7个中国Leber遗传性视神经病变家系线粒体DNA突变分析

The analysis of mitochondrial DNA mutation in seven Chinese families with Leber＇s hereditary optic neuropathy

【摘要】目的观察7个中国Leber遗传性视神经病变（LHON）家系的分子遗传学特征。方法对7个家系先证者及其母系成员和134例正常健康者进行临床眼科检查。除7个先证者外，还确诊2例LHON患者。用24对有部分重叠的引物对受检者线粒体DNA全序列进行扩增，双向测序，结果与修正的剑桥参照序列进行比对，分析突变位点。计算突变位点的外显率，分析家系的单体型。结果7个家系先证者及其母系成员均未携带ND4G11778A、ND1G3460A和ND6T14484C这3个常见的原发突变位点，但均携有与LHON相关的ND1 T3394C突变位点。134位正常健康者中仅发现4例携带此突变位点。7个家系的ND1T3394C外显率分别为12．50％、22．22％、16．67oA、6．25％、9．09％、11．11％、28．57％。根据本亚线粒体单体型系统进化树分析结果，7个家系分别属于东亚线粒体单体型M9、M9、M、D4、M、M9、M9。结论中国LHON家系中存在ND1 T3394C突变位点，该突变位点的外显率为6．25％～28．57％，表现度不一。

Objective To observe the molecular genetic characteristics of seven Chinese families with Leber＇s hereditary optic neuropathy （LHON）. Methods Ophthalmologic examinations were performed on seven probands, maternal members from seven Chinese families and 134 healthy controls. There were two LHON patients in seven Chinese families except probands. The entire mitochondrial genome was amplified using 24 pairs of oligonucleotide primers with overlapping fragments. The mutational site was analyzed through comparison of the results and Cambridge reference sequence. The penetrance of mutation site was calculated and the haplotype was analyzed. Results Molecular analysis of mitochondrial DNA （mtDNA） in these pedigrees revealed the absence of three common LHON associated with ND4 Gl1778A, ND1 G3460A and ND6 T14484C mutations. The ND1 T3394C mutation in probands and other matrilineal relatives was present in four out of 134 Chinese healthy controls. Strikingly, these families exhibited very low penetrance of visual impairment. The penetrance was 12.50%, 22.22%, 16.76%, 6.25%, 9. 090/oo, 11.11% and 28.57%. The results of phylogenetic tree analysis of submitochondrial haplotype showed that these mtDNA polymorphism sites belong to the Asian haplogroups M9, M9, M, D4, M, M9 and M9. Conclusions T3394C mutation exists in seven Chinese LHON pedigrees, and the penetrance was ranged from 6.25% to 28.57 %. The patients have different clinical manifestations.