Rett综合征患儿2例MECP2基因大片段缺失突变分析

Large deletion of MECP2 gene in two children with Rett syndrome

目的研究Rett综合征患儿2例MECP2基因用常规突变筛查方法未检出异常者是否存在大片段的缺失突变。方法用标准的盐析法从外周血提取基因组DNA,用多重连接依赖的探针扩增法(MLPA)进行突变分析,对存在突变的样本进一步用长片段PCR-DNA直接测序进行验证,同时确定突变在基因组序列中的位置。结果2例典型的Rett综合征患儿发现第四外显子有大片段缺失突变。例1用MLPA方法发现在第四外显子的4d探针位置存在缺失,长片段PCR-DNA直接测序证实在cDNA的第905至1138位之间缺失234个核苷酸,并且插入三个核苷酸(c.905-1138delinsCAC);例2用MLPA方法发现在第四外显子的4d和4a探针位置存在缺失,长片段PCR-DNA直接测序证实在cDNA的第1047至1198位之间缺失152个核苷酸(c.1047-1198del152)。结论对于常规的突变筛查不能检出MECP2有突变的Rett综合征患儿,进一步进行MLPA筛查是必要的。MLPA不仅简便、快速,而且能够发现大片断缺失。

Objective To study the spectrum of mutations of Rett syndrome （RTT） without an identified methyl-CpG binding protein 2 （MECP2） gene mutation by current PCR mediated screening sequence strategies. Methods Genomie DNA was extracted using standard procedures from the peripheral blood leukocytes of each patient. First, multiplex ligation-dependent probe amplification （MLPA） was used for detecting mutations. When the mutations were found, a long-range PCR was employed to confirm them and identify breakpoint locations. Results In case one the 4d probe site was lost by MLPA and 234bp deletion at complementary deoxyribonucleic acid （cDNA） position 905 - 1138 and three nucleotides （CAC） insert by long range-PCR and DNA sequencing. In case two the 4a and 4d probe sites were lost by MLPA and 152 bp deletion at cDNA 1047- 1198 by long range-PCR and DNA sequeneing. Conclusion It is essential to screen the RTT patients by MLPA, whose mutations of MECP2 do not identify using general PCR screening. MLPA is a rapid, simple and robust method to identify the large deletions.