1
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Aguilar C, Williams D, Kurapati R, Bains RS, Mburu P, Parker A, Williams J, Concas D, Tateossian H, Haynes AR, Banks G, Vikhe P, Heise I, Hutchison M, Atkins G, Gillard S, Starbuck B, Oliveri S, Blake A, Sethi S, Kumar S, Bardhan T, Jeng JY, Johnson SL, Corns LF, Marcotti W, Simon M, Wells S, Potter PK, Lad HV. Pleiotropic brain function of whirlin identified by a novel mutation. iScience 2024; 27:110170. [PMID: 38974964 PMCID: PMC11225360 DOI: 10.1016/j.isci.2024.110170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 04/26/2024] [Accepted: 05/31/2024] [Indexed: 07/09/2024] Open
Abstract
Despite some evidence indicating diverse roles of whirlin in neurons, the functional corollary of whirlin gene function and behavior has not been investigated or broadly characterized. A single nucleotide variant was identified from our recessive ENU-mutagenesis screen at a donor-splice site in whirlin, a protein critical for proper sensorineural hearing function. The mutation (head-bob, hb) led to partial intron-retention causing a frameshift and introducing a premature termination codon. Mutant mice had a head-bobbing phenotype and significant hyperactivity across several phenotyping tests. Lack of complementation of head-bob with whirler mutant mice confirmed the head-bob mutation as functionally distinct with compound mutants having a mild-moderate hearing defect. Utilizing transgenics, we demonstrate rescue of the hyperactive phenotype and combined with the expression profiling data conclude whirlin plays an essential role in activity-related behaviors. These results highlight a pleiotropic role of whirlin within the brain and implicate alternative, central mediated pathways in its function.
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Affiliation(s)
- Carlos Aguilar
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Debbie Williams
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
- Mary Lyon Centre at MRC Harwell, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Ramakrishna Kurapati
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Rasneer S. Bains
- Mary Lyon Centre at MRC Harwell, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Philomena Mburu
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Andy Parker
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Jackie Williams
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Danilo Concas
- Mary Lyon Centre at MRC Harwell, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Hilda Tateossian
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Andrew R. Haynes
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Gareth Banks
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Pratik Vikhe
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Ines Heise
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Marie Hutchison
- Mary Lyon Centre at MRC Harwell, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Gemma Atkins
- Mary Lyon Centre at MRC Harwell, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Simon Gillard
- Mary Lyon Centre at MRC Harwell, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Becky Starbuck
- Mary Lyon Centre at MRC Harwell, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Simona Oliveri
- Mary Lyon Centre at MRC Harwell, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Andrew Blake
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Siddharth Sethi
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Saumya Kumar
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Tanaya Bardhan
- School of Biosciences, University of Sheffield, Sheffield, South Yorkshire S10 2TN, UK
| | - Jing-Yi Jeng
- School of Biosciences, University of Sheffield, Sheffield, South Yorkshire S10 2TN, UK
| | - Stuart L. Johnson
- School of Biosciences, University of Sheffield, Sheffield, South Yorkshire S10 2TN, UK
| | - Lara F. Corns
- School of Biosciences, University of Sheffield, Sheffield, South Yorkshire S10 2TN, UK
| | - Walter Marcotti
- School of Biosciences, University of Sheffield, Sheffield, South Yorkshire S10 2TN, UK
- Neuroscience Institute, University of Sheffield, Sheffield, South Yorkshire S10 2TN, UK
| | - Michelle Simon
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Sara Wells
- Mary Lyon Centre at MRC Harwell, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Paul K. Potter
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
| | - Heena V. Lad
- MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Didcot, Oxfordshire OX11 0RD, UK
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Mathur PD, Zou J, Neiswanger G, Zhu D, Wang Y, Almishaal AA, Vashist D, Hammond HK, Park AH, Yang J. Adenylyl cyclase 6 plays a minor role in the mouse inner ear and retina. Sci Rep 2023; 13:7075. [PMID: 37127773 PMCID: PMC10151359 DOI: 10.1038/s41598-023-34361-y] [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: 12/24/2022] [Accepted: 04/28/2023] [Indexed: 05/03/2023] Open
Abstract
Adenylyl cyclase 6 (AC6) synthesizes second messenger cAMP in G protein-coupled receptor (GPCR) signaling. In cochlear hair cells, AC6 distribution relies on an adhesion GPCR, ADGRV1, which is associated with Usher syndrome (USH), a condition of combined hearing and vision loss. ADGRV1 is a component of the USH type 2 (USH2) protein complex in hair cells and photoreceptors. However, the role of AC6 in the inner ear and retina has not been explored. Here, we found that AC6 distribution in hair cells depends on the USH2 protein complex integrity. Several known AC6 regulators and effectors, which were previously reported to participate in ADGRV1 signaling in vitro, are localized to the stereociliary compartments that overlap with AC6 distribution in hair cells. In young AC6 knockout (Adcy6-/-) mice, the activity of cAMP-dependent protein kinase, but not Akt kinase, is altered in cochleas, while both kinases are normal in vestibular organs. Adult Adcy6-/- mice however exhibit normal hearing function. AC6 is expressed in mouse retinas but rarely in photoreceptors. Adcy6-/- mice have slightly enhanced photopic but normal scotopic vision. Therefore, AC6 may participate in the ADGRV1 signaling in hair cells but AC6 is not essential for cochlear and retinal development and maintenance.
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Affiliation(s)
- Pranav Dinesh Mathur
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT, 84132, USA
- Department of Neurobiology, University of Utah, Salt Lake City, UT, 84132, USA
- Vecprobio Inc., San Diego, CA, 92126, USA
| | - Junhuang Zou
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT, 84132, USA
| | - Grace Neiswanger
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT, 84132, USA
| | - Daniel Zhu
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT, 84132, USA
| | - Yong Wang
- Division of Otolaryngology, Department of Surgery, University of Utah, Salt Lake City, UT, 84132, USA
| | - Ali A Almishaal
- Department of Communication Sciences and Disorders, University of Utah, Salt Lake City, UT, 84112, USA
- Department of Speech-Language Pathology and Audiology, College of Applied Medical Sciences, University of Hail, Hail, 81451, Saudi Arabia
| | - Deepti Vashist
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT, 84132, USA
| | - H Kirk Hammond
- Division of Cardiovascular Medicine, Department of Medicine, University of California, San Diego, VA San Diego Healthcare System, San Diego, CA, 92161, USA
| | - Albert H Park
- Division of Otolaryngology, Department of Surgery, University of Utah, Salt Lake City, UT, 84132, USA
| | - Jun Yang
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT, 84132, USA.
- Department of Neurobiology, University of Utah, Salt Lake City, UT, 84132, USA.
- Division of Otolaryngology, Department of Surgery, University of Utah, Salt Lake City, UT, 84132, USA.
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Yang Q, Liu J, Wang Z. 4.1N-Mediated Interactions and Functions in Nerve System and Cancer. Front Mol Biosci 2021; 8:711302. [PMID: 34589518 PMCID: PMC8473747 DOI: 10.3389/fmolb.2021.711302] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 08/16/2021] [Indexed: 01/05/2023] Open
Abstract
Scaffolding protein 4.1N is a neuron-enriched 4.1 homologue. 4.1N contains three conserved domains, including the N-terminal 4.1-ezrin-radixin-moesin (FERM) domain, internal spectrin–actin–binding (SAB) domain, and C-terminal domain (CTD). Interspersed between the three domains are nonconserved domains, including U1, U2, and U3. The role of 4.1N was first reported in the nerve system. Then, extensive studies reported the role of 4.1N in cancers and other diseases. 4.1N performs numerous vital functions in signaling transduction by interacting, locating, supporting, and coordinating different partners and is involved in the molecular pathogenesis of various diseases. In this review, recent studies on the interactions between 4.1N and its contactors (including the α7AChr, IP3R1, GluR1/4, GluK1/2/3, mGluR8, KCC2, D2/3Rs, CASK, NuMA, PIKE, IP6K2, CAM 1/3, βII spectrin, flotillin-1, pp1, and 14-3-3) and the 4.1N-related biological functions in the nerve system and cancers are specifically and comprehensively discussed. This review provides critical detailed mechanistic insights into the role of 4.1N in disease relationships.
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Affiliation(s)
- Qin Yang
- Molecular Biology Research Center & Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, China.,School of Medical Laboratory, Shao Yang University, Shaoyang, China
| | - Jing Liu
- Molecular Biology Research Center & Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, China
| | - Zi Wang
- Molecular Biology Research Center & Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, China
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4
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Rich SK, Baskar R, Terman JR. Propagation of F-actin disassembly via Myosin15-Mical interactions. SCIENCE ADVANCES 2021; 7:7/20/eabg0147. [PMID: 33980493 PMCID: PMC8115926 DOI: 10.1126/sciadv.abg0147] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 03/23/2021] [Indexed: 06/12/2023]
Abstract
The F-actin cytoskeleton drives cellular form and function. However, how F-actin-based changes occur with spatiotemporal precision and specific directional orientation is poorly understood. Here, we identify that the unconventional class XV myosin [Myosin 15 (Myo15)] physically and functionally interacts with the F-actin disassembly enzyme Mical to spatiotemporally position cellular breakdown and reconstruction. Specifically, while unconventional myosins have been associated with transporting cargo along F-actin to spatially target cytoskeletal assembly, we now find they also target disassembly. Myo15 specifically positions this F-actin disassembly by associating with Mical and using its motor and MyTH4-FERM cargo-transporting functions to broaden Mical's distribution. Myo15's broadening of Mical's distribution also expands and directionally orients Mical-mediated F-actin disassembly and subsequent cellular remodeling, including in response to Semaphorin/Plexin cell surface activation signals. Thus, we identify a mechanism that spatiotemporally propagates F-actin disassembly while also proposing that other F-actin-trafficked-cargo is derailed by this disassembly to directionally orient rebuilding.
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Affiliation(s)
- Shannon K Rich
- Departments of Neuroscience and Pharmacology and Neuroscience Graduate Program, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Raju Baskar
- Departments of Neuroscience and Pharmacology and Neuroscience Graduate Program, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jonathan R Terman
- Departments of Neuroscience and Pharmacology and Neuroscience Graduate Program, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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5
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Zhu Y, Delhommel F, Cordier F, Lüchow S, Mechaly A, Colcombet-Cazenave B, Girault V, Pepermans E, Bahloul A, Gautier C, Brûlé S, Raynal B, Hoos S, Haouz A, Caillet-Saguy C, Ivarsson Y, Wolff N. Deciphering the Unexpected Binding Capacity of the Third PDZ Domain of Whirlin to Various Cochlear Hair Cell Partners. J Mol Biol 2020; 432:5920-5937. [PMID: 32971111 DOI: 10.1016/j.jmb.2020.09.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 09/11/2020] [Accepted: 09/15/2020] [Indexed: 10/23/2022]
Abstract
Hearing is a mechanical and neurochemical process, which occurs in the hair cells of inner ear that converts the sound vibrations into electrical signals transmitted to the brain. The multi-PDZ scaffolding protein whirlin plays a critical role in the formation and function of stereocilia exposed at the surface of hair cells. In this article, we reported seven stereociliary proteins that encode PDZ binding motifs (PBM) and interact with whirlin PDZ3, where four of them are first reported. We solved the atomic resolution structures of complexes between whirlin PDZ3 and the PBMs of myosin 15a, CASK, harmonin a1 and taperin. Interestingly, the PBM of CASK and taperin are rare non-canonical PBM, which are not localized at the extreme C terminus. This large capacity to accommodate various partners could be related to the distinct functions of whirlin at different stages of the hair cell development.
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Affiliation(s)
- Yanlei Zhu
- Unité Récepteurs-Canaux, Institut Pasteur, 75015 Paris, France; Complexité du Vivant, Sorbonne Université, 75005 Paris, France
| | - Florent Delhommel
- Unité Récepteurs-Canaux, Institut Pasteur, 75015 Paris, France; Complexité du Vivant, Sorbonne Université, 75005 Paris, France
| | | | | | - Ariel Mechaly
- Plateforme de Cristallographie, Institut Pasteur, Paris, France
| | - Baptiste Colcombet-Cazenave
- Unité Récepteurs-Canaux, Institut Pasteur, 75015 Paris, France; Complexité du Vivant, Sorbonne Université, 75005 Paris, France
| | | | - Elise Pepermans
- Complexité du Vivant, Sorbonne Université, 75005 Paris, France; Unité de génétique et physiologie de l'audition, Institut Pasteur, 75015 Paris, France
| | - Amel Bahloul
- Unité de génétique et physiologie de l'audition, Institut Pasteur, 75015 Paris, France
| | - Candice Gautier
- Istituto Pasteur - Fondazione C. Bolognetti, Sapienza Università di Roma, Rome, Italy
| | - Sébastien Brûlé
- Plateforme de Biophysique Moléculaire, Institut Pasteur, Paris, France
| | - Bertrand Raynal
- Plateforme de Biophysique Moléculaire, Institut Pasteur, Paris, France
| | - Sylviane Hoos
- Plateforme de Biophysique Moléculaire, Institut Pasteur, Paris, France
| | - Ahmed Haouz
- Plateforme de Cristallographie, Institut Pasteur, Paris, France
| | | | - Ylva Ivarsson
- Department of Chemistry-BMC, Uppsala University, Sweden
| | - Nicolas Wolff
- Unité Récepteurs-Canaux, Institut Pasteur, 75015 Paris, France.
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Chytła A, Gajdzik-Nowak W, Olszewska P, Biernatowska A, Sikorski AF, Czogalla A. Not Just Another Scaffolding Protein Family: The Multifaceted MPPs. Molecules 2020; 25:molecules25214954. [PMID: 33114686 PMCID: PMC7662862 DOI: 10.3390/molecules25214954] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 10/16/2020] [Accepted: 10/20/2020] [Indexed: 01/03/2023] Open
Abstract
Membrane palmitoylated proteins (MPPs) are a subfamily of a larger group of multidomain proteins, namely, membrane-associated guanylate kinases (MAGUKs). The ubiquitous expression and multidomain structure of MPPs provide the ability to form diverse protein complexes at the cell membranes, which are involved in a wide range of cellular processes, including establishing the proper cell structure, polarity and cell adhesion. The formation of MPP-dependent complexes in various cell types seems to be based on similar principles, but involves members of different protein groups, such as 4.1-ezrin-radixin-moesin (FERM) domain-containing proteins, polarity proteins or other MAGUKs, showing their multifaceted nature. In this review, we discuss the function of the MPP family in the formation of multiple protein complexes. Notably, we depict their significant role for cell physiology, as the loss of interactions between proteins involved in the complex has a variety of negative consequences. Moreover, based on recent studies concerning the mechanism of membrane raft formation, we shed new light on a possible role played by MPPs in lateral membrane organization.
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Affiliation(s)
- Agnieszka Chytła
- Department of Cytobiochemistry, Faculty of Biotechnology, University of Wroclaw, 50-383 Wroclaw, Poland; (A.C.); (W.G.-N.); (P.O.); (A.B.)
| | - Weronika Gajdzik-Nowak
- Department of Cytobiochemistry, Faculty of Biotechnology, University of Wroclaw, 50-383 Wroclaw, Poland; (A.C.); (W.G.-N.); (P.O.); (A.B.)
| | - Paulina Olszewska
- Department of Cytobiochemistry, Faculty of Biotechnology, University of Wroclaw, 50-383 Wroclaw, Poland; (A.C.); (W.G.-N.); (P.O.); (A.B.)
| | - Agnieszka Biernatowska
- Department of Cytobiochemistry, Faculty of Biotechnology, University of Wroclaw, 50-383 Wroclaw, Poland; (A.C.); (W.G.-N.); (P.O.); (A.B.)
| | - Aleksander F. Sikorski
- Research and Development Center, Regional Specialist Hospital, Kamieńskiego 73a, 51-154 Wroclaw, Poland;
| | - Aleksander Czogalla
- Department of Cytobiochemistry, Faculty of Biotechnology, University of Wroclaw, 50-383 Wroclaw, Poland; (A.C.); (W.G.-N.); (P.O.); (A.B.)
- Correspondence: ; Tel.: +48-71375-6356
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7
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Interaction of protocadherin-15 with the scaffold protein whirlin supports its anchoring of hair-bundle lateral links in cochlear hair cells. Sci Rep 2020; 10:16430. [PMID: 33009420 PMCID: PMC7532178 DOI: 10.1038/s41598-020-73158-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 09/07/2020] [Indexed: 11/26/2022] Open
Abstract
The hair bundle of cochlear hair cells is the site of auditory mechanoelectrical transduction. It is formed by three rows of stiff microvilli-like protrusions of graduated heights, the short, middle-sized, and tall stereocilia. In developing and mature sensory hair cells, stereocilia are connected to each other by various types of fibrous links. Two unconventional cadherins, protocadherin-15 (PCDH15) and cadherin-23 (CDH23), form the tip-links, whose tension gates the hair cell mechanoelectrical transduction channels. These proteins also form transient lateral links connecting neighboring stereocilia during hair bundle morphogenesis. The proteins involved in anchoring these diverse links to the stereocilia dense actin cytoskeleton remain largely unknown. We show that the long isoform of whirlin (L-whirlin), a PDZ domain-containing submembrane scaffold protein, is present at the tips of the tall stereocilia in mature hair cells, together with PCDH15 isoforms CD1 and CD2; L-whirlin localization to the ankle-link region in developing hair bundles moreover depends on the presence of PCDH15-CD1 also localizing there. We further demonstrate that L-whirlin binds to PCDH15 and CDH23 with moderate-to-high affinities in vitro. From these results, we suggest that L-whirlin is part of the molecular complexes bridging PCDH15-, and possibly CDH23-containing lateral links to the cytoskeleton in immature and mature stereocilia.
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8
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Moser T, Grabner CP, Schmitz F. Sensory Processing at Ribbon Synapses in the Retina and the Cochlea. Physiol Rev 2020; 100:103-144. [DOI: 10.1152/physrev.00026.2018] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In recent years, sensory neuroscientists have made major efforts to dissect the structure and function of ribbon synapses which process sensory information in the eye and ear. This review aims to summarize our current understanding of two key aspects of ribbon synapses: 1) their mechanisms of exocytosis and endocytosis and 2) their molecular anatomy and physiology. Our comparison of ribbon synapses in the cochlea and the retina reveals convergent signaling mechanisms, as well as divergent strategies in different sensory systems.
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Affiliation(s)
- Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany; Synaptic Nanophysiology Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; and Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Medical School, Saarland University, Homburg, Germany
| | - Chad P. Grabner
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany; Synaptic Nanophysiology Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; and Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Medical School, Saarland University, Homburg, Germany
| | - Frank Schmitz
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany; Synaptic Nanophysiology Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; and Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Medical School, Saarland University, Homburg, Germany
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9
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Wang L, Wei B, Fu X, Wang Y, Sui Y, Ma J, Gong X, Hao J, Xing S. Identification of whirlin domains interacting with espin: A study of the mechanism of Usher syndrome type II. Mol Med Rep 2019; 20:5111-5117. [PMID: 31638198 PMCID: PMC6854525 DOI: 10.3892/mmr.2019.10728] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 08/19/2019] [Indexed: 11/23/2022] Open
Abstract
Usher syndrome is the most common condition of combined blindness and deafness and is classified into three types (USH1-USH3). USH2 is the most commonly diagnosed of all Usher syndrome cases. There are three identified proteins (usherin, GPR98 and whirlin) that form the USH2 complex. Defects in any of these proteins may cause failure in the formation of the USH2 complex, which is the primary cause of USH2. Whirlin is a scaffold protein and is essential for the assembly of the USH2 protein complex. It has been reported that espin is an interacting partner protein for whirlin. However, which fragment of whirlin interacts with espin remains unclear. In the present study, whirlin N- and C-terminal fragments in the pEGFP-C2 vectors were constructed. The recombinant plasmids were transfected into COS-7 cells to observe the co-localization by confocal laser scanning microscopy. The interactions between whirlin and espin were investigated by co-immunoprecipitation using the 293 cell line. It was demonstated that only the whirlin N-terminal fragment was able to interact with espin and the PR (proline-rich) region in whirlin may be important for the interaction. However, the present study did not investigate the interaction between whirlin and espin without the PR domain which warrants future research. Our findings elucidated a primary mechanism of interaction between whirlin and espin, which are crucial for further study on the USH2 complex and USH2 pathogenesis.
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Affiliation(s)
- Le Wang
- Department of Ophthalmology, First Hospital, Jilin University, Changchun, Jilin 130021, P.R. China
| | - Bo Wei
- Department of Neurosurgery, China‑Japan Union Hospital, Jilin University, Changchun, Jilin 130033, P.R. China
| | - Xueqi Fu
- Edmond H. Fischer Signal Transduction Laboratory, School of Life Sciences, Jilin University, Changchun, Jilin 130012, P.R. China
| | - Yuchen Wang
- Edmond H. Fischer Signal Transduction Laboratory, School of Life Sciences, Jilin University, Changchun, Jilin 130012, P.R. China
| | - Yuan Sui
- Edmond H. Fischer Signal Transduction Laboratory, School of Life Sciences, Jilin University, Changchun, Jilin 130012, P.R. China
| | - Junfeng Ma
- Edmond H. Fischer Signal Transduction Laboratory, School of Life Sciences, Jilin University, Changchun, Jilin 130012, P.R. China
| | - Xianhui Gong
- Department of Opthalmology, Eye Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, P.R. China
| | - Jilong Hao
- Department of Ophthalmology, First Hospital, Jilin University, Changchun, Jilin 130021, P.R. China
| | - Shu Xing
- Edmond H. Fischer Signal Transduction Laboratory, School of Life Sciences, Jilin University, Changchun, Jilin 130012, P.R. China
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10
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Klotz L, Wendler O, Frischknecht R, Shigemoto R, Schulze H, Enz R. Localization of group II and III metabotropic glutamate receptors at pre- and postsynaptic sites of inner hair cell ribbon synapses. FASEB J 2019; 33:13734-13746. [PMID: 31585509 DOI: 10.1096/fj.201901543r] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Glutamate is the major excitatory neurotransmitter in the CNS binding to a variety of glutamate receptors. Metabotropic glutamate receptors (mGluR1 to mGluR8) can act excitatory or inhibitory, depending on associated signal cascades. Expression and localization of inhibitory acting mGluRs at inner hair cells (IHCs) in the cochlea are largely unknown. Here, we analyzed expression of mGluR2, mGluR3, mGluR4, mGluR6, mGluR7, and mGluR8 and investigated their localization with respect to the presynaptic ribbon of IHC synapses. We detected transcripts for mGluR2, mGluR3, and mGluR4 as well as for mGluR7a, mGluR7b, mGluR8a, and mGluR8b splice variants. Using receptor-specific antibodies in cochlear wholemounts, we found expression of mGluR2, mGluR4, and mGluR8b close to presynaptic ribbons. Super resolution and confocal microscopy in combination with 3-dimensional reconstructions indicated a postsynaptic localization of mGluR2 that overlaps with postsynaptic density protein 95 on dendrites of afferent type I spiral ganglion neurons. In contrast, mGluR4 and mGluR8b were expressed at the presynapse close to IHC ribbons. In summary, we localized in detail 3 mGluR types at IHC ribbon synapses, providing a fundament for new therapeutical strategies that could protect the cochlea against noxious stimuli and excitotoxicity.-Klotz, L., Wendler, O., Frischknecht, R., Shigemoto, R., Schulze, H., Enz, R. Localization of group II and III metabotropic glutamate receptors at pre- and postsynaptic sites of inner hair cell ribbon synapses.
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Affiliation(s)
- Lisa Klotz
- Institute for Biochemistry (Emil-Fischer-Zentrum), Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Olaf Wendler
- Division of Phoniatrics and Pediatric Audiology, Department of Otorhinolaryngology, Head and Neck Surgery, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Renato Frischknecht
- Department of Biology, Animal Physiology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Ryuichi Shigemoto
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Holger Schulze
- Department of Otorhinolaryngology, Head and Neck Surgery, Experimental Otolaryngology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Ralf Enz
- Institute for Biochemistry (Emil-Fischer-Zentrum), Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
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11
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Mathur PD, Yang J. Usher syndrome and non-syndromic deafness: Functions of different whirlin isoforms in the cochlea, vestibular organs, and retina. Hear Res 2019; 375:14-24. [PMID: 30831381 DOI: 10.1016/j.heares.2019.02.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2018] [Revised: 01/30/2019] [Accepted: 02/20/2019] [Indexed: 12/15/2022]
Abstract
Usher syndrome (USH) is the leading cause of inherited combined vision and hearing loss. However, mutations in most USH causative genes lead to other diseases, such as hearing loss only or vision loss only. The molecular mechanisms underlying the variable disease manifestations associated with USH gene mutations are unclear. This review focuses on an USH type 2 (USH2) gene encoding whirlin (WHRN; previously known as DFNB31), mutations in which have been found to cause either USH2 subtype USH2D or autosomal recessive non-syndromic deafness type 31 (DFNB31). This review summarizes the current knowledge about different whirlin isoforms encoded by WHRN orthologs in animal models, the interactions of different whirlin isoforms with their partners, and the function of whirlin isoforms in different cellular and subcellular locations. The recent findings regarding the function of whirlin isoforms suggest that disruption of different isoforms may be one of the mechanisms underlying the variable disease manifestations caused by USH gene mutations. This review also presents recent findings about the vestibular defects in Whrn mutant mouse models, which suggests that previous assumptions about the normal vestibular function of USH2 patients need to be re-evaluated. Finally, this review describes recent progress in developing therapeutics for diseases caused by WHRN mutations.
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Affiliation(s)
- Pranav Dinesh Mathur
- Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, UT, 84132, USA; Department of Neurobiology and Anatomy, University of Utah, Salt Lake City, UT, 84132, USA
| | - Jun Yang
- Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, UT, 84132, USA; Department of Neurobiology and Anatomy, University of Utah, Salt Lake City, UT, 84132, USA; Department of Otolaryngology Head and Neck Surgery, University of Utah, Salt Lake City, UT, 84132, USA.
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12
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Photoreceptor actin dysregulation in syndromic and non-syndromic retinitis pigmentosa. Biochem Soc Trans 2018; 46:1463-1473. [PMID: 30464047 DOI: 10.1042/bst20180138] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Revised: 09/26/2018] [Accepted: 10/12/2018] [Indexed: 01/11/2023]
Abstract
Retinitis pigmentosa (RP) is the leading cause of inherited blindness. RP is a genetically heterogeneous disorder, with more than 100 different causal genes identified in patients. Central to disease pathogenesis is the progressive loss of retinal photoreceptors. Photoreceptors are specialised sensory neurons that exhibit a complex and highly dynamic morphology. The highly polarised and elaborated architecture of photoreceptors requires precise regulation of numerous cytoskeletal elements. In recent years, significant work has been placed on investigating the role of microtubules (specifically, the acetylated microtubular axoneme of the photoreceptor connecting cilium) and their role in normal photoreceptor function. This has been driven by the emerging field of ciliopathies, human diseases arising from mutations in genes required for cilia formation or function, of which RP is a frequently reported phenotype. Recent studies have highlighted an intimate relationship between cilia and the actin cystoskeleton. This review will focus on the role of actin in photoreceptors, examining the connection between actin dysregulation in RP.
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13
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Saifetiarova J, Bhat MA. Ablation of cytoskeletal scaffolding proteins, Band 4.1B and Whirlin, leads to cerebellar purkinje axon pathology and motor dysfunction. J Neurosci Res 2018; 97:313-331. [PMID: 30447021 DOI: 10.1002/jnr.24352] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 10/12/2018] [Accepted: 10/12/2018] [Indexed: 12/23/2022]
Abstract
The cerebellar cortex receives neural information from other brain regions to allow fine motor coordination and motor learning. The primary output neurons from the cerebellum are the Purkinje neurons that transmit inhibitory responses to deep cerebellar nuclei through their myelinated axons. Altered morphological organization and electrical properties of the Purkinje axons lead to detrimental changes in locomotor activity often leading to cerebellar ataxias. Two cytoskeletal scaffolding proteins Band 4.1B (4.1B) and Whirlin (Whrn) have been previously shown to play independent roles in axonal domain organization and maintenance in myelinated axons in the spinal cord and sciatic nerves. Immunoblot analysis had indicated cerebellar expression for both 4.1B and Whrn; however, their subcellular localization and cerebellum-specific functions have not been characterized. Using 4.1B and Whrn single and double mutant animals, we show that both proteins are expressed in common cellular compartments of the cerebellum and play cooperative roles in preservation of the integrity of Purkinje neuron myelinated axons. We demonstrate that both 4.1B and Whrn are required for the maintenance of axonal ultrastructure and health. Loss of 4.1B and Whrn leads to axonal transport defects manifested by formation of swellings containing cytoskeletal components, membranous organelles, and vesicles. Moreover, ablation of both proteins progressively affects cerebellar function with impairment in locomotor performance detected by altered gait parameters. Together, our data indicate that 4.1B and Whrn are required for maintaining proper axonal cytoskeletal organization and axonal domains, which is necessary for cerebellum-controlled fine motor coordination.
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Affiliation(s)
- Julia Saifetiarova
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, Long School of Medicine, University of Texas Health Science Center, San Antonio, Texas
| | - Manzoor A Bhat
- Department of Cellular and Integrative Physiology, Center for Biomedical Neuroscience, Long School of Medicine, University of Texas Health Science Center, San Antonio, Texas
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14
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Trans-differentiation of outer hair cells into inner hair cells in the absence of INSM1. Nature 2018; 563:691-695. [PMID: 30305733 PMCID: PMC6279423 DOI: 10.1038/s41586-018-0570-8] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 08/14/2018] [Indexed: 01/09/2023]
Abstract
The mammalian cochlea contains two types of mechanosensory hair cells (HCs) that play different and critical roles in hearing. Inner hair cells (IHCs), with an elaborate presynaptic apparatus, signal to cochlear neurons and communicate sound information to the brain. Outer hair cells (OHCs) mechanically amplify sound-induced vibrations, enabling enhanced sensitivity to sound and sharp tuning. Cochlear HCs are solely generated during development and their death, most often of OHCs, is the main cause of deafness. OHCs and IHCs, together with supporting cells, originate embryonically from the prosensory region of the otocyst, but how HCs differentiate into two different types is unknown1–3. Here we show that Insm1, which encodes a zinc finger protein transiently expressed in nascent OHCs, consolidates their fate by preventing trans-differentiation into IHCs. In the absence of INSM1 many HCs born embryonically as OHCs switch fates to become mature IHCs. In order to identify the genetic mechanisms by which Insm1 operates, we compared transcriptomes of immature IHCs vs OHCs, as well as OHCs with and without INSM1. OHCs lacking INSM1 upregulate a set of genes, most of which are normally preferentially expressed by IHCs. The homeotic cell transformation of OHCs without INSM1 into IHCs reveals for the first time a mechanism by which these neighboring mechanosensory cells begin to differ: INSM1 represses a core set of early IHC-enriched genes in embryonic OHCs and makes them unresponsive to an IHC-inducing gradient, so that they proceed to mature as OHCs. Without INSM1, some of the OHCs upregulating these few IHC-enriched transcripts trans-differentiate into IHCs, revealing the first candidate genes for IHC-specific differentiation.
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15
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Seki Y, Miyasaka Y, Suzuki S, Wada K, Yasuda SP, Matsuoka K, Ohshiba Y, Endo K, Ishii R, Shitara H, Kitajiri SI, Nakagata N, Takebayashi H, Kikkawa Y. A novel splice site mutation of myosin VI in mice leads to stereociliary fusion caused by disruption of actin networks in the apical region of inner ear hair cells. PLoS One 2017; 12:e0183477. [PMID: 28832620 PMCID: PMC5568226 DOI: 10.1371/journal.pone.0183477] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 08/04/2017] [Indexed: 01/03/2023] Open
Abstract
An unconventional myosin encoded by the myosin VI gene (MYO6) contributes to hearing loss in humans. Homozygous mutations of MYO6 result in nonsyndromic profound congenital hearing loss, DFNB37. Kumamoto shaker/waltzer (ksv) mice harbor spontaneous mutations, and homozygous mutants exhibit congenital defects in balance and hearing caused by fusion of the stereocilia. We identified a Myo6c.1381G>A mutation that was found to be a p.E461K mutation leading to alternative splicing errors in Myo6 mRNA in ksv mutants. An analysis of the mRNA and protein expression in animals harboring this mutation suggested that most of the abnormal alternatively spliced isoforms of MYO6 are degraded in ksv mice. In the hair cells of ksv/ksv homozygotes, the MYO6 protein levels were significantly decreased in the cytoplasm, including in the cuticular plates. MYO6 and stereociliary taper-specific proteins were mislocalized along the entire length of the stereocilia of ksv/ksv mice, thus suggesting that MYO6 attached to taper-specific proteins at the stereociliary base. Histological analysis of the cochlear hair cells showed that the stereociliary fusion in the ksv/ksv mutants, developed through fusion between stereociliary bundles, raised cuticular plate membranes in the cochlear hair cells and resulted in incorporation of the bundles into the sheaths of the cuticular plates. Interestingly, the expression of the stereociliary rootlet-specific TRIO and F-actin binding protein (TRIOBP) was altered in ksv/ksv mice. The abnormal expression of TRIOBP suggested that the rootlets in the hair cells of ksv/ksv mice had excessive growth. Hence, these data indicated that decreased MYO6 levels in ksv/ksv mutants disrupt actin networks in the apical region of hair cells, thereby maintaining the normal structure of the cuticular plates and rootlets, and additionally provided a cellular basis for stereociliary fusion in Myo6 mutants.
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Affiliation(s)
- Yuta Seki
- Mammalian Genetics Project, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Yuki Miyasaka
- Mammalian Genetics Project, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.,Division of Experimental Animals, Center for Promotion of Medical Research and Education, Graduate School of Medicine, Nagoya University, Nagoya, Aichi, Japan
| | - Sari Suzuki
- Mammalian Genetics Project, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Kenta Wada
- Mammalian Genetics Project, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.,Laboratory of Animal Biotechnology, Department of Bioproduction, Faculty of Bioindustry, Tokyo University of Agriculture, Abashiri, Hokkaido, Japan
| | - Shumpei P Yasuda
- Mammalian Genetics Project, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Kunie Matsuoka
- Mammalian Genetics Project, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Yasuhiro Ohshiba
- Mammalian Genetics Project, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Kentaro Endo
- Histology Laboratory, Advanced Technical Support Department, Center for Basic Technology Research, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Rie Ishii
- Laboratory for Transgenic Technology, Animal Research Division, Center for Basic Technology Research, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Hiroshi Shitara
- Laboratory for Transgenic Technology, Animal Research Division, Center for Basic Technology Research, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Shin-Ichiro Kitajiri
- Department of Otolaryngology-Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Naomi Nakagata
- Division of Reproductive Engineering, Center for Animal Resources and Development (CARD), Kumamoto University, Kumamoto, Japan
| | - Hirohide Takebayashi
- Division of Neurobiology and Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
| | - Yoshiaki Kikkawa
- Mammalian Genetics Project, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
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16
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Disease mechanisms of X-linked retinitis pigmentosa due to RP2 and RPGR mutations. Biochem Soc Trans 2017; 44:1235-1244. [PMID: 27911705 DOI: 10.1042/bst20160148] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 08/16/2016] [Accepted: 08/18/2016] [Indexed: 01/24/2023]
Abstract
Photoreceptor degeneration is the prominent characteristic of retinitis pigmentosa (RP), a heterogeneous group of inherited retinal dystrophies resulting in blindness. Although abnormalities in many pathways can cause photoreceptor degeneration, one of the most important causes is defective protein transport through the connecting cilium, the structure that connects the biosynthetic inner segment with the photosensitive outer segment of the photoreceptors. The majority of patients with X-linked RP have mutations in the retinitis pigmentosa GTPase regulator (RPGR) or RP2 genes, the protein products of which are both components of the connecting cilium and associated with distinct mechanisms of protein delivery to the outer segment. RP2 and RPGR proteins are associated with severe diseases ranging from classic RP to atypical forms. In this short review, we will summarise current knowledge generated by experimental studies and knockout animal models, compare and discuss the prominent hypotheses about the two proteins' functions in retinal cell biology.
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17
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Zebrafish Models for the Mechanosensory Hair Cell Dysfunction in Usher Syndrome 3 Reveal That Clarin-1 Is an Essential Hair Bundle Protein. J Neurosci 2015; 35:10188-201. [PMID: 26180195 DOI: 10.1523/jneurosci.1096-15.2015] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Usher syndrome type III (USH3) is characterized by progressive loss of hearing and vision, and varying degrees of vestibular dysfunction. It is caused by mutations that affect the human clarin-1 protein (hCLRN1), a member of the tetraspanin protein family. The missense mutation CLRN1(N48K), which affects a conserved N-glycosylation site in hCLRN1, is a common causative USH3 mutation among Ashkenazi Jews. The affected individuals hear at birth but lose that function over time. Here, we developed an animal model system using zebrafish transgenesis and gene targeting to provide an explanation for this phenotype. Immunolabeling demonstrated that Clrn1 localized to the hair cell bundles (hair bundles). The clrn1 mutants generated by zinc finger nucleases displayed aberrant hair bundle morphology with diminished function. Two transgenic zebrafish that express either hCLRN1 or hCLRN1(N48K) in hair cells were produced to examine the subcellular localization patterns of wild-type and mutant human proteins. hCLRN1 localized to the hair bundles similarly to zebrafish Clrn1; in contrast, hCLRN1(N48K) largely mislocalized to the cell body with a small amount reaching the hair bundle. We propose that this small amount of hCLRN1(N48K) in the hair bundle provides clarin-1-mediated function during the early stages of life; however, the presence of hCLRN1(N48K) in the hair bundle diminishes over time because of intracellular degradation of the mutant protein, leading to progressive loss of hair bundle integrity and hair cell function. These findings and genetic tools provide an understanding and path forward to identify therapies to mitigate hearing loss linked to the CLRN1 mutation. SIGNIFICANCE STATEMENT Mutations in the clarin-1 gene affect eye and ear function in humans. Individuals with the CLRN1(N48K) mutation are born able to hear but lose that function over time. Here, we develop an animal model system using zebrafish transgenesis and gene targeting to provide an explanation for this phenotype. This approach illuminates the role of clarin-1 and the molecular mechanism linked to the CLRN1(N48K) mutation in sensory hair cells of the inner ear. Additionally, the investigation provided an in vivo model to guide future drug discovery to rescue the hCLRN1(N48K) in hair cells.
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18
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Megaw RD, Soares DC, Wright AF. RPGR: Its role in photoreceptor physiology, human disease, and future therapies. Exp Eye Res 2015; 138:32-41. [PMID: 26093275 PMCID: PMC4553903 DOI: 10.1016/j.exer.2015.06.007] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 06/03/2015] [Accepted: 06/04/2015] [Indexed: 12/21/2022]
Abstract
Mammalian photoreceptors contain specialised connecting cilia that connect the inner (IS) to the outer segments (OS). Dysfunction of the connecting cilia due to mutations in ciliary proteins are a common cause of the inherited retinal dystrophy retinitis pigmentosa (RP). Mutations affecting the Retinitis Pigmentosa GTPase Regulator (RPGR) protein is one such cause, affecting 10-20% of all people with RP and the majority of those with X-linked RP. RPGR is located in photoreceptor connecting cilia. It interacts with a wide variety of ciliary proteins, but its exact function is unknown. Recently, there have been important advances both in our understanding of RPGR function and towards the development of a therapy. This review summarises the existing literature on human RPGR function and dysfunction, and suggests that RPGR plays a role in the function of the ciliary gate, which controls access of both membrane and soluble proteins to the photoreceptor outer segment. We discuss key models used to investigate and treat RPGR disease and suggest that gene augmentation therapy offers a realistic therapeutic approach, although important questions still remain to be answered, while cell replacement therapy based on retinal progenitor cells represents a more distant prospect.
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Affiliation(s)
- Roly D Megaw
- Scottish Centre for Regenerative Medicine, University of Edinburgh, 5 Little France Drive, Edinburgh EH16 4UU, United Kingdom.
| | - Dinesh C Soares
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom.
| | - Alan F Wright
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom.
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19
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Membrane rafts in the erythrocyte membrane: a novel role of MPP1p55. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 842:61-78. [PMID: 25408337 DOI: 10.1007/978-3-319-11280-0_5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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20
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Genetics of auditory mechano-electrical transduction. Pflugers Arch 2014; 467:49-72. [PMID: 24957570 PMCID: PMC4281357 DOI: 10.1007/s00424-014-1552-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 06/04/2014] [Accepted: 06/05/2014] [Indexed: 12/29/2022]
Abstract
The hair bundles of cochlear hair cells play a central role in the auditory mechano-electrical transduction (MET) process. The identification of MET components and of associated molecular complexes by biochemical approaches is impeded by the very small number of hair cells within the cochlea. In contrast, human and mouse genetics have proven to be particularly powerful. The study of inherited forms of deafness led to the discovery of several essential proteins of the MET machinery, which are currently used as entry points to decipher the associated molecular networks. Notably, MET relies not only on the MET machinery but also on several elements ensuring the proper sound-induced oscillation of the hair bundle or the ionic environment necessary to drive the MET current. Here, we review the most significant advances in the molecular bases of the MET process that emerged from the genetics of hearing.
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21
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Ueyama T, Sakaguchi H, Nakamura T, Goto A, Morioka S, Shimizu A, Nakao K, Hishikawa Y, Ninoyu Y, Kassai H, Suetsugu S, Koji T, Fritzsch B, Yonemura S, Hisa Y, Matsuda M, Aiba A, Saito N. Maintenance of stereocilia and apical junctional complexes by Cdc42 in cochlear hair cells. J Cell Sci 2014; 127:2040-52. [PMID: 24610943 DOI: 10.1242/jcs.143602] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Cdc42 is a key regulator of dynamic actin organization. However, little is known about how Cdc42-dependent actin regulation influences steady-state actin structures in differentiated epithelia. We employed inner ear hair-cell-specific conditional knockout to analyze the role of Cdc42 in hair cells possessing highly elaborate stable actin protrusions (stereocilia). Hair cells of Atoh1-Cre;Cdc42(flox/flox) mice developed normally but progressively degenerated after maturation, resulting in progressive hearing loss particularly at high frequencies. Cochlear hair cell degeneration was more robust in inner hair cells than in outer hair cells, and began as stereocilia fusion and depletion, accompanied by a thinning and waving circumferential actin belt at apical junctional complexes (AJCs). Adenovirus-encoded GFP-Cdc42 expression in hair cells and fluorescence resonance energy transfer (FRET) imaging of hair cells from transgenic mice expressing a Cdc42-FRET biosensor indicated Cdc42 presence and activation at stereociliary membranes and AJCs in cochlear hair cells. Cdc42-knockdown in MDCK cells produced phenotypes similar to those of Cdc42-deleted hair cells, including abnormal microvilli and disrupted AJCs, and downregulated actin turnover represented by enhanced levels of phosphorylated cofilin. Thus, Cdc42 influenced the maintenance of stable actin structures through elaborate tuning of actin turnover, and maintained function and viability of cochlear hair cells.
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Affiliation(s)
- Takehiko Ueyama
- Laboratory of Molecular Pharmacology, Biosignal Research Center, Kobe University, Kobe 657-8501, Japan
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22
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Olt J, Mburu P, Johnson SL, Parker A, Kuhn S, Bowl M, Marcotti W, Brown SDM. The actin-binding proteins eps8 and gelsolin have complementary roles in regulating the growth and stability of mechanosensory hair bundles of mammalian cochlear outer hair cells. PLoS One 2014; 9:e87331. [PMID: 24475274 PMCID: PMC3903700 DOI: 10.1371/journal.pone.0087331] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 12/19/2013] [Indexed: 11/21/2022] Open
Abstract
Sound transduction depends upon mechanosensitive channels localized on the hair-like bundles that project from the apical surface of cochlear hair cells. Hair bundles show a stair-case structure composed of rows of stereocilia, and each stereocilium contains a core of tightly-packed and uniformly-polarized actin filaments. The growth and maintenance of the stereociliary actin core are dynamically regulated. Recently, it was shown that the actin-binding protein gelsolin is expressed in the stereocilia of outer hair cells (OHCs) and in its absence they become long and straggly. Gelsolin is part of a whirlin scaffolding protein complex at the stereocilia tip, which has been shown to interact with other actin regulatory molecules such as Eps8. Here we investigated the physiological effects associated with the absence of gelsolin and its possible overlapping role with Eps8. We found that, in contrast to Eps8, gelsolin does not affect mechanoelectrical transduction during immature stages of development. Moreover, OHCs from gelsolin knockout mice were able to mature into fully functional sensory receptors as judged by the normal resting membrane potential and basolateral membrane currents. Mechanoelectrical transducer current in gelsolin-Eps8 double knockout mice showed a profile similar to that observed in the single mutants for Eps8. We propose that gelsolin has a non-overlapping role with Eps8. While Eps8 is mainly involved in the initial growth of stereocilia in both inner hair cells (IHCs) and OHCs, gelsolin is required for the maintenance of mature hair bundles of low-frequency OHCs after the onset of hearing.
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MESH Headings
- Adaptor Proteins, Signal Transducing/metabolism
- Animals
- Cytoskeletal Proteins/metabolism
- Gelsolin/genetics
- Gelsolin/metabolism
- Hair Cells, Auditory, Outer/metabolism
- Hair Cells, Auditory, Outer/physiology
- Hair Cells, Auditory, Outer/ultrastructure
- Immunohistochemistry
- Mechanoreceptors/metabolism
- Mechanoreceptors/physiology
- Mechanoreceptors/ultrastructure
- Mechanotransduction, Cellular/physiology
- Mice
- Mice, Knockout
- Microfilament Proteins/metabolism
- Microscopy, Electron, Scanning
- Patch-Clamp Techniques
- Physical Stimulation
- Pyridinium Compounds
- Quaternary Ammonium Compounds
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Affiliation(s)
- Jennifer Olt
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Philomena Mburu
- Medical Research Council (MRC), Mammalian Genetics Unit, Harwell, United Kingdom
| | - Stuart L. Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Andy Parker
- Medical Research Council (MRC), Mammalian Genetics Unit, Harwell, United Kingdom
| | - Stephanie Kuhn
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Mike Bowl
- Medical Research Council (MRC), Mammalian Genetics Unit, Harwell, United Kingdom
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
- * E-mail: (WM); (SDMB)
| | - Steve D. M. Brown
- Medical Research Council (MRC), Mammalian Genetics Unit, Harwell, United Kingdom
- * E-mail: (WM); (SDMB)
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23
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Green JA, Yang J, Grati M, Kachar B, Bhat MA. Whirlin, a cytoskeletal scaffolding protein, stabilizes the paranodal region and axonal cytoskeleton in myelinated axons. BMC Neurosci 2013; 14:96. [PMID: 24011083 PMCID: PMC3844453 DOI: 10.1186/1471-2202-14-96] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 09/03/2013] [Indexed: 11/28/2022] Open
Abstract
Background Myelinated axons are organized into distinct subcellular and molecular regions. Without proper organization, electrical nerve conduction is delayed, resulting in detrimental physiological outcomes. One such region is the paranode where axo-glial septate junctions act as a molecular fence to separate the sodium (Na+) channel-enriched node from the potassium (K+) channel-enriched juxtaparanode. A significant lack of knowledge remains as to cytoskeletal proteins which stabilize paranodal domains and underlying cytoskeleton. Whirlin (Whrn) is a PDZ domain-containing cytoskeletal scaffold whose absence in humans results in Usher Syndromes or variable deafness-blindness syndromes. Mutant Whirlin (Whrn) mouse model studies have linked such behavioral deficits to improper localization of critical transmembrane protein complexes in the ear and eye. Until now, no reports exist about the function of Whrn in myelinated axons. Results RT-PCR and immunoblot analyses revealed expression of Whrn mRNA and Whrn full-length protein, respectively, in several stages of central and peripheral nervous system development. Comparing wild-type mice to Whrn knockout (Whrn−/−) mice, we observed no significant differences in the expression of standard axonal domain markers by immunoblot analysis but observed and quantified a novel paranodal compaction phenotype in 4 to 8 week-old Whrn−/− nerves. The paranodal compaction phenotype and associated cytoskeletal disruption was observed in Whrn−/− mutant sciatic nerves and spinal cord fibers from early (2 week-old) to late (1 year-old) stages of development. Light and electron microscopic analyses of Whrn knockout mice reveal bead-like swellings in cerebellar Purkinje axons containing mitochondria and vesicles by both. These data suggest that Whrn plays a role in proper cytoskeletal organization in myelinated axons. Conclusions Domain organization in myelinated axons remains a complex developmental process. Here we demonstrate that loss of Whrn disrupts proper axonal domain organization. Whrn likely contributes to the stabilization of paranodal myelin loops and axonal cytoskeleton through yet unconfirmed cytoskeletal proteins. Paranodal abnormalities are consistently observed throughout development (2 wk-1 yr) and similar between central and peripheral nervous systems. In conclusion, our observations suggest that Whrn is not required for the organization of axonal domains, but once organized, Whrn acts as a cytoskeletal linker to ensure proper paranodal compaction and stabilization of the axonal cytoskeleton in myelinated axons.
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Affiliation(s)
- James A Green
- Department of Cell and Molecular Physiology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA.
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Darville LN, Sokolowski BH. In-depth proteomic analysis of mouse cochlear sensory epithelium by mass spectrometry. J Proteome Res 2013; 12:3620-30. [PMID: 23721421 PMCID: PMC3777728 DOI: 10.1021/pr4001338] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Proteomic analysis of sensory organs such as the cochlea is challenging due to its small size and difficulties with membrane protein isolation. Mass spectrometry in conjunction with separation methods can provide a more comprehensive proteome, because of the ability to enrich protein samples, detect hydrophobic proteins, and identify low abundant proteins by reducing the proteome dynamic range. GELFrEE as well as different separation and digestion techniques were combined with FASP and nanoLC-MS/MS to obtain an in-depth proteome analysis of cochlear sensory epithelium from 30-day-old mice. Digestion with LysC/trypsin followed by SCX fractionation and multiple nanoLC-MS/MS analyses identified 3773 proteins with a 1% FDR. Of these, 694 protein IDs were in the plasmalemma. Protein IDs obtained by combining outcomes from GELFrEE/LysC/trypsin with GELFrEE/trypsin/trypsin generated 2779 proteins, of which 606 additional proteins were identified using the GELFrEE/LysC/trypsin approach. Combining results from the different techniques resulted in a total of 4620 IDs, including a number of previously unreported proteins. GO analyses showed high expression of binding and catalytic proteins as well as proteins associated with metabolism. The results show that the application of multiple techniques is needed to provide an exhaustive proteome of the cochlear sensory epithelium that includes many membrane proteins. The mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium with the data set identifier PXD000231.
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Affiliation(s)
- Lancia N.F. Darville
- University of South Florida, Morsani College of Medicine, 12901 Bruce B. Downs Blvd. Department of Otolaryngology – HNS, Otology Laboratory, MDC83, Tampa FL 33647
| | - Bernd H.A. Sokolowski
- University of South Florida, Morsani College of Medicine, 12901 Bruce B. Downs Blvd. Department of Otolaryngology – HNS, Otology Laboratory, MDC83, Tampa FL 33647
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Cao H, Yin X, Cao Y, Jin Y, Wang S, Kong Y, Chen Y, Gao J, Heller S, Xu Z. FCHSD1 and FCHSD2 are expressed in hair cell stereocilia and cuticular plate and regulate actin polymerization in vitro. PLoS One 2013; 8:e56516. [PMID: 23437151 PMCID: PMC3577914 DOI: 10.1371/journal.pone.0056516] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 01/10/2013] [Indexed: 12/03/2022] Open
Abstract
Mammalian FCHSD1 and FCHSD2 are homologous proteins containing an amino-terminal F-BAR domain and two SH3 domains near their carboxyl-termini. We report here that FCHSD1 and FCHSD2 are expressed in mouse cochlear sensory hair cells. FCHSD1 mainly localizes to the cuticular plate, whereas FCHSD2 mainly localizes along the stereocilia in a punctuate pattern. Nervous Wreck (Nwk), the Drosophila ortholog of FCHSD1 and FCHSD2, has been shown to bind Wsp and play an important role in F-actin assembly. We show that, like its Drosophila counterpart, FCHSD2 interacts with WASP and N-WASP, the mammalian orthologs of Drosophila Wsp, and stimulates F-actin assembly in vitro. In contrast, FCHSD1 doesn’t bind WASP or N-WASP, and can’t stimulate F-actin assembly when tested in vitro. We found, however, that FCHSD1 binds via its F-BAR domain to the SH3 domain of Sorting Nexin 9 (SNX9), a well characterized BAR protein that has been shown to promote WASP-Arp2/3-dependent F-actin polymerization. FCHSD1 greatly enhances SNX9’s WASP-Arp2/3-dependent F-actin polymerization activity. In hair cells, SNX9 was detected in the cuticular plate, where it colocalizes with FCHSD1. Our results suggest that FCHSD1 and FCHSD2 could modulate F-actin assembly or maintenance in hair cell stereocilia and cuticular plate.
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Affiliation(s)
- Huiren Cao
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, Institute of Developmental Biology, School of Life Sciences, Shandong University, Jinan, Shandong, People’s Republic of China
| | - Xiaolei Yin
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, Institute of Developmental Biology, School of Life Sciences, Shandong University, Jinan, Shandong, People’s Republic of China
| | - Yujie Cao
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, Institute of Developmental Biology, School of Life Sciences, Shandong University, Jinan, Shandong, People’s Republic of China
| | - Yecheng Jin
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, Institute of Developmental Biology, School of Life Sciences, Shandong University, Jinan, Shandong, People’s Republic of China
| | - Shan Wang
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, Institute of Developmental Biology, School of Life Sciences, Shandong University, Jinan, Shandong, People’s Republic of China
| | - Yanhui Kong
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, Institute of Developmental Biology, School of Life Sciences, Shandong University, Jinan, Shandong, People’s Republic of China
| | - Yuexing Chen
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, Institute of Developmental Biology, School of Life Sciences, Shandong University, Jinan, Shandong, People’s Republic of China
| | - Jiangang Gao
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, Institute of Developmental Biology, School of Life Sciences, Shandong University, Jinan, Shandong, People’s Republic of China
| | - Stefan Heller
- Departments of Otolaryngology – Head & Neck Surgery and Molecular & Cellular Physiology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Zhigang Xu
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, Institute of Developmental Biology, School of Life Sciences, Shandong University, Jinan, Shandong, People’s Republic of China
- * E-mail:
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Hackney CM, Furness DN. The composition and role of cross links in mechanoelectrical transduction in vertebrate sensory hair cells. J Cell Sci 2013; 126:1721-31. [DOI: 10.1242/jcs.106120] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The key components of acousticolateralis systems (lateral line, hearing and balance) are sensory hair cells. At their apex, these cells have a bundle of specialized cellular protrusions, which are modified actin-containing microvilli, connected together by extracellular filaments called cross links. Stereociliary deflections open nonselective cation channels allowing ions from the extracellular environment into the cell, a process called mechanoelectrical transduction. This produces a receptor potential that causes the release of the excitatory neurotransmitter glutamate onto the terminals of the sensory nerve fibres, which connect to the cell base, causing nerve signals to be sent to the brain. Identification of the cellular mechanisms underlying mechanoelectrical transduction and of some of the proteins involved has been assisted by research into the genetics of deafness, molecular biology and mechanical measurements of function. It is thought that one type of cross link, the tip link, is composed of cadherin 23 and protocadherin 15, and gates the transduction channel when the bundle is deflected. Another type of link, called lateral (or horizontal) links, maintains optimal bundle cohesion and stiffness for transduction. This Commentary summarizes the information currently available about the structure, function and composition of the links and how they might be relevant to human hearing impairment.
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Zhu J, Shang Y, Chen J, Zhang M. Structure and function of the guanylate kinase-like domain of the MAGUK family scaffold proteins. ACTA ACUST UNITED AC 2012. [DOI: 10.1007/s11515-012-1244-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Kikkawa Y, Seki Y, Okumura K, Ohshiba Y, Miyasaka Y, Suzuki S, Ozaki M, Matsuoka K, Noguchi Y, Yonekawa H. Advantages of a mouse model for human hearing impairment. Exp Anim 2012; 61:85-98. [PMID: 22531723 DOI: 10.1538/expanim.61.85] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Hearing is a major factor in human quality of life. Mouse models are important tools for discovering the genes that are responsible for genetic hearing loss, and these models often allow the processes that regulate the onset of deafness in humans to be analyzed. Thus far, in the study of hearing and deafness, at least 400 mutants with hearing impairments have been identified in laboratory mouse populations. Analysis of through a combination of genetic, morphological, and physiological studies is revealing valuable insights into the ontogenesis, morphogenesis, and function of the mammalian ear. This review discusses the advantages of the mouse models of human hearing impairment and highlights the identification of the molecules required for stereocilia development in the inner ear hair cells by analysis of various mouse mutants.
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Affiliation(s)
- Yoshiaki Kikkawa
- Mammalian Genetics Project, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
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Lapan SW, Reddien PW. Transcriptome analysis of the planarian eye identifies ovo as a specific regulator of eye regeneration. Cell Rep 2012; 2:294-307. [PMID: 22884275 DOI: 10.1016/j.celrep.2012.06.018] [Citation(s) in RCA: 147] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Revised: 05/12/2012] [Accepted: 06/22/2012] [Indexed: 11/24/2022] Open
Abstract
Among the millions of invertebrate species with visual systems, the genetic basis of eye development and function is well understood only in Drosophila melanogaster. We describe an eye transcriptome for the planarian Schmidtea mediterranea. Planarian photoreceptors expressed orthologs of genes required for phototransduction and microvillus structure in Drosophila and vertebrates, and optic pigment cells expressed solute transporters and melanin synthesis enzymes similar to those active in the vertebrate retinal pigment epithelium. Orthologs of several planarian eye genes, such as bestrophin-1 and Usher syndrome genes, cause eye defects in mammals when perturbed and were not previously described to have roles in invertebrate eyes. Five previously undescribed planarian eye transcription factors were required for normal eye formation during head regeneration. In particular, a conserved, transcription-factor-encoding ovo gene was expressed from the earliest stages of eye regeneration and was required for regeneration of all cell types of the eye.
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Affiliation(s)
- Sylvain W Lapan
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
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dyschronic, a Drosophila homolog of a deaf-blindness gene, regulates circadian output and Slowpoke channels. PLoS Genet 2012; 8:e1002671. [PMID: 22532808 PMCID: PMC3330124 DOI: 10.1371/journal.pgen.1002671] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 03/09/2012] [Indexed: 01/10/2023] Open
Abstract
Many aspects of behavior and physiology are under circadian control. In Drosophila, the molecular clock that regulates rhythmic patterns of behavior has been extensively characterized. In contrast, genetic loci involved in linking the clock to alterations in motor activity have remained elusive. In a forward-genetic screen, we uncovered a new component of the circadian output pathway, which we have termed dyschronic (dysc). dysc mutants exhibit arrhythmic locomotor behavior, yet their eclosion rhythms are normal and clock protein cycling remains intact. Intriguingly, dysc is the closest Drosophila homolog of whirlin, a gene linked to type II Usher syndrome, the leading cause of deaf-blindness in humans. Whirlin and other Usher proteins are expressed in the mammalian central nervous system, yet their function in the CNS has not been investigated. We show that DYSC is expressed in major neuronal tracts and regulates expression of the calcium-activated potassium channel SLOWPOKE (SLO), an ion channel also required in the circadian output pathway. SLO and DYSC are co-localized in the brain and control each other's expression post-transcriptionally. Co-immunoprecipitation experiments demonstrate they form a complex, suggesting they regulate each other through protein–protein interaction. Furthermore, electrophysiological recordings of neurons in the adult brain show that SLO-dependent currents are greatly reduced in dysc mutants. Our work identifies a Drosophila homolog of a deaf-blindness gene as a new component of the circadian output pathway and an important regulator of ion channel expression, and suggests novel roles for Usher proteins in the mammalian nervous system. In most organisms, endogenous circadian clocks help to restrict adaptive activities such as foraging and mating to ecologically appropriate periods of the day–night cycle. The fruit fly Drosophila melanogaster has been a crucial genetic model system for understanding the molecular underpinnings of the clock. Here, using a forward-genetic screen for mutant flies that lack circadian patterns of locomotion, we identify a novel gene critical to circadian behavior, which we have termed dyschronic (dysc). Interestingly, DYSC is not part of the molecular clock itself, but acts in an intermediate circuit between clock cells and motor neurons to regulate temporal alterations in locomotion. DYSC contains several protein-binding domains, suggesting a role as a scaffolding protein. Indeed, we show that DYSC forms a mutually dependent complex with the SLOWPOKE Ca2+–activated potassium channel, an ion channel required for circadian output. DYSC regulates SLOWPOKE expression and SLOWPOKE-dependent currents in the fly brain. Furthermore, dysc is the closest Drosophila homolog of whirlin, a locus mutated in the human deaf-blindness disease Type II Usher syndrome. Our results identify a novel ion channel regulator that impacts neuronal physiology and complex behavior, and suggest new roles for Whirlin in the human nervous system.
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Yang J, Wang L, Song H, Sokolov M. Current understanding of usher syndrome type II. Front Biosci (Landmark Ed) 2012; 17:1165-83. [PMID: 22201796 DOI: 10.2741/3979] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Usher syndrome is the most common deafness-blindness caused by genetic mutations. To date, three genes have been identified underlying the most prevalent form of Usher syndrome, the type II form (USH2). The proteins encoded by these genes are demonstrated to form a complex in vivo. This complex is localized mainly at the periciliary membrane complex in photoreceptors and the ankle-link of the stereocilia in hair cells. Many proteins have been found to interact with USH2 proteins in vitro, suggesting that they are potential additional components of this USH2 complex and that the genes encoding these proteins may be the candidate USH2 genes. However, further investigations are critical to establish their existence in the USH2 complex in vivo. Based on the predicted functional domains in USH2 proteins, their cellular localizations in photoreceptors and hair cells, the observed phenotypes in USH2 mutant mice, and the known knowledge about diseases similar to USH2, putative biological functions of the USH2 complex have been proposed. Finally, therapeutic approaches for this group of diseases are now being actively explored.
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Affiliation(s)
- Jun Yang
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, Utah 84132
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Guanylate kinase domains of the MAGUK family scaffold proteins as specific phospho-protein-binding modules. EMBO J 2011; 30:4986-97. [PMID: 22117215 DOI: 10.1038/emboj.2011.428] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Accepted: 11/02/2011] [Indexed: 12/29/2022] Open
Abstract
Membrane-associated guanylate kinases (MAGUKs) are a large family of scaffold proteins that play essential roles in tissue developments, cell-cell communications, cell polarity control, and cellular signal transductions. Despite extensive studies over the past two decades, the functions of the signature guanylate kinase domain (GK) of MAGUKs are poorly understood. Here we show that the GK domain of DLG1/SAP97 binds to asymmetric cell division regulatory protein LGN in a phosphorylation-dependent manner. The structure of the DLG1 SH3-GK tandem in complex with a phospho-LGN peptide reveals that the GMP-binding site of GK has evolved into a specific pSer/pThr-binding pocket. Residues both N- and C-terminal to the pSer are also critical for the specific binding of the phospho-LGN peptide to GK. We further demonstrate that the previously reported GK domain-mediated interactions of DLGs with other targets, such as GKAP/DLGAP1/SAPAP1 and SPAR, are also phosphorylation dependent. Finally, we provide evidence that other MAGUK GKs also function as phospho-peptide-binding modules. The discovery of the phosphorylation-dependent MAGUK GK/target interactions indicates that MAGUK scaffold-mediated signalling complex organizations are dynamically regulated.
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Wang L, Zou J, Shen Z, Song E, Yang J. Whirlin interacts with espin and modulates its actin-regulatory function: an insight into the mechanism of Usher syndrome type II. Hum Mol Genet 2011; 21:692-710. [PMID: 22048959 DOI: 10.1093/hmg/ddr503] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Whirlin mutations cause retinal degeneration and hearing loss in Usher syndrome type II (USH2) and non-syndromic deafness, DFNB31. Its protein recruits other USH2 causative proteins to form a complex at the periciliary membrane complex in photoreceptors and the ankle link of the stereocilia in hair cells. However, the biological function of this USH2 protein complex is largely unknown. Using a yeast two-hybrid screen, we identified espin, an actin-binding/bundling protein involved in human deafness when defective, as a whirlin-interacting protein. The interaction between these two proteins was confirmed by their coimmunoprecipitation and colocalization in cultured cells. This interaction involves multiple domains of both proteins and only occurs when espin does not bind to actin. Espin was partially colocalized with whirlin in the retina and the inner ear. In whirlin knockout mice, espin expression changed significantly in these two tissues. Further studies found that whirlin increased the mobility of espin and actin at the actin bundles cross-linked by espin and, eventually, affected the dimension of these actin bundles. In whirlin knockout mice, the stereocilia were thickened in inner hair cells. We conclude that the interaction between whirlin and espin and the balance between their expressions are required to maintain the actin bundle network in photoreceptors and hair cells. Disruption of this actin bundle network contributes to the pathogenic mechanism of hearing loss and retinal degeneration caused by whirlin and espin mutations. Espin is a component of the USH2 protein complex and could be a candidate gene for Usher syndrome.
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Affiliation(s)
- Le Wang
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT 84132, USA
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Insights into the Function of the Unstructured N-Terminal Domain of Proteins 4.1R and 4.1G in Erythropoiesis. Int J Cell Biol 2011; 2011:943272. [PMID: 21904552 PMCID: PMC3166722 DOI: 10.1155/2011/943272] [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: 04/20/2011] [Accepted: 06/20/2011] [Indexed: 01/26/2023] Open
Abstract
Membrane skeletal protein 4.1R is the prototypical member of a family of four highly paralogous proteins that include 4.1G, 4.1N, and 4.1B. Two isoforms of 4.1R (4.1R(135) and 4.1R(80)), as well as 4.1G, are expressed in erythroblasts during terminal differentiation, but only 4.1R(80) is present in mature erythrocytes. One goal in the field is to better understand the complex regulation of cell type and isoform-specific expression of 4.1 proteins. To start answering these questions, we are studying in depth the important functions of 4.1 proteins in the organization and function of the membrane skeleton in erythrocytes. We have previously reported that the binding profiles of 4.1R(80) and 4.1R(135) to membrane proteins and calmodulin are very different despite the similar structure of the membrane-binding domain of 4.1G and 4.1R(135). We have accumulated evidence for those differences being caused by the N-terminal 209 amino acids headpiece region (HP). Interestingly, the HP region is an unstructured domain. Here we present an overview of the differences and similarities between 4.1 isoforms and paralogs. We also discuss the biological significance of unstructured domains.
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Audo I, Bujakowska K, Mohand-Saïd S, Tronche S, Lancelot ME, Antonio A, Germain A, Lonjou C, Carpentier W, Sahel JA, Bhattacharya S, Zeitz C. A novel DFNB31 mutation associated with Usher type 2 syndrome showing variable degrees of auditory loss in a consanguineous Portuguese family. Mol Vis 2011; 17:1598-606. [PMID: 21738389 PMCID: PMC3123164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Accepted: 06/10/2011] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To identify the genetic defect of a consanguineous Portuguese family with rod-cone dystrophy and varying degrees of decreased audition. METHODS A detailed ophthalmic and auditory examination was performed on a Portuguese patient with severe autosomal recessive rod-cone dystrophy. Known genetic defects were excluded by performing autosomal recessive retinitis pigmentosa (arRP) genotyping microarray analysis and by Sanger sequencing of the coding exons and flanking intronic regions of eyes shut homolog-drosophila (EYS) and chromosome 2 open reading frame 71 (C2orf71). Subsequently, genome-wide homozygosity mapping was performed in DNA samples from available family members using a 700K single nucleotide polymorphism (SNP) microarray. Candidate genes present in the significantly large homozygous regions were screened for mutations using Sanger sequencing. RESULTS The largest homozygous region (~11 Mb) in the affected family members was mapped to chromosome 9, which harbors deafness, autosomal recessive 31 (DFNB31; a gene previously associated with Usher syndrome). Mutation analysis of DFNB31 in the index patient identified a novel one-base-pair deletion (c.737delC), which is predicted to lead to a truncated protein (p.Pro246HisfsX13) and co-segregated with the disease in the family. Ophthalmic examination of the index patient and the affected siblings showed severe rod-cone dystrophy. Pure tone audiometry revealed a moderate hearing loss in the index patient, whereas the affected siblings were reported with more profound and early onset hearing impairment. CONCLUSIONS We report a novel truncating mutation in DFNB31 associated with severe rod-cone dystrophy and varying degrees of hearing impairment in a consanguineous family of Portuguese origin. This is the second report of DFNB31 implication in Usher type 2.
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Affiliation(s)
- Isabelle Audo
- INSERM, U968, Paris, France,CNRS, UMR_7210, Paris, France,UPMC Univ Paris 06, UMR_S 968, Department of Genetics, Institut de la Vision, Paris, France,Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, INSERM-DHOS CIC 503,Paris, France,Department of Molecular Genetics, Institute of Ophthalmology, London, UK
| | - Kinga Bujakowska
- INSERM, U968, Paris, France,CNRS, UMR_7210, Paris, France,UPMC Univ Paris 06, UMR_S 968, Department of Genetics, Institut de la Vision, Paris, France
| | - Saddek Mohand-Saïd
- INSERM, U968, Paris, France,CNRS, UMR_7210, Paris, France,UPMC Univ Paris 06, UMR_S 968, Department of Genetics, Institut de la Vision, Paris, France,Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, INSERM-DHOS CIC 503,Paris, France
| | - Sophie Tronche
- Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, INSERM-DHOS CIC 503,Paris, France,Commission Expertise et Evaluation de la SFORL, Paris, France
| | - Marie-Elise Lancelot
- INSERM, U968, Paris, France,CNRS, UMR_7210, Paris, France,UPMC Univ Paris 06, UMR_S 968, Department of Genetics, Institut de la Vision, Paris, France
| | - Aline Antonio
- INSERM, U968, Paris, France,CNRS, UMR_7210, Paris, France,UPMC Univ Paris 06, UMR_S 968, Department of Genetics, Institut de la Vision, Paris, France,Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, INSERM-DHOS CIC 503,Paris, France
| | - Aurore Germain
- INSERM, U968, Paris, France,CNRS, UMR_7210, Paris, France,UPMC Univ Paris 06, UMR_S 968, Department of Genetics, Institut de la Vision, Paris, France
| | - Christine Lonjou
- Plate-forme Post-Génomique P3S, Hôpital Pitié Salpêtrière UPMC, Faculté de Médecine, Paris, France
| | - Wassila Carpentier
- Plate-forme Post-Génomique P3S, Hôpital Pitié Salpêtrière UPMC, Faculté de Médecine, Paris, France
| | - José-Alain Sahel
- INSERM, U968, Paris, France,CNRS, UMR_7210, Paris, France,UPMC Univ Paris 06, UMR_S 968, Department of Genetics, Institut de la Vision, Paris, France,Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, INSERM-DHOS CIC 503,Paris, France,Department of Molecular Genetics, Institute of Ophthalmology, London, UK,Fondation Ophtalmologique Adolphe de Rothschild, Paris, France
| | - Shomi Bhattacharya
- INSERM, U968, Paris, France,CNRS, UMR_7210, Paris, France,UPMC Univ Paris 06, UMR_S 968, Department of Genetics, Institut de la Vision, Paris, France,Department of Molecular Genetics, Institute of Ophthalmology, London, UK,Department of Cellular Therapy and Regenerative Medicine, Andalusian Molecular Biology and Regenerative Medicine Centre (CABIMER), Seville, Spain
| | - Christina Zeitz
- INSERM, U968, Paris, France,CNRS, UMR_7210, Paris, France,UPMC Univ Paris 06, UMR_S 968, Department of Genetics, Institut de la Vision, Paris, France
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Manor U, Disanza A, Grati M, Andrade L, Lin H, Di Fiore PP, Scita G, Kachar B. Regulation of stereocilia length by myosin XVa and whirlin depends on the actin-regulatory protein Eps8. Curr Biol 2011; 21:167-72. [PMID: 21236676 DOI: 10.1016/j.cub.2010.12.046] [Citation(s) in RCA: 144] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Revised: 12/01/2010] [Accepted: 12/22/2010] [Indexed: 12/24/2022]
Abstract
Myosin XVa (MyoXVa) and its cargo whirlin are implicated in deafness and vestibular dysfunction and have been shown to localize at stereocilia tips and to be essential for the elongation of these actin protrusions [1-4]. Given that whirlin has no known actin-regulatory activity, it remains unclear how these proteins work together to influence stereocilia length. Here we show that the actin-regulatory protein Eps8 [5] interacts with MyoXVa and that mice lacking Eps8 show short stereocilia compared to MyoXVa- and whirlin-deficient mice. We show that Eps8 fails to accumulate at the tips of stereocilia in the absence of MyoXVa, that overexpression of MyoXVa results in both elongation of stereocilia and increased accumulation of Eps8 at stereocilia tips, and that the exogenous expression of MyoXVa in MyoXVa-deficient hair cells rescues Eps8 tip localization. We find that Eps8 also interacts with whirlin and that the expression of both Eps8 and MyoXVa at stereocilia tips is reduced in whirlin-deficient mice. We conclude that MyoXVa, whirlin, and Eps8 are integral components of the stereocilia tip complex, where Eps8 is a central actin-regulatory element for elongation of the stereocilia actin core.
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Affiliation(s)
- Uri Manor
- Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
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Abstract
Mammals have an astonishing ability to sense and discriminate sounds of different frequencies and intensities. Fundamental for this process are mechanosensory hair cells in the inner ear that convert sound-induced vibrations into electrical signals. The study of genes that are linked to deafness has provided insights into the cell biological mechanisms that control hair cell development and their function as mechanosensors.
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Affiliation(s)
- Martin Schwander
- Department of Cell Biology, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
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38
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Mburu P, Romero MR, Hilton H, Parker A, Townsend S, Kikkawa Y, Brown SDM. Gelsolin plays a role in the actin polymerization complex of hair cell stereocilia. PLoS One 2010; 5:e11627. [PMID: 20661277 PMCID: PMC2905391 DOI: 10.1371/journal.pone.0011627] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2009] [Accepted: 06/15/2010] [Indexed: 01/05/2023] Open
Abstract
A complex of proteins scaffolded by the PDZ protein, whirlin, reside at the stereocilia tip and are critical for stereocilia development and elongation. We have shown that in outer hair cells (OHCs) whirlin is part of a larger complex involving the MAGUK protein, p55, and protein 4.1R. Whirlin interacts with p55 which is expressed exclusively in outer hair cells (OHC) in both the long stereocilia that make up the stereocilia bundle proper as well as surrounding shorter microvilli that will eventually regress. In erythrocytes, p55 forms a tripartite complex with protein 4.1R and glycophorin C promoting the assembly of actin filaments and the interaction of whirlin with p55 indicates that it plays a similar role in OHC stereocilia. However, the components directly involved in actin filament regulation in stereocilia are unknown. We have investigated additional components of the whirlin interactome by identifying interacting partners to p55. We show that the actin capping and severing protein, gelsolin, is a part of the whirlin complex. Gelsolin is detected in OHC where it localizes to the tips of the shorter rows but not to the longest row of stereocilia and the pattern of localisation at the apical hair cell surface is strikingly similar to p55. Like p55, gelsolin is ablated in the whirler and shaker2 mutants. Moreover, in a gelsolin mutant, stereocilia in the apex of the cochlea become long and straggly indicating defects in the regulation of stereocilia elongation. The identification of gelsolin provides for the first time a link between the whirlin scaffolding protein complex involved in stereocilia elongation and a known actin regulatory molecule.
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Affiliation(s)
- Philomena Mburu
- Medical Research Council Mammalian Genetics Unit, Harwell Science and Innovation Campus, Oxfordshire, United Kingdom
| | - María Rosario Romero
- Medical Research Council Mammalian Genetics Unit, Harwell Science and Innovation Campus, Oxfordshire, United Kingdom
| | - Helen Hilton
- Medical Research Council Mammalian Genetics Unit, Harwell Science and Innovation Campus, Oxfordshire, United Kingdom
| | - Andrew Parker
- Medical Research Council Mammalian Genetics Unit, Harwell Science and Innovation Campus, Oxfordshire, United Kingdom
| | - Stuart Townsend
- Medical Research Council Mammalian Genetics Unit, Harwell Science and Innovation Campus, Oxfordshire, United Kingdom
| | - Yoshiaki Kikkawa
- Department of Bioproduction, Tokyo University of Agriculture, Abashiri, Japan
| | - Steve D. M. Brown
- Medical Research Council Mammalian Genetics Unit, Harwell Science and Innovation Campus, Oxfordshire, United Kingdom
- * E-mail:
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Yang J, Liu X, Zhao Y, Adamian M, Pawlyk B, Sun X, McMillan DR, Liberman MC, Li T. Ablation of whirlin long isoform disrupts the USH2 protein complex and causes vision and hearing loss. PLoS Genet 2010; 6:e1000955. [PMID: 20502675 PMCID: PMC2873905 DOI: 10.1371/journal.pgen.1000955] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Accepted: 04/19/2010] [Indexed: 12/25/2022] Open
Abstract
Mutations in whirlin cause either Usher syndrome type II (USH2), a deafness-blindness disorder, or nonsyndromic deafness. The molecular basis for the variable disease expression is unknown. We show here that only the whirlin long isoform, distinct from a short isoform by virtue of having two N-terminal PDZ domains, is expressed in the retina. Both long and short isoforms are expressed in the inner ear. The N-terminal PDZ domains of the long whirlin isoform mediates the formation of a multi-protein complex that includes usherin and VLGR1, both of which are also implicated in USH2. We localized this USH2 protein complex to the periciliary membrane complex (PMC) in mouse photoreceptors that appears analogous to the frog periciliary ridge complex. The latter is proposed to play a role in photoreceptor protein trafficking through the connecting cilium. Mice carrying a targeted disruption near the N-terminus of whirlin manifest retinal and inner ear defects, reproducing the clinical features of human USH2 disease. This is in contrast to mice with mutations affecting the C-terminal portion of whirlin in which the phenotype is restricted to the inner ear. In mice lacking any one of the USH2 proteins, the normal localization of all USH2 proteins is disrupted, and there is evidence of protein destabilization. Taken together, our findings provide new insights into the pathogenic mechanism of Usher syndrome. First, the three USH2 proteins exist as an obligatory functional complex in vivo, and loss of one USH2 protein is functionally close to loss of all three. Second, defects in the three USH2 proteins share a common pathogenic process, i.e., disruption of the PMC. Third, whirlin mutations that ablate the N-terminal PDZ domains lead to Usher syndrome, but non-syndromic hearing loss will result if they are spared.
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Affiliation(s)
- Jun Yang
- The Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, United States of America
| | - Xiaoqing Liu
- The Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, United States of America
| | - Yun Zhao
- The Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, United States of America
| | - Michael Adamian
- The Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, United States of America
| | - Basil Pawlyk
- The Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, United States of America
| | - Xun Sun
- The Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, United States of America
| | - D. Randy McMillan
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - M. Charles Liberman
- Department of Otology and Laryngology, Harvard Medical School and Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, United States of America
| | - Tiansen Li
- The Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, United States of America
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40
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Myosin motor function: the ins and outs of actin-based membrane protrusions. Cell Mol Life Sci 2010; 67:1239-54. [PMID: 20107861 DOI: 10.1007/s00018-009-0254-5] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2009] [Revised: 12/15/2009] [Accepted: 12/28/2009] [Indexed: 10/19/2022]
Abstract
Cells build plasma membrane protrusions supported by parallel bundles of F-actin to enable a wide variety of biological functions, ranging from motility to host defense. Filopodia, microvilli and stereocilia are three such protrusions that have been the focus of intense biological and biophysical investigation in recent years. While it is evident that actin dynamics play a significant role in the formation of these organelles, members of the myosin superfamily have also been implicated as key players in the maintenance of protrusion architecture and function. Based on a simple analysis of the physical forces that control protrusion formation and morphology, as well as our review of available data, we propose that myosins play two general roles within these structures: (1) as cargo transporters to move critical regulatory components toward distal tips and (2) as mediators of membrane-cytoskeleton adhesion.
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41
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Okumura K, Mochizuki E, Yokohama M, Yamakawa H, Shitara H, Mburu P, Yonekawa H, Brown SD, Kikkawa Y. Protein 4.1 expression in the developing hair cells of the mouse inner ear. Brain Res 2010; 1307:53-62. [DOI: 10.1016/j.brainres.2009.10.039] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2009] [Revised: 10/14/2009] [Accepted: 10/14/2009] [Indexed: 01/11/2023]
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42
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Erythrocyte scaffolding protein p55/MPP1 functions as an essential regulator of neutrophil polarity. Proc Natl Acad Sci U S A 2009; 106:19842-7. [PMID: 19897731 DOI: 10.1073/pnas.0906761106] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
As mediators of innate immunity, neutrophils respond to chemoattractants by adopting a highly polarized morphology. Efficient chemotaxis requires the formation of one prominent pseudopod at the cell front characterized by actin polymerization, while local inhibition suppresses the formation of rear and lateral protrusions. This asymmetric control of signaling pathways is required for directional migration along a chemotactic gradient. Here, we identify the MAGUK protein p55/MPP1 as a mediator of the frontness signal required for neutrophil polarization. We developed a p55 knockout (p55(-/-)) mouse model, and demonstrate that p55(-/-) neutrophils form multiple transient pseudopods upon chemotactic stimulation, and do not migrate efficiently in vitro. Upon agonist stimulation, p55 is rapidly recruited to the leading edge of neutrophils in mice and humans. Total F-actin polymerization, along with Rac1 and RhoA activation, appear to be normal in p55(-/-) neutrophils. Importantly, phosphorylation of Akt is significantly decreased in p55(-/-) neutrophils upon chemotactic stimulation. The activity of immunoprecipitated phosphatidylinositol 3-kinase gamma (PI3Kgamma), responsible for chemoattractant-induced synthesis of PIP(3) and Akt phosphorylation, is unperturbed in p55(-/-) neutrophils. Although the total amount of PIP(3) is normal in p55(-/-) neutrophils, PIP(3) is diffusely localized and forms punctate aggregates in activated p55(-/-) neutrophils, as compared to its accumulation at the leading edge membrane in the wild type neutrophils. Together, these results show that p55 is required for neutrophil polarization by regulating Akt phosphorylation through a mechanism that is independent of PI3Kgamma activity.
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43
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Tian G, Zhou Y, Hajkova D, Miyagi M, Dinculescu A, Hauswirth WW, Palczewski K, Geng R, Alagramam KN, Isosomppi J, Sankila EM, Flannery JG, Imanishi Y. Clarin-1, encoded by the Usher Syndrome III causative gene, forms a membranous microdomain: possible role of clarin-1 in organizing the actin cytoskeleton. J Biol Chem 2009; 284:18980-93. [PMID: 19423712 DOI: 10.1074/jbc.m109.003160] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Clarin-1 is the protein product encoded by the gene mutated in Usher syndrome III. Although the molecular function of clarin-1 is unknown, its primary structure predicts four transmembrane domains similar to a large family of membrane proteins that include tetraspanins. Here we investigated the role of clarin-1 by using heterologous expression and in vivo model systems. When expressed in HEK293 cells, clarin-1 localized to the plasma membrane and concentrated in low density compartments distinct from lipid rafts. Clarin-1 reorganized actin filament structures and induced lamellipodia. This actin-reorganizing function was absent in the modified protein encoded by the most prevalent North American Usher syndrome III mutation, the N48K form of clarin-1 deficient in N-linked glycosylation. Proteomics analyses revealed a number of clarin-1-interacting proteins involved in cell-cell adhesion, focal adhesions, cell migration, tight junctions, and regulation of the actin cytoskeleton. Consistent with the hypothesized role of clarin-1 in actin organization, F-actin-enriched stereocilia of auditory hair cells evidenced structural disorganization in Clrn1(-/-) mice. These observations suggest a possible role for clarin-1 in the regulation and homeostasis of actin filaments, and link clarin-1 to the interactive network of Usher syndrome gene products.
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Affiliation(s)
- Guilian Tian
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106-4965, USA
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44
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Seo PS, Quinn BJ, Khan AA, Zeng L, Takoudis CG, Hanada T, Bolis A, Bolino A, Chishti AH. Identification of erythrocyte p55/MPP1 as a binding partner of NF2 tumor suppressor protein/Merlin. Exp Biol Med (Maywood) 2009; 234:255-62. [PMID: 19144871 DOI: 10.3181/0809-rm-275] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Neurofibromatosis type 2 is an inherited disorder characterized by the development of benign and malignant tumors on the auditory nerves and central nervous system with symptoms including hearing loss, poor balance, skin lesions, and cataracts. Here, we report a novel protein-protein interaction between NF2 protein (merlin or schwannomin) and erythrocyte p55, also designated as MPP1. The p55 is a conserved scaffolding protein with postulated functions in cell shape, hair cell development, and neural patterning of the retina. The FERM domain of NF2 protein binds directly to p55, and surface plasmon resonance analysis indicates a specific interaction with a kD value of 3.7 nM. We developed a specific monoclonal antibody against human erythrocyte p55, and found that both p55 and NF2 proteins are colocalized in the non-myelin-forming Schwann cells. This finding suggests that the p55-NF2 protein interaction may play a functional role in the regulation of apico-basal polarity and tumor suppression pathways in non-erythroid cells.
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Affiliation(s)
- Pil-Soo Seo
- UIC Cancer Center, COMRB, Room 5099, 909 South Wolcott Avenue, Chicago, IL 60612-3725, USA
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45
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Dynamic length regulation of sensory stereocilia. Semin Cell Dev Biol 2008; 19:502-10. [PMID: 18692583 DOI: 10.1016/j.semcdb.2008.07.006] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Accepted: 07/15/2008] [Indexed: 01/02/2023]
Abstract
Stereocilia, the mechanosensory organelles of hair cells, are a distinctive class of actin-based cellular protrusions with an unparalleled ability to regulate their lengths over time. Studies on actin turnover in stereocilia, as well as the identification of several deafness-related proteins essential for proper stereocilia structure and function, provide new insights into the mechanisms and molecules involved in stereocilia length regulation and long-term maintenance. Comparisons of ongoing investigations on stereocilia with studies on other actin protrusions offer new opportunities to further understand common principles for length regulation, the diversity of its mechanisms, and how the specific needs of each cell are met.
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46
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Gosens I, den Hollander AI, Cremers FPM, Roepman R. Composition and function of the Crumbs protein complex in the mammalian retina. Exp Eye Res 2008; 86:713-26. [PMID: 18407265 DOI: 10.1016/j.exer.2008.02.005] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2007] [Revised: 01/09/2008] [Accepted: 02/18/2008] [Indexed: 11/27/2022]
Abstract
The Crumbs proteins (CRBs) are transmembrane proteins, homologous to Drosophila Crumbs, with a key role in defining the apical membrane domain in photoreceptors as well as in embryonic epithelia. Crumbs proteins are conserved between species and their intracellular domains are involved in organizing a conserved macromolecular protein scaffold with important roles in cell polarity as well as morphogenesis and maintenance of the retina. Mutations in the gene encoding human CRB1, the first one identified out of the three human orthologs, have been associated with a number of retinal dystrophies including Leber amaurosis and retinitis pigmentosa type 12. Although no other mammalian Crumbs complex members as of yet have been associated with retinal degeneration, disruption of different zebrafish and fruitfly orthologs can lead to various retinal defects. The core Crumbs complex localizes apical to the outer limiting membrane, where photoreceptors and Müller glia contact each other. Correct functioning of Crumbs ensures adhesion between these cells by an unknown mechanism. This review summarizes the current view on the composition and function of the Crumbs prsotein complex in the mammalian retina. Recently, a number of new members of the Crumbs protein complex have been identified. These include most members of the membrane palmitoylated protein family (MPP), involved in assembly of macromolecular protein complexes. Some components of the complex are found to exert a function in the photoreceptor synapses and/or at the region of the connecting cilium. Studies using polarized cell cultures or model organisms, like Drosophila and zebrafish, suggest important links of the Crumbs protein complex to several biological processes in the mammalian eye, including retinal patterning, ciliogenesis and vesicular transport.
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Affiliation(s)
- Ilse Gosens
- Department of Human Genetics and Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Geert Grooteplein Zuid 10, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
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47
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Quiet as a mouse: dissecting the molecular and genetic basis of hearing. Nat Rev Genet 2008; 9:277-90. [PMID: 18283275 DOI: 10.1038/nrg2309] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Mouse genetics has made crucial contributions to the understanding of the molecular mechanisms of hearing. With the help of a plethora of mouse mutants, many of the key genes that are involved in the development and functioning of the auditory system have been elucidated. Mouse mutants continue to shed light on the genetic and physiological bases of human hearing impairment, including both early- and late-onset deafness. A combination of genetic and physiological studies of mouse mutant lines, allied to investigations into the protein networks of the stereocilia bundle in the inner ear, are identifying key complexes that are crucial for auditory function and for providing profound insights into the underlying causes of hearing loss.
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48
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Mogensen MM, Rzadzinska A, Steel KP. The deaf mouse mutant whirler suggests a role for whirlin in actin filament dynamics and stereocilia development. ACTA ACUST UNITED AC 2007; 64:496-508. [PMID: 17326148 PMCID: PMC2682331 DOI: 10.1002/cm.20199] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Stereocilia, finger-like projections forming the hair bundle on the apical surface of sensory hair cells in the cochlea, are responsible for mechanosensation and ultimately the perception of sound. The actin cytoskeleton of the stereocilia contains hundreds of tightly cross-linked parallel actin filaments in a paracrystalline array and it is vital for their function. Although several genes have been identified and associated with stereocilia development, the molecular mechanisms responsible for stereocilia growth, maintenance and organisation of the hair bundle have not been fully resolved. Here we provide further characterisation of the stereocilia of the whirler mouse mutant. We found that a lack of whirlin protein in whirler mutants results in short stereocilia with larger diameters without a corresponding increase in the number of actin filaments in inner hair cells. However, a decrease in the actin filament packing density was evident in the whirler mutant. The electron-density at the tip of each stereocilium was markedly patchy and irregular in the whirler mutants compared with a uniform band in controls. The outer hair cell stereocilia of the whirler homozygote also showed an increase in diameter and variable heights within bundles. The number of outer hair cell stereocilia was significantly reduced and the centre-to-centre spacing between the stereocilia was greater than in the wildtype. Our findings suggest that whirlin plays an important role in actin filament packing and dynamics during postnatal stereocilium elongation.
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MESH Headings
- Actin Cytoskeleton/genetics
- Actin Cytoskeleton/metabolism
- Animals
- Cilia/metabolism
- Cilia/ultrastructure
- Cochlea/metabolism
- Cochlea/ultrastructure
- Deafness/genetics
- Deafness/metabolism
- Ear, Inner/metabolism
- Ear, Inner/ultrastructure
- Hair Cells, Auditory, Inner/metabolism
- Hair Cells, Auditory, Inner/ultrastructure
- Hair Cells, Auditory, Outer/metabolism
- Hair Cells, Auditory, Outer/ultrastructure
- Homozygote
- Intercellular Signaling Peptides and Proteins
- Membrane Proteins/genetics
- Membrane Proteins/physiology
- Mice
- Mice, Mutant Strains
- Microscopy, Electron, Scanning
- Mutation
- Proteins/genetics
- Proteins/metabolism
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Affiliation(s)
- Mette M Mogensen
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom.
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49
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Gosens I, Sessa A, den Hollander AI, Letteboer SJF, Belloni V, Arends ML, Le Bivic A, Cremers FPM, Broccoli V, Roepman R. FERM protein EPB41L5 is a novel member of the mammalian CRB-MPP5 polarity complex. Exp Cell Res 2007; 313:3959-70. [PMID: 17920587 DOI: 10.1016/j.yexcr.2007.08.025] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Revised: 08/19/2007] [Accepted: 08/23/2007] [Indexed: 01/02/2023]
Abstract
Cell polarity is induced and maintained by separation of the apical and basolateral domains through specialized cell-cell junctions. The Crumbs protein and its binding partners are involved in formation and stabilization of adherens junctions. In this study, we describe a novel component of the mammalian Crumbs complex, the FERM domain protein EPB41L5, which associates with the intracellular domains of all three Crumbs homologs through its FERM domain. Surprisingly, the same FERM domain is involved in binding to the HOOK domain of MPP5/PALS1, a previously identified interactor of Crumbs. Co-expression and co-localization studies suggested that in several epithelial derived tissues Epb4.1l5 interacts with at least one Crumbs homolog, and with Mpp5. Although at early embryonic stages Epb4.1l5 is found at the basolateral membrane compartment, in adult tissues it co-localizes at the apical domain with Crumbs proteins and Mpp5. Overexpression of Epb4.1l5 in polarized MDCK cells affects tightness of cell junctions and results in disorganization of the tight junction markers ZO-1 and PATJ. Our results emphasize the importance of a conserved Crumbs-MPP5-EPB41L5 polarity complex in mammals.
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Affiliation(s)
- Ilse Gosens
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Geert Grooteplein Zuid 10, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
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50
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Longo-Guess CM, Gagnon LH, Fritzsch B, Johnson KR. Targeted knockout and lacZ reporter expression of the mouse Tmhs deafness gene and characterization of the hscy-2J mutation. Mamm Genome 2007; 18:646-56. [PMID: 17876667 PMCID: PMC2613174 DOI: 10.1007/s00335-007-9049-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2007] [Accepted: 06/14/2007] [Indexed: 01/03/2023]
Abstract
The Tmhs gene codes for a tetraspan transmembrane protein that is expressed in hair cell stereocilia. We previously showed that a spontaneous missense mutation of Tmhs underlies deafness and vestibular dysfunction in the hurry-scurry (hscy) mouse. Subsequently, mutations in the human TMHS gene were shown to be responsible for DFNB67, an autosomal recessive nonsyndromic deafness locus. Here we describe a genetically engineered null mutation of the mouse Tmhs gene (Tmhs ( tm1Kjn )) and show that its phenotype is identical to that of the hscy missense mutation, confirming the deleterious nature of the hscy cysteine-to-phenylalanine substitution. In the targeted null allele, the Tmhs promoter drives expression of a lacZ reporter gene. Visualization of beta-galactosidase activity in Tmhs ( tm1Kjn ) heterozygous mice indicates that Tmhs is highly expressed in the cochlear and vestibular hair cells of the inner ear. Expression is first detectable at E15.5, peaks around P0, decreases slightly at P6, and is absent by P15, a duration that supports the involvement of Tmhs in stereocilia development. Tmhs reporter gene expression also was detected in several cranial and cervical sensory ganglia, but not in the vestibular or spiral ganglia. We also describe a new nontargeted mutation of the Tmhs gene, hscy-2J, that causes abnormal splicing from a cryptic splice site within exon 2 and is predicted to produce a functionally null protein lacking 51 amino acids of the wild-type sequence.
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