A one-of-a-kind baby that was born using a controversial new procedure that combines the DNA of three parents appears to be healthy, according to doctors in the US who oversaw the treatment. This is the first reported successful ‘three-parent’ birth.
Story of birth
The baby was born on 6 April after his Jordanian parents travelled to Mexico where they were cared for by US fertility specialists. The parents sought the help of John Zhang, a doctor from the New Hope Fertility Center in New York City, to have a baby that would be genetically related to them but would not inherit their genetic diseases. The boy’s mother carried genes for a disorder known as Leigh Syndrome, a fatal nervous system disorder that was passed down to her two previous children who both died of the disease. She had also suffered four miscarriages.
Zhang and his colleagues found after testing the boy’s mitochondria that less than 1 percent carry the mutation. “Hopefully, this is too low to cause any problems; generally, it is thought to take around 18 percent of mitochondria to be affected before problems start. It’s very good,” says Dusko Ilic from Kings College London who was involved in the work.
As the United States had not approved the “three-parent method” for fertility purposes, Zhang went to Mexico to perform the procedure. Speaking to the New Scientist, Zhang said he went to Mexico where “there are no rules” and insisted that doing so was right. “To save lives is the ethical thing to do,” he said.
How it works
The boy’s mother carries genes for the fatal Leigh syndrome, which harms the developing nervous system. The faults affect the DNA in mitochondria, the tiny battery-like structures that provide cells with energy, and are passed down from mother to child. Since the mother carried the genes for the disease in DNA that is passed down from the maternal side, Zhang used a technique known as spindle nuclear transfer to combine the mother’s nuclear DNA with mitochondria from an egg donor. “He removed the nucleus from one of the mother’s eggs and inserted it into a donor egg that had had its own nucleus removed,” said the report. “The resulting egg –- with nuclear DNA from the mother and mitochondrial DNA from a donor -– was then fertilized with the father’s sperm.”
Zhang and his team are expected to describe their method at the American Society for Reproductive Medicine meeting in Salt Lake City, Utah next month.
Although an abstract describing the research has been published in the Journal of Fertility and Sterility, experts said that much more remains to be understood about the research.
Bert Smeets at Maastricht University in the Netherlands cautions that the team needs to monitor the child to make sure the levels stay low as there’s a chance that faulty mitochondria could be better at replicating. “We need to wait for more births, and to carefully judge them,” he said.
Controversy surrounding the procedure
David Clancy, an expert and a lecturer at Lancaster University, recalled that experiments in monkeys have shown that maternal mitochondrial DNA can expand from low levels to significantly higher levels “which would allow the disease to again be transmitted, so we must expect the possibility in humans.”
Justin St John, professor and Director of the Centre for Genetic Diseases at Monash University, criticised the manner in which the outcome was announced, stating that a manuscript should have been submitted for full peer review given the seminal and controversial nature of the treatment.
Because the work is yet to be published several questions remain unanswered. Dusko Ilic comments that by performing the operation in Mexico where laws are less stringent there is no way of knowing how skilful or prepared they were, and how risky it was. Furthermore, it is unclear if this was the first time they performed that technique or if there were other attempts and this was only reported because it was successful.
Previous attempt
The baby is not the first child to be born with DNA from three people. In the 1990s, fertility doctors tried to enhance the quality of women’s eggs the cellular material that contains mitochondria (cytoplasm), from healthy donor eggs. The procedure led to several babies being born with DNA from the parents plus the healthy donor. Some of the children developed genetic disorders and the procedure was banned.
Legalised in the UK
The UK is the only country to have introduced laws to permit the technique. The European country legalized the treatment in 2015. The treatment is aimed at parents who have a high risk of passing on debilitating and even fatal genetic diseases to their children. The successful treatment may be the boost needed to tame the most ardent critics, and may possibly be the catalyst for the birth of the first ‘three-parent’ baby in the UK.
The translation of mitochondrial donation to a clinical procedure is not a race but a goal to be achieved with caution to ensure both safety and reproducibility”, said Alison Murdoch, a fertility doctor at Newcastle University.
