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16 DISCOVERMAGAZINE.COM

LEFT: GUNILLA ELAM/SCIENCE SOURCE. RIGHT: OREGON HEALTH AND SCIENCE UNIVERSITY

5

Human Embryo Gets

CRISPR Treatment

❯

IN JUST A FEW SHORT

YEARS, the gene-editing

tool CRISPR-Cas9 has

infiltrated biology labs around the

world. This summer, scientists

working in a U.S. lab announced

they’d used CRISPR to modify

viable human embryos, which

were kept alive just a few days.

The research is a first in the

United States, though scientists

in China have conducted similar

experiments.

This latest effort, led by

researchers at Oregon Health and

Science University, also succeeded

in avoiding unintended effects —

something that’s plagued other

researchers. The team fixed a

mutation by removing a disease-

causing gene from an embryo.

The repair, reported in August in

Nature, corrected an inheritable

heart condition, passed down by

the embryo’s father, the study’s

lone sperm donor.

“This embryo gene correction

method — if proven safe — can

potentially be used to prevent

transmission of genetic disease

to future generations,” says study

co-author Paula Amato. Once

it is proven safe, researchers

hope to start clinical trials. That

would mean implanting the

gene-edited embryo into a woman

and studying the genetically

engineered child. If clinical trials

don’t get FDA approval, study

leader Shoukhrat Mitalipov says

they would pursue them abroad.

Exactly how the mutation

was fixed was surprising to

Mitalipov’s team.

They expected that their use

of CRISPR would introduce a

“template” to guide the DNA to

fix the faulty gene. Instead, the

embryo replaced the targeted

bad gene with a healthy gene

from the mother — a conclusion

that’s been criticized by a group

of prominent scientists. They

questioned the mechanism

involved in the repair of the

mutation.  ERIC BETZ

Scientists

Urge Caution

Researchers should tread

lightly when it comes to

editing the genes of human

embryos, according to

guidelines handed down

in February. The report —

issued by dozens of experts

convened by the National

Academy of Sciences and

the National Academy of

Medicine — says so-called

germline editing, in which

genetic changes are passed

to future generations,

should happen only when

there’s no “reasonable

alternative” treatment.

Doctors already can remove

problematic embryos and

implant healthy ones using

in vitro fertilization. The

panel also said the genes

of embryos shouldn’t be

edited for reasons other

than treating or preventing

disease or disability.  E.B.

Researchers at Oregon Health and Science University captured the development

of human embryos in images as part of their work using a gene-editing tool. It’s the

first time a U.S. lab successfully repaired a genetic mutation in a human embryo.

In CRISPR-Cas9 gene

editing, a guide RNA

sequence (green)

helps Cas9 protein

(purple) cut DNA at

the correct spot.