Mitochondrial defects affect an estimated 1 in 4,000 children, and can cause rare and often fatal diseases such as carnitine deficiency, which prevents the body from using fats for energy.
Mitochondria have their own DNA and are inherited only from the mother, so replacing defective mitochondria in eggs from mothers who have a high risk of passing on such diseases could spare the children.
A team of researchers has now emoved the nucleus from an unfertilized human egg, leaving behind all of that cell’s mitochondria, and injected it into another unfertilized egg that had had its nucleus removed. They then fertilized the egg in vitro and allowed the embryos to develop to the blastocyst stage — a ball of about 100 cells. The cells looked like those from normal embryos, but with mitochondria exclusively from the donor (abstract)."