慢性进行性眼外肌瘫痪和Kearns-Sayre综合征的线粒体DNA突变分析

目的 探讨慢性进行性眼外肌瘫痪(chronic progressive external ophthalmoplegia，CPEO)和Kearns-Sayre综合征(Kearns—Sayre syndrome，KSS)的线粒体DINA(mitochondrial DNA，mtDNA)突变特点。方法 用Southern印迹方法检测7例CPEO和4例KSS患者的肌肉组织mtDNA，并进一步用聚合酶链反应产物直接测序来明确缺失的具体范围；用聚合酶链反应-限制性内切酶分析法检测有无mtDNA A3243G点突变。结果 发现5例患者(2例CPEO和3例KSS)存在mtDNA的大片段缺失；1例KSS患者存在A3243G点突变。5例大片段缺失的大小及缺失范围各不相同，从3．0～8．0kb不等，缺失型mtDNA占总mtDNA的比例为37．6％～87．0％。聚合酶链反应产物测序表明这5例缺失类型均未见文献报道。结论 与CPEO和KSS患者相关的最常见的mtDNA突变为大片段缺失，A3243G点突变也可在少数患者中检测到。

Mitochondrial DNA mutations in patients with chronic progressive external ophthalmoplegia and Kearns-Sayre syndrome

OBJECTIVE: Kearns-Sayre syndrome (KSS) and chronic progressive external ophthalmoplegia (CPEO) belong to neurological diseases caused by a defect in the energy-producing system of mitochondria, and are known to be associated with a deletion in the mitochondrial genome. This study was aimed to understand with greater clearness the characteristics of mitochondrial DNA (mtDNA) mutations in 11 Chinese patients with CPEO (7 cases) or KSS (4 cases). METHODS: Densitometry of the bands on Southern blot, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and sequencing were performed to search large scale deletions and A3243G point mutation in patients' muscle mtDNA. RESULTS: Large deletions in mtDNA were detected in 2 CPEO and 3 KSS patients, the size of deletion ranged from 3.0 kb to 8.0 kb. Moreover, mtDNA A3243G point mutation was identified in 1 KSS patient. The proportion of mutant mtDNA was 37.6%-87.0%. Direct sequencing of the PCR products revealed 5 novel large deletions not reported by others. CONCLUSION: The findings in this study being consistent with the reports by others, large scale deletions of mtDNA are frequently found in Chinese patients with KSS and CPEO. mtDNA A3243G mutation may also exist in some patients with KSS and CPEO.