Mitochondria are the powerhouses that provide our bodies’ cells with the energy they need to function. So when mitochondrial genes go awry, the result is hereditary disorders that wreak havoc on organs with high energy requirements, like the brain and the heart. In September, researchers announced that they had demonstrated a way to replace defective mitochondria with healthy ones. Moreover, they were able to perform the repair before an egg cell was even fertilized.
Geneticist Shoukhrat Mitalipov of Oregon Health and Science University and his team took the nucleus out of an egg from a macaque monkey, removing almost all of the genetic material but leaving the mitochondria and their DNA. The researchers then injected the nucleus of an egg from a second macaque, fertilized the cell with sperm, and implanted it in the second monkey’s womb. The technique has yielded four healthy babies. The same procedure could be used to transplant DNA from a human egg with mitochondrial disorders into one with healthy mitochondria.
“This offers real treatment for many diseases,” Mitalipov says. “And not in 20 years. It can be used now to prevent thousands of birth defects.” The process would yield a baby with two biological mothers, raising prickly legal and ethical questions. But Mitalipov points out that only 37 mitochondrial genes would be replaced; the 25,000 nuclear genes that make up an embryo’s DNA and define all of a person’s external traits would remain unchanged.