The gene-editing technology CRISPR is already making a huge difference across many scientific fields, but its importance could be about to grow even further – scientists have discovered a new technique that can leave out particular sections of a gene, essentially ‘skipping’ them.
This new method, called CRISPR-SKIP, could be used to control how genes are expressed and regulated. For treating conditions caused by mutations in the genome, like Duchenne muscular dystrophy and Huntington’s disease, that could be invaluable.
The research team from the University of Illinois at Urbana-Champaign have highlighted the ways their new tool improves on current CRISPR techniques in certain scenarios.
“Given the problems with traditional gene editing by breaking the DNA, we have to find ways of optimising tools to accomplish gene modification,” says one of the team, Pablo Perez-Pinera.
“This is a good one because we can regulate a gene without breaking genomic DNA.”
The typical CRISPR-Cas9 technique works by targeting a piece of DNA through a specific gene, breaking the DNA at that point, and binding it back together in a different form. It’s a bit like using a pair of molecular scissors.
The method has been used with a lot of success so far, but it’s not perfect: DNA breaks can miss their targets, and broken DNA can attach to different chromosomes, leading to unpredictable genetic mutations.
What CRISPR-SKIP does is to mark certain segments of gene code, called exons, as blank. When the cell transcribes the gene into RNA ready to turn into a protein, that exon gets ignored – as per the DNA instructions edited by CRISPR-SKIP.
“When the cell treats the exon as non-coding DNA, that exon is not included in mature RNA, effectively removing the corresponding amino acids from the protein,” explains one of the researchers, Michael Gapinske.
While the amino acids might be missing, the resulting proteins can often still function as normal, or partly as normal. When it comes to restoring function in some genetic diseases, that could be important.
And the technique is clean enough to work better than existing methods of manipulating gene expression in this way – because it alters the DNA blueprint, it means changes are permanent and treatments don’t need repeating.
The technique has yet to be tested on living organisms, but it has worked on both human and mouse tissue in the lab, using cancerous and non-cancerous samples (certain types of cancers could also be treated using CRISPR-SKIP).
In particular, the researchers were able to make changes in the oncogenes that can turn into tumours. Exons could be skipped with high levels of efficiency, the study shows, and CRISPR-SKIP can also skip multiple exons in a single gene.
It’s still early days, and the scientists did notice some genetic mutations away from the edited areas that need to be minimised. Even if the technique isn’t completely effective, though, it can still make a difference.
“In Duchenne muscular dystrophy, for example, just correcting 5 to 10 percent of the cells is enough to achieve a therapeutic benefit,” says Perez-Pinera.
“With CRISPR-SKIP, we have seen modification rates of more than 20 to 30 percent in many of the cell lines we have studied.”
Perhaps we’ll end up with a variety of CRISPR editing techniques to help treat diseases and avoid mutations. CRISPR-STOP, which can also be used to truncate proteins using a different genetic blocking method, is also referenced by the researchers.
For now the work continues to investigate just how effective and useful CRISPR-SKIP could be. Like CRISPR-Cas9, we’re going to have to make absolutely sure the technology is safe before treatments can be developed.
“We hope that future improvements to gene editing technologies will increase the specificity of CRISPR-SKIP so we can begin to address some of the problems that have kept gene therapy from being widely applied in the clinic,” says one of the team, Jun Song.
The research has been published in Genome Biology.