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Mutator phenotype of MUTYH-null mouse embryonic stem cells
Seiki Hirano1, Yohei Tominaga, Akimasa Ichinoe
1Division of Neurofunctional Genomics, Medical Institute of Bioregulation, Kyushu University, and Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Corporation, Fukuoka, 812-8582, Japan.
The Journal of Biological Chemistry
|August 15, 2003
Summary
The Mutyh gene, encoding adenine DNA glycosylase, is crucial for preventing mutations. Its absence in mouse cells doubled spontaneous mutation rates, highlighting its role in DNA repair and guarding against a mutator phenotype.
Area of Science:
- Molecular Biology
- Genetics
- DNA Repair Mechanisms
Background:
- The Mutyh gene encodes adenine DNA glycosylase, an enzyme critical for DNA repair.
- This enzyme excises adenine misincorporated opposite 8-oxoguanine, a common oxidative DNA lesion.
- Defects in DNA repair pathways can lead to increased mutation rates and disease.
Purpose of the Study:
- To investigate the antimutagenic role of the mammalian Mutyh gene.
- To determine the functional significance of specific Mutyh mutations in DNA repair.
- To assess the link between Mutyh mutations and colorectal adenoma development.
Main Methods:
- Generation of MUTYH-null mouse embryonic stem (ES) cells.
- Assessing spontaneous mutation rates in wild type and MUTYH-null ES cells.
- Expression of wild type and mutant mouse Mutyh (mMUTYH) proteins in null cells.
- Enzyme activity assays for recombinant and cellular mMUTYH proteins.
Main Results:
- MUTYH-null ES cells exhibited a 2-fold increase in spontaneous mutation rate compared to wild type cells.
- Expression of wild type mMUTYH restored normal mutation rates.
- A mutant mMUTYH (G365D), analogous to a human germ-line mutation, failed to suppress the elevated mutation rate.
- Recombinant mMUTYH(G365D) showed activity, but the mutant protein lacked detectable activity within MUTYH-null ES cells.
Conclusions:
- The Mutyh gene plays a significant antimutagenic role by repairing adenine misincorporations.
- The G365D mutation in mMUTYH, corresponding to a human germ-line mutation (G382D), impairs its DNA repair function in vivo.
- This impaired function likely contributes to a mutator phenotype observed in patients with this MUTYH germ-line mutation, potentially increasing colorectal cancer risk.