title: The roles of USH1 proteins and PDZ domain-containing USH proteins in USH2 complex integrity in cochlear hair cells.
abstract: Usher syndrome (USH) is the most common cause of inherited deaf-blindness, manifested as USH1, USH2 and USH3 clinical types. The protein products of USH2 causative and modifier genes, USH2A, ADGRV1, WHRN and PDZD7, interact to assemble a multiprotein complex at the ankle link region of the mechanosensitive stereociliary bundle in hair cells. Defects in this complex cause stereociliary bundle disorganization and hearing loss. The four USH2 proteins also interact in vitro with USH1 proteins including myosin VIIa, USH1G (SANS), CIB2 and harmonin. However, it is unclear whether the interactions between USH1 and USH2 proteins occur in vivo and whether USH1 proteins play a role in USH2 complex assembly in hair cells. In this study, we identified a novel interaction between myosin VIIa and PDZD7 by FLAG pull-down assay. We further investigated the role of the above-mentioned four USH1 proteins in the cochlear USH2 complex assembly using USH1 mutant mice. We showed that only myosin VIIa is indispensable for USH2 complex assembly at ankle links, indicating the potential transport and/or anchoring role of myosin VIIa for USH2 proteins in hair cells. However, myosin VIIa is not required for USH2 complex assembly in photoreceptors. We further showed that, while PDZ protein harmonin is not involved, its paralogous USH2 proteins, PDZD7 and whirlin, function synergistically in USH2 complex assembly in cochlear hair cells. In summary, our studies provide novel insight into the functional relationship between USH1 and USH2 proteins in the cochlea and the retina as well as the disease mechanisms underlying USH1 and USH2.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT 84132, USA.
authors.forename: Junhuang
authors.initials: J
authors.lastname: Zou
authors.affiliation: Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT 84132, USA.
authors.forename: Qian
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Department of Communication Sciences and Disorders, University of Utah, 390 South 1530 East, Salt Lake City, UT 84112, USA.
authors.forename: Ali
authors.initials: A
authors.lastname: Almishaal
authors.affiliation: Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT 84132, USA.|Department of Neurobiology and Anatomy, University of Utah, 20 North 1900 East, Salt Lake City, UT 84132, USA.
authors.forename: Pranav Dinesh
authors.initials: PD
authors.lastname: Mathur
authors.affiliation: Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT 84132, USA.
authors.forename: Tihua
authors.initials: T
authors.lastname: Zheng
authors.affiliation: Department of Otolaryngology, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: Cong
authors.initials: C
authors.lastname: Tian
authors.affiliation: Department of Otolaryngology, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: Qing Y
authors.initials: QY
authors.lastname: Zheng
authors.affiliation: Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT 84132, USA.|Department of Neurobiology and Anatomy, University of Utah, 20 North 1900 East, Salt Lake City, UT 84132, USA.|Division of Otolaryngology, Department of Surgery, University of Utah, 50 North Medical Drive, Salt Lake City, UT 84132, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics*; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D016326:Extracellular Matrix Proteins / Q000737:chemistry / Q000235:genetics*; D006198:Hair Cells, Auditory / Q000473:pathology; D006801:Humans; D051379:Mice; D046912:Multiprotein Complexes / Q000737:chemistry / Q000235:genetics; D000081412:Myosin VIIa; D009218:Myosins / Q000737:chemistry / Q000235:genetics*; D054731:PDZ Domains / Q000235:genetics; D012160:Retina / Q000378:metabolism / Q000473:pathology; D059547:Stereocilia / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D052245:Usher Syndromes / Q000235:genetics* / Q000473:pathology
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D016326:Extracellular Matrix Proteins; C000631455:MYO7A protein, human; D046912:Multiprotein Complexes; C000631456:Myo7a protein, mouse; D000081412:Myosin VIIa; C112735:USH2A protein, human; C492262:Ush1c protein, mouse; C491810:Ush2a protein, mouse; D009218:Myosins