The Micronucleus test, also known as the Micronucleus assay, is a cornerstone in genotoxicity testing. It identifies chromosomal damage in cells exposed to a compound — a critical step in evaluating the safety of chemicals, pharmaceuticals, and cosmetics.
This article explores the biological principle, methodologies (in vitro and in vivo), regulatory context, and how GenEvolutioN supports robust, GLP-compliant genotoxicity studies.
What is a micronucleus?
A micronucleus is a small extranuclear body formed during cell division when chromosome fragments or entire chromosomes fail to be incorporated into the main daughter nuclei.
- Clastogenic mechanisms cause chromosome breaks.
- Aneugenic mechanisms lead to whole-chromosome mis-segregation.
Because it detects both, the micronucleus test is broader than the traditional chromosome aberration test.
Principle of the micronucleus test
- Expose cultured cells or animal tissues to the test substance.
- Allow one or two mitotic cycles to occur.
- Fix and stain the cells.
- Count the frequency of micronucleated cells compared to controls.
- Apply statistical analysis to determine genotoxic significance.
This test offers high sensitivity, reproducibility, and compatibility with both in vitro and in vivo systems.
In vitro vs. In vivo methodologies
- In vitro Micronucleus Assay (OECD 487):
Uses mammalian cell lines (e.g., human lymphocytes, CHO, TK6). The cytokinesis block technique (cytochalasin B) allows detection in binucleated cells.
- In vivo Micronucleus Test:
Typically performed in rodents, assessing bone marrow or peripheral blood erythrocytes. It captures the effect of metabolism and systemic distribution — crucial for regulatory confirmation.
Applications across industries
- Pharmaceuticals: Required by ICH S2(R1) for genotoxicity packages.
- Chemicals & cosmetics: REACH, CLP, and cosmetic safety dossiers.
- Environmental biomonitoring: Detecting chromosomal damage in exposed populations.
Why it matters
The Micronucleus assay remains one of the most widely accepted genotoxicity assays, providing predictive and mechanistic insights into DNA damage, while fulfilling global regulatory standards.
GenEvolutioN know-how
At GenEvolutioN, our GLP-compliant laboratory combines advanced imaging including FISH staining of telomers and centromers, validated OECD 487 methods, and integrated regulatory support to ensure reliable, traceable results — from screening to dossier submission.
Contact our experts to learn more about Micronucleus testing for your compound.
