Scientists at Weill Cornell Medicine are trying to use the gene-editing technology CRISPR to edit DNA within human sperm, but some experts are questioning whether the practice is ethical, Rob Stein writes for NPR's "Shots."

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Why researchers are focusing on sperm

CRISPR allows scientists to make precise changes in DNA, and reproductive biologists at Weill Cornell are attempting to use the technique to prevent disorders caused by genetic mutations that are passed down from men, including some forms of infertility, Stein writes. The scientists at Weill Cornell currently are focused on targeting a gene called BRCA2. Mutations in BRCA2 can increase a person's risk of breast, ovarian, prostate, and other cancers, according to Stein.

In theory, editing DNA within human sperm could be safer than editing DNA in embryos—on which CRISPR scientists typically focus, Stein writes. According to Stein, it is easy to inconsistently edit and even miss cells within embryos. But by editing sperm DNA, any changes to the sperm DNA would be present in each cell of the resulting embryo, eliminating the risk that scientists might miss cells.

June Wang, one of the lab technicians conducting the experiments at Weill Cornell, said, "I know that things can get dangerous and things can get kind of out of hand quickly. But on the other hand, I think that CRISPR can do so much. It has a lot of potential."

But editing DNA in sperm comes with its own challenges, Stein notes, including figuring out how to deliver the CRISPR tool to the DNA. According to Stein, DNA is tightly-packed inside each sperm's head.

The scientists at Weill Cornell are using a technique called electroporation, which involves delivering an electric shock to the cells. "The hope is that the shock will cause the sperm to kind of loosen up a little bit for just a moment," Wang said. She explained, "When the cell loosens up, the CRISPR gene-editing tool will hopefully get inside."

So far, the team's experiments have not been successful, Stein writes.

Research raises ethics questions

CRISPR experiments, including those at Weill Cornell, have raised ethics questions from experts, Stein writes. According to Stein, some worry that the technology could open the door to people creating so-called "designer babies," and others wonder if scientists should be trying to manipulate the human gene pool in ways that could affect generations.

Françoise Baylis, a bioethicist at Dalhousie University in Canada and the World Health Organization's advisor on gene editing, said, "It doesn't matter whether you're manipulating the embryo or you're manipulating the sperm. The concern is what kind of world are you creating as you move down the path to start manipulating human genetics. We're on the cusp of prospective parents controlling the genetics of their offspring."

Ben Hurlbut, a bioethicist at Arizona State University, expressed concerns about what might happen if CRISPR technologies are developed without considering their potential consequences. "There's reason to worry about undertaking the research before we've asked the question properly whether we would ever actually want to use those techniques," he said. "Once those techniques are developed, it becomes much harder to govern them. If you've done the hard work of developing the recipe, someone else can bake the cake."

But Gianpiero Palermo, a professor of embryology in obstetrics and gynecology at Weill Cornell who runs the lab where the experiments are being conducted, said CRISPR could be used to prevent common conditions, such as male infertility. "If we can wipe out a particular gene, it would be incredible," and a "major benefit to society," he said. Palermo added that it's "important from the scientific point of view to investigate in an ethical manner to be able to learn if [editing sperm with CRISPR is] possible."

Kyle Orwig, a professor in the department of obstetrics, gynecology, and reproductive sciences at the University of Pittsburgh School of Medicine, said, "Male infertility is a very common condition. And there are some diseases that are incredibly devastating to families. And for those diseases, for me, if you could get rid of it, why wouldn't you get rid of it?" (Stein, "Shots," NPR, 8/22).