CRISPR

Someone just asked me about CRISPR and how it can help us understand Sturge-Weber syndrome. The person asked if CRISPR can lead to a cure for SWS.


What is CRISPR?

CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats. It’s often described along with some associated proteins so it’s CRISPR-Cas9. That’s a mouthful, so let’s just pronounce it “crisper.”

Viruses are really interesting things. They tend to be very small—much smaller than a cell in your body. These little viruses can infect cells and cause problems from the common cold to terrible diseases. Viruses aren’t exactly living things; they exist on the borderline of the definition of life. They do have DNA (like living things), and they evolve over time, but they can’t live on their own.

The tree of life has three great branches (bacteria, other small organisms called archaea, and the eukaryotes that include a range of creatures such as plants, fungi, and animals). It turns out the viruses infect all three branches of life. Bacteria and archaea tend to live as just single cells; but they also have to worry about getting infected by viruses. And they developed a remarkable defense system called CRISPR. CRISPR is basically like an immune system for bacteria (and archaea) to protect them from viruses. Like our immune system there is a “memory” of which viruses attack a bacterium over time.

If you’re a bacterium, CRISPR is great. A virus attacks you, and CRISPR fights back: it recognizes the DNA in the virus, attacks it, cuts it, and gets rid of it. And it somehow makes sure NOT to attack the bacterium’s own DNA. It’s very, very specific.

Scientists first discovered CRISPR in the 1990s. By about 2013 researchers understood CRISPR well enough to start a revolution in biology. The rate of progress is dizzyingly fast.

 

What can you do with CRISPR?

Biologists now control CRISPR and use it to edit the genome. That means they can make changes to the DNA. Here is just some of what you can do with CRISPR.

·      Take a human cell—say for example a human endothelial cell line growing in a flask in someone’s lab. Use the CRISPR machinery to introduce any single change (that’s 1 base out of 3,000,000,000). As one example, you can knock out a gene (to study the effects). As another example, you can “turn on a gene.” We can introduce the GNAQ R183Q mutation. Why is that a good thing? We can then test the effects of the mutation on cells, and study whether drugs are helpful.

·      You can edit two genes at once. For example, GNAQ and a second gene that we think might interact with it and be important in SWS.

·      Instead of cutting DNA to edit a gene, you can “turn on” a gene. (In the language we speak in the lab, we can use CRISPR to recruit transcriptional activators.)

·      CRISPR is now used to image DNA in live cells.

·      You can use CRISPR “libraries,” as they’re called, to search for genes that affect some pathway. This could teach us more about how GNAQ functions with other genes to cause SWS and port-wine birthmarks.

 

How much can CRISPR help us advance knowledge and treatment of SWS?

CRISPR-Cas9 and related systems are techniques to edit the genome. I see them as tools that are available today to ask questions about how genes work. I don’t see CRISPR tools as leading to an immediate cure for Sturge-Weber syndrome or any other disease. I do see these tools as leading to immediate progress, or at least short-term progress in the upcoming years, to help us better understand GNAQ and how to search for drugs that can be helpful in someday treating SWS.

And the research community is carefully studying the tough question of whether CRISPR actually causes harm. It’s possible that it cuts DNA in ways we don’t yet understand. For any intervention we balance possible benefit and harm, and with new methods it can take time to figure out possible downsides.

 

A Goal

CRISPR is amazing. I love reading about tremendous advances being made across a range of areas and especially about diseases. Now let’s see some CRISPR advances for Sturge-Weber syndrome.