Radiation-induced genomic instability: Delayed mutagenic and cytogenetic effects of X rays and alpha particles
Radiation-induced genomic instability: Delayed mutagenic and cytogenetic effects of X rays and alpha particles
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DOI：
10.2307/3579514
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发表时间：
1997-10-01
影响因子：
3.4
通讯作者：
Vetrovs, H
中科院分区：
文献类型：
--
作者：
Little, JB;Nagasawa, H;Vetrovs, H
在暴露于0-12 Gy X射线或2 Gy a粒子的单细胞中，对中国仓鼠卵巢细胞克隆群体的Hprt位点突变频率进行了测量。在辐照后23倍的446个克隆群体中，约有8-9%的人表现出高频率的晚发突变，突变分数比背景高10(2)-10(4)倍。粒子照射和X照射发生克隆的频率相似，在4-12 Gy范围内，X照射没有明显的剂量依赖性。Hprt突变的分子结构通过对所有9个外显子的多重聚合酶链反应分析确定。在暴露于X射线后直接引起的突变中，75%涉及部分或全部基因缺失。只有19-23%的迟发突变与缺失有关，这些缺失主要是涉及一个或两个外显子的部分缺失。这个光谱与自发产生的突变非常相似。为了确定延迟突变是否为非克隆突变，研究了来自单个克隆群体的29个部分缺失突变的外显子缺失谱。结果表明，这些突变体中至少有15个是独立产生的。为了研究延迟突变的发生与染色体不稳定性之间的关系，从克隆群体中分离出60个Hprt突变亚克隆，显示出高频率的延迟突变，在体外连续培养。其中，14个表现出生长缓慢的表型，多倍体细胞频率高（10-38%），非克隆染色体重排频率显著增加，包括染色体型和染色单体型畸变。这些克隆还显示耐瓦巴因突变的频率增加了3至30倍；X照射未直接诱导出抗瓦苦素突变体。这些结果表明，在表现出高频率延迟突变的克隆中，可能存在一个特别不稳定的细胞亚群；选择生长缓慢的表型具有选择这一染色体不稳定亚群的效果。(C) 1997年，辐射研究学会。
The frequency of mutations at the Hprt locus was measured in clonal populations of Chinese hamster ovary cells derived from single cells surviving exposure to 0-12 Gy of X rays or 2 Gy of a particles. Approximately 8-9% of 446 clonal populations examined 23 population doublings after irradiation showed high frequencies of late-arising mutations as indicated by mutant fractions 10(2)-10(4)-fold above background. The frequency with which such clones occurred was similar for alpha-particle irradiation and X irradiation, with no apparent dose dependence for X irradiation over the range of 4-12 Gy. The molecular structure of Hprt mutations was determined by analysis by multiplex polymerase chain reaction of all nine exons. Of mutations induced directly after exposure to X rays, 75% involved partial or total gene deletions. Only 19-23% of late-arising (delayed) mutations were associated with deletions, the preponderance of these being partial deletions involving one or two exons. This spectrum was very similar to that for spontaneously arising mutations. To determine whether delayed mutations were non-clonal, the spectrum of exons deleted was examined among 29 mutants with partial deletions derived from a single clonal population. The results indicated that at least 15 of these mutants arose independently. To examine the relationship between the occurrence of delayed mutations and chromosomal instability, 60 Hprt mutant subclones isolated from a clonal population showing a high frequency of delayed mutations were serially cultivated in vitro. Of these, 14 showed a slow-growth phenotype with a high frequency of polyploid cells (10-38%) and a markedly enhanced frequency of non-clonal chromosomal rearrangements including both chromosome-type and chromatid-type aberrations. These clones also showed a 3- to 30-fold increase in the frequency of ouabain-resistant mutations; no ouabain-resistant mutants were induced directly by X irradiation. These results suggest that among clones showing a high frequency of delayed mutations there may be a subpopulation of cells that are particularly unstable; selection for the slow-growth phenotype has the effect of selecting for this chromosomally unstable subpopulation. (C) 1997 by Radiation Research Society.