The CRISPR Gene Editing Method:
Scientists have recently acquired a new and exciting toy that has the potential to save millions of lives: the CRISPR editing tool. CRISPR (clustered regularly interspaced palindromic repeats) is a tool used to edit genomes. It allows for the manipulation of gene sequences leading to many possible therapeutic and preventative uses when it comes to genetic disease. Our DNA is made up 25,000 genes that are codes for how to make all the billions of proteins that we need. In sickle cell anaemia for example, a part of the code of the haemoglobin gene is mutated i.e. changed, leading to a faulty protein being made. This faulty protein is haemoglobin, which is responsible for carrying oxygen in our red blood cells and doesn’t function normally making the cell sickle shaped. We could hypothetically use this tool to change the sequence back to what it should be and then we would get a functioning protein and eradicate the disease. Initial experiments doing this exactly thing on mice have been successful, however we are still years away from using it on humans as the efficiency of the method is still too low.
CRISPR can be thought of as a pair of scissors. It can find a gene, cut it out using the Cas9 enzyme from bacterial cells and replace it with another gene. When bacteria are attacked by viruses they will incorporate part of the viral DNA into their genome for recognition and to be able to direct its killing machinery towards it in case of a future attack. Cas9 is used to cut out the DNA of the invader, guided by an RNA (a single stranded sequence of nucleotides). By modifying this RNA CRISPR can now direct Cas9 to any desired gene.
In 2015 CRISPR saved a little girl’s life. Suffering from untreatable acute lymphoblastic leukaemia, a very nasty blood cancer, this one year old was permitted to try this experimental therapy with genetically engineered T-cells that could attack cancer cells. Interestingly, mosquitos have also been a target of CRISPR to combat Malaria by genetically engineering them to avoid the parasite that causes the disease. The applications of this method are so vast and have such a beneficial impact that we are just starting to unravel its potential.
Changing genes or turning them on and off sounds so simple, but the importance of these events in the human body can determine life or death, disease or health. There are many other thousands of genetic disorders this can also be applied to. Some concerns however have been raised due to the ability of this tool to practical edit anything. CRISPR can be used for germline editing, which means making changes to the genetic information that can be passed down to the next generations. It could be used to edit organisms to make them more desirable in appearance e.g. eye colour or ameliorate their performance. As much as it may be exciting, scientists need to be careful about its use and ethical committees need to regulate this.
