Could some inherited diseases become a thing of the past?
They might, if four baby macaque monkeys in Oregon named Mito, Tracker, Spindler and Spindy are any indication. The foursome is living proof that the technology to eliminate certain heritable conditions may already exist -- at least for non-human primates, that is.
Researchers from the Oregon National Primate Research Center report that they have developed a new technique that prevents the inheritance of mutations. Furthermore, they have successfully used the technique in monkeys. Their findings are published in the journal Nature.
Specifically, the researchers were able to alter the mitochondrial DNA -- one of the two types of DNA in a cell -- in order to prevent the baby monkeys from developing the same genetic disorder their mother had.
The finding has big implications if the results can one day be borne out in humans as well. Some 150 diseases are known to be caused by mutations in mitochondrial DNA. Myoclonic epilepsy with ragged red fibers (MERRF); mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS); and Leber hereditary optic neuropathy (LHON) are just three of the known inherited diseases caused by mutations in mitochondrial DNA.
Though many of these incurable diseases result from spontaneous mutations in mitochondrial DNA, others are inherited.
"About one in 6,000 people have mutations in inherited mitochondrial DNA that could cause disease," said Dr. Shoukhrat Mitalipov, one of the researchers at the Oregon National Primate Research Center.
But while the researchers had their sights set on mitochondrial diseases, at least one researcher not affiliated with the study said the finding could have other applications as well.
"The application that the authors talk about is mitochondrial disease, but the more common application might be to battle ... age-related infertility," said Dr. Richard Paulson, professor of obstetrics and gynecology and chief of reproductive endocrinology and infertility at the University of Southern California Keck School of Medicine. "If it turns out -- as many of us think -- that the aging egg has bad mitochondria, then this technique might allow for the first time pregnancy in older moms using their own genetics.
"This is huge."
A Tale of Two DNAs
Unlike nuclear DNA, which comes from both parents, mitochondrial DNA comes only from the mother. Hence, lead study author Dr. Masahito Tachibana said, "Mitochondrial DNA is passed (only) through eggs."
Armed with this knowledge, the researchers removed nuclear DNA from an unfertilized diseased egg cell and transplanted it into another unfertilized, healthy egg cell whose nuclear DNA had been removed. These eggs were then fertilized with sperm cells to yield embryos.
In essence, the researchers were able to snip out the bad parts while keeping the good ones.
The researchers said they hope this method could one day be used in humans to produce healthy children in families confirmed to have inherited mitochondrial DNA diseases, though much more research will be needed to determine whether this is feasible.
But Paulson said that if the technique could indeed be used in humans, it could be a boon for infertile mothers who wish to have children who are genetically related to them.
"At the present time, older moms have to use egg donors, meaning that their children have the genetic inheritance from the egg donor," Paulson said. But he added that if the technique that is described in this paper is applicable to humans, then the infertile mother's genes can be inserted into a donor egg.
"The older mom will still get to pass on her genetics, and the baby will simply have the mitochondria from the egg donor," Paulson said.
Not Ready for Humans, Researchers Say
So what's to keep researchers from attempting this in human cells?
First, the researchers have yet to see whether the four baby monkeys in this experiment will develop into healthy adults; if they don't, it could be a sign that the technique is not safe for humans, either.
Additionally, the baby monkeys' ability to reproduce remains unknown.
Further complicating such findings in humans is that existing laws currently prevent federal dollars from being used in such research. According to Mitalipov, the U.S. Food and Drug Administration has placed a ban on experiments like this on human cells. This ban keeps federal funding for human experiments off limits.
Hence, Mitalipov added, state or private sponsorship would be required to fund any such human tests.