CRISPR-Cas9: A Triple-Edged Sword
Now, it’s up to us to determine how we’re going to swing it.
By Aaron Zhao
A double-edged sword. That was how the science community described CRISPR-Cas9 gene editing when it first made headlines a decade ago. Never before had scientists witnessed such a precise and effective method of editing human DNA, genetic material within cells that code for proteins and make life possible. Amid the jubilee emerged concerns over its flaws — naturally, considering how novel the technology was. But, what really caught the world’s attention was the controversial conversation that CRISPR sparked: genetically edited babies. A double edged sword affects only the wielder and the opponent, but now, it seems like future generations could be affected too. Perhaps the sword was never double-edged to begin with, but… triple-edged.
Back in the 2000s, CRISPR, short for Clustered Regularly Interspaced Short Palindromic Repeats, was only known to be an “immune system for bacteria” to fight against viruses whose sole purpose was to inject viral DNA into bacteria to hijack them. Using CRISPR, bacteria create a special class of proteins called “Cas” that carry specific segments of genetic material called crRNAs, which when combined cuts and destroys the injected viral DNA, thereby protecting the bacteria.
It wasn’t long until in 2012, when geneticists Emmanuelle Charpentier and Jennifer Doudna realized that a specific Cas protein, Cas9, combined with lab-developed crRNA could be used to make cuts to a diseased cell’s own genome. It turned out to be an absolute success. Hemophilia, the inability for blood to clot, is caused by an erroneous change to DNA that codes for the beta-globin protein but thanks to CRISPR-Cas9, this error can be deleted and replaced by healthy DNA. Similar approaches have been used to treat hereditary blindness and sickle cell disease, yielding promising results.
However, as appealing as CRISPR-Cas9 sounds, it’s not entirely fail-proof. When Cas9 makes a cut, it sometimes removes too much of the neighboring DNA in a process called “off-target” effects, leading to disastrous impacts to the organism, such as the death of the cell or more mutations. A research study led by Dieter Egli of Columbia University found that when CRISPR was used to cut out blindness-causing DNA in embryos, over half of them had too much neighboring, healthy DNA removed. What had been intended to fix errors was now found to be creating more errors.
But, wait. Embryos are precisely why CRISPR’s influence stretches far beyond the laboratory. In 2018, the world’s first gene-edited babies were born, twin girls whose DNA had been edited with CRISPR to produce HIV immunity. The lead researcher, Dr. He Kiankui of China, essentially demonstrated just how convenient it had become to control traits of human beings, and that is most troubling. Who was to say that embryos couldn’t be edited to demonstrate intellectual prowess over their peers in the future? Athletic prowess? Attractiveness? These “designer babies” would lead to questions over a “superior” human race, which doesn’t sound particularly fair to most. This triple-edged sword has been lifted. Now, it’s up to us to determine how we’re going to swing it.