Scientists create baby mice with only female DNA

For the first time, scientists have succeeded in producing baby mice from an unfertilized egg. Parthenogenesis, animals only DNA inherited, common in nature, but unheard of in mammals.

Fish, reptiles, spiders, insects, all these creatures can only be born from an unfertilized egg. In mammals, however, new life is produced by fertilization, that is, by combining male and female genetic material.

This process is important because it creates genetic diversity: we carry different DNA codes from our ancestors, and this can help us as a species, for example, be more resistant to disease.

However, not every gene is expressed. Even more interestingly, previous research has found that while most cells express both copies of DNA, some do not in mammals. In these, only the genetic material of the mother or father is converted into real traits.

Bypassing genomic imprinting

It was these exceptions that prompted experts to carry out parthenogenesis of mice. One hurdle, however, was genomic imprinting: maternal and paternal alleles activate and deactivate the expression of certain genes, some of which are crucial for the formation of new life.

To circumvent the problem, researchers used CRISPR to edit the DNA of eggs. Thanks to this technique, it was possible to activate the same points of the genetic code that the alleles would change.

And finally the eggs can be implanted in the female’s womb and become a fetus. All the offspring survived birth, but only one reached adulthood – the lucky one may even produce offspring of their own.

The results of the study show that parthenogenesis is possible in mammals. The future refinement that must take place in the process could lead to a useful technique for application in industries such as agriculture or drug development.

ARTICLE Proceedings of the National Academy of Sciences: doi.org/10.1073/pnas.2115248119