氨基糖甙类抗生素致聋家系线粒体DNA12S和16S rRNA基因突变分析

目的 研究线粒体rRNA基因突变与氨基糖甙类抗生素致聋遗传易感性的关系，为建立相应的基因诊断方法提供依据。方法 收集了五个有明确氨基糖甙类抗生素应用史的耳聋家系共27名成员的外周静脉血标本。从白细胞中提取DNA，PCR扩增线粒体DNA片段。Alw26I限制性内切酶分析和DNA序列分析检测A1555G点突变，并对其中一个家系进行了线粒体DNAl2S和16SrRNA基因的全序列分析。结果家系A．C．D和E的2l份样品均为A1555G点突变阳性，家系B的6份样品为A1555G点突变阴性。家系B线粒体DNAl2S和16SrRNA基因全序列分析显示该家系存在16SrRNA基因第2227位“AA”插入突变。结论 本研究发现了一个A1555G点突变阴性的氨基糖甙类抗生素致聋家系，说明线粒体DNA A1555G点突变不是氨基糖甙类抗生素遗传易感性唯一的分子基础，对氨基糖甙类抗生素致聋遗传易感性的预测仅检测A1555G点突变是不够的。应与mtDNA其它相关突变位点的检测结合起来。     

线粒体DNA突变与氨基糖甙类抗生素致聋研究进展

线粒体脱氧核糖核酸（mitochondrial deoxyroibose nucleic acid,mtDNA）是唯一存在于核外的遗传物质,具有独特的遗传特性,如严格的母系遗传、具有半自主性、不与组蛋白结合,修复能力低下,容易发生碱基突变。氨基糖甙类抗生素耳聋具有家族聚集的现象,遗传的线粒体突变是氨基糖甙类抗生素致聋（aminoglycoside antibiotics induced deafness,AAID）等非综合征耳聋的原因之一。     

线粒体DNA1555位点突变、非综合征性聋与氨基糖甙类抗生素关系研究

氨基糖甙类抗生素致聋是导致儿童重度感音神经性聋的主要原因，而且具有家族聚集性与易感性。目前认为线粒体DNA1555位点突变是导致氨基糖甙类所致非综合征聋的主要遗传基础。本文试图从线粒体基因1555位点突变结构特点、发病机理、突变的外显率、临床意义等方向作一综述。     

一个氨基糖甙类药物致聋家系线粒体DNA全序列分析

目的 评估线粒体单倍型对一个氨基糖甙类药物致聋家系中12S rRNA A827G突变表型的影响.方法 用基因组DNA抽提试剂盒提取外周血DNA,PCR扩增家系成员mtDNA 12S rRNA基因进行A827G突变的测序验证,对携带A827G突变的家系先证者进行mtDNA全序列PCR扩增和测序分析,结果 与修正的剑桥参考序列比对,识别除A827G以外的突变位点.结果 5名母系成员mtDNA 12S rRNA序列分析均检测到A827G突变.与修正的剑桥参考序列及家系配偶相比,先证者的mtDNA全序列分析显示出独特的多态性改变,除已知的12S rRNAA827G突变外,另检测到24个碱基变异,其中12S rRNA基因A783C、G786C以及ND4基因C11720A突变(L319A)为首次发现.系统进化法分析显示,上述多态性位点均位于mtDNA非保守区域.结论 线粒体单倍型对该家系mtDNA A827G突变的表型表达无明显影响.     

氨基糖甙类抗生素致聋家系线粒体DNA1555^G点突变分析

目的 考察１５５５＾Ｇ点在糖甙类抗生素致聋的对应关系，建立相应的基因诊断方法提供依据。方法 收集了３个有明确氨基糖甙类抗生素应用史的母系遗传耳聋家系１３人（包括聋人和听力正常者）的外周静脉血标本，聚合酶链反应扩增线粒体ＤＮＡ，Ａｌｗ２６Ｉ限制性内切酶分析、ＤＮＡ斑点杂交和ＤＮＡ序列分析检测１５５５＾Ｇ点突变。结果 家系１和３的７份样品均为１５５５＾Ｇ点突变阳性，家系２的６份样品为１５５５＾Ｇ点突变     

氨基糖甙类抗生素致聋家系线粒体DNA1555G点突变分析

目的考察１５５５Ｇ点突变与氨基糖甙类抗生素致聋的对应关系，建立相应的基因诊断方法提供依据。方法收集了３个有明确氨基糖甙类抗生素应用史的母系遗传耳聋家系１３人（包括聋人和听力正常者）的外周静脉血标本，聚合酶链反应扩增线粒体ＤＮＡ，Ａｌｗ２６Ｉ限制性内切酶分析、ＤＮＡ斑点杂交和ＤＮＡ序列分析检测１５５５Ｇ点突变。结果家系１和３的７份样品均为１５５５Ｇ点突变阳性，家系２的６份样品为１５５５Ｇ点突变阴性。结论发现１个１５５５Ｇ点突变阴性的氨基糖甙类抗生素致聋家系，说明线粒体ＤＮＡ１５５５Ｇ点突变不是氨基糖甙类抗生素遗传易感性唯一的分子基础。     

五例氨基糖甙类抗生素致聋家系报道

目的 本文报导了5个药物性耳聋家系。耳聋患者大都有明确的氨基糖甙类抗生素应用史。研究小组赴当地访问了五个家系共28名成员。对所有受访者进行了全身体检．耳鼻咽喉专科检查．纯音测听．声导抗及听性脑干诱发电位检查，其中有12人为中重度感音神经性听力下降。听力图为高频曲线型中的高频陡降型为主，未见其他系统的异常改变。遗传图谱分析显示。五个家系均符合母系遗传特征。提示为线粒体遗传方式。五个家系共采集了23名成员的静脉血样，这些临床资料的收集，为我们下一步进行致聋基因突变的分析奠定了良好的基础。     

氨基糖甙类抗生素致聋的家族性与交叉易感性

对3个家族中氨基糖甙类抗生素中毒性耳聋患者的家族进行调查及分析，发现几种氨基糖甙类药物之间存在家族性和交叉易感性，即在有家族性耳毒性药物致聋的家族成员中，应用任何一种氨基糖甙类抗生素，都比一般人容易发生耳中毒；即使用量不大，也易引起严重后果，特别是年幼者。此种家族性与交叉易感性属常染色体显性遗传。提示临床医生用药前应仔细询问病史，特别是有母系家族耳聋史者应禁用氨基糖甙类全部抗生素，以预防子代耳聋的发生。     

氨基糖甙类抗生素中毒聋易感性与线粒体DNA突变的研究

应用PCR-限制性内切酶酶切片段长度多态性技术,对164例过去应用过氨基糖甙类药物目前听力严重下降的患者外周血线粒体DNA进行了研究。结果发现6例聋哑患者线粒体DNA12srRNA基因1555位点发生了点突变,突变率3．6％,100例听力正常人无一例在此位点有突变。我们对国外学者的研究方法加以改良,使结果更容易判断。我们推测在线粒体DNA上还有其它与中毒聋易感性相关的突变位点尚未被发现。     

Deafness due to A1555G mitochondrial mutation without use of aminoglycoside

OBJECTIVES/HYPOTHESIS: The objective was to clarify the characteristics of deafness associated with the A1555G mutation within mitochondrial 12S ribosomal RNA gene in the absence of aminoglycoside exposure. STUDY DESIGN: Clinical and genetic studies in family members with the A1555G mitochondrial mutation were performed. METHODS: The subjects were 123 maternally related members of a large Japanese family with the A1555G mutation. All subjects had no previous history of exposure to aminoglycosides. Hearing disability and handicap, tinnitus, and medical histories were analyzed by interviews in all of the subjects, genetic testing was performed in 41 subjects, and pure-tone audiometry was conducted in 26 subjects with hearing disability and handicap. RESULTS: The A1555G mutation was detected in a homoplasmic form (meaning that all the mitochondrial DNA carries the mutation) in all 41 subjects who were screened. The risk for developing postlingual hearing loss was likely to be much higher in the present subjects than in the general population. Both the severity and age at onset of the phenotype were similar in affected subjects within the same sibling group. Pure-tone averages were significantly worse in subjects who developed hearing loss before age 10 years than in those who developed hearing loss later. CONCLUSION: The present study demonstrated that the prevalence of deafness in individuals with the A1555G mitochondrial mutation was likely to be high even in the absence of aminoglycoside exposure and clearly showed the association of severe to profound hearing loss with the onset of hearing loss before age 10 years.     

非综合征型耳聋患者mtDNA A1555G异质性突变比例与临床表型的关系

目的定量检测非综合征型耳聋患者线粒体DNA(mitochondrial DNA,mtDNA)1555突变型/野生型的拷贝数,探讨突变型/野生型比例与临床表型之间的关系。方法建立实时定量PCR技术和扩增阻滞突变系统(Real-time quantitative PCR和Amplification refractory mutation system,RT-ARMS-qPCR系统)对含突变型和野生型mtDNA 1555位点的拷贝数进行定量检测并计算比例。共检测散发组12例、家系组7例异质性突变患者,结合耳聋患者的临床资料,分析突变型与野生型的比例与耳聋严重程度的关系。结果散发组mtDNA A1555G异质性突变的患者中,突变型mtDNA所占的比例与耳聋轻重程度相关(r=0.771,P=0.003);家系组患者中,突变型mtD-NA所占的比例亦与耳聋轻重程度相关(r=0.850,P=0.015)。结论突变型mtDNA占所有mtDNA的比例与耳聋的严重程度密切相关,是非综合征型耳聋临床表型多样性的分子基础。     

Audiovestibular findings in patients with mitochondrial A1555G mutation

OBJECTIVE: The aims of this study were to explore the prevalence of the A1555G mutation among a group of Japanese patients and to assess the pathophysiology of the hearing impairment associated with the mutation. STUDY DESIGN: Genetic study and retrospective chart review. METHODS: We screened for the mitochondrial DNA A1555G mutation in 138 unrelated Japanese deaf patients, including 63 sporadic cases and 75 familial cases with different patterns of inheritance. When available, patients carrying the mutation received audiovestibular examinations, including speech audiometry, distortion-product otoacoustic emission (DPOAE) testing, electrocochleography (ECochG), and electronystagmography. RESULTS: One of 63 sporadic cases (1.6%) and 6 of 75 familial cases (8.0%) carried the A1555G mutation. Patients with the mutation and a familial history included two with autosomal recessive inheritance and four with maternal inheritance. In addition, two of six patients (33.3%) presenting with aminoglycoside-induced sensorineural hearing loss (SNHL) were associated with the A1555G mutation. All but one of the patients carrying the mutation showed high-frequency SNHL. Distortion-product levels of DPOAE were reduced to the noise levels, suggesting the A1555G mutation caused cochlear deafness. Cochlear microphonics in ECochG showed elevation of the detection thresholds and corresponding audiometric thresholds. The ECochG data implied that patients with high-frequency SNHL had impairment of the cochlear hair cells that was most severe toward the basal turn. The electronystagmographic findings indicated no apparent vestibular dysfunction. CONCLUSIONS: Screening for the A1555G mutation, even in patients with idiopathic bilateral SNHL, likely would be useful for preventing further development and/or acceleration of the deafness.     

Audiological features and mitochondrial DNA sequence in a large family carrying mitochondrial A1555G mutation without use of aminoglycoside

To elucidate the pathophysiological and genetic mechanisms of hearing loss associated with the homoplasmic mitochondrial A1555G mutation in the absence of aminoglycoside exposure, we conducted audiological and genetic analyses on 67 maternally related members of a large Japanese family carrying this mutation. A consistent pattern was evident in the audiograms, with features of sensory presbycusis, cochlear origin at all levels of hearing loss, and a high degree of vulnerability of outer hair cells. That the degree of hearing loss was similar in affected subjects within the same sibling group but differed between sibling groups suggests the involvement of nuclear modifier genes. Total mitochondrial DNA sequences were completely identical among subjects with various levels of hearing loss, and lacked additional pathogenic mutations. For the diagnosis of sensorineural hearing loss, the mitochondrial A1555G mutation should be considered when these features are present even in the absence of aminoglycoside exposure.     

Different clinical characteristics of aminoglycoside-induced profound deafness with and without the 1555 A-->G mitochondrial mutation

Recent genetic studies have shown that hereditary susceptibility to aminoglycoside antibiotics is caused by the 1555 A-->G mitochondrial mutation. We found the 1555 mutation in 4 out of 68 postlingual deaf patients who were candidates for cochlear implantation. All 4 patients developed bilateral profound hearing loss following administration of aminoglycosides. The pedigree of the family shows exclusively maternal transmission of hearing impairment in each case. On comparison with neuro-otological findings from aminoglycoside-induced deaf patients without the 1555 mutation, four distinct characteristics were noted: (1) a progressive nature of hearing loss; (2) better residual pure-tone thresholds; (3) lower thresholds for electrical promontory stimulation, and (4) well-preserved vestibular function. Although other factors such as differing dosages and/or administration routes may also be involved, profound hearing loss associated with the 1555 mutation may be due to a different pathogenic mechanism, i.e., strial dysfunction rather than a direct insult to the hair cells.