The Future of Gene Editing: The Pros & Cons of CRISPR

Megan Wei '23

A recent leap forward in genetic editing is the creation of CRISPR-Cas9, a new gene-editing technique that allows researchers to easily alter DNA sequences and modify gene function. Genetic editing, also known as genome editing or genome engineering is a type of genetic engineering in which DNA is inserted, erased, revised, or replaced in the genome of a living organism.

During the 20th century, scientists began uncovering more information about genetic coding and DNA. The subsequent step was to devise methods to manipulate it. Targeted genetic editing practices such as zinc finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs) were invented in 2005 and 2010 respectively. However, both of these methods require the use of proteins to identify DNA sequences.

The latest development in genetic editing technology, CRISPR-Cas9, allows for ribonucleotide complex formation and not protein/DNA recognition. The two main components of the CRISPR-Cas9 system are modified RNA and the Cas9 enzyme. The system begins with scientists creating a small piece of RNA that contains a short "guide" sequence that attaches to a specific target sequence of DNA in a genome. Once attached to the target DNA, the Cas9 enzyme cuts the DNA at the targeted location. The cut DNA is then left to either self-repair through adding and deleting pieces of genetic material or a customized DNA sequence is used as replacement.

The impacts of CRISPR are limitless, the most important of which is the ability to tackle and defeat diseases. A notable example of a disease that CRISPR has shown tremendous potential in treating is sickle cell anemia. Sickle cell disease affects millions of people worldwide and is caused by a defect and variation in a single base in the ß-globin gene. This gene is crucial in the production of hemoglobin, a component in red blood cells critical for oxygen transportation. Those with sickle cell disease often get blood transfusions or a bone marrow transplant to increase oxygen-carrying capacity and decrease the proportion of sickle hemoglobin S cells in the bloodstream. However, these treatment methods pose countless risks such as organ damage, cataracts, and even death.

With the creation of CRISPR, patients with sickle cell disease can decrease their symptoms through the process CTX001. This technique withdraws blood cells from the patient and utilizes CRISPR-Cas9 to edit the ß-globin gene so that the cells produce high levels of fetal hemoglobin. Fetal hemoglobin binds to oxygen more strongly than adult hemoglobin which allows for the reduction of symptoms in sickle cell disease by decreasing the risk of low oxygen. While fetal hemoglobin is produced in newborns less than four months in age, CRISPR-Cas9 allows for the introduction of this protein in patients of various ages.

Besides serving as a treatment for sickle cell anemia, scientists are currently studying CRISPR’s utility as a tool to combat numerous medical conditions such as high cholesterol, HIV, cancer, Huntington’s Disease, and many others. Many of these diseases were thought to be incurable by the scientific community for years. But with the recent introduction of CRISPR, many doors of treatment have been opened. That’s not to imply that there aren’t risks of many of these treatments. After all, altering DNA can have a tremendous impact on humans. There’s a chance that CRISPR could accidentally edit DNA that appears similar but that’s not its target. Therefore, researchers approach the use of genetic editing with a lot of caution.

While a wide array of benefits may come from genetic editing, there have also been many issues brought up by the scientific community. The most notable are ethical concerns and the creation of “designer babies.” The term 'designer baby' refers to a baby that has been assigned particular traits through genetic engineering. This assignment of attributes is done by modifying the genes of the egg, sperm, or embryo. These traits can, in theory, even include gender selection.

In 2018, a Chinese researcher named He Jiankui disclosed that he had utilized CRISPR to create the world’s first designer babies. In the embryos of seven couples, he used CRISPR to modify the CCR5 gene to make them resistant to HIV. One of the couples gave birth to twins, Lulu and Nana, known to be resistant to HIV due to this experiment. Jiankui's actions sparked an international outcry, and he was sentenced to prison for three years for violating government bans on the clinical practices of gene-editing on human embryos for reproductive pursuits.

Additionally, concerns with genetic editing extend beyond science but even into income inequality. Using the CRISPR technique for genetic engineering is costly, given that it is a complicated procedure with significant risks. The pricing implies that only the rich can afford such methods. When children of the wealthy have biological advantages over other children, human equality goes out the window. DNA editing has social inequality written all over it.

The development of CRISPR is relatively new, and scientists are looking forward to more information about this genetic editing technique, whether that is knowledge of its potential cures or risks. The current trials employing CRISPR-based treatments are in their early phases, and that means that even if the treatments are safe and effective, it would likely take a few more years for FDA approval and be vastly available to patients. For now, CRISPR is revolutionizing therapies for genetic disorders and has continued to progress and improve over the years since its development. But, the question of where the red line falls in editing genes remains.

References

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