Researchers relied on a newer
gene-editing technique that may make it possible to engineer embryos, a
prospect that has long alarmed bioethicists.
·
Scientists
at Columbia University have successfully edited DNA in early human embryos with
unprecedented precision.
·
The
achievement could advance the possibility of correcting genetic disorders
before birth.
·
Researchers
employed base editing, a
newer and more precise form of gene editing.
·
Unlike
traditional CRISPR, base editing changes individual DNA letters without cutting
large sections of DNA.
·
The
technology could help repair disease-causing genetic mutations in embryos.
·
It may
improve outcomes for families at risk of passing on hereditary disorders.
·
Previous
embryo-editing experiments using CRISPR caused:
o Large DNA deletions.
o Chromosome damage.
o Failed gene repairs in many embryos.
·
Researchers
described some of the outcomes as catastrophic.
·
Scientists
successfully edited:
o PCSK9,
linked to cholesterol levels and heart disease risk.
o HBG,
involved in fetal hemoglobin
production.
·
In
some cases, both genes were edited simultaneously in the same embryo.
·
Researchers
found no evidence of the extensive chromosome damage previously associated with
CRISPR-based embryo editing.
·
The
technique was not completely successful in all cells.
·
Some
embryos became mosaics,
containing both edited and unedited cells.
·
Such
genetic inconsistencies could create health risks if embryos develop into
babies.
·
The
study has been posted online and is currently under review for publication.
·
Researchers
emphasized that the technology is not yet ready for clinical use.
·
While
the technology could prevent inherited diseases, critics fear it could be used
to select or enhance traits.
·
Some
bioethicists warn that such applications could resemble modern forms of
eugenics.
·
The
debate intensified after He Jiankui used CRISPR to edit embryos that later
resulted in the birth of genetically modified children.
·
The
experiment was widely condemned, and the scientist was imprisoned by Chinese
authorities.
·
Nucleus
Genomics is supporting further research.
·
The
company already screens IVF embryos for genetic disorders and predicts risks
for certain diseases and traits.
·
Critics
argue that embryo editing could eventually be used to influence characteristics
such as:
o Height
o Intelligence
o Disease susceptibility
·
However,
most human traits are influenced by hundreds or thousands of genes, making such
enhancements technically difficult.
·
Future
studies will focus on:
o Reducing mosaicism.
o Testing the technology on larger embryos
commonly used in IVF clinics.
o Assessing long-term safety and unintended
genetic effects.
·
Scientists
and bioethicists stress that many risks remain unknown.
·
Potential
harmful effects may not become apparent until after birth or later in life.
The
Columbia University study marks a significant advance in embryo gene-editing
technology by demonstrating safer and more precise DNA modification through
base editing. While the breakthrough could eventually help prevent inherited
diseases, major scientific, ethical, and regulatory challenges remain before
the technology could be considered for clinical use in human reproduction.
[ABS News Service/05.06.2026]
Scientists
at Columbia University have edited the DNA of early human embryos with
unprecedented accuracy, an achievement that could open the way to babies
engineered with particular characteristics.
The
prospect has fueled controversy for years. On the one
hand, the technology might one day enable parents to safely repair
disease-causing mutations in embryos. But it might also be used to select
desired traits — a practice that some ethicists have argued is nothing short of
eugenics.
Dieter
Egli, a geneticist at Columbia University who led the research, called for a
public conversation about the pros and cons of altering embryonic DNA. “As a
scientist, you can provide the data for discussion, but then essentially there
you stop and let others take over,” he said.
With
a newer technology called base editing, Dr. Egli and his colleagues were able
to meticulously replace individual genetic letters in sequences of DNA without
causing the damage often observed with an earlier form of gene editing, CRISPR.
Dr.
Egli cautioned that the research left unanswered many questions about harmful
side effects. “We’re not saying this is going to be used tomorrow in the
clinics,” he said.
Dr.
Egli and his colleagues posted their study online. The research is under review
for publication in a scientific journal.
The
possibility of editing the DNA of human embryos became a matter of serious
debate more than a decade ago, after the invention of CRISPR.
In
2012, scientists discovered how to create customized molecules that could snip
out a targeted segment of DNA. CRISPR quickly became a standard tool for
scientists — a cheap, easy way to discover how genes function by tweaking the
genome.
A
number of medical companies sprang up, seeking to use the technology to treat
hereditary diseases. In 2023, the Food and Drug Administration approved a
CRISPR-based treatment for sickle cell anemia.
But
scientists knew it was not perfect. In some cells, CRISPR molecules failed to
find their targets in DNA, or sometimes snipped out the wrong genetic bits.
Those
concerns did not stop a Chinese scientist, He Jiankui, from using CRISPR to
alter the DNA of human embryos in 2018.
Dr.
He later said his goal was to give children a genetic resistance to H.I.V.
infection. But experts condemned his work as reckless, and Chinese authorities
imprisoned him for three years.
Dr.
He’s experiment led to three “healthy, beautiful babies,” he claimed in a
January interview with The New York Times. But the status of the children has
never been independently evaluated.
In
2020, Dr. Egli and his colleagues carried out an experiment to see how CRISPR
behaves in human embryos.
They
obtained donated sperm from men with a mutation in a gene called EYS causing
hereditary blindness. The researchers used the sperm to fertilize healthy eggs,
producing human embryos with one working copy of EYS and one defective copy.
The researchers used CRISPR to cut out the mutant region of EYS.
Previous
studies suggested that the embryo might repair the gene by using the healthy
version as a guide. Only some embryos did so, ending up with two working copies
of EYS.
But
the repair failed in about half of them. Some chopped off long stretches of
DNA. Some destroyed the entire chromosome on which the EYS gene is located.
“It
had absolutely catastrophic consequences,” Dr. Egli said.
Many
scientists and bioethicists saw these results as further evidence that editing
human embryos was far too risky to even consider — at least, for the time
being.
But
in 2016, David Liu, a geneticist at Harvard University, and colleagues combined
one of the CRISPR molecules with other compounds to create base editing, a new
method for editing genes. Rather than chop out a segment of DNA, base editors
made a tiny nick in one strand. They could then guide the cell to fix the
mutation.
Base
editing has proved to be often superior to earlier CRISPR methods. Last year, a
baby was cured of a potentially lethal genetic disorder after receiving a
customized set of base editing molecules.
Dr.
Egli decided to try it on human embryos.
For
the new experiments, he and his colleagues set out to alter two genes. One,
called PCSK9, can carry mutations that raise levels of LDL in the blood — and
the risk of heart disease. The other gene, HBG, directs hemoglobin
production in fetuses.
Dr.
Egli and his colleagues delivered their base editors into fertilized eggs and
into two-cell embryos donated by parents. The researchers didn’t find any of
the extensive damage associated with CRISPR.
Instead,
the researchers were able to successfully change both the PCSK9 and HBG genes.
In some experiments, they simultaneously changed both genes in the same embryo.
But
the edits were still not perfect. Sometimes the base editing molecules failed
to find their target DNA. As a result, some cells in the embryos retained the
original versions of the genes, while others were altered.
Those
embryos became genetic mixtures, so-called mosaics. Having cells with different
versions of the same gene could have led to medical problems had the embryos
developed into babies.
Despite
those failures, the new results were strong enough that Dr. Paula Amato, a
fertility expert at Oregon Health & Science University who was not involved
in the study, thought the method was “promising.”
Still,
she said it would be important to examine the final results when they’re
published in a journal.
Ana
Iltis, a bioethicist at Wake Forest University, worried that assessing the
safety of base-edited embryos will require far more scrutiny than simply
looking for damaged chromosomes.
“It
is possible that some of the potentially harmful effects would not be evident
until after birth,” she warned.
Nathan
Treff, the chief clinical officer of Nucleus Genomics and a co-author of the
new study, said that the ability to fix disease-causing mutations in embryos
could be a boon to those using I.V.F., allowing them to implant embryos that
they otherwise would have discarded.
“There’s
still work to do before getting to that point, but this research gets us
closer,” Dr. Treff said.
Nucleus
Genomics will support the next stage of Dr. Egli’s research. (The federal
government does not fund studies on human embryos for research purposes.)
Some
upcoming studies will look for ways to avoid mosaic embryos. The researchers
will also test base editing on embryos that contain about 100 cells. Fertility
clinics typically freeze and test embryos at that stage.
Nucleus
Genomics, founded in 2021, screens I.V.F. embryos for thousands of genetic
disorders. The company also makes predictions about an embryo’s risks for
conditions such as heart disease and diabetes. And it looks at genes linked to
traits such as height and intelligence.
In
November, the firm stirred controversy when it plastered ads on New York City
subways telling commuters to “have your best baby.” Geneticists have criticized
the predictions Nucleus Genomics makes for traits, such as IQ, as having low
accuracy.
And
critics have accused the company of promoting a biotech spin on eugenics — a
charge the company rejects.
“We
see ourselves as a natural pathway for eventually bringing technologies like
this into clinical care as part of a broader genetics platform — a full
‘Genetic Optimization’ stack,” Kaitlyn Gallacher, head of communications at
Nucleus Genomics, wrote in an email.
Fyodor
Urnov, a geneticist at the University of California, Berkeley, who was not
involved in the study, said the results were in line with earlier studies of
base editing in living cells.
But
the prospect of using the method on embryos was both novel and risky, Dr. Urnov said. In regular I.V.F., embryos are screened for
genetic abnormalities. That made much more sense, he argued, than resorting to
a new technique with so many open questions.
“Do
we do what we’ve done safely and effectively 15 million times since 1978, or do
we instead try something that we can never truly de-risk, and where the risks
are clear?” he asked.
Dr.
Urnov speculated that the new method, once perfected,
would appeal to people who don’t merely want to address inherited diseases, but
to enhance traits by engineering embryos.
“What
they are really doing is providing the ‘baby improvers’ with a how-to manual
for forays beyond the ethical pale,” Dr. Urnov wrote
in an email.
Whether
anyone could actually alter babies in this way is not yet settled, though. Many
human traits are influenced by hundreds, or thousands, of genes.
Dr.
Egli noted that the more genes in a single embryo that scientists try to
rewrite, the higher the risk that they will fail.
“I
think you can probably combine three or four, maybe even five, but I think
there’s a limit,” he said. “Where that limit is remains to be determined.”