Chinese Scientists Create Healthy Mice from Two Male Parents

Chinese Scientists Successfully Breed Healthy Mice Using Only Two Sperm Cells (Image: Canva)

It started with a question that once seemed impossible. Can mammals be created without a mother? Now, researchers from China may have brought science one step closer to answering it. In a detailed study, scientists have managed to breed healthy, fertile mice using just two sperm cells — no egg, no female DNA.

The experiment was conducted by a team at Shanghai Jiao Tong University and published in the Proceedings of the National Academy of Sciences on 23 June 2025.

What the Study Achieved

This isn’t the first time researchers have produced mice without one biological parent. But earlier attempts led to weak or short-lived offspring. The difference this time is the survival and fertility of the mice. Out of 250 embryos created using DNA from two sperm, three pups survived birth, and two remained healthy and fertile.

The researchers achieved this feat using targeted reprogramming of DNA methylation — a process known as epigenetic programming. This involves altering gene activity without changing the DNA sequence itself. Scientists used the CRISPR-Cas editing system to carefully reprogram imprinting marks, which are vital for development.

The success highlights the major role imprinting plays in reproduction and suggests that it’s possible to bypass biological barriers once thought immovable.

Behind the Genetic Engineering

To carry out the experiment, researchers used sperm from two different strains of mice. One strain was bred in European labs; the other came from wild mice in Thailand. They removed the genome from an unfertilised egg and injected two sperm heads into the cell.

This gave the embryo both XX and XY chromosome combinations. They avoided YY combinations, which are nonviable due to the essential genes on the X chromosome. Using CRISPR, scientists then modified the methylation patterns to mimic female DNA at key sites.

After implantation into surrogate females, some embryos developed successfully. One baby mouse died within a day because it was unusually large, but two others survived and were fertile — marking a rare success for male-only reproduction.

Scientists Urge Caution for Human Applications

Experts, however, have warned that the experiment cannot be directly applied to humans. The process requires hundreds of eggs, many surrogates, and has a very low success rate. Dr Christophe Galichet from the Sainsbury Wellcome Centre in the UK called it “unthinkable” for human reproduction.

Still, the findings support decades of research into imprinting — where males and females chemically mark DNA differently to control gene activity. Understanding this could help scientists explore infertility, embryo development, and even animal conservation.

Previous Experiments and Limitations

The road to this achievement has been long. Back in 2004, scientists created a mouse with two mothers, famously named Kaguya. Later studies showed embryos could form from two eggs or two sperm, but the resulting mice were unhealthy or died early.

This recent success is limited too. Only a few embryos developed, and modifying all the required imprinting sites remains a challenge. Off-target effects — where unintended parts of DNA get edited — still pose risks.

Despite this, the research confirms imprinting as a major hurdle in single-sex reproduction, one that scientists may one day learn to reliably manage.

According to the source: Moneycontrol.