Eight healthy babies who have genes derived from three different parents have been born healthy in the United Kingdom. This happy result was reported in The New England Journal of Medicine. The treatment involved taking the nucleus from a fertilized egg that contained defective mitochondria and installing it into a donor egg with healthy mitochondria whose nucleus had been removed. Thus, the DNA comprising these babies' genes are derived from the mothers, fathers, and the egg donors. Mitochondrial DNA represents about 1 percent of total cellular DNA (about 1000 to 10,000 copies per cell). Mitochondria are the chief energy-producing organelles inside our bodies' cells. Mitochondrial disorders affect between 1 in 6,000 and 1 in 8,000 live births, making them almost as common as childhood cancer.
Many more families might have benefited over the past couple of decades from similar treatments pioneered a quarter of a century ago, except that handwringing bioethicists helped to persuade the U.S. Food and Drug Administration (FDA) to essentially ban them.
Back in 2001, fertility researcher Jacques Cohen and his colleagues at the Institute for Reproductive Medicine and Science at St. Barnabas Medical Center in New Jersey announced the births of 15 three-parent babies. In this case, the researchers injected mitochondria-containing cytoplasm taken from healthy donor eggs into those of women who were experiencing infertility.
