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Review
. 2020 Feb 24;21(4):1534.
doi: 10.3390/ijms21041534.

Micronucleus Assay: The State of Art, and Future Directions

Sylwester Sommer  1 , Iwona Buraczewska  1 , Marcin Kruszewski  1   2
Affiliations
Review

Micronucleus Assay: The State of Art, and Future Directions

Sylwester Sommer et al. Int J Mol Sci. .

Abstract

During almost 40 years of use, the micronucleus assay (MN) has become one of the most popular methods to assess genotoxicity of different chemical and physical factors, including ionizing radiation-induced DNA damage. In this minireview, we focus on the position of MN among the other genotoxicity tests, its usefulness in different applications and visibility by international organizations, such as International Atomic Energy Agency, Organization for Economic Co-operation and Development and International Organization for Standardization. In addition, the mechanism of micronuclei formation is discussed. Finally, foreseen directions of the MN development are pointed, such as automation, buccal cells MN and chromothripsis phenomenon.

Keywords: biological dosimetry; biomonitoring; buccal cells; genotoxicity; genotoxicity tests; lymphocytes; micronucleus assay.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
A principle of cytokinesis-block micronucleus assay. 1. Nucleus with damaged DNA. 2. Inhibition of cytokinesis by the addition of cytochalasin B. 3. The Mn frequency is scored in binucleated cells only. Upper part—control binucleated cells without Mn, lower part—two binucleated cells with 1 or 6 Mn visible in the cytoplasm.
Figure 2
Figure 2
Mammalian erythrocyte micronucleus assay. (1). Immature erythrocyte in bone marrow contains nucleus and RNA in its cytoplasm. When DNA damage is induced in vivo, micronucleus can arise in the nucleated erythrocyte. When nucleus is excluded during erythrocyte maturation the micronucleus stays in the cytoplasm. (2). In bone marrow, immature erythrocytes consist of around 50% of all erythrocytes. Occasionally these immature erythrocytes may contain Mn. (3). Sometimes the immature erythrocytes are released to peripheral blood, where they constitute less than 5% of all erythrocytes. The immature erythrocytes in blood can be recognized due to their specific surface receptors or RNA content. Flow cytometry technique makes the EMn feasible in peripheral blood of rodents and humans.
Figure 3
Figure 3
Buccal micronucleus assay. (1) Mn are induced in vivo by genotoxic agents in rapidly dividing buccal epithelial tissue. Epithelial cells differentiate and move towards outer layer of oral mucosa. (2) Mn frequency can be estimated in smears of exfoliated buccal cells.
Figure 4
Figure 4
Automatic/semiautomatic scoring by microscope aided systems (Metasystems). (1) Nuclei of cytokinesis-block cells are visible. System recognizes binucleated cells when both nuclei are the same size and they are in proximity to each other. (2) Motorized microscope with image analysis system safe galleries of binucleated cells and recognize Mn in an automatic manner. (3) Gallery of binucleated cells. Mathematical algorithms to recognize binucleated cells implemented in Metasystems has been used many times with good results [55,115,116]. (4) Each cell from the gallery can be localized and e.g., false positive Mn can be verified in high magnification. Such semiautomatic scoring gives better results than automatic scoring.
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References

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