Leber遗传性视神经病变一家系的线粒体分子遗传学研究

背景Leber遗传性视神经病变（LHON）是由线粒体DNA（mtDNA）遗传的可致盲眼病，了解DNA突变位点对该疾病发生的影响具有重要意义。目的分析一个Leber遗传性视神经病变家系mtDNA突变与疾病发生之间的关系。方法收集江西省鹰潭市一个LHON家系中72名母系成员进行系谱分析和突变基因筛选，对其中的11例患者、13例突变基因携带者和49名正常者进行常规眼科检查，按照视力损害的程度分级，视力〉0．3者为正常，0．1～0．3者为轻度损害，〈0．05～0．1者为中度损害，〈0．02～0．05者为重度损害，〈0．01者为极重度损害，分析该家系的临床特征。收集受检者周围静脉血2—4ml进行单个核细胞分离，用改进高盐法提取mtDNA，进行PCR扩增，对突变基因位点进行DNA测序。结果突变基因的PCR扩增产物DNA测序结果显示72名受检的家系成员中，有24例同时具有G11778A和T14502C两个突变位点，包括11例LHON患者，其余13名为突变基因携带者，但至今尚未发病，故该家系的LHON外显率不足50％，而其他家系成员未检测到G11778A和T14502C突变位点。11例患者的发病年龄为8～50岁，平均为24．36岁，显著低于13例基因携带者年龄5～72岁，平均40．38岁，差异有统计学意义（t=2．102，P=0．049）。结论该家系成员的线粒体DNAC11778A和T14502C突变是LHON发病的主要原因，原发性mtDNA突变为LHON发病所必需，但其并非充分条件，一个有效的“二次打击”过程同样具有重要的作用。

Mitochondrial molecular genetics for a pedigree with Leber hereditary optic neuropathy

Background Leber hereditary optic neuropathy （LHON）is a mitochondrial DNA （mtDNA） hereditary disease,so it is significant to understand the influence of DNA mutation on the occurrence of LHON. Objective This survey was to evaluate the role of mtDNA mutation in the development of LHON. Methods This survey study was approved by the Ethic Committee of Wuhan General Hospital of Guangzhou Military Command and written informed consent was obtained from each subject before the relative medial examination. Seventy-two matrilineal relatives from a family with LHON were collected for a pedigree analysis and mutation screening. Regular eye examination was performed on 11 patients, 13 mutant gene carriers and 49 individuals with normal phenotype,and the degree of visual damage was graded as follows： 〉0.3 was normal,0. 1-0.3 was mild damage, 〈0.05-0. 1 was moderate damage,〈0.02-0.05 was severe damage and 〈0.01 was very severe damage. Clinical characteristics of LHON was evaluated, The periphery blood sample of 2 -4 ml was colleeted from individuals to separate the mononuclear cells,and the mtDNA was extracted by modified high salt method. MtDNA was amplified by PCR and the mutation loci was sequenced. Results PCR amplification product sequencing of mutant gene showed that both G11778A and T14502C mutations were detected in 24 of 72 matrilineal relatives,but only 11 of 24 carriers developed LHON. No abnormal clinical findings were seen in the 13 carriers, showing a less 50% penetranee in this family. There was no G11778A or/and T14502C mutation in the normal phenotype individuals of this family. The onset age for vision impairment in 11 affected matrilineal relatives varied fi＇om 8 to 50 years old,with the mean age of 24.36 years old,showing a significantly lower age than that of the 13 carriers（5-72 years old ,mean 40.38 years old） （t=2. 102, P=0. 049）. Conclusions This study suggests that the G11778A and T14502C mutation in mitochondrial DNA is one of causes in the development of LHON. The primary GlI778A mutation together with T14502C mutation in mtDNA is a factor for the occurrence of LHON, but it is not sufficient to the development of LIAON. An effective ＂second hit＂ process will play an inducing role for LHON.