Localization and expression of clarin-1, the Clrn1 gene product, in auditory hair cells and photoreceptors.
The Usher syndrome 3A (CLRN1) gene encodes clarin-1, which is a member of the tetraspanin family of transmembrane proteins. Although identified more than 6 years ago, little is known about its localization or function in the eye and ear. We developed a polyclonal antibody that react with all clarin-1 isoforms and used it to characterize protein expression in cochlea and retina. In the cochlea, we observe clarin-1expression in the stereocilia of P0 mice, and in synaptic terminals present at the base of the auditory hair cells from E18 to P6. In the retina, clarin-1 localizes to the connecting cilia, inner segment of photoreceptors and to the ribbon synapses. RT-PCR from P0 cochlea and P28 retina show mRNAs encoding only isoforms 2 and 3. Western blots show that only isoform 2 is present in protein extracts from these same tissues. We examined clarin-1 expression in the immortomouse-derived hair cell line UB/OC-1. Only isoform 2 is expressed in UB/OC-1 at both mRNA and protein levels, suggesting this isoform is biologically relevant to hair cell function. The protein co-localizes with microtubules and post-transgolgi vesicles. The subcellular localization of clarin-1 in hair cells and photoreceptors suggests it functions at both the basal and apical poles of neurosensoriepithelia.
Zallocchi
Marisa
M
Boys Town National Research Hospital, Omaha, NE 68131, USA. zallocchim@boystown.org
Meehan
Daniel T
DT
Delimont
Duane
D
Askew
Charles
C
Garige
Suneetha
S
Gratton
Michael Anne
MA
Rothermund-Franklin
Christie A
CA
Cosgrove
Dominic
D
D000818:Animals; D000831:Animals, Newborn; D001483:Base Sequence; D002460:Cell Line; D003051:Cochlea / Q000196:embryology / Q000254:growth & development / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D005260:Female; D015870:Gene Expression; D005865:Gestational Age; D006198:Hair Cells, Auditory / Q000378:metabolism*; D008565:Membrane Proteins / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism*; D011247:Pregnancy; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics
C512668:Clrn1 protein, mouse; D017931:DNA Primers; D008565:Membrane Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D034741:RNA, Small Interfering