1. The Mechanosensory Structure of the Hair Cell Requires Clarin-1, a Protein Encoded by Usher Syndrome III Causative Gene.
- Author
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Ruishuang Geng, Melki, Sami, Chen, Daniel H.-C., Tian, Guilian, Furness, David N., Tomoko Oshima-Takago, Neef, Jakob, Moser, Tobias, Askew, Charles, Horwitz, Geoff, Holt, Jeffrey R., Yoshikazu Imanishi, and Alagramam, Kumar N.
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HAIR cells ,USHER'S syndrome ,GENETIC mutation ,TETRASPANIN ,IMMUNOHISTOCHEMISTRY ,SYNAPSES ,LABORATORY mice - Abstract
Mutation in the clarin-1 gene (Clrn1) results in loss of hearing and vision in humans(Ushersyndrome III), but the role of clarin-1 in the sensory hair cells is unknown. Clarin-1 is predicted to be a four transmembrane domain protein similar to members of the tetraspanin family. Mice carrying null mutation in the clarin-1 gene (Clrn1
-/- )show loss of hair cell function and a possible defect in ribbon synapse. We investigated the role of clarin-1 using various in vitro and in vivo approaches. We show by immunohistochemistry and patch-clamp recordings of Ca2+ currents and membrane capacitance from inner hair cells that clarin-1 is not essential for formation or function of ribbon synapse. However, reduced cochlear microphonic potentials, FM1-43 [N-(3-triethylammoniumpropyl)-4-(4-(dibutylamino)styryl) pyridinium dibromide] loading, and transduction currents pointed to diminished cochlear hair bundle function in Clrn1-/- mice. Electron microscopy of cochlear hair cells revealed loss of some tall stereocilia and gaps in the v-shaped bundle, although tip links and staircase arrangement of stereocilia were not primarily affected by Clrn1-/- mutation. Human clarin-1 protein expressed in transfected mouse cochlear hair cells localized to the bundle; however, the pathogenic variant p.N48K failed to localize to the bundle. The mouse model generated to study the in vivo consequence of p.N48K in clarin-1 (Clrn1N48K ) supports our in vitro and Clrn1-/- mouse data and the conclusion that CLRN1 is an essential hair bundle protein. Furthermore, the ear phenotype in the Clrn1N48K mouse suggests that it is a valuable model for ear disease in CLRN1N48K , the most prevalent Usher syndrome III mutation in North America. [ABSTRACT FROM AUTHOR]- Published
- 2012
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