Scientists Edit DNA Of Early Human Embryos

 

 

“A DNA-editing feat involving editing the genes of early stage embryos -- a far cry from designer babies, but nevertheless a step in that direction -- was announced last week.

 

Dieter Egli, an associate professor of developmental cell biology at Columbia University, and his co-authors, including Nathan Treff of Nucleus Genomics, a New York-based DNA-testing startup, say the technology could help fix disease-causing mutations in embryos.

 

"We're not throwing the final 'OK, you will have gene-edited babies tomorrow' at the public," said Egli. "That is a process that can occur through discussion matched with scientific progress."

 

The research was published online last week on a preprint server, which enabled the researchers to put out the paper before it was vetted by outside reviewers. Such vetting is common practice with scientific research.

 

Previous gene-editing efforts have often used Crispr, which can cut out parts of the DNA sequence, but the technology can also cause damage if the wrong DNA is targeted or cut out. In 2018, Chinese scientist He Jianku said he used Crispr to tweak DNA in human embryos and was imprisoned for the work.

 

The technology Egli's group used, called base editing [1], allows them to target individual DNA letters in sequences more precisely with fewer adverse effects.

 

That said, sometimes off-target or incomplete editing happens with base editing, resulting in so-called "mosaics," which are genetic mixtures of edited and unedited cells. In Egli's study, nearly 80% of embryos became mosaics, meaning if those embryos grew into babies, they would likely still have cells with the disease-causing mutations.

 

Egli's group focused on altering two genes, one that can raise the risk of heart disease and one that is tied to blood disorders like sickle cell disease, and the research showed they were sometimes able to do so successfully, in the same embryo, without damage.

 

"I am generally supportive of the concept of embryo editing to prevent genetic disease," said Dr. Paula Amato, a fertility expert at Oregon Health & Science University who wasn't involved in the research. This method of gene editing appears more promising than others, she said, but added the mosaic issue needs to be resolved for this to move forward.

 

Base editing has been used in human embryos before. The technology was used to correct a disease-causing mutation and an Alzheimer's disease-risk gene variant, said Alexis Komor, associate professor of biochemistry and molecular biophysics at the University of California, San Diego, who wasn't involved in the work.

 

"There really is not any unmet medical or clinical need for this, especially from an in vitro fertilization perspective," Komor said.

 

Using embryo editing to create babies is illegal in the U.S. and many other countries. Scientists have long worried that it is a slippery slope and that the technology could ultimately be used to promote eugenics.” [2]

 

1. Base editing is a precise gene-editing technology that allows scientists to chemically convert one single DNA nucleotide base into another without breaking the double-stranded DNA backbone. By avoiding DNA cuts, it minimizes unwanted genetic errors—such as insertions or deletions—making it highly accurate and safe for treating genetic diseases.

 

How It Works

•           Targeting: It uses a customized guide RNA and a modified, catalytically "dead" or nickase Cas9 enzyme (which cannot cut DNA) to find a specific genetic sequence.

•           Chemical Conversion: Once locked onto the target, the attached enzyme (a deaminase) directly alters the chemical structure of the target base.

Primary Types of Base Editors

•           Cytosine Base Editors (CBEs): Convert a Cytosine-Guanine (C → G) base pair into a Thymine-Adenine (T → A) base pair.

•           Adenine Base Editors (ABEs): Convert an Adenine-Thymine (A → T) base pair into a Guanine-Cytosine (G → C) base pair.

Key Advantages over Traditional CRISPR-Cas9

•     No Double-Strand Breaks: Traditional CRISPR acts like scissors, cutting both strands of the DNA, which relies on the cell’s own repair machinery and often leads to unwanted genetic rearrangements. Base editors chemically modify the base directly, sidestepping this issue.

•           High Efficiency: Base editing is highly efficient in both dividing and non-dividing cells.

•           Broad Therapeutic Potential: Because approximately half of all known pathogenic human genetic variants involve a single-letter point mutation, base editing is a powerful tool for developing precision genetic medicines to correct diseases.

 

2. U.S. News: Scientists Edit DNA Of Early Human Embryos. Woodward, Aylin; Janin, Alex.  Wall Street Journal, Eastern edition; New York, N.Y.. 08 June 2026: A3.