New details about a baby boy born with genetic material from his mother, his father and a female donor show the promise and drawbacks of a technique used to produce a “three-parent baby.” Called spindle transfer (SN Online: 10/18/2016), the technique is designed to avoid passing on potentially harmful DNA mutations in the mother’s mitochondria, powerhouse organelles that contain their own genetic material.
Now 6 months old, the baby boy appears to be healthy, John Zhang of New Hope Fertility Center in New York City said October 19 during a news conference at a meeting in Salt Lake City of the American Society for Reproductive Medicine. The baby’s average portion of mitochondrial DNA from his mother — some of whose mitochondria have a mutation that causes a fatal neurological disorder called Leigh syndrome — is less than 1.6 percent, Zhang and colleagues wrote in an abstract. The rest came from the healthy donor. Future checkups will examine whether the mitochondria the boy received from his mother increase in number (SN: 6/25/16, p. 8).
The procedure, performed in Mexico, resulted in five fertilized oocytes, four of which continued developing, Zhang and colleagues reported. Only one of those four blastocytes — the one that belonged to the baby boy — had the right number of chromosomes.
Mitochondrial DNA is inherited from mothers. Because the baby is a boy, any potentially harmful mitochondrial mutations wouldn’t be passed on to his children.