CRISPR is a gene editing technology which is very simple and efficient. The Experts in this field claims that this technology of editing gene is going to influence our earth, improving the individual capability and also the other creatures that live with us. In this post we will discuss in detail about what is CRISPR technology, its origin, how this gene editing technology works, its various uses and limitations.
What is CRISPR, A Gene Editing Technology
CRISPR is a simple and powerful technology for gene editing. It helps scientists to alter DNA and modify function. Clustered Regularly Interspaced Short Palindromic Repeats is the expanded form of CRISPR. It is primarily a bacterial defense system that has formed the foundation for genome editing technology.
Fig. 1 – Introduction to CRISPR, the Gene Editing Technology
In the field of genome engineering, CRISPR or CRISPR-Cas9 is often used to refer to the various CRISPR-Cas9 and -CPF1 systems that are programmed to target specific genetic code. After targeting it is used to edit DNA at exact locations. The other possible uses of this technology are also being explored and one such use is a tool for diagnostic.
Origin of CRISPR
It was first discovered in archaea and then also found in bacteria by Francisco Mojica, a microbiologist at the University of Alicante. He suggested that CRISPRs function as part of the bacterial immune system. It defends against invading viruses.
Fig. 2 – Francisco Mojica, Inventor of CRISPR
It is essentially a repeating sequence of genetic code, interrupted by spacer sequences. A spacer sequence is the remains of genetic code from past attackers. It acts as a genetic memory and helps the cell detect and destroy bacteriophage -the attackers when they strike again. The first method to engineer CRISPR and use it to edit the gene in mouse and human was published in January 2013.
How CRISPR Works
The spacer sequences of CRISPR is first transcribed into short RNA sequences and is called as CRISPR RNAs or crRNAs. When the CRISPR Cas9 protein is added to a cell along with a piece of guide RNA, it moves along the strands of DNA until it locates and binds to a matching 20-DNA-letter long sequence.
After guiding the system to a matching format of DNA, the target DNA is identified by the Cas9 (an enzyme produced by the system) and it binds to the DNA. What usually happens next is the Cas9 protein cuts the DNA at the target. When the repair process begins, mutations are introduced and this may disable a gene. This is called Genome Editing or Gene Editing.
Fig. 3 – How CRISPR Works
Customized Cas proteins are also being created. These do not cut or alter DNA but turn genes on or off i.e. CRISPRa and CRISPRi respectively. Some others, called Base Editors are capable of changing one letter of the DNA code to another.
Uses of CRISPR
The potential of edititing a gene at a precise location holds enormous potential. It can aid in the growth of life science research, biotechnology, and also offer improvised treatment options for human disease. Its potential applications include correction of genetic defects, treatment and prevention of the spread of diseases and improving crops. Examples of diseases that can be treated using CRISPR include cystic fibrosis, cataracts and Fanconi anemia.
This technology in the food and agricultural industry helps to engineer probiotic cultures and to vaccinate industrial cultures against viruses. It can be used in crops to improve yield, enhance drought tolerance and lock in more nutritional properties.
Fig. 4 – Key Applications of CRISPR
One of the more interesting and possible application of CRISPR is to create gene drives. Gene drives are genetic systems that can increase the probability of a desired trait passing on from parent to children. Gene drives can help to control the spread of diseases such as malaria by conferring and enhancing sterility of female Anopheles gambiae mosquitoes.
It might be one of the more efficient and easier way to use gene editing technology compared to other tools but it is not without limitations .
CRISPR technology can’t deliver hundred percent efficiency every time. The genome-editing efficiencies can vary between 50 to 80 percentage success. There is also a possibility of “off-target effects,” where DNA is cut at sites other than the target. This can lead to unintended mutations.
Apart from Variable efficacy, off-target effects that pose safety concerns, the applications of this technology also raise ethical merits questions and consequences of tampering with genes. For example, introduction of a trait can spread beyond the target population to other organisms through crossbreeding and genetic drives could also reduce the genetic diversity of the target population.
CRISPR system offers researchers ability to permanently modify genes in living cells and organisms. And in the future, it might be possible to correct mutations at precise locations in the human genome in order to treat genetic causes of disease or pass on a desired trait but the progress has to be made with caution and ethical grounds should always be considered.