The in vitro micronucleus test (FC-MNT) is used to detect structural or numerical changes to chromosomes in cells exposed to test article.
Chromosomal damage is detected by the presence of micronuclei in the cytoplasm of interphase cells that originate from acentric fragments, or whole chromosomes that failed to segregate correctly during anaphase.This means the MNT is sensitive to both clastogenic and aneugenic mechanisms of genotoxicity*.
The assay can be conducted in either the absence or presence of cytochalasin B, with micronuclei assessed from either mononucleate cells where the population is within 1.5 – 2 population doublings (non-cytochalasin B blocked) or binucleate cells restricted to 1 population doubling by the cytokinesis blocking action of cytochalasin B. Micronuclei are typically scored by microscopy, with upwards of 1000 cells scored per culture, per compound dose. The in vitro MNT is covered by OECD guideline 487 and is included in the ICH guidance as part of the in vitro genotoxicity regulatory battery of tests (ICH S2R1).
Recently, enumeration of micronuclei has been automated by the use of high-content image analysis and flow cytometry platforms. Whilst these detection platforms are not yet adopted for use in regulatory versions of the in vitro MNT, they are frequently used in pre-regulatory testing regimes and in early development, hazard identification screening approaches.
Micronucleus Test at Gentronix
Gentronix currently offers the MicroFlow® flow cytometric MNT developed by Litron Laboratories as a part of our genotoxicity testing service. This method utilises a dual-labelling approach to allow automated, flow cytometric enumeration of micronuclei from TK6 cells, exposed to test chemical in the absence or presence of metabolic activation using S9 fraction.
Gentronix micronucleus testing services provides our clients with:
- Automated, higher throughput scoring than microscopy based methods.
- Collection of 10,000 nucleated events per dose.
- Discrimination between micronuclei and chromatin from apoptotic/necrotic cells.
- Low test chemical requirement.
* Parry, J., Parry, E., Bourner, R., Doherty, A., Ellard, S., O’Donovan, J., Hoebee, B., et al. (1996) The detection and evaluation of aneugenic chemicals. Mutation Research, 353: 11-46.