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 The milestone, reported in a paper released online August 2 in
Nature, was confirmed last week by Oregon Health and Science
University (OHSU), which collaborated with the Salk Institute and
Korea's Institute for Basic Science to use a technique known as
CRISPR-Cas9 to correct a genetic mutation for hypertrophic
cardiomyopathy.
Until now, published studies using the technique had been done in
China with mixed results.
CRISPR-Cas9 works as a type of molecular scissors that can
selectively trim away unwanted parts of the genome, and replace it
with new stretches of DNA.
"We have demonstrated the possibility to correct mutations in a
human embryo in a safe way and with a certain degree of efficiency,"
said Juan Carlos Izpisua Belmonte, a professor in Salk's Gene
Expression Laboratory and a co-author of the study.
To increase the success rate, his team introduced the genome editing
components along with sperm from a male with the targeted gene
defect during the in vitro fertilization process. They found that
the embryo used the available healthy copy of the gene to repair the
mutated part.
The Salk/OHSU team also found that its gene correction did not cause
any detectable mutations in other parts of the genome - a major
concern for gene editing.
Still, the technology was not 100 percent successful. It increased
the number of repaired embryos from 50%, which would have occurred
naturally, to 74%.
The embryos, tested in the laboratory, were allowed to develop for
only a few days.
"There is still much to be done to establish the safety of the
methods, therefore they should not be adopted clinically," Robin
Lovell-Badge, a professor at London's Francis Crick Institute who
was not involved in the study, said in a statement.
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'UTMOST CAUTION'
Washington's National Academy of Sciences (NAS) earlier this year
softened its previous opposition to the use of gene editing
technology in human embryos, which has raised concerns it could be
used to create so-called designer babies. There is also a fear of
introducing unintended mutations into germline cells.
"No one is thinking about this because it is practically impossible
at this point," Izpisua Belmonte said. "This is still very basic
research ... let alone something as complex as what nature has done
for millions and millions of years of evolution."
An international group of 11 organizations, including the American
Society of Human Genetics and Britain's Wellcome Trust, on Wednesday
issued a policy statement recommending against genome editing that
culminates in human implantation and pregnancy, while supporting
publicly funded research into its potential clinical applications.
Salk's Izpisua Belmonte, emphasizing that much more study is needed,
said the most important practical application for the new technology
could be in correcting genetic mutations in babies either in utero
or right after they are born.
"It is crucial that we continue to proceed with the utmost caution,
paying the highest attention to ethical considerations," he said.
SOURCE: http://go.nature.com/2wm4g1v
Nature 2017.
(This story was refiled Refiling with source link at end of story
and modifications throughout for professional readers)
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