Isolation of the Gene for Progressive Myoclonus Epilepsy (EPM1)

Unverricht-Lundborg型进行性肌阵挛癫痫（EPM 1）是一种常染色体隐性遗传疾病，以严重的刺激敏感性肌阵挛和全身强直阵挛发作为特征。通过遗传连锁分析，EPM 1基因定位于人类染色体21q22.3。通过连锁不平衡分析，EPM 1基因的定位已进一步缩小到D21 S25、PFKL和D21 S154位点周围0.3 cM或更小的区域。为了分离该疾病的致病基因，我们首先尝试在该候选区域构建YAC重叠群。对21号染色体特异性的CEPH YAC文库的筛选显示，该区域在YAC中似乎是不可克隆的或非常不稳定的。然后，我们筛选了21号染色体特异性KU 21 D粘粒文库（6个基因组当量）和人基因组BAC文库（平均插入大小110 kb：3个基因组当量），这两个文库都是在我们的实验室中构建的。因此，我们使用17个BAC和98个粘粒克隆构建了覆盖标记D21 S1458-D21 S25-PFKL-D21 S154-D21 S171的1.2Mb的粘粒重叠群。这些有序的克隆被用来执行外显子捕获，我们分离出的候选基因EPM 1，包括KNP 1，KNP 3，和KNP 4基因。

The progressive myoclonus epilepsy of Unverricht-Lundborg type (EPM1) is an autosomal recessive disorder characterized by severe stimulus-sensitive myoclonus and generalized tonic-clonic seizures. The EPM1 gene has been mapped to human chromosome 21q22.3 by genetic linkage analysis. With linkage disequilibrium analysis, the localization of the EPM1 gene has been further narrowed to a 0.3-cM or smaller region around loci D21S25, PFKL,and D21S154. In order to isolate the pathogenic gene for this disease, we first attempted to construct a YAC contig in this candidate region. Screening of a chromosome 21-Specific ordered CEPH YAC library revealed that this region seems unclonable or very unstable in YACs. We then screened for a chromosome 21-specific KU21D cosmid library (6 genome equivalents) and a human genomic BAC library (average insert size 110 kb : 3 genome equivalents) both of which have been constructed in our laboratory. As a result, we have constructed a cosmid contig of 1.2 Mb covering markers D21S1458-D21S25-PFKL-D21S154-D21S171 using 17BAC and 98 cosmid clones. These ordered clones were used to perform exon trapping and we isolated candidate genes for EPM1, including KNP1, KNP3, and KNP4 genes.