Mice with two fathers survive adulthood

In a world-first, scientists in China have successfully created mice with two biological fathers. The mice not only survived birth but grew into adulthood, marking a significant step in understanding a complex biological process called "imprinting."

The research, led by Zhi-Kun Li at the Chinese Academy of Sciences in Beijing, used advanced gene-editing tools to overcome challenges that have stumped scientists for decades.

Imprinting is a natural process where certain genes behave differently depending on whether they come from the mother or father. For healthy development, embryos need a balanced "dose" of these genes from both parents. Without this balance, embryos often develop abnormalities. Previous attempts to create mice with two fathers failed because of these imbalances.

According to a report from MIT Technology Review, Li's team used CRISPR, a powerful gene-editing tool, to target 20 key imprinted genes in mouse stem cells. They then combined these edited cells with sperm and injected them into egg cells stripped of their nuclei. The resulting embryos were placed into female mice, leading to the birth of seven live pups. However, the success rate was low, and the mice had health issues, including enlarged organs, shorter lifespans, and infertility.

While the experiment is a scientific milestone, experts caution that applying this to humans is far off and ethically fraught. "Editing 20 imprinted genes in humans would not be acceptable, and producing individuals who could not be healthy or viable is simply not an option," Li said. For now, the work remains a fascinating glimpse into the complexities of life.