This Jordanian newborn represents the first successful birth in a new wave of "three parent" techniques — ones that are more sophisticated and that will likely stick around much longer.
For now, there is no country where the method used to conceive the baby boy is explicitly legal. Zhang performed the procedure in Mexico, where, he told New Scientist, "there are no rules."
These techniques involve the transfer of mitochondrial DNA or mtDNA. Often called the "power plants" of the cell, the mitochondria convert energy from food into energy that can power a cell. When someone's mitochondria don't function properly, it's bad news indeed for cells. Mitochondrial diseases can cause a whole host of life-threatening problems, and it's estimated that as many as 4,000 children are born with such conditions in the United States each year. In this case, the couple had experienced four miscarriages and lost two children at young ages to Leigh syndrome, a neurological disorder caused by a mutation in the mother's mitochondrial DNA.
Mitochondrial DNA, which contains just 37 genes compared to the staggering 20,000 or so carried by DNA in a cell's nucleus, comes entirely from the egg cell — the sperm cell contributes no mitochondria to the fertilized embryo, so there's no chance of a father's healthy genes picking up the slack after conception. Replacing the mother's faulty mitochondria with donor mitochondria in the newly conceived embryonic cells can produce a healthy baby while preserving the vast majority of its mother's DNA.
The United Kingdom recently approved a technique where two eggs (one from the mother and one from a donor) are fertilized with the father's sperm. The parents' genetic information is inserted into the donor's embryo, which has had everything but the mitochondria cleared out.
Because the parents who sought Zhang's help are devout Muslims, they didn't want to use a technique where embryos were destroyed. So instead, Zhang used a technique that does the cutting and pasting before fertilization takes place: The nucleus of a mother's egg cell is placed directly into a donor egg, replacing its original nucleus.
The baby seems to be healthy, New Scientist reports, but don't expect kids with 2.001 parents to become mainstream just yet: The baby was one of five embryos created for his parents using the technique, and he was the only one to develop normally after fertilization. He also still carries a small percentage of mitochondria with his mother's genetic mutation. His doctors hope and expect that he will develop normally, but there's no way of knowing how the presence of those malfunctioning genes might affect his health.
And then there are the legal hurdles: While the United Kingdom has embraced research on the genetic engineering of embryos — one three parent technique has already been approved, and scientists have been given the green light to more extensively modify human embryos in the lab for research purposes — the United States is at a standstill. In February, an expert panel of scientists and ethicists gathered by the Food and Drug Administration offered their approval of some applications of these techniques. But the omnibus fiscal 2016 budget bill passed by Congress in 2015 prohibited the use of government funds for experiments that genetically alter human embryos.
Zhang's team will describe their methods in more detail at the American Society for Reproductive Medicine’s Scientific Congress in Salt Lake City in October.