Separating News from Noise

By treating mouse fibroblasts with varying concentrations of tumor necrosis factor (TNF) and measuring the resulting shifts in the production of transcription factors NFB and ATF-2, the researchers determined that individual cells are essentially capable of a one-bit response to this ligand, where signaling is simply on or ‘off.’ Many intermediate steps lie between TNF and NFB, and the authors modeled signal transmission in this pathway as a ‘tree’ network. In this model, information is transmitted along a single ‘trunk,’ in which noise can have a major impact and introduce bottlenecks in signal transmission, before branching out to yield different outputs. Endogenously-produced TNF inhibitors can dampen noise arising within this system, but also limit the ultimate dynamic range of signal response.