A new tool to swap out faulty genes

The CRISPR gene-editing system can snip out a gene responsible for disease and replace it with a corrected copy, but this process can cause chromosomal deletions or rearrangements that are harmful to cells. Now MIT researchers have designed a new tool that can do the job in a safer and more efficient way.

The technique, called PASTE (programmable addition via site-specific targeting elements), combines the precise targeting of CRISPR-Cas9, a set of molecules derived from bacterial defense systems, with enzymes called integrases, which viruses use to insert their own genetic material into a bacterial genome. 

The researchers used PASTE to deliver 13 genes, including some that could be therapeutically useful, to nine genomic locations in several types of human cells, with a success rate ranging from 5 to 60% and few unwanted edits. They were also able to insert some new genes into humanized livers in mice.

They are now exploring the use of this tool to replace the defective gene behind cystic fibrosis. It could also target genes involved in hemophilia, Huntington’s disease, and other disorders.

“It’s a new genetic way of potentially targeting these really hard-to-treat diseases,” says Omar Abudayyeh ’12, PhD ’18; he and Jonathan Gootenberg ’13, both McGovern fellows, are senior authors of a paper on the research. “We wanted to work toward what gene therapy was supposed to do at its original inception, which is to replace genes, not just correct individual mutations.”