Dystrophin基因外显子无缺失或重复家系的基因诊断及产前诊断

Genetic diagnosis for a family without exonic deletions and duplications of dystrophin gene

目的对一个Dystrophin基因外显子无缺失或重复家系进行基因诊断及产前诊断。方法首先应用多重连接依赖探针扩增（multiplexligation-dependentprobeamplification，MLPA）技术检测该家系成员Dystrophin基因外显子缺失或重复情况，然后应用PCR_测序技术分析患者及孕妇Dystrophin基因79个外显子编码序列及其碱基突变情况。最后，根据上述检测结果确定该家系Dystrophin基因致病突变并指导其产前诊断。结果MLPA结果显示患者及其家系成员Dystrophin基因外显子未见缺失或重复；PCR-测序结果显示患者Dystrophin基因第70外显子第22位存在无义突变C〉T，使密码子由CGA突变为终止密码子TGA，孕妇及其女儿该位点为杂合突变（C／T）。羊水标本Y染色体性别决定基因阳性，Dystrophin基因外显子未见缺失或重复，第70外显子第22位存在纯合突变（C〉T），且连锁分析显示其继承的母源X染色体与患者相同。结论明确了该家系Dystrophin基因的致病突变，并对其进行了产前基因诊断。

Objective To conduct genetic diagnosis for a family in which no exonic deletions and duplications of the dystrophin gene were detected. Methods Potential exonic deletions and duplications of the dystrophin gene were initially analyzed with using multiplex ligation-dependent probe amplification （MLPA）. Subsequently, all of the 79 exons of the dystrophin gene of the proband and a pregnant woman from the family were analyzed with PCR amplification and DNA sequencing. Following identification of the causative mutation, prenatal diagnosis was provided. Results MLPA analysis had detected no exonic deletions and duplications of the dystrophin gene. Sequence analysis has identified a C〉T mutation on the 22nd nucleotide position of the 70th exon of the dystrophin gene （c. 10108 C〉T）, which has replaced the codon CGA to a stop codon （TGA）. The patient＇s mother and sister were both heterozygous for the same mutation. Upon prenatal diagnosis, the fetus was found to be positive for the Y chromosome sex- determining gene （SRY） and has carried above mutation. The result of short tandem repeat linkage analysis also confirmed that the fetus has inherited the mutant X chromosome. Conclusion The causative mutation of the dystrophin gene has been discovered in an affected family, which has enabled prenatal diagnosis of the disease.