Background Leber hereditary optic neuropathy (LHON) is a maternally inherited disorder characterized by a bilateral acute or subacute painless central visual loss in young adults,predominately in males.So far no one theory can completely explain all clinical manifestations of LHON.Objective This study was to investigate whether there is a linkage between X-chromosomal and mitochondrial mutation in the inheritance of a Chinese LHON pedigree with only male patients.Methods This study was approved by Ethic Committee of Affiliated First Hospital of Zhengzhou University and followed by Declaration of Helsinki.A Chinese LHON pedigree was included in Anyang city from January 2008 to August 2016.Periphery blood of 5-10 ml was collected from 4 sufferers,13 maternal members and 10 non-maternal members for DNA extraction and PCR sequencing.The gene scanning and genotyping analysis were performed by ABI-PRISM 3100 genetic analyzer and Genotyper 3.7 software,and linkage analysis was carried out with Linkage software for the calculation of logarithm of odds (LOD).Mitochondrial DNA (mtDNA) sequence,fluorescence-based Genescan for X-chromosomal sequence were analyzed in the propositus and haplotype was evaluated.Results A total of 5 generations and 71 families were included in the pedigree,with 6 male sufferers,30 maternal members and 41 non-maternal members.The visual acuity was ≤0.10,and the central visual field defection,the optic nerve flushing was found in the acute phase,different levels of the optic nerve fibers atrophy were found in the chronic phase;visual evoked potential (VEP) amplitude was low and peak latency were found in the male patients,and no any ocular abnormality was seen in the maternal members,meeting a maternally inherited characteristics,with the penetranee of 20％.The three primnary mutations were not been found in this family bv PCR sequencing,mtDNA sequencing appeared 31 variation of loci in the proband,including a known G3635A mutation,as well as an unknown ND5 A12340G missense mutation and ND4 T11809C synonymous mutation as well as 28 polymorphism of locus,and the proband was mitochondrial haplotype F1.The maternal families were mutation carriers of G3635A and AI2340G loci,while the same mutation was not found in the normal family members and 107 controls.The maximum two point parametric LOD score was 1.46(θ=0.0) for marker DXS1060,1oeated at Xp22.3,and the two-point and multipoint non-parametric linkage analysis were significant (all at P＞0.05).Conclusions The ND5 A12340G and ND1 G3635A mutations coexist in this LHON family,and the ND5 A12340G mutation is a newly reported mutation.There is no evidence for an X-linked modifiers loci in this Chinese LHON family.%背景 Leber遗传性视神经病变(LHON)是由线粒体DNA(mtDNA)错义突变引起的母系遗传性致盲眼病,表现为双侧视神经急性或亚急性病变和无痛性中心视力丧失,且具有不完全外显和男性患病偏倚的临床特点.迄今为止,仍没有一个理论可以完整解释其所有的临床表现. 目的 对一汉族LHON家系突变基因进行检测,探讨其男性患病偏倚的机制.方法 2008年1月至2016年8月收集河南省安阳市一汉族LHON家系,采集此家系中4例患病者、13名母系成员和10名非母系成员的外周静脉血5～ 10 ml,纳入107个与该家系无血缘关系的正常人样本作为对照.用PCR进行DNA测序,用ABI-PRISM 3100基因分析仪进行基因扫描,用Genotyper 3.7软件进行基因型分析,Linkage软件进行连锁分析,计算两点参数优势对数比值比(LOD),检测该家系是否携带3个原发突变.对先证者mtDNA进行全测序,将测序结果与修正的mtDNA剑桥标准序列进行比对,确定该家系的突变位点;采用微卫星荧光标记基因组扫描法扫描X染色体进行家系连锁分析,绘制单倍体型图. 结果 该家系5代共71位成员,患病者6例,均为男性,视力≤0.10,均存在中心视野缺损;急性期视盘色红,慢性期有不同程度的视神经纤维层萎缩;视觉诱发电位(VEP)振幅较低,峰潜时延长;母系成员共30名,母系家系的女性成员视力及眼部检查未发现异常,符合母系遗传特征,家族中LHON外显率为20％.PCR测序证实该家系成员均未携带3个原发突变.先证者mtDNA全测序发现31个改变位点,包括1个已报道的致病突变位点G3635A和未报道过的ND5 A12340G错义突变及ND4 T11809C同义突变,其他28个突变点均为已报道的线粒体多态,先证者属于线粒体单倍体型F1.母系成员均同时携带G3635A和A12340G突变,而正常家系成员和107位正常对照者不存在该突变.连锁分析在DXS1060得到最大两点LOD值1.46(θ=0.0),但是两点非参数分析和多点非参数分析结果显示所有标记的差异均无统计学意义(均P＞0.05). 结论 此家系同时携带A12340G和G3635A 2个突变位点,其中A12340G突变为首次报道;在此家系中并未发现与LHON有关的X连锁修饰基因位点.
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