良性家族性婴儿惊厥一家系基因定位及钾离子通道基因测序研究

Linkage mapping of benign familial infantile convulsions (BFIC) and sequencing analysis of KCNQ2 gene in a BFIC family

目的 对一良性家族性婴儿惊厥家系进行基因定位 ,并对候选基因钾离子通道基因KCNQ2进行测序分析。方法 共抽取 14例血样 ,包括全部 9例患者。同时对家系全部成员行脑电图、全身及神经系统检查。在 19qD19S2 4 5至D19S2 5 0间选择 6对微卫星标记 ,在 2 0q13 3区域选择4对微卫星标记及另一良性家族性新生儿惊厥 (BFNC)位点 8q2 4选择 2对微卫星标记进行连锁分析。KCNQ2基因外显子测序引物序列采用Biervert等所报道的序列。结果 该家系两点间连锁结果排除了与 19q及 8q2 4连锁的可能。在 2 0q13 3(D2 0S4 80 )最大LOD值为 0 6 0 (外显率 90 % )。染色体单体型分析提示可能与 2 0q13 3连锁。KCNQ2基因测序发现外显子 6有一C/T杂合突变多态性 ,外显子17有 1个A/C错义多态性 ,内含子 14有一 4个碱基插入多态性。结论 该家系的连锁结果排除了与19q的连锁可能 ,提示BFIC的遗传多态性。该家系所发现的多态性变化对其他癫家系的连锁分析及其他癫综合征分子遗传学机制的研究 。

Objective Benign familial infantile convulsions (BFIC) is an autosomal dominant epileptic disorder with onset at age 3 to 12 months and a favorable outcome This syndrome was described by Vigevano et al as an autosomal dominant disorder occurring in families of Italian ancestry Guipponi et al mapped the BFIC gene to chromosome 19 by linkage analysis We performed a linkage analysis at the BFIC locus of 19q and screened linkage analysis at other epileptic syndromes loci We also performed sequencing on candidate genes in linkage region for finding out mutation Methods Fourteen blood samples were collected from all the 9 affected members of this family At the same time EEG recordering, physical and neurological examination were performed for every family member Six microsatellite markers of 19q were selected between D19S245 and D19S250; 4 microsatellite markers from 20q13 3 and 2 linkage markers from 8q24 were chosen according to BFNC loci Primers sequences reported by Biervert et al were utilized for KCNQ2 exon intron boundaries amplification Results The results of 2 point linkage analysis of 19q from this family suggested that this BFIC family is not linked to 19q and 8q24 At 20q13 3 we obtained a maximum LOD score of 0 6 at D20S480 with penetrance of 90% Haplotype analysis supported a possibly linkage region at 20q13 3 The results of candidate gene KCNQ2 sequencing analysis showed that there was a C/T polymorphism in exon 6, an A/C polymorphism in exon 17 and 4bp insertion polymorphism in intron 14 Conclusion This BFIC family is different from the reported families and has not linkage to 19q, which suggested genetics heterogeneity of BFIC The polymorphic findings from this family will be very helpful to do linkage analysis of other epileptic families and to understand molecular genetic background of other epileptic syndrome