May 6, 2022 — A fertility procedure that mixes genetic material from three people to prevent couples from having children with certain debilitating and potentially fatal inherited disorders is now legal in two countries: the U.K. and Australia.

Australia’s senate passed a bill on March 30 amending pre-existing laws to allow the procedure in certain circumstances.

The goal of this procedure is to prevent genetic disorders caused by defective mitochondria, the power plants inside our cells that provide energy for normal growth and development. When mitochondria don’t produce any energy at all, the resulting genetic disorders are quickly fatal. When mitochondria make only a little energy, children can have severe illnesses and disabilities.

“The outcomes from this problem are really severe, and it’s highly likely that the baby will be very sick or die,” says Arthur Caplan, PhD, head of the division of medical ethics at the New York University Grossman School of Medicine in New York City.

Mitochondria have a little bit of DNA, and children inherit them from their mother. To avoid children inheriting this damaged genetic material, mitochondrial donation, also known as three-parent in vitro fertilization (IVF), takes the nucleus, which contains most of the DNA that makes us who we are, from an egg of the mother and puts it into a donated egg from a woman with healthy mitochondria.

The egg is then fertilized with sperm through IVF, and the resulting embryo has genetic material from two women and one man.

One ethnical conundrum about mitochondrial donation is that any child conceived this way would inherit modified DNA and pass that along to their own children.

“I think it’s likely that we are going to go down this road to repair disease,” Caplan says. “I don’t think all genetic engineering of embryos is wrong, but we have to draw the line between enhancement versus treating disease.”

For couples who want a child that shares at least some of their own DNA, there are other ways to have a child without damaged mitochondria. One option would be genetic screening of their embryos to find healthy embryos without this defect, which would work for some women who have relatively few mitochondrial mutations. Another alternative is using a donor egg from a woman with healthy mitochondria.

Mitochondrial donation may appeal to couples who want their children to have a genetic connection to both parents, Caplan says. But prospective parents also need to be aware that this procedure is relatively new and, unlike egg donation, doesn’t have a long track record of success.

“It looks promising, but we don’t have the full safety picture yet and we’re not going to start to get it for another decade or so,” Caplan cautions. “I do think it’s worth offering as one option, but you also have to get people to think about how important it is to have a biological child together and make sure that they understand that even if we try this technique, we don’t know the long-term outcomes for children yet.”



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