Shindo Susumu, Ikezono Tetsuo, Ishizaki Masamichi, Sekiguchi Satomi, Mizuta Kunihiro, Li Lishu, Takumida Masaya, Pawankar Ruby, Yagi Toshiaki
Department of Otorhinolaryngology, Nippon Medical School, Tokyo, Japan.
Neurosci Lett. 2008 Oct 24;444(2):148-52. doi: 10.1016/j.neulet.2008.07.091. Epub 2008 Aug 6.
Cochlin (encoded by COCH) constitutes 70% of non-collagenous protein in the inner ear, and the expression of cochlin is highly specific to the inner ear. Eleven missense mutation and one in-frame deletion have been reported in the COCH gene, causing hereditary progressive sensorineural hearing loss and vestibular dysfunction, DFNA9. These data imply that cochlin should bear an essential and crucial role in the inner ear function. However, the role of cochlin has not been fully clarified. We have investigated the spatiotemporal expression of cochlin in the inner ear of rats during postnatal development to better understand the functional role of cochlin. By immunohistochemistry, cochlin expression was faint in the cochlea and vestibule on the 6th day after birth (DAB6). At DAB70, strong expression of cochlin was detected in the spiral limbus and spiral ligament within the cochlea, and in the stromata of the maculae of otolithic organs and crista ampullaris within the vestibule. Immunoreactivity for cochlin increased during the postnatal development. Western blot analysis also showed an increase in the expression of cochlin isoforms. Furthermore, the dominant isoform of cochlin expressed changed from p63s to p40s between DAB24 and DAB70. These results suggest that the expression of cochlin may be related to the maturation of inner ear function, and the change in isoforms of cochlin expressed will provide important insight into the understanding of both cochlin function and formation of cochlin isoforms. This is the first to report about the spatiotemporal expression of cochlin in the developing rat inner ear.
耳蜗素（由COCH基因编码）占内耳非胶原蛋白的70%，且耳蜗素的表达在内耳中具有高度特异性。COCH基因已报道有11种错义突变和1种框内缺失，可导致遗传性进行性感音神经性听力损失和前庭功能障碍，即DFNA9。这些数据表明耳蜗素在内耳功能中应起着至关重要的作用。然而，耳蜗素的作用尚未完全阐明。我们研究了大鼠内耳在出生后发育过程中耳蜗素的时空表达，以更好地理解耳蜗素的功能作用。通过免疫组织化学方法，出生后第6天（DAB6）耳蜗和前庭中的耳蜗素表达较弱。在DAB70时，在耳蜗内的螺旋缘和螺旋韧带以及前庭内的耳石器官的黄斑和壶腹嵴的基质中检测到耳蜗素的强表达。耳蜗素的免疫反应性在出生后发育过程中增加。蛋白质免疫印迹分析也显示耳蜗素同工型的表达增加。此外，在DAB24和DAB70之间，表达的耳蜗素的主要同工型从p63s变为p40s。这些结果表明，耳蜗素的表达可能与内耳功能的成熟有关，耳蜗素同工型表达的变化将为理解耳蜗素功能和耳蜗素同工型的形成提供重要线索。这是首次报道耳蜗素在发育中的大鼠内耳中的时空表达。
