This year’s winners of the 2020 Nobel Prize in chemistry harnessed the humble bacteria’s long-evolved protection mechanism to construct an efficient gene-editing method that some think is revolutionizing medicine. Jennifer Doudna, PhD, and Emmanuelle Charpentier, PhD, created the technology which is derived from the bacterial immune response. It enables scientists to take out “poor” DNA that can cause disease and substitute it with safe DNA if necessary. The idea of editing genes is not new, but for scientists it has been a tricky and elusive business. Clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9), transcription activator-like effector nucleases ( TALENs), zinc-finger nucleases ( ZFNs), and homing endonucleases or meganucleases are the current most widely used genome editing technologies to promote change and edit DNA. Study laboratories around the world have embraced these new technologies in only a few years, making it easier to make specific improvements to the DNA of humans, other animals , and plants. The “CRISPR” technology solution is much simpler and easier compared to previous genome editing technologies. Not only has it changed the way scientific research is done, but also the way we can now think of disease care.
What is CRISPR technology?
CRISPR is an acronym for Clustered Regularly Interspaced Short Palindromic Repeat. This name refers to the specific organisation in the genomes of bacteria and other microorganisms of small, partially palindromic repeated DNA sequences found. Every living thing is made up of DNA and, more precisely, of its four cardinal components: adenine, cytosine , guanine and thymine, also referred to as A, C , G and T. These letters are organised in specific patterns that code for our biological and physical life, of which we contain billions. But things can go wrong sometimes. CRISPR enables scientists to alter these patterns and, in turn, to alter biology: in order to manipulate physical or physiological characteristics, the gene-editing technique will change, erase, insert and replace these “letters.”
How does it work?
There are similarly short variable sequences called spacers (FIGURE 1) interspersed between the short DNA repeats of bacterial CRISPRs. These spacers are extracted from the DNA of viruses that have invaded the host bacterium previously[3]. Spacers, therefore, function as a ‘genetic memory’ of past infections. If there is another infection with the same virus, any viral DNA sequence matching the spacer sequence will be cut off by the CRISPR protection mechanism to protect the bacteria from viral attack. It is done in three stages:
- Stage One – Adaptation
DNA is processed from an invading virus into short segments that are incorporated as new spacers into the CRISPR chain.
- Stage Two – CRISPR RNA production
In bacterial DNA, CRISPR repeats and spacers undergo transcription, the process of copying DNA into RNA ( ribonucleic acid). The resulting RNA is a single-chain molecule, unlike the double-chain helix framework of DNA. This chain of RNA is broken into small pieces known as CRISPR RNAs.
- Stage Three – Target
Bacterial molecular machinery is directed by CRISPR RNAs to kill the viral material. Since CRISPR RNA sequences are copied from the sequences of viral DNA acquired during adaptation, they fit the viral genome exactly and thus serve as excellent guides.
CRISPR technology is being used, among many other uses, to tackle cancer, research coral, examine neurodegenerative diseases and better understand the biology of heart conditions.For industrial processes that use bacterial cultures, such as the food processing industry, the inherent functions of the CRISPR system are beneficial. In order to make these cultures more immune to viral attack, CRISPR-based immunity can be used, which would otherwise hinder efficiency. Scientists have learned how to use CRISPR technology in the laboratory to make accurate improvements in the genes of species as diverse as fruit flies, fish, mice, plants and even human cells, beyond applications involving bacterial immune defences. Many are looking at medical applications of CRISPR technology with early achievements in the lab. For the treatment of genetic disorders, one application is. The first proof that CRISPR can be used in a living animal to correct a mutated gene and reverse disease symptoms was published earlier this year.
The rocketing development of CRISPR, however, though allowing for new scientific and medical endeavours, has raised questions about how it could be used. Even scientists with the purest of motives may inadvertently introduce harmful changes to an organism. Of course, it takes some time to comprehend and perfect every modern technology. It will be necessary to verify that a particular RNA guide is particular for its target gene, so that other genes are not mistakenly targeted by the CRISPR system. Finding a way to deliver CRISPR therapies into the body would also be necessary before they can become commonly used in medicine. Although there is still a lot to be learned, there is no question that CRISPR has become a powerful research instrument. In reality, there is enough interest in the field to warrant the launch of several biotech start-ups hoping to use technology inspired by CRISPR to treat human diseases.
