title: A short splice form of Xin-actin binding repeat containing 2 (XIRP2) lacking the Xin repeats is required for maintenance of stereocilia morphology and hearing function.
abstract: Approximately one-third of known deafness genes encode proteins located in the hair bundle, the sensory hair cell's mechanoreceptive organelle. In previous studies, we used mass spectrometry to characterize the hair bundle's proteome, resulting in the discovery of novel bundle proteins. One such protein is Xin-actin binding repeat containing 2 (XIRP2), an actin-cross-linking protein previously reported to be specifically expressed in striated muscle. Because mutations in other actin-cross-linkers result in hearing loss, we investigated the role of XIRP2 in hearing function. In the inner ear, XIRP2 is specifically expressed in hair cells, colocalizing with actin-rich structures in bundles, the underlying cuticular plate, and the circumferential actin belt. Analysis using peptide mass spectrometry revealed that the bundle harbors a previously uncharacterized XIRP2 splice variant, suggesting XIRP2's role in the hair cell differs significantly from that reported in myocytes. To determine the role of XIRP2 in hearing, we applied clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9-mediated genome-editing technology to induce targeted mutations into the mouse Xirp2 gene, resulting in the elimination of XIRP2 protein expression in the inner ear. Functional analysis of hearing in the resulting Xirp2-null mice revealed high-frequency hearing loss, and ultrastructural scanning electron microscopy analyses of hair cells demonstrated stereocilia degeneration in these mice. We thus conclude that XIRP2 is required for long-term maintenance of hair cell stereocilia, and that its dysfunction causes hearing loss in the mouse.
authors: Departments of Neuroscience.
authors: Shimon P
authors: SP
authors: Francis
authors: Oregon Hearing Research Center & Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239, and.
authors: Jocelyn F
authors: JF
authors: Krey
authors: National Institute for Deafness and Communications Disorders, National Institute of Health, Bethesda, Maryland 20892.
authors: Evan S
authors: ES
authors: Krystofiak
authors: National Institute for Deafness and Communications Disorders, National Institute of Health, Bethesda, Maryland 20892.
authors: Runjia
authors: R
authors: Cui
authors: Departments of Neuroscience.
authors: Sonali
authors: S
authors: Nanda
authors: Gene Targeting and Transgenic Facility, University of Virginia, Charlottesville, Virginia 22908.
authors: Wenhao
authors: W
authors: Xu
authors: National Institute for Deafness and Communications Disorders, National Institute of Health, Bethesda, Maryland 20892.
authors: Bechara
authors: B
authors: Kachar
authors: Oregon Hearing Research Center & Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239, and.
authors: Peter G
authors: http://orcid.org/0000-0002-9787-5860
authors: PG
authors: Barr-Gillespie
authors: Departments of Neuroscience, Brain, Immunology, and Glia Center, and js2ee@virginia.edu.
authors: Jung-Bum
authors: JB
authors: Shin
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002642:Chick Embryo; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006198:Hair Cells, Auditory / Q000378:metabolism* / Q000502:physiology; D006309:Hearing; D034381:Hearing Loss / Q000235:genetics; D060588:LIM Domain Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D051381:Rats; D059547:Stereocilia / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D060588:LIM Domain Proteins; D009687:Nuclear Proteins; D020033:Protein Isoforms; C500305:XIRP2 protein, mouse
keywords: CRISPR; XIRP2; hair bundle; hair cell; hearing; stereocilia
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