Scientists successfully edit human embryos in a path breaking new study

In what could be hailed as the country’s first attempt to create genetically modified embryos, U.S. scientists have successfully edited the DNA of viable human embryos using the powerful gene-editing tool CRISPR.

This work adds to the promise of CRISPR, and it stands as an important step toward the birth of the first genetically modified humans.

As powerful as the gene-editing technique is—researchers are using it to make malaria-proof mosquitoes, disease-resistant tomatoes, live bacteria thumb drives, and all kinds of other crazy stuff—so far US scientists have had one bright line: no heritable modifications of human beings.

But ever since Chinese researchers announced the first gene editing of a human embryo 2 years ago, many expected that similar work in the United States was inevitable. Last night, the MIT Technology Review broke the news that such an experiment, led by embryologist Shoukhrat Mitalipov of the Oregon Health and Science University has happened.

The first experiment using CRISPR to alter the DNA of human embryos, in 2015, used embryos obtained from fertility clinics that had such serious genetic defects they could never have developed. In this new work however, Mitalipov and his colleagues have created human embryos using sperm donated by men with the genetic mutation that they planned to try

to repair with CRISPR.

The team allowed the embryos to develop for a few days, after which a battery of tests revealed that the resulting embryos took up the desired genetic changes in the majority of their cells with few errors.

In altering the DNA code of human embryos, the objective of scientists is to show that they can eradicate or correct genes that cause inherited diseases. The process is termed “germline engineering” because any genetically modified child would then pass the changes on to subsequent generations via their own germ cells—the egg and sperm.

Although none of the embryos were allowed to develop for more than a few days—and there was never any intention of implanting them into a womb—the experiments are a milestone on what may prove to be an inevitable journey toward the birth of the first genetically modified humans.

Presently, the study has also triggered warnings about “designer babies,” in which parents customize their IVF embryos by adding, removing, or changing genes for certain traits. A recent report on genome editing from the National Academies did not call for a moratorium on research into germline editing, arguing that it might one day be a way for some parents to have healthy, biological children, such as when both mother and father carry genetic mutations that cause severe diseases.

However, Stanford University law professor and bioethicist Hank Greely tweeted that “the key point” is that no one has tried to implant any edited embryos. “Research embryos” that are “not to be transferred for possible implantation” are “not a big deal,” he argued.