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Takita S, Jahan S, Imanishi S, Harikrishnan H, LePage D, Mann RJ, Conlon RA, Miyagi M, Imanishi Y. Rhodopsin mislocalization drives ciliary dysregulation in a novel autosomal dominant retinitis pigmentosa knock-in mouse model. FASEB J 2024; 38:e23606. [PMID: 38648465 PMCID: PMC11047207 DOI: 10.1096/fj.202302260rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 03/22/2024] [Accepted: 03/29/2024] [Indexed: 04/25/2024]
Abstract
Rhodopsin mislocalization encompasses various blind conditions. Rhodopsin mislocalization is the primary factor leading to rod photoreceptor dysfunction and degeneration in autosomal dominant retinitis pigmentosa (adRP) caused by class I mutations. In this study, we report a new knock-in mouse model that harbors a class I Q344X mutation in the endogenous rhodopsin gene, which causes rod photoreceptor degeneration in an autosomal dominant pattern. In RhoQ344X/+ mice, mRNA transcripts from the wild-type (Rho) and RhoQ344X mutant rhodopsin alleles are expressed at equal levels. However, the amount of RHOQ344X mutant protein is 2.7 times lower than that of wild-type rhodopsin, a finding consistent with the rapid degradation of the mutant protein. Immunofluorescence microscopy indicates that RHOQ344X is mislocalized to the inner segment and outer nuclear layers of rod photoreceptors in both RhoQ344X/+ and RhoQ344X/Q344X mice, confirming the essential role of the C-terminal VxPx motif in promoting OS delivery of rhodopsin. The mislocalization of RHOQ344X is associated with the concurrent mislocalization of wild-type rhodopsin in RhoQ344X/+ mice. To understand the global changes in proteostasis, we conducted quantitative proteomics analysis and found attenuated expression of rod-specific OS membrane proteins accompanying reduced expression of ciliopathy causative gene products, including constituents of BBSome and axonemal dynein subunit. Those studies unveil a novel negative feedback regulation involving ciliopathy-associated proteins. In this process, a defect in the trafficking signal leads to a reduced quantity of the trafficking apparatus, culminating in a widespread reduction in the transport of ciliary proteins.
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Affiliation(s)
- Shimpei Takita
- Department of Ophthalmology, Eugene and Marilyn Glick Eye Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Sultana Jahan
- Department of Ophthalmology, Eugene and Marilyn Glick Eye Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Sanae Imanishi
- Department of Ophthalmology, Eugene and Marilyn Glick Eye Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Hemavathy Harikrishnan
- Department of Ophthalmology, Eugene and Marilyn Glick Eye Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - David LePage
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Rachel J. Mann
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Ronald A. Conlon
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Masaru Miyagi
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Yoshikazu Imanishi
- Department of Ophthalmology, Eugene and Marilyn Glick Eye Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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2
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Hollingsworth TJ, Wang X, White WA, Simpson RN, Jablonski MM. Chronic Proinflammatory Signaling Accelerates the Rate of Degeneration in a Spontaneous Polygenic Model of Inherited Retinal Dystrophy. Front Pharmacol 2022; 13:839424. [PMID: 35387333 PMCID: PMC8978607 DOI: 10.3389/fphar.2022.839424] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 02/21/2022] [Indexed: 11/18/2022] Open
Abstract
Collectively, retinal neurodegenerative diseases are comprised of numerous subtypes of disorders which result in loss of a varying cell types in the retina. These diseases can range from glaucoma, which results in retinal ganglion cell death, to age-related macular degeneration and retinitis pigmentosa, which result in cell death of the retinal pigment epithelium, photoreceptors, or both. Regardless of the disease, it’s been recently found that increased release of proinflammatory cytokines and proliferation of active microglia result in a remarkably proinflammatory microenvironment that assists in the pathogenesis of the disease; however, many of the details of these inflammatory events have yet to be elucidated. In an ongoing study, we have used systems genetics to identify possible models of spontaneous polygenic age-related macular degeneration by mining the BXD family of mice using single nucleotide polymorphism analyses of known genes associated with the human retinal disease. One BXD strain (BXD32) was removed from the study as the rate of degeneration observed in these animals was markedly increased with a resultant loss of most all photoreceptors by 6 months of age. Using functional and anatomical exams including optokinetic nystamography, funduscopy, fluorescein angiography, and optical coherence tomography, along with immunohistochemical analyses, we show that the BXD32 mouse strain exhibits a severe neurodegenerative phenotype accompanied by adverse effects on the retinal vasculature. We also expose the concurrent establishment of a chronic proinflammatory microenvironment including the TNFα secretion and activation of the NF-κB and JAK/STAT pathways with an associated increase in activated macrophages and phagoptosis. We conclude that the induced neuronal death and proinflammatory pathways work synergistically in the disease pathogenesis to enhance the rate of degeneration in this spontaneous polygenic model of inherited retinal dystrophy.
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Affiliation(s)
- T J Hollingsworth
- Hamilton Eye Institute, Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, TN, United States.,Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Xiangdi Wang
- Hamilton Eye Institute, Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, TN, United States
| | - William A White
- Hamilton Eye Institute, Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Raven N Simpson
- Hamilton Eye Institute, Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Monica M Jablonski
- Hamilton Eye Institute, Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, TN, United States.,Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, United States.,Department of Pharmaceutical Sciences, University of Tennessee Health Science Center, Memphis, TN, United States.,Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, United States
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Proinflammatory Pathways Are Activated in the Human Q344X Rhodopsin Knock-In Mouse Model of Retinitis Pigmentosa. Biomolecules 2021; 11:biom11081163. [PMID: 34439829 PMCID: PMC8393353 DOI: 10.3390/biom11081163] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 07/17/2021] [Accepted: 08/03/2021] [Indexed: 12/27/2022] Open
Abstract
Retinitis pigmentosa (RP) is a hereditary disease of the retina that results in complete blindness. Currently, there are very few treatments for the disease and those that exist work only for the recessively inherited forms. To better understand the pathogenesis of RP, multiple mouse models have been generated bearing mutations found in human patients including the human Q344X rhodopsin knock-in mouse. In recent years, the immune system was shown to play an increasingly important role in RP degeneration. By way of electroretinography, optical coherence tomography, funduscopy, fluorescein angiography, and fluorescent immunohistochemistry, we show degenerative and vascular phenotypes, microglial activation, photoreceptor phagocytosis, and upregulation of proinflammatory pathway proteins in the retinas of the human Q344X rhodopsin knock-in mouse. We also show that an FDA-approved pharmacological agent indicated for the treatment of rheumatoid arthritis is able to halt activation of pro-inflammatory signaling in cultured retinal cells, setting the stage for pre-clinical trials using these mice to inhibit proinflammatory signaling in an attempt to preserve vision. We conclude from this work that pro- and autoinflammatory upregulation likely act to enhance the progression of the degenerative phenotype of rhodopsin Q344X-mediated RP and that inhibition of these pathways may lead to longer-lasting vision in not only the Q344X rhodopsin knock-in mice, but humans as well.
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Ganzen L, Ko MJ, Zhang M, Xie R, Chen Y, Zhang L, James R, Mumm J, van Rijn RM, Zhong W, Pang CP, Zhang M, Tsujikawa M, Leung YF. Drug screening with zebrafish visual behavior identifies carvedilol as a potential treatment for an autosomal dominant form of retinitis pigmentosa. Sci Rep 2021; 11:11432. [PMID: 34075074 PMCID: PMC8169685 DOI: 10.1038/s41598-021-89482-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 04/23/2021] [Indexed: 02/04/2023] Open
Abstract
Retinitis Pigmentosa (RP) is a mostly incurable inherited retinal degeneration affecting approximately 1 in 4000 individuals globally. The goal of this work was to identify drugs that can help patients suffering from the disease. To accomplish this, we screened drugs on a zebrafish autosomal dominant RP model. This model expresses a truncated human rhodopsin transgene (Q344X) causing significant rod degeneration by 7 days post-fertilization (dpf). Consequently, the larvae displayed a deficit in visual motor response (VMR) under scotopic condition. The diminished VMR was leveraged to screen an ENZO SCREEN-WELL REDOX library since oxidative stress is postulated to play a role in RP progression. Our screening identified a beta-blocker, carvedilol, that ameliorated the deficient VMR of the RP larvae and increased their rod number. Carvedilol may directly on rods as it affected the adrenergic pathway in the photoreceptor-like human Y79 cell line. Since carvedilol is an FDA-approved drug, our findings suggest that carvedilol can potentially be repurposed to treat autosomal dominant RP patients.
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Affiliation(s)
- Logan Ganzen
- grid.169077.e0000 0004 1937 2197Department of Biological Sciences, Purdue University, West Lafayette, IN 47907 USA ,grid.169077.e0000 0004 1937 2197Purdue University Life Sciences Program, Purdue University, West Lafayette, IN 47907 USA
| | - Mee Jung Ko
- grid.169077.e0000 0004 1937 2197Purdue University Life Sciences Program, Purdue University, West Lafayette, IN 47907 USA ,grid.169077.e0000 0004 1937 2197Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907 USA
| | - Mengrui Zhang
- grid.213876.90000 0004 1936 738XDepartment of Statistics, University of Georgia, Athens, GA 30602 USA
| | - Rui Xie
- grid.170430.10000 0001 2159 2859Department of Statistics and Data Science, University of Central Florida, Orlando, FL 32816 USA
| | - Yongkai Chen
- grid.213876.90000 0004 1936 738XDepartment of Statistics, University of Georgia, Athens, GA 30602 USA
| | - Liyun Zhang
- grid.21107.350000 0001 2171 9311Wilmer Eye Institute, John Hopkins School of Medicine, Baltimore, MD 21205 USA
| | - Rebecca James
- grid.169077.e0000 0004 1937 2197Department of Biological Sciences, Purdue University, West Lafayette, IN 47907 USA
| | - Jeff Mumm
- grid.21107.350000 0001 2171 9311Wilmer Eye Institute, John Hopkins School of Medicine, Baltimore, MD 21205 USA
| | - Richard M. van Rijn
- grid.169077.e0000 0004 1937 2197Purdue University Life Sciences Program, Purdue University, West Lafayette, IN 47907 USA ,grid.169077.e0000 0004 1937 2197Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907 USA ,grid.169077.e0000 0004 1937 2197Purdue Institute for Integrative Neuroscience, Purdue University, 610 Purdue Mall, West Lafayette, IN 47907 USA ,grid.169077.e0000 0004 1937 2197Purdue Institute for Drug Discovery, Purdue University, 610 Purdue Mall, West Lafayette, IN 47907 USA
| | - Wenxuan Zhong
- grid.213876.90000 0004 1936 738XDepartment of Statistics, University of Georgia, Athens, GA 30602 USA
| | - Chi Pui Pang
- grid.10784.3a0000 0004 1937 0482Department of Ophthalmology and Visual Sciences, Chinese University of Hong Kong, Hong Kong, China ,grid.263451.70000 0000 9927 110XJoint Shantou International Eye Center, Shantou University and the Chinese University of Hong Kong, Shantou, China
| | - Mingzhi Zhang
- grid.263451.70000 0000 9927 110XJoint Shantou International Eye Center, Shantou University and the Chinese University of Hong Kong, Shantou, China
| | - Motokazu Tsujikawa
- grid.136593.b0000 0004 0373 3971Department of Ophthalmology, Osaka University Graduate School of Medicine, Osaka, Japan ,grid.136593.b0000 0004 0373 3971Department of Clinical Laboratory and Biomedical Sciences, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Yuk Fai Leung
- grid.169077.e0000 0004 1937 2197Department of Biological Sciences, Purdue University, West Lafayette, IN 47907 USA ,grid.257413.60000 0001 2287 3919Department of Biochemistry and Molecular Biology, Indiana University School of Medicine Lafayette, 625 Harrison Street, West Lafayette, IN 47907 USA ,grid.169077.e0000 0004 1937 2197Purdue Institute for Integrative Neuroscience, Purdue University, 610 Purdue Mall, West Lafayette, IN 47907 USA ,grid.169077.e0000 0004 1937 2197Purdue Institute for Drug Discovery, Purdue University, 610 Purdue Mall, West Lafayette, IN 47907 USA
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Bales KL, Bentley MR, Croyle MJ, Kesterson RA, Yoder BK, Gross AK. BBSome Component BBS5 Is Required for Cone Photoreceptor Protein Trafficking and Outer Segment Maintenance. Invest Ophthalmol Vis Sci 2020; 61:17. [PMID: 32776140 PMCID: PMC7441369 DOI: 10.1167/iovs.61.10.17] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 07/15/2020] [Indexed: 01/07/2023] Open
Abstract
Purpose To identify the role of the BBSome protein Bardet-Biedl syndrome 5 (BBS5) in photoreceptor function, protein trafficking, and structure using a congenital mutant mouse model. Methods Bbs5-/- mice (2 and 9 months old) were used to assess retinal function and morphology. Hematoxylin and eosin staining of retinal sections was performed to visualize histology. Electroretinography was used to analyze rod and cone photoreceptor function. Retinal protein localization was visualized using immunofluorescence (IF) within retinal cryosections. TUNEL staining was used to quantify cell death. Transmission electron microscopy (TEM) was used to examine retinal ultrastructure. Results In the Bbs5-/- retina, there was a significant loss of nuclei in the outer nuclear layer accompanied by an increase in cell death. Through electroretinography, Bbs5-/- mice showed complete loss of cone photoreceptor function. IF revealed mislocalization of the cone-specific proteins M- and S-opsins, arrestin-4, CNGA3, and GNAT2, as well as a light-dependent arrestin-1 mislocalization, although perpherin-2 was properly localized. TEM revealed abnormal outer segment disk orientation in Bbs5-/-. Conclusions Collectively, these data suggest that, although BBS5 is a core BBSome component expressed in all ciliated cells, its role within the retina mediates specific photoreceptor protein cargo transport. In the absence of BBS5, cone-specific protein mislocalization and a loss of cone photoreceptor function occur.
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Affiliation(s)
- Katie L. Bales
- Department of Optometry and Vision Sciences, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Melissa R. Bentley
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Mandy J. Croyle
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Robert A. Kesterson
- Department of Genetics, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Bradley K. Yoder
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Alecia K. Gross
- Department of Optometry and Vision Sciences, University of Alabama at Birmingham, Birmingham, Alabama, United States
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama, United States
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6
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Zelinka CP, Sotolongo-Lopez M, Fadool JM. Targeted disruption of the endogenous zebrafish rhodopsin locus as models of rapid rod photoreceptor degeneration. Mol Vis 2018; 24:587-602. [PMID: 30210230 PMCID: PMC6128699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2018] [Accepted: 08/24/2018] [Indexed: 12/05/2022] Open
Abstract
Purpose Retinitis pigmentosa (RP) is a collection of genetic disorders that results in the degeneration of light-sensitive photoreceptor cells, leading to blindness. RP is associated with more than 70 loci that may display dominant or recessive modes of inheritance, but mutations in the gene encoding the visual pigment rhodopsin (RHO) are the most frequent cause. In an effort to develop precise mutations in zebrafish as novel models of photoreceptor degeneration, we describe the generation and germline transmission of a series of novel clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-induced insertion and deletion (indel) mutations in the major zebrafish rho locus, rh1-1. Methods One- or two-cell staged zebrafish embryos were microinjected with in vitro transcribed mRNA encoding Cas9 and a single guide RNA (gRNA). Mutations were detected by restriction fragment length polymorphism (RFLP) and DNA sequence analyses in injected embryos and offspring. Immunolabeling with rod- and cone-specific antibodies was used to test for histological and cellular changes. Results Using gRNAs that targeted highly conserved regions of rh1-1, a series of dominant and recessive alleles were recovered that resulted in the rapid degeneration of rod photoreceptors. No effect on cones was observed. Targeting the 5'-coding sequence of rh1-1 led to the recovery of several indels similar to disease-associated alleles. A frame shift mutation leading to a premature stop codon (T17*) resulted in rod degeneration when brought to homozygosity. Immunoblot and fluorescence labeling with a Rho-specific antibody suggest that this is indeed a null allele, illustrating that the Rho expression is essential for rod survival. Two in-frame mutations were recovered that disrupted the highly conserved N-linked glycosylation consensus sequence at N15. Larvae heterozygous for either of the alleles demonstrated rapid rod degeneration. Targeting of the 3'-coding region of rh1-1 resulted in the recovery of an allele encoding a premature stop codon (S347*) upstream of the conserved VSPA sorting sequence and a second in-frame allele that disrupted the putative phosphorylation site at S339. Both alleles resulted in rod death in a dominant inheritance pattern. Following the loss of the targeting sequence, immunolabeling for Rho was no longer restricted to the rod outer segment, but it was also localized to the plasma membrane. Conclusions The efficiency of CRISPR/Cas9 for gene targeting, coupled with the large number of mutations associated with RP, provided a backdrop for the rapid isolation of novel alleles in zebrafish that phenocopy disease. These novel lines will provide much needed in-vivo models for high throughput screens of compounds or genes that protect from photoreceptor degeneration.
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Affiliation(s)
- Christopher P. Zelinka
- Department of Biological Science, Florida State University, Tallahassee, FL
- Program in Neuroscience, Florida State University, Tallahassee, FL
| | | | - James M. Fadool
- Department of Biological Science, Florida State University, Tallahassee, FL
- Program in Neuroscience, Florida State University, Tallahassee, FL
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Bales KL, Ianov L, Kennedy AJ, Sweatt JD, Gross AK. Autosomal dominant retinitis pigmentosa rhodopsin mutant Q344X drives specific alterations in chromatin complex gene transcription. Mol Vis 2018; 24:153-164. [PMID: 29463953 PMCID: PMC5815338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 02/13/2018] [Indexed: 10/25/2022] Open
Abstract
Purpose Epigenetic and transcriptional mechanisms have been shown to contribute to long-lasting functional changes in adult neurons. The purpose of this study was to identify any such modifications in diseased retinal tissues from a mouse model of rhodopsin mutation-associated autosomal dominant retinitis pigmentosa (ADRP), Q344X, relative to age-matched wild-type (WT) controls. Methods We performed RNA sequencing (RNA-seq) at poly(A) selected RNA to profile the transcriptional patterns in 3-week-old ADRP mouse model rhodopsin Q344X compared to WT controls. Differentially expressed genes were determined by DESeq2 using the Benjamini & Hochberg p value adjustment and an absolute log2 fold change cutoff. Quantitative western blots were conducted to evaluate protein expression levels of histone H3 phosphorylated at serine 10 and histone H4. qRT-PCR was performed to validate the expression patterns of differentially expressed genes. Results We observed significant differential expression in 2151 genes in the retina of Q344X mice compared to WT controls, including downregulation in the potassium channel gene, Kcnv2, and differential expression of histone genes, including the H1 family histone member, H1foo; the H3 histone family 3B, H3f3b; and the histone deacetylase 9, Hdac9. Quantitative western blots revealed statistically significant decreased protein expression of both histone H3 phosphorylated at serine 10 and histone H4 in 3-week-old Q344X retinas. Furthermore, qRT-PCR performed on select differentially expressed genes based on our RNA-seq results revealed matched expression patterns of up or downregulation. Conclusions These findings provide evidence that transcriptomic alterations occur in the ADRP mouse model rhodopsin Q344X retina and that these processes may contribute to the dysfunction and neurodegeneration seen in this animal model.
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Affiliation(s)
- Katie L. Bales
- School of Optometry, Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL
| | - Lara Ianov
- School of Medicine, Civitan International Research Center, University of Alabama at Birmingham, AL
| | - Andrew J. Kennedy
- Department of Chemistry and Biochemistry, Bates College, Lewiston, ME
| | - J. David Sweatt
- School of Medicine, Department of Pharmacology, Vanderbilt University, TN
| | - Alecia K. Gross
- School of Optometry, Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL,School of Medicine, Civitan International Research Center, University of Alabama at Birmingham, AL
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Bales KL, Gross AK. Aberrant protein trafficking in retinal degenerations: The initial phase of retinal remodeling. Exp Eye Res 2015; 150:71-80. [PMID: 26632497 DOI: 10.1016/j.exer.2015.11.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 11/04/2015] [Accepted: 11/09/2015] [Indexed: 12/18/2022]
Abstract
Retinal trafficking proteins are involved in molecular assemblies that govern protein transport, orchestrate cellular events involved in cilia formation, regulate signal transduction, autophagy and endocytic trafficking, all of which if not properly controlled initiate retinal degeneration. Improper function and or trafficking of these proteins and molecular networks they are involved in cause a detrimental cascade of neural retinal remodeling due to cell death, resulting as devastating blinding diseases. A universal finding in retinal degenerative diseases is the profound detection of retinal remodeling, occurring as a phased modification of neural retinal function and structure, which begins at the molecular level. Retinal remodeling instigated by aberrant trafficking of proteins encompasses many forms of retinal degenerations, such as the diverse forms of retinitis pigmentosa (RP) and disorders that resemble RP through mutations in the rhodopsin gene, retinal ciliopathies, and some forms of glaucoma and age-related macular degeneration (AMD). As a large majority of genes associated with these different retinopathies are overlapping, it is imperative to understand their underlying molecular mechanisms. This review will discuss some of the most recent discoveries in vertebrate retinal remodeling and retinal degenerations caused by protein mistrafficking.
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Affiliation(s)
- Katie L Bales
- University of Alabama at Birmingham, Birmingham, AL, United States
| | - Alecia K Gross
- University of Alabama at Birmingham, Birmingham, AL, United States.
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Roman-Sanchez R, Wensel TG, Wilson JH. Nonsense mutations in the rhodopsin gene that give rise to mild phenotypes trigger mRNA degradation in human cells by nonsense-mediated decay. Exp Eye Res 2015; 145:444-449. [PMID: 26416182 DOI: 10.1016/j.exer.2015.09.013] [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: 06/02/2015] [Revised: 08/20/2015] [Accepted: 09/22/2015] [Indexed: 02/02/2023]
Abstract
Eight different nonsense mutations in the human rhodopsin gene cause retinitis pigmentosa (RP), an inherited degenerative disease of the retina that can lead to complete blindness. Although all these nonsense mutations lead to premature termination codons (PTCs) in rhodopsin mRNA, some display dominant inheritance, while others are recessive. Because nonsense-mediated decay (NMD) can degrade mRNAs containing PTCs and modulate the inheritance patterns of genetic diseases, we asked whether any of the nonsense mutations in the rhodopsin gene generated mRNAs that were susceptible to degradation by NMD. We hypothesized that nonsense mutations that caused mild RP phenotypes would trigger NMD, whereas those that did not engage NMD would cause more severe RP phenotypes-presumably due to the toxicity of the truncated protein. To test our hypothesis, we transfected human rhodopsin nonsense mutants into HEK293 and HT1080 human cells and measured transcript levels by qRT-PCR. In both cell lines, rhodopsin mutations Q64X and Q344X, which cause severe phenotypes that are dominantly inherited, yielded the same levels of rhodopsin mRNA as wild type. By contrast, rhodopsin mutations W161X and E249X, which cause recessive RP, showed decreased rhodopsin mRNA levels, consistent with NMD. Rhodopsin mutant Y136X, a dominant mutation that causes late-onset RP with a very mild pathology, also gave lower mRNA levels. Treatment of cells with Wortmannin, an inhibitor of NMD, eliminated the degradation of Y136X, W161X, and E249X rhodopsin mRNAs. These results suggest that NMD modulates the severity of RP in patients with nonsense mutations in the rhodopsin gene.
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Affiliation(s)
- Ramon Roman-Sanchez
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA; Program in Integrative Molecular and Biomedical Sciences, Baylor College of Medicine, Houston, TX 77030, USA
| | - Theodore G Wensel
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA; Program in Integrative Molecular and Biomedical Sciences, Baylor College of Medicine, Houston, TX 77030, USA
| | - John H Wilson
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA; Program in Integrative Molecular and Biomedical Sciences, Baylor College of Medicine, Houston, TX 77030, USA.
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Ceredig RA, Massotte D. Fluorescent knock-in mice to decipher the physiopathological role of G protein-coupled receptors. Front Pharmacol 2015; 5:289. [PMID: 25610398 PMCID: PMC4284998 DOI: 10.3389/fphar.2014.00289] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 12/12/2014] [Indexed: 12/21/2022] Open
Abstract
G protein-coupled receptors (GPCRs) modulate most physiological functions but are also critically involved in numerous pathological states. Approximately a third of marketed drugs target GPCRs, which places this family of receptors in the main arena of pharmacological pre-clinical and clinical research. The complexity of GPCR function demands comprehensive appraisal in native environment to collect in-depth knowledge of receptor physiopathological roles and assess the potential of therapeutic molecules. Identifying neurons expressing endogenous GPCRs is therefore essential to locate them within functional circuits whereas GPCR visualization with subcellular resolution is required to get insight into agonist-induced trafficking. Both remain frequently poorly investigated because direct visualization of endogenous receptors is often hampered by the lack of appropriate tools. Also, monitoring intracellular trafficking requires real-time visualization to gather in-depth knowledge. In this context, knock-in mice expressing a fluorescent protein or a fluorescent version of a GPCR under the control of the endogenous promoter not only help to decipher neuroanatomical circuits but also enable real-time monitoring with subcellular resolution thus providing invaluable information on their trafficking in response to a physiological or a pharmacological challenge. This review will present the animal models and discuss their contribution to the understanding of the physiopathological role of GPCRs. We will also address the drawbacks associated with this methodological approach and browse future directions.
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Affiliation(s)
- Rhian A Ceredig
- CNRS, Institut des Neurosciences Cellulaires et Intégratives, UPR 3212 Strasbourg, France
| | - Dominique Massotte
- CNRS, Institut des Neurosciences Cellulaires et Intégratives, UPR 3212 Strasbourg, France
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Nucleotide bound to rab11a controls localization in rod cells but not interaction with rhodopsin. J Neurosci 2014; 34:14854-63. [PMID: 25378153 DOI: 10.1523/jneurosci.1943-14.2014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Precise vectorial transport of rhodopsin is essential for rod photoreceptor health and function. Mutations that truncate or extend the C terminus of rhodopsin disrupt this transport, and lead to retinal degeneration and blindness in human patients and in mouse models. Here we show that such mutations disrupt the binding of rhodopsin to the small GTPase rab11a. The rhodopsin-rab11a interaction is a direct binding interaction that does not depend on the nucleotide binding state of rab11a. Expression of EGFP-rab11a fusion proteins in Xenopus laevis photoreceptors revealed that the nucleotide binding status of rab11a affects its subcellular localization, with GTP-locked mutants concentrated in the inner segment and GDP-locked mutants concentrated in the outer segment. shRNA-mediated knockdown of rab11a in rods led to shortened outer segments and retinal degeneration. Together, our results show the critical importance of direct rhodopsin-rab11a interactions for the formation and maintenance of vertebrate photoreceptors.
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