‘Three-Parent-Baby’ Gene Technique Can Now Produce Healthy Infants, Scientists Say

The controversial "three-parent-baby" gene treatment has been tested for the first time and may now be safe enough to conduct human trials within two to three years, scientists said.

This gene fertility treatment aims to create human embryos free of hereditary mitochondrial disease. Children who are at risk of serious diseases caused by defective mitochondria passed down by their mothers would be beneficiaries of this treatment.

Mitochondria are the "power packs" that provide energy to all living cells. Defective mitochondria may cause children to develop degenerative disorders because their cells don't function properly.

The defective mitochondria are located in the body of the egg, separated from the rest of its DNA, which is stored in the nucleus. The researchers have developed a technique that will prevent these faulty mitochondria from being passed on by fertilizing the egg, then the nucleus will be removed and transferred into a nucleus-free egg from a donor with healthy mitochondria.  

The resulting embryo would inherit DNA from the mother, the father, and the small amount of mitochondrial DNA from the egg donor, thus being called the "three-parent" treatment.

In 2010, researchers from the Wellcome Trust Center for Mitochondrial Disease at Newcastle University in UK showed that this technique worked. But questions of its safety were raised because they used donor eggs that were discarded from IVF treatments due to defects, and so the technique may not produce healthy embryos.

But now, scientists improved the technique to reduce the amount of faulty mitochondria carried to the healthy donor egg, according to a report published in Science News.

In the refined and improved study, scientists carefully removed the nucleus and manipulated the chemical solution used during the removal.

Of the total embryos created, 79 percent had less than 2 percent defective mitochondrial DNA.

According to Mary Herbert, reproductive biologist and co-leader of the Newcastle team, the decrease in defective mitochondria doesn't eliminate the risk of disease resurgence.

"The focus of our current research is to get that carryover as close to zero as we possibly can," she added.

The team also increased the embryos' survival rate by extracting the nucleus sooner after fertilization - within eight hours instead of 24, according to a report in New Scientist.