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Haggerty KN, Eshelman SC, Sexton LA, Frimpong E, Rogers LM, Agosto MA, Robichaux MA. Super-resolution mapping in rod photoreceptors identifies rhodopsin trafficking through the inner segment plasma membrane as an essential subcellular pathway. PLoS Biol 2024; 22:e3002467. [PMID: 38190419 PMCID: PMC10773939 DOI: 10.1371/journal.pbio.3002467] [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: 05/12/2023] [Accepted: 12/10/2023] [Indexed: 01/10/2024] Open
Abstract
Photoreceptor cells in the vertebrate retina have a highly compartmentalized morphology for efficient phototransduction and vision. Rhodopsin, the visual pigment in rod photoreceptors, is densely packaged into the rod outer segment sensory cilium and continuously renewed through essential synthesis and trafficking pathways housed in the rod inner segment. Despite the importance of this region for rod health and maintenance, the subcellular organization of rhodopsin and its trafficking regulators in the mammalian rod inner segment remain undefined. We used super-resolution fluorescence microscopy with optimized retinal immunolabeling techniques to perform a single molecule localization analysis of rhodopsin in the inner segments of mouse rods. We found that a significant fraction of rhodopsin molecules was localized at the plasma membrane, at the surface, in an even distribution along the entire length of the inner segment, where markers of transport vesicles also colocalized. Thus, our results collectively establish a model of rhodopsin trafficking through the inner segment plasma membrane as an essential subcellular pathway in mouse rod photoreceptors.
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Affiliation(s)
- Kristen N. Haggerty
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Shannon C. Eshelman
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Lauren A. Sexton
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Emmanuel Frimpong
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Leah M. Rogers
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Melina A. Agosto
- Retina and Optic Nerve Research Laboratory, Department of Physiology and Biophysics, and Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Michael A. Robichaux
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
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Bi Y, Ren D, Yuan F, Zhang Z, Zhou D, Yi X, Ji L, Li K, Yang F, Wu X, Li X, Xu Y, Liu Y, Wang P, Cai C, Liu C, Ma Q, He L, Shi Y, He G. TULP4, a novel E3 ligase gene, participates in neuronal migration as a candidate in schizophrenia. CNS Neurosci Ther 2023. [PMID: 37650344 DOI: 10.1111/cns.14423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 07/26/2023] [Accepted: 08/14/2023] [Indexed: 09/01/2023] Open
Abstract
BACKGROUND TUB-like protein 4 (TULP4) is one of the distant members of tubby family proteins, whose function remains largely unknown. In the present study, we intend to identify the role of TULP4 in schizophrenia from human samples and animal models. METHODS Whole-exome sequencing was used to detect the four schizophrenia families collected. In different cell lines, the effects of identified variants in TULP4 gene on its expression and localization were analyzed. Knockdown models in utero and adult mice were employed to investigate the role of Tulp4 on neuronal migration and schizophrenia-related behavior. Subsequently, co-IP assays were used to search for proteins that interact with TULP4 and the effects of mutants on the molecular function of TULP4. RESULTS For the first time, we identified five rare variants in TULP4 from schizophrenia families, of which three significantly reduced TULP4 protein expression. Knockdown the expression of Tulp4 delayed neuronal migration during embryological development and consequently triggered abnormal behaviors in adult mice, including impaired sensorimotor gating and cognitive dysfunction. Furthermore, we confirmed that TULP4 is involved in the formation of a novel E3 ligase through interaction with CUL5-ELOB/C-RNF7 and the three deleterious variants affected the binding amount of TULP4 and CUL5 to a certain extent. CONCLUSIONS Together, we believe TULP4 plays an important role in neurodevelopment and subsequent schizophrenic-related phenotypes through its E3 ubiquitin ligase function.
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Affiliation(s)
- Yan Bi
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Shanghai Jiao Tong University, Shanghai, China
- The Collaborative Innovation Center for Brain Science, and Brain Science and Technology Research Center, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Decheng Ren
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Shanghai Jiao Tong University, Shanghai, China
- The Collaborative Innovation Center for Brain Science, and Brain Science and Technology Research Center, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Fan Yuan
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Shanghai Jiao Tong University, Shanghai, China
- The Collaborative Innovation Center for Brain Science, and Brain Science and Technology Research Center, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhou Zhang
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Shanghai Jiao Tong University, Shanghai, China
- The Collaborative Innovation Center for Brain Science, and Brain Science and Technology Research Center, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Burning Rock Biotech, Guangzhou, China
| | - Daizhan Zhou
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Shanghai Jiao Tong University, Shanghai, China
- The Collaborative Innovation Center for Brain Science, and Brain Science and Technology Research Center, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xin Yi
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Shanghai Jiao Tong University, Shanghai, China
- The Collaborative Innovation Center for Brain Science, and Brain Science and Technology Research Center, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Lei Ji
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Shanghai Jiao Tong University, Shanghai, China
- The Collaborative Innovation Center for Brain Science, and Brain Science and Technology Research Center, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Keyi Li
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Shanghai Jiao Tong University, Shanghai, China
- The Collaborative Innovation Center for Brain Science, and Brain Science and Technology Research Center, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Fengping Yang
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Shanghai Jiao Tong University, Shanghai, China
- The Collaborative Innovation Center for Brain Science, and Brain Science and Technology Research Center, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xi Wu
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Shanghai Jiao Tong University, Shanghai, China
- The Collaborative Innovation Center for Brain Science, and Brain Science and Technology Research Center, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xingwang Li
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Shanghai Jiao Tong University, Shanghai, China
- The Collaborative Innovation Center for Brain Science, and Brain Science and Technology Research Center, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yifeng Xu
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yun Liu
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Peng Wang
- Wuhu Fourth People's Hospital, Wuhu, China
| | | | - Chuanxin Liu
- School of Mental Health, Jining Medical University, Jining, China
| | - Qian Ma
- Laboratory Animal Centre, Shanghai Jiao Tong University, Shanghai, China
| | - Lin He
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Shanghai Jiao Tong University, Shanghai, China
- The Collaborative Innovation Center for Brain Science, and Brain Science and Technology Research Center, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yi Shi
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Shanghai Jiao Tong University, Shanghai, China
- The Collaborative Innovation Center for Brain Science, and Brain Science and Technology Research Center, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Guang He
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Shanghai Jiao Tong University, Shanghai, China
- The Collaborative Innovation Center for Brain Science, and Brain Science and Technology Research Center, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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Haggerty KN, Eshelman SC, Sexton LA, Frimpong E, Rogers LM, Agosto MA, Robichaux MA. Mapping rhodopsin trafficking in rod photoreceptors with quantitative super-resolution microscopy. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.20.537413. [PMID: 37131638 PMCID: PMC10153271 DOI: 10.1101/2023.04.20.537413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Photoreceptor cells in the vertebrate retina have a highly compartmentalized morphology for efficient long-term phototransduction. Rhodopsin, the visual pigment in rod photoreceptors, is densely packaged into the rod outer segment sensory cilium and continuously renewed through essential synthesis and trafficking pathways housed in the rod inner segment. Despite the importance of this region for rod health and maintenance, the subcellular organization of rhodopsin and its trafficking regulators in the mammalian rod inner segment remain undefined. We used super-resolution fluorescence microscopy with optimized retinal immunolabeling techniques to perform a single molecule localization analysis of rhodopsin in the inner segments of mouse rods. We found that a significant fraction of rhodopsin molecules was localized at the plasma membrane in an even distribution along the entire length of the inner segment, where markers of transport vesicles also colocalized. Thus, our results collectively establish a model of rhodopsin trafficking through the inner segment plasma membrane as an essential subcellular pathway in mouse rod photoreceptors.
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Affiliation(s)
- Kristen N. Haggerty
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
| | - Shannon C. Eshelman
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
| | - Lauren A. Sexton
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
| | - Emmanuel Frimpong
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
| | - Leah M. Rogers
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
| | - Melina A. Agosto
- Retina and Optic Nerve Research Laboratory, Department of Physiology and Biophysics, and Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, NS, B3H 4R2, Canada
| | - Michael A. Robichaux
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
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Ciliary Proteins Repurposed by the Synaptic Ribbon: Trafficking Myristoylated Proteins at Rod Photoreceptor Synapses. Int J Mol Sci 2022; 23:ijms23137135. [PMID: 35806143 PMCID: PMC9266639 DOI: 10.3390/ijms23137135] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 06/22/2022] [Accepted: 06/23/2022] [Indexed: 12/25/2022] Open
Abstract
The Unc119 protein mediates transport of myristoylated proteins to the photoreceptor outer segment, a specialized primary cilium. This transport activity is regulated by the GTPase Arl3 as well as by Arl13b and Rp2 that control Arl3 activation/inactivation. Interestingly, Unc119 is also enriched in photoreceptor synapses and can bind to RIBEYE, the main component of synaptic ribbons. In the present study, we analyzed whether the known regulatory proteins, that control the Unc119-dependent myristoylated protein transport at the primary cilium, are also present at the photoreceptor synaptic ribbon complex by using high-resolution immunofluorescence and immunogold electron microscopy. We found Arl3 and Arl13b to be enriched at the synaptic ribbon whereas Rp2 was predominantly found on vesicles distributed within the entire terminal. These findings indicate that the synaptic ribbon could be involved in the discharge of Unc119-bound lipid-modified proteins. In agreement with this hypothesis, we found Nphp3 (Nephrocystin-3), a myristoylated, Unc119-dependent cargo protein enriched at the basal portion of the ribbon in close vicinity to the active zone. Mutations in Nphp3 are known to be associated with Senior–Løken Syndrome 3 (SLS3). Visual impairment and blindness in SLS3 might thus not only result from ciliary dysfunctions but also from malfunctions of the photoreceptor synapse.
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Ebke LA, Sinha S, Pauer GJT, Hagstrom SA. Photoreceptor Compartment-Specific TULP1 Interactomes. Int J Mol Sci 2021; 22:ijms22158066. [PMID: 34360830 PMCID: PMC8348715 DOI: 10.3390/ijms22158066] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 07/06/2021] [Accepted: 07/12/2021] [Indexed: 12/16/2022] Open
Abstract
Photoreceptors are highly compartmentalized cells with large amounts of proteins synthesized in the inner segment (IS) and transported to the outer segment (OS) and synaptic terminal. Tulp1 is a photoreceptor-specific protein localized to the IS and synapse. In the absence of Tulp1, several OS-specific proteins are mislocalized and synaptic vesicle recycling is impaired. To better understand the involvement of Tulp1 in protein trafficking, our approach in the current study was to physically isolate Tulp1-containing photoreceptor compartments by serial tangential sectioning of retinas and to identify compartment-specific Tulp1 binding partners by immunoprecipitation followed by liquid chromatography tandem mass spectrometry. Our results indicate that Tulp1 has two distinct interactomes. We report the identification of: (1) an IS-specific interaction between Tulp1 and the motor protein Kinesin family member 3a (Kif3a), (2) a synaptic-specific interaction between Tulp1 and the scaffold protein Ribeye, and (3) an interaction between Tulp1 and the cytoskeletal protein microtubule-associated protein 1B (MAP1B) in both compartments. Immunolocalization studies in the wild-type retina indicate that Tulp1 and its binding partners co-localize to their respective compartments. Our observations are compatible with Tulp1 functioning in protein trafficking in multiple photoreceptor compartments, likely as an adapter molecule linking vesicles to molecular motors and the cytoskeletal scaffold.
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Affiliation(s)
- Lindsey A. Ebke
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH 44195, USA; (L.A.E.); (S.S.); (G.J.T.P.)
| | - Satyabrata Sinha
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH 44195, USA; (L.A.E.); (S.S.); (G.J.T.P.)
| | - Gayle J. T. Pauer
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH 44195, USA; (L.A.E.); (S.S.); (G.J.T.P.)
| | - Stephanie A. Hagstrom
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH 44195, USA; (L.A.E.); (S.S.); (G.J.T.P.)
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH 44195, USA
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH 44195, USA
- Correspondence:
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6
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Kerek EM, Yoon KH, Luo SY, Chen J, Valencia R, Julien O, Waskiewicz AJ, Hubbard BP. A conserved acetylation switch enables pharmacological control of tubby-like protein stability. J Biol Chem 2020; 296:100073. [PMID: 33187986 PMCID: PMC7948452 DOI: 10.1074/jbc.ra120.015839] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 10/30/2020] [Accepted: 11/13/2020] [Indexed: 12/29/2022] Open
Abstract
Tubby-like proteins (TULPs) are characterized by a conserved C-terminal domain that binds phosphoinositides. Collectively, mammalian TULP1-4 proteins play essential roles in intracellular transport, cell differentiation, signaling, and motility. Yet, little is known about how the function of these proteins is regulated in cells. Here, we present the protein–protein interaction network of TULP3, a protein that is responsible for the trafficking of G-protein-coupled receptors to cilia and whose aberrant expression is associated with severe developmental disorders and polycystic kidney disease. We identify several protein interaction nodes linked to TULP3 that include enzymes involved in acetylation and ubiquitination. We show that acetylation of two key lysine residues on TULP3 by p300 increases TULP3 protein abundance and that deacetylation of these sites by HDAC1 decreases protein levels. Furthermore, we show that one of these sites is ubiquitinated in the absence of acetylation and that acetylation inversely correlates with ubiquitination of TULP3. This mechanism is evidently conserved across species and is active in zebrafish during development. Finally, we identify this same regulatory module in TULP1, TULP2, and TULP4 and demonstrate that the stability of these proteins is similarly modulated by an acetylation switch. This study unveils a signaling pathway that links nuclear enzymes to ciliary membrane receptors via TULP3, describes a dynamic mechanism for the regulation of all tubby-like proteins, and explores how to exploit it pharmacologically using drugs.
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Affiliation(s)
- Evan M Kerek
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Kevin H Yoon
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Shu Y Luo
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Jerry Chen
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Robert Valencia
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Olivier Julien
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Andrew J Waskiewicz
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Basil P Hubbard
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada.
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7
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Palfi A, Yesmambetov A, Millington-Ward S, Shortall C, Humphries P, Kenna PF, Chadderton N, Farrar GJ. AAV-Delivered Tulp1 Supplementation Therapy Targeting Photoreceptors Provides Minimal Benefit in Tulp1-/- Retinas. Front Neurosci 2020; 14:891. [PMID: 32973439 PMCID: PMC7482550 DOI: 10.3389/fnins.2020.00891] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 07/30/2020] [Indexed: 12/23/2022] Open
Abstract
With marketing approval of the first ocular gene therapy, and other gene therapies in clinical trial, treatments for inherited retinal degenerations (IRDs) have become a reality. Biallelic mutations in the tubby like protein 1 gene (TULP1) are causative of IRDs in humans; a mouse knock-out model (Tulp1−/−) is characterized by a similar disease phenotype. We developed a Tulp1 supplementation therapy for Tulp1−/− mice. Utilizing subretinal AAV2/5 delivery at postnatal day (p)2–3 and rhodopsin-kinase promoter (GRK1P) we targeted Tulp1 to photoreceptor cells exploring three doses, 2.2E9, 3.7E8, and 1.2E8 vgs. Tulp1 mRNA and TULP1 protein were assessed by RT-qPCR, western blot and immunocytochemistry, and visual function by electroretinography. Our results indicate that TULP1 was expressed in photoreceptors; achieved levels of Tulp1 mRNA and protein were similar to wild type levels at p20. However, the thickness of the outer nuclear layer (ONL) did not improve in treated Tulp1−/− mice. There was a small and transient electroretinography benefit in the treated retinas at 4 weeks of age (not observed by 6 weeks) when using 3.7E8 vg dose. Dark-adapted mixed rod and cone a- and b-wave amplitudes were 24.3 ± 13.5 μV and 52.2 ± 31.7 μV in treated Tulp1−/− mice, which were significantly different (p < 0.001, t-test), from those detected in untreated eyes (7.1 ± 7.0 μV and 9.4 ± 15.1 μV, respectively). Our results indicate that Tulp1 supplementation in photoreceptors may not be sufficient to provide robust benefit in Tulp1−/− mice. As such, further studies are required to fine tune the Tulp1 supplementation therapy, which, in principle, should rescue the Tulp1−/− phenotype.
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Affiliation(s)
- Arpad Palfi
- Department of Genetics, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland
| | - Adlet Yesmambetov
- Department of Genetics, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland
| | - Sophia Millington-Ward
- Department of Genetics, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland
| | - Ciara Shortall
- Department of Genetics, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland
| | - Pete Humphries
- Department of Genetics, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland
| | - Paul F Kenna
- Department of Genetics, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland
| | - Naomi Chadderton
- Department of Genetics, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland
| | - G Jane Farrar
- Department of Genetics, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland
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8
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Palfi A, Yesmambetov A, Humphries P, Hokamp K, Farrar GJ. Non-photoreceptor Expression of Tulp1 May Contribute to Extensive Retinal Degeneration in Tulp1-/- Mice. Front Neurosci 2020; 14:656. [PMID: 32655363 PMCID: PMC7325604 DOI: 10.3389/fnins.2020.00656] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 05/27/2020] [Indexed: 12/24/2022] Open
Abstract
Mutations in tubby like protein 1 gene (TULP1) are causative of early-onset recessive inherited retinal degenerations (IRDs); similarly, the Tulp1-/- mouse is also characterized by a rapid IRD. Tulp1 mRNA and protein expression was analyzed in wild type mouse retinas and expression data sets (NCBI) during early postnatal development. Comparative histology was undertaken in Tulp1-/-, rhodopsin-/- (Rho-/-) and retinal degeneration slow-/- (Rds-/-) mouse retinas. Bioinformatic analysis of predicted TULP1 interactors and IRD genes was performed. Peak expression of Tulp1 in healthy mouse retinas was detected at p8; of note, TULP1 was detected in both the outer and inner retina. Bioinformatic analysis indicated Tulp1 expression in retinal progenitor, photoreceptor and non-photoreceptor cells. While common features of photoreceptor degeneration were detected in Tulp1-/-, Rho-/-, and Rds-/- retinas, other alterations in bipolar, amacrine and ganglion cells were specific to Tulp1-/- mice. Additionally, predicted TULP1 interactors differed in various retinal cell types and new functions for TULP1 were suggested. A pilot bioinformatic analysis indicated that in a similar fashion to Tulp1, many other IRD genes were expressed in both inner and outer retinal cells at p4-p7. Our data indicate that expression of Tulp1 extends to multiple retinal cell types; lack of TULP1 may lead to primary degeneration not only of photoreceptor but also non-photoreceptor cells. Predicted interactors suggest widespread retinal functions for TULP1. Early and widespread expression of TULP1 and some other IRD genes in both the inner and outer retina highlights potential hurdles in the development of treatments for these IRDs.
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Affiliation(s)
- Arpad Palfi
- Department of Genetics, Trinity College Dublin, Dublin, Ireland
| | | | - Pete Humphries
- Department of Genetics, Trinity College Dublin, Dublin, Ireland
| | - Karsten Hokamp
- Department of Genetics, Trinity College Dublin, Dublin, Ireland
| | - G Jane Farrar
- Department of Genetics, Trinity College Dublin, Dublin, Ireland
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9
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Forward genetic analysis using OCT screening identifies Sfxn3 mutations leading to progressive outer retinal degeneration in mice. Proc Natl Acad Sci U S A 2020; 117:12931-12942. [PMID: 32457148 DOI: 10.1073/pnas.1921224117] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Retinal disease and loss of vision can result from any disruption of the complex pathways controlling retinal development and homeostasis. Forward genetics provides an excellent tool to find, in an unbiased manner, genes that are essential to these processes. Using N-ethyl-N-nitrosourea mutagenesis in mice in combination with a screening protocol using optical coherence tomography (OCT) and automated meiotic mapping, we identified 11 mutations presumably causative of retinal phenotypes in genes previously known to be essential for retinal integrity. In addition, we found multiple statistically significant gene-phenotype associations that have not been reported previously and decided to target one of these genes, Sfxn3 (encoding sideroflexin-3), using CRISPR/Cas9 technology. We demonstrate, using OCT, light microscopy, and electroretinography, that two Sfxn3 -/- mouse lines developed progressive and severe outer retinal degeneration. Electron microscopy showed thinning of the retinal pigment epithelium and disruption of the external limiting membrane. Using single-cell RNA sequencing of retinal cells isolated from C57BL/6J mice, we demonstrate that Sfxn3 is expressed in several bipolar cell subtypes, retinal ganglion cells, and some amacrine cell subtypes but not significantly in Müller cells or photoreceptors. In situ hybridization confirmed these findings. Furthermore, pathway analysis suggests that Sfxn3 may be associated with synaptic homeostasis. Importantly, electron microscopy analysis showed disruption of synapses and synaptic ribbons in the outer plexiform layer of Sfxn3 -/- mice. Our work describes a previously unknown requirement for Sfxn3 in retinal function.
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10
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Wang M, Xu Z, Kong Y. The tubby-like proteins kingdom in animals and plants. Gene 2018; 642:16-25. [DOI: 10.1016/j.gene.2017.10.077] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2017] [Revised: 08/15/2017] [Accepted: 10/27/2017] [Indexed: 11/28/2022]
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11
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Waldner DM, Giraldo Sierra NC, Bonfield S, Nguyen L, Dimopoulos IS, Sauvé Y, Stell WK, Bech-Hansen NT. Cone dystrophy and ectopic synaptogenesis in a Cacna1f loss of function model of congenital stationary night blindness (CSNB2A). Channels (Austin) 2018; 12:17-33. [PMID: 29179637 PMCID: PMC5972796 DOI: 10.1080/19336950.2017.1401688] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 10/22/2017] [Accepted: 10/31/2017] [Indexed: 01/05/2023] Open
Abstract
Congenital stationary night blindness 2A (CSNB2A) is an X-linked retinal disorder, characterized by phenotypically variable signs and symptoms of impaired vision. CSNB2A is due to mutations in CACNA1F, which codes for the pore-forming α1F subunit of a L-type voltage-gated calcium channel, Cav1.4. Mouse models of CSNB2A, used for characterizing the effects of various Cacna1f mutations, have revealed greater severity of defects than in human CSNB2A. Specifically, Cacna1f-knockout mice show an apparent lack of visual function, gradual retinal degeneration, and disruption of photoreceptor synaptic terminals. Several reports have also noted cone-specific disruptions, including axonal abnormalities, dystrophy, and cell death. We have explored further the involvement of cones in our 'G305X' mouse model of CSNB2A, which has a premature truncation, loss-of-function mutation in Cacna1f. We show that the expression of genes for several phototransduction-related cone markers is down-regulated, while that of several cellular stress- and damage-related markers is up-regulated; and that cone photoreceptor structure and photopic visual function - measured by immunohistochemistry, optokinetic response and electroretinography - deteriorate progressively with age. We also find that dystrophic cone axons establish synapse-like contacts with rod bipolar cell dendrites, which they normally do not contact in wild-type retinas - ectopically, among rod cell bodies in the outer nuclear layer. These data support a role for Cav1.4 in cone synaptic development, cell viability, and synaptic transmission of cone-dependent visual signals. Although our novel finding of cone-to-rod-bipolar cell contacts in this mouse model of a retinal channelopathy may challenge current views of the role of Cav1.4 in photopic vision, it also suggests a potential new target for restorative therapy.
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Affiliation(s)
- D. M. Waldner
- Department of Neuroscience, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - N. C. Giraldo Sierra
- Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - S. Bonfield
- Department of Neuroscience, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - L. Nguyen
- Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - I. S. Dimopoulos
- Department of Ophthalmology and Visual Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Y. Sauvé
- Department of Ophthalmology and Visual Sciences, University of Alberta, Edmonton, Alberta, Canada
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
| | - W. K. Stell
- Department of Cell Biology and Anatomy and Department of Surgery, Hotchkiss Brain Institute, and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - N. T. Bech-Hansen
- Department of Medical Genetics, and Department of Surgery, Alberta Children's Hospital Research Institute, and Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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The Disease Protein Tulp1 Is Essential for Periactive Zone Endocytosis in Photoreceptor Ribbon Synapses. J Neurosci 2016; 36:2473-93. [PMID: 26911694 DOI: 10.1523/jneurosci.2275-15.2016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Mutations in the Tulp1 gene cause severe, early-onset retinitis pigmentosa (RP14) in humans. In the retina, Tulp1 is mainly expressed in photoreceptors that use ribbon synapses to communicate with the inner retina. In the present study, we demonstrate that Tulp1 is highly enriched in the periactive zone of photoreceptor presynaptic terminals where Tulp1 colocalizes with major endocytic proteins close to the synaptic ribbon. Analyses of Tulp1 knock-out mice demonstrate that Tulp1 is essential to keep endocytic proteins enriched at the periactive zone and to maintain high levels of endocytic activity close to the synaptic ribbon. Moreover, we have discovered a novel interaction between Tulp1 and the synaptic ribbon protein RIBEYE, which is important to maintain synaptic ribbon integrity. The current findings suggest a new model for Tulp1-mediated localization of the endocytic machinery at the periactive zone of ribbon synapses and offer a new rationale and mechanism for vision loss associated with genetic defects in Tulp1.
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A Novel Approach to Identify Photoreceptor Compartment-Specific Tulp1 Binding Partners. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 854:605-11. [PMID: 26427465 DOI: 10.1007/978-3-319-17121-0_80] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
Photoreceptors (PRs) are highly polarized and compartmentalized cells with large amounts of proteins synthesized in the inner segment (IS) and transported to the outer segment (OS) and synaptic terminal. The PR-specific protein, Tulp1, is localized to the IS and synapse and is hypothesized to be involved in protein trafficking. To better understand the molecular processes that regulate protein trafficking in PRs, we aimed to identify compartment-specific Tulp1 binding partners. Serial tangential sectioning of Long Evans rat retinas was utilized to isolate the IS and synaptic PR compartments. Tulp1 binding partners in each of these layers were identified using co-immunoprecipitation (co-IP) with Tulp1 antibodies. The co-IP eluates were separated by SDS-PAGE, trypsinized into peptide fragments, and proteins were identified by liquid chromatography tandem mass spectrometry. In the IS, potential Tulp1-binding partners included cytoskeletal scaffold proteins, protein trafficking molecules, as well as members of the phototransduction cascade. In the synaptic region, the majority of interacting proteins identified were cytoskeletal. A separate subset of proteins were identified in both the IS and synapse including chaperones and family members of the GTPase activating proteins. Tulp1 has two distinct PR compartment-specific interactomes. Our results support the hypothesis that Tulp1 is involved in the trafficking of proteins from the IS to the OS and the continuous membrane remodeling and vesicle cycling at the synaptic terminal.
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Khan AO, Bergmann C, Eisenberger T, Bolz HJ. ATULP1founder mutation, p.Gln301*, underlies a recognisable congenital rod–cone dystrophy phenotype on the Arabian Peninsula. Br J Ophthalmol 2014; 99:488-92. [DOI: 10.1136/bjophthalmol-2014-305836] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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15
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Regus-Leidig H, Fuchs M, Löhner M, Leist SR, Leal-Ortiz S, Chiodo VA, Hauswirth WW, Garner CC, Brandstätter JH. In vivo knockdown of Piccolino disrupts presynaptic ribbon morphology in mouse photoreceptor synapses. Front Cell Neurosci 2014; 8:259. [PMID: 25232303 PMCID: PMC4153300 DOI: 10.3389/fncel.2014.00259] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Accepted: 08/13/2014] [Indexed: 01/08/2023] Open
Abstract
Piccolo is the largest known cytomatrix protein at active zones of chemical synapses. A growing number of studies on conventional chemical synapses assign Piccolo a role in the recruitment and integration of molecules relevant for both endo- and exocytosis of synaptic vesicles, the dynamic assembly of presynaptic F-actin, as well as the proteostasis of presynaptic proteins, yet a direct function in the structural organization of the active zone has not been uncovered in part due to the expression of multiple alternatively spliced isoforms. We recently identified Piccolino, a Piccolo splice variant specifically expressed in sensory ribbon synapses of the eye and ear. Here we down regulated Piccolino in vivo via an adeno-associated virus-based RNA interference approach and explored the impact on the presynaptic structure of mouse photoreceptor ribbon synapses. Detailed immunocytochemical light and electron microscopical analysis of Piccolino knockdown in photoreceptors revealed a hitherto undescribed photoreceptor ribbon synaptic phenotype with striking morphological changes of synaptic ribbon ultrastructure.
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Affiliation(s)
- Hanna Regus-Leidig
- Department of Biology, Animal Physiology, Friedrich-Alexander-University of Erlangen-Nuremberg Erlangen, Germany
| | - Michaela Fuchs
- Department of Biology, Animal Physiology, Friedrich-Alexander-University of Erlangen-Nuremberg Erlangen, Germany
| | - Martina Löhner
- Department of Biology, Animal Physiology, Friedrich-Alexander-University of Erlangen-Nuremberg Erlangen, Germany
| | - Sarah R Leist
- Department of Biology, Animal Physiology, Friedrich-Alexander-University of Erlangen-Nuremberg Erlangen, Germany ; Department of Infection Genetics, Helmholtz Centre for Infection Research Braunschweig, Germany
| | - Sergio Leal-Ortiz
- Department of Psychiatry and Behavioral Sciences, Stanford University Palo Alto, CA, USA
| | - Vince A Chiodo
- Department of Ophthalmology, College of Medicine, University of Florida Gainesville, FL, USA
| | - William W Hauswirth
- Department of Ophthalmology, College of Medicine, University of Florida Gainesville, FL, USA
| | - Craig C Garner
- Department of Psychiatry and Behavioral Sciences, Stanford University Palo Alto, CA, USA ; Deutsches Zentrum für Neurodegenerative Erkrankungen Charité, Berlin, Germany
| | - Johann H Brandstätter
- Department of Biology, Animal Physiology, Friedrich-Alexander-University of Erlangen-Nuremberg Erlangen, Germany
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Jacobson SG, Cideciyan AV, Huang WC, Sumaroka A, Roman AJ, Schwartz SB, Luo X, Sheplock R, Dauber JM, Swider M, Stone EM. TULP1 mutations causing early-onset retinal degeneration: preserved but insensitive macular cones. Invest Ophthalmol Vis Sci 2014; 55:5354-64. [PMID: 25074776 DOI: 10.1167/iovs.14-14570] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To investigate visual function and outer and inner retinal structure in the rare form of retinal degeneration (RD) caused by TULP1 (tubby-like protein 1) mutations. METHODS Retinal degeneration patients with TULP1 mutations (n = 5; age range, 5-36 years) were studied by kinetic and chromatic static perimetry, en face autofluorescence imaging, and spectral-domain optical coherence tomography (OCT) scans. Outer and inner retinal laminar thickness were measured and mapped across the central retina. Comparisons were made with results from patients with RD associated with four ciliopathy genotypes (MAK, RPGR, BBS1, and USH2A). RESULTS The TULP1-RD patients were severely affected already in the first decade of life and there was rapidly progressive visual loss. No evidence of rod function was present at any age. Small central islands showed melanized retinal pigment epithelium by autofluorescence imaging and well-preserved photoreceptor laminar thickness by OCT imaging. There was extracentral loss of laminar architecture and increased inner retinal thickening. Structure-function relationships in residual foveal cone islands were made in TULP1-RD patients and in other retinopathies considered ciliopathies. Patients with TULP1-RD, unlike the others, had greater dysfunction for the degree of foveal structural preservation. CONCLUSIONS Retinal degeneration with TULP1 mutations leads to a small central island of residual foveal cones at early ages. These cones are less sensitive than expected from the residual structure. The human phenotype is consistent with experimental evidence in the Tulp1 knockout mouse model that visual dysfunction could be complicated by abnormal processes proximal to cone outer segments.
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Affiliation(s)
- Samuel G Jacobson
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Artur V Cideciyan
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Wei Chieh Huang
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Alexander Sumaroka
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Alejandro J Roman
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Sharon B Schwartz
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Xunda Luo
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Rebecca Sheplock
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Joanna M Dauber
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Malgorzata Swider
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Edwin M Stone
- Department of Ophthalmology, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States Howard Hughes Medical Institute, Iowa City, Iowa, United States
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Pardue MT, Barnes CS, Kim MK, Aung MH, Amarnath R, Olson DE, Thulé PM. Rodent Hyperglycemia-Induced Inner Retinal Deficits are Mirrored in Human Diabetes. Transl Vis Sci Technol 2014; 3:6. [PMID: 24959388 DOI: 10.1167/tvst.3.3.6] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Accepted: 04/28/2014] [Indexed: 02/05/2023] Open
Abstract
PURPOSE To evaluate the utility of low luminance stimuli to functionally probe inner retinal rod pathways in the context of diabetes mellitus in both rat and human subjects. METHODS Inner retinal dysfunction was assessed using oscillatory potential (OP) delays in diabetic rats. Scotopic electroretinograms (ERGs) in response to a series of increasing flash luminances were recorded from streptozotocin (STZ)-treated and control Sprague-Dawley rats after 7, 14, 20, and 29 weeks of hyperglycemia. We then evaluated OP delays in human diabetic subjects with (DR) and without (DM) diabetic retinopathy using the International Society for Clinical Electrophysiology in Vision (ISCEV) standard scotopic protocol and two additional dim test flashes. RESULTS Beginning 7 weeks after STZ, OP implicit times in diabetic rats were progressively delayed in response to dim, but not bright stimuli. In many diabetic subjects the standard ISCEV dim flash failed to illicit measureable OPs. However, OPs became measurable using a brighter, nonstandard dim flash (Test Flash 1, -1.43 log cd s/m2), and exhibited prolonged implicit times in the DM group compared with control subjects (CTRL). CONCLUSIONS Delays in scotopic OP implicit times are an early response to hyperglycemia in diabetic rats. A similar, inner retinal, rod-driven response was detected in diabetic human subjects without diabetic retinopathy, only when a nonstandard ISCEV flash intensity was employed during ERG testing. TRANSLATIONAL RELEVANCE The addition of a dim stimulus to standard ISCEV flashes with assessment of OP latency during ERG testing may provide a detection method for early retinal dysfunction in diabetic patients.
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Affiliation(s)
- Machelle T Pardue
- Rehab R&D Center of Excellence, Veterans Affairs Medical Center, Decatur, GA ; Department of Ophthalmology, Emory University, Atlanta, GA ; Neuroscience Program, Emory University, Atlanta, GA
| | - Claire S Barnes
- Rehab R&D Center of Excellence, Veterans Affairs Medical Center, Decatur, GA ; Department of Ophthalmology, Emory University, Atlanta, GA
| | - Moon K Kim
- Rehab R&D Center of Excellence, Veterans Affairs Medical Center, Decatur, GA ; Department of Ophthalmology, Emory University, Atlanta, GA
| | - Moe H Aung
- Neuroscience Program, Emory University, Atlanta, GA
| | - Raj Amarnath
- Rehab R&D Center of Excellence, Veterans Affairs Medical Center, Decatur, GA
| | - Darin E Olson
- Medical Service, Veterans Affairs Medical Center, Decatur, GA ; Division of Endocrinology, Metabolism, & Lipids, Emory University, Atlanta, GA
| | - Peter M Thulé
- Medical Service, Veterans Affairs Medical Center, Decatur, GA ; Division of Endocrinology, Metabolism, & Lipids, Emory University, Atlanta, GA
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18
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Retinal neurodegenerative changes in the adult insulin receptor substrate-2 deficient mouse. Exp Eye Res 2014; 124:1-10. [PMID: 24792588 DOI: 10.1016/j.exer.2014.04.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Revised: 04/17/2014] [Accepted: 04/22/2014] [Indexed: 11/23/2022]
Abstract
Insulin receptor substrate-2 (Irs2) mediates peripheral insulin action and is essential for retinal health. Previous investigations have reported severe photoreceptor degeneration and abnormal visual function in Irs2-deficient mice. However, molecular changes in the Irs2(-)(/)(-) mouse retina have not been described. In this study, we examined retinal degenerative changes in neuronal and glial cells of adult (9- and 12-week old) Irs2(-)(/)(-) mice by immunohistochemistry. 9-week old Irs2(-)(/)(-) mice showed significant thinning of outer retinal layers, concomitant to Müller and microglial cell activation. Photoreceptor cells displayed different signs of degeneration, such as outer/inner segment atrophy, redistribution of rod- and cone-opsins and spatial disorganization of cone cells. This was accompanied by synaptic changes at the outer plexiform layer, including the retraction of rod-spherules, reduction of photoreceptor synaptic ribbons and synaptic remodeling in second order neurons (i.e. loss and sprouting of dendritic processes in rod bipolar and horizontal cells). By 12 weeks of age, the thickness of inner retinal layers was severely affected. Although inner plexiform layer stratification remained unchanged at this stage, rod bipolar cell axon terminals were significantly depleted. Significant loss of Brn3a(+) retinal ganglion cells occurred in 12-week old Irs2(-)(/)(-) mice, in contrast to younger ages. Adult Irs2(-)(/)(-) mice showed clear hallmarks of neurodegeneration and disruption of the inner retina with increasing age. Pharmacological stimulation of Irs2 signaling pathway may provide additional neuroprotection in certain degenerative retinopathies.
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Guo Y, Prokudin I, Yu C, Liang J, Xie Y, Flaherty M, Tian L, Crofts S, Wang F, Snyder J, Donaldson C, Abdel-Magid N, Vazquez L, Keating B, Hakonarson H, Wang J, Jamieson RV. Advantage of Whole Exome Sequencing over Allele-Specific and Targeted Segment Sequencing in Detection of Novel TULP1 Mutation in Leber Congenital Amaurosis. Ophthalmic Genet 2014; 36:333-8. [PMID: 24547928 DOI: 10.3109/13816810.2014.886269] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND Leber congenital amaurosis (LCA) is a severe form of retinal dystrophy with marked underlying genetic heterogeneity. Until recently, allele-specific assays and Sanger sequencing of targeted segments were the only available approaches for attempted genetic diagnosis in this condition. A broader next-generation sequencing (NGS) strategy, such as whole exome sequencing, provides an improved molecular genetic diagnostic capacity for patients with these conditions. MATERIALS AND METHODS In a child with LCA, an allele-specific assay analyzing 135 known LCA-causing variations, followed by targeted segment sequencing of 61 regions in 14 causative genes was performed. Subsequently, exome sequencing was undertaken in the proband, unaffected consanguineous parents and two unaffected siblings. Bioinformatic analysis used two independent pipelines, BWA-GATK and SOAP, followed by Annovar and SnpEff to annotate the variants. RESULTS No disease-causing variants were found using the allele-specific or targeted segment Sanger sequencing assays. Analysis of variants in the exome sequence data revealed a novel homozygous nonsense mutation (c.1081C > T, p.Arg361*) in TULP1, a gene with roles in photoreceptor function where mutations were previously shown to cause LCA and retinitis pigmentosa. The identified homozygous variant was the top candidate using both bioinformatic pipelines. CONCLUSIONS This study highlights the value of the broad sequencing strategy of exome sequencing for disease gene identification in LCA, over other existing methods. NGS is particularly beneficial in LCA where there are a large number of causative disease genes, few distinguishing clinical features for precise candidate disease gene selection, and few mutation hotspots in any of the known disease genes.
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Affiliation(s)
- Yiran Guo
- a Center for Applied Genomics, The Children's Hospital of Philadelphia , Philadelphia , PA , USA
| | - Ivan Prokudin
- b Eye and Developmental Genetics Research Group, Western Sydney Genetics Program, The Children's Hospital at Westmead , Sydney , NSW , Australia .,c Children's Medical Research Institute , Westmead , Sydney , NSW , Australia
| | - Cong Yu
- d College of Life Sciences, Sichuan University, Key Laboratory for Bio-resources and Eco-environment of Ministry of Education, Sichuan Key Laboratory of Molecular Biology and Biotechnology , Chengdu , PR China .,e BGI-Shenzhen , Shenzhen , China
| | | | - Yi Xie
- e BGI-Shenzhen , Shenzhen , China
| | - Maree Flaherty
- f Department of Ophthalmology , The Children's Hospital at Westmead , Sydney , NSW , Australia
| | - Lifeng Tian
- a Center for Applied Genomics, The Children's Hospital of Philadelphia , Philadelphia , PA , USA
| | - Stephanie Crofts
- f Department of Ophthalmology , The Children's Hospital at Westmead , Sydney , NSW , Australia
| | - Fengxiang Wang
- a Center for Applied Genomics, The Children's Hospital of Philadelphia , Philadelphia , PA , USA
| | - James Snyder
- a Center for Applied Genomics, The Children's Hospital of Philadelphia , Philadelphia , PA , USA
| | - Craig Donaldson
- f Department of Ophthalmology , The Children's Hospital at Westmead , Sydney , NSW , Australia
| | - Nada Abdel-Magid
- a Center for Applied Genomics, The Children's Hospital of Philadelphia , Philadelphia , PA , USA
| | - Lyam Vazquez
- a Center for Applied Genomics, The Children's Hospital of Philadelphia , Philadelphia , PA , USA
| | - Brendan Keating
- a Center for Applied Genomics, The Children's Hospital of Philadelphia , Philadelphia , PA , USA .,g Division of Human Genetics , The Children's Hospital of Philadelphia , Philadelphia , PA , USA .,h Department of Pediatrics , The Perelman School of Medicine, University of Pennsylvania , Philadelphia , PA , USA
| | - Hakon Hakonarson
- a Center for Applied Genomics, The Children's Hospital of Philadelphia , Philadelphia , PA , USA .,g Division of Human Genetics , The Children's Hospital of Philadelphia , Philadelphia , PA , USA .,h Department of Pediatrics , The Perelman School of Medicine, University of Pennsylvania , Philadelphia , PA , USA
| | - Jun Wang
- e BGI-Shenzhen , Shenzhen , China .,i Department of Biology , University of Copenhagen , Copenhagen , Denmark .,j King Abdulaziz University , Jeddah , Saudi Arabia
| | - Robyn V Jamieson
- b Eye and Developmental Genetics Research Group, Western Sydney Genetics Program, The Children's Hospital at Westmead , Sydney , NSW , Australia .,c Children's Medical Research Institute , Westmead , Sydney , NSW , Australia .,k Discipline of Ophthalmology & Save Sight Institute, University of Sydney , Sydney , Australia , and.,l Disciplines of Paediatrics and Child Health & Genetic Medicine, University of Sydney , Sydney , NSW , Australia
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20
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Grossman GH, Ebke LA, Beight CD, Jang GF, Crabb JW, Hagstrom SA. Protein partners of dynamin-1 in the retina. Vis Neurosci 2013; 30:129-39. [PMID: 23746204 PMCID: PMC3936680 DOI: 10.1017/s0952523813000138] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Dynamin proteins are involved in vesicle generation, providing mechanical force to excise newly formed vesicles from membranes of cellular compartments. In the brain, dynamin-1, dynamin-2, and dynamin-3 have been well studied; however, their function in the retina remains elusive. A retina-specific splice variant of dynamin-1 interacts with the photoreceptor-specific protein Tubby-like protein 1 (Tulp1), which when mutated causes an early onset form of autosomal recessive retinitis pigmentosa. Here, we investigated the role of the dynamins in the retina, using immunohistochemistry to localize dynamin-1, dynamin-2, and dynamin-3 and immunoprecipitation followed by mass spectrometry to explore dynamin-1 interacting proteins in mouse retina. Dynamin-2 is primarily confined to the inner segment compartment of photoreceptors, suggesting a role in outer segment protein transport. Dynamin-3 is present in the terminals of photoreceptors and dendrites of second-order neurons but is most pronounced in the inner plexiform layer where second-order neurons relay signals from photoreceptors. Dynamin-1 appears to be the dominant isoform in the retina and is present throughout the retina and in multiple compartments of the photoreceptor cell. This suggests that it may function in multiple cellular pathways. Surprisingly, dynamin-1 expression and localization did not appear to be disrupted in tulp1−/− mice. Immunoprecipitation experiments reveal that dynamin-1 associates primarily with proteins involved in cytoskeletal-based membrane dynamics. This finding is confirmed by western blot analysis. Results further implicate dynamin-1 in vesicular protein transport processes relevant to synaptic and post-Golgi pathways and indicate a possible role in photoreceptor stability.
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Affiliation(s)
- Gregory H Grossman
- Department of Ophthalmic Research, Cleveland Clinic Cole Eye Institute, Cleveland, Ohio
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Rod photoreceptors protect from cone degeneration-induced retinal remodeling and restore visual responses in zebrafish. J Neurosci 2013; 33:1804-14. [PMID: 23365220 DOI: 10.1523/jneurosci.2910-12.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Humans are largely dependent upon cone-mediated vision. However, death or dysfunction of rods, the predominant photoreceptor subtype, results in secondary loss of cones, remodeling of retinal circuitry, and blindness. The changes in circuitry may contribute to the vision deficit and undermine attempts at restoring sight. We exploit zebrafish larvae as a genetic model to specifically characterize changes associated with photoreceptor degenerations in a cone-dominated retina. Photoreceptors form synapses with two types of second-order neurons, bipolar cells, and horizontal cells. Using cell-specific reporter gene expression and immunolabeling for postsynaptic glutamate receptors, significant remodeling is observed following cone degeneration in the pde6c(w59) larval retina but not rod degeneration in the Xops:mCFP(q13) line. In adults, rods and cones are present in approximately equal numbers, and in pde6c(w59) mutants glutamate receptor expression and synaptic structures in the outer plexiform layer are preserved, and visual responses are gained in these once blind fish. We propose that the abundance of rods in the adult protects the retina from cone degeneration-induced remodeling. We test this hypothesis by genetically manipulating the number of rods in larvae. We show that an increased number and uniform distribution of rods in lor/tbx2b(p25bbtl) or six7 morpholino-injected larvae protect from pde6c(w59)-induced secondary changes. The observations that remodeling is a common consequence of photoreceptor death across species, and that in zebrafish a small number of surviving photoreceptors afford protection from degeneration-induced changes, provides a model for systematic analysis of factors that slow or even prevent the secondary deteriorations associated with neural degenerative disease.
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Roosing S, van den Born LI, Hoyng CB, Thiadens AAHJ, de Baere E, Collin RWJ, Koenekoop RK, Leroy BP, van Moll-Ramirez N, Venselaar H, Riemslag FCC, Cremers FPM, Klaver CCW, den Hollander AI. Maternal uniparental isodisomy of chromosome 6 reveals a TULP1 mutation as a novel cause of cone dysfunction. Ophthalmology 2013; 120:1239-46. [PMID: 23499059 DOI: 10.1016/j.ophtha.2012.12.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 12/04/2012] [Accepted: 12/04/2012] [Indexed: 11/28/2022] Open
Abstract
PURPOSE The majority of the genetic causes of autosomal recessive (ar) cone dystrophy (CD) and cone-rod dystrophy (CRD) are currently unknown. We used a high-resolution homozygosity mapping approach in a cohort of patients with CD or CRD to identify new genes for ar cone disorders. DESIGN Case series. PARTICIPANTS A cohort of 159 patients with ar CD and 91 patients with CRD. METHODS The genomes of 83 patients with ar CD and 73 patients with CRD were analyzed for homozygous regions using single nucleotide polymorphism (SNP) microarrays. One patient showed homozygosity of SNPs across chromosome 6, and segregation analysis was performed using microsatellite markers. Direct sequencing of all retinal disease genes on chromosome 6 revealed a novel pathogenic TULP1 mutation in this patient. A cohort of 159 individuals with CD and 91 individuals with CRD was screened for this particular mutation using the restriction enzyme HhaI. The medical history of patients carrying the TULP1 mutation was reviewed and additional ophthalmic examinations were performed, including electroretinography (ERG), perimetry, optical coherence tomography (OCT), fundus autofluorescence (FAF), and fundus photography. MAIN OUTCOME MEASURES TULP1 mutations, age at diagnosis, visual acuity, fundus appearance, color vision defects, visual field, ERG, FAF, and OCT findings. RESULTS In 1 patient, homozygosity mapping and subsequent segregation analysis revealed maternal uniparental disomy (UPD) of chromosome 6. A novel homozygous missense mutation (p.Arg420Ser) was identified in TULP1, whereas no mutations were detected in other retinal disease genes on chromosome 6. The mutation affects a highly conserved amino acid residue in the Tubby domain and is predicted to be pathogenic. The same homozygous mutation was also identified in an additional, unrelated patient with CRD. Both patients carrying the p.Arg420Ser mutation presented with a bull's eye maculopathy. The first patient had progressive loss of visual acuity with a relatively preserved ERG, whereas the second patient developed loss of visual acuity, peripheral degeneration, and severely reduced ERG responses in a cone-rod pattern. CONCLUSIONS Maternal UPD of chromosome 6 unmasked a mutation in the TULP1 gene as a novel cause of cone dysfunction. This expands the disease spectrum of TULP1 mutations from Leber congenital amaurosis and early-onset retinitis pigmentosa to cone-dominated disease. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.
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Affiliation(s)
- Susanne Roosing
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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O'Quin KE, Yoshizawa M, Doshi P, Jeffery WR. Quantitative genetic analysis of retinal degeneration in the blind cavefish Astyanax mexicanus. PLoS One 2013; 8:e57281. [PMID: 23437360 PMCID: PMC3577753 DOI: 10.1371/journal.pone.0057281] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Accepted: 01/22/2013] [Indexed: 01/26/2023] Open
Abstract
The retina is the light-sensitive tissue of the eye that facilitates vision. Mutations within genes affecting eye development and retinal function cause a host of degenerative visual diseases, including retinitis pigmentosa and anophthalmia/microphthalmia. The characin fish Astyanax mexicanus includes both eyed (surface fish) and eyeless (cavefish) morphs that initially develop eyes with normal retina; however, early in development, the eyes of cavefish degenerate. Since both surface and cave morphs are members of the same species, they serve as excellent evolutionary mutant models with which to identify genes causing retinal degeneration. In this study, we crossed the eyed and eyeless forms of A. mexicanus and quantified the thickness of individual retinal layers among 115 F2 hybrid progeny. We used next generation sequencing (RAD-seq) and microsatellite mapping to construct a dense genetic map of the Astyanax genome, scan for quantitative trait loci (QTL) affecting retinal thickness, and identify candidate genes within these QTL regions. The map we constructed for Astyanax includes nearly 700 markers assembled into 25 linkage groups. Based on our scans with this map, we identified four QTL, one each associated with the thickness of the ganglion, inner nuclear, outer plexiform, and outer nuclear layers of the retina. For all but one QTL, cavefish alleles resulted in a clear reduction in the thickness of the affected layer. Comparative mapping of genetic markers within each QTL revealed that each QTL corresponds to an approximately 35 Mb region of the zebrafish genome. Within each region, we identified several candidate genes associated with the function of each affected retinal layer. Our study is the first to examine Astyanax retinal degeneration in the context of QTL mapping. The regions we identify serve as a starting point for future studies on the genetics of retinal degeneration and eye disease using the evolutionary mutant model Astyanax.
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Affiliation(s)
- Kelly E O'Quin
- Department of Biology, University of Maryland, College Park, Maryland, United States of America.
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Chen SF, Tsai YC, Fan SS. Drosophila king tubby (ktub) mediates light-induced rhodopsin endocytosis and retinal degeneration. J Biomed Sci 2012; 19:101. [PMID: 23228091 PMCID: PMC3541268 DOI: 10.1186/1423-0127-19-101] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2012] [Accepted: 12/04/2012] [Indexed: 11/10/2022] Open
Abstract
Background The tubby (tub) and tubby-like protein (tulp) genes encode a small family of proteins found in many organisms. Previous studies have shown that TUB and TULP genes in mammalian involve in obesity, neural development, and retinal degeneration. The purpose of this study was to investigate the role of Drosophila king tubby (ktub) in rhodopsin 1 (Rh1) endocytosis and retinal degeneration upon light stimulation. Results Drosophila ktub mutants were generated using imprecise excision. Wild type and mutant flies were raised in dark or constant light conditions. After a period of light stimulation, retinas were dissected, fixed and stained with anti-Rh1 antibody to reveal Rh1 endocytosis. Confocal and transmission electron microscope were used to examine the retinal degeneration. Immunocytochemical analysis shows that Ktub is expressed in the rhabdomere domain under dark conditions. When flies receive light stimulation, the Ktub translocates from the rhabdomere to the cytoplasm and the nucleus of the photoreceptor cells. Wild type photoreceptors form Rh1-immunopositive large vesicles (RLVs) shortly after light stimulation. In light-induced ktub mutants, the majority of Rh1 remains at the rhabdomere, and only a few RLVs appear in the cytoplasm of photoreceptor cells. Mutation of norpA allele causes massive Rh1 endocytosis in light stimulation. In ktub and norpA double mutants, however, Rh1 endocytosis is blocked under light stimulation. This study also shows that ktub and norpA double mutants rescue the light-induced norpA retinal degeneration. Deletion constructs further demonstrate that the Tubby domain of the Ktub protein participates in an important role in Rh1 endocytosis. Conclusions The results in this study delimit the novel function of Ktub in Rh1 endocytosis and retinal degeneration.
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Affiliation(s)
- Shu-Fen Chen
- Department of Life Science, Tunghai University, R,O,C 407, Taiwan
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Fuchs M, Scholz M, Sendelbeck A, Atorf J, Schlegel C, Enz R, Brandstätter JH. Rod photoreceptor ribbon synapses in DBA/2J mice show progressive age-related structural changes. PLoS One 2012; 7:e44645. [PMID: 22957094 PMCID: PMC3434146 DOI: 10.1371/journal.pone.0044645] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Accepted: 08/06/2012] [Indexed: 02/06/2023] Open
Abstract
The DBA/2J mouse is a commonly used animal model in glaucoma research. The eyes of DBA/2J mice show severe age-related changes that finally lead to the degeneration of retinal ganglion cells and the optic nerve. Recent electroretinogram studies identified functional deficits, which suggest that also photoreceptor cells are involved in the pathological processes occurring in the DBA/2J mouse retina. In a comparative study, we examined anatomical and molecular changes in the retinae of DBA/2J and C57BL/6 control mice with light and electron microscopy and with PCR analyses. In the retina of the DBA/2J mouse, we found a thinning of the outer plexiform layer, the first synaptic layer in the transfer of visual signals, and age-dependent and progressive degenerative structural changes at rod photoreceptor ribbon synapses. The structural ribbon changes represent a photoreceptor synaptic phenotype that has not yet been described in this animal model of secondary angle-closure glaucoma. Furthermore, genes of the classical complement cascade were upregulated in the photoreceptor cells of aging DBA/2J mice, suggesting a putative link between ribbon synapse degradation and the innate immune system.
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Affiliation(s)
- Michaela Fuchs
- Department of Biology, Animal Physiology, FAU Erlangen-Nuremberg, Erlangen, Germany
| | - Michael Scholz
- Institut für Anatomie Lehrstuhl II, FAU Erlangen-Nuremberg, Erlangen, Germany
| | - Anna Sendelbeck
- Department of Biology, Animal Physiology, FAU Erlangen-Nuremberg, Erlangen, Germany
| | - Jenny Atorf
- Department of Ophthalmology, University Hospital Erlangen, Erlangen, Germany
| | - Christine Schlegel
- Department of Biology, Animal Physiology, FAU Erlangen-Nuremberg, Erlangen, Germany
| | - Ralf Enz
- Institute for Biochemistry, FAU Erlangen-Nuremberg, Erlangen, Germany
- * E-mail: (RE); (JHB)
| | - Johann Helmut Brandstätter
- Department of Biology, Animal Physiology, FAU Erlangen-Nuremberg, Erlangen, Germany
- * E-mail: (RE); (JHB)
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López-del Hoyo N, Fazioli L, López-Begines S, Fernández-Sánchez L, Cuenca N, Llorens J, de la Villa P, Méndez A. Overexpression of guanylate cyclase activating protein 2 in rod photoreceptors in vivo leads to morphological changes at the synaptic ribbon. PLoS One 2012; 7:e42994. [PMID: 22912773 PMCID: PMC3418235 DOI: 10.1371/journal.pone.0042994] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 07/16/2012] [Indexed: 11/19/2022] Open
Abstract
Guanylate cyclase activating proteins are EF-hand containing proteins that confer calcium sensitivity to retinal guanylate cyclase at the outer segment discs of photoreceptor cells. By making the rate of cGMP synthesis dependent on the free intracellular calcium levels set by illumination, GCAPs play a fundamental role in the recovery of the light response and light adaptation. The main isoforms GCAP1 and GCAP2 also localize to the synaptic terminal, where their function is not known. Based on the reported interaction of GCAP2 with Ribeye, the major component of synaptic ribbons, it was proposed that GCAP2 could mediate the synaptic ribbon dynamic changes that happen in response to light. We here present a thorough ultrastructural analysis of rod synaptic terminals in loss-of-function (GCAP1/GCAP2 double knockout) and gain-of-function (transgenic overexpression) mouse models of GCAP2. Rod synaptic ribbons in GCAPs-/- mice did not differ from wildtype ribbons when mice were raised in constant darkness, indicating that GCAPs are not required for ribbon early assembly or maturation. Transgenic overexpression of GCAP2 in rods led to a shortening of synaptic ribbons, and to a higher than normal percentage of club-shaped and spherical ribbon morphologies. Restoration of GCAP2 expression in the GCAPs-/- background (GCAP2 expression in the absence of endogenous GCAP1) had the striking result of shortening ribbon length to a much higher degree than overexpression of GCAP2 in the wildtype background, as well as reducing the thickness of the outer plexiform layer without affecting the number of rod photoreceptor cells. These results indicate that preservation of the GCAP1 to GCAP2 relative levels is relevant for maintaining the integrity of the synaptic terminal. Our demonstration of GCAP2 immunolocalization at synaptic ribbons at the ultrastructural level would support a role of GCAPs at mediating the effect of light on morphological remodeling changes of synaptic ribbons.
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Affiliation(s)
| | - Lucrezia Fazioli
- Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain
| | | | - Laura Fernández-Sánchez
- Department of Physiology, Genetics and Microbiology, Universidad de Alicante, Alicante, Spain
| | - Nicolás Cuenca
- Department of Physiology, Genetics and Microbiology, Universidad de Alicante, Alicante, Spain
| | - Jordi Llorens
- Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain
- Department of Physiological Sciences II, University of Barcelona-Bellvitge Health Science Campus, Barcelona, Spain
| | - Pedro de la Villa
- Department of Physiology, University of Alcalá de Henares, Madrid, Spain
| | - Ana Méndez
- Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain
- Department of Pathology and Experimental Therapeutics, University of Barcelona-Bellvitge Health Science Campus, Barcelona, Spain
- * E-mail:
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The dynamic architecture of photoreceptor ribbon synapses: cytoskeletal, extracellular matrix, and intramembrane proteins. Vis Neurosci 2012; 28:453-71. [PMID: 22192503 DOI: 10.1017/s0952523811000356] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Rod and cone photoreceptors possess ribbon synapses that assist in the transmission of graded light responses to second-order bipolar and horizontal cells of the vertebrate retina. Proper functioning of the synapse requires the juxtaposition of presynaptic release sites immediately adjacent to postsynaptic receptors. In this review, we focus on the synaptic, cytoskeletal, and extracellular matrix proteins that help to organize photoreceptor ribbon synapses in the outer plexiform layer. We examine the proteins that foster the clustering of release proteins, calcium channels, and synaptic vesicles in the presynaptic terminals of photoreceptors adjacent to their postsynaptic contacts. Although many proteins interact with one another in the presynaptic terminal and synaptic cleft, these protein-protein interactions do not create a static and immutable structure. Instead, photoreceptor ribbon synapses are remarkably dynamic, exhibiting structural changes on both rapid and slow time scales.
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Maddox DM, Ikeda S, Ikeda A, Zhang W, Krebs MP, Nishina PM, Naggert JK. An allele of microtubule-associated protein 1A (Mtap1a) reduces photoreceptor degeneration in Tulp1 and Tub Mutant Mice. Invest Ophthalmol Vis Sci 2012; 53:1663-9. [PMID: 22323461 DOI: 10.1167/iovs.11-8871] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To identify genes that modify photoreceptor cell loss in the retinas of homozygous Tulp1(tm1Pjn) and Tub(tub) mice, which exhibit juvenile retinitis pigmentosa. METHODS Modifier loci were identified by genetic quantitative trait locus analysis. F2 Tulp1(tm1Pjn/tm1Pjn) mutant mice from a B6-Tulp1(tm1Pjn/tm1Pjn) × AKR/J intercross were genotyped with a panel of single nucleotide polymorphism markers and phenotyped by histology for photoreceptor nuclei remaining at 9 weeks of age. Genotype and phenotype data were correlated and examined with Pseudomarker 2.02 using 128 imputations to map modifier loci. Thresholds for the 63%, 10%, 5%, and 1% significance levels were obtained from 100 permutations. A significant, protective candidate modifier was identified by bioinformatic analysis and confirmed by crossing transgenic mice bearing a protective allele of this gene with Tulp1- and Tub-deficient mice. RESULTS A significant, protective modifier locus on chromosome 2 and a suggestive locus on chromosome 13 that increases photoreceptor loss were identified in a B6-Tulp1(tm1Pjn/tm1Pjn) × AKR/J intercross. The chromosome 2 locus mapped near Mtap1a, which encodes a protein associated with microtubule-based intracellular transport and synapse function. The protective Mtap1a(129P2/OlaHsd) allele was shown to reduce photoreceptor loss in both Tulp1(tm1Pjn/tm1Pjn) and Tub(tub/tub) mice. CONCLUSIONS It was demonstrated that the gene Mtap1a, which modifies hearing loss in Tub(tub/tub) mice, also modifies retinal degeneration in Tub(tub/tub) and Tulp1(tm1Pjn/tm1Pjn) mice. These results suggest that functionally nonredundant members of the TULP family (TUB and TULP1) share a common functional interaction with MTAP1A.
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Tulp1 is involved in specific photoreceptor protein transport pathways. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 723:783-9. [PMID: 22183407 DOI: 10.1007/978-1-4614-0631-0_100] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Isolating Photoreceptor Compartment-Specific Protein Complexes for Subsequent Proteomic Analysis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 723:701-7. [DOI: 10.1007/978-1-4614-0631-0_89] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
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Mohlin C, Liljekvist-Soltic I, Johansson K. Further assessment of neuropathology in retinal explants and neuroprotection by human neural progenitor cells. J Neural Eng 2011; 8:066012. [DOI: 10.1088/1741-2560/8/6/066012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Grossman GH, Watson RF, Pauer GJT, Bollinger K, Hagstrom SA. Immunocytochemical evidence of Tulp1-dependent outer segment protein transport pathways in photoreceptor cells. Exp Eye Res 2011; 93:658-68. [PMID: 21867699 DOI: 10.1016/j.exer.2011.08.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Revised: 07/21/2011] [Accepted: 08/03/2011] [Indexed: 10/17/2022]
Abstract
Tulp1 is a protein of unknown function exclusive to rod and cone photoreceptor cells. Mutations in the gene cause autosomal recessive retinitis pigmentosa in humans and photoreceptor degeneration in mice. In tulp1-/- mice, rod and cone opsins are mislocalized, and rhodopsin-bearing extracellular vesicles accumulate around the inner segment, indicating that Tulp1 is involved in protein transport from the inner segment to the outer segment. To investigate this further, we sought to define which outer segment transport pathways are Tulp1-dependent. We used immunohistochemistry to examine the localization of outer segment proteins in tulp1-/- photoreceptors, prior to retinal degeneration. We also surveyed the condition of inner segment organelles and rhodopsin transport machinery proteins. Herein, we show that guanylate cyclase 1 and guanylate cyclase activating proteins 1 and 2 are mislocalized in the absence of Tulp1. Furthermore, arrestin does not translocate to the outer segment in response to light stimulation. Additionally, data from the tulp1-/- retina adds to the understanding of peripheral membrane protein transport, indicating that rhodopsin kinase and transducin do not co-transport in rhodopsin carrier vesicles and phosphodiesterase does not co-transport in guanylate cyclase carrier vesicles. These data implicate Tulp1 in the transport of selective integral membrane outer segment proteins and their associated proteins, specifically, the opsin and guanylate cyclase carrier pathways. The exact role of Tulp1 in outer segment protein transport remains elusive. However, without Tulp1, two rhodopsin transport machinery proteins exhibit abnormal distribution, Rab8 and Rab11, suggesting a role for Tulp1 in vesicular docking and fusion at the plasma membrane near the connecting cilium.
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Affiliation(s)
- Gregory H Grossman
- Department of Ophthalmic Research, i31, Cole Eye Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA
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Abstract
The tubby mouse shows a tripartite syndrome characterized by maturity-onset obesity, blindness and deafness. The causative gene Tub is the founding member of a family of related proteins present throughout the animal and plant kingdoms, each characterized by a signature carboxy-terminal tubby domain. This domain consists of a β barrel enclosing a central α helix and binds selectively to specific membrane phosphoinositides. The vertebrate family of tubby-like proteins (TULPs) includes the founding member TUB and the related TULPs, TULP1 to TULP4. Tulp1 is expressed in the retina and mutations in TULP1 cause retinitis pigmentosa in humans; Tulp3 is expressed ubiquitously in the mouse embryo and is important in sonic hedgehog (Shh)-mediated dorso-ventral patterning of the spinal cord. The amino terminus of these proteins is diverse and directs distinct functions. In the best-characterized example, the TULP3 amino terminus binds to the IFT-A complex, a complex important in intraflagellar transport in the primary cilia, through a short conserved domain. Thus, the tubby family proteins seem to serve as bipartite bridges through their phosphoinositide-binding tubby and unique amino-terminal functional domains, coordinating multiple signaling pathways, including ciliary G-protein-coupled receptor trafficking and Shh signaling. Molecular studies on this functionally diverse protein family are beginning to provide us with remarkable insights into the tubby-mouse syndrome and other related diseases.
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Affiliation(s)
- Saikat Mukhopadhyay
- Department of Cell Regulation, Genentech Inc., South San Francisco, CA 94080, USA.
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Giannelli SG, Demontis GC, Pertile G, Rama P, Broccoli V. Adult Human Müller Glia Cells Are a Highly Efficient Source of Rod Photoreceptors. Stem Cells 2011; 29:344-56. [DOI: 10.1002/stem.579] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Bramall AN, Wright AF, Jacobson SG, McInnes RR. The genomic, biochemical, and cellular responses of the retina in inherited photoreceptor degenerations and prospects for the treatment of these disorders. Annu Rev Neurosci 2011; 33:441-72. [PMID: 20572772 DOI: 10.1146/annurev-neuro-060909-153227] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The association of more than 140 genes with human photoreceptor degenerations, together with studies of animal models of these monogenic diseases, has provided great insight into their pathogenesis. Here we review the responses of the retina to photoreceptor mutations, including mechanisms of photoreceptor death. We discuss the roles of oxidative metabolism, mitochondrial reactive oxygen species, metabolic stress, protein misfolding, and defects in ciliary proteins, as well as the responses of Müller glia, microglia, and the retinal vasculature. Finally, we report on potential pharmacologic and biologic therapies, the critical role of histopathology as a prerequisite to treatment, and the exciting promise of gene therapy in animal models and in phase 1 trials in humans.
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Affiliation(s)
- Alexa N Bramall
- Programs in Genetics and Developmental Biology, The Research Institute, The Hospital for Sick Children, Toronto M5G1L7, Canada.
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West EL, Pearson RA, Barker SE, Luhmann UFO, Maclaren RE, Barber AC, Duran Y, Smith AJ, Sowden JC, Ali RR. Long-term survival of photoreceptors transplanted into the adult murine neural retina requires immune modulation. Stem Cells 2010; 28:1997-2007. [PMID: 20857496 PMCID: PMC3272388 DOI: 10.1002/stem.520] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Stem cell therapy presents an opportunity to replace photoreceptors that are lost as a result of inherited and age-related degenerative disease. We have previously shown that murine postmitotic rod photoreceptor precursor cells, identified by expression of the rod-specific transcription factor Nrl, are able to migrate into and integrate within the adult murine neural retina. However, their long-term survival has yet to be determined. Here, we found that integrated Nrl.gfp(+ve) photoreceptors were present up to 12 months post-transplantation, albeit in significantly reduced numbers. Surviving cells had rod-like morphology, including inner/outer segments and spherule synapses. In a minority of eyes, we observed an early, marked reduction in integrated photoreceptors within 1 month post-transplantation, which correlated with increased numbers of amoeboid macrophages, indicating acute loss of transplanted cells due to an inflammatory response. In the majority of transplants, similar numbers of integrated cells were observed between 1 and 2 months post-transplantation. By 4 months, however, we observed a significant decrease in integrated cell survival. Macrophages and T cells were present around the transplantation site, indicating a chronic immune response. Immune suppression of recipients significantly increased transplanted photoreceptor survival, indicating that the loss observed in unsuppressed recipients resulted from T cell-mediated host immune responses. Thus, if immune responses are modulated, correctly integrated transplanted photoreceptors can survive for extended periods of time in hosts with partially mismatched H-2 haplotypes. These findings suggest that autologous donor cells are optimal for therapeutic approaches to repair the neural retina, though with immune suppression nonautologous donors may be effective.
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Affiliation(s)
- Emma L. West
- Department of Genetics, University College London Institute of Ophthalmology, London, United Kingdom
| | - Rachael A. Pearson
- Department of Genetics, University College London Institute of Ophthalmology, London, United Kingdom
| | - Susie E. Barker
- Department of Genetics, University College London Institute of Ophthalmology, London, United Kingdom
| | - Ulrich F. O. Luhmann
- Department of Genetics, University College London Institute of Ophthalmology, London, United Kingdom
| | - Robert E. Maclaren
- Department of Genetics, University College London Institute of Ophthalmology, London, United Kingdom
| | - Amanda C. Barber
- Department of Genetics, University College London Institute of Ophthalmology, London, United Kingdom
| | - Yanai Duran
- Department of Genetics, University College London Institute of Ophthalmology, London, United Kingdom
| | - Alexander J. Smith
- Department of Genetics, University College London Institute of Ophthalmology, London, United Kingdom
| | - Jane C. Sowden
- Developmental Biology Unit, University College London Institute of Child Health, London, United Kingdom
| | - Robin R. Ali
- Department of Genetics, University College London Institute of Ophthalmology, London, United Kingdom
- NIHR Biomedical Research Centre for Ophthalmology, London, United Kingdom
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Caberoy NB, Zhou Y, Li W. Tubby and tubby-like protein 1 are new MerTK ligands for phagocytosis. EMBO J 2010; 29:3898-910. [PMID: 20978472 DOI: 10.1038/emboj.2010.265] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Accepted: 09/27/2010] [Indexed: 12/29/2022] Open
Abstract
Tubby and tubby-like protein 1 (Tulp1) are newly identified phagocytosis ligands to facilitate retinal pigment epithelium (RPE) and macrophage phagocytosis. Both proteins without classical signal peptide have been demonstrated with unconventional secretion. Here, we characterized them as novel MerTK ligands to facilitate phagocytosis. Tulp1 interacts with Tyro3, Axl and MerTK of the TAM receptor tyrosine kinase subfamily, whereas tubby binds only to MerTK. Excessive soluble MerTK extracellular domain blocked tubby- or Tulp1-mediated phagocytosis. Both ligands induced MerTK activation with receptor phosphorylation and signalling cascade, including non-muscle myosin II redistribution and co-localization with phagosomes. Tubby and Tulp1 are bridging molecules with their N-terminal region as MerTK-binding domain and C-terminal region as phagocytosis prey-binding domain (PPBD). Five minimal phagocytic determinants (MPDs) of K/R(X)(1-2)KKK in Tulp1 N-terminus were defined as essential motifs for MerTK binding, receptor phosphorylation and phagocytosis. PPBD was mapped to the highly conserved 54 amino acids at the C-terminal end of tubby and Tulp1. These data suggest that tubby and Tulp1 are novel bridging molecules to facilitate phagocytosis through MerTK.
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Affiliation(s)
- Nora B Caberoy
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL 33136, USA
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Piccolo and bassoon maintain synaptic vesicle clustering without directly participating in vesicle exocytosis. Proc Natl Acad Sci U S A 2010; 107:6504-9. [PMID: 20332206 DOI: 10.1073/pnas.1002307107] [Citation(s) in RCA: 133] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Piccolo and bassoon are highly homologous multidomain proteins of the presynaptic cytomatrix whose function is unclear. Here, we generated piccolo knockin/knockout mice that either contain wild-type levels of mutant piccolo unable to bind Ca(2+) (knockin), approximately 60% decreased levels of piccolo that is C-terminally truncated (partial knockout), or <5% levels of piccolo (knockout). All piccolo mutant mice were viable and fertile, but piccolo knockout mice exhibited increased postnatal mortality. Unexpectedly, electrophysiology and electron microscopy of piccolo-deficient synapses failed to uncover a major phenotype either in acute hippocampal slices or in cultured cortical neurons. To unmask potentially redundant functions of piccolo and bassoon, we thus acutely knocked down expression of bassoon in wild-type and piccolo knockout neurons. Despite a nearly complete loss of piccolo and bassoon, however, we still did not detect an electrophysiological phenotype in cultured piccolo- and bassoon-deficient neurons in either GABAergic or glutamatergic synaptic transmission. In contrast, electron microscopy revealed a significant reduction in synaptic vesicle clustering in double bassoon/piccolo-deficient synapses. Thus, we propose that piccolo and bassoon play a redundant role in synaptic vesicle clustering in nerve terminals without directly participating in neurotransmitter release.
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Edwards MM, Marín de Evsikova C, Collin GB, Gifford E, Wu J, Hicks WL, Whiting C, Varvel NH, Maphis N, Lamb BT, Naggert JK, Nishina PM, Peachey NS. Photoreceptor degeneration, azoospermia, leukoencephalopathy, and abnormal RPE cell function in mice expressing an early stop mutation in CLCN2. Invest Ophthalmol Vis Sci 2010; 51:3264-72. [PMID: 20071672 DOI: 10.1167/iovs.09-4887] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To determine the molecular basis and the pathologic consequences of a chemically induced mutation in a mouse model of photoreceptor degeneration, nmf240. METHODS Mice from a G3 N-ethyl-N-nitrosourea mutagenesis program were screened by indirect ophthalmoscopy for abnormal fundi. A chromosomal position for the recessive nmf240 mutation was determined by a genome-wide linkage analysis by use of simple sequence length polymorphic markers in an F2 intercross. The critical region was refined, and candidate genes were screened by direct sequencing. The nmf240 phenotype was characterized by histologic analysis of the retina, brain, and male reproductive organs and by electroretinogram (ERG)-based studies of the retina and retinal pigment epithelium (RPE). RESULTS Clinically, homozygous nmf240 mutants exhibit a grainy retina that progresses to panretinal patches of depigmentation. The mutation was localized to a region on chromosome 16 containing Clcn2, a gene associated with retinal degeneration. Sequencing identified a missense C-T mutation at nucleotide 1063 in Clcn2 that converts a glutamine to a stop codon. Mice homozygous for the Clcn2(nmf240) mutation experience a severe loss of photoreceptor cells at 14 days of age that is preceded by an elongation of RPE apical microvilli. Homozygous mutants also experience leukoencephalopathy in multiple brain areas and male sterility. Despite a normal retinal histology in nmf240 heterozygotes, the ERG light peak, generated by the RPE, is reduced. CONCLUSIONS The nmf240 phenotype closely resembles that reported for Clcn2 knockout mice. The observation that heterozygous nmf240 mice present with a reduced ERG light peak component suggests that CLCN2 is necessary for the generation of this response component.
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