CRISPR: Deconstructed for Comprehension
CRISPR stands for “Clustered Regularly Interspaced Short Palindromic Repeats.” It is a simple yet powerful tool of technology used for editing of genomes. It is an easy to use tool that researchers utilize to change DNA sequences and transform gene function. CRISPR is used vastly for amendments of genetic defaults, treatment and prevention of diseases, and improvement of agricultural crops. “CRISPR-Cas9” is the shortened form that got popularity; CRISPRs are specialized stretches of DNA that have two different characteristics: the existence of nucleotide repeats and spacers. The protein Cas9 is an enzyme that works as a pair of molecular scissors that can cut strands of DNA.
Its working can be explained simply by taking bacteria as an example; in this case, the spacers are obtained from viruses that initially attacked the organism. These spacers act as a bank of memories that empowers the bacteria to identify the viruses and fight off future assaults.
Background of CRISPR
In 1987, CRISPR sequences were discovered for the first time in the E. coli genome, but their utility as the safeguard against bacteriophages was not explicated until 2007. It was the hypothesis of scientists that prokaryotes used CRISPR like a part of an adaptive immune system; prokaryotes used numerous CRISPR-associated (Cas) genes to keep a record of attacking phages and also to terminate the phages upon re-contact.
In precise, specialized Cas proteins cut foreign DNA into small fragments almost 20 bp in length and cement them into adjoining sections of DNA that are called CRISPR arrays. CRISPR RNAs (crRNAs) are then generated by CRISPR loci that are expressed and processed by separate Cas proteins. These crRNAs lead a Cas nuclease, using sequence homology, to the specified exogenous genetic material that must also have a species-specific sequence that is known as a protospacer adjacent motif (PAM). The CRISPR complex bores to the foreign DNA and cuts it to terminate the invader.
The CRISPR-Cas9 was proved experimentally for the first time in 2007 at a food ingredient company, Danisco, by Rodolphe Barrangou and a research team. Researchers used the bacteria, Streptococcus thermophilus, that can easily be found in yogurt and other dairy products. In their observations, researchers noticed that after a virus attack, there were new spacers assimilated into the CRISPR area, and these spacers’ DNA sequence was identical to the parts of the virus genome. The researchers arranged the spacers by putting in new viral or taking out virus-affected DNA sequences. As the outcome of this research, they were able to improve the bacteria’s struggle to an attack by a specific virus. This research proved that CRISPRs perform a critical role in the regulation of bacterial immunity. Zhang lab published the first method to use CRISPR in 2013 to edit the genome in the mouse and human cells.
Throughout the whole time until the present, CRISPR has been used in many clinical tests to find out treatments related to different diseases and other things like for improving and making new fruits, changing the color of flowers from violet to white, etc. Researcher report that clinical tests are being conducted to test a treatment on volunteering people; the purpose of these tests is to test the safety, side effects, and efficacy of the treatment. There are two levels of these clinical tests; first, to check the safety and side effects, second to check the effectiveness, and do a comparison of the said treatment with other new theories. The current CRISPR clinical tests are all in the early level or stages.
Following are some basic clinical tests of CRISPR that are currently under process:
Cancer is categorized as a part of diseases that create an abnormal or uncontrolled growth of cells. Currently, CRISPR-based research theories are focused on the treatment of blood cancers like leukemia and lymphoma. Clinical trials of CRISPR-based therapy have succeeded in treating two volunteer patients during the late-stage; it is the first study in the US that has utilized CAR-T and PD-1 as a combination immunotherapy approach.
China is also investing considerable amounts in CRISPR-based clinical trials; seven active or recruiting trials have been included in the US clinical trial database, but China is also facing some major issues like improper clinical trial infrastructure, oversight, informed consent of patients and research rigor.
“The FDA has approved CAT-T therapies and PD-1 pathway inhibitors that don’t use genome editing. This is reason to be optimistic: the proof-of-principle work for these therapies has already been done!”
Due to the Mutation gene, two genetic disorders emerged that can cause severe issues like chronic pain, organ damage, strokes, and anemia; these two genetic disorders are beta-thalassemia and sickle cell disease (SCD).
“The first use of an ex vivo CRISPR-based therapy to treat a genetic disease,” a patient of thalassemia had been treated in Germany, and it was recently revealed by CRISPR Therapeutic that the treatment seems to be working for this first patient. According to a report, two patients, one with beta-thalassemia and the other one with sickle cell disease, have potentially been cured of their illness. This is the first clinical trial that proves that the CRISPR tool can be used to cure genetic diseases.
Leber’s Congenital Amaurosis (LCA) is a rare genetic disorder in which retinal dysfunction causes vision loss. LCA usually occurs at birth. LCA10 is the most common type of LCA, a genetic disease in which a person loss partial or complete vision within the first few months of his or her life. The first trial has not been held until now, but the FDA has approved the human testing of the treatment of LCA10. Currently, Editas Medicine and Allergan are looking for patient volunteers from all over the US.
Future of CRISPR
The implication of the CRISPR, a gene-editing technological tool, seems unlimited. Currently, the implications that researchers have been shown are as follows:
Turning pigs into Organ donors
As of right now, more than 114,000 people are waiting for a transplant in the US only. But, attempts to implanting an animal’s organ in a human body have been failed, but researchers believe that CRISPR can enable them to find a solution to make animals, an organ donor.
Making new and improved fruits
CRISPR has been used by the researchers to produce new, improved, domestic fruits with early development. It is suggested that CRISPR can help in increasing the nutritional value of food and to keep the crops safe from extreme weather and climate change.
Changing flowers from violet to white
Researchers are focusing on using CRISPR to target a specific gene, DFR-B. The researchers are trying to the color of the flower of a green plant.
Creating new treatments for cancer and blood disorders
After the success of the first trials, scientists are focusing on the second stage of the level of clinical trials and trying to find possible treatments for blood cancer and beta-thalassemia and Sickle cell disease.
Malaria is the most common and dangerous disease caused by mosquitoes. Researchers are focusing on altering a doublesex gene that is responsible for female development in mosquitoes. By modifying this gene, the researcher estimated the eradication of mosquitoes.
CRISPR is a most useful technological tool that can easily and effectively alter or edit genes of any living organism. It is more effective and result-driven as compared to the past or other gene-editing tools. Scientists and researchers have been using it since 2007 for various purposes specified in medical treatment. This genetic tool promises great findings and treatments in the near future.