Science & Tech Correspondent
The birth of the world’s first three-parent baby was announced in New Scientist magazine On Sept. 27.
This technique, developed by reproductive scientists, allows parents to overcome mitochondrial mutations and conceive a healthy child.
The extremely controversial method involves transferring the DNA from a mother’s egg with defected mitochondria to an egg cell of a donor with healthy mitochondria. Prior to this transfer, the nuclear DNA must be removed from the donor’s egg. The new egg can then be fertilized by the father’s sperm.
Mitochondria are organelles present in most cells and are important in providing energy for the cell. When these structures are mutated, many critical organs can be affected, generally resulting in the death of the babies who are affected. Nuclear DNA, not mitochondria, is responsible for the genes that determine inherited traits and characteristics. For example, if a white woman were to use an Asian donor’s mitochondria, the resulting baby would only be white.
Prior to this new technique, researchers had tried simpler methods, involving only the injection of healthy mitochondria into an egg. However, it was found to be ineffective at preventing mitochondrial diseases. In fact, this process led to additional genetic disorders.
Desperate to conceive a healthy baby, a Jordanian couple consulted with James Grifo, M.D. in 2011. More than two decades ago, Grifo had established that DNA swapping was successful in mice. He referred them to John Zhang, M.D., medical director of the New Hope Fertility Center in New York, who had attempted the method once before in China. Although the babies died due to being born prematurely, their mitochondria were found to be normal.
At first, the couple was hesitant in attempting the technique. The couple had already given birth to a child with Leigh syndrome, a mitochondrial disease. A quarter of the woman’s mitochondria were mutated and the mitochondria were randomly distributed, meaning some of her eggs may have had healthy mitochondria. There was no way of knowing which egg would be fertilized. They took their chances, but their second baby too, was born with Leigh syndrome. This disease is particularly devastating. The babies eventually lose any ability to move and breathe. Sadly, both children died; the first at six years, the second at eight months.
The couple eventually decided to go forward with the mitochondrial transfer technique. Due to the ban of this technique in the U.S., the couple traveled to the New Hope Fertility Center clinic in Mexico. Even before the child was born, the couple had a strong inkling that this baby would be normal. The fetus was active in the womb, something the woman had not experienced with her earlier pregnancies. The baby was in fact born a healthy boy with healthy mitochondria. He is now five months old and will continue to be monitored.
Scientists hope that this success story shines light on the technique and on the fact that it is banned in the United States. Many scientists also stress that the term “three-parent baby” is misleading and does not accurately embody the technique. Some are optimistic that this DNA swapping method will yield a high success rate, yet others remain cautious; still, this birth can be considered an exciting advancement in the scientific community.