A baby boy with the DNA of three people was born on 6 April and appears to be healthy, according to doctors from the US who carried out the revolutionary new procedure. The boy was born to a Jordanian couple after Dr John Zhang and his colleagues from the New Hope Fertility Centre in New York City, performed mitochondrial donation in order to provide the couple with a healthy child.
The couple had previously lost two children and undergone several miscarriages before tests revealed that the mother carried the gene for Leigh’s syndrome, a severe neurological disorder, in roughly a quarter of her mitochondria. While the mother herself was healthy, unfortunately this disease resulted in the deaths of her children.
Mitochondria are tiny, energy-producing structures inside almost every cell. They only have 37 genes, which is less than 0.1% of the total DNA of the cell; the rest of the DNA is stored in the cell’s nucleus.
Zhang removed the nuclei from both the mother’s egg and an anonymous donor egg with healthy mitochondria. The mother’s nucleus was then placed into the donor egg and fertilised with the father’s sperm. This technique, called spindle nuclear transfer, means that the child inherits the majority of his DNA from his mother and father, whilst his mitochondrial DNA comes from the donor.
Despite the novelty of this method, this is not the first time that a baby was created using the DNA of three people. In the 1990s, embryologists injected mitochondrial DNA into eggs of women who had undergone multiple failed attempts of IVF. Unfortunately, two of the foetuses developed genetic disorders and, as a result, the technique was banned by US Food and Drug Administration.
Last year, the UK approved mitochondrial transfer and remains the only country to formally legalize this technique. However, Zhang carried out the procedure in Mexico where, although not officially legalized, there are no laws that prohibit it.
While the successful application of this new technique is exciting, there are some concerns about the choice to perform mitochondrial donation in a country with less stringent regulations. In addition, few details have been published so far, leaving unanswered questions about the reproducibility and safety of the procedure. It is hoped that these issues will be addressed when Zhang and his colleagues present their findings at the American Society for Reproductive Medicine meeting in October.