Leber's hereditary optic neuropathy--the spectrum of mitochondrial DNA mutations in Chinese patients

PURPOSE: To investigate the spectrum of mitochondrial DNA (mtDNA) mutations in Chinese patients with Leber's hereditary optic neuropathy (LHON), optic atrophy of unknown etiology, and optic neuropathy of known etiology. METHODS: Twenty-seven patients from 25 LHON pedigrees, 22 patients with bilateral optic atrophy of unknown etiology, 21 patients with optic neuropathy of known etiology, and 25 normal healthy controls were included in this study. Twelve pairs of primers that covered the 21 reported mtDNA mutations were utilized. Single-strand conformation polymorphism analysis and DNA sequencing were used to detect base substitutions in mtDNA. RESULTS: Twenty-three LHON pedigrees (92%) had the 11778 mtDNA primary mutation. Two pedigrees (8%) had the 14484 mutation. No 3460 mutations were detected in this group. Thirteen other sequence changes were found in these patients, but only the 4216 mutation had been reported previously. Thirteen pedigrees had multi-mutation patterns consisting of one primary mutation together with other sequence changes. No primary mutations were found in patients with optic atrophy of unknown etiology or in patients with optic neuropathy of known etiology. CONCLUSIONS: High frequency of 11778 mtDNA mutation was found in Chinese patients with LHON. No specific multi-mutation pattern such as the European mtDNA haplogroup J was found.     

中国人Leber遗传性视神经病变线粒体DNA突变频谱

目的 分析中国人Leber遗传性视神经病变（Leber′s hereditary optic neuropathy, LHON）线粒体DNA（mitochondrial DNA, mtDNA）3个原发致病基因突变的频谱及其遗传特征。 方法 分别用突变特异性引物聚合酶链反应(mutation-specific priming polymerase chain reaction, MSP-PCR)、异源双链-单链构象多态性（heteroduplex-single strand conformation polymorphism polymerase chain reaction,HA-SSCP ） 、限制性片段长度多态性(restriction fragment length polymorphisms,RFLP)和DNA测序等方法,对140个LHON家系的先证者（男120人,女20人）进行mtDNA 3个原发致病突变位点,即G11778A、G3460A和T14484C的检测,并对这些患者的家系进行遗传分析。 结果 在140例LHON 先证者中,130例（男113人,女17人）为G11778A位点突变,占92.9%;2例（男、女各1人）为G3460A位点突变,占1.4％;8例（男6人,女2人）为T14484C位点突变,占5.7%。 结论 中国人LHON患者mtDNA 3个原发致病突变中,以G11778A位点突变为主,少数为G3460A 和T14484C位点的突变。（中华眼底病杂志,2003,19：269-332）     

Increase of mitochondrial DNA in blood cells of patients with Leber's hereditary optic neuropathy with 11778 mutation

AIMS: To investigate the change of mitochondrial DNA (mtDNA) content in Leber's hereditary optic neuropathy (LHON) with 11778 mutation. METHODS: Mitochondrial DNA content in 27 LHON patients with 11778 mutation, 26 asymptomatic maternal relatives, and 23 normal controls was measured using a competitive polymerase chain reaction (PCR) method. RESULTS: The mean relative content of mtDNA (with respect to the beta actin gene) in LHON patients, asymptomatic maternal relatives, and normal controls was 245.5 (162.3), 238.2 (118.4), and 156.5 (61.6), respectively. There was a statistically significant difference between patients and controls and between relatives and controls. However, no statistically significant difference between patients and unaffected relatives was found. There was no statistically significant difference in the relative content of mtDNA between all males and females carrying 11778 mtDNA mutation CONCLUSION: The results suggest that the increase in mtDNA content in LHON patients with 11778 mtDNA mutation may be due to a compensatory effect for respiratory chain defects of mitochondria. However, the increase of mtDNA content is the result rather than the cause of defective mtDNA. It still cannot explain the pathogenesis of LHON.     

Mitochondrial DNA mutation in Leber's hereditary optic neuropathy.

Leber's hereditary optic neuropathy (LHON) causes acute or subacute central visual loss in healthy young males. Recently, it has been thought to be caused by a single nucleotide change in the ND4 gene in the mitochondrial genome. Mitochondrial DNA (mtDNA) of leukocytes and hair follicle cells from five patients in four families with LHON and nine relatives were analyzed by Sfa NI and Mae III enzyme digestion and DNA sequencing. Loss of Sfa NI site was found in all patients and maternal lineages but not in nonmaternal lineages and normal controls. Mae III digested all the mtDNAs that lost the Sfa NI site. The restriction fragment pattern of polymerase chain reaction (PCR) products exhibited mtDNA heteroplasmy in the hair follicle cells but not in blood cells of the proband in one family. Direct sequencing of PCR-amplified mtDNA fragments encompassing the ND4 gene of the patients disclosed a transition from guanine to adenine at nucleotide position 11778. These results confirm previous reports that a G to A point mutation is associated with LHON and that tissue variability and heteroplasmy of mtDNA exist in some, but not all, LHON patients.     

全血样等位基因特异性聚合酶链反应法筛查Leber遗传性视神经病变线粒体DNA G11778A位点突变

目的建立全血样等位基因特异性聚合酶链反应(PCR)法快速筛查Leber遗传性视神经病变(LHON)患者线粒体DNA G11778A位点突变。方法采用直接以全血样为模板的等位基因特异性PCR法检测14例阳性对照和10例阴性对照血样。同时对22例血样进行双盲检测。 结果24份对照血样检测结果表明该方法的准确率为100%,而且以全血样为模板的PCR特异性优于以纯化DNA为模板的。双盲检测22例血样发现7例阳性结果和15例阴性结果,与预期结果相一致。结论该方法简便、快速、准确、经济,非常适合临床基因诊断线粒体DNA G11778A位点突变的LHON患者,具有重要的临床推广应用价值。     

Segregation patterns and heteroplasmy prevalence in Leber's hereditary optic neuropathy

PURPOSE. To investigate the segregation pattern of the mitochondrial DNA mutation at nucleotide position 3460 responsible for Leber's hereditary optic neuropathy (LHON) and to determine the prevalence of heteroplasmy for the three primary LHON mutations at positions 11778, 3460, and 14484. METHODS. Segregation analysis was performed in a cross-sectional study by determining the level of heteroplasmy in blood leukocytes of 23 LHON patients and unaffected carriers from four unrelated families. One family comprising two affected and three unaffected carriers was followed over 5.5 years for a longitudinal segregation analysis of heteroplasmy. The percentage of mutant mtDNA was determined using a novel procedure of fluorescence-based primer extension and restriction fragment length polymorphism analysis. The prevalence of heteroplasmy was assessed by determining the number of genealogically unrelated LHON pedigrees with heteroplasmic maternal family members from the LHON patient records of the Department of Ophthalmology, University of Tübingen, Germany. RESULTS. The authors observed a marked variability in the degree of heteroplasmy levels within each pedigree and a tendency toward a higher mutant allele frequency in offspring generations. Disease expression was correlated with higher levels of mutant mtDNA molecules. Longitudinal analysis revealed no statistically significant decrease in the heteroplasmy level in the family studied but a reduction of 11% and 12% in one affected and one unaffected individual, respectively. In 167 genealogically unrelated LHON families the prevalence of heteroplasmy was 5.6%, 40%, and 36.4% for the 11778, 3460, and 14484 LHON mutations, respectively. CONCLUSIONS. Cross-sectional studies of heteroplasmy for the 3460 LHON mutation suggest that the genotype shifts toward a higher mutational load in offspring generations. Long-term decrease in the blood mutant load in single cases indicates negative selection of the mutant allele in the hematopoietic cell system. The prevalence of heteroplasmy varies significantly between the different primary LHON mutations, suggesting genotypical differences in disease expression.     

Analysis of Mitochondrial Gene Mutations in Chinese Pedigrees of Leber''s Hereditary Optic Neuropathy

PURPOSE: To investigate the frequency of common pathogenic primary mitochondrial DNA mutations in Leber's hereditary optic neuropathy (LHON) families. METHODS: Polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and DNA sequencing were used to detect mitochondrial DNA mutations. Sixty-six Chinese examiners from 15 families, including 22 visual affected and their 44 unaffected maternal relatives, underwent molecular genetic evaluation. Eleven normal individuals underwent evaluation as control. RESULTS: Of the 15 families with suspicion of LHON, 13 had nucleotide position (nt) G11778A mutations, 2 had nt T14484C mutations. All examiners had nt G11719A mutations. CONCLUSIONS: The mutations at nucleotides 11778 and 14484 are primary LHON mutations. Molecular genetic findings suggest that the silent mutation at nt G11719A may be a common genetic polymorphism in Chinese.     

中国人Leber遗传性视神经病变线粒体DNA突变的主要类型和临床特征

目的 探讨国人Leber遗传性视神经病变（LHON）患者线粒体DNA(mtDNA)突变的主要类型和临床特征。 方法 对来自117个家系的119例双眼视神经疾病患者分2组进行基因检测，A组37例为临床确诊LHON患者，B组82例属可疑LHON患者。2组均采用单链构像多态分析，采用突变特异性引物多聚酶链反应确定11778位点, 采用序列分析法确定3 460及14484位点。对检测结果为11778位点突变的LHON患者，收集其病史和临床资料。 结果 A组中11778位点突变和14484位点突变者分别为33例（89.2%）和3例（8.1%），B组中仅有26例（31.7%）11778位点突变者。2组均未检测到3460位点突变者；所有11778位点突变者均有特征性临床表现：中心视力急性或缓慢下降，不伴眼球疼痛，多在10～25岁发病，视野检查 结果显示中心或旁中心暗点等，视力恢复率为8.6%～11.6%。 结论 我国LHON患者中11778位点突变率高，临床特征与白种人11778位点突变LHON患者相似。 （中华眼底病杂志，2004，20：78-80）     

Clinical Analysis of Leber＇s Hereditary Optic Neuropathy Harboring mtDNA Mutation at nt11778

Purpose: To improve our diagnostic technique through the analysis of clinical features of Leber‘s hereditalw optic neuropathy (LHON) harboring mtDNA point mutation at nt11778. Methods: Detection of nt11778 mutation was performed on 38 patients clinically diagnosed as LHON in our ophthalmic center from year 1998 to 2000. Circumstances of onset and family history were obtained and ophthalmoscopy, fundus fluorescein angiography, visual field and visual evoked potential were performed on all 38 patients. Result: 30 In 38 patients (78.95 % ) harbor nt11778 mutation, including 28 male (93.33%) and 2 female (6.67%). The ratio of affected male to female is 14: 1. Patients harboring nt11778 mutation display typical clinical manifestations. Cenelusion: Identification of one of the three LHON specifically associated mtDNA mutations is essential to confirm the diagnosis. Eye Science 2001: 17: 31 - 34.     

Clinical Analysis of Leber''''s Hereditary Optic Neuropathy Harboring mtDNA Mutation at ntl1778

Purpose: To improve our diagnostic technique through the analysis of clinical features of Leber's hereditary optic neuropathy (LHON) harboring mtDNA point mutation at nt11778.Methods: Detection of nt11778 mutation was performed on 38 patients clinically diagnosed as LHON in our ophthalmic center from year 1998 to 2000. Circumstances of onset and family history were obtained and ophthalmoscopy, fundus fluorescem angiography, visual field and visual evoked potential were performed on all 38 patients. Result: 30 In 38 patients (78.95 % ) harbor nt11778 mutation, including 28 male (93. 33 % ) and 2 female (6. 67 % ) . The ratio of affected male to female is 14 : 1. Patients harboring nt11778 mutation display typical clinical manifestations. Conclusion: Identification of one of the three LHON specifically associated mtDNA mutations is essential to confirm the diagnosis.