The CRISPR gene-editing tool has been modified so that it can add or remove methyl groups at specific positions on DNA, allowing researchers to test how such changes affect gene expression.

DNA methylation helps to regulate gene expression, but its role at specific sites has been difficult to determine. Rudolf Jaenisch and his colleagues at the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, altered the Cas9 enzyme — which can be programmed to bind to and cut specific regions of DNA — so that it would bind to DNA without cutting it. The team then fused the disabled Cas9 to enzymes that either add or remove methyl groups.

The authors found that removing methyl groups from two specific regions induced the expression of certain genes. The approach worked both in cultured mouse cells and in live mice.

Cell http://doi.org/bqzj (2016)