A more efficient method to generate null mutants using Hprt-Cre with floxed alleles

Area of Science:

• Developmental Biology
• Genetics
• Mouse Models

Background:

• Generating homozygous null mouse embryos is resource-intensive, with standard null/+ breedings yielding only 25% mutants.
• Efficient production of homozygous null mutants is crucial for genetic studies and disease modeling.

Purpose of the Study:

• To evaluate a novel Hypoxanthine-guanine phosphoribosyltransferase-Cre (Hprt)-Cre mating strategy to increase homozygous null mouse embryo yield.
• To confirm that Hprt-Cre generated homozygous null mutants are phenotypically indistinguishable from those produced by traditional methods.

Main Methods:

• Utilized a conditional Fgfr2IIIb(flox) allele, which mimics the null allele upon recombination.
• Generated F1 females (Fgfr2IIIb(rec/+); Hprt(Cre/+)) and mated them with Fgfr2IIIb(flox/flox) males to produce F2 embryos.
• Genotyped F2 embryos and analyzed the morphology and histology of key organs (lungs, intestine, limbs, brain).

Main Results:

• The Hprt-Cre strategy yielded 51% homozygous null embryos, significantly higher than the 23% from standard null/+ breedings.
• Homozygous null embryos generated via Hprt-Cre did not express Fgfr2IIIb transcript.
• Phenotypic analysis confirmed these embryos were identical to those from standard breedings.

Conclusions:

• The Hprt-Cre mating strategy effectively doubles the yield of homozygous null mouse embryos per litter without impacting litter size.
• This method provides a resource-efficient and reliable way to generate phenotypically consistent homozygous null mutants.
• Recommended for researchers requiring homozygous null embryos in their mouse models.