摘要
目的研究miR-140在正常小鼠内耳毛细胞的表达分布及其对编码突触蛋白Dynamin-1的Dnm1基因的靶向调控作用。方法取正常成年C57BL/6小鼠耳蜗基底膜,免疫荧光染色和原位杂交法观察Dynamin-1与miR-140的表达定位情况。构建荧光素酶报告基因载体转染293T细胞,通过荧光素酶活性变化明确Dnm1是否是miR-140的靶基因。携带miR-140前体及空载的腺相关病毒(adenoassociated virus,AAV)通过圆窗膜注射传递到耳蜗中,14 d后RT-PCR检测miR-140及Dnm1的mRNA表达水平,Western blot检测Dynamin-1蛋白的表达水平。结果 miR-140表达于内外毛细胞细胞质,Dynamin-1主要表达于内毛细胞细胞质;荧光素酶活性检测结果显示,miR-140抑制Dnm1的3'UTR荧光素酶报告基因活性(P<0.05)。RT-PCR及Western blot检测结果显示:转染AAV-miR-140后miR-140的相对表达量明显升高,Dnm1的mRNA及其蛋白表达水平显著降低(P<0.05)。结论Dnm1是miR-140的靶基因,且miR-140可以抑制内耳毛细胞中Dynamin-1的表达,表明miR-140可能通过抑制Dynamin-1蛋白负向调控内毛细胞突触囊泡内吞过程,进而影响听觉信号的传递。
Objective To investigate the expression and distribution of miR-140 in mouse inner ear hair cells and its targeting regulation on Dnm1,the gene encoding synaptophysin Dynamin-1. Methods After the cochlear basement membrane was harvested from healthy adult C57 BL/6 J mice( 8 weeks old),immunofluorescence staining and in situ hybridization were used to observe the expression and location of Dynamin-1 and miR-140. The luciferase reporter gene vector was constructed and then transfected into 293 T cells to determine whether Dnm1 is the target gene of miR-140. Adeno-associated viral vectors carrying miR-140 precursor and blank gene were injected into the cochlea of the mice via circular window membrane.After 14 d,the mRNA expression of miR-140 and Dnm1 was detected by RT-PCR,and Dynamin-1 protein was detected by Western blotting. Results miR-140 was expressed in the cytoplasm of inner and outer hair cells,and Dynamin-1 was mainly expressed in the cytoplasm of inner hair cells. The luciferase activity assay showed that miR-140 could inhibit the enzyme reporter activity of 3' UTR of Dnm1( P < 0. 05). The mRNA expression of miR-140 was significantly increased after transfection of AAV-miR-140,while the mRNA level of Dnm1 and its protein level were decreased significantly( P < 0. 05). Conclusion Dnm1 is the target gene of miR-140,and the latter can inhibit the expression of Dynamin-1 in inner ear hair cells,suggesting that it may negatively regulate the process of synaptic vesicle endocytosis of inner hair cells by inhibiting Dynamin,and then affect the transmission of auditory signals.
引文
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