Gene Editing (CRISPR)

“It gives us hope that gene-therapy approaches may work in humans”

 So, What Exactly is Gene Editing?

Gene editing is a set of molecular technologies used to modify the sequence of a gene. Scientists have essentially found a method to “cut” parts of the gene out and “paste” it back into a different nucleotide sequence. Gene editing more specifically requires the use of an enzyme, particularly nucleases, which are engineered to make a “break” and target the DNA at a specific location on the genome. This process is where parts of nucleic acid sequences can be added, removed, or altered through the cell’s DNA repair mechanism. In simpler terms, gene editing changes the DNA in cells of animals or humans primarily to treat diseases and research. Gene editing is part of a vaster medical field of study called gene therapy, which focuses on remedying diseases by modifying genes and treating them as therapeutic cells. There are two types of gene therapy: germline therapy and somatic therapy. Germline therapies target DNA changes in reproductive cells (such as sperm and egg) that pass down from generation to generation. Contrarily, somatic therapies involve changes to non-reproductive cells that only affect the person who receives the gene therapy. The evolution of this cutting-edge technology has allowed scientists to alter genes for disease therapeutics and agriculture. As with most research, further development in the industry along with technological advances have paved the way for fundamental molecular tools such as CRISPR and CRISPR-Cas9, which will be discussed later on.

Gene editing is an emerging field with massive potential in the coming decades, but given its future implications, it has unquestionably divided the public. Firstly, you have advocates who believe that gene editing can revolutionize the world for the better if put to proper use. Envision a world where once incurable diseases are now curable, a world where people can undergo genetic engineering to have more favorable or better qualities, such as having blue eyes or taller stature. On the other hand, critics argue that gene editing raises ethical concerns. There have been talks of using gene editing on embryos, which violates human rights since there is no consent. Moreover, if this technology becomes exploited for political or military purposes, it can bring about grave consequences relating to corruption and abuse of power. Therefore, it is imperative that rigid regulations are formed to prevent the aforementioned issues from happening. While gene editing has great potential in treating lethal viruses and diseases, it has raised many ethical concerns with its future implications.

CRISPR

While the concept of gene editing is not exactly foreign, it has become more prevalent due to the emergence of CRISPR. CRISPR, more formally known as “clustered regularly interspaced short palindromic repeats” technology, is a tool used for precise gene modifications that can alter the human genome and correct defects or mutations. This technology was first introduced and created in 1987 by molecular biologist Yoshizumi Ishino. CRISPR can “alter genes in gametes, oocytes, and spermatozoa used to create embryos (Lerner, 2021). What this means is that scientists can use the CRISPR tool to cleave and cut DNA molecules at specific locations with much greater precision and accuracy, thus allowing the removal and addition of genes to be a thorough and meticulous process. There was a breakthrough in 2012 when American biochemist Jennifer Doudna and French microbiologist Emmanuelle Charpentier discovered and founded CRISPR-Cas9, an evolved version of the same tool that proved to be more efficient in treating faulty genes that cause inherited diseases. This latest generation of technology relies on the use of the protein nine enzyme, Cas9, which is “used to cut or snip targeted gene sequences surrounding a defective gene” (Lerner, 2021). In 2013, Feng Zhang, a Chinese-born American biochemist, used the CRISPR-Cas9 tool to successfully make genomic edits in mammalian cells. Since then, CRISPR-Cas9 has been “used in more than 1000 labs worldwide and used commercially in disease therapeutics and agriculture”, opening up a world of many possibilities. The nascent CRISPR technology continues to grow and improve, with scientists placing a heavy emphasis on improving precision and efficiency. Recent developments made by American biochemist David Lui include base editing and prime editing. Base editing involves single base-pair alterations, while prime editing aids with single-base pair changes and only requires single-strand breaks. As you can see, CRISPR technology is a powerful and effective tool to treat fatal diseases that also can be applied for further experimentation and research.

Applications of Gene Editing and CRISPR

        As mentioned earlier, one of the more common applications of gene editing is treating incurable and heritable diseases. Most of these chronic, deadly diseases are due to mutations. Mutations are changes made to the DNA sequence due to mistakes or errors during cell divisions or exposure to mutagens such as chemicals, radiation particles, or infectious agents.  DNA sequences become permanently altered and heritable because of mutations. This explains why diseases such as Tay-Sachs disease and Huntington’s Disease have no known cure or require stringent procedures, such as stem cell or bone marrow transplants for sickle cell Anemia. However, with innovations in genome editing, scientists speculate that it is possible to remedy these once-untreatable diseases with CRISPR-based therapeutics. As mentioned earlier, CRISPR-Cas9 is the latest version of CRISPR technology used to examine and study cancer genomics, embryo development, and mental health. CRISPR-Cas9 therapies are also utilized to target a disease caused by single nucleotide polymorphisms (SNP). SNPs are more commonly known as point mutations, where one nucleotide is altered in one gene. With the aid of CRISPR-Cas9 therapies, scientists have conducted more research and experimentation concerning point mutations because they now better understand and comprehend their effects, as compared to more complex genetic mutations caused by cancer or human immunodeficiency virus (HIV).

One early target of CRISPR-Cas9-based therapeutics is sickle cell anemia. Sickle cell anemia is a red blood cell disorder in which the body does not produce enough red blood cells to carry oxygen throughout the body and thereby lowers blood oxygen. This condition increases the risk of blood clotting and significantly decreases life expectancy. The sickle cell trait, for instance, is a point mutation in a gene that codes for the hemoglobin protein, which is responsible for carrying oxygen in red blood cells. The sickle cell trait SNP results in a less functional and misfolded hemoglobin protein because “the beta-globin gene, encoding the beta chain of hemoglobin, has a point mutation replacing the amino acid glutamic acid with valine” (Anderson 2021). As a result, the misfolded hemoglobin carries blood at a less effective and efficient rate and causes red blood cells to be sickle-shaped. Therefore, sickle cell anemia has become one main area of focus because it is a fairly common condition among the U.S. population, and the effect of glutamic acid on valine mutation is well understood. Currently, there are several clinical trials for humans underway from multiple organizations that have shown proof of concept through CRISPR-Cas9-based therapies. Since the trials are still ongoing and in the early stages, additional testing is necessary before the therapies can be offered on the market. There has been some development, with some patients not requiring blood transfusions, a sign of good promise. Additionally, clinical trials are underway for other diseases such as esophageal cancer, HIV infection, and multiple myeloma. Gene editing has also been able to treat blood cancer through the augmentation of CAR T-cell therapies, which has proven to “increase persistence, safety, and efficacy, and which may withstand the risk of relapse due to antigen loss in certain cancers” (Cohrt, 2021).

For gene editing to become implemented for human testing, scientists have first tested the effectiveness of the CRISPR technology on other animal species. For example, mice are commonly used as laboratory test subjects for gene editing because they share a similar genetic makeup as humans and thus are a good candidate for experimentation. One study showed that a “gene-silencing technique based on CRISPR was found to relieve pain in mice”. In this experiment, a team of researchers “gave mice a spinal injection of the gene-silencing therapy” (Remmel, 2021), then proceeded to inject the animals with chemotherapy drugs or inflammatory agents to further induce chronic pain. They found out that mice suffering from long-term chronic pain benefitted from the therapy, and results show that the pain relief lasted as long as 44 weeks after the injection. The study also shows that mice who received the chemotherapy drugs became extremely sensitive to pain but lost that sensitivity once they were given the gene therapy. This is promising news as it provides an approach and basis for possibly treating chronic pain in humans. Chronic pain is especially prevalent in Europe and the United States, with some estimates suggesting that as many as 50% of the population experiences chronic pain. Margarita Calvo, a pain physician at the Pontifical University of Chile, is excited about the CRISPR-based technique because “it’s a real challenge that the best drugs we have to treat pain give us another disease” (Remmel, 2021). With the new CRISPR-based technique seemingly in place for the future, scientists no longer have to rely on prescribed opioids as pain relief and need not worry about the risk of patients developing possible addictions. While this specific technique or therapy is still in its infancy, scientists anticipate breakthroughs within the coming years that will be revolutionary in treating chronic pain.

Bioethics and Future Implications

        As I have discussed earlier above, gene editing has immense potential in the future, but like most topics, will have supporters and critics. There are a handful of countries, including Norway, China, and the United States, that have voiced their support for advancements in gene editing and CRISPR. The United States government has even received advice and recommendations from experts to fund and support gene editing and CRISPR research. Proponents of CRISPR technology postulate that “gene editing may eventually eliminate many inherited diseases, including cystic fibrosis, Huntington's, Tay-Sachs, and beta-thalassemia” (Lerner, 2021). On the other hand, critics argue that gene-editing technology raises ethical concerns and requires stringent regulations to preserve human rights. In 2018, He Jiankui, a Chinese biophysicist, successfully used CRISPR technology to genetically modify the genes of twin babies before birth to make them more resistant to HIV. His work was novel but angered many scientists, who called a halt on “genetic editing because it violates medical ethics” (Lerner, 2021). He was later convicted and sentenced to three years in jail. Critics contend that gene editing may be exploited by wealthy individuals for personal benefits, such as the desire to create "designer babies". All things considered, the prospect of genetically modified humans that never age and the end of diseases is absolutely within reason, although there must be a universal system of regulations established to ensure gene editing does not fall into the wrong hands.

Bibliography

Anderson, Lauren. "Gene Editing." The Gale Encyclopedia of Science, edited by Katherine H. Nemeh and Jacqueline L. Longe, 6th ed., vol. 3, Gale, 2021, pp. 1928-1930. Gale In Context: Science, link.gale.com/apps/doc/CX8124401078/SCIC?u=wash_main&sid=SCIC&xid=1570fb5b. Accessed 9 May 2021.

Lerner, K. Lee. "CRISPR technology." Gale Science Online Collection, Gale, 2021. Gale In Context: Science, link.gale.com/apps/doc/YLWMOT062637330/SCIC?u=wash_main&sid=SCIC&xid=c29b65f1. Accessed 9 May 2021.

Remmel, Ariana. “CRISPR-Based Gene Therapy Dampens Pain in Mice.” Nature News, Nature Publishing Group, 12 Mar. 2021, www.nature.com/articles/d41586-021-00644-5.

Cohrt, Karen. “News: Clinical Roundup: Gene-Edited CAR T Therapies.” CRISPR Medicine, 31 Mar. 2021, crisprmedicinenews.com/news/clinical-roundup-gene-edited-car-t-therapies/.

Devery, Nathan. “3D Rendering CRISPR DNA Editing.” Https://Www.news-Medical.net/News/20190730/First-Ever-American-Gene-Editing-Treatment-Using-CRISPR-for-Genetic-Disease.aspx, Shutterstock, 30 July 2019.