A proposed new fertility treatment that could prevent certain types of genetic diseases is likely to be safe, according to the latest scientific assessment of the procedure by a scientific review panel in the United Kingdom. But the panel, which issued its report today, says more research in a few areas is necessary before the technique, called mitochondrial DNA replacement therapy, is used in patients.
Mitochondria are organelles that provide the cell with energy. They carry their own DNA, called mtDNA, and mutations in those genes cause mitochondrial disease. The symptoms are variable, but organs that use lots of energy such as the brain, muscles, and heart are often affected. Because mitochondria are passed on through the egg cell, the diseases are inherited from the mother. The technique could potentially allow women who carry disease-causing mutations in their mitochondrial DNA to have healthy biological children.
Researchers have developed ways to transfer the genetic material from an egg cell that carries faulty mitochondria into a donor egg cell that has healthy mitochondria. The resulting embryo carries nuclear DNA from the mother and father and mitochondrial DNA from an egg donor.
The procedure is currently forbidden in the United Kingdom because it would alter the genetic material of an egg or embryo. In February, after years of scientific and ethical assessments and public consultations, the government issued draft regulations that would change the law to allow the Human Fertilisation and Embryology Authority (HFEA) to grant licenses to clinics to offer the procedure. The public consultation on the proposal closed on 21 May, and the Department of Health is expected to issue its response in the coming months. The government must still decide whether to present the proposed law to Parliament for a vote.
In the United States, the Food and Drug Administration (FDA) held a meeting in February to discuss the issue. There is no federal law that regulates such in vitro fertilization procedures, but FDA has said clinicians would need the agency’s permission before trying it.
Today’s report is the third such assessment from the United Kingdom’s HFEA, which regulates the country’s fertility clinics and embryo research. HFEA’s five-member panel concludes that, consistent with the 2011 and 2013 assessments, there is no strong evidence to suggest that the procedure would be unsafe.
The latest report examined worries by some researchers that mismatches between the nuclear DNA of the parents and the mitochondrial DNA of the oocyte donor might cause unanticipated problems, as some animal research had suggested. The panel concluded that the risk of such problems is low, but it does recommend that so-called haplotype matching—looking for a donor whose mtDNA type might be similar to the mother’s—be part of the process for choosing an egg donor “as a precautionary step.”
The panel concluded that more research in several areas is needed before the technique is applied in patients. For example, it said, not enough is known about how a mix of mtDNA in a cell might affect development and the health of a potential child. (Such a mix could arise if faulty mtDNA from the original egg was unintentionally transferred along with the nuclear DNA.) It also called for more data on human embryos created with the technique. The embryos would not be implanted in a mother, but would be compared with control embryos and perhaps used to derive embryonic stem cells, which could then be studied to learn more about downstream effects of the procedure.