The US National Academy of Medicine is encouraging the US Food and Drug Administration to approve a technique used to transfer DNA from normal human eggs, to those with disease-causing genetic mutations. The gene therapy technique involves the transfer of mitochondria – the energy producing organelle in the cell, which has its own DNA – from the healthy ova of one women, to an egg harvested from another.
Researchers are hoping to use this technique to prevent the inheritance of mitochondrial DNA-based diseases. As with all techniques involving manipulation of human embryos, US regulators are concerned about the safety and ethicality of the procedure, which would effectively mean the resulting child would have three biological parents.
In the guidance released by the academy panel, it suggested that the technique should only be applied to male embryos to prevent the transmission of the modified mitochondria. Children inherit their mitochondria from their mother alone, so researchers would be advised against using the gene editing technique on female embryos.
The report also specifies that children born using this technique should be monitored for multiple years after birth, to ensure the safety of the procedure. The committee outlines a number of other steps for researchers to follow, and says that if further study indicates the mitochondria replacement is safe and effective, it could be used on female embryos in the future.
The technique was approved in the UK in 2015, with no restrictions for use based on the gender of the embryo. Unfortunately for researchers in the US, the 2016 government spending bill enacted at the beginning of this year may prevent the start of clinical trials that would use the technique to implant embryos into women.
“It’s good news, but the future seems very hazy compared to a few months ago,” said Shoukhrat Mitalopov, a reproductive biologist at the Oregon Health Sciences University in Portland. Despite the potential regulatory hurdles, Mitalopov is testing the technique on monkeys in his lab to determine if there are any negative side-effects as the mitochondrial DNA is passed down through subsequent generations.
Some are more concerned about the ethical implications of using such a technique. According to Marcy Darnovsky, president of the non-profit Center for Genetics and Society in California, the study “realized all the concerns and leapt to the conclusion that things should go forward despite all the concerns. I would have more faith in the argument if allowing this technology isn’t going to pave the way for more concerning forms of germline editing.”