Stored in each human's DNA is the genetic code that determines everything from the color of our eyes and hair to our strength against genetic diseases. For years, scientists have looked for ways to target RNA, the intermediary genetic material that is linked to many of these diseases, and now, researchers at University of California, San Diego School of Medicine have discovered how to do this using the CRISPR-Cas9 gene-editing technique.
"This work is the first example, to our knowledge, of targeting RNA in living cells with CRISPR-Cas9," said Gene Yeo, senior author of the study. "Our current work focuses on tracking the movement of RNA inside the cell, but future developments could enable researchers to measure other RNA features or advance therapeutic approaches to correct disease-causing RNA behaviors."
The location of cellular RNA can influence the production of proteins and determine whether they are created at the right place and time. Failure of this transport and production at the proper moment can lead to a wide variety of conditions, including autism and cancer.
The researchers found that they could use the CRISPR-Cas9 system - which so far has only been used to edit DNA - to target RNA in live cells by using a new procedure they have called RNA-targeted Cas9 (RCas9).
RCas9 was created by the alteration of several features of the CRISPR-Cas9 system, allowing them to design a short nucleic acid called PAMmer that guides Cas9 to RNA molecules along with a guide RNA.
Yeo and his team tested the new system by targeting the RNA responsible for encoding the ACTB, TFRC and CCNA2 proteins and observed Cas9 by marking it with a fluorescent protein. They observed the movement of RNA into stress granules, clusters of proteins in the cell's cytosol that form when the cell is under stress and are linked to numerous neurodegenerative disorders.
"CRISPR-Cas9 is supporting a revolution in genomics and medicine based on its ability to target and modify human DNA," said David Nelles, first author of the study. "DNA is the fundamental building block of life and we are just beginning to see the implications of genome engineering with CRISPR-Cas9, but many diseases including cancer and autism are linked to problems with another fundamental biological molecule - RNA."
The findings were published in the March 17 issue of the journal Cell.