Analysis of tissue-specific mutations induced by radiation in HITEC mice

HITEC 小鼠辐射诱导的组织特异性突变分析

• 批准号: 11680561
• 负责人: OOTSUYAMA Akira
• 金额: $ 2.37万
• 依托单位: University of Occupational & Environmental Health
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11680561/
• 关键词: Radiation-induced; gamma-rays; organ-specific; HITEC mouse; transgenic mouse; time course; New HITEC マウス

It is thought that mutations cause various disorders including malformations and cancers. However, relation between mutations and disorders in vivo is difficult to find from in vitro experiments.Therefore, we have studied mutations induced in vivo by radiation with use of a transgenic mouse. We investigated difference in mutation frequencies in the testis, spleen, liver, brain and thymus using the rpsL transgenic mice so called HITEC (Hypersensitive In Vivo Test of Carcinogenisity). Transgenic mouse systems are very useful for the study of in vivo somatic mutations induced by radiations in various mouse organs. We investigated tissue-specific differences of radiation-induced mutagenesis in the mutant frequencies and the kinetics of mutant induction by using the HITEC and p53 (-/-)-HITEC mice. The mice were exposed to a whole-body dose of 5 Gy of ^<137>Cs Gamma-rays, and animals were killed 30, 60, 120 and 180 days later. Then the brain, thymus, liver, spleen, testes of each mouse were removed.Intriguingly, the pattern of change in the mutation frequency with time after irradiation varied for the different organs. In HITEC mice, spontaneous mutation frequencies observed were 5×10^<-5> for testis, 8×10^<-5> for brain, 1.5×10^<-4> for spleen and 6×10^<-5> for liver. When measured 30 to 60 days after irradiation, the mutation frequencies were 2 to 3-fold higher than the control level for the brain and then turned to the spontaneous rate. The frequencies of spontaneous and radiation-induced mutation in the testis were significantly lower than that in other organs. In p53(-/-)-HITEC mice, there were no findings that the accumulation of mutations in any organs.Therefore, the mutation assay system with the rpsL transgene is low in sensitivity but useful for detection of gene mutations in male germ cells after irradiation.

人们认为突变会导致各种疾病，包括畸形和癌症。然而，从体外实验中很难发现体内突变与疾病之间的关系。因此，我们利用转基因小鼠研究了辐射在体内诱导的突变。我们使用rpsL转基因小鼠，即所谓的HITEC (Hypersensitive in Vivo Test of carcinogenity)，研究了睾丸、脾脏、肝脏、大脑和胸腺的突变频率差异。转基因小鼠系统对于研究辐射在小鼠各器官引起的体内体细胞突变具有重要意义。我们利用HITEC和p53 (-/-)-HITEC小鼠研究了辐射诱变在突变频率和突变诱导动力学方面的组织特异性差异。小鼠全身暴露于5gy的^<137>Cs γ射线中，动物在30、60、120和180天后被杀死。然后取出每只小鼠的大脑、胸腺、肝脏、脾脏、睾丸。有趣的是，照射后不同器官的突变频率随时间的变化模式不同。在HITEC小鼠中，观察到的自发突变频率为睾丸5×10^<-5>，大脑8×10^<-5>，脾脏1.5×10^<-4>和肝脏6×10^<-5>。照射后30 ~ 60天测量，突变频率比对照水平高2 ~ 3倍，然后转向自发率。睾丸自发和辐射诱发突变的频率明显低于其他器官。在p53(-/-)- hitec小鼠中，没有发现任何器官的突变积累。因此，rpsL转基因突变检测系统灵敏度较低，但可用于检测辐照后男性生殖细胞的基因突变。