U.S. regulators are deciding whether to allow testing in humans of mitochrondrial replacement, which combines parts of two human eggs with sperm to create a baby free of certain inherited diseases. So far, the research has been limited to monkeys.
According to Bloomberg, "The process works by replacing potentially variant DNA in the unfertilized eggs of a hopeful mother with disease-free genes from a donor."
An advisory committee of the Food and Drug Administration recently met to "discuss oocyte modification in assisted reproduction for the prevention of transmission of mitochondrial disease or treatment of infertility."
"Because the process would change only a small, specific part of genetic code, scientists say a baby would largely retain the physical characteristics of the parents," wrote Bloomberg's Elizabeth Lopatto. "Still, DNA from all three — mother, father and donor — would remain with the child throughout a lifetime, opening questions about long-term effects for this generation and potentially the next. Ethicists worry that allowing pre-birth gene manipulation may one day lead to build-to-order designer babies."
“Once you make this change, if a female arises from the process and goes on to have children, that change is passed on, so it’s forever,” Phil Yeske, chief science officer of the United Mitochondrial Disease Foundation, told Lopatto. “That’s uncharted territory; we just don’t know what it means. Permanent change of the human germline has never been done before, and we don’t know what will happen in future generations.”
Both parents pass nuclear DNA to offspring, while mitochondrial DNA comes only from the mother. The new technology, engineered at Oregon Health & Science University in Portland, Ore., removes the nucleus of the donor's egg and uses the mother's nucleus with the healthy mitochondria from the donor. The resulting egg is then fertilized with the father's sperm in vitro and implanted in the mother's womb.
The procedure could potentially allow a woman to avoid passing on certain genetic diseases that are inheritable, proponents say.
Not all scientists are enthusiastic. Researchers in Germany and Australia published a paper in the journal Science last September that noted a lack of studies on the health effects such modification would have on the humans who resulted from such genetic modification. They raised questions about the procedure's ultimately safety and said it requires more study.
At the recent hearing, covered by BioNews, out of the United Kingdom, "Supporters argued that the technique, if allowed, could be used to prevent mitochondrial diseases. Some critics, however, said this would lead to 'designer babies.' Regardless, scientists were asked to advise only on the scientific implications of the technique, not its legal or ethical implications."
The BioNews article noted that "more than 4,000 children are born with inherited mitochondrial diseases every year. Mitochondrial diseases can be impossible to diagnose prenatally and are incurable."
Meanwhile, government health officials in the United Kingdom have just published a paper on "how the creation of three-person babies using new IVF techniques" could be regulated there, according to a recent Medical News Today story. Tentative approval has been given for use of the procedure in the United Kingdom, but the details of regulation are being worked out.
The comment period on the United Kingdom's "consultation document" closes in mid-May.
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