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Hao K, Zhu X, Yan X. Purification and Immunostaining of Mouse Ependymal Ciliary Shafts. Bio Protoc 2022; 12:e4467. [PMID: 35978574 PMCID: PMC9350923 DOI: 10.21769/bioprotoc.4467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Revised: 06/08/2022] [Accepted: 06/02/2022] [Indexed: 12/29/2022] Open
Abstract
Cilia and flagella are microtubule-based hair-like organelles protruding from the surface of most eukaryotic cells, and play essential roles in cell locomotion, left-right asymmetry, embryo development, and tissue homeostasis. With isolated cilia and flagella, great progress has been made in understanding the composition, structure, and function of cilia. However, the current cilia/flagella isolation methods are deficient in the integrity or productivity of purified cilia when applied to mammalian motile cilia. Here, we describe a new protocol that isolates cilia shafts from mouse ependymal cells, by horizontal shear force and mild detergent. This method enables the production of virtually integral cilia with high yields and less cell body contamination. It is suitable for immunostaining, puromycin labeling assay, and proximity ligation assay of mammalian motile cilia. Graphical abstract.
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Affiliation(s)
- Kai Hao
- State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
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University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xueliang Zhu
- State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
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University of Chinese Academy of Sciences, Beijing 100049, China
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School of Life Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China
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*For correspondence:
;
| | - Xiumin Yan
- Ministry of Education-Shanghai Key Laboratory of Children’s Environmental Health, Institute of Early Life Health, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200092, China
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*For correspondence:
;
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2
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Baur K, Hölzl-Wenig G, Ciccolini F. A flow cytometry-based approach for the study of primary cilia. Methods Cell Biol 2022; 175:17-31. [PMID: 36967140 DOI: 10.1016/bs.mcb.2022.07.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
Primary cilia provide a specialized subcellular environment favoring ordered and timely interaction and modification of signaling molecules, necessary for the sensing and transduction of extracellular signals and environmental conditions. Crucial to the understanding of ciliary function is the knowledge of the signaling molecules composing the ciliary compartment. While proteomes of primary cilia have been published recently, the selective isolation of primary cilia from specific cell types and whole tissue still proves difficult, and many laboratories instead resort to the analysis of cultured cells, which may introduce experimental artifacts. Here we present a flow cytometry-based method to isolate and characterize primary cilia from the murine ventricular-subventricular zone. After deciliation, primary cilia are immunolabeled with antibodies against ciliary markers. As an example, we here use a double-staining with acetylated tubulin, which stains the ciliary axoneme, and ciliary membrane protein ADP-ribosylation-like factor 13b (Arl13b); additionally, we triple-labeled primary cilia using the ciliary marker adenylate cyclase 3 (AC3). Besides analysis at the single particle level, fluorescence activated cell sorting (FACS) allows collection of pure preparations of primary cilia suited for subsequent proteomic analyses like mass spectrometry or western blot. As an example of analytical application, we performed triple immunostaining and FACS analysis to reveal cilia heterogeneity. Thus, our cilia isolation method, which can readily be applied to other tissues or cell culture, will facilitate the study of this key cellular organelle and shed light on its role in normal conditions and disease.
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3
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Lin CJ, Dang A, Hernandez E, Hsieh JT. DAB2IP modulates primary cilia formation associated with renal tumorigenesis. Neoplasia 2020; 23:169-180. [PMID: 33341566 PMCID: PMC7750127 DOI: 10.1016/j.neo.2020.12.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 12/07/2020] [Accepted: 12/08/2020] [Indexed: 11/16/2022] Open
Abstract
Primary cilium is a microtubule-based organelle that projects from the surfaces of most mammalian cell types and protrudes into the extracellular milieu as an antenna-like sensor to senses extracellular physical and biochemical signals, and then transmits signals into cytoplasm or nucleus to regulate numerous physical and developmental processes. Therefore, loss of primary cilia is associated to multiple cancer progression, including skin, breast, pancreas, ovarian, prostate, and kidney cancers. Our previous studies demonstrate that high prevalent loss of DAB2 Interacting Protein (DAB2IP) is associated with renal cell carcinoma, and we found a kinesin-like protein, kinesin family member 3A (KIF3a), was significantly increased in DAB2IP-interacting protein fraction. KIF3 is one of the most abundant kinesin-2 family proteins expressed in cells, and it is necessary for ciliogenesis. In this study, we observed that loss of DAB2IP in normal kidney epithelial cell significantly impair primary cilia formation. We unveiled a new mechanism of primary cilia stability via DAB2IP and KIF3a physical interaction at DAB2IP-PH domain. Furthermore, we found that KIF3a also act as a tumor suppressor in renal cell carcinoma, affect tumor development and patient survival.
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Affiliation(s)
- Chun-Jung Lin
- UT Southwestern Department of Urology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Andrew Dang
- UT Southwestern Department of Urology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Elizabeth Hernandez
- UT Southwestern Department of Urology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jer-Tsong Hsieh
- UT Southwestern Department of Urology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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Corkins ME, Krneta-Stankic V, Kloc M, McCrea PD, Gladden AB, Miller RK. Divergent roles of the Wnt/PCP Formin Daam1 in renal ciliogenesis. PLoS One 2019; 14:e0221698. [PMID: 31469868 PMCID: PMC6716777 DOI: 10.1371/journal.pone.0221698] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 08/13/2019] [Indexed: 12/16/2022] Open
Abstract
Kidneys are composed of numerous ciliated epithelial tubules called nephrons. Each nephron functions to reabsorb nutrients and concentrate waste products into urine. Defects in primary cilia are associated with abnormal formation of nephrons and cyst formation in a wide range of kidney disorders. Previous work in Xenopus laevis and zebrafish embryos established that loss of components that make up the Wnt/PCP pathway, Daam1 and ArhGEF19 (wGEF) perturb kidney tubulogenesis. Dishevelled, which activates both the canonical and non-canonical Wnt/PCP pathway, affect cilia formation in multiciliated cells. In this study, we investigated the role of the noncanoncial Wnt/PCP components Daam1 and ArhGEF19 (wGEF) in renal ciliogenesis utilizing polarized mammalian kidney epithelia cells (MDCKII and IMCD3) and Xenopus laevis embryonic kidney. We demonstrate that knockdown of Daam1 and ArhGEF19 in MDCKII and IMCD3 cells leads to loss of cilia, and Daam1's effect on ciliogenesis is mediated by the formin-activity of Daam1. Moreover, Daam1 co-localizes with the ciliary transport protein Ift88 and is present in cilia. Interestingly, knocking down Daam1 in Xenopus kidney does not lead to loss of cilia. These data suggests a new role for Daam1 in the formation of primary cilia.
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Affiliation(s)
- Mark E. Corkins
- Department of Pediatrics, Pediatric Research Center, UTHealth McGovern Medical School, Houston, Texas, United States of America
| | - Vanja Krneta-Stankic
- Department of Pediatrics, Pediatric Research Center, UTHealth McGovern Medical School, Houston, Texas, United States of America
- MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Program in Genes and Development, Houston, Texas, United States of America
- MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Program in Genetics & Epigenetics, Houston, Texas, United States of America
| | - Malgorzata Kloc
- Houston Methodist, Research Institute, Houston, Texas, United States of America
- Department of Genetics, University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
| | - Pierre D. McCrea
- MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Program in Genetics & Epigenetics, Houston, Texas, United States of America
- Department of Genetics, University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
| | - Andrew B. Gladden
- MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Program in Genetics & Epigenetics, Houston, Texas, United States of America
- Department of Genetics, University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
| | - Rachel K. Miller
- Department of Pediatrics, Pediatric Research Center, UTHealth McGovern Medical School, Houston, Texas, United States of America
- MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Program in Genetics & Epigenetics, Houston, Texas, United States of America
- Department of Genetics, University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
- MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Program in Biochemistry & Cell Biology, Houston, Texas, United States of America
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5
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Monaco S, Baur K, Hellwig A, Hölzl-Wenig G, Mandl C, Ciccolini F. A Flow Cytometry-Based Approach for the Isolation and Characterization of Neural Stem Cell Primary Cilia. Front Cell Neurosci 2019; 12:519. [PMID: 30692915 PMCID: PMC6339872 DOI: 10.3389/fncel.2018.00519] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 12/12/2018] [Indexed: 01/15/2023] Open
Abstract
In the adult mammalian brain, the apical surface of the subependymal zone (SEZ) is covered by many motile ependymal cilia and a few primary cilia originating from rare intermingled neural stem cells (NSCs). In NSCs the primary cilia are key for the transduction of essential extracellular signals such as Sonic hedgehog (SHH) and platelet-derived growth factor (PDGF). Despite their importance, the analysis of NSC primary cilia is greatly hampered by the fact that they are overwhelmingly outnumbered by the motile cilia. We here take advantage of flow cytometry to purify the two cilia types and allow their molecular characterization. Primary cilia were identified based on immunoreactivity to the marker adenylate cyclase type III (AC3) and differential levels of prominin-1 whereas motile cilia displayed immunoreactivity only to the latter. Consistent with the morphological differences between the two classes of cilia, enrichment of motile cilia positively correlated with size. Moreover, we observed age-dependent variations in the abundance of the two groups of ciliary organelles reflecting the changes associated with their development. The two cilia groups also differed with respect to the expression of signaling molecules, since PDGF receptor (PDGFR)α, smoothened (Smo) and CXC chemokine receptor (CXCR)4 were only detected in isolated primary but not motile cilia. Thus, our novel method of cilia isolation and characterization by flow cytometry has the potential to be extended to the study of cilia from different tissues and organs, providing a powerful tool for the investigation of primary cilia in physiological and pathological conditions.
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Affiliation(s)
- Sara Monaco
- Interdisciplinary Center for Neurosciences (IZN), Department of Neurobiology, University of Heidelberg, Heidelberg, Germany
| | - Katja Baur
- Interdisciplinary Center for Neurosciences (IZN), Department of Neurobiology, University of Heidelberg, Heidelberg, Germany
| | - Andrea Hellwig
- Interdisciplinary Center for Neurosciences (IZN), Department of Neurobiology, University of Heidelberg, Heidelberg, Germany
| | - Gabriele Hölzl-Wenig
- Interdisciplinary Center for Neurosciences (IZN), Department of Neurobiology, University of Heidelberg, Heidelberg, Germany
| | - Claudia Mandl
- Interdisciplinary Center for Neurosciences (IZN), Department of Neurobiology, University of Heidelberg, Heidelberg, Germany
| | - Francesca Ciccolini
- Interdisciplinary Center for Neurosciences (IZN), Department of Neurobiology, University of Heidelberg, Heidelberg, Germany
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Yang Y, Mlodzik M. Wnt-Frizzled/planar cell polarity signaling: cellular orientation by facing the wind (Wnt). Annu Rev Cell Dev Biol 2016; 31:623-46. [PMID: 26566118 DOI: 10.1146/annurev-cellbio-100814-125315] [Citation(s) in RCA: 254] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The establishment of planar cell polarity (PCP) in epithelial and mesenchymal cells is a critical, evolutionarily conserved process during development and organogenesis. Analyses in Drosophila and several vertebrate model organisms have contributed a wealth of information on the regulation of PCP. A key conserved pathway regulating PCP, the so-called core Wnt-Frizzled PCP (Fz/PCP) signaling pathway, was initially identified through genetic studies of Drosophila. PCP studies in vertebrates, most notably mouse and zebrafish, have identified novel factors in PCP signaling and have also defined cellular features requiring PCP signaling input. These studies have shifted focus to the role of Van Gogh (Vang)/Vangl genes in this molecular system. This review focuses on new insights into the core Fz/Vangl/PCP pathway and recent advances in Drosophila and vertebrate PCP studies. We attempt to integrate these within the existing core Fz/Vangl/PCP signaling framework.
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Affiliation(s)
- Yingzi Yang
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115;
| | - Marek Mlodzik
- Department of Developmental and Regenerative Biology, Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029;
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7
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Becirovic E, Böhm S, Nguyen ONP, Riedmayr LM, Hammelmann V, Schön C, Butz ES, Wahl-Schott C, Biel M, Michalakis S. AAV Vectors for FRET-Based Analysis of Protein-Protein Interactions in Photoreceptor Outer Segments. Front Neurosci 2016; 10:356. [PMID: 27516733 PMCID: PMC4963399 DOI: 10.3389/fnins.2016.00356] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 07/14/2016] [Indexed: 11/18/2022] Open
Abstract
Fluorescence resonance energy transfer (FRET) is a powerful method for the detection and quantification of stationary and dynamic protein-protein interactions. Technical limitations have hampered systematic in vivo FRET experiments to study protein-protein interactions in their native environment. Here, we describe a rapid and robust protocol that combines adeno-associated virus (AAV) vector-mediated in vivo delivery of genetically encoded FRET partners with ex vivo FRET measurements. The method was established on acutely isolated outer segments of murine rod and cone photoreceptors and relies on the high co-transduction efficiency of retinal photoreceptors by co-delivered AAV vectors. The procedure can be used for the systematic analysis of protein-protein interactions of wild type or mutant outer segment proteins in their native environment. Conclusively, our protocol can help to characterize the physiological and pathophysiological relevance of photoreceptor specific proteins and, in principle, should also be transferable to other cell types.
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Affiliation(s)
- Elvir Becirovic
- Department of Pharmacy - Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität MünchenMunich, Germany; Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität MünchenMunich, Germany
| | - Sybille Böhm
- Department of Pharmacy - Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität MünchenMunich, Germany; Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität MünchenMunich, Germany
| | - Ong N P Nguyen
- Department of Pharmacy - Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität MünchenMunich, Germany; Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität MünchenMunich, Germany
| | - Lisa M Riedmayr
- Department of Pharmacy - Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität MünchenMunich, Germany; Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität MünchenMunich, Germany
| | - Verena Hammelmann
- Department of Pharmacy - Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität MünchenMunich, Germany; Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität MünchenMunich, Germany
| | - Christian Schön
- Department of Pharmacy - Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität MünchenMunich, Germany; Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität MünchenMunich, Germany
| | - Elisabeth S Butz
- Department of Pharmacy - Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität MünchenMunich, Germany; Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität MünchenMunich, Germany
| | - Christian Wahl-Schott
- Department of Pharmacy - Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität MünchenMunich, Germany; Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität MünchenMunich, Germany
| | - Martin Biel
- Department of Pharmacy - Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität MünchenMunich, Germany; Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität MünchenMunich, Germany
| | - Stylianos Michalakis
- Department of Pharmacy - Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität MünchenMunich, Germany; Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität MünchenMunich, Germany
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Nguyen AM, Jacobs CR. Emerging role of primary cilia as mechanosensors in osteocytes. Bone 2013; 54:196-204. [PMID: 23201223 PMCID: PMC3624072 DOI: 10.1016/j.bone.2012.11.016] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 10/06/2012] [Accepted: 11/19/2012] [Indexed: 01/08/2023]
Abstract
The primary cilium is a solitary, immotile microtubule-based extension present on nearly every mammalian cell. This organelle has established mechanosensory roles in several contexts including kidney, liver, and the embryonic node. Mechanical load deflects the cilium, triggering biochemical responses. Defects in cilium function have been associated with numerous human diseases. Recent research has implicated the primary cilium as a mechanosensor in bone. In this review, we discuss the cilium, the growing evidence for its mechanosensory role in bone, and areas of future study.
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Affiliation(s)
- An M Nguyen
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
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Abstract
BACKGROUND Most cells in the body possess a single primary cilium. These cilia are key transducers of sensory stimuli, and defects in cilia have been linked to several diseases. Evidence suggests that some transduction of sensory stimuli by the primary cilium depends on ion-conducting channels. However, the tiny size of the cilium has been a critical barrier to understanding its electrical properties. We report a novel method that allows sensitive, repeatable electrical recordings from primary cilia. Adherent cells were grown on small, spherical beads that could be easily moved within the recording chamber. In this configuration, an entire cilium could be pulled into a recording microelectrode. RESULTS In 47% of attempts, suction resulted in a seal with high input resistance. Single channels could be recorded while the cilium remained attached to the cell. When the pipette was raised into the air, the cell body was pulled off at the air-bath interface. The pipette retained the cilium and could then be immersed in various solutions that bathed the cytoplasmic face of the membrane. In excised cilia, ionic currents through ciliary channels were modulated by cytoplasmic Ca(2+) and transmembrane voltage. CONCLUSIONS Ciliary recording is a direct way to learn the effects of second messengers and voltage changes on ciliary transduction channels.
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Hsiao YC, Tuz K, Ferland RJ. Trafficking in and to the primary cilium. Cilia 2012; 1:4. [PMID: 23351793 PMCID: PMC3541539 DOI: 10.1186/2046-2530-1-4] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Accepted: 04/25/2012] [Indexed: 01/08/2023] Open
Abstract
Polarized vesicle trafficking is mediated by small GTPase proteins, such as Rabs and Arls/Arfs. These proteins have essential roles in maintaining normal cellular function, in part, through regulating intracellular trafficking. Moreover, these families of proteins have recently been implicated in the formation and function of the primary cilium. The primary cilium, which is found on almost every cell type in vertebrates, is an organelle that protrudes from the surface of the cell and functions as a signaling center. Interestingly, it has recently been linked to a variety of human diseases, collectively referred to as ciliopathies. The primary cilium has an exceptionally high density of receptors on its membrane that are important for sensing and transducing extracellular stimuli. Moreover, the primary cilium serves as a separate cellular compartment from the cytosol, providing for unique spatial and temporal regulation of signaling molecules to initiate downstream events. Thus, functional primary cilia are essential for normal signal transduction. Rabs and Arls/Arfs play critical roles in early cilia formation but are also needed for maintenance of ciliary function through their coordination with intraflagellar transport (IFT), a specialized trafficking system in primary cilia. IFT in cilia is pivotal for the proper movement of proteins into and out of this highly regulated organelle. In this review article, we explore the involvement of polarized vesicular trafficking in cilia formation and function, and discuss how defects in these processes could subsequently lead to the abnormalities observed in ciliopathies.
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Affiliation(s)
- Yi-Chun Hsiao
- Department of Biology, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.,Albany Medical College, Center for Neuropharmacology and Neuroscience, Albany, NY 12208, USA
| | - Karina Tuz
- Albany Medical College, Center for Neuropharmacology and Neuroscience, Albany, NY 12208, USA
| | - Russell J Ferland
- Albany Medical College, Center for Neuropharmacology and Neuroscience, Albany, NY 12208, USA.,Department of Neurology, Albany Medical College, Albany, NY 12208, USA
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Hu Q, Nelson WJ. Ciliary diffusion barrier: the gatekeeper for the primary cilium compartment. Cytoskeleton (Hoboken) 2011; 68:313-24. [PMID: 21634025 DOI: 10.1002/cm.20514] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Accepted: 05/04/2011] [Indexed: 11/08/2022]
Abstract
The primary cilium is a cellular antenna that detects and transmits chemical and mechanical cues in the environment through receptors and downstream signal proteins enriched along the ciliary membrane. While it is known that ciliary membrane proteins enter the cilium by way of vesicular and intraflagellar transport, less is known about how ciliary membrane proteins are retained in, and how apical membrane proteins are excluded from the cilium. Here, we review evidence for a membrane diffusion barrier at the base of the primary cilium, and highlight the recent finding of a septin cytoskeleton diffusion barrier. We also discuss candidate ciliopathy genes that may be involved in formation of the barrier, and the role of a diffusion barrier as a common mechanism for compartmentalizing membranes and lipid domains.
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Affiliation(s)
- Qicong Hu
- Department of Biology, Stanford University, Stanford, California 94305., USA
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Abstract
Planarians have recently become a popular model system for the study of adult stem cells, regeneration and polarity. The system is attractive for both undergraduate and graduate research labs, since planarian colonies are low cost and easy to maintain. Also in situ hybridization, immunofluorescence and RNA-interference (RNAi) gene knockdown techniques have been developed for planarian studies. However, imaging of live worms (particularly at high magnifications) is difficult because animals are strongly photophobic; they quickly move away from light sources and out of frame. The current methods available to inhibit movement in planarians include RNAi injection and exposure to cold temperatures. The former is labor and time intensive, while the latter precludes the use of many fluorescent reporter dyes. Here, we report a simple, inexpensive and reversible method to immobilize planarians for live imaging. Our data show that a short 1 hour treatment with 3% ethanol (EtOH) is sufficient to inhibit both the fine and gross movements of Schmidtea mediterranea planarians, of the typical size used (4–6 mm), with full recovery of movement within 3–4 hours. Importantly, EtOH treatment did not interfere with regeneration, even after repeated exposure, nor lyse epithelial cells (as assayed by H&E staining). We demonstrate that a short exposure to a low concentration of EtOH is a quick and effective method of immobilizing planarians, one that is easily adaptable to planarians of all sizes and will increase the accessibility of live imaging assays to planarian researchers.
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