How CRISPR works
See below for a concise summary of how CRISPR technology can be used as a powerful gene editing tool.
How CRISPR works
CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) is a revolutionary gene editing technology that allows scientists to make precise changes to the genetic material of living organisms. CRISPR works by using a bacterial immune system to cut DNA at specific locations and then replace or delete genetic sequences. This technology has opened up new possibilities in medical research, agriculture, and biotechnology.
There are several different types of CRISPR systems, each with its unique properties and advantages. The most commonly used CRISPR system is based on the Cas9 protein, but there are also other variants such as Cas12a, CRISPRi, and CRISPRa.
Cas9 is a protein that acts as a molecular scissors to cut DNA at a specific location. The Cas9 protein can be programmed to target any DNA sequence, and then it cuts the DNA strands, allowing researchers to introduce specific changes or repairs to the genome. Cas9 is the most commonly used CRISPR protein for gene editing, and it has been extensively studied and optimised.
Cas12a, also known as Cpf1, is another CRISPR protein that can be used for gene editing. Cas12a differs from Cas9 in several ways, including the fact that it requires a different guide RNA (crRNA) and has a different cutting mechanism. Cas12a cuts DNA in a staggered pattern, which can make it easier to insert new genetic sequences. Additionally, Cas12a can target a broader range of DNA sequences than Cas9.
CRISPRi and CRISPRa are two other CRISPR systems that do not involve cutting DNA. Instead, they use a deactivated Cas protein to target specific genes and either inhibit or activate their expression. CRISPRi and CRISPRa can be used to study gene function and could have applications in gene therapy.
The "Cas" part in CRISPR-Cas systems refers to the CRISPR-associated proteins that are involved in the system's immune response. These proteins are encoded by genes located near the CRISPR array in bacterial and archaeal genomes. There are different types of Cas proteins that have unique functions and are associated with different CRISPR systems.
| Cas Systems and Types | |
|---|---|
| l | The system targets and cleaves DNA. |
| ll | The system targets and cleaves DNA. |
| ll | Targets and cleaves both DNA and RNA. |
| lV | Targets and cleaves DNA. |
| V | Targets both DNA and RNA. |
| Vl | Targets and cleaves RNA. |
| Cas Type | System | Description |
|---|---|---|
| Cas9 | ll | This system is widely used for genetic engineering, gene therapy and research applications. |
| Cas10 | lll | It has potential applications in gene regulation, epigenome editing, and antiviral defence. |
| Cas12 | V | Recognises a different protospace adjacent motif (PAM) sequence compared to Cas9 and has a different cleavage mechanism. It can also process its own guide RNA from a single CRISPR RNA (crRNA). This system has potential application in genome editing and diagnostics. |
| Cas13 | Vl | This system has potential applications in RNA editing and detection, including for diagnostic tests and for viral infections. |
| Cas14 | V | This system has potential applications in genome editing, DNA detection and diagnostics. |