French scientist Emmanuelle Charpentier and American Jennifer A. Doudna have won the Nobel Prize in chemistry for developing a method of gene editing likened to “molecular scissors”, known as the CRispr/Cas9 System.
What is Gene Editing?
Genome editing (also called gene editing) is a group of technologies that give scientists the ability to change an organism’s DNA. These technologies allow genetic material to be added, removed, or altered at particular locations in the genome.
Genome editing is of great interest in the prevention and treatment of human diseases.
DNA is inserted, deleted or replaced in the genome of a living organismusing engineered nucleases or molecular scissors.
Currently, there are four families of engineered nucleases which are being used 1) Meganucleases, 2) Zinc finger nucleases (ZFNs), 3) Transcription activator-like effector-based nucleases (TALEN), 4) Clustered regularly interspaced short palindromic repeats (CRISPR)-Cas system.
These nucleases create site-specific double-strand breaks (DSBs) at desired locations in the genome.
What is CRISPR-Cas9 Technology?
CRISPR is a technology that can be used to edit genes .
The essence of CRISPR is simple: it’s a way of finding a specific bit of DNA inside a cell. After that, the next step in CRISPR gene editing is usually to alter that piece of DNA.CRISPR/Cas9 – a specific, efficient and versatile gene-editing technology we can harness to modify, delete or correct precise regions of our DNA.CRISPR/Cas9 edits genes by precisely cutting DNA and then letting natural DNA repair processes to take over.
The system consists of two parts: the Cas9 enzyme and a guide RNA.
Cas9 stands for CRISPR-associated protein 9 and is an enzyme.
CRISPR-Cas9, which is short for clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9, is a genome editing technology.
Genome editing (also called gene editing) is a group of technologies that give scientists the ability to change an organism’s DNA. These technologies allow genetic material to be added, removed, or altered at particular locations in the genome
- CRISPR-Cas9 was adapted from a naturally occurring genome editing system in bacteria.
- The bacteria capture snippets of DNA from invading viruses and use them to create DNA segments known as CRISPR arrays.
- The CRISPR arrays allow the bacteria to “remember” the viruses (or closely related ones). If the viruses attack again, the bacteria produce RNA segments from the CRISPR arrays to target the viruses’ DNA.
- The bacteria then use Cas9 or a similar enzyme to cut the DNA apart, which disables the virus.
Procedure of Crispr/Cas9 System:
The CRISPR-Cas9 system works similarly in the lab.
- Researchers create a small piece of RNA with a short “guide” sequence that attaches (binds) to a specific target sequence of DNA in a genome.
- The RNA also binds to the Cas9 enzyme.
- As in bacteria, the modified RNA is used to recognize the DNA sequence, and the Cas9 enzyme cuts the DNA at the targeted location.
- Although Cas9 is the enzyme that is used most often, other enzymes (for example Cpf1) can also be used.
- Once the DNA is cut, researchers use the cell’s own DNA repair machinery to add or delete pieces of genetic material, or to make changes to the DNA by replacing an existing segment with a customized DNA sequence
The medical applications of CRISPR have taken the spotlight, especially after the intense criticism that surged after a Chinese scientist revealed to the world the birth of ‘CRISPR twins’, the first humans to be born from a gene-edited embryo.
Other Applications include accelerating research into cancers, mental illness, potential animal to human organ transplants, better food production, eliminating malaria-carrying mosquitoes and saving animals from disease.
CRISPR is currently making a huge impact in health. There are clinical trials on its use for blood disorders such as sickle cell disease or beta-thalassemia, for the treatment of the most common cause of inherited childhood blindness (Leber congenital amaurosis) and for cancer immunotherapy.
CRISPR also has great potential in food production. It can be used to improve crop quality, yield, disease resistance and herbicide resistance.
Used on livestock, it can lead to better disease resistance, increased animal welfare and improved productive traits – that is, animals producing more meat, milk or high-quality wool.