1
|
Chen J, Curcio CA, Crosson JN. Shotgun lipidomics of human subretinal fluids under rod-dominant retina reveals cone-dominated lipids. Exp Eye Res 2024; 240:109807. [PMID: 38278468 DOI: 10.1016/j.exer.2024.109807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 01/08/2024] [Accepted: 01/22/2024] [Indexed: 01/28/2024]
Abstract
Subretinal fluid (SRF) accumulates between photoreceptor outer segments and retinal pigment epithelium during rhegmatogenous retinal detachment. Biomolecular components such as lipids originate from cells surrounding the SRF. Knowledge of the composition of these molecules in SRF potentially provides mechanistic insight into the physiologic transfer of lipids between retinal tissue compartments. Using mass spectrometry and tandem mass spectrometry analysis on an electrospray ionization quadrupole-time-of-flight mass spectrometer, we identified a total of 115 lipid molecular species of 11 subclasses and 9 classes in two samples from two patients with rhegmatogenous retinal detachment. These included 47 glycerophosphocholines, 6 glycerophosphoethanolamines, 1 glycerophosphoinositol, 18 sphingomyelins, 9 cholesteryl esters, free cholesterol, 3 ceramides, 22 triacylglycerols and 8 free fatty acids. Glycerophosphocholines were of the highest intensity. By minimizing the formation of different adduct forms or clustering ions of different adducts, we determined the relative intensity of lipid molecular species within the same subclasses. The profiles were compared with those of retinal cells available in the published literature. The glycerophosphocholine profile of SRF was similar to that of cone outer segments, suggesting that outer segment degradation products are constitutively released into the interphotoreceptor matrix, appearing in SRF during detachment. This hypothesis was supported by the retinal distributions of corresponding lipid synthases' mRNA expression obtained from an online resource based on publicly available single-cell sequencing data. In contrast, based on lipid profiles and relevant gene expression in this study, the sources of free cholesterol and cholesteryl esters in SRF appeared more ambiguous, possibly reflecting that outer retina takes up plasma lipoproteins. Further studies to identify and quantify lipids in SRF will help better understand etiology of diseases relevant to outer retina.
Collapse
Affiliation(s)
- Jianzhong Chen
- Center for Biotechnology & Genomic Medicine, Medical College of Georgia, Augusta University, GA, United States; Department of Cellular Biology & Anatomy, Medical College of Georgia, Augusta University, GA, United States; Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL, United States.
| | - Christine A Curcio
- Department of Ophthalmology and Visual Sciences, The University of Alabama at Birmingham, Birmingham, AL, United States.
| | - Jason N Crosson
- Department of Ophthalmology and Visual Sciences, The University of Alabama at Birmingham, Birmingham, AL, United States
| |
Collapse
|
2
|
Williams RC, Harrison WW, Carkeet A, Ostrin LA. Twenty-four hour diurnal variation in retinal oxygen saturation. Vision Res 2023; 213:108314. [PMID: 37657366 PMCID: PMC11148934 DOI: 10.1016/j.visres.2023.108314] [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: 05/20/2023] [Revised: 07/12/2023] [Accepted: 08/16/2023] [Indexed: 09/03/2023]
Abstract
Retinal oxygen saturation is influenced by systemic and local vasculature, intraocular pressure (IOP), and individual cellular function. In numerous retinal pathologies, early changes take place at the level of the microvasculature, thereby affecting retinal oxygenation. The purpose of this study was to investigate diurnal variations in retinal oximetry measures and evaluate the relationship with other ocular and systemic physiological processes. Healthy adults (n = 18, mean age 27 ± 5.5 years) participated. Ocular and systemic measures were collected every four hours over 24 h and included retinal oximetry, IOP, optical coherence tomography (OCT), OCT-angiography (OCTA), biometry, blood pressure, and partial pressure of oxygen. Amplitude and acrophase for retinal oxygen saturation, axial length, retinal and choroidal thickness, OCTA parameters, and mean arterial and ocular perfusion pressure (MAP, MOPP) were determined were determined using cosine fits, and multiple regression analysis was performed to compare metrics. Retinal oxygenation saturation demonstrated a significant diurnal variation with an amplitude of 5.84 ± 3.86% and acrophase of 2.35 h. Other parameters that demonstrated significant diurnal variation included IOP, MOPP, axial length, choroidal thickness, superficial vessel density, heart rate, systolic blood pressure, and MAP. Diurnal variations in retinal oxygen saturation were in-phase with choroidal thickness, IOP, and density of the superficial vascular plexus and out-of-phase with axial length and MOPP. In conclusion, retinal oxygenation saturation undergoes diurnal variations over 24 h. These findings contribute to a better understanding of intrinsic and extrinsic factors influencing oxygenation of the area surrounding the fovea.
Collapse
Affiliation(s)
- Rachel C Williams
- University of Houston College of Optometry, 4401 Martin Luther King Blvd, Houston, TX 77204, United States
| | - Wendy W Harrison
- University of Houston College of Optometry, 4401 Martin Luther King Blvd, Houston, TX 77204, United States
| | - Andrew Carkeet
- Queensland University of Technology, School of Optometry and Vision Science QUT, Kelvin Grove, Qld 4059, Australia
| | - Lisa A Ostrin
- University of Houston College of Optometry, 4401 Martin Luther King Blvd, Houston, TX 77204, United States.
| |
Collapse
|
3
|
Bhoi JD, Goel M, Ribelayga CP, Mangel SC. Circadian clock organization in the retina: From clock components to rod and cone pathways and visual function. Prog Retin Eye Res 2023; 94:101119. [PMID: 36503722 PMCID: PMC10164718 DOI: 10.1016/j.preteyeres.2022.101119] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 08/22/2022] [Accepted: 08/25/2022] [Indexed: 12/13/2022]
Abstract
Circadian (24-h) clocks are cell-autonomous biological oscillators that orchestrate many aspects of our physiology on a daily basis. Numerous circadian rhythms in mammalian and non-mammalian retinas have been observed and the presence of an endogenous circadian clock has been demonstrated. However, how the clock and associated rhythms assemble into pathways that support and control retina function remains largely unknown. Our goal here is to review the current status of our knowledge and evaluate recent advances. We describe many previously-observed retinal rhythms, including circadian rhythms of morphology, biochemistry, physiology, and gene expression. We evaluate evidence concerning the location and molecular machinery of the retinal circadian clock, as well as consider findings that suggest the presence of multiple clocks. Our primary focus though is to describe in depth circadian rhythms in the light responses of retinal neurons with an emphasis on clock control of rod and cone pathways. We examine evidence that specific biochemical mechanisms produce these daily light response changes. We also discuss evidence for the presence of multiple circadian retinal pathways involving rhythms in neurotransmitter activity, transmitter receptors, metabolism, and pH. We focus on distinct actions of two dopamine receptor systems in the outer retina, a dopamine D4 receptor system that mediates circadian control of rod/cone gap junction coupling and a dopamine D1 receptor system that mediates non-circadian, light/dark adaptive regulation of gap junction coupling between horizontal cells. Finally, we evaluate the role of circadian rhythmicity in retinal degeneration and suggest future directions for the field of retinal circadian biology.
Collapse
Affiliation(s)
- Jacob D Bhoi
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA; Neuroscience Honors Research Program, William Marsh Rice University, Houston, TX, USA
| | - Manvi Goel
- Department of Neuroscience, Wexner Medical Center, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Christophe P Ribelayga
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA; Neuroscience Honors Research Program, William Marsh Rice University, Houston, TX, USA.
| | - Stuart C Mangel
- Department of Neuroscience, Wexner Medical Center, College of Medicine, The Ohio State University, Columbus, OH, USA.
| |
Collapse
|
4
|
Ontogenetic expression rhythms of visual opsins in senegalese sole are modulated by photoperiod and light spectrum. J Comp Physiol B 2020; 190:185-204. [PMID: 32048006 DOI: 10.1007/s00360-020-01264-7] [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: 05/27/2019] [Revised: 01/05/2020] [Accepted: 01/19/2020] [Indexed: 10/25/2022]
Abstract
In the fish retina, rods and cones are responsible for nocturnal vision and colour perception, respectively, and exhibit a repertoire of light-sensitive opsin photopigments that permits the adaptation to different photic environment. The metamorphosis of Senegalese sole determines a migration from pelagic to benthic environments, which is accompanied by essential changes in light intensity and spectrum. In this paper, we analysed the daily expression rhythms of rod opsin and five cone opsins during sole ontogeny in animals maintained under light-dark cycles of white (LDW), blue (LDB), red (LDR) and continuous white (LL) lights. We showed that the expression of visual opsins at early stages of development was enhanced under LDB in relation to LDW, LDR and LL. Moreover, daily rhythms of opsins were more robust under LDW and LDB conditions, in particular, before and after metamorphosis. A shift in the phase of opsin rhythms was observed between hatching and pre-metamorphosis. Metamorphosis was accompanied by a transient loss in the expression rhythms for most of the opsins, which were significantly influenced by light photoperiod and spectrum. In LDR, transcript levels and rhythms were markedly affected for the majority of the opsins analysed. Under LL, most of the opsins examined exhibited endogenous rhythms, although amplitudes and acrophases changed considerably. To the best of our knowledge, this is the first study on the daily expression rhythms of visual opsins during the ontogeny of a metamorphic flatfish and further emphasises the importance of using natural lighting conditions for proper development of Senegalese sole.
Collapse
|
5
|
Schietroma C, Parain K, Estivalet A, Aghaie A, Boutet de Monvel J, Picaud S, Sahel JA, Perron M, El-Amraoui A, Petit C. Usher syndrome type 1-associated cadherins shape the photoreceptor outer segment. J Cell Biol 2017; 216:1849-1864. [PMID: 28495838 PMCID: PMC5461027 DOI: 10.1083/jcb.201612030] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 02/26/2017] [Accepted: 03/21/2017] [Indexed: 01/19/2023] Open
Abstract
Usher syndrome type 1 (USH1) causes combined hearing and sight defects, but USH1 protein function in the retina is unclear. Schietroma et al. use Xenopus to model the deficiency in two USH1 proteins—protocadherin-15 and cadherin-23—and identify crucial roles for these molecules in shaping the photoreceptor outer segment. Usher syndrome type 1 (USH1) causes combined hearing and sight defects, but how mutations in USH1 genes lead to retinal dystrophy in patients remains elusive. The USH1 protein complex is associated with calyceal processes, which are microvilli of unknown function surrounding the base of the photoreceptor outer segment. We show that in Xenopus tropicalis, these processes are connected to the outer-segment membrane by links composed of protocadherin-15 (USH1F protein). Protocadherin-15 deficiency, obtained by a knockdown approach, leads to impaired photoreceptor function and abnormally shaped photoreceptor outer segments. Rod basal outer disks displayed excessive outgrowth, and cone outer segments were curved, with lamellae of heterogeneous sizes, defects also observed upon knockdown of Cdh23, encoding cadherin-23 (USH1D protein). The calyceal processes were virtually absent in cones and displayed markedly reduced F-actin content in rods, suggesting that protocadherin-15–containing links are essential for their development and/or maintenance. We propose that calyceal processes, together with their associated links, control the sizing of rod disks and cone lamellae throughout their daily renewal.
Collapse
Affiliation(s)
- Cataldo Schietroma
- Institut Pasteur, Génétique et Physiologie de l'Audition, 75015 Paris, France.,Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche-UMRS 1120, France.,Sorbonne Universités, UPMC University Paris, Complexité du Vivant, 75005 Paris, France.,Syndrome de Usher et Autres Atteintes Rétino-Cochléaires, Institut de la Vision, 75012 Paris, France
| | - Karine Parain
- Paris-Saclay Institute of Neuroscience, Centre National de la Recherche Scientifique, Université Paris Sud, Université Paris-Saclay, 91405 Orsay, France
| | - Amrit Estivalet
- Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche-UMRS 1120, France.,Sorbonne Universités, UPMC University Paris, Complexité du Vivant, 75005 Paris, France.,Syndrome de Usher et Autres Atteintes Rétino-Cochléaires, Institut de la Vision, 75012 Paris, France
| | - Asadollah Aghaie
- Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche-UMRS 1120, France.,Sorbonne Universités, UPMC University Paris, Complexité du Vivant, 75005 Paris, France.,Syndrome de Usher et Autres Atteintes Rétino-Cochléaires, Institut de la Vision, 75012 Paris, France
| | - Jacques Boutet de Monvel
- Institut Pasteur, Génétique et Physiologie de l'Audition, 75015 Paris, France.,Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche-UMRS 1120, France.,Sorbonne Universités, UPMC University Paris, Complexité du Vivant, 75005 Paris, France
| | - Serge Picaud
- Sorbonne Universités, UPMC University Paris, Complexité du Vivant, 75005 Paris, France.,Retinal information processing - Pharmacology and Pathology, Institut de la Vision, 75012 Paris, France
| | - José-Alain Sahel
- Sorbonne Universités, UPMC University Paris, Complexité du Vivant, 75005 Paris, France.,Retinal information processing - Pharmacology and Pathology, Institut de la Vision, 75012 Paris, France
| | - Muriel Perron
- Paris-Saclay Institute of Neuroscience, Centre National de la Recherche Scientifique, Université Paris Sud, Université Paris-Saclay, 91405 Orsay, France.,Centre d'Etude et de Recherche Thérapeutique en Ophtalmologie, Retina France, 94405 Orsay, France
| | - Aziz El-Amraoui
- Institut Pasteur, Génétique et Physiologie de l'Audition, 75015 Paris, France.,Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche-UMRS 1120, France.,Sorbonne Universités, UPMC University Paris, Complexité du Vivant, 75005 Paris, France
| | - Christine Petit
- Institut Pasteur, Génétique et Physiologie de l'Audition, 75015 Paris, France .,Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche-UMRS 1120, France.,Sorbonne Universités, UPMC University Paris, Complexité du Vivant, 75005 Paris, France.,Syndrome de Usher et Autres Atteintes Rétino-Cochléaires, Institut de la Vision, 75012 Paris, France.,Collège de France, 75005 Paris, France
| |
Collapse
|
6
|
Johnson AM, Stanis S, Fuller RC. Diurnal lighting patterns and habitat alter opsin expression and colour preferences in a killifish. Proc Biol Sci 2013; 280:20130796. [PMID: 23698009 DOI: 10.1098/rspb.2013.0796] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Spatial variation in lighting environments frequently leads to population variation in colour patterns, colour preferences and visual systems. Yet lighting conditions also vary diurnally, and many aspects of visual systems and behaviour vary over this time scale. Here, we use the bluefin killifish (Lucania goodei) to compare how diurnal variation and habitat variation (clear versus tannin-stained water) affect opsin expression and the preference to peck at different-coloured objects. Opsin expression was generally lowest at midnight and dawn, and highest at midday and dusk, and this diurnal variation was many times greater than variation between habitats. Pecking preference was affected by both diurnal and habitat variation but did not correlate with opsin expression. Rather, pecking preference matched lighting conditions, with higher preferences for blue at noon and for red at dawn/dusk, when these wavelengths are comparatively scarce. Similarly, blue pecking preference was higher in tannin-stained water where blue wavelengths are reduced. In conclusion, L. goodei exhibits strong diurnal cycles of opsin expression, but these are not tightly correlated with light intensity or colour. Temporally variable pecking preferences probably result from lighting environment rather than from opsin production. These results may have implications for the colour pattern diversity observed in these fish.
Collapse
Affiliation(s)
- Ashley M Johnson
- Department of Animal Biology, University of Illinois, Shelford Vivarium, 606 E. Healey Street, Champaign, IL 61820, USA.
| | | | | |
Collapse
|
7
|
Corless JM. Cone outer segments: a biophysical model of membrane dynamics, shape retention, and lamella formation. Biophys J 2012; 102:2697-705. [PMID: 22735519 DOI: 10.1016/j.bpj.2012.04.052] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Revised: 04/25/2012] [Accepted: 04/30/2012] [Indexed: 10/28/2022] Open
Abstract
An hypothesis is developed to explain how the unique, right circular conical geometry of cone outer segments (COSs) in Xenopus laevis and other lower vertebrates is maintained during the cycle of axial shortening by apical phagocytosis and axial elongation via the addition of new basal lamellae. Extension of a new basal evagination (BE) applies radial (lateral) traction to membrane and cytoplasmic domains, achieving two coupled effects. 1), The bilayer domain is locally stretched/dilated, creating an entropic driving force that draws membrane components into the BE from the COS's distributed bilayer phase, i.e., plasmalemma and older lamellae (membrane recycling). Membrane proteins, e.g., opsins, are carried passively in this advective, bilayer-driven process. 2), With BE stretching, hydrostatic pressure within the BE cytoplasm is reduced slightly with respect to that of the axonemal cytoplasmic reservoir, allowing cytoplasmic flow into the BE. Attendant lowering of the reservoir's hydrostatic pressure facilitates the subsequent transfer of cytoplasm from lamellar domains to the reservoir (cytoplasmic recycling). The geometry of the BE reflects the membrane/cytoplasm ratio needed for its construction, and essentially specifies the ratio of components recycled from older lamellae. Length and taper angle of the COS reflect the ratio of recycled/new components constructing a new BE. The model also integrates the trajectories and dynamics of lamella open margin lattice components. Although not fully evaluated, the initial model has been assessed against the relevant literature, and three experimental predictions are derived.
Collapse
Affiliation(s)
- Joseph M Corless
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina, USA.
| |
Collapse
|
8
|
A simplified mass-transfer model for visual pigments in amphibian retinal-cone outer segments. Biophys J 2011; 100:525-534. [PMID: 21281566 DOI: 10.1016/j.bpj.2010.11.085] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2010] [Revised: 11/10/2010] [Accepted: 11/15/2010] [Indexed: 11/22/2022] Open
Abstract
When radiolabeled precursors and autoradiography are used to investigate turnover of protein components in photoreceptive cone outer segments (COSs), the labeled components--primarily visual pigment molecules (opsins)--are diffusely distributed along the COS. To further assess this COS labeling pattern, we derive a simplified mass-transfer model for quantifying the contributions of advective and diffusive mechanisms to the distribution of opsins within COSs of the frog retina. Two opsin-containing regions of the COS are evaluated: the core axial array of disks and the plasmalemma. Numerical solutions of the mass-transfer model indicate three distinct stages of system evolution. In the first stage, plasmalemma diffusion is dominant. In the second stage, the plasmalemma density reaches a metastable state and transfer between the plasmalemma and disk region occurs, which is followed by an increase in density that is qualitatively similar for both regions. The final stage consists of both regions slowly evolving to the steady-state solution. Our results indicate that autoradiographic and cognate approaches for tracking labeled opsins in the COS cannot be effective methodologies for assessing new disk formation at the base of the COS.
Collapse
|
9
|
Novales Flamarique I. Unique photoreceptor arrangements in a fish with polarized light discrimination. J Comp Neurol 2011; 519:714-37. [DOI: 10.1002/cne.22544] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
|
10
|
Abstract
Although outnumbered more than 20:1 by rod photoreceptors, cone cells in the human retina mediate daylight vision and are critical for visual acuity and color discrimination. A variety of human diseases are characterized by a progressive loss of cone photoreceptors but the low abundance of cones and the absence of a macula in non-primate mammalian retinas have made it difficult to investigate cones directly. Conventional rodents (laboratory mice and rats) are nocturnal rod-dominated species with few cones in the retina, and studying other animals with cone-rich retinas presents various logistic and technical difficulties. Originating in the early 1900s, past research has begun to provide insights into cone ultrastructure but has yet to afford an overall perspective of cone cell organization. This review summarizes our past progress and focuses on the recent introduction of special mammalian models (transgenic mice and diurnal rats rich in cones) that together with new investigative techniques such as atomic force microscopy and cryo-electron tomography promise to reveal a more unified concept of cone photoreceptor organization and its role in retinal diseases.
Collapse
|
11
|
Allison WT, Dann SG, Veldhoen KM, Hawryshyn CW. Degeneration and regeneration of ultraviolet cone photoreceptors during development in rainbow trout. J Comp Neurol 2006; 499:702-15. [PMID: 17048226 DOI: 10.1002/cne.21164] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Ultraviolet-sensitive (UVS) cones disappear from the retina of salmonid fishes during a metamorphosis that prepares them for deeper/marine waters. UVS cones subsequently reappear in the retina near sexual maturation and the return migration to natal streams. Cellular mechanisms of this UVS cone ontogeny were investigated using electroretinograms, in situ hybridization, and immunohistochemistry against opsins during and after thyroid hormone (TH) treatments of rainbow trout (Oncorhynchus mykiss). Increasing TH levels led to UVS cone degeneration. Labeling demonstrated that UVS cone degeneration occurs via programmed cell death and caspase inhibitors can inhibit this death. After the cessation of TH treatment, UVS cones regenerated in the retina. Bromodeoxyuridine (BrdU) was applied after the termination of TH treatment and was detected in the nuclei of cells expressing UVS opsin. BrdU was found in UVS cones but not other cone types. The most parsimonious explanation for the data is that UVS cones degenerated and UVS cones were regenerated from intrinsic retinal progenitor cells. Regenerating UVS cones were functionally integrated such that they were able to elicit electrical responses from second-order neurons. This is the first report of cones regenerating during natural development. Both the death and regeneration of cones in retinae represent novel mechanisms for tuning visual systems to new visual tasks or environments.
Collapse
Affiliation(s)
- W Ted Allison
- Department of Biology, University of Victoria, Victoria, British Columbia V8W 3N5, Canada
| | | | | | | |
Collapse
|
12
|
Eckmiller MS. Energy Depletion Hypothesis for Retinitis Pigmentosa. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 533:277-85. [PMID: 15180274 DOI: 10.1007/978-1-4615-0067-4_34] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Affiliation(s)
- Marion S Eckmiller
- Vogt Brain Research Institute, University Clinic, Heinrich Heine University of Düsseldorf, Postfach 101007, D-40001 Düsseldorf, Germany.
| |
Collapse
|
13
|
Schmitt A, Wolfrum U. Identification of novel molecular components of the photoreceptor connecting cilium by immunoscreens. Exp Eye Res 2001; 73:837-49. [PMID: 11846514 DOI: 10.1006/exer.2001.1086] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The connecting cilium of photoreceptor cells is the only intracellular link between the morphologically, functionally and biochemically different compartments of the inner and outer segments. The non-motile modified cilium plays an important role in the organization and the function of photoreceptor cells, namely in delivery and turnover of enzymes and substrates of the visual transduction cascade, and the photosensitive membranes of the outer segment. The protein components of the cilium participate in the intracellular transport through the cilium, in the outer segment disk morphogenesis and in the maintenance of discrete membrane domains. In order to identify yet unknown cytoskeletal components of the connecting cilium, a combined biochemical and molecular biological strategy was applied. For this purpose, antibodies were raised against proteins of photoreceptor cell axonemes. Using this AX-4-antiserum, a rat retina cDNA expression library was immunoscreened and clones encoding partial sequences of (i) already known photoreceptor specific proteins; (ii) ubiquitously expressed proteins; (iii) clones with homologies to retinal ESTs; and (iv) clones coding for cytoskeletal proteins were isolated. Further analysis revealed that these candidate clones have homologies to Drosophila flightless I, mouse APC-binding protein EB2, human microtubule associated protein 4 (MAP4), human centrin 3, human cytoplasmic dynein intermediate chain 2C, and human dynamitin.The immunoscreening approach used here was successfully applied to isolate genes encoding yet unknown cytoskeletal proteins of photoreceptor cell axonemes. The obtained information will provide further insight into the role of the connecting cilium in photoreceptor cell function.
Collapse
Affiliation(s)
- A Schmitt
- Institute of Zoology, Johannes Gutenberg-University of Mainz, Mainz, Germany
| | | |
Collapse
|
14
|
Abstract
Unlike in birds and cold-blooded vertebrates' retinas, the photoreceptors of mammalian retinas were long supposed to be morphologically uniform and difficult to distinguish into subtypes. A number of new techniques have now begun to overcome the previous limitations. A hitherto unexpected variability of spectral and morphological subtypes and topographic patterns of distribution in the various retinas are being revealed. We begin to understand the design of the photoreceptor mosaics, the constraints of evolutionary history and the ecological specialization of these mosaics in all the mammalian subgroups. The review discusses current cytological identification of mammalian photoreceptor types and speculates on the likely "bottleneck-scenario" for the origin of the basic design of the mammalian retina. It then provides a brief synopsis of current data on the photoreceptors in the various mammalian orders and derives some trends for phenomena such as rod/cone dualism, spectral range, preservation or loss of double cones and oil droplets, photopigment co-expression and mono- and tri-chromacy. Finally, we attempt to demonstrate that, building on the limits of an ancient rod dominant (probably dichromatic) model, mammalian retinas have developed considerable radiation. Comparing the nonprimate models with the intensively studied primate model should provide us with a deeper understanding of the basic design of the mammalian retina.
Collapse
Affiliation(s)
- P K Ahnelt
- Institut für Physiologie, Medizinische Fakultät, Universität Wien, Wien, Austria.
| | | |
Collapse
|
15
|
Nguyen-Legros J, Hicks D. Renewal of photoreceptor outer segments and their phagocytosis by the retinal pigment epithelium. INTERNATIONAL REVIEW OF CYTOLOGY 2000; 196:245-313. [PMID: 10730217 DOI: 10.1016/s0074-7696(00)96006-6] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The discovery of disc protein renewal in rod outer segments, in 1960s, was followed by the observation that old discs were ingested by the retinal pigment epithelium. This process occurs in both rods and cones and is crucial for their survival. Photoreceptors completely degenerate in the Royal College of Surgeons mutant rat, whose pigment epithelium cannot ingest old discs. The complete renewal process includes the following sequential steps involving both photoreceptor and pigment epithelium activity: new disc assembly and old disc shedding by photoreceptor cells; recognition and binding to pigment epithelium membranes; then ingestion, digestion, and segregation of residual bodies in pigment epithelium cytoplasm. Regulating factors are involved at each step. While disc assembly is mostly genetically controlled, disc shedding and the subsequent pigment epithelium phagocytosis appear regulated by environmental factors (light and temperature). Disc shedding is rhythmically controlled by an eye intrinsic circadian oscillator using endogenous dopamine and melatonin as light and dark signal, respectively. Of special interest is the regulation of phagocytosis by multiple receptors, including specific phagocytosis receptors and receptors for neuroactive substances released from the neuroretina. The candidates for phagocytosis receptors are presented, but it is acknowledged that they are not completely known. The main neuromodulators are adenosine, dopamine, glutamate, serotonin, and melatonin. Although the transduction mechanisms are not fully understood, attention was brought to cyclic AMP, phosphoinositides, and calcium. The chapter points to the multiplicity of regulating factors and the complexity of their intermingling modes of action. Promising areas for future research still exist in this field.
Collapse
Affiliation(s)
- J Nguyen-Legros
- Institut National de la Santé et de la Recherche Médicale (INSERM, U-450) Laboratoire de NeuroCytologie Oculaire, Paris, France
| | | |
Collapse
|