Fenech Michael
CSIRO Human Nutrition, Adelaide BC, South Australia, Australia.
Methods Mol Biol. 2008;410:185-216. doi: 10.1007/978-1-59745-548-0_12.
The study of DNA damage at the chromosome level is an essential part of genetic toxicology because chromosomal mutation is an important event in carcinogenesis. Micronucleus assays have emerged as one of the preferred methods for assessing chromosome damage because they enable both chromosome loss and chromosome breakage to be measured reliably. Because micronuclei can only be expressed in cells that complete nuclear, division a special method was developed that identifies such cells by their binucleate appearance when blocked from performing cytokinesis by cytochalasin-B, a microfilament-assembly inhibitor. The cytokinesis-block micronucleus (CBMN) assay allows better precision because the data obtained are not confounded by altered cell division kinetics caused by cytotoxicity of agents tested or suboptimal cell culture conditions. The method is now applied to various cell types for population monitoring of genetic damage, screening of chemicals for genotoxic potential and for specific purposes such as the prediction of the radiosensitivity of tumors and the interindividual variation in radiosensitivity. In its current basic form the CBMN assay can provide, using simple morphological criteria, the following measures of genotoxicity and cytotoxicity: chromosome breakage, chromosome loss, chromosome rearrangement (nucleoplasmic bridges), gene amplification (nuclear buds), cell division inhibition, necrosis and apoptosis. The cytosine arabinoside modification of the CBMN assay allows for measurement of excision repairable lesions. The use of molecular probes enables chromosome loss to be distinguished from chromosome breakage and importantly nondisjunction in nonmicronucleated binucleated cells can be efficiently measured. The CBMN technique therefore provides multiple and complementary measures of genotoxicity and cytotoxicity which can be achieved with relative ease within one system. The basic principles and methods (including detailed scoring criteria for all the genotoxicity and cytotoxicity end points) of the CBMN assay are described and areas for future development identified.
在染色体水平上研究DNA损伤是遗传毒理学的重要组成部分，因为染色体突变是致癌过程中的一个重要事件。微核试验已成为评估染色体损伤的首选方法之一，因为它能够可靠地测量染色体丢失和染色体断裂。由于微核只能在完成核分裂的细胞中表达，因此开发了一种特殊方法，当用细胞松弛素B（一种微丝组装抑制剂）阻止细胞进行胞质分裂时，通过双核外观来识别此类细胞。胞质分裂阻断微核（CBMN）试验具有更高的精度，因为所获得的数据不会因受试物的细胞毒性或次优细胞培养条件导致的细胞分裂动力学改变而混淆。该方法目前已应用于各种细胞类型，用于群体遗传损伤监测、化学物质遗传毒性潜力筛选以及特定目的，如预测肿瘤的放射敏感性和个体间放射敏感性差异。在其当前的基本形式中，CBMN试验可以使用简单的形态学标准提供以下遗传毒性和细胞毒性测量指标：染色体断裂、染色体丢失、染色体重排（核质桥）、基因扩增（核芽）、细胞分裂抑制、坏死和凋亡。CBMN试验的阿糖胞苷修饰允许测量可切除修复的损伤。使用分子探针能够区分染色体丢失和染色体断裂，重要的是，可以有效地测量非微核双核细胞中的不分离现象。因此，CBMN技术提供了多种互补的遗传毒性和细胞毒性测量指标，并且可以在一个系统中相对容易地实现。本文描述了CBMN试验的基本原理和方法（包括所有遗传毒性和细胞毒性终点的详细评分标准），并确定了未来的发展方向。
