Cochlear outer hair cells in a dominant-negative connexin26 mutant mouse preserve non-linear capacitance in spite of impaired distortion product otoacoustic emission.

连接蛋白26基因(GJB2)突变是先天性双侧非综合征性感音神经性耳聋最常见的遗传原因。建立了携带带有R75W突变的人Cx26的转基因小鼠，该突变在一个常染色体显性负遗传的聋人家庭中被发现[Kudo T等人。(2003)Hum Mol Genet 12：995-1004]。显性阴性的Gjb2 R75W转基因小鼠模型显示耳蜗支持细胞发育不完全，导致出生时就严重耳聋[Inoshita A等人。(2008)神经科学156：1039-1047]。Gjb2 R75W转基因小鼠中的Cx26缺陷仅限于支持细胞；尚不清楚为什么尽管存在外毛细胞(OHC)，听觉反应仍受到严重干扰。本研究旨在评价R75W转基因小鼠体内和体外OHC功能的发育变化，以及OHC及其邻近支持细胞的精细结构。在R75W转基因小鼠的整个发育过程中，在任何频率下都没有观察到可检测到的失真产物耳声发射。在这些小鼠身上观察到的一个特征表型是没有Corti隧道、Nuel‘s间隙和OHC周围的间隙；OHC被周围的支持细胞压缩和挤压。另一方面，OHC发展正常。侧壁的结构特征，如质膜下的膜下池，完好无损。用免疫组织化学方法在转基因和非转基因小鼠的OHC基底膜上观察到电压依赖性运动蛋白Prestin的表达。在转基因小鼠和对照小鼠之间，没有观察到发育过程中分离的毛细胞电动活动的显著差异。本研究表明，支持细胞的正常发育对于OHC的正常细胞功能是必不可少的。

Mutations in the connexin26 gene (GJB2) are the most common genetic cause of congenital bilateral non-syndromic sensorineural hearing loss. Transgenic mice were established carrying human Cx26 with the R75W mutation that was identified in a deaf family with autosomal dominant negative inheritance [Kudo T et al. (2003) Hum Mol Genet 12:995-1004]. A dominant-negative Gjb2 R75W transgenic mouse model shows incomplete development of the cochlear supporting cells, resulting in profound deafness from birth [Inoshita A et al. (2008) Neuroscience 156:1039-1047]. The Cx26 defect in the Gjb2 R75W transgenic mouse is restricted to the supporting cells ; it is unclear why the auditory response is severely disturbed in spite of the presence of outer hair cells (OHCs). The present study was designed to evaluate developmental changes in the in vivo and in vitro function of the OHC, and the fine structure of the OHC and adjacent supporting cells in the R75W transgenic mouse. No detectable distortion product otoacoustic emissions were observed at any frequencies in R75W transgenic mice throughout development. A characteristic phenotype observed in these mice was the absence of the tunnel of Corti, Nuel's space, and spaces surrounding the OHC ; the OHC were compressed and squeezed by the surrounding supporting cells. On the other hand, the OHC developed normally. Structural features of the lateral wall, such as the membrane-bound subsurface cisterna beneath the plasma membrane, were intact. Prestin, the voltage-dependent motor protein, was observed by immunohistochemistry in the OHC basolateral membranes of both transgenic and non-transgenic mice. No significant differences in electromotility of isolated OHCs during development was observed between transgenic and control mice. The present study indicates that normal development of the supporting cells is indispensable for proper cellular function of the OHC.