Dravet综合征患者电压依赖性钠通道α1亚基基因5’-非翻译区外显子的遗传变异

Genetic analysis of 5＇-untranslated region of voltage-gated sodium channel alpha 1-subunit gene in Dravet syndrome

目的筛查Dravet综合征患者的电压依赖性钠通道α1亚基（voltage—gated sodium channel α1—subunit，SCN1A）基因5’-非翻译区外显子突变位点，分析并预测其致病易患性。方法收集24例Dravet综合征患者的外周血，抽提基因组DNA，采用直接测序法进行SCN1A基因5’-非翻译区外显子突变位点的筛查；用生物信息学方法分析SCN1A基因5’-非翻译区外显子变异位点邻近序列的保守性及潜在的转录因子结合元件，推测其致病易患性。结果发现位于外显子h2u上的突变位点166．642．520G〉A，先证者1为新生突变，而先证者2的突变来自临床表型正常的母亲，该突变位点在100名健康对照者中均未发现。突变位点在哺乳动物中呈中度保守（62．5％），人与其他哺乳动物之间在突变位点邻近序列的平均同源率高达88．5％；166．642．520野生型位点的序列上预测得到一种转录因子结合元件，而突变型位点的序列上预测得到两种转录因子结合元件。结论突变位点166．642．520G〉A与Dravet综合征存在一定程度的相关性，其致病机制有待于进一步实验证实。

Objective To screen and analyze nucleotide variants in 5＇-untranslated region （5＇- UTR） in voltage-gated sodium channel α1-subunit gene （SCN1A） in patients with Dravet syndrome and to evaluate the association of the variants with disease. Methods Peripheral blood of 24 patients with Dravet syndrome and 100 unrelated normal persons were collected and genomic DNA was extracted. PCR- sequencing of SCN1A 5＇-UTR in these DNA was performed. To evaluate the possibility of mutation inducing disease, bioinformaties analysis was applied to analyze the conservation of the sequences around the mutation site and predict the potential transcription elements. Results The nueleotide variant of 166. 642.520G→A in exon 2 was identified in two patients, but not in normal controls. The mutation was a de novo mutation in a patient with early-onset. In the second proband, the mutation was also carried by his clinically asymptomatic mother. The nucleotide site 166. 642.520 was moderately conserved in mammals （62.5%）. The average nucleotide identity rate between human and other mammals species in the region adjacent to 166. 642. 520 was 88.5%. Two potential transcription regulatory elements were predicted on the sequence with the mutation of 166. 642. 520G 〉 A, and only one on the sequence with wild-type. Conclusions The mutation 166. 642. 520G 〉 A may be associated with Dravet syndrome and further studied should be performed to verify it and demonstrate its pathogenic mechanisms.