Genome editing has an enormous potential, but it is a technology still in development, which could do anything from curing harmful diseases to making blind people see again, to creating more efficient bioterror weapons, and perhaps the most stupefying of all: inducing God-like changes in our own evolution path.
In 2012, American scientist Jennifer Doudna, French scientist Emmanuelle Charpentier, and their colleagues discovered CRISPR-Cas9, an innovative technology in genome engineering. As a result, Doudna and Charpentier became the sixth and seventh women to win the Nobel prize in Chemistry in 2020. CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats, and the acronym is pronounced “crisper”. It has been used in various trials ever since — first on simple organisms, then animals, and recently even humans —, many of which are still ongoing. Though it has not been widely approved yet, it can potentially alter not just the way we prevent and cure diseases, but also how we produce food and the way we protect ourselves from environmental dangers. That being said, gene editing does have serious ethical implications, especially if applied to humans — one of its main goals. The CRISPR-Cas9 technology is not the first one to be invented, but it is currently the most advanced, both in cost-efficiency and success rate.
Here is how CRISPR-Cas9 works: CRISPR was first discovered as a natural process in the 1970’s. It is the way our immune system protects certain bacteria in our body from viruses. Simply put, when a bacterium is attacked by a virus, a protein called Cas cuts out a segment of the virus’s DNA and attaches it to the CRISPR region of the bacterium, in this way protecting it from the virus, should it attack again. Now scientists are applying this mechanism originally used to destroy a virus, to cut and modify the organism’s own DNA.
In the early days, CRISPR could only be applied to cut out “harmful” segments of the DNA (where inclination to a certain disease was encoded). Since then, CRISPR 2.0, and later CRISPR 3.0, have been elaborated. There are four DNA bases: A, T, C, and G. Instead of cutting the DNA, CRISPR 2.0 converts one base letter into another, called base editing. Swapping is safer than cutting, because when the DNA is cut, there is a chance of an important gene being excised. CRISPR 3.0, also known as prime editing, allows scientists to replace bits of DNA or insert entirely new chunks of genetic code. Just one corrective gene could potentially cure all the diseases encoded in the DNA. Gene editing technologies are very similar to mRNA vaccines, as they both consist of genetic instructions wrapped in nanoparticles and sent to cells in the body.
Genetic modification — or at least its predecessor — has been around for thousands of years. Closer to its modern meaning, GMOs (genetically modified organisms) have been around for decades. They have been mostly used to “enhance” crops and make agriculture more productive and less exposed to variations in climate or dangers posed by invasive insects. With CRISPR, genetic engineering is bound to improve and open new possibilities for farmers around the world, but it is hard to say where the line should be drawn.
There are two fundamental ways to protect crops from agricultural pests: modifying the genome of crops to make them more resistant or that of the pests to prevent them from spreading bacteria. Making edits to the crops’ genome is more straightforward, it would blunt the impact of the disease transmitted to them. However, in many cases it would pose a complicated task, as there are bugs that impact a wide range of plants, for example the fruit fly. Targeting insects seems to be a non-immediate, but good long-term solution, as it would take a couple of generations to spread across the species. Tests are being done to see if gene-edited bugs can still survive in the wild. It is the first time scientists are deeply trying to understand the biology of pests, because their primary goal until now was killing them with pesticides. Now, researchers have to identify the segment of the insects’ DNA that makes them harm plants, and edit it. To fasten the process, so-called gene drives could also be applied, as these increase the chance of certain genes being inherited across generations. These are also being examined in mosquitos, to stop them from spreading malaria. One day, we might even live in a world where mosquitos are not interested in human blood. Insects destroy about 40% of global crop production each year, but it is essential to take into consideration the possible effects of permanently modifying whole species of insects, including the process’ impact across environments.
Farmers are also looking to make fish more resistant to infections, and operating on various farm animals to increase their muscles, such experiments resulting in more meat. This has been tried on pigs, sheep, rabbits, and goats, but many of them did not survive infancy and ended up having exceptionally large tongues. These animals are not only used for increasing the production of food, but some scientists are also experimenting with pigs genetically engineered to lack a certain sugar, so that their organs could be transplanted into humans.
As for humans, pioneers of gene engineering have come up with everything ranging from curing small diseases to “designing your offspring”. Experiments are being done to treat volunteers with HIV and blood diseases by editing their genome. For now, companies are mostly thinking about severe widespread diseases, for two main reasons: they almost have a moral obligation to deal with imperative cases first, but they also want to make money out of it, so they will not care about rare diseases, even if gene editing could help those few people as well. Obviously, the price tag is expected to be hefty, at least initially. In fact, there are experts who do not think many would undergo such risky procedures, that are known to have no reverse mechanism, instead of going with the traditional cures. Even though the technology’s promoters say that with just one shot, you would not need to worry for the rest of your life.
Just like with most — if not all — advances in medicine, genome engineering is also primarily expected to increase the human lifespan. On the other hand, it is also being tested on embryos, to create “designer babies”. These offspring could have genetically engineered perfect vision, high intelligence, even an arbitrary eye colour, but they can also be made resistant to smallpox, HIV, cholera, Alzheimer’s, and a range of other diseases. This extreme usage of the technology is still seen as too unpredictable by a large part of the scientific community, and it is the application stirring the most ethical concerns and debates. Although CRISPR has immense potential, it is important to see that genome editing is still being developed, and experts only have a narrow understanding of how deeply and widely these small alterations could permanently change human beings.