CRISPR Technology Explained
Does “gene editing” make you think of designer babies? But what if, instead of selecting for desired ‘traits,’ the edits are used to prevent serious, debilitating, and life-threatening, conditions and diseases?
CRISPR technology may make this possible. CRISPR stands for Clustered Regularly-Interspaced Short Palindromic Repeats. It’s a technology researchers are using to edit, or fix, genes within cells. The technology uses the immune system of bacteria and other microorganisms to make these edits.
Let’s break down…..
What does Clustered Regularly-Interspaced Short Palindromic Repeats mean? Palindromes are sequences of DNA that read the same forward as backwards (like the word ‘kayak’). Palindromes are repeated throughout the genome in groups (clusters) that are evenly spaced (regularly-interspaced) throughout the genome.
How does it work?
If a bacteria has a viral infection, it can attack using it’s CRISPR immune system to destroy the genome of “enemy virus”. The bacteria cuts up the DNA of the virus and inserts it into the bacteria’s own genome; this is known as spacer DNA and is found between the palindromes. This creates a memory for the bacteria; if the bacteria encounter the same virus, there is a memory of that virus and it is attacked. The repeating palindrome sequences have been coined CRISPR. A CRISPR RNA is produced and targets and destroys the genome of the virus. The virus relies on the cell’s machinery to replicate its genome to continue infecting other cells; so, by destroying the genome, the cell destroys the virus.
There are different CRISPR systems, the most popular is the Cas system discovered in the labs of Jennifer Doudna and Emmanuelle Charpentier. The Cas system is found in the bacteria, Streptococcus pyogenes. The only Cas protein this bacteria has is called Cas9 (other CRISPR systems have multiple Cas proteins). It has two places where it can cut DNA. These labs are creating a RNA, guide RNA or gRNA for short, which fits into the Cas9 protein. This gRNA helps the Cas9 find a particular point in the DNA. Cas9 then acts like molecular scissors, snipping at a precise point in the cell’s DNA. If the scissors snip within a gene, the gene is inactivated. A new gene or sequence of DNA can be inserted or the gene can be left inactivated.
How can we use this system in research and medicine?
If we could hijack the CRISPR system we could use it to inactivate genes, or even incorporate new genes into genomes.
It is possible in the near future we could use this technology to fix defective segments of genes in diseases like Cystic Fibrosis, Sickle Cell Anemia, Tay-Sachs disease etc. Some labs have already reported successful trials treating mice with genetic diseases by using this gene editing technology.
Very recently (March 17th), the journal Cell published an article making history, because scientists were able to target RNA in living cells using the CRISPR/Cas9 system (RNA-targeted Cas9). By targeting RNA in living cells, the possibilities are vast. Diseases such as HIV and cancer could be cured. But we aren’t quite there yet!
The battle over who owns the CRISPR patent is currently being fought. There is a lot at stake as CRISPR could be worth hundreds of millions of dollars and could revolutionize science. A motion for patent interference was granted by the United States Patent and Trademark Office. Which party ends up winning may influence who is allowed to use the technology — and under what terms. Currently, labs can use CRISPR freely for research and academic purposes.