Development of detection systems for chemicals that induce abnormality in DNA methylation

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Chemicals that induce genetic abnormality are designated as mutagens, and chemicals that induce epigenetic abnormality are designated as "epimutagens" (Holliday, 1991). Only a limited number of epimutagens are currently known, including cytidine analogues, metal compounds such as arsenic or nickel, and drugs such as valproate (an antiepileptic agent) and procainamide (an antiarrhythmic agent), and so on. The number is very small compared with that of mutagens, and this is possibly because there are no efficient assay systems for epimutagens. Therefore, it is critically important to develop an efficient detection system for epimutagens. We have already developed a prototype detection system for demethylating agents (Fig. ) (Okochi-Takada et al., 2004). Currently, we are developing a highly sensitive system, which can be used in a high-throughput platform.


Fig. Establishment of an assay system for CpG demethylating agents
Under a methylated endogenous promoter CpG islands (CGI), a fluorescence-expressing marker gene was introduced. The addition of 5-aza-dC to introduced cells led to demethylation of the CGI, and expression of the marker gene. As expected, fluorescence was confirmed by fluorescence microscopy.