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Lee SJ, Emery D, Vukmanic E, Wang Y, Lu X, Wang W, Fortuny E, James R, Kaplan HJ, Liu Y, Du J, Dean DC. Metabolic transcriptomics dictate responses of cone photoreceptors to retinitis pigmentosa. Cell Rep 2023; 42:113054. [PMID: 37656622 PMCID: PMC10591869 DOI: 10.1016/j.celrep.2023.113054] [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: 05/08/2023] [Revised: 06/21/2023] [Accepted: 08/15/2023] [Indexed: 09/03/2023] Open
Abstract
Most mutations in retinitis pigmentosa (RP) arise in rod photoreceptors, but cone photoreceptors, responsible for high-resolution daylight and color vision, are subsequently affected, causing the most debilitating features of the disease. We used mass spectroscopy to follow 13C metabolites delivered to the outer retina and single-cell RNA sequencing to assess photoreceptor transcriptomes. The S cone metabolic transcriptome suggests engagement of the TCA cycle and ongoing response to ROS characteristic of oxidative phosphorylation, which we link to their histone modification transcriptome. Tumor necrosis factor (TNF) and its downstream effector RIP3, which drive ROS generation via mitochondrial dysfunction, are induced and activated as S cones undergo early apoptosis in RP. The long/medium-wavelength (L/M) cone transcriptome shows enhanced glycolytic capacity, which maintains their function as RP progresses. Then, as extracellular glucose eventually diminishes, L/M cones are sustained in long-term dormancy by lactate metabolism.
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Affiliation(s)
- Sang Joon Lee
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA; Department of Ophthalmology, Kosin University College of Medicine, #262 Gamcheon-ro, Seo-gu, Busan 49267, Korea
| | - Douglas Emery
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Eric Vukmanic
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Yekai Wang
- Departments of Ophthalmology and Visual Sciences and Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506, USA
| | - Xiaoqin Lu
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Wei Wang
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Enzo Fortuny
- Department of Neurosurgery, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Robert James
- Department of Neurosurgery, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Henry J Kaplan
- Department of Ophthalmology, St. Louis University School of Medicine, St. Louis MO 63110, USA
| | - Yongqing Liu
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Jianhai Du
- Departments of Ophthalmology and Visual Sciences and Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506, USA.
| | - Douglas C Dean
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA.
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Moran AL, Fehilly JD, Floss Jones D, Collery R, Kennedy BN. Regulation of the rhythmic diversity of daily photoreceptor outer segment phagocytosis in vivo. FASEB J 2022; 36:e22556. [PMID: 36165194 PMCID: PMC9828801 DOI: 10.1096/fj.202200990rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 08/30/2022] [Accepted: 09/06/2022] [Indexed: 01/12/2023]
Abstract
Outer segment phagocytosis (OSP) is a highly-regulated, biological process wherein photoreceptor outer segment (OS) tips are cyclically phagocytosed by the adjacent retinal pigment epithelium (RPE) cells. Often an overlooked retinal process, rhythmic OSP ensures the maintenance of healthy photoreceptors and vision. Daily, the photoreceptors renew OS at their base and the most distal, and likely oldest, OS tips, are phagocytosed by the RPE, preventing the accumulation of photo-oxidative compounds by breaking down phagocytosed OS tips and recycling useful components to the photoreceptors. Light changes often coincide with an escalation of OSP and within hours the phagosomes formed in each RPE cell are resolved. In the last two decades, individual molecular regulators were elucidated. Some of the molecular machinery used by RPE cells for OSP is highly similar to mechanisms used by other phagocytic cells for the clearance of apoptotic cells. Consequently, in the RPE, many molecular regulators of retinal phagocytosis have been elucidated. However, there is still a knowledge gap regarding the key regulators of physiological OSP in vivo between endogenous photoreceptors and the RPE. Understanding the regulation of OSP is of significant clinical interest as age-related macular degeneration (AMD) and inherited retinal diseases (IRD) are linked with altered OSP. Here, we review the in vivo timing of OSP peaks in selected species and focus on the reported in vivo environmental and molecular regulators of OSP.
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Affiliation(s)
- Ailis L. Moran
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland,UCD Conway InstituteUniversity College DublinDublinIreland
| | - John D. Fehilly
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland,UCD Conway InstituteUniversity College DublinDublinIreland
| | - Daniel Floss Jones
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland,UCD Conway InstituteUniversity College DublinDublinIreland
| | - Ross Collery
- Department of Cell Biology, Neurobiology and AnatomyMedical College of WisconsinMilwaukeeWisconsinUSA,Department of Ophthalmology and Visual SciencesMedical College of Wisconsin Eye InstituteMilwaukeeWisconsinUSA
| | - Breandán N. Kennedy
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland,UCD Conway InstituteUniversity College DublinDublinIreland
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3
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Navneet S, Rohrer B. Elastin turnover in ocular diseases: A special focus on age-related macular degeneration. Exp Eye Res 2022; 222:109164. [PMID: 35798060 PMCID: PMC9795808 DOI: 10.1016/j.exer.2022.109164] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 06/08/2022] [Accepted: 06/20/2022] [Indexed: 12/30/2022]
Abstract
The extracellular matrix (ECM) and its turnover play a crucial role in the pathogenesis of several inflammatory diseases, including age-related macular degeneration (AMD). Elastin, a critical protein component of the ECM, not only provides structural and mechanical support to tissues, but also mediates several intracellular and extracellular molecular signaling pathways. Abnormal turnover of elastin has pathological implications. In the eye elastin is a major structural component of Bruch's membrane (BrM), a critical ECM structure separating the retinal pigment epithelium (RPE) from the choriocapillaris. Reduced integrity of macular BrM elastin, increased serum levels of elastin-derived peptides (EDPs), and elevated elastin antibodies have been reported in AMD. Existing reports suggest that elastases, the elastin-degrading enzymes secreted by RPE, infiltrating macrophages or neutrophils could be involved in BrM elastin degradation, thus contributing to AMD pathogenesis. EDPs derived from elastin degradation can increase inflammatory and angiogenic responses in tissues, and the elastin antibodies are shown to play roles in immune cell activity and complement activation. This review summarizes our current understanding on the elastases/elastin fragments-mediated mechanisms of AMD pathogenesis.
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Affiliation(s)
- Soumya Navneet
- Department of Ophthalmology, Medical University of South Carolina, Charleston, SC, USA.
| | - Bärbel Rohrer
- Department of Ophthalmology, Medical University of South Carolina, Charleston, SC, USA; Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA; Ralph H. Johnson VA Medical Center, Division of Research, Charleston, SC, USA.
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4
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DeVera C, Dixon J, Chrenek MA, Baba K, Le YZ, Iuvone PM, Tosini G. The Circadian Clock in the Retinal Pigment Epithelium Controls the Diurnal Rhythm of Phagocytic Activity. Int J Mol Sci 2022; 23:5302. [PMID: 35628111 PMCID: PMC9141420 DOI: 10.3390/ijms23105302] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 04/26/2022] [Accepted: 05/03/2022] [Indexed: 02/04/2023] Open
Abstract
The diurnal peak of phagocytosis by the retinal pigment epithelium (RPE) of photoreceptor outer segments (POS) is under circadian control and believed that this process involves interactions from the retina and RPE. Previous studies have demonstrated that a functional circadian clock exists within multiple retinal cell types and RPE. Thereby, the aim of this study was to determine whether the clock in the retina or RPE controls the diurnal phagocytic peak and whether disruption of the circadian clock in the RPE would affect cellular function and the viability during aging. To that, we generated and validated an RPE tissue-specific KO of the essential clock gene, Bmal1, and then determined the daily rhythm in phagocytic activity by the RPE in mice lacking a functional circadian clock in the retina or RPE. Then, using electroretinography, spectral domain-optical coherence tomography, and optomotor response of visual function we determined the effect of Bmal1 removal in young (6 months) and old (18 months) mice. RPE morphology and lipofuscin accumulation was determined in young and old mice. Our data shows that the clock in the RPE, rather than the retina clock, controls the diurnal phagocytic peak. Surprisingly, absence of a functional RPE clock and phagocytic peak does not result in any detectable age-related degenerative phenotype in the retina or RPE. Thus, our results demonstrate that the circadian clock in the RPE controls the daily peak of phagocytic activity. However, the absence of the clock in the RPE does not result in deterioration of photoreceptors or the RPE during aging.
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Affiliation(s)
- Christopher DeVera
- Department of Pharmacology & Toxicology and Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA 30310, USA; (C.D.); (K.B.)
| | - Jendayi Dixon
- Department of Ophthalmology and Emory Eye Center, Emory University School of Medicine, Atlanta, GA 30322, USA; (J.D.); (M.A.C.); (P.M.I.)
| | - Micah A. Chrenek
- Department of Ophthalmology and Emory Eye Center, Emory University School of Medicine, Atlanta, GA 30322, USA; (J.D.); (M.A.C.); (P.M.I.)
| | - Kenkichi Baba
- Department of Pharmacology & Toxicology and Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA 30310, USA; (C.D.); (K.B.)
| | - Yun Z. Le
- Departments of Medicine, Cell Biology, and Ophthalmology and Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA;
| | - P. Michael Iuvone
- Department of Ophthalmology and Emory Eye Center, Emory University School of Medicine, Atlanta, GA 30322, USA; (J.D.); (M.A.C.); (P.M.I.)
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Gianluca Tosini
- Department of Pharmacology & Toxicology and Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA 30310, USA; (C.D.); (K.B.)
- Department of Ophthalmology and Emory Eye Center, Emory University School of Medicine, Atlanta, GA 30322, USA; (J.D.); (M.A.C.); (P.M.I.)
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5
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Circadian Regulation of Retinal Pigment Epithelium Function. Int J Mol Sci 2022; 23:ijms23052699. [PMID: 35269840 PMCID: PMC8910459 DOI: 10.3390/ijms23052699] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 02/16/2022] [Accepted: 02/21/2022] [Indexed: 12/22/2022] Open
Abstract
The retinal pigment epithelium (RPE) is a single layer of cells located between the choriocapillaris vessels and the light-sensitive photoreceptors in the outer retina. The RPE performs physiological processes necessary for the maintenance and support of photoreceptors and visual function. Among the many functions performed by the RPE, the timing of the peak in phagocytic activity by the RPE of the photoreceptor outer segments that occurs 1-2 h. after the onset of light has captured the interest of many investigators and has thus been intensively studied. Several studies have shown that this burst in phagocytic activity by the RPE is under circadian control and is present in nocturnal and diurnal species and rod and cone photoreceptors. Previous investigations have demonstrated that a functional circadian clock exists within multiple retinal cell types and RPE cells. However, the anatomical location of the circadian controlling this activity is not clear. Experimental evidence indicates that the circadian clock, melatonin, dopamine, and integrin signaling play a key role in controlling this rhythm. A series of very recent studies report that the circadian clock in the RPE controls the daily peak in phagocytic activity. However, the loss of the burst in phagocytic activity after light onset does not result in photoreceptor or RPE deterioration during aging. In the current review, we summarized the current knowledge on the mechanism controlling this phenomenon and the physiological role of this peak.
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6
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Jauregui-Lozano J, Hall H, Stanhope SC, Bakhle K, Marlin MM, Weake VM. The Clock:Cycle complex is a major transcriptional regulator of Drosophila photoreceptors that protects the eye from retinal degeneration and oxidative stress. PLoS Genet 2022; 18:e1010021. [PMID: 35100266 PMCID: PMC8830735 DOI: 10.1371/journal.pgen.1010021] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 02/10/2022] [Accepted: 01/08/2022] [Indexed: 12/28/2022] Open
Abstract
The aging eye experiences physiological changes that include decreased visual function and increased risk of retinal degeneration. Although there are transcriptomic signatures in the aging retina that correlate with these physiological changes, the gene regulatory mechanisms that contribute to cellular homeostasis during aging remain to be determined. Here, we integrated ATAC-seq and RNA-seq data to identify 57 transcription factors that showed differential activity in aging Drosophila photoreceptors. These 57 age-regulated transcription factors include two circadian regulators, Clock and Cycle, that showed sustained increased activity during aging. When we disrupted the Clock:Cycle complex by expressing a dominant negative version of Clock (ClkDN) in adult photoreceptors, we observed changes in expression of 15–20% of genes including key components of the phototransduction machinery and many eye-specific transcription factors. Using ATAC-seq, we showed that expression of ClkDN in photoreceptors leads to changes in activity of 37 transcription factors and causes a progressive decrease in global levels of chromatin accessibility in photoreceptors. Supporting a key role for Clock-dependent transcription in the eye, expression of ClkDN in photoreceptors also induced light-dependent retinal degeneration and increased oxidative stress, independent of light exposure. Together, our data suggests that the circadian regulators Clock and Cycle act as neuroprotective factors in the aging eye by directing gene regulatory networks that maintain expression of the phototransduction machinery and counteract oxidative stress. Age-associated changes to the retinal transcriptome often correlate with physiological changes, such as loss of visual function and increase in cell death. However, the mechanisms that contribute to these transcriptomic changes are poorly understood. Here, we used a genomics/bioinformatics approach to identify transcription factor binding sites with differential activity in aging Drosophila retina outer photoreceptors. Amongst these age-regulated transcription factors, we identify the circadian regulators Clock and Cycle. Using a genetics approach, we find that photoreceptor-specific disruption of the Clock:Cycle complex makes the Drosophila eye susceptible to light-dependent retinal degeneration, and light-independent increase of oxidative stress, showing that a functional circadian clock contributes to visual health and function in Drosophila. Because disruption of circadian rhythms has been associated with the onset of several age-related eye diseases, our data shows that the Drosophila retina serves as a useful model to study how disruption of the circadian clock contributes to neurodegeneration in the retina.
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Affiliation(s)
- Juan Jauregui-Lozano
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
| | - Hana Hall
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
- Purdue Institute for Integrative Neuroscience, Purdue University, West Lafayette, Indiana, United States of America
| | - Sarah C. Stanhope
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
| | - Kimaya Bakhle
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
| | - Makayla M. Marlin
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
| | - Vikki M. Weake
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
- Purdue Institute for Integrative Neuroscience, Purdue University, West Lafayette, Indiana, United States of America
- Purdue Center for Cancer Research, Purdue University, West Lafayette, Indiana, United States of America
- * E-mail:
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7
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Mosig RA, Kojima S. Timing without coding: How do long non-coding RNAs regulate circadian rhythms? Semin Cell Dev Biol 2021; 126:79-86. [PMID: 34116930 DOI: 10.1016/j.semcdb.2021.04.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 04/12/2021] [Accepted: 04/21/2021] [Indexed: 12/13/2022]
Abstract
Long non-coding RNAs (lncRNAs) are a new class of regulatory RNAs that play important roles in disease development and a variety of biological processes. Recent studies have underscored the importance of lncRNAs in the circadian clock system and demonstrated that lncRNAs regulate core clock genes and the core clock machinery in mammals. In this review, we provide an overview of our current understanding of how lncRNAs regulate the circadian clock without coding a protein. We also offer additional insights into the challenges in understanding the functions of lncRNAs and other unresolved questions in the field. We do not cover other regulatory ncRNAs even though they also play important roles; readers are highly encouraged to refer to other excellent reviews on this topic.
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Affiliation(s)
- Rebecca A Mosig
- Department of Biological Sciences, Fralin Life Sciences Institute, Virginia Tech 1015 Life Science Circle, Blacksburg, VA 24061, USA
| | - Shihoko Kojima
- Department of Biological Sciences, Fralin Life Sciences Institute, Virginia Tech 1015 Life Science Circle, Blacksburg, VA 24061, USA.
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8
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Solanki AK, Biswal MR, Walterhouse S, Martin R, Kondkar AA, Knölker HJ, Rahman B, Arif E, Husain S, Montezuma SR, Nihalani D, Lobo GP. Loss of Motor Protein MYO1C Causes Rhodopsin Mislocalization and Results in Impaired Visual Function. Cells 2021; 10:cells10061322. [PMID: 34073294 PMCID: PMC8229726 DOI: 10.3390/cells10061322] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 05/24/2021] [Accepted: 05/25/2021] [Indexed: 12/12/2022] Open
Abstract
Unconventional myosins, linked to deafness, are also proposed to play a role in retinal cell physiology. However, their direct role in photoreceptor function remains unclear. We demonstrate that systemic loss of the unconventional myosin MYO1C in mice, specifically causes rhodopsin mislocalization, leading to impaired visual function. Electroretinogram analysis of Myo1c knockout (Myo1c-KO) mice showed a progressive loss of photoreceptor function. Immunohistochemistry and binding assays demonstrated MYO1C localization to photoreceptor inner and outer segments (OS) and identified a direct interaction of rhodopsin with MYO1C. In Myo1c-KO retinas, rhodopsin mislocalized to rod inner segments (IS) and cell bodies, while cone opsins in OS showed punctate staining. In aged mice, the histological and ultrastructural examination of the phenotype of Myo1c-KO retinas showed progressively shorter photoreceptor OS. These results demonstrate that MYO1C is important for rhodopsin localization to the photoreceptor OS, and for normal visual function.
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Affiliation(s)
- Ashish K. Solanki
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, USA; (A.K.S.); (S.W.); (B.R.); (E.A.)
| | - Manas R. Biswal
- Department of Pharmaceutical Sciences, Taneja College of Pharmacy, University of South Florida, Tampa, FL 33612, USA;
| | - Stephen Walterhouse
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, USA; (A.K.S.); (S.W.); (B.R.); (E.A.)
| | - René Martin
- Faculty of Chemistry, Technische Universität Dresden, Bergstraße 66, 01069 Dresden, Germany; (R.M.); (H.-J.K.)
| | - Altaf A. Kondkar
- Department of Ophthalmology, College of Medicine, King Saud University, Riyadh 11411, Saudi Arabia;
| | - Hans-Joachim Knölker
- Faculty of Chemistry, Technische Universität Dresden, Bergstraße 66, 01069 Dresden, Germany; (R.M.); (H.-J.K.)
| | - Bushra Rahman
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, USA; (A.K.S.); (S.W.); (B.R.); (E.A.)
| | - Ehtesham Arif
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, USA; (A.K.S.); (S.W.); (B.R.); (E.A.)
| | - Shahid Husain
- Department of Ophthalmology, Medical University of South Carolina, Charleston, SC 29425, USA;
| | - Sandra R. Montezuma
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, 516 Delaware Street S.E., 9th Floor, Minneapolis, MN 55455, USA;
| | - Deepak Nihalani
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health, Bldg. 2DEM, Room 6085, 6707 Democracy Blvd., Bethesda, MD 20817, USA
- Correspondence: (D.N.); (G.P.L.)
| | - Glenn Prazere Lobo
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425, USA; (A.K.S.); (S.W.); (B.R.); (E.A.)
- Department of Ophthalmology, Medical University of South Carolina, Charleston, SC 29425, USA;
- Department of Ophthalmology and Visual Neurosciences, Lions Research Building, University of Minnesota, 2001 6th Street S.E., Room 225, Minneapolis, MN 55455, USA
- Correspondence: (D.N.); (G.P.L.)
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9
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Wang Z, Ji S, Huang Y, Liao K, Cui Z, Chu F, Chen J, Tang S. The daily gene transcription cycle in mouse retina. Exp Eye Res 2021; 207:108565. [PMID: 33838143 DOI: 10.1016/j.exer.2021.108565] [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: 12/16/2020] [Revised: 03/23/2021] [Accepted: 03/30/2021] [Indexed: 12/13/2022]
Abstract
Many physiological retinal processes, such as outer segment disk shedding and visual sensitivity, exhibit a daily rhythm. However, the detailed transcriptome dynamics and related biological processes of the retina are not fully understood. Retinal tissues were collected from C57BL/6J male mice housed in a 12h light/12h dark (LD) cycle for 4 weeks, at Zeitgeber time (ZT) 0, 4, 8, 12, 16, and 20. Total RNA was extracted from the tissues and used for unique identifier RNA sequencing experiments. The rhythmicity of gene expression was determined using the MetaCycle R package. We found that 1741 genes (10.26%) were rhythmically expressed in the retina. According to the expression patterns, the rhythmically expressed genes were assigned to four clusters, each with about 361-492 genes, using the Mfuzz R package. The Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analyses were conducted to identify pathways and biological processes of the profiled genes. Genes in Clusters 1 and 4 were associated with glycolysis and energy production, showed higher activity at night (from ZT16 to ZT20), and were enriched in the Hif-1α signaling pathway and low-oxygen-related terms. Genes in Cluster 2 were predominantly involved in cilium assembly and organization and were relatively upregulated during the day. Genes in Cluster 3 were associated with ribosome biosynthesis and were highly expressed during the day-night transition period. Taken together, these results demonstrate that a large proportion of retinal genes are expressed rhythmically. Genes involved in energy production and glycolysis are highly expressed at night, leading to relative hypoxia and activation of the Hif-1α signaling pathway. Genes associated with the formation of photoreceptor cilia are expressed during the day.
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Affiliation(s)
- Zhijie Wang
- Aier School of Ophthalmology, Central South University, Changsha, China; Aier Eye Institute, Changsha, China
| | | | - Yinhua Huang
- Aier School of Ophthalmology, Central South University, Changsha, China; Aier Eye Institute, Changsha, China
| | - Kai Liao
- Aier School of Ophthalmology, Central South University, Changsha, China; Aier Eye Institute, Changsha, China
| | | | - Feixue Chu
- Hangzhou Xihu Zhijiang Eye Hospital, China
| | - Jiansu Chen
- Aier School of Ophthalmology, Central South University, Changsha, China; Aier Eye Institute, Changsha, China; Key Laboratory for Regenerative Medicine, Ministry of Education, Jinan University, Guangzhou, China; Institute of Ophthalmology, Medical College, Jinan University, Guangzhou, China.
| | - Shibo Tang
- Aier School of Ophthalmology, Central South University, Changsha, China; Aier Eye Institute, Changsha, China; CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China.
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10
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Abstract
The field of phosphoinositide signaling has expanded significantly in recent years. Phosphoinositides (also known as phosphatidylinositol phosphates or PIPs) are universal signaling molecules that directly interact with membrane proteins or with cytosolic proteins containing domains that directly bind phosphoinositides and are recruited to cell membranes. Through the activities of phosphoinositide kinases and phosphoinositide phosphatases, seven distinct phosphoinositide lipid molecules are formed from the parent molecule, phosphatidylinositol. PIP signals regulate a wide range of cellular functions, including cytoskeletal assembly, membrane budding and fusion, ciliogenesis, vesicular transport, and signal transduction. Given the many excellent reviews on phosphoinositide kinases, phosphoinositide phosphatases, and PIPs in general, in this review, we discuss recent studies and advances in PIP lipid signaling in the retina. We specifically focus on PIP lipids from vertebrate (e.g., bovine, rat, mouse, toad, and zebrafish) and invertebrate (e.g., Drosophila, horseshoe crab, and squid) retinas. We also discuss the importance of PIPs revealed from animal models and human diseases, and methods to study PIP levels both in vitro and in vivo. We propose that future studies should investigate the function and mechanism of activation of PIP-modifying enzymes/phosphatases and further unravel PIP regulation and function in the different cell types of the retina.
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Affiliation(s)
- Raju V S Rajala
- Departments of Ophthalmology, Physiology, and Cell Biology, and Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104.
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11
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Goyal V, DeVera C, Laurent V, Sellers J, Chrenek MA, Hicks D, Baba K, Iuvone PM, Tosini G. Dopamine 2 Receptor Signaling Controls the Daily Burst in Phagocytic Activity in the Mouse Retinal Pigment Epithelium. Invest Ophthalmol Vis Sci 2020; 61:10. [PMID: 32396631 PMCID: PMC7405625 DOI: 10.1167/iovs.61.5.10] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Purpose A burst in phagocytosis of spent photoreceptor outer fragments by RPE is a rhythmic process occurring 1 to 2 hours after the onset of light. This phenomenon is considered crucial for the health of the photoreceptors and RPE. We have recently reported that dopamine, via dopamine 2 receptor (D2R), shifts the circadian rhythm in the RPE. Methods Here, we first investigated the impact of the removal of D2R on the daily peak of phagocytosis by RPE and then we analyzed the function and morphology of retina and RPE in the absence of D2R. Results D2R knockout (KO) mice do not show a daily burst of phagocytic activity after the onset of light. RNA sequencing revealed a total of 394 differentially expressed genes (DEGs) between ZT 23 and ZT 1 in the control mice, whereas in D2R KO mice, we detected 1054 DEGs. Pathway analysis of the gene expression data implicated integrin signaling to be one of the upregulated pathways in control but not in D2R KO mice. Consistent with the gene expression data, phosphorylation of focal adhesion kinase (FAK) did not increase significantly in KO mice at ZT 1. No difference in retinal thickness, visual function, or morphology of RPE cells was observed between wild-type (WT) and D2R KO mice at the age of 3 and 12 months. Conclusions Our data suggest that removal of D2R prevents the burst of phagocytosis and a related increase in the phosphorylation of FAK after light onset. The pathway analysis points toward a putative role of D2R in controlling integrin signaling, which is known to play an important role in the control of the daily burst of phagocytosis by the RPE. Our data also indicate that the absence of the burst of phagocytic activity in the early morning does not produce any apparent deleterious effect on the retina or RPE up to 1 year of age.
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12
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Role of Non-Coding RNAs in Lung Circadian Clock Related Diseases. Int J Mol Sci 2020; 21:ijms21083013. [PMID: 32344623 PMCID: PMC7215637 DOI: 10.3390/ijms21083013] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 04/19/2020] [Accepted: 04/21/2020] [Indexed: 02/06/2023] Open
Abstract
Circadian oscillations are regulated at both central and peripheral levels to maintain physiological homeostasis. The central circadian clock consists of a central pacemaker in the suprachiasmatic nucleus that is entrained by light dark cycles and this, in turn, synchronizes the peripheral clock inherent in other organs. Circadian dysregulation has been attributed to dysregulation of peripheral clock and also associated with several diseases. Components of the molecular clock are disrupted in lung diseases like chronic obstructive pulmonary disease (COPD), asthma and IPF. Airway epithelial cells play an important role in temporally organizing magnitude of immune response, DNA damage response and acute airway inflammation. Non-coding RNAs play an important role in regulation of molecular clock and in turn are also regulated by clock components. Dysregulation of these non-coding RNAs have been shown to impact the expression of core clock genes as well as clock output genes in many organs. However, no studies have currently looked at the potential impact of these non-coding RNAs on lung molecular clock. This review focuses on the ways how these non-coding RNAs regulate and in turn are regulated by the lung molecular clock and its potential impact on lung diseases.
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13
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Lakkaraju A, Umapathy A, Tan LX, Daniele L, Philp NJ, Boesze-Battaglia K, Williams DS. The cell biology of the retinal pigment epithelium. Prog Retin Eye Res 2020; 78:100846. [PMID: 32105772 PMCID: PMC8941496 DOI: 10.1016/j.preteyeres.2020.100846] [Citation(s) in RCA: 170] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 02/19/2020] [Accepted: 02/23/2020] [Indexed: 02/07/2023]
Abstract
The retinal pigment epithelium (RPE), a monolayer of post-mitotic polarized epithelial cells, strategically situated between the photoreceptors and the choroid, is the primary caretaker of photoreceptor health and function. Dysfunction of the RPE underlies many inherited and acquired diseases that cause permanent blindness. Decades of research have yielded valuable insight into the cell biology of the RPE. In recent years, new technologies such as live-cell imaging have resulted in major advancement in our understanding of areas such as the daily phagocytosis and clearance of photoreceptor outer segment tips, autophagy, endolysosome function, and the metabolic interplay between the RPE and photoreceptors. In this review, we aim to integrate these studies with an emphasis on appropriate models and techniques to investigate RPE cell biology and metabolism, and discuss how RPE cell biology informs our understanding of retinal disease.
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Affiliation(s)
- Aparna Lakkaraju
- Department of Ophthalmology, University of California, San Francisco, San Francisco, CA, USA
| | - Ankita Umapathy
- Department of Ophthalmology and Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Li Xuan Tan
- Department of Ophthalmology, University of California, San Francisco, San Francisco, CA, USA
| | - Lauren Daniele
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Nancy J Philp
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA, USA
| | - Kathleen Boesze-Battaglia
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - David S Williams
- Department of Ophthalmology and Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
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14
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DeVera C, Tosini G. Circadian analysis of the mouse retinal pigment epithelium transcriptome. Exp Eye Res 2020; 193:107988. [PMID: 32105725 DOI: 10.1016/j.exer.2020.107988] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 02/21/2020] [Accepted: 02/21/2020] [Indexed: 01/01/2023]
Abstract
The presence of a phagocytic peak of photoreceptor outer segments by the retinal pigment epithelium (RPE) one or 2 h after the onset of light has been reported for several diurnal and nocturnal species. This peak in phagocytic activity also persists under constant lighting conditions (i.e., constant light or dark) thus demonstrating that the timing of this peak is driven by a circadian clock. The aim of this study was to investigate the change in RPE whole transcriptome at two different circadian times (CT; 1 h before (CT23) and 1 h after (CT1) subjective light onset). C57BL/6J male mice were maintained in constant dark conditions for three days and euthanized under red light (<1 lux) at CT23 and CT1. RPE was isolated from whole eyes for RNA library preparation and sequencing on an Illumina HiSeq4000 platform. 14,083 mouse RPE transcripts were detected in common between CT23 and CT1. 12,005 were protein coding transcripts and 2078 were non-protein coding transcripts. 2421 protein coding transcripts were significantly upregulated whereas only 3 transcripts were significantly downregulated and 12 non-protein coding transcripts were significantly upregulated and 31 non-protein coding transcripts were significantly downregulated at CT1 when compared to CT23 (p < 0.05, fold change ≥ ±2.0). Of the protein coding transcripts, most of them were characterized as: enzymes, kinases, and transcriptional regulators with a large majority of activity in the cytoplasm, nucleus, and plasma membrane. Non-protein coding transcripts included biotypes such as long-non coding RNAs and pseudogenes. Gene ontology analysis and ingenuity pathway analysis revealed that differentially expressed transcripts were associated with integrin signaling, oxidative phosphorylation, protein phosphorylation, and actin cytoskeleton remodeling suggesting that these previously identified phagocytic pathways are under circadian control. Our analysis identified new pathways (e.g., increased mitochondrial respiration via increased oxidative phosphorylation) that may be involved in the circadian control of phagocytic activity. In addition, our dataset suggests a possible regulatory role for the identified non-protein coding transcripts in mediating the complex function of RPE phagocytosis. Finally, our results also indicate, as seen in other tissues, about 20% of the whole RPE transcriptome may be under circadian clock regulation.
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Affiliation(s)
- Christopher DeVera
- Department of Pharmacology and Toxicology, Atlanta, GA, USA, 30310; Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA, USA, 30310
| | - Gianluca Tosini
- Department of Pharmacology and Toxicology, Atlanta, GA, USA, 30310; Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA, USA, 30310.
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15
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Blond F, Léveillard T. Functional Genomics of the Retina to Elucidate its Construction and Deconstruction. Int J Mol Sci 2019; 20:E4922. [PMID: 31590277 PMCID: PMC6801968 DOI: 10.3390/ijms20194922] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 10/01/2019] [Indexed: 12/20/2022] Open
Abstract
The retina is the light sensitive part of the eye and nervous tissue that have been used extensively to characterize the function of the central nervous system. The retina has a central position both in fundamental biology and in the physiopathology of neurodegenerative diseases. We address the contribution of functional genomics to the understanding of retinal biology by reviewing key events in their historical perspective as an introduction to major findings that were obtained through the study of the retina using genomics, transcriptomics and proteomics. We illustrate our purpose by showing that most of the genes of interest for retinal development and those involved in inherited retinal degenerations have a restricted expression to the retina and most particularly to photoreceptors cells. We show that the exponential growth of data generated by functional genomics is a future challenge not only in terms of storage but also in terms of accessibility to the scientific community of retinal biologists in the future. Finally, we emphasize on novel perspectives that emerge from the development of redox-proteomics, the new frontier in retinal biology.
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Affiliation(s)
- Frédéric Blond
- Department of Genetics, Sorbonne Université, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, F-75012 Paris, France.
| | - Thierry Léveillard
- Department of Genetics, Sorbonne Université, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, F-75012 Paris, France.
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16
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Felder-Schmittbuhl MP, Buhr ED, Dkhissi-Benyahya O, Hicks D, Peirson SN, Ribelayga CP, Sandu C, Spessert R, Tosini G. Ocular Clocks: Adapting Mechanisms for Eye Functions and Health. Invest Ophthalmol Vis Sci 2019; 59:4856-4870. [PMID: 30347082 PMCID: PMC6181243 DOI: 10.1167/iovs.18-24957] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Vision is a highly rhythmic function adapted to the extensive changes in light intensity occurring over the 24-hour day. This adaptation relies on rhythms in cellular and molecular processes, which are orchestrated by a network of circadian clocks located within the retina and in the eye, synchronized to the day/night cycle and which, together, fine-tune detection and processing of light information over the 24-hour period and ensure retinal homeostasis. Systematic or high throughput studies revealed a series of genes rhythmically expressed in the retina, pointing at specific functions or pathways under circadian control. Conversely, knockout studies demonstrated that the circadian clock regulates retinal processing of light information. In addition, recent data revealed that it also plays a role in development as well as in aging of the retina. Regarding synchronization by the light/dark cycle, the retina displays the unique property of bringing together light sensitivity, clock machinery, and a wide range of rhythmic outputs. Melatonin and dopamine play a particular role in this system, being both outputs and inputs for clocks. The retinal cellular complexity suggests that mechanisms of regulation by light are diverse and intricate. In the context of the whole eye, the retina looks like a major determinant of phase resetting for other tissues such as the retinal pigmented epithelium or cornea. Understanding the pathways linking the cell-specific molecular machineries to their cognate outputs will be one of the major challenges for the future.
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Affiliation(s)
- Marie-Paule Felder-Schmittbuhl
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives (UPR 3212), Strasbourg, France
| | - Ethan D Buhr
- Department of Ophthalmology, University of Washington Medical School, Seattle, Washington, United States
| | - Ouria Dkhissi-Benyahya
- Univ Lyon, Université Claude Bernard Lyon 1, Inserm, Stem Cell and Brain Research Institute U1208, Bron, France
| | - David Hicks
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives (UPR 3212), Strasbourg, France
| | - Stuart N Peirson
- Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Christophe P Ribelayga
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, United States
| | - Cristina Sandu
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives (UPR 3212), Strasbourg, France
| | - Rainer Spessert
- Institute of Functional and Clinical Anatomy, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Gianluca Tosini
- Neuroscience Institute and Department of Pharmacology & Toxicology, Morehouse School of Medicine, Atlanta, Georgia, United States
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17
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On the Relationships between LncRNAs and Other Orchestrating Regulators: Role of the Circadian System. EPIGENOMES 2018. [DOI: 10.3390/epigenomes2020009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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18
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Mustafi D, Kevany BM, Bai X, Golczak M, Adams MD, Wynshaw-Boris A, Palczewski K. Transcriptome analysis reveals rod/cone photoreceptor specific signatures across mammalian retinas. Hum Mol Genet 2018; 25:4376-4388. [PMID: 28172828 DOI: 10.1093/hmg/ddw268] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Revised: 07/28/2016] [Accepted: 07/29/2016] [Indexed: 01/26/2023] Open
Abstract
A defined set of genetic instructions encodes functionality in complex organisms. Delineating these unique genetic signatures is essential to understanding the formation and functionality of specialized tissues. Vision, one of the five central senses of perception, is initiated by the retina and has evolved over time to produce rod and cone photoreceptors that vary in a species-specific manner, and in some cases by geographical region resulting in higher order visual acuity in humans. RNA-sequencing and use of existing and de novo transcriptome assemblies allowed ocular transcriptome mapping from a diverse set of rodent and primate species. Global genomic refinements along with systems-based comparative and co-expression analyses of these transcriptome maps identified gene modules that correlated with specific features of rod versus cone retinal cellular composition. Organization of the ocular transcriptome demonstrated herein defines the molecular basis of photoreceptor architecture and functionality, providing a new paradigm for neurogenetic analyses of the mammalian retina in health and disease.
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Affiliation(s)
- Debarshi Mustafi
- Departments of Pharmacology and Cleveland Center for Membrane and Structural Biology
| | - Brian M Kevany
- Departments of Pharmacology and Cleveland Center for Membrane and Structural Biology
| | | | - Marcin Golczak
- Departments of Pharmacology and Cleveland Center for Membrane and Structural Biology
| | | | | | - Krzysztof Palczewski
- Departments of Pharmacology and Cleveland Center for Membrane and Structural Biology
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19
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Zelinger L, Swaroop A. RNA Biology in Retinal Development and Disease. Trends Genet 2018; 34:341-351. [PMID: 29395379 DOI: 10.1016/j.tig.2018.01.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 12/28/2017] [Accepted: 01/03/2018] [Indexed: 02/06/2023]
Abstract
For decades, RNA has served in a supporting role between the genetic carrier (DNA) and the functional molecules (proteins). It is finally time for RNA to take center stage in all aspects of biology. The retina provides a unique opportunity to dissect the molecular underpinnings of neuronal diversity and disease. Transcriptome profiles of the retina and its resident cell types have unraveled unique features of the RNA landscape. The discovery of distinct RNA molecules and the recognition that RNA processing is a major cause of retinal neurodegeneration have prompted the design of biomarkers and novel therapeutic paradigms. We review here RNA biology as it pertains to the retina, emphasizing new avenues for investigations in development and disease.
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Affiliation(s)
- Lina Zelinger
- Neurobiology-Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Anand Swaroop
- Neurobiology-Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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20
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Orban T, Leinonen H, Getter T, Dong Z, Sun W, Gao S, Veenstra A, Heidari-Torkabadi H, Kern TS, Kiser PD, Palczewski K. A Combination of G Protein-Coupled Receptor Modulators Protects Photoreceptors from Degeneration. J Pharmacol Exp Ther 2017; 364:207-220. [PMID: 29162627 DOI: 10.1124/jpet.117.245167] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2017] [Accepted: 11/20/2017] [Indexed: 02/03/2023] Open
Abstract
Degeneration of retinal photoreceptor cells can arise from environmental and/or genetic causes. Since photoreceptor cells, the retinal pigment epithelium (RPE), neurons, and glial cells of the retina are intimately associated, all cell types eventually are affected by retinal degenerative diseases. Such diseases often originate either in rod and/or cone photoreceptor cells or the RPE. Of these, cone cells located in the central retina are especially important for daily human activity. Here we describe the protection of cone cells by a combination therapy consisting of the G protein-coupled receptor modulators metoprolol, tamsulosin, and bromocriptine. These drugs were tested in Abca4-/-Rdh8-/- mice, a preclinical model for retinal degeneration. The specificity of these drugs was determined with an essentially complete panel of human G protein-coupled receptors. Significantly, the combination of metoprolol, tamsulosin, and bromocriptine had no deleterious effects on electroretinographic responses of wild-type mice. Moreover, putative G protein-coupled receptor targets of these drugs were shown to be expressed in human and mouse eyes by RNA sequencing and quantitative polymerase chain reaction. Liquid chromatography together with mass spectrometry using validated internal standards confirmed that metoprolol, tamsulosin, and bromocriptine individually or together penetrate the eye after either intraperitoneal delivery or oral gavage. Collectively, these findings support human trials with combined therapy composed of lower doses of metoprolol, tamsulosin, and bromocriptine designed to safely impede retinal degeneration associated with certain genetic diseases (e.g., Stargardt disease). The same low-dose combination also could protect the retina against diseases with complex or unknown etiologies such as age-related macular degeneration.
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Affiliation(s)
- Tivadar Orban
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (T.O., H.L., T.G., S.G., A.V., H.H.-T., T.S.K., P.D.K., K.P.); Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio (T.S.K., P.D.K.); and Polgenix Inc., Cleveland, Ohio (Z.D., W.S.)
| | - Henri Leinonen
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (T.O., H.L., T.G., S.G., A.V., H.H.-T., T.S.K., P.D.K., K.P.); Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio (T.S.K., P.D.K.); and Polgenix Inc., Cleveland, Ohio (Z.D., W.S.)
| | - Tamar Getter
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (T.O., H.L., T.G., S.G., A.V., H.H.-T., T.S.K., P.D.K., K.P.); Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio (T.S.K., P.D.K.); and Polgenix Inc., Cleveland, Ohio (Z.D., W.S.)
| | - Zhiqian Dong
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (T.O., H.L., T.G., S.G., A.V., H.H.-T., T.S.K., P.D.K., K.P.); Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio (T.S.K., P.D.K.); and Polgenix Inc., Cleveland, Ohio (Z.D., W.S.)
| | - Wenyu Sun
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (T.O., H.L., T.G., S.G., A.V., H.H.-T., T.S.K., P.D.K., K.P.); Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio (T.S.K., P.D.K.); and Polgenix Inc., Cleveland, Ohio (Z.D., W.S.)
| | - Songqi Gao
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (T.O., H.L., T.G., S.G., A.V., H.H.-T., T.S.K., P.D.K., K.P.); Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio (T.S.K., P.D.K.); and Polgenix Inc., Cleveland, Ohio (Z.D., W.S.)
| | - Alexander Veenstra
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (T.O., H.L., T.G., S.G., A.V., H.H.-T., T.S.K., P.D.K., K.P.); Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio (T.S.K., P.D.K.); and Polgenix Inc., Cleveland, Ohio (Z.D., W.S.)
| | - Hossein Heidari-Torkabadi
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (T.O., H.L., T.G., S.G., A.V., H.H.-T., T.S.K., P.D.K., K.P.); Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio (T.S.K., P.D.K.); and Polgenix Inc., Cleveland, Ohio (Z.D., W.S.)
| | - Timothy S Kern
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (T.O., H.L., T.G., S.G., A.V., H.H.-T., T.S.K., P.D.K., K.P.); Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio (T.S.K., P.D.K.); and Polgenix Inc., Cleveland, Ohio (Z.D., W.S.)
| | - Philip D Kiser
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (T.O., H.L., T.G., S.G., A.V., H.H.-T., T.S.K., P.D.K., K.P.); Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio (T.S.K., P.D.K.); and Polgenix Inc., Cleveland, Ohio (Z.D., W.S.)
| | - Krzysztof Palczewski
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (T.O., H.L., T.G., S.G., A.V., H.H.-T., T.S.K., P.D.K., K.P.); Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio (T.S.K., P.D.K.); and Polgenix Inc., Cleveland, Ohio (Z.D., W.S.)
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21
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Sawant OB, Horton AM, Zucaro OF, Chan R, Bonilha VL, Samuels IS, Rao S. The Circadian Clock Gene Bmal1 Controls Thyroid Hormone-Mediated Spectral Identity and Cone Photoreceptor Function. Cell Rep 2017; 21:692-706. [PMID: 29045837 PMCID: PMC5647869 DOI: 10.1016/j.celrep.2017.09.069] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 08/15/2017] [Accepted: 09/20/2017] [Indexed: 10/18/2022] Open
Abstract
Circadian clocks regulate various aspects of photoreceptor physiology, but their contribution to photoreceptor development and function is unclear. Cone photoreceptors are critical for color vision. Here, we define the molecular function of circadian activity within cone photoreceptors and reveal a role for the clock genes Bmal1 and Per2 in regulating cone spectral identity. ChIP analysis revealed that BMAL1 binds to the promoter region of the thyroid hormone (TH)-activating enzyme type 2 iodothyronine deiodinase (Dio2) and thus regulates the expression of Dio2. TH treatment resulted in a partial rescue of the phenotype caused by the loss of Bmal1, thus revealing a functional relationship between Bmal1 and Dio2 in establishing cone photoreceptor identity. Furthermore, Bmal1 and Dio2 are required to maintain cone photoreceptor functional integrity. Overall, our results suggest a mechanism by which circadian proteins can locally regulate the availability of TH and influence tissue development and function.
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Affiliation(s)
- Onkar B Sawant
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA
| | - Amanda M Horton
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA
| | - Olivia F Zucaro
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA
| | - Ricky Chan
- Institute for Computational Biology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Vera L Bonilha
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA; Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, USA
| | - Ivy S Samuels
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA; Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH 44106, USA
| | - Sujata Rao
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA; Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, USA.
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22
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Negative regulators of angiogenesis: important targets for treatment of exudative AMD. Clin Sci (Lond) 2017; 131:1763-1780. [PMID: 28679845 DOI: 10.1042/cs20170066] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 03/17/2017] [Accepted: 04/03/2017] [Indexed: 12/12/2022]
Abstract
Angiogenesis contributes to the pathogenesis of many diseases including exudative age-related macular degeneration (AMD). It is normally kept in check by a tightly balanced production of pro- and anti-angiogenic factors. The up-regulation of the pro-angiogenic factor, vascular endothelial growth factor (VEGF), is intimately linked to the pathogenesis of exudative AMD, and its antagonism has been effectively targeted for treatment. However, very little is known about potential changes in expression of anti-angiogenic factors and the role they play in choroidal vascular homeostasis and neovascularization associated with AMD. Here, we will discuss the important role of thrombospondins and pigment epithelium-derived factor, two major endogenous inhibitors of angiogenesis, in retinal and choroidal vascular homeostasis and their potential alterations during AMD and choroidal neovascularization (CNV). We will review the cell autonomous function of these proteins in retinal and choroidal vascular cells. We will also discuss the potential targeting of these molecules and use of their mimetic peptides for therapeutic development for exudative AMD.
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23
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Wan P, Su W, Zhuo Y. Precise long non-coding RNA modulation in visual maintenance and impairment. J Med Genet 2017; 54:450-459. [PMID: 28003323 PMCID: PMC5502309 DOI: 10.1136/jmedgenet-2016-104266] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 11/27/2016] [Accepted: 11/28/2016] [Indexed: 12/20/2022]
Abstract
Long non-coding RNAs (lncRNAs) are remarkably powerful, flexible and pervasive cellular regulators. With the help of cheaper RNA-seq, high-throughput screening of lncRNAs has become widely applied and has identified large numbers of specific lncRNAs in various physiological or pathological processes. Vision is known to be a complex and vital perception that comprises 80% of the sensory information we receive. A consensus has been reached that normal visual maintenance and impairment are primarily driven by gene regulation. Recently, it has become understood that lncRNAs are key regulators in most biological processes, including cell proliferation, apoptosis, differentiation, immune responses, oxidative stress and inflammation. Our review is intended to provide insight towards a comprehensive view of the precise modulation of lncRNAs in visual maintenance and impairment. We also highlight the challenges and future directions in conducting lncRNA studies, particularly in patients whose lncRNAs may hold expanded promise for diagnostic, prognostic and therapeutic applications.
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Affiliation(s)
- Peixing Wan
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Wenru Su
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Yehong Zhuo
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, Guangdong, China
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24
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Ikarashi R, Akechi H, Kanda Y, Ahmad A, Takeuchi K, Morioka E, Sugiyama T, Ebisawa T, Ikeda M, Ikeda M. Regulation of molecular clock oscillations and phagocytic activity via muscarinic Ca 2+ signaling in human retinal pigment epithelial cells. Sci Rep 2017; 7:44175. [PMID: 28276525 PMCID: PMC5343479 DOI: 10.1038/srep44175] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 02/06/2017] [Indexed: 12/12/2022] Open
Abstract
Vertebrate eyes are known to contain circadian clocks, however, the intracellular mechanisms regulating the retinal clockwork remain largely unknown. To address this, we generated a cell line (hRPE-YC) from human retinal pigmental epithelium, which stably co-expressed reporters for molecular clock oscillations (Bmal1-luciferase) and intracellular Ca2+ concentrations (YC3.6). The hRPE-YC cells demonstrated circadian rhythms in Bmal1 transcription. Also, these cells represented circadian rhythms in Ca2+-spiking frequencies, which were canceled by dominant-negative Bmal1 transfections. The muscarinic agonist carbachol, but not photic stimulation, phase-shifted Bmal1 transcriptional rhythms with a type-1 phase response curve. This is consistent with significant M3 muscarinic receptor expression and little photo-sensor (Cry2 and Opn4) expression in these cells. Moreover, forskolin phase-shifted Bmal1 transcriptional rhythm with a type-0 phase response curve, in accordance with long-lasting CREB phosphorylation levels after forskolin exposure. Interestingly, the hRPE-YC cells demonstrated apparent circadian rhythms in phagocytic activities, which were abolished by carbachol or dominant-negative Bmal1 transfection. Because phagocytosis in RPE cells determines photoreceptor disc shedding, molecular clock oscillations and cytosolic Ca2+ signaling may be the driving forces for disc-shedding rhythms known in various vertebrates. In conclusion, the present study provides a cellular model to understand molecular and intracellular signaling mechanisms underlying human retinal circadian clocks.
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Affiliation(s)
- Rina Ikarashi
- Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama city, Toyama 930-8555, Japan
| | - Honami Akechi
- Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama city, Toyama 930-8555, Japan
| | - Yuzuki Kanda
- Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama city, Toyama 930-8555, Japan
| | - Alsawaf Ahmad
- Graduate School of Innovative Life Science, University of Toyama, 3190 Gofuku, Toyama city, Toyama 930-8555, Japan
| | - Kouhei Takeuchi
- Graduate School of Innovative Life Science, University of Toyama, 3190 Gofuku, Toyama city, Toyama 930-8555, Japan
| | - Eri Morioka
- Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama city, Toyama 930-8555, Japan
| | - Takashi Sugiyama
- Advanced Core Technology Department, Research and Development Division, Olympus Co. Ltd., 2-3 Kuboyama, Hachioji, Tokyo 192-8512, Japan
| | - Takashi Ebisawa
- Department of Psychiatry, Tokyo Metropolitan Police Hospital, 4-22-1 Nakano, Nakano-ku, Tokyo 164-8541, Japan
| | - Masaaki Ikeda
- Department of Physiology, Saitama Medical University, 38 Morohongo, Moroyama, Iruma-gun, Saitama 350-0495, Japan.,Molecular Clock Project, Project Research Division, Research Center for Genomic Medicine, Saitama Medical University, 1397-1 Yamane, Hidaka city, Saitama, 350-1241, Japan
| | - Masayuki Ikeda
- Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama city, Toyama 930-8555, Japan.,Graduate School of Innovative Life Science, University of Toyama, 3190 Gofuku, Toyama city, Toyama 930-8555, Japan
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Chen Y, Palczewska G, Masuho I, Gao S, Jin H, Dong Z, Gieser L, Brooks MJ, Kiser PD, Kern TS, Martemyanov KA, Swaroop A, Palczewski K. Synergistically acting agonists and antagonists of G protein-coupled receptors prevent photoreceptor cell degeneration. Sci Signal 2016; 9:ra74. [PMID: 27460988 DOI: 10.1126/scisignal.aag0245] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Photoreceptor cell degeneration leads to visual impairment and blindness in several types of retinal disease. However, the discovery of safe and effective therapeutic strategies conferring photoreceptor cell protection remains challenging. Targeting distinct cellular pathways with low doses of different drugs that produce a functionally synergistic effect could provide a strategy for preventing or treating retinal dystrophies. We took a systems pharmacology approach to identify potential combination therapies using a mouse model of light-induced retinal degeneration. We showed that a combination of U.S. Food and Drug Administration-approved drugs that act on different G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptors (GPCRs) exhibited synergistic activity that protected retinas from light-induced degeneration even when each drug was administered at a low dose. In functional assays, the combined effects of these drugs were stimulation of Gi/o signaling by activating the dopamine receptors D2R and D4R, as well as inhibition of Gs and Gq signaling by antagonizing D1R and the α1A-adrenergic receptor ADRA1A, respectively. Moreover, transcriptome analyses demonstrated that such combined GPCR-targeted treatments preserved patterns of retinal gene expression that were more similar to those of the normal retina than did higher-dose monotherapy. Our study thus supports a systems pharmacology approach to identify treatments for retinopathies, an approach that could extend to other complex disorders.
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Affiliation(s)
- Yu Chen
- Yueyang Hospital and Clinical Research Institute of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 200437, China. Department of Pharmacology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
| | | | - Ikuo Masuho
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Songqi Gao
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Hui Jin
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | | | - Linn Gieser
- Neurobiology-Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Matthew J Brooks
- Neurobiology-Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Philip D Kiser
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA. Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH 44106, USA
| | - Timothy S Kern
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA. Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH 44106, USA. Department of Medicine, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Kirill A Martemyanov
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Anand Swaroop
- Neurobiology-Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Krzysztof Palczewski
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA. Polgenix Inc., Cleveland, OH 44106, USA.
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Abstract
Ocular clocks, first identified in the retina, are also found in the retinal pigment epithelium (RPE), cornea, and ciliary body. The retina is a complex tissue of many cell types and considerable effort has gone into determining which cell types exhibit clock properties. Current data suggest that photoreceptors as well as inner retinal neurons exhibit clock properties with photoreceptors dominating in nonmammalian vertebrates and inner retinal neurons dominating in mice. However, these differences may in part reflect the choice of circadian output, and it is likely that clock properties are widely dispersed among many retinal cell types. The phase of the retinal clock can be set directly by light. In nonmammalian vertebrates, direct light sensitivity is commonplace among body clocks, but in mice only the retina and cornea retain direct light-dependent phase regulation. This distinguishes the retina and possibly other ocular clocks from peripheral oscillators whose phase depends on the pace-making properties of the hypothalamic central brain clock, the suprachiasmatic nuclei (SCN). However, in mice, retinal circadian oscillations dampen quickly in isolation due to weak coupling of its individual cell-autonomous oscillators, and there is no evidence that retinal clocks are directly controlled through input from other oscillators. Retinal circadian regulation in both mammals and nonmammalian vertebrates uses melatonin and dopamine as dark- and light-adaptive neuromodulators, respectively, and light can regulate circadian phase indirectly through dopamine signaling. The melatonin/dopamine system appears to have evolved among nonmammalian vertebrates and retained with modification in mammals. Circadian clocks in the eye are critical for optimum visual function where they play a role fine tuning visual sensitivity, and their disruption can affect diseases such as glaucoma or retinal degeneration syndromes.
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Affiliation(s)
- Joseph C Besharse
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI
| | - Douglas G McMahon
- Department of Biological Sciences, Vanderbilt University, Nashville, TN
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27
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Wong BH, Chan JP, Cazenave-Gassiot A, Poh RW, Foo JC, Galam DLA, Ghosh S, Nguyen LN, Barathi VA, Yeo SW, Luu CD, Wenk MR, Silver DL. Mfsd2a Is a Transporter for the Essential ω-3 Fatty Acid Docosahexaenoic Acid (DHA) in Eye and Is Important for Photoreceptor Cell Development. J Biol Chem 2016; 291:10501-14. [PMID: 27008858 DOI: 10.1074/jbc.m116.721340] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Indexed: 12/22/2022] Open
Abstract
Eye photoreceptor membrane discs in outer rod segments are highly enriched in the visual pigment rhodopsin and the ω-3 fatty acid docosahexaenoic acid (DHA). The eye acquires DHA from blood, but transporters for DHA uptake across the blood-retinal barrier or retinal pigment epithelium have not been identified. Mfsd2a is a newly described sodium-dependent lysophosphatidylcholine (LPC) symporter expressed at the blood-brain barrier that transports LPCs containing DHA and other long-chain fatty acids. LPC transport via Mfsd2a has been shown to be necessary for human brain growth. Here we demonstrate that Mfsd2a is highly expressed in retinal pigment epithelium in embryonic eye, before the development of photoreceptors, and is the primary site of Mfsd2a expression in the eye. Eyes from whole body Mfsd2a-deficient (KO) mice, but not endothelium-specific Mfsd2a-deficient mice, were DHA-deficient and had significantly reduced LPC/DHA transport in vivo Fluorescein angiography indicated normal blood-retinal barrier function. Histological and electron microscopic analysis indicated that Mfsd2a KO mice exhibited a specific reduction in outer rod segment length, disorganized outer rod segment discs, and mislocalization of and reduction in rhodopsin early in postnatal development without loss of photoreceptors. Minor photoreceptor cell loss occurred in adult Mfsd2a KO mice, but electroretinography indicated visual function was normal. The developing eyes of Mfsd2a KO mice had activated microglia and up-regulation of lipogenic and cholesterogenic genes, likely adaptations to loss of LPC transport. These findings identify LPC transport via Mfsd2a as an important pathway for DHA uptake in eye and for development of photoreceptor membrane discs.
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Affiliation(s)
- Bernice H Wong
- From the Signature Research Program in Cardiovascular and Metabolic Disorders
| | - Jia Pei Chan
- From the Signature Research Program in Cardiovascular and Metabolic Disorders
| | - Amaury Cazenave-Gassiot
- the Department of Biochemistry, National University of Singapore, 8 Medical Drive, Block MD 7, Singapore 117597, Singapore
| | - Rebecca W Poh
- the Carl Zeiss Pte. Ltd., Microscopy Business Group, Singapore, 50 Kaki Bukit Place, 05-01, Singapore 415926, Singapore
| | - Juat Chin Foo
- the Department of Biochemistry, National University of Singapore, 8 Medical Drive, Block MD 7, Singapore 117597, Singapore
| | - Dwight L A Galam
- From the Signature Research Program in Cardiovascular and Metabolic Disorders
| | - Sujoy Ghosh
- From the Signature Research Program in Cardiovascular and Metabolic Disorders, Centre for Computational Biology, and
| | - Long N Nguyen
- the Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 5 Science Drive 2, Building MD4, Level 1-03A, Singapore 117545, Singapore
| | - Veluchamy A Barathi
- the Singapore Eye Research Institute, 11 Third Hospital Ave., Singapore 168751, Singapore, the Yong Loo Lin School of Medicine, National University of Singapore, 1E Kent Ridge Rd 119228, NUHS Tower Block, Level 11, Singapore 117597, Singapore, and ACP Ophthalmology, Duke-National University of Singapore Graduate Medical School, 8 College Road, Singapore 169857, Singapore
| | - Sia W Yeo
- the Singapore Eye Research Institute, 11 Third Hospital Ave., Singapore 168751, Singapore
| | - Chi D Luu
- the Singapore Eye Research Institute, 11 Third Hospital Ave., Singapore 168751, Singapore, the Centre for Eye Research Australia, Level 1, 32 Gisborne St., East Melbourne, Victoria 3002, Australia
| | - Markus R Wenk
- the Department of Biochemistry, National University of Singapore, 8 Medical Drive, Block MD 7, Singapore 117597, Singapore
| | - David L Silver
- From the Signature Research Program in Cardiovascular and Metabolic Disorders,
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Adijanto J, Du J, Moffat C, Seifert EL, Hurle JB, Philp NJ. The retinal pigment epithelium utilizes fatty acids for ketogenesis. J Biol Chem 2015; 289:20570-82. [PMID: 24898254 DOI: 10.1074/jbc.m114.565457] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Every day, shortly after light onset, photoreceptor cells shed approximately a tenth of their outer segment. The adjacent retinal pigment epithelial (RPE) cells phagocytize and digest shed photoreceptor outer segment, which provides a rich source of fatty acids that could be utilized as an energy substrate. From a microarray analysis, we found that RPE cells express particularly high levels of the mitochondrial HMG-CoA synthase 2 (Hmgcs2) compared with all other tissues (except the liver and colon), leading to the hypothesis that RPE cells, like hepatocytes, can produce β-hydroxybutyrate (β-HB) from fatty acids. Using primary human fetal RPE (hfRPE) cells cultured on Transwell filters with separate apical and basal chambers, we demonstrate that hfRPE cells can metabolize palmitate, a saturated fatty acid that constitutes .15% of all lipids in the photoreceptor outer segment, to produce β-HB. Importantly, we found that hfRPE cells preferentially release β-HB into the apical chamber and that this process is mediated primarily by monocarboxylate transporter isoform 1 (MCT1). Using a GC-MS analysis of (13)C-labeled metabolites, we showed that retinal cells can take up and metabolize (13)C-labeled β-HB into various TCA cycle intermediates and amino acids. Collectively, our data support a novel mechanism of RPE-retina metabolic coupling in which RPE cells metabolize fatty acids to produce β-HB, which is transported to the retina for use as a metabolic substrate.
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Farnoodian M, Kinter JB, Yadranji Aghdam S, Zaitoun I, Sorenson CM, Sheibani N. Expression of pigment epithelium-derived factor and thrombospondin-1 regulate proliferation and migration of retinal pigment epithelial cells. Physiol Rep 2015; 3:3/1/e12266. [PMID: 25602019 PMCID: PMC4387751 DOI: 10.14814/phy2.12266] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Age‐related macular degeneration (AMD) is the leading cause of vision loss among elderly. Although the pathogenesis of AMD is associated with retinal pigmented epithelium (RPE) dysfunction and abnormal neovascularization the detailed mechanisms remain unresolved. RPE is a specialized monolayer of epithelial cells with important functions in ocular homeostasis. Pathological RPE damage contributes to major ocular conditions including retinal degeneration and irreversible loss of vision in AMD. RPE cells also assist in the maintenance of the ocular angiogenic balance by production of positive and negative regulatory factors including vascular endothelial growth factor (VEGF), thrombospondin‐1 (TSP1), and pigment epithelium‐derived factor (PEDF). The altered production of PEDF and TSP1, as endogenous inhibitors of angiogenesis and inflammation, by RPE cells have been linked to pathogenesis of AMD and choroidal and retinal neovascularization. However, lack of simple methods for isolation and culture of mouse RPE cells has resulted in limited knowledge regarding the cell autonomous role of TSP1 and PEDF in RPE cell function. Here, we describe a method for routine isolation and propagation of RPE cells from wild‐type, TSP1, and PEDF‐deficient mice, and have investigated their impact on RPE cell function. We showed that expression of TSP1 and PEDF significantly impacted RPE cell proliferation, migration, adhesion, oxidative state, and phagocytic activity with minimal effect on their basal rate of apoptosis. Together, our results indicated that the expression of PEDF and TSP1 by RPE cells play crucial roles not only in regulation of ocular vascular homeostasis but also have significant impact on their cellular function. Here, we report the isolation of RPE cells from wild‐type and transgenic mice retina. We demonstrate that lack of thrompospondin‐1 or pigment epithelium‐derived factor impacts the proliferation, migration, adhesion, oxidative state, and phagocytic activity of these cells.
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Affiliation(s)
- Mitra Farnoodian
- Department of Ophthalmology and Visual Sciences, Clinical Investigation Graduate Program, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin
| | - James B Kinter
- Department of Ophthalmology and Visual Sciences, Clinical Investigation Graduate Program, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin
| | - Saeed Yadranji Aghdam
- Department of Ophthalmology and Visual Sciences, Clinical Investigation Graduate Program, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin
| | - Ismail Zaitoun
- Department of Ophthalmology and Visual Sciences, Clinical Investigation Graduate Program, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin
| | - Christine M Sorenson
- Department of Pediatrics, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin McPherson Eye Research Institute, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin
| | - Nader Sheibani
- Department of Ophthalmology and Visual Sciences, Clinical Investigation Graduate Program, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin McPherson Eye Research Institute, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin Department of Biomedical Engineering, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin
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30
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Pfeifer CR, Shomorony A, Aronova MA, Zhang G, Cai T, Xu H, Notkins AL, Leapman RD. Quantitative analysis of mouse pancreatic islet architecture by serial block-face SEM. J Struct Biol 2015; 189:44-52. [PMID: 25448885 PMCID: PMC4305430 DOI: 10.1016/j.jsb.2014.10.013] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 10/24/2014] [Accepted: 10/30/2014] [Indexed: 11/24/2022]
Abstract
We have applied serial block-face scanning electron microscopy (SBF-SEM) to measure parameters that describe the architecture of pancreatic islets of Langerhans, microscopic endocrine organs that secrete insulin and glucagon for control of blood glucose. By analyzing entire mouse islets, we show that it is possible to determine (1) the distributions of alpha and beta cells, (2) the organization of blood vessels and pericapillary spaces, and (3) the ultrastructure of the individual secretory cells. Our results show that the average volume of a beta cell is nearly twice that of an alpha cell, and the total mitochondrial volume is about four times larger. In contrast, nuclear volumes in the two cell types are found to be approximately equal. Although the cores of alpha and beta secretory granules have similar diameters, the beta granules have prominent halos resulting in overall diameters that are twice those of alpha granules. Visualization of the blood vessels revealed that every secretory cell in the islet is in contact with the pericapillary space, with an average contact area of 9±5% of the cell surface area. Our data show that consistent results can be obtained by analyzing small numbers of islets. Due to the complicated architecture of pancreatic islets, such precision cannot easily be achieved by using TEM of thin sections.
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Affiliation(s)
- C R Pfeifer
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20854, USA
| | - A Shomorony
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20854, USA
| | - M A Aronova
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20854, USA
| | - G Zhang
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20854, USA
| | - T Cai
- National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20854, USA
| | - H Xu
- National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20854, USA
| | - A L Notkins
- National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20854, USA
| | - R D Leapman
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20854, USA
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31
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Mustafi D, Kikano S, Palczewski K. Serial block face-scanning electron microscopy: a method to study retinal degenerative phenotypes. ACTA ACUST UNITED AC 2014; 4:197-204. [PMID: 25621191 DOI: 10.1002/9780470942390.mo140169] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Retinal degenerative conditions can vary in their clinical features and often present with subtle phenotypic features before the onset of clinically overt disease. To capture these isolated events that precipitate disease, large representative areas of the retina must be imaged at high resolution. Compared to light microscopic methods, traditional electron microscopy can provide images at sufficient resolution to detect subtle pathologic changes in the retina, but are limited to the area being surveyed. The advent of serial block face-scanning electron microscopy (SBF-SEM) provides the resolution needed with the unprecedented advantage of imaging large volumes of retinal tissue. Furthermore, automation of SBF-SEM bypasses errors from manual sectioning and can produce reliable serial sections as thin as 25 nanometers. Moreover, the three-dimensional structures generated can highlight cellular connectivity and interactions in the retina and reveal pathological changes. Using SBF-SEM, we have identified subtle phenotypic features in mouse models of various human retinal dystrophies. This method will allow researchers to identify and monitor the time course of these pathologies. This article provides details on SBF-SEM methodology and its application to mouse models of retinal degeneration.
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Affiliation(s)
- Debarshi Mustafi
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio
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32
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Palczewski K. Chemistry and biology of the initial steps in vision: the Friedenwald lecture. Invest Ophthalmol Vis Sci 2014; 55:6651-72. [PMID: 25338686 DOI: 10.1167/iovs.14-15502] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Visual transduction is the process in the eye whereby absorption of light in the retina is translated into electrical signals that ultimately reach the brain. The first challenge presented by visual transduction is to understand its molecular basis. We know that maintenance of vision is a continuous process requiring the activation and subsequent restoration of a vitamin A-derived chromophore through a series of chemical reactions catalyzed by enzymes in the retina and retinal pigment epithelium (RPE). Diverse biochemical approaches that identified key proteins and reactions were essential to achieve a mechanistic understanding of these visual processes. The three-dimensional arrangements of these enzymes' polypeptide chains provide invaluable insights into their mechanisms of action. A wealth of information has already been obtained by solving high-resolution crystal structures of both rhodopsin and the retinoid isomerase from pigment RPE (RPE65). Rhodopsin, which is activated by photoisomerization of its 11-cis-retinylidene chromophore, is a prototypical member of a large family of membrane-bound proteins called G protein-coupled receptors (GPCRs). RPE65 is a retinoid isomerase critical for regeneration of the chromophore. Electron microscopy (EM) and atomic force microscopy have provided insights into how certain proteins are assembled to form much larger structures such as rod photoreceptor cell outer segment membranes. A second challenge of visual transduction is to use this knowledge to devise therapeutic approaches that can prevent or reverse conditions leading to blindness. Imaging modalities like optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) applied to appropriate animal models as well as human retinal imaging have been employed to characterize blinding diseases, monitor their progression, and evaluate the success of therapeutic agents. Lately two-photon (2-PO) imaging, together with biochemical assays, are revealing functional aspects of vision at a new molecular level. These multidisciplinary approaches combined with suitable animal models and inbred mutant species can be especially helpful in translating provocative cell and tissue culture findings into therapeutic options for further development in animals and eventually in humans. A host of different approaches and techniques is required for substantial progress in understanding fundamental properties of the visual system.
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Affiliation(s)
- Krzysztof Palczewski
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, United States
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33
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Hardeland R. Melatonin, noncoding RNAs, messenger RNA stability and epigenetics--evidence, hints, gaps and perspectives. Int J Mol Sci 2014; 15:18221-52. [PMID: 25310649 PMCID: PMC4227213 DOI: 10.3390/ijms151018221] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 09/21/2014] [Accepted: 09/24/2014] [Indexed: 02/06/2023] Open
Abstract
Melatonin is a highly pleiotropic regulator molecule, which influences numerous functions in almost every organ and, thus, up- or down-regulates many genes, frequently in a circadian manner. Our understanding of the mechanisms controlling gene expression is actually now expanding to a previously unforeseen extent. In addition to classic actions of transcription factors, gene expression is induced, suppressed or modulated by a number of RNAs and proteins, such as miRNAs, lncRNAs, piRNAs, antisense transcripts, deadenylases, DNA methyltransferases, histone methylation complexes, histone demethylases, histone acetyltransferases and histone deacetylases. Direct or indirect evidence for involvement of melatonin in this network of players has originated in different fields, including studies on central and peripheral circadian oscillators, shift work, cancer, inflammation, oxidative stress, aging, energy expenditure/obesity, diabetes type 2, neuropsychiatric disorders, and neurogenesis. Some of the novel modulators have also been shown to participate in the control of melatonin biosynthesis and melatonin receptor expression. Future work will need to augment the body of evidence on direct epigenetic actions of melatonin and to systematically investigate its role within the network of oscillating epigenetic factors. Moreover, it will be necessary to discriminate between effects observed under conditions of well-operating and deregulated circadian clocks, and to explore the possibilities of correcting epigenetic malprogramming by melatonin.
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Affiliation(s)
- Rüdiger Hardeland
- Johann Friedrich Blumenbach Institute of Zoology and Anthropology, University of Göttingen, Berliner Str. 28, Göttingen D-37073, Germany.
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Sundermeier TR, Zhang N, Vinberg F, Mustafi D, Kohno H, Golczak M, Bai X, Maeda A, Kefalov VJ, Palczewski K. DICER1 is essential for survival of postmitotic rod photoreceptor cells in mice. FASEB J 2014; 28:3780-91. [PMID: 24812086 DOI: 10.1096/fj.14-254292] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Photoreceptor cell death is the proximal cause of blindness in many retinal degenerative disorders; hence, understanding the gene regulatory networks that promote photoreceptor survival is at the forefront of efforts to combat blindness. Down-regulation of the microRNA (miRNA)-processing enzyme DICER1 in the retinal pigmented epithelium has been implicated in geographic atrophy, an advanced form of age-related macular degeneration (AMD). However, little is known about the function of DICER1 in mature rod photoreceptor cells, another retinal cell type that is severely affected in AMD. Using a conditional-knockout (cKO) mouse model, we report that loss of DICER1 in mature postmitotic rods leads to robust retinal degeneration accompanied by loss of visual function. At 14 wk of age, cKO mice exhibit a 90% reduction in photoreceptor nuclei and a 97% reduction in visual chromophore compared with those in control littermates. Before degeneration, cKO mice do not exhibit significant defects in either phototransduction or the visual cycle, suggesting that miRNAs play a primary role in rod photoreceptor survival. Using comparative small RNA sequencing analysis, we identified rod photoreceptor miRNAs of the miR-22, miR-26, miR-30, miR-92, miR-124, and let-7 families as potential factors involved in regulating the survival of rods.
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Affiliation(s)
| | | | - Frans Vinberg
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, Missouri, USA
| | | | | | | | | | - Akiko Maeda
- Department of Pharmacology, Department of Ophthalmology and Visual Sciences, Case Western Reserve University, School of Medicine, Cleveland, Ohio, USA; and
| | - Vladimir J Kefalov
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, Missouri, USA
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McMahon DG, Iuvone PM, Tosini G. Circadian organization of the mammalian retina: from gene regulation to physiology and diseases. Prog Retin Eye Res 2013; 39:58-76. [PMID: 24333669 DOI: 10.1016/j.preteyeres.2013.12.001] [Citation(s) in RCA: 127] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 11/27/2013] [Accepted: 12/01/2013] [Indexed: 01/27/2023]
Abstract
The retinal circadian system represents a unique structure. It contains a complete circadian system and thus the retina represents an ideal model to study fundamental questions of how neural circadian systems are organized and what signaling pathways are used to maintain synchrony of the different structures in the system. In addition, several studies have shown that multiple sites within the retina are capable of generating circadian oscillations. The strength of circadian clock gene expression and the emphasis of rhythmic expression are divergent across vertebrate retinas, with photoreceptors as the primary locus of rhythm generation in amphibians, while in mammals clock activity is most robust in the inner nuclear layer. Melatonin and dopamine serve as signaling molecules to entrain circadian rhythms in the retina and also in other ocular structures. Recent studies have also suggested GABA as an important component of the system that regulates retinal circadian rhythms. These transmitter-driven influences on clock molecules apparently reinforce the autonomous transcription-translation cycling of clock genes. The molecular organization of the retinal clock is similar to what has been reported for the SCN although inter-neural communication among retinal neurons that form the circadian network is apparently weaker than those present in the SCN, and it is more sensitive to genetic disruption than the central brain clock. The melatonin-dopamine system is the signaling pathway that allows the retinal circadian clock to reconfigure retinal circuits to enhance light-adapted cone-mediated visual function during the day and dark-adapted rod-mediated visual signaling at night. Additionally, the retinal circadian clock also controls circadian rhythms in disk shedding and phagocytosis, and possibly intraocular pressure. Emerging experimental data also indicate that circadian clock is also implicated in the pathogenesis of eye disease and compelling experimental data indicate that dysfunction of the retinal circadian system negatively impacts the retina and possibly the cornea and the lens.
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Affiliation(s)
- Douglas G McMahon
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
| | - P Michael Iuvone
- Department of Ophthalmology, Emory University School of Medicine, Atlanta, GA, USA; Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, USA
| | - Gianluca Tosini
- Neuroscience Institute and Department of Pharmacology and Toxicology, Morehouse School of Medicine, Atlanta, 30310 GA, USA.
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