Another step closer to curing cancer and genetic diseases: All you need to know about CRISPR-Cas9

Imagine if you had a technology that could give you superpowers. No, we are not talking about gamma rays or radioactive spiders but something pretty similar. If you’ve watched Marvel’s Luke Cage series, you may have heard of a gene-editing tool called CRISPR. The protagonist gets super strength and unbreakable skin when a mollusc DNA was fused into his DNA.   As bizarre as it may sound, CRISPR-Cas9 (the shorter and more colloquial name is CRISPR) is a real thing and it can selectively cut and paste DNA pieces from and to your DNA. Though the plan for this tool does not include creating super soldiers. Instead, scientists believe that CRISPR-Cas9 could be a ray of hope for those suffering from inherited genetic disorders like down syndrome, cystic fibrosis and thalassemia.   [caption id=“attachment_7656521” align=“alignleft” width=“380”]  Representational image. Image source: Getty Images.[/caption] The technology isn’t just theoretical anymore. A study, to be presented next month at a meeting of the American Society of Hematology, conducted on three cancer patients to test the safety of the tool has shown promising results. And it isn’t the only one - more studies are recruiting and being conducted to bring gene editing to life.  

So what is CRISPR-Cas9

CRISPR (pronounced Crisper) is an acronym for Clusters of Regularly Interspaced Short Palindromic Repeats. The Cas9 stands for a CRISPR-associated protein 9. Nature has quipped bacteria with an ability to protect itself from invading viruses. When a virus attacks a bacterium, viral DNA gets embedded in the bacterium’s DNA. This creates a new element within the bacterial DNA called CRISPR. If the same virus then attacks the bacterium again, it uses CRISPR to identify the virus.   CRISPR does this by creating RNA - a molecule that carries messages out from the DNA to the rest of the cell. The RNA is the one that identifies the viral DNA invading the cell (or bacteria). Then, the Cas9 present in the bacteria chops off the invading virus’ DNA, thus neutralising the threat.   The new gene-editing tool for humans is based on this same concept. This innovative tool was, rather unimaginatively, then named CRISPR-Cas9.

CRISPR-Cas9 as a tool

The gene-editing tool CRISPR-Cas9 is a bit different from its bacterial version. It contains a small chain of RNA along with Cas9, instead of DNA. This cuts out one step of the bacterial process.     CRISPR-Cas9 could be really helpful for those suffering from genetic diseases. A genetic disease happens due to glitches in the DNA sequence. They usually begin inside the fetus when all your body cells are still dividing. Every time a cell divides, its DNA divides along with it to send a copy of the genome into the new cell. But, a fault can sometimes happen in the copying process. This can alter the complete genetic code, creating a mutation - which leads to genetic disease. This is where CRISPR-Cas9 comes in. The RNA in the tool identifies the “error” in the genetic code. It then binds with the faulty part of the DNA. Cas9 then cuts off that faulty piece.   The original version of the CRISPR-Cas9 tool would only find and cut out the error in the DNA. This creates a gap in the DNA code, which needs to be ‘repaired’. The original tool couldn’t do so, and would thus necessarily leave the repair process up to the cell. The cell would either join the broken ends of the DNA or insert a new piece to fill the void. Clearly, while this gets rid of the anomaly in the cell, what happens to the genetic code afterwards wasn’t in the tool’s control. This made the outcome uncertain. With the new version of the CRISPR-Cas9 tool, scientists can now take control of the repair process as well. We can now add an entirely new DNA sequence of our choice in the removed region and not just fix an anomaly but even introduce new traits into the organism. Think of this as a find-replace tool in your word editor, as opposed to just the find(-delete) tool. Currently, there is no cure for genetic diseases. CRISPR-Cas9 is a promising step forward. Scientists have already used it to treat some diseases in plants and animals. Health articles in Firstpost are written by myUpchar.com, India’s first and biggest resource for verified medical information. At myUpchar, researchers and journalists work with doctors to bring you information on all things health. For more information, please read our article on   Hemophilia_, a genetic condition which prevents blood from clotting._