PerspectiveMolecular Biology

Reliable Noise

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Science  26 Feb 2010:
Vol. 327, Issue 5969, pp. 1088-1089
DOI: 10.1126/science.1187268

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Most measurements of gene expression assess large numbers of cells to improve precision and reduce the “standard error” (the standard deviation of the mean). Yet, the standard deviation of the fluctuations of a measured property, such as cell proliferation, over time in a single cell (in a system at equilibrium or steady state) or across a cell population, scaled to the mean of the measured property, is defined as “noise.” Despite this pejorative, a full accounting of noise provides insights into the pathways and mechanisms controlling a measured property. On page 1142 of this issue, To and Maheshri demonstrate that noise itself can generate a system that switches spontaneously between high and low gene expression (1). This finding implies that fluctuation in the numbers of regulatory molecules may drive physiological transitions without having to precisely specify the numbers of other molecules needed to prepare chromatin and make RNA. However, these same fluctuations might initiate and sustain pathological states, so mechanisms to suppress such fluctuations must also exist.