Two teams show how a genome-editing system can be used to screen human cells for genes of interest.

The CRISPR system allows biologists to edit specific genes using 'guide' RNA molecules that target them. Feng Zhang at the Broad Institute in Cambridge, Massachusetts, and his colleagues created a library of 64,751 guide RNA sequences that target 18,080 genes in human cells. Using this library, the researchers pinpointed genes that are required by cancer and stem cells to survive. They also teased out genes that, when lost, allow cancer cells to fend off the melanoma drug vemurafenib.

A separate team led by Eric Lander at the Broad Institute and David Sabatini at the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, used a library of 73,000 guide RNAs to screen for several genes, including those involved in resistance to the chemotherapy drug etoposide.

Science 343, 80–84; 84–87 (2014)