Genotoxicity Testing Services
In addition to the specific mutagenicity assays provided by EBPI Analytics, a line of general genotoxicity tests are offered. These assays use modified bacteria that have the induction of a SOS DNA response gene coupled to a gene that expresses a measurable colorimetric endpoint. The degree of induction of the SOS response can be quantified by the degree of colour change, and correlates with the amount of DNA damage in the cell from toxicant exposure. These assays conform to international ISO standards and were suggested for incorporation into legislation for waste water effluent testing as part of the OSPAR commission (2002). They are currently mandated in Europe as part of the water framework directive (WFD).
We believe that these assays are ideal to screen multiple environmental samples, waste water effluent and pure compounds for drug approval. These genotoxic tests provide results not seen in the traditional Ames assays, and are ideal for individual screening experiments, or used in conjunction with other mutagenicity assays.
Genotoxicity assays can be coupled with S9 fraction addition when using traditional methods for toxicant bioactivation. However, EBPI Analytics also offers testing services using our recently developed UMU-Express and SOS-Express assays which have been genetically engineered to express either the human CYP 450 1A2 or the GST T1-1 enzymes. These test methods are a to traditional UMU and SOS assays, as they use the similar bacterial strains, but they show marked improvement in sensitivity, biological relevance and environmental screening ability. We are very excited about these assays and believe that they offer the next step in rapid genotoxic evaluation with increased human health and environmental implications.
The test employs Salmonella typhimurium TA 1535 [pSK 1002] in which the SOS DNA repair response umuC gene has been linked to the β gal gene responsible for producing the β-galactosidase enzyme. The degree of DNA damage repair using the SOS gene pathway is directly linked to the production of β-galactosidase, which is measured by the enzyme’s reaction with a blue chromogen. Strain TA 1535 [pSK 1002] contains both the rfa mutation, which produces a defective, more permeable cell membrane, and the uvrB mutation, which eliminates the accurate excision DNA repair mechanism, resulting in more repair by error-prone mechanisms. The results from this assay agree very closely with traditional Ames mutagenicity tests, with the added advantage of only using a single bacterial strain.
The SOS line of assays are designed for rapid detection of genotoxicity or DNA damage and utilizes the synthesis of the B-galactosidase enzyme whose gene (LacZ) is connected to an SOS promoter. Once a lesion has been detected, the SOS promoter is induced to start the transcription of the SOS genes and the LacZ gene is transcribed as well. This gene produces an enzyme which is assayed using a simple colour change. The degree of colorimetric expression is quantified and given as the SOS-inducing potency (SOSIP). Although the SOS tests also correlate well with the Ames assays, they have been shown to be slightly less sensitive, although they also report less false-positive results.
Both of these assay systems are:
- Reliable and produce easy to measure endpoints with quantification
- Excellent for testing multiple samples on one test plate
- Rapid tests that can be run in one day for immediate results.
- Excellent indicators of genotoxic damage that may not be mutagen dependant.