二例甲基丙二酸血症患儿基因突变分析并中国人群MMACHC基因c.609G>A突变频率检测

Mutations analysis of two children with methylmalonic acidemia and detection of frequency of MMACHC gene mutation c.609G>A in Chinese population

目的对2例合并型甲基丙二酸血症患儿进行基因突变和临床表型分析,检测中国人群MMACHC基因c.609G>A突变携带频率,建立这一突变的快速检测方法。方法收集整理患儿临床资料,提取患儿及家属基因组DNA,扩增其MMACHC基因外显子及外显子与内含子交接区序列,进行sanger测序并与正常序列进行比对;利用PCR-RFLP方法检测200例正常儿童MMACHC基因c.609G>A突变携带率。结果在1例患儿MMACHC基因中检测到复合杂合突变:c.80A>G(p.Q27R)和c.609G>A(p.W203X);在另1患儿MMACHC基因中检测到纯合突变c.609G>A(p.W203X)。在200例正常儿童MMACHC基因中未检测到c.609G>A突变,推测中国人群c.609G>A携带频率低于0.5%(1/200)。结论 MMACHC基因c.609G>A突变是合并型MMA的致病性突变,同时也是中国人群热点突变,其所导致的MMA患儿发病较早,病情较重,中国人群中由这一突变引起的合并型MMA的发生率低于1∶40 000(1/200*1/200)。

Objective：To analyze the gene mutations and clinical phenotypes in two cases of children with combined methylmalonic acidemia,and to detect the frequency of c.609G〉A mutation in MMACHC gene in Chinese population,and to establish a rapid detection method for this mutation. Methods：The clinical data of the children were collected,and the genomic DNA of the children and their families was extracted. The sequences of exons of MMACHC gene and the junctions of the exons and introns were amplified and sequenced directly,the results were compared with normal sequences. PCR-RFLP method was used to detect the carrying rate of the MMACHC gene mutation c.609G〉A in 200 normal children. Results：Compound heterozygous MMACHC mutations were detected in one case：c.80 AG（p.Q27 R）and c.609G〉A（p.W203 X）;homozygous MMACHC mutations were detected in the other patient. c.609G〉A（p.W203 X）. c.609G〉A was not detected in the MMACHC gene of 200 normal children. It is speculated that the frequency of c.609G〉A in Chinese population is less than 0.5%（1/200）. Conclusion：The MMACHC gene mutation c.609G〉A is pathogenic mutation of combined MMA,and it is also a hot spot mutation in the Chinese population,MMA caused by this mutation has an earlier onset and is in a more severe condition,and its morbidity is less than 1∶40 000（1/200＊1/200）.