全面性癫痫伴热性惊厥附加症家系致病基因的连锁定位和突变分析

目的 筛查中国全面性癫痫伴热性惊厥附加症(GEFS+)家系的致病基因.方法 采集2个GEFS+家系所有成员的外周静脉血提取基因组DNA,选取GEFS+的候选基因(SCN1B、SCN1A、SCN2A和GABRG2)附近10个微卫星位点用于遗传连锁分析,连锁分析所用的软件为LINKAGE软件包5.1版,根据两点间的LOD值判断连锁关系,以确定两家系致病基因的大致位置.限定性定位后筛选候选致病基因,并对家系所有成员进行候选基因突变分析.结果 标记SCN1A、SCN2A和SCN1B基因的多个微卫星位点在两家系患者中均没有共享等位基因,基本排除两家系与上述3个基因连锁可能.田氏家系在标记GABRG2基因的微卫星位点D5S820、D5S422和D5S1403均有共享等位基因.经两点间连锁分析,在外显率为70%,重组率为0时,D5S820、D5S422和D5S1403处的LOD值分别为0.67,1.00和0.79,提示可能有连锁关系.邸氏家系仅在标记GABRG2基因的微卫星位点D5S1403有共享等位基因.对两家系GABRG2基因9个外显子测序结果 显示,第5号外显子出现一个单核苷酸同义多态位点(c.588C>T),第3号外显子出现一个单核苷酸多态位点(c.604C>T),第7号外显子的非编码区出现一个单核苷酸多态位点,为G/A杂合性改变,未发现GABRG2基因致病突变.结论 我国新发现的两个GEFS+家系的致病基因与目前已知候选基因SCN1B、SCN1A、SCN2A和GABRG2无关.GEFS+家系的常见致病基因仍不清楚.

Linkage location and mutation analysis of generalized epilepsy with febrile seizures plus

Objective To study the etiologic genes of generalized epilepsy with febrile seizure plus (GEFS+). Methods Peripheral blood samples were collected from 25 persons of 2 families, including 2 probands. DNA was extracted from the peripheral blood leukocytes using phenol-chloroform method. Ten microsatellite markers spanning the critical regions of SCN1B, SCN1A, SCN2A, and GABRG2 genes were genotyped for linkage analysis by the software LINKAGE v5.1. The two-point linkage relation was determined by LOD score definiing the approximate position of etiologic genes of the 2 GEFS+families. Mutation analysis of the candidate etiologic genes in all members of these 2 families was performed. Results No sharing allele was discovered among the several microsatellite markers flanking SCN1A, SCN2A, and SCN1B genes, and the involvement of these genes in these 2 families could be excluded. In the family named Tian, sharing alleles were discovered among the markers D5S820, D5S422, and D5S1403 flanking GABRG2 gene. The two-point LOD scores at θ=0 were 0.67,1.0, and 0.79 for the marker D5S820, D5S422, and D5S1403, thus indicating possible linkage. In the family named Di, sharing allele was discovered only in the marker D5S1403 flanking the GABRG2 gene. Sequence analysis was performed for nine exons of the GABRG2 gene in these 2 families. Three single nucleotide variations were discovered on the exon 5 (c.588 C>T) , exon 3 (c.604 C>T) , and noncoding region of the exon 7. No mutation change of the GABRG2 gene was observed in these 2 families. Conclusion No evidence supports the causal relation between the SCN1B, SCN1A, SCN2A, and GABRG2 mutation and the etiologic genes in the two families with GEFS+. It is still not clear what is the common etiologic genes of GEFS+.