CRISPR Gene Editing - An Overview

Introduction:

Genetic medicine has recently witnessed a revolutionary breakthrough in the development of many new technologies to aid mankind. Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) have emerged as powerful tools for gene editing. This gene editing technology has opened up new possibilities in multiple fields, such as medicine, agriculture, and biotechnology. It has greatly reduced the time and expense of making specific genomic changes. This article explains the application, components, and mechanism of CRISPR gene editing.

What Is CRISPR-Cas9?

CRISPR-Cas9 is a gene-editing technology causing a major change in medical research. This gene editing technology helps to correct mistakes in the genome and makes it possible to remove or add genes to cells quickly, cheaply, and with less effort. Scientists have used this system to create a versatile and highly efficient gene-editing tool.

CRISPR has various clinical applications, such as functional genomic screens (modifying gene function and checking the phenotype results), rapid generation of cellular and animal models, and live imaging of the cellular genome. This gene editing technology has successfully proven that it can be used to repair defective DNA in mice for curing genetic disorders, and scientists suggest that this methodology can be implicated in human embryos by modifying the gene.

Treatment for infectious diseases such as HIV, gene therapy (modifying a person's genes to treat or cure disease), and engineering custom-made gene patterns to treat cancer and other diseases are a few other potential clinical applications of CRISPR.

What Are the Components of CRISPR-Cas9?

The key components of CRISPR-Cas9 include the CRISPR array, guide RNA (gRNA), and the Cas9 protein, which introduce a change into the DNA.

• Cas9 Protein - The Cas9 protein, an endonuclease, acts as molecular scissors that help to cut the two strands of DNA at a specific location, which creates a break in the DNA. This break activates the cell's repair machinery, which can then introduce changes to the DNA sequence by adding or removing bits of DNA during the repair process.

• Guide RNA (gRNA) - The guided RNA consists of a small piece of pre-designed RNA sequence located within a longer RNA scaffold. These gRNAs guide the Cas9 protein to the exact location on the DNA where the desired modification is to occur.

• CRISPR Array: The CRISPR array consists of short, repeated DNA sequences found in the genomes of bacteria and archaea. These sequences of DNA are interspersed with unique DNA sequences derived from past invaders, such as viruses. The CRISPR array serves as a molecular memory bank, allowing the host organism to recognize and mount a defense against specific invaders.

How Does This Work?

The CRISPR system works on adaptive immunity. The Cas9 protein is the most widely used by researchers. It utilizes Cas nucleases, which can easily be programmed to find and bind to almost any target sequence simply by adding a piece of RNA to guide it in its search. When a virus infects an organism, it uses a Cas nuclease to snip off a piece of viral DNA. The chipped fragment is stored in the bacterial genome along with other virus fragments that have previously infected the cell, and this acts as an immune memory. These viral fragments are placed between the sequences of DNA, and this arrangement of viral spacer fragments and palindromic repeats gives rise to CRISPR.

When the organism is reinfected with the same virus, the bacterium can recognize and destroy it with Cas9. The CRISPR Cas9 protein and guide RNA are added to a cell. For instance, Cas9 acts as scissors, and the gRNA acts as the hand directing them to cut. The Cas9 protein joins with the guide RNA and then moves along the DNA strands until it finds and attaches to a 20-DNA-letter long sequence that matches the guide RNA sequence. The DNA in human cells has around six billion letters and is two meters long.

The Cas9 protein cuts the DNA at the target site when the required DNA strand is identified. The cut will be repaired, and changes that usually disable a gene will be made. This is the most common application of CRISPR, also called genome editing or gene editing. CRISPR can also make changes, such as true genome editing and replacing faulty genes. However, this process is considered difficult, and more research is needed.

What Are the Applications of CRISPR-Cas9?

• Genetic Medicine - CRISPR has revolutionized medical genetics with the potential to cure various genetic disorders, such as blood disorders, neurodegenerative diseases, eye diseases, and cancer. CRISPR can generate chimeric antigen receptor (CAR) T cells used in immunotherapy to treat cancer. The T cells are extracted from patients, and changes are made before re-injection into the body. The CAR allows the T cells to target and destroy the specific cancer cells in the patient's body more precisely. It has also been shown to have effective results in pediatric cancer treatment.

• Diagnosis - During the COVID-19 pandemic, CRISPR was also used as a diagnostic tool for the coronavirus. The SHERLOCK CRISPR SARS-CoV-2 test kit, STOP Covid, and CRISPR-based DETECTR assay are some diagnostic kits that use Cas9’s search function to find genetic material from the virus. Similar diagnostics that use the search function of Cas9 have also been designed to identify infectious and genetic diseases.

• Agriculture - Gene editing technology has great potential, even in agriculture. CRISPR-Cas9 helps modify crop genomes to enhance traits such as resistance to pests and diseases, drought resistance, and nutritional content. This helps to develop more resilient and productive crops. It can also be used to prolong the shelf-life of foods by reducing food waste and giving people access to healthy foods at relatively low cost.

• Livestock Improvement - The technology can create genetically modified livestock with desirable traits like disease resistance or improved meat quality.

• Bioenergy - Bioenergy is a leading alternative to fossil fuels, which are very limited, so bioenergy has been under the spotlight for a while now. With the help of CRISPR, scientists have also recently made some advances in this area. The technology can be applied to engineer microorganisms to produce biofuels, pharmaceuticals, and other valuable compounds.

Conclusion:

CRISPR Cas9 is a gene-editing technology causing a major revolution in biomedical research. The applications of this tool span from correcting genetic disorders to enhancing agricultural productivity. However, the ethical considerations surrounding its use and the need for responsible research and application are important. Many studies are being conducted to refine and expand the capabilities of CRISPR-Cas9 shortly.