The New York-based team that performed mitochondrial replacement therapy to enable a Jordanian couple to avoid passing on a rare genetic disease to their son has published its technique, but New Scientist notes that there may be some issues with how the work was conducted.
In Reproductive BioMedicine Online, the New Hope Fertility Center's John Zhang and colleagues describe the approach they used to transfer the nucleus from the mother's egg into the cytoplasm of a donor egg. The mother is a carrier of Leigh's syndrome, a mitochondrial disorder, and she'd previously passed the condition on to two children, who died young.
Mitochondrial transfer therapy aimed to limit the number of maternal mitochondria passed on to the infant. The team reports that the baby boy, who was seven months old and healthy at the time the paper was written, had an mtDNA mutation load ranging between 2.4 percent and 9.2 percent, which Zhang and his colleagues say is below the expected threshold for disease.
"This brilliant technology is exciting for mankind," Zhang says in a statement.
But New Scientist points out that an editorial appearing alongside the paper raises ethical and other questions about the work. For instance, the journal editors write that the Zhang and his colleagues received Internal Review Board approval from the clinic in Mexico where they transferred the embryo, but did not seek IRB approval in New York, contravening American Medical Association policies for international research. In addition, the editors point out that though the authors say the mother was counseled, the consent form she signed didn't include the specific risks of mitochondrial transfer therapy, New Scientist adds.
The editors add that they hope that their publication of the paper, despite its weaknesses, will stimulate constructive criticism and evaluation.