中文摘要：

目的通过细胞学方法，分析药物性聋和非综合征性聋相关的线粒体DNA C1494T突变对细胞功能的影响。方法将从携带C1494T突变的中国家系成员的淋巴细胞中的线粒体分别转移到线粒体DNA缺乏的p^0206细胞中，分别形成融合细胞系，然后对耳聋相关的线粒体12S rRNA C1494T突变进行生化特性的研究。其中，来自2名听力正常者的6个融合细胞系，来自听力下降者的9个融合细胞系，均有线粒体DNA C1494T突变。结果来自听力下降者的融合细胞系的线粒体DNA标记速率分别比对照组4名成员的12个融合细胞系下降了38％和43％，这一缺陷显然造成了携带C1494T突变的融合细胞（不论来自听力正常者还是来自听力下降者）的细胞总体呼吸率下降，或苹果酸，谷氨酸、琥珀酸，3一磷酸甘油及TMPD／抗坏血酸所始动的呼吸率下降。而且，和对照组的细胞系相比，有C1494T突变的听力正常者或听力下降者的融合细胞系在含有（或不含）高浓度巴龙霉素的DMEM培养液中，细胞倍增时间有非常显著的一致增加。结论我们的试验结果首次以直接的生化学证据证明：线粒体12SrRNA的A位点是氨基糖甙类药物性聋的主要作用位点；而且细胞核背景在线粒体DNA 12S rRNA C1494T突变导致的非综合征性聋和氨基糖甙类耳毒性的发病中起着关键性的作用。

英文摘要：

Objective To analysis biochemical characterization of the deafness-associated mitochondrial 12S rRNA C1494T mutation. Methods We examined the biochemical characterization of the deafness-associated mitochondrial 12S rRNA C1494T mutation using 27 cybrid cell lines constructed by transferring mitochondria from 9 lymphoblastoid cell lines derived from a Chinese family into human mitochondrial DNA （mtDNA）-less （p^0206） cells. Results Six cybrids derived from two asymptomatic members, and nine cybrids derived from three symptomatic members of the Chinese family carrying the C1494T mutation exhibited 38 and 43% decrease in the rate of mitochondrial protein labeling, respectively, compared with twelve cybrids derived from four Chinese control individuals. These defects are apparently a primary contributor to significant reductions in the rate of overall respiratory capacity or the rate of malate/glutamate promoted respiration, or succinate/G3P-promoted respiration, or TMPD/ascorbate-promoted respiration in mutant cybrid cell lines derived from either symptomatic or asymptomatic individuals. Furthermore, the very significant/nearly identical increase in the ratio of doubling times in DMDM medium in the presence/ahsence of high concentration of parnmomycin was observed in symptomatic or asymptnmatic cybrid cell lines carrying the C1494T mutation as compared with the average rate in control cell lines. Conehlsion Our data strongly support the idea that the A site of mitochondrial 12S rRNA is the primary target for aminoglycoside-induced deafness. In addition, these data provide the first biochemical evidence that nuclear background plays a critical role in the phenotypic manifestation of nonsyndromic hearing loss and aminoglycoside toxicity associated with the C1494T mutation in the mitochondrial 12S rRNA gene.