Transgenic expression of a dominant-negative connexin26 causes degeneration of the organ of Corti and non-syndromic deafness
Transgenic expression of a dominant-negative connexin26 causes degeneration of the organ of Corti and non-syndromic deafness
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DOI：
10.1093/hmg/ddg116
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发表时间：
2003-05-01
影响因子：
3.5
通讯作者：
Matsubara, Y
中科院分区：
文献类型：
--
作者：
Kudo, T;Kure, S;Matsubara, Y
大约每2000名儿童中就有1人患有遗传性耳聋，GJB2基因突变是不同种族的主要原因。GJB2编码连接蛋白26，这是一种可能存在于耳蜗间隙连接的通道成分。然而，GJB2突变导致听力损失的机制仍不清楚。Gjb2基因敲除的小鼠是胚胎致死的，这一事实阻碍了研究连接蛋白26在听力过程中功能的小鼠模型的产生。为了建立存活的模型小鼠，我们产生了表达突变的连接蛋白26的转基因小鼠，该突变带有R75W突变，该突变在一个常染色体显性遗传的聋人家庭中被发现。先前的表达分析表明，R75W连接蛋白26以显性-负性方式抑制共表达的正常连接蛋白26的缝隙通道功能。我们建立了两个转基因小鼠系，表现为重度至深度听力损失、支持细胞畸形、Corti隧道形成失败和感觉毛细胞变性。尽管转基因表达旺盛，但在富含连接蛋白26并产生内淋巴的血管纹或螺旋韧带中没有观察到明显的结构变化。正常情况下，耳蜗内淋巴的高静息电位是毛细胞兴奋所必需的。这些结果表明，由于支持细胞K+转运受损，GJB2突变扰乱了皮层淋巴(感觉毛细胞周围的细胞外空间)的动态平衡，导致Corti器官的降解，而不是影响小鼠和可能是人类的内淋巴动态平衡。
Hereditary deafness affects about 1 in 2000 children and mutations in the GJB2 gene are the major cause in various ethnic groups. GJB2 encodes connexin26, a putative channel component in cochlear gap junction. However, the pathogenesis of hearing loss caused by the GJB2 mutations remains obscure. The generation of a mouse model to study the function of connexin26 during hearing has been hampered by the fact that Gjb2 knockout mice are embryonic lethal. To establish viable model mice we generated transgenic mice expressing a mutant connexin26 with R75W mutation that was identified in a deaf family with autosomal-dominant inheritance. The previous expression analysis revealed that the R75W connexin26 inhibited the gap channel function of the co-expressed normal connexin26 in a dominant-negative fashion. We established two lines of transgenic mice that showed severe to profound hearing loss, deformity of supporting cells, failure in the formation of the tunnel of Corti and degeneration of sensory hair cells. Despite robust expression of the transgene, no obvious structural change was observed in the stria vascularis or spiral ligament that is rich in connexin26 and generates the endolymph. The high resting potential in cochlear endolymph essential for hair cell excitation was normally sustained. These results suggest that the GJB2 mutation disturbs homeostasis of cortilymph, an extracellular space surrounding the sensory hair cells, due to impaired K+ transport by supporting cells, resulting in degradation of the organ of Corti, rather than affecting endolymph homeostasis in mice and probably in humans.