In Vivo Micronucleus Assay
The micronucleus test (MNT) is used to determine if a compound is genotoxic by evaluating the presence of micronuclei. Micronuclei may contain chromosome fragments produced from DNA breakage (clastogens) or whole chromosomes produced by disruption of the mitotic apparatus (aneugens).
Screening and Regulatory Support for Micronucleus Assays
Our scientific experts provide the screening and regulatory support you need for your micronucleus assays and will ensure that your program stays on budget and within timelines, while preventing setbacks.
- Male and/or female rats or mice are treated with the test compound at three dose levels, usually two or three times at 24-hour intervals
- Approximately 24 hours after the final dose, bone marrow or peripheral blood is collected to determine the frequency of micronucleated polychromatic erythrocytes (MN-PCEs) or micronucleated reticulocytes (MN-RETs), respectively
- A positive outcome is characterized by a statistically significant, dose-dependent increase in MN-PCEs or MN-RETs that exceeds historical control limits
- Can be combined with standard toxicology tests, the comet assay, and the Pig-a assay
- Administration routes include oral, intravenous, infusion, and inhalation
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How Your Micronucleus Assays Fit with Other Studies
Micronucleus Assays (OECD 474) can be combined with standard toxicology tests, the comet assay, and the Pig-a assay. Administration routes include oral, intravenous, infusion, and inhalation.
When to Perform Micronucleus Assays
Determining when to perform micronucleus assays can depend on the endpoint you have in mind. Our experts can help you identify when a micronucleus assay is needed for your program.
- Micronucleus assays are conducted when screening — abbreviated formats available or can be added to non-GLP tolerability studies
- IND-enabling — as part of the ICH S2(R1) standard battery (Option 1 or 2)
- REACH requirement — to follow up a positive result in any of the Annex VII or VIII genotoxicity tests
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Want to learn more?
Whether you’re interested in starting your micronucleus study or just want to learn more about our capabilities, our experts are available to get your questions answered.
Frequently Asked Questions (FAQs) About Rodent Micronucleus Assay
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How does a micronucleus assay work?
Genotoxicity is commonly evaluated during the chemical safety assessment together with other toxicological endpoints. Since human exposure to genotoxic agents in the polluted environment has increased, many tests classified as “in vivo biomonitoring” are available to determine the level of exposure and health risks. The micronucleus test is considered one of the best and the most popular and the micronucleus assay is widely used to test genotoxicity, as well as many different techniques that use certain specific conditions.
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What is a micronucleus?
Micronuclei are extra-nuclear bodies that contain damaged chromosome fragments and/or whole chromosomes that were not incorporated into the nucleus after cell division. Historically, the micronucleus was recognized in the end of the 19th century when Howell and Jolly found small inclusions in the blood taken from cats and rats.
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How do you identify a micronucleus?
Micronuclei is hardly seen in the peripheral blood of rats and humans because erythrocytes including micronuclei are rapidly and effectively captured and destroyed by the spleen. In mice, micro-nucleated erythrocytes exist just the same as normal cells in the peripheral blood. While the assay using bone marrow evaluates an acute effect of chemicals, the method using mouse peripheral blood erythrocytes can evaluate a chronic effect of the test chemical by analyzing the mature erythrocytes.