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

connexin26基因（GJB2）突变是先天性双侧非综合征感音神经性听力损失最常见的遗传原因。在一个常染色体显性负遗传的失聪家族中发现了R75W突变的人Cx26转基因小鼠[Kudo T et al. (2003) Hum Mol Genet 12:995-1004]。显性阴性Gjb2 R75W转基因小鼠模型显示耳蜗支持细胞发育不完全，导致出生时深度耳聋[Inoshita A et al. (2008) Neuroscience 156:1039-1047]。Gjb2 R75W转基因小鼠的Cx26缺陷仅限于支持细胞；尽管有外毛细胞（ohc）存在，但为什么听觉反应受到严重干扰尚不清楚。本研究旨在评价R75W转基因小鼠OHC在体内和体外功能的发育变化，以及OHC和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，在任何频率下均未观察到可检测到的畸变产物耳声发射。在这些小鼠中观察到的特征表型是缺乏Corti隧道，Nuel空间和OHC周围的空间；热盐被周围的支撑细胞压缩和挤压。另一方面，OHC发育正常。侧壁的结构特征，如质膜下膜结合的地下池，完好无损。免疫组化方法在转基因和非转基因小鼠OHC基底外侧膜中观察到电压依赖性运动蛋白Prestin。转基因小鼠和对照小鼠在发育过程中分离的OHCs电动力无显著差异。目前的研究表明，支撑细胞的正常发育是OHC正常细胞功能的必要条件。

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.