Hu J, Chen Z C, Zhang Y Z, Han P, Ma W J, Zhang Q, Xu M
Department of Otorhinolaryngology Head and Neck Surgery, Second Affiliated Hospital, Xi'an Jiaotong University School of Medicine, Xi'an 710004, China.
Department of Otorhinolaryngology Head and Neck Surgery, First Affiliated Hospital, Xi'an Jiaotong University School of Medicine, Xi'an 710061, China.
Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 2018 Feb 7;53(2):110-117. doi: 10.3760/cma.j.issn.1673-0860.2018.02.006.
To test the mechanism and upstream pathway of outer hair cell apoptosis in Cadherin 23 (Cdh23) gene mutant mice. The mutant 23() 57/6 (6) . 70 . - () . () () . -- () / () . . . 23 . The ABR thresholds in mice were significantly higher than those in B6 mice at the age of 1 and 3 months (both <0.05). The surface preparation with TUNEL staining confirmed OHC apoptosis in mouse cochleae which showed a higher TUNEL positive cell ratio than B6 mouse(=11.291, <0.01). The ER stress marker and mRNA were upregulated in the mouse inner ear, when compared with those in the B6 mouse(both <0.05). The BiP protein extracted from the mouse cochleae was significantly higher than that of B6 mouse measured by Western blot (=3.66, =0.02). Immunostaining showed that BiP and CHOP were highly detected in the OHC in mouse cochleae, and was mainly detected in the perinuclear region of OHC. However, a bare BiP and CHOP signal were shown in B6 mouse cochleae. The CDH23 protein was specifically localized at the top of the OHC in B6 mice, indicating the localization of the tip links in hair bundle stereocilia. On the contrary, the CDH23 protein was found to be localized from the top to the nuclei of the OHC in mice. Portions of the CDH23 proteins failed to reach the top of the hair bundles and remained in the OHC cytoplasm. As the downstream response of the Cdh23 gene mutation, portions of the mutant CDH23 protein was accumulated in ER lumen resulting in the increase of ER loading and ultimately triggered ER stress and hair cell apoptosis in mouse cochleae.
为了测试钙黏蛋白23（Cdh23）基因敲除小鼠中外毛细胞凋亡的机制及上游信号通路。突变体23()57/6(6)。70。-()。()()。--()/()。。。23。1月龄和3月龄的突变体小鼠的听性脑干反应（ABR）阈值显著高于B6小鼠（均P<0.05）。TUNEL染色的表面标本证实突变体小鼠耳蜗中外毛细胞发生凋亡，其TUNEL阳性细胞比例高于B6小鼠（F=11.291，P<0.01）。与B6小鼠相比，突变体小鼠内耳中内质网应激标志物和mRNA上调（均P<0.05）。通过蛋白质免疫印迹法测得，从突变体小鼠耳蜗中提取的结合免疫球蛋白蛋白（BiP）显著高于B6小鼠（F=3.66，P=0.02）。免疫染色显示，在突变体小鼠耳蜗的外毛细胞中高度检测到BiP和C/EBP同源蛋白（CHOP），且主要在外毛细胞的核周区域检测到。然而，在B6小鼠耳蜗中几乎没有检测到BiP和CHOP信号。在B6小鼠中，CDH23蛋白特异性定位于外毛细胞顶部，表明其在毛束静纤毛中的顶连接定位。相反，在突变体小鼠中，发现CDH23蛋白定位于外毛细胞的顶部至细胞核。部分CDH23蛋白未能到达毛束顶部并滞留在外毛细胞胞质中。作为Cdh23基因突变的下游反应，部分突变的CDH23蛋白在内质网腔中积累，导致内质网负荷增加，最终引发突变体小鼠耳蜗中的内质网应激和毛细胞凋亡。
