Crispr-CAS9 and the promise of simple gene editing

Submitted by Carlyn Zwarenstein on December 10, 2013 - 14:00

A top story for this year has got to be the Crispr-CAS9 technique for targeted gene editing. Many of you will be aware of this exciting development in genetics. Its gotten a fair bit of breathless and sometimes incomprehensible science media coverage lately (Crispr, or Clustered Regularly Interspaced Short Palindromic Repeats, were discovered in bacteria back in the late 80s but considered junk DNA; seminal research on use of the Crispr-associated enzyme CAS9 in gene editing was published by Jennifer Doudna and Emanuelle Charpentier last August; since then its been tested on numerous different organisms; as of earlier this year, that list includes human cells).

In the Independent, Craig Mello, (co-winner of the 2006 Nobel for Physiology or Medicine for his work on RNA interference), was quoted for example as saying of the new Crispr technique that “It’s one of those things that you have to see to believe. I read the scientific papers like everyone else but when I saw it working in my own lab, my jaw dropped. A total novice in my lab got it to work.” 

Sounds too good to be true, but breakthroughs in genetics techniques can quickly revolutionize the entire field of study, as Mellos research did.

Crispr seems to be a dramatic improvement upon previous cumbersome or haphazard DNA-cutting techniques: modified viruses, zinc fingers and Talens. It allows for targeted editing of the human (or another) genome using an RNA molecule programmed to match a unique DNA sequence—along with the DNA-cutting enzyme, CAS9, that helps target the specific sequence of interest in the DNA. Once the RNA aligns with the target DNA strands, CAS9 cuts both strands of DNA at the target location—at which point new DNA can be inserted right at that spot, or defective DNA can be removed.

The nucleotide-level precision that is possible with this technique raises the possibility of safe, simple gene therapy for many hereditary diseases, both in patients in advanced stages of illness and going as far back as into the egg or sperm.

The Independent has simplified graphic that makes the process fairly straightforward.

And here, some researchers responding to the question of whether this genetic microsurgery is being over-hyped.

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