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Aplin C, Cerione RA. Probing the mechanism by which the retinal G protein transducin activates its biological effector PDE6. J Biol Chem 2024; 300:105608. [PMID: 38159849 PMCID: PMC10838916 DOI: 10.1016/j.jbc.2023.105608] [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: 10/22/2023] [Revised: 11/23/2023] [Accepted: 12/14/2023] [Indexed: 01/03/2024] Open
Abstract
Phototransduction in retinal rods occurs when the G protein-coupled photoreceptor rhodopsin triggers the activation of phosphodiesterase 6 (PDE6) by GTP-bound alpha subunits of the G protein transducin (GαT). Recently, we presented a cryo-EM structure for a complex between two GTP-bound recombinant GαT subunits and native PDE6, that included a bivalent antibody bound to the C-terminal ends of GαT and the inhibitor vardenafil occupying the active sites on the PDEα and PDEβ subunits. We proposed GαT-activated PDE6 by inducing a striking reorientation of the PDEγ subunits away from the catalytic sites. However, questions remained including whether in the absence of the antibody GαT binds to PDE6 in a similar manner as observed when the antibody is present, does GαT activate PDE6 by enabling the substrate cGMP to access the catalytic sites, and how does the lipid membrane enhance PDE6 activation? Here, we demonstrate that 2:1 GαT-PDE6 complexes form with either recombinant or retinal GαT in the absence of the GαT antibody. We show that GαT binding is not necessary for cGMP nor competitive inhibitors to access the active sites; instead, occupancy of the substrate binding sites enables GαT to bind and reposition the PDE6γ subunits to promote catalytic activity. Moreover, we demonstrate by reconstituting GαT-stimulated PDE6 activity in lipid bilayer nanodiscs that the membrane-induced enhancement results from an increase in the apparent binding affinity of GαT for PDE6. These findings provide new insights into how the retinal G protein stimulates rapid catalytic turnover by PDE6 required for dim light vision.
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Affiliation(s)
- Cody Aplin
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA
| | - Richard A Cerione
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA; Department of Molecular Medicine, Cornell University, Ithaca, New York, USA.
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2
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Gulati S, Palczewski K. Structural view of G protein-coupled receptor signaling in the retinal rod outer segment. Trends Biochem Sci 2023; 48:172-186. [PMID: 36163145 PMCID: PMC9868064 DOI: 10.1016/j.tibs.2022.08.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 08/26/2022] [Accepted: 08/29/2022] [Indexed: 01/26/2023]
Abstract
Visual phototransduction is the most extensively studied G protein-coupled receptor (GPCR) signaling pathway because of its quantifiable stimulus, non-redundancy of genes, and immense importance in vision. We summarize recent discoveries that have advanced our understanding of rod outer segment (ROS) morphology and the pathological basis of retinal diseases. We have combined recently published cryo-electron tomography (cryo-ET) data on the ROS with structural knowledge on individual proteins to define the precise spatial limitations under which phototransduction occurs. Although hypothetical, the reconstruction of the rod phototransduction system highlights the potential roles of phosphodiesterase 6 (PDE6) and guanylate cyclases (GCs) in maintaining the spacing between ROS discs, suggesting a plausible mechanism by which intrinsic optical signals are generated in the retina.
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Affiliation(s)
| | - Krzysztof Palczewski
- Gavin Herbert Eye Institute and the Department of Ophthalmology, Center for Translational Vision Research, Department of Physiology and Biophysics, Department of Chemistry, Molecular Biology, and Biochemistry, University of California Irvine, 850 Health Sciences Road, Irvine, CA 92697-4375, USA.
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3
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Berkowitz BA, Podolsky RH, Childers KL, Roberts R, Katz R, Waseem R, Robbings BM, Hass DT, Hurley JB, Sweet IR, Goodman C, Qian H, Alvisio B, Heaps S. Transducin-Deficient Rod Photoreceptors Evaluated With Optical Coherence Tomography and Oxygen Consumption Rate Energy Biomarkers. Invest Ophthalmol Vis Sci 2022; 63:22. [PMID: 36576748 PMCID: PMC9804021 DOI: 10.1167/iovs.63.13.22] [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] [Indexed: 12/29/2022] Open
Abstract
Purpose To test the hypothesis that rod energy biomarkers in light and dark are similar in mice without functional rod transducin (Gnat1rd17). Methods Gnat1rd17 and wildtype (WT) mice were studied in canonically low energy demand (light) and high energy demand (dark) conditions. We measured rod inner segment ellipsoid zone (ISez) profile shape, external limiting membrane-retinal pigment epithelium (ELM-RPE) thickness, and magnitude of a hyporeflective band (HB) intensity dip located between photoreceptor tips and apical RPE; antioxidants were given in a subset of mice. Oxygen consumption rate (OCR) and visual performance indexes were also measured. Results The lower energy demand expected in light-adapted wildtype retinas was associated with an elongated ISez, thicker ELM-RPE, and higher HB magnitude, and lower OCR compared to high energy demand conditions in the dark. Gnat1rd17 mice showed a wildtype-like ISez profile shape at 20 minutes of light that became rounder at 60 minutes; at both times, ELM-RPE was smaller than wildtype values, and the HB magnitude was unmeasurable. OCR was higher than in the dark. Light-adapted Gnat1rd17 mice biomarkers were unaffected by anti-oxidants. Gnat1rd17 mice showed modest outer nuclear layer thinning and no reduction in visual performance indexes. Conclusions Light-stimulated changes in all biomarkers in WT mice are consistent with the established light-induced decrease in net energy demand. In contrast, biomarker changes in Gnat1rd17 mice raise the possibility that light increases net energy demand in the absence of rod phototransduction.
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Affiliation(s)
- Bruce A Berkowitz
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Robert H Podolsky
- Biostatistics and Study Methodology, Children's National Hospital, Silver Spring, Maryland, United States
| | - Karen Lins Childers
- Beaumont Research Institute, Beaumont Health, Royal Oak, Michigan, United States
| | - Robin Roberts
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Ryan Katz
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Rida Waseem
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Brian M Robbings
- Department of Biochemistry, Department of Ophthalmology, University of Washington, Seattle, Washington, United States.,Department of Medicine, UW Medicine Diabetes Institute, University of Washington, Seattle, Washington, United States
| | - Daniel T Hass
- Department of Biochemistry, Department of Ophthalmology, University of Washington, Seattle, Washington, United States
| | - James B Hurley
- Department of Biochemistry, Department of Ophthalmology, University of Washington, Seattle, Washington, United States
| | - Ian R Sweet
- Department of Medicine, UW Medicine Diabetes Institute, University of Washington, Seattle, Washington, United States
| | - Cole Goodman
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Haohua Qian
- Visual Function Core, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Bruno Alvisio
- OSIO Bioinformatics Core, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Sam Heaps
- OSIO Bioinformatics Core, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
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4
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Cao Y, Fajardo D, Guerrero-Given D, Samuel MA, Ohtsuka T, Boye SE, Kamasawa N, Martemyanov KA. Post-developmental plasticity of the primary rod pathway allows restoration of visually guided behaviors. Curr Biol 2022; 32:4783-4796.e3. [PMID: 36179691 PMCID: PMC9691582 DOI: 10.1016/j.cub.2022.09.016] [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: 06/27/2022] [Revised: 08/17/2022] [Accepted: 09/08/2022] [Indexed: 01/24/2023]
Abstract
The formation of neural circuits occurs in a programmed fashion, but proper activity in the circuit is essential for refining the organization necessary for driving complex behavioral tasks. In the retina, sensory deprivation during the critical period of development is well known to perturb the organization of the visual circuit making the animals unable to use vision for behavior. However, the extent of plasticity, molecular factors involved, and malleability of individual channels in the circuit to manipulations outside of the critical period are not well understood. In this study, we selectively disconnected and reconnected rod photoreceptors in mature animals after completion of the retina circuit development. We found that introducing synaptic rod photoreceptor input post-developmentally allowed their integration into the circuit both anatomically and functionally. Remarkably, adult mice with newly integrated rod photoreceptors gained high-sensitivity vision, even when it was absent from birth. These observations reveal plasticity of the retina circuit organization after closure of the critical period and encourage the development of vision restoration strategies for congenital blinding disorders.
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Affiliation(s)
- Yan Cao
- Department of Neuroscience, UF Scripps Biomedical Research, Jupiter, FL 33458, USA
| | - Diego Fajardo
- Division of Cellular and Molecular Therapy, Department of Pediatrics, University of Florida, Gainesville, FL, USA
| | - Debbie Guerrero-Given
- The Imaging Center, Electron Microscopy Core Facility, Max Planck Florida Institute, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Melanie A Samuel
- Department of Neuroscience, Huffington Center on Aging, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Toshihisa Ohtsuka
- Department of Biochemistry, Graduate School of Medicine, Faculty of Medicine, University of Yamanashi, Yamanashi 409-3898, Japan
| | - Shannon E Boye
- Division of Cellular and Molecular Therapy, Department of Pediatrics, University of Florida, Gainesville, FL, USA
| | - Naomi Kamasawa
- The Imaging Center, Electron Microscopy Core Facility, Max Planck Florida Institute, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Kirill A Martemyanov
- Department of Neuroscience, UF Scripps Biomedical Research, Jupiter, FL 33458, USA.
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5
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Yadav RP, Boyd K, Artemyev NO. Molecular insights into the maturation of phosphodiesterase 6 by the specialized chaperone complex of HSP90 with AIPL1. J Biol Chem 2022; 298:101620. [PMID: 35065964 PMCID: PMC8857470 DOI: 10.1016/j.jbc.2022.101620] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 01/10/2022] [Accepted: 01/11/2022] [Indexed: 12/18/2022] Open
Abstract
Phosphodiesterase 6 (PDE6) is a key effector enzyme in vertebrate phototransduction, and its maturation and function are known to critically depend on a specialized chaperone, aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1). Defects in PDE6 and AIPL1 underlie several severe retinal diseases, including retinitis pigmentosa and Leber congenital amaurosis. Here, we characterize the complex of AIPL1 with HSP90 and demonstrate its essential role in promoting the functional conformation of nascent PDE6. Our analysis suggests that AIPL1 preferentially binds to HSP90 in the closed state with a stoichiometry of 1:2, with the tetratricopeptide repeat domain and the tetratricopeptide repeat helix 7 extension of AIPL1 being the main contributors to the AIPL1/HSP90 interface. We demonstrate that mutations of these determinants markedly diminished both the affinity of AIPL1 for HSP90 and the ability of AIPL1 to cochaperone the maturation of PDE6 in a heterologous expression system. In addition, the FK506-binding protein (FKBP) domain of AIPL1 encloses a unique prenyl-binding site that anchors AIPL1 to posttranslational lipid modifications of PDE6. A mouse model with rod PDE6 lacking farnesylation of its PDE6A subunit revealed normal expression, trafficking, and signaling of the enzyme. Furthermore, AIPL1 was unexpectedly capable of inducing the maturation of unprenylated cone PDE6C, whereas mutant AIPL1 deficient in prenyl binding competently cochaperoned prenylated PDE6C. Thus, we conclude neither sequestration of the prenyl modifications is required for PDE6 maturation to proceed, nor is the FKBP-lipid interaction involved in the conformational switch of the enzyme into the functional state.
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Affiliation(s)
- Ravi P Yadav
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
| | - Kimberly Boyd
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
| | - Nikolai O Artemyev
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, Iowa, USA; Department of Ophthalmology and Visual Sciences, The University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.
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6
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Acquired night blindness due to rod dysfunction after long-term hemodialysis. Jpn J Ophthalmol 2021; 66:1-7. [PMID: 34741231 DOI: 10.1007/s10384-021-00883-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 09/17/2021] [Indexed: 10/19/2022]
Abstract
PURPOSE To report the clinical findings in 6 patients who developed night blindness after long-term hemodialysis. STUDY DESIGN Retrospective case series. PATIENTS AND METHODS The medical charts of the 6 patients were examined. The fundus photographs, spectral-domain optical coherence tomographic (SD-OCT) images, full-field ERGs, and blood chemistry panels were analyzed. RESULTS The mean age of the 6 patients (4 men) at the time of diagnosis was 69.1 ± 5.9 years. The mean duration of the hemodialysis was 21.8 ± 13.4 years (7-41 years). The visual acuity of the patients was preserved at 20/30 or better except in 1 eye. Ophthalmoscopy showed white flecks that were scattered over the midperipheral retina in all the eyes. SD-OCT showed mild macular degeneration in 5 eyes. The scotopic ERGs elicited by dim flashes were absent, and those elicited by bright flashes had negative waveforms. The photopic ERGs were relatively well preserved. These data indicated a rod-specific dysfunction that may account for the night blindness. The plasma concentration of vitamin A was within the normal range in 4 of the patients and slightly lower than the normal limit in 1 of the patients. Administration of vitamin A was performed for 1 patient, and the symptom of night blindness and scotopic ERGs were improved 3 months later. DISCUSSION Long-term hemodialysis can be associated with the night blindness that may be caused by vitamin A deficiency, even though the plasma concentration of vitamin A in these patients was within the normal range.
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7
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Jiang X, Mahroo OA. Negative electroretinograms: genetic and acquired causes, diagnostic approaches and physiological insights. Eye (Lond) 2021; 35:2419-2437. [PMID: 34127841 PMCID: PMC8377097 DOI: 10.1038/s41433-021-01604-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 05/05/2021] [Accepted: 05/10/2021] [Indexed: 02/07/2023] Open
Abstract
The dark-adapted human electroretinogram (ERG) response to a standard bright flash includes a negative-going a-wave followed by a positive-going b-wave that crosses the baseline. An electronegative waveform (or negative ERG) results when the b-wave is selectively reduced such that the ERG fails to cross the baseline following the a-wave. In the context of a normally sized a-wave, it indicates a site of retinal dysfunction occurring after phototransduction (commonly at the photoreceptor to bipolar cell synapse). This is an important finding. In genetic disease, the pattern of ERG abnormality can point to variants in a small group of genes (frequently those associated with congenital stationary night blindness and X-linked retinoschisis, but negative ERGs can also be seen in other conditions including syndromic disease). In acquired disease, there are numerous causes, but specific features may point to melanoma-associated retinopathy (MAR). In some cases, the visual symptoms precede the diagnosis of the melanoma and so the ERG findings can initiate investigations facilitating early detection and treatment. Negative ERGs can occur in other paraneoplastic conditions, and in a range of other diseases. This review will outline the physiological basis for the negative ERG, report prevalences in the literature from different cohorts, discuss the range of causes, displaying examples of a number of ERG phenotypes, highlight features of a clinical approach to patients, and briefly discuss further insights relating to current flows shaping the a-wave trough and from single-cell transcriptome analysis.
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Affiliation(s)
- Xiaofan Jiang
- grid.83440.3b0000000121901201Institute of Ophthalmology, University College London, London, UK ,grid.439257.e0000 0000 8726 5837Retinal and Genetics Services, Moorfields Eye Hospital, London, UK ,grid.425213.3Section of Ophthalmology and Department of Twin Research and Genetic Epidemiology, King’s College London, St Thomas’ Hospital Campus, London, UK
| | - Omar A. Mahroo
- grid.83440.3b0000000121901201Institute of Ophthalmology, University College London, London, UK ,grid.439257.e0000 0000 8726 5837Retinal and Genetics Services, Moorfields Eye Hospital, London, UK ,grid.425213.3Section of Ophthalmology and Department of Twin Research and Genetic Epidemiology, King’s College London, St Thomas’ Hospital Campus, London, UK ,grid.5335.00000000121885934Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
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8
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Kim HM, Joo K, Han J, Woo SJ. Clinical and Genetic Characteristics of Korean Congenital Stationary Night Blindness Patients. Genes (Basel) 2021; 12:genes12060789. [PMID: 34064005 PMCID: PMC8224030 DOI: 10.3390/genes12060789] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 05/11/2021] [Accepted: 05/18/2021] [Indexed: 01/27/2023] Open
Abstract
In this study, we investigated the clinical and genetic characteristics of 19 Korean patients with congenital stationary night blindness (CSNB) at two tertiary hospitals. Clinical evaluations, including fundus photography, spectral-domain optical coherence tomography, and electroretinography, were performed. Genetic analyses were conducted using targeted panel sequencing or whole exome sequencing. The median age was 5 (3–21) years at the initial examination, 2 (1–8) years at symptom onset, and 11 (5–28) years during the final visit. Genetic mutations were identified as CNGB1 and GNAT1 for the Riggs type (n = 2), TRPM1 and NYX for the complete type (n = 3), and CACNA1F (n = 14) for the incomplete type. Ten novel variants were identified, and best-corrected visual acuity (BCVA) and spherical equivalents (SE) were related to each type of CSNB. The Riggs and TRPM1 complete types presented mild myopia and good BCVA without strabismus and nystagmus, whereas the NYX complete and incomplete types showed mixed SE and poor BCVA with strabismus and nystagmus. This is the first case series of Korean patients with CSNB, and further studies with a larger number of subjects should be conducted to correlate the clinical and genetic aspects of CSNB.
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Affiliation(s)
- Hyeong-Min Kim
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam 13620, Korea; (H.-M.K.); (K.J.)
| | - Kwangsic Joo
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam 13620, Korea; (H.-M.K.); (K.J.)
| | - Jinu Han
- Institute of Vision Research, Department of Ophthalmology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, Korea
- Correspondence: (J.H.); (S.-J.W.); Tel.: +82-2-2019-3445 (J.H.); +82-31-787-7377 (S.-J.W.); Fax: +82-2-3463-1049 (J.H.); +82-31-787-4057 (S.-J.W.)
| | - Se-Joon Woo
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam 13620, Korea; (H.-M.K.); (K.J.)
- Correspondence: (J.H.); (S.-J.W.); Tel.: +82-2-2019-3445 (J.H.); +82-31-787-7377 (S.-J.W.); Fax: +82-2-3463-1049 (J.H.); +82-31-787-4057 (S.-J.W.)
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9
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The PDE-Opathies: Diverse Phenotypes Produced by a Functionally Related Multigene Family. Trends Genet 2021; 37:669-681. [PMID: 33832760 DOI: 10.1016/j.tig.2021.03.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 03/07/2021] [Accepted: 03/09/2021] [Indexed: 12/30/2022]
Abstract
The phosphodiesterase (PDE)-opathies, an expanding set of disorders caused by germline mutations in cyclic nucleotide PDEs, present an intriguing paradox. The enzymes encoded by the PDE family all hydrolyze cAMP and/or cGMP, but mutations in different family members produce very divergent phenotypes. Three interacting factors have been shown recently to contribute to this phenotypic diversity: (i) the 21 genes encode over 80 different isoforms, using alternative mRNA splicing and related mechanisms; (ii) the various isoforms have different regulatory mechanisms, mediated by their unique amino-terminal regulatory domains; (iii) the isoforms differ widely in their pattern of tissue expression. These mechanisms explain why many PDE-opathies are gain-of-function mutations and how they exemplify uniqueness and redundancy within a multigene family.
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10
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Clinical Phenotype of PDE6B-Associated Retinitis Pigmentosa. Int J Mol Sci 2021; 22:ijms22052374. [PMID: 33673512 PMCID: PMC7956818 DOI: 10.3390/ijms22052374] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 02/17/2021] [Accepted: 02/21/2021] [Indexed: 11/25/2022] Open
Abstract
In this retrospective, longitudinal, observational cohort study, we investigated the phenotypic and genotypic features of retinitis pigmentosa associated with variants in the PDE6B gene. Patients underwent clinical examination and genetic testing at a single tertiary referral center, including best-corrected visual acuity (BCVA), kinetic visual field (VF), full-field electroretinography, full-field stimulus threshold, spectral domain optical coherence tomography, and fundus autofluorescence imaging. The genetic testing comprised candidate gene sequencing, inherited retinal disease gene panel sequencing, whole-genome sequencing, and testing for familial variants by Sanger sequencing. Twenty-four patients with mutations in PDE6B from 21 families were included in the study (mean age at the first visit: 32.1 ± 13.5 years). The majority of variants were putative splicing defects (8/23) and missense (7/23) mutations. Seventy-nine percent (38/48) of eyes had no visual acuity impairment at the first visit. Visual acuity impairment was mild in 4% (2/48), moderate in 13% (6/48), and severe in 4% (2/48). BCVA was symmetrical in the right and left eyes. The kinetic VF measurements were highly symmetrical in the right and left eyes, as was the horizontal ellipsoid zone (EZ) width. Regarding the genetic findings, 43% of the PDE6B variants found in our patients were novel. Thus, this study contributed substantially to the PDE6B mutation spectrum. The visual acuity impairment was mild in 83% of eyes, providing a window of opportunity for investigational new drugs. The EZ width was reduced in all patients and was highly symmetric between the eyes, making it a promising outcome measure. We expect these findings to have implications on the design of future PDE6B-related retinitis pigmentosa (RP) clinical trials.
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11
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Winkler PA, Ramsey HD, Petersen-Jones SM. A novel mutation in PDE6B in Spanish Water Dogs with early-onset progressive retinal atrophy. Vet Ophthalmol 2020; 23:792-796. [PMID: 32639685 DOI: 10.1111/vop.12792] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Revised: 05/13/2020] [Accepted: 05/15/2020] [Indexed: 01/23/2023]
Abstract
OBJECTIVE To identify the underlying mutation in a recently identified early-onset progressive retinal atrophy (PRA) in the Spanish Water Dog (SWD) breed. ANIMAL STUDIED Eighteen SWDs were used in this study. Six SWDs diagnosed with PRA and 12 phenotypically normal SWDs. PROCEDURES An exclusion analysis using an established microsatellite panel to screen PRA candidate genes was combined with whole genome sequencing of two affected SWD siblings and two phenotypically normal SWDs (a sibling and the dam). RESULTS A 6-bp deletion was identified in exon 19 of PDE6B removing two highly conserved amino acids from the enzymatic domain of the PDE6B protein (c.2218-2223del; p.Phe740_Phe741del). This segregated with the disease status in the small study pedigree. CONCLUSIONS Identification of this novel PDE6B mutation adds to the already described PDE6B mutations responsible for PRA in the Irish Setter, Sloughi, and American Staffordshire Terrier dog breeds. A DNA-based test was designed to allow breeders to genotype their animals and make informed breeding decisions in the effort to eradicate PRA from the SWD breed.
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Affiliation(s)
- Paige A Winkler
- Department of Small Animal Clinical Sciences, Veterinary Medical Center, Michigan State University, East Lansing, MI, USA
| | - Harrison D Ramsey
- Department of Small Animal Clinical Sciences, Veterinary Medical Center, Michigan State University, East Lansing, MI, USA.,Biology Program, Kalamazoo College, Kalamazoo, MI, USA
| | - Simon M Petersen-Jones
- Department of Small Animal Clinical Sciences, Veterinary Medical Center, Michigan State University, East Lansing, MI, USA
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12
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Kubota D, Oishi N, Gocho K, Kikuchi S, Yamaki K, Igarashi T, Takahashi H, Ishida N, Iwata T, Mizota A, Kameya S. Novel homozygous in-frame deletion of GNAT1 gene causes golden appearance of fundus and reduced scotopic ERGs similar to that in Oguchi disease in Japanese family. Ophthalmic Genet 2019; 40:480-487. [PMID: 31696758 DOI: 10.1080/13816810.2019.1686159] [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: 10/25/2022]
Abstract
Background: The GNAT1 gene encodes the alpha-subunit of transducin in rod photoreceptors and is an important part of the phototransduction cascade. Defects in GNAT1 are very rare but have been identified in autosomal dominant and recessive congenital stationary night blindness (CSNB) and autosomal recessive rod-cone dystrophy. The purpose of this study was to determine the phenotype-genotype relationship in a non-consanguineous Japanese family with a GNAT1 mutation.Methods: Detailed ophthalmic examinations were performed on the patients and their family members. Whole exome sequencing (WES) was applied to the DNA obtained from the family members. Sanger sequencing and co-segregation analyses were performed to identify the most likely pathogenic variant.Results: Two female (13- and 11-years) and one male (15-years) patients from a family had night blindness from their childhood. The fundus had a mild golden appearance regardless of the state of light- or dark-adaptation. Electroretinographic (ERG) analyses showed that the scotopic a-wave was extinguished, and the mixed rod-cone responses were severely reduced with an electronegative form in patients. The shapes of the dark-adapted ERGs were similar to those recorded from patients with Oguchi disease. We identified a homozygous in-frame deletion c.818_820delAGA, p.Lys273del in the GNAT1 gene. Variants were verified by Sanger sequencing and co-segregated with the disease in five members of the family.Conclusions: Our findings indicate that a recessive GNAT1 mutation found in this family could be the cause of the golden appearance of the fundus and negative ERGs with reduced a-waves, and nearly absent b-waves in the mixed rod-cone ERGs.
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Affiliation(s)
- Daiki Kubota
- Department of Ophthalmology, Nippon Medical School Chiba Hokusoh Hospital, Inzai, Chiba, Japan
| | - Noriko Oishi
- Department of Ophthalmology, Nippon Medical School Chiba Hokusoh Hospital, Inzai, Chiba, Japan
| | - Kiyoko Gocho
- Department of Ophthalmology, Nippon Medical School Chiba Hokusoh Hospital, Inzai, Chiba, Japan
| | - Sachiko Kikuchi
- Department of Ophthalmology, Nippon Medical School Chiba Hokusoh Hospital, Inzai, Chiba, Japan
| | - Kunihiko Yamaki
- Department of Ophthalmology, Nippon Medical School Chiba Hokusoh Hospital, Inzai, Chiba, Japan
| | - Tsutomu Igarashi
- Department of Ophthalmology, Nippon Medical School, Tokyo, Japan
| | | | | | - Takeshi Iwata
- Division of Molecular and Cellular Biology, National Institute of Sensory Organs, Tokyo, Japan
| | - Atsushi Mizota
- Department of Ophthalmology, Teikyo University School of Medicine, Tokyo, Japan
| | - Shuhei Kameya
- Department of Ophthalmology, Nippon Medical School Chiba Hokusoh Hospital, Inzai, Chiba, Japan
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13
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Liu HY, Huang J, Xiao H, Zhang MJ, Shi FF, Jiang YH, Du H, He Q, Wang ZY. Pseudodominant inheritance of autosomal recessive congenital stationary night blindness in one family with three co-segregating deleterious GRM6 variants identified by next-generation sequencing. Mol Genet Genomic Med 2019; 7:e952. [PMID: 31677249 PMCID: PMC6900388 DOI: 10.1002/mgg3.952] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 08/12/2019] [Accepted: 08/13/2019] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND The congenital stationary night blindness (CSNB) affects the patients' dim light vision or dark adaption by impairing the normal function of retina. It is a clinically and genetically heterogeneous disorder and can be inherited in an X-linked, autosomal dominant or autosomal recessive pattern. Several genetic alterations to the genes involved in visual signal transduction of photoreceptors and/or bipolar cells underlie its pathogenesis. METHODS In this study, we used Sanger sequencing and next-generation sequencing (NGS)-based gene panel screening to investigate a family of three patients with CSNB inherited in an apparent autosomal dominant pattern. We expected to find out the disease-causing gene defects carried by this family. RESULTS We found that the patients in this family did not carry the RHO, GNAT1, or PDE6B mutation, but carried compound heterozygotes mutations of GRM6. Three deleterious GRM6 variants, p.Arg621Ter, p.Gly51Val, and p.Gly464Arg, were found to be co-segregating with the disease, causing a pseudodominant inheritance of GRM6-related autosomal recessive complete CSNB. CONCLUSION This study presents a rare case of autosomal recessive CSNB (arCSNB) pseudodominant inheritance, which potentially leads us to expand our gene candidate list in future genetic testing for apparent dominant pedigrees. The discovery of the two novel likely pathogenic variants p.Gly51Val and p.Gly464Arg could broaden our knowledge about the genetics of CSNB and provide insights into the structure and function of the GRM6 protein.
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Affiliation(s)
- Hong-Yan Liu
- Institute of Medical Genetics, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, School of Clinical Medicine, Henan University, Zhengzhou, China
| | - Jia Huang
- Institute of Medical Genetics, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, School of Clinical Medicine, Henan University, Zhengzhou, China
| | - Hai Xiao
- Institute of Medical Genetics, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, School of Clinical Medicine, Henan University, Zhengzhou, China
| | - Ming-Jie Zhang
- Institute of Medical Genetics, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, School of Clinical Medicine, Henan University, Zhengzhou, China
| | - Fei-Fei Shi
- Institute of Medical Genetics, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, School of Clinical Medicine, Henan University, Zhengzhou, China
| | - Ying-Hai Jiang
- Institute of Medical Genetics, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, School of Clinical Medicine, Henan University, Zhengzhou, China
| | - Han Du
- Institute of Medical Genetics, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, School of Clinical Medicine, Henan University, Zhengzhou, China
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14
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Hayashi T, Hosono K, Kurata K, Katagiri S, Mizobuchi K, Ueno S, Kondo M, Nakano T, Hotta Y. Coexistence of GNAT1 and ABCA4 variants associated with Nougaret-type congenital stationary night blindness and childhood-onset cone-rod dystrophy. Doc Ophthalmol 2019; 140:147-157. [PMID: 31583501 DOI: 10.1007/s10633-019-09727-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 09/24/2019] [Indexed: 10/25/2022]
Abstract
PURPOSE A single variant (p.G38D) in the GNAT1 gene, encoding the rod-specific transducin α-subunit in phototransduction, has been reported only in one French family with Nougaret-type autosomal dominant congenital stationary night blindness (CSNB). We identified a Japanese family with Nougaret-type CSNB and cone-rod dystrophy (CORD). METHODS Five patients with CSNB and two patients with childhood-onset CORD were recruited. We performed a comprehensive ophthalmic examination including electroretinography (ERG). Disease-causing variants were identified by whole exome sequencing, with candidates confirmed by Sanger sequencing in nine family members. RESULTS The GNAT1 variant (p.G38D) was identified in all four CSNB patients, whereas the two CORD patients carried biallelic truncated known ABCA4 variants as well as the GNAT1 variant. Clinically, no remarkable findings were observed in fuduscopy, fundus autofluorescence, or optical coherence tomography images from the CSNB patients. No response was detectable by rod ERG. The a-waves of standard and bright flash ERG were delayed and broadened rather than biphasic, and b/a-wave amplitude ratio was negative. Cone and 30-Hz flicker responses were normal, and overall, the ERG findings were compatible with previous descriptions of Nougaret-type CSNB. ERG of the CORD patients with macular atrophy showed non-recordable rod response and severely decreased standard flash, cone and 30-Hz flicker responses. CONCLUSIONS This is the second report of a Nougaret-type CSNB family with the GNAT1 variant. Our novel findings suggest that coexistence of the GNAT1 and biallelic ABCA4 variants is associated with an overlapping phenotype with both Nougaret-type CSNB and CORD.
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Affiliation(s)
- Takaaki Hayashi
- Department of Ophthalmology, The Jikei University School of Medicine, Minato-ku, Tokyo, Japan. .,Department of Ophthalmology, Katsushika Medical Center, The Jikei University School of Medicine, 6-41-2 Aoto, Katsushika-ku, Tokyo, 125-8506, Japan.
| | - Katsuhiro Hosono
- Department of Ophthalmology, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan
| | - Kentaro Kurata
- Department of Ophthalmology, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan
| | - Satoshi Katagiri
- Department of Ophthalmology, The Jikei University School of Medicine, Minato-ku, Tokyo, Japan
| | - Kei Mizobuchi
- Department of Ophthalmology, The Jikei University School of Medicine, Minato-ku, Tokyo, Japan
| | - Shinji Ueno
- Department of Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan
| | - Mineo Kondo
- Department of Ophthalmology, Mie University Graduate School of Medicine, Tsu, Mie, Japan
| | - Tadashi Nakano
- Department of Ophthalmology, The Jikei University School of Medicine, Minato-ku, Tokyo, Japan
| | - Yoshihiro Hotta
- Department of Ophthalmology, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan
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15
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Das RG, Becker D, Jagannathan V, Goldstein O, Santana E, Carlin K, Sudharsan R, Leeb T, Nishizawa Y, Kondo M, Aguirre GD, Miyadera K. Genome-wide association study and whole-genome sequencing identify a deletion in LRIT3 associated with canine congenital stationary night blindness. Sci Rep 2019; 9:14166. [PMID: 31578364 PMCID: PMC6775105 DOI: 10.1038/s41598-019-50573-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 09/05/2019] [Indexed: 01/11/2023] Open
Abstract
Congenital stationary night blindness (CSNB), in the complete form, is caused by dysfunctions in ON-bipolar cells (ON-BCs) which are secondary neurons of the retina. We describe the first disease causative variant associated with CSNB in the dog. A genome-wide association study using 12 cases and 11 controls from a research colony determined a 4.6 Mb locus on canine chromosome 32. Subsequent whole-genome sequencing identified a 1 bp deletion in LRIT3 segregating with CSNB. The canine mutant LRIT3 gives rise to a truncated protein with unaltered subcellular expression in vitro. Genetic variants in LRIT3 have been associated with CSNB in patients although there is limited evidence regarding its apparently critical function in the mGluR6 pathway in ON-BCs. We determine that in the canine CSNB retina, the mutant LRIT3 is correctly localized to the region correlating with the ON-BC dendritic tips, albeit with reduced immunolabelling. The LRIT3-CSNB canine model has direct translational potential enabling studies to help understand the CSNB pathogenesis as well as to develop new therapies targeting the secondary neurons of the retina.
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Affiliation(s)
- Rueben G Das
- Department of Clinical Sciences and Advanced Medicine, School of Veterinary Medicine, University of Pennsylvania, Pennsylvania, United States of America
| | - Doreen Becker
- Department of Clinical Sciences and Advanced Medicine, School of Veterinary Medicine, University of Pennsylvania, Pennsylvania, United States of America.,Institute of Genome Biology, Leibniz Institute for Farm Animal Biology, Dummerstorf, Germany
| | | | - Orly Goldstein
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Evelyn Santana
- Department of Clinical Sciences and Advanced Medicine, School of Veterinary Medicine, University of Pennsylvania, Pennsylvania, United States of America
| | - Kendall Carlin
- Department of Clinical Sciences and Advanced Medicine, School of Veterinary Medicine, University of Pennsylvania, Pennsylvania, United States of America
| | - Raghavi Sudharsan
- Department of Clinical Sciences and Advanced Medicine, School of Veterinary Medicine, University of Pennsylvania, Pennsylvania, United States of America
| | - Tosso Leeb
- Institute of Genetics, University of Bern, Bern, Switzerland
| | - Yuji Nishizawa
- Department of Biomedical Sciences, Chubu University, Kasugai, Aichi, Japan
| | - Mineo Kondo
- Department of Ophthalmology, Mie University Graduate School of Medicine, Tsu, Mie, Japan
| | - Gustavo D Aguirre
- Department of Clinical Sciences and Advanced Medicine, School of Veterinary Medicine, University of Pennsylvania, Pennsylvania, United States of America
| | - Keiko Miyadera
- Department of Clinical Sciences and Advanced Medicine, School of Veterinary Medicine, University of Pennsylvania, Pennsylvania, United States of America.
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16
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Klaus C, Caruso G, Gurevich VV, DiBenedetto E. Multi-scale, numerical modeling of spatio-temporal signaling in cone phototransduction. PLoS One 2019; 14:e0219848. [PMID: 31344066 PMCID: PMC6657853 DOI: 10.1371/journal.pone.0219848] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Accepted: 07/02/2019] [Indexed: 12/20/2022] Open
Abstract
Mammals have two types of photoreceptors, rods and cones. While rods are exceptionally sensitive and mediate vision at very low illumination levels, cones operate in daylight and are responsible for the bulk of visual perception in most diurnal animals, including humans. Yet the mechanisms of phototransduction in cones is understudied, largely due to unavailability of pure cone outer segment (COS) preparations. Here we present a novel mathematical model of cone phototransduction that explicitly takes into account complex cone geometry and its multiple physical scales, faithfully reproduces features of the cone response, and is orders of magnitude more efficient than the standard 3D diffusion model. This is accomplished through the mathematical techniques of homogenization and concentrated capacity. The homogenized model is then computationally implemented by finite element method. This homogenized model permits one to analyze the effects of COS geometry on visual transduction and lends itself to performing large numbers of numerical trials, as required for parameter analysis and the stochasticity of rod and cone signal transduction. Agreement between the nonhomogenized, (i.e., standard 3D), and homogenized diffusion models is reported along with their simulation times and memory costs. Virtual expression of rod biochemistry on cone morphology is also presented for understanding some of the characteristic differences between rods and cones. These simulations evidence that 3D cone morphology and ion channel localization contribute to biphasic flash response, i.e undershoot. The 3D nonhomogenized and homogenized models are contrasted with more traditional and coarser well-stirred and 1D longitudinal diffusion models. The latter are single-scale and do not explicitly account for the multi-scale geometry of the COS, unlike the 3D homogenized model. We show that simpler models exaggerate the magnitude of the current suppression, yield accelerated time to peak, and do not predict the local concentration of cGMP at the ionic channels.
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Affiliation(s)
- Colin Klaus
- The Mathematical Biosciences Institute, The Ohio State University, Columbus, OH, United States of America
| | | | - Vsevolod V. Gurevich
- Department of Pharmacology, Vanderbilt University, Nashville, TN, United States of America
| | - Emmanuele DiBenedetto
- Department of Mathematics, Vanderbilt University, Nashville, TN, United States of America
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17
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Wang W, Zhang X, Zhou X, Zhang Y, La Y, Zhang Y, Li C, Zhao Y, Li F, Liu B, Jiang Z. Deep Genome Resequencing Reveals Artificial and Natural Selection for Visual Deterioration, Plateau Adaptability and High Prolificacy in Chinese Domestic Sheep. Front Genet 2019; 10:300. [PMID: 31001329 PMCID: PMC6454055 DOI: 10.3389/fgene.2019.00300] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2018] [Accepted: 03/19/2019] [Indexed: 01/02/2023] Open
Abstract
Sheep were one of the earliest domesticated animals. Both artificial and natural selection during domestication has resulted in remarkable changes in behavioral, physiological, and morphological phenotypes; however, the genetic mechanisms underpinning these changes remain unclear, particularly for indigenous Chinese sheep. In the present study, we performed pooled whole-genome resequencing of 338 sheep from five breeds representative of indigenous Chinese breeds and compared them to the wild ancestors of domestic sheep (Asian mouflon, Ovis orientalis) for detection of genome-wide selective sweeps. Comparative genomic analysis between domestic sheep and Asian mouflon showed that selected regions were enriched for genes involved in bone morphogenesis, growth regulation, and embryonic and neural development in domestic sheep. Moreover, we identified several vision-associated genes with funtional mutations, such as PDE6B (c.G2994C/p.A982P and c.C2284A/p.L762M mutations), PANK2, and FOXC1/GMSD in all five Chinese native breeds. Breed-specific selected regions were determined including genes such as CYP17 for hypoxia adaptability in Tibetan sheep and DNAJB5 for heat tolerance in Duolang sheep. Our findings provide insights into the genetic mechanisms underlying important phenotypic changes that have occurred during sheep domestication and subsequent selection.
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Affiliation(s)
- Weimin Wang
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China
| | - Xiaoxue Zhang
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China
| | - Xiang Zhou
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, Huazhong Agricultural University, Wuhan, China.,Department of Animal Sciences, Washington State University, Pullman, WA, United States
| | - Yangzi Zhang
- Department of Animal Sciences, Washington State University, Pullman, WA, United States
| | - Yongfu La
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China
| | - Yu Zhang
- Department of Animal Sciences, Washington State University, Pullman, WA, United States
| | - Chong Li
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China
| | - Youzhang Zhao
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China
| | - Fadi Li
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China.,The State Key Laboratory of Grassland Agro-Ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China.,Engineering Laboratory of Sheep Breeding and Reproduction Biotechnology in Gansu Province, Minqin, China
| | - Bang Liu
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, Huazhong Agricultural University, Wuhan, China
| | - Zhihua Jiang
- Department of Animal Sciences, Washington State University, Pullman, WA, United States
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18
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Natural models for retinitis pigmentosa: progressive retinal atrophy in dog breeds. Hum Genet 2019; 138:441-453. [PMID: 30904946 DOI: 10.1007/s00439-019-01999-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 03/14/2019] [Indexed: 01/24/2023]
Abstract
Retinitis pigmentosa (RP) is a heterogeneous group of inherited retinal disorders eventually leading to blindness with different ages of onset, progression and severity. Human RP, first characterized by the progressive degeneration of rod photoreceptor cells, shows high genetic heterogeneity with more than 90 genes identified. However, about one-third of patients have no known genetic causes. Interestingly, dogs are also severely affected by similar diseases, called progressive retinal atrophy (PRA). Indeed, RP and PRA have comparable clinical signs, physiopathology and outcomes, similar diagnosis methods and most often, orthologous genes are involved. The many different dog PRAs often segregate in specific breeds. Indeed, undesired alleles have been selected and amplified through drastic selection and excessive use of inbreeding. Out of the 400 breeds, nearly 100 have an inherited form of PRA, which are natural animal models that can be used to investigate the genetics, disease progression and therapies in dogs for the benefit of both dogs and humans. Recent knowledge on the canine genome and access to new genotyping and sequencing technologies now efficiently allows the identification of mutations involved in canine genetic diseases. To date, PRA genes identified in dog breeds correspond to the same genes in humans and represent relevant RP models, and new genes found in dogs represent good candidate for still unknown human RP. We present here a review of the main advantages of the dog models for human RP with the genes already identified and an X-linked PRA in the Border collie as a model for orphan X-linked RPs in human.
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19
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Maryam A, Vedithi SC, Khalid RR, Alsulami AF, Torres PHM, Siddiqi AR, Blundell TL. The Molecular Organization of Human cGMP Specific Phosphodiesterase 6 (PDE6): Structural Implications of Somatic Mutations in Cancer and Retinitis Pigmentosa. Comput Struct Biotechnol J 2019; 17:378-389. [PMID: 30962868 PMCID: PMC6434069 DOI: 10.1016/j.csbj.2019.03.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 02/24/2019] [Accepted: 03/03/2019] [Indexed: 01/12/2023] Open
Abstract
In the cyclic guanosine monophosphate (cGMP) signaling pathway, phosphodiesterase 6 (PDE6) maintains a critical balance of the intracellular concentration of cGMP by catalyzing it to 5′ guanosine monophosphate (5′-GMP). To gain insight into the mechanistic impacts of the PDE6 somatic mutations that are implicated in cancer and retinitis pigmentosa, we first defined the structure and organization of the human PDE6 heterodimer using computational comparative modelling. Each subunit of PDE6αβ possesses three domains connected through long α-helices. The heterodimer model indicates that the two chains are likely related by a pseudo two-fold axis. The N-terminal region of each subunit is comprised of two allosteric cGMP-binding domains (Gaf-A & Gaf-B), oriented in the same way and interacting with the catalytic domain present at the C-terminal in a way that would allow the allosteric cGMP-binding domains to influence catalytic activity. Subsequently, we applied an integrated knowledge-driven in silico mutation analysis approach to understand the structural and functional implications of experimentally identified mutations that cause various cancers and retinitis pigmentosa, as well as computational saturation mutagenesis of the dimer interface and cGMP-binding residues of both Gaf-A, and the catalytic domains. We studied the impact of mutations on the stability of PDE6αβ structure, subunit-interfaces and Gaf-cGMP interactions. Further, we discussed the changes in interatomic interactions of mutations that are destabilizing in Gaf-A (R93L, V141 M, F162 L), catalytic domain (D600N, F742 L, F776 L) and at the dimer interface (F426A, F248G, F424 N). This study establishes a possible link of change in PDE6αβ structural stability to the experimentally observed disease phenotypes.
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Affiliation(s)
- Arooma Maryam
- Department of Biosciences, COMSATS University Islamabad (CUI), Park Road, Islamabad, Pakistan.,Department of Biochemistry, University of Cambridge, 80 Tennis Court Rd, Cambridge CB2 1GA, UK
| | | | - Rana Rehan Khalid
- Department of Biosciences, COMSATS University Islamabad (CUI), Park Road, Islamabad, Pakistan
| | - Ali F Alsulami
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Rd, Cambridge CB2 1GA, UK
| | | | - Abdul Rauf Siddiqi
- Department of Biosciences, COMSATS University Islamabad (CUI), Park Road, Islamabad, Pakistan
| | - Tom L Blundell
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Rd, Cambridge CB2 1GA, UK
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20
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Riggs-type dominant congenital stationary night blindness: ERG findings, a new GNAT1 mutation and a systemic association. Doc Ophthalmol 2018; 137:57-62. [PMID: 30051303 DOI: 10.1007/s10633-018-9651-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 07/13/2018] [Indexed: 10/28/2022]
Abstract
PURPOSE Complete congenital stationary night blindness (CSNB) is most often x-linked or recessive, and associated with a transmission defect from photoreceptors to bipolar cells. This produces a characteristic "negative" Schubert-Bornschein type of scotopic rod-cone electroretinogram (ERG) with a large a-wave and minimal b-wave. CSNB from abnormalities in phototransduction can be recessive or dominant and is much less common. This produces a Riggs type of ERG with loss of the rod a-wave as well as the b-wave. We report the clinical and ERG findings from a family with autosomal dominant CSNB that was shown previously to have a new GNAT1 mutation with a novel mechanism of action. They provide a classic demonstration of the Riggs-type ERG and have an unusual systemic association. METHODS Clinical case report of a father and daughter. RESULTS A Chinese father and daughter presented with good visual acuity, moderate myopia, and lifelong night blindness. Both show normal fundi except for mild myopia, and fundus autofluorescence and OCT images are normal. Their ERGs illustrate the typical Riggs-type ERG with no rod a-wave (they have only a small cone-dominated combined response). They also have postural orthostatic tachycardia syndrome (POST), which is an autonomic dysfunction disorder thought usually to be sporadic. The retinal gene analyses revealed no abnormalities that might account for POST. CONCLUSIONS Our family's ERG showed essentially no rod response, consistent with a Danish GNAT1 pedigree but different from the Nougaret GNAT1 pedigree that shows partial preservation of rod signal. A genetic connection between CSNB and POST would be intriguing, but we found no evidence for this.
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21
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A Novel Heterozygous Missense Mutation in GNAT1 Leads to Autosomal Dominant Riggs Type of Congenital Stationary Night Blindness. BIOMED RESEARCH INTERNATIONAL 2018; 2018:7694801. [PMID: 29850563 PMCID: PMC5937575 DOI: 10.1155/2018/7694801] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 03/13/2018] [Indexed: 01/03/2023]
Abstract
Autosomal dominant congenital stationary night blindness (adCSNB) is rare and results from altered phototransduction giving a Riggs type of electroretinogram (ERG) with loss of the rod a-wave and small b-waves. These patients usually have normal vision in light. Only few mutations in genes coding for proteins of the phototransduction cascade lead to this condition; most of these gene defects cause progressive rod-cone dystrophy. Mutation analysis of an adCSNB family with a Riggs-type ERG revealed a novel variant (c.155T>A p.Ile52Asn) in GNAT1 coding for the α-subunit of transducin, cosegregating with the phenotype. Domain predictions and 3D-modelling suggest that the variant does not affect the GTP-binding site as other GNAT1 adCSNB mutations do. It affects a predicted nuclear localization signal and a part of the first α-helix, which is distant from the GTP-binding site. The subcellular protein localization of this and other mutant GNAT1 proteins implicated in CSNB are unaltered in mammalian GNAT1 overexpressing cells. Our findings add a third GNAT1 mutation causing adCSNB and suggest that different pathogenic mechanisms may cause this condition.
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22
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Bujakowska KM, Liu Q, Pierce EA. Photoreceptor Cilia and Retinal Ciliopathies. Cold Spring Harb Perspect Biol 2017; 9:cshperspect.a028274. [PMID: 28289063 DOI: 10.1101/cshperspect.a028274] [Citation(s) in RCA: 126] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Photoreceptors are sensory neurons designed to convert light stimuli into neurological responses. This process, called phototransduction, takes place in the outer segments (OS) of rod and cone photoreceptors. OS are specialized sensory cilia, with analogous structures to those present in other nonmotile cilia. Deficient morphogenesis and/or dysfunction of photoreceptor sensory cilia (PSC) caused by mutations in a variety of photoreceptor-specific and common cilia genes can lead to inherited retinal degenerations (IRDs). IRDs can manifest as isolated retinal diseases or syndromic diseases. In this review, we describe the structure and composition of PSC and different forms of ciliopathies with retinal involvement. We review the genetics of the IRDs, which are monogenic disorders but genetically diverse with regard to causality.
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Affiliation(s)
- Kinga M Bujakowska
- Ocular Genomics Institute, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114
| | - Qin Liu
- Ocular Genomics Institute, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114
| | - Eric A Pierce
- Ocular Genomics Institute, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114
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23
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Gopalakrishna KN, Boyd K, Artemyev NO. Mechanisms of mutant PDE6 proteins underlying retinal diseases. Cell Signal 2017; 37:74-80. [PMID: 28583373 DOI: 10.1016/j.cellsig.2017.06.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Revised: 05/30/2017] [Accepted: 06/01/2017] [Indexed: 12/15/2022]
Abstract
Mutations in PDE6 genes encoding the effector enzymes in rods and cones underlie severe retinal diseases including retinitis pigmentosa (RP), autosomal dominant congenital stationary night blindness (adCSNB), and achromatopsia (ACHM). Here we examined a spectrum of pathogenic missense mutations in PDE6 using the system based on co-expression of cone PDE6C with its specialized chaperone AIPL1 and the regulatory Pγ subunit as a potent co-chaperone. We uncovered two mechanisms of PDE6C mutations underlying ACHM: (a) folding defects leading to expression of catalytically inactive proteins and (b) markedly diminished ability of Pγ to co-chaperone mutant PDE6C proteins thereby dramatically reducing the levels of functional enzyme. The mechanism of the Rambusch adCSNB associated with the H258N substitution in PDE6B was probed through the analysis of the model mutant PDE6C-H262N. We identified two interrelated deficits of PDE6C-H262N: disruption of the inhibitory interaction of Pγ with mutant PDE6C that markedly reduced the ability of Pγ to augment the enzyme folding. Thus, we conclude that the Rambusch adCSNB is triggered by low levels of the constitutively active PDE6. Finally, we examined PDE6C-L858V, which models PDE6B-L854V, an RP-linked mutation that alters the protein isoprenyl modification. This analysis suggests that the type of prenyl modifications does not impact the folding of PDE6, but it modulates the enzyme affinity for its trafficking partner PDE6D. Hence, the pathogenicity of PDE6B-L854V likely arises from its trafficking deficiency. Taken together, our results demonstrate the effectiveness of the PDE6C expression system to evaluate pathogenicity and elucidate the mechanisms of PDE6 mutations in retinal diseases.
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MESH Headings
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/metabolism
- Animals
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Color Vision Defects/genetics
- Color Vision Defects/metabolism
- Cyclic Nucleotide Phosphodiesterases, Type 6/analysis
- Cyclic Nucleotide Phosphodiesterases, Type 6/genetics
- Cyclic Nucleotide Phosphodiesterases, Type 6/metabolism
- Eye Diseases, Hereditary/genetics
- Eye Diseases, Hereditary/metabolism
- Eye Proteins/analysis
- Eye Proteins/genetics
- Eye Proteins/metabolism
- Gene Expression
- Genetic Diseases, X-Linked/genetics
- Genetic Diseases, X-Linked/metabolism
- HEK293 Cells
- Humans
- Mice
- Models, Molecular
- Mutation, Missense
- Myopia/genetics
- Myopia/metabolism
- Night Blindness/genetics
- Night Blindness/metabolism
- Protein Folding
- Protein Prenylation
- Retinal Diseases/genetics
- Retinal Diseases/metabolism
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Affiliation(s)
- Kota N Gopalakrishna
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, IA 52242, United States
| | - Kimberly Boyd
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, IA 52242, United States
| | - Nikolai O Artemyev
- Department of Molecular Physiology and Biophysics, The University of Iowa Carver College of Medicine, Iowa City, IA 52242, United States; Department of Ophthalmology and Visual Sciences, The University of Iowa Carver College of Medicine, Iowa City, IA 52242, United States.
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24
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Gopalakrishna KN, Boyd K, Yadav RP, Artemyev NO. Aryl Hydrocarbon Receptor-interacting Protein-like 1 Is an Obligate Chaperone of Phosphodiesterase 6 and Is Assisted by the γ-Subunit of Its Client. J Biol Chem 2016; 291:16282-91. [PMID: 27268253 DOI: 10.1074/jbc.m116.737593] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Indexed: 12/26/2022] Open
Abstract
Phosphodiesterase 6 (PDE6) is the effector enzyme in the phototransduction cascade and is critical for the health of both rod and cone photoreceptors. Its dysfunction, caused by mutations in either the enzyme itself or AIPL1 (aryl hydrocarbon receptor-interacting protein-like 1), leads to retinal diseases culminating in blindness. Progress in research on PDE6 and AIPL1 has been severely hampered by failure to express functional PDE6 in a heterologous expression system. Here, we demonstrated that AIPL1 is an obligate chaperone of PDE6 and that it enables low yield functional folding of cone PDE6C in cultured cells. We further show that the AIPL1-mediated production of folded PDE6C is markedly elevated in the presence of the inhibitory Pγ-subunit of PDE6. As illustrated in this study, a simple and sensitive system in which AIPL1 and Pγ are co-expressed with PDE6 represents an effective tool for probing structure-function relationships of AIPL1 and reliably establishing the pathogenicity of its variants.
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Affiliation(s)
| | - Kimberly Boyd
- From the Departments of Molecular Physiology and Biophysics and
| | - Ravi P Yadav
- From the Departments of Molecular Physiology and Biophysics and
| | - Nikolai O Artemyev
- From the Departments of Molecular Physiology and Biophysics and Ophthalmology and Visual Sciences, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242
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25
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Neuillé M, Malaichamy S, Vadalà M, Michiels C, Condroyer C, Sachidanandam R, Srilekha S, Arokiasamy T, Letexier M, Démontant V, Sahel JA, Sen P, Audo I, Soumittra N, Zeitz C. Next-generation sequencing confirms the implication of SLC24A1 in autosomal-recessive congenital stationary night blindness. Clin Genet 2016; 89:690-9. [PMID: 26822852 DOI: 10.1111/cge.12746] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 01/25/2016] [Accepted: 01/25/2016] [Indexed: 01/17/2023]
Abstract
Congenital stationary night blindness (CSNB) is a clinically and genetically heterogeneous retinal disorder which represents rod photoreceptor dysfunction or signal transmission defect from photoreceptors to adjacent bipolar cells. Patients displaying photoreceptor dysfunction show a Riggs-electroretinogram (ERG) while patients with a signal transmission defect show a Schubert-Bornschein ERG. The latter group is subdivided into complete or incomplete (ic) CSNB. Only few CSNB cases with Riggs-ERG and only one family with a disease-causing variant in SLC24A1 have been reported. Whole-exome sequencing (WES) in a previously diagnosed icCSNB patient identified a homozygous nonsense variant in SLC24A1. Indeed, re-investigation of the clinical data corrected the diagnosis to Riggs-form of CSNB. Targeted next-generation sequencing (NGS) identified compound heterozygous deletions and a homozygous missense variant in SLC24A1 in two other patients, respectively. ERG abnormalities varied in these three cases but all patients had normal visual acuity, no myopia or nystagmus, unlike in Schubert-Bornschein-type of CSNB. This confirms that SLC24A1 defects lead to CSNB and outlines phenotype/genotype correlations in CSNB subtypes. In case of unclear clinical characteristics, NGS techniques are helpful to clarify the diagnosis.
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Affiliation(s)
- M Neuillé
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, Paris, France
| | - S Malaichamy
- SN ONGC Department of Genetics and Molecular Biology, Vision Research Foundation, Chennai, India
| | - M Vadalà
- Ophthalmology Section, Department of Experimental Medicine and Clinical Neuroscience, University of Palermo, Palermo, Italy
| | - C Michiels
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, Paris, France
| | - C Condroyer
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, Paris, France
| | - R Sachidanandam
- Department of Optometry, Medical Research Foundation, Chennai, India
| | - S Srilekha
- SN ONGC Department of Genetics and Molecular Biology, Vision Research Foundation, Chennai, India
| | - T Arokiasamy
- SN ONGC Department of Genetics and Molecular Biology, Vision Research Foundation, Chennai, India
| | | | - V Démontant
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, Paris, France
| | - J-A Sahel
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, Paris, France.,CHNO des Quinze-Vingts, DHU Sight Restore, INSERM-DHOS CIC 1423, Paris, France.,Institute of Ophthalmology, University College of London, London, UK.,Fondation Ophtalmologique Adolphe de Rothschild, Paris, France.,Académie des Sciences, Institut de France, Paris, France
| | - P Sen
- Department of Vitreo-Retinal Services, Medical Research Foundation, Chennai, India
| | - I Audo
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, Paris, France.,CHNO des Quinze-Vingts, DHU Sight Restore, INSERM-DHOS CIC 1423, Paris, France.,Institute of Ophthalmology, University College of London, London, UK
| | - N Soumittra
- SN ONGC Department of Genetics and Molecular Biology, Vision Research Foundation, Chennai, India
| | - C Zeitz
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, Paris, France
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26
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Veleri S, Lazar CH, Chang B, Sieving PA, Banin E, Swaroop A. Biology and therapy of inherited retinal degenerative disease: insights from mouse models. Dis Model Mech 2015; 8:109-29. [PMID: 25650393 PMCID: PMC4314777 DOI: 10.1242/dmm.017913] [Citation(s) in RCA: 179] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Retinal neurodegeneration associated with the dysfunction or death of photoreceptors is a major cause of incurable vision loss. Tremendous progress has been made over the last two decades in discovering genes and genetic defects that lead to retinal diseases. The primary focus has now shifted to uncovering disease mechanisms and designing treatment strategies, especially inspired by the successful application of gene therapy in some forms of congenital blindness in humans. Both spontaneous and laboratory-generated mouse mutants have been valuable for providing fundamental insights into normal retinal development and for deciphering disease pathology. Here, we provide a review of mouse models of human retinal degeneration, with a primary focus on diseases affecting photoreceptor function. We also describe models associated with retinal pigment epithelium dysfunction or synaptic abnormalities. Furthermore, we highlight the crucial role of mouse models in elucidating retinal and photoreceptor biology in health and disease, and in the assessment of novel therapeutic modalities, including gene- and stem-cell-based therapies, for retinal degenerative diseases.
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Affiliation(s)
- Shobi Veleri
- Neurobiology-Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Csilla H Lazar
- Neurobiology-Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA. Molecular Biology Center, Interdisciplinary Research Institute on Bio-Nano Sciences, Babes-Bolyai-University, Cluj-Napoca, 400271, Romania
| | - Bo Chang
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
| | - Paul A Sieving
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Eyal Banin
- Neurobiology-Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA. Center for Retinal and Macular Degenerations, Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem 91120, Israel
| | - Anand Swaroop
- Neurobiology-Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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27
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Vinberg F, Wang T, Molday RS, Chen J, Kefalov VJ. A new mouse model for stationary night blindness with mutant Slc24a1 explains the pathophysiology of the associated human disease. Hum Mol Genet 2015; 24:5915-29. [PMID: 26246500 DOI: 10.1093/hmg/ddv319] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 07/31/2015] [Indexed: 11/12/2022] Open
Abstract
Mutations that affect calcium homeostasis (Ca(2+)) in rod photoreceptors are linked to retinal degeneration and visual disorders such as retinitis pigmentosa and congenital stationary night blindness (CSNB). It is thought that the concentration of Ca(2+) in rod outer segments is controlled by a dynamic balance between influx via cGMP-gated (CNG) channels and extrusion via Na(+)/Ca(2+), K(+) exchangers (NCKX1). The extrusion-driven lowering of rod [Ca(2+)]i following light exposure controls their light adaptation and response termination. Mutant NCKX1 has been linked to autosomal-recessive stationary night blindness. However, whether NCKX1 contributes to light adaptation has not been directly tested and the mechanisms by which human NCKX1 mutations cause night blindness are not understood. Here, we report that the deletion of NCKX1 in mice results in malformed outer segment disks, suppressed expression and function of rod CNG channels and a subsequent 100-fold reduction in rod responses, while preserving normal cone responses. The compensating loss of CNG channel function in the absence of NCKX1-mediated Ca(2+) extrusion may prevent toxic Ca(2+) buildup and provides an explanation for the stationary nature of the associated disorder in humans. Surprisingly, the lack of NCKX1 did not compromise rod background light adaptation, suggesting additional Ca(2+)-extruding mechanisms exist in these cells.
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Affiliation(s)
- Frans Vinberg
- Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO, USA
| | - Tian Wang
- Cell and Neurobiology, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA, USA and
| | - Robert S Molday
- Biochemistry/Molecular Biology, University of British Columbia, Vancouver, Canada
| | - Jeannie Chen
- Cell and Neurobiology, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA, USA and
| | - Vladimir J Kefalov
- Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO, USA,
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28
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Kuniyoshi K, Sakuramoto H, Yoshitake K, Ikeo K, Furuno M, Tsunoda K, Kusaka S, Shimomura Y, Iwata T. Reduced rod electroretinograms in carrier parents of two Japanese siblings with autosomal recessive retinitis pigmentosa associated with PDE6B gene mutations. Doc Ophthalmol 2015; 131:71-9. [PMID: 25827439 DOI: 10.1007/s10633-015-9497-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 03/25/2015] [Indexed: 10/23/2022]
Abstract
PURPOSE To present the clinical and genetic findings in two siblings with autosomal recessive retinitis pigmentosa (RP) and their non-symptomatic parents. METHODS We studied two siblings, a 48-year-old woman and her 44-year-old brother, and their parents. They had general ophthalmic examinations including ophthalmoscopy, perimetry, and electroretinography (ERG). Their whole exomes were analyzed by the next-generation sequence technique. RESULTS The two siblings had night blindness for a long time, and clinical examinations revealed diffuse retinal degeneration with bone spicule pigmentation, constriction of the visual field, and non-recordable ERGs. Their parents were non-symptomatic and had normal fundi; however, their rod ERGs were reduced. Genetic examination revealed compound heterozygous mutations of I535N and H557Y in the PDE6B gene in the siblings, and the parents were heterozygous carriers of the mutations. CONCLUSIONS Heterozygous mutation in the PDE6B gene can cause a reduction in the rod function to different degrees. The retinal function of non-symptomatic carriers of autosomal recessive RP should be evaluated with care.
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Affiliation(s)
- Kazuki Kuniyoshi
- Department of Ophthalmology, Kinki University Faculty of Medicine, 377-2 Ohno-Higashi, Osaka-Sayama City, Osaka, 589-8511, Japan,
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29
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Nash BM, Wright DC, Grigg JR, Bennetts B, Jamieson RV. Retinal dystrophies, genomic applications in diagnosis and prospects for therapy. Transl Pediatr 2015; 4:139-63. [PMID: 26835369 PMCID: PMC4729094 DOI: 10.3978/j.issn.2224-4336.2015.04.03] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Retinal dystrophies (RDs) are degenerative diseases of the retina which have marked clinical and genetic heterogeneity. Common presentations among these disorders include night or colour blindness, tunnel vision and subsequent progression to complete blindness. The known causative disease genes have a variety of developmental and functional roles with mutations in more than 120 genes shown to be responsible for the phenotypes. In addition, mutations within the same gene have been shown to cause different disease phenotypes, even amongst affected individuals within the same family highlighting further levels of complexity. The known disease genes encode proteins involved in retinal cellular structures, phototransduction, the visual cycle, and photoreceptor structure or gene regulation. This review aims to demonstrate the high degree of genetic complexity in both the causative disease genes and their associated phenotypes, highlighting the more common clinical manifestation of retinitis pigmentosa (RP). The review also provides insight to recent advances in genomic molecular diagnosis and gene and cell-based therapies for the RDs.
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Affiliation(s)
- Benjamin M Nash
- 1 Eye Genetics Research Group, Children's Medical Research Institute, University of Sydney, The Children's Hospital at Westmead and Save Sight Institute, Sydney, NSW, Australia ; 2 Sydney Genome Diagnostics, The Children's Hospital at Westmead, Sydney, NSW, Australia ; 3 Discipline of Paediatrics and Child Health, Sydney Medical School, University of Sydney, NSW, Australia
| | - Dale C Wright
- 1 Eye Genetics Research Group, Children's Medical Research Institute, University of Sydney, The Children's Hospital at Westmead and Save Sight Institute, Sydney, NSW, Australia ; 2 Sydney Genome Diagnostics, The Children's Hospital at Westmead, Sydney, NSW, Australia ; 3 Discipline of Paediatrics and Child Health, Sydney Medical School, University of Sydney, NSW, Australia
| | - John R Grigg
- 1 Eye Genetics Research Group, Children's Medical Research Institute, University of Sydney, The Children's Hospital at Westmead and Save Sight Institute, Sydney, NSW, Australia ; 2 Sydney Genome Diagnostics, The Children's Hospital at Westmead, Sydney, NSW, Australia ; 3 Discipline of Paediatrics and Child Health, Sydney Medical School, University of Sydney, NSW, Australia
| | - Bruce Bennetts
- 1 Eye Genetics Research Group, Children's Medical Research Institute, University of Sydney, The Children's Hospital at Westmead and Save Sight Institute, Sydney, NSW, Australia ; 2 Sydney Genome Diagnostics, The Children's Hospital at Westmead, Sydney, NSW, Australia ; 3 Discipline of Paediatrics and Child Health, Sydney Medical School, University of Sydney, NSW, Australia
| | - Robyn V Jamieson
- 1 Eye Genetics Research Group, Children's Medical Research Institute, University of Sydney, The Children's Hospital at Westmead and Save Sight Institute, Sydney, NSW, Australia ; 2 Sydney Genome Diagnostics, The Children's Hospital at Westmead, Sydney, NSW, Australia ; 3 Discipline of Paediatrics and Child Health, Sydney Medical School, University of Sydney, NSW, Australia
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30
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Zhang Z, He F, Constantine R, Baker ML, Baehr W, Schmid MF, Wensel TG, Agosto MA. Domain organization and conformational plasticity of the G protein effector, PDE6. J Biol Chem 2015; 290:12833-43. [PMID: 25809480 DOI: 10.1074/jbc.m115.647636] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Indexed: 11/06/2022] Open
Abstract
The cGMP phosphodiesterase of rod photoreceptor cells, PDE6, is the key effector enzyme in phototransduction. Two large catalytic subunits, PDE6α and -β, each contain one catalytic domain and two non-catalytic GAF domains, whereas two small inhibitory PDE6γ subunits allow tight regulation by the G protein transducin. The structure of holo-PDE6 in complex with the ROS-1 antibody Fab fragment was determined by cryo-electron microscopy. The ∼11 Å map revealed previously unseen features of PDE6, and each domain was readily fit with high resolution structures. A structure of PDE6 in complex with prenyl-binding protein (PrBP/δ) indicated the location of the PDE6 C-terminal prenylations. Reconstructions of complexes with Fab fragments bound to N or C termini of PDE6γ revealed that PDE6γ stretches from the catalytic domain at one end of the holoenzyme to the GAF-A domain at the other. Removal of PDE6γ caused dramatic structural rearrangements, which were reversed upon its restoration.
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Affiliation(s)
- Zhixian Zhang
- From the Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030 and
| | - Feng He
- From the Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030 and
| | - Ryan Constantine
- Department of Ophthalmology, Moran Eye Center, University of Utah, Salt Lake City, Utah 84132
| | - Matthew L Baker
- From the Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030 and
| | - Wolfgang Baehr
- Department of Ophthalmology, Moran Eye Center, University of Utah, Salt Lake City, Utah 84132
| | - Michael F Schmid
- From the Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030 and
| | - Theodore G Wensel
- From the Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030 and
| | - Melina A Agosto
- From the Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030 and
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31
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Brennenstuhl C, Tanimoto N, Burkard M, Wagner R, Bolz S, Trifunovic D, Kabagema-Bilan C, Paquet-Durand F, Beck SC, Huber G, Seeliger MW, Ruth P, Wissinger B, Lukowski R. Targeted ablation of the Pde6h gene in mice reveals cross-species differences in cone and rod phototransduction protein isoform inventory. J Biol Chem 2015; 290:10242-55. [PMID: 25739440 DOI: 10.1074/jbc.m114.611921] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Indexed: 11/06/2022] Open
Abstract
Phosphodiesterase-6 (PDE6) is a multisubunit enzyme that plays a key role in the visual transduction cascade in rod and cone photoreceptors. Each type of photoreceptor utilizes discrete catalytic and inhibitory PDE6 subunits to fulfill its physiological tasks, i.e. the degradation of cyclic guanosine-3',5'-monophosphate at specifically tuned rates and kinetics. Recently, the human PDE6H gene was identified as a novel locus for autosomal recessive (incomplete) color blindness. However, the three different classes of cones were not affected to the same extent. Short wave cone function was more preserved than middle and long wave cone function indicating that some basic regulation of the PDE6 multisubunit enzyme was maintained albeit by a unknown mechanism. To study normal and disease-related functions of cone Pde6h in vivo, we generated Pde6h knock-out (Pde6h(-/-)) mice. Expression of PDE6H in murine eyes was restricted to both outer segments and synaptic terminals of short and long/middle cone photoreceptors, whereas Pde6h(-/-) retinae remained PDE6H-negative. Combined in vivo assessment of retinal morphology with histomorphological analyses revealed a normal overall integrity of the retinal organization and an unaltered distribution of the different cone photoreceptor subtypes upon Pde6h ablation. In contrast to human patients, our electroretinographic examinations of Pde6h(-/-) mice suggest no defects in cone/rod-driven retinal signaling and therefore preserved visual functions. To this end, we were able to demonstrate the presence of rod PDE6G in cones indicating functional substitution of PDE6. The disparities between human and murine phenotypes caused by mutant Pde6h/PDE6H suggest species-to-species differences in the vulnerability of biochemical and neurosensory pathways of the visual signal transduction system.
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Affiliation(s)
- Christina Brennenstuhl
- From the Institute of Pharmacy, Department of Pharmacology, Toxicology and Clinical Pharmacy
| | | | - Markus Burkard
- From the Institute of Pharmacy, Department of Pharmacology, Toxicology and Clinical Pharmacy
| | - Rebecca Wagner
- From the Institute of Pharmacy, Department of Pharmacology, Toxicology and Clinical Pharmacy
| | | | | | - Clement Kabagema-Bilan
- From the Institute of Pharmacy, Department of Pharmacology, Toxicology and Clinical Pharmacy
| | | | | | | | | | - Peter Ruth
- From the Institute of Pharmacy, Department of Pharmacology, Toxicology and Clinical Pharmacy
| | - Bernd Wissinger
- the Molecular Genetics Laboratory, Centre for Ophthalmology, University of Tuebingen, 72076 Tuebingen, Germany
| | - Robert Lukowski
- From the Institute of Pharmacy, Department of Pharmacology, Toxicology and Clinical Pharmacy,
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32
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Congenital stationary night blindness: An analysis and update of genotype–phenotype correlations and pathogenic mechanisms. Prog Retin Eye Res 2015; 45:58-110. [DOI: 10.1016/j.preteyeres.2014.09.001] [Citation(s) in RCA: 207] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 09/25/2014] [Accepted: 09/30/2014] [Indexed: 01/18/2023]
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33
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Baehr W. Membrane protein transport in photoreceptors: the function of PDEδ: the Proctor lecture. Invest Ophthalmol Vis Sci 2014; 55:8653-66. [PMID: 25550383 DOI: 10.1167/iovs.14-16066] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
This lecture details the elucidation of cGMP phosphodiesterase (PDEδ), discovered 25 years ago by Joe Beavo at the University of Washington. PDEδ, once identified as a fourth PDE6 subunit, is now regarded as a promiscuous prenyl-binding protein and important chaperone of prenylated small G proteins of the Ras superfamily and prenylated proteins of phototransduction. Alfred Wittinghofer's group in Germany showed that PDEδ forms an immunoglobulin-like β-sandwich fold that is closely related in structure to other lipid-binding proteins, for example, Uncoordinated 119 (UNC119) and RhoGDI. His group cocrystallized PDEδ with ARL (Arf-like) 2(GTP), and later with farnesylated Rheb (ras homolog expressed in brain). PDEδ specifically accommodates farnesyl and geranylgeranyl moieties in the absence of bound protein. Germline deletion of the Pde6d gene encoding PDEδ impeded transport of rhodopsin kinase (GRK1) and PDE6 to outer segments, causing slowly progressing, recessive retinitis pigmentosa. A rare PDE6D null allele in human patients, discovered by Tania Attié-Bitach in France, specifically impeded trafficking of farnesylated phosphatidylinositol 3,4,5-trisphosphate (PIP3) 5-phosphatase (INPP5E) to cilia, causing severe syndromic ciliopathy (Joubert syndrome). Binding of cargo to PDEδ is controlled by Arf-like proteins, ARL2 and ARL3, charged with guanosine-5'-triphosphate (GTP). Arf-like proteins 2 and 3 are unprenylated small GTPases that serve as cargo displacement factors. The lifetime of ARL3(GTP) is controlled by its GTPase-activating protein, retinitis pigmentosa protein 2 (RP2), which accelerates GTPase activity up to 90,000-fold. RP2 null alleles in human patients are associated with severe X-linked retinitis pigmentosa (XLRP). Germline deletion of RP2 in mouse, however, causes only a mild form of XLRP. Absence of RP2 prolongs the activity of ARL3(GTP) that, in turn, impedes PDE6δ-cargo interactions and trafficking of prenylated protein to the outer segments. Hyperactive ARL3(GTP), acting as a hyperactive cargo displacement factor, is predicted to be key in the pathobiology of RP2-XLRP.
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Affiliation(s)
- Wolfgang Baehr
- Department of Ophthalmology, John A. Moran Eye Center, University of Utah Health Science Center, University of Utah, Salt Lake City, Utah, United StatesDepartment of Neurobiology and Anatomy, University of Utah Health Science Center, University of Utah, Salt Lake City, Utah, United StatesDepartment of Biology, University of Utah, Salt Lake City, Utah, United States
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34
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Ahmad F, Murata T, Shimizu K, Degerman E, Maurice D, Manganiello V. Cyclic nucleotide phosphodiesterases: important signaling modulators and therapeutic targets. Oral Dis 2014; 21:e25-50. [PMID: 25056711 DOI: 10.1111/odi.12275] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 07/09/2014] [Indexed: 02/06/2023]
Abstract
By catalyzing hydrolysis of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), cyclic nucleotide phosphodiesterases are critical regulators of their intracellular concentrations and their biological effects. As these intracellular second messengers control many cellular homeostatic processes, dysregulation of their signals and signaling pathways initiate or modulate pathophysiological pathways related to various disease states, including erectile dysfunction, pulmonary hypertension, acute refractory cardiac failure, intermittent claudication, chronic obstructive pulmonary disease, and psoriasis. Alterations in expression of PDEs and PDE-gene mutations (especially mutations in PDE6, PDE8B, PDE11A, and PDE4) have been implicated in various diseases and cancer pathologies. PDEs also play important role in formation and function of multimolecular signaling/regulatory complexes, called signalosomes. At specific intracellular locations, individual PDEs, together with pathway-specific signaling molecules, regulators, and effectors, are incorporated into specific signalosomes, where they facilitate and regulate compartmentalization of cyclic nucleotide signaling pathways and specific cellular functions. Currently, only a limited number of PDE inhibitors (PDE3, PDE4, PDE5 inhibitors) are used in clinical practice. Future paths to novel drug discovery include the crystal structure-based design approach, which has resulted in generation of more effective family-selective inhibitors, as well as burgeoning development of strategies to alter compartmentalized cyclic nucleotide signaling pathways by selectively targeting individual PDEs and their signalosome partners.
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Affiliation(s)
- F Ahmad
- Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, Bethesda, MD, USA
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35
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Zeng-Elmore X, Gao XZ, Pellarin R, Schneidman-Duhovny D, Zhang XJ, Kozacka KA, Tang Y, Sali A, Chalkley RJ, Cote RH, Chu F. Molecular architecture of photoreceptor phosphodiesterase elucidated by chemical cross-linking and integrative modeling. J Mol Biol 2014; 426:3713-3728. [PMID: 25149264 DOI: 10.1016/j.jmb.2014.07.033] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Revised: 07/01/2014] [Accepted: 07/28/2014] [Indexed: 11/20/2022]
Abstract
Photoreceptor phosphodiesterase (PDE6) is the central effector enzyme in visual excitation pathway in rod and cone photoreceptors. Its tight regulation is essential for the speed, sensitivity, recovery and adaptation of visual detection. Although major steps in the PDE6 activation/deactivation pathway have been identified, mechanistic understanding of PDE6 regulation is limited by the lack of knowledge about the molecular organization of the PDE6 holoenzyme (αβγγ). Here, we characterize the PDE6 holoenzyme by integrative structural determination of the PDE6 catalytic dimer (αβ), based primarily on chemical cross-linking and mass spectrometric analysis. Our models built from high-density cross-linking data elucidate a parallel organization of the two catalytic subunits, with juxtaposed α-helical segments within the tandem regulatory GAF domains to provide multiple sites for dimerization. The two catalytic domains exist in an open configuration when compared to the structure of PDE2 in the apo state. Detailed structural elements for differential binding of the γ-subunit to the GAFa domains of the α- and β-subunits are revealed, providing insight into the regulation of the PDE6 activation/deactivation cycle.
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Affiliation(s)
- Xiaohui Zeng-Elmore
- Department of Molecular, Cellular & Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA; Hubbard Center for Genome Studies, University of New Hampshire, Durham, NH 03824, USA
| | - Xiong-Zhuo Gao
- Department of Molecular, Cellular & Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
| | - Riccardo Pellarin
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA
| | - Dina Schneidman-Duhovny
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA
| | - Xiu-Jun Zhang
- Department of Molecular, Cellular & Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
| | - Katie A Kozacka
- Department of Molecular, Cellular & Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
| | - Yang Tang
- Department of Molecular, Cellular & Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA; Hubbard Center for Genome Studies, University of New Hampshire, Durham, NH 03824, USA
| | - Andrej Sali
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA; Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143, USA; California Institute for Quantitative Biosciences, University of California, San Francisco, CA 94158, USA
| | - Robert J Chalkley
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143, USA
| | - Rick H Cote
- Department of Molecular, Cellular & Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
| | - Feixia Chu
- Department of Molecular, Cellular & Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA; Hubbard Center for Genome Studies, University of New Hampshire, Durham, NH 03824, USA.
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Otero C, Peñaloza JP, Rodas PI, Fernández-Ramires R, Velasquez L, Jung JE. Temporal and spatial regulation of cAMP signaling in disease: role of cyclic nucleotide phosphodiesterases. Fundam Clin Pharmacol 2014; 28:593-607. [PMID: 24750474 DOI: 10.1111/fcp.12080] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 03/28/2014] [Accepted: 04/17/2014] [Indexed: 01/19/2023]
Abstract
Since its discovery, cAMP has been proposed as one of the most versatile second messengers. The remarkable feature of cAMP to tightly control highly diverse physiological processes, including metabolism, homeostasis, secretion, muscle contraction, cell proliferation and migration, immune response, and gene transcription, is reflected by millions of different articles worldwide. Compartmentalization of cAMP in space and time, maintained by mainly phosphodiesterases, contributes to the maintenance of equilibrium inside the cell where one signal can trigger many different events. Novel cAMP sensors seem to carry out certain unexpected signaling properties of cAMP and thereby to permit delicate adaptations of biologic responses. Measuring space and time events with biosensors will increase our current knowledge on the pathophysiology of diseases, such as chronic obstructive pulmonary disease, asthma, cognitive impairment, cancer, and renal and heart failure. Further insights into the cAMP dynamics will help to optimize the pharmacological treatment for these diseases.
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Affiliation(s)
- Carolina Otero
- Center for Integrative Medicine and Innovative Science, Universidad Andres Bello, Santiago, Chile; Centro para el Desarrollo de la Nanociencia y Nanotecnologia, Santiago, Chile
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Abstract
Photoreceptors adapt to changes in illumination by altering transduction kinetics and sensitivity, thereby extending their working range. We describe a previously unknown form of rod photoreceptor adaptation in wild-type (WT) mice that manifests as a potentiation of the light response after periods of conditioning light exposure. We characterize the stimulus conditions that evoke this graded hypersensitivity and examine the molecular mechanisms of adaptation underlying the phenomenon. After exposure to periods of saturating illumination, rods show a 10-35% increase in circulating dark current, an adaptive potentiation (AP) to light exposure. This potentiation grows as exposure to light is extended up to 3 min and decreases with longer exposures. Cells return to their initial dark-adapted sensitivity with a time constant of recovery of ∼7 s. Halving the extracellular Mg concentration prolongs the adaptation, increasing the time constant of recovery to 13.3 s, but does not affect the magnitude of potentiation. In rods lacking guanylate cyclase activating proteins 1 and 2 (GCAP(-/-)), AP is more than doubled compared with WT rods, and halving the extracellular Mg concentration does not affect the recovery time constant. Rods from a mouse expressing cyclic nucleotide-gated channels incapable of binding calmodulin also showed a marked increase in the amplitude of AP. Application of an insulin-like growth factor-1 receptor (IGF-1R) kinase inhibitor (Tyrphostin AG1024) blocked AP, whereas application of an insulin receptor kinase inhibitor (HNMPA(AM)3) failed to do so. A broad-acting tyrosine phosphatase inhibitor (orthovanadate) also blocked AP. Our findings identify a unique form of adaptation in photoreceptors, so that they show transient hypersensitivity to light, and are consistent with a model in which light history, acting via the IGF-1R, can increase the sensitivity of rod photoreceptors, whereas the photocurrent overshoot is regulated by Ca-calmodulin and Ca(2+)/Mg(2+)-sensitive GCAPs.
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Affiliation(s)
- Alex S McKeown
- Department of Vision Sciences, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Timothy W Kraft
- Department of Vision Sciences, University of Alabama at Birmingham, Birmingham, AL 35294
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Manes G, Cheguru P, Majumder A, Bocquet B, Sénéchal A, Artemyev NO, Hamel CP, Brabet P. A truncated form of rod photoreceptor PDE6 β-subunit causes autosomal dominant congenital stationary night blindness by interfering with the inhibitory activity of the γ-subunit. PLoS One 2014; 9:e95768. [PMID: 24760071 PMCID: PMC3997432 DOI: 10.1371/journal.pone.0095768] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 03/31/2014] [Indexed: 11/25/2022] Open
Abstract
Autosomal dominant congenital stationary night blindness (adCSNB) is caused by mutations in three genes of the rod phototransduction cascade, rhodopsin (RHO), transducin α-subunit (GNAT1), and cGMP phosphodiesterase type 6 β-subunit (PDE6B). In most cases, the constitutive activation of the phototransduction cascade is a prerequisite to cause adCSNB. The unique adCSNB-associated PDE6B mutation found in the Rambusch pedigree, the substitution p.His258Asn, leads to rod photoreceptors desensitization. Here, we report a three-generation French family with adCSNB harboring a novel PDE6B mutation, the duplication, c.928-9_940dup resulting in a tyrosine to cysteine substitution at codon 314, a frameshift, and a premature termination (p.Tyr314Cysfs*50). To understand the mechanism of the PDE6β1-314fs*50 mutant, we examined the properties of its PDE6-specific portion, PDE6β1-313. We found that PDE6β1-313 maintains the ability to bind noncatalytic cGMP and the inhibitory γ-subunit (Pγ), and interferes with the inhibition of normal PDE6αβ catalytic subunits by Pγ. Moreover, both truncated forms of the PDE6β protein, PDE6β1-313 and PDE6β1-314fs*50 expressed in rods of transgenic X. laevis are targeted to the phototransduction compartment. We hypothesize that in affected family members the p.Tyr314Cysfs*50 change results in the production of the truncated protein, which binds Pγ and causes constitutive activation of the phototransduction thus leading to the absence of rod adaptation.
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Affiliation(s)
- Gaël Manes
- Inserm U1051, Institute for Neurosciences of Montpellier, Montpellier, France; University of Montpellier 1, Montpellier, France; University of Montpellier 2, Montpellier, France
| | - Pallavi Cheguru
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, United States of America
| | - Anurima Majumder
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, United States of America
| | - Béatrice Bocquet
- Inserm U1051, Institute for Neurosciences of Montpellier, Montpellier, France; University of Montpellier 1, Montpellier, France; University of Montpellier 2, Montpellier, France
| | - Audrey Sénéchal
- Inserm U1051, Institute for Neurosciences of Montpellier, Montpellier, France; University of Montpellier 1, Montpellier, France; University of Montpellier 2, Montpellier, France
| | - Nikolai O Artemyev
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, United States of America; Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa, United States of America
| | - Christian P Hamel
- Inserm U1051, Institute for Neurosciences of Montpellier, Montpellier, France; University of Montpellier 1, Montpellier, France; University of Montpellier 2, Montpellier, France; CHRU, Genetics of Sensory Diseases, Montpellier, France
| | - Philippe Brabet
- Inserm U1051, Institute for Neurosciences of Montpellier, Montpellier, France; University of Montpellier 1, Montpellier, France; University of Montpellier 2, Montpellier, France
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Azevedo MF, Faucz FR, Bimpaki E, Horvath A, Levy I, de Alexandre RB, Ahmad F, Manganiello V, Stratakis CA. Clinical and molecular genetics of the phosphodiesterases (PDEs). Endocr Rev 2014; 35:195-233. [PMID: 24311737 PMCID: PMC3963262 DOI: 10.1210/er.2013-1053] [Citation(s) in RCA: 196] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 11/06/2013] [Indexed: 12/31/2022]
Abstract
Cyclic nucleotide phosphodiesterases (PDEs) are enzymes that have the unique function of terminating cyclic nucleotide signaling by catalyzing the hydrolysis of cAMP and GMP. They are critical regulators of the intracellular concentrations of cAMP and cGMP as well as of their signaling pathways and downstream biological effects. PDEs have been exploited pharmacologically for more than half a century, and some of the most successful drugs worldwide today affect PDE function. Recently, mutations in PDE genes have been identified as causative of certain human genetic diseases; even more recently, functional variants of PDE genes have been suggested to play a potential role in predisposition to tumors and/or cancer, especially in cAMP-sensitive tissues. Mouse models have been developed that point to wide developmental effects of PDEs from heart function to reproduction, to tumors, and beyond. This review brings together knowledge from a variety of disciplines (biochemistry and pharmacology, oncology, endocrinology, and reproductive sciences) with emphasis on recent research on PDEs, how PDEs affect cAMP and cGMP signaling in health and disease, and what pharmacological exploitations of PDEs may be useful in modulating cyclic nucleotide signaling in a way that prevents or treats certain human diseases.
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Affiliation(s)
- Monalisa F Azevedo
- Section on Endocrinology Genetics (M.F.A., F.R.F., E.B., A.H., I.L., R.B.d.A., C.A.S.), Program on Developmental Endocrinology Genetics, Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD), National Institutes of Health (NIH), Bethesda, Maryland 20892; Section of Endocrinology (M.F.A.), University Hospital of Brasilia, Faculty of Medicine, University of Brasilia, Brasilia 70840-901, Brazil; Group for Advanced Molecular Investigation (F.R.F., R.B.d.A.), Graduate Program in Health Science, Medical School, Pontificia Universidade Catolica do Paraná, Curitiba 80215-901, Brazil; Cardiovascular Pulmonary Branch (F.A., V.M.), National Heart, Lung, and Blood Institute, NIH, Bethesda, Maryland 20892; and Pediatric Endocrinology Inter-Institute Training Program (C.A.S.), NICHD, NIH, Bethesda, Maryland 20892
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Goldstein O, Mezey JG, Schweitzer PA, Boyko AR, Gao C, Bustamante CD, Jordan JA, Aguirre GD, Acland GM. IQCB1 and PDE6B mutations cause similar early onset retinal degenerations in two closely related terrier dog breeds. Invest Ophthalmol Vis Sci 2013; 54:7005-19. [PMID: 24045995 DOI: 10.1167/iovs.13-12915] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To identify the causative mutations in two early-onset canine retinal degenerations, crd1 and crd2, segregating in the American Staffordshire terrier and the Pit Bull Terrier breeds, respectively. METHODS Retinal morphology of crd1- and crd2-affected dogs was evaluated by light microscopy. DNA was extracted from affected and related unaffected controls. Association analysis was undertaken using the Illumina Canine SNP array and PLINK (crd1 study), or the Affymetrix Version 2 Canine array, the "MAGIC" genotype algorithm, and Fisher's Exact test for association (crd2 study). Positional candidate genes were evaluated for each disease. RESULTS Structural photoreceptor abnormalities were observed in crd1-affected dogs as young as 11-weeks old. Rod and cone inner segment (IS) and outer segments (OS) were abnormal in size, shape, and number. In crd2-affected dogs, rod and cone IS and OS were abnormal as early as 3 weeks of age, progressing with age to severe loss of the OS, and thinning of the outer nuclear layer (ONL) by 12 weeks of age. Genome-wide association study (GWAS) identified association at the telomeric end of CFA3 in crd1-affected dogs and on CFA33 in crd2-affected dogs. Candidate gene evaluation identified a three bases deletion in exon 21 of PDE6B in crd1-affected dogs, and a cytosine insertion in exon 10 of IQCB1 in crd2-affected dogs. CONCLUSIONS Identification of the mutations responsible for these two early-onset retinal degenerations provides new large animal models for comparative disease studies and evaluation of potential therapeutic approaches for the homologous human diseases.
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Affiliation(s)
- Orly Goldstein
- Baker Institute for Animal Health, Cornell University College of Veterinary Medicine, Ithaca, New York
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Atypical retinal degeneration 3 in mice is caused by defective PDE6B pre-mRNA splicing. Vision Res 2012; 57:1-8. [PMID: 22326271 DOI: 10.1016/j.visres.2012.01.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Revised: 01/20/2012] [Accepted: 01/26/2012] [Indexed: 01/23/2023]
Abstract
Mutations in the key rod phototransduction enzyme phosphodiesterase 6 (PDE6) are known to cause recessive retinitis pigmentosa in humans. Mouse models of mutant PDE6 represent a common approach to understanding the mechanisms of visual disorders related to PDE6 defects. Mutation N605S in the PDE6B subunit is linked to atypical retinal degeneration 3 (atrd3) in mice. We examined PDE6 in atrd3 mice and an atrd3 mutant counterpart of human cone PDE6C expressed in rods of transgenic Xenopus laevis. These animal models revealed remarkably different phenotypes. In contrast to dramatic downregulation of the mutant rod PDE6 protein and activity levels in mice, expression and localization of the cone PDE6C in X. laevis were essentially unaffected by this mutation. Examination of the PDE6B mRNA in atrd3 retina showed that the mutation-carrying exon 14 was spliced-out in the majority of the transcript. Thus, retinal degeneration in atrd3 mice is caused by low levels of PDE6 protein due to defective processing of PDE6B pre-mRNA rather than by deleterious effects of the N605S mutation on PDE6 folding, stability or function.
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Proteomic identification of RREB1, PDE6B, and CD209 up-regulated in primitive gut tube differentiated from human embryonic stem cells. Pancreas 2012; 41:65-73. [PMID: 21792086 DOI: 10.1097/mpa.0b013e3182223e35] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
OBJECTIVES This study aimed to identify proteins important for the primitive gut tube differentiation from human embryonic stem cells (hESCs) by derivation method for pancreatic cells. METHODS Proteins with altered expression levels in the process of differentiating to primitive gut tube from definitive endoderm of hESCs were investigated by comparative proteomic analysis using 2-dimensional gel electrophoresis and mass spectrometric analyses. RESULTS Differentiation to primitive gut tube from hESCs was analyzed using differentiation marker genes and proteins. Twenty-seven protein spots with significant changes in intensity were found by 2-dimensional gel electrophoresis, and 24 proteins were further identified. These proteins were functionally annotated based on gene ontology. The expression levels of 3 proteins, RREB1, PDE6B, and CD209, involved in signal transduction, were validated using quantitative reverse transcription-polymerase chain reaction and Western blot. Their mRNA and protein expression levels increased in primitive gut tube but not in definitive endoderm or embryonic body. CONCLUSIONS The increase in expression of RREB1, PDE6B, and CD209 suggests that these proteins might play important roles in the differentiation of primitive gut tube cells from hESCs and in human primitive gut tube development into pancreas. Therefore, they could be developed as differentiation markers for identifying primitive gut tube cells.
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Peiró AM, Tang CM, Murray F, Zhang L, Brown LM, Chou D, Rassenti L, Kipps TJ, Kipps TA, Insel PA. Genetic variation in phosphodiesterase (PDE) 7B in chronic lymphocytic leukemia: overview of genetic variants of cyclic nucleotide PDEs in human disease. J Hum Genet 2011; 56:676-81. [PMID: 21796143 DOI: 10.1038/jhg.2011.80] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Expression of cyclic adenosine monophosphate-specific phosphodiesterase 7B (PDE7B) mRNA is increased in patients with chronic lymphocytic leukemia (CLL), thus suggesting that variation may occur in the PDE7B gene in CLL. As genetic variation in other PDE family members has been shown to associate with numerous clinical disorders (reviewed in this manuscript), we sought to identify single-nucleotide polymorphisms (SNPs) in the PDE7B gene promoter and coding region of 93 control subjects and 154 CLL patients. We found that the PDE7B gene has a 5' non-coding region SNP -347C>T that occurs with similar frequency in CLL patients (1.9%) and controls (2.7%). Tested in vitro, -347C>T has less promoter activity than a wild-type construct. The low frequency of this 5' untranslated region variant indicates that it does not explain the higher PDE7B expression in patients with CLL but it has the potential to influence other settings that involve a role for PDE7B.
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Affiliation(s)
- Ana M Peiró
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093-0636, USA
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Riazuddin SA, Shahzadi A, Zeitz C, Ahmed ZM, Ayyagari R, Chavali VR, Ponferrada VG, Audo I, Michiels C, Lancelot ME, Nasir IA, Zafar AU, Khan SN, Husnain T, Jiao X, MacDonald IM, Riazuddin S, Sieving PA, Katsanis N, Hejtmancik JF. A mutation in SLC24A1 implicated in autosomal-recessive congenital stationary night blindness. Am J Hum Genet 2010; 87:523-31. [PMID: 20850105 DOI: 10.1016/j.ajhg.2010.08.013] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 08/03/2010] [Accepted: 08/26/2010] [Indexed: 10/19/2022] Open
Abstract
Congenital stationary night blindness (CSNB) is a nonprogressive retinal disorder that can be associated with impaired night vision. The last decade has witnessed huge progress in ophthalmic genetics, including the identification of three genes implicated in the pathogenicity of autosomal-recessive CSNB. However, not all patients studied could be associated with mutations in these genes and thus other genes certainly underlie this disorder. Here, we report a large multigeneration family with five affected individuals manifesting symptoms of night blindness. A genome-wide scan localized the disease interval to chromosome 15q, and recombination events in affected individuals refined the critical interval to a 10.41 cM (6.53 Mb) region that harbors SLC24A1, a member of the solute carrier protein superfamily. Sequencing of all the coding exons identified a 2 bp deletion in exon 2: c.1613_1614del, which is predicted to result in a frame shift that leads to premature termination of SLC24A1 (p.F538CfsX23) and segregates with the disorder under an autosomal-recessive model. Expression analysis using mouse ocular tissues shows that Slc24a1 is expressed in the retina around postnatal day 7. In situ and immunohistological studies localized both SLC24A1 and Slc24a1 to the inner segment, outer and inner nuclear layers, and ganglion cells of the retina, respectively. Our data expand the genetic basis of CSNB and highlight the indispensible function of SLC24A1 in retinal function and/or maintenance in humans.
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Dvir L, Srour G, Abu-Ras R, Miller B, Shalev SA, Ben-Yosef T. Autosomal-recessive early-onset retinitis pigmentosa caused by a mutation in PDE6G, the gene encoding the gamma subunit of rod cGMP phosphodiesterase. Am J Hum Genet 2010; 87:258-64. [PMID: 20655036 DOI: 10.1016/j.ajhg.2010.06.016] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2010] [Revised: 06/21/2010] [Accepted: 06/23/2010] [Indexed: 11/28/2022] Open
Abstract
Retinitis pigmentosa (RP) is the most common form of hereditary retinal degeneration, with a worldwide prevalence of 1 in 4000. Over 30 genes and loci have been implicated in nonsyndromic autosomal-recessive (ar) RP. Genome-wide homozygosity mapping was conducted in two sibships from an extended consanguineous Muslim Arab Israeli family segregating ar severe early-onset RP. A shared homozygous region on chromosome 17q25.3 was identified in both sibships, with an overlap of 4.7 Mb. One of the genes located in this interval is PDE6G, encoding for the inhibitory gamma subunit of rod photoreceptor cyclic GMP-phosphodiesterase. Mutations in the genes encoding for the catalytic subunits of this holoenzyme, PDE6A and PDE6B, cause arRP. Sequencing of all coding exons, including exon-intron boundaries, revealed a homozygous single base change (c.187+1G>T) located in the conserved intron 3 donor splice site of PDE6G. This mutation cosegregated with the disease in the extended family. We used an in vitro splicing assay to demonstrate that this mutation leads to incorrect splicing. Affected individuals had markedly constricted visual fields. Both scotopic and photopic electroretinograms were severely reduced or completely extinct. Funduscopy showed typical bone spicule-type pigment deposits spread mainly at the midperiphery, as well as pallor of the optic disk. Macular involvement was indicated by the lack of foveal reflex and typical cystoid macular edema, proved by optical coherence tomography. These findings demonstrate the positive role of the gamma subunit in maintaining phosphodiesterase activity and confirm the contribution of PDE6G to the etiology of RP in humans.
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Affiliation(s)
- Liron Dvir
- Rappaport Family Institute for Research in the Medical Sciences, Haifa 31096, Israel
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Berger W, Kloeckener-Gruissem B, Neidhardt J. The molecular basis of human retinal and vitreoretinal diseases. Prog Retin Eye Res 2010; 29:335-75. [PMID: 20362068 DOI: 10.1016/j.preteyeres.2010.03.004] [Citation(s) in RCA: 404] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
During the last two to three decades, a large body of work has revealed the molecular basis of many human disorders, including retinal and vitreoretinal degenerations and dysfunctions. Although belonging to the group of orphan diseases, they affect probably more than two million people worldwide. Most excitingly, treatment of a particular form of congenital retinal degeneration is now possible. A major advantage for treatment is the unique structure and accessibility of the eye and its different components, including the vitreous and retina. Knowledge of the many different eye diseases affecting retinal structure and function (night and colour blindness, retinitis pigmentosa, cone and cone rod dystrophies, photoreceptor dysfunctions, as well as vitreoretinal traits) is critical for future therapeutic development. We have attempted to present a comprehensive picture of these disorders, including biological, clinical, genetic and molecular information. The structural organization of the review leads the reader through non-syndromic and syndromic forms of (i) rod dominated diseases, (ii) cone dominated diseases, (iii) generalized retinal degenerations and (iv) vitreoretinal disorders, caused by mutations in more than 165 genes. Clinical variability and genetic heterogeneity have an important impact on genetic testing and counselling of affected families. As phenotypes do not always correlate with the respective genotypes, it is of utmost importance that clinicians, geneticists, counsellors, diagnostic laboratories and basic researchers understand the relationships between phenotypic manifestations and specific genes, as well as mutations and pathophysiologic mechanisms. We discuss future perspectives.
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Affiliation(s)
- Wolfgang Berger
- Division of Medical Molecular Genetics and Gene Diagnostics, Institute of Medical Genetics, University of Zurich, Schorenstrasse 16, CH-8603 Schwerzenbach, Switzerland.
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Is the lifetime of light-stimulated cGMP phosphodiesterase regulated by recoverin through its regulation of rhodopsin phosphorylation? Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00039522] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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