Development of the gene deletion model rats by random mutagenesis

用苯丁酸氮芥随机诱变，以产生一些新的突变大鼠。为了确定苯丁酸氮芥的最佳剂量和诱变的最佳交配时间，我们计数了用几个剂量的苯丁酸氮芥给药的雌性大鼠与雄性大鼠交配所生的新生大鼠的数量。因此，很明显，苯丁酸氮芥每公斤体重5毫克至15毫克之间是良好的药物，并且在苯丁酸氮芥药物治疗后三周至六周之间进行交配是良好的。雌性（G1代）大鼠是通过给药10 mg苯丁酸氮芥的BN品系雄性大鼠与正常F344雌性大鼠杂交获得的。这只雌鼠有受孕的能力。将雌性大鼠（G2代）与雄性大鼠（G3代）杂交获得雄性大鼠（G3代）。然后，我们将这些大鼠杂交，获得了6只大鼠。当这6只大鼠饲养约一年时，其中一只患皮肤癌，另一只出现糖尿病症状。推测这些大鼠是某些基因发生突变的突变体。此外，还观察到了体型约为正常大鼠30%的侏儒大鼠。在几乎所有的情况下，侏儒大鼠在断奶前死亡，但少数侏儒大鼠生长到成年。虽然成年侏儒鼠能够受孕，但它们同样通过与正常大鼠交配而生下一些侏儒鼠。为了确认发生了哪种基因突变，使用DNA微阵列对G5代大鼠进行基因表达分析。因此，证明至少有十种基因在G5大鼠中没有表达。推测这些基因的表达被每个基因中的缺失型突变所抑制。

Random mutagenesis with chlorambucil was performed in order to produce some new mutant rats. To identify the optimal quantity of chlorambucil and the optimal mating time for mutagenesis, we counted the number of new born rats born from female rats mated with the male rat medicated with several dose of chlorambucil. Consequently, it became clear that between 5mg and 15mg per kg weight of chlorambucil are good for medication, and it is good to perform mating between three weeks and six weeks after the medication of chlorambucil. The female (G1 generation) rat was obtained as a result of crossing between the male rat of BN strain medicated with 10mg chlorambucil and a normal F344 female rat. This female rat has the capability to conceive. A male rat (G3 generation) was obtained from a cross the female rat (G2 generation) with the male rat (G3 generation). Then we crossed these rats and obtained six rats. When these six rats were bred for about one year, one of the rats had skin cancer and another one showed diabetes symptom. It was presumed that these rats are the mutants by which mutation was occurred in some genes. In addition, the dwarfish rat whose size of the body is about 30% of a normal rat was also observed. In almost all cases, the dwarfish rats died before weaning, but a few dwarfish rats grew to the adult. Although the adult dwarfish rats was able to be conceived, they born some dwarfish rats by mating with a normal rat similarly. In order to confirm to which gene mutation has happened, gene expression analysis was performed for the G5 generation rats using DNA microarray. Consequently, it was proved that at least ten kinds of genes was not expressed in the G5 rats. These genes were presumed that the expression of these genes was suppressed by deletion type of mutation in each genes.