A boy born in April with three genetic parents is the first infant born using a new technique that incorporates DNA from two women and one man, New Scientist reported Tuesday. The technique offers promise to help children avoid often-fatal genetic diseases passed down by their mothers, but has raised thorny ethical questions and is not allowed in the United States.
The boy was born in Mexico to Jordanian parents who tapped researchers from the New Hope Fertility Center in New York to help them conceive a healthy child, according to New Scientist.
The boy’s mother has genes for a condition called Leigh syndrome, a neurological condition that killed her two prior children, according to the report. But because those genes are carried in her cells’ mitochondria, the scientists were able to swap in healthy mitochondrial DNA from another woman, and now the boy appears to be healthy at 5 months old.
Mitochondria are organelles that help power cells. They contain a tiny bit of DNA — 37 genes — that is passed down from mothers to their children.
Other children have been born via so-called mitochondrial donation, a broad class of treatments that aim to replace eggs’ diseased mitochondria with healthy ones. (Some of those children, however, developed genetic problems.) Those embryos were created by injecting healthy cytoplasm — think of it like the white of a chicken’s egg — into the recipient egg.
But newer approaches transfer the nucleus — the “yolk” in our analogy — instead, which is more promising for actually curing mitochondrial diseases.
In the case of this infant, scientists replaced the nucleus of a donor egg cell with the nucleus taken from the mother’s egg cell. The resulting egg has the nucleus of the child-to-be’s mother — and thus the vast majority of her DNA — but the healthy mitochondrial DNA from the donor. Then scientists fertilize the egg with sperm from the father, and are able to implant the resulting embryo into the mother’s womb if it is clear it is developing normally.
In this case, the boy was delivered after a full nine-month pregnancy, the New Scientist reported. About 1 percent of the boy’s mitochondria includes the faulty genes for the syndrome, which scientists believe should not cause problems unless they replicate faster than his healthy mitochondria, according to the report.
The United Kingdom has approved another technique for the creation of “three-parent” embryos. And in the United States, an expert panel in February recommended that the government allow clinical trials for such a technique that could eliminate many inherited mitochondrial diseases.
Federal regulators have said they are reviewing the idea, but that laws that prohibit the creation of embryos for research purposes have pushed back when they can fully consider applications. A researcher in Oregon who has bred “three-parent” monkeys and says they are healthy has previously asked the Food and Drug Administration to use the technique in humans.
Dr. John Zhang, who led the scientific team, told New Scientist that the boy was born in Mexico because “there are no rules” there.