With the first experiments to use CRISPR in people underway, the gene-editing technique is showing promising signs in a few patients. But it turns out not all DNA is amenable to CRISPR.
Some genetic diseases, like those caused by mutations in the genome of the mitochondria — the body’s energy sources — can’t be corrected with CRISPR. [July 8], a team at the Broad Institute of MIT and Harvard and the University of Washington School of Medicine announced that they figured out how to precisely edit mitochondria for the first time.
The discovery could help scientists better understand mitochondrial diseases and test treatments for these disorders, which affect about 1,000 to 4,000 babies born in the United States every year.
To test the editing system, the researchers used it to make single-letter edits in five different human mitochondrial genes. One of the genes they modified is called MT-ND4, which plays a role in the cell’s energy production processes. When they changed a single C to T, mimicking a mutation, the mitochondria began to break down. Across their experiments, they found that the new method edited about 20% to 40% of the mitochondria that they aimed to change.
“20% to 40% might not sound particularly impressive, but many genetic diseases can be treated by levels of correction that are in that ballpark,” [researcher David] Liu says. “You rarely need to correct 100% of genes to have a benefit to a prospective patient.”
