By Megan Cooley
Streptococcus pyogenes Cas 9, or better known as CRISPR-Cas9, continues to make headlines with potential applications of its use. January’s Nature publication mentioned a new or “domesticated” version of CRISPR-Cas 9, coined High-fidelity CRISPR-Cas 9.
CRISPR-Cas 9 was initially isolated bacteria; Cas 9 was identified as a component of a bacterial immune system. Specifically, as stated in an article in Nature International Weekly Journal of Science Cas 9 in bacteria is responsible for recognition of viral or non-native DNA. It destroys the non-native DNA and moves it to the CRISPR locus where an RNA template of the interfering DNA is produced and sent out to repair damage to the native bacterial DNA enabling the bacteria to survive. A publication in 2015 by Bolukbasi et al in Nature Methods showed that this enzyme, led by guide RNA, could be used to edit DNA in human cells with impressive accuracy. Because the bacterial genome is not the same as the human genome, the system was not perfect and off-target effects were observed. Nonetheless, this system could identify mutations in DNA rapidly and with improved specificity compared to traditional cross-breeding of animals.
From a research perspective, this was a monumental achievement. Experiments for gene-editing done traditionally by cross-breeding animals with altered genomes to achieve new mutations of interests could take a year or more with several animals required to ensure that the desired mutation(s) were achieved. CRISPR can do this in half the time with half the number of animals. It’s not uncommon for animal studies to consume the majority of money awarded in grants limiting additional studies.
Kleinstiver et al have now improved CRISPR-Cas 9, with greater than 85% of targets matched compared to the original CRISPR-Cas 9. This advancement not only improves its use in genome editing for research purposes, but also its potential as a therapeutic. Significant effort has gone into targeted drug therapies over the last decade. One approach was the use of antibody-drug conjugates. This approach can lack specificity, and because of issues with drug delivery, drug concentrations need to be high to observe an effect. In order to improve specificity of CRISPR-Cas 9, Kleinstiver and coworkers systematically broke down how enzymes bind to DNA and used this to eliminate mismatched pairings.
In the same Nature International Weekly Journal there was an article discussing research that had produced the first genetically modified monkey(s) which exhibited autism symptoms like those in humans. Monkeys possessing the autism related gene MECP2 produced obsessive tendencies accompanied with avoidance of other monkeys. The researcher’s next steps will be better to identify a location in the brain that is responsible for inducing the behavior. They plan to use CRISPR-Cas 9 for this research. This demonstrates the vast utility of this system as researchers have struggled for years to show a genetic link to patients with autism. CRISPR has only been on the scene for two years. It will be interesting to see how this technology continues to develop and to what areas of research it will be applied.
Where do you see CRISPR evolving? If you’d like to see the AAPS Blog cover a specific angle of this developing technology, please let us know in the comments!
Megan Cooley is not authorized to speak on behalf of MRIGlobal, and the opinions expressed are my personal opinions and not those of MRIGlobal.