Related Experiment Videos
Mutagen-induced diploid human lymphoblast variants containing altered hypoxanthine guanine phosphoribosyl transferase
Abstract:
The human lymphoblast line MGL8 was treated with HAT and subsequently "mutagenized" with EMS (200 microgram/ml) to give 15% survival, and 6-thioguanine-resistant cells were selected by cloning in soft agarose containing the drug (1 microgram/ml). Eighteen sublines of independently derived resistant clones were isolated and studied in detail. One subline had a low residual HGPRT activity of about 1% of the parental cells. The HGPRT of this subline had a higher Km for PRPP, was more sensitive to heat, and was degraded faster by trypsin than the enzyme in extracts of MGL8 cells. This resistant subline and three others contained CRM levels of 1--38%, compared to the wild-type, so they probably represent true structural mutants of the HGPRT gene. All the variants maintained the karyotype of the parental line (46, XY, 6p-).
Insights
Researchers developed drug-resistant cell lines to study hypoxanthine-guanine phosphoribosyltransferase (HGPRT) gene mutations. Several cell lines showed altered HGPRT enzyme properties, indicating structural gene mutations.
Area of Science:
- Genetics
- Molecular Biology
- Biochemistry
Background:
- Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) is crucial for purine metabolism.
- Mutations in the HGPRT gene cause Lesch-Nyhan syndrome.
- Understanding HGPRT mutations aids in studying genetic diseases and drug resistance.
Purpose of the Study:
- To generate and characterize HGPRT-deficient human lymphoblast cell lines.
- To identify structural mutations in the HGPRT gene.
- To investigate the biochemical properties of mutant HGPRT enzymes.
Main Methods:
- Human lymphoblast cell line MGL8 was treated with ethyl methanesulfonate (EMS) for mutagenesis.
- 6-thioguanine-resistant cells were selected using soft agarose cloning.
- Eighteen independently derived resistant sublines were isolated and analyzed.
- Residual HGPRT activity, enzyme kinetics, heat sensitivity, and cross-reacting material (CRM) levels were assessed.
Main Results:
- One subline exhibited only 1% residual HGPRT activity.
- The HGPRT enzyme in this subline showed increased Km for PRPP, heightened heat sensitivity, and faster tryptic degradation.
- Three other resistant sublines displayed CRM levels between 1-38% of wild-type.
- All analyzed variants maintained the parental karyotype (46, XY, 6p-).
Conclusions:
- The characterized resistant cell lines likely represent true structural mutants of the HGPRT gene.
- Altered biochemical properties of HGPRT indicate specific structural changes in the enzyme.
- These cell lines serve as valuable tools for studying HGPRT gene function and mutations.