Scientists in Oregon have created embryos with genes from one man and
two women, using a provocative technique that could someday be used to prevent
babies from inheriting certain rare incurable diseases.
The researchers at Oregon Health & Sciences University said they are
not using the embryos to produce children, and it is not clear when or even if
this technique will be put to use. But it has already stirred a debate over its
risks and ethics in Britain, where scientists did similar work a few years ago.
The British experiments, reported in 2008, led to headlines about the
possibility someday of babies with three parents. But that’s an overstatement.
The DNA from the second woman amounts to less than 1 percent of the embryo’s
genes, and it isn’t the sort that makes a child look like Mom or Dad. The
procedure is simply a way of replacing some defective genes that sabotage the
normal workings of cells.
The British government is asking for public comment on the technology
before it decides whether to allow its use in the future. One concern it cites
is whether such DNA alteration could be an early step down a slippery slope
toward “designer babies” _ ordering up, say, a petite, blue-eyed girl or tall,
dark-haired boy.Questions have also arisen about the safety of the technique,
not only for the baby who results from the egg, but also for the child’s
descendants.
In June, an influential British bioethics group concluded that the
technology would be ethical to use if proven safe and effective. An expert
panel in Britain said in 2011 that there was no evidence the technology was
unsafe but urged further study.
Laurie Zoloth, a bioethicist at Northwestern University in Evanston,
Ill., said in an interview that safety problems might not show up for several
generations. She said she hopes the United States will follow Britain’s lead in
having a wide-ranging discussion of the technology. While the kind of diseases
it seeks to fight can be terrible, “this might not be the best way to address
it,” Zoloth said.
Over the past few years, scientists have reported that such experiments
produced healthy monkeys and that tests in human eggs showed encouraging
results. The Oregon scientists reported Wednesday that they have produced about
a dozen early human embryos and found the technique is highly effective in
replacing DNA.
The genes they want to replace aren’t the kind most people think of,
which are found in the nucleus of cells and influence traits such as eye color
and height. Rather, these genes reside outside the nucleus in energy-producing structures
called mitochondria. These genes are passed along only by mothers, not fathers.
About 1 in every 5,000 children inherits a disease caused by defective
mitochondrial genes. The defects can cause many rare diseases with a host of
symptoms, including strokes, epilepsy, dementia, blindness, deafness, kidney
failure and heart disease. The new technique, if approved someday for routine
use, would allow a woman to give birth to a baby who inherits her nucleus DNA
but not her mitochondrial DNA.
Here’s how it would work:
Doctors would need unfertilized eggs from the patient and a healthy
donor. They would remove the nucleus DNA from the donor eggs and replace it
with nucleus DNA from the patient’s eggs. So, they would end up with eggs that
have the prospective mother’s nucleus DNA, but the donor’s healthy
mitochondrial DNA.
In a report published online Wednesday by the journal Nature, Shoukhrat
Mitalipov and others at OHSU report transplanting nucleus DNA into 64 unfertilized eggs from healthy donors.
After fertilization, 13 eggs showed normal development and went on to form early
embryos. The researchers also reported that four monkeys born in 2009 from eggs
that had DNA transplants remain healthy, giving some assurance on safety. Mitalipov
said in an interview that the researchers hope to get federal approval to test
the procedure in women, but that current restrictions on using federal money on
human embryo research stand in the way of such studies.
The research was funded by the university and the Leducq Foundation in
Paris. Dr. Douglass Turnbull of Newcastle University in Britain, whose team has
transplanted DNA between eggs using a different technique, called the new
research “very important and encouraging” in showing that such transplants
could work. But “clearly, safety is an issue” with either technique if it is
applied to humans, he said.
Washington Times
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