中文摘要：

收集了3个具有典型临床特征的中国汉族Leber遗传性视神经病变（Leber′s hereditary optic neuropathy,LHON）家系。通过对先证者和家系其他成员进行眼科临床（如视力损害程度和发病年龄）检查,发现这些家系成员中视力损害的外显率很低,经mtDNA测序分析,在tRNAGlu上发现了A14693G同质性突变位点,多态性位点分别属于东亚单体型Y1b、Y1和Y1,没有发现其他高度保守和有功能意义的突变位点。A14693G突变位于线粒体tRNAGlu高度保守区（通用位点为54位）,可能导致tRNA空间结构和稳定性发生改变,继而影响tRNA的代谢,导致线粒体蛋白合成功能受损和ATP障碍,最终导致视力损害。所以,tRNAGluA14693G突变可能是与视神经病变相关的致病性线粒体突变位点。

英文摘要：

We reported here the clinical,genetic and molecular characterization of three Han Chinese families with Le-ber’s hereditary optic neuropathy.Ophthalmologic examinations revealed the variable severity and age-at-onset of visual loss among probands and other matrilineal relatives of these families.Strikingly,these families exhibited extremely low penetrances of visual impairment.Sequence analysis of complete mitochondrial genomes in these pedigrees identified the known homoplasmic tRNAG luA14693G mutation and distinct sets of polymorphism belonging to haplogroups Y1b,Y1 and Y1,respectively.The A14693G mutation occurs at the extremely conserved nucleotide（conventional position 54）of tRNA Glu .Thus,this mutation may alter structural formation and stabilization of functional tRNAs,thereby leading to a fail-ure in tRNA metabolism and mitochondrial dysfunction involved in visual impairment.However,none of other variants showed the evolutionary conservation and functional significance.These observations suggested that the tRNA Glu A14693G mutation may be involved in the pathogenesis of optic neuropathy in these families.