This approach eliminates the risk of change of genes by mistake, which is seen as a major problem, and potentially opens up the way for the use of the technique Crispr to treat human diseases devastating.
"Although many studies have demonstrated that CRISPR/Cas9 can be applied as a powerful tool for gene therapy, there are growing concerns regarding unwanted mutations generated by the double-strand breaks through this technology", said senior author Juan Carlos Izpisua Belmonte, a professor in Salk's Gene Expression Laboratory.
While Crispr/Cas9 corrects genes by cutting accurately to the defective parts of the DNA, the new version allows you to selectively activate genes, say the researchers, whose work was published Thursday in Cell. "We were able to get around that concern". Instead, dCas9 has been coupled with transcriptional activation domains-molecular switches-that turn on targeted genes. But the entire protein, consisting of dCas9, the switches and the guide RNAs, is too big to fit inside one of these AAVs.
It took a lot of experimenting with different combinations of guide RNAs and switches before Belmonte and his team landed on a two-virus setup that worked together as a team inside the cell, targeting exactly right gene and flipping the switch. They also optimized the guide RNAs to make sure all the pieces ended up at the desired place in the genome, and that the targeted gene was strongly activated.
To test this new technique, the researchers used mice in which they induced a disease severe renal, type 1 diabetes, and a form of muscular dystrophy.
When they activated two genes involved in kidney function, they saw kidney function improve. For type 1 diabetes, they aimed to boost the activity of genes that could generate insulin-producing cells.
"We have been very satisfied with the results obtained in these mice which showed that by inducing the activation of certain genes, we can at the same time to observe physiological changes", says Fumiyuki Hatanaka, a scientist at the Salk Institute, one of the main co-authors of the study.
Researchers are hoping to hone the technique further and conduct more safety trials in animals before the technique can be tried in people.