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Human Gene Editing: Great Power, Great Responsibility

Modifying the human germline has profound implications and must be approached with extraordinary care

This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American


We are at the point where our technology will soon surpass our humanity. It used to be that what we had in our jeans was just what we had in our genes. But we no longer are reliant on choosing our parents wisely. It was always going to happen. The new gene editing techniques were always going to be used to alter the genome in non-medically indicated cases. But it wasn’t anticipated we’d so soon have nontherapeutic application in human embryos.

On November 28, 2018, He Jiankui, from the Southern University of Science and Technology in Guangdong China, revealed that he had performed ex vivo gene editing on two human embryos. This was presented at the International Summit on Human Genome Editing in Hong Kong. It was not a therapeutic, medically indicated procedure, but, regardless, it was unethical and illegal in most countries.

 As an actual practicing scientist and as a human, I strongly advocate for advancement of science and leveraging our advances to enhance our species. Despite that, and somewhat ironically, when I began writing my most recent book, Chasing Captain America: How Advances in Science, Engineering, and Biotechnology Will Produce a Superhuman—a book explicitly focused on examining the science of altering human biology—I was skeptical about enhancing humanity. I challenged my perspective while writing and came to think we have an obligation to modify human form and function so we have the best chance to flourish on Earth and in space. Given the recently revealed experiments in which human embryos underwent nontherapeutic gene edits and were brought to term, we need to consider deeply the implications of this and ensure that what we do and how we proceed are grounded in ethical principles agreed upon by all of us.


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The idea of genetic engineering contained in gene editing is really no different in outcome than the pioneering work of Gregor Mendel in the mid-19th century and his detailed experiments with plants, particularly beans and peas. Mendel’s detailed observations of more than 10,000 plants taken over just about 10 years were published in 1866 and revealed the targeted changes in a living organism that could be obtained by breeding for desired characteristics.

Instead of producing desired characteristics, most of the biomedical work on gene therapy in our modern age focuses on therapeutic, medically indicated applications in inherited diseases and cancers. Many of these medical conditions arise because of dysfunctions in cellular metabolism, growth and viability. Of course, it is probably natural that along with the therapeutic application, there’s been interest in applications not aimed at “curing” disease but rather altering human performance in the otherwise “healthy.”

Gene editing techniques generally involve proteins that cut DNA, such as those employed in CRISPR-Cas9, transcription activator-like effector nucleases (TALENs) and zinc-finger nucleases. The most commonly used Cas enzyme, Cas9, comes from Streptococcus pyogenes—the one that gives you strep throat and was proven viable in mouse and human cells in 2013. The basic process is that the CRISPR molecule is programmed to search for a specific nucleotide sequence among the 3 billion in the human genome. Once the correct sequence is identified, CRISPR unwinds the coils of DNA coils and “snips” the sequence out of the strand. DNA strands are then repaired in the case of a gene deletion, or, for an insertion, a new sequence can be included to alter the genome.

Performed in an embryonic germ line cell, an egg or a sperm cell, gene “edits” will be part of the genetic code that goes to the next generation. But there can be errors—in other words, editing more than intended—with targeting associated with the guide RNA used to target the deletions. It is the presence of these “off-target repeats” that indicates extreme caution and a need for better regulation before techniques like CRISPR can have safe clinical application.

As such, we as scientists and society must also balance the potential good associated with new techniques and the prospect of doing something just because we could. Gene editing places great power over altering the fundamental principles of biology, and our whole society needs to part of the discussion on what is okay to do and what is not. And we need to move quickly but not in a hurry.

It’s critical to think about the path ahead—which one to take and to where—before we arrive. Scientists and engineers at work right now are working to enable the realization of our common futures. But guiding the implementation of that future is the right and responsibility of us all and cannot be entrusted exclusively to those at work in the field and laboratories, nor to those who attempt to regulate their work, our lawmakers and bureaucrats.

The future we invent can be bright—but there are strings attached. The most important string is that we need input from as many sectors in our society as possible. The decisions that are made will literally affect the future of our species and cannot be made in isolation from our society as a whole.

Science works as a machine of chance effects with experimental outcomes; tested against a backdrop of random occurrences and biological evolution is the emergence of chance survival characteristics expanding over millions of years. There is a pace and timing to adaptations. Yet, any modifying of the human germ line—editing sperm or egg cells—has direct implications for the next generation and must be done carefully in light of regulations specifically addressing this kind of experimentation. In many countries there is a de facto moratorium on human germ line and embryo editing because such work is illegal. It is also completely unethical, not least of all because of lack of consent.

Eike-Henner Kluge from the University of Victoria has written that “germ line alteration would be performed without the consent of those who are most affected: namely, future generations.” And C.S. Lewis, when he wasn’t enthralling us with the Chronicles of Narnia, wrote in 1965’s The Abolition of Man that if a society gains power to make descendants “what it pleases, all men who live after it are patients of that power … the rule of a few hundreds of men over billions upon billions of men.”

All of us citizens, scientists, engineers and future users of human enhancement methodologies must proceed with conviction but also caution, with purpose but also extreme care. It’s critical to appreciate the implications of the power of science as articulated by Richard Dawkins that “science is the most powerful way to do whatever it is you want to do. If you want to do good, it’s the most powerful way of doing good. If you want to do evil, it’s the most powerful way to do evil.” Never before have we—or any other species on this planet—had such influence and so much power over the fundamental nature of our own biology.

The nontherapeutic use of gene editing on human embryos was and remains unethical and illegal on every level. Yet, now we need to leverage attention on gene editing and human enhancement into a real conversation about the future our species. As the late Stan Lee wrote back in 1962 in Amazing Fantasy, the first comic book featuring Spider-Man, “with great power there must also come—great responsibility!”

Both must be exercised judiciously here and now in real life.

E. Paul Zehr is professor of neuroscience and kinesiology at the University of Victoria in British Columbia. His research focuses on the neural control of arm and leg movement during gait and recovery of walking after neurotrauma. His recent pop-sci books include "Becoming Batman: The Possibility of a Superhero (2008)", "Inventing Iron Man: The Possibility of a Human Machine (2011)", "Project Superhero (2014)", and "Chasing Captain America: How Advances in Science, Engineering and Biotechnology Will Produce a Superhuman (2018)". In 2012 he won the University of Victoria Craigdarroch Research Communications Award for Knowledge Mobilization and in 2015 the Science Educator Award from the Society for Neuroscience. Project Superhero won the 2015 Silver Medal for teen fiction from the Independent Book Sellers of North America. Paul is also a regular speaker at San Diego International Comic-Con, New York Comic-Con, and Wonder Con. He has a popular neuroscience blog "Black Belt Brain" at Psychology Today.

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