New Infertility Strategy Turns Skin Cell into an Egg

Key points:

• In a new study, researchers advanced a promising technique that treats infertility by turning a skin cell into an egg.
• Experimenting in mice, the new study resulted in embryos with chromosomes contributed from both parents.
• The technique raises the possibility of men in same-sex relationships having children who are genetically related to both parents.

Researchers at Oregon Health & Science University have advanced a promising technique that treats infertility by turning a skin cell into an egg that is capable of producing viable embryos.

In a new study, published in Science Advances, scientists describe the technique in three steps:

1. Researchers transplant the nucleus of a mouse skin cell into a mouse egg that is stripped of its own nucleus
2. Prompted by cytoplasm within the donor egg, the implanted skin cell nucleus discards half of its chromosomes. The process is similar to meiosis, when cells divide to produce mature sperm or egg cells. This is the key step, resulting in a haploid egg with a single set of chromosomes.
3. Researchers then fertilize the new egg with sperm. This creates a diploid embryo with two sets of chromosomes—which would ultimately result in healthy offspring with equal genetic contributions from both parents.

The team previously demonstrated the proof of concept in a study published in January 2022, but the new study goes further by meticulously sequencing the chromosomes. The researchers found that the skin cell’s nucleus segregated its chromosomes each time it was implanted in the donor egg. In rare cases, this happened perfectly, with one from each pair of matching egg and sperm chromosomes.

In 1996, researchers famously used this technique to clone a sheep in Scotland named Dolly. In that case, researchers created a clone of just one parent. In contrast, the new Oregon study results in embryos with chromosomes contributed from both parents. The technique raises the possibility of men in same-sex relationships having children who are genetically related to both parents. It could also be used by women of advanced maternal age or for those who are unable to produce viable eggs due to previous treatment for cancer or other causes.

“This publication basically shows how we achieved haploidy,” said senior study author Shoukhrat Mitalipov, director of the OHSU Center for Embryonic Cell and Gene Therapy. “In the next phase of this research, we will determine how we enhance that pairing so each chromosome-pair separates correctly.”