Related Experiment Videos
Low persistence of the induced mutant phenotype in Chinese hamster cells
1Institut du Cancer de Montréal, Quebec, Canada.
Abstract:
We have analysed the recovery of individual CHO-derived mutants during the generations immediately following their induction. This characteristic, which we call persistence, was measured by propagating mutagenized cultures in non-selective medium after subdivision into many very small populations, each containing either zero or one mutant. The recovery of most hypoxanthine phosphoribosyltransferase (hprt)-deficient mutants induced by ethyl methanesulphonate was low, and we have previously shown that this was usually due to an apparent rapid loss of the mutant phenotype with continued culture in non-selective medium (Bradley, 1980). A minority of about 15% manifest high persistence. We now show that most adenine phosphoribosyltransferase (aprt)-deficient mutants and some ouabain-resistant mutants had low persistence. Mutants induced by UV irradiation also generally exhibited low persistence but those induced by X-irradiation had significantly higher persistence than what was seen among EMS-induced mutants. Among various sublines of CHO cells which were tested for persistence of induced mutants, only one group consistently yielded mutants of high persistence. These were lines which carried glucose-6-phosphate dehydrogenase mutations which themselves had been originally induced by EMS.
Insights
Most induced mutants in Chinese hamster ovary (CHO) cells show low persistence, often losing their mutant phenotype rapidly. However, X-ray induced mutants and specific glucose-6-phosphate dehydrogenase mutants exhibit higher persistence.
Area of Science:
- Cell Biology
- Genetics
- Toxicology
Background:
- Understanding mutant recovery in cell lines is crucial for genetic studies and toxicology.
- Ethyl methanesulfonate (EMS) is a common mutagen, but its induced mutants in CHO cells often show rapid phenotype loss.
- The persistence of induced mutations varies depending on the gene, mutagen, and cell line.
Purpose of the Study:
- To quantify the recovery and persistence of various induced mutants in Chinese hamster ovary (CHO) cells.
- To investigate factors influencing mutant phenotype stability after induction.
- To compare the persistence of mutants induced by different mutagens (EMS, UV, X-rays) and in different CHO cell sublines.
Main Methods:
- Culturing mutagenized CHO cell populations in non-selective media.
- Subdividing cultures into small populations to isolate zero or one mutant per population.
- Measuring the recovery rate (persistence) of hypoxanthine phosphoribosyltransferase (hprt), adenine phosphoribosyltransferase (aprt), and ouabain-resistant mutants.
- Assessing persistence of mutants induced by EMS, UV, and X-irradiation.
Main Results:
- Most EMS-induced hypoxanthine phosphoribosyltransferase (hprt)-deficient mutants displayed low persistence, with rapid loss of mutant phenotype.
- A minority (approx. 15%) of EMS-induced hprt mutants showed high persistence.
- Adenine phosphoribosyltransferase (aprt)-deficient and ouabain-resistant mutants generally exhibited low persistence.
- X-ray induced mutants showed significantly higher persistence compared to EMS-induced mutants.
- CHO cell lines carrying pre-existing glucose-6-phosphate dehydrogenase mutations (induced by EMS) consistently yielded high-persistence mutants.
Conclusions:
- Mutant persistence in CHO cells is highly variable and influenced by the specific gene, mutagen, and cell line.
- X-irradiation appears to induce more stable mutations than EMS or UV in CHO cells.
- Specific genetic backgrounds, like those with EMS-induced G6PD mutations, may enhance the persistence of newly induced mutations.