Gene editing using the CRISPR system is transforming genetic research and could be poised to transform the treatment of genetic diseases such as hemophilia and cystic fibrosis. Now a University of Virginia School of Medicine researcher has found a safer and highly efficient way to use the system to silence genes.
Mazhar Adli, PhD, and his team have developed a technique to prevent genes from carrying out their function without causing the extensive DNA damage the current approach requires. This is important because silencing genes allows scientists to understand what individual genes do and identify the ones that cause disease. Gene silencing also may one day let doctors better treat and even cure genetic diseases with abnormal gene activity.
Rebuilding Genes
Our genes – the blueprints for life – are segments of the long double strands of DNA in our cells. To silence genes using the current approach, the CRISPR system cuts both strands. Doing this too often causes the cells to die –– a major limitation for CRISPR. Even cuts that are not fatal to cells can have unintended effects that result from the body’s efforts to repair the broken DNA.
Adli’s approach, on the other hand, avoids cutting the DNA altogether. Instead, it takes advantage of the fact that DNA is made of four main building blocks: cytosine, adenine, guanine and thymine. Adli’s method lets scientists use CRISPR to convert one building block into another to artificially create what are called stop codons – the “off” switches that naturally occur at the end of genes. Turn cytosine into thymine, for example, and the whole gene is silenced, meaning there is no protein production from that gene.
“We found around 17,000 genes we can target this way, and, as you know, we have roughly 20,000 genes,” Adli explained. “So a very large fraction of the genome we can target with this CRISPR stop approach.”
He noted the benefits of the new technique’s genetic alchemy: “It’s about as efficient as what we used previously,” he said. “But more importantly, it is safer. It doesn’t cause cell death.” Further, the new approach is compatible with high-throughput screening that lets scientists do their research much more quickly. “You can delete basically every single gene [of certain types] in a population of cells and then watch the entire population to see what’s going to happen to them,” he said. “So with a single experiment you can interrogate the function of thousands and thousands of genes.”
Benefiting the World
Adli, of UVA’s Department of Biochemistry and Molecular Genetics, is making his technique available for free to scientists around the world. Any lab that uses CRISPR should have the capability to use it, he said. He expects it will initially be used for research in labs like his, but, with the first human tests of gene editing now beginning, that may change in the future.
Adli’s team has outlined the new technique in an article in the scientific journal Nature Methods. The article was written by Cem Kuscu, Mahmut Parlak, Turan Tufan, Jiekun Yang, Karol Szlachta, Xiaolong Wei, Rashad Mammadov and Adli.
The work was supported by a V Scholar award from the V Cancer Research Foundation and a pilot project award from the UVA Cancer Center.
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