Mutation burst by conflict of two mouse subspecies genomes

我们进行了两个实验来阐明在两个小鼠亚种之间重组MHC单倍型小鼠中诱导高频自发突变（重组诱导突变：Rim）的机制。首先，我们尝试利用mhc重组小鼠的精子dna，通过基于聚合酶链反应（pcr）监测Rim型突变，检测与Rim相似的基因组改变。因此，我们无法通过这种方法观察到预期的pcr产物。一种解释这一结果的可能性是，有不同类型的机制诱导Rim。或者，目前的mhc重组小鼠已经失去了产生Rim的活性。其次，我们试图开发一种有效的检测系统来检测单个雄性小鼠的dna双链断裂和随后的重组。为此，我们构建了Prdm9蛋白重组靶DNA序列（已知通过引入Histon3化学修饰作为热点标记确定重组位点）和连接Prdm9靶序列的GFP报告基因组成的DNA构建体。现在我们通过Tol2转座子系统将该结构引入小鼠基因组。

We carried out two experiments to elucidate mechanism by which high-frequency spontaneous mutations(Recombination-induced-mutation : Rim) is induced in mice with recombinant MHC haplotypes between two mouse subspecies. First, we tried to detect genome alterations similar to Rim by PCR-based monitoring of Rim-type mutations using pooled sperm DNAs of intra-MHC recombinant mice. As a result, we could not observe expected PCR-products by this method. One possibility to explain this result is that there are different types of mechanism for induction of Rim. Alternatively, present intra-MHC recombinant mice have lost the activity to give rise to Rim. Second, we tried to develop an efficient assay system to detect DNA-double strand breaks and subsequent recombination for single male mouse. To do this, now we constructed the DNA construct that consists of recombination-target DNA sequence for Prdm9 protein, which is known to determine recombination site by introducing Histon3 chemical modification as hotspot mark, and of GFP reporter connected to the Prdm9 target sequence. Now we are introducing this construct into mouse genome by means of Tol2 transposon system.