1
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Mat A, Vu HH, Wolf E, Tessmar-Raible K. All Light, Everywhere? Photoreceptors at Nonconventional Sites. Physiology (Bethesda) 2024; 39:0. [PMID: 37905983 DOI: 10.1152/physiol.00017.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 10/29/2023] [Accepted: 10/29/2023] [Indexed: 11/02/2023] Open
Abstract
One of the biggest environmental alterations we have made to our species is the change in the exposure to light. During the day, we typically sit behind glass windows illuminated by artificial light that is >400 times dimmer and has a very different spectrum than natural daylight. On the opposite end are the nights that are now lit up by several orders of magnitude. This review aims to provide food for thought as to why this matters for humans and other animals. Evidence from behavioral neuroscience, physiology, chronobiology, and molecular biology is increasingly converging on the conclusions that the biological nonvisual functions of light and photosensory molecules are highly complex. The initial work of von Frisch on extraocular photoreceptors in fish, the identification of rhodopsins as the molecular light receptors in animal eyes and eye-like structures and cryptochromes as light sensors in nonmammalian chronobiology, still allowed for the impression that light reception would be a relatively restricted, localized sense in most animals. However, light-sensitive processes and/or sensory proteins have now been localized to many different cell types and tissues. It might be necessary to consider nonlight-responding cells as the exception, rather than the rule.
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Affiliation(s)
- Audrey Mat
- Max Perutz Labs, University of Vienna, Vienna BioCenter, Vienna, Austria
- VIPS2, Vienna BioCenter, Vienna, Austria
| | - Hong Ha Vu
- Institute of Molecular Physiology, Johannes Gutenberg-University, Mainz, Germany
| | - Eva Wolf
- Institute of Molecular Physiology, Johannes Gutenberg-University, Mainz, Germany
- Institute of Molecular Biology, Mainz, Germany
| | - Kristin Tessmar-Raible
- Max Perutz Labs, University of Vienna, Vienna BioCenter, Vienna, Austria
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Carl-von-Ossietzky University, Oldenburg, Germany
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2
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Mizoguchi K, Sato M, Saito R, Koshikuni M, Sakakibara M, Manabe R, Harada Y, Uchikawa T, Ansai S, Kamei Y, Naruse K, Fukamachi S. Behavioral photosensitivity of multi-color-blind medaka: enhanced response under ultraviolet light in the absence of short-wavelength-sensitive opsins. BMC Neurosci 2023; 24:67. [PMID: 38097940 PMCID: PMC10722765 DOI: 10.1186/s12868-023-00835-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 11/20/2023] [Indexed: 12/17/2023] Open
Abstract
BACKGROUND The behavioral photosensitivity of animals could be quantified via the optomotor response (OMR), for example, and the luminous efficiency function (the range of visible light) should largely rely on the repertoire and expression of light-absorbing proteins in the retina, i.e., the opsins. In fact, the OMR under red light was suppressed in medaka lacking the red (long-wavelength sensitive [LWS]) opsin. RESULTS We investigated the ultraviolet (UV)- or blue-light sensitivity of medaka lacking the violet (short-wavelength sensitive 1 [SWS1]) and blue (SWS2) opsins. The sws1/sws2 double or sws1/sws2/lws triple mutants were as viable as the wild type. The remaining green (rhodopsin 2 [RH2]) or red opsins were not upregulated. Interestingly, the OMR of the double or triple mutants was equivalent or even increased under UV or blue light (λ = 350, 365, or 450 nm), which demonstrated that the rotating stripes (i.e., changes in luminance) could fully be recognized under UV light using RH2 alone. The OMR test using dichromatic stripes projected onto an RGB display consistently showed that the presence or absence of SWS1 and SWS2 did not affect the equiluminant conditions. CONCLUSIONS RH2 and LWS, but not SWS1 and SWS2, should predominantly contribute to the postreceptoral processes leading to the OMR or, possibly, to luminance detection in general, as the medium-wavelength-sensitive and LWS cones, but not the SWS cones, are responsible for luminance detection in humans.
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Affiliation(s)
- Kiyono Mizoguchi
- Laboratory of Evolutionary Genetics, Department of Chemical and Biological Sciences, Japan Women's University, Mejirodai 2-8-1, Bunkyo-Ku, Tokyo, 112-8681, Japan
| | - Mayu Sato
- Laboratory of Evolutionary Genetics, Department of Chemical and Biological Sciences, Japan Women's University, Mejirodai 2-8-1, Bunkyo-Ku, Tokyo, 112-8681, Japan
| | - Rina Saito
- Laboratory of Evolutionary Genetics, Department of Chemical and Biological Sciences, Japan Women's University, Mejirodai 2-8-1, Bunkyo-Ku, Tokyo, 112-8681, Japan
| | - Mayu Koshikuni
- Laboratory of Evolutionary Genetics, Department of Chemical and Biological Sciences, Japan Women's University, Mejirodai 2-8-1, Bunkyo-Ku, Tokyo, 112-8681, Japan
| | - Mana Sakakibara
- Laboratory of Evolutionary Genetics, Department of Chemical and Biological Sciences, Japan Women's University, Mejirodai 2-8-1, Bunkyo-Ku, Tokyo, 112-8681, Japan
| | - Ran Manabe
- Laboratory of Evolutionary Genetics, Department of Chemical and Biological Sciences, Japan Women's University, Mejirodai 2-8-1, Bunkyo-Ku, Tokyo, 112-8681, Japan
| | - Yumi Harada
- Laboratory of Evolutionary Genetics, Department of Chemical and Biological Sciences, Japan Women's University, Mejirodai 2-8-1, Bunkyo-Ku, Tokyo, 112-8681, Japan
| | - Tamaki Uchikawa
- Laboratory of Evolutionary Genetics, Department of Chemical and Biological Sciences, Japan Women's University, Mejirodai 2-8-1, Bunkyo-Ku, Tokyo, 112-8681, Japan
| | - Satoshi Ansai
- Laboratory of Bioresources, National Institute for Basic Biology, Aichi, 444-8585, Japan
- Graduate School of Life Sciences, Tohoku University, Miyagi, 980-8577, Japan
- Laboratory of Genome Editing Breeding, Graduate School of Agriculture, Kyoto University, Kyoto, 606-8507, Japan
| | - Yasuhiro Kamei
- Spectrography and Bioimaging Facility, National Institute for Basic Biology, Aichi, 444-8585, Japan
- Department of Basic Biology, School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Aichi, 444-8585, Japan
| | - Kiyoshi Naruse
- Laboratory of Bioresources, National Institute for Basic Biology, Aichi, 444-8585, Japan
- Department of Basic Biology, School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Aichi, 444-8585, Japan
| | - Shoji Fukamachi
- Laboratory of Evolutionary Genetics, Department of Chemical and Biological Sciences, Japan Women's University, Mejirodai 2-8-1, Bunkyo-Ku, Tokyo, 112-8681, Japan.
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3
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Pan D, Wang Z, Chen Y, Cao J. Melanopsin-mediated optical entrainment regulates circadian rhythms in vertebrates. Commun Biol 2023; 6:1054. [PMID: 37853054 PMCID: PMC10584931 DOI: 10.1038/s42003-023-05432-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2023] [Accepted: 10/09/2023] [Indexed: 10/20/2023] Open
Abstract
Melanopsin (OPN4) is a light-sensitive protein that plays a vital role in the regulation of circadian rhythms and other nonvisual functions. Current research on OPN4 has focused on mammals; more evidence is needed from non-mammalian vertebrates to fully assess the significance of the non-visual photosensitization of OPN4 for circadian rhythm regulation. There are species differences in the regulatory mechanisms of OPN4 for vertebrate circadian rhythms, which may be due to the differences in the cutting variants, tissue localization, and photosensitive activation pathway of OPN4. We here summarize the distribution of OPN4 in mammals, birds, and teleost fish, and the classical excitation mode for the non-visual photosensitive function of OPN4 in mammals is discussed. In addition, the role of OPN4-expressing cells in regulating circadian rhythm in different vertebrates is highlighted, and the potential rhythmic regulatory effects of various neuropeptides or neurotransmitters expressed in mammalian OPN4-expressing ganglion cells are summarized among them.
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Affiliation(s)
- Deng Pan
- Laboratory of Anatomy of Domestic Animals, National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Haidian, 100193, Beijing, China
| | - Zixu Wang
- Laboratory of Anatomy of Domestic Animals, National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Haidian, 100193, Beijing, China
| | - Yaoxing Chen
- Laboratory of Anatomy of Domestic Animals, National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Haidian, 100193, Beijing, China
| | - Jing Cao
- Laboratory of Anatomy of Domestic Animals, National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Haidian, 100193, Beijing, China.
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4
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Fujiyabu C, Sato K, Ohuchi H, Yamashita T. Diversification processes of teleost intron-less opsin genes. J Biol Chem 2023:104899. [PMID: 37295773 PMCID: PMC10339062 DOI: 10.1016/j.jbc.2023.104899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 05/31/2023] [Accepted: 06/01/2023] [Indexed: 06/12/2023] Open
Abstract
Opsins are universal photosensitive proteins in animals. Vertebrates have a variety of opsin genes for visual and non-visual photoreceptions. Analysis of the gene structures shows that most opsin genes have introns in their coding regions. However, teleosts exceptionally have several intron-less opsin genes which are presumed to have been duplicated by an RNA-based gene duplication mechanism, retroduplication. Among these retrogenes, we focused on the Opn4 (melanopsin) gene responsible for non-image-forming photoreception. Many teleosts have five Opn4 genes including one intron-less gene, which is speculated to have been formed from a parental intron-containing gene in the Actinopterygii. In this study, to reveal the evolutionary history of Opn4 genes, we analyzed them in teleost (zebrafish and medaka) and non-teleost (bichir, sturgeon and gar) fishes. Our synteny analysis suggests that the intron-less Opn4 gene emerged by retroduplication after branching of the bichir lineage. In addition, our biochemical and histochemical analyses showed that, in the teleost lineage, the newly acquired intron-less Opn4 gene became abundantly used without substantial changes of the molecular properties of the Opn4 protein. This stepwise evolutionary model of Opn4 genes is quite similar to that of rhodopsin genes in the Actinopterygii. The unique acquisition of rhodopsin and Opn4 retrogenes would have contributed to the diversification of the opsin gene repertoires in the Actinopterygii and the adaptation of teleosts to various aquatic environments.
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Affiliation(s)
- Chihiro Fujiyabu
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Keita Sato
- Department of Cytology and Histology, Okayama University Faculty of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan
| | - Hideyo Ohuchi
- Department of Cytology and Histology, Okayama University Faculty of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan
| | - Takahiro Yamashita
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
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5
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Abstract
Melanopsin is a light-activated G protein coupled receptor that is expressed widely across phylogeny. In mammals, melanopsin is found in intrinsically photosensitive retinal ganglion cells (ipRGCs), which are especially important for "non-image" visual functions that include the regulation of circadian rhythms, sleep, and mood. Photochemical and electrophysiological experiments have provided evidence that melanopsin has at least two stable conformations and is thus multistable, unlike the monostable photopigments of the classic rod and cone photoreceptors. Estimates of melanopsin's properties vary, challenging efforts to understand how the molecule influences vision. This article seeks to reconcile disparate views of melanopsin and offer a practical guide to melanopsin's complexities.
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Affiliation(s)
- Alan J. Emanuel
- F.M. Kirby Neurobiology Center and Department of Neurology, Boston Children’s Hospital and Harvard Medical School. Boston, MA, USA
- Present address: Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA
| | - Michael Tri H. Do
- F.M. Kirby Neurobiology Center and Department of Neurology, Boston Children’s Hospital and Harvard Medical School. Boston, MA, USA
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6
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Karthikeyan R, Davies WI, Gunhaga L. Non-image-forming functional roles of OPN3, OPN4 and OPN5 photopigments. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY 2023. [DOI: 10.1016/j.jpap.2023.100177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/07/2023] Open
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7
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Salgado D, Mariluz BR, Araujo M, Lorena J, Perez LN, Ribeiro RDL, Sousa JDF, Schneider PN. Light-induced shifts in opsin gene expression in the four-eyed fish Anableps anableps. Front Neurosci 2022; 16:995469. [PMID: 36248668 PMCID: PMC9556854 DOI: 10.3389/fnins.2022.995469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 09/08/2022] [Indexed: 11/13/2022] Open
Abstract
The development of the vertebrate eye is a complex process orchestrated by several conserved transcriptional and signaling regulators. Aside from partial or complete loss, examples of exceptional modifications to this intricate organ are scarce. The unique eye of the four-eyed fish Anableps anableps is composed of duplicated corneas and pupils, as well as specialized retina regions associated with simultaneous aerial and aquatic vision. In a previous transcriptomic study of the A. anableps developing eye we identified expression of twenty non-visual and eleven visual opsin genes. Here, we surveyed the expression territories of three non-visual melanopsins genes (opn4×1, opn4×2, opn4m3), one teleost multiple tissue opsin (tmt1b) and two visual opsins (lws and rh2-1) in dorsal and ventral retinas. Our data showed that asymmetry of non-visual opsin expression is only established after birth. During embryonic development, while inside pregnant females, the expression of opn4×1, opn4×2, and tmt1b spans the whole retina. In juvenile fish (post birth), the expression of opn4×1, opn4×2, opn4m3, and tmt1b genes becomes restricted to the ventral retina, which receives aerial light. Raising juvenile fish in clear water instead of the murky waters found in its natural habitat is sufficient to change gene expression territories of opn4×1, opn4×2, opn4m3, tmt1b, and rh2-1, demonstrating that different lighting conditions can shift opsin expression and potentially contribute to changes in spectral sensitivity in the four eyed fish.
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Affiliation(s)
- Daniele Salgado
- Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Brazil
| | - Bertha R. Mariluz
- Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Brazil
| | - Maysa Araujo
- Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Brazil
| | - Jamily Lorena
- Department of Integrative Biology, Michigan State University, East Lansing, MI, United States
| | - Louise N. Perez
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, United States
| | | | - Josane de F. Sousa
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, United States
| | - Patricia N. Schneider
- Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Brazil
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, United States
- *Correspondence: Patricia N. Schneider,
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8
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Dekens MPS, Fontinha BM, Gallach M, Pflügler S, Tessmar‐Raible K. Melanopsin elevates locomotor activity during the wake state of the diurnal zebrafish. EMBO Rep 2022; 23:e51528. [PMID: 35233929 PMCID: PMC9066073 DOI: 10.15252/embr.202051528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Revised: 01/24/2022] [Accepted: 02/04/2022] [Indexed: 11/28/2022] Open
Abstract
Mammalian and fish pineals play a key role in adapting behaviour to the ambient light conditions through the release of melatonin. In mice, light inhibits nocturnal locomotor activity via the non‐visual photoreceptor Melanopsin. In contrast to the extensively studied function of Melanopsin in the indirect regulation of the rodent pineal, its role in the intrinsically photosensitive zebrafish pineal has not been elucidated. Therefore, it is not evident if the light signalling mechanism is conserved between distant vertebrates, and how Melanopsin could affect diurnal behaviour. A double knockout of melanopsins (opn4.1‐opn4xb) was generated in the diurnal zebrafish, which manifests attenuated locomotor activity during the wake state. Transcriptome sequencing gave insight into pathways downstream of Melanopsin, implying that sustained repression of the melatonin pathway is required to elevate locomotor activity during the diurnal wake state. Moreover, we show that light induces locomotor activity during the diurnal wake state in an intensity‐dependent manner. These observations suggest a common Melanopsin‐driven mechanism between zebrafish and mammals, while the diurnal and nocturnal chronotypes are inversely regulated downstream of melatonin.
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Affiliation(s)
- Marcus P S Dekens
- Max Perutz Laboratory Centre for Molecular Biology University of Vienna and Medical University of Vienna Vienna Austria
| | - Bruno M Fontinha
- Max Perutz Laboratory Centre for Molecular Biology University of Vienna and Medical University of Vienna Vienna Austria
| | - Miguel Gallach
- Max Perutz Laboratory Centre for Molecular Biology University of Vienna and Medical University of Vienna Vienna Austria
- Max Perutz Laboratory Centre for Integrative Bioinformatics University of Vienna and Medical University of Vienna Vienna Austria
| | - Sandra Pflügler
- Max Perutz Laboratory Centre for Molecular Biology University of Vienna and Medical University of Vienna Vienna Austria
| | - Kristin Tessmar‐Raible
- Max Perutz Laboratory Centre for Molecular Biology University of Vienna and Medical University of Vienna Vienna Austria
- Research Platform “Marine Rhythms of Life” University of Vienna Vienna Austria
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9
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Ma H, Yang MS, Zhang YT, Qiu HT, You XX, Chen SX, Hong WS. Expressions of melanopsins in telencephalon imply their function in synchronizing semilunar spawning rhythm in the mudskipper Boleophthalmus pectinirostris. Gen Comp Endocrinol 2022; 315:113926. [PMID: 34653434 DOI: 10.1016/j.ygcen.2021.113926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 09/22/2021] [Accepted: 10/09/2021] [Indexed: 11/04/2022]
Abstract
The mudskipper Boleophthalmus pectinirostris inhabits intertidal mudflats, exhibiting semilunar reproductive rhythms. To investigate whether melanopsin is possibly involved in the synchronization of the semilunar spawning rhythm in the female mudskipper, we first cloned all four melanopsin subtypes (opn4m1, opn4m3, opn4x1, opn4x2) in B. pectinirostris. Results from RTq-PCR showed that significantly higher transcription levels of all four melanopsin subtypes were observed in the eyes rather than other tissues. In brain, all four melanopsin subtypes were also detectable in different regions, including the telencephalon, in which the expression of melanopsin has not been reported in other teleosts. The transcription levels of opn4m3 and opn4x1 in the telencephalon exhibited a daily fluctuation pattern. When females entered the spawning season, opn4m1 and opn4x1 transcript levels increased significantly in the telencephalon. During the spawning season, the transcript levels of opn4m3 and opn4x1 in the telencephalon appeared to have a cyclic pattern associated with semilunar periodicity, exhibiting two cycles with a peak around the first or the last lunar quarters. Results from ISH showed that, opn4x1 mRNA was localized in the medial of dorsal telencephalic area, dorsal nucleus of ventral telencephalic area (Vd), ventral nucleus of ventral telencephalic area (Vv), anterior part of parvocellular preoptic nucleus, magnocellular part of the magnocellular preoptic nucleus (PMmc), habenular and ventral zone of hypothalamus. Intriguingly, gnrh3 mRNA was also located in Vd, Vv and PMmc. Taken together, our results suggested that melanopsins, e.g. opn4x1, expressed in the telencephalon might mediate semilunar spawning activity in the female mudskipper.
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Affiliation(s)
- He Ma
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Ming Shu Yang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Yu Ting Zhang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Heng Tong Qiu
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Xin Xin You
- Shenzhen Key Laboratory of Marine Genomics, Marine and Fisheries Institute, BGI-Shenzhen, Shenzhen 518083, China
| | - Shi Xi Chen
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China; State-Province Joint Engineering Laboratory of Marine Bioproducts and Technology, Xiamen University, Xiamen 361102, China.
| | - Wan Shu Hong
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China; State-Province Joint Engineering Laboratory of Marine Bioproducts and Technology, Xiamen University, Xiamen 361102, China.
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10
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Eilertsen M, Clokie BGJ, Ebbesson LOE, Tanase C, Migaud H, Helvik JV. Neural activation in photosensitive brain regions of Atlantic salmon (Salmo salar) after light stimulation. PLoS One 2021; 16:e0258007. [PMID: 34587204 PMCID: PMC8480854 DOI: 10.1371/journal.pone.0258007] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 09/16/2021] [Indexed: 11/24/2022] Open
Abstract
Photoreceptive inputs to the teleost brain are perceived as image of the visual world and as photo-modulation of neuroendocrine and neuronal signals. The retina and pineal organ are major receptive organs with projections to various parts of the brain, but in the past decades deep brain photoreceptors have emerged as candidates for photoreceptive inputs, either independent or in combination with projections from light sensory organs. This study aimed to test the effects of narrow bandwidth light using light-emitting diodes technology on brain neural activity through putative opsin stimulation in Atlantic salmon. The expression of c-fos, a known marker of neural activity, was compared in situ between dark-adapted salmon parr and following light stimulation with different wavelengths. c-fos expression increased with duration of light stimulation and the strongest signal was obtained in fish exposed to light for 120 minutes. Distinct and specific brain regions were activated following dark to light stimulation, such as the habenula, suprachiasmatic nucleus, thalamus, and hypothalamus. The c-fos expression was overlapping with photoreceptors expressing melanopsin and/or vertebrate ancient opsin, suggesting a potential direct activation by light. Interestingly in the habenula, a distinct ring of vertebrate ancient opsin and melanopsin expressing cells is overlapping with c-fos expression after neural activation. Salmon exposed to different spectra had neural activation in similar brain regions. The most apparent difference was melanopsin expression in the lateral cells of the lateral tuberal nuclus in the hypothalamus, which appeared to be specifically activated by red light. Light-stimulated neuronal activity in the deep brain was limited to subpopulations of neurons, mainly in regions with neuronal modulation activity, retinal and pineal innervations and known presence of nonvisual photoreceptors. The overlapping expression patterns of c-fos and nonvisual opsins support direct light stimulation of deep brain photoreceptors and the importance of these systems in light induced brain activity.
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Affiliation(s)
- Mariann Eilertsen
- Department of Biological Sciences, University of Bergen, Bergen, Norway
- * E-mail:
| | - Benjamin G. J. Clokie
- Institute of Aquaculture, University of Stirling, Stirling, Scotland, United Kingdom
| | - Lars O. E. Ebbesson
- Department of Biological Sciences, University of Bergen, Bergen, Norway
- Norce, Bergen, Norway
| | | | - Herve Migaud
- Institute of Aquaculture, University of Stirling, Stirling, Scotland, United Kingdom
| | - Jon Vidar Helvik
- Department of Biological Sciences, University of Bergen, Bergen, Norway
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11
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Matsuo M, Kamei Y, Fukamachi S. Behavioural red-light sensitivity in fish according to the optomotor response. ROYAL SOCIETY OPEN SCIENCE 2021; 8:210415. [PMID: 34386255 PMCID: PMC8334835 DOI: 10.1098/rsos.210415] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 07/06/2021] [Indexed: 05/12/2023]
Abstract
Various procedures have been adopted to investigate spectral sensitivity of animals, e.g. absorption spectra of visual pigments, electroretinography, optokinetic response, optomotor response (OMR) and phototaxis. The use of these techniques has led to various conclusions about animal vision. However, visual sensitivity should be evaluated consistently for a reliable comparison. In this study, we retrieved behavioural data of several fish species using a single OMR procedure and compared their sensitivities to near-infrared light. Besides cavefish that lack eyes, some species were not appropriate for the OMR test because they either stayed still or changed swimming direction frequently. Eight of 13 fish species tested were OMR positive. Detailed analyses using medaka, goldfish, zebrafish, guppy, stickleback and cichlid revealed that all the fish were sensitive to light at a wavelength greater than or equal to 750 nm, where the threshold wavelengths varied from 750 to 880 nm. Fish opsin repertoire affected the perception of red light. By contrast, the copy number of long-wavelength-sensitive (LWS) genes did not necessarily improve red-light sensitivity. While the duplication of LWS and other cone opsin genes that has occurred extensively during fish evolution might not aid increasing spectral sensitivity, it may provide some other advantageous ophthalmic function, such as enhanced spectral discrimination.
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Affiliation(s)
- Megumi Matsuo
- Laboratory of Evolutionary Genetics, Department of Chemical and Biological Sciences, Japan Women's University, Tokyo 112-8681, Japan
| | - Yasuhiro Kamei
- Spectrography and Bioimaging Facility, National Institute for Basic Biology, Aichi 444-8585, Japan
- Department of Basic Biology, School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Aichi 444-8585, Japan
| | - Shoji Fukamachi
- Laboratory of Evolutionary Genetics, Department of Chemical and Biological Sciences, Japan Women's University, Tokyo 112-8681, Japan
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12
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Hickey DG, Davies WIL, Hughes S, Rodgers J, Thavanesan N, MacLaren RE, Hankins MW. Chimeric human opsins as optogenetic light sensitisers. J Exp Biol 2021; 224:270919. [PMID: 34151984 PMCID: PMC8325934 DOI: 10.1242/jeb.240580] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Accepted: 06/08/2021] [Indexed: 12/03/2022]
Abstract
Human opsin-based photopigments have great potential as light-sensitisers, but their requirement for phototransduction cascade-specific second messenger proteins may restrict their functionality in non-native cell types. In this study, eight chimeric human opsins were generated consisting of a backbone of either a rhodopsin (RHO) or long-wavelength-sensitive (LWS) opsin and intracellular domains from Gq/11-coupled human melanopsin. Rhodopsin/melanopsin chimeric opsins coupled to both Gi and Gq/11 pathways. Greater substitution of the intracellular surface with corresponding melanopsin domains generally showed greater Gq/11 activity with a decrease in Gi activation. Unlike melanopsin, rhodopsin and rhodopsin/melanopsin chimeras were dependent upon exogenous chromophore to function. By contrast, wild-type LWS opsin and LWS opsin/melanopsin chimeras showed only weak Gi activation in response to light, whilst Gq/11 pathway activation was not detected. Immunocytochemistry (ICC) demonstrated that chimeric opsins with more intracellular domains of melanopsin were less likely to be trafficked to the plasma membrane. This study demonstrates the importance of Gα coupling efficiency to the speed of cellular responses and created human opsins with a unique combination of properties to expand the range of customised optogenetic biotools for basic research and translational therapies. Summary: Combining different domains of human visual opsins and melanopsin creates functionally unique chimeric opsins with potential optogenetic applications.
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Affiliation(s)
- Doron G Hickey
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, OX1 3QU, UK.,The Royal Victorian Eye and Ear Hospital, Melbourne, VIC 3002, Australia
| | - Wayne I L Davies
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, OX1 3QU, UK.,Umeå Centre for Molecular Medicine, Umeå University, Umeå, S-90187, Sweden.,School of Life Sciences, College of Science, Health and Engineering, La Trobe University, Melbourne, VIC 3086, Australia
| | - Steven Hughes
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, OX1 3QU, UK.,Sleep and Circadian Neuroscience Institute, University of Oxford, Oxford, OX1 3QU, UK
| | - Jessica Rodgers
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, OX1 3QU, UK.,Sleep and Circadian Neuroscience Institute, University of Oxford, Oxford, OX1 3QU, UK.,Division of Neuroscience and Experimental Psychology, University of Manchester, Manchester, M13 9PT, UK
| | | | - Robert E MacLaren
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, OX1 3QU, UK.,Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust and Oxford NIHR Biomedical Research Centre, Oxford, OX3 9DU,UK
| | - Mark W Hankins
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, OX1 3QU, UK.,Sleep and Circadian Neuroscience Institute, University of Oxford, Oxford, OX1 3QU, UK
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13
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Kitahashi T, Kurokawa D, Ogiso S, Suzuki N, Ando H. Light-induced and circadian expressions of melanopsin genes opn4xa and opn4xb in the eyes of juvenile grass puffer Takifugu alboplumbeus. FISH PHYSIOLOGY AND BIOCHEMISTRY 2021; 47:191-202. [PMID: 33559801 DOI: 10.1007/s10695-020-00901-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Accepted: 11/16/2020] [Indexed: 06/12/2023]
Abstract
Animals regulate a variety of aspects of physiology according to environmental light conditions via nonvisual opsins such as melanopsin. In order to study photic regulation of fish physiology, expression changes of the genes for melanopsin (opn4xa and opn4xb) and effects of light on them were examined in juvenile grass puffer Takifugu alboplumbeus using quantitative real-time PCR. In the brain of juvenile fish, no significant diurnal nor circadian changes were observed in opn4x mRNA levels. On the other hand, in the eyes, the mRNA level of opn4xa showed a significant diurnal rhythm with a peak at Zeitgeber time (ZT) 4, while no apparent circadian changes were observed. The mRNA level of opn4xb in the eyes showed a diurnal change similar to that of opn4xa, while it showed a significant circadian change. Furthermore, continuous exposure to light during a subjective night significantly increased the mRNA levels of opn4xa in the eyes at ZT24, suggesting that light induces gene expression of opn4xa in the eyes and that the induction occurs only during the night-day transition period. These results suggest that Opn4xa and Opn4xb play differential roles in the eyes of juvenile grass puffer to mediate the physiological effects of environmental light information.
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Affiliation(s)
- Takashi Kitahashi
- Sado Marine Biological Station, Sado Island Center for Ecological Sustainability, Niigata University, 87 Tassha, Sado-shi, Niigata, 952-2135, Japan.
- , Toda-cho 5-33-17, Moriguchi-shi, 570-0014, Osaka, Japan.
| | - Daisuke Kurokawa
- Misaki Marine Biological Station, Graduate School of Science, The University of Tokyo, 1024 Koajiro, Misaki, Miura, Kanagawa, 238-0225, Japan
| | - Shouzo Ogiso
- Noto Marine Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, 4-1 Mu, Ogi, Noto-cho, Ishikawa, 927-0553, Japan
| | - Nobuo Suzuki
- Noto Marine Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, 4-1 Mu, Ogi, Noto-cho, Ishikawa, 927-0553, Japan
| | - Hironori Ando
- Sado Marine Biological Station, Sado Island Center for Ecological Sustainability, Niigata University, 87 Tassha, Sado-shi, Niigata, 952-2135, Japan
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14
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Fang X, Peden AA, van Eeden FJM, Malicki JJ. Identification of additional outer segment targeting signals in zebrafish rod opsin. J Cell Sci 2021; 134:jcs.254995. [PMID: 33589494 DOI: 10.1242/jcs.254995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 02/01/2021] [Indexed: 11/20/2022] Open
Abstract
In vertebrate photoreceptors, opsins are highly concentrated in a morphologically distinct ciliary compartment known as the outer segment (OS). Opsin is synthesized in the cell body and transported to the OS at a remarkable rate of 100 to 1000 molecules per second. Opsin transport defects contribute to photoreceptor loss and blindness in human ciliopathies. Previous studies revealed that the rhodopsin C-terminal tail, of 44 amino acids, is sufficient to mediate OS targeting in Xenopus photoreceptors. Here, we show that, although the Xenopus C-terminus retains this function in zebrafish, the homologous zebrafish sequence is not sufficient to target opsin to the OS. This functional difference is largely caused by a change of a single amino acid present in Xenopus but not in other vertebrates examined. Furthermore, we find that sequences in the third intracellular cytoplasmic loop (IC3) and adjacent regions of transmembrane helices 6 and 7 are also necessary for opsin transport in zebrafish. Combined with the cytoplasmic tail, these sequences are sufficient to target opsin to the ciliary compartment.
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Affiliation(s)
- Xiaoming Fang
- Bateson Centre and Department of Biomedical Science, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK
| | - Andrew A Peden
- Department of Biomedical Science, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK
| | - Fredericus J M van Eeden
- Bateson Centre and Department of Biomedical Science, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK
| | - Jarema J Malicki
- Bateson Centre and Department of Biomedical Science, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK
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15
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Zang J, Neuhauss SCF. Biochemistry and physiology of zebrafish photoreceptors. Pflugers Arch 2021; 473:1569-1585. [PMID: 33598728 PMCID: PMC8370914 DOI: 10.1007/s00424-021-02528-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 01/25/2021] [Accepted: 01/28/2021] [Indexed: 02/06/2023]
Abstract
All vertebrates share a canonical retina with light-sensitive photoreceptors in the outer retina. These photoreceptors are of two kinds: rods and cones, adapted to low and bright light conditions, respectively. They both show a peculiar morphology, with long outer segments, comprised of ordered stacks of disc-shaped membranes. These discs host numerous proteins, many of which contribute to the visual transduction cascade. This pathway converts the light stimulus into a biological signal, ultimately modulating synaptic transmission. Recently, the zebrafish (Danio rerio) has gained popularity for studying the function of vertebrate photoreceptors. In this review, we introduce this model system and its contribution to our understanding of photoreception with a focus on the cone visual transduction cascade.
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Affiliation(s)
- Jingjing Zang
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrase 190, CH - 8057, Zürich, Switzerland
| | - Stephan C F Neuhauss
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrase 190, CH - 8057, Zürich, Switzerland.
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16
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Fontinha BM, Zekoll T, Al-Rawi M, Gallach M, Reithofer F, Barker AJ, Hofbauer M, Fischer RM, von Haeseler A, Baier H, Tessmar-Raible K. TMT-Opsins differentially modulate medaka brain function in a context-dependent manner. PLoS Biol 2021; 19:e3001012. [PMID: 33411725 PMCID: PMC7837489 DOI: 10.1371/journal.pbio.3001012] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 01/26/2021] [Accepted: 12/10/2020] [Indexed: 12/13/2022] Open
Abstract
Vertebrate behavior is strongly influenced by light. Light receptors, encoded by functional opsin proteins, are present inside the vertebrate brain and peripheral tissues. This expression feature is present from fishes to human and appears to be particularly prominent in diurnal vertebrates. Despite their conserved widespread occurrence, the nonvisual functions of opsins are still largely enigmatic. This is even more apparent when considering the high number of opsins. Teleosts possess around 40 opsin genes, present from young developmental stages to adulthood. Many of these opsins have been shown to function as light receptors. This raises the question of whether this large number might mainly reflect functional redundancy or rather maximally enables teleosts to optimally use the complex light information present under water. We focus on tmt-opsin1b and tmt-opsin2, c-opsins with ancestral-type sequence features, conserved across several vertebrate phyla, expressed with partly similar expression in non-rod, non-cone, non-retinal-ganglion-cell brain tissues and with a similar spectral sensitivity. The characterization of the single mutants revealed age- and light-dependent behavioral changes, as well as an impact on the levels of the preprohormone sst1b and the voltage-gated sodium channel subunit scn12aa. The amount of daytime rest is affected independently of the eyes, pineal organ, and circadian clock in tmt-opsin1b mutants. We further focused on daytime behavior and the molecular changes in tmt-opsin1b/2 double mutants, and found that-despite their similar expression and spectral features-these opsins interact in part nonadditively. Specifically, double mutants complement molecular and behavioral phenotypes observed in single mutants in a partly age-dependent fashion. Our work provides a starting point to disentangle the highly complex interactions of vertebrate nonvisual opsins, suggesting that tmt-opsin-expressing cells together with other visual and nonvisual opsins provide detailed light information to the organism for behavioral fine-tuning. This work also provides a stepping stone to unravel how vertebrate species with conserved opsins, but living in different ecological niches, respond to similar light cues and how human-generated artificial light might impact on behavioral processes in natural environments.
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Affiliation(s)
- Bruno M. Fontinha
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
- Research Platform ‘‘Rhythms of Life,” University of Vienna, Vienna, Austria
| | - Theresa Zekoll
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
- Research Platform ‘‘Rhythms of Life,” University of Vienna, Vienna, Austria
| | - Mariam Al-Rawi
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
- Research Platform ‘‘Rhythms of Life,” University of Vienna, Vienna, Austria
| | - Miguel Gallach
- Center for Integrative Bioinformatics Vienna, Max F. Perutz Laboratories, University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Florian Reithofer
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
- Research Platform ‘‘Rhythms of Life,” University of Vienna, Vienna, Austria
| | | | - Maximilian Hofbauer
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
- Research Platform ‘‘Rhythms of Life,” University of Vienna, Vienna, Austria
- loopbio, Vienna, Austria
| | - Ruth M. Fischer
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
| | - Arndt von Haeseler
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
- Research Platform ‘‘Rhythms of Life,” University of Vienna, Vienna, Austria
- Center for Integrative Bioinformatics Vienna, Max F. Perutz Laboratories, University of Vienna and Medical University of Vienna, Vienna, Austria
- Bioinformatics and Computational Biology, Faculty of Computer Science, University of Vienna, Vienna, Austria
| | - Herwig Baier
- Max Planck Institute of Neurobiology, Martinsried, Germany
| | - Kristin Tessmar-Raible
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
- Research Platform ‘‘Rhythms of Life,” University of Vienna, Vienna, Austria
- FENS-Kavli Network of Excellence, Brussels, Belgium
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17
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Steindal IAF, Whitmore D. Zebrafish Circadian Clock Entrainment and the Importance of Broad Spectral Light Sensitivity. Front Physiol 2020; 11:1002. [PMID: 32922310 PMCID: PMC7456917 DOI: 10.3389/fphys.2020.01002] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Accepted: 07/23/2020] [Indexed: 11/25/2022] Open
Abstract
One of the key defining features of an endogenous circadian clock is that it can be entrained or set to local time. Though a number of cues can perform this role, light is the predominant environmental signal that acts to entrain circadian pacemakers in most species. For the past 20 years, a great deal of work has been performed on the light input pathway in mammals and the role of intrinsically photosensitive retinal ganglion cells (ipRGCs)/melanopsin in detecting and sending light information to the suprachiasmatic nucleus (SCN). In teleost fishes, reptiles and birds, the biology of light sensitivity is more complicated as cells and tissues can be directly light responsive. Non-visual light signalling was described many years ago in the context of seasonal, photoperiodic responses in birds and lizards. In the case of teleosts, in particular the zebrafish model system, not only do peripheral tissues have a circadian pacemaker, but possess clear, direct light sensitivity. A surprisingly wide number of opsin photopigments have been described within these tissues, which may underpin this fundamental ability to respond to light, though no specific functional link for any given opsin yet exists. In this study, we show that zebrafish cells show wide spectral sensitivities, as well as express a number of opsin photopigments – several of which are under direct clock control. Furthermore, we also show that light outside the visual range, both ultraviolet and infrared light, can induce clock genes in zebrafish cells. These same wavelengths can phase shift the clock, except infrared light, which generates no shift even though genes such as per2 and cry1a are induced.
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Affiliation(s)
- Inga A Frøland Steindal
- Centre for Cell and Molecular Dynamics, Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - David Whitmore
- Centre for Cell and Molecular Dynamics, Department of Cell and Developmental Biology, University College London, London, United Kingdom.,College of Public Health, Medical and Veterinary Sciences, Department of Molecular and Cell Biology, James Cook University, Townsville, QLD, Australia
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18
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Pende M, Vadiwala K, Schmidbaur H, Stockinger AW, Murawala P, Saghafi S, Dekens MPS, Becker K, Revilla-i-Domingo R, Papadopoulos SC, Zurl M, Pasierbek P, Simakov O, Tanaka EM, Raible F, Dodt HU. A versatile depigmentation, clearing, and labeling method for exploring nervous system diversity. SCIENCE ADVANCES 2020; 6:eaba0365. [PMID: 32523996 PMCID: PMC7259959 DOI: 10.1126/sciadv.aba0365] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 03/27/2020] [Indexed: 06/11/2023]
Abstract
Tissue clearing combined with deep imaging has emerged as a powerful alternative to classical histological techniques. Whereas current techniques have been optimized for imaging selected nonpigmented organs such as the mammalian brain, natural pigmentation remains challenging for most other biological specimens of larger volume. We have developed a fast DEpigmEntation-Plus-Clearing method (DEEP-Clear) that is easily incorporated in existing workflows and combines whole system labeling with a spectrum of detection techniques, ranging from immunohistochemistry to RNA in situ hybridization, labeling of proliferative cells (EdU labeling) and visualization of transgenic markers. With light-sheet imaging of whole animals and detailed confocal studies on pigmented organs, we provide unprecedented insight into eyes, whole nervous systems, and subcellular structures in animal models ranging from worms and squids to axolotls and zebrafish. DEEP-Clear thus paves the way for the exploration of species-rich clades and developmental stages that are largely inaccessible by regular imaging approaches.
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Affiliation(s)
- Marko Pende
- Department for Bioelectronics, FKE, Vienna University of Technology, Gußhausstraße 25-25A, building CH, 1040 Vienna, Austria
- Section for Bioelectronics, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria
| | - Karim Vadiwala
- Max Perutz Labs and Research Platform “Rhythms of Life”, University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9/4, 1030 Vienna, Austria
| | - Hannah Schmidbaur
- Department of Neuroscience and Development, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Alexander W. Stockinger
- Max Perutz Labs and Research Platform “Rhythms of Life”, University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9/4, 1030 Vienna, Austria
| | - Prayag Murawala
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter, Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Saiedeh Saghafi
- Department for Bioelectronics, FKE, Vienna University of Technology, Gußhausstraße 25-25A, building CH, 1040 Vienna, Austria
| | - Marcus P. S. Dekens
- Max Perutz Labs and Research Platform “Rhythms of Life”, University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9/4, 1030 Vienna, Austria
| | - Klaus Becker
- Department for Bioelectronics, FKE, Vienna University of Technology, Gußhausstraße 25-25A, building CH, 1040 Vienna, Austria
- Section for Bioelectronics, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria
| | - Roger Revilla-i-Domingo
- Max Perutz Labs and Research Platform “Rhythms of Life”, University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9/4, 1030 Vienna, Austria
| | - Sofia-Christina Papadopoulos
- Department for Bioelectronics, FKE, Vienna University of Technology, Gußhausstraße 25-25A, building CH, 1040 Vienna, Austria
| | - Martin Zurl
- Max Perutz Labs and Research Platform “Rhythms of Life”, University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9/4, 1030 Vienna, Austria
| | - Pawel Pasierbek
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Oleg Simakov
- Department of Neuroscience and Development, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Elly M. Tanaka
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter, Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Florian Raible
- Max Perutz Labs and Research Platform “Rhythms of Life”, University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9/4, 1030 Vienna, Austria
| | - Hans-Ulrich Dodt
- Department for Bioelectronics, FKE, Vienna University of Technology, Gußhausstraße 25-25A, building CH, 1040 Vienna, Austria
- Section for Bioelectronics, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090 Vienna, Austria
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19
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Saratani Y, Takeuchi Y, Okano K, Okano T. Clock Gene Expression in the Eye Exhibits Circadian Oscillation and Light Responsiveness but is Not Necessary for Nocturnal Locomotor Activity of Japanese Loach, Misgurnus anguillicaudatus. Zoolog Sci 2020; 37:177-192. [PMID: 32282149 DOI: 10.2108/zs190110] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2019] [Accepted: 12/03/2019] [Indexed: 11/17/2022]
Abstract
There are few model fish that are both edible and suitable for use in the laboratory. The Japanese loach (Misgurnus anguillicaudatus) is a traditional food in Japan, but is highly neglected despite its great nutritional value. To understand its circadian system and photic input pathway for synchronization of physiological activities to environmental light-dark cycles, we measured locomotor activity under light-dark and constant dark (DD) conditions. Locomotor activity was found to be higher in the nighttime than daytime, and its rhythmicity was weakened under DD conditions. The nocturnal activity of the Japanese loach is mainly controlled by environmental light, rather than the circadian clock. We explored the circadian regulation and light-responsiveness of clock gene expression in the eyes of loaches. The daily expression profiles of its mRNA revealed that most of the examined Cry and Per genes were likely regulated by internal circadian and/or environmental light signals. Among the Opsin genes transcribed in the eye, we detected the retinal photopigment porphyropsin at the protein level, which was lower than in mice. This property of loach eyes prompted us to analyze the locomotor activities of eye-enucleated fish. As a result, they still showed nocturnal circadian activity. Thus, it is likely that extraocular photoreceptive tissue(s) also contribute to the photic input pathway, although loach eyes are a circadian photosensitive tissue. This suggests that the loach mainly uses not its vision but other stimuli, such as mechanical or chemical stimuli, detected by barbels, to coordinate its nocturnal behavior.
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Affiliation(s)
- Yuya Saratani
- Department of Electrical Engineering and Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, Wakamatsu-cho 2-2, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Yuki Takeuchi
- Department of Electrical Engineering and Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, Wakamatsu-cho 2-2, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Keiko Okano
- Department of Electrical Engineering and Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, Wakamatsu-cho 2-2, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Toshiyuki Okano
- Department of Electrical Engineering and Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, Wakamatsu-cho 2-2, Shinjuku-ku, Tokyo 162-8480, Japan,
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20
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Melanopsin and the Intrinsically Photosensitive Retinal Ganglion Cells: Biophysics to Behavior. Neuron 2020; 104:205-226. [PMID: 31647894 DOI: 10.1016/j.neuron.2019.07.016] [Citation(s) in RCA: 139] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 06/19/2019] [Accepted: 07/12/2019] [Indexed: 12/19/2022]
Abstract
The mammalian visual system encodes information over a remarkable breadth of spatiotemporal scales and light intensities. This performance originates with its complement of photoreceptors: the classic rods and cones, as well as the intrinsically photosensitive retinal ganglion cells (ipRGCs). IpRGCs capture light with a G-protein-coupled receptor called melanopsin, depolarize like photoreceptors of invertebrates such as Drosophila, discharge electrical spikes, and innervate dozens of brain areas to influence physiology, behavior, perception, and mood. Several visual responses rely on melanopsin to be sustained and maximal. Some require ipRGCs to occur at all. IpRGCs fulfill their roles using mechanisms that include an unusual conformation of the melanopsin protein, an extraordinarily slow phototransduction cascade, divisions of labor even among cells of a morphological type, and unorthodox configurations of circuitry. The study of ipRGCs has yielded insight into general topics that include photoreceptor evolution, cellular diversity, and the steps from biophysical mechanisms to behavior.
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21
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Lindner M, Gilhooley MJ, Palumaa T, Morton AJ, Hughes S, Hankins MW. Expression and Localization of Kcne2 in the Vertebrate Retina. Invest Ophthalmol Vis Sci 2020; 61:33. [PMID: 32191288 PMCID: PMC7401445 DOI: 10.1167/iovs.61.3.33] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To characterize the retinal expression and localization of Kcne2, an ancillary (β) ion-channel subunit with an important role in fine-tuning cellular excitability. Methods We analyzed available single-cell transcriptome data from tens of thousands of murine retinal cells for cell-type-specific expression of Kcne2 using state-of-the-art bioinformatics techniques. This evidence at the transcriptome level was complemented with a comprehensive immunohistochemical characterization of mouse retina (C57BL/6, ages 8-12 weeks) employing co-labeling techniques and cell-type-specific antibody markers. We furthermore examined how conserved the Kcne2 localization pattern in the retina was across species by performing immunostaining on zebrafish, cowbird, sheep, mice, and macaque. Results Kcne2 is distinctly expressed in cone photoreceptors and rod bipolar cells. At a subcellular level, the bulk of Kcne2 immunoreactivity can be observed in the outer plexiform layer. Here, it localizes into cone pedicles and likely the postsynaptic membrane of the rod bipolar cells. Thus, the vast majority of Kcne2 immunoreactivity is observed in a thin band in the outer plexiform layer. In addition to this, faint Kcne2 immunoreactivity can also be observed in cone inner segments and the somata of a small subset of cone ON bipolar cells. Strikingly, the localization of Kcne2 in the outer plexiform layer was preserved among all of the species studied, spanning at least 300 million years of evolution of the vertebrate kingdom. Conclusions The data we present here suggest an important and specific role for Kcne2 in the highly specialized photoreceptor-bipolar cell synapse.
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22
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Sapède D, Chaigne C, Blader P, Cau E. Functional heterogeneity in the pineal projection neurons of zebrafish. Mol Cell Neurosci 2020; 103:103468. [PMID: 32027966 DOI: 10.1016/j.mcn.2020.103468] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 01/31/2020] [Accepted: 02/01/2020] [Indexed: 01/11/2023] Open
Abstract
The zebrafish pineal organ is a photoreceptive structure containing two main neuronal populations (photoreceptors and projections neurons). Here we describe a subpopulation of projection neurons that expresses the melanopsin gene, opn4xa. This new pineal cell type, that displays characteristics of both projection neurons and photoreceptors, share a similar dependency for BMP and Notch signalling pathways with classical non-photosensitive projection neurons (PN). Functionally, however, whereas classical, opn4xa-negative PNs display an achromatic LIGHT OFF response, the novel cell type we describe exhibit a LIGHT ON character that is elicited by green and blue light. Taken together, our data suggest a previously unanticipated heterogeneity in the projection neuron population in the zebrafish pineal organ raising the question of the importance of these differences in pineal function.
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Affiliation(s)
- Dora Sapède
- Centre de Biologie du Développement (CBD, UMR5547), Centre de Biologie Intégrative (CBI, FR 3743), Université de Toulouse, CNRS, UPS, France; IRMB, Université de Montpellier, INSERM, Montpellier, France
| | - Clair Chaigne
- Centre de Biologie du Développement (CBD, UMR5547), Centre de Biologie Intégrative (CBI, FR 3743), Université de Toulouse, CNRS, UPS, France
| | - Patrick Blader
- Centre de Biologie du Développement (CBD, UMR5547), Centre de Biologie Intégrative (CBI, FR 3743), Université de Toulouse, CNRS, UPS, France
| | - Elise Cau
- Centre de Biologie du Développement (CBD, UMR5547), Centre de Biologie Intégrative (CBI, FR 3743), Université de Toulouse, CNRS, UPS, France.
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23
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Zhao Q, Zhang R, Xiao Y, Niu Y, Shao F, Li Y, Peng Z. Comparative Transcriptome Profiling of the Loaches Triplophysa bleekeri and Triplophysa rosa Reveals Potential Mechanisms of Eye Degeneration. Front Genet 2020; 10:1334. [PMID: 32010191 PMCID: PMC6977438 DOI: 10.3389/fgene.2019.01334] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2019] [Accepted: 12/06/2019] [Indexed: 12/30/2022] Open
Abstract
Eye degeneration is one of the most obvious characteristics of organisms restricted to subterranean habitats. In cavefish, eye degeneration has evolved independently numerous times and each process is associated with different genetic mechanisms. To gain a better understanding of these mechanisms, we compared the eyes of adult individuals of the cave loach Triplophysa rosa and surface loach Triplophysa bleekeri. Compared with the normal eyes of the surface loach, those of the cave loach were found to possess a small abnormal lens and a defective retina containing photoreceptor cells that lack outer segments. Sequencing of the transcriptomes of both species to identify differentially expressed genes (DEGs) and genes under positive selection revealed 4,802 DEGs and 50 genes under positive selection (dN/dS > 1, FDR < 0.1). For cave loaches, we identified one Gene Ontology category related to vision that was significantly enriched in downregulated genes. Specifically, we found that many of the downregulated genes, including pitx3, lim2, crx, gnat2, rx1, rho, prph2, and β|γ-crystallin are associated with lens/retinal development and maintenance. However, compared with those in the surface loach, the lower dS rates but higher dN rates of the protein-coding sequences in T. rosa indicate that changes in amino acid sequences might be involved in the adaptation and visual degeneration of cave loaches. We also found that genes associated with light perception and light-stimulated vision have evolved at higher rates (some genes dN/dS > 1 but FDR > 0.1). Collectively, the findings of this study indicate that the degradation of cavefish vision is probably associated with both gene expression and amino acid changes and provide new insights into the mechanisms underlying the degeneration of cavefish eyes.
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Affiliation(s)
- Qingyuan Zhao
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Southwest University School of Life Sciences, Chongqing, China
| | - Renyi Zhang
- School of Life Sciences, Guizhou Normal University, Guiyang, China
| | - Yingqi Xiao
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Southwest University School of Life Sciences, Chongqing, China
| | - Yabing Niu
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Southwest University School of Life Sciences, Chongqing, China
| | - Feng Shao
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Southwest University School of Life Sciences, Chongqing, China
| | - Yanping Li
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Southwest University School of Life Sciences, Chongqing, China
| | - Zuogang Peng
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Southwest University School of Life Sciences, Chongqing, China
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Liu Y, Zhang W, Du X, Liu Y, Qu J, Liu X, Liu J, Zhang Q. Genome-wide identification of nonvisual opsin family reveals amplification of RPE-retinal G protein receptor gene (RGR) and offers novel insights into functions of RGR(s) in Paralichthys olivaceus (Paralichthyidae, Teleostei). JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2019; 334:25-36. [PMID: 31743605 DOI: 10.1002/jez.b.22914] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 09/08/2019] [Accepted: 10/10/2019] [Indexed: 12/20/2022]
Abstract
Opsins play important roles in the image-forming visual pathways and numerous biological systems such as the biological clock and circadian rhythm. However, the nonvisual opsins involved in nonimage forming process are not clear to date. The aim of this study was to characterize nonvisual opsins in Paralichthys olivaceus. A total of 24 nonvisual opsin genes were identified. Expressions of these genes in eye, brain, heart, testis, and fin were investigated by quantitative real-time polymerase chain reaction (qRT-PCR). Testis contained a surprisingly large number of nonvisual opsins including Opn4m2, Tmt2a, Tmt3b, Opn3, RRH, Opn7a, and Opn7b. Syntenic and phylogenetic analyses confirmed that the RGRa and RGRb originated from the teleost-specific genome duplication (TSGD). qRT-PCR results demonstrated high RGRa and RGRb expression in the eye, while the expression levels in the brain, heart, testis, and fin were relatively weak. In situ hybridization results presented here revealed the presence of both RGRa and RGRb mRNA-positive signals in the ganglion cell layer but absence in the intracellular compartment of retinal pigment epithelium (RPE) and Müller glial cells. Therefore, we hypothesized that RGRa and RGRb had undergone subfunctionalization in P. olivaceus after TSGD. In conclusion, this study provides novel insights into the evolutionary fates of the RGR genes, still, further studies need to be done to explore the mechanism about the lack of RGR genes' expression in RPE.
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Affiliation(s)
- Yuezhong Liu
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, College of Marine Life Science, Ocean University of China, Qingdao, China
| | - Wei Zhang
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, College of Marine Life Science, Ocean University of China, Qingdao, China
| | - Xinxin Du
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, College of Marine Life Science, Ocean University of China, Qingdao, China
| | - Yuxiang Liu
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, College of Marine Life Science, Ocean University of China, Qingdao, China
| | - Jiangbo Qu
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, College of Marine Life Science, Ocean University of China, Qingdao, China
| | - Xiaobing Liu
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, College of Marine Life Science, Ocean University of China, Qingdao, China
| | - Jinxiang Liu
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, College of Marine Life Science, Ocean University of China, Qingdao, China.,Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
| | - Quanqi Zhang
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, College of Marine Life Science, Ocean University of China, Qingdao, China.,Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
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25
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Hauzman E, Kalava V, Bonci DMO, Ventura DF. Characterization of the melanopsin gene (Opn4x) of diurnal and nocturnal snakes. BMC Evol Biol 2019; 19:174. [PMID: 31462236 PMCID: PMC6714106 DOI: 10.1186/s12862-019-1500-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 08/22/2019] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND A number of non-visual responses to light in vertebrates, such as circadian rhythm control and pupillary light reflex, are mediated by melanopsins, G-protein coupled membrane receptors, conjugated to a retinal chromophore. In non-mammalian vertebrates, melanopsin expression is variable within the retina and extra-ocular tissues. Two paralog melanopsin genes were classified in vertebrates, Opn4x and Opn4m. Snakes are highly diversified vertebrates with a wide range of daily activity patterns, which raises questions about differences in structure, function and expression pattern of their melanopsin genes. In this study, we analyzed the melanopsin genes expressed in the retinas of 18 snake species from three families (Viperidae, Elapidae, and Colubridae), and also investigated extra-retinal tissue expression. RESULTS Phylogenetic analysis revealed that the amplified gene belongs to the Opn4x group, and no expression of the Opn4m was found. The same paralog is expressed in the iris, but no extra-ocular expression was detected. Molecular evolutionary analysis indicated that melanopsins are evolving primarily under strong purifying selection, although lower evolutionary constraint was detected in snake lineages (ω = 0.2), compared to non-snake Opn4x and Opn4m (ω = 0.1). Statistical analysis of selective constraint suggests that snake phylogenetic relationships have driven stronger effects on melanopsin evolution, than the species activity pattern. In situ hybridization revealed the presence of melanopsin within cells in the outer and inner nuclear layers, in the ganglion cell layer, and intense labeling in the optic nerve. CONCLUSIONS The loss of the Opn4m gene and extra-ocular photosensitive tissues in snakes may be associated with a prolonged nocturnal/mesopic bottleneck in the early history of snake evolution. The presence of melanopsin-containing cells in all retinal nuclear layers indicates a globally photosensitive retina, and the expression in classic photoreceptor cells suggest a regionalized co-expression of melanopsin and visual opsins.
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Affiliation(s)
- Einat Hauzman
- Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Professor Mello Moraes, 1721, Bloco A - Sala D9. Butantã, São Paulo, SP, 05508-030, Brazil. .,Instituto Israelita de Ensino e Pesquisa Albert Einstein, São Paulo, Brazil.
| | | | - Daniela Maria Oliveira Bonci
- Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Professor Mello Moraes, 1721, Bloco A - Sala D9. Butantã, São Paulo, SP, 05508-030, Brazil.,Instituto Israelita de Ensino e Pesquisa Albert Einstein, São Paulo, Brazil
| | - Dora Fix Ventura
- Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Professor Mello Moraes, 1721, Bloco A - Sala D9. Butantã, São Paulo, SP, 05508-030, Brazil.,Instituto Israelita de Ensino e Pesquisa Albert Einstein, São Paulo, Brazil
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26
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Li L. Circadian Vision in Zebrafish: From Molecule to Cell and from Neural Network to Behavior. J Biol Rhythms 2019; 34:451-462. [DOI: 10.1177/0748730419863917] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Most visual system functions, such as opsin gene expression, retinal neural transmission, light perception, and visual sensitivity, display robust day-night rhythms. The rhythms persist in constant lighting conditions, suggesting the involvement of endogenous circadian clocks. While the circadian pacemakers that control the rhythms of animal behaviors are mostly found in the forebrain and midbrain, self-sustained circadian oscillators are also present in the neural retina, where they play important roles in the regulation of circadian vision. This review highlights some of the correlative studies of the circadian control of visual system functions in zebrafish. Because zebrafish maintain a high evolutionary proximity to mammals, the findings from zebrafish research may provide insights for a better understanding of the mechanisms of circadian vision in other vertebrate species including humans.
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Affiliation(s)
- Lei Li
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana
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27
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Eilertsen M, Valen R, Drivenes Ø, Ebbesson LOE, Helvik JV. Transient photoreception in the hindbrain is permissive to the life history transition of hatching in Atlantic halibut. Dev Biol 2018; 444:129-138. [PMID: 30342886 DOI: 10.1016/j.ydbio.2018.10.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 10/13/2018] [Accepted: 10/15/2018] [Indexed: 12/22/2022]
Abstract
In nonmammalian vertebrates, photoreception takes place in the deep brain already early in development, but knowledge is lacking about the functions of these nonvisual photoreceptive systems. Prior to hatching, Atlantic halibut has a transient bilateral cluster of photoreceptive cells in the hindbrain. The cluster is imbedded in a neuronal network projecting to the narrow belt of hatching glands in the yolk sac. In halibut, hatching is inhibited in light and activated by transfer to darkness and c-fos analysis during hatching shows that the hindbrain cluster and hatching glands have neural activation. Unexpectedly, the hindbrain cluster expresses dual photopigments, vertebrate ancient opsin and melanopsin. Evolutionarily, these opsins are believed to belong to different classes of photopigments found in rhabdomeric and ciliary photoreceptors. The concept that an organism develops transient light sensitivity to target critical aspects of life history transitions as hatching provides a fascinating landscape to investigate the timing of other biological events.
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Affiliation(s)
- Mariann Eilertsen
- Department of Biological Sciences, University of Bergen, N- 5020 Bergen, Norway.
| | - Ragnhild Valen
- Department of Molecular Biology, University of Bergen, N- 5020 Bergen, Norway
| | - Øyvind Drivenes
- Department of Molecular Biology, University of Bergen, N- 5020 Bergen, Norway
| | - Lars O E Ebbesson
- Department of Biological Sciences, University of Bergen, N- 5020 Bergen, Norway; Uni Research AS, Thormøhlensgt. 55, N-5008 Bergen, Norway
| | - Jon Vidar Helvik
- Department of Biological Sciences, University of Bergen, N- 5020 Bergen, Norway
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28
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Stachurska A, Sarna T. Regulation of Melanopsin Signaling: Key Interactions of the Nonvisual Photopigment. Photochem Photobiol 2018; 95:83-94. [DOI: 10.1111/php.12995] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 07/26/2018] [Indexed: 02/06/2023]
Affiliation(s)
- Anna Stachurska
- Labolatory of Imaging and Force Spectroscopy; Malopolska Centre of Biotechnology; Jagiellonian University; Krakow Poland
| | - Tadeusz Sarna
- Department of Biophysics; Faculty of Biochemistry, Biophysics and Biotechnology; Jagiellonian University; Krakow Poland
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29
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Frøland Steindal IA, Beale AD, Yamamoto Y, Whitmore D. Development of the Astyanax mexicanus circadian clock and non-visual light responses. Dev Biol 2018; 441:345-354. [PMID: 29909064 PMCID: PMC6141809 DOI: 10.1016/j.ydbio.2018.06.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 06/06/2018] [Accepted: 06/13/2018] [Indexed: 12/25/2022]
Abstract
Most animals and plants live on the planet exposed to periods of rhythmic light and dark. As such, they have evolved endogenous circadian clocks to regulate their physiology rhythmically, and non-visual light detection mechanisms to set the clock to the environmental light-dark cycle. In the case of fish, circadian pacemakers are not only present in the majority of tissues and cells, but these tissues are themselves directly light-sensitive, expressing a wide range of opsin photopigments. This broad non-visual light sensitivity exists to set the clock, but also impacts a wide range of fundamental cell biological processes, such as DNA repair regulation. In this context, Astyanax mexicanus is a very intriguing model system with which to explore non-visual light detection and circadian clock function. Previous work has shown that surface fish possess the same directly light entrainable circadian clocks, described above. The same is true for cave strains of Astyanax in the laboratory, though no daily rhythms have been observed under natural dark conditions in Mexico. There are, however, clear alterations in the cave strain light response and changes to the circadian clock, with a difference in phase of peak gene expression and a reduction in amplitude. In this study, we expand these early observations by exploring the development of non-visual light sensitivity and clock function between surface and cave populations. When does the circadian pacemaker begin to oscillate during development, and are there differences between the various strains? Is the difference in acute light sensitivity, seen in adults, apparent from the earliest stages of development? Our results show that both cave and surface populations must experience daily light exposure to establish a larval gene expression rhythm. These oscillations begin early, around the third day of development in all strains, but gene expression rhythms show a significantly higher amplitude in surface fish larvae. In addition, the light induction of clock genes is developmentally delayed in cave populations. Zebrafish embryonic light sensitivity has been shown to be critical not only for clock entrainment, but also for transcriptional activation of DNA repair processes. Similar downstream transcriptional responses to light also occur in Astyanax. Interestingly, the establishment of the adult timing profile of clock gene expression takes several days to become apparent. This fact may provide mechanistic insight into the key differences between the cave and surface fish clock mechanisms. Non-visual light sensitivity is developmentally delayed in cave strains of Astyanax. Neither strains of Astyanax show clock gene oscillations in dark raised larvae. The timing of the circadian molecular clock rhythm is delayed by 6-h in Pachon. Expression CPD photolyase is raised in constant darkness in Pachon. The clock has gained greater regulation over light-responsive genes in cave strains.
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Affiliation(s)
- Inga A Frøland Steindal
- Department of Cell and Developmental Biology, University College London, 21 University Street, London WC1E 6DE, UK
| | - Andrew D Beale
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK
| | - Yoshiyuki Yamamoto
- Department of Cell and Developmental Biology, University College London, 21 University Street, London WC1E 6DE, UK
| | - David Whitmore
- Department of Cell and Developmental Biology, University College London, 21 University Street, London WC1E 6DE, UK.
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30
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Verasztó C, Gühmann M, Jia H, Rajan VBV, Bezares-Calderón LA, Piñeiro-Lopez C, Randel N, Shahidi R, Michiels NK, Yokoyama S, Tessmar-Raible K, Jékely G. Ciliary and rhabdomeric photoreceptor-cell circuits form a spectral depth gauge in marine zooplankton. eLife 2018; 7:36440. [PMID: 29809157 PMCID: PMC6019069 DOI: 10.7554/elife.36440] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 05/28/2018] [Indexed: 02/02/2023] Open
Abstract
Ciliary and rhabdomeric photoreceptor cells represent two main lines of photoreceptor-cell evolution in animals. The two cell types coexist in some animals, however how these cells functionally integrate is unknown. We used connectomics to map synaptic paths between ciliary and rhabdomeric photoreceptors in the planktonic larva of the annelid Platynereis and found that ciliary photoreceptors are presynaptic to the rhabdomeric circuit. The behaviors mediated by the ciliary and rhabdomeric cells also interact hierarchically. The ciliary photoreceptors are UV-sensitive and mediate downward swimming in non-directional UV light, a behavior absent in ciliary-opsin knockout larvae. UV avoidance overrides positive phototaxis mediated by the rhabdomeric eyes such that vertical swimming direction is determined by the ratio of blue/UV light. Since this ratio increases with depth, Platynereis larvae may use it as a depth gauge during vertical migration. Our results revealed a functional integration of ciliary and rhabdomeric photoreceptor cells in a zooplankton larva.
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Affiliation(s)
- Csaba Verasztó
- Max Planck Institute for Developmental Biology, Tübingen, Germany.,Living Systems Institute, University of Exeter, Exeter, United Kingdom
| | - Martin Gühmann
- Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Huiyong Jia
- Department of Biology, Emory University, Atlanta, United States
| | | | - Luis A Bezares-Calderón
- Max Planck Institute for Developmental Biology, Tübingen, Germany.,Living Systems Institute, University of Exeter, Exeter, United Kingdom
| | | | - Nadine Randel
- Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Réza Shahidi
- Max Planck Institute for Developmental Biology, Tübingen, Germany.,Living Systems Institute, University of Exeter, Exeter, United Kingdom
| | - Nico K Michiels
- Department of Biology, University of Tübingen, Tübingen, Germany
| | - Shozo Yokoyama
- Department of Biology, Emory University, Atlanta, United States
| | | | - Gáspár Jékely
- Max Planck Institute for Developmental Biology, Tübingen, Germany.,Living Systems Institute, University of Exeter, Exeter, United Kingdom
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31
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Bertolesi GE, McFarlane S. Seeing the light to change colour: An evolutionary perspective on the role of melanopsin in neuroendocrine circuits regulating light-mediated skin pigmentation. Pigment Cell Melanoma Res 2018; 31:354-373. [PMID: 29239123 DOI: 10.1111/pcmr.12678] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 12/05/2017] [Indexed: 12/17/2022]
Abstract
Melanopsin photopigments, Opn4x and Opn4m, were evolutionary selected to "see the light" in systems that regulate skin colour change. In this review, we analyse the roles of melanopsins, and how critical evolutionary developments, including the requirement for thermoregulation and ultraviolet protection, the emergence of a background adaptation mechanism in land-dwelling amphibian ancestors and the loss of a photosensitive pineal gland in mammals, may have helped sculpt the mechanisms that regulate light-controlled skin pigmentation. These mechanisms include melanopsin in skin pigment cells directly inducing skin darkening for thermoregulation/ultraviolet protection; melanopsin-expressing eye cells controlling neuroendocrine circuits to mediate background adaptation in amphibians in response to surface-reflected light; and pineal gland secretion of melatonin phased to environmental illuminance to regulate circadian and seasonal variation in skin colour, a process initiated by melanopsin-expressing eye cells in mammals, and by as yet unknown non-visual opsins in the pineal gland of non-mammals.
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Affiliation(s)
- Gabriel E Bertolesi
- Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Department of Cell Biology and Anatomy, University of Calgary, Calgary, AB, Canada
| | - Sarah McFarlane
- Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Department of Cell Biology and Anatomy, University of Calgary, Calgary, AB, Canada
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32
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Melanopsin mRNA in the Iris of Red-Eared Slider Turtles (Trachemys scripta elegans). J HERPETOL 2017. [DOI: 10.1670/16-046] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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33
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de Busserolles F, Cortesi F, Helvik JV, Davies WIL, Templin RM, Sullivan RKP, Michell CT, Mountford JK, Collin SP, Irigoien X, Kaartvedt S, Marshall J. Pushing the limits of photoreception in twilight conditions: The rod-like cone retina of the deep-sea pearlsides. SCIENCE ADVANCES 2017; 3:eaao4709. [PMID: 29134201 PMCID: PMC5677336 DOI: 10.1126/sciadv.aao4709] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 10/17/2017] [Indexed: 06/07/2023]
Abstract
Most vertebrates have a duplex retina comprising two photoreceptor types, rods for dim-light (scotopic) vision and cones for bright-light (photopic) and color vision. However, deep-sea fishes are only active in dim-light conditions; hence, most species have lost their cones in favor of a simplex retina composed exclusively of rods. Although the pearlsides, Maurolicus spp., have such a pure rod retina, their behavior is at odds with this simplex visual system. Contrary to other deep-sea fishes, pearlsides are mostly active during dusk and dawn close to the surface, where light levels are intermediate (twilight or mesopic) and require the use of both rod and cone photoreceptors. This study elucidates this paradox by demonstrating that the pearlside retina does not have rod photoreceptors only; instead, it is composed almost exclusively of transmuted cone photoreceptors. These transmuted cells combine the morphological characteristics of a rod photoreceptor with a cone opsin and a cone phototransduction cascade to form a unique photoreceptor type, a rod-like cone, specifically tuned to the light conditions of the pearlsides' habitat (blue-shifted light at mesopic intensities). Combining properties of both rods and cones into a single cell type, instead of using two photoreceptor types that do not function at their full potential under mesopic conditions, is likely to be the most efficient and economical solution to optimize visual performance. These results challenge the standing paradigm of the function and evolution of the vertebrate duplex retina and emphasize the need for a more comprehensive evaluation of visual systems in general.
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Affiliation(s)
- Fanny de Busserolles
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia
- Red Sea Research Center, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Fabio Cortesi
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Jon Vidar Helvik
- Department of Biology, University of Bergen, Bergen 5020, Norway
| | - Wayne I. L. Davies
- The Oceans Institute, The University of Western Australia, Crawley, Western Australia 6009, Australia
- School of Biological Science, The University of Western Australia, Crawley, Western Australia 6009, Australia
- Lions Eye Institute, The University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Rachel M. Templin
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Robert K. P. Sullivan
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Craig T. Michell
- Red Sea Research Center, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
- Department of Environmental and Biological Sciences, University of Eastern Finland, Yliopistokatu 7, FI-80101 Joensuu, Finland
| | - Jessica K. Mountford
- The Oceans Institute, The University of Western Australia, Crawley, Western Australia 6009, Australia
- School of Biological Science, The University of Western Australia, Crawley, Western Australia 6009, Australia
- Lions Eye Institute, The University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Shaun P. Collin
- The Oceans Institute, The University of Western Australia, Crawley, Western Australia 6009, Australia
- School of Biological Science, The University of Western Australia, Crawley, Western Australia 6009, Australia
- Lions Eye Institute, The University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Xabier Irigoien
- Red Sea Research Center, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
- Marine Research, AZTI - Tecnalia, Herrera Kaia, Portualdea z/g, 20110 Pasaia (Gipuzkoa), Spain
- IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
| | - Stein Kaartvedt
- Red Sea Research Center, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
- Department of Biosciences, University of Oslo, Oslo 0316, Norway
| | - Justin Marshall
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia
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34
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Dexamethasone Modulates Nonvisual Opsins, Glucocorticoid Receptor, and Clock Genes in Danio rerio ZEM-2S Cells. BIOMED RESEARCH INTERNATIONAL 2017; 2017:8459385. [PMID: 28589149 PMCID: PMC5446867 DOI: 10.1155/2017/8459385] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 03/19/2017] [Accepted: 03/22/2017] [Indexed: 12/31/2022]
Abstract
Here we report, for the first time, the differential cellular distribution of two melanopsins (Opn4m1 and Opn4m2) and the effects of GR agonist, dexamethasone, on the expression of these opsins and clock genes, in the photosensitive D. rerio ZEM-2S embryonic cells. Immunopositive labeling for Opn4m1 was detected in the cell membrane whereas Opn4m2 labeling shows nuclear localization, which did not change in response to light. opn4m1, opn4m2, gr, per1b, and cry1b presented an oscillatory profile of expression in LD condition. In both DD and LD condition, dexamethasone (DEX) treatment shifted the peak expression of per1b and cry1b transcripts to ZT16, which corresponds to the highest opn4m1 expression. Interestingly, DEX promoted an increase of per1b expression when applied in LD condition but a decrease when the cells were kept under DD condition. Although DEX effects are divergent with different light conditions, the response resulted in clock synchronization in all cases. Taken together, these data demonstrate that D. rerio ZEM-2S cells possess a photosensitive system due to melanopsin expression which results in an oscillatory profile of clock genes in response to LD cycle. Moreover, we provide evidence that glucocorticoid acts as a circadian regulator of D. rerio peripheral clocks.
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35
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Light- and circadian-controlled genes respond to a broad light spectrum in Puffer Fish-derived Fugu eye cells. Sci Rep 2017; 7:46150. [PMID: 28418034 PMCID: PMC5394683 DOI: 10.1038/srep46150] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 03/10/2017] [Indexed: 11/08/2022] Open
Abstract
Some cell lines retain intrinsic phototransduction pathways to control the expression of light-regulated genes such as the circadian clock gene. Here we investigated the photosensitivity of a Fugu eye, a cell line established from the eye of Takifugu rubripes, to examine whether such a photosensitive nature is present. Microarray analysis identified 15 genes that showed blue light-dependent change at the transcript level. We investigated temporal profiles of the light-induced genes, as well as Cry and Per, under light-dark, constant light (LL), and constant dark (DD) conditions by quantitative RT-PCR. Transcript levels of Per1a and Per3 genes showed circadian rhythmic changes under both LL and DD conditions, while those of Cry genes were controlled by light. All genes examined, including DNA-damage response genes and photolyase genes, were upregulated not only by blue light but also green and red light, implying the contribution of multiple photopigments. The present study is the first to identify a photosensitive clock cell line originating from a marine fish. These findings may help to characterize the molecular mechanisms underlying photic synchronization of the physiological states of fishes to not only daily light-dark cycles but also to various marine environmental cycles such as the lunar or semi-lunar cycle.
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Fritsch R, Ullmann JFP, Bitton PP, Collin SP, Michiels NK. Optic-nerve-transmitted eyeshine, a new type of light emission from fish eyes. Front Zool 2017; 14:14. [PMID: 28261313 PMCID: PMC5327540 DOI: 10.1186/s12983-017-0198-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 02/15/2017] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Most animal eyes feature an opaque pigmented eyecup to assure that light can enter from one direction only. We challenge this dogma by describing a previously unknown form of eyeshine resulting from light that enters the eye through the top of the head and optic nerve, eventually emanating through the pupil as a narrow beam: the Optic-Nerve-Transmitted (ONT) eyeshine. We characterize ONT eyeshine in the triplefin blenny Tripterygion delaisi (Tripterygiidae) in comparison to three other teleost species, using behavioural and anatomical observations, spectrophotometry, histology, and magnetic resonance imaging. The study's aim is to identify the factors that determine ONT eyeshine occurrence and intensity, and whether these are specifically adapted for that purpose. RESULTS ONT eyeshine intensity benefits from locally reduced head pigmentation, a thin skull, the gap between eyes and forebrain, the potential light-guiding properties of the optic nerve, and, most importantly, a short distance between the head surface and the optic nerves. CONCLUSIONS The generality of these factors and the lack of specifically adapted features implies that ONT eyeshine is widespread among small fish species. Nevertheless, its intensity varies considerably, depending on the specific combination and varying expression of common anatomical features. We discuss whether ONT eyeshine might affect visual performance, and speculate about possible functions such as predator detection, camouflage, and intraspecific communication.
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Affiliation(s)
- Roland Fritsch
- Institute of Evolution and Ecology, University of Tübingen, 72076 Tübingen, Baden-Württemberg Germany
| | - Jeremy F P Ullmann
- Centre for Advanced Imaging, University of Queensland, Brisbane, 4072 Queensland Australia.,Department of Neurology, Boston Children's Hospital & Harvard Medical School, Boston, MA 02115 USA
| | - Pierre-Paul Bitton
- Institute of Evolution and Ecology, University of Tübingen, 72076 Tübingen, Baden-Württemberg Germany
| | - Shaun P Collin
- School of Biological Sciences and the Oceans Institute, University of Western Australia, Crawley, 6009 Western Australia Australia
| | - Nico K Michiels
- Institute of Evolution and Ecology, University of Tübingen, 72076 Tübingen, Baden-Württemberg Germany
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Morrow JM, Lazic S, Dixon Fox M, Kuo C, Schott RK, de A Gutierrez E, Santini F, Tropepe V, Chang BSW. A second visual rhodopsin gene, rh1-2, is expressed in zebrafish photoreceptors and found in other ray-finned fishes. ACTA ACUST UNITED AC 2016; 220:294-303. [PMID: 27811293 DOI: 10.1242/jeb.145953] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 10/25/2016] [Indexed: 12/19/2022]
Abstract
Rhodopsin (rh1) is the visual pigment expressed in rod photoreceptors of vertebrates that is responsible for initiating the critical first step of dim-light vision. Rhodopsin is usually a single copy gene; however, we previously discovered a novel rhodopsin-like gene expressed in the zebrafish retina, rh1-2, which we identified as a functional photosensitive pigment that binds 11-cis retinal and activates in response to light. Here, we localized expression of rh1-2 in the zebrafish retina to a subset of peripheral photoreceptor cells, which indicates a partially overlapping expression pattern with rh1 We also expressed, purified and characterized Rh1-2, including investigation of the stability of the biologically active intermediate. Using fluorescence spectroscopy, we found the half-life of the rate of retinal release of Rh1-2 following photoactivation to be more similar to that of the visual pigment rhodopsin than to the non-visual pigment exo-rhodopsin (exorh), which releases retinal around 5 times faster. Phylogenetic and molecular evolutionary analyses show that rh1-2 has ancient origins within teleost fishes, is under similar selective pressure to rh1, and likely experienced a burst of positive selection following its duplication and divergence from rh1 These findings indicate that rh1-2 is another functional visual rhodopsin gene, which contradicts the prevailing notion that visual rhodopsin is primarily found as a single copy gene within ray-finned fishes. The reasons for retention of this duplicate gene, as well as possible functional consequences for the visual system, are discussed.
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Affiliation(s)
- James M Morrow
- Department of Cell and Systems Biology, University of Toronto, Toronto, Canada, M5S 3G5.,Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada, M5S 3B2
| | - Savo Lazic
- Department of Molecular Genetics, University of Toronto, Toronto, Canada, M5S 1A8
| | - Monica Dixon Fox
- Department of Cell and Systems Biology, University of Toronto, Toronto, Canada, M5S 3G5
| | - Claire Kuo
- Department of Cell and Systems Biology, University of Toronto, Toronto, Canada, M5S 3G5
| | - Ryan K Schott
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada, M5S 3B2
| | - Eduardo de A Gutierrez
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada, M5S 3B2
| | - Francesco Santini
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Vincent Tropepe
- Department of Cell and Systems Biology, University of Toronto, Toronto, Canada, M5S 3G5.,Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Canada, M5T 3A9.,Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Canada, M5S 3B2
| | - Belinda S W Chang
- Department of Cell and Systems Biology, University of Toronto, Toronto, Canada, M5S 3G5 .,Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada, M5S 3B2.,Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Canada, M5S 3B2
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Prolonged Inner Retinal Photoreception Depends on the Visual Retinoid Cycle. J Neurosci 2016; 36:4209-17. [PMID: 27076420 DOI: 10.1523/jneurosci.2629-14.2016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 03/08/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED In addition to rods and cones, mammals have inner retinal photoreceptors called intrinsically photosensitive retinal ganglion cells (ipRGCs), which use the photopigment melanopsin and mediate nonimage-forming visual responses, such as pupil reflexes and circadian entrainment. After photic activation, photopigments must be reverted to their dark state to be light-sensitive again. For rods and to some extent cones, photopigment regeneration depends on the retinoid cycle in the adjacent retinal pigment epithelium (RPE). By contrast, ipRGCs are far from the RPE, and previous work suggests that melanopsin is capable of light-dependent self-regeneration. Here, we used in vitro ipRGC recording and in vivo pupillometry to show that the RPE is required for normal melanopsin-based responses to prolonged light, especially at high stimulus intensities. Melanopsin-based photoresponses of rat ipRGCs were remarkably sustained when a functional RPE was attached to the retina, but became far more transient if the RPE was removed, or if the retinoid cycle was inhibited, or when Müller glia were poisoned. Similarly, retinoid cycle inhibition markedly reduced the steady-state amplitude of melanopsin-driven pupil reflexes in both mice and rats. However, melanopsin photoresponses in RPE-separated rat retinas became more sustained in the presence of an 11-cis-retinal analog. In conclusion, during prolonged illumination, melanopsin regeneration depends partly on 11-cis-retinal from the RPE, possibly imported via Müller cells. Implications for RPE-related eye diseases and the acne drug isotretinoin (a retinoid cycle inhibitor) are discussed. SIGNIFICANCE STATEMENT Intrinsically photosensitive retinal ganglion cells (ipRGCs) contain the photopigment melanopsin and drive subconscious physiological responses to light, e.g., pupillary constriction and neuroendocrine regulation. In darkness, each photopigment molecule in ipRGCs, as well as rod/cone photoreceptors, contains 11-cis-retinal (a vitamin A derivative) and light isomerizes it to all-trans-retinal, which activates the photopigment. To make this photopigment excitable again,all-trans-retinal must be reisomerized to 11-cis-retinal. For rods and to some extent cones, this reisomerization occurs in the adjacent retinal pigment epithelium (RPE), but because ipRGCs are far from the RPE, they are thought to regenerate excitable melanopsin exclusively through RPE-independent means. Here, we present electrophysiological and behavioral evidence that ipRGCs depend on the RPE to continuously regenerate melanopsin during intense prolonged photostimulation.
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Kelley JL, Davies WIL. The Biological Mechanisms and Behavioral Functions of Opsin-Based Light Detection by the Skin. Front Ecol Evol 2016. [DOI: 10.3389/fevo.2016.00106] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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40
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Sonoda T, Schmidt TM. Re-evaluating the Role of Intrinsically Photosensitive Retinal Ganglion Cells: New Roles in Image-Forming Functions. Integr Comp Biol 2016; 56:834-841. [DOI: 10.1093/icb/icw066] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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41
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Beale AD, Whitmore D, Moran D. Life in a dark biosphere: a review of circadian physiology in "arrhythmic" environments. J Comp Physiol B 2016; 186:947-968. [PMID: 27263116 PMCID: PMC5090016 DOI: 10.1007/s00360-016-1000-6] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 05/05/2016] [Accepted: 05/17/2016] [Indexed: 11/25/2022]
Abstract
Most of the life with which humans interact is exposed to highly rhythmic and extremely predictable changes in illumination that occur with the daily events of sunrise and sunset. However, while the influence of the sun feels omnipotent to surface dwellers such as ourselves, life on earth is dominated, in terms of biomass, by organisms isolated from the direct effects of the sun. A limited understanding of what life is like away from the sun can be inferred from our knowledge of physiology and ecology in the light biosphere, but a full understanding can only be gained by studying animals from the dark biosphere, both in the laboratory and in their natural habitats. One of the least understood aspects of life in the dark biosphere is the rhythmicity of physiology and what it means to live in an environment of low or no rhythmicity. Here we describe methods that may be used to understand rhythmic physiology in the dark and summarise some of the studies of rhythmic physiology in "arrhythmic" environments, such as the poles, deep sea and caves. We review what can be understood about the adaptive value of rhythmic physiology on the Earth's surface from studies of animals from arrhythmic environments and what role a circadian clock may play in the dark.
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Affiliation(s)
- Andrew David Beale
- Department of Cell and Developmental Biology, Centre for Cell and Molecular Dynamics, University College London, 21 University Street, London, WC1E 6BT, UK.
| | - David Whitmore
- Department of Cell and Developmental Biology, Centre for Cell and Molecular Dynamics, University College London, 21 University Street, London, WC1E 6BT, UK
| | - Damian Moran
- Plant and Food Research, Seafood Technologies Group, Nelson, New Zealand.
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Kingston ACN, Cronin TW. Diverse Distributions of Extraocular Opsins in Crustaceans, Cephalopods, and Fish. Integr Comp Biol 2016; 56:820-833. [PMID: 27252200 DOI: 10.1093/icb/icw022] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Non-visual and extraocular photoreceptors are common among animals, but current understanding linking molecular pathways to physiological function of these receptors is lacking. Opsin diversity in extraocular tissues suggests that many putative extraocular photoreceptors utilize the "visual" phototransduction pathway-the same phototransduction pathway as photoreceptors within the retina dedicated to light detection for image sensing. Here, we provide a brief overview of the current understanding of non-visual and extraocular photoreceptors, and contribute a synopsis of several novel putative extraocular photoreceptors that use both visual and non-visual phototransduction pathways. Crayfish, cephalopods, and flat fish express opsins in diverse tissues, suggesting the presence of extraocular photoreceptors. In most cases, we find that these animals use the same phototransduction pathway that is utilized in the retinas for image-formation. However, we also find the presence of non-visual phototransduction components in the skin of flounders. Our evidence suggests that extraocular photoreceptors may employ a number of phototransduction pathways that do not appear to correlate with purpose or location of the photoreceptor.
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Affiliation(s)
- Alexandra C N Kingston
- Department of Biological Sciences, University of Maryland Baltimore County 1000 Hilltop Circle, Baltimore, MD 21250, USA
| | - Thomas W Cronin
- Department of Biological Sciences, University of Maryland Baltimore County 1000 Hilltop Circle, Baltimore, MD 21250, USA
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Torii M, Kojima D, Nishimura A, Itoh H, Fukada Y. Light-dependent activation of G proteins by two isoforms of chicken melanopsins. Photochem Photobiol Sci 2016; 14:1991-7. [PMID: 26411960 DOI: 10.1039/c5pp00153f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In the chicken pineal gland, light stimuli trigger signaling pathways mediated by two different subtypes, Gt and G11. These G proteins may be activated by any of the three major pineal opsins, pinopsin, OPN4-1 and OPN4-2, but biochemical evidence for the coupling has been missing except for functional coupling between pinopsin and Gt. Here we investigated the relative expression levels and the functional difference among the three pineal opsins. In the chicken pineal gland, the pinopsin mRNA level was significantly more abundant than the others, of which the OPN4-2 mRNA level was higher than that of OPN4-1. In G protein activation assays, Gt was strongly activated by pinopsin in a light-dependent manner, being consistent with previous studies, and weakly activated by OPN4-2. Unexpectedly, illuminated OPN4-2 more efficiently activated G protein(s) that was endogenously expressed in HEK293T cells in culture. On the other hand, Gq, the closest analogue of G11, was activated only by OPN4-1 although the activity was relatively weak under these conditions. These results suggest that OPN4-1 and OPN4-2 couple with Gq and Gt, respectively. Two melanopsins, OPN4-1 and OPN4-2, appear to have acquired mutually different functions through the evolution.
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Affiliation(s)
- Masaki Torii
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
| | - Daisuke Kojima
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
| | - Akiyuki Nishimura
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan
| | - Hiroshi Itoh
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan
| | - Yoshitaka Fukada
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
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Sato K, Yamashita T, Haruki Y, Ohuchi H, Kinoshita M, Shichida Y. Two UV-Sensitive Photoreceptor Proteins, Opn5m and Opn5m2 in Ray-Finned Fish with Distinct Molecular Properties and Broad Distribution in the Retina and Brain. PLoS One 2016; 11:e0155339. [PMID: 27167972 PMCID: PMC4864311 DOI: 10.1371/journal.pone.0155339] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 04/27/2016] [Indexed: 12/02/2022] Open
Abstract
Opn5 is a group within the opsin family of proteins that is responsible for visual and non-visual photoreception in animals. It consists of several subgroups, including Opn5m, the only subgroup containing members found in most vertebrates, including mammals. In addition, recent genomic information has revealed that some ray-finned fishes carry paralogous genes of Opn5m while other fishes have no such genes. Here, we report the molecular properties of the opsin now called Opn5m2 and its distributions in both the retina and brain. Like Opn5m, Opn5m2 exhibits UV light-sensitivity when binding to 11-cis-retinal and forms a stable active state that couples with Gi subtype of G protein. However, Opn5m2 does not bind all-trans-retinal and exhibits exclusive binding to 11-cis-retinal, whereas many bistable opsins, including fish Opn5m, can bind directly to all-trans-retinal as well as 11-cis-retinal. Because medaka fish has lost the Opn5m2 gene from its genome, we compared the tissue distribution patterns of Opn5m in medaka fish, zebrafish, and spotted gar, in addition to the distribution patterns of Opn5m2 in zebrafish and spotted gar. Opn5m expression levels showed a gradient along the dorsal–ventral axis of the retina, and preferential expression was observed in the ventral retina in the three fishes. The levels of Opn5m2 showed a similar gradient with preferential expression observed in the dorsal retina. Opn5m expression was relatively abundant in the inner region of the inner nuclear layer, while Opn5m2 was expressed in the outer edge of the inner nuclear layer. Additionally, we could detect Opn5m expression in several brain regions, including the hypothalamus, of these fish species. Opn5m2 expression could not be detected in zebrafish brain, but was clearly observed in limited brain regions of spotted gar. These results suggest that ray-finned fishes can generally utilize UV light information for non-image-forming photoreception in a wide range of cells in the retina and brain.
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Affiliation(s)
- Keita Sato
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Takahiro Yamashita
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Yoshihiro Haruki
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Hideyo Ohuchi
- Department of Cytology and Histology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Masato Kinoshita
- Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Yoshinori Shichida
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
- * E-mail:
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Shirzad-Wasei N, DeGrip WJ. Heterologous expression of melanopsin: Present, problems and prospects. Prog Retin Eye Res 2016; 52:1-21. [DOI: 10.1016/j.preteyeres.2016.02.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 01/25/2016] [Accepted: 02/01/2016] [Indexed: 12/12/2022]
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Díaz NM, Morera LP, Guido ME. Melanopsin and the Non-visual Photochemistry in the Inner Retina of Vertebrates. Photochem Photobiol 2015; 92:29-44. [DOI: 10.1111/php.12545] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 10/09/2015] [Indexed: 01/28/2023]
Affiliation(s)
- Nicolás M. Díaz
- Departamento de Química Biológica-CIQUIBIC (CONICET); Facultad de Ciencias Químicas; Universidad Nacional de Córdoba (UNC); Córdoba Argentina
| | - Luis P. Morera
- Departamento de Química Biológica-CIQUIBIC (CONICET); Facultad de Ciencias Químicas; Universidad Nacional de Córdoba (UNC); Córdoba Argentina
| | - Mario E. Guido
- Departamento de Química Biológica-CIQUIBIC (CONICET); Facultad de Ciencias Químicas; Universidad Nacional de Córdoba (UNC); Córdoba Argentina
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Davies WIL, Tamai TK, Zheng L, Fu JK, Rihel J, Foster RG, Whitmore D, Hankins MW. An extended family of novel vertebrate photopigments is widely expressed and displays a diversity of function. Genome Res 2015; 25:1666-79. [PMID: 26450929 PMCID: PMC4617963 DOI: 10.1101/gr.189886.115] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 07/15/2015] [Indexed: 11/24/2022]
Abstract
Light affects animal physiology and behavior more than simply through classical visual, image-forming pathways. Nonvisual photoreception regulates numerous biological systems, including circadian entrainment, DNA repair, metabolism, and behavior. However, for the majority of these processes, the photoreceptive molecules involved are unknown. Given the diversity of photophysiological responses, the question arises whether a single photopigment or a greater diversity of proteins within the opsin superfamily detect photic stimuli. Here, a functional genomics approach identified the full complement of photopigments in a highly light-sensitive model vertebrate, the zebrafish (Danio rerio), and characterized their tissue distribution, expression levels, and biochemical properties. The results presented here reveal the presence of 42 distinct genes encoding 10 classical visual photopigments and 32 nonvisual opsins, including 10 novel opsin genes comprising four new pigment classes. Consistent with the presence of light-entrainable circadian oscillators in zebrafish, all adult tissues examined expressed two or more opsins, including several novel opsins. Spectral and electrophysiological analyses of the new opsins demonstrate that they form functional photopigments, each with unique chromophore-binding and wavelength specificities. This study has revealed a remarkable number and diversity of photopigments in zebrafish, the largest number so far discovered for any vertebrate. Found in amphibians, reptiles, birds, and all three mammalian clades, most of these genes are not restricted to teleosts. Therefore, nonvisual light detection is far more complex than initially appreciated, which has significant biological implications in understanding photoreception in vertebrates.
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Affiliation(s)
- Wayne I L Davies
- School of Animal Biology and University of Western Australia Oceans Institute, University of Western Australia, Perth, Western Australia 6009, Australia; Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, United Kingdom
| | - T Katherine Tamai
- Centre for Cell and Molecular Dynamics, Department of Cell and Developmental Biology, University College London, London, WC1E 6DE, United Kingdom
| | - Lei Zheng
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, United Kingdom
| | - Josephine K Fu
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, United Kingdom
| | - Jason Rihel
- Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, United Kingdom
| | - Russell G Foster
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, United Kingdom
| | - David Whitmore
- Centre for Cell and Molecular Dynamics, Department of Cell and Developmental Biology, University College London, London, WC1E 6DE, United Kingdom
| | - Mark W Hankins
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, United Kingdom
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Tsukamoto H, Kubo Y, Farrens DL, Koyanagi M, Terakita A, Furutani Y. Retinal Attachment Instability Is Diversified among Mammalian Melanopsins. J Biol Chem 2015; 290:27176-27187. [PMID: 26416885 DOI: 10.1074/jbc.m115.666305] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Indexed: 01/12/2023] Open
Abstract
Melanopsins play a key role in non-visual photoreception in mammals. Their close phylogenetic relationship to the photopigments in invertebrate visual cells suggests they have evolved to acquire molecular characteristics that are more suited for their non-visual functions. Here we set out to identify such characteristics by comparing the molecular properties of mammalian melanopsin to those of invertebrate melanopsin and visual pigment. Our data show that the Schiff base linking the chromophore retinal to the protein is more susceptive to spontaneous cleavage in mammalian melanopsins. We also find this stability is highly diversified between mammalian species, being particularly unstable for human melanopsin. Through mutagenesis analyses, we find that this diversified stability is mainly due to parallel amino acid substitutions in extracellular regions. We propose that the different stability of the retinal attachment in melanopsins may contribute to functional tuning of non-visual photoreception in mammals.
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Affiliation(s)
- Hisao Tsukamoto
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, Okazaki, 444-8585, Japan,; Department of Structural Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa 240-0193, Japan,.
| | - Yoshihiro Kubo
- Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan,; Department of Physiological Sciences, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa 240-0193, Japan
| | - David L Farrens
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239-3098
| | - Mitsumasa Koyanagi
- Department of Biology and Geosciences, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan
| | - Akihisa Terakita
- Department of Biology and Geosciences, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan
| | - Yuji Furutani
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, Okazaki, 444-8585, Japan,; Department of Structural Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa 240-0193, Japan
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Diversification of non-visual photopigment parapinopsin in spectral sensitivity for diverse pineal functions. BMC Biol 2015; 13:73. [PMID: 26370232 PMCID: PMC4570685 DOI: 10.1186/s12915-015-0174-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 07/27/2015] [Indexed: 02/08/2023] Open
Abstract
Background Recent genome projects of various animals have uncovered an unexpectedly large number of opsin genes, which encode protein moieties of photoreceptor molecules, in most animals. In visual systems, the biological meanings of this diversification are clear; multiple types of visual opsins with different spectral sensitivities are responsible for color vision. However, the significance of the diversification of non-visual opsins remains uncertain, in spite of the importance of understanding the molecular mechanism and evolution of varied non-visual photoreceptions. Results Here, we investigated the diversification of the pineal photopigment parapinopsin, which serves as the UV-sensitive photopigment for the pineal wavelength discrimination in the lamprey, linking it with other pineal photoreception. Spectroscopic analyses of the recombinant pigments of the two teleost parapinopsins PP1 and PP2 revealed that PP1 is a UV-sensitive pigment, similar to lamprey parapinopsin, but PP2 is a blue-sensitive pigment, with an absorption maximum at 460–480 nm, showing the diversification of non-visual pigment with respect to spectral sensitivity. We also found that PP1 and PP2 exhibit mutually exclusive expressions in the pineal organs of three teleost species. By using transgenic zebrafish in which these parapinopsin-expressing cells are labeled, we found that PP1-expressing cells basically possess neuronal processes, which is consistent with their involvement in wavelength discrimination. Interestingly, however, PP2-expressing cells rarely possess neuronal processes, raising the possibility that PP2 could be involved in non-neural responses rather than neural responses. Furthermore, we found that PP2-expressing cells contain serotonin and aanat2, the key enzyme involved in melatonin synthesis from serotonin, whereas PP1-expressing cells do not contain either, suggesting that blue-sensitive PP2 is instead involved in light-regulation of melatonin secretion. Conclusions In this paper, we have clearly shown the different molecular properties of duplicated non-visual opsins by demonstrating the diversification of parapinopsin with respect to spectral sensitivity. Moreover, we have shown a plausible link between the diversification and its physiological impact by discovering a strong candidate for the underlying pigment in light-regulated melatonin secretion in zebrafish; the diversification could generate a new contribution of parapinopsin to pineal photoreception. Current findings could also provide an opportunity to understand the “color” preference of non-visual photoreception. Electronic supplementary material The online version of this article (doi:10.1186/s12915-015-0174-9) contains supplementary material, which is available to authorized users.
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Baker GE, de Grip WJ, Turton M, Wagner HJ, Foster RG, Douglas RH. Light sensitivity in a vertebrate mechanoreceptor? J Exp Biol 2015; 218:2826-9. [PMID: 26206352 PMCID: PMC4582172 DOI: 10.1242/jeb.125203] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 07/15/2015] [Indexed: 12/22/2022]
Abstract
Using immunohistochemistry and western blot analysis, we demonstrate that melanopsin is localised in cells around the central pore of lateral line neuromasts in the African clawed frog, Xenopus laevis. Since melanopsin is a known photoreceptor pigment with diverse functions in vertebrates, we suggest that the lateral line of Xenopus laevis, which is primarily a mechanoreceptor, might also be light sensitive. Potential functions of such photosensitivity are discussed, including its role in mediating locomotor responses following dermal illumination.
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Affiliation(s)
- Gary E Baker
- Department of Optometry & Visual Science, School of Health Sciences, City University London, Northampton Square, London EC1V 0HB, UK
| | - Willem J de Grip
- Department of Biochemistry, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 HP Nijmegen, The Netherlands
| | - Michael Turton
- Nuffield Laboratory of Ophthalmology, University of Oxford, Levels 5-6 West Wing, John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK
| | - Hans-Joachim Wagner
- Anatomisches Institut, Universität Tübingen, Ősterbergstrasse 3, Tübingen 72074, Germany
| | - Russell G Foster
- Nuffield Laboratory of Ophthalmology, University of Oxford, Levels 5-6 West Wing, John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK
| | - Ron H Douglas
- Department of Optometry & Visual Science, School of Health Sciences, City University London, Northampton Square, London EC1V 0HB, UK
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