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. The active ingredients this time are transcriptional activation domains, which act like molecular switches to turn specific genes on or off. But the entire protein, consisting of dCas9, the switches and the guide RNAs, is too big to fit inside one of these AAVs. In other words, Cas9 or dCas9 was packaged into one AAV, and the switches and guide RNAs were packaged into another. These are coupled to the dCas9, along with the usual guide RNAs that help them locate the desired section of DNA.
"The components all work together in the organism to influence endogenous genes", says Hsin-Kai (Ken) Liao, a staff researcher in the Izpisua Belmonte lab and co-first author of the new paper.
To test the method, the researchers used mouse models of acute kidney injury, type 1 diabetes and a form of muscular dystrophy.
Instead, CRISPR/Cas9 can be harnessed to simply change how genes are expressed, and jumpstart the healing process in certain diseases. For muscular dystrophy, the researchers expressed genes that have been previously shown to reverse disease symptoms, including one particularly large gene that can not easily be delivered via traditional virus-mediated gene therapies.
But perhaps the most dramatic result was achieved with mice suffering from Duchenne muscular dystrophy, a lethal muscle-wasting disorder that can be traced back to a mutation in a single gene called dystrophin.
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.
In the case of kidney pathology, scientists have enabled two genes known to play a role in the renal function, and have not only found increased levels of proteins related to these genes, but also an improvement in the functioning of these bodies.
When they activated insulin-producing genes in mice with type 1 diabetes, they saw a lowering of blood glucose levels.