DNA is what allows all cells to function the way they do in any living organism. They contain the instructions for cells to produce proteins to complete certain functions. Mutations in that DNA can also cause certain genetic disorders in some individuals. Furthermore, that same DNA is what causes every organism to be different. Changing that DNA wills the power to change an organism for the better and obtains the potential to grant a greater quality of life to so many. This is where gene editing, more specifically CRISPR/Cas technology comes into play as it allows scientists to precisely and easily edits the genome of an organism more than ever before.
CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeat which are sequences found within the genome. They were originally discovered in the E. coli genome in 1987. Although scientists were unaware at the time that their function was to protect against bacteriophages, they hypothesized that CRISPR is used as a part of the adaptive immune system in prokaryotes. Within this system, Cas genes can keep a record of invading phages and then know to destroy them upon re-exposure. If CRISPR could be programmed then the possibilities of changing the aspects of the genome of an organism would be endless, and that’s exactly what Dr. Doudna proposed. Jennifer Doudna is credited as co-inventor of CRISPR technology along with Emmanuelle Charpentier. They speculated that the microbial immunity mechanism that exists could be the key to one of the most efficient gene-editing technologies. With previous techniques being time-consuming, tedious, and arguably inefficient, their discovery with CRISPR technology has forever changed the world of gene-editing. It is now possible to change an infinite number of things about an organism through its genetic makeup.
Currently, CRISPR-Cas 9 technology is the most versatile, efficient, and precise tool for genetic editing and gene manipulation. The teams lead by Jennifer Doudna and Emmanuelle Charpentier discovered that designing guide RNA to target a certain region in the genome would allow for this new system to be used as a “cut-and-paste” tool in order to modify genomes, hence creating the first biochemical description of CRISPR. This technology has a two-component system that consists of a guide RNA and a Cas9 nuclease. Within the 20-nucleotide area designated by the guide RNA, the Cas9 nuclease breaks the DNA. Algorithms have been developed for CRISPR to assess the likelihood of off-target impacts. More specifically, the cas9 enzyme can cut a part of the double-helix DNA at an exact part of the genome, this way sections of the DNA can be removed and added. The guide RNA (gRNA) is made up of a part of a pre-designed, 20 base-long RNA sequence. This would be in a longer RNA scaffold, a bioinformatics technique where non-contiguous sequences of genomic sequences are linked together. The scaffold binds to the DNA, and the pre-designed sequence directs Cas9 to the correct location in the genome. This ensures that the Cas9 enzyme cuts the genome at the correct location. The way that the guide RNA is ensured to bind only to the target region lies in how it is designed. It is made up of bases that are complementary to the bases in the DNA, so it only binds to that part of the sequence. The Cas9 enzyme trails the guide RNA to that location on the sequence and allows for a cross-cut to be created on both of the strands of the double helix DNA. Scientists can come in at this stage, because the cell will begin to try and repair that part of the sequence of the DNA, and here they will try to program the cellular repair machinery to edit the genome. Not only has the basis of CRISPR technology changed the genomics field, but since its creation, there have been many steps towards its use and application that have proven its growing effectiveness as a gene-editing tool. CRISPR demonstrated that it could be programmed to target DNA cleavage in Vitro in 2012. 6 years later in 2018, PubMed listed over 6,300 CRISPR-related publications. Many of these publications demonstrate work to enhance and change CRISPR technology in different aplicaions as well as its accuracy and orthogonality with various species.
Currently, CRISPR-Cas 9 technology has many implications in terms of potential to cure various medical conditions as well as promising possibility to attempt to do so with previously incurable issues. The treatement of cancer is one of CRISPR technology’s more advanced appliciations. Here the tool is used to edit the genome and remove a protein called PD-1 that is found within T cells. These proteins play a large role in cancer, as tumor cells bind to them which simultaneously blocks the immune response against cancer. China has been the first to have a clinical trial using CRISPR technology to treat cancer patients. The universty of Penssylvania in the US has also tried using CRISPR technology to treat cancer but differently. With this method, the gene editing tool is used to remove 3 genes that are partly responsible for cancer cells evading the immune system as well as adding genes that would help the immune system identify the tumor cells. The results of ths study were very promising and hold hope for the treatment of cancer. In more recent years, research with mice has shown the potential that CRISPR technology has with treating muscular dystrophy. Duchenne’s Muscular dystrophy is caused by mutations in the gene which codes for the protein which is responsible for the contraction of muscles. In 2018, US researchers utilized CRISPR technology to cut 12 locations of the DNA sequence which had a high concentration of mutations. This covers the estimated 3000 mutations that cause this disease. Another application of CRISPR technology would be its involvement with the treatment of heridetary blindness. Many forms of this type of blindness are caused by specific genetic mutations allowing this genetic tool, CRISPR Cas-9, to alleviate the blindness by modifying one gene. A company called Editas Medicine is currently making progress with the use of CRISPR therapy to treat the most common form of childhood, hereditary blindness called, Leber congenital amaurosis, for which there is currently no cure. By addressing the disease’s most prevalent mutation, the treatment aims to restore the function of light-sensitive cells before the children lose their vision completely. Hence, through this tool, a once-incurable genetic issue now has a treatment with promise.
All in all, CRISPR Cas-9 technology is the most effective and efficient genetic editing tool to date and since its discovery, massive steps have been taken in the genomics, bioinformatics, and medical fields. This progress is measured not only in the general research of gene engineering but also with how the technology can be used to actively assist with the treatments and cures. This gene editing tool will most definetly shape the scientific community in the years to come.