CRISPR stands for clustered regularly interspaced short palindromic repeats. It’s a genome editing technique that has turned the biomedical community on it’s head. Basically, CRISPR is a group of molecules that can edit DNA and unlike other gene-editing methods it’s cheap, quick and “easy” to use. In 2015, CRISPR was labeled the breakthrough of the year, and it could be the technology to cure many diseases, including cancer.
CRISPR-Cas9 can be programmed to seek and find a certain sequence of DNA, say a mutation you don’t want, and snip it out. By placing an alternate DNA code in the nearby vicinity, the new DNA will be repaired into the DNA code. For example many diseases, such as cystic fibrosis or muscular dystrophy, are the result of a faulty gene that could be replaced. Researchers have used CRISPR-Cas9 to alter the genome of mice with a severe form of muscular dystrophy. Their results show the mice were able to make an essential muscle protein allowing them to build strength during growth.
The Cas9 of CRISPR-Cas9 is a CRISPR associated protein 9. The Cas9 is the protein/enzyme derived from a bacteria used to unravel DNA and cut out the unwanted DNA. The enzyme (the scissors) is paired with an RNA strand that guides or programs the enzyme to the sequences at specific locations in the genome to cut. Together they can be programmed to cut DNA at precise points on the genome. This precision is extremely valuable.
Since the discovery of CRISPR-Cas9, hundreds of papers have been published discovering the wide applications of CRISPR-Cas9 technology. Discoveries beyond the straight forward use have often been called, “hacking CRISPR.” Scientists have used the CRISPR technology to hack a way to help remove cancer cells from infected individuals. Cancer attacks immune cells, the very same cells that should destroy cancer cells. CRISPR-Cas9 can disable the gene that puts a stop on a cell’s immune response, giving them the ability again to fight and destroy cancer cells. The first clinical trials using some of this CRISPR-Cas9 technology in humans in the US will be sometime this year.
Another hack of CRISPR is using the technology to not just cut out DNA but to alter the epigenome. Simply, your DNA codes for proteins which make up your body. Not all of your DNA codes are turned on and many are turned off. By altering what codes are turned on or off, effects what your body displays. Think of twins – they have the same genetic makeup (same DNA), yet their physical appearance is different – they look and act different. This has a lot to do with their epigenome and environmental factors that have turned off some genes and on others. Using the CRISPR technology scientists are sending proteins to precise spots on the DNA to turn on or off certain DNA codes. This is yet another way genes can be altered to select for certain traits or lessen others.
This technology comes with great responsibility. Changing the genome of one organism in the population will effect the entire population, and what change will that cause in the ecologic system? Let’s look at the zika virus for a second. It’s a deadly virus carried by only a few species of mosquitoes. Using CRISPR-Cas9 scientists could alter the genome of a mosquito to make it unable to carry the zika virus. When this mosquito reproduced it’s offspring would carry the same DNA and soon the entire species would not be able to carry the virus, essentially destroying the virus. But, what if when the mosquito was altered it made it distasteful to it’s predators? The mosquito population would explode. And what if it could now carry a different even more deadly virus? The point is, the ecologic systems are highly complex and connected. If these CRISPR-Cas9 genes enter the environment, the ramifications could be extreme.
And how far are we willing to modify the human genetic genome? Would you like your child to express more of their DNA code for longer thicker hair? Would you like to ensure they don’t have the gene for early onset Alzheimers? Where is the line drawn?