Eight babies in the U.K. were born free from inheritable mitochondrial disease, and have continued to develop normally, thanks to a pioneering IVF technique, according to two papers published in the New England Journal of Medicine. The technique, known as pronuclear transfer, uses the majority of DNA from a man and woman and a small portion from another donor egg.
The process involves "transplanting the nuclear genome from an egg carrying a mitochondrial DNA mutation to an egg donated by an unaffected woman that has had its nuclear genome removed," said a press release. The resulting embryo inherits its mitochondrial DNA "predominantly from the donated egg." The technique has been legal in the U.K. since 2015, but this is the first proof that it can lead to children born without mutations.
Approximately one in 5,000 children is born with mitochondrial mutations each year. Defective mitochondria can "leave the body with insufficient energy to keep the heart beating" and cause "brain damage, seizures, blindness, muscle weakness and organ failure," said the BBC. While no cure exists for mitochondrial defects once inherited, this method could prevent them from being passed on at all.
Gene-editing techniques have been a subject of controversy, as some fear it would "open the doors to genetically modified 'designer' babies," said the BBC. The use of pronuclear transfer is not allowed in the U.S. due to "regulatory restrictions on techniques that result in heritable changes to the embryo," Zev Williams, the director of the Columbia University Fertility Center, said to The Associated Press. | 
