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Ou H, Simon JA, Rubel EW, Raible DW. Screening for chemicals that affect hair cell death and survival in the zebrafish lateral line. Hear Res 2012; 288:58-66. [PMID: 22310494 PMCID: PMC3371178 DOI: 10.1016/j.heares.2012.01.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Revised: 01/05/2012] [Accepted: 01/23/2012] [Indexed: 02/09/2023]
Abstract
The zebrafish lateral line is an efficient model system for the evaluation of chemicals that protect and damage hair cells. Located on the surface of the body, lateral line hair cells are accessible for manipulation and visualization. The zebrafish lateral line system allows rapid screens of large chemical libraries, as well as subsequent thorough evaluation of interesting compounds. In this review, we focus on the results of our previous screens and the evolving methodology of our screens for chemicals that protect hair cells, and chemicals that damage hair cells using the zebrafish lateral line.
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Pavan WJ, Raible DW. Specification of neural crest into sensory neuron and melanocyte lineages. Dev Biol 2012; 366:55-63. [PMID: 22465373 PMCID: PMC3351495 DOI: 10.1016/j.ydbio.2012.02.038] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 02/29/2012] [Indexed: 11/27/2022]
Abstract
Elucidating the mechanisms by which multipotent cells differentiate into distinct lineages is a common theme underlying developmental biology investigations. Progress has been made in understanding some of the essential factors and pathways involved in the specification of different lineages from the neural crest. These include gene regulatory networks involving transcription factor hierarchies and input from signaling pathways mediated from environmental cues. In this review, we examine the mechanisms for two lineages that are derived from the neural crest, peripheral sensory neurons and melanocytes. Insights into the specification of these cell types may reveal common themes in the specification processes that occur throughout development.
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Suli A, Watson GM, Rubel EW, Raible DW. Rheotaxis in larval zebrafish is mediated by lateral line mechanosensory hair cells. PLoS One 2012; 7:e29727. [PMID: 22359538 PMCID: PMC3281009 DOI: 10.1371/journal.pone.0029727] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 12/02/2011] [Indexed: 11/19/2022] Open
Abstract
The lateral line sensory system, found in fish and amphibians, is used in prey detection, predator avoidance and schooling behavior. This system includes cell clusters, called superficial neuromasts, located on the surface of head and trunk of developing larvae. Mechanosensory hair cells in the center of each neuromast respond to disturbances in the water and convey information to the brain via the lateral line ganglia. The convenient location of mechanosensory hair cells on the body surface has made the lateral line a valuable system in which to study hair cell damage and regeneration. One way to measure hair cell survival and recovery is to assay behaviors that depend on their function. We built a system in which orientation against constant water flow, positive rheotaxis, can be quantitatively assessed. We found that zebrafish larvae perform positive rheotaxis and that, similar to adult fish, larvae use both visual and lateral line input to perform this behavior. Disruption or damage of hair cells in the absence of vision leads to a marked decrease in rheotaxis that recovers upon hair cell repair or regeneration.
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Prendergast A, Linbo TH, Swarts T, Ungos JM, McGraw HF, Krispin S, Weinstein BM, Raible DW. The metalloproteinase inhibitor Reck is essential for zebrafish DRG development. Development 2012; 139:1141-52. [PMID: 22296847 DOI: 10.1242/dev.072439] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The neural crest is a migratory, multipotent cell lineage that contributes to myriad tissues, including sensory neurons and glia of the dorsal root ganglia (DRG). To identify genes affecting cell fate specification in neural crest, we performed a forward genetic screen for mutations causing DRG deficiencies in zebrafish. This screen yielded a mutant lacking all DRG, which we named sensory deprived (sdp). We identified a total of four alleles of sdp, all of which possess lesions in the gene coding for reversion-inducing cysteine-rich protein containing Kazal motifs (Reck). Reck is an inhibitor of metalloproteinases previously shown to regulate cell motility. We found reck function to be both necessary for DRG formation and sufficient to rescue the sdp phenotype. reck is expressed in neural crest cells and is required in a cell-autonomous fashion for appropriate sensory neuron formation. In the absence of reck function, sensory neuron precursors fail to migrate to the position of the DRG, suggesting that this molecule is crucial for proper migration and differentiation.
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McGraw HF, Drerup CM, Culbertson MD, Linbo T, Raible DW, Nechiporuk AV. Lef1 is required for progenitor cell identity in the zebrafish lateral line primordium. Development 2011; 138:3921-30. [PMID: 21862556 DOI: 10.1242/dev.062554] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The zebrafish posterior lateral line (pLL) is a sensory system that comprises clusters of mechanosensory organs called neuromasts (NMs) that are stereotypically positioned along the surface of the trunk. The NMs are deposited by a migrating pLL primordium, which is organized into polarized rosettes (proto-NMs). During migration, mature proto-NMs are deposited from the trailing part of the primordium, while progenitor cells in the leading part give rise to new proto-NMs. Wnt signaling is active in the leading zone of the primordium and global Wnt inactivation leads to dramatic disorganization of the primordium and a loss of proto-NM formation. However, the exact cellular events that are regulated by the Wnt pathway are not known. We identified a mutant strain, lef1(nl2), that contains a lesion in the Wnt effector gene lef1. lef1(nl2) mutants lack posterior NMs and live imaging reveals that rosette renewal fails during later stages of migration. Surprisingly, the overall primordium patterning, as assayed by the expression of various markers, appears unaltered in lef1(nl2) mutants. Lineage tracing and mosaic analyses revealed that the leading cells (presumptive progenitors) move out of the primordium and are incorporated into NMs; this results in a decrease in the number of proliferating progenitor cells and eventual primordium disorganization. We concluded that Lef1 function is not required for initial primordium organization or migration, but is necessary for proto-NM renewal during later stages of pLL formation. These findings revealed a novel role for the Wnt signaling pathway during mechanosensory organ formation in zebrafish.
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Ghysen A, Dambly-Chaudière C, Raible DW. Patterning the nervous system through development and evolution. THE INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 2010; 54:S1-S14. [PMID: 21136381 DOI: 10.1387/ijdb.103182ag] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We report presentations and discussions at a meeting held in May 2010 in the small village of Minerve, in the south of France. The meeting was devoted mostly but not exclusively to patterning in the nervous system, with an emphasis on two model organisms, Drosophila Melanogaster and Danio rerio. Among the major issues presented were fear and its neuroanatomy, life in darkness, patterning of sensory systems, as well as fundamental issues of neural connectivity, including the role of lineage in neural development. Talks on large-scale patterning and re-patterning, and on the mouse as a third model system, concluded the meeting.
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Coffin AB, Ou H, Owens KN, Santos F, Simon JA, Rubel EW, Raible DW. Chemical screening for hair cell loss and protection in the zebrafish lateral line. Zebrafish 2010; 7:3-11. [PMID: 20192852 DOI: 10.1089/zeb.2009.0639] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
In humans, most hearing loss results from death of hair cells, the mechanosensory receptors of the inner ear. Two goals of current hearing research are to protect hair cells from degeneration and to regenerate new hair cells, replacing those that are lost due to aging, disease, or environmental challenges. One limitation of research in the auditory field has been the relative inaccessibility of the mechanosensory systems in the inner ear. Zebrafish possess hair cells in both their inner ear and their lateral line system that are morphologically and functionally similar to human hair cells. The external location of the mechanosensory hair cells in the lateral line and the ease of in vivo labeling and imaging make the zebrafish lateral line a unique system for the study of hair cell toxicity, protection, and regeneration. This review focuses on the lateral line system as a model for understanding loss and protection of mechanosensory hair cells. We discuss chemical screens to identify compounds that induce hair cell loss and others that protect hair cells from known toxins and the potential application of these screens to human medicine.
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Curran K, Lister JA, Kunkel GR, Prendergast A, Parichy DM, Raible DW. Interplay between Foxd3 and Mitf regulates cell fate plasticity in the zebrafish neural crest. Dev Biol 2010; 344:107-18. [PMID: 20460180 DOI: 10.1016/j.ydbio.2010.04.023] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Revised: 04/21/2010] [Accepted: 04/22/2010] [Indexed: 01/13/2023]
Abstract
Pigment cells of the zebrafish, Danio rerio, offer an exceptionally tractable system for studying the genetic and cellular bases of cell fate decisions. In the zebrafish, neural crest cells generate three types of pigment cells during embryogenesis: yellow xanthophores, iridescent iridophores and black melanophores. In this study, we present evidence for a model whereby melanophores and iridophores descend from a common precursor whose fate is regulated by an interplay between the transcription factors Mitf and Foxd3. Loss of mitfa, a key regulator of melanophore development, resulted in supernumerary ectopic iridophores while loss of foxd3, a mitfa repressor, resulted in fewer iridophores. Double mutants showed a restoration of iridophores, suggesting that one of Foxd3's roles is to suppress mitfa to promote iridophore development. Foxd3 co-localized with pnp4a, a novel marker of early iridophore development, and was necessary for its expression. A considerable overlap was found between iridoblast and melanoblast markers but not xanthoblast markers, which resolved as cells began to differentiate. Cell lineage analyses using the photoconvertible marker, EosFP, revealed that both melanophores and iridophores develop from a mitfa+ precursor. Taken together, our data reveal a Foxd3/mitfa transcriptional switch that governs whether a bi-potent pigment precursor will attain either an iridophore or a melanophore fate.
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59
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Eames BF, Singer A, Smith GA, Wood ZA, Yan YL, He X, Polizzi SJ, Catchen JM, Rodriguez-Mari A, Linbo T, Raible DW, Postlethwait JH. UDP xylose synthase 1 is required for morphogenesis and histogenesis of the craniofacial skeleton. Dev Biol 2010; 341:400-15. [PMID: 20226781 DOI: 10.1016/j.ydbio.2010.02.035] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2009] [Revised: 02/13/2010] [Accepted: 02/24/2010] [Indexed: 11/20/2022]
Abstract
UDP-xylose synthase (Uxs1) is strongly conserved from bacteria to humans, but because no mutation has been studied in any animal, we do not understand its roles in development. Furthermore, no crystal structure has been published. Uxs1 synthesizes UDP-xylose, which initiates glycosaminoglycan attachment to a protein core during proteoglycan formation. Crystal structure and biochemical analyses revealed that an R233H substitution mutation in zebrafish uxs1 alters an arginine buried in the dimer interface, thereby destabilizing and, as enzyme assays show, inactivating the enzyme. Homozygous uxs1 mutants lack Alcian blue-positive, proteoglycan-rich extracellular matrix in cartilages of the neurocranium, pharyngeal arches, and pectoral girdle. Transcripts for uxs1 localize to skeletal domains at hatching. GFP-labeled neural crest cells revealed defective organization and morphogenesis of chondrocytes, perichondrium, and bone in uxs1 mutants. Proteoglycans were dramatically reduced and defectively localized in uxs1 mutants. Although col2a1a transcripts over-accumulated in uxs1 mutants, diminished quantities of Col2a1 protein suggested a role for proteoglycans in collagen secretion or localization. Expression of col10a1, indian hedgehog, and patched was disrupted in mutants, reflecting improper chondrocyte/perichondrium signaling. Up-regulation of sox9a, sox9b, and runx2b in mutants suggested a molecular mechanism consistent with a role for proteoglycans in regulating skeletal cell fate. Together, our data reveal time-dependent changes to gene expression in uxs1 mutants that support a signaling role for proteoglycans during at least two distinct phases of skeletal development. These investigations are the first to examine the effect of mutation on the structure and function of Uxs1 protein in any vertebrate embryos, and reveal that Uxs1 activity is essential for the production and organization of skeletal extracellular matrix, with consequent effects on cartilage, perichondral, and bone morphogenesis.
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60
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Ou HC, Santos F, Raible DW, Simon JA, Rubel EW. Drug screening for hearing loss: using the zebrafish lateral line to screen for drugs that prevent and cause hearing loss. Drug Discov Today 2010; 15:265-71. [PMID: 20096805 DOI: 10.1016/j.drudis.2010.01.001] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2009] [Revised: 12/01/2009] [Accepted: 01/06/2010] [Indexed: 12/17/2022]
Abstract
Several animal models have been used for the study of mechanosensory hair cells and hearing loss. Because of the difficulty of tissue acquisition and large animal size, these traditional models are impractical for high-throughput screening. The zebrafish has emerged as a powerful animal model for screening drugs that cause and prevent hair cell death. The unique characteristics of the zebrafish enable rapid in vivo imaging of hair cells and hair cell death. We have used this model to screen for and identify multiple drugs that protect hair cells from aminoglycoside-induced death. The identification of multiple drugs and drug-like compounds that inhibit multiple hair cell death pathways might enable the development of protective cocktails to achieve complete hair cell protection.
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Curran K, Raible DW, Lister JA. Foxd3 controls melanophore specification in the zebrafish neural crest by regulation of Mitf. Dev Biol 2009; 332:408-17. [PMID: 19527705 DOI: 10.1016/j.ydbio.2009.06.010] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 06/04/2009] [Accepted: 06/08/2009] [Indexed: 12/25/2022]
Abstract
We describe a mechanistic model whereby Foxd3, a forkhead transcription factor, prevents neural crest-derived precursors from acquiring a melanophore fate. Foxd3 regulates this fate choice by repressing the mitfa promoter in a subset of neural crest cells. mitfa is only expressed in a Foxd3-negative subset of neural crest cells, and foxd3 mutants show an increase in the spatial domain of mitfa expression, thereby suggesting that Foxd3 limits the mitfa domain. Furthermore, foxd3:gfp transgenic zebrafish reveal foxd3 expression in xanthophore precursors and iridophores, but not in terminally differentiated melanophores. Luciferase experiments and embryo mRNA injections indicate Foxd3 acts directly on the mitfa promoter to negatively regulate mitfa expression. Taken together, our data suggests the presence of Foxd3 in a subset of precursors leads to mitfa repression and suppression of melanophore fate. MITF, the human mitfa ortholog, has recently been described as an oncogene and implicated in various forms of melanoma. Understanding the mechanisms that regulate mitfa and melanophore development could prove informative in the treatment and prevention of these human diseases.
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62
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Cooper CD, Linbo TH, Raible DW. Kit and foxd3 genetically interact to regulate melanophore survival in zebrafish. Dev Dyn 2009; 238:875-86. [PMID: 19301400 DOI: 10.1002/dvdy.21910] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
We have investigated the role of foxd3 activity in conjunction with signaling by the kit tyrosine kinase receptor in zebrafish black pigment cell (melanophore) development. As loss-of-function of these molecules individually has distinct effects on melanophore number, we have examined the phenotype of double mutants. Individuals with a null mutation in kit have fewer melanophores than wild-type, with cells lost through death. When kit mutants are injected with foxd3 antisense morpholino oligonucleotides or crossed with a foxd3 zebrafish mutant, they have more melanophores than their uninjected or foxd3+ counterparts. Examination of foxd3 loss-of-function in two additional kit mutants that differentially alter kit-dependent migration and survival indicates a change in melanophore number in survival mutants only. Consistently, TUNEL (terminal deoxynucleotidyl transferase-mediated deoxyuridinetriphosphate nick end-labeling) analysis confirms a partial rescue of melanophores from cell death. Ectopic expression of foxd3 indicates that foxd3 promotes early melanophore death only when kit is inactive. Taken together, these data suggest a kit-dependent role for foxd3 in the regulation of melanophore survival.
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Coffin AB, Reinhart KE, Owens KN, Raible DW, Rubel EW. Extracellular divalent cations modulate aminoglycoside-induced hair cell death in the zebrafish lateral line. Hear Res 2009; 253:42-51. [PMID: 19285547 DOI: 10.1016/j.heares.2009.03.004] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Revised: 02/11/2009] [Accepted: 03/04/2009] [Indexed: 10/21/2022]
Abstract
Aminoglycoside antibiotics cause death of sensory hair cells. Research over the past decade has identified several key players in the intracellular cascade. However, the role of the extracellular environment in aminoglycoside ototoxicity has received comparatively little attention. The present study uses the zebrafish lateral line to demonstrate that extracellular calcium and magnesium ions modulate hair cell death from neomycin and gentamicin in vivo, with high levels of either divalent cation providing significant protection. Imaging experiments with fluorescently-tagged gentamicin show that drug uptake is reduced under high calcium conditions. Treating fish with the hair cell transduction blocker amiloride also reduces aminoglycoside uptake, preventing the toxicity, and experiments with variable calcium and amiloride concentrations suggest complementary effects between the two protectants. Elevated magnesium, in contrast, does not appear to significantly attenuate drug uptake, suggesting that the two divalent cations may protect hair cells from aminoglycoside damage through different mechanisms. These results provide additional evidence for calcium- and transduction-dependent aminoglycoside uptake. Divalent cations provided differential protection from neomycin and gentamicin, with high cation concentrations almost completely protecting hair cells from neomycin and acute gentamicin toxicity, but offering reduced protection from continuous (6 h) gentamicin exposure. These experiments lend further support to the hypothesis that aminoglycoside toxicity occurs via multiple pathways in a both a drug and time course-specific manner.
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Owens KN, Coffin AB, Hong LS, Bennett KO, Rubel EW, Raible DW. Response of mechanosensory hair cells of the zebrafish lateral line to aminoglycosides reveals distinct cell death pathways. Hear Res 2009; 253:32-41. [PMID: 19285126 DOI: 10.1016/j.heares.2009.03.001] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Revised: 02/15/2009] [Accepted: 03/04/2009] [Indexed: 01/01/2023]
Abstract
We report a series of experiments investigating the kinetics of hair cell loss in lateral line neuromasts of zebrafish larvae following exposure to aminoglycoside antibiotics. Comparisons of the rate of hair cell loss and the differential effects of acute versus chronic exposure to gentamicin and neomycin revealed markedly different results. Neomycin induced rapid and dramatic concentration-dependent hair cell loss that is essentially complete within 90 min, regardless of concentration or exposure time. Gentamicin-induced loss of half of the hair cells within 90 min and substantial additional loss, which was prolonged and cumulative over exposure times up to at least 24h. Small molecules and genetic mutations that inhibit neomycin-induced hair cell loss were ineffective against prolonged gentamicin exposure supporting the hypothesis that these two drugs are revealing at least two cellular pathways. The mechanosensory channel blocker amiloride blocked both neomycin and gentamicin-induced hair cell death acutely and chronically indicating that these aminoglycosides share a common entry route. Further tests with additional aminoglycosides revealed a spectrum of differential responses to acute and chronic exposure. The distinctions between the times of action of these aminoglycosides indicate that these drugs induce multiple cell death pathways.
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66
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Ou HC, Cunningham LL, Francis SP, Brandon CS, Simon JA, Raible DW, Rubel EW. Identification of FDA-approved drugs and bioactives that protect hair cells in the zebrafish (Danio rerio) lateral line and mouse (Mus musculus) utricle. J Assoc Res Otolaryngol 2009; 10:191-203. [PMID: 19241104 DOI: 10.1007/s10162-009-0158-y] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2008] [Accepted: 01/20/2009] [Indexed: 11/24/2022] Open
Abstract
The hair cells of the larval zebrafish lateral line provide a useful preparation in which to study hair cell death and to screen for genes and small molecules that modulate hair cell toxicity. We recently reported preliminary results from screening a small-molecule library for compounds that inhibit aminoglycoside-induced hair cell death. To potentially reduce the time required for development of drugs and drug combinations that can be clinically useful, we screened a library of 1,040 FDA-approved drugs and bioactive compounds (NINDS Custom Collection II). Seven compounds that protect against neomycin-induced hair cell death were identified. Four of the seven drugs inhibited aminoglycoside uptake, based on Texas-Red-conjugated gentamicin uptake. The activities of two of the remaining three drugs were evaluated using an in vitro adult mouse utricle preparation. One drug, 9-amino-1,2,3,4-tetrahydroacridine (tacrine) demonstrated conserved protective effects in the mouse utricle. These results demonstrate that the zebrafish lateral line can be used to screen successfully for drugs within a library of FDA-approved drugs and bioactives that inhibit hair cell death in the mammalian inner ear and identify tacrine as a promising protective drug for future studies.
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67
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Brignull HR, Raible DW, Stone JS. Feathers and fins: non-mammalian models for hair cell regeneration. Brain Res 2009; 1277:12-23. [PMID: 19245801 DOI: 10.1016/j.brainres.2009.02.028] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Revised: 02/09/2009] [Accepted: 02/11/2009] [Indexed: 11/18/2022]
Abstract
Death of mechanosensory cells in the inner ear results in two profound disabilities: hearing loss and balance disorders. Although mammals lack the capacity to regenerate hair cells, recent studies in mice and other rodents have offered valuable insight into strategies for stimulating hair cell regeneration in mammals. Investigations of model organisms that retain the ability to form new hair cells after embryogenesis, such as fish and birds, are equally important and have provided clues as to the cellular and molecular mechanisms that may block hair cell regeneration in mammals. Here, we summarize studies on hair cell regeneration in the chicken and the zebrafish, discuss specific advantages of each model, and propose future directions for the use of non-mammalian models in understanding hair cell regeneration.
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Gorden NT, Arts HH, Parisi MA, Coene KLM, Letteboer SJF, van Beersum SEC, Mans DA, Hikida A, Eckert M, Knutzen D, Alswaid AF, Ozyurek H, Dibooglu S, Otto EA, Liu Y, Davis EE, Hutter CM, Bammler TK, Farin FM, Dorschner M, Topçu M, Zackai EH, Rosenthal P, Owens KN, Katsanis N, Vincent JB, Hildebrandt F, Rubel EW, Raible DW, Knoers NVAM, Chance PF, Roepman R, Moens CB, Glass IA, Doherty D. CC2D2A is mutated in Joubert syndrome and interacts with the ciliopathy-associated basal body protein CEP290. Am J Hum Genet 2008; 83:559-71. [PMID: 18950740 DOI: 10.1016/j.ajhg.2008.10.002] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2008] [Revised: 10/01/2008] [Accepted: 10/02/2008] [Indexed: 12/18/2022] Open
Abstract
Joubert syndrome and related disorders (JSRD) are primarily autosomal-recessive conditions characterized by hypotonia, ataxia, abnormal eye movements, and intellectual disability with a distinctive mid-hindbrain malformation. Variable features include retinal dystrophy, cystic kidney disease, and liver fibrosis. JSRD are included in the rapidly expanding group of disorders called ciliopathies, because all six gene products implicated in JSRD (NPHP1, AHI1, CEP290, RPGRIP1L, TMEM67, and ARL13B) function in the primary cilium/basal body organelle. By using homozygosity mapping in consanguineous families, we identify loss-of-function mutations in CC2D2A in JSRD patients with and without retinal, kidney, and liver disease. CC2D2A is expressed in all fetal and adult tissues tested. In ciliated cells, we observe localization of recombinant CC2D2A at the basal body and colocalization with CEP290, whose cognate gene is mutated in multiple hereditary ciliopathies. In addition, the proteins can physically interact in vitro, as shown by yeast two-hybrid and GST pull-down experiments. A nonsense mutation in the zebrafish CC2D2A ortholog (sentinel) results in pronephric cysts, a hallmark of ciliary dysfunction analogous to human cystic kidney disease. Knockdown of cep290 function in sentinel fish results in a synergistic pronephric cyst phenotype, revealing a genetic interaction between CC2D2A and CEP290 and implicating CC2D2A in cilium/basal body function. These observations extend the genetic spectrum of JSRD and provide a model system for studying extragenic modifiers in JSRD and other ciliopathies.
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69
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Cooper CD, Raible DW. Mechanisms for reaching the differentiated state: Insights from neural crest-derived melanocytes. Semin Cell Dev Biol 2008; 20:105-10. [PMID: 18935965 DOI: 10.1016/j.semcdb.2008.09.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Accepted: 09/25/2008] [Indexed: 01/02/2023]
Abstract
Black pigment cells, or melanocytes, are the major contributing cells to pigmentation in vertebrate organisms. Although the function of these cells is distinct depending on the organism, the events involved in their development are remarkably similar. Here, we review the mechanisms involved in the early development of melanocytes from neural crest, many of which are conserved in organisms as diverse as zebrafish, birds and humans. We also discuss recent studies that provide further insight into how melanocyte differentiation is achieved and maintained.
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Abstract
During development, organ primordia reorganize to form repeated functional units. In zebrafish (Danio rerio), mechanosensory organs called neuromasts are deposited at regular intervals by the migrating posterior lateral line (pLL) primordium. The pLL primordium is organized into polarized rosettes representing proto-neuromasts, each with a central atoh1a-positive focus of mechanosensory precursors. We show that rosettes form cyclically from a progenitor pool at the leading zone of the primordium as neuromasts are deposited from the trailing region. fgf3/10 signals localized to the leading zone are required for rosette formation, atoh1a expression, and primordium migration. We propose that the fibroblast growth factor (FGF) source controls primordium organization, which, in turn, regulates the periodicity of neuromast deposition. This previously unrecognized mechanism may be applicable to understanding segmentation and morphogenesis in other organ systems.
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71
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Chiu LL, Cunningham LL, Raible DW, Rubel EW, Ou HC. Using the zebrafish lateral line to screen for ototoxicity. J Assoc Res Otolaryngol 2008; 9:178-90. [PMID: 18408970 DOI: 10.1007/s10162-008-0118-y] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2008] [Accepted: 03/05/2008] [Indexed: 10/22/2022] Open
Abstract
The zebrafish is a valuable model for studying hair cell development, structure, genetics, and behavior. Zebrafish and other aquatic vertebrates have hair cells on their body surface organized into a sensory system called the lateral line. These hair cells are highly accessible and easily visualized using fluorescent dyes. Morphological and functional similarities to mammalian hair cells of the inner ear make the zebrafish a powerful preparation for studying hair cell toxicity. The ototoxic potential of drugs has historically been uncovered by anecdotal reports that have led to more formal investigation. Currently, no standard screen for ototoxicity exists in drug development. Thus, for the vast majority of Food and Drug Association (FDA)-approved drugs, the ototoxic potential remains unknown. In this study, we used 5-day-old zebrafish larvae to screen a library of 1,040 FDA-approved drugs and bioactives (NINDS Custom Collection II) for ototoxic effects in hair cells of the lateral line. Hair cell nuclei were selectively labeled using a fluorescent vital dye. For the initial screen, fish were exposed to drugs from the library at a 100-muM concentration for 1 h in 96-well tissue culture plates. Hair cell viability was assessed in vivo using fluorescence microscopy. One thousand forty drugs were rapidly screened for ototoxic effects. Seven known ototoxic drugs included in the library, including neomycin and cisplatin, were positively identified using these methods, as proof of concept. Fourteen compounds without previously known ototoxicity were discovered to be selectively toxic to hair cells. Dose-response curves for all 21 ototoxic compounds were determined by quantifying hair cell survival as a function of drug concentration. Dose-response relationships in the mammalian inner ear for two of the compounds without known ototoxicity, pentamidine isethionate and propantheline bromide, were then examined using in vitro preparations of the adult mouse utricle. Significant dose-dependent hair cell loss in the mouse utricle was demonstrated for both compounds. This study represents an important step in validating the use of the zebrafish lateral line as a screening tool for the identification of potentially ototoxic drugs.
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Owens KN, Santos F, Roberts B, Linbo T, Coffin AB, Knisely AJ, Simon JA, Rubel EW, Raible DW. Identification of genetic and chemical modulators of zebrafish mechanosensory hair cell death. PLoS Genet 2008; 4:e1000020. [PMID: 18454195 PMCID: PMC2265478 DOI: 10.1371/journal.pgen.1000020] [Citation(s) in RCA: 157] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2007] [Accepted: 01/10/2008] [Indexed: 11/18/2022] Open
Abstract
Inner ear sensory hair cell death is observed in the majority of hearing and balance disorders, affecting the health of more than 600 million people worldwide. While normal aging is the single greatest contributor, exposure to environmental toxins and therapeutic drugs such as aminoglycoside antibiotics and antineoplastic agents are significant contributors. Genetic variation contributes markedly to differences in normal disease progression during aging and in susceptibility to ototoxic agents. Using the lateral line system of larval zebrafish, we developed an in vivo drug toxicity interaction screen to uncover genetic modulators of antibiotic-induced hair cell death and to identify compounds that confer protection. We have identified 5 mutations that modulate aminoglycoside susceptibility. Further characterization and identification of one protective mutant, sentinel (snl), revealed a novel conserved vertebrate gene. A similar screen identified a new class of drug-like small molecules, benzothiophene carboxamides, that prevent aminoglycoside-induced hair cell death in zebrafish and in mammals. Testing for interaction with the sentinel mutation suggests that the gene and compounds may operate in different pathways. The combination of chemical screening with traditional genetic approaches is a new strategy for identifying drugs and drug targets to attenuate hearing and balance disorders. Loss of sensory hair cells in the inner ear is observed in the majority of hearing and balance disorders, affecting the health of more than 600 million people worldwide. Exposure to environmental toxins and certain pharmaceutical drugs such as aminoglycoside antibiotics and some cancer chemotherapy agents account for many of these hearing and balance problems. Variation in the genetic makeup between individuals plays a major role in establishing differences in susceptibility to environmental agents that damage the inner ear. Using zebrafish larvae, we developed a screen to uncover genes leading to differences in antibiotic-induced death of hair cells and to identify compounds that protect hair cells from damage. The combination of chemical screening with traditional genetic approaches offers a new strategy for identifying drugs and drug targets to attenuate hearing and balance disorders.
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MESH Headings
- Aminoglycosides/antagonists & inhibitors
- Aminoglycosides/toxicity
- Animals
- Base Sequence
- Cell Death/drug effects
- Cell Death/genetics
- Cisplatin/toxicity
- Codon, Terminator/genetics
- DNA Primers/genetics
- DNA, Complementary/genetics
- Drug Evaluation, Preclinical
- Epistasis, Genetic
- Hair Cells, Auditory, Inner/cytology
- Hair Cells, Auditory, Inner/drug effects
- Hair Cells, Auditory, Inner/physiology
- Hearing Loss/etiology
- Hearing Loss/genetics
- Hearing Loss/prevention & control
- Humans
- Mice
- Neomycin/antagonists & inhibitors
- Neomycin/toxicity
- Point Mutation
- Saccule and Utricle/drug effects
- Saccule and Utricle/pathology
- Thiophenes/chemistry
- Thiophenes/pharmacology
- Zebrafish/anatomy & histology
- Zebrafish/genetics
- Zebrafish/physiology
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73
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Raible DW, Ungos JM. Specification of sensory neuron cell fate from the neural crest. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 589:170-80. [PMID: 17076281 DOI: 10.1007/978-0-387-46954-6_10] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
How distinct cell fates are generated from initially homogeneous cell populations is a driving question in developmental biology. The neural crest is one such cell population that is capable of producing an incredible array of derivatives. Cells as different in function and form as the pigment cells in the skin or the neurons and glia of the peripheral nervous system are all derived from neural crest. How do these cells choose to migrate along distinct routes, populate defined regions of the embryo and differentiate into specific cell types? This chapter focuses on the development of one particular neural crest derivative, sensory neurons, as a model for studying these questions of cell fate specification. In the head, sensory neurons reside in the trigeminal and epibranchial ganglia, while in the trunk they form the spinal or dorsal root ganglia (DRG). The development of the DRG will be the main focus of this review. The neurons and glia of the DRG derive from trunk neural crest cells that coalesce at the lateral edge of the spinal cord (Fig. 1). These neural crest cells migrate along the same routes as neural crest cells that populate the autonomic sympathetic ganglia located along the dorsal aorta. Somehow DRG precursors must make the decision to stop and adopt a sensory fate adjacent to the spinal cord rather than continuing on to become part of the autonomic ganglia. Moreover, once the DRG precursors aggregate in their final positions there are still a number of fate choices to be made. The mature DRG is composed of many neurons with different morphologies and distinct biochemical properties as well as glial cells that support these neurons.
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Ou HC, Raible DW, Rubel EW. Cisplatin-induced hair cell loss in zebrafish (Danio rerio) lateral line. Hear Res 2007; 233:46-53. [PMID: 17709218 PMCID: PMC2080654 DOI: 10.1016/j.heares.2007.07.003] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Revised: 07/03/2007] [Accepted: 07/09/2007] [Indexed: 11/27/2022]
Abstract
We have used time-lapse imaging to study cisplatin-induced hair cell death in lateral line neuromasts of zebrafish larvae in vivo. We found that cisplatin-induced hair cell death occurred much more slowly than had been shown to occur in aminoglycoside-induced hair cell death. By prelabeling hair cells with FM1-43FX, and assessing hair cell damage, it was established that cisplatin causes hair cell loss in the lateral line in a dose-dependent fashion. The kinetics of hair cell loss during exposure to different concentrations of cisplatin was also assessed and it was found that the onset of hair cell loss correlated with the accumulated dose of cisplatin. These data demonstrate the feasibility and repeatability of cisplatin damage protocols in the zebrafish lateral line and set the stage for future evaluations of modulation of cisplatin-induced hair cell death.
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Owens KN, Cunningham DE, MacDonald G, Rubel EW, Raible DW, Pujol R. Ultrastructural analysis of aminoglycoside-induced hair cell death in the zebrafish lateral line reveals an early mitochondrial response. J Comp Neurol 2007; 502:522-43. [PMID: 17394157 DOI: 10.1002/cne.21345] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Loss of the mechanosensory hair cells in the auditory and vestibular organs leads to hearing and balance deficits. To investigate initial, in vivo events in aminoglycoside-induced hair cell damage, we examined hair cells from the lateral line of the zebrafish, Danio rerio. The mechanosensory lateral line is located externally on the animal and therefore allows direct manipulation and observation of hair cells. Labeling with vital dyes revealed a rapid response of hair cells to the aminoglycoside neomycin. Similarly, ultrastructural analysis revealed structural alteration among hair cells within 15 minutes of neomycin exposure. Animals exposed to a low, 25-microM concentration of neomycin exhibited hair cells with swollen mitochondria, but little other damage. Animals treated with higher concentrations of neomycin (50-200 microM) had more severe and heterogeneous cellular changes, as well as fewer hair cells. Both necrotic-like and apoptotic-like cellular damage were observed. Quantitation of the types of alterations observed indicated that mitochondrial defects appear earlier and more predominantly than other structural alterations. In vivo monitoring demonstrated that mitochondrial potential decreased following neomycin treatment. These results indicate that perturbation of the mitochondrion is an early, central event in aminoglycoside-induced damage.
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