Science Breakdown: What is CRISPR and Why should I Care About it?

The CRISPR gene editing technology is one of those hot topics today in science, everyone wants to get involved in researching it. This post is inspired by an editorial from nature talking about how Chinese scientists plan to pioneer the first human CRISPR trial.

What is CRISPR?

CRISPR or Clustered Regularly Interspaced Short Palendromic Repeats, is the name of the prokaryotic immune system. It is the method by which a prokaryotic cell deals with invading DNA (whether that DNA come from viruses, or is just sitting around in the environment). Briefly, there is a region in the genome of the prokaroyte where short segments of an invaders DNA are stored, these short segments are separated by repeating regions of the same sequence of DNA. This region is called CRISPR (in the image above section 1 labeled CRISPR array).

But WAIT! How the hell are people going to use that for human trials?

They aren't. There is more to it, as you can see from the above image this immune system is a multi step process involving a lot of different moving parts. There are proteins associated with this DNA array called CAS (which means Crispr ASsociated). These proteins do a variety of roles for the immune system, and for Bio-technologists can be applied to do a variety of functions for us.

VERY BRIEF rundown of how the immune system works:

Essentially the CRISPR array is made into short RNA segments consisting of one repeat and one of the small pieces of foreign material that were inserted into it. This is called a Guide RNA. (This is in part 2 of the above figure) Other proteins bind this guide RNA and use it to find the region in foreign DNA that is complementary to it (as RNA is single stranded and nucleic acid bases bind to their complementary ends A with T and C with G. So the complex finds the region in the foreign DNA that is complementary to the RNA. Here is the important part a separate enzyme then comes and binds to the complex that cuts the foreign DNA where the guide RNA has bound, chopping it into pieces and effectively destroying it. If that DNA belonged to a virus it can no longer replicate and that virus is dead. (In the image above this is performed by a protein called Cas3, for biotechnology there is a homologous protein called Cas9 that everyone uses which performs this function.)

Summary and What The Scientists Are Going to DO with This and WHY YOU SHOULD CARE:

When we say CRISPR we are referring to the Cas9 protein rather than the system as a whole. We use the directable cutting ability of Cas9 (with a guide RNA that we can design to bind to a very specific target), to induce damage to DNA or change a mutated base in a gene of someone with a genetic disease. Another possible use is to inactivate the cutting ability of the Cas9 protein but still use its ability to target a specific location on our genome in order to deliver a payload (like a different protein, or a drug or anything we want to attach to the Cas9). It allows for extremely targeted therapies that no other technique at this point make possible.

So There you have it, when you see CRISPR in the news this is a rundown of what people are talking about. 

I intend for these posts to be informative. Please let me know anything else you would like for me to add to help you take away more from it!

Sources:

Image of a cell from: http://www.wonderwhizkids.com/biology/human-physiology/human-cells-tissues

All other images and content are my own.

Edit: To the people flaging this post. Try actually posting content where it belongs instead of trying to scam. This is a post about science, in the correct location. Posted by someone with the background to actually discuss and interpret said material.