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Ahluwalia K, Du Z, Martinez-Camarillo JC, Naik A, Thomas BB, Pollalis D, Lee SY, Dave P, Zhou E, Li Z, Chester C, Humayun MS, Louie SG. Unveiling Drivers of Retinal Degeneration in RCS Rats: Functional, Morphological, and Molecular Insights. Int J Mol Sci 2024; 25:3749. [PMID: 38612560 PMCID: PMC11011632 DOI: 10.3390/ijms25073749] [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: 01/16/2024] [Revised: 03/12/2024] [Accepted: 03/22/2024] [Indexed: 04/14/2024] Open
Abstract
Retinal degenerative diseases, including age-related macular degeneration and retinitis pigmentosa, significantly contribute to adult blindness. The Royal College of Surgeons (RCS) rat is a well-established disease model for studying these dystrophies; however, molecular investigations remain limited. We conducted a comprehensive analysis of retinal degeneration in RCS rats, including an immunodeficient RCS (iRCS) sub-strain, using ocular coherence tomography, electroretinography, histology, and molecular dissection using transcriptomics and immunofluorescence. No significant differences in retinal degeneration progression were observed between the iRCS and immunocompetent RCS rats, suggesting a minimal role of adaptive immune responses in disease. Transcriptomic alterations were primarily in inflammatory signaling pathways, characterized by the strong upregulation of Tnfa, an inflammatory signaling molecule, and Nox1, a contributor to reactive oxygen species (ROS) generation. Additionally, a notable decrease in Alox15 expression was observed, pointing to a possible reduction in anti-inflammatory and pro-resolving lipid mediators. These findings were corroborated by immunostaining, which demonstrated increased photoreceptor lipid peroxidation (4HNE) and photoreceptor citrullination (CitH3) during retinal degeneration. Our work enhances the understanding of molecular changes associated with retinal degeneration in RCS rats and offers potential therapeutic targets within inflammatory and oxidative stress pathways for confirmatory research and development.
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Affiliation(s)
- Kabir Ahluwalia
- Mann School of Pharmacy and Pharmaceutical Sciences, University of Southern California, Los Angeles, CA 90089, USA; (K.A.); (A.N.); (P.D.); (E.Z.); (Z.L.); (C.C.)
| | - Zhaodong Du
- USC Ginsburg Institute of for Biomedical Therapeutics, University of Southern California, Los Angeles, CA 90033, USA; (Z.D.); (J.C.M.-C.); (B.B.T.); (D.P.); (S.Y.L.); (M.S.H.)
| | - Juan Carlos Martinez-Camarillo
- USC Ginsburg Institute of for Biomedical Therapeutics, University of Southern California, Los Angeles, CA 90033, USA; (Z.D.); (J.C.M.-C.); (B.B.T.); (D.P.); (S.Y.L.); (M.S.H.)
- Roski Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Aditya Naik
- Mann School of Pharmacy and Pharmaceutical Sciences, University of Southern California, Los Angeles, CA 90089, USA; (K.A.); (A.N.); (P.D.); (E.Z.); (Z.L.); (C.C.)
| | - Biju B. Thomas
- USC Ginsburg Institute of for Biomedical Therapeutics, University of Southern California, Los Angeles, CA 90033, USA; (Z.D.); (J.C.M.-C.); (B.B.T.); (D.P.); (S.Y.L.); (M.S.H.)
- Roski Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Dimitrios Pollalis
- USC Ginsburg Institute of for Biomedical Therapeutics, University of Southern California, Los Angeles, CA 90033, USA; (Z.D.); (J.C.M.-C.); (B.B.T.); (D.P.); (S.Y.L.); (M.S.H.)
- Roski Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Sun Young Lee
- USC Ginsburg Institute of for Biomedical Therapeutics, University of Southern California, Los Angeles, CA 90033, USA; (Z.D.); (J.C.M.-C.); (B.B.T.); (D.P.); (S.Y.L.); (M.S.H.)
- Roski Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
- Department of Physiology & Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Priyal Dave
- Mann School of Pharmacy and Pharmaceutical Sciences, University of Southern California, Los Angeles, CA 90089, USA; (K.A.); (A.N.); (P.D.); (E.Z.); (Z.L.); (C.C.)
| | - Eugene Zhou
- Mann School of Pharmacy and Pharmaceutical Sciences, University of Southern California, Los Angeles, CA 90089, USA; (K.A.); (A.N.); (P.D.); (E.Z.); (Z.L.); (C.C.)
| | - Zeyang Li
- Mann School of Pharmacy and Pharmaceutical Sciences, University of Southern California, Los Angeles, CA 90089, USA; (K.A.); (A.N.); (P.D.); (E.Z.); (Z.L.); (C.C.)
| | - Catherine Chester
- Mann School of Pharmacy and Pharmaceutical Sciences, University of Southern California, Los Angeles, CA 90089, USA; (K.A.); (A.N.); (P.D.); (E.Z.); (Z.L.); (C.C.)
| | - Mark S. Humayun
- USC Ginsburg Institute of for Biomedical Therapeutics, University of Southern California, Los Angeles, CA 90033, USA; (Z.D.); (J.C.M.-C.); (B.B.T.); (D.P.); (S.Y.L.); (M.S.H.)
- Roski Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Stan G. Louie
- Mann School of Pharmacy and Pharmaceutical Sciences, University of Southern California, Los Angeles, CA 90089, USA; (K.A.); (A.N.); (P.D.); (E.Z.); (Z.L.); (C.C.)
- USC Ginsburg Institute of for Biomedical Therapeutics, University of Southern California, Los Angeles, CA 90033, USA; (Z.D.); (J.C.M.-C.); (B.B.T.); (D.P.); (S.Y.L.); (M.S.H.)
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2
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Lieffrig SA, Gyimesi G, Mao Y, Finnemann SC. Clearance phagocytosis by the retinal pigment epithelial during photoreceptor outer segment renewal: Molecular mechanisms and relation to retinal inflammation. Immunol Rev 2023; 319:81-99. [PMID: 37555340 PMCID: PMC10615845 DOI: 10.1111/imr.13264] [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: 05/15/2023] [Accepted: 07/18/2023] [Indexed: 08/10/2023]
Abstract
Mammalian photoreceptor outer segment renewal is a highly coordinated process that hinges on timed cell signaling between photoreceptor neurons and the adjacent retinal pigment epithelial (RPE). It is a strictly rhythmic, synchronized process that underlies in part circadian regulation. We highlight findings from recently developed methods that quantify distinct phases of outer segment renewal in retinal tissue. At light onset, outer segments expose the conserved "eat-me" signal phosphatidylserine exclusively at their distal, most aged tip. A coordinated two-receptor efferocytosis process follows, in which ligands bridge outer segment phosphatidylserine with the RPE receptors αvβ5 integrin, inducing cytosolic signaling toward Rac1 and focal adhesion kinase/MERTK, and with MERTK directly, additionally inhibiting RhoA/ROCK and thus enabling F-actin dynamics favoring outer segment fragment engulfment. Photoreceptors and RPE persist for life with each RPE cell in the eye servicing dozens of overlying photoreceptors. Thus, RPE cells phagocytose more often and process more material than any other cell type. Mutant mice with impaired outer segment renewal largely retain functional photoreceptors and retinal integrity. However, when anti-inflammatory signaling in the RPE via MERTK or the related TYRO3 is lacking, catastrophic inflammation leads to immune cell infiltration that swiftly destroys the retina causing blindness.
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Affiliation(s)
- Stephanie A. Lieffrig
- Center for Cancer, Genetic Diseases and Gene Regulation, Department of Biological Sciences, Fordham University, Bronx, NY
| | - Gavin Gyimesi
- Center for Cancer, Genetic Diseases and Gene Regulation, Department of Biological Sciences, Fordham University, Bronx, NY
| | | | - Silvia C. Finnemann
- Center for Cancer, Genetic Diseases and Gene Regulation, Department of Biological Sciences, Fordham University, Bronx, NY
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3
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Zihni C, Georgiadis A, Ramsden CM, Sanchez-Heras E, Haas AJ, Nommiste B, Semenyuk O, Bainbridge JWB, Coffey PJ, Smith AJ, Ali RR, Balda MS, Matter K. Spatiotemporal control of actomyosin contractility by MRCKβ signaling drives phagocytosis. J Biophys Biochem Cytol 2022; 221:213476. [PMID: 36121394 PMCID: PMC9485704 DOI: 10.1083/jcb.202012042] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 07/08/2022] [Accepted: 08/19/2022] [Indexed: 12/24/2022] Open
Abstract
Phagocytosis requires actin dynamics, but whether actomyosin contractility plays a role in this morphodynamic process is unclear. Here, we show that in the retinal pigment epithelium (RPE), particle binding to Mer Tyrosine Kinase (MerTK), a widely expressed phagocytic receptor, stimulates phosphorylation of the Cdc42 GEF Dbl3, triggering activation of MRCKβ/myosin-II and its coeffector N-WASP, membrane deformation, and cup formation. Continued MRCKβ/myosin-II activity then drives recruitment of a mechanosensing bridge, enabling cytoskeletal force transmission, cup closure, and particle internalization. In vivo, MRCKβ is essential for RPE phagocytosis and retinal integrity. MerTK-independent activation of MRCKβ signaling by a phosphomimetic Dbl3 mutant rescues phagocytosis in retinitis pigmentosa RPE cells lacking functional MerTK. MRCKβ is also required for efficient particle translocation from the cortex into the cell body in Fc receptor–mediated phagocytosis. Thus, conserved MRCKβ signaling at the cortex controls spatiotemporal regulation of actomyosin contractility to guide distinct phases of phagocytosis in the RPE and represents the principle phagocytic effector pathway downstream of MerTK.
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Affiliation(s)
- Ceniz Zihni
- UCL Institute of Ophthalmology, University College London, London, UK
| | - Anastasios Georgiadis
- UCL Institute of Ophthalmology, University College London, London, UK.,Gene and Cell Therapy Group, UCL Institute of Ophthalmology, University College London, London, UK
| | - Conor M Ramsden
- UCL Institute of Ophthalmology, University College London, London, UK
| | | | - Alexis J Haas
- UCL Institute of Ophthalmology, University College London, London, UK
| | - Britta Nommiste
- UCL Institute of Ophthalmology, University College London, London, UK
| | - Olha Semenyuk
- UCL Institute of Ophthalmology, University College London, London, UK.,Gene and Cell Therapy Group, UCL Institute of Ophthalmology, University College London, London, UK
| | - James W B Bainbridge
- UCL Institute of Ophthalmology, University College London, London, UK.,Gene and Cell Therapy Group, UCL Institute of Ophthalmology, University College London, London, UK.,National Institute for Health and Care Research Biomedical Research Centre at Moorfields Eye Hospital National Health Service Foundation Trust, London, UK
| | - Peter J Coffey
- UCL Institute of Ophthalmology, University College London, London, UK
| | - Alexander J Smith
- Gene and Cell Therapy Group, UCL Institute of Ophthalmology, University College London, London, UK
| | - Robin R Ali
- UCL Institute of Ophthalmology, University College London, London, UK.,Gene and Cell Therapy Group, UCL Institute of Ophthalmology, University College London, London, UK.,National Institute for Health and Care Research Biomedical Research Centre at Moorfields Eye Hospital National Health Service Foundation Trust, London, UK
| | - Maria S Balda
- UCL Institute of Ophthalmology, University College London, London, UK
| | - Karl Matter
- UCL Institute of Ophthalmology, University College London, London, UK
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Acute RhoA/Rho Kinase Inhibition Is Sufficient to Restore Phagocytic Capacity to Retinal Pigment Epithelium Lacking the Engulfment Receptor MerTK. Cells 2021; 10:cells10081927. [PMID: 34440696 PMCID: PMC8394172 DOI: 10.3390/cells10081927] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 07/26/2021] [Accepted: 07/26/2021] [Indexed: 12/27/2022] Open
Abstract
The diurnal phagocytosis of spent photoreceptor outer segment fragments (POS) by retinal pigment epithelial (RPE) cells is essential for visual function. POS internalization by RPE cells requires the assembly of F-actin phagocytic cups beneath surface-tethered POS and Mer tyrosine kinase (MerTK) signaling. The activation of the Rho family GTPase Rac1 is necessary for phagocytic cup formation, and Rac1 is activated normally in MerTK-deficient RPE. We show here that mutant RPE lacking MerTK and wild-type RPE deprived of MerTK ligand both fail to form phagocytic cups regardless of Rac1 activation. However, in wild-type RPE in vivo, a decrease in RhoA activity coincides with the daily phagocytosis burst, while RhoA activity in MerTK-deficient RPE is constant. Elevating RhoA activity blocks phagocytic cup formation and phagocytosis by wild-type RPE. Conversely, inhibiting RhoA effector Rho kinases (ROCKs) rescues both F-actin assembly and POS internalization of primary RPE if MerTK or its ligand are lacking. Most strikingly, acute ROCK inhibition is sufficient to induce the formation and acidification of endogenous POS phagosomes by MerTK-deficient RPE ex vivo. Altogether, RhoA pathway inactivation is a necessary and sufficient downstream effect of MerTK phagocytic signaling such that the acute manipulation of cytosolic ROCK activity suffices to restore phagocytic capacity to MerTK-deficient RPE.
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Sakti DH, Cornish EE, Mustafic N, Zaheer A, Retsas S, Rajagopalan S, Chung CW, Ewans L, McCluskey P, Nash BM, Jamieson RV, Grigg JR. MERTK retinopathy: biomarkers assessing vision loss. Ophthalmic Genet 2021; 42:706-716. [PMID: 34289798 DOI: 10.1080/13816810.2021.1955278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
PURPOSE Mer tyrosine kinase-retinitis pigmentosa (MERTK-RP) causes a primary defect in the retinal pigment epithelium, which subsequently affects rod and cone photoreceptors. The study aims to identify the most appropriate MERTK-RP biomarkers to measure disease progression for deciding the optimum therapeutic trial intervention time. MATERIALS AND METHODS Patients' data from baseline (BL) and last follow-up (LFU) were reviewed. Best corrected visual acuity (BCVA), spectral domain-optical coherence tomography (SD-OCT), ultra-widefield fundus autofluorescence (UWF-FAF) patterns, kinetic perimetry (KP), and electroretinography (ERG) parameters were analyzed. RESULTS Five patients were included with the mean age of 17.7 ± 14.4 years old (6.7-42.3) at BL and mean BCVA follow-up of 8.4 ± 5.1 years. Mean BCVA at BL and LFU were 0.84 ± 0.86 LogMAR and 1.14 ± 0.86 LogMAR, respectively. The BCVA decline rate was 0.05 ± 0.03 LogMAR units/year. Ellipzoid zones (EZ) were measurable in eight eyes with mean BL length of 1293.75 ± 421.07 µm and reduction of 140.95 ± 69.28 µm/year and mean BL CMT of 174.2 ± 37.52 µm with the rate of 11.2 ± 12.77 µm declining/year. Full-field ERG (ffERG) and pattern ERG (pERG) were barely recordable. UWF-FAF showed central macular hyper-autofluorescence (hyperAF). KP (III4e and V4e) was normal in two eyes, restricted nasally in four eyes, superior wedge defect in two eyes and undetectable in two eyes. The four restricted nasally KPs became worse, while the others stayed almost unchanged. CONCLUSIONS This cohort showed early visual loss, moderately rapid EZ reduction and macular hyperAF. EZ, CMT, and BCVA were consistently reduced. Relative rapid decline in these biomarkers reflecting visual function suggests an early and narrow timespan for intervention.
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Affiliation(s)
- Dhimas H Sakti
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia.,Department of Ophthalmology, Faculty of Medicine, Public Health and Nursing; Universitas Gadjah Mada, Yogyakarta, Indonesia
| | - Elisa E Cornish
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia.,Eye Genetics Research Unit, Children's Medical Research Institute, the Children's Hospital at Westmead, Save Sight Institute, University of Sydney, Sydney, NSW, Australia
| | - Nina Mustafic
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia
| | - Afsah Zaheer
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia
| | - Stephanie Retsas
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia
| | - Sulekha Rajagopalan
- Department of Clinical Genetics, Liverpool Hospital, Liverpool BC, NSW, Australia
| | - Clara Wt Chung
- Department of Clinical Genetics, Liverpool Hospital, Liverpool BC, NSW, Australia.,School of Women's & Children's Health, University of NSW, Sydney, NSW, Australia
| | - Lisa Ewans
- Department of Clinical Genetics, Royal Prince Alfred Hospital, Camperdown, NSW, Australia.,Faculty of Medicine and Health Central Clinical School, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - Peter McCluskey
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia
| | - Benjamin M Nash
- Eye Genetics Research Unit, Children's Medical Research Institute, the Children's Hospital at Westmead, Save Sight Institute, University of Sydney, Sydney, NSW, Australia.,Disciplines of Genomic Medicine & Child and Adolescent Health, Sydney Medical School, University of Sydney, Sydney, NSW, Australia.,Sydney Genome Diagnostics, Western Sydney Genetics Program, the Children's Hospital at Westmead, Sydney, NSW, Australia
| | - Robyn V Jamieson
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia.,Eye Genetics Research Unit, Children's Medical Research Institute, the Children's Hospital at Westmead, Save Sight Institute, University of Sydney, Sydney, NSW, Australia.,Disciplines of Genomic Medicine & Child and Adolescent Health, Sydney Medical School, University of Sydney, Sydney, NSW, Australia.,Department of Clinical Genetics, Western Sydney Genetics Program, the Children's Hospital at Westmead, Sydney, NSW, Australia
| | - John R Grigg
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia.,Eye Genetics Research Unit, Children's Medical Research Institute, the Children's Hospital at Westmead, Save Sight Institute, University of Sydney, Sydney, NSW, Australia
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MERTK-Mediated LC3-Associated Phagocytosis (LAP) of Apoptotic Substrates in Blood-Separated Tissues: Retina, Testis, Ovarian Follicles. Cells 2021; 10:cells10061443. [PMID: 34207717 PMCID: PMC8229618 DOI: 10.3390/cells10061443] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Revised: 06/05/2021] [Accepted: 06/07/2021] [Indexed: 01/22/2023] Open
Abstract
Timely and efficient elimination of apoptotic substrates, continuously produced during one’s lifespan, is a vital need for all tissues of the body. This task is achieved by cells endowed with phagocytic activity. In blood-separated tissues such as the retina, the testis and the ovaries, the resident cells of epithelial origin as retinal pigmented epithelial cells (RPE), testis Sertoli cells and ovarian granulosa cells (GC) provide phagocytic cleaning of apoptotic cells and cell membranes. Disruption of this process leads to functional ablation as blindness in the retina and compromised fertility in males and females. To ensure the efficient elimination of apoptotic substrates, RPE, Sertoli cells and GC combine various mechanisms allowing maintenance of tissue homeostasis and avoiding acute inflammation, tissue disorganization and functional ablation. In tight cooperation with other phagocytosis receptors, MERTK—a member of the TAM family of receptor tyrosine kinases (RTK)—plays a pivotal role in apoptotic substrate cleaning from the retina, the testis and the ovaries through unconventional autophagy-assisted phagocytosis process LAP (LC3-associated phagocytosis). In this review, we focus on the interplay between TAM RTKs, autophagy-related proteins, LAP, and Toll-like receptors (TLR), as well as the regulatory mechanisms allowing these components to sustain tissue homeostasis and prevent functional ablation of the retina, the testis and the ovaries.
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Williamson B, Pilla Reddy V. Blood retinal barrier and ocular pharmacokinetics: Considerations for the development of oncology drugs. Biopharm Drug Dispos 2021; 42:128-136. [PMID: 33759216 DOI: 10.1002/bdd.2276] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 03/09/2021] [Accepted: 03/14/2021] [Indexed: 12/12/2022]
Abstract
Tyrosine kinase inhibitors (TKIs) are an example of targeted drug therapy to treat cancer while minimizing damage to healthy tissue. In contrast to traditional oncology drugs, the toxicity profile of targeted therapies is less well understood and can include severe ocular adverse events, which are among the most common toxicity reported by these therapeutics. Inhibition of Mer receptor tyrosine kinase (MERTK) promotes innate tumor immunity by decreasing M2-macrophage polarization and efferocytosis. This mechanism offers the opportunity for targeted immunotherapy to treat cancer; however, the ocular expression of MERTK increases the difficulty for developing a targeted drug due to toxicity concerns. In this article we review the pharmacokinetic (PK) parameters and in vitro absorption, distribution, metabolism, and excretion (ADME) assays available to evaluate ocular disposition and assess the relationship between clinical PK and reported ocular events for TKIs to allow backtranslation to preclinical models. Understanding the ocular disposition in the context of PK and safety remains an evolving area and is likely to be a key aspect of developing safe and efficacious oncology drugs, devoid of ocular toxicity.
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Affiliation(s)
- Beth Williamson
- Drug Metabolism and Pharmacokinetics, Early Oncology, Oncology R&D, AstraZeneca, Cambridge, UK
| | - Venkatesh Pilla Reddy
- Modelling and Simulation, Early Oncology, Oncology R&D, AstraZeneca, Cambridge, UK.,Clinical Pharmacology and Quantitative Pharmacology, Biopharmaceuticals R&D, AstraZeneca, Cambridge, UK
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Biswas P, Borooah S, Matsui H, Voronchikhina M, Zhou J, Zawaydeh Q, Raghavendra PB, Ferreyra H, Riazuddin SA, Wahlin K, Frazer KA, Ayyagari R. Detection and validation of novel mutations in MERTK in a simplex case of retinal degeneration using WGS and hiPSC-RPEs model. Hum Mutat 2020; 42:189-199. [PMID: 33252167 DOI: 10.1002/humu.24146] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 11/03/2020] [Accepted: 11/24/2020] [Indexed: 12/30/2022]
Abstract
Inherited retinal degenerations (IRDs) are a group of genetically heterogeneous conditions with a broad phenotypic heterogeneity. Here, we report detection and validation of the underlying cause of progressive retinal degeneration in a nuclear family of European descent with a single affected individual. Whole genome sequencing of the proband and her unaffected sibling identified a novel intron 8 donor splice site variant (c.1296 + 1G>A) and a novel 731 base pair deletion encompassing exon 9 (Chr2:g.112751488_112752218 del) resulting in c.1297_1451del; p.K433_G484fsTer3 in the Mer tyrosine kinase protooncogene (MERTK), which is highly expressed in the retinal pigment epithelium (RPE). The proband carried both variants in the heterozygous state, which segregated with disease in the pedigree. These MERTK variants are predicted to result in the defective splicing of exon 8 and loss of exon 9 respectively. To evaluate the impact of these novel variants, peripheral blood mononuclear cells of the proband and her parents were reprogrammed to humaninduced pluripotent stem cell (hiPSC) lines, which were subsequently differentiated to hiPSC-RPE. Analysis of the proband's hiPSC-RPE revealed the absence of both MERTK transcript and its respective protein as well as abnormal phagocytosis when compared with the parental hiPSC-RPE. In summary, whole genome sequencing identified novel compound heterozygous variants in MERTK as the underlying cause of progressive retinal degeneration in a simplex case. Further, analysis using an hiPSC-RPE model established the functional impact of novel MERTK mutations and revealed the potential mechanism underlying pathology in the proband.
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Affiliation(s)
- Pooja Biswas
- Shiley Eye Institute, University of California San Diego, La Jolla, California, USA.,REVA University, Bengaluru, Karnataka, India
| | - Shyamanga Borooah
- Shiley Eye Institute, University of California San Diego, La Jolla, California, USA
| | - Hiroko Matsui
- Institute for Genomic Medicine, University of California, San Diego, La Jolla, California, USA
| | - Marina Voronchikhina
- Shiley Eye Institute, University of California San Diego, La Jolla, California, USA
| | - Jason Zhou
- Shiley Eye Institute, University of California San Diego, La Jolla, California, USA
| | - Qais Zawaydeh
- Shiley Eye Institute, University of California San Diego, La Jolla, California, USA
| | - Pongali B Raghavendra
- REVA University, Bengaluru, Karnataka, India.,School of Regenerative Medicine, Manipal University-MAHE, Bangalore, India
| | - Henry Ferreyra
- Shiley Eye Institute, University of California San Diego, La Jolla, California, USA
| | - S Amer Riazuddin
- Wilmer Eye Institute, Johns Hopkins Univesity School of Medicine, Baltimore, Maryland, USA
| | - Karl Wahlin
- Shiley Eye Institute, University of California San Diego, La Jolla, California, USA
| | - Kelly A Frazer
- Institute for Genomic Medicine, University of California, San Diego, La Jolla, California, USA.,Department of Pediatrics, Rady Children's Hospital, Division of Genome Information Sciences, San Diego, California, USA
| | - Radha Ayyagari
- Shiley Eye Institute, University of California San Diego, La Jolla, California, USA
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Ying G, Boldt K, Ueffing M, Gerstner CD, Frederick JM, Baehr W. The small GTPase RAB28 is required for phagocytosis of cone outer segments by the murine retinal pigmented epithelium. J Biol Chem 2018; 293:17546-17558. [PMID: 30228185 PMCID: PMC6231133 DOI: 10.1074/jbc.ra118.005484] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 09/12/2018] [Indexed: 12/19/2022] Open
Abstract
RAB28, a member of the RAS oncogene family, is a ubiquitous, farnesylated, small GTPase of unknown function present in photoreceptors and the retinal pigmented epithelium (RPE). Nonsense mutations of the human RAB28 gene cause recessive cone-rod dystrophy 18 (CRD18), characterized by macular hyperpigmentation, progressive loss of visual acuity, RPE atrophy, and severely attenuated cone and rod electroretinography (ERG) responses. In an attempt to elucidate the disease-causing mechanism, we generated Rab28-/- mice by deleting exon 3 and truncating RAB28 after exon 2. We found that Rab28-/- mice recapitulate features of the human dystrophy (i.e. they exhibited reduced cone and rod ERG responses and progressive retina degeneration). Cones of Rab28-/- mice extended their outer segments (OSs) to the RPE apical processes and formed enlarged, balloon-like distal tips before undergoing degeneration. The visual pigment content of WT and Rab28-/- cones was comparable before the onset of degeneration. Cone phagosomes were almost absent in Rab28-/- mice, whereas rod phagosomes displayed normal levels. A protein-protein interaction screen identified several RAB28-interacting proteins, including the prenyl-binding protein phosphodiesterase 6 δ-subunit (PDE6D) and voltage-gated potassium channel subfamily J member 13 (KCNJ13) present in the RPE apical processes. Of note, the loss of PDE6D prevented delivery of RAB28 to OSs. Taken together, these findings reveal that RAB28 is required for shedding and phagocytosis of cone OS discs.
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Affiliation(s)
- Guoxin Ying
- From the Department of Ophthalmology and Visual Sciences, University of Utah Health Science Center, Salt Lake City, Utah 84132,
| | - Karsten Boldt
- the Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Elfriede-Aulhorn-Strasse 7, D-72076 Tübingen, Germany, and
| | - Marius Ueffing
- the Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Elfriede-Aulhorn-Strasse 7, D-72076 Tübingen, Germany, and
| | - Cecilia D Gerstner
- From the Department of Ophthalmology and Visual Sciences, University of Utah Health Science Center, Salt Lake City, Utah 84132
| | - Jeanne M Frederick
- From the Department of Ophthalmology and Visual Sciences, University of Utah Health Science Center, Salt Lake City, Utah 84132
| | - Wolfgang Baehr
- From the Department of Ophthalmology and Visual Sciences, University of Utah Health Science Center, Salt Lake City, Utah 84132,
- the Departments of Neurobiology and Anatomy and
- Biology, University of Utah, Salt Lake City, Utah 84112
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Ravesh Z, Dianatpour M, Fardaei M, Taghdiri M, Hashemi-Gorji F, Yassaee VR, Miryounesi M. Advanced molecular approaches pave the road to a clear-cut diagnosis of hereditary retinal dystrophies. Mol Vis 2018; 24:679-689. [PMID: 30416334 PMCID: PMC6197863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 10/17/2018] [Indexed: 11/18/2022] Open
Abstract
Purpose The aim of this study was to identify the molecular genetic basis of hereditary retinal dystrophies (HRDs) in five unrelated Iranian families. Methods Whole exome sequencing and Sanger sequencing were performed in all families. Variants were analyzed using various bioinformatics databases and software. Results Based on the selected strategies, we identified potentially causative variants in five families with HRDs: the novel homozygous deletion mutation c.586_589delTTTG (p.F196Sfs*56) in the TTC8 gene of family A, the novel homozygous missense mutation c.2389T>C (p.S797P) in the CRB1 gene in family B, the novel homozygous frameshift mutation c.2707dupA (p.S903Kfs*66) in the LRP5 gene in family C, the novel homozygous splice mutation c.584-1G>T in the MERTK gene in family D, and the novel homozygous missense mutation c.1819G>C (p.G607R) rs61749412 in the ABCA4 gene of family E. Conclusions This study highlights the presence of five novel variants associated with retinal dystrophies in selected Iranian families with hereditary blindness.
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Affiliation(s)
- Zeinab Ravesh
- Genomic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mahdi Dianatpour
- Department of Medical Genetics, School of Medical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Majid Fardaei
- Department of Medical Genetics, School of Medical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Maryam Taghdiri
- Comprehensive Medical Genetic Center, Shiraz University of Medical Sciences, Shiraz, Iran
| | | | - Vahid Reza Yassaee
- Genomic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mohammad Miryounesi
- Genomic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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Analysis of natural product regulation of opioid receptors in the treatment of human disease. Pharmacol Ther 2018; 184:51-80. [DOI: 10.1016/j.pharmthera.2017.10.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Murase H, Tsuruma K, Kuse Y, Shimazawa M, Hara H. Progranulin increases phagocytosis by retinal pigment epithelial cells in culture. J Neurosci Res 2017; 95:2500-2510. [PMID: 28509387 DOI: 10.1002/jnr.24081] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 03/28/2017] [Accepted: 04/18/2017] [Indexed: 11/07/2022]
Abstract
Retinal pigment epithelium (RPE) cells take part in retinal preservation, such as phagocytizing the shed photoreceptor outer segments (POS), every day. The incomplete phagocytic function accelerates RPE degeneration and formation of the toxic by-product lipofuscin. Excessive lipofuscin accumulation is characteristic of various blinding diseases in the human eye. Progranulin is a cysteine-rich protein that has multiple biological activities, and it has a high presence in the retina. Progranulin has been recognized to be involved in macrophage phagocytosis in the brain. The purpose of this study is to determine whether progranulin influences phagocytosis by RPE cells. All experiments were performed on primary human RPE (hRPE) cells in culture. pHrodo was used to label the isolated porcine POS, and quantification of pHrodo fluorescence was used to determine the degree of phagocytosis. Western blotting and immunohistochemistry of key proteins involved in phagocytosis were used to clarify the mechanism of progranulin. Progranulin increased RPE phagocytosis in hydrogen peroxide-treated and nontreated RPE cells. The phosphorylated form of Mer tyrosine kinase, which is important for POS internalization, was significantly increased in the progranulin-exposed cells. This increase was attenuated by SU11274, an inhibitor of hepatic growth factor receptor. Under the oxidative stress condition, exposure to progranulin led to an approximately twofold increase in integrin alpha-v, which is associated with the first step in recognition of POS by RPE cells. These results suggest that progranulin could be an effective stimulator for RPE phagocytosis and could repair RPE function. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Hiromi Murase
- Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu, 501-1196, Japan
| | - Kazuhiro Tsuruma
- Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu, 501-1196, Japan
| | - Yoshiki Kuse
- Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu, 501-1196, Japan
| | - Masamitsu Shimazawa
- Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu, 501-1196, Japan
| | - Hideaki Hara
- Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu, 501-1196, Japan
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Fronk AH, Vargis E. Methods for culturing retinal pigment epithelial cells: a review of current protocols and future recommendations. J Tissue Eng 2016; 7:2041731416650838. [PMID: 27493715 PMCID: PMC4959307 DOI: 10.1177/2041731416650838] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 04/23/2016] [Indexed: 12/17/2022] Open
Abstract
The retinal pigment epithelium is an important part of the vertebrate eye, particularly in studying the causes and possible treatment of age-related macular degeneration. The retinal pigment epithelium is difficult to access in vivo due to its location at the back of the eye, making experimentation with age-related macular degeneration treatments problematic. An alternative to in vivo experimentation is cultivating the retinal pigment epithelium in vitro, a practice that has been going on since the 1970s, providing a wide range of retinal pigment epithelial culture protocols, each producing cells and tissue of varying degrees of similarity to natural retinal pigment epithelium. The purpose of this review is to provide researchers with a ready list of retinal pigment epithelial protocols, their effects on cultured tissue, and their specific possible applications. Protocols using human and animal retinal pigment epithelium cells, derived from tissue or cell lines, are discussed, and recommendations for future researchers included.
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Affiliation(s)
- Aaron H Fronk
- Department of Biological Engineering, Utah State University, Logan, UT, USA
| | - Elizabeth Vargis
- Department of Biological Engineering, Utah State University, Logan, UT, USA
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