AMOLECULAR BIOLOGICAL STUDY FOR THE SPONTANEOUSLY EPILEPTIC RATS

采用定位克隆的方法研究了自发性癫痫大鼠癫痫海绵状脑病（epilepsy with spongiform encephalopathy，SE）的致病基因震颤（tremor，TM）和震颤（zitter，TM）突变基因（SER）。遗传连锁分析表明，TM和ZI基因紧密连锁的突触泡蛋白-2（SYB 2）基因，编码一个完整的膜蛋白在突触囊泡，在10号染色体上，和朊病毒蛋白（PRNP）基因，编码朊病毒疾病的关键膜分子，在3号染色体上，分别使他们的候选人的突变基因。TRM大鼠品系SYB 2基因的基因组DNA序列（TM的纯合子）和ZI大鼠品系的PRNP基因的外显子2此外，在TRM、ZI和WTC脑的北方印迹分析中，没有检测到SYB 2和PRNP基因表达的差异，提示SYB 2和PRNP基因分别不是TM和ZI。尽管有这一发现，我们希望保留这两个基因作为候选基因，因为SYB 2和PRNP基因的生物学功能尚未完全了解。将TM和ZI基因定位于大鼠染色体10 q24和3q 35将是克隆TM和ZI基因的第一步。

A positional cloning approach is taken for the study of tremor (TM) and zitter (ZI) mutant genes, causative genes for epilepsy with spongiform encephalopathy in spontaneously epileptic rat (SER, a homozygote for zitter (ZI) and tremor (TM) mutant genes). Genetic linkage analysys revealed that the TM and ZI genes were tightly linked to the synaptobrevin-2 (SYB2) gene, coding an integral membrane protein in synaptic vesicles, on chromosome 10, and the prion protein (PRNP) gene, coding a key membrane molecule of prion diseases, on chromosome 3, respectively, making them candidates for the mutant genes. The genomic DNA sequence of the SYB2 gene of the TRM rat strain (homozygote for the TM) and the exon 2 of the PRNP gene of the ZI rat strain (homozygote for the ZI) were identical to those of a control strain WTC.In addition, no difference was detected for expression of the SYB2 and the PRNP genes on the Northern blot analyzes of TRM, ZI and WTC brain, suggesting that the SYB2 and PRNP genes are not the TM and the ZI, respectively. Despite this finding, we would like to retain the two genes as candidates, since the biological functions of the SYB2 and PRNP genes are not yet perfectly understood. The assignments of the TM and ZI genes to rat chromosome 10q24 and 3q35 will be the first step towards the cloning of the TM and ZI genes.