - Luis Puelles
- Department of Human Anatomy and Psychobiology, School of Medicine, University of Murcia, E30100, Murcia, Spain.,Instituto Murciano de Investigaciones Biosanitarias (IMIB-Arrixaca), E30100, Murcia, Spain
| | - Matías Hidalgo-Sánchez
- Department of Cell Biology, School of Science, University of Extremadura, E06071, Badajoz, Spain.
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19
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Ma JH, Kim HP, Shin JO. CTCF deficiency causes expansion of the sensory domain in the mouse cochlea. Biochem Biophys Res Commun 2019; 512:896-901. [PMID: 30929920 DOI: 10.1016/j.bbrc.2019.03.127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Accepted: 03/19/2019] [Indexed: 01/08/2023]
Abstract
The cochlea in the mammalian inner ear is a sensitive and sharply organized sound-detecting structure. The proper specification of neurosensory-competent domain in the otic epithelium is required for the formation of mature neuronal and sensory domains. Genetic studies have provided many insights into inner ear development, but there have been few epigenetic studies of inner ear development. CTCF is an epigenetic factor that plays a pivotal role in the organization of global chromatin conformation. To determine the role of CTCF in the otic sensory formation, we made a conditional knockout of Ctcf in the developing otic epithelium by crossing Ctcffl/fl mice with Pax2-Cre mice. Ctcf deficiency resulted in extra rows of auditory hair cells in the shortened cochlea on mouse embryonic day 14.5 (E14.5) and E17.5. The massive and ectopic expression of sensory specifiers such as Jag1 and Sox2 indicated that the sensory domain was expanded in the Ctcf-deficient cochlea. Other regulators of the sensory domain such as Bmp4, Gata3, and Fgf10 were not affected. These results suggest that CTCF plays a role in the regulation of the sensory domain in mammalian cochlear development.
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Affiliation(s)
- Ji-Hyun Ma
- Department of Anatomy, Yonsei University College of Medicine, Seoul, 03722, Republic of Korea
| | - Hyoung-Pyo Kim
- Department of Environmental Medical Biology, Yonsei University College of Medicine, Seoul, 03722, Republic of Korea; BK21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, 03722, Republic of Korea
| | - Jeong-Oh Shin
- Department of Anatomy, Yonsei University College of Medicine, Seoul, 03722, Republic of Korea.
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20
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Montalbano G, Capillo G, Laurà R, Abbate F, Levanti M, Guerrera MC, Ciriaco E, Germanà A. Neuromast hair cells retain the capacity of regeneration during heavy metal exposure. Ann Anat 2018; 218:183-189. [PMID: 29719206 DOI: 10.1016/j.aanat.2018.03.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 01/30/2018] [Accepted: 03/07/2018] [Indexed: 12/14/2022]
Abstract
The neuromast is the morphological unit of the lateral line of fishes and is composed of a cluster of central sensory cells (hair cells) surrounded by support and mantle cells. Heavy metals exposure leads to disruption of hair cells within the neuromast. It is well known that the zebrafish has the ability to regenerate the hair cells after damage caused by toxicants. The process of regeneration depends on proliferation, differentiation and cellular migration of sensory and non-sensory progenitor cells. Therefore, our study was made in order to identify which cellular types are involved in the complex process of regeneration during heavy metals exposure. For this purpose, adult zebrafish were exposed to various heavy metals (Arsenic, cadmium and zinc) for 72h. After acute (24h) exposure, immunohistochemical localization of S100 (a specific marker for hair cells) in the neuromasts highlighted the hair cells loss. The immunoreaction for Sox2 (a specific marker for stem cells), at the same time, was observed in the support and mantle cells, after exposure to arsenic and cadmium, while only in the support cells after exposure to zinc. After chronic (72h) exposure the hair cells were regenerated, showing an immunoreaction for S100 protein. At the same exposure time to the three metals, a Sox2 immunoreaction was expressed in support and mantle cells. Our results showed for the first time the regenerative capacity of hair cells, not only after, but also during exposure to heavy metals, demonstrated by the presence of different stem cells that can diversify in hair cells.
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Affiliation(s)
- G Montalbano
- Department of Veterinary Sciences, University of Messina, Zebrafish Neuromorphology Lab, Italy
| | - G Capillo
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Italy
| | - R Laurà
- Department of Veterinary Sciences, University of Messina, Zebrafish Neuromorphology Lab, Italy
| | - F Abbate
- Department of Veterinary Sciences, University of Messina, Zebrafish Neuromorphology Lab, Italy
| | - M Levanti
- Department of Veterinary Sciences, University of Messina, Zebrafish Neuromorphology Lab, Italy
| | - M C Guerrera
- Department of Veterinary Sciences, University of Messina, Zebrafish Neuromorphology Lab, Italy.
| | - E Ciriaco
- Department of Veterinary Sciences, University of Messina, Zebrafish Neuromorphology Lab, Italy
| | - A Germanà
- Department of Veterinary Sciences, University of Messina, Zebrafish Neuromorphology Lab, Italy
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21
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Gou Y, Vemaraju S, Sweet EM, Kwon HJ, Riley BB. sox2 and sox3 Play unique roles in development of hair cells and neurons in the zebrafish inner ear. Dev Biol 2018; 435:73-83. [PMID: 29355523 DOI: 10.1016/j.ydbio.2018.01.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 01/15/2018] [Accepted: 01/15/2018] [Indexed: 11/24/2022]
Abstract
Formation of neural and sensory progenitors in the inner ear requires Sox2 in mammals, and in other species is thought to rely on both Sox2 and Sox3. How Sox2 and/or Sox3 promote different fates is poorly understood. Our mutant analysis in zebrafish showed that sox2 is uniquely required for sensory development while sox3 is uniquely required for neurogenesis. Moderate misexpression of sox2 during placodal stages led to development of otic vesicles with expanded sensory and reduced neurogenic domains. However, high-level misexpression of sox2 or sox3 expanded both sensory and neurogenic domains to fill the medial and lateral halves of the otic vesicle, respectively. Disruption of medial factor pax2a eliminated the ability of sox2/3 misexpression to expand sensory but not neurogenic domains. Additionally, mild misexpression of fgf8 during placodal development was sufficient to specifically expand the zone of prosensory competence. Later, cross-repression between atoh1a and neurog1 helps maintain the sensory-neural boundary, but unlike mouse this does not require Notch activity. Together, these data show that sox2 and sox3 exhibit intrinsic differences in promoting sensory vs. neural competence, but at high levels these factors can mimic each other to enhance both states. Regional cofactors like pax2a and fgf8 also modify sox2/3 functions.
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Affiliation(s)
- Yunzi Gou
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA
| | - Shruti Vemaraju
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA
| | - Elly M Sweet
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA
| | - Hye-Joo Kwon
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA
| | - Bruce B Riley
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA.
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22
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Rigon F, Gasparini F, Shimeld SM, Candiani S, Manni L. Developmental signature, synaptic connectivity and neurotransmission are conserved between vertebrate hair cells and tunicate coronal cells. J Comp Neurol 2018; 526:957-971. [PMID: 29277977 DOI: 10.1002/cne.24382] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 12/15/2017] [Accepted: 12/18/2017] [Indexed: 11/08/2022]
Abstract
In tunicates, the coronal organ represents a sentinel checking particle entrance into the pharynx. The organ differentiates from an anterior embryonic area considered a proto-placode. For their embryonic origin, morphological features and function, coronal sensory cells have been hypothesized to be homologues to vertebrate hair cells. However, vertebrate hair cells derive from a posterior placode. This contradicts one of the principle historical criteria for homology, similarity of position, which could be taken as evidence against coronal cells/hair cells homology. In the tunicates Ciona intestinalis and C. robusta, we found that the coronal organ expresses genes (Atoh, Notch, Delta-like, Hairy-b, and Musashi) characterizing vertebrate neural and hair cell development. Moreover, coronal cells exhibit a complex synaptic connectivity pattern, and express neurotransmitters (Glu, ACh, GABA, 5-HT, and catecholamines), or enzymes for their synthetic machinery, involved in hair cell activity. Lastly, coronal cells express the Trpa gene, which encodes an ion channel expressed in hair cells. These data lead us to hypothesize a model in which competence to make secondary mechanoreceptors was initially broadly distributed through placode territories, but has become confined to different placodes during the evolution of the vertebrate and tunicate lineages.
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Affiliation(s)
- Francesca Rigon
- Dipartimento di Biologia, Università di Padova, Padova, Italy
| | - Fabio Gasparini
- Dipartimento di Biologia, Università di Padova, Padova, Italy
| | | | - Simona Candiani
- Dipartimento di Scienze della Terra dell'Ambiente e della Vita, Università di Genova, Genova, Italy
| | - Lucia Manni
- Dipartimento di Biologia, Università di Padova, Padova, Italy
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23
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Macchiarulo S, Morrow BE. Tbx1 and Jag1 act in concert to modulate the fate of neurosensory cells of the mouse otic vesicle. Biol Open 2017; 6:1472-1482. [PMID: 28838968 PMCID: PMC5665468 DOI: 10.1242/bio.027359] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The domain within the otic vesicle (OV) known as the neurosensory domain (NSD), contains cells that will give rise to the hair and support cells of the otic sensory organs, as well as the neurons that form the cochleovestibular ganglion (CVG). The molecular dynamics that occur at the NSD boundary relative to adjacent OV cells is not well defined. The Tbx1 transcription factor gene expression pattern is complementary to the NSD, and inactivation results in expansion of the NSD and expression of the Notch ligand, Jag1 mapping, in part of the NSD. To shed light on the role of Jag1 in NSD development, as well as to test whether Tbx1 and Jag1 might genetically interact to regulate this process, we inactivated Jag1 within the Tbx1 expression domain using a knock-in Tbx1Cre allele. We observed an enlarged neurogenic domain marked by a synergistic increase in expression of NeuroD and other proneural transcription factor genes in double Tbx1 and Jag1 conditional loss-of-function embryos. We noted that neuroblasts preferentially expanded across the medial-lateral axis and that an increase in cell proliferation could not account for this expansion, suggesting that there was a change in cell fate. We also found that inactivation of Jag1 with Tbx1Cre resulted in failed development of the cristae and semicircular canals, as well as notably fewer hair cells in the ventral epithelium of the inner ear rudiment when inactivated on a Tbx1 null background, compared to Tbx1Cre/− mutant embryos. We propose that loss of expression of Tbx1 and Jag1 within the Tbx1 expression domain tips the balance of cell fates in the NSD, resulting in an overproduction of neuroblasts at the expense of non-neural cells within the OV. Summary: Normal dosages of Tbx1 and Jag1 are required to maintain a proper balance of cell types within the neurosensory domain of the otic vesicle to form the inner ear.
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Affiliation(s)
- Stephania Macchiarulo
- Department of Genetics, Albert Einstein College of Medicine, 1301 Morris Park Avenue, Bronx, NY 10461, USA
| | - Bernice E Morrow
- Department of Genetics, Albert Einstein College of Medicine, 1301 Morris Park Avenue, Bronx, NY 10461, USA .,Departments of Obstetrics and Gynecology and Pediatrics, Albert Einstein College of Medicine, 1301 Morris Park Avenue, Bronx, NY 10461, USA
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24
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Chagnaud BP, Engelmann J, Fritzsch B, Glover JC, Straka H. Sensing External and Self-Motion with Hair Cells: A Comparison of the Lateral Line and Vestibular Systems from a Developmental and Evolutionary Perspective. BRAIN, BEHAVIOR AND EVOLUTION 2017; 90:98-116. [PMID: 28988233 DOI: 10.1159/000456646] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Detection of motion is a feature essential to any living animal. In vertebrates, mechanosensory hair cells organized into the lateral line and vestibular systems are used to detect external water or head/body motion, respectively. While the neuronal components to detect these physical attributes are similar between the two sensory systems, the organizational pattern of the receptors in the periphery and the distribution of hindbrain afferent and efferent projections are adapted to the specific functions of the respective system. Here we provide a concise review comparing the functional organization of the vestibular and lateral line systems from the development of the organs to the wiring from the periphery and the first processing stages. The goal of this review is to highlight the similarities and differences to demonstrate how evolution caused a common neuronal substrate to adapt to different functions, one for the detection of external water stimuli and the generation of sensory maps and the other for the detection of self-motion and the generation of motor commands for immediate behavioral reactions.
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Affiliation(s)
- Boris P Chagnaud
- Ludwig-Maximilians-Universität München, Department Biology II, Division of Neurobiology, Martinsried-Planegg, Germany
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25
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Schwarzer S, Spieß S, Brand M, Hans S. Dlx3b/4b is required for early-born but not later-forming sensory hair cells during zebrafish inner ear development. Biol Open 2017; 6:1270-1278. [PMID: 28751305 PMCID: PMC5612237 DOI: 10.1242/bio.026211] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Morpholino-mediated knockdown has shown that the homeodomain transcription factors Dlx3b and Dlx4b are essential for proper induction of the otic-epibranchial progenitor domain (OEPD), as well as subsequent formation of sensory hair cells in the developing zebrafish inner ear. However, increasing use of reverse genetic approaches has revealed poor correlation between morpholino-induced and mutant phenotypes. Using CRISPR/Cas9-mediated mutagenesis, we generated a defined deletion eliminating the entire open reading frames of dlx3b and dlx4b (dlx3b/4b) and investigated a potential phenotypic difference between mutants and morpholino-mediated knockdown. Consistent with previous findings obtained by morpholino-mediated knockdown of Dlx3b and Dlx4b, dlx3b/4b mutants display compromised otic induction, the development of smaller otic vesicles and an elimination of all indications of otic specification when combined with loss of foxi1, a second known OEPD competence factor in zebrafish. Furthermore, sensorigenesis is also affected in dlx3b/4b mutants. However, we find that only early-born sensory hair cells (tether cells), that seed and anchor the formation of otoliths, are affected. Later-forming sensory hair cells are present, indicating that two genetically distinct pathways control the development of early-born and later-forming sensory hair cells. Finally, impairment of early-born sensory hair cell formation in dlx3b/4b mutant embryos reverses the common temporal sequence of neuronal and sensory hair cell specification in zebrafish, resembling the order of cell specification in amniotes; Neurog1 expression before Atoh1 expression. We conclude that the Dlx3b/4b-dependent pathway has been either acquired newly in the fish lineage or lost in other vertebrate species during evolution, and that the events during early inner ear development are remarkably similar in fish and amniotes in the absence of this pathway. Summary: The transcription factors Dlx3b and Dlx4b control the formation of early-born sensory hair cells or tether cells in the developing zebrafish inner ear.
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Affiliation(s)
- Simone Schwarzer
- Technische Universität Dresden, Biotechnology Center and DFG-Center for Regenerative Therapies Dresden Cluster of Excellence, Tatzberg 47-49, 01307 Dresden, Germany
| | - Sandra Spieß
- Technische Universität Dresden, Biotechnology Center and DFG-Center for Regenerative Therapies Dresden Cluster of Excellence, Tatzberg 47-49, 01307 Dresden, Germany
| | - Michael Brand
- Technische Universität Dresden, Biotechnology Center and DFG-Center for Regenerative Therapies Dresden Cluster of Excellence, Tatzberg 47-49, 01307 Dresden, Germany
| | - Stefan Hans
- Technische Universität Dresden, Biotechnology Center and DFG-Center for Regenerative Therapies Dresden Cluster of Excellence, Tatzberg 47-49, 01307 Dresden, Germany
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26
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Fritzsch B, Elliott KL. Gene, cell, and organ multiplication drives inner ear evolution. Dev Biol 2017; 431:3-15. [PMID: 28866362 DOI: 10.1016/j.ydbio.2017.08.034] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 04/27/2017] [Accepted: 08/25/2017] [Indexed: 12/14/2022]
Abstract
We review the development and evolution of the ear neurosensory cells, the aggregation of neurosensory cells into an otic placode, the evolution of novel neurosensory structures dedicated to hearing and the evolution of novel nuclei in the brain and their input dedicated to processing those novel auditory stimuli. The evolution of the apparently novel auditory system lies in duplication and diversification of cell fate transcription regulation that allows variation at the cellular level [transforming a single neurosensory cell into a sensory cell connected to its targets by a sensory neuron as well as diversifying hair cells], organ level [duplication of organ development followed by diversification and novel stimulus acquisition] and brain nuclear level [multiplication of transcription factors to regulate various neuron and neuron aggregate fate to transform the spinal cord into the unique hindbrain organization]. Tying cell fate changes driven by bHLH and other transcription factors into cell and organ changes is at the moment tentative as not all relevant factors are known and their gene regulatory network is only rudimentary understood. Future research can use the blueprint proposed here to provide both the deeper molecular evolutionary understanding as well as a more detailed appreciation of developmental networks. This understanding can reveal how an auditory system evolved through transformation of existing cell fate determining networks and thus how neurosensory evolution occurred through molecular changes affecting cell fate decision processes. Appreciating the evolutionary cascade of developmental program changes could allow identifying essential steps needed to restore cells and organs in the future.
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Affiliation(s)
- Bernd Fritzsch
- University of Iowa, Department of Biology, Iowa City, IA 52242, United States.
| | - Karen L Elliott
- University of Iowa, Department of Biology, Iowa City, IA 52242, United States
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27
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Warchol ME, Stone J, Barton M, Ku J, Veile R, Daudet N, Lovett M. ADAM10 and γ-secretase regulate sensory regeneration in the avian vestibular organs. Dev Biol 2017; 428:39-51. [PMID: 28526588 PMCID: PMC5873298 DOI: 10.1016/j.ydbio.2017.05.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 05/15/2017] [Accepted: 05/15/2017] [Indexed: 11/19/2022]
Abstract
The loss of sensory hair cells from the inner ear is a leading cause of hearing and balance disorders. The mammalian ear has a very limited ability to replace lost hair cells, but the inner ears of non-mammalian vertebrates can spontaneously regenerate hair cells after injury. Prior studies have shown that replacement hair cells are derived from epithelial supporting cells and that the differentiation of new hair cells is regulated by the Notch signaling pathway. The present study examined molecular influences on regeneration in the avian utricle, which has a particularly robust regenerative ability. Chicken utricles were placed in organotypic culture and hair cells were lesioned by application of the ototoxic antibiotic streptomycin. Cultures were then allowed to regenerate in vitro for seven days. Some specimens were treated with small molecule inhibitors of γ-secretase or ADAM10, proteases which are essential for transmission of Notch signaling. As expected, treatment with both inhibitors led to increased numbers of replacement hair cells. However, we also found that inhibition of both proteases resulted in increased regenerative proliferation. Subsequent experiments showed that inhibition of γ-secretase or ADAM10 could also trigger proliferation in undamaged utricles. To better understand these phenomena, we used RNA-Seq profiling to characterize changes in gene expression following γ-secretase inhibition. We observed expression patterns that were consistent with Notch pathway inhibition, but we also found that the utricular sensory epithelium contains numerous γ-secretase substrates that might regulate cell cycle entry and possibly supporting cell-to-hair cell conversion. Together, our data suggest multiple roles for γ-secretase and ADAM10 in vestibular hair cell regeneration.
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Affiliation(s)
- Mark E Warchol
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO 63110, United States
| | - Jennifer Stone
- The Virginia Merrill Bloedel Hearing Research Center and Department of Otolaryngology-Head and Neck Surgery, University of Washington School of Medicine, Seattle, WA 98195, United States
| | - Matthew Barton
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO 63110, United States
| | - Jeffrey Ku
- Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110, United States
| | - Rose Veile
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO 63110, United States; Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110, United States
| | - Nicolas Daudet
- Center for Auditory Research, University College London, London, United Kingdom
| | - Michael Lovett
- Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110, United States; NHLI, Imperial College, London, United Kingdom
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28
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Nawaz M, Fatima F. Extracellular Vesicles, Tunneling Nanotubes, and Cellular Interplay: Synergies and Missing Links. Front Mol Biosci 2017; 4:50. [PMID: 28770210 PMCID: PMC5513920 DOI: 10.3389/fmolb.2017.00050] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 07/03/2017] [Indexed: 12/15/2022] Open
Abstract
The process of intercellular communication seems to have been a highly conserved evolutionary process. Higher eukaryotes use several means of intercellular communication to address both the changing physiological demands of the body and to fight against diseases. In recent years, there has been an increasing interest in understanding how cell-derived nanovesicles, known as extracellular vesicles (EVs), can function as normal paracrine mediators of intercellular communication, but can also elicit disease progression and may be used for innovative therapies. Over the last decade, a large body of evidence has accumulated to show that cells use cytoplasmic extensions comprising open-ended channels called tunneling nanotubes (TNTs) to connect cells at a long distance and facilitate the exchange of cytoplasmic material. TNTs are a different means of communication to classical gap junctions or cell fusions; since they are characterized by long distance bridging that transfers cytoplasmic organelles and intracellular vesicles between cells and represent the process of heteroplasmy. The role of EVs in cell communication is relatively well-understood, but how TNTs fit into this process is just emerging. The aim of this review is to describe the relationship between TNTs and EVs, and to discuss the synergies between these two crucial processes in the context of normal cellular cross-talk, physiological roles, modulation of immune responses, development of diseases, and their combinatory effects in tissue repair. At the present time this review appears to be the first summary of the implications of the overlapping roles of TNTs and EVs. We believe that a better appreciation of these parallel processes will improve our understanding on how these nanoscale conduits can be utilized as novel tools for targeted therapies.
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Affiliation(s)
- Muhammad Nawaz
- Department of Pathology and Forensic Medicine, Ribeirao Preto Medical School, University of São PauloSão Paulo, Brazil.,Department of Rheumatology and Inflammation Research, Sahlgrenska Academy, University of GothenburgGothenburg, Sweden
| | - Farah Fatima
- Department of Pathology and Forensic Medicine, Ribeirao Preto Medical School, University of São PauloSão Paulo, Brazil
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29
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Hoijman E, Fargas L, Blader P, Alsina B. Pioneer neurog1 expressing cells ingress into the otic epithelium and instruct neuronal specification. eLife 2017; 6. [PMID: 28537554 PMCID: PMC5476427 DOI: 10.7554/elife.25543] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2017] [Accepted: 05/23/2017] [Indexed: 11/30/2022] Open
Abstract
Neural patterning involves regionalised cell specification. Recent studies indicate that cell dynamics play instrumental roles in neural pattern refinement and progression, but the impact of cell behaviour and morphogenesis on neural specification is not understood. Here we combine 4D analysis of cell behaviours with dynamic quantification of proneural expression to uncover the construction of the zebrafish otic neurogenic domain. We identify pioneer cells expressing neurog1 outside the otic epithelium that migrate and ingress into the epithelialising placode to become the first otic neuronal progenitors. Subsequently, neighbouring cells express neurog1 inside the placode, and apical symmetric divisions amplify the specified pool. Interestingly, pioneer cells delaminate shortly after ingression. Ablation experiments reveal that pioneer cells promote neurog1 expression in other otic cells. Finally, ingression relies on the epithelialisation timing controlled by FGF activity. We propose a novel view for otic neurogenesis integrating cell dynamics whereby ingression of pioneer cells instructs neuronal specification. DOI:http://dx.doi.org/10.7554/eLife.25543.001 The inner ear is responsible for our senses of hearing and balance, and is made up of a series of fluid-filled cavities. Sounds, and movements of the head, cause the fluid within these cavities to move. This activates neurons that line the cavities, causing them to increase their firing rates and pass on information about the sounds or head movements to the brain. Damage to these neurons can result in deafness or vertigo. But where do the neurons themselves come from? It is generally assumed that all inner ear neurons develop inside an area of the embryo called the inner ear epithelium. Cells in this region are thought to switch on a gene called neurog1, triggering a series of changes that turn them into inner ear neurons. However, using advanced microscopy techniques in zebrafish embryos, Hoijman, Fargas et al. now show that this is not the whole story. While zebrafish do not have external ears, they do possess fluid-filled structures for balance and hearing that are similar to those of other vertebrates. Zebrafish embryos are also transparent, which means that activation of genes can be visualized directly. By imaging zebrafish embryos in real time, Hoijman, Fargas et al. show that the first cells to switch on neurog1 do so outside the inner ear epithelium. These pioneer cells then migrate into the inner ear epithelium and switch on neurog1 in their new neighbors. A substance called fibroblast growth factor tells the inner ear epithelium to let the pioneers enter, and thereby controls the final number of inner ear neurons. The work of Hoijman, Fargas et al. reveals how coordinated activation of genes and movement of cells gives rise to inner ear neurons. This should provide insights into the mechanisms that generate other types of sensory tissue. In the long term, the advances made in this study may lead to new strategies for repairing damaged sensory nerves. DOI:http://dx.doi.org/10.7554/eLife.25543.002
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Affiliation(s)
- Esteban Hoijman
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain
| | - L Fargas
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain
| | - Patrick Blader
- Centre de Biologie du Développement, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Berta Alsina
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain
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30
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Dyballa S, Savy T, Germann P, Mikula K, Remesikova M, Špir R, Zecca A, Peyriéras N, Pujades C. Distribution of neurosensory progenitor pools during inner ear morphogenesis unveiled by cell lineage reconstruction. eLife 2017; 6:22268. [PMID: 28051766 PMCID: PMC5243114 DOI: 10.7554/elife.22268] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 12/23/2016] [Indexed: 01/01/2023] Open
Abstract
Reconstructing the lineage of cells is central to understanding how the wide diversity of cell types develops. Here, we provide the neurosensory lineage reconstruction of a complex sensory organ, the inner ear, by imaging zebrafish embryos in vivo over an extended timespan, combining cell tracing and cell fate marker expression over time. We deliver the first dynamic map of early neuronal and sensory progenitor pools in the whole otic vesicle. It highlights the remodeling of the neuronal progenitor domain upon neuroblast delamination, and reveals that the order and place of neuroblasts' delamination from the otic epithelium prefigure their position within the SAG. Sensory and non-sensory domains harbor different proliferative activity contributing distinctly to the overall growth of the structure. Therefore, the otic vesicle case exemplifies a generic morphogenetic process where spatial and temporal cues regulate cell fate and functional organization of the rudiment of the definitive organ.
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Affiliation(s)
- Sylvia Dyballa
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain
| | - Thierry Savy
- Multilevel Dynamics in Morphogenesis Unit, USR3695 CNRS, Gif sur Yvette, France
| | - Philipp Germann
- Systems Biology Unit, Center for Genomic Regulation, Barcelona, Spain
| | - Karol Mikula
- Department of Mathematics, Slovak University of Technology, Bratislava, Slovakia
| | - Mariana Remesikova
- Department of Mathematics, Slovak University of Technology, Bratislava, Slovakia
| | - Róbert Špir
- Department of Mathematics, Slovak University of Technology, Bratislava, Slovakia
| | - Andrea Zecca
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain
| | - Nadine Peyriéras
- Multilevel Dynamics in Morphogenesis Unit, USR3695 CNRS, Gif sur Yvette, France
| | - Cristina Pujades
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain
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31
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Dvorakova M, Jahan I, Macova I, Chumak T, Bohuslavova R, Syka J, Fritzsch B, Pavlinkova G. Incomplete and delayed Sox2 deletion defines residual ear neurosensory development and maintenance. Sci Rep 2016; 6:38253. [PMID: 27917898 PMCID: PMC5137136 DOI: 10.1038/srep38253] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 11/07/2016] [Indexed: 11/09/2022] Open
Abstract
The role of Sox2 in neurosensory development is not yet fully understood. Using mice with conditional Islet1-cre mediated deletion of Sox2, we explored the function of Sox2 in neurosensory development in a model with limited cell type diversification, the inner ear. In Sox2 conditional mutants, neurons initially appear to form normally, whereas late- differentiating neurons of the cochlear apex never form. Variable numbers of hair cells differentiate in the utricle, saccule, and cochlear base but sensory epithelium formation is completely absent in the apex and all three cristae of the semicircular canal ampullae. Hair cells differentiate only in sensory epithelia known or proposed to have a lineage relationship of neurons and hair cells. All initially formed neurons lacking hair cell targets die by apoptosis days after they project toward non-existing epithelia. Therefore, late neuronal development depends directly on Sox2 for differentiation and on the survival of hair cells, possibly derived from common neurosensory precursors.
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Affiliation(s)
- Martina Dvorakova
- Institute of Biotechnology CAS, Prague, Czechia
- Faculty of Science, Charles University, Prague, Czechia
| | - Israt Jahan
- Department of Biology, University of Iowa, Iowa City, IA, USA
| | - Iva Macova
- Institute of Biotechnology CAS, Prague, Czechia
- Faculty of Science, Charles University, Prague, Czechia
| | | | | | - Josef Syka
- Institute of Experimental Medicine CAS, Prague, Czechia
| | - Bernd Fritzsch
- Department of Biology, University of Iowa, Iowa City, IA, USA
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32
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McLean WJ, McLean DT, Eatock RA, Edge ASB. Distinct capacity for differentiation to inner ear cell types by progenitor cells of the cochlea and vestibular organs. Development 2016; 143:4381-4393. [PMID: 27789624 DOI: 10.1242/dev.139840] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 10/11/2016] [Indexed: 01/16/2023]
Abstract
Disorders of hearing and balance are most commonly associated with damage to cochlear and vestibular hair cells or neurons. Although these cells are not capable of spontaneous regeneration, progenitor cells in the hearing and balance organs of the neonatal mammalian inner ear have the capacity to generate new hair cells after damage. To investigate whether these cells are restricted in their differentiation capacity, we assessed the phenotypes of differentiated progenitor cells isolated from three compartments of the mouse inner ear - the vestibular and cochlear sensory epithelia and the spiral ganglion - by measuring electrophysiological properties and gene expression. Lgr5+ progenitor cells from the sensory epithelia gave rise to hair cell-like cells, but not neurons or glial cells. Newly created hair cell-like cells had hair bundle proteins, synaptic proteins and membrane proteins characteristic of the compartment of origin. PLP1+ glial cells from the spiral ganglion were identified as neural progenitors, which gave rise to neurons, astrocytes and oligodendrocytes, but not hair cells. Thus, distinct progenitor populations from the neonatal inner ear differentiate to cell types associated with their organ of origin.
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Affiliation(s)
- Will J McLean
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA 02114, USA.,Eaton-Peabody Laboratories of Auditory Physiology, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA.,Program in Speech and Hearing Bioscience and Technology, Division of Health Sciences and Technology, Harvard & MIT, Cambridge, MA 02139, USA
| | - Dalton T McLean
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA 02114, USA.,Eaton-Peabody Laboratories of Auditory Physiology, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA
| | - Ruth Anne Eatock
- Department of Neurobiology, University of Chicago, Chicago, IL 60637, USA
| | - Albert S B Edge
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA 02114, USA .,Eaton-Peabody Laboratories of Auditory Physiology, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA.,Program in Speech and Hearing Bioscience and Technology, Division of Health Sciences and Technology, Harvard & MIT, Cambridge, MA 02139, USA.,Harvard Stem Cell Institute, Cambridge, MA 02138, USA
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33
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Lineage tracing of Sox2-expressing progenitor cells in the mouse inner ear reveals a broad contribution to non-sensory tissues and insights into the origin of the organ of Corti. Dev Biol 2016; 414:72-84. [PMID: 27090805 DOI: 10.1016/j.ydbio.2016.03.027] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Revised: 03/09/2016] [Accepted: 03/26/2016] [Indexed: 11/22/2022]
Abstract
The transcription factor Sox2 is both necessary and sufficient for the generation of sensory regions of the inner ear. It regulates expression of the Notch ligand Jag1 in prosensory progenitors, which signal to neighboring cells to up-regulate Sox2 and sustain prosensory identity. However, the expression pattern of Sox2 in the early inner ear is very broad, suggesting that Sox2-expressing progenitors form a wide variety of cell types in addition to generating the sensory regions of the ear. We used Sox2-CreER mice to follow the fates of Sox2-expressing cells at different stages in ear development. We find that Sox2-expressing cells in the early otocyst give rise to large numbers of non-sensory structures throughout the inner ear, and that Sox2 only becomes a truly prosensory marker at embryonic day (E)11.5. Our fate map reveals the organ of Corti derives from a central domain on the medial side of the otocyst and shows that a significant amount of the organ of Corti derives from a Sox2-negative population in this region.
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34
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Lim R, Brichta AM. Anatomical and physiological development of the human inner ear. Hear Res 2016; 338:9-21. [PMID: 26900072 DOI: 10.1016/j.heares.2016.02.004] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 01/20/2016] [Accepted: 02/12/2016] [Indexed: 01/05/2023]
Abstract
We describe the development of the human inner ear with the invagination of the otic vesicle at 4 weeks gestation (WG), the growth of the semicircular canals from 5 WG, and the elongation and coiling of the cochlea at 10 WG. As the membranous labyrinth takes shape, there is a concomitant development of the sensory neuroepithelia and their associated structures within. This review details the growth and differentiation of the vestibular and auditory neuroepithelia, including synaptogenesis, the expression of stereocilia and kinocilia, and innervation of hair cells by afferent and efferent nerve fibres. Along with development of essential sensory structures we outline the formation of crucial accessory structures of the vestibular system - the cupula and otolithic membrane and otoconia as well as the three cochlea compartments and the tectorial membrane. Recent molecular studies have elaborated on classical anatomical studies to characterize the development of prosensory and sensory regions of the fetal human cochlea using the transcription factors, PAX2, MAF-B, SOX2, and SOX9. Further advances are being made with recent physiological studies that are beginning to describe when hair cells become functionally active during human gestation. This article is part of a Special Issue entitled <Annual Reviews 2016>.
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Affiliation(s)
- Rebecca Lim
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, The University of Newcastle, NSW, Australia.
| | - Alan M Brichta
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, The University of Newcastle, NSW, Australia
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35
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Basch ML, Brown RM, Jen H, Groves AK. Where hearing starts: the development of the mammalian cochlea. J Anat 2016; 228:233-54. [PMID: 26052920 PMCID: PMC4718162 DOI: 10.1111/joa.12314] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/14/2015] [Indexed: 12/11/2022] Open
Abstract
The mammalian cochlea is a remarkable sensory organ, capable of perceiving sound over a range of 10(12) in pressure, and discriminating both infrasonic and ultrasonic frequencies in different species. The sensory hair cells of the mammalian cochlea are exquisitely sensitive, responding to atomic-level deflections at speeds on the order of tens of microseconds. The number and placement of hair cells are precisely determined during inner ear development, and a large number of developmental processes sculpt the shape, size and morphology of these cells along the length of the cochlear duct to make them optimally responsive to different sound frequencies. In this review, we briefly discuss the evolutionary origins of the mammalian cochlea, and then describe the successive developmental processes that lead to its induction, cell cycle exit, cellular patterning and the establishment of topologically distinct frequency responses along its length.
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Affiliation(s)
- Martin L. Basch
- Department of NeuroscienceBaylor College of MedicineHoustonTXUSA
| | - Rogers M. Brown
- Program in Developmental BiologyBaylor College of MedicineHoustonTXUSA
| | - Hsin‐I Jen
- Program in Developmental BiologyBaylor College of MedicineHoustonTXUSA
| | - Andrew K. Groves
- Department of NeuroscienceBaylor College of MedicineHoustonTXUSA
- Program in Developmental BiologyBaylor College of MedicineHoustonTXUSA
- Department of Molecular and Human GeneticsBaylor College of MedicineHoustonTXUSA
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36
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Cochlear afferent innervation development. Hear Res 2015; 330:157-69. [DOI: 10.1016/j.heares.2015.07.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 06/02/2015] [Accepted: 07/21/2015] [Indexed: 01/11/2023]
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37
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Jahan I, Pan N, Elliott KL, Fritzsch B. The quest for restoring hearing: Understanding ear development more completely. Bioessays 2015. [PMID: 26208302 DOI: 10.1002/bies.201500044] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Neurosensory hearing loss is a growing problem of super-aged societies. Cochlear implants can restore some hearing, but rebuilding a lost hearing organ would be superior. Research has discovered many cellular and molecular steps to develop a hearing organ but translating those insights into hearing organ restoration remains unclear. For example, we cannot make various hair cell types and arrange them into their specific patterns surrounded by the right type of supporting cells in the right numbers. Our overview of the topologically highly organized and functionally diversified cellular mosaic of the mammalian hearing organ highlights what is known and unknown about its development. Following this analysis, we suggest critical steps to guide future attempts toward restoration of a functional organ of Corti. We argue that generating mutant mouse lines that mimic human pathology to fine-tune attempts toward long-term functional restoration are needed to go beyond the hope generated by restoring single hair cells in postnatal sensory epithelia.
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Affiliation(s)
- Israt Jahan
- Department of Biology, CLAS, University of Iowa, Iowa City, IA, USA
| | - Ning Pan
- Department of Biology, CLAS, University of Iowa, Iowa City, IA, USA
| | - Karen L Elliott
- Department of Biology, CLAS, University of Iowa, Iowa City, IA, USA
| | - Bernd Fritzsch
- Department of Biology, CLAS, University of Iowa, Iowa City, IA, USA
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38
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Golden EJ, Benito-Gonzalez A, Doetzlhofer A. The RNA-binding protein LIN28B regulates developmental timing in the mammalian cochlea. Proc Natl Acad Sci U S A 2015; 112:E3864-73. [PMID: 26139524 PMCID: PMC4517247 DOI: 10.1073/pnas.1501077112] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Proper tissue development requires strict coordination of proliferation, growth, and differentiation. Strict coordination is particularly important for the auditory sensory epithelium, where deviations from the normal spatial and temporal pattern of auditory progenitor cell (prosensory cell) proliferation and differentiation result in abnormal cellular organization and, thus, auditory dysfunction. The molecular mechanisms involved in the timing and coordination of auditory prosensory proliferation and differentiation are poorly understood. Here we identify the RNA-binding protein LIN28B as a critical regulator of developmental timing in the murine cochlea. We show that Lin28b and its opposing let-7 miRNAs are differentially expressed in the auditory sensory lineage, with Lin28b being highly expressed in undifferentiated prosensory cells and let-7 miRNAs being highly expressed in their progeny-hair cells (HCs) and supporting cells (SCs). Using recently developed transgenic mouse models for LIN28B and let-7g, we demonstrate that prolonged LIN28B expression delays prosensory cell cycle withdrawal and differentiation, resulting in HC and SC patterning and maturation defects. Surprisingly, let-7g overexpression, although capable of inducing premature prosensory cell cycle exit, failed to induce premature HC differentiation, suggesting that LIN28B's functional role in the timing of differentiation uses let-7 independent mechanisms. Finally, we demonstrate that overexpression of LIN28B or let-7g can significantly alter the postnatal production of HCs in response to Notch inhibition; LIN28B has a positive effect on HC production, whereas let-7 antagonizes this process. Together, these results implicate a key role for the LIN28B/let-7 axis in regulating postnatal SC plasticity.
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Affiliation(s)
- Erin J Golden
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205; Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Ana Benito-Gonzalez
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205; Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Angelika Doetzlhofer
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205; Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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39
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Vendrell V, López-Hernández I, Durán Alonso MB, Feijoo-Redondo A, Abello G, Gálvez H, Giráldez F, Lamonerie T, Schimmang T. Otx2 is a target of N-myc and acts as a suppressor of sensory development in the mammalian cochlea. Development 2015; 142:2792-800. [PMID: 26160903 DOI: 10.1242/dev.122465] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 06/29/2015] [Indexed: 12/30/2022]
Abstract
Transcriptional regulatory networks are essential during the formation and differentiation of organs. The transcription factor N-myc is required for proper morphogenesis of the cochlea and to control correct patterning of the organ of Corti. We show here that the Otx2 gene, a mammalian ortholog of the Drosophila orthodenticle homeobox gene, is a crucial target of N-myc during inner ear development. Otx2 expression is lost in N-myc mouse mutants, and N-myc misexpression in the chick inner ear leads to ectopic expression of Otx2. Furthermore, Otx2 enhancer activity is increased by N-myc misexpression, indicating that N-myc may directly regulate Otx2. Inactivation of Otx2 in the mouse inner ear leads to ectopic expression of prosensory markers in non-sensory regions of the cochlear duct. Upon further differentiation, these domains give rise to an ectopic organ of Corti, together with the re-specification of non-sensory areas into sensory epithelia, and the loss of Reissner's membrane. Therefore, the Otx2-positive domain of the cochlear duct shows a striking competence to develop into a mirror-image copy of the organ of Corti. Taken together, these data show that Otx2 acts downstream of N-myc and is essential for patterning and spatial restriction of the sensory domain of the mammalian cochlea.
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Affiliation(s)
- Victor Vendrell
- Instituto de Biología y Genética Molecular, Universidad de Valladolid y Consejo Superior de Investigaciones Científicas, C/Sanz y Forés 3, Valladolid E-47003, Spain
| | - Iris López-Hernández
- Instituto de Biología y Genética Molecular, Universidad de Valladolid y Consejo Superior de Investigaciones Científicas, C/Sanz y Forés 3, Valladolid E-47003, Spain
| | - María Beatriz Durán Alonso
- Instituto de Biología y Genética Molecular, Universidad de Valladolid y Consejo Superior de Investigaciones Científicas, C/Sanz y Forés 3, Valladolid E-47003, Spain
| | - Ana Feijoo-Redondo
- Instituto de Biología y Genética Molecular, Universidad de Valladolid y Consejo Superior de Investigaciones Científicas, C/Sanz y Forés 3, Valladolid E-47003, Spain
| | - Gina Abello
- CEXS, Universitat Pompeu Fabra, Parc de Recerca Biomédica de Barcelona, Barcelona E-08003, Spain
| | - Héctor Gálvez
- CEXS, Universitat Pompeu Fabra, Parc de Recerca Biomédica de Barcelona, Barcelona E-08003, Spain
| | - Fernando Giráldez
- CEXS, Universitat Pompeu Fabra, Parc de Recerca Biomédica de Barcelona, Barcelona E-08003, Spain
| | - Thomas Lamonerie
- Institut de Biologie Valrose, University of Nice Sophia Antipolis, UMR UNS/CNRS 7277/INSERM 1091, Nice F-06108, France
| | - Thomas Schimmang
- Instituto de Biología y Genética Molecular, Universidad de Valladolid y Consejo Superior de Investigaciones Científicas, C/Sanz y Forés 3, Valladolid E-47003, Spain
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40
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Fritzsch B, Pan N, Jahan I, Elliott KL. Inner ear development: building a spiral ganglion and an organ of Corti out of unspecified ectoderm. Cell Tissue Res 2015; 361:7-24. [PMID: 25381571 PMCID: PMC4426086 DOI: 10.1007/s00441-014-2031-5] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Accepted: 10/09/2014] [Indexed: 01/21/2023]
Abstract
The mammalian inner ear develops from a placodal thickening into a complex labyrinth of ducts with five sensory organs specialized to detect position and movement in space. The mammalian ear also develops a spiraled cochlear duct containing the auditory organ, the organ of Corti (OC), specialized to translate sound into hearing. Development of the OC from a uniform sheet of ectoderm requires unparalleled precision in the topological developmental engineering of four different general cell types, namely sensory neurons, hair cells, supporting cells, and general otic epithelium, into a mosaic of ten distinctly recognizable cell types in and around the OC, each with a unique distribution. Moreover, the OC receives unique innervation by ear-derived spiral ganglion afferents and brainstem-derived motor neurons as efferents and requires neural-crest-derived Schwann cells to form myelin and neural-crest-derived cells to induce the stria vascularis. This transformation of a sheet of cells into a complicated interdigitating set of cells necessitates the orchestrated expression of multiple transcription factors that enable the cellular transformation from ectoderm into neurosensory cells forming the spiral ganglion neurons (SGNs), while simultaneously transforming the flat epithelium into a tube, the cochlear duct, housing the OC. In addition to the cellular and conformational changes forming the cochlear duct with the OC, changes in the surrounding periotic mesenchyme form passageways for sound to stimulate the OC. We review molecular developmental data, generated predominantly in mice, in order to integrate the well-described expression changes of transcription factors and their actions, as revealed in mutants, in the formation of SGNs and OC in the correct position and orientation with suitable innervation. Understanding the molecular basis of these developmental changes leading to the formation of the mammalian OC and highlighting the gaps in our knowledge might guide in vivo attempts to regenerate this most complicated cellular mosaic of the mammalian body for the reconstitution of hearing in a rapidly growing population of aging people suffering from hearing loss.
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Affiliation(s)
- Bernd Fritzsch
- College of Liberal Arts and Sciences, Department of Biology, University of Iowa, 143 BB, 123 Jefferson Avenue, Iowa City, IA 52242, USA,
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Chumak T, Bohuslavova R, Macova I, Dodd N, Buckiova D, Fritzsch B, Syka J, Pavlinkova G. Deterioration of the Medial Olivocochlear Efferent System Accelerates Age-Related Hearing Loss in Pax2-Isl1 Transgenic Mice. Mol Neurobiol 2015; 53:2368-83. [PMID: 25990412 DOI: 10.1007/s12035-015-9215-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 05/07/2015] [Indexed: 11/28/2022]
Abstract
The development, maturation, and maintenance of the inner ear are governed by temporal and spatial expression cascades of transcription factors that form a gene regulatory network. ISLET1 (ISL1) may be one of the major players in this cascade, and in order to study its role in the regulation of inner ear development, we produced a transgenic mouse overexpressing Isl1 under the Pax2 promoter. Pax2-regulated ISL1 overexpression increases the embryonic ISL1(+) domain and induces accelerated nerve fiber extension and branching in E12.5 embryos. Despite these gains in early development, the overexpression of ISL1 impairs the maintenance and function of hair cells of the organ of Corti. Mutant mice exhibit hyperactivity, circling behavior, and progressive age-related decline in hearing functions, which is reflected in reduced otoacoustic emissions (DPOAEs) followed by elevated hearing thresholds. The reduction of the amplitude of DPOAEs in transgenic mice was first detected at 1 month of age. By 6-9 months of age, DPOAEs completely disappeared, suggesting a functional inefficiency of outer hair cells (OHCs). The timing of DPOAE reduction coincides with the onset of the deterioration of cochlear efferent terminals. In contrast to these effects on efferents, we only found a moderate loss of OHCs and spiral ganglion neurons. For the first time, our results show that the genetic alteration of the medial olivocochlear (MOC) efferent system induces an early onset of age-related hearing loss. Thus, the neurodegeneration of the MOC system could be a contributing factor to the pathology of age-related hearing loss.
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Affiliation(s)
- Tetyana Chumak
- Institute of Experimental Medicine, CAS, Prague, Czechia
| | - Romana Bohuslavova
- Laboratory of Molecular Pathogenetics, Institute of Biotechnology, CAS, Prague 4, CZ-142 20, Prague, Czechia
| | - Iva Macova
- Laboratory of Molecular Pathogenetics, Institute of Biotechnology, CAS, Prague 4, CZ-142 20, Prague, Czechia
| | - Nicole Dodd
- Laboratory of Molecular Pathogenetics, Institute of Biotechnology, CAS, Prague 4, CZ-142 20, Prague, Czechia
| | | | - Bernd Fritzsch
- Department of Biology, University of Iowa, Iowa City, IA, 52242, USA
| | - Josef Syka
- Institute of Experimental Medicine, CAS, Prague, Czechia
| | - Gabriela Pavlinkova
- Laboratory of Molecular Pathogenetics, Institute of Biotechnology, CAS, Prague 4, CZ-142 20, Prague, Czechia.
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Fritzsch B, Jahan I, Pan N, Elliott KL. Evolving gene regulatory networks into cellular networks guiding adaptive behavior: an outline how single cells could have evolved into a centralized neurosensory system. Cell Tissue Res 2014; 359:295-313. [PMID: 25416504 DOI: 10.1007/s00441-014-2043-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Accepted: 10/20/2014] [Indexed: 12/18/2022]
Abstract
Understanding the evolution of the neurosensory system of man, able to reflect on its own origin, is one of the major goals of comparative neurobiology. Details of the origin of neurosensory cells, their aggregation into central nervous systems and associated sensory organs and their localized patterning leading to remarkably different cell types aggregated into variably sized parts of the central nervous system have begun to emerge. Insights at the cellular and molecular level have begun to shed some light on the evolution of neurosensory cells, partially covered in this review. Molecular evidence suggests that high mobility group (HMG) proteins of pre-metazoans evolved into the definitive Sox [SRY (sex determining region Y)-box] genes used for neurosensory precursor specification in metazoans. Likewise, pre-metazoan basic helix-loop-helix (bHLH) genes evolved in metazoans into the group A bHLH genes dedicated to neurosensory differentiation in bilaterians. Available evidence suggests that the Sox and bHLH genes evolved a cross-regulatory network able to synchronize expansion of precursor populations and their subsequent differentiation into novel parts of the brain or sensory organs. Molecular evidence suggests metazoans evolved patterning gene networks early, which were not dedicated to neuronal development. Only later in evolution were these patterning gene networks tied into the increasing complexity of diffusible factors, many of which were already present in pre-metazoans, to drive local patterning events. It appears that the evolving molecular basis of neurosensory cell development may have led, in interaction with differentially expressed patterning genes, to local network modifications guiding unique specializations of neurosensory cells into sensory organs and various areas of the central nervous system.
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Affiliation(s)
- Bernd Fritzsch
- Department of Biology, University of Iowa, CLAS, 143 BB, Iowa City, IA, 52242, USA,
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Cai T, Groves AK. The Role of Atonal Factors in Mechanosensory Cell Specification and Function. Mol Neurobiol 2014; 52:1315-1329. [PMID: 25339580 DOI: 10.1007/s12035-014-8925-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 10/07/2014] [Indexed: 10/24/2022]
Abstract
Atonal genes are basic helix-loop-helix transcription factors that were first identified as regulating the formation of mechanoreceptors and photoreceptors in Drosophila. Isolation of vertebrate homologs of atonal genes has shown these transcription factors to play diverse roles in the development of neurons and their progenitors, gut epithelial cells, and mechanosensory cells in the inner ear and skin. In this article, we review the molecular function and regulation of atonal genes and their targets, with particular emphasis on the function of Atoh1 in the development, survival, and function of hair cells of the inner ear. We discuss cell-extrinsic signals that induce Atoh1 expression and the transcriptional networks that regulate its expression during development. Finally, we discuss recent work showing how identification of Atoh1 target genes in the cerebellum, spinal cord, and gut can be used to propose candidate Atoh1 targets in tissues such as the inner ear where cell numbers and biochemical material are limiting.
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Affiliation(s)
- Tiantian Cai
- Program in Developmental Biology, Baylor College of Medicine, Houston, USA
| | - Andrew K Groves
- Program in Developmental Biology, Baylor College of Medicine, Houston, USA. .,Department of Neuroscience, Baylor College of Medicine, Houston, USA. .,Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA.
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