Studies of Somatic Mutation Frequencies and Spectra with a Sensitive and Efficient Detection Method by Using Transgenic Mice.

我们已经开发了一个转基因系统，检测体细胞突变，在体内使用大肠杆菌rpsL基因作为一个积极的选择标记。除了pML 4穿梭载体之外，还将新构建的pSSW引入小鼠中。结果：1）背景突变频率降低到1 × 10 ~（-1）<-5>; 2）检测效率提高3倍; 3）甲基化穿梭载体在大肠杆菌中得到拯救; 4）突变模式在两种穿梭系统之间是不可区分的。诱变剂，即，到目前为止，MNU、MeIQx、AOM、AFBI和Trp-P-2已被检测。同时研究了叶绿素和表没食子酸没食子酸酯的抗突变作用。在大肠杆菌系统中，根据宿主的突变体和/或rpsL基因中的热点序列，广泛分析了rpsL的致突变性。除了MutaMouse和BigBlue外，还使用gpt和cII转基因小鼠与新开发的阳性选择系统进行了比较。在小鼠和果蝇中发现了延迟辐射效应，这是未来研究的候选系统。从pML 4-或pSSW-转基因小鼠与XPA或MLH 1基因缺陷小鼠的交配中获得后代。突变谱研究表明，有可能区分致突变性效应和给药药物的细胞毒性效应。

We have developed a transgenic system to detect somatic mutations in vivo by using the E.coli rpsL gene as a positively selectable marker. In addition to the pML4 shuttle vector, a newly constructed pSSW was also introduced into mice. As results ; 1) the background mutant frequency was reduced to 1x10^<-5>,2) the efficiency of the detection increased 3-fold, 3) methylated shuttle vectors were rescued in E.coli, 4) the mode of mutations was the indistinguishable between two shuttle systems. Mutagens, i.e., MNU,MeIQx, AOM,AFBI and Trp-P-2 were examined so far. Effects of antimutagenicity of chlorophirin and EGCG were also studied. The mutagenicity of rpsL was extensively analyzed in the E.coli system in terms of mutators of hosts and/or hot spot sequences in the rpsL gene. The comparison was made with newly developed positive selection systems with the gpt and cII transgenic mice in addition to MutaMouse and BigBlue. The delayd radiation effects were recognized in mice as well as Drosophila, which are the candidate systems for the future research. Progenies were obtained from the mating of pML4-or pSSW-transgenic mice to the mice deficient for the XPA or MLH1 gene. The mutation spectra studies suggested the possibility to distinguish the effect of mutagenicity from the effect of cytotoxicity of an administered agent.