Scientists at the Salk Institute for Biological Studies in California have successfully used the CRISPR-Cas9 gene editing tool to restore insulin-producing cells in mice, raising hopes for a cure for Type 1 diabetes in humans. Gene expression was activated, without making any cuts to the DNA.
CRISPR-Cas9 can be used to make precise edits to genes. The gene editing tool allows scientists to insert new genes, or edit out genetic defects. While the technique has been shown to be effective in animal models, trials using CRISPR-Cas9 in humans are only just commencing.
While it was initially thought that the gene editing tool had no off-target effects, concern is growing that CRISPR-Cas9 could cause unwanted mutations. The targeted gene defect could be corrected, only for potentially harmful edits to be made, especially as the tool makes double-strand breaks in the DNA.
For the latest study, rather than edit out genes or insert new genetic material, the scientists wanted to test whether CRISPR-Cas9 could be used to activate genes without making cuts to the DNA. CRIPSR is the guide section of the gene editing tool, which isolates the specific part of the DNA strand where the cut is made. That cut is made by the Cas9 component.
For the latest study, the scientists used a new version of Cas9 that did not have the ability to make a cut. Instead, they combined the technology with a molecular switch that was able to manipulate the epigenome without making any cuts to the DNA. Introducing the new system for in vivo activation of genes was problematic, as their system was too bulky to introduce into cells. The researchers were able to develop a system using two viruses to introduce CRISPR-Cas9, rather than a single virus which is more typically used.
The researchers were able to successfully demonstrate the effectiveness of their technique on mouse models of type 1 diabetes, and were able to restore insulin-producing cells. The researchers also demonstrated the effectiveness of the system for treating mouse models of acute kidney disease and muscular dystrophy. In all cases, the new system resulted in the amelioration of disease symptoms.
The researchers point out that this system is not a cure for any disease. Professor Juan Carlos Izpisua Belmonte, Salk Institute for Biological Studies said, “We are not fixing the gene; the mutation is still there.” However, the researchers were able to restore activity of specific genes and reduce the symptoms of certain diseases.
The new technique has only been shown to be effective in mice, and long-term studies would be necessary to determine whether the technique had any negative impact. However, the researchers are hopeful that the same technique could be used in humans, with out the risk of off-target effects and DNA damage resulting from unintentional DNA cuts. The team is now working on improving the safety of the system and will attempt to target a wider variety of cell types.
The research study – In Vivo Target Gene Activation via CRISPR/Cas9-Mediated Trans-epigenetic Modulation – has recently been published in the journal Cell.