良性家族性婴儿惊厥和阵发性运动障碍综合征基因位点异质性:5个家系的研究

背景良性家族性婴儿惊厥(benignfamilial infantile convulsion,BFIC)疾病基因定位研究主要在西方国家进行,尽管现在已经报道了3个染色体位点与疾病基因连锁,但直到目前疾病基因仍未被找到和证实.要最终克隆BFIC疾病基因首先要对BFIC疾病基因进行定位和位点异质性研究.目的研究BFIC家系的疾病基因与BFIC位点的连锁关系并检测是否存在疾病基因位点异质性.设计以5个BFIC家系成员的基因型为研究对象,回顾性观察对比研究.单位一所大学的细胞生物学与医学遗传学研究室.对象本研究于2001-07月/2003-07在郑州大学医学院细胞生物学与医学遗传学教研室完成.共采集5个BFIC家系(图1-5),分别来自河南省新乡、南阳、周口、鹤璧四地区,受试者共70例,其中BFIC患者28例,非BFIC患者42例.纳入标准①符合国际抗癫痫联盟颁布的癫痫发作分类的标准确诊者;排除标准脑电图、脑CT、磁共振检测结果有异常以及有中毒、脑外伤病史者.方法应用聚合酶链反应(PCR)、变性聚丙烯酰胺凝胶电泳和银染技术得到家系成员的基因型.从BFIC家系成员外周血中抽提DNA,选择D19S245,D19S250,D16S3131,D16S3133,D2S399和D2S2330等6个基因短片段重复序列(STR)作为DNA标记,检测家系成员的基因型.将基因型信息输入计算机由LINKAGE软件包中的MLINK程序完成连锁分析边.最后,由LINKAGE软件包中的MLINK程序检测疾病基因位点异质性.主要观察指标家系成员基因型的连锁分析结果和异质性检测结果.结果连锁分析结果显示,在常染色体显性遗传(AD)模式下,标记位点D19S250处,家系2,3,5在重组率为0.000,外显率为90%时,获得最大两点检测限(LOD)值总和为2.151;标记位点D16S3131处,家系2,5在重组率为0.085,外显率为70%,60%时,获得最大两点LOD值分别为1.056,1.155;提示这两个位点与疾病基因可能存在连锁关系.在其它位点处未获得提示连锁关系的信息.异质性检测显示,可能与D16S3131存在连锁关系的家系占39.8%,可能与D19S250存在连锁关系的家系占41.3%,而与这两个标记位点均不存在连锁关系的家系占18.8%.BFIC家系之间存在位点异质性.结论本研究发现了BFIC致病基因可能与D19S250或D16S3131存在连锁关系,BFIC存在位点异质性,从而为精确定位BFIC疾病基因提供了重要信息.

Gene mapping and locus heterogeneity of benign familial infantile convulsion and paroxysmal dyskinesia-study on five Chinese pedigrees

BACKGROUND: Research on mapping the gene for benign familial infantile convulsion(BFIC) has been conducted mainly in western countries. Although three chromosome loci have been found by three research groups, up to now the gene responsible for BFIC has been neither found nor identified. Mapping the gene and studying locus heterogeneity is the first step toward cloning the disease gene.OBJECTIVE: To explore the relation between BFIC loci and the gene for BFIC in five Chinese pedigrees with BFIC. Locus heterogeneity among these pedigrees will be revealed based on the findings so as to further map the gene.DESIGN: Retrospective and observational controlled study using five Chinese pedigrees with BFIC as subjects.SETTING: Laboratory of cell biology and medical genetics in a university.PARTICIPANTS: The study was conducted in the Laboratory of Cell Biology and Medical Genetics of Zhengzhou University from July 2001 to July 2003. Five BFIC pedigrees of 70 subjects, 28 BFIC patients and 42 non-BFIC patients, from Xinxiang, Nanyang, Zhoukou, and Hebi of Henan Province,China, were involved. Inclusion criteria: Those met the epileptic seizure classification criteria issued by the International Anti-epilepsy Commissi6n[2].Exclusion criteria: The patients were excluded from the group of the affected members if any of the three examinations, namely, interictal electroencephalograms, computed-tomography scanning and magnetic-resonance imagining, was abnormal. The same exclusion criteria applied to patients who had suffered either toxicosis or cerebral damage.METHODS: To get the genotypes of these family members, such techniques as polymerase chain reaction, polyacrlamide and agarose gels electrophresis and sliver straining were used. The procedure was as follows: first, DNA was extracted from the peripheral blood of the members of five pedigrees with BFIC. Then, six short tandem repeat(STR) loci, namely, D19S245,D19S250, D16S3131, D16S3133, D2S399 and D2S2330, were used to detect genotype of each family member, followed by input of the genotypes into the computer and linkage analysis by MLINK program from LINKAGE package. Finally, the results of linkage analysis were analyzed by HOMOGM program and locus heterogeneity was obtained.MAIN OUTCOME MEASURES: Analysis results of genotype of each subject and the results of heterogeneity detection.RESULTS: One maximum two-point limit of detection (LOD) score of 2. 151 for D19S250 was obtained at recombination rate of 0. 000 under autosomal dominant model with 90% penetrance. For D16S3131, two maximum two-point LOD scores of 1. 056 and 1. 155 were obtained at recombination rate of 0. 085 under autosomal dominant model with 70% and 60% penetrance. This suggested that the gene for BFIC pedigree might be linked to D16S3131 or D19S250. At the other DNA markers, no information suggested that linkage was produced. The results of heterogeneity detection showed that there was locus heterogeneity among the BFIC pedigrees.CONCLUSION: The gene for BFIC may be linked to D16S3131 or D19S250. Heterogeneity exists in BFIC, which serves as primary information for the further study of mapping the disease gene for BFIC.