携带线粒体tRNA^(Thr)15910C>T突变和12S rRNA 1555A>G突变的非综合征型耳聋家系的线粒体功能研究

The Study of Mitochondrial Function in A Nonsyndromic Hearing Loss Family Carrying Mitochondria tRNA^(Thr) 15910C>T and 12S rRNA 1555A>G Mutations

该研究旨在探讨一个非综合征型耳聋(nonsyndromic hearing impairment,NSHI)家系中线粒体t RNAThr 15910C>T和12S r RNA 1555A>G基因突变共同作用对线粒体功能的影响。该研究建立了同时携带线粒体t RNAThr 15910C>T和12S r RNA 1555A>G基因突变(双突变组)、仅携带12S r RNA 1555A>G基因突变(单突变组)和对照组的永生化淋巴细胞,这3组细胞系的线粒体DNA单体型均属于R单体型。对该家系的临床资料进行分析,当包括使用氨基糖苷类抗生素(aminoglycoside antibiotics,Am An)的药物性耳聋家系成员时,此家系耳聋外显率为37.5%;当排除用药的耳聋成员时,耳聋外显率是25.0%;相比之下,在用药和未用药的情况下,已报道的14个m.1555A>G的耳聋家系的平均外显率只有12.8%和6.1%。通过对双突变组、单突变组和对照组永生化细胞系的线粒体功能进行研究,结果发现与对照组相比,双突变和单突变组细胞系的ROS水平分别上升了19.08%(P=0.005 4)和9.05%(P=0.003 7);ΔΨm水平分别下降了47.78%(P=0.006 3)和35.39%(P=0.0245);复合体II活力分别下降了8.26%(P=0.721 1)和19.48%(P=0.004 9),复合体IV活力分别下降了32.75%(P=0.033 5)和27.44%(P=0.180 5)。m.1555A>G与m.15910C>T共同作用,导致ROS生成量升高,ΔΨm水平下降以及线粒体呼吸链复合体IV活力降低等线粒体功能缺陷,提示m.15910C>T可能是m.1555A>G导致耳聋的继发性突变。

In this study, we investigated the mitochondrial function of 12S rRNA 1555A〉G and mitochondria tRNA^Thr 15910C〉T mutations in a nonsyndromic hearing loss （NSHL） family. We established three groups of lymphoblastoid cell lines in this study, including the double mutations group, the single mutation group and the controls, which all belong to the Eastem Asian haplogroup R. The double mutations group are 3 subjects carried both m. 1555A〉G and m. 15910C〉T. The single mutation group are 3 subjects carried m. 1555A〉G mutation only. The controls are 3 subjects with normal auditory sense. To analyze the clinical data of the family, the penetrance of deafness is 37.5% or 25.0% which contains or excludes the family members who have used AmAn drugs; while the penetrance of deafness is 12.8% or 6.1% which contains or excludes the family members who have used AmAn drugs in the 14 reported deafness families with m. 1555A〉G mutation. Compared with controls, the ROS level in the double-mutations group has been raised 19.08% （P=0.005 4） and the single-mutation group only raised 9.05% （P=0.003 7）. Compared with controls, the mitochondrial membrane potential decreased 47.78% （P=0.006 3） and 35.39% （P=0.024 5） in the double-mutations group and the single-mutation group, respectively. It showed that 8.26% （P=0.721 1） and 19.48% （P=0.004 9） decrease in the activity of respiratory chain complex II while 32.75% （P=0.033 5） and 27.44% （P=0.180 5） decrease in the activity of respiratory chain complex IV in the double-mutations group and the single-mutation group compared with controls. These results showed that m.1555A〉G and m.15910C〉T led to mitochondrial dysfunction, included ROS raise up, mitochondrial membrane potential and the activity of respiratory chain complex IV decreased. Thus, m. 15910C〉T worsens the mitochondrial function associated with m. 1555A〉G, and is probably a secondary mutation of m. 1555A〉G caused deafness.