Erika Check Hayden in Nature:
Regulators in the United States are considering whether to permit trials of a controversial assisted-reproduction technique intended to help women to avoid passing certain genetic defects on to their children. On 22 October, the US Food and Drug Administration (FDA) is scheduled to meet in Silver Spring, Maryland, to discuss a method that could prevent transmission of defects in mitochondria — cellular components that contain a small amount of DNA — from mother to child. The defects, which can cause fatal developmental conditions, affect as many as 4,000 US births a year. The technique places nuclear DNA from the egg of a woman with a mitochondrial defect into a donated egg that has had its nuclear DNA removed, but contains healthy mitochondrial DNA. Once the egg is fertilized, the resulting embryo would, in a sense, have three parents, because the donor mitochondrial DNA is passed down along with the mother and father’s nuclear DNA.
The FDA was asked to look into the issue by developmental biologist Shoukhrat Mitalipov at Oregon Health and Science University in Beaverton, who last year created early human embryos with the technique (see Nature http://doi.org/n76; 2012). When the manipulated eggs were fertilized, genetic abnormalities were detected in half of them — but seemingly normal embryonic stem-cell lines could be extracted from 38% of the rest. Trying to obtain stem cells from unmanipulated eggs results in a similar success rate. Mitalipov had used the same technique in 2009 to create apparently healthy rhesus monkeys. Now he wants to begin a clinical trial in humans.