-- An infant born thanks to a breakthrough procedure that used genetic material from three people could give hope to thousands in the U.S. struggling with mitochondrial disease.
The baby boy was born without a mutation in his mitochondria, which he would otherwise have inherited from his mother, and is the first infant to be born as the result of a new procedure that involves genetic material from three people. While popularly called a "three-parent" baby, the infant gets 99.9 percent of his genetic material from his two biological parents, with a fraction of material coming from a donor's healthy mitochondria.
The breakthrough was revealed Tuesday by the American Society for Reproductive Medicine (ASRM), a multidisciplinary organization dedicated to the advancement of the science and practice of reproductive medicine. Dr. John Zhang, a New York-based doctor at the New Hope Fertility Clinic, is credited with performing the procedure and has submitted an abstract about the case to ASRM.
The ASRM did not reveal the sex of the infant but the New Scientist reported that it was a boy.
Zhang is expected to present more about the child and his process at the an ASRM meeting in October.
The infant was reportedly born thanks to spindle nuclear transfer -- in which the "spindle" of the egg that contains a mother's chromosomes but not her mitochondria is places into a donor egg. The donor egg's nuclear genetic material is removed. The eggs were then fertilized with the sperm of the woman's partner, according to the ASRM.
It is a variation on a procedure approved in the U.K. in which the nucleus of a fertilized egg from a couple is transferred to a fertilized donor egg. In that procedure, the donor's nucleus is removed and destroyed. The destruction of that nucleus reportedly was not acceptable to the couple, leading them to seek out an alternative through Zhang, according to the New Scientist report.
Zhang and the couple went to Mexico to perform the procedure, since it has not been approved in the U.S., according to New Scientist.
Every year, 1,000 to 4,000 children are born with mitochondrial disease in the U.S. and many families have no idea that their children are at risk for developing the dangerous disease until they're diagnosed, according to the United Mitochondrial Disease Foundation. Symptoms include fatigue, gastrointestinal problems and seizures, and can start as key organs lack energy to function properly.
Mitochondria are the structures inside the cell that generate energy and have DNA distinct from the cell's nuclear DNA. Mitochondrial DNA is inherited from the mother only.
Tracie Leeper, of Colony, Texas, is a carrier for mitochondrial disease, as is her husband. The couple did not know they were carriers until their son Jack was diagnosed at 10 months old. He died last year at 18 months after being born with Leigh disease, one kind of mitochondrial disease. Leeper said she's happy about the breakthrough so that others with mitochondrial disease may have more reproduction options. However, Leeper said she still wanted more information about the child's health.
"It's definitely mixed [emotions]. I'm so excited for the science," Leeper said, noting, however, that questions remain. "Is he going to get sick in a year or is it going to manifest in a different way?"
Mitochondrial disease often results from a mutation in the mitochondrial DNA, which can be passed solely from the mother to the child. It can also be caused by a nuclear DNA mutation in either mother or father that causes dysfunction in mitochondria. Since mitochondria are the energy sources for cells in the body, if they fail or do not work properly, it causes a range of symptoms that can be fatal in severe cases.
“This work represents an important advancement in reproductive medicine," ASRM President Dr. Owen Davis said in a statement on Tuesday. "Mitochondrial disease has been an important, and challenging problem. If subsequent research determines the safety and efficacy of spindle nuclear transfer, we look forward to it being an option for patients who risk transmitting mitochondrial diseases to their children."
Philip Yeske, the science officer for the United Mitochondrial Foundation, said the procedure may sound like science fiction but that people should remember the child's DNA will be 99.9 percent from their biological parents and not the donor. For parents who risk passing this disease to their children, the procedure could literally be a lifesaver.
"First and foremost this is absolutely about the prevention about the transmission of disease from mother to child," Yeske said. "These techniques afford [women with mitochondrial disease] the opportunity to have a biologically related child without the disease."
However, he said researchers will need to continue to study the child to see if they develop any further complications.
"What we lack are long-term studies introducing a third genome, whether that has implications for that child," Yeske explained.
There are an estimated 12,000 women of child-bearing age in the U.S. with mitochondrial disease, Yeske said. The procedure will not help everyone with mitochondrial disease, as some mutations arise from the nuclear DNA that is not changed in through this procedure.