On the table of contents of the 13 May 2008 issue of Science Signaling, the one-sentence description of this Editors' Choice summary indicated that the screen was performed in yeast. This is incorrect.

The correct one-sentence description is

"A systematic, functional screen of extracellular proteins identified a previously unknown receptor-ligand pair: the cytokine interleukin-34 and its receptor."

--The editors of Science Signaling