Corporate Banner
Satellite Banner
Stem Cells, Cellular Therapy & Biobanking
>
Scientific Community
 
Become a Member | Sign in
Home>News>This Article
  News
Return

Powerful Gene-Editing Tool Appears to Cause Off-Target Mutations in Human Cells

Published: Wednesday, June 26, 2013
Last Updated: Wednesday, June 26, 2013
Bookmark and Share
Results indicate need to improve precision of CRISPR-Cas RNA-guided nucleases.

In the past year a group of synthetic proteins called CRISPR-Cas RNA-guided nucleases (RGNs) have generated great excitement in the scientific community as gene-editing tools.

Exploiting a method that some bacteria use to combat viruses and other pathogens, CRISPR-Cas RGNs can cut through DNA strands at specific sites, allowing the insertion of new genetic material.  However, a team of Massachusetts General Hospital (MGH) researchers has found a significant limitation to the use of CRISPR-Cas RGNs, production of unwanted DNA mutations at sites other than the desired target.

"We found that expression of CRISPR-Cas RGNs in human cells can have off-target effects that, surprisingly, can occur at sites with significant sequence differences from the targeted DNA site," says J. Keith Joung, MD, PhD, associate chief for Research in the Massachusetts General Hospital (MGH) Department of Pathology and co-senior author of the report receiving online publication in Nature Biotechnology.  "RGNs continue to have tremendous advantages over other genome editing technologies, but these findings have now focused our work on improving their precision."

Consisting of a DNA-cutting enzyme called Cas 9, coupled with a short, 20-nucleotide segment of RNA that matches the target DNA segment, CRISPR-Cas RGNs mimic the primitive immune systems of certain bacteria.  When these microbes are infected by viruses or other organisms, they copy a segment of the invader's genetic code and incorporate it into their DNA, passing it on to future bacterial generations.  If the same pathogen is encountered in the future, the bacterial enzyme called Cas9, guided by an RNA sequence the matches the copied DNA segment, inactivates the pathogen by cutting its DNA at the target site.

About a year ago, scientists reported the first use of programmed CRISPR-Cas RGNs to target and cut specific DNA sites.  Since then several research teams, including Joung's, have succesfully used CRISPR-Cas RGNs to make genomic changes in fruit flies, zebrafish, mice and in human cells – including induced pluripotent stem cells which have many of the characteristics of embryonic stem cells.  The technology's reliance on such a short RNA segment makes CRISPR-Cas RGNs much easier to use than other gene-editing tools called zinc finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs), and RGNs can be programmed to introduce several genetic changes at the same time.

However, the possibility that CRISPR-Cas RGNs might cause additional, unwanted genetic changes has been largely unexplored, so Joung's team set out to investigate the occurrence of "off-target" mutations in human cells expressing CRISPR-Cas RGNs.  Since the interaction between the guiding RNA segment and the target DNA relies on only 20 nucleotides, they hypothesized that the RNA might also recognize DNA segments that differed from the target by a few nucleotides.

Although previous studies had found that a single-nucleotide mismatch could prevent the action of some CRISPR-Cas RGNs, the MGH team's experiments in human cell lines found multiple instances in which mismatches of as many as five nucleotides did not prevent cleavage of an off-target DNA segment.  They also found that the rates of mutation at off-target sites could be as high or even higher than at the targeted site, something that has not been observed with off-target mutations associated with ZFNs or TALENs.

"Our results don't mean that RGNs cannot be important research tools, but they do mean that researchers need to account for these potentially confounding effects in their experiments.  They also suggest that the existing RGN platform may not be ready for therapeutic applications," says Joung, who is an associate professor of Pathology at Harvard Medical School.  "We are now working on ways to reduce these off-target effects, along with methods to identify all potential off-target sites of any given RGN in human cells so that we can assess whether any second-generation RGN platforms that are developed will be actually more precise on a genome-wide scale.  I am optimistic that we can further engineer this system to achieve greater specificity so that it might be used for therapy of human diseases."


Further Information
Access to this exclusive content is for Technology Networks Premium members only.

Join Technology Networks Premium for free access to:

  • Exclusive articles
  • Presentations from international conferences
  • Over 2,500+ scientific posters on ePosters
  • More than 3,700+ scientific videos on LabTube
  • 35 community eNewsletters


Sign In



Forgotten your details? Click Here
If you are not a member you can join here

*Please note: By logging into TechnologyNetworks.com you agree to accept the use of cookies. To find out more about the cookies we use and how to delete them, see our privacy policy.


Scientific News
The Mending Tissue - Cellular Instructions for Tissue Repair
NUS-led collaborative study identifies universal mechanism that explains how tissue shape regulates physiological processes such as wound healing and embryo development.
Tissue Bank Pays Dividends for Brain Cancer Research
Checking what’s in the bank – the Brisbane Breast Bank, that is – has paid dividends for UQ cancer researchers.
iPS Cells Discover Drug Target for Muscle Disease
Researchers have designed a model that reprograms fibroblasts to the early stages of their differentiation into intact muscle cells in a step towards a therapeutic for Duchenne muscular dystrophy.
Engineered Hot Fat Implants Reduce Weight Gain
Scientists at UC Berkeley have developed a novel way to engineer the growth and expansion of energy-burning “good” fat, and then found that this fat helped reduce weight gain and lower blood glucose levels in mice.
Transplanted Stem Cells Can Benefit Retinal Disease Sufferers
Tests on animal models show that MSCs secrete growth factors that suppress causes of diabetic retinopathy and macular degeneration.
MRI Scanners Can Steer Therapeutics to Specific Target Sites
Scientists from the University of Sheffield have discovered MRI scanners, normally used to produce images, can steer cell-based, tumour busting therapies to specific target sites in the body.
Team Finds Early Inflammatory Response Paralyzes T Cells
Findings could have enormous implications for immunotherapy, autoimmune disorders, transplants and other aspects of immunity.
Early Detection of Lung Cancer
The University of Manchester has signed a collaboration agreement with Abcodia to perform proteomics studies on a cohort of non-small cell lung cancer cases from the UKCTOCS biobank, with the aim of discovering new blood-based biomarkers for earlier detection of the disease.
Researchers Identify Drug Candidate for Skin, Hair Regeneration
Formerly undiscovered role of protein may lead to the development of new medications that stimulate hair and skin regeneration in trauma or burn victims.
Basis for New Treatment Options for a Fatal Leukemia in Children Revealed
Detailed molecular analyses allow new insights into the function of tumour cells and options for new treatments.
Skyscraper Banner

Skyscraper Banner
Go to LabTube
Go to eposters
 
Access to the latest scientific news
Exclusive articles
Upload and share your posters on ePosters
Latest presentations and webinars
View a library of 1,800+ scientific and medical posters
2,500+ scientific and medical posters
A library of 2,500+ scientific videos on LabTube
3,700+ scientific videos
Close
Premium CrownJOIN TECHNOLOGY NETWORKS PREMIUM FREE!