Scientists have modified the CRISPR-Cas9 system so they have the flexibility to undo gene edits and carefully control the amount of gene suppression.

In a study published in Cell Stem Cell, researchers at Gladstone Institutes used a modified version of CRISPR called CRISPR interference (CRISPRi) to mute genes rather than deleting a precise part of the genome by making small cuts in a cell’s DNA, as the standard CRISPR system does.

CRISPRi effectively acts like a master switch, enabling the scientists to reverse gene suppression by simply removing the chemical that turns on the gene inhibitor.

“We were amazed by the dramatic difference in performance between the two systems,” said the study’s senior author and senior investigator in the Gladstone Institute of Cardiovascular Disease and Roddenberry Stem Cell Center at Gladstone, Bruce Conklin.

“We thought that permanently cutting the genome would be the more effective way to silence a gene, but in fact, CRISPRi is so precise and binds so tightly to the genome that it is actually a better way to silence a gene.”

Gladstone Institutes researchers discovered that the CRISPRi system also alleviates concerns that the standard CRISPR-Cas9 system causes off-target changes in gene expression.

They discovered that in more than 95% of the cells created using CRISPRi, the target gene was silenced, compared with only 60 to 70% of cells grown from CRISPR-Cas9. CRISPRi also did not cause any undesired insertions or deletions to the cell’s genome, which is a concern with CRISPR-Cas9.

Additionally, the researchers were able to tune how much they silenced a gene by changing the amount of the chemicals they added.

Gladstone Institutes researchers believe their findings will allow more versatile investigations into the role of certain genes that affect development and disease.

“CRISPRi holds a major advantage in making disease-relevant cell types,” said first author Mohammad Mandegar, DPhil, a research scientist at Gladstone. “Using this technology, we can mimic disease in a homogenous population of heart cells created from iPSCs. This development allows us to study genetic diseases more easily and potentially identify new therapeutic targets.”