1
|
Tan AL, Christensen SE, Baker AK, Riley BB. Fgf, Hh, and pax2a differentially regulate expression of pax5 and pou3f3b in vestibular and auditory maculae in the zebrafish otic vesicle. Dev Dyn 2023; 252:1269-1279. [PMID: 37171017 DOI: 10.1002/dvdy.599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Revised: 04/02/2023] [Accepted: 04/30/2023] [Indexed: 05/13/2023] Open
Abstract
BACKGROUND The vertebrate inner ear contains distinct sensory epithelia specialized for auditory or vestibular function. In zebrafish, the first sensory epithelia form at opposite ends of the otic vesicle and are functionally distinct: the anterior utricular macula is essential for vestibular function whereas the posterior saccular macula is critical for hearing. Mechanisms distinguishing these maculae are not clear. Here, we examined the effects of manipulating Fgf or Hh on expression of pax5 and pou3f3b, unique markers of utricular and saccular identity. We also examined the roles of pax2a and atoh1a/b, early regulators of sensory specification. RESULTS fgf3 and fgf8a were uniquely required for pax5 and pou3f3b, respectively. Elevating Fgf or blocking Hh expanded expression of pax5 but repressed pou3f3b, while blocking Fgf had the opposite effect. Blocking sensory specification did not affect pax5 or pou3f3b, but both markers were lost in pax2a-/- mutants. Maintenance of pax2a expression requires Fgf, Hh and Pax2a itself. CONCLUSION Specification of utricular identity requires high Fgf and is repressed by Hh, whereas saccular identity requires Hh plus low Fgf. pax2a acts downstream of Fgf and Hh to maintain both fates. Comparison with mouse suggests this may reflect a broadly conserved developmental mechanism.
Collapse
Affiliation(s)
- Amy L Tan
- Biology Department, Texas A&M University, Texas, USA
| | | | | | - Bruce B Riley
- Biology Department, Texas A&M University, Texas, USA
| |
Collapse
|
2
|
Rai V, Tu S, Frank JR, Zuo J. Molecular Pathways Modulating Sensory Hair Cell Regeneration in Adult Mammalian Cochleae: Progress and Perspectives. Int J Mol Sci 2021; 23:ijms23010066. [PMID: 35008497 PMCID: PMC8745006 DOI: 10.3390/ijms23010066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 12/20/2021] [Accepted: 12/20/2021] [Indexed: 12/30/2022] Open
Abstract
Noise-induced, drug-related, and age-related disabling hearing loss is a major public health problem and affect approximately 466 million people worldwide. In non-mammalian vertebrates, the death of sensory hair cells (HCs) induces the proliferation and transdifferentiation of adjacent supporting cells into new HCs; however, this capacity is lost in juvenile and adult mammalian cochleae leading to permanent hearing loss. At present, cochlear implants and hearing devices are the only available treatments and can help patients to a certain extent; however, no biological approach or FDA-approved drug is effective to treat disabling hearing loss and restore hearing. Recently, regeneration of mammalian cochlear HCs by modulating molecular pathways or transcription factors has offered some promising results, although the immaturity of the regenerated HCs remains the biggest concern. Furthermore, most of the research done is in neonates and not in adults. This review focuses on critically summarizing the studies done in adult mammalian cochleae and discusses various strategies to elucidate novel transcription factors for better therapeutics.
Collapse
Affiliation(s)
| | | | | | - Jian Zuo
- Correspondence: ; Tel.: +1-(402)-280-2916
| |
Collapse
|
3
|
Riley BB. Comparative assessment of Fgf's diverse roles in inner ear development: A zebrafish perspective. Dev Dyn 2021; 250:1524-1551. [PMID: 33830554 DOI: 10.1002/dvdy.343] [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: 02/09/2021] [Revised: 03/26/2021] [Accepted: 03/26/2021] [Indexed: 01/21/2023] Open
Abstract
Progress in understanding mechanisms of inner ear development has been remarkably rapid in recent years. The research community has benefited from the availability of several diverse model organisms, including zebrafish, chick, and mouse. The complexity of the inner ear has proven to be a challenge, and the complexity of the mammalian cochlea in particular has been the subject of intense scrutiny. Zebrafish lack a cochlea and exhibit a number of other differences from amniote species, hence they are sometimes seen as less relevant for inner ear studies. However, accumulating evidence shows that underlying cellular and molecular mechanisms are often highly conserved. As a case in point, consideration of the diverse functions of Fgf and its downstream effectors reveals many similarities between vertebrate species, allowing meaningful comparisons the can benefit the entire research community. In this review, I will discuss mechanisms by which Fgf controls key events in early otic development in zebrafish and provide direct comparisons with chick and mouse.
Collapse
Affiliation(s)
- Bruce B Riley
- Biology Department, Texas A&M University, College Station, Texas, USA
| |
Collapse
|
4
|
Lu Y, Zhang M, Wei Q, Chen Z, Xing G, Yao J, Cao X. Disruption of Gprasp2 down-regulates Hedgehog signaling and leads to apoptosis in auditory cells. Biochem Biophys Res Commun 2021; 574:1-7. [PMID: 34418635 DOI: 10.1016/j.bbrc.2021.08.034] [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: 07/01/2021] [Revised: 08/10/2021] [Accepted: 08/11/2021] [Indexed: 11/25/2022]
Abstract
GPRASP2 is implicated in nervous system diseases, tumors and immune inflammation. In our previous study, G protein-coupled receptor associated sorting protein 2 (GPRASP2) was identified as a novel causal gene for X-linked recessive syndromic hearing loss (SHL). However, the role of GPRASP2 in auditory function has not been elucidated. The Gprasp2-knockout (KO) mouse HEI-OC1 auditory cells were constructed using CRISPR/Cas9-mediated gene editing. RNA-sequencing (RNA-seq) was used to investigate the differentially expressed genes (DEGs) and DEGs-enriched signaling pathways, which was verified by Western blot. Flow cytometry assay was used to examine cell apoptosis. The cytological pathology was evaluated by laser scanning confocal microscopy (LSCM) and transmission electron microscopy (TEM). Mitochondrial damage was observed in Gprasp2-KO HEI-OC1 cells. RNA-seq analysis suggested that Gprasp2-KO was implicated in the apoptosis process, which could be mediated by Hedgehog (Hh) signaling pathway. The key molecules in Hh signaling pathway (Smo, Gli1, Gli2) were detected to be down-regulated in Gprasp2-KO HEI-OC1 cells. The differential expression of apoptosis molecules (Bcl2, Bax, Caspase-3/cleaved-Caspase-3) indicated that Gprasp2-KO induced apoptosis in HEI-OC1 cells. The treatment of smoothened agonist (Purmorphamine, PUR) activated the Hh-Gli signaling pathway and reduced apoptosis in Gprasp2-KO HEI-OC1 cells. This study revealed that Gprasp2-disruption inhibited Hh signaling pathway and led to cell apoptosis in HEI-OC1 cells, which might provide the potential molecular mechanism of GPRASP2 mutation associated with human SHL.
Collapse
Affiliation(s)
- Yajie Lu
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, 211166, China; Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, 211166, China
| | - Min Zhang
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, 211166, China
| | - Qinjun Wei
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, 211166, China; Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, 211166, China
| | - Zhibin Chen
- Department of Otolaryngology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210009, China
| | - Guangqian Xing
- Department of Otolaryngology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210009, China
| | - Jun Yao
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, 211166, China; Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, 211166, China.
| | - Xin Cao
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, 211166, China; Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, 211166, China.
| |
Collapse
|
5
|
Hartwell RD, England SJ, Monk NAM, van Hateren NJ, Baxendale S, Marzo M, Lewis KE, Whitfield TT. Anteroposterior patterning of the zebrafish ear through Fgf- and Hh-dependent regulation of hmx3a expression. PLoS Genet 2019; 15:e1008051. [PMID: 31022185 PMCID: PMC6504108 DOI: 10.1371/journal.pgen.1008051] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 05/07/2019] [Accepted: 02/27/2019] [Indexed: 12/16/2022] Open
Abstract
In the zebrafish, Fgf and Hh signalling assign anterior and posterior identity, respectively, to the poles of the developing ear. Mis-expression of fgf3 or inhibition of Hh signalling results in double-anterior ears, including ectopic expression of hmx3a. To understand how this double-anterior pattern is established, we characterised transcriptional responses in Fgf gain-of-signalling or Hh loss-of-signalling backgrounds. Mis-expression of fgf3 resulted in rapid expansion of anterior otic markers, refining over time to give the duplicated pattern. Response to Hh inhibition was very different: initial anteroposterior asymmetry was retained, with de novo duplicate expression domains appearing later. We show that Hmx3a is required for normal anterior otic patterning, and that otic patterning defects in hmx3a-/- mutants are a close phenocopy to those seen in fgf3-/- mutants. However, neither loss nor gain of hmx3a function was sufficient to generate full ear duplications. Using our data to infer a transcriptional regulatory network required for acquisition of otic anterior identity, we can recapitulate both the wild-type and the double-anterior pattern in a mathematical model. Understanding how signalling molecules impart information to developing organ systems, and how this is interpreted through networks of gene activity, is a key goal of developmental genetic analysis. In the developing zebrafish inner ear, differences in gene expression arise between the anterior and posterior poles of the ear placode, ensuring that sensory structures in the ear develop in their correct positions. If signalling pathways are disrupted, a mirror-image ear can result, developing with two anterior poles. We have used genetic, pharmacological and mathematical modelling approaches to decipher the pathway of gene action required to specify anterior structures in the zebrafish ear. Patterns of gene expression are dynamic and plastic, with two different routes leading to the formation of duplicate anterior structures. Expression of the hmx3a gene is an early response to the anterior signalling molecule Fgf3, but is not sufficient to drive the formation of ectopic anterior structures at the posterior of the ear. The hmx3a gene codes for a protein that regulates other genes, and in humans, mutation of HMX genes results in diseases affecting inner ear function. Our work provides a framework for understanding the dynamics of early patterning events in the developing inner ear.
Collapse
Affiliation(s)
- Ryan D. Hartwell
- Bateson Centre and Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Samantha J. England
- Department of Biology, Syracuse University, Syracuse, New York, United States of America
| | - Nicholas A. M. Monk
- School of Mathematics and Statistics, University of Sheffield, Sheffield, United Kingdom
| | - Nicholas J. van Hateren
- Bateson Centre and Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Sarah Baxendale
- Bateson Centre and Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Mar Marzo
- Bateson Centre and Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Katharine E. Lewis
- Department of Biology, Syracuse University, Syracuse, New York, United States of America
| | - Tanya T. Whitfield
- Bateson Centre and Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
- * E-mail:
| |
Collapse
|
6
|
Sculpting the labyrinth: Morphogenesis of the developing inner ear. Semin Cell Dev Biol 2017; 65:47-59. [DOI: 10.1016/j.semcdb.2016.09.015] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 07/26/2016] [Accepted: 09/25/2016] [Indexed: 01/23/2023]
|
7
|
Baxendale S, Whitfield TT. Methods to study the development, anatomy, and function of the zebrafish inner ear across the life course. Methods Cell Biol 2016; 134:165-209. [PMID: 27312494 DOI: 10.1016/bs.mcb.2016.02.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The inner ear is a remarkably intricate structure able to detect sound, motion, and gravity. During development of the zebrafish embryo, the ear undergoes dynamic morphogenesis from a simple epithelial vesicle into a complex labyrinth, consisting of three semicircular canals and three otolithic sensory organs, each with an array of differentiated cell types. This microcosm of biology has led to advances in understanding molecular and cellular changes in epithelial patterning and morphogenesis, through to mechanisms of mechanosensory transduction and the origins of reflexive behavior. In this chapter, we describe different methods to study the zebrafish ear, including high-speed imaging of otic cilia, confocal microscopy, and light-sheet fluorescent microscopy. Many dyes, antibodies, and transgenic lines for labeling the ear are available, and we provide a comprehensive review of these resources. The developing ear is amenable to genetic, chemical, and physical manipulations, including injection and transplantation. Chemical modulation of developmental signaling pathways has paved the way for zebrafish to be widely used in drug discovery. We describe two chemical screens with relevance to the ear: a fluorescent-based screen for compounds that protect against ototoxicity, and an in situ-based screen for modulators of a signaling pathway involved in semicircular canal development. We also describe methods for dissection and imaging of the adult otic epithelia. We review both manual and automated methods to test the function of the inner ear and lateral line, defects in which can lead to altered locomotor behavior. Finally, we review a collection of zebrafish models that are generating new insights into human deafness and vestibular disorders.
Collapse
Affiliation(s)
- S Baxendale
- University of Sheffield, Sheffield, United Kingdom
| | | |
Collapse
|
8
|
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.
Collapse
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
| |
Collapse
|
9
|
Goodrich LV. Early Development of the Spiral Ganglion. THE PRIMARY AUDITORY NEURONS OF THE MAMMALIAN COCHLEA 2016. [DOI: 10.1007/978-1-4939-3031-9_2] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
10
|
Hernández-Bejarano M, Gestri G, Spawls L, Nieto-López F, Picker A, Tada M, Brand M, Bovolenta P, Wilson SW, Cavodeassi F. Opposing Shh and Fgf signals initiate nasotemporal patterning of the zebrafish retina. Development 2015; 142:3933-42. [PMID: 26428010 PMCID: PMC4712879 DOI: 10.1242/dev.125120] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 09/21/2015] [Indexed: 01/12/2023]
Abstract
The earliest known determinants of retinal nasotemporal identity are the transcriptional regulators Foxg1, which is expressed in the prospective nasal optic vesicle, and Foxd1, which is expressed in the prospective temporal optic vesicle. Previous work has shown that, in zebrafish, Fgf signals from the dorsal forebrain and olfactory primordia are required to specify nasal identity in the dorsal, prospective nasal, optic vesicle. Here, we show that Hh signalling from the ventral forebrain is required for specification of temporal identity in the ventral optic vesicle and is sufficient to induce temporal character when activated in the prospective nasal retina. Consequently, the evaginating optic vesicles become partitioned into prospective nasal and temporal domains by the opposing actions of Fgfs and Shh emanating from dorsal and ventral domains of the forebrain primordium. In absence of Fgf activity, foxd1 expression is established irrespective of levels of Hh signalling, indicating that the role of Shh in promoting foxd1 expression is only required in the presence of Fgf activity. Once the spatially complementary expression of foxd1 and foxg1 is established, the boundary between expression domains is maintained by mutual repression between Foxd1 and Foxg1. Summary: In the fish eye, Hh signalling from the ventral forebrain regulates spatial identity in the retina by promoting foxd1 expression. This role is required only in the presence of Fgf activity.
Collapse
Affiliation(s)
| | - Gaia Gestri
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1 6BT, UK
| | - Lana Spawls
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1 6BT, UK
| | - Francisco Nieto-López
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), C/Nicolás Cabrera 1, 28049, Madrid, Spain
| | - Alexander Picker
- Center of Regenerative Therapies Dresden (CRTD), Biotechnology Center, Dresden University of Technology, 01062 Dresden, Germany
| | - Masazumi Tada
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1 6BT, UK
| | - Michael Brand
- Center of Regenerative Therapies Dresden (CRTD), Biotechnology Center, Dresden University of Technology, 01062 Dresden, Germany
| | - Paola Bovolenta
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), C/Nicolás Cabrera 1, 28049, Madrid, Spain CIBER de Enfermedades Raras (CIBERER), C/Nicolás Cabrera 1, 28049, Madrid, Spain
| | - Stephen W Wilson
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1 6BT, UK
| | - Florencia Cavodeassi
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), C/Nicolás Cabrera 1, 28049, Madrid, Spain CIBER de Enfermedades Raras (CIBERER), C/Nicolás Cabrera 1, 28049, Madrid, Spain
| |
Collapse
|
11
|
Monroe JD, Rajadinakaran G, Smith ME. Sensory hair cell death and regeneration in fishes. Front Cell Neurosci 2015; 9:131. [PMID: 25954154 PMCID: PMC4404912 DOI: 10.3389/fncel.2015.00131] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Accepted: 03/21/2015] [Indexed: 01/31/2023] Open
Abstract
Sensory hair cells are specialized mechanotransductive receptors required for hearing and vestibular function. Loss of hair cells in humans and other mammals is permanent and causes reduced hearing and balance. In the early 1980’s, it was shown that hair cells continue to be added to the inner ear sensory epithelia in cartilaginous and bony fishes. Soon thereafter, hair cell regeneration was documented in the chick cochlea following acoustic trauma. Since then, research using chick and other avian models has led to great insights into hair cell death and regeneration. However, with the rise of the zebrafish as a model organism for studying disease and developmental processes, there has been an increased interest in studying sensory hair cell death and regeneration in its lateral line and inner ears. Advances derived from studies in zebrafish and other fish species include understanding the effect of ototoxins on hair cells and finding otoprotectants to mitigate ototoxin damage, the role of cellular proliferation vs. direct transdifferentiation during hair cell regeneration, and elucidating cellular pathways involved in the regeneration process. This review will summarize research on hair cell death and regeneration using fish models, indicate the potential strengths and weaknesses of these models, and discuss several emerging areas of future studies.
Collapse
Affiliation(s)
- Jerry D Monroe
- Department of Biology, Western Kentucky University Bowling Green, KY, USA
| | - Gopinath Rajadinakaran
- Department of Genetics and Genome Sciences, University of Connecticut Health Center Farmington, CT, USA
| | - Michael E Smith
- Department of Biology, Western Kentucky University Bowling Green, KY, USA
| |
Collapse
|
12
|
Forristall CA, Stellabotte F, Castillo A, Collazo A. Embryological manipulations in the developing Xenopus inner ear reveal an intrinsic role for Wnt signaling in dorsal-ventral patterning. Dev Dyn 2014; 243:1262-74. [PMID: 24500889 DOI: 10.1002/dvdy.24116] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2013] [Revised: 01/02/2014] [Accepted: 01/17/2014] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND The inner ear develops from an ectodermal thickening known as the otic placode into a complex structure that is asymmetrical along both the anterior-posterior (A-P) and dorsal-ventral (D-V) axes. Embryological manipulations in Xenopus allow us to test regenerative potential along specific axes and timing of axis determination. We explore the role of Wnt signaling with gain and loss of function experiments. RESULTS In contrast to A or P half ablations, D or V half ablations almost never result in mirror duplications or normal ears. Instead there is a loss of structures, especially those associated with the ablated region. Rotation experiments inverting the D-V axis reveal that it is determined by stage 24-26 which is just before expression of the dorsal otic marker Wnt3a. Conditional blocking of canonical Wnt signaling results in reductions in the number of sensory organs and semicircular canals which could be placed in one of three categories, the most common phenotypes being similar to those seen after dorsal ablations. CONCLUSIONS There is less regenerative potential along the D-V axis. Wnt3a protein alone is sufficient to rescue the severe loss of inner ear structures resulting from dorsal but not ventral half ablations.
Collapse
|
13
|
Sensational placodes: neurogenesis in the otic and olfactory systems. Dev Biol 2014; 389:50-67. [PMID: 24508480 PMCID: PMC3988839 DOI: 10.1016/j.ydbio.2014.01.023] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 01/27/2014] [Accepted: 01/28/2014] [Indexed: 11/22/2022]
Abstract
For both the intricate morphogenetic layout of the sensory cells in the ear and the elegantly radial arrangement of the sensory neurons in the nose, numerous signaling molecules and genetic determinants are required in concert to generate these specialized neuronal populations that help connect us to our environment. In this review, we outline many of the proteins and pathways that play essential roles in the differentiation of otic and olfactory neurons and their integration into their non-neuronal support structures. In both cases, well-known signaling pathways together with region-specific factors transform thickened ectodermal placodes into complex sense organs containing numerous, diverse neuronal subtypes. Olfactory and otic placodes, in combination with migratory neural crest stem cells, generate highly specialized subtypes of neuronal cells that sense sound, position and movement in space, odors and pheromones throughout our lives.
Collapse
|
14
|
Adolphe C, Nieuwenhuis E, Villani R, Li ZJ, Kaur P, Hui CC, Wainwright BJ. Patched 1 and patched 2 redundancy has a key role in regulating epidermal differentiation. J Invest Dermatol 2014; 134:1981-1990. [PMID: 24492243 DOI: 10.1038/jid.2014.63] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Revised: 12/05/2013] [Accepted: 12/30/2013] [Indexed: 11/09/2022]
Abstract
The Patched 1 (Ptch1) receptor has a pivotal role in inhibiting the activity of the Hedgehog (Hh) pathway and is therefore critical in preventing the onset of many human developmental disorders and tumor formation. However, the functional role of the mammalian Ptch2 paralogue remains elusive, particularly the extent to which it contributes to regulating the spatial and temporal activity of Hh signaling. Here we demonstrate in three independent mouse models of epidermal development that in vivo ablation of both Ptch receptors results in a more severe phenotype than loss of Ptch1 alone. Our studies indicate that concomitant loss of Ptch1 and Ptch2 activity inhibits epidermal lineage specification and differentiation. These results reveal that repression of Hh signaling through a dynamic Ptch regulatory network is a crucial event in lineage fate determination in the skin. In general, our findings implicate Ptch receptor redundancy as a key issue in elucidating the cellular origin of Hh-induced tumors.
Collapse
Affiliation(s)
- Christelle Adolphe
- Division of Molecular Genetics and Development, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Erica Nieuwenhuis
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Rehan Villani
- Division of Molecular Genetics and Development, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Zhu Juan Li
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Pritinder Kaur
- Epithelial Stem Cell Biology Laboratory, Research Division, Peter MacCallum Cancer Center, Melbourne, Victoria, Australia
| | - Chi-Chung Hui
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.
| | - Brandon J Wainwright
- Division of Molecular Genetics and Development, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia.
| |
Collapse
|
15
|
Geng FS, Abbas L, Baxendale S, Holdsworth CJ, Swanson AG, Slanchev K, Hammerschmidt M, Topczewski J, Whitfield TT. Semicircular canal morphogenesis in the zebrafish inner ear requires the function of gpr126 (lauscher), an adhesion class G protein-coupled receptor gene. Development 2013; 140:4362-74. [PMID: 24067352 PMCID: PMC4007713 DOI: 10.1242/dev.098061] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Morphogenesis of the semicircular canal ducts in the vertebrate inner ear is a dramatic example of epithelial remodelling in the embryo, and failure of normal canal development results in vestibular dysfunction. In zebrafish and Xenopus, semicircular canal ducts develop when projections of epithelium, driven by extracellular matrix production, push into the otic vesicle and fuse to form pillars. We show that in the zebrafish, extracellular matrix gene expression is high during projection outgrowth and then rapidly downregulated after fusion. Enzymatic disruption of hyaluronan in the projections leads to their collapse and a failure to form pillars: as a result, the ears swell. We have cloned a zebrafish mutant, lauscher (lau), identified by its swollen ear phenotype. The primary defect in the ear is abnormal projection outgrowth and a failure of fusion to form the semicircular canal pillars. Otic expression of extracellular matrix components is highly disrupted: several genes fail to become downregulated and remain expressed at abnormally high levels into late larval stages. The lau mutations disrupt gpr126, an adhesion class G protein-coupled receptor gene. Expression of gpr126 is similar to that of sox10, an ear and neural crest marker, and is partially dependent on sox10 activity. Fusion of canal projections and downregulation of otic versican expression in a hypomorphic lau allele can be restored by cAMP agonists. We propose that Gpr126 acts through a cAMP-mediated pathway to control the outgrowth and adhesion of canal projections in the zebrafish ear via the regulation of extracellular matrix gene expression.
Collapse
Affiliation(s)
- Fan-Suo Geng
- MRC Centre for Developmental and Biomedical Genetics and Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Abstract
The inner ear is a structurally complex vertebrate organ built to encode sound, motion, and orientation in space. Given its complexity, it is not surprising that inner ear dysfunction is a relatively common consequence of human genetic mutation. Studies in model organisms suggest that many genes currently known to be associated with human hearing impairment are active during embryogenesis. Hence, the study of inner ear development provides a rich context for understanding the functions of genes implicated in hearing loss. This chapter focuses on molecular mechanisms of inner ear development derived from studies of model organisms.
Collapse
Affiliation(s)
- Doris K Wu
- National Institute on Deafness and Other Communication Disorders, Rockville, Maryland 20850, USA.
| | | |
Collapse
|
17
|
McCarroll MN, Lewis ZR, Culbertson MD, Martin BL, Kimelman D, Nechiporuk AV. Graded levels of Pax2a and Pax8 regulate cell differentiation during sensory placode formation. Development 2012; 139:2740-50. [PMID: 22745314 PMCID: PMC3392703 DOI: 10.1242/dev.076075] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/10/2012] [Indexed: 01/11/2023]
Abstract
Pax gene haploinsufficiency causes a variety of congenital defects. Renal-coloboma syndrome, resulting from mutations in Pax2, is characterized by kidney hypoplasia, optic nerve malformation, and hearing loss. Although this underscores the importance of Pax gene dosage in normal development, how differential levels of these transcriptional regulators affect cell differentiation and tissue morphogenesis is still poorly understood. We show that differential levels of zebrafish Pax2a and Pax8 modulate commitment and behavior in cells that eventually contribute to the otic vesicle and epibranchial placodes. Initially, a subset of epibranchial placode precursors lie lateral to otic precursors within a single Pax2a/8-positive domain; these cells subsequently move to segregate into distinct placodes. Using lineage-tracing and ablation analyses, we show that cells in the Pax2a/8+ domain become biased towards certain fates at the beginning of somitogenesis. Experiments involving either Pax2a overexpression or partial, combinatorial Pax2a and Pax8 loss of function reveal that high levels of Pax favor otic differentiation whereas low levels increase cell numbers in epibranchial ganglia. In addition, the Fgf and Wnt signaling pathways control Pax2a expression: Fgf is necessary to induce Pax2a, whereas Wnt instructs the high levels of Pax2a that favor otic differentiation. Our studies reveal the importance of Pax levels during sensory placode formation and provide a mechanism by which these levels are controlled.
Collapse
Affiliation(s)
- Matthew N. McCarroll
- Department of Cell and Developmental Biology, Oregon Health & Science University, Portland, Oregon, 97239, USA
| | - Zachary R. Lewis
- Department of Cell and Developmental Biology, Oregon Health & Science University, Portland, Oregon, 97239, USA
| | - Maya Deza Culbertson
- Department of Cell and Developmental Biology, Oregon Health & Science University, Portland, Oregon, 97239, USA
| | | | - David Kimelman
- Department of Biochemistry, Box 357350, Seattle, Washington 98195, USA
| | - Alex V. Nechiporuk
- Department of Cell and Developmental Biology, Oregon Health & Science University, Portland, Oregon, 97239, USA
| |
Collapse
|
18
|
Groves AK, Fekete DM. Shaping sound in space: the regulation of inner ear patterning. Development 2012; 139:245-57. [PMID: 22186725 DOI: 10.1242/dev.067074] [Citation(s) in RCA: 176] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The inner ear is one of the most morphologically elaborate tissues in vertebrates, containing a group of mechanosensitive sensory organs that mediate hearing and balance. These organs are arranged precisely in space and contain intricately patterned sensory epithelia. Here, we review recent studies of inner ear development and patterning which reveal that multiple stages of ear development - ranging from its early induction from the embryonic ectoderm to the establishment of the three cardinal axes and the fine-grained arrangement of sensory cells - are orchestrated by gradients of signaling molecules.
Collapse
Affiliation(s)
- Andrew K Groves
- Departments of Neuroscience and Molecular and Human Genetics, BCM295, Baylor College of Medicine, Houston, TX 77030, USA.
| | | |
Collapse
|
19
|
Hammond KL, Whitfield TT. Fgf and Hh signalling act on a symmetrical pre-pattern to specify anterior and posterior identity in the zebrafish otic placode and vesicle. Development 2011; 138:3977-87. [PMID: 21831919 PMCID: PMC3160093 DOI: 10.1242/dev.066639] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/01/2011] [Indexed: 11/20/2022]
Abstract
Specification of the otic anteroposterior axis is one of the earliest patterning events during inner ear development. In zebrafish, Hedgehog signalling is necessary and sufficient to specify posterior otic identity between the 10 somite (otic placode) and 20 somite (early otic vesicle) stages. We now show that Fgf signalling is both necessary and sufficient for anterior otic specification during a similar period, a function that is completely separable from its earlier role in otic placode induction. In lia(-/-) (fgf3(-/-)) mutants, anterior otic character is reduced, but not lost altogether. Blocking all Fgf signalling at 10-20 somites, however, using the pan-Fgf inhibitor SU5402, results in the loss of anterior otic structures and a mirror image duplication of posterior regions. Conversely, overexpression of fgf3 during a similar period, using a heat-shock inducible transgenic line, results in the loss of posterior otic structures and a duplication of anterior domains. These phenotypes are opposite to those observed when Hedgehog signalling is altered. Loss of both Fgf and Hedgehog function between 10 and 20 somites results in symmetrical otic vesicles with neither anterior nor posterior identity, which, nevertheless, retain defined poles at the anterior and posterior ends of the ear. These data suggest that Fgf and Hedgehog act on a symmetrical otic pre-pattern to specify anterior and posterior otic identity, respectively. Each signalling pathway has instructive activity: neither acts simply to repress activity of the other, and, together, they appear to be key players in the specification of anteroposterior asymmetries in the zebrafish ear.
Collapse
Affiliation(s)
- Katherine L. Hammond
- MRC Centre for Developmental and Biomedical Genetics and Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK
| | - Tanya T. Whitfield
- MRC Centre for Developmental and Biomedical Genetics and Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK
| |
Collapse
|
20
|
Evron T, Philipp M, Lu J, Meloni AR, Burkhalter M, Chen W, Caron MG. Growth Arrest Specific 8 (Gas8) and G protein-coupled receptor kinase 2 (GRK2) cooperate in the control of Smoothened signaling. J Biol Chem 2011; 286:27676-86. [PMID: 21659505 DOI: 10.1074/jbc.m111.234666] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The G protein-coupled receptor (GPCR)-like molecule Smoothened (Smo) undergoes dynamic intracellular trafficking modulated by the microtubule associated kinase GRK2 and recruitment of β-arrestin. Of this trafficking, especially the translocation of Smo into primary cilia and back to the cytoplasm is essential for the activation of Hedgehog (Hh) signaling in vertebrates. The complete mechanism of this bidirectional transport, however, is not completely understood. Here we demonstrate that Growth Arrest Specific 8 (Gas8), a microtubule associated subunit of the Dynein Regulatory Complex (DRC), interacts with Smo to modulate this process. Gas8 knockdown in ciliated cells reduces Smo signaling activity and ciliary localization whereas overexpression stimulates Smo activity in a GRK2-dependent manner. The C terminus of Gas8 is important for both Gas8 interaction with Smo and facilitating Smo signaling. In zebrafish, knocking down Gas8 results in attenuated Hh transcriptional responses and impaired early muscle development. These effects can be reversed by the co-injection of Gas8 mRNA or by constitutive activation of the downstream Gli transcription factors. Furthermore, Gas8 and GRK2 display a synergistic effect on zebrafish early muscle development and some effects of GRK2 knockdown can be rescued by Gas8 mRNA. Interestingly, Gas8 does not interfere with cilia assembly, as the primary cilia architecture is unchanged upon Gas8 knock down or heterologous expression. This is in contrast to cells stably expressing both GRK2 and Smo, in which cilia are significantly elongated. These results identify Gas8 as a positive regulator of Hh signaling that cooperates with GRK2 to control Smo signaling.
Collapse
Affiliation(s)
- Tama Evron
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
| | | | | | | | | | | | | |
Collapse
|
21
|
Radosevic M, Robert-Moreno À, Coolen M, Bally-Cuif L, Alsina B. Her9 represses neurogenic fate downstream of Tbx1 and retinoic acid signaling in the inner ear. Development 2011; 138:397-408. [DOI: 10.1242/dev.056093] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Proper spatial control of neurogenesis in the inner ear ensures the precise innervation of mechanotransducing cells and the propagation of auditory and equilibrium stimuli to the brain. Members of the Hairy and enhancer of split (Hes) gene family regulate neurogenesis by inhibiting neuronal differentiation and maintaining neural stem cell pools in non-neurogenic zones. Remarkably, their role in the spatial control of neurogenesis in the ear is unknown. In this study, we identify her9, a zebrafish ortholog of Hes1, as a key gene in regulating otic neurogenesis through the definition of the posterolateral non-neurogenic field. First, her9 emerges as a novel otic patterning gene that represses proneural function and regulates the extent of the neurogenic domain. Second, we place Her9 downstream of Tbx1, linking these two families of transcription factors for the first time in the inner ear and suggesting that the reported role of Tbx1 in repressing neurogenesis is in part mediated by the bHLH transcriptional repressor Her9. Third, we have identified retinoic acid (RA) signaling as the upstream patterning signal of otic posterolateral genes such as tbx1 and her9. Finally, we show that at the level of the cranial otic field, opposing RA and Hedgehog signaling position the boundary between the neurogenic and non-neurogenic compartments. These findings permit modeling of the complex genetic cascade that underlies neural patterning of the otic vesicle.
Collapse
Affiliation(s)
- Marija Radosevic
- Developmental Biology Laboratory, Dept. Ciències Experimentals i de la Salut, Universitat Pompeu Fabra-Parc de Recerca Biomèdica de Barcelona, Dr Aiguader 88, 08003 Barcelona, Spain
| | - Àlex Robert-Moreno
- Developmental Biology Laboratory, Dept. Ciències Experimentals i de la Salut, Universitat Pompeu Fabra-Parc de Recerca Biomèdica de Barcelona, Dr Aiguader 88, 08003 Barcelona, Spain
| | - Marion Coolen
- Laboratory of Neurobiology and Development, Institute of Neurobiology Alfred Fessard, CNRS, Avenue de Terrasse, 91198 cedex, Gif-sur-Yvette, France
| | - Laure Bally-Cuif
- Laboratory of Neurobiology and Development, Institute of Neurobiology Alfred Fessard, CNRS, Avenue de Terrasse, 91198 cedex, Gif-sur-Yvette, France
| | - Berta Alsina
- Developmental Biology Laboratory, Dept. Ciències Experimentals i de la Salut, Universitat Pompeu Fabra-Parc de Recerca Biomèdica de Barcelona, Dr Aiguader 88, 08003 Barcelona, Spain
| |
Collapse
|
22
|
Transient retinoic acid signaling confers anterior-posterior polarity to the inner ear. Proc Natl Acad Sci U S A 2010; 108:161-6. [PMID: 21173260 DOI: 10.1073/pnas.1010547108] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Vertebrate hearing and balance are based in complex asymmetries of inner ear structure. Here, we identify retinoic acid (RA) as an extrinsic signal that acts directly on the ear rudiment to affect its compartmentalization along the anterior-posterior axis. A rostrocaudal wave of RA activity, generated by tissues surrounding the nascent ear, induces distinct responses from anterior and posterior halves of the inner ear rudiment. Prolonged response to RA by posterior otic tissue correlates with Tbx1 transcription and formation of mostly nonsensory inner ear structures. By contrast, anterior otic tissue displays only a brief response to RA and forms neuronal elements and most sensory structures of the inner ear.
Collapse
|
23
|
BMP/SMAD signaling regulates the cell behaviors that drive the initial dorsal-specific regional morphogenesis of the otocyst. Dev Biol 2010; 347:369-81. [PMID: 20837004 DOI: 10.1016/j.ydbio.2010.09.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 09/02/2010] [Accepted: 09/02/2010] [Indexed: 12/20/2022]
Abstract
During development of the otocyst, regional morphogenesis establishes a dorsal vestibular chamber and a ventral auditory chamber, which collectively constitute the membranous labyrinth of the inner ear. We identified the earliest morphogenetic event heralding the formation of the vestibular chamber, a rapid thinning and expansion of the dorsolateral wall of the otocyst, and showed that this process is generated by changes in otocyst cell shape from columnar to squamous, as opposed to changes in other cell behaviors, such as localized changes in cell proliferation or cell death. Moreover, we showed that thinning and expansion of the dorsolateral otocyst is regulated by BMP/SMAD signaling, which is both sufficient and necessary for localized thinning and expansion. Finally, we showed that BMP/SMAD signaling causes fragmentation of E-cadherin in the dorsolateral otocyst, occurring concomitantly with cell shape change, suggesting that BMP/SMAD signaling regulates cell-cell adhesion during the initial morphogenesis of the otocyst epithelium. Collectively, our results show that BMP signaling via SMADs regulates the cell behaviors that drive the initial dorsal-specific morphogenesis of the otocyst, providing new information about how regional morphogenesis of a complex organ rudiment, the developing membranous labyrinth, is initiated.
Collapse
|