The mechanosensory structure of the hair cell requires clarin-1, a protein encoded by Usher syndrome III causative gene.
Mutation in the clarin-1 gene (Clrn1) results in loss of hearing and vision in humans (Usher syndrome 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 Ca(2+) 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 (Clrn1(N48K)) 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 Clrn1(N48K) mouse suggests that it is a valuable model for ear disease in CLRN1(N48K), the most prevalent Usher syndrome III mutation in North America.
Otolaryngology Head and Neck Surgery, University Hospitals Case Medical Center, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Ruishuang
R
Geng
Sami
S
Melki
Daniel H-C
DH
Chen
Guilian
G
Tian
David N
DN
Furness
Tomoko
T
Oshima-Takago
Jakob
J
Neef
Tobias
T
Moser
Charles
C
Askew
Geoff
G
Horwitz
Jeffrey R
JR
Holt
Yoshikazu
Y
Imanishi
Kumar N
KN
Alagramam
D000161:Acoustic Stimulation; D000367:Age Factors; D000429:Alcohol Oxidoreductases / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001216:Asparagine / Q000235:genetics; D001464:Barium / Q000494:pharmacology; D055592:Biophysical Phenomena / Q000235:genetics; D015820:Cadherins / Q000235:genetics; D002461:Cell Line, Transformed; D003051:Cochlea / Q000166:cytology* / Q000254:growth & development*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004195:Disease Models, Animal; D016057:Evoked Potentials, Auditory, Brain Stem / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006198:Hair Cells, Auditory / Q000502:physiology* / Q000648:ultrastructure; D006801:Humans; D008239:Lysine / Q000235:genetics; D008465:Mechanoreceptors / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D008565:Membrane Proteins / Q000172:deficiency / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008855:Microscopy, Electron, Scanning / Q000379:methods; D009154:Mutation / Q000235:genetics; D009412:Nerve Fibers / Q000473:pathology / Q000648:ultrastructure; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D010812:Physical Stimulation / Q000379:methods; D011571:Psychoacoustics; D011726:Pyridinium Compounds / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D018091:Receptors, AMPA / Q000378:metabolism; D013569:Synapses / Q000473:pathology / Q000648:ultrastructure; D014162:Transfection; D052245:Usher Syndromes / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology
C437067:CLRN1 protein, human; D015820:Cadherins; C489083:Cdh2 protein, mouse; C512668:Clrn1 protein, mouse; D004268:DNA-Binding Proteins; C073804:FM1 43; D008565:Membrane Proteins; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D018091:Receptors, AMPA; D049452:Green Fluorescent Proteins; D001464:Barium; D001216:Asparagine; D000429:Alcohol Oxidoreductases; C096794:C-terminal binding protein; D008239:Lysine; C104722:glutamate receptor ionotropic, AMPA 2