The researchers were also keen to find out if their method could be used to screen for genes that worked in, or inhibited specific molecular pathways. Screens in whole flies for genes that modify the effect of a particular genetic mutation have proved powerful, though time consuming. By adding two sets of double stranded RNA to each well, one that targeted the tumor suppressor gene pten and the other the gene to be tested, the researchers found that they were able to identify genes that modified the effects of inhibiting pten in cells. "These results demonstrate that modifier screens, as previously done in vivo, can be extended to RNAi screening methodology in cell culture", write the researchers.
Drug companies are becoming interested in this technique, as the rate-limiting step in cell-based drug discovery is finding out which protein is inhibited by a particular drug. Using Perrimon's method they can screen to see which gene, when inhibited, changes the cell in the same way as adding the drug.
"RNAi screens can complement classical Drosophila genetics to assign functions to both known and novel genes," write the researchers. "The same technology can be easily adapted to a wide variety of cell-based studies and a greater genomic scale."
Baum says, "The major difference between this and whole fly screens is that here we can be systematic. We can choose to look at any cell biological process and systematically test the set of genes that could be involved. In the future we will be able to screen the full genome in a few weeks, and look at any cell biological phenomenon.
Contact: Gemma Bradley