The medical field has transformed dramatically due to technology. The quality of human life has augmented due to new innovations in medicine. Notably, more effective diagnostic procedures and treatments in areas such as genetic engineering and nuclear medicine have emerged, improving the overall health outcomes of individuals in the global society. Today, scientists use CRISPR systems for gene editing since it is highly reliable as compared to others. CRISPR fosters the transference of edited genes to patients’ bodies. The system increases the hope of developing a cure for cancer and other hereditary disorders since it can rewrite the genetic code of human beings.
What is CRISPER Cas9
CRISPR-Cas9 is a remarkable device used by scientists to edit genomes. According to Hsu, Lander, and Zhang ( 2014), the system enables these professionals to eliminate, add, and even modify parts of the human DNA. Ishino et at. first discovered the technology in the year 1987 (Ratan et al., 2018). The scientists further identified a cryptic DNA structure in the genome Escherichia coli, which comprises short direct repeats which are disjointed by short, distinctive arrangements. Evidently, there are three types of CRISPR technology. The type II system which is composed of Cas9 proteins and originates from Streptococcus thermophilus is the most productive genome engineering tool as it also has the ability to split double-stranded DNA (Adli, 2018). CRISPR/Cas9 is reliable and characterized by immense simplicity, encouraging the exploration of its potential to treat and manage vast incurable diseases.
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Mechanism of CRISPR Cas9
The system uses natural mechanisms which are also applied by many types of bacteria as an intracellular immune structure to fight against viral contagions. The microorganisms use Guide sequences as opposed to antibodies, a replica of viral DNA. Guide sequences then guide RNAs and associate with CRISPR-related proteins (Cas). The outcome of this process is RNA-protein which bind to the hostile virus, splitting its DNA, matching the deoxyribonucleic acid of the guide sequence. Jiang and Doudna (2017) fittingly observe that the cuts eventually lead to the annihilation of viral DNA and the infection stops. Undeniably, the technology is highly effective. A scientist has discovered that they can adjust genes especially if the two DNA threads are split at the targeted location. CRISPR saves time as compared to previous technologies which necessitated the development of new proteins to break each targeted part, a difficult and time-consuming procedure. CRISPR enables these professionals to design effective RNA guides to match the intended DNA.
CRISPR-interceded genome alteration involves several steps. Inserting this technology’s constituents into cells is the first primary step. After this accomplishment, the genome is skimmed to determine target sites using Cas9-sgRNA multifaceted scans (Jiang and Doudna, 2017). Thereafter, Cas9 binds to specific locations in the DNA of the organism, for instance, the mouse genome. Artificial sgRNA then pairs with the DNA of the mouse. If the genome DNA is compatible with the sequence of sgRNA, Cas9 splits the two DNA threads of the intended double helix. It is typical for the cells of the organism to repair its DNA since cuts have adverse effects instantly . Two principal mechanisms are used to restore broken DNA strands in cells.
One of the processes is susceptible to errors while the other is precise. The non-homologous end joining (NHEJ) is the first. In this process, the ends of the DNA are sewn together, and any fissures are filled with unsystematic nucleotides. The primary outcome of this process is gene mutation as a result of the obliteration or addition of a base pair in the broken sequence. The additional DNA piece transforms the entire gene sequence, which often leads to the non-functionality of the protein encrypted by the gene. Notably, this is one of the main flaws of CRISPR.
The homology-direct repair (HDR) is the second mechanism used for reconstruction . The process allows the insertion of new sequences into genomes, and any desired gene is added to a specific chromosomal location. The procedure compares to the one that takes place during sexual reproduction, in which stretches of DNA are exchanged. To further demonstrate, the majority of animal cells are comprised two replicas of each chromosome, one from the ale and the other from the female (Jiang and Doudna, 2017). The broken parts of the DNA are repaired by replicating a similar DNA sequence from similar chromosomes in the cell. Hence, to fix a damaged maternal chromosome III in the cell of a mouse, for instance, requires the cell to find undamaged DNA sequences in the paternal chromosomes. The broken strands of the DNA are therefore repaired using the paternal chromosomes.
Through CRISPR , the error-correcting mechanisms of the cells can be tricked through the insertion of DNA pieces composed of extended fragments of related nucleotides into the cells surrounding the areas targeted by CRISPR. The cells are then compelled to think that there is an analogous chromosome nearby. The method enables geneticists to substitute defective genes with healthy ones. CRISPR also allows new genes to be placed in place of damaged ones in various genomic locations. HDR is more productive even though it is rarely used as compared to NHEJ. CRISPR, therefore, fosters the deactivation of genes through mutation.
Application of CRISPR Cas9 to Gene Therapy
Recently, studies have discovered that genes play a critical role in the pathogenesis of many hereditary disorders. CRISPR Cas9 has advanced biological research. The technology has fostered genetic interruption in different types of cells. According to Kruminis-Kaszkiel et al. ( 2018), the application of CRISPR Cas9 to hereditary movement disorders has proven quite effective. The system is designed to guide a Cas9 endonuclease to target and split DNA. The disruption of the genome DNA leads to the activation of the DNA repair mechanism. CRISPR intends to develop disease-altering treatment approaches which will eradicate defective genes from human cells. Huntington’s disease (HD), Alzheimer’s disease, and amyotrophic lateral sclerosis are excellent examples of hereditary disorders which can be treated by gene editing. CRISPR allows the modification of irregular production of proteins, inhibiting their accumulation, which is a productive treatment strategy.
Gene editing is possible in different cell lines using CRISPR. A number of gene therapy methods such as silencing and virus-interceded gene delivery in genetically induced movement ailments has become the main focus of geneticists in contemporary society. Recently, a doctor named Nicolas Merienne in collaboration with some of his colleagues conducted a study aimed at the diminution of mutant huntingtin aggression through CRISPR to eliminate the open reading frame of the HTT gene, resulting in the loss of mHtt expression (Singh et al., 2018). The studies proved that the system could lessen the deposit of mutant huntingtin in the striatum of rodents. The research demonstrates the technology’s potential to change the genes that cause transmissible movement diseases. Other studies show that the CRISPR-related knock in of designer receptors fosters the control of neurons resulting from (hPSC) by chemical composites. The relocation of hPSC-resultant human midbrain dopaminergic neurons into PD mice prototypes showed a reversal and improvement in the motor abilities of these organisms by DREADD ligands.
CRISPR -Cas9 also has a great potential to improve cancer treatment. The system aim in cancer research is to determine various vulnerabilities inherent in genes. The identification of a cancerous gene is a critical step in the development of a cure for cancer (Kruminis-Kaszkiel et al., 2018). CRISPR is very useful in detecting the desired genes. CRISPR studies are intended to discovering essential genes across different cancer cell lines. The application of this technology in cancer-related studies has proven fruitful since it has led to the discovery of one thousand five hundred significant genes (Zhang, Wen, and Guo, 2014). The number is five times greater than the one that was previously determined by shRNA screens. One of the greatest achievements of CASPR is the identification of significant genes for acute myeloid leukemia.
CRISPR is also applied in the dissection of chemical-genetic interactions, which has enabled researchers to acquire valuable knowledge on the different reactions of cancer to different treatments, which is a critical step towards the determination of the cure for cancer. The combination of a CRISPR screening with drugs can also aid in the detection of gene knockouts that act synergistically with or confer resistance to the agent.
Therapeutic Implications of CRISPR -Cas9
CRISPR -Cas9 has several therapeutic implications, some positive and others negative. Previous literature on the topic fails to show any unanticipated effects of using this system for gene editing. Recent studies stress that this technology may lead to many unforeseen mutations which may jeopardize the quality of human life. Extensive research has been carried out on the mouse and human cells. Ratan et al. (2018) reveal that CRISPR often results in broad mutations, which usually occur at a considerable distance from the target side. The studies further demonstrate that a vast number of cells have massive genetic reorganizations due to gene attachment and deletion. Evidently, the transformations can result in the switch of genes on and off, which is anticipated to have devastating implications for the use of this device in therapies. Notably, most of the gene-related changes occur too far from the target site (Yang, Tu, Sun, and Li, 2016), making it difficult for scientists to view them merely with standard genotyping strategies. It is apparent that previous studies overlook the severe changes in DNA that occasion the use of this system. Hence, those who intend on using the technology are urged to proceed with caution to ensure that they determine any potential harmful effects.
The discovery of new drugs to treat genetic diseases is also one of the main implications of CRISPR/Cas9. The detection and improvement of new medicines is intricate and not to mention time-consuming process. The technology will be quite beneficial to the field of oncology. One of the main aims of drug discovery in this field is the identification of molecules against genetic abnormalities in oncogenes and tumor suppressor genes that result in the development of different types of tumors (Im, Moon, and Kim, 2016). CRISPR has fostered the identification of imatinib which primarily targets BCR-ABLI fusions in prolonged myeloid leukemia, among others. The system has been productive in achieving one of its core goals, which is to determine disease-causing genes. Undeniably, the technology has the potential to increase this process, as well as the authentication of high-value targets. CRISPR is projected to identify molecules which can be suppressed and eliminated to prevent the emergence of various disorders.
Today, the wellbeing of individuals in the society is reliant on the availability of advanced technologies. The innovations have not only transformed medical practice but also improved the overall health of individuals in the global community . CRISPR is one of the most intriguing developments in the field of biomedical research and therapy. The technology fosters cheap, simple, and accurate genetic alteration. Contemporary geneticists are able to delete and replace defective genes in human cells. They no longer over-rely on random modifications in an entire organism, preferably , they employ this system to trigger many mutations in cell lines, as well as to determine the genes that have the best traits. CRISPR has the potential to eradicate faulty genes, preventing the occurrence of hereditary diseases. Nonetheless, further studies should be conducted on this system, to ascertain its effectiveness in treating various diseases.
References
Adli, M., 2018. The CRISPR tool kit for genome editing and beyond. Nature Communications , 9 (1), p.1911.
Hsu, P.D., Lander, E.S. and Zhang, F., 2014. Development and applications of CRISPR-Cas9 for genome engineering. Cell , 157 (6), pp.1262-1278.
Im, W., Moon, J. and Kim, M., 2016. Applications of CRISPR/Cas9 for gene editing in hereditary movement disorders. Journal of movement disorders , 9 (3), p.136.
Jiang, F. and Doudna, J.A., 2017. CRISPR–Cas9 structures and mechanisms. Annual review of biophysics , 46 , pp.505-529.
Kruminis -Kaszkiel, E., Juranek, J., Maksymowicz, W. and Wojtkiewicz, J., 2018. CRISPR/Cas9 technology as an emerging tool for targeting Amyotrophic Lateral Sclerosis (ALS ). International journal of molecular sciences , 19 (3), p.906.
Ratan, Z.A., Son, Y.J., Haidere , M.F., Uddin, B.M.M., Yusuf, M.A., Zaman, S.B., Kim, J.H.,Banu, L.A. and Cho, J.Y., 2018. CRISPR-Cas9: a promising genetic engineering approach in cancer research. Therapeutic advances in medical oncology , 10 , p.1758834018755089.
Singh, K., Evens, H., Nair, N., Rincón, M.Y., Sarcar , S., Samara-Kuko, E., Chuah, M.K. and VandenDriessche, T., 2018. Efficient In Vivo Liver-Directed Gene Editing Using CRISPR/Cas9. Molecular Therapy , 26 (5), pp.1241-1254.
Yang, W., Tu, Z., Sun, Q. and Li, X.J., 2016. CRISPR/Cas9: implications for modeling and therapy of neurodegenerative diseases. Fraontiers in molecular neuroscience , 9 , p.30.
Zhang, F., Wen, Y. and Guo, X., 2014. CRISPR/Cas9 for genome editing: progress, implications, and challenges. Human molecular genetics , 23 (R1), pp. R40-R46.
