Dina Fine Maron’s Scientific American article concerning new technologies that could marry DNA from three individuals, creating three-parent children, is a good overview of the technology’s position in the United States right now. (I’m for it, for whatever it’s worth, in that preventing inherited mitochondrial DNA diseases in children is a good thing.)
Scientists have already had successes with this type of reproductive approach in monkeys and in human embryos, and are now eager to launch human clinical trials. First, however, they must get the green light from the U.S. Food and Drug Administration, which will convene a public hearing before an advisory committee on February 25.
The technology, called oocyte modification (but sometimes nicknamed “three-parent IVF”), involves scooping out potentially mutated mitochondrial DNA (mtDNA) from a woman’s egg and replacing it with the mtDNA of an unaffected donor woman. The process is designed to prevent the transmission of some debilitating inherited mitochondrial diseases, which can result in vision loss, seizures and other maladies. Such inherited diseases, often unfortunately known by acronyms for complex medical names that include LHON, for Leber’s Hereditary Optic Neuropathy, along with MELAS, MERRF and NARP, occur in about one in every 5,000 live births and are incurable.
Once the mtDNA has been swapped out, the egg could be fertilized in the lab by the father’s sperm and the embryo would be implanted back into mom where pregnancy would proceed. The resulting child would be the genetic offspring of the intended mother but would carry healthy mitochondrial genes from the donor.
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Scientists already have evidence for the promise of this type of oocyte modification. Shoukhrat Mitalipov of the Oregon Health & Science University and his colleagues created human embryos in this way, although they did not implant those embryos to make babies. Their findings were published in October 2012 in Nature. Other work from that same team also found that in monkeys the process could lead to the birth of healthy offspring that remained free of complications into adulthood. (Scientific American is part of Nature Publishing Group).
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But wading into this type of approach is also fraught with ethical issues. Marcy Darnovsky, executive director of the Center for Genetics and Society, fears that this reproductive approach could soon lead to tampering with other traits, such as intelligence or sports ability. “Life is full of slippery slopes and we need brakes,” she says. “This is described as saving lives but it is not aimed at people who are sick,” she adds. The FDA advisory committee does not plan to consider ethical issues at this meeting. Instead it will focus on the scientific aspects of future clinical trial considerations, including long-term risk of carryover of abnormal mtDNA, the potential benefits and harm to mothers and future children, and the need for multigenerational follow-up in any trials (because female children could pass on mitochondrial disease to future offspring). “Our job will be purely to air the issue and bring it out into the open,” says Evan Snyder, chair of the committee and director of the Stem Cell and Regenerative Biology Program at Sanford–Burnham Medical Research Institute in La Jolla, Calif. “We’re not going to come out at the end of the meeting and say we are advocating for clinical trials or any particular technique. This is educational,” he says.