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A new gene-editing technique might cure almost any disease

Illustration By Harry Campbell

In April 2015, genetic scientists at Sun Yat-sen University in Guangzhou, China, published a paper describing their effort to repair the genomes of 86 embryos afflicted with the genetic defect of beta thalassemia, a rare inherited blood disorder that is often fatal. Though the study used abnormal, nonviable embryos and yielded good findings, the response from academics and the public ranged from scientific censure to professional condemnation.

The outrage was largely the result of the ethical implications of such research, which applied a new gene-editing technique known as CRISPR-Cas9. CRISPR is short for “clustered regularly interspaced short palindromic repeats,” the foundation for this type of molecular editing; Cas9 is the enzyme that makes it work. Essentially, scientists can use Cas9 to remove the undesirable DNA sequence and replace it with “normal” gene assemblies.

Barely four years old, this method of gene manipulation promises everything from the creation of fungi-resistant crops to cures for cancer and AIDS. But it also opens the door, for those who can afford it, to “designer babies” and eugenics.

CRISPR is not the first tool in gene splicing, but its speed and efficiency are unique. For single-defective-gene diseases like beta thalassemia, the repair at the embryonic stage of development would result in a permanent cure of the affected cell. So a person who would be destined to develop that illness would never experience the disease or pass on the defect to subsequent generations.

That’s a lot to be enthusiastic about. But CRISPR and related tools are giving us the ability to alter the human genome before we really have a full understanding of how it all works. We do not yet know, for example, the full impact of “turning off” a gene, however undesirable that gene may be, or how CRISPR interacts with outside influences over time. In the case of sickle cell anemia, when this “defect” is present in recessive mode, it protects against the most virulent form of malaria. Is it, then, a good idea to eliminate that trait?

We already live in a world of “free-market eugenics,” where affluent parents can select their future in-vitro progeny on the basis of gender and probable physical and intellectual characteristics. In recent weeks, for example, model Chrissy Teigen, wife of singer John Legend, caused an uproar by proudly declaring she had “picked the girl” during in-vitro fertilization because she wanted to see her husband with a daughter. CRISPR and other gene-editing technologies could take this practice to the next level, enabling the creation of “designer” humans, future generations of which could be created in a deliberate effort to control intelligence, appearance, physical strength and even docility.

It’s not a question of if, but when this will happen. Although the Chinese study showed the world it won’t be tomorrow—too many embryos failed and there were far too many off-target mutations—the very existence of the study shows how fast this science is moving. There are CRISPR-based startups, and the pharmaceutical and agricultural industries are heavily invested in the technique. Given the potential power of this technology, how do we extend our lifespans without losing sight of what makes us human?

Dan Carlin, a physician, is CEO of WorldClinic, a New London, N.H.-based telemedicine practice.

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