Induction of gene mutations in mice: the multiple endpoint approach

Area of Science:

• Mammalian mutagenesis
• Genetic toxicology
• Developmental genetics

Background:

• Assessing the genetic effects of mutagens requires robust screening methods.
• Existing methods often focus on single genetic endpoints, limiting comprehensive analysis.
• A multi-endpoint approach in mammals can provide a more holistic view of mutagenicity.

Purpose of the Study:

• To present a multiple endpoint mammalian mutagenesis approach for screening various genetic alterations.
• To evaluate the mutation rates for different genetic endpoints using ethylnitrosourea (ENU), procarbazine, and X-rays.
• To compare the observed mutation frequencies across distinct genetic loci.

Main Methods:

• Developed a multi-endpoint system screening for recessive specific locus alleles, dominant cataract mutations, protein-charge changes, and enzyme-activity alterations in mice.
• Treated male mice with ethylnitrosourea (ENU), procarbazine, and X-rays.
• Scored offspring for mutations across approximately 70 genetic loci and confirmed mutations via breeding tests.

Main Results:

• Mutations were recovered for all genetic endpoints in treatment groups with sufficient offspring.
• Ethylnitrosourea (ENU) treatment at 250 mg/kg resulted in high mutation rates: 93.6 X 10(-5) for specific locus and 66.0 X 10(-5) for enzyme-activity alleles.
• Mutation rates for specific locus and enzyme-activity alleles were consistently higher than those for dominant cataract (6.1 X 10(-5)) and protein-charge (3.1 X 10(-5)) alleles.

Conclusions:

• The developed multiple endpoint mammalian mutagenesis approach is effective in screening diverse genetic alterations.
• Specific locus and enzyme-activity mutations occur at higher frequencies than dominant cataract and protein-charge mutations following mutagenic treatment.
• This model provides a valuable tool for comprehensive genetic toxicology assessment.