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Barrett LM, Meighan PC, Mitchell DM, Varnum MD, Stenkamp DL. Assessing Rewiring of the Retinal Circuitry by Electroretinogram (ERG) After Inner Retinal Lesion in Adult Zebrafish. Methods Mol Biol 2023; 2636:421-435. [PMID: 36881314 DOI: 10.1007/978-1-0716-3012-9_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
Abstract
Adult zebrafish respond to retinal injury with a regenerative response that replaces damaged neurons with Müller glia-derived regenerated neurons. The regenerated neurons are functional, appear to make appropriate synaptic connections, and support visually mediated reflexes and more complex behaviors. Curiously, the electrophysiology of damaged, regenerating, and regenerated zebrafish retina has only recently been examined. In our previous work, we demonstrated that electroretinogram (ERG) recordings of damaged zebrafish retina correlate with the extent of the inflicted damage and that the regenerated retina at 80 days post-injury exhibited ERG waveforms consistent with functional visual processing. In this paper we describe the procedure for obtaining and analyzing ERG recordings from adult zebrafish previously subjected to widespread lesions that destroy inner retinal neurons and engage a regenerative response that restores retinal function, in particular the synaptic connections between photoreceptor axon terminals and the dendritic trees of retinal bipolar neurons.
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Affiliation(s)
- Lindsey M Barrett
- Department of Biological Sciences, University of Idaho, Moscow, ID, USA
| | - Peter C Meighan
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA, USA
| | - Diana M Mitchell
- Department of Biological Sciences, University of Idaho, Moscow, ID, USA
| | - Michael D Varnum
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA, USA
| | - Deborah L Stenkamp
- Department of Biological Sciences, University of Idaho, Moscow, ID, USA.
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Zang J, Gesemann M, Keim J, Samardzija M, Grimm C, Neuhauss SCF. Circadian regulation of vertebrate cone photoreceptor function. eLife 2021; 10:e68903. [PMID: 34550876 PMCID: PMC8494479 DOI: 10.7554/elife.68903] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 09/20/2021] [Indexed: 12/16/2022] Open
Abstract
Eukaryotes generally display a circadian rhythm as an adaption to the reoccurring day/night cycle. This is particularly true for visual physiology that is directly affected by changing light conditions. Here we investigate the influence of the circadian rhythm on the expression and function of visual transduction cascade regulators in diurnal zebrafish and nocturnal mice. We focused on regulators of shut-off kinetics such as Recoverins, Arrestins, Opsin kinases, and Regulator of G-protein signaling that have direct effects on temporal vision. Transcript as well as protein levels of most analyzed genes show a robust circadian rhythm-dependent regulation, which correlates with changes in photoresponse kinetics. Electroretinography demonstrates that photoresponse recovery in zebrafish is delayed in the evening and accelerated in the morning. Functional rhythmicity persists in continuous darkness, and it is reversed by an inverted light cycle and disrupted by constant light. This is in line with our finding that orthologous gene transcripts from diurnal zebrafish and nocturnal mice are often expressed in an anti-phasic daily rhythm.
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Affiliation(s)
- Jingjing Zang
- University of Zurich, Department of Molecular Life SciencesZurichSwitzerland
| | - Matthias Gesemann
- University of Zurich, Department of Molecular Life SciencesZurichSwitzerland
| | - Jennifer Keim
- University of Zurich, Department of Molecular Life SciencesZurichSwitzerland
| | - Marijana Samardzija
- Lab for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of ZurichZurichSwitzerland
| | - Christian Grimm
- Lab for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of ZurichZurichSwitzerland
| | - Stephan CF Neuhauss
- University of Zurich, Department of Molecular Life SciencesZurichSwitzerland
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Venkatraman P, Mills-Henry I, Padmanabhan KR, Pascuzzi P, Hassan M, Zhang J, Zhang X, Ma P, Pang CP, Dowling JE, Zhang M, Leung YF. Rods Contribute to Visual Behavior in Larval Zebrafish. Invest Ophthalmol Vis Sci 2021; 61:11. [PMID: 33049059 PMCID: PMC7571310 DOI: 10.1167/iovs.61.12.11] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Purpose Although zebrafish rods begin to develop as early as 2 days postfertilization (dpf), they are not deemed anatomically mature and functional until 15 to 21 dpf. A recent study detected a small electroretinogram (ERG) from rods in a cone mutant called no optokinetic response f (nof) at 5 dpf, suggesting that young rods are functional. Whether they can mediate behavioral responses in larvae is unknown. Methods We first confirmed rod function by measuring nof ERGs under photopic and scotopic illumination at 6 dpf. We evaluated the role of rods in visual behaviors using two different assays: the visual-motor response (VMR) and optokinetic response (OKR). We measured responses from wild-type (WT) larvae and nof mutants under photopic and scotopic illuminations at 6 dpf. Results Nof mutants lacked a photopic ERG. However, after prolonged dark adaptation, they displayed scotopic ERGs. Compared with WT larvae, the nof mutants displayed reduced VMRs. The VMR difference during light onset gradually diminished with decreased illumination and became nearly identical at lower light intensities. Additionally, light-adapted nof mutants did not display an OKR, whereas dark-adapted nof mutants displayed scotopic OKRs. Conclusions Because the nof mutants lacked a photopic ERG but displayed scotopic ERGs after dark adaptation, the mutants clearly had functional rods. WT larvae and the nof mutants displayed comparable scotopic light-On VMRs and scotopic OKRs after dark adaptation, suggesting that these responses were driven primarily by rods. Together, these observations indicate that rods contribute to zebrafish visual behaviors as early as 6 dpf.
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Affiliation(s)
- Prahatha Venkatraman
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States
| | - Ishara Mills-Henry
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, United States
| | | | - Pete Pascuzzi
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States.,Purdue University Center for Cancer Research, Purdue University, West Lafayette, Indiana, United States.,Purdue University Libraries, Purdue University, West Lafayette, Indiana, United States
| | - Menna Hassan
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States
| | - Jingyi Zhang
- Center for Statistical Science, Tsinghua University, Beijing, China
| | - Xinlian Zhang
- Department of Statistics, University of Georgia, Athens, Georgia, United States
| | - Ping Ma
- Department of Statistics, University of Georgia, Athens, Georgia, United States
| | - Chi Pui Pang
- Department of Ophthalmology and Visual Sciences, Chinese University of Hong Kong, Hong Kong.,Joint Shantou International Eye Center, Shantou University and the Chinese University of Hong Kong, Shantou, China
| | - John E Dowling
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, United States
| | - Mingzhi Zhang
- Joint Shantou International Eye Center, Shantou University and the Chinese University of Hong Kong, Shantou, China
| | - Yuk Fai Leung
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States.,Department of Biochemistry and Molecular Biology, Indiana University School of Medicine Lafayette, West Lafayette, Indiana, United States.,Purdue Institute for Integrative Neuroscience, Purdue University, West Lafayette, Indiana, United States.,Purdue Institute for Drug Discovery, Purdue University, West Lafayette, Indiana, United States
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4
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Abstract
I was drawn into research in George Wald's laboratory at Harvard, where as an undergraduate and graduate student, I studied vitamin A deficiency and dark adaptation. A chance observation while an assistant professor at Harvard led to the major research of my career-to understand the functional organization of vertebrate retinas. I started with a retinal circuit analysis of the primate retina with Brian Boycott and intracellular retinal cell recordings in mudpuppies with Frank Werblin. Subsequent pharmacology studies with Berndt Ehinger primarily with fish focused on dopamine and neuromodulation. Using zebrafish, we studied retinal development, neuronal connectivity, and the effects of genetic mutations on retinal structure and function. Now semi-retired, I have returned to primate retinal circuitry, undertaking a connectomic analysis of the human fovea in Jeffrey Lichtman's laboratory.
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Affiliation(s)
- John E Dowling
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA;
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5
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Quadros VA, Costa FV, Canzian J, Nogueira CW, Rosemberg DB. Modulatory role of conspecific alarm substance on aggression and brain monoamine oxidase activity in two zebrafish populations. Prog Neuropsychopharmacol Biol Psychiatry 2018; 86:322-330. [PMID: 29588212 DOI: 10.1016/j.pnpbp.2018.03.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 02/05/2018] [Accepted: 03/22/2018] [Indexed: 02/07/2023]
Affiliation(s)
- Vanessa A Quadros
- Laboratory of Experimental Neuropsychobiology, Department of Biochemistr and Molecular Biology, Natural and Exact Sciences Center, Federal University of Santa Maria, 1000 Roraima Avenue, Santa Maria, RS 97105-900, Brazil; Graduate Program in Biological Sciences: Toxicological Biochemistry, Federal University of Santa Maria, 1000 Roraima Avenue, Santa Maria, RS 97105-900, Brazil.
| | - Fabiano V Costa
- Laboratory of Experimental Neuropsychobiology, Department of Biochemistr and Molecular Biology, Natural and Exact Sciences Center, Federal University of Santa Maria, 1000 Roraima Avenue, Santa Maria, RS 97105-900, Brazil; Graduate Program in Biological Sciences: Toxicological Biochemistry, Federal University of Santa Maria, 1000 Roraima Avenue, Santa Maria, RS 97105-900, Brazil
| | - Julia Canzian
- Laboratory of Experimental Neuropsychobiology, Department of Biochemistr and Molecular Biology, Natural and Exact Sciences Center, Federal University of Santa Maria, 1000 Roraima Avenue, Santa Maria, RS 97105-900, Brazil
| | - Cristina W Nogueira
- Graduate Program in Biological Sciences: Toxicological Biochemistry, Federal University of Santa Maria, 1000 Roraima Avenue, Santa Maria, RS 97105-900, Brazil
| | - Denis B Rosemberg
- Laboratory of Experimental Neuropsychobiology, Department of Biochemistr and Molecular Biology, Natural and Exact Sciences Center, Federal University of Santa Maria, 1000 Roraima Avenue, Santa Maria, RS 97105-900, Brazil; Graduate Program in Biological Sciences: Toxicological Biochemistry, Federal University of Santa Maria, 1000 Roraima Avenue, Santa Maria, RS 97105-900, Brazil; The International Zebrafish Neuroscience Research Consortium (ZNRC), 309 Palmer Court, Slidell, LA 70458, USA.
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6
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Pregnancy-Associated Plasma Protein-aa Regulates Photoreceptor Synaptic Development to Mediate Visually Guided Behavior. J Neurosci 2018; 38:5220-5236. [PMID: 29739870 DOI: 10.1523/jneurosci.0061-18.2018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 04/04/2018] [Accepted: 04/30/2018] [Indexed: 02/08/2023] Open
Abstract
To guide behavior, sensory systems detect the onset and offset of stimuli and process these distinct inputs via parallel pathways. In the retina, this strategy is implemented by splitting neural signals for light onset and offset via synapses connecting photoreceptors to ON and OFF bipolar cells, respectively. It remains poorly understood which molecular cues establish the architecture of this synaptic configuration to split light-onset and light-offset signals. A mutant with reduced synapses between photoreceptors and one bipolar cell type, but not the other, could reveal a critical cue. From this approach, we report a novel synaptic role for pregnancy-associated plasma protein aa (pappaa) in promoting the structure and function of cone synapses that transmit light-offset information. Electrophysiological and behavioral analyses indicated pappaa mutant zebrafish have dysfunctional cone-to-OFF bipolar cell synapses and impaired responses to light offset, but intact cone-to-ON bipolar cell synapses and light-onset responses. Ultrastructural analyses of pappaa mutant cones showed a lack of presynaptic domains at synapses with OFF bipolar cells. pappaa is expressed postsynaptically to the cones during retinal synaptogenesis and encodes a secreted metalloprotease known to stimulate insulin-like growth factor 1 (IGF1) signaling. Induction of dominant-negative IGF1 receptor expression during synaptogenesis reduced light-offset responses. Conversely, stimulating IGF1 signaling at this time improved pappaa mutants' light-offset responses and cone presynaptic structures. Together, our results indicate Pappaa-regulated IGF1 signaling as a novel pathway that establishes how cone synapses convey light-offset signals to guide behavior.SIGNIFICANCE STATEMENT Distinct sensory inputs, like stimulus onset and offset, are often split at distinct synapses into parallel circuits for processing. In the retina, photoreceptors and ON and OFF bipolar cells form discrete synapses to split neural signals coding light onset and offset, respectively. The molecular cues that establish this synaptic configuration to specifically convey light onset or offset remain unclear. Our work reveals a novel cue: pregnancy-associated plasma protein aa (pappaa), which regulates photoreceptor synaptic structure and function to specifically transmit light-offset information. Pappaa is a metalloprotease that stimulates local insulin-like growth factor 1 (IGF1) signaling. IGF1 promotes various aspects of synaptic development and function and is broadly expressed, thus requiring local regulators, like Pappaa, to govern its specificity.
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7
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Nakaya N, Sultana A, Tomarev SI. Impaired AMPA receptor trafficking by a double knockout of zebrafish olfactomedin1a/b. J Neurochem 2017; 143:635-644. [PMID: 28975619 DOI: 10.1111/jnc.14231] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 09/15/2017] [Accepted: 09/27/2017] [Indexed: 01/06/2023]
Abstract
The olfm1a and olfm1b genes in zebrafish encode conserved secreted glycoproteins. These genes are preferentially expressed in the brain and retina starting from 16 h post-fertilization until adulthood. Functions of the Olfm1 gene is still unclear. Here, we produced and analyzed a null zebrafish mutant of both olfm1a and olfm1b genes (olfm1 null). olfm1 null fish were born at a normal Mendelian ratio and showed normal body shape and fertility as well as no visible defects from larval stages to adult. Olfm1 proteins were preferentially localized in the synaptosomes of the adult brain. Olfm1 co-immunoprecipitated with GluR2 and soluble NSF attachment protein receptor complexes indicating participation of Olfm1 in both pre- and post-synaptic events. Phosphorylation of GluR2 was not changed while palmitoylation of GluR2 was decreased in the brain synaptosomal membrane fraction of olfm1 null compared with wt fish. The levels of GluR2, SNAP25, flotillin1, and VAMP2 were markedly reduced in the synaptic microdomain of olfm1 null brain compared with wt. The internalization of GluR2 in retinal cells and the localization of VAMP2 in brain synaptosome were modified by olfm1 null mutation. This indicates that Olfm1 may regulate receptor trafficking from the intracellular compartments to the synaptic membrane microdomain, partly through the alteration of post-translational GluR2 modifications such as palmitoylation. Olfm1 may be considered a novel regulator of the composition and function of the α-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor complex.
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Affiliation(s)
- Naoki Nakaya
- Section of Retinal Ganglion Cell Biology, Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, NIH, Bethesda, Maryland, USA
| | - Afia Sultana
- Section of Retinal Ganglion Cell Biology, Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, NIH, Bethesda, Maryland, USA
| | - Stanislav I Tomarev
- Section of Retinal Ganglion Cell Biology, Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, NIH, Bethesda, Maryland, USA
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8
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Aose M, Linbo TH, Lawrence O, Senoo T, Raible DW, Clark JI. The occhiolino (occ) mutant Zebrafish, a model for development of the optical function in the biological lens. Dev Dyn 2017; 246:915-924. [PMID: 28422363 PMCID: PMC6800130 DOI: 10.1002/dvdy.24511] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 03/16/2017] [Accepted: 04/03/2017] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND Zebrafish visual function depends on quality optics. An F3 screen for developmental mutations in the Zebrafish nervous system was conducted in wild-type (wt) AB Zebrafish exposed to 3 mM of N-ethyl-N-nitrosourea (ENU). RESULTS Mutant offspring, identified in an F3 screen, were characterized by a small pupil, resulting from retinal hypertrophy or hyperplasia and a small lens. Deficits in visual function made feeding difficult after hatching at approximately 5-6 days postfertilization (dpf). Special feeding conditions were necessary for survival of the occhiolino (occ) mutants after 6 dpf. Optokinetic response (OKR) tests measured defects in visual function in the occ mutant, although electroretinograms (ERGs) were normal in the mutant and wt. Consistent with the ERGs, histology found normal retinal structure in the occ mutant and wt Zebrafish. However, lens development was abnormal. Multiphoton imaging of the developmental stages of live embryos confirmed the formation of a secondary mass of lens cells in the developing eye of the mutant Zebrafish at 3-4 dpf, and laminin immunohistochemistry indicated the lens capsule was thin and disorganized in the mutant Zebrafish. CONCLUSIONS The occ Zebrafish is a novel disease model for visual defects associated with abnormal lens development. Developmental Dynamics 246:915-924, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Masamoto Aose
- Department of Ophthalmology, Dokkyo Medical University, Tochigi, Japan
| | - Tor H Linbo
- Department of Biological Structure, University of Washington, Seattle, Washington
| | - Owen Lawrence
- Department of Biological Structure, University of Washington, Seattle, Washington
| | - Tadashi Senoo
- Department of Ophthalmology, Dokkyo Medical University, Tochigi, Japan
| | - David W Raible
- Department of Biological Structure, University of Washington, Seattle, Washington
| | - John I Clark
- Department of Biological Structure, University of Washington, Seattle, Washington
- Department of Ophthalmology, University of Washington, Seattle, Washington
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9
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Daniele LL, Emran F, Lobo GP, Gaivin RJ, Perkins BD. Mutation of wrb, a Component of the Guided Entry of Tail-Anchored Protein Pathway, Disrupts Photoreceptor Synapse Structure and Function. Invest Ophthalmol Vis Sci 2017; 57:2942-54. [PMID: 27273592 PMCID: PMC4898200 DOI: 10.1167/iovs.15-18996] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
PURPOSE Tail-anchored (TA) proteins contain a single hydrophobic domain at the C-terminus and are posttranslationally inserted into the ER membrane via the GET (guided entry of tail-anchored proteins) pathway. The role of the GET pathway in photoreceptors is unexplored. The goal of this study was to characterize the zebrafish pinball wizard mutant, which disrupts Wrb, a core component of the GET pathway. METHODS Electroretinography, optokinetic response measurements (OKR), immunohistochemistry, and electron microscopy analyses were employed to assess ribbon synapse function, protein expression, and ultrastructure in 5-day-old zebrafish larvae. Expression of wrb was investigated with real-time qRT-PCR and in situ hybridization. RESULTS Mutation of wrb abolished the OKR and greatly diminished the ERG b-wave, but not the a-wave. Ribeye and SV2 were partially mislocalized in both photoreceptors and hair cells of wrb mutants. Fewer contacts were seen between photoreceptors and bipolar cells in wrb-/- mutants. Expression of wrb was observed throughout the nervous system and Wrb localized to the ER and synaptic region of photoreceptors. Morpholino knockdown of the cytosolic ATPase trc40, which targets TA proteins to the ER, also diminished the OKR. Overexpression of wrb fully restored contrast sensitivity in mutants, while overexpression of mutant wrbR73A, which cannot bind Trc40, did not. CONCLUSIONS Proteins Wrb and Trc40 are required for synaptic transmission between photoreceptors and bipolar cells, indicating that TA protein insertion by the TRC pathway is a critical step in ribbon synapse assembly and function.
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Affiliation(s)
- Lauren L Daniele
- Department of Ophthalmic Research Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | - Farida Emran
- Centre for Research in Neuroscience, McGill University, Montreal, Quebec, Canada
| | - Glenn P Lobo
- Department of Ophthalmic Research Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | - Robert J Gaivin
- Department of Ophthalmic Research Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | - Brian D Perkins
- Department of Ophthalmic Research Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
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10
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Wang MS, Zhang RW, Su LY, Li Y, Peng MS, Liu HQ, Zeng L, Irwin DM, Du JL, Yao YG, Wu DD, Zhang YP. Positive selection rather than relaxation of functional constraint drives the evolution of vision during chicken domestication. Cell Res 2016; 26:556-73. [PMID: 27033669 PMCID: PMC4856766 DOI: 10.1038/cr.2016.44] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 01/18/2016] [Accepted: 02/22/2016] [Indexed: 01/05/2023] Open
Abstract
As noted by Darwin, chickens have the greatest phenotypic diversity of all birds, but an interesting evolutionary difference between domestic chickens and their wild ancestor, the Red Junglefowl, is their comparatively weaker vision. Existing theories suggest that diminished visual prowess among domestic chickens reflect changes driven by the relaxation of functional constraints on vision, but the evidence identifying the underlying genetic mechanisms responsible for this change has not been definitively characterized. Here, a genome-wide analysis of the domestic chicken and Red Junglefowl genomes showed significant enrichment for positively selected genes involved in the development of vision. There were significant differences between domestic chickens and their wild ancestors regarding the level of mRNA expression for these genes in the retina. Numerous additional genes involved in the development of vision also showed significant differences in mRNA expression between domestic chickens and their wild ancestors, particularly for genes associated with phototransduction and photoreceptor development, such as RHO (rhodopsin), GUCA1A, PDE6B and NR2E3. Finally, we characterized the potential role of the VIT gene in vision, which experienced positive selection and downregulated expression in the retina of the village chicken. Overall, our results suggest that positive selection, rather than relaxation of purifying selection, contributed to the evolution of vision in domestic chickens. The progenitors of domestic chickens harboring weaker vision may have showed a reduced fear response and vigilance, making them easier to be unconsciously selected and/or domesticated.
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Affiliation(s)
- Ming-Shan Wang
- State Key Laboratory of Genetic Resources and Evolution, Yunnan Laboratory of Molecular Biology of Domestic Animals
- Kunming College of Life Science, Unisversity of Chinese Academy of Sciences, Kunming, Yunnan 650204, China
| | - Rong-wei Zhang
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Ling-Yan Su
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Kunming, Yunnan 650223, China
- Kunming College of Life Science, Unisversity of Chinese Academy of Sciences, Kunming, Yunnan 650204, China
| | - Yan Li
- State Key Laboratory of Genetic Resources and Evolution, Yunnan Laboratory of Molecular Biology of Domestic Animals
- Kunming College of Life Science, Unisversity of Chinese Academy of Sciences, Kunming, Yunnan 650204, China
| | - Min-Sheng Peng
- State Key Laboratory of Genetic Resources and Evolution, Yunnan Laboratory of Molecular Biology of Domestic Animals
- Kunming College of Life Science, Unisversity of Chinese Academy of Sciences, Kunming, Yunnan 650204, China
| | - He-Qun Liu
- State Key Laboratory of Genetic Resources and Evolution, Yunnan Laboratory of Molecular Biology of Domestic Animals
- Kunming College of Life Science, Unisversity of Chinese Academy of Sciences, Kunming, Yunnan 650204, China
| | - Lin Zeng
- State Key Laboratory of Genetic Resources and Evolution, Yunnan Laboratory of Molecular Biology of Domestic Animals
- Kunming College of Life Science, Unisversity of Chinese Academy of Sciences, Kunming, Yunnan 650204, China
| | - David M Irwin
- State Key Laboratory of Genetic Resources and Evolution, Yunnan Laboratory of Molecular Biology of Domestic Animals
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
- Banting and Best Diabetes Centre, University of Toronto, Toronto, Canada
| | - Jiu-Lin Du
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Yong-Gang Yao
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Kunming, Yunnan 650223, China
- Kunming College of Life Science, Unisversity of Chinese Academy of Sciences, Kunming, Yunnan 650204, China
| | - Dong-Dong Wu
- State Key Laboratory of Genetic Resources and Evolution, Yunnan Laboratory of Molecular Biology of Domestic Animals
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Kunming, Yunnan 650223, China
| | - Ya-Ping Zhang
- State Key Laboratory of Genetic Resources and Evolution, Yunnan Laboratory of Molecular Biology of Domestic Animals
- Kunming College of Life Science, Unisversity of Chinese Academy of Sciences, Kunming, Yunnan 650204, China
- Laboratory for Conservation and Utilization of Bio-resource, Yunnan University, Kunming, Yunnan 650091, China
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11
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Popova E. ON-OFF Interactions in the Retina: Role of Glycine and GABA. Curr Neuropharmacol 2014; 12:509-26. [PMID: 25977678 PMCID: PMC4428025 DOI: 10.2174/1570159x13999150122165018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 12/19/2014] [Accepted: 12/22/2014] [Indexed: 01/03/2023] Open
Abstract
In the vertebrate retina, visual signals are segregated into parallel ON and OFF pathways, which provide information for light increments and decrements. The segregation is first evident at the level of the ON and OFF bipolar cells and it apparently remains as signals propagate to higher brain visual centers. A fundamental question in visual neuroscience is how these two parallel pathways function: are they independent from each other or do they interact somehow? In the latter case, what kinds of mechanisms are involved and what are the consequences from this cross-talk? This review summarizes current knowledge about the types of interactions between the ON and OFF channels in nonmammalian and mammalian retina. Data concerning the ON-OFF interactions in distal retina revealed by recording of single bipolar cell activity and electroretinographic ON (b-wave) and OFF (d-wave) responses are presented. Special emphasis is put on the ON-OFF interactions in proximal retina and their dependence on the state of light adaptation in mammalian retina. The involvement of the GABAergic and glycinergic systems in the ON-OFF crosstalk is also discussed.
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Affiliation(s)
- Elka Popova
- Department of Physiology, Medical Phaculty, Medical University, 1431 Sofia, Country Bulgaria
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12
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Yao C, Vanderpool KG, Delfiner M, Eddy V, Lucaci AG, Soto-Riveros C, Yasumura T, Rash JE, Pereda AE. Electrical synaptic transmission in developing zebrafish: properties and molecular composition of gap junctions at a central auditory synapse. J Neurophysiol 2014; 112:2102-13. [PMID: 25080573 PMCID: PMC4274921 DOI: 10.1152/jn.00397.2014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Accepted: 07/29/2014] [Indexed: 11/22/2022] Open
Abstract
In contrast to the knowledge of chemical synapses, little is known regarding the properties of gap junction-mediated electrical synapses in developing zebrafish, which provide a valuable model to study neural function at the systems level. Identifiable "mixed" (electrical and chemical) auditory synaptic contacts known as "club endings" on Mauthner cells (2 large reticulospinal neurons involved in tail-flip escape responses) allow exploration of electrical transmission in fish. Here, we show that paralleling the development of auditory responses, electrical synapses at these contacts become anatomically identifiable at day 3 postfertilization, reaching a number of ∼6 between days 4 and 9. Furthermore, each terminal contains ∼18 gap junctions, representing between 2,000 and 3,000 connexon channels formed by the teleost homologs of mammalian connexin 36. Electrophysiological recordings revealed that gap junctions at each of these contacts are functional and that synaptic transmission has properties that are comparable with those of adult fish. Thus a surprisingly small number of mixed synapses are responsible for the acquisition of auditory responses by the Mauthner cells, and these are likely sufficient to support escape behaviors at early developmental stages.
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Affiliation(s)
- Cong Yao
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - Kimberly G Vanderpool
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado; and
| | - Matthew Delfiner
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - Vanessa Eddy
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - Alexander G Lucaci
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - Carolina Soto-Riveros
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - Thomas Yasumura
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado; and
| | - John E Rash
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado; and Program in Molecular, Cellular and Integrative Neurosciences, Colorado State University, Fort Collins, Colorado
| | - Alberto E Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York;
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Wasfy MM, Matsui JI, Miller J, Dowling JE, Perkins BD. myosin 7aa(-/-) mutant zebrafish show mild photoreceptor degeneration and reduced electroretinographic responses. Exp Eye Res 2014; 122:65-76. [PMID: 24698764 DOI: 10.1016/j.exer.2014.03.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 03/18/2014] [Accepted: 03/19/2014] [Indexed: 01/20/2023]
Abstract
Mutations in myosin VIIa (MYO7A) cause Usher Syndrome 1B (USH1B), a disease characterized by the combination of sensorineural hearing loss and visual impairment termed retinitis pigmentosa (RP). Although the shaker-1 mouse model of USH1B exists, only minor defects in the retina have been observed during its lifespan. Previous studies of the zebrafish mariner mutant, which also carries a mutation in myo7aa, revealed balance and hearing defects in the mutants but the retinal phenotype has not been described. We found elevated cell death in the outer nuclear layer (ONL) of myo7aa(-/-) mutants. While myo7aa(-/-) mutants retained visual behaviors in the optokinetic reflex (OKR) assay, electroretinogram (ERG) recordings revealed a significant decrease in both a- and b-wave amplitudes in mutant animals, but not a change in ERG threshold sensitivity. Immunohistochemistry showed mislocalization of rod and blue cone opsins and reduced expression of rod-specific markers in the myo7aa(-/-) ONL, providing further evidence that the photoreceptor degeneration observed represents the initial stages of the RP. Further, constant light exposure resulted in widespread photoreceptor degeneration and the appearance of large holes in the retinal pigment epithelium (RPE). No differences were observed in the retinomotor movements of the photoreceptors or in melanosome migration within the RPE, suggesting that myo7aa(-/-) does not function in these processes in teleosts. These results indicate that the zebrafish myo7aa(-/-) mutant is a useful animal model for the RP seen in humans with USH1B.
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Affiliation(s)
- Meagan M Wasfy
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA
| | - Jonathan I Matsui
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA
| | - Jessica Miller
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA
| | - John E Dowling
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA
| | - Brian D Perkins
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA.
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14
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Loss of Pde6 reduces cell body Ca(2+) transients within photoreceptors. Cell Death Dis 2013; 4:e797. [PMID: 24030149 PMCID: PMC3789190 DOI: 10.1038/cddis.2013.332] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 07/21/2013] [Accepted: 07/29/2013] [Indexed: 11/30/2022]
Abstract
Modulation of Ca2+ within cells is tightly regulated through complex and dynamic interactions between the plasma membrane and internal compartments. In this study, we exploit in vivo imaging strategies based on genetically encoded Ca2+ indicators to define changes in perikaryal Ca2+ concentration of intact photoreceptors. We developed double-transgenic zebrafish larvae expressing GCaMP3 in all cones and tdTomato in long-wavelength cones to test the hypothesis that photoreceptor degeneration induced by mutations in the phosphodiesterase-6 (Pde6) gene is driven by excessive [Ca2+]i levels within the cell body. Arguing against Ca2+ overload in Pde6 mutant photoreceptors, simultaneous analysis of cone photoreceptor morphology and Ca2+ fluxes revealed that degeneration of pde6cw59 mutant cones, which lack the cone-specific cGMP phosphodiesterase, is not associated with sustained increases in perikaryal [Ca2+]i. Analysis of [Ca2+]i in dissociated Pde6βrd1mouse rods shows conservation of this finding across vertebrates. In vivo, transient and Pde6-independent Ca2+ elevations (‘flashes') were detected throughout the inner segment and the synapse. As the mutant cells proceeded to degenerate, these Ca2+ fluxes diminished. This study thus provides insight into Ca2+ dynamics in a common form of inherited blindness and uncovers a dramatic, light-independent modulation of [Ca2+]i that occurs in normal cones.
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Abstract
Acetylcholine is present in and released from starburst amacrine cells in the inner plexiform layer (IPL), but its role in retinal function except, perhaps, in early development, is unclear. Nicotinic acetylcholine receptors are thought to be present on ganglion, amacrine, and bipolar cell processes in the IPL, and it is known that acetylcholine increases the spontaneous and light-evoked responses of retinal ganglion cells. The effects of acetylcholine on bipolar cells are not known, and here we report the effects of nicotine on the b-wave of the electroretinogram in larval zebrafish. The b-wave originates mainly from ON-bipolar cells, and the larval zebrafish retina is cone-dominated. Only small rod responses can be elicited with dim lights in wild-type larval zebrafish retinas, but rod responses can be recorded over a range of intensities in a mutant ( n o optokinetic response f ) fi sh that has no cone function. We fi nd that nicotine strongly enhances cone-driven b-wave response amplitudes but depresses rod driven b-wave response amplitudes without, however, affecting rod- or cone-driven b-wave light sensitivity.
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16
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Zhang L, Chong L, Cho J, Liao PC, Shen F, Leung YF. Drug Screening to Treat Early-Onset Eye Diseases: Can Zebrafish Expedite the Discovery? ASIA-PACIFIC JOURNAL OF OPHTHALMOLOGY (PHILADELPHIA, PA.) 2012; 1:374-83. [PMID: 26107731 DOI: 10.1097/apo.0b013e31827a9969] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The molecular basis of many early-onset eye diseases has been uncovered, but the number of available drug treatments for improving deteriorated vision is still scarce. Consequently, there is a high demand for new drugs to treat these diseases. This review first provides a brief synopsis of the use of zebrafish model for screening drugs with vision benefits. In particular, visual-motor response, the activity response of larvae to a change in light stimuli, is proposed to serve as a simple and efficient tool for screening drugs that may improve vision in various zebrafish visual mutants. The second part of the review discusses the identification of novel drug candidates, with particular emphasis on naturally derived chemicals including traditional Chinese medicines and nutritional therapies on retinal degenerative diseases. Many of these chemicals have been used in neuroprotection and/or have been consumed by many populations for good health and vision; thus, the screening of these chemicals with various zebrafish visual mutants would expedite the development of novel drugs for treating early-onset eye diseases.
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Affiliation(s)
- Liyun Zhang
- From the *Department of Biological Sciences, Purdue University; and †Department of Biochemistry and Molecular Biology, Indiana University School of Medicine Lafayette, West Lafayette, IN
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17
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Zebrafish inner retina: local signals for spatial position, luminance, and color contrast. Vis Neurosci 2012; 29:229-36. [PMID: 22877609 DOI: 10.1017/s0952523812000259] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The retina of the zebrafish (Danio rerio) provides an unusually favorable preparation for genetic and developmental studies of the retina. Although the retina has been studied extensively for two decades, the neuronal response of the inner retina is largely unknown. This report describes a prominent local field potential of the inner retina, the Proximal Negative Response (PNR). It is best evoked by small (100 μm) precisely positioned spots of light and is exceedingly sensitive to negative luminance contrast. The polarity, waveform, and other properties of the PNR suggest that it arises primarily from ON-OFF neurons of the proximal retina. The dominant response to negative contrast and its enhancement by light adaptation is believed due to a dominant presynaptic input from OFF bipolar cells. Color contrast was investigated by analyzing responses to a green bar moving on green versus red backgrounds. Over an intermediate range of irradiance, the response to green on red was larger than the response to green on green, thereby providing evidence for the encoding of color contrast. The present findings complement the classic principle of color contrast for human vision known as Kirschmann's third law and bring to mind the view of Walls that color contrast may have been the driving force for the evolution of color vision in lower vertebrates. In sum, the PNR of zebrafish provides clear evidence for the encoding of color and luminance contrast in the inner retina. It exhibits the defining properties common to many other vertebrates, reinforcing the view that the zebrafish may further serve as a model for retinal function and that the PNR may provide a new approach for studies of development, genetics, and retinal degeneration in zebrafish.
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18
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Novel expression patterns of metabotropic glutamate receptor 6 in the zebrafish nervous system. PLoS One 2012; 7:e35256. [PMID: 22523578 PMCID: PMC3327648 DOI: 10.1371/journal.pone.0035256] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 03/14/2012] [Indexed: 12/24/2022] Open
Abstract
The metabotropic glutamate receptor 6 (mGluR6 or GRM6) belongs to the class III of the metabotropic glutamate receptor family. It is the only known mGluR that mediates direct synaptic transmission in the nervous system and is thought to mediate the ON-response in the ON-pathway of the vertebrate retina. Phylogenetic and gene structure analysis indicated that the zebrafish genome harbours two mglur6 paralogs, mglur6a and mglur6b. Besides expression in the inner nuclear layer and distinct regions in the brain, both mglur6 paralogs are expressed in ganglion cells of the retina, an expression pattern which can also be observed in the downstream effector molecules gnaoa and gnaob. This unexpected expression pattern is consistent with immunohistological labeling using a peptide antibody specific for the mGluR6b paralog. These expression patterns contradict the existing view that mGluR6 is solely located on ON-bipolar cells where it functions in signal transmission. Consistent with expression in ON-bipolar cells, we report a decreased b-wave amplitude in the electroretinogram after morpholino-based downregulation of mGluR6b, showing a function in the ON response. Our data suggest more widespread functions of mGluR6 mediated signaling in the central nervous system, possibly including sign reversing synapses in the inner retina.
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Lewis A, Wilson N, Stearns G, Johnson N, Nelson R, Brockerhoff SE. Celsr3 is required for normal development of GABA circuits in the inner retina. PLoS Genet 2011; 7:e1002239. [PMID: 21852962 PMCID: PMC3154962 DOI: 10.1371/journal.pgen.1002239] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Accepted: 06/28/2011] [Indexed: 12/30/2022] Open
Abstract
The identity of the specific molecules required for the process of retinal circuitry formation is largely unknown. Here we report a newly identified zebrafish mutant in which the absence of the atypical cadherin, Celsr3, leads to a specific defect in the development of GABAergic signaling in the inner retina. This mutant lacks an optokinetic response (OKR), the ability to visually track rotating illuminated stripes, and develops a super-normal b-wave in the electroretinogram (ERG). We find that celsr3 mRNA is abundant in the amacrine and ganglion cells of the retina, however its loss does not affect synaptic lamination within the inner plexiform layer (IPL) or amacrine cell number. We localize the ERG defect pharmacologically to a late-stage disruption in GABAergic modulation of ON-bipolar cell pathway and find that the DNQX-sensitive fast b1 component of the ERG is specifically affected in this mutant. Consistently, we find an increase in GABA receptors on mutant ON-bipolar terminals, providing a direct link between the observed physiological changes and alterations in GABA signaling components. Finally, using blastula transplantation, we show that the lack of an OKR is due, at least partially, to Celsr3-mediated defects within the brain. These findings support the previously postulated inner retina origin for the b1 component and reveal a new role for Celsr3 in the normal development of ON visual pathway circuitry in the inner retina. Visual information is transmitted through the retina from photoreceptors to bipolars to ganglion cells, the output neurons connecting to the brain. This vertical transmission of information is modulated by inhibitory lateral interneurons. Normal vision requires the proper transmission and processing of these neuronal signals. In the inner retina, amacrine cells are the main class of inhibitory interneurons. They modulate the information from bipolar to ganglion cells and are functionally responsible for adjusting image brightness and for detecting motion. Physiological studies have revealed important aspects of the mechanisms of inhibitory modulation, and anatomical studies have identified the many amacrine subclasses and their non-random arrangement within the retina. Although cell–cell interactions are thought to be critical for establishing the important physiological and morphological features of this cell class, the precise molecules and their functions are mostly unknown. In this paper we report the discovery of a mutant that identifies the atypical cell adhesion molecule, Celsr3, as critical for proper development of GABA-signaling pathways in the inner retina.
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Affiliation(s)
- Alaron Lewis
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Neil Wilson
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - George Stearns
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Nicolas Johnson
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Ralph Nelson
- Basic Neurosciences Program, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Rockville, Maryland, United States of America
| | - Susan E. Brockerhoff
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- * E-mail:
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20
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Bachmann-Gagescu R, Phelps IG, Stearns G, Link BA, Brockerhoff SE, Moens CB, Doherty D. The ciliopathy gene cc2d2a controls zebrafish photoreceptor outer segment development through a role in Rab8-dependent vesicle trafficking. Hum Mol Genet 2011; 20:4041-55. [PMID: 21816947 PMCID: PMC3177654 DOI: 10.1093/hmg/ddr332] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Ciliopathies are a genetically and phenotypically heterogeneous group of human developmental disorders whose root cause is the absence or dysfunction of primary cilia. Joubert syndrome is characterized by a distinctive hindbrain malformation variably associated with retinal dystrophy and cystic kidney disease. Mutations in CC2D2A are found in ∼10% of patients with Joubert syndrome. Here we describe the retinal phenotype of cc2d2a mutant zebrafish consisting of disorganized rod and cone photoreceptor outer segments resulting in abnormal visual function as measured by electroretinogram. Our analysis reveals trafficking defects in mutant photoreceptors affecting transmembrane outer segment proteins (opsins) and striking accumulation of vesicles, suggesting a role for Cc2d2a in vesicle trafficking and fusion. This is further supported by mislocalization of Rab8, a key regulator of opsin carrier vesicle trafficking, in cc2d2a mutant photoreceptors and by enhancement of the cc2d2a retinal and kidney phenotypes with partial knockdown of rab8. We demonstrate that Cc2d2a localizes to the connecting cilium in photoreceptors and to the transition zone in other ciliated cell types and that cilia are present in these cells in cc2d2a mutants, arguing against a primary function for Cc2d2a in ciliogenesis. Our data support a model where Cc2d2a, localized at the photoreceptor connecting cilium/transition zone, facilitates protein transport through a role in Rab8-dependent vesicle trafficking and fusion.
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Affiliation(s)
- Ruxandra Bachmann-Gagescu
- HHMI and Division of Basic Science, Fred Hutchinson Cancer Research Center, Seattle, WA 98109-1024, USA.
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21
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Emran F, Dowling JE. Larval zebrafish turn off their photoreceptors at night. Commun Integr Biol 2011; 3:430-2. [PMID: 21057632 DOI: 10.4161/cib.3.5.12158] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Accepted: 04/24/2010] [Indexed: 11/19/2022] Open
Abstract
Studies in several vertebrate species have shown that visual sensitivity and a number of other retinal phenomena are regulated by circadian mechanisms. For example, ultra-structural studies of 5 day old zebrafish larvae have shown that synaptic ribbons in photoreceptor terminals undergo dramatic diurnal alterations. These synaptic ribbons are very prominent during the day, but are almost completely absent at night. The implications of this circadian driven process on visual function are not well understood. We recently showed that larval zebrafish essentially lose visual responsiveness at night. This shut-down of retinal function at night is regulated by at least two mechanisms: the disassembly of synaptic ribbons in cone pedicles and a decrease of outer segment activity. Here, we summarize our recently reported observations and further discuss our hypothesis on how this phenomenon of shutting-down retinal function at night may provide a means for zebrafish larvae to conserve energy.
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Affiliation(s)
- Farida Emran
- Department of Molecular and Cellular Biology; Harvard University; Cambridge, MA USA
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22
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Stujenske JM, Dowling JE, Emran F. The bugeye mutant zebrafish exhibits visual deficits that arise with the onset of an enlarged eye phenotype. Invest Ophthalmol Vis Sci 2011; 52:4200-7. [PMID: 21460263 DOI: 10.1167/iovs.10-6434] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
PURPOSE The bugeye mutant has an enlarged eye phenotype, presumably because of elevated intraocular pressure. Since elevated intraocular pressure is a significant risk factor for glaucoma, the bugeye zebrafish mutant may be a model organism for the disease. METHODS The optomotor response (OMR) was used to assess visual responsiveness in both larval and adult zebrafish. Electroretinograms (ERGs) were recorded to measure outer retinal function, and histologic analyses were performed on WT and mutant eyes. RESULTS At 5 days old, bugeye mutants have an OMR, ERGs, and retinal morphology indistinguishable from those of wild-type (WT) animals. By 2 months of age, bugeye mutants begin to develop an enlarged eye phenotype. At 3 months, some mutants show deficits in the OMR assay, including lower contrast sensitivity. The data suggest that there is a correlation between the size of the enlarged eye and the degree of OMR deficit. Histologic analysis of the bugeye mutant retina revealed decreases in retinal ganglion cell densities by 3 months. By 5 months, the mutant's ERG b-wave had smaller amplitudes and longer latencies at brighter light intensities than those of the WT fish. CONCLUSION After phenotypic onset at 3 months, the bugeye mutants begin to develop visual deficits. At 3 months, bugeye mutants exhibit a decrease in retinal cell densities and by 5 months, they show diminished outer retinal function. In summary, the bugeye mutant provides a means of studying glaucoma-associated phenotypes in the zebrafish.
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Affiliation(s)
- Joseph M Stujenske
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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23
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Abstract
AbstractZebrafish are an existing model for genetic and developmental studies due to their rapid external development and transparent embryos, which allow easy manipulation and observation of early developmental stages. The application of the zebrafish model to vision research has allowed for examination of retinal development and the characteristics of different retinal cell types, including bipolar cells. In particular, bipolar cell development, including differentiation, maturation, and gene expression, has been documented, as has physiological properties, such as voltage- and ligand-gated currents, and neurotransmitter receptor and ion channel expression. Mutant strains and transgenic lines have been used to document how bipolar cell connections and/or development may be altered, and toxicological studies examining how environmental factors may impact bipolar cell activity have been performed. The purpose of this paper was to review the existing literature on zebrafish bipolar cells, to provide a comprehensive overview of current information pertaining to this retinal cell type.
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Abstract
Mutations in ubiquitously expressed metabolic genes often lead to CNS-specific effects, presumably because of the high metabolic demands of neurons. However, mutations in omnipresent metabolic pathways can conceivably also result in cell type-specific effects because of cell-specific requirements for intermediate products. One such example is the zebrafish noir mutant, which we found to be mutated in the pdhb gene, coding for the E1 beta subunit of the pyruvate dehydrogenase complex. This vision mutant is described as blind and was isolated because of its vision defect-related darker appearance. A detailed morphological, behavioral, and physiological analysis of the phenotype revealed an unexpected specific effect on the retina. Surprisingly, the cholinergic amacrine cells of the inner retina are affected earlier than the photoreceptors. This might be attributable to the inability of these cells to maintain production of their neurotransmitter acetylcholine. This is reflected in an earlier loss of motion vision, followed only later by a general loss of light perception. Since both characteristics of the phenotype are attributable to a loss of acetyl-CoA production by pyruvate dehydrogenase, we used a ketogenic diet to bypass this metabolic block and could indeed partially rescue vision and prolong survival of the larvae. The noir mutant provides a case for a systemic disease with ocular manifestation with a surprising specific effect on the retina given the ubiquitous requirement for the mutated gene.
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25
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Ile KE, Kassen S, Cao C, Vihtehlic T, Shah SD, Mousley CJ, Alb JG, Huijbregts RPH, Stearns GW, Brockerhoff SE, Hyde DR, Bankaitis VA. Zebrafish class 1 phosphatidylinositol transfer proteins: PITPbeta and double cone cell outer segment integrity in retina. Traffic 2010; 11:1151-67. [PMID: 20545905 DOI: 10.1111/j.1600-0854.2010.01085.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Phosphatidylinositol transfer proteins (PITPs) in yeast co-ordinate lipid metabolism with the activities of specific membrane trafficking pathways. The structurally unrelated metazoan PITPs (mPITPs), on the other hand, are an under-investigated class of proteins. It remains unclear what biological activities mPITPs discharge, and the mechanisms by which these proteins function are also not understood. The soluble class 1 mPITPs include the PITPalpha and PITPbeta isoforms. Of these, the beta-isoforms are particularly poorly characterized. Herein, we report the use of zebrafish as a model vertebrate for the study of class 1 mPITP biological function. Zebrafish express PITPalpha and PITPbeta-isoforms (Pitpna and Pitpnb, respectively) and a novel PITPbeta-like isoform (Pitpng). Pitpnb expression is particularly robust in double cone cells of the zebrafish retina. Morpholino-mediated protein knockdown experiments demonstrate Pitpnb activity is primarily required for biogenesis/maintenance of the double cone photoreceptor cell outer segments in the developing retina. By contrast, Pitpna activity is essential for successful navigation of early developmental programs. This study reports the initial description of the zebrafish class 1 mPITP family, and the first analysis of PITPbeta function in a vertebrate.
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Affiliation(s)
- Kristina E Ile
- Department of Cell & Developmental Biology, Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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26
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Abstract
Structural features of neurons create challenges for effective production and distribution of essential metabolic energy. We investigated how metabolic energy is distributed between cellular compartments in photoreceptors. In avascular retinas, aerobic production of energy occurs only in mitochondria that are located centrally within the photoreceptor. Our findings indicate that metabolic energy flows from these central mitochondria as phosphocreatine toward the photoreceptor's synaptic terminal in darkness. In light, it flows in the opposite direction as ATP toward the outer segment. Consistent with this model, inhibition of creatine kinase in avascular retinas blocks synaptic transmission without influencing outer segment activity. Our findings also reveal how vascularization of neuronal tissue can influence the strategies neurons use for energy management. In vascularized retinas, mitochondria in the synaptic terminals of photoreceptors make neurotransmission less dependent on creatine kinase. Thus, vasculature of the tissue and the intracellular distribution of mitochondria can play key roles in setting the strategy for energy distribution in neurons.
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27
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Abstract
Darkness serves as a stimulus for vertebrate photoreceptors; they are actively depolarized in the dark and hyperpolarize in the light. Here, we show that larval zebrafish essentially turn off their visual system at night when they are not active. Electroretinograms recorded from larval zebrafish show large differences between day and night; the responses are normal in amplitude throughout the day but are almost absent after several hours of darkness at night. Behavioral testing also shows that larval zebrafish become unresponsive to visual stimuli at night. This phenomenon is largely circadian driven as fish show similar dramatic changes in visual responsiveness when maintained in continuous darkness, although light exposure at night partially restores the responses. Visual responsiveness is decreased at night by at least two mechanisms: photoreceptor outer segment activity decreases and synaptic ribbons in cone pedicles disassemble.
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28
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Alvarez Y, Chen K, Reynolds AL, Waghorne N, O'Connor JJ, Kennedy BN. Predominant cone photoreceptor dysfunction in a hyperglycaemic model of non-proliferative diabetic retinopathy. Dis Model Mech 2010; 3:236-45. [PMID: 20142328 DOI: 10.1242/dmm.003772] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Approximately 2.5 million people worldwide are clinically blind because of diabetic retinopathy. In the non-proliferative stage, the pathophysiology of this ocular manifestation of diabetes presents as morphological and functional disruption of the retinal vasculature, and dysfunction of retinal neurons. However, it is uncertain whether the vascular and neuronal changes are interdependent or independent events. In addition, the identity of the retinal neurons that are most susceptible to the hyperglycaemia associated with diabetes is unclear. Here, we characterise a novel model of non-proliferative diabetic retinopathy in adult zebrafish, in which the zebrafish were subjected to oscillating hyperglycaemia for 30 days. Visual function is diminished in hyperglycaemic fish. Significantly, hyperglycaemia disrupts cone photoreceptor neurons the most, as evidenced by prominent morphological degeneration and dysfunctional cone-mediated electroretinograms. Disturbances in the morphological integrity of the blood-retinal barrier were also evident. However, we demonstrate that these early vascular changes are not sufficient to induce cone photoreceptor dysfunction, suggesting that the vascular and neuronal complications in diabetic retinopathy can arise independently. Current treatments for diabetic retinopathy target the vascular complications. Our data suggest that cone photoreceptor dysfunction is a clinical hallmark of diabetic retinopathy and that the debilitating blindness associated with diabetic retinopathy may be halted by neuroprotection of cones.
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Affiliation(s)
- Yolanda Alvarez
- UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute, University College Dublin, Belfield, Dublin D4, Ireland
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A spectral model for signal elements isolated from zebrafish photopic electroretinogram. Vis Neurosci 2009; 26:349-63. [PMID: 19723365 DOI: 10.1017/s0952523809990113] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The zebrafish photopic electroretinogram (ERG) sums isolatable elements. In each element, red-, blue-, green-, and UV- (r, g, b, and u) cone signals combine in a way that reflects retinal organization. ERG responses to monochromatic stimuli of different wavelengths and irradiances were recorded on a white rod suppressing background using superfused eyecups. Onset elements were isolated with glutamatergic blockers and response subtractions. CNQX-blocked ionotropic (AMPA/kainate) glutamate receptors; l-AP4 or CPPG-blocked metabotropic (mGluR6) glutamate receptors; TBOA-blocked glutamate transporters; and l-aspartate inactivated all glutamatergic mechanisms. Seven elements emerged: photopic PIII, the l-aspartate-isolated cone response; b1, a CNQX-sensitive early b-wave element of inner retinal origin; PII, a photopic, CNQX-insensitive composite b-wave element from ON bipolar cells; PIIm, an l-AP4/CPPG-sensitive, CNQX-insensitive, metabotropic subelement of PII; PIInm, an l-AP4/CPPG/CNQX-insensitive nonmetabotropic subelement of PII; a1nm, a TBOA-sensitive, CNQX/l-AP4/CPPG-insensitive, nonmetabotropic, postphotoreceptor a-wave element; and a2, a CNQX-sensitive a-wave element linked to OFF bipolar cells. The first five elements were fit with a spectral model that demonstrates independence of cone-color pathways. From this, Vmax and half-saturation values (k) for the contributing r-, g-, b-, and u-cone signals were calculated. Two signal patterns emerged. For PIII or PIInm, the Vmax order was Vr > Vg >> Vb approximately Vu. For b1, PII, and PIIm, the Vmax order was Vr approximately Vb > Vg > Vu. In either pattern, u-cone amplitude (Vu) was smallest, but u-cone sensitivity (ku362) was greatest, some 10-30 times greater than r cone (kr570). The spectra of b1/PII/PIIm elements peaked near b- and u-cone absorbance maxima regardless of criteria, but the spectra of PIII/PIInm elements shifted from b- toward r-cone absorbance maxima as criterion levels increased. The greatest gains in Vmax relative to PIII occurred for the b- and u-cone signals in the b1/PII/PIIm b-wave elements. This suggests a high-gain prolific metabotropic circuitry for b- and u-cone bipolar cells.
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31
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Nevin LM, Taylor MR, Baier H. Hardwiring of fine synaptic layers in the zebrafish visual pathway. Neural Dev 2008; 3:36. [PMID: 19087349 PMCID: PMC2647910 DOI: 10.1186/1749-8104-3-36] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2008] [Accepted: 12/16/2008] [Indexed: 11/30/2022] Open
Abstract
Background Neuronal connections are often arranged in layers, which are divided into sublaminae harboring synapses with similar response properties. It is still debated how fine-grained synaptic layering is established during development. Here we investigated two stratified areas of the zebrafish visual pathway, the inner plexiform layer (IPL) of the retina and the neuropil of the optic tectum, and determined if activity is required for their organization. Results The IPL of 5-day-old zebrafish larvae is composed of at least nine sublaminae, comprising the connections between different types of amacrine, bipolar, and ganglion cells (ACs, BCs, GCs). These sublaminae were distinguished by their expression of cell type-specific transgenic fluorescent reporters and immunohistochemical markers, including protein kinase Cβ (PKC), parvalbumin (Parv), zrf3, and choline acetyltransferase (ChAT). In the tectum, four retinal input layers abut a laminated array of neurites of tectal cells, which differentially express PKC and Parv. We investigated whether these patterns were affected by experimental disruptions of retinal activity in developing fish. Neither elimination of light inputs by dark rearing, nor a D, L-amino-phosphono-butyrate-induced reduction in the retinal response to light onset (but not offset) altered IPL or tectal lamination. Moreover, thorough elimination of chemical synaptic transmission with Botulinum toxin B left laminar synaptic arrays intact. Conclusion Our results call into question a role for activity-dependent mechanisms – instructive light signals, balanced on and off BC activity, Hebbian plasticity, or a permissive role for synaptic transmission – in the synaptic stratification we examined. We propose that genetically encoded cues are sufficient to target groups of neurites to synaptic layers in this vertebrate visual system.
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Affiliation(s)
- Linda M Nevin
- Department of Physiology, University of California, San Francisco, CA 94158, USA.
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Recent papers on zebrafish and other aquarium fish models. Zebrafish 2008; 1:305-11. [PMID: 18248239 DOI: 10.1089/zeb.2004.1.305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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OFF ganglion cells cannot drive the optokinetic reflex in zebrafish. Proc Natl Acad Sci U S A 2007; 104:19126-31. [PMID: 18025459 DOI: 10.1073/pnas.0709337104] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Whereas the zebrafish retina has long been an important model system for developmental and genetic studies, little is known about the responses of the inner retinal neurons. Here we report single-unit ganglion cell recordings from 5- to 6-day-old zebrafish larvae. In wild-type larvae we identify at least five subtypes of ganglion cell responses to full-field illumination, with ON-OFF and ON-type cells predominating. In the nrc mutant retina, in which the photoreceptor terminals develop abnormally, we observe normal OFF responses but abnormal ON-OFF responses and no ON responses. Previously characterized as blind, these mutants lack an optokinetic reflex (OKR), but in another behavioral assay nrc mutant fish have near-normal responses to the offset of light and slow and sluggish responses to the onset of light. Pharmacological block of the ON pathway mimics most of the nrc visual defects. We conclude that the abnormal photoreceptor terminals in nrc mutants predominantly perturb the ON pathway and that the ON pathway is necessary to drive the OKR in larval zebrafish.
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Abstract
Over the last decade, the use of the zebrafish as a genetic model has moved beyond the proof-of-concept for the analysis of vertebrate embryonic development to demonstrated utility as a mainstream model organism for the understanding of human disease. The initial identification of a variety of zebrafish mutations affecting the eye and retina, and the subsequent cloning of mutated genes have revealed cellular, molecular and physiological processes fundamental to visual system development. With the increasing development of genetic manipulations, sophisticated techniques for phenotypic characterization, behavioral approaches and screening strategies, the identification of novel genes or novel gene functions will have important implications for our understanding of human eye diseases, pathogenesis, and treatment.
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Affiliation(s)
- James M Fadool
- Department of Biological Science, Graduate Program in Neuroscience, Florida State University, Tallahassee, FL 32312, USA.
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Matsui JI, Egana AL, Sponholtz TR, Adolph AR, Dowling JE. Effects of ethanol on photoreceptors and visual function in developing zebrafish. Invest Ophthalmol Vis Sci 2006; 47:4589-97. [PMID: 17003456 PMCID: PMC2408731 DOI: 10.1167/iovs.05-0971] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Children born to mothers who have consumed alcohol during pregnancy have an array of retinal abnormalities and visual dysfunctions. In the past, rodent systems have been used to study the teratogenic effects of ethanol on vertebrate embryonic development. The exact developmental windows in which ethanol causes specific developmental defects have been difficult to determine because rodents and other mammals develop in utero. In this study, we characterized how ethanol affects the function and development of the visual system in an ex utero embryonic system, the zebrafish. METHODS Zebrafish embryos were raised in fish water containing various concentrations of ethanol from 2 to 5 days after fertilization. The effects of ethanol on retinal morphology were assessed by histologic and immunohistochemical analyses and those on retinal function were analyzed by optokinetic response (OKR) and electroretinography (ERG). RESULTS Zebrafish embryos exposed to moderate and high levels of ethanol during early embryonic development had morphological abnormalities of the eye characterized by hypoplasia of the optic nerve and inhibition of photoreceptor outer segment growth. Ethanol treatment also caused an increased visual threshold as measured by the OKR. Analysis with the ERG indicated that there was a severe reduction of both the a- and b-waves, suggesting that ethanol affects the function of the photoreceptors. Indeed, low levels of ethanol that did not cause obvious morphologic changes in either the body or retina did affect both the OKR visual threshold and the a- and b-wave amplitudes. CONCLUSIONS Ethanol affects photoreceptor function at low concentrations that do not disturb retinal morphology. Higher levels of ethanol inhibit photoreceptor development and cause hypoplasia of the optic nerve.
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Affiliation(s)
- Jonathan I Matsui
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
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Yu CJ, Li L. Dopamine modulates voltage-activated potassium currents in zebrafish retinal on bipolar cells. J Neurosci Res 2006; 82:368-76. [PMID: 16206280 DOI: 10.1002/jnr.20637] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We report a study of the characterization of voltage-activated potassium (K+) currents in retinal ON bipolar cells in zebrafish. At single-channels levels, the open probability of the K+ channels increased when the membrane potential was increased. The maximal open proportion was 0.76+/-0.05 under our testing conditions. In whole-cell recordings, the K+ current displayed two exponential components with the activation time constants of 11-22 msec (tau1) and 0.8-4 msec (tau2). Dopamine modulated the K+ current. Dopamine reduced the time constant tau2 when the membrane potential was depolarized to high voltages. A decrease in K+ current was seen when dopamine D1 receptors were selectively activated by SKF38393 or when the D1 receptor-coupled G-proteins were activated by GTP-gamma-S. The activation of adenylate cyclase by forskolin or the increase of intracellular cAMP concentrations by 8-Br-cAMP or Sp-cAMPS also resulted in a decrease in K+ current. Together, the data suggest that dopamine modulates the K+ current via D1 receptor-coupled G-protein pathways.
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Affiliation(s)
- Chuan-Jiang Yu
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556, USA
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Wong KY, Adolph AR, Dowling JE. Retinal bipolar cell input mechanisms in giant danio. I. Electroretinographic analysis. J Neurophysiol 2004; 93:84-93. [PMID: 15229213 DOI: 10.1152/jn.00259.2004] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
UNLABELLED Electroretinograms (ERGs) were recorded from the giant danio (Danio aequipinnatus) to study glutamatergic input mechanisms onto bipolar cells. Glutamate analogs were applied to determine which receptor types mediate synaptic transmission from rods and cones to on and off bipolar cells. Picrotoxin, strychnine, and tetrodotoxin were used to isolate the effects of the glutamate analogs to the photoreceptor-bipolar cell synapse. Under photopic conditions, the group III metabotropic glutamate receptor (mGluR) antagonist (RS)-alpha-cyclopropyl-4-phosphonophenylglycine (CPPG) only slightly reduced the b-wave, whereas the excitatory amino acid transporter (EAAT) blocker dl-threo-beta-benzyl-oxyaspartate (TBOA) removed most of it. Complete elimination of the b-wave required both antagonists. The alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)/kainate receptor antagonist 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide (NBQX) blocked the d-wave. Under scotopic conditions, rod and cone inputs onto on bipolar cells were studied by comparing the sensitivities of the b-wave to photopically matched green and red stimuli. The b-wave was >1 log unit more sensitive to the green than to the red stimulus under control conditions. In CPPG or l-AP4 (l-(+)-2-amino-4-phosphonobutyric acid, a group III mGluR agonist), the sensitivity of the b-wave to the green stimulus was dramatically reduced and the b-waves elicited by the 2 stimuli became nearly matched. The d-wave elicited by dim green stimuli, which presumably could be detected only by the rods, was eliminated by NBQX. IN CONCLUSION 1) cone signals onto on bipolar cells involve mainly EAATs but also mGluRs (presumably mGluR6) to a lesser extent; 2) rods signal onto on bipolars by mainly mGluR6; 3) off bipolar cells receive signals from both photoreceptor types by AMPA/kainate receptors.
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Affiliation(s)
- Kwoon Y Wong
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA.
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