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Xu J, Zhao C, Kang Y. The Formation and Renewal of Photoreceptor Outer Segments. Cells 2024; 13:1357. [PMID: 39195247 DOI: 10.3390/cells13161357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2024] [Revised: 08/12/2024] [Accepted: 08/13/2024] [Indexed: 08/29/2024] Open
Abstract
The visual system is essential for humans to perceive the environment. In the retina, rod and cone photoreceptor neurons are the initial sites where vision forms. The apical region of both cone and rod photoreceptors contains a light-sensing organelle known as the outer segment (OS), which houses tens of thousands of light-sensitive opsins. The OSs of photoreceptors are not static; they require rhythmic renewal to maintain normal physiological functions. Disruptions in OS renewal can lead to various genetic disorders, such as retinitis pigmentosa (RP). Understanding the patterns and molecular mechanisms of photoreceptor OS renewal remains one of the most intriguing topics in visual biology. This review aims to elucidate the structure of photoreceptor OSs, the molecular mechanisms underlying photoreceptor OS renewal, and the retinal diseases resulting from defects in this renewal process. Additionally, we will explore retinal diseases related to photoreceptor OS renewal and potential therapeutic strategies, concluding with a discussion on future research directions for OS renewal.
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Affiliation(s)
- Jingjin Xu
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
- MoE Key Laboratory of Evolution and Marine Biodiversity, Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao 266003, China
| | - Chengtian Zhao
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
- MoE Key Laboratory of Evolution and Marine Biodiversity, Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao 266003, China
| | - Yunsi Kang
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
- MoE Key Laboratory of Evolution and Marine Biodiversity, Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao 266003, China
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2
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Sánchez-Bellver L, Toulis V, Marfany G. On the Wrong Track: Alterations of Ciliary Transport in Inherited Retinal Dystrophies. Front Cell Dev Biol 2021; 9:623734. [PMID: 33748110 PMCID: PMC7973215 DOI: 10.3389/fcell.2021.623734] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 02/09/2021] [Indexed: 01/14/2023] Open
Abstract
Ciliopathies are a group of heterogeneous inherited disorders associated with dysfunction of the cilium, a ubiquitous microtubule-based organelle involved in a broad range of cellular functions. Most ciliopathies are syndromic, since several organs whose cells produce a cilium, such as the retina, cochlea or kidney, are affected by mutations in ciliary-related genes. In the retina, photoreceptor cells present a highly specialized neurosensory cilium, the outer segment, stacked with membranous disks where photoreception and phototransduction occurs. The daily renewal of the more distal disks is a unique characteristic of photoreceptor outer segments, resulting in an elevated protein demand. All components necessary for outer segment formation, maintenance and function have to be transported from the photoreceptor inner segment, where synthesis occurs, to the cilium. Therefore, efficient transport of selected proteins is critical for photoreceptor ciliogenesis and function, and any alteration in either cargo delivery to the cilium or intraciliary trafficking compromises photoreceptor survival and leads to retinal degeneration. To date, mutations in more than 100 ciliary genes have been associated with retinal dystrophies, accounting for almost 25% of these inherited rare diseases. Interestingly, not all mutations in ciliary genes that cause retinal degeneration are also involved in pleiotropic pathologies in other ciliated organs. Depending on the mutation, the same gene can cause syndromic or non-syndromic retinopathies, thus emphasizing the highly refined specialization of the photoreceptor neurosensory cilia, and raising the possibility of photoreceptor-specific molecular mechanisms underlying common ciliary functions such as ciliary transport. In this review, we will focus on ciliary transport in photoreceptor cells and discuss the molecular complexity underpinning retinal ciliopathies, with a special emphasis on ciliary genes that, when mutated, cause either syndromic or non-syndromic retinal ciliopathies.
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Affiliation(s)
- Laura Sánchez-Bellver
- Departament de Genètica, Microbiologia i Estadística, Universitat de Barcelona, Barcelona, Spain
- Institute of Biomedicine (IBUB-IRSJD), Universitat de Barcelona, Barcelona, Spain
| | - Vasileios Toulis
- Departament de Genètica, Microbiologia i Estadística, Universitat de Barcelona, Barcelona, Spain
- CIBERER, ISCIII, Universitat de Barcelona, Barcelona, Spain
| | - Gemma Marfany
- Departament de Genètica, Microbiologia i Estadística, Universitat de Barcelona, Barcelona, Spain
- Institute of Biomedicine (IBUB-IRSJD), Universitat de Barcelona, Barcelona, Spain
- CIBERER, ISCIII, Universitat de Barcelona, Barcelona, Spain
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3
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Drivas TG, Lucas A, Zhang X, Ritchie MD. Mendelian pathway analysis of laboratory traits reveals distinct roles for ciliary subcompartments in common disease pathogenesis. Am J Hum Genet 2021; 108:482-501. [PMID: 33636100 PMCID: PMC8008498 DOI: 10.1016/j.ajhg.2021.02.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 02/05/2021] [Indexed: 12/17/2022] Open
Abstract
Rare monogenic disorders of the primary cilium, termed ciliopathies, are characterized by extreme presentations of otherwise common diseases, such as diabetes, hepatic fibrosis, and kidney failure. However, despite a recent revolution in our understanding of the cilium's role in rare disease pathogenesis, the organelle's contribution to common disease remains largely unknown. Hypothesizing that common genetic variants within Mendelian ciliopathy genes might contribute to common complex diseases pathogenesis, we performed association studies of 16,874 common genetic variants across 122 ciliary genes with 12 quantitative laboratory traits characteristic of ciliopathy syndromes in 452,593 individuals in the UK Biobank. We incorporated tissue-specific gene expression analysis, expression quantitative trait loci, and Mendelian disease phenotype information into our analysis and replicated our findings in meta-analysis. 101 statistically significant associations were identified across 42 of the 122 examined ciliary genes (including eight novel replicating associations). These ciliary genes were widely expressed in tissues relevant to the phenotypes being studied, and eQTL analysis revealed strong evidence for correlation between ciliary gene expression levels and laboratory traits. Perhaps most interestingly, our analysis identified different ciliary subcompartments as being specifically associated with distinct sets of phenotypes. Taken together, our data demonstrate the utility of a Mendelian pathway-based approach to genomic association studies, challenge the widely held belief that the cilium is an organelle important mainly in development and in rare syndromic disease pathogenesis, and provide a framework for the continued integration of common and rare disease genetics to provide insight into the pathophysiology of human diseases of immense public health burden.
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Affiliation(s)
- Theodore George Drivas
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19194, USA; Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.
| | - Anastasia Lucas
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19194, USA
| | - Xinyuan Zhang
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19194, USA
| | - Marylyn DeRiggi Ritchie
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19194, USA; Institute for Biomedical Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19194, USA.
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4
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Zebrafish as an animal model for biomedical research. Exp Mol Med 2021; 53:310-317. [PMID: 33649498 PMCID: PMC8080808 DOI: 10.1038/s12276-021-00571-5] [Citation(s) in RCA: 167] [Impact Index Per Article: 55.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2020] [Revised: 01/15/2021] [Accepted: 01/18/2021] [Indexed: 12/15/2022] Open
Abstract
Zebrafish have several advantages compared to other vertebrate models used in modeling human diseases, particularly for large-scale genetic mutant and therapeutic compound screenings, and other biomedical research applications. With the impactful developments of CRISPR and next-generation sequencing technology, disease modeling in zebrafish is accelerating the understanding of the molecular mechanisms of human genetic diseases. These efforts are fundamental for the future of precision medicine because they provide new diagnostic and therapeutic solutions. This review focuses on zebrafish disease models for biomedical research, mainly in developmental disorders, mental disorders, and metabolic diseases.
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Zang J, Neuhauss SCF. Biochemistry and physiology of zebrafish photoreceptors. Pflugers Arch 2021; 473:1569-1585. [PMID: 33598728 PMCID: PMC8370914 DOI: 10.1007/s00424-021-02528-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 01/25/2021] [Accepted: 01/28/2021] [Indexed: 02/06/2023]
Abstract
All vertebrates share a canonical retina with light-sensitive photoreceptors in the outer retina. These photoreceptors are of two kinds: rods and cones, adapted to low and bright light conditions, respectively. They both show a peculiar morphology, with long outer segments, comprised of ordered stacks of disc-shaped membranes. These discs host numerous proteins, many of which contribute to the visual transduction cascade. This pathway converts the light stimulus into a biological signal, ultimately modulating synaptic transmission. Recently, the zebrafish (Danio rerio) has gained popularity for studying the function of vertebrate photoreceptors. In this review, we introduce this model system and its contribution to our understanding of photoreception with a focus on the cone visual transduction cascade.
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Affiliation(s)
- Jingjing Zang
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrase 190, CH - 8057, Zürich, Switzerland
| | - Stephan C F Neuhauss
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrase 190, CH - 8057, Zürich, Switzerland.
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6
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Ma L, Ng M, van der Weele CM, Yoshizawa M, Jeffery WR. Dual roles of the retinal pigment epithelium and lens in cavefish eye degeneration. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2020; 334:438-449. [PMID: 31930686 DOI: 10.1002/jez.b.22923] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 11/04/2019] [Accepted: 12/21/2019] [Indexed: 01/03/2023]
Abstract
Astyanax mexicanus consists of two forms, a sighted surface dwelling form (surface fish) and a blind cave-dwelling form (cavefish). Embryonic eyes are initially formed in cavefish but they are subsequently arrested in growth and degenerate during larval development. Previous lens transplantation studies have shown that the lens plays a central role in cavefish eye loss. However, several lines of evidence suggest that additional factors, such as the retinal pigment epithelium (RPE), which is morphologically altered in cavefish, could also be involved in the eye regression process. To explore the role of the RPE in cavefish eye degeneration, we generated an albino eyed (AE) strain by artificial selection for hybrid individuals with large eyes and a depigmented RPE. The AE strain exhibited an RPE lacking pigment granules and showed reduced expression of the RPE specific enzyme retinol isomerase, allowing eye development to be studied by lens ablation in an RPE background resembling cavefish. We found that lens ablation in the AE strain had stronger negative effects on eye growth than in surface fish, suggesting that an intact RPE is required for normal eye development. We also found that the AE strain develops a cartilaginous sclera lacking boney ossicles, a trait similar to cavefish. Extrapolation of the results to cavefish suggests that the RPE and lens have dual roles in eye degeneration, and that deficiencies in the RPE may be associated with evolutionary changes in scleral ossification.
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Affiliation(s)
- Li Ma
- Department of Biology, University of Maryland, College Park, Maryland
| | - Mandy Ng
- Department of Biology, University of Maryland, College Park, Maryland
| | | | - Masato Yoshizawa
- Department of Biology, University of Maryland, College Park, Maryland
| | - William R Jeffery
- Department of Biology, University of Maryland, College Park, Maryland
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7
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Baehr W, Hanke-Gogokhia C, Sharif A, Reed M, Dahl T, Frederick JM, Ying G. Insights into photoreceptor ciliogenesis revealed by animal models. Prog Retin Eye Res 2018; 71:26-56. [PMID: 30590118 DOI: 10.1016/j.preteyeres.2018.12.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 12/10/2018] [Accepted: 12/18/2018] [Indexed: 12/11/2022]
Abstract
Photoreceptors are polarized neurons, with very specific subcellular compartmentalization and unique requirements for protein expression and trafficking. Each photoreceptor contains an outer segment, the site of photon capture that initiates vision, an inner segment that houses the biosynthetic machinery and a synaptic terminal for signal transmission to downstream neurons. Outer segments and inner segments are connected by a connecting cilium (CC), the equivalent of a transition zone (TZ) of primary cilia. The connecting cilium is part of the basal body/axoneme backbone that stabilizes the outer segment. This report will update the reader on late developments in photoreceptor ciliogenesis and transition zone formation, specifically in mouse photoreceptors, focusing on early events in photoreceptor ciliogenesis. The connecting cilium, an elongated and narrow structure through which all outer segment proteins and membrane components must traffic, functions as a gate that controls access to the outer segment. Here we will review genes and their protein products essential for basal body maturation and for CC/TZ genesis, sorted by phenotype. Emphasis is given to naturally occurring mouse mutants and gene knockouts that interfere with CC/TZ formation and ciliogenesis.
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Affiliation(s)
- Wolfgang Baehr
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences, Salt Lake City, UT, 84132, USA.
| | - Christin Hanke-Gogokhia
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences, Salt Lake City, UT, 84132, USA
| | - Ali Sharif
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences, Salt Lake City, UT, 84132, USA
| | - Michelle Reed
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences, Salt Lake City, UT, 84132, USA
| | - Tiffanie Dahl
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences, Salt Lake City, UT, 84132, USA
| | - Jeanne M Frederick
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences, Salt Lake City, UT, 84132, USA
| | - Guoxin Ying
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences, Salt Lake City, UT, 84132, USA
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Lewis TR, Kundinger SR, Link BA, Insinna C, Besharse JC. Kif17 phosphorylation regulates photoreceptor outer segment turnover. BMC Cell Biol 2018; 19:25. [PMID: 30458707 PMCID: PMC6245759 DOI: 10.1186/s12860-018-0177-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 11/07/2018] [Indexed: 12/02/2022] Open
Abstract
Background KIF17, a kinesin-2 motor that functions in intraflagellar transport, can regulate the onset of photoreceptor outer segment development. However, the function of KIF17 in a mature photoreceptor remains unclear. Additionally, the ciliary localization of KIF17 is regulated by a C-terminal consensus sequence (KRKK) that is immediately adjacent to a conserved residue (mouse S1029/zebrafish S815) previously shown to be phosphorylated by CaMKII. Yet, whether this phosphorylation can regulate the localization, and thus function, of KIF17 in ciliary photoreceptors remains unknown. Results Using transgenic expression in zebrafish photoreceptors, we show that phospho-mimetic KIF17 has enhanced localization along the cone outer segment. Importantly, expression of phospho-mimetic KIF17 is associated with greatly enhanced turnover of the photoreceptor outer segment through disc shedding in a cell-autonomous manner, while genetic mutants of kif17 in zebrafish and mice have diminished disc shedding. Lastly, cone expression of constitutively active tCaMKII leads to a kif17-dependent increase in disc shedding. Conclusions Taken together, our data support a model in which phosphorylation of KIF17 promotes its photoreceptor outer segment localization and disc shedding, a process essential for photoreceptor maintenance and homeostasis. While disc shedding has been predominantly studied in the context of the mechanisms underlying phagocytosis of outer segments by the retinal pigment epithelium, this work implicates photoreceptor-derived signaling in the underlying mechanisms of disc shedding. Electronic supplementary material The online version of this article (10.1186/s12860-018-0177-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Tylor R Lewis
- Department of Cell Biology, Neurobiology, and Anatomy Medical College of Wisconsin, Milwaukee, WI, USA
| | - Sean R Kundinger
- Department of Ophthalmology and Visual Sciences Medical College of Wisconsin, Milwaukee, WI, USA
| | - Brian A Link
- Department of Cell Biology, Neurobiology, and Anatomy Medical College of Wisconsin, Milwaukee, WI, USA
| | - Christine Insinna
- Department of Cell Biology, Neurobiology, and Anatomy Medical College of Wisconsin, Milwaukee, WI, USA.,Laboratory of Cell and Developmental Signaling National Cancer Institute-Frederick, Frederick, MD, USA
| | - Joseph C Besharse
- Department of Cell Biology, Neurobiology, and Anatomy Medical College of Wisconsin, Milwaukee, WI, USA. .,Department of Ophthalmology and Visual Sciences Medical College of Wisconsin, Milwaukee, WI, USA.
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Schwarz N, Lane A, Jovanovic K, Parfitt DA, Aguila M, Thompson CL, da Cruz L, Coffey PJ, Chapple JP, Hardcastle AJ, Cheetham ME. Arl3 and RP2 regulate the trafficking of ciliary tip kinesins. Hum Mol Genet 2017; 26:2480-2492. [PMID: 28444310 PMCID: PMC5808637 DOI: 10.1093/hmg/ddx143] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 04/07/2017] [Accepted: 04/11/2017] [Indexed: 11/14/2022] Open
Abstract
Ciliary trafficking defects are the underlying cause of many ciliopathies, including Retinitis Pigmentosa (RP). Anterograde intraflagellar transport (IFT) is mediated by kinesin motor proteins; however, the function of the homodimeric Kif17 motor in cilia is poorly understood, whereas Kif7 is known to play an important role in stabilizing cilia tips. Here we identified the ciliary tip kinesins Kif7 and Kif17 as novel interaction partners of the small GTPase Arl3 and its regulatory GTPase activating protein (GAP) Retinitis Pigmentosa 2 (RP2). We show that Arl3 and RP2 mediate the localization of GFP-Kif17 to the cilia tip and competitive binding of RP2 and Arl3 with Kif17 complexes. RP2 and Arl3 also interact with another ciliary tip kinesin, Kif7, which is a conserved regulator of Hedgehog (Hh) signaling. siRNA-mediated loss of RP2 or Arl3 reduced the level of Kif7 at the cilia tip. This was further validated by reduced levels of Kif7 at cilia tips detected in fibroblasts and induced pluripotent stem cell (iPSC) 3D optic cups derived from a patient carrying an RP2 nonsense mutation c.519C > T (p.R120X), which lack detectable RP2 protein. Translational read-through inducing drugs (TRIDs), such as PTC124, were able to restore Kif7 levels at the ciliary tip of RP2 null cells. Collectively, our findings suggest that RP2 and Arl3 regulate the trafficking of specific kinesins to cilia tips and provide additional evidence that TRIDs could be clinically beneficial for patients with this retinal degeneration.
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Affiliation(s)
- Nele Schwarz
- UCL Institute of Ophthalmology, London EC1V 9EL, UK
| | - Amelia Lane
- UCL Institute of Ophthalmology, London EC1V 9EL, UK
| | | | | | | | - Clare L. Thompson
- Institute of Bioengineering, School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, UK
| | - Lyndon da Cruz
- UCL Institute of Ophthalmology, London EC1V 9EL, UK
- Moorfields Eye Hospital, London EC1V 2PD, UK
| | | | - J. Paul Chapple
- William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary University of London, London EC1M 6BQ, UK
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Lewis TR, Kundinger SR, Pavlovich AL, Bostrom JR, Link BA, Besharse JC. Cos2/Kif7 and Osm-3/Kif17 regulate onset of outer segment development in zebrafish photoreceptors through distinct mechanisms. Dev Biol 2017; 425:176-190. [PMID: 28341548 PMCID: PMC5558849 DOI: 10.1016/j.ydbio.2017.03.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 03/20/2017] [Accepted: 03/20/2017] [Indexed: 12/19/2022]
Abstract
Zebrafish morphants of osm-3/kif17, a kinesin-2 family member and intraflagellar transport motor, have photoreceptor outer segments that are dramatically reduced in number and size. However, two genetic mutant lines, osm-3/kif17sa0119 and osm-3/kif17sa18340, reportedly lack any observable morphological outer segment defects. In this work, we use TALENs to generate an independent allele, osm-3/kif17mw405, and show that both osm-3/kif17sa0119 and osm-3/kif17mw405 have an outer segment developmental delay in both size and density that is fully recovered by 6 days post-fertilization. Additionally, we use CRISPRs to generate cos2/kif7mw406, a mutation in the kinesin-4 family member cos2/kif7 that has been implicated in controlling ciliary architecture and Hedgehog signaling to test whether it may be functioning redundantly with osm-3/kif17. We show that cos2/kif7mw406 has an outer segment developmental delay similar to the osm-3/kif17 mutants. Using a three-dimensional mathematical model of outer segments, we show that while cos2/kif7mw406 and osm-3/kif17mw405 outer segments are smaller throughout the first 6 days of development, the volumetric rates of outer segment morphogenesis are not different among wild-type, cos2/kif7mw406, and osm-3/kif17mw405 after 60hpf. Instead, our model suggests that cos2/kif7mw406 and osm-3/kif17mw405 impact outer segment morphogenesis through upstream events that that are different for each motor. In the case of cos2/kif7mw406 mutants, we show that early defects in Hedgehog signaling lead to a general, non-photoreceptor-specific delay of retinal neurogenesis, which in turn causes the secondary phenotype of delayed outer segment morphogenesis. In contrast, the osm-3/kif17mw405 outer segment morphogenesis delays are linked specifically to initial disc morphogenesis of photoreceptors rather than an upstream event. Further, we show that osm-3/kif17 mutant mice also exhibit a similarly delayed outer segment development, suggesting a role for osm-3/kif17 in early outer segment development that is conserved across species. In conclusion, we show that both osm-3/kif17 and cos2/kif7 have comparable outer segment developmental delays, although through independent mechanisms.
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Affiliation(s)
- Tylor R Lewis
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Sean R Kundinger
- Department of Ophthalmology and Visual Sciences, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Amira L Pavlovich
- Department of Ophthalmology and Visual Sciences, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Jonathan R Bostrom
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Brian A Link
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Joseph C Besharse
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA; Department of Ophthalmology and Visual Sciences, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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Brockerhoff SE. Genome Editing to Study Ca 2+ Homeostasis in Zebrafish Cone Photoreceptors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1016:91-100. [PMID: 29130155 DOI: 10.1007/978-3-319-63904-8_5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Photoreceptors are specialized sensory neurons with unique biological features. Phototransduction is well understood due in part to the exclusive expression and function of the molecular components of this cascade. Many other processes are less well understood, but also extremely important for understanding photoreceptor function and for treating disease. One example is the role of Ca2+ in the cell body and overall compartmentalization and regulation of Ca2+ within the cell. The recent development of CRISPR/Cas9 genome editing techniques has made it possible to rapidly and cheaply alter specific genes. This will help to define the biological function of elusive processes that have been more challenging to study. CRISPR/Cas9 has been optimized in many systems including zebrafish, which already has some distinct advantages for studying photoreceptor biology and function. These new genome editing technologies and the continued use of the zebrafish model system will help advance our understanding of important understudied aspects of photoreceptor biology.
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Affiliation(s)
- Susan E Brockerhoff
- Departments of Biochemistry and Ophthalmology, University of Washington, UW Medicine, 750 Republican St, Box 358058, Seattle, WA, 98109, USA.
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12
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Unexpected Roles for Ciliary Kinesins and Intraflagellar Transport Proteins. Genetics 2016; 203:771-85. [PMID: 27038111 DOI: 10.1534/genetics.115.180943] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 03/22/2016] [Indexed: 11/18/2022] Open
Abstract
Transport of proteins in the ciliary shaft is driven by microtubule-dependent motors, kinesins. Prior studies suggested that the heterotrimeric ciliary kinesin may be dispensable for certain aspects of transport in specialized cilia of vertebrate photoreceptor cells. To test this possibility further, we analyzed the mutant phenotype of the zebrafish kif3a gene, which encodes the common motor subunit of heterotrimeric ciliary kinesins. Cilia are absent in all organs examined, leading to the conclusion that kif3a is indispensable for ciliogenesis in all cells, including photoreceptors. Unexpectedly, kif3a function precedes ciliogenesis as ciliary basal bodies are mispositioned in mutant photoreceptors. This phenotype is much less pronounced in intraflagellar transport (IFT) mutants and reveals that kif3a has a much broader role than previously assumed. Despite the severity of their basal body phenotype, kif3a mutant photoreceptors survive longer compared to those in IFT mutants, which display much weaker basal body mispositioning. This effect is absent in kif3a;IFT double mutants, indicating that IFT proteins have ciliary transport-independent roles, which add to the severity of their photoreceptor phenotype. kif3a is dispensable for basal body docking in otic vesicle sensory epithelia and, surprisingly, short cilia form in mechanosensory cristae even in the absence of kif3a In contrast to Kif3a, the functions of the Kif3c-related protein, encoded by the kif3c-like (kif3cl) gene, and the homodimeric ciliary kinesin, kif17, are dispensable for photoreceptor morphogenesis. These studies demonstrate unexpected new roles for both ciliary heterotrimeric kinesins and IFT particle genes and clarify the function of kif17, the homodimeric ciliary kinesin gene.
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Abstract
Visual defects affect a large proportion of humanity, have a significant negative impact on quality of life, and cause significant economic burden. The wide variety of visual disorders and the large number of gene mutations responsible require a flexible animal model system to carry out research for possible causes and cures for the blinding conditions. With eyes similar to humans in structure and function, zebrafish are an important vertebrate model organism that is being used to study genetic and environmental eye diseases, including myopia, glaucoma, retinitis pigmentosa, ciliopathies, albinism, and diabetes. This review details the use of zebrafish in modeling human ocular diseases.
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Affiliation(s)
- Brian A Link
- Department of Cell Biology, Neurobiology & Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin 53226; ,
| | - Ross F Collery
- Department of Cell Biology, Neurobiology & Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin 53226; ,
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14
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Jiang L, Tam BM, Ying G, Wu S, Hauswirth WW, Frederick JM, Moritz OL, Baehr W. Kinesin family 17 (osmotic avoidance abnormal-3) is dispensable for photoreceptor morphology and function. FASEB J 2015; 29:4866-80. [PMID: 26229057 DOI: 10.1096/fj.15-275677] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 07/27/2015] [Indexed: 01/22/2023]
Abstract
In Caenorhabditis elegans, homodimeric [kinesin family (KIF) 17, osmotic avoidance abnormal-3 (OSM-3)] and heterotrimeric (KIF3) kinesin-2 motors are required to establish sensory cilia by intraflagellar transport (IFT) where KIF3 and KIF17 cooperate to build the axoneme core and KIF17 builds the distal segments. However, the function of KIF17 in vertebrates is unresolved. We expressed full-length and motorless KIF17 constructs in mouse rod photoreceptors using adeno-associated virus in Xenopus laevis rod photoreceptors using a transgene and in ciliated IMCD3 cells. We found that tagged KIF17 localized along the rod outer segment axoneme when expressed in mouse and X. laevis photoreceptors, whereas KIF3A was restricted to the proximal axoneme. Motorless KIF3A and KIF17 mutants caused photoreceptor degeneration, likely through dominant negative effects on IFT. KIF17 mutant lacking the motor domain translocated to nuclei after exposure of a C-terminal nuclear localization signal. Germ-line deletion of Kif17 in mouse did not affect photoreceptor function. A rod-specific Kif3/Kif17 double knockout mouse demonstrated that KIF17 and KIF3 do not act synergistically and did not prevent rhodopsin trafficking to rod outer segments. In summary, the nematode model of KIF3/KIF17 cooperation apparently does not apply to mouse photoreceptors in which the photosensory cilium is built exclusively by KIF3.
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Affiliation(s)
- Li Jiang
- *Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada; State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China; Department of Ophthalmology, University of Florida College of Medicine, Gainesville, Florida, USA; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
| | - Beatrice M Tam
- *Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada; State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China; Department of Ophthalmology, University of Florida College of Medicine, Gainesville, Florida, USA; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
| | - Guoxing Ying
- *Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada; State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China; Department of Ophthalmology, University of Florida College of Medicine, Gainesville, Florida, USA; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
| | - Sen Wu
- *Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada; State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China; Department of Ophthalmology, University of Florida College of Medicine, Gainesville, Florida, USA; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
| | - William W Hauswirth
- *Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada; State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China; Department of Ophthalmology, University of Florida College of Medicine, Gainesville, Florida, USA; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
| | - Jeanne M Frederick
- *Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada; State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China; Department of Ophthalmology, University of Florida College of Medicine, Gainesville, Florida, USA; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
| | - Orson L Moritz
- *Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada; State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China; Department of Ophthalmology, University of Florida College of Medicine, Gainesville, Florida, USA; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
| | - Wolfgang Baehr
- *Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada; State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China; Department of Ophthalmology, University of Florida College of Medicine, Gainesville, Florida, USA; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
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15
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Jiang L, Wei Y, Ronquillo CC, Marc RE, Yoder BK, Frederick JM, Baehr W. Heterotrimeric kinesin-2 (KIF3) mediates transition zone and axoneme formation of mouse photoreceptors. J Biol Chem 2015; 290:12765-78. [PMID: 25825494 DOI: 10.1074/jbc.m115.638437] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Indexed: 11/06/2022] Open
Abstract
Anterograde intraflagellar transport (IFT) employing kinesin-2 molecular motors has been implicated in trafficking of photoreceptor outer segment proteins. We generated embryonic retina-specific (prefix "emb") and adult tamoxifen-induced (prefix "tam") deletions of KIF3a and IFT88 in adult mice to study photoreceptor ciliogenesis and protein trafficking. In (emb)Kif3a(-/-) and in (emb)Ift88(-/-) mice, basal bodies failed to extend transition zones (connecting cilia) with outer segments, and visual pigments mistrafficked. In contrast, (tam)Kif3a(-/-) and (tam)Ift88(-/-) photoreceptor axonemes disintegrated slowly post-induction, starting distally, but rhodopsin and cone pigments trafficked normally for more than 2 weeks, a time interval during which the outer segment is completely renewed. The results demonstrate that visual pigments transport to the retinal outer segment despite removal of KIF3 and IFT88, and KIF3-mediated anterograde IFT is responsible for photoreceptor transition zone and axoneme formation.
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Affiliation(s)
- Li Jiang
- From the Departments of Ophthalmology and Visual Sciences and
| | - Yuxiao Wei
- From the Departments of Ophthalmology and Visual Sciences and
| | | | - Robert E Marc
- From the Departments of Ophthalmology and Visual Sciences and
| | - Bradley K Yoder
- the Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama 35294, and
| | | | - Wolfgang Baehr
- From the Departments of Ophthalmology and Visual Sciences and the Department of Biology, University of Utah, Salt Lake City, Utah 84112 Neurobiology and Anatomy, University of Utah Health Science Center, Salt Lake City, Utah 84132,
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16
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Santi-Rocca J, Chenouard N, Fort C, Lagache T, Olivo-Marin JC, Bastin P. Imaging intraflagellar transport in trypanosomes. Methods Cell Biol 2015; 127:487-508. [PMID: 25837405 DOI: 10.1016/bs.mcb.2015.01.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Trypanosoma brucei is a flagellated eukaryotic pathogen responsible for sleeping sickness in central Africa. Because of the presence of a long motile flagellum (>20 μm) and its amenity to genetic manipulation, it is becoming an attractive model to study the assembly and the functions of cilia and flagella. In recent years, several aspects have been investigated, especially intraflagellar transport (IFT) that has been exhaustively characterized at the light microscopy level. In this manuscript, we review various methods to express fluorescent fusion proteins and to record IFT in living trypanosomes in normal or mutant contexts. We present an approach for separating anterograde and retrograde IFT, hence facilitating quantification of train speed, frequency, and size. A statistical analysis to discriminate different subpopulations of IFT trains is also summarized. These methods have proven their efficiency for the study of IFT in trypanosomes and could be applied to any other organism.
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Affiliation(s)
- Julien Santi-Rocca
- Trypanosome Cell Biology Unit, Institut Pasteur & CNRS URA2581, Paris, France
| | - Nicolas Chenouard
- Bio Image Analysis Unit, Institut Pasteur & CNRS URA2582, Paris, France
| | - Cécile Fort
- Trypanosome Cell Biology Unit, Institut Pasteur & CNRS URA2581, Paris, France
| | - Thibault Lagache
- Bio Image Analysis Unit, Institut Pasteur & CNRS URA2582, Paris, France
| | | | - Philippe Bastin
- Trypanosome Cell Biology Unit, Institut Pasteur & CNRS URA2581, Paris, France
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17
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Pearring JN, Salinas RY, Baker SA, Arshavsky VY. Protein sorting, targeting and trafficking in photoreceptor cells. Prog Retin Eye Res 2013; 36:24-51. [PMID: 23562855 DOI: 10.1016/j.preteyeres.2013.03.002] [Citation(s) in RCA: 137] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 03/22/2013] [Accepted: 03/26/2013] [Indexed: 01/24/2023]
Abstract
Vision is the most fundamental of our senses initiated when photons are absorbed by the rod and cone photoreceptor neurons of the retina. At the distal end of each photoreceptor resides a light-sensing organelle, called the outer segment, which is a modified primary cilium highly enriched with proteins involved in visual signal transduction. At the proximal end, each photoreceptor has a synaptic terminal, which connects this cell to the downstream neurons for further processing of the visual information. Understanding the mechanisms involved in creating and maintaining functional compartmentalization of photoreceptor cells remains among the most fascinating topics in ocular cell biology. This review will discuss how photoreceptor compartmentalization is supported by protein sorting, targeting and trafficking, with an emphasis on the best-studied cases of outer segment-resident proteins.
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Affiliation(s)
- Jillian N Pearring
- Department of Ophthalmology, Duke University Medical Center, Durham, NC 27710, USA
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