The functions of all 20,000 human protein-coding genes are still not known, partly because large gene-knockout libraries are not available for human cells.

One strategy for making such a library is to use a retroviral gene trap that disrupts gene expression when inserted into different genes. But this does not work for human cells, which have two copies of most genes. Now a team led by four researchers — Tilmann Bürckstümmer of biotech firm Haplogen in Vienna, Austria, and Thijn Brummelkamp, Giulio Superti-Furga and Sebastian Nijman of the Research Center for Molecular Medicine of the Austrian Academy of Sciences in Vienna — has overcome this problem.

The team used a cancer-cell line that has only one copy of most genes (near-haploid) to assemble a knockout library of 3,396 human genes. The collection should enable screens of a range of phenotypes, the team reports.

Nature Meth. http://doi.org/nmw (2013)