The technology is now in place for three different parents to contribute DNA to an embryo - two of them providing the 98% of DNA in the cell nucleus, while another provides the crucial 2% that is mitochondrial DNA.
Why does this matter? Mitochondrial DNA is passed on exclusively by the mother, but some women carry mutations in their mitochondria that can cause severe health problems for their children. Researchers are hoping to create donor eggs that possess mutation-free mitochondrial DNA, leaving the nucleus to be fertilized by the other two parents.
There are a couple ways to accomplish this. One technique is known as maternal spindle transfer, in which nuclear DNA is taken from one woman's egg and inserted into the empty nucleus of another woman's egg, which can then be fertilized with the man's sperm. This has already been tested in monkeys, and researchers at the Oregon National Primate Research Center found the technique had the same birth success rate as monkeys born using traditional in-vitro fertilization.
The other option is called pronuclear transfer, where a woman's egg is first fertilized by the man's sperm. The nucleus of this egg is then removed and placed in another, emptied nucleus. Doug Turnbull and his fellow researchers at Newcastle University have created 80 human embryos using this method, but it's currently illegal to place these embryos in a mother's uterus.
Turnbull's team is awaiting the go-ahead from the relevant medical authorities, and they got some very encouraging news this week when the Human Fertilization and Embryology Authority issued their report:
"The techniques of maternal spindle transfer and pronuclear transfer are potentially useful for a specific and defined group of patients whose offspring may have severe or lethal genetic disease, and who have no other option of having their own genetic child. The evidence currently available does not suggest that the techniques are unsafe."
"Not unsafe" isn't exactly a ringing endorsement, but it's a big step towards the first three-parent babies. And, unlike surrogate pregnancies, all three parties really do contribute genetic material to the child. To be sure, mitochondrial DNA doesn't have a fraction of the influence that nuclear DNA has, but it does hang around for a very, very long time. After all, there's a reason why we're still talking about mitochondrial Eve all these hundreds of thousands of years later.
So then, feel free to add the terms "nuclear mother" and "mitochondrial mother" to your social science fiction toolkit, but then we might have to start really using those terms in a few years anyway.
Via New Scientist.