scholarly journals Accumulation of non-outer segment proteins in the outer segment underlies photoreceptor degeneration in Bardet–Biedl syndrome

2015 ◽  
Vol 112 (32) ◽  
pp. E4400-E4409 ◽  
Author(s):  
Poppy Datta ◽  
Chantal Allamargot ◽  
Joseph S. Hudson ◽  
Emily K. Andersen ◽  
Sajag Bhattarai ◽  
...  
Keyword(s):  
Protein Trafficking ◽  
Outer Segment ◽  
Primary Cilia ◽  
Leucine Zipper ◽  
Photoreceptor Cells ◽  
Photoreceptor Degeneration ◽  
Photoreceptor Outer Segment ◽  
Bardet Biedl Syndrome ◽  
Major Function ◽  
Underlying Mechanisms

Compartmentalization and polarized protein trafficking are essential for many cellular functions. The photoreceptor outer segment (OS) is a sensory compartment specialized for phototransduction, and it shares many features with primary cilia. As expected, mutations disrupting protein trafficking to cilia often disrupt protein trafficking to the OS and cause photoreceptor degeneration. Bardet–Biedl syndrome (BBS) is one of the ciliopathies associated with defective ciliary trafficking and photoreceptor degeneration. However, precise roles of BBS proteins in photoreceptor cells and the underlying mechanisms of photoreceptor degeneration in BBS are not well understood. Here, we show that accumulation of non-OS proteins in the OS underlies photoreceptor degeneration in BBS. Using a newly developed BBS mouse model [Leucine zipper transcription factor-like 1 (Lztfl1)/Bbs17 mutant], isolated OSs, and quantitative proteomics, we determined 138 proteins that are enriched more than threefold in BBS mutant OS. In contrast, only eight proteins showed a more than threefold reduction. We found striking accumulation of Stx3 and Stxbp1/Munc18-1 and loss of polarized localization of Prom1 within the Lztfl1 and Bbs1 mutant OS. Ultrastructural analysis revealed that large vesicles are formed in the BBS OS, disrupting the lamellar structure of the OS. Our findings suggest that accumulation (and consequent sequestration) of non-OS proteins in the OS is likely the primary cause of photoreceptor degeneration in BBS. Our data also suggest that a major function of BBS proteins in photoreceptors is to transport proteins from the OS to the cell body or to prevent entry of non-OS proteins into the OS.

Retinal Diseases with Ciliopathies

2021 ◽  
pp. 271-278
Keyword(s):  
Retinitis Pigmentosa ◽  
Outer Segment ◽  
Usher Syndrome ◽  
Joubert Syndrome ◽  
Retinal Diseases ◽  
Bardet Biedl Syndrome ◽  
Retinal Photoreceptors ◽  
Underlying Mechanisms ◽  
Larsson Syndrome ◽  
Functional Defects

Ciliopathies are a group of diseases that affects cells containing the cilia organel. Retinal involvement is frequent in ciliopathies. The outer segment of retinal photoreceptors is composed of the cilium. Functional defects limited to the photoreceptors cilia, in particular, are classified as non-syndromic ciliopathies like Leber congenital amaurosis and retinitis pigmentosa. Photoreceptor disease also manifests as a part of syndromic ciliopathies with the involvement of multiple tissues as Usher syndrome, Joubert syndrome, Meckel-Gruber syndrome, Senior-Loken syndrome, Sjögren-Larsson syndrome, Bardet-Biedl syndrome, and Alstrom syndrome. Underlying mechanisms of pathology remain largely unclear in these diseases. Symptoms are treated using current methods. This paper describes the pathogenesis, clinics, diagnosis, and treatment of retinal diseases occurring due to ciliopathy.

scholarly journals The Bardet-Biedl protein Bbs1 controls photoreceptor outer segment protein and lipid composition

2021 ◽  
Author(s):  
Markus Masek ◽  
Christelle Etard ◽  
Claudia Hofmann ◽  
Andreas Huelsmeier ◽  
Jingjing Zang ◽  
...  
Keyword(s):  
Retinal Degeneration ◽  
Lipid Composition ◽  
Quantitative Proteomics ◽  
Primary Cilia ◽  
Cholesterol Content ◽  
Lipid Homeostasis ◽  
Photoreceptor Outer Segment ◽  
Bardet Biedl Syndrome ◽  
Visual Deficits ◽  
Associated Proteins

Primary cilia are key sensory organelles whose dysfunction leads to ciliopathy disorders such as Bardet-Biedl syndrome (BBS). Retinal degeneration is common in ciliopathies, since the outer segments (OSs) of photoreceptors are highly specialized primary cilia. BBS1, encoded by the most commonly mutated BBS-associated gene, is part of the BBSome protein complex. Using a new bbs1 zebrafish mutant, we show that retinal development and photoreceptor differentiation are unaffected by Bbs1-loss, supported by an initially unaffected transcriptome. Quantitative proteomics and lipidomics on isolated OSs show that Bbs1 is required for BBSome-entry into OSs and that Bbs1-loss leads to accumulation of membrane-associated proteins in OSs, with enrichment in proteins involved in lipid homeostasis. Disruption of the tightly regulated OS lipid composition with increased OS cholesterol content are paralleled by early functional visual deficits, which precede progressive OS morphological anomalies. Our findings identify a new role for Bbs1/BBSome in OS lipid homeostasis and suggest a new pathomechanism underlying retinal degeneration in BBS.

scholarly journals A Computational Pipeline for Functional Gene Discovery

2021 ◽  
Author(s):  
Aolani Colon ◽  
Rishabh Hirday ◽  
Ami Patel ◽  
Amrita Poddar ◽  
Emma Tuberty-Vaughan ◽  
...  
Keyword(s):  
Candidate Genes ◽  
Outer Segment ◽  
Gene Discovery ◽  
Immunohistochemical Analysis ◽  
Transcriptome Profiling ◽  
Photoreceptor Cells ◽  
Functional Gene ◽  
Mouse Retina ◽  
Computational Pipeline ◽  
Photoreceptor Outer Segment

Abstract Many computational pipelines exist for the detection of differentially expressed genes. However, computational pipelines for functional gene detection are rarely exist. We developed a new computational pipeline for functional gene identification from transcriptome profiling data. Key features of the pipeline include clustering optimization by gap statistics, gene ontology analysis for each cluster, and literature analysis for functional gene discovery. By leveraging this pipeline on RNA-seq datasets of mouse retinal development studies, we identified 14 candidate genes involved in the formation of the photoreceptor outer segment. The expression of top three candidate genes (Pde8b, Laptm4b, and Nr1h4) in the outer segment of the developing mouse retina were experimentally validated by immunohistochemical analysis. This computational pipeline can accurately predict novel functional gene for a specific biological process, e.g., the outer segment development of the photoreceptor cells in the mouse retina. This pipeline is also applicable to functional gene discovery for any other biological processes and in any other organs and tissues.

scholarly journals ARL2BP, a protein linked to retinitis pigmentosa, is needed for normal photoreceptor cilia doublets and outer segment structure

2018 ◽  
Vol 29 (13) ◽  
pp. 1590-1598 ◽  
Author(s):  
Abigail R. Moye ◽  
Ratnesh Singh ◽  
Victoria A. Kimler ◽  
Tanya L. Dilan ◽  
Daniella Munezero ◽  
...  
Keyword(s):  
Retinitis Pigmentosa ◽  
Outer Segment ◽  
Photoreceptor Cells ◽  
Visual Response ◽  
Photoreceptor Degeneration ◽  
Progressive Reduction ◽  
Ciliary Protein ◽  
Vertically Aligned ◽  
And Function

The outer segment (OS) of photoreceptor cells is an elaboration of a primary cilium with organized stacks of membranous disks that contain the proteins needed for phototransduction and vision. Though ciliary formation and function has been well characterized, little is known about the role of cilia in the development of photoreceptor OS. Nevertheless, progress has been made by studying mutations in ciliary proteins, which often result in malformed OSs and lead to blinding diseases. To investigate how ciliary proteins contribute to OS formation, we generated a knockout (KO) mouse model for ARL2BP, a ciliary protein linked to retinitis pigmentosa. The KO mice display an early and progressive reduction in visual response. Before photoreceptor degeneration, we observed disorganization of the photoreceptor OS, with vertically aligned disks and shortened axonemes. Interestingly, ciliary doublet microtubule (MT) structure was also impaired, displaying open B-tubule doublets, paired with loss of singlet MTs. On the basis of results from this study, we conclude that ARL2BP is necessary for photoreceptor ciliary doublet formation and axoneme elongation, which is required for OS morphogenesis and vision.

scholarly journals A computational pipeline for functional gene discovery

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aolani Colon ◽  
Rishabh Hirday ◽  
Ami Patel ◽  
Amrita Poddar ◽  
Emma Tuberty-Vaughan ◽  
...  
Keyword(s):  
Candidate Genes ◽  
Outer Segment ◽  
Gene Discovery ◽  
Immunohistochemical Analysis ◽  
Transcriptome Profiling ◽  
Photoreceptor Cells ◽  
Functional Gene ◽  
Mouse Retina ◽  
Computational Pipeline ◽  
Photoreceptor Outer Segment

AbstractMany computational pipelines exist for the detection of differentially expressed genes. However, computational pipelines for functional gene detection rarely exist. We developed a new computational pipeline for functional gene identification from transcriptome profiling data. Key features of the pipeline include batch effect correction, clustering optimization by gap statistics, gene ontology analysis of clustered genes, and literature analysis for functional gene discovery. By leveraging this pipeline on RNA-seq datasets from two mouse retinal development studies, we identified 7 candidate genes involved in the formation of the photoreceptor outer segment. The expression of top three candidate genes (Pde8b, Laptm4b, and Nr1h4) in the outer segment of the developing mouse retina were experimentally validated by immunohistochemical analysis. This computational pipeline can accurately predict novel functional gene for a specific biological process, e.g., development of the outer segment and synapses of the photoreceptor cells in the mouse retina. This pipeline can also be useful to discover functional genes for other biological processes and in other organs and tissues.

scholarly journals Photoreceptor discs form through peripherin-dependent suppression of ciliary ectosome release

2017 ◽  
Vol 216 (5) ◽  
pp. 1489-1499 ◽  
Author(s):  
Raquel Y. Salinas ◽  
Jillian N. Pearring ◽  
Jin-Dong Ding ◽  
William J. Spencer ◽  
Ying Hao ◽  
...  
Keyword(s):  
Primary Cilium ◽  
Outer Segment ◽  
Genetic Material ◽  
Photoreceptor Cells ◽  
Specific Protein ◽  
Photoreceptor Outer Segment ◽  
Extracellular Signals ◽  
Membrane Surfaces ◽  
Light Capture ◽  
Innate Ability

The primary cilium is a highly conserved organelle housing specialized molecules responsible for receiving and processing extracellular signals. A recently discovered property shared across many cilia is the ability to release small vesicles called ectosomes, which are used for exchanging protein and genetic material among cells. In this study, we report a novel role for ciliary ectosomes in building the elaborate photoreceptor outer segment filled with hundreds of tightly packed “disc” membranes. We demonstrate that the photoreceptor cilium has an innate ability to release massive amounts of ectosomes. However, this process is suppressed by the disc-specific protein peripherin, which enables retained ectosomes to be morphed into discs. This new function of peripherin is performed independently from its well-established role in maintaining the high curvature of disc edges, and each function is fulfilled by a separate part of peripherin’s molecule. Our findings explain how the outer segment structure evolved from the primary cilium to provide photoreceptor cells with vast membrane surfaces for efficient light capture.

scholarly journals Distribution of guanylate cyclase within photoreceptor outer segments

1996 ◽  
Vol 109 (7) ◽  
pp. 1803-1812
Author(s):  
M.A. Hallett ◽  
J.L. Delaat ◽  
K. Arikawa ◽  
C.L. Schlamp ◽  
F. Kong ◽  
...  
Keyword(s):  
Guanylate Cyclase ◽  
Actin Filaments ◽  
Outer Segment ◽  
Essential Role ◽  
Photoreceptor Cells ◽  
Rod Photoreceptor ◽  
Light Activation ◽  
Photoreceptor Outer Segment ◽  
Photoreceptor Outer Segments ◽  
Vertebrate Photoreceptor

Guanylate cyclases play an essential role in the recovery of vertebrate photoreceptor cells after light activation. Here, we have investigated how one such guanylate cyclase, RetGC-1, is distributed within light- and dark-adapted rod photoreceptor cells. Guanylate cyclase activity partitioned with the photoreceptor outer segment (OS) cytoskeleton in a light-sensitive manner. RetGC-1 was found to bind actin filaments in actin blot overlays, suggesting a mechanism for its association with the OS cytoskeleton. In retinal sections, this enzyme was immunodetected only in the OSs, where it appeared to be distributed throughout the disk membranes.

scholarly journals Deletion of prominin-1 in mice results in disrupted photoreceptor outer segment protein homeostasis

2021 ◽  
Vol 14 (9) ◽  
pp. 1334-1344
Author(s):  
Yu-Shu Xiao ◽  
◽  
Min Gao ◽  
Jun-Ran Sun ◽  
Yang Liu ◽  
...  
Keyword(s):  
Outer Segment ◽  
Outer Nuclear Layer ◽  
Underlying Mechanism ◽  
Immunoblot Analysis ◽  
Protein Homeostasis ◽  
Functional Tests ◽  
Photoreceptor Degeneration ◽  
Mice Model ◽  
Photoreceptor Outer Segment ◽  
Normal Quantity

AIM: To illustrate the underlying mechanism how prominin-1 (also known as Prom1) mutation contribute to progressive photoreceptor degeneration. METHODS: A CRISPR-mediated Prom1 knockout (Prom1-KO) mice model in the C57BL/6 was generated and the photoreceptor degeneration phenotypes by means of structural and functional tests were demonstrated. Immunohistochemistry and immunoblot analysis were performed to reveal the localization and quantity of related outer segment (OS) proteins. RESULTS: The Prom1-KO mice developed the photoreceptor degeneration phenotype including the decreased outer nuclear layer (ONL) thickness and compromised electroretinogram amplitude. Immunohistochemistry analysis revealed impaired trafficking of photoreceptor OS proteins. Immunoblot data demonstrated decreased photoreceptor OS proteins. CONCLUSION: Prom1 deprivation causes progressive photoreceptor degeneration. Prom1 is essential for maintaining normal trafficking and normal quantity of photoreceptor OS proteins. The new light is shed on the pathogenic mechanism underlying photoreceptor degeneration caused by Prom1 mutation.

scholarly journals Syntaxin 3 is essential for photoreceptor outer segment protein trafficking and survival

2020 ◽  
Vol 117 (34) ◽  
pp. 20615-20624
Author(s):  
Mashal Kakakhel ◽  
Lars Tebbe ◽  
Mustafa S. Makia ◽  
Shannon M. Conley ◽  
David M. Sherry ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Protein Trafficking ◽  
Outer Segment ◽  
Functional Decline ◽  
Structural Defects ◽  
Photoreceptor Outer Segment ◽  
Photoreceptor Membrane ◽  
Synaptic Region ◽  
Syntaxin 3

Trafficking of photoreceptor membrane proteins from their site of synthesis in the inner segment (IS) to the outer segment (OS) is critical for photoreceptor function and vision. Here we evaluate the role of syntaxin 3 (STX3), in trafficking of OS membrane proteins such as peripherin 2 (PRPH2) and rhodopsin. Photoreceptor-specificStx3knockouts [Stx3f/f(iCre75)andStx3f/f(CRX-Cre)] exhibited rapid, early-onset photoreceptor degeneration and functional decline characterized by structural defects in IS, OS, and synaptic terminals. Critically, in the absence of STX3, OS proteins such as PRPH2, the PRPH2 binding partner, rod outer segment membrane protein 1 (ROM1), and rhodopsin were mislocalized along the microtubules to the IS, cell body, and synaptic region. We find that the PRPH2 C-terminal domain interacts with STX3 as well as other photoreceptor SNAREs, and our findings indicate that STX3 is an essential part of the trafficking pathway for both disc (rhodopsin) and rim (PRPH2/ROM1) components of the OS.

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