Thursday, August 27, 2009
By Malcolm Ritter, AP Science Writer
NEW YORK
(AP)—An experimental procedure that someday may enable women to avoid passing
certain genetic diseases on to their children has gained an early success, with
the birth of four healthy monkeys, scientists report.
The technique still faces safety questions and perhaps
ethical hurdles, but an expert called the work exciting.
The experiment, which involved transferring DNA between eggs
from rhesus macaques, was described Wednesday on the Web site of the journal
Nature by researchers from the Oregon Health and Science University.
Someday, the technique may be used against diseases caused
by inherited defects in the "power plants" of cells, called
mitochondria. These conditions are uncommon and unfamiliar to most people, such
as Leber hereditary optic neuropathy. Roughly one person in every 4,000 or
5,000 either has one of these mitochondrial diseases or is at risk for one.
Symptoms of these potentially fatal illnesses include muscle
weakness, dementia, movement disorders, blindness, hearing loss, and problems
of the heart, muscle and kidney.
An egg contains the vast majority of its DNA in the nucleus,
but mitochondria contain DNA elsewhere in the egg. So if a woman has a disease
caused by defects in the mitochondrial DNA, the new technique might someday
make it possible for her to pass on her normal DNA from the nucleus but not the
flawed DNA from the mitochondria.
To allow for that, doctors may transplant nucleus DNA from
the eggs of such women into donor eggs that have healthy mitochondria. The
donor eggs would have had their own nucleus DNA removed. After test-tube
fertilization, this egg would in theory produce a baby without mitochondrial
defects. (Fathers do not pass along their mitochondria.)
Researcher Shoukhrat Mitalipov said more safety studies must
be done in monkeys. He noted that the technique would face regulatory hurdles
for human studies because it would change the DNA inherited by future
generations, an idea that has long provoked ethical concerns.
Douglas Wallace of the University
of California, Irvine, an authority on mitochondria who
wasn't involved in the federally funded experiment, said the results were
exciting and the technique is "potentially very interesting."
But "there are safety issues that are going to need to
be addressed before one could think about it in humans," Wallace said.
Information
on mitochondrial disease
SOURCE: The Associated Press